• 자원리싸이클링
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• 제15권3호
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• pp.66-73
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• 2006

망간단괴 제련 과정에서 니켈 이온의 회수량을 높임과 동시에 니켈 폐수를 제거하기 위한 기초 연구를 수행하기 위해 인공니켈 폐수와 실폐수에 대해 흡착제로 망간단괴를 사용하여 고정층 연속 흡착 실험을 하였다. 인공니켈폐수에 대한 고정층 흡착 칼럼의 충전층 높이, 유입수의 유량, 그리고 유입되는 니켈폐수의 농도를 변화시키면서 흡착 특성의 변화양방을 검토하였다. 흡착실험의 결과를 Bohart-Adams식에 적용하여 고정층 칼럼에서의 흡착량 및 흡착속도상수를 계산하여 비교하였다. 또한 고정 흡착층 파과곡선으로부터 유입수의 유량과 흡착질의 초기농도의 변화에 따른 각 칼럼의 흡착량의 변화를 검토하였다. 직렬 연결 칼럼들에 대해 초기 칼럼에서 최종 칼럼으로 흡착이 진행됨에 따라 흡착량은 상승하는 것으로 파악되었다. 실폐수를 고정층 칼럼에 유입하여 흡착특성을 살펴 본 결과, 충전층 높이에 따른 흡착양상의 변화가 인공폐수와 달리 뚜렷하게 관찰되지 않았는데 이는 인공폐수에 비해 실폐수 중의 $Ni^{2+}$의 농도가 현저히 높기 때문인 것으로 판단되었다. 실폐수의 흡착율에 미치는 망간단괴 입자크기의 영향에 대한 검토에서는 흡착제 입자가 작아질수록 니켈 이온의 흡착율이 다소 상승하는 것으로 파악되었다.

• 충청수학회지
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• 제14권2호
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• pp.55-66
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• 2001

A new stability analysis of QR factorizations using the two types of Householder reflections is presented. It shows that the use of the common type(the first) in QR factorizations with pivoting for size by row and column exchanges leas to rowwise more stability, although the second type has been used in Householder transformation for the better purpose. A row-oriented backward error bound for the second type Householder QR factorizations with column pivoting is drived.

• 한국대기환경학회지
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• 제16권1호
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• pp.1-10
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• 2000

The behavior of aerosos due to gravitational coagulation was studied experimentally and numerically. In experimental study, the geometric mean particel size increased as time elapsed in a vertical tube column, while the size decreased when the tube was set horizontally. The particle size distribution was observed to maintain the lognormal form during the coagulation process. Separately, numerical calculations were performed for studying the aerosol behavior under gravitational and Brownian coagulation using the moment method. By comparing the expeimented results with the numerical predictions, the governing mechanism of the aerosol behavior proved to be gravitational coagulation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.347-352
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• 2002

Recent trends in the construction of building frame feature the increase use of composite steel concrete members functioning together in what terms of mixed structural systems. One of such systems, RCS(reinforced concrete column and steel beam) system is introduced and closely examined focusing on bearing strength of the composite joint in this paper. The main objective of this study was to develope one of details to increase bearing capacity while bearing failure is one of the two primary modes of failure in RCS system. Local bearing tests with specimens about 1/3 of the actual concrete column size were performed applying uniform load through steel plate with 100$\times$110mm size. Test results show that specimens with the bearing reinforcement detail developed in this study enhanced the bearing strength by 1.71~3.02 compared to concrete cylinder strength.

• 한국해양공학회지
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• 제22권5호
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• pp.138-141
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• 2008

This paper treats the development of a new type of deep draught semisubmersible offshore structural shape that has excellent heave motion response and less down-time. This new type of semisubmersible shape is characterized by heave dampers at each pontoon corner and appropriate column size adjustment to achieve the desired cancellation and resonance motion period. It was found that the final model had efficient workability, based on the wavescatter diagrams for the GoM and North Atlantic ocean, due to less heave motion, although the specific heave response at the 100 year return period wave condition in the North Atlantic was more or less increased.

