Rectangular Perforations Research Articles

1504 SPONGE TRAINER A NOVEL SIMPLE TRAINING MODEL FOR PERCUTANEOUS RENAL ACCESS

You have accessJournal of UrologyTechnology & Instruments: Surgical Education & Skills Assessment/Ureteroscopy II1 Apr 20121504 SPONGE TRAINER A NOVEL SIMPLE TRAINING MODEL FOR PERCUTANEOUS RENAL ACCESS Ahmad Tawfik, Mohamed Gaber, Osama El-Gamal, Yasser Farahat, Ahmad Ramadan, Abdelhamid El-Bahnasy, and Mohamed Rasheed Ahmad TawfikAhmad Tawfik Tanta, Egypt More articles by this author , Mohamed GaberMohamed Gaber Tanta, Egypt More articles by this author , Osama El-GamalOsama El-Gamal Tanta, Egypt More articles by this author , Yasser FarahatYasser Farahat Tanta, Egypt More articles by this author , Ahmad RamadanAhmad Ramadan Tanta, Egypt More articles by this author , Abdelhamid El-BahnasyAbdelhamid El-Bahnasy Tanta, Egypt More articles by this author , and Mohamed RasheedMohamed Rasheed Tanta, Egypt More articles by this author View All Author Informationhttps://doi.org/10.1016/j.juro.2012.02.1271AboutPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissionsReprints ShareFacebookTwitterLinked InEmail INTRODUCTION AND OBJECTIVES The co-ordination of fluoroscopic guidance and spatial movement of the puncture needle is the most demanding and steady step in learning curve for percutaneous renal access (PRA). Unlike laparoscopic box trainer, there is no currently available cheap training model for PRA. Either animal models or virtual trainers are expensive training solutions which are not usually available in many centers. This study was designated to evaluate the efficacy of our novel sponge trainer to provide junior urologists with initial skills for PRA. METHODS • Trainer design: Three sheets of 10cm thick sponge (60x70cm) were arranged horizontally over each other. A rectangular perforation was done just lateral to the midline of the middle sheet. The upper sheet was thinned out at both sides to simulate human back with radiopaque bands (simulating human ribs) are fixed to its surface. All sheets were fixed together on fluoroscopic table. • Training schedule: Single then multiple small metal balls were fixed in the hole of the middle sheet and covered with the upper one. Under perpendicular and oblique fluoroscopic control, every trainee was asked to pass Chiba needle from a surface puncture point (selected by a supervisor PCNL expert) to the selected metal ball. After success, he was asked to pass the needle through a horizontal then vertical metal ring (instead of the ball) and finally to pass the needle through a plastic model of the kidney filled with radio-opaque solution and pass a guidewire through its ureter. Twelve junior urologists were included in this study. Training sessions were done every other day for 10 sessions. After last session, all trainees were asked to describe their experience with this model on 5-points scale. Trainees who could get successful first trial in all models at last session were shifted to a single supervised patients' trial. RESULTS The median number of trials required to touch a single ball, one of multiple balls, pass the needle in horizontal then vertical ring and put the wire in the plastic models decreased from 6, 9, 8, 10 and 9 trials at the first training session to 1, 1, 2, 2 and 3 trials at the last session respectively. Nine of the trainees described the experience gained as “excellent”, while the other three described it as “very good”. Four out five trainees (80%), who had successful first trial in all models, could successfully achieve PRA on their first trial in PCNL patients. CONCLUSIONS Sponge trainer is a simple, cheap and effective mean for PRA training. It applies the necessary navigation and hands-eye coordination skills to deal with PCNL puncture needles under fluoroscopic guidance. © 2012 by American Urological Association Education and Research, Inc.FiguresReferencesRelatedDetails Volume 187Issue 4SApril 2012Page: e609 Advertisement Copyright & Permissions© 2012 by American Urological Association Education and Research, Inc.MetricsAuthor Information Ahmad Tawfik Tanta, Egypt More articles by this author Mohamed Gaber Tanta, Egypt More articles by this author Osama El-Gamal Tanta, Egypt More articles by this author Yasser Farahat Tanta, Egypt More articles by this author Ahmad Ramadan Tanta, Egypt More articles by this author Abdelhamid El-Bahnasy Tanta, Egypt More articles by this author Mohamed Rasheed Tanta, Egypt More articles by this author Expand All Advertisement Advertisement PDF downloadLoading ...

