BACKGROUND Total knee arthroplasty(TKA)using implants with a high level of constraint has generally been recommended for patients with osteoarthritis(OA)who have valgus alignment.However,studies have reported favorabl...BACKGROUND Total knee arthroplasty(TKA)using implants with a high level of constraint has generally been recommended for patients with osteoarthritis(OA)who have valgus alignment.However,studies have reported favorable outcomes even with cruciate-retaining(CR)implants.AIM To evaluate the coronal plane stability of CR-TKA in patients with valgus OA at the mid-term follow-up.METHODS Patients with primary valgus OA of the knee who underwent TKA from January 2014 to January 2021 were evaluated through stress radiography using a digital stress device with 100 N of force on both the medial and lateral side.Gap openings and degrees of angulation change were determined.Descriptive statistical analysis was performed for both continuous and categorical variables.Inter-rater reliability of the radiographic measurements was evaluated using Cronbach’s alpha.RESULTS This study included 25 patients(28 knees)with a mean preoperative mechanical valgus axis of 11.3(3.6-27.3)degrees.The mean follow-up duration was 3.4(1.04-7.4)years.Stress radiographs showed a median varus and valgus gap opening of 1.6(IQR 0.6-3.0)mm and 1.7(IQR 1.3-2.3)mm and varus and valgus angulation changes of 2.5(IQR 1.3-4.8)degrees and 2.3(IQR 2.0-3.6)degrees,respectively.No clinical signs of instability,implant loosening,or revision due to instability were observed throughout this case series.CONCLUSION The present study demonstrated that using CR-TKA for patients with valgus OA of the knee promoted excellent coronal plane stability.展开更多
Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynt...Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.展开更多
Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the...Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4-5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne VIII is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne VIII is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.展开更多
Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists re...Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists regarding which of these finishing lines will leave the most amount of residual dentine coronally on maxillary lateral incisors and mandibular incisors. Objective: To assess the coronal residual dentine thickness after different cervical finishing lines for anterior crown preparations. Materials and Methods: A prospective comparative study was conducted including mandibular incisors and maxillary laterals that were taken from subjects from 18 to 30 years old. Teeth in each of the three groups were randomly separated into three cervical margin preparation groups: knife edge, chamfer and shoulder. The teeth were then prepared for single crown coverage using these finishing lines. The teeth were sectioned halfway through the crown preparation, and a digital caliper was used to determine the residual dentine thickness at the buccal, lingual, mesial and distal areas. The Tukey test was used for mean comparison, and ANOVA analysis was used to evaluate the variation in mean residual dentine thickness. Results: For upper lateral incisors, knife edge finishing lines showed the highest amount of remaining dentine thickness—1.5 mm. lingually, while the upper lateral incisors mesially had the least amount of 0.53 mm for shoulder finishing lines. The least residual dentine (0.53 mm for the shoulder and 0.70 mm for the chamfer finishing line) was found in the interproximal portions of all the teeth that were selected. Lower central incisors had the least amount of residual dentine 0.61 mm for shoulder preparations mesially whiles lower lateral incisors had the least amount of residual dentine for shoulder preparations 0.58 mm distally. There was a statistically significant difference of 0.001 across the groups. Conclusion: The thickness of residual dentine seen coronally after the three finishing line preparations showed a statistically significant difference and the knife edge finishing line provided enough coronal protection within the scope of this study.展开更多
Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristic...Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristics of X-ray and radio emissions sensitively depend on the energy distribution of FEBs,which usually have a power-law energy spectrum.As FEBs travel in the solar atmosphere,their energy distribution can considerably vary due to the interaction with ambient plasmas.Tang et al.investigated the evolution of the energy spectrum of the FEBs traveling along a flare loop and discussed the possible effects on associated hard X-ray(HXR) and radio emissions.Considering the ubiquitous coronal loops in active regions,in the present paper,we investigate the parametric evolution of the energy spectra of FEBs when propagating along coronal loops.Here,we take the sunpot atmospheric model as an approximate coronal loop atmosphere model.The results show that the energy loss has an important impact on the cutoff behavior and energy spectra of FEBs when precipitating in a coronal loop with density ratio n_(b)/n_(e)= 0.01.The initially single power-law spectrum with a steepness cutoff can evolve into a more complex double power-law spectrum or two “knees” power-law spectrum with a flattened steepness cutoff behavior or saturation cutoff behavior.Our calculations also demonstrate that the energy spectrum evolution is not obvious if n_(b)/n_(0)= 0.001 as Tang et al.asserted.The present results are helpful for a more comprehensive understanding of the dynamic spectra of HXR and radio emissions from FEBs.展开更多
The extraction of high-temperature regions in active regions(ARs)is an important means to help understand the mechanism of coronal heating.The important observational means of high-temperature radiation in ARs is the ...The extraction of high-temperature regions in active regions(ARs)is an important means to help understand the mechanism of coronal heating.The important observational means of high-temperature radiation in ARs is the main emission line of Fe XVⅢin the 94?of the Atmospheric Imaging Assembly.However,the diagnostic algorithms for Fe XVⅢ,including the differential emission measure(DEM)and linear diagnostics proposed by Del based on the DEM,have been greatly limited for a long time,and the results obtained are different from the predictions.In this paper,we use the outlier detection method to establish the nonlinear correlation between 94?and 171,193,211?based on the former researches by others.A neural network based on 171,193,211?is constructed to replace the low-temperature emission lines in the ARs of 94?.The predicted results are regarded as the low-temperature components of 94?,and then the predicted results are subtracted from 94?to obtain the outlier component of 94?,or Fe XVⅢ.Then,the outlier components obtained by neural network are compared with the Fe XVⅢobtained by DEM and Del's method,and a high similarity is found,which proves the reliability of neural network to obtain the high-temperature components of ARs,but there are still many differences.In order to analyze the differences between the Fe XVⅢobtained by the three methods,we subtract the Fe XVⅢobtained by the DEM and Del's method from the Fe XVⅢobtained by the neural network to obtain the residual value,and compare it with the results of Fe XIV in the temperature range of 6.1-6.45 MK.It is found that there is a great similarity,which also shows that the Fe XVⅢobtained by DEM and Del's method still has a large low-temperature component dominated by Fe XIV,and the Fe XVⅢobtained by neural network is relatively pure.展开更多
