Efficient acquiring information from a quantum state is important for research in fundamental quantum physics and quantum information applications. Instead of using standard quantum state tomography method with recons...Efficient acquiring information from a quantum state is important for research in fundamental quantum physics and quantum information applications. Instead of using standard quantum state tomography method with reconstruction algorithm, weak values were proposed to directly measure density matrix elements of quantum state. Recently, similar to the concept of weak value, modular values were introduced to extend the direct measurement scheme to nonlocal quantum wavefunction. However, this method still involves approximations, which leads to inherent low precision. Here, we propose a new scheme which enables direct measurement for ideal value of the nonlocal density matrix element without taking approximations. Our scheme allows more accurate characterization of nonlocal quantum states, and therefore has greater advantages in practical measurement scenarios.展开更多
Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradien...Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradient effects with moderate stiffness. By analyzingperiodic perturbations to an equilibrium, one canmeasure the variations in electron energy flux andelectron temperature gradient over the perturbation cycle, obtaining the flux as a function ofgradient over the range of parameters generated by the perturbation. Although time-dependenttransport analysis is very sensitive to noise in the input data, averaging over many cycles of aperiodic perturbation can provide data of sufficient quality. The analyses presented here are basedon the ECE temperature data with high spatial and temporal resolution and full profile coverage onDIII-D for sawteeth and modulated ECH heating.展开更多
Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the ele...Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the electrocaloric effect in P(VDF-TrFE-CFE)film was directly analysed using infrared imaging.P(VDF-TrFE-CFE)64.8%/27.4%/7.8%(in mole)film of(15±1)mm thickness was deposited on polyethylene naphthalate substrate.Direct ECE of P(VDF-TrFE-CFE)film was measured from 15 to 35C at different electric fields.A maximum adiabatic temperature change(DTad)of 3.58 K was measured during the cooling cycle at a field of 100 V/mm at 30C.Finite element analysis of temperature dissipation through the sample estimated that the actual temperature change within P(VDF-TrFE-CFE)film was 4.3 K.Despite the thermal mass of the substrate,a substantial ECE was observed in P(VDF-TrFE-CFE)films.This electrocaloric terpolymer composition could be of interest for electrocaloric cooling applications.展开更多
In 2014, the National Natural Science Foundation of China （NSFC） approved the Jinping Underground Nuclear Astrophysics laboratory （JUNA） project, which aims at direct cross-section measurements of four key stellar...In 2014, the National Natural Science Foundation of China （NSFC） approved the Jinping Underground Nuclear Astrophysics laboratory （JUNA） project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch （AGB） stars, measuring the key 19F（p,a）16O reaction at effective burning energies （i.e., at Gamow window） is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.展开更多
The electrocaloric effect(ECE)in lead-free BaSn_(x)Ti_(1-x)O_(3)(BSnT,x=0.05,0.10 and 0.15)ceramics were investigated using a direct ECE measurement.Results indicate that the maximum ECE occurs near the Curie temperat...The electrocaloric effect(ECE)in lead-free BaSn_(x)Ti_(1-x)O_(3)(BSnT,x=0.05,0.10 and 0.15)ceramics were investigated using a direct ECE measurement.Results indicate that the maximum ECE occurs near the Curie temperature and it slightly shifts towards high temperatures.The directly measured ECE is larger than that calculated using the Maxwell relation and P-E loops.A maximum electrocaloric efficiencyΔT=ΔE=0.49-10-6 KmV-1 was procured for the composition with x=0.15 at T=299.2 K.And it also shows a broad peak in the temperature range of 250–320 K.展开更多
The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring tr...The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring transition in Rb-87. The multi-peak fitting approach is used to eliminate the frequency shift affected by the neighboring transition. With locking the carrier envelope offset frequency at 1/4 repetition frequency, the transition frequency is measured to be 770569132739.9 +/- 5.8 kHz, which agrees well with the previous result recommended by Comite International des Poids et Mesures.展开更多
The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previousl...The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previously been made either directly by mounting thrusters to the m easurement system or indirectly by mounting a target in the direct path of the e jected propellant.Several typical direct and indirect thrust-stands are presen ted and discussed in detail to illustrate the principles.Typical calibration me thods are also expounded.Finally,the resolution,uncertainty and thrust range of each thrust-stand are given,which may be helpful for the future thrust stan d design and micro-thrusters research.展开更多
Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the...Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the influences of atmospheric conditions,settled height,view angle of infrared thermography,and investigating time of temperature measuring on the performance of the CWSI.Three irrigation treatments were used to create different soil water conditions during the 2020-2021 and 2021-2022 winter wheat-growing seasons.The CWSI was calculated using the CWSI-E(an empirical approach)and CWSI-T(a theoretical approach)based on the T_(c).Weather conditions were recorded continuously throughout the experimental period.The results showed that atmospheric conditions influenced the estimation of the CWSI;when the vapor pressure deficit(VPD)was>2000 Pa,the estimated CWSI was related to soil water conditions.The height of the installed infrared thermograph influenced the T_(c)values,and the differences among the T_(c)values measured at height of 3,5,and 10 m was smaller in the afternoon than in the morning.However,the lens of the thermometer facing south recorded a higher T_(c)than those facing east or north,especially at a low height,indicating that the direction of the thermometer had a significant influence on T_(c).There was a large variation in CWSI derived at different times of the day,and the midday measurements(12:00-15:00)were the most reliable for estimating CWSI.Negative linear relationships were found between the transpiration rate and CWSI-E(R^(2)of 0.3646-0.5725)and CWSI-T(R^(2)of 0.5407-0.7213).The relations between fraction of available soil water(FASW)with CWSI-T was higher than that with CWSI-E,indicating CWSI-T was more accurate for predicting crop water status.In addition,The R^(2)between CWSI-T and FASW at 14:00 was higher than that at other times,indicating that 14:00 was the optimal time for using the CWSI for crop water status monitoring.Relative higher yield of winter wheat was obtained with average seasonal values of CWSI-E and CWSI-T around 0.23 and 0.25-0.26,respectively.The CWSI-E values were more easily influenced by meteorological factors and the timing of the measurements,and using the theoretical approach to derive the CWSI was recommended for precise irrigation water management.展开更多
Gas holdup is one of the key parameters in flotation process. Gas holdup as measured by a differential pressure method was investigated and the relative errors compared to the average gas holdup from the volume expans...Gas holdup is one of the key parameters in flotation process. Gas holdup as measured by a differential pressure method was investigated and the relative errors compared to the average gas holdup from the volume expansion method. The errors were used to establish optimum measurement positions. The results show that the measurement position should be in the middle of the column and in the region half way from the center to the wall (the half-radius). The gas holdup along the axial direction is lower at the bottom and higher at the top of the floatation column. The gas holdup along the radial direction is lower near the wall and higher near the center of the flotation column. The average gas holdup measure- ment can be replaced by regional gas holdup values.展开更多
The object of present study is to investigate the bed shear stress on a slope under regular breaking waves by a novel instrument named Micro-Electro-Mechanical System （MEMS） flexible hot-film shear stress sensor. Th...The object of present study is to investigate the bed shear stress on a slope under regular breaking waves by a novel instrument named Micro-Electro-Mechanical System （MEMS） flexible hot-film shear stress sensor. The sensors were calibrated before application, and then a wave flume experiment was conducted to study the bed shear stress for the case of regular waves spilling and plunging on a 1 ： 15 smooth PVC slope. The experiment shows that the sensor is feasible for the measurement of the bed shear stress under breaking waves. For regular incident waves, the bed shear stress is mainly periodic in both outside and inside the breaking point. The fluctuations of the bed shear stress increase significantly after waves breaking due to the turbulence and vortexes generated by breaking waves. For plunging breaker, the extreme value of the mean maximum bed shear stress appears after the plunging point, and the more violent the wave breaks, the more dramatic increase of the maximum bed shear stress will occur. For spilling breaker, the increase of the maximum bed shear stress along the slope is gradual compared with the plunging breaker. At last, an empirical equation about the relationship between the maximum bed shear stress and the surf similarity parameter is given, which can be used to estimate the maximum bed shear stress under breaking waves in practice.展开更多
This paper reports on two nuclear astrophysics experiments performed in collabora- tion with Ruhr University. In a 12C＋2C fusion reaction, the 12C（12C, a）20e and 12C（12C, p）23Na reactions were studied in the ener...This paper reports on two nuclear astrophysics experiments performed in collabora- tion with Ruhr University. In a 12C＋2C fusion reaction, the 12C（12C, a）20e and 12C（12C, p）23Na reactions were studied in the energy range of E = 2.10 MeV to 4.75 MeV using -y-ray spectroscopy. The deduced astrophysical S（E）＊ factor exhibited a new, strong resonance at E -= 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the ^-channel by a factor of five near T = 8 ~ l0s K. The electron screening in d（d, p）t was stud- ied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D2 target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d（d, p）t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing tempera- ture. These data represent the first observations of the temperature dependence of a nuclear cross section.展开更多
We investigate the air-sea momentum flux in the marine atmospheric boundary layer using a tower-based direct measurement method.First,we compare the collected data with previous observations,and the results are roughl...We investigate the air-sea momentum flux in the marine atmospheric boundary layer using a tower-based direct measurement method.First,we compare the collected data with previous observations,and the results are roughly consistent.Next,in the low-to-moderate winds,the exchange coefficients(or drag coefficients)deviate between onshore and offshore winds,which exhibits the influence of surface wave on the momentum flux.Furthermore,we use a surface-wave-involved parameterization scheme to explain the dependence of momentum flux on surface wave.The results consolidate the influence of surface wave on momentum flux on the one hand,and validate the surface-wave-involved parameterization scheme on the other hand.展开更多
