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83 results on '"Nakamura, Yuji"'

1. Teacher Assessment and Peer Assessment in Practice. Educational Studies 44.

Author

International Christian Univ., Tokyo (Japan). and Nakamura, Yuji

Abstract

This study examined teacher and peer assessment of English language oral presentation skills in Japanese classrooms. Twelve graduate university students' oral class presentations were assessed by a teacher and four peers. After presentations were rated, teachers calculated the evaluations, and classmates shared their opinions on the top three presenters. The teacher gave summary comments on all presenters. The Many-Facet Rasch Measurement Model was used to investigate three areas (student ability, item difficulty, and rater severity). This analysis provided information on the relationship between the three facets (raters, students, and items); rater severity and fit statistic; student ability and fit statistic; item difficulty and fit statistic; and functioning of rating categories. Results suggest that the test can be improved by examining the fit statistics (misfit items) statistically and by having discussions with raters or students when they are misfitting. The study indicates that peer assessment can successfully motivate students to improve their presentations, students can be reliable peer raters, and the Rasch model can yield considerable significant data on several factors involved in presentation assessment (student academic adequacy, item difficulty, rater severity, and ability of students to adjust socially). (Contains 11 tables.) (SM)

Published
2002

2. Rasch Based Analysis of Reading Ability Questionnaire.

Author

Nakamura, Yuji

Abstract

This paper examines the results of a questionnaire on reading ability in English by Japanese college students, which was formerly analyzed using raw scores, from the viewpoint of Rasch measured scores. In the Rasch analysis, the basic requirements for measuring are the following: (1) reduction of experience to one dimensional abstraction; (2) comparisons among persons and items; (3) the linear magnitude inherent in positioning objects along a line; and (4) a unit determined by a process that can be repeated without modification over the range of the variable. With these requirements in mind, this article deals with the rating scale data by focusing on the idea of linearity. Results are examined along a continuum. It is concluded that reading for testing has two components: contents and skills. Contents should be authentic materials because students use skills to comprehend or draw conclusions from the contents. The eventual scores given by the tests are the end product of their comprehension. Thus the process of reading is analyzed by examining three factors: students are given authentic materials; they struggle to comprehend the material and try to use it; their scores are calculated. (6 references.) (KFT)

Published
2000

3. Many-Facet Rasch Based Analysis of Communicative Language Testing Results.

Author

Nakamura, Yuji

Abstract

This highly technical, data-rich paper examines how the Many-Facet Rasch Measurement Model can be applied to communicative language test data analyses and how beneficial the model is to language teachers. The results for a 20-item conversational response test and a 15-item sociolinguistic test of oral communication ability in English for 30 university students in Japan are presented and evaluated. (Contains 15 references.) (KFT)

Published
2000

4. Measuring Speaking Skills through Multidimensional Performance Tests.

Author

Nakamura, Yuji

Abstract

This paper investigates the effectiveness of students' real communication capabilities by investigating the target language use in monologue, dialogue, and conversational "multilogue" situations. It explores Japanese college students' oral English proficiency by focusing on the linguistic and pragmatic aspects in six types of teaching tests: (1) one way monologue: speech-making overall test; (2) monologue/semi-dialogue: tape-mediated sociolinguistic test; (3) dialogue: face-to-face interview test; (4) dialogue/semi-multilogue: group interview test; (5) small-size multilogue: small-group discussion test; and (6) large-size multilogue: large-group discussion. The results demonstrate that some students who are good at monologue tests or even dialogue tests are not good at larger discussion-oriented or group activity tests. Students should be urged to develop oral communication-oriented learning habits as fluent oral communication in the target language is the ultimate goal for most if not all students. It is uncertain if a lesser ability to communicate in multilogue settings is related to Japanese culture or to some other variable. (Contains 12 references.) (KFT)

Published
1999

5. The Two Crisis over the 2020 Tokyo Olympic and Paralympic Games

Author

NAKAMURA, Yuji

Subjects
Resignation of Chairman of the Organization Committee, Held without spectators, Pros and cons of holding the Tokyo Olympics, Audiences from overseas will not be accepted, 海外観客受け入れ断念, 組織委会長辞任, 無観客開催, 東京五輪開催の是非
Abstract

text, 紀要論文 / Departmental Bulletin Paper

Published
2021

6. The 2020 Tokyo Olympic and Paralympic Games at the Critical Moment

Author

NAKAMURA, Yuji

Subjects
Tokyo Olympics held, 危機状況の発生, 東京五輪開催の可否, 経済浮揚策, New Coronavirus Countermeasures, Economic levitation measures, Crisis situation, 新型コロナウイルス対策
Abstract

text, 紀要論文 / Departmental Bulletin Paper

Published
2021

30. 低重力場における煙流動の再現法に関する検討

Author

Nakamura, Yuji

Abstract

第30回宇宙環境利用シンポジウム (2016年1月19日-20日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)), 相模原市, 神奈川県, Space Utilization Research (January 19-20, 2016. Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency(JAXA)(ISAS)), Sagamihara, Kanagawa Japan, 資料番号: SA6000048013, レポート番号: G-09

