Low High Ratio Research Articles

3-D-Printed Ka-Band Circularly Polarized Monopulse Antenna Array With High Gain and Low Axial Ratio

3-D-Printed Ka-Band Circularly Polarized Monopulse Antenna Array With High Gain and Low Axial Ratio

Mechanism investigation of stability enhancement by slot on a transonic compressor

Abstract As aircraft engine blades develop towards high loads and low aspect ratios, the flow conditions in the tip region of transonic compressor rotors become more complex. The interaction between shock waves and boundary layers tends to induce fluid separation, thereby reducing the stable operating range of the rotor. To enhance the stability margin of the rotor, this study employs numerical simulation techniques to design jet slots on the rotor 37. Research results show that, without compromising the performance of the rotor, the slotted rotor can effectively enhance the stability margin of the rotor at both design and off-design speeds, with increases of 60.9% and 47.9% in surge margins compared to the prototype.

Achieving high strength and low yield ratio by constructing the network martensite-ferrite heterogeneous in low carbon steels

Achieving high strength and low yield ratio by constructing the network martensite-ferrite heterogeneous in low carbon steels

Response of variation of electrical control parameters to coatings prepared in organo-silicon electrolyte by plasma electrolytic oxidation

This study aims to explore the influence of control parameters from the perspective of the amorphous ceramic coating formation process. Three preparation processes were preferred based on the thickness, appearance and corrosion resistance of the coatings by orthogonal experiment. The surface morphology, cross-sectional structure, phase composition and micro-hardness of PEO coatings were examined using scanning electron microscopy (SEM)/Energy dispersive X-ray spectroscopy (EDS), X-ray diffractometry (XRD) and hardness measurement techniques. Findings indicate that voltage exerts the most significant impact on coating thickness and appearance, whereas the influence of other parameters becomes more pronounced as the voltage increases. Three amorphous ceramic coatings prepared in 20 min with thicknesses of 27.4 μm, 83.2 μm and 193.3 μm increased the surface hardness of 6061 aluminium alloy by 6–8 times, and decreased the corrosion current density of 6061 aluminium alloy by 3 orders of magnitude in 1 mol L−1 HCl solution. Moreover, the thickening of the coating primarily occurs within a few minutes after the voltage reaches its peak, and high frequency and low duty ratio are prerequisites for better appearance under higher voltage conditions.

Comparison of fish biological indicators of Clarias gariepinus hybrids grown in ras and pond farming conditions

To improve technologies in the field of commercial cultivation of aquaculture objects and further development of the warm-water aquaculture sector in Russia, we previously undertook breeding methods and approaches to obtain high-quality planting material for a promising commercial object — the African catfish Clarias gariepinus. This article presents, in a comparative aspect, the experience of growing hybrid offspring of African catfish, obtained from crossing two breeds — Mikhailovskaya and Tamanskaya, in a closed water supply system and in a pond farm in the Astrakhan region in the summer. It was shown that hybrid individuals of clariid catfish bred in a pond farm during the feeding period under consideration (from July to September) were characterized by a high specific growth rate and low feed ratio compared to hybrids grown in a recirculation system, respectively, 11.4% versus 9.87% and 0.96 versus 1. Also, based on the results of fishing, over two months of cultivation in a pond farm, hybrids of clariid catfish increased the total biomass by 13 times, while in a recirculating system it increased by 15 times, but the final biomass of fish turned out to be greater when reared in open reservoir (46.875 versus 10.87 kg). It was shown that the final individual mass of hybrid fish cultured in pond conditions was 11.0% higher than the final mass of individuals in the recirculation system. The conducted studies showed that in the climatic conditions of the Astrakhan region (VI fish-breeding zone), a promising direction for aquaculture of African catfish is the feeding cultivation of hybrid juveniles in pond farms. It should be taken into account that in order to obtain marketable fish products (i.e. individuals weighing over 1000 g), it is necessary to use fish seeding material with an average weight of at least 100 g.

