Normal Rack Grid Generation Method for Screw Machines with Large Helix Angles

Improving the efficiency of the screw machine is highly significant for industry. Numerical simulation is an important tool in developing these machines. The 3D computational fluid dynamic simulation can give a valuable insight into the flow parameters of screw machines. However, it is currently difficult to generate high quality computational grids required for screw rotors with large helix angle. This is mainly due to the excessively high cell skewness of the rotors with large helix angel, which would introduce errors in numerical simulation. This paper presents a novel grid generation algorithm used for the screw rotors with large helix angel. This method is based on the principles developed for the grid generation in transverse cross-section. Such mesh is generated by SCORGTM using normal rack grid generation method which means numerical meshes are generated in a plane normal to the pitch helix line. The mesh lines are then parallel to the helix line and thus an orthogonal mesh will be produced. The main flow and leakage flow directions are orthogonal to the mesh, potentially reducing numerical diffusion. This developed algorithm could also be employed for single screw machines

Numerical investigation of oil injection in a Roots blower operated as expander

The adoption of positive displacement machines as expanders in Organic Rankine Cycles (ORCs) is increasingly common, especially in the low to medium power range. At the same time, these devices often serve as compressor in Vapor-Compression Refrigeration Systems. In both cases, the application of Computation Fluid Dynamics (CFD) to optimize such machines has become an integrated tool in the design process. As a consequence, several challenges associated with the numerical simulation have to be taken into account. For example, the modeling of the gap represents a challenge for the stability of the numerical analysis. The dynamic of the process, combined with deformations of the clearances and of the working chamber has to be considered with extra care. To raise the efficiency of the machine, oil is typically injected. Its numerical modeling imply an extra challenge in the simulation of the actual operation of the machine. The present work is mainly focused on the multi-phase nature of the flow, with a particular analysis of the lubricant oil injected. In this work, a two-lobe Roots blower operated as expander has been simulated with the open-source software OpenFOAM-v1812, using the SCORG-V5.2.2. This analysis highlights the areas that are affected the most by the oil presence in order to highlight the sealing effect it provides

A search for rotating radio transients and fast radio bursts in the Parkes high-latitude pulsar survey

Discoveries of rotating radio transients and fast radio bursts (FRBs) in pulsar surveys suggest that more of such transient sources await discovery in archival data sets. Here we report on a single-pulse search for dispersed radio bursts over a wide range of Galactic latitudes (|b| < $60^{\circ}$) in data previously searched for periodic sources by Burgay et al. We re-detected 20 of the 42 pulsars reported by Burgay et al. and one rotating radio transient reported by Burke-Spolaor. No FRBs were discovered in this survey. Taking into account this result, and other recent surveys at Parkes, we corrected for detection sensitivities based on the search software used in the analyses and the different backends used in these surveys and find that the all-sky FRB event rate for sources with a fluence above 4.0 Jy ms at 1.4 GHz to be ${\cal R} = 4.4^{+5.2}_{-3.1} \times 10^3$ FRBs day$^{-1}$ sky$^{-1}$, where the uncertainties represent a $99\%$ confidence interval. While this rate is lower than inferred from previous studies, as we demonstrate, this combined event rate is consistent with the results of all systematic FRB searches at Parkes to date and does not require the need to postulate a dearth of FRBs at intermediate latitudes.Comment: Accepted, 10 pages, 6 figure

Grid deformation strategies for CFD analysis of screw compressors

Customized grid generation of twin screw machines for CFD analysis is widely used by the refrigeration and air-conditioning industry today, but is currently not suitable for topologies such as those of single screw, variable pitch or tri screw rotors. This paper investigates a technique called key-frame re-meshing that supplies pre-generated unstructured grids to the CFD solver at different time steps. To evaluate its accuracy, the results of an isentropic compression-expansion process in a reciprocating piston cylinder arrangement have been compared. Three strategies of grid deformation; diffusion equation mesh smoothing, user defined nodal displacement and key-frame remeshing have been assessed. There are many limitations to key-frame re-meshing. It requires time consuming pre-processing, has limited applicability to complex meshes and leads to inaccuracies in conservation of calculated variables. It was concluded that customized tools for generation of CFD grids are required for complex screw machines

