Objective:The aim of the study was to evaluate the quality of sleep in nurses performing shift work in therapeutic and surgical depar tments and to establish possible relationships between level of blood pressure(BP)a...Objective:The aim of the study was to evaluate the quality of sleep in nurses performing shift work in therapeutic and surgical depar tments and to establish possible relationships between level of blood pressure(BP)and quality of sleep.Methods:A total of 20 nurses of the therapeutic depar tments and 20 nurses of the surgical depar tments were enrolled in the study.Sleep quality was assessed using the Pittsburgh Sleep Quality Index(PSQI).BP was measured according to the standard protocol using the Korotkoff method;a sphygmomanometer was used for this twice with an interval of 2 min between 10:00 a.m.and 10:30 a.m.The average value for the 2 indicators was calculated.The diagnosis of essential ar terial hyper tension(AH)was established according to the recommendations of the European Association of Cardiology and the European Association of Hypertension(2018).Results:The overall assessment of the sleep quality of the nurses involved in shift work indicates poor sleep quality;this was true in respondents of both the surgical and therapeutic profiles.However,it was observed that the quality of sleep was significantly lower in nurses of the therapeutic departments.Moreover,poor sleep quality was associated with AH,which was diagnosed in 65%of the nurses of the therapeutic departments and 45%of the nurses of the surgical departments,that is,in almost all of the subjects.Herewith,in the nurses of the therapeutic departments,the level of systolic BP exceeded that of the nurses of the surgical departments.Conclusions:Poor sleep quality is a significant risk factor for AH development and is relevant to nurses performing shift work.Additional clinical studies should be conducted to better understand the mechanisms underlying such adverse cardiometabolic outcomes associated with sleep disorders in the health-sector shift workers.展开更多
Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments a...Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.展开更多
AIM:To evaluate intraocular pressure(IOP)-lowering effect and ocular tolerability of brimonidine/timolol,dorzolamide/timolol and latanoprost/timolol fixed combination therapies in the management of primary open angle ...AIM:To evaluate intraocular pressure(IOP)-lowering effect and ocular tolerability of brimonidine/timolol,dorzolamide/timolol and latanoprost/timolol fixed combination therapies in the management of primary open angle glaucoma.· METHODS:Each drug was administered for two months, after which a circadian tonometric curve was recorded using a Goldmann applanation tonometer.Ocular discomfort(conjunctival hyperemia, burning or stinging, foreign body sensation, itching, ocular pain) of each eye was assessed by the subject on a standardized ocular discomfort scale.RESULTS:Among the three study groups, there were no significant differences in the mean baseline IOP measurements, mean 2ndmo IOP measurements, and mean(%) change of IOPs from baseline. Among the three study groups, there were no significant differences in the mean IOP measurements obtained at circadian tonometric curves at baseline and at two months controls. In sum brimonidine/timolol, dorzolamide/timolol and latanoprost/timolol fixed combination therapies showed similar effects on IOP levels.· CONCLUSION:Brimonidine/timolol, dorzolamide/timolol and latanoprost/timolol fixed combination therapies showed similar lowering efficaties on IOP levels whereas there was no any difference between each other.展开更多
This paper presents the evolution process of pressure angles from planar parallel mechanisms to spatial parallel mechanisms. Manipulability and condition number, which are frequently used in the optimum design of para...This paper presents the evolution process of pressure angles from planar parallel mechanisms to spatial parallel mechanisms. Manipulability and condition number, which are frequently used in the optimum design of parallel mechanisms, are introduced from serial robots at first. Then, both theoretical analysis and practical experiences demonstrate that these concepts seem imperfect when they are used in parallel mechanisms. For this reason, this paper introduces the pressure angles in planar 4-bar mechanisms to spatial parallel mechanisms, which include redundant parallel mechanisms. Two kinds of pressure angles extracted from the determinant of direct and indirect Jacobian matrices are investigated. Moreover, two comprehensive and visible global performance indices are defined, showing the advantages in evaluating the workspace, singularity and motion/force transmission capabilities. With a 2-DOF planar and a 3-DOF spatial parallel mechanism as examples, the application of the performance indices is investigated and compared with the condition number at last. The proposed concept can be extended to other spatial parallel mechanisms.展开更多
AIM: To compare the effect of phacoemulsification on intraocular pressure(IOP) in patients with primary open angle glaucoma(POAG) and pseudoexfoliation glaucoma(PXG). METHODS: A retrospective comparative case series c...AIM: To compare the effect of phacoemulsification on intraocular pressure(IOP) in patients with primary open angle glaucoma(POAG) and pseudoexfoliation glaucoma(PXG). METHODS: A retrospective comparative case series conducted at the Glaucoma Department at the Association to Prevent Blindness in Mexico. The study enrolled consecutive patients having phacoemulsification with intraocular lens(IOL) implantation and a diagnosis of POAG or PXG. Data about IOP values and number of glaucoma medications used was collected at baseline, 1, 3, 6 and 12 mo postoperatively. RESULTS: The study enrolled 88 patients(88 eyes). After phacoemulsification, there was a statistically significant reduction in IOP values and glaucoma medications use compared to baseline in both POAG and PXG patients(P<0.001). In the POAG group, a 20% decrease in IOP values was evidenced, and a 56.5% reduction in the number of medications used at the one-year follow-up. The PXG group showed a 20.39%, and a 34.46% decrease in IOP and number of medications used, respectively. A significant difference in the mean ΔIOP(postoperative changes in IOP) was evidenced between groups(P=0.005). The reduction of the postsurgical IOP mean values in both groups, the POAG group showed a greater reduction in IOP values compared to the PXG group.CONCLUSION: In both types of glaucoma, phacoemulsification cataract surgery can result in a significant IOP reduction(20%) over a 12 mo follow-up period. The number of medications used is also significantly reduced up to 12 mo after surgery, especially in the PXG group.展开更多
