The influence of the maternal heart rate on the uterine artery pulsatility index in the pregnant ewe

We investigated the influence of the maternal heart rate on the uterine artery pulsatility index in pregnant ewes. We used an external pacemaker to alter the heart rate of 5 pregnant ewes at 16-17 weeks of pregnancy and examined the effect of changes in the maternal heart rate on the uterine artery flow velocity waveforms and the pulsatility index, as determined by Doppler velocimetry. The uterine artery pulsatility index showed a significant negative correlation with the maternal heart rate. There were no significant changes in other hemodynamic parameters. The maternal heart rate had a significant influence on the uterine artery pulsatility index.     

Synthesis and mechanical properties of porous alumina from anisotropic alumina particles

A porous alumina body was synthesized from anisotropic alumina particles (platelets). The uniaxial pressure in fabricating the green compact body had an influence on the relative density of the alumina body after heating. When green compacts, which had been uniaxially pressed at 1 and 3 MPa, were heated at 1400 °C for 1 h, the relative densities of the resulting alumina bodies were 25.0% and 35.5%, respectively. The compressive strength of compacts that were uniaxially pressed at 1 and 3 MPa were 0.8 and 4.3 MPa, respectively. In an attempt to increase the compressive strength of these porous alumina bodies, aluminum nitrate and magnesium nitrate solution treatments were performed, followed by reheating to 1400 °C for 1 h. When a 0.5 mol/l aluminum nitrate solution was used, the compressive strength of the porous alumina body uniaxially pressed at 1 MPa changed from 0.8 MPa (without solution treatment) to 1.5 MPa. Furthermore, when 0.1 mol/l magnesium nitrate solution was used, the compressive strength of the porous alumina increased to 1.7 MPa. Thus, solution treatment of the porous alumina body had a strong positive effect on its mechanical strength.     

Conflict over a hydropower plant project between Tajikistan and Uzbekistan

Following the dissolution of the Soviet Union, Central Asian countries struggled to reach an agreement on the use of their shared fresh water resources. The conflict between Tajikistan and Uzbekistan regarding construction of the Rogun Hydropower Plant in the Amu Darya Basin seems deadlocked at present, despite copious efforts made by donor agencies. Therefore, this paper examines each country’s position using the numbers featured in the media.     

由柏木制备纳米孔结构炭材料Ⅰ.制备与孔结构

柏木条经过热蒸气处理,成功地制备了纳米孔炭,无需另行活化,比表面积就可达1000m^2/g以上。如果在800℃～870℃炭化,柏木炭外表面积可达400m^2/g以上,与同样温度在氩气中炭化得到的柏木炭相比,后者微孔面积仅为30m^2/g～40m^2/g。在900℃以上炭化得到的柏木炭,微孔表面积高达800m^2/g以上,外表面积约为150m^2/g。柏木炭的孔结构可以通过调节过热蒸气的温度得到控制。     

Strongly thixotropic viscosity behavior of dimethylsulfoxide solution of polyrotaxane comprising α-cyclodextrin and low molecular weight poly(ethylene glycol)

A strong thixotropic viscosity behavior was observed when polyrotaxane prepared from α-cyclodextrins (CDs) and poly(ethylene glycol) (PEG) with a molecular weight of 2000 was dissolved in dimethylsulfoxide (DMSO). A 10 wt% solution liquefied by vigorous shaking was rapidly gelated by standing - this sol-gel transition was reversible. The time for recovering the viscosity was dependent on the polyrotaxane concentration, i.e., a 10 wt% solution regelated within 30 s, whereas several hours were required for the gelation of a 2.5 wt% solution. The thixotropic nature of the solution was also confirmed by the clockwise hysteresis curve of the viscosity when the shear rate was increased and decreased. The gel permeation chromatography (GPC) measurement of the polyrotaxane in DMSO exhibited peaks in the high molecular weight region. The peak disappeared after the phenylcarbamoylation of polyrotaxane, suggesting that the peak was due to loose aggregations of polyrotaxane in DMSO. On the other hand, the DMSO solution of polyrotaxane prepared from CD and PEG with a molecular weight of 3350 - whose inclusion ratio (51%) is slightly lower than that of PEG2000 polyrotaxane (72%) - neither demonstrated the abovementioned thixotropic viscosity nor the peak corresponding to the aggregations occurring during the GPC measurement. The thixotropic behavior was speculated to be caused by the combined contribution of intermolecular attractive hydrogen bonding and higher rigidity of polyrotaxane prepared from PEG2000 than that of polyrotaxane prepared from PEG3350, presumably due to the higher inclusion ratio of the former than that of the latter.     

