A sensitivity study in probabilistic fracture mechanics analysis of light water reactor carbon steel pipe

Through the efforts in leak-before-break research for light water reactor pipings based on deterministic fracture mechanics analysis, simple models which evaluate pipe fracture behavior are being established. Using these models it is also becoming possible to apply probabilistic fracture mechanics analysis. This paper describes an example of such an analysis, using these proposed models.

Since the authors' interests are in the range of uncertainty of the calculated failure probability, the effects of changes in the input parameters or the analytical conditions are also estimated by a sensitivity analysis. The results show that the calculated failure probability may be influenced significantly by changes in parameters concerning initial crack size distributions, and that effects due to a change in the leak detection model may appear after long operation of the plant.     

A research program for dynamic fracture evaluation of Japanese carbon steel pipes

A research program was developed to investigate the dynamic load effect on fracture behavior of Japanese carbon steel STS410 pipe. The program comprises material tests, pipe fracture tests and development of estimation scheme. Material property tests showed that the flow stress was nearly constant or slightly increased with strain rate. Pipe tests showed that fracture load was nearly predicted by the net-section collapse criterion for both quasi-static and dynamic loading. Significant dynamic effect was not observed for STS410 carbon steel piping. Crack growth was well formulated by using J-integral parameter for low cycle fatigue with large scale yielding. Combining the crack growth behavior and unstable fracture criterion, an estimation scheme was newly developed and validated for constant amplitude cyclic loading conditions.     

The dependency of the crack growth rate on the loading pattern and temperature in stress corrosion cracking of strain-hardened 316L stainless steels in a simulated BWR environment

The stress corrosion cracking (SCC) growth rate of a warm-rolled (WR) 316L stainless steel contoured double cantilever (CDCB) specimen was measured in high purity water at various temperatures and under various loading patterns. An alternating current potential drop (ACPD) technique was used to monitor the crack growth kinetics throughout the tests. The fracture surface exhibited typical intergranular SCC characteristics. Depending on the test conditions, three kinds of crack growth kinetics, i.e., increasing with time then becoming steady, being constant during the whole period, decreasing with time then becoming steady, were identified and are described. The steady state crack growth rate (CGR) values are used to quantify the effects of the loading pattern and the environmental temperature. A moderate increase in the crack growth rate was encountered by employing periods of unloading and reloading to form a trapezoidal loading pattern and the enhancement factor was found to depend on the holding time and the times for unloading and reloading. It was found that the crack growth is thermally activated; however, the apparent activation energy is not constant but seems to be greater at higher temperatures. Several types of temperature-dependent crack growth kinetics are proposed based on the rate-determining step for the crack growth. The present experimental results can be rationalized by considering multiple element processes such as aqueous mass transport and solid-state mass transport in the crack growth. The cracking mode, the temperature dependence of the crack growth rate, and the transient crack growth behavior for WR 316L SS after changing the environmental temperature are quite similar to those for a cold-worked(CW) 316L SS tested in the same environment, despite their different absolute crack growth rate values. The effect of yield strength on CGR is more significant at lower temperatures and the apparent activation energy for the crack growth rate seems to be lower in the material with a higher yield strength. Time-lag crack growth behavior was found at points during several test steps on WR 316L SS, for example, just after in situ pre-cracking and after increasing or decreasing the temperature, which is quite consistent with the results obtained with CW 316L SS. The importance of in situ monitoring of the crack growth for obtaining steady state crack growth rates is emphasized, especially for those steps for which a nonlinear crack growth period occurs after changing the test condition.     

Interpersonal Style and Japanese American Organizational Involvement

This paper reports on an initial effort to develop survey items that measure Japanese American interpersonal style. Based upon the theoretical work of Miyamoto. Fugita, and Kashima (2002) it was hypothesized that Japanese American interpersonal style is an important factor in their forming large numbers of voluntary organizations both historically and contemporarily. A survey was administered to 344 Japanese Americans living in the Seattle, WA and San Jose, CA areas. An initial pool of 16 items yielded a 10-item measure with three subscales that was related to involvement in Japanese American organizations and other indicators of ethnic community participation.

     

Acute non-cancer mortality excess after polychlorinated biphenyls and polychlorinated dibenzofurans mixed exposure from contaminated rice oil: Yusho

In Japan in 1968, rice-oil contaminated by polychlorinated biphenyls and polychlorinated dibenzofurans caused severe food poisoning, termed “Yusho” (oil disease). Several previous studies attempted to evaluate the effects targeting officially-certified Yusho patients. However, these studies have several limitations such as the left-truncated nature of the registry or residual confounding arising from the referent population selection. We thus conducted an area-based standardized mortality ratios (SMRs) study using vital statistics. A severely affected area (Tamanoura area) was adopted as the exposure group, with a reference population from Nagasaki prefecture in Kyushu, which included the Tamanoura. A large number of residents in Tamanoura were exposed to the rice-oil (28% of all the certified cases as of 2009). We estimated SMRs of non-cancer and cancer diseases for the years 1968-2002. Shortly after the exposure, SMRs of all causes, diabetes mellitus, cardiovascular disease, pneumonia/bronchitis, and bronchus/lung cancer were elevated. In particular, SMRs of heart disease were 1.97 [95% confidence intervals (CI): 1.09-3.56] in 1968, 2.05 (95% CI: 1.16-3.60) in 1969, and 1.89 (95% CI: 1.05-3.41) in 1975. However, we did not observe clear increase in SMRs more than 10 years after the exposure. This study provides further evidence in Yusho, especially on acute effects on non-cancer mortality.     

