• 대한전자공학회논문지TC
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• 제42권12호
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• pp.171-176
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• 2005

본 논문에서는 DCS와 WiBro 및 ISM 수용이 가능한 기지국용 광대역 다중공진 평판 안테나를 설계 및 제작하였다. 제안한 안테나는 기존의 모노폴 구조를 개방 루프 형태(폴디드 형태)로 수정하여 개방 부분의 결합에 의한 캐패시턴스를 증가시킨 광대역 다중공진 안테나를 설계하였다. 제안된 안테나는 도파관 급전 방법의 인쇄형 평판 안테나로 단일 층으로 구현되어 MMIC 및 LTCC의 이용이 용이하며 기존의 안테나보다 크기가 작고 높은 이득을 갖는다. 안테나 구조의 개방 부분의 간격과 루프 형태의 높이를 조절하여 공진 거리 및 대역폭을 조절 할 수 있다. 설계한 안테나의 대역폭은 정재파비 2 이하를 기준으로 DCS와 WiBro 및 ISM대역을 모두 충족하였으며 전체의 대역폭은 $1.575GHz\~2.985GHz(1.41GHz)$의 $58.75\%$의 주파수 대역폭을 얻었다. 또한, 안테나의 방사패턴은 1.6GHz, 2.3GHz, 2.8GHz에서의 Co-Polarization과 Cross-Polarization의 특성을 측정하였다.

• 전기전자학회논문지
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• 제7권2호
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• pp.223-229
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• 2003

본 논문에서는 2.4GHz와 5.8GHz 대역의 무선 랜카드에 사용되는 듀얼 역-F형 내부 안테나의 설계 값에 따른 안테나 특성을 분석하였다. 노트북용 WLAN card의 PCB 기판에 인쇄된 형태로 설계하여 안테나의 길이, 단락 스터브의 두께, 피드선과 단락 스터브 사이의 간격, 안테나와 접지면 사이의 간격, 안테나의 두께 및 기판의 두께와 기판의 유전율에 따른 특성 변화를 연구하였다. 설계 값에 따른 특성변화 그래프로부터 설계 값을 튜닝하여 최적의 안테나를 설계하였다. 설계된 안테나는 VSWR이 1.6과 1.14이며, 주파수 대역폭은 170MHz와 500MHz 이며, 최대이득 3.5dBi 의 값을 얻었다.

• 한국전자파학회논문지
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• 제15권10호
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• pp.922-930
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• 2004

본 논문에서는 보다 소형화된 마이크로스트립 패치 안테나를 제작하기 위해 패치 밑면과 접지면 상에 Iris를 수직으로 부착한 3차원 구조의 마이크로스트립 안테나를 설계$\cdot$제작하였다. 부착된 Iris에 의해 패치 밑면에 흐르는 전류의 경로 증가 및 패치 내부의 유전율이 증가되는 효과를 얻고자 하였으며, 제작결과 중심주파수 1.575 GHz에서 높이 9 mm의 평면형 마이크로스트립 패치 안테나(패치 길이 81.5 mm$\times$패치 폭 90 mm)와 비교하여, 지그재그형으로 Iris를 부착한 경우 최대 $79.1\%$(17 mm$\times$90 mm)의 안테나 길이 단축 효과가 나타났다. 이때 측정된 이득 -1.15 dBd, -10 dB 대역폭 $6.2\%$(98 MHz), E-면 HPBW $154^{\circ}$를 나타내어 본 논문에서 제안된 Iris 를 부착한 마이크로스트립 안테나가 소형화에 유효함을 확인하였다.

• Journal of Nutrition and Health
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• 제39권2호
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• pp.109-114
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• 2006

The effects of the erect bipedal stance exercise on bone mass and the biomarkers of bone formation and resorption were investigated in rats. Five-week old rats were assigned into control and exercise groups. The rats of exercise group were weight-bearing-trained for 13 weeks in the cage designed to adjust progressively the height from 26.5 cm to 31.5 cm to force the rats rising an erect bipedal stance for feeding and drinking. There was no significant difference in food intakes between two groups. But body weight gain was significantly increased in control group. The lengths of femur, tibia, humerus and radius were significantly longer in control group than exercise group, but the femur and tibia weights per body weight were significantly higher in exercise group than control group. Also the breaking force of femur and tibia in exercise group were higher than control group significantly. The calcium contents of femur and tibia were significantly increased in exercise group than control group. The activity of bone specific alkaline phosphatase (B-ALP) and the osteocalcin contents of serum (the biomarkers of bone formation) in exercise group were higher than control group, but the carboxyterminal propeptide of type I procollagen (P1CP) contents of serum did not show any difference between two groups. However the urinary deoxypridinolin (DPD) excretion, biomarker of bone resorption, was significantly lower in exercise group than control group. From these results, it has been indicated that the erect bipedal stance exercise enhanced the density and the strength of femur and tibia by increasing biomarkers of bone formation and suppressing a biomarker of bone resorption in rats.

