中国农村信用的演化路径研究

中国农村信用是通过自发的、松散的非正式组织形式实现的,在基于血缘、地缘关系的特殊信任主义系统里,农村信用的实施机制和信用保护机制事实上是在一个关联博弈中进行的。当农村非正式社会结构向正式社会结构转轨时,由于契约的法律执行机制的不完善以及交易范围的扩展诱致的信息不完备和非对称,使得关联博弈和信息完备性的基础逐渐丧失,仅靠声誉和关系交易的维系成本急剧上升,人格化交易面临规模不经济和信用风险的双重约束。

中国金融制度变迁的演化逻辑分析

中国的金融制度由于“国家悖论”、政府效用函数最大化以及政府偏好序列的约束,及各个既得利益集团为获取制度租金而采取的博弈,使政府供给主导型的强制性金融制度变迁具有强势路径依赖的特征,锁定在低效状态。要退出中国金融制度锁定,必须引入新的内生变量和外生变量,实施动态的制度变迁,从而达到高效的路径替代。

孟加拉国和中国服装产业质量控制的对比分析

中国和孟加拉国现分别是世界第一和第二大服装出口国。两国服装业的竞争主要基于生产力和品质。通过孟加拉国和中国制造商对同一服装品牌的质量控制流程、质量管理体系及管理过程的分析,旨在从两国应用的质量管理系统找出两者间的差异。指出了两国服装产业的主要增长驱动力、面临的挑战及相关表现。

Numerical Simulations of Hydromagnetic Mixed Convection Flow of Nanofluids inside a Triangular Cavity on the Basis of a Two-Component Nonhomogeneous Mathematical Model

Nanofluids have enjoyed a widespread use in many technological applications due to their peculiar properties.Numerical simulations are presented about the unsteady behavior of mixed convection of Fe_(3)O_(4)-water,Fe_(3)O_(4)-kerosene,Fe_(3)O_(4)-ethylene glycol,and Fe_(3)O_(4)-engine oil nanofluids inside a lid-driven triangular cavity.In particular,a two-component non-homogeneous nanofluid model is used.The bottom wall of the enclosure is insulated,whereas the inclined wall is kept a constant(cold)temperature and various temperature laws are assumed for the vertical wall,namely:
θ=1(Case 1),θ=Yð1YÞ(Case 2),andθ=sinð2-YÞ(Case 3).A tilted magnetic field of uniform strength is also present in the fluid domain.From a numerical point of view,the problem is addressed using the Galerkin weighted residual finite element method.The role played by different parameters is assessed,discussed critically and interpreted from a physical standpoint.We find that a higher aspect ratio can produce an increase in the average Nusselt number.Moreover,the Fe_(3)O_(4)-EO and Fe_(3)O_(4)-H2O nanofluids provide the highest and smallest rate of heat transfer,respectively,for all the considered(three variants of)thermal boundary conditions.

Impacts of Heat Flux Distribution, Sloping Magnetic Field and Magnetic Nanoparticles on the Natural Convective Flow Contained in a Square Cavity

In the present paper,the effect of the heat flux distribution on the natural convective flow inside a square cavity in the presence of a sloping magnetic field and magnetic nanoparticles is explored numerically.The nondimensional governing equations are solved in the framework of a finite element method implemented using the Galerkin approach.The role played by numerous model parameters in influencing the emerging thermal and concentration fields is examined;among them are:the location of the heat source and its lengthH
,the magnitude of the thermal Rayleigh number,the nanoparticles shape and volume fraction,and the Hartmann number.It is found that the nanofluid velocity becomes higher when the thermal source length,the nanoparticles volume fraction and/or the thermal Rayleigh number are increased,while it decreases as the Hartmann number Ha grows and the position of the heat source moves toward the center of the lower wall of the cavity.Moreover,the temperature of the nanofluid grows with the extension of the thermal source and decreases slowly when the heat flux position moves toward the center of the lower wall.The outcomes of the research also indicate that the average Nusselt number becomes smaller on increasing Hartmann number Ha and heat source length H^(*).The addition of Fe_(3)O_(4) to engine oil leads to a higher rate of heat transfer with respect to the addition of SiO_(2) particles.Blade-shaped nanoparticles generate the highest value of the Nusselt number compared to all the other considered shapes.

现阶段人民币升值压力分析与对策

2003年以来，国际上要求人民币汇率升值的呼声日趋高涨，国内外许多学者也纷纷发表各自的见解，而我国官方则在多种场合宣称人民币汇率会继续保持稳定，国内一些媒体甚至还打出了“保卫人民币”的口号。

Deposition behavior and tribological properties of diamond-like carbon coatings on stainless steels via chemical vapor deposition

A systematic investigation was carried out to observe the deposition rate of a diamond-like carbon(DLC) coating on two stainless steel substrates by chemical vapor deposition(CVD). The objective of this research is to study the deposition behavior of the DLC coating and its tribological properties in different combinations of methane(CH_4) and nitrogen, which were used as precursor gases. The results reveal that the deposition rate increases with increasing CH_4 content up to 50 vol%. The hardness of the DLC-deposited layer also increases while the friction coefficient decreases with increasing CH_4 gas content up to 50% in the precursor gas mixture.

