• Journal of the Korean Institute of Telematics and Electronics
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• v.14 no.3
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• pp.18-24
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• 1977

In this paper, a series inverter circuit is constructed by using the pinch-off characteristics of FET, and itsoutput characteristics is analysed for the variation of gate bias frequency and load. The above constructed circuit could eliminate the unstable output characteristics of SCR-series inverter fir chit by the changes of gate bias frequency and load resistor. But the current capacity of the FET-series inverter circuit is relatively small, and is recommended to be used for light loads.

• Proceedings of the Korean Geotechical Society Conference
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• 2006.10a
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• pp.490-496
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• 2006

In order to design accurately plastic board drain (PBB) method, it is important to determine the equivalent circle of PBD. In this paper, a series of numerical analyses on soft ground improved by PBD were carried out, in order to investigate the resonable equivalent circle of PBD considering consolidation behavior of improved soft ground by PBD. The applicability of numerical analyses, in which an elasto-viscoplastic three-dimensional consolidation finite element method was applied, could be confirmed comparing with results of a series of model tests on consolidation behaviors of soft ground improved by PBD. And, through the results of the numerical analyses, consolidation behaviors of soft ground during consolidation was elucidated, together with the equivalent circle of PBD considering consolidation behaviors.

• The Journal of Engineering Geology
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• v.23 no.2
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• pp.105-115
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• 2013

Increasing the river cross-section by barrage construction causes rises in the average river water levels and discharge rates in the rainy season. The time series patterns for groundwater levels measured at 23 riverside monitoring wells along the lower Nakdong River are compared for two cases: before and after water-filling at the Changnyeong-Haman Barrage. Monthly average groundwater levels indicate a distinct increase in groundwater levels in the upstream riverside close to the barrage. River-water level management by barrage gate control in August, during the rainy season, resulted in a 0.1 m decrease in groundwater levels, while water-filling at the barrage in December caused a 1.3 m increase in groundwater levels. The results of hierarchical cluster analysis indicate that seven groundwater monitoring wells and river water levels were in the same group before barrage construction, but that this number increased to 14 after barrage construction. Principal component analysis revealed that the explanation power of two principal components corresponding to river fluctuation, PC1 and PC2, was approximately 82% before barrage construction but decreased to 45% after construction. This finding indicates that the effect of the river level component that contributes to change in groundwater level, decreases after barrage construction; consequently, other factors, including groundwater pumping, become more important. Continuous surveying and monitoring is essential for understanding change in the hydrological environment. Water policy that takes groundwater-surface water interaction into consideration should be established for riverside areas.

• Journal of Korea Water Resources Association
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• v.35 no.6
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• pp.807-816
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• 2002

The purpose of the present study was to evaluate the changes of flow duration characteristics of a large river basin due to construction of a dam. The changes of water surface are quantified from remote sensing film taken before and after dam construction. Gongiu gauging station was selected to analyze the changes of flow duration, and annual exceedance series of Gongju and Kyuam gauging station were selected to estimate the changes of flood quantile before and after dam construction. From the analysing results, it was found that the construction of dam contributes to make new duration stable and to decrease flood flow. In conclusion, it was confirmed that the construction of the dam is useful for water supply and flood prevention.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.1140-1147
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• 2009

Productivity measurement of construction machinery is a significant issue faced by many contractors especially those involved in earthwork projects. Traditionally, equipment production rate has been estimated using data available in manufacturers' catalogues, results of previous construction projects, or personal experience and assessments of the site personnel. Actual production rates obtained after the completion of a project demonstrate the fact that most of these methods fail to provide accurate results and as a direct consequence, may lead to unrealistic project cost estimations prepared by the contractors. What makes this more critical is that in most cases, inadequate cost estimations lead the entire project to exceed the initial budget or fall behind the schedule. In this paper, a linear regression method to estimate bulldozer productivity is introduced. This method has been developed using SPSS-16 software package. The presented method is used to estimate the productivity of Komatsu D-155A1 series which is commonly used in many earthmoving operations in Iran. The data required for the numerical analysis has been collected from actual site observation and productivity measurement of 60 pieces of D-155A1 series currently being used in several earthmoving projects in Iran. Comparative analysis of the output data of the presented regression method and the existing productivity tables provided by the manufacturer shows that when compared to the actual productivity data collected on the jobsite, a significant increase in accuracy and a remarkable reduction of data variance can be achieved by using the presented regression method.

