Assembly line balancing often has significant impact on performance of manufacturing systems, and is usually a multiple-objective
problem. Neither an algorithmic nor a procedural assembly line balancing methodology is usually effective in solving these
problems. This article proposes a data envelopment analysis (DEA) approach to solve an assembly line balancing problem. A
computer-aided assembly line balancing tool as Flexible Line Balancing software is used to generate a considerable number
of solutions alternatives as well as to generate quantitative decision-making unit outputs. The quantitative performance measures
were considered in this article. Then DEA was used to solve the multiple-objective assembly line balancing problem. An illustrative
example shows the effectiveness of the proposed methodology. 相似文献
In the realization step of any microstrip filter according to the required electrical characteristics, coupling factors and external quality factor (Qext) are related to the physical parameters of the structure using time consuming full wave simulations. This paper presents a simple, fast, and accurate parametric model of the coupling between the coupled square open loop resonators (SOLRs) and Qext of these resonators versus physical parameters of the structure and substrate characteristics utilizing active learning method (ALM). In the modeling process the multi-dimensional functions of coupling factor and Qext are broken down into their simpler aspects, their behaviors are extracted and then final model will be constructed by combining these simpler aspects. ALM allows the overall model for coupling factor and Qext to be developed through the use of small number of initial data. Once the modeling process is completed it provides a fast and accurate prediction of the required physical parameters for a given coupling factor and Qext. Using the constructed model for a distinct SOLR, which its accuracy was validated by comparison with the full wave simulation results a filter was designed and fabricated. Good agreement between measured and simulated response confirms the accuracy of the modeling procedure. 相似文献
In this study, the impact of TiN as a sintering aid on the relative density and microstructure of TiB2 ceramic was investigated. Monolithic TiB2 and TiB2 doped with 5?wt% TiN were sintered at 1900?°C for 7?min dwell time under the pressure of 40?MPa by spark plasma. The addition of TiN affected the microstructure of TiB2-based sample considerably depicting the finer grains in the as-sintered ceramic. X-ray diffraction evaluation indicated that no interaction occurred between the initial materials. However, detail investigation by the map analysis and energy dispersive spectroscopy results revealed the formation of in-situ nano-sized hBN secondary phase in the TiN-doped TiB2. In addition, TiN played a remarkable role on increasing the relative density of TiN-doped TiB2 ceramic producing a nearly fully dense ceramic with relative density of 99.9% in comparison with the monolithic ceramic having 96.7% relative density. 相似文献
In this paper, a novel full-duplex overlay cognitive wireless powered communication network (FD-OCWPCN) is proposed where a full-duplex (FD) hybrid-access point (H-AP) supports the full access of all battery-free secondary users (SUs). The H-AP broadcasts wireless power to empower the nearby SUs in the downlink (DL) phase while decoding the information transmitted uplink (UL) phase by the SUs, simultaneously. To overcome the self-interference (SI) phenomenon in FD-OCWPCN, the problem of maximizing the system sum-throughput with optimal UL-DL transmission/reception time and H-AP’s transmit power allocation is considered. This problem is non-convex under perfect/imperfect SI cancelation (SIC), so we employ the active interference temperature control and the gradient projection techniques to effectively reduce it into a convex problem. Closed-form expressions for the perfect/imperfect SIC cases are also derived. To assess the performance of the FD-OCWPCN, a comparison with a half-duplex OCWPCN (HD-OCWPCN) is provided. The achievable average sum-throughput for different FD/HD-OCWPCN is compared in the context of the average and peak transmit power at the H-AP, the number of SUs, path loss exponent and fairness metric. The simulation results depict the superiority of the FD-OCWPCN over the HD-OCWPCN for the perfect SIC and the effective imperfect SIC.
Beyond the catalytic activity of nanocatalysts, the support with architectural design and explicit boundary could also promote the overall performance through improving the diffusion process, highlighting additional support for the morphology-dependent activity. To delineate this, herein, a novel mazelike-reactor framework, namely multi-voids mesoporous silica sphere (MVmSiO2), is carved through a top-down approach by endowing core-shell porosity premade Stöber SiO2 spheres. The precisely-engineered MVmSiO2 with peripheral one-dimensional pores in the shell and interconnecting compartmented voids in the core region is simulated to prove combined hierarchical and structural superiority over its analogous counterparts. Supported with CuZn-based alloys, mazelike MVmSiO2 nanoreactor experimentally demonstrated its expected workability in model gas-phase CO2 hydrogenation reaction where enhanced CO2 activity, good methanol yield, and more importantly, a prolonged stable performance are realized. While tuning the nanoreactor composition besides morphology optimization could further increase the catalytic performance, it is accentuated that the morphological architecture of support further boosts the reaction performance apart from comprehensive compositional optimization. In addition to the found morphological restraints and size-confinement effects imposed by MVmSiO2, active sites of catalysts are also investigated by exploring the size difference of the confined CuZn alloy nanoparticles in CO2 hydrogenation employing both in-situ experimental characterizations and density functional theory calculations. 相似文献
This research presents the influence of Al addition on microstructure and mechanical behavior of ZrB2–SiC ultra-high temperature ceramic matrix composite (UHTCMC) fabricated by spark plasma sintering (SPS). A 2.5?wt% Al-doped ZrB2–20?vol% SiC UHTCMC was produced by SPS method at 1900?°C under a pressure of 40?MPa for 7?min. The microstructural and phase analysis of the composite showed that aluminum-containing compounds were formed in-situ during the SPS as a result of chemical reactions between Al and surface oxide films of the raw materials (i.e. ZrO2 and SiO2 on the surfaces of ZrB2 and SiC particles, respectively). The Al dopant was completely consumed and converted to the intermetallic Al3Zr and Al4Si compounds as well as Al2O3 and Al2SiO5. A relative density of 99.8%, a hardness (HV5) of 21.5?GPa and a fracture toughness (indentation method) of 6.3?MPa?m1/2 were estimated for the Al-doped ZrB2–SiC composite. Crack bridging, branching, and deflection were identified as the main toughening mechanisms. 相似文献
Abstract—The necessity of using a 3D model is one of the main problems for modeling Roebel bar transposition in turbo-generators by the finite-element method. This article proposes a 2D dual model for computing strand current distribution in the Roebel bar of turbo-generators. Considering the leakage and mutual inductances for each strand and the coupling inductances between them, the end winding region is modeled in this 2D dual model. In this article, the Roebel bar structure including 16 strands was considered, and these distributions are calculated for different transpositions using the finite-element method. In the finite-element method model, the circulating currents are calculated by subtracting a load current at each strand from the total of strand current. Also, for different transpositions, such as 90°, 180°, 360°, and 540°, the circulating currents are calculated using an analytical method. The obtained strand current distributions from the 2D dual model have good agreement with the obtained results from the analytical method for the 180° and 360° transposed coil models. 相似文献
Preceramic polymer resins are attractive for the 3D printing of net-shaped ceramic components. Recently various processes have been demonstrated for 3D printing of polymer-derived ceramics (PDCs). Ultimately in these processes, the process outcomes strongly depend on the process parameters. In particular, for PDCs the ceramic density, and ceramic yield are affected by the catalyst concentration and cross-linking duration. Here, we use thermal analysis and FTIR to quantify the interrelation of the process parameters on the process outcome for polysilazanes and demonstrate 3D printing of PDC components based on the best-identified process parameters. The results of this work can be used as guidelines for future additive manufacturing of PDCs. 相似文献