Magnetic fields play a key role in driving a broad range of dynamic phenomena in the atmospheres of the Sun and other stars.Routine and accurate measurements of the magnetic fields at all the atmospheric layers are of...Magnetic fields play a key role in driving a broad range of dynamic phenomena in the atmospheres of the Sun and other stars.Routine and accurate measurements of the magnetic fields at all the atmospheric layers are of critical importance to understand these magnetic activities,but in the solar and stellar coronae such a measurement is still a challenge due to the weak field strength and the high temperature.Recently,a magnetic-field-induced transition(MIT)of Fe X at 257.26A has been proposed for the magnetic field measurements in the solar and stellar coronae.In this review,we present an overview of recent progresses in the application of this method in astrophysics.We start by introducing the theory underlying the MIT method and reviewing the existing atomic data critical for the spectral modeling of Fe X lines.We also discuss the laboratory measurements that verify the potential capability of the MIT technique as a probe for diagnosing the plasma magnetic fields.We then continue by investigating the suitability and accuracy of solar and stellar coronal magnetic field measurements based on the MIT method through forward modeling.Furthermore,we discuss the application of the MIT method to the existing spectroscopic observations obtained by the Extreme-ultraviolet Imaging Spectrometer onboard Hinode.This novel technique provides a possible way for routine measurements of the magnetic fields in the solar and stellar coronae,but still requires further efforts to improve its accuracy.Finally,the challenges and prospects for future research on this topic are discussed.展开更多
Using solar wind observation near PSP perihelions as constraints,we have investigated the parameters in various PFSS model methods.It is found that the interplanetary magnetic field extrapolation with source surface h...Using solar wind observation near PSP perihelions as constraints,we have investigated the parameters in various PFSS model methods.It is found that the interplanetary magnetic field extrapolation with source surface height R_(SS)=2 Rs is better than that with R_(SS)=2.5 Rs.HMI and GONG magnetograms show similar performances in the simulation of magnetic field variation,but the former appears to have a slight advantage in reconstruction of intensity while the latter is more adaptable to sparser grids.The finite-difference method of constructing eigenvalue problems for potential fields can achieve similar accuracy as the analytic method and greatly improve the computational efficiency.MHD modeling performs relatively less well in magnetic field prediction,but it is able to provide rich information about solar-terrestrial space.展开更多
The origin of the heliospheric magnetic flux on the Sun,and hence the origin of the solar wind,is a topic of hot debate.While the prevailing view is that the solar wind originates from outside the coronal streamer hel...The origin of the heliospheric magnetic flux on the Sun,and hence the origin of the solar wind,is a topic of hot debate.While the prevailing view is that the solar wind originates from outside the coronal streamer helmets,there also exists the suggestion that the open magnetic field spans a far wider region.Without the definitive measurement of the coronal magnetic field,it is difficult to unambiguously resolve the conflict between the two scenarios.We present two 2-dimensional, Alfvénic-turbulence-based models of the solar corona and solar wind,one with and the other without a closed magnetic field region in the inner corona.The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the Fe XⅢ 10747 line,where open magnetic field lines seem to penetrate the streamer base.The boundary conditions at the coronal base are able to account for important observational constraints,especially those on the magnetic flux distribution.Interestingly,the two models provide similar polarized brightness（pB）distributions in the field of view（FOV）of SOHO/LASCO C2 and C3 coronagraphs.In particular,a dome-shaped feature is present in the C2 FOV even for the model without a closed magnetic field.Moreover,both models fit the Ulysses data scaled to 1 AU equally well.We suggest that：1）The pB observations cannot be safely taken as a proxy for the magnetic field topology,as is often implicitly assumed.2）The Ulysses measurements,especially the one showing a nearly uniform distribution with heliocentric latitude of the radial magnetic field,do not rule out the ubiquity of open magnetic fields on the Sun.展开更多
Intensity fluctuations are frequently observed in different regions and structures of the solar corona.These fluctuations may be caused by magneto-hydrodynamic(MHD)waves in coronal plasma.MHD waves are prime candidate...Intensity fluctuations are frequently observed in different regions and structures of the solar corona.These fluctuations may be caused by magneto-hydrodynamic(MHD)waves in coronal plasma.MHD waves are prime candidates for the dynamics,energy transfer,and anomalous temperature of the solar corona.In this paper,analysis is conducted on intensity and temperature fluctuations along the active region coronal loop(NOAA AR 13599)near solar flares.The intensity and temperature as functions of time and distance along the loop are extracted using images captured by the Atmospheric Imaging Assembly(AIA)instrument onboard the Solar Dynamics Observatory(SDO)space telescope.To observe and comprehend the causes of intensity and temperature fluctuations,after conducting initial processing,and applying spatial and temporal frequency filters to data,enhanced distance-time maps of these variables are drawn.The space-time maps of intensities show standing oscillations at wavelengths of 171,193,and 211A with greater precision and clarity than earlier findings.The amplitude of these standing oscillations(waves)decreases and increases over time.The average values of the oscillation period,damping time,damping quality,projected wavelength,and projected phase speed of standing intensity oscillations are in the range of 15-18 minutes,24-31 minutes,1.46″-2″,132″-134″,and 81-100 km s^(-1),respectively.Also,the differential emission measure peak temperature values along the loop are found in the range of 0.51-3.98 MK,using six AIA passbands,including 94,131,171,193,211,and 335?.Based on the values of oscillation periods,phase speeds,damping time,and damping quality,it is inferred that the fluctuations in intensity are related to standing slow magneto-acoustic waves with weak damping.展开更多
