• Journal of Advanced Navigation Technology
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• v.27 no.1
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• pp.96-101
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• 2023

In this work, an energy harvester (EH) on the rotating shaft has been proposed for a wireless sensor system (WSS) applications. The EH was designed and implemented to the shaft with a diameter of 20 cm to continuously power a wireless sensor system (WSS). The rotor has coils wound in pairs on seven U-shaped cores attached to the shaft. The stator consists of eight pairs of magnets attached to eight I-cores and they are fixed to an outer fixture. The generated power of the EH was investigated as function of the air gap between the rotor and stator, the number of turn of coils, and shaft speed. The fabricated EH produced power up to 2.87 W at 300 rpm and the 3 mm air gap.

• Journal of the Korea Society of Computer and Information
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• v.29 no.7
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• pp.139-148
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• 2024

In the post-pandemic era, the demand for online education platforms has surged, leading to increased consumer reliance on online reviews for decision-making. This study investigates the impact of Chinese online customer reviews on consumer purchase behavior in online education. By examining the role of trust, review sentiment, and the quantity and timeliness of reviews, the research aims to understand how these factors influence consumer decisions. By using regression model, findings reveal that negative reviews, timely feedback, and a higher volume of reviews positively affect consumer purchase decisions, while course pricing demonstrates an inverse relationship. Furthermore, cognitive and affective trust mediate the relationship between reviews and purchase behavior, highlighting a reverse U-shaped effect on consumer decision inclination. These insights provide valuable implications for online education providers, emphasizing the need to manage and leverage online reviews to foster consumer trust and improve sales performance.

• Childhood Kidney Diseases
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• v.8 no.1
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• pp.26-32
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• 2004

Purpose : Hypercoagulability is present in patients with nephrotic syndrome. Plasminogen activator inhibitor type 1(PAI-1) is a major inhibitor of plasminogen activators. PAI-1 inactivates both tissue plasminogen activator(tPA) and urokinase plasminogen activator(uPA) by rapid formation of inactive 1:1 stoichiometric complexes. Recently some studies showed that the enhanced PAI-1 expression may be involved in the intraglomerular fibrinogen/fibrinrelated antigen deposition seen in nephrotic syndrome. Methods : PAI-1 gene promoter -844(G/A) polymorphism was evaluated in 146 children with minimal change nephrotic syndrome(MCNS) and 230 control subjects. The patients with MCNS were subdivided into 85 infrequent-relapser(IR) group and 61 frequent relapser(FR) group. PCR of PAI-1 gene promoter region including -844(G/A) and RFLP using the restriction enzyme Xhol were performed for each DNA samples extracted from the groups. Results : The distribution of PAI-1 genotype in the control group was G/G 81(32.5%), A/A 42(16.9%), and G/A 126(50.6%). The distribution of PAI-1 genotypes in the IR group of MCNS was G/G 29(34.1%), A/A 15(17.7%), and G/A 41(48.2%). The distribution of PAI-1 genotype in the FR group of MCNS was G/G 17(27.9%), A/A 18(29.5%), and G/A 26(42.6%). There was a significantly increased frequency of A/A genotype(P=0.0251) in the FR group of MCNS. Conclusion : Our results indicate that the PAI-1 gene promoter A/A genotype may be associated with the FR in MCNS.

• Conservation Science in Museum
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• v.20
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• pp.13-30
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• 2018

Ancient metal objects with inlaid designs were mainly decorated using the wire inlay technique in which "V"- or "U"-shaped grooves were cut in a metal object and then filled with gold or silver. Previous studies on ancient metal objects featuring wire inlay generally attempted to ascertain the inlay techniques applied by examining photomicroscopes acquired during conservation treatment. However, they had limitations when examining wire inlay technique to the minute details. Wire inlay technique can be better investigated by enlarging X-ray films of relics using stereoscopic microscopy under transmitted light. The core processes of the wire inlay technique involve cutting grooves using a chisel and creating the inlay wires, but researchers hold varying opinions about the two processes. This study analyzed the entirety of the materials able to shed light on the main processes applied in Baekje wire inlay by examining X-ray films of relics through stereoscopic microscopy. This exhaustive research revealed that two types of techniques were used for wire inlay during the Baekje period. One is a plastic process of engraving dotted lines using a chisel and is found mostly in objects from the Cheonan and Gongju areas. The other is a cutting process that incises fine lines and was used mostly in relics from the Osan, Seosan, and Wanju areas. It is likely that the Baekje wire inlay techniques feature regional differences because the respective techniques were used or introduced by different groups of people.

