• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.1 s.256
• /
• pp.26-35
• /
• 2007

The vehicle of urban transit is a complex system that consists of various electric, electronic, and mechanical equipments, and the maintenance cost of this complex and large-scale system generally occupies sixty percent of the LCC (Life Cycle Cost). For reasonable establishing of maintenance strategies, safety security and cost limitation must be considered at the same time. The concept of system reliability has been introduced and optimized as the key of reasonable maintenance strategies. For optimization, three preceding studies were accomplished; standardizing a maintenance classification, constructing RBD (Reliability Block Diagram) of VVVF (Variable Voltage Variable Frequency) urban transit, and developing a web based reliability evaluation system. Historical maintenance data in terms of reliability index can be derived from the web based reliability evaluation system. In this paper, we propose applying inverse problem analysis method and hybrid neuro-genetic algorithm to system reliability optimization for using historical maintenance data in database of web based system. Feed-forward multi-layer neural networks trained by back propagation are used to find out the relationship between several component reliability (input) and system reliability (output) of structural system. The inverse problem can be formulated by using neural network. One of the neural network training algorithms, the back propagation algorithm, can attain stable and quick convergence during training process. Genetic algorithm is used to find the minimum square error.

• 기술발표회
• /
• s.2006
• /
• pp.279-291
• /
• 2006

This study shows decision-making process for selection of cutoff wall on a wastewater treatment project. There are 10 different cut-off wall methods So, we examine the site to gather information for find appropriate methods. After using that information, 10 cutoff wall methods are reviewed for analysis. Through brainstorming, four alternatives are selected for design VE item. Following the standard VE process, we established performance criteria and evaluated function score(F) using questionnaire. The questionnaires, brainstorming and AHP method for weighting on performance criteria and evaluate function score increased the reliability of this selection process. Water Jet method, one of four methods, has the best function score(F=92.71) and the lease construction cost(as cost index 1,000). The value score also highest as 92.7, so we select the method. The result is value innovation type In addition, the authors try to calculate the environmental burden in selection process using LCA. We cannot conduct the full LCA as defined ISO, so perform Simple LCA In LCA result, the cut-off grouting has the least environmental burden as index 9.09E+01 and Water Jet method has following as the second. To selection best method to specific area and purpose, design VE/LCG process used as useful tool and it is needed to develop integrated method that evaluate VEILCC and LCA as one-set process.

• Journal of Aerospace System Engineering
• /
• v.12 no.5
• /
• pp.76-88
• /
• 2018

Space agencies such as NASA, ESA, and the US military provide guidelines and standards for PA(product assurance) requirements and plans. In recent years, major satellite manufacturers around the world have been mitigating PA requirements and processes by tailoring. PA tailoring has been implemented to improve the cost and schedule efficiency. PA tailoring can be accomplished based on various factors such as mission, classification of mission risk, complexity, development cost, life cycle, etc. In this study, PA tasks according to the mission risk classification proposed by NASA are investigated, and the tailoring method is suggested for the optimization of the development cost and schedule. In particular, the classification of mission risk for the satellites under development or operation in Korea is performed, and PA characteristics in accordance with mission risk are analyzed.

• Journal of Korea Society of Industrial Information Systems
• /
• v.5 no.2
• /
• pp.47-55
• /
• 2000

To date many software engineering cost models have been developed to predict cost, schedule, and effort of the software under development. The COCOMO Ⅱ is well- suited for the new software development life cycle such as non-sequential and rapid- development processes. The traditional regression approach based on the least square criterion is the most commonly used technique for empirical calibration in the COCOMO Ⅱ model. It has a few assumptions frequently violated by software engineering data sets. The source data is also generally imprecise in reporting size effort, and cost-driver ratings, particularly across different organizations. And that the outlier for the source data is a peculiarity and indicates a data point. To cope with difficulties, in this paper, we propose a new regression method for calibrating COCOMO Ⅱ post-architecture model based on the minimum relative error(MRE) criterion. The characteristic of the proposed method is insensitive to the extreme values of the data in the empirical calibration. As the experimental results, It is evident that our proposed calibration method MRE was shown to be superior to the traditional regression approach for model calibration, as illustrated by the values obtained for standard deviation(^σ), and prediction at level LPRED(L) measures.

