The development of 1D nanostructures with enhanced material properties has been an attractive endeavor for applications in energy and environmental fields, but it remains a major research challenge. ...Herein, this work demonstrates a simple, gel‐derived method to synthesize uniform 1D elongated sub‐nanotubes with an anatase/bronze TiO2 nanocrystal wall (TiO2 SNTs). The transformation mechanism of TiO2 SNTs is studied by various ex situ characterization techniques. The resulting 1D nanostructures exhibit, synchronously, a high aspect ratio, open tubular interior, and anatase/bronze nanocrystal TiO2 wall. This results in excellent properties of electron/ion transport and reaction kinetics. Consequently, as an anode material for sodium‐ion batteries (SIBs), the TiO2 SNTs display an ultrastable long‐life cycling stability with a capacity of 107 mAh g−1 at 16 C after 4000 cycles and a high‐rate capacity of 94 mAh g−1 at 32 C. This a high‐rate and long‐life performance is superior to any report on pure TiO2 for SIBs. This work provides new fundamental information for the design and fabrication of inorganic structures for energy and environmental applications.
1D elongated sub‐nanotubes with an anatase/bronze TiO2 nanocrystal wall are synthesized through a gel‐derived method. This new structure exhibits a high aspect ratio, open interior, and an anatase/bronze nanocrystal wall, that results in fast electron/Na+ transport and large storage sites. This work enables new paths to the design and fabrication of inorganical structures for energy and environmental applications.
Validated by experimental data, this paper performs computational fluid dynamics (CFD) simulations to investigate the influence of tree plantings on urban airflow and vehicular CO exposure in ...two-dimensional (2D) street canyons with various aspect ratios (building height/street width, AR = H/W = 0.5, 1, 3, 5) and ground-level source. The impacts of tree canopy bottom height (Htb = 2 m, 6 m), tree stand density (y-density = 0.33, 0.67, 1) and leaf area density (LAD = 0.5, 1, 2 m2/m3) are considered. Personal intake fraction (P_IF) and its spatial mean value in leeward and windward sides ( lee, wind) and for entire streets (street intake fraction, ) are adopted to assess overall pollutant exposure.
For cases without trees, only one main vortex exists in shallow streets with AR = 0.5-3 and as AR = 3 (5.80 ppm) slightly exceeds AR = 0.5-1 (3.98-3.84 ppm). However, two counter-rotating vortexes appear in deep streets (AR = 5), inducing 1-2 orders smaller pedestrian-level velocity (U/Uref~10−4-10−3) and one-order greater (46.80 ppm) than shallow streets. Trees always weaken wind in streets and raise more in shallower streets by 46.0% as AR = 0.5 (3.98 ppm-5.81 ppm), 26.0-45.9% as AR = 1 (3.84 ppm to 4.84-5.60 ppm), 16.2-50.3% as AR = 3 (5.80 ppm to 6.74-8.72 ppm), but only 8.5-23.4% as AR = 5 (46.80 ppm to 50.78-57.73 ppm). Particularly, as AR = 1, trees raise lee (5.87 ppm) by 27.1-57.2%, while wind (1.80 ppm) only by 0%-23.3%. Higher Htb, smaller y-density or LAD produce less increase of . As AR = 3, vegetation increases lee (8.84 ppm) by 21.2%-66.4% but little affects wind (2.76 ppm). Lower Htb produces smaller differing from AR = 1. As AR = 5, vegetation increases wind (63.97 ppm) by 15.1-36.6% but reduces lee (29.63 ppm) by 5.2-8.5%. Although further investigations are still required for design purpose, this paper provides effective methodologies to quantify how vegetation influences street-scale pollutant exposure.
