Channel Region Research Articles

Second Order Rate Regions of Gaussian Broadcast Channels Under Heterogeneous Blocklength Constraints

Second Order Rate Regions of Gaussian Broadcast Channels Under Heterogeneous Blocklength Constraints

The Generalized Degrees-of-Freedom Region of the Two-User MIMO Broadcast Channel With Delayed CSIT

The Generalized Degrees-of-Freedom Region of the Two-User MIMO Broadcast Channel With Delayed CSIT

XFEM-Based Study of Fatigue Crack Propagation in Rocket Deflector Troughs under Coupled High-Temperature and Impact Conditions

This research investigated fatigue crack propagation on the lower surface of rocket deflector troughs in offshore rocket launch platforms. Initially, a numerical model of an offshore rocket launch platform was established using ABAQUS based on the Extended Finite Element Method (XFEM). Subsequently, two variable parameters—the initial crack length and initial tilt angle—were introduced. This research systematically analysed the impact of these parameters on the fatigue crack propagation patterns in both the maximum stress and maximum deformation regions of the deflector channels under the combined conditions of high temperature and impact. Finally, the research indicated that the propagation length of surface cracks in the deflector trough exhibited an initial increase followed by a decrease with the rise in the pre-set inclination angle. Notably, the stable propagation rate of the crack in the region of maximum deformation surpassed that observed in the region of maximum stress. Through meticulous comparative analysis, it was evident that temperature loading significantly exacerbated the initiation and propagation of cracks, particularly in the upper region of the deflector channel’s lower surface.

Enhanced oxidation of organic pollutants by regulating the interior reaction region of reactive electrochemical membranes

Reactive electrochemical membrane (REM) emerges as an attractive strategy for the elimination of refractory organic pollutants that exist in wastewater. However, the limited reaction sites in traditional REMs greatly hinder its practical application. Herein, a feed-through coating methodology was developed to realize the uniform loading of SnO2-Sb catalysts on the interior surface of a REM. The uniformly coated REM (Unif-REM) exhibited 2.4 times higher reaction kinetics (0.29 min–1) than that of surface coated REM (Surf-REM) for the degradation of 2 mM 4-chlorophenol (4-CP), rendering an energy consumption as low as 0.016 kWh gTOC–1. The fast degradation of various emerging contaminants, e.g., sulfamethoxazole (SMX), ofloxacin (OFLX), and tetracycline (TC), also confirms its superior oxidation capability. Besides, the Unif-REM exhibited good performance in generating hydroxyl radicals (•OH) and a relatively long service lifetime. The simulation of spatial current distribution demonstrates that the interior reaction region in the Unif-REM channels can be drastically extended, thereby maximizing the surface coupling of mass diffusion and electron transfer. This study offers an in-depth look at the spatially confined reactions in REM and provides a reference for the design of electrochemical systems with economically efficient water purification.

Optimization of DE-QG TFET using novel CIP and DCT techniques

In this paper, two novel techniques Channel-Intermediate-Pocket (CIP) and Dual-Channel-Type (DCT) are proposed to optimize the Drain Engineered-Quadruple Gate TFET (DE-QG TFET). The proposed DCT technique is realized by making half of the channel area with lightly doped n- and the other half with the lightly doped p- channel. The CIP technique is implemented by inserting a pocket exactly at the junction of lightly doped n- &p- channel regions. Using the proposed techniques, the Ioff is reduced by ∼3.3 times (2 × 10-17 A/μm), the Iamb is reduced by a magnitude of two orders (2.39 × 10-17 A/μm) and by using the Dual-Oxide technique, the Ion is increased by 5 times (0.641 mA/μm) that of the conventional DE-QG TFET. Also, a steeper subthreshold swing (SS) of ∼57 mV/dec and one order of magnitude increase in the Ion/Ioff ratio of 3.19 × 1013 is achieved. Further, the peak overshoot voltage is suppressed by 86%, the transconductance (gm) is increased by ∼3 times (757 μA/V), and both the cut-off frequency (fT) and the Gain Bandwidth Product (GBW) are increased by ∼2.3 times (49 GHz & 5.2 GHz) respectively. The proposed device is mainly targeted towards Analog/RF applications.