Published
2016

43. Study of laser-induced spontaneous ignition of solid combustibles in depressurized enclosure

Author

Nakamura, Yuji, Aoki, Akiyo, Ito, Hiroyuki, Fujita, Osamu, and Kusano, Shinichiro

Subjects
着火, 酸素濃度, partial pressure, 分圧, 酸素, 熱伝達, セルロース, spontaneous combustion, laser heating, cellulose, 着火限界, 自発着火, oxygen concentration, heat transmission, ignitable map, spontaneous ignition, レーザ加熱, ignition, 自然燃焼, ignition limit, 対流, oxygen, 着火範囲, convection
Abstract

Irradiated ignition characteristics of cellulose sheet under low pressure are investigated experimentally. Our final goal of the present study is to establish the standard for fire safety in space enclosure environments. In this paper, two represented sample orientations (either vertical and horizontal) are considered. Total pressure and oxygen concentration are varied from 20 kPa to 100 kPa and from 15 percent to 100 percent. Ignition by CO2 laser is observed and the critical partial pressure of oxygen for ignition is determined as a measure of the fire risk. Results showed that critical amount of oxygen for ignition with both sample orientations are reduced as total pressure is reduced till 40 kPa monotonically. Our results suggest that more severe regulation for fire safety should be applied in the space habitat. In the future work, effect of sample orientation on ignition should be more clarified., 資料番号: AA0063349033

Published
2007

44. Study of flame spread over polymer-insulated wire in depressurized enclosure

Author

Nakamura, Yuji, Matsumura, Tomohiro, Yoshimura, Nobuko, Ito, Hiroyuki, and Fujita, Osamu

Subjects
火炎伝播, polyethylene, 高分子被覆電線, 温度測定, pressure dependence, flame propagation, polymer-insulated wire, 燃焼速度, 低圧, ポリエチレン, burning rate, 電線, 燃焼, flame spread rate, space habitant environment, flame, low pressure, electric wire, 圧力依存性, 火炎広がり速度, 宇宙居住環境, temperature measurement, 火炎, combustion
Abstract

Flame spread character along Polyethylene (PE)-insulated wire as a model of electric devices, which is most possible fire source in space, in quiescent closed chamber is examined experimentally. Sub-atmospheric pressure range from 20 kPa to 100 kPa is of interest to simulate the space habitant environment. Throughout the study, ambient gas composition is fixed at 79 volume percent of nitrogen and 21 volume percent of oxygen (same as air), hence the partial pressure of oxygen is decreased as the pressure in the chamber is decreased. Flame spread subsequent forced ignition is observed and the spread rate is determined as a measure of the fire damage. Three types of chamber configuration are demonstrated to investigate the enclosure effect on flame spread; such as (a) with ceiling and side walls (severely confined case), (b) with ceiling but no side wall, (c) open (no obstacle. Least confined case). Results showed that the spread rate is quite sensitive on the imposed enclosure configuration near the extinction condition; the spread rate decreased with ceiling and side walls but no decrement trend is observed in open configuration. It is suspected that the burned gas tends to stagnant near the combustion regime in severely confined case and the oxygen component to be burned is limited. Without any confined effect, faster spread rate is achieved in depressurized environment. It is addressed that the severe regulation for fire safety should be applied in the space habitant., 資料番号: AA0063349034

Published
2007

45. Study of Acetone-OH Simultaneous PLIF for Combustion Diagnostics of Turbulent Premixed Flames

Author

MANOME, Satoshi, NAKAMURA, Yuji, HAYASHI, Naoki, YAMAMOTO, Kazuhiro, and YAMASHITA, Hiroshi

Subjects
Acetone, Turbelent Flow, Premixed Combustion, OH, Flame Front Curvature, Laser, Flame Zone Thickness
Abstract

This paper described an availability of acetone-OH simultaneous PLIF scheme for combustion diagnostics on turbulent premixed flame. Distinctive signal gap is found between acetone (seeded in the premixed gas) and OH (combustion product) with single excitation wavelength and single CCD camera to achieve relatively low cost measurement of flame zone. Flame zone thickness includes much flame information, e.g. the location of heat release region, local burning velocity. Considered turbulent condition throughout the present study is relatively weak and categorized in laminar flamelet regime. As the equivalence ratio of premixed mixture (acetone-seeded methane-air premixed gas) is varied from 0.64 to 0.90 (burning velocity is increased), measured local flame zone thickness (mode value) is decreased, however 3-D movement of the observed flame front makes the measured flame zone thickness wider than the laminar flame condition. In addition, results show that flame front curvature (convex toward unburned is positive) is positively correlated with flame zone thickness. It is ensured an applicability of the present scheme to survey the relation between flame zone thickness and flame front curvature in turbulent premixed flame.

