Horizontal Slot Research Articles

FREQUENCY NOTCHED WIDE BAND PLANAR MONOPOLE ANTENNAS

The characteristics of an ultra-wideband (UWB) planar monopole antenna with multiple simple slots is presented. By placing a pair of symmetrical horizontal slots on the sides of the monopole antenna a tune-able notch characteristic can be obtained. The length, width and height of the slot can be used to tune the centre frequency, bandwidth and re∞ection coe-cient of the notch. Placing two pairs of horizontal slots on the sides of the monopole antenna two tune-able notched characteristics can be obtained. Based on slot length and slot position an approximate formula for the notch centre frequency is given. The results of simulation and measurement are presented and discussed.

The effects of a newly designed twin-slot bracket on severely malpositioned teeth--a typodont experimental study

The aims of this study were to design a twin-slot bracket featuring two horizontal slots and to examine its efficiency in tooth displacement. Based on the structure of a traditional edgewise bracket, an additional slot was added to a twin-slot bracket and the prototype products were fabricated for the typodont experiments. The orthodontic correction of malpositioned canines was conducted on a typodont to examine the efficiency of the twin-slot bracket in tooth displacement compared with a single-slot edgewise bracket. Three modalities of tooth movement requiring a heavy force moment, namely, axial rotation, mesiodistal tipping, and bodily translation, were conducted. The canine positions before and after simulation were measured and the changes identified. Statistical analysis was undertaken using a t-test to determine the significance of the differences in canine repositioning between the two bracket types. The results showed that in the twin-slot bracket group, the treatment changes in the canine position by derotation and uprighting were 40 +/- 3 and 25 +/- 2 degrees, respectively, compared with 20 +/- 5 and 10 +/- 2 degrees in the edgewise group (P < 0.01). When retracted into an extraction space with an initial 10 degrees of mesial tip, the mesiodistal angulation of the canines in the twin-slot bracket group remained unchanged while in the edgewise group the canines became distally tipped by 5 +/- 2 degrees (P < 0.01). The twin-slot bracket significantly increased the bracket width without reducing the interbracket span and therefore can generate increased force moments within the bracket, leading to an improved manipulation in tooth repositioning.

Viscosity stratification and the horizontal scale of end-driven cellular flow

We analyze isothermal viscosity-stratified creeping flow in a horizontal semi-infinite slot. The slot top and bottom are traction-free, and a cellular motion is driven by a given uniform shear stress applied at the vertical end. The viscosity is a prescribed function of depth: A thin low-viscosity channel of uniform viscosity mμ and thickness αD overlies a thick sublayer of viscosity μ and thickness D. By coupling a lubrication analysis of the channel to an exact solution for the sublayer, we show that in the limit of α→0, with ε=m∕α3 fixed, the flow has horizontal scale given for ε&amp;lt;5 by ℓ=2D∕3ε. The analysis is motivated by the long-standing suggestion that the presence of a low-viscosity layer could explain the existence of long end-driven cells beneath the Pacific and the Indo-Australian plates. Our formula supports that suggestion; applied to published viscosity profiles, it predicts that viscosity stratification could allow a cell length of up to seven times that for isoviscous flow.

Study of High Efficiency Grating Couplers for Silicon-Based Horizontal Slot Waveguides

Horizontal slot waveguides are becoming a very promising waveguide configuration for silicon photonics nonlinear applications. In this letter, the design of grating couplers for highly efficient coupling between standard single-mode fibers and horizontal slot waveguides is reported. Parameters have been optimized to achieve maximum coupling efficiency for lambda = 1550 nm and transverse magnetic polarization. Maximum coupling efficiencies of 61% and 48% have been achieved for negative and positive detuned grating couplers, respectively, by means of simulations. A 35-nm 1-dB bandwidth spectral response has also been obtained.

