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1
Kumar, K. M., P. Venkateswaran, and P. Suresh. "Effective Fuel Consumption by Improving Cooling Water Flow Rate in IC Engine." Applied Mechanics and Materials 812 (November 2015): 112–17. http://dx.doi.org/10.4028/www.scientific.net/amm.812.112.
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The coolant (water) pump assumes an important role of cooling system in IC engines. With upgrading of the engine power by turbocharging and turbo inter cooling, the water pump capacity needs to be increased corresponding to the power. This capacity enhancement has to be achieved without calling for a major change in the existing water pump, envelop and related fitment details. This requires a clear understanding of centrifugal pump for its performance parameter. One such engine is upgraded by turbocharging from 195PS to 240PS @2200 rpm. Improving water pump flow by changing the impeller dimensions, impeller casing, increase the suction, delivery pipe diameter had been done. Validation of the water pump in its actual engine installation was taken up as a part of the research work. Flow rate comparison of the new pump with the existing pump was made and the results were analyzed. The new water pump gives better flow rates for the engine speeds up to1800 rpm, beyond which the flow rate is slightly lesser than the existing pump.
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Tang, Gary X., and James Graham. "A possible elasticplastic framework for unsaturated soils with high-plasticity." Canadian Geotechnical Journal 39, no. 4 (August 1, 2002): 894–907. http://dx.doi.org/10.1139/t02-024.
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The paper proposes a new elasticplastic framework for unsaturated, high-plasticity, clayey soils and sandclay mixtures. The framework considers possible coupling of stress- and suction-induced hardening, leading to a yield surface that is closed or "capped" as suctions increase. This produces a stress state boundary surface in three-dimensional pqs stress space (where p is the net mean stress, q is the deviator stress, and s is the matric suction) which differs from that of other conceptual models of its kind. Yielding, a hardening law, and failure criteria for saturated soils are incorporated into the stress state boundary surface. Two parameters, equivalent pressure pe and stress ratio ηs, are introduced to form the basis of the proposed elasticplastic framework for highly plastic soils with high suctions. This provides an alternative for the stress variables net mean stress and matric suction that are commonly used in modeling unsaturated soils with lower plasticity and lower suctions. This framework has allowed results of experiments on an unsaturated sandbentonite mixture to be successfully described using elastoplasticity. Yield and failure envelopes associated with the proposed state boundary surface in pqs space can be normalized using pe and ηs in such a way that they agree with a comparable envelope for saturated specimens. Key words: unsaturated, elasticplastic, triaxial, matric suction, state boundary surface, sand-bentonite.
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Gong, Xiu Bin, Qing Lai Fan, and Ke Wu. "Bearing Capacity of Suction Caisson for Offshore Floating Wind Turbine." Advanced Materials Research 243-249 (May 2011): 4718–22. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.4718.
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Presented in this paper are the three-dimensional nonlinear finite element analyses of the failure envelopes of suction caisson under torsion, vertical and lateral pullout combined load in soft clay. The soft clay under undrained condition is simulated by perfectly elasto-plastic Tresca model. Through the numerical analyses, the failure envelopes for combined loading (V-T、H-T、V-H-T) of suction caisson is reviewed. And the mathematical expression of failure envelope is deduced. It is shown that (1) the circular plastic failure area is outward-extending. (2) The bearing capacity of suction caisson foundation in V-T、H-T load spaces is increasing with the aspect ratio L/D. (3) The equation of failure envelope can be used to evaluate the stability of suction caisson foundation for offshore floating wind turbine.
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Hossain, Md Akhtar, and Jian-Hua Yin. "Shear strength and dilative characteristics of an unsaturated compacted completely decomposed granite soil." Canadian Geotechnical Journal 47, no. 10 (October 2010): 1112–26. http://dx.doi.org/10.1139/t10-015.
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Shear strength and dilative characteristics of a re-compacted completely decomposed granite (CDG) soil are studied by performing a series of single-stage consolidated drained direct shear tests under different matric suctions and net normal stresses. The axis-translation technique is applied to control the pore-water and pore-air pressures. A soil-water retention curve (SWRC) is obtained for the CDG soil from the equilibrium water content corresponding to each applied matric suction value for zero net normal stress using a modified direct shear apparatus. Shear strength increases with matric suction and net normal stress, and the failure envelope is observed to be linear. The apparent angle of internal friction and cohesion intercept increase with matric suction. A greater dilation angle is found at higher suctions with lower net normal stresses, while lower or zero dilation angles are observed under higher net normal stresses with lower suctions, also at a saturated condition. Experimental shear strength data are compared with the analytical shear strength results obtained from a previously modified model considering the SWRC, effective shear strength parameters, and analytical dilation angles. The experimental shear strength data are slightly higher than the analytical results under higher net normal stresses in a higher suction range.
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Gan, J. K. M., D. G. Fredlund, and H. Rahardjo. "Determination of the shear strength parameters of an unsaturated soil using the direct shear test." Canadian Geotechnical Journal 25, no. 3 (August 1, 1988): 500–510. http://dx.doi.org/10.1139/t88-055.
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Multistage direct shear tests have been performed on saturated and unsaturated specimens of a compacted glacial till. A conventional direct shear apparatus was modified in order to use the axis-translation technique for direct shear tests on unsaturated soils. The soil can be subjected to a wide range of matric suctions. The testing procedure and some typical results are presented. Nonlinearity in the failure envelope with respect to matric suction was observed. Suggestions are made as to how best to handle the nonlinearity from a practical engineering standpoint. Key words: shear strength, unsaturated soils, negative pore-water pressures, soil suction, direct shear.
