On-Line, Real-Time Diagnostics of a Single Fluid Atomization System

A drop tube-Impulse Atomization technique was used to produce copper droplets. In this method, energy is transferred to a liquid by plunger movement resulting in spherical droplets emanating from orifices. A mathematical model of the evolution of droplet velocity and temperature at various heights for different sized droplets was developed. A two-color pyrometer, DPV-2000, and a shadowgraph were used to measure droplets radiant energy, diameter and velocity. The temperature values from the model were used to assess the two color pyrometer assumption over the temperature range of measurement. The DVP 2000 measurements were found to be dependent of droplet size wavelength and position of droplets below the atomizing nozzle. By calibrating the instrument for effective emissivity over the range of measurements, the thermal history of droplets may be recorded using a single color pyrometer approach

Heterogeneous nucleation of the primary phase in the rapid solidification of Al-4.5wt%Cu alloy droplet

International audienceThis paper reports on rapid solidification of Al-Cu alloys. A heterogeneous nucleation/growth model coupled with a thermal model of a falling droplet through a stagnant gas was developed. The primary undercooling as well as the number of nucleation points was compared with Al-Cu alloy droplets produced by Impulse Atomization (IA). Based on experimental results from Neutron Diffraction, secondary (eutectic) phases were obtained. Then, primary and secondary undercoolings were estimated using the metastable extensions of solidus and liquidus lines calculated by Thermo-Calc. Moreover, Synchrotron X-ray micro-tomography has been performed on Al-4.5wt%Cu droplets. The undercoolings are in good agreement. Results also evidence the presence of one nucleation point and are in agreement with the experimental observations. 1. Introduction Manufacturing of most metallic alloy products involves solidification at some stage. Mechanical properties of these products are generally related to their solidification microstructures. Depending on the final application of a product, a certain type of microstructure is more appropriate compared to another. For a product that requires directional properties, a microstructure of columnar grains is needed while isotropic properties are satisfied with an equiaxed structure. Generally, post-processing of the solidified materials is required to obtain the final product with desired properties. These post-solidification treatments are generally time-consuming and therefore increase the production cost without fully eliminating solidification related defects such as segregation. Therefore, it is important to understand all the dynamics involved in the formation of solidification microstructures in order to control the properties of the final products. As dendrites growth from an undercooled melt depends a great deal on the nucleation undercooling. Therefore, determination of undercooling and the resulting growth rate, recalescence, microsegregation/phase fraction and grain size is very important. Al-Cu alloys (4.5, 5, 10 and 17 wt% Cu) have been produced by IA and the last three compositions were analysed in our previous papers [1, 2]. IA is a single fluid atomization technique that is capable of producing droplets of controlled size having a relatively narrow distribution and a predictable cooling rate. The alloys (350 to 450g) were melted in a graphite crucible by means of an induction furnace and atomized at 850ºC in an almost oxygen free chamber (10ppm) under Nitrogen, Helium or Argon atmospheres. The atomized droplets rapidly solidify during their fall by losing heat to th

