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Design of Pneumatic Conveying Device for Straw Micro-Crusher Based on CFD-DEM Simulation
No full textTo solve the problem that the complexity of the internal airflow field of the machine leads to low conveying capacity and affects the crushing and classifying performance of the impact crusher in the process of straw micro-crushing, conveying and classifying, a straw micro-crusher pneumatic conveying device is designed. Based on the force analysis of straw in the conveying channel, this study combines theoretical calculations and numerical simulations to determine the suspension velocity of straw particle, conveying airflow velocity, and volumetric flow rate in pneumatic conveying. Simulation experiments are carried out using the coupled Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) to investigate the airflow distribution patterns and the motion characteristics of straw particles in the process of pneumatic conveying, to clarify the key parameters affecting the conveying efficiency, to determine the optimal values of the key parameters - air inlet width, inlet airflow velocity and flow deflector diameter by the single-factor experiments. A prototype is manufactured, and the relative error in conveying capacity is regarded as an evaluation index to carry out conveying performance tests of pneumatic conveying device. The test results verify the reasonableness of the structural design of the conveying device and the correctness of the theoretical calculations and CFD-DEM coupled simulation results. The findings of this study provide a reference for the design of efficient pneumatic conveying equipment for biomass powder
The analytical impact of extracellular vesicles PSA on different commercial total PSA measurement methods
No full textIntroduction: Prostate-specific antigen (PSA) can circulate bound to extracellular vesicles (EVs) and its measurement (ev-PSA) can be useful in prostate cancer. Although not designed with that purpose, total PSA assays react with ev-PSA. We evaluated the analytical performance of several total PSA assays in ev-PSA quantification and the impact of ev-PSA on total PSA measurement.
Materials and methods: Extracellular vesicles were isolated from 83 serum samples from prostate cancer patients by size exclusion chromatography or ultracentrifugation. PSA was quantified in serum, EVs, International Standard for PSA 17/100 from the World Health Organization (WHO IS 17/100) and exosomes from lymph node carcinoma of the prostate (LNCaP) cell line, using commercial immunoassays (Elecsys, Atellica, Immulite, Liaison and Kryptor).
Results: Nanoparticle tracking analysis showed that the WHO IS 17/100 contains significantly less EVs than serum (P Immulite > Liaison > Kryptor. Ev-PSA could be detected in all serum samples with Elecsys and Atellica, but not with Immulite (87.8%), Liaison (58.5%) or Kryptor (48.8%). Bland-Altman analysis showed a proportional bias in ev-PSA quantification between Elecsys and other methods. Addition of ev-PSA to serum samples caused a proportional bias in PSA measurement between Elecsys and Immulite methods, with a relationship (r2 = 0.99; P < 0.001) between ev-PSA and the difference in total PSA concentration between both methods.
Conclusions: While ev-PSA can be measured using commercial kits, notable differences exist between methods, which could lead to potential discrepancies in serum total PSA results across various assays
Numerical and experimental study of the seakeeping performance for a novel fish farming vessel considering nets
Get PDFTo improve the economic feasibility of offshore aquaculture, this study proposes a novel concept of fish farming vessel which is retrofitted by an old bulk carrier. Large open farming tanks has been created by replacing the side hull plates with rigid metal nets and retaining the transverse bulkhead. The seakeeping performance of the vessel is evaluated through numerical simulations which are validated against experimental results. A numerical model based on the potential flow based boundary element method is developed using panel elements for the hull and dipole elements for the nets. The effects of net solidity ratio and wave slope variation on seakeeping performance are analyzed. Results show that increasing solidity ratio leads to higher peaks near the natural frequencies in the Response Amplitude Operators (RAOs). Besides, the installation of net generally reduces RAOs due to wave energy dissipation through nets and decreased wave excitation. Comparisons with experimental results from free decay, regular waves, and white noise waves tests demonstrate good agreement in terms of natural frequencies and trends of RAOs. Discrepancies in natural frequencies, especially in pitch motion, are attributed to the underestimation of added mass in the numerical model. The findings validate the feasibility of using dipole elements to represent net structures and underscore the importance of accounting for wave slope in seakeeping analysis of net-integrated offshore structures