The automatic detection and analysis of sunspots play a crucial role in understanding solar dynamics and predicting space weather events.This paper proposes a novel method for sunspot group detection and classificatio...The automatic detection and analysis of sunspots play a crucial role in understanding solar dynamics and predicting space weather events.This paper proposes a novel method for sunspot group detection and classification called the dual stream Convolutional Neural Network with Attention Mechanism(DSCNN-AM).The network consists of two parallel streams each processing different input data allowing for joint processing of spatial and temporal information while classifying sunspots.It takes in the white light images as well as the corresponding magnetic images that reveal both the optical and magnetic features of sunspots.The extracted features are then fused and processed by fully connected layers to perform detection and classification.The attention mechanism is further integrated to address the“edge dimming”problem which improves the model’s ability to handle sunspots near the edge of the solar disk.The network is trained and tested on the SOLAR-STORM1 data set.The results demonstrate that the DSCNN-AM achieves superior performance compared to existing methods,with a total accuracy exceeding 90%.展开更多
With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence...With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.展开更多
The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Obs...The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of E G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycle, is different： it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.展开更多
Olbers’s paradox, known as the dark night paradox, is an argument in astrophysics that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. Big-Bang theory was used ...Olbers’s paradox, known as the dark night paradox, is an argument in astrophysics that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. Big-Bang theory was used to partially explain this paradox, while introducing new problems. Hereby, we propose a better theory, named Sun Matters Theory, to explain this paradox. Moreover, this unique theory supports and extended the Einstein’s static universe model proposed by Albert Einstein in 1917. Further, we proposed our new universe model, “Sun Model of Universe”. Based on the new model and novel theory, we generated innovative field equation by upgrading Einstein’s Field Equation through adding back the cosmological constant, introducing a new variable and modifying the gravitationally-related concepts. According to the Sun Model of Universe, the dark matter and dark energy comprise the so-called “Sun Matters”. The observed phenomenon like the red shift is explained as due to the interaction of ordinary light with Sun Matters leading to its energy and frequency decrease. In Sun Model, our big universe consists of many universes with ordinary matter at the core mixed and surrounded with the Sun Matters. In those universes, the laws of physics may be completely or partially different from that of our ordinary universe with parallel civilizations. The darkness of night can be easily explained as resulting from the interaction of light with the Sun Matters leading to the sharp decrease in the light intensity. Sun Matters also scatter the light from a star, which makes it shining as observed by Hubble. Further, there is a kind of Sun Matters named “Sun Waters”, surrounding every starts. When lights pass by the sun, the Sun Waters deflect the lights to bend the light path. According to the Sun Model, it is the light bent not the space bent that was proposed in the theory of relativities.展开更多
The scattered stray light of a coronagraph is a type of stray light that is generated by the objective lens as its surface defects are irradiated by sunlight.The defects mainly include dust and blemishes on the lens s...The scattered stray light of a coronagraph is a type of stray light that is generated by the objective lens as its surface defects are irradiated by sunlight.The defects mainly include dust and blemishes on the lens surface,microroughness of the lens surface,and impurity and inhomogeneity of the glass.Unlike the other types of relatively stable defects introduced when the objective lens is being manufactured,the scattered stray light caused by dusts on the lens surface is difficult to quantify accurately due to the disorder and randomness of the dust accumulation.The contribution of this type of stray light to the overall stray light level is difficult to determine through simulations and experiments.This can result in continuous deterioration of the stray light level of a coronagraph and thus affect the observation capabilities of the instrument.To solve this issue,through analyzing the forming mechanism of scattered stray light and ghost image generated by the inner-occulted coronagraph,we propose a novel method to monitor the scattered stray light from dusts by utilizing different stray light correlation coefficients.In this method,we first simulate and measure the level of stray light from the ghost image of the objective lens,and then determine the flux ratio of scattered light and ghost image on the conjugate plane.Although the flux ratio varies with the accumulation of dusts on the lens surface,it remains constant on the image plane.Therefore,the level of dust scattering light on the image plane can be obtained by using this ratio together with the level of ghost image stray light.The accuracy of this method has been validated in a laboratory by applying the objective lens with numerous surface cleanliness levels.展开更多
In this article,we compare the properties of two coronal mass ejections(CMEs)that show similar source region characteristics but different evolutionary behaviors in the later phases.We discuss the two events in terms ...In this article,we compare the properties of two coronal mass ejections(CMEs)that show similar source region characteristics but different evolutionary behaviors in the later phases.We discuss the two events in terms of their near-Sun characteristics,interplanetary evolution and geoeffectiveness.We carefully analyzed the initiation and propagation parameters of these events to establish the precise CMEinterplanetary CME(ICME)connection and their near-Earth consequences.The first event is associated with poor geomagnetic storm disturbance index(Dst≈-20 n T)while the second event is associated with an intense geomagnetic storm of DST≈-119 n T.The configuration of the sunspots in the active regions and their evolution are observed by Helioseismic and Magnetic Imager(HMI).For source region imaging,we rely on data obtained from Atmospheric Imaging Assembly(AIA)on board Solar Dynamics