• Title/Summary/Keyword: passive pressure

검색결과 331건 처리시간 0.026초

수동(受動)말뚝에 작용(作用)하는 측방토압(側方土壓) (Lateral Earth Pressures Acting on Passive Piles)

  • 홍원표
    • 대한토목학회논문집
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    • 제4권2호
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    • pp.77-88
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    • 1984
  • 이미 유도제안(誘導提案)된 수동(受動)줄말뚝에 작용(作用)하는 측방토압(側方土壓)의 산정이론식(算定理論式)을 단일(單一)말뚝에까지 발전(發展)시킴과 동시(同時)에 본산정이론식(本算定理論式)에 포함되어 있는 지반(地盤)과 말뚝에 관한 요소(要素)들을 조사(調査)하여 사용(使用)하기 간편한 형태(形態)의 식(式)으로 정리(整理)하고자 한다. 즉, 본연구(本硏究)를 통하여 수동(受動)말뚝의 측방토압산정이론식(側方土壓算定理論式)은 측방토압계수(側方土壓係數) $K_{p1}$$K_{p2}$를 도입(導入)함에 의하여 점착력(粘着力) c와 지반변형방향(地盤變形方向)에 대항하여 말뚝열(列) 후면(後面)에 작용(作用)하는 수평토압(水平土壓) ${\sigma}_H$의 항(項)으로 구성(構成)된 간단(簡單)한 선형식(線形式)으로 정리제안(整理提案)된다. 그 밖에도 본이론식(本理論式)을 현장(現場)에 적용(適用)할 경우 수평토압(水平土壓) ${\sigma}_H$로는 주동토압(主動土壓)을 채용(採用)함이 합리적(合理的)이라는 점에 대한 타당성(妥當性)이 이론치(理論値)와 실측치(實測値)의 비교검토(比較檢討)를 통하여 입증(立證)되어 진다.

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950℃ 불순물을 포함한 헬륨 환경에서 CVD β-SiC의 산화 (Oxidation of CVD β-SiC in Impurity-Controlled Helium Environment at 950℃)

  • 김대종;김원주;장지은;윤순길;김동진;박지연
    • 한국세라믹학회지
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    • 제48권5호
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    • pp.426-432
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    • 2011
  • The oxidation behavior of CVD ${\beta}$-SiC was investigated for Very High Temperature Gas-Cooled Reactor (VHTR) applications. This study focused on the surface analysis of the oxidized CVD ${\beta}$-SiC to observe the effect of impurity gases on active/passive oxidation. Oxidation test was carried out at $950^{\circ}C$ in the impurity-controlled helium environment that contained $H_2$, $H_2O$, CO, and $CH_4$ in order to simulate VHTR coolant chemistry. For 250 h of exposure to the helium, weight changes were barely measurable when $H_2O$ in the bulk gas was carefully controlled between 0.02 and 0.1 Pa. Surface morphology also did not change based on AFM observation. However, XPS analysis results indicated that a very small amount of $SiO_2$ was formed by the reaction of SiC with $H_2O$ at the initial stage of oxidation when $H_2O$ partial pressure in the CVD ${\beta}$-SiC surface placed on the passive oxidation region. As the oxidation progressed, $H_2O$ consumed and its partial pressure in the surface decreased to the active/passive oxidation transition region. At the steady state, more oxidation did not observable up to 250 h of exposure.

Investigation of the Thermal Performance of a Vertical Two-Phase Closed Thermosyphon as a Passive Cooling System for a Nuclear Reactor Spent Fuel Storage Pool

  • Kusuma, Mukhsinun Hadi;Putra, Nandy;Antariksawan, Anhar Riza;Susyadi, Susyadi;Imawan, Ficky Augusta
    • Nuclear Engineering and Technology
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    • 제49권3호
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    • pp.476-483
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    • 2017
  • The decay heat that is produced by nuclear reactor spent fuel must be cooled in a spent fuel storage pool. A wickless heat pipe or a vertical two-phase closed thermosyphon (TPCT) is used to remove this decay heat. The objective of this research is to investigate the thermal performance of a prototype model for a large-scale vertical TPCT as a passive cooling system for a nuclear research reactor spent fuel storage pool. An experimental investigation and numerical simulation using RELAP5/MOD 3.2 were used to investigate the TPCT thermal performance. The effects of the initial pressure, filling ratio, and heat load were analyzed. Demineralized water was used as the TPCT working fluid. The cooled water was circulated in the water jacket as a cooling system. The experimental results show that the best thermal performance was obtained at a thermal resistance of $0.22^{\circ}C/W$, the lowest initial pressure, a filling ratio of 60%, and a high evaporator heat load. The simulation model that was experimentally validated showed a pattern and trend line similar to those of the experiment and can be used to predict the heat transfer phenomena of TPCT with varying inputs.

