• The Journal of the Korea institute of electronic communication sciences
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• v.15 no.3
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• pp.421-432
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• 2020

This paper proposes a 2-kW solid-state power amplifier (SSPA) developed by employing power amplifier pallets designed using gallium-nitride high electron mobility transistors, which is used in S-band military radars and to replace existing traveling-wave tube amplifier (TWTA). The SSPA consists of a high-power amplifier module, which combines eight power amplifier pallets, a drive amplifier module, a digital control module, and a power supply unit. First, the amplifier module and component were integrated into a small package to account for space limitations; next, an on-board harmonic filter was fabricated to reject spurious components; and finally, an auto gain control system was designed for various duty ratios because recent military radar systems are all active phase radars using the pulse operation mode. The developed SSPA exhibited a max gain of 48 dB and an output power ranging between 63-63.6 dBm at a frequency band of 3.1 to 3.5 GHz. The auto gain control function showed that the output power is regulated around 63 dBm despite the fluctuation of the input power from 15-20 dBm. Finally, reliability of the developed system was verified through a temperature environment test for nine hours at high (55 ℃) / low (-40℃) temperature profile in accordance with military standard 810. The developed SSPA show better performance such as light weight, high output, high gain, various safety function, low repair cost and short repair time than existing TWTA.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.04a
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• pp.86-92
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• 1993

자동차의 현가장치에 대한 능동제어연구는 국내외적으로 활발히 진행되어 왔다. 수동식현가장치는 단순히 스프링과 감쇠기로 차체의 진동을 수동 제어 하므로 성능 향상에 한계가 존재하게 된다. 수동식 현가장치가 강성계수와 감쇠계수를 조절함으로써 차체로 들어오는 진동을 억제하는 반면, 능동식제 어는 보통 유압을 이용하여 효율적으로 차체에 들어오는 진동을 억제시키게 된다. 일반적으로 자동차가 능동현가장치 설계시 요구되는 사항은 탑승자의 승차감, 조종성, 현가장치의 공간확보 문제, 경제성(제어력), 실제적으로 자동 차에 적용할 수 있는 능동제어기법인가 하는 문제이다. 자동차 능동식 현가 장치는 보통 1/4 car (2자유도계), Full-car 모델 (7자유도계) 등으로 모델링 을 하여 능동제어기를 설계한다. 1/4 car 모델의 특징은 해석이 비교적 단순 하고 현가장치의 동적거동을 이해하는데 유용하고 실험을 하거나 실제 자동 차에 적용하기 쉬운 반면에 Full-car 모델에 비해 제어력의 효율이 떨어진다 는 단점이 있다. 그 이유는 1/4 car 모델은 차체의 동역학적 특성을 고려하 여 설계하지 않았기 때문에 4개의 독립현가차축에서는 오직 그 현가축방향 으로 발생하는 수직방향의 진동만을 제어하기 때문이다. 따라서 동역학적 역 성에 기인하는 운동을 제어하는 비효율적인 제어력이 공급된다는 단점을 갖 는다. 이에 비해 full-car 모델은 주행모드(수직, 롤링, 피칭운동)간의 연성을 고려하여 제어기를 설계할 수 있기 때문에 1/4 car 모델에 비해 제어력의 효 율이 높다는 장점이 있는 반면에 모델이 수학적으로 복잡하므로 제어력을 구하는데 계산량이 많고, 실제 자동차에 적용하기에 복잡하다는 단점을 갖고 있다. 따라서 본 논문에서는 쉽게 실험할 수 있고, 실용화할 수 있는 1/4 car 모델에 대하여 능동제어기를 설계하여 실제자동차에 능동제어기를 적용할 때 참고가 될 수 있도록 하였다. 자동차는 저주파영역의 밴드통과필터 역할 을 하므로 저주파에서의 성능, 특히 탑승자가 민감하게 느끼는 0.5Hz - 10Hz 부근의 주파수성능은 승차감, 조종성에 상당히 중요하다. 이에 본 논문 에서는 0.5Hz - 10Hz 부근의 승차감, 조종성의 향상에 초점을 두고 차체의 속도를 출력변수로 한 LQG/LTR 제어기를 설계하였다. LQG/LTR 설계기법 은 안정도-강인성이 좋은 체계적인 설계기법으로서 전 상태를 측정할 필요 가 없으므로 실제 적용시 효과적이다. 또한 자동차의 제원의 변화에 대한 고 유치의 민감도해석과 새로운 개념으로 안정도-강인성(Robustness)해석을 하 여 수동시스템과 능동시스템의 강인성을 비교하였다.

