Small Height Research Articles

Forced air flow through a rectangular channel with 3D turbulence enhancers: fluid-dynamics and thermal analysis by Large Eddy Simulations

Many newer engineering applications, like the cooling of automotive batteries and high-performance CPUs, require heat exchangers (HEs) with large contact areas and very small heights. Performances of this type of HEs can be significantly improved by using surfaces enhanced with optimized 3D structures. The project Mood4hex aims at designing new geometries with optimized morphology, starting from a large database of experimental data on ribbed surfaces. In order to perform an optimization algorithm on such surfaces, analyses are carried out on CFD models with increasing complexity and computational time, to find a fast-running code that preserves the physical meaning. Until recently we used RANS models, and now we began to investigate the use of Large Eddy Simulations (LES) as a higher order validation tool for simpler models. In this paper, we present the results of LES along with experimental data of a forced air flow inside a streamwise periodic rectangular channel of high aspect ratio, i.e., 1:10, equipped with standard transverse ribs (α = 90°). More specifically, the ribs are placed only on the lower wall that is operated at constant heat flux, while air flowing at Re 500 or 1000. Comparison of experimental data vs LES results shows weaknesses and strengths of the model.

Effects of coated sodium butyrate on the growth performance, serum biochemistry, antioxidant capacity, intestinal morphology, and intestinal microbiota of broiler chickens.

This study examined the impact of adding coated sodium butyrate (CSB) to the diet on the growth performance, serum biochemistry, antioxidant capacity, intestinal morphology, and cecal microbiota of yellow-feathered broiler chickens. In this study, 240 yellow-feathered broiler chickens at 26 days old were divided into two groups: the control group (CON group) received a standard diet, and the experimental group (CSB group) received a diet with 0.5 g/kg of a supplement called CSB. Each group had 6 replicates, with 20 chickens in each replicate, and the experiment lasted for 36 days. Compared to the CON group, the CSB group showed a slight but insignificant increase in average daily weight gain during the 26-62 day period, while feed intake significantly decreased. The CSB group exhibited significant increases in serum superoxide dismutase, catalase, and total antioxidant capacity. Additionally, the CSB group had significant increases in total protein and albumin content, as well as a significant decrease in blood ammonia levels. Compared to the CON group, the CSB group had significantly increased small intestine villus height and significantly decreased jejunal crypt depth. The abundance of Bacteroidetes and Bacteroides in the cecal microbiota of the CSB group was significantly higher than that of the CON group, while the abundance of Proteobacteria, Deferribacteres, and Epsilonbacteraeota was significantly lower than that of the CON group. These results suggest that adding CSB to the diet can improve the growth performance and antioxidant capacity of yellow-feathered broiler chickens while maintaining intestinal health.

Service performance evaluation of light-transmitting concrete lane markings on highways based on accelerated pavement testing

Applying light-transmitting concrete (LTC) to highway lane markings is a novel idea to increase the visual recognition distance and promote traffic safety. However, compared to its excellent visual recognition performance, its service performance has received little attention in the current research. This paper conducted an accelerated pavement test to investigate the behaviour of rutting depth, British Pendulum Number (BPN) and water permeability coefficient of the LTC lane markings. The results show that rutting depth of LTC is lower than that of asphalt pavement. As a result, small height steps appeared at the seam of the two parts. For the anti-sliding performance represented by the BPN, the BPN of LTC gradually exceeds asphalt pavement and maintains a slightly higher value. For the water permeability coefficient, the LTC is almost un-permeable, avoiding water damage during service. According to these findings, the LTC lane markings meet the requirements of highway service performance. .

Aeroacoustic characteristics of a strut-braced high-lift device

The aerodynamic and aeroacoustic performance of a strut-based high-lift device were evaluated and demonstrated for six different strut models. The primary objective of the study was to investigate the impact of strut modifications on reducing noise levels. The aerodynamic characteristics are presented with the aid of surface pressure distribution on the airfoil that remained consistent across all the tested configurations. The aeroacoustic results are presented as the near-field surface pressure fluctuations and far-field noise measurements to attain a profound comprehension of the noise generation mechanism. Although the Albatros strut exhibited the greatest reduction in tonal noise, the directivity pattern and the overall sound pressure level of the radiated noise demonstrated that the medium height strut configuration can achieve noise reduction of up to 8 dB. The near-field unsteady surface pressure measurements are suggestive of harmonic oscillations. The coherence studies carried out have shown a decrease in the tonal coherence for the small height strut configuration while the velocity field measurements performed in the wake of the high-lift device show no significant variation in flow patterns between different strut configurations.

