Oblique Holes Research Articles

Sound absorption of acoustic resonant absorbers with rough oblique perforations

Micro-perforated panel sound absorbers are widely used in the field of noise reduction due to their good sound absorption performance. For micro-perforated panel, the acoustic impedance characteristics of the perforation hole play an extremely important role in the sound absorption performance. Here, the acoustic metamaterial in the form of a perforated panel with rough oblique holes is proposed for low-frequency sound absorption. By introducing surface roughness, the acoustic performance of the oblique perforation holes can be adjusted, and the low-frequency sound absorption performance of the perforated panel sound absorber is improved. The theoretical prediction of sound performance has been verified by finite element simulation, and a good consistency has been achieved. The results show that the introduction of surface roughness effectively reduces the resonant frequency and increases the value of sound absorption peak. The introduction of surface roughness and oblique configuration can provide additional acoustic resistance and reactance for impedance matching with air without increasing the thickness of the structure, resulting in more effective low-frequency sound absorption. Physically, the surface roughness causes the periodic concentration effect of the fluid vibration in the hole, which increases the viscosity loss and improves the sound absorption performance of the sound absorber. The theoretical and the numerical models, as well as the low-frequency perfect sound absorption performance (α>0.99) of the proposed metamaterial, are validated by experimental measurements. This work is of great significance to the application of perforated panel absorbers in low-frequency sound absorption.

Turbulent flame propagation enhancement by application of dielectric barrier discharge to fuel-air mixtures

The promotional effect of non-thermal plasma (NTP) on lean flame propagation in turbulent fuel-air mixtures in a reciprocating engine-like high-temperature and -pressure environment was investigated. A turbulent flow was created by installing a perforated plate with oblique holes in the combustion chamber of a rapid compression and expansion machine (RCEM). Ignition was conducted by conventional spark plug. The NTP was generated by a dielectric-barrier discharge (DBD) device installed in the combustion chamber near the spark plug. A portion of the lean fuel-air mixture (ϕ = 0.5) in the chamber passed through the NTP and diffused throughout the chamber before spark ignition. To elucidate whether the effect persisted even when the plasma-affected volume was diffused by the flow, two types of experiments with temporal delay were conducted. The fuels evaluated were n-heptane as a representative fuel with a strong low-temperature oxidation reaction, i-octane as a representative fuel with a weak low-temperature reaction, and a primary reference fuel consisting of a mixture of these two fuels. Temporal growth of the flame was observed using a high-speed camera with an image intensifier. The evolution of in-cylinder pressure was also monitored and the characteristic time of the mass fraction burned was evaluated accordingly. It was found that flame propagation was promoted by DBD for n-heptane-containing mixtures at a certain initial temperature while the i-octane-air mixture did not exhibit such enhancement. The results obtained suggest that long-lived intermediate chemical species formed by the plasma diffuse into the cylinder, affecting flame propagation through promotion of a low-temperature oxidation reaction. In addition to these findings, the effect of NTP on burning periods were evaluated.

Angled etching of Si by ClF3–Ar gas cluster injection

Reactive gas cluster injection is an etching method that uses a neutral cluster beam without ions. This process can avoid damage caused by energetic ion irradiation and vacuum UV light from plasma. ClF3–Ar gas cluster injection was performed using a nozzle placed at various angles in the range of 0–78° from the normal to the sample. The Si substrate was anisotropically etched in the direction of the cluster beam, although the incident angle of the cluster beam was oblique. Oblique holes of 100 nm diameter and oblique square pillars of 3 µm width were fabricated with a high aspect ratio by angled cluster injection. It is expected that this process will create unprecedented structures for use in micro-electromechanical systems (MEMSs) or photonic crystals.

Oblique Drilling by Ti:sapphire fs Laser in Silicon

Femtosecond laser ablation results in sharp edges and high aspect ratio holes in case of most solid materials. In this work it is shown that oblique drilling is possible by oblique illumination even in high thermal conductivity materials. Experiments were performed on silicon by varying the number and the angle of the incident laser pulses of a Ti:sapphire laser. Three phases of the formation of the oblique holes were distinguished and described: 1. A cone-like hole is formed in the direction of laser irradiation. 2. The bottom of the hole is widened. 3. The shape of the ablated hole becomes tube-like. It is shown, that reflections from the inner walls have an influence on the shape of the holes. Two models were set up to calculate energy distribution in conical and tube-like holes to describe the hole formation.

