scholarly journals Assessing visible aerosol generation during vitrectomy in the era of Covid-19

2020 ◽  
Author(s):  
Sidath Liyanage ◽  
Pathma Ramasamy ◽  
Omar Elhaddad ◽  
Kieren Darcy ◽  
Andrew Hudson ◽  
...  
Keyword(s):  
Physical Model ◽  
High Speed ◽  
Fluid Interface ◽  
Aerosol Generation ◽  
Maximum Cut ◽  
Hand Piece ◽  
Vitrectomy Surgery ◽  
Corneoscleral Rim ◽  
25 Gauge Vitrectomy ◽  
Air Exchange

AbstractObjectiveTo assess visible aerosol generation during simulated vitrectomy surgery. Methods: A model comprising a human cadaveric corneoscleral rim mounted on an artificial anterior chamber was used. Three-port 25 gauge vitrectomy simulated surgery was performed with any visible aerosol production recorded using high speed 4K camera. The following were assessed: (1) vitrector at maximum cut rate in static and dynamic conditions inside the model, (2) vitrector at air-fluid interface in physical model, (3) passive fluid-air exchange with a backflush hand piece, (4) valved cannulas under air, and (5) defective valved cannula under air.ResultsNo visible aerosol or droplets were identified when the vitrector was used within the model. In the physical model, no visible aerosol or droplets were seen when the vitrector was engaged at the air-fluid interface. Droplets were produced from the opening of backflush hand piece during passive fluid-air exchange. No visible aerosol was produced from the intact valved cannulas under air pressure, but droplets were seen at the beginning of fluid-air exchange when the valved cannula was defective.ConclusionsWe found no evidence of visible aerosol generation during simulated vitrectomy surgery with competent valved cannulas. In the physical model, no visible aerosol was generated by the high-speed vitrector despite cutting at the air-fluid interface.

A Solid-State On-Load Tap Changer for the Power Transformers of 10—0.4 kV Distribution Networks

Vestnik MEI ◽  
2020 ◽  
Vol 6 (6) ◽  
pp. 82-90
Author(s):  
Dmitriy I. Panfilov ◽  
◽  
Mikhail G. Astashev ◽  
Aleksandr V. Gorchakov ◽  
◽  
...  
Keyword(s):  
Solid State ◽  
Physical Model ◽  
High Speed ◽  
Power Transformer ◽  
Voltage Control ◽  
Power Transformers ◽  
Control Algorithms ◽  
Load Voltage ◽  
Tap Changer ◽  
Load Tap Changer

The specific features relating to voltage control of power transformers at distribution network transformer substations are considered. An approach to implementing high-speed on-load voltage control of serially produced 10/0.4 kV power transformers by using a solid-state on-load tap changer (SOLTC) is presented. An example of the SOLTC circuit solution on the basis of thyristor switches is given. On-load voltage control algorithms for power transformers equipped with SOLTC that ensure high reliability and high-speed operation are proposed. The SOLTC performance and the operability of the suggested voltage control algorithms were studied by simulation in the Matlab/Simulink environment and by experiments on the SOLTC physical model. The structure and peculiarities of the used simulation Matlab model are described. The SOLTC physical model design and its parameters are presented. The results obtained from the simulating the SOLTC operation on the Matlab model and from the experiments on the SOLTS physical model jointly with a power transformer under different loads and with using different control algorithms are given. An analysis of the experimental study results has shown the soundness of the adopted technical solutions. It has been demonstrated that the use of an SOLTC ensures high-speed voltage control, high efficiency and reliability of its operation, and arcless switching of the power transformer regulating taps without load voltage and current interruption. By using the SOLTC operation algorithms it is possible to perform individual phase voltage regulation in a three-phase 0.4 kV distribution network. The possibility of integrating SOLTC control and diagnostic facilities into the structure of modern digital substations based on the digital interface according to the IEC 61850 standard is noted.

scholarly journals Impact of cleaning regimes on dental water unit contamination

2011 ◽  
Vol 9 (4) ◽  
pp. 647-652 ◽  
Author(s):  
Soad A. Abdallah ◽  
Ahmed I. Khalil
Keyword(s):  
High Speed ◽  
Tap Water ◽  
Daily Basis ◽  
Dental Chair ◽  
Dental Clinics ◽  
Significant Difference ◽  
Before And After ◽  
Hand Piece ◽  
Viable Bacteria ◽  
Dental Unit Waterlines

Microorganisms that have been identified in dental unit waterlines (DUWLs) are of concern because they can cause infections, especially in immunocompromised patients. This study aimed to assess the incidence of microbial contamination in DUWLs before and after intervention to reduce contamination, and to investigate the presence of coliforms, Escherichia coli and Pseudomonas aeruginosa. Water samples were collected aseptically from the waterlines. The high-speed hand-piece and dental chair units were served by one distillation apparatus, which was fed by the potable tap water of four dental clinics. Different interventions were used: chlorination, flushing before clinics and between patients, draining at the end of the day, and freshly distilled water on a daily basis. There was a significant difference between the level of contamination in the high-speed hand-piece (1.5–2.7 log CFU/ml) and dental chair unit water (2.0–3.5 log CFU/ml). Coliforms (0.9%) E. coli (0.9%) and Pseudomonas (1.8%) were detected during 2008. This study indicates the need to monitor water quality regularly and prevent stagnation in DUWLs to reduce the number of viable bacteria to <100 CFU/ml. We recommend flushing the DUWL for 2 min before the first patient and for 10–20 s between patients, flushing the dental unit at the end of the day and draining it overnight to reduce the development of biofilms, and chlorination of the DUWLs.

