Ratio Fins Research Articles

Ultra-High Aspect Ratio InP Junctionless FinFETs by a Novel Wet Etching Method

Junctionless FinFETs with an array of ultra-high aspect ratio (HAR) fins, enabled by inverse metal-assisted chemical etching, are developed to achieve high on-current per fin. The novel device fabrication process eliminates dry etching-induced plasma damage, high energy ion implantation damage, and subsequent high-temperature annealing thermal budget, ensuring interface quality between the high- $k$ gate dielectric and the HAR fin channel. Indium phosphide junctionless FinFETs, of record HAR (as high as 50:1) fins, are demonstrated for the first time with excellent subthreshold slope (63 mV/dec) and ON/OFF ratio ( $3\times 10^{5}$ ).

Experimental investigation and CFD analysis of rectangular profile FINS in a square channel for forced convection regimes

Steady-state heat transfer from rectangular fin arrays is examined experimentally and numerically for turbulent fully developed flow. The effects of geometrical parameters on heat transfer coefficient and Nusselt number are investigated. For different inter fin ratios, Reynolds number and Nusselt number dependence of the results is investigated. A generalized empirical correlation for Nusselt number is developed for rectangular fins for a Reynolds number range of 17 × 107 < Re < 2.47 × 108, and an aspect ratio of 0.089 < d/w < 0.0625, 0.24875 < t/L < 0.729. The correlation can predict the results with a relative rms error of 11.14%.

Aqueous exposure to the progestin, levonorgestrel, alters anal fin development and reproductive behavior in the eastern mosquitofish (Gambusia holbrooki)

Endogenous progestogens are important regulators of vertebrate reproduction. Synthetic progestins are components of human contraceptive and hormone replacement pharmaceuticals. Both progestogens and progestins enter the environment through a number of sources, and have been shown to cause profound effects on reproductive health in various aquatic vertebrates. Progestins are designed to bind human progesterone receptors, but they also have been shown to strongly activate androgen receptors in fish. Levonorgestrel (LNG) activates fish androgen receptors and induces development of male secondary sex characteristics in females of other species. Although behavior has been postulated to be a sensitive early indicator of exposure to certain environmental contaminants, no such research on the reproductive behavior of gestagen-exposed fish has been conducted to date. The goal of our study was to examine the exposure effects of a human contraceptive progestin, LNG, on the reproductive development and behavior of the viviparous eastern mosquitofish (Gambusia holbrooki). Internal fertilization is a requisite characteristic of viviparous species, and is enabled by an androgen driven elongation of the anal fin into the male gonopodium (i.e., phallus). In this study, we exposed adult mosquitofish to ethanol (EtOH control), 10ng/L, and 100ng/L LNG for 8d using a static replacement exposure design. After 8d, a subset of males and females from each treatment were examined for differences in the 4:6 anal fin ratio. In addition, paired social interaction trials were performed using individual control males and control females or females treated 10ng/L or 100ng/L LNG. Female mosquitofish exposed to LNG were masculinized as evidenced by the elongation of the anal fin rays, a feature normal to males and abnormal to females. LNG caused significant increases in the 4:6 anal fin ratios of female mosquitofish in both the 10ng/L and 100ng/L treatments, although these differences were not significant between the two treatments. LNG caused significant increases in the 4:6 anal fin ratio of males exposed to 100ng/L, with no effects observed in the 10ng/L treatment. In addition, the reproductive behavior of control males paired with female mosquitofish exposed to 100ng/L LNG was also altered, for these males spent more time exhibiting no reproductive behavior, had decreased attending behavior, and a lower number of gonopodial thrusts compared to control males paired to control female mosquitofish. Given the rapid effects on both anal fin morphology and behavior observed in this study, the mosquitofish is an excellent sentinel species for the detection of exposure to LNG and likely other 19-nortestosterone derived contraceptive progestins in the environment.

Water flow and fin shape polymorphism in coral reef fishes.