Observatory(SDO)and Hαfiltergrams from the Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences(ARIES).For both the CMEs,flux rope eruptions from the source region triggered flares of similar intensities(≈M1).At the solar source region of the eruptions,we observed a circular ribbon flare(CRF)for both cases,suggesting fan-spine magnetic configuration in the active region corona.The multi-channel SDO observations confirm that the eruptive flares and subsequent CMEs were intimately related to the filament eruption.Within the Large Angle and Spectrometric Coronograph(LASCO)field of view(FOV)the two CMEs propagated with linear speeds of 671 and 631 km s-1,respectively.These CMEs were tracked up to the Earth by Solar Terrestrial Relations Observatory(STEREO)instruments.We find that the source region evolution of CMEs,guided by the large-scale coronal magnetic field configuration,along with near-Sun propagation characteristics,such as CME-CME interactions,played important roles in deciding the evolution of CMEs in the interplanetary medium and subsequently their geoeffectiveness.展开更多
The history of our solar system has been greatly influenced by the fact that there is a large gas giant planet, Jupiter that has a nearly circular orbit. This has allowed relics of the early solar system formation to ...The history of our solar system has been greatly influenced by the fact that there is a large gas giant planet, Jupiter that has a nearly circular orbit. This has allowed relics of the early solar system formation to still be observable today. Since Jupiter orbits the Sun with a period of approximately 12 years, it has always been thought that this could be connected to the nearly 11-year periodic peak in the number of sunspots observed. In this paper, the Sun and planets are considered to be moving about a center of mass point as the different planets orbit the Sun. This is the action of gravity that holds the solar system together. The center of mass for the Jupiter-Sun system actually lies outside the Sun. The four gas giant planets dominate such effects and the four gas giant Jovian planets can be projected together to determine an effective distance from the Sun’s center. Taken together these effects do seem to function as a sunspot forcing factor with a periodicity very close to 11 years. These predictions are made without consideration of any details of what is happening in the interior of the Sun. From these estimates, sunspot cycle 25 will be expected to peak in about September-October of 2025. Sunspot cycle 26 should peak in the year March of 2037.展开更多
In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration...In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019.During this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot only.We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and 24.These are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.展开更多
Information is given on thermal radiation from the Sun, considered in practical engineering calculations of heat exchange. It was found that although the surface temperature of the Sun is assumed to be about 5800 K, t...Information is given on thermal radiation from the Sun, considered in practical engineering calculations of heat exchange. It was found that although the surface temperature of the Sun is assumed to be about 5800 K, the solar spectrum data measured by Kondratyev lead to a value of at least 7134 K. Such a higher value can be obtained by interpreting the Planck formula for the black radiation spectrum for the Kondratyev data. In addition, using the Stefan-Boltzmann law, the energetic emissivity of the Sun’s surface was determined to be 0.431. Furthermore, based on Petela’s formulae for exergy of thermal radiation, the exergetic emissivity of the Sun’s surface was also calculated at the level of 0.426.展开更多
文摘BACKGROUND Total knee arthroplasty(TKA)using implants with a high level of constraint has generally been recommended for patients with osteoarthritis(OA)who have valgus alignment.However,studies have reported favorable outcomes even with cruciate-retaining(CR)implants.AIM To evaluate the coronal plane stability of CR-TKA in patients with valgus OA at the mid-term follow-up.METHODS Patients with primary valgus OA of the knee who underwent TKA from January 2014 to January 2021 were evaluated through stress radiography using a digital stress device with 100 N of force on both the medial and lateral side.Gap openings and degrees of angulation change were determined.Descriptive statistical analysis was performed for both continuous and categorical variables.Inter-rater reliability of the radiographic measurements was evaluated using Cronbach’s alpha.RESULTS This study included 25 patients(28 knees)with a mean preoperative mechanical valgus axis of 11.3(3.6-27.3)degrees.The mean follow-up duration was 3.4(1.04-7.4)years.Stress radiographs showed a median varus and valgus gap opening of 1.6(IQR 0.6-3.0)mm and 1.7(IQR 1.3-2.3)mm and varus and valgus angulation changes of 2.5(IQR 1.3-4.8)degrees and 2.3(IQR 2.0-3.6)degrees,respectively.No clinical signs of instability,implant loosening,or revision due to instability were observed throughout this case series.CONCLUSION The present study demonstrated that using CR-TKA for patients with valgus OA of the knee promoted excellent coronal plane stability.
文摘Coronal shear fractures of the femoral neck (CSFF) are the most challenging to treat among proximal femur fractures, directly affecting the life expectancy of patients with osteoporosis. However, an adequate osteosynthesis method has not been elucidated yet. This study investigated the displacement direction of the femoral head fragment and its effect on the bone using finite element method. A finite element model for CSFF was developed from CT image data of a patient with osteoporosis using Mechanical Finder (ver. 11). Subsequently, finite element analyses were performed on six osteosynthesis models under maximum load applied during walking. The compressive stresses, tensile stresses, and compressive strains of each model were examined. The results suggested that the compressive and tensile stress distributions were concentrated on the anterior side of the femoral neck. Compressive strain distribution in the femoral head and neck was concentrated in four areas: at the tip of the blade or lag screw, the anteroinferior side of the blade or lag screw near the fracture site, and the upper right and lower left near the junction of the blade or lag screw and nail. Thus, the distribution of both these stresses revealed that the femoral head fragment was prone to anterior and inferior displacement. Distribution of compressive strains revealed the direction of the stress exerted by the osteosynthetic implant on the bone. The same results were observed in all osteosynthetic implants;thus, the findings could lay the foundation for developing methods for placing osteosynthetic implants less prone to displacement and the osteosynthetic implants themselves. In particular, the study provides insight into the optimal treatment of CSFF.
