• 제목/요약/키워드: concentration ratio

검색결과 6,415건 처리시간 0.038초

모래다짐말뚝으로 개량된 연약지반의 응력분담특성 (Stress Concentration Characteristics of Soft Ground Treated by Sand Compaction Pile)

  • 유남재;박병수;정길수;김상진
    • 산업기술연구
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    • 제22권A호
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    • pp.145-151
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    • 2002
  • This paper is results of extensive centrifuge model experiments about design factors influencing the bearing capacity and the settlement behaviors of SCP (Sand Compaction Pile). Centrifuge model tests were carried out changing design factors for SCP method such as replacement area ratio (as= 20, 40, 70%), Improvement ratio to footing width (W/B = 1, 2, 3), and amount of fines m sand pile (#200 = 5, 10, 15). Therefore, the effects of these design factors on the bearing capacity and the settlement behavior of SCP were investigated and changes of stress concentratio rato due to such an design factors were also investigated. Centrifuge model testing technique for preparing and installing centrifuge model of sand compaction pile, using freezing them, was also developed. As results of centrifuge model tests, more fines in sand compaction pile increases the bearing capacity of SCP. Optimum improvement ratio to footing width was found to be 2. Values of stress concentration ratio was in the ranges of 1.5 - 3.5. The depth of bulging in sand plies was found in the range of 2.0 - 2.5 times of pile diameter.

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SCP 및 GCP로 개량된 복합지반의 변위 양상에 관한 원심모델링 (Centrifuge Modeling on Displacement Shapes of Composite Ground Improved by SCP and GCP)

  • 허열;정소전;이처근;안광국
    • 한국지반환경공학회 논문집
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    • 제7권5호
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    • pp.57-66
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    • 2006
  • 본 연구에서는 모래다짐말뚝(SCP) 및 쇄석다짐말뚝(GCP)으로 개량된 복합 지반의 응력 분담비, 말뚝 및 지반의 변형형태를 파악하기 위하여 말뚝의 치환율(20%, 40%, 60%)을 변화시키면서 연성재하 원심모형실험을 수행하였다. 실험결과, 동일 치환율에서 쇄석 다짐말뚝에 작용하는 응력이 모래다짐말뚝에 작용하는 응력보다 크게 나타났다. 치환율 40%에서 쇄석다짐말뚝으로 개량된 연약점토지반의 평균 응력분담비가 모래다짐말뚝을 설치한 경우보다 약간 크게 나타났다. GCP는 팽창파괴가 발생되었으며, SCP는 팽창 및 전단파괴가 동시에 발생함을 확인할 수 있었다.

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원심모델링을 이용한 CSCP 및 SCP로 개량된 연약지반의 거동 (Behavior of Soft Ground Improved by CSCP and SCP Using Centrifuge Modeling)

  • 안광국
    • 한국지반공학회논문집
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    • 제22권4호
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    • pp.21-30
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    • 2006
  • 본 연구에서는 조립질 말뚝으로 개량된 점토지반의 지지력, 응력분담비, 말뚝 및 지반의 변형형태를 파악하기 위하여 말뚝의 종류(CSCP, SCP)와 치환율(0, 20, 40, 60%)을 변화시키면서 원심모형실험을 수행하였다. 실험결과, CSCP와 SCP로 개량된 지반의 하중비는 치환율이 증가함에 따라 비례적으로 증가하였고, CSCP로 개량된 지반의 평균 지지력비가 SCP로 개량한 경우보다 $8{\sim}21%$ 정도 크게 평가되었다. CSCP로 개량된 지반의 평균 응력분담비가 SCP보다 크게 나타나 CSCP가 더 큰 응력을 부담하는 것으로 평가되었다. CSCP로 보강된 지반에서는 팽창파괴가 발생하였고, SCP로 보강된 지반에서는 팽창 및 전단파괴가 동시에 발생하였다.

High concentration ratio approximation of linear effective properties of materials with cubic inclusions

  • Mejak, George
    • Coupled systems mechanics
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    • 제7권1호
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    • pp.61-77
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    • 2018
  • This paper establish a high concentration ratio approximation of linear elastic properties of materials with periodic microstructure with cubic inclusions. The approximation is derived using first few terms of power series expansion of the solution of the equivalent eigenstrain problem with a homogeneous eigenstrain approximation. Viability of the approximation at high concentration ratios is proved by comparison with a numerical solution of the homogenization problem. To this end some theoretical result of symmetry properties of the homogenization problem are given. Using these results efficient numerical computation on a reduced computational domain is presented.

The Effect of HPMC Concentration on the Morphology and Post Drawing of Wet Spun Regenerated SF/HPMC Blend Filaments

  • Ko, Jae-Sang;Um, In-Chul
    • International Journal of Industrial Entomology and Biomaterials
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    • 제19권1호
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    • pp.181-185
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    • 2009
  • In this paper, the regenerated silk fibroin (SF)/hydroxypropyl methylcellulose (HPMC) blend filaments were prepared by wet spinning and the effect of HPMC concentration on the post drawing and morphology of blend filaments was elucidated. The result of maximum draw ratio indicated that the wet spinnability of wet spun SF / HPMC was improved with increasing HPMC concentration until 8% and remained constant after that concentration. The SEM observation revealed that the enhanced wet spinnability of blend filaments was strongly related to the morphological change by increasing HPMC concentration. Regardless of HPMC concentration, as SF content was reduced, the wet spinnability of blend film decreased resulting in reduced maximum draw ratio. It was also found by SEM observation that the cross section of blend filament deviated from circularity with an increase of HPMC content.

