Width Ratio Research Articles

Study on heat transfer and pressure steady-state characteristics of a floating nozzle under a moving wall

This work considers the flow field as two-dimensional turbulent flow and studies the steady-state properties of heat transfer and the pressure of the suspension nozzle. An adiabatic wall parallel to the moving wall and two slit entrances at either end of the adiabatic wall make up the rectangular flow field. The SST k-ω\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$k - \\omega$$\\end{document} turbulence model is used in the turbulence computation. Both qualitative and quantitative analyses are conducted on the distribution of the flow field, temperature field, local Nusselt number, local pressure coefficient, average Nusselt number, and average pressure coefficient under various combination conditions. The findings indicate that when the suspension nozzle's flow field varies greatly, wall-jet velocity ratio is 0.1. A rise in Jet inclination angle is not helpful for the wall's suspension, and it has minimal effect on the flow field. The flow field is greatly influenced by separation space-slit width ratio. Larger separation space-slit width ratio values are advantageous for the wall's heat transmission but unfavorable for the wall's suspension. The flow field is most influenced by wall-jet velocity ratio. The wall's ability to convey heat is stronger the higher the wall-jet velocity ratio, but its ability to support weight falls.

Exploring the complexities of plant UV responses; distinct effects of UV-A and UV-B wavelengths on Arabidopsis rosette morphology.

UV-B radiation can substantially impact plant growth. To study UV-B effects, broadband UV-B tubes are commonly used. Apart from UV-B, such tubes also emit UV-A wavelengths. This study aimed to distinguish effects of different UV-B intensities on Arabidopsis thaliana wildtype and UVR8 mutant rosette morphology, from those by accompanying UV-A. UV-A promotes leaf-blade expansion along the proximal-distal, but not the medio-lateral, axis. Consequent increases in blade length: width ratio are associated with increased light capture. However, petiole length is not affected by UV-A exposure. This scenario is distinct from the shade avoidance driven by low red to far-red ratios, whereby leaf blade elongation is impeded but petiole elongation is promoted. Thus, the UV-A mediated elongation response is phenotypically distinct from classical shade avoidance. UV-B exerts inhibitory effects on petiole length, blade length and leaf area, and these effects are mediated by UVR8. Thus, UV-B antagonises aspects of both UV-A mediated elongation and classical shade avoidance. Indeed, this study shows that accompanying UV-A wavelengths can mask effects of UV-B. This may lead to potential underestimates of the magnitude of the UV-B induced morphological response using broadband UV-B tubes.

Combined Genioplasty and External Oblique Line Grafting: An Innovative Method to Improve Lower Facial Contour.

Microgenia and the accompanying plump cheeks or hamster-like facial contour are all unattractive appearances among the Asian. Genioplasty with autogenous bone grafting is one of the effective ways to improve microgenia, in which a suitable donor area with less additional damage, lower infection rate, and more excellent effect is crucial. Patients who had undergone genioplasty and autogenous external oblique line grafting (G-EOL) were followed up. The operation-related complications, preoperative, and long-term follow-up 3-dimensional spiral computed tomography (3D-CT) were collected and analyzed. Eight female patients who had received G-EOL and received 1 to 3 years of follow-up were included in this study. There were no short-term or long-term complications. CT data of bone of 8 patients and CT data of soft tissue of 6 patients at the preoperative and long term were compared. Through comparing CT data, the width at the level of the intersection of EOL and mandibular body, and the protrusion of the bony chin had improved significantly; the P values were all <0.001. Through measuring the soft tissue and analyzing the data, the ratio of lower and middle facial width, and the distance from the lower lip to Ricketts' line were all improved, with the P values 0.042 and 0.001, respectively. For patients with microgenia and hamster-like facial contour, the combination of genioplasty and autogenous external oblique line grafting is innovative and effective in improving both the front and side contour of the lower face simultaneously, with excellent stability, bone healing, and low complication rates.

