• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.24 no.11
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• pp.1055-1063
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• 2013

Low noise amplifiers(LNAs) are an integral component of RF receivers and are frequently required to operate at wide frequency bands for various wireless systems. For wideband operation, important performance metrics such as voltage gain, return loss, noise figures and linearity have been carefully investigated and characterized for the proposed LNA. An inductive shunt feedback configuration is successfully employed in the input stage of the proposed LNA which incorporates cascaded networks with a peaking inductor in the buffer stage. Design equations for obtaining low and high input matching frequencies are easily derived, leading to a relatively simple method for circuit implementation. Careful theoretical analysis explains that poles and zeros are characterized and utilized for realizing the wideband response. Linearity is significantly improved because the inductor between gate and drain decreases the third-order harmonics at the output. Fabricated in $0.18{\mu}m$ CMOS process, the chip area of this LNA is $0.202mm^2$, including pads. Measurement results illustrate that input return loss shows less than -7 dB, voltage gain greater than 8 dB, and a little high noise figure around 7~8 dB over 1.5~13 GHz. In addition, good linearity(IIP3) of 2.5 dBm is achieved at 8 GHz and 14 mA of current is consumed from a 1.8 V supply.

• Korean Journal of Construction Engineering and Management
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• v.17 no.2
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• pp.31-38
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• 2016

In a construction project, the portion for maintenance costs for a building is considerable compared to the initial construction cost. As such, Life Cycle Cost (LCC) analysis is being increasingly utilized to assess the design value of engineering work in Korea. Additionally, the Public Procurement Service in Korea announced that it will be mandatory for all domestic construction projects to adopt BIM. Furthermore, the paradigm for architectural design has shifted from 2D to 3D, and to BIM, which includes a data management system. Within this background, however, there is currently no adequate BIM-based LCC analysis software and the requirements of cost estimation for repair and replacement cost for a building is not completely adequate in BIM tools such as Revit and Archicad. Therefore, this study suggests a process of cost estimation for repair and replacement (R&R) cost based on IFC data. First, we analyzed existing R&R criteria and defined BIM-based requirements when calculating R&R costs. These requirements were extracted from relevant IFC data. Subsequently, this was saved to a database and a BIM-based database was built for R&R cost estimation. Finally, this database was connected with external databases such as R&R Criteria DB and Cost Information DB to calculate R&R costs. This process is expected to improve upon the traditional process of cost estimation of R&R cost by applying a BIM model. The proposed process can contribute to a further standardizing of BIM-based LCC analysis thru application to initial construction costs, energy costs, and other maintenance costs.

• Journal of Sericultural and Entomological Science
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• v.51 no.1
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• pp.20-29
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• 2013

Countries of the world are competing for the collection and utilization of genetic resources, which is a resource of value-added industrialization. We are building database of silkworm and mulberry resources with morphological, genetic characteristics data etc. Moreover, recent bioactive compound has been receiving increasing attention. So we analyzed 1-deoxynojirimycin(1-DNJ) content as a this item in addition to the basic information using 363 strains(varieties) of mulberry genetic resources. They were grown under the same environment and conditions. Mulberry leaves were collected and then freeze-dried and powdered for 1-DNJ test. As a result, 1-DNJ mean content of 363 mulberry strains was $0.176{\pm}0.077%$, and the coefficient of variation (CV) was 43.5%. The variation between the strains was greatly severe. Among the tested strains, 'C1D89/29' was showed the highest content of 0.47%, whereas 'Pumbo 24' and 'Turkey E' were showed the lowest content of 0.05% respectively. The content of 1-DNJ of 16 mulberry varieties for silkworm rearing were compared. Average concentration was $0.17{\pm}0.04%$, and the coefficient of variation (CV) was 22.8%. Variation among cultivars was not significant. Finally we selected 1-DNJ high-containing 11 strains. They are as follows. 'C1D89/29', 'Hiihak', 'Jeokasibmunja', 'Gweonchil', 'Botongsibmunja', 'Jeokchuk', 'bulguksang', 'Geunsookgojo', 'Busanggeum', 'Guksang 20' and 'Taekwang' which are more than twice of the overall average content.

