[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theo...[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theoretical basis for improving the pruning techniques of Korla fragrant pear trees. [Method] The light response curve and CO2 response curve of the trees trained to three systems were measured by LI-6400 portable photosynthesis system. The SPAD value was measured using SPAD-502 chlorophyll meter, and specific leaf weight was calculated, to evaluate the effects of the three training systems. [Result] The CO2 response curves of the three training systems were basically in agreement with their light response curves, but there were some differences in their characteristic parameters. Among the three training systems, the maximum net photosynthetic rate, apparent quantum yield and light compensation point of espalier trained trees were the highest, while their light saturation point was the lowest. The CO2 saturation point of delayed-open central leader trained trees and open center trained trees were 1 752 and 1 665 μmol/mol, both of which were much higher than that of espalier trained trees. In addition, the carboxylation efficiency and photorespiration rate of espalier trained trees were both higher than those of delayed-open central leader trained trees and open center trained trees, while the CO2 compensation point of espalier trained trees was the lowest. The leaf SPAD value of espalier trained trees was the largest, followed by that of open center trained trees, and the leaf SPAD value of delayed-open central leader trained trees was the smallest. In addition, the leaf area and specific leaf weight of espalier trained trees were both the highest, followed by those of open center trained trees. [Conclusion] Among the training systems for Korla fragrant pear trees, the espalier training system had better ability to capture light, higher photosynthetic productivity and strongest adaptability to light environment, and open center training system takes the second place. On the contrary, delayed-open central leader training system has the weakest adaptability to light environment, but it can adapt to a higher CO2 concentration. In summary, for the training of Korla fragrant pear trees, espalier training system, which has the highest theoretical yield, is the best among the three training systems, and delayed-open central leader training system is the worst.展开更多
In this paper, we propose a new approach to the problem of degree reduction of Bézier curves based on the given endpoint constraints. A differential term is added for the purpose of controlling the smoothness to ...In this paper, we propose a new approach to the problem of degree reduction of Bézier curves based on the given endpoint constraints. A differential term is added for the purpose of controlling the smoothness to a certain extent. Considering the adjustment of second derivative in curve design, a modified objective function including two parts is constructed here. One part is a kind of measure of the distance between original high order Bézier curve and degree-reduced curve. The other part represents the second derivative of degree-reduced curve. We tackle two kinds of conditions which are position vector constraint and tangent vector constraint respectively. The explicit representations of unknown points are presented. Some examples are illustrated to show the influence of the differential terms to approximation and smoothness effect.展开更多
We derive an effective Hamiltonian for a spin-1/2 particle confined within a curved thin layer with non-uniform thickness using the confining potential approach.Our analysis reveals the presence of a pseudo-magnetic f...We derive an effective Hamiltonian for a spin-1/2 particle confined within a curved thin layer with non-uniform thickness using the confining potential approach.Our analysis reveals the presence of a pseudo-magnetic field and effective spin–orbit interaction(SOI)arising from the curvature,as well as an effective scalar potential resulting from variations in thickness.Importantly,we demonstrate that the physical effect of additional SOI from thickness fluctuations vanishes in low-dimensional systems,thus guaranteeing the robustness of spin interference measurements to thickness imperfection.Furthermore,we establish the applicability of the effective Hamiltonian in both symmetric and asymmetric confinement scenarios,which is crucial for its utilization in one-side etching systems.展开更多