The wavelet transformation is applied to the high current transformer.The high current transformer elaborated in the paper is mainly applied to the measurement of AC/DC high current.The principle of the transformer is...The wavelet transformation is applied to the high current transformer.The high current transformer elaborated in the paper is mainly applied to the measurement of AC/DC high current.The principle of the transformer is the Hall direct measurement principle.The transformer has the following three characteristics:firstly, the effect of the remnant field of the iron core on the measurement is decreased;secondly,because the temperature compensation is adopted,the transformer has good temperature charactreristic;thirdly,be cause the wavelet transfomation technology is adopted,the transformer has the capacity of good antijanming.展开更多
Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios o...Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios of the Qimantag metallogenic belt,part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau,western Central Orogenic Belt of China,and overcome the limitation of the traditional electronic probe,five different measurement methods are proposed and their respective advantages and disadvantages evaluated,with the composition data of the magnetite obtained using electron probe microanalysis(EPMA).The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3,but the accuracy and uniformity of the results are low.The valence method(Flank method)based on the spectral intensity ratio of Lαto Lβfor iron is also unreliable for FeO and Fe_(2)O^(3) measurements because it is difficult to establish a relationship between Lβ/Lα,the spectral intensity ratio,and the Fe^(2+)/Fe^(3+) content ratio.In comparison,the charge difference method,the surplus-oxygen method and the Mössbauer spectrum method are still the most favorable.Mössbauer spectroscopy,with its isomer movement particularly sensitive to the oxidation state of iron,yields results closer to 0.5,which is relatively reliable.Earlier magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ratios,whereas later magnetite deposits are farther away from intrusions and have low Fe^(2+)/Fe^(3+) ratios.The transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also studied.No large volume changes,such as pore filling and shrinkage fracture,were detected in the metallogenic belt,and the transformation mechanism is more similar to a reoxidation and reduction mechanism.展开更多
We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze R...We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze River Economic Belt in 2003–2013.Results show that both the subprime mortgage crisis and ‘the new normal' had significant negative effects on productivity growth,leading to the different spatial patterns between 2003–2008 and 2009–2013.Before 2008,green poles had gathered around some capital cities and formed a tripartite pattern,which was a typical core-periphery pattern.Due to a combination of the polarization and the diffusion effects,capital cities became the growth poles and ‘core' regions,while surrounding areas became the ‘periphery'.This was mainly caused by the innate advantage of capital cities and ‘the rise of central China' strategy.After 2008,the tripartite pattern changed to a multi-poles pattern where green poles continuously and densely spread in the midstream and downstream areas.This is due to the regional difference in the leading effect of green poles.The leading effect of green poles in midstream and downstream areas has changed from polarization to diffusion,while the polarization effect still leads in the upstream area.展开更多
The distribution transformer is the mainstay of the power system.Its internal temperature study is desirable for its safe operation in the power system.The purpose of the present study is to determine direct comprehen...The distribution transformer is the mainstay of the power system.Its internal temperature study is desirable for its safe operation in the power system.The purpose of the present study is to determine direct comprehensive thermal distribution in the distribution transformers for different loading conditions.To achieve this goal,the temperature distribution in the oil,core,and windings are studied at each loading.An experimental study is performed with a 10/0.38 kV,10 kVA oil–immersed transformer equipped with forty–two PT100 sensors(PTs)for temperature measurement installed inside during its manufacturing process.All possible locations for the hottest spot temperature(HST)are considered that made by finite element analysis(FEA)simulation and losses calculations.A resistive load is made to achieve 80%to 120%loading of the test transformer for this experiment.Working temperature is measured in each part of the transformer at all provided loading conditions.It is observed that temperature varies with loading throughout the transformer,and a detailed map of temperature is obtained in the whole test transformer.From these results,the HST stays in the critical section of the primary winding at all loading conditions.This work is helpful to understand the complete internal temperature layout and the location of the HST in distribution transformers.展开更多
Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic d...Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic data.This log is an important tool for analyzing the properties of rocks and interpreting seismic data to identify potential areas of oil and gas reserves.However,these logs are often not collected due to cost constraints or poor borehole conditions possibly leading to poor data quality,though there are various approaches in practice for estimating shear wave velocity.In this study,a detailed review of the recent advances in the various techniques used to measure shear wave(S-wave)velocity is carried out.These techniques include direct and indirect measurement,determination of empirical relationships between S-wave velocity and other parameters,machine learning,and rock physics models.Therefore,this study creates a collection of employed techniques,enhancing the existing knowledge of this significant topic and offering a progressive approach for practical implementation in the field.展开更多
Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate and rapid soil bulk density measurement techniques play a significant role in agricul...Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate and rapid soil bulk density measurement techniques play a significant role in agricultural experimental research. This review is a comprehensive summary of existing measurement methods and evaluates their advantages, disadvantages, potential sources of error,and directions for future development. These techniques can be broadly categorised as direct and indirect methods. Direct methods include core, clod, and excavation sampling, whereas indirect methods include the radiation and regression approaches. The core method is most widely used, but it is time consuming and difficult to use for sampling multiple soil depths. The size of the coring cylinder used, operator experience, sampling depth, and in-situ soil moisture content significantly affect its accuracy. The clod method is suitable for use with heavy clay soils, and its accuracy is dependent on equipment calibration, drying time, and operator experience, but the process is complicated and time consuming. Excavation techniques are most commonly used to evaluate the bulk density of forest soils, but have major limitations as they cannot be used in soils with large pores and their measurement accuracy is strongly influenced by soil texture and the type of analysis selected. The indirect methods appear to have greater accuracy than direct approaches, but have higher costs, are more complex, and require greater operator experience. One such approach uses gamma radiation, and its accuracy is strongly influenced by soil depth. Regression methods are economical as they can make indirect measurements, but these depend on good, quality data of soil texture and organic matter content and geographical and climatic properties. Also, like most of the other approaches, its accuracy decreases with sampling depth.展开更多
Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to dire...Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.展开更多
Low-carbon economic development is at the heart of the post-pandemic green recovery scheme worldwide.It requires economic recovery without compromising on the environment,implying a critical role that green productivi...Low-carbon economic development is at the heart of the post-pandemic green recovery scheme worldwide.It requires economic recovery without compromising on the environment,implying a critical role that green productivity plays in achieving the carbon neutrality goal.Green productivity measures the quality of economic growth with consideration for energy consumption and environmental pollution.This study employs the slacks-based measure directional distance function(SBM-DDF)approach and the Malmquist-Luenberger(ML)index to calculate green productivity and its components of 30 provinces in China between 2001 and 2018.Using a spatial panel data model,we empirically analyzed the conditionalβ-convergence of China's green productivity.We found that overall,since 2001,China's green productivity has demonstrated a continuous upward trend.When taking into account spatial factors,China's green productivity demonstrates a significant conditionalβ-convergence.In terms of regional effects,the results indicate that the green productivity of the eastern and western regions demonstrates club convergence,implying a more balanced green economic development.Moreover,the convergence rate of China's green productivity increases with the addition of environmental regulation variable,and so the corresponding convergence time decreases.It indicates that environmental regulations help to facilitate the convergence of China's green productivity,narrowing the gap between the regional green economic development.The findings provide guideline for achieving a low-carbon development and carbon neutrality from a regional green productivity perspective.展开更多
基金Project supported by National Key Research and Development Program of China (Grant No. 2019YFA0705000)the National Natural Science Foundation of China (Grant No. 11974178)。
文摘Efficient acquiring information from a quantum state is important for research in fundamental quantum physics and quantum information applications. Instead of using standard quantum state tomography method with reconstruction algorithm, weak values were proposed to directly measure density matrix elements of quantum state. Recently, similar to the concept of weak value, modular values were introduced to extend the direct measurement scheme to nonlocal quantum wavefunction. However, this method still involves approximations, which leads to inherent low precision. Here, we propose a new scheme which enables direct measurement for ideal value of the nonlocal density matrix element without taking approximations. Our scheme allows more accurate characterization of nonlocal quantum states, and therefore has greater advantages in practical measurement scenarios.
基金the US Department of Energy under grant DE-FG03-97-ER54415
文摘Electron thermal transport is one of the most complex processes in fusionplasmas. It is generally described by a simple thermal diffusivity in transport analyses ofdischarges, but there is evidence of critical gradient effects with moderate stiffness. By analyzingperiodic perturbations to an equilibrium, one canmeasure the variations in electron energy flux andelectron temperature gradient over the perturbation cycle, obtaining the flux as a function ofgradient over the range of parameters generated by the perturbation. Although time-dependenttransport analysis is very sensitive to noise in the input data, averaging over many cycles of aperiodic perturbation can provide data of sufficient quality. The analyses presented here are basedon the ECE temperature data with high spatial and temporal resolution and full profile coverage onDIII-D for sawteeth and modulated ECH heating.
基金Fonds National de la Recherche(FNR)of Luxembourg under the grant THERMODIMAT/C20/MS/14718071//Defay,CAMELHEAT/C17/MS/11703691/Defay,MASSENA PRIDE/MASSENA/15/10935404/Defay Siebentritt and CALPOL BRIDGES 2O2O/MS/15410586/Defay.