The SPEED System: An Overview of the Appliance and Clinical Performance

The SPEED appliance (Strite Industries Ltd., 298 Shepherd Ave., Cambridge, Ontario, N3C 1V1 Canada), invented by Dr. G. Herbert Hanson in the early 1970s, is a miniaturized self-ligating bracket with an active spring clip. This fully preadjusted edgewise appliance, which is available in both 0.018″ and 0.022″ slot size, has been in clinical use since 1977 and commercially available since 1980. During the past 25 years, the SPEED design has been highly refined. Refinements include the incorporation of a superelastic nickel titanium spring clip for greater precision of tooth movement throughout treatment, a "labial window" that enhances ease of opening the spring clip, and a horizontal auxiliary slot in the bracket body that facilitates segmental archwire mechanics. Although the SPEED bracket is compatible with virtually any archwire selection, specific archwires have been designed to fully exploit SPEED's inherent benefits. These include Supercable (Strite Industries Ltd.), a seven-stranded coaxial nickel titanium archwire, Hills Dual-Geometry archwire (Strite Industries Ltd.), and SPEED archwires. Whether traditional or specialty archwires are used, SPEED, with its highly flexible spring clip, creates a unique mechanical system that is ideally suited for ultra-precise orthodontic tooth movement.

Blockage in vertical slots: Experimental measurement of minimum slot width for a variety of granular materials

The design of some processing equipment requires knowledge of the safe minimum dimensions of slots, channels or conduits for flowing granular materials. This work was prompted by the need to ensure that when narrow slots were used in equipment of this type, they were capable of providing a continuous and uninterrupted flow. There are some data in the literature for blockage of openings in the horizontal plane, but there is very little published information of any sort on vertical slots. The materials tested in this investigation included agricultural seeds (amaranth, panicum, millet, rape, wheat, barley), various plastic granules used in extrusion processes (polyethylene pellets, high impact plastic in the form of cut rod), and a sample of urea. These materials all had narrow size distributions and had maximum dimensions in the range 1 mm to 8 mm, and bulk densities in the range 600 to 800 kg/m 3. Widths at blockage were obtained for vertical slots, horizontal slots and also horizontal orifices. Conservative guidelines are given for selection of the minimum size of openings for reliable flow of non-cohesive grains; for vertical slots, the ratio of minimum slot width to characteristic particle dimension is 4.6, for horizontal slots the ratio is 3.3 and for horizontal orifices, the ratio of orifice diameter to characteristic particle dimension is 6.4.

Lateral leakage in symmetric SOI rib-type slot waveguides

We theoretically investigate the lateral leakage in fully symmetric horizontal rib-type slot waveguides caused by coupling between the TM-like slot mode and a TE slab mode. The leakage mechanism is described and the dependence on the geometry parameters is studied using the variational mode-matching method. In addition, the effective-index method to solve the transcendent eigenmode equation of rib-type slot waveguides is applied and compared with the aforementioned rigorous numerical method. We show that this semi-analytical approach yields results with sufficiently high accuracy. For design purposes the influence of structural deviations caused by the fabrication process is studied. We show that the usable range of the geometry parameters can be widely extended by exploiting leakage suppressing mechanisms.

Comparison of vertical and horizontal slot die coatings

AbstractComparison of vertical and horizontal slot coatings was carried out experimentally using aqueous glycerin solutions with varying viscosity on a laboratory‐scale slot coater. The maximum coating speeds achieved in vertical slot coating were found to be higher than those of horizontal slot coating for low‐viscosity solutions. The coating defects observed below the minimum wet thickness changed from ribbing to air entrainment at a critical solution viscosity of around μ = 75 mPa s. Above this critical viscosity, a lower minimum wet thickness was obtained for the horizontal coating but not for vertical coating. The difference between vertical and horizontal coating was mainly the length of the coating bead. The dimensionless minimum wet thickness was correlated as a function of Reynolds number. There existed three regions of minimum wet thickness depending on Reynolds number. Initially, the dimensionless wet thickness increased in the low Reynolds number region (Region I), then reached a plateau in the intermediate Re region (Region II), finally dropped off sharply in the high Re region (Region III). The boundaries of these three regions were identified by two critical Reynolds numbers, i.e., Re = 1 and 20. Only Regions I and II of the wet thickness could be found for horizontal coating, while mainly Regions II and III were obtained for vertical coating, depending on the viscosity of the coating solution. POLYM. ENG. SCI., 47:1927–1936, 2007. © 2007 Society of Plastics Engineers

