• Journal of Electrical Engineering and Technology
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• 제13권5호
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• pp.2004-2010
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• 2018

We propose a small active antenna to receive Global Navigation Satellite System (GNSS) signals, i.e., Global Positioning System (GPS) L1 (1,575MHz) and Russian Global Navigation Satellite System (GLONASS) L1 (1,600 MHz) signals. A two-stage low-noise amplifier (LNA) with more than 27 dB gain is implemented in the bottom layer of a three-layer antenna package. In addition, a hybrid coupler is used to combine signals from pair of proximately coupled orthogonal feeds with $90^{\circ}$ phase difference to achieve the circular polarization (CP) characteristic. Three layers of high permittivity (${\varepsilon}_r=10$) substrates are stacked and effectively integrated to have a small dimension of $64mm{\times}64mm{\times}7.42mm$ (including both circuit and antenna). The reflection coefficient of the fabricated antenna at the target frequency is below -10 dB, the measured antenna gain is above 26 dBic and the measured noise figure is less than 1.4 dB.

• 한국정밀공학회지
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• 제29권7호
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• pp.723-729
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• 2012

Spring-like leg models have been employed to explain various dynamic characteristics in human walking. However, this leg stiffness model has limitations to represent complex motion of actual human gait, especially the behaviors of each lower limb joint. The purpose of this research was to determine changes of total leg stiffness and lower limb joint stiffness with gait speed in knee osteoarthritis. Joint stiffness defined as the ratio of the joint torque change to the angular displacement change. Eight subjects with knee osteoarthritis participated to this study. The subject walked on a 12 m long and 1 m wide walkway with three sets of four different randomly ordered gait speeds, ranging from their self-selected speed to maximum speed. Kinetic and kinematic data were measured using three force plates and an optical marker system, respectively. Joint torques of lower limb joints calculated by a multi-segment inverse dynamics model. Total leg and each lower limb joint had constant stiffness during single support phase. The leg and hip joint stiffness increased with gait speed. The correlation between knee joint angles and torques had significant changed by the degree of severity of knee osteoarthritis.

• 한국의상디자인학회지
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• 제9권1호
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• pp.161-171
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• 2007

The purpose of this study was to classify the lower body of the lost women and to investigate the three-dimensional characteristics of each lower body somatotype of them. The subject were ninety seven women whose. age were twenties and whose height and bust girth were in the range of mean$\pm1\delta$ of typical body size of twenties' Korean women. The forty one variables of their lower body were measured by Martin's Anthropometric Instrument. And they were analyzed for mean, standard deviations factor analysis, and cluster analysis. In the second phase of analysis, the three participants were re-selected in each type were measured by Sliding Guage and analyzed their lower body somatotype. The results were as follows; The components of lower body of 20s' women were extracted with 7 factors through factor analysis and orthogonal rotation by the method of Varimax. The rate of the cumulative contribution was 84.1% the first factor was the thickness of lower body, the second factor was the vertical size of lower body the third factor was the front shape of hip, the forth factor was the vertical size of hip, the fifth factor was the shape of abdomen, the six factor was the flat-ratio of waist and the seventh factor was flat-ratio of hip. The somatotype of 20's women's lower body can be classified into 3 types. Type 1 is the standard somatotype of 20's women's lower body and the 34.0% of the participants in the study was categorized into type 1. Type 2 is a short and corpulency type with protruded abdomen and hip and the 29.9% of the participants in the study was categorized into type 2. And the type 3 is a tall and thin type with plat abdomen and hip and the 37.1% of the participants was categorized into type 3.

• 한국분말재료학회지
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• 제25권5호
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• pp.408-414
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• 2018

This study investigates the microstructure and wear properties of cermet (ceramic + metal) coating materials manufactured using high velocity oxygen fuel (HVOF) process. Three types of HVOF coating layers are formed by depositing WC-12Co, WC-20Cr-7Ni, and Cr3C2-20NiCr (wt.%) powders on S45C steel substrate. The porosities of the coating layers are $1{\pm}0.5%$ for all three specimens. Microstructural analysis confirms the formation of second carbide phases of $W_2C$, $Co_6W_6C$, and $Cr_7C_3$ owing to decarburizing of WC phases on WC-based coating layers. In the case of WC-12Co coating, which has a high ratio of $W_2C$ phase with high brittleness, the interface property between the carbide and the metal binder slightly decreases. In the $Cr_3C_2-20CrNi$ coating layer, decarburizing almost does not occur, but fine cavities exist between the splats. The wear loss occurs in the descending order of $Cr_3C_2-20NiCr$, WC-12Co, and WC-20Cr-7Ni, where WC-20Cr-7Ni achieves the highest wear resistance property. It can be inferred that the ratio of the carbide and the binding properties between carbide-binder and binder-binder in a cermet coating material manufactured with HVOF as the primary factors determine the wear properties of the cermet coating material.