Water flow gradients have been linked to phenotypic differences and swimming performance across a variety of fish assemblages. However, the extent to which water motion shapes patterns of phenotypic divergence within species remains unknown. We tested the generality of the functional relationship between swimming morphology and water flow by exploring the extent of fin and body shape polymorphism in 12 widespread species from three families (Acanthuridae, Labridae, Pomacentridae) of pectoral-fin swimming (labriform) fishes living across localized wave exposure gradients. The pectoral fin shape of Labridae and Acanthuridae species was strongly related to wave exposure: individuals with more tapered, higher aspect ratio (AR) fins were found on windward reef crests, whereas individuals with rounder, lower AR fins were found on leeward, sheltered reefs. Three of seven Pomacentridae species showed similar trends, and pectoral fin shape was also strongly related to wave exposure in pomacentrids when fin aspect ratios of three species were compared across flow habitats at very small spatial scales (<100 m) along a reef profile (reef slope, crest, and back lagoon). Unlike fin shape, there were no intraspecific differences in fish body fineless ratio across habitats or depths. Contrary to our predictions, there was no pattern relating species' abundances to polymorphism across habitats (i.e., abundance was not higher at sites where morphology is better adapted to the environment). This suggests that there are behavioral and/or physiological mechanisms enabling some species to persist across flow habitats in the absence of morphological differences. We suggest that functional relationships between swimming morphology and water flow not only structure species assemblages, but are yet another important variable contributing to phenotypic differences within species. The close links between fin shape polymorphism and local water flow conditions appear to be important for understanding species' distributions as well as patterns of diversification across environmental gradients.

A successful application of homotopy perturbation method for efficiency and effectiveness assessment of longitudinal porous fins

In our previous works, thermal performance of straight fins with both constant and temperature-dependent thermal conductivity has been investigated in detail and dimensionless analytical expressions of fin efficiency and fin effectiveness have been developed for the first time in literature via homotopy perturbation method. In this study, previous works have been extended to porous fins. Governing equations have been formulated by performing Darcy’s model. Dimensionless temperature distribution along the length of porous fin has been determined as a function of porosity and convection parameters. The ratio of porous fin to solid fin heat transfer rate has also been evaluated as a function of thermo-geometric fin parameter. The results have been compared with those of finite difference method for a specific case and an excellent agreement has been observed. The expressions developed are beneficial for thermal engineers for preliminary assessment of thermophysical systems instead of consuming time in heat conduction problems governed by strongly nonlinear differential equations.

Simple Correlation to Evaluate Efficiency of Annular Elliptical Fin Circumscribing Circular Tube

Efficiency of annular elliptical fin has been studied numerically. Results show that constant temperature lines do not remain circular in lower aspect ratio fins. So, it is expected that some common methods such as equivalent fin area or sector method do not have enough accuracy. For this reason, at first, a new simple correlation has been proposed to approximate annular circular fin efficiency based on longitudinal fin efficiency and then, comparing to the numerical results, it has been shown that the proposed formula is still applicable if one uses arithmetic mean of elliptical fin lengths and geometric mean of elliptical fin radiuses.

Conformal doping of topographic silicon structures using a radial line slot antenna plasma source

Fin extension doping for 10 nm front end of line technology requires ultra-shallow high dose conformal doping. In this paper, we demonstrate a new radial line slot antenna plasma source based doping process that meets these requirements. Critical to reaching true conformality while maintaining fin integrity is that the ion energy be low and controllable, while the dose absorption is self-limited. The saturated dopant later is rendered conformal by concurrent amorphization and dopant containing capping layer deposition followed by stabilization anneal. Dopant segregation assists in driving dopants from the capping layer into the sub silicon surface. Very high resolution transmission electron microscopy-Energy Dispersive X-ray spectroscopy, used to prove true conformality, was achieved. We demonstrate these results using an n-type arsenic based plasma doping process on 10 to 40 nm high aspect ratio fins structures. The results are discussed in terms of the different types of clusters that form during the plasma doping process.

Directional Stability Study of Torpedo Anchors

After a torpedo anchor is released into water during its installation, the directional stability of this anchor is an important factor for its penetration performance. In this paper, a CFD method is used to simulate the falling behavior of the anchor, and detailed parametric studies are conducted to analyze the effects of various parameters to the directional stability. The results show that some parameters like weight, gravity center, and aspect ratio of fin have significant influence on the directional stability.