Finite Element Analysis of Elastic Stresses around Holes in Plate Subjected to Uniform Tensile Loading

The author reported stress analysis of infinite isotropic plate with a cylindrical circular hole and oblique hole. The present work deals with infinite isotropic plate under uniform tensile load. Three components of different material with different obliquity angle were used for analysis. These components having holes circular & oblique at angles 0, 30 and 60 degree are considered for study. The long twisted blades of gas turbine blade will be treated as infinite plate with oblique holes/cooling holes constituting a geometrically complex, three- dimensional body that is subjected to the action of systems centrifugal force. Stress concentration and stress field around oblique holes is a major challenge area in design of aerofoil in aerospace applications for safety because of their highly specialized applications in aerospace field under severe operating conditions. In design, Stress Concentration Factor (SCF) can be used as multiplication factor, and using that maximum stress can be predicted, thus it shows the stress field around local region. The experimental methods used are photo elastic and strain gauge techniques. When a infinite plate containing a cylindrical oblique hole is subjected to remotely applied uniform tensile load, the circumferential stresses along the boundary of the hole are produced which have been successfully used to predict stresses around holes. The resulting Stress Concentration Factor (SCF) obtained by Finite Element (FE) analysis are compared with experimentally obtained values. The results of FEA technique are in good agreement with experimental values, thus providing a means of analysing more effectively realistic Gas turbine blades. For analysis FEA software MSC/PATRAN, MSC/ NASTRAN-NX v7.0 has been used.

Evaluating groutability at the Kamal-Saleh Dam based on Lugeon tests

Water leakage from a dam is always important, but particularly where the preservation of water is essential in semi-dry areas, such Iran. At Kamal-Saleh Dam, the rock mass rating (RMR) and geological strength index(GSI) systems were used to identify the quality of the rock mass, which is particularly important in a foliated material. The RMR results were compared with Lugeon tests undertaken in vertical and oblique holes along the dam foundation and abutments. Although the rock quality designation values could not be used to indicate the quality of the rock mass, they had a direct relationship with the Lugeon values.

New Vienna Applicator Design for Distal Parametrial Disease in Cervical Cancer

Purpose: To present an applicator design based on the classical Vienna ring applicator which allows sufficient dose coverage for cervical tumors with distal parametrial disease at the time of brachytherapy and is clinically feasible. Materials and Methods: A modified Vienna ring applicator was constructed which allows interstitial needles to be implanted parallel (Vienna ring) and oblique (angle 20°) to the intrauterine tandem by a specially designed removable semi-template which has clockwise oblique holes and can be fixed to the ring. MRI treatment planning based on standard loading pattern for the intracavitary applicator with stepwise dwell weight adaptation and needle loading (max. 20% of intracavitary contribution) was performed to achieve optimal dose coverage and sparing of organs at risk. This new applicator was tested in 6 patients with distal parametrial disease at the time of brachytherapy. Results: Needle insertion could be guided by clinical examination and MRI before insertion. The necessary needle position could be determined and superimposed on the clockwise oblique ring holes situated between the parallel holes. The distal part of the HR CTV could be accurately reached in all cases. The insertion depth (tissue) had a 4-cm mean. The additional oblique needles in combination with tandem-ring and parallel needles enabled target coverage up to 25 mm lateral to point A. Six patients with HR CTVs of mean 50 cm3 (max 93 cm3) were treated with mean D90 of 86 Gy EQD2 and mean 92% coverage (V100). Mean D2cc for organs at risk was 79 Gy, 61 Gy and 67 Gy for bladder, rectum, and sigmoid, respectively. Conclusions: The applicator design leads to precise and reproducible distal parametrial positioning of the needles. Needle insertion using this applicator is clinically feasible. Adequate D90 coverage of HR CTV with distal parametrial extension can be achieved respecting dose volume constraints for OAR.

SU‐FF‐T‐407: Prediction and Optimization of Stereo Tactic Frame Placement for Collision Avoidance in Gamma Knife Radio Surgery

