• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2004년도 춘계학술발표회
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• pp.58-65
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• 2004

Recently, the top & down method with drilled shafts as a foundation of high rise building is often adopted for the purpose of construction period reduction and construction cost effectiveness. It is common to omit the loading test as a Quality assurance on account of the high capacity of drilled shafts for the top & down method. It seems that the capacity of drilled shaft in recent top & down method is beyond that of conventional loading test method.However, the quality assurance for the drilled shaft as foundation of high rise building becomes much more important since the drilled shaft should bear much higher working load. It may be a small scale test pile could be an alternative as a quality assurance for the drilled shaft with high capacities. Through a case study, this paper gives an idea for solving the limitation of the conventional loading test method for the quality assurance of drilled shaft with high capacities. In particular, this paper analyzed the scale effect for a small drilled shaft installed into bedrock, which could be used for an alternative.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2006년도 춘계학술논문 발표대회 제6권1호
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• pp.137-140
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• 2006

As underground construction is a large component of the cost of construction and a term of works in Top-Down construction, it is important to reduce the term of works in underground construction. The purpose of this study is to analyse buckling stress and load of prefounded columns as the process of excavation is changed, and propose a suitable process of excavation to increase the speed of works. When several floors are excavated, the valid buckling length of profounded column is increase and allowable buckling stress is decreased. The result shows that all columns are safe in buckling down to B3th story whether 2 stories or 3 stories are excavated straightly. However, several columns are not safe from B4th story when 2 or 3 stories are excavated straightly. With these results, a process can be designed that first B3 stories are excavated straightly, and then excavate B4th story putting concrete on B1st and B2nd story.

• 국제학술발표논문집
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• The 3th International Conference on Construction Engineering and Project Management
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• pp.788-793
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• 2009

Constructing substructures by using Top-Down or Downward method needs an efficient formwork system because of difficulties in supporting concrete slabs from the bottom while excavation is in process. Existing underground formwork systems can be classified by three types: graded ground supported type (Slab On Grade, Beam On Grade), suspension type (Non Supporting Top Down Method), and bracket supported type (Bracket Supported R/C Downward). Each method has its own advantages and limits. Application of a specific formwork system for a given construction site is determined by various conditions and affect construction time and cost. This paper presents a newly developed underground non-supporting formwork system, which combines the advantages of a suspension type and a bracket supported type while it overcomes limits of two types. The developed system has a moving formwork which is supported by suspension cables hanging from the bracket placed at the top of pre-installed substructure columns. Then, the moving formwork is repeatedly lowered down for the next floor below to support concrete slab during curing. The details of this bracket and cable supported system have been investigated for the improvement of easiness in construction.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2001년도 추계학술대회 논문집
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• pp.321-325
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• 2001

This paper describes the basic structure of high-precision warm forging process for ball joint socket. If this research is successfully finished, We expect that productivity improvement, reduction of material cost and machining process, and cost down than conventional warm forging process.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 하계종합학술대회 논문집(5)
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• pp.107-110
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• 2002

Soft masks mean that part or all of the program code for operating system or applications are located in the EEPROM or flash ROM. Since Soft masks allow errors to be corrected and programs to be modified quickly and at minimal cost, they are used primarily during testing and in the field trials. This paper introduces a hardware architecture of IC card for soft masks. We suggest a new down loading scheme for soft-mask ROM connected by an I/O interface. This scheme saves the new IC card development cost and time.

• 대한토목학회논문집
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• 제41권2호
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• pp.151-159
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• 2021

국내 건설공사 단가의 적정성과 시장 상황과의 괴리에 대한 논란은 오랜 기간 지속되어 왔다. 국내 건설공사 단가는 특정 소수의 공공기관이 주체가 되어 수립되는 공공기관 중심의 Top-Down 방식으로 수립된다. 실제 시장가격은 유가, 자재비, 노무비 등에 따라 변동이 심하며 소수의 공공기관에서 수많은 업체의 시장가격에 대한 방대한 조사를 수행하여 단가를 수립한다는 것은 사실상 물리적으로 불가능하다. 해외 선진국의 경우, 공공 건설공사 단가의 보완하기 위한 수단으로 민간업체가 주체가 되어 수립되는 민간 중심의 다양한 원가정보가 함께 존재하며 국내에서도 공공뿐만 아니라 민간 중심의 단가 정보 확대를 통한 효율적인 공사비관리가 필요하다. 본 연구에서는 국내 공공 중심의 건설공사 단가체계의 한계를 보완하는 민간 중심의 Bottom-Up 방식의 단가 수립 체계 개발을 목적으로 개발의 기본 방향을 설정하기 위한 연구를 수행하였다. 국내 건설공사 단가 수립 체계 분석을 통하여 문제점을 도출하고 해외 건설공사 단가 체계를 벤치마킹하여 개선 방향을 도출하였으며, 분석결과를 종합하여 국내 민간 중심의 건설공사 단가 수립 체계 개발을 위한 기본 방향을 설정하였다.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• 제5B권3호
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• pp.277-282
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• 2005

This paper describes a step-down AC voltage regulator using an AC chopper and auxiliary transformer, which is a series connected to the main input. The detail design of the AC regulator, logic and PWM pattern of the AC chopper is described and the three-phase AC regulator using two single­phase AC choppers with a three transformer configuration is proposed for three-phase application. The proposed three-phase system has the advantages of lower system cost due to reduced switch number and gate driver circuit as well as advantages of decreased size and weight because it uses a series compensated scheme. The proposed AC regulator has many benefits such as fast voltage control, high efficiency and simple control logic. Experimental results indicate that it can be used as a step-down AC voltage regulator for power saving purposes very efficiently.

• 교육녹색환경연구
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• 제13권1호
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• pp.50-57
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• 2014

The educational facilities is the facility wining the specific gravity which is the most abundant by 269s (25.5%) among the godfather lease application facilities (1056)s of the abolition of school. In case of reusing the closing down a school as the educational facilities there is no legal matter which is under the separate punishment in comparison with the other facility according to the materials of the Ministry of Environment in 2013, and I am analyze that minimum cost is spent on a remodeling and it is most much used. The pattern study thinks about a purpose with the master plan through the plan characteristic derivation according to the analysis of current situation of the domestic closing down a school application educational facilities in which the related study is nonexistent and type in the educational facilities plan of the closing down a school still afterward in being utilized for reference data and guide book.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2004년도 하계종합학술대회 논문집(1)
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• pp.201-204
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• 2004

In this paper, a down-converter that can work for L-band RF front-end of DMB receiver is designed. Since DRK-02, a reference for our work, had been designed for a stationary receiver, not for mobile one, the supply voltage is set relatively high of 8.5V. We improve it with 3.3V and save design space and cost by employing only one Mixer and IF_Amp comparing to the reference one in which two Mixers and two IF_Amps are used.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.43-46
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• 2008

In Top-Down construction for underground structures, the placement of slab as a horizontal supporting member against lateral earth pressure is an important process in determining construction time and cost. Usually, a reinforced concrete perimeter girder distributes concentrated lateral loads from earth retaining structures such as Cast-in-place (CIP) piles. By combining the function of the R/C perimeter girder and horizontal slabs, the Opened Slab Method is efficient for reducing construction time by elimination of time-consuming formwork for traditional perimeter girders. The structural performance of the method is also discussed in this paper.