• Journal of Welding and Joining
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• 제9권1호
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• pp.40-47
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• 1991

The most fatigue tests carried out under the either stress or strain control, but machines and structures had taken variable stress. This variable stress was treated as statistics based on p-type distributions. In this paper, the cumulative fatigue damage of SM45C round bar specimens having a center hole resulting from block loading with p-distributions in rotating bending conditions, is presented. The value of p was changed in the range from 0.25 to 1; 0.25, 0.5, 0.75, 1. The following conclusions were obtained through the constant stress amplitude experiments and the block loading experiments. (1) In constant loading test, fatigue life was affected by cyclic rate. From experimental data, N$_{f}$ (100cpm)/N$_{f}$(3000cpm)equal to 0.56. (2) In case of the cyclic rate 100cpm and 3000cpm, at the high stress amplitude level the crack propagation life N$_{*}$f is longer than the low stress amplitude level. (3) Miner's hypothesis may be valid for p=0.75 and prediction of fatigue life by Haibach's method agree with experimental data well for the case p=0.5, while the modified Miner's method agree with experimental data well for the case p=0.25.5.

• Journal of Mechanical Science and Technology
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• 제20권4호
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• pp.513-521
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• 2006

The performances of porous bearings under different operating conditions were experimentally investigated in this study. Material groups studied are 90%Cu + 10%Sn bronze and 1%C + % balance Fe iron-based self-lubricating P/M bearings at constant (85%) density. In the experiments, the variation of the coefficient of friction and wear ratio of those two different group materials for different sliding speeds, loads, and temperatures were investigated. As a result, the variation of the friction coefficient-temperature for both constant load, and constant sliding speed, friction coefficient-average bearing pressure, PV-wear loss and temperature-wear loss curves were plotted and compared with each other for two materials, separately. The test results showed that Cu-based bearings have better friction and wear properties than Fe-based bearings.

• 소음진동
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• 제8권2호
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• pp.336-345
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• 1998

The dynamic instability of cylindrical shell with clamped-free boundary condition subjected to constant follower force or $P_0 + P_1cos {\Omega}_t$ type pulsating follower force is analyzed. The motion of shell is modeled using the shell theory considering rotary inertia and shear deformation, and analyzed with finite element method. In case of constant follower force, the changes of eigenvalues dependent on the magnitude of applied load are investigated and the critical loads are obtained. In case pulsating follower force, instability regions of exicitation frequency are obtained by modal transform with right and left modal matrix and by multiple scales method. The effects of thickness ratio and aspect ratio on the instability of shell are studied.

• 환경위생공학
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• 제22권1호
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• pp.49-56
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• 2007

The effects of pH, time, dielectric constant of solvent and crosslink on adsorption of metal ions by 1-aza-18-crown-6-styrene-DVB(divinylbenzene) resin(resin) adsorbent were investigated. The metal ions were showed fast adsorption on the resins in over pH 3. The equilibrium time for adsorption of metallic ions was about two hours and the adsorption selectivity determined in methanol was in increasing order $UO_2^{2+}>Mg^{2+}>Ho^{3+}$ ions. The adsorption was in the order of 1%, 2% and 4% crosslink resin and adsorption of resin decreased in proportion to the order of dielectric constant of solvents.

• 환경위생공학
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• 제17권3호
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• pp.31-36
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• 2002

The effects of pH, time, dielectric constant of solvent and crosslink on adsorption of metal ions by resin(cryptand resin) adsorbent were investigated. The metal ions were showed fast adsorption on the resins in over pH 3. The equilibrium time for adsorption of metallic ions was about two hours and the adsorption selectivity determined in methanol was in increasing order $UO^{2+}$ > $Mn^{2+}$ > $Gd^{3+}$ ion. The adsorption was in the order of 1%, 2% and 5% crosslink resin and adsorption of resin decreased in proportion to the order of dielectric constant of solvents.