• Journal of Life Science
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• v.13 no.5
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• pp.634-641
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• 2003

In order to examine whether arsenic, one of environmental stress, contribute to augumentation and relaxation of rat aorta, this study was performed in vivo and in vitro, using intacted or denuded rats aorta ring preparation, respectively. The carotid arterial pressure was recorded on an ink-writing physiograph(Grass Co. 79E) connected to strain gauge. The contractile response of vascular ring with or without endothelium preparation isolated from rat were determined in organ bath and was recorded on physiograph connected to isometric transducer. Vasopressin-,and phenylephrine- induced increase in arterial pressure significantly enhanced in arsenic-treated rats; increase of 19.1%, and 46.6%, respectively. Vascular contractile response was measured in vitro preparations exposed to 0, 0.5, 1, 2 and 4 mM of arsenic for 1, 3, 5 and 8 hours. The dose-vascular responses of phenylephrine augmented by increasing dose of arsenic in the strips exposed to arsenic for 8 hours, and did not augmented for 1, 3, 5 hours. The phenomenon was not affected by strips denuded endothelium. And the response of relaxation of rat aorta induced by nitroprusside was not influenced by arsenic stress, but acetylcholine was a little increased. compared to that of control. There were no significant difference in relaxation between control and arsenic treated rings with endothelium or denuded. All of the results, phenyleprine-induced vascular contraction was significantly enhanced in 4 mM arsenic-treated rat aortic rings compared with control, whether endothelium was present or denuded at 8 hours after arsenic treatment. It may be a mechanism by which long-term arsenic stresses play a role in development of hypertension.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.17 no.3
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• pp.267-274
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• 2017

Recently, several researches have been studied on agricultural automation system according to convergence of IT technology with agriculture. An automatic control system of the growth environment in crops is one of the these researches. The controls of damages caused by diseases and insects pest in crops are mainly carried out by manual mode or semi-automatic mode because of farmer's concerns for poor efficiency. But, this situation needs to be improved because it occurs various problems, such as human exposure to toxic pesticides, environmental pollution and waste due to drug overuse. In order to solve these problems, we developed an automatic quantity control system which based on the amount of pesticides for area under cultivation. The amount of pesticides is calculated according to the manufacturer's instruction for pesticides. To verify the effectiveness of our developed automatic system, we also compared with the systems of manual mode and the semi-automatic mode. The experimental results of a pest control performance of an automatic quantity control system showed that automatic system can reduce overuse of drugs. These results suggested that it can be expected to replace the existing system, with equivalent effectiveness to the manual mode.

• Applied Chemistry for Engineering
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• v.28 no.6
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• pp.632-637
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• 2017

The vehicle lubricant occupies upto 35% in a total lubricant market and engine oil occupies upto 77% in the vehicle lubricant market in Korea. A suitable quality management of the circulating engine oil is necessary for driver and engine protection. But, KS and synthetic engine oil products (involved over 30% synthetic oil) are exempt to any quality management under Petroleum and Alternative Fuel Business Act. It is also known that synthetic oils such as PAO (poly alpha olefin) have excellent properties and performance like anti-wear, varnish control and oxidation stability than those of mineral oils. For this reason, PAO has been used for an engine oil, rotary screw and reciprocating compressor in addition to heavy duty and other extreme service applications. In this study, our research group analyzed the chromatogram pattern for the mineral oil, PAO and mineral oil involved a typical ratio of PAO using SIMDIST (simulated distillation). In the SIMDIST chromatogram, the mineral oil showed a broad peak, while PAO showed a sharp typical peak. Also the oil with a large viscosity grade exhibited a long retention time due to the heavy molecular weight and high boiling point. In particular, the blended mineral oil with 20% PAO sample showed a distinctly different pattern compared to that of using the conventional mineral oil. For monitoring PAO contents in distributing engine oils, we analyzed the SIMDIST for 27 kinds of engine oils which were popularly sold in Korea. The analytic results indicate that all kinds of engine oils showed that PAO contents were below 20% in engine oil products. Moreover, the PAO titled product was found to have a small amount of PAO. Thus, we conclude that the related laws for the proper quality management of synthetic oils are needed to be established.

