Rigid Column Research Articles

Hierarchical Buckling on Surfaces of Soft Laminae

Buckling in solid thin films supported by soft substrates has been well-studied. Many of those buckling features discovered, however, are monotonous without any hierarchical organizations. We report our finding of a substantial 2D hierarchical buckling atop a molecular type of multistacks or lamellae. This multistacked structure is a direct self-assembly from aminopropyltriethoxysilane, in which the polar amine groups promote the absorption of a large amount of water. We found that the resulting soft structures are good candidates to allow the formation of a complex buckling along the surface normal. Revealed cauliflower-like, hierarchical patterns are modeled by considering rigid columns standing on a soft substrate. In return, the hierarchical structures demonstrated could find applications in nanofabrication and enrich emerging fields, such as flexible electronics or optics.

Current transfer in dc non-transferred arc plasma torches

Fundamentals of current transfer to the anodes in dc non-transferred arc plasma torches are investigated. Specially designed anodes made of three mutually isolated sections and external dc axial magnetic fields of various strengths are utilized to explore the conditions for different diffused and constricted attachments of the arc with the anode. A number of new facts are revealed in the exercise. Under constricted attachment, formation of arc root takes place. Spontaneous and magnetically induced movements of the arc root, their dependence on the arc current and the strength of the external magnetic field, most probable arc root velocity, variation of the root velocity with strength of the applied magnetic field, the effect of swirl on the rotational speed of the arc root are some of the important features investigated. Two new techniques are introduced: one for measurement of the arc root diameter and the other for determination of the negative electric field in the boundary layer over the anode. While the first one exploits the rigid column behaviour of the arcs, the second one utilizes the shooting back of the residual electrons over an arc spot. Sample calculations are provided.

Unstable Operation of Francis Pump-Turbine at Runaway: Rigid and Elastic Water Column Oscillation Modes

This paper presents a numerical simulation study of the transient behavior of a <TEX>$2{\times}340MW$</TEX> pump-turbine power plant, where the results show an unstable behavior at runaway. First, the modeling of hydraulic components based on equivalent schemes is presented. Then, the 2 pump-turbine test case is presented. The transient behavior of the power plant is simulated for a case of emergency shutdown with servomotor failure on Unit 1. Unstable operation at runaway with a period of 15 seconds is properly simulated using a 1-dimensional approach. The simulation results points out a switch after 200 seconds of the unstable behavior between a period of oscillations initially of 15 seconds to a period of oscillation of 2.16 seconds corresponding to the hydraulic circuit first natural period. The pressure fluctuations related to both the rigid and elastic water column mode are presented for oscillation mode characterization. This phenomenon is described as a switch between a rigid and an elastic water column oscillation mode. The influence of the rotating inertia on the switch phenomenon is investigated through a parametric study.

Preparation of a super‐long two column chromatography system and its application in separating glycosylated puerarin

Separation of Puerarin-7-O-glucoside from its precursor, puerarin, using a common chromatography column packed with AB-8 macroporous resin was unsuccessful. Therefore, in this study a 8 m super-long flexible reinforced PVC column was externally added to the common column in order to improve the chromatography efficiency by increasing the number of theoretical plates. Both the PVC and common columns were separately packed with AB-8 macroporous resin slurry. The packed PVC column was coiled after washing and stored until use. The microbial transformation mixture with puerarin-7-O-glucoside and puerarin (250 mL) was loaded onto the common column, followed by washing with 2000 mL H(2)O. After attaching the coiled external PVC column to the common column, a linear gradient of 10-30% ethanol was applied to elute the target compound. Two peaks appeared: peak I contained puerarin-7-O-glucoside at 97.9% purity and 88.1% recovery rate, and peak II was puerarin at 98.7% purity and 87.0% recovery rate. The use of the coiled external flexible reinforced PVC column avoided spatial restriction for long columns, which made it much more convenient for column packing and chromatography operations. Furthermore, this method eliminated the resin blockage problem caused by stationary water pressure in a rigid vertical long column. Using an external super-long column, the PVC tube was connected with the common column only during elution, which avoided delay in time period during sample loading and column washes associated with the use of long external columns.