• Proceedings of the Korean Society for Bio-Environment Control Conference
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• 2001.04b
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• pp.100-102
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• 2001

본 연구에서는 온실의 난방에 사용되는 열풍식 난방기 등의 배기 연통에 부착하여 배출되는 가스로부터 열을 회수할 수 있는 장치를 개발함에 있어서 연통과 열회수 장치간의 열 교환 성능을 3가지 상이하게 설계된 열 교환 장치(Fig. 1 참조)에 대하여 실험적으로 비교 분석하였다. Fig. 1-(a)는 열 교회수기 개발을 위해 기존에 사용한 장치로서 회수용 공기의 흐름방향이 배기 연통과 직각을 이룬 형식이며, Fig. 1-(b) 및 (c)는 열 회수 성능 개선을 위해 새로 설계된 형식으로서 각각 열 교환 파이프의 배치형식이 상이하나 회수용 공기의 흐름방향이 180도로 굴곡되는 U-자형 흐름이 이루어지도록 하였다. 실험에 사용된 공기 순환 펜의 용량은 AB-형의 경우에는 최대 25㎥/min이고, C-형 및 D-형의 경우는 공히 최대 42㎥/min으로서 송풍전압 조절장치를 이용하여 풍량을 연속적으로 조절할 수 있도록 하였다. U-자형 흐름형식인 C-형 및 D-형의 경우 흐름 방향의 굴곡으로 인한 마찰저항이 있을 것으로 예상은 했으나 당초 예상했던 것에 비해 마찰 저항이 지나치게 큰 것으로 밝혀졌다. 비록 설계된 열교환 튜브의 배열형식별 열 교환기의 외부 모양이 달라 회수기의 표면을 통한 대류 열 교환이 다소 차이를 보일 것으로 예상되지만 본 연구에서는 열 회수장치에 내장된 열 교환 튜브부분만을 통한 열 회수율을 중심으로 형식간의 성능을 비교하였다. 실험을 통하여 측정된 자료중 대표적인 예는 Fig-2와 같으며, 측정자료를 기준으로 분석된 열회수 성능에 대한 설계형식별 비교 결과는 Table-1과 같으며, 분석된 결과를 요약하면 다음과 같다: 1. AB-형 열회수시스템의 경우, 초기 투자비용과 현재의 농용 전력요금 하에서 에너지 절감규모를 비교하면, 대체로 1년을 전후하여 투자에 대한 보상이 충분히 가능할 것으로 판단된다. 2. C-형 및 D-형 열회수시스템의 경우, 열 회수용 공기의 흐름방향이 동일 공간내에서 180도 굴절됨으로서 저항이 크게 발생되어 송풍 펜의 전압 증가에 따른 유속증가가 미미하였으며, 굴절형의 열교환장치는 비록 열교환면적은 직선형과 유사하더라도 송풍 펜의 공기저항이 커져서 결국 열 회수성능이 기대했던 것만큼 크게 개선되지는 못했다. 3. 송풍펜의 용량은 AB-형에 사용된 용량인 25㎥/min 전후가 적절할 것으로 판단되며, 적정 송풍 펜용량 하에서 열 회수성능은 굴절형이 직선형보다 효과적인 것으로 나타났다. 다만, 곡선형은 물론 직선형에서도 열교환 튜브의 배치밀도, 튜브 길이 및 두께 등의 변화에 따른 최적화 연구가 수반되어야 할 것으로 판단된다.

• Journal of dental hygiene science
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• v.17 no.1
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• pp.38-45
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• 2017

We evaluated the association between sleep duration, dental caries, and periodontitis by using representative nationwide data. We examined 8,356 subjects aged ${\geq}19$ years who participated in the sixth Korea National Health and Nutrition Examination Survey (2013~2014). Sleep duration were grouped into ${\leq}5$, 6, 7, 8, and ${\geq}9$ hours. Presence of dental caries was defined as caries in ${\geq}1$ permanent tooth on dental examination. Periodontal status was assessed by using the community periodontal index (CPI), and a CPI code of ${\geq}3$ was defined as periodontitis. A chi-square test and multiple logistic regression analysis were used to determine statistical significance. Model 1 was adjusted for age and sex, model 2 for household income, educational level, and marital status plus model 1, and model 3 for smoking status, alcohol consumption, blood pressure level, fasting blood glucose level, total cholesterol level, and body mass index plus model 2. The prevalence of dental caries according to sleep duration showed a U-shaped curve of 33.4%, 29.4%, 28.4%, 29.4%, and 31.8% with ${\leq}5$, 6, 7, 8, and ${\geq}9$ hours of sleep, respectively. In the fully adjusted model 3, the risk of developing dental caries was significantly higher with ${\leq}5$ than with 7 hours of sleep (odds ratio, 1.23; 95% confidence interval, 1.06~1.43). The prevalence of periodontitis according to sleep duration showed a U-shaped curve of 34.4%, 28.6%, 28.1%, 31.3%, and 32.5%, respectively. The risk of periodontitis was significantly higher with ${\geq}9$ than with 7 hours of sleep in models 1 and 2, whereas the significant association disappeared in model 3. In a nationally representative sample, sleep duration was significantly associated with dental caries formation and weakly associated with periodontitis. Adequate sleep is required to prevent oral diseases such as dental caries and periodontitis.