Ab initio two-phase molecular dynamics simulations were performed on silica at pressures of 20-160 GPa and temperatures of 2 500-6 000 K to examine its solid-liquid phase boundary. Results indicate a melting temperatu...Ab initio two-phase molecular dynamics simulations were performed on silica at pressures of 20-160 GPa and temperatures of 2 500-6 000 K to examine its solid-liquid phase boundary. Results indicate a melting temperature （Tin） of 5 900 K at 135 GPa. This is 1 100 K higher than the temperature considered for the core-mantle boundary （CMB） of about 3 800 K. The calculated melting temperature is fairly consistent with classical MD （molecular dynamics） simulations. For liquid silica, the O-O coordination number is found to be 12 along the Tm and is almost unchanged with increasing pressure. The self-diffusion coefficients of O and Si atoms are determined to be 1.3×10^-9-3.3×10^-9 m2/s, and the viscosity is 0.02-0.03 Pa＇s along the Tin. We find that these transport properties depend less on pressure in the wide range up of more than 135 GPa. The eutectic temperatures in the MgO-SiO2 systems were evaluated and found to be 700 K higher than the CMB temperature, though they would decrease considerably in more realistic mantle compositions.展开更多
The problem of constructing curve on parametric surface (or surface that canbe parameterized) such that it interpolates a sequence of points with prescribed tangent directionand curvature vector (or geodesic curvature...The problem of constructing curve on parametric surface (or surface that canbe parameterized) such that it interpolates a sequence of points with prescribed tangent directionand curvature vector (or geodesic curvature) at every point and the issue of curve blending on thiskind of surface are researched. The mapping and tangent mapping from the surface to its parametricplane are introduced and thus several conclusions with differential geometry are deduced. Based onthose conclusions, the problem of interpolating (or blending) curve on a parametric surface isconverted to a similar one on its parametric plane. The final solution curve of either interpolationor blending issue is explicit and can still be expressed by parametric form. And so, unlikeexisting methods, the presented method needs not to use any surface/ surface intersectionalgorithms, usually a troublesome process, for displaying such interpolation curve. Experimentresults show the presented methods are feasible and applicable to CAD/CAM and computer graphics展开更多
In order to relieve the deficiency of the usual cubic Hermite spline curves,the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic...In order to relieve the deficiency of the usual cubic Hermite spline curves,the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic Hermite spline curves are given. And the characteristics of the quartic Hermite spline curves are discussed.The quartic Hermite spline curves not only have the same interpolation and continuity properties of the usual cubic Hermite spline curves, but also can achieve local or global shape adjustment and C;continuity by the shape parameters when the interpolation conditions are fixed.展开更多
Isoactivity curves of MgO in the ternary slag MgO-B2O3-SiO2 have been determined at 1723 K using a slag-metal equilibrium technique in a common tin-bath medium. The results approximately fit a partial ideal solution m...Isoactivity curves of MgO in the ternary slag MgO-B2O3-SiO2 have been determined at 1723 K using a slag-metal equilibrium technique in a common tin-bath medium. The results approximately fit a partial ideal solution model proposed previously.展开更多
Pythagorean-hodograph(PH)curve is widely used in curve modeling because of its advantages in arc length and equidistant curve calculation.This paper discusses the G^(2)continuous blending of cubic PH curves under tota...Pythagorean-hodograph(PH)curve is widely used in curve modeling because of its advantages in arc length and equidistant curve calculation.This paper discusses the G^(2)continuous blending of cubic PH curves under total arc length constraint.Given three points including two end control points and a joint point,construct two cubic PH curves such that they interpolate the end control points and are G^(2)continuous at joint point with prescribed total arc length.It can also be regarded as a curve extension problem.According to the arc length formula of cubic PH curve and the condition of G^(2)blending,the problem is transformed into a constrained minimization problem.Several examples are served to illustrate our method.展开更多
