• Journal of Power Electronics
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• v.19 no.3
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• pp.727-743
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• 2019

This paper presents a pulse-width modulation strategy to eliminate the common mode voltage (CMV) with reduced CMV spikes in multilevel inverters since a high CMV magnitude and its fast variations dv/dt result in bearing failure of motors, overvoltage at motor terminals, and electromagnetic interference (EMI). The proposed method only utilizes the zero CMV states in a space vector diagram and it is implemented by a carrier-based pulse-width modulation (CBPWM) method. This method is generalized for odd number levels of inverters including neutral-point-clamped (NPC) and cascaded H-bridge inverters. Then it is extended to the over-modulation mode. The over-modulation mode is implemented by using the two-limit trajectory principle to maintain linear control and to avoid look-up tables. Even though the CMV is eliminated, CMV spikes that can cause EMI and bearing current problems still exist due to the deadtime effect. As a result, the deadtime effect is analyzed. By taking the deadtime effect into consideration, the proposed method is capable of reducing CMV spikes. Simulation and experimental results verify the effectiveness of the proposed strategy.

• Proceedings of the Korean Information Science Society Conference
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• 2012.06b
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• pp.205-207
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• 2012

본 논문은 Use Case 기반 개발에서 요구사항부터 테스트 케이스를 자동 추출하는 메커니즘을 제안 하고자 한다. 제안한 메커니즘은 기존의 테스트케이스 생성 메커니즘을 Use Case 메커니즘과 접목한 것이다. 그리고 그 기반으로 자동 도구 구현을 통해 모든 가능한 테스트 케이스 추출하는데 있다. 이는 최소의 테스트 케이스로 100%의 기능적인 요구사항 커버리지 만족시킨다는 Gary 방법을 이용하고자 함이다. 이 도구의 단계는 확장된 UML 다이어그램으로부터 원인-결과 다이어그램을 전환 한 후, 결정 테이블화한다. 마지막 단계는 이를 통하여 테스트케이스가 자동적으로 발생 한다.

• Korean System Dynamics Review
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• v.14 no.2
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• pp.31-53
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• 2013

This article deals with a Causal-Loop analysis of the characteristics of Ouroboros effects. The meaning of the effects is that solutions to problems are usually intended as final fixes, but more often than not, while solving one problem, they generate more problems. It means 'to worsen through attempts to make better.' The Ouroboros effects are very dangerous because they are regarded as a kind of self-destructive mechanisms. While existing researchers recognize the risks of the effects, they are not able to solve the systematic problem but only to describe the symptom. Such a way to deal with the effects results in difficulty to clarify the cause-and-effect relationship within the system. Thus the authors are focusing on explaining the effects by SD (System Dynamics), which are considered as the sole methodology to do effectively so far since SD is a great tool to discover structural causes. To solve the self-destructive problem of the effects, the authors analyze the characteristics of several cases of the effects in elaborating the CLD (Causal Loop Diagram) for each case. The analysis reveals the structural characteristics of the effects and how to correct them towards maintaining the sustainability of systems.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.40 no.1
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• pp.114-123
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• 2017

The global small and mid-sized display market is changing from thin film transistor-liquid crystal display to organic light emitting diode (OLED). Reflecting these market conditions, the domestic and overseas display panel industry is making great effort to innovate OLED technology and incease productivity. However, current OLED production technology has not been able to satisfy the quality requirement levels by customers, as the market demand for OLED is becoming more and more diversified. In addition, as OLED panel production technology levels to satisfy customers' requirement become higher, product quality problems are persistently generated in OLED deposition process. These problems not only decrease the production yield but also cause a second problem of deteriorating productivity. Based on these observations, in this study, we suggest TRIZ-based improvement of defects caused by glass pixel position deformation, which is one of quality deterioration problems in small and medium OLED deposition process. Specifically, we derive various factors affecting the glass pixel position shift by using cause and effect diagram and identify radical reasons by using XY-matrix. As a result, it is confirmed that glass heat distortion due to the high temperature of the OLED deposition process is the most influential factor in the glass pixel position shift. In order to solve the identified factors, we analyzed the cause and mechanism of glass thermal deformation. We suggest an efficient method to minimize glass thermal deformation by applying the improvement plan of facilities using contradiction matrix in TRIZ. We show that the suggested method can decrease the glass temperature change by about 23% through an experiment.

