Revolution Rate Research Articles

Different ECLS Pump Configurations for Temporary Right Ventricular Assist Device in LVAD Patients: A Retrospective Case–Control Study

Background: Acute right ventricular failure is a critical complication after left ventricular assist device (LVAD) implantation, often managed with a temporary paracorporeal right ventricular assist device (RVAD). This study examined three extracorporeal life support (ECLS) systems regarding mortality, bleeding complications, and intensive care unit (ICU) stay duration. Methods: This monocentric, retrospective case–control study included all patients receiving LVAD with paracorporeal RVAD between 2009 and 2020. Three patient groups were formed: CentrimagTM (A), CardiohelpTM (B), and DeltastreamTM (C). Results: A total of 245 patients were included. Preoperative parameters were similar between the CentrimagTM and DeltastreamTM groups, but CardiohelpTM patients had worse Interagency Registry for Mechanically Assisted Circulatory Support (INTERMACS) Scores (A: 1.7 ± 0.8, B: 1.36 ± 0.5, C: 1.9 ± 0.9; p < 0.05). In-hospital death rates were A: 61 (41.8%), B: 15 (32.6%), C: 29 (54.7%); p < 0.05, and reoperation due to bleeding rates were A: 32 (21.9%), B: 8 (17.4%), C: 25 (47.2%); p < 0.05, with the DeltastreamTM group showing the highest rates. This group also had increased thrombocyte consumption and prolonged ICU stays. Conclusions: Temporary RVADs lead to bleeding complications, affecting patient outcomes. The DeltastreamTM group had significantly higher bleeding complications, likely due to high pump revolution rates and thrombocyte decline. Due to the study’s retrospective nature and complex patient profiles, these interesting findings should be validated in future studies.

An efficient method to simulate ship self-propulsion in shallow waters and its application to optimize hull lines

Emerging environmental challenges, such as pronounced low water levels and a constantly increasing transport volume, underscore the need to address logistical complexities and to refocus attention on the performance of self-propulsion vessels in restricted and confined waters. Recognizing the demand for an accurate and efficient ship design method, we modified an actuator disk model to predict ship propulsion. This model was designed to be applicable to various kinds of ships, with special features tailored to meet the specific requirements of inland water vessels, particularly those equipped with ducted propellers. We implemented this model into the open-source CFD software library OpenFOAM to be used in conjunction with either single- or multiphase incompressible solvers. We validated this implemented model against model test data, thereby demonstrating its capability to accurately predict propulsion performance of a typical inland waterway vessel. Following validation, we employed this model in an automated optimization process, demonstrating its robust and efficient applicability for a practical user-defined case to improve a ship's afterbody lines. Meticulous grid convergence studies ensured the predictive convergence of our simulations. Our validation covered various ship speeds at three distinct water depths, ranging from a moderate water depth-to-draft ratio h/T of 2.67 to an extreme shallow water depth-to-draft ratio h/T of 1.25. We validated our simulated results against data extracted from our own previous model tests, comprising measured ship trim and ship sinkage, propeller thrust, duct thrust, propeller torque, propeller revolution rate, and propulsion power. We investigated the influence of water depth also on various parameters, such as friction and pressure distributions, free surface interactions, and velocity patterns. Finally, we integrated the developed method into an automated optimization process that we tailored for a selected test cases of the considered ship operating in water depth to draft ratios h/T of 2.67. This integrated process facilitated the systematic refinement of the ship's afterbody lines, representing a crucial step in the pursuit to enhance ship performance.

Experimental investigation on the preparation of macroscopic 0–1 mm powdered coal by a vertical spindle mill

The vertical spindle mill (VSM) is the key equipment to realize the preparation of 0–1 mm fuel used in powdered-coal-fired circulating fluidized bed combustion technology (PC-CFB). In this paper, a pilot-scale VSM test system was set up to explore the feasibility and operating performance of coarse-grained pulverized coal preparation. The effects of loading force, table revolution rate, and ventilation rate on the product size distribution, as well as the energy consumption of the grinding process were emphatically discussed. The results show that the product size of VSM increases with the decrease of loading force and the increase of ventilation rate, but too small a loading force will affect the normal output of VSM. Additionally, the product size of VSM decreases firstly and then increases with the increase of table revolution rate. Further, the energy consumption of the powdered coal preparation process was quantitatively described, and a semi-empirical model of comminution energy based on the powdered coal particle size distribution was proposed and verified by the measured values with an average accuracy of ±30 %. This model can estimate the power consumption of the mill, which can be used as an input parameter of the heat balance calculation model for the PC-CFB pulverizing system.

