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Number of results: 70
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Abstract

Mechanical ventilation (MV) is a supportive and life-saving therapy, however, it can cause ventilator-induced lung injury as a common complication. Thus, recruitment manoeuvres (RM) are applied to open the collapsed alveoli to ensure sufficient alveolar surface area for gas exchange. In the light of the fact that positive pressure ventilation is currently the standard treat- ment for improving pulmonary function, extrathoracic negative pressure is considered as an alter- native form of respiratory support. The aim of this study was to estimate the proinflammatory and oxidative response during MV and lung injury as well as the response after RM. All studied parameters were assessed at the following time points: T1-spontaneous breathing, T2- MV, T3- lung injury, T4 –RM. During MV (T2) elastase, MPO, ALP release, nitrite and superoxide generation significantly increased, whereas in later measurements a decrease in these values was noted. The MDA plasma concentration significantly (p<0.05) increased at T2, reaching a level of 13.30±0.87 nmol/ml; at other time points the values obtained were similar to the baseline value of 9.94±0.94 nmol/ml, whereas a gradual decrease in SOD activity at time T2-T4 points in comparison with the baseline value was found. During the study both neutrophil activity and oxi- dative stress indicate exacerbated response after MV and lung injury by bronchoalveolar lavage; however, extrathoracic negative pressure system as the MR ameliorates damaging changes which could further lead to serious lung injury.
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Abstract

Scientists are increasingly specializing in narrower fields, and communication is often difficult between physicists researching elementary particles and those studying semiconductors, not to mention between physicists and biologists or doctors. This makes interdisciplinary work difficult. And yet sometimes they succeed. One thread of work underway at the PAS Institute of High Pressure Physics offers a good example.
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Abstract

In this work the design aspects of a piezoelectric-based resonance ceramic pressure sensor made using low-temperature co-fired ceramic (LTCC) technology and designed for high-temperature applications is presented. The basic pressure-sensor structure consists of a circular, edge-clamped, deformable diaphragm that is bonded to a ring, which is part of the rigid ceramic structure. The resonance pressure sensor has an additional element – a piezoelectric actuator – for stimulating oscillation of the diaphragm in the resonance-frequency mode. The natural resonance frequency is dependent on the diaphragm construction (i.e., its materials and geometry) and on the actuator. This resonance frequency then changes due to the static deflection of the diaphragm caused by the applied pressure. The frequency shift is used as the output signal of the piezoelectric resonance pressure sensor and makes it possible to measure the static pressure. The characteristics of the pressure sensor also depend on the temperature, i.e., the temperature affects both the ceramic structure (its material and geometry) and the properties of the actuator. This work is focused on the ceramic structure, while the actuator will be investigated later.
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Abstract

Helical coil heat exchangers are widely used in a variety of industry applications such as refrigeration systems, process plants and heat recovery. In this study, the effect of Reynolds number and the operating temperature on heat transfer coefficients and pressure drop for laminar flow conditions was investigated. Experiments were carried out in a shell and tube heat exchanger with a copper coiled pipe (4 mm ID, length of 1.7 m and coil pitch of 7.5 mm) in the temperature range from 243 to 273 K. Air – propan-2-ol vapor mixture and coolant (methylsilicone oil) flowed inside and around the coil, respectively. The fluid flow in the shell-side was kept constant, while in the coil it was varied from 6.6 to 26.6 m/s (the Reynolds number below the critical value of 7600). Results showed that the helical pipe provided higher heat transfer performance than a straight pipe with the same dimensions. The convective coefficients were determined using theWilson method. The values for the coiled pipe were in the range of 3–40 W/m2 ·K. They increased with increasing the gas flow rate and decreasing the coolant temperature.
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Abstract

The theoretical aspects of a new type of piezo-resistive pressure sensors for environments with rapidly changing temperatures are presented. The idea is that the sensor has two identical diaphragms which have different coefficients of linear thermal expansion. Therefore, when measuring pressure in environments with variable temperature, the diaphragms will have different deflection. This difference can be used to make appropriate correction of the sensor output signal and, thus, to increase accuracy of measurement. Since physical principles of sensors operation enable fast correction of the output signal, the sensor can be used in environments with rapidly changing temperature, which is its essential advantage. The paper presents practical implementation of the proposed theoretical aspects and the results of testing the developed sensor.
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Abstract

