Effects of PHC on Water Quality of Jiaozhou Bay Ⅵ.Transfer Laws

According to the investigation data of PHC content in Jiaozhou Bay,China from 1979 to 1983,the content,sources,horizontal,vertical and seasonal distribution,and transfer laws of PHC in the water of the bay were analyzed on spatial scale,and the processes of pollution sources,land transfer,sedimentation,and water transfer of PHC in Jiaozhou Bay were discussed on temporal scale. These laws and changing processes could provide theoretical foundation for studies on water transfer of PHC and other heavy metals.

Optimization of heat transfer and heat-work conversion based on generalized heat transfer law

Examples of heat transfer and heat-work conversion are optimized with entropy generation and entransy loss,respectively based on the generalized heat transfer law in this paper.The applicability of entropy generation and entransy loss evaluation in these optimization problems is analyzed and discussed.The results show that the entransy loss rate reduces to the entransy dissipation rate in heat transfer processes,and that the entransy loss evaluation is effective for heat transfer optimization.However,the maximum heat transfer rate does not correspond to the minimum entropy generation rate with prescribed heat transfer temperature difference,which indicates that the entropy generation minimization is not always appropriate to heat transfer optimization.For heat-work conversion processes,the maximum entransy loss rate and the minimum entropy generation rate both correspond to the maximum output power,and they are both appropriate to the optimization of the heat-work conversion processes discussed in this paper.

Optimal configuration of a class of endoreversible heat engines for maximum efficiency with radiative heat transfer law

Optimal configuration of a class of endoreversible heat engines with fixed duration,input energy and radiative heat transfer law (q∝Δ(T4)) is determined. The optimal cycle that maximizes the efficiency of the heat engine is obtained by using opti-mal-control theory,and the differential equations are solved by the Taylor series expansion. It is shown that the optimal cycle has eight branches including two isothermal branches,four maximum-efficiency branches,and two adiabatic branches. The interval of each branch is obtained,as well as the solutions of the temperatures of the heat reservoirs and the working fluid. A numerical example is given. The obtained results are compared with those obtained with the Newton’s heat transfer law for the maximum efficiency objective,those with linear phe-nomenological heat transfer law for the maximum efficiency objective,and those with radiative heat transfer law for the maximum power output objective.

Optimal configuration for a finite high-temperature source heat engine cycle with the complex heat transfer law

The optimal configuration of a heat engine operating between a finite high-temperature source and an infinite low-temperature reservoir is derived by using finite time thermodynamics based on a complex heat transfer law,including Newtonian heat transfer law,linear phenomenological heat transfer law,radiative heat transfer law,Dulong-Petit heat transfer law,generalized convective heat transfer law and generalized radiative heat transfer law,q ∝(△T n). In the engine model the only irreversibility of finite rate heat transfer is considered. The optimal relation between the power output and efficiency of the heat engine is also derived by using an equivalent temperature of the hot reservoir. The obtained results include those obtained in recent literature and can provide some theoretical guidance for the designs of practical engines.

Maximum power output of a class of irreversible non-regeneration heat engines with a non-uniform working fluid and linear phenomenological heat transfer law

Maximum power output of a class of irreversible non-regeneration heat engines with non-uniform working fluid,in which heat transfers between the working fluid and the heat reservoirs obey the linear phenomenological heat transfer law [q ∝Δ(T-1)],are studied in this paper. Optimal control theory is used to determine the upper bounds of power of the heat engine for the lumped-parameter model and the distributed-parameter model,respectively. The results show that the maximum power output of the heat engine in the distributed-parameter model is less than or equal to that in the lumped-parameter model,which could provide more realistic guidelines for real heat engines. Analytical solutions of the maximum power output are obtained for the irreversible heat engines working between constant temperature reservoirs. For the irreversible heat engine operating between variable temperature reservoirs,a numerical example for the lumped-parameter model is provided by numerical calculation. The effects of changes of reservoir's temperature on the maximum power of the heat engine are analyzed. The obtained results are,in addition,compared with those obtained with Newtonian heat transfer law [q ∝Δ(T)].