Jet milling‐activated direct synthesis of octenyl succinic anhydride modified starch: an analysis of structural and application properties

SummaryThe synthesis of octenyl succinic anhydride‐modified starch was achieved through a fluidised bed activated by jet milling with graded revolution rates of 1200, 1800, 2400, 3000, and 3600 rpm. This study investigated the changes in the structural, physicochemical, and application properties of modified starch after jet milling. The results showed that modified starch can be synthesised using a one‐step jet milling process. The degree of substitution increased with a decrease in the starch particle size, resulting in a rough granule morphology. Structural analysis revealed that crystalline areas were destroyed in the modified starches. In the Fourier‐infrared spectrum, typical peaks appeared at 1724 and 1573 cm−1 upon introduction of the octenyl succinic anhydride group, whereas a new sodium peak appeared in the XPS spectrogram. The 1H‐NMR spectrum indicated that the esterification reaction mainly occurred on OH2 groups. The emulsification properties of the modified starch were significantly enhanced and increased with the crushing strength. The octenyl succinic anhydride‐modified starch has potential as a wall material for microcapsules, with good embedding rate and thermal stability. This novel synthesis method represents an innovative method for the synthesis of OSA‐starches.

Study case on the characteristics and performances of a propulsion system for a crude oil tanker

This paper presents aspects regarding the analysis of the characteristics and performances of a propulsion system for a crude oil tanker. The study involved several steps: first, the ship’s resistance and the necessary propulsive power were calculated to choose and design the main components: engine, transmission and propeller; to obtain maxim propulsive efficiency at the desired speed, with low fuel consumption and reduced CO2 emissions. Four slow Diesel engines were selected and the optimal propellers were designed to analyse and adopt the more efficient solution. A number of factors were taken into account for ship propulsion system components selection such as: required power, revolution rate to ensure an optimal propeller diameter to be located behind the ship, the specific fuel consumption parameters, desired ship speed, etc.

Enhancing resilience in marine propulsion systems by adopting machine learning technology for predicting failures and prioritising maintenance activities

With the rapid transition towards Industry 4.0, many industries have recognised the need to develop intelligent maintenance systems and predictive analytics tools that are able to optimise the performance of complex assets throughout their entire lifecycle. This paper adopts a machine learning (ML) technology to enhance the resilience of marine propulsion systems by predicting mean-time between failures (MTBF) and prioritising condition-based maintenance (CBM) activities. The factors considered for the analysis include a series of attributes (in total 16 features) which directly or indirectly represent the state of the system subject to degradation. From the results obtained, it is found out that the feed-forward neural network (FFNN) has the least mean square errors (MSE) and, thus, it is the most suitable method for numerical and discretized estimations. The results from a greedy search algorithm also show that two attributes of ‘gas generator rate of revolutions’ and ‘gas turbine rate of revolutions’ are the most significant parameters influencing system reliability, and therefore, they require closer monitoring. Furthermore, a decision support system (DSS) dashboard is designed to help marine propulsion system operators make informed maintenance decisions and find an improved balance in their spare parts inventory.

Boosting the photocatalytic activity for H2 production of Bi2O2Se/CdS heterojunction

To overcome the drawback of CdS applied in photocatalytic process, Bi2O2Se with narrow band gap and unique optical and electrochemical properties was prepared and used for fabricating Bi2O2Se/CdS heterojunctions by a facile in-situ self-assembly hydrothermal method. The synthesized Bi2O2Se/CdS heterojunctions exhibited significant stronger visible-light adsorption compared with that of CdS. Bi2O2Se/CdS with a mass ratio of 2% showed the best H2 production performance (λ ≥ 420 nm), the H2 revolution rate was 424 μmol g−1 h−1 which was 24 times higher than that of CdS. This work provided fresh insights into designing heterojunction interface based on CdS to synthesize novel photocatalysts with high efficiency.

