• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.493-493
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• 2014

The manufacturing cost of thin-film photovoltics can potentially be lowered by minimizing the amount of a semiconductor material used to fabricate devices. Thin-film solar cells are typically only a few micrometers thick, whereas crystalline silicon (c-Si) wafer solar cells are $180{\sim}300\mu}m$ thick. As such, thin-film layers do not fully absorb incident light and their energy conversion efficiency is lower compared with that of c-Si wafer solar cells. Therefore, effective light trapping is required to realize commercially viable thin-film cells, particularly for indirect-band-gap semiconductors such as c-Si. An emerging method for light trapping in thin film solar cells is the use of metallic nanostructures that support surface plasmons. Plasmon-enhanced light absorption is shown to increase the cell photocurrent in many types of solar cells, specifically, in c-Si thin-film solar cells and in poly-Si thin film solar cell. By proper engineering of these structures, light can be concentrated and coupled into a thin semiconductor layer to increase light absorption. In many cases, silver (Ag) nanoparticles (NP) are formed either on the front surface or on the rear surface on the cells. In case of poly-Si thin film solar cells, Ag NPs are formed on the rear surface of the cells due to longer wavelengths are not perfectly absorbed in the active layer on the first path. In our cells, shorter wavelengths typically 300~500 nm are also not effectively absorbed. For this reason, a new concept of plasmonic nanostructure which is NPs formed both the front - and the rear - surface is worth testing. In this simulation Al NPs were located onto glass because Al has much lower parasitic absorption than other metal NPs. In case of Ag NP, it features parasitic absorption in the optical frequency range. On the other hand, Al NP, which is non-resonant metal NP, is characterized with a higher density of conduction electrons, resulting in highly negative dielectric permittivity. It makes them more suitable for the forward scattering configuration. In addition to this, Ag NP is located on the rear surface of the cell. Ag NPs showed good performance enhancement when they are located on the rear surface of our cells. In this simulation, Al NPs are located on glass and Ag NP is located on the rear Si surface. The structure for the simulation is shown in figure 1. Figure 2 shows FDTD-simulated absorption graphs of the proposed and reference structures. In the simulation, the front of the cell has Al NPs with 70 nm radius and 12.5% coverage; and the rear of the cell has Ag NPs with 157 nm in radius and 41.5% coverage. Such a structure shows better light absorption in 300~550 nm than that of the reference cell without any NPs and the structure with Ag NP on rear only. Therefore, it can be expected that enhanced light absorption of the structure with Al NP on front at 300~550 nm can contribute to the photocurrent enhancement.

• Journal of Environmental Health Sciences
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• v.41 no.4
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• pp.231-240
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• 2015

Objectives: Blood mercury levels among adults living in certain areas of the Gyeongsang Provinces have been shown to be very high (Kunwee County $29.6{\mu}g/L$, Yeongcheon-city $26.7{\mu}g/L$). The purpose of this project was to determine mercury exposure levels in schoolchildren and factors related with their mercury levels in high mercury exposure areas identifyed by the 2007 Korea National Environmental Health Survey. Methods: From June to September 2010, 1,097 students from grades 3 to 6 at 19 elementary schools participated in this study, including 294 students from 10 elementary schools in Kunwee County, 529 students from Yeongcheon City, 122 students from two elementary schools in Pohang City, North Gyeongsang Province, and 152 students from two elementary schools in Ulsan Metropolitan City. Biological samples from schoolchildren, including whole blood, urine and hair, were collected to measure total mercury at the time of a health check up. Information about children was collected by questionnaire. Total mercury concentrations in blood were measured using the Direct Mercury Analyzer 80 with the gold-amalgam collection method. Results: The mean mercury levels were $2.70{\mu}g/L$ in 1,091 blood samples, $2.25{\mu}g/g-creat.$ in 820 urine samples and $1.03{\mu}g/g$ in 1,064 hair samples. Blood mercury levels in the schoolchildren was slightly higher than the result of $2.4{\mu}g/L$ from a 2006 survey of elementary school children on exposure and health effects of mercury by the National Institute of Environmental Research. However, 0.3% and 4.5% of participants exceeded the reference level of blood mercury by CHBMII ($15{\mu}g/L$) and the US EPA ($5.8{\mu}g/L$), respectively. The reference level of urine by CHBMII ($20{\mu}g/L$) was exceeded by 0.4% of participants. As factors, residence period in the study areas, residence type, father's education level and income all showed significant associations with mercury level in the biological samples. The number of dental amalgam sides showed an association with urine mercury. Fish intake preference and fish intake frequency were important factors in mercury levels. In particular, intake of shark meat and recent intake of shark meat were associated with higher mercury levels. In this regard, participation in the performance of an ancestral rite showed a relation with higher mercury levels. Conclusion: The intake of shark meat was very important factor to high mercury exposure level. It is recommended to monitor and manage students with high mercury exposures who exceeded CHBM II and EPA guidelines, and include blood mercury testing in the Children's Health check up for this province.