• Journal of KIBIM
• /
• v.5 no.4
• /
• pp.53-62
• /
• 2015

Korea has been at the forefront of green growth initiatives. In 2008, the government declared the new vision toward 'low-carbon society and green growth'. The government subsidies and Feed-in Tariff (FIT) increased domestic usage of solar power by supplying photovoltaic housing and photovoltaic generation systems. Since 2000, solar power industry has been the world's fastest growing source with the annual growth rate of 52.5%. Especially, BIPV(Building Integrated Photovoltaic) systems are capturing a growing portion of the renewable energy market due to several reasons. BIPV consists of photovoltaic cells and modules integrated into the building envelope such as a roof or facades. By avoiding the cost of conventional materials, the incremental cost of photovoltaics is reduced and its life-cycle cost is improved. When it comes to atypical building, numerous problems occur because PV modules are flat, stationary, and have its orientation determined by building surface. However, previous studies mainly focused on improving installations of solar PV technologies on ground and rooftop photovoltaic array and developing prediction model to estimate the amount of produced electricity. Consequently, this paper discusses the problem during a planning and design stage of BIPV systems and suggests the method to select optimal design of the systems by applying the national strategy and economic policies. Furthermore, the paper aims to develop BIM tool based on the engineering knowledge from experts in order for non-specialists to design photovoltaic generation systems easily.

• Journal of the Society of Naval Architects of Korea
• /
• v.58 no.5
• /
• pp.294-302
• /
• 2021

In this study, the 3D printing technique called design for additive manufacturing (DfAM) that is widely used in various industries was applied to marine leisure ships of equipment. The DfAM for the stanchion for crew safety was applied to the equipment used in an actual recreational craft. As design constraints, the design alternatives were not to exceed the safety and weight of the existing stainless steel material, which were reviewed, and the production of a low-cost FFF-type 3D printing method that can be used even in small shipyards was considered. Until now, additive manufacturing has been used for manufacturing only prototypes owing to its limitations of high manufacturing cost and low strength; however, in this study, it was applied to the mass production process to replace existing products. Thus, a design was developed with low manufacturing cost, adequate performance maintenance, and increased design freedom, and the optimal design was derived via structural analysis comparisons for each design alternative. In addition, a life-cycle assessment based on the ISO 1404X was conducted to develop sustainable products. Through this study, the effectiveness of additive manufacturing was examined for future applications in the shipbuilding industry.

• Journal of Korean Tunnelling and Underground Space Association
• /
• v.20 no.1
• /
• pp.131-144
• /
• 2018

The urban center of a large city has a high concentration ratio of population, commerce, and traffic. Therefore, the expected effect is high from the introduction of the urban utility tunnel and it also has sufficient economic feasibility considering life cycle cost. Moreover, the construction cost can be greatly reduced if it is included in a large underground development such as a subway or a complex transfer center construction. However, it is not reflected in actual underground development plan. When planning a urban utility tunnel in Korea, it is expected to have difficulties such as the cost of relocation of the existing Life-Line, conflicts among the individual facility institutions, procurement of construction resources and sharing. Furthermore, it is possible to promote the project only if a consensus is drawn up by a collective council composed of all facilities and project developers. Therefore, an optimal alternative should be proposed using economic analysis and feasibility assessment system. In this study, the analytic hierarchy process (AHP) is performed considering the characteristics of urban areas and the importance of each indicator is quantified. As a result, we can support reasonable design capacity optimization using the feasibility assessment system.