Flat Steel Ribbon Wound Pressure Vessels (FSRWPVs) are used in many important industry areas. There is no such kind of pressure vessel exploding on operation for its reasonable structure design. Many explosion experim...Flat Steel Ribbon Wound Pressure Vessels (FSRWPVs) are used in many important industry areas. There is no such kind of pressure vessel exploding on operation for its reasonable structure design. Many explosion experiments on Flat Steel Ribbon Wound Pressure Vessel showed that their limited load pressure is related to the winding angle of the steel ribbons. FSRWPVs with reasonable winding angle have better security and lower cost. Reasonable angels given at the end of this paper facilitate engineering design.展开更多
A method of setting up a pressure-stroke characteristic of the working liquid in hydraulic drawing is studied. A pressure-stroke characteristic and software for controlling its forming process are also developed. And ...A method of setting up a pressure-stroke characteristic of the working liquid in hydraulic drawing is studied. A pressure-stroke characteristic and software for controlling its forming process are also developed. And a set of pressure controlling devices with PLC as a central processor are designed. It can be got from the relevant experiments that the pressure-stroke characteristic is correct and its control for forming process is available.展开更多
The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1) + [BMIM][DBP](2) were measured at different ...The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1) + [BMIM][DBP](2) were measured at different temperature and in the ILs mole fraction range from 0.1 to 0.6 with a static equilibrium apparatus. The measured vapor pressures were correlated with Non-Random Two Liquid (NRTL) activity coefficient model and the average relative deviations (ARD) between experimental and correlated vapor pressures for these binary solutions were 3.19%, 2.42% and 2.95%, respectively. Then, the vapor pressures of two set of ternary solutions H2O(1) + CH3OH(2)/C2H5OH(2) + [BMIM][DBP](3) were measured with an inclined boiling apparatus and further predicted with NRTL activity coefficient model based on the binary interaction parameters coming from fitting the vapor pressures of the binary solutions. The results indicated that the ternary solutions containing [BMIM][DBP] were shown a strong negative deviation from Raoult's Law when the mole fraction of [BMIM][DBP] was larger than 0.2, which meant that ternary solutions could absorb the refrigerant vapors at the same or below solution temperature. Meanwhile, the average relative deviations between experimental and predicted vapor pressures for ternary solutions were 2.92% and 3.06%, respectively. Consequently, the NRTL active coefficient model used for non-electrolyte solutions was still valid for predicting vapor-liquid equilibrium of binary or ternary solutions containing ILs.展开更多
According to the shearing force character and the deformation coordination condition of shell at the station of supports, the mathematical models to calculate contact angle and contact pressure distribution between ty...According to the shearing force character and the deformation coordination condition of shell at the station of supports, the mathematical models to calculate contact angle and contact pressure distribution between tyre and shell were set up, the formulae of bending moment and bending stress of tyre were obtained. Taking the maximum of tyre fatigue life as the optimal objective, the optimization model of tyre support angle was built. The computational results show that when tyre support angle is 30°, tyre life is far less than that when tyre support angle is optimal, which is 35.6°, and it is unsuitable to stipulate tyre support angle to be 30° in traditional design. The larger the load, the less the nominal stress amplitude increment of tyre, the more favorable the tyre fatigue life when tyre support angle is optimal.展开更多
AIM: To describe a newly-recognized entity,illustrated by five cases of glaucoma in whom trauma to the head,but not the eye,resulted in marked,transient elevation of intraocular pressure (IOP).METHODS: Retrospective c...AIM: To describe a newly-recognized entity,illustrated by five cases of glaucoma in whom trauma to the head,but not the eye,resulted in marked,transient elevation of intraocular pressure (IOP).METHODS: Retrospective case series.Chart review.RESULTS: All five cases had a diagnosis of primary open-angle glaucoma prior to the experience of trauma to the head.All cases had an unusual elevation of IOP (around 70 percent) for days to weeks following the trauma,after which the IOP fell to pre-accident levels.No cause other than the trauma could be determined.CONCLUSION: The relationship between head trauma and elevation of IOP appears real.展开更多
There is growing interest in the correlation between working time and environmental pressures,but prior empirical studies mostly focused on static methodologies.This article used dynamic panel regression approaches to...There is growing interest in the correlation between working time and environmental pressures,but prior empirical studies mostly focused on static methodologies.This article used dynamic panel regression approaches to examine and compare the relationship among western,southern,and northern European countries over the period 1970-2010,and proved the existence of strongly significant relationships in all models.Furthermore,this article detected the relationship between working hours and environmental indicators(carbon emission and energy use) at different phases.We contribute to a further understanding of the environmental effects of the working time reduction policy by comparing the differences among various periods and country groups in a system generalized method of moments(GMM) dynamic framework.展开更多