• The Journal of the Korea Contents Association
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• v.20 no.6
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• pp.460-469
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• 2020

This study analyzes online news articles and cafe articles on the '5-day Rotation Mask Distribution System', which is emerging as a recent issue due to the COVID-19 incident, to identify the mass media and social media agendas containing media and public reactions. This study figured out the difference between mass media and social media. For analysis, we collected 2,096 full text articles from Naver and 1,840 posts from Naver Cafe, and conducted word frequency analysis, word cloud, and LDA topic modeling analysis through data preprocessing and refinement. As a result of analysis, social media showed real-life topics such as 'family members' purchase', 'the postponement of school opening', ' mask usage', and 'mask purchase', reflecting the characteristics of personal media. Social media was found to play a role of exchanging personal opinions, emotions, and information rather than delivering information. With the application of the research method applied to this study, social issues can be publicized through various media analysis and used as a reference in the process of establishing a policy agenda that evolves into a government agenda.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.18 no.4 s.119
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• pp.372-378
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• 2007

This paper presents an improvement of field uniformity in a reverberation chamber with QRDs(Quadratic Residue Diffuser) and also shows the optimal dimension of the QRDs. The QRD is designed for $1{\sim}3\;GHz$ frequency band and the FDTD(finite-Difference Time-Domain) method is used to analyze the field characteristics. At 2 GHz, the standard deviation of test volume in the reverberation chamber is the smallest when the QRD has $30{\sim}60\;%$ coverage of one side of the reverberation chamber and the field uniformity is worsened when the coverage of the QRD is either below 20 % or above 70 % of the area of the side wall. Particularly, the standard deviation of test volume in the reverberation chamber with 30 % coverage of QRD is improved by 1.53 dB compared to that of the reference chamber with no QRDs.

• Asian Pacific Journal of Cancer Prevention
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• v.15 no.22
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• pp.9899-9903
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• 2014

Nasopharyngeal carcinoma (NPC) is an uncommon disease in most countries but occurs with much greater frequency in southern China. This study aimed to examine the secular trends of NPC in urban Guangzhou over the time period of 2000-2011 using data from the Guangzhou Cancer Registry. Age-adjusted annual incidence rates of NPC were calculated by the direct method using the WHO World Standard Population (1960) as the reference. The average annual percentage change (AAPC) was used as an estimate of the trend. A total of 7,532 new cases of NPC and 3,449 related deaths were registered. In both genders, the peak incidence occurred in the 50- to 59-year age group, and this age distribution pattern remained similar throughout. The AAPC in NPC incidence rates was -3.26% (95% CI: -5.4%--1.1) for males and -5.74% (95% CI: -8.9%--2.5) for females, resulting in a total decrease of 39.3% (from 22.14 to 13.44 per 100,000 population) for males and 48.6% (from 10.1 to 5.18 per 100,000 population) for females over this 12-year period. The AAPCs in NPC mortality rates were -4.62% (95%CI: -3.5%--5.7) for males and -6.75% (95% CI: -5.2%--8.3) for females, resulting in a total decrease of -46.1% (from 12.1 to 6.54 per 100,000 population) for males and 51.7% (from 4.14 to 2.00 per 100,000 population) for females. The age-adjusted incidence and mortality rates of NPC declined during 2000-2011 in urban Guangzhou but remained high. Future efforts to improve prevention, early detection and treatment strategies are needed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.3
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• pp.594-600
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• 2017

This paper proposes a global search based motion estimation algorithm for high performance HEVC encoder and its hardware architecture. To eliminate temporal redundancy, motion estimation in HEVC inter-view prediction uses global search and fast search algorithm to search for a predicted block having a high correlation with the current PU in an interpolated reference picture. The global search method predicts the motion of all candidate blocks in a given search area, thus ensuring optimal results, but has a disadvantage of large computation time. Therefore we propose a new algorithm that reduces computational complexity by reusing SAD operation in global search to reduce computation time of inter prediction. As a result of applying the proposed algorithm to standard software HM16.12, the computation time was reduced by 61%, BDBitrate by 11.81%, and BDPSNR by about 0.5% compared with the existing search algorithm. As a result of hardware design, the maximum operating frequency is 255 MHz and the total number of gates is 65.1K.

