Pneumomediastinum following a dental procedure

Background: Subcutaneous emphysema is a common presentation to the emergency department. The presence of emphysema in the head and neck region due to dental procedure is not common, and the presence of pneumomediastinum is exceedingly rare. Case Report: A young lady, presented to the emergency department with chest pain, found to have pneumomediastinum following a dental procedure including a wisdom tooth extraction. Conclusion: Complications following dental procedures are not uncommon, hence there should be a high index of suspicion for the emergency physicians for such patients, especially those where air turbine dental tools have been used.

Effects of Removal Conditions on Mercury Amount Remaining in the Oral Cavity and inside Drainage System after Removing Dental Amalgams

Mercury is produced and drained into the environment by removing dental amalgams, which may cause mercury pollution. This study aimed to clarify the mercury amount remaining in the oral cavity and inside the drain system after removal. The effects of the removal conditions and differences in drainage systems were also investigated. Dental amalgams filled in the tooth and placed in a phantom head were removed using an air turbine under several conditions (two removal methods, absence of cooling water, and intraoral suction). Then, the oral cavity was rinsed with 100 mL of water (oral rinse water), and 500 mL of water was suctioned to wash the inside of the drainage system (system rinse water). Both water samples were collected in two ways (amalgam separator and gas-liquid separator), and their mercury amounts were measured. It was found that the amount of mercury left in the oral cavity and drainage system after dental amalgams removal could be reduced when the amalgams were removed by being cut into fragments as well as using cooling water and intraoral suction. In addition, using amalgam separators can significantly reduce the amount of mercury in the discharge water and prevent the draining of mercury into the environment.

Design of Duct Passages for an Air Turbine Starter Test Rig

In a typical air turbine starter (ATS) engine testing application, compressed air is supplied to the turbine by means of an inlet duct usually with a 90 degree bend and discharged from the turbine into the exhaust chimney through a combination of two duct passages. The primary duct is integral to the engine for connecting to the containment ring. The secondary duct is a transition piece for connecting to the exhaust chimney. As these ducts consume additional pressure and adversely affect the performance of the ATS under test. The design of pressure-efficient outlet ducts is therefore essential, and is the topic of present study. The aerodynamic performance of the overall passage depends on the (i) angle of bend, (ii) the shape of the connecting bolt, (iii) the outlet area and shape of the exhaust duct transiting between the bend and the chimney. Combinations of different angular bends, different shaped bolts and varying size of transition pieces are analyzed using the enterprise version of CFD tool, ANSYS. Three dimensional mesh independent simulations using k-epsilon turbulence model are carried out for a combined geometry of inlet duct, rotor-stator combination, outlet ducts together with the bolts. A combination of the duct passages that has resulted in lowest possible pressure drop is suggested as result of the study i.e. the 90 degree bend duct gives 9% pressure difference between inlet and outlet and this might slightly affect the efficiency of the air turbine stator, however the mass flow rate values remains similar to the stator inlet mass flow rate. Hence the 90 degree bend duct is suitable for the test rig. The static pressure loss and total pressure gain is about 0.04% and −0.004% respectively for baseline and aggressive duct of stator and rotor, hence the baseline duct profile is better than aggressive duct. Among different shapes of connecting bolt, the baseline geometry gives slightly lower efficiency of 85.6% when compared to all other models. But due to manufacturing feasibility the baseline geometry is preferred. Exhaust duct model 7 gives pressure drop as 0.062 bar twice the amount of pressure drop in model 6, but it does not affect the efficiency of air turbine starter. The shapes and sizes of the bend, bolts and the transition piece are recommended.