Device-Circuit Co-Optimization for Robust Design of FinFET-Based SRAMs

A set of device-circuit co-design techniques oriented to increase the resilience of FinFET SRAMs circuits is presented in this paper. Co-optimization of fin ratio, thickness, orientation and height are investigated and its impact on performance and area evaluated.

Unified Scaling for Flapping Fins

Conventional scaling for steady-fin or flapping-fin forces in a uniform flow is by definition incompatible with the scaling that has been developed for hovering flapping fins. Most flapping-fin-based vehicles will need to operate in all three operating regimes: fixed fin in cruise, flapping in cruise, and flapping in hover. A unified normalization scheme is proposed to enable smooth and optimal transition of the scaling rules between these regimes. A rigid flapping foil was experimentally tested in a towing tank. The generated side force was found to be a function only of the fin bias angle and the vector magnitude of the inflow and flapping speeds. The thrust was found to be a function of the ratio of fin flapping speed to total speed magnitude in addition to bias and speed magnitude. As an application of this scaling, an algorithm to synthesize the foil motion parameters for a desired thrust and side force regardless of vehicle speed was tested experimentally on a single foil in real time.

Thermal Analysis of Orthotropic Pin Fins With Contact Resistance: A Closed-Form Analytical Solution

Light weight composite fins are considered to deal with thermal management problems for many microelectronic components. These composite fins are inherently anisotropic, therefore cannot be handled by a traditional one-dimensional approach; however, these materials can be designed to provide high thermal conductivity values in the desired direction to handle application-specific demands. In this article, we present analytical solutions for temperature distribution and heat transfer rate for orthotropic two-dimensional pin fins subject to convective-tip boundary condition and the contact resistance at the fin base. The generalized results are presented in terms of fin aspect ratio (fin length-to-radius ratio) and three dimensionless fin parameters that relate the internal conductive resistance to three convective resistances discussed in terms of dimensionless variables such as contact, tip, and axial Biot numbers, in addition to the axial-to-radial conductivity ratio. Several special cases including the insulated tip boundary condition are presented. It is demonstrated that the temperature distribution and heat transfer rate from the two-dimensional isotropic annular fin introduced earlier in the literature, can easily be recovered from the benchmark solutions presented in this article. Furthermore, dimensionless heat transfer rates are presented for the pin fins with contact resistance that can help to solve design and optimization problems of many natural-to-forced convection composite fins that are typically encountered in many microelectronic applications.

Female preference for male lateral projection area in Poecilia reticulata

The lateral projection area (LPA) hypothesis was investigated by presenting female guppies, Poecilia reticulata with a series of paired males in three experiments. One trait was held constant in each experiment (dorsal fin size in expt I, body size in expt II, and total LPA in expt III) while body: dorsal fin ratio varied. Females spent more time near dummies of greater body and dorsal fin size in experiments I and II. The preference functions based on the first two sets of stimuli showed a similar pattern: the greater the LPA difference between paired dummies, the stronger the preference for the larger of the two. However, in the third experiment, neither fin size, body size, nor any particular dorsal fin + body size combination was preferred. These findings support the LPA hypothesis suggesting that increased LPA is more stimulating to sexually receptive females, and that females consequently prefer larger males. Preference for increased male dorsal fin size/LPA in both P. latipinna and P. mexicana as demonstrated in previous studies, and the more distantly related P. reticulata (shown here) is consistent with common ancestry of the sensory/neural systems in females of all three species and perhaps the entire Poeciliid family.

Hybrid differential transformation and finite difference method to annular fin with temperature-dependent thermal conductivity

A hybrid numerical technique which combines the differential transformation and finite difference method is utilized to investigate the annular fin with temperature-dependent thermal conductivity. The exposed surfaces of the fin dissipate heat to the surroundings by convection and radiation. The influences of the convective heat transfer coefficient, absorptivity, emissivity and thermal conductivity parameter on the temperature distribution are examined. The results show that the convective heat transfer plays a dominant role for heat dissipation under the convection–radiation condition. The optimum radii ratio of fin which maximizes the heat transfer rate and fin efficiency is also discussed.