In order to exactly provide scientific basis for pressure dynamic balance control of working chamber of earth pressure balance shield (EPBS),study on optimal arrangement of pressure measurement points in working chamb...In order to exactly provide scientific basis for pressure dynamic balance control of working chamber of earth pressure balance shield (EPBS),study on optimal arrangement of pressure measurement points in working chamber was conducted. Based on mathematical description of optimal arrangement for pressure measurement points,fuzzy clustering analysis and discriminant analysis were used to divide pressure regions of nodes on bulkhead. Finally,the selection method of optimal measurement points was proposed,and by selecting d6.28 m EPBS as study object,the case study was conducted. By contrast,based on optimal arrangement scheme of pressure measurement points,through adopting weighted algorithm,the absolute error mean of equivalent pressure of working chamber is the smallest. In addition,pressure curve of optimal arrangement points presents parabola,and it can show the state of pressure distribution on bulkhead truly. It is concluded that the optimal arrangement method of pressure measurement points in working chamber is effective and feasible,and the method can provide basis for realizing high precision pressure control of EPBS.展开更多
The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer(GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on pla...The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer(GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon(C_4H_8/H_2) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer(MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy(FT–IR), field emission scanning electron microscope(SEM) and white-light interferometer(WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C_4H_8/H_2 plasma reduces with an increase in the working pressure. At a low working pressure, the C–H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH_3/CH_2 ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa,the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 μm h^(-1), and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.展开更多
The tapered angles of an artery significantly influence the local hemodynamics. However, as gravity is considered, little is known about the effect of tapered angles on the hemodynamics. In this study, we explored whe...The tapered angles of an artery significantly influence the local hemodynamics. However, as gravity is considered, little is known about the effect of tapered angles on the hemodynamics. In this study, we explored whether the effect of tapered angles on the distribution of blood flow pressure (DBFP) differed with gravity considered or not. Numerical simulations of the DBFP in a single vessel were performed based on such tapered angles as 0°, 0.5° and 1°. In the model used for simulation, gravity was introduced as a body force. We obtained the following simulations: i) The larger the tapered angles were, the better distributed the blood flow pressure;ii) The tapered effect was an important factor leading to nonlinearity in blood flow pressure;iii) Gravity affected DBFP coupling with the tapered angles, yet independently influenced the dimension of the DBFP. At the same time, the effective intensity of gravity decreased with the increase of tapered angles.展开更多
·AIM:To evaluate morphological changes in the iridocorneal angle after pediatric cataract surgery.·METHODS:Children who underwent primary infantile cataract surgery were included and 64 eyes from 41 children...·AIM:To evaluate morphological changes in the iridocorneal angle after pediatric cataract surgery.·METHODS:Children who underwent primary infantile cataract surgery were included and 64 eyes from 41 children,including 18 with unilateral cataracts(18 eyes)and 23 with bilateral cataracts(46 eyes)were examined.All patients underwent two gonioscopic examinations to evaluate the iridocorneal angle,before the primary lens removal and before the secondary intraocular lens implantation.The anatomical changes in the iridocorneal angle and the relationship between intraocular pressure(IOP)and iridocorneal angle changes were also analyzed.·RESULTS:The iridocorneal angle was wide in 64 eyes before and after surgery.The trabecular meshwork pigmentation,number of iris processes in every quadrant of the iridocorneal angle,and the width of the ciliary body band in the superior and inferior quadrants at the second gonioscopic examination were significantly increased compared to those at the first examination(P<0.001,P<0.05,P<0.05.and P<0.05,respectively).IOP gradually increased at 1 mo after operation,and returned to the preoperative level at 3 mo.However,IOP still increased significantly at 6 and 12 mo.·CONCLUSION:The main changes after pediatric cataract surgery include an increase in trabecular meshwork pigmentation and number of iris processes,IOP gradually increase and has positive correlation with trabecular meshwork pigmentation and anterior insertion of iris process.展开更多
The working profile of whole cycloidal gear is made up of epicycloid and hypocycloid entirely,according to the theory of meshing of gears and the properties of the cycloid,deals with the derivation of the pressure ang...The working profile of whole cycloidal gear is made up of epicycloid and hypocycloid entirely,according to the theory of meshing of gears and the properties of the cycloid,deals with the derivation of the pressure angle formula for the whole cycloidal gear in theory,and reveals changes of the pressure angle of whole cycloidal gear through examples,finds the application relationships between the pressure angle and other design parameters of the whole cycloidal gear,proves the possibility that the whole cycloidal gear can be used in internal parallel move gear mechanism,also provides theoretic fundament for designing internal parallel move whole cycloidal gear correctly.展开更多