• 한국재료학회지
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• 제29권10호
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• pp.586-591
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• 2019

This study describes the doping effect of $Yb_2O_3$ on microstructure, electrical and dielectric properties of $ZnO-V_2O_5-MnO_2-Nb_2O_5$ (ZVMN) ceramic semiconductors sintered at a temperature as low as $900^{\circ}C$. As the doping content of $Yb_2O_3$ increases, the ceramic density slightly increases from 5.50 to $5.54g/cm^3$; also, the average ZnO grain size is in the range of $5.3-5.6{\mu}m$. The switching voltage increases from 4,874 to 5,494 V/cm when the doping content of $Yb_2O_3$ is less than 0.1 mol%, whereas further doping decreases this value. The ZVMN ceramic semiconductors doped with 0.1 mol% $Yb_2O_3$ reveal an excellent nonohmic coefficient as high as 70. The donor density of ZnO gain increases in the range of $2.46-7.41{\times}10^{17}cm^{-3}$ with increasing doping content of $Yb_2O_3$ and the potential barrier height and surface state density at the grain boundaries exhibits a maximum value (1.25 eV) at 0.1 mol%. The dielectric constant (at 1 kHz) decreases from 592.7 to 501.4 until the doping content of $Yb_2O_3$ reaches 0.1 mol%, whereas further doping increases it. The value of $tan{\delta}$ increases from 0.209 to 0.268 with the doping content of $Yb_2O_3$.

• Animal Bioscience
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• 제34권10호
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• pp.1653-1662
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• 2021

Objective: This experiment was conducted to investigate the effect of insoluble cellulose supplementation to diets on the growth performance, intestinal morphology, the incidence of diarrhea, nutrients digestibility, and inflammatory responses in altering environmental conditions of animals housing. Methods: A total of 108 male pigs (Duroc×[Yorkshire×Landrace]) were randomly allocated to one of three dietary treatments (cellulose 0%, 1%, 2%) and two environmental conditions (good sanitary condition vs. poor sanitary condition) to give 6 replicate pens per treatment with three pigs per each pen at 14 days post-weaning. Results: Pigs were in good sanitary condition had higher average daily gain (p<0.01) and improved feed efficiency (p<0.05) from day 1 to 14 after weaning compared to their counterparts. The interactions were found between environmental conditions and dietary treatments (day 7: crypt depth [p<0.01], villous height to crypt depth [p<0.001]; day 14: crypt depth [p<0.001], villous to crypt ratio [p<0.01]) in ileum morphology. Crypt depth was decreased (p<0.05), and villous to crypt ratio was increased (p<0.05) only in poor sanitary conditions. Pigs exposed to the good sanitary condition had higher (p<0.05) apparent ileal digestibility (day 7, gross energy; day 14, dry matter), apparent total tract digestibility (day 14, dry matter and crude protein) compared to pigs housed in the poor sanitary condition. Meanwhile, pigs fed a diet supplemented with 2% cellulose had decreased (p<0.05) apparent ileal digestibility (day 7, dry matter; day 14, crude protein), apparent total tract digestibility (day 7, dry matter; day 14, crude protein, gross energy) compared to pigs fed a diet supplemented with 0% or 1% cellulose. Conclusion: Our results indicated that a diet supplemented with 1% cellulose increased villous to crypt ratio, however feeding a diet containing cellulose (1% or 2%) impaired nutrient digestibility for 14 day after weaning in both good sanitary and poor sanitary conditions.

• Asian-Australasian Journal of Animal Sciences
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• 제32권1호
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• pp.110-117
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• 2019

Objective: An experiment was conducted to evaluate the effects of dietary glutamine (Gln) and arginine (Arg) supplementation on performance, intestinal morphology and ascites mortality in broilers. Methods: A total of 675 day old chicks were randomly allocated to 9 experimental groups in a $3{\times}3$ factorial arrangement based on a completely randomized design with 5 replicates of 15 chicks. Three levels of dietary Gln (0%, 0.5%, and 1%) and Arg (100%, 130%, and 160% of Ross recommendation) supplementation were used in ascites inducing condition ($15^{\circ}C{\pm}1^{\circ}C$) from 7 to 42 days of age. Results: Dietary supplementation of Gln increased body weight gain during grower, finisher and total periods (p<0.05) and increased feed intake during total period. Ascites mortality was decreased by Gln supplementation (p<0.05). Gln supplementation increased the villus height (VH) and crypt depth (CD) in duodenum and jejunum (p<0.05). Arg supplementation decreased CD in duodenum and jejunum, and increased ileum villus width (VW) and also VH/CD ratio in duodenum and jejunum (p<0.05). Both Gln and Arg increased the goblet cell number (GCN) in duodenum whereas Gln supplementation decreased GCN in jejunum and ileum (p<0.05). The $Gln{\times}Arg$ interaction were observed for right ventricle (RV)/total ventricular (TV) ratio, VH, VW, CD, VH/CD. Conclusion: It was concluded that dietary 0.5% Gln alone or along with 130% Arg of Ross requirement, improve the intestinal morphology and performance and hence decrease the ascites mortality in broiler chickens with cold induced ascites.