• Steel and Composite Structures
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• 제45권2호
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• pp.205-218
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• 2022

Proper calculation of splitting tensile strength (STS) of concrete has been a crucial task, due to the wide use of concrete in the construction sector. Following many recent studies that have proposed various predictive models for this aim, this study suggests and tests the functionality of three hybrid models in predicting the STS from the characteristics of the mixture components including cement compressive strength, cement tensile strength, curing age, the maximum size of the crushed stone, stone powder content, sand fine modulus, water to binder ratio, and the ratio of sand. A multi-layer perceptron (MLP) neural network incorporates invasive weed optimization (IWO), cuttlefish optimization algorithm (CFOA), and electrostatic discharge algorithm (ESDA) which are among the newest optimization techniques. A dataset from the earlier literature is used for exploring and extrapolating the STS behavior. The results acquired from several accuracy criteria demonstrated a nice learning capability for all three hybrid models viz. IWO-MLP, CFOA-MLP, and ESDA-MLP. Also in the prediction phase, the prediction products were in a promising agreement (above 88%) with experimental results. However, a comparative look revealed the ESDA-MLP as the most accurate predictor. Considering mean absolute percentage error (MAPE) index, the error of ESDA-MLP was 9.05%, while the corresponding value for IWO-MLP and CFOA-MLP was 9.17 and 13.97%, respectively. Since the combination of MLP and ESDA can be an effective tool for optimizing the concrete mixture toward a desirable STS, the last part of this study is dedicated to extracting a predictive formula from this model.

• 한국잠사곤충학회지
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• 제33권1호
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• pp.32-36
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• 1991

해충의 미생물적 방제를 위하여 Bacillus thuringiensis 살충제 개발에 관한 기초자료를 얻고자 3종의 B. thuringiensis var. kurstaki, dendrolimus, aizawai를 이용하여 배지내에서 생장특성을 조사하고 이들의 내독소단백질의 분리를 위해 Renograffin 불연속중층법을 이용한 새로운 분리법을 시도하였다. 1. 각공시균주의 생장곡선을 조사한 결과는 3균주 모두 접종후 3시간 이내에 exponential phase에 이르렀고, 7-8시간 정도에서 stationary phase에 이르렀다. 2. 배지내 pH변화는 exdponential phase때 원래 배지에서 1.4정도 저하하였다가 sporulation의 개시에 따라 회복되기 시작하여 후기에 거의 평형상태를 나타내서 균주간에 차이가 없는 것으로 확인되었다. 3. Renograffin 불연속중층법을 이용한 새로운 B. thuringiensis 내독소단백질 분리법은 50$m\ell$ 원심분리관에 10$m\ell$의 시료를 중층, fixed angel rotor를 이용하여 27,000g에서 1시간 원심했을 경우 99.0% 순도와 5.8%의 회수율을 나타내어 지금까지 보고된 방법들보다 더욱 효율적인 것으로 확인되었다.

• Ocean and Polar Research
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• 제33권3호
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• pp.309-319
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• 2011

This is a preliminary study of the feasibility of obtaining reliable tidal current harmonic constants, using one month of current observations, to verify the accuracy of a tidal model. An inference method is commonly used to separate out the tidal harmonic constituents when the available data spans less than a synodic period. In contrast to tidal constituents, studies of the separation of tidal-current harmonics are rare, basically due to a dearth of the long-term observation data needed for such experiments. We conducted concurrent and monthly harmonic analyses for tidal current velocities and heights, using 2 years (2006 and 2007) of current and sea-level records obtained from the Tidal Current Signal Station located in the narrow waterway in front of Incheon Lock, Korea. Firstly, the l-year harmonic analyses showed that, with the exception of $M_2$ and $S_2$ semidiurnal constituents, the major constituents were different for the tidal currents and heights. $K_1$, for instance, was found to be the 4th major tidal constituent but not an important tidal current constituent. Secondly, we examined monthly variation in the amplitudes and phase-lags of the $S_2$ and $K_1$ current-velocity and tide constituents over a 23-month period. The resultant patterns of variation in the amplitudes and phase-lags of the $S_2$ tidal currents and tides were similar, exhibiting a sine curve form with a 6-month period. Similarly, variation in the $K_1$ tidal constant and tidal current-velocity phase lags showed a sine curve pattern with a 6-month period. However, that of the $K_1$ tidal current-velocity amplitude showed a somewhat irregular sine curve pattern. Lastly, we investigated and tested the inference methods available for separating the $K_2$ and $S_2$ current-velocity constituents via monthly harmonic analysis. We compared the effects of reduction in monthly variability in tidal harmonic constants of the $S_2$ current-velocity constituent using three different inference methods and that of Schureman (1976). Specifically, to separate out the two constituents ($S_2$ and $K_2$), we used three different inference parameter (i.e. amplitude ratio and phase-lag diggerence) values derived from the 1-year harmonic analyses of current-velocities and tidal heights at (near) the short-term observation station and from tidal potential (TP), together with Schureman's (1976) inference (SI). Results from these four different methods reveal that TP and SI are satisfactorily applicable where results of long-term harmonic analysis are not available. We also discussed how to further reduce the monthly variability in $S_2$ tidal current-velocity constants.

