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.     

Application of the Gyrotron FU II Submillimeter Wave Radiation Source to Plasma Scattering Measurements

Gyrotron FU II has been successfully applied as a submillimeter wave radiation source to plasma scattering measurements on the Compact Helical System (CHS) in National Institute for Fusion Science (NIFS) in Japan. The gyrotron operates in a long pulse mode (the pulse width is about 600 ms) at a frequency of about 350 GHz (the corresponding wavelength is 0.85 mm). The output power is about 110 W. The output power is transmitted along a circular waveguide system and converted to a Gaussian-like beam by a quasi-optical antenna. After that, the beam is directed onto the CHS plasma and the scattered signal is detected by a homodyne detection system. The frequency and the wave number of the scattered signal are analyzed. The results suggest that a broad band low frequency (several tens to several hundreds kHz) density fluctuation is excited in the CHS plasma only during neutral beam injection (NBI) or ion cyclotron resonance (ICR) heating.     

Development of a compact high-density microbial hydrogen reactor for portable bio-fuel cell system

The development of a compact high-density microbial reactor for hydrogen production is described with possible implications to use as a portable bio-fuel cell system. To construct the compact bioreactor, mainly, the cell density and immobilization methods were optimized in this paper. The encapsulation of hydrogen producing bacterium, Escherichia coli strain MC13-4, in alginate gel beads provided approximately three-fold increase in hydrogen production in comparison with the free cell suspension. The immobilized cells (cell density; O.D. 100) and 500 mM glucose solution were packed into a 20 mL glass bottle that was connected to the fuel cell. This system has generated electricity of over 20 mW for 20 min.     

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.     

Dependence of single-longitudinal-mode probability on DFB laser facet structure

The probability of single-longitudinal-mode (SLM) operation is calculated for three kinds of DFB facet structures. To obtain high SLM probability, a DFB laser with cleaved facets requires relatively large kL, but the introduction of asymmetry to facet reflectivity greatly relaxes the kL requirements.     

Simple and quick turnaround time fabrication process for deepsubmicrometer CMOS generation

Process simplification and turnaround time reduction for deep submicrometer CMOS fabrication are discussed. Process step analysis is carried out for standard 1Poly/1Metal CMOS structure, and consequently, both isolation and gate formation processes are extracted as items for process simplification. A combination of shallow trench isolation with retrograde well structure and single mask step well/gate doping technique is proposed for deep submicrometer CMOS fabrication. This simplified CMOS process can achieve a reduction of five mask steps and eliminates both well drive-in annealing and field oxidation without performance deterioration. As a result, a 10% process step reduction and a 20% manufacturing turnaround time reduction have been realized in comparison to the standard 1Poly/1Metal CMOS process with LOCOS isolation     

16 dB 80 GHz InGaP/GaAs HBT distributed amplifier

A high-gain and broadband distributed amplifier using high-performance high-reliability InGaP/GaAs HBTs is reported. A novel two-block configuration is used in gain cells in this distributed amplifier, which achieves a bandwidth of 80 GHz with a gain of 16 dB, resulting in a gain-bandwidth product of 504 GHz.     

Calcification in the basal ganglia with chronic active Epstein-Barr virus infection

The objective of this study was to determine whether measurements of human CRH in the inferior petrosal sinuses could distinguish patients with Cushing's syndrome from those with pseudo-Cushing states or normal physiology. Twenty-five patients with Cushing's disease, 17 patients with the syndrome of ectopic ACTH, 7 patients with Cushing's syndrome of adrenal origin, 6 patients with pseudo-Cushing states, and 11 volunteers believed to have normal hypothalamic-pituitary-adrenal axes were studied. Basal plasma human CRH and ACTH were measured at two time points in the petrosal sinuses and in a peripheral vein. Most subjects were studied after the administration of intravenous diazepam or midazolam and fentanyl, but because of the known inhibitory effects of such sedation on CRH secretion, 2 normal volunteers and 3 patients with pseudo-Cushing states were studied without sedation. Human CRH levels were near or below the detection limit of the assay in all subjects. Although the normal volunteers and patients with pseudo-Cushing states who were studied without sedation had significantly greater inferior petrosal sinus ACTH levels than those who received sedation, there were no differences in measured human CRH levels for any of the groups. We conclude that inferior petrosal sinus human CRH levels are not easily measured in the inferior petrosal sinuses and cannot be used to determine whether individual patients may have hypersecretion of CRH causing their ACTH secretion.