Higher Average Pressure Research Articles

Estimating surface pressure on flexible structures subjected to flow-induced vibrations

A conventional flag is placed downstream of the inverted half cylinder to study pressure over the flag's surface due to fluid-flexible body interaction between the flag and the vortices generated by the half cylinder. An immersed boundary method provides a reliable and fast solution to the fluid-structure interaction problems, albeit with limitation. One such limitation is the accurate pressure profile over the Lagrangian grid, i.e., the structure boundary. A pressure prediction algorithm is proposed which couples with the improved immersed boundary method to predict pressure over flag's surface. The effect of flow patterns on flag's surface pressure is studied by varying flag's distance from the bluff body. The pressure results are analyzed as negative and positive pressure fluctuations from the assigned reference pressure in the far field. Results show high flag surface pressure at a smaller stream-wise distance. A subsequent decrease in flow pressure is observed, when the stream-wise distance is increased. Changing span-distance shows that the highest pressure occurs at Gy = 0.25 with a significant drop at span positions of 0 and 0.5. The average pressure over the flag's surface is also affected by the vibration modes and the vortex shedding from the surface of the flag. The deflected mode appears at a smaller stream-wise distance accompanied by additional vortex shedding from the flag surface resulting in a high average pressure. Whereas biased and conventional flapping modes appear as stream-wise distance is progressively decreased resulting in reduced average pressure. Hydrodynamic analysis shows that the vortices originating from the bluff body and their subsequent interaction with the flag serve as the primary source of pressure fluctuations resulting in a change in the pressure profile over the surface of the flag.

Impact of Pressure Distribution and Magnitude on the Performance of Lithium Metal Anodes

Li metal anodes are a critical battery technology due to their ability to substantially increase the energy density of Li-based batteries. It is well known that pressure greatly impacts the performance of a Li-metal anode. However, precisely how the pressure value and distribution of pressure affect performance is unclear. Furthermore, the solid-electrolyte interphase composition that forms under varying pressure distributions remains a key parameter for practical lithium metal anodes. In this work, different pressure distributions were employed by using differently shaped and oriented mechanical springs in the coin cells, resulting in varying contact points. Pressure-sensitive films were used to spatially map the pressure and correlate it to the performance. It was found that higher average pressure does not necessarily have a positive effect on performance. When high pressure is paired with poor pressure uniformity, the performance is in fact worse likely due to the current focusing effect, rendering unsatisfied cycling stability. This work points to the importance of controlling the relationship between average pressure and pressure uniformity.

Comparative occipital pressure mapping in the operating room.

Hospital-acquired occipital pressure injuries are a preventable cause of morbidity and mortality in the perioperative setting. To find the occipital cushion/pillow with the lowest measured peak pressures and the highest measured surface area using pressure mapping technology. A quality improvement project involving 3 operating room staff volunteers was conducted using pressure mapping. Five different pillows were tested based on what the study location commonly used and had available. The pillows included: standard pillow with pillowcase, non-powered fluidized positioner, medium-sized (17 × 17 × 1.5 inches) static seat cushion placed under the shoulders and head, pediatric-sized (13 × 13 × 2 inches) static air cushion placed under the head, and foam donut. The non-powered fluidized positioner had the highest average pressure and peak pressure for all 3 volunteers. The medium static air seat cushion had the lowest average and peak pressures for 2 out of 3 volunteers. None of the head cushions consistently demonstrated a larger surface area of pressure distribution. The medium-sized static air seat cushion, placed under the shoulders and head, demonstrated the most favorable pressure redistribution properties. The non-powered fluidized positioner demonstrated the least favorable pressure redistribution properties.

BENDING OF AN ELASTIC PLATE IN A HIGH PRESSURE FIELD

The derivation of the equation of static cylindrical bending of a thin plate under the action of pressures on its surface and end edges is given. The reduction over the thickness of the plate is taken into account, the effect of which becomes noticeable at high average pressure. The refined value of the transverse distributed force is used. The dependence of the bending on the average pressure and the rigidity of the supports in the longitudinal direction is considered.

Influence of cantilever tip geometry and contact model on AFM elasticity measurement of cells.

