Fracture behaviour of boride-dispersed composites fabricated by hot-pressing amorphous Ni60Mo30B10 powder

Microstructural and mechanical property characteristics were investigated for three boride-dispersed composites fabricated by hot-pressing amorphous Ni60Mo30B10 powder. The first composite was tested in the as-hot-pressed condition (HP) whilst the other specimens were subjected to a solution treatment (ST) and further ageing (STA). X-ray diffraction showed the HP and ST composites to consist of Mo2NiB2 particles in a Ni-rich matrix whilst the STA material contained Mo2NiB2 particles in a NiB3Mo matrix. The hardness and fracture toughness decreased and increased, respectively, for the ST material compared to the HP case whilst the STA case showed increased and decreased hardness and fracture toughness, respectively, compared to the ST composite. These results were explained in terms of the brittle–ductile–brittle fracture modes for the HP–ST–STA specimens. In addition, the HP specimen showed only a 15% decrease in compressive strength at 973 K compared to 303 K.     

A pectoral fin analysis for diving rajiform-type fish robots by fluid dynamics

In this paper, we analyze a propulsive force generated from pectoral fins for a rajiform-type fish robot from fluid dynamic aspects. A pectoral fin of the rajiform-type fish robot is constructed by multiple fin rays, which move independently, and a film of pushing water. Then, the propulsive force of the fish robot is analyzed from the momentum of the fluid surrounding for every fin between fin rays. The total propulsive force for one pectoral fin is the sum of these momenta. The propulsive speed of a fish robot is determined from the difference of the propulsive force generated from pectoral fins, and the resistance force that the fish robot receives from the water when moving forward. The effectiveness of the proposed method is examined through numerical simulation and actual experimental results.     

A method of reducing the windage power loss in a laser scanner motor using spiral-groove aerodynamic thrust bearings functioning as a viscous vacuum pump

We propose a spiral-groove aerodynamic thrust bearing functioning as a viscous vacuum pump in a laser scanner motor to reduce the windage power loss of a polygon mirror. The proposed bearing pumps out the air in the scanner housing using the pumping effect of the spiral-groove thrust bearing, reducing the inner pressure of the housing. The pumping performances and the static characteristics of the spiral-groove thrust bearings were investigated numerically and experimentally. Two numerical calculation methods were used to study the pumping characteristics of the spiral-groove thrust bearing. It was found that a bearing with 15 spiral grooves reduced the inner pressure of the housing to <0.01 MPa at 20,000 rpm and at bearing clearance of 2.5 μm, and this has sufficient load-carrying capacity to support the rotating shaft and the mirror.     

Biochemical oscillations in delayed negative cyclic feedback: Existence and profiles

In this paper, we propose a theoretical framework to systematically analyze the existence and the profiles of chemical oscillations in gene regulatory networks with negative cyclic feedback. In particular, we analytically derive the existence conditions and the profiles of oscillations in terms of reaction kinetic parameters and reveal dimensionless quantities that essentially characterize the oscillatory dynamics. These discoveries then allow us to provide general biological insights that are useful for the design of synthetic gene circuits and wet-lab experiments. We point out that time delays due to splicing and transport play an important role for both of the existence and the profiles of oscillations. To this end, we first show that local instability leads to oscillations in cyclic gene regulatory networks, and we derive the existence conditions based on local instability analysis. Then, we analyze the period, phase and amplitude of oscillations using multivariable harmonic balance analysis. These results are demonstrated with two existing biochemical networks, the Pentilator and a self-repression network of a Hes protein.     

Formation of porous poly(ethylene‐co‐vinyl alcohol) membrane via thermally induced phase separation

Crystalline poly(ethylene‐co‐vinyl alcohol) (EVOH) membranes were prepared by a thermally induced phase separation (TIPS) process. The diluents used were 1,3‐propanediol and 1,3‐butanediol. The dynamic crystallization temperature was determined by DSC measurement. No structure was detected by an optical microscope in the temperature region higher than the crystallization temperature. This means that porous membrane structures were formed by solid–liquid phase separation (polymer crystallization) rather than by liquid–liquid phase separation. The EVOH/butanediol system showed a higher dynamic crystallization temperature and equilibrium melting temperature than those of the EVOH/propanediol system. SEM observation showed that the sizes of the crystalline particles in the membranes depended on the polymer concentration, cooling rate, and kinds of diluents. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 79: 2449–2455, 2001     