Water purification from pesticides by spiral wound nanofiltration membrane

  • Bottino, A.;Capannelli, G.;Comite, A.;Ferrari, F.;Firpo, R.
    • Membrane and Water Treatment
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    • 제2권1호
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    • pp.63-74
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    • 2011
  • A spiral wound nanofiltration (NF) membrane (GE Osmonics, DK 4040F) was used to remove pesticides from water. Several solutions of single pesticides and their mixtures were prepared. The pesticides initial concentration ranged from ca. 50 ng/L (single pesticide) to ca. 700 ng/L (as sum of 14 pesticides) and progressively increased with time since the NF experiments were carried out in a concentration mode up to a Volume Concentration Ratio, VCR = 10. Permeate flux and pesticides retention were evaluated as a function of the Volume Concentration Ratio. The permeate flux did not practically change by varying VCR. Pesticide retention was found to be around 97-98% both in the cases of single pesticide solutions and different mixtures of pollutants, and was not affected by the VCR. Pesticides concentration in permeate samples was found to be lower than the maximum concentration level fixed in European directive.

사각 평판에서 타원의 형상 변화에 따른 응력집중계수에 관한 연구 (A Study on the Stress Concentration Coefficient due to the Change of Ellipse on a Square Plate)

  • 박정호;김형준;박기훈;조우석;제승봉;김현수
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2003년도 춘계학술대회 논문집
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    • pp.1434-1437
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    • 2003
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio a/b increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces. As the plate with three holes. the stress $\sigma$$\_$x/ and $\tau$$\_$xy/ of hole 1,3 becomes high, especially $\sigma$$\_$x/ dominant and high.

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입자 농도가 Digital Holographic PTV 측정에 미치는 영향에 관한 연구 (Effect of Particle Concentration on Digital Holographic PTV Measurement)

  • 김석;이상준
    • 대한기계학회논문집B
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    • 제30권10호
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    • pp.929-934
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    • 2006
  • The digital HPTV(holographic particle tracking velocimetry) velocity field measurement system consists of four steps: recording, numerical reconstruction, particle extraction and velocity extraction. In the velocity extraction process, we improved the two frame PTV algorithm to extract 3-D displacement information of each particle located in 3D space. Because a digital CCD camera was used, some factors such as spatial resolution, numerical aperture, and particle concentration influenced on the performance of the developed digital HPTV. Especially, the particle concentration $(C_o)$ affected the reconstruction efficiency and recovery ratio in the numerical reconstruction and particle extraction procedure. In this paper, the effect of particle concentration reconstruction efficiency and recovery ratio were analyzed experimentally. Optimal particle concentration was found to be in the range of $C_o=11{\sim}17\;particles/mm^3$.

사각 평판에서 타원의 위치와 형상 변화에 따른 응력집중계수의 변화에 관한 연구 (A Study on the Stress Concentration Coefficient due to the Change of Position and Shape of Ellipse on a Square Plate)

  • 최경호;권영석;박기훈;김현수
    • 한국정밀공학회:학술대회논문집
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    • 한국정밀공학회 2002년도 추계학술대회 논문집
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    • pp.833-836
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    • 2002
  • Sometimes open holes are required for the function and the weight reduction of structure and machinery. However, the serious stress concentration occurs because of the geometric discontinuity caused by the holes and cutting section. In this study, it is attempted to obtain the stress concentration coefficients of the inner surface of the hole boundary by changing the position and the shape of holes on the homogeneous isotropic plate. And the effects on the plate are investigated. The results show that the stress level becomes low and the distribution area widens the position of stress concentration changes as the ratio ah increases and change to a circle. And as the ratio a/l decreases, the stress concentration reduces.

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초기 톨루엔 농도가 톨루엔- NOx-공기 혼합물의 광산화 반응에 미치는 영향 - II. 입자상 물질의 생성 및 성장 (Effect of Initial Toluene Concentration on the Photooxidation of Toluene-NOx-Air Mixture -II. Aerosol Formation and Growth)

  • 이영미;배귀남;이승복;김민철;문길주
    • 한국대기환경학회지
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    • 제21권1호
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    • pp.27-38
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    • 2005
  • An experimental investigation of the gas-phase photooxidation of toluene-NO$_{x}$-air mixtures at sub-ppm concentrations has been carried out in a 6.9 ㎥, indoor smog chamber irradiated by blacklights. Measured parameters in the toluene-NO$_{x}$ experiments included aerosol, $O_3$, NO, NO$_2$, NO$_{x}$ CO, SO$_2$ toluene, and air temperature. The initial toluene concentration ranged from 225 ppb to 991 ppb and the initial concentration ratio of toluene/NO$_{x}$ in ppbC/ppb was in the range of 5~20. It was found that the variation of aerosol number concentration with irradiation time caused by the photooxidation of toluene-NO$_{x}$-air mixtures depended on the initial toluene concentration for similar concentration ratio of toluene/NO$_{x}$. The dependency of initial toluene concentration on the photooxidation of toluene-NO$_{x}$-air mixtures for toluene/NO$_{x}$= 5~6 seemed to be opposite to that for toluene/NO$_{x}$=10~11. The maximum number concentration of aerosols formed by photooxidation and the aerosol yield depended on both initial toluene concentration and initial concentration ratio of toluene/NO$_{x}$. In this study, the aerosol yield, defined as aerosol formed per unit toluene consumed, was found to be 0.01~0.16.und to be 0.01~0.16.