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Hoyos, Laureano R., Jairo E. Yepes, Claudia L. Velosa, and Anand J. Puppala. "Unsaturated Shear Strength of Compacted Clayey Soil via Suction-controlled Ring Shear Testing." E3S Web of Conferences 195 (2020): 03024. http://dx.doi.org/10.1051/e3sconf/202019503024.
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An experimental program has been undertaken to assess both peak and residual shear strength parameters of statically compacted, moderate plasticity clayey soil under suction-controlled conditions, resulting in a defined set of suction-dependent peak and residual failure envelopes over a relatively wide range of suction states, from 0 to 300 kPa. The experimental program was accomplished in a servo/suction-controlled ring shear apparatus, which is suitable for testing unsaturated soils under large deformations via the axis-translation technique. Test results substantiate the crucial role that has been observed to be played by the imposed matric suction on the residual shear strength of compacted clayey soils. For the range of net normal stress (0-200 kPa) and matric suction (0-300 kPa) states investigated, the increase in either peak or residual shear strength, with increasing matric suction, was found to be manifestly nonlinear. Furthermore, a distinct correspondence was observed between the nonlinearity of the peak shear strength envelope, with respect to increasing matric suction, and the soil-water retention properties of the clayey soil. Results, in general, suggest that a conceptual residual shear strength framework for unsaturated soils, similar to that postulated for peak shear strength, can eventually be formulated as more experimental evidence of this kind is made available.
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Vilar, Orencio Monje. "A simplified procedure to estimate the shear strength envelope of unsaturated soils." Canadian Geotechnical Journal 43, no. 10 (October 1, 2006): 1088–95. http://dx.doi.org/10.1139/t06-055.
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Procedures that allow the prediction of some properties of unsaturated soils or the minimization of the number of tests needed to measure them are advantageous because the control of suction during testing is a formidable task that is time consuming and involves a great degree of expertise. A simplified procedure is proposed in this paper to estimate the shear strength of an unsaturated soil. The procedure is based on an empirical hyperbolic function that has been successfully used to fit experimental data. The function requires two input values, namely the shear strength of a saturated sample and the shear strength of an air-dried sample tested without the need for suction control. Samples tested under a controlled suction larger than the maximum suction expected in the problem can, alternatively, replace the air-dried samples. Both alternatives were tested against results for various soils reported in the literature. The good agreement between the estimates and the experimental data indicates that the proposed procedure is promising and reliable for estimating preliminary unsaturated shear strength parameters.Key words: unsaturated soil, suction, shear strength, prediction, laboratory tests.
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Kabošová, Lenka, Isak Foged, Stanislav Kmeť, and Dušan Katunský. "Hybrid design method for wind-adaptive architecture." International Journal of Architectural Computing 17, no. 4 (November 8, 2019): 307–22. http://dx.doi.org/10.1177/1478077119886528.
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The linkage of individual design skills and computer-based capabilities in the design process offers yet unexplored environment-adaptive architectural solutions. The conventional perception of architecture is changing, creating a space for reconfigurable, “living” buildings responding, for instance, to climatic influences. Integrating the element of wind to the architectural morphogenesis process can lead toward wind-adaptive designs that in turn can enhance the wind microclimate in their vicinity. Geometric relations coupled with material properties enable to create a tensegrity-membrane structural element, bending in the wind. First, the properties of such elements are investigated by a hybrid method, that is, computer simulations are coupled with physical prototyping. Second, the system is applied to basic-geometry building envelopes and investigated using computational fluid dynamics simulations. Third, the findings are transmitted to a case study design of a streamlined building envelope. The results suggest that a wind-adaptive building envelope plays a great role in reducing the surface wind suction and enhancing the wind microclimate.
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Wang, Zhi Yun, Mao Tian Luan, and Lu Shen. "Bearing Capacity of Suction Caisson Foundations Using FEM Analysis." Advanced Materials Research 243-249 (May 2011): 2112–15. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2112.
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To understand features of bearing capacity of suction caisson foundation is one of the key issues in design and construction of deep-water marine structures. In this paper, the general-purpose finite element analysis package ABAQUS is employed to conduct three-dimensional numerical analyses on load-carrying features of suction caisson foundation under vertically uplift load, horizontal load and moment. Then the ultimate bearing capacity of suction caisson foundation for undrained condition of the soil is evaluated by displacing-controlling procedure. Moreover, three-dimensional failure envelope of suction caisson foundation under combine loading condition are established by the proposed numerical procedure.
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Hoyos, Laureano, Roya Davoodi-Bilesavar, Ujwalkumar Patil, Jairo Yepes-Heredia, Diego Pérez-Ruiz, and José Cruz. "Behavior of unsaturated cohesive-frictional soils over a whole range of suction/thermo-controlled stress paths and modes of deformation." Soils and Rocks 44, no. 3 (July 20, 2021): 1–12. http://dx.doi.org/10.28927/sr.2021.066621.
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The present work documents some of the most recent experimental evidence of the thermohydro-mechanical behavior of compacted soils over a whole range of suction- and/or thermo-controlled stress paths and modes of deformation, including data from a series of triaxial, true triaxial, plane strain, ring shear, and resonant column tests conducted on different types of cohesive-frictional soils in the low-to-medium matric suction range under either room temperature or thermally controlled conditions. The work has been accomplished at the Advanced Geomechanics Laboratory of the University of Texas at Arlington, focusing primarily on the following essential features of unsaturated soil behavior: (1) Loading-collapse and apparent tensile strength loci assessed from suction-controlled triaxial and true triaxial testing on clayey sand, (2) Critical state lines from suction-controlled plane strain testing on silty soil, (3) Peak and residual failure envelopes from suction-controlled ring shear testing on clayey soil, (4) Frequency response curves and cyclic stress-strain hysteretic loops from thermo-controlled, constant-water content resonant column testing on clayey soil, and (5) Residual failure envelopes from suction/thermo-controlled ring shear testing on clayey soil. The work is intended to serve as a succinct yet reasonably thorough state-of-the-art paper contribution to PanAm-UNSAT 2021: Third Pan-American Conference on Unsaturated Soils, Rio de Janeiro, Brazil, July 21-25, 2021.
