An Experimental Study of Influence of the Steam Injection on the Profile Surface on the Turbine Nozzle Cascade Performance

2014 ◽  
Author(s):  
Vladimir Gribin ◽  
Aleksandr Tishchenko ◽  
Victor Tishchenko ◽  
Ilya Gavrilov ◽  
Sergey Khomiakov ◽  
...  
Keyword(s):  
Liquid Phase ◽  
Laser Diagnostics ◽  
Experimental Studies ◽  
Steam Injection ◽  
Trailing Edge ◽  
Heating Steam ◽  
Wide Range ◽  
Steam Parameters ◽  
Diagnostics System ◽  
The Impact

The paper presents the results of experiments on the effect of steam injection on the performance of the wet steam turbine nozzle cascade. The steam injection destroys a liquid film on the surface of the blade and reduces erosion and dangerous droplets after cascade. The results obtained in the vane package cascade which include a slot on the concave surface of the airfoil near the trailing edge of blades. Experimental studies were carried out on wet and superheated steam. A pneumatic measurement system was used to determine the parameters of the main and injection steam. A laser diagnostics system “POLIS” that includes PIV/PTV was used to analyze the impact of heating steam injection on the characteristics of the liquid phase. Profile losses were obtained at different steam parameters and steam injection speeds. The characteristics of the liquid phase behind the trailing edge were obtained in a wide range of operating parameters.

scholarly journals Image Statistics Preserving Encrypt-then-Compress Scheme Dedicated for JPEG Compression Standard

Entropy ◽  
2021 ◽  
Vol 23 (4) ◽  
pp. 421
Author(s):  
Dariusz Puchala ◽  
Kamil Stokfiszewski ◽  
Mykhaylo Yatsymirskyy
Keyword(s):  
Statistical Analysis ◽  
Image Encryption ◽  
Experimental Studies ◽  
Quality Measures ◽  
Input Image ◽  
Jpeg Compression ◽  
Image Statistics ◽  
Compression Stage ◽  
Wide Range ◽  
The Impact

In this paper, the authors analyze in more details an image encryption scheme, proposed by the authors in their earlier work, which preserves input image statistics and can be used in connection with the JPEG compression standard. The image encryption process takes advantage of fast linear transforms parametrized with private keys and is carried out prior to the compression stage in a way that does not alter those statistical characteristics of the input image that are crucial from the point of view of the subsequent compression. This feature makes the encryption process transparent to the compression stage and enables the JPEG algorithm to maintain its full compression capabilities even though it operates on the encrypted image data. The main advantage of the considered approach is the fact that the JPEG algorithm can be used without any modifications as a part of the encrypt-then-compress image processing framework. The paper includes a detailed mathematical model of the examined scheme allowing for theoretical analysis of the impact of the image encryption step on the effectiveness of the compression process. The combinatorial and statistical analysis of the encryption process is also included and it allows to evaluate its cryptographic strength. In addition, the paper considers several practical use-case scenarios with different characteristics of the compression and encryption stages. The final part of the paper contains the additional results of the experimental studies regarding general effectiveness of the presented scheme. The results show that for a wide range of compression ratios the considered scheme performs comparably to the JPEG algorithm alone, that is, without the encryption stage, in terms of the quality measures of reconstructed images. Moreover, the results of statistical analysis as well as those obtained with generally approved quality measures of image cryptographic systems, prove high strength and efficiency of the scheme’s encryption stage.

scholarly journals Assessment of Machine-Learned Turbulence Models Trained for Improved Wake-Mixing in Low-Pressure Turbine Flows

Energies ◽  
2021 ◽  
Vol 14 (24) ◽  
pp. 8327
Author(s):  
Roberto Pacciani ◽  
Michele Marconcini ◽  
Francesco Bertini ◽  
Simone Rosa Taddei ◽  
Ennio Spano ◽  
...  
Keyword(s):  
Boundary Layers ◽  
Three Dimensional ◽  
Turbulence Models ◽  
Reynolds Numbers ◽  
Computational Domain ◽  
Trailing Edge ◽  
Low Pressure Turbine ◽  
Wide Range ◽  
Turbulence Closures ◽  
The Impact

This paper presents an assessment of machine-learned turbulence closures, trained for improving wake-mixing prediction, in the context of LPT flows. To this end, a three-dimensional cascade of industrial relevance, representative of modern LPT bladings, was analyzed, using a state-of-the-art RANS approach, over a wide range of Reynolds numbers. To ensure that the wake originates from correctly reproduced blade boundary-layers, preliminary analyses were carried out to check for the impact of transition closures, and the best-performing numerical setup was identified. Two different machine-learned closures were considered. They were applied in a prescribed region downstream of the blade trailing edge, excluding the endwall boundary layers. A sensitivity analysis to the distance from the trailing edge at which they are activated is presented in order to assess their applicability to the whole wake affected portion of the computational domain and outside the training region. It is shown how the best-performing closure can provide results in very good agreement with the experimental data in terms of wake loss profiles, with substantial improvements relative to traditional turbulence models. The discussed analysis also provides guidelines for defining an automated zonal application of turbulence closures trained for wake-mixing predictions.