We have measured the elastic properties of live cells by Atomic Force Microscope (AFM) using different tip geometries commonly used in AFM studies. Soft 4-sided pyramidal probes (spring constant = 12 mN/m and 30 mN/m, radius 20 nm), 3-sided pyramidal probes (spring constant = 100 mN/m, radius of curvature 65-75 nm), flat (circular) probes (spring constant = 63 mN/m, radius 290 nm) and spherical probes (spring constant = 43 mN/m, radius 5 μm) have been used. Cells (3T3 fibroblasts) having elastic moduli around 0.5 kPa were investigated. We found that cell measured stiffness shows a systematic dependence on tip geometry: the sharper the tip, the higher the average modulus values. We hypothesize that the blunter the tip, the larger the contact area over which the mechanical response is measured or averaged. If there are small-scale stiffer areas (like actin bundles) they will be easier to pick up by a sharp probe. This effect can be seen in the wider distribution of the histograms of the measured elastic moduli on cells. Furthermore, non-linear responses of cells may be present due to the high average pressures applied by sharp probes, which would lead to an overestimation of the Young's modulus. Pressure versus contact radius simulations for the different tip geometries for a 0.5 kPa sample suggested similar average pressure for Bio-MLCTs, PFQNM and cut tips, except spherical tips that showed much lower average pressure at the same 400 nm indentation. However, real data of the cells suggested different results. Using the same indentation depth (400 nm) PFQNM and Bio-MLCTs showed similar average pressure and it decreased for cut and spherical tips. The calculated contact area at 400 nm cell indentation, using the obtained apparent Young's modulus for each tip geometry, showed the following distribution: Bio-MLCTs < PFQNM < cut << spherical. In summary, tip geometry as well as average pressure and tip-sample contact area are important parameters to take into account when measuring mechanical properties of soft samples. The larger the tip radius, the larger the contact area that will lead to a more evenly distribution of the applied pressure.

PS-P03-8: INFLUENCE OF AVERAGE AIR TEMPERATURE, PRESSURE AND AIR RELATIVE HUMIDITY ON BLOOD PRESSURE

Objective: To investigate the influence of average air temperature, pressure and air relative humidity on blood pressure (BP) and blood pressure variability in population. Methods: A total of 97,784 participants were included from the May Month Measurement 2020 in China. BP was measured three times consecutively in the sitting position with a 1-minute interval, using a validated electronic BP monitor. Trained volunteer investigators administered a questionnaire to collect information on medical history, lifestyle, and use of medications. Average air temperature, pressure, and air relative humidity of the day were recorded. The mean BP was taken as the mean of the second and third BP, and the systolic blood pressure variability (SBPV) was the standard deviation/mean of three systolic blood pressures (SBP). Statistical analysis was performed using SAS 9.4. Results: Linear regression analysis found that the average air temperature was negatively correlated with the mean SBP and SBPV in all participants and hypertensive subjects (P &lt; 0.0001, P = 0.01). The average pressure was positively correlated with the mean SBP and SBPV in all participants and hypertensive subjects (P &lt; 0.0001, P &lt; 0.0001). The average air relative humidity was negatively correlated with SBPV in hypertensive subjects (P = 0.03). The relationship between average air relative humidity and SBP in all participants and hypertensive subjects, between average air relative humidity and SBPV in all participants was not found. After adjustment for age, sex, body mass index, taking antihypertensive medicine, smoking, alcohol consumption, diabetes, history of heart disease and previous stroke, the average air temperature and pressure remained associated with mean SBP in all participants and in hypertensive subjects. Logistic regression analysis showed that for every 1°C increase in air temperature, the risk of hypertension decreased by 1.8%, and for every 10hpa increase in pressure and 1% increase in air relative humidity, the risk of hypertension increased by 0.3% and 0.4%, respectively. When air temperature increased 1°C, the happen of hypertension control increased by 2.3%, and decreased by 0.2% for every 1% increase in air relative humidity. The relationship was not found between mean pressure and control of hypertension. Conclusion: The lower average air temperature and higher average pressure are possibly related with higher SBP, more likely to suffer hypertension, while the lower average air temperature and the higher average air relative humidity may resulted in more difficult hypertensive control.

Influence of meteorological factors on development of spontaneous pneumothorax.

