Variation Of Gap Width Research Articles

A novel strain-based bone-fracture healing algorithm is able to predict a range of healing outcomes.

Fracture healing is a complex process which sometimes results in non-unions, leading to prolonged disability and high morbidity. Traditional methods of optimising fracture treatments, such as in vitro benchtop testing and in vivo randomised controlled trials, face limitations, particularly in evaluating the entire healing process. This study introduces a novel, strain-based fracture-healing algorithm designed to predict a wide range of healing outcomes, including both successful unions and non-unions. The algorithm uses principal strains as mechanical stimuli to simulate fracture healing in response to local mechanical environments within the callus region. The model demonstrates good agreement with experimental data from ovine metatarsal osteotomies across six fracture cases with varying gap widths and inter-fragmentary strains, replicates physiological bony growth patterns, and is independent of the initial callus geometry. This computational approach provides a framework for developing new fracture-fixation devices, aid in pre-surgical planning, and optimise rehabilitation strategies.

Analysis of canal discharge management through remodeled structure at Guddu Barrage

As vital hydraulic infrastructure, barrages and canals are crucial for agricultural irrigation in Sindh Province, Pakistan. Any deviation from the intended design discharge can significantly impact water resource management, leading to economic losses. The Ghotki Canal in Sindh faced challenges in receiving its allocated inflow, prompting an extension of the divide wall at Guddu Barrage to 589.59 ft. However, this extension inadvertently exacerbated the problem by reducing the Ghotki canal's inflow, resulting in a 166.7 ft gap between the original and extended divide wall segments. This study takes a unique approach, using a non-distorted physical model at a scale ratio of 1:85, to assess the influence of the divide wall gap across five scenarios, varying gap width and river flow rates from 100,000 to 500,000 cusecs. The findings highlighted the disruptive effects of the gap on flow regimes, notably affecting critical infrastructure such as the silt excluder and left pocket capacity. Alterations in the divide wall gap width predominantly impact the Ghotki Canal discharge while minimally affecting the Rainee Canal. Without a divide wall gap, the Ghotki Canal's head regulator draws 88% of the designated capacity, while the Rainee Canal consistently receives its total inflow share of 10,000 Cusecs. In conclusion, this study underscores the importance of structure remodeling in barrages for effective water resource management, emphasizing the need for nuanced approaches to optimize canal performance and sustain agricultural livelihoods and regional development.

Investigating the impact of Trombe wall parameters on thermal performance and room temperature in the Iraqi climate

AbstractTrombe wall serves as an effective passive heating element, and its performance is heavily reliant on local climate conditions. This study involved both experimental and numerical analyses of a full‐scale test room equipped with a Trombe wall under Iraqi climate conditions. To facilitate this investigation, an experimental test room was constructed in Kirkuk city with dimensions of 4.0 m × 3.0 m × 2.75 m. In addition, a numerical simulation method based on computational fluid dynamics was developed and a computer code was created to investigate the performance of the system. The accuracy of the developed numerical approach was validated against experimental data collected from the test room. This analysis was conducted specifically for the period of February 17–18, which represents the coldest month of winter in the study area. The performance of the system was assessed with respect to various parameters; air gap width variations (2, 4, 6, and 10 cm), massive wall thickness ranging from 15 to 35 cm with 5 cm increments, channel width options (3, 5, 10, 15, and 20 cm), and vent heights ranging from 5 to 20 cm in 5 cm increments. Furthermore, an investigation of the impact of replacing the air in the air gap with inert gases, specifically argon, krypton, and a mixture of these gases with air was conducted, as well. The outcomes indicate that both the channel width and vent height do not have a significant impact on the system's performance. However, the width of the air gap has a modest effect on system performance, and the best performance was observed with a smaller gap width, specifically 2 cm. The most significant impact on room temperature is observed when the storage wall thickness is varied. In the case of wall thickness of 15 cm, there is a notably higher fluctuation in room temperature between the maximum and minimum values, reaching approximately 16°C. For a wall thickness of 35 cm, however, this fluctuation is significantly reduced to about 3°C. The system efficiency as determined after 24 h of operation period improved significantly when the air was replaced by an inert gases or a mixture of gases in the air gap. Compared to air, the increase in efficiency is about 14.8% for argon, 17.7% for krypton, and 20.6% for the mixture of gases.

Designing stepping-stones landscapes: a 2D perspective does not lead to more standardization than an in-situ perspective.

