Perimeter Region Research Articles

Bulk acoustic wave resonator with suppressed energy loss using improved lateral structure

A bulk acoustic wave (BAW) resonator with suppressed energy loss is proposed. Implemented with air edge reflector and current spreading electrode along the perimeter region of the BAW, the resonator successfully suppresses the acoustic wave leakage and the electric energy loss as well. As results of optimized lateral structure, the Q-factor at anti-resonance frequency (Qa) is significantly improved to over 2100. Furthermore, the peak insertion loss exhibits as low as 0.04dB and effective electro-mechanical coupling coefficient (kt2), which is essential to achieve wide band-width of RF filters, is 6.54%.

The linear spin-up of a stratified, rotating fluid in a square cylinder

AbstractHere we present experimental and theoretical results for how a stratified fluid, initially rotating as a solid body with constant angular velocity, $\Omega $, within a closed cylinder of square cross-section, is spun up when subject to a small, impulsive increase, $ \mrm{\Delta} \Omega $, in the cylinder’s rotation rate. The fluid’s adjustment to the new state of solid rotation can be characterized by: (a) an inviscid, horizontal starting flow which conserves the vorticity of the initial condition; (b) the eruption of Ekman layer fluid from the perimeter region of the cylinder’s base and lid; (c) horizontal-velocity Rayleigh layers that grow into the interior from the container’s sidewalls; and (d) the formation and decay of columnar vortices in the vertical corner regions. Asymptotic results describe the inviscid starting flow, and the subsequent interior spin-up that occurs due to the combined effects of Ekman suction through the base and lid Ekman layers, and the growth of the sidewall Rayleigh layers. Attention is focused on the flow development over the spin-up time scale ${T}_{s} = {E}^{\ensuremath{-} 1/ 2} {\Omega }^{\ensuremath{-} 1} $, where $E$ is the Ekman number. (The spin-up process over the much longer diffusive time scale, ${T}_{d} = {E}^{\ensuremath{-} 1} {\Omega }^{\ensuremath{-} 1} $, is not considered here.) Experiments were performed using particle imaging velocimetry (PIV) to measure horizontal velocity components at fixed heights within the flow interior and at regular stages during the spin-up period. The velocity data obtained are shown to be in excellent agreement with the asymptotic theory.

CHILD CAR SEAT WITH ENHANCED FEATURES

A child car seat with electronic entertainment features is herein disclosed, comprising an integral sound system with pre-recorded sounds or music, and a pair of speakers embedded in the car seat near the child's head. Also, a plurality of flashing lights that can be synchronized with the music is provided along a perimeter region. Finally, a vibrating mechanism in the base of the seat may operate in a synchronous manner with the music or provide a soothing and comforting effect thereto the child to lull the child to sleep. The seat is capable of manual or automatic operation as selected using a front-mounted switch control panel or may be controlled remotely via a handheld wireless controller. The car seat is powered by connection to a cigarette lighter socket within the vehicle.

Degradation mechanism analysis in temperature stress tests on III–V ultra-high concentrator solar cells using a 3D distributed model

A temperature stress test was carried out on GaAs single-junction solar cells to analyze the degradation suffered when working at ultra-high concentrations. The acceleration of the degradation was realized at two different temperatures: 130 °C and 150 °C. In both cases, the degradation trend was the same, and only gradual failures were observed. A fit of the dark I–V curve at 25 °C with a 3D distributed model before and after the test was done. The fit with the 3D distributed model revealed degradation at the perimeter because the recombination current in the depletion region of the perimeter increased by about fourfold after the temperature stress test. Therefore, this test did not cause any morphological change in the devices, and although the devices were isolated with silicone, the perimeter region was revealed as the most fragile component of the solar cell. Consequently, the current flowing beneath the busbar favors the progression of defects in the device in the perimeter region.

Transmission characteristics of metallic equilateral triangular nanohole arrays

Transmission spectra through arrays of equilateral triangular nanoapertures show significant transmission increases for most conditions when normalized to the area ratio and compared to those of circular and square apertures. Also, the spectral features of the triangular holes are occasionally shifted when viewed with circular and square arrays of the same periodicity. The authors note that for apertures of the same area, the circumference of a triangular hole is about 75% larger than that of a square hole and about 100% larger than that of a circular hole, indicating that the perimeter region of the apertures may play a larger role in the transmission characteristics of nanoholes than has previously been noted. The authors suggest that the corresponding increase in metal surface area inside the apertures leads to a larger role played by the plasmon which is supported inside the apertures. The authors also suggest that the periodicity of the aperture arrays leads to diffraction effects which also affect the complex spectral characteristics of the transmitted light. Finally, for very small holes (less than 100nm in diameter), the significance of the triangular shape is diminished.

Size matters: bleaching dynamics of the coral Oculina patagonica

A 2-yr continuous photographic monitoring of a tagged population of the encrusting coral Oculina patagonica in the Mediterranean was conducted to study intra-colonial bleaching dynamics and the relationship between bleaching, mortality, and colony size. Surveys of non-tagged colonies showed that during the peak bleaching season (August, sea surface temperature = 31°C), non-bleached colonies were frequently found to be small colonies averaging 4.6 ± 2.3 cm in diameter. Within tagged colonies, percent bleached surface area was correlated to water temperature. In colonies that underwent bleaching, the perimeter of the colony was affected first, and, as water tem- peratures increased, bleaching progressed toward the colony center. During the summer months, partial mortality occurred in the perimeter region of bleached colonies in 22% of the tagged colonies and 25% of the tagged colonies died; 40% of the colonies that died belonged to the largest size group. This partial mortality caused an average decline of 46 ± 27% in the average colony size, resulting in a shift to a smaller size group within the monitored population. Since in this species, colonies as small as 2 cm in diameter are reproductive, bleaching may have a less significant effect on the reproductive fitness of the small size groups in the population. The high mortality of large colonies, high survivorship of the small colonies, and the decline in colony size, due to partial mortality, suggest that, in the case of bleaching in populations of O. patagonica, small colony size is advantageous.

