• 한국분말재료학회지
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• 제30권5호
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• pp.409-414
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• 2023

YSZ (Y₂O₃-stabilized zirconia)-based ceramics have excellent mechanical properties, such as high strength and wear resistance. In the application, YSZ is utilized in the bead mill, a fine-grinding process. YSZ-based parts, such as the rotor and pin, can be easily damaged by continuous application with high rpm in the bead mill process. In that case, adding WC particles improves the tribological and mechanical properties. YSZ-30 vol.% WC composite ceramics are manufactured via hot pressing under different pressures (10/30/60 MPa). The hot-pressed composite ceramics measure the physical properties, such as porosity and bulk density values. In addition, the phase formation of these composite ceramics is analyzed and discussed with those of physical properties. For the increased applied pressure of hot pressing, the tetragonality of YSZ and the crystallinity of WC are enhanced. The mechanical properties indicate an improved tendency with the increase in the applied pressure of hot pressing.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.16-24
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• 2024

Denting of steam generator (SG) tube is defined as the reduction in tube diameter due to the stresses exerted by the corrosion products formed on the outer diameter surface. This phenomenon is mostly observed in the crevices between SG tube and the top-of tubesheet or tube support plate. Despite the replacement of SG tube with Alloy 690, which has better corrosion resistance than Alloy 600, the denting of SG tube still remains a potential problem that could decrease the SG integrity. Deformation of SG tube by denting phenomenon can affect the surface properties and microstructure of SG tube. In this study, the effects of plastic deformation on surface properties and microstructure of Alloy 690 thermally treated (TT) tube was investigated by using the various analysis techniques. The plastic deformation of Alloy 690 increased the surface roughness and area. Many surface defects such as ripped surface and micro-cracks were observed on the deformed Alloy 690TT specimen. Based on the electron backscatter diffraction analysis, the dislocation density of deformed SG tube increased compared to non-deformed SG tube. In addition, the effects of changes in surface properties and microstructure of SG tube on general corrosion behavior were discussed.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.49-55
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• 2024

Stainless 630 (or 17-4PH) is a precipitation-hardening martensitic stainless steel that has excellent mechanical properties and corrosion resistance. These characteristics make the STS630 to be used as a consisting material for various components such as spider, pin, spring, and spring retainer, of the control rod drive mechanism (CRDM) in pressurized water reactors (PWRs). In general, it is well known that the oxide layer of stainless steel consists of a duplex layer, a compact inner layer of FeCr₂O₄ spinel, and a coarse-grained outer layer of Fe₃O₄ spinel in PWR primary coolant condition. However, the characteristics of the oxide layer can be sensitively influenced by various water chemistry conditions such as temperature, dissolved oxygen, dissolved hydrogen, pH, pH adjuster type, and exposure time. In this work, we investigate the corrosion properties of the STS630 as a function of coolant temperature in an NH3 alkaline solution for its boron-free application in a small modular reactor, to confirm the feasibility for usage as a boron-free SMR structural material. As a result, oxide layer of corroded STS630 is consist of double-layer oxides consisting of a Cr-rich dense inner oxide and a Fe-rich polyhedral outer particles like as that in commercial PWR primary coolant. The corrosion rate of STS630 increases with increase in test time and temperature and the corrosion rate-time model equation was developed based on experimental data. Overall, it is expected that the results in this study provides useful data for the corrosion behavior of STS630 in alkaline environments, contributing to the development of selecting suitable materials for SMRs.

• 한국압력기기공학회 논문집
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• 제20권1호
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• pp.56-65
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• 2024

Cast austenitic stainless steels (CASS) and austenitic stainless steel weldments with a ferrite-austenite duplex structure are widely used in nuclear power plants, incorporating ferrite phase to enhance strength, stress relief, and corrosion resistance. Thermal aging at 290-325℃ can induce embrittlement, primarily due to spinodal decomposition and G-phase precipitation in the ferrite phase. This study evaluates the effects of thermal aging by collecting and analyzing various mechanical properties, such as Charpy impact energy, ferrite microhardness, and tensile strength, from various literature sources. Different model expressions, including hyperbolic tangent and phase transformation equations, are applied to calculate activation energy (Q) of room-temperature impact energies, and the results are compared. Additionally, predictive models for Q based on material composition are evaluated, and the potential of machine learning techniques for improving prediction accuracy is explored. The study also examines the use of ferrite microhardness and tensile strength in calculating Q and assessing thermal embrittlement. The findings provide insights for developing advanced prediction models for the thermal embrittlement behavior of CASS and the weldments of austenitic steels, contributing to the safety and reliability of nuclear power plant components.

