Based on the entropy generation concept of thermodynamics, this paper estabfished a general theoretical model for the analysis of entropy generation to optimize fins, in which the minimum entropy generation was select...Based on the entropy generation concept of thermodynamics, this paper estabfished a general theoretical model for the analysis of entropy generation to optimize fins, in which the minimum entropy generation was selected as the object to be studied. The irreversibility due to heat transfer and friction was taken into account so that the minimum entropy generation number has been analyzed with respect to second law of thermodynamics in the forced cross-flow. The optimum dimensions of cylinder pins were discussed. It's found that the minimum entropy generation number depends on parameters related to the fluid and fin physical parameters. Varlatioms of the minimum entropy generation number with different parameters were analyzed.展开更多
In all convective heat transfer situations, losses occur in the flow field (by dissipation) as well as in the temperature field (by conduction). Typically these losses are more or less quantified by the friction f...In all convective heat transfer situations, losses occur in the flow field (by dissipation) as well as in the temperature field (by conduction). Typically these losses are more or less quantified by the friction factorfwith respect to losses in the flow field, and the Nusselt number Nu for the heat transfer quality. Assessing the process of convective heat transfer as a whole, then becomes problematic because two different non-dimensional quantities, f and Nu, have to be combined somehow. From a thermodynamics point of view, there is a reasonable alternative: Since all losses become manifest in corresponding entropy generation rates, these rates are determined in the velocity as well as in the temperature field. Based on the integration of the entropy generation fields, an energy devaluation number is introduced. It basically determines how much oftbe so-called entropic potential of the energy involved in a convective heat transfer process is used within it. This approach is called SLA (second law analysis).展开更多
The present article aimed to analyze the application of the economic analysis of Law as a reference for the reasoning of judicial decisions.To that end,an analysis was carried out on the definitions of what is hermene...The present article aimed to analyze the application of the economic analysis of Law as a reference for the reasoning of judicial decisions.To that end,an analysis was carried out on the definitions of what is hermeneutics and economic analysis of law,based on the construction of the matrix rule of conduct for public administration.The method of the approach followed was empirical-dialectical,using bibliographic,legislative and jurisprudential research,having a reference to the Law and Economics.展开更多
In the present article,we perform the second law analysis of classical Blasius flow accounting the effects of nonlinear radiation and frictional heating.The two-dimensional boundary layer momentum and energy equations...In the present article,we perform the second law analysis of classical Blasius flow accounting the effects of nonlinear radiation and frictional heating.The two-dimensional boundary layer momentum and energy equations are converted to self-similar equations using similarity transformations.The set of resultant ordinary differential equations are solved numerically.The numerical results obtained from solutions of dimensionless momentum and energy equations are used to calculate the entropy generation number and Bejan number.The velocity profile f'(ξ),temperature distributionθ(ξ),entropy production number Ns and Bejan number Be are plotted against the physical flow parameters and are discussed in detail.Further,for the sake of validation of our numerical code,the obtained results are reproduced using Matlab built-in boundary value solver bvp4c resulting in an excellent agreement.It is observed that entropy generation is increasing function of heating parameter,Prandtl number,Eckert number and radiation parameter.Further,it is observed that entropy generation can be minimized by reducing the operating temperatureΔT=T_(w)−T_(∞).展开更多
A socialist legal system with distinct Chinese features has taken shape in 2010 as required by the general objective of the "rule of law" strategy and legislation work put forward by the Party's 15th national congr...A socialist legal system with distinct Chinese features has taken shape in 2010 as required by the general objective of the "rule of law" strategy and legislation work put forward by the Party's 15th national congress. Up to the present,China has already made 237 laws,including the Constitution,699 administrative decrees and regulations and more than 8,600 local laws and regulations.1 They cover seven legal regimes,three tiers of laws. Laws concerning human rights are an important component展开更多
Stretchable electronics, which offers the performance of conventional wafer-based devices and mechan- ical properties of a rubber band, enables many novel applications that are not possible through conven- tional elec...Stretchable electronics, which offers the performance of conventional wafer-based devices and mechan- ical properties of a rubber band, enables many novel applications that are not possible through conven- tional electronics due to its brittle nature. One effective strategy to realize stretchable electronics is to design the inorganic semiconductor material in a stretchable format on a compliant elastomeric substrate. Engineering thermal management is essential for the development of stretchable electronics to avoid adverse thermal effects on its performance as well as in applications involving human body and biological tissues where even 1-2℃ temperature increase is not allowed. This article reviews the recent advances in thermal management of stretchable inorganic electronics with focuses on the thermal models and their comparisons to experiments and finite element simulations.展开更多
