• Proceedings of the International Microelectronics And Packaging Society Conference
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• 2002.09a
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• pp.79-94
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• 2002

Root cause -Thermal expansion coefficient mismatch -Tape warpage -Initial die crack (die roughness) Guideline for failure prevention -Optimized tape/Substrate design for minimizing the warpage -Fine surface of die backside Root cause -Thermal expansion coefficient mismatch - Repetitive bending of a signal trace during TC cycle - Solder mask damage Guideline for failure prevention - Increase of trace width - Don't make signal trace passing the die edge - Proper material selection with thick substrate core Root cause -Thermal expansion coefficient mismatch -Creep deformation of solder joint(shear/normal) -Material degradation Guideline for failure Prevention -Increase of solder ball size -Proper selection of the PCB/Substrate thickness -Optimal design of the ball array -Solder mask opening type : NSMD -In some case, LGA type is better

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.322-325
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• 2007

Dent resistance is an important characteristic to avoid damage on automotive outer panels. From a practical point of view, dents can be caused in a number of ways. Considering doors as an example, denting can occur from stone impacts or from the careless opening of an adjacently parked vehicle door. Denting can occur where the door surface is smooth and may not have sufficient curvature to resist dent. These exterior body parts are designed to improve dent resistance using a combination of work hardening and bake hardening. In brief, dent is affected by the shape of the parts and the material properties such as yield strength, strain and thickness. In this work, forming of door outer panel is investigated by Taguchi method. Main parameters are yield strength, thickness, blank size, blank holding force and so on. For the given value of design parameters, forming analysis of the thirty six cases are carried out according to L18 orthogonal array. After comparing the performance by simple conversion of simulation results into dent resistance, the final suggestion of the forming parameters is verified for the best improvement of dent resistance.

• Journal of Power System Engineering
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• v.13 no.5
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• pp.59-66
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• 2009

High temperature and pressure valves in power plant have been used for fluid flowing and leakage occurred owing to valve internal damage such as disc wear, crack and inserting of foreign objects etc. in these valves. Recently, multi-measuring technique applied both ultrasonic and acoustic method have been used for evaluation of valve internal leakage in order to raise measurement reliability. Therefore, we have performed various leakage tests using ultrasonic and acoustic measuring system and acquired leakage data for the various leakage conditions. In this study, we developed the estimation method of regression model through leakage data, and expectation method for valve opening ratio, which is directly proportion to leakage rate, using the established estimation model from the measured data, valve size and fluid pressure so as to enhance data reliability. As a result of this study, it was founded that expectation method of leakage rate by statistical analysis method is appropriate to valve leakage evaluation.

• Transactions of Materials Processing
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• v.16 no.4 s.94
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• pp.254-259
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• 2007

Dent resistance is an important characteristic to avoid damage on automotive outer panels. From a practical point of view, dents can be caused in a number of ways. Considering doors as an example, denting can occur from stone impacts or from the careless opening of an adjacently parked vehicle door. Denting can occur where the door surface is smooth and may not have sufficient curvature to resist dent. These exterior body parts are designed to improve dent resistance using a combination of work hardening and bake hardening. In brief, dent is affected by the shape of the parts and the material properties such as yield strength, strain and thickness. In this work, forming of door outer panel is investigated by Taguchi method. Main parameters are yield strength, thickness, blank size, blank holding force and so on. For the given value of design parameters, forming analysis of the eighteen cases are carried out according to L18 orthogonal array. After comparing the performance by simple conversion of simulation results into dent resistance, the final suggestion of the forming parameters is verified for the optimal improvement of dent resistance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.4A
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• pp.337-342
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• 2010

Generally most sluice gates are closed and opened by a mechanical winch, a winch using an oil-pressure, or a winch mixing both. Because of their size and structure, they should be safely operated with more than two pulling devices helping each other. At the moment of their opening and closing, there usually occur some additional loads to the structure which cannot be exactly measurable at the stage of designing. Such additional loads can cause the sluice gate to be unbalanced and make it hard to open and close the gate, and by also overloading a winch, they can inflict a significant damage to the safety of the sluice gate. This paper explains a FDC(Force-Displacement Control) system which simultaneously considered the oil-pressure and displacement in order to evenly distribute the force and make a winch balanced at the opening and closing motion. This FDC system was implemented by means of the PID(Proportional Integral Derivative) function of XG 5000 program. It was experimented on a model of the sluice gate winch with the hydraulic oil pressure cylinder. The experiments showed that the developed FDC system made the winch of hydraulic oil pressure cylinder open and close cooperatively in spite of various external loads. Therefore the FDC system is proven effective when it is applied to a winch of sluice gate.