Droplet pair breakup in microfluidic expansion channel

Previous studies on droplet splitting mainly focus on monodisperse droplets, and the understanding of the breakup of polydisperse droplet systems is still lacking. In this work, we experimentally study the breakup of droplet pairs in the expansion region of microfluidic channel. The results show that with the increase in the size ratio of the droplets in the droplet pair, the breakup mode of droplet pairs changes from rear droplet breakup to front droplet breakup, and then to front droplet alternate breakup. The expansion angle can affect the critical size ratio of the splitting mode transition, but it cannot change the transition trend. The expansion angle plays a major role in the splitting time and distance of the droplet pair. When the expansion angle is increased, the splitting time of the droplet pair is reduced and the splitting distance is shorter. Our study extends the understanding of the breakup of non-monodisperse droplet systems and provides a feasible approach for the selective and controllable splitting of droplets, which is important for laboratory-on-a-chip droplet volume manipulation and has potential applications.

DSTCNet: Deep Spectro-Temporal-Channel Attention Network for Speech Emotion Recognition.

Speech emotion recognition (SER) plays an important role in human-computer interaction, which can provide better interactivity to enhance user experiences. Existing approaches tend to directly apply deep learning networks to distinguish emotions. Among them, the convolutional neural network (CNN) is the most commonly used method to learn emotional representations from spectrograms. However, CNN does not explicitly model features' associations in the spectral-, temporal-, and channel-wise axes or their relative relevance, which will limit the representation learning. In this article, we propose a deep spectro-temporal-channel network (DSTCNet) to improve the representational ability for speech emotion. The proposed DSTCNet integrates several spectro-temporal-channel (STC) attention modules into a general CNN. Specifically, we propose the STC module that infers a 3-D attention map along the dimensions of time, frequency, and channel. The STC attention can focus more on the regions of crucial time frames, frequency ranges, and feature channels. Finally, experiments were conducted on the Berlin emotional database (EmoDB) and interactive emotional dyadic motion capture (IEMOCAP) databases. The results reveal that our DSTCNet can outperform the traditional CNN-based and several state-of-the-art methods.

Eukaryotic plankton species diversity and community structure in the Xiao Jiang River (the primary tributary of Upper Yangtze River), Yunnan.

The Xiao Jiang River, as a crucial element of ecological restoration in the upper reaches of the Yangtze River, plays an indispensable role in agricultural water utilization and water ecology within its watersheds. The water quality status of the Xiao Jiang River not only impacts local water-ecological equilibrium and economic benefits but also holds paramount importance for sustaining ecosystem health in the Yangtze River basin. Plankton surveys and environmental physicochemical detection were conducted in the major channel region of the Xiao Jiang River in dry and wet periods in 2022 to better understand the diversity of eukaryotic plankton and its community structure characteristics. Environmental DNA is an emerging method that combines traditional ecology with second-generation sequencing technology. It can detect species from a single sample that are difficult to find by traditional microscopy, making the results of plankton diversity studies more comprehensive. For the first time, environmental DNA was used to investigate eukaryotic plankton in the Xiao Jiang River . The results showed that a total of 881 species of plankton from 592 genera in 17 phyla were observed. During the dry period, 480 species belonging to 384 genera within17 phyla were detected, while, during the wet period, a total of 805 species belonging to 463 genera within 17 phyla were recorded. The phylum Ciliophora dominated the zooplankton, while the phylum Chlorophyta and Bacillariophyta dominated the phytoplankton. The presence of these dominant species indicate that the water quality conditions in the study area are oligotrophic and mesotrophic. Principal coordinate analysis and difference test showed that the number of plankton ASVs, abundance, species richness, dominating species, and diversity indices differed between the dry and wet periods. Spearman correlation analysis and redundancy analysis (RDA) of relative abundance data with environmental physicochemical factors revealed that water temperature (WT), dissolved oxygen (DO), potential of hydrogenacidity (pH), ammonia nitrogen (NH3-N), total nitrogen (TN), electrical conductivity (EC) and the determination of redox potential (ORP) were the main environmental physicochemical factors impacting the plankton community structure. The results of this study can serve as a provide data reference at the plankton level for water pollution management in the Xiao Jiang River, and they are extremely important for river ecological restoration and biodiversity recovery in the Yangtze River basin.