Purpose: To develop a positioning assistive device (PAD) and system that optimizes the use of gamma knife stereo tactic frame placement before treatment in avoiding frame‐collimator collisions during treatment. Method and Materials: Prior to stereo tactic frame application, pretreatment MRI or CT images are used for tumor localization. The PAD system has been designed and constructed to predict the optimal frame placement coordinates. The PAD device is used to assist in applying the stereo tactic frame, utilizing optimized frame placement coordinates, with respect to a fiducial marker placed on a phantom prior to scanning. The PAD device has been constructed using high grade plastic curved to accommodate a cervical collar on its inner surface and a steel block and rod system to its outer surface. The block and rod system consists of a horizontal (y‐axis) and a vertical (z‐axis) rod with a 90 degree bend at the top (x‐axis). The two rods are attached via a block with two oblique holes each taped with a screw to allow for adjustment along the respective axis. The x‐axis portion has a block with a dovetail grove to allow attachment of the stereo tactic frame. The block and rod system allows for translation and rotation about each axis enabling six degrees of freedom in a compact design. This ensures that the placement of the stereo tactic frame is level and accurate. Results: The PAD system has been found to optimize frame placement and predict frame/collimator collisions. PAD allowed for accurate and reproducible frame applications. Conclusion: The PAD system will allow the neurosurgeon the ability to apply the stereo tactic frame to the patient in a more accurate and reproducible way. PAD does lead to easier treatment planning, faster treatment delivery, and reduced patient stress. Demonstration of the device will be presented.

Drying of a Dilute Suspension in a Revolving Flow Fluidized Bed of Inert Particles

Revolving air flow was generated by oblique holes on air distribution board in a fluidized bed dryer. Such a revolving air flow shows a large scale velocity fluctuation in radial as well as tangential directions. This turbulent flow of air can fluidize the inert particles with superior performance than vibrated fluidized bed. The revolving fluidized bed is simpler in fabrication and easier in operation. For two types of inert particles tested, 4 mm glass beads and 4 mm × 5 mm Teflon cylindrical extrudates, the volumetric heat transfer coefficients were found to increase with the liquid feed flowrate and air flow velocity but decrease with the air inlet temperature, height of static bed, and liquid concentration. The revolving fluidized bed gives an increase of volumetric heat transfer coefficient by 1 kW/m3 K, and represents a 15–25% enhancement from ordinary fluidized bed operated at a bed height of 60 mm, bed diameter of 140 mm, superficial air flow velocity of 3.5 m/s, liquid feed (Soya milk) flowrate of 20 mL/min at a concentration of 6.7%, and a temperature ranges of 80–140°C using Teflon extrudates as inert particles.

Stress Analysis of Holes in Thick Plates

A review of the Stress Concentration Factors (SCFs) obtained from normal and oblique holes in thick flat plates loaded in uniaxial tension has been conducted. The review focuses on values from the plate surface and discusses the ramifications of making a plane stress assumption.

Development of a mask-scan electron beam mask writer

Mask-scan strategy for writing large complex patterns such as oblique lines and contact holes with assist bar and serif is more effective for decreasing the number of shots than is variable shaped beam (VSB) strategy and character projection strategy. In a simple case, the number of shots for writing the oblique lines can be as small as 1/600 of that of VSB strategy. Oblique parallel lines of 250 nm width and assist bar of 120 nm width were projected using the mask-scan strategy.

Determination of Stress Concentration Factors for Holes in Cylinders Using Thermoelastic Stress Analysis

AbstractThermoelastic stress analysis is used to obtain the stress concentration factors (SCFs) from a variety of circular holes in cylinders. The cylinders are loaded in uniaxial tension, uniaxial compression and a combination of bending and compression. Firstly, radial holes are investigated and the results from the thermoelastic data obtained by the SPATE equipment are compared with previous experimental and numerical work. SCFs are then obtained from offset, oblique and offset–oblique holes using the Deltatherm system. The effect of hole obliquity and direction of applied load relative to the hole geometry are discussed in detail. Finally, the results from the cylinders are compared with predictions of the SCFs in cylinders from a previous study of oblique holes in flat plates.

Thermoelastic stress analysis of oblique holes in flat plates

The stresses in the region of an oblique hole in a flat plate are analysed using the thermoelastic stress analysis technique. Particular attention is given to the obliquity of the hole and to the line of action of the applied load in relation to the hole axes. The effects of varying plate thickness are also studied. The data from around the rim and along the internal axis of the hole are presented as a series of stress concentration factors. The results are compared to those from previous studies and discussed in detail. These confirm the findings of the previous work in that increases in hole obliquity increase the stress at the hole, the maximum principal stress is obtained when the load is applied normal to the major axis of the surface ellipse and that as the thickness of plate increases the stresses on the surface of the plate decrease. Issues such as differences in the material’s Poisson’s ratio value are also discussed. The effect of any non-adiabatic behaviour on the thermoelastic output is described.

Galea-cranium suture method for prevention of the subcutaneous fluid collection--technical note.