The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as the method of its high-pressure die casting and the measurement results concerning the castability of the obtained composite. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. There were found the regression equations describing the change of castability of the examined composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained results.
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Abstract

The paper analyzes the changing public-private dynamics in higher education in Poland in 1990-2016 and beyond, focusing on the processes of internal and external de-privatization of the system. De-privatization of higher education – viewed also as its republicization – is caused by declining demographics and may lead to the demise of the largely demand-absorbing private higher education. Poland is shown as moving against the two powerful global trends related to privatization: private sector growth and increasing reliance on cost-sharing. Data related to funding and provision in 1990-2005 (expansion) and 2006 and beyond (contraction) are analyzed in detail, and policy implications of ongoing and expected changes are discussed.
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Abstract

The paper deals with the impact of technological parameters on the heat transfer coefficient and microstructure in AlSi12 alloy using squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze casting method. The goal was to affect crystallization by pressure with a value 100 and 150 MPa. The pressure applied to the melt causes a significant increase of the coefficient of heat transfer between the melt and the mold. There is an increase in heat flow by approximately 50% and the heat transfer coefficient of up to 100-fold, depending on the casting conditions. The change in cooling rate influences the morphology of the silicon particles and intermetallic phases. A change of excluded needles to a rod-shaped geometry with significantly shorter length occurs when used gravity casting method. By using the pressure of 150 MPa during the crystallization process, in the structure can be observed an irregular silica particles, but the size does not exceed 25 microns.
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Abstract

The disposal of ash in a thermal plant through the slurry pipe is subjected to some erosion wear due to the abrasive characteristics of the slurry. A simulation study of particle-liquid erosion of mild steel pipe wall based on CFD-FLUENT that considers the solid-liquid, solid-solid and solid-wall interaction is presented in this work. The multi-phase Euler-Lagrange model with standard k-epsilon turbulence modeling is adopted to predict the particulate erosion wear caused by the flow of bottom ash-water suspension. Erosion rate for different particle size and concentration is evaluated at variable flow rate. It is observed that the pressure drop and erosion rate share direct relationships with flow velocity, particle size and concentration. The flow velocity is found to be the most influencing parameter. A model capable of predicting the erosion wear at variable operating conditions is presented. The simulation findings show good agreement with the published findings.
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Abstract

The flow of a viscous incompressible fluid in small gaps hydraulic devices and devices based on the hop boundary changes in viscosity. For the distribution model adopted dynamic viscosity was integrate the equations of fluid motion, whereby expressions are obtained for the velocity of the liquid height of the gap. The expressions for calculation of the fall capacity flow section are determined. Examples of the calculation of distributions velocity and falling bandwidth to a narrow gap are given.The estimation of the limits of applicability of classical approach to the calculation of viscous flow in micro gap is executed.
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Abstract

The method of pressure die casting of composites with AlSi11 alloy matrix reinforced with 10 vol. % of SiC particles and the analysis of the distribution of particles within the matrix is presented. The composite castings were produced at various values of the piston velocity in the second stage of injection, at diverse intensification pressure values, and various injection gate width values. The distribution of particles over the entire cross-section of the tensile specimen is shown. The index of distribution was determined on the basis of particle count in elementary measuring fields. The regression equation describing the change of the considered index was found as a function of the pressure die casting parameters. The conclusion presents an analysis of the obtained results and their interpretation.
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Abstract

The measurement results concerning the abrasive wear of AlSi11-SiC particles composites are presented in paper. The method of preparing a composite slurry composed of AlSi11 alloy matrix and 10, 20% vol.% of SiC particles, as well as the method of its highpressure die casting was described. Composite slurry was injected into metal mould of cold chamber pressure die cast machine and castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. Very good uniform arrangement of SiC particles in volume composite matrix was observed and these results were publicated early in this journal. The kinetics of abrasive wear and correlation with SiC particles arrangement in composite matrix were presented. Better wear resistance of composite was observed in comparison with aluminium alloy. Very strong linear correlation between abrasive wear and particle arrangement was observed. The conclusion gives the analysis and the interpretation of the obtained results.
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Abstract