Evaluation of Anisotropic Biaxial Stress in Extremely-Thin Body (100) Silicon-Germanium-on-Insulator p-Type Metal-Oxide-Semiconductor Field-Effect-Transistor by Oil-Immersion Raman Spectroscopy

Background and ObjectiveSilicon germanium (SiGe)-on-insulator (SGOI) p-MOSFETs are expected for obtaining low power consumption and high current drive of CMOS since SiGe has higher hole career mobility than Si and the compressive strain can be induced in the SiGe channel without complicated heterostructures. In addition, the buried oxide between the Si substrate and the SiGe layer realizes suppression of leak current, and an extremely thin body (ETB) SGOI prevents short-channel effects. Strain engineering is important for improving the performance of p-MOSFETs because the hole mobility increases due to the compressive strain in the channel region. In previous studies, we have reported that anisotropic strain in ETB GOI channels of p-MOSFET improved electrical properties [1]. However, there are few reports regarding the detailed stress evaluation in ETB SGOI p-MOSFETs. The strain state has changed complicatedly by the SiGe device process. Therefore, a detailed stress measurement is indispensable to determine career mobility enhancement in the actual channel fabrication. In this study, we evaluated the anisotropic biaxial stress in the channel region of the ETB (100) SGOI p-MOSFETs by oil-immersion Raman spectroscopy.Experiments We prepared (100) SGOI p-MOSFETs along <110> with a channel thickness of approximately 10 nm by applying the Ge condensation process with slow cooling on the 60 nm-thick Si0.75Ge0.25 films epitaxially grown on SOI substrates with 10 nm-thick superficial Si layer [2]. We used the Ge condensation process that combined oxidation and intermixing annealing in order to suppress strain relaxation in the Ge-rich region [3] and obtained Ge-rich SiGe layer (Ge fraction: from 65 to 70%). For the evaluation of anisotropic biaxial stress in the SiGe channel region, we measured longitudinal optical (LO) and transverse optical (TO) phonon modes of Raman spectra for Ge-Ge vibration mode derived from SiGe by using oil-immersion Raman spectroscopy. In the oil-immersion Raman measurements, the wavelength of the excitation light source was 532 nm, the laser power at the sample surface was less than 1 mW, and the focal length of the spectrometer was 2,000 mm. The numerical aperture of the oil-immersion lens was 1.4, and the reflective index of oil was 1.5. We measured p-MOSFETs with different channel widths to examine the channel width dependence.Results and DiscussionFigure 1(a) and (b) show the Raman spectra of the LO and TO phonon modes obtained from the SiGe channel region at channel width (Wch) = 738 nm, respectively. We observed that Raman peaks of LO phonon mode shifted toward the higher wavenumber side compared to the Raman peak of strain-free SiGe. These results suggest that the high compressive strain is induced in the SiGe channel.Figure 1(c) shows the calculated transverse stress (σxx) and longitudinal stress (σyy) of the samples using LO and TO Raman shift for four different channel widths under the assumption of the anisotropic biaxial stress and Ge fraction 68% in the SiGe layer. From Fig. 1(c), we observed transverse stress (σxx) decreases with narrowing channel width. On the other hand, the longitudinal stress (σyy) did not significantly change regardless of channel width. These results suggest that the strain states in the SiGe channel region became closer to the uniaxial strain with narrowing the channel width. These changes are in good agreement with the previous electrical characteristics studies of the GOI p-MOSFETs [1], and it is expected that the compressive strain enhances the hole mobility in the ETB SGOI p-MOSFETs as well.AcknowledgementsThis work was supported by JSPS KAKENHI Grant Number 22H00208, Japan. A part of this work was conducted at Takeda Sentanchi Supercleanroom, The University of Tokyo, supported by "Nanotechnology Platform Program" of MEXT, Japan, Grant Number JPMXP09F-20-UT-0007. Reference [1] C. -T. Chen et al., IEEE Trans. Electron Devices 69, 1 (2022).[2] C. -T. Chen et al., Proc. IEEE Symp. VLSI Technology (2021).[3] K. -W. Jo et al., Appl. Phys. Lett. 114, 062101 (2019). Figure 1

A Dimension-Reduced Line-Element Method to Model Unsaturated Seepage Flow in Porous Media