In order to precisely measure the ion parameters in a microwave electron cyclotron resonance plasma using an ion sensitive probe,the dependences of the current-voltage(I-V)characteristics on the shielding height(h)and...In order to precisely measure the ion parameters in a microwave electron cyclotron resonance plasma using an ion sensitive probe,the dependences of the current-voltage(I-V)characteristics on the shielding height(h)and the potential difference between inner and outer electrodes(V_B)have been investigated at different working pressures of 0.03 Pa and 0.8 Pa.Results show that the I-V curves at higher pressure are more sensitive to the variation of h than those at lower pressure.The influence of V_B on ion temperature(T_i)measurement becomes more prominent when the pressure is increased from 0.03 Pa to 0.8 Pa.Under both pressures,the optimized h is obtained at the condition where the current reaches zero in the positive voltage region with a suitable V_B of-1.5 V because of effective shielding of the electron E×B drift.展开更多
The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment...The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment,10 nozzles with different structures are designed to comprehensively cover various geometric factors.In terms of simulation,steady-state simulation with less computational complexity is used to study the flow inside the nozzle.The results show that the diameter of the inlet and outlet,the direction of the inlet,the diameter of the swirl chamber,and the height of the swirl chamber all affect the atomization performance,and the diameter of the inlet and outlet has a greater impact.It is found that under the same flow rate and pressure,the geometric differences do have a significant impact on the atomization characteristics,such as spray angle and SMD(Sauter mean diameter).Specific nozzle structures can be customized according to the actual needs.Data analysis shows that the spray angle is related to the swirl number,and the SMD is related to turbulent kinetic energy.Through data fitting,the equations for predicting the spray angle and the SMD are obtained.The error range of the fitting equation for the prediction of spray angle and SMD is within 15% and 10% respectively.The prediction is expected to be used in engineering to estimate the spray performance at the beginning of a real project.展开更多
An experimental analysis has been conducted to study the process of fluid accumulation for different borehole trajectories.More specifically,five heel angles have been experimentally realized to simulate the borehole ...An experimental analysis has been conducted to study the process of fluid accumulation for different borehole trajectories.More specifically,five heel angles have been experimentally realized to simulate the borehole trajectory of the sloping section of the formation.The fluid-carrying capacity,pressure drop and fluid discharge volatility have been investigated for these conditions and,accordingly,the relationship between heel angle and wellbore pressure drop fluid-carrying capacity has been determined.The results show that while the reasonable roll angle can increase the pressure loss in the wellbore,it is beneficial to drainage.In terms of pressure loss and liquid-carrying capacity,when the heeling angle is 50°,the latter is increased while the former becomes very high,which indicates that when drilling and completing wells on site,a 50°roll angle should be avoided.It is found that the main reason for the increase of the total pressure drop in the wellbore is the increase of the local pressure loss in the inclined section.From the perspective of drainage stability,when there is heeling in the inclined section of the horizontal well,the fluctuation of the wellbore drainage tends to be enhanced.Through the comparison of the Beggs-Brill(B-B)and Mukherjee-Brill liquid holdup methods,it is found that B-B method better predicts liquid holdup.A new method for calculating the pressure drop in the inclined section in the presence of lateral inclination is obtained by taking into account the pressure drop in the curved section.Through comparison with experimental data,it is found that the error is within 20%,and the prediction accuracy is high.展开更多
文摘Objective:The aim of the study was to evaluate the quality of sleep in nurses performing shift work in therapeutic and surgical depar tments and to establish possible relationships between level of blood pressure(BP)and quality of sleep.Methods:A total of 20 nurses of the therapeutic depar tments and 20 nurses of the surgical depar tments were enrolled in the study.Sleep quality was assessed using the Pittsburgh Sleep Quality Index(PSQI).BP was measured according to the standard protocol using the Korotkoff method;a sphygmomanometer was used for this twice with an interval of 2 min between 10:00 a.m.and 10:30 a.m.The average value for the 2 indicators was calculated.The diagnosis of essential ar terial hyper tension(AH)was established according to the recommendations of the European Association of Cardiology and the European Association of Hypertension(2018).Results:The overall assessment of the sleep quality of the nurses involved in shift work indicates poor sleep quality;this was true in respondents of both the surgical and therapeutic profiles.However,it was observed that the quality of sleep was significantly lower in nurses of the therapeutic departments.Moreover,poor sleep quality was associated with AH,which was diagnosed in 65%of the nurses of the therapeutic departments and 45%of the nurses of the surgical departments,that is,in almost all of the subjects.Herewith,in the nurses of the therapeutic departments,the level of systolic BP exceeded that of the nurses of the surgical departments.Conclusions:Poor sleep quality is a significant risk factor for AH development and is relevant to nurses performing shift work.Additional clinical studies should be conducted to better understand the mechanisms underlying such adverse cardiometabolic outcomes associated with sleep disorders in the health-sector shift workers.
