• 한국구조물진단유지관리공학회 논문집
• /
• 제7권2호
• /
• pp.159-167
• /
• 2003

Cracks in reinforced concrete structures reduce overall durability by allowing the penetration of water and aggressive agents, thereby accelerating the deterioration of the reinforcing steel. Highway pavement and bridge decks are especially susceptible to this type of deterioration since these structures exhibit high rates of shrinkage and are frequently exposed to aggressive environmental conditions. The objectives of this investigation included the development of experimental procedures for assessing shrinkage cracking potential of recycled aggregate concrete, the evaluation of mix composition on shrinkage cracking potential, and the development of theoretical models to simulate early-age cracking behavior. Specifically, the influences of shrinkage-reducing admixture(SRA) and recycled aggregate concrete were investigated. The shrinkage-reducing admixture substantially reduces free shrinkage and restrains shrinkage cracking while providing similar mechanical properties. A fracture mechanics modeling approach was developed to predict the behavior of a variety of restrained concrete specimens. This modeling approach was used to successfully explain experimental results from a variety of mixture compositions. The model was used to demonstrate the influence of material and structural properties on the potential for cracking.

• Nuclear Engineering and Technology
• /
• 제55권3호
• /
• pp.839-849
• /
• 2023

The development of automation technology to reduce human error by minimizing human intervention is accelerating with artificial intelligence and big data processing technology, even in the nuclear field. Among nuclear power plant operation modes, the startup and shutdown operations are still performed manually and thus have the potential for human error. As part of the development of an autonomous operation system for startup operation, this paper proposes an action coordinating strategy to obtain the optimal actions. The lower level of the system consists of operating blocks that are created by analyzing the operation tasks to achieve local goals through soft actor-critic algorithms. However, when multiple agents try to perform conflicting actions, a method is needed to coordinate them, and for this, an action coordination strategy was developed in this work as the upper level of the system. Three quantification methods were compared and evaluated based on the future plant state predicted by plant parameter prediction models using long short-term memory networks. Results confirmed that the optimal action to satisfy the limiting conditions for operation can be selected by coordinating the action sets. It is expected that this methodology can be generalized through future research.

• 한국지반환경공학회 논문집
• /
• 제13권7호
• /
• pp.31-38
• /
• 2012

현재 지반주입공법에 사용되는 약액으로는 물유리계가 주로 사용되고 있다. 최근 국내에서는 지반개량 재료로 무기질계 급결재와 초미립자 시멘트를 주원료로 하는 NDS(Natural and Durable Stabilizer)공법 등의 개발이 활발하게 연구되어 왔다. 그러나 일반적으로 주입공법의 경우, 주입 효과에 대한 확인이 어렵고 지반 및 지하수의 오염 등 환경 공해의 우려가 있는 문제점이 있다. 따라서, 이암으로 성토된 지반에 대한 주입공법 적용시 주입재료별(물유리계 및 무기질계) 주입률에 따른 강도 및 차수특성을 파악하여 적정주입량을 산정하기 위하여 일축압축강도시험, 어독성시험, 삼축투수시험을 실시하였다. SGR(Space Grouting Roket)과 NDS의 경우 재령 28일의 공시체를 기준으로 주입률 50%까지는 강도 및 차수성 증대가 현저하다가 50% 이상에서는 증대량이 미미한 바, 적정 주입률을 50%로 결정하였다.