The paper presents the method of preparing a composite slurry composed of AlSi11 alloy matrix and 10 vol.% of SiC particles, as well as the method of its high-pressure die casting and the measurement results concerning the tensile strength, the yield point, the elongation and hardness of the obtained composite. Composite castings were produced at various values of the piston velocity in the second stage of injection, diverse intensification pressure values, and various injection gate width values. There were found the regression equations describing the change of mechanical properties of the examined composite as a function of pressure die casting process parameters. The conclusion gives the analysis and the interpretation of the obtained results.
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Abstract

The nonlinearity parameter B/A, internal pressure, and acoustic impedance are calculated for a room temperature ionic liquid, i.e. for 1-ethyl-3-methylimidazolium bis[(trifluoromethyl)sulfonyl]imide for temperatures from (288.15 to 318.15) K and pressures up to 100 MPa. The B/A calculations are made by means of a thermodynamic method. The decrease of B/A values with the increasing pressure is observed. At the same time B/A is temperature independent in the range studied. The results are compared with corresponding data for organic molecular liquids. The isotherms of internal pressure cross at pressure in the vicinity of 70 MPa, i.e. in this range the internal pressure is temperature independent.
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Abstract

The paper presents the results of investigations concerning the influence of negative (relative) pressure in the die cavity of high pressure die casting machine on the porosity of castings made of AlSi9Cu3 alloy. Examinations were carried out for the VertaCast cold chamber vertical pressure die casting machine equipped with a vacuum system. Experiments were performed for three values of the applied gauge pressure: -0.3 bar, -0.5 bar, and -0.7 bar, at constant values of other technological parameters, selected during the formerly carried initial experiments. Porosity of castings was assessed on the basis of microstructure observation and the density measurements performed by the method of hydrostatic weighing. The performed investigation allowed to find out that – for the examined pressure range – the porosity of castings decreases linearly with an increase in the absolute value of negative pressure applied to the die cavity. The negative pressure value of -0.7 bar allows to produce castings exhibiting porosity value less than 1%. Large blowholes arisen probably by occlusion of gaseous phase during the injection of metal into the die cavity, were found in castings produced at the negative pressure value of -0.3 bar. These blowholes are placed mostly in regions of local thermal centres and often accompanied by the discontinuities in the form of interdendritic shrinkage micro-porosity. It was concluded that the high quality AlSi9Cu3 alloy castings able to work in elevated temperatures can be achieved for the absolute value of the negative pressure applied to the die cavity greater than 0.5 bar at the applied set of other parameters of pressure die casting machine work.
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Abstract

The paper deals with the impact of technological parameters on the mechanical properties and microstructure in AlSi12 alloy using squeeze casting technology. The casting with crystallization under pressure was used, specifically direct squeeze casting method. The goal was to affect crystallization by pressure with a value 100 and 150 MPa. From the experiments we can conclude that operating pressure of 100 MPa is sufficient to influence the structural characteristics of the alloy AlSi12. The change in cooling rate influences the morphology of the silicon particles and intermetallic phases. A change of excluded needles to a rod-shaped geometries with significantly shorter length occurs when used gravity casting method. At a pressure of 100 MPa was increased of tensile strength on average of 20%. At a pressure of 150 MPa was increased of tensile strength on average of 30%. During the experiment it was also observed, that increasing difference between the casting temperature and the mold temperature leads to increase of mechanical properties.
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Abstract

Recent research in the process of aluminum alloy die castings production, which is nowadays deeply implemented into the rapidly growing automobile, shipping and aircraft industries, is aimed at increasing the useful qualitative properties of the die casting in order to obtain its high mechanical properties at acceptable economic cost. Problem of technological factors of high pressure die casting has been a subject of worldwide research (EU, US, Japan, etc.). The final performance properties of die castings are subjected to a large number of technological factors. The main technological factors of high pressure die casting are as follows: plunger pressing speed, specific (increase) pressure, mold temperature as well as alloy temperature. The contribution discusses the impact of the plunger pressing speed and specific (increase) pressure on the mechanical properties of the casting aluminum alloy.
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Abstract