पिंजऱ्यातील मत्स्यशोतिचे पर्यावरणावरील परिणाम आणि त्यांचे उपशमन

Cage aquaculture requires suitable site, materials to fabricate cage, nutritionally balance feed and healthy seed. The cage farm depending upon intensification generates the considerable wastes which include uneaten food, excretory products (faecal matter and urinary products). Many cage aquaculture activities utilize chemicals for prophylactic as well as therapeutic purpose which further contributes to the total waste discharge. Further, microorganisms and parasites associated with caged fish also contribute towards cumulative environmental degradation

Secure Authentication Using Click Draw Based Graphical Password Scheme

Graphical passwords are an alternative to alphanumeric passwords in which users click on images to authenticate themselves rather than type alphanumeric strings. We have developed one such system, called Secure Authentication using Click Draw Based graphical password scheme, and evaluated it with human users. Secure Authentication using Click Draw Based graphical password scheme, including USAbility and security evaluations, and implementation considerations. An important USAbility goal for knowledge-based authentication systems is to support users in selecting passwords of higher security, in the sense of being from an expanded effective security pace. We use the sequence of multiple images along with a dummy image and alsoa pattern on any single image to influence user choice in click draw based graphical passwords, encouraging users to select more random, and hence more difficult to guess patterns

समुद्रातल्या पिंजऱ्यातली संगोपन मत्स्यशोति

For the grow-out trials, circular cages of diameter ranging from 6-15 meters have been tried by CMFRI. However, cage diameter 6-10 is recommended for the culture of Mullet, Cobia, Pompano, Sea bass and Pearl spot. The grow-out of candidate species in caged enclosures requires proper planning and management. The critical inputs like right kind of seed, nutritionally balanced feed and routine cage maintenance activity decide the success of grow-out production. Unlike closed or semi-closed culture systems, marine environment is more diverse and dynamic, thus did not offer much scope for the environmental as well as biological manipulations. After proper site selection and cage installations, cages should be stocked with recommended numbers of seed depending upon water volume/ cage area

Subarachnoid haemorrhage due to intracranial vertebral artery dissection presenting with atypical cauda equina syndrome features: case report

BACKGROUND: Failing to recognise the signs and symptoms of subarachnoid haemorrhage (SAH) causes diagnostic delay and may result in poorer outcomes. We report a rare case of SAH secondary to a vertebral artery dissection (VAD) that initially presented with cauda equina-like features, followed by symptoms more typical of SAH. CASE PRESENTATION: A 55-year-old man developed severe lower back pain after sudden movement. Over the next 5 days he developed paraesthesiaes in the feet, progressing to the torso gradually, and reported constipation and reduced sensation when passing urine. On day six he developed left facial palsy, and later gradual-onset headache and intermittent confusion. Magnetic resonance imaging of the brain showed diffuse subarachnoid FLAIR hyperintensity, concerning for blood, including a focus of cortical/subcortical high signal in the left superior parietal lobule, which was confirmed by computed tomography. Digital subtraction angiography demonstrated a left VAD with a fusiform aneurysm. CONCLUSION: We present a very rare case of intracranial VAD with SAH initially presenting with spinal symptoms. The majority of subsequent clinical features were consistent with a parietal focus of cortical subarachnoid blood, as observed on neuroimaging

A retrospective study on ectopic pregnancy aspiration by transvaginal ultrasound at Institute of Kidney Diseases And Research Centre

Background: Majority of the reports suggest that the frequency of ectopic pregnancies have grown in the last 30 years, especially in patients conceived through artificial reproductive techniques (ART). To prevent severe morbidity and mortality its prompt diagnosis and appropriate management is important. In a select patient population, most of the unruptured, live ectopic pregnancies can be successfully managed without surgical intervention using trans-vaginal ultrasound guided aspiration and instillation of local injection KCl or administration of systemic Inj. Methotrexate. Methods: This study is a hospital based retrospective cohort study from January 2014 to December 2022 on patients who presented to Institute of Kidney Diseases and Research Centre (IKDRC) with unruptured ectopic pregnancy confirmed with ultrasound and β HCG. All the patients were analyzed according to history, clinical presentation, investigations, treatment and complications. Results: β-HCG day 1 or 2 post procedure dropped in all cases but in variable levels ranging from 1.3% to 85.88%, while the drop during days 7-10, was more significant and reassuring; ranged from 48.69% to 98.95%. Conclusions: By aspiration of ectopic gestational sac transvaginally under ultrasonographic guidance it is able to preserve the integrity of uterus and fallopian tube and thus the future fertility. The study will educate other healthcare professionals.