• 벤처창업연구
• /
• 제15권4호
• /
• pp.17-25
• /
• 2020

벤처부채는 벤처의 스케일업 촉진을 위한 대표적인 자금공급 수단이다. 성장 단계에서 대규모 자금 공급이 필요한 벤처기업은 지분 희석 없이 벤처부채를 지렛대로 성장을 가속화할 수 있고, 벤처캐피탈은 투자 기업의 성장이 가속화됨으로써 신속히 투자자금을 회수할 수 있다. 은행은 벤처부채의 공급을 통해 대출에 편중된 자산운용을 다양화할 수 있고 자산수익률도 제고할 수 있다. 해외 실리콘밸리은행의 사례와 같이 벤처부채 공급을 위해서는 부채자본 공급자인 은행과 지분자본을 공급하는 벤처캐피탈의 긴밀한 협력이 전제되어야 한다. 이를 위한 시장 조성 방안으로 "신용위험 분담형 벤처대출"과 "벤처대출 풀링"을 제안한다. 전자는 모태펀드와 정책보증과 같은 정책금융기관이 벤처대출에 내재한 위험을 선별하거나 우선 인수함으로써 은행의 벤처투자 시장 참여를 촉진하며, 후자는 은행과 창업벤처전문 사모펀드가 공동으로 벤처대출을 증권화함으로써 은행의 개별적인 벤처대출 실행에 따른 부담을 감소시킨다.

• Journal of Korean Neurosurgical Society
• /
• 제40권3호
• /
• pp.180-185
• /
• 2006

Objective : Middle cerebral artery occlusion[MCAO] has widely been used to produce ischemic brain lesions. The lesions induced by MCAO tend to be variable in size because of the variance in the collateral blood supply found in the mouse brain. To establish a less invasive and reproducible focal ischemia model in mice, we modified the technique used for rat photo thrombosis model. Methods : Male C57BL/6 mice were subjected to focal cerebral ischemia by photothrombosis of cortical microvessels. Cerebral infarction was produced by intraperitoneal injection of Rose Bengal, a photosensitive dye and by focal illumination through the skull. Motor impairment was assessed by the accelerating rotarod and staircase tests. The brain was perfusion-fixed for histological determination of infarct volume four weeks after stroke. Results : The lesion was located in the frontal and parietal cortex and the underlying white matter was partly affected. A relatively constant infarct volume was achieved one month after photothrombosis. The presence of the photothrombotic lesion was associated with severe impairment of the motor performance measured by the rotarod and staircase tests. Conclusion : Photothrombotic infarction in mice is highly reproducible in size and location. This procedure can provide a simple method to produce cerebral infarction in a unilateral motor cortex lesion. In addition, it can provide a suitable model for study of potential neuroprotective and therapeutic agents in human stroke.

• Archives of Reconstructive Microsurgery
• /
• 제4권1호
• /
• pp.9-15
• /
• 1995

Free vascularized composite tissue transfer is more frequently underwent for reconstruction of complicated tissue defects with the recent advance of microsurgery. But postoperative result was not satifactory because of donor site morbidity, flap bulkiness and cosmetic problem. So would no longer be a problem if we can obtain the exact donor tissue required for the recipient site as allotransplantation and designing the flap. Allotransplantation has been resolved with the recent development of immunosuppressive agents, while reconstruction has made great progress with the refinement of microsurgical techniques in the last 20 years. The final sucess or failure of the operative procedure in transplantation is so utterly dependent no the availability of strategies that can control the immune system effectively, selectively, safely to allow allotransplantation of a nonvital body part. 1 used 2 strains of rats, BUF and LEW, for the limb allotransplantation as a composite tissue transfer. The primary goal of this program is to improve results in clinical transplantation by accelerating the transformation of new immunological knowledge into useful medicine. Two of the most promising new immunosuppressive compounds are FK-t06(FK) and rapamycin(RPM). Both drugs are antibiotic macrolide fungal fermentation products that presumably suppress the immune system in ways similar to cyclosporin(CyA). This study shows that two new immunosuppressive drugs compare the immunosuppressive activity and effectiveness of FK-506 and RPM for prevention of the limb allograft rejection in the rat. Additional experiments investigate the dose, route of administration and histologic findings. These data demonstrates that rapamycin is far more potent and effective than FK-506 when both compounds are administered by the intraperitoneal route, as well as prolonged graft survival significantly in a dose-route dependent manner. These results lead to the view that vascularized allograft composite tissue transfer can become a reality with the expectation of possible future application in reconstructive surgery of humans.