A study of an interactive fuzzy multi‐objective optimal power flow

As the necessity of high‐quality electric power supply increases, it has been required to develop sophisticated power system operations in which several requirements stemming from economy, security, and environmental aspects are simultaneously satisfied. In general, a problem of satisfying several noncommensurable criteria is called a multiobjective optimization problem. Although the most powerful means to obtain desirable system operations is optimal power flow (OPF), a straightforward application of the conventional OPF optimizes only one objective and the remaining objectives must be treated as constraints. However, since such objectives are in trade‐off relationships with each other, it is necessary to develop an efficient multiobjective OPF. In this paper, we propose a solution method of multiobjective OPF by means of fuzzy coordination. In the first step, the degree of Decision Maker (DM) satisfaction on each objective would be maximized with a prespecified membership function. The membership function would be updated in accordance with the DM's preference information and target value of the objective function. The degree of satisfaction will be improved step by step by updating the membership functions. Finally, the satisficing solution for the DM would be obtained. The proposed method has been applied to the IEEE 57 and 118 test systems, producing successful results. © 1999 Scripta Technica, Electr Eng Jpn, 130(1): 59–67, 2000     

Oligomeric Structural Transition of HspB1 from Chinese Hamster

HspB1 is a mammalian sHsp that is ubiquitously expressed in almost all tissues and involved in regulating many vital functions. Although the recent crystal structure of human HspB1 showed that 24 monomers form the oligomeric complex of human HspB1 in a spherical configuration, the molecular architecture of HspB1 is still controversial. In this study, we examined the oligomeric structural change of CgHspB1 by sedimentation velocity analytical ultracentrifugation. At the low temperature of 4 °C, CgHspB1 exists as an 18-mer, probably a trimeric complex of hexamers. It is relatively unstable and partially dissociates into small oligomers, hexamers, and dodecamers. At elevated temperatures, the 24-mer was more stable than the 18-mer. The 24-mer is also in dynamic equilibrium with the dissociated oligomers in the hexameric unit. The hexamer further dissociates to dimers. The disulfide bond between conserved cysteine residues seems to be partly responsible for the stabilization of hexamers. The N-terminal domain is involved in the assembly of dimers and the interaction between hexamers. It is plausible that CgHspB1 expresses a chaperone function in the 24-mer structure.     

Ab Initio Calculations of the Atomic and Electronic Structure of β-Silicon Nitride

The atomic and electronic structure of the β-silicon nitride (β-Si₃N₄) crystal have been determined using the ab initio pseudopotential method based on the density functional theory. We have obtained the stable lattice parameters and the stable positions of 14 atoms in the unit cell for the structure P 6₃/ m for the first time. The electronic structure and the charge distribution indicate that the Si–N bond has both ionic and covalent characters. The band structure is in good agreement with the other first-principles results and consistent with the experiments.     

Development of bubble column for foam separation

The foam separation of metal in model wastewater is performed by using two different bubble columns in a continuous operation mode. The equipment and operation conditions are changed, and the foam flow rate and metal concentration in foam flow are measured. The foam flow ratio (the ratio of foam flow rate to the inlet one) increases with increasing gas velocity, with decreasing liquid velocity, with decreasing foam layer height and with decreasing metal concentration in model wastewater. Metal enrichment (the ratio of metal concentration in foam flow to that in inlet flow) shows the reverse tendencies. When a draft tube is inserted in the bubbling layer, the foam flow rate decreases. The enrichment is strongly governed by the foam flow ratio. Since the foam flow ratio is adjusted by means of the equipment and operation conditions, the metal concentration in foam flow is controlled to be a desired value. This paper was presented at The 5th International Symposium on Separation Technology-Korea and Japan held at Seoul between August 19 and 21, 1999.     

The New and the Rare: Luxury and Convenience in Japanese Depa-chika

In the face of economic adversity, the food sections of Japan's department stores have prospered, attracting large numbers of customers with their fresh produce, luxurious dishes and buzzing market-like atmospheres. Masaaki Takahashi describes how these depa-chika have not only met the demand for prepared foods among busy working people, but have also stimulated it. Selling the finest delicacies, they tempt their customers with rare items that are often bought for their novelty value alone.