Characteristics of hydrogen-fueled gas turbine cycle with intercooler,hydrogen turbine and hydrogen heater

The performances of a hydrogen-fueled gas turbine cycle equipped with an intercooler, regenerator, hydrogen turbine and recuperative hydrogen heater are analyzed. The intercooler is very effective to prevent the condensation and freezing of water vapor in cooling the suction air. The operation of hydrogen turbine in low-temperature range can also be prevented by adopting hydrogen heater. Thermodynamic analysis has revealed that the thermal efficiency and the specific output are considerably improved compared to those of the simple gas turbine cycle.     

Surface Hardening of Carbon Steel Using High Powered YAG Laser

A high powered YAG laser with kaleidoscope for surface modification was applied to the surface hardening of carbon steels containing 0. 18-0.54 wt% C without the absorbents, and the relationships between laser processing and surface hardening were investigated by hardness and microstructure. The structure of the hardened zone underwent complete martensitic transformation in all of the carbon steels tested, and its hardness increased with greater carbon content. Under identical irradiated conditions, the hardened zone expanded with increasing carbon content. A hardened zone extending from the surface to a depth of 1.0 mm was obtained at a laser power of 1.0 kW and a scanning speed of 1 mm/sec. It was found that in the surface hardening of carbon steels, a high powered YAG laser can be used to control the hardened zone by selecting the appropriate irradiation conditions, however, the hardened zone was affected by the assistant gas and the flow rate.     

Molecular valve consisting of poly(acrylic acid) gel

A molecular valve, consisting of poly(acrylic acid) gel-coated Au mesh, was developed based on volume change of the gel in response to cation concentration. The valve closed when concentration of cations such as H⁺, Na⁺, K⁺, Ca²⁺, Cu²⁺, or Al³⁺ was low, whereas opened upon increase in its concentration. The valve re-closed when water was flowed. The concentration where the valve opens was found to increase in the order of Al³⁺, Ca²⁺, and Na⁺ (2 × 10⁻⁴, 5 × 10⁻⁴, and 6 × 10⁻³ M, respectively). The response to Cu²⁺ ion showed similar behaviour, but the opening concentration was ca. 2 × 10⁻⁴ M, which is lower than that of Ca²⁺ ion. The valve appeared to close over the pH range from 3 to 12, whereas to open below and above it. The fastest response time to open the valve (less than 1 min) was obtained for a solution of pH 1–2. The valve showed repeatability at least 25 cycles upon successive loading of a solution of pH 2 and water. Effects of anions and pressure were also studied.     

Al对含P,Mo奥氏体不锈钢应力腐蚀性能的影响

用点焊接试验方法评价了合金元素Ａｌ对含Ｐ和Ｍｏ奥氏体不锈钢应力腐蚀破裂性能的影响。结果表明，单独添加Ａｌ没有改善应力腐蚀破裂性能，而复合添加Ａｌ和Ｃｕ有效地提高了抗应力腐蚀性能。１４Ｃｒ－１６Ｎｉ－２Ｃｕ－３Ａｌ钢中添加Ｍｏ，虽然降低应力腐蚀性能，但影响较小。含０．３％Ｍｏ时应力腐蚀破裂临界温度可达１２０℃。ＡＥＳ分析表明，Ａｌ和Ｃｕ元素在表面膜中富集。Ａｌ和ｃｕ的联合作用使钢表面膜的钝化能力得到加强，从而提高了抗应力腐蚀性能。     

Development of Modified 304 Stainless Steel Resistant to Stress Corrosion Cracking in Chloride Environment

Ｓｔａｉｎｌｅｓｓｓｔｅｅｌｓａｒｅ ｐｒａｃｔｉｃａｌｌｙｕｓｅｄｉｎｎｅｕｔｒａｌｍｅｄｉａｌｗｈｉｃｈｄｏｎ’ｔｉｎｉｔｉａｔｅｓｔｒｅｓｓｃｏｒｒｏｓｉｏｎｃｒａｃｋｉｎｇ(ＳＣＣ)ａｓｌｏｎｇａｓｔｈｅｓｔｅｅｌｓａｒｅｐｒｏｔｅｃｔｅｄｆｒｏｍｌｏｃａｌ ｉｚｅｄｃｏｒｒｏｓｉｏｎ[1] .Ｔｈｅｏｒｉｇｉｎａｌ 30 4ｓｔｅｅｌｃａｎａｖｏｉｄｐｉｔｔｉｎｇｂｕｔｃｒｅｖｉｃｅｃｏｒｒｏｓｉｏｎ .Ｉｆｃｒｅｖｉｃｅｃｏｒｒｏｓｉｏｎｉｓａｖｏｉｄｅｄｂｙａｄｄｉｔｉｏｎａｌａｌｌｏｙｉｎｇｔｏ…     

