Establishment time of liquid flow in a bath agitated by bottom gas injection

The establishment time of gas-liquid two-phase flows in a cylindrical bath agitated by bottom gas injection through a central single-hole bottom nozzle was investigated. Because the turbulence intensity in the bath was comparable to or larger than the unity, the conventional definition of the flow establishment time based on the history of mean velocity was not suitable for the present case. In fact, it was difficult to determine the flow establishment time based on the well-known 90 or 99 pct criterion for the mean velocity. Accordingly, two methods of determining the flow establishment time by focusing on the turbulence components instead of the mean velocity components were proposed. Velocity measurements were made with a two-channel laser Doppler velocimeter. The flow establishment time was correlated as a function of gas flow rate. Close agreement was obtained by the two methods.     

Changes in Aging Behavior and Defect Structure of Yttria-Fully-Stabilized ZrO2 with Sc2O3 Doping

Methods of suppressing decreased conductivity in 8 mol% Y₂O₃-stabilized–92 mol% ZrO₂ (8YSZ) with aging were investigated. Different amounts of Sc₂O₃ were doped into 8YSZ. The electrochemical properties of Sc₂O₃-doped 8YSZ were measured, and the microstructural and local structural changes were characterized. The present results indicate that an appropriate amount of Sc₂O₃ doping, 3 or 4 mol%, effectively suppresses decreased conductivity with aging in 8YSZ.     

Topology optimization for fluid–thermal interaction problems under constant input power

This paper deals with density-based topology optimization considering fluid and thermal interactions, in which the Navier–Stokes and heat transport equations are coupled. We particularly focus on designing heat exchangers. In the engineering context, heat exchangers are designed while considering a certain amount of input power. Therefore it is important to maximize the performance of a heat exchanger under a constant input power. In this paper we propose a way to control the input power by introducing an extra integral equation. To be more precise, in the fluid analysis, the inlet pressure is determined by solving the extra integral equation together with the Navier–Stokes equation. By doing this we can keep the inlet power constant even when the flow channels are changed in the optimization process. Consequently, the system of equations of the fluid field takes an integrodifferential form. On the other hand, in the heat transport analysis, a single governing equation is defined for simultaneously modeling both the solid and fluid parts. The design variable is a fluid fraction whose distribution represents the topology of the solid and fluid domains. When designing heat exchangers, two different heat conditions are considered in the formulation of the optimization problems, namely temperature-dependent and temperature-independent heat sources. Through the numerical examples for designing flow channels in a heat exchanger, it is shown that distinct topologies can be obtained according to the input power and the heat source conditions.     

Triglyceride analysis by combined argentation/nonaqueous reversed phase high performance liquid chromatography

Full analysis of triglycerides of natural fats and oils has been investigated by the combination of argentation high performance liquid chromatography (HPLC) with nonaqueous reversed phase (NARP) HPLC. An infrared detector was used in argentation HPLC, because it indicated molar responsibility to all triglycerides. After peak trapping with argentation HPLC, each triglyceride fraction was analyzed with NARP chromatography using the glyceride-selective post-column reactor detector. The results of the analyses of triglycerides of palm oil and cocoa butter by the proposed method agreed well with those reported earlier.     

Fabrication of nanoscale tungsten tip arrays for scanning probemicroscopy-based devices

A new fabrication process for nanoscale tungsten tip arrays was developed for scanning probe microscopy-based devices. It is suitable to make a huge array on a device chip and is potentially compatible with CMOS technology. In this study, tungsten was selected as a tip material because of its hardness and conductivity. The newly developed fabrication process mainly consists of several important techniques: a combination of optical lithography and electron beam (EB) lithography to reduce the total exposure time with high resolution and chromium/tungsten/chromium (Cr/W/Cr) sandwich deposition and etching in which the first chromium layer is used as a mask and a second one is used as an etch stop. A periodic array of dots in an EB resist with a spot diameter of less than 50 nm was obtained by a combination of optical lithography and EB lithography with a positive resist (polymethylmethacrylate) in which all processing conditions were optimized carefully. A thin and uniform chromium film, deposited by ion-beam sputtering, allowed the use of thin polymethylmethacrylate (PMMA) film which led to the high resolution. The conditions of dc magnetron sputtering were also optimized in order to deposit a densely packed and low-resistivity film. The resulting tungsten tip arrays had a cylindrical shape with diameters of less than 60 nm and heights of 300 nm     

Effect of CNTs on Activation Volume and Mobile Dislocation Exhaustion Rate of CNTs/Al under Compression Loading

In this study, stress relaxation compression tests were performed to investigate the strain rate sensitivity, activation volume and mobile dislocations in carbon nanotubes/aluminum (CNTs/Al) composites. The results reveal that, with the addition of CNTs, the strain rate sensitivity of CNTs/Al increased. Meanwhile, a smaller V^* of CNTs/Al compared with pure Al was attributed mainly to the CNT-Al interfaces and partly to the increased forest dislocations cutting activities in grain interior, which was related to the tendency of short ranges order formation during plastic deformation. The incorporation of CNTs also improved the dislocation storage capability and reduced the dislocation velocity, leading to a lower mobile dislocation exhaustion rate.     