Contrary to the continuum hypothesis, which averages water flow across the entire domain, including both grains and pores, the line-element model concentrates unsaturated flow in the pore space in the intermediate region of horizontal and vertical channels. The flux equivalent principle is used to deduce the equivalent unsaturated hydraulic conductivity, the flow velocity and the continuity equations. It is found that the relative hydraulic conductivities derived from the line-element model and the continuum model are identical. The continuity equations in the two models are also similar, except that the coefficient in the water content term is half that in the line-element model. Thus, the unsaturated flow problem in porous media is transformed into a one-dimensional problem. A dimension-reduced finite line-element method is proposed that includes a complementary algorithm for Signorini’s-type boundary conditions involving the seepage-face boundary and the infiltration boundary. The validity of the proposed model is then proved by good agreement with analytical, experimental and simulated results for one-dimensional infiltration in a vertical soil column, unsaturated flow in a sand flume with drainage tunnels, and transient unsaturated flow water-table recharge in a soil slab, respectively. In general, the proposed method has good computational efficiency, especially for smaller mesh sizes and short time intervals.

Stress Relaxation of Extremely-Thin-Body Ge-on-Insulator p-Type Metal-Oxide-Semiconductor Field-Effect Transistor Along and Observed By Oil-Immersion Raman Spectroscopy

Background and purpose Strain techniques and channel materials with high carrier mobility are the principal technology boosters for the realization of high-performance logic devices composed of group IV semiconductors such as silicon (Si). In particular, strain engineering plays an important role in improving the performance of metal-oxide semiconductor field-effect transistors (MOSFETs) from the viewpoint of reducing the effective carrier mass. It is important to evaluate the stress relaxation in group IV semiconductor devices for the optimization of the carrier mobility and the device structure. In this paper, we demonstrated the stress evaluation of extremely-thin-body Ge-on-insulator (ETB GOI) p-type MOSFET along the <110> and <100> longitudinal directions by oil-immersion Raman spectroscopy with the high-numerical-aperture (high-NA) lens to realize precise evaluation of strain states in the Ge channels. Experiments Biaxially-strained (001) GOI layer was prepared by applying optimized Ge condensation technique on epitaxially-grown Si/Si0.75Ge0.25/Si-on-insulator substrates with 4-hour slow cooling [1, 2]. After the removal of the thermal oxide, narrow channel patterning was performed by electron-beam (EB) lithography. GOI channel was further thinned down by the cyclic digital etching process (plasma oxidation and wet etching). Surface passivation process was then immediately performed to fabricate GeO x and Al2O3 by plasma oxidation and atomic layer deposition at 300oC, respectively. The source-drain regions were formed with EB evaporated Ni through a lift-off process and Al deposition was performed as the back gate electrode.We used the Raman spectrometer with spectrograph focal length of 2,000 mm. The numbers of grating grooves were 2,400 mm-1 and a visible laser was used as the incident excitation light source whose wavelength was 532 nm. To realize anisotropic stress evaluation assuming the channel region of the ETB GOI MOSFET, we used a high-NA immersion lens for the selective excitation of both LO and TO phonon modes [3]. The high-NA and refractive index n of the oil were approximately 1.4 and 1.5, respectively. Using a high-NA immersion lens, a z-polarized light component can be effectively obtained owing to the aperture angle. Therefore, TO phonons can be excited on the basis of Raman selection rules for (001)-oriented GOI [3, 4]. Results and discussion Figure 1 shows the channel width dependence of the anisotropic biaxial stress of ETB GOI MOSFET along the <100> longitudinal direction obtained by the oil-immersion Raman spectra. Anisotropic biaxial compressive stress at the GOI channel width direction of the GOI channels was observed even when the GOI channel width is wide (GOI channel width ~ 630 nm). The stress along the GOI channel length (the <100> longitudinal direction) is relatively high. These results are clearly different from the stress relaxation in the ETB GOI MOSFET along the <110> longitudinal direction. In previous studies, a clear stress relaxation at the GOI channel width direction was observed as the GOI channel width becomes narrower of the ETB GOI MOSFET along the <110> longitudinal direction (from channel width ~ 200 nm) [5]. The results observed in this study are generally well correlated with the results obtained in strain relaxation measurements of carbon-doped Si nanowires along <100> by X-ray diffraction with synchrotron radiation [6]. The difference in the strain relaxation mechanism depending on the GOI channel direction may affect the electrical properties, and we consider that it is useful to be physical elucidation of the carrier mobility enhancement. Acknowledgements This work was supported by JSPS KAKENHI Grant Number 22H00208, Japan. A part of this work was con-ducted at Takeda Sentanchi Supercleanroom, The University of Tokyo, supported by "Nanotechnology Platform Program" of MEXT, Japan, Grant Number JPMXP09F-20-UT-0007.