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•Personal intake fraction (P_IF) quantifies pollutant exposure with various H/Ws.•As H/W = 5, (~50 ppm) is 1-order larger than H/W = 0.5, 1, 3 (~4–6 ppm).•Trees weaken ventilation and raise by 16–50% as H/W = 0.5–3, 9–23% as H/W = 5.•Trees raise leeward-side C more than windward as H/W = 0.5–3 but opposite as H/W = 5.•Trees affect the whole canyon as H/W = 1 but area below 16th, 7th floor as H/W = 3, 5.
•Performance decreases with uneven cross-flow in higher channel length ARs.•Smaller performance change due to uneven cross flow than in experiment.•Neutron radiography indicates more water buildup in ...high AR than low AR.•Liquid water handling probable cause of majority of performance variation.•Significant interaction between channel AR and stoichiometry for system performance.
The goal of this study was to determine the main cause of performance improvement in decreasing aspect ratio interdigitated flow fields, where aspect ratio is the channel length to width ratio. An experimental test cell with an interdigitated flow field operated under various aspect ratios found increasing net power densities with decreasing aspect ratio, after accounting for parasitic pump losses. In-situ neutron radiography found there was more water present in high aspect ratio flow field designs than in low aspect ratio designs. It also found more water in the 1.5/2 stoichiometry conditions than in the 2/4 stoichiometry conditions further indicating liquid water is a probable cause of performance changes. A single phase model used to determine the difference in power from the changing distribution of cross flow found decreasing aspect ratio resulted in higher overall performance. The experiment had significantly greater losses in power density with increasing aspect ratio, indicating liquid water removal was the major contributor to the improvement in net power density rather than the distribution of cross flow. Designers of PEMFCs should use a low aspect ratio design for interdigitated flow fields, or include a water removal mechanism for situations where high aspect ratio is required.
Slender objects have a large aspect ratio and are generally oriented, resulting in poor performance of current general detectors on slender object detection tasks. Therefore, an adaptive label ...assignment scheme for slender object detection is proposed in this paper. Specifically, the central axis prior to positive training samples is proposed to make the final position distribution of positive training samples more reasonable. Secondly, it is proposed that the number of positive training samples of slender objects could be further increased to solve the problem of positive training sample imbalance between slender objects and regular objects. Experimental results on the MS COCO dataset demonstrate the effectiveness of the proposed method.
•Enhanced damage in reinforced concrete columns is due to 2D blast wave propagation.•The 2D wave propagation transitions into 1D wave propagation in walls.•A 500 g TNT contact explosion on square ...column resulted in damage index of 1.•67% increase in width reduced damage index to 0.71 when subjected to 500-g TNT.•140% in width reduced damage index from 1 to 0.48 when subjected to breach charge mass.
The response of reinforced concrete (RC) members subjected to contact explosion effects is more severe than the response to non-contact explosions due to local material failure. The shock-wave reflection within the RC member causes severe local material damage. The resulting loss of concrete cross-section reduces the axial load and bending capacity of the RC member. It is hypothesized that the concrete loss from the sides can be prevented by increasing the aspect ratio of the cross-section. In a low aspect ratio RC column, the reflection is from three faces whereas in RC slabs and high aspect ratio columns the shock-wave reflection from the back-face only is significant. This study experimentally investigates the response of rectangular RC columns with varying widths of the cross-section, subjected to contact explosion effects. A range of aspect ratios was investigated to preclude the side face damage for a given depth of rectangular RC column. High fidelity numerical models were developed to predict the blast-response and the residual axial capacity of the blast-damaged rectangular columns. The numerical models were validated, and the results show a good correlation with the experimental results. Using a rectangular RC column aspect ratio with a width that precludes the side face spall significantly improves the residual axial capacity of the blast-damaged columns. Furthermore, parametric analyses were performed to numerically investigate the influence of the width on the residual axial load carrying capacity of rectangular RC columns subjected to contact explosion effects of breach-charge mass required for the provided depth. An increase in the width of the column improved the damage resistance even though the rectangular column was breached around the point of detonation. Hence, increasing the width of the rectangular RC columns can be effectively used to mitigate contact explosion effects.