Experimental Mg-Al-RE type magnesium alloys for high-pressure die-casting are presented. Alloys based on the commercial AM50 magnesium alloy with 1, 3 and 5 mass % of rare earth elements were fabricated in a foundry and cast in cold chamber die-casting machines. The obtained experimental casts have good quality surfaces and microstructure consisting of an α(Mg)-phase, Al11RE3, Al10RE2Mn7 intermetallic compound and small amount of α+γ eutectic and Al2RE phases.
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Abstract

Experimental investigation was conducted on the thermal performance and pressure drop of a convective cooling loop working with ZnO aqueous nanofluids. The loop was used to cool a flat heater connected to an AC autotransformer. Influence of different operating parameters, such as fluid flow rate and mass concentration of nanofluid on surface temperature of heater, pressure drop, friction factor and overall heat transfer coefficient was investigated and briefly discussed. Results of this study showed that, despite a penalty for pressure drop, ZnO/water nanofluid was a promising coolant for cooling the micro-electronic devices and chipsets. It was also found that there is an optimum for concentration of nanofluid so that the heat transfer coefficient is maximum, which was wt. %=0.3 for ZnO/water used in this research. In addition, presence of nanoparticles enhanced the friction factor and pressure drop as well; however, it is not very significant in comparison with those of registered for the base fluid.
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Abstract

The upper section of the Bystrzyca River has a character of trout and grayling zone of river. The aim of the study was to determine the species composition of fish in the upper section of the Bystrzyca River and attempt to evaluate angling pressure on fish in this section of river based on analysis of records of amateur fishing. To determine the fish composition the control fishing was conducted using electric fishing gear. The assessment of angling pressure was based on the analysis of 2135 records of fishing in the mountain type rivers in 2012 year, obtained from PAA Lublin. The brown trout and grayling were a dominant fish species in the upper section of the Bystrzyca River, and the first of them was present on the whole length of the river and had the highest average density. The changes of fish community along the river course from Salmonids lead to an increase of the share of Cyprinids fish has been observed. Analysis of records of ama-teur fish catch revealed that the upper section of the Bystrzyca River is under considerable of angling pressure and the most commonly fished species was brown trout. However, the properly carried fishery management on this section of river and the establishment of „no kill” zone allows for proper maintenance of the populations of fish species valuable for anglers.
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Abstract

The aim of the study was to determine species structure of aquatic bugs in four anthro-pogenic water reservoirs. Heteroptera structure observed in studied reservoirs was clearly differen-tiated, which refers to age of the ponds. Newly created water reservoirs become quickly colonized mainly by pioneering species Corixinae, which led to formation of taxonomic group population of density exceeding 2700 indiv. m-2. In older reservoirs there were fish, which potential predation pressure led to almost a complete decline of bugs. The reason of bugs poverty in water reservoirs colonized by fish was also probably a small habitat diversity, leading to lack of refuges from predators.
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Abstract

The paper presents a method for wireless measurement of car wheel air pressure and temperature using the Tire Pressure Monitoring System, or TPMS module - one of the latest safety systems introduced by the automotive industry - with readings taken on a specifically designed test bench. The paper describes the structure and operating principle of the test bench key elements and how they work with the sensors, the TPMS module, and reference instruments, as well as the data format and accuracy of data transmission between TPMS and the host computer. The software designed for an embedded system emulating the real on-board computer allows for observing raw sensor readings and the effect of calibration in two points of the characteristics.
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Abstract

The paper describes issues related to pressure drop that accompanies the phenomenon of maldistribution of working fluid between the channels of a model minichannel plate heat exchanger. The research concerns a single exchanger’s plate containing 51 (in every geometry) parallel rectangular minichannels of hydraulic diameters 461 μm, 571 μm, 750 μm, and 823 μm. In addition, more complex geometry has been investigated, equipped with additional diagonal channels (so called extended geometry). The moment of the liquid phase transition through the heat exchanger was recorded at the flow rates ranging from 0.83 g/s to 13.33 g/s in the inlet manifold. The paper discusses the total pressure drop as a function of the flow rate and the characteristic dimension of minichannels, as well as the pressure drop as a function of the time of the fluid passage through the main part of the measuring section in which measurements were done. The resulting profiles correlate with the images of the flow distribution between channels recorded using the fast shutter speed camera, that allows to draw a further conclusions about the specifics of the maldistribution process. The impact of the total pressure drop on the actual range of optimum operating conditions of the heat exchanger was analyzed.
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