Incremental Ratio Research Articles

Thermal-mechanical modelling on cumulative freeze-thaw deformation of porous rock in elastoplastic state based on Drucker-Prager criterion considering dilatancy

The comprehensive understanding of freeze-thaw (F-T) deterioration and deformation properties of rock is a critical basis for frost damage prevention on cold regional rock engineering. In freezing process, plastic strain generates in rock when the stress induced by pore ice pressure (PIP) becomes higher than yield strength, and unrecoverable deformation accumulates in rock under multiple F-T cycles. Therefore, this study presents a thermal-mechanical modelling on cumulative F-T deformation of rock under cyclic F-T action. In the modelling of mechanical action, the microporomechanics theory is applied with a spherical element model in the derivation of equilibrium equations of rock, and the Drucker-Prager criterion is utilized with dilatancy effect of rock considered to describe unrecoverable plastic deformation cumulated in rock under multiple F-T cycles. The thermal process is modelled with unfrozen water content and latent heat accounted. The proposed thermal-mechanical modelling method is validated based on experiments and numerical simulations of F-T deformation of sandstone, and it is able to simulate the temperature and F-T deformation of rock in acceptable precision. The numerical distributions of temperature, PIP, maximum principal strain and displacement are exhibited and show that the plastic region begins to develop in rock matrix with PIP exceeding the elastoplastic critical pressure when temperature drops to about −2 °C and grows rapidly when temperature drops from −2 to −6 °C. Several F-T cycles later, large unrecoverable plastic strain remains in sandstone though PIP dissipates after thawing. The cumulative F-T deformation, porosity increment and maximum of plastic volume ratio are much greater under condition with freezing temperature of −20 °C, compared with condition −10 °C. Besides, as cycle number increases, the plastic volume ratio becomes smaller and its decrease rate attenuates.

Effects of microwave irradiation at various temperatures on biosludge disintegration

ABSTRACT The waste biological sludge disintegration by using microwave irradiation was investigated at a ramping rate of 2°C/min and 5 min holding time at various target temperatures. Significant disintegration of biosludge was observed and the highest disintegration degree was determined about 82% at the temperature of 110°C. Increase of target temperature elevated the energy needs to 98, 123 and 148 kWh/kg TS at the temperatures of 75°C, 90°C and 110°C, respectively. The gradual increase of sugar and protein in the sludge slurry with increasing temperatures indicates successful degradation. The microwave pretreatment increased the specific surface area of the sludge by particle size reduction. The specific surface area of raw sludge was 70 m2/kg and rose to approximately 253.7 m2/kg at 110°C with an increment ratio of 260%. Although a significant NH4–N release was not observed, PO4–P concentrations increased from 11.0 mg/L to 16.3, 20.7 and 29.2 mg/L at the temperatures of 75°C, 90°C, 110°C, respectively. While the specific filter resistance of waste biological sludge was about 1.0 × 1013, increasing the microwave target temperature, the ability of dewatering decreased and the highest SFR value of 5.1 × 1014 was observed at the temperature of 110°C.

Economic evaluation of two-Strain covid-19 compartmental epidemic model with pharmaceutical and non-pharmaceutical interventions and spatio-temporal patterns

This paper is a novel attempt to analyze different aspects of a two-strain epidemic model. The paper introduces a novel approach to analyzing a two-strain epidemic model, emphasizing the efficacy of combining non-pharmaceutical interventions and vaccination, particularly against new variants. Additionally, it presents a unique spatio-temporal model to assess spatial distribution of infections, offering fresh insights into how spatial factors influence disease transmission and control. The analysis involves stability analysis(local and global) and optimal control. Time-dependent social/non-pharmaceutical interventions coupled with vaccination of the susceptible class in the presence of both strains are analyzed using Pontryagin’s Maximum Principle. The numerical section shows the behavior of the infected class with and without control, the control intensity trend for the scenario when only non-pharmaceutical interventions (NPI) are practiced for the original strain, and when both NPI and vaccination are incorporated with the emergence of the new strain. The evaluation of the Incremental average ratio (IAR) and Incremental cost-effectiveness ratio (ICER) determines that NPI and vaccination as a combination is better and ideal in terms of costs incurred and effectiveness as a whole in averting infection in the presence of a new variant. Finally, we have also proposed a spatio-temporal pattern for the new strain model to analyze patterns using the finite element method by PDE Toolbox to show the effect of different initial conditions and geometry on the density of the infected population.

