Proper Gap Research Articles

Experimental investigation of compact metamaterial for high efficiency mid-range wireless power transfer applications

We investigate a compact metamaterial for enhanced magnetic coupling in a resonator coupled wireless power transfer system operating at around 6.5 MHz. The metamaterial is constructed by realizing an array of three-turn spiral resonators on a thin slab. Although the metamaterial has its own loss, the experimental results show that the proposed metamaterial slab enhances the power transmission capability. The number of unit cells in the array is an important parameter, because exceeding a certain number of unit cells does not enhance the efficiency due to the loss of the slab. Furthermore, strong surface mode resonance is observed when two slabs are assembled with proper gap spacing between them. By using the optimization approach, we achieve a significant efficiency improvement at a mid-range distance. The measured efficiencies are 71.1% and 54.3% at a 0.6 and 1.0 m distance, respectively. At a 1.0 m distance, this efficiency performance corresponds to a 270% improvement compared to a case with no metamaterial slab. In addition, we experimentally confirm the threshold distances above which the metamaterial shows enhanced performance.

A Broadband Rectangular Microstrip Patch Antenna for Wireless Communications

In this paper, a simple design of wideband rectangular patch antenna is presented by using asymmetrical feed and a reduction in ground plane with proper gap distance. The frequency-dependent characteristic impedance included in the proposed procedure is addressed to eliminate possible errors in the high-frequency broadband applications. The antenna proposed in this research provides 2.3GHz bandwidth (frequency range: 0.9GHz - 3.2GHz) which can be utilized in various broadband applications such as remote sensing, biomedical and mobile radio. The proposed procedure in this research is compatible with CAD applications and is valuable contribution as it permits quick and easy design for RF engineers.

The Surgeon and his Experience is the Thing!

Dr. Merrill Ritter, an outstanding expert on total knee replacement (TKR), has written an interesting paper evaluating results with posterior cruciate retaining (PCR) and posterior-substituting total knee replacement (PS). His center is a high-volume center for total knee replacement, and the study encompasses results in 8,607 total knee replacements. His findings demonstrate an expected slight increase in flexion for the PS TKR in comparison to the PCR TKR (about 3°) with slightly better function in the PCR TKR. However, the results varied from surgeon to surgeon in the group using these different implants, and this was a major variable in the results. Surgeon results varied and were not consistently better with one implant or another. Some surgeons had excellent results with the PCR knee and others less good results with the PCR knee. The same was true for the PS TKR. This led to the conclusion that surgeon preference and experience with a particular implant was the important variable in patient outcome. Many factors influence the clinical outcome after TKR aside from prosthetic selection. This is particularly true in the high-flexion knee or gender-specific knee where results are not better than with conventional TKR. In the end, it is surgical technique and patient factors which predict the outcome of an arthroplasty far more than prosthetic design in the knee. Soft-tissue balancing in the medial-lateral and antero-posterior planes is key to knee flexion and ultimate function. Surgical experience and attention to technique will determine proper gap balancing which influences patient motion and outcome. PCR knees require careful balancing of the posterior cruciate ligament for knee motion, and a surgeon’s ability to balance this may vary. A comfort zone for improved outcomes exists and will vary from one implant to another for a surgeon. My philosophy has correlated with Dr. Ritter’s findings and was first advocated by Michael Freeman, knee innovator from London. Dr. Freeman taught that a surgeon should find a time-proven prosthesis he knows well and is able to implant consistently with excellent soft-tissue balancing and alignment. The surgeon should not move from implant to implant looking for better outcomes but should excel with a particular design and stay with it. He will be able to obtain better results with it in knees of varying severity including the most deformed. Outcomes, function, pain relief, and range of motion will be better in this setting than attributing poor results to implant design alone. Dr. Ritter has validated this important aspect of knee surgery in determining end results. The long-term controversy of PCR vs PS is less so today and is of less importance than surgical experience and excellence of technique regardless of prosthetic selection.

Experimental study on conduction current of positive nanosecond-pulse diffuse discharge at atmospheric pressure

Nanosecond pulsed discharges have various discharge modes, such as corona, diffuse discharge, spark or arc. A dense diffuse discharge is particularly desirable for various applications at atmospheric pressure. In this paper, a magnetic-compression pulse generator was used to produce repetitive positive nanosecond pulses for excitation of a diffuse discharge. The output pulse of the generator had a rise time of about 25 ns and a full width at half maximum of 40 ns. Electrical characteristics of the diffuse discharge were studied by measuring its voltage and current waveforms, as well as images of the discharge. The conduction current was calculated by the measured voltage and current, which was a true discharge current. The experimental results show that a stable diffuse discharge could be obtained at atmospheric pressure, and the conduction current was unipolar and had similar amplitude of several amperes under our experimental condition, which has the similar amplitude with the displacement current. Furthermore, the air gap spacing and pulse repetition frequency (PRF) affected the intensity and mode transition of the diffuse discharge. The conduction current increased with the PRF but decreased with the air gap spacing. Therefore, the diffuse discharge was likely available under some conditions of proper air gap, high PRF with positive pulse.