Towards an Integrated PHM framework of the Mutriku Wave Power Plant. Air Turbine Case Study

The Mutriku Wave Power Plant (WPP) is a wave energy conversion plant based on the oscillating water column technology that was commissioned by the Basque Energy Agency in 2011 (Torre-Enciso, Ortubia, De Aguileta, & Marqués, 2009). The Basque Energy Agency is currently the responsible for the operation and maintenance tasks of the plant. From the beginning of the operation of the plant, different degradation and failure events have been reported for WPP components including air-turbines and electric generators (Lekube, Ajuria, Ibeas, Igareta,& Gonzalez,2018), which required unplanned maintenance actions. Despite the thorough monitoring system included in the WPP, a-posteriori root cause failure diagnostics has been challenging due to the lack of experience in similar systems. In this context, without a direct cause-effect correlation between failures and events, the implementation of maintenance actions has been implemented through trial-and-error events, i.e. replacement of components based on intuition and expert knowledge, until the system recovered its optimal operation mode. The Mutriku WPP is designed as a test facility and it is located onshore into the breakwater. Therefore, the operational consequence of unplanned maintenance actions are not as critical as in future commercial open ocean WPPs. However, all the monitored information collected over the years of operation can be used to develop diagnostics models that integrate statistical learning strategies with expert knowledge and accordingly assist engineers in the maintenance decision-making processes of future WPPs. This paper presents an integrated prognostics & health management (PHM) framework for the Mutriku WPP. Figure 1 shows the conceptual block diagram. FIGURE 1 (see attached PDF) The expert knowledge of plant engineers will be combined with collected data and signal-processing methods to detect anomalies, diagnose the failure cause, and predict the remaining useful life (RUL) of plant components and the overall plant (Aizpurua & Catterson, 2015). The development of this approach will permit the prompt detection of anomalies for future operation events and avoid unplanned maintenance actions. The main components evaluated in this paper will be the air-turbines, including different information of the WPP, such as rotational speed, bearing vibration, generated power of the turbine, and pressure loss through the turbine impeller. Firstly, the paper will provide a detailed view of the developed PHM framework for Mutriku WPP (cf. Figure 1). Secondly, after the identification of abnormal patterns, a conditional anomaly detection model will be designed (Catterson, McArthur, & Moss, 2010) from the characteristic operation curve of the turbine and operation condition of the plant as shown in Figure 2. FIGURE 2 (see attached PDF) The proposed approach will be validated with real on-site monitored data. Figure 3 shows the empirical characteristic curve of an air turbine. FIGURE 3 (see attached PDF) Based on the normal operation of the turbines, including contextual information, such as sea-state and plant operational state, probabilistic multivariate models will be developed for the turbines and the operation environment and then their probabilistic correlations will be defined so as to estimate the probability of a turbine being healthy, given the operational information (see Figure 2). Figure 4 shows early results of the anomaly detection model, where it is possible to observe anomalies with very low likelihood. FIGURE 4 (see attached PDF) Vertical dashed line in Figure 4 indicates end of training data, and gray dashed area indicates confidence intervals for improved decision-making under uncertainty.

Local Exhaust Ventilation to Control Dental Aerosols and Droplets

Dental procedures produce aerosols that may remain suspended and travel significant distances from the source. Dental aerosols and droplets contain oral microbes, and there is potential for infectious disease transmission and major disruption to dental services during infectious disease outbreaks. One method to control hazardous aerosols often used in industry is local exhaust ventilation (LEV). The aim of this study was to investigate the effect of LEV on aerosols and droplets produced during dental procedures. Experiments were conducted on dental mannequins in an 825.4-m3 open-plan clinic and a 49.3-m3 single surgery. Ten-minute crown preparations were performed with an air-turbine handpiece in the open-plan clinic and 10-min full-mouth ultrasonic scaling in the single surgery. Fluorescein was added to instrument irrigation reservoirs as a tracer. In both settings, optical particle counters (OPCs) were used to measure aerosol particles between 0.3 and 10.0 µm, and liquid cyclone air samplers were used to capture aerosolized fluorescein tracer. In addition, in the open-plan setting, fluorescein tracer was captured by passive settling onto filter papers in the environment. Tracer was quantified fluorometrically. An LEV device with high-efficiency particulate air filtration and a flow rate of 5,000 L/min was used. LEV reduced aerosol production from the air-turbine handpiece by 90% within 0.5 m, and this was 99% for the ultrasonic scaler. OPC particle counts were substantially reduced for both procedures and air-turbine settled droplet detection reduced by 95% within 0.5 m. The effect of LEV was substantially greater than suction alone for the air-turbine and was similar to the effect of suction for the ultrasonic scaler. LEV reduces aerosol and droplet contamination from dental procedures by at least 90% in the breathing zone of the operator, and it is therefore a valuable tool to reduce the dispersion of dental aerosols.

