• Journal of Korea Society of Industrial Information Systems
• /
• v.22 no.2
• /
• pp.79-89
• /
• 2017

The Optimization of a Closed-Loop Supply Chain (CLSC) Model Using an Adaptive Hybrid Genetic Algorithm (AHGA) Approach is Considered in this Paper. With Forward and Reverse Logistics as an Integrated Logistics Concept, The CLSC Model is Consisted of Various Facilities Such as Part Supplier, Product Manufacturer, Collection Center, Recovery Center, etc. A Mathematical Model and the AHGA Approach are Used for Representing and Implementing the CLSC Model, Respectively. Several Conventional Approaches Including the AHGA Approach are Used for Comparing their Performances in Numerical Experiment.

• Journal of Educational Research in Mathematics
• /
• v.15 no.1
• /
• pp.57-74
• /
• 2005

The aim of this study is to reflect Vygotsky's theory of Zone of Proximal Development and other scholars' scaffolding theories emboding the theory and to examine the effects of mathematics instruction by scaffolding. The subjects of this study consist of 8 fifth graders attending S elementary school which is located in San-Chung county. The teaching-learning processes were videotaped and analysed according to scaffolding components. The results between pretest and posttest regarding to fraction were compared and the responses of students to a questionnaire on the mathematical attitude before and after the teaching experiment. It concludes that mathematics instruction by scaffolding was effective to improve students' mathematical learning ability and positive mathematical attitude.

• International Journal of Reliability and Applications
• /
• v.15 no.2
• /
• pp.85-98
• /
• 2014

Accelerated life testing (ALT) is a well famous technique in life testing and reliability studies, this is particularly used to induce so high stress leading to failure of the highly reliable units quickly under stipulated duration of time. The step-stress ALT is one of the systematic experimental strategy of ALT applied to fail the units in steps. In this article we focus on two important issues (i) necessity of life tests at higher steps with relevant causes (ii) to develop a new optimum test plan for 3-step SSALT under the modified cumulative exposure model proposed by Khamis and Higgins (1998). It is assumed that the lifetime of test units follows Rayleigh distribution and its scale parameter at constant stress level is assumed to be a log-linear function of the stress. The maximum likelihood estimates of the parameters involved in the step-stress ALT model are obtained. A simulation study is performed for numerical investigation of the proposed new optimum plan 3-step, step-stress ALT. The necessity of the life test units at 3-step step-stress is also numerically examined in comparison to simple step-stress setup.

• East Asian mathematical journal
• /
• v.24 no.5
• /
• pp.527-545
• /
• 2008

One of the education purpose of the section "Figures" in the eighth grade is to develop students' deductive reasoning ability, which is basic and essential for living in a democratic society. However, most or middle school students feel much more difficulty or even frustration in the study of formal arguments for geometric situations than any other mathematical fields. It is owing to the big gap between inductive reasoning in elementary school education and deductive reasoning, which is not intuitive, in middle school education. Also, it is very burden for students to describe geometric statements exactly by using various appropriate symbols. Moreover, Usage of the same symbols for angle and angle measurement or segments and segments measurement makes students more confused. Since geometric relations is mainly determined by the measurements of geometric objects, students should be able to interpret the geometric properties to the algebraic properties, and vice verse. In this paper, we first compare and contrast inductive and deductive reasoning approaches to justify geometric facts and relations in school curricula. Convincing arguments are based on experiment and experience, then are developed from inductive reasoning to deductive proofs. We introduce teaching methods to help students's understanding for deductive reasoning in the textbook by using stepwise visualization materials. It is desirable that an effective proof instruction should be able to provide teaching methods and visual materials suitable for students' intellectual level and their own intuition.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.4
• /
• pp.8-15
• /
• 2016

Most machines lose a lot of energy due to friction. Wear due to friction also reduces performance. Therefore, it is important to reduce friction on the surface to improve energy efficiency and decrease wear. Surface texturing refers to making patterns on the surface for reducing friction. There are many surface texturing methods, such as using lasers, abrasive jet machining, and so on. Recently, mechanical manufacturing methods, such as cutting and grinding, have been highlighted. Among them, the grinding method has the advantage of making patterns in large areas quickly. Therefore, it is appropriate for surface texturing on large machines. This paper is a study on the slope change of the surface texturing pattern using grinding. Therefore, we researched the slopes of the patterns corresponding to "spindle speed and feed rate" and "curvature of workpiece surface" using a mathematical model and experiment. As a result, we made a proper mathematical model concerning our research. Therefore, using the mathematical model in this paper, we could predict the slope change of the pattern according to grinding conditions.