This study investigated the correlation between spontaneous pneumothorax (SP) and meteorological factors during different seasons. Patients who visited emergency rooms (ERs) in large cities in Korea and were discharged with SP from 2014 to 2016 were included in this study. Data on temperature, air pressure, and wind speed for each region were collected to obtain each factor's daily maximum, minimum, average, and changes. Days with more than 1 case of SP per million were referred to as pneumothorax days (PD) and those with less than 1 case of SP per million were referred to as non-pneumothorax days (NPD). The environmental factors were assessed on the same day (Day 0), 1 day prior (Day-1), and 2 days prior (Day-2) to PD and NPD per season. A total of 17,846 patients were included in this study. During winter, 4080 patients with SP visited the ERs of large cities with low population densities. The maximum temperature (0.16°C vs 0.76°C, 0.04°C vs 0.87°C, and 0.09°C vs 0.91°C), change in temperature (0.24°C vs 0.90°C, 0.38°C vs 0.81°C, and 0.41°C vs 0.83°C), average atmospheric pressure (0.16 vs 0.52 hPa, 0.25 vs 0.42 hPa, 0.34 vs 0.40 hPa), and maximum atmospheric pressure (0.15 vs 0.53 hPa, 0.28 vs 0.49 hPa, 0.33 vs 0.71 hPa) were greater for Day 0, Day-1, and Day-2, respectively, in PD than in NPD. Meanwhile, the average (0.31 vs 0.48 m/s, 0.28 vs 0.46 m/s, 0.20 vs 0.40 m/s), minimum (0.20 vs 0.31 m/s, 0.18 vs 0.25 m/s, 0.16 vs 0.25 m/s), and maximum (0.44 vs 0.67 m/s, 0.36 vs 0.71 m/s, 0.26 vs 0.58 m/s) wind speeds were slower, and the changes in wind speed (0.44 vs 0.67 m/s, 0.36 vs 0.71 m/s, 0.16 vs 0.25 m/s) were lower for all 3 days in PD than in NPD. High average and change in temperature, slow and unchanging wind speed, and high average and maximum atmospheric pressure were associated with SP. Since many findings of this study were contradictory to previous studies, it is assumed that the interaction of various factors affects SP.

Extremity Pressure in Splints Wrapped With an Elastic Bandage Versus Bias Cut Stockinette: An Experimental Model.

Many variables affect the pressure caused by splinting or casting. The purpose of this study was to compare pressure underlying a splint wrapped with either an elastic bandage or a bias cut stockinette. Thirty-two plaster volar resting splints were applied to a simulated extremity with a saline bag secured to it. A pressure transducer was connected to the saline bag to monitor changes in pressure once splints were applied, and 15 mL increments of saline were added to the bag to simulate swelling. Each dressing type was tested with normal application and tight application. Normal application splints wrapped with either bias cut stockinette or an elastic bandage demonstrated similar initial splint pressures (P = .81). With simulated swelling, splints wrapped with bias cut stockinette demonstrated a 15 mmHg (95% confidence interval [CI], 1.5-28.5) higher average pressure than those wrapped with an elastic bandage (P = .035). Tight application splints with an elastic bandage wrap demonstrated a 46 mmHg (95% CI, 16-77) higher initial splint pressure than those wrapped with bias cut stockinette (P = .009). Splints wrapped using either an elastic bandage or bias cut stockinette appear to have a similar safety profile, although in cases of excessive swelling, an elastic bandage may provide additional compliance. Tight splint application appears to be more hazardous with the use of an elastic bandage compared with a bias cut stockinette. Further study of the use of elastic bandages and bias cut stockinettes in the clinical setting may be warranted.

On the statistical properties of fluid flows with transitional power-law rheology in heterogeneous porous media