Wet Gas Measurement with Slotted Orifice Meter--Effect of Geometry of Slots and Pressure

Wet gas metering by differential pressure flow meters is gaining prominence in the oil and gas industry, owing to their simple construction. Slotted orifice, a modified version of the standard orifice meter has been found promising by many researchers. This novel flow meter is shown to be insensitive to the upstream flow profile with lower head loss and faster pressure recovery compared to the standard orifice. In the present work, the effect of geometry of slots and pressure on the performance of the slotted orifice has been studied by CFD modeling of the wet gas flow. The performance of slotted orifice with rectangular perforations (1.5 ≤ l/w ≤ 3.0) and circular perforations has been compared with that of the standard orifice having same β-ratio of 0.40. Simulation results reveal that the shape of perforation of the slotted orifice has no effect on the differential pressure. However, the pressure recovery with the rectangular slots is found to increase with increasing aspect ratio. Moreover, at low pressure, slotted orifice is found to be more sensitive to liquid presence than the standard orifice. The relatively higher over reading values obtained in this work is consistent with the results of Geng et al (2006) that for slotted orifice, a low beta ratio is more sensitive to the liquid presence in the stream and hence is preferable for wet gas metering. Homogeneous model, Steven’s and De Leeuw’s correlations, are found to be better than orifice correlations for wet gas mass flow prediction.

Study of the geometry of a voided clay brick using rectangular perforations to optimize its thermal properties

This study was undertaken to optimize the equivalent transmittance of a wall consisting of voided clay bricks using ceramic material Termoarcilla ® 29 ECO, complying with the Spanish UNE [1] , European EN [2] and international ISO [3] , [4] , [5] , [6] , [7] standards. Various geometries were investigated for the bricks’ cross sections, starting from a commercialized block and improvements in its thermal conductivity were studied by varying parameters such as a number of rows in the brick, the type of tongue and grooving and the alternation between contiguous rows in the brick. Simulations were made using a finite elements application [9] . The conclusions of the study were that the thermal properties of a brick are improved by placing the perforations of the voids in a quincunx (in parallel rows, so that every hole is placed between those of the immediate rows, forming equilateral triangles) and that the greater the number of rows, the better the thermal behaviour. Further, if these perforations are extended to the tongue and groove area and a certain clearance is left between the tongue and groove of each brick, the wall’s equivalent transmittance is reduced. ► This study tries to optimize the equivalent transmittance of a wall of bricks. ► Thermal properties of a brick are improved by placing the perforations in a quincunx. ► If perforations are extended to the tongue the wall’s transmittance is reduced. ► A clearance left in the joint of the bricks, reduces the wall’s transmittance. ► A brick with 26 rows of rectangles with Ueq<0.57 W/m 2 -K is obtained.

MULTI-SCALE APPROACH FOR THE ELECTROMAGNETIC SIMULATION OF FINITE SIZE AND THICK FREQUENCY SELECTIVE SURFACES

The scattering analysis from metallic Grid FSS consisting of rectangular perforations on a thick metallic screen illuminated by an oblique incident plane wave is presented. The grid structure is analyzed using Scale Changing Technique (SCT) which is based on the partition of the grid-plane into planar sub-domains deflned at various scale-levels. Electromagnetic interaction between subsequent scales is modeled by mutually independent Scale-Changing Networks and flnally the complete structure is simply represented by a cascade of these networks. Very good agreement is obtained between simulation results from SCT and the Finite Element Method (FEM) when computing the re∞ection/transmission coe-cients and electromagnetic fleld backscattered by thick and flnite size frequency selective surfaces. The computation time is signiflcantly reduced when using SCT-based software compared with the FEM simulation tool. The accurate prediction of the electromagnetic scattering by flnite size arrays is of great practical interest in the design and optimization of modern frequency selective surfaces (FSSs), re∞ect-arrays and transmit-arrays. A complete full-wave analysis of these structures requires generally enormous computational resources due to their large electrical dimensions which would require prohibitively large number of unknowns to be solved. The unavailability of e-cient and accurate design tools for these applications limits the engineers with the choice of low performance simplistic designs that do