BACKGROUND Magnetic resonance imaging(MRI)with multiparametric dynamic contrast plays a critical role in the assessment of breast lesions.Dynamic curves are a critical parameter in determining the benign or malignant ...BACKGROUND Magnetic resonance imaging(MRI)with multiparametric dynamic contrast plays a critical role in the assessment of breast lesions.Dynamic curves are a critical parameter in determining the benign or malignant nature of lesions.Dynamic curves of type 1 are known to represent benign masses,while dynamic curves of type 3 are known to identify malignant masses.Type 2 dynamic curves have a sensitivity of 42.6%and specificity of 75%for malignancy detection.AIM To investigate the pathological diagnosis of lesions with type 2 dynamic curves.METHODS We evaluated breast MRI examinations performed between 2020 and 2021 retrospectively and included lesions with type 2 dynamic curves.We included 38 lesions from 33 patients.The lesions were evaluated for their pathological diagnosis and morphological characteristics.RESULTS Twenty-six lesions were malignant,while twelve were benign.The most frequently encountered benign lesion(7/12,58.3%)was sclerosing adenosis,while the most frequently encountered malignant diagnosis was invasive ductal cancer.The presence of a type 2 dynamic curve had a sensitivity of 40.2%and specificity of 73.4%for predicting malignancy.By combining type 2 curves and morphological features,the sensitivity and specificity were increased.CONCLUSION The high rates of malignancy detected histopathologically among patients with type 2 dynamic curves in our study are remarkable.Type 2 dynamic curves can be detected in benign breast masses,especially in sclerosing adenosis cases.Considering morphological features can increase the diagnostic accuracy in cases with type 2 dynamic curves.展开更多
Amorphous–microcrystalline MoS_(2)thin films are fabricated using the sol-gel method to produce MoS_(2)/Si-based solar cells. The generation mechanisms of the S-shaped current density–voltage(J–V) curves of the sol...Amorphous–microcrystalline MoS_(2)thin films are fabricated using the sol-gel method to produce MoS_(2)/Si-based solar cells. The generation mechanisms of the S-shaped current density–voltage(J–V) curves of the solar cells are analyzed. To improve the performance of the solar cells and address the problem of the S-shaped J–V curve, a MoS_(2)film and a p^(+) layer are introduced into the front and back interfaces of the solar cell, respectively, which leads to the formation of a p–n junction between the p-Si and the MoS_(2)film as well as ohmic contacts between the MoS_(2)film and the ITO, improving the S-shaped J–V curve. As a result of the high doping characteristics and the high work function of the p^(+) layer, a high–low junction is formed between the p;and p layers along with ohmic contacts between the p;layer and the Ag electrode. Consequently,the S-shaped J–V curve is eliminated, and a significantly higher current density is achieved at a high voltage. The device exhibits ideal p–n junction rectification characteristics and achieves a high power-conversion efficiency(CE) of 7.55%. The findings of this study may improve the application of MoS_(2)thin films in silicon-based solar cells, which are expected to be widely used in various silicon-based electronic and optical devices.展开更多
The investigation of Thermal performance in nanofluids and hybrid nanofluids over a curved stretching infinite region strengthens its roots in engineering and industry.Therefore,the comparative thermal analysis in SiO...The investigation of Thermal performance in nanofluids and hybrid nanofluids over a curved stretching infinite region strengthens its roots in engineering and industry.Therefore,the comparative thermal analysis in SiO_(2)–H_(2)O and(MoS_(2)–SiO_(2))–H_(2)O is conducted over curved stretching surface.The model is reduced in the dimensional version via similarity transformation and then treated numerically.The velocity and thermal behavior for both the fluids is decorated against the preeminent parameters.From the analysis,it is examined that the motion of under consideration fluids declines against Fr and.The thermal performance enhances for higher volumetric fraction and.Further,it is noticed that thermal performance prevailed in(MoS_(2)–SiO_(2))–H_(2)O throughout the analysis.Therefore,(MoS_(2)–SiO_(2))–H_(2)O is better for industrial and engineering uses where high heat transfer is required to accomplished different processes of production.展开更多
Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is...Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is not very great,but their magnetic behaviours are different from each other.The magnetization loops of these compounds have been measured at 77K.The coexistence of superconductivity with magnetic ordering (COSM) found in the samples with RE=Gd,Dy,Ho,Er,Tm,indicates that there are two possible ways of coexistence in the samples.These expertments show that the relation of paramagnetism to the atomtc number of rare earth elements for these superconductors is similar to that of rare earth ions in some paramagnetic salt crystals,which indicates that the magnetism of the samples origi- nates from the local magnetic moments of rare earth ions.In some samples there is antiferromagnetie ordering at low temperatures,and the effective Bohr magneton numbers are consistent with that of free rare earth ions. Some superconducting parameters including the critical current density are calculated according to Ginzburg-Landau theory and the critical state model.展开更多
