Hole Pattern Research Articles

Study of gas discharge thyratron-type interrupter with sector hole in the screen in high-voltage pulse generator circuit with inductive energy storage

The work presents experimental study results of gas discharge interrupter with a sector hole in the screen and a circular grid hole being asymmetrically placed regarding central axis as part of a high-voltage pulse generator with inductive energy storage. According to the results received the device under consideration managed to decrease minimum turn-off time by 6 times up to 30 ns compared to a switch with inverse hole pattern in a grid node. Limiting pulse voltage amplitude is fixed at the level of 50 kV, peak pulse power increase up to 13 MW is achieved.

파라메트릭디자인을 이용한 제품의 홀 패턴 디자인 방법

파라메트릭디자인을 이용한 제품의 홀 패턴 디자인 방법

Performance Assessment of Steel Moment Connections Retrofitted with Various Reduced Section Patterns

It is of high importance in seismic retrofitting of lateral load-bearing systems to increase the connections performance. The crucial point in the steel frame retrofitting process is to create plastic hinges in these types of frames. The formation of plastic hinges in beams and near columns generates large strains on column flanges as well as welding metal and heated surroundings, which can lead to brittle failure. The connection should be designed in such a way as to allow plastic hinge formation at certain points of the beam. One such method suggested for retrofit connections is to reduce the beam section locally away from the connection zone. There are various patterns available to locally reduce the beam section, such as circular, elliptical, and symmetric/asymmetric. In recent years, different proposals have been presented to design these connections which vary from older instructions. For this study, radiused cuts in the flange and slotted holes in the web of connection beams were selected for retrofitting analysis. Cyclic behavior, energy damping levels, and ductility of these connections were studied and compared before and after the retrofit by using nonlinear dynamic analysis. The results showed that the symmetrical circular hole pattern in the beam flanges demonstrated reliable performance.

Evaluation of hybrid textured tool performance under minimum quantity lubrication while turning of AISI 304 steel

Nowadays, the surface texture of tool is an attractive machining technique due to the benefits in any chip removal machining process performance. However, surface texture design on texture tool plays a significant role in improving the turning process performance, in this context, a novel hybrid surface texture design has been proposed in the current work. The present work focused on the machinability improvement of AISI 304 material by employing the surface texture tool under minimum quantity lubrication (MQL) condition. In this work, comparative evaluation of turning performance has been carried out with a fabricated single texture tool which consists of circular pit holes pattern (T-1) and a fabricated novel hybrid texture tool combination of linear grooves and circular dimples (T-2), respectively, during machining of AISI 304 material at increasing cutting velocity condition. From the result, it was observed that the proposed hybrid texture tool (T-2) significantly reduced the cutting temperature (Tm), tool flank wear (Vb) and surface roughness (Ra) to a maximum of 26%, 31% and 34%, respectively, when compared to T-1. Further, low built-up edge (BUE) was found in T-2 tool over T-1, respectively.

Iterative optimization of photonic crystal nanocavity designs by using deep neural networks

Abstract Devices based on two-dimensional photonic-crystal nanocavities, which are defined by their air hole patterns, usually require a high quality (Q) factor to achieve high performance. We demonstrate that hole patterns with very high Q factors can be efficiently found by the iteration procedure consisting of machine learning of the relation between the hole pattern and the corresponding Q factor and new dataset generation based on the regression function obtained by machine learning. First, a dataset comprising randomly generated cavity structures and their first principles Q factors is prepared. Then a deep neural network is trained using the initial dataset to obtain a regression function that approximately predicts the Q factors from the structural parameters. Several candidates for higher Q factors are chosen by searching the parameter space using the regression function. After adding these new structures and their first principles Q factors to the training dataset, the above process is repeated. As an example, a standard silicon-based L3 cavity is optimized by this method. A cavity design with a high Q factor exceeding 11 million is found within 101 iteration steps and a total of 8070 cavity structures. This theoretical Q factor is more than twice the previously reported record values of the cavity designs detected by the evolutionary algorithm and the leaky mode visualization method. It is found that structures with higher Q factors can be detected within less iteration steps by exploring not only the parameter space near the present highest-Q structure but also that distant from the present dataset.

