• 한국의학물리학회지:의학물리
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• 제33권4호
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• pp.164-171
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• 2022

The number of facilities using radiation generators increases and related regulations are strengthened, the establishment of a shielding management and evaluation technology has become important. The characteristics of the radiation generator used in previous report differ from those of currently available high-frequency radiation generators. This study aimed to manufacture lead, iron, and concrete shielding materials for the re-verification of half-value layers, tenth-value layers, and attenuation curve. For a comparison of attenuation ratio, iron, lead, and concrete shields were manufactured in this study. The initial dose was measured without shielding materials, and doses measured under different types and thicknesses of shielding material were compared with the initial dose to calculate the transmission rate on 50-300 kVp X-ray. All the three shielding materials showed a tendency to require greater shielding thickness for higher energy. The attenuation graph showed an exponential shape as the thickness decreased and a straight line as the thickness increased. The difference between the measurement results and the previous study, except in extrapolated parts, may be due to the differences in the radiation generation characteristics between the generators used in the two studies. The attenuated graph measured in this study better reflects the characteristics of current radiation generators, which would be more effective for shield designing.

• Journal of Veterinary Science
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• 제24권5호
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• pp.49.1-49.15
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• 2023

Background: Hystricomorpha rodents display a similar placentation model to humans. The present study was carried out considering the scarcity of information concerning the placental development in agouti. Objective: Describe the microscopy of the placenta, subplacenta and yolk sac of agoutis in early pregnancy and report on the inversion of the yolk sac. Methods: Fifteen females between the 14^th-32^nd day of gestation were used following euthanasia. Gestational buttons were collected, fixed, processed, stained to optical microscopy or immunohistochemistry. Results: Chorioallantoic placenta (CP) ranged from conical to a half-sphere, as follows: from the 14^th to 17^th day, the CP displays an inverted "V" shape, predominantly formed by cytotrophoblasts; from 20 to 22 days, formed almost entirely by cytotrophoblasts; at 28 days, a half sphere, with distinct lobes and interlobular area, numerous maternal gaps delimited by syncytiotrophoblasts and trophoblast giant cells; at 32 days, globose and undergoing the maturation process. Subplacenta, located between decidua and CP, initially presents septa consisting of simple columnar epithelium and after 17 days, comprising stratified epithelium. Visceral yolk sac (VYS) is attached to two CP projections between 14 and 17 days, formed by a simple cubic epithelium and inverted. Between 20 and 22 days, the epithelium displays apical villous projections with cytoplasmic vacuoles and a vascularized mesoderm. After the 24^th day, the VYS near the placenta is pleated, very vascularized and villous, with decreased villi sizes further away from the placenta. Conclusion: The agouti CP displays similar characteristics to other hystricomorpha, including placenta lobulation, a subplacenta and an inverted vitelline placenta.

• Corrosion Science and Technology
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• 제22권5호
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• pp.359-367
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• 2023

The localized corrosion resistance of the Ni-based Inconel 718 alloy after solution heat treatment was evaluated using electrochemical techniques in a solution of 25 wt% NaCl and 0.5 wt% acetic acid. Solution heat treatment at 1050 ℃ for 2.5 hours resulted in an increased average grain diameter. Both Ti carbides (10 ㎛ diameter) and Nb-Mo carbides (1 - 9 ㎛ diameter) were distributed throughout the material. Despite heat treatment, the shape and composition of these carbides remained consistent. An increase in solution temperature led to a decrease in pitting potential value. However, the pitting potential value of solution heat-treated Inconel 718 was consistently higher than that of as-received Inconel 718 at all tested temperatures. Localized corrosion initiation occurred at 0.4 V_SSE in a temperature environment of 80 ℃ for both as-received and solution heat-treated Inconel 718 alloys. X-ray photoelectron spectroscopic analysis indicated that the composition of the passive film formed on specimen surfaces remained largely unchanged after solution heat treatment, with O1s, Cr2p_3/2, Fe2p_3/2, and Ni2p_3/2 present. The difference in localized corrosion resistance between as-received and solution heat-treated Inconel 718 alloys was attributable to microstructural changes induced by the heat treatment process.

