Diameter Ratio Research Articles

Effects of Liquid Nitrogen Freezing, Immersion Freezing, and Air Freezing on Properties of Perca fluviatilis Fillets and Analysis of Potential Protein Markers Based on Label-Free Proteomics

The effects of liquid nitrogen freezing (LNF), immersion freezing (IF), and air freezing (AF) combined with thawing in running water at 20°C on the quality of Perca fluviatilis fillets were investigated using label-free proteomics technology. The ice crystal equivalent diameter (12.30±0.33 μm) and ice crystal area ratio (7.61±2.81%) of LNF were significantly lower than IF and AF (P < 0.05). The ice crystals of LNF were small and evenly distributed, and the mechanical damage to the cell structure is small. LNF samples were closer to fresh samples regarding texture. Proteomic analysis identified a total of 11 differentially abundant proteins (DAPs) associated with LNF, IF, and AF. Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis indicated that these DAPs were primarily catalytic proteins, metabolic enzymes, and structural proteins involved in metabolic pathways such as pyruvate metabolism, glycolysis, and arginine and proline metabolism. Among them, tubulin beta chain (A0A8C3G6F1), carbonic anhydrase (A0A2P1JP97), immunoglobulin-like and fibronectin type III domain-containing protein 1 (A0A484DE91), and tubulin are predicted to serve as potential protein markers for freezing, thawing loss, hardness, and springiness of Perca fluviatilis fillets post-thawing. These findings provide a basis for further research into the quality change induced by protein degradation of frozen Perca fluviatilis.

Elastic Stable Intramedullary Nailing in Length Stable Versus Unstable Pediatric Femoral Shaft Fractures: A Comparison of Clinical, Radiographic, and Pedobarographic Outcomes.

Pediatric diaphyseal femoral fracture (PDFF) is one of the most common injuries requiring hospitalization. Elastic stable intramedullary nailing (ESIN) is commonly used for PDFFs in ages 5 to 11. The optimal treatment method for length unstable PDFF is a subject of ongoing debate. This study aimed to compare clinical, radiographic, and pedobarographic outcomes of ESIN between length stable and unstable PDFF. We retrospectively reviewed patients undergoing ESIN treatment for isolated PDFF between 2016 and 2021. Exclusion criteria were (1) history of ipsilateral or contralateral lower extremity fractures, (2) highly comminuted or segmental fractures, (3) body weight >50kg, and (4) comorbidities affecting bone quality, range of motion, or neurologic status. The patients were divided into 2 groups according to length stability. Clinical, radiographic, and pedobarographic data were then assessed to compare groups. Twenty-five patients were included (17 length stable and 8 length unstable PDFF) with a mean age of 73.6±17.8 months. There was no significant difference between groups in age, side of injury, body weight, follow-up duration, and nail-canal diameter ratio. Mean deformity in the fracture site in the early postoperative x-rays was not significantly different between groups (P=0.661). After a mean follow-up of 27.8±14.2 months (range, 12-67), there was no significant difference in mechanical axis deviation, distal femur joint orientation angle, or limb-length discrepancy in both groups. The pedobarographic assessment revealed that the length unstable group had a significantly higher external foot progression angle in the injured extremity (9.8°±6.9° vs. 1.3°±5.6°, P=0.031). However, the length stable group had no significant difference in the foot progression angle (4.9°±5° vs. 3°±4.3°, P=0.326). There was no significant difference in either group for other pedobarographic parameters. ESIN is a safe and effective option for length-unstable PDFF, yet attention should be paid to the rotational alignment. Although significant external rotation deformity occurs in length-unstable PDFF, it has no implications for the other pedobarographic parameters. Level IV.

Nuclear long diameter as a new criterion to distinguish high-grade urothelial carcinoma cells from benign reactive cells.