Optical spectra of periodically patterned dielectric surface simulated by finite-different time-domain method

A dielectric film imprinted with a hexagonal periodical pattern of nanosphere holes can be fabricated by a two-step process of depositing a dielectric thin film on a hexagonally patterned array of nanospheres fabricated by convective deposition, and then removing the nanosphere particles. In this work, the optical transmission through a dielectric slab with hexagonal pattern of half-sphere holes was simulated by finite-different time-domain (FDTD) methods. In the simulation, a short gaussian pulse of electromagnetic waves was generated and propagated through the dielectric patterned slab and the near-field diffraction from the structure was collected as a function of time. Using a Fourier transformation, the optical spectra of the structure were evaluated. The far-field diffraction was also investigated by evaluating the analytical Green’s function at given points. Several parameters of the optical response including full width at half maximum and relative intensities of high order diffraction peaks were examined for various structure sizes. The structures examined were composed of a periodic hexagonal pattern of half nanosphere holes (radius of 290 nm). In addition, the effect on the optical response of 10% elliptical shape deformation of the half-sphere holes was studied. Our calculations enable us to identify parameter schemes where the third order diffraction exceeds second order diffraction efficiency from gratings.

A novel sieve plate hole pattern: effect on gas hold-up and flow regimes in a bubble column

The effect of an innovative sieve plate orifice layout on the hydrodynamics of a cylindrical bubble column is investigated. The classical triangular layout is compared with a novel spiraled layout, using the same number and diameter of orifices. The experiments include two different column aspect ratios and two liquid phases of different coalescing nature. According to the holdup data, if the spiraled layout is used, the flow regimes evolve from a pseudo-homogeneous regime to a heterogeneous regime going through a transition regime, as the superficial gas velocity increases. When the triangular layout is used, the homogeneous regime is not detected and pure heterogeneous regime is obtained at all superficial gas velocities. When using the spiraled layout, the gas retention increases, resulting 24% higher in the homogeneous regime and 13% higher in the heterogeneous regime with respect to the gas retention obtained with the triangular layout. If bubble coalescence is modified by the addition of NaCl, the holdup increases for both layouts, but to a lower extent in the spiraled layout (10%) compared to the triangular layout (24%). The reason behind the reduction of coalescence and higher gas holdup values is the ability of the spiraled layout to produce bubbles that do not interact with each other during a longer path along the column.

Large eddy simulation of passive jet flow control on the wake of flow around a circular cylinder

This study presents a passive jet flow control method to suppress the wake of a circular cylinder based on a computational fluid dynamics (CFD) numerical simulation at a high Reynolds number of 5.0 × 104. The investigation mainly focuses on the control effectiveness of the pattern of jet holes on the hollow pipe. First, the three-dimensional (3D) flow past a circular cylinder at a Reynolds number of 3900 is addressed based on the large-eddy simulation (LES) method to validate the feasibility of a numerical simulation. Then, the control effects of the passive jet flow on the aerodynamic forces and the wake flow of the circular cylinder are studied at different directions, angles, and heights of the jet holes. An optimal parameter scheme for suppressing the wake of a circular cylinder is then determined according to a comparison of the control effectiveness of the aerodynamic forces. The results indicate that the jet flow from the backward holes of the circular cylinder effectively separates the shear layers rolled up on both sides of the circular cylinder, which forces the vortex formation region downstream. This control measure can dramatically reduce the aerodynamic forces and suppress the wake of the circular cylinder.

