• 동력기계공학회지
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• 제8권4호
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• pp.11-16
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• 2004

In this study, to investigate the effects of omitting low-amplitude cycles from a flight-simulation loading, crack growth tests were conducted on 2124-T851 aluminum alloy specimens. Three test spectra were generated by omitting small load ranges as counted by the rain-flow count method. The crack growth test results were compared with the data obtained from the flight-simulation loading. The experimental results show that the ranges equal to or smaller than 5% of the maximum load do not contribute to crack growth behavior because these are below the initial stress intensity factor range. Omitting these from the flight-simulation loading, test time can be reduced by 54%. However, in the case of omitting the load ranges below 15% of the maximum load, crack growth rates decreased, and crack growth curve deviated from the crack growth data under the flight-simulation loading because loading cycles above fatigue fracture toughness were omitted.

• 환경영향평가
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• 제8권1호
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• pp.41-49
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• 1999

This study was carried out to estimate the runoff loading characteristics of the non-point source pollutions in the Youngsan river basins by the method of land-use types and rainfall. The lysimeter test, rainfall and stream flowmeter measurement were performed to develop the pollutant loading unit discharged from the non-point sources. As the non-point sources, the unit pollutant discharge rates were different from the land-use types such as paddy field, upland, forest, housing site and others. The pollutant loading units classified by land-use types in the Youngsan river basins are as follows: The total BOD loading rate is 15.3 ton/day and the housing site is discharged 50.6%, the total T-N loading rate is 6.0 ton/day and the paddy field and upland is discharged 77.6%, and the total T-P loading rate is 0.39 ton/day and the paddy field and upland is discharged 81.2%. The pollutant loadings by rainfall in the Youngsan river basins are about 7,425 ton/year of BOD, 324 ton/year of T-N and 118 ton/year of T-P, respectively.

• 한국해양환경ㆍ에너지학회지
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• 제9권1호
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• pp.14-20
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• 2006

수산물 가공공장 폐수의 생물학적 처리를 위하여 미생물 강제포획방식인 EMMC 공정을 적용하여 유기물 및 질소의 동시제거 가능성을 평가하였다. 처리도 실험은 도시하수처리장에서 가져온 활성슬러지를 cellulose triacetate를 이용한 gel matrix에 고정시켜 실험을 수행하였다. anoxic조와 oxic조로 구성된 시스템에 유기물 및 질소부하 율을 증가시켜가며 실험한 결과 비교적 안정된 형태의 운전이 가능하였다. 적용 유기물부하는 $0.65{\sim}1.72kgCOD/m^3{\cdot}d$, 총질소 부하는 $0.119{\sim}1.317kgT-N/m^3{\cdot}d$의 범위에서 4단계로 나누어 적용시켰다. 본 연구에 사용한 수산물 가공공장폐수의 경우 공장폐수의 유출수 총질소 농도 규제치인 60 mg/l 이하를 기준으로할 때 T-N의 경우 한계 적용용적부하는 약 $0.3kgT-N/m^3{\cdot}d$인 것으로 나타났다. T-N의 경우는 부하율 증가에 따른 제거효율 저하가 뚜렷하였으나 ${NH_4}^+-N$의 경우는 각 단계별로 부하율을 증가시키면서 실험해본 결과 부하율 증가에도 불구하고 제거 효율 변화는 완만하여 본 실험에 적용한 시스템의 경우 질산화 반응은 부하변동에 관계없이 효율적으로 이루어지는 것으로 평가되었다. 실험 기간 중 Anoxic조의 질산성 질소 제거율은 각 단계별로 평균 $99.51{\sim}98.62%$로 나타났으며 oxic조의 질산화 제거율은 $94.0{\sim}96.9%$로 나타났다. 시스템 전체로는 적용 용적부하율하에서 화학적 산소요구량(COD: Chemical Oxygen Demand)의 경우 $94.2%{\sim}96.6%$, 총질소의 경우 $73.4{\sim}83.4%$ 의 제거효율을 나타내었다.

• 한국환경과학회지
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• 제2권4호
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• pp.299-310
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• 1993

This study was aimed to evaluate the effects of effluent recycling on the UASB reactor performances at the various organic loading rates and influent substrate concentrations. The organic removal efficiency of the reactors operated with effluent recycle were above 85%. However, the efficiencies of the reactors operated without the recycle were below 40% even though the effort to increase the efficiencies was made by changing the influent substrate concentrations and the organic loading rates, and introducing the effluent recycle at the final stage of the experiment. It was realized that the certain amount of effluent recycling from the start-up stage in UASB reactors seemed to be necessary to provide the effective contact chances between the substrate and granular sludge for better performances of the UASB process.