添加合金元素对奥氏体不锈钢等离子渗氮和渗碳的影响

奥氏体不锈钢众所周知有良好的耐蚀性,但是在工业上没有用于承受摩擦的工件上,因为它的硬度低,摩擦磨损性能差。奥氏体不锈钢经低温等离子体渗氮或渗碳能生成一层特殊的氮化物或碳化物层,称为S相,它具有高的硬度和优良的耐蚀性。这项研究中各种奥氏体不锈钢都经低温等离子体渗氮或渗碳,用各种分析技术研究了添加合金元素对S相特性的影响,用了光学显微镜和电子显微镜观察,做了X射线衍射分析,在5%H2SO4溶液中测量阳极极化,用球对平面摩擦装置做摩擦磨损测试。氮化物或碳化物层厚度随处理温度增加而加厚,AISI316钢上生成的渗层厚度是所有的基体钢材中最厚的。超过临界温度,由于氮化铬工碳化铬沉淀使耐蚀性降低。临界温度由渗氮的基材决定。另一方面,在渗碳层中临界温度不随基材变化。大部分样品上S相层的耐蚀性比没有处理的不锈钢的低。但是,AISI316和JIS-SUS304J3钢在400℃渗碳后都有和未处理钢一样优良的耐蚀性。每种不锈钢经渗氮或渗碳后耐磨性都有明显的改进。     

Effect of ductile fracture criteria on chevron crack formation and evolution in drawing

The purpose of this study is to clarify the mechanics of ductile fracture in bulk metal forming processes by finite-element analysis and experiments. The author has developed a computer program, based on a conventional computer program involving the finite-element method, by which the behavior of crack propagation after ductile fracture can be analyzed. The phenomenon in which a ‘chevron crack’ appears periodically in the axial direction during drawing has been simulated using the developed computer program. Special attention is focused on the effect of various kinds of ductile fracture criteria on chevron crack formation and evolution during drawing. Results obtained are summarized as follows. First, the analytical results obtained using Gurson's fracture criterion and using Oyane's fracture criterion agree well with the experimental result. Second, the analytical results using Cockcroft and Latham's fracture criterion and using Brozzo et al.'s fracture criterion agree somewhat with the experimental result. Finally, the analytical result obtained using Freudenthal's fracture criterion does not agree with the experimental result.     

Effect of 26,26,26,27,27,27-Hexafluoro-1,25-dihydroxyvitamin D3 on the expression of vitamin-D-responsive genes in vitamin-D-deficient mice

26,26,26,27,27,27-Hexafluoro-1,25-dihydroxyvitamin D3 (ST-630) is a newly developed agent to maintain the levels of calcium and phosphorus in blood. Herein, we investigated the effect of this compound on the expression of vitamin-D-responsive genes in vitamin-D-deficient mice. ST-630 was more effective than 1, 25-dihydroxyvitamin D3 [1,25(OH)2D3] with respect to the induction of Cyp24 and calbindin-D9k mRNAs in the kidney and in the small intestine. Moreover, the increase in mRNA levels of vitamin-D-responsive genes induced by ST-630 lasted longer than that induced by 1,25(OH)2D3. These results indicate that ST-630 was more effective in inducing Cyp24 and calbindin-D9k gene expression than 1, 25(OH)2D3 when both compounds were injected into vitamin-D-deficient mice.     

An upper bound method for analysis of three-dimensional deformation in the flat rolling of bars

A new upper bound method for the analysis of three-dimensional deformation in the flat rolling of bars is proposed. In the conventional upper bound method, stress distribution is not calculated. Hence, a new method of calculating stress distribution is proposed in which the hydrostatic stress in each element and the contact stress on the contact surface between material and roll in each element are calculated. In the conventional upper bound method, the structure of the computer program also depends highly on the kinematically admissible velocity fields assumed. Hence, a new method of analysis in which the structure of the computer program depends minimally on the kinematically admissible velocity fields assumed is proposed. In the analysis of strip rolling, the calculated roll force and roll torque agree with the roll force and roll torque calculated from Sims’ slab method. In the analysis of the flat rolling of bars, the calculated width spread agrees with the width spread obtained by experiments reported in the literature. The effects of a reduction in thickness, roll radius, material width-to-height ratio, front tension, back tension, and front and back tensions on the width spread, forward slip, roll force and roll torque are demonstrated. Hence, the validity of the new upper bound method is confirmed.