• Wind and Structures
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• 제29권4호
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• pp.247-270
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• 2019

Wind-resistant design of existing cooling tower structures overlooks the impacts of rainfall. However, rainstorm will influence aerodynamic force on the tower surface directly. Under this circumstance, the structural response of the super-large cooling tower (SLCT) will become more complicated, and then the stability and safety of SLCT will receive significant impact. In this paper, surrounding wind fields of the world highest (210 m) cooling tower in Northwest China underthree typical wind velocities were simulated based on the wind-rain two-way coupling algorithm. Next, wind-rain coupling synchronous iteration calculations were conducted under 9 different wind speed-rainfall intensity combinations by adding the discrete phase model (DPM). On this basis, the influencing laws of different wind speed-rainfall intensity combinations on wind-driving rain, adhesive force of rain drops and rain pressure coefficients were discussed. The acting mechanisms of speed line, turbulence energy strength as well as running speed and trajectory of rain drops on structural surface in the wind-rain coupling field were disclosed. Moreover, the fitting formula of wind-rain coupling equivalent pressure coefficient of the cooling tower was proposed. A systematic contrast analysis on its 3D distribution pattern was carried out. Finally, coupling model of SLCT under different working conditions was constructed by combining the finite element method. Structural response, buckling stability and local stability of SLCT under different wind velocities and wind speed-rainfall intensity combinations were compared and analyzed. Major research conclusions can provide references to determine loads of similar SLCT accurately under extremely complicated working conditions.

• 한국재료학회지
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• 제16권2호
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• pp.137-143
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• 2006

The effects of Cu and Fe additions on the thermal stability, microstructure and mechanical properties of $Al_{85}-Ni_{8.5}-Mm_{6.5},\;Al_{84}-Ni_{8.5}-Mm_{6.5}Cu_1,\;Al_{84}-Ni_{8.5}-M_{m6.5}Fe_1$ alloys, manufactured by gas atomization, degassing and hot-extrusion were investigated. Gas atomization, with a wide super-cooled liquid region, allowed the alloy powders to exhibit varying microstructure depending primarily on the powder size and composition. Al hotextruded alloys consisted of homogeneously-distributed fine-grained fcc-Al matrix and intermetallic compounds. A substitution of 1 at.% Al by Cu increased the thermal stability of the amorphous phase and produced alloy microstructure with smaller fcc-Al grains. On the other hand, the same substitution of 1 at.% Al by Fe decreased the stability of the amorphous phase and produced larger fcc-Al grains. The formation of intermetallic compounds such as $Al_3Ni,\;Al_{11}Ce_3\;and\;Al_{11}La_3$ was suppressed by the addition of Cu or Fe. Among the three alloys examined, the highest Vickers hardness and compressive strength were obtained for $Al_{84}-Ni_{8.5}-M_{m6.5}Cu_1$ alloy, and related to the finest fcc-Al grain size attained from increased thermal stability with Cu addition.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.609-612
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• 2008

마그네시아 인산염 시멘트를 사용한 보수용 모르타르의 접착강도 특성을 검토하기 위하여 모의 부재 시험체를 이용한 실험을 실시하였다. 접착강도 실험 결과 칩핑 처리를 한 시험체가 표면 처리를 한 시험체 보다 우수한 강도발현을 하였으며, 건식처리가 습식처리보다 우수한 강도발현을 하는 것으로 나타났다. 칩핑 건식 시험체의 경우 온도에 관계없이 재령 28일의 접착강도는 3.0MPa 이상의 높은 강도를 발현을 하는 것으로 나타나 일반 모르타르의 접착강도와 비교 시 매우 높은 접착성능으로써 우수한 접착성능이 요구되는 보수재료로서의 활용을 기대할 수 있을 것으로 판단된다.

• 정보처리학회논문지C
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• 제14C권5호
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• pp.411-416
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• 2007

대부분의 무선 네트워크 보안 기법은 암호학적인 안정성을 기반으로 통신 내용을 악의적인 호스트로 부터 보호하는 기밀성을 제공하지만 통신의 논리/물리적 주소를 노출시킨다. 이는 악의적인 노드에게 통신 내용은 숨길 수 있지만 대략의 전송량과 송신자와 수신자를 노출시키는 단점을 갖는다. 본 논문에서 제안하는 은닉주소 체계는 송신자와 수신자의 주소를 초증가 수열을 사용한 knapsack problem을 응용하여 생성된 은닉주소로 치환한다. 또한 은닉주소의 잦은 변환을 통해 악의적인 사용자가 공격 대상을 감시하거나 측정 호스트를 공격 대상으로 삼는 것을 원천적으로 차단한다. 이 기법은 공격 목표가 되는 호스트의 주소가 계속 변화하므로 DDoS 공격을 시도하려는 공격자가 공격 목표를 특정 할 수 없다.

