A NEW DUAL PORT CUTTER SYSTEM FOR VITRECTOMY SURGERY

To determine the influence of port geometry on water and vitreous flow rates and test novel vitreous cutter tips in specific surgical situations. Custom 20-gauge and 25-gauge vitreous cutter tips with different sized ports were evaluated through porcine vitreous and water flow rates. Five cutter tips were designed and fabricated for specific surgical functionalities. Tips were compared with a normal control tip and evaluated by water and porcine vitreous flow rates, vacuum level required to cut porcine retina, time required to cut and aspirate a porcine lens, and surgical evaluation in enucleated porcine eyes. Both vitreous and water flow asymptotically approached a maximum flow as the port diameter increased. Some tips removed water faster than the normal control tip, but none removed vitreous or lens faster. Several tips required higher vacuum levels to cut retina than the normal tip. Increasing the port diameter of a vitreous cutter to increase flow becomes less effective as the port becomes larger. Furthermore, modifying the port geometry of a vitreous cutter affects its surgical interactions with tissue. In the future, combinational instruments or surgery specific instruments may allow the surgeon to use an optimal port for a specific surgical task.

In 2021, estimation shows that the worldwide annual hydrogen production is around 94 Mt. Exploitation of native hydrogen being not mature, it is obtained by its separation from other elements by different methods such as steam methane reforming, and electrolysis of water. The latter supplied by a renewable power source will take part in the development of a green hydrogen economy [1]. In this context, Proton Exchange Membrane (PEM) Electrolyzer is a promising technology due to its flexibility and very quick adaptation to load variations. However, its current development still confronts some limitations at a large industrial scale. For instance, efficiency and durability are directly impacted by the mass transport and electrical transfer within the porous materials at the anode side. Limitation of the water supply to the catalyst layer happens once there is a poor oxygen evacuation which decreases the performance of the device by inducing high overpotential. Furthermore, the PTL has an important role as an electrical conductor for charge transfer from the catalyst layer [1]. The efficiency of all the transport phenomena through the PTL and porous electrode assembly depends on their transport properties which are related to their microstructure and operating conditions. For instance, PTL with a large pore size allows good water and gas transport, while produced electrons choose a long-distance path generating an electrical resistance higher than that in the case of PTL with a small pore size [1]. So, controlled and optimum porosity and pore size could contribute to efficient water, gas, and electron transport. To define the best porous layers morphologies, a deep and accurate understanding of the phenomena is developed in this work by combining modeling and experiments.The magnetic resonance imaging (MRI) technique was used to quantify the water content within the porous layer during the two-phase flow. Instead of the real PTL made of titanium which is paramagnetic and cannot be used in the MRI, borosilicate filters with thickness, porosity, and pore size similar to the PTL were used. After positioning the sample in the 600 MHz vertical imager (Figure 1-A), a constant water flow rate is introduced while the gas flow rate is varied. The saturation profiles measured through the porous material depend on the gas flow rate and a semi-dryness of the sample occurs (Figure 1-B) with a residual quantity trapped between pores (minimum stable water content). The water flow rate variation in the channel does not affect saturation, but a higher gas flow rate is needed to reach a minimum stable water content for higher water flow rate.The gas pressure drop through the porous medium was measured and bubble formation in the channel was also analyzed. The results show that the pressure drops and types of flow (slug, annular, and bubble flow) depend on orientation of the water channel (horizontally and vertically) and flow direction (up or downward), and on the water and gas flow rates.To reach a better understanding of the dynamic characteristics of water and oxygen transport over the PTL, the phase-field model based on the Cahn-Hilliard theory was used to simulate the two-phase flow through a porous medium [2]. In this model, the modified Navier-Stokes equations for two phases are coupled with a phase-field equation for describing the diffuse interface. Numerical simulations performed in the COMSOL® multiphysics software were carried on 2D geometries composed of spherical solid grains of different sizes, having properties similar to the PTL used in the MRI experiments. Gas is injected on one side of the sample and flows through the porous medium initially saturated and evacuated on another side in contact with the water channel (Figure 1-C). Gas flow in the porous medium and bubble formation in the water channel are studied while varying the gas and water flow rates. The simulation results give information about the gas pathways within the porous medium and the saturation profiles over time, depending on the gas/water flow rates, which will be compared with experimental results.[1] J. Parra-Restrepo, “Caractérisation des hétérogénéités de fonctionnement et de dégradation au sein d’un électrolyseur à membrane échangeuse de protons (PEM),” Université de Lorraine, 2020.[2] J. W. Cahn and J. E. Hilliard, “Free Energy of a Nonuniform System. I. Interfacial Free Energy,” The Journal of Chemical Physics, vol. 28, no. 2, pp. 258–267, Feb. 1958. Figure 1

