• Title/Summary/Keyword: time-dependent effect

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The Characteristics of Fluid Flow in a Channel by Oscillating Vortex Generator (가진되는 와류발생기에 의한 채널내의 유동 특성)

  • Bang, Chang-Hoon;Kim, Jung-Soo;Choo, Hong-Lok
    • Journal of the Korean Society of Safety
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    • v.22 no.2 s.80
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    • pp.1-7
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    • 2007
  • A problem of a unsteady time-dependent flow in a channel is of practical importance and widely considered in the design of devices such as heat exchangers, duct, and electronic equipments. The characteristics of fluid flow in channel with oscillating vortex generator was investigated experimentally. The main object of this study was to investigate the effect of the excited frequency, the excited amplitude, and Reynolds numbers on the generated frequency. Flow patterns were visualized using smoke generator and generated frequencies were measured using hot wire anemometer. When the excited frequency is increased, excited amplitude decreased and Reynolds number increased, the strength of PSD of generated frequency is decreased.

An Analysis of Wave Height Distribution in the Vicinity of Samcheon New-Harbor (삼천포 신항의 파고분포 해석)

  • Jang, Dae-Jeong;Ham, Gye-Un
    • Journal of Ocean Engineering and Technology
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    • v.24 no.1
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    • pp.39-46
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    • 2010
  • The calmness inside a harbor plays an important role in the appropriate disposition of harbor structures. However, it is not easy to acquire accurate computational results because these are affected by many factors concerned with wave transformation. Recently, numerical model tests, which are quicker and more economical than hydraulic model experiments, were carried out for the purpose of analyzing wave height distributions in harbors. This paper presents a numerical model that is able to calculate wave heights inside a harbor. It is based on a time-dependent mild slope involving wave refraction, diffraction, shoaling effect, and reflection. In particular, arbitrary reflectivity is used at the boundary in order to simulate the real harbor reflection condition. The proposed numerical model is applied to Samcheon new-harbor in order to investigate harbor calmness.

Effect of Radiation on mRNA Expression of Ceruloplasmin Gene (방사선 조사에 따른 U-937 세포의 Ceruloplasmin 유전자에서 mRNA 발현 변화)

  • 오연경;임희영;김종수;윤충효;김인규;윤병수
    • Toxicological Research
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    • v.20 no.1
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    • pp.31-36
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    • 2004
  • Against environmental stress, ceruloplasmin which is a plasma protein, are believed to play central roles in antioxidant- or peroxidase-activity in blood stream to remove free radicals, which may be caused by exposing of $\gamma$-irradiation. In human U-937 cells exposed to $\gamma$-irradiation, the levels of mRNA in ceruloplasmin gene were measured on 0, 4, 12, 24 hr after exposing by using comparative RT-PCR (Reverse transcriptase-polymerase chain reaction) which was achieved to compare with house keeping genes such as $\beta$-actin and hprt. After $\gamma$-irradiation of 100 rads or 200 rads, the total quantities of RNA were increased as dose and time dependent manner. On the contrary, the variation of mRNA expression in ceruloplasmin was not found until 4 hr after irradiation. After 12 hr and 24 hr of irradiation, the levels of mRNA in ceruloplasmin were significantly increased as dose and time dependent manner than un-exposed cells.

Immobilization Imparts Stability to Watermelon Urease to Work in Water Miscible Organic Media

  • Prakash, Om;Upadhyay, Lata Sheo Bachan
    • Biotechnology and Bioprocess Engineering:BBE
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    • v.11 no.2
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    • pp.140-145
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    • 2006
  • The behaviour of alginate immobilized and soluble watermelon (Citrullus vulgaris) urease in water miscible organic solvents like, acetonitrile, dimethylformamide (DMF), ethanol, methanol, and propanol is described. The organic solvents exhibited a concentration dependent inhibitory effect on both the immobilized and the soluble urease in the presence of urea. Pretreatment of soluble enzyme preparations with organic solvents in the absence of substrate for 10 min at $30^{\circ}C$ led to rapid loss in the activity, while similar pretreatment of immobilized urease with 50% (v/v) of ethanol, propanol, and acetonitrile was ineffective. Time-dependent inactivation of immobilized urease, both in the presence and in the absence of urea, revealed stability for longer duration of time even at very high concentration of organic solvents. The soluble enzyme, on the other hand, was rapidly inactivated even at fairly lower concentrations. The results suggest that the immobilization of watermelon urease in calcium alginate make it suitable for its application in organic media. The observations are discussed.

A Study on Behaviors of Prestressed Bridge Girders Made Continuous (연속화된 Prestress 거더교의 거동연구)

  • 구민세;최인식;김진헌
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • 2002.10a
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    • pp.396-403
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    • 2002
  • To eliminate deck joints, continuous span bridges are becoming an attractive option. Defferent continuty methods and construction sequences have different time-dependent effects on the behavior of the bridge system. This paper is carried out to evaluate the restraint moments generated at interior span of bridges constructed with full-span prestessed concrete bridge. Especially, effects of creep and shrinkage between ACI209-95 and Eurocode 2 are compared in this paper. Time-dependent effects in prestressed concrete bridges include creep and shrinkage of concrete. Creep due to prestress makes the girders camber up and cause positive restraint moments. The most significant effect of shrinkage in continuous bridges is the differential shrinkage that occurs because of the difference in type and age of girder and deck concrete. Differential shrinkage between the precast girder and the deck typically causes negative res03int moments.

