• Atmosphere
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• v.17 no.1
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• pp.45-53
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• 2007

In order to investigate the impacts of heat wave on human health, cluster analysis of meteorological elements (e.g., temperature, dewpoint, sea level pressure, visibility, cloud amount, and wind components) for identifying offensive synoptic air masses is employed. Meteorological data at Seoul during the past 30 years are used. The daily death data at Seoul are also employed. Occurrence frequency of heat waves which is defined by daily maximum temperature greater than the threshold temperature (i.e., $31.2^{\circ}C$) was analyzed. The result shows that the frequency and duration of heat waves at Seoul are increasing during the past 30 years. In addition, the increasing trend of the frequency and duration clearly appears in late spring and early autumn as well as summer. Factor analysis shows that 65.1% of the total variance can be explained by 4 components which are linearly independent. Eight clusters (or synoptic air masses) were classified and found to be optimal for representing the summertime air masses at Seoul, Korea. The results exhibit that cluster-mean values of meteorological variables of an offensive air mass (or cluster) are closely correlated with the observed and standardized deaths.

• Proceedings of the KIEE Conference
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• 1998.11a
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• pp.125-127
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• 1998

The widely used power supply (Switched Mode Power Supply : SMPS) as a source in order to stabilize direct current for electronics or communication systems has merits, when it is compared to the existing source for stability, such as high efficiency, small size, light weight by means of switching process of the semiconductor device which controls the flow of power. However, due to existence of inductors and capacitors used for charging energy, the source part in electronic or communication systems hasn't reached the speed, that is supposed to get, for achieving smaller size and lighter weight. In order to got smallness in size, it is necessary to increase switching frequency. And that makes devices for measuring energy smaller. Nevertheless, the rise switching frequency brings increases in switching loss, inductor loss, and power loss. Also, the occurrence of surge and noise caused by high frequency switching is setting higher. The resonant converter has been considered as one of methods that give solutions for the problems of SMPS and that method has been paid attention as a source technology in electronics and communication.

• The Journal of Industrial Distribution & Business
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• v.13 no.9
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• pp.37-50
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• 2022

Purpose: The purpose of this study is to explore and compare research trends in Korea and overseas academic papers on social media marketing, and to present new academic perspectives for the future direction in Korea. Research design, data and methodology: We used English abstract of research paper (Korea's: 1,349, overseas': 5,036) for word frequency analysis, topic modeling, and trend analysis for each topic. Results: The results of word frequency and co-occurrence frequency analysis showed that Korea researches focused on the experiential values of users, and overseas researches focused on platforms and content. Next, 13 topics and 12 topics for Korea and overseas researches were derived from topic modeling. And, trend analysis showed that Korean studies were different from overseas in applying marketing methods to specific industries and they were interested in the short-term performance of social media marketing. Conclusions: We found that the long-term strategies of social media marketing and academic interest in the overall industry will necessary in the future researches. Also, data mining techniques will necessary to generate more general results by quantifying various phenomena in reality. Finally, we expected that continuous and various academic approaches for volatile social media is effective to derive practical implications.

• The Transactions of the Korean Institute of Power Electronics
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• v.26 no.4
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• pp.271-276
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• 2021

Arc fault detector based on multilevel DWT with analysis of high-frequency noise components over 100 kHz is proposed in this study to improve the performance in detecting serial arcs and distinguishing them from inverter noise in PV systems. PV inverters generally operate at a frequency range of 20-50 kHz for switching operation and maximum power tracking control, and the effect of these frequency components on the signal for arc detection leads to negative arc detection. High-speed ADC and multilevel DWT are used in this study to analyze frequency components above 100 kHz. Such high frequency components are less influenced by inverter noise and utilized to detect as well as separate DC series arc from inverter noise. Arc detectors identify the input current of PV inverters using a Rogowski coil. The sensed signal is filtered, amplified, and used in 800kSPS ADC and DWT analysis and arc occurrence determination in DSP. An arc detection simulation facility in UL1699B was constructed and AFD tests the proposed detector were conducted to verify the performance of arc detection and performance of distinction of the negative arc. The satisfactory performance of the arc detector meets the standard of arc detection and extinguishing time of UL1699B with an arc detection time of approximately 0.11 seconds.

• Anatomy and Cell Biology
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• v.56 no.4
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• pp.469-473
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• 2023

Anomalies of anterior cerebral artery (ACA) include aplasia, hypoplasia and variations in number. Magnetic resonance angiography (MRA) is a non-invasive diagnostic technique for assessment of anomalies of cerebral arteries. The aim of the study was to determine the role of MRA in detection of variants of ACA in adults. This study is an observational retrospective study. This study included forty-nine adult cases (28 males and 21 females), mean age 48±12.9 SD with anomalies of ACA in MRA. Magnetic resonance imaging of the brain and MRA were done to all patients. Cerebral MRA and magnetic resonance images were evaluated for frequency and distribution of variants of anterior cerebral arteries, associated aneurysms and infarctions. Odds ratios (ORs) and relative risk were calculated to determine risk of occurrence of cerebral infarctions in patients with anomalies of ACA. Hypoplasia of ACA was the commonest anomaly of ACA (51% of cases). Risk of occurrence of cerebral infarctions was higher in cases with azygos variant (OR, 3.3; P=0.35) than in those with hypoplastic ACA (OR, 2; P=0.58). MRA was highly reliable in identification of different variants of ACA and concomitant vascular changes.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.36 no.3
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• pp.135-145
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• 2020