Characterization of Single-Cylinder Small-Bore 4-Stroke CIDI Engine Combustion

Direct injection diesel engines power most of the heavy-duty vehicles. Due to their superior fuel economy, high power density and low carbon dioxide emissions, turbocharged, small bore, high speed, direct injection diesel engines are being considered to power light duty vehicles. Such vehicles have to meet stringent emission standards. However, it is difficult to meet these standards by modifying the in-cylinder thermodynamic and combustion processes to reduce engine-out emissions. After-treatment devices will be needed to achieve even lower emission targets required in the production engines to account for the anticipated deterioration after long periods of operation in the field. To reduce the size, mass and cost of the after-treatment devices, there is a need to reduce engine-out emissions and optimize both the engine and the aftertreatment devices as one integrated system. For example, the trade-off between engine-out NOx and PM, suggests that one of these species can be minimized in the engine, with a penalty in the other, which can be addressed efficiently in the after-treatment devices. Controlling engine-out emissions can be achieved by optimizing many engine design and operating parameters. The design parameters include, but are not limited to, the type of injection system: (CRS) Common Rail System, (HEUI ) Hydraulically Actuated and Electronically controlled Unit Injector, or (EUI) Electronic Unit Injector; engine compression ratio, combustion chamber design (bowl design), reentrance geometry, squish area and intake and exhaust ports design. With four-valve engines, the swirl ratio depends on the design of both the tangential and helical ports and their relative locations. For any specific engine design, the operating variables need also to be optimized. These include injection pressure, injection rate, injection duration and timing (pilot, main, and post injection), EGR ratio, and swirl ratio. The goal of the program is to gain a better understanding of the spray behavior under high injection pressures in small-bore, high compression ratio, high-speed, direct-injection diesel engines equipped with advanced fuel injection system. The final results demonstrate the capability of the engine in reducing the engine-out emissions and improve the trade-off between nitrogen oxides (NOx), particulate matter, other emissions and fuel economy. This report introduces a new phenomenological model for the fuel distribution and combustion, and emissions formation in the small bore, high speed, direct injection diesel engine. This will be followed by an analysis of the effect of each of injection pressure, EGR, injection advance and retard and swirl ratio on engine-out emissions and fuel economy. A discussion will be given on the 2-D and 3-D trade of maps. Finally a discussion will be made on the low temperature combustion regimes, its major problems and proposed solutions

Development of virtual ophthalmic surgical skills training

Background: This study aims to assess whether ophthalmic surgical skills can be taught successfully online to a diverse international and interprofessional student group. Methods: Mixed methods study involving 20 students and 5 instructors. Each student completed a pre-session and post-session questionnaire to assess their perceptions regarding online instruction. Changes in questionnaire responses were analysed using Wilcoxon signed rank (SPSS 25). Semi-structured interviews were conducted to assess instructor perceptions towards virtual surgical skills teaching. Thematic analysis was undertaken using NVivo 12.0 software. Results: There was a 100% completion rate of pre- and post-session questionnaires. Prior to the session, lack of instructor supervision and inability to provide constructive feedback were emergent themes from students. Pre-session concerns regarding online delivery: 40% of students thought their view of skills demonstration would be negatively impacted, 60% their level of supervision and 55% their interaction with instructors. Following the session 10%, 15% and 5% held this view respectively. All students were ‘satisfied’ or ‘very satisfied’ regarding the ‘Surgeon’s View’ camera angle as well as the use of breakout rooms. 75% perceived an improvement in their confidence in instrument handling, 80% in cable knot tying and 70% in suture tying. Overall student rating for the virtual surgical skills session was 8.85 (±1.19) out of 10 (10 being most satisfied). Conclusions: We demonstrate that successful delivery of a virtual ophthalmic surgical skills course is feasible. We were able to widen accessibility and participation through virtual delivery, which has future implications for ophthalmic surgical teaching and its reach

Outcomes of Descemet's membrane endothelial keratoplasty performed in combination with, before, or after cataract surgery in Fuchs' endothelial dystrophy: A review of the literature and meta-analysis

This review aimed to compare the outcomes of Descemet's membrane endothelial keratoplasty (DMEK) in combination with (category 1), before (category 2), or after cataract surgery (category 3) in patients with Fuchs' endothelial dystrophy (FED). Primary outcome was gain in best-corrected log of minimum angle of resolution (logMAR) visual acuity (BCVA). Secondary outcomes were graft detachment, rebubbling rates, rejection, failure, and endothelial cell loss (ECL). In category 1, 2, and 3, 12 studies (N = 1932) were included (five in category 1 [n = 696], one in category 2 [n = 286], and two in category 3 [n = 950], and the remaining four compared between two of the three categories). At 6 months, the gain in BCVA was 0.34 ± 0.04, 0.25 ± 0.03, and 0.38 ± 0.03 logMAR in category 1, 2, and 3, respectively. The difference was significant between categories 1 and 2 (Chi2 = 11.47, P < 0.01) and categories 2 and 3 (Chi2 = 35.53, P < 0.01). At 12 months, the gain in BCVA was 0.52 ± 0.05 and 0.38 ± 0.06 logMAR in categories 1 & 3 (Chi2 = 14.04, P < 0.01). The rebubbling rates were 15%, 4%, and 10% (P < 0.01) and the graft detachment rates were 31%, 8%, and 13% (P < 0.01) in categories 1, 2, and 3, respectively. However, graft rejection, survival rates, and ECL at 12 months were not different between categories 1 and 3. There is low certainty evidence that gain in BCVA in category 1 was comparable to category 3 at 6 months; however, it was significantly better with category 3 at 12 months. Although rebubbling and graft detachment rates were highest in category 1, there was no significant difference in graft rejection, survival rates, and ECL. Further high-quality studies are likely to change the effect estimate and have an impact on the confidence of the estimate