Online modeling and prediction of maritime autonomous surface ship maneuvering motion under ocean waves

The development of maritime autonomous surface ships (MASS) has attracted much attention at present. As a necessary technology of MASS, ship motion prediction still has some problems, such as low efficiency, poor real-time performance, and easy to be affected by sea conditions. Aiming at the above problems, based on the mathematical model of ship maneuvering motion, this paper uses the least squares support vector machine (LS-SVM) identification algorithm, to establish an offline black-box identification model of MASS motion considering rudder angle and propeller revolution rates, and effectively predicts the motion of ships. On this basis, a sliding window is designed, and an error-based online modeling method of ship motion is proposed to realize adaptive prediction of MASS motion under the effect of ocean waves. A large MASS was selected for modeling and simulation experiments. The results show that compared with the traditional LS-SVM modeling algorithm, the model built by this method has a strong adaptive ability and can maintain high accuracy for a long time, meeting the needs of real-time prediction of MASS motion in practical applications.

Fabrication and enhanced visible-light photocatalytic H2 production of B-doped N-deficient g-C3N4/CdS Hybrids with robust 2D/2D hetero-interface interaction

2D layered photocatalysts with proper electronic structure have sparked much attention in the field of visible-light photocatalysis for H2 production. Herein, by simply calcining the mixture of ultrathin g-C3N4 (CNN) and NaBH4, heteroatom B and N defect were simultaneously introduced into g-C3N4. The obtained modified g-C3N4 (BDCNN) was further coupled with 2D flower-like CdS nanosheet. The optimal 2D/2D BDCNN/CdS-15% heterojunction behaved ideal photocatalytic activity for H2 revolution by water splitting, and the highest H2 revolution rate was as high as 1013.8 μmol g−1 h−1, which was 6.7 times, 2 times, and 5.8 times of the corresponding values of pristine CNN, BDCNN and CdS respectively. It was evidenced that the band structure of 2D/2D BDCNN/CdS-15% was well tuned for better visible-light adsorption and higher separation efficiency of photo-induced carriers for enhancing H2 revolution performance. The achievement in this study provided informative principles for exploring g-C3N4 based heterojunctions with higher H2-production performance.

A NUMERICAL AND STATISTICAL APPROACH OF DRILLING PERFORMANCE ON MACHINING OF Ti–6Al–4V ALLOY

Drilling, which constitutes one third of the machining operations, is widely used in many areas of the manufacturing industry. Various difficulties are encountered in the drilling process since the chip is formed in a closed limited chip flows. These difficulties directly affect the output parameters such as energy consumption, surface quality, and cutting force. Therefore, it is necessary to determine the ideal processing parameters to achieve the best performance. However, experimental research on machining processes requires both a long time and a high cost. For these reasons, machining outputs can be estimated by conducting drilling simulations with the finite element method. In this study, the finite element method is used in order to investigate the influence of different cutting parameters and different helix angles on the power and thrust force of Ti–6Al–4V (grade 5) alloy that is commonly used in the aviation industry. The study selected three different cutting speeds, feed rates, and helix angles as the cutting parameters. The experimental design was made according to the response surface method (RSM) Box–Behnken design in the Design-Expert program. Drilling simulations were performed using the ThirdWave AdvantEdgeTM software. The lowest thrust force measured is 1241.39 N at 40° helix angle, 2000-rpm revolution rate, and 0.05-mm/rev feed rate, while the lowest power consumed is 765.025 W at 30° helix angle, 1500-rpm revolution rate, and 0.05-mm/rev feed rate. As a result, it was determined that the most effective parameter for power and thrust force was the feed rate.