Sensitivity analysis of ring-shaped slotted photonic crystal waveguides for mid-infrared refractive index sensing

In this paper, the sensitivity of slotted photonic crystal waveguides (SPCW) with triangular lattice pattern of ring-shaped holes is analyzed in order to realize highly refractive index (RI) sensor devices at mid-infrared wavelengths. The sensing principle is based on the shift of the transmission spectrum edge of these specific ring hole SPCW waveguides giving rise to reinforced light–matter interaction. The 3D simulation results applied to silicon waveguides on membrane show that this guide geometry leads to a very high sensitivity to variations in the ambient environment index, with very dependent trends on the opto-geometric factors of the waveguides. As a matter of example, a $$720 \,\mathrm{nm}$$ wavelength position band edge shift is predicted, corresponding to a sensitivity of more than $$1450 \,\mathrm{nm}$$ per refractive index unit with a device insertion loss level of $$-\,3 \,\mathrm{dB}$$ .

Design of hole pattern in static rock fracture process due to expansion pressure

The process of rock fracturing is one of important operations in quarry mining. The process can be done by controlled blasting or by soundless fracturing by Non-Explosive Expansion Material (NEEM) in hard rocks. Application of the NEEMs is so easy, safe, and very controllable but it is slow process and most of the time cost of the production by the NEEM is higher than controlled blasting method. On the other hand, usage of blasting methods (in quarry mining) are restricted in some locations or countries. Therefore, an investigation has been done on static rock fracturing by expansion process. In the research a semi-analytical and experimental model has been suggested by dimensional analysis which is based on field measurements in a granite quarry mine in Iran and a physical model (concrete block) and some numerical modeling. The model is a formula which can estimate the hole spacing in different rocks and concrete by several NEEMs and hole's diameter. Main parameters of the suggested model are NEEM's pressure, tensile strength of the intact rock, Young's modulus of the intact rock, hole's diameter, rock fracture toughness, temperature, and CaO content in the NEEM. More than twenty data have been used for verification of the suggested model which they were some data from the granite mine, some of them were from physical modeling and numerical modeling, and the others were from other researchers' experiences.

Transparent laser-structured glasses with superhydrophilic properties for anti-fogging applications

Ultrashort pulse laser structuring enables direct modification of glass surfaces to generate superhydrophilic properties for anti-fogging applications. This approach makes coatings dispensable and the generated surfaces remain thermally, mechanically, and chemically resistant. However, the laser-generated structures usually cause scattering, which decreases transmission and may disturb the vision through the modified glass in the dry state. The aim of this study was to find a laser-processing strategy to achieve superhydrophilic, anti-fogging properties on glass surfaces with maximum transmission and minimal visual perception of the generated structure. For this purpose, we used an ultrashort-pulsed laser to generate periodic patterns of rippled circles or rough holes with varying pitch. The water contact angle and transmission of the structured glasses were measured as a function of the structured area. It was found that a periodic pattern of holes, which covers less than 1% of the surface, is already sufficient to reach the superhydrophilic state (contact angle < 5°) and provides nearly the same transmission as pristine glass. Pictures of objects imaged through dry, structured glasses, which were placed close to the lens or object, showed in both cases only a minimal decrease of contrast. If this minor drawback can be accepted, this direct laser structuring approach could be an interesting alternative to coating-based techniques and leaves even room to apply additional coatings for the fabrication of multi-functional special glasses.

A novel two-dimensional mechanical metamaterial with negative Poisson’s ratio

Artificial auxetic materials with negative Poisson’s ratio enable distinctive elastic response in the direction orthogonal to the loaded direction, i.e. shrinking when compressed and expanding when stretched, compared to conventional materials. Such distinctive mechanical characteristic makes auxetic materials unique in practice. Current studies in this aspect focus mainly on the realization of beam-dominated microstructures such as re-entrant and chiral lattices and of cellular microstructures with orthogonal elliptical hole pattern. In this study, a novel two-dimensional auxetic microstructure is designed by introducing peanut-shaped holes in solid bulk matrix. Compared to the microstructure with elliptical hole pattern, the present design can produce slightly larger negative Poisson’s ratio and achieve significantly lower stress level. The samples consisting of a number of centimeter-scale unit cells with the peanut-shaped holes are fabricated efficiently via additive manufacturing technique. Experiment and finite element simulation of tensile test are carried out on the specific sample to demonstrate the auxetic effect of the present design and simultaneously verify the computational model. Finally, effects of some parameters on Poisson’s ratio, which may control the auxetic behavior of the present microstructure, are discussed for better understanding deformation mechanism of the proposed auxetic material.