In this paper, an IoT based system that alerts the authorities about an imminent flood is introduced. The water flow rate is detected using IR Sensor and the water level is detected using Ultrasonic sensor in rivers and drains and sent over Wi-Fi to the main controller which checks these received sensor values and if the values vary beyond a particular threshold , the alarm (buzzer) and also a alert Short Message Service(SMS) is sent to mobile. A website provides the plot of the water levels and the water flow rates. Also the weather forecast information obtained from the internet is provided in the website.The controller used to process the sensor data, obtain the water level and flow rate values, and transmit the obtained values is the Node Microcontroller Unit (NodeMCU). The controller used to receive the transmitted data, interpret it, perform the actuation (buzzer and SMS) and update the website is RaspberryPi3(RPi3)

There are several elements that affect the flow rate of water. One of the most convincing factors that resist the flow of water is the salinity. When the salinity takes place in a pipe the minerals of calcium and magnesium carbonates stick to the surfaces of pipes, which restricts water flow in the pipe. The main goal of this project is to investigate the effect of salinity on the flow rate of water. To achieve project aims, this project includes two experiments, the effect of salinity on the flow rate of water experiment and the effect of salt size on water flow rate experiment. The design of two experiments components is same but the type of salt will be changed. In general, the investigation of salinity influence on water flow rate is observed under fixed temperature and initial flow rate. At the end of the experiments, the results are mentioned in tables and in the line graphs to describe the effect of salinity on the flow rate of water. In the effect of salinity on the flow rate of water experiment, the results show inversely proportional relation between salinity and flow rate of water.To illustrate, when the amount of salinity increase the flow rate will decrease because the salt will restrict the flow of water. On the other hand, the results of the influence of salt size on the flow rate of water experiment show the big size salt restricts the flow of water more than small size salt. So, the using different size of salt will change the flow rate of water that flows in the piping system.

Water flow rate plays an important role in the modeling prediction, fault detection and diagnosis, and performance optimization of the variable water flow air‐conditioning (VWFAC) system. However, flowmeters employed by the system's terminals have not been widely used in engineering applications for the constraints in installation space and high installation and retrofit costs. Therefore, in this study, a terminal flow rate estimation method is proposed for the VWFAC system to reduce the dependency on flowmeters. The water flow rate estimation model is developed based on the flow resistance characteristics inside the air handling unit (AHU) and was trained and verified at the Monitoring and Control Laboratory established in the Dalian University of Technology. The results indicate that the maximum root‐mean‐square error (RMSE) during the training and validation sessions are 0.038 m3/h and 0.028 m3/h, respectively, while the corresponding mean absolute percentage error (MAPE) are below 1.4% and 6.5%, which is acceptable for engineering applications. To improve the flow rate estimation accuracy of the model, water temperature, water flow rate, and pressure difference are suggested to cover a wide varied range during the training session as much as possible. Systematic error is an important index in determining the demands for sensor's accuracy class. According to the results of water flow rate, the systematic errors of the estimates are ranged between 0.51% and 0.76%, only about 1/4 to 1/3 of the measurements systematic errors. Based on the error propagation theory, the water flow rate estimates would be reliable if the systematic error of the pressure measurements does not over twice that of the water flow rate measurements. This flow rate estimation method can be further applied to other thermal engineering systems to bring considerable economic benefits for engineering applications.

A series of experiments have been performed to find out the effect of the mixing port length of Y-jet atomizers on the spray performance, using air and water as the test fluids. Water and air flow rates and the drop sizes were measured. Variation of the air flow rate with change of the mixing port length was insignificant. However, the water flow rate was very much susceptible to the mixing port length. Mixing point pressure was found to be very much influenced by the mixing port length. Flow pattern of the air/water mixture inside the mixing port was postulated through the experimental observations; and the variations of spatial distribution of Sauter Mean Diameter(SMD, D₃₂) and the cross-section-averaged SMD(D_32m) with different mixing port length and air/water mass flow rate ratio were examined. Generally, the mean drop size decreased and became spatially even when the mixing port length was reduced. Tentative correlations showing the mixing port length effect on the mixing point pressure and the cross-section-averaged drop size were provided.

