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41.
This article considers an inbound ordering and outbound dispatching problem for a single product in a third-party warehouse, where the demands are dynamic over a discrete and finite time horizon, and moreover, each demand has a time window in which it must be satisfied. Replenishing orders are shipped in containers and the freight cost is proportional to the number of containers used. The problem is classified into two cases, i.e. non-split demand case and split demand case, and a mathematical model for each case is presented. An in-depth analysis of the models shows that they are very complicated and difficult to find optimal solutions as the problem size becomes large. Therefore, genetic algorithm (GA) based heuristic approaches are designed to solve the problems in a reasonable time. To validate and evaluate the algorithms, finally, some computational experiments are conducted. 相似文献
42.
Mild functionalization of carbon nanotubes filled epoxy composites: Effect on electromagnetic interferences shielding effectiveness 下载免费PDF全文
The effect of nitric acid mild functionalized multiwalled carbon nanotubes (MWCNTs) on electromagnetic interference (EMI) shielding effectiveness (SE) of epoxy composites was examined. MWCNTs were oxidized by concentrated nitric acid under reflux conditions, with different reaction times. The dispersion of MWCNTs after functionalization was improved due to the presence of oxygen functional groups on the nanotubes surface. Functionalization at 2 h exhibits the highest EMI SE and electrical conductivity of MWCNTs filled epoxy composites. However, EMI shielding performance of MWCNTs filled epoxy composite declined when the functionalization reaction time was prolonged. This was due to extensive damage on the MWCNT structure, as verified by a Raman spectroscope. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42557. 相似文献
43.
M. Luo C. G. Koh M. Gao W. Bai 《International journal for numerical methods in engineering》2015,103(4):235-255
A new numerical approach for solving incompressible two‐phase flows is presented in the framework of the recently developed Consistent Particle Method (CPM). In the context of the Lagrangian particle formulation, the CPM computes spatial derivatives based on the generalized finite difference scheme and produces good results for single‐phase flow problems. Nevertheless, for two‐phase flows, the method cannot be directly applied near the fluid interface because of the abrupt discontinuity of fluid density resulting in large change in pressure gradient. This problem is resolved by dealing with the pressure gradient normalized by density, leading to a two‐phase CPM of which the original singlephase CPM is a special case. In addition, a new adaptive particle selection scheme is proposed to overcome the problem of ill‐conditioned coefficient matrix of pressure Poisson equation when particles are sparse and non‐uniformly spaced. Numerical examples of Rayleigh–Taylor instability, gravity current flow, water‐air sloshing and dam break are presented to demonstrate the accuracy of the proposed method in wave profile and pressure solution. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
44.
Younghun Sung Jaehoon Lim Jai Hyun Koh Byoung Koun Min Jeffrey Pyun Kookheon Char 《Korean Journal of Chemical Engineering》2016,33(8):2287-2290
Pt-decorated CdSe tetrapods with different arm lengths were tested for the photocatalytic hydrogen generation reaction. Well-defined CdSe tetrapods with controlled wurtzite arm lengths were synthesized by the continuous precursor injection (CPI) approach. Pt nanocrystals with an extremely small size of ~1 nm were directly decorated on the overall surfaces of CdSe tetrapods. Ligand-exchanged Pt-decorated CdSe tetrapods with different arm lengths were employed as photocatalysts for photocatalytic hydrogen generation reaction in the presence of hole scavengers. Pt-decorated CdSe tetrapods with shorter arm length showed the highest photocatalytic efficiency, which is due to higher probability of charge separation. 相似文献
45.
Stephen Buckman Mara Latorre M. Martin Bosman Neveen Nawawy Bomin Koh 《Papers in Regional Science》2019,98(2):679-699
As cities are compelled to compete for new sources of investment and revenue, arts-based economic development strategies have become the norm. The purpose of this paper is to revisit and reevaluate some of the conventional claims about the arts as an important economic development strategy by exploring a case study called “The Space at 2106 Main” in a rapidly gentrifying neighbourhood called West Tampa. The results of this study suggest that the arts are indeed assuming a greater role in economic policy under the auspices of West Tampa community redevelopment areas (CRA) and the direct actions of various arts related entrepreneurs. The results however, point to a mixed picture that raises difficult questions about the medium to long-term effects of this urban redevelopment strategy, especially on the poor and mostly minority residents of West Tampa. 相似文献
46.