• Journal of Gifted/Talented Education
• /
• v.16 no.1
• /
• pp.81-100
• /
• 2006

In this paper, it conducted the following works to develop the selective test for the gifted of information science in elementary schools. First, it presented the discrete mathematical thinking as an essential competence of elementary information science gifted, through theoretical research with many expert's studies, in order to investigate the definition and characteristics of information science gifted. Second, it developed a test to measure the discrete mathematical thinking, according to the results of analysis of discrete mathematical elements, appeared in the 7th national mathematics curriculum, in order to extract the characteristics of selective test for elementary information science gifted. Third, regarding the verification of items in a newly developed test, it adjusted the difficulty and discrimination by conducting 2 sessions of preliminary test, and then finally confirmed that the standards of items in the test, by testifying sufficient level of validity after the application to a main experiment.

• Journal of Biosystems Engineering
• /
• v.10 no.2
• /
• pp.36-46
• /
• 1985

This study was intended to develop the mathematical model of the head-fed type threshing unit. As the first step, the physical model of the threshing phenomena was considered to consist of four separate processes as 1) detachment process of grains, 2) movement of grains between the cylinder and concave, 3) grain penetration through stems of bundle, and 4) grain passing through concave. The mathematical and computer models were developed based on the physical models. Threshing experiments were performed and determined the distribution of grain accumulation along the cylinder shaft by varying the moisture content of grains, feeding rate, and cylinder speed. It was found that the model developed coincided very well with the experimental results for the varied operational conditions. Greater concentration of grains passing through concave toward the thresher inlet was equally true for the model and experiment work for the threshing of grains with higher moisture content and with higher cylinder-speed. The model could be used for obtaining the optimized design or for optimizing the performance of the head-fed type threshing unit if term as to power requirement for threshing may be additionally included in the developed model.

• Wind and Structures
• /
• v.35 no.6
• /
• pp.369-383
• /
• 2022

Wind tunnel experiment was carried out to study the cross-wind layer forces on a square cross-section building model using a synchronous multi-pressure sensing system. The stationarity of measured wind loadings are firstly examined, revealing the non-stationary feature of cross-wind forces. By converting the measured non-stationary wind forces into an energetically equivalent stationary process, the characteristics of local wind forces are studied, such as power spectrum density and spanwise coherence function. Mathematical models to describe properties of cross-wind forces at different layers are thus established. Then, a conditional simulation method, which is able to ex-tend pressure measurements starting from experimentally measured points, is proposed for the cross-wind loading. The method can reproduce the non-stationary cross-wind force by simulating a stationary process and the corresponding time varying amplitudes independently; in this way the non-stationary wind forces can finally be obtained by combining the two parts together. The feasibility and reliability of the proposed method is highlighted by an ex-ample of across wind loading simulation, based on the experimental results analyzed in the first part of the paper.

• Journal of the Korean School Mathematics Society
• /
• v.4 no.2
• /
• pp.27-32
• /
• 2001

The paper describes some principles how we design the mathematics curriculum through mathematical Modelling. since the motivation for modelling is that it give us a cheap and rapid method of answering illposed problem concerning the real world situations. The experiment was focussed on the possibility that they can involved in modelling problem sets and carry modelling process. The main principles could be described as follows. principle 1. we as a teacher should introduce the modelling problems which have many constraints at the begining situation, but later eliminate those constraints possibly. principle 2. we should avoid the modelling real situations which contain the huge data collection in the classroom, but those could be involved in the mathematics club and job oriented problem solving. principle 3. Analysis of modelling situations should be much emphasized in those process of mathematics curriculum principle 4. As a matter of decision, the teachers should have their own activities that do mathematics curriculum free. principle 5. New strategies appropriate in solving modelling problem could be developed, so that these could contain those of polya's heusistics

• Environmental Engineering Research
• /
• v.13 no.2
• /
• pp.98-104
• /
• 2008

In this study, chromate and cetylperidinium chloride (CPC) removal from artificial wastewater was monitored by using micellar enhanced ultrafiltration (MEUF) and activated carbon fibre (ACF) adsorption hybrid processes. For the efficient chromate removal, molar concentration of the CPC should be five times that of chromate and it should be at least one critical micelle concentration (CMC). The MEUF was found to be effective in the chromate removal while ACF in the CPC adsorption to produce chromate and CPC free effluents. The chromate and CPC removal was 99.8% from MEUF-ACF process. Effluent chromate concentration was exponentially correlated with molar ratio of CPC to chromate and pH.