Structure of the Third Intracellular Loop of the Vasopressin V2 Receptor and Conformational Changes upon Binding to gC1qR

The V2 vasopressin receptor is a G-protein-coupled receptor that regulates the renal antidiuretic response. Its third intracellular loop is involved in the coupling not only with the GαS protein but also with gC1qR, a potential chaperone of G-protein-coupled receptors. In this report, we describe the NMR solution structure of the V2 i3 loop under a cyclized form (i3_cyc) and characterize its interaction with gC1qR. i3_cyc formed a left-twisted α-helical hairpin structure. The building of a model of the entire V2 receptor including the i3_cyc NMR structure clarified the side-chain orientation of charged residues, in agreement with literature mutagenesis reports. In the model, the i3 loop formed a rigid helical column, protruding deep inside the cytoplasm, as does the i3 loop in the recently elucidated structure of squid rhodopsin. However, its higher packing angle resulted in a different structural motif at the intracellular interface, which may be important for the specific recognition of GαS. Moreover, we could estimate the apparent K d of the i3_cyc/gC1qR complex by anisotropy fluorescence. Using a shorter and more soluble version of i3_cyc, which encompassed the putative site of gC1qR binding, we showed by NMR saturation transfer difference spectroscopy that the binding surface corresponded to the central arginine cluster. Binding to gC1qR induced the folding of the otherwise disordered short peptide into a spiral-like path formed by a succession of I and IV turns. Our simulations suggested that this folding would rigidify the arginine cluster in the entire i3 loop and would alter the conformation of the cytosolic extensions of TM V and TM VI helices. In agreement with this conformational rearrangement, we observed that binding of gC1qR to the full-length receptor modifies the intrinsic tryptophan fluorescence binding curves of V2 to an antagonist.

Consolidation around stone columns. Influence of column deformation

AbstractA solution is presented for the radial consolidation around stone columns under constant surcharge load. The solution considers the influence of vertical and radial deformation of the column, either in elastic and elastoplastic regimes.The solution is in terms of the average excess pore pressure in the soil. It is based on previous solutions, initially developed for rigid column, or including only vertical deformation. For elastic column, the solution gives the variation of strains and stresses between the undrained and final states, for which it coincides with the existing elastic solutions.All the results are given in closed form, and both the elastic and plastic deformations of the column lead to an equivalent coefficient of consolidation for the radial flow, which enables the application of the existing methods of integration of the consolidation equation.A parametric study is presented, showing the influence of the main problem features. A design example is used to illustrate the application to practical cases. Copyright © 2008 John Wiley &amp; Sons, Ltd.

Finite Element Analysis of Spinal Cord Injury in the Rat

A three-dimensional (3D) finite element model (FEM) that simulates the Impactor weight-drop experimental model of traumatic spinal cord injury (SCI) was developed. The model consists of the rat spinal cord, with distinct element sets for the gray and white matter, the cerebrospinal fluid (CSF), the dura mater, a rigid rat spinal column, and a rigid impactor. Loading conditions were taken from the average impact velocities determined from previous parallel weight-drop experiments employing a 2.5-mm-diameter, 10-g rod dropped from either 12.5 or 25 mm. The mechanical properties were calibrated by comparing the predicted displacement of the spinal cord at the impact site to that measured experimentally. Parametric studies were performed to determine the sensitivity of the model to the relevant material properties, loading conditions, and essential boundary conditions, and it was determined that the shear modulus had the greatest influence on spinal cord displacement. Additional simulations were performed where gray and white matter were prescribed different material properties. These simulations generated similar drop trajectories to the homogeneous model, but the stress and strain distributions better matched patterns of acute albumin extravasation across the blood-spinal cord barrier following weight-drop SCI, as judged by a logit analysis. A final simulation was performed where the impact site was shifted laterally by 0.35 mm. The off-center impact had little effect on the rod trajectory, but caused marked shifts in the location of stress and strain contours. Different combinations of parameter values could reproduce the impactor trajectory, which suggests that another experimental measure of the tissue response is required for validation. The FEM can be a valuable tool for understanding the injury biomechanics associated with experimental SCI to identify areas for improvement in animal models and future research to identify thresholds for injury.