Statistical Model for Impact and Energy Absorption of 3D Printed Coconut Wood-PLA

Fused deposition modeling(FDM)-3D printing has been the favored technology to build functional components in various industries.The present study investigates infill percentage and infill pattern effects on the printed parts’impact properties through the 3D printing technique using coconut wood-filled PLA composites.Mathematical models are also proposed in the present study with the aim for future property prediction.According to the ASTM standard,fifteen specimens with different parameter combinations were printed using a low-cost FDM 3D printer to evaluate their impact properties.Statistical analysis was performed using MINITAB to validate the experimental data and model development.The experimental outcomes reveal the honeycomb pattern with 75%infill density achieves the highest energy absorption(0.837 J)and impact energy(5.1894 kJ/m^(2)).The p-value from statistical analysis clearly shows that all the impact properties are less than the alpha value of 0.05,suggesting all the properties are vital to determine the impact properties.The validation process affirms that the generated mathematical model for the energy absorbed and the impact energy is reliable at an acceptable level to predict their respective properties.The errors between the experimental value and the predicted value are 3.98%for the energy absorbed and 4.06%for impact energy.The findings are expected to provide insights on the impact behavior of the coconut wood-filled PLA composites prepared by FDM-3D printing and a mathematical model to predict the impact properties.

Expression of Heterosis for Productive Traits in Bottle Gourd Hybrids

An intensive study was conducted in bottle gourd to assessment the magnitude of heterosis for yield and its thirteen yield related traits.Twenty one bottle gourd hybrids generated from 7×7 diallel cross(excluding reciprocals)along with their seven parents evaluated in a RCBD with three replication at the Olericulture Division of Horticulture Research Centre,BARI,Gazipur,Bangladesh during 2018-19.Maximun cross combinations were found significant heterobeltiosis for earliness.The maximum heterobeltiotic effect was observed in P2XP7 and P4XP7.The best heterotic cross for fruit length was P4XP5.Maximum heterotic effect in respect of fruit number per plant was found in the cross P1XP6 and P4XP6.In terms of yield the highest heterobeltiosis was shown by the crosses P3XP4,P3XP5,P4XP5 and P4XP7.In the overall analysis,both additive and non-additive gene actions were found important with predominance of the additive gene effects in the inheritance of bottle gourd.

Natural convective heat transfer in a square enclosure utilizing magnetic nanoparticles

In the present paper,unsteady natural convective heat transfer flow inside a square enclosure filled with nanofluids containing magnetic nanoparticles using nonhomogeneous dynamic model is investigated numerically.The horizontal top wall of the enclosure is considered a colder wall and the bottom wall is maintained at uniform temperature whereas two other vertical walls of the cavity are thermally insulated.The Galerkin weighted residual finite element method has been used to solve the governing non-dimensional partial differential equations.In numerical simulations,four types of nanoparticles such as magnetite(Fe_(3)O_(4)),cobalt ferrite(CoFe_(2)O_(4)),Mn-Zn ferrite(Mn-ZnFe_(2)O_(4)),and silicon dioxide(SiO2),and three types of base fluids such as water(H_(2)O),engine oil(EO)and kerosene(Ke)have been considered.Comparisons with previously published work are performed and excellent agreement is obtained.The effects of various model parameters such as thermal Rayleigh number,nanoparticles volume fraction and nanoparticles shape factor are studied.The results show that the average Nusselt number increases as the thermal Rayleigh number and nanoparticles volume fraction intensify.The results indicate that the average Nusselt numbers are higher for the blade shape of nanoparticles.

Roles of Superthermal Electrons and Adiabatic Heavy Ions on Heavy-Ion-Acoustic Solitary and Shock Waves in a Multi-Component Plasma

Heavy-ion-acoustic(HIA) waves in an unmagnetized collisionless plasma system comprising superthermal electrons, Boltzmann distributed light ions, and adiabatic positively charged inertial heavy ions have been investigated both numerically and analytically. The well-known reductive perturbation method has been used to derive the Kortewegde Vries(K-d V) and Burgers(BG) equations. The parametric regimes for the existence of both the positive and negative solitary and shock waves have been obtained. The effects of adiabaticity of heavy ions and superthermality of electrons,which are found to notably modify the fundamental features(viz. polarity, amplitude, phase speed, etc.) of HIA solitary and shock waves, are precisely studied. The results of our theoretical investigation can be applicable to understand the characteristics and basic nonlinear structures of HIA waves both in space and laboratory plasma situations.

Cylindrical and Spherical Electron-Acoustic Shock Waves in Electron-Positron-Ion Plasmas with Nonextensive Electrons and Positrons

Electron-acoustic shock waves （EASWs） in an unmagnetized four-component plasma （containing hot elec- trons and positrons following the q-nonextensiv.e distribution, cold mobile viscous electron fluid, and immobile positive ions） are studied in nonplanar （cylindrical and spherical） geometry. With the help of the reductive perturbation method, the modified Burgers equation is derived. Analytically, the effects of nonplanar geometry, nonextensivity, relative number density and temperature ratios, and cold electron kinematic viscosity on the basic properties （viz. amplitude, width, speed, etc.） of EASWs are discussed. It is exarmined that the EASWs in nonplanar geometry significantly differ from those in planar geometry. The results of this investigation can be helpful in understanding the nonlinear features of EASWs in various astrophysical plasmas.