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321.
We report a development of a portable dewar with a double-stage ADR in it, and its cooling test results. The purpose of this system is to establish a cooling cycle of double-stage adiabatic demagnetization from 4.2 K to 50 mK, which is strongly desired for future space science missions. In our test dewar, two units of ADR are installed in parallel at the bottom of a liquid He tank. We used 600 g of GGG (Gadolinium Gallium Garnet) for the higher temperature stage (4 Tesla) and ∼90 g of CPA (Chromic Potassium Alum) for the lower temperature stage (3 Tesla). A passive gas-gap heat switch (PGGHS) is used between these two stages, while a mechanical heat switch between the He tank and the GGG stage. Using this system, 50 mK was achieved, and various kinds of cooling cycles with different operating temperatures and different sequences of magnetization were tested. We also evaluated the performance of the PGGHS, and interference of the magnetic field with each other during a stable temperature control.  相似文献   
322.
Crevice corrosion of iron was evaluated using the multichannel electrode method in which 10 individual working electrodes (WEs) of pure iron were embedded in resin, placed in an artificial crevice in the range from 0.5 mm to 2.0 mm, and immersed in 0.51 mol dm−3 NaCl solution. The WEs were connected to an electronic circuit which allowed galvanic coupling between them and measurement of their individual coupling current or open circuit potential. Time-transient of the spatial distribution of coupling current and open circuit potential showed sequential transition of the coupling current on WEs at the middle position of the crevice from cathode to anode. The WE near the opening of the crevice initially showed a large anodic current, then a decreasing the anodic current corresponding to the current transition of other WEs, and finally a large cathodic current coupled with the other anodic WEs in the crevice. The transition of coupling current was explained by the change in pH and concentration of dissolved oxygen in the crevice. Thickness of the gap of the artificial crevice affected the transition behavior of coupling current distribution. For example, slower current transition with smaller coupling current was found in the case of a narrower gap. Such properties were related to the introduction and consumption of dissolved oxygen in the crevice solution and the circulation of gap solution from/to the outside of the crevice.  相似文献   
323.
The creep rupture test has been carried out for 18Cr-10Ni-0.1 wt pct C stainless steels bearing individually Ti, Nb(Cb), and V, followed by the microstructural study. The highest value of 700°C-104 h rupture strength in a titanium and niobium series (the steel containing various amounts of titanium and niobium, respectively) has been obtained at Ti/C and Nb/C atomic ratio of 0.8 and 0.2 to 0.4, respectively. On the other hand, in a vanadium series, the creep rupture strength of the steel showed its maximum at V/C atomic ratio of about unity in the testing at the temperature of 700° and 800°C, but at 600°C, the strength increases monotonically with vanadium content up to 1.53 wt pct. Such high strength in the steels con-taining proper amount of Ti, Nb, and V is related mainly with the fine distribution of M23C6 precipitates which is caused by the acceleration of nucleation due to the foregoing precipi-tation of a MC type carbide within the austenite grains. And it has been deduced that the solid solution strengthening effect of the vanadium contributes also to the remarkable in-crease in the rupture strength of the vanadium steel at 600°C.  相似文献   
324.
The dehydrogenation of propane over a silica-supported gallium oxide catalyst was investigated at temperatures ranging from 793 to 853K under atmospheric pressure. The catalyst was found to be moderately active and highly selective to propene in the dehydrogenation of propane. The amount of carbonaceous deposits on the catalyst in the dehydrogenation was around 1/10th of that on a silica-supported chromium oxide catalyst. Lower reaction temperatures and lower concentrations of propane in the feed would be favorable for selective production of propene.  相似文献   
325.
Apatite thin films of calcium phosphate were successfully prepared by rf-magnetron sputtering, followed by postannealing, from calcium phosphate glass targets with Ca/P atomic ratios of 0.6 to 0.75, much lower than the stoichio-metric value of 1.67 for hydroxyapatite. Using targets with low Ca/P ratios of 0.65 to 0.25, tricalcium and pyrocalcium phosphate thin films were obtained. The formation of these calcium phosphates phases was attributed to the phosphorus oxide losses during sputtering. H2O vapor was effective in the formation of the apatite phase at high temperatures; apatite was the exclusive phase in the ambient H2O, even when the target with the low Ca/P ratio of 0.4 was used. Based on phase stability at high temperatures, it was assumed that various kinds of apatites, such as stoichiometric and nonstoichiometric hydroxy- and Ca-deficient hydroxy-apatites were formed, depending on the composition of the glass targets.  相似文献   
326.