基金Hui Tian, Jian-Sen He, Bo Tan, and Shuo Yao are supported by the National Natural Science Foundation of China under Grants 40574078, 40336053 and40436015by the Beijing Education Project XK100010404+4 种基金the foundation Major Project of National Basic Research, under contract 2006CB806305Hui Tian is also supported by China Scholarship Council for his stay in the Max-Planck-Institut fr Sonnen system for schung in GermanyLi-Dong Xia is supported by the National Natural Science Foundation of China under Grant 40574064the Programme for New Century Excellent Talents in University (NCET)supported by DLR, CNES, NASA, and the ESA PRODEX programme (Swiss contribution).
文摘Using the correlation between the radiance or Doppler velocity and the extrapolated magnetic field, we determined the emission heights of a set of solar transition region lines in an equatorial coronal hole and in the surrounding quiet Sun region. We found that for all of the six lower-transition-region lines, the emission height is about 4-5 Mm in the equatorial coronal hole, and around 2 Mm in the quiet Sun region. This result confirms the previous findings that plasma with different temperature can coexist at the same layer of transition region. In the quiet Sun region, the emission height of the upper-transition-region line Ne VIII is almost the same that of the lower-transition-region line, but in the coronal hole, it is twice as high. This difference reveals that the outflow of Ne VIII is a signature of solar wind in the coronal hole and is just a mass supply to the large loops in the quiet Sun.
文摘Background: Knife edge, chamfer, and shoulder are the three distinct finishing lines utilized in crown preparations. Each finishing line has relative benefits and drawbacks. However, not much scientific data exists regarding which of these finishing lines will leave the most amount of residual dentine coronally on maxillary lateral incisors and mandibular incisors. Objective: To assess the coronal residual dentine thickness after different cervical finishing lines for anterior crown preparations. Materials and Methods: A prospective comparative study was conducted including mandibular incisors and maxillary laterals that were taken from subjects from 18 to 30 years old. Teeth in each of the three groups were randomly separated into three cervical margin preparation groups: knife edge, chamfer and shoulder. The teeth were then prepared for single crown coverage using these finishing lines. The teeth were sectioned halfway through the crown preparation, and a digital caliper was used to determine the residual dentine thickness at the buccal, lingual, mesial and distal areas. The Tukey test was used for mean comparison, and ANOVA analysis was used to evaluate the variation in mean residual dentine thickness. Results: For upper lateral incisors, knife edge finishing lines showed the highest amount of remaining dentine thickness—1.5 mm. lingually, while the upper lateral incisors mesially had the least amount of 0.53 mm for shoulder finishing lines. The least residual dentine (0.53 mm for the shoulder and 0.70 mm for the chamfer finishing line) was found in the interproximal portions of all the teeth that were selected. Lower central incisors had the least amount of residual dentine 0.61 mm for shoulder preparations mesially whiles lower lateral incisors had the least amount of residual dentine for shoulder preparations 0.58 mm distally. There was a statistically significant difference of 0.001 across the groups. Conclusion: The thickness of residual dentine seen coronally after the three finishing line preparations showed a statistically significant difference and the knife edge finishing line provided enough coronal protection within the scope of this study.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.12173076,42174195,11873018 and 41531071)by Lishui University Initial Funding under grant QD2182by NSF of Jiangsu Province under grant BK20191513。
文摘Fast electron beams(FEBs) are one of the main products of various active events and are ubiquitous in solar,space and cosmic plasmas.They reveal themselves in hard X-ray and radio emissions.The observed characteristics of X-ray and radio emissions sensitively depend on the energy distribution of FEBs,which usually have a power-law energy spectrum.As FEBs travel in the solar atmosphere,their energy distribution can considerably vary due to the interaction with ambient plasmas.Tang et al.investigated the evolution of the energy spectrum of the FEBs traveling along a flare loop and discussed the possible effects on associated hard X-ray(HXR) and radio emissions.Considering the ubiquitous coronal loops in active regions,in the present paper,we investigate the parametric evolution of the energy spectra of FEBs when propagating along coronal loops.Here,we take the sunpot atmospheric model as an approximate coronal loop atmosphere model.The results show that the energy loss has an important impact on the cutoff behavior and energy spectra of FEBs when precipitating in a coronal loop with density ratio n_(b)/n_(e)= 0.01.The initially single power-law spectrum with a steepness cutoff can evolve into a more complex double power-law spectrum or two “knees” power-law spectrum with a flattened steepness cutoff behavior or saturation cutoff behavior.Our calculations also demonstrate that the energy spectrum evolution is not obvious if n_(b)/n_(0)= 0.001 as Tang et al.asserted.The present results are helpful for a more comprehensive understanding of the dynamic spectra of HXR and radio emissions from FEBs.
