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排序方式: 共有1319条查询结果,搜索用时 37 毫秒
111.
As a sequel to our studies on isobutylene (IB) homopolymerizations, we have investigated the copolymerization of IB/isoprene
(IP) mixtures containing up to ∼20 mole% IP in the feed by the use of the in situ (CH3)3Si[B(C6F5)4] initiating system in close-to-neat monomers in the temperature range from −35 to −8 (reflux)°C. The effects of temperature
and IB/IP feed ratio on copolymer molecular weights were determined and compared with those produced by AlCl3. The molecular weights of butyl rubbers obtained by the novel initiating system under a variety of conditions are invariably
and significantly higher than those made with AlCl3. High molecular weight gel-free rubbers containing up to ∼5 mol% unsaturation can be obtained at relatively high temperatures.
Copolymer compositions can be controlled by the IB/IP ratio in the feed. Product molecular weights decrease with increasing
IP content. To gain insight into the copolymerization mechanism, the activation enthalpy of molecular weights (ΔH‡=−5.9 kcal/mol, −24.7 kJ/mol) and the reactivity ratios (rIB= 1.8, rIP= 1.5) have been determined.
Received: 8 July 1998/Revised version: 16 October 1998/Accepted: 16 October 1998 相似文献
112.
In this article we propose a multiple-output parity bit signature generation method for exhaustive testing of VLSI circuits. Given a multiple-output combinational circuit, a parity bit signature is generated by first EXORing all the outputs to produce a new output function and then feeding this resulting function to a single-output parity bit signature generator. The method preserves all the desirable properties of the conventional single-output circuits response analyzers and can be readily implemented using the current VLSI technology. 相似文献
113.
The loss of zero-voltage-switching (ZVS) of active switches has been a serious limitation of full-bridge (FBZVS) converters.
Many techniques have been proposed in the past to extend the range of ZVS operation over the wider and also the full range
of operation. However, in these techniques ZVS is achieved at the expense of additional conduction loss in active switches
and losses in the auxiliary components. In this paper, the analysis for the additional losses in various full-range FBZVS
DC-DC converters and their comparative evaluation is reported. Closed form expressions are derived for average value of device
currents and losses. The loss curves for various topologies are plotted and compared. The analytical results are found to
be consistent with the experimental efficiency tests performed on 500 W, 100 kHz prototype. It is concluded that a recently
proposed new topology has the least penalty of additional losses. 相似文献
114.
Harinder Singh Oberoi Sunil Bansal & Gurpreet Singh Dhillon 《International Journal of Food Science & Technology》2008,43(8):1499-1504
Among the five Kluyveromyces marxianus strains tested for β-galactosidase production, K. marxianus NCIM 3465 showed maximum enzyme activity of 1.62 IU mg−1 dry weight. Different levels (5–25%, w/v) of dried cauliflower waste were incorporated into whey to evaluate the effect of its supplementation on enzyme production. Although a marginal increase in enzyme production was seen by incorporating 5% and 10% cauliflower waste in whey, nearly 15% increase in β-galactosidase production was observed when cauliflower waste level was increased to 20% compared with whey alone. Supplementing whey with 20% cauliflower waste also decreased the production time. Lactose concentration in whey, mainly responsible for increasing the biological oxygen demand load of the effluent water, decreased from 4.2% to nearly 0% at 24 h. Thus, this study demonstrated that both these by-products/residues could be effectively used for β-galactosidase production at commercial scale. 相似文献
115.
C. Hsein Juang David Kun Li Sunny Ye Fang Zhuzhao Liu Eng Hui Khor 《Canadian Metallurgical Quarterly》2008,134(8):1050-1058
This paper presents an innovative approach for a probabilistic analysis of liquefaction hazard at a given site in a specified exposure time based on the U.S. Geological Survey (USGS) National Seismic Hazard Maps data. The foundation of this new approach is a simplified procedure for obtaining a joint distribution of peak ground surface acceleration (amax) and moment magnitude of earthquake (Mw) at any given locality in the United States based on the USGS website data. The developed joint probability distribution of amax and Mw can be readily combined with the conditional probability of liquefaction (given a pair of amax and Mw) to obtain the total probability of liquefaction at a given site in a specified exposure time. Detailed formulation of the new approach is presented and demonstrated with examples. 相似文献
116.
