§** †† The Japan Aerospace Exploration Agency (JAXA) is now developing a 20N-class thruster valve for spacecraft propulsion systems. We intend to develop this valve with the high reliability, and a robust and durable design. The suspended armature type was chosen for the base design of the new 20N valve based on the results of a trade-off study. Experiments and analysis were performed for the critical parts and manufacturing process. The results enabled us to manufacture a prototype model with single type 20N thruster valves. Good results were obtained in functional tests. We will now proceed to the next phase and complete the detailed design for series redundancy and prepare for the qualification test. Nomenclature a σ = stress amplitude B σ = tensile yield stress m σ = mean stress max σ = maximum stress min σ = minimum stress w σ = Endurance limit when completely reversed
The deoxidation equilibrium of magnesium in liquid nickel and nickel-niobium alloys has been measured at the temperature ranges from 1873 to 1973 K and 1873 K respectively, by the use of magnesia crucible with a view to understanding the equilibrium between magnesium and oxygen, and the effect of niobium on the activity coefficients of oxygen and magnesium in liquid nickel.For the deoxidation reaction in pure liquid nickel, i.e. :MgO(s)=Mg+Othe effect of the temperature on the equilibrium constant, KMg(Ni) ( =aMg·ao/aMgO), was found to be :log KMg(Ni)=-25500/T + 7.78while the effect of magnesium on the activity coefficient of oxygen in liquid nickel was expressed to be :logfMgO(Ni) = (-126300/T + 39.0)[%Mg] 0.003<[%Mg]<0.07The deoxidation equilibrium of magnesium in liquid nickel-niobium alloys with 0.005-0.042 mass% magnesium has been measured up to 8 mass% niobium. The activity coefficients of magnesium and oxygen in liquid nickel-niobium alloys were given by the expression :logfNbO(Ni) + logfNbMg(Ni) = -0.12[%Nb] [%Nb]<8
The effective dose (ED) in computed tomography (CT) may be calculated by multiplying the dose–length product (DLP) by a conversion factor. As children grow, automatic exposure control increases the DLP, while the conversion factor decreases; these two changes affect the ED in opposite ways. The aim of this study was to investigate the methods of ED estimation according to age in pediatric brain CT. We retrospectively analyzed 980 brain CT scans performed for various clinical indications in children. The conversion factor at each age, in integer years, was determined based on the values at 0, 1, 5, and 10 years provided by the International Commission on Radiological Protection (ICRP), using a curve (curve method) or lines (linear method). In the simple method, the ED was estimated using the ICRP conversion factor for the closest age. We also analyzed the ED estimated by a radiation dose management system. Although the median DLP at each age increased with age, the median ED estimated by the curve method was highest at 0 years, decreased with age, and then plateaued at 9 years. The linear method yielded mildly different results, especially at 2 and 3 years. The ED estimated by the simple method or the radiation dose management system showed inconsistent, up-and-down changes with age. In conclusion, the ED in pediatric brain CT decreases with age despite increased DLP. Determination of the conversion factor at each age using a curve is expected to contribute to estimating the ED in pediatric CT according to age.
The deoxidation equilibrium of calcium in liquid nickel has been measured by the sampling technique at the temperature ranges from 1873 to 1973 K using calcia crucibles. The effect of tantalum on the activity coefficient of oxygen in liquid nickel have been also investigated in order to understand the effect of the alloying element on the activity coefficient of oxygen for the production of superalloys. The effect of temperature on the equilibrium constants, Kca (= aca ·ao/acao), for the deoxidation reaction in liquid nickel, i.e:CaO(s) =Ca+Owas found to be :logKca = - 19430/T + 5.35while the temperature dependence of the deoxidation product, K'ca ( = [%Ca] [%O]), and the effect of calcium on the activity coefficient of oxygen in liquid nickel were determined by the expressions :logK'ca = logKca - (-75900/T +28.7) ( [%Ca] +2.51 [%O])logf ca O=(-75900/T + 28.7) [%Ca] 0.01 < mass%Ca < 0.13 The results below 0.01mass% calucium obtained at 1973K have been discussed.Further, the effect of tantalum on the activity coefficients of oxygen and calcium in liquid nickel-tantalum alloys at 1873 K were given by :logfTa O + logfTa Ca = - 0.12 [%Ta] mass%Ta <4.
The denaturation kinetics of bacteriorhodopsin induced by light irradiation was measured in the temperature range between 80 and 86°C, which was just above the melting point of the two-dimensional crystal composed of bacteriorhodopsin molecules in the purple membrane. Bacteriorhodopsin was stable in the dark but gradually denatured under the irradiation of visible light longer than 520 nm. Analyzing the time course of the light-induced denaturation phenomenon, the kinetic constant of the denaturation from a photointermediate state was estimated. The temperature dependence of the kinetic constant lead to the effective activation energy of about 41 kcal/mol. The stability of a photointermediate state was discussed on the basis of the light-induced denaturation behavior.
