• Journal of the Korea Institute of Building Construction
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• v.18 no.6
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• pp.595-602
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• 2018

Network-based scheduling methods can be classified into CPM method and PERT method. In the network scheduling chart, critical path can be estimated by performing the forward calculation and the backward calculation though the paths in the network chart. In PERT method, however, it is unreasonable to simply estimate the critical path by adding the sum of the activity durations in a specific path, since it does not incorporate probabilistic concept of PERT. The critical path of a PERT network can change according to the target period and deviation, and in some cases, the expected time of the critical path may not be the path with longest expected time. Based on this concept, this study proposes a technique to derive the most-likely critical path by comparing the sum of estimated time with the target time. It also proposes a method of systematically deriving all alternate paths for a network of repetitive activities. Case studies demonstrated that the most-likely critical path is not a fixed path and may vary according to the target period and standard deviation. It is expected that the proposed method of project duration forecasting will be useful in construction environment with varying target date situations.

• 월간 기계설비
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• no.11 s.220
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• pp.44-47
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• 2008

많은 난관을 극복하고 조기착공에 성공한 후에, 우선적으로 고려할 사항은 주공정(Crtical Path) 을 관리하는 것이다. 주공정(critical Path)의 초기 작업에 필요한 자재, 장비, 인원의 준비를 재점검하고 하도급추진을 하는 한편, 계약서상의 요구조건, 승인사항에 미흡한 점이 없는지를 검토하고 보완한다. 계약서상의 요구사항을 미비하거나 무시했을 경우, 반드시 그에 상응하는 경제적 대가를 치루어야 한다는 것을 명심해야 한다. 시공을 하기 위해서는 자재승인 후 작업도면(Working Drawing/ Construction Drawing/ Shop Drawing)의 승인을 받고, 작업방법(Method Statement)을 제출하고, 설명화 Presentation) 및 시험시공(Demonstration 또는 Mockup)을 거쳐 감리자의 시공허락을 받아야 하며 각종 Test를 통해 품질관리를 실행해야 한다. 시공지는 시방서에서 요구하는 품질이 보장되는 범위 내에서, 최대한 공기를 단축할 수 있도록 공사초기부터 노력을 해야 하며, 공사의 모든 과정에서 항상 claim 여부, 공기내 준공, 하자 Zero, 최단 시일 내에 최대의 기성취하에 역점을 두고, 이에 장애요인을 해결하는 것으로 공사를 진행해야 한다.

• 월간 기계설비
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• no.12 s.221
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• pp.62-64
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• 2008

현장에서는 주공정과 예산관리를 중심으로 공사진행을 하고, 공정이 90% 이상 달성되었거나 또는 잔여공기가 9개윌 정도 남아 있으면 모든 공정을 재검토하기 바란다. 우선 하청시로부터 잔여 공사에 대한 공정표를 받아, 잔여공시 1개월 전에 준공될 수 있는지 검토한다. 9개월 정도 앞서 준공기일을 검토하는 것은, 자재납기가 장기간(7개월 정도) 소요되는(플랜트 Control Panel 등) 자재의 발주여부를 검토하고, 잔여공기 내에 정상 작업으로 공기 내 준공이 불가하다고 예측될 경우, 3개월 또는 6개월 돌관작업 계획을 세우기 위함이다. 잔여공기가 3개월 정도 남아 있을 때, 시설물을 인계(Hand Over) 하기 위해 본격적인 준비를 한다. 준공이란 "계약적으로 발주자가 실제적으로 계약서에 의도된 목적으로 사용할 수 있는 상태(표준계악일반조건 48. 1)"를 말하므로, 이 점에 착안하여 발주자가 시설물을 제때에 사용하지 못함으로써 발생되는 지체보상금(Liquidated Damage)을 물지 않도록 작전을 세운다.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2006.05a
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• pp.1240-1245
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• 2006

PCB는 수십개의 주공정과 보조공정으로 구성된 제품으로 동일한 생산라인에서 로트 단위로 다품종 혼류 생산되고 있다. 따라서 PCB 제조라인에서는 많은 공정수, 높은 불량률, 다양한 공정설비 및 빈번한 설비고장, 중소기업의 낮은 설계 및 생산기술력, 빈번한 수주 변경 및 다품종 혼류, 긴급 수주 등과 같이 제조원가를 증가시키는 다양한 교란요인들이 항상 발생하고 있다. 본 연구에서는 생산성, 품질 등을 고려하면서 리드 타임을 단축하기 위하여 TOC DBR 기법을 개선한 2개의 DBR 개념을 도입하여 성공적으로 리드타임을 개선한 사례를 소개하고자 한다.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2002.05a
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• pp.109-114
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• 2002

건설공사의 공종 중 거푸집공사는 전체공사기간의 대략 25％를 차지하고 있으며 공사비 비율은 일반적으로 전체공사비의 10～15％, 철근콘크리트공사비의 20～30％를 차지하고 있어 구조물의 안전성, 경제성 및 작업성과 품질관리에 중요한 역할을 한다. 또한 거푸집은 콘크리트가 양생되면 곧 해체되는 가설구조물로써 작업상에서 많은 위험요소를 포함하고 있으며 특히, 아파트공사의 경우 전체 재해발생의 17％로 가장 높은 비율을 차지하고 있다. 이와 같이 거푸집공사는 가장 우선적으로 관리하여야 할 위험공종이며 전체공기를 좌우하는 주공정으로서 이를 재해발생의 측면에서 제어하는 것이 안전관리에 있어서 가장 효율적이며 큰 효과를 나타낼 수 있는 것으로 생각된다.(중략)