FinFET SRAM Optimization With Fin Thickness and Surface Orientation

In this paper, the design space, including fin thickness <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(T_{\rm fin})$ </tex></formula> , fin height <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(H_{\rm fin})$</tex></formula> , fin ratio of bit-cell transistors, and surface orientation, is researched to optimize the stability, leakage current, array dynamic energy, and read/write delay of the FinFET SRAM under layout area constraints. The simulation results, which consider the variations of both <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm fin}$</tex></formula> and threshold voltage <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$(V_{\rm th})$</tex></formula> , show that most FinFET SRAM configurations achieve a superior read/write noise margin when compared with planar SRAMs. However, when two fins are used as pass gate transistors (PG) in FinFET SRAMs, enormous array dynamic energy is required due to the increased effective gate and drain capacitance. On the other hand, a FinFET SRAM with a one-fin PG in the (110) plane shows a smaller write noise margin than the planar SRAM. Thus, the one-fin PG in the (100) plane is suitable for FinFET SRAM design. The one-fin PG FinFET SRAM with <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$T_{\rm fin} = \hbox{10}\ \hbox{nm}$</tex></formula> and <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex Notation="TeX">$H_{\rm fin} = \hbox{40}\ \hbox{nm}$</tex></formula> in the (100) plane achieves a three times larger noise margin when compared with the planar SRAM and consumes a 17% smaller bit-line toggling array energy at a cost of a 22% larger word-line toggling energy. It also achieves a 2.3 times smaller read delay and a 30% smaller write delay when compared with the planar SRAM.

Forced convective cooling of a fin in a channel

A numerical study of forced convection in a horizontal parallel-plate channel with a transverse fin located at lower channel wall is investigated. Through the use of a stream function vorticity transformation, solution of the transformed governing equations for the system is obtained using the control-volume method with non-uniform grid. The effects of the Reynolds number, thermal conductivity ratio of fin to fluid and fin profile area on heat transfer rate of the fin are presented. The results indicate that the optimum aspect ratio of a fin corresponding to the fin with maximum heat transfer rate increases with increasing Re but decreases with K for a fixed fin profile area. In addition, the optimum aspect ratio of a fin obtained from this study for smaller fin profile area and Re tends to approach that of analytical solution assuming constant heat-transfer coefficient. Finally, good agreements are found between the numerical predictions of this study and other experimental data.

Analysis and optimization of electrokinetic microchannel heat sink

A mixed (electroosmotic and pressure-driven) flow microchannel heat sink has been studied and optimized with the help of three-dimensional numerical analysis, surrogate methods, and the multi-objective evolutionary algorithm. Two design variables; the ratio of the microchannel width-to-depth and the ratio of fin width-to-depth of the microchannel are selected as the design variables while design points are selected through a four-level full factorial design. The single-objective optimization is performed taking overall thermal resistance as the objective function and Radial Basis Neural Network as the surrogate model while for multi-objective optimization pumping power is considered as the objective function along with the thermal resistance. It is observed that the optimum design shifted towards the lower values of the ratio of the channel width-to-depth and the higher values of the ratio of fin width-to-depth of channel with increase of the driving source. The trade-off between the two conflicting objectives has been found and discussed in detail in light of the distribution of Pareto-optimal solutions in the design space. The ratio of channel width-to-depth is found to be higher Pareto-sensitive (sensitivity along the Pareto-optimal front) than the ratio of fin width-to-depth of the channel.

Measurements of Flow Around an Escort Tug Model with a Yaw Angle

This paper presents the results of experiments to measure flow velocities around the hull of an escort tug model operating at a yaw angle of 45 deg using particle image velocimetry (PIV). The paper describes the setup, calibration, and operation of the PIV system and the analysis of the results, including an estimate of the experimental uncertainty. Flow vectors are given within planes normal to the direction of motion of the tug. One plane was on the upstream side of the hull, and the other plane was on the downstream side of the hull. The downstream measurements were made with and without a low aspect ratio fin, typical of many modern escort tug designs. The results showed that the fin, when fitted, created a large vortex under the hull of the tug. Smaller features of the flow, such as the separation of the flow at the upstream and downstream bilge corners were also defined. The intention of these experiments was to create a data set that can be used to validate computational fluid dynamics (CFD) predictions of flow vectors around an escort tug at a large yaw angle.