Published
2007

46. Study on Suppression of PAHs Formation through Partial Premixing Approach

Author

ISHII, Daisuke, NAKAMURA, Yuji, HAYASHI, Naoki, YAMAMOTO, Kazuhiro, and YAMASHITA, Hiroshi

Subjects
Partial Premixing, PAHs, Counterflow Flame, Chemical Reaction, Soot, Combustion, Pollutant
Abstract

The depletion mechanism of polycyclic aromatic hydrocarbons (PAHs) in a partially-premixed methane-air counterflow flame is investigated. The oxygen added to fuel flow is varied in the range from 0.0％ to 5.0％, corresponding equivalence ratio is from ∞ to 30, respectively. 1-D structures of PAHs and C3, C4 hydrocarbon species are analyzed by a gas chromatograph mass spectrometer (GC/MS). Numerical analysis (based on GRI-mech 3.0) for corresponding 1-D flames is performed to obtain detail flame structure up to C2 class of hydrocarbons. As partial premixing proceeded, most of PAHs except for cyclopentadience (C5H6) in the flame are decreased, while C3, C4 species remains as nearly constant value. In order to elucidate major PAHs depletion pathways, possible mass production rate is calculated by using experimentally-measured PAHs concentrations and numerically-predicted radical concentration. It is indicated that benzene (C6H6) is oxidized mainly by O2 and HO2 and decreased as the partial premixing proceeded, then subsequent PAHs formation is decreased according to the benzene depletion. In addition, higher-class of PAHs could be decomposed by way of benzene and cyclopentadiene.

Published
2006

48. Arrangement of Flame Structure by Reaction Progress Variable and Its Gradient in Unsteady Counterflow Premixed Flame

Author

HAYASHI, Naoki, YAMASHITA, Hiroshi, NAKAMURA, Yuji, and YAMAMOTO, Kazuhiro

Subjects
Numerical Analysis, Counterflow, Premixed Flame, Reaction Progress Variable, Unsteady Behavior
Abstract

Dominant parameters in unsteady flame structure of methane/air counterflow premixed flame are investigated by numerical simulation with detailed chemical kinetics model. Two boundary conditions are used for comparison of the difference in the countered gas. One is the twin counterflow premixed flames, which is spouted premixed gas from both nozzles, and the other is the single counterflow premixed flame countered premixed gas and air. In order to investigate unsteady flame behavior, a sinusoidal fluctuation is added to the spout velocity. The influences of average velocity and the fluctuation frequency of the spout velocity on flame structure are examined. It is shown that the flame structure in the single-flame is governed by a reaction progress variable defined with mass fraction of oxygen, Co, q, and its gradient,∇Co,q evaluated at flame front. In the twin-flame,∇Co,q and the gradient of a progress variable defined with temperature evaluated at flame front, ∇Ct,q,dominate the flame structure.

Published
2006

49. Numerical Study on Unsteady Two-Dimensional Premixed Flame Using Elementary Reaction Mechanism (The Validity of Progress Variable and Its Gradient as Descriptor of Premixed Flame Structure)

Author

KATOH, Toshihiro, HAYASHI, Naoki, YAMASHITA, Hiroshi, NAKAMURA, Yuji, and YAMAMOTO, Kazuhiro

Subjects
Flame Propagation Direction, Numerical Analysis, Flame Curvatute, Premixed Flame, Unsteady Behavior, Progress Variable
Abstract

The flame structure of unsteady two-dimensional premixed flame is numerically simulated with elementary reaction mechanism. In order to investigate unsteady behavior, a sinusoidal fluctuation is added to the inlet velocity of methane-air premixed mixture as follows: u0=um{1＋A・sin(2πky)・sin(2πft)}. The average volocity um is 1.25-2.00 m/s, the amplitude A is fixed to 1.0, the frequency f is 100, 250, 500 Hz, and the wavenumber k is 0.1-0.4 mm^-1. The Smooke's skeletal mechanism is adopted as the elementary reaction mechanism. The equivalence ratio is fixed to 0.75. The unsteady behavior and flame structure of premixed flame are examined by using the progress variable defined with mass fraction of oxidizer Cq and its gradient (dC/dn)q at flame front. The obtained results are as follows: The total heat release rate, the temperature gradient, the maximum concentration of species are determined by Cq and (dC/dn)q. Consequently, they are the most important descriptors of premixed flame which dominate the flame structure of premixed flame. The unsteady behavior is classified by the flame curvature and the flame propagation direction, and the classified regions are related to Cq and (dC/dn)q.

Published
2005

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