Improved hydrodynamic properties and enhanced resistance to particle deposition and membrane fouling by millimeter-scale patterned membranes

Membrane fouling is considered a persistent challenge in membrane technology for water and wastewater treatment. Membrane surface patterning is a chemical-free means of controlling membrane fouling. Previous studies mainly focused on nano- and micro-scale patterns, with little attention paid on millimeter-scale patterns on the membrane surface. In this study, the millimeter-scale patterned microfiltration membranes with different pattern heights (PM50, PM55 and PM60) were fabricated, the performances in resisting particle deposition and membrane fouling with synthetic wastewater were examined compared with flat-sheet membrane (FM), and the underlying hydrodynamic mechanism was unveiled using computational fluid dynamics (CFD). CFD simulation results reveal that compared to micro- and nano-scale patterns, millimeter-scale patterns exert a notable increase in maximum velocity, average shear stress and maximum shear stress. All the three millimeter-scale patterned membranes exhibit superior resistance to both particle deposition and membrane fouling than FM, owing to the improvement of hydrodynamic properties instead of enlarged membrane area. PM55 shows the lowest flux decline ratios and least particle/foulant deposition among the three millimeter-scale patterned membranes in both particle deposition and membrane fouling experiments. Pattern height plays a crucial role, as small pattern height cannot generate significant vortices, while high pattern height leads to flow separation. For PM55, the vortices form in the valley regions and locate close to bulk flow, which help transport the deposited particles or foulants back to the bulk flow. The design of pattern configuration is suggested to be tailored based on particle size. Future research can focus on the pilot testing of millimeter-scale patterned membranes, as well as the long-term stability with actual influent.

Solidification behavior and continuous preparation process of high-quality Zr-based metallic glass plates based on twin-roll strip casting

Metallic glasses exhibit excellent comprehensive properties in a variety of disciplines including mechanics, magnetism, electricity, and chemistry, making them highly promising for various applications. However, the current lack of continuous and efficient preparation technology for metallic glasses not only hinders the research and application of various metallic glass products but also contributes to the high cost associated with their production. In this study, we incorporate the twin-roll strip casting technology into the continuous fabrication process of metallic glass plates. By conducting numerical simulations and practical experiments, we elucidated the solidification process of metallic glasses in the twin-roll strip casting process. A process control strategy was developed focusing on "small molten pool height and low exit temperature", which enabled successful preparation of high-quality Zr55Cu30Al10Ni5 metallic glass plates ranging from 0.13 to 0.56 mm in thickness. A reduced pool height can enhance the cooling rate of metallic glasses and suppress the formation of vortices and crystals within the molten pool. By employing a lower exit temperature, it is possible to achieve a metallic glass plate characterized by high-energy microstructure, exceptional mechanical properties, as well as superior shape and surface quality. This research provides valuable guidance for continuous production of superior-grade metallic glass plates using twin-roll strip casting technique.

Investigating strengthening and softening mechanisms in Al/Ni multilayers via molecular dynamics simulations of uniaxial compression

Due to their nanoscale features, nanometric multilayers can have a large variation in properties for varying bilayer heights. While the hardening at small feature sizes and the consequent softening at even smaller feature sizes have been observed for decades, the underlying mechanisms are still under debate. In this study, molecular dynamics uniaxial compression simulations are employed to study the mechanical properties of Al/Ni multilayers for bilayer heights h from 100 nm down to 5 nm. The effect of the microstructure on Young’s modulus and the yield strength was investigated. Furthermore, the mechanical properties of equiatomic and equivolumetric multilayers were compared. A comparison with experimental results from the literature showed good agreement. Both the hardening at intermediate bilayer heights as well as the softening at very small bilayer heights were observed. The results are discussed in the context of possible hardening and softening mechanisms. While the Hall–Petch effect with a h−1/2 scaling is not contradicted, it is shown that, although the underlying mechanisms are different, both the hardening as well as the softening are based on a general size effect with a scaling of ln(h)/h.