English

Escort tugs operate at high yaw angles in order to produce forces to steer and stop the vessel they are escorting in an emergency. In this paper, RANS predictions of forces and flow patterns around the hull of an escort tug model are compared with experimental data. Two alternative meshing strategies were used, one using tetrahedral elements with triangular faces and one using hexahedral elements with quadrilateral faces. Experiments were carried out with and without the low aspect ratio fin that is typical of many escort tugs. Lift and drag forces were measured experimentally for yaw angles from 15 to 45 degrees. Flow measurements around the tug at 45 degrees yaw were obtained using a stereoscopic particle image velocimetry (PIV) system. The results from each CFD simulation were compared to the measured flow patterns using a numerical procedure that led to a quantitative measure of the accuracy of the predicted results. The analysis of the flow patterns indicated that the main features of the flow were predicted, and that on average, the predicted velocity magnitudes were within 10% of the measured values. Neither mesh approach had a significant effect on the accuracy of the flow pattern predictions. The hexahedral mesh gave more accurate force predictions that the tetrahedral mesh. Forces were predicted by the CFD code with this mesh to within 5 % of the experimentally obtained values.

Biorobotic insights into how animals swim

Many animals maneuver superbly underwater using their pectoral appendages. These animals range from sunfish, which have flexible, low aspect ratio fins, to penguins, which have relatively stiff, high aspect ratio wings. Biorobotics is a means of gaining insight into the mechanisms these animals use for maneuvering. In this study, experiments were carried out with models of abstracted penguin wings, and hydrodynamic characteristics -- in particular, efficiency -- were measured directly. A cross-flow vortex model of the unsteady force mechanism was developed that can compute instantaneous lift and drag forces accurately. This makes use of the steady characteristics of the fin and proposes that cross-flow drag vortices of bluff bodies in steady flow are analogous to dynamic stall vortices and that fin oscillation is a means for keeping the vortices attached to the fin. From what has been reported for sunfish with pectoral fins to our current measurements for single abstracted penguin wings, we infer that the maximum hydrodynamic efficiency has remained largely unchanged. A selection algorithm was used to rapidly find the fin oscillation parameters for optimum efficiency. Finally, we compared the measurements on the penguin-like relatively stiff fins and the reported flow visualization of flexible sunfish pectoral fins. The flexible pectoral fins of station-keeping sunfish exhibit a rich repertoire of capability such as the formation of dynamic stall vortices simultaneously on two leading edges during part of the cycle, changes in projected area in different planes, and the vectoring of jets. However, such fins may not be scalable to larger biorobotic vehicles and relatively stiff fins appear to be better suited instead, albeit with somewhat limited station-keeping ability.

Biorobotic insights into how animals swim

SUMMARY Many animals maneuver superbly underwater using their pectoral appendages. These animals range from sunfish, which have flexible, low aspect ratio fins, to penguins, which have relatively stiff, high aspect ratio wings. Biorobotics is a means of gaining insight into the mechanisms these animals use for maneuvering. In this study, experiments were carried out with models of abstracted penguin wings, and hydrodynamic characteristics – in particular, efficiency – were measured directly. A cross-flow vortex model of the unsteady force mechanism was developed that can compute instantaneous lift and drag forces accurately. This makes use of the steady characteristics of the fin and proposes that cross-flow drag vortices of bluff bodies in steady flow are analogous to dynamic stall vortices and that fin oscillation is a means for keeping the vortices attached to the fin. From what has been reported for sunfish with pectoral fins to our current measurements for single abstracted penguin wings, we infer that the maximum hydrodynamic efficiency has remained largely unchanged. A selection algorithm was used to rapidly find the fin oscillation parameters for optimum efficiency. Finally, we compared the measurements on the penguin-like relatively stiff fins and the reported flow visualization of flexible sunfish pectoral fins. The flexible pectoral fins of station-keeping sunfish exhibit a rich repertoire of capability such as the formation of dynamic stall vortices simultaneously on two leading edges during part of the cycle, changes in projected area in different planes, and the vectoring of jets. However, such fins may not be scalable to larger biorobotic vehicles and relatively stiff fins appear to be better suited instead, albeit with somewhat limited station-keeping ability.