Spinal curvature and trunk muscle tone in rhythmic gymnasts and untrained girls

The aim of this study was to compare spinal curvature and muscle tone characteristics in elite female rhythmic gymnasts (n = 32) and untrained controls (n = 48). Results showed that the angles of lumbar lordosis (LL) and thoracic kyphosis (TK) were lower (p < 0.001) in gymnasts in comparison with the control group. It was evident that the vertebral column of gymnasts had straightened in thoracic as well as in lumbar part of the spine. The trunk flexors in gymnasts were undertoned, the tone of rectus abdominis muscle was lower (p < 0.001) in gymnasts compared to that of the control group, while tone of erector spinae muscle (trunk extensor) was not differed from the control group. The tone of spinal muscles was higher (p < 0.001) than that of abdominal muscles in gymnasts, whereas the tone of these muscles did not differ significantly in controls. In the control group, the tone of trunk flexor and extensor muscles were in balance, whereas in gymnasts it was imbalanced. The indicator of tone imbalance of the trunk flexor and extensor muscles correlated negatively with the difference in body height in supine and standing positions (L) (r = −0.66, p < 0.001) for the group of gymnasts. In gymnast, TK and LL correlated negatively with Oswestry score (r = −0.68, p < 0.05 and r = −0.66, p < 0.05, respectively) and positively with L (r = 0.63, p < 0.05 and r = 0.60, p < 0.05 respectively). This indicates that the more rigid vertebral column, flattened in thoracal and lumbar part that appeared in gymnasts, associated with imbalance in muscle tone and low back pain (LBP). In 50% of measured gymnasts, LBP incidence

상수관망시스템에서의 장기간 모의를 위한 동역학적 모형의 개발

본 연구에서는 점진적인 유량 및 압력이 변화하는 상수관망에서 Rigid Water Column Theory를 이용하여 정상모형의 확장기간 모의해석보다 정확하고 수충격 해석보다는 계산비용 및 노력 측면에서 효율적으로 장시간 부정류 해석 모형을 개발하였다. 개발된 모형을 이용하여 실제관망에 대하여 24 시간 열 수요량을 고려한 부정류 해석 및 밸브폐쇄로 인한 수충격해석 모의에 적용하였고 해석 결과는 다음과 같다. 24 시간 일변화 모의의 경우에 수요량이 증가할 경우 모든 관로에서 압력감소가 나타났으며 수요량이 감소할 경우 압력증가가 나타났다. 그리고 일 수요량의 변화에 따라 나타난 절점에서의 유량 및 압력 변화폭은 각 절점마다 다르고 수요량과 유량의 변화양상이 반대로 나타나는 관로도 발생하고 있으며 KYPIPE2의 결과와 본 모형의 유량 및 압력차이도 발생하고 있어 상수관망의 동역학적 해석의 필요성이 대두되었다. 밸브폐쇄로 인한 수충격모의에 본 모형이 적용되었을 때 본 모형은 유체의 압축성을 무시함으로 인해 밸브 완전 폐쇄와 동시에 압력과 유량의 변화가 전 관망에 발생하였고 수충격모형은 유체의 탄성으로 인해 발생된 압력파의 도달시간이 필요함으로 압력과 유량변화가 지체되어 나타났으나 전체적인 변화양상 및 변화폭의 크기 등은 유사한 경향을 나타내어 본 모형의 적용성을 입증하였다. 본 연구에서 개발된 프로그램은 장기간 점진적인 관로 부정류를 비교적 정확하게 해석할 수 있을 것으로 판단되며 이를 이용하여 관로내 오염물의 확산해석, 수요량을 고려한 절점에서의 압력제어 및 누수저감, 장기간 관로내의 유량 및 압력 변화를 고려한 관망관리 등의 분야에서 효율적으로 이용될 수 있을 것으로 기대되었다. In this study, a long-term unsteady simulation model has been developed using rigid water column theory which is more accurate than Extended-period model and more efficient comparing with water-hammer simulation model. The developed model is applied to 24-hours unsteady simulation considering daily water-demand and water-hammer analysis caused by closing a valve. For the case of 24-hours daily simulation, the pressure of each node decreases as the water demand increase, and when the water demand decrease, the pressure increases. During the simulation, the amplitudes of flow and pressure variation are different in each node and the pattern of flow variation as well as water demand is quite different than that of KYPIPE2. Such discrepancy necessitates the development of unsteady flow analysis model in water distribution network system. When the model is applied to water-hammer analysis, the pressure and flow variation occurred simultaneously through the entire network system by neglecting the compressibility of water. Although water-hammer model shows the lag of travel time due to fluid elasticity, in the aspect of pressure and flow fluctuation, the trend of overall variation and quantity of the result are similar to that of water-hammer model. This model is expected for the analysis of gradual long-term unsteady flow variations providing computational accuracy and efficiency as well as identifying pollutant dispersion, pressure control, leakage reduction corresponding to flow-demand pattern, and management of long-term pipeline net work systems related with flowrate and pressure variation in pipeline network systems