T형 Slot을 삽입한 삼각형 안테나

본 논문에서는 T형 슬롯을 삽입한 정삼각형 패치 안테나의 특성을 관찰하였고, 정삼각형 패치 내부에 얇은 가로 또는 세로 슬롯을 삽입하였을 때, 슬롯의 변화에 따른 이중 공진 주파수의 변화를 관찰하여 유전체의 높이가 매우 낮은 기판에 적합한 T형 슬롯을 삽입한 정삼각형 패치 안테나를 제안하였다. 제안된 안테나는 <TEX>${\epsilon}_r=3.38$</TEX>, 유전체의 높이가 8[mils] (=0.2032mm)인 기판을 사용하였고, 비교된 가로와 세로 슬롯의 안테나의 특성은 앙상블8.0 시뮬레이터를 이용하여 비교하였으며, 제작된 안테나의 이론적, 실험적 결과들이 비교되었다. This paper observed characteristics of a triangular microstrip patch antenna with T-slot. When a narrow horizontal slot or vertical slot is embedded in a triangular microstrip antenna, we investigated variations of dual resonant frequency according to slot lengths and then we could make a triangular microstrip antenna with T-type slot suitable to a very low dielectric substrate. The proposed antennas used a dielectric substrate which has relative dielectric constant <TEX>${\epsilon}_r=3.38$</TEX> and a height of 8 [mils] (=0.2032mm) and antenna characteristics of horizontal or vertical slot antennas are compared by a ensemble 8.0 simulator. Theoretical and experimental results of manufactured antennas are compared.

Double-component convection due to different boundary conditions in an infinite slot diversely oriented to the gravity

Onset of small-amplitude oscillatory and both small- and finite-amplitude steady double-component convection arising due to component different boundary conditions in an infinite slot is studied for various slot orientations to the gravity. The main focus is on two compensating background gradients of the components. The physical mechanisms underlying steady and oscillatory convection are analyzed from the perspective of a universally consistent understanding of the effects of different boundary conditions. In a horizontal slot with inviscid fluid addressed by Welander [P. Welander, Tellus Ser. A 41 (1989) 66], oscillatory convection sets in with the most unstable wave number and oscillation frequency being zero. Exact expressions for the critical fixed-value background gradient and the respective group velocity at zero wave number are derived from the long-wavelength expansion both for the horizontal slot with independently varying background gradients and for the inclined slot with the compensating gradients. In the horizontal slot with viscous fluid, the dissipation of along-slot perturbation-cell motion reduces efficiency of the oscillatory instability feedback and thus prevents the most unstable wavelength from being infinite. Based on this interpretation, the oscillatory instability of a three-dimensional (3D) nature is predicted for an interval of long two-dimensional (2D) wavelengths in an inclined slot, and such 3D instability is indeed shown to arise. Related general conditions for three-dimensionality of most unstable disturbances are also formulated. As the slot orientation changes from the horizontal by angle θ (⩾π/2), the oscillatory 2D marginal-stability boundaries in inviscid and viscous fluid are expected to eventually transform into respective steady ones. Oscillatory instability in the vertical slot with viscous fluid, first reported by Tsitverblit [N. Tsitverblit, Phys. Rev. E 62 (2000) R7591], is of a quasi-steady nature. Its (new) mechanism is identified. It is underlain by differential gradient diffusion. As the horizontal slot at θ = π, addressed by Tsitverblit [N. Tsitverblit, Phys. Fluids 9 (1997) 2458], changes its orientation to vertical, the wave number interval of linear steady instability shrinks to the vicinity of the most unstable zero wave number and vanishes. Consistently with the basic nature of finite-amplitude steady convection being the same in the horizontal and vertical slots, the respective convective flows are continuously transformed into each other. The dissimilarity between the nature of finite-amplitude steady convective flows in the horizontal slot with θ = 0, revealed by Tsitverblit [N. Tsitverblit, Phys. Lett. A 329 (2004) 445], and that in the vertical slot is shown to eventually give rise to a region of hysteresis in θ ∈ (0, π/2).