• Advances in nano research
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• 제16권4호
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• pp.413-426
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• 2024

This paper investigates the dynamic behavior of a simply supported viscoelastic plate made of functionally graded carbon nanotube reinforced composite under dynamic loading. Carbon nanotubes are distributed in 5 different shapes: U, V, A, O and X, depending on the shape they form through the thickness of the plate. The displacement fields are derived in the Laplace domain using a higher-order shear deformation theory. Equations of motion are obtained through the application of the energy method and Hamilton's principle. The resulting equations of motion are solved using Navier's method. Transforming the Laplace domain displacements into the time domain involves Durbin's modified inverse Laplace transform. To validate the accuracy of the developed algorithm, a free vibration analysis is conducted for simply supported plate made of functionally graded carbon nanotube reinforced composite and compared against existing literature. Subsequently, a parametric forced vibration analysis considers the influence of various parameters: volume fractions of carbon nanotubes, their distributions, and ratios of instantaneous value to retardation time in the relaxation function, using a linear standard viscoelastic model. In the forced vibration analysis, the dynamic distributed load applied to functionally graded carbon nanotube reinforced composite viscoelastic plate is obtained in terms of double trigonometric series. The study culminates in an examination of maximum displacement, exploring the effects of different carbon nanotube distributions, volume fractions, and ratios of instantaneous value to retardation times in the relaxation function on the amplitudes of maximum displacements.

• 한국식품영양학회:학술대회논문집
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• 한국식품영양학회 2001년도 동계 학술심포지움
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• pp.39-74
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• 2001

The endeavors enhancing the grain quality of high-yielding japonica rice were steadily continued during 1980s∼1990s along with the self-sufficiency of rice production and the increasing demands of high-quality rices. During this time, considerably great, progress and success was obtained in development of high-quality japonica cultivars and qualify evaluation techniques including the elucidation of interrelationship between the physicochemical properties of rice grain and the physical or palatability components of cooked rice. In 1990s, some high-quality japonica rice caltivars and special rices adaptable for food processing such as large kernel, chalky endosperm aromatic and colored rices were developed and its objective preference and utility was also examined by a palatability meter, rapid-visco analyzer and texture analyzer. The water uptake rate and the maximum water absorption ratio showed significantly negative correlations with the K/Mg ratio and alkali digestion value(ADV) of milled rice. The rice materials showing the higher amount of hot water absorption exhibited the larger volume expansion of cooked rice. The harder rices with lower moisture content revealed the higher rate of water uptake at twenty minutes after soaking and the higher ratio of maximum water uptake under the room temperature condition. These water uptake characteristics were not associated with the protein and amylose contents of milled rice and the palatability of cooked rice. The water/rice ratio (in w/w basis) for optimum cooking was averaged to 1.52 in dry milled rices (12% wet basis) with varietal range from 1.45 to 1.61 and the expansion ratio of milled rice after proper boiling was average to 2.63(in v/v basis). The major physicochemical components of rice grain associated with the palatability of cooked rice were examined using japonica rice materials showing narrow varietal variation in grain size and shape, alkali digestibility, gel consistency, amylose and protein contents, but considerable difference in appearance and torture of cooked rice. The glossiness or gross palatability score of cooked rice were closely associated with the peak. hot paste and consistency viscosities of viscogram with year difference. The high-quality rice variety “Ilpumbyeo” showed less portion of amylose on the outer layer of milled rice grain and less and slower change in iodine blue value of extracted paste during twenty minutes of boiling. This highly palatable rice also exhibited very fine net structure in outer layer and fine-spongy and well-swollen shape of gelatinized starch granules in inner layer and core of cooked rice kernel compared with the poor palatable rice through image of scanning electronic mcroscope. Gross sensory score of cooked rice could be estimated by multiple linear regression formula, deduced from relationship between rice quality components mentioned above and eating quality of cooked rice, with high Probability of determination. The ${\alpha}$ -amylose-iodine method was adopted for checking the varietal difference in retrogradation of cooked rice. The rice cultivars revealing the relatively slow retrogradation in aged cooked rice were Ilpumbyeo, Chucheongbyeo, Sasanishiki, Jinbubyeo and Koshihikari. A Tongil-type rice, Taebaegbyeo, and a japonica cultivar, Seomjinbyeo, shelved the relatively fast deterioration of cooked rice. Generally, the better rice cultivars in eating quality of cooked rice showed less retrogiadation and much sponginess in cooled cooked rice. Also, the rice varieties exhibiting less retrogradation in cooled cooked rice revealed higher hot viscosity and lower cool viscosity of rice flour in amylogram. The sponginess of cooled cooked rice was closely associated with magnesium content and volume expansion of cooked rice. The hardness-changed ratio of cooked rice by cooling was negatively correlated with solids amount extracted during boiling and volume expansion of cooked rice. The major physicochemical properties of rice grain closely related to the palatability of cooked rice may be directly or indirectly associated with the retrogradation characteristics of cooked rice. The softer gel consistency and lower amylose content in milled rice revealed the higher ratio of popped rice and larger bulk density of popping. The stronger hardness of rice grain showed relatively higher ratio of popping and the more chalky or less translucent rice exhibited the lower ratio of intact popped brown rice. The potassium and magnesium contents of milled rice were negatively associated with gross score of noodle making mixed with wheat flour in half and the better rice for noodle making revealed relatively less amount of solid extraction during boiling. The more volume expansion of batters for making brown rice bread resulted the better loaf formation and more springiness in rice bread. The higher protein rices produced relatively the more moist white rice bread. The springiness of rice bread was also significantly correlated with high amylose content and hard gel consistency. The completely chalky and large gram rices showed better suitability for fermentation and brewing. Our breeding efforts on rice quality improvement for the future should focus on enhancement of palatability of cooked rice and marketing qualify as well as the diversification in morphological and physicochemical characteristics of rice grain for various value-added rice food processings.