This paper presents a method for creating modificable quartic and quintic curves with shape parameters. The curves can achieve C 2 even C 3 continuity and unify both interpolation and approximation to the control poin...This paper presents a method for creating modificable quartic and quintic curves with shape parameters. The curves can achieve C 2 even C 3 continuity and unify both interpolation and approximation to the control points without solving a system of equations or inserting additional control points. They have the local properties like the cubic B spline. Besides, the quintic curve would be able globally to tend the control polygon.展开更多
In order to smooth the trajectory of a robot and reduce dwell time,a transition curve is introduced between two adjacent curves in three-dimensional space.G2 continuity is guaranteed to transit smoothly.To minimize th...In order to smooth the trajectory of a robot and reduce dwell time,a transition curve is introduced between two adjacent curves in three-dimensional space.G2 continuity is guaranteed to transit smoothly.To minimize the amount of calculation,cubic and quartic Bezier curves are both analyzed.Furthermore,the contour curve is characterized by a transition parameter which defines the distance to the corner of the deviation.How to define the transition points for different curves is presented.A general move command interface is defined for receiving the curve limitations and transition parameters.Then,how to calculate the control points of the cubic and quartic Bezier curves is analyzed and given.Different situations are discussed separately,including transition between two lines,transition between a line and a circle,and transition between two circles.Finally,the experiments are carried out on a six degree of freedom(DOF) industrial robot to validate the proposed method.Results of single transition and multiple transitions are presented.The trajectories in the joint space are also analyzed.The results indicate that the method achieves G2 continuity within the transition constraint and has good efficiency and adaptability.展开更多
Pore structure reflected from capillary pressure curves plays an important role in low-permeability formation evaluation. It is a common way to construct capillary pressure curves by Nuclear Magnetic Resonance（NMR） ...Pore structure reflected from capillary pressure curves plays an important role in low-permeability formation evaluation. It is a common way to construct capillary pressure curves by Nuclear Magnetic Resonance（NMR） log. However, the method＇s efficiency will be severely affected if there is no NMR log data or it cannot reflect pore structure well. Therefore, on the basis of J function and diagenetic facies classification, a new empirical model for constructing capillary pressure curves from conventional logs is proposed here as a solution to the problem. This model includes porosity and the relative value of natural gamma rays as independent variables and the saturation of mercury injection as a dependent variable. According to the 51 core experimental data sets of three diagenetic facies from the bottom of the Upper Triassic in the western Ordos Basin, China, the model＇s parameters in each diagenetic facies are calibrated. Both self-checking and extrapolation tests show a positive effect, which demonstrates the high reliability of the proposed capillary pressure curve construction model. Based on the constructed capillary pressure curves, NMR T_2 spectra under fully brine-saturated conditions are mapped by a piecewise power function. A field study is then presented. Agreement can be seen between the mapped NMR T_2 spectra and the MRIL-Plog data in the location of the major peak, right boundary, distribution characteristics and T_2 logarithmic mean value. In addition, the capillary pressure curve construction model proposed in this paper is not affected by special log data or formation condition. It is of great importance in evaluating pore structure, predicting oil production and identifying oil layers through NMR log data in low-permeability sandstones.展开更多
We present a relation between the Mathieu equation and a particular elliptic curve. We find that the Floquet exponent of the Mathieu equation, for both q《1 and q》1, can be obtained from the integral of a differentia...We present a relation between the Mathieu equation and a particular elliptic curve. We find that the Floquet exponent of the Mathieu equation, for both q《1 and q》1, can be obtained from the integral of a differential one form along the two homology cycles of the elliptic curve. Certain higher order differential operators are needed to generate the WKB expansion. We make a few conjectures about the general structure of these differential operators.展开更多