In this work, we study non-Newtonian fluid flow in heterogeneous porous media. We are interested in fluids presenting a specific change in rheology: Newtonian below a certain shear rate and power law above. Since porous media generally exhibit strong spatial heterogeneity at large geological scales, we study the interaction between such inhomogeneity and the nonlinear rheology of the fluid. The coupling between permeability heterogeneity and nonlinear rheology significantly affects the flow. We are particularly in the statistical properties of the velocity field (mean, variance, correlation, etc). Depending on the imposed mean pressure gradient, three macroscopic flow regimes are identified. For a low or high average pressure gradient, the average flow rate increases linearly or according to a power law, respectively. In the latter regime, we observe that the velocity field is more heterogeneous for shear-thinning fluids than for shear-thickening fluids. This is corresponding to a channeling effect of shear-thinning fluids. The intermediate regime corresponds to a progressive and inhomogeneous change of the local rheology. This transient regime is then characterized in terms of pressure gradient range. The flow field is also analyzed statistically. The spatial distribution of the regions above the rheology threshold shows interesting statistical properties. For instance, they exhibit multiscale characteristics (fractal), similar to other critical systems (percolation, avalanches, etc.). If the distribution of their area follows a power-law, the exponent is independent of the disorder. This suggests a kind of “universality” in this problem. More surprisingly, even though some statistical properties are independent of the parameters, an interesting abrupt rotation of the correlations is found for a particular set of parameters. This is explained by using some symmetries of the problem. • The flow of a non-Newtonian fluid in heterogeneous macroscopic porous media is studied. • If the rheology shows a change in behavior, a strong coupling between nonlinear rheology and heterogeneity is observed. • Three macroscopic flow regimes are observed. • The transient flow regime shows multiscale (fractal) properties that are independent of the parameters and the magnitude of the heterogeneity. • An abrupt change in the direction of correlation is also observed for a certain set of parameters.

Experimental study on the effect of equivalent ratio on working characteristics of gasoline fuel two-phase rotating detonation engine

To understand the effect of equivalent ratio on the working characteristics of gasoline fuel two-phase rotating detonation engine, a gas-liquid two-phase rotating detonation experimental study with high total temperature air as oxidant has been carried out in this work. The outer diameter, inner diameter and length of rotating detonation engine annular combustor are 202, 166 and 155 mm, respectively. Gasoline and high temperature air are injected into the combustor through a nozzle-gap impinging model constructed of high pressure atomizing nozzles and annular gap to improve the mixing effect and chemical activity of propellant. A pre-detonator tube is used as ignition device. In experiments, the equivalent ratio of propellant is controlled by changing the mass flow rate of gasoline with constant mass flow rate of air. Based on high frequency dynamic pressure signals and average static pressure measured in the combustor, the propagation mode and propagation characteristics of the gas-liquid two-phase rotating detonation wave and working characteristics of the engine were analyzed in details. Experimental results show that continuous self-sustained propagation of rotating detonation wave is realized in the combustor during the equivalent ratio ranging from 0.79 to 1.25. With the increase of the equivalent ratio, the propagation mode of detonation wave transforms from double wave collision/single wave mixed mode to single wave mode. By reducing the equivalent ratio to 0.61−0.66, the propagation stability of detonation wave becomes worse, and the propagation mode transforms to the intermittent detonation or sporadic detonation. When reducing the equivalent ratio to 0.52, the detonation initiation fails. In addition, with the increase of the equivalent ratio, both the average absolute pressure in the combustor and the average propagation frequency of detonation wave increase and then decrease, and the maximum value appears around the equivalent ratio of 1.19. Under this condition, the best experimental results are obtained. The average propagation frequency of detonation wave is 1 900.91 Hz, and corresponding average propagation speed is 1 110.8 m/s, which are consistent with the main frequency obtained from Fast Fourier Transform of high frequency pressure signal. There is a heavy velocity deficit existing during the propagation of detonation wave.

Use of LNG Cold Potential in the Cogeneration Cycle of Ship Power Plants

This paper presents the results of a numerical study on the parameters that affect the efficiency of the cogeneration cycle of a ship’s power plant. The efficiency was assessed based on the excess power (Ngen.) of a free turbine, operated with the inflow of gaseous nitrogen, which was used to generate electricity. A mathematical model and simulation of the regenerative cycle were created and adjusted to operate with a dual-fuel (diesel-liquid natural gas (LNG)) six-cylinder four-stroke engine, where the energy of the exhaust gas was converted into mechanical work of the regenerative cycle turbine. The most significant factors for Ngen. were identified by parametrical analysis of the cogeneration cycle: in the presence of an ‘external’ unlimited cold potential of the LNG, Ngen. determines an exhaust gas temperature Teg of power plant; the pressure of the turbo unit and nitrogen flow are directly proportional to Ngen. When selecting the technological units for cycle realization, it is rational to use high flow and average πT pressure (~3.0–3.5 units) turbo unit with a high adiabatic efficiency turbine. The effect of the selected heat exchangers with an efficiency of 0.9–1.0 on Ngen. did not exceed 10%. With LNG for ‘internal’ use in a ship as a fuel, the lowest possible temperature of N2 is necessary, because each 10 K increment in N2 entering the compressor decreases Ngen. by 5–8 kW, i.e., 5–6%.

