Electrical resistivity, oxidation resistivity and hardness of single crystal compounds in the Er–Rh–B system

Single crystals of ternary borides ErRh₃B (cubic,Pm3m), ErRh₃B₂ (monoclinic, C2/m) and ErRh₄B₄ (tetragonal, P4₂/nmc) have been grown from copper solution by slow cooling method. The electrical resistivity, oxidation resistivity and Vickers microhardness were studied. The electrical resistivities at room temperature of the (100) face of ErRh₃B, (001) face of ErRh₃B₂ and (100) face of ErRh₄B₄ are 25.6 μΩ·cm, 50.0 μΩ·cm and 106.8 μΩ·cm, respectively. According to thermogravimetric and differential thermal analyses, the oxidation of ErRh₃B, ErRh₃B₂ and ErRh₄B₄ start at 1030°C, 373°C and 690°C, respectively. The weight gain of the same compounds after heating in air up to 1200°C is 0.7%, 15.44% and 5.4%, respectively. The values of the Vickers microhardness for the (100) face of ErRh₃B, the (100) face of ErRh₃B₂ and the (110) face of ErRh₄B₄ are 4.8–5.0 GPa, 10.4–10.9 GPa and 10.9–11.3 GPa, respectively. The effect of boron content and crystal structure of each compound on the electrical resistivity, oxidation resistivity and Vickers microhardness are discussed.     

Deformation behavior and mechanical properties of braided rectangular pipes

The purpose of this study is to clarify the deformation behavior and the relationship between the braiding angle and mechanical properties for the braided rectangular pipe. Three-point bending test was performed for each specimen. Furthermore, the effect of the solid-core bar on the deformation state of the rectangular pipe was studied by finite element method (FEM). Moreover, the effect of the braiding angle on the deformation behavior in detail was investigated. The bending modulus and the bending strength for each specimen were decreased with an increase in the braiding angle. The local deformations occurred at the compression side under loading nose and decreased with an increase in stiffness properties in circumferential direction. From FEM analysis, using the aluminum solid-core bar was effective to restrain the local deformation. The difference between the bending moduli of experiments and FEM was decreased with an increase in the modulus in transverse direction.     

A method of estimating the output fluctuation of many photovoltaic power generation systems dispersed in a wide area

The largest output fluctuation is an index used to quantify the disturbance of a power grid caused by wind power plants and photovoltaic power generation systems connected to it. In order to develop its estimation method, we investigate the relationship between the largest output fluctuation and the standard deviation of a newly proposed random variable generated by differencing the output variation of photovoltaic power generation systems. Output fluctuation coefficients are defined and estimated using measured data of photovoltaic power generation systems located at 52 places. An approximation equation is presented to predict geographical correlations between the proposed random variables for photovoltaic power systems by using the distances between their locations. Finally, it is shown that the largest output fluctuation of many photovoltaic power generation systems dispersed in a wide area is predictable by using the output fluctuation coefficients and the equation approximating the geographical correlations of output fluctuations. ©2008 Wiley Periodicals, Inc. Electr Eng Jpn, 166(4): 9–19, 2009; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20723     

Cathode catalysts for fuel cell development: A theoretical study based on band structure calculations for tungsten nitride and cobalt tungsten nitrides

Band structure calculations were performed for tungsten nitride, cobalt tungsten nitrides, and platinum slabs. The major requirements for the development of a superior cathode catalyst are: (1) that the Fermi level of the cathode catalyst is close to the energy level of the lowest unoccupied molecular orbital of O₂, the lowest unoccupied atomic orbital of an oxygen atom, and the lowest unoccupied atomic orbital of a hydrogen atom so that they can readily interact with one another; and (2) that the cathode catalysts have smaller ΔE value which represent the difference between the Fermi level and the peak position of the density of states of the O_p orbital of O₂ adsorbed on the catalyst. The active site structures of cobalt tungsten nitrides for activation of the oxygen reduction reaction were found to have the surface structure of Co–O–Co, which lowered the unoccupied orbital of the oxygen atom to approximately that of the Fermi level. However, this structure concomitantly lowered the Fermi level, which resulted in an increase in ΔE. Consequently, the optimal cathode catalyst regarding the surface conformation contains a Co–O–Co structure that is dispersed on the surface of the cobalt tungsten nitride. The cobalt tungsten oxynitride exhibited a catalytic activity for the oxygen reduction reaction. A linear dependence is observed between the ΔE and the oxygen reduction reaction offset potentials of the tungsten nitride, cobalt tungsten nitride, cobalt tungsten oxynitride, and platinum.     

Study on the Effect of Elastic Stress and Microstructure of Low Carbon Steels on Barkhausen Noise

The present study investigates the effect of elastic stress and microstructure on Barkhausen noise in low carbon steels subjected to different heat treatments. Barkhausen noise in an as-received test piece and a test piece heated at 450 ^°C for 1.5 hours was found to increase with increasing elastic stress. However, in a test piece heated at 700 ^°C for 10 hours, Barkhausen noise was observed to saturate with increasing elastic stress following an initial increase. To clarify the reason for this saturation behavior, magnetization measurements were carried out and the microstructure and texture of the test pieces were evaluated using microscopy and electron backscatter diffraction. The results indicated that for the test piece heated at 700 ^°C for 10 hours, a drastic change in the microstructure occurred compared to that for the other test pieces. From the experimental and analytical results, it was concluded that for the former test piece, Barkhausen noise saturated under a low elastic stress due to the globularization of pearlite, which caused 90^° domain walls to become 180^° domain walls when a low elastic stress is applied.     