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Hamid, Tariq B., and Gerald A. Miller. "Shear strength of unsaturated soil interfaces." Canadian Geotechnical Journal 46, no. 5 (May 2009): 595–606. http://dx.doi.org/10.1139/t09-002.
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Unsaturated soil interfaces exist where unsaturated soil is in contact with structures such as foundations, retaining walls, and buried pipes. The unsaturated soil interface can be defined as a layer of unsaturated soil through which stresses are transferred from soil to structure and vice versa. In this paper, the shearing behavior of unsaturated soil interfaces is examined using results of interface direct shear tests conducted on a low-plasticity fine-grained soil. A conventional direct shear test device was modified to conduct direct shear interface tests using matric suction control. Further, the results were used to define failure envelopes for unsaturated soil interfaces having smooth and rough counterfaces. Results of this study indicate that matric suction contributes to the peak shear strength of unsaturated interfaces; however, postpeak shear strength did not appear to vary with changes in matric suction. Variations in net normal stress affected both peak and postpeak shear strength. Failure envelopes developed using the soil-water characteristic curve (SWCC) appeared to capture the nonlinear influence of matric suction on shear strength of soil and interfaces.
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Kabošová, Lenka, Stanislav Kmeť, and Dušan Katunský. "Wind flow around buildings of basic shapes with and without a wind-adaptive envelope." Selected Scientific Papers - Journal of Civil Engineering 15, no. 1 (September 1, 2020): 59–75. http://dx.doi.org/10.1515/sspjce-2020-0007.
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Abstract Together with the natural environment, the built, artificial environment represents a barrier to the wind fluxes. Especially in the densely built cities, the wind flow pattern and the wind speed are considerably altered by buildings, which can lead to zones of an accelerated wind and turbulent flow. Incorporating the wind into the early conceptual stage of architectural design, this reciprocal interaction of the built environment and the wind fluxes can be analyzed and controlled to create zones of calmer wind around buildings. Presently, building envelopes are designed to withstand extreme load cases, which, however, demands thicker and bulkier structures. The subject of this study is a proposal and investigation of a lightweight, adaptive building envelope, which is able of a local, passive morphing in the wind. This local shape change leads to creating a textured, dimpled building surface; the final shape depends on the wind direction and force. The wind-induced dimpled surface influences the wind flow around the building, as well as surface wind pressure acting on the building, and the drag force. The analysis of three fundamental building shapes using the CFD (Computational Fluid Dynamics) simulation is performed for the variants with and without the proposed adaptive envelope. Concluding from the wind simulations, the wind flow can be decelerated, the turbulence reduced, and calmer zones around buildings can be created, by certain conditions. Moreover, the envelope, morphing with the instant wind force, can contribute to the reduction of the surface wind suction on buildings. Strikingly, the dimpled geometry of the wind-adaptive envelope can decrease the wind drag force by up to 28.4 %, which is again dependent on the global form, as well as the initial wind speed.
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Wu, Ke, Ming Yue Ma, and Shu Cai Li. "Study on the Failure Envelope of Suction Bucket Foundation under Torsion Shear Load." Applied Mechanics and Materials 90-93 (September 2011): 1780–84. http://dx.doi.org/10.4028/www.scientific.net/amm.90-93.1780.
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As an advanced technology in coastal and offshore engineering, wind-driven generator, the suction bucket foundation is one new offshore foundation. It is not only subjected to the long-term action of vertical load(V) induced by all weights of platform and equipment, but also is imposed by both horizontal load(H), moment(M) and torsion(T) caused by wind and wave as well as current. The judgment standard of bearing capacity behavior and practical performance of suction bucket foundation under many freedom loads have been established, which was one key of problems to appraise the stability of foundation. According to the existing results, the features of ultimate bearing capacity and failure envelopes of bucket foundation under combined loads was evaluated in the framework of the general-purpose FEM software package ABAQUS. Results indicated that the failure envelopes of bucket foundation in different loading spaces were plotted, which could be used to evaluate the stability of bucket foundation.
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Anderson, M. G., and M. J. Kemp. "Suction-controlled triaxial testing: Laboratory procedures in relation to resistance envelope methods." Earth Surface Processes and Landforms 12, no. 6 (November 1987): 649–54. http://dx.doi.org/10.1002/esp.3290120608.
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Tekinsoy, M. A., C. Kayadelen, M. S. Keskin, and M. Söylemez. "An equation for predicting shear strength envelope with respect to matric suction." Computers and Geotechnics 31, no. 7 (October 2004): 589–93. http://dx.doi.org/10.1016/j.compgeo.2004.08.001.
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Cheng, L., M. S. Hossain, Y. Hu, Y. H. Kim, and S. N. Ullah. "Failure envelope of suction caisson anchors subjected to combined loadings in sand." Applied Ocean Research 114 (September 2021): 102801. http://dx.doi.org/10.1016/j.apor.2021.102801.
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Michalski, Jan P. "Parametric Method Applicable in Assessing Breakout Force and Time for Lifting Slender Bodies from Seabed." Polish Maritime Research 27, no. 2 (June 1, 2020): 69–75. http://dx.doi.org/10.2478/pomr-2020-0028.
