• Proceedings of the KIEE Conference
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• 1996.11a
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• pp.279-281
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• 1996

This paper deals with the two stage surge protection device by using varistor and LC low pass filter. Recently varistor alone has been used with overvoltage protection devices for the AC power mains and has same problems associated with high remnant voltage and noise. In this work, in order to improve the cutoff performance of surge protection device, the lightning surge protection device having two stage hybrid circuit for an AC single phase mains was designed and fabricated. Operation characteristics and surge clamping performance of the surge protection device in an $8/20{\mu}s$ surge current are investigated. As a consequence, it is found that the proposed two stage surge protective device for AC power mains has a variety of advantages such as a smaller clamping voltage, high frequency noise reduction and large clamping capacity.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2009.04a
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• pp.239-244
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• 2009

This paper suggests a precision positioning control technique of a precision positioning stage with coupling effects. The precision positioning stage is supported by four flexible spring hinges and driven by two piezoelectric actuators. The dynamic characteristics of the precision positioning stage is modeled and identified by the FEM analysis. The dynamic characteristics of the stage are also identified by the frequency domain modeling technique based on the experimental data. Reliability of two modeling methods is examined by comparing the numerically and experimentally produced responses of the stage. This paper proposes a sliding mode control technique with integrator to improve the tracking ability of the precision positioning stage to the complex input signal using. To demonstrate the effectiveness of the proposed modeling schemes and control algorithm, experiment validations are performed.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.19 no.7
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• pp.60-66
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• 2005

This paper presents the single-stage TSFC(Two-Switch Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contests of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output. The principle of operation, feature and design considerations is illustrated and verified through the experiment with a 200[W](5[V], 40[A]) 100[kHz] MOSFET based experimental circuit.

• Journal of Global Scholars of Marketing Science
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• v.13
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• pp.135-158
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• 2004

On-line consumers have some visit behavior characteristics when they visit internet-shopping mall between visit-stage and purchase-stage. Therefore, information of on-line consumers have influenced on internet-shopping mall's profitabilities at site manager's perspectives. For examples, Are any on-line consumers continuous visiting under any situations? Or are any on-line consumers purchased on any specific internet-shopping mall? Expecially in this paper, researcher tried to understand visit behavioral characteristics of on-line consumers using two-stage mixture regression analysis. Throughout this process, it could be proposed method, which could be reinforced competitiveness of internet-shopping mall by segmental decision-making method. Additionally, it is expected that visit behavioral characteristics' information could be supplied strategic implications between visit-stage and purchase-stage Throughout empirical test it could be proved two-stage decision-making process, which decision-making process of on-line consumers would be processed visit-stage and purchase-stage. In this study, researcher proposed suitable response strategy after understanding visiting behavioral characteristics of on-line consumers. This paper has some academical contributions, which visit behavioral characteristics of on-line consumers could be grasped the meaning by site stickiness and navigation pattern.

• The Korean Journal of Applied Statistics
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• v.13 no.2
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• pp.575-590
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• 2000

In this paper, we extended the Kim et al.'s two-stage unrelated question model(1992) and the Lee et al.'s improved unrelated question model(1998) to two sample unrelated question model of using two independent samples in the case of unknown $\pi_y$.

• Journal of Korean Academy of Nursing
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• v.28 no.4
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• pp.970-979
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• 1998

Cancer has been considered a life-threatening disease and coping patterns could have a strong impact the physical and psychological health of patients and their family. The purpose of this study was to identify the change of coping patterns according to the phases of illness in the patients with cancer and their family caregivers and to compare the coping patterns of patients with those of their caregivers. The phases of illness consisted of 1st(initial) stage, 2nd(metastatic or recurred) stage and 3rd (terminal) stage based on literature. The coping methods were measured using the modified Ways of Coping Questionnaire by Lazarus & Folkman(1984). Seventy-nine patients(35 in stage 1, 31 in stage 2, and 13 in stage 3) and ninety-two caregivers (38 in stage 1, 30 in stage 2 and 24) agreed to participate from two general hospitals in Seoul and Choongnam. No significant changes were found in the coping patterns according to the phases of illness in both groups. Patients in stage 2 and caregivers in stages 2 and 3 problem-focused coping methods were significantly used more than emotion-focused coping methods. Patients in stage 1 significantly used two coping strategies that were cognitive reconstruction and emotion expression more than caregivers. Patients in stage 2 significantly used emotion-focused coping methods including minimizing threat, blame, and emotion expression excepting wishful thinking more than caregivers. We need more research to identify the relationship between the coping methods and their efficiencies through longterm observation and attempt to develope the nursing interventions that could have an improvement on positive coping methods and provide guidance on the problems the patients experience.

