• Transactions of the Korean Society of Mechanical Engineers A
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• v.28 no.6
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• pp.677-684
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• 2004

Plastic and creep deformations of solder joints during thermal cycling are the main factors of misalignments and power losses in optical telecommunication components. Furthermore, the increased mismatch between solder Joint-bonded areas may cause severe failure in the components. Darveaux's creep model was implemented into a finite element program (ABAQUS) to simulate creep response of solder. Based on the finite element results, thermal fatigue reliability was predicted by using various fatigue life prediction models. Also, the effects of ramp conditions, dwelling time, and solder joint-embedding materials on the reliability were investigated under the thermal cycling conditions of the Telcordia schedule (-40∼75$^{\circ}C$).

• The Korean Journal of Ecology
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• v.6 no.4
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• pp.250-256
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• 1983

Dehiscence of ginseng seeds under the various conditions, growing experiment in the different soil conditions, and growing experiment with extracts obtained by water passed the pot of 4 year ginseng plants were performed. The results obtained are as follows: The survival rate of ginseng plants in the soil of ginseng field sterilized by MIYAZAWA's method was higher than that of the non-sterilized, but lower than that of the control. The survival rate of ginseng plants on the sterilized soil of ginseng field was lower than that on the surrounding soil. The growth of ginseng plants cultivated with the water passed through the pot-planted 4-year-old ginseng plants was strongly inhibited in comparison with the control. Besides biological cause, chemical products excreted from the root of ginseng plants might be the important factors of soil sickness in the successive cultivation of the same plants.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2007.11a
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• pp.1302-1306
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• 2007

Joints are used extensively in various industries. For instance, structural adhesives are used in place of the traditional mechanical fasteners, such as screws and bolts, because they are much lighter and spread the stresses more uniformly across the joints. For efficient designs of joints, knowledge of static and dynamic characteristics of joints is essential. Most analysis of joints are carried out using analytical equations or finite element method. In this paper, the characteristics of four conditions of lap-joint beam are investigated experimentally. The mode shapes and nodal points of beam show that there are different deformations in each condition. These deformations may cause high stresses and may initiate local cracking and delamination failures.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2004.11a
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• pp.211-216
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• 2004

This paper presented a actual conditions on a false-tripping of ELB(Electrical Leakage Breaker) and an assessment of the harmonics due to non-linear electronic equipment such as personal computers, printers, fax machines, and test equipments in several office buildings. Actual conditions on a failure of ELB were surveyed and analyzed by making up a question to safety managers of in office buildings. Also, power quality measurements such as harmonic currents, voltage and current waveforms and current imbalance were made at various office buildings where nuisance tripping of ELB is often occurred. The results of this study can be used in making decisions regarding cause of ELB trip and operating md tripping characteristics test of ELB when subjected to distorted current waveforms.

• Journal of Electrical Engineering and Technology
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• v.10 no.6
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• pp.2262-2270
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• 2015

Generally, internal parameters of the motors and generators can be divided to the resistance and inductance components. They can become a cause of the changing internal parameters because they have sensitive characteristics due to external conditions. The changed parameters can generate the outputs which include error values from the speed and current controllers. Also, it can bring the temperature increase and mechanical damage to the system. Therefore, internal parameters of the motors and generators need to obtain their values according to the external conditions because it can prevent the mechanical damage caused by the changed parameters. In this paper, the off-line parameter identification method is verified using the Goertzel algorithm. The motor used in the simulation and experiments is an interior permanent magnet synchronous motor (IPMSM), and the proposed algorithm is verified by the simulation and experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.15 no.6 s.99
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• pp.738-748
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• 2005

The ship radiated noise level fluctuates by the difference of interference and reverberation according to measurement methods and environmental conditions. These phenomena cause error of the source level estimation even in the same environment conditions. This paper describes a quantitative analysis and a reduction method for an error value to the source level estimation in spatial and temporal interference environment. The design criteria of the radiated noise measurement array composed of omni-directional hydrophones and the source level accuracy in the deep water range are given. The source level accuracy in the shallow water range is also derived based on the statistical model of the multiple reflection paths. The results are verified using the water tank experiment and the sea trial.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.230-235
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• 2004

A new design based on the appropriate geometry of molded part and type of runner system under the optimal processing conditions was proposed to minimize the micro weld lines on the sub deco surface molded by two shot molding. Theoretical and experimental studies were conducted to examine the cause of the weld lines during the overmolding process in two shot molding. Various dimensions and geometries of substrate$(1^{st}shot)$ and the wall thickness of overmold$(2^{nd}shot)$ have been proposed to avoid the weld lines which are the most inevitable appearance defects occurred on the sub deco. The each design proposal was analyzed by mold flow analysis after part modeling. The analysis results were compared with molded part from mass production tool. It could be seen that from the analysis that the proper geometry of plastic part and type of runner system considering pressure drop under the optimal processing conditions were the most influential factors to avoid weld lines occured on the sub deco.

• Journal of the korean Society of Automotive Engineers
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• v.14 no.3
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• pp.90-101
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• 1992

An experimental study was carried out to investigate the characteristics of cyclic variability of combustion in a single cylinder spark ignition engine. Cylinder pressure of 240 consecutive cycles were measured for various engine operating conditions. From these data, a thermody-n amic analysis was performed for the typical cases in order to identify the cause and effect re -lation of the cyclic variation. In determining the number of cycles required for estimating the coefficient of variation of IMEP and so on, the oprating conditions must be cosidered to fit the objective of the analysis. It is thought that the variation in early flame stage is amplified through the flame propagation and results in the phase change between pressure and volume, which can be the major reason of cyclic variation of IMEP in case of lean operation.

• Structural Engineering and Mechanics
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• v.66 no.4
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• pp.515-529
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• 2018

Multiple hazards (multihazard) conditions may cause significant risk to structures that are originally designed for individual hazard scenarios. Such a multihazard condition arises when an earthquake strikes to a bridge pre-exposed to scour at foundations due to flood events. This study estimates the impact spectrum of flood-induced scour on seismic vulnerability of bridges. Characteristic river-crossing highway bridges are formed based on the information obtained from bridge inventories. These bridges are analyzed under earthquake-only and the abovementioned multihazard conditions, and bridge fragility curves are developed at component and system levels. Research outcome shows that bridges having pile shafts as foundation elements are protected from any additional seismic vulnerability due to the presence of scour. However, occurrence of floods can increase seismic fragility of bridges at lower damage states due to the adverse impact of scour on bridge components at superstructure level. These findings facilitate bridge design under the stated multihazard condition.

• Journal of Korean Society of Rural Planning
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• v.1 no.2
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• pp.103-121
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• 1995

This study was carried out to identify the problems and policy alternatives for the improvement of living conditions and environmentally friendly agriculture. The results of surveys on the current situations of living conditions in the rural areas revealed that the main cause of depopulation in Korean rural villages was the lack of social infrastructure and income sources. The current government policies for agriculture geared mainly for improvement of international comparative competitiveness will result in the further disadvantage against the mountainous regions with marginal agricultural lands. Therefore, it is recommended that the agricultural policy should be complemented by the environmental and social policies in the less favoured areas. This can be justified by the fact that the demand for environmental public goods such as recreational opportunities in rural settings uncontaminated by the industrial wastes is growing.