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AbstractThe article presents a parametric method applicable in assessing the suction force of a slender body to the seabed, and prognosing the body extrication time. Along with the body weight in water, the information on the suction force is essential for assessing the force needed to lift the object from the seabed. Based on the Foda theory and the resulting integral equation, which relates the maximum suction force with basic parameters of the issue of concern, the parametric method has been developed which can be widely applied in engineering practice of lifting objects. A set of discrete values of parameters selected from the range of typical values for engineering practice was the basis for developing algebraic formulas approximating the integral Foda equation for slender bodies. The included results of tests present the variability of suction force characteristics and the envelopes of maximum forces needed to extricate the body from the seabed.
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Oommen, Alex, Thara Augustine, and E. V. Gopi. "Active versus passive drainage after modified radical mastectomy in breast cancer." International Surgery Journal 5, no. 7 (June 25, 2018): 2616. http://dx.doi.org/10.18203/2349-2902.isj20182784.
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Background: Active drains are routinely used after Modified Radical Mastectomy (MRM) and is an important factor contributing to increased hospital stay as the patients are often discharged only after their removal. Amongst various factors that influence the amount of post operative drainage, the negative suction pressure applied to the drain has been reported to be of great significance. Against this background a study was conducted to compare the amount and duration of drainage between suction and dependent drainage in patients following Modified Radical Mastectomy.Methods: Patients were randomised using randomly ordered sealed envelopes, which were opened immediately before the closure of the wound, to decide on whether suction or dependent drain was to be given. Drains were removed when output was less than 30 ml per day. Patients were followed up from the day of surgery till the day of drain removal. Statistical analysis was performed with SPSS.Results: There is significant increase in the drain per day in post MRM patients with active suction drain. But, there is no relation between the type of drain and either total drain output or the total number of days of drain. The study also revealed that there is no significant difference in the number of days of hospital stay in both groups of patients.Conclusions: Suction drains do not have any significant advantage over dependent drains after Modified Radical Mastectomy in breast cancer patients.
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He, Peng, Liuying Sun, and Zhen Wang. "Direct Shear Test of Unsaturated Soil." Earth Sciences Research Journal 21, no. 4 (October 1, 2017): 183–88. http://dx.doi.org/10.15446/esrj.v21n4.66103.
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The present study focuses on some tentative laboratory tests using a newly-constructed modified direct shear test apparatus. The single-stage and multistage direct shear tests were performed to determine the shear rate and test scheme of unsaturated shear test. Shear strength parameters of unsaturated soil in different conditions are obtained and the tests indicate good agreement with typical theories of unsaturated soil, the nonlinear matric suction failure envelope is determined. Some shear strength equations are also fitted through the experimental results.
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Lee, In-Mo, Sang-Gyu Sung, and Gye-Chun Cho. "Effect of stress state on the unsaturated shear strength of a weathered granite." Canadian Geotechnical Journal 42, no. 2 (April 1, 2005): 624–31. http://dx.doi.org/10.1139/t04-091.
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The effect of stress state on the unsaturated shear strength of a Korean residual soil was studied using modified triaxial tests. Experimental results show that the soil-water characteristic curve and shear strength of this soil are significantly affected by the change of net normal stresses. This effect should be taken into consideration in the model to precisely describe the shear strength envelope of unsaturated soils. Thus, a new model for estimation of unsaturated shear strength is proposed using the soil-water characteristic curve and the saturated shear strength parameters.Key words: prediction model, soil-water characteristic curve, matric suction, triaxial test, unsaturated shear strength.
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Fu, Dengfeng, Britta Bienen, Christophe Gaudin, and Mark Cassidy. "Undrained capacity of a hybrid subsea skirted mat with caissons under combined loading." Canadian Geotechnical Journal 51, no. 8 (August 2014): 934–49. http://dx.doi.org/10.1139/cgj-2013-0330.
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Skirted mudmats are commonly used to support offshore infrastructure. However, these may not be able to provide sufficient capacity to notably withstand the lateral loads applied by jumpers and connectors. The concept of hybrid foundation system was therefore proposed to enhance the capacity in a targeted fashion, through addition of internal suction caisson compartments. This paper presents a numerical investigation into the undrained bearing capacity of a rectangular-shaped hybrid foundation with two caisson units. Uniaxial capacities under vertical, horizontal, and moment loading are reported, but the focus lies on the horizontal–moment planes due to the anticipated low vertical load on the foundation. Detailed discussion highlights the contribution of the internal caisson compartments to the significant increases in horizontal capacity compared to a simple rectangular skirted mat through changes in the failure mechanism. This results not only in changes in size, but also in shape, of the capacity envelope. The study was extended to more general horizontal–moment loading conditions, where the shape of the capacity envelope was found to remain approximately constant. This applies to the hybrid foundation and the rectangular skirted mat in the homogeneous soil considered here. An expression is proposed that provides a slightly conservative approximation of the capacity envelope under combined horizontal and moment loading from any direction.
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Gryskiewicz, Joe M. "Submental Suction-Assisted Lipectomy without Platysmaplasty: Pushing the (Skin) Envelope to Avoid a Face Lift for Unsuitable Candidates." Plastic and Reconstructive Surgery 112, no. 5 (October 2003): 1393–405. http://dx.doi.org/10.1097/01.prs.0000083222.41089.dd.