Overtopping performance of a multi-level CROWN wave energy convertor: A numerical study

The multi-level overtopping device is suitable to the wave climate characteristics in China, including small wave heights and large tidal ranges. In this study, an innovative overtopping device with multi-level conical reservoirs was proposed and studied numerically. A numerical model was established based on the commercial computational fluid dynamic platform ANSYS-Fluent® 16.0, which was carefully verified and validated using experimental results. The numerical model has good accuracy and capability in predicting complicated air-water interactions during overtopping processes. The slope ratio and guide-vane number for the reservoirs were optimized. In addition, the smaller opening mouth width of the lower reservoir benefits the overtopping performance of the upper reservoir. The optimized shape parameters could be employed for practical design of a prototype multi-level overtopping device.

High-Speed Near-Surface Tracking for Fast Atomic Force Microscope Scan Switching Based on the Squeeze Film Damping Effect

Atomic force microscope (AFM) is a crucial metrology tool in the semiconductor industry. However, the bottleneck of the AFM technique is its low efficiency, primarily owing to the time-consuming scanning point switching. The traditional method takes approximately one minute for a single switching. To shield the probe and sample, the switching should first lift the probe a considerable distance, move it to the next point, and finally engage the probe slowly to the sample surface. We propose a near-surface tracking method for use in fast scanning point switching. The probe-sample distance was sensed by the squeeze air film damping effect, and the probe was kept at a small constant height during the switching via feedback control. The method can decrease the lift and engage distance from approximately 1 mm to 5 μm, which was two order of reduction; thereby shortening the single switching time from 45 s to 6.1 s, which is an 87% reduction. Generally, the fast switching method can improve the measurement efficiency of the existing AFM working in the air, but it can not be used in liquid and vacuum. Furthermore, the proposed squeeze film damping effect based distance sensing method can be applied in various fields, such as vibration sensing and temperature drift measurement.

Stability of buoyancy–thermocapillary convection in molten silicon liquid bridge between two disks with different radii under gravity

By employing a linear stability analysis based on the spectral element method, we investigated the impact of radius ratio (Γr) on the stability of buoyancy–thermocapillary convection in a molten silicon liquid bridge (Pr = 0.011). This liquid bridge was located between two coaxial disks with different radii under the influence of gravity. The aspect ratio of the liquid bridge was maintained at Γ = 1, with a volume ratio Γv = 1 and a fixed height. To explore the physical mechanisms behind convection instability, a perturbation energy analysis was adopted. The free surface shape was determined using the Young–Laplace equation, and two distinct heating strategies were employed. In a top-heated liquid bridge, the convection stability under gravity is always stronger than under zero-gravity. However, in a bottom-heated liquid bridge, the convection stability under gravity is not consistently stronger than under zero-gravity; specifically, when 0.522 < Γr < 0.673, the convection stability under gravity is weaker than under zero-gravity. Despite the small height of the liquid bridge (approximately 2 mm), the maximum relative difference of the critical Marangoni number (Mac) between gravity and zero-gravity conditions reaches as high as 227.8%. In a bottom-heated liquid bridge, oscillatory instability occurs at larger radius ratios (Γr = 0.8) compared to the zero-gravity condition. Furthermore, all instabilities for various radius ratios and heating strategies were found to be of hydrodynamic in nature.

Spatial variability in herbaceous plant phenology is mostly explained by variability in temperature but also by photoperiod and functional traits.