• Journal of Sericultural and Entomological Science
• /
• v.2
• /
• pp.49-61
• /
• 1962

The insect Diplosis mori Yokoyama is causing extensive destruction of mulberry trees in Korea with a resultant loss in silk production. This study was made to determine an effective method of control. Methods and Materials Used Preliminary studies were made to determine more exactly the life cycle of the insect. Based on this information, various control measures were tested, including the use of spray methods with BHC and control of larvae by tilling. Results Obtained 1. Life cycle studies (a) In the Suwon area, this-insect has 5 generations per year. The first starts in the later part of June and the final cycle ends in the later part of September. (b) The adult insects appear about 7: 00-8: 00 P.M. and live for 2-5 days. Females live in longer periods than the male. (c) Larvae lives inside the second and third stipules (A. B.) before mulberry leaf development. They cause extensive damage to the leaves at the point where they are attached to the stem. (d) Weather conditions considerably affect the life cycle. The pupa particularly are affected and not be able to change into the moth stage when there is a long period of no rain. (e) Larvae are large......0.3 to 2.0mm......and are milky-white immediately after hatching but turn to pinkish as the worm matures. The matured worm has a jumping ability up to 15-20cm. The worm burrows into the ground 1.5 to 3.0 cm before changing into the pupal stage. (f) The pupal stage usually lasts 7-8 days, in summer weather conditions and the pupa is surrounded with a coarse cocoon. (g) These insects, as a general rule, overwinter as pupae but sometimes as larvae. 2. Control measures (a) BHC dust applied on the ground seem most effective. It should be done 4-5 days after the worm has burrowed into the ground. For this control, it is recommended that 6kg of a 2% formation Tanbo(l0ares) be used. (b) For the effective spraying against the fly, it is recommended that a formulation of liquid BHC spray terials be used at the rate of 400-600 liters per Tanbo. (c) Tillage methods which provide a cover of soil 5cm or more in depth above infested areas will effect-maively prevent the emergence of the fly from the pupal stage. 3. Conclusions Methods of control against Diplosis mori Yokoyama can be tied more closely to the life cycle of the insect with more effective results. Further studies are needed to complete information on possible controls during or after hibernation. Economic studies on the cost of these control measures are also needed.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.33 no.2
• /
• pp.791-800
• /
• 2013

Needs for developing a better way of cost estimating process for public construction projects have been widely recognized. Those needs are mainly from the early phases of the project through the construction life cycle due to the its importance to the control process. In contrast to the traditional estimating method based on unit-price references, this research utilized this following process. The first step is analyzing the real cost data from actual cost activities (2000~2010) about the statement of P.S.C(Prestressed Concrete) Box Girder Bridge. The collected data was broken into four categories based on technical construction methods such as I.L.M(Incremental Launching Method), M.S.S(Movable Scaffolding System), F.S.M(Full Staging Method), and F.C.M(Free Cantilever Method). The second, actual design documents including the actual cost estimating documents, drawings and specifications were carefully reviewed to cluster the cost itemized statement from four categories. It was also attempted to seek the proper breakdown of standard works that are responsible for more than 95 percentage in each categories in terms of its cost. The third, this research comes up the index for standard unit materials and unit price of standard work and develops the approximate estimating model applying for the specification(length and breadth of bridges) per square area that the user takes as well as suggests the practical application plan within the original time alloted.

• Korean Journal of Construction Engineering and Management
• /
• v.22 no.6
• /
• pp.96-106
• /
• 2021

The PC structure based on the OSC (Off-Site Construction) is mentioned as a representative method of innovation in the construction industry that converts the existing construction environment from site-centered to factory production-transportation-site assembly. However, recent research on PC method has focused on improving the functions of subsidiary materials and improving the production system to increase productivity and institutional / policy R&D that can be universally applied to the life-cycle stage of ordering / design /construction is insufficient. In particular, the absence of standardized cost calculation standards makes it difficult to calculate and verify of objectified appropriate construction cost. So which is an obstacle to the activation of the PC method. In this study, the standards for construction costs of domestic and foreign PC method were surveyed and similar Construction Standard Production Rates were analyzed to confirm the product structure suitable for PC method. Subsequently, the construction procedures and input resources for each PC subsidiary materials were identified through on-site surveys to derive component for subsidiary materials, and the factors of change in the product according to the construction characteristics(height, weight of subsidiary material) were verified. As a result the standard product calculation system suitable for the site installation of the PC method for apartment was presented.