Water hammer dissipation in pneumatic slug tests

We model and measure the dissipation of water hammer induced by well casing and water elasticity with rapid valve opening at the start of a pneumatic slug test. The higher‐frequency water hammer can obscure slower, aquifer‐controlled, underdamped oscillations of the rigid water column, so a quantitative description of the elastic motion improves the ability of a slug test to calibrate the aquifer permeability k. Internal friction attenuates the water hammer, subject to a known headspace pressure at the air/water interface and equilibrium pressure at the top of the well screen. An analytical elastic solution is presented and matched to an existing rigid motion analysis, with matching predicated on k exceeding 7 × 10−14 m2 and appreciable water hammer dissipation during the first cycle of the slug test. The model is accurately calibrated with data from underdamped slug tests in a PVC monitoring well in the Plymouth‐Carver Aquifer. The calibrated casing elasticity value suggests that effective lateral soil stress appreciably stiffened the casing.

Improved Simulation of Flow Regime Transition in Sewers: Two-Component Pressure Approach

Operational problems and system damage have been linked to the flow regime transition between free surface and pressurized flow in rapidly filling stormwater and combined sewer systems. In response, emphasis has been placed on the development of numerical models to describe hydraulic bores and other flow phenomena that may occur in these systems. Current numerical models are based on rigid column analyses, shock-fitting techniques, or shock-capturing procedures employing the Preissmann slot concept. The latter approach is appealing due to the comparative simplicity, but suffers from the inability to realistically describe subatmospheric full-pipe flows. A new modeling framework is proposed for describing the flow regime transition utilizing a shock-capturing technique that decouples the hydrostatic pressure from surcharged pressures occurring only in pressurized conditions, effectively overcoming the cited Preissmann slot limitation. This new approach exploits the identity between the unsteady incompressible flow equations for elastic pipe walls and the unsteady open-channel flow equations, and the resulting numerical implementation is straightforward with only minor modifications to standard free surface flow models required. A comparison is made between the model predictions and experimental data; good agreement is achieved.

柱状剛体基礎の水平支持力に対する地盤反力~変位関係の影響(その2)

柱状剛体基礎の水平支持力に対する地盤反力~変位関係の影響(その2)

シェルの環境条件不連続点近傍における応力集中の実用評価法 : 解析解と粗いメッシュ分割の有限要素法の併用

Stress concentration appears around discontinuous points of support conditions in case that plates or shells are supported by different structures. for example, partly by rigid columns and partly by thin walls. A practical method to evaluate the stress concentration by using the asymototic analytical solution and a coarse-mesh FEM is proposed here. In this method, the stress resultant intensity factor (SRIF) which is an unknown coefficient in the analytical solution is calculated with use of the displacement results of coarse-mesh FEM without much labour and time for computation neither. And, by putting that SRIF into the analytical solution of stress resultants, the precise stress resultants are obtained. The SRIF does not only show the intensity of the stress concentration, but could also be used as the index'of fracture condition.

Dorsal Intercarpal Augmentation Ligamentoplasty for Scapholunate Dissociation

Carpal instability secondary to scapholunate ligament tears can lead to significant disability of the wrist. Disruption of the ligamentous stabilizers of the scaphoid causes rotatory subluxation of the scaphoid and subsequent abnormal loads across the radioscaphoid joint. Arthritic changes involving the radioscaphoid and midcarpal joint will develop if the wrist is untreated. Treatment of scapholunate ligament tears has varied widely in the literature. Today, most surgeons perform either a soft tissue reconstruction using local tissue or a limited fusion. Motion of the wrist favors soft tissue reconstructions. Also, the relative intercarpal motion with a more flexible carpus may prevent abnormal load patterns that are associated with a rigid radial column and limited fusions. We have reconstructed flexible subacute (>3 weeks) and chronic (>2 months) scapholunate dissociations with a radial-based dorsal intercarpal ligament. Clinical results have demonstrated increased grip strength, decreased pain, and improved intercarpal alignment.