文摘Poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)P(VDF-TrFE-CFE)is a relaxor ferroelectric polymer,which exhibits a temperature-independent electrocaloric effect at room temperature.In this work,the electrocaloric effect in P(VDF-TrFE-CFE)film was directly analysed using infrared imaging.P(VDF-TrFE-CFE)64.8%/27.4%/7.8%(in mole)film of(15±1)mm thickness was deposited on polyethylene naphthalate substrate.Direct ECE of P(VDF-TrFE-CFE)film was measured from 15 to 35C at different electric fields.A maximum adiabatic temperature change(DTad)of 3.58 K was measured during the cooling cycle at a field of 100 V/mm at 30C.Finite element analysis of temperature dissipation through the sample estimated that the actual temperature change within P(VDF-TrFE-CFE)film was 4.3 K.Despite the thermal mass of the substrate,a substantial ECE was observed in P(VDF-TrFE-CFE)films.This electrocaloric terpolymer composition could be of interest for electrocaloric cooling applications.
基金supported by the National Natural Science Foundation of China(Grant Nos.114905621149056011135005 and 11321064)
文摘In 2014, the National Natural Science Foundation of China （NSFC） approved the Jinping Underground Nuclear Astrophysics laboratory （JUNA） project, which aims at direct cross-section measurements of four key stellar nuclear reactions right down to the Gamow windows. In order to solve the observed fluorine overabundances in Asymptotic Giant Branch （AGB） stars, measuring the key 19F（p,a）16O reaction at effective burning energies （i.e., at Gamow window） is established as one of the scientific research sub-projects. The present paper describes this sub-project in details, including motivation, status, experimental setup, yield and background estimation, aboveground test, as well as other relevant reactions.
基金supported by the Natural Science Foundation of China(Grant Nos.51872053 and 51372042)Guangdong Provincial Natural Science Foundation(2015A030308004)the NSFC-Guangdong Joint Fund(Grant No.U1501246)。
文摘The electrocaloric effect(ECE)in lead-free BaSn_(x)Ti_(1-x)O_(3)(BSnT,x=0.05,0.10 and 0.15)ceramics were investigated using a direct ECE measurement.Results indicate that the maximum ECE occurs near the Curie temperature and it slightly shifts towards high temperatures.The directly measured ECE is larger than that calculated using the Maxwell relation and P-E loops.A maximum electrocaloric efficiencyΔT=ΔE=0.49-10-6 KmV-1 was procured for the composition with x=0.15 at T=299.2 K.And it also shows a broad peak in the temperature range of 250–320 K.
基金Supported by the National Natural Science Foundation of China under Grant Nos 91336103,10934010 and 61078026
文摘The optical frequency comb has been widely used in precision measurement. In this study, a multi-peak fitting approach is first proposed to fit the two-photon transition spectrum which overlaps with the neighboring transition in Rb-87. The multi-peak fitting approach is used to eliminate the frequency shift affected by the neighboring transition. With locking the carrier envelope offset frequency at 1/4 repetition frequency, the transition frequency is measured to be 770569132739.9 +/- 5.8 kHz, which agrees well with the previous result recommended by Comite International des Poids et Mesures.
基金National Natural Science Foundation of China (No.91216201, No.51205403)
文摘The applications of the micro-thrust e r and the challenges of micro-thrust measuring are introduced.The developments in measuring techniques for the micro-thrust are reviewed.Micro-thrust measu rements have previously been made either directly by mounting thrusters to the m easurement system or indirectly by mounting a target in the direct path of the e jected propellant.Several typical direct and indirect thrust-stands are presen ted and discussed in detail to illustrate the principles.Typical calibration me thods are also expounded.Finally,the resolution,uncertainty and thrust range of each thrust-stand are given,which may be helpful for the future thrust stan d design and micro-thrusters research.
基金supported by the Project of State Grid Hebei Electric Power Co.,Ltd.(SGHEYX00SCJS2100077).