Previous research found that when participants across the lifespan could be the architect of their own stepping-stones landscapes, they create nonstandardized configurations with gap-width variation. Yet, architects often use standardized dimensions in their designs for playgrounds and outdoor fitness areas. To scrutinize why architects tend to seek for more standardized designs than the examined target users, we tested the hypothesis that the difference is caused by a different perspective during the making process. After all, landscape architects generally design on 2D maps, while the participants designed in situ. We asked 67 participants to design a stepping-stones landscape on a 2D map and 67 other participants to create the landscape in situ. Contrary to our expectations, we found no indications that designing on a 2D map leads to more standardized configurations. We end with discussing other characteristics of the design processes that could potentially explain the omnipresent standardization in design.

On the Unsteady Rotationally Symmetric Flow Between a Stationary and a Finite Rotating Disk With a Given Change in the Axial Velocity

Abstract We consider the scenario of an unsteady viscous flow between two coaxial finite disks, one stationary and the other rotating with an axial velocity changing impulsively from zero to a constant value. The three-dimensional (3D) incompressible Navier–Stokes equations are analytically solved by postulating the polynomial profiles for the axial and circumferential velocity components and by employing the open-end condition of zero pressure difference and an integral approach. It is shown that the time-dependent squeezing of the fluid between the disks and the edge effects of the finite open-ended disks in the flow domain are determined by the compressing Reynolds number and the rotating Reynolds number for the case of laminar flow at low Reynolds numbers and small aspect ratios. The general explicit formulae are derived for the velocity and pressure distributions as a function of the compressing and rotating Reynolds numbers in this unsteady flow process (and the steady-state solutions are then obtainable as the compressing Reynolds number vanishes). A simple theoretical relationship between the radial and axial pressure gradients is deduced to hinge the radial and circumferential velocity components together. The values of the compression and rotation Reynolds numbers suitable to this theory are also suggested for the problem of rotating disk flows at low Reynolds numbers. The validity of the theoretical predictions for the circumferential, radial, and axial velocity components is partially verified through comparison with previous steady experimental and numerical results. These analytical results have the immediate engineering applications of fluid flows with varying gap widths, including wet brakes, wet clutches, hydrostatic bearings, face seals, and rotating heat exchangers.

Modelling and simulations of reactor neutron noise induced by mechanical vibrations

Mechanical vibrations of core internals are among the main perturbations that induce oscillations in the neutron flux field, also known as neutron noise. In this work, different simulation models for the study of the influence of the mechanical vibrations of fuel assemblies on the neutron flux in the reactor core have been discussed. These methodologies employ the diffusion approximation, with or without a previous homogenization model, to simulate the neutron noise in the time or the frequency domain. The diffusion-based approach is expected to be less accurate in the vicinity of the vibrating fuel assemblies, but correct when considering distances larger than a few diffusion lengths away from the perturbation. All methodologies provide consistent results and can reproduce typical features of the neutron noise induced by mechanical vibrations of core components. First, FEMFFUSION can perform simulations in both the time and frequency domains. Second, CORE SIM + can be used to study various neutron noise scenarios in realistic three-dimensional reactor configurations. The third methodology is centred on using commercial codes as CASMO-5, SIMULATE-3 and SIMULATE-3K. This methodology allows time domain simulations of the neutron noise induced by different neutron noise sources in a nuclear reactor. Finally, a model for time-dependent geometry is implemented for the code system ATHLET/QUABOX-CUBBOX employing a cross-section-based approach for encoding water gap width variations at the reflector.

An experimental investigation on the characteristics of heat pipes with annular type composite wick structure

An experimental investigation has been conducted on the hydraulic characteristics of annular type wick structures for heat pipes. An experimental facility which can measure porosity, permeability, and effective pore radius of the wick structures in a vacuum condition is established. Nine different types of multi-layered (6 layers in total) composite screen meshes are characterized. Based on the measurement results, a wick structure composed of one layer of 100 × 100 mesh, three layers of 400 × 400 mesh, and two layers of 60 × 60 mesh is determined to have the highest permeability to effective pore radius ratio (K/reff) and was selected as a targeted sample. The wick-to-wall gap effect on the hydraulic characteristics of annular type wick structure is also investigated by measuring the permeability and effective pore radius of the sample wick structure with varying gap widths. The result shows that the permeability increases as the gap increases from 0 mm to 1.2 mm. After a peak at 1.2 mm, the permeability decreases as the gap increases and converges to the value of the case measured without a wall structure. The effective pore radius becomes smaller as the gap increases, making a peak at a gap distance of 1.2 mm. This result implies that there is an optimal point in gap distance which is determined to be 1.2 mm for the selected composite mesh structure. A capillary limitation correlation with a multiplying factor which explains the enhanced performance of the wick due to the gap is suggested. An annular wick type heat pipe is constructed and tested. The capillary limitation of the heat pipe showed good agreement with the suggested correlation.