• Korean Journal of Environmental Agriculture
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• v.18 no.1
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• pp.41-47
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• 1999

To investigate the combined effect of gamma ray irradiation and NaCl treatment on Tradescantia somatic cell pink mutations, potted plants of Tradescantia 4430 were evenly sprayed with NaCl solution(170mM) 24 hours before irradiation(NaCl+${\gamma}$) and after irradiation(${\gamma}$+NaCl). Irradiation doses were 0.3, 0.5, 1.0 and 2.0 Gy of gamma-ray. The plants irradiated only with gamma radiation were used as control group(CT). Frequency of pink mutation increased linearly with irradiation close and the peak interval of elevated mutation frequencies appeared during 6∼12 days aver irradiation in all the experimental groups. The slope of dose-response curve in CT was 5.99($r^2$=0.99), while it were 4.55($r^2$=0.98) in NaCl+${\gamma}$ and 4.33($r^2$=0.99) in ${\gamma}$+NaCl. It seemed that pre- and post-treatment of NaCl had a protective effect it against radiation-induced cell damages since it decreased the slope value by more than 24%. It is suggested that protective effect on DNA damages can be invoked in irradiated stamen hair cells by NaCl treatment.

• The Journal of the Korea Contents Association
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• v.14 no.1
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• pp.128-138
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• 2014

Local festivals quite often give their visitors and local residents a good opportunity to experience the regional culture thoroughly. Also, the festivals empower the cultural pride and communal sociality, and create new jobs improving local economy. In Korea, more than 700 local festivals are held every year. Each festival is organized and operated upon all different purpose and mission. It is unfortunate, however, that many festivals fail to balance between making profits and accomplishing their purpose. Festival's marketing plan and content management should be cohesive, but at the same time, they also should be different depending on the festival's purpose and program. Especially in case of performance natured festivals, the role and function of festival directing should be more weighed on content management. Namhaean Byeolsingut is one of performance natured festivals, in which its archetype or primitive form is well maintained. This study observes the primitive form of NB from the director's viewpoint, and then provides a solid foundation on how those main characteristics of NB could be applied to invigorating local festival directing. The directing suggestions here are motivated by NB's ritual, performative, and play form.

• Journal of Energy Engineering
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• v.21 no.4
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• pp.435-443
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• 2012

The combination of space shortage and the high population density concentrated in urban areas of South Korea has resulted in the growth of large-scale high-rise residential complexes, naturally affecting water and hot water usage patterns as well. But the current designs for water and hot water supply in South Korea rely mostly on international design standards and data calculated on site due to the severe shortage of basic data in relation to actual use, which result in the frequent problem of the under-or over-design of water and hot water supply. The following study measures the hot water supplier's conditions and the user's heat usage to realize the amount of time required for hot water supply load generation and the pattern of actual use in order to create basic data for effective hot water supply facility design and maintenance.

• Journal of Biomedical Engineering Research
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• v.25 no.4
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• pp.269-275
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• 2004

Different biological tissues have different values of electrical resistivity. In EIT (electrical impedance tomography), we try to provide cross-sectional images of a resistivity distribution inside an electrically conducting subject such as the human body mainly for functional imaging. However, it is well known that the image reconstruction problem in EIT is ill-posed and the quality of a reconstructed image highly depends on the measurement error. This requires us to develop a high-performance EIT system. In this paper, we describe the development of a 16-channel digital EIT system including a single constant current source, 16 voltmeters, main controller, and PC. The system was designed and implemented using the FPGA-based digital technology. The current source injects 50KHz sinusoidal current with the THD (total harmonic distortion) of 0.0029% and amplitude stability of 0.022%. The single current source and switching circuit reduce the measurement error associated with imperfect matching of multiple current sources at the expense of a reduced data acquisition time. The digital voltmeter measuring the induced boundary voltage consists of a differential amplifier, ADC, and FPGA (field programmable gate array). The digital phase-sensitive demodulation technique was implemented in the voltmeter to maximize the SNR (signal-to-noise ratio). Experimental results of 16-channel digital voltmeters showed the SNR of 90dB. We used the developed EIT system to reconstruct resistivity images of a saline phantom containing banana objects. Based on the results, we suggest future improvements for a 64-channel muff-frequency EIT system for three-dimensional dynamic imaging of bio-impedance distributions inside the human body.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.7
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• pp.423-442
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• 2018

This study observes the psychological changes of unemployed people according to their unemployment period. With this what psychological changes they face according to their unemployment period and what psychological characteristics they show, whether if psychological changes and job hunting activities are in relation, and whether if psychological changes affect job hunting activities. The study subjects received unemployment wage and were divided according to before employment, 1~3 months unemployed, and 4 months or more unemployed. An in-depth research of 8 people was conducted within the period of 2017.05~08. The psychological characteristics of people, in the period from when they first sense unemployment possibilities until three months of unemployment, are anger, anxiety, fear, which is a mixed characteristic that does not disappear but continues deepening. In study there was no significant difference in depression, anxiety, anger, social phobia, alcohol, religion factors, low self-esteem, and low self-efficacy in before employment, 1~3 months unemployed, and 4 months or more unemployed. However, the average levels of anger anxiety, depression, and social phobia were higher when the unemployment period was longer and the results of low self-esteem and low self-efficacy support further research.