Whereas temporal variability of plant phenology in response to climate change has already been well studied, the spatial variability of phenology is not well understood. Given that phenological shifts may affect biotic interactions, there is a need to investigate how the variability in environmental factors relates to the spatial variability in herbaceous species' phenology by at the same time considering their functional traits to predict their general and species-specific responses to future climate change. In this project, we analysed phenology records of 148 herbaceous species, which were observed for a single year by the PhenObs network in 15 botanical gardens. For each species, we characterised the spatial variability in six different phenological stages across gardens. We used boosted regression trees to link these variabilities in phenology to the variability in environmental parameters (temperature, latitude and local habitat conditions) as well as species traits (seed mass, vegetative height, specific leaf area and temporal niche) hypothesised to be related to phenology variability. We found that spatial variability in the phenology of herbaceous species was mainly driven by the variability in temperature but also photoperiod was an important driving factor for some phenological stages. In addition, we found that early-flowering and less competitive species characterised by small specific leaf area and vegetative height were more variable in their phenology. Our findings contribute to the field of phenology by showing that besides temperature, photoperiod and functional traits are important to be included when spatial variability of herbaceous species is investigated.

Mosaic Form of Turner Syndrome

Objective: To report a case of breast growth disorder in a mosaic form of Turner Syndrome. Turner syndrome is a chromosomal condition characterized by small height and primary ovarian insufficiency that affects one in every 2500 female births. Mosaicism is likely to occur when monosomy X develops in only a few cells during development. The clinical presentation of Turner syndrome mosaicism is atypical, with symptom severity varying based on the number of affected cells. This case discusses issues with secondary sex development, including mild hyperandrogenism, and explores how combination hormonal treatment can aid in enhancing secondary sex development.
 Method: Case Report.
 Case: A 21-year-old woman presented with chief complaint of the lack of breast enlargement. She exhibited normal genitalia internally and externally and had a regular menstrual cycle. Karyotyping revealed a mosaic pattern of 45, X/46, XX (1 percent/99%) with normal estradiol levels and elevated testosterone levels (indicating mild hyperandrogenism). The patient underwent two cycles of hormone therapy using Ethinyl Estradiol and Drospirenone, resulting in breast growth progression from Tanner stage 1 to Tanner stage 2.
 Conclusion: Mosaicism in Turner syndrome is plausible, and the severity of clinical symptoms correlates with the number of defective chromosomes. The presentation of Turner syndrome mosaicism varies, and therapy should be tailored to address specific symptoms. While breast development is observed in some girls with Turner Syndrome, instances of breast growth disorder may occur, involving estrogen activity and estrogen receptor sensitivity. Although the exact cause of impaired breast growth remains unknown, administering estrogen in such cases can improve secondary sexual characteristics.
 Keywords: mild hyperandrogenism, mosaicism, turner syndrome

Testing the hydrodynamic behavior of a loam soil by beerkan infiltration runs with six heights of water pouring

Interpreting and simulating rainfall partition into infiltration and surface runoff has to consider that surface soil hydraulic properties, including saturated soil hydraulic conductivity (Ks) and sorptivity (S), could change even at very short temporal scales. Soil deterioration due to water impact can be tested in the field by the multi-height beerkan (MHB) method, that is, by pouring water on the infiltration surface from different heights. Soil hydraulic properties can be estimated coupling the MHB method with the steady version of the Beerkan Estimation of Soil Transfer parameters procedure (BEST-steady). The MHB method with six heights of water pouring (H) in the range 0.03–2 m was applied on a relatively dry loam soil to investigate height of water pouring effects on i) the established infiltration process, and ii) Ks, S, the scale parameter of the water retention curve (hg) and the characteristic microscopic pore radius (λm). Higher heights of water pouring generally induced a slowdown of the infiltration process, smaller S, Ks and λm values and higher |hg| values. The S, Ks, |hg| and λm vs. H relationships were statistically significant but the fitted relationships for S and Ks were stronger than those for |hg| and λm, indicating a different sensitivity of the considered parameters to the height of water pouring. Small or negligible soil deterioration was observed for both small (H ≤ 0.25 m) and large (H ≥ 1.5 m) heights. Between these two extremes, the soil deteriorated as H increased, suggesting that the external solicitations were high enough to overcome the resistance of the porous medium but not so high to determine a complete soil alteration. The tested methodology appears promising to determine the effects of water impact on the soil hydrodynamic behavior and it could be applied to perform a soil hydraulic characterization usable for modelling hydrological processes.