Guiding migrating salmonid smolts: Experimentally assessing the performance of angled and inclined screens with varying gap widths

The loss of longitudinal connectivity in regulated rivers, both up- and downstream, has been detrimental for biodiversity worldwide. While progress has been made regarding upstream fish passage solutions, many questions remain unanswered regarding downstream passage alternatives. To address these knowledge gaps, we used Atlantic salmon (S. salar) smolts to experimentally assess the guidance efficiency and passage rates produced by several common screen-and-bypass fish guidance systems. Vertical screens with horizontally oriented bars extending across a turbine intake channel at a shallow angle (angled guidance screens), combined with a single, full-depth bypass entrance at their downstream end, were on average 20% more effective and produced passage rates that were 10 times higher than screens which extended perpendicularly across a turbine intake channel with vertically oriented bars that rose gradually towards the surface (inclined guidance screens) and with a bypass at the surface, on either side of the screen. Among inclined screens, gap width was negatively associated with guidance efficiencies and the smallest gap width (15 mm) exhibited a 41% greater guidance efficiency than the largest (30 mm). Among angled screens, performance was more closely linked to construction material as metal racks produced passage rates over three times faster than flexible Kevlar netting. Overall, passage through the guidance screens, and therefore into a tentative turbine intake area, was positively associated with gap width and was twice as prevalent among the inclined relative to angled guidance screens. Ultimately, an angled guidance screen with a 30 mm gap width produced the highest guidance efficiency and passage rates (a 30% improvement over the next best screen), while an inclined screen with a 30 mm gap width produced the lowest guidance efficiencies and passage rates. These results have implications for the suitability and performance of downstream fish passage solutions at both large- and small-scale hydropower plants where passage solutions are currently lacking or inadequate.

Instability of co-flow in a Hele-Shaw cell with cross-flow varying thickness

We analyse the stability of the interface between two immiscible fluids both flowing in the horizontal direction in a thin cell with vertically varying gap width. The dispersion relation for the growth rate of each mode is derived. The stability is approximately determined by the sign of a simple expression, which incorporates the density difference between the fluids and the effect of surface tension in the along- and cross-cell directions. The latter arises from the varying channel width: if the non-wetting fluid is in the thinner part of the channel, the interface is unstable as it will preferentially migrate into the thicker part. The density difference may suppress or complement this effect. The system is always stable to sufficiently large wavenumbers owing to the along-flow component of surface tension.

High-temperature thermal expansion behaviour of C/SiC studied using an in-situ optical visualisation method and numerical simulations in a quartz lamp array heating environment

The thermal expansion behaviour and thermal insulation performance of high-temperature structural ceramics have attracted considerable attention in the aerospace field. To further understand the high-temperature deformation behaviour and mechanism of C/SiC, an in-situ optical visualisation system was used to observe the variation in the gap width between C/SiC specimens in a quartz lamp array heating test. By using sub-pixel edge detection for the images recorded by the CCD camera and calculating the variation in gap width, it was found that the gap width first decreased and then increased during the heating process. Numerical simulations showed that the variation was caused by heat conduction and expansion of the base under the C/SiC specimens. The variation in the gap width under different working conditions was studied, and the thermal insulation performance of the specimens with and without thermal barrier coatings was compared. This work provides a new route with theoretical support for the study of the thermal expansion behaviour of high-temperature structural ceramics.

Influence of Air Infiltration on Combustion Process Changes in a Rotary Tilting Furnace

Air infiltration into the combustion chambers of industrial furnaces is an unwanted phenomenon causing loss of thermal efficiency, fuel consumption increase, and the subsequent increase in operating costs. In this study, a novel design for a rotary tilting furnace door with improved construction features is proposed and tested experimentally in a laboratory-scale furnace, aimed at air infiltration rate reduction by decreasing the gap width between the static furnace door and the rotating body. Temperatures in the combustion chamber and oxygen content in the dry flue gas were measured to document changes in the combustion process with the varying gap width. Volumetric flow values of infiltrating air calculated based on measured data agree well with results of numerical simulations performed in ANSYS and with the reference calculation procedure used in relevant literature. An achievable air infiltration reduction of up to 50% translates into fuel savings of around 1.79 to 12% of total natural gas consumption of the laboratory-scale furnace. The average natural gas consumption increase of around 1.6% due to air infiltration into industrial-scale furnaces can thus likewise be halved, representing fuel savings of almost 0.3 m3 per ton of charge.