Effects of fermentation conditions and soybean peptide supplementation on hyaluronic acid production by Streptococcus thermophilus strain YIT 2084 in milk

To increase the hyaluronic acid (HA) yield from Streptococcus thermophilus YIT 2084, fermentation conditions (pH, temperature, agitation, aeration) were optimized in milk-based medium, and the effects of supplemental soybean peptides, which have different molecular weight distributions, were determined. HA production was enhanced to approximately 100 mg/l at pH 6.8 and 33–40 °C. Agitation speed and aeration rate slightly affected HA production. Soybean peptides including those of high molecular weight (approximately 27 to 130 kDa) further increased HA production to 208 mg/l under the optimal condition (pH 6.8, 35 °C, 100 rpm), which was 20-fold greater than non-optimal condition. HA production was no longer related to the specific growth rate. The HA produced under the optimal condition included a large amount of high-molecular-weight fraction of 100 to 2000 kDa, compared with under the basal condition without optimization.     

Molecular structures of gellan gum imaged with atomic force microscopy (AFM) in relation to the rheological behavior in aqueous systems in the presence of sodium chloride

Aqueous solutions of gellan gum with comparable molecular mass but with different acyl contents were investigated by atomic force microscopy and rheological measurements in the presence of sodium chloride (NaCl). Results obtained were discussed in relation to our previous report using potassium chloride (KCl) as an added salt. For a low-acyl sample, continuous fibrous network structures were identified microscopically as in the case of KCl. The network structures were more heterogeneous than those formed with KCl in terms of the height distribution of molecular assemblies. Rheological thermal hysteresis between sol–gel transitions was detected as in the case of KCl. The storage modulus (G′) of the gelled system was ca. 15% of the corresponding data with KCl at 20 °C. For a high-acyl sample, no continuous network structures were identified but branches with observable ends were identified as in the case of KCl. The hysteresis was less evident than the corresponding data with KCl and for the low-acyl sample with NaCl. Also, G′ values at 20 °C were ca. 30% and 20% of the corresponding data with KCl and for the low-acyl sample with NaCl, respectively. Continuousness and homogeneity of network structures related to the hysteresis and elasticity of the system, respectively.     

High-reliability, high-performance RF micromachined switch using liquid metal

Existing mechanical relays have reliability-related issues including unstable contact resistance and limited cycle life. These problems are caused by mechanical fatigue and wearing of the contact surfaces. In the liquid metal micro switch (LiMMS), we employ a liquid-liquid contact to address these issues. The switching operation is achieved by forming a gap in the liquid metal using gas expansion. Our prototype has a microchannel on a glass substrate to hold a tiny amount of mercury, 0.15 mm in width and 0.1 mm in height, and TaN thin-film heaters on a ceramic substrate to expand the operating gas by heating. The substrates are bonded together and the total size of the device is 5/spl times/5/spl times/1.4 mm. We successfully demonstrated 70-m/spl Omega/ on-resistance, 1 ms-switching speed, the ability to handle up to 1 A of dc current and over 1/spl times/10/sup 8/ cycle operation. LiMMS also has good RF performance, better than 1 dB insertion loss, and better than 20 dB isolation up to 18 GHz.     

Evaluation of MRCP compared to ERCP in the diagnosis of biliary and pancreatic duct

Recently, Magnetic Resonance Cholangiopancreatography (MRCP) is developed as a noninvasive diagnostic modality in the diagnosis of biliary and pancreatic tract. Using Endoscopic Retrograde Cholangiopancreatography (ERCP) as the gold standard, we evaluated the diagnostic quality of MRCP and direct cholangiography. Fifty-six patients (9 cases of cholangiocarcinoma, 5 of gallbladder carcinoma, 1 of gallbladder carcinoma and anomalous arrangement of pancreaticobiliary ductal system, 4 of cholecystlithiasis, 3 of papillary carcinoma, 1 of adenomyomatosis of the gallbladder, 1 of primary sclerosing cholangitis, 1 of hepatolithiasis and postoperative bile duct stricture, 4 of mucin producing pancreatic tumor, 13 of pancreatic carcinoma, 1 of chronic pancreatitis and pancreas divisum, 9 of chronic pancreatitis, and 1 of chronic pancreatitis and biliary stricture) are studied prospectively with MRCP and direct cholangiography (included ERCP and percutaneous transhepatic cholangiography). The image of MRCP accorded with direct cholangiography in twenty-two of 27 patients with biliary tract disease, and in sixteen of 29 patients with pancreatic disease. The different diagnosis is observed in ten of 56 patients. In cases of not visualized gallbladder, pancreatic cyst without communicated to the pancreatic duct, and pre-stenotic dilatation of biliary and pancreatic duct, the image of MRCP was better than that of ERCP. However, the image of MRCP for the diagnosis of either benign or malignant strictures, mucin producing pancreatic tumor, and a branch of pancreatic duct in patients with pancreatic carcinoma were not suitable for evaluation than that of ERCP. In our study, ERCP is superior to MRCP due to the important information for diagnosis such as mentioned above. Therefore we advocate using ERCP as the first diagnostic tool in the diagnosis of biliary and pancreatic duct.