• Nuclear Engineering and Technology
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• 제51권6호
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• pp.1514-1524
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• 2019

Hydrogen-steam gas mixture may be injected into containment with flow regime varying both spatially and transiently due to wall effect and pressure difference between primary loop and containment in severe accidents induced by loss of coolant accident. Preliminary CFD analysis is conducted to gain information about the helium flow regime transition process from jet to buoyancy plume for forthcoming experimental study. Physical models of impinging jet and wall condensation are validated using separated effect experimental data, firstly. Then helium transportation is analyzed with the effect of jet momentum, buoyancy and wall cooling discussed. Result shows that helium distribution is totally dominated by impinging jet in the beginning, high concentration appears near gas source and wall where jet momentum is strong. With the jet weakening, stable light gas layer without recirculating eddy is established by buoyancy. Transient reversed helium distribution appears due to natural convection resulted from wall cooling, which delays the stratification. It is necessary to concern about hydrogen accumulation in lower space under the containment external cooling strategy. From the perspective of experiment design, measurement point should be set at the height of connecting pipe and near the wall for stratification stability criterion and impinging jet modelling validation.

• 농업과학연구
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• 제46권2호
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• pp.285-292
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• 2019

This study was done to evaluate the effects of a mixture of essential oils and organic acid supplementation on growth performance, blood profiles, leg bone length and intestinal morphology in Ross broilers. A total of 40 Ross 308 broilers ($1140{\pm}80g$) were randomly allocated to 2 groups, a basal diet (CON) and a basal diet + 0.05% $Avi-protect^{(R)}$ (AVI, Mixture of 25% citric, 16.7 sorbic, 1.7% thymol, and 1.0% vanillin), with 20 replicates for every group and 1 chicken per replicate per cage. The broilers were raised in a temperature-controlled room maintained at $24{\pm}1^{\circ}C$ and $50{\pm}5%$ humidity. The body weight (p < 0.05) and weight gain (p < 0.05) of the broilers were increased in the AVI group compared with the CON group. The triglyceride (p < 0.05) and low density lipoprotein (LDL) (p < 0.05) contents were significantly decreased in the AVI group compared with the CON group. There was no significant difference in the leg bone length between the AVI and CON groups (p > 0.05). The villi height (p < 0.05) and goblet cell count (p < 0.05) were significantly increased in the AVI group compared with the CON group. In conclusion, $Avi-protect^{(R)}$ as a feed additive improved the growth performance and lipid metabolism and promoted the development of the intestinal morphology of broilers.

• Journal of Animal Science and Technology
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• 제63권3호
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• pp.563-574
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• 2021

A total of 1512 Ross 308 broilers (one - day - old) were assigned (random blocks) to 1of 3 dietary treatments with 28 replicates of 18 chicks/cage. The dietary treatments were Cornsoybean-meal based basal diet supplemented with 0%, 0.1%, and 0.2% of commercial yeast hydrolysate (YH [Saccharomyces cerevisiae]). The graded level of YH supplementation has linearly increased broilers body weight gain on d 21, 35, and overall (p = 0.044, 0.029, and 0.036, respectively) experimental period. In addition, the increased level of YH supplementation has linearly reduced feed conversation ratio of broilers on d 21, 35, and overall trial period (p = 0.041, 0.052, and 0.032, respectively). However, the feed intake and mortality of broilers were not affected by the graded level of YH supplementation. Though nutrient digestibility of dry matter (p = 0.012) and nitrogen (p = 0.021) was linearly increased in broilers fed YH supplementation, at the end of the trial it fails to affect the total track digestible energy. Dietary inclusion of YH supplementation showed a beneficial effect on the microbial population as linearly improved lactobacillus (p = 0.011) and reduced Escherichia coli counts (p = 0.042). An increasing level of YH supplementation has tended to decrease NH₃ (p = 0.069) and linearly decrease H₂S (p = 0.027) of noxious gas emission in broilers. Moreover, dietary YH supplements trend to increase the glucose (p = 0.066) and reduced cholesterol (p = 0.069) level. At the end of the test, YH supplementation elicited a linear reduction in drip loss on days 5 and 7, respectively (p = 0.045, and 0.021). Furthermore, dietary inclusion of YH supplementation had linearly increased villus height (p = 0.051) but fails to affect crypt depth. Therefore, in terms of positive effects on the broiler's overall performance, we suggest that dietary supplements containing graded YH levels in the broilers diet could serve as a potential alternative for growth promoters.