• Design & Manufacturing
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• 제16권1호
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• pp.9-14
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• 2022

A lot of research is being done on metal materials to improve the lifespan of molded parts. As a result, excellent mold materials have been developed that withstand high hardness at high temperatures and frictional heat generated from high-speed cutting. In this study, the press mold life of powder high-speed tool steel and general high-speed tool steel was compared. Powdered high-speed steel is composed of alloying elements such as tungsten, maldividene, cobalt, chromium, and vanadium in steel, which improves wear resistance compared to high-hardness and high-speed tool steels. The mold parts of both steel types were manufactured in the same way from heat treatment to machining, and the powder high-speed tool steel was 66HRC and the high-speed tool steel was 61HRC. As a result of the experiment, it was observed that the number of punching of powder high-speed tool steel was improved by 40-50%, and powder high-speed tool steel had fewer impurities, uniform texture, and excellent surface structure. It has a microscopic structure.

• 한국지역지리학회지
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• 제15권3호
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• pp.421-433
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• 2009

불투수율은 물, 공기, 자연 생태계 등 전체 환경을 악화시키는 요인이 되기 때문에 도시지역의 총체적인 환경 질을 대표하는 지표로서 활용되고 있다. 본 연구는 Google Earth와 수치지도를 이용하여 대학 캠퍼스 불투수율을 정략적으로 비교 평가하는 방안을 제안한다. 경북대학교와 홍콩대학교 사례연구지역으로 선정되었으며 61cm의 공간해상도를 지닌 퀵버드 영상은 수치지도에서 추출한 레이어와 결합되어 도로, 건물, 주차장 등 세부적인 불투수면의 유형을 추출하였다. 경북대학교 캠퍼스는 도로와 주차장의 숲으로 뒤덮여 있는 것이 확인되었으며 반면에 홍콩대학교는 수목비율이 31%로 경북대보다 2배 정도 높은 것으로 평가되었다. Google Earth를 이용한 불투수면 감시기법은 동일한 데이터와 일관된 작업과정을 적용할 수 있어 다수의 조사자에 의한 주관적 판단과 대상 지역의 차이에 따른 불규칙적인 기준 적용의 문제점을 보완할 수 있는 현실적인 대안이 될 수 있을 것이다.

• Design & Manufacturing
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• 제15권2호
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• pp.30-35
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• 2021

The casting method uses a mold to solidify a liquid metal to make a solid metal. Since it uses a liquid metal with the least deformation resistance, it has the characteristic that it can easily manufacture even a complex shape. However, the process of solidifying a liquid metal into a solid metal inevitably involves a volume change and contains internal defects such as shrinkage holes. Therefore, in the design of the casting plan, an excess volume called a pressurization compensates for the volume shrinkage. in the product, and it induces the shrinkage hole defects to occur in parts other than the product1). In this study, casting analysis was performed using casting analysis software (anycasting) in order to optimize the design of the tilting gravity casting method for automobile brackets. In particular, the filling and solidification analysis according to the shape and volume of the pressurized metal was conducted, and applied to the actual product to study the effect of the pressurized metal on the shrinkage defect. Through this study, it is possible to understand the effect of the pressure metal on shrinkage defects in the actual product and propose a design of the pressure metal that improves reliability and productivity.

• Biomolecules & Therapeutics
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• 제31권6호
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• pp.599-610
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• 2023

According to recent evidence, ferroptosis is a major cell death mechanism in the pathogenesis of kidney injury and fibrosis. Despite the renoprotective effects of classical ferroptosis inhibitors, therapeutic approaches targeting kidney ferroptosis remain limited. In this study, we assessed the renoprotective effects of melatonin and zileuton as a novel therapeutic strategy against ferroptosis-mediated kidney injury and fibrosis. First, we identified RSL3-induced ferroptosis in renal tubular epithelial HK-2 and HKC-8 cells. Lipid peroxidation and cell death induced by RSL3 were synergistically mitigated by the combination of melatonin and zileuton. Combination treatment significantly downregulated the expression of ferroptosis-associated proteins, 4-HNE and HO-1, and upregulated the expression of GPX4. The expression levels of p-AKT and p-mTOR also increased, in addition to that of NRF2 in renal tubular epithelial cells. When melatonin (20 mg/kg) and zileuton (20 mg/kg) were administered to a unilateral ureteral obstruction (UUO) mouse model, the combination significantly reduced tubular injury and fibrosis by decreasing the expression of profibrotic markers, such as α-SMA and fibronectin. More importantly, the combination ameliorated the increase in 4-HNE levels and decreased GPX4 expression in UUO mice. Overall, the combination of melatonin and zileuton was found to effectively ameliorate ferroptosis-related kidney injury by upregulating the AKT/mTOR/ NRF2 signaling pathway, suggesting a promising therapeutic strategy for protection against ferroptosis-mediated kidney injury and fibrosis.