A CFD study of low pressure wet gas metering using slotted orifice meters

Wet gas metering is becoming an increasingly important problem to many industries, in particular the oil and gas industry. Extensive studies have been done in the past on Venturi and standard orifice differential pressure (DP) flow meters to tackle wet gas flow problems. However in recent years, the slotted orifice flow meter has been developed in the attempt to improve the performance of the standard orifice meter. The novel flow meter is shown to be insensitive to the upstream flow profile with lower head loss and faster pressure recovery. This paper describes the numerical studies to establish the effect of different geometrical perforations on the performance of the slotted orifice. Three sets of slotted orifices with varying aspect ratios ( 1.5 ≤ l / w ≤ 3.0 ), of rectangular perforations and one slotted orifice with a circular perforation and a β ratio of 0.40 are simulated in a 1.6 m horizontal pipe using the k – ε turbulence model over a range of parameters, i.e. gas volume fraction (GVF) and gas mass flow rate. The commercial CFD code, FLUENT 6.3 was used to model the wet gas flow. Simulation results revealed that the shape of the perforation has no effect on the differential pressure, However, a marginally better pressure recovery was observed with rectangular perforations of l / w = 3.0 . The relatively higher over-reading values obtained in this work are consistent with the results of Geng et al. (2006) [1] that for a slotted orifice, a low β ratio is more sensitive to the liquid presence in the stream and hence is preferable for wet gas metering. Mass flow prediction by wet gas correlations showed that the homogeneous model, Steven’s and De Leeuw’s correlations had the best performance, with a calculated mean error of 4%–5%.

Enhancement of natural convection heat transfer from a fin by rectangular perforations with aspect ratio of two

In this study, the enhancement of natural convection heat transfer from a horizontal rectangular fin embedded with rectangular perforations of aspect ratio of two has been examined using finite element technique. The results for perforated fin have been compared with its equivalent solid one. A parametric study for geometrical dimensions and thermal properties of the fin and the perforations was carried out. The study investigated the gain in fin area and of heat transfer coefficients due to perforations. It was found that, for certain range of rectangular dimension and spaces between perforations, there is an augmentation in heat dissipation and a reduction in weight over that of the equivalent solid one. Also, the heat transfer enhancement of the perforated fin increases as the fin thickness and thermal conductivity increase. Key words: Finite element, perforated fin, heat dissipation, heat transfer augmentation, natural convection, rectangular perforations.

Small amplitude, transverse vibrations of circular plates with an eccentric rectangular perforation elastically restrained against rotation and translation on both edges

The Rayleigh–Ritz variational method is applied to the determination of the first four frequency coefficients for small amplitude, transverse vibrations of circular plates with an eccentric, rectangular perforation that is elastically restrained against rotation and translation on both edges. Coordinate functions are used which identically satisfy the boundary conditions at the outer circular edge, while the restraining boundary conditions at the inner edge of the cutout are dealt with directly through the energetic terms in the functional expressions. The procedure seems to show very good numerical stability and convergence properties. As an added bonus, the method allows for increased flexibility in dealing with boundary conditions at the edge of the cutout.

Pragtvognen fra Fredbjerg

Pragtvognen fra Fredbjerg

A novel method for switching and tuning of PBG structures

AbstractPhotonic band‐gap (PBG) structures are utilized in microwave components as filters to suppress unwanted signals. In this work, rectangular perforations were created in the ground plane of a microstrip line to construct a PBG structure. A gold‐coated alumina substrate was utilized to switch or tune the bandstop characteristics of this structure. It was demonstrated that the bandstop characteristics were switched off from −35 to −1 dB at 16 GHz. Tuning of the bandstop edge with a shift of 1.5 GHz was also shown. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 43: 334–337, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20462

Effect of aspect ratio on the elastic buckling of uniaxially loaded plates with eccentric holes

