• 콘크리트학회논문집
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• 제23권2호
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• pp.203-209
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• 2011

시멘트 산업은 에너지 다소비형이며 석회석을 원료로 하고 있어 지구 온난화의 주범인 CO를 배출하여, 환경문제로 인해 가까운 시기에 큰 어려움을 겪을 것으로 예상되고 있다. 오늘날 첨단산업의 발전과 지구환경 문제의 심각성에 대한 인식이 증가하여 시멘트 산업에서도 다각화 측면에서 다양한 종류의 기술 등이 활성화되고 있는 시점이다. 이 연구에서는 최근에 새로이 검토되고 있는 시멘트 대체 재료로서 천연 제올라이트를 주원료로 사용한 제올라이트 시멘트 모르타르에 관한 재료적 특성을 분석하는데 목적이 있으며 그 방법으로 물($H_2O$)대신 알칼리 활성제(NaOH)를 사용하여 알칼리 경화반응을 이용한 제올라이트 모르타르를 제조하여, 강도 특성 및 적정 배합비를 구하였다. 그 결과 알칼리 활성제의 양과 경화 온도에 따른 천연 제올라이트 시멘트 모르타르의 7일 압축강도가 42 MPa로 측정되는 등 기존 시멘트보다 뛰어난 성능을 나타내는 것으로 판단되어지며, 기존 건설용 재료를 대체할 가능성이 충분히 있다고 사료된다.

• Journal of Electrochemical Science and Technology
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• 제12권2호
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• pp.279-284
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• 2021

The high theoretical specific capacity of lithium-sulfur (Li-S) batteries makes them a more promising energy storage system than conventional lithium-ion batteries (LIBs). However, the slow kinetics of the electrochemical conversion reaction seriously hinders the utilization of Li-S as an active battery material and has prevented the successful application of Li-S cells. Therefore, exploration of alternatives that can overcome the sluggish electrochemical reaction is necessary to increase the performance of Li-S batteries. In this work, an ionic liquid (IL) is proposed as a functional additive to promote the electrochemical reactivity of the Li-S cell. The sluggish electrochemical reaction is mainly caused by precipitation of low-order polysulfide (l-PS) onto the positive electrode, so the IL is adopted as a solubilizer to remove the precipitated l-PS from the positive electrode to promote additional electron transfer reactions. The ILs effectively dissolve l-PS and greatly improve the electrochemical performance by allowing greater utilization of l-PS, which results in a higher initial specific capacity, together with a moderate retention rate. The results presented here confirmed that the use of an IL as an additive is quite effective at enhancing the overall performance of the Li-S cell and this understanding will enable the construction of highly efficient Li-S batteries.

• International Journal of Naval Architecture and Ocean Engineering
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• 제13권1호
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• pp.405-430
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• 2021

Production planning is a key part of production management of manufacturing enterprises. Since computerization began, modern production planning has been developed starting with Material Requirement Planning (MRP), and today Enterprise Resource Planning (ERP), Advanced Planning and Scheduling (APS), Supply Chain Management (SCM) has been spreading and advanced. However, in the shipbuilding field, rather than applying these general-purpose production planning methodologies, in most cases, each shipyard has developed its own production planning system. This is because the applications of general-purpose production planning methods are limited due to the order-taking industry such as shipbuilding with highly complicated construction process consisting of millions of parts per ship. This study introduces the design and development of the production planning system reflecting the production environment of heavy shipyards in Korea. Since Korean shipyards such as Hyundai, Daewoo and Samsung build more than 10 ships per year (50-70 ships in the case of large shipyards), a planning system for the mixed production with complex construction processes is required. This study draws requirements using PI/BPR (process innovation and business process reengineering) methodology to develop a production planning system for shipyards that simultaneously build several ships. Then, CBD software development methodology was applied for the design and implementation of planning system with drawn requirements. It is expected that the systematic development procedure as well as the requirements and functional elements for the development of the shipyard production planning system introduced in this study will be able to present important guidelines in the related research field of shipbuilding management.