• Bulletin of the Korean Chemical Society
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• 제22권6호
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• pp.559-564
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• 2001

A method for calculating the main characteristics of a potentiometric titration curve in a carboxylic ion exchanger has been investigated. The potentiometric titration curves of simple electrolyte and ion exchangers (polyelectrolytes) showed a great difference between them. The acidity parameters of the ion exchangers, the thermodynamic constant (pK0), apparent equilibrium constant (K), and correction for the apparent equilibrium constant (b), were introduced and used to express the characteristics of the carboxylic ion exchanger. A characteristic equation related to the acidity parameters of the ion exchangers systems was derived. A fibrous carboxylic cation exchanger was used and potentiometric titration curves at different concentrations of the supporting electrolyte were obtained . To prove the validity of the characteristic equation, the concentration of the supporting electroyte was varied. In the present study, good agreement between the data points and the fitted curves was found in all the cases. The g (number of moles of alkali to 1 g of ion exchanger) of carboxylic ion exchanger was calculated from the concentration of supporting electrolyte (C), pH of the solution, and degree of neutralization of ion exchanger (x).

• 대한수학회논문집
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• 제29권3호
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• pp.421-428
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• 2014

We explicitly calculate the polarization and unconditional constants of $\mathcal{P}(^2d_*(1,{\omega})^2)$.

• 한국생물공학회:학술대회논문집
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• 한국생물공학회 2000년도 추계학술발표대회 및 bio-venture fair
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• pp.380-383
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• 2000

불완전 곰팡이의 일종인 Aureobasidium pullulans ATCC 42023 균주를 이용한 pullulan의 최적조건 및 pH 조절에 따른 pullulan의 생성 그리고 균체형태와 고분자 pullulan 생산에 미치는 영향을 조사 하였다. 삼각플라스크 내에서 최대의 pullulan 생산은 초기 pH 6.5일때 11.98 g/l의 pullulan을 생산하였고, 회분식 발효에서는 산소 공급속도 0.5 vvm일때 15.16 g/l의 최대의 pullulan생산량을 나타내었다. pH조절에 따른 실험에서는 pH 4.5일때 13.31 g/l의 pullulan 생산량을 보였고, 이때 균체의 형태는 효모형과 균사형태의 성장을 하였다. 그러나 분자량 생성면에서는 pH 6.5일때 100만 이상의 고분자가 가장 많이 생산되었다.

• Reproductive and Developmental Biology
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• 제33권3호
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• pp.119-123
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• 2009

The two dimensional quantitative structure-activity relationships (2D-QSARs) models concerning the binding affinity constants ($p[Od.]_{50}$) between 2-cyclohexyltetrahydropyrane and 2-cyclohexyltetrahydrofurane analogues as substrates, and bovine odorant binding protein (bOBP) as receptor were derived by multiple regression analyses method and discussed. The statistical quality of the optimized 2D-QSAR model (5) was good (r=0.907). From the model, the binding affinity constants ($p[Od.]_{50}$) were dependent upon the optimal value ($(TL)_{opt.}$=2.737) of total lipole (TL) of substrate molecules. Based on these findings, the high active compounds predicted by optimized 2D-QSAR model (5) were 2-(dimethylcyclohexyl)tetrahydropyrane molecule and their isomer molecules. The binding affinity constants regarding bOBP of the tetrahydrofuryl-2-yl family compounds were dependent upon the hydrophobicity (logP) of whole substrate molecules. In any case of porcine odorant-binding proteins (pOBP), the constants were dependent upon the hydrophobicity (${\pi}x={\log}P_X-{\log}P_H$) of substituents (R) in substrate molecules. Also, from the optimal values of hydrophobic constant, the hydrophobicity for bOBP influenced ca. twice time bigger (bOBP>pOBP) than that for pOBP.

• 태양에너지
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• 제20권1호
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• pp.11-20
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• 2000

To get more insight into the buffering effects of the p-${\mu}c$-Si:H Inserted at the p-a-SiC:H/i-a-Si:H interface, we present a systematic numerical simulation using Gummel-Schafetter method. The reduced recombination loss at the p/i interface due to a constant bandgap buffer is analysed in terms of the variation of the p/i Interface region with a short lifetime and the characterisitics of the buffer such as mobility bandgap, acceptor concentration, and D-state density. The numerical modeling on the constant bandgap buffer demonstrates clearly that the buffering effects of the thin p-${\mu}c$-Si:H originate from the shrinkage of highly defective region with a short lifetime in the vicinity of the p/i interface.