Effects of reinforcement slippage on the non‐linear response under cyclic loadings of RC frame structures

AbstractThis paper discusses the importance of including the bond‐slip effects in assessing the response under cyclic loads of reinforced concrete frames. The discussion is based on analyses performed using numerical models which are simple, computationally efficient and capable of representing the salient features of reinforced concrete frames under both static and dynamic loads. The numerical models comprise a displacement‐based, reinforced concrete frame element with bond‐slip and a rigid beam column joint element with bond‐slip. Two applications illustrate the model accuracy and show the importance of including bond‐slip. The first application considers a reinforced concrete beam‐column subassemblage experimentally tested under cyclic loads. The second application considers the shaking table test of a two‐story one‐bay reinforced concrete frame In both cases the analytical results correlate well with the experimental results in terms of strength, displacement demands and hysteretic energy dissipation. Furthermore, the paper shows how the analyses that include bond‐slip yield a better correlation with the experimental results with respect to the analyses that assume a perfect bond. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Inclined Plane Studies of the Newmark Sliding Block Procedure

This study considers the shaking-induced displacement and dynamic response of a rigid block and deformable columns of soil on an inclined plane. This work demonstrates that because of the coupled d...

Advances in capillary electrochromatography and micro-high performance liquid chromatography monolithic columns for separation science.

Over the last decade, monoliths or continuous beds have emerged as an alternative to traditional packed-bed columns for use in capillary electrochromatography (CEC) and micro-high performance liquid chromatography (micro-HPLC). Monolithic columns can be divided into two categories: silica-based monolithic columns and rigid organic polymer-based monolithic columns resulting from the polymerization of acrylamide, styrene, acrylate or methacrylate monomers. In this paper, the chemistry and most recent applications of these various types of monoliths in both CEC and micro-HPLC are presented.

Effects of Free Outflow in Rising Mains with Air Chamber

Air chamber design is usually accomplished by the use of charts or numerical models based on the classic boundary condition of a constant-level downstream reservoir. However, a constant-level downstream reservoir typically does not exist in currently operating facilities. The downstream end of the rising main is usually designed with the outlet at a level above the maximum allowed in the receiving reservoir. Such a scheme is usually chosen in order to avoid the loss of stored water in case of leakage or breakdown of the pipeline. For this reason, the final section of the discharge pipeline is often fitted with a vertical pipe with free outflow. This particular downstream condition influences the transient state that occurs following a power failure in the pump. In this paper, we focus on the variations of maximum and minimum pressures and water-level oscillations that arise in the terminal section of the rising main, by means of complete transient analysis. The rigid water column model is used to provide ...

The Instability of a Viscoelastic Conducting Cylindrical Interface Supporting Free-surface Currents

The stability of a viscoelastic interface acted upon by an oscillating azimuthal magnetic field is studied. The interface separates two rigid magnetic fluid columns. Only azimuthal disturbrance modes are considered in a linear perturbation technique. Weak viscoelastic effects are taken into consideration, so that their contributions are demonstrated in the boundary conditions. The presence or absence of free surface currents resulted in a dispersion equation with complex coefficients of the Mathieu type. It is found that the surface currents disappear when the stratified magnetic field becomes unity. The phenomenon of coupled resonance is observed. Several special cases are reported. A set of graphs are drawn to illustrate the influence of the various parameters on the stability of the considered system.

Hysteretic Modeling of Thin-Walled Circular Steel Columns under Biaxial Bending

To ensure the safety of elevated highway bridges under major earthquakes, it is important to predict the ultimate behavior of columns used as bridge piers. After the Kobe earthquake, many analytical and experimental studies have been conducted to examine the ultimate seismic behavior of thin-walled steel columns. However, these studies are mostly restricted to the in-plane behavior of the columns. As observed in the Kobe earthquake, the damages to the columns are usually influenced by the two-dimensional horizontal seismic excitations. Therefore, it is more desirable to consider the effect of biaxial bending at the ultimate stage of earthquake response in the design of steel columns. Herein, we propose a hysteretic model of thin-walled circular steel columns under biaxial bending to predict the ultimate seismic behavior of cantilever-type thin-walled circular steel columns with constant axial load. The proposed column model consists of a concentrated mass and a rigid column with multiple nonlinear springs located at the column base. As the hysteretic constitutive relation for each spring, we adopt the Dafalias and Popov’s bounding-line model by modifying the original model in order to take into account the local buckling behavior. The material constants of the modified bounding-line model can be determined, based on the in-plane hysteretic behavior of the column obtained either by FEM shell analyses or by experiments. The validity of the proposed model is examined by comparing it with results of the two-dimensional horizontal earthquake-response analyses, using the FEM shell model.