Niranjan Mahendra Singh Jha Sunil 《The International Journal of Advanced Manufacturing Technology》2015,80(9-12):1895-1902
The International Journal of Advanced Manufacturing Technology - Magnetorheological (MR) finishing is a smart finishing processes applied to a variety of applications. In the present work, an... 相似文献
117.
Debajyoti Ray P. Sunny Gils Guru P. Mohanta R. Manavalan Prafulla K. Sahoo 《应用聚合物科学杂志》2010,116(2):959-968
In this study, interpenetrating polymer network (IPN) hydrogel based on polyvinyl alcohol (PVA) networking with polyacrylic acid (PAA) were prepared by a non‐conventional emulsion method without any added crosslinker, using benzoyl peroxide as initiator and sodium chloride (NaCl) as additive. The IPN hydrogel was characterized by using Fourier transformed infrared (FTIR) spectrophotometry, Thermo gravimetric analysis (TGA), and Scanning electron microscopy (SEM). (PVA‐co‐PAA)/NaCl normal IPN hydrogel (H) were fabricated into hydrogel microspheres (HM) by modified emulsion crosslinking method using glutaraldehyde‐saturated toluene as crosslinker and were loaded with Diltiazem hydrochloride (DL). The IPN hydrogel showed more swelling in simulated intestinal fluid (SIF). (PVA‐co‐PAA)/NaCl HM formulation A1 showed comparatively higher DL entrapment (79%) and better control over DL release up to 24 h. By comparing antihypertensive activity of DL loaded two formulations in normotensive rats, HM formulation A1 found more effective in reducing blood pressure to 40.1%. The experimental results demonstrated that (PVA‐co‐PAA)/NaCl HM had the greater potential than normal hydrogel to be used as a drug carrier. A single use of the prepared hydrogel microsphere system of DL can effectively control hypertension in rats. The system holds promise for clinical studies. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 相似文献
118.
The dry hot syngas cleaning process appears to be potentially more efficient and cleaner than the proven wet cleaning or semi-wet cleaning processes but it is still far from commercialisation. There are several technological barriers responsible such as poor availability factor, degeneration of sorbent and several stages of separation. This paper summarises the reported current status of dry hot cleaning of syngas from coal gasification processes along with the shortcomings of reporting of dry hot syngas cleaning performance results. The paper also proposes and discusses a rational method of performance reporting, a novel pulse less filtration concept and a system to prevent failure of filter elements. 相似文献
119.
CO2 flooding, which is an efficient method of enhanced oil recovery, is a very complicated process involving phase behavior. To understand the performance of CO2 flooding and provide accurate data for designing reservoir development, a comprehensive investigation of the phase behavior of CO2 miscible flooding and an accurate compositional reservoir simulation needs to be conducted. In PVT modeling, an effective and more physically reasonable equation of state model was achieved and the feasibility of CO2 miscible flooding was determined by multiple contact minimum miscibility pressure (MCMMP) calculation. Furthermore, compositional reservoir simulation studies for predicting CO2 miscible performance were designed and constructed with core flooding data. By matching with laboratory core flooding data, we can estimate parameters with uncertainty. The objective of this study was to find a work flow for parameter estimation in CO2 miscible flooding process that can be used to design and optimize field CO2 miscible floods. 相似文献
120.
Chi-Kong Chan Harry K.H. Chow Sunny K.P. So Henry C.B. Chan 《Expert systems with applications》2012,39(13):11325-11334
In this paper, we propose a multi-agent-based framework to facilitate process automation for the air cargo industry. The focus is on enhancing two labor-intensive flight planning processes, namely cargo consolidation and equalization. By employing a software agent-based flight planning module, which is linked with an RFID-based warehouse management system, air cargo items received at a freight forwarder’s warehouse can be processed more efficiently and flight plans can be generated automatically. In particular, we employ agents equipped with simulated annealing optimization engines to handle the time-consuming tasks of optimization. By doing so, the latest flight plans can be generated more efficiently. The system has been evaluated experimentally by both simulated and real-life data. The results are encouraging. For example, operation steps that normally require over 30 minutes to complete can now be carried out in as quickly as two minutes, and produce a better solution. 相似文献