文摘Crop water stress index(CWSI)is widely used for efficient irrigation management.Precise canopy temperature(T_(c))measurement is necessary to derive a reliable CWSI.The objective of this research was to investigate the influences of atmospheric conditions,settled height,view angle of infrared thermography,and investigating time of temperature measuring on the performance of the CWSI.Three irrigation treatments were used to create different soil water conditions during the 2020-2021 and 2021-2022 winter wheat-growing seasons.The CWSI was calculated using the CWSI-E(an empirical approach)and CWSI-T(a theoretical approach)based on the T_(c).Weather conditions were recorded continuously throughout the experimental period.The results showed that atmospheric conditions influenced the estimation of the CWSI;when the vapor pressure deficit(VPD)was>2000 Pa,the estimated CWSI was related to soil water conditions.The height of the installed infrared thermograph influenced the T_(c)values,and the differences among the T_(c)values measured at height of 3,5,and 10 m was smaller in the afternoon than in the morning.However,the lens of the thermometer facing south recorded a higher T_(c)than those facing east or north,especially at a low height,indicating that the direction of the thermometer had a significant influence on T_(c).There was a large variation in CWSI derived at different times of the day,and the midday measurements(12:00-15:00)were the most reliable for estimating CWSI.Negative linear relationships were found between the transpiration rate and CWSI-E(R^(2)of 0.3646-0.5725)and CWSI-T(R^(2)of 0.5407-0.7213).The relations between fraction of available soil water(FASW)with CWSI-T was higher than that with CWSI-E,indicating CWSI-T was more accurate for predicting crop water status.In addition,The R^(2)between CWSI-T and FASW at 14:00 was higher than that at other times,indicating that 14:00 was the optimal time for using the CWSI for crop water status monitoring.Relative higher yield of winter wheat was obtained with average seasonal values of CWSI-E and CWSI-T around 0.23 and 0.25-0.26,respectively.The CWSI-E values were more easily influenced by meteorological factors and the timing of the measurements,and using the theoretical approach to derive the CWSI was recommended for precise irrigation water management.
基金supports for this work provided by the NationalKey Technology R&D Program in the 11th Five-Year Plan of China(No. 2008BAB31B03)
文摘Gas holdup is one of the key parameters in flotation process. Gas holdup as measured by a differential pressure method was investigated and the relative errors compared to the average gas holdup from the volume expansion method. The errors were used to establish optimum measurement positions. The results show that the measurement position should be in the middle of the column and in the region half way from the center to the wall (the half-radius). The gas holdup along the axial direction is lower at the bottom and higher at the top of the floatation column. The gas holdup along the radial direction is lower near the wall and higher near the center of the flotation column. The average gas holdup measure- ment can be replaced by regional gas holdup values.
基金supported by the National Key Scientific Instrument and Equipment Development Project(Grant No.2013YQ04091108)the National Natural Science Foundation of China(Grant No.51309158)
文摘The object of present study is to investigate the bed shear stress on a slope under regular breaking waves by a novel instrument named Micro-Electro-Mechanical System （MEMS） flexible hot-film shear stress sensor. The sensors were calibrated before application, and then a wave flume experiment was conducted to study the bed shear stress for the case of regular waves spilling and plunging on a 1 ： 15 smooth PVC slope. The experiment shows that the sensor is feasible for the measurement of the bed shear stress under breaking waves. For regular incident waves, the bed shear stress is mainly periodic in both outside and inside the breaking point. The fluctuations of the bed shear stress increase significantly after waves breaking due to the turbulence and vortexes generated by breaking waves. For plunging breaker, the extreme value of the mean maximum bed shear stress appears after the plunging point, and the more violent the wave breaks, the more dramatic increase of the maximum bed shear stress will occur. For spilling breaker, the increase of the maximum bed shear stress along the slope is gradual compared with the plunging breaker. At last, an empirical equation about the relationship between the maximum bed shear stress and the surf similarity parameter is given, which can be used to estimate the maximum bed shear stress under breaking waves in practice.
基金supported by the National Basic Research Program of China (Nos. 2003CB716704, 2007CB815003)
文摘This paper reports on two nuclear astrophysics experiments performed in collabora- tion with Ruhr University. In a 12C＋2C fusion reaction, the 12C（12C, a）20e and 12C（12C, p）23Na reactions were studied in the energy range of E = 2.10 MeV to 4.75 MeV using -y-ray spectroscopy. The deduced astrophysical S（E）＊ factor exhibited a new, strong resonance at E -= 2.14 MeV, which lay at the high-energy tail of the Gamow peak. The resonance increased the reaction rate of the ^-channel by a factor of five near T = 8 ~ l0s K. The electron screening in d（d, p）t was stud- ied for a series of deuterated metal, insulator and semiconductor targets. Compared with the measurements performed with a gaseous D2 target, a large effect was observed in most metals, while a comparatively small effect was found in the insulators and semiconductors. Subsequently the temperature dependence of the electron screening in the d（d, p）t reaction was studied for the deuterated metals Pt and Co. Enhanced electron screening decreased with increasing tempera- ture. These data represent the first observations of the temperature dependence of a nuclear cross section.
基金The National Natural Science Foundation of China under contract Nos 41830533,41806028 and 41876003the National Key Research and Development Program of China under contract Nos 2017YFA0604102 and 2016YFC1401404。
文摘We investigate the air-sea momentum flux in the marine atmospheric boundary layer using a tower-based direct measurement method.First,we compare the collected data with previous observations,and the results are roughly consistent.Next,in the low-to-moderate winds,the exchange coefficients(or drag coefficients)deviate between onshore and offshore winds,which exhibits the influence of surface wave on the momentum flux.Furthermore,we use a surface-wave-involved parameterization scheme to explain the dependence of momentum flux on surface wave.The results consolidate the influence of surface wave on momentum flux on the one hand,and validate the surface-wave-involved parameterization scheme on the other hand.
