Unsteady flow generator for gases using an isothermal chamber

We propose a chamber called an ‘isothermal chamber’ that can produce almost isothermal conditions due to its large heat transfer area obtained by filling it with steel wool. Using this chamber, a simple method to measure flow rates of ideal gases has been developed. In this paper, we propose an unsteady flow generator for gases using the isothermal chamber that can be useful for measuring the dynamic characteristics of gaseous flow meters. The mass flow rate is generated by controlling the pressure change during air discharge in the isothermal chamber using a servo valve. Steady and unsteady oscillatory flow is generated with the generator, and the effectiveness of the generator is demonstrated.     

Organization and expression of basement membrane collagen IV genes and their roles in human disorders

PURPOSE: The prevalence of reflux in the deep and superficial venous systems in the Edinburgh population and the relationship between patterns of reflux and the presence of venous disease on clinical examination were studied. METHODS: A cross-sectional survey was done on men and women ranging in age from 18 to 64 years, randomly selected from 12 general practices. The presence of varicose veins and chronic venous insufficiency was noted on clinical examination, as was the duration of venous reflux by means of duplex scanning in 8 vein segments on each leg. Results were compared using cut-off points for reflux duration (RD) of 0.5 seconds or more (RD >/= 0.5) and more than 1.0 second (RD > 1.0) to define reflux. RESULTS: There were 1566 study participants, 867 women and 699 men. The prevalence of reflux was similar in the right and left legs. The proportion of participants with reflux was highest in the lower thigh long saphenous vein (LSV) segment (18.6% in the right leg and 17.5% in the left leg for RD >/= 0.5), followed by the above knee popliteal segments (12.3% in the right leg and 11.0% in the left leg for RD >/= 0.5), the below knee popliteal (11.3% in the right leg and 9.5% in the left leg for RD >/= 0.5), upper LSV (10.0% in the right leg and 10.8% in the left leg for RD >/= 0.5) segments, the common femoral vein segments (7.8% in the right leg and 8.0% in the left leg for RD >/= 0.5), the lower superficial femoral vein (SFV) segments (6.6% in the right leg and 6.4% in the left leg for RD >/= 0.5), and the upper SFV (5.2% in the right leg and 4.7% in the left leg for RD >/= 0.5) and short saphenous vein (SSV) (4.6% in the right leg and 5.6% in the left leg for an RD >/= 0.5) segments. In the superficial vein segments, there was little difference in the occurrence of reflux whether RD >/= 0.5 or RD > 1.0 was used; but in the different deep vein segments, the prevalence of reflux was 2 to 4 times greater for RD >/= 0.5 rather than RD > 1.0. Men had a higher prevalence of reflux in the deep vein segments than women, reaching statistical significance (P /= 0.5. In general, the prevalence of reflux increased with age. Those with "venous disease" had a significantly higher prevalence of reflux in all vein segments than those with "no disease" (P 相似文献   

Dispersion Behavior of ZrB2 Powder in Aqueous Solution

Dispersion conditions of ZrB₂ powder in water were investigated using poly(ethyleneimine) (PEI) as a dispersant. Pulverization of ZrB₂ powder to submicrometer size was difficult and a substantial amount of large particles remained after an intensive planatery milling for 72 h. The isoelectric point (IEP) of ZrB₂ powder was measured to be pH 5.8 by electrophoresis, which shifted to pH 6.2 after milling. The application of PEI changed the IEP of the boride slurry to ∼pH 11. Well-dispersed aqueous ZrB₂ slurries with a high solid loading (up to 45 vol%) were fabricated at pH 6.5–7.5 by the application of 1.5 wt% PEI.     

Analysis of heavy metal pollution in soil using transversely excited atmospheric CO2 laser-induced plasma by trapping the soil in microstructured holes on metal subtargets

A unique technique for direct analysis of soil samples utilizing a special advantage of a transversely excited atmospheric (TEA) CO(2) laser-induced plasma generated at atmospheric pressure on a metal target has been developed. In this technique, a metal subtarget, such as nickel plate, structured with intentional microholes on its surface, each with dimensions of around 100 microm in diameter and depth, was used to selectively trap small sized soil particles by immersing the metal plate subtarget into the polluted soil sample. The trapped small soil particles on the metal subtarget were irradiated by a TEA CO(2) laser (10.6 microm, 1.5 J, 200 ns) at atmospheric pressure under defocused condition with a spot size of 3 mm x 3 mm. This trapping and confining scheme substantially suppresses the blowing off effect; thus, the trapped soil particles can effectively be dissociated and atomized in the microstructured holes. Using this method of a microstructured metal plate subtarget, quantitative analysis was carried out on loam soil samples polluted by Pb. A linear calibration curve was obtained with a detection limit of approximately 50 mg/kg. Preliminary quantitative studies were carried out for a quartz sand sample containing Cr and Hg, resulting in linear calibration curves with detection limits of approximately 25 mg/kg and 10 mg/kg, respectively, at this stage. This technique is promising as a potential field screening tool for soil analysis.     

