• Title, Summary, Keyword: Modification

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Pre-service teachers' errors and difficulties in task modification focusing on cognitive demand (수학 예비교사들이 과제의 인지적 노력 수준 변형에서 겪는 오류와 어려움)

  • Kang, Hyangim;Choi, Eunah
    • The Mathematical Education
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    • v.60 no.1
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    • pp.61-76
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    • 2021
  • The purpose of this study is to analyze the errors and difficulties which pre-service secondary teachers shows during the task modification in consideration of the cognitive demand and to provide significant implications to the pre-service teacher education program related to the modification of the mathematical tasks. In the pursuit of this purpose, tasks were selected from perpendicular bisector units and 24 pre-service teachers were asked to modify the tasks to higher and lower level tasks. After the modification activities, opportunities for reflection and modification were provided. The findings from analysis are as follows. Pre-service teachers had a difficulty to distinguish between PNC tasks and PWC tasks. Also, We identified the interference phenomena that pre-service teachers depended on the apparent elements of the task. Pre-service teachers showed a tendency to overlook the learning objectives and learning hierarchy during the task modification, and to focus on some types of task modification. However, pre-service teachers were able to have meaningful learning opportunities and extend the category of tools to technology including Geogebra through self-reflection and correction activities on task modification. The above results were summed up and we presented the implications to the task modification program in the pre-service secondary teacher education.

An Improvement for Determining Response Modification Factor in Bridge Load Rating (응력보정계수 산정 방법 개선)

  • Koo, Bong-Kuen;Shin, Jae-In;Lee, Sang-Soon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.5 no.1
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    • pp.169-175
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    • 2001
  • Bridge load rating calculations provide a basis for determining the safe load capacity of bridge. Load rating requires engineering judgement in determining a rating value that is applicable to maintaining the safe use of the bridge and arriving at posting and permit decisions. Load testing is an effective means in calculating the rating value of bridge. In Korea, load carrying capacity of bridge is modified by response modification factor that is determined from comparisons of measured values and analysis results. The response modification factor may be corrupted by vehicle location error that is defined as the gap of test vehicle location between load testing and analysis. In this study, the effects of vehicle location error to structural response and response modification factor are investigated, and a new method for evaluating response modification factor is proposed. The random data analysis shows that the proposed method is less sensitive to vehicle location error than the present method.

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접촉식 측정시스템에 의한 공작물의 자동인식 및 오차보상

  • 신동수;정성종
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • pp.121-125
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    • 1991
  • In order to minimize fixing error of workpieces, prismatic and cylindrical types. Modification Rule by Indexing Table and Modification Rule by NC Program are developed for machining centers by using touch trigger probes. The Modification Rule by Indexing Table means the alignment of workpiece to NC program through degree of freedoms of indexing table. The Modification Rule by NC Program is the alignment of NC program to workpiece set-up condition via the generation of NC program. A postprocessing module is also developed for generating NC-part Program (User Macro) to compensate for Machining errors in end milling and boring processes. Developed methods are verified by experiments.

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Evaluation of Response Modification Factore for Earthquake Resistant Design of Moment-Resisting Steel Frames (모멘트-연성 강구조물의 내진설계를 위한 반응수정계수의 평가)

  • 송종걸
    • Proceedings of the Earthquake Engineering Society of Korea Conference
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    • pp.201-208
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    • 1997
  • In most seismic codes such as the Uniform Building Code(UBC), the response modification factor(or the force reduction factor)is used to reflect the capability of a structure in dissipating energy through inelastic behavior. The response modification factor is assigned according to structural system type. Ductile systems such as special moment-resisting steel frames are assigned larger values of the response modification factor, and are consequently designed for smaller seismic design forces. Therefore, structural damage may occur during a severe earthquake. To ensure safety of the structures, the suitability of the response modification factor used in aseismic design procedures shall be evaluated. The object of this study is to develop a method for the evaluating of the response modification factor. The validity of the evaluating method has been examined for several cases of different structures and different earthquake excitations.

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The Effect of Exercise Combined with Behavior Modification Therapy on the Degree of Obesity, Blood Lipid Level and Self-Esteem in Obese Middle-Aged Women (운동.행동수정요법을 병행한 프로그램이 중년기 비만 여성의 비만도 혈중지질 및 자아존중감에 미치는 영향)

  • Kim In-Hong
    • Journal of Korean Academy of Fundamentals of Nursing
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    • v.8 no.2
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    • pp.234-243
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    • 2001
  • Purpose : To investigate the effects of exercise combined with behavior modification therapy on the degree of obesity. blood lipid level and self-esteem in obese middle aged women. Method : 18 obese middle-aged women volunteers with a BMI over 30% were assigned to exercise combined with behavior modification therapy (n=9) or to a control group(n=9). For the intervention the experiment group used walking outdoors as excercise and behavior modification therapy for 12 weeks. Result Body weight, BMI, TC, TG, LDL-C, and % TC/HDL-C were significantly decreased in experimental group. Changes in HDL-C and self-esteem were significantly increased in the experimental group. Conclusion : This study provides evidence that regular exercise combined with behavior modification is effective in changing the degree of obesity, blood lipid level and self esteem in obese middle-aged women over 12 weeks.