Synthesis of Cobalt Nanoparticle and Fabrication of Magnetoresistance Devices by Ion-Assisted Aerosol Generation Method

The ionization chemical vapor deposition (ionization CVD) method, which is one of the ion-assisted aerosol generation methods, was used to synthesize Co nanoparticles and fabricate a magnetoresistance device using them. A cobalt tricarbonyl nitrosyl vapor is ionized by a high-pressure ionizer before being fed into the reactor. It reacts and forms nanoparticles by a thermal decomposition reaction in the furnace reactor. Particles deposit electrostatically on an insulator substrate that has two Au electrodes and fill the gap between the electrodes. This Co-nanoparticle device is then annealed under hydrogen gas to deoxidize the deposited particles. After annealing, two copper wires are attached to the two Au electrodes to connect with a DC voltage supplier and an ammeter. The magnetoresistance of the device was evaluated by measuring its electrical resistance using a superconducting quantum interference device (SQUID) magnetometer. The X-ray diffraction patterns of the nanoparticles before and after annealing revealed CoO and Co, respectively. Two fabricated devices with number densities of Co nanoparticles of 4.25 × 10¹⁰ and 1.16 × 10¹¹ cm^?2 showed magnetoresistance ratios of 73% and 1002%, respectively, at an applied voltage of 30 V, a measurement temperature of 5 K, and a magnetic field of ?1 ～ 1 T. It was found from the experimental results that the method developed in this article was useful to fabricate the Co-nanoparticle magnetoresistance device.     

Radiation-inducible TNF-α gene expression under stress-inducible promoter gadd 153 for cancer therapy

We demonstrated the effectiveness of radiation-inducible expression of the TNF-α gene for cancer therapy in vitro. The TNF-α gene under the control of the stress-inducible promoter, gadd 153, was introduced into the human glioma cell line, U251-SP. Without cobalt-60 gamma irradiation, no cytotoxicity against the transfected cells was observed. When the transfected cells were irradiated with 10 or 20 gray (Gy), the gadd 153 promoter was highly induced and the expression level of TNF-α increased. Five days after the irradiation, the TNF-α productions of each cell irradiated with 10 and 20 Gy were 30 and 100 times higher than the basal level, respectively. The cytotoxicities against the transfected cells 5 d after irradiation with 10 and 20 Gy were 79% or 91%, respectively, which are much higher than those against the nontransfected cells that were irradiated at the same dose (43% and 78%, respectively). These results demonstrate that the gadd 153-TNF-α system may be an effective tool for radiosurgery of malignant brain tumors.     

New Pb-based 1212 Superconductor Containing Phosphorus, (Pb0.75P0.25)Sr2(Y1?xCax)Cu2Oz

New Pb-based 1212 compounds containing phosphorus have been discovered in the (Pb_1−y P _y )Sr₂(Y_1−x Ca _x )Cu₂O _z system; almost the single 1212 phase samples can be obtained for the composition range of 0.0≤x≤0.6 and y=0.25. The crystal structure for each sample has a tetragonal symmetry with the typical lattice parameters a=0.3828 nm and c=1.182 nm. Among them, the sample with x=0.6 and y=0.25 shows the onset of resistivity drop at about 39 K and zero-resistivity at about 17 K. Moreover, the sample shows a diamagnetic signal at about 38 K. These phenomena are found to originate from superconductivity with the bulk feature.     

Novel refrigeration lubricants for use with HFC refrigerants

A series of fluorinated alkyl aryl ethers composed of hydrocarbon components, fluorinated alkyl groups and ether linkage groups were evaluated as refrigeration lubricants for use with hydrofluorocarbon (HFC) refrigerants. The novel structure of these lubricants eliminates the problems of poor stability and high moisture absorption that are associated with conventional refrigeration lubricants for use with HFC refrigerants, such as polyalkylene glycol or polyol ester, which have a polar structure. The fluorinated alkyl aryl ethers show high miscibility with HFC refrigerants, high stability, excellent lubricity, and low moisture absorption. These characteristics make fluorinated alkyl aryl ethers well suited to serve as refrigeration lubricants for use with HFC refrigerants.     

Surface acid property and its relation to SCR activity of phosphorus added to commercial V2O5(WO3)/TiO2 catalyst

To examine the influence of phosphorus on the commercial V₂O₅(WO₃)/TiO₂ SCR catalyst, measurements were carried out by means of infrared and Raman spectroscopy, XPS, and NO reduction measurement as a function of phosphorus loading. Phosphorus added to the catalyst was found to disperse well over the catalyst without a significant agglomeration up to 5 wt% P₂O₅ addition. The number of the hydroxyl groups bonded to the vanadium and titanium species decreased readily with increasing amount of phosphorus. Correspondingly, the hydroxyl groups bonded to the phosphorus species were formed. NH₃ adsorbed on both hydroxyl groups bonded to vanadium and phosphorus as ammonium ions, implying that the P–OH groups formed are also responsible for the Brønsted acidity. The NO reduction activity was found to be decreased with increasing amount of phosphorus; however, the influence of phosphorus was relatively small irrespective of the large amount of phosphorus addition. The deactivation might be caused by the change in the nature of the surface hydroxyl groups as Brønsted acid sites. Phosphorus species might partially wrap the surface V=O and W=O groups, which might also contribute to the deactivation.