Optimal two-dimensional roughness for transition delay in high-speed boundary layer

The influence of surface roughness on transition to turbulence in a Mach 4.5 boundary layer is studied using direct numerical simulations. Transition is initiated by the nonlinearly most dangerous inflow disturbance, which causes the earliest possible breakdown on a flat plate for the prescribed inflow energy and Mach number. This disturbance is primarily comprised of two normal second-mode instability waves and an oblique first mode. When localized roughness is introduced, its shape and location relative to the synchronization points of the inflow waves are confirmed to have a clear impact on the amplification of the second-mode instabilities. The change in modal amplification coincides with the change in the height of the near-wall region where the instability wave-speed is supersonic relative to the mean flow; the net effect of a protruding roughness is destabilizing when placed upstream of the synchronization point and stabilizing when placed downstream. Assessment of the effect of the roughness location is followed by an optimization of the roughness height, abruptness and width with the objective of achieving maximum transition delay. The optimization is performed using an ensemble-variational (EnVar) approach, while the location of the roughness is fixed upstream of the synchronization points of the two second-mode waves. The optimal roughness disrupts the phase of the near-wall pressure waves, suppresses the amplification of the primary instability waves, and mitigates the nonlinear interactions that lead to breakdown to turbulence. The outcome is a sustained non-turbulent flow throughout the computational domain

The driver responses to the vibration of tractor

Whole body vibration is one of the main causes of musculoskeletal disorders of drivers. The purpose of this study was to investigate the allowable exposer time, the care limit and driver response to the vibrations of the seat of ITM 475 Tractor. A three-way accelerometer was used to carry out the tests in the present study based on the ISO 2631-1 international vibration standard. The studied factors were engine rotational speed at three levels of 1000, 1500 and 2000 rpms, gear ratio (1, 2 and 3) and road at two level, dirt and asphalt. The obtained data were analyzed through factorial experiment based on completely randomized design with 18 treatments and three replications. The results showed that effects of the main factors and those of their interactions on the total vibration emitted from the tractor seat were significant at 1% probability level. The highest amount of whole body vibration on a dirt road was 1.49 m s-2 which took placed at 2000 rpm and the 3rd gear ratio. Consequently, the minimum exposure time and the driver care time limit were 1.16 and 0.14 h, respectively. This treatment was in very uncomfortable range. The maximum whole body vibration for 8 h ride on ITM 475 was 0.85 m s-2. Therefore, it is necessary to reduce whole body vibration of the studied tractor via designing a cabin and/or a new seat

Survey of epidemiological of parasitic and bacterial infection in cultured fishes of Khouzestan Province

In this study which was carried out in khouzestan province, 1914 Pieces (1160 Pieces silver carp, Hypophthalmychthys molitrix; 498 Pieces common carp, cyprinus carpio; 172 Pieces Grass carp, ctenophryngodon idella and 84 Pieces Big head, Arysthychthys nobilis) from different parts of the province were examined. In three year period, 1378 to 1381, fish samples from four stations were transferred a live to the lab. Water samples also were taken and tested for some of the physicochemical factors. From a total of 1914 fish examined, 1190 showed parasitic infestation and bacterial infections (62.2%). Infestation study, infestation with these parasites have been found: Ichthophthirius, cryptobia, Trichodina, Costia, Hexamita, Dactylogyrus, Gyrodactylus, Lernea, Bothrio cephalus, Diplostomum and Capillaria. Also some species of Aeromonas, staphylococcus, Moraxella, Pectobacterium, Flavobacterium, Citrobacteria, pasteurella, Psedomonas and Alcaligenese were identified in the samples, which normally occur in Water, but in some conditions (High pH, temperature and ammonia) could cause disease and lesions specially in gills. Infestation with dactylogyrus and Gyrodactylus was found in all four kind of fishes with different infestation rate. But the highest infestation rate with dactylogyrus was in silver carp (55.2%) and lowest in common carp (14.6%). The highest infestation rate with gyrodactylus was in grass carp (42.4%) and lowest in common carp (10.6%). Ich, Bothrio cephalus and capillalia were found only in common carp and grass carp. Infestation with adult lernea and copepodid stage of lernea had greater percentage in the gills and derm of grass carp. The data showed infestation with this parasites (especially protozoans and lernea) and bacterial infection had occurred in all seasons especially in C area

Recent advances in hydrothermal carbonisation:from tailored carbon materials and biochemicals to applications and bioenergy