• Korean Circulation Journal
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• 제53권6호
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• pp.406-417
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• 2023

Background and Objectives: Pathophysiological changes of right ventricle (RV) after repair of tetralogy of Fallot (TOF) are coupled with a highly compliant low-pressure pulmonary artery (PA) system. This study aimed to determine whether pulmonary vascular function was associated with RV parameters and exercise capacity, and its impact on RV remodeling after pulmonary valve replacement. Methods: In a total of 48 patients over 18 years of age with repaired TOF, pulmonary arterial elastance (Ea), RV volume data, and RV-PA coupling ratio were calculated and analyzed in relation to exercise capacity. Results: Patients with a low Ea showed a more severe pulmonary regurgitation volume index, greater RV end-diastolic volume index, and greater effective RV stroke volume (p=0.039, p=0.013, and p=0.011, respectively). Patients with a high Ea had lower exercise capacity than those with a low Ea (peak oxygen consumption [peak VO₂] rate: 25.8±7.7 vs. 34.3±5.5 mL/kg/min, respectively, p=0.003), while peak VO₂ was inversely correlated with Ea and mean PA pressure (p=0.004 and p=0.004, respectively). In the univariate analysis, a higher preoperative RV end-diastolic volume index and RV end-systolic volume index, left ventricular end-systolic volume index, and higher RV-PA coupling ratio were risk factors for suboptimal outcomes. Preoperative RV volume and RV-PA coupling ratio reflecting the adaptive PA system response are important factors in optimal postoperative results. Conclusions: We found that PA vascular dysfunction, presenting as elevated Ea in TOF, may contribute to exercise intolerance. However, Ea was inversely correlated with pulmonary regurgitation (PR) severity, which may prevent PR, RV dilatation, and left ventricular dilatation in the absence of significant pulmonary stenosis.

• Clinical Nutrition Research
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• 제12권3호
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• pp.218-228
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• 2023

Recent studies have evaluated the association between specific beverage intake and metabolic risks in adults. However, more evidence is needed to examine the association between the Healthy Beverage Index (HBI) and metabolic factors. Therefore, this study investigated the relationship between HBI and metabolic factors in adults. In this cross-sectional study, 338 overweight and obese individuals living in Tabriz, Iran were selected. Data on beverage consumption, demographics, physical activity, and anthropometric characteristics were evaluated using validated standard protocols. The predefined HBI was calculated based on previous studies. The mean value of HBI index among all of the participants was 59.76 ± 6.51. Those at the higher HBI scores had significantly lower waist circumference, waist-to-hip ratio, fat mass, and weight (p < 0.05). HBI and triglyceride scores also had a significant relationship. It has been shown that at higher HBI scores compared to lower scores, high-density lipoprotein cholesterol levels increase while homeostatic model assessment for insulin resistance, low-density lipoprotein cholesterol, total cholesterol, and blood pressure decrease. HBI scores higher among Iranian adults were associated with a better chance of losing weight and weight loss and a better lipid profile, and lower blood pressure. Therefore, HBI can be a useful and helpful tool for assessing the overall quality of beverages adults consume. However, further studies are warranted to confirm the possible health effects of healthy beverage index.

• 대한지역사회영양학회지
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• 제29권3호
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• pp.212-221
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• 2024

Objectives: Metabolic disease is strongly associated with future insulin resistance, and its prevalence is increasing worldwide. Thus, identifying early biomarkers of metabolic-related disease based on serum profiling is useful to control future metabolic disease. Our study aimed to assess the association of serum branched chain amino acids (BCAAs) and aromatic amino acids (AAAs) ratio and metabolic disease according to body mass index (BMI) status among Korean adults. Methods: This cross-sectional study included 78 adults aged 20-59 years in Korea. We compared serum amino acid (AA) levels between adults with normal-weight and adults with obesity and investigated biomarkers of metabolic disease. We examined serum AA levels, blood profile, and body composition. We also evaluated the association between serum AAs and metabolic-related disease. Results: The height, weight, BMI, waist circumference, hip circumference, waist-hip-ratio, body fat mass, body fat percent, skeletal muscle mass, systolic blood pressure, and diastolic blood pressure were higher in the group with obesity compared to normal weight group. The group with obesity showed significantly higher levels of BCAA, AAA, and BCAA and AAA ratio. Further, BCAA and AAA ratio were significantly positively correlated with triglyceride, body weight, and skeletal muscle mass. The evaluation of metabolic disease risks revealed an association between the ratios of BCAAs and AAAs, hypertension, and metabolic syndrome. Conclusions: Our study is showed the associations between BCAA and AAA ratio, obesity, and obesity-related diseases using various analytical approaches. The elevated BCAA and AAA ratio could be early biomarkers for predicting future metabolic diseases in Korean population.