Baseplate inferior offset affects shoulder range of motion in reverse shoulder arthroplasty in Asian population

BackgroundImpingement is a common complication of reverse shoulder arthroplasty. Placement of the baseplate with a wide impingement-free angle is ideal; however, there are few studies on Asian populations, which have smaller height and physique, and there is a lack of guidance on achieving optimal outcomes. The purpose of the present study was to explore the impingement-free range of motion reverse shoulder arthroplasty and analyze the suitable baseplate position or tilt for the Asian population using simulation software.MethodsWe uploaded computed tomography scan data from 20 Asian patients to three-dimensional (3D) simulation software. The implantation of the reverse shoulder arthroplasty component was performed on the 3D humerus and scapula using software, and range of motion was assessed until impingement occurred.ResultsThe range of motion in flexion significantly improved when the baseplate was lowered up to 3 mm inferiorly. Range of motion in abduction and internal and external rotation significantly improved as the baseplate was lowered up to 4 mm. There was no significant difference in range of motion in any motion after changing the inferior tilt, except in internal and external rotation.ConclusionsThe range of motion in abduction, flexion, and internal and external rotations significantly improved with increased inferior offset. These results may prove valuable in determining the optimal baseplate position for RSA, particularly in Asian populations.

Study of non-constant local cavitation suppression in micro-wedge structure

To alleviate the negative impacts of cavitation phenomenon on hydrodynamic machinery, such as mechanical vibration and noise, a hydrofoil model is established based on the micro-wedge structure, and numerical simulation of the hydrofoil is carried out by using the modified turbulence model k–omega shear stress transport (SST k–ω) to analyze the lift coefficient of drag, pressure pulsation, cavitation volume fraction, cavitation volume morphology, and turbulent kinetic energy distribution, and to reveal the inhibition of cavitation mechanism of the chord direction of the placement and the height of the micro-wedge structure coupling. The results show that the height of the micro-wedge structure determined by the thickness of the boundary layer is an important parameter affecting the cavitation performance, and the micro-wedge structure with a smaller height will produce better cavitation suppression, and the height of 0.05 mm has the best suppression effect, and the suppression of the main frequency of pulsation and the amplitude of pulsation shows a positive effect. The micro-wedge structure arranged on the hydrofoil can delay the change cycle of the cavitation volume to different degrees, in which the chordwise position of 3.5 mm has the best cavitation suppression effect, and the cavitation suppression rate is about 16.7%.

Pollination biology of Impatiens capensis Meerb. in non-native range.

Pollination biology in the widespread species Impatiens capensis Meerb. has only been studied in America, specifically in zones of the U.S.A. and Canada. In this study, we investigated the pollination biology of I. capensis using an integrative identification approach using morphological and molecular tools in four populations of Northwest Poland. We also determined and compared the functional characteristics of the pollinators of the introduced species from the study sites and the native ones reported, for the latter collecting information from bibliographic sources. Visitors were identified using standard morphological keys, including identifying and classifying insect mouthparts. Molecular identification was carried out using mitochondrial DNA's cytochrome oxidase subunit I (COI). We morphologically identified 20 species of visitors constituted by 17 pollinators and three nectar robbers. DNA barcoding of 59 individuals proved the identification of 18 species (also 18 BINs). The frequency of pollinator species was primarily made up of representatives of both Hymenoptera (75%) and Diptera (21%). The morphological traits, such as the chewing and sucking mouthparts, small and big body height, and robber and pollinator behavior explained mainly the native and introduced visitors' arrangements that allow pollination success. However, to understand the process comprehensively, further investigation of other causalities in pollination success and understanding the diversity of pollinators in outer native ranges are necessary.

Enhancing flexographic printing process with laser-induced microstructured printing forms for adjustable material transfer

Polymer optical waveguides are efficiently produced using flexographic printing, enabling fast and cost-effective manufacturing. However, the small print height results in a cross-sectional area too small for effective light coupling. To address this, multiple layers are printed to achieve the required waveguide dimensions. This sequential printing process prolongs processing time as material is repeatedly fed into the machine, potentially leading to issues like dust inclusions and oxygen inhibition. This study demonstrates modifying flexographic printing forms to increase transferred material height by up to 20 % in a single pass. Different microstructure geometries (hexagon, triangle, and square) with varying depths were inserted into the printing form to analyze their effects on material transfer. The use of a UV-nanosecond laser and a mask-based process allowed for precise insertion of the microstructures, resulting in high geometric accuracy and homogeneous ablation.