A data-driven framework for attainable ship speed uncertainty under stochastic weather conditions
Get PDFThis paper presents a data-driven framework for quantifying attainable ship speed uncertainty considering weather forecast uncertainty. The methodology integrates two parallel workflows: weather forecast processing and ship performance simulation. Weather forecast data from NOAA and GFS sources are collected at multiple lead times (0-24h, 24-72h, 72-120h, 120-168h). The data undergo spatial discretisation over a North Atlantic rectangular grid, extracting the main meteorological variables, including significant wave height, peak period, wave direction, wind speed, and wind direction. Ship performance simulations were done using Wärtsilä NaviTrainer NTPRO 5000 and HydroComp NavCad to generate attainable ship speed lookup tables under varying conditions: intended speeds (14.5, 13.5, 12.0 kn), wave heights (0-14 m according to WMO Sea State Codes 0-8), and wave encounter angles (0°-180°). Multiple metrics were used for uncertainty quantification, including RMSE, MAE, Bias, UGR, CRPS, IoA, and FSS for meteorological variables, alongside CMAE for directional parameters. These metrics are subsequently applied to estimated attainable ship speeds, establishing response variable uncertainties. Correlation analysis was conducted between the uncertainty of meteorological variables and the uncertainty in attainable ship speed, providing important insights for estimated time of arrival (ETA) calculations and voyage planning under weather uncertainty
GHG Emissions from Forest Operations in Mediterranean Chestnut Coppices
Get PDFThis study investigated the greenhouse gas (GHG) emissions associated with various mechanisation levels and extraction methods in Mediterranean chestnut (Castanea sativa L.) coppice forests. Located in central Italy, these forests play a significant role in economic as well as ecological terms. This study addressed a critical gap in emissions data for broadleaf forest operations by examining the productivity and environmental impact of four logging systems. These systems integrate semi-mechanised and mechanised felling methods with skidding and forwarding extraction techniques. The results revealed that mechanised felling significantly boosts productivity by 44–66% compared to semi-mechanised felling but generates over three times the GHG emissions per cubic meter of wood. Notably, extraction operations account for the largest share of total emissions, with skidding emitting nearly three times more than forwarding, primarily due to its lower work productivity. Specifically, forwarding in a Cut-to-Length (CTL) system achieved productivity of over double that of skidding and reduced emissions per cubic meter of extracted wood by up to 63%. Key findings suggested that improving work productivity through optimised extraction methods, operator training, and efficient road network layouts can substantially lower emissions. Among the systems tested, CTL forwarding paired with mechanised felling showed the highest productivity and lowest emissions, presenting a promising model for sustainable chestnut coppice management in Mediterranean regions
Numerical study on the influence of localized damage effect of explosives on steel plate structure damage under underwater contact explosions
Get PDFThis study investigates the fluid-structure interaction dynamics induced by underwater explosive, focusing on the impact of localized damage effects of explosive on the transient interaction between plate structures. To accurately characterize this localized effect, numerical experiments were conducted on the damage to a steel plate subjected to underwater explosive shock under various charge and explosion distance conditions. Results indicate that the diameter of plate perforations caused by contact explosions is smaller than that under conditions with a certain explosion distance. By establishing the relationship between relative explosion distance and plate perforation diameter, the optimal range for the localized damage effect of explosive is determined to be a relative explosion distance of 1.1–2. Furthermore, the relationship between the impact factor and the structural dimensionless factor, established based on the plate damage results, conforms to a quadratic function dependency. This relationship characterizes the role of the local effect of the munition in the inherent local damage mechanism of the target structure. These research findings provide empirical guidance for enhancing the lethality of underwater weapons and optimizing the efficiency of underwater mining, underwater de-icing, and other engineering operations
Skupovi i događaji: Završna konferencija uspostavnog istraživačkog projekta “Pametni sustavi za dostavu lijeka pri liječenju tumora kosti”
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