• Journal of Biosystems Engineering
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• 제37권4호
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• pp.215-224
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• 2012

Purpose: This study was conducted to classify the energy efficiency of 131 tractor models tested during from 2006 to 2010 in Korea. Methods: Four sub-indexes were developed using the fuel consumptions at 60% and 90% of rated speed with partial loads and at pull speeds of 3.0 km/h and 7.5 km/h with maximum drawbar pull. Weighting factors of the sub-indexes were also considered to reflect the characteristics of tractor's actual working hours in Korea. Four sub-indexes were integrated into a classification index. Using the developed classification index, a five-classification system was made on the basis of normal distribution of tractors over the classification range. Percentage of $1^{st}$ grade interval was expected to be close to 15%, $2^{nd}$ grade 20%, $3^{rd}$ grade 30%, $4^{th}$ grade 20%, $5^{th}$ grade 15%. Results: Number of $1^{st}$ grade was 21, $2^{nd}$ grade 23, $3^{rd}$ grade 39, $4^{th}$ grade 33, $5^{th}$ grade 15 among 131 models. Conclusions: Classification index was developed by integrating four sub-indexes. By the classification method using developed index, distribution of classified tractors was acceptable for practical application.

• 자원리싸이클링
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• 제30권2호
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• pp.46-52
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• 2021

타이타늄의 제련 및 가공 공정에서 산소 농도가 높은 off-grade 스크랩이 발생되고 있다. 본 연구에서 이러한 off-grade Ti 스크랩을 혼합 염화물을 플럭스로 사용하여 Mg으로 탈산하였다. 실험은 α-Ti 영역(1,023~1,123 K)에서 실시하였으며, 반응 시간, 반응 온도, Mg양, 염화물 비율의 영향에 대하여 조사하였다. 플럭스로 사용된 YCl3가 MgO와 반응하여 αMgO의 활동도를 낮추어 Mg에 의한 Ti의 탈산이 가능하였으며, 1,073 K, 6시간 조건에서 Mg=3.6 g, $X_{YCl_3}=0.22$ 일때 Ti scrap의 산소 농도가 0.5 %에서 최저 농도인 0.1117 %까지 감소하였다.

• Nuclear Engineering and Technology
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• 제55권6호
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• pp.2206-2214
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• 2023

The existing wet reconversion processes for the recovery of scraps generated in manufacturing of nuclear fuel are complex and require several unit operation steps. In this study, it is attempted to simplify the recovery process of high-quality fuel-grade UO₂ powder. A novel wet reconversion process for uranyl nitrate hexahydrate solution is suggested by using a newly developed pulsed fluidized bed reactor, and the resultant chemical characteristics are evaluated for the intermediate ammonium uranate hydrate product and subsequently converted UO₂ powder, as well as the compliance with nuclear fuel specifications and advantages over existing wet processes. The UO₂ powder obtained by the suggested process improved fuel pellet properties compared to those derived from the existing wet conversion processes. Powder performance tests revealed that the produced UO₂ powder satisfies all specifications required for fuel pellets, including the sintered density, increase in re-sintered density, and grain size. Therefore, the processes described herein can aid realizing a simplified manufacturing process for nuclear-grade UO₂ powders that can be used for nuclear power generation.

• Investigative Magnetic Resonance Imaging
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• 제26권2호
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• pp.104-116
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• 2022

The purpose of this study is to systematically determine an optimal percentile cut-off in histogram analysis for calculating the mean parameters obtained from a non-Gaussian continuous-time random-walk (CTRW) diffusion model for differentiating individual glioma grades. This retrospective study included 90 patients with histopathologically proven gliomas (42 grade II, 19 grade III, and 29 grade IV). We performed diffusion-weighted imaging using 17 b-values (0-4000 s/mm²) at 3T, and analyzed the images with the CTRW model to produce an anomalous diffusion coefficient (D_m) along with temporal (𝛼) and spatial (𝛽) diffusion heterogeneity parameters. Given the tumor ROIs, we created a histogram of each parameter; computed the P-values (using a Student's t-test) for the statistical differences in the mean D_m, 𝛼, or 𝛽 for differentiating grade II vs. grade III gliomas and grade III vs. grade IV gliomas at different percentiles (1% to 100%); and selected the highest percentile with P < 0.05 as the optimal percentile. We used the mean parameter values calculated from the optimal percentile cut-offs to do a receiver operating characteristic (ROC) analysis based on individual parameters or their combinations. We compared the results with those obtained by averaging data over the entire region of interest (i.e., 100th percentile). We found the optimal percentiles for D_m, 𝛼, and 𝛽 to be 68%, 75%, and 100% for differentiating grade II vs. III and 58%, 19%, and 100% for differentiating grade III vs. IV gliomas, respectively. The optimal percentile cut-offs outperformed the entire-ROI-based analysis in sensitivity (0.761 vs. 0.690), specificity (0.578 vs. 0.526), accuracy (0.704 vs. 0.639), and AUC (0.671 vs. 0.599) for grade II vs. III differentiations and in sensitivity (0.789 vs. 0.578) and AUC (0.637 vs. 0.620) for grade III vs. IV differentiations, respectively. Percentile-based histogram analysis, coupled with the multi-parametric approach enabled by the CTRW diffusion model using high b-values, can improve glioma grading.

