• Proceedings of the IEEK Conference
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• 2006.06a
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• pp.495-498
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• 2006

This paper reports a high power 60 GHz push-push oscillator fabricated using 0.12 um metamorphic high electron-mobility transistors (mHEMTs). The devices with a $0.1{\mu}m$ gate-length exhibited good DC and RF characteristics such as a maximum drain current of 700 mA/mm, a peak gm of 660 mS/mm, and an $f_T$ of 170 GHz. By combining two sub-oscillators having $6{\times}50{\mu}m$ periphery mHEMT, the push-push oscillator achieved a 6.3 dBm of output power at 59.5 GHz with more than -35 dBc fundamental suppression. This is one of the highest output power obtained using mHEMT technology without buffer amplifier, and demonstrates the potential of mHEMT technology for cost effective millimeter-wave commercial applications.

• The Research Journal of the Costume Culture
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• v.15 no.4
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• pp.580-592
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• 2007

The purpose of this study is to analyse the foreigner's opinion about 'Hanllyu', and their buying behavior of clothes carried in Korean domestic market. The study was implemented through a normative-descriptive survey using self-administered questionnaires. The samples consisted of 75 foreigners residing in Korea. Data were analyzed by following statistical methods: frequency analysis, ${\chi}^2-test$, t-test, ANOVA, Scheffe's multiple range test. Results are as follows: There was no difference in the opinion about 'Hanllyu' between Chinese and Japanese. They regarded 'Hanllyu' as the phenomenon of the wave of Korean popular culture. Korean soap operas and movies were the main information sources on 'Hanllyu' stars for them. Significant differences were found in the behavior toward 'Hanllyu' stars according to sex and country, but there was no difference in the behavior according to their age. They mainly buy clothes in Dongdaemoon market and the main motivation of purchase were good design and price. The reason for dis-purchase was poor design. Respondents thought 'Hanllyu' fashion is gorgeous. There was significant difference in the behavior toward Korean culture according to sex.

• Journal of Ocean Engineering and Technology
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• v.20 no.2 s.69
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• pp.1-7
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• 2006

This paper, presents a comparison between numerical analysis and field test on a real offshore platform in Bohai Bay, China. This platform is a steel jacket offshore platform with vertical piles. The field testing under wave-induced force and wind force etc. was conducted, in order to obtain the dynamic parameters of the structure, including the frequencies of the jacket platform, as well as the corresponding damping ratios and mode shapes. The natural excitation technology (NexT) combined with eigensystem realization algorithm (ERA) and the peak picking (PP) method in frequency domain are carried out for modal parameter indentification under operational conditions. The three-dimeansional finite element model (FEM) is constructed by ANSYS and analytical modal analysis is performed to generate modal parameters. The analytical results were compared with experimental results. A good agreement was achieved between the finite element and analysis and field test results. It is further demonstrated that the numerical and experimental modal analysis provide a comprehensive study on the dynamic properties of the jacket platform. According to the analysis results, the modal parameters identification under ambient excitation can calibrate finite element model of the jacket platform structures, or can be used for the structural health monitoring system.

• International Journal of Ocean System Engineering
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• v.1 no.3
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• pp.171-179
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• 2011

This paper presents the concept design procedure of a floating-type combined renewable energy platform based on hydrodynamic analyses and is focused on the fatigue design of taut-type mooring lines of the platform. Two types of combined renewable energy platforms are considered: a combination of wind turbine, wave turbine and photovoltaic energy plant and a combination of wind turbine, current turbine and photovoltaic energy plant. The basic configurations are conceptually determined from the understanding of floating offshore plants, while the main dimensions have been determined based on a hydrostatic calculation. Fully coupled hydrodynamic analyses have been carried out to identify the motion characteristics of the floating body and the tension histories of the mooring lines. The tension history is used for the fatigue life prediction based on the rain-flow cycle counting method. For the fatigue life prediction, tension life curves from API and the Palmgren-Miner rule are employed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.9
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• pp.2362-2372
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• 1996

This paper deals with the design and development of an Injection-Locking Coupled Oscillators(ILCO), which functions like phase-shifter in the Active Intergrated Phased Array Antenna(AIPAA). This linear array 2-element ILCO consists of two Injection Locking Hair-pin Resonator Oscillators(ILHRO) and an unilateral amplifier. The first and second elements of the ILCO have same frequency tuning range but locking bandwidths of 11.5MHz and 14MHz respectively. A phase shift of .DELTA..PHI.=158.4.deg.(-78.0.deg. to 80.4.deg.) could be obtained inthe second element of ILCO when the first elementof the ILCO was in the reference locking mode(.DELTA..PHI.=0.deg.). When the ILCO is applied to the AIPAA, the predicted beam scanning angle value will be 38.4.deg.. Each ILCO gives good frequency stability and lower AM, FM, and PM noise charactheristics in the mutual coupling lockingmode. The ILCO can not only play a part as the phase shifter for the AIPAA but it can also be usedas the power combining device in the mm-wave frequency range and as a part of a T/R MMIC module.