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Pandey, Vinod Kumar, Dhruv Chandra, Raj Kumar, Anil Singh, Tej Pratap, Shubham Agarwal, and Ashish Yadav. "Role of subcutaneous vacuum suction drain in prevention of abdominal wound complication in emergency laparotomy." International Surgery Journal 7, no. 6 (May 26, 2020): 1873. http://dx.doi.org/10.18203/2349-2902.isj20202399.
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Background: Some of the most common wound complications following laparotomy include hematoma formation, seroma formation, wound infection, burst abdomen and wound dehiscence. Closed-suction drains (CSDs) help to drain any wound collection and also reduce any dead space in the wound thereby promoting healing and preventing complication.Methods: We conducted a prospective study and included patients presenting with acute abdomen in emergency department. Patients were selected as per inclusion and exclusion criteria. Two groups (group A and B) with equal number of patients were created based on closed envelope technique. CSD was placed in the wound of patients in group A. Wound healing and complications were compared between the two groups.Results: 50 patients were included in the study with 25 in each group. Hematoma formation was found to be significantly more among group B (24.0%) compared to group A (4.0%). Seroma formation (p value =0.03917), SSI rate (p value =0.039) and wound dehiscence/burst abdomen (p value =0.0415) was more in group B than group A. The mean wound healing time (days) and mean hospital stay (days) was significantly more in group B.Conclusions: Placing a subcutaneous vacuum suction drain at the time of abdominal wall closure during emergency laparotomy results in better wound healing and reduces postoperative wound complication, hospital stay time, morbidity and also decreases overall healthcare cost.
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Osterberg, N., and R. Albertani. "Investigation of self-deploying high-lift effectors applied to membrane wings." Aeronautical Journal 121, no. 1239 (March 30, 2017): 660–79. http://dx.doi.org/10.1017/aer.2017.10.
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ABSTRACTFlow separation followed by aerodynamic stall limits the operation of aircraft. Expanding the flight envelope of aircraft has been a goal of aerodynamicists for decades. This work presents findings from tests in the Oregon State University wind tunnel investigating the effectiveness of a passively actuated suction-surface flap on membrane wings. Experiments were conducted on a rigid plate and membrane wings with and without a pop-up flap. All wings had an aspect ratio of 2, while membrane pre-strain and Reynolds number were varied. An increase in lift at stall was observed for all testing conditions with flap deployment. The observed average increase in maximum lift varied from 5% to 15% for different test conditions. The variation in flap effectiveness is compared to membrane pre-strain, Reynolds number, and wing camber. A quadratic relationship between modelled camber and flap effectiveness is observed, and an optimal level of membrane camber is found to maximise flap effectiveness.
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Friedland, Jack A. "Submental Suction-Assisted Lipectomy without Platysmaplasty: Pushing the (Skin) Envelope to Avoid a Face Lift for Unsuitable Candidates; Joe M. Gryskiewicz, M.D." Plastic and Reconstructive Surgery 112, no. 5 (October 2003): 1406–7. http://dx.doi.org/10.1097/01.prs.0000083223.55234.03.
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Tran, Thi Phuong An, and Delwyn G. Fredlund. "Verification of the Fredlund (2019) Unsaturated Shear Strength Function." Geosciences 11, no. 4 (March 26, 2021): 151. http://dx.doi.org/10.3390/geosciences11040151.
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There has been a proliferation of equations proposed to describe the unsaturated shear strength envelope going back to the 1970s. However, there have been limited studies to verify the suitability of one unsaturated shear strength equation over another. Most proposed shear strength equations have attempted to relate the shear strength of an unsaturated soil to some aspect(s) of the soil–water characteristic curve (SWCC). Estimation procedures have generally focused on using that of air-entry value (AEV) as defined by the drying (or desorption) branch of the degree of saturation SWCC (S-SWCC). This paper studies the suitability of using two “anchor points” (or reference points) along the drying S-SWCC to estimate the unsaturated soil shear strength function. The anchor points referred to are the air-entry value (AEV) of the soil and the “residual suction point” of the soil defined in terms of the S-SWCC. Shear strength conditions associated with both so-called anchor points are used as “boundary conditions” that should be satisfied when estimating the shear strength function for unsaturated soils. Past research laboratory measurements published in the research literature are used as part of the verification process for this study.
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Taylor, Oliver-Denzil S., Katherine E. Winters, Woodman W. Berry, Lucas A. Walshire, and Pamela G. Kinnebrew. "Near-surface soils: self-supported unconfined drained sand specimens." Canadian Geotechnical Journal 56, no. 3 (March 2019): 307–19. http://dx.doi.org/10.1139/cgj-2017-0261.
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Knowledge about soil behaviour in the near surface is fundamental to a broad range of military strategic research efforts. The prevailing mathematical representations of near-surface shear strength do not necessarily reflect the observed shear strengths. This paper presents an experimental procedure for testing self-supported, unconfined-drained specimens to investigate the shear strength of a poorly graded sand with the inferred unsaturated behaviour from typical effective stress expressions. The impact of soil suction is quantified from the soil–water characteristic curve obtained from a modified, unsaturated, one-dimensional oedometer device: Fredlund’s device. Seventy-seven unconfined tests illustrate that while individual or discrete states can be explained by effective stress relationships, those expressions do not accurately quantify the observed shear strength from one state to the next. Saturation failure is observed when the degree of saturation is between 70.5% and 76.5%, well below the assumed threshold. The results show that the dry shear resistance is a function of the initial density state, but as the degree of saturation increases, the shear resistance becomes independent of the initial density, and converges to the saturation failure. These findings expose the limitations of effective stress expressions and suggest a revised nonlinear, three-dimensional, unconfined Mohr failure envelope based on an applied external stress.
