Reduction of reverse leakage current at the TiO2/GaN interface in field plate Ni/Au/n-GaN Schottky diodes

This paper presents the fabrication procedure of TiO2 passivated field plate Schottky diode and gives a comparison of Ni/Au/n-GaN Schottky barrier diodes without field plate and with field plate of varying diameters from 50 to 300 µm. The influence of field oxide (TiO2) on the leakage current of Ni/Au/n-GaN Schottky diode was investigated. This suggests that the TiO2 passivated structure reduces the reverse leakage current of Ni/Au/n-GaN Schottky diode. Also, the reverse leakage current of Ni/Au/n-GaN Schottky diodes decreases as the field plate length increases. The temperature-dependent electrical characteristics of TiO2 passivated field plate Ni/Au/n-GaN Schottky diodes have shown an increase of barrier height within the temperature range 300…475 K.

Analysis and Study on Bending Vibration Frequency of New Corrugated Steel Web Composite Box Girder

In order to accurately analyze the bending vibration frequency of the new composite box girder, the effects of web folding effect, shear lag, and shear deformation are comprehensively considered in this paper, and the elastic control differential equation and natural boundary conditions of the composite box girder are established by using the Hamilton principle. A one-span composite box girder with corrugated steel webs is used as a numerical example. The effects of height span ratio, width span ratio, web thickness, cantilever plate length, and fold effect on the vertical vibration frequency of the new composite box girder are analyzed. The results show that the analytical solution is in good agreement with the finite element solution. When considering the shear lag and fold effect, the vibration frequency of composite box girder decreases. With the increase in order, the influence of shear lag and fold effect on its frequency becomes stronger. The changes of height span ratio and web thickness of composite box girder have a great influence on its folding effect, while the changes of width span ratio and cantilever plate length have little influence on it. The conclusion can provide a reference for the design of medium section new composite bridge in practical engineering.

Theoretical and Experimental Study of Wave Propagation in Stressed Plate

Detection of stresses in structures is widely required. Acoustic stress measurement is a NonDestructive Evaluation (NDE) method. In this paper wave propagation in a stressed plate is studied, using numerical simulations. We used ABAQUS, a commercial finite element software, to model the plate. Many parameters affect the wave propagation as plate thickness, plate length, and frequency of the wave signal are studied. When compressive and tensile loads are applied to a plate, the wave propagation is investigated. It was concluded that the effect of stress on the wave propagation decreases with increasing plate length and also with increasing plate thickness, wherewith increasing frequency the effect of stress in wave propagation is clearer.

Flow Characteristics and Fluid Forces Reduction of Flow Past Two Tandem Cylinders in Presence of Attached Splitter Plate

Numerical simulations are carried out to study the flow around two tandem square cylinders (SC) under the effect of spacing ratio(g/D) and splitter plate length (l/D) for a fixed Reynolds number (Re) = 100. The g/D is varied from 0 to 10 and l/D is varied from 0.5 to 10. The splitter plate length is found to have strong effect on vortex shedding and fluid forces. The maximum reduction in mean drag coefficient is observed at l/D = 8, that is 15% and 78% for upstream and downstream cylinders, respectively. The maximum reduction in root-mean-square value of lift coefficient is found at l/D = 10, that is 99%. The flow pattern at both of these points is steady flow. There is 100% vortex shedding suppression for l/D > 5. The observed flow patterns for flow past tandem cylinders without splitter plate are; single bluff body (SBB), steady flow (SF), quasi-steady flow (QSF), fully developed flow (FDF) and fully developed two-row vortex street flow (FDTRVS) regimes. SBB, QSF and SF regimes were observed in presence of splitter plate.