• Journal of Korean Society on Water Environment
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• v.34 no.1
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• pp.96-108
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• 2018

Large efforts have recently been made on research and development of sustainable and energy-efficient short-cut nitrogen removal processes owing to strong attention to the energy neutral/positive wastewater treatment system. Anaerobic ammonium oxidizing bacteria (anammox bacteria) have been highlighted since 1990's due to their unique advantages including 60% less energy consumption, nearly 100% reduction for carbon source requirement, and 80% less sludge production. Side-stream short-cut nitrogen removal using anammox bacteria and partial nitritation anammox (PN/A) has been well established, whereas substantial challenges remain to be addressed mainly due to undesired main-stream conditions for anammox bacteria. These include low temperature, low concentrations of ammonia, nitrite, free ammonia, free nitrous acid or a combination of those. In addition, an anammox side-stream nitrogen management is insufficient to reduce overall energy consumption for energy-neutral or energy positive water resource recovery facility (WRRF) and at the same time to comply with nitrogen discharge regulation. This implies the development of the successful main-stream anammox based technology will accelerate a conversion of current wastewater treatment plants to sustainable water and energy recovery facility. This study discusses the status of the research, key mechanisms & interactions of the protagonists in the main-stream PN/A, and control parameters and major challenges in process development.

• Korean Journal of Construction Engineering and Management
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• v.6 no.6 s.28
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• pp.81-89
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• 2005

Construction projects are characterized that exposed high risks so feel strongly necessity of actively risk management that manage the time of project. but recent generally time management tools are not satisfied sufficient supporting the risk identify and risk analysis. Therefore this study purposed development the time management model that in order to improve existing problem of time management model in construction project and developed model could perform practical risk management in construction field. The new time management model focused on the risk management will be able to conduct critical path management and risk critical path management simultaneously.

• Journal of Arbitration Studies
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• v.32 no.4
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• pp.103-141
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• 2022

Traditionally, schedule analysis in Korea has been used, mainly through the Critical Path Method, to evaluate the claim for extension of time and/or the amount of liquidated damages for delay. Critical path method, however, cannot identify the delay event and its impact occurred in non-critical path especially in multi facility projects. In multi facility projects that comprise several independent but related facilities or structures, each facility has its own facility critical path the duration of which will be impacted by facility specific critical delays. Thus, only through the non-critical delay analysis along with the critical delay analysis damages not attributable to contractors may be remedied in full. Because all the records and pictures can reveal what has actually happened in post contract review, only the retrospective analysis rather than the prospective analysis based on the assumptions can establish the cause and allocate the each parties' responsibilities appropriately.

• Horticultural Science & Technology
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• v.31 no.1
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• pp.117-122
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• 2013

This research was carried out to clarify the germination characteristics with reference to hard seed coat in safflower. Morphologically, seed coat surface has hilum and micropyle which were evident during seed development stage. In the flower of developing seeds, the hilum area is connected with placenta of maternal tissue while the micropyle area is connected with the style of pistil. When the seeds imbibed, the hilum surface began to crack and the embryo protrudes through the hilum. To investigate the route for moisture absorption and gas exchange on the seed coat, the hilum and the micropyle were artificially sealed by paraffin. The seeds whose hilum were sealed could not germinate, which indicates that the exchange of moisture and oxygen takes place through hilum in safflower seeds. The germination was tested at $15^{\circ}C$, $20^{\circ}C$, and $25^{\circ}C$ by three substrates with different moisture conditions; top of paper method (hilum submerged in water), between-paper method, and soil seeding. The germination percentages were 31.3% at $15^{\circ}C$, 15.7% at $20^{\circ}C$ and 6.0% at $25^{\circ}C$ in the top of paper method; and 45.5% at $15^{\circ}C$, 30.0% at $20^{\circ}C$ and 14.0% at $25^{\circ}C$ in the between-paper method; and 80.0% at $15^{\circ}C$, 77.0% at $20^{\circ}C$ and 78.0% at $25^{\circ}C$ in the soil seeding, respectively. When the internal structure of hilum was investigated through SEM, it was found out consisting of vascular bundle element. In conclusion, the hilum of safflower seed was closely related with water absorption and gas exchange during initial germination process.

• Korean Journal of Construction Engineering and Management
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• v.13 no.3
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• pp.34-42
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• 2012

Green frame technology intended to facilitate the remodeling of apartment housing complexes in Korea and extend their service life has been developed. Green frame design is a Rahmen structure using composite precast concrete members and, unlike a bearing-wall structure, lifting and installing structural members accounts for major steps of structural construction. Therefore, if green frame structure construction is to be scheduled appropriately, systematic lifting plan needs to be developed in advance. Development of lifting plan also requires unit lifting process of composite PC members (columns and beams) that consist of green frame to be analyzed first. Therefore, this study attempts to analyze the lifting process of composite PC members used in green frame structure. To that end, lifting procedure and time of composite PC column and beam are estimated and applied to a project case to analyze the lifting cycle of reference floor. Outcomes produced herein will be used as key data for development of lifting plan in subsequent green frame structure construction.