A simple method is described for preventing cerebrospinal fluid (CSF) from collecting in the subcutaneous space following a supratentorial osteoplastic craniotomy. A few pairs of oblique holes through which suture materials may pass are made by drilling in the surface cortex of the bone flap. The galea aponeurotica is sutured to the bone flap by means of these holes. These galea-cranium sutures reduce the subgaleal free space in which pooling of CSF or hematoma may occur.

Numerical analysis of stresses at oblique holes in plates subjected to tension and bending

Stress analysis of a series of thick, wide, flat plates with oblique holes subjected to uniaxial tension and out-of-plane bending has been carried out using the finite element method (FEM), and in some cases the boundary element method (BEM). Different plate thickness-hole diameter ratios, angles of hole obliquity and orientation have been considered to provide stress concentration factors at such holes. The work covers plate thickness-hole diameter ratios from 1.3 to 3.0, hole obliquity angles from 0 to 60° and orientation of the major axis of the surface ellipse relative to the applied load direction of 0 to 90°. The results for uniaxial tension have been compared with those determined using the photoelastic frozen-stress technique in order to verify the finite element models before proceeding to the bending cases, which provide new data.

On the Stresses at Arrays of Oblique Holes in Thick Plates under Equi-Biaxial in-Plane Loading

Previous work is reviewed, emphasis being given to the results of a photoelastic investigation of a series of hole arrays in thick plates subjected to uniaxial loading. The design of the tested arrays and their relationship to the principal features of a square array of penetrations in a part-spherical pressure vessel end are explained. Stress indices resulting from equi-biaxial loading in normal arrays (obliquity angle zero) and oblique arrays (obliquity angle of 45°) are obtained from the uniaxial data by superposition. Results for holes at the array boundaries and remote from the boundaries are presented and critically discussed.

Stress concentrations at an oblique hole in a thick flat plate under an arbitrary in-plane biaxial loading

The results of an extensive ‘frozen-stress’ photoelastic investigation of the stresses at isolated oblique holes in thick wide plates subjected to uniform uniaxial tension are used to provide stress concentration factors at holes resulting from any form of biaxial in-plane loading. The work covers plate thickness/hole diameter ratios from 1.3 to 3.0 and hole obliquity angles up to 60 degrees. Over these ranges the effects of changes in the plate thickness/hole diameter ratio are not of major importance but the effects of changes in the angle of obliquity are considerable.

Stress concentration around the shroud hole of steam turbine blades

Results of study of the stress-strain state around shroud holes of steam-turbine rotor blades are presented. Methods of volumetric photoeleasticity with “freezing” were used for experiments on models of blade elements in the form of plates with oblique holes passing through the plates which are diamond-shaped in the plan of their thickening. The angle between the hole axis and thickening face plane was varied while that between this axis and plane of the plate was fixed. Dependences between thickening parameters and maximum stress values are obtained. These facilitate selection of an optimum version of a structure during design.

Photoelastic investigation of stresses at an oblique hole in a thick flat plate under uniform uniaxial tension

The magnitudes and positions of the principal stress indices at a series of isolated oblique holes in thick, wide plates subjected to uniaxial tension have been determined using the photoelastic frozen-stress technique. The model series covered nominal plate thickness to hole diameter ratios of 1.33, 2.0, and 3.0, hole obliquity angles of 0, 15, 30, 45, and 60 degrees, and applied load directions of 0, 30, 60, and 90 degrees relative to the major axis of the surface ellipse. The results are discussed in detail and compared with other independent values available in the literature.

The Huckstep nail for ipsilateral fractures of the hip and femoral shaft and for subtrochanteric fractures

The Huckstep nail is a square, solid titanium aluminum-6, vanadium-4 alloy nail of 12.5-mm diameter with 4.6 mm holes at 15-mm intervals. The proximal end of the nail has four oblique holes at 130° for use with screws on the femoral neck and head, while the rest of the nail has transverse screw holes. We studied ten fractures of the femur fixed with the Huckstep nail. The fractures treated with this operative fixation were of the unstable subtrochanteric and the combined intertrochanteric hip and femoral shaft type. The average operative time was three hours 53 minutes, with an average intraoperative blood loss of 1,240 mL. All fractures except one showed radiographic evidence of healing within four months. Complications included inadequate fixation with one distal screw and a near perforation of the distal cortex with the rod. The Huckstep nail is a versatile nail that can be used for a variety of fracture patterns but probably is most useful for the unstable subtrochanteric fracture and the combined hip and shaft fracture.