Glans–urethral meatus–shaft score and penile parameters as preoperative assessment tools for hypospadias surgery outcome

Background Our prospective study aims to assess if penile parameters and GMS score can predict the postoperative outcome of patients with hypospadias repaired with the TIP technique. Methods This prospective study included patients (6 months–11 years old) with coronal, distal or mid penile hypospadias who underwent Tubularized incised plate (TIP) urethroplasty technique from 2015 to 2017. All patients were assessed preoperatively using GMS score. GMS score included a scale for each component, with the more unfavorable characteristics assigned higher scores. Penile length, urethral plate length, and penoscrotal length were measured using a ruler. Glans width was measured by using a caliper ruler. Demographics and complications were assessed within 3 months of the procedure. Results There was a statistically significant difference between complicated and non-complicated patients regarding GMS score, glans width, penoscrotal length, penile length, and urethral plate length/penile length ratio. According to the ROC curve, the cutoff values for GMS score, glans width and penoscrotal length were 6, 14 mm and 5 cm, respectively. The area under the ROC curve for penile length and for urethral plate/penile length ratio was poor and so we could not get a specific cutoff value for either parameters. According to Stepwise logistic regression, the GMS score was the only significant independent parameter while controlling all the other factors. Any increase in the GMS score by one unit would increase the risk of complications 3 times. Conclusion GMS score and penile parameters are good predictors and complete each other in preoperative assessment for hypospadias patients. Patients with a high GMS score (above 6) have a higher risk of complication and patients with a Glans width of 14 mm or more and a penoscrotal length of 5 cm or more are associated with less risk of complication.

Dimensionless Correlations for Natural Convection Heat Transfer from a Pair of Vertical Staggered Plates Suspended in Free Air

Buoyancy-induced convection from a pair of staggered heated vertical plates suspended in free air is studied numerically with the main scope to investigate the basic heat and momentum transfer features and to determine in what measure any independent variable affects the thermal performance of each plate and both plates. A computational code based on the SIMPLE-C algorithm for pressure-velocity coupling is used to solve the system of the governing conservation equations of mass, momentum and energy. Numerical simulations are carried out for different values of the Rayleigh number based on the plate length, as well as of the horizontal separation distance between the plates and their vertical alignment, which are both normalized by the plate length. It is observed that an optimal separation distance between the plates for the maximum heat transfer rate related to the Rayleigh number and the vertical alignment of the plates does exist. Based on the results obtained, suitable dimensionless heat transfer correlations are developed for each plate and for the entire system.

Numerical Study of the Effect of Different Variables on the Cooling of a Flat Plate Using a Synthetic Jet

A synthetic jet is caused by the periodic motion of a diaphragm within a cavity. There is one or more orifices or outlets in this cavity. The main advantage of this type of jet compared to a continuous jet is that the synthetic jet is composed of transverse flow, and therefore, it does not need a continuous source of fluid, unlike the continuous jet. In recent years, synthetic jets have received a great deal of attention so that they have been used in a wide range of applications such as controlling separation and turbulence, besides, the cooling of electronic equipment and propulsion. In the present study, the jet is placed perpendicular to the flat plane with constant heat flux, thereafter, the effect of some geometric parameters were evaluated numerically such as the ratio of the distance between the jet and the impinging plate to the nozzle width, the ratio of the impinging plate length to the jet nozzle width, the ratio of cavity width of the synthetic jet to the nozzle width, the ratio of the cavity height to the nozzle width, the angle of the impinging plate, besides, the diaphragm specifications including amplitude and frequency of the jet diaphragm in heat transfer using OpenFOAM open-source software. The results show that the frequency and the length of the impinging plate are the most effective parameters, respectively, in terms of the diaphragm and geometry.

Influence of the liner-type treatment on the trailing-edge noise generated by a flat plate