Influence of Structural Parameters of Gearbox Seal System of Electrical Multiple Units on Seal Performance

The gearbox seal system is a critical component of the electrical multiple units drive system, with a direct impact on the safety and reliability of train operations. This study intends to analyze how structural parameters of the gearbox seal system influence the seal performance from the viewpoint of “oil–air separation and scavenge oil” by using a discrete phase model and volume of fluid. The results show that the oil–air separation performance is mainly affected by the oil droplets’ inertia force and the airflow traction force, and the scavenge oil performance is decided by the oil–air separation performance of each seal chamber. The relationships between seal chamber size, axial seal clearance width, height difference, scavenge oil hole diameter, and seal performance are analyzed, and the study also found that optimizing the stator chamber depth–width ratio of the seal system studied in this paper at 2.5, reducing the rotor chamber depth–width ratio and axial seal clearance width, and increasing the relative height difference can improve the seal performance. And increasing the scavenge oil hole diameter also enhances the seal system’s performance. The simulation results can be used as design references for gearbox seal systems.

New formula of vegetation roughness height and Darcy–Weisbach friction factor in channel flow

Assessing the flow resistance caused by vegetation in rivers is a hot topic in the field of hydraulics and eco-hydrology. Based on mathematical experiments by first-order closure models, new roughness height of vegetation is proposed linked with the three factors that vegetation arrangement concentration, submergence ratio, and the ratio of width to height of vegetation. Besides, new Darcy–Weisbach friction factor is built for vegetated flow. Moreover, both collected and present experimental data are adopted for verification of the roughness height and friction factor. Compared with models from other research groups, results show that the new formulas proposed in this study have high accuracy for predicting vegetation resistance in ecological restoration and water resources management in rivers.

Numerical investigation of the overall thermal and thermodynamic performance of a high concentration ratio parabolic trough solar collector with a novel modified twisted tape insert using supercritical CO2 as the working fluid

Supercritical CO2 (sCO2) is favoured as the next-generation working fluid for advanced high-temperature and high-concentration ratio parabolic trough solar collectors (PTSC) due to the fluid’s low cost, availability and thermal stability at high temperatures. However, the lower thermal transport properties of sCO2 compared to conventional working fluids necessitate heat transfer enhancement of receivers using sCO2. In this study, a combined and extensively validated approach using Monte-Carlo ray tracing for optical analysis and computational fluid dynamics (CFD) for thermal and thermodynamic analysis were used to investigate the overall thermal and thermodynamic performance of a high concentration ratio sCO2-based PTSC with a modified twisted tape (MTT) inserts in the receiver. MTT inserts with twist ratios in the range of 2.0 to 4.0 and width ratios in the range of 0.75 to 0.95 were investigated. Results show enhancement of the heat transfer performance by up to 73% and thermal efficiency by 6%, and reduction of the receiver heat losses and circumferential temperature gradients when the MTT inserts are used. In addition to presenting results using the first law of thermodynamics, this study also considered the second law of thermodynamics by evaluating the entropy generation rates due to heat transfer and fluid friction irreversibilities. Results showed that the use of MTT inserts caused a reduction in the total entropy generation rates, with the lowest irreversibility occurring at a Reynolds number of 1,650,000 for a twist ratio of 2.0 and width ratio of 0.95.

Investigation of the predictive value of systemic immune inflammation index (SII) and prognostic nutritional index (PNI) on mortality in patients with endoprosthesis after hip fracture.