• 한국고분자학회:학술대회논문집
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• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
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• pp.202-202
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• 2006

With a modern size exclusion chromatography (SEC) column, molecular weight analysis of a polymer sample takes about 10 min. However, it is desirable to reduce the analysis time further, in particular, for high throughput measurements required in combinatorial analyses or 2D-HPLC analyses. We implemented the high temperature SEC for the purpose. By inserting a narrow bore tubing between the column and the detector, a sufficient backpressure can be maintained to prevent the mobile phase from boiling and the effluent is cooled down enough when it reaches the detector. Therefore, a normal SEC detector can be used without any modification. The SEC resolution is greatly improved at the elevated temperature at high flow rate which allows high speed operation.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.21-24
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• 2006

An experimental investigation was earned out to evaluate the fire performance of high strength concrete column made with different section size. Two different high strength concrete columns measuring 3,428mm in height and with the same tie spacing of 150mm were prepared to evaluate the effect of section size of $305{\times}305mm$ and $500{\times}500mm$ on the fire resistance. Compressive strength was 138MPa at the time of fire resistance fire testing. Based on the test result, fire resistance of column with the larger section of $500{\times}500mm$ exhibited the better performance than that of the smaller section of $305{\times}305mm$. The former withstood against the very high temperature over 240minutes, while the latter resisted during 176minutes.

• Earthquakes and Structures
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• 제8권1호
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• pp.1-18
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• 2015

A simple method of assessing the risk of overturning of precast reinforced concrete columns is presented in this paper. The displacement-based methodology introduced herein is distinguished from conventional force-based codified methods of aseismic design of structures. As evidenced by results from field tests precast reinforced concrete columns can be displaced to a generous limit without sustaining damage and then fully recover from most of the displacement afterwards. Realistic predictions of the displacement demand of such (rocking) system in conjunction with the displacement capacity estimates enable fragility curves for overturning to be constructed. The interesting observation from the developed fragility curves is that the probability of failure of the precast soft-storey column decreases with increasing size of the column importantly illustrating the "size effect" phenomenon.

• Steel and Composite Structures
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• 제47권4호
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• pp.539-550
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• 2023

Owing to the obstruction of section steel on the moisture diffusion in concrete, the existing shrinkage prediction models overestimate the time-dependent deformation of steel reinforced concrete (SRC) columns, particularly for the SRC columns with enclosed section steels. To solve this issue, this study deals with analytical and experimental studies on the drying shrinkage for this type of column. First, an effective method for predicting the drying shrinkage of concrete based on finite element model is introduced and two crucial parameters for simulation of humidity field are determined. Then, the drying shrinkage of SRC columns with enclosed section steels is investigated and two modified parameters, which depend on the ambient relative humidity and the ratio of section steel size to column size, are introduced to the B3 model. Finally, an experiment on the shrinkage deformation of SRC columns with enclosed section steels is conducted. Comparing the predicted results with the experimental ones, it demonstrates that the modified B3 model is quite reasonable.

• 대한기계학회논문집A
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• 제24권6호
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• pp.1479-1490
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• 2000

The design process of the motor driven tilt/telescopic steering column is established by axiomatic design approach in conceptual design stage. By selecting independent design variables for improvin g performance of the steering system, each detailed design can be carried out independently. In the detailed design, the safety in crash environment and vibration reduction are considered. An occupant analysis code SAFE(Safety Analysis For occupant crash Environment) is utilized to simulate the body block test. Segments, contact ellipsoids and spring-damper elements are used to model the steering column in SAFE. The model is verified by the result of the body block test. After the model is validated, the energy absorbing components are designed using an orthogonal array. Occupant analyses are performed for the cases of the orthogonal array. Final design is determined for the minimum occupant injury. For vibrational analysis, a finite element model of the steering column is defined for the modal analysis. The model is validated by the vibration experiment. Size and shape variables are selected for the optimization process. An optimization is conducted to minimize the weight subjected to various constraints.