Pulsed electrical breakdown in liquid helium in the μs range

Information about breakdown time-lags under pulsed voltage stress is prerequisite to the insulation design of superconducting devices. Experiments have been carried out using a pulse generator which provides a step voltage with 200 ns rise time and a long decay time constant of more than 1 ms. The present experiments may bridge the information gap between time lag measurements in the ns range using extremely high field strengths, and existing data found with usual lightning impulse voltage. The test device is described in the paper, and some typical results are discussed in detail     

Environmental stress relaxation studies of polymers: Effect of alcohols on polyethylene

The method of stress relaxation has been used to study stress decay behavior in polyethylene–alcohol systems. The behavior of stress decay in polyethylene under alcohols was observed and the respective activity forward stress decay of alcohols on polyethylene was obtained.     

Studies on synthesis and permeability of special polymer membranes

Summary The permeation characteristics of polymer blend membranes from poly(vinylidene fluoride) and poly-(ethylene glycol) to aqueous polymer solution were investigated under carefully controlled conditions. The permeation characteristics were influenced significantly by the blend ratio, the temperature and time of heat treatment, which changed the structure of the resulting membranes.     

Mechanism of breakdown in the interface region of glass reinforced polyester by artificial weathering

Laboratory studies were conducted to elucidate the mechanism of breakdown in the interface region of glass-fibre reinforced polyester (GRP) composites on outdoor weathering. GRP composites were subjected to the effects of moisture, temperature and radiation. Breakdown in the interface region occurred when the GRP sheets were aged in the presence of water and physically-induced stress (thermally and/or by moisture). The stresses involved are complex, the most predominant being axial shear stresses. Fracture characteristics of breakdown produced during laboratory ageing were very similar to those occurring on outdoor weathering.According to the mechanism proposed, the resin in the interface region is subjected, during environmental ageing, to a stress-fatigue resulting from the differential dimensional changes between glass and matrix induced by moisture and/or temperature cyclic variations. Under the influence of alternating cyclic stresses and in conjunction with the chemical degradation of the matrix, the interface region undergoes cracking, fracture and fibre delamination. This type of breakdown may be referred to as environmental stress cracking.     

Shear properties of metal-free wooden load-bearing walls using plywood jointed with a combination of adhesive tape and wood dowels

In this study, the potential of wood-only (metal-free) load-bearing walls was proposed and tested based on the idea of using the same type of material throughout wherever possible while improving basic properties such as strength, sound insulation, and heat insulation. Specifically, a technique was tested of combining pressure sensitive adhesive tape and wood dowels in place of nails for load-bearing structures with panel reinforcement represented by wood-frame construction. For this paper, its strength was evaluated by conducting in-plane shear tests, which revealed that the initial rigidity and maximum load of the proposed test specimens were greater than that of specimens using nails for jointing. However, the shear load factor, which is calculated based on some strength parameters and which forms the foundation of housing strength design, was slightly lower than that of the nail-jointed specimen. This was because there was a large decline in post-collapse resistance and a lower calculated absorbed energy caused by brittleness. The early detachment of panels was also revealed as a problem in the tests.     

Discovering characteristic patterns from collections of classical Japanese poems

Waka is a form of traditional Japanese poetry with a 1300-year history. In this paper, we attempt to discover characteristics common to a collection ofwaka poems. As a schema for characteristics, we use regular patterns where the constant parts are limited to sequences of auxiliary verbs and postpostional particles. We call such patternsfushi. The problem is to automate the process of finding significantfushi patterns that characterize the poems. Solving this problem requires a reliable significance measure for the patterns. Brāzma et al. (1996) proposed such a measure according to the MDL principle. Using this method, we report successful results in finding patterns from five anthologies. Some of the results are quite stimulating, and we hope that they will lead to new discoveries. Mayumi Yamasaki, M.A.: She received her B.E. and M.A. degrees from Kyushu Institute of Technology in 1997 and from Kyushu University in 1999, respectively. Her research interests include machine discovery and datamining. Presently, she works at Fujitsu FIP Corporation. Masayuki Takeda, Dr. Eng.: He is an Associate Professor in Department of informatics at Kyushu University. He received his B.S., M.S., and Dr. Eng. degrees from Kyushu University in 1987, 1989 and 1996 respectively. His present research interests include pattern matching algorithims, text compression, discovery science, information retrieval and natural language processing. He is a member of Information Processing Society of Japan, Japanese Society for Artificial Intelligence and Japanese Society for Soft-ware Science and Technology. Tomoko Fukuda, M.A.: She is a Lecturer at Fukuoka Jo Gakuin University and at Junshin Women’s Junior College, She received her B.A. and M.A. degrees from Fukuoka Women’s University in 1987 and from Kyushu University in 1992 respectively. Her present research interests are in Japanese literature in the Heian period and classical 31-syllable Japanese poems. She is a member of Waka-Bungaku Kai (Society for Study of Japanese Poems) and Chuko-Bungaku Kai (Society for Study of Japanese Literature in the Heian Period). Ichiro Nanri, M.A.: He is an Associate Professor at Junshin Women’s Juior College. He received his B.A. and M.A. degrees from Kyushu University in 1990 and 1995 respectively. His present research interests are in Japanese language in the Heian-Kamakura period and classical 31-syllable Japanese poems. He is a member of Kokugo Gakkai (Society for Study of Japanese Language) and Kuntengo Gakkai (Society for Studyy of Old Language).     

The Effects of Insulin on Immortalized Rat Schwann Cells,IFRS1

Schwann cells play an important role in peripheral nerve function, and their dysfunction has been implicated in the pathogenesis of diabetic neuropathy and other demyelinating diseases. The physiological functions of insulin in Schwann cells remain unclear and therefore define the aim of this study. By using immortalized adult Fischer rat Schwann cells (IFRS1), we investigated the mechanism of the stimulating effects of insulin on the cell proliferation and expression of myelin proteins (myelin protein zero (MPZ) and myelin basic protein (MBP). The application of insulin to IFRS1 cells increased the proliferative activity and induced phosphorylation of Akt and ERK, but not P38-MAPK. The proliferative potential of insulin-stimulated IFRS1 was significantly suppressed by the addition of LY294002, a PI3 kinase inhibitor. The insulin-stimulated increase in MPZ expression was significantly suppressed by the addition of PD98059, a MEK inhibitor. Furthermore, insulin-increased MBP expression was significantly suppressed by the addition of LY294002. These findings suggest that both PI3-K/Akt and ERK/MEK pathways are involved in insulin-induced cell growth and upregulation of MPZ and MBP in IFRS1 Schwann cells.