In this research, we aimed to investigate the predictive value of the systemic immune inflammation index and prognostic nutritional index on mortality among patients with an endoprosthesis after a hip fracture. In this retrospective, cross-sectional study, a total of 915 patient files applied to our hospital between 2020 and 2023 with an endoprosthesis after a hip fracture were subjected to the study. The patients were divided into 2 groups: alive (n = 396; 43.3%) and deceased (n = 519; 56.7%). The eosinophil-to-lymphocyte ratio, hemoglobin-to-red cell distribution width ratio (HRR), mean platelet volume-to-platelet ratio (MPVPR), neutrophil-to-lymphocyte ratio, monocyte/lymphocyte ratio, platelet-to-lymphocyte ratio, MPV-to-lymphocyte ratio, monocyte-to-eosinophil ratio (MER), neutrophile-to-monocyte ratio, systemic inflammation index (SII), and prognostic nutritional index (PNI) parameters of the patients were evaluated. The mortality rate was higher among male patients, with a statistically significant difference (P < .05). The follow-up duration, albumin, HGB, eosinophil, lymphocyte, eosinophil %, eosinophil-to-lymphocyte ratio, HRR, and PNI means were significantly higher in the living group (P < .05). Age, MPV, MPVPR, neutrophil-to-lymphocyte ratio, monocyte/lymphocyte ratio, platelet-to-lymphocyte ratio, MPV-to-lymphocyte ratio, MER, and systemic inflammation index were significantly higher in the deceased group (P < .05). The predictive value of gender (B = -0.362; P < .01), age (B = 0.036; P < .01), HRR (B = -1.100; P < .01), MPVPR (B = 8.209; P < .01), MER (B = 0.006; P < .01), and PNI (B = -0.078; P < .01) were statistically significant at the multivariate level. The time of death was significantly predicted by gender (B = 0.10; P < .05), age (B = -0.02; P < 0 = 1), HRR (B = 0.61; P < .01), MPVPR (r = -4.16; P < .01), MER (B = -0.01; P < .05), and PNI (B = 0.03; P < .01). The predictive value of PNI for the 30-day mortality rate was statistically significant (AUC: 0.643; P < .01). For a PNI cutoff value of 34.475, sensitivity was 69.7%, and specificity was 51.1%. The PNI has predictive value both in estimating overall mortality and in predicting the 30-day mortality rates among patients undergoing endoprosthesis after a hip fracture.

Geometric influence of width ratio and contraction ratio on droplet dynamics in microchannel using a 3D numerical simulation

AbstractMicrochannel geometry is an important factor in determining droplet dynamics in droplet‐based microfluidic systems, much like fluid properties and flow conditions. In this context, two important geometric parameters—the contraction ratio () and the width ratio ()—that are limited to particular value ranges are taken into consideration for evaluation. These parameters interact with the capillary number () and viscosity ratio () to affect different aspects of droplet migration and manipulation, such as trap and squeeze regimes. A theoretical model is proposed, and a three‐dimensional numerical simulation method is used in this work. This model predicts the change from trap to squeeze, which is caused by the interaction of the previously mentioned variables. Interestingly, an inverse correlation exists between the width ratio and the critical capillary number for this transition, which is determined as . Furthermore, the investigation explores the droplet elongation and velocity ratio during their passage through the microchannel. By matching input parameters with microchannel geometry, this information may be useful for the design of microfluidic systems, which would facilitate the careful control and manipulation of droplets.

In-situ observations of cloud microphysics over Arabian Sea during dust transport events

The unique in situ measurements of clouds and precipitation within the shallow and deep cumulus over the north-eastern Arabian Sea region during the Indian monsoon are illustrated in this study with a focus on droplet spectral parameters. The observational period showed a significant incursion of Arabian dust and the presence of giant cloud condensation nuclei (GCCN), modifying the cloud and precipitation spectral properties. Warm rain microphysics supported the mixed-phase development in these clouds and exhibited hydrometeors of snow, graupel and large aggregates as part of ice processes. Cloud base droplet number concentration is about 142 ± 79 cm−3 which is one third of the cloud condensation nuclei (CCN) number concentration at 0.2% supersaturation. A rapid broadening of droplet size distribution (DSD) near to the cloud base was noted in contrast to polluted continental clouds. Relationship between the relative dispersion ( ε; the ratio of DSD spectral width ( σ ) to mean radius ( rm )) and liquid water adiabatic fraction (AF) indicates that the entrainment effect has increased relative dispersion significantly (2–3 times larger) in these clouds. Effective radius ( reff ) is found to be proportional to mean volume radius ( rv ) with a proportionality constant ( β ) that varies between 1.0–1.6, depending on the spectral dispersion parameter. Drop size distributions for the small cloud droplets with size range 2–50 μ m and the large drizzle drops (or ice hydrometeors) with size range 100–6400 μ m are parameterized using the gamma function distributions useful for large-scale cloud models.

