• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.485-488
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• 2006

This research has evaluated flowability of ultra flowing self-compacting concrete, which is limitedly used for traditional building structures, in accordance with the first class regulations of Japan Society of Civil Engineering(JSCE) that can be applied to overcrowding-arrangement of bar, as a part of application methods that ultra flowing self-compacting concrete is applied to both precast and prestress bridge structures. The experimental results show that the flowability is acceptable in ternary blended among binary and ternary blended mixings, which satifies the first class regulation of JSCE. It is also concluded to use fly ash to increase viscosity of concrete in the case of segregation resistance because of low viscosity in the mixture of slag from blast furnace and limestone micropowder. Satisfying goals of every mixing after U-box self-compacting experiment, we conclude that ultra flowing self-compacting concrete is applicable to bridges and civil constructions of overcrowding arrangement of bar with evaluation of flowability of ultra flowing self-compacting concrete.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.489-492
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• 2006

Needs for the new technologies and cutting-edge Ultra Flowing Self-Compacting Concrete are emerging as the concrete structures are becoming bigger and more specialized recently. In North America and Europe, SCC, which has high resistance against flow ability and segregation, is being used as concrete material in applications such as precast and prestressed bridges, where reinforcing bars are overcrowdedly placed. In Korea, SCC has been utilized limitedly in building structures but its utilization should be expanded to engineering structures such as bridges. In this study, for the application in precast and prestressed bridges with overlycrowded reinforcing bars, USCC was mixed with admixtures to give a binary system and a ternary system according to the 1st grade rules by JSCE (Japan Society of Civil Engineers). Compressive strength and splitting tensile strength of the resulting USCCs were tested. Elastic modulus were compared with the values suggested in CEB-FIP code and ACI 318-05.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 추계 학술발표회 논문집
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• pp.401-404
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• 2006

This study is the part of the investigation of the state of the art in ultra high flowing concrete (UHFC), applied in practical field construction, in order to develop the technology for improving workability. This paper includes a brief introduction of water content variance properties in UHFC before and after the pumping operation. Test showed that water content in all parameters decreased after the pumping. This is due to the increase of an absorption ratio of coarse aggregate by the pressure of the pumping operation. thus decreasing the water content. Therefore it should be considered to find out the possibility, which can improve the workability, suffering from over viscosity by the lower water content, in field construction.

• Nuclear Engineering and Technology
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• 제53권11호
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• pp.3517-3527
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• 2021

New 80-MW (electric) ultra-long-life sodium cooled fast reactor core having inherent safety characteristics is designed with heterogeneous fuel assemblies comprised of driver and blanket fuel rods. Several options using upper sodium plenum and SSFZ (Special Sodium Flowing Zone) for reducing sodium void reactivity are neutronically analyzed in this core concept in order to improve the inherent safety of the core. The SSFZ allowing the coolant flow from the peripheral fuel assemblies increases the neutron leakage under coolant expansion or voiding. The Monte Carlo calculations were used to design the cores and analyze their physics characteristics with heterogeneous models. The results of the design and analyses show that the final core design option has a small burnup reactivity swing of 618 pcm over ~54 EFPYs cycle length and a very small sodium void worth of ~35pcm at EOC (End of Cycle), which leads to the satisfaction of all the conditions for inherent safety with large margin based on the quasi-static reactivity balance analysis under ATWS (Anticipated Transient Without Scram).

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 1998년도 춘계학술대회 논문집
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• pp.203-206
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• 1998

In this paper, specimens stirred with the several kinds of benzotriazole(following as BTA) addition which is very effective to decrease the streaming electrification, are tested to investigate the change of properties for insulating fluid using in ultra-high voltage transformer, and it will give a guideline to find out a proper quantity of BTA addition for the most effective suppression against the streaming electrification. In GC, we could not find out the change of the physical properties in an insulating fluid by BTA. In a flowing transformer oil, the characteristics on dielectric of specimen contained BTA 10[ppm] are superior to the others.