Tailoring Parallel Channel Flow Fields for Efficient Mass Transport and Compression in Proton Exchange Membrane Fuel Cells

The adverse effects of global warming have made it critical to transition our reliance on fossil fuels to more sustainable energy sources. Renewable energy can be stored in the form of hydrogen to continuously produce clean energy using a proton exchange membrane (PEM) fuel cell. However, to accelerate commercialization, especially in heavy-duty applications, the performance and durability of the fuel cell needs to be improved. Particularly, PEM fuel cell performance is strongly dependent on the flow fields which should be designed to optimize the transport of reactants and byproducts while maintaining uniform compression of the fuel cell materials. An important flow field design parameter is the channel aspect ratio (channel width by height) which directly influences compression and the transport of reactants and products. Although novel flow field configurations have been studied previously, an investigation on the effects of channel aspect ratio on cell performance using electrochemical testing and operando X-ray imaging has yet to be performed. In this study, we compared the water saturation and electrochemical performance across varying flow field channel aspect ratios from 0.5-2.0 with a fixed active area. The ohmic and mass transport resistances were quantified using electrochemical impedance spectroscopy. Operando X-ray imaging was performed to spatially resolve water saturation under the land and channel regions of the flow fields. We observed that lower channel aspect ratios (or higher number of channels for the given active area) led to lower ohmic resistances but resulted in significant water saturation at higher current densities due to ineffective water removal from the smaller channels. Notably, from these results we elucidated that there exists an ideal channel to rib width ratio to facilitate an effective balance of enhanced water removal using the channels and contact between the porous microstructures under the lands of the flow fields.

(Invited) GaN Photoconductive Semiconductor Switches for Efficient High-Voltage Power Conversion Applications

Gallium nitride (GaN) photoconductive switch (PCSS) technology can revolutionize high-voltage, efficient power-switching capabilities. PCSSs are optically driven, which advantageously isolates sensitive control circuitry from electromagnetic interference (EMI) resulting from rapidly switching high voltages and currents (high dI/dt or dV/dt). Fast switching times and extremely low on-resistances are achievable in PCSSs. The conductive channel region during on-state (under illumination) also serves as the voltage hold-off region in the off-state (dark) and does not require an additional drift layer that limits conventional unipolar device performance. In addition, the on-state resistivity can be further reduced by increasing the driving optical power density. Carbon-doped GaN (GaN:C) can result in extremely low dark currents, high blocking voltages, as well as support very low on-resistances.Lateral and vertical GaN PCSSs are fabricated. Lateral GaN:C PCSS structures consist of a 4 µm thick GaN:C layer grown by metal organic chemical vapor deposition (MOCVD) on a SiC substrate. Vertical GaN:C PCSS structures consist of a 100 µm thick GaN:C layer grown by hydrive vapor phase epitaxy (HVPE) on a native GaN substrate. Contacts were formed by evaporation of Ti/Au (25 nm /250 nm). The PCSS devices are driven with a 3 W commercial off-the-shelf (COTS) ultraviolet (UV) light emitting diode (LED) with peak output at 365 nm and a 10 nm full width half maximum.Vertical GaN PCSSs demonstrate exceptional on-state characteristics with an on-state current density of ~150A/cm2 , or an on-state resistivity of 66 mΩ-cm2. The off-state (dark) blocking capability exceeds 1 kV (maximum value tested). The transient switching characteristics of GaN:C PCSS will be characterized, and discussion will be provided relating to device design and optical driving conditions, including GaN:C carbon doping density, GaN:C layer thickness considerations, design for reduced contact resistance, illumination power density, and illumination wavelength.

