• Proceedings of the Korea Water Resources Association Conference
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• 2020.06a
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• pp.217-217
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• 2020

인간 물이용 중심의 하천 관리로 하천에 인위적으로 설치되는 횡단구조물은 물의 흐름을 막아 수질환경을 악화시킬 뿐 아니라 하천의 연속성을 단절하여 생물의 이동을 차단하여 생태계에 악영향을 미친다. 이러한 인위적인 구조물로서 약 34000여개의 농업용 보와 약 16000여개로 추정되는 낙차공이 다수 존재하고 있다. 이러한 구조물은 유수에 의하여 하상으로 전달되는 유수에너지를 저감하기 위하여 다양한 형태의 하상보호공을 설치하여 하천횡단구조물을 보호하도록 되어있다. 그러나 하상보호공에 사용되는 기술 중 사석 및 돌망태와 같은 기술은 시공비용이 적고 빠른 시간에 시공 할 수 있지만 급격한 홍수에 쉽게 파괴 및 유실이 되는 단점이 있으며, 콘크리트 소재 공법은 세굴방지에 좋은 효과를 발휘하는 장점을 지니지만, 시간이 지남에 따라 마모/변형되거나 포락/유실되어 하상을 지속적으로 보호하지 못하게 되며 과도한 세굴은 구조물의 안전성에도 영향을 미친다고 할 수 있다. 최근 기후변화로 인하여 돌발호우 및 강우량의 증가로 돌변하는 하천환경에 대한 적용기술은 미비한 실정이기 때문에, 많은 연구자들은 이에 대한 해결책을 찾기 위하여 자연친화적 생태복원 기술을 개발하고 있다. 본 연구에서는 바이오폴리머를 다층다공성 하상보호기술에 대하여 에너지 저감 효율, 고유속에서 한계 소류력, 소재 이탈 실험을 최대유량 10 ㎥/s, 유속 8m/s를 재현할 수 있는 실규모 하천실험장에서 진행하여 과학적인 안전성을 확인하였다.

• Journal of the Korean Society of Clothing and Textiles
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• v.30 no.3 s.151
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• pp.481-486
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• 2006

There are attempts to utilize Hanji for apparel material, but, the reason that the strength and durability of Hanji decrease to a great extent in the wet condition, restricts the usability of Hanji. In order to improve the resistance against water, Hanji was treated with silicone type water repellent agents. The treatment was carried out by conventional pad-dry-cure method. The optimum treatment condition was obtained by varying the concentration of repellent agent, curing temperature and time. Water repellency was tested by spray rating method. Wet and dry tensile strength, tearing resistance and abrasion resistance were examined after the treatment. Flexural stiffness and wrinkle recovery angles of hanji were also measured. In result, the optimum condition of treatment was at resin concentration of 40g/l, catalyst concentration of 20g/l(half of resin concentration), curing temperature of 160$^{circ}C$, curing time of 120 sec. Flexural stiffness of Hanji was hardly increased and wrinkle recovery angle of Hanji was improved a little by resin treatment. After the treatment, in dry condition, tensile strength and tearing resistance were little changed but abrasion resistance was improved. In wet condition, tensile strength, tearing strength and abrasion resistance were improved.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.3
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• pp.27-34
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• 2017

Recently, the importance of the industrial warehouse floor has been increasing due to the development of the distribution and logistics industry. In this present study, an early-hardening polymer floor mortar which can compensate for the limitation of conventional cement based floor mortar regarding fluidity and long curing time was developed. In order to achieve the early-hardening of mortar characteristic ultra rapid hardening cement was used as binder. Four types of mixture proportions in accordance with the vinyl acetate ethylene(VAE) polymer contents with range from 10% to 20% and the other proto proportion without VAE polymer were designed. Mechanical experiments including the fluidity test, compressive strength test, bending test, bond test, and abrasion test were conducted for all mixture proportions. From the flow test result, it was possible to achieve the high flow with 250 mm by controlling the amount of superplasticizer. The incorporation of VAE polymer was found to affect the compressive strength reduction, however, the flexural strength was higher than that of the proto mixture, and it was evaluated to increase the compressive strength / flexural strength ratio. Moreover, at least 2.6 times higher bond strength and more than 4 times higher abrasion resistance were secured. From the mechanical experiments results, the optimum mixing ratio of the VAE polymer was determined to be 10%. As a result of application and monitoring, it shows that it has excellent resistance to cracking, discoloration, impact, and scratch as well as bond performance compared to the cement based floor mortar.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.12
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• pp.8637-8642
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• 2015

