C-shaped Channel Research Articles

Vertical N-Type and P-Type Nanosheet FETs With C-Shaped Channel

We presented and demonstrated both n- and p-type vertical C-shaped-channel nanosheet field-effect transistors (VCNFETs) featured with precise control of both channel thickness and gate length. The VCNFETs were fabricated by high-quality Si/SiGe epitaxy and atomic layer deposition to obtain nanometer-scale process control and self-aligned high- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${k}$ </tex-math></inline-formula> metal gate (HKMG). The integration flow is compatible with the process used in the mainstream industry and it can be easily extended to vertically stacked devices. Both the gate length and the channel thickness of the VCNFETs are mainly determined by the thicknesses of Si/SiGe films grown by epitaxy, instead of lithography and etch techniques. Perfect subthreshold swing (SS), small drain-induced barrier lowering (DIBL), and large <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{ \mathrm{\scriptscriptstyle ON}}/{I}_{ \mathrm{\scriptscriptstyle OFF}}$ </tex-math></inline-formula> ratio were achieved for both n- and p-VCNFETs due to the crystalline silicon channel and the well-defined doping profiles. The device performance and optimization were also investigated and discussed. Used as access transistors in dynamic random access memory (DRAM) array, VCNFETs were also demonstrated for the potential applications to 10-nm DRAM and beyond.

Performance enhancement of a C-shaped printed circuit heat exchanger in supercritical CO2 Brayton cycle: A machine learning-based optimization study

The present work is focused on enhancing the overall thermo-hydraulic performance of a previously proposed C-shaped printed circuit heat exchanger (PCHEs) using Machine Learning (ML) Algorithms. In this context, CFD analysis is carried out on 81 different channel configurations of the C-shaped channel geometry, and computed data is used to train three ML algorithms. Later, C-shaped channel geometry is optimized by coupling the trained ML model with the multi-objective genetic algorithm (MOGA). Finally, the optimized channel geometry (called optimized ML ) is investigated numerically for a wide range of Reynolds numbers. Its performance is compared with the zigzag geometry, C-shaped base geometry, and previously optimized C-shape channel geometry using response surface methodology (RSM). The findings showed that the multilayered approach combining MOGA, CFD, and machine learning techniques is beneficial to accomplish a robust and realistic optimized solution. Comparing the thermo-hydraulic characteristics of the optimized ML channel geometry with zigzag channel geometry shows that the former is up to 1.24 times better than the latter based on the performance evaluation criteria (PEC). Furthermore, the overall performance of the optimize ML channel geometry was found up to 21% and 16% higher than the optimized RSM geometry on the cold and hot sides, respectively.

Root canal anatomy and morphology evaluation of mandibular molars according to gender by cone-beam computed tomography in Iranian population

Introduction: This study aimed to evaluate anatomy and morphology of mandibular permanent molars using cone-beam computed tomography (CBCT) in a selected Iranian population.Methods and Materials: CBCT images of 638 first and second mandibular molars (322 of males and 316 of females) were included in this in vitro study. Number of roots and root canals, Vertucci’s configuration of each root, radix paramolaris (RP), radix entomolaris (RE), and C-shaped canals were determined in both genders. Data were analyzed by Pearson-Chi square test using SPSS (V.22) software (P = 0.05).Results: The most common configuration of distal roots were type I for both genders. Among 266 first molars, 97.3% teeth had two roots, 0.75% had RP and 1.87% had RE. All RP and RE were type I. C-shaped canals were found in 1.12% teeth and all were in male population, significantly at the left side (P=0.045). Among 372 second molars, 94.08% had two roots, 0.53% had RP and 0.26% had RE. The prevalent canal configuration of mesial roots was type III (52.96%) with significant difference between right (P=0.006) and left (P=0.049). C-shaped canals were found in 5.64% of second molars and more specifically detected in male group. Significant difference was observed between two genders in the right (P=0.024) and the left (P=0.009).Conclusion: Vertucci’s type III and type II were the most prevalent configurations in mesial roots while for distal roots the predominant configuration was type I. RE, RP, and C-shaped channels were not common in mandibular molars between Iranian population and their prevalence were higher among male population.