• Korean Journal of Radiology
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• 제25권6호
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• pp.511-517
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• 2024

Objective: To prospectively investigate the influence of the menstrual cycle on the background parenchymal signal (BPS) and apparent diffusion coefficient (ADC) of the breast on diffusion-weighted MRI (DW-MRI) in healthy premenopausal women. Materials and Methods: Seven healthy premenopausal women (median age, 37 years; range, 33-49 years) with regular menstrual cycles participated in this study. DW-MRI was performed during each of the four phases of the menstrual cycle (four examinations in total). Three radiologists independently assessed the BPS visual grade on images with b-values of 800 sec/mm² (b800), 1200 sec/mm² (b1200), and a synthetic 1500 sec/mm² (sb1500). Additionally, one radiologist conducted a quantitative analysis to measure the BPS volume (%) and ADC values of the BPS (ADC_BPS) and fibroglandular tissue (ADC_FGT). Changes in the visual grade, BPS volume (%), ADC_BPS, and ADC_FGT during the menstrual cycle were descriptively analyzed. Results: The visual grade of BPS in seven women varied from mild to marked on b800 and from minimal to moderate on b1200 and sb1500. As the b-value increased, the visual grade of BPS decreased. On b800 and sb1500, two of the seven volunteers showed the highest visual grade in the early follicular phase (EFP). On b1200, three of the seven volunteers showed the highest visual grades in EFP. The BPS volume (%) on b800 and b1200 showed the highest value in three of the six volunteers with dense breasts in EFP. Three of the seven volunteers showed the lowest ADC_BPS in the EFP. Four of the seven volunteers showed the highest ADC_BPS in the early luteal phase (ELP) and the lowest ADC_FGT in the late follicular phase (LFP). Conclusion: Most volunteers did not exhibit specific BPS patterns during their menstrual cycles. However, the highest BPS and lowest ADC_BPS were more frequently observed in EFP than in the other menstrual cycle phases, whereas the highest ADC_BPS was more common in ELP. The lowest ADC_FGT was more frequent in LFP.

• 지적과 국토정보
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• 제51권2호
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• pp.141-150
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• 2021

미세먼지는 사람의 건강에 많은 영향을 미치는 물질로서 이와 관련하여 다양한 연구가 이루어지고 있다. 미세먼지의 인체 영향으로 인해 서울시 모니터링 네트워크에서 측정된 과거 데이터를 활용하여 미세먼지를 예측하려는 다양한 연구가 진행되고 있다. 본 연구는 2019년 5월 서울시의 미세먼지를 중점으로 진행하였으며, 학습에 사용한 변수는 SO₂, CO, NO₂, O₃와 같은 대기오염물질 데이터를 활용하였다. 예측모델은 Adaboost에 기반하여 구축하였고, 훈련모델은 PM₁₀과 PM_2.5로 구분하였다. 에러 메트릭스를 통한 예측모델의 정확도 평가 결과로 Adaboost가 시도되었다. 대기오염물질은 초미세먼지와 더 높은 상관성을 보이는 것으로 나타났지만, 보다 효과적인 분포등급을 제시하기 위해서는 많은 양의 데이터를 학습하고, PM₁₀과 PM_2.5의 공간분포 등급을 효과적으로 예측하기 위해서 교통량 등의 추가적인 변수를 활용할 필요성이 있다고 판단된다.

• 한국축산식품학회지
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• 제41권5호
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• pp.779-787
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• 2021