The effect of jet disturbance on flame propagation characteristics of multi-component natural gas/hydrogen mixed fuel

Gas explosions mostly occur in turbulent environments in practical situations. Meanwhile, the current research on the explosion characteristics of hydrogen-doped natural gas is mostly methane/hydrogen mixed fuel, ignoring the influence of other components of natural gas on the explosion characteristics of the actual situation. Therefore, the effects of different jet intensities (Pjet), hydrogen-doping ratios (XH2) and equivalence ratios (φ) on the explosion characteristics of multi-component natural gas/hydrogen mixed fuel are experimentally investigated in cylindrical tanks of 30 L. Additionally, it extensively explored the dual influence of jet disturbance and gas inerting effect on the flame propagation characteristics of multi-component natural gas/hydrogen mixed fuel. With the increase of Pjet, both Pmax and (dp/dt)max initially increase and then decrease, while τ continuously decreases. When Pjet = 0.4 MPa, the promotion effect on Pmax and (dp/dt)max is most significant. The lifting of XH2 leads to a gradual increase in Pmax and decreasing τ. (dp/dt)max exhibits a trend of initially increasing and then decreasing with the elevation of XH2, reaching its maximum at XH2 = 40%. The introduction of jet flow significantly reduces the promotion or inhibition effect on explosions of high hydrogen blending ratio mixtures. Furthermore, the introduction of jet flow is more effective in promoting the explosive performance of multi-component natural gas/hydrogen mixed fuel with high equivalence ratios and low hydrogen doping ratios under rich fuel conditions. This study can provide a key reference for the explosion hazard assessment during the practical application of natural gas/hydrogen mixed fuel.

Design and optimization of space nuclear power system with sCO2 Brayton cycle on Mars

As human exploration of outer space deepens, the demand for space power increases. This requires not only higher thermoelectric conversion efficiency but also a more compact system. Space nuclear power based on the sCO2 Brayton cycle is better suited for the surface of Mars due to its high efficiency and low ratio of mass to electric power. This paper designs a 6 MWt sCO2 Brayton cycle power generation system, and the following system configurations are mainly studied including Simple Heat Recovery Cycle (SRC), Re-Compress Heat Recovery Cycle (RC), Reheating Heat Recovery Cycle (RRC), and Reheating Re-Compress Cycle (RHRC). A thermodynamic calculation model of the system was developed based on the aforementioned cycle configurations. Additionally, a quality assessment model was developed separately for each component within the system, according to its respective category. The effects of parameters such as temperature, compressor pressure ratio, and bypass ratio on the system efficiency and total system mass are also examined for each of the four-cycle configurations. The study conducted a global multiparameter optimization using a genetic algorithm to optimize system efficiency and the ratio of mass to electric power. The RHRC configuration achieved the highest cycle efficiency at 39.47%, while the SRC cycle had the lowest system efficiency at 35.46%. The RRC configuration had the minimum ratio of mass to electric power at 7.419 kg/kWe with an efficiency of 33.13%.

Conductivity at varying frequencies as a method for differentiating strawberry ripeness and association with colour acceptance of strawberry nectars.

Identifying the best strawberries to produce colour stable nectars is a priority for the juice industry. Although riper strawberries produce nectars with better colour stability, variability between cultivars means that surface colour cannot be used as a single quality attribute to determine stability. Conductivity and bio-impedance measurements can be used to differentiate ripeness of strawberries. The commercially available PEF Control System (ELEA) can measure cell disruption by measuring conductivity at different frequencies. Updated software measured strawberry conductivity at 121 frequencies between 100 Hz and 1 MHz to determine whether conductivity at these frequencies could differentiate ripeness, and be compared with the colour acceptance and stability of nectars produced from these strawberries. A high-low ratio (HLR) was calculated by dividing the conductivity at frequency 1 MHz by conductivity at 1 kHz. HLR could be used to separate five strawberry ripeness stages, with decreasing HLR associated with increasing ripeness. HLR was then compared with the colour of nectars produced from these strawberries. Although there was a good correlation between HLR and an acceptable colour to consumers on initial production (r = -0.823, P < 0.001) and after 12 weeks of storage (-0.759, P < 0.001), cultivars differed greatly in both HLR and colour stability. Additionally, HLR had a strong correlation with firmness. The PEF Control System could be used to differentiate ripeness of strawberries by HLR, and therefore was associated with colour stability. However, no additional information on colour stability was gained from conductivity beyond what could already be deduced from differentiating ripeness based on surface colour. © 2024 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Optimizing heat transport in a permeable cavity with an isothermal solid block: Influence of nanoparticles volume fraction and wall velocity ratio

