• 한국전자파학회논문지
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• 제21권12호
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• pp.1335-1342
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• 2010

본 논문에서는 능동 배열 레이더 시스템에 적용 가능한 S-band, $\bigcirc$ kW급 반도체형 송수신기의 설계 및 제작측정에 관해서 소개하였다. 이득 63 dB, 최장 펄스 폭 200 usec, 최대 duty 10 %, 펄스간 안정도 63 dB의 송신 특성을 가지며, 이득 23 dB, 잡음 지수 3.2 dB의 수신 특성을 갖는다. 펄스간 안정도 분석을 위해 펄스 네트워크 분석기를 수신 모드로 사용하여 별도의 실험 셋업을 구성하였다. 측정 결과, 제시된 특성을 모두 만족하는 것을 확인하였다.

• 한국통신학회논문지
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• 제19권5호
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• pp.920-927
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• 1994

본 논문에서는 소형, 저가격으로 데이터와 음성 신호의 양방향 전송을 위한 VSAT용 14.0~14.5GHz3Watt SSPA의 설계와 실험결과를 기술하였다. 설계된 SSPA는 VSAT에서 요구되는 성능을 만족시키기 위하여 저잡음 GaAs FET를 이용한 두단의 저잡음 증폭기, 중전력 GaAs FET를 이용한 두단의 중전력 증폭기, \ulcorner시 고출력 증폭을 위하여 내부 정합된 전력 GaAs FET와 3dB branch line coupler를 이용한 balanced 증폭기를 포함하는 삼단 전력증폭기로 구성 하였다. 제작된 SSpA의 특성으로 소신호 전력이득 42dB, 잡음지수 7dB, 1dB 이득 억압점에서 출력 신호 35dBm. 그리고 입출력 VSWR로 2.0 그리고 1.5를 측정할 수 있었다.

• Safety and Health at Work
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• 제12권3호
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• pp.365-369
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• 2021

Background: Law enforcement communications (i.e., 911 dispatch and call takers) is a challenging and stressful occupation. The purpose of this study is to identify the main stressors associated with employment in law enforcement communications, and to identify and provide context to how these stressors affect workers' health and wellbeing. Methods: This research study included focus groups with 23 call takers and 911 dispatchers employed by a large, urban law enforcement agency in 2018. Thematic analyses were conducted to identify trends. Results: Four themes of stressors emerged (i.e., the high stakes nature of some 911 calls for service, understaffing, supervisor-related stress, and recruiting practice). Two health-related themes emerged as being occupation-related: weight gain and poor sleep patterns/insufficient sleep). Specifically, participants reported negative eating habits resulting in weight gain and obesity, lack of sleep and irregular sleep schedules, and development of hypertension and/or diabetes since beginning their jobs. Conclusion: Law enforcement communications professionals experience a number of the same stressors facing law enforcement officers in patrol. These stressors, combined with the sedentary nature of the job, could result in long-term, chronic health problems.

• Journal of the Korean Wood Science and Technology
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• 제51권3호
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• pp.222-237
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• 2023

Eucalyptus pellita is one of the fast-growing tree species and has become predominant in Indonesian forest plantations. Meanwhile, tree breeding programs with clone development are the best way to provide greater genetic advantages. A better understanding of genetic control on growth and basic density in E. pellita is important for increasing wood productivity and quality. In this study, growth characteristics (tree height, diameter, and volume), basic density and its genetic parameters (heritability, genetic gain and genetic correlation) were determined. The number of clones tested in both trials was 50, divided into 5 blocks, and 5 trees/plot. The results showed that there were significant differences in growth and basic density among clones. There was an interaction between genetics and the environment further indicating the existence of unstable clones. The high heritability was found in tree height (0.82-0.86), diameter (0.82-0.90), and basic density (0.91-0.93). This implies that E. pellita has good opportunities for genetic improvement to increase wood productivity and quality. In addition, the results of genetic correlations among growth characteristics (height, diameter, and volume) and basic density showed positive moderate to highly significant value. It is suggested that these characters may be used to the advantage of the breeder for bringing improvement in these traits simultaneously. Therefore, this study provides important information of the genetic improvement of wood quality in E. pellita in Indonesia.

