• Current Optics and Photonics
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• 제6권4호
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• pp.381-391
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• 2022

Two-photon-polymerization additive-manufacturing systems feature high resolution and precision. However, there are few reports on specific methods and possible problems concerning the use of small lasers to independently build such platforms. In this paper, a femtosecond-laser two-photon-polymerization additive-manufacturing system containing an optical unit, control unit, monitoring unit, and testing unit is built using a miniature femtosecond laser, with a detailed building process and corresponding control software that is developed independently. This system has integrated functions of light-spot detection, interface searching, micro-/nanomanufacturing, and performance testing. In addition, possible problems in the processes of platform establishment, resin preparation, and actual polymerization for two-photon-polymerization additive manufacturing are explained specifically, and the causes of these problems analyzed. Moreover, the impacts of different power levels and scanning speeds on the degree of polymerization are compared, and the influence of the magnification of the object lens on the linewidth is analyzed in detail. A qualitative analysis model is established, and the concepts of the threshold broadening and focus narrowing effects are proposed, with their influences and cooperative relation discussed. Besides, a linear structure with micrometer accuracy is manufactured at the millimeter scale.

• 대한수학교육학회지:학교수학
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• 제15권4호
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• pp.723-742
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• 2013

본 연구는 초등학교 5학년 학생들을 대상으로 수학 학습에 비구조화된 문제의 해결활동을 적용하여 문제 해결 과정에 나타난 초등학생의 비례적 추론 과정을 분석하여 학생들의 비례적 추론 수준과 형태의 특징을 알아보는 것을 목적으로 하였다. 연구 결과 학생들은 주어진 비구조화된 문제를 해결하면서 모둠별로 다양한 양상으로 비논리적(illogical) 접근, 덧셈적(additive) 접근, 곱셈적(multipicative) 접근, 함수적(functional) 접근의 비례적 추론 수준과 형태를 나타내었다. 또한 학생들은 비구조화된 문제를 [문제 이해하기]-[해 구하기]-[적용하기]의 과정을 통해 해결하면서 [양의 인식]-[비례적 관계 발견]-[비례적 관계 확장]의 흐름으로 비례적 추론의 모습을 나타냈다. 학생들로 하여금 실생활에서의 비, 비례 상황에서 여러 가지 양들을 비례적으로 추론할 기회를 갖도록 하여 비례적 추론을 발전시킬 수 있도록 해야 할 것이다.

• 대한기계학회논문집
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• 제14권2호
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• pp.339-348
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• 1990

Techniques which are able to predict and control dynamic characteristics, not affecting the vibrational characteristics on the modification of structural design, are being studied. As one of these techniques, experimental modal analysis is widely applied by many researchers. In this study, modal analysis is performed using transfer matrix method by a macro computer. The developed program would estimate the structural modal parameters precisely, and the validity of this program is certified by comparing with the experimental results of .GAMMA A. structure. Estimated modal parameters(natural frequency, vibrational mode, equivalent mass, etc.) are in accord with the experimental results. Also, the optimal location of the additive mass is determined by the evaluation of the vibrational mode and the equivalent mass. The relation between the additive mass and the equivalent mass is specified, and we come to know that the ratio of equivalent mass to additive mass alter linearly within the range of 20%.

• Geomechanics and Engineering
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• 제15권6호
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• pp.1219-1225
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• 2018

In this study, a comprehensive laboratory experimental programme was conducted on expansive soil with a high swelling potential to study the influence of different additive materials on swelling pressure and index properties. Lime, sand, multifilament fiber and fibrillated fiber were used for stabilization of expansive soil. Lime, sand and fibers were respectively added to the expansive soil at 0-7%, 0-80%, 0-0.5%. On each mixture that was prepared by the proportions mentioned above, Atterberg limits, compaction, and swelling pressure tests were conducted. From the result of these experiments, the swelling pressure-time relation could be replaced by a rectangular hyperbola established to facilitate the prediction of ultimate percent swelling with a few initial data points. The best type of additive and its optimum ratio for engineering purposes could be estimated rapidly by this approach.