• Food Science and Biotechnology
• /
• 제15권1호
• /
• pp.5-12
• /
• 2006

Degradation performance of environmentally friendly plastics that can be disintegrated by combination of sunlight, microbes in soil, and heat produced in landfills was evaluated for use in industries. Two multi-degradable master batches (MCC-101 and MCC-102 were manufactured, separately mixed with polyethylene using film molding machine to produce 0.025 mm thick films, and exposed to sunlight, microbes, and heat. Low- and high-density polyethylene (LDPE and HDPE) films containing MCC-101 and MCC-102 became unfunctional by increasing severe cleavage at the surface and showed high reduction in elongation after 40 days of exposure to ultraviolet light. LDPE and HDPE films showed significant physical degradation after 100 and 120 days, respectively, of incubation at $68{\pm}2^{\circ}C$. SEM images of films cultured in mixed mold spore suspension at $30^{\circ}C$ and 85% humidity for 30 days revealed accelerated biodegradation on film surfaces by the action of microbes. LDPE films containing MCC-l01 showed absorption of carbonyls, photo-sensitive sites, at $1710\;cm${-1}$ when exposed to light for 40 days, whereas those not exposed to ultraviolet light showed no absorption at the same frequency. MCC-101-based LDPE films showed much lower $M_w$ distribution after exposure to UV than its counterpart, due to agents accelerating photo-degradation contained in MCC-101.

• 한국토양비료학회지
• /
• 제42권Spc호
• /
• pp.20-28
• /
• 2009

생물비료는 아직도 한국에서는 생소한 용어다. 한국에서 생물비료라 함은 식물추출액, 퇴비류-다양한 형태의 미생물 혼합제 등으로 인식되고 있다. 그러나 최근에는 식물영양요소의 흡수나 이용도를 증진시키는 토양미생물 사용으로 언급하기도 한다. 본 개관은 식물성장을 증진시키는 것으로 알려진 PGPR 서로 다른 기작과 실질적 역할에 대하여 검토하였다.

• 한국수산과학회지
• /
• 제35권6호
• /
• pp.709-714
• /
• 2002

본 실험은 동해안 특산 어종인 까나리 액젓의 속성제조를 위하여 발효촉진제 (오징어 내장, koji 및 효소)를 첨가한 다음 15$^{\circ}C$에서 숙성 중 여러 가지 성분변화를 분석하였다. 숙성기간 동안 수분은 모든 실험구에서 감소하는 경향을 나타내었으며 단백질 함량은 모든 시료에서 숙성 1개월째까지 급격히 증가하였으며 그 이후의 숙성기간에서는 미세한 증가 현상을 나타내었다. 조지방은 숙성 기간 동안 오징어 내장 첨가구에서 가장 높은 함량을 나타내었으며 탄수화물은 koji 첨가군이 가장 높게 나타났다. 조회분은 숙성기간동안 모든 실험구에서 꾸준히 증가하는 경향을 나타내었으며 pH는 모든 실험구에서 큰 변화는 나타나지 않았으며 오징어 내장 첨가구가 가장 낮게 나타내었다. TMA 함량은 모든 실험구에서 숙성 3개월째까지 계속 증가하다가 그 후 다소 감소하는 경향을 나타내었으며 아미노태 질소량은 모든 실험구에서 숙성 3개월째까지 완만하게 증가하였으며 숙성 4개월이하부터는 모든 실험구에서 급격한 증가량을 나타내었다. VBN 함량은 모든 실험구에서 숙성 2개월까지 미세하게 증가하였으나 숙성 3개월째에 모든 발효 촉진제 첨가구에서 급격히 증가하였으며 전 숙성 기간에 걸쳐 오징어 내장 첨가군이 가장 높은 VBN 함량을 나타내었다. 숙성 중 오징어 내장 첨가군에서는 본 논문에서는 자료를 제시하지 않았지만 숙성 3개월째 다른 첨가군과는 다른 독특한 고소한 향과 감칠맛을 나타내었다. 속성 까나리 어간장을 제조하기 위한 속성 발효제로서 오징어내장 및 koji는 발효기간을 단축시킬 수 있을 뿐 아니라 독특한 맛을 형성하므로 까나리 어간장의 속성제조에 발효촉진제로 사용이 가능하다고 보여진다.