Compressibility effects on quasistationary vortex and transient hole patterns through vortex merger

The effect of compressibility in the process of vortex merging is discussed. In past, in the incompressible limit, it has been observed that the merging of a collection of intense point-like vortices arranged uniformly outside a circular vortex, can lead to quasistationary vortex patch and transient hole pattern inside the patch via nonlinear merger process leading to ‘vortex crystals’. Weak compressibility is seen to introduce a natural acoustic scale to the problem. We find that the natural mode is independent of the number of point-like vortices and the amplitude scales linearly with compressibility. Further, it is identified that after a merger, the system exhibits oscillation at a natural frequency together with its harmonics and beats with its own harmonics. The power of the frequency is found to scale as M−2, where M is the Mach number. Also the vortex crystals formed are found to ‘melt’ faster as compressibility is increased from M = 0 to 0.5.

Spatial pattern of pika holes and their effects on vegetation coverage on the Tibetan Plateau: An analysis using unmanned aerial vehicle imagery

Abstract The pika (Ochotona curzoniae) hole is an important landscape feature in the Tibetan Plateau (TP) grasslands, and it indicates grassland degradation levels due to the destruction caused by pika burrowing activities on grasslands. However, no studies have ever explored landscape patterns of pika holes and their effects on adjacent vegetation coverage. Taking meadow grasslands in Northern Tibet as an example, this study gathered unmanned aerial vehicle (UAV) images and explored landscape patterns of pika holes and their effects on grass coverage in the surroundings. The performances of two classification methods, including the decision tree classification based on Fully Constrained Least Squares (FDC) and the object-oriented classification (OBC) were compared in recognizing sizes and shapes of pika holes. The results showed that: (1) The object-oriented classification exhibits higher classification accuracy in identifying pika holes. (2) The average size of pika holes in the study area is 0.01 m2 and they exhibit clustered distribution patterns. The average distance between any two nearest pika hole patches is 0.79 m. (3) It presents a significant quadratic relationship between the number of pika holes and grass coverage. (4) The average effective distance of pika holes on the surrounding grass coverage is 20 cm. The findings of this study can provide guidelines for pika control and improve grassland management on the TP.

Coupled fluid and energy flow in fabrication of microstructured optical fibres

We consider the role of heating and cooling in the steady drawing of a long and thin viscous thread with an arbitrary number of internal holes of arbitrary shape. The internal holes and the external boundary evolve as a result of the axial drawing and surface-tension effects. The heating and cooling affects the evolution of the thread because both the viscosity and surface tension of the thread are assumed to be functions of the temperature. We use asymptotic techniques to show that, under a suitable transformation, this complicated three-dimensional free boundary problem can be formulated in such a way that the transverse aspect of the flow can be reduced to the solution of a standard Stokes flow problem in the absence of axial stretching. The solution of this standard problem can then be substituted into a system of three ordinary differential equations that completely determine the flow. We use this approach to develop a very simple numerical method that can determine the way that thermal effects impact on the drawing of threads by devices that either specify the fibre tension or the draw ratio. We also develop a numerical method to solve the inverse problem of determining the initial cross-sectional geometry, draw tension and, importantly, heater temperature to obtain a desired cross-sectional shape and change in cross-sectional area at the device exit. This precisely allows one to determine the pattern of air holes in the preform that will achieve the desired hole pattern in the stretched fibre.