• Structural Engineering and Mechanics
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• v.74 no.1
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• pp.69-82
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• 2020

A significant defect of space structures is the progressive collapse issue which may restrict their applicability. Force limiting devices (FLDs) have been designed to overcome this deficiency, though they don't operate efficiently in controlling the force displacement characteristics. To overcome this flaw, a new type of FLD is introduced in the present study. The "all steel accordion force limiting device" (AFLD) which consists of three main parts including cylindrical accordion solid core, tubular encasing and joint system is constructed and its behavior has been studied experimentally. To improve AFLD's behavior, Finite element analysis has been carried out by developing models in ABAQUS software. A comprehensive parametric study is done by considering the effective design parameters such as core material, accordion wave length and accordion inner diameter. From the results, it is found that AFLD can obtain a perfect control on the force-displacement characteristics as well as attaining the elastic-perfect plastic behavior. Obtaining higher levels of ultimate load carrying capacity, dissipated energy and ductility ratio can be encountered as the main privileges of this device. Ease of construction and erection are found to be further advantages of AFLD. Based on the obtained results, a procedure for predicting AFLD's behavior is offered.

• Asia-Pacific Journal of Business
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• v.9 no.1
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• pp.77-89
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• 2018

Today, the sports teams are in a highly competitive environment where they don't know what may happen in the near future. While the front-runner teams suffer a serious slump, the teams in lower ladder stacks victories. This recent phenomenon proves that no team can secure the sustainable competitive edge over others. This is the time when a complete change of the mindset about the short-term competitive edge is needed. Therefore, we conducted the case study to the short-term competitive edges by selecting OK Savings Bank Rush & Cash volleyball team(hereafter referred to as OK Savings Bank). Thus, we presented the Transient Advantage Wave which describes the five stages of Initiating-Promotion-Utilization-Reconstruction-Withdrawal as a framework for the case study. Finally, we organized the results of the analysis and based on this result, we discussed the significance and the limitation of the short-term competitive edge that the sports team should pursue. This study contributed to the changes in strategies & tactics of various sports teams by suggesting the new strategy called short-term competitive edges that teams should utilize in order to get the best results in the sports league that has the strong quality of Time-based system.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2004.03a
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• pp.192-197
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• 2004

Recently, fluidic thrust vectoring methods have been preferably employed to control the movement of propulsive systems due to relatively simpler design and lower cost than mechanical thrust vectoring methods. For An application of the thrust vectoring to flight bodies, it is necessary to understand very complicated exhaust flows which are often subject to shock waves and boundary layer separation. But researches for the thrust vector control using counterflow have been few. In the present study, experiments have been performed to investigate the characteristics of supersonic jets controlled by a thrust vectoring method using counterflow. The primary jet is expanded through a two-dimensional primary nozzle shrouded by collars, and is deflected by the suction of the air near nozzle into an upper slot placed between the primary nozzle and the upper collar. A shadowgraph method is used to visualize the supersonic jet flowfields. Primary nozzle pressure ratios and suction nozzle pressure ratios are varied from 3.0 to 5.0, and from 0.2 to 1.0 respectively. The present experimental results showed that, for a given primary nozzle pressure ratio, a decrease in the suction nozzle pressure ratio produced an increased thrust vector angle. As the suction nozzle pressure ratios were increased and decreased, the hysteresis of the thrust vectoring was observed through the wall pressure distributions

• Steel and Composite Structures
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• v.4 no.2
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• pp.149-167
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• 2004

Offshore platforms have to serve in harsh environments and hence are likely to be damaged due to wave induced fatigue and environmental corrosion. Welded tubular joints in offshore platforms are most vulnerable to fatigue damage. Such damages endanger the integrity of the structure. Therefore it is all the more essential to assess the capacity of damaged structure from the point of view of its safety. Eight internally ring stiffened fatigue damaged tubular joints with nominal chord and brace diameter of 324 mm and 219 mm respectively and thickness 12 mm and 8 mm respectively were tested under axial brace compression loading to evaluate the reserve capacity of the joints. These joints had earlier been tested under fatigue loading under corrosive environments of synthetic sea water and hence they have been cracked. The extent of the damage varied from 35 to 50 per cent. One stiffened joint was also tested under axial brace tension loading. The residual strength of fatigue damaged stiffened joint tested under tension loading was observed to be less than one fourth of that tested under compression loading. It was observed in this experimental investigation that in the damaged condition, the joints possessed an in-built load-transfer mechanism. A bi-linear stress-strain model was developed in this investigation to predict the reserve capacity of the joint. This model considered the strain hardening effect. Close agreement was observed between the experimental and predicted results. The paper presents in detail the experimental investigation and the development of the analytical model to predict the reserve capacity of internally ring stiffened joints.

• Journal of Families and Better Life
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• v.29 no.6
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• pp.137-151
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• 2011

This study examines the condition of transfers between mothers and adult children, analyzing the influencing factors in such transfers. Specifically the study examines the influence of financial transfers and economic resources on financial transfers and grandchild caregiving between mothers and adult children. The sample of 3719 mothers with adult children was extracted from the first wave of the Korean Longitudinal Survey of Women and Families. The major findings are as follows. Mothers's socio-demographic characteristics are important factors in explaining financial transfers between mothers and adult children. Mothers who have jobs and spouses are more likely to provide economic resource to their adult children than those who don't have. In terms of receiving economic resources from adult children, statistically meaningful factors are mothers' age, labor market participation, marital status, household income, household asset, and children's labor market participation. Especially, labor market participation of mothers and adult children is statistically powerful factor in financial transfers and caregiving.