Recently, the nuclear area has attracted attention as a morphological parameter to differentiate high-grade urothelial carcinoma (HGUC) cells from benign reactive cells. The nuclear long diameter (NLD) strongly correlates with the nuclear area and is easy to subjectively estimate. Therefore, this study examined the usefulness of the NLD-to-neutrophil diameter ratio for detecting HGUC cells in urine cytology. This study included 29, 26 and 18 patients with HGUC, glomerular disease and urolithiasis respectively. An image analysis system was used to measure the NLD of HGUC and benign reactive cells (reactive renal tubular cells and reactive urothelial cells) and the neutrophil diameter that appeared in the voided urine in these cases. The NLD index was calculated using the NLD-to-neutrophil diameter ratio. We subsequently compared HGUC and benign reactive cells with respect to NLD and NLD indices. In addition, the HGUC cell group and benign reactive cell group were compared by selecting the five cells with the largest NLD and NLD index on each slide. The NLD and NLD indices of HGUC cells were significantly higher than those of benign reactive cells in all cells and in the five cells with the largest NLD and NLD indices. The cut-off value of the NLD index for detecting HGUC cells was 1.25 in all cells and 1.80 in the five cells with the largest NLD index. The NLD index is a useful parameter that can be introduced into routine microscopic examinations to differentiate HGUC cells from benign reactive cells.

Discrete element model for effective electrical conductivity of spark plasma sintered porous materials

AbstractThis paper aims to analyse electrical conduction in partially sintered porous materials using an original resistor network model within discrete element framework. The model is based on sintering geometry, where two particles are connected via neck. Particle-to-particle conductance depends on neck size in sintered materials. Therefore, accurate evaluation of neck size is essential to determine conductance. The neck size was determined using volume preservation criterion. Additionally, grain boundary correction factor was introduced to compensate for any non-physical overlaps between particles, particularly at higher densification. Furthermore, grain boundary resistance was added to account for the porosity within necks. For numerical analysis, the DEM sample was generated using real particle size distribution, ensuring a heterogeneous and realistic microstructure characterized by a maximum-to-minimum particle diameter ratio of 15. The DEM sample was subjected to hot press simulation to obtain geometries with different porosity levels. These representative geometries were used to simulate current flow and determine effective electrical conductivity as a function of porosity. The discrete element model (DEM) was validated using experimentally measured electrical conductivities of porous NiAl samples manufactured using spark plasma sintering (SPS). The numerical results were in close agreement with the experimental results, hence proving the accuracy of the model. The model can be used for microscopic analysis and can also be coupled with sintering models to evaluate effective properties during the sintering process.

Numerical investigation of CH4/H2/air micro-mixing combustion flow in a micro gas turbine combustor with different head-end structures

In order to investigate the premixed combustion characteristics of CH4/H2/air in a micro-mixing combustor, the effects of different micro-mixing head-ends (HE1, HE2, HE3) and hydrogen mixing ratios on the temperature distribution, heat transfer process, emission characteristic, flames shape are analyzed. The results show that compared with swirl head-end combustion, the micro-mixing combustion performance is better. Among the three head-ends, HE3 has the best combustion characteristics and stable flames. The temperature distribution in the high-temperature zone is uniform, and low-temperature zone is concentrated near the jet, which can suppress the flashback. The velocity and temperature gradient near the central axis of jet streams show a strong synergistic effect. The flames are plume shaped and flames stability is mainly influenced by the H2 combustion process. Increasing the jet diameter, decreasing the jet spacing and increasing the hydrogen mixing ratio all contribute to the flames stability, but these three methods can stabilize the flames by affecting fluid Reynolds number, interaction between small flames and combustion rate, respectively. Moreover, small jet diameter and high hydrogen mixing ratio can reduce OTDF, which contributes to improve outlet temperature uniformity.