Impact of dual-credit policy on diffusion of technology R & D among automakers: Based on an evolutionary game model with technology-spillover in complex network

Dual-credit policy promotes new-energy vehicle (NEV) automakers to invest in technology R & D by granting NEV with better technological performance to higher NEV-credit. Based on the complex network evolutionary game theory, this paper constructs a technology R & D diffusion model of automakers considering the technology spillover effects, and explores the dynamic impact of adjusting different dual-credit policy parameters on technology R & D diffusion among automakers. Our results show that: (1) increasing the annual increment of NEV-credit requirement ratio can encourage more NEV automakers to invest in technology R & D, but also lead to significant increase in NEV-credit price. (2) Reducing the CAFE target coefficient can simultaneously promote the diffusion of NEV technology R & D and GV green-technology R & D, but excessive reduction can hinder GV automakers from entering NEV market. (3) Lowering the upper limit of credit per unit NEV suppresses the diffusion of NEV technology R & D. (4) Reducing technology-spillover is conducive to the incentive of dual-credit policy on the diffusion of technology R & D.

Genetic counseling and subsequent cascade genetic testing for women with a family history of pathogenic BRCA1 mutation: A cost-effectiveness model.

10621 Background: BRCA1 pathogenic mutations significantly increase the lifetime risk for breast and ovarian cancer, but risk reducing interventions such as bilateral salpingo-oophorectomy (RRBSO) and mastectomy (RRM) can improve outcomes. For women with a known family history of pathogenetic mutation, genetic counseling and testing is recommended. We sought to determine the cost-effectiveness (CE) of referral to genetic counseling with subsequent cascade testing. Methods: A decision analytic model was created using TreeAgePro 2023 software to evaluate the strategies of routine genetics consultation with Ambry panel testing versus no referral. It was assumed that known BRCA1 carriers would undergo annual breast cancer screening with mammogram and MRI at 25yo, RRBSO at 35yo, and RRM at 40yo. Non-carriers underwent routine annual mammogram at 40yo. Additionally, women who did not undergo genetic testing initially do so at the time of diagnosis of first cancer (breast of ovary) and subsequently underwent all recommended risk reducing strategies if found to have a pathogenic BRCA1 mutation. Outcomes included cost, quality adjusted life years (QALYs), ovarian and breast cancer cases and deaths. Univariate and multi-variate analyses were used to investigate the impact of the strategies. Results: In a Monte Carlo Microsimulation cohort of 10,000 women with a first degree relative with a pathogenic BRCA1 mutation, referral to genetic counseling with testing was the dominate strategy. This strategy resulted in a similar mean cost ($185,543 vs $185,171), but with 2,322 additional QALYs and incremental CE ratio (ICER) of 1,605 per QALY. This dominant strategy also resulted in 73 fewer ovarian cancer cases and 545 fewer breast cancer cases. Sensitivity analysis for the age of RRM was remarkable for an annual reduction in breast cancer cases by 97 cases and an annual cost savings of 375,658 for year prior to age 40 that mastectomy was performed. Conclusions: Routine genetic counseling and screening for all patients with a known family history of pathogenic BRCA1 mutation reduces breast and ovarian cancer diagnoses by prompting risk-reducing procedures without significant increase in cost when compared to diagnosis-based testing. Routine access to genetic counseling in a high-risk population would help inform earlier counseling and further decrease cancer risk, particularly as earlier RRM may improve outcomes. This is further supported by the low cost to implement. Improvement in identification and early referral could be targeted. [Table: see text]

The influence of debromination and TR on the microstructure and properties of CMSMs