Patient-specific templates for image-guided intervention - a phantom study

Purpose: To evaluate the in vitro accuracy of a new device and method for simultaneous stereotactic CT-guided punctures.Material and methods: 240 needle paths were planned in 1 mm, 1.5 mm and 3 mm slice thickness with a custom-designed software. The data were transferred to a three-axis tabletop CNC machine that then drilled the hole pattern for the needles into square plastic plates. Kirschner wires were slid through the holes of the two parallel fixed plates to aim at the chosen targets inside the phantom. The accuracy was calculated by taking control CTs and measuring the Euclidean distance and the normal distance between the wire and the entry and target point.Results: The mean Euclidean distance of the wire tip to the target for the 1 mm, 1.5mm and 3 mm slice thickness were 2.5 mm (SD ± 0.64), 2.71mm (SD ± 0.78) and 2.8 mm (SD ± 1.0). The mean normal distance was 1.42 mm (SD ± 0.65), 1.43mm (SD ± 0.75) and 1.9 mm (SD ± 1.1), respectively.Conclusion: The system yields satisfactory accuracy comparable to other image-guided intervention systems. Involuntary movements of the patient need to be taken into account in a clinical setting.

Morphologic and functional outcomes of different optical coherence tomography patterns of myopic foveoschisis after vitrectomy and inner limiting membrane peeling.

To evaluate the morphologic and functional outcomes of different optical coherence tomography (OCT) patterns of myopic foveoschisis after vitrectomy with Inner Limiting Membrane (ILM) peeling. In this prospective non-randomised study, 62 consecutive eyes with Myopic Foveoschisis were categorised into three groups according to OCT pattern: retinoschisis type (Rt) Group (23/62), foveal detachment type (FDt) Group (20/62) and macular hole type (MHt) Group (19/62). All patients underwent 25-Gauge vitrectomy and ILM peeling. Air or gas tamponade was used. All patients were observed at month 1, 2, 4 and 6 after surgery. surgical success as resolution of myopic foveoschisis, central retinal thickness (CRT), IS/OS junction recovery and best-corrected visual acuity (BCVA) measurement. Any complication was reported. In all eyes OCT showed a resolution of the retinoschisis, foveal detachment and macular hole pattern, respectively. CRT significantly decreased in all Groups (p < .001), mainly in MHt. IS/OS junction recovery was mainly observed in MHt. BCVA significantly increased in all Groups (p < .01). A functional gain ≥2 Snellen lines occurred in 70, 85 and 68% in the Rt, FDt and MHt Group, respectively. Final BCVA was correlated with preoperative BCVA (R 0.74, p < 0.0001), postoperative CRT (R -0.49, p < 0.0001), and the recovery of IS/OS junction at 6 months (R 0.76, p < 0.0001). Few postoperative complications occurred. Vitrectomy with ILM peeling results in favourable anatomic and functional outcomes for different patterns of myopic foveoschisis.

A 3D printed modular phantom for quality assurance of image-guided small animal irradiators: Design, imaging experiments, and Monte Carlo simulations.

