• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.38-41
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• 2003

Better understanding and sharing information are getting important to manage interdisciplinary product development team in a globally-distributed company. This study propose a solution to implement RPD(Rapid Product Development) system, focusing on rapid production process, for better understanding between development team members in different place and easy sharing of product information. The system developed by this research shows that SOAP(Simple Object Access Protocol) operates in distributed environment more efficiently than other RPC(Remote Procedure Call) techniques and it does not respond sensitively to firewall. And SOAP is an excellent RPC and messaging technique to exchange structured data. Procedures developed with use of SOAP are worked together with web, and users can use remote services as an application program in their computer.

• Journal of Mechanical Science and Technology
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• v.16 no.4
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• pp.427-435
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• 2002

This paper presents a development result for image processed tracking system of multiple moving objects based on Kalman filter and a simple window tracking method. The proposed algorithm of foreground detection and background adaptation (FDBA) is composed of three modules: a block checking module(BCM), an object movement prediction module(OMPM), and an adaptive background estimation module (ABEM). The BCM is processed for checking the existence of objects. To speed up the image processing time and to precisely track multiple objects under the object's mergence, a concept of a simple window tracking method is adopted in the OMPM. The ABEM separates the foreground from the background in the reset simple tracking window in the OMPM. It is shown through experimental results that the proposed FDBA algorithm is robustly adaptable to the background variation in a short processing time. Furthermore, it is shown that the proposed method can solve the problems of mergence, cross and split that are brought up in the case of tracking multiple moving objects.

• Journal of Information Technology Application
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• v.1
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• pp.173-211
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• 1999

The task of classification permeates all walks of life, from business and economics to science and public policy. In this context, nonlinear techniques from artificial intelligence have often proven to be more effective than the methods of classical statistics. The objective of knowledge discovery and data mining is to support decision making through the effective use of information. The automated approach to knowledge discovery is especially useful when dealing with large data sets or complex relationships. For many applications, automated software may find subtle patterns which escape the notice of manual analysis, or whose complexity exceeds the cognitive capabilities of humans. This paper explores the utility of a collaborative learning approach involving integrated models in the preprocessing and postprocessing stages. For instance, a genetic algorithm effects feature-weight optimization in a preprocessing module. Moreover, an inductive tree, artificial neural network (ANN), and k-nearest neighbor (kNN) techniques serve as postprocessing modules. More specifically, the postprocessors act as second0order classifiers which determine the best first-order classifier on a case-by-case basis. In addition to the second-order models, a voting scheme is investigated as a simple, but efficient, postprocessing model. The first-order models consist of statistical and machine learning models such as logistic regression (logit), multivariate discriminant analysis (MDA), ANN, and kNN. The genetic algorithm, inductive decision tree, and voting scheme act as kernel modules for collaborative learning. These ideas are explored against the background of a practical application relating to financial fraud management which exemplifies a binary classification problem.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.1115-1119
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• 2005

The paper proposes the elastic modulus evaluation technique of a cantilever beam by vibration analysis based on time-average electronic speckle pattern interferometry (TA-ESPI) with non-contact and nondestructive and Euler-Bernoulli equation. General approaches for the measurement of elastic modulus of thin film are Nano indentation test, Bulge test and Micro-tensile test and so on. They each have strength and weakness in the preparation of test specimen and the analysis of experimental result. ESPI has been developed as a common measurement method for vibration mode visualization and surface displacement. Whole-field vibration mode shape (surface displacement distribution) at a resonance frequency can be visualized by ESPI. And the maximum surface displacement distribution from ESPI is a clue to find the resonance frequency at each vibration mode shape. And the elastic modules of test material can be easily estimated from the measured resonance frequency and Euler-Bernoulli equation. The TA-ESPI vibration analysis technique is able to give the elastic modulus of materials through the simple processing of preparation and analysis.

• Journal of the Korean Mathematical Society
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• v.51 no.1
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• pp.87-98
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• 2014

Let R be a commutative ring with identity and M an R-module. In this paper, we associate a graph to M, say ${\Gamma}(M)$, such that when M = R, ${\Gamma}(M)$ is exactly the classic zero-divisor graph. Many well-known results by D. F. Anderson and P. S. Livingston, in [5], and by D. F. Anderson and S. B. Mulay, in [6], have been generalized for ${\Gamma}(M)$ in the present article. We show that ${\Gamma}(M)$ is connected with $diam({\Gamma}(M)){\leq}3$. We also show that for a reduced module M with $Z(M)^*{\neq}M{\backslash}\{0\}$, $gr({\Gamma}(M))={\infty}$ if and only if ${\Gamma}(M)$ is a star graph. Furthermore, we show that for a finitely generated semisimple R-module M such that its homogeneous components are simple, $x,y{\in}M{\backslash}\{0\}$ are adjacent if and only if $xR{\cap}yR=(0)$. Among other things, it is also observed that ${\Gamma}(M)={\emptyset}$ if and only if M is uniform, ann(M) is a radical ideal, and $Z(M)^*{\neq}M{\backslash}\{0\}$, if and only if ann(M) is prime and $Z(M)^*{\neq}M{\backslash}\{0\}$.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.1
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• pp.86-92
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• 2009

