• The Journal of the Acoustical Society of Korea
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• v.6 no.3
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• pp.31-42
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• 1987

An ultrasonic pulse-echo diagnostic system for tissue characterization with the estimation of attenuation coefficients is developed and its performance has been examined by system implementation. The system divided into the ultrasonic generator, A/D converter, data communication, computer for signal processing. The methods for estimating the spatial distribution of acoustic attenuation coefficients using the moment analysis are proposed. The experimental results indicate the potential of the methods for tissue characterization.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.222-225
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• 2007

본 논문에서는 항공기가 레이다 감시를 회피하고 미사일의 공격으로부터 효과적으로 대응하기 위한 채프의 RCS 계산 방법에 대해 다루었다. 공중에 투하된 채프의 RCS 값은 바람, 비행체의 속도, 대기확산 속도 등에 따라서 달라진다. 채프를 레이다 사용주파수 대역에서 다이폴 안테나로 가정하고, 다이폴 안테나의 산란특성 분석을 통하여 RCS 값을 예측하였다. 본 논문에서는 다이폴 모델로 계산한 채프의 RCS값을 CST-MWS를 이용하여 계산 하였으며 기존에 소개된 실험값들과 비교하여 유사한 특성을 얻었다.

• The Journal of the Acoustical Society of Korea
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• v.19 no.2
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• pp.46-53
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• 2000

In coastal bay waters, bubbles are generated by relatively heavy ship-traffic, breaking waves due to man-made structures and biological activities. Therefore, the bubble-generating mechanism as well as the bubble density distribution in the bay are quite different from the open ocean where breaking waves are major contributor for bubble density distribution. High frequency surface-backscattered signals were obtained in the coastal bay waters and they were analyzed to compare with those from the open waters in terms of the sea-surface backscattering strength at various grazing angles, the reverberation characteristics in the sub-surface layer and spectral spreading of the scattered signals. The results show that, the surface scattered signals have an irregular distribution of amplitude in time and the width of the spectral spreading is wider than that of the open sea with rough surface. Furthermore, the amplitude distribution of the reverberation signals is not following the Rayleigh distribution, that is eon to be a typical pattern for the open ocean. The results of our analysis imply that the bubble size and the bubble density in the bay are quite different from those observed in the open waters.

• Korean Journal of Poultry Science
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• v.43 no.3
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• pp.191-195
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• 2016

This study aimed to investigate the physicochemical properties of chicken breast ham manufactured with broiler (BR), spent broiler breeder hen (SBBH), and spent laying hen (SLH). The water holding capacity and final yield of chicken breast ham manufactured with SLH was significantly lower than chicken breast ham manufactured with BR and SBBH (P<0.05). The lightness and redness of chicken breast ham manufactured with SBBH were significantly higher than those of chicken breast ham manufactured with SLH (P<0.05). The yellowness of chicken breast ham manufactured with BR and SLH was significantly higher than that of chicken breast ham manufactured with SBBH (P<0.05). The shear force of chicken breast ham manufactured with SLH was the highest. The tenderness and overall acceptability of chicken breast ham manufactured with BR and SBBH were significantly higher than those of chicken breast ham manufactured with SLH. Therefore, SBBH and SLH can lead to various textures of chicken breast hams.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.2
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• pp.195-205
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• 2020

Oceanic conditions in walleye pollock habitat in the East Sea have shown decadal fluctuations between warm and cold periods in turn. Specifically, sea surface temperature (SST) has shown a dramatic increase between the late 1980s and the middle 2000s, and abrupt decreasing patterns after the late 2000s. Oceanic conditions in the Dong-han Bay (spawning ground) and middle eastern coastal waters (fishing ground), however, indicated different fluctuation trends in SST, increasing in the Dong-han Bay after the late 1980s, and decreasing after the late 2000s. These fluctuation patterns were especially clear in February and March. Sea surface temperature in the middle eastern coastal waters of Korea soared continuously after the late 1980s, but did not show a distinct decreasing pattern after the late 2000s compared with Dong han Bay, except for February SST values. These long term water temperature changes in both walleye pollock spawning and fishing ground are related to variation in walleye pollock landings. Especially, abrupt changes in spawning ground SST can be one of the factors influencing survival in the early ontogenesis of walleye pollock, including egg and yolk larval stages. During the 1980s, the area of suitable spawning temperature (2-5℃) was wider, and the length of Walleye pollock egg and larval stages greater compared with past and present oceanographic environments. However, such patterns did not correspond with the optimal spawning temperature range and greater length of development of walleye pollock during the late 1980s likely triggering a decline in pollock stock. In conclusion, it has been supposed that the dramatic decrease in walleye pollock landings in the East Sea since the late 1980s was caused by increasing water temperature leading to both early mortality and unsuitable spawning conditions.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.12 no.2
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• pp.193-198
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• 2001

접지된 유전체슬랩 위에 주기적으로 스트립이 놓여있는 격자구조에 대한 전자파 산란현상을 반사격자(reflection grating) 관점과 누설파안테나(leaky wave antenna) 관점에서 조사하였다. 수치해석 결과로 입사파의 편파에 무관한 Bragg blazing 현실과 동시에 Bragg 및 off-Bragg blazing 현상이 확인되는 경우를 조사하였으며 그 특성(복소전파상수, 복사패턴, 산란특성)에 대하여 논의하였다.