• Journal of Convergence for Information Technology
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• v.11 no.8
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• pp.84-91
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• 2021

In the 21st century, a number of storm and flood disasters caused by rapidly changing climate change is increasing, and the number of flood accidents at construction sites is also increasing. However, no specific reduction measures have been presented and thereby safety management to prevent flood accident need to be improved. Therefore, in this study, the inundation pattern by downpour at the excavation site was interpreted and the inundation risk quantification method was used to classify the risk magnitude. Finally, using the fish-bone diagram, we derived the major reasons of inundation accident at construction site systematically. The simulation results showed that the inundation depths of small-scale excavation sites and excavation sites exceeded 3 m due to the fluid flowing through the excavation surface. In addition, depending on the excavation site, a high velocity temporarily observed and decreased due to the storage effect, or high velocity surpassing 10 m/s continued. Since this type of flooding can pose a risk to most or all workers, if proper management measures are insufficient, fatal damage to life and property could occur. Consideration of the roots of these disasters is judged to be helpful in understanding the causes of inundation accidents that result in casualties and presenting accident reduction measures.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.1232_1233
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• 2009

Paraquat is well-known to cause hepatotoxic responses in human and other mammal species. In solution, it forms free radicals and charge-transfer complex of which formation plays an important role in determination of its biological activity in the presence of various anions. The HepG2 cells were cultured onto a quartz crystal sensor which is possible to detect the density and a viscosity changes using the resonance frequency (F) and the resonance resistance (R). The plot of F-R diagram is able to explain the rheological change of cells onto the surface of the quartz crystal sensor. In this paper, we investigated the physical properties of the HepG2 cells cultured onto a ITO electrode of the quartz crystal sensor according to the paraquat injection at various concentrations (100 mM, 10 mM, 1 mM). We also observed the morphological changes with a micro CCD camera, simultaneously. The HepG2 cells were cultured onto the ITO electrode surface of the quartz crystal modified a collagen film in $CO_2$ incubator. After the paraquat injection, we observed the changes of the morphologies by the micro CCD camera depending on time and analyzed the physical changes of cells on the electrode surface of quartz crystal using F-R diagram. From all results, we proved the effect of paraquat at various concentrations which is led to an apoptosis such as weakening and death of the cells by oxidation and reduction reaction that were produced the superoxide anions and other free radicals.

• Journal of KIISE
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• v.43 no.10
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• pp.1104-1114
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• 2016

Software is continuously changing during development and after development. When a change is required, it is difficult to precisely grasp the scope of impact intuitively. A systematic method is needed to accomplish the required change. The purpose of impact analysis on software change is to avoid missing any information by recognizing the ripple effect that the change might cause. This paper proposes a dynamic method that can easily identify the scope of change request by using the association between use-case scenarios and artifacts of UML modeling in object-oriented development environment. By using this approach, the scope of impact that the change might have on other components such as class diagram and sequence diagram in use-case scenarios can be identified by forward tracing. In addition, analysis of influence of possible further changes due to changes in other components can be identified iteratively through backward tracing. The results of this paper are not limited to impact analysis on artifacts and change type. They can also be used as basic guidelines during impact analysis for various change requests.

• Journal of Korean Society for Quality Management
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• v.38 no.3
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• pp.340-353
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• 2010

Properly designed and well-executed services enable e-commerce companies to capture the unique needs and preferences of customers, help them build customer loyalty, and thereby, strengthen their competitiveness in the marketplace. An object of this study is the new open-market company and it has only 3 percent of the market share. Therefore, it is needed to raise the market share by improving the service qualities. This article presents a six sigma project for service quality improvement in the open-market company. This study was carried out based on five steps of DMAIC which is six sigma technique. First, a defect rate was defined as unsatisfaction rate. In addition, 50-people data was analyzed and it was shown that the defect level was 2.5 sigma level. In this study, in order to raise the sigma level, novel eight action items were determined based on SIPOC, FDPM, cause and effect diagram, matrix chart, Pareto chart and statistical analysis.

• Journal of Astronomy and Space Sciences
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• v.24 no.4
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• pp.451-456
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• 2007

Data coming from devices shall be transported to a specific task to be used in a software with the most accurate time and data integrity. During this process, a potential cause for invoking structured hazard and performance degradation is dormant. In this paper, a method which can protect the data integrity from the possible data corruption when collision has happened during I/O data exchange between device and tasks is presented. Also, an example diagram of mechanism according to the method is shown and the effect, merits and demerits of the method is evaluated.

• Industrial Engineering and Management Systems
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• v.9 no.3
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• pp.251-261
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• 2010

This article demonstrated the application of the Fuzzy Data Envelopment Analytical Hierarchy Process (FDEAHP) to evaluate the root causes of critical defect problems occurring in the production of liquid medicine. The methodology of the research began by collecting the defect data by using Check Sheets, and ranking the significant problems by using a Pareto Diagram. Two types of major problems were found to occur, including glass fragments in the medicine and damaged lid threads. The causes of each problem were then analyzed by using Cause and Effect Diagrams. The significant causes were ranked by FDEAHP under three criteria, Severity (S), Occurrence (O) and Detection (D), followed by the framework of the FMEA Technique. Two causes with the highest Final Weight (FW) of each problem were selected to be improved, such as installing auxiliary equipment, using the Poka-Yoke system, setting the scale of the shaft and lathing the bushes of each bottle size. The results demonstrated a reduction in defects from 3.209% to 1.669% and showed that improving a few significant root causes, identified by an experienced decision maker, was sufficient to reduce the defect rate.