• International Journal of Fluid Machinery and Systems
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• v.6 no.3
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• pp.160-169
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• 2013

Two-stage turbocharging is an important way to raise engine power density, to realize energy saving and emission reducing. At present, turbine matching of two-stage turbocharger is based on MAP of turbine. The matching method does not take the effect of turbines' interaction into consideration, assuming that flow at high pressure turbine outlet and low pressure turbine inlet is uniform. Actually, there is swirl flow at outlet of high pressure turbine, and the swirl flow will influence performance of low pressure turbine which influencing performance of engine further. Three-dimension models of turbines with two-stage turbocharger were built in this paper. Based on the turbine models, mechanism of swirl flow at high pressure turbine outlet influencing low pressure turbine performance was studied and a two-stage radial counter-rotation turbine system was raised. Mechanisms of the influence of counter-rotation turbine system acting on low-pressure turbine were studied using simulation method. The research result proved that in condition of small turbine flow rate corresponding to engine low-speed working condition, counter-rotation turbine system can effectively decrease the influence of swirl flow at high pressure turbine outlet imposing on low pressure turbine and increases efficiency of the low-pressure turbine, furthermore increases the low-speed performance of the engine.

• Journal of KIISE:Information Networking
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• v.37 no.3
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• pp.249-253
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• 2010

Resource of wireless frequency bandwidth is gradually going to be deficient due to explosive increase of traffic and saturated non-licensed frequency band such as ISM. In the contrary, many licensed frequency bands are revealed to be low in utilization by several measurement based researches. To alleviate this inefficiency, a concept of cognitive radio is suggested. Cognitive radio lets non-licensed user exploit the licensed frequency band as long as non-licensed user does not interfere licensed user and as a result, it is possible to harness wireless frequency more efficiently. IEEE 802.22 is the first standard network with cognitive radio technology and it employs Two-Stage channel sensing mechanism to accomplish both enough licensed user protection and efficient channel utilization. In this paper, we analyze the overhead of Two-Stage channel sensing mechanism and identify the influence of channel sensing time to the overhead.

• Journal of Environmental Health Sciences
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• v.37 no.2
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• pp.141-149
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• 2011

This study aimed for developing a two stage dual media filtration system. It has a sand and activated carbon layer above the under-drain system, and a sand layer above the middle-drain system for pretreatment. When retrofitting an old sand filter bed or designing a new one, this technology can substitute the existing sand filter bed without requiring a new plant site. The removal rate of total particle is 93, and 3~7 ${\mu}m$ and 5~15 ${\mu}m$ particles are all 97%. These high removal efficiencies of each pollutant due to adsorption and biological oxidation in activated carbon filter layer. The best backwashing method of two stage dual media filtration system is ascertained by air injection, air + water injection and water injection sequence. In this study, a pilot plant of two stage and dual filtration system was operated for 4 months in water treatment plant. The stability of turbidity was maintained below 1 NTU. The TOC, THMFP and HAAFP were removed about 90% by two stage and dual media filtration system, which is almost 2 times higher than existing water treatment plant.

• Journal of Environmental Science International
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• v.23 no.4
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• pp.737-742
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• 2014

This study aimed for evaluating the applicability of the two stage dual media filtration system in field water treatment plant. The field plant of two stage and dual media filtration system was operated for 2 months. Average iron concentrations of the settled water, existing filtered water and second stage filtered water was 0.041 mg/L, 0.007 mg/L and 0.005 mg/L, respectively. Removal efficiency of iron concentration in the second stage is appropriately 35% more than in existing filtered water. Also removal efficiency of residual chlorine in the dual media filtration system is relatively 42.3% more than in existing filtered water due to adsorption of activated carbon, but the removal of ammonia nitrogen by adsorption is insufficient. Average concentrations of THM and chloroform in the settled water are 0.033 mg/L, 0.026 mg/L, respectively and in existing filtered water are 0.023 mg/L and 0.023 mg/L. Average concentrations of THM and chloroform in the dual media filtration system are 0.008 mg/L and 0.013 mg/L. Therefore removal efficiency of THM concentration in second stage is more than 66.4% in existing filtrated water. Also removal efficiency of chloroform in the dual media filtration system is more than 50.0% in existing filtered water because of the adsorption of activated carbon. In this case backwashing period in dual stage system is 4~5 days, but in existing filtration system is 1~2 days.