Analysis of indoor PM2.5 exposure in Asian countries using time use survey

Most household fuels used in Asian countries are solid fuels such as coal and biomass (firewood, crop residue and animal dung). The particulate matter (PM), CO, NOx and SOx produced through the combustion of these fuels inside the residence for cooking and heating has an adverse impact on people's health. PM 2.5 in particular, consisting of particles with an aerodynamic diameter of 2.5 μm or less, penetrates deep into the lungs and causes respiratory system and circulatory system diseases and so on. As a result, the World Health Organization (WHO) established guideline values for this type of particulate matter in 2005. In this study, the authors focused on PM 2.5 and estimated indoor exposure concentrations for PM 2.5 in 15 Asian countries. For each environment used for cooking, eating, heating and illumination in which people are present temporarily (microenvironment), exposure concentrations were estimated for individual cohorts categorized according to sex, age and occupation status. To establish the residence time in each microenvironment for each of the cohorts, data from time use surveys conducted in individual countries were used. China had the highest estimate for average exposure concentration in microenvironment used for cooking at 427.5 μg/m³ , followed by Nepal, Laos and India at 285.2 μg/m³, 266.3 μg/m³ and 205.7 μg/m³ , respectively. The study found that, in each country, the PM2.5 exposure concentration was highest for children and unemployed women between the ages of 35 and 64. The study also found that the exposure concentration for individual cohorts in each country was greatly affected by people's use of time indoors. Because differences in individual daily life activities were reflected in the use of time and linked to an assessment of exposure to indoor air-polluting substances, the study enabled detailed assessment of the impact of exposure.     

Trajectory formation based on physiological characteristics of skeletal muscles

Human arm trajectories in natural unrestricted reaching movements were studied. They have particular properties such that a hand path is a rather simple straight or curved line, and a tangential velocity profile of hand is bell-shaped. Also these properties are invariant, independent of movement duration and hand-held load. In this study, trajectory formation is investigated on the basis of physiological characteristics of skeletal muscles, and a criterion prescribed by a derivative of isometric muscle torque is proposed. Subsequently, optimal trajectories are formulated under various conditions of movement to account for a planning strategy of human arm trajectories. In addition to such a theoretical approach, human arm trajectories are experimentally observed by a measuring system which provides a visual sensor and a target tracking device, enabling totally unrestricted movements. Then, optimal trajectories are quantitatively evaluated in comparison with experimental data in which essential properties of human arm trajectories are demonstrated. These results support the idea that human arm trajectories are planned in order to minimize the proposed criterion which is determined from physiological aspects. Finally, the physiological advantages of human arm trajectories are discussed with regard to the analysis of observed and optimal trajectories.     

''Alice in Wonderland'' syndrome as a precursor of depressive disorder

The effect of a single dose of morphine (50 mg/kg) and ethanol (2 g/kg) on total magnesium content in blood serum, brain, heart, lung, kidney, liver, femoral muscle and spleen in mice was studied. Significant decrease of magnesium serum concentration was observed after morphine and ethanol administration but not after both drugs given simultaneously. Morphine caused the evident decrease of magnesium content in brain, lung, kidney and muscle, while it was elevated in heart and spleen and unchanged in liver. Ethanol produced significant decrease of magnesium content in heart, lung and kidney and it's increase in liver and spleen. Concomitant administration of both drugs was connected with the diminished amount of magnesium in heart, lung, kidney and muscle and led to the rising of magnesium content in spleen. It is concluded that even a single dose of investigated drugs is sufficient to produce promptly some risk of alterations in magnesium homeostasis.     

Linear InGaAsP edge-emitting LED's for single-mode fibercommunications

A 1.3-μm edge-emitting diode with a linear radiance and high coupled power into a fiber is described. The LED yields 60 μW of coupled power into a single-mode fiber at a driving current of 100 mA and an ambient temperature of 25°C. A V-groove structure with an optical absorption region separated from an active region is used. At active layer thicknesses below 0.14 μm, linear current-light output characteristics are obtained. The spectral modulation depth is 0% over the entire emission spectral width of 75 nm, and coherence length is 22.5 μm. LED characteristics are achieved in the range from -30 to 85°C at a driving current of 100 mA. The LEDs exhibit a cutoff frequency of 250 MHz. LED reliability is discussed using results of accelerated aging carried out at the ambient temperatures of 50, 125, and 200°C. The activation energy of degradation is determined to be 0.63 eV, and LED half-lives are estimated to be in excess of 10⁶ h     

Time compression multiplex transmission system using a 1.3 μmsemiconductor laser as a transmitter and a receiver

A bidirectional system using 1.3 μm lasers as a transmitter and a receiver are investigated. The lasers considered are commercially available Fabry-Perot and distributed-feedback lasers. It is found that the poor performance of a laser receiver, compared to a PIN receiver, stems from three factors: low responsivity, high capacitance, and polarization dependence of responsivity, high capacitance, and polarization dependence of responsivity. The effect of each factor is evaluated. It has been clarified that the polarization dependence of sensitivity originates from the TE and TM modes dependence of both mode confinement factor and reflection at a facet. Using the measured parameters, 1.3-μm laser receiver sensitivity for a 10^-9 error rate is estimated. Burst data transmission experiments show that estimated sensitivities agree well with the measured values. Optical ping-pong transmission distance of narrowband services is determined based on estimated sensitivity