Numerical Simulation of Internal Fire Whirls in an Inclined Shaft

In order to understand the characteristics of fire whirls in the inclined shaft with corner gap, large eddy simulations (LES) of thermal flow field in a 9-meter-high inclined shaft were employed. In the inclined shaft, the conrner gap is 0.3m and 0.7m in width, and the inclination angle is 5°, 30°, 45°, 50° and 55° from the vertical orientation axes respectively. It is found that a whirling flow field could be formed under proper inclination angles and corner gap width. Rotational axis of fire whirls in the inclined shaft would have same inclination angles with the shaft. Similar to the case of fire whirls in a vertical shaft, the width of corner gap of inclined shaft also influences the whirling motion of the flame. In this paper, for the same fire and inclination angle, the 0.3-meter-wide corner gap is easier to form stable fire whirls than the 0.7-meter-wide corner gap. By comparison with buoyancy, the slightly greater Coriolis force was found above a height 3m for inclined fire whirls when the width of croner gap is 0.3m, however, the Coriolis force acts only on the lower part of the shaft when the width of croner gap is 0.7m.

Effect of gap on plasma and molten pool dynamics during laser lap welding for T-joints

The aim of the present research is to discuss the effect of gap on plasma plume, keyhole, and molten pool dynamics during laser lap welding for T-joints. The authors observe plasma plume, keyhole opening, and molten pool images by high-speed camera in different gaps during CO2 laser overlap welding of T-joints. The results show that gap causes beam energy fluctuations in the keyhole and leads to the instability of welding process. In laser spot welding, zero-gap and small gap greatly affect the stability of plasma and keyhole, which causes the formation of cavities in the weld metal, while a proper gap can help prevent porosity formation. In laser continuous welding, the disruption and closure of front keyhole wall at the gap periodically changes with the gap, which causes the formation of plenty of porosities at the gap. The instability of keyhole is closely related to dynamics of plume and molten pool, which gives an insight into the mechanism of porosity formation during laser overlap welding.

Numerical and experimental investigation of pulsating blankholder effect on drawing of cylindrical part of aluminum alloy in deep drawing process

In this study, the effect of a new pulsating blankholder system has been investigated on improving the formability of aluminum 1050 alloy. By using this system, during each pulsating cycle, first, the metal was easily flowed into the die through removing the blankholder force, and then the blankholder force applied by springs was employed to prevent excessive metal flow and wrinkling. Deep drawing of cylindrical cup was simulated by ABAQUS6.7 software. Cup depth, tearing, and thickness distribution of the experimental and numerical analyses were then compared. The results indicated that by using the pulsating blankholder system coupled with proper frequency and gap, the cup depth can be increased and thickness distribution can be improved. Further, good agreement was observed between simulation and experimental results.

SU‐E‐T‐30: Estimation of Dynamic Leaf Gap for IMRT Dose Calculation

Purpose: To obtain the proper dynamic leaf gap (DLG) of a Millennium 120 MLC such that the calculated dose matches the measured. Methods: The DLG for round leaves is often measured via extrapolating the size of fields formed by sweeping synchronized MLC leaves to the size under which the measured dose equals the MLC transmission. In this situation, the tongue and groove effect would be minimal. However, practical IMRT fields are formed by non‐synchronized MLC leaves. Therefore, we measured doses from both synchronized and non‐synchronized dynamic fields. Each non‐synchronized field had fixed but different neighbouring leaf extensions (tongue‐and‐grove, T&G). The DLG was obtained for each set. Doses calculated with various values of DLG and transmission rate (TR) were compared with the measured dose. The relative discrepancies were put into a lookup table as function of gap and T&G. The table was used to estimate the pass rate of patient IMRT plans, in which each field was decomposed into sub‐fields. Each sub‐field was formed by a pair of opposite leaves. The T&G was calculated from the neighbouring leaves formed the sub‐field. Results: The extrapolated DLG was 1.8, 1.6, 1.7, 2.5 and 1.6mm for the T&G 0, 5, 10, 15 and 20mm, respectively. The MLC TR was 1.6%. For typical patient IMRT plans, the T&G values were broadly distributed from 0 to 20mm but with median around 15mm. From investigating many combinations of TR and T&G, we see the pass rate was extremely sensitive to the combination, and the highest pass rate went to the combination of transmission 1.6% and T&G 2.3mm. This Result excellently agreed with IMRT QA. Conclusion: The extrapolated DLG depends on the T&G. The proper value of DLG can be estimated from the study of non‐synchronized sweeping gaps and T&G distributions in typical patient IMRT plans.