The S shape of a granular pile in a rotating drum

The shape of a granular pile in a rotating drum is investigated. Using Discrete Elements Method (DEM) simulations we show that the "S shape" obtained for high rotation speed can be accounted for by the friction on the end plates. A theoretical model which accounts for the effect of the end plates is presented and the equation of the shape of the free surface is derived. The model reveals a dimensionless number which quantifies the influence of the end plates on the shape of the pile. Finally, the scaling laws of the system are discussed and numerical results support our conclusions

Optical aberrations following implantation of multifocal intraocular lenses: a systematic review and meta-analysis protocol

INTRODUCTION: Multifocal intraocular lens (IOLs) are used to restore vision at different focal distances. The technology of multifocal IOLs is continually advancing. Optical aberrations a property of lenses that causes spreading of light over a region resulting in a blurred or distorted image. This study aims to systematically review investigator measured and patient reported optical aberrations following implantation of multifocal IOLs during phacoemulsification surgery to treat presbyopia in adults. METHODS AND ANALYSIS: We will conduct an electronic database search for randomised controlled trials, prospective non-randomised studies, observational studies in Ovid MEDLINE, Ovid EMBASE, Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, Scopus and ClinicalTrials.gov in March 2021. Eligibility criteria will include quantitative articles written in English and containing data on optical aberrations. Two independent reviewers will screen titles and abstracts and extract data from full texts, reporting outcomes according to Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Data extraction of key characteristics will be completed using customised forms. Methodological quality will be assessed using Cochrane Handbook 6.2. ETHICS AND DISSEMINATION: Ethics approval is not required for this review, as it will only include published data. Findings will be published in a peer-reviewed journal and disseminated across ophthalmic networks. We anticipate that the findings of this work will be of interest to multiple stakeholders: people who have undergone cataract surgery, eye health professionals, ophthalmic surgeons, device manufacturers and policy-makers. It will also inform researchers to where there are gaps in evidence and identify areas for future research. PROSPERO REGISTRATION NUMBER: CRD42021271050

Materials Research in Microgravity 2012

Reducing gravitational effects such as thermal and solutal buoyancy enables investigation of a large range of different phenomena in materials science. The Symposium on Materials Research in Microgravity involved 6 sessions composed of 39 presentations and 14 posters with contributions from more than 14 countries. The sessions concentrated on four different categories of topics related to ongoing reduced-gravity research. Highlights from this symposium will be featured in the September 2012 issue of JOM. The TMS Materials Processing and Manufacturing Division, Process Technology and Modeling Committee and Solidification Committee sponsored the symposium

Evaluation of Left Atrial Size and Function: Relevance for Clinical Practice

Left atrial (LA) structural and functional evaluation have recently emerged as powerful biomarkers for adverse events in a variety of cardiovascular conditions. Moreover, noninvasive evaluation of LA pressure has gained importance in the characterization of the hemodynamic profile of patients. This review describes the methodology, benefits and pitfalls of measuring LA size and function by echocardiography and provides a brief overview of the prognostic utility of newer echocardiographic metrics of LA geometry and function (i.e., three-dimensional volumes, longitudinal strain, and phasic function parameters)