Characterization of chip scale packaging materials

The mechanical stability of Chip Scale Packages (CSP) used in surface mount technology is of primary concern. The dominant issues are package warpage and solder fatigue in solder joints under cyclic loads. To address these issues, molding compound and die attach film were characterized with finite element method which employed a viscoelastic and viscoplastic constitutive model. The model was verified with experiments on package warpage, PCB warpage and solder joint reliability. After the correlation was observed, the effect of molding compound and die attach film on package warpage and solder joint reliability was investigated. It was found that package warpage tremendously affected solder joint reliability. Furthermore, a die attach film was developed based on results of the modeling. CSP with the developed die attach film are robust and capable of withstanding the thermal stresses, humidity and high temperatures encountered in typical package assembly and die attach processes. Also, a lead free solder is discussed based on the results of creep testing. This paper presents the viscoelastic and viscoplastic constitutive model and its verification, the optimum material properties, the experimental and simulated reliability and performance results of the u*BGA packages, and the lead free solder creep.     

Investigation of dynamic polarization stability of 850-nmGaAs-based vertical-cavity surface-emitting lasers grown on (311)B and(100) substrates

The polarization stability of 850-nm GaAs-based vertical-cavity surface-emitting lasers (VCSELs) under dynamic operation was investigated by comparing the characteristics of VCSELs grown on (311)B and (100) GaAs substrates. Significantly larger suppression ratios of the two orthogonal polarization modes was obtained for VCSELs on (311)B substrates than those on (100) substrates under zero-bias modulation. Time-dependent orthogonal polarization suppression ratio measurements also showed that the polarization direction was more stable in the VCSEL on (311)B substrates than that on (100) substrates. Error-free transmission was realized from VCSELs on (311)B substrates with and without a polarizer in both back-to-back and 100-m multimode fiber transmission     

Interface characterization of duplex metal-coated SiC fiber-reinforced Ti-15-3 matrix composites

The interfacial reaction behavior of duplex metal (Cu/Mo and Cu/W)-coated SiC (SCS-6) fiber-reinforced Ti-15-3 composites, before and after thermal exposure, has been studied. The effect of thermal exposure on the shear sliding resistance of these composites was also obtained using a thin-specimen push-out test. The results are compared to those of an original SiC (SCS-6) fiber-reinforced Ti-15-3 composite. The interfacial reaction behavior is strongly affected by the existence of a coating layer. Both the Cu/Mo and Cu/W coating layers prevent the growth of a reaction layer. However, the coatings could not effectively prevent diffusion of alloying elements; only the W layer exists after the thermal exposure. On the other hand, the interface shear sliding stress minimally depends on the duplex metal coating layers prior to the thermal exposure, and this sliding stress in both the SiC/Cu/Mo/Ti-15-3 and SiC/Cu/W/Ti-15-3 composites decreases slightly relative to that in the SiC/Ti-15-3 composite. After thermal exposure, the interface shear sliding stress increases for the SiC/Ti-15-3 composite. In distinction, the interface shear sliding stress significantly decreases after thermal exposure in both the SiC/Cu/Mo/Ti-15-3 and SiC/Cu/W/Ti-15-3 composites. Theses behaviors are attributed to the decrease of radial clamping stress, which originates from a volume expansion associated with the β → α phase transformation.     

Observation of fatigue damage process in SiC fiber-reinforced Ti-15-3 composite at high temperature

Unnotched SiC (SCS-6) fiber-reinforced Ti-15-3 alloy composite is subjected to a tension-tension fatigue test in a vacuum of 2×10⁻³ Pa at 293 and 823 K with a frequency of 2 Hz and R=0.1. Direct observation of the damage evolution process during the test is carried out by scanning electron microscopy (SEM). Test temperature dependent and independent fatigue damage behaviors are observed. The early stage fiber fractures observed at the polished surface are not influenced by the test temperature; however, matrix crack initiation and propagation behaviors differ greatly with temperature. The evolution of interface wear damage also differs with temperature, becoming more severe at 823 K, and the interface wear damage zone increases with the increase of the number of fatigue cycles. The macroscopic fatigue damage appears as a modulus reduction associated with interface sliding, matrix crack propagation, and plastic deformation of the matrix. The deformation zone of the composite tested at 823 K spreads more than that at 293 K. The fatigue life of the composite tested at 823 K is longer than that at 293 K. This behavior is related to the difference in spread of the damage zone in the matrix.