Several liner-type treatments (three different rectangular grooves covered by three different low porosity wire-mesh screens) on the trailing edge of a flat plate have been investigated in the anechoic wind-tunnel of Université de Sherbrooke. Far-field acoustic directivity measurements have been achieved at Reynolds numbers based on the plate length from [Formula: see text] to [Formula: see text], yielding radiation maps of all possible liner combinations that are then compared to the reference solid flat plate and to the plate with inserts alone. Noise from the flat plate corresponds to dipolar trailing-edge scattering with an extra shallow hump attributed to the unsteady flow recirculation behind the thick plate. When grooves are added, the latter contribution is amplified and additional cavity noise is observed with several tones and humps. The tones are shown to be resonance between high order modified Rossiter modes and cavity depthwise modes. The hump is a combination of drag dipoles and cavity monopoles from the groove row. The addition of screens always reduces the amplification of the dipolar edge scattering but exhibits very different non-linear responses for the cavity noise. The combination screen with the smallest cells and the insert with the shallowest cavities (corresponding to the same type of treatment applied previously on the Controlled-Diffusion airfoil) yields the lowest levels overall, while the screen with intermediate cell size almost always triggers noise amplification and the screen with a coarse mesh has an intermediate behavior. At high frequencies, the previously reported roughness noise is also observed.

The effect of surgeon-controlled variables on construct stiffness in lateral locked plating of distal femoral fractures

Background Nonunion following treatment of supracondylar femur fractures with lateral locked plates (LLP) has been reported to be as high as 21 %. Implant related and surgeon-controlled variables have been postulated to contribute to nonunion by modulating fracture-fixation construct stiffness. The purpose of this study is to evaluate the effect of surgeon-controlled factors on stiffness when treating supracondylar femur fractures with LLPs: Does plate length affect construct stiffness given the same plate material, fracture working length and type of screws? Does screw type (bicortical locking versus bicortical nonlocking or unicortical locking) and number of screws affect construct stiffness given the same material, fracture working length, and plate length? Does fracture working length affect construct stiffness given the same plate material, length and type of screws? Does plate material (titanium versus stainless steel) affect construct stiffness given the same fracture working length, plate length, type and number of screws? Methods Mechanical study of simulated supracondylar femur fractures treated with LLPs of varying lengths, screw types, fractureworking lenghts, and plate/screw material. Overall construct stiffness was evaluated using an Instron hydraulic testing apparatus. Results Stiffness was 15 % higher comparing 13-hole to the 5-hole plates (995 N/mm849N vs. /mm, p = 0.003). The use of bicortical nonlocking screws decreased overall construct stiffness by 18 % compared to bicortical locking screws (808 N/mm vs. 995 N/mm, p = 0.0001). The type of screw (unicortical locking vs. bicortical locking) and the number of screws in the diaphysis (3 vs. 10) did not appear to significantly influence construct stiffness (p = 0.76, p = 0.24). Similarly, fracture working length (5.4 cm vs. 9.4 cm, p = 0.24), and implant type (titanium vs. stainless steel, p = 0.12) did also not appear to effect stiffness. Discussion Using shorter plates and using bicortical nonlocking screws (vs. bicortical locking screws) reduced overall construct stiffness. Using more screws, using unicortical locking screws, increasing fracture working length and varying plate material (titanium vs. stainless steel) does not appear to significantly alter construct stiffness. Surgeons can adjust plate length and screw types to affect overall fracture-fixation construct stiffness; however, the optimal stiffness to promote healing remains unknown.

The Effect of MoS2 Active Site Dispersion on Suppression of Polycondensation Reactions during Heavy Oil Hydroconversion

In this work, the composition, structural and morphological features, and particle size of the active phase of the catalyst (MoS2), synthesized in-situ during the heavy oil hydroconversion performed in continuous flow reactor on lab-scale pilot flow unit at T = 450 °C, P = 6.0–9.0 MPa, V = 1.0 h−1, H2/feed = 1000 nL/L, catalyst concentration C (Mo) = 0.01–0.08%wt have been studied. It has been shown that MoS2 formed during hydroconversion is represented by nanosized particles stabilized by polycondensation products as a result of strong adsorption and aggregation with the components of the hydroconversion reaction medium. The influence of morphological characteristics of catalyst nanoparticles on the feed conversion, the yield of gaseous and liquid products, and the quality of distillate fractions, as well as the yield of polycondensation products, have been studied. It has been established that an increase in MoS2 active site dispersion, both due to a decreased plate length and lower stacking numbers in MoS2 cluster, enhances hydroconversion effectivity, particularly, in suppressing polycondensation reactions.