Active control of a cylinder wake flow by using a streamwise oscillating foil

In this study, numerical experiments are carried out to control the vortex shedding of a circular cylinder by utilizing an oscillating foil. The thin foil of elliptic shape undergoes prescribed harmonic oscillations in the streamwise direction in the near wake region. This simplified model is intended to study how wake dynamics are modified via localized wake disturbance, and then to stabilize the global wake instability. The results show that, at proper gap spacing, the oscillating foil can completely suppress the wake unsteadiness and recover the recirculating bubble type flow. The global instability suppression is then established on the imposition of local symmetry into the reversed flow behind the cylinder. It is revealed that the dynamic interaction between the main shears layer and oscillatory boundary layers is responsible for the wake stabilization mechanism. In addition, the kinematic/dynamic parameters related to foil motions and flow properties are widely discussed to reveal their effects on the performance of wake stabilization and drag reduction.

PMBC: Pattern mining from biological sequences with wildcard constraints

Patterns/subsequences frequently appearing in sequences provide essential knowledge for domain experts, such as molecular biologists, to discover rules or patterns hidden behind the data. Due to the inherent complex nature of the biological data, patterns rarely exactly reproduce and repeat themselves, but rather appear with a slightly different form in each of its appearances. A gap constraint (In this paper, a gap constraint (also referred to as a wildcard) is a character that can be substituted for any character predefined in an alphabet.) provides flexibility for users to capture useful patterns even if their appearances vary in the sequences. In order to find patterns, existing tools require users to explicitly specify gap constraints beforehand. In reality, it is often nontrivial or time-consuming for users to provide proper gap constraint values. In addition, a change made to the gap values may give completely different results, and require a separate time-consuming re-mining procedure. Therefore, it is desirable to automatically and efficiently find patterns without involving user-specified gap requirements. In this paper, we study the problem of frequent pattern mining without user-specified gap constraints and propose PMBC (namely P̲atternM̲ining from B̲iological sequences with wildcard C onstraints) to solve the problem. Given a sequence and a support threshold value (i.e. pattern frequency threshold), PMBC intends to discover all subsequences with their support values equal to or greater than the given threshold value. The frequent subsequences then form patterns later on. Two heuristic methods (one-way vs. two-way scans) are proposed to discover frequent subsequences and estimate their frequency in the sequences. Experimental results on both synthetic and real-world DNA sequences demonstrate the performance of both methods for frequent pattern mining and pattern frequency estimation.

Effect of Flavone from Forestry Waste <i>C.Cathayensis</i> Exocarp on Photosynthetic Characteristics of Crops

Using six kinds of concentration (ranged from 0.0 to 2.0mg.L-1) of flavone extract from C.cathayensis exocarp treats corn, soybean, wheat and mung bean seedlings, in order to study the photosynthetic rate, stomatal conductance, transpiration rate, intercellular CO2 on the seedling leaf. Results show that effects of flavone extract (0.1-0.5mg.L-1) increase content of the chlorophyll a, b and total chlorophyll, promote photosynthetic rate, stomatal conductance, transpiration rate, proper increase cell gap inside the CO2 concentration.0.1mg.L-1 treatment effect is the most obvious compare with the control, the total chlorophyll and photosynthetic rate increase by 20.9 % and 21% respectively; More than 0.5mg.L-1, the chlorophyll content, photosynthetic rate, stomatal conductance, transpiration rate decrease, the intercellular CO2 rapid increase. Research shows that, the appropriate concentration of flavone can increase the chlorophyll content in the leaf, promote stomatal opening, increase of intracellular CO2 supply, improve leaf photosynthesis efficiency.