Influence of Length to Diameter Ratio of the Skirt on Horizontal Bearing Characteristics of Tripod Suction Jacket Foundation in Sandy Soil

Influence of Length to Diameter Ratio of the Skirt on Horizontal Bearing Characteristics of Tripod Suction Jacket Foundation in Sandy Soil

On the Spanwise Periodicity within the Gap between Two Different-Sized Tandem Circular Cylinders at Re = 3900

Although the spanwise periodicity within the gap between two tandem circular cylinders has been observed by some researchers, there is a lack of systematic research on the properties of this periodicity. For the spanwise periodicity within the gap, this study aims to ascertain its characteristics, its influences on the flow field, and its variation trend with increasing spacing ratio. By numerically simulating the flow around two tandem circular cylinders with a diameter ratio of d/D = 0.6 and seventeen spacing ratios (L/D = 1.00~6.00) at Re = 3900, this study shows four flow regimes: Reattachment Flow (L/D = 1.00~3.15), Bi-stable Flow (L/D = 3.24), Intermittent Lock-in Co-shedding (L/D = 3.30~3.50), and Subharmonic Lock-in Co-shedding (L/D = 4.00~6.00). Further, depending on the spanwise periodicity length of the time-averaged flow structures (i.e., Pz) within the gap, Reattachment Flow is, for the first time, subdivided into three new sub-flow regimes: Small-scale Periodic Reattachment (L/D = 1.00~1.50, Pz/D = (0, 4]), Large-scale Periodic Reattachment (L/D = 2.00~2.25, Pz/D &gt; 4) and Non-periodic Reattachment (L/D = 2.50~3.15, no spanwise periodicity). The formation mechanisms are elaborated by analyzing the combined effect of both the L/D value and the spanwise-averaged time-averaged reattachment angle of the downstream cylinder. Moreover, this study proves that the newly defined Small-scale Periodic Reattachment and Large-scale Periodic Reattachment are responsible for the pronounced asymmetry of the flow along the transverse direction within the gap. In addition, detailed flow properties and statistical parameters are provided for each flow regime, such as velocity, vorticity, force coefficient, separation/reattachment angle, Strouhal number, and Q-criterion.

Investigation of Spray Characteristics for Detonability: A Study on Liquid Fuel Injector and Nozzle Design

Detonation engines are gaining prominence as next-generation propulsion systems that can significantly enhance the efficiency of existing engines. This study focuses on developing an injector utilizing liquid fuel and a gas oxidizer for application in detonation engines. In order to better understand the spray characteristics suitable for the pulse detonation engine (PDE) system, an injector was fabricated by varying the Venturi nozzle exit diameter ratio and the geometric features of the fuel injection hole. Analysis of high-speed camera images revealed that the Venturi nozzle exit diameter ratio plays a crucial role in determining the characteristics of air-assist or air-blast atomization. Under the conditions of an exit diameter ratio of Re/Ri = 1.0, the formation of a liquid film at the exit was observed, and it was identified that the film’s length is influenced by the geometric characteristics of the fuel injection hole. The effect of the fuel injection hole and Venturi nozzle exit diameter ratio on SMD was analyzed by using droplet diameter measurement. The derived empirical correlation indicates that the atomization mechanism varies depending on the Venturi nozzle exit diameter ratio, and it also affects the distribution of SMD. The characteristics of the proposed injector, its influence on SMD, and its velocity, provide essential groundwork and data for the design of detonation engines employing liquid fuel.

Study of Buffeting Excitation Acting On Coil Tube Bundles in Cross Flow

Abstract Although the amplitudes induced by random excitation forces on the tubes are relatively small, the vibrations do cause continuous friction between the tube and supports, which results in gradual failure of the tubes due to fretting wear. Therefore, it is very important to determine the guild lines of the random excitation force spectrum for the coil tube. To the authors&amp;amp;amp;amp;#39; knowledge, there are no published studies on the normalized force spectrum of coil tube. A simplified three-layer experimental model was established. The robustness of the numerical method was demonstrated by comparing the experimental and simulated results, including the vibration response and the fluid excitation force spectrum. And then a semi-empirical equation for predicting the dominant frequency of turbulent buffeting was constructed by employing the threshold envelope method. Through the observation of time history and RMS data, it was found that pitch diameter ratio between adjacent tube layers had the greatest influence on the force coefficients. Pitch diameter ratio in the same layer and helix angle had little effect on the force coefficients. With the increase of a, the flow instability in the shell-side flow enhanced and the fluctuation of force coefficients became larger. Finally, the mechanism of the tube position, Reynolds number and bundle structure on the normalized force spectrum was studied. The normalized envelope force spectrum for coil tube was proposed as the guidelines to predict and evaluate the random excitation force acting on the tubes.