Experimental study of aerodynamic noise performance of improved air distributor for ships

In ships, aerodynamic noise from the variable-air-volume fan is a common problem. This study experimentally explores the strategy of reshaping the traditional C-shaped channel structure to an L-shape to reduce noise. The noise level and resistance coefficient of the improved air distributor are analysed, and the results show that the noise of the original air distributor is 56.3 dB(A) under the rated working conditions (static pressure of 800 Pa and flow rate of 350 m3/h), which exceeds the International Maritime Organisation’s (IMO) ship noise limit (55 dB(A)). For the improved air distributor, the noise pressure level is 38.5 dB(A), the sound pressure level of high-frequency noise is reduced by 48% and the peak sound pressure level appears at 125 to 250 Hz, a frequency below the threshold of human hearing. Thus, the reshaping of the channel has a significant noise reduction effect. When the static pressure is 400 Pa and the flow rate is 100 to 500 m3/h, the sound pressure level of the improved air distributor is reduced by 29.9% to 32.2% to become less than 55 dB(A). Thus, the sound pressure level at the outlet of the improved air distributor meets the IMO ship noise standard.

Thermal mixing performances of shear-thinning non-Newtonian fluids inside Two-Layer Crossing Channels Micromixer using entropy generation method: Comparative study

In this work, a numerical comparative study is carried out to investigate a laminar steady flow behavior of shear-thinning non-Newtonian fluids in three chaotic geometries: Two-Layer Crossing Channel Micromixer, C-shaped channel and serpentine channel. The process is validated for non-Newtonian flow in a complex geometry which heated by a constant flux. Secondary flow structures are formed in the chosen geometries enhance significantly the fluid dynamic performances. To characterize this performance Poincaré map method is presented for different geometries with various cases of fluid power-law index. Thermal mixing behavior with two different inlet temperatures of shear-thinning fluids in the considered geometries is performed. For various cases of fluid power-law indexes, the TLCCM displayed thermal mixing degree enhancement of 42–84% relative to the thermal mixing degree in both C-shaped and serpentine channels. The second law of thermodynamics is controlled in terms of entropy generation due to the thermal and hydrodynamic process, as a function of low rates of generalized Reynolds number and power-law index, under the effects chaotic advection. Thereby, the TLCCM configuration exhibited very important enhancement of mixing degree than that obtained in other considered geometries, with minimization of friction and thermal irreversibilities.

Effect of printed circuit heat exchanger’s different designs on the performance of supercritical carbon dioxide Brayton cycle

Several fin configurations have been proposed in the literature to address the poor hydraulic performance associated with the PCHEs. However, the effect of the heat exchangers with proposed channel geometries on the performance of supercritical carbon dioxide(sCO2) power cycle is missing. In this context, the current study deals with the effects of different designs of the PCHEs varied by proposed channel configurations, heat exchanger’s effectiveness and design value of inlet Reynolds number on the performance of sCO2 power cycle. Moreover, a multi-object optimization study to find the best bargain between cycle’s efficiency and heat exchanger’s size is carried out using five different fin configurations (straight, zigzag, C-shaped, S-shaped, and airfoil fin channel configuration), heat exchanger’s effectiveness and inlet Reynolds number as a design variable. Results shows that enhancement in the hydraulic characteristics for a channel geometry that comes at the cost of thermal performance may not benefit the system’s efficiency. Optimization results suggest that C-shaped channel and zigzag channel geometries correspond to the cycle’s maximum efficiency and heat exchanger’s minimum size respectively. Optimization results further highlight that the comparison of channel geometries should be performed while in the setting of complete power generation cycle to account for all the variables involved.