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Olaiz, Austin, Mohammad Mosawi, and Claudia Zapata. "An improved framework for volume change of shrink/swell soils subjected to time-varying climatic effects." Soils and Rocks 44, no. 3 (August 27, 2021): 1–14. http://dx.doi.org/10.28927/sr.2021.065621.
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The ability to estimate soil volume change as a function of time is a valuable tool in the design or forensic analysis of shallow foundations and pavement structures. This paper presents an improved framework for estimating the volume change of shrink/swell soils due to time-varying climatic effects using the Lytton et al. (2005) approach with the suction envelope models created by Vann & Houston (2021) and updated considerations of short-term varying climate. The procedure can be easily implemented in any country due to its mechanistic-empirical nature. The authors present an example calculation of the proposed framework using the data from an American Association of State Highway and Transportation Officials (AASHTO) Long-Term Pavement Performance (LTPP) Seasonal Monitoring Program (SMP) section, located approximately 80 miles northeast of Dallas, Texas. The volume change estimated from the proposed framework was compared to 70 measured data points from sections from the SMP study and the results look promising. The models are universal and can be used in any part of the world provided measured data is available to calibrate for local conditions. Ongoing calibration effort with the remaining LTPP SMP sections will allow obtaining calibration factors for the proposed framework that will improve the estimation of the volume change predictions under pavements and facilitate the implementation into current design procedures.
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Peranić, Josip, Mariagiovanna Moscariello, Sabatino Cuomo, and Željko Arbanas. "Determination of hydraulic conductivity and shear strength properties of unsaturated residual soil from flysch rock mass." E3S Web of Conferences 195 (2020): 03022. http://dx.doi.org/10.1051/e3sconf/202019503022.
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Slopes in flysch deposits areas wide within Europe are highly prone to landslide occurrence. Depending on the material properties and climate conditions, instabilities in a form of earthflows, shallow and deep-seated landslides were observed in these formations. Typically, slope instabilities occurred after prolonged periods of rainfall. The Rječina River Valley, Croatia, built in flysch formation, is well known by several landslides occurred in the past. The weathering process of flysch rock mass and local climate conditions resulted in a specific engineering geological profile of the valley, with the unsaturated residual soil covering the bedrock. Although the behaviour of residual soil is important for a landslide triggering both through the rainfall infiltration process and (unsaturated) shear strength, hydro-mechanical properties of this material in unsaturated conditions were not investigated in the past. This paper summarizes the results of different laboratory tests performed on intact samples for hydro-mechanical characterization of the residual soil from flysch rock mass. It was found that the unique shear strength envelope could be used to determine failure conditions both for saturated and unsaturated conditions. The results obtained from strain-controlled and wetting tests performed in conventional and modified direct shear apparatuses indicated high values of the apparent cohesion that the near-surface soil can experience due to the increase of matric suction. The hysteresis effects and hydraulic paths to which soil was exposed to in the past were found to affect the soil behaviour, while the soil formation process results with a complex soil structure that imposes the necessity of using intact soil samples for proper hydraulic characterization of the soil.
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Bommarito, Marco, and Mark Meyer. "Large Multisite Clinical Field Study Characterizing Contamination Levels in Patient Used Endoscopes After Manual Cleaning." Infection Control & Hospital Epidemiology 41, S1 (October 2020): s11—s12. http://dx.doi.org/10.1017/ice.2020.483.
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Background: Multiple outbreaks multidrug-resistant organisms (MDROs) have been associated with flexible endoscopes resulting in unacceptable patient mortality and morbidity. Evidence highlights the importance of effective cleaning to achieve effective high-level disinfection (HLD). This study presents an analysis of >700,000 measurements of adenosine-triphosphate (ATP) contamination levels found in flexible endoscopes after manual cleaning. Method: This 2018–2019 study consists of 702,768 measurements of ATP levels found in the suction/biopsy channel of instruments used on patients after manual cleaning: gastroscopes (267,533 measurements from 223 sites), duodenoscopes (123,697 measurements from 161 sites), colonoscopes (252,249 measurements from 229 sites), and bronchoscopes (59,289 measurements from 107 sites). Sites were located across the United States and employed protocols that included routine cleaning verification performed by the reprocessing technicians using a handheld luminometer and the associated ATP water test (3M Clean-Trace). Results: Figure 1 shows a boxplot analysis of the ATP levels by endoscope type. Upper gastrointestinal (GI) endoscopes (gastroscopes and duodenoscopes) show a significantly (P < .005) greater level of ATP contamination after manual cleaning. The pairwise mean differences are all significant (P < .005) except for colonoscopes when compared to bronchoscopes (P = .203). Also shown on Fig. 1 is a literature supported adequate cleanliness value of 200 RLUs [=2.3log(RLUs)] (MJ Alfa et al.; Am J Infec Control 2013;41:245–253 and ANSI/AAMI ST91; 2015). A 95% confidence interval analysis performed against this literature value (Table 1) showed that a high number of gastroscopes (12%) and duodenoscopes (10%) are not adequately clean. Figure 2 shows a box-plot analysis of the data set by endoscope type and by site. There is significant (P < .005) site-to-site variability for all endoscope types as demonstrated by variation in mean values, box size, and many outliers. Conclusions: This study highlights the importance of using a quantitative cleaning verification method to better understand process capability and to provide more robust quality assurance for manual cleaning. Significant differences were detected in the level of cleanliness between upper GI scopes and lower GI scopes and bronchoscopes. When compared to a literature-supported level for adequate cleanliness, upper GI scopes exhibited failure rates in excess of 10%. Furthermore, significant site-to-site variability occurred, and many outliers fell well beyond the normal process envelope, representing significant cleaning lapses. Root causes to these concerning findings could range from inadequate execution of the cleaning protocol, to device design, to age and existing damage that could prevent achieving adequate cleaning and possibly impair the effectiveness of HLD.Funding: NoneDisclosures: Marco Bommarito, 3M (salary)
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Saffari, Pooya, Mohd Jamaludin Md Noor, Shervin Motamedi, Roslan Hashim, Zubaidah Ismail, and Basharudin Abdul Hadi. "EXPERIMENTAL STUDY ON NONLINEAR SHEAR STRENGTH BEHAVIOR OF A TROPICAL GRANITIC RESIDUAL SOIL (GRADE VI) AT VARIOUS INITIAL MOISTURE CONTENTS." Jurnal Teknologi 79, no. 2 (January 31, 2017). http://dx.doi.org/10.11113/jt.v79.8955.