Horizontal single and multiple slot waveguides: optical transmission at λ = 1550 nm

We experimentally demonstrate the optical transmission at 1550 nm of the fundamental slot modes (quasi-TM modes) in horizontal single and multiple slot waveguides and ring resonators consisting of deposited amorphous silicon and silicon dioxide. We demonstrate that the horizontal multiple slot configuration provides enhanced optical confinement in low index slot regions compared to a horizontal single slot structure with the same total SiO2 layer thickness by comparing their thermo-optic coefficients for the horizontal slot ring resonators. We show in these early structures that horizontal slot waveguides have low propagation loss of 6 approximately 7 dB/cm. The waveguide loss is mainly due to a-Si material absorption. The addition of a-Si/SiO(2) interfaces does not introduce significant scattering loss in a horizontal multiple slot waveguide compared to a horizontal single slot waveguide.

Comparison of Rheological Measurement Techniques for Semi-Solid Aluminium Alloys

Alloys of a specific microstructure exhibit a shear-rate history-dependent flow behaviour in the semi-solid state. Rheological studies have been carried out using various experimental techniques such as concentric cylinder rheometers of Couette or Searle type as well as capillary rheometers and parallel plate compression tests. With the Searle type rheometer and the capillary rheometer two different approaches of rheological measurement techniques are discussed and compared regarding advantages, potentials and its distinct characteristics. Experiments using the Searle type rheometer have been conducted under steady-state or oscillating conditions and have been used to verify time-dependency of step responses due to discontinuous or linear variances of the shear rate. These experiments provide all types of flow curve parameters as implemented in the numerical simulation. However the variances of the commonly used Couette and Searle type rheometers are limited to shear-rates which are significantly lower than that appearing in the technical thixo- or rheocasting processes. For that reason an additional experimental set-up with a horizontal slot capillary integrated in a shot-controlled high-pressure die-casting machine is used in order to examine flow properties at shear rate conditions similar to those in real thixocasting processes. After an initial examination of low temperature model alloys, such as PbSn15, the experimental set-up is then adjusted in order to obtain rheological data for light metal alloys such as Aluminium AlSi7Mg0.3. The Aluminium alloy is processed within each rheometer either as partially solidified or partially remelted in order to represent conditions of both, the conventional thixocasting and the lately introduced rheocasting process. Finally the appearance of physical phenomena which affects the accuracy of rheological experiments such as wall slip is considered for both types of rheometers.

Dual-Mode Bandpass Filters Using Microstrip Slotted Equilateral Triangular Patch Resonators

SUMMARY Two compact and low loss dual-mode filters are proposed by using degenerate modes of slotted triangular microstrip patch resonators. The geometrical size and radiation loss of the triangular patch are reduced simultaneously by loading both horizontal and vertical slots. The resonant frequencies of two degenerate modes can be easily controlled by varying the dimensions and positions of the slots. A two-pole dualmode filter operating at 3.94 GHz with a fractional bandwidth of 4.3% is designed, fabricated, and measured. The measured results verify well the

Machining of free-form surfaces. Part II: Calibration and forces

In the machining simulations of 3D free-form surfaces by ball-end milling, calibration coefficients play very critical role in force predictions. In other words, obtaining the calibration coefficients from calibration tests is a very influential process in the prediction of cutting forces. Accurately obtained calibration coefficients lead to better force predictions. In the literature, the calibration coefficients are assumed to be independent of start and exit angles of the engagement region, thus they are assumed to be identical for any engagement region. Calibration coefficients are obtained from the horizontal slot cutting tests and these tests are repeated for different depth of cuts. In this paper, in order to achieve more accurate force predictions in free-form machining simulations, a new modification algorithm for calibration coefficients is presented. In this research, with theoretical analysis and experimental force signals, it is shown that the inclination angle has a great importance in calibration and in force simulation of 3D free-form machining.