DEVELOPMENT OF BOOST SYSTEMS FOR FORCED DIESEL ENGINES

The paper analyzes the world experience in boosting diesel engines by improving the air supply system, i.e. the installation of drive superchargers and (turbochargers) TKR. Two main types of mechanical superchargers, rotary and centrifugal, are considered. The most common models of rotatory superchargers, Roots, Eaton and Lysholm, the scheme and principle of operation of centrifugal superchargers are analyzed. The main disadvantage of mechanical supercharging is that all the power needed to compress the air is taken from the engine crankshaft. Therefore, gas turbine supercharging is considered the most promising. Single-stage boost systems are analyzed using the example of well-known car manufacturers such as Pegaso and Volkswagen. It has been established that the use of turbocharging increases engine efficiency, which leads to a decrease in specific effective fuel consumption. The further development is aimed at improving single-stage turbocharging systems, reducing the size of turbochargers, reducing inertia, using turbine controls and using two-stage boost systems. In addition, an analysis is made of the work of well-known companies developing boost systems (ABB Turbo Systems, MTU, MAN, Borg Warner Turbo System), which showed that for diesel engines with a liter capacity of more than 60 kW / l it is rational to use a two-stage boost system with intermediate cooling of the charge air. The advantages of using a two-stage boost system are: high torque at low engine speeds; increase in rated power; increase in boost pressure; reduction in fuel consumption; smoke reduction; high potential to reduce NOx emissions; improved transient characteristics. The use of a two-stage controlled turbocharging with cooling of the charge air type R2S achieves a high average effective pressure. Depending on the setting, the system can be implemented both at low and high engine speeds.

In silico investigation of sneezing in a full real human upper airway using computational fluid dynamics method

Background and objectiveSneezing is one of the most critical conditions that can occur in the human upper airway. As some reports confirm the injury to the human upper respiratory airway while sneezing. Therefore, the accurate study of the distribution of pressure and velocity in this case is of great importance. MethodsIn the present study, using a real human upper airway model, the pressure and velocity of the airflow generated in the tract during the sneezing have been investigated. Also, considering the results from a spirometer device as a boundary condition in the simulation process, the calculations have become reliable. ResultsAccording to the results, during sneezing, taking into account that the average outlet flow rate from the mouth is 4.79 L/s, the velocity of outlet airflow from the mouth and nose reaches 5.3 and 8.4 m/s, respectively. These values were 11.5 and 19, respectively, when the desired maximum flow rate was 10.58 L/s. It can be concluded that the increasing of trachea flow rate, leads to higher percentage of the outlet flow rate from the nose . The highest average pressure and velocity have been occurred in the trachea. Among other salient results of this report, increased average static pressure of larynx to approximately 10 kPa can be pointed which indicates that this area is critical so that the thyroid cartilage defect is likely to occur. It is also noteworthy that the increase of speed at nasopharynx is up to 125 m/s so that the cross-section changing in this area leads the fluid acts as a jet flow. Due to the specific geometry of the nasal cavity, some streams similar to poor shocks are formed, these shocks get stronger by increasing of the flow rate. The thyroid cartilage and nasal cavity are exposed to maximum static pressure extremums, respectively. ConclusionsWe introduced a model simulating a normal sneezing for two cases using a healthy 30-year-old male person. We believe that the model should be applied for different persons and an atlas of data could be obtained from different cases. This may help the medical system to have more data about the sneezing process.

Refreshing Extension of the Operation of High Pressure Rotors and Average Pressure Rotors of the Turbine K-200-130 at the Kurakhovska Heat Power Plant

Refreshing Extension of the Operation of High Pressure Rotors and Average Pressure Rotors of the Turbine K-200-130 at the Kurakhovska Heat Power Plant

Modeling and Optimization of Inductively Coupled Wireless Bio-Pressure Sensor System Using the Design of Experiments Method