Bearing Behavior of Engineered Cementitious Composite and Ultra-High-Performance Concrete Filled-In Double Steel Tubular Composite Columns Subjected to Eccentrical Load

To study the eccentric compression mechanical properties of ECC and UHPC filled-in double steel tubular (EUFDST) composite columns, 35 full-scale EUCFDST composite column specimens were designed by ABAQUS software with the slenderness ratio (λ), UHPC cylinder compressive strength (fcu), inner and outer steel tubular strength (fy1, fy2), inner and outer steel tubular thickness (t1, t2), inner and outer steel tubular diameter ratio (Ω), eccentricity (e), and fiber content (γ) as the main parameters. By comparison with the simulation of the existing test, the correctness of the finite element modeling is verified. The parameter analysis of 35 full-scale EUFDST composite columns was carried out to obtain the eccentric load-mid-span deflection curve of the specimens. The failure mechanism, ductility coefficient, and stiffness degradation of the composite columns under different parameters were analyzed, and the section of the composite column was verified to satisfy the plane section assumption. The variation trend of maximum load-bearing capacity and the ductility of composite columns under different parameter conditions was obtained. By introducing the eccentricity correction coefficient and slenderness ratio correction coefficient, the calculation equation of the eccentric maximum load-bearing capacity of EUCFDST composite columns is statistically regressed, which provides a basis for the practical use of these columns.

Canopy Architectural Characteristics of Ten New Olive (Olea europaea L.) Genotypes and Their Potential for Cultivation in Super-High-Density Orchards.

In recent years, there has been growing interest in olive genotypes (Olea europaea L.) suitable for super-high-density (SHD > 1200 trees/hectare) orchards. To date, only a few cultivars are considered fitting for such cultivation system. In this study, the first results on the architectural characteristics of the canopy of ten new olive genotypes are presented. Their suitability for SHD orchards was evaluated and compared with the cultivar 'Arbequina', which is considered suitable for SHD olive orchards and, for this reason, was used as the control. Several canopy measurements were taken, and some architectural parameters, such as branching frequency, branching density, and branch diameter/stem diameter ratio were calculated. The branching frequency value was greater than 0.20 in 'Arbequina' and in only four of the genotypes. The branching density in five genotypes was similar to 'Arbequina'. 'Arbequina' had the lowest value for the branch diameter/stem diameter ratio, and only three genotypes had similar values. These initial results showed that only one genotype has all canopy architectural characteristics comparable to those of the cv. 'Arbequina'. Further studies are needed to evaluate the production traits of these new genotypes and complete their characterization.

Effective diameter of the abdominal aorta in children.

Measure out of the standard interval in the aorta diameter is a clue for aortic aneurysm or hypoplasia. Pediatric studies focusing specifically on the normal diameter of the abdominal aorta (AA) were limited in the literature. Therefore, the main goal of this work was to determine changes in the effective diameter of AA in healthy children aged 1-18years for diagnosis of vascular diseases. This retrospective work focused on abdominopelvic computed tomography views of 180 children (sex: 90 males / 90 females, average age: 9.50 ± 5.20years) without any abdominopelvic disease to measure diameters of AA, common iliac artery (CIA), external iliac artery (EIA), and first lumbar vertebra (L1). Vessel and vertebra diameters increased in pediatric subjects between 1 and 18years (p < 0.001). Considering pediatric age periods, vessel diameters increased steadily, but L1 diameter showed an irregular growth pattern between age periods. All parameters were greater in males than females (p < 0.05), except from effective diameters of AA over the coeliac trunk (p = 0.084) and over the renal artery (p = 0.051). The ratios of diameters of vessels to L1 increased depending on ages between 1 and 18years. Considering pediatric age periods, the ratios increased from infancy period to postpubescent period in irregular pattern; however, the ratios for right and left CIA, and AA over the aortic bifurcation did not alter after late childhood period. All ratios for males were similar to females (p > 0.05). Our age-specific ratios may be beneficial for surgeons and radiologists for the diagnosis of vascular disorders such as aortic aneurysm.