• 한국정밀공학회지
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• 제10권2호
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• pp.54-65
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• 1993

The paper describes and alternative method based on a new idea to measure the circular movement of machining centers. ISO has employed three testing methods for the acceptance tests of machine tools; the first is a rotating one-dimensional probe method, the second is a two-dimensional probe and a master circular ring, and the third is a kinematic ball bar. The last two methods were proposed and introduced by W. Knapp and J. B. Bryan, respectively. The newly developed method is superior to above two methods; the rotating angle can be detected and the rotating radius is variable. Circular movement errors of machining centers were investigated by the analysis of data measured by R- .THETA. method. Followint observations are obtained 1) The errors which depend on positions, i.e., periodical errors by the pitch of ball screws, errors by compensation of backlash and errors by perpendicularity of X and Y-axis, were analyzed. 2) The errors which depend on NC control system, i.e., errors by the unbalance of position-loop-gaians, errors by velocity-loop-gains and errors by feed speeds, were quantiatively analyzed. 3) The method of extracting error information, which uses moving technique of averaging angle and fourier's analysis data mesured by the R- .THETA. method, was proposed.

• Fisheries and Aquatic Sciences
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• 제5권2호
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• pp.122-126
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• 2002

A feeding trial was conducted to determine compensatory growth of juvenile olive flounder in the spring. Five treatments of fish with 3 replicates were prepared: the control group fish (C) fed twice daily for 8 weeks, the Sl, S2, S3 and S4 fish fed for 7, 6, 5 and 4 weeks after 1, 2, 3 and 4 weeks of starvation, respectively. Survival of olive flounder was not significantly different among treatments. Weight gain of flounder in S2 was significantly (P<0.05) higher than that of fish in S3 or S4, but not significantly different from that of fish in C or Sl. The poorest weight gain was observed in fish of S4 treatment. Specific growth rate (SGR) for flounder in S2 was significantly (P<0.05) higher than that for fish in C or S4, but not significantly different from that of fish in Sl or S3. Feed intake (g/fish) was proportional to duration of days of feeding except for flounder in S2, but not significantly different among C, Sl or S2. Feed efficiency ratio (FER) and protein efficiency ratio (PER) for flounder in S2 were significantly (P<0.05) higher than for fish in C, but not significantly different from those for fish in Sl, S3 or S4. Hepatosomatic index (HSI) and condition factor (CF) for flounder in Sl, S3 and S4 were not significantly different from those for fish in C, but significantly (P<0.05) lower than S2 except for CF in Sl at the end of the experiment. Proximate composition of the whole body of flounder was not significantly different among treatments. In considering results of the experiment, juvenile olive flounder achieved compensatory growth when properly fed after starved up to 2 weeks in the spring. Compensatory growth of fish was supported by improvement in SGR, FER and PER in fish starved.

• Asian-Australasian Journal of Animal Sciences
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• 제21권8호
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• pp.1171-1177
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• 2008

The performance of growing rabbits fed Ruzi grass (Brachiaria ruziziensis), head lettuce (Lactuca sativa) residue, Mimosa pigra and water spinach (Ipomoea aquatica) was studied in an experiment using 64 rabbits (4 males and 4 females per treatment) of 2 breeds, New Zealand White and a crossbred between New Zealand White and native breed. The rabbits had an average initial weight of 668 g, were about 6 weeks old and were housed in individual pens. The foliages were fed ad libitum and a commercial concentrate was fed at a restricted level of 2% of body weight on a dry matter (DM) basis. In the digestibility experiment, the rabbits, 4 per foliage and males only, were fed the same foliages as in the growth experiment but without concentrate. Daily weight gain was lower in the group fed Ruzi grass, 14.8 g/d (p<0.001) compared to 17.6, 18.5 and 18.4 g/d for head lettuce, Mimosa pigra and water spinach, respectively. Feed intake and feed conversion ratio were lowest for the rabbits fed water spinach, 66 g DM/d and 3.6 kg DM/kg live weight, respectively. The New Zealand White breed had a higher daily gain than the crossbred rabbits (p<0.05), 18.0 and 16.7 g/d, respectively. There were no significant differences in feed intake, growth or feed conversion ratio due to sex. The digestibility coefficients of DM, organic matter, crude protein, crude fiber, neutral detergent fiber and acid detergent fiber were significantly lower (p<0.001) in the rabbits fed Ruzi grass. Breed and sex had no effect on digestibility. In conclusion, feeding head lettuce residue, Mimosa pigra and water spinach resulted in higher growth rate and digestibility than feeding Ruzi grass and can be recommended as alternative feeds.