Typical aging for the rubber using the current military adhesive combat boots was spread with a regular aging caused by heat stress. In this study, the aging test of the rubber for combat boots was carried out and the reaction rate constant, k was calculated at aging temperature $60^{\circ}C$, $80^{\circ}C$ and $100^{\circ}C$, using the Arrhenius equation. The lifetime limit was assumed that the tensile strength of the product is reduced to 30%, the elongation is reduced to 50% and abrasion resistance ratio is 380%. ln($P/P_0$) and the lifetime was predicted with the consideration of the activation energy constant. According to the above, the lifetime of the rubber for combat boots with influenced by aging temperature was predicted. As the result, the estimate lifetime at $20^{\circ}C$ was confirmed more than 10 years.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.3
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• pp.53-60
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• 2011

As Construction & Demolition(C&D) debris increase every year, a system has enforced for recycled aggregate made out of C&D debris, then recycled aggregate usage increased in construction field. But as environmental problem by alkalinity of recycled aggregate occurred, the study for lowering alkalinity of recycled aggregate is needed. In this study we made alkalinity reducing facility and installed in the C&D debris midterm-treat field. Then we certified effect of lowering alkalinity and quality of recycled aggregates before and after carbonation. As a result, the most effective carbonation condition is 30seconds in carbonation time, -50~100 kPa of reaction pressure with change of 3cycles. This condition made pH 9.33~9.8 of recycled aggregate possible. The quality of recycled aggregate after carbonation was better than before carbonation in terms of plasticity index, modified CBR, abrasion loss, sand equivalent, liquid limit, size distribution, density and water absorption.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.38 no.9
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• pp.943-951
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• 2014

The tip geometries of the pyramidal and conical indenters used for micro/nano-indentation tests are not sharp. They are inevitably rounded because of their manufacturability and wear. In many indentation studies, the tip geometries of the pyramidal indenters are simply assumed to be spherical, and the theoretical solution for spherical indentation is simply applied to the geometry at a shallow indentation depth. This assumption, however, has two problems. First, the accuracy of the theoretical solution depends on the material properties and indenter shape. Second, the actual shapes of pyramidal indenter tips are not perfectly spherical. Hence, we consider the effects of these two problems on indentation tests via finite element analysis. We first show the relationship between the Poisson's ratio and load-displacement curve for spherical indentation, and suggest improved solutions. Then, using a possible geometry for a Berkovich indenter tip, we analyze the characteristics of the load-displacement curve with respect to the indentation depth.

• Journal of the Korean GEO-environmental Society
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• v.6 no.3
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• pp.17-23
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• 2005

In Korea, the production of reclaimed concrete materials has been increased due to the increase in the concrete structures taken down every year. The reclaimed concrete materials have been reused as road materials. However, the studies on their mechanical and environmental properties have been very limited. The recycled rate of the materials is currently low in Korea. This paper presents the investigation of mechanical and environmental properties of the reclaimed concrete materials, as well as the comparisons with those of gravel. For the evaluation of the mechanical and environmental characteristics, following tests were conducted on both reclamed materials and gravel; liquid limit, plasticity index, CBR, sand equivalent test, abrasion test, pH test, and column leaching test. The test results showed that the reclaimed concretes satisfy the requirements for use as roadbase, subbase, and subgrade materials, except base materials. The pH of reclaimed concrete materials was less than 11 and the leaching test results satisfied the regulatory requirement of Waste Management Act in Korea. Based on the investigations, it appears that the reclaimed concrete materials are environmentally safe and applicable for use as road materials.

• Journal of Internet of Things and Convergence
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• v.9 no.3
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• pp.81-86
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• 2023

SSD (solid state disk), which is flash memory-based storage device, has the advantages of high density and fast data processing. Therefore, it is being utilized as a storage device for high-capacity data storage systems that manage rapidly increasing big data. However, flash memory, a storage media, has a physical limitation that when the write/erase operation is repeated more than a certain number of times, the cells are worn out and can no longer be used. In this paper, we propose a method for converting defective multi-bit cells into single-bit cells to reduce the defect rate of flash memory and extend its lifetime. The proposed idea distinguishes the defects and treatment methods of multi-bit cells and single-bit cells, which have different physical characteristics but are treated as the same defect, and converts the expected defective multi-bit cells into single-bit cells to improve the defect rate and extend the overall lifetime. Finally, we demonstrate the effectiveness of our proposed idea by measuring the increased lifetime of SSD through simulations.