CALCULATION OF THE SPECIFIC CUTTING COEFFICIENTS AND GEOMETRICAL ASPECTS IN SCULPTURED SURFACE MACHINING

ABSTRACT This article presents a method for obtaining the shear and ploughing specific cutting coefficients for a ball-end milling cutting force model. Thus, by using the proposed calculation method, the need for introducing variable shear cutting coefficients has been identified. This fact is due to the dependency among the specific cutting coefficients and the cutting edge inclination angle, which is variable in ball-end mills. Linear, quadratic and cubic polynomial shear cutting coefficients have been calculated, and the degree of adjustment obtained in each approach has been analyzed. At the same time, the expressions of the ploughing specific coefficients have been analyzed. The proposed calculation method has been applied to the following materials: a 7075-T6 aluminum alloy and a 52HRC AISI H13 tool steel. The results obtained from the validation demonstrate how the obtained coefficients are capable of predicting cutting forces over a wide range of cutting conditions. Finally, the results from applying the coefficients calculated in horizontal slot milling tests have been introduced in a model capable of calculating cutting forces in slope milling cases, which validates the calculation method proposed as a generic method for estimation of cutting coefficients.

English

Rarely do rock pile characterization methods allow for examination and sampling of the undisturbed interior of large rock piles in-situ. The regrading of the Goathill North (GHN) rock pile at the Molycorp Questa mine, New Mexico provided a unique opportunity to examine and sample the undisturbed, interior of a large rock pile through the construction of trenches cut into the rock pile as earth-moving progressed. Weekly during the regrading of the GHN rock pile, contractors excavated a trench to allow for sampling of rock pile material. Trenches typically had four benches, which were 1.5 m wide and did not exceed 1.2 m in height, to give an overall slope of 1.4 horizontal to 1.0 vertical within the trench. Each trench extended for a length sufficient to explore site conditions, maintain the regraded 2:1 slope, and ensure personnel safety. Once excavated, trench walls and benches were surveyed using a differential global positioning system. For every trench, maps and logs of each bench were created to describe the different mine soil units, including the thickness, dip and extent of the units. Units were defined based on color, grain size, stratigraphic position, and other physical properties that could be determined in the field. Units were correlated between benches and to both sides of each trench, and several units were correlated downward through the series of successively excavated trenches. The field sampling crew began sampling within each of the identified units after the unit boundaries were identified and mapped. The following in situ measurements were taken along either the horizontal or vertical surfaces of each exposed bench and along the base of the trench: sand cone (density), tensiometer (matric suction), gravimetric moisture content, grain size, infiltration, and nuclear gauge measurements (density, moisture content). Gravimetric water content samples were collected at the locations selected for the measurement of matric suction and infiltration tests. Samples were collected from each defined unit for geochemical, geotechnical (including shear box tests, slake durability tests), biological, and electron microprobe analyses. Channel sampling for pyrite reserve modeling was performed in short 1.5-m long horizontal slots using a rock hammer to chip material to be placed into a sample bag. Additional material from selected layers was collected for potential weathering-cell tests in the future. Typically, paste pH increases with distance from the outer, oxidized zone (west) towards the interior, unoxidized zone (east) of the GHN rock pile.

Mechanisms of Sand Production Through Horizontal Well Slots in Primary Production

Abstract Cold production in unconsolidated heavy oil reservoirs, where sand production is encouraged (CHOPS), has proven to be successful for vertical wells. However, the application of CHOPS to horizontal wells has been less profitable due mainly to excessive sand cleanout costs. Therefore, reducing sand cleanout costs by controlling sand production into horizontal wells while enhancing the surrounding permeability of the formation is an important factor in optimizing cold production from unconsolidated heavy oil reservoirs. This paper presents the results of an experimental investigation of the flow of oil and sand in the vicinity of a horizontal well under cold production. Specifically, the experiments physically simulated the flow of oil and sand into a slot in a horizontal well liner. The parameters studied include slot width and sand properties (morphology and grain size distribution). Experimental results suggest that sand production through horizontal well slots can be controlled, depending more on sand grain sorting than on grain morphology or average diameter. The sand cut had a tendency to be higher at the beginning of the sand production period and to decline with time. In most tests, the decline in sand cuts continued until no more sand was produced. Significant changes in the permeability and porosity were determined in the vicinity of the slot. The changes in the parameters were less significant away from the slot. The largest fractions of the sand (bigger than 500 µm) have an important role in arch/bridge formation. Introduction Cold production is a primary non-thermal process used in unconsolidated heavy oil reservoirs in Alberta and Saskatchewan, Canada. In this process, sand and oil are produced together in order to enhance oil recovery(1–3). A comprehensive review of cold production has been presented by Tremblay et al.(1). Hall and Harrisberger(4) found that arch stability was flow rate sensitive at low confining stress but independent of flow rate at high confining stress levels. They observed that angular sand without compaction did not form an arch. When a moderate compaction was applied, it could lead to a slightly stable arch. A better interlocking of the surface grains was the explanation for this result. For round sand, arching was not observed for a loose or dense pack at low loads. Yim et al.(5) observed that in addition to the flow rate, the arch stability was strongly dependent on the granulometry of the sand and on the size of the perforation. Larger perforations required larger grains to form stable arches. McCormack(6) conducted experimental work with spherical particles to determine the arching/bridging mechanism that influenced the performance of wire-wrapped sand screens. Selby and Farouq Ali(7) showed that sand production increased as the overburden pressure and the fluid flow rate were increased. They also found that spherical small grain sand packs can produce more sand than angular large grain sand packs. Cleary et al.(8) observed that the structure of an arch depended on the stress distribution in a sand pack. The cohesive force was shown to have an important role in arch stability when different hydrocarbons liquids were used.

