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Enhanced Mechanical Properties of Orthorhombic Ti₂AlNb-Based Intermetallic Alloy
Hagiwara, M.,Emura, S.,Araoka, A.,Kong, B.O.,Tang, F. 대한금속재료학회 2003 METALS AND MATERIALS International Vol.9 No.3
Attempts were made to improve the mechanical properties of an orthorhombic Ti₂AlNb-based Ti-22Al-27Nb intermetallic alloy through microstructural and compositional modifications, and the dispersion of fine TiB particulates. A Ti-22Al-27Nb alloy with a prior B2 grain size ranging from 8 mm to 49 ㎛ was successfully obtained using spherical α₂particles as obstacles to grain growth. The finest grained material showed an excellent combination of room temperature tensile strength (around 1,000 MPa) and tensile ductility (more than 15 %). Transition metal elements such as Mo, V and W for a portion of the Nb in the Ti-22Al-27Nb were substituted. The guideline for this compositional modification required that the beta phase stability in the modified alloy be equal to that of the Ti-22Al-27Nb. It was found that the substitution of 2 % W for 7 % Nb was quite effective in increasing tensile strength at temperatures above 923 K and reducing the steady state creep rate and primary creep strain. The Ti-22Al-27Nb alloy-based particulate composites reinforced with 6.5 % TiB were successfully produced with the gas atomization P/M method. The dispersion of extremely small TiB was very uniform. Most of the mechanical properties of the composites, including the yield stress, tensile strength, Young's modulus, resistance to creep, and high cycle fatigue strength were greatly superior to those of the matrix alloy.
M. Hagiwara,T. Sanami,K. Masumoto,Y. Iwamoto,N. Matsuda,Y. Sakamoto,Y. Nakane,H. Nakashima,Y. Uwamino 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
Nuclear data on proton-induced neutron and γ-ray production in the energy range from 10 to 20 MeV is important to estimate the shield design and activation of low-energy cyclotron facilities for medical use such as production of radiopharmaceuticals in positron emission tomography (PET). We have measured double-differential thick target yields (TTYs) of neutrons and γ-rays from a ^(18)O-enriched water (H^(18)_2O) target induced by 18 MeV protons in order to estimate leakage radiations from a cyclotron and the neutron-induced activation in the production process of the ^(18)F-tagged fluorodeoxyglucose (FDG) which is a common radiopharmaceuticals for PET. Neutrons and γ-rays were measured with 5.08 cm diameter × 5.08 cm long NE213 scintillators for eight laboratory angles between 15- and 150-degrees. After applying a neutron-γ-ray event separation using the pulse-shape-discrimination (PSD) technique the neutron and γ-ray events were analyzed by a time-of-flight (TOF) technique and an unfolding technique, respectively. The measured TTYs were compared with TENDL-2009 data library and the physical model calculations with MCNPX and PHITS. The calculated TTYs roughly agree with the measured data.
RADIATION SAFETY STUDIES AT TOHOKU UNIVERSITY CYRIC
Yamadera, M. Baba A.,Miura, T.,Aoki, T.,Hagiwara, M.,Kawata, N. 대한방사선 방어학회 2001 방사선방어학회지 Vol.26 No.3
A brief introduction is presented on the radiation safety studies at Tohoku University Cyclotron & Radioisotope Center. Studios on two subject are described; (1) measurement of the thick target neutron yield and radioisotope production / activation cross section for ten's of MeV neutrons and ions using K=110 Tohoku University cyclotron to provide basicdata fur accelerator shielding, and (2) development of techniques for high sensitive radiation detection and profile measurement using an Imaging Plate which is a high sensitive two-dimensional radiation sensor. Application of the Imaging Plate techniques to localization of very weak radioactivity and to neutron profile measurement is described.
T. Sanami,M. Hagiwara,H. Iwase,M. Takada,D. Satoh,Y. Iwamoto,S. Kunieda,H. Yashima,A. Tamii,M. Baba 한국물리학회 2011 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.59 No.23
The experimental program to measure double differential cross section (DDX) data for fragment production is launched to establish reaction models and parameters for proton induced reaction on light-medium nuclei for the energy range from threshold to a few hundred MeV. In this program, a Bragg Curve Counter (BCC) that is improved to cover entire energy range of fragment is employed as a detector. DDXs of lithium, beryllium, boron and carbon emission at 30, 60, 90, and 135 degree were measured for 40, 50, 70, and 80 MeV proton on carbon, nitrogen, oxygen and aluminium Theoretical calculation results using three different intra-nuclear cascade models were compared with experimental data. By choosing appropriate model, the calculation generally reproduces the DDXs except for fragments having relatively high energy and small emission angle, and fragments from two body reaction.
τ polarization in SUSY cascade decays
Choi, S.Y.,Hagiwara, K.,Kim, Y.G.,Mawatari, K.,Zerwas, P.M. North-Holland Pub. Co 2007 Physics letters. Section B Vol.648 No.2-3
τ leptons emitted in cascade decays of supersymmetric particles are polarized. The polarization may be exploited to determine spin and mixing properties of the neutralinos and stau particles involved. The sensitivity of the method is illustrated in comparison with predictions for models of universal extra space dimensions. Details of the analysis including experimental effects such as transverse momentum cuts are presented for τ->π decays, which can readily be generalized to other decay modes.