In order to evaluate the effects of structural control and energy transition for the base-isolation with energy transducer (BIET), shaking table tests on a steel frame model (BIET system) with scale of 1:4 were c...In order to evaluate the effects of structural control and energy transition for the base-isolation with energy transducer (BIET), shaking table tests on a steel frame model (BIET system) with scale of 1:4 were conducted and the results were compared with the lead rubber beating (LRB) isolation system for the same model. Then numerical analysis of the system was carried out, in which the improved Wen analytic model was used to simulate the hysteretic law of transducers. The results show that the structural system can transform the partial earthquake energy to hydraulic energy ; furthermore, the effect of structural control can reach or be close to that of the LRB isolation system. The agreements between numerical analysis results and those of shaking table tests demonstrate the accuracy of the numerical model.展开更多
A second-law thermodynamic analysis was conducted for stoichiometric premixed dimethyl ether(DME)/hydrogen(H2)/air flames at atmospheric pressure.The exergy losses from the irreversibility sources,i.e.,chemical reacti...A second-law thermodynamic analysis was conducted for stoichiometric premixed dimethyl ether(DME)/hydrogen(H2)/air flames at atmospheric pressure.The exergy losses from the irreversibility sources,i.e.,chemical reaction,heat conduction and species diffusion,and those from partial combustion products were analyzed in the flames with changed fuel blends.It is observed that,regardless of the fuel blends,chemical reaction contributes most to the exergy losses,followed by incomplete combustion,and heat conduction,while mass diffusion has the least contribution to exergy loss.The results also indicate that increased H2 substitution decreases the exergy losses from reactions,conduction,and diffusion,primarily because of the flame thickness reduction at elevated H2 substitution.The decreases in exergy losses by chemical reactions and heat conduction are higher,but the exergy loss reduction by diffusion is slight.However,the exergy losses from incomplete combustion increase with H2 substitution,because the fractions of the unbumed fuels and combustion intermediates,e.g.,H2 and OH radical,increase.The overall exergy losses in the DME/H2 flames decrease by about 5%with increased H2 substitution from 0%to 100%.展开更多
The forming limit diagram(FLD) is an important tool to be used when characterizing the formability of metallic sheets used in metal forming processes. Experimental measurement and determination of the FLD is timecon...The forming limit diagram(FLD) is an important tool to be used when characterizing the formability of metallic sheets used in metal forming processes. Experimental measurement and determination of the FLD is timeconsuming and therefore the analytical prediction based on theory of plasticity and instability criteria allows a direct and efficient methodology to obtain critical values at different loading paths, thus carrying significant practical importance.However, the accuracy of the plastic instability prediction is strongly dependent on the choice of the material constitutive model [1–3]. Particularly for materials with hexagonal close packed(HCP) crystallographic structure, they have a very limited number of active slip systems at room temperature and demonstrate a strong asymmetry between yielding in tension and compression [4, 5]. Not only the magnitude of the yield locus changes, but also the shape of the yield surface is evolving during the plastic deformation [4]. Conventional phenomenological constitutive models of plasticity fail to capture this unconventional mechanical behavior [4, 6]. Cazacu and Plunkett [6] have proposed generic yield criteria, by using the transformed principal stress, to account for the initial plastic anisotropy and strength differential(SD) effect simultaneously. In this contribution, a generic FLD MATLAB script was developed based on Marciniak–Kuczynski analytical theory and applied to predict the localized necking. The influence of asymmetrical effect on the FLD was evaluated. Several yield functions such as von Mises, Hill, Barlat89, and Cazacu06 were incorporated into analysis. The paper also presents and discusses the influence of different hardening laws on the formability of materials with HCP crystal structures. The findings indicate that the plastic instability theory coupled with Cazacu model can adequately predict the onset of localized necking for HCP materials under different strain paths.展开更多
文摘Based on the entropy generation concept of thermodynamics, this paper estabfished a general theoretical model for the analysis of entropy generation to optimize fins, in which the minimum entropy generation was selected as the object to be studied. The irreversibility due to heat transfer and friction was taken into account so that the minimum entropy generation number has been analyzed with respect to second law of thermodynamics in the forced cross-flow. The optimum dimensions of cylinder pins were discussed. It's found that the minimum entropy generation number depends on parameters related to the fluid and fin physical parameters. Varlatioms of the minimum entropy generation number with different parameters were analyzed.