Acoustic bubble-based drug manipulation: Carrying, releasing and penetrating for targeted drug delivery using an electromagnetically actuated microrobot

This paper presents a new type of microrobotic drug delivery technology where an electromagnetically actuated untethered microrobot swimming inside human blood vessels performs targeted drug delivery operations: carrying, releasing, and penetrating drugs to target tissues using acoustic excitation of bubbles. The novel microrobot is capable of not only transporting liquid forms of drugs in an aqueous medium but also wirelessly manipulating drugs without using complex mechanical parts. For the electromagnetic actuation of a microrobot, an electromagnetic system consisting of a pair of Helmholtz and Maxwell electric coils is fabricated. Using the developed electromagnetic system, the actuation of the microrobot made of a cylindrical neodymium magnet is successfully demonstrated in a T-shaped channel. For the drug manipulation, selective acoustic excitation of bubbles is investigated. The drug release actuation is studied using a microtube which is a drug container consisting of two bubbles with different volumes. Then, the effect of acoustic bubble-induced microstreaming on the drug penetration to tissues is investigated for three different conditions: pure diffusion, penetration with an acoustic wave, and microstreaming using an agarose gel. As a proof of concept, the proposed sequential drug manipulation (carrying, releasing, and penetrating) is experimentally demonstrated using the prototype of a microrobot enabling propulsion in a low Reynolds number environment using an electromagnetic system and drug manipulation using acoustic bubbles in a C-shaped channel filled with liquid. The proposed microrobot can be applied to various biomedical applications such as targeted drug delivery, cell manipulation, and microsurgery.

Numerical Calculation on the Performance of a C-shaped Channel Viscous Micropump

Numerical Calculation on the Performance of a C-shaped Channel Viscous Micropump

Development of chaotic advection in laminar flow of a non-Newtonian nanofluid: A novel application for efficient use of energy

The current research aims to investigate energy efficiency and flow characteristics of a non-Newtonian nanofluid containing TiO2 nanoparticles in a chaotic geometry. For this purpose, hydrothermal features of the nanofluid are assessed in the C-shaped channel and compared with the straight channel. Heat transfer and pressure drop in the C-shaped channel are higher than those in the straight channel. This finding is due to intense mixing in the C-shaped channel resulting from chaotic perturbations, such that the velocity and temperature profiles in the C-shaped channel are more uniform than those in the straight one. Convective heat transfer coefficient in chaotic channel has a periodic trend in which it increases in regions where boundary layer is disturbed while decreases in regions where boundary layer is allowed to grow. In comparison with base fluid, applying the nanofluid in both channels presents better cooling along with higher pressure drop. At low Reynolds numbers, development of chaotic advection causes more increment in heat transfer rate in comparison with pumping power and therefore, the value for Figure of Merit (FoM) becomes greater than 1. Simultaneous use of nanofluids and chaotic advection can result in not only greater energy efficiency, but also preventing sedimentation of nanoparticles.

Miniature Viscous Disk Pump: Performance Variations From Non-Newtonian Elastic Turbulence

Within the present investigation, a miniature viscous disk pump (VDP) is utilized to characterize and quantify non-Newtonian fluid elastic turbulence effects, relative to Newtonian flow behavior. Such deviations from Newtonian behavior are induced by adding polyacrylamide to purified water. The VDP consists of a 10.16 mm diameter disk that rotates above a C-shaped channel with inner and outer radii of 1.19 mm and 2.38 mm, respectively. A channel depth of 230 μm is employed. Fluid inlet and outlet ports are located at the ends of the C-shaped channel. Experimental data are given for rotational speeds of 126 1/s, 188 1/s, 262 1/s, and 366 1/s, pressure rises as high as 700 Pa, and flow rates up to approximately 0.00000005 m3/s. Reynolds number ranges from 2.9 to 6.5 for the non-Newtonian polyacrylamide solution flows and from 51.6 to 149.8 for the Newtonian pure water flows. To characterize deviations due to non-Newtonian elastic turbulence phenomena, two new parameters are introduced, PrR and HCR, where HCR is the ratio of head coefficient (HC) for the polyacrylamide solution and head coefficient for the water solution, and PrR is the ratio of pump power for the polyacrylamide solution and pump power for the water solution. Relative to Newtonian, pure water flows, the polyacrylamide solution flows give pump head coefficient data, dimensional pressure rise data, slip coefficients (SCs), specific speed (SS) values, and dimensional power data, which show significant variations and differences as they vary with flow coefficient (FC) or dimensional volumetric flow rate. Also important are different ranges of specific speed (SS) for the pure water and polyacrylamide solutions, and a lower range of SC or slip coefficient values for the polyacrylamide solution flows, compared to the pure water flows. These variations are due to increased elastic turbulence losses, which occur as viscosity magnitudes increase and the elastic polymers are excited by mechanical stress, which causes them to extend, deform, stretch, and intertwine.