The Finite Element Method (FEM) has been employed to determine the elastic buckling load of uniaxially loaded rectangular perforated plates with length a and width b. Plates with simply supported edges in the out-of-plane direction and subjected to uniaxial end compression in their longitudinal direction are considered. Integer plate aspect ratios, a/ b=1, 2, 3 and 4, have been chosen to assess the effect of aspect ratio on the plate buckling load. Two perforation shapes of different sizes are considered; circular, and rectangular with curved corners. The rectangular perforation is oriented such that either its long or its short side is parallel to the longitudinal direction of the plate. The center of perforation was chosen at different locations of the plate. The study shows that the buckling load of a rectangular perforated plate that could be divided into equal square panels is not the same as that of the square panel that contains the perforation when treated as a separate square plate. For rectangular plates, the study recommends not to have the center of a circular hole placed in a critical zone defined by the end half of the outer square panel, to try always to put the hole in an interior panel of the plate, and to have the distance between the edge of a circular hole and the nearest unloaded edge of the plate not less than 0.1 b. The study concludes also that the use of a rectangular hole, with curved corners, with its short dimension positioned along the longitudinal direction of the plate is a better option than using a circular hole, from the plate stability point of view.

Elastic buckling of plates with eccentrically positioned rectangular perforations

The conjugate load/displacement method is used to analyze square plates with perforations, and results are presented for geometries with rectangular holes offset from one or both axes of symmetry. Results are given for uniaxial and shear loading, and simply supported and fully fixed boundaries. Design guidance for the location of perforations and the effect of longitudinal or lateral slots is explained. The potential to increase the elastic critical load for an unperforated plate by the introduction of a small perforation is reported.

Load‐Eccentricity Effects on Cold‐Formed Steel Lipped‐Channel Columns

The effects of loading eccentricity on axial strength of cold‐formed steel lipped channels are investigated in a series of 48 individual long‐column tests. Experimental results are compared with flexural and torsional‐flexural buckling‐strength predictions based on the American Iron and Steel Institute (AISI) 1986 specification, with local buckling treated using the uniform‐effective‐width approach. Widely spaced, rectangular web perforations are modeled using an “unstiffened‐strip” method, with the web idealized as two unstiffened elements, one on either side of the perforation. A method for predicting weak‐axis flexural buckling and the load‐versus‐lateral‐deflection response of eccentrically loaded, initially imperfect columns is also examined. Estimates of the actual loading eccentricities are made by comparing the predicted and empirical load‐versus‐deflection responses. Axial strength is shown to be very sensitive to small eccentricities. Conservative strength predictions are obtained with the AISI procedures by including loading eccentricity effects and modeling the perforations using the unstiffened‐strip method.

Unstiffened Strip Approach for Perforated Wall Studs

Local buckling behavior of cold‐formed steel wall studs with rectangular web perforations is investigated experimentally and analytically. Stub column tests on short sections not subject to overall buckling are examined. The unified effective width approach to local buckling presented in the 1986 Specification for the Design of Cold‐Formed Steel Structural Members of the American Iron and Steel Institute (AISI) is modified to model the perforated section. The web is idealized as two unstiffened elements extending the length of the member. In addition, the current AISI stub column‐based empirical approach and a “simplified” method used by some designers are examined. In the simplified approach, perforation effects are ignored unless the perforation is located in a portion of the web that is at least partially effective. Comparisons made between predictions of post‐buckling strengths using the unstiffened strip approach and the stub column test results show the unstiffened strip model to be a useful design methodology.

Natural frequencies and bending mode shapes of thin perforated plates using a variational method

A theoretical method to predict eigenfrequencies and mode shapes of a perforated plate was developed by building its Hamiltonian as a functional of the displacement field. The displacement functional base was chosen to be the natural base of a nonperforated plate having the same geometrical and mechanical characteristics as the perforated one with simply supported boundary conditions. Limiting the base vectors to a finite number, the extremization of the Hamiltonian was transformed into a Rayleigh-Ritz problem. Formulas of this analytical development were implemented on a computer to solve the eigenvalue problem for any kind of rectangular perforations. Numerical singularities were encountered, regarding the holes' shapes and sizes, and vector sets. They were removed by using some simple physical considerations. The program developed for this study was tested by treating special cases, well known in the literature. For example, the case of a full plate with free boundary conditions was simulated by introducing a crown of holes around the edges of the plate, setting it free of its supports. Several cases of perforated plates were also computed. This work is the first part of a more general study on sound radiation from plates with holes and perforations.