CFD Simulation Study on the Performance of a Modified Ram Air Turbine (RAT) for Power Generation in Aircrafts

The present paper aims to study the possibility of dispensing an auxiliary power unit (APU) in an aircraft powered by fossil fuels to reduce air pollution. It particularly seeks to evaluate the amount of power generated by the ram air turbine (RAT) using the novel counter-rotating technique while characterizing its optimum axial distance. The ram air turbine (RAT), which is already equipped in aircrafts, was enhanced to generate the amount of energy produced by the APU. The approach was implemented by a CRRAT system. Six airfoil profiles were tested based on 2D models and the best airfoil was chosen for implantation on the RAT and CRRAT systems. The performance of the conventional single-rotor RAT and CRRAT were analyzed using FLUENT software based on 3D models. The adopted numerical scheme was the Navier–Stokes equation with k–ω SST turbulence modeling. The dynamic mesh and user-defined function (UDF) were used to revolve the rotor turbine via wind. The results indicated that the FX63-137 airfoil profile showed a higher performance in terms of the lift-to-drag ratio compared to the other airfoils. The optimum axial distance between the two rotors was 0.087 m of the rotor diameter and the efficiency of the new CRRAT increased to almost 45% compared to the single-rotor RAT.

Heating of natural gas before expander - generator unit

The article discusses the replacement of throttling at the stations of technological lowering of the pressure of main natural gas by an expander-generator technology that allows the production of a cheap one with high environmental indicators. The disadvantage of this method of generating electricity is a significant cooling of the gas at the outlet of the expander, which necessitates its heating. The efficiency of the expander-generator set is largely determined by the adopted gas heating scheme. Achieving such heating temperatures is possible only by using high-potential energy resources, which are present in the technological equipment of gas distribution stations in the form of gas heaters with an intermediate heat carrier, designed to heat gas before expansion. Calculations of the amount of fuel gas required for heating the main natural gas in front of the expander-generator unit at the gas distribution stations under consideration have been carried out. The results of the study of the influence of the temperature of gas heating in front of the expander on the consumption of fuel gas supplied for heating and the numbers of heaters are presented. An analytical dependence of the electric power of the heat pump installation on the difference between the total power consumption of the compressor and the power of the air turbine is obtained.

In Vivo Study of Aerosol, Droplets and Splatter Reduction in Dentistry

Oral health care workers (OHCW) are exposed to pathogenic microorganisms during dental aerosol-generating procedures. Technologies aimed at the reduction of aerosol, droplets and splatter are essential. This in vivo study assessed aerosol, droplet and splatter contamination in a simulated clinical scenario. The coolant of the high-speed air turbine was colored with red concentrate. The red aerosol, droplets and splatter contamination on the wrists of the OHCW and chests of the OHCW/volunteer protective gowns, were assessed and quantified in cm2. The efficacy of various evacuation strategies was assessed: low-volume saliva ejector (LV) alone, high-volume evacuator (HV) plus LV and an extra-oral dental aerosol suction device (DASD) plus LV. The Kruskal–Wallis rank-sum test for multiple independent samples with a post-hoc test was used. No significant difference between the LV alone compared to the HV plus LV was demonstrated (p = 0.372059). The DASD combined with LV resulted in a 62% reduction of contamination of the OHCW. The HV plus LV reduced contamination by 53% compared to LV alone (p = 0.019945). The DASD demonstrated a 50% reduction in the contamination of the OHCWs wrists and a 30% reduction in chest contamination compared to HV plus LV. The DASD in conjunction with LV was more effective in reducing aerosol, droplets and splatter than HV plus LV.