One unique challenging in achieving advanced carbon molecular sieve membranes (CMSMs) is tailoring their gas separation properties from the precursor. To clarify this, we designed two homo-polyimides with a bromine (PI-Br) and a hydroxyl (PI-OH) groups in the ortho position of imide group, and carbonized them into CMSMs at 550 °C (PI-Br-550 and PI-OH-550). There are debromination (510 °C) and carbonization occurred for PI-Br-550 whereas the PI-OH underwent thermally rearrangement (TR, 450 °C) and then pyrolysis to CMSM. After carbonization, both CMSMs showed excellent gas separation properties, with their CO2/CH4 separation performance surpassed the latest 2019 pure-gas and 2018 mixed-gas trade-off curves, additionally, the PI-Br-550 demonstrated a relatively smaller CO2 permeability (12462 vs 14,253 Barrer), lower PCO2 increment ratio (199 vs 1480), and less CO2/CH4 dropping ratio (69.7 to 45.5 vs 87.5 to 36.1) than the PI-OH-550 from their precursors. Their XPS, Raman, and WXRD characterization results indicated that debromination boosts the gas separation performance of CMSM by creating more ultra-micropore “plate” (pyrrolic-N of 36.0 % vs 19.0 %) and smaller d-spacing (3.89 vs 4.15 Å) than the TR precursor, which boosts the permeability of CMSM is due to the high stability of PBO intermediates that retarded the decomposition of the polymer main chian and caused some big pores. The above results provided a good route to get highly efficient CMSM by molecular designing of their precursors.

Development of a Solar-Powered Barley Sprouting Room

The study aims to develop a sprouting room for barley powered by solar energy instead of traditional alternating-current rooms to suit remote areas. The cooling, lighting, and irrigation systems were developed and replaced with another that operates on 12 V DC. An air cooling device based on the Peltier module has been developed as an alternative to air conditioning devices. Four cooling units of the air cooler were tested with three lighting durations of 6, 9, and 12 h and three irrigation rates of 1.7, 1.85, and 2 m3 ton-1. The measurements included evaluating the performance of the developed air cooler device. The vegetative and quality characteristics and a chemical analysis of sprouted barley for the solar-powered room compared to the room before the modification were estimated. The solar room's productivity and electrical energy consumption rates were estimated, and an economic evaluation of the development was conducted. The maximum electrical power consumption for the solar-powered sprouting room was 63.275 kWh ton-1, compared with 117.19 kWh ton-1 for the alternating current-managed room before modification. The interaction between the utilized developing DC air cooling, lighting, and irrigation achieved standard rates for the produced barley vegetative and quality characteristics. The maximal productivity from sprouted barley was 1.22 tons, per 7 days with an increment ratio over control of 31.97%. The net earnings for the developed sprouting room were maximized relative to the significant decrease in electrical production costs. The developed room fits the livestock sector by providing good economic alternative fodder sources.

Does capital efficiency influence economic growth in Bangladesh? Application of the Harrod-Domar model

PurposeThe main purpose of this paper is to analyse the influence of capital efficiency on the economic growth of Bangladesh using the Harrod-Domar (H-D) model.Design/methodology/approachWe use annual data from 1980 to 2019 for this paper. Three steps are taken in the data analysis. First, to check the existence of a unit root, we use the augmented Dickey-Fuller (ADF) test and to determine co-integration among the variables, we use the Johansen-Juselius co-integration test. Next, for long-run estimation, we use the dynamic ordinary least square (DOLS) estimator. The sensitivity of the long-run estimations is further checked by the fully modified OLS (FMOLS) and autoregressive distributed lag (ARDL) estimators. Lastly, we use the Granger causality test to determine the long-run causality among the variables.FindingsThe long-run co-integration test validates the co-integrating relationship among the variables. DOLS estimations reveal that the economic growth of Bangladesh is negatively associated with the incremental capital output ratio (ICOR), validating the notion that capital efficiency matters for achieving higher economic growth. On average, an increase in ICOR by a unit tends to reduce economic growth in the long term by 0.75 percent. Our results also reveal no significant relationship between savings and economic growth when the model is extended. Finally, causality results indicate unidirectional causality between ICOR and economic growth.Practical implicationsBased on the results obtained, we argue that the enhancement of capital productivity could bring efficiency because ICOR is an inverse of capital productivity. Since Bangladesh’s capital productivity is considerably low compared with other neighbouring countries, it is suggested that firms should gradually move towards technological advancement and enhance economies of scale, etc. in the long run. Moreover, policies in favour of continuous skill development programmes could be highly effective in increasing capital productivity given that capital follows a vintage structure.Originality/valueThis is the first paper to analyse the economic growth pattern of Bangladesh using the traditional H-D model by incorporating variables such as savings and ICOR and also by relaxing the assumption of time-invariant (i.e. fixed) data of the variables. Moreover, this paper extends the traditional H-D empirical model by introducing key indicators and time breaks for Bangladesh’s economy through a stepwise regression process.

