• Title/Summary/Keyword: equivalent class

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Validating the Translated Version of CARS(Changes in Attitude About the Relevance of Science), Exploring Variables Related to CARS Scores, and Constructing Two Equivalent Test Sets of CARS (과학 관련성 태도 변화 검사도구(CARS-Changes in Attitude about the Relevance of Science) 번역본의 타당도와 관련 변인 탐색 및 동형 검사 도구 구성)

  • Park, Eunju;Lee, Sangeui;Rachmatullah, Arif;Ha, Minsu
    • Journal of Science Education
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    • v.41 no.2
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    • pp.179-194
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    • 2017
  • The purpose of this study is to construct two equivalent science relevance recognition test tool after confirming the reliability and validity of the CARS(Changes in Attitude of Relevance to Science) questionnaire to determine the applicability of the items to Korean students and to compare gender and school differences. For this study, 59 items of the CARS scientific relevance test were translated and assigned to 787 middle and high school students (analyed the answer of 300 middle school students and 431 high school students). In order to determine the fit of the CARS question to Korean students and to overcome the limitation of the number of questions, we used the item-linking method of the Rasch model. By analyzing the results of the research, we constructed two equivalent scientific relevance recognition questionnaires of CARS-A and CARS-B with 25 items. The Pearson correlation coefficient of the Rasch scores of the two equivalent test was 0.78. The two types of scientific relevance recognition test tools generated through this study can be used to confirm students' attitude of scientific relevance to daily life, or to confirm the change after a certain class or grade. Through this study, we will discuss the implications of students' perceptions of science associations in science education, and the development and application of tools.

Impacts of Mt. Bongeui on Atmospheric Purification in Chuncheon

  • Piao, Zhi Hui;Jo, Hyun-Kil
    • Journal of Forest and Environmental Science
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    • v.34 no.2
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    • pp.165-168
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    • 2018
  • Mt. Bongeui is a neighborhood park of 66.4 ha as a major natural landscape resource located in the center of Chuncheon City. This study quantified the reduction of carbon, $SO_2$, $NO_2$, $O_3$, and $PM_{2.5}$, and the production of $O_2$ to explore the role for Mt. Bongeui to contribute to annual atmospheric purification. The main forest types and age classes of the study site included age-class III broadleaved forest at 35.8%, age-class VI coniferous forest at 17.2%, and age-class IV broadleaved forest at 15.7%. The annual atmospheric purification effect per unit area was as follows: 7.6 t carbon/ha/yr, 16.6 kg $SO_2/ha/yr$, 40.4 kg $NO_2/ha/yr$, 41.5 kg $O_3/ha/yr$, 53.7 kg $PM_{2.5}/ha/yr$, and 20.2 t $O_2/ha/yr$. The economic value of these effects was equivalent to about 12.9 million KRW/ha/yr. The study site annually offset carbon emissions of about 300 citizens, $SO_2$ emissions of 220 citizens, and $NO_2$ emissions of 92 citizens in Chuncheon. It also played an important role in annually producing 1.5% of the amount of $O_2$ necessary for the respiration of Chuncheon's total population. This study pioneers in comprehensively quantifying the atmospheric purification effect and could be useful in guiding the planning and management to improve the effect.

Analysis and Implementation of a Half Bridge Class-DE Rectifier for Front-End ZVS Push-Pull Resonant Converters

  • Ekkaravarodome, Chainarin;Jirasereeamornkul, Kamon
    • Journal of Power Electronics
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    • v.13 no.4
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    • pp.626-635
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    • 2013
  • An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter's components are described. A prototype was constructed with a 62-88 kHz variable switching frequency, a 12 $V_{DC}$ input voltage, a 380 $V_{DC}$ output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.

Comparative Study for the Validation of TPNSim++ and its Applicability to Military Simulation (TPNSim++의 검증 및 군사 시뮬레이션 분야의 활용성)

  • 최상영;김대운
    • Journal of the military operations research society of Korea
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    • v.23 no.2
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    • pp.1-14
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    • 1997
  • TPNSim++ is the object-oriented framework for the discrete event simulation of military systems, developed by authors. The simulation world view of TPNSim++ is on the basis of activity scanning. TPNSim++ is implemented as C++ class library under Windows 95/NT. It uses the extended timed Petri nets which are called TPNSim nets for simulation modeling tool. The aim of this study is to conduct a comparative study of TPNSim++ and SLAM II in the simulation of military maintenance systems for the validation and the applicability of TPNSim++. From this study, TPNSim++ and SLAMII have given the same results under the equivalent assumption. Thus we can get the validation of TPNSim++ and its applicability to the simulation of maintenance systems.

