Suitable parameters of single-mode optical fibre

A new method for determining suitable single-mode fibre parameters is examined. Suitable fibre parameters are determinable by minimising cabling- and splicing-loss increases. An eight-fibre cable was manufactured and the loss increases were measured. ? = 0.2% and V = 2.2 are the values selected using this method and for the experimental results.     

Carbonyl sulphide in fire gases

The toxic gases released by combustion/pyrolysis of wool include CO, HCN and four compounds containing sulphur. Animal test data suggest that the toxicity of the sulphur compounds is significant. Wool was pyrolysed and the gases were analysed by GC-MS. SO² was the main sulphur-containing gas produced by flaming combustion in an oxygen-enriched atmosphere. In pyrolysis under various conditions COS was a major sulphur-containing product. Although it is a highly toxic gas, COS has not so far been reported by workers engaged in the toxicity of fire gases. It is suggested that analysis of COS be included in the analytical toxicology of sulphur-containing polymers.     

Ultrastructural studies of experimental acute pancreatitis

Acute pancreatitis was studied by electron microscopy after retrograde infusion of either trypsin, and/or beta-glucuronidase into the canine pancreatic duct. Marked changes were induced by the mixture of trypsin and beta-glucuronidase. (1) The acinar cells were initially excavated from the acinar lumen and formed cystic bodies in themselves. The cystic bodies were then disrupted at their marginal membranes, and the acinar cells were filled with a large amount of fibrillar materials which originated from the contents of the cystic bodies. At this time, the luminal margin of the acinar cells completely disappeared. (2) The cellular organellas and the intracellular fibrillar materials in the acinar cells were discharged into the interstitial space through the disrupted basal lamina. Infection in the pancreatic ductal system was considered to play an important role in the pathogenesis of acute hemorrhagic pancreatitis.     

Analysis of air pollution and prevalence rate of allergic diseases among elementary school children in Kawaguchi and Hatogaya city

Kawaguchi and Hatogaya City are located on the northern edge of Tokyo. We analysed between air pollution and prevalence rate of allergic diseases among elementary school children in this area. A prevalence rate of allergic diseases in 1996 May and June was as follows; bronchial asthma 13.5%, atopic dermatitis 24.5%, allergic rhinitis and/or conjunctivitis 22.8%, urticaria 12.4%, food allergy 7.8% and drug allergy 2.2%, respectively. Air pollution of this area was analysed to check the levels of nitrogen dioxide (NO2), sulfur dioxide (SO2) and suspended particulate matters (SPM). NO2 pollution was relatively high in urban area, and SPM pollution was especially high around the highways. SO2 pollution was lower than the environmental standard. No relationship was found between the prevalence rate of bronchial asthma, atopic dermatitis, allergic rhinitis and/or conjunctivitis and air pollution, but it was found that these diseases are slightly related to population density (p < 0.1, p < 0.01, p < 0.1, respectively).     

Decoupled preview control system and its application to inductionmotor drive

This paper shows that optimal preview control system approaches to a decoupled preview control system as the weighting factors for the control input variables in the quadratic performance index tend towards zero. Therefore, to examine the characteristics of the decoupled preview control system also means to examine the asymptotic characteristics of the optimal preview control system. By this property, relationships between the design parameters and the response of the optimal preview control system become clear and the design of the optimal preview control can be simplified by utilizing the properties that the decoupled preview control system features. Further, the decoupled preview control method is applied to the vector control system for an induction motor drive. By this application, a trade off between the conditions of the vector control and the magnitude of input variables becomes easy. To demonstrate the significance of this proposed method, simulation results of this application are carried out     

Formation mechanism of InxGa1−xAs ohmic contacts to n-type GaAs prepared by radio frequency sputtering

The formation mechanisms of InAs/Ni/W ohmic contacts to n-type GaAs prepared by radio-frequency (rf) sputtering were studied by measuring contact resistances (R_c) using a transmission line method and by analyzing the interfacial structure mainly by x-ray diffraction and transmission electron microscopy. Current-voltage characteristics of the InAs/Ni/W contacts after annealing at temperatures above 600°C showed “ohmic-like behavior.” In order to obtain the “ohmic” behavior in the contacts, pre-heating at 300°C prior to high temperature annealing was found to be essential. The contacts showed ohmic behavior after annealing at temperatures in the range of 500∼850°C and contact resistance values of as low as ∼0.3Ω-mm were obtained. By analyzing the interfacial structures of these contacts, In_xGa_1−xAs layers with low density of misfit dislocations at the In_xGa_1−xAs and GaAs interface were observed to grow epitaxially on the GaAs substrate upon heating at high temperatures. This intermediate In_xGa_1−xAs layer is believed to divide the high energy barrier at the contact metal and GaAs interface into two low barriers, resulting in reduction of the contact resistance. In addition, Ni was found to play a key role to relax a strain in the In_xGa_1−xAs layer (introduced due to lattice mismatch between the In_xGa_1−xAs and GaAs) by forming an intermediate Ni_xGaAs layer on the GaAs surface prior to formation of the In_xGa_1−xxAs layer.     

Analysis of wall conditioning by using plasma impact desorption in the tandem mirror GAMMA 10

A method for evaluating wall condition by using plasma impact desorption (PID) technique has been developed and successfully applied to the tandem mirror GAMMA 10 as a monitor for wall conditioning. A magnetically shielded quadrupole mass spectrometer was installed in the vacuum chamber of the GAMMA 10 central cell. The behaviour of the partial pressure of various gas molecules desorbed by ICRF-heated plasma discharges were analyzed. The predominant increase of the partial pressure due to PID (ΔP_PID) was hydrogen (M = 2) and a small amount of impurity as CO (M = 28), CH₃ (M = 15), H₂O (M = 18) and CO₂ (M = 44) was observed in the wall-conditioning discharges. The reduction of hydrogen pressure as well as ΔP_PID of the above impurities was observed with the progress of wall conditioning. This behavior has a good correlation with the increase of partial pressures due to electron-impact desorption measured at the same period. The relation between ΔP_PID and the charge-exchange flux was investigated.