基金Supported by National Natural Science Foundation of China (Grant Nos.51621061,51139007,51409247)National Science and Technology Support Project of China(Grant No.2015BAD20B01)
文摘Pressure fluctuation may cause high amplitude of vibration of double-suction centrifugal pumps, but the impact of impeller stagger angles is still not well understood. In this paper, pressure fluctuation experiments are carried out for five impeller configurations with different stagger angles by using the same test rig system. Results show that the stagger angles exert negligible effects on the characteristics of head and efficiency. The distributions of pressure fluctuations are relatively uniform along the suction chamber wall, and the maximum pressure fluctuation amplitude is reached near the suction inlet tongue region. The pressure fluctuation characteristics are affected largely by impeller rotation, whose dominant frequencies include impeller rotation frequency and its harmonic frequencies, and half blade passage frequency. The stagger angle exerts a small effect on the pressure fluctuations in the suction chamber while a great effect on the pressure fluctuation in volute casing, especially on the aspect of decreasing the amplitude on blade passage frequency. Among the tested cases, the distribution of pressure fluctuations in the volute becomes more uniform than the other impeller configurations and the level of pressure fluctuation may be reduced by up to 50% when the impeller stagger angle is close to 24° or 360°.The impeller structure pattern needs to be taken into consideration during the design period, and the halfway staggered impeller is strongly recommended.
文摘AIM:To evaluate intraocular pressure(IOP)-lowering effect and ocular tolerability of brimonidine/timolol,dorzolamide/timolol and latanoprost/timolol fixed combination therapies in the management of primary open angle glaucoma.· METHODS:Each drug was administered for two months, after which a circadian tonometric curve was recorded using a Goldmann applanation tonometer.Ocular discomfort(conjunctival hyperemia, burning or stinging, foreign body sensation, itching, ocular pain) of each eye was assessed by the subject on a standardized ocular discomfort scale.RESULTS:Among the three study groups, there were no significant differences in the mean baseline IOP measurements, mean 2ndmo IOP measurements, and mean(%) change of IOPs from baseline. Among the three study groups, there were no significant differences in the mean IOP measurements obtained at circadian tonometric curves at baseline and at two months controls. In sum brimonidine/timolol, dorzolamide/timolol and latanoprost/timolol fixed combination therapies showed similar effects on IOP levels.· CONCLUSION:Brimonidine/timolol, dorzolamide/timolol and latanoprost/timolol fixed combination therapies showed similar lowering efficaties on IOP levels whereas there was no any difference between each other.
基金Supported by the National Natural Science Foundation of China(No.51305293)Tianjin Technical Innovation Funds for the Minor Sci-tech Enterprise(No.14C26211200362)
文摘This paper presents the evolution process of pressure angles from planar parallel mechanisms to spatial parallel mechanisms. Manipulability and condition number, which are frequently used in the optimum design of parallel mechanisms, are introduced from serial robots at first. Then, both theoretical analysis and practical experiences demonstrate that these concepts seem imperfect when they are used in parallel mechanisms. For this reason, this paper introduces the pressure angles in planar 4-bar mechanisms to spatial parallel mechanisms, which include redundant parallel mechanisms. Two kinds of pressure angles extracted from the determinant of direct and indirect Jacobian matrices are investigated. Moreover, two comprehensive and visible global performance indices are defined, showing the advantages in evaluating the workspace, singularity and motion/force transmission capabilities. With a 2-DOF planar and a 3-DOF spatial parallel mechanism as examples, the application of the performance indices is investigated and compared with the condition number at last. The proposed concept can be extended to other spatial parallel mechanisms.