Deconvoluting the Surface Area and Geometric Effects of Fastener Heads on Galvanic Corrosion Prediction through FEM Modelling

Galvanic couples are common in commercial and military aerospace applications and arise from a difference in the substrate and fastener materials. These couples are often formed between aluminum alloys (e.g., AA7075-T6) with stainless steels (e.g., SS316L) or Ti-6Al-4V and can cause extensive corrosion damage to occur. This work uses laboratory techniques, including polarization curves and rotating disk electrode testing, to determine the kinetics of the electrochemical reactions. Collecting over a range of revolution rates on the RDE allows for the determination of the dependence of limiting current density due to oxygen diffusion at variable water layer thicknesses. Constructing geometries in commercial software that will be comparable to aerospace structures, coupled with experimentally-determined boundary conditions, allows for quantification and prediction of galvanic corrosion in aerospace applications. With the wide array of fasteners used, many material and geometric combinations are possible. This work focuses on the deconvolution of the impact of surface area and geometry on the prediction of the galvanic corrosion through the FEM software to better understand their effects.

Analysis of Uncertainties in Open Water Test of B-Series Propeller at Indonesian Hydrodynamic Laboratory

A propeller’s performance characteristics in open water typically refer to the variation of its thrust, torque, and efficiency with speed and revolution rate. This investigation provides a method for gaining a better understanding of the achievable accuracy. of the open water propeller test and presents an example of how to conduct a comprehensive uncertainty analysis of prediction models4 blades B-series model propeller, diameter 157.59 mm, pitch ratio 1.133 and Blade Area Ratio (BAR) 0.65 was carried out for this study. The methodologies presented using the ITTC recommended procedure to obtain individual measurement systems, measurement of individual variables, data reduction and experimental results. The bias limits for the individual measurement systems are estimated: propeller geometry, speed, thrust, torque, propeller rate of revolution, and temperature/density. The precision limits for single and multiple runs have been determined for the thrust coefficient (K T ) and torque coefficient (K Q ) for one advance coefficient (J), 5 sets of tests with 3-speed measurements in each set are conducted, totaling 15 test runs. The experimental test results have represented as relative numbers the bias for K T represents 98.1 % and the bias for K Q represents 99.4 % of the total uncertainty for the mean value of 15 tests. The uncertainty analysis results of the open water propeller were recommended in an acceptable range of the 95% level of confidence.

Zn-P bond induced S-scheme heterojunction for efficient photocatalytic tetracycline degradation synergistic H2 generation

A Zn-P bond oriented black phosphorus/CuInZnS S-scheme heterojunction was successfully constructed for tetracycline (TC) degradation and synergistic H2 generation. An enhanced photocatalytic H2 revolution rate of 2056.0 μmol/h/g was achieved with triethanolamine (TEOA) as the hole sacrifice agent, which was nearly two times higher than that of CuInZnS (CIZS) and 170 times that of black phosphorus (BP). To further improve the hole utilization rate and reduce the energy consumption, an appropriate amount of TC was added instead of TEOA, and an improved photocatalytic H2 generation rate of 1921.2 μmol/g was obtained with the synergistic degradation of TC by 82%. The types of heterojunctions and the transfer process of carriers were investigated by the combination of Mott-Schottky curves, Ultraviolet photoelectron spectroscopy, UV–vis diffuser reflectance spectra, and density functional theory. The results showed that a S-scheme heterojunction is built in BP/CIZS, which maintained the high redox ability of electron-hole pairs based on the successful separation of carriers. In addition, the novel Zn-P bond provided a charge transport channel and catalytic reaction active center upon photocatalysis. The design and application of photocatalysts proposed in this work offered a new idea for the coordinated resolution of environmental purification and energy conversion problems.

HARD MACHINING OF P235GH STEEL WITH DIFFERENT PARAMETERS USING GSRS MODELLING

The high-strength and heat-resistant P235GH steel finds wide applications in pressure vessels and heat exchangers. It is a difficult-to-handle material, which reduces the life of the tool during machining, hence spoiling the finish of machined surface. Cutting fluids can improve the life of tools and surface finish. The current investigation observes the effect of machining parameters (revolution and feed rate) and different cutting environments (SAE-40 oil with 5 % boric acid, soybean oil and nanofluid) on the surface finish and flank wear in hard turning of P235GH steel. Machining trials are designed using an L18 orthogonal array with replications. A hybrid approach of grey system based response surface (GSRS) modelling is employed to study the effects of various parameters and their interactions. The chip morphology and flank wear are analysed using scanning electron microscopic images and the predicted optimal machining condition for a better surface finish and reduced tool wear is also validated.