基金ThispaperissupportedbyNationalNatureScienceFoundationofChina (No 60 1760 2 0 )
文摘The wavelet transformation is applied to the high current transformer.The high current transformer elaborated in the paper is mainly applied to the measurement of AC/DC high current.The principle of the transformer is the Hall direct measurement principle.The transformer has the following three characteristics:firstly, the effect of the remnant field of the iron core on the measurement is decreased;secondly,because the temperature compensation is adopted,the transformer has good temperature charactreristic;thirdly,be cause the wavelet transfomation technology is adopted,the transformer has the capacity of good antijanming.
基金obtained grants from the National Key Research and Development Program Project"Enhanced Bioremediation Technology and Equipment for Chromium Residuation Site",the Scientific Research Project of Hunan Provincial Department of Education(Grant No.19C1178)the Construction Program for the First-Class Disciplines(Geography)of Hunan Province,China.The anonymous reviewers and editors are thanked for constructive suggestions on improving the quality of the manuscript.
文摘Determination of Fe^(2+)/Fe^(3+) ratios from metallogenic belts to explore controlling physical and chemical conditions of rock formation is of great significance.In order to explore magnetite Fe^(2+)/Fe^(3+) ratios of the Qimantag metallogenic belt,part of the Eastern Kunlun orogenic belt in the northeastern margin of the Qinghai–Tibetan plateau,western Central Orogenic Belt of China,and overcome the limitation of the traditional electronic probe,five different measurement methods are proposed and their respective advantages and disadvantages evaluated,with the composition data of the magnetite obtained using electron probe microanalysis(EPMA).The direct oxygen measurement method has a significant impact on the determination results of FeO and Fe2O3,but the accuracy and uniformity of the results are low.The valence method(Flank method)based on the spectral intensity ratio of Lαto Lβfor iron is also unreliable for FeO and Fe_(2)O^(3) measurements because it is difficult to establish a relationship between Lβ/Lα,the spectral intensity ratio,and the Fe^(2+)/Fe^(3+) content ratio.In comparison,the charge difference method,the surplus-oxygen method and the Mössbauer spectrum method are still the most favorable.Mössbauer spectroscopy,with its isomer movement particularly sensitive to the oxidation state of iron,yields results closer to 0.5,which is relatively reliable.Earlier magnetite deposits are located in intrusions or contact zones and formed by magmatic fluids with high Fe2+/Fe3+ratios,whereas later magnetite deposits are farther away from intrusions and have low Fe^(2+)/Fe^(3+) ratios.The transformation mechanism of hematite and magnetite in the Qimantage metallogenic belt is also studied.No large volume changes,such as pore filling and shrinkage fracture,were detected in the metallogenic belt,and the transformation mechanism is more similar to a reoxidation and reduction mechanism.
基金Under the auspices of the post-funded project of National Social Science Foundation of China(No.16FJL009)
文摘We use the directional slacks-based measure of efficiency and inverse distance weighting method to analyze the spatial pattern evolution of the industrial green total factor productivity of 108 cities in the Yangtze River Economic Belt in 2003–2013.Results show that both the subprime mortgage crisis and ‘the new normal' had significant negative effects on productivity growth,leading to the different spatial patterns between 2003–2008 and 2009–2013.Before 2008,green poles had gathered around some capital cities and formed a tripartite pattern,which was a typical core-periphery pattern.Due to a combination of the polarization and the diffusion effects,capital cities became the growth poles and ‘core' regions,while surrounding areas became the ‘periphery'.This was mainly caused by the innate advantage of capital cities and ‘the rise of central China' strategy.After 2008,the tripartite pattern changed to a multi-poles pattern where green poles continuously and densely spread in the midstream and downstream areas.This is due to the regional difference in the leading effect of green poles.The leading effect of green poles in midstream and downstream areas has changed from polarization to diffusion,while the polarization effect still leads in the upstream area.
文摘The distribution transformer is the mainstay of the power system.Its internal temperature study is desirable for its safe operation in the power system.The purpose of the present study is to determine direct comprehensive thermal distribution in the distribution transformers for different loading conditions.To achieve this goal,the temperature distribution in the oil,core,and windings are studied at each loading.An experimental study is performed with a 10/0.38 kV,10 kVA oil–immersed transformer equipped with forty–two PT100 sensors(PTs)for temperature measurement installed inside during its manufacturing process.All possible locations for the hottest spot temperature(HST)are considered that made by finite element analysis(FEA)simulation and losses calculations.A resistive load is made to achieve 80%to 120%loading of the test transformer for this experiment.Working temperature is measured in each part of the transformer at all provided loading conditions.It is observed that temperature varies with loading throughout the transformer,and a detailed map of temperature is obtained in the whole test transformer.From these results,the HST stays in the critical section of the primary winding at all loading conditions.This work is helpful to understand the complete internal temperature layout and the location of the HST in distribution transformers.