HumanPoseNet: An all-transformer architecture for pose estimation with efficient patch expansion and attentional feature refinement

Human pose estimation from images is an exceedingly challenging task due to occlusion, blur, illumination, and size variations. Several research works have addressed this problem by designing novel encoders that extract discriminative features from input images. However, the design of decoders is an understudied problem as most approaches use the conventional transposed convolution for feature upsampling. In this paper, we propose a novel transformer-based pose estimation architecture, HumanPoseNet with a novel decoder design. The encoder is a transformer with dual-attention for highlighting important spatial and channel regions. The decoder contains a novel Patch Expansion module for feature upsampling which is computationally more efficient than the traditional transpose convolution. The decoder also contains an Attentional Feature Refinement Block that is integrated with the attention mechanism to extract refined features. Extensive experiments conducted on the MS COCO benchmark dataset proves that HumanPoseNet beats other state-of-the-art models, achieving an average precision (AP) score of 77.3. A qualitative analysis is conducted and the results prove that HumanPoseNet is able to predict accurate pose keypoints, even in occluded/blurred images. An ablation study is done to verify the complementary contributions of Patch Expansion and Attentional Feature Refinement Module. HumanPoseNet is easy to train as the model converges swiftly in merely 50 epochs while existing state-of-the-art methods are usually trained for 200 epochs or more.

Demonstration of a Frequency Doubler Using a Tunnel Field-Effect Transistor with Dual Pocket Doping

In this study, a frequency doubler that consists of a tunnel field-effect transistor (TFET) with dual pocket doping is proposed, and its operation is verified using technology computer-aided design (TCAD) simulations. The frequency-doubling operation is important to having symmetrical current characteristics, which eliminate odd harmonics and the need for extra filter circuitry. The proposed TFET has intrinsically bidirectional and controllable currents that can be implemented by pocket doping, which is located at the junction between the source/drain (S/D) and the channel region, to modify tunneling probabilities. The source-to-channel (ISC) and channel-to-drain currents (ICD) can be independently changed by managing each pocket doping concentration on the source and drain sides (NS,POC and ND,POC). After that, the current matching process was investigated through NS,POC and ND,POC splits, respectively. However, it was found that the optimized doping condition achieved at the device level (namely, a transistor evaluation) is not suitable for a frequency doubler operation because the voltage drop generated by a load resistor in the frequency doubler circuit configuration causes the currents to be unbalanced between ISC and ICD. Therefore, after symmetrical current matching was performed by optimizing NS,POC and ND,POC at the circuit level, it was clearly seen that the output frequency was doubled in comparison to the input sinusoidal signal. In addition, the effects of the S/D and pocket doping variations that can occur during process integration were investigated to determine how much frequency multiplications are affected, and these variations have the immunity of S/D doping and pocket doping length changes. Furthermore, the impact of device scaling with gate length (LG) variations was evaluated. Based on these findings, the proposed frequency doubler is anticipated to offer benefits for circuit design and low-power applications compared to the conventional one.

Biofilm dynamic changes in drip irrigation emitter flow channels using reclaimed water

Reusing reclaimed water through drip irrigation offers an effective way to overcome freshwater scarcity. However, biofilm accumulation in the flow channel of drip emitters is the primary obstacle. So far, biofilm development in the emitters remains largely unknown. Here, industrial computed tomography was used to quantify the emitter biofilm developments. Results showed that biofilm typically accumulated in the inlet of the emitter flow channel and decreased toward the flow direction. Biofilm was also typically accumulated in dead areas having low flow velocities, such as edge, corner, and adjacent surface zones in flow channels. The dynamics of the emitter biofilm variation mechanisms were also elucidated. Specifically, particle and nutrient transport appeared to be dominant in shaping the initial biofilm formation (i.e., 5% emitter clogging degree), resulting in biofilm abundant in the inlet of the flow channel. However, it changed the hydraulic conditions in emitter flow channels, increased local water shear stress, which made the biofilm easier to be washed away in the inlet, and caused biofilm to grow faster in the middle and outlet regions of the flow channel at 20% emitter clogging degree. At 50% clogging degree, biofilm in inlet regions grew faster again. Finally, some biofilm control approaches such as water quality management and emitter flow channel structure optimization were proposed. This study provided a better understanding of biofilm formation mechanisms in the emitter flow channels, which is critical for designing appropriate biofilm control technologies and will facilitate the reuse of reclaimed water in agricultural irrigation.