Effect of ammonia energy ratio and diesel pilot-injection strategy on the performance of ammonia-diesel dual fuel engine

ABSTRACT The combustion strategy under a higher ammonia energy ratio (AER) is expected to improve the combustion performance of ammonia-diesel dual-fuel (ADDF) engines, leading to additional reductions in greenhouse gas (GHG) emissions. In order to meet the engine’s performance requirements while achieving the low carbon emissions, this study utilized CFD numerical simulations to analyze the combustion and emission characteristics for an ADDF engine at AER levels from 0% to 90%. It focused primarily on evaluating the effectiveness of diesel pilot-injection strategy in reducing GHG emissions at AER50%. The obtained results showed that the unburned NH3 and N2O emissions exhibited an upward trend with the increment of AER, leading to a degradation in the indicated thermal efficiency (ITE), while GHG emissions were more significant than in the original diesel-only combustion mode. Based on AER50%, the ITE exhibited a trend of initially rising and then falling with the increment of diesel pilot-injection ratio (DPR) from 0% to 60%, reaching a maximum value of 47.1% at DPR 40%. At this point, the unburned NH3 emission decreased by 42.4% compared to the DPR0%, and no longer declined after the DPR exceeded 40%. Based on AER 50% and DPR 40%, ITE peaked at 48.1% with the optimal timing for diesel pilot-injection, which represented a 1.6% rise in ITE relative to the original diesel-only combustion mode, while GHG emissions decreased by 35%, and NO emissions increased by 25%.

Curing parameters development and long-term performance of ohmic heating cured conductive cementitious composites: A comparative study on fiber fraction

Ohmic heating (OH) curing is a new method for concrete production in cold areas, while the changing regularity for the curing parameters including electric voltage, current, resistivity and curing temperature during the curing process, and the long-term performance evolution law are still unrevealed. In this research, this method was used to fabricate carbon fibers (CFs) reinforced conductive cementitious composites under −20 °C, the early-age curing parameter and the long-term performance evolution law of the specimen were clarified. Higher CFs dosage showed benefits on the electrical conductivity and heating performance of OH pre-cured specimens. To be specific, simulation and experimental results evidenced that the electrical conductivity of fresh mixture was much improved with 0.6 vol% CFs with the electrical resistivity decremental ratio of 74.82 %. Also, the curing temperature was enlarged in the presence of 0.75 vol% CFs with the incremental ratio around 50 %, indicating the much-improved heating efficiency. Strength test results showed that 1-day OH pre-cured specimens possessed the comparable 150-day strength with RT prepared specimens. Moreover, the hydration products and pore structure test results further verified the feasibility of OH curing with high hydration forming ability and denser microstructure at longer duration. In addition, the “RER” was introduced to evaluate the variation law of electrical resistivity in further curing process, and the corresponding prediction equation was derived.

Incremental Healthcare Costs of Diabetes Mellitus in a Middle-Income Country Using Administrative Healthcare Data

ObjectivesTo estimate the incremental medical cost of diabetes mellitus using information from administrative databases in Colombia. MethodsWe carried out a retrospective cohort study with administrative health databases from Colombian population affiliated in the contributory health insurance scheme. We used an operative definition to select the cohort with diabetes. Incremental cost and cost ratio of diabetes were estimated using an inverse probability weighting of treatment approach to find the causal effect of having the disease. Weights were calculated by a propensity score method using a Random Forest model. The flexibility of this machine learning algorithm allows to have a better specification and bias reduction. Additionally, we reported incremental costs and cost ratios with confidence intervals using bootstrapping and analyzed costs by age groups and complications associated with diabetes. ResultsThe estimated prevalence of diabetes was 2834 per 100 000 cases, in 2018. The group with diabetes was comprised 634 015 people and the control group 1 524 808. The calculated annual direct medical cost was $860, for which the incremental cost was $493 and the cost ratio 2.34. The incremental annual cost for some type of complication ranges from $1239 to $2043, renal complication being the most expensive. Incremental cost by age groups ranges from $347 to $878, being higher in younger people. ConclusionsAlthough the cost of diabetes in Colombia ranges among the global averages and is similar to other Latin-American countries, a greater incremental cost was found in patients with renal, circulatory, and neurologic complications.