Miniature Wideband Non-Uniform Metasurface Antenna Using Equivalent Circuit Model

A miniaturized wideband non-uniform metasurface antenna is proposed and analyzed using an equivalent circuit model. The nonuniform metasurface consists of an array of rectangular metallic patches separated by varying gaps. The effects of the varying gap widths on the resonant frequencies of the dual-mode non-uniform metasurface antenna are studied using the proposed equivalent circuit model. The resonant frequency of the first TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">10</sub> mode decreases with narrowing of either the center or side gaps; the resonant frequency of the antiphase TM <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">20</sub> mode is hardly affected by the center gap width but decreases while reducing the side gap width. The miniaturization of the metasurface antenna is therefore achieved by narrowing the side gaps, and the wide bandwidth with good impedance matching is realized by widening the center gap. A proof-of-concept prototype demonstrates a peak gain of 7.2 dBi over a -10 dB reflection coefficient bandwidth of 21.8%, with a miniaturized non-uniform metasurface of 0.46λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.49λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.06λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> (λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> is the center operating wavelength in free space) which achieves 54% size reduction compared with the earlier developed wideband antenna with a uniform metasurface of 0.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.7λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> × 0.06λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0</sub> .

3D flow simulations and pressure measurements for the evaluation of cavitation dynamics and flow aggressiveness in ultrasonic erosion devices with varying gap widths.

Cavitation induced wall loads at an ultrasonic horn facility are analyzed by 3D flow simulations and temporally high-resolved pressure measurements for varying gap widths between horn and stationary erosion specimen. Piezoelectric polyvinylidene fluoride (PVDF) probes are placed at different radial wall positions at the stationary specimen opposite of the oscillation horn and yield a declining flow aggressiveness with increasing radial position and gap width. The measurement results are reproduced by virtual probes in CFD simulations. Pressure measurement results yield a measure of flow aggressiveness in terms of wall load collectives that correlate well with incubation times obtained by erosion tests. A maximum aggressiveness at the specimen at 0.5mm gap width is obtained. Subharmonic frequencies associated with horn-attached void cavities increase with gap width which is well captured by the simulation. Due to the revealing of 3D flow patterns by the validated CFD results, detailed flow mechanisms associated with flow aggressiveness are discussed. The subharmonic frequency characteristics vs. gap width is associated with the shielding of the inner attached cavity region for small gaps and prevents the cavity from subharmonic collapse for several horn cycles. This shielding is less pronounced for larger gaps and leads to a shorter life time of the attached cavity and therefore to higher subharmonic frequencies.

Numerical and Experimental Study on the Savonius Rotor Performance with The Gap Width Variations of Ventilation in Middle Blades

In previous research, the use of ventilation at 15° from the outer end of the blade Savonius was able to increase the efficiency of Savonius windmill. This study aims to determine how the influence of the fixed ventilation on middle of the blade towards a performance of the Savonius windmill. There are one model of the conventional Savonius windmill and three models of the ventilated Savonius windmill that simulated by CFD and tested in the wind tunnels. Simulation variabels used are variations for ventilation width and the rotation angle position of the rotor. Experimental variables were variations for the gap width of ventilation and wind speed. The ventilated Savonius with ventilation position in the middle of the rotor blades turns out to have the average power coefficient (Cp) lower than the conventional Savonius windmill. The wider the gap from the ventilation will further reduce the performance of the ventilated Savonius rotor. In this study, the SV65-10 model produced the worst performance. This power coefficient of the SV65-10 model is 29% lower than a conventional Savonius rotor..

Adaptive control of the filler wire rate during laser beam welding of squared butt joints with varying gap width

Adding filler wire control to autogenous laser beam welding of squared butt joints offers a means to widen up the tight fit-up tolerances associated with this process. When the gap width varies, the filler wire rate should be controlled to assure a constant geometry of the resulting weld seam. A dual mode sensing system is proposed to estimate the joint gap width and thereby control the filler wire rate. A vision camera integrated into the welding tool together with external LED illumination and a laser line projection enables two sensing modes, one surface feature extraction mode and one laser triangulation-based mode. Data from the both modes are fused in a Kalman filter, and comparisons show that the fusing of the data gives more robust estimation than estimates from each single mode. A feed-forward control system adaptively adjusts the filler wire rate based on the estimations of the joint gap width in front of the keyhole. The focus is on keeping the data processing simple and affordable, and the real-time performance of the sensor and control system has been evaluated by welding experiments. It is shown that the proposed system can be used for on-line control of the filler wire rate to achieve a constant weld geometry during varying joint gap widths.

