• 유체기계공업학회:학술대회논문집
• /
• 2006.08a
• /
• pp.561-564
• /
• 2006

Because of new requirements related to the employment of SMT(Surface Mounting Technology) manufacturing and the diversity of components on high density PCB(printed circuit boards), Thermal control of the reflow process is required in oder to achieve acceptable yields and reliability of SMT assemblies. Accurate control of the temperature distribution during the reflow process is one of the major requirements, especially in lead-free assembly. This study has been performed for reflow process using the commercial CFD tool(Fluent) for predicting flow and temperature distributions. There was flow recirculation region that had a weak point in the temperature uniformity. Porous plate was installed to prevent and minimize flow recirculation region for acquiring uniform temperature in oven. This paper provided design concept from CFD results of the steady state temperature distribution and flow field inside a reflow oven.

• Proceedings of the KIEE Conference
• /
• 2008.07a
• /
• pp.1871-1872
• /
• 2008

본 논문에서는 AR 매뉴얼을 이용한 신속한 조립 정보 제공 방법을 제안한다. 제안된 정보 제공 방법이 기존의 웹이나 BOOK 매뉴얼을 이용한 방법과 비교하여 사용자에게 얼마나 효과적인지를 실제 실험을 통하여 검토된다. 특히 가장 널리 보급된 개인용 컴퓨터 하드웨어 부품에 대한 실험이 제안된 방법의 타당성 검토를 위하여 고찰된다. 기존의 웹과 BOOK 매뉴얼을 이용한 실험과 비교해 보았을 때 제안한 방법이 매우 효율적인 성능을 나타내었다.

• Journal of Mechanical Science and Technology
• /
• v.15 no.3
• /
• pp.339-350
• /
• 2001

To overcome problems in tracking error related to the unmodeled dynamics in the high speed operation of industrial robots, many researchers have used sliding mode control, which is robust against parameter variations and payload changes. However, these algorithms cannot reduce the inherent chattering which is caused by excessive switching inputs around the sliding surface. This study proposes a fuzzy-sliding mode control algorithm to reduce the chattering of the sliding mode control by fuzzy rules within a pre-determined dead zone. Trajectory tracking simulations and experiments show that chattering can be reduced prominently by the fuzzy-sliding mode control algorithm compared to a sliding mode control with two dead zones, and the proposed control algorithm is robust to changes in payload. The proposed control algorithm is implemented to the SCARA (selected compliance articulated robot assembly) robot using a DSP (digital signal processor) for high speed calculations.

• Journal of Mechanical Science and Technology
• /
• v.14 no.7
• /
• pp.782-788
• /
• 2000

In this paper, we present a new approach to visual feedback control using image-based visual servoing with stereo vision. In order to control the position and orientation of a robot with respect to an object, a new technique is proposed using binocular stereo vision. The stereo vision enables us to calculate an exact image Jacobian not only around a desired location but also at other locations. The suggested technique can guide a robot manipulator to the desired location without providing a priori knowledge such as the relative distance to the desired location or the model of an object even when the initial positioning error is large. This paper describes a model of stereo vision and how to generate feedback commands. The performance of the proposed visual servoing system is illustrated by experimental results and compared with conventional control methods for an assembly robot.

• Journal of Environmental Impact Assessment
• /
• v.13 no.3
• /
• pp.103-114
• /
• 2004

As most of environmental impacts caused by development projects are irrevocable, a thorough review is utmost necessary. Ecological-economic integrated approach inspired by Norgaard's co-evolution theory should be applied to the environmentally adjusted CBA, which plays a decisive role in the feasibility analysis. Based on case studies of NamHan River Management Project and Yeongsangang Wetland Reclamation Project, this paper attempts to show the usefulness of linking basic plan and implimentation design to EIA and suggests to integrate EACBA into the current EIA system institutionally as a more effective policy tool for realizing sustainable development in Korea.

• Journal of Welding and Joining
• /
• v.28 no.4
• /
• pp.81-86
• /
• 2010

In resistance spot welding, regardless of the optimal condition, bad weld quality was still produced due to complicated manufacturing processes such as electrode wear, misalignment between the electrode and workpiece, poor part fit-up, and etc.. Therefore, the goal of this study was to measure the process signal which contains weld quality information, and to develop the process fault monitoring system. Welding force signal obtained through variety experimental conditions was analyzed and divided into three categories: good, shunt, and poor fit-up group. And then a monitoring algorithm made up of an artificial neural network that could estimate the process fault of each different category based on pattern was developed.

• Journal of the Korean Society of Environmental Restoration Technology
• /
• v.5 no.1
• /
• pp.51-58
• /
• 2002

Since planning of green-network is deeply being discussed, natural environmental disruption from an enlarged civilization is causing serious problems for urban communities. The purpose of this research is to support green-network infrastructure of Gangnam-gu, Seoul, considering ecological environmental planning for urban parks. The Methodologies for this study are landcover classification, NDVI and subjective analysis, and residents' survey. Findings of this research are as follows : 1) Based on the results, the area adjacent to Daemo mountain shows significant differences between 1985 and 1999. These results imply that the green space has been decreasing and deeply destroying. 2) Residents' survey shows that people want to live with wild animals and plants in the natural park. Future development planning of urban park should consider primary factors : ecosystem, increasing inhabitants' participation.

• Applied Chemistry for Engineering
• /
• v.7 no.6
• /
• pp.1142-1146
• /
• 1996

Cholesterol-containing surfactant was synthesized, and it was sonicated with monomer in water to form a vesicle solution. This vesicle solution was dried to construct a membrane which had a molecular multilayer structure. Using UV irradiation the monomer in this membrane were polymerized, and then surfactant was extracted by organic solvent. Using a X-ray diffractometer, the thickness of one layer and the regularity of the multilayer were measured. And scanning electron microscopy was conducted for fractured polymer film.

• IE interfaces
• /
• v.16 no.spc
• /
• pp.87-92
• /
• 2003

Progressive mesh representation and generation have become one of the most important issues in network-based computer graphics. However, current researches are mostly focused on triangular mesh models. On the other hand, solid models are widely used in industry and are applied to advanced applications such as product design and virtual assembly. Moreover, as the demand to share and transmit these solid models over the network is emerging, the generation and the transmission of progressive solid models depending on specific engineering needs and purpose are essential. In this paper, we present a Cellular Topology-based approach to generating and transmitting progressive solid models from a feature-based solid model for internet-based design and collaboration. The proposed approach introduces a new scheme for storing and transmitting solid models over the network. The Cellular Topology (CT) approach makes it possible to effectively generate progressive solid models and to efficiently transmit the models over the network with compact model size.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2009.10a
• /
• pp.315-317
• /
• 2009

We report the preparation of novel nanofiber organic semiconductors that can be utilized as the active channel materials in the field effect transistors (FETs). The nanofibers produced by the electrospinning reveals the excellent performances (mobility ~ 0.16 $cm^2$/V) due to thier highly ordered molecular packing in the polymer matrix.