Numerical simulation and optimization of nanofluid in a C-shaped chaotic channel

ABSTRACTIn this study, numerical calculations using single- and two-phase models of CuO/water nanofluid forced convection in a three-dimensional C-shaped channel with constant heat flux are investigated. The laminar heat transfer enhancement using a nanofluid in a chaotic flow is first validated with the available data in the literature and the maximum discrepancy is within 3%; then further it is extended to design the C-shaped geometry. In addition, after comparisons of the numerical results with single- and two-phase models, the multiparameter constrained the optimization procedure integrating the design of experiments (DOE), response surface methodology (RSM), genetic algorithm (GA), and computational fluid dynamics (CFD) is proposed to design the nanofluid laminar convection of three-dimensional C-shaped channels. The thermal performance factors predicted by the regression function for the C-shaped channel case are in good agreement with the numerical results of CFD, with the difference being within 10%.

Cyclic behaviour of novel blind bolted joints with different stiffening elements

Because of the difficulty of accessing the interior of structural hollow sections, emerging technology using blind bolts has been recently developed for fabricating connections to concrete-filled steel tubular (CFST) columns. However, two issues limit the structural benefits of this joint system including the limited transfer of hogging moment and high susceptibility of the steel tube to local failure. Therefore, the authors proposed four methods to enhance the CFST column’s stiffness in the connection region, namely, using inner binding bars, welding two internal rings, externally welding two C-shaped channels, and internally embedding a short segment of I-section in the steel tube. A total of 6 joints were tested under cyclic loading accordingly. The experimental results are analysed in this paper to evaluate the efficiency of different stiffening methods. It indicates that the C-shaped channels and embedded I-section are very effective in enhancing the performance of the joint, and the joint’s strength and deformation capacity can be significantly improved with large bending deformation developed in the end plate. In contrast, welding binding bars or internal rings has only moderate influence on the joint performance.

Not all participatory styles are created equal

In this study, hydrothermal characteristics of the water–TiO2 nanofluid are evaluated in the rectangular C-shaped chaotic channel by applying the two-phase Euler–Lagrange method. The results show that the fluid temperature distribution in the C-shaped channel is much more uniform than that in the straight rectangular channel due to the intense mixing in the chaotic geometry. By increasing the concentration and reducing the particle size, both convective heat transfer and pressure drop increase in the chaotic channel. For finer particles, due to more intense particle migration related to the Brownian motion, more uniform concentration distribution is obtained at the channel cross section. The model of mean convective heat transfer coefficient and pressure drop in terms of concentration and particle size was developed by neural network. In order to obtain some cases of the variables (i.e. size and concentration of nanoparticles) in which maximum heat transfer along with minimum pressure drop occurs, optimization on neural network model was implemented using methods of two-objective as well as single-objective (i.e. genetic algorithm coupled with compromise programming decision making method). Eventually, optimum cases were suggested for different importance levels of objective functions.

Numerical investigation and optimization of flow and thermal characteristics of nanofluid within a chaotic geometry

In this study, hydrothermal characteristics of the water–TiO2 nanofluid are evaluated in the rectangular C-shaped chaotic channel by applying the two-phase Euler–Lagrange method. The results show that the fluid temperature distribution in the C-shaped channel is much more uniform than that in the straight rectangular channel due to the intense mixing in the chaotic geometry. By increasing the concentration and reducing the particle size, both convective heat transfer and pressure drop increase in the chaotic channel. For finer particles, due to more intense particle migration related to the Brownian motion, more uniform concentration distribution is obtained at the channel cross section. The model of mean convective heat transfer coefficient and pressure drop in terms of concentration and particle size was developed by neural network. In order to obtain some cases of the variables (i.e. size and concentration of nanoparticles) in which maximum heat transfer along with minimum pressure drop occurs, optimization on neural network model was implemented using methods of two-objective as well as single-objective (i.e. genetic algorithm coupled with compromise programming decision making method). Eventually, optimum cases were suggested for different importance levels of objective functions.