文摘[Objective] This study was conducted to evaluate three training systems for Korla fragrant pear trees by comparing the characteristic parameters of light response curve and CO2 response curve, and to provide some theoretical basis for improving the pruning techniques of Korla fragrant pear trees. [Method] The light response curve and CO2 response curve of the trees trained to three systems were measured by LI-6400 portable photosynthesis system. The SPAD value was measured using SPAD-502 chlorophyll meter, and specific leaf weight was calculated, to evaluate the effects of the three training systems. [Result] The CO2 response curves of the three training systems were basically in agreement with their light response curves, but there were some differences in their characteristic parameters. Among the three training systems, the maximum net photosynthetic rate, apparent quantum yield and light compensation point of espalier trained trees were the highest, while their light saturation point was the lowest. The CO2 saturation point of delayed-open central leader trained trees and open center trained trees were 1 752 and 1 665 μmol/mol, both of which were much higher than that of espalier trained trees. In addition, the carboxylation efficiency and photorespiration rate of espalier trained trees were both higher than those of delayed-open central leader trained trees and open center trained trees, while the CO2 compensation point of espalier trained trees was the lowest. The leaf SPAD value of espalier trained trees was the largest, followed by that of open center trained trees, and the leaf SPAD value of delayed-open central leader trained trees was the smallest. In addition, the leaf area and specific leaf weight of espalier trained trees were both the highest, followed by those of open center trained trees. [Conclusion] Among the training systems for Korla fragrant pear trees, the espalier training system had better ability to capture light, higher photosynthetic productivity and strongest adaptability to light environment, and open center training system takes the second place. On the contrary, delayed-open central leader training system has the weakest adaptability to light environment, but it can adapt to a higher CO2 concentration. In summary, for the training of Korla fragrant pear trees, espalier training system, which has the highest theoretical yield, is the best among the three training systems, and delayed-open central leader training system is the worst.
文摘In this paper, we propose a new approach to the problem of degree reduction of Bézier curves based on the given endpoint constraints. A differential term is added for the purpose of controlling the smoothness to a certain extent. Considering the adjustment of second derivative in curve design, a modified objective function including two parts is constructed here. One part is a kind of measure of the distance between original high order Bézier curve and degree-reduced curve. The other part represents the second derivative of degree-reduced curve. We tackle two kinds of conditions which are position vector constraint and tangent vector constraint respectively. The explicit representations of unknown points are presented. Some examples are illustrated to show the influence of the differential terms to approximation and smoothness effect.
基金This work was supported in part by the National Natural Science Foundation of China(Grant No.12104239)National Natural Science Foundation of Jiangsu Province of China(Grant No.BK20210581)+2 种基金Nanjing University of Posts and Telecommunications Science Foundation(Grant Nos.NY221024 and NY221100)the Science and Technology Program of Guangxi,China(Grant No.2018AD19310)the Jiangxi Provincial Natural Science Foundation(Grant No.20224BAB211020).
文摘We derive an effective Hamiltonian for a spin-1/2 particle confined within a curved thin layer with non-uniform thickness using the confining potential approach.Our analysis reveals the presence of a pseudo-magnetic field and effective spin–orbit interaction(SOI)arising from the curvature,as well as an effective scalar potential resulting from variations in thickness.Importantly,we demonstrate that the physical effect of additional SOI from thickness fluctuations vanishes in low-dimensional systems,thus guaranteeing the robustness of spin interference measurements to thickness imperfection.Furthermore,we establish the applicability of the effective Hamiltonian in both symmetric and asymmetric confinement scenarios,which is crucial for its utilization in one-side etching systems.
