Development of Skutterudite Thermoelectric Materials and Modules

Multifilling with La, Ba, Ga, and Ti in p-type skutterudite and Yb, Ca, Al, Ga, and In in n-type skutterudite remarkably reduces their thermal conductivity, resulting in enhancement of their dimensionless figure of merit ZT to ZT?=?0.75 for p-type (La,Ba,Ga,Ti)₁(Fe,Co)₄Sb₁₂ and ZT?=?1.0 for n-type (Yb,Ca,Al,Ga,In)_0.7(Co,Fe)₄Sb₁₂. A thermoelectric module technology suitable for these skutterudites including diffusion barrier and electrode materials has been established. The diffusion barrier materials allow the electrode to coexist stably with the p/n skutterudites in the module??s working temperature range of room temperature to 600°C. Under conditions of hot/cold-side temperatures of 600°C/50°C, a skutterudite module with size of 50?mm?×?50?mm?×?7.6?mm exhibited generation performance of 32?W power output and 8% thermoelectric conversion efficiency.     

Effect of cooling procedure after annealing on electrical properties of Cd0.2Hg0.8Te epitaxial films grown by liquid phase epitaxy

Effect of cooling procedure after annealing on the electrical properties of Cd_0.2Hg_0.8Te (CMT) epitaxial films grown by liquid phase epitaxy has been investigated to obtain the CMT films with low carrier concentration of 10¹⁴ cm⁻³ reproducibly. Annealing has been performed at the temperature range from 260 to 350°C for 8 h in a fixed Hg vapor pressure. The quenching and the gradual cooling over a duration of 200 min after annealing have been employed for the cooling procedures. For quenched CMT samples, hole concentration decreases with decreasing anneal temperature and conduction type conversion from p to n is observed at 300°C. For the gradual cooling, all samples show n-type conduction for all annealing temperatures. Electrical properties of annealed layers strongly depend on the cooling procedure. The difference in electrical properties of the annealed CMT between two types of cooling procedure is mainly attributed to the difference in the annihilation of Hg vacancies during cooling procedure. The decrease of Hg vacancies during quenching is negligible, while Hg vacancies are annihilated during gradual cooling by rapid Hg diffusion. The diffusion coefficient of Hg is estimated more than 10⁻⁹ cm²/s and this value is two orders of magnitude larger than that obtained by radiotracer technique.     

Isotropic conductive adhesives with fusible filler particles

A new low-temperature assembly process using a new class of isotropic conductive adhesives (ICAs) with fusible filler particles was proposed to realize a low-temperature, fluxless and cost-effective, alternative, solder flip-chip interconnection technology. New ICA formulations were developed using two different resin materials and fusible filler particles. The curing behavior of the resin materials and the melting of the fusible filler were observed by differential scanning calorimetry (DSC). The coalescence and wetting states, the size distribution of the fusible fillers, and the formation of the conduction path in each ICA formulation were observed with a laser microscope. It was found that two different types of electrical conductive paths, necking type and bump type, were produced. The bump-type conductive path was more effective than that of the necking type in achieving a lower electrical resistance through resistance measurement. The reduction capability of the base resin material was effective for the coalescence and the wetting of the fusible fillers and affected the conductive path type. A good metallurgical connection was formed between the fusible fillers in ICAs and between the fusible fillers and the copper surface even at the lower filler-volume fraction of 30%.     

Power-Generation Performance and Durability of a Skutterudite Thermoelectric Generator

By using a p-type (La, Ba, Ga, Ti)₁(Fe, Co)₄Sb₁₂ skutterudite with a dimensionless figure of merit, ZT, = 0.75 at 500°C and an n-type (Yb, Ca, Al, Ga, In)_0.7(Co, Fe)₄Sb₁₂ skutterudite with ZT = 1.0 at 500°C, we fabricated a thermoelectric power-generation module capable of working at high temperatures (up to 600°C). When its hot and cold sides were at 600°C and 30°C, respectively, the power output of a 50 mm × 50 mm × 7.6 mm skutterudite module was 34 W and its thermoelectric conversion efficiency was 8%. In a durability test with the module’s hot and cold sides continuously maintained at 600°C and 80°C, respectively, for 8000 h, power generation first decreased by approximately 6% in the initial 300 h then remained constant.     

Extended selection of switching target faults in CONT algorithm for test generation

We describe an extended selection of switching target faults in the CONT algorithm. The main difficulty in test generation is the conflict that arises in the process of determining the signal values due to reconvergent fanouts. Conventional approaches for test generation change a signal value, which causes conflicts to another possible choice for backtracking. In the CONT algorithm, a strategy of switching target fault was proposed as a new backtracking mechanism. In this method, the target fault is switched to a new target fault instead of making an alternative assignment on the primary input value when a conflict occurs. A disadvantage of the CONT algorithm is that unjustified lines exist in the process of test generation. These unjustified lines make the procedure of switching targets complicated and restrict the possible choice in selecting the new target fault. In the new version of CONT, called CONT-2, we have removed the unjustified lines in the process of test generation and have extended to two target-fault types for switching targets. Implementing CONT-2 by a Fortran program, ISCAS85 benchmark circuits are examined. Experiments on a combined system with fault simulation followed by CONT-2 are also presented.     