• Journal of Arbitration Studies
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• v.26 no.1
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• pp.89-105
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• 2016

2008 began with the American financial crisis which gave way to the liquidity crisis (Fannie Mae and Freddie Mac) situation in which 'the withdrawal of investment initiated from the insufficiency of the U.S. subprime mortgage loan companies', 'the large size loss situation of the financial company (Bear Stearns) due to the American structured bond insufficiency' and the second half opening part national debt mortgage company. Within the American financial crisis was propagated the crisis of international derivatives. Due to this, the withdrawal of foreign investment progressed in the interior of a country with the considerable. By the end of 2007, the exchange rate fluctuation was absorbed in the domestic financial circle on the belief the potentiality of the domestic financial market had been growing drastically through the expansion of the foreign currency debt according to this and it came to the defence but while the exchange rate jumped up to the dollar shortage according to the international crisis, the small and medium companies making the banks and exchange rate-related derivatives contract were going bankrupt due to the derivatives loss. The small and medium factories establish the bank exchange rate-related derivatives has nose (KIKO), pivot (PIVOT), and snowball (Snowball) etc. at that time and the damage which it is the KIKO grasped at 6 end of the months in 2008 caused by reaches to 1 thousand billion 4 thousand hundred million dollars. Small and medium companies in which the dollar which it has to denounce among small and medium companies bearing the KIKO contract in fact with the Knock-In generation city bank exceeds the amount of sales were known to be 68 enterprises among 480 enterprises. This paper departs in this awareness of a problem and tries to look into the risk factor of the derivatives, including nose and study the essential ring risk management plan of small and medium manufacturer.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.31 no.3
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• pp.15-22
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• 2003

The fatigue crack growth model is derived and the retardation model is proposed. The fatigue crack growth model considers the residual plastic stretch on the crack surface which results from the plastic deformation at the tip of fatigue crack. The fatigue crack growth rate is calculated by using the cumulative fatigue damage and plastic strain energy in the material elements at the crack tip. This model gives the crack growth rate in reasonable agreement with test data for aluminum alloy AL6061-T651 and 17-4PH casting steel. The fatigue crack growth retardation model is based on the residual plastic stretch produced from a tensile overload which reduced the plastic strain range of the following load cycles. A strip-yield model of a crack tip plasticity is used for the calculation of a plastic zone size. The proposed retardation model characterized the observed features and delayed retardation of the fatigue crack growth under tensile overload.

• Korean Chemical Engineering Research
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• v.60 no.3
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• pp.347-355
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• 2022

The safety valve (PSV) is a safety device that automatically releases a spring when the pressure generated by various causes reaches the set pressure, and is restored to a normal state when the pressure falls below a certain level. Periodic inspection and monitoring of safety valves are essential so that they can operate normally in abnormal conditions such as pressure rise. However, as the current safety inspection is performed only at a set period, it is difficult to ensure the safety of normal operation. Therefore, evaluation items were developed by finding failure modes and causative factors of safety valves required for safety management. In addition, it is intended to provide decision-making information for securing safety by deriving the priority of items. To this end, a Delphi survey was conducted three times to derive evaluation factors that were judged to be important in relation to the Failure Mode Cause Factor (FMCFs) of the safety valve (PSV) targeting 15 experts. As a result, 6 failure modes of the safety valve and 22 evaluation factors of its sub-factors were selected. In order to analyze the priorities of the evaluation factors selected in this way, the hierarchical structure was schematized, and the hierarchical decision-making method (AHP) was applied to the priority calculation. As a result of the analysis, the failure mode priorities of FMCFs were 'Leakage' (0.226), 'Fail to open' (0.201), 'Fail to relieve req'd capacity' (0.152), 'Open above set pressure' (0.149), 'Spuriously' 'open' (0.146) and 'Stuck open' (0.127) were confirmed in the order. The lower priority of FMCFs is 'PSV component rupture' (0.109), 'Fail to PSV size calculation' (0.068), 'PSV Spring aging' (0.065), 'Erratic opening' (0.059), 'Damage caused by improper installation and handling' (0.058), 'Fail to spring' (0.053), etc. were checked in the order. It is expected that through efficient management of FMCFs that have been prioritized, it will be possible to identify vulnerabilities of safety valves and contribute to improving safety.

