In this paper, we study a class of manufacturing systems which consist of multiple plants and each of the plants has capability of producing multiple distinct products. The production lines of a certain plant may swit...In this paper, we study a class of manufacturing systems which consist of multiple plants and each of the plants has capability of producing multiple distinct products. The production lines of a certain plant may switch between producing different kinds of products in a time-sharing mode. We optimize the capacity configuration of such a system s production lines with the objective to maximize the overall profit in the capacity planning horizon. Uncertain demand is incorporated in the model to achieve a robust configuration solution. The optimization problem is formulated as a nonlinear polynomial stochastic programming problem, which is difficult to be efficiently solved due to demand uncertainties and large search space. We show the NP-hardness of the problem first, and then apply ordinal optimization(OO) method to search for good enough designs with high probability. At lower level, an mixed integer programming(MIP) solving tool is employed to evaluate the performance of a design under given demand profile.展开更多
Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(bt...Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(btb)2 (btb = 1,3,5-benzenetribenzoate), and the activated carbon MSC-30. The Dubinin-Astakhov model was applied to calculated absolute adsorption isotherms as a function of the fugacity to determine the adsorption enthalpy at ambient temperature. Comparisons of the calculated enthalpies and the surface excess concentration (excess adsorption per square meter of surface) show that Zn4O(btb)2 has an adsorption enthalpy comparable to MSC-30, but that the spacing between adsorbed molecules is much larger.展开更多
This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility...This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.展开更多
We have optimized the input pulse width and injection time to achieve the highest possible output pulse energy in a double-pass laser amplifier using two Nd:YAG rods. For this purpose, we have extended the Frantz–Nod...We have optimized the input pulse width and injection time to achieve the highest possible output pulse energy in a double-pass laser amplifier using two Nd:YAG rods. For this purpose, we have extended the Frantz–Nodvik equation by simultaneously including both spontaneous emission and pump energy variation. The effective pump energy of the flash lamp was 8.84 J for each gain medium. The energy of 1 J could be amplified to an output energy of 12.17 J with the maximum achieved extraction efficiency of 63.18% when an input pulse having a pulse width of 168 μs is sent 10 μs after the absorbed pump energy becomes the maximum value.展开更多
基金supported by a contract between General Motors Company and Tsinghua University,National Natural Science Foundation of China(61425027,60736027,61021063,61074034,61174105)
文摘In this paper, we study a class of manufacturing systems which consist of multiple plants and each of the plants has capability of producing multiple distinct products. The production lines of a certain plant may switch between producing different kinds of products in a time-sharing mode. We optimize the capacity configuration of such a system s production lines with the objective to maximize the overall profit in the capacity planning horizon. Uncertain demand is incorporated in the model to achieve a robust configuration solution. The optimization problem is formulated as a nonlinear polynomial stochastic programming problem, which is difficult to be efficiently solved due to demand uncertainties and large search space. We show the NP-hardness of the problem first, and then apply ordinal optimization(OO) method to search for good enough designs with high probability. At lower level, an mixed integer programming(MIP) solving tool is employed to evaluate the performance of a design under given demand profile.
文摘Hydrogen adsorption isotherms were measured at ambient temperature to pressures exceeding 300 bar for three benchmark adsorbents: two metal-organic frameworks, Cu3(btc)2 (btc = 1,3,5-benzenetricarboxylate) and Zn4O(btb)2 (btb = 1,3,5-benzenetribenzoate), and the activated carbon MSC-30. The Dubinin-Astakhov model was applied to calculated absolute adsorption isotherms as a function of the fugacity to determine the adsorption enthalpy at ambient temperature. Comparisons of the calculated enthalpies and the surface excess concentration (excess adsorption per square meter of surface) show that Zn4O(btb)2 has an adsorption enthalpy comparable to MSC-30, but that the spacing between adsorbed molecules is much larger.
文摘This paper provides an overview of alloy and process developments in aluminum and magnesium castings for lightweight automotive applications. Wear-resistant aluminum alloys, creep-resistant and high strength/ductility magnesium alloys have been developed for automotive applications. On the process front, vacuumassisted die casting and high vacuum die casting technologies have been developed for high-integrity body and chassis applications. Thin-wall and hollow casting components are being produced by low-pressure die casting processes for structural applications. Overcasting technology is gaining traction and has enabled mixed material designs for automotive sub-systems such as engine cradles and instrument panel beams. Simulation tools developed to predict the interfacial interactions of the dissimilar components and the structural integrity of the overcast systems are being validated in the casting trials.
基金supported by the Industrial Strategic Technology development program,10048964the Ministry of Trade,Industry&Energy(MI,Korea)
文摘We have optimized the input pulse width and injection time to achieve the highest possible output pulse energy in a double-pass laser amplifier using two Nd:YAG rods. For this purpose, we have extended the Frantz–Nodvik equation by simultaneously including both spontaneous emission and pump energy variation. The effective pump energy of the flash lamp was 8.84 J for each gain medium. The energy of 1 J could be amplified to an output energy of 12.17 J with the maximum achieved extraction efficiency of 63.18% when an input pulse having a pulse width of 168 μs is sent 10 μs after the absorbed pump energy becomes the maximum value.