文摘In all convective heat transfer situations, losses occur in the flow field (by dissipation) as well as in the temperature field (by conduction). Typically these losses are more or less quantified by the friction factorfwith respect to losses in the flow field, and the Nusselt number Nu for the heat transfer quality. Assessing the process of convective heat transfer as a whole, then becomes problematic because two different non-dimensional quantities, f and Nu, have to be combined somehow. From a thermodynamics point of view, there is a reasonable alternative: Since all losses become manifest in corresponding entropy generation rates, these rates are determined in the velocity as well as in the temperature field. Based on the integration of the entropy generation fields, an energy devaluation number is introduced. It basically determines how much oftbe so-called entropic potential of the energy involved in a convective heat transfer process is used within it. This approach is called SLA (second law analysis).
文摘The present article aimed to analyze the application of the economic analysis of Law as a reference for the reasoning of judicial decisions.To that end,an analysis was carried out on the definitions of what is hermeneutics and economic analysis of law,based on the construction of the matrix rule of conduct for public administration.The method of the approach followed was empirical-dialectical,using bibliographic,legislative and jurisprudential research,having a reference to the Law and Economics.
文摘In the present article,we perform the second law analysis of classical Blasius flow accounting the effects of nonlinear radiation and frictional heating.The two-dimensional boundary layer momentum and energy equations are converted to self-similar equations using similarity transformations.The set of resultant ordinary differential equations are solved numerically.The numerical results obtained from solutions of dimensionless momentum and energy equations are used to calculate the entropy generation number and Bejan number.The velocity profile f'(ξ),temperature distributionθ(ξ),entropy production number Ns and Bejan number Be are plotted against the physical flow parameters and are discussed in detail.Further,for the sake of validation of our numerical code,the obtained results are reproduced using Matlab built-in boundary value solver bvp4c resulting in an excellent agreement.It is observed that entropy generation is increasing function of heating parameter,Prandtl number,Eckert number and radiation parameter.Further,it is observed that entropy generation can be minimized by reducing the operating temperatureΔT=T_(w)−T_(∞).
文摘A socialist legal system with distinct Chinese features has taken shape in 2010 as required by the general objective of the "rule of law" strategy and legislation work put forward by the Party's 15th national congress. Up to the present,China has already made 237 laws,including the Constitution,699 administrative decrees and regulations and more than 8,600 local laws and regulations.1 They cover seven legal regimes,three tiers of laws. Laws concerning human rights are an important component
基金supported by the Zhejiang Provincial Natural Science Foundation of China(Grant No.LR15A020001)the National Natural Science Foundation of China(Grant Nos.11502009,11372272 and 11321202)the National Basic Research Program of China(Grant No.2015CB351900)
文摘Stretchable electronics, which offers the performance of conventional wafer-based devices and mechan- ical properties of a rubber band, enables many novel applications that are not possible through conven- tional electronics due to its brittle nature. One effective strategy to realize stretchable electronics is to design the inorganic semiconductor material in a stretchable format on a compliant elastomeric substrate. Engineering thermal management is essential for the development of stretchable electronics to avoid adverse thermal effects on its performance as well as in applications involving human body and biological tissues where even 1-2℃ temperature increase is not allowed. This article reviews the recent advances in thermal management of stretchable inorganic electronics with focuses on the thermal models and their comparisons to experiments and finite element simulations.