Nursery cultural practices influence morphological and physiological aspen seedling traits: Implications for post-fire restoration

Aspen forests are threatened by the impacts of a changing climate and are showing large-scale mortality with meager natural regeneration to restore these loses. Therefore, there is an increasing demand for high quality aspen seedlings to assist with forest restoration efforts. Nursery cultural practices can be used to alter aspen seedling traits to improve adaptability to dry planting conditions. In this study, the effects of container size (SC10 and D30; 158 ml and 490 ml, respectively) and nursery irrigation treatment (High and Low irrigation; 90% and 70% container capacity, respectively) on seedling growth and a suite of morphological and physiological traits were investigated. The combination of large container size and low irrigation treatment resulted in seedlings with lowest height to diameter ratio and specific leaf area, which are desired traits for seedling performance on dry sites. Additionally, seedlings exposed to low irrigation conditions at the nursery stage had a lower (more negative) osmotic potential at full turgor suggesting a higher likelihood of drought tolerance. Overall results from this study provide insight on utilizing nursery cultural practices to produce seedlings with target characteristics that may ultimately lead to establishment on harsh, dry planting sites in large scale reforestation projects.

Numerical study on solar photovoltaic/thermal system with tesla valve

In recent years, photovoltaic/thermal (PV/T) systems have played a crucial role in reducing energy consumption and environmental degradation, nonetheless, the low energy conversion efficiency presents a considerable obstacle for PV/T systems. Therefore, improving heat conversion efficiency is essential to enhance energy efficiency. In this paper, the PV/T system with the Tesla valve is proposed to solve this problem. Firstly, the cooling effect is simulated and analyzed in the system with four different flow channel structures: semicircle, rectangle, triangle and Tesla valve. The results indicate that the system with the Tesla valve exhibits superior cooling performance. Subsequently, several factors including angle, valve number, valve type, and pipe diameter ratio for the Tesla valve are further studied through numerical and simulation analysis. The results reveal that Tesla valves demonstrate optimal cooling performance when possessing the following structural parameters: complete symmetry, more valves, a 30-degree angle and a pipe diameter ratio of 1. Finally, four different types of fluid are selected to explore the Tesla valve. The conclusion shows that nanofluids with high density, low specific heat, and high thermal conductivity also improve the cooling performance. Thus, the PV/T system with the Tesla valve exhibits good heat dissipation and energy storage efficiency, electrical efficiency can reach 16.32% and thermal efficiency reach 59.65%.

Stress Concentration Factors of Concrete-Filled Double-Skin Tubular K-Joints

Tubular joints are important connecting parts of a welded steel tube structure. The S-N curves based on the hot spot stress (HSS) method are often used to evaluate the fatigue life of tubular joints in practical engineering. The stress concentration factor (SCF) is a key parameter to calculate HSS. In this paper, stress concentration tests of hollow-section and concrete-filled double-skin tubular (CFDST) K-joints were carried out, respectively, and then finite element models of K-joints considering the weld were established. The developed models were validated with the experimental results. The influence of key geometrical parameters, such as the diameter ratio of brace to chord β, the diameter to thickness ratio of chord γ, the wall thickness ratio of brace to chord τ, brace angle θ, and hollow section ratio ζ on the distribution and key position of SCFs along the weld toe, was discussed. Parametric studies were conducted to obtain the calculating equations for the SCF values of CFDST K-joints. The results demonstrate that infill concrete can effectively reduce SCFs along the weld on the chord. When the hollow section ratio was reduced to 0.317, the SCF was reduced by 77.2%. Notably, the SCF reduction rate was sensitive to γ and θ, with a decrease observed as γ increased. The hollow section ratio ζ had a less pronounced effect on SCF distribution patterns, but as ζ decreased, the chord’s stiffness improved, suggesting a potential approach to enhance joint performance. The distribution of SCFs is similar for joints of the same type but different geometric configurations. The innovatively integrated hollow section ratio in the CFDST design equation significantly simplifies and enhances the precision of SCF calculations for CFDST K-joints.