• Journal of the Korea Computer Graphics Society
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• v.23 no.5
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• pp.9-17
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• 2017

Filming using multiple cameras is required for the production of the multi-screen content. It can fill the viewer's field of view (FOV) entirely to provide an increased sense of immersion. In such a filming scenario, it is very important to monitor how images captured by multiple cameras are displayed as a single content or how the content will be displayed in an actual theatre. Most recent studies on creating the content of special format have been focused on their own purposes, such as stereoscopic and panoramic images. There is no research on content creation optimized for theatres that use three screens that are spreading recently. In this paper, we propose a novel content production system with a rig that can control three cameras and monitoring software specialized for multi-screen content. The proposed rig can precisely control the angles between the cameras and capture wide angle of view with three cameras. It works with monitoring software via remote communication. The monitoring software automatically aligned the content in real time, and the alignment of the content is updated according to the angle of camera rig. Futher, the producion efficiency is greatly improved by making the alignment information available for post-production.

• Radiation Oncology Journal
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• v.20 no.4
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• pp.375-380
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• 2002

Purpose : To develop a practical film dosimetry system for routine Quality Assurance (QA). Materials and Methods :An One Click Film (OCF) Dosimetry system was designed to perform swift routine QA with functions including automatic fog value elimination, angle adjustment, automatic symmetry calculation, and realtime profile generation with the ability to display realtime three-dimensional dose distributions. Results : The most frequently used functions for routine QA, such as the elimination of the fog value, conversion into an H&D curve, symmetry, and isodose distribution, can be achieved with only one click. Conclusion : Reliable results were achieved with the OCF dosimetry with simpler steps than other commercially available film dosimetry systems for routine QA. More research on the refined user interface will make this system be clinically useful.

• Fire Science and Engineering
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• v.30 no.1
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• pp.104-110
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• 2016

Positive displacement pumps with high pressure and water capacity are used large fires in various high-rise buildings. This study provides information for a performance approval standard of fire pumps for fire trucks based on centrifugal pump standards enacted in 2012. An experiment was conducted with a positive displacement pump for three levels of performance from the approval standard (V-1, 2, and 3). The efficiency of the pump was included in the reference, which requires the approval of 65% performance, the same as a centrifugal pump. The water pressure is between 1.5 and 2.5 MPa, and the required flow rate was established as at least $0.31m^3/min$ and up to $3.0m^3/min$. A relief valve was added to adjust the shut-off pressure due to the structural characteristics of the positive displacement pump. A strainer was also installed to prevent damage to the inside of the pump due to foreign matter. However, the strainer includes a difference from the positive displacement pump to operate without a vacuum pump and the centrifugal pump. This is due to the additional approval standard portion of the positive displacement pump, which is expected to be selected for more variety of fire-fighting equipment and proactive responses to fire suppression in a high-rise buildings and large fires. In conclusion, this approval standard was enacted in January 2016.

• Korean Journal of Environmental Agriculture
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• v.2 no.2
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• pp.114-119
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• 1983

Several supplementary heating methods were investigated to find their effects on night air temperature, injury in plant, growth and yield with Hokowase strawberry(Fragaria grandiflora) under greenhouse, during early spring season in 1981 and 1982. Kerosene lamp as a supplementary heating was not suitable because of its severe injury on strawberry plants, danger of accidental fire and bad smell. Paraffine candle and electric wire heating did not injure on strawberry plant, raised the minimum air temperature in greenhouse at night, enhanced growth, flowering and harvesting time of strawberry. Paraffine candle was effective as a supplementary heating method for short period growing under greenhouse, whereas electric wire heating was suitable for long period cultivation.

• Korean Journal of Food Science and Technology
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• v.31 no.2
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• pp.285-292
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• 1999

An analytical method applicable to quality control and its optimum conditions were studied for rapid and efficient analysis of sorbic and benzoic acids used as preservatives in the commercial soybean paste. In gas chromatographic analysis of sorbic and benzoic acids, the application of HP-FFAP (acid modified polyethylene) wide bore column improved the separation ability significantly. By setting the oven temperature of GC to $200^{\circ}C$, the total elapsed time for quantitative analysis was also reduced to the level required in using packed column. By extracting sorbic and benzoic acids from soybean paste with an automatic steam distillation device, the elapsed time for analysis was reduced by 80% more compared to using conventional steam distillation method. The recoveries of sorbic and benzoic acids by the automatic steam distillation were 98.1% and 99.9%, respectively. The sorbic acid was found in 3 samples of 14 commercial soybean pastes, of which contents were $466{\sim}530ppm$, while $0.3{\sim}4.4ppm$ of benzoic acid was found in all the samples.