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991.
Aluminum, used as a material for heat exchangers in air conditioners, often has problems of leakage of refrigerant on the Al surface due to corrosion. The problems originate from pitting corrosion of the Al in an external environment. To understand corrosion problems, it is necessary to study the corrosion behavior of Al in various environments. In this study, the effects of environmental factors on the corrosion behavior of Al were studied by the surface analysis and electrochemical testing in 3.5 wt% NaCl solutions, with changes of dissolved oxygen, temperature, and concentration of Cl− and S ions. Among the external environmental factors, the presence of oxygen and the increase of Cl− ion concentration do not significantly affect the corrosion potential of Al, leading to an increase of only 1.1 and 6 times, respectively. There was a significant decrease in the corrosion resistance of Al, approximately 40 and 800 times, respectively, with the increase of concentration of S and temperature. 相似文献
992.
This paper proposes a methodological approach in risk analysis of interdependent manufacturing systems which is based on Ghosh model - a variation of the Leontief input-output model. The proposed approach is able to quantify the impact of supply perturbations in a manufacturing system in terms of cost-price increase in production output due to increase in prices of value-added input brought about by degraded supply resulting from natural or man-made disasters and sudden policy changes. Unlike demand-driven perturbation models presented in literature, the supply-driven inoperability input-output model (SIIM) appears to be more relevant particularly in make-to-order manufacturing systems as demand is usually pre-determined and production costs typically increase when prices of inputs increase. An actual case study was carried out in a furniture manufacturing firm in central Philippines and three scenarios were presented to illustrate the proposed approach: (1) a sudden log ban in the location of the supplier, (2) increase in labor costs and (3) metal shortage caused by severe weather condition. Results show that supply perturbation of upstream processes does not impact downstream processes as long as these processes remain independent of the perturbed upstream process as described in firm's system structure and topology. This also shows that the magnitude of impact of non-perturbed process depends on its nature of interdependence of the perturbed process. The proposed approach is highly relevant for manufacturing practitioners in formulating and implementing mitigation and adaptation policies. 相似文献
993.
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995.
This paper investigates the global output-feedback stabilization for a class of uncertain time-varying nonlinear systems. The remarkable structure of the systems is the presence of uncertain control coefficients and unmeasured states dependent growth whose rate is inherently time-varying and of unknown polynomial-of-output, and consequently the systems have heavy nonlinearities, serious uncertainties/unknowns and serious time-variations. This forces us to explore a time-varying plus adaptive methodology to realize the task of output-feedback stabilization, rather than a purely adaptive one. Detailedly, based on a time-varying observer and transformation, an output-feedback controller is designed by skillfully combining adaptive technique, time-varying technique and well-known backstepping method. It is shown that, with the appropriate choice of the design parameters/functions, all the signals of the closed-loop system are bounded, and furthermore, the original system states globally converge to zero. It is worth mentioning that, the heavy nonlinearities are compensated by an updating law, while the serious unknowns and time-variations are compensated by a time-varying function. The designed controller is still valid when the system has an additive input disturbance which, essentially different from those studied previously, may not be periodic or bounded by any known constant. 相似文献
996.
997.
本文对12Cr2Mo1R耐热钢板进行了正火+回火处理(NT),然后再进行模拟焊后热处理(SPWHT),研究了这两种状态钢板在不同温度下的J-Δa阻力曲线,并对断裂韧度J0.2BL值进行了分析。研究结果表明,这两种热处理态组织均以贝氏体为主,所含碳化物都由M3C、M2C、M7C3和M23C6组成,其中M代表合金元素Cr、Mo、Mn和Fe或者它们的组合;在相同热处理的状态下,温度越高,断裂韧度值越高;相同温度情况下,正火+回火态12Cr2Mo1R耐热钢表现出较高的断裂韧度,因为其碳化物含量较小,碳化物之间的间距相对较大。 相似文献
998.
《Energy Policy》2016
The construction industry in China exerts significant environmental impacts and uses considerable resources because of rapid urbanization. This study conducted a structural path analysis (SPA) based on the multi-regional input–output table to quantify environmental impact transmission in the entire supply chain. Results indicated that the direct resource input (the first stage) along with on-site construction (the zeroth stage) consumed the highest amount of energy in the supply chain and accounted for approximately 50% of total energy consumption. Regional analysis showed that energy consumption in the construction industry at the provincial level was self-sufficient. Sectoral analysis demonstrated that the direct inputs from the sectors of “manufacture of non-metallic mineral products” and “smelting and pressing of metals” generated the most important energy flows, whereas the sectors of “production and distribution of electric power and heat power” and “extraction of petroleum and natural gas” significantly but indirectly influenced energy use. Sensitivity analysis exhibited that the system boundary of SPA could be narrowed down into the first two upstream stages that contained nearly 50% of energy flow information or expanded toward the first five upstream stages that represented 80% of total energy consumption. 相似文献
999.
Jnyana Ranjan Pati Subhajit Dutta Philippe Eliaers Pinakeswar Mahanta Pradip Kumar Chatterjee 《Drying Technology》2016,34(9):1073-1084
The intensification of interfacial mass, heat, and momentum transfer makes vortex chambers potentially interesting for the efficient drying of paddy, allowing shorter drying times and/or more compact equipment. The presence of a shell introduces particular challenges. Intraparticle diffusion limitations are strong and may reduce the advantage from intensified interfacial mass and heat transfer and the efficiency of air usage. Furthermore, high shear and normal stresses in the fast rotating particle bed may cause damage to the paddy shell, posing problems for transport and storage. With these specific aspects in mind, the use of vortex chambers for paddy drying is experimentally evaluated. 相似文献
1000.
Novel heat‐resistant N‐substituted poly(benzimidazole imide)s (PBIIs) with good solubility were synthesized via a C ? N coupling reaction. A model reaction was carried out to assist in determining the optimal reaction conditions for the polymerization and to elucidate the chemical structures of the polymers. The structures of the resulting polymers were characterized by means of Fourier transform infrared and elemental analysis; the results showed good agreement with the proposed structures. The resulting PBIIs exhibited high glass transition temperatures (Tg > 290 oC) and good thermostability (T5% > 440 oC). The thermal behavior in air of the PBII polymers suggests that they can be considered as a new class of high performance polyimides. © 2016 Society of Chemical Industry 相似文献