This paper presents an approach for modeling and design of inductively coupled wireless bio-pressure sensor system for chronic intracardiac pressure monitoring. Making use of recent advances in microelectromechanical systems and semiconductor technology, bio-pressure sensor is developed as a series LC resonant circuit with a featured pressure-dependent capacitance working at the medical implant communication service band of 402–405 MHz for wireless sensing without power consumption. The microfabricated sensor consists of a planar spiral gold (Au) coil, a series capacitor, an SU-8-based frame structure, and an encapsulated bio-compatible PDMS membrane. Bio-pressure sensor is designed with a small footprint of 3.2 mm $\times $ 3.2 mm for reducing the bleeding and infection risks in surgery. With a limited footprint and desired working frequency, there are many mutually dependent geometry parameters with numerous combined groups of values involved in the full optimization of the system. In order to maximize the performance of system under the design requirements, RF characteristics that affect inductive sensitivity and pressure sensitivity are theoretically analyzed first, and then design of experiments method is applied to model and optimize 3-D electromagnetic models of sensor and sensor system on the derived RF characteristics. The large number of combined groups of values in factorial simulations is thus reduced to a few performance-related design factors. By monitoring the induced peak impedance of the readout coil, the pressure-dependent resonant frequency of the sensor can be detected and measured. The experimental results show that the optimized wireless sensor system has a relatively high average pressure sensitivity of 5.3 KHz/mm Hg at a telemetry distance of 10 mm demonstrating its potential for intracardiac pressure monitoring.

Water-use dynamics of an alien-invaded riparian forest within the Mediterranean climate zone of the Western Cape, South Africa

Abstract. In South Africa, the invasion of riparian forests by alien trees has the potential to affect the country's limited water resources. Tree water-use measurements have therefore become an important component of recent hydrological studies. It is difficult for South African government initiatives, such as the Working for Water (WfW) alien clearing program, to justify alien tree removal and implement rehabilitation unless hydrological benefits are known. Consequently, water use within a riparian forest along the Buffeljags River in the Western Cape of South Africa was monitored over a 3-year period. The site consisted of an indigenous stand of Western Cape afrotemperate forest adjacent to a large stand of introduced Acacia mearnsii. The heat ratio method of the heat pulse velocity sap flow technique was used to measure the sap flow of a selection of indigenous species in the indigenous stand, a selection of A. mearnsii trees in the alien stand and two clusters of indigenous species within the alien stand. The indigenous trees in the alien stand at Buffeljags River showed significant intraspecific differences in the daily sap flow rates varying from 15 to 32 L day−1 in summer (sap flow being directly proportional to tree size). In winter (June), this was reduced to only 7 L day−1 when limited energy was available to drive the transpiration process. The water use in the A. mearnsii trees showed peaks in transpiration during the months of March 2012, September 2012 and February 2013. These periods had high average temperatures, rainfall and high daily vapor pressure deficits (VPDs – average of 1.26 kPa). The average daily sap flow ranged from 25 to 35 L in summer and approximately 10 L in the winter. The combined accumulated daily sap flow per year for the three Vepris lanceolata and three A. mearnsii trees was 5700 and 9200 L, respectively, clearly demonstrating the higher water use of the introduced Acacia trees during the winter months. After spatially upscaling the findings, it was concluded that, annually, the alien stand used nearly 6 times more water per unit area than the indigenous stand (585 mm a−1 compared to 101 mm a−1). This finding indicates that there would be a gain in groundwater recharge and/or streamflow if the alien species are removed from riparian forests and rehabilitated back to their natural state.

Evaluation of the Environmental Bias on Accelerometer-Measured Total Daily Activity Counts and Owner Survey Responses in Dogs with Osteoarthritis.

Objective To determine if environmental variables affect the average daily activity counts (AC) of dogs with osteoarthritis (OA) and/or owners' perception of their dog's clinical signs or quality of life. Methods The AC and Canine Brief Pain Inventory (CBPI) owner questionnaires of 62 dogs with OA were compared with daily environmental variables including the following: average temperature (°C), high temperature (°C), low temperature (°C), relative humidity (%), total precipitation (mm), average barometric pressure (hPa) and total daylight hours. Results Daily AC significantly correlated with average temperature and total daylight hours, but average temperature and total daylight hours accounted for less than 1% of variation in AC. No other significant relationships were found between daily AC and daily high temperature, low temperature, relative humidity, total precipitation or average barometric pressure. No statistical relationship was found between daily AC and the CBPI, nor between environmental variables and the CBPI. Canine Brief Pain Inventory scores for pain severity and pain interference decreased significantly over the test period. Clinical Significance The relationship between daily AC and average temperature and total daylight hours was significant, but unlikely to be clinically significant. Thus, environmental variables do not appear to have a clinically relevant bias on AC or owner CBPI questionnaires. The decrease over time in CBPI pain severity and pain interference values suggests owners completing the CBPI in this study were influenced by a caregiver placebo effect.