• 한국수학교육학회지시리즈A:수학교육
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• 제46권2호
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• pp.141-153
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• 2007

The purpose of the study is to analyze children's proportional reasoning and problem solving in proportional problems with/without iconic representations. Proportional problems include 3 tasks such as (a) without any picture, (b) with simple picture, and (c) with/without iconic representation. As a result, children didn't show any significant differences in two tasks such as (a) and (b). However, children showed better proportional reasoning with iconic representation. In addition, 'build-up expression' strategy was used mostly in solving problems and 'additive strategy' was shown as an error which students didn't make an appropriate proportional relation expression and they made a wrong additive strategy.

• 한국수학교육학회지시리즈A:수학교육
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• 제46권2호
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• pp.155-171
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• 2007

One second grader, Junsu, was observed 4 times before and after formal multiplication lesson in Grade 2. This study describes how solution strategies in multiplication problems develop over time and investigates awareness of the relation between situation and computation in simple measurement and partitive division problems as informally experienced. It was found that Junsu used additive calculation for small-number multiplication problems but could not solve large-number multiplication problems and that he did not have concept of mathematical terms at first interview stage. After formal teaching, Junsu learned a variety of multiplication solution strategies and transferred from additive calculation to multiplicative calculation. The cognitive processing load of each strategy was gradually reduced. Junsu experienced measurement division as a dealing strategy and partitive division as a estimate-adjust strategy dealing more than one object in the first round.

• 한국식품조리과학회지
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• 제7권4호
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• pp.23-34
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• 1991

This study was to investigate consumer recognition of food safety and food additives. The results of this study are as follows: 1. When shopping for food, the food safety was rated as foremost concern for the respondents and the details checked most often were manufacture date, packing condition and axpiration date, respectively. When asked their opinion about harmful factors in relation to food safety, the most important consideration was food additives. The highest rating for credibility regarding the sources of information on food was given to scientists in university and institute, lowest one was given to food manufacturer. 2. Government regulation on the use of food additives was known to exist, but control of the uses of food additive was considered inadequate by 60% of the respondents. These results showed significant differences for age (p<0.05), for education level (p<.01) and for income (p<.05) respectively. 3. 47.9% of the respondents indicated that they were willing to purchase the additive free foods, although it was expensive. More than 70% made an effort to eat food with less food additive and were concerned about possible effects of food additives on health, showing significant differences for age (p<0.05), for education level (p<0.05) and for income (p<0.05). 4. Labeling for food additive found on food package was shown to be unsatisfactory, showing significant difference only for income (p<0.05) and more information about food was needed by over 91.3% of the respondents, showing significant difference for education level (p<0.05). 5. Although approximately 80% of the respondents were concerned about artificial preservative, artificial flavor, artificial color and artificial sweetener, the concern about artificial preservative was the highest. Primary causes that respondents felt fear toward food additives were the unknown harms and cancer, and primary sources that respondents got information on food were televison and radio, respectively. From these results, it was shown that consumer considered food safety important and they felt a great deal of concern about food additives.

• 대한수학회논문집
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• 제35권4호
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• pp.1075-1085
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• 2020

We investigate the relation between the notion of e-exactness, recently introduced by Akray and Zebary, and some functors naturally related to it, such as the functor P : Mod-R → Spec(Mod-R), where Spec(Mod-R) denotes the spectral category of Mod-R, and the localization functor with respect to the singular torsion theory.

• 대한의용생체공학회:의공학회지
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• 제11권1호
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• pp.65-70
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• 1990

The phenomenon of color sensory has been mainly studied on the relation with the stimulus source of light source color according to dispersed energy of light. However, it has not been definitely found that the phenomenon of color sensory be collcerned with evoked potentials stimulated by object color. This paper proposes the method that evoked potentials stimulated by object colors are analyzed and examined on the phenomemon of color sensory. The model of evoked potentials is assumed that it is consisted of an additive noise and a transient signal caused by stimulus. The method which is used to estimate the signal is time-varying filtering.

• 대한전기학회논문지
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• 제45권3호
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• pp.393-398
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• 1996

In this paper, we consider H.inf. control of nonlinear systems which have not only additive uncertainties but also input-multiplicative uncertainties. Using the relation between the L$_{2}$ gain of a nonlinear system and the Hamilton-Jacobi-Isaacs inequality, we define