• 한국건축시공학회지
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• 제9권3호
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• pp.95-101
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• 2009

Constructing large-scale mat foundation mass concrete is increasing for the stability of building structure, because a lot of high rise building are being built in order to make full use of limited space. However, It is of increasing concerns that because limited placing equipments, available job-site and systems for mass concete placement in construction field do not allow to place great quantity of concrete at the same time in large scale mat foundation, consistency between placement lift can not be secured. And also, it is likely to crack due to stress caused by the difference of hydration heat generation time. To find out the solution against above problems, this study is to reconfirm the performance of normal concrete designed by mix proportion and super retarding concrete. The Fundamental test shows what happens if low heat proportioning and control method of setting time are applied at the job-site of newly constructed high rise building. The test result show that slump flow of concrete has been somewhat increased as the target retarding time gets longer, while the air content has been slightly decreased but this is no great difference from normal concrete. The setting time shows to be retarded as target retarding time gets longer, the range of retarding time increases. It is necessary to increase the amount of mix of super retarding agent in the proportion ration by setting curing temperature high since outdoor curing is about 6 hours faster than standard curing, which means the temperature of the concrete will be higher than the temperature of the surrounding environment, due to its high hydration heat when applying in a construction site. The compressive strength of super retarding concrete appears to be lower than normal concrete due to the retarding action in the early stage. However, as the time goes by, the compressive strength gets higher, and by the 28th day the strength becomes the same or higher than normal concrete.

• 방송공학회논문지
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• 제24권4호
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• pp.633-642
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• 2019

최근, 단일 이미지 초해상도 복원 기법(super-resolution)에서 컨볼루션 신경망 모델은 매우 성공적이다. 잔여 학습 기법은 컨볼루션 신경망 훈련의 안전성과 성능을 향상시킬 수 있다. 본 논문은 저해상도 입력 이미지에서 고해상도 목표 이미지로 비선형 매핑 학습을 위해 고밀도 스킵 연결(dense skip-connection)을 통한 재귀 잔차 구조를 이용한 단일 이미지 초해상도 복원 기법을 제안한다. 제안하는 단일 이미지 초해상도 복원 기법은 고밀도 스킵 연결 방식을 통해 재귀 잔차 학습 방법을 채택해서 깊은 신경망에서 학습이 어려운 문제를 완화하고 더 쉽게 최적화하기 위해 신경망 안에 불필요한 레이어를 제거한다. 제안하는 방법은 매우 깊은 신경망의 사라지는 변화도(vanishing gradient) 문제를 완화할 뿐만 아니고 낮은 복잡성으로 뛰어난 성능을 얻음으로써 단일 이미지 초해상도 복원 기법의 성능을 향상시킨다. 실험 결과를 통해 제안하는 알고리듬이 기존의 알고리듬 보다 결과가 더 우수함을 보인다.

• 농업과학연구
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• 제43권2호
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• pp.249-257
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• 2016

In this study, rapeseed extracts were obtained by supercritical carbon dioxide fluid extraction of defatted rapeseed to evaluate the stability and antioxidant activity of an oil-in-water (O/W) emulsion system. The oil-in-water emulsions were prepared from stripped soybean oil with different concentrations (0.3, 0.4, 0.5, and 0.6%) of rapeseed extract as an emulsifier. Their emulsion stability was compared to that of emulsions prepared with the commercial emulsifier, Tween 20 (Polysorbate 20, 0.2%). After stripping the soybean oil, the total tocopherol content was reduced from 51.4 g/100 g to 1.1 g/100 g. Emulsion stability and oxidative stability of emulsions prepared with Tween 20 and rapeseed extract as emulsifiers were evaluated. For 30 days droplet sizes of emulsions containing rapeseed extract (0.4, 0.5, and 0.6%) were not significantly different (p > 0.05). Similar results were obtained for emulsion stability (ES) and Turbiscan analysis, suggesting that the addition of rapeseed extract increased emulsion stability. The addition of rapeseed extract at more than 0.4% resulted in an emulsion stability comparable to the addition of 0.2% Tween 20. The antioxidative ability of rapeseed extract increased with the amount added in the emulsion. Moreover, the addition of 0.6% rapeseed extract resulted in the lowest emulsion peroxide values (10.3 mEq/L) among all treatments. Therefore, according to the stability of its antioxidative and physical stability properties, rapeseed extract from super critical extraction could be successfully applied to the food and cosmetic industries.