• The Transactions of the Korean Institute of Power Electronics
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• v.8 no.1
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• pp.70-79
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• 2003

In this paper, T5 28-watt fluorescent lamp ballast using a piezoelectric transformer is fabricated and its characteristic is investigated. Developed electronic ballast is composed of basic circuits and blocks, such as rectifier part, active power factor corrector part, frequency oscillation part using microcontroller and feedback control, piezoelectric transformer and resonant half bridge inverters. The fabricated ballast uses to variable frequency methode in external so exciting that the frequency of piezoelectric transformer could be generated by voltage control oscillator using microcontroller(AT90S4433). The current of fluorescent lamp is detected by feedback control circuit. The signal of inverter output is received using Piezoelectric transformer, and then its output transmitted to fluorescent lamp. Traditional electromagnetic ballasts operated at 50-60Hz have been suffered from noticeable flicker, high loss, large crest factor and heavy weight. A new electronic ballast is operated at high frequency about 75kHz, and then Input power factor, distortion of total harmonic and lamp current crest factor are measured about 0.9!35, 12H and 1.5, respectively Accordingly, the traditional ballast is by fabricated electronic ballast using piezoelectric transformer and voltage control oscillator because of its lighter weight, high efficiency, economic merit and saving energy.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.06a
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• pp.18-18
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• 2010

전기적 에너지를 기계적 에너지로 변환하고 또한, 기계적 에너지를 전기적 에너지로 변환할 수 있는 압전 세라믹스는 압전 변압기 (piezoelectric transformer), 초음파 모터, 센서 등과 같은 응용분야에 광범위하게 사용되고 있다. 특히, 전원장치에 있어서 현재 주요 전자제품에 사용되고 있는 권선형 변압기와 같은 전자 변환기의 대체품으로 압전 세라믹스 소재의 특성을 이용한 압전변압기의 개발과 응용연구는 국내외적으로 활발히 연구되어왔다. 압전변압기는 권선형 변압기와 비교 하였을 때 누설자속이 없어 노이즈 발생이 없고, 공진주파수만을 이용하므로 출력의 파형이 정현파에 가까워 고조파 잡음이 없으며, 불연성의 특징을 가지고 있다. 추가적으로 압전 변압기는 소형화, 슬림화, 경량화가 가능하며 90%이상의 높은 효율을 얻을 수 있다. 또한, 단판형 압전변압기의 출력한계를 개선하기 위해 높은 승압비와 고출력을 갖는 적층타입의 압전변압기가 제안되었다. 압전변압기용 조성 세라믹스는 높은 에너지 변환효율을 위해서 전기기계결합계수 ($k_p$)가 커야 하며, 발열에 의한 온도 상승을 억제하기 위하여 기계적 품질계수(Qm)가 큰 것이 바람직하다. 또한, 높은 전류를 발생하기 위해서는 유전상수가 커 압전변압기의 출력측 정전용량을 크게 하여야한다. 이러한 압전변압기의 제작 조건을 위해 우수한 압전 및 유전특성을 갖는 PZT계 세라믹스가 주로 사용 되어져 왔다. 그러나, PZT계 세라믹스의 우수한 압전 및 유전특성에도 불구하고 $1000^{\circ}C$에서 급격히 휘발하는 PbO의 성질 때문에 환경적으로나 인체의 건강문제로 인해 전세계적으로 그 사용량을 제한하고 있다. 또한 적층 압전변압기의 구조적 특성상 내부전극과 함께 소결하여야 하는데, 이때 소결온도가 높으면 값비싼 Pd합량이 높은 전극을 사용하여야 한다. Pd함량이 10%미만인 Ag/Pd 전극을 사용하기 위해서는 $950^{\circ}C$ 이하에서 저온소결이 가능한 세라믹스 제조가 필수적이라 할 수 있다. 소결온도를 낮추는 방법으로는 다른 물질들을 치환하여 소결온도를 낮추는 방법과 미세분말을 만들어 그레인사이즈를 미세화 하는 방법들이 있다. 많은 미세 분말 제조 방법 중에서 Attrition mill은 일반적인 ball mill에 비해 분말의 입도를 미세하게 할 수 있어 증가된 분말의 비표면적에 의하여 반응을 촉진시킴으로써 저온소결이 가능한 세라믹스를 만들 수 있다. 따라서 본 연구에서는 소결온도가 낮으면서도 유전 및 압전특성이 우수한 조성을 사용하여 적층 압전변압기를 제작하여 전기적 특성을 조사하였다.