Performance of a Nozzle to Control Bath Level Oscillations and Turbulence of the Metal-Flux Interface in Slab Molds

The characterization of the turbulent flow of liquid steel in a slab mold using a commercial nozzle was carried out through physical experiments and mathematical models. Six ultrasonic sensors were located at each side of the nozzle to obtain real-time plotting of the bath levels during the experimental time. An ultrasonic transducer located in the mold, 20 mm below the meniscus, determines the velocities and the turbulent variables along with the distance from the narrow face to the position of the nozzle’s outer wall. These data, together with the mathematical simulations, demonstrated a high correlation of bath level oscillations and the time-dependent behavior of the discharging jets. The flow inside the mold shows low-frequency non-symmetric patterns without a severe turbulent in the meniscus. The source of this instability is the partial opening of the slide valve gate used to control the mass flow of liquid.

Dam break analysis using 1D geometry at Jatigede Dam, Sumedang

Dam breaks can result in flash floods which have enormous destructive power. This destructive force becomes even more significant when the dam break occurs in a dam with a large capacity. An example is the Jatigede Dam, which has a capacity of 1,060 million m3. To determine the flash flood characteristics and potential impact of the collapse of the Jatigede Dam, an analysis of the dam break was carried out using HEC-RAS software. The dam break scenario uses a Probable Maximum Flood (PMF) inflow with the partial opening of two spillway gates in the middle, which causes the dam overtopping. The Froehlich and Von Thun, and Gillette regression methods were used to defining the breach parameters. Based on the dam break analysis, the simulated flash flood of the Von Thun-Gillette method resulted in a higher velocity and lower water surface elevation than the Froehlich method. The difference in the velocity, dimension of the breach shape, water surface elevation, and discharge is caused by the breaching shape and breach formation time.

Distinct roles of the Na+ binding sites in the allosteric coupling mechanism of the glutamate transporter homolog, GltPh.

Glutamate transporters carry out the concentrative uptake of glutamate by harnessing the ionic gradients present across cellular membranes. A central step in the transport mechanism is the coupled binding of Na+ and substrate. The sodium coupled Asp transporter, GltPh is an archaeal homolog of glutamate transporters that has been extensively used to probe the transport mechanism. Previous studies have shown that hairpin-2 (HP2) functions as the extracellular gate for the aspartate binding site and plays a key role in the coupled binding of sodium and aspartate to GltPh. The binding sites for three Na+ ions (Na1-3) have been identified in GltPh but the specific roles of the individual Na+ sites in the binding process has not been elucidated. In this study, we developed assays to probe Na+ binding to the Na1 and Na3 sites and to monitor the conformational switch in the NMDGT motif. We used these assays along with a fluorescence assay to monitor HP2 movement and EPR spectroscopy to show that Na+ binding to the Na3 site is required for the NMDGT conformational switch while Na+ binding to the Na1 site is responsible for the partial opening of HP2. Complete opening of HP2 requires the conformational switch of the NMDGT motif and therefore Na+ binding to both the Na1 and the Na3 sites. Based on our studies we also propose an alternate pathway for the coupled binding of Na+ and Asp.

Numerical modelling of the sand particle flow in pelton turbine injector

Pelton turbine is commonly employed high head impulse type turbine. Pelton turbine injector is an integrated part of the Pelton turbine machine which serves the purpose of converting entire pressure energy of water to kinetic energy and also regulates the water flowrate, with partial opening hence governing the power production. Severe erosion in Pelton turbine injector is reported from field setting research studies. Since the jet is atmospheric pressure jet, there is few chances of occurrence of cavitation hence it can be understood that impact of sand particles is the major cause of erosion. Furthermore, with turbine operating in partial flow condition, more erosion is reported in the needle of injector. For a long spear type injector, this study explores the cause of erosion by modeling the motion of the sand particle flow in steady state jet. For numerical modeling of the flow, the realizable k-epsilon model is used and for modeling the particle flow, the Discrete Phase Model (DPM) is used. Three different operating condition of the injector is considered and 77000 particles were injected to the flow domain. It is observed from the numerical simulations that the more sand particle hits the nozzle-needle surface with partial opening of the injector.

