Kenjiro Suzuki

Thermoelectric power of quasi-one-dimensional Nb3X4 with X=S, Se andTe

Abstract The thermoelectric power of linear chain synthetic metals Nb 3 X 4 (with X = S , Se and Te ) was measured from 5 to 300 K. The thermopower is negative indicating a dominant transport by electrons. Common to three compounds, in lower temperature regions the thermopower rises linearly with temperature but soon saturates. With respect to Nb 3 S 4 and Nb 3 Se 4 we have found no special anomaly of the thermopower except for a little higher magnitude. With respect to Nb 3 Te 4 anomalies in the thermopower vs temperature appear at about 80 and 20 K which are explained in terms of the charge- density-wave phase transition from the simultaneous measurement of the resistivity and the observation of the electron diffraction patterns.

Superlattice structure of Nb3Te4 at low temperatures

Abstract A quasi-one-dimensional metal Nb3Te4 exhibits a superlattice structure below about 100 K. The phenomenon is revealed by electron diffraction for the first time. A clear domain pattern is observed by electron microscope images by both host lattice diffraction and superlattice diffraction beams. The wavevectors for the superlattice are described by q ∗ ± = 1 1.5a ∗ ± 3 7c ∗ with reciprocal lattice vectors. The cause of the superlattice generation is attributed to the charge-density-wave which couples strongly with lattice waves so that a deformation of the crystal lattice resulted.

The sound velocity of liquid TeSe mixtures

Abstract We have measured the sound velocity of liquid Te70Se30, Te50Se50 and Te30Se70 mixtures and obtained their adiabatic compressibility βs. There appear prominent maxima in the temperature variations of βS. It is concluded that the pressure-induced semiconductor-to-metal transition previously observed for liquid Te-Se mixtures is associated with the structural change from Se-like loosely packed to Te-like densely packed structure.

Sound Velocity Measurements of Molten Germanium

The temperature dependence of the sound velocity of molten germanium was measured up to 1200° C using a newly developed high-temperature ultrasonic measurement system. The system is based on the phase-comparison method and provides highly precise sound-velocity measurement. The temperature dependence of sound velocity of molten germanium showed softening near the melting temperature during both heating and cooling processes. This could be attributed to microscopic structural changes in the liquid.

Stripe and charge-density-wave domain structures of Nb3Te4

Abstract By means of electron microscopy, superlattice reflections from charge-density-wave domains were observed in a quasi-one-dimensional conductor Nb3Te4. Print-out effect was observed for the martensitic stripe domain structure at low temperature, suggesting the occurrence of radiation damage for electron beam acceleration voltage over 350 kV. By cooling the specimen, CDW and stripe domains appeared nearly simultaneously at 100 ± 5 K. By warming, however, the former disappeared at 105 ± 5 K, while the latter at 115–120 K.

Ultrasonic Pulse Transmission/Echo Technique for Sound Velocity Measurements in High Temperature and High Pressure Liquid Metals

We report the details of an ultrasonic pulse transmission/echo technique which has been newly developed for sound velocity measurements in liquid metals up to temperatures around 1600°C and pressures around 2000 bars. The results of sound velocity measurements in the metal-nonmetal transition region of Hg near its critical point (Tcr=1480°C, Pcr=1600 bar) are also reported.

Solving Applied Geometric Design Problems with the Use of 3D-CAD

With the wide spread use of 3D-CAD in industrial fields, some people say that traditional descriptive geometry is no longer any use. In fact, typical descriptive geometry problems such as finding the true length of a straight line and the intersection lines between two solid objects can be solved much more precisely and much more quickly with the use of 3D-CAD than with hand drawings based upon traditional descriptive geometry. Is the traditional descriptive geometry really no longer any practical use? In order to get some insight into this question, we solve some applied geometric design problems with the use of 3D-CAD, and compare the solution processes with those in traditional descriptive geometry. The results of comparison show the followings: (1) Solution strategies in 3D-CAD are basically similar to those in traditional descriptive geometry. Even in 3D-CAD solutions, the use of graphics representations (i.e., 2-dimensional representations) such as projection from a specified direction, development and sectioning are quite useful. (2) It is, however, not necessary to use traditional rules and compasses to get such graphics representations. Projection function and sectioning function in 3D-CAD are useful in getting graphic representations. (3) Much easier solution strategies are sometimes available in 3D-CAD by applying rich 3D-CAD geometric processing functions such as assembly function. (4) Knowledge on spatial geometry just behind traditional descriptive geometry is, needless to say, still important in 3D-CAD solutions.

Present Status of Garphic Science and Graphic Representation Education

図法幾何学は, 立体の図的表現法―投影法―と図による立体図形の解析を扱う学問・技術の体系であり, 設計技術者や造形芸術関係者等, 立体形状を取り扱う者に必須な基礎知識である.この内容は大学・短大・高等専門学校における機械系, 建築・土木系, 芸術・デザイン系学科では, 図学という科目名のもとで教えられてきた.しかし, CG/CADの普及により, 図学, および, 図的表現法に関する教育は大きな変革期を迎えている.日本図学会では, このように変革期にある図学教育の現状を把握するとともに, 新しい図学教育のあり方を探るため, 2002年度から2003年度にかけて図学, および, 図的表現法に関する教育についてアンケート調査を実施した.調査項目は所属, 講義実施状況, 養成したい能力, 講義内容である.調査の主要な結果は以下のとおりである. (1) 3次元形状を生成し分析する能力に比べて, 図面を描く能力および情報伝達能力が重要視されている. (2) CG/CADの導入は普及しつつあるが, 手描きによる作図や図法幾何学も重要視されている.本文ではこれらの調査内容の概要について述べる.

A Mental Cutting Test Using Stereographic System Conducted to the Middle Scoring Group of the Test

MCTにおける解答時間を立体視の影響という側面から分析するために, 従来, MCTに対して中・低得点群とされている女子を対象に立体視MCTと透視図MCTを行った結果, 以下のことが明らかになった. (1) 立体視することでMCTの全解答時間は約30%短縮された. (2) 両テストともに解答時間が短い問題ほど正解率が高い傾向にあった. (3) 立体視では, 両眼視差によって奥行情報が得やすくなり, MCTにおける情報処理過程のうち, 『図から立体および切断面を認識する』過程が容易になった結果, この過程に要する時間が短縮されると共に, 同過程において生ずる誤答が減少した. (4) 『立体の切断面による切り口を求め, (切断面を回転するなどして) 実形を認識する. (必要とあれば) 量判断を行う.』過程に主たる誤答原因がある問題では, (3) に関わる過程では処理に要する解答時間が減少するものの, 誤答の原因が他の過程にあるため正解率が上昇しなかった.

Multivariate Analysis on the Performance of a Mental Cutting Test

本研究では, コンピュータ・ネットワークを使用して切断面実形視テスト (MCT) を実施するシステムを開発し, 理工系の大学生1208名を対象に調査を行った.得られた得点, 及び, 解答時間について多変量解析により分析した.主な結果は以下の通りである.まず, 各問題の解答時間を因子分析した結果, MCTには, 主に「イメージ解答過程」, 「分析的考察過程」の二つの解答過程が存在することが示された.また, 各問題の解答時間と得点の重回帰分析を行った結果, 高得点者は低得点者に比べ, 単純なパターン判別問題については短時間でイメージを生成して解答しており, 量判別問題や高難度のパターン判別問題の一部については分析的考察に時間をかけて解答していることが示された.さらに, 各問題の誤答のクラスター分析, 及び, 相関分析を行った結果, MCTにおけるイメージ生成能力と分析的考察能力の間には高い相関関係があることが示された.