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The Optimum Modification of Dynamic Characteristics of Stiffened Plate Structure Including the Number of Stiffener (보강재의 수를 포함한 보강판 구조물의 동특성의 최적변경)

  • 박성현;고재용
    • Journal of the Korean Institute of Navigation
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    • v.25 no.4
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    • pp.461-469
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    • 2001
  • The purpose of this paper is the optimum modification of dynamic characteristics of stiffened plate structure including the number of stiffener. This paper shows the optimum structural modification method by dynamic sensitivity analysis and quasi-least squares method and considers it's validity. In the method of the optimization, finite element method, sensitivity analysis and optimum structural modification method are used. The change of natural frequency and total weight are made to be an objective function. Thickness of plate, the number of stiffener and cross section moment of stiffener become a design variable. The dynamic characteristics of stiffened plate structure is analyzed using finite element method. Next, rate of change of dynamic characteristics by the change of design variable is calculated using the sensitivity analysis. Then, amount of change of design variable is calculated using optimum structural modification method. It is shown that the results are effective in the optimum modification for dynamic characteristics of the stiffened plate structure including the number of stiffener.

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Tooth modification of helical gears for minimization of vibration and noise

  • Chong, Tae-Hyong;Myong, Jae-Hyong;Kim, Ki-Tae
    • International Journal of Precision Engineering and Manufacturing
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    • v.2 no.4
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    • pp.5-11
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    • 2001
  • Vibration and noise of gears is doc to the transmission error and the vibration exciting force caused by the periodically alternating tooth stiffness. Transmission error is the rotation delay between driving and driven gear caused by manufacturing error, alignment error in assembly and so on. Tooth stiffness changes with the proceeding mesh of teeth. The purpose of this study is to develop how to calculate simultaneously the optimum amounts of tooth profile modification. end relief and crowning by minimizing the vibration exciting force of helical gears. We estimate the vibration exciting force by the meshing analysis of gears. Formulated constraints of this problem consist of contact ratio and strengths of gear teeth such as tooth bending strength, surface durability, and scoring. ADS(Automated Design Synthesis) is used as an optimization tool. We also investigate the relation between the aspect ratio and the optimum values of tooth modification. The proposed method can calculate the optimum amount of tooth modification automatically and is expected to be practically useful to resolve the problem of vibration of helical gears.

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Effect of Divergent Trailing Edge Modification of Supercritical Airfoil in Transonic Flow (천음속유동에서 초임계익형 후연확대수정의 영향)

  • Yoo, Neung-Soo
    • Journal of Industrial Technology
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    • v.17
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    • pp.183-189
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    • 1997
  • The computation of the flow around a supercritical airfoil with a divergent trailing edge(DTE) modification(DLBA 243) is compared to that of original supercritical airfoil(DLBA 186). For this computation, Reynolds-Averaged Navier-Stokes equations are solved with a linearized block implicit ADI method and a mixing length turbulence model. Results show the effects of the shock and separated flow regions on drag reduction due to DTE modification. Results also show that DTE modification accelerates the boundary layer flow near the trailing edges which has an effect similar to a chordwise extension that increases circulation and is consistent with the calculated increase in the recirculation region in the wake. Airfoil with DTE modification achieves the same lift coefficient at a lower incidence and thus at a lower drag coefficient, so that lift-to-drag ratio is increased in transonic cruise conditions compared to the original airfoil. The reduction in drag due to DTE modification is associated with weakening of shock strength and delay of shock which is greater than the increase in base drag.

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Structural Dynamics Modification via Reorientation of Modification Elements (구조물의 결합 위치 변경을 통한 구조물 변경법)

  • Jung, Eui-Il;Park, Youn-Sik
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • pp.666-669
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    • 2004
  • Substructures position is considered as design parameter to obtain optimal structural changes to raise its dynamic characteristics. In conventional SDM (structural dynamics modification) method, the layout of modifying substructures position is first fixed and at that condition the structural optimization is performed by using the substructures size and/or material property as design parameters. But in this paper as a design variable substructures global translational and rotational position is treated. For effective structural modification the eigenvalue sensitivity with respect to that design parameter is derived based on measured frequency response function. The optimal structural modification is calculated by combining eigenvalue sensitivities and eigenvalue reanalysis technique iteratively. Numerical examples are presented to the case of beam stiffener optimization to raise the natural frequency of plate.

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Current Situation and Modification of Kitchen Space by Elderly-headed Household (노인단독가구의 부엌공간 실태와 개조에 관한 연구)

  • Kwon, Oh-Jung;Kim, Mi-Hee;Ha, Hae-Wha
    • Proceeding of Spring/Autumn Annual Conference of KHA
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    • pp.144-148
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    • 2006
  • Kitchen space is one of the most dangerous places for the elderly. Modification of kitchen space for improving safety and independence for older residents is very important factor for aging -in-place. The purpose of this study wes to identify the current situation and modification of kitchen space by elderly-headed household. The sample included 108 respondents over the age 65 who consisted of elderly-couple or single person household with homeownership in Seoul. The data were analyzed by descriptive statistics. Based on the findings of the study, the present incidence and recognition of future need in kitchen modification were identified. Changes in kitchen space made tended to be nonstructural or relatively inexpensive items. In conclusion, this study suggests several ideas for improving current physical problems of kitchen space to support daily living of older residents.

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