• Journal of Environmental Health Sciences
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• v.39 no.6
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• pp.522-531
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• 2013

Objectives: A field survey was conducted in a hog-raising industry in order to help develop personal protective equipment for workers which would secure the safety and the health of these workers. The attempt by this study will help enhance safety in the livestock industry and contribute to the advancement of the industry. Method: The study first selected a total of 111 workers from the hog-raising industry as research participants and designed a survey with questions on general characteristics, indoor and outdoor working environments, how the workers would in practice wear or purchase the working clothes, what needs to be improved in these new working clothes, how much the workers would be likely to accept the working clothes and protective equipment, and lastly, conditions of the communicable disease control overgarment. The collected data underwent frequency analysis and cross analysis with SPSS 21.0. Result: The research targets' average age was 50 years. Work efficiency by environmental factor was normal, but all age groups had experience of accidents (79.3%). Major wounded parts were under elbow and under knee. Protective equipment most commonly worn was helmet (83.4%), gloves (98.2%) and boots (99.1%), and satisfaction with them was normal at 3.41. Working clothing most commonly worn was old clothing (31.8%) and everyday wear (17.6%) and satisfaction with it was low. Considering the improvement of working clothing, they required attached pouches, elasticity and deodorization. The acceptability of improved working clothing was high at 69.2%. Conclusion: After problems have been addressed in relevant future research, what has been learned from the concerned study will be referred to as a useful basic reference when the relevant field works to develop high-quality working clothing and protective equipment for workers in the hog-raising industry.

• The Journal of the Acoustical Society of Korea
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• v.18 no.8
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• pp.84-93
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• 1999

Determination of grain size of heat-treated stainless steel based fm digital ultrasonic signal processing technique is presented. This techniques consist in evidence accumulation with multiple feature parameters, difference absolute mean value(DAMV), variance(VAR), mean frequency (MEANF), auto regressive model coefficient(ARC) and linear cepstrum coefficient(LCC). Feature parameters were extracted from ultrasonic echo signal of heat-treated metals. It was found that a few parameters might not be sufficient to exactly evaluate the grain size of heat-treated metals. The determination of grain size of heat-treated metals was carried out through the evidence accumulation procedure using the distances measured with reference parameters. A fuzzy mapping function is designed to transform the distances for the application of the evidence accumulation method. In the work presented, heat-treated stainless steel samples with various grain sizes are examined. The processed experimental results supports the feasibility of the grain size determination technique presented.

• The Korean Journal of Food And Nutrition
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• v.27 no.5
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• pp.771-784
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• 2014

The purpose of this study was to estimate the relationships between dietary factors and the stress perception levels of College students. A survey was conducted in June, 2010, targeting 332 college students in Gwangju. General environmental factors, stress perception levels, dietary behaviors, and dietary action guide performance of the subjects were evaluated by questionnaire, and food intakes was determined by the 24-hour recall method. The results are summarized as follows.: The score of frequency experiencing was $45.1{\pm}16.9$ for male students, and $47.0{\pm}16.7$ for female students. The importance scores were $50.8{\pm}18.5$ for males, and $53.3{\pm}18.7$ for females. The total score for dietary action guide performance was $39.6{\pm}7.2$ for males and $40.6{\pm}6.5$ for females. Nutrient intake levels were evaluated based on dietary reference intake (DRI), revealing energy intakes to be 68.5% EER in males and 73.9% in females. The mean intakes of nutrient were 54.2% RI for calcium, 73.6% RI for riboflavin, and 51.2% RI for vitamin C but 203.6% AI for sodium, which indicates an imbalance in nutrient intake. Analysis of the correlations between stress perception levels and dietary factors, scholarship achievements, financial problems, future problems, value senses, and family relationships revealed significant correlations with general environment factors, dietary behaviors, Dietary action guide performance, and nutrient intakes (p<0.05). The higher the stress perception levels of the students, the higher the energy, coffee and alcohol intake, which predicts that appropriate stress control in college students will lead to better dietary habits. It is expected that the results above will be used as basic data for the development of proper nutrition education programs and stress control strategies.

• Journal of IKEEE
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• v.18 no.4
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• pp.586-592
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• 2014

In this paper, high efficiency power management IC(PMIC) with DT-CMOS(Dynamic threshold voltage Complementary MOSFET) switching device is presented. PMIC is controlled PWM control method in order to have high power efficiency at high current level. The DT-CMOS switch with low on-resistance is designed to decrease conduction loss. The control parts in Buck converter, that is, PWM control circuit consist of a saw-tooth generator, a band-gap reference(BGR) circuit, an error amplifier, comparator circuit, compensation circuit, and control block. The saw-tooth generator is made to have 1.2MHz oscillation frequency and full range of output swing from supply voltage(3.3V) to ground. The comparator is designed with two stage OP amplifier. And the error amplifier has 70dB DC gain and $64^{\circ}$ phase margin. DC-DC converter, based on current mode PWM control circuits and low on-resistance switching device, achieved the high efficiency nearly 96% at 100mA output current. And Buck converter is designed along LDO in standby mode which fewer than 1mA for high efficiency. Also, this paper proposes two protection circuit in order to ensure the reliability.