Abstract This study examines the influence of wall velocity ratio on mixed convective heat transport in a permeable cavity containing an isothermal solid block at its center. The analysis considers the characteristics of various flow variables, i.e., Darcy number, wall velocity ratio, Richardson number, and volume fraction of suspended nanoparticles, on heat transport and material flow characteristics. The principal equations are solved implementing the semi-implicit method for pressure linked equations algorithm, and the outcomes are compared with existing literature. The study shows that rising estimations of Darcy number, velocity ratio, Richardson number, and nanoparticles volume fraction lead to improved heat transfer rates. For example, at high Richardson number (100) and solid volume fraction (0.05), increasing the velocity ratio from 0.5 to 1.5 results in a 6% (5%) upsurge in heat transport rate. Conversely, at smaller Richardson number (0.01), the heat transport rate upsurges by 29% (28%). Similarly, at high Darcy numbers and low wall velocity ratios, a 3% (4%) escalate in heat transport rate is observed with an increase in nanoparticles concentration from 0 to 0.05, while a 9% (8%) increase in thermal performance is achieved at low Darcy numbers. The study emphasizes the importance of optimizing the combination of nanoparticles volume fraction, Darcy number, velocity ratio, and Richardson number to maximize thermal performance in the porous cavity.

Nonspecific stress biomarkers for mortality prediction in older emergency department patients presenting with falls: a prospective multicenter observational study.

Older patients presenting to the emergency department (ED) after falling are increasingly prevalent. Falls are associated with functional decline and death. Biomarkers predicting short-term mortality might facilitate decisions regarding resource allocation and disposition. D-dimer levels are used to rule out thromboembolic disease, while copeptin and adrenomedullin (MR-proADM) may be used as measures of the patient`s stress level. These nonspecific biomarkers were selected as potential predictors for mortality. Prospective, international, multicenter, cross-sectional observation was performed in two tertiary and two regional hospitals in Germany and Switzerland. Patients aged 65years or older presenting to the ED after a fall were enrolled. Demographic data, Activities of Daily Living (ADL), and D-dimers were collected upon presentation. Copeptin and MR-proADM levels were determined from frozen samples. Primary outcome was 30-day mortality; and secondary outcomes were mortality at 90, 180, and 365days. Five hundred and seventy-two patients were included. Median age was 83 [IQR 78, 89] years, 236 (67.7%) were female. Mortality overall was 3.1% (30d), 5.4% (90d), 7.5% (180d), and 13.8% (365d), respectively. Non-survivors were older, had a lower ADL index and higher levels of all three biomarkers. Elevated levels of MR-proADM and D-dimer were associated with higher risk of mortality. MR-proADM and D-dimer showed high sensitivity and low negative likelihood ratio regarding short-term mortality, whereas copeptin did not. D-dimer and MR-proADM levels might be useful as prognostic markers in older patients presenting to the ED after a fall, by identifying patients at low risk of short-term mortality. ClinicalTrials.gov Identifier: NCT02244983.

Preparation and Properties of Lightweight Geopolymer by Bio-Based Foaming Agent.