基金supported by the National Natural Science Foundation of China under Grant Nos.U2031140,11873027,and 12073077。
文摘The extraction of high-temperature regions in active regions(ARs)is an important means to help understand the mechanism of coronal heating.The important observational means of high-temperature radiation in ARs is the main emission line of Fe XVⅢin the 94?of the Atmospheric Imaging Assembly.However,the diagnostic algorithms for Fe XVⅢ,including the differential emission measure(DEM)and linear diagnostics proposed by Del based on the DEM,have been greatly limited for a long time,and the results obtained are different from the predictions.In this paper,we use the outlier detection method to establish the nonlinear correlation between 94?and 171,193,211?based on the former researches by others.A neural network based on 171,193,211?is constructed to replace the low-temperature emission lines in the ARs of 94?.The predicted results are regarded as the low-temperature components of 94?,and then the predicted results are subtracted from 94?to obtain the outlier component of 94?,or Fe XVⅢ.Then,the outlier components obtained by neural network are compared with the Fe XVⅢobtained by DEM and Del's method,and a high similarity is found,which proves the reliability of neural network to obtain the high-temperature components of ARs,but there are still many differences.In order to analyze the differences between the Fe XVⅢobtained by the three methods,we subtract the Fe XVⅢobtained by the DEM and Del's method from the Fe XVⅢobtained by the neural network to obtain the residual value,and compare it with the results of Fe XIV in the temperature range of 6.1-6.45 MK.It is found that there is a great similarity,which also shows that the Fe XVⅢobtained by DEM and Del's method still has a large low-temperature component dominated by Fe XIV,and the Fe XVⅢobtained by neural network is relatively pure.
基金supported by the National Natural Science Foundation of China(NSFC,Grant Nos.11825301,12103066 and12073004).
文摘Magnetic fields play a key role in driving a broad range of dynamic phenomena in the atmospheres of the Sun and other stars.Routine and accurate measurements of the magnetic fields at all the atmospheric layers are of critical importance to understand these magnetic activities,but in the solar and stellar coronae such a measurement is still a challenge due to the weak field strength and the high temperature.Recently,a magnetic-field-induced transition(MIT)of Fe X at 257.26A has been proposed for the magnetic field measurements in the solar and stellar coronae.In this review,we present an overview of recent progresses in the application of this method in astrophysics.We start by introducing the theory underlying the MIT method and reviewing the existing atomic data critical for the spectral modeling of Fe X lines.We also discuss the laboratory measurements that verify the potential capability of the MIT technique as a probe for diagnosing the plasma magnetic fields.We then continue by investigating the suitability and accuracy of solar and stellar coronal magnetic field measurements based on the MIT method through forward modeling.Furthermore,we discuss the application of the MIT method to the existing spectroscopic observations obtained by the Extreme-ultraviolet Imaging Spectrometer onboard Hinode.This novel technique provides a possible way for routine measurements of the magnetic fields in the solar and stellar coronae,but still requires further efforts to improve its accuracy.Finally,the challenges and prospects for future research on this topic are discussed.
文摘Using solar wind observation near PSP perihelions as constraints,we have investigated the parameters in various PFSS model methods.It is found that the interplanetary magnetic field extrapolation with source surface height R_(SS)=2 Rs is better than that with R_(SS)=2.5 Rs.HMI and GONG magnetograms show similar performances in the simulation of magnetic field variation,but the former appears to have a slight advantage in reconstruction of intensity while the latter is more adaptable to sparser grids.The finite-difference method of constructing eigenvalue problems for potential fields can achieve similar accuracy as the analytic method and greatly improve the computational efficiency.MHD modeling performs relatively less well in magnetic field prediction,but it is able to provide rich information about solar-terrestrial space.
基金supported by the National Natural Science Foundation of China(Grant Nos.40904047and 41174154)the Ministry of Education of China(20110131110058 and NCET-11-0305)by the Specialized Research Fund for State Key Laboratories
文摘The origin of the heliospheric magnetic flux on the Sun,and hence the origin of the solar wind,is a topic of hot debate.While the prevailing view is that the solar wind originates from outside the coronal streamer helmets,there also exists the suggestion that the open magnetic field spans a far wider region.Without the definitive measurement of the coronal magnetic field,it is difficult to unambiguously resolve the conflict between the two scenarios.We present two 2-dimensional, Alfvénic-turbulence-based models of the solar corona and solar wind,one with and the other without a closed magnetic field region in the inner corona.The purpose of the latter model is to test whether it is possible to realize a picture suggested by polarimetric measurements of the corona using the Fe XⅢ 10747 line,where open magnetic field lines seem to penetrate the streamer base.The boundary conditions at the coronal base are able to account for important observational constraints,especially those on the magnetic flux distribution.Interestingly,the two models provide similar polarized brightness（pB）distributions in the field of view（FOV）of SOHO/LASCO C2 and C3 coronagraphs.In particular,a dome-shaped feature is present in the C2 FOV even for the model without a closed magnetic field.Moreover,both models fit the Ulysses data scaled to 1 AU equally well.We suggest that：1）The pB observations cannot be safely taken as a proxy for the magnetic field topology,as is often implicitly assumed.2）The Ulysses measurements,especially the one showing a nearly uniform distribution with heliocentric latitude of the radial magnetic field,do not rule out the ubiquity of open magnetic fields on the Sun.
文摘Intensity fluctuations are frequently observed in different regions and structures of the solar corona.These fluctuations may be caused by magneto-hydrodynamic(MHD)waves in coronal plasma.MHD waves are prime candidates for the dynamics,energy transfer,and anomalous temperature of the solar corona.In this paper,analysis is conducted on intensity and temperature fluctuations along the active region coronal loop(NOAA AR 13599)near solar flares.The intensity and temperature as functions of time and distance along the loop are extracted using images captured by the Atmospheric Imaging Assembly(AIA)instrument onboard the Solar Dynamics Observatory(SDO)space telescope.To observe and comprehend the causes of intensity and temperature fluctuations,after conducting initial processing,and applying spatial and temporal frequency filters to data,enhanced distance-time maps of these variables are drawn.The space-time maps of intensities show standing oscillations at wavelengths of 171,193,and 211A with greater precision and clarity than earlier findings.The amplitude of these standing oscillations(waves)decreases and increases over time.The average values of the oscillation period,damping time,damping quality,projected wavelength,and projected phase speed of standing intensity oscillations are in the range of 15-18 minutes,24-31 minutes,1.46″-2″,132″-134″,and 81-100 km s^(-1),respectively.Also,the differential emission measure peak temperature values along the loop are found in the range of 0.51-3.98 MK,using six AIA passbands,including 94,131,171,193,211,and 335?.Based on the values of oscillation periods,phase speeds,damping time,and damping quality,it is inferred that the fluctuations in intensity are related to standing slow magneto-acoustic waves with weak damping.