The optimal path of piston motion for Otto cycle with linear phenomenological heat transfer law

An Otto cycle engine with internal and external irreversibilities of friction and heat leakage, in which the heat transfer between the working fluid and the environment obeys linear phenomenological heat transfer law [q ∝△(T -1)], is studied in this paper. The optimal piston motion trajectory for maximizing the work output per cycle is derived for the fixed total cycle time and fuel consumed per cycle. Optimal control theory is applied to determine the optimal piston trajectories for the cases of with and without piston acceleration constraint on each stroke and the optimal distribution of the total cycle time among the strokes. The optimal piston motion with acceleration constraint for each stroke consists of three segments, including initial maximum acceleration and final maximum deceleration boundary segments, respectively. Numerical examples for optimal configuration are provided, and the obtained results are compared with those obtained with Newton’s heat transfer law [q ∝△(T )]. The results also show that optimizing the piston motion can improve power and efficiency of the engine by more than 9%. This is primarily due to the decrease in heat leakage loss on the initial portion of the power stroke.

The minimum heat consumption for heat-driven binary separation processes with linear phenomenological heat transfer law

The optimal performance of heat-driven binary separation processes with linear phenomenological heat transfer law(q∝△(T-1)) is analyzed by taking the processes as heat engines which work between high-and low-temperature reservoirs and produce enthalpy and energy flows out of the system,and the temperatures of the heat reservoirs are assumed to be time-and space-variables.A numerical method is employed to solve convex optimization problem and Lagrangian function is employed to solve the average optimal control problem.The dimensionless entropy production rate coefficient and dimensionless enthalpy flow rate coefficient are adopted to indicate the major influence factors on the performance of the separation process,such as the properties of different materials and various separation requirements for the separation process.The dimensionless minimum average entropy production rate and dimensionless minimum average heat consumption of the heat-driven binary separation processes are obtained.The obtained results are compared with those obtained with the Newtonian heat transfer law(q∝△(T)).

Optimal paths for a light-driven engine with a linear phenomenological heat transfer law

An irreversible light-driven engine is described in this paper, in which the heat transfer between the working fluid and the environment obeys a linear phenomenological heat transfer law [ q ∝Δ(T -1)], with a working fluid composed of the bimolecular reacting system 2SO 3 F■S 2 O 6 F2. Piston trajectories maximizing work output and minimizing entropy generation are determined for such an engine with rate-dependent loss mechanisms of friction and heat leakage. The optimal control theory is applied to determine the optimal configurations of the piston motion trajectory and the fluid temperature. Numerical examples for the optimal configuration are provided, and the obtained results are compared with those derived with Newtonian heat transfer law [ q ∝Δ(T )].

Hamilton-Jacobi-Bellman equations and dynamic programming for power-optimization of a multistage heat engine system with generalized convective heat transfer law

A multistage endoreversible Carnot heat engine system operating between a finite thermal capacity high-temperature fluid reservoir and an infinite thermal capacity low-temperature environment with generalized convective heat transfer law [q∝(ΔT) m ] is investigated in this paper.Optimal control theory is applied to derive the continuous Hamilton-Jacobi-Bellman (HJB) equations,which determine the optimal fluid temperature configurations for maximum power output under the conditions of fixed initial time and fixed initial temperature of the driving fluid.Based on the universal optimization results,the analytical solution for the Newtonian heat transfer law (m=1) is also obtained.Since there are no analytical solutions for the other heat transfer laws (m≠1),the continuous HJB equations are discretized and dynamic programming algorithm is performed to obtain the complete numerical solutions of the optimization problem.The relationships among the maximum power output of the system,the process period and the fluid temperature are discussed in detail.The results obtained provide some theoretical guidelines for the optimal design and operation of practical energy conversion systems.

η_m FOR THE HEAT-TRANSFER LAW q∞△1/T

Curzon and Ahlborn considered firstly the irreversibility of heat-transfer in the Carnot cycle, and derived the efficiency of a Carnot cycle at maximum power

Calculations of Heat Transfer in Torch Furnaces by Gas Volume Radiation Laws

The results stemming from the calculation of heat transfer in torch furnaces by the laws, relating to radiation from solid surfaces and gas volumes are analyzed. The article presents the laws for radiation from gas volumes and the procedure for calculating heat transfer in torch furnaces, fire boxes, and combustion chambers, elaborated on their basis. The example of heat transfer calculation in a torch furnace is given, and it is significantly non-uniform in nature. Non-uniformity of heat flux distribution on heating surfaces is given. According to the results of calculations, a new furnace is designed to decrease the non-uniformity of ingot heating, fuel rate, and increase the furnace capacity. The calculation results of the distribution of heat fluxes on the heating surfaces are given in changing torch geometric dimensions. These results are confirmed by experimental studies.