• Journal of Chest Surgery
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• 제37권1호
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• pp.35-42
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• 2004

배경: 허혈성 좌주간 관동맥 협착병변은 돌연사의 위험성이 높아 조속한 재관류를 요한다. 본 교실에서는 단독 좌주간 관동맥 협착병변으로 좌측 내흉동맥에 요골동맥이나 우위대망동맥을 Y모양으로 연결하여 관상동맥우회로 조성술을 시행했던 경우를 분석함으로써 내흉동맥만으로 심근의 혈액요구량을 충분하게 감당할 수 있는지의 여부와 경계부 협착을 보이는 좌주간 관동맥 협착병변에서 경쟁혈류에 의한 우회혈관의 재구성이 초래되는가를 알아보았다. 대상 및 방법: 2000년 3월부터 2003년 4월까지 관상동맥우회로 조성술을 시행받은 247명의 환자 중 단독 좌주간 관동맥 협착병변으로 진단되어 동맥이식편만을 이용한 관상동맥우회로 조성술을 시행받은 12명(4.8%)의 환자를 대상으로 하여 의무기록과 본 교실의 database를 기초로 역행성 연구를 시행하였다. 결과: 좌전하행지 문합은 전예에서 인공심폐기를 사용하지 않고 시행하였으나 둔각변연분지 문합 중 2예에서는 인공심폐기 가동 후 심박동하에서 문합하였다. 직경이 1 mm 이상되는 좌회선분지가 없어 문합을 시행하지 못한 1예를 제외한 11예에서 Y-도관을 이용한 완전재관류를 시행하였으며 환자 1인당 문합 수는 평균 2.0개이었다. 좌주간동맥의 협착이 75% 이하이었던 경우에서는 좌전하행지 문합 중 1예에서 좌내흉동맥에 string sign을 보였으며 좌회선분지 문합 7예 중 완전히 막힌 경우 2예, slender sign 1예가 있었으며 문합 원위부 관상동맥 혈류 형태가 도관의존성인 경우는 없었다. 그러나 이와는 반대로 90% 이상의 협착 병변에서는 문합된 관상동맥 모두에서 도관의존성의 원위부 혈류 형태를 보였다. 결론: 90% 이상의 협착을 보인 좌주간동맥 협착병변에서는 동맥이식편을 V-도관으로 만들어 TAR를 시행하더라도 심근의 혈류요구량을 충분하게 감당할 수 있을 것으로 판단된다. 그러나 경계부 협착을 가진 환자의 경우에는 고정된 치료방침을 택하기보다는 면밀한 진단을 통하여 정맥도관이나 동맥도관의 대동맥에 직접 문합 또는 경피적 관동맥중재술과의 보완 치료 등 좀 더 유연하고 신중한 치료방침의 결정이 필요할 것으로 생각된다.

• 한국터널지하공간학회 논문집
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• 제19권6호
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• pp.1059-1075
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• 2017