Adam Alemayehu Dominika Zákutná Soňa Kohúteková Václav Tyrpekl 《Journal of the American Ceramic Society》2022,105(7):4621-4631
Ceria, pure or doped, is an important electrolyte material in solid oxide fuel cells, catalysts, and plutonium surrogates. Even though ceria is a widely studied material, its coprecipitation with the most common doping element, gadolinium, remains mostly overlooked. Here, we present a comprehensive study of gadolinium–cerium oxalates prepared by coprecipitation of gadolinium (III) and cerium (III) salts by oxalic acid under different reaction conditions and element ratios. For this purpose, we assessed the effects of basic precipitation conditions on the final oxalate size, shape, and conversion into the corresponding oxides. The results showed that coprecipitation with oxalic acid yields and ideal solid solution, which translates into the oxides. This low-cost and straightforward synthetic route provides then high-quality solid solutions of Ge–Gd in the oxide lattice. Thus, this approach has a high industrialization potential, with significant advantages over hydrolysis or hydrothermal techniques. 相似文献
47.
ZnBO-doped (Ba, Sr)TiO3 ceramics were investigated for low-temperature co-fired ceramics (LTCCs) applications. Until now, B2O3 and Li2CO3 dopants have been commonly employed as the low-temperature sintering aids. In this paper, we suggest ZnBO as an alternative dopant to the B2O3 and Li2CO3. To reduce the sintering temperature of (Ba, Sr)TiO3, we have added 1–5 wt.% of ZnBO to (Ba, Sr)TiO3. ZnBO-doped (Ba, Sr)TiO3 ceramics were respectively sintered from 750 to 1350 °C by 50 °C to confirm the sintering temperature with different dopant contents. By adding 5 wt.% of ZnBO to the (Ba, Sr)TiO3 ceramics, the sintering temperature of (Ba, Sr)TiO3 ceramics can be reduced to 1100 °C. From the XRD analysis, ZnBO-doped (Ba, Sr)TiO3 has no pyro phase. By adding ZnBO dopants to (Ba, Sr)TiO3 ceramics, both of relative dielectric permittivity and loss tangent were decreased. From the frequency dispersion of dielectric properties, the relative dielectric permittivity and loss tangent of 5 wt.% ZnBO-doped (Ba, Sr)TiO3 were 1180 and 3.3 × 10−3, while those of BST were 1585 and 4.8 × 10−3, respectively. 相似文献
48.
Low loss ferroelectric materials have been extensively investigated for the high frequency device applications. Especially, weak frequency dispersion materials with high dielectric permittivity and low loss tangent have enormous potential for electronic components including filters, and embedded capacitors. Ag(Ta0.5Nb0.5)O3 thick films have been prepared by low temperature sintering aid Li2CO3 (0, 1, 3 and 5 wt%). Ag(Ta0.5Nb0.5)O3 thick films were characterized by X-ray diffraction analysis and scanning electron microscopy. The dielectric and ferroelectric properties were also investigated. We observed very weak frequency dispersion of dielectric permittivity at the microwave frequency range. 相似文献
49.
A series of novel hexene‐1–propylene random copolymers with isotactic sequence of propylene was synthesized with a MgCl2‐supported Cr(acac)3 catalyst. The molecular weight distribution of copolymers and homopolymers was considerably narrower than that of typical polyolefins produced by heterogeneous Ziegler–Natta catalysts. The crystallizability of the copolymers having a propylene‐unit content of more than 50 mol % drastically decreased with decreasing propylene‐unit content, and the copolymers with a propylene content of less than 50 mol % were completely amorphous. In the present novel type of random copolymers with crystallizable and noncrystallizable units, a single glass transition was observed between pure polypropylene and polyhexene‐1, and a major component was found to govern the final morphology and the mechanical characteristics. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2949–2954, 2004 相似文献
50.
Landing helicopters on rough unprepared terrain has always been considered hazardous, since the massive dust cloud generated by wind drafts from the helicopter's rotors completely obstructs the pilot's view of the landing area. This article presents a performance assessment of a proposed millimeter-wave (MMW) three-dimensional imaging radar system, specifically meant for helicopter assisted landing. The assessment includes simulation of radar backscattering from the underlying rough terrain, in addition to the signal attenuation and scattering from dust clouds generated by the helicopter's rotors. Terrain scattering is simulated in two steps: 1) generation of a two-scale random rough surface according to prescribed statistics of a large-scale undulation and a small-scale surface roughness; and 2) simulation of the returned signal, including the effects of the real-aperture radar parameters and the terrain-backscatter response. Details of the three-dimensional imaging algorithm are presented. Single-scattering theory is used to simulate the effects of a dust cloud - including signal attenuation and backscatter clutter generation - on the radar's performance. It is shown that operating in the upper millimeter-wave regime (70 GHz-220 GHz) is the most practical solution for a compact, high-resolution, three-dimensional imaging system for this problem. 相似文献