Effect of thermal conductivity on heat transfer for a power-law non-Newtonian fluid over a continuous stretched surface with various injection parameters

The two-dimensional non-Newtonian steady flow on a power-law stretched surface with suction or injection is studied. Thermal conductivity is assumed to vary as a linear function of temperature. The transformed governing equations in the present study are solved numerically using the Runge-Kutta method. Through a comparison, results for a special case of the problem show excellent agreement with those in a previous work. Two cases are considered, one corresponding to a cooled surface temperature and the other to a uniform surface temperature. Numerical results show that the thermal conductivity variation parameter, the injection parameter, and the power-law index have significant influences on the temperature profiles and the Nusselt number.

Mathematical model and general laws of wet compression

Wet compression is an effective way to enhance the performance of gas turbines and it has attracted a good deal of attention in recent years. The one sidedness and inaccuracy of previous studies,which took concentration gradient as mass transfer potential are discussed. The mass transfer process is analyzed from the viewpoint of non equilibrium thermodynamics,by taking generalized thermodynamic driving force as mass transfer potential,and the corresponding mass transfer coefficient is obtained using the heat and mass transfer equilibrium occurring between moist air and water droplets at wet bulb temperature for the sake of avoiding complex tests and providing more accurate formulas. A mathematical model of wet compression is therefore established,and the general laws of wet compression are investigated. The results show that the performance of atomizer is critical for wet compression and wet compression is more suitable for compressors with higher pressure ratio and longer compression time.

On energy boundary layer equations in power law non-Newtonian fluids

The hear transfer mechanism and the constitutive models for energy boundary layer in power law fluids were investigated.Two energy transfer constitutive equations models were proposed based on the assumption of similarity of velocity field momentum diffusion and temperature field heat transfer.The governing systems of partial different equations were transformed into ordinary differential equations respectively by using the similarity transformation group.One model was assumed that Prandtl number is a constant,and the other model was assumed that viscosity diffusion is analogous to thermal diffusion.The solutions were presented analytically and numerically by using the Runge-Kutta formulas and shooting technique and the associated transfer characteristics were discussed.

地铁小半径曲线段双非减振扣件系统横向力传递特性分析

为了探究地铁小半径曲线段上部锁紧式双层非线性减振扣件系统在服役时横向力的传递特性,通过室内试验测得荷载-位移曲线,根据实际尺寸建立减振扣件系统精细化有限元模型,在与试验对比验证的基础上,分析其内部的横向力传递过程及各个部件的受力情况,并由此开展相关因素对减振扣件系统横向力传递的影响规律。研究结果表明:上部锁紧式双层非线性减振扣件系统在横向荷载的作用下,横向力的内部传递过程较为复杂,表现出明显的非线性特征;同时施加垂向和横向荷载时,减振扣件系统的整个横向传力过程分为工作边轨距块静摩擦力被克服、非工作边轨距块静摩擦力被克服、非工作边侧轨下垫板压缩变形、非工作边轨距块横向支承、轨下垫板静摩擦力增幅减缓5个阶段;钢轨轨底和轨距块之间的摩擦因数、扣压力是影响轨距块由最大静摩擦力变为动摩擦力所需要外荷载大小的关键因素,摩擦因数越大,所需要的外荷载越大;而钢轨轨底与轨下垫板之间的摩擦因数对减振系统的横向力传递行为影响较小,这是因为钢轨轨底与轨下垫板之间一直都是静摩擦力,削弱了因摩擦因数的变化对整个横向力传递过程的影响。该研究旨在为今后减振扣件系统的横向刚度设计优化及轮轨动力学仿真计算提供实验依据和理论指导。