본 연구의 목적은 한랭지역에서 운용중인 지하 콘크리트 구조물에서 발생한 누수를 처리하기 위하여 기존 유도배수시스템의 동결융해 저항성을 평가하는 것이다. 유도배수시스템의 동결융해 저항성을 평가하기 위하여 4가지 종류의 유도배수시스템 시험체를 제작하여 실내 동결융해 실험을 수행하였다. 유도배수판의 모서리 부분과 유도배수판 연결부분에 적용할 방수재료인 Hotty-gel의 4가지 연결 방법에 대한 동결융해 저항성을 평가하였다. 또한 Hotty-gel이 부착된 유도배수판을 콘크리트 시편 표면에 고정시키 위한 2가지 방법에 대하여서도 동결융해 저항성을 평가하였다. 실내 동결융해 실험에서 1 cycle은 48시간(동결 24시간과 융해 24시간)을 적용하였고 동결과 융해 온도는 각각 $-18^{\circ}C$와 $10^{\circ}C$를 적용하였다. 4가지 종류의 Hotty-gel 연결 방법 중 유도배수판 모서리 부분에 적용된 'V'자형 홈을 가진 Hotty-gel 연결 방법에서만 동결융해 28 cycles (8 weeks)후 누수가 발생하였다. 나머지 3가지 종류의 Hotty-gel 연결 방법들에서는 누수가 발생하지 않았다. 2가지 고정방법 중 와셔, 나사못 및 칼브럭을 이용하여 유도배수판을 콘크리트 시편에 고정시키는 방법에서 누수가 발생하였다. 동결융해 10 cycles (3 weeks) 후 1개 지점에서 누수가 발생하였고 동결융해 28 cycles (8 weeks) 후에는 총 5개 지점에서 누수가 발생하였다. 시간이 경과함에 따라 누수 지점은 증가되지 않았지만 각각의 누수지점에서 누수량이 증가되었다. 공압타카, 타카핀 및 와셔를 사용한 고정방법에서는 누수가 발생하지 않았다. Hotty-gel연결 형상의 제작 시간 및 제작 방법을 고려한 제작 효율성에서 Hotty-gel 가로면 대각선 형상이 가장 높게 평가되었다. 고정방법에서 시공 시간 및 시공 방법을 고려한 시공 효율은 공압타카, 타카핀 및 와셔를 사용한 방법이 우수하였다.

• 대한원격탐사학회지
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• 제39권3호
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• pp.297-309
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• 2023

최근 조식동물로 인한 갯녹음 현상으로 인해 연안 생태계 및 어장환경의 황폐화가 가속화되고 있다. 이러한 갯녹음 현상을 모니터링하고 방지대책을 세우기 위해서는 광범위한 해역에 대한 원격탐사 기반의 모니터링 기술 도입이 필요하다. 본 연구에서는 수중에서 촬영된 동영상으로부터 조식동물을 탐지하고 모니터링하기 위한 딥러닝 기반 객체 탐지 모델의 강인성(robustness)을 비교 분석하였다. 우리나라 연안의 대표적인 조식동물 7종을 대상으로 이미지 데이터셋을 구축하였으며, 이를 활용하여 딥러닝 기반 객체 탐지 모델인 You Only Look Once (YOLO)v7과 YOLOv8을 훈련시켰다. 총 6개의 YOLO 모델(YOLOv7, YOLOv7x, YOLOv8s, YOLOv8m, YOLOv8l, YOLOv8x)에 대해 탐지 성능과 탐지 속도를 평가하였으며, 수중환경에서 촬영 시 발생할 수 있는 다양한 이미지 왜곡에 대해서 강인성 평가를 실시하였다. 평가결과 YOLOv8 계열 모델이 파라미터(parameter) 수 대비 더 높은 탐지 속도(약 71-141 FPS [frame per second])를 보였다. 탐지 성능에 있어서도 YOLOv8 계열 모델(mean average precision [mAP] 0.848-0.882)이 YOLOv7 계열 모델(mAP 0.847-0.850)에 비해 더 높은 성능을 보이는 것을 확인하였다. 모델의 강인함에 있어서 형태 왜곡에 대해서는 YOLOv7 계열 모델이 YOLOv8 계열 모델에 비해 강인한 것을 확인하였으며, 색상 왜곡에 대해서는 YOLOv8 계열 모델이 상대적으로 강인한 것을 확인 하였다. 따라서 실해역에서 수중 영상 촬영 시, 형태 왜곡은 발생 빈도가 낮으며 색상 왜곡은 연안에서 빈번하게 발생한다는 점을 고려했을 때, 연안해역에서 조식동물 탐지와 모니터링을 위해서는 YOLOv8 계열 모델을 활용하는 것이 타당한 것으로 판단된다.