• Proceedings of the Acoustical Society of Korea Conference
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• 1992.06a
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• pp.96-99
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• 1992

섬유강화 복합재료의 동탄성계수와 감쇠특성을 규명하기 위하여 랜덤하게 분포된 무한 실린더 형상의 산란체를 가진 매질내에서, 조화운동을 하는 압축 및 SV탄성파의 전파에 관하여 연구하였다. 단일 실린더에 대한 산란계수로부터 La의 준결정근사법을 이용하여 다중산란에 관한 이론을 유도하였고, 매질내에서의 파동전파 특성을 내포하는 분산관계식을 얻었다. 수치적으로 분산관계식의 해를 구함으로써 2 차원 유효체적강성, 횡방향 유효전단강성 및 각 파동의 전파에 따른 감쇠계수를 주파수와 체적비의 함수로서 제시하였다.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.174-181
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• 2005

In this paper, a hybrid model is developed, which can estimate scattering properties of a target embedded inside a forest. The model uses a physic-based channel model for a forest to accurately calculate the penetrated field through a forest canopy. The channel model is based on a fractal tree geometry and single scattering theory. To calculate scattering from the target physical optics(PO) is used to compute an induced current on the target surface since the dimension of the target is generally very large and the shape is very complicated. Then using reciprocity theorem, scattering generated by the PO current is calculated without an extra computational complexity.

• Korean Journal of Poultry Science
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• v.49 no.4
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• pp.189-197
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• 2022

This study was conducted to compare the egg productivity, egg quality, and blood characteristics of laying hens with different laying rates, and the frequency and cumulative duration of the sitting behavior observed before laying was investigated. Twelve 45-week-old Hy-Line Brown laying hens were randomly assigned to two treatment groups with three replicates. Treatment groups were classified as layers laying over 80%(high egg performance layers; HEP) and layers laying below 50%(poor egg performance layers; PEP). The experiment lasted 4 weeks. HEP showed higher hen-house egg production ratio and egg mass and lower feed conversion ratio(FCR) (P<0.05) compared with PEP, although egg weight was higher in PEP (P<0.05). In terms of egg quality, PEP showed differences in eggshell quality (eggshell color, eggshell thickness, and eggshell weight) (P<0.05). Additionally, HEP showed high triglycerides(TG), and PEP showed high alanine transaminase(ALT) level (P<0.05) in serum collected in the morning. In the afternoon, the HEP showed higher lactate dehydrogenase(LDH) levels (P<0.05). No differences in the Ca: P ratio were observed between layers with different laying rates. One hour before egg laying, HEP exhibited sitting behavior 4 times on average, each lasting 25 minutes. In conclusion, egg production and quality differ between HEP and PEP, and HEP showed frequent sitting behavior before egg laying. However, additional research is necessary to explore approaches other than specific behavioral observation to distinguish poor layers in the flock for application in farms.

• Korean Journal of Poultry Science
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• v.36 no.2
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• pp.149-155
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• 2009

The present study was conducted to compare the carcass yields and meat characteristics of three types of commercial male chicks White mini broilers, Ross broilers and Hy-Line brown chicks under the identical feeding condition. One-hundred 1-d chicks of each type were randomly placed into four pens per group (25 chicks per pen) and fed corn-soybean meal based commercial diets for 35d, 18d or 49d, respectively. At the end of the feeding trial, the birds were sacrificed and subjected to carcass measurements. The dressing percentages of White mini broilers and Ross broilers were significantly higher (P<0.05) than that of Hy-Line brown cockerels. The rate of breast meat of Hy-Line brown cockerels was significantly lower (P<0.05) than those of White mini broilers and Ross broilers. However, Hy-Line brown cockerels showed higher (P<0.05) leg meats than the others. There were no significant differences in serum total cholesterol and the activities of glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase among the groups. The breast meats of White mini broilers presented highest lightness value. The yellowness of breast and redness of leg meats of White mini broilers and Ross broilers were significantly higher (P<0.05) than those of Hy-Line brown cockerels. There were no significant differences in the SOD-like activity and change of pH in edible meats among the groups. The meat color in White mini broilers was significantly higher than that of Hy-Line brown cockerels. No significant differences were observed in term of flavor, tenderness and overall acceptability. In conclusion, the physico-chemical properties and sensory characteristics of edible meats were not greatly affected by genotype if they were similar body weights and kept under the identical feeding condition. But the Hy-Line brown cockerels were less desirable as a meat-type strain due to lower carcass yields and inferior growth and feed conversion ratio.