基金supported by the Japan Society for the Promo-tion of Science (No. 21740330) to Yusuke Usui, (No. 19740331) to Taku Tsuchiya, a fellowship from the Global-COE program "Deep Earth Mineralogy" to Yusuke Usui
文摘Ab initio two-phase molecular dynamics simulations were performed on silica at pressures of 20-160 GPa and temperatures of 2 500-6 000 K to examine its solid-liquid phase boundary. Results indicate a melting temperature （Tin） of 5 900 K at 135 GPa. This is 1 100 K higher than the temperature considered for the core-mantle boundary （CMB） of about 3 800 K. The calculated melting temperature is fairly consistent with classical MD （molecular dynamics） simulations. For liquid silica, the O-O coordination number is found to be 12 along the Tm and is almost unchanged with increasing pressure. The self-diffusion coefficients of O and Si atoms are determined to be 1.3×10^-9-3.3×10^-9 m2/s, and the viscosity is 0.02-0.03 Pa＇s along the Tin. We find that these transport properties depend less on pressure in the wide range up of more than 135 GPa. The eutectic temperatures in the MgO-SiO2 systems were evaluated and found to be 700 K higher than the CMB temperature, though they would decrease considerably in more realistic mantle compositions.
基金This project is supported by National Natural Science Foundation of China(No.50475041)Huo Ying-Dong Education Foundation, China (No.03-91053).
文摘The problem of constructing curve on parametric surface (or surface that canbe parameterized) such that it interpolates a sequence of points with prescribed tangent directionand curvature vector (or geodesic curvature) at every point and the issue of curve blending on thiskind of surface are researched. The mapping and tangent mapping from the surface to its parametricplane are introduced and thus several conclusions with differential geometry are deduced. Based onthose conclusions, the problem of interpolating (or blending) curve on a parametric surface isconverted to a similar one on its parametric plane. The final solution curve of either interpolationor blending issue is explicit and can still be expressed by parametric form. And so, unlikeexisting methods, the presented method needs not to use any surface/ surface intersectionalgorithms, usually a troublesome process, for displaying such interpolation curve. Experimentresults show the presented methods are feasible and applicable to CAD/CAM and computer graphics
基金Hunan Provincial Natural Science Foundation(2017JJ3124)of Chinathe Scientific Research Fund(14B099)of Hunan Provincial Education Department of China
文摘In order to relieve the deficiency of the usual cubic Hermite spline curves,the quartic Hermite spline curves with shape parameters is further studied in this work. The interpolation error and estimator of the quartic Hermite spline curves are given. And the characteristics of the quartic Hermite spline curves are discussed.The quartic Hermite spline curves not only have the same interpolation and continuity properties of the usual cubic Hermite spline curves, but also can achieve local or global shape adjustment and C;continuity by the shape parameters when the interpolation conditions are fixed.
文摘Isoactivity curves of MgO in the ternary slag MgO-B2O3-SiO2 have been determined at 1723 K using a slag-metal equilibrium technique in a common tin-bath medium. The results approximately fit a partial ideal solution model proposed previously.
基金Supported by the National Natural Science Foundation of China(Grant No.11801225)University Science Research Project of Jiangsu Province(Grant No.18KJB110005)the Research Foundation for Advanced Talents of Jiangsu University(Grant No.14JDG034).
文摘Pythagorean-hodograph(PH)curve is widely used in curve modeling because of its advantages in arc length and equidistant curve calculation.This paper discusses the G^(2)continuous blending of cubic PH curves under total arc length constraint.Given three points including two end control points and a joint point,construct two cubic PH curves such that they interpolate the end control points and are G^(2)continuous at joint point with prescribed total arc length.It can also be regarded as a curve extension problem.According to the arc length formula of cubic PH curve and the condition of G^(2)blending,the problem is transformed into a constrained minimization problem.Several examples are served to illustrate our method.