Cross-sectional geometry effect on bending strength of gold micro-cantilever with trapezoidal cross-section

Gold is a promising material for movable components in MEMS devices by the high mass density, which allows reduction of the Brownian noise. Mechanical properties of metallic materials are known to be affected by the sample size effect. When bending test is utilized, the sample geometry effect is another factor. In this study, effects of the shape of the cross-section, or the cross-sectional geometry effect, are evaluated using micro-cantilevers with a trapezoidal cross-section. The yield stresses are ranged from 112 MPa to 185 MPa in micro-cantilevers composed of single crystalline gold, and the yield stresses varied from 372 MPa to 489 MPa in polycrystalline gold micro-cantilevers. The yield stress is found to be higher in the micro-cantilever having a smaller ratio of the top width over the bottom width, which demonstrates the cross-sectional geometry effect. Also, the cross-sectional geometry effect is more significant in the polycrystalline micro-cantilevers.

Analysis of the interactive effects of scavenge parameters on spark ignition two-stroke diesel engines

The scavenging efficiency of a two-stroke diesel engine affects the formation of the mixture in the engine cylinder, which in turn affects the engine’s performance. A one-dimensional simulation model of a two-stroke diesel engine is established using GT-POWER, and the model with original experimental data is calibrated as boundary conditions. Firstly, the influence of crankcase compression ratio on engine performance of the two-stroke engine was investigated to obtain an appropriate crankcase compression ratio; Then, based on the optimization index of scavenging efficiency, the optimal combination of engine air port structure and timing is obtained through orthogonal optimization calculation method. To achieve higher scavenging efficiency, when the phase of the air port remains unchanged, a scavenging port width ratio of 1.0 and an exhaust port width ratio of 0.8 can achieve a scavenging efficiency of 97.2%; When the air port size remains unchanged, the engine scavenging efficiency reaches 96.44% when the scavenging port timing is 123° CA and the exhaust port timing is 89° CA.

Unveiling very young O stars

Context. O-type stars are known to significantly contribute to both the dynamics and evolution of galaxies. Massive and luminous, they probably control and regulate the galaxies star formation rates. The stellar feedback generated by such cosmic beasts can strongly affect the local star formation rate, with effects in the current (and future) generations of low and intermediate mass stars, and possibly also in the disruption process of the galaxies’ giant gas reservoirs. Aims. For this work I performed a redetermination of the spectral types and effective temperatures of the Galactic O-type stars MSP182, MSP183, MSP199, VPHAS-01338, and VPHAS-01273. Methods. From a careful examination of the spectral features present in the blue optical spectral region, it was possible to identify several nitrogen lines usually only seen in the blue optical spectra of O2–O3 stars. From the nitrogen ionic equivalent width ratios measured in the spectra of MSP182, MSP183, MSP199, VPHAS-01338, and VPHAS-01273, and in those of standard stars of the O2–O4 spectral types, earlier spectral types and hotter effective temperature values were derived. Results. Two O2V((f*))z, together with three new O3 V stars are now firmly identified in the Westerlund 2 region. Besides RFS1 in NGC 3603, the O2 V stars found in Westerlund 2 are the only other exemplars known to date in the Milky Way. From the nitrogen equivalent width line ratios measured in the spectra of standard stars of the O2–O4 spectral types, linear relations between the N IVλ4058/N IIIλ4640 ratio and the effective temperature in the 47 000–51 000 K range were derived. Based on my spectroscopic analysis of the science targets and the use of a HRD, a mean heliocentric distance of 5 kpc to Westerlund 2 was computed, a result that is in line with the mean heliocentric distance of 5.3 ± 1.5 kpc obtained from the associated Gaia DR3 parallaxes and distances. Conclusions. The Westerlund 2 massive stars studied in this work probably share a common evolutionary process that might be representative of the evolutionary ages of a large fraction of the cluster’s O-type stellar population, which seems to be much younger than 1 Myr.

A strain gage technique for measuring the mode II stress intensity factors

In this paper, we propose a strain gage technique that allows an accurate measurement of the mode II stress intensity factors (SIFs). In order to ensure a good KII measurement, the size of the correct radial location of the strain gages is identified by using a methodology based on finite element analysis (FEA) and consolidated by solid theoretical foundations. The extent r1,max and r2,max of the validity of the five- and six-term representation of generalized Westergaard stress functions, which requires the use of two and three strain gages, respectively, is determined using the proposed method, and its dependence on the crack length to width ratio is also investigated. Numerical results obtained are in good agreement with the theoretical predictions, and confirm that the present method makes it possible to determine the KII with high precision when two (or three) strain gages are well placed within r1,max (or r2,max). Also, the numerical experiments show that the use of three strain gages is necessary when the size of the linear behavior region r1,max is very small. In addition, the effect of friction between the crack lips was checked and shown to have no effect on KII in pure mode II.