Comparative Economics of Different Management Tactics by Novel Insecticides against Pest Complex on Capsicum (Capsicum annuum L.) under Protected Conditions

Field experiment was conducted under shade net house at Hi-Tech Horticulture Farm, Rajasthan Agricultural Research Institute, Durgapura (Sri Karan Narendra Agriculture University, Jobner), Jaipur, Rajasthan to work out the economics and cost benefit ratio of different management strategies by three spraying of eleven bio-rationale and newer pesticides against Yellow Mite, Polyphagotarsonemus latus (Banks), thrips, Scirtothrips dorsalis Hood, aphids (Aphis gossypii Glover, Myzus persicae Sulzer), Whitefly, Bemisia tabaci (Gennadius) and Beat army worm, Spodoptera exigua (Hubner) during summer 2014 and 2015 on capsicum (Capsicum annuum L.). The result on the basis of pooled data indicated that maximum net profit of Rs 77185/ha was obtained in the treatment of fipronil 0.005% with the yield of 51.46 q/ha followed by emamectin benzoate 0.002% (Rs 67422/ha) with the yield of 49.77 q/ha. The minimum net profit of Rs 23840/ha was recorded in the treatment of NSKE 5% followed by azadirachtin 0.0003% (Rs 29876). The net profit ranging from Rs 53613/ha to Rs 60263/ha was computed in the treatment of acephate (Rs 53613/ha), spiromesifen (Rs 59971/ha), spinosad (Rs 58262/ha) and indoxacarb (Rs 60263/ha), whereas, Rs 39125/ha to 41476/ha was found in propargite and novaluron. The maximum incremental cost benefit ratio (1:20.23) was found in fipronil (0.005%) followed by 1:17.99 in the treatment of acephate (0.075%). The minimum ICBR (1:4.64) was recorded in the treatments of novaluron followed by spinosad (1:5.96). Study revealed that three spray of fipronil 5 SC @ 1 ml/l or emamectin benzoate 5 SG @ 0.4 g/l can be suggested to the farmers for the management of pest complex on capsicum under shade net house conditions during summer for off season production.

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra.

Pulsating hydraulic fracturing has been an environmentally friendly method to improve the permeability of rock formations to stimulate gas production and reduce hazard risks. It has the advantage of fracturing the reservoir with lower cracking pressure and less water volume, as the mechanical strength of rock materials has been reduced by the hydraulic pulse pressure. Many researchers have found significant changes in hard rocks after cyclic loading. However, the existing work still cannot clearly explain the mechanism of the rock damage by pulsating hydraulic fracturing within a short-time experiment. To solve the issue, an investigation of the effects of pulsating hydraulic fracturing on CBM production has been carried out in lab and field applications. Results indicate that the long-term hydraulic pulse pressure can cause a linear decline in cracking pressure directly measured in the lab. It plays an essential role in the permeability enhancement by generating more flow channels for CBM production. The low-field NMR quantitatively evaluates the increase in porosity, which reveals significant incremental ratios of over 20% in the porosity of macropores, mesopores, and micropores of coal caused by fatigue damage. It is first proven that hydraulic pulse pressure has a significant influence on the porosity components of macropores, mesopores, and micropores. To validate the effectiveness of the technique on the field scale, a field application of pulsating hydraulic fracturing has been carried out in a coal mine. It shows that gas production has been largely enhanced with a long and stable production stage and higher gas flux after the applied pulsating load. The gas concentration and gas flux of the fractured boreholes are about 2 times that of the nonfractured boreholes. This work provides an investigation of the effects of pulsating hydraulic fracturing on CBM production, which gives a better understanding of the mechanism for the engineers in the field.

Responses of metro shield tunnels to an adjacent deep excavation in Shanghai soft ground

Deformation in metro shield tunnels is a consequence of conducting adjacent deep excavations. Accordingly, this research examines the response of existing metro shield tunnels in Shanghai’s soft ground to nearby deep excavations, focusing on how tunnel deformation correlates with the distance to the excavation. Utilizing actual measurement data from metro shield tunnels located 12-45 m from an 11.5-24.1-m-deep excavation, the study initiates with a project overview before analyzing the deformation data of the metro tunnels. This analysis includes the settlement and transverse convergence of both upward and downward lines. Furthermore, by integrating the settlement history curve and settlement increment ratio statistics, the study explores the deformation of the metro tunnels across different construction stages of the adjacent excavation. Additionally, the effect of the distance to the excavation on metro tunnel deformation is discussed, considering identical excavation depths, supporting stiffness, construction levels, and soil conditions. This investigation aims to provide insights applicable to similar cases and inform future research.