Numerical simulation of multi-size bubbly flow in a continuous casting mold using population balance model

Acid recovery from copper metallurgical process streams polluted with arsenic by diffusion dialysis

Energy consumption in membrane capacitive deionization for different water recoveries and flow rates, and comparison with reverse osmosis

A study of steam condensation in countercurrent stratified flow of steam and subcooled water has been carried out in a rectangular channel inclined 33 deg to the horizontal. The variables in this experiment were the inlet water and steam flow rates, and the inlet water temperature. Condensation heat transfer coefficients were determined as functions of local steam and water flow rates, and the degree of subcooling. Correlations are given for the local Nusselt number for the smooth and for the rough interface regimes, and also for the dimensionless wave amplitude. A turbulence-centered model is also developed. It is shown that better agreement with the data can be obtained if the characteristic scales in the turbulent Nusselt number and Reynolds numbers are related to measured interfacial parameters rather than the bulk flow parameters. The important effect of interfacial shear, missing in previous eddy-transport models, is thus implicitly included.

The cold-end system of a nuclear power plant is a key complex node connecting the power generation system with the variable environmental conditions, and its operation, economy, and stability have become the main obstacles to further improving the performance of the first and second circuits. The current research on the interactions between the cold-end system and the thermal cycle of nuclear power mainly adopts the micropower model, while the existing condenser model does not take into account the influence of the turbine exhaust resistance and exhaust flow and other factors on the condenser vacuum change caused by the change in the circulating water flow rate and temperature in determining the optimal vacuum. This ignores the interactions between the equipment and the interconnections between the parameters, which results in the reduction of the model’s accuracy. This paper takes a nuclear power unit as an example, adopts the “constant flow calculation” method to calculate the heat balance of the two-loop thermal system of the nuclear power plant, and constructs an integrated simulation model of the reaction environment variables, the cold-end system, and the thermal cycle. Taking the circulating water temperature and flow rate as variables, the errors of the separate condenser model and the coupled model in circulating water parameter changes were obtained under the condition of satisfying the thermal system operation, and the circulating water temperature and flow rate change ranges applied by the separate condenser model were analyzed in order to reduce the amount of calculations when the unit power error was 1%. The results show that the circulating water temperature is 4 °C, the applicable range of the circulating water flow rate is 42 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 20 °C, the applicable range of the circulating water flow rate is 32.12 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 26 °C, the applicable range of the circulating water flow rate is 38.63 m3/s to the rated flow rate, the applicable range of the circulating water temperature is 30 °C, and the applicable range of the circulating water flow rate is 45 m3/s to the rated flow rate. At a circulating water temperature of 26 °C, the applicable range of the circulating water flow is between 38.63 m3/s and the rated flow; at a circulating water temperature of 30 °C, the applicable range of the circulating water flow is between 45.64 m3/s and the rated flow.

Air in the pressure system of hydropower plants may have negative effects on their operation and energy production as well as on the structure itself. These negative effects include an increase of the friction pressure drop, pressure fluctuations and high pressure pulses. Furthermore, the trapped air result in a reduction of the efficiency of turbines and pumps. For this reason hydropower plants are designed so that no air is entrained into the system. Nevertheless this cannot completely be achieved in practice, either due to design limitations or construction costs. This problem appears to be increasing in the future because of the rising demand of energy and a more flexible operation, in terms of peak power production. The air can be evacuated from the pressure system by means of structural deaeration device. These consist of a deaeration chamber at the ridge of the tunnel, separating the air from the water and a pipe or drill hole on top of the chamber, evacuating the air. The experience of the last years showed that there is a lack in specific knowledge of air-water flow in pressure tunnels, in deaeration chambers and in deaeration pipes for the design of such deaeration devices. This thesis intends to close this gap and to develop design guidelines for structural deaeration device. To carry out large scale model tests, two experimental rigs were built at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) at ETH Zurich. These allowed the investigation of the air-water flow in horizontal and downwardly inclined large conduits (D = 0.484 m), in deaeration chambers as well as in standpipes was investigated. The flow pattern of the air-water flow in conduits depends mainly on the flow rate of the two phases and the inclination angle of the pipe. For each investigated air- and water flow rate and inclination angle of the conduit a different bubble size distribution are observed. In downwardly inclined pressure pipes air bubbles are either transported downstream with the water flow or ascent in opposite direction. With downward slopes from 0.4% to 1.7%, up to a critical water velocity in the conduit, all air bubbles rise in opposite direction to the water flow. With increasing water velocities a portion of air is transported with the water flow. For each inclination angle and water velocity there exists a limit value for the volume flow rate of the transported air. Due to the research findings, the direction and the flow rate of the air can be evaluated. The air-water flow pattern in the deaeration chamber was investigated and the percentage of the deaerated air was measured depending on its size and the air- and water flow rate. Based on the percentage of the deaerated air the dimensions of the deaeration chamber were found for witch the transported air in the conduit is completely evacuated. Depending on the air flow rate, the pipe diameter and the way the air is entering the deaeration pipe the flow pattern was observed and the average void fraction was measured. The observed flow pattern in the deaeration pipe are in good agreement with those stated in the technical literature. The drift-flux model allows the calculation of the average and maximum two-phase mixture level swell.