Stability of Plates with Rectangular Holes

The conjugate load/displacement method for elastic stability analysis is applied to square plates with a range of centrally located rectangular perforation sizes and shapes, subjected to various in-plane loading conditions. Results are presented for both fully fixed and simply supported boundary conditions giving lowest buckling coefficients. The increase of buckling coefficient with the removal of material, which occurs in many cases, is explained.

Iterative analysis of finite-sized planar frequency selective surfaces with rectangular patches or perforations

Frequency selective surfaces (FSS) and other periodic gratings are often analyzed under the assumption that they are infinite in extent. Most existing methods for analyzing periodic structures are based on the use of a Floquet-type representation of the fields in a unit cell whose dimensions are typically comparable to the wavelength. In this work, a finite, truncated, version of an infinite periodic structure is dealt with directly, without the benefit of the assumption that the structure is periodic. This, in turn, requires the handling of a large number of unknowns and makes it difficult to solve the problem using conventional matrix methods. Two different iteration approaches to solving the finite FSS problem are discussed in the paper both of which employ the spectral domain formulation. The first of these employs the spectral iteration technique and the second one uses the conjugate gradient (CG) iteration algorithm. Convergence characteristics of both of these methods are investigated and the results are reported.

Successful Sand Control Design for High Rate Oil and Water Wells

Successful sand control in high rate oil and water wells can be achieved by following this procedure: define the sand, design the gravel, control the placement, and stabilize the pack once it is in place. Introduction A key factor affecting the profitability of waterflooding heavy-oil, unconsolidated-sand reservoirs is the ability to achieve effective sand control completions in response and injection wells. Effective sand control reduces liner failures, simplifies individual well operating problems, and protects expensive pumping equipment required for high producing rates. A survey of the literature and current completion practices indicates that the gravel flow packed liner practices indicates that the gravel flow packed liner completion is the best method currently available for controlling sand in unconsolidated sand reservoirs subjected to high rate waterflooding. However, to be effective over the life of a typical waterflood (10 years or more), the gravel flow packed completion must be carefully designed and properly installed. Presented here is a method for designing a gravel flow packed liner completion, based on the following considerations:formation analysis,gravel-to-sand ratio,formation sand uniformity, andvelocity through slots. The technique is developed from the technology and experience of the water-well and petroleum industries, noting that continual improvement in well completions is necessary to achieve or maintain profitable secondary recovery projects. Literature Survey For over 30 years a number of investigators looked for a way to control sand. Laboratory experiments with sand, bridging over rectangular perforations, brought about the designed slotted liner. But even with reasonable empirical formulas and factors of safety, only a measure of control was possible in unconsolidated sand reservoirs. The problem increased when secondary recovery operations made possible the production of relatively large volumes possible the production of relatively large volumes of fluid. How was it, then, that water wells could produce thousands of barrels of sand-free fluid through small intervals? The water-well industry had been using the gravel flow pack completion method with such success that, in many areas, the technique was a standard completion practice as early as 1916. The oil industry rapidly began to research the gravel flow pack. By the mid-forties there were enough field data pack. By the mid-forties there were enough field data to confirm the investigators' theoretical conclusions. Once the basic design requirements were established, completion techniques were improved so that today practically every aspect of a well designed flow pack is practically every aspect of a well designed flow pack is defined in the literature. Basic Design Considerations The function of the gravel flow pack is to act as a filter, allowing natural fluid movement but preventing formation sand grains and other solids from entering the wellbore. Bridging of the formation against the gravel pack is the key to the control of sand movement. When effective bridging is achieved, sand and other solid particles carried by the formation fluids are deposited at the pack's periphery, allowing clean fluids to be produced. JPT P. 1193

2060 長方形の開口部をもつ鉄筋コンクリート梁の曲げ耐力に関する研究(構造)

2060 長方形の開口部をもつ鉄筋コンクリート梁の曲げ耐力に関する研究(構造)

2061 鉄筋コンクリート有孔ばりに関する研究 : その4・角孔をもつ有孔ばり小形試験体実験(構造)

2061 鉄筋コンクリート有孔ばりに関する研究 : その4・角孔をもつ有孔ばり小形試験体実験(構造)

Irske bronzeøkser fra Ulstrup

Irske bronzeøkser fra Ulstrup