Behavior of V-shaped angle shear connectors: experimental and parametric study

In this paper a new shear connector called V-shaped angle shear connector for steel–concrete composite system is proposed. This shear connector was proven to improve some mechanical properties of shear connectors, including high shear transfer, uplift resistance, sufficient ductility, and strength degradation resistance under cyclic loading, as well as to being cost effective compared with similar shear connectors, such as C-shaped channel and angle shear connectors. A total of 14 push-out tests were performed on composite beams with these connectors under monotonic and low cyclic loading. The failure mode, shear resistance, and ductility of the push-out specimens were investigated. The study also comprises of finite element and parametric analysis using an effective numerical model of the experimental push-out tests using the program ABAQUS. The finite element models were validated against the test results presented in experimental tests. Results showed that V-shaped angle shear connector has excellent behavior in terms of both shear strength and ductility. In addition, high resistance under cyclic loading was exhibited since the shear resistance of this connector was almost similar in both monotonic and cyclic loadings. Finite element results show good agreement with experimental results. The results discussed on the ductility and strength of this connector with different size and slope of inclination. In addition, the channel and angle shear connectors were compared with V-shaped angle shear connectors. V-shaped angle shear connectors behave much better than other similar connectors, such as normal angle shear connectors, and are superior to channel shear connectors in most specimens.

Numerical simulation of nanofluid application in a C-shaped chaotic channel: A potential approach for energy efficiency improvement

This study aims to evaluate the energy efficiency of nanofluid as a heat transfer fluid in a chaotic channel. To this end, hydrothermal characteristics of the water–Al2O3 nanofluid are numerically investigated in C-shaped and straight channels using single- and two-phase methods and then, the results are compared with each other. In the C-shaped channel, heat transfer and pressure drop show higher values in comparison with the straight channel, which is due to intense mixing in the chaotic geometry, such that the velocity and temperature contours in the C-shaped channel are more uniform than those in the straight one. Using the two-phase method, the concentration distribution is obtained non-uniform at the cross section of the straight channel, while intense mixing in the C-shaped channel makes distribution of the nanoparticles uniform. In comparison with water, using the nanofluid through both channels presents higher heat transfer and pressure drop. However, merit of using the nanofluid in the C-shaped channel is greater than that in the straight one. In this regard, simultaneous application of nanofluids, as heat transfer fluids, and chaotic channel, as a modified geometry, can result in not only higher energy efficiency, but also preventing nanoparticles agglomeration due to the intense mixing.

Deviations Due to Non-Newtonian Influences Within a Miniature Viscous Disk Pump

A miniature viscous disk pump (VDP) is utilized to characterize and quantify non-Newtonian fluid deviations due to non-Newtonian influences relative to Newtonian flow behavior. Such deviations from Newtonian behavior are induced by adding different concentrations of sucrose to purified water, with increasing non-Newtonian characteristics as sucrose concentration increases from 0% (pure water) to 10% by mass. The VDP consists of a 10.16 mm diameter disk that rotates above a C-shaped channel with inner and outer radii of 1.19 mm, and 2.38 mm, respectively, and a channel depth of 200 μm. Fluid inlet and outlet ports are located at the ends of the C-shaped channel. Within the present study, experimental data are given for rotational speeds of 1200–2500 rpm, fluid viscosities of 0.001–0.00134 Pa s, pressure rises of 0–220 Pa, and flow rates up to approximately 0.00000005 m3/s. The theory of Flumerfelt is modified and adapted for application to the present VDP environment. Included is a new development of expressions for dimensionless volumetric flow rate, and normalized local circumferential velocity for Newtonian and non-Newtonian fluid flows. To quantify deviations due to the magnitude non-Newtonian flow influences, a new pressure rise parameter is employed, which represents the dimensional pressure rise change at a particular flow rate and sucrose concentration, as the flow changes from Newtonian to non-Newtonian behavior. For 5% and 10% sucrose solutions at rotational speeds of 1200–2500 rpm, this parameter increases as the disk dimensional rotational speed increases and as the volumetric flow rate decreases. Associated magnitudes of the pressure difference parameter show that the fluid with the larger sucrose concentration (by mass) produces significantly larger differences between Newtonian and non-Newtonian fluid flow, for each value of dimensional volumetric flow rate. For each disc rotational speed, compared to Newtonian data, dimensional pressure rise variations with dimensional volumetric flow rate, which are associated with the non-Newtonian data, are generally lower when compared at a particular volumetric flow rate. Agreement with analytic results, for any given flow rate, rotational speed, and flow passage height, validates the shear stress model employed to represent non-Newtonian behavior, as well as the analytic equations and tools (based upon the Navier–Stokes equations) which are employed to predict measured behavior over the investigated range of experimental conditions.

