Hydrolytic degradation of poly(1,4‐butylene terephthalate‐co‐tetramethylene oxalate) copolymer

Experimentally synthesized poly(1,4‐butylene terephthalate‐co‐tetramethylene oxalate) (PBT–PTMO) monofilaments were evaluated for hydrolytic stability in salt water (SW) and distilled water (DW) at temperature below and above glass transition temperature (T_g), along with commercially available poly(hexamethylene adipamide) (NY), poly(ethylene terephthalate) (PET), and polypropylene (PP) monofilaments. There was no decrease in mechanical properties in case of NY, PET, and PP in either DW or SW below their T_g. The breaking strength, ultimate elongation, and thermal shrinkage of the PBT–PTMO, however, decreased as the ageing time increased. Total strength loss occurred after approximately 300 days at 25°C in either DW and SW. This can be attributed to the chain scission that occurs in the PBT–PTMO copolymer chain. The poor hydrolytic stability of the PBT–PTMO may be attributed to the higher moisture regain. The salinity of water did not have a significant effect on the breaking strength loss of the materials. The mode of hydrolytic degradation of aged PBT–PTMO polymer was confirmed by the increasing generation of the acid carbonyl and hydroxyl groups with concomitant increasing consumption of ester groups, regardless of ageing conditions. Above T_g, the hydrolytic rate constant (k^′_H, day⁻¹) of the PBT–PTMO, estimated by the rate of formation of acid carbonyl groups, is greater at a higher ageing temperature. © 1999 John Wiley & Sons, Inc. J Appl Polym Sci 74: 921–936, 1999     

Dye distribution in the dyeing of mixed denier polyester fabrics

Microfibre polyester is sometimes blended with higher denier fibres to achieve good aesthetic effects at lower cost. Two polyester yarns of 1.4 and 0.7 denier were dyed singly and together with a range of depths of CI Disperse Blue 79, and the dye distribution over the course of the dyeings was examined. The uptake is initially greater on the microfibre, but as dyeing is continued the distribution becomes more even, and eventually the same concentration of dye is present on both fibres. Based on the common observation that a given concentration of dye produces a lighter shade on a microfibre, the redistribution of dye during the process causes a continuing shade change even though the bath exhaustion is constant. A mixture of three dyes produced a stable hue on a fabric of 1.0 denier polyester after 20 min at a fixed dyeing temperature, but when dyed on a fabric of 1.0 and 0.5 denier yarns, a change in hue continued for more than 60 min.     

Efficient data synchronization method on integrated computing environment

The Journal of Supercomputing - To execute scientific applications and simulations of enormous scale, the computing paradigm is evolving into one of cluster computing and cloud computing that can...     

A framework for elastic QoS provisioning in the cdma2000 1/spl times/EV-DV packet core network

With the fast proliferation of QoS-enabled wireless packet networks, the need for effective QoS control is increasing. In this article, we focus on QoS provisioning in the cdma2000 1/spl times/ evolution for high-speed integrated data and voice (1/spl times/EV-DV) packet core network. We investigate a dynamic bandwidth provisioning method that is able to increase a service provider's revenue. It is achieved by releasing unutilized bandwidth for use by other profitable services. The proposed method is implemented as an SNMP-compliant management information base and deployed at the packet data serving node. The experiments conducted on the LG Telecom 1/spl times/EV-DV testbed show that the method can increase the bandwidth for the conversational class and guarantee adequate service quality for the background class as well.     

Development of prox (preferential oxidation of CO) system for 1 kWe PEMFC

PROX is known as one of the most promising technologies which prevent the anode of PEMFC from being poisoned by carbon monoxide. Hence, commercialization of the PEMFC system is highly dependent on the development of the corresponding PROX system. This study is focused on the development of the PROX system for 1 kW_e PEMFC, and the results can be used to predict the performance of a higher-scaled system. Pt-Ru/Al₂O₃ catalyst made by incipient wetness method has been used for the reaction, since this catalyst shows high activity and selectivity for CO oxidation over a wide range of temperature. With the catalyst, a 1 kW_e proto-type PROX system was set up and its performance was evaluated for the steady state as well as the transient conditions. The outlet CO con-centration of the system was below 10 ppm at its steady state. Also, even at transient conditions, in which sudden flow rate change occurred, the resulting CO concentration still remained under 10 ppm. This paper is dedicated to Professor Wha Young Lee on the occasion of his retirement from Seoul National University     

8 Gb 3-D DDR3 DRAM Using Through-Silicon-Via Technology

An 8 Gb 4-stack 3-D DDR3 DRAM with through-Si-via is presented which overcomes the limits of conventional modules. A master-slave architecture is proposed which decreases the standby and active power by 50 and 25%, respectively. It also increases the I/O speed to > 1600 Mb/s for 4 rank/module and 2 module/channel case since the master isolates all chip I/O loadings from the channel. Statistical analysis shows that the proposed TSV check and repair scheme can increase the assembly yield up to 98%. By providing extra VDD/VSS edge pads, power noise is reduced to < 100 mV even if all 4 ranks are refreshed every clock cycle consecutively.     

Inactivation of Clostridium sporogenes spores on stainless-steel using heat and an organic acidic chemical agent

The efficacy of a food grade acidic chemical agent for the reduction of Clostridium sporogenes spores on a stainless steel surface was investigated. The chemical agent was a combination of selected fatty acids and lactate esters. Distilled deionized water and 35% hydrogen peroxide were used as negative and positive controls, respectively. Approximately 3 log cfu reductions in viable spore numbers were detected on the steel surfaces for all treatments at room temperature, except the controls. Reductions in the viable spore numbers significantly increased with increasing exposure times and concentrations of the acidic agent. Five log reduction of viable spore number was achieved after 10 min treatment with the 10% agent solution at 68 °C. No viable spores were observed on the 10% agent treated sample after a 60 min exposure time at 75 °C. This research showed that the acidic sanitizer tested in this study could be used to reduce the number of C. sporogenes spores on stainless steel surfaces.