This paper gives a brief description of the development of dissolved air flotation DAF (or so-called high pressure flotation) as an unit operation for removal of solids in water and wastewater treatment during the last 80 years up to this time. The first DAF-systems used in the water industry were the ADKA and Sveen-Pedersen ones from the 1920s. Some of these are still in use. The tanks in which the flotation phenomenon takes place in these systems are very shallow and narrow as well as rather long. The flow rate of water is some 2-3 m/h (at most less than 5 m/h only) and there is a very thin micro-bubble blanket below the water surface between the dry sludge blanket on that and the clarified water which flows almost horizontally below the bubble blanket toward the end of the tanks to be taken out there from near the bottom. The second generation of DAF was introduced in the 1960s and these units are widely in use today. Their tanks are almost square ones having usually a little bit more length than breadth. They are rather deep, too. There is an under-flow wall in front of the back wall of the units having a narrow horizontal gap on the bottom of the tanks for letting out the clarified water from the flotation space. The flow rate of water is usually 5-7 m/h or at most less than 10 m/h. The direction of flow is 30-45 degrees below the horizontal. There is a rather thick micro-bubble bed at the beginning of the tank below the dry sludge blanket. This bubble-bed becomes clearly thinner, when going toward the end of the tank. There are also round DAF tanks which are based on the same hydraulic principles as the rectangular ones presented above. A special application of DAF called the flotation filter was invented at the very end of the 1960s. It is a combination of flotation and rapid sand filtration, both of those being placed in the same tank. Flotation takes place in the upper part of the tank and the filter has been placed in the lower part of it. The direction of water flow is now vertically down from the free surface of water in the tank toward the deep-bed filter. This controls the direction of flow in the flotation space of the tank above the filter bed. The flow rate of water in flotation filters may be 10-15 m/h, but the flow conditions are still laminar. It is the threat that the head-loss of filters would grow too rapidly which in practice is limiting the hydraulic flow rate of flotation filters in this area. The third generation of DAF has been developed at the end of the 1990s. The operational idea is based on that of the flotation filter. The filter bed on the bottom of the tank has been replaced by a thin stiff plate with plenty of round orifices throughout the plate. This plate, having a very much lower flowing resistance than a sand filter can have, controls the vertical flow of water in the flotation space above the plate and distributes it evenly throughout the horizontal cross-section of the tank. The flotation tank is almost square seen from above and its depth is clearly more than the length and breadth of it. This kind of flotation unit can be operated with flow rates of water in the range 25-40 m/l. Even a flow rate of more than 60 m/h has been reported from this kind of DAF-units. There is no risk of clogging of the plate by suspended solids which could limit the flow rate. This is to say that it is possible to operate DAF also in turbulent flow conditions. The depth of the micro-bubble bed below the surface of water can be 1.5-2.5 m. There actually is a continuously regenerated micro-bubble bed in the tank filtering water which is going through this bed. The lower surface of the micro-bubble bed is really a horizontal one a little bit above the plate controlling the flow in the flotation space. The clarified water below the micro-bubble bed is totally clear. It can be said that in this case the removal of suspended solids takes place much more by filtering water by a deep-bed micro-bubble filter than by attaching micro-bubbles onto solids, when both of these are mixed with each other in the inlet shaft of the flotation unit, because the retention time of water in the inlet shaft is very short indeed.

Our study focuses on the potential usefulness of surface geophysical data to constrain the water content within an alluvial aquifer. On a study area where two wells have been drilled, we have performed several geophysical measurements, including ground penetrating radar, DC resistivity prospecting, seismic refraction survey and magnetic resonance soundings. From these data, we estimated several parameters, namely, the water height in the deposits, the effective porosity, the water content, the permeability, and the transmissivity of alluvial deposits. These physical parameters allow us to characterize the alluvial deposits in order to constrain the estimation of the potential water flow. The lithology and water flow rate known from the wells enabled us to compare geophysical results obtained in a high water flow rate zone to those in a low water flow rate zone. Correlation has been found between the water flow rate observed in both wells and the geophysical data obtained in the vicinity of these wells.

Performance analysis of heat exchanger- evacuated tube assisted drying system (HE-ETADS) under unload condition