The Fourth Industrial Revolution and high Unemployment Rates in South Africa: A Youth Context

This paper is conceptual and uses a desktop survey to gather literature about the Fourth Industrial Revolution (4IR), its advantages and disadvantages, and its impact on the South African job market. The paper intends to uncover the impact of the 4IR on the South African job market. In an attempt to deal with one of South Africa’s triple challenges (poverty, inequality and unemployment), namely unemployment, South Africa finds itself in the introduction of the 4IR, with which it must acquaint itself. It is, however, worrying when looking at the year-by-year escalation of South Africa’s high unemployment rate. When looking at the dire status and escalation of the unemployment rate (which is affecting South Africans, most particularly the youth), it is not ironic that South Africa is inadequately prepared and inept to embrace the changes that the 4IR brings. While the country is making amendments in the education sector in terms of preparing the youth for the skills that will be relevant to the changes and give them access to employment, this has come a bit late to be able to address the high unemployment rate. There is already a high rate of retrenchments within the banking sector, which is cause for concern in terms of labour unrest that the country is (in)famous for.

Analysis of an Unmanned Underwater Vehicle Propulsion Model for Motion Control

The knowledge of dynamic models to describe the behaviors of unmanned underwater vehicles allows to design a precise navigation, guidance, and control system. A practical identification strategy is presented in this contribution, a procedure that can be easily executed during field trials and that is able to obtain a rapid assessment about the characteristics of the vehicle dynamic model. The developed procedure is designed for small-size-class remotely operated vehicles, characterized by low operative speeds. The vehicle is equipped with proprioceptive sensors in charge of measuring data needed to identify its dynamic model. Building on the proposed practical identification experiments, different vehicle propulsion models are considered and analyzed: the first is a general theoretical model accounting for the vehicle hydrodynamics (standard marine Fossen model); the others are modified models introducing additional terms in the produced thrust (torque), namely, a term proportional to the rate of change of the propeller revolutions per minute (r.p.m.), (where is the revolution rate of the propeller), and a delayed copy of the terms connected to the fluid axial flow velocity. For all considered degrees of freedom, the fitting performance of the proposed models resulted to be superior to the first. Moreover, a control system building on the obtained dynamic characterization is described.

Least squares modeling of the depth of cut of reservoir rock from real-time drilling parameters

Exploration is the process of a wellbore being drilled below the Earth’s surface, and produced through a production tubing to the wellhead. In drilling modeling, optimization and statistical analysis are important. Optimizing drilling process is a technical strategy to drill wells more productively. This paper aims at least squares modeling and statistical analysis of the depth of cut of reservoir rock from real-time drilling parameters. Real-time drilling data was obtained from drilling process of the reservoir rock in North Brae Sea (offshore) with the coordinate “58.70 N 1.30 E”. Within the data set, “Revolution Per Minute (RPM)” (rev/min), “Rate of penetration (ROP)” (ft/min), are the independent variables, and the “depth of cut”, the response variable. Maximum depth of cut is found to be 1.0533 and achieved at Revolution Per Minute (RPM) and Rate of penetration (ROP) values of 81.4626 and 85.8096, respectively. Least squares method was assessed for fitting the data set and found to provide a decent fit to the drilling data. Statistical analysis reveals that the model is highly significant with R squared value, adjusted R squared value and Predicted R squared values value of 100.00%, 100.00% and 99.99%, respectively. Hence, the linear model developed could be used for predicting the depth of cut of the reservoir rock.

Flow Simulation And Performance Analysis Of Centrifugal Compressor Using Cfd_Tool

This paper is concerned the flow simulation and performance analysis of the Centrifugal Compressor Using CFD – Tool. The complex internal flow of centrifugal compressor can be well analyzed, and the unique design system needs to be developed. It should be early to use the interface and also flexible for input and output. A 3-D flow simulation of turbulent – fluid flow is presented to visualize the flow pattern in-terms of velocity, streamline and pressure distribution on the blade surface are graphically interpreted. The standard K- e turbulence model and the simple model algorithm were chosen for turbulence model and pressure distribution well determined. The simulation was steady Heat transfer and moving reference frame was used to consider the impeller interaction under high resolution. Furthermore, A computational Fluid Dynamics (CFD) 3-D simulation is done to analyze the impeller head and efficiency required of centrifugal compressor. The impeller is rotated for a constant revolution and mass flow rate, in this study initially the geometry of centrifugal compressor impeller is created by an ANSYS Vista CCD, and the Blade modeller done by Bladegen, Finally, CFD analysis was performed in ANSYS CFX using the ANSYS Turbo grid meshing tool. According to the analysis, as the number of impeller blades increases, so does the value of the head and power imparted, as well as the impeller’s efficiency.