• ETRI Journal
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• 제42권4호
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• pp.549-561
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• 2020

We developed a 0.1-㎛ metamorphic high electron mobility transistor and fabricated a W-band monolithic microwave integrated circuit chipset with our in-house technology to verify the performance and usability of the developed technology. The DC characteristics were a drain current density of 747 mA/mm and a maximum transconductance of 1.354 S/mm; the RF characteristics were a cutoff frequency of 210 GHz and a maximum oscillation frequency of 252 GHz. A frequency multiplier was developed to increase the frequency of the input signal. The fabricated multiplier showed high output values (more than 0 dBm) in the 94 GHz-108 GHz band and achieved excellent spurious suppression. A low-noise amplifier (LNA) with a four-stage single-ended architecture using a common-source stage was also developed. This LNA achieved a gain of 20 dB in a band between 83 GHz and 110 GHz and a noise figure lower than 3.8 dB with a frequency of 94 GHz. A W-band image-rejection mixer (IRM) with an external off-chip coupler was also designed. The IRM provided a conversion gain of 13 dB-17 dB for RF frequencies of 80 GHz-110 GHz and image-rejection ratios of 17 dB-19 dB for RF frequencies of 93 GHz-100 GHz.

• 한국위성정보통신학회논문지
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• 제2권2호
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• pp.10-15
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• 2007

위성방송수신 및 위성 양방향 인터넷, VSAT 등의 위성통신서비스를 차량 이동 시에도 이용할 수 있기 위해서는 차량에 탑재하기 용이하도록 소형이며 높이가 낮은 안테나 구조가 요구된다. 또한 중위도 지역에서 평면 안테나 상태로 45도 빔틸트 특성을 갖고, Ku 밴드의 위성통신용으로 충분한 고이득을 얻기 위해, 빔폭이 좁고 사이드로브가 적으며 저손실 구조의 배열안테나 개발이 필요하다. 본 논문에서는 이러한 성능을 만족시키기 위해, 진행파형 누설파 모드를 기초로 한 수직 편파로 동작하는 도파관 종방향 슬롯 배열안테나를 제안하였다. 16개 누설파 소자의 배열안테나 이득은 30 dBi 이었으며, 빔폭은 4.9도, 사이드로브 레벨은 -20 dB 이하, 중심주파수에서 빔틸트 각도는 45도를 얻었다. 급전선로는 도파관의 병렬급전 방식으로 설계하여 광대역, 저손실 특성을 얻을 수 있었다.

• 한국양식학회지
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• 제11권1호
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• pp.31-38
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• 1998

A 20-week growth trial was conducted in flow-through aquarium system to investigate the effects of supplemental macroalgae and spirulina in the diets on growth and body cmposition in juvenile abalone (Haliotis discus hannai). Four replicate groups of the abalone averaging 65mg were fed one of ten isonitrogenous (34%) and isolipidic (7.5%) diets containing 8.1% Ulva, 7.5% Undaria, 11% Laminara, 11% Sargassum, spirulina (5, 10 and 15%), or dried Undaria powder (10 and 20%). In addition, these formulated diets were compared with natural food(dried Undaria). Survival rate of abalone were not significantly affected by the different dietary macoralgae sources, spirulina or dried Undaria powder levels (P>0.05). Weight gain and soft body weight of abalone fed the diet containing Sargassum was significantly higher (P<0.05) than those of abalone fed the diets containing Laminaria, 20% dried Undaria powder and natural food. Survival rate, weight gain, soft body weight and shell length of abalone fed natural food were lowest (P<0.05) among all diet. Moisture, protein and lipid contents of soft body were not influenced by experimental diets except natural food. Lipid content of abalones fed natural food was significantly lower than those of abalone fed other diets (P<0.05). These data indicate that abalone can more efficiently utilize Sargassum than Ulva, Undaria, Laminaria or spirulina.