• International conference on construction engineering and project management
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• 2020.12a
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• pp.63-74
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• 2020

The assembly of modular construction requires a series of thoroughly-considered decisions for crane lifting including the crane model selection, crane location planning, and lift path planning. Traditionally, this decision-making process is empirical and time-consuming, requiring significant human inputs. Recently, research efforts have been dedicated to improving lift planning practices by leveraging cutting-edge technologies such as automated data acquisition, Building Information Modelling (BIM) and computational algorithms. It has been demonstrated that these technologies have advanced lift planning to some degree. However, the advancements tend to be fragmented and isolated. There are two hurdles prevented a systematic improvement of lift planning practices. First, the lack of formalized lift planning workflow, outlining the procedure and necessary information. Secondly, there is also an absence of a shared information environment, enabling storages, updates and the distribution of information to stakeholders in a timely manner. Thus, this paper aims to overcome the hurdles. The study starts with a literature review in combination with document analysis, enabling the initial workflow and information flow. These were contextualised through a series of interviews with Australian practitioners in the crane-related industry, and systematically analysed and schematically validated through an expert panel. Findings included formalized workflow and corresponding information exchanges in a traditional lift planning practice via a Business Process Model and Notation (BPMN). The traditional practice is thus reviewed to identify opportunities for further enhancements. Finally, a BIM-based lift planning workflow is proposed, which integrates the scattered technologies (e.g. BIM and computational algorithms) with the aim of supporting lift planning automation. The resulting framework is setting out procedures that need to be developed and the potential obstacles towards automated lift planning are identified.

• 한국방재학회:학술대회논문집
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• 2009.02b
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• pp.153.2-153.2
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• 2009

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.279-284
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• 2002

Prestressed concrete(PSC) bridge structures with a number of continuous spans has been segmentally built in many countries. These methods include incremental launching method, movable scaffolding method, full staging method and balanced cantilever method. In these segmentally constructed prestressed concrete bridges, many construction joints exist and these construction joints are weak points in PSC bridges. The prestress force can be introduced prestress force continuously through the construction joints of PSC bridge superstructure using tendon couplers. The main objective of this study is to evaluate the structural behavior and ultimate flexural strength of construction joints in PSC girder bridge members. To this end, a comprehensive experimental program has been set up and a series of full-scale tests have been performed. Ultimate flexural strength of construction joint in PSC members with tendon couplers is decreased by approximately 10% for non-coupled members.

• KIEAE Journal
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• v.13 no.2
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• pp.33-38
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• 2013

Limited resources for construction material in the Mae-Hae region, a remote Northern Thailand, acted as an impetus to introduce a new way for constructing their dwellings. The new construction material brought new construction methodology, namely, using earth and bamboo which are indigenous materials, readily available for them to use. Using indigenous material at Mae-Hae region was most ecological and logical method for establishing sustainable dwellings both in terms of monetary and ecological reasons. Prior to the construction at Mae-Hae, Thailand, series of experimental tests on the strength of rammed earth were performed off site at our university and also brought soil samples from the actual job site at Mae-Hae for detailed soil analysis. Through the tests, integrity of the earth and characteristics of the soil were established to build a small senior citizen center as an example. This appropriate technology is expected to contribute to the sustainable construction at Mae-Hae.

• Journal of the Korean Society of Safety
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• v.11 no.1
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• pp.108-120
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• 1996

It is a problems in industrial accidents that the knowledge for industrial accidents is obtained by experience, not by experiment. This experiential knowledge is obtained by Investigating accident cases and utilizing those for safety education. Therefore, in this paper, the situation about the serious accident of construction is analyzed by occupation, a kind of construction, time group, season, type of accident, and accidental cause. And the mutual · relations of these factors are studied. The most frequent type of the serious accidents of construction Is the falling accident. It happenes most frequently at apartment construction among kinds of construction and to structural worker, finishing worker, normal worker in order among occupations. And it is found that the most critical causes of the falling accident are the imperfection of safety facilities and unwearing of protection equipments, so a number of accidents can be reduced by the expansion of safety facilities and wearing of protection equipments absolutely. The counterplan of prohibition of accidents and the direction of government policy are presented by a series of nalyses for accident cases.