Rasch Analysis of the Pediatric Outcomes Data Collection Instrument in 720 Patients With Cerebral Palsy

The pediatric outcomes data collection instrument (PODCI) was originally developed to carry out a functional assessment of children and adolescents (including patients with cerebral palsy), focusing on musculoskeletal health. Validated questionnaires are important for assessing the functional outcome of cerebral palsy, and are meant to have unidimensionality, proper item gap, no ceiling and floor effects, and no item redundancy. The advances in health measurements have led to the application of Rasch analysis to assess questionnaires. This study evaluated PODCI in patients with cerebral palsy using Rasch analyses. The study included a total of 720 patients with gross motor function classification system level I to III, 192 with unilateral involvement and 528 with bilateral involvement. Rasch analysis was performed to obtain information on (1) the information weight fit statistic to assess the unidimensionality and redundancy of the items in each domain; (2) average item calibration to detect the item separation; and (3) item map to evaluate the ceiling and floor effects. The PODCI worked best in the sports/physical function domain. In information weight fit statistics, there were 4 items violating unidimensionality, which included "putting on his/her coat" in transfer/basic mobility and "getting together and do things with friends" in sports/physical function. There were 4 items with item redundancy. Inadequate item separation was observed in the transfer/basic mobility domain. A ceiling effect was found in all domains, except for the sports/physical function. The sports/physical function domain in PODCI generally satisfies the requirements of Rasch item response theory and is an appropriate measure of the function in cerebral palsy. Although some individual items do not fit well, the PODCI can be improved by eliminating the redundant items and by adding more difficult tasks to fill in the gaps. Level II.

Engineering of oriented myocardium on three-dimensional micropatterned collagen-chitosan hydrogel.

Surface topography and electrical field stimulation are important guidance cues that aid the organization and contractility of cardiomyocytes in vivo. We report here on the use of these biomimetic cues in vitro to engineer an implantable contractile cardiac tissue. Photocrosslinkable collagen-chitosan hydrogels with microgrooves of 10 µm, 20 µm and 100 µm in width were fabricated using polydimethylsiloxane (PDMS) molds. The hydrogels were seeded with cardiomyocytes, placed into a bioreactor array with the microgrooves aligned with the electrical field lines, and stimulated with biphasic square pulses at 1 Hz and 2.5 V/cm. At Day 6, cardiomyocytes were aligned in the direction of the microgrooves. When cultivated without electrical stimulation, the excitation threshold of engineered cardiac tissues using micropatterned hydrogels was significantly lower than using smooth hydrogels, thus showing the importance of cell alignment to cardiac function. The success rate of achieving beating constructs was higher with the application of electrical stimulation. In addition, formation of dense contractile cardiac organoids was observed in groups with both biomimetic cues. The cultivation of cardiomyocytes on hydrogels with 10 µm grooves yielded 100% beating tissues with or without electrical stimulation, thus suggesting a smaller groove width is necessary for cells to communicate and form proper gap junctions. However, electrical field stimulation further increased cell density and enhanced tissue morphology which may be essential for the integration of the tissue construct to the native heart tissue upon implantation. The biodegradability of the hydrogel substrate allows for the rapid translation of the engineered, oriented cardiac tissue to clinical applications.

Effect of fluid inertia on probe-tack adhesion

One way of determining the adhesive strength of liquids is provided by a probe-tack test, which involves measuring the force required to pull apart two parallel flat plates separated by a thin fluid film. The large majority of existing theoretical and experimental work on probe-tack adhesion use very viscous fluids and considers relatively low lifting plate velocities, so that effects due to fluid inertia can be neglected. However, the employment of low-viscosity fluids and the increase in operating speeds of modern lifting apparatus can modify this scenario. By dealing with a proper gap averaging of the Navier-Stokes equation, we obtain a modified Darcy-law-like description of the problem and derive an adhesion force which incorporates the effects of fluid inertia, fluid viscosity (for Newtonian and power law fluids), and the contribution of the compliance and inertia of the probe-tack apparatus. Our results indicate that fluid inertia may have a significant influence on the adhesion force profiles, inducing a considerable increase in the force peaks and producing oscillations in the force-displacement curves as the plate-plate separation is increased. The combined role of inertial and non-Newtonian fluid behaviors on the adhesion force response is also investigated.

Process control for ultrasonic hole-drilling in hard brittle materials

Ultrasonic drilling offers a solution to bore sub-millimetre holes of high diameter-to depth ratio in difficult to machine brittle materials. A key aspect of the process is to maintain a proper gap between tool and work piece. This paper presents the successful solution developed to address this issue. In our approach, we vibrate the work piece and control the motion of the tool, which is constrained by an aerostatic bearing and generated by a voice coil actuator. We use the voice coil to measure the force acting between tool and work piece. We measure the tool displacement with an Eddy current sensor. Using the two sensor measurements, we developed a control algorithm in which the tool is displaced in such a way as to maintain the tool-work piece interaction force constant. The paper presents experimental details of the characterization of the control loop and results of drilling experiments.