Non-Invasive Retinal Vessel Analysis as a Predictor for Cardiovascular Disease.

Cardiovascular disease (CVD) is the most frequent cause of death worldwide. The alterations in the microcirculation may predict the cardiovascular mortality. The retinal vasculature can be used as a model to study vascular alterations associated with cardiovascular disease. In order to quantify microvascular changes in a non-invasive way, fundus images can be taken and analysed. The central retinal arteriolar (CRAE), the venular (CRVE) diameter and the arteriolar-to-venular diameter ratio (AVR) can be used as biomarkers to predict the cardiovascular mortality. A narrower CRAE, wider CRVE and a lower AVR have been associated with increased cardiovascular events. Dynamic retinal vessel analysis (DRVA) allows the quantification of retinal changes using digital image sequences in response to visual stimulation with flicker light. This article is not just a review of the current literature, it also aims to discuss the methodological benefits and to identify research gaps. It highlights the potential use of microvascular biomarkers for screening and treatment monitoring of cardiovascular disease. Artificial intelligence (AI), such as Quantitative Analysis of Retinal vessel Topology and size (QUARTZ), and SIVA-deep learning system (SIVA-DLS), seems efficient in extracting information from fundus photographs and has the advantage of increasing diagnosis accuracy and improving patient care by complementing the role of physicians. Retinal vascular imaging using AI may help identify the cardiovascular risk, and is an important tool in primary cardiovascular disease prevention. Further research should explore the potential clinical application of retinal microvascular biomarkers, in order to assess systemic vascular health status, and to predict cardiovascular events.

Automated segmentation and volume prediction in pediatric Wilms’ tumor CT using nnu-net

BackgroundRadiologic volumetric evaluation of Wilms’ tumor (WT) is an important indicator to guide treatment decisions. However, due to the heterogeneity of the tumors, radiologists have main-guard differences in diagnosis that can lead to misdiagnosis and poor treatment. The aim of this study was to explore whether CT-based outlining of WT foci can be automated using deep learning.MethodsWe included CT intravenous phase images of 105 patients with WT and double-blind outlining of lesions by two radiologists. Then, we trained an automatic segmentation model using nnUnet. The Dice similarity coefficient (DSC) and 95th percentile Hausdorff distance (HD95) were used to assess the performance. Next, we optimized the automatic segmentation results based on the ratio of the three-dimensional diameter of the lesion to improve the performance of volumetric assessment.ResultsThe DSC and HD95 was 0.83 ± 0.22 and 10.50 ± 8.98 mm. The absolute difference and percentage difference in tumor size was 72.27 ± 134.84 cm3 and 21.08% ± 30.46%. After optimization according to our method, it decreased to 40.22 ± 96.06 cm3 and 10.16% ± 9.70%.ConclusionWe introduce a novel method that enhances the accuracy of predicting WT volume by integrating AI automated outlining and 3D tumor diameters. This approach surpasses the accuracy of using AI outcomes alone and has the potential to enhance the clinical evaluation of pediatric patients with WT. By intertwining AI outcomes with clinical data, this method becomes more interpretive and offers promising applications beyond Wilms tumor, extending to other pediatric diseases.