Lightweight geopolymers have the advantages of a wide source of raw materials, chemical corrosion resistance, high mechanical strength and excellent durability, and are expected to replace traditional building insulation materials. In this paper, a green bio-based foaming agent with a small 1 h settlement distance, high average foaming multiple and low bleeding ratio was obtained by a Cetyltrimethylammonium Bromide/yeast solution. When the amount of Cetyltrimethylammonium Bromide is 0.50 wt%, the foam prepared by the yeast and Cetyltrimethylammonium Bromide solution exhibits the improved 1 h settlement distance, the large average foaming multiple, the small bleeding ratio and uniform foam size. Subsequently, a lightweight geopolymer based on metakaolin and fly ash (or silica fume) was successfully prepared by the bio-based foaming agent, and the effects of different foam content on the properties of the geopolymer, such as dry density, water absorption, thermal conductivity, compressive strength and morphology, were studied. With an increase in foam content, the dry density, thermal conductivity and compressive strength of the geopolymer gradually decrease, the water absorption increases, regardless of whether silica fume or fly ash are added. Herein, it is confirmed that the foaming agent based on yeast can be effectively used to prepare lightweight geopolymers, which can provide vast opportunities to turn into candidates for novel inorganic thermal insulation materials.

Spatial Sensitivity of River Flooding to Changes in Climate and Land Cover Through Explainable AI

AbstractExplaining the spatially variable impacts of flood‐generating mechanisms is a longstanding challenge in hydrology, with increasing and decreasing temporal flood trends often found in close regional proximity. Here, we develop a machine learning‐informed approach to unravel the drivers of seasonal flood magnitude and explain the spatial variability of their effects in a temperate climate. We employ 11 observed meteorological and land cover (LC) time series variables alongside 8 static catchment attributes to model flood magnitude in 1,268 catchments across Great Britain over four decades. We then perform a sensitivity analysis to assess how a 10% increase in precipitation, a 1°C rise in air temperature, or a 10 percentage point increase in urban or forest LC may affect flood magnitude in catchments with varying characteristics. Our simulations show that increasing precipitation and urbanization both tend to amplify flood magnitude significantly more in catchments with high baseflow contribution and low runoff ratio, which tend to have lower values of specific discharge on average. In contrast, rising air temperature (in the absence of changing precipitation) decreases flood magnitudes, with the largest effects in dry catchments with low baseflow index. Afforestation also tends to decrease floods more in catchments with low groundwater contribution, and in dry catchments in the summer. Our approach may be used to further disentangle the joint effects of multiple flood drivers in individual catchments.

A New Solution of Drag for Newtonian Fluid Droplets in a Power-Law Fluid

Understanding flow behaviors of multiple droplets in complex non-Newtonian fluids is crucial in many science and engineering applications. In this study, a new and improved analytical solution is developed based on the free surface cell model for the flow drag of swamp of Newtonian fluid drops through a power-law fluid. The developed solution is accurate and compares well to the numerical solutions. The improvement involves a new quantification of shear stress boundary condition at the interface and a more consistent approximation in linearizing the power-law fluid flow governing equation. The Newtonian fluid solutions can be reasonably used to linearize the flow governing equation. The approximation of the boundary conditions at the interface, however, has a major impact on the model prediction. The main improvement in the new solution is observed under the condition of comparable viscosities of the Newtonian drops and the outside power-law fluid when the results are sensitive to the interface boundary condition. Under the two extreme conditions of high viscosity ratio (approaching particles) and low ratio (approaching bubbles), the present and existing solutions converge.