Novel optical f iber-based laser direct writing process for micromachining of metal

A laser micromachining technique for the fabrication of metallic microstructures is proposed. The fabrication of microstructures is done by laser-induced wet etching that adopts an optical fiber as a machining tool. The laser beam delivered through the multimode fiber directly irradiates on the workpiece while maintaining a proper gap to avoid fiber damage. The manufacture of microstructures with high surface quality and good size uniformity is realized. Microgrooves with aspect ratio over 10 and microholes with a nearly straight cross-section can be produced by the proposed technique. The overall etching results are examined closely with respect to process variables.

Numerical Optimization Research on the Dielectric Barrier Discharge for NOx Removal

Numerical optimization research was made for the dielectric barrier discharge (DBD) reactor for NOx removal in order to improve the efficiency of the DBD reactor. In this paper, the optimization method proposed by our studying team was adopted to carry out the numerical optimization research on the discharge gap of the reactor. As a result, the breakdown strength of reactor was 44.8kV/cm at a 2mm discharge gap and the discharge started at 25μs. When the discharge gap increased to 8mm, the breakdown strength was 34.1kV/cm and the discharge time was 33μs. The removal rates under the two conditions varied little due to the similar electron mean energy, then experiment was conducted to validate the accuracy of the simulation. When the discharge gap increased, the gas handing capacity of the reactor got higher.Therefore, proper discharge gap has important influence on removal efficiency of NO during DBD.

Flow fluctuation measurement in the flow-through path of continuous electric-discharge CO2-laser contour

We have experimentally proved the applicability of hot-wire anemometer method to measure fluctuations at low pressures and gas flow rates when medium is no longer considered as continuous. Use of individual calibration at working conditions serves to apply standard technique for determination of sensitivity coefficients of hot-wire probes. Additional investigations are necessary to take into account influence of Knudsen number and, possibly, other parameters in heat transfer law presented as criterial dependence of Nusselt number on Reynolds number. Hot-wire measurement of mean velocity distribution and their fluctuations in the flow-through path of electric-discharge CO2 laser have been performed. The level of velocity fluctuations in the vicinity of anode is high that is caused by the zone of interacting flows from the ventilators rotating in opposite directions forming in the symmetry plane. Placing of the damping screen between the ventilator and air gap allows decreasing fluctuations intensity to the acceptable level. It has been ascertained that the vortex shedding with high intensity of fluctuations which influence is noticeable in significant part of air gap is formed in the wake behind the streamlined cathode. However, pulsation level in the proper gap does not exceed permissible values.

Gap Distribution Between Fragile Insert and Mold in Plastic Boundary Injection Forming

Plastic inserts may enhance the performance of a product, enlarge its application scope or make it possible to apply plastic in situations where this material may not have been applied previously. The type of insert may vary from metal to plastic, ceramic, glass, or fireproof materials on a macro-scale. Glass is a typical type of fragile material. As an insert, this fragile part is easily broken or scraped during the processing of PVC injection molding, and flashes may occur at the shared boundaries of PVC and insert. The proper gap should be set between the core or cavity and the insert. In this paper, the function of the pressure attenuation and the shear flowing distribution variation along the runner is set to get the optimal gap distribution. First, two types of power loss functions are set. These functions relate pressure and shearing flow during transverse filling in a runner. Second, the summation of the two types of power loss is obtained using functions that are proportional and inversely proportional to the mold gap. Third, by discretizeing the long and narrow runner, according to the pressure distribution, the optimal gap is obtained at each point. Next, the simplified algorithm and the post-processing calculations of the fitting gap at arbitrary points are proposed. As an application, the experimental procedures and results of injection forming circular freeform materials which are used in vehicles as PVC-lined safety inserts are described in detail. Through geometrical measurement and mechanical testing on PVC and glass, we have shown that the mold gap distribution and the processing operations can ensure the technical requirement of the plastic part with fragile insert.

Thermomechanical Coupling Analysis of Two Concentric Cylinders with Initial Gap Using DG Finite Element Method

In this paper, thermomechanical coupling analysis of two concentric cylinders with initial gap is investigated by using the discontinuous Galerkin (DG) finite element method. The thermomechanical coupling analysis is divided into a thermal subproblem and a mechanical subproblem in the sequencial coupling algorithm. The Picard iteration procedure with a relaxation technique is also employed to accelerate the rate of convergence of the iterative procedure and avoid numerical instability. Due to the existence of the thermal contact resistance (TCR) between these two cylinders, some interesting thermomechanical coupling phenomena appeared. It is found that a proper initial gap may greatly reduce the maximum equivalent stress in structures. Moreover, the DG finite element method not only can be used to simulate the thermomechanical coupling problems effectively, but also can find out this proper initial gap, which is valuable in engineering design and structural safety assessment.