This study compared the meat quality characteristics, palatability, and histochemical characteristics of low-marbled Hanwoo and Holstein steers of different beef quality grades (1, 2, and 3). No differences were observed in muscle pH_{24 h} and cooking loss between the groups (p>0.05); however, quality grade 1 of Hanwoo steers (HA1) showed a darker muscle surface compared to grade 1 of Holstein steers (HO1) (30.9 vs. 33.9, p<0.05). The HA2 group exhibited a lower value of Warner-Bratzler shear force compared to the HO1 and HO3 groups (60.8 vs. 69.2 and 87.8 N, p<0.001). For sensory quality attributes, steaks from the HA1 group showed higher scores of softness, initial tenderness, and amount of perceptible residue than steaks from the HO1 group (p<0.001). Within the quality grade 2, Hanwoo steers had a higher score of softness compared to Holstein steers (p<0.001). There were no differences in juiciness and flavor intensity between Hanwoo and Holstein steers at the same quality grade (p>0.05). This difference in tenderness attributes between the breeds within the quality grade was associated with morphological traits of muscle bundle, and Hanwoo steers had smaller bundle area (0.37 vs. 0.50 mm², p<0.05) and higher fiber number per bundle (88.2 vs. 121, p<0.05) compared to Holstein steers. Therefore, bundle characteristics of longissimus thoracis muscle can be crucial for explaining factor for the explanation of tenderness variations between different breeds at the same beef quality grade or marbling.

• Journal of Electrochemical Science and Technology
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• 제14권4호
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• pp.326-332
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• 2023

The high cost of Si-based solar cells remains a substantial challenge to their widespread adoption. To address this issue, it is essential to reduce the production cost of solar-grade Si, which is used as raw material. One approach to achieve this is Si electrodeposition in molten salts containing Si sources, such as SiO₂. In this study, we present the pulse electrodeposition of Si in molten CaCl₂ containing SiO₂ nanoparticles. Theoretically, SiO₂ nanoparticles with a diameter of less than 20 nm in molten CaCl₂ at 850℃ have a comparable diffusion coefficient with that of ions in aqueous solutions at room temperature. However, we observed a slower-than-expected diffusion of the SiO₂ nanoparticles, probably because of their tendency to aggregate in the molten CaCl₂. This led to the formation of a non-uniform Si film with low current efficiency during direct current electrodeposition. We overcome this issue using pulse electrodeposition, which enabled the facile supplementation of SiO₂ nanoparticles to the substrate. This approach produced a uniform and thick electrodeposited Si film. Our results demonstrate an efficient method for Si electrodeposition in molten CaCl₂ containing SiO₂ nanoparticles, which can contribute to a reduction in production cost of solar-grade Si.

• 대한영상의학회지
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• 제83권1호
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• pp.102-111
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• 2022

목적 요추 중심부 협착증(central lumbar spinal stenosis; 이하 CLSS)에 대하여 Lee grading system과 외과적 수술과의 상관관계를 평가하고 이것이 CLSS에 대하여 치료 방법을 정하기 위한 의사 결정 도구로 사용될 수 있는지 평가하고자 하였다. 대상과 방법 이 후향적 연구에는 290명의 환자가 포함되었다(남:여 = 156:134; 평균 연령, 46 ± 16세). 영상의학과 전문의들은 CLSS를 4등급으로 분류하는 Lee grading system에 따라 협착 지점에서 CLSS의 유무와 등급을 평가했다. Spearman 순위 상관관계를 사용하여 Lee의 등급과 수술 시행 여부 간의 상관 계수를 계산했다. 결과 수술을 시행한 환자에서 2등급이 가장 흔했고(50%-58%), 3등급이 다음으로 흔했으며(35%), 0등급이 가장 흔하지 않았다(2%-3%). 수술을 받지 않은 환자의 경우 1등급이 가장 흔했고(63%-65%), 0등급이 그 다음(15%-16%), 3등급이 가장 흔하지 않았다(8%). 등급 분포는 수술 치료군과 비수술 치료군 사이에서 유의하게 차이가 있었다(p < 0.001). 수술을 받은 환자의 25% 미만에서 0과 1등급이 있었던 반면 2등급과 3등급이 88% 이상이었다. 등급과 수술 사이에 중간 정도(moderate)의 상관관계가 있었다(r_s = 0.632 and r_s = 0.583). 결론 Lee grading system은 수술적 치료 시행과 중간 정도의 상관관계가 있었다. Lee grading system은 CLSS의 치료 방법 결정에서 유용하게 사용할 수 있다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4215-4219
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• 2022

The Cd_0.95Mn_0.05Te_0.98Se_0.02 (CMTS) ingot was grown by the vertical Bridgman technique at low pressure. All wafers showed high resistivity, which suggests potential as a room-temperature semiconductor detector. The resistivity of the CMTS planar detector was 1.47 × 10¹⁰ Ω·cm and mobility lifetime product of electrons was 1.29 × 10^-3 cm²/V. The spectroscopic property with Am-241 and Co-57 was evaluated. The energy resolution about 59.5 keV gamma-ray of Am-241 was 11% and the photo-peak of 122 keV gamma-ray from Co-57 was clearly distinguished. The result shows the first detector-grade CMTS in the world and proves CMTS's potential as a radiation detector operating at room temperature.