New Score for Predicting Results after Catheter Ablation for Atrial Fibrillation: VAT-DHF.

Catheter ablation (CA) for atrial fibrillation (AF) has been proven to have the highest efficacy in maintaining sinus rhythm. Several studies have proposed different scores for predicting post-procedural success, but most have not been validated in prospective cohorts. Further research is required to determine the optimal formulae. This study aimed to identify independent predictors of AF recurrence after CA and develop a composite score. Consecutive patients with persistent and paroxysmal AF who underwent CA were retrospectively analyzed. The independent predictors of recurrence were used to create a new predictive score. The cohort included 263 patients with a follow-up of 37.6 ± 23.4 months. Persistent AF, f-waves < 0.1 mV, indexed left atrium volume, the presence of type 2 diabetes, and smaller height were independent predictors of recurrence and were used to create a new scoring model, VAT-DHF (V = Volume, AT = AF Type, D = Diabetes, H = Height, F = f waves). The ROC curve for this new score showed an AUC of 0.869, p < 0.0001, 95% CI [0.802-0.936], while those for APPLE and CHA2DS2-VASc showed an AUC of 0.765, 95% CI [0.637-0.893] and an AUC of 0.655, 95% CI [0.580-0.730], respectively. Patients who had a VAT-DHF score between 0 and 3.25, 3.25 and 6, and ≥6, had success rates of 95.7%, 76.3%, and 25% (p < 0.0001), respectively. The novel VAT-DHF score is easy to calculate and may be a useful clinical tool for identifying patients with a low, intermediate, or high risk of AF recurrence after CA.

Scalable In‐Plane Directional Crystallization for The Printable Hole‐Conductor‐Free Perovskite Solar Cell Based on The Carbon Electrode

AbstractPopular solution‐processed approaches for producing the active layer of perovskite solar cells (PSCs) generally have to make compromise between crystallinity and compactness by inducing a rapid crystallization process with explosive nucleation and limited growth via removing solvent quickly. Here, a practical growth‐dominated in‐plane directional crystallization technique (IPDC) with a deeply retarded crystallization process for the scalable preparation of PSCs are reported. During the low‐temperature annealing, a tiny chamber with a small height is built atop the wet perovskite precursor film to restrain the vertical diffusion and removal of solvent vapor. The chamber eliminates the vertical solvent vapor gradient and induce a horizonal in‐plane gradient of solvent vapor pressure (SVP) toward the preset exhaust port which allows the slow escape of solvent vapor to outer space. In this way, nucleation is induced preferentially near the port and the as‐formed heterogeneous nuclei then grow continuously and directionally. With IPDC, sufficient filling of perovskite with high crystallinity and obvious growth orientation is realized in non‐ordered mesoporous scaffolds. An encouraging power conversion efficiency of 19.35% and 16.53% is achieved respectively for the 0.1 and 52.3‐cm2 printable mesoscopic hole‐conductor‐free PSCs with carbon electrodes.

Highly Crystalized MAPbX3 Perovskite Triangular Nanowire Arrays for Optoelectronic Applications.

Here, a facile fabrication approach for the high-quality 1D perovskite triangular nanowire (TNW) array synthesis through space-confined effect is reported. A soft stamp containing 1D triangular linear array pattern is used to confine the MAPbX3 solution and to guide the growth of the nanowires along the prescribed direction with good crystallinity. The further constructed photodetectors based on the obtained MAPbI3 TNWs exhibit superior photoresponse properties with a responsivity of (125.2 ± 2.5) A W-1 and detectivity of (2.8 ± 0.8) × 1013 Jones at the wavelength of 650 nm. This excellent performance is attributed to the highly crystalline TNW with optical anisotropy and a small asymptotic height, which reduces the probability of the photon reflection and promotes the carrier transport. More interestingly, the increased surface area of the triangular device can present superior flexibility after a couple of thousands of bending cycles. Furthermore, by fabricating 7 × 7 photodetector arrays, the potential image sensor application is demonstrated. The perovskite nanowire fabrication approach is scalable and compatible with current semiconductor manufacturing, which indicates their great potential in broad applications.