基于数值模拟的桩网复合地基加固效果对比分析

利用有限元分析软件ABAQUS建立了二维桩网复合地基模型,分析了预应力高强度混凝土(prestressed high-strength concrete,简称PHC)桩网复合地基、桩承式复合地基、PHC桩砂桩复合地基这3种复合地基加固方式,在路堤荷载下的变形、受力特性。数值计算结果表明:桩承式复合地基的路面沉降最小,PHC桩网复合地基其次,PHC桩砂桩复合地基最大;桩承式复合地基的桩土应力比、桩体荷载分担比最大,土拱效应最明显。计算分析数据说明,针对复杂的、软土较深厚的高速公路、铁路的路基,可采用桩承式复合地基加固,加固效果更好。

活动断裂带下聚氨酯固化道床受力与变形传递规律及其影响

为研究活动断裂带下聚氨酯固化道床结构的受力和变形传递规律及其影响,针对活动断裂带地质特征和聚氨酯固化道床结构特点,基于有限元法和仿真分析软件建立相应的有限元模型。研究结果表明:断裂所致的基础错动将直接映射到轨面,形成明显轨道不平顺,轨面不平顺线形与断裂面线形相近,但不完全重合;断裂位移导致轨面高低、方向变化率增量大于断裂角影响,断裂位移由5 mm增至20 mm,轨面高低、方向变化率增量分别为2.18,0.77 mm/m,断裂角由30°增至90°,轨面高低、方向变化率增量分别为0.11,0.03 mm/m,断裂位移是影响轨道不平顺的主要因素;正断层和走滑断层形成的钢轨变形波长分别为6.1~7.0 m和17.0~19.6 m,后者约为前者的3倍;正断层作用下,固化道床底部离缝宽度随断裂竖向位移v的增加而增大,断裂位置离缝明显,断裂位移为20 mm时,最大离缝宽度达10 mm以上;固化道床纵向应力分布连续,变形曲率最大处应力最大,但应力水平整体较低。

基于半解析有限元的结构载荷传递规律可视化

针对结构内部载荷传递规律的量化表达问题,提出了一种基于半解析有限元的载荷传递规律可视化方法。给出了结构内局部区域载荷传递量可视化的基本原理,利用半解析有限元法推导了结构内部载荷传递量计算的数学表达。借助单元生死技术模拟载荷传递量计算过程中结构内局部区域材料的不断移除与恢复过程,并通过二次开发给出载荷传递规律的可视化流程。以矩形悬臂平板、带孔平板、三点弯曲平板和三维弯曲梁结构为例,分别计算其内部载荷传递规律,得到了结构内部载荷传递的大小及方向。

基于双荷载箱自平衡法的黄土地区桩基承载特性试验研究

为探究双荷载箱自平衡法在黄土地区的适用性,以陕西地区某城市立交工程2根抗压试桩为研究对象,对桩基竖向承载力进行检测,分析了桩底压浆前、后桩基承载力的提升程度及组成差异,并从桩身轴力、桩侧摩阻力及桩端阻力3个方面对荷载传递规律进行研究。结果表明:压浆后桩基极限承载力相较于压浆前提升了51.74%,其中桩端阻力值增加到压浆前的2.5倍,且占桩基承载力的比重明显增大;双荷载箱自平衡试验中,桩身轴力在上荷载箱处产生并达到最大值,向桩顶和桩底逐渐衰减,轴力向下衰减速率明显更快;桩侧摩阻力由上荷载箱处开始发挥,沿桩身传递过程中,由于桩土相对位移逐渐减小,最终衰减至最小值;下部桩身桩端反力-位移曲线与传统静载试验的荷载-位移曲线类似,但两者桩周土应力场存在差异。

论建立企业数据财产权的意义——以相关误区的澄清为视角

企业数据权利问题是近年来我国数据基础制度建设的重点和学术增长点,建立企业数据财产权也得到了多数学者的支持。但部分学者对建立企业数据财产权的意义存在认知误区,并提出了反对意见,这使得企业数据的权属问题迄今仍未达成共识,并对数据基础制度建设造成了一定的阻碍。基于财产权本体论分析可知,建立企业数据财产权的效力意义在于赋予企业数据宽窄可把握的法律排他效力和最完备的法律处分效力,但不包括数据的事实支配效力。企业数据财产权的现实意义不仅仅在于激励数据的生产供给,其所赋予的数据排他效力与数据权利的可让渡效力在激励高质量数据的生产供给、有效促进数据的开放与社会化流通等方面均具有重要的现实意义。