First multicenter experience using the Silk Vista flow diverter in 60 consecutive intracranial aneurysms: technical aspects

BackgroundThe aim of this study was to assess the technical success and procedural safety of the new Silk Vista device (SV) by evaluating the intraprocedural and periprocedural complication rate after its use in several institutions worldwide.MethodsThe study involved a retrospective review of multicenter data regarding a consecutive series of patients with intracranial aneurysms, treated with the SV between September 2020 and January 2021. Clinical, intra/periprocedural and angiographic data, including approach, materials used, aneurysm size and location, device/s, technical details and initial angiographic aneurysm occlusion, were analyzed.Results60 aneurysms were treated with SV in 57 procedures. 66 devices were used, 3 removed and 63 implanted. The devices opened instantaneously in 60 out of 66 (91%) cases and complete wall apposition was achieved in 58 out of 63 (92%) devices implanted. In 4 out of 66 (6%) devices a partial opening of the distal end occurred, and in 5 (8%) devices incomplete apposition was reported. There were 3 (5%) intraprocedural thromboembolic events managed successfully with no permanent neurological morbidity, and 4 (7%) postprocedural events. There was no mortality in this study. The initial occlusion rates in the 60 aneurysms were as follows: O’Kelly–Marotta (OKM) A in 34 (57%) cases, OKM B in 15 (25%) cases, OKM C in 6 (10%) cases, and OKM D in 5 (8%) cases.ConclusionsOur study demonstrated that the use of the new flow diverter Silk Vista for the treatment of intracranial aneurysms is feasible and technically safe.

Teaching During Covid-19

The recent outbreak of COVID-19 has enor- mously affected every aspect of global arrange- ments with its fast and lethal reach. Originating from Wuhan, a Chinese city, this highly infectious virus has forced to impose nationwide closures in many countries impacting onsite educational systems to shut down. Considering the safety of students and following the steps taken by many infected countries, the Pakistan government initially closed all the edu- cational institutions and later allowed partial opening of schools where 30-50 % of students were allowed to attend classes in a cyclic manner. The direct and most immediate impact of this decision was an untimely break and loss of learning opportunities for all students. In order to continue with teaching and learning, Higher education commission, developed online tea- ching guidelines with the instructions to resume tea- ching, by following these guidelines. The guidelines included development and implementation of both online and hybrid curricula. Online teaching-learning is based on application of information technology tools to ensure access to learning resources for all students in the absence of face to face classes. It is conducted in the form of asynchronous or synchronous communication where-in asynchronous system tools like e-mail, discussion boards, learning newsgroups are used. For synchronous system webcasting, live chat and audio/video technologies are used for realtime class. Hybrid learning can be defined as a learning approach that combines both remote learning and inperson learning to improve student experience and ensure learning continuity.

Myanmar: Pandemic in a Time of Transition

This chapter examines how Myanmar faced distinct disadvantages in its ability to respond to the Covid-19 pandemic relative to regional neighbours. This is due to its continued grappling with simultaneous political, economic, and conflict-related transitions: Myanmar was a largely closed-off military dictatorship for nearly fifty years prior to its partial opening in 2011. In conjunction with structural factors, the triple transition had several important implications for Myanmar’s response to the pandemic. First, many of the aggressive approaches to countering Covid-19 that were effective in other contexts were infeasible for Myanmar, as the state lacked the capacity to enforce comprehensive population movement controls and large-scale testing and contact tracing. Second, Myanmar’s structural conditions prevented a uniform response to the pandemic. Third, Myanmar has several high-risk subgroups that complicated responses to the pandemic.

The effect of the coronavirus on garden tourism.

This chapter is essentially a postscript written as the effects of COVID-19 changed, so dramatically, the nature of garden operation and visitation. Much of the impact is drawn from the American Public Gardens Association (APGA) surveys of its member gardens in March (the immediate effects) and April 2020 (the results of the closure on revenue, staffing, and programs). In the final paragraphs the measures being taken to permit a (partial) reopening and the effects of the partial opening are examined. A case study is presented of Longwood Gardens, Kennett Square, Pennsylvania, USA, after COVID-19.