Self-starting and performance improvement of a Darrieus type wind turbine using the plasma actuator

Although the popularity of Darrieus-type vertical axis wind turbines is growing for small-scale electricity generation, these turbines have severe challenges in self-starting. This paper proposes a flow control method, namely, the plasma actuator, to solve the self-starting problem besides enhancing the turbine performance. The Darrieus turbine is numerically investigated using a pressure-based finite volume method to solve the unsteady Reynolds-averaged Navier–Stokes and the γ–Reθt transitional model equations. Simulation of the blade rotation is performed using the sliding mesh technique accompanied by the turbine equation of motion to enable the blade rotational degree of freedom. Furthermore, the body forces associated with the plasma actuator are determined by calibrating the Shyy plasma model parameters. The plasma actuator is assessed at both the constant and free rotational speeds. The constant rotational speed results in plasma off condition show negative torque generation for tip speed ratios lower than 1.5, known as the origin of turbine self-starting challenges. The plasma actuator improves the negative torque by 128% in the tip speed ratio of 0.5 and turns it positive. Also, at larger tip speed ratios, it reduces the negative torque generation and enhances the turbine power production by up to 260%. Furthermore, the plasma actuator in free rotational speed improves the tip speed ratio increment by up to 8%, reducing the total time of turbine self-starting.

Dynamic compressive behavior of steel fiber synergistically reinforced cellular concrete under high strain-rate loading

To better understand the reinforcement and toughness effects of steel fibers, a 75-mm split Hopkinson pressure bar (SHPB) device was used to test the uniaxial dynamic compression properties of steel fiber synergistically reinforced cellular concrete (SFSRCC) under high strain rates. The dynamic compression performance characteristics of the SFSRCC, including the stressstrain curve, dynamic strength, impact toughness and failure mode, were analyzed. The results showed that the dynamic strength, peak strain and impact toughness of SFSRCC increase with increasing strain rate. Compared with that of cellular concrete (SAP10S0), a higher steel fiber volume ratio corresponded to a greater enhancement in the dynamic performance characteristic indices of the SFRCC. The maximum increases were 138.4%, 180.0% and 280.0% for the DIF, peak strain, and impact toughness, respectively. The damage degree of the SFSRCC specimen decreased with increasing fiber content, and a larger area of residual "core retention" was observed, which indicated that the impact resistance of the SFSRCC with a high fiber content was improved. An empirical formula that can accurately characterize the dynamic strength increase factor (DIF) of SFSRCC with high strain rates was proposed, and the prediction results obtained by using the DIF of the SFSRCC were highly consistent with the test results, which confirmed its effectiveness. To further quantify the strain rate enhancement effect and fiber content for the reinforcement and toughening ability of SFSRCC, the relationships between the peak strength/peak strain/impact toughness and strain rate and between the DIF increment ratio/strain energy density increment ratio and fiber volume fraction were determined. In conclusion, the dynamic compression performance characteristics of SFSRCC can be enhanced by incorporating an appropriate quantity of steel fibers with a dynamic impact load.

Large eddy simulation for jet noise characteristics of liquid rocket engine with guide groove

The study of jet noise characteristics of liquid rocket engines is a prerequisite for evaluating the noise level of rockets and effectively controlling the noise. To obtain the effect of engine operating and structural parameters on jet noise, the Large Eddy Simulation combined with the FW-H integration method is applied for the scaled engine with guide groove under different chamber pressures and nozzle expansion ratios. The simulation results show that the noise field distribution of the jet with a guide groove is highly symmetrical and has obvious directivity. The noise caused by jet impingement on the guide groove is strongly correlated to the distribution of high vorticity regions. Remarkably, higher chamber pressure leads to longer potential jet length, higher noise sound pressure levels, and greater enhancement effect of impact on noise. However, the frequency spectral characteristics are basically invariant. When the chamber pressure is constant, the increment of the nozzle expansion ratio in a certain range results in lower noise peak frequency and weaker impact effect.