• Journal of Electrical Engineering and Technology
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• 제5권2호
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• pp.342-351
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• 2010

The SiC-$ZrB_2$ composites were fabricated by combining 30, 35, 40, 45 and 50 vol. % of zirconium diboride ($ZrB_2$) powders with silicon carbide (SiC) matrix. The SiC-$ZrB_2$ composites and the sintered compacts were produced through spark plasma sintering (SPS) under argon atmosphere, and its physical, electrical, and mechanical properties were examined. Also, the thermal image analysis of the SiC-$ZrB_2$ composites was examined. Reactions between $\beta$-SiC and $ZrB_2$ were not observed via x-ray diffraction (XRD) analysis. The apparent porosity of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$, SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were 7.2546, 0.8920, 0.6038, 1.0981, and 10.0108%, respectively. The XRD phase analysis of the sintered compacts demonstrated a high phase of SiC and $ZrB_2$. Among the $SiC+ZrB_2$ composites, the SiC+50vol.%$ZrB_2$ composite had the lowest flexural strength, 290.54MPa, the other composites had more than 980MPa flexural strength except the SiC+30vol.%$ZrB_2$ composite; the SiC+40vol.%$ZrB_2$ composite had the highest flexural strength, 1011.34MPa, at room temperature. The electrical properties of the SiC-$ZrB_2$ composites had positive temperature coefficient resistance (PTCR). The V-I characteristics of the SiC-$ZrB_2$ composites had a linear shape in the temperature range from room to $500^{\circ}C$. The electrical resistivities of the SiC+30vol.%$ZrB_2$, SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ SiC+45vol.%$ZrB_2$ and SiC+50vol.%$ZrB_2$ composites were $4.573\times10^{-3}$, $1.554\times10^{-3}$, $9.365\times10^{-4}$, $6.999\times10^{-4}$, and $6.069\times10^{-4}\Omega{\cdot}cm$, respectively, at room temperature, and their resistance temperature coefficients were $1.896\times10^{-3}$, $3.064\times10^{-3}$, $3.169\times10^{-3}$, $3.097\times10^{-3}$, and $3.418\times10^{-3}/^{\circ}C$ in the temperature range from room to $500^{\circ}C$, respectively. Therefore, it is considered that among the sintered compacts the SiC+35vol.%$ZrB_2$, SiC+40vol.%$ZrB_2$ and SiC+45vol.%$ZrB_2$ composites containing the most outstanding mechanical properties as well as PTCR and V-I characteristics can be used as an energy friendly ceramic heater or ohmic-contact electrode material through SPS.

• 한국균학회지
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• 제49권1호
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• pp.87-100
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• 2021

많은 사람들이 다녀가는 도시공원과 해변 환경의 효모 특성을 알아보기 위해 대전광역시 월평공원 갑천 누리길과 내원사 주변의 야생화와 토양 75점에서 모두 88균주의 야생 효모들을 분리, 동정하였다. 또한 전북 부안의 격포해수욕장과 격포항 주변 야생화와 토양 35점에서 30균주의 야생 효모들을 분리하였다. 이들 분리 야생 효모들 중 A. porosum ASCM32-1, A. scarabaeorum WP49-1, C. athensensis WP4-90-3, C. berkhoutiae WP34-2, C. bracarensis WP35-1, Cy. amylophila GP19-1, K. gamospora WP9-1, M. carpophila BN-17-1, T. namnaoensis WP4-89-1, V. taibaiensis WP13-2 등 10종의 국내 미기록종 후보 균주들을 선별하여 균학적 특성을 확인하였다. 이들 미기록 효모들은 주로 구형~타원형으로 모두 출아방식으로 영양 증식을 하였고 V. taibaiensis WP13-2와 K. gamospora WP9-1, C. athensensis WP4-90-3 외 7종의 미기록 효모들은 자낭포자를 형성하지 않은 무포자 효모들이었으며A. porosum ASCM32-1만이 의균사를 생성하였다. 대부분의 균주들은 YPD 배지와 YM 배지에서생육하였고V. taibaiensis WP13-2와K. gamospora WP9-1, T. namnaoensis WP4-89-1 균주들은 15% NaCl을 함유한 YPD 배지에서 생육하는 호염성 효모들이었고, Cy. amylophila GP19-1 균주는 40℃에서도 생육하였다. C. athensensis WP4-90-3 균주 등 5균주들이 10% 에탄올 내성을 보였고C. athensensis WP4-90-3 균주는 Li²⁺ 등 많은 중금속들에 대해서 내성을 보였다. 국내 미기록 효모들과 비병원성 야생 효모 균주 무세포추출물들의 β-glucuronidase 저해 활성은 C. oleophila WP5-19-1의 무세포 추출물이 49.0%로 가장 높았고 미기록 효모인 K. gamospora WP9-1의 무세포 추출물도 27.7%를 보였다. 호중구 elastase 저해 활성은 W. anomalus HO9-2가 38.4%로 우수하여 건강 소재로 생산에 매우 유용한 균주로 활용될 것으로 기대된다.