Viscoelastic modelling and analysis of two-dimensional woven CNT-based multiscale fibre reinforced composite material system

Carbon nanotube (CNT) has fostered research as a promising nanomaterial for a variety of applications due to its exceptional mechanical, optical, and electrical characteristics. The present article proposes a novel and comprehensive micromechanical framework to assess the viscoelastic properties of a multiscale CNT-reinforced two-dimensional (2D) woven hybrid composite. It also focuses on demonstrating the utilisation of the proposed micromechanics in the dynamic analysis of shell structure. First, the detailed constructional attributes of the proposed trans-scale composite material system are described in detail. Then, according to the nature of the constructional feature, mathematical modelling of each constituent phase or building block’s material properties is established to evaluate the homogenised viscoelastic properties of the proposed composite material system. To highlight the novelty of this study, the viscoelastic characteristics of the modified matrix are developed using the micromechanics method of Mori–Tanaka (MT) in combination with the weak viscoelastic interphase (WI) theory. In the entire micromechanical framework, the CNTs are considered to be randomly oriented. The strength of the material (SOM) approach is used to establish mathematical frameworks for the viscoelastic characteristics of yarns, whereas the unit cell method (UCM) is used to determine the viscoelastic properties of the representative unit cell (RUC). Different numerical results have been obtained by varying the CNT composition, interface conditions, agglomeration, carbon fibre volume percentage, excitation frequency, and temperature. The influences of geometrical parameters like yarn thickness, width, and the gap length to yarn width ratio on the viscoelasticity of such composite material systems are also explored. The current study also addresses the issue of resultant anisotropic viscoelastic properties due to the use of dissimilar yarn thickness. The results of this micromechanical analysis provide valuable insights into the viscoelastic properties of the proposed composite material system and suggest its potential applications in vibration damping. To demonstrate the application of developed novel micromechanics in vibration analysis, as one of the main contributions, comprehensive numerical experiments are conducted on a shell panel. The results show a significant reduction in vibration amplitudes compared to traditional composite materials in the frequency response and transient response analyses. To focus on the aspect of micromechanical behaviour on dynamic response and for the purpose of brevity, only linear strain displacement relationships are considered for dynamic analysis. These insights could inform future research and development in the field of composite materials.

Reverse sural island flap for reconstruction of ankle and posterior heel defect: clinical experience with surgical modifications of pedicle

Introduction: Soft tissue defects around the ankle and posterior heel need stable flap coverage for proper healing and satisfactory recovery of function. Constant and reliable vascular supply of reverse sural island flap (RSIF) have made it a popular choice for reconstruction of these defects. In this study, the outcome of RSIF with few modifications in the pedicle area were discussed. Methods: This prospective study was carried out in National Institute of Traumatology and Orthopedic Rehabilitation (NITOR), Dhaka duing April 2019 to June 2020. Total 31 patients with soft tissue defect around ankle and posterior heel were reconstructed with reverse sural artery island flap. The soft-tissue defects were located, infront of ankle in 3 cases, over lateral malleolus in 7 cases, over medial malleolus in 5 cases, over tendoachilles in 12 cases, involving two or more areas of posterior heel, tendoachilles and lateral malleolus in 4 cases. Average Flap length and width were 9.67(+1.60) cm &amp; 6.38(+0.76) cm respectively. Pedicle area of flap was modified by including a 2 cm skin extension in the middle along with additional adipofascial tissue on both sides to improve venous return. Pedicle length to width ratio was maximum of 3:1. Average length of pedicle was 7.2 + 1.7 cm. Results: All flaps except three survived completely without any complications. One patient (3%) had partial necrosis and another one (3%) had marginal necrosis of flap due to venous congestion. Epidermolysis was observed in 3% cases. Conclusions: The distally based superficial sural artery island flap is a versatile, reliable procedure useful in reconstruction of the lower extremity. Modifying the design of pedicle area increases safety by reducing venous congestion which ultimately leads to increase flap survivability. J Bangladesh Coll Phys Surg 2024; 42: 126-132