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Long-term deflection of high-strength fiber reinforced concrete beams

  • Ashour, Samir A.;Mahmood, Khalid;Wafa, Faisal F.
    • Structural Engineering and Mechanics
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    • v.8 no.6
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    • pp.531-546
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    • 1999
  • The paper presents an experimental and theoretical study on the influence of steel fibers and longitudinal tension and compression reinforcements on immediate and long-term deflections of high-strength concrete beams of 85 MPa (12,300 psi) compressive, strength. Test results of eighteen beams subjected to sustained load for 180 days show that the deflection behavior depends on the longitudinal tension and compression reinforcement ratios and fiber content; excessive amount of compression reinforcement and fibers may have an unfavorable effect on the long-term deflections. The beams having the ACI Code's minimum longitudinal tension reinforcement showed much higher time-dependent deflection to immediate deflection ratio, when compared with that of the beams having about 50 percent of the balanced tension reinforcement. The results of theoretical analysis of tested beams and those of a parametric study show that the influence of steel fibers in increasing the moment of inertia of cracked transformed sections is most pronounced in beams having small amount of longitudinal tension reinforcement.

Densification of Aggregated Alumina Powder under Cyclin Compaction (반복압축하의 응집된 알루미나 분말의 치밀화)

  • Kim, K.T.;Son, G.S.;Suh, J.
    • Journal of the Korean Ceramic Society
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    • v.29 no.2
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    • pp.136-142
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    • 1992
  • The effects of cyclic stress, frequency and bias-pressure on densification of Al2O3 powder cyclic compaction are investigated. The effect of frequency was not significant on densification of Al2O3 powder under cyclic compaction. The higher the cyclic stress and the lower the bias pressure, the higher densification was achieved. To obtain a higher densification, cyclic compaction was more efficient than 1 stroke compaction. A densification equation was proposed to describe an cyclic time dependent pressure-volume relation for Al2O3 powder under cyclic compaction. This equation was obtained empirically, based on the pressure-volume equation proposed by Cooper and Eaton, the time dependent densification equation by Kim and Suh and experimental data for Al2O3 powder under cyclic compaction. The agreement between the proposed equation and experimental data for Al2O3 powder under cyclic compaction was very good.

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Experimental study on long-term behavior of prestressed steel I-beam-concrete composite beams

  • Sung, Deokyong;Hong, Seongwon
    • Steel and Composite Structures
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    • v.42 no.5
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    • pp.671-683
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    • 2022
  • To investigate and predict the long-term time-dependent behavior, such as creep, shrinkage, and relaxation of PS strands, and prestress loss in prestressed steel-concrete composite beams, named Precom, full-scale tests were conducted and the collected data were compared with those obtained from the two proposed analytical models. The combined effective modulus method (EMM)-empirical model proposed with a flowchart considered the creep effect to determine the prestress loss. Conversely, the age-adjusted effective modulus method (AEMM) with CEB-FIP equation was developed to account for the concrete aging. The results indicated that the AEMM with CEB-FIP model predicts the long-term behavior of Precom effectively.

A Study on Electroless Ni-B Plating with DMAB as Reducing Agent. I. The Electrochemical Behavior of Precipitation Reaction on Austenite Stainless Steel Substrates (DMAB를 사용한 무전해 Ni-B 합금 도금 I. 오스테나이트 스텐레스강 상의 석출반응에 대한 전기화학적 거동)

  • 이창래;박해덕;강성군
    • Journal of Surface Science and Engineering
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    • v.32 no.2
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    • pp.172-181
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    • 1999
  • The effect of the DMAB concentration, temperature, deposition time, and stabilizer concentration on the precipitation reaction of the electroless nickel plating using dimethylamine borane (DMAB) as reducing agent was investigated to by the weight gain and electrochemical method. The deposition rate was dependent with DMAB concentration. The polarization resistance of the precipitation reaction was reduced with DMAB concentration. The precipitation reaction rate of Ni-B deposits was controlled by the oxidation rate of DMAB as the source of electron. The boron content of the deposit was constant at about 5.5wt%, even when DMAB concentration in the solution was increased. The effect of temperature and stabilizer ($Pb(NO_3)_2$) concentration on deposition rate was shown to have co-dependent behaviors.

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Effect of Ceramide on Cell Growth and Cell Cycle Related Proteins in U-937 Cells (U-937 세포에서 세라마이드의 세포증식과 세포주기 조절단백질에 대한 작용)

  • Lee, Jae-Hoon;Choi, Kwan-Soo;Kim, Mie-Young
    • YAKHAK HOEJI
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    • v.41 no.1
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    • pp.94-98
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    • 1997
  • Ceramide. a product of sphingomyelin hydrolysis, has been proposed as a lipid second messenger mediating antiproliferative activation. In this study, we examined the role of the cell cycle-related proteins in the ceramide-mediated growth suppression. Treatment of U-937 cells with C$_2$-ceramide(N-acetylsphingosine) resulted in growth suppression in a time- and concentration dependent manner. Ceramide induced concentration dependent dephosphorylation of retinoblastoma gene product (Rb). Rb remains hypophosphorylated in synchronized cells even after serum stimulation in the presence of ceramide. Ceramide decreased the expression of cyclin D$_1$ and cyclin E levels. These results suggest that antiproliferative effect of ceramide is associated with hypophosphorylation of Rb and decreased expression of cyclin D1 and cyclin E.

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