High Purity Solvents for qNMR Measurement

Quantitative NMR (qNMR) has been adopted by documentary standards, including the Japanese Pharmacopoeia (JP), United States Pharmacopoeia (USP), and International Organization for Standardization (ISO), owing to its reliability and efficiency. Note that qNMR can be used for quantifying target components using the signal integration ratio of an analyte to a reference. In qNMR, a modern NMR instrument with high resolution and sensitivity is used to record reliable spectra. This instrument can detect small signals from impurities in a solvent, which may result in inaccurate signal integration in the spectrum. In this study, we investigated the influence of solvent quality on qNMR accuracy focusing on organic impurities, water content, and deuteration ratio. If signals from organic impurities and signals from the analyte overlap, the duplication of signal integration will directly affect the qNMR analytical result. To examine overlapping, we performed blank solvent tests. Additionally, a high water content and low deuteration ratio affect the detection sensitivity, thus reducing the signal-to-noise (S/N) ratio of the target. Thus, these factors must be considered to obtain accurate qNMR results.

Effect of early peri-operative arterial lactate concentration level ratios on post-hepatectomy liver failure

BackgroundPost-hepatectomy liver failure (PHLF) is a serious complication after hepatectomy and a major cause of death. The current criteria for PHLF diagnosis (ISGLS consensus) require laboratory data of elevated INR level and hyperbilirubinemia on or after postoperative day 5. This study aims to propose a new indicator for the early clinical prediction of PHLF.MethodsThe peri-operative arterial lactate concentration level ratios were derived from time points within the 3 days before surgery and within POD1, the patients were divided into two groups: high lactate ratio group (≥ 1) and low lactate ratio group (< 1). We compared the differences in morbidity rates between the two groups. Utilized logistic regression analysis to identify the risk factors associated with PHLF development and ROC curves to compare the predictive value of lactate ratio and other liver function indicators for PHLF.ResultsA total of 203 patients were enrolled in the study. Overall morbidity and severe morbidity occurred in 64.5 and 12.8 per cent of patients respectively. 39 patients (19.2%) met the criteria for PHLF, including 15 patients (7.4%) with clinically relevant Post-hepatectomy liver failure (CR-PHLF). With a significantly higher incidence of PHLF observed in the lactate ratio ≥ 1 group compared to the lactate ratio < 1 group (n = 34, 26.8% vs. n = 5, 6.6%, P < 0.001). Multivariable logistic regression analysis revealed that a lactate ratio ≥ 1 was an independent predictor for PHLF (OR: 3.239, 95% CI 1.097–9.565, P = 0.033). Additionally, lactate ratio demonstrated good predictive efficacy for PHLF (AUC = 0.792).ConclusionsEarly assessment of peri-operative arterial lactate concentration level ratios may provide experience in early intervention of complications in patients with hepatocellular carcinoma, which can reduce the likelihood of PHLF occurrence and improve patient prognosis.

A Critical Review on Room-Temperature Sodium-Sulfur Batteries: From Research Advances to Practical Perspectives.

Room-temperature sodium-sulfur (RT-Na/S) batteries are promising alternatives for next-generation energy storage systems with high energy density and high power density. However, some notorious issues are hampering the practical application of RT-Na/S batteries. Besides, the working mechanism of RT-Na/S batteries under practical conditions such as high sulfur loading, lean electrolyte, and low capacity ratio between the negative and positive electrode (N/P ratio), is of essential importance for practical applications, yet the significance of these parameters has long been disregarded. Herein, it is comprehensively reviewed recent advances on Na metal anode, S cathode, electrolyte, and separator engineering for RT-Na/S batteries. The discrepancies between laboratory research and practical conditions are elaborately discussed, endeavors toward practical applications are highlighted, and suggestions for the practical values of the crucial parameters are rationally proposed. Furthermore, an empirical equation to estimate the actual energy density of RT-Na/S pouch cells under practical conditions is rationally proposed for the first time, making it possible to evaluate the gravimetric energy density of the cells under practical conditions. This review aims to reemphasize the vital importance of the crucial parameters for RT-Na/S batteries to bridge the gaps between laboratory research and practical applications.