Introduced in the literature in 1913 by Bergius, who at the time was studying biomass coalification, hydrothermal carbonisation, as many other technologies based on renewables, was forgotten during the "industrial revolution". It was rediscovered back in 2005, on the one hand, to follow the trend set by Bergius of biomass to coal conversion for decentralised energy generation, and on the other hand as a novel green method to prepare advanced carbon materials and chemicals from biomass in water, at mild temperature, for energy storage and conversion and environmental protection. In this review, we will present an overview on the latest trends in hydrothermal carbonisation including biomass to bioenergy conversion, upgrading of hydrothermal carbons to fuels over heterogeneous catalysts, advanced carbon materials and their applications in batteries, electrocatalysis and heterogeneous catalysis and finally an analysis of the chemicals in the liquid phase as well as a new family of fluorescent nanomaterials formed at the interface between the liquid and solid phases, known as hydrothermal carbon nanodots

Study on the performance of solar cells cooled with heatsink and nanofluid added with aluminum nanoparticle

The cooling of photovoltaic (PV) panels based on nanofluids is one of the emerging cooling methods to improve the efficiency of PV panels. In this study, the effects of aluminum nanoparticles on the cooling performance and conversion efficiency of PV panels were investigated experimentally. The surface temperature, output power, and efficiency of the PV panels were assessed in Mashhad, Iran on a sunny winter day in November 2020 under ambient temperatures between 10 and 17 °C. Experimental results indicated that the nanofluid with aluminum nanoparticle improved the solar panel efficiency and solar PV panel's output power by an average of 13.5 and 13.7%, respectively compared to that of water cooling without aluminum nanoparticles. A temperature reduction between 13.08 and 16.34 °C on the solar PV panels surface was observed for heatsink cooling with nanofluid containing aluminum nanoparticles. Overall, the results suggest that nanofluid added with aluminum nanoparticles is effective in improving the conversion efficiency of PV panels

Impact of roof rain water harvesting of runoff capture and household consumption

In recent years, the occurrence of floods is one of the most important challenges facing in Hamadan city. In the absence/inefficiency of urban drainage systems, rainwater harvesting (RWH) systems as low-impact development (LID) methods can be considered as a measure to reduce the floods. In this study, three scenarios concerning the RWH from the roof surfaces are studied to evaluate the type of the harvested water on reducing flooding. In the first scenario, which indicates the current situation in the studied area, it is indicated that there is no harvest of the roof surfaces in the studied area. The second scenario is about the use of water harvested from the roof surfaces for household purposes. The third scenario also refers to the use of harvested water for irrigation of gardens. The simulation results of these three scenarios using the Soil Conservation Service (SCS) method in the Hydrologic Modeling System (HEC-HMS) model reveal that if the second scenario is implemented, the runoff volume decreases from 28 to 12% for the return period from 2 to 100 years. However, in the third scenario, this reduction in runoff volume will be 48 and 27% for return periods of 2 to 100 years, respectively. Therefore, the results of this study indicate that the use of harvested water can also affect the reduction on runoff volume

Neuropsychiatric manifestations of COVID-19 can be clustered in three distinct symptom categories

Several studies have reported clinical manifestations of the new coronavirus disease. However, few studies have systematically evaluated the neuropsychiatric complications of COVID-19. We reviewed the medical records of 201 patients with confirmed COVID-19 (52 outpatients and 149 inpatients) that were treated in a large referral center in Tehran, Iran from March 2019 to May 2020. We used clustering approach to categorize clinical symptoms. One hundred and fifty-one patients showed at least one neuropsychiatric symptom. Limb force reductions, headache followed by anosmia, hypogeusia were among the most common neuropsychiatric symptoms in COVID-19 patients. Hierarchical clustering analysis showed that neuropsychiatric symptoms group together in three distinct groups: anosmia and hypogeusia; dizziness, headache, and limb force reduction; photophobia, mental state change, hallucination, vision and speech problem, seizure, stroke, and balance disturbance. Three non-neuropsychiatric cluster of symptoms included diarrhea and nausea; cough and dyspnea; and fever and weakness. Neuropsychiatric presentations are very prevalent and heterogeneous in patients with coronavirus 2 infection and these heterogeneous presentations may be originating from different underlying mechanisms. Anosmia and hypogeusia seem to be distinct from more general constitutional-like and more specific neuropsychiatric symptoms. Skeletal muscular manifestations might be a constitutional or a neuropsychiatric symptom