Studies on melt spinning. VII. Temperature profile within the filament

An attempt was made to numerically compute the temperature profile within the melt spinning filament without assuming axisymmetry and using the data on the variation of the coefficient of heat transfer from a cylinder cooled by cross flow of air as given by Eckert.⁴ The computed constant-temperature contours were approximately concentric circles with their center shifted from the filament center in the downstream direction of the cooling air flow. A filament yarn melt spun under spinning conditions corresponding to the computation was dyed, and its cross sections were observed under the microscope. The border between the dyed and undyed portion of the cross sections approximately coincided with one of the computed temperature contours, suggesting indirectly the general validity of the computed temperature profile.     

High-speed test of thermal effects for a machine-tool structure based on modal analysis

A new test method has been developed to evaluate the temperature rise of machine-tool structures. In this method, which uses short period data obtained during a warm-up run, the machine-tool structure is modelled by the finite element method (FEM) and is analysed in terms of the eigenvalues of the thermal equation. Characteristic temperature rise curves for the structure are obtained, which have variable parameters. The values of these depend upon the strength of heat sources. Then, by determining the parameters such that the characteristic temperature rise curves fit those obtained during a warm-up run, it is possible to identify the strength of the heat sources, and thus the values of temperature rise for any point in the structure. Experiments have been carried out which verify the effectiveness of the method.     

Conformational studies of N-acetyl-N-methyl-l-alanine dimethylamide-d6 by n.m.r. spectroscopy

Nuclear magnetic resonance of $\text{N-}\text{acetyl}\text{-N-}\text{methyl-}\text{l}\text{-alanine dimethylamide-d}{}_6$ in methylene $\text{chloride}\text{-d}{}_2\text{dichloroacetic acid}$ was investigated. In methylene chloride-d₂ the amide assumed nearly all-trans conformation. Small signals corresponding to trace amounts of cis confirmation were observed. Dichloroacetic acid induced the shift of the resonance signals immediately after the addition. On leaving the solution containing dichloroacetic acid, the amide nitrogen was protonated and the isomerization around the amide bond took place. After a sufficient time lapse a complex spectrum resulted, which corresponded to at least five different conformations. On heating the solution several signals disappeared without coalescence and the resonance signals corresponding to three different conformations remained at 120°C. These conformations should include non-planar conformations as well as planar cis and trans conformations.     

Electrical conductivity of a sintered pellet of octalithium zirconate

The conductivity of a sintered pellet of Li₈ZrO₆ was measured in dry or wet argon atmosphere by the two-terminal technique with an AC Wheatstone bridge in the temperature range 350–1050 K. The temperature dependence of conductivity multiplied by temperature $\text{(σT)}$ of Li₈ZrO₆ in a dry environment had two transition points at 426 and 833 K. The activation energies of conductivity in high, middle and low temperature regions were 103.2, 52.1 and 37.4 kJ/mol, respectively. The activation energies of conductivity agreed well with those obtained by temperature dependence of spin-lattice relaxation time $\text{T}{}_1$ of ⁷Li with pulsed nuclear magnetic resonance.     

High-field Magnetization of SrMn3P4O14 Having Magnetization Plateau and Ferrimagnetic Long-range Order

It has not been studied sufficiently whether quantum-mechanical character can exist in classical magnetic long-range order of systems with large spins. Very recently, it has been shown that a quantum-mechanical 1/3 magnetization plateau and classical ferrimagnetic long-range order coexist in SrMn₃P₄O₁₄ possessing spin-5/2 [T. Yang et al. in Inorg. Chem. 47:2562, 2008]. Magnetism of this substance has not been explained quantitatively, although the origin of the plateau is inferred to be a trimerized spin chain. We performed high-field magnetization measurements on SrMn₃P₄O₁₄ powders. We consider a spin system in this substance.     

Reaction analysis of a direct methanol fuel cell employing a porous carbon plate operated at high methanol concentrations

It is known that a small amount of intermediate products, i.e., formaldehyde, formic acid and so on, is exhausted from a direct methanol fuel cell (DMFC). The production rates of such intermediates are affected by the methanol and water concentrations at the anode, and also the distribution of these products is variable. We investigated the production of the intermediates from a passive DMFC containing a porous carbon plate (PCP), which allows the use of methanol at high concentrations up to 100% due to the high resistivity to the methanol transport through the PCP. The production rates of each intermediate and their distribution were measured not only for a DMFC employing various PCPs with different transportation resistivities, but also for a DMFC without PCP. The results were analyzed in terms of the rate of methanol crossover (MCO) and water flux through the membrane. The detected intermediates were formaldehyde, formic acid, and methylformate, in accordance with previous reports. The production rates of the intermediates were strongly dependent on the flux of the MCO rather than the apparent methanol concentration. When the DMFC was operated under the rate limiting conditions of the methanol transport by the PCP, the production rates of the intermediates were low. However, when it was operated outside of the rate limiting conditions, the production rate increased with the increasing rate of methanol crossover.