• 한국수산과학회지
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• 제12권3호
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• pp.125-130
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• 1979

1978년 8월 23일 부터 동년 10월 20일 사이에 우리 나라의 남부와 싱가폴 북부 해상에서 새바다호의 순항, 예망, 표박시의 선박소음에 관하여 실험한 결과를 요약하면 다음과 같다. 1. 외부 갑판상의 가장 높은 소음원은 연돌로 돌출하는 배기소음이고, 연돌뒤(No.9)에서 순항, 예망, 표박시 92,90,87dB로 가장 높았으며, 선수(No. 1)에서 65,63,53dB로 가장 낮았다. 2. 학생 거주구역에서는 주기소음보다 통풍기나 에이콘의 가동소음이 주소음원을 이루었는데 통풍기를 가동하면 표박할때와 에이콘을 가동하면서 순항때를 비교하면, 출입구(No. 14)에서 85,69dB로 가장 높았고 학생실(No. 22)에서 45,40dB로 가장 낮았다. 3. 중앙부의 선원거주구역에서는 순항소음압이 예망소음압보다 2dBwjd도로 선원식당(No. 30)까지는 높게 나타났고, 급냉실(No. 31)로 부터는 반대로 낮게 측정 되었다. 또 이 구역에서는 출입문을 닫았을 때 선장실(No, 25)에서 13dB, 선원식당(No, 30)에서 3dB씩 낮아졌다. 4. 순항시 주기소음압은 Pitch $8^{\circ}$와 $12^{\circ}$때 103, 105dB 였는데, Pitch $8^{\circ}$로 예망시는 106dB로서 3dB의 증가를 보였다. 5. 선형과 기관이 같은 오대산호와 소음을 비교 하면 식당, 싸롱, 학생식에서 $4\~6dB$씩 낮았고 작업갑판상에서는 14dB나 높은 음압이였다.

• Journal of Yeungnam Medical Science
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• 제16권2호
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• pp.181-192
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• 1999