Evaluation of lesion contrast in the walk-through long axial FOV PET scanner simulated with XCAT anthropomorphic phantoms

BackgroundThis study evaluates the lesion contrast in a cost-effective long axial field of view (FOV) PET scanner, called the walk-through PET (WT-PET). The scanner consists of two flat detector panels covering the entire torso and head, scanning patients in an upright position for increased throughput. High-resolution, depth-of-interaction capable, monolithic detector technology is used to provide good spatial resolution and enable detection of smaller lesions.MethodsMonte Carlo GATE simulations are used in conjunction with XCAT anthropomorphic phantoms to evaluate lesion contrast in lung, liver and breast for various lesion diameters (10, 7 and 5 mm), activity concentration ratios (8:1, 4:1 and 2:1) and patient BMIs (18–37). Images were reconstructed iteratively with listmode maximum likelihood expectation maximization, and contrast recovery coefficients (CRCs) were obtained for the reconstructed lesions.ResultsResults shows notable variations in contrast recovery coefficients (CRC) across different lesion sizes and organ locations within the XCAT phantoms. Specifically, our findings reveal that 10 mm lesions consistently exhibit higher CRC compared to 7 mm and 5 mm lesions, with increases of approximately 54% and 330%, respectively, across all investigated organs. Moreover, high contrast recovery is observed in most liver lesions regardless of diameter or activity ratio (average CRC = 42%), as well as in the 10 mm lesions in the lung. Notably, for the 10 mm lesions, the liver demonstrates 42% and 62% higher CRC compared to the lung and breast, respectively. This trend remains consistent across lesion sizes, with the liver consistently exhibiting higher CRC values compared to the lung and breast: 7 mm lesions show an increase of 96% and 41%, while 5 mm lesions exhibit approximately 294% and 302% higher CRC compared to the lung and breast, respectively.ConclusionA comparison with a conventional pixelated LSO long axial FOV PET shows similar performance, achieved at a reduced cost for the WT-PET due to a reduction in required number of detectors.

Numerical evaluation of low-head inverted cross-flow turbine design method: A comprehensive study

This study aimed to address the challenges of micro-hydropower generation in low-head environments to expand the proportion of hydropower in renewable energy and achieve a carbon neutrality policy. To achieve these goals, various factors affecting the micro-hydro systems, including geographical constraints, construction costs, and grid connectivity, were reviewed and assessed. The results concluded that a novel type of cross-flow turbine with inverted structures, improved the economic feasibility, productivity, and installability of micro-hydropower plants by reducing head losses in open channels or small streams. The parametric studies consisted of four steps: first, designing the initial inverted cross-flow turbine based on the traditional design rules; for the second and third steps, a parametric study for comparing the runner diameter ratio and the number of blades is conducted; and in the last step optimized turbine was designed. The best efficiency point of the optimized inverted cross-flow turbine was 72.92 % at a runner rotational speed of 170 RPM with a 0.75 runner diameter ratio and 35 blades. The optimized turbine was improved by 7.8 % in power and 7.35 % in efficiency, higher than the initial turbine. From the hill chart comparison between the initial and optimized turbine, operation range expansion was confirmed. Overall, this research demonstrates the potential of the inverted cross-flow turbine under low-head conditions.

Effects of Beam Mode on Hole Properties in Laser Processing

The laser beam mode affects the power density distribution on the irradiated target, directly influencing the product quality in laser processing, especially the hole quality in laser drilling. The Gaussian beam shape, Mexican-Hat beam shape, Double-Hump beam shape, and Top-Hat beam shape are four typical laser beam modes used as a laser heat source and introduced into our proficient laser-drilling model, which involves complex physical phenomena such as heat and mass transfer, solid/liquid/gas phase changes, and two-phase flow. Simulations were conducted on an aluminum target, and the accuracy was verified using experimental data. The results of the simulations for the fundamental understanding of this laser–material interaction are presented in this paper; in particular, the hole shape, including the depth–diameter ratio and the angle of the cone, as well as spatter phenomena and, thus, the formed recast layer, are compared and analyzed in detail in this paper. This study can provide a reference for the optimization of the laser-drilling process, especially the selection of laser beam mode.