文摘The automatic detection and analysis of sunspots play a crucial role in understanding solar dynamics and predicting space weather events.This paper proposes a novel method for sunspot group detection and classification called the dual stream Convolutional Neural Network with Attention Mechanism(DSCNN-AM).The network consists of two parallel streams each processing different input data allowing for joint processing of spatial and temporal information while classifying sunspots.It takes in the white light images as well as the corresponding magnetic images that reveal both the optical and magnetic features of sunspots.The extracted features are then fused and processed by fully connected layers to perform detection and classification.The attention mechanism is further integrated to address the“edge dimming”problem which improves the model’s ability to handle sunspots near the edge of the solar disk.The network is trained and tested on the SOLAR-STORM1 data set.The results demonstrate that the DSCNN-AM achieves superior performance compared to existing methods,with a total accuracy exceeding 90%.
基金supported by the National Natural Science Foundation of China under grant Nos.12393854,12022502 and 12263007by the High-level Talent Support program of Yunnan Province。
文摘With great advance of ground-based extensive air shower arrays,such as LHAASO and HAWC,many very high energy(VHE)gamma-ray sources have been discovered and are being monitored regardless of the day and the night.Hence,the Sun and Moon would have some impacts on the observation of gamma-ray sources,which have not been taken into account in previous analysis.In this paper,the influence of the Sun and Moon on the observation of very high energy gamma-ray sources when they are near the line of sight of the Sun or Moon is estimated.The tracks of all the known VHE sources are scanned and several VHE sources are found to be very close to the line of sight of the Sun or Moon during some period.The absorption of very high energy gamma rays by sunlight is estimated with detailed method and some useful conclusions are achieved.The main influence is the block of the Sun and Moon on gamma rays and the shadow on the cosmic ray background.The influence is investigated considering the detector angular resolution and some strategies on data analysis are proposed to avoid the underestimation of the gamma-ray emission.
文摘The atmospheric activity of the Sun and Sun-like stars is analyzed involving observations from the HK-project at the Mount Wilson Observatory, the California and Carnegie Planet Search Program at the Keck and Lick Observatories and the Magellan Planet Search Program at the Las Campanas Observatory. We show that for stars of E G and K spectral classes, the cyclic activity, similar to the 11-yr solar cycle, is different： it becomes more prominent in K-stars. Comparative study of Sun-like stars with different levels of chromospheric and coronal activity confirms that the Sun belongs to stars with a low level of chromospheric activity and stands apart among these stars by its minimum level of coronal radiation and minimum level of variations in photospheric flux.
文摘Olbers’s paradox, known as the dark night paradox, is an argument in astrophysics that the darkness of the night sky conflicts with the assumption of an infinite and eternal static universe. Big-Bang theory was used to partially explain this paradox, while introducing new problems. Hereby, we propose a better theory, named Sun Matters Theory, to explain this paradox. Moreover, this unique theory supports and extended the Einstein’s static universe model proposed by Albert Einstein in 1917. Further, we proposed our new universe model, “Sun Model of Universe”. Based on the new model and novel theory, we generated innovative field equation by upgrading Einstein’s Field Equation through adding back the cosmological constant, introducing a new variable and modifying the gravitationally-related concepts. According to the Sun Model of Universe, the dark matter and dark energy comprise the so-called “Sun Matters”. The observed phenomenon like the red shift is explained as due to the interaction of ordinary light with Sun Matters leading to its energy and frequency decrease. In Sun Model, our big universe consists of many universes with ordinary matter at the core mixed and surrounded with the Sun Matters. In those universes, the laws of physics may be completely or partially different from that of our ordinary universe with parallel civilizations. The darkness of night can be easily explained as resulting from the interaction of light with the Sun Matters leading to the sharp decrease in the light intensity. Sun Matters also scatter the light from a star, which makes it shining as observed by Hubble. Further, there is a kind of Sun Matters named “Sun Waters”, surrounding every starts. When lights pass by the sun, the Sun Waters deflect the lights to bend the light path. According to the Sun Model, it is the light bent not the space bent that was proposed in the theory of relativities.
基金supported by the National Key R&D Program of China No.2021YFA0718600the National Natural Science Foundation of China(grant Nos.41904168,42274227 and U1931122)the Chinese Meridian Project。
文摘The scattered stray light of a coronagraph is a type of stray light that is generated by the objective lens as its surface defects are irradiated by sunlight.The defects mainly include dust and blemishes on the lens surface,microroughness of the lens surface,and impurity and inhomogeneity of the glass.Unlike the other types of relatively stable defects introduced when the objective lens is being manufactured,the scattered stray light caused by dusts on the lens surface is difficult to quantify accurately due to the disorder and randomness of the dust accumulation.The contribution of this type of stray light to the overall stray light level is difficult to determine through simulations and experiments.This can result in continuous deterioration of the stray light level of a coronagraph and thus affect the observation capabilities of the instrument.To solve this issue,through analyzing the forming mechanism of scattered stray light and ghost image generated by the inner-occulted coronagraph,we propose a novel method to monitor the scattered stray light from dusts by utilizing different stray light correlation coefficients.In this method,we first simulate and measure the level of stray light from the ghost image of the objective lens,and then determine the flux ratio of scattered light and ghost image on the conjugate plane.Although the flux ratio varies with the accumulation of dusts on the lens surface,it remains constant on the image plane.Therefore,the level of dust scattering light on the image plane can be obtained by using this ratio together with the level of ghost image stray light.The accuracy of this method has been validated in a laboratory by applying the objective lens with numerous surface cleanliness levels.