Unconfined fishway design, implementation, and assessment for the emerald Shiner (Notropis atherinoides) in the Upper Niagara River, New York

An engineered seawall in need of repair along the Upper Niagara River in Buffalo, NY, was previously identified as a hydrodynamic barrier to the migration of a small but important prey fish, the emerald shiner (Notropis atherinoides), and its connection to the upstream environs of Lake Erie. This study proposed a novel unconfined fishway design to be incorporated into existing plans for rehabilitation of the seawall at Broderick Park. The proposed fishway was developed using a two-dimensional depth-averaged numerical model, it was explored by placing the target fish into a physical model, and the constructed demonstration project was assessed using field measurements and observations. The numerical model showed that modular baffles attached to the seawall reduced the nearshore flow velocities to about 0.4 to 0.6 m s−1, which was within the acceptable range of velocities for the upstream migration of the emerald shiners. The physical experiments demonstrated that most emerald shiners chose to swim toward, within, or close to the proposed fishway in the presence of higher flow velocities within the main channel region. The proposed fishway design was integrated into the seawall repair as part of a demonstration project supervised by the US Army Corps of Engineers-Buffalo District. Post-construction assessment of the installation showed that (1) the modular baffles reduced time-averaged flow velocities near the seawall and water surface, (2) while very few shiners were observed swimming along the pre-construction seawall, large numbers were observed swimming upstream within this reduced flow velocity corridor created by the baffles, and (3) the structural integrity of the installation proved to be durable and resilient to extremely harsh environmental conditions. This study explored a new approach to fishway design for the passage of relatively small fish in large rivers, and it effectively melded fishway requirements into seawall restoration in concert with the expectations of multiple stakeholders.

Reynolds number asymptotics of wall-turbulence fluctuations

In continuation of our earlier work (Chen &amp; Sreenivasan, J. Fluid Mech., vol. 908, 2021, R3; Chen &amp; Sreenivasan, J. Fluid Mech., vol. 933, 2022a, A20 – together referred to as CS hereafter), we present a self-consistent Reynolds number asymptotics for wall-normal profiles of variances of streamwise and spanwise velocity fluctuations as well as root-mean-square pressure, across the entire flow region of channel and pipe flows and flat-plate boundary layers. It is first shown that, when normalized by peak values, the Reynolds number dependence and wall-normal variation of all three profiles can be decoupled, in excellent agreement with available data, sharing the common inner expansion of the type $\phi (y^+)=f_0(y^+)+f_1(y^+)/Re^{1/4}_\tau$ , where $\phi$ is one of the quantities just mentioned, the functions $f_0$ and $f_1$ depend only on $y^+$ , and $Re_\tau$ is the friction Reynolds number. Here, the superscript $+$ indicates normalization by wall variables. We show that this result is completely consistent with CS. Secondly, by matching the above inner expansion and the outer flow similarity form, a bounded variation $\phi (y^\ast )=\alpha _\phi -\beta _{\phi }y^{{\ast {1}/{4}}}$ is derived for the outer region where, for each $\phi$ , the constants $\alpha _\phi$ and $\beta _{\phi }$ are independent of $Re_\tau$ and $y^\ast$ $\equiv y^+/Re_\tau$ – also in excellent agreement with simulations and experimental data. One of the predictions of the analysis is that, for asymptotically high Reynolds numbers, a finite plateau $\phi \approx \alpha _\phi$ appears in the outer region. This result sheds light on the intriguing issue of the outer shoulder of the variance of the streamwise velocity fluctuation, which should be bounded by the asymptotic plateau of approximately 10.

Influence of JFET Width on Short-Circuit Robustness of 1200 V SiC Power MOSFETs

This paper investigates and compares the static performance and short-circuit (SC) robustness of 1200 V SiC MOSFETs with varying JFET widths (WJFET = 2.0–5.0 μm). Short-circuit measurements as well as electrical-thermal simulations are used to identify thermal distribution and maximum electrical field, providing valuable insights into the design limits. The devices under test (DUTs) with narrow and wide WJFET exhibit different failure mechanisms under SC stress. After the short-circuit failure, interlayer dielectric (ILD) cracks are observed in DUTs with narrow JFET width (WJFET &lt; 3 μm). In contrast, it is discovered that the burn mark is located in the channel region of the device with a wide JFET width. Moreover, the short-circuit withstand time (SCWT) of DUTs with narrow and wide WJFET exhibits varying trends under high temperature conditions (100 °C). These results can help verify the different failure mechanisms and determine an optimal JFET design to improve the trade-off between the static performance and SC ruggedness of the SiC MOSFETs.

Retracted: Study on Transmission Channel and Pollution Sources Region of O3 in Qingyuan City

Retracted: Study on Transmission Channel and Pollution Sources Region of O₃ in Qingyuan City