文摘BACKGROUND Magnetic resonance imaging(MRI)with multiparametric dynamic contrast plays a critical role in the assessment of breast lesions.Dynamic curves are a critical parameter in determining the benign or malignant nature of lesions.Dynamic curves of type 1 are known to represent benign masses,while dynamic curves of type 3 are known to identify malignant masses.Type 2 dynamic curves have a sensitivity of 42.6%and specificity of 75%for malignancy detection.AIM To investigate the pathological diagnosis of lesions with type 2 dynamic curves.METHODS We evaluated breast MRI examinations performed between 2020 and 2021 retrospectively and included lesions with type 2 dynamic curves.We included 38 lesions from 33 patients.The lesions were evaluated for their pathological diagnosis and morphological characteristics.RESULTS Twenty-six lesions were malignant,while twelve were benign.The most frequently encountered benign lesion(7/12,58.3%)was sclerosing adenosis,while the most frequently encountered malignant diagnosis was invasive ductal cancer.The presence of a type 2 dynamic curve had a sensitivity of 40.2%and specificity of 73.4%for predicting malignancy.By combining type 2 curves and morphological features,the sensitivity and specificity were increased.CONCLUSION The high rates of malignancy detected histopathologically among patients with type 2 dynamic curves in our study are remarkable.Type 2 dynamic curves can be detected in benign breast masses,especially in sclerosing adenosis cases.Considering morphological features can increase the diagnostic accuracy in cases with type 2 dynamic curves.
基金Project supported by the Science and Technology Research Project of Hebei Province Colleges and Universities (Grant No. QN2020113)Tangshan Applied Basic Research Project (Grant No. 19130227g)。
文摘Amorphous–microcrystalline MoS_(2)thin films are fabricated using the sol-gel method to produce MoS_(2)/Si-based solar cells. The generation mechanisms of the S-shaped current density–voltage(J–V) curves of the solar cells are analyzed. To improve the performance of the solar cells and address the problem of the S-shaped J–V curve, a MoS_(2)film and a p^(+) layer are introduced into the front and back interfaces of the solar cell, respectively, which leads to the formation of a p–n junction between the p-Si and the MoS_(2)film as well as ohmic contacts between the MoS_(2)film and the ITO, improving the S-shaped J–V curve. As a result of the high doping characteristics and the high work function of the p^(+) layer, a high–low junction is formed between the p;and p layers along with ohmic contacts between the p;layer and the Ag electrode. Consequently,the S-shaped J–V curve is eliminated, and a significantly higher current density is achieved at a high voltage. The device exhibits ideal p–n junction rectification characteristics and achieves a high power-conversion efficiency(CE) of 7.55%. The findings of this study may improve the application of MoS_(2)thin films in silicon-based solar cells, which are expected to be widely used in various silicon-based electronic and optical devices.
文摘The investigation of Thermal performance in nanofluids and hybrid nanofluids over a curved stretching infinite region strengthens its roots in engineering and industry.Therefore,the comparative thermal analysis in SiO_(2)–H_(2)O and(MoS_(2)–SiO_(2))–H_(2)O is conducted over curved stretching surface.The model is reduced in the dimensional version via similarity transformation and then treated numerically.The velocity and thermal behavior for both the fluids is decorated against the preeminent parameters.From the analysis,it is examined that the motion of under consideration fluids declines against Fr and.The thermal performance enhances for higher volumetric fraction and.Further,it is noticed that thermal performance prevailed in(MoS_(2)–SiO_(2))–H_(2)O throughout the analysis.Therefore,(MoS_(2)–SiO_(2))–H_(2)O is better for industrial and engineering uses where high heat transfer is required to accomplished different processes of production.
基金Supported by the Chinese National Science Foundation and originally published in J.Chin.RE Soc.(Chin.ed.),1989,7(2),63.