α″ martensite engineering: A strategy to achieve high yield strength and low yield ratio synergy for dual-phase titanium alloy

To breakthrough the long-term contradictory issue of high yield strength and low yield ratio for titanium alloys, and achieving the superior balance between these two key mechanical parameters. We have proposed an efficient “Quenching → Cold deformation → Recrystallization annealing” (QCR) strategy, which realizes the high yield strength (900 MPa) and low yield ratio (0.74) synergy for a model Ti6Al4V5.5Cu (wt.%) alloy which characterized with the unique multi-scale heterogeneous structure. The developed QCR processing route is based on the subtle utilization of orthorhombic α″ martensite, which plays the various roles in each processing step. By elaborately manipulating the recrystallization degree, chemical stability, effective domain of β phase and αt nano-precipitates in β phase, the stress-induced α″ martensite transformation (SIM α″) can be controlled effectively and even postponed until after yielding induced by dislocation mechanisms, thus leading to substantially improvement of yield strength. After yielding, abundant proliferation of SIM α″which assisted by multi-scale α phases and their interactions are the fundamental reasons for achieving higher work-hardening ability, tensile strength (1215 MPa) and uniform elongation (11%). Thus, the core strategy to realize the excellent combination of high yield strength and low yield ratio is manipulating the activation sequence of the plastic deformation carriers.

Sealing performance and optimization design of squamous textured mechanical seal

The work focuses on the optimization of surface texturing and their geometrical characteristics to improve the sealing performance of mechanical seal. The hydrodynamic model is developed to predict the sealing performance of four textures, including dimple, triangle, chevron and squamous textures. Result indicates that the squamous texture exhibits better sealing performance with high ratio of load-carrying capacity to leakage and ratio of oil film stiffness to leakage at various angular speeds and pressures. Furthermore, the functions of squamous texture characteristics with the load-carrying capacity and leakage ratio are revealed by the response surface methodology. And the squamous texture is optimized with high load-carrying capacity and low leakage ratio through the multi-objective optimization algorithm NSGA-II to achieve the Pareto-optimal set.

Reducing rubber-plastic friction in syringes through microstructured surface design and manufacturing

Plastic syringes often rely on silicone oil lubrication to reduce plunger-barrel friction, leading to potential issues like oil droplet release and drug aggregation. This study explored an alternative approach combining two-photon polymerization, laser machining, and microinjection molding to manufacture micro-dimpled structures for low friction. Plastic microdimples with high area density and low aspect ratio significantly reduced the coefficient of friction against rubber, while the dimple profile proved crucial in facilitating replication and demolding. The results of this study provide valuable insights into reducing friction between rubber and plastic, particularly in applications like syringes.

The role of ischemia-modified albumin, presepsin, delta neutrophil index, and inflammatory markers in diagnosing acute cholecystitis.

The purpose of this study is to determine the significance of markers such as C-reactive protein, procalcitonin, complete blood count parameters, delta neutrophil index, ischemia-modified albumin, presepsin, and oxidative stress indicators, which are associated with inflammation, oxidative stress, and ischemia in the pathology and diagnosis of acute cholecystitis in adults. Patients diagnosed with acute cholecystitis in the emergency department and healthy individuals in the control group were included in the study. Routine blood count and biochemistry analyses were performed on the participants. Blood serum was used to measure ischemia-modified albumin, presepsin, and oxidative stress indicators. White blood cell count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, delta neutrophil index, C-reactive protein, procalcitonin, ischemia-modified albumin, ischemia-modified albumin to albumin ratio, presepsin, and oxidative stress indicators were significantly higher in patients with cholecystitis compared to the control group. Measurements of white blood cell count, neutrophil-to-lymphocyte ratio, platelet-to-lymphocyte ratio, and delta neutrophil index can be included as part of the complete blood count. The complete blood count parameters are readily available and do not incur additional costs to the healthcare system. The authors believe that the neutrophil-to-lymphocyte ratio, delta neutrophil index, ischemia-modified albumin, ischemia-modified albumin to albumin ratio, and presepsin values can be used as new markers in the diagnosis of acute cholecystitis due to their high sensitivity, specificity, and low negative likelihood ratio.