• Journal of Oral Medicine and Pain
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• v.26 no.3
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• pp.189-204
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• 2001

본 연구는, 기존의 나열식 분류체계의 문제점을 극복할 수 있는 GRAIL을 이용하여 두경부의 해부학적 구조물들 및 구강 악안면 영역의 주요 질병들과 관련된 치의학 개념들의 모델을 구축한 뒤, 완성된 치의학 개념 모델이 두경부의 해부학적 구조물들 및 구강 악안면 영역의 주요 질병들을 잘 표현할 수 있는지와 기존의 GRAIL 모델이 지닌 특징에 잘 부합하는지를 평가하고자 시행되었다. 서울대학교 치과병원 내원 환자 중 포괄적인 치과 치료 병력을 지닌 환자 150명의 치과 의무기록을 내용별로 분석하고, 각종 치의학 교과서와 기존의 의학용어 분류체계에서도 모델 구축에 필요한 치의학 용어를 선택하였다. 이들 자료를 바탕으로, GRAIL 모델 구축을 진행하고 구축된 모델을 평가할 수 있는 소프트웨어 프로그램인 'KnoME'에서 치의학 개념 모델을 구축하고 평가하여, 다음과 같은 결론을 얻었다. 1. 환자 150명의 치과 의무기록을 내용별로 분석한 결과, 우선적으로 모델 구축이 필요한 치의학 용어로는, 해부학적 구조물의 경우 치아, 치은, 악관절, 입술, 턱, 혀 등의 순서로 나타났으며, 구강악안면 영역의 병소에서는 치아 우식증, 치주염, 치은염, 악관절 장애, 매복 지치, 치경부 마모 등의 순서로 나타났다. 2. GRAIL을 이용하여 치아, 치주조직, 구강점막조직, 치아 우식증, 치수 및 치근단 병소, 치주질환, 구강점막질환의 모델 구축을 시행한 결과, 치의학 개념간의 다양한 관계가 대다수 잘 표현되었다. 그러나, 구강 악안면 영역의 해부학적 구조물에 대한 공간 정의의 한계성과 구강 악안면 질환의 진행 양상에 있어서 표현의 어려움이 관찰되었다. 이러한 부분은 GRAIL을 치의학 분야에 적용할 때, 극복해야 할 한계로 나타났다. 3. 치의학 개념들에 관한 다양한 질의를 시행한 후 그 응답 내용을 평가한 결과, 완성된 모델 내에서 치의학 개념의 자동적인 분류가 이루어 졌으며, 다양한 목적의 검색이 가능하였다. 이와 같은 사실로 미루어 보아서, 완성된 모델은 기존의 GRAIL 모델의 특성에 잘 부합되는 것으로 생각되었다.

• KIPS Transactions on Software and Data Engineering
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• v.12 no.10
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• pp.445-454
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• 2023

Recently, various fault diagnosis studies are being conducted utilizing data from collaborative robots. Existing studies performing fault diagnosis on collaborative robots use static data collected based on the assumed operation of predefined devices. Therefore, the fault diagnosis model has a limitation of increasing dependency on the learned data patterns. Additionally, there is a limitation in that a diagnosis reflecting the characteristics of collaborative robots operating with multiple joints could not be conducted due to experiments using a single motor. This paper proposes an LSTM diagnostic model that can overcome these two limitations. The proposed method selects representative normal patterns using the correlation analysis of vibration and current data in single-axis and multi-axis work environments, and generates residual patterns through differences from the normal representative patterns. An LSTM model that can perform gear wear diagnosis for each axis is created using the generated residual patterns as inputs. This fault diagnosis model can not only reduce the dependence on the model's learning data patterns through representative patterns for each operation, but also diagnose faults occurring during multi-axis operation. Finally, reflecting both internal and external data characteristics, the fault diagnosis performance was improved, showing a high diagnostic performance of 98.57%.