Numerical study of strength reduction-induced capillary rise effect for unsaturated soil

  • Shwan, Bestun J.
    • Geomechanics and Engineering
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    • 제31권4호
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    • pp.385-393
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    • 2022
  • Previous studies postulated insignificant capillary rise (hc) effect above the water table (Hw) for unsaturated soils. In addition, these studies utilised dry unit weight above Hw. This paper, therefore, addresses the effect of these postulations on strength where the influence of hc using a modified upper bound approach, Discontinuity Layout Optimization (UNSAT-DLO) for a simulated soil was predicted. Two different parametric studies to model passive earth pressure and bearing capacity problems are carried out to provide an insight into the effect of capillary rise on strength. Significant increase in strength, owing to unsaturated conditions, was obtained where the maximum increase was when suction slightly less or greater than the air entry suction. On the other hand, the results showed a negative effect of hc. For example, up to 8.24% decrease in passive thrust (Pp) was obtained at Hw=0 m when hc rose 1 m from 0 m. To put this into perspective, this was equivalent to a decrease of about 2° in 𝜙 at Hw=0 m and hc =0 m in order to obtain the same result at hc =1 m. For the bearing capacity problem, the effect was seen to be higher, up to 18.4% decrease in N𝛾 was obtained when hc rose from 0 m to 2.5 m at Hw =0 m. In addition, the results revealed a negative influence of assigning dry unit weight above Hw or hc.. However, considerable increase in strength was obtained when unsaturated unit weight above hc was assigned.

Overview of separate effect and integral system tests on the passive containment cooling system of SMART100

  • Jin-Hwa Yang;Tae-Hwan Ahn;Hong Hyun Son;Jin Su Kwon;Hwang Bae;Hyun-Sik Park;Kyoung-Ho Kang
    • Nuclear Engineering and Technology
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    • 제56권3호
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    • pp.1066-1080
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    • 2024
  • SMART100 has a containment pressure and radioactivity suppression system (CPRSS) for passive containment cooling system (PCCS). This prevents overheating and over-pressurization of a containment through direct contact condensation in an in-containment refueling water storage tank (IRWST) and wall condensation in a CPRSS heat exchanger (CHX) in an emergency cool-down tank (ECT). The Korea Atomic Energy Research Institute (KAERI) constructed scaled-down test facilities, SISTA1 and SISTA2, for the thermal-hydraulic validation of the SMART100 CPRSS. Three separate effect tests were performed using SISTA1 to confirm the heat removal characteristics of SMART100 CPRSS. When the low mass flux steam with or without non-condensable gas is released into an IRWST, the conditions for mitigation of the chugging phenomenon were identified, and the physical variables were quantified by the 3D reconstruction method. The local behavior of the non-condensable gas was measured after condensation inside heat exchanger using a traverse system. Stratification of non-condensable gas occurred in large tank of the natural circulation loop. SISTA2 was used to simulate a small break loss-of-coolant accident (SBLCOA) transient. Since the test apparatus was a metal tank, compensations of initial heat transfer to the material and effect of heat loss during long-term operation were important for simulating cooling performance of SMART100 CPRSS. The pressure of SMART100 CPRSS was maintained below the design limit for 3 days even under sufficiently conservative conditions of an SBLOCA transient.

자연재생방식 DPF시스템 부착 경유승용차량의 PM재생 특성 연구 (A Study on PM Regeneration Characteristics of Diesel Passenger Vehicle with Passive Regeneration DPF System)

  • 이진욱;조규백;김홍석;정용일
    • 대한기계학회논문집B
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    • 제31권2호
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    • pp.188-194
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    • 2007
  • New diesel engines equipped with common-rail injection systems and advanced engine management control allow drastic decreases in the production of particulate matters and nitrogen oxides with a significant advantage in terms of the fuel consumption and $CO_2$ emissions. Nevertheless, the contribution of exhaust gas after treatment in the ultra low emission vehicles conception has become unavoidable today. Recently the passive type DPF(Diesel Particulate Filter Trap) system for diesel passenger vehicle has been manufactured into mass production from a French automotive maker since the year of 2000. This passive DPF system fully relies on the catalytic effects from additives blended into the diesel fuel and additives injected into the DPF system. In this study, the effects of PM regeneration in the commercial diesel passenger vehicle with the passive type DPF system were investigated in chassis dynamometer CVS(constant volume sampler)-75 mode. As shown in this experimental results, the DPF regeneration was observed at temperature as low as $350^{\circ}C$. And the engine-controlled the DPF regeneration founded to be one of the most promising regeneration technologies. Moreover, the durability of this DPF system was evaluated with a season weather in terms of the differential pressure and exhaust gas temperature traces from a road test during the total mileage of 80,000km.