Aerodynamic characteristics and wake formation behind a pair of side-by-side rectangular cylinders using the lattice Boltzmann method

In this work, the lattice Boltzmann method is used to numerically analyze the interactions of flowing fluid with two side-by-side rectangular cylinders at a fixed Reynolds number of 150. The gap ratios between the cylinders are varied from 0.5 to 5 while the aspect ratios of both cylinders are varied from 0.25 to 4. The deflected, bistable, flip-flopping, chaotic, single bluff body, two pairs’ street of anti-phase vortex shedding, anti-phase synchronized, and in-phase non-synchronized wake patterns are observed upon varying the aspect ratios as well as the gap ratios. The observed results show that the mean drag coefficients of both side-by-side rectangular cylinders, as well as that of the single cylinder, exhibit decreasing trends till the aspect ratio = 2 and become almost constant afterward. The Strouhal number varies abruptly at the gap ratio of 0.5 and becomes steady for gap ratios = 2 and 5. The root-mean-square values of lift coefficients of two side-by-side rectangular cylinders exhibit variations till the aspect ratio equal to 1.5 and then becomes constant afterward. This study also reveals that an increment in aspect ratios results in the minimization of the drag force and controls the wake, while the increment in gap ratio results in stabilizing the chaos produced in the flow structure due to jet flow influence. The wake patterns in this study are found to be consistent with the numerical and experimental work of other researchers.

Photocatalytic Characteristic of Semiconducting Mineral Anatase and Microbial Community in the Marine Euphotic Zone of the Beibu Gulf, South China Sea

This study has thoroughly uncovered the characteristics of the marine euphotic zone system in the Beibu Gulf, featuring adjacent semiconducting minerals and electrochemically active microbes, via mineralogical characterization, photoelectrochemical measurements, and microbiological analysis techniques. Notably, results of Raman and ESEM with EDS indicated that anatase, the semiconducting mineral with prominent photocatalytic performance, exists in large quantities in the Beibu Gulf. Photoelectrochemical measurements tested photoelectric response and redox activity of suspended particulate minerals, demonstrating the suspended particulates dominated by titanium and iron oxide semiconducting minerals presented excellent photo-response property and distinct photoelectric catalytic potential under visible light irradiation. Its significant property of photoelectric response with 110.483% increment ratio of the average photocurrent density relative to the dark current density. 16S amplicon sequence analysis revealed that the euphotic zone was dominated by Proteobacteria, Actinobacteria, and Cyanobacteria at the phylum level, and by Synechococcus CC9902, Cyanobium PCC-6307 and unclassified Ilumatobacteraceae at the genus level. Halomonas (0.2–1.2%), Vibrio (0.7–1.8%), and Nautella (0.1–1.1%), closely related to semiconducting minerals reduction reaction, were also presented in YL and RGS samples of the Beibu Gulf. This work firstly revealed that the neglected characteristics of the marine euphotic zone system in the Beibu Gulf of the South China Sea, which is an important natural ecosystem for microorganisms to uptake energy sources. It will provide a new perspective for further research on novel ways for microorganisms to acquire energy sources through semiconducting minerals in the marine euphotic zone system.

Effects of elevated temperature exposure on the mechanical properties of recycled fine aggregate concrete

ABSTRACT In this work, a compound waste material was made up of raw construction waste concrete, waste tiles, and waste bricks was mixed at a weight ratio of 6:3:1. They were ground into recycled fine aggregates (RFA). RFA substituted the local river sand in proportions of 0%, 30%, 50%, 70%, and 100% for preparing recycled fine aggregate concrete (RFAC) with varied water-to-cement ratios. It intended to explore concrete’s mechanical properties and ultrasonic pulse velocity changes before and after high temperatures (300–800°C). The loss on ignition (LOI) of concrete was simultaneously determined to compare the performance in resisting elevated temperature. Test results presented that the higher the replacement ratio of RFA, the gradually higher the reduction in the concrete splitting tensile, compressive, and residual compressive strengths and ultrasonic pulse velocity after elevated temperature exposure. A rapid reduction was especially found at the heated temperature of exceeding 440°C. Furthermore, the old cement paste adhered to the surface of the raw construction waste had a relatively higher LOI. This led to the consequence that the RFAC had an increased LOI with the increment of the RFA replacement ratio, while the LOI of RFAC dropped with the increment of the originally heated temperature.