• Journal of Bio-Environment Control
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• v.23 no.4
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• pp.293-302
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• 2014

This study was carried out to develop rain shelter which can make an appropriate size and environment for Chinese cabbage rainproof cultivation. Fifty three farms with chinese cabbage rainproof cultivation system have been investigated to set up width and height of rain shelter. Mostly the width of 6m was desired for rain shelter and the height of 1.6m for their eaves, so these values were chosen as the dimensions for rain shelter. After an analysis of their structural safety and installation costs by the specifications of the rafter pipe, Ø$25.4{\times}1.5t$ and 90cm have been set as the size of rafter that such size costs the least. This size is stable with $27m{\cdot}s^{-1}$ of wind velocity and 17cm of snow depth. Therefore it is difficult to apply this dimension to area with higher climate load. In order to sort out such problem, the rain shelter has been designed to avoid damage on frame by opening plastic film to the ridge. Once greenhouse band is loosen by turning the manual switch at the both sides of rain shelter and open button of controller is pushed then switch motor rises up along the guide pipe and plastic film is opened to the ridge. Chinese cabbage can be damaged by insects if rain shelter is opened completely as revealed a field. To prevent this, farmers can install an insect-proof net. Further, the greenhouse can be damaged by typhoon while growing Chinese cabbage therefore the effect of an insect-proof net on structural safety has been analyzed. And then structural safety has been analyzed through using flow-structure interaction method at the wind condition of $40m{\cdot}s^{-1}$. And it assumed that wind applied perpendicular to side of the rain shelter which was covered by insect-proof net. The results indicated that plastic film was directly affected by wind therefore high pressure occurred on the surface. But wind load on insect-proof net was smaller than on plastic film and pressure distribution was also uniform. The results of structural analysis by applying pressure data extracted from flow analysis indicated that the maximum stress occurred at the end of pipe which is the ground part and the value has been 54.6MPa. The allowable stress of pipe in the standard of structural safety must be 215 MPa or more therefore structural safety of this rain shelter is satisfied.

• Journal of Korean society of Dental Hygiene
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• v.11 no.1
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• pp.103-111
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• 2011

Objectives : This study of oral health problems was conducted to 311 students in Special Schools in order to inquire into the state of their oral health behaviors, to find out the main obstacles against dental services, to secure dental reasonable basis for oral health promotion. Methods : A questionnaire survey was conducted in the Special School of the 311 students in the area of the metropolitan Seoul. By means of Chi-squared test and Fisher's exact test, oral hygiene habits for each type of the subjects, the contents of dental care services, the prerequisites to improve oral health, were inquired. To evaluate the effects to the current oral health status of types of disability, 2-way ANOVA was practiced. Results : The handicapped with Visual impairment, mental retardation, multiplicity with disabilities, answered negatively in their own oral health status. 47.4% of the deaf can do brush for theirselves without the inconvenience, but in other types of disability they showed that they were helped by others. Subjects did not use the secondary oral hygiene necessaries because, except brain damage, almost of types of disability impeded the convenient use. 60 to 88.2 percent of the total respondents were the recent visitors to dental clinique within 1 year, and the most common motives of the visiting dentist, is a routine medical examination, their movements to the dentist in all types of disabilities, needed helps of others. Most of them received medical treatment at a private dentist, the handicapped preferred the private care and place(49.8%). Only in the case of the brain disorders, extremely much of the disabled answered that they were needed the preventive treatment, and the another cases of disability were largely needed the treatment of the decayed teeth. To improve the oral health of the people with disabilities, at the opening of the clinics and hospitals over a certain size, the mandatory medical facilities for the care of the disabled should be preceded and followed by the improvement of dental insurance system so as to reduce the burdens of the cost of dental care. Conclusions : The improvement of oral health policy for the disabled are needed inevitably: Development of secondary oral hygienic easy to use for the disabled, the building systems of medical dental hospital with the disabled facilities, by the improvement of the insurance system, the reduction of the burden of payments.