• Wind and Structures
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• 제28권4호
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• pp.255-270
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• 2019

Aerodynamic configurations of bridge decks have significant effects on the aerostatic torsional divergence and flutter forsuper long-span bridges, which are onset for selection of suitable bridge decksfor those bridges. Based on a cable-stayed bridge with double main spans of 1500 m, considering typical twin-box, stiffening truss and closed-box section, which are the most commonly used form of bridge decks and assumed that the rigidity of those section is completely equivalent, are utilized to investigate the effects of aerodynamic configurations of bridge decks on aerodynamic instability performance comprised of the aerostatic torsional divergence and flutter, by means of wind tunnel tests and numerical calculations, including three-dimensional (3D) multimode flutter analysis and nonlinear aerostatic analysis. Regarding the aerostatic torsional divergence, the results obtained in this study show twin-box section is the best, closed-box section the second-best, and the stiffening truss section the worst. Regarding the flutter, the flutter stability of the twin-box section is far better than that of the stiffening truss and closed-box section. Furthermore, wind-resistance design depends on the torsional divergence for the twin-box and stiffening truss section. However, there are obvious competitive relationships between the aerostatic torsional divergence and flutter for the closed-box section. Flutter occur before aerostatic instability at initial attack angle of $+3^{\circ}$ and $0^{\circ}$, while the aerostatic torsional divergence occur before flutter at initial attack angle of $-3^{\circ}$. The twin-box section is the best in terms of both aerostatic and flutter stability among those bridge decks. Then mechanisms of aerostatic torsional divergence are revealed by tracking the cable forces synchronous with deformation of the bridge decksin the instability process. It was also found that the onset wind velocities of these bridge decks are very similar at attack angle of $-3^{\circ}$. This indicatesthat a stable triangular structure made up of the cable planes, the tower, and the bridge deck greatly improves the aerostatic stability of the structure, while the aerodynamic effects associated with the aerodynamic configurations of the bridge decks have little effects on the aerostatic stability at initial attack angle of $-3^{\circ}$. In addition, instability patterns of the bridge depend on both the initial attack angles and aerodynamic configurations of the bridge decks. This study is helpful in determining bridge decksfor super long-span bridges in future.

• 수산해양기술연구
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• 제20권1호
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• pp.37-42
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• 1984

응력집중부에 존재하는 균열에 대해서 J 평가식은 그 주위의 응력집중부의 국부변형과의 관계에 대해서 인장 및 압축이 있는 두곳에서 BEM 해석과 광탄성 실험한 결과와 COD 및 J치의 무차원량 J 하(E) /$\sigma$ 하(y) 상(2) a와 그 경우의 평균변형 및 항복변형의 비(e/e 하(y) )와의 관계는 균열의 길이에 의하지 않고 응력집중부의 형태에 거의 지배적으로 결정되는 일의적 대응관계가 있다. 2. 무한연속부 내부의 어떤 결함에 의한 평가식으로 부터 구한 값을 불연속 구조물내의 응력집중부에 존재하는 결함에 비하여 비교 정리하면, J 하(E) /$\sigma$ 하(y) 상(2) a=3.345(e/e 하(y) ) 상(2) 의 구간은 e/e 하(y) $\leq$1이고, J 하(E) /$\sigma$ 하(y) 상(2) a=3.345(e/e 하(y) )의 구간은 e/e 하(y) $\geq$1로서 이식들은 결함부 J평가식으로 사용할 수 있다. 3. 경계요소법에 의한 J식의 값과의 사이에는 가공경화율은 E/100을 사용하므로 이론과 실험결과가 거의 일치함을 보이고 상기 J식은 불연속평판 구조물이 결함을 가질 때 응력설계곡선의 자료가 될 수 있다.

• 대한수학회논문집
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• 제20권3호
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• pp.505-509
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• 2005

We show that every $\varepsilon-approximate$ Jordan functional on a Banach algebra A is continuous. From this result we obtain that every $\varepsilon-approximate$ Jordan mapping from A into a continuous function space C(S) is continuous and it's norm less than or equal $1+\varepsilon$ where S is a compact Hausdorff space. This is a generalization of Jarosz's result [3, Proposition 5.5].