Design method for a new control system for an autonomous underwater vehicle using linear matrix inequalities

The independent administrative corporation Japan Agency for Marine–Earth Science and Technology (JAMSTEC) has developed a small light autonomous underwater vehicle (AUV) named marine robot experimental 1 (MR-X1).¹ The motion control of MR-X1 is considered in this article. Since the dynamics of MR-X1 mainly depends on its own speed, the motion control is a nonlinear control system. We propose a new controller design method for this system using linear matrix inequalities (LMIs). This algorithm gives a solution as a linear matrix inequality, and can be adapted to solve many LMIs simultaneously. LMIs can be obtained by substituting several speeds into the dynamics of the MR-X1. The proposed controller, which can be derived from the solution of the LMIs, was adapted to MR-X1 and showed good performance in experiments. This work was presented in part at the 11th International Symposium on Artificial Life and Robotics, Oita, Japan, January 23–25, 2006     

Development of a new underwater positioning system based on sensor network

In those days, the performance of underwater robot is improving because requirements for it are becoming higher and more complex than before. For those work, a highly precise and wide regional underwater positioning system is indispensable. However, the conventional positioning system that has three standard stations, is applicable for the field with no obstacle, because its principal depends on the time based measurement. Therefore, we developed a new underwater positioning system based on sensor network technology that is using a lot of standard stations equipping hydrophone and GPS sensor on the water surface. And decreasing the cost of sensor, we applied a simple method for measurement of distance, which is using sound power level. Therefore, this study has started with confirming the new principal for underwater positioning method. This paper is showing the availability with theoretical analysis and the performance of new method under the noise and reflection of sound in the water, and suggestions for the measures and an error compensation method. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

Micromagnetic simulation on dynamics of spin transfer torque magnetization reversal

I study the magnetization dynamics induced by spin transfer torque in CoFe/Ru/CoFe/Cu/NiFe nano-pillars using LLG micromagnetic simulations. The required current for spin transfer torque magnetization reversal was investigated with the switching speed and the temperature. The required current in rectangular nanopillars is much larger than that in elliptical nanopillers. The temperature dependence is pretty complicated. The antiparallel to parallel magnetization reversal at 77 K requires a smaller current than at 300 K. The parallel to antiparallel magnetization reversal at 77 K requires a smaller current than at 300 K only when the pulse duration time is very short.     

Numerical study of flow and heat-transfer characteristics of cryogenic slush fluid in a horizontal circular pipe (SLUSH-3D)

Cryogenic slush fluids, such as slush hydrogen and slush nitrogen, are two-phase, single-component fluids containing solid particles in a liquid. Since their density and refrigerant capacity are greater than those of liquid-state fluids alone, there are high expectations for use of slush fluids as functionally thermal fluids in various applications, such as fuels for spacecraft engines, clean energy fuels to improve the efficiency of transportation and storage, and as refrigerants for high-temperature superconducting equipment. In this research, a three-dimensional numerical simulation code (SLUSH-3D), including the gravity effect based on the thermal non-equilibrium, two-fluid model, was constructed to clarify the flow and heat-transfer characteristics of cryogenic slush fluids in a horizontal circular pipe. The calculated results of slush nitrogen flow performed using the numerical code were compared with the authors’ experimental results obtained using the PIV method. As a result of these comparisons, the numerical code was verified, making it possible to analyze the flow and heat-transfer characteristics of slush nitrogen with sufficient accuracy. The numerical results obtained for the flow and heat-transfer characteristics of slush nitrogen and slush hydrogen clarified the effects of the pipe inlet velocity, solid fraction, solid particle size, and heat flux on the flow pattern, solid-fraction distribution, turbulence energy, pressure drop, and heat-transfer coefficient. Furthermore, it became clear that the difference of the flow and heat-transfer characteristics between slush nitrogen and slush hydrogen were caused to a large extent by their thermo-physical properties, such as the solid–liquid density ratio, liquid viscosity, and latent heat of fusion.