This paper reviews the recent advances in reaction-ion etching (RIE) for application in high-aspect-ratio microfabrication. High-aspect-ratio etching of materials used in micro- and nanofabrication ...has become a very important enabling technology particularly for bulk micromachining applications, but increasingly also for mainstream integrated circuit technology such as three-dimensional multi-functional systems integration. The characteristics of traditional RIE allow for high levels of anisotropy compared to competing technologies, which is important in microsystems device fabrication for a number of reasons, primarily because it allows the resultant device dimensions to be more accurately and precisely controlled. This directly leads to a reduction in development costs as well as improved production yields. Nevertheless, traditional RIE was limited to moderate etch depths (e.g., a few microns). More recent developments in newer RIE methods and equipment have enabled considerably deeper etches and higher aspect ratios compared to traditional RIE methods and have revolutionized bulk micromachining technologies. The most widely known of these technologies is called the inductively-coupled plasma (ICP) deep reactive ion etching (DRIE) and this has become a mainstay for development and production of silicon-based micro- and nano-machined devices. This paper will review deep high-aspect-ratio reactive ion etching technologies for silicon, fused silica (quartz), glass, silicon carbide, compound semiconductors and piezoelectric materials.
The majority of the accidents were happening perpetually due to driver drowsiness over the decades. Automation has been playing key role in many fields to provide conformity and improve the quality ...of life of the users. Though various drowsiness detection systems have been developed during last decade based on many factors, still the systems were demanding an improvement in terms of efficiency, accuracy, cost, speed, and availability, etc. In this paper, proposed an integrated approach depends on the Eye and mouth closure status (PERCLOS) along with the calculation of the new proposed vector FAR (Facial Aspect Ratio) similarly to EAR and MAR. This helps to find the status of the closed eyes or opened mouth like yawning, and any frame finds that has hand gestures like nodding or covering opened mouth with hand as innate nature of humans when trying to control the sleepiness. The system also integrated the methods and textural-based gradient patterns to find the driver's face in various directions identify the sunglasses on the driver's face and the scenarios like hands-on eyes or mouth while nodding or yawning were also recognized and addressed. The proposed work tested on datasets such as NTHU-DDD, YawDD, and a proposed dataset EMOCDS (Eye and Mouth Open Close Data Set) and proved better in terms of accuracy and provides results in general by considering various circumstances.
The rectangular twisted torus is an attractive alternative to the classic torus as interconnection topology of high-performance computers. In this article, we establish the analytical expression of ...the diameter of a rectangular twisted torus with any aspect ratio and any twist slope. The result validates the optimality of a rectangular twisted torus with width-height-slope ratio 2:1:1.
Materials patterned with high‐aspect‐ratio nanostructures have features on similar length scales to cellular components. These surfaces are an extreme topography on the cellular level and have become ...useful tools for perturbing and sensing the cellular environment. Motivation comes from the ability of high‐aspect‐ratio nanostructures to deliver cargoes into cells and tissues, access the intracellular environment, and control cell behavior. These structures directly perturb cells' ability to sense and respond to external forces, influencing cell fate, and enabling new mechanistic studies. Through careful design of their nanoscale structure, these systems act as biological metamaterials, eliciting unusual biological responses. While predominantly used to interface eukaryotic cells, there is growing interest in nonanimal and prokaryotic cell interfacing. Both experimental and theoretical studies have attempted to develop a mechanistic understanding for the observed behaviors, predominantly focusing on the cell–nanostructure interface. This review considers how high‐aspect‐ratio nanostructured surfaces are used to both stimulate and sense biological systems.
High‐aspect‐ratio nanostructured surfaces trigger a wide range of biological responses and can be thought to act as biological metamaterials. Their nanoscale structuring is comparable with that of intracellular machinery, interacting directly with the cell membrane and cytoskeleton. They are used for molecular delivery, intracellular sensing, and as biomechanical cues. Different applications and open research questions are summarized.
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