Numerical quantification and minimization of perimeter losses in high-efficiency silicon solar cells

This paper presents a quantitative analysis of perimeter losses in high-efficiency silicon solar cells. A new method of numerical modelling is used, which provides the means to simulate a full-sized solar cell, including its perimeter region. We analyse the reduction in efficiency due to perimeter losses as a function of the distance between the active cell area and the cut edge. It is shown how the optimum distance depends on whether the cells in the panel are shingled or not. The simulations also indicate that passivating the cut-face with a thermal oxide does not increase cell efficiency substantially. Therefore, doping schemes for the perimeter domain are suggested in order to increase efficiency levels above present standards. Finally, perimeter effects in cells that remain embedded in the wafer during the efficiency measurement are outlined.

Perimeter recombination in planar solar cells

The recombination in the perimeter region of a planar solar cell is analyzed. A simple, quasi-analytical model is developed that allows the calculation of perimeter current in a variety of situations. Experimental confirmation of the model is obtained by measuring the current collected by the cell when the perimeter is illuminated. This measurement also informs us of internal cell parameters. Cells with high resistivity bases show the greatest perimeter recombination currents. In small size concentration cells this can cause a significant reduction of open circuit voltage: about 5 mV in our 1.5 cm2 cells at one sun that means 16 mV in 1 mm2 cells of the same technology. However, it is shown that the importance of this recombination component decreases as the concentration increases. Some methods for minimizing it are also discussed.

Two-dimensional simulation on the electric field spike of indium antimonide charge injection devices

The surface breakdown induced by the electric-field spike existing in the gate overlay region and the device perimeter region is suspected to be one of the main factors which limit the charge storage capacity of a narrow bandgap InSb dual-gate metal-insulator-semiconductor (MIS) charge injection device (CID). In this study, a two-dimensional theoretical simulation is used to investigate the effect of device parameters, including bias voltage, oxide thickness, gate structure, gate overlay length, and field oxide thickness on the electric-field spike height in an InSb CID. In addition, it is found that a graded oxide structure can be used to lower the electric field spike.

Steady-state heat losses from the core and perimeter regions of a slab-on-ground floor

In order to assess the likely effectiveness of insulating a concrete slab floor laid on the ground, it is useful to be able to estimate the relative magnitudes of the heat losses from the core and perimeter regions, where the latter is usually a strip of constant width. New analytical expressions are derived for such losses in the steady-state, as a function of the slab dimensions, wall thickness, soil conductivity, and average surface film conductance. A simplified expression, useful for hand calculations, is given for rectangular floors, and the ratio of core to total heat loss is presented graphically for some typical cases. The results support the generally held view that most of the losses occur from a relatively narrow perimeter region.

Growth of Selective Tungsten on Self‐Aligned Ti and PtNi Silicides by Low Pressure Chemical Vapor Deposition

The deposition and material properties of tungsten films selectively deposited on pure Ti, , and by low pressure CVD have been investigated using AES, TEM, STEM/EDS, electron diffraction, and ESCA. The deposition of W on results in the consumption of Si from the upper 40–50 nm of silicide. The dissociated Ti remains and contains large amounts of O and F. was identified as a reaction product. Polycrystalline W and product layers were formed on pure Ti, suggesting that both a Si and Ti reduction reaction of occur with . structures contained no detectable F or O derived from the growth reactions, and displayed no measurable amount of Si consumption within the continuous region of the silicide. However, Si void defect structures were observed at the perimeter region of contacts, a consequence of W encroachment along the original silicide‐Si interface.

Reduction of solar cell efficiency by edge defects across the back-surface-field junction:— A developed perimeter model

Material imperfections, impurity clusters and fabrication defects across the back-surface-field junction can degrade the performance of high-efficiency solar cells. The degradation from defects appearing on the circumference of a solar cell is analyzed using a two-region developed perimeter device model. The width of the defective perimeter region is characterized by the range or the distance-of-influence of the defective edge and this width is about two diffusion lengths. The defective edge is characterized by a surface recombination velocity. Family of theoretical curves and numerical examples are presented to show that significant reduction of open-circuit voltage can occur in high-efficiency cells which are thin compared with the diffusion length. In one example, the degradation is decreased from 135 mV to 75 mV when the cell size is increased from 10 to 100 times the diffusion length in a thin cell whose thickness is 1% of the diffusion length.

Dynamic Characteristics of an Inherently Compensated, Square, Gas Film Bearing

A rectangular gas film bearing with inherently compensated feedholes evenly distributed around the interior is analyzed. The feedhole boundary between the enclosed central region and the exterior perimeter region is modeled as a line source. A periodic load disturbance is imposed on the externally pressurized bearing, and the dynamic pressure distribution is determined by small perturbations of the Reynolds’ equation. The solution for the square bearing is obtained by numerical methods. Design curves are presented for the load capacity, mass flow, stiffness, and damping as a function of squeeze number, external pressure, restrictor coefficient, and source location. A design methodology is presented.