요통에서의 pressure biofeedback unit(stabilizer)를 사용한 안정화 운동 (The study of stability exercise using pressure biofeedback unit for low back pain)

  • 김국주;공관우;권순오;장용근;황희준;박준기
    • 대한물리치료과학회지
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    • 제19권2호
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    • pp.63-71
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    • 2012
  • Purpose : This study aimed to acquire a basic knowledge about lumbar stability and inquire into exercise approach of pressure biofeedback unit for lumbar stability. Methods : This study was composed with reviewed theory of lumbar stability and several books and articles for exercise using pressure biofeedback unit. Results : The stability of lumbar should work symmetrical with passive, active, control subsystem in neutral zone, and local muscles should be using for stability. Especially, selective using of transverse abdominis work for lumbar stability importantly. The control of using pressure biofeedback unit may important not only examination but treatment. Conclusion : The stability of lumbar need co-contraction of specific local muscle and training for timing as well as using pressure biofeedback unit for accurate control may use for examination and therapedic approach.

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고혈압 전단계자들에 대한 골격근 Group III 자극 시 시간에 따른 심혈관 반응 (Cardiovascular Responses over the Time Course during Muscle Group III Stimulation in Prehypertensive Individuals)

  • 박원일;박시영;최현민;이준희;전종목;김종경;심재근;노호성
    • 생명과학회지
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    • 제19권11호
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    • pp.1568-1574
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    • 2009
  • 본 연구는 고혈압전단계자들에 대한 지속적인 건 스트레치시 시간에 따른 생리학적 반응을 분석하여 정상혈압자와 고혈압전단계자에 대한 EPR의 한 요소인 기계적 수용기가 혈압 및 혈역학 반응에 어떠한 영향을 주는지를 검토하였다. 그 결과, 안정 시와 시간에 따른 혈압 반응은 고혈압전단계자에 있어 SBP, MAP가 평균 20sec에서 통계적으로 가장 높은 경향을 보였으며(p<0.05), 정상혈압자에서는 SBP, DBP, MAP가 평균 45sec에서 가장 높은 경향을 보였다(p<0.05). 이는 고혈압 전단계자의 지속적인 수동적 건 스트레치 시 정상혈압자에 비해 Group III mechanoreceptors의 역기능에 따른 상승된 혈압 반응이 초기에 나타내었다고 사료된다. 또한 혈역학 반응에서 안정 시와 비교하여 지속적인 수동적건 스트레치 시 고혈압전단계자에서의 HR, SV, CO, TPR 모두 유의한 차이를 보이지 않았으나 정상혈압자에서 SV, CO가 통계적으로 유의한 차이를 보였다(p<0.05). 이는 CO, SV, HR, TPR이 정상혈압자에 비해 고혈압전단계자에 있어 높은 경향을 나타내었지만, 혈역학 반응은 본 연구를 통해 차이를 보이지 않아 앞으로 연구가 필요할 것으로 사료된다.

여성 소비자의 식생활 라이프스타일에 따른 체중 조절 행위에 관한 연구 (A Study on Weight Control Behavior by Female Consumers Eating Life Styles)

  • 한인경;하애화
    • 한국식품영양학회지
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    • 제22권2호
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    • pp.177-184
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    • 2009
  • The study investigated the eating lifestyles of female consumers and whether they influenced weight control behavior. The findings of the study can be summarized as follows. First, the eating lifestyles of the subjects were presented four types: 'active eating life pursuit type', 'safe economical type', 'gourmet type' and 'passive negligence type'. In general, most cases were of the 'passive negligence type'. Second, weight control behavior was analyzed according to eating lifestyle. The results of the analysis indicated that the female consumers of the 'active eating life pursuit type' and 'safe economy type' had high behavior levels in each aspect of weight control attitude, subjective regulation, perceived behavior control, and behavior intention. Third, the 'gourmet type', with a strong preference for taste, and the 'passive negligence type', with fewer eating considerations in general, showed weaker attitudes towards weight control and the recognition of pressure from people around them. As such, the level of consideration for food or eating was correlated with weight control. These findings impliedy that the more active, safer, and economical women are in their general eating style, the stronger they perceive weight control issues.

다공벽을 이용한 충격파 강도의 피동제어 (Passive control of strength of shock wave)

  • 최영상;권순범;조철영
    • 대한기계학회논문집B
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    • 제21권1호
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    • pp.174-184
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    • 1997
  • A shock wave, being an irreversible process, gives rise to entropy increase. A great deal of effort has been made to control shock wave and boundary layer interaction related to energy losses as well as problems of vibration and noise. In the present study, tests are performed on a roof mounted half circular arc in an indraft type supersonic wind tunnel to evaluate the effects of porosity, length and depth of cavity in passive control of shock wave on the attenuation of shock strength by reviewing the measured static pressures at the porous wall and cavity. Also the flow field is visualized by a Schlieren system. The results show that in the present study the porosity of 8% produced the largest reduction of pressure fluctuations and that for the same porosity, the strength of shock wave decreases with the increasings of the depth and length of cavity.