만성 문맥압 항진증에서 관찰되는 과혈류 순환과 말초혈관 이완에 대한 산화질소의 역할을 규명하기 위해 본 연구를 시행하였다. 실험동물은 수컷 흰쥐를 이용하여 문맥을 부분결찰하여 문맥 고혈압을 유발시킨 군과 겉보기 수술만을 시행한 대조군으로 구분하고 문맥 고혈압군은 문맥 부분 결찰후 부터 혈역학 측정 전까지 식수를 경구 투여한 식수 투여군과 산화질소 억제제인 $N^{\omega}$-Nitro-L-Arginine(1mg/kg/day)를 경구 투여한 NNA 투여군으로 나누었다. 혈역학적 측정은 수술 2주 후에 시행하였고 $^{51}Cr$과 $^{57}Co$-labeled microspheres를 이용하여 심박출량, 조직 혈류량, 문맥-전신 단락률, 문맥압, 말초혈관 저항 내장혈관 저항 등을 측정하였다. 평균 동맥압은 대조군 $129.3{\pm}9.6mmHg$, 식수 투여군은 $111.3{\pm}5.5mmHg$로 대조군에 비해 유의하게 감소되어 있었고, NNA 투여군은 $128.7{\pm}19.8mmHg$로 식수 투여군에 비해 증가되어 있었다. 심박출량은 대조군의 $105.2{\pm}6.5ml/min$에 비해 식수 투여군에서 $144.2{\pm}17.9ml/min$로 증가되었으며, NNA 투여군은 $89.9{\pm}14.4ml/min$로 식수 투여군에 비해 감소되어 있었다. 전말초 저항은 식수 투여군에서 $6.0{\pm}0.9dyne/sec/cm^5{\times}10^5$로 대조군의 $9.5{\pm}0.8dyne/sec/cm^5{\times}10^5$에 비해 감소되었고, NNA 투여군은 $11.2{\pm}2.1dyne/sec/cm^5{\times}10^5$로 식수 투여군에 비해 증가되어 있었다. 문맥으로 유입되는 혈류량은 대조군 $16.61{\pm}5.03ml/min$, 식수 투여군은 $29.66{\pm}4.27ml/min$로 식수 투여군에서 유의한 증가가 있었으며, NNA 투여군은 $11.43{\pm}2.24ml/min$로 식수 투여군에 비해 감소되어 있었다. 내장혈관 저항은 식수 투여군에서 $2.59{\pm}0.44dyne/sec/cm^5{\times}10^5$로 대조군의 $6.61{\pm}3.08$dyne/sec/$cm^5{\times}10^5$에 비해 감소되었으며, NNA 투여군은 $8.09{\pm}2.04$dyne/sec/$cm^5{\times}10^5$로 식수 투여군에 비해 증가되어 있었다. 문맥-전선 단락율은 대조군의 $1.35{\pm}0.42%$ 에 비해 식수 투여군은 $95.42{\pm}2.73%$로 증가되었으며, NNA 투여군은 $73.36{\pm}17.67%$로 식수 투여군보다 감소되어 있었다. 문맥압은 대조군 $7.94{\pm}1.29mmHg$, 식수 투여군 $17.16{\pm}3.17mmHg$, NNA 투여군은 $16.67{\pm}2.24mmHg$로 대조군에 비해 식수 투여군과 NNA 투여군에서 증가되었으나, 양군 사이에 유의한 차이는 없었다. 문맥 저항은 NNA 투여군에서 $12.23{\pm}3.93dyne/sec/cm^5{\times}10^5$로 식수 투여군의 $4.74{\pm}1.20yne/sec/cm^5{\times}10^5$에 비해 증가되었다. 결론적으로 문맥의 부분결찰로 유도된 만성 문맥압 항진 쥐에서 산화질소 합성 억제제인 NNA를 투여할 경우 문맥압의 변화 없이 동맥압의 증가, 심박출량의 감소, 내장 및 전신 혈관 저항의 증가 등이 유발되었다. 이상의 결과를 고려해 볼 때 만성 문맥압 항진증시 관찰되는 과혈류 순환의 형성에 산화질소가 중요한 역할을 하는 것으로 생각된다.

• 한국육종학회지
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• 제51권4호
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• pp.504-514
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• 2019

'예찬'은 농촌진흥청 국립식량과학원에서 재배안정성이 확대된 최고품질 중만생 벼 품종을 개발하고자 육성되었다. 단간 내도복이면서 밥맛이 좋은 최고품질 중만생 벼 '호품'을 모본으로 하고 복합내병성으로 내수발아성을 갖춘 최고품질 중생 벼 '해품'을 부본으로 단교잡 인공교배하여 육성되었다. 조기에 고정계통을 확보하고자 F₁ 식물체를 약배양하여 계통육성과정 중 최고품질 벼 선정 기준에 선발압을 두고 우량계통을 선발하여 생산력 검정시험과 지역적응성 검정시험을 거쳐 육성되었다. '예찬'은 보통기 보비재배에서 평균 출수기 8월 14일로 '남평'에 비해 1일 늦은 중만생종이다. '예찬'은 간장이 66 cm로 '남평'보다 9 cm 작은 단간 품종으로 도복에 안정적인 특성을 나타냈다. '예찬'은 도열병, 벼흰잎마름병 및 줄무늬잎마름병 등 벼의 삼대병에 모두 강한 복합내병성 품종이며, 특히 병원성이 강한 벼흰잎 마름병 K3a 균계까지 저항성을 갖추고 있어 최고품질 중만생벼 품종의 내병성 향상에 기여할 것으로 판단된다. 수량성은 보통기 보비재배에서 중만생 벼 표준품종인 '남평'과 비슷한 수준을 나타내 적정 수량성을 갖추고 있다. '예찬'은 쌀의 외관품위와 도정 특성이 좋고 밥맛이 우수하여 최고품질 품종에 선정되었다. '예찬'은 내도복성과 복합내병성을 갖춘 최고품질 벼 품종으로 남부평야지 재배에 적합하며 우리나라 밥쌀용 벼 품종의 품질 향상과 재배안정성 확대를 위한 육종사업에 활용되고 있다(품종보호권 등록번호: 제7647호; 2019. 4. 5.).