Heating rate effects on the crystallization behavior of isotactic polypropylene from mesophase – A de-polarized light transmission study

It was ever reported in a communication of this journal that the large crystal grains having “bamboo leaf-like (BL)” morphology were produced by a rapid heating of isotactic polypropylene (iPP) from the mesophase. In order to optimize the condition to generate the BL crystals, heating rate effects on the crystallization behavior from the mesophase of iPP have been studied by utilizing a de-polarized light transmission (DPLT) method. The DPLT sensitively detected not only the cold crystallization from the mesophase around 100–120 °C but also the crystal grain growth in a narrow temperature region just below the melting temperature. With increasing the heating rate, both the temperature regions of the cold crystallization and the crystal grain growth shifted toward the higher temperatures. When the heating rate is slow (<20 °C/min), the crystal grain growth was not conspicuous. With increasing the heating rate, the rate of the crystal grain growth increased and showed a maximum when the heating rate is approximately 60–80 °C/min. However, excessively fast heating (>100 °C/min) also suppressed the crystal grain growth.     

Initial rotor position estimation of interior permanent magnet synchronous motor using optimal voltage vector

The initial rotor position estimation is a serious problem affecting sensorless drives of permanent magnet synchronous motors. This paper presents an estimation method of initial rotor position for interior permanent magnet synchronous motors. The principle of the estimation is based on the nonlinear magnetization characteristics of the stator core caused by the magnet of the rotor. The estimation is performed using the variation of the current response caused by the magnetic saturation when the voltage vector is applied to the motor. This method can be performed without motor parameters and any additional hardware. Decision method of the optimal voltage vector applied to the motor is also proposed to accurately implement the estimation. Experimental results show that the initial rotor position can be estimated without rotating the rotor by using the optimal voltage vector. It is found that the average of the estimation error is ±1.34 electrical degrees, and the estimation is completed within 15.2 ms in the test motor. © 2006 Wiley Periodicals, Inc. Electr Eng Jpn, 156(4): 69–76, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.20062     

Refinement of solid layers via wetting on homogeneous lyophilic surfaces

Surface control additives (SCAs), or surfactants, can obstruct the wetting of liquid films on lyophilic surfaces even though they lower surface tension. In this work, this unusual behavior was used to decrease the widths of printed organic and nanoparticle lines on different homogeneous surfaces. A decrease in line width accompanied a change in its cross section. The ability of a SCA to decrease the line width was correlated with contact angle but not the surface tension of the solution. Line refinement was consequently attributed to an increase in contact angle. Because there were no reports that surfactants increased contact angles, the mechanisms to increase contact angle were discussed in static and dynamic terms. First, Owens and Wendt’s theory revealed that contact angle changes depended on SCA-induced modification of polar and dispersive interfacial components. However, a definitive increase in contact angle could not be deduced from this theory alone. Second, the effect of solutal Marangoni forces induced by the SCAs on contact angle was discussed by considering the wetting behaviors of binary solvents. SCA concentration dependence of surface tension at higher than the initial SCA concentration correlated well with the ability of the SCA to decrease line width.     

Timing of menopause, reproductive years, and bone mineral density: a cross-sectional study of postmenopausal Japanese women

Age at menopause has been found to be associated positively with bone mineral density, and age at menarche has been found to be associated negatively with bone mineral density. However, there have been few studies on the relations of timing of menopause and length of the reproductive period with bone mineral density. The purpose of this study was to examine the relations of timing of menopause and reproductive years (calculated as age at menopause minus age at menarche) with mineral density of the second metacarpal bone in postmenopausal Japanese women. The study population consisted of 1,035 naturally menopausal women aged 40-70 years who were screened in 1996-1997. Using computed x-ray densitometry, the authors measured bone mineral density by analyzing radiographic films of the right second metacarpal bone. Using the women with early menopause (age < 49 years) as the reference group and adjusting for age, subjects with late menopause were at decreased risk for low bone mineral density (odds ratio (OR) = 0.69, 95% confidence interval (CI) 0.49-0.97). After adjustment for additional covariates (grip strength, physical activity, body mass index, smoking, and calcium intake), the association was unchanged (OR = 0.70, 95% CI 0.50-0.99). Postmenopausal women with more reproductive years (> or = 40 years) were at decreased risk for low bone mineral density compared with those with fewer reproductive years, after adjustment for age (OR = 0.73, 95% CI 0.40-1.30) and potentially confounding factors (OR = 0.76, 95% CI 0.41-1.37); the p-value for trend was not statistically significant. In multiple linear regression analysis, early menopause and fewer reproductive years were independent predictors of low bone mineral density. In this study, postmenopausal Japanese women who had a late menopause and more reproductive years were at decreased risk for low bone mineral density, and may therefore be less prone to osteoporosis.     

Levels of dioxins in Japanese fruit in 1999 to 2002 and estimation of their intake

A total of 148 samples of nine species of fruit were collected between 1999 and 2002 and analyzed for PCDDs, PCDFs (PCDD/Fs) and Coplanar PCBs. Sampling points within about 1 km of operational municipal waste incinerators that were considered sources of dioxins were defined as "near-source" areas, and all other sampling points were defined as "general" areas. The TEQ of apples collected from near-source areas was significantly higher than that from general areas (p < 0.05). 3,3',4,4',5-PeCB (#126) was the main contributor to this difference in TEQs between apples collected from near-source areas and from general area. A principal component analysis performed to estimate the source of this congener revealed that not only the municipal waste incinerators, but also PCBs in the environment were associated with the high TEQ in apples collected from near-source areas. The daily intakes of PCDD/Fs and Coplanar PCBs from the fruits including skin were estimated to be 0.0082 pg-TEQ/kg b.w./day (ND = 0) and 0.072 pg-TEQ/ kg b.w./day (ND = 1/2 LOQ). Though these values are likely to be overestimates, they are far lower than the tolerable daily intake set in Japan for PCDD/Fs and Coplanar PCBs (4 pg-TEQ/kg b.w./day). It is thought that fruit intake is not an important pathway of human exposure to PCDD/Fs and Coplanar PCBs.     

The fate of dioxins during green tea manufacture

Dioxin concentrations and homologue profiles were examined in plucked new shoots, crude tea and its hot water extracts, soils and atmosphere in tea orchards. The rate of dry provisions in crude tea has increased 4 times as that of the plucked new shoots. However, dioxin concentrations except O8CDD in crude tea have increased only 2 to 3 times as those of the plucked new shoots. O8CDD concentration increased remarkably during processing. Little dioxins were detected in hot water extracts of crude tea leaves.     

Development of small-sized friction stirs welding equipment for hand-operated welding

Much attention has been paid to FSW as a useful joining process that provides superior characteristics compared with conventional fusion welding. However, the FSW equipment must have a high stiffness due to the applied load and the tool torque, which increases the size of the equipment. Therefore, it is difficult to use the FSW technique on-site for repairs and/or hand-operated welding. In this study, the relationship between the FSW parameters and the process loads was investigated for the FSW with a counterbalanced tool and preheating to evaluate the possible miniaturization of the equipment. The results revealed that the counterbalanced tool concept with preheating was effective for the miniaturization of the equipment because it reduces the applied l and the tool torque during the FSW. Welding direction force Fx and transverse direction force Fy can be reduced below 70 N and 50 N respectively.