This paper presents development of 6kw ZVS(Zero Voltage Switching) boost converter by 4-parallel operation. To realize a high capacity converter with 6 kw, 4-parallel operation of 1.5kW unit module is proposed in this paper. To meet high ratio input to output voltage, isolated type booster converter is designed. To achieve ZVS operation of 4-switches of full bridge and protect a voltage overshoot caused by switch turn-off, simple active-clamp circuit is applied to the primary side. For parallel operation of 4-modules, master-slave control method is proposed to achieve input current sharing of 4-unit converter modules accurately. For performance tests, simulation is carried out. Also, load and experimental tests of the developed booster converter, 230Vdc/6kW, are carried out under various conditions. For field tests, the developed converter is applied for boosting a battery power to high DC_link voltage for a VSI inverter which starts a micro-turbine(MT) installed in vehicle and it's performance is verified through high speed motoring a MT up to tens of thousands of rpm.

• 연구논문집
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• s.32
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• pp.85-94
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• 2002

Even in the world wide automobile companies where a few simple modules are put into practical use, the front subframe modules of which performances of durability, NVH and crash are significantly important are under planing. In this study, design technology for the automobile front subframe module, which consists of an engine, a transmission and steering parts, structural components (frame, upper arm, lower arm and brake etc.) and rubber components(engine mount, axle mount and rubber disc etc.), was developed. A FEM-based analytical approach was used to evaluate the multiaxial high cycle fatigue damage of the front subframe module. Strain-life fatigue database system and expert system for fatigue properties of welded materials were developed. Stiffness values of the various rubber bushes mounted on the front subframe were evaluated by experimental method and FEM. TWB(Tailor Welded Blank) technology was applied to forming the cross member of the front subframe. Performance evaluations in relation to NVH and crash were conducted by using CAE technologies.

• Current Photovoltaic Research
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• v.2 no.2
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• pp.63-68
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• 2014

In recent years, discoloration defects, called as snail trail, have been observed at many crystalline photovoltaic modules after a period of time ranging from several months to several years after initial installation. It has been reported that this phenomenon doesn't impact on the performance of photovoltaic modules, but it can be detected through simple visual inspection. The origin and detailed mechanism for the formation have not been identified. In this study, non-destructive analysis by Raman spectroscopy has been carried out to investigate the origin of this phenomenon. In parallel, destructive analysis by scanning electron microscopt and transmission electron microscopy was also performed in order to confirm the results from non-destructive method. Through the extensive analysis, it was found that the main cause for discoloration is the formations of $Ag_2CO_3$ and $AgC_2H_3O_2$. Detailed mechanism for the formation of these particles was indentified through systematic studies.

• Journal of Power Electronics
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• v.9 no.4
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• pp.544-552
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• 2009

This paper presents a novel spring pressure contact interconnect technique for medium power integrated power electronics modules (IPEMs). The key technology of this interconnection is a spring which is made from Be-Cu alloy. By means of the string pressure contact, sufficient press-contact force and good electrical interconnection can be achieved. Another important advantage is that the spring exhibits excellent performance in enduring thermo-mechanical stress. In terms of manufacture procedure, it is also comparatively simple. A 4 kW half-bridge power inverter module is fabricated to demonstrate the performance of the proposed pressure contact technique. Electrical, thermal and mechanical test results of the packaged device are reported. The results of both the simulation and experiment have proven that a good performance can be achieved by the proposed pressure contact technique for the medium power IPEMs.

• Ceramist
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• v.22 no.2
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• pp.122-132
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• 2019

Wearable electronic devices with batteries must be lightweight, flexible and highly durable. Most importantly, the battery should be able to self-generate to operate the devices without having to be too frequently charged externally. An eco-friendly energy harvesting technology from various sources, such as solar energy, electromagnetic energy and wind energy, has been developed for a self-charging flexible battery. Although the energy harvesting from such sources are often unstable according to the surrounding environment, the energy harvesting from body movements and vibrations has been less affected by the surrounding environment. In this regard, flexible piezoelectric modules are the most attractive solution for this issue, because they convert mechanical energy to electrical energy and harvest energy from the human body motions. Among the various flexible piezoelectric modules, piezoelectric nanofibers have advantages when used as an energy harvester in wearable devices, due to their simple manufacturing process with good applicability to polymers and ceramics. This review focused on diverse flexible piezoelectric nanofibers and discusses their applications as various energy harvesting systems.