Investigation of natural convection and entropy generation of non-Newtonian flow in molten polymer-filled odd-shaped cavities using finite difference lattice Boltzmann method

This study examines the natural convection heat transfer (NCHT) and entropy generation (EG) of a non-Newtonian (NN) flow inside an odd-shaped cavity filled with molten polymer. The cavity configuration comprises hot internal walls, cold external walls, and insulated remaining walls. The finite difference lattice Boltzmann method (FDLBM) is employed to solve the governing equations involved. The input parameters span a range of values, with Rayleigh number (Ra) varying from 104 to 105, power-law index (n) covering a range from 0.5 to 1.5, and width ratio (WR) ranging from 0.2 to 0.4, while maintaining Prandtl number (Pr) at a constant value of 10. The results revealed that at Ra values of 104 and 105, the overall entropy increases as the WR increases from 0.2 to 0.4 and decreases as the n index increases. In contrast to dilatant fluids, where heat transfer (HT) decreases as the n index increases from 1 to 1.5, pseudo-plastic fluids show an opposite trend with HT increasing as the n index decreases from 1 to 0.5. This trend is attributed to the general decrease in the average Nusselt number (Nu) as the n index increases. Additionally, it is observed that the n index has no significant impact on the average Nu due to low buoyancy force at Ra = 104 and WRs of 0.2 and 0.3. However, it notably influences the Bejan number (Be) across all WRs. Overall, the present model demonstrates excellent agreement with previous numerical results, affirming the FDLBM as a superior, reliable, and well-suited technique for relevant applications. These results suggest the potential to extend the application of the FDLBM approach to various cavity shapes, allowing for a comprehensive exploration of NCHT and EG under various conditions.

Bladder height to width ratio as a surrogate marker for non-physiological storage pressures in children with spinal dysraphism.

Spinal dysraphism is the most frequent cause of neurogenic bladder. Urodynamic study (UDS) is an important component of the follow-up of a child with neurogenic bladder. However, it suffers from a lack of widespread availability and is further hampered by technical difficulties and difficulty in its interpretation in children. A neurogenic bladder often appears vertically elongated; only limited and sparse literature is available regarding objectively defining the bladder shape and the urodynamic parameters in the cohort. This study aimed to investigate the usefulness of the bladder's height-to-width ratio (HWR) on cystogram as a screening tool for identifying "non-physiological" bladder pressures in children with spinal dysraphism. A prospective study was undertaken to evaluate children operated for spinal dysraphism. Cystogram, ultrasonography and UDS evaluation were performed. HWR was calculated by the ratio of the maximum height to the maximum bladder width at maximum cystometric capacity (MCC), where MCC was calculated using standard Koff's formula, given by (age in years + 2) *30ml in children more than one year and weight *7ml for infants. The children were categorised into groups based on maximum detrusor pressure (MDP) into two groups (MDP ≥ 30cmH2O and MDP < 30cmH2O). A receiver-operative characteristic curve was constructed to analyse the sensitivity and specificity of HWR in predicting the MDP. A total of 53 children, operated for spinal dysraphism, met the study criteria during the study period, from March 2021 to September 2022. The median age of children was 4years (IQR-3-5.5years). The HWR ratio was compared between the two groups and was significantly higher for the non-physiological pressure bladders than for physiological pressure bladders (mean of 1.55 vs 1.26, p = 0.001). On evaluating the sensitivity and specificity of HWR for discerning children with non-physiological bladder pressures were 87.5% and 48.28%, respectively. The area under the curve (AUC) was 0.781, with a cut-off value of 1.3. We attempted to evaluate the HWR based on bladder shape objectively. We demonstrated a moderate correlation between the bladder shape and the bladder pressures. An HWR of 1.3 or higher could be significant for identifying a non-physiological bladder storage pressure. The height to width ratio of the bladder on cystogram is a useful tool as a surrogate marker for non-physiological storage pressures in bladders of children with spinal dysraphism.