Evaluation of the Efficacy of Cyclosporin A Combined with Recombined Human Erythropoietin in the Treatment of Patients with Chronic Aplastic Anemia

Objective To compare the efficacy and safety of cyclosporin A(CsA)and CsA combined with recombined human erythropoietin(rhEPO)in the treatment of patients with chronic aplastic anemia(CAA).Methods Data of 79 patients with CAA treated at Department of Hematology,PUMC Hospital between January 2016 and June 2018 were collected for retrospective analysis.Forty-five patients were treated with CsA+rhEPO,and the other 34 patients with CsA alone.All the enrolled patients were treated for at least 1.5-2.0 years and followed for at least 1.0 year.The efficacy,side effects,long-term outcomes were compared between the two groups,and factors that may influence the efficacy were analyzed.Results The patients treated with CsA+rhEPO included 14 males and 31 females,with a median age of 43(19,73)years old.The median treatment duration of CsA and rhEPO was 26(12,38)and 4(3,6)months,respectively,and the median followed-up time was 24(12,42)months.The patients treated with CsA alone included 16 males and 18 females,with a median age of 36(16,85)years old.The median CsA treatment duration was 24(12,40)months and the median follow-up time was 25(12,40)months.There was no statistical difference in baseline characteristics between the two groups(all P>0.05).After 6 months of treatment,CsA+rhEPO group had higher overall response(OR)rate(55.6% vs. 31.3%;χ 2=4.456,P=0.040)and partial response(PR)rate(53.3% vs. 25.0%;χ2=6.181,P=0.019)than CsA group,and the complete response(CR)rate showed no statistical difference between the two groups(2.2% vs. 6.3%;χ2=0.810,P=0.567).The CR,PR,and OR rates showed no statistical difference between the two groups after 3 and 12 months of treatment and at the end of follow-up(all P>0.05).Similarly,the hemoglobin level at the sixth month of treatment with CsA+rhEPO was higher than that with CsA alone [(102.6±24.0)g/L vs.(90.3±29.1)g/L;t=2.017,P=0.047].However,it showed no significant difference between the two groups at other time points(all P>0.05).The side effects,including an increase in serum creatinine,slight increase in bilirubin,increase in aminotransferase,mild to moderate gingival hyperplasia,gastrointestinal reaction,and muscular fibrillation,had no significant differences between the two groups(all P>0.05),except that 11.1%(5/45)patients in the CsA+rhEPO group reported soreness at the injection site.The two groups showed similar rates of clonal revolution during the follow-up period and no death.No clinical factor was found for prediction of the efficacy of CsA+rhEPO. Conclusion CsA+rhEPO has higher OR rate and hemoglobin level than CsA alone at the sixth month of treatment,and it has similar side effects compared with CsA alone.

An integrated prediction and optimization method for drilling rate of penetration

The rate of penetration (ROP) is a crucial indicator in drilling engineering and has been the focus of interest for decades. Previous researches established many models in terms of rock physical and mechanical properties, drilling technology and equipment capabilities, drilling fluid rheological properties, and drilling engineering parameters. However, most of the above models are based on engineering experience and logical reasoning. In this paper, we investigate drilling modeling and optimization based on machine learning and intelligent optimization algorithms. The ROP modeling is achieved using a BP neural network model, which is further applied in the optimization of weight on bit (WOB) and revolution rate (RPM). The results demonstrated that the optimized operational parameters, as recommended by WOB and RPM, can increase the drilling efficiency by 12.3%. This methodology can be further applied in actual field operations as suggested parameters to the drilling efficiency further.