文摘In this article,we compare the properties of two coronal mass ejections(CMEs)that show similar source region characteristics but different evolutionary behaviors in the later phases.We discuss the two events in terms of their near-Sun characteristics,interplanetary evolution and geoeffectiveness.We carefully analyzed the initiation and propagation parameters of these events to establish the precise CMEinterplanetary CME(ICME)connection and their near-Earth consequences.The first event is associated with poor geomagnetic storm disturbance index(Dst≈-20 n T)while the second event is associated with an intense geomagnetic storm of DST≈-119 n T.The configuration of the sunspots in the active regions and their evolution are observed by Helioseismic and Magnetic Imager(HMI).For source region imaging,we rely on data obtained from Atmospheric Imaging Assembly(AIA)on board Solar Dynamics Observatory(SDO)and Hαfiltergrams from the Solar Tower Telescope at Aryabhatta Research Institute of Observational Sciences(ARIES).For both the CMEs,flux rope eruptions from the source region triggered flares of similar intensities(≈M1).At the solar source region of the eruptions,we observed a circular ribbon flare(CRF)for both cases,suggesting fan-spine magnetic configuration in the active region corona.The multi-channel SDO observations confirm that the eruptive flares and subsequent CMEs were intimately related to the filament eruption.Within the Large Angle and Spectrometric Coronograph(LASCO)field of view(FOV)the two CMEs propagated with linear speeds of 671 and 631 km s-1,respectively.These CMEs were tracked up to the Earth by Solar Terrestrial Relations Observatory(STEREO)instruments.We find that the source region evolution of CMEs,guided by the large-scale coronal magnetic field configuration,along with near-Sun propagation characteristics,such as CME-CME interactions,played important roles in deciding the evolution of CMEs in the interplanetary medium and subsequently their geoeffectiveness.
文摘The history of our solar system has been greatly influenced by the fact that there is a large gas giant planet, Jupiter that has a nearly circular orbit. This has allowed relics of the early solar system formation to still be observable today. Since Jupiter orbits the Sun with a period of approximately 12 years, it has always been thought that this could be connected to the nearly 11-year periodic peak in the number of sunspots observed. In this paper, the Sun and planets are considered to be moving about a center of mass point as the different planets orbit the Sun. This is the action of gravity that holds the solar system together. The center of mass for the Jupiter-Sun system actually lies outside the Sun. The four gas giant planets dominate such effects and the four gas giant Jovian planets can be projected together to determine an effective distance from the Sun’s center. Taken together these effects do seem to function as a sunspot forcing factor with a periodicity very close to 11 years. These predictions are made without consideration of any details of what is happening in the interior of the Sun. From these estimates, sunspot cycle 25 will be expected to peak in about September-October of 2025. Sunspot cycle 26 should peak in the year March of 2037.
基金partially supported by the Institute of Eminence(Io E)Program(Scheme No:6031)of BHU,Varanasi。
文摘In this present study,we have analyzed different types of X-ray solar flares(C,M,and X classes)coming out from different classes of sunspot groups(SSGs).The data which we have taken under this study cover the duration of 24 yr from 1996 to 2019.During this,we observed a total of 15015 flares(8417 in SC-23 and 6598 in SC-24)emitted from a total of 33780 active regions(21746 in SC-23 and 12034 in SC-24)with sunspot only.We defined the flaring potential or flare-production potential as the ratio of the total number of flares produced from a particular type of SSG to the total number of the same-class SSGs observed on the solar surface.Here we studied yearly changes in the flaring potential of different McIntosh class groups of sunspots in different phases of SC-23 and 24.In addition,we investigated yearly variations in the potential of producing flares by different SSGs(A,B,C,D,E,F,and H)during different phases(ascending,maximum,descending,and minimum)of SC-23 and 24.These are our findings:(1)D,E,and F SSGs have the potential of producing flares≥8 times greater than A,B,C and H SSGs;(2)The larger and more complex D,E,and F SSGs produced nearly 80%of flares in SC-23 and 24;(3)The A,B,C and H SSGs,which are smaller and simpler,produced only 20%of flares in SC-23 and 24;(4)The biggest and most complex SSGs of F-class have flaring potential 1.996 and 3.443 per SSG in SC-23 and 24,respectively.(5)The potential for producing flares in each SSG is higher in SC-24 than in SC-23,although SC-24 is a weaker cycle than SC-23.(6)The alterations in the number of flares(C+M+X)show different time profiles than the alterations in sunspot numbers during SC-23 and 24,with several peaks.(7)The SSGs of C,D,E,and H-class have the highest flaring potential in the descending phase of both SC-23 and 24.(8)F-class SSGs have the highest flaring potential in the descending phase of SC-23 but also in the maximum phase of SC-24.
文摘Information is given on thermal radiation from the Sun, considered in practical engineering calculations of heat exchange. It was found that although the surface temperature of the Sun is assumed to be about 5800 K, the solar spectrum data measured by Kondratyev lead to a value of at least 7134 K. Such a higher value can be obtained by interpreting the Planck formula for the black radiation spectrum for the Kondratyev data. In addition, using the Stefan-Boltzmann law, the energetic emissivity of the Sun’s surface was determined to be 0.431. Furthermore, based on Petela’s formulae for exergy of thermal radiation, the exergetic emissivity of the Sun’s surface was also calculated at the level of 0.426.
