Effect of algal extracellular polymer substances on UF membrane fouling

Low-pressure membrane processes, such as ultrafiltration (UF), are effective for treating algae-laden eutrophic source waters. However, fouling caused by algae excreted organics can be a major obstacle to the smooth operation of membrane processes. In this study, three algae species, with a similar cell size and shape, but a different amount of extracellular polymeric substances (EPS), were selected. The characteristics of the bound EPS, including its amount and constituents, mainly polysaccharide and protein, were analyzed. Cell suspensions were filtered through a dead-end stirred cell with a regenerated cellulose UF membrane. Based on the observations of permeate flux decline at higher transmembrane pressure (TMP) and critical flux values, it can be concluded that algae cell EPS do affect membrane fouling, and the constituents of EPS may also play a role.     

The preparation of PLZT ceramics from a sol-gel process

Sol-gel process is employed to prepare PLZT ceramic with the composition 9/56/44 (La/Zr/Ti). Complete crystallization of the sol-gel derived powders is achieved after 600°, 1 hr. calcination. The sintered density of the PLZT pellet decreases as the sintering time increases. A ninety-nine percent theoretical density is obtained for samples sintered at 1250° for one hour. The dielectric properties and optical transmission of the sol-gel derived samples are measured and compared with those of the hot-pressed PLZT ceramics reported in the literature. Sol-gel derived powders, when properly sintered, possess sufficient optical transparency for optoelectrical device applications.     

Thermal and electrical stability of ZnO varistors with glass additives

Glasses in the PbO-B₂O₃-Al₂O₃-BaO-CaO-SiO₂ system were employed as the dopant to ZnO varistors. The thermal stability of the varistor is enhanced with glass additives. The temperature coefficient of threshold field for the sample doped with 1 w/o glass (65 w/o PbO - 23 w/o B₂O₃ - 12 w/o SiO₂) is 1 × 10^-4/K as compared to 3.3 × 10^-3/K for that of the undoped sample. The change in the temperature dependence of the field-current density characteristics is more related to the barrier height change than the refractory behavior of the glass employed. Heat treatment is very effective in recovering the degraded samples by providing the activation energy for the diffusion of Zn interstitials. The experimental results can be explained with a Schottky barrier model.     

Grinding characteristics of diamond film using composite electro-plating in-process sharpening method

To finish a chemical vapor deposition (CVD) diamond film surface, composite electro-plating is introduced during the grinding process to sharpen the grinder, a method named as composite electro-plating in-process sharpening (CEPIS). In the grinding process, the grinder for the cathode and the nickel plate for the anode are connected to a DC power supply and immersed in an electrolyte solution containing diamond particles of 10 μm in size so that metal ions with diamond particles are deposited onto the grinder in process to expose fresh sharp grains. Results show that the removal rate of the diamond film increases with increasing current density. The removal rate of the diamond film at a current density of 7.5 ASD is 3.8 times higher than at 0 ASD as in the traditional grinding method. Based on the experimental results of the observations of the coated surface of the grinder and the variations in the coating thickness, a sharpening mechanism for the CEPIS method is deduced. This mechanism allows the coating thickness of the grinder to be increased with grinding time using the CEPIS method. The higher removal capability is achieved due to the higher active grit density.     

Code-pattern insensitive embedded ROMs using dynamic bitline shielding technique

A dynamic bitline shielding (DBS) technique is proposed for high-speed via-programming ROMs, to eliminate code-pattern-dependent crosstalk-induced read failure (CIRF) and increase code-pattern coverage. Fabricated 256 Kb conventional and DBS ROMs demonstrated that the DBS technique can eliminate the CIRF and operate with a small sensing margin.     

Experimental study on temperature distributions within the workpiece during friction stir welding of aluminum alloys

This study aims to experimentally explore the thermal histories and temperature distributions in a workpiece during a friction stir welding (FSW) process involving the butt joining of aluminum 6061-T6. Different types of thermocouple layout are devised to measure the temperature histories during FSW at different locations on the workpiece in the welding direction. Successful welding processes are achieved by appropriately controlling the maximum temperatures during the welding process. Regression analyses by the least squares method are used to predict the temperatures at the joint line. A second-order polynomial curve is found to best fit the experimental temperature values in the width direction of the workpiece. The Vickers hardness test is conducted on the welds to evaluate the hardness distribution in the thermal-mechanical affected zone, the heat affected zone, and the base metal zone. Tensile tests are also carried out, and the tensile strength of the welded product is compared with that of the base metal.     

BCB-bridged distributed wideband SPST switch using 0.25-/spl mu/m In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As metamorphic HEMTs

In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As metamorphic high-electron mobility transistor (mHEMT) dc-30 GHz distributed single-pole-single through (SPST) switches were designed and fabricated using the low-/spl kappa/ benzocyclobutene (BCB) bridged technology. The current gain cutoff frequency, and the electron transit time of In/sub 0.5/Al/sub 0.5/As--In/sub 0.5/Ga/sub 0.5/As mHEMTs have been investigated. By analyzing the extrinsic total delay time, the effective velocity of electrons can be estimated, and the average velocity is 2.3/spl times/10/sup 7/cm/s. The dc-30 GHz distributed wideband SPST switch exhibits an insertion loss of less than 5.5 dB, and an isolation larger than 30 dB, which is the first demonstration of the high-isolation of InAlAs-InGaAs mHEMTs monolithic switch. As to the power performance, this switch can handle the power up to 12 dBm at 2.4 GHz. After over 250 h of 85-85 (temperature =85/spl deg/C, humidity =85%) environmental evaluation, this BCB passivated and bridged microwave and monolithic integrated circuit switch demonstrates reliable RF characteristics without any significant performance change, which proves that this process using the low-/spl kappa/ BCB layer is attractive for millimeter-wave circuit applications.