scholarly journals Airborne Aerosol Generation During Endonasal Procedures in the Era of COVID-19: Risks and Recommendations

2020 ◽  
Vol 163 (3) ◽  
pp. 465-470 ◽  
Author(s):  
Alan D. Workman ◽  
Aria Jafari ◽  
D. Bradley Welling ◽  
Mark A. Varvares ◽  
Stacey T. Gray ◽  
...  
Keyword(s):  
High Speed ◽  
Airborne Particulate Matter ◽  
Mitigation Strategies ◽  
Nasal Endoscopy ◽  
Clinical Activity ◽  
Aerosol Sampling ◽  
Aerosol Generation ◽  
High Speed Drilling ◽  
Surgical Conditions ◽  
Hand Instrumentation

Objective In the era of SARS-CoV-2, the risk of infectious airborne aerosol generation during otolaryngologic procedures has been an area of increasing concern. The objective of this investigation was to quantify airborne aerosol production under clinical and surgical conditions and examine efficacy of mask mitigation strategies. Study Design Prospective quantification of airborne aerosol generation during surgical and clinical simulation. Setting Cadaver laboratory and clinical examination room. Subjects and Methods Airborne aerosol quantification with an optical particle sizer was performed in real time during cadaveric simulated endoscopic surgical conditions, including hand instrumentation, microdebrider use, high-speed drilling, and cautery. Aerosol sampling was additionally performed in simulated clinical and diagnostic settings. All clinical and surgical procedures were evaluated for propensity for significant airborne aerosol generation. Results Hand instrumentation and microdebridement did not produce detectable airborne aerosols in the range of 1 to 10 μm. Suction drilling at 12,000 rpm, high-speed drilling (4-mm diamond or cutting burs) at 70,000 rpm, and transnasal cautery generated significant airborne aerosols ( P < .001). In clinical simulations, nasal endoscopy ( P < .05), speech ( P < .01), and sneezing ( P < .01) generated 1- to 10-μm airborne aerosols. Significant aerosol escape was seen even with utilization of a standard surgical mask ( P < .05). Intact and VENT-modified (valved endoscopy of the nose and throat) N95 respirator use prevented significant airborne aerosol spread. Conclusion Transnasal drill and cautery use is associated with significant airborne particulate matter production in the range of 1 to 10 μm under surgical conditions. During simulated clinical activity, airborne aerosol generation was seen during nasal endoscopy, speech, and sneezing. Intact or VENT-modified N95 respirators mitigated airborne aerosol transmission, while standard surgical masks did not.

Dynamic Response of the Vertical Rotor System to Base Excitation

2008 ◽  
Author(s):  
Jianli Zuo ◽  
Jianjun Wu ◽  
Ping Li ◽  
Shenjian Su
Keyword(s):  
Dynamic Response ◽  
Physical Model ◽  
High Speed ◽  
Lagrange Equation ◽  
Rotor System ◽  
Operating Speed ◽  
Base Excitation ◽  
Rotating Machine ◽  
Vertical Rotor ◽  
Rotary Speed

The physical model of a high-speed vertical rotating machine was taken as the example. The motion differential equations of the rotor system were established by the Lagrange equation and numerically solved by the Wilson-θ method. The whirling characteristics of the rotor excited by the base’s harmonic motions have been analyzed. The whirling directions are different between the rotor’s upper and lower ends. And the whirling characteristics of the rotor vary with the frequency of the base’s motion. Besides, there exists such a region of the rotor’s rotary speed, in which the whirling characteristics and amplitudes of the rotor system are relatively steady, so the aseismic tests at a certain lower speed can be done to examine the aseismic capability of the rotor system at operating speed.

Pantograph-Catenary Model Simulation Based on DSPACE

2012 ◽  
Vol 256-259 ◽  
pp. 2967-2970
Author(s):  
Shuai Lin ◽  
Zhi Qiang Ju
Keyword(s):  
Real Time ◽  
Physical Model ◽  
High Speed ◽  
Model Simulation ◽  
The State ◽  
Rail Transit ◽  
High Speed Rail ◽  
Simulation Based ◽  
Primary Means ◽  
The City

With the city subway and high speed rail opened, development of rail transit pays more and more people's attention. And the pantograph is the primary means of train running at high speed to get power. Using Simulink and dSPACE in combination, real-time captures the pantograph and catenary's motion. According to the state of the pantograph’s motion, analyses physical model, so as to achieve the purpose of independent manufacturing pantograph pantograph.

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