文摘AIM: To compare the effect of phacoemulsification on intraocular pressure(IOP) in patients with primary open angle glaucoma(POAG) and pseudoexfoliation glaucoma(PXG). METHODS: A retrospective comparative case series conducted at the Glaucoma Department at the Association to Prevent Blindness in Mexico. The study enrolled consecutive patients having phacoemulsification with intraocular lens(IOL) implantation and a diagnosis of POAG or PXG. Data about IOP values and number of glaucoma medications used was collected at baseline, 1, 3, 6 and 12 mo postoperatively. RESULTS: The study enrolled 88 patients(88 eyes). After phacoemulsification, there was a statistically significant reduction in IOP values and glaucoma medications use compared to baseline in both POAG and PXG patients(P<0.001). In the POAG group, a 20% decrease in IOP values was evidenced, and a 56.5% reduction in the number of medications used at the one-year follow-up. The PXG group showed a 20.39%, and a 34.46% decrease in IOP and number of medications used, respectively. A significant difference in the mean ΔIOP(postoperative changes in IOP) was evidenced between groups(P=0.005). The reduction of the postsurgical IOP mean values in both groups, the POAG group showed a greater reduction in IOP values compared to the PXG group.CONCLUSION: In both types of glaucoma, phacoemulsification cataract surgery can result in a significant IOP reduction(20%) over a 12 mo follow-up period. The number of medications used is also significantly reduced up to 12 mo after surgery, especially in the PXG group.
文摘Flat Steel Ribbon Wound Pressure Vessels (FSRWPVs) are used in many important industry areas. There is no such kind of pressure vessel exploding on operation for its reasonable structure design. Many explosion experiments on Flat Steel Ribbon Wound Pressure Vessel showed that their limited load pressure is related to the winding angle of the steel ribbons. FSRWPVs with reasonable winding angle have better security and lower cost. Reasonable angels given at the end of this paper facilitate engineering design.
基金This project is supported by Provincial Natural ScienceFoundation of Shanxi. Selected form Proceedings of 2000the First Inte
文摘A method of setting up a pressure-stroke characteristic of the working liquid in hydraulic drawing is studied. A pressure-stroke characteristic and software for controlling its forming process are also developed. And a set of pressure controlling devices with PLC as a central processor are designed. It can be got from the relevant experiments that the pressure-stroke characteristic is correct and its control for forming process is available.
基金Supported by the National Natural Science Foundation of China （51076021）
文摘The ionic liquid, 1-butyl-3-methylimidazolium dibutylphosphate ([BMIM][DBP]) was prepared and the vapor pressures of three set of binary solutions H2O(1)/CH3OH(1)/C2H5OH(1) + [BMIM][DBP](2) were measured at different temperature and in the ILs mole fraction range from 0.1 to 0.6 with a static equilibrium apparatus. The measured vapor pressures were correlated with Non-Random Two Liquid (NRTL) activity coefficient model and the average relative deviations (ARD) between experimental and correlated vapor pressures for these binary solutions were 3.19%, 2.42% and 2.95%, respectively. Then, the vapor pressures of two set of ternary solutions H2O(1) + CH3OH(2)/C2H5OH(2) + [BMIM][DBP](3) were measured with an inclined boiling apparatus and further predicted with NRTL activity coefficient model based on the binary interaction parameters coming from fitting the vapor pressures of the binary solutions. The results indicated that the ternary solutions containing [BMIM][DBP] were shown a strong negative deviation from Raoult's Law when the mole fraction of [BMIM][DBP] was larger than 0.2, which meant that ternary solutions could absorb the refrigerant vapors at the same or below solution temperature. Meanwhile, the average relative deviations between experimental and predicted vapor pressures for ternary solutions were 2.92% and 3.06%, respectively. Consequently, the NRTL active coefficient model used for non-electrolyte solutions was still valid for predicting vapor-liquid equilibrium of binary or ternary solutions containing ILs.
基金Project(2005038227) supported by the China Postdoctoral Science Foundation project(04JJ3050) supported by the Hu-nan Natural Science Foundation
文摘According to the shearing force character and the deformation coordination condition of shell at the station of supports, the mathematical models to calculate contact angle and contact pressure distribution between tyre and shell were set up, the formulae of bending moment and bending stress of tyre were obtained. Taking the maximum of tyre fatigue life as the optimal objective, the optimization model of tyre support angle was built. The computational results show that when tyre support angle is 30°, tyre life is far less than that when tyre support angle is optimal, which is 35.6°, and it is unsuitable to stipulate tyre support angle to be 30° in traditional design. The larger the load, the less the nominal stress amplitude increment of tyre, the more favorable the tyre fatigue life when tyre support angle is optimal.
文摘AIM: To describe a newly-recognized entity,illustrated by five cases of glaucoma in whom trauma to the head,but not the eye,resulted in marked,transient elevation of intraocular pressure (IOP).METHODS: Retrospective case series.Chart review.RESULTS: All five cases had a diagnosis of primary open-angle glaucoma prior to the experience of trauma to the head.All cases had an unusual elevation of IOP (around 70 percent) for days to weeks following the trauma,after which the IOP fell to pre-accident levels.No cause other than the trauma could be determined.CONCLUSION: The relationship between head trauma and elevation of IOP appears real.