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The conventional theories of soil mechanics use linear envelope to derive shear strength; this however, leads to an overestimation of the factor of safety in the examination of slopes. Therefore, the incorporation of methods that acknowledge the existence of non-linear characteristics of shear strength is necessary in the analysis of slopes specifically. This is due to the substantial influence of non-linear shear strength behavior on the slope failure mechanism when they are at low stress levels. In this paper, the nonlinearity of shear strength for grade VI granitic residual soil is studied. “Non-Axis Translation Consolidated Drained Triaxial” tests were performed at various ranges of net stress and suction. Thereafter, to characterize shear strength behavior, shear strength parameters were derived. The soil-water characteristic curve was plotted after conducting “Pressure Plate Extractor” test at a series of suction. The result substantiated the non-linearity of shear strength for granitic residual soil based on net stress and suction.
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"Evaluation of static equilibrium soil suction envelopes for predicting climate-induced soil suction changes occurring beneath covered surfaces." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 26, no. 3-4 (July 1989): A178. http://dx.doi.org/10.1016/0148-9062(89)92551-5.
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"Suction-controlled triaxial testing: laboratory procedures in relation to resistance envelope methods. Short communication." International Journal of Rock Mechanics and Mining Sciences & Geomechanics Abstracts 25, no. 4 (August 1988): A161. http://dx.doi.org/10.1016/0148-9062(88)91527-6.
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Abou Khedr, Nouran Abd El-Aziz, Tarek Mahmoud Hussein, and Ayat Mohamed El-Sayed Abd El-Fatah. "Comparing the role of subcision suction method with and without the injection of platelet-rich plasma in the treatment of depressed scars." Journal of Surgical Dermatology 2, no. 2 (February 14, 2017). http://dx.doi.org/10.18282/jsd.v2.i2.90.
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<p class="BodyText1">Among wound-healing modalities, platelet-rich plasma (PRP) has been used for wound healing, through the release of multiple growth factors. The platelets mediate wound healing by initiating the clotting pathway and the subsequent matrix remodelisation. The aim of the work was to study the role of injection of platelet-rich plasma in the treatment of scars. This study was conducted on thirty patients who were divided into two groups (A and B). Each group included fifteen patients. The two groups were randomly distributed by using individual sealed envelopes. Group A was subjected to subcision of their acne scars using Nokor needle, followed by suction. Group B patients were subjected to the same treatment but followed by an injection of platelet-rich plasma once per month over three months. In Group A, 6 patients (40%) showed moderate improvement, 5 patients (33.3%) showed slight improvement and 4 patients (26.7%) showed significant improvement. In Group B, 7 patients (46.7%) showed moderate improvement, 5 patients (33.3%) showed marked improvement and 3 patients (20%) showed significant improvement. There was a statistically significant difference on the independent observer’s after-treatment assessment between the groups (P=0.014). In conclusion, subcision suction leads to a persistent improvement of acne scars in a short time, and the coupling with injection of PRP is the most effective in the treatment of depressed facial scars.</p>
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Winka, James R., Joshua B. Anderson, Emily J. Boyd, David G. Bogard, and Michael E. Crawford. "Convex Curvature Effects on Film Cooling Adiabatic Effectiveness." Journal of Turbomachinery 136, no. 6 (November 28, 2013). http://dx.doi.org/10.1115/1.4025691.
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Surface curvature is known to have significant effects on film cooling performance, with convex curvature inducing increased film effectiveness and concave curvature causing decreased film effectiveness. Generally, these curvature effects have been presumed to scale with 2r/d at the film cooling hole location, where r is the radius of curvature and d is coolant hole diameter. In this study, the validity of this scaling of curvature effects are examined by performing experiments in regions of large and low curvature on a model vane. Single rows of cylindrical holes were placed at various locations along the high curvature section of the suction side of the vane. For the first series of experiments, a single row of holes was placed at two locations with different local surface curvature. The coolant hole diameters were then adjusted to match 2r/d values. Results from these experiments showed that there was better correspondence of film performance when using the 2r/d scaling, but there was not an exact matching of performance. A second series of experiments focused on evaluating the effects of curvature downstream of the coolant holes. One row of holes was placed at a position upstream of the highest curvature, while another row was placed at a downstream position such that the radius of curvature was equivalent for the two rows of holes. Results indicated that the local radius of curvature is not sufficient in understanding the performance of film cooling. Instead, the curvature envelope downstream of the coolant holes plays a significant role on the performance of film cooling for cylindrical holes.
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Saavedra, J., and G. Paniagua. "Transient Performance of Separated Flows: Characterization and Active Flow Control." Journal of Engineering for Gas Turbines and Power 141, no. 1 (September 7, 2018). http://dx.doi.org/10.1115/1.4040685.