Automated segmentation of acetabulum and femoral head from 3-d CT images

This paper describes several new methods and software for automatic segmentation of the pelvis and the femur, based on clinically obtained multislice computed tomography (CT) data. The hip joint is composed of the acetabulum, cavity of the pelvic bone, and the femoral head. In vivo CT data sets of 60 actual patients were used in the study. The 120 (60 /spl times/ 2) hip joints in the data sets were divided into four groups according to several key features for segmentation. Conventional techniques for classification of bony tissues were first employed to distinguish the pelvis and the femur from other CT tissue images in the hip joint. Automatic techniques were developed to extract the boundary between the acetabulum and the femoral head. An automatic method was built up to manage the segmentation task according to image intensity of bone tissues, size, center, shape of the femoral heads, and other characters. The processing scheme consisted of the following five steps: 1) preprocessing, including resampling 3-D CT data by a modified Sine interpolation to create isotropic volume and to avoid Gibbs ringing, and smoothing the resulting images by a 3-D Gaussian filter; 2) detecting bone tissues from CT images by conventional techniques including histogram-based thresholding and binary morphological operations; 3) estimating initial boundary of the femoral head and the joint space between the acetabulum and the femoral head by a new approach utilizing the constraints of the greater trochanter and the shapes of the femoral head; 4) enhancing the joint space by a Hessian filter; and 5) refining the rough boundary obtained in step 3) by a moving disk technique and the filtered images obtained in step 4). The above method was implemented in a Microsoft Windows software package and the resulting software is freely available on the Internet. The feasibility of this method was tested on the data sets of 60 clinical cases (5000 CT images).     

Novel interconnection method using electrically conductive paste with fusible filler

A new class of electrically conductive adhesives (ECAs) was developed using fusible filler particles. Differential scanning calorimetry (DSC) was used to examine the curing behavior of the base resin material and the melting behavior of the filler particles. The formation of the interconnection before and after the curing process was observed by means of a microfocus x-ray system. The cross-sectional morphology of the electrical conduction path was investigated by optical microscopy. It is believed that the wetting and coalescence behavior of the molten filler particles are the main driving forces leading to the production of the interconnection between the electrodes. In addition, the metallurgical connections both between the particles and between the particles and the copper substrate were observed using scanning electron microscopy and electron probe microanalysis (EPMA).     

The lethal effect of a benzamide derivative, 3-methoxybenzamide, can be suppressed by mutations within a cell division gene, ftsZ, in Bacillus subtilis

3-Methoxybenzamide (3-MBA), which is known to be an inhibitor of ADP-ribosyltransferase, inhibits cell division in Bacillus subtilis, leading to filamentation and eventually lysis of cells. Our genetic analysis of 3-MBA-resistant mutants indicated that the primary target of the drug is the cell division system involving FtsZ function during both vegetative growth and sporulation.     

Anti-inflammatory and analgesic effects of a novel pyrazole derivative, FR140423

The pharmacological profile of a novel and newly discovered non-steroidal anti-inflammatory and analgesic compound, 3-(difluoromethyl)-1-(4-methoxyphenyl)-5-[4-(methylsulfinyl)phenyl]pyraz ole (FR140423), was investigated. In recombinant human cyclooxygenase enzyme assays, the inhibition of prostaglandin E2 formation by FR140423 was 150 times more selective for cyclooxygenase-2 than cyclooxygenase-1. Oral administration of FR140423 dose dependently reduced carrageenin-induced paw edema and adjuvant arthritis. These effects were two- to three-fold more potent than those of indomethacin. Unlike indomethacin, FR140423 did not induce mucosal lesions in the stomach. FR140423 showed dose-dependent anti-hyperalgesic effects in the yeast-induced hyperalgesic model. This effect was five-fold more potent than that of indomethacin. Furthermore, FR140423 increased the pain threshold in non-inflamed paws and, unlike indomethacin, it produced an analgesic effect in the tail-flick test. These analgesic effects were blocked by the mu-opioid antagonist naloxone. These results suggest that FR140423, a selective cyclooxygenase-2 inhibitor, is a potent non-steroidal anti-inflammatory drug (NSAID) without gastrointestinal side effects and is a unique compound having morphine-like analgesic effects.     

Improvement of impact fatigue strength of adhesive joint by CTBN modification

Impact fatigue behaviors of the steel/CTBN-modified adhesive/steel butt joint were investigated. The adhesive butt joint specimens used in the present work were bonded with epoxy–polyamide and CTBN-modified epoxy–polyamide adhesives. Fatigue tests were also conducted under nonimpact stress conditions to compare with the results from the impact fatigue test. The experiments showed that for the joint specimen from the adhesive modified with the CTBN the fatigue strength becomes higher under both of the stress conditions. In particular, the fatigue strength was improved remarkably under impact stress condition, that is, the distinct stress cycles dependence of impact strength was decreased by modifying the adhesive with CTBN. Furthermore, the effect of adhesive thickness on the fatigue strength was also discussed for the adhesive joint modified with CTBN. Under impact stress conditions, the relation between the fatigue strength and the adhesive layer thickness is different from that under the nonimpact one.