Wave actions on the side caissons of the Venice gates

The present study originates from a construction problem found in the planned deployment of the side caissons of the Venice gates barrier. Each of these caissons is made to float, then sunk into a lateral trench and jointed to the soil at its bottom. As a result, a C-shaped channel forms between the vertical caisson surfaces and the surrounding trench. Incoming storm waves propagating from the sea can then induce forced oscillations in this C-channel. An analytical model based on the method of matched asymptotics is developed in order to obtain the free surface oscillations in the channel, caused by a grazing incident wave. The resonant response of the basin and the amplification factors are then determined. From the free surface elevation, the pressure field and hence the total forces are also found. The analysis moves on to irregular wave motion. The analytical solution enables us to compute the dynamic actions, showing that their magnitude can be significant, due to the excitation of different resonant modes.

Miniature Single-Disk Viscous Pump (Single-DVP), Performance Characterization

The development and testing of a rotating single-disk viscous pump are described. This pump consists of a 10.16mm diameter spinning disk, and a pump chamber, which are separated by a small gap that forms the fluid passage. The walls of the pump chamber form a C-shaped channel with an inner radius of 1.19mm, an outer radius of 2.38mm, and a depth of 40, 73, 117, or 246μm. Fluid inlet and outlet ports are located at the ends of the C-shaped channel. Experimental flow rate and pressure rise data are obtained for rotational speeds from 100to5000rpm, fluid chamber heights from 40to246μm, flow rates from 0to4.75ml∕min, pressure rises from 0to31.1kPa, and fluid viscosities from 1to62mPas. An analytical expression for the net flow rate and pressure rise, as dependent on the fluid chamber geometry, disk rotational speed, and fluid viscosity, is derived and found to agree with the experimental data. The flow rate and pressure rise of the pump vary nearly linearly with rotational speed. The volumetric flow rate does not change significantly with changes in fluid viscosity for the same rotational speed and pumping circuit. Advantages of the disk pumps include simplicity, ease of manufacture, ability to produce continuous flow with a flow rate that does not vary significantly in time, and ability to pump biological samples without significant alteration or destruction of cells, protein suspension, or other delicate matter.

Optimal geometry of L and C-shaped channels for maximum heat transfer rate in natural convection

The present paper documents the geometric optimization of L and C-shaped channels in laminar natural convection subject to global constraints. The objective is to maximize the heat transfer rate from the hot wall to the coolant fluid. Three different configurations were considered: (i) an L-shaped asymmetric vertical heated channel with an adiabatic horizontal inlet, (ii) an asymmetric vertical heated channel with an adiabatic vertical outlet, and finally, (iii) a C-shaped vertical channel with horizontal inlet and outlet. The two first configurations are free to morph according to two degrees of freedom: the wall-to-wall spacing and inlet (or outlet) height. The third configuration is optimized with respect to the wall-to-wall spacing, and the heights of the inlet and outlet ports. The effect of the inlet or outlet horizontal adiabatic duct lengths is also investigated. The optimization is performed numerically by using the finite element technique, in the range 10 5 < Ra < 10 7 for Pr = 0.7, where Ra is the Rayleigh number based on a fixed total height H of the channel. The numerical results show that optimization is relevant, since the three degrees of freedom considered have a strong effect on the heat transfer delivered from the hot wall to the fluid. The optimal geometric characteristics obtained numerically (i.e., optimal spacing, optimal height and lengths) are reported and correlated within a 7.5% maximal disagreement range.