Sliding friction and wear experiments and electron microscopy and diffraction studies were conducted to examine the metallurgical microstructure of a metallic glass surface strained in sliding contact. Friction and wear experiments were conducted with aluminium oxide spheres 3.2 and 6.4 mm in diameter sliding, in reciprocating motion, on a metallic foil with a composition of Fe67Co18B14Si1 at a sliding velocity of 1.5 mm s-1 (frictional heating is negligible) with a load of 2.5 N at room temperature and in a laboratory air atmosphere.The results of the investigation indicate that the amorphous alloy (metallic glass) can be crystallized during mechanical contact. Crystallites with a size range of 10–150 nm are produced on the wear surface of the amorphous alloy. A diffused honeycomb-shaped structure formed by dark gray bands is also produced during sliding. Considerable plastic flow occurs on an amorphous alloy surface with sliding and the flow film of the alloy transfers to the aluminium oxide pin surface. Multiple slip bands due to shear deformation are observed on the side of the wear track. Two distinct types of wear debris were observed as a result of sliding: an alloy wear debris and/or powdery and whiskery oxide debris. The wear rate of Fe67Co18B14Si1 was 5 × 10-9 mm3 N-1.  相似文献   
327.
Hydrofluoric and hydrochloric acid solutions and a mixture of them were tested as pickling solutions for AZ91 D Mg alloy before application of stannate coatings. Optical microscopy and energy dispersive X-ray spectroscopy (EDX) of the alloy surface after the pickling process showed that the Mg-rich α phase dissolved preferentially rather than the Al-rich β phase in hydrochloric acid solution. On the other hand, in hydrofluoric acid solution, Mg dissolved in a form of pitting corrosion. Pickling pretreatment with a mixture of these acids at an optimal concentration and an optimal pickling time resulted in relatively uniform dissolution of the alloy surface. The potentiodynamic polarization technique was used to investigate the anodic behavior of the uncoated and coated magnesium alloy in borate buffer solution. The morphology of the coatings was observed using a scanning electron microscope (SEM) before and after corrosion tests. The experimental results showed that coating film density and corrosion resistance of stannate-coated samples prepared with pickling pretreatment were improved compared with those of the coated sample without pickling pretreatment.  相似文献   
328.
In residential applications, an air-to-water CO2 heat pump is used in combination with a domestic hot water storage tank, and the performance of this system is affected significantly not only by instantaneous ambient air and city water temperatures but also by hourly changes of domestic hot water consumption and temperature distribution in the storage tank. In this paper, the performance of a CO2 heat pump water heating system is analyzed by numerical simulation. A simulation model is created based on thermodynamic equations, and the values of model parameters are estimated based on measured data for existing devices. The calculated performance is compared with the measured one, and the simulation model is validated. The system performance is clarified in consideration of seasonal changes of ambient air and city water temperatures.  相似文献   
329.
Many chemicals that are not structurally related to estrogen have estrogen-like activity. In this study, we tried to apply a quail embryo culture system for assessing the in vivo effects of such chemicals on the development of quail embryos. Beta-estradiol induced feminization of the gonads of genetically male embryos, which was confirmed by the increase in the size of the left gonad and female-specific aromatase expression, while male-specific SOX9 expression was not affected. Nonylphenol, which has a weak estrogenic activity, reduced the viability and body weight of embryos. Simultaneously, several genetically male embryos were feminized in terms of gonadal size and aromatase expression. These results indicate that the avian embryo culture system was useful for evaluating endocrine disrupters.  相似文献   
330.
The service restoration to sound sections within a short period as much as possible, performed after the permanent fault occurs in a distribution system, is significant for maintaining power supply reliability. This paper proposes an efficient method to find service restoration procedures based on fault searching and the optimal work scheduling of crews, considering the power supply priorities of loads and the probability of occurrence of faults. The proposed method is composed of two-stage problems to reduce the outage sections efficiently: (i) the problem to find a series of searching procedures for unknown fault locations in the first stage and (ii) the optimization problem of work schedules of crews in the second stage. In the first stage, the order of operation of switches opened for searching for the fault direction is determined, constituting the searching tree. After that, the proposed optimization method can efficiently solve the work scheduling problem by formulating it as a mixed-integer linear programming problem in the second stage. The computational experiments using a large-scale distribution system model with many remote and manual switches show that the proposed method can provide efficient service restoration procedures within a reasonable computational time.  相似文献   
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