• Computers and Concrete
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• 제12권4호
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• pp.537-552
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• 2013

Computation of flexural ductility of reinforced concrete beam sections has been proposed by taking into account strain rate sensitive constitutive behavior of concrete and steel, confinement of core concrete and degradation of cover concrete during load reversal under earthquake loading. The estimate of flexural ductility of reinforced concrete rectangular sections has been made for a wide range of tension and compression steel ratios for confined and unconfined concrete at a strain rate varying from $3.3{\times}10^{-5}$ to 1.0/sec encountered during normal and earthquake loading. The parametric studies indicated that flexural ductility factor decreases at increasing strain rates. Percentage decrease is more for a richer mix concrete with the similar reinforcement. The confinement effect has marked influence on flexural ductility and increase in ductility is more than twice for confined concrete (0.6 percent volumetric ratio of transverse steel) compared to unconfined concrete. The provisions in various codes for achieving ductility in moment resisting frames have been discussed.

• Environmental Engineering Research
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• 제10권1호
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• pp.7-14
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• 2005

The feasibility of hydrogen production with a raw seed sludge through direct acclimation of feedstock was investigated at acidogenic stage, and methane was harvested at followed methanogenic stage in an anaerobic two-stage process. Hydrogen content was higher than 57% at all tested organic loading rates (OLRs) and the yield of hydrogen ranged from 1.5 to 2.4 mol H2/mol hexose consumed and peaked at 6 gVSl-1day-1. Normal butyrate and acetate were main volatile fatty acids (VFAs), whereas the concentration of propionate was insignificant. The hydrogen-producing bacteria, Clostridium thermosaccharolyticum, was detected with strong intensity at all tested organic loading rates (OLRs) by denaturing gradient gel electrophoresis (DGGE) of the polymerase chain reaction (PCR) analysis. From COD balance in the process, the fraction of the feed-COD converted to the hydrogen-COD at acidogenic stage ranged from 7.9% to 9.3% and peaked at 6 gVSl-1day-1, whereas the fraction of feed-COD converted to the methane-COD at methanogenic stage ranged from 66.2% to 72.3% and peaked at 3 gVSl-1day-1.

• 대한기계학회논문집A
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• 제23권11호
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• pp.1886-1895
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• 1999

The delamination behavior of multidirectional carbon-fiber/epoxy composite laminates under 10NA intermediate and high rates of test, up to rate of about 11.4m s has been investigated using the double cantilever beam specimens. The mode I loading under rates above l.0m/s showed considerable dynamic effects on the load-time curves and thus higher values of the average crack velocity than that expected from a simple proportional relationship with the test rate. The modified beam analysis utilizing only the opening displacement and crack length exhibited an effective means for evaluating the dynamic fracture energy $G_{IC}$. Based on the assumption of constant flexural modulus, values of $G_{IC}$ at the crack initiation and arrest were decreased with an increase of the test rate up to 5.7m/s, but the maximum $G_{IC}$ was increased at 11.4m/s.

• 한국농공학회지
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• 제41권4호
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• pp.37-46
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• 1999

Field experimnet of constructed wetland for rural wastewater treatment was performed from July 1998 to April 1999 including winter to examine the seasonal effect on the wetland performance. The system worked without freezing even under $-10^{\circ}C$ of air temperature as long as watewater was flowing. BOD removal rates varied in similar pattern as the air temperature, and winter performance was relatively lower than that in the growing season. However, removing performance during winter was still significant, and BOD removal rates were almost the the same as in the growing season. SS removal rate was relativelyless affected by temmperature, but lower decay rate during the winter can result in accumulation of the SS in the system, which releases constituents in the next spring and can affect whole system performance. The winter removal rates of nutrients like T-N and T-P were decreased about half compared to the growing season and low temperature. To maintain stabilized wetland performanced including winter time, supplying minimum heating for plants could be an alternative in field application. Experimental data was compared with NADB(North Americal Wetlands for Water Quality treatment database), and general performance of the system was within the reasonable range. The pollutant loading and effluent concentration of the experimented system were in high margin. Base on the experiment and databases, the required effluent water quality could be achieved if loading rate adjusted as ilulstrated in the database.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.107-112
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• 2003

Mechanical properties of the materials used for transportations and industrial machinery under high strain rate loading conditions such as high impact loading are required to provide appropriate safety assessment to varying dynamically loaded mechanical structures. The Split Hopkinson Pressure Bar(SHPB) technique with a special experimental apparatus can be used to obtain the material behavior under high strain rate loading conditions. In this paper, the dynamic deformation behavior of a brass under both high strain rate compressive loading conditions has been determined using the SHPB technique.

• Steel and Composite Structures
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• 제34권6호
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• pp.877-889
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• 2020

This work features the outcomes of an empirical investigation into the characteristics of steel reinforced grout (SRG) composite - concrete interfaces. The parameters varied were loading rate, densities of steel fibres and types of load displacement responses or measurements (slip and machine grips). The following observations and results were derived from standard single-lap shear tests. Interfacial debonding of SRG - concrete joints is a function of both fracture of matrix along the bond interface and slippage of fibre. A change in the loading rate results in a variation in peak load (P_max) and the correlative stress (σ_max), slip and machine grips readings at measured peak load. Further analysis of load responses revealed that the behaviour of load responses is shaped by loading rate, fibre density as well as load response measurement variable. Notably, the out-of-plane displacement at peak load increased with increments in load rates and were independent of specimen fibre densities.