基金Sponsored by the Hebei Scientific and Technological Research and Development Plans (Grant No.07215615)
文摘In order to evaluate the effects of structural control and energy transition for the base-isolation with energy transducer (BIET), shaking table tests on a steel frame model (BIET system) with scale of 1:4 were conducted and the results were compared with the lead rubber beating (LRB) isolation system for the same model. Then numerical analysis of the system was carried out, in which the improved Wen analytic model was used to simulate the hysteretic law of transducers. The results show that the structural system can transform the partial earthquake energy to hydraulic energy ; furthermore, the effect of structural control can reach or be close to that of the LRB isolation system. The agreements between numerical analysis results and those of shaking table tests demonstrate the accuracy of the numerical model.
基金the National Natural Science Foundation of China(Grant No.51776124)Key Laboratory of Low-Grade Energy Utilization Technologies&Systems of MOE(Grant No.LLEUTS-201803).
文摘A second-law thermodynamic analysis was conducted for stoichiometric premixed dimethyl ether(DME)/hydrogen(H2)/air flames at atmospheric pressure.The exergy losses from the irreversibility sources,i.e.,chemical reaction,heat conduction and species diffusion,and those from partial combustion products were analyzed in the flames with changed fuel blends.It is observed that,regardless of the fuel blends,chemical reaction contributes most to the exergy losses,followed by incomplete combustion,and heat conduction,while mass diffusion has the least contribution to exergy loss.The results also indicate that increased H2 substitution decreases the exergy losses from reactions,conduction,and diffusion,primarily because of the flame thickness reduction at elevated H2 substitution.The decreases in exergy losses by chemical reactions and heat conduction are higher,but the exergy loss reduction by diffusion is slight.However,the exergy losses from incomplete combustion increase with H2 substitution,because the fractions of the unbumed fuels and combustion intermediates,e.g.,H2 and OH radical,increase.The overall exergy losses in the DME/H2 flames decrease by about 5%with increased H2 substitution from 0%to 100%.
基金support from the Portuguese Foundation for Science and Technology (FCT) via the projects PTDC/EMS-TEC/2404/2012, and PTDC/EMS-TEC/1805/2012FEDER funds through the program COMPETE-‘‘Programa Operacional Factores de Competitividade’’ is greatly acknowledged
文摘The forming limit diagram(FLD) is an important tool to be used when characterizing the formability of metallic sheets used in metal forming processes. Experimental measurement and determination of the FLD is timeconsuming and therefore the analytical prediction based on theory of plasticity and instability criteria allows a direct and efficient methodology to obtain critical values at different loading paths, thus carrying significant practical importance.However, the accuracy of the plastic instability prediction is strongly dependent on the choice of the material constitutive model [1–3]. Particularly for materials with hexagonal close packed(HCP) crystallographic structure, they have a very limited number of active slip systems at room temperature and demonstrate a strong asymmetry between yielding in tension and compression [4, 5]. Not only the magnitude of the yield locus changes, but also the shape of the yield surface is evolving during the plastic deformation [4]. Conventional phenomenological constitutive models of plasticity fail to capture this unconventional mechanical behavior [4, 6]. Cazacu and Plunkett [6] have proposed generic yield criteria, by using the transformed principal stress, to account for the initial plastic anisotropy and strength differential(SD) effect simultaneously. In this contribution, a generic FLD MATLAB script was developed based on Marciniak–Kuczynski analytical theory and applied to predict the localized necking. The influence of asymmetrical effect on the FLD was evaluated. Several yield functions such as von Mises, Hill, Barlat89, and Cazacu06 were incorporated into analysis. The paper also presents and discusses the influence of different hardening laws on the formability of materials with HCP crystal structures. The findings indicate that the plastic instability theory coupled with Cazacu model can adequately predict the onset of localized necking for HCP materials under different strain paths.