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The aerothermal performance of the low-pressure turbine in unmanned aerial vehicles is significantly abated at high altitude, due to boundary layer separation. Different flow control strategies have been proposed to prevent boundary layer separation, such as dielectric barrier discharges (DBD) and synthetic jets. However, the optimization of the control approach requires a better characterization of the separated regions at transient conditions. The present investigation analyzes the behavior of separated flows, reporting the inception and separation length, allowing the development of efficient flow control methods under nontemporally uniform inlet conditions. The development of separated flows was investigated with numerical simulations including Unsteady Reynolds average Navier–Stokes (URANS) and large Eddy simulations (LES). The present research was performed on a wall-mounted hump, which imposes a pressure gradient representative of the suction side of low pressure turbines. Through sudden flow accelerations, we looked into the dynamic response of the shear layer detachment as it is modulated by the mean flow evolution. Similarly, we studied the behavior of the recirculation bubble under periodic disturbances imposed at various frequencies ranging from 10 to 500 Hz, at which the Reynolds number oscillates between 40,000 and 180,000. As a first step into the flow control, we added a slot to allow flow injection and ingestion upstream of the separation inception. Exploring the behavior of the separated region at different conditions, we defined the envelope for its periodic actuation. We found that by matching the actuator frequency with the frequency response of the separated region, the performance of the actuation is boosted.
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Xu, Chi, Cheng-Qi Jia, Feng-Chih Kuo, Wei Chai, Ming-Hua Zhang, and Ji-Ying Chen. "Does the use of a closed-suction drain reduce the effectiveness of an antibiotic-loaded spacer in two-stage exchange Arthroplasty for Periprosthetic hip infection? A prospective, randomized, controlled study." BMC Musculoskeletal Disorders 20, no. 1 (December 2019). http://dx.doi.org/10.1186/s12891-019-2974-5.
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Abstract Background There is a concern regarding the use of a closed-suction drain (CSD) in two-stage exchange arthroplasty for periprosthetic joint infection as it may decrease the antibiotic concentrations in the joint fluids. The purpose of this study was to identify whether the use of a CSD could reduce local antibiotic concentrations following spacer implantation. Methods A prospective, randomized, controlled trial was conducted at our institution between January 2018 and November 2018. We enrolled 32 patients undergoing two-stage exchange arthroplasty for periprosthetic hip infection with an interim cement spacer containing 4-g vancomycin and 2-g meropenem per 40-g methyl-methacrylate cement polymer. Patients were randomized and evenly divided into the study group (non-CSD) and control group (CSD group) by sealed envelopes. Drainage samples of joint fluids (n = 160) were collected every 24 h for the first five days following spacer implantation. The antibiotic concentrations of drainage samples were measured by high-performance liquid chromatography, and the bioactivities of the drainage samples against methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA) and E. coli were assessed. Results There was no significant difference in the decrease of vancomycin (study group vs. control group: 163.20 ± 77.05 vs. 162.39 ± 36.31; p = 0.917) and meropenem concentration (123.78 ± 21.04 vs. 117.27 ± 19.38; P = 0.548) between the two groups during the first five days following spacer implantation. All joint drainage samples in each group exhibited antibacterial activity against MSSA, MRSA and E. coli. Conclusions The use of CSD following the implantation of an antibiotic-loaded cement spacer does not reduce the effectiveness of such a spacer in two-stage exchange arthroplasty. (Chinese Clinical Trial Registry, ChiCTR-INR-17014162. Registered 26 December 2017.)
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Lattimer, Christopher Richard, and Alfred Obermayer. "Venous return simplified with air-plethysmography, modelling and Sack Theory." Journal of Theoretical and Applied Vascular Research 5, no. 3 (2020). http://dx.doi.org/10.24019/jtavr.109.
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The usual mantra taught by experts is to explain venous return using (i) pressure gradients, (ii) ankle joint movements and (iii) the suction effect of inspiration. This is supported with data obtained directly from venous pressure measurements and indirectly using ultrasound calculations. Whilst these veno-dynamic factors undoubtedly assist in the venous return process, the primary mechanism is missing from the standard teaching curriculum. Evidence for this is the observation that most patients with calf muscle pump (CMP) inactivity or failure of active inspiration have an excellent venous return. Examples include persons on mechanical ventilation, in a wheelchair from paralysis or amputees. Chair sleeping is another example. The first strategy of this paper is to explain venous return using calf volume changes in response to gravitational positioning. It relies on the premise that arterial supply volume equals venous drainage volume. When this system is challenged by gravitational positioning, the resulting calf volume changes demand an explanation in terms of an inequality in the inflow = outflow hypothesis. Large volume shifts illustrate the powerful ability of gravity to change venous drainage dynamics. The second strategy is to use modelling with water, beakers, bags and tubes to explain upward flow against hydrostatic columns over a metre high. Whilst this is a data free exercise, the experiments are easily repeatable and understandable. They will depict pressure using height instead of pressure transducers (which are themselves calibrated using liquid columns). Most important, it will demonstrate that pressure is not the cause of the flow but the expression of the feature of a hydrodynamic system. The final strategy is to place Sack Theory into context as the hidden environment making venous drainage possible. It relies on the fact that our bodies are made of collapsible “sacks”, liquids and tissues that compress like liquids. These are surrounded by a hierarchy of enveloping membranes with each absorbing their enclosed weight and transferring their contents into weightless tissue. Once transformed, gravitational forces are negated making upward flow energy efficient. Collapsible venous drainage tubes are recognised as one such envelope (sack). Elementary child-friendly models are illustrated, and the role of trans-membrane pressure neutralisation is highlighted. Veno-dynamic equations will not be used.