Oil spill cleanup using vacuum technique ☆

A vacuum technique is established for oil spill cleanup. It consists of environmental tank, oil-collecting unit, vacuum system, and air distributors. The vacuum technique is found very effective under all possible operating conditions. Several operating parameters are investigated such as hole arrangement (vertical and horizontal slots), air distributors location (one-side and two-sides strategies), air volumetric flow rate over the range of 0.0–0.667×10 −3 m 3/s, salinity concentration (0.0–30 kg NaCl/m 3), temperature (5–35 °C), amount of crude oil added (0.25×10 −3–10 −3 m 3), and surfactant concentration (0.0–0.3% of Triton X-100). The installation and implementation of the vacuum technique are quick, simple, and efficient. The proposed technique does not require any further processes to extract the crude oil. It provides excellent economical operating results.

Prediction of heat transfer from impinging knife-jets using a dynamic subgrid stress model

The turbulent flow field and heat transfer due to the knife-jets impinging on a flat surface have been numerically investigated. The large-eddy simulation (LES) technique has been used to model the turbulent flow that has both large- and small-scale structures. A dynamic subgrid scale model has been used to account for the subgrid scale stresses and heat transfer. The Nusselt number distributions for the impinging jets emanating from an array of horizontal slot nozzles are presented within the Reynolds number range of 600-3000. Two different jet exit-angles, namely 0? and 60? have been considered. The reattachment of the horizontal-knife-jets is obtained due to the Coanda effect. The flow field on the impinging plate due to the horizontal-knife-jets culminates in an oscillatory flow dominated by vortical motions. Such motions play a significant role in enhancing heat transfer. Heat transfer due to the horizontal-knife-jet with 60? exit-angle has been found to be greater than that of the axial slot jet.

Wall fire behavior in an under-ventilated room

An experimental setup has been designed and built to study, at a laboratory scale, the behavior of a wall fire in a semi-confined compartment both in naturally ventilated and vitiated (combustion products) atmospheres. A diffusion flame is stabilized along a vertical porous flat burner located at the rear of an enclosure. The combustion is supplied by injection of propane through the vertical burner surface. Air enters into the compartment by natural convection through a door, topped by a soffit, opposite the burner. After reaching a thermal steady state, the temperature field in the compartment is characterized. Then, the door is closed leaving only a horizontal free slot (0.06 m height) between the top of the door and the bottom of the soffit. The flame behavior completely changes, the intensity of the spontaneous flame emission decreases drastically and a weakly blue vertical flame leaves the burner surface and moves, at low velocity, through the chamber, up to the open slot. Visualizations of the flame and measurements of the temperature and main stable chemical species fields are performed in order to characterize the behavior of a flame referred as a ghosting flame. This flame displacement mode has been already observed in full-scale fires by Audouin (Fifth International Symposium on Fire Safety Science, 1997, Melbourne, p. 1261–1272). After the initial “flame propagation”, combustion can be stabilized at the room aperture that participates to the development of the fire outside the compartment. This work contributes to a better understanding of this phenomenon in order to prevent such a fire.