• Journal of Service Research and Studies
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• v.7 no.3
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• pp.57-70
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• 2017

It is anticipated that the employment structure of the whole industry will change drastically as the Fourth Industrial Revolution era arrives. Particularly, there are numerous reseraches that the development of artifical intelligence will promote automation causing jobs in manufacturing industry to decrease; thus, the economy will be reorganized with service-centered jobs, which heavily depend on human ability. This study was conducted to verify the trend-forecasting model based on the theoretical analysis. We analyzed the change in employment structure over the past decades in each country and period to gain insights from the changes in the employment structure caused by the Fourth Industrial Revoltion. The results of this study are as follows: First, we investigaed whether the current economy is moving along the U-shaped model suggested by an existing researcher. As a result of the analysis, the data substantiated that the change of the employment structure is moving along the U-shaped model. It is also suggested that this U-shaped trend is expected to accelerate in the era of the Fourth Industrial Revolution. In the future, more accurate data analyses are needed to verify the model, and additional researches on the change in the employment structed is also needed.

• Journal of Biomedical Engineering Research
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• v.20 no.2
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• pp.221-230
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• 1999

A new technique for the preparation of porous polyurethane vascular prostheses was investigated. Synthetic vascular grafts with porous wall have been widely proposed, claiming that strength, suture retention, kink resistance, and other handling properties are improved over those with nonporous solid wall. Related to these facts, the control of pores and compliance match have been very important and interesting issues. Two kinds of polymer sheets were compared. One was the porous PU-sheet made at room temerature by the solvent/non-solvent exchange. And the other was the porous PU-sheet fabricated by thermal phase transition and solvent/non-solvent exchange in the thermal controlled bath. According to the result of the above experiments, polyurethane solution was injected into a mold designed for U-type graft. After freezing at low temperature, solvent was dissolved out with alcohol at < $0^{\circ}C$ and water at room temperature to form porous vessels. The average pore size and pore occupation were easily changed by changing polyurethane concentration and freezing rate. This technique can give a proper pore size for tissue ingrowth, and suitable compliances for matching with arteries and veins. In addition, the fabrication of more complicated shaped vessels such as the U-type vascular grafts is easily controlled by using a mold. This method might give a desired compliact graft for artificial implantaion with the commercially available medical polymers.

• Journal of the Korean earth science society
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• v.41 no.6
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• pp.557-574
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• 2020

The purpose of this study is to analyze the cause of high PM2.5 mass concentrations in Cheongju for the period of non-Asian dust days using the weather chart, the stream lines at 850 hPa, the backward trajectory, and the weather and air quality model. As a result of analyzing the time series of PM2.5 concentrations and weather charts for the episodic days in Cheongju, the weather patterns were shown in related to long-range transport of PM2.5 from China or surrounding areas. In fact, in the PM2.5 time series, 60-80 ㎍ m-3, which is more than 2-3 times higher than the concentration attributed to Cheongju activities, was observed as a background concentration related to long-range transport. The distribution of high PM2.5 concentration was typically dependent on the locations of the high and low pressures above the ground while the upper jet stream passed through the Korean Peninsula. Consequently, the high PM2.5 concentration in Cheongju is due to massive air pollutants in the form of smog originated from industrial, household and energy combustion sources of Beijing and other nearby regions of China. These air pollutants move along a fast zonal wind caused by the atmospheric pressure arrangement. high concentration of PM2.5 in Cheongju City is because the mass of air pollutants in the form of smog generated from industrial, household and energy combustion origins in Beijing or other nearby regions of China move along a fast wind speed zone according to the atmospheric pressure arrangement of long-distance transportation. Air pollutants including PM2.5 show an M-shaped pattern that passes through the topography of the Cheongju basin from north to south as a belt or band-shaped pollutant. The ground high pressure according to the above-ground high pressure expansion area and cut-off low or low pressure arrangement, or the bands in the form of river stems appear in a gradual incremental pattern that changes into a U-shape under the influence of the wind.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.3
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• pp.329-335
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• 2014

A maglev vehicle of middle-low speed subjected to both a lift force and a guidance force by a U-shaped single electromagnet is operated over a curved guideway without a guidance controller. Therefore, it is required to carefully decide the curve shape for preventing contact between the vehicle and the guiderail for the case that a Maglev vehicle is operated over a curved guideway with a small radius. Specifically, the shape of the transition curve is very important from the stability viewpoint. This study analyzes the influence of curve shape on maglev stability through parametric composition of the transition curve during vehicle guidance. To this end, a multibody dynamics-based threedimensional Maglev vehicle model was developed. The model was integrated with the vehicle, curved guideway, electromagnets, and their controllers. Using this model, a realistic parametric study including the curved guideway was carried out. The results of research should be considered usefully in the design of bogies and the curve shape.