文摘Some high T_c superconductors REBa_2Cu_3O_(7-x)(RE=Sm,Eu,Gd,Dy,Ho,Er,Tm) with zero resist- ance temperatures were about 90K have been prepared.The effect of magnetic rare earth ions on the transi- tion temperatures is not very great,but their magnetic behaviours are different from each other.The magnetization loops of these compounds have been measured at 77K.The coexistence of superconductivity with magnetic ordering (COSM) found in the samples with RE=Gd,Dy,Ho,Er,Tm,indicates that there are two possible ways of coexistence in the samples.These expertments show that the relation of paramagnetism to the atomtc number of rare earth elements for these superconductors is similar to that of rare earth ions in some paramagnetic salt crystals,which indicates that the magnetism of the samples origi- nates from the local magnetic moments of rare earth ions.In some samples there is antiferromagnetie ordering at low temperatures,and the effective Bohr magneton numbers are consistent with that of free rare earth ions. Some superconducting parameters including the critical current density are calculated according to Ginzburg-Landau theory and the critical state model.
文摘This paper presents a method for creating modificable quartic and quintic curves with shape parameters. The curves can achieve C 2 even C 3 continuity and unify both interpolation and approximation to the control points without solving a system of equations or inserting additional control points. They have the local properties like the cubic B spline. Besides, the quintic curve would be able globally to tend the control polygon.
基金Supported by the National Natural Science Foundation of China(No.61573358)Research and Development of Large Multi-function Demolition Equipment in Disaster Site(No.2015BAK06B00)
文摘In order to smooth the trajectory of a robot and reduce dwell time,a transition curve is introduced between two adjacent curves in three-dimensional space.G2 continuity is guaranteed to transit smoothly.To minimize the amount of calculation,cubic and quartic Bezier curves are both analyzed.Furthermore,the contour curve is characterized by a transition parameter which defines the distance to the corner of the deviation.How to define the transition points for different curves is presented.A general move command interface is defined for receiving the curve limitations and transition parameters.Then,how to calculate the control points of the cubic and quartic Bezier curves is analyzed and given.Different situations are discussed separately,including transition between two lines,transition between a line and a circle,and transition between two circles.Finally,the experiments are carried out on a six degree of freedom(DOF) industrial robot to validate the proposed method.Results of single transition and multiple transitions are presented.The trajectories in the joint space are also analyzed.The results indicate that the method achieves G2 continuity within the transition constraint and has good efficiency and adaptability.
基金supported by the Scientific Research Starting Foundation of China University of Petroleum-Beijing at Karamay(No.RCYJ2016B-01-008)the Major National Oil&Gas Specific Project of China(No.2016ZX05050008)
文摘Pore structure reflected from capillary pressure curves plays an important role in low-permeability formation evaluation. It is a common way to construct capillary pressure curves by Nuclear Magnetic Resonance（NMR） log. However, the method＇s efficiency will be severely affected if there is no NMR log data or it cannot reflect pore structure well. Therefore, on the basis of J function and diagenetic facies classification, a new empirical model for constructing capillary pressure curves from conventional logs is proposed here as a solution to the problem. This model includes porosity and the relative value of natural gamma rays as independent variables and the saturation of mercury injection as a dependent variable. According to the 51 core experimental data sets of three diagenetic facies from the bottom of the Upper Triassic in the western Ordos Basin, China, the model＇s parameters in each diagenetic facies are calibrated. Both self-checking and extrapolation tests show a positive effect, which demonstrates the high reliability of the proposed capillary pressure curve construction model. Based on the constructed capillary pressure curves, NMR T_2 spectra under fully brine-saturated conditions are mapped by a piecewise power function. A field study is then presented. Agreement can be seen between the mapped NMR T_2 spectra and the MRIL-Plog data in the location of the major peak, right boundary, distribution characteristics and T_2 logarithmic mean value. In addition, the capillary pressure curve construction model proposed in this paper is not affected by special log data or formation condition. It is of great importance in evaluating pore structure, predicting oil production and identifying oil layers through NMR log data in low-permeability sandstones.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 10675061 adn 11175090
文摘We present a relation between the Mathieu equation and a particular elliptic curve. We find that the Floquet exponent of the Mathieu equation, for both q《1 and q》1, can be obtained from the integral of a differential one form along the two homology cycles of the elliptic curve. Certain higher order differential operators are needed to generate the WKB expansion. We make a few conjectures about the general structure of these differential operators.