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NUMERICAL SOLUTION OF A CLASS OF TWO-DIMENSIONAL NONLINEAR VOLTERRA INTEGRAL EQUATIONS OF THE FIRST KIND

  • Tari, Abolfazl;Shahmorad, Sedaghat
    • Journal of applied mathematics & informatics
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    • v.30 no.3_4
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    • pp.463-475
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    • 2012
  • In this work, we investigate solving two-dimensional nonlinear Volterra integral equations of the first kind (2DNVIEF). Here we convert 2DNVIEF to the two-dimensional linear Volterra integral equations of the first kind (2DLVIEF) and then we solve it by using operational approach of the Tau method. But for solving the 2DLVIEF we convert it to an equivalent equation of the second kind and then by giving some theorems we formulate the operational Tau method with standard base for solving the equation of the second kind. Finally, some numerical examples are given to clarify the efficiency and accuracy of presented method.

A Linear Sliding Surface Design Method for a Class of Uncertain Systems with Mismatched Uncertainties (불확실성이 매칭조건을 만족시키지 않는 선형 시스템을 위한 슬라이딩 평면 설계 방법)

  • 최한호
    • Journal of Institute of Control, Robotics and Systems
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    • v.9 no.11
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    • pp.861-867
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    • 2003
  • We propose a sliding surface design method for linear systems with mismatched uncertainties in the state space model. In terms of LMIs, we derive a necessary and sufficient condition for the existence of a linear sliding surface such that the reduced-order equivalent sliding mode dynamics restricted to the linear sliding surface is not only stable but completely invariant to mismatched uncertainties. We give an explicit formula of all such linear switching surfaces in terms of solution matrices to the LMI existence condition. We also give a switching feedback control law, together with a design algorithm. Additionally, we give some hints for designing linear switching surfaces guaranteeing pole clustering constraints or linear quadratic performance bound constraints. Finally, we give a design example in order to show the effectiveness of the proposed methodology.

Rings which satisfy the Property of Inserting Regular Elements at Zero Products

  • Kim, Hong Kee;Kwak, Tai Keun;Lee, Yang;Seo, Yeonsook
    • Kyungpook Mathematical Journal
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    • v.60 no.2
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    • pp.307-318
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    • 2020
  • This article concerns the class of rings which satisfy the property of inserting regular elements at zero products, and rings with such property are called regular-IFP. We study the structure of regular-IFP rings in relation to various ring properties that play roles in noncommutative ring theory. We investigate conditions under which the regular-IFPness pass to polynomial rings, and equivalent conditions to the regular-IFPness.

ON SUBDIRECT PRODUCT OF PRIME MODULES

  • Dehghani, Najmeh;Vedadi, Mohammad Reza
    • Communications of the Korean Mathematical Society
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    • v.32 no.2
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    • pp.277-285
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    • 2017
  • In the various module generalizations of the concepts of prime (semiprime) for a ring, the question "when are semiprime modules subdirect product of primes?" is a serious question in this context and it is considered by earlier authors in the literature. We continue study on the above question by showing that: If R is Morita equivalent to a right pre-duo ring (e.g., if R is commutative) then weakly compressible R-modules are precisely subdirect products of prime R-modules if and only if dim(R) = 0 and R/N(R) is a semi-Artinian ring if and only if every classical semiprime module is semiprime. In this case, the class of weakly compressible R-modules is an enveloping for Mod-R. Some related conditions are also investigated.

A NOTE ON STRONGLY *-CLEAN RINGS

  • CUI, JIAN;WANG, ZHOU
    • Journal of the Korean Mathematical Society
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    • v.52 no.4
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    • pp.839-851
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    • 2015
  • A *-ring R is called (strongly) *-clean if every element of R is the sum of a projection and a unit (which commute with each other). In this note, some properties of *-clean rings are considered. In particular, a new class of *-clean rings which called strongly ${\pi}$-*-regular are introduced. It is shown that R is strongly ${\pi}$-*-regular if and only if R is ${\pi}$-regular and every idempotent of R is a projection if and only if R/J(R) is strongly regular with J(R) nil, and every idempotent of R/J(R) is lifted to a central projection of R. In addition, the stable range conditions of *-clean rings are discussed, and equivalent conditions among *-rings related to *-cleanness are obtained.

A CLASS OF NEW NEAR-PERFECT NUMBERS

  • LI, YANBIN;LIAO, QUNYING
    • Journal of the Korean Mathematical Society
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    • v.52 no.4
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    • pp.751-763
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    • 2015
  • Let ${\alpha}$ be a positive integer, and let $p_1$, $p_2$ be two distinct prime numbers with $p_1$ < $p_2$. By using elementary methods, we give two equivalent conditions of all even near-perfect numbers in the form $2^{\alpha}p_1p_2$ and $2^{\alpha}p_1^2p_2$, and obtain a lot of new near-perfect numbers which involve some special kinds of prime number pairs. One kind is exactly the new Mersenne conjecture's prime number pair. Another kind has the form $p_1=2^{{\alpha}+1}-1$ and $p_2={\frac{p^2_1+p_1+1}{3}}$, where the former is a Mersenne prime and the latter's behavior is very much like a Fermat number.