scholarly journals RESEARCH OF EFFICIENCY ECOLOGICAL DIAGNOSTICS SYSTEM OF HEAT ENGINES AND BOILER PLANTS

2019 ◽  
Vol 6 (152) ◽  
pp. 73-78
Author(s):  
A. Polivyanchuk ◽  
M. Smirny ◽  
S. Romanenko ◽  
R. Semenenko ◽  
R. Plotnikova ◽  
...  
Keyword(s):  
Particulate Matter ◽  
Measurement Errors ◽  
Experimental Studies ◽  
Diagnostic System ◽  
Measuring System ◽  
Methodological Error ◽  
Heat Engines ◽  
Accuracy Of Measurements ◽  
Diagnostics System ◽  
The Impact

A universal, multifunctional system of environmental diagnostics of heat engines and boiler plants has been created, which allows one to determine indicators characterizing the chemical and physical effect of these objects on the environment: concentrations, mass, specific and average operational emissions of pollutants, noise, thermal pollution, vibration. This measuring system consists of instrumental, testing, demonstration and laboratory modules, which allows you to use it as a diagnostic tool, training and test bench and laboratory; as well as apply it in various fields: transport, energy, environmental and educational fields. The diagnostic system implements methods for monitoring and improving the accuracy of measurements of average operating emissions of pollutants: method for determining the resulting measurement errors of the average operational emissions of gaseous pollutants and particulate matter – GAS and РT indicators, which allows you to evaluate the impact on the data of the value of the errors of the measuring equipment of the diagnostic system; a method for increasing the accuracy of measurements of the normalized РT index by taking into account the methodological error of measurements of a given value due to the influence of the temperature of the sample in the tunnel on the measured emission of particulate matter - δРТt. Experimental studies of the diagnostic system and methods for increasing its accuracyon full-scale objects were carried out: diesel engines: tractor 4CHN12/14 tractor D65M, diesel locomotive diesel engine DEL-01 and boiler units: gas - DKVR-20/13 and AOGV-100E, solid fuel - KCHM-2M-4. Transport diesels were tested according to the cycles established by the UNECE Regulations R-49, R-96 and the international standard ISO-8178. As a result of tests of these engines, the coefficients KРi, KMgasi and KMрmi were determined, which are used to assess the accuracy of measurements of GAS and РT indicators, the resulting measurement errors of these values were investigated and the range of variation of the methodical error δРТt was determined.

scholarly journals The Impact of Peer Assessment on Academic Performance: A Meta-analysis of Control Group Studies

2018 ◽  
Author(s):  
Kit S Double
Keyword(s):  
Academic Performance ◽  
Peer Assessment ◽  
Meta Analysis ◽  
Experimental Studies ◽  
Teacher Assessment ◽  
Medium Effect ◽  
Practice Research ◽  
Control Group ◽  
Wide Range ◽  
The Impact

Peer assessment has been the subject of considerable research interest over the last three decades, with numerous educational researchers advocating for the integration of peer assessment into schools and instructional practice. Research synthesis in this area has, however, largely relied on narrative reviews to evaluate the efficacy of peer assessment. Here we present a meta-analysis (54 studies, k = 141) of experimental and quasi-experimental studies that evaluated the effect of peer assessment on academic performance in primary, secondary, or tertiary students across subjects and domains. An overall small to medium effect of peer assessment on academic performance was found (g = 0.31, p < .001). The results suggest that peer assessment improves academic performance compared with no assessment (g = 0.31, p < .001) and teacher assessment (g = 0.28, p = .007), but was not significantly different in its effect from self-assessment (g = 0.23, p = .209). Additionally, meta-regressions examined the moderating effects of several feedback and educational characteristics (e.g. online vs offline, frequency, education level etc.). Results suggested that the effectiveness of peer assessment was remarkably robust across a wide range of contexts. These findings provide support for peer assessment as a formative practice and suggest several implications for the implementation of peer assessment into the classroom.

Impact of performance properties of regenerated engine oil on marine diesel wear when it runs on different grades of fuel

2019 ◽  
Vol 2019 (4) ◽  
pp. 71-81
Author(s):  
Валерий Тарасов ◽  
Valery Tarasov ◽  
Анатолий Соболенко ◽  
Anatoly Sobolenko
Keyword(s):  
Diesel Engine ◽  
Experimental Studies ◽  
Motor Fuel ◽  
Engine Oil ◽  
Oil Refining ◽  
Fuel Quality ◽  
Marine Fuel ◽  
Wide Range ◽  
Marine Diesel ◽  
The Impact

The article focuses on studying the operational properties of regenerated engine oils in terms of the impact on the wear of friction units of the trunk diesel engine when it works on the fuel of different grades. There have been built generalized models of marine diesel parts wear on the basis of experimental studies. Diesel 2Ч10,5/13 was used for experiments. Wear was determined by the method of artificial bases and by weighting. Four groups of the main indicators of fuels used on ships have been considered (depending on the quality indicator). The first group includes distillate fuels and low-viscosity marine fuel which is close in its characteristics to foreign fuels. The second group includes motor fuel, naval fuel oil and export fuels (medium viscosity fuels). The third group presents high-viscosity marine fuel; the fourth group - fuels made from the remains of oil refining. The description of the generalized model of details wear of the tested diesel engine was carried out by a polynomial of the second order. To obtain the model, a non-position plan was chosen for three test variables: concentration of additives in oil, a fuel quality factor and a level of diesel forcing. The superposition of the hypersurfaces of the response of wear functions of the internal combustion engine with diesel boosting factors at zero, lower, and upper levels with visualizing the effect on engine wear parameters depending on the additives concentration and quality of the fuel used in testing regenerated engine oil has been illustrated