The stability of laser welding with an off-axis wire feed

The concept using an off-axis filler wire during laser welding is introduced here in order to provide added process robustness considering gap width variations. Its stability is investigated with respect to gap width, welding speeds and powers. Geometry of the welds is analysed by tracing of weld cap edges and joint cross sections, connecting trends to weld parameters. High speed imaging and streak images are used to further study and describe sequences of events, including undercut formation. Formation of imperfections are found to be mainly correlated to wire feed position variations at the surface due to irregular melting of the wire tip.

Comparative Evaluation of the Strength of Denture Base Resin repaired with Glass Fiber-reinforced Acrylic Resin: Anin vitroStudy

The present study aimed at evaluating and comparing the transverse strength of heat polymerizing acrylic resin samples repaired using glass fiber-reinforced autopolymerizing acrylic resin with varying gap widths at the fracture site. Heat polymerizing acrylic resin samples of dimensions 65 * 10 * 2.5 mm each were fabricated. Ten of these were used as control. In the rest of samples, two grooves were fabricated and surface treated with ethyl acetate. The repair gap width was standardized at 4, 3, 2, and 1 mm. Totally, 80 samples were equally divided into these four groups. Glass fiber-reinforced autopolymerizing acrylic resin was used to repair these samples. The repaired samples and the control groups were subjected to three-point bending test, and the findings were analyzed statistically. It was observed that with increase in gap width, their transverse strength decreased. Most of the fractures occurred at the joint interface of parent and repair material. The fracture within the repaired material occurred highest in the group that had 4 mm gap, followed by groups that had 3 and 2 mm gaps. In the group with 1 mm gap, there was no occurrence of fracture within the repaired material. To achieve optimum repair strength of a repaired denture, the gap width should not be greater than 1 mm. The study will aid in determining the ideal gap width for denture repair to prevent fracture and also the clinical application of glass fiber-reinforced autopolymerizing acrylic resin.

Microstructure of diffusion-brazing repaired IN738LC superalloy with uneven surface defect gap width

ABSTRACTSlots with uneven width were cut by femtosecond laser in small plates of IN738LC superalloy to imitate service cracks. The ‘cracks’ were repaired by diffusion brazing using BNi-1a or a mixed filler alloy at 1100°C. The joint region was composed of isothermal solidification zone (ISZ), diffusion affected zone (DAZ) and precipitate zone (PZ). The compositions were different between the upper and lower ISZ due to the variation of gap width. The sample, repaired with two kinds of filler metals, had similar DAZ microstructure. PZ of mixed filler alloy bonded sample had a similar microstructure with that of BNi-1a, but less borides. The maximum gap sizes of complete isothermal solidification were almost the same for different filler alloys, followed a square root relationship with time. However, PZ of BNi-1a bonded was larger, resulting from a more base metal dissolution. The relationship between the PZ, ISZ and crack width is discussed.

DNA-graphene interactions during translocation through nanogaps.

We study how double-stranded DNA translocates through graphene nanogaps. Nanogaps are fabricated with a novel capillary-force induced graphene nanogap formation technique. DNA translocation signatures for nanogaps are qualitatively different from those obtained with circular nanopores, owing to the distinct shape of the gaps discussed here. Translocation time and conductance values vary by ∼ 100%, which we suggest are caused by local gap width variations. We also observe exponentially relaxing current traces. We suggest that slow relaxation of the graphene membrane following DNA translocation may be responsible. We conclude that DNA-graphene interactions are important, and need to be considered for graphene-nanogap based devices. This work further opens up new avenues for direct read of single molecule activitities, and possibly sequencing.

Numerical analysis of terahertz surface plasmon polaritons propagating in a parallel plate configuration

In this paper, we present numerical analysis of terahertz (THz) surface plasmon polaritons propagating in a parallel plate configuration. A planar metal surface has the ability to support loosely bound surface waves, called Zenneck waves at terahertz frequencies. Two parallel metal plates separated by a narrow vacuum region can lead to the highly confined terahertz surface plasmon modes at specific frequencies. The frequency of the terahertz mode can be changed with a change in the gap between the plates. Further, we observed that the carrier concentration of plates strongly effect the frequency of the terahertz mode as well as its properties. We have examined in detail the dispersion properties of the terahertz surface plasmons supported by the parallel plate configuration with a varying gap width as well as carrier density of the plates.