• 대한토목학회논문집
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• 제28권1A호
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• pp.155-163
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• 2008

최근 구조물이 대형화, 특수화 및 초고층화 되고 있는 건설현장에서는 일반콘크리트보다 더 뛰어난 고성능 콘크리트의 시험적인 시공이 증가하고 있는 추세이다. 교량의 경우 과거 동바리 공법에 의한 시공은 소음 및 분진과 공사기간의 장기화 등의 문제로 점점 감소되었으며, 최근에는 시공기간 단축 및 도심지 환경에 적합한 프리캐스트로 시공하는 현장이 급속히 증가하고 있다. 교량구조물의 경우 휨에 대한 안전성을 확보하기 위하여 과밀배근된 부재를 생산하고 있는 실정이며, 과밀배근된 부재를 생산하기 위하여 일반콘크리트보다 유동과 충전성능이 월등한 초유동 자기충전 콘크리트가 적용되는 것이 바람직하다고 판단된다. 본 연구에서는 고로슬래그 및 플라이애쉬를 2성분계 및 3성분계 배합을 통하여 과밀배근된 교량구조물에 초유동 자기충전 콘크리트를 적용하기 위한 방법으로 과밀배근된 구조물에 적용할 수 있는 일본 토목학회의 JSCE 1등급 규정에 따른 초유동 자기충전 콘크리트의 유동 특성을 검토하였다.

• 상하수도학회지
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• 제26권4호
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• pp.521-533
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• 2012

Interest in application of ultraviolet light technology for primary disinfection that used for the treatment of water for consumption and wastewater has increased significantly in recent years. Analysis of these systems has been carried out using Computational Fluid Dynamics (CFD) procedure. It offers advantages over other techniques in specific circumstances. CFD has emerged as a powerful tool to aid design of a UV reactor by providing the UV dose delivered by the proposed reactor design and allowing engineers to evaluate alternative designs in much less time and at a reasonable cost. In this study, five different configurations of the apparatus depending on the location of the exit are evaluated in terms of maximum dose, minimum dose, flow patterns, particle tracks and transient dose. The configuration 3 results have higher minimum UV dose value and uniform particle distribution of the UV dose on the outlet than other's.

• 반도체디스플레이기술학회지
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• 제20권1호
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• pp.25-31
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• 2021

The semiconductor and display equipment demands an ultra-fine precision of several nm to several ㎛, and the scale is getting smaller due to the explosive development. The manufacturing process equipment for such products with ultra-fine precision is very sensitive to ultra-small vibrations flowing from the floor, resulting in problems of production defects and yield degradation. The vibration criteria are a standard that regulates the vibration environment of the floor where such precision process equipment will be installed. The BBN vibration criteria defined the allowable vibration velocity level in the frequency domain with a flat and inclined line and presented a rating according to it. However, the actual vibration criteria have appeared with various magnitudes in the frequency domain according to the dynamic characteristics of individual equipment. In this study, the relationship between the relative motion of two major points in the equipment and the vibration magnitude of the floor is presented using the frequency response function of a simple 3-DOF model. It is describing the magnitudes according to the frequency of the floor vibration that guarantees the allowable relative motion and this can be used as the vibration criteria. In order to obtain the vibration criteria experimentally a method of extracting through a modal test was introduced and verified analytically. It provides vulnerable frequency and magnitude to floor vibration in consideration of the dynamic characteristics of individual equipment. And it is possible to know necessary to improve the dynamic characteristics of the equipment, and it can be used to check the vibration compatibility of the place where the equipment will be installed.

• 한국초전도저온공학회:학술대회논문집
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• 한국초전도저온공학회 2002년도 학술대회 논문집
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• pp.27-30
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• 2002

The particle velocity in superfluid helium (He II) induced by a gas dynamic shock wave impingement onto He II free surface were studied experimentally by using Schlieren visualization method with an ultra-high speed video camera. It is found form visualization results that a dark zone in the immediate vicinity of the vapor-He II interface region is formed because of the high compressibility of He II and is developed toward bulk He II with the flowing-down speed of the vapor-He II interface. The mass velocity behind a transmitted compression shock wave that is equal to the contraction speed of He II amounts to 10 m/sec, the Reynolds number of which reaches $10^{7}$. This fact suggests that the superfluid shock tube facility can be applied to an experimental facility for high Reynols number flow as an alternative to the superfluid wind tunnel.

• 전기학회논문지
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• 제59권8호
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• pp.1406-1415
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• 2010

As process technology for semiconductor goes beyond the ultra-deep submicrometer regime, interconnect reliability on a chip has become a serious design concern. As process parameters scale, interconnect widths are reduced rapidly while the current flowing through the interconnect does not decrease in a proportional manner. This trend increases current densities in metal interconnects which may lead to poor reliability for electromigration. Hence, it is critical to estimate the current amount passing through the interconnects earlier in semiconductor design stages. The purpose of this paper is to propose a fast yet accurate current estimation technique that can offer not only analysis time equivalent to those offered by the previous approximation methods but also a relatively precise estimation by using closed-form equations. The accuracy of the proposed technique was confirmed to be about 8 times better on average when compared to the previous work.