Numerical investigation on the hydrodynamic and conversion performance of a dual cylindrical OWC integrated into a caisson-type breakwater

The hydrodynamic performance of an integrated oscillating water column (OWC) combined with a cylindrical caisson type breakwater was investigated. A three-dimensional numerical wave tank was established to simulate the overall energy conversion performance and hydrodynamics of the integrated system with the software Star-CCM+. The developed Computational Fluid Dynamics (CFD) model was initially verified with the published physical results and numerical results derived from an analytical solution. The effects of the structural geometry and the pneumatic damping of the PTO system on the wave absorption and power conversion efficiency of the proposed device were investigated using this developed model. Based on this proposed numerical model, the velocity of the air flow, the corresponding air pressure characteristics in the air turbine nozzle and chamber zone were discussed. The results indicate that this proposed half-open land based OWC is adapted to absorb shorter nearshore waves, characterized by dimensionless wave number kd approaching 1.49. Furthermore, a larger opening inlet zone for this proposed OWC would shift the resonant corresponding kd to higher wave frequencies, while lowering the opening inlet could help to increase the power extraction efficiency for long waves. The peak hydrodynamic efficiency is observed at a ratio of OWC inlet width to diameter B/D of 0.97, which is approximately six times larger than that at B/D = 0.5. The inclusion of an impulse turbine yields a more uniform pressure distribution within the central chamber and effectively mitigates wave reflection for smaller incident waves, with maximum efficiency achieved using 37 blades. The property of the efficiency mitigation with insufficient certain intake depth of the wave chamber should be avoided for system design.

Geometrical Optimization of Segmented Thermoelectric Generators (TEGs) Based on Neural Network and Multi-Objective Genetic Algorithm

In this study, a neural network and a multi-objective genetic algorithm were used to optimize the geometric parameters of segmented thermoelectric generators (TEGs) with trapezoidal legs, including the cold end width of thermoelectric (TE) legs (Wc), the ratios of cold-segmented length to the total lengths of the n- and p-legs (Sn,c and Sp,c), and the width ratios of the TE legs between the hot end and the cold end of the n- and p-legs (Kn and Kp). First, a neural network with high prediction accuracy was trained based on 5000 sets of parameters and the corresponding output power values of the TEGs obtained from finite element simulations. Then, based on the trained neural network, the multi-objective genetic algorithm was applied to optimize the geometric parameters of the segmented TEGs with the objectives of maximizing the output power (P) and minimizing the semiconductor volume (V). The optimal geometric parameters for different semiconductor volumes were obtained, and their variations were analyzed. The results indicated that the optimal Sn,c, Sp,c, Kn, and Kp remained almost unchanged when V increased from 52.8 to 216.2 mm3 for different semiconductor volumes. This work provides practical guidance for the design of segmented TEGs with trapezoidal legs.

Multi-Objective Design of a Horizontal Flow Subsurface Wetland

An artificial wetland is used to treat gray, waste, storm or industrial water. This is an engineering system that uses natural functions of vegetation, soil and organisms to provide secondary treatment to gray water. In the physical design of each artificial wetland, there are various action factors that must meet certain characteristics so that the level of gray-water pollution is reduced. In this sense, several design methodologies have been developed and reported in the literature, but some are customized designs and often do not meet the required decontamination objectives. This challenge increases as the complexity of the task in its structure also increases. Particularly in this work, a multi-objective evolutionary algorithm is used to optimize the physical design of a horizontal flow subsurface wetland (HFSW) for gray-water treatment. The study aims to achieve two objectives: first, to minimize the physical volume, and second, to maximize the contaminant removal efficiency. The defined objective functions depend on six design variables called hydraulic retention time, width, length, water depth inside the wetland, substrate depth and slope. Three constraint functions are also defined: removal efficiency greater than 95%, physical volume below 500 m3 and compliance with a length–width ratio is 3:1, varying the population size and number of generations equal to 200, 400, and 600. The set of solutions according to the number of generations as well as the Pareto front corresponds to the best solution that complies with the constraints of the problem of oversizing the HFSW, and the Pareto front shows the interaction between the objectives and their behavior, reflecting the problem’s nature as minimization–maximization.