文摘Shear logs,also known as shear velocity logs,are used for various types of seismic analysis,such as determining the relationship between amplitude variation with offset(AVO)and interpreting multiple types of seismic data.This log is an important tool for analyzing the properties of rocks and interpreting seismic data to identify potential areas of oil and gas reserves.However,these logs are often not collected due to cost constraints or poor borehole conditions possibly leading to poor data quality,though there are various approaches in practice for estimating shear wave velocity.In this study,a detailed review of the recent advances in the various techniques used to measure shear wave(S-wave)velocity is carried out.These techniques include direct and indirect measurement,determination of empirical relationships between S-wave velocity and other parameters,machine learning,and rock physics models.Therefore,this study creates a collection of employed techniques,enhancing the existing knowledge of this significant topic and offering a progressive approach for practical implementation in the field.
基金the Government and Ministry of Higher Education and Scientific Research, Iraq, for providing funding for this study as a scholarship for Ph.D. student for the first author Ahmed Abed Gatea Al-Shammary
文摘Measurement of soil bulk density is important for understanding the physical, chemical, and biological properties of soil. Accurate and rapid soil bulk density measurement techniques play a significant role in agricultural experimental research. This review is a comprehensive summary of existing measurement methods and evaluates their advantages, disadvantages, potential sources of error,and directions for future development. These techniques can be broadly categorised as direct and indirect methods. Direct methods include core, clod, and excavation sampling, whereas indirect methods include the radiation and regression approaches. The core method is most widely used, but it is time consuming and difficult to use for sampling multiple soil depths. The size of the coring cylinder used, operator experience, sampling depth, and in-situ soil moisture content significantly affect its accuracy. The clod method is suitable for use with heavy clay soils, and its accuracy is dependent on equipment calibration, drying time, and operator experience, but the process is complicated and time consuming. Excavation techniques are most commonly used to evaluate the bulk density of forest soils, but have major limitations as they cannot be used in soils with large pores and their measurement accuracy is strongly influenced by soil texture and the type of analysis selected. The indirect methods appear to have greater accuracy than direct approaches, but have higher costs, are more complex, and require greater operator experience. One such approach uses gamma radiation, and its accuracy is strongly influenced by soil depth. Regression methods are economical as they can make indirect measurements, but these depend on good, quality data of soil texture and organic matter content and geographical and climatic properties. Also, like most of the other approaches, its accuracy decreases with sampling depth.
基金supported by the National Natural Science Foundation of China(Grant Nos.11490560 and 11321064)the National Basic Research Program of China(Grant No.2013CB834406)
文摘Jinping Underground laboratory for Nuclear Astrophysics(JUNA) will take the advantage of the ultra-low background of CJPL lab and high current accelerator based on an ECR source and a highly sensitive detector to directly study for the first time a number of crucial reactions occurring at their relevant stellar energies during the evolution of hydrostatic stars. In its first phase, JUNA aims at the direct measurements of^(25)Mg(p,γ)^(26)Al,^(19)F(p,α)^(16)O,^(13)C(α,n)^(16)O and ^(12)C(α,γ)^(16)O reactions. The experimental setup,which includes an accelerator system with high stability and high intensity, a detector system, and a shielding material with low background, will be established during the above research. The current progress of JUNA will be given.
基金supported by the Humanities and Social Science Fund of Ministry of Education of the People's Republic of China(19YJC790044).
文摘Low-carbon economic development is at the heart of the post-pandemic green recovery scheme worldwide.It requires economic recovery without compromising on the environment,implying a critical role that green productivity plays in achieving the carbon neutrality goal.Green productivity measures the quality of economic growth with consideration for energy consumption and environmental pollution.This study employs the slacks-based measure directional distance function(SBM-DDF)approach and the Malmquist-Luenberger(ML)index to calculate green productivity and its components of 30 provinces in China between 2001 and 2018.Using a spatial panel data model,we empirically analyzed the conditionalβ-convergence of China's green productivity.We found that overall,since 2001,China's green productivity has demonstrated a continuous upward trend.When taking into account spatial factors,China's green productivity demonstrates a significant conditionalβ-convergence.In terms of regional effects,the results indicate that the green productivity of the eastern and western regions demonstrates club convergence,implying a more balanced green economic development.Moreover,the convergence rate of China's green productivity increases with the addition of environmental regulation variable,and so the corresponding convergence time decreases.It indicates that environmental regulations help to facilitate the convergence of China's green productivity,narrowing the gap between the regional green economic development.The findings provide guideline for achieving a low-carbon development and carbon neutrality from a regional green productivity perspective.