Vessel sealing comparison: old school is still hip.

Ligation with either absorbable or non-absorbable sutures has been the traditional state of the art, but a proliferation of technology now offers a host of methods to close and divide vessels. Only limited data are available that objectively compare different vessel sealing methods. The objective of this study was to compare a broad variety of methods of surgical vessel closure in a reproducible, independent, standardized test-to-failure ex vivo pressure challenge. Ten of the most common surgical sealing devices were represented in this study, including both mechanical and energy devices. Unfixed porcine carotid arteries were selected for testing. They were connected to a pump, and automated controlled infusion was initiated. Upon identification of a leak at the source of sealing, the maximum pressure in mmHg was logged. There were a total of 184 trials conducted using the 10 vessel sealing methods. The average burst pressure across all trials was 1100mmHg with a range of 51.3-5171mmHg. Suture-based methods displayed the highest average pressure until failure. Stapling methods showed the lowest burst pressures. All methods showed mean burst pressures above the "physiologically relevant" level of 250mmHg. This study presents an independent, reproducible, ex vivo comparison of multiple methods of surgical arterial closure. In these laboratory conditions, tests to failure demonstrated widely varying sealing strength, highly dependent on method. All hemostatic modalities tested are capable of securing vessels safely and well above physiologic blood pressures, while suture-based methods were significantly stronger than other mechanical methods or modern energy devices.

Tokamak elongation – how much is too much? Part 2. Numerical results

The analytic theory presented in Paper I is converted into a form convenient for numerical analysis. A fast and accurate code has been written using this numerical formulation. The results are presented by first defining a reference set of physical parameters based on experimental data from high performance discharges. Scaling relations of maximum achievable elongation (${\it\kappa}_{max}$) versus inverse aspect ratio (${\it\varepsilon}$) are obtained numerically for various values of poloidal beta (${\it\beta}_{p}$), wall radius $(b/a)$ and feedback capability parameter (${\it\gamma}{\it\tau}_{w}$) in ranges near the reference values. It is also shown that each value of ${\it\kappa}_{max}$ occurs at a corresponding value of optimized triangularity (${\it\delta}$), whose scaling is also determined as a function of ${\it\varepsilon}$. The results show that the theoretical predictions of ${\it\kappa}_{max}$ are slightly higher than experimental observations for high performance discharges, as measured by high average pressure. The theoretical ${\it\delta}$ values are noticeably lower. We suggest that the explanation is associated with the observation that high performance involves not only $n=0$ MHD stability, but also $n\geqslant 1$ MHD modes described by ${\it\beta}_{N}$ in the Troyon limit and transport as characterized by ${\it\tau}_{E}$. Operation away from the $n=0$ MHD optimum may still lead to higher performance if there are more than compensatory gains in ${\it\beta}_{N}$ and ${\it\tau}_{E}$. Unfortunately, while the empirical scaling of ${\it\beta}_{N}$ and ${\it\tau}_{E}$ with the elongation (${\it\kappa}$) has been determined, the dependence on ${\it\delta}$ has still not been quantified. This information is needed in order to perform more accurate overall optimizations in future experimental designs.

A study on (K, Na) NbO3 based multilayer piezoelectric ceramics micro speaker

A flat panel micro speaker was fabricated from (K, Na) NbO3 (KNN)-based multilayer piezoelectric ceramics by a tape casting and cofiring process using Ag-Pd alloys as an inner electrode. The interface between ceramic and electrode was investigated by scanning electron microscope (SEM) and transmission electron microscope (TEM). The acoustic response was characterized by a standard audio test system. We found that the micro speaker with dimensions of 23 × 27 × 0.6 mm3, using three layers of 30 μm thickness KNN-based ceramic, has a high average sound pressure level (SPL) of 87 dB, between 100 Hz–20 kHz under five voltage. This result was even better than that of lead zirconate titanate (PZT)-based ceramics under the same conditions. The experimental results show that the KNN-based multilayer ceramics could be used as lead free piezoelectric micro speakers.