Recently, the disaster rate of the construction industry has increased with high-rise, and complexity of the building, unlike the decrease in the disaster rate in other industries. Although risk assessment is performed to reduce the occurrence of disasters, it is difficult to estimate the risks accurately due to activity in which no disaster has occurred, and inconsistencies in the level of details of work. In this study, in order to evaluate the risk of the major activity for the apartment construction work, the activity was identified by referring to the risk assessment model of construction industry type by the KOSHA. The construction work types and activities were consistently organized in level of work into nine work types and 82 activities were through experts consultation. Analyzing the disaster types that occurred during work through KOSHA disaster cases, calculating the probability of disaster occurrence according to the type of disaster, and combining the probability of disaster with the severity of disaster to estimate the risk assessment method was presented. Using the daily report of the construction site of the apartment, the results of a case study confirmed the validity of the risk calculation method presented in this study.

• Asian Pacific Journal of Cancer Prevention
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• v.14 no.2
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• pp.969-975
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• 2013

Aim: The aim of this study was to determine the impact of age on the occurrence, severity, and timing of acute side effects related to radiotherapy. Materials and Methods: We analysed the data of 423 patients. Results: Of the patients, 295 (70%) were under the age of 65 (group 1) and 128 (30%) were over the age of 65 (group 2). The frequencies of radiotherapy-induced side effects were 89% in group 1 and 87% in group 2 (p=0.286). The mean times to occurrence were $2.5{\pm}0.1$ weeks in group 1 and $2.2{\pm}0.1$ weeks in group 2 (p=0.013). Treatment was ended in 2% of patients in group 1 and 6% of those in group 2 (p=0.062). Treatment interruption was identified in 18% of patients in group 1 and 23% in group 2 (p=0.142). Changes in performance status were greater in older patients (p=0.013). There were no significant differences according to the frequency or severity of side effects, except skin and genitourinary complications, between the groups. Conclusions: Early normal tissue reactions were not higher in older versus younger patients, though there was a tendency towards an earlier appearance.

• The Korean Journal of Food And Nutrition
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• v.30 no.6
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• pp.1299-1309
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• 2017

The aim of this study was to investigate status of safety accidents of school foodservice cooks in Daegu and to analyze the factors affecting the occurrence of the accidents in order to seek effective ways for preventing safety accidents in school foodservice. The survey showed that the most frequent safety accidents were 'bruises', followed by 'burns', 'contact with harmful substances such as disinfectants', 'fall-off ' and 'sprains'. The mental fatigue perception of the respondents was generally lower than the physical fatigue perception. The means of the perception levels of work intensity, cooking environment of the foodservice place, and safety-related behaviors, and consciousness were 3.15, 2.99, and 4.06 out of 5 points, respectively. In addition, the annual average of the number of participating in the accident prevention training per person was 17.34 times, that is, the respondents received the training at least once a month on average. A multiple regression analysis was conducted to investigate the variables affecting the occurrence of safety accidents that happened to foodservice cooks. It revealed that the work intensity perception and the cooking environment perception influenced the frequency of safety accidents.

• Nuclear Engineering and Technology
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• v.50 no.8
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• pp.1217-1233
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• 2018

Following a surge of interest in multi-unit risk in the last few years, many recent studies have suggested methods for multi-unit probabilistic safety assessment (MUPSA) and addressed several related aspects. Most of the existing studies though focused on two-unit nuclear power plant (NPP) sites or used rather simplified probabilistic safety assessment (PSA) models to demonstrate the proposed approaches. When considering an NPP site with three or more units, some approaches are inapplicable or yield very conservative results. Since the number of such sites is increasing, there is a strong need to develop and validate practical approaches to the related MUPSA. This article provides several detailed approaches that are applicable to multi-unit Level 1 PSA for sites with up to six or more reactor units. To validate the approaches, a multi-unit Level 1 PSA model is developed and the site core damage frequency is estimated for each of four representative multi-unit initiators, as well as for the case of a simultaneous occurrence of independent single-unit initiators in multiple units. For this purpose, an NPP site with six identical OPR-1000 units is considered, with full-scale Level 1 PSA models for a specific OPR-1000 plant used as the base single-unit models.

• Journal of Electrical Engineering and Technology
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• v.1 no.2
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• pp.192-199
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• 2006

This paper presents an improved anti-islanding algorithm for utility interconnection of multiple distributed fuel cell powered generations (DFPGs). A cross-correlation method is proposed and implemented in conjunction with the anti-islanding algorithm developed in the previous work [I]. While the power control algorithm continuously perturbs $({\pm}5%)$ the reactive power supplied by the DFPG, the proposed algorithm calculates the cross-correlation index of a rate of change of the frequency deviation with respect to $({\pm}5%)$ the reactive power to confirm islanding. If this index is above 50%, the algorithm further initiates $({\pm}10%)$ the reactive power perturbation and continues to calculate the correlation index. If the index exceeds 80%, the occurrence of islanding can be confirmed. The proposed method is robust and capable of detecting the occurrence of islanding in the presence of several DFPGs, which are independently operating. Viability of the cross-correlation method is verified by the simulation. Experimental results are presented to support the findings of the proposed method.