• Asian-Australasian Journal of Animal Sciences
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• 제18권8호
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• pp.1164-1170
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• 2005

This study was conducted to evaluate performance, breast (thigh) muscle yield, nutrient digestibility and serum biochemical parameters of broilers fed low-protein diets supplemented with various threonine to lysine ratios (Thr/Lys). Three hundred and twenty four day-old male Arbor Acres broilers were randomly allotted to six dietary treatments with six replicates per treatment and nine broilers per replicate. Six treatments included one control diet [formulated according to NRC (1994)], and five experimental diets (treatments 1-5). In treatments 1-5, the crude protein level was 2% lower than that of the NRC control diet. The Thr/Lys in treatments 1-5 was 0.65, 0.70, 0.75, 0.80 and 0.85 during the starter and grower phases and 0.70, 0.75, 0.80, 0.85 and 0.90 during the finisher phase with other nutrient levels kept consistent. The results showed that: (1) With increasing Thr/Lys, ADG of treatments 1, 3 and 4 were lower (p<0.05) than those of the NRC control diet during the starter phase; ADG of treatments 1-5 were lower (p<0.05) than those of the NRC control during the grower phase, and ADG of treatment 1 was lower (p<0.05) than that of the NRC control during the finisher phase. Average daily feed intake in treatments 1 and 4 were lower (p<0.05) than that of broilers on the NRC control diet during the grower phase. Feed/gain (F/G) of the NRC control diet was lowest (p<0.05) during the starter phase. F/G in treatments 2 and 5 were higher (p<0.05) than that of NRC during the grower phase. (2) Breast muscle proportion on d 21 increased linearly (p<0.05) in response to graded levels of Thr/Lys. (3) No differences were detected for dry matter, energy and crude protein digestibility among all seven treatments. (4) On d 21, serum triglyceride of broilers on dietary treatments 3 and 5 was higher (p<0.05) than that of broilers in control. The results indicate that the low-protein diets supplemented with an appropriate Thr/Lys could not support the same performance that was achieved by the broilers fed the NRC control diet.

• Asian-Australasian Journal of Animal Sciences
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• 제30권12호
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• pp.1796-1802
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• 2017

Objective: This experiment was conducted to evaluate the optimal space allowance on growth performance, blood profile and pork quality of growing-finishing pigs. Methods: A total of ninety crossbred pigs [$(Yorkshire{\times}Landrace){\times}Duroc$, $30.25{\pm}1.13kg$] were allocated into three treatments (0.96: four pigs/pen, $0.96m^2/pig$; 0.80: five pigs/pen, $0.80m^2/pig$; 0.69: six pigs/pen, $0.69m^2/pig$) in a randomized complete block design. Pigs were housed in balanced sex and had free access to feed in all phases for 14 weeks (growing phase I, growing phase II, finishing phase I, and finishing phase II). Results: There was no statistical difference in growing phase, but a linear decrease was observed on average daily gain (ADG, p<0.01), average daily feed intake (ADFI, p<0.01), and body weight (BW, p<0.01) with decreasing space allowance in late finishing phase. On the other hand, a quadratic effect was observed on gain to feed ratio in early finishing phase (p<0.03). Consequently, overall ADG, ADFI, and final BW linearly declined in response to decreased space allowance (p<0.01). The pH of pork had no significant difference in 1 hour after slaughter, whereas there was a linear decrease in 24 h after slaughter with decreasing space allowance. Floor area allowance did not affect pork colors, but shear force linearly increased as floor space decreased (p<0.01). There was a linear increase in serum cortisol concentration on 14 week (p<0.05) with decreased space allocation. Serum IgG was linearly ameliorated as space allowance increased on 10 week (p<0.05) and 14 week (p<0.01). Conclusion: Data from current study indicated that stress derived from reduced space allowance deteriorates the immune system as well as growth performance of pigs, resulting in poor pork quality. Recommended adequate space allowance in a grow-to-finish production system is more than $0.80m^2/pig$ for maximizing growth performance and production efficiency.

• 대한화학회지
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• 제26권6호
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• pp.414-420
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• 1982

유한요소법을 이용하여 니켈입자가 분산된 폴리에틸렌의 기계적 성질을 추정하였다. 이 해석에서 다음 2단계의 과정을 통해 조사하였다. 첫 단계는 모재의 중심부에 구상의 물질을 포함하는 이른바 단일요소 모델을 생각하여 이것을 유한요소법에 의해 계산하였고, 다음 단계는 이러한 단일요소 모델이 모여 전체를 구성하고 있으므로 이 단일 모델이 조합된 형태의 전체 모델을 설정하여 해석 하는 것이다. 이 두 과정에서 니켈과 폴리에틸렌의 두상만을 고려한 2상 모델과, 니켈과 폴리에틸렌의 복합재료에서 이른 바 transcrystalline 구역이 관찰되어 이 구역을 고려한 3상 모델의 두 모델을 각각 사용하여 그 차이를 살펴 보았다. 유한요소법은 임의의 하중에서 응력 및 변위의 계산을 가능하게 한다. 이 컴퓨터로 계산된 출력으로 부터 탄성계수, poisson 비 및 복합재료의 응력 분포등을 얻을 수 있었다. 이 유한요소법에 의한 계산과 인장 실험을 통한 실험결과는 서로 잘 일치한다.