基金supported by the State Scholarship Fund under the China Scholarship Council[grant number 201306240017]
文摘There is growing interest in the correlation between working time and environmental pressures,but prior empirical studies mostly focused on static methodologies.This article used dynamic panel regression approaches to examine and compare the relationship among western,southern,and northern European countries over the period 1970-2010,and proved the existence of strongly significant relationships in all models.Furthermore,this article detected the relationship between working hours and environmental indicators(carbon emission and energy use) at different phases.We contribute to a further understanding of the environmental effects of the working time reduction policy by comparing the differences among various periods and country groups in a system generalized method of moments(GMM) dynamic framework.
基金Project(2007CB714006) supported by the National Basic Research Program of China
文摘In order to exactly provide scientific basis for pressure dynamic balance control of working chamber of earth pressure balance shield (EPBS),study on optimal arrangement of pressure measurement points in working chamber was conducted. Based on mathematical description of optimal arrangement for pressure measurement points,fuzzy clustering analysis and discriminant analysis were used to divide pressure regions of nodes on bulkhead. Finally,the selection method of optimal measurement points was proposed,and by selecting d6.28 m EPBS as study object,the case study was conducted. By contrast,based on optimal arrangement scheme of pressure measurement points,through adopting weighted algorithm,the absolute error mean of equivalent pressure of working chamber is the smallest. In addition,pressure curve of optimal arrangement points presents parabola,and it can show the state of pressure distribution on bulkhead truly. It is concluded that the optimal arrangement method of pressure measurement points in working chamber is effective and feasible,and the method can provide basis for realizing high precision pressure control of EPBS.
基金financially supported by National Natural Science Foundation of China (No. 51401194)
文摘The effects of working pressure on the component, surface morphology, surface roughness, and deposition rate of glow discharge polymer(GDP) films by a trans-2-butene/hydrogen gas mixture were investigated based on plasma characteristics diagnosis. The composition and ion energy distributions of a multi-carbon(C_4H_8/H_2) plasma mixture at different working pressures were diagnosed by an energy-resolved mass spectrometer(MS) during the GDP film deposition process. The Fourier transform infrared spectroscopy(FT–IR), field emission scanning electron microscope(SEM) and white-light interferometer(WLI) results were obtained to investigate the structure, morphology and roughness characterization of the deposited films, respectively. It was found that the degree of ionization of the C_4H_8/H_2 plasma reduces with an increase in the working pressure. At a low working pressure, the C–H fragments exhibited small-mass and high ion energy in plasma. In this case, the film had a low CH_3/CH_2 ratio, and displayed a smooth surface without any holes, cracks or asperities. While the working pressure increased to 15 Pa,the largest number of large-mass fragments led to the deposition rate reaching a maximum of 2.11 μm h^(-1), and to hole defects on the film surface. However, continuing to increase the working pressure, the film surface became smooth again, and the interface between clusters became inconspicuous without etching pits.
文摘The tapered angles of an artery significantly influence the local hemodynamics. However, as gravity is considered, little is known about the effect of tapered angles on the hemodynamics. In this study, we explored whether the effect of tapered angles on the distribution of blood flow pressure (DBFP) differed with gravity considered or not. Numerical simulations of the DBFP in a single vessel were performed based on such tapered angles as 0°, 0.5° and 1°. In the model used for simulation, gravity was introduced as a body force. We obtained the following simulations: i) The larger the tapered angles were, the better distributed the blood flow pressure;ii) The tapered effect was an important factor leading to nonlinearity in blood flow pressure;iii) Gravity affected DBFP coupling with the tapered angles, yet independently influenced the dimension of the DBFP. At the same time, the effective intensity of gravity decreased with the increase of tapered angles.
基金Supported by the National Natural Science Foundation of China(No.81870680)National Science Foundation of Zhejiang Province(No.LQ20H120002)。
文摘·AIM:To evaluate morphological changes in the iridocorneal angle after pediatric cataract surgery.·METHODS:Children who underwent primary infantile cataract surgery were included and 64 eyes from 41 children,including 18 with unilateral cataracts(18 eyes)and 23 with bilateral cataracts(46 eyes)were examined.All patients underwent two gonioscopic examinations to evaluate the iridocorneal angle,before the primary lens removal and before the secondary intraocular lens implantation.The anatomical changes in the iridocorneal angle and the relationship between intraocular pressure(IOP)and iridocorneal angle changes were also analyzed.·RESULTS:The iridocorneal angle was wide in 64 eyes before and after surgery.The trabecular meshwork pigmentation,number of iris processes in every quadrant of the iridocorneal angle,and the width of the ciliary body band in the superior and inferior quadrants at the second gonioscopic examination were significantly increased compared to those at the first examination(P<0.001,P<0.05,P<0.05.and P<0.05,respectively).IOP gradually increased at 1 mo after operation,and returned to the preoperative level at 3 mo.However,IOP still increased significantly at 6 and 12 mo.·CONCLUSION:The main changes after pediatric cataract surgery include an increase in trabecular meshwork pigmentation and number of iris processes,IOP gradually increase and has positive correlation with trabecular meshwork pigmentation and anterior insertion of iris process.
基金Supported by Beijing city institution of higher learning talent education program project foundation (PHR200906213,PHR201007234)School fond of Beijing Information Science & Technology University(5026010911)
文摘The working profile of whole cycloidal gear is made up of epicycloid and hypocycloid entirely,according to the theory of meshing of gears and the properties of the cycloid,deals with the derivation of the pressure angle formula for the whole cycloidal gear in theory,and reveals changes of the pressure angle of whole cycloidal gear through examples,finds the application relationships between the pressure angle and other design parameters of the whole cycloidal gear,proves the possibility that the whole cycloidal gear can be used in internal parallel move gear mechanism,also provides theoretic fundament for designing internal parallel move whole cycloidal gear correctly.
基金supported by National Natural Science Foundation of China(No.10875093)
文摘In order to precisely measure the ion parameters in a microwave electron cyclotron resonance plasma using an ion sensitive probe,the dependences of the current-voltage(I-V)characteristics on the shielding height(h)and the potential difference between inner and outer electrodes(V_B)have been investigated at different working pressures of 0.03 Pa and 0.8 Pa.Results show that the I-V curves at higher pressure are more sensitive to the variation of h than those at lower pressure.The influence of V_B on ion temperature(T_i)measurement becomes more prominent when the pressure is increased from 0.03 Pa to 0.8 Pa.Under both pressures,the optimized h is obtained at the condition where the current reaches zero in the positive voltage region with a suitable V_B of-1.5 V because of effective shielding of the electron E×B drift.
基金supported by the National Key Research and Development Program(2022YFB3504000)the National Natural Science Foundation of China(22122815,21978296)the NSFC-EU project(31961133018)。
文摘The structure of the pressure swirl nozzle is an important factor affecting its spray performance.This work aims to study pressure swirl nozzles with different structures by experiment and simulation.In the experiment,10 nozzles with different structures are designed to comprehensively cover various geometric factors.In terms of simulation,steady-state simulation with less computational complexity is used to study the flow inside the nozzle.The results show that the diameter of the inlet and outlet,the direction of the inlet,the diameter of the swirl chamber,and the height of the swirl chamber all affect the atomization performance,and the diameter of the inlet and outlet has a greater impact.It is found that under the same flow rate and pressure,the geometric differences do have a significant impact on the atomization characteristics,such as spray angle and SMD(Sauter mean diameter).Specific nozzle structures can be customized according to the actual needs.Data analysis shows that the spray angle is related to the swirl number,and the SMD is related to turbulent kinetic energy.Through data fitting,the equations for predicting the spray angle and the SMD are obtained.The error range of the fitting equation for the prediction of spray angle and SMD is within 15% and 10% respectively.The prediction is expected to be used in engineering to estimate the spray performance at the beginning of a real project.
基金the support provided by the National Natural Science Foundation of China(No.62173049)the Open Fund of the Key Laboratory of Exploration Technologies for Oil and Gas Resources(Yangtze University),Ministry of Education(Grant K2021-17).
文摘An experimental analysis has been conducted to study the process of fluid accumulation for different borehole trajectories.More specifically,five heel angles have been experimentally realized to simulate the borehole trajectory of the sloping section of the formation.The fluid-carrying capacity,pressure drop and fluid discharge volatility have been investigated for these conditions and,accordingly,the relationship between heel angle and wellbore pressure drop fluid-carrying capacity has been determined.The results show that while the reasonable roll angle can increase the pressure loss in the wellbore,it is beneficial to drainage.In terms of pressure loss and liquid-carrying capacity,when the heeling angle is 50°,the latter is increased while the former becomes very high,which indicates that when drilling and completing wells on site,a 50°roll angle should be avoided.It is found that the main reason for the increase of the total pressure drop in the wellbore is the increase of the local pressure loss in the inclined section.From the perspective of drainage stability,when there is heeling in the inclined section of the horizontal well,the fluctuation of the wellbore drainage tends to be enhanced.Through the comparison of the Beggs-Brill(B-B)and Mukherjee-Brill liquid holdup methods,it is found that B-B method better predicts liquid holdup.A new method for calculating the pressure drop in the inclined section in the presence of lateral inclination is obtained by taking into account the pressure drop in the curved section.Through comparison with experimental data,it is found that the error is within 20%,and the prediction accuracy is high.