The goal of this work was to develop and test a cylindrical tissue-equivalent quality assurance (QA) phantom for micro computed tomography (microCT) image-guided small animal irradiators that overcomes deficiencies of existing phantoms due to its mouse-like dimensions and composition. The 8.6-cm-long and 2.4-cm-diameter phantom was three-dimensionally (3D) printed out of Somos NeXt plastic on a stereolithography (SLA) printer. The modular phantom consisted of four sections: (a) CT number evaluation section, (b) spatial resolution with slanted edge (for the assessment of longitudinal resolution) and targeting section, (c) spatial resolution with hole pattern (for the assessment of radial direction) section, and (d) uniformity and geometry section. A Python-based graphical user interface (GUI) was developed for automated analysis of microCT images and evaluated CT number consistency, longitudinal and radial modulation transfer function (MTF), image uniformity, noise, and geometric accuracy. The phantom was placed at the imaging isocenter and scanned with the small animal radiation research platform (SARRP) in the pancake geometry (long axis of the phantom perpendicular to the axis of rotation) with a variety of imaging protocols. Tube voltage was set to 60 and 70kV, tube current was set to 0.5 and 1.2mA, voxel size was set to 200 and 275μm, imaging times of 1, 2, and 4min were used, and frame rates of 6 and 12 frames per second (fps) were used. The phantom was also scanned in the standard (long axis of the phantom parallel to the axis of rotation) orientation. The quality of microCT images was analyzed and compared to recommendations presented in our previous work that was derived from a multi-institutional study. Additionally, a targeting accuracy test with a film placed in the phantom was performed. MicroCT imaging of the phantom was also simulated in a modified version of the EGSnrc/DOSXYZnrc code. Images of the resolution section with the hole pattern were acquired experimentally as well as simulated in both the pancake and the standard imaging geometries. The radial spatial resolution of the experimental and simulated images was evaluated and compared to experimental data. For the centered phantom images acquired in the pancake geometry, all imaging protocols passed the spatial resolution criterion in the radial direction (>1.5lp/mm @ 0.2MTF), the geometric accuracy criterion (<200μm), and the noise criterion (<55HU). Only the imaging protocol with 200-μm voxel size passed the criterion for spatial resolution in the longitudinal direction (>1.5lp/mm @ 0.2MTF). The 70-kV tube voltage dataset failed the bone CT number consistency test (<55HU). Due to cupping artifacts, none of the imaging protocols passed the uniformity test of <55HU. When the phantom was scanned in the standard imaging geometry, image uniformity and longitudinal MTF were satisfactory; however, the CT number consistency failed the recommended limit. A targeting accuracy of 282 and 251μm along the x- and z-direction was observed. Monte Carlo simulations confirmed that the radial spatial resolution for images acquired in the pancake geometry was higher than the one acquired in the standard geometry. The new 3D-printed phantom presents a useful tool for microCT image analysis as it closely mimics a mouse. In order to image mouse-sized animals with acceptable image quality, the standard protocol with a 200-μm voxel size should be chosen and cupping artifacts need to be resolved.

OPTIMIZING ANT COLONY ALGORITHM PARAMETERS USING TAGUCHI METHOD

In the present study, Taguchi Method (TM) is applied to determine the optimum Ant Colony Optimization (ACO) parameters. The Tool Path Optimization (TPO) for drilling a hole pattern on the Printed Circuit Board (PCB) with 220 holes was examined as a case study. Experimental verification shows that, with the optimal ACO parameters the tool path length is reduced about 2 times and the convergence rate is significantly approved against their average values in the initial data. This setting variant is also confirmed to be actually the best in comparison with available ones. This allows to reduce not only time for machining but also the one for program execution.

Resist-Free Direct Stamp Imprinting of GaAs via Metal-Assisted Chemical Etching.

We introduce a method for the direct imprinting of GaAs substrates using wet-chemical stamping. The predefined patterns on the stamps etch the GaAs substrates via metal-assisted chemical etching. This is a resist-free method in which the stamp and the GaAs substrate are directly pressed together. Imprinting and etching occur concurrently until the stamp is released from the substrate. The stamp imprinting results in a three-dimensional anisotropic etching profile and does not impair the semiconductor crystallinity in the wet-chemical bath. Hole, trench, and complex patterns can be imprinted on the GaAs substrate after stamping with pillar, fin, and letter shapes. In addition, we demonstrate the formation of sub-100 nm trench patterns on GaAs through a single-step stamping process. Consecutive imprinting using a single stamp is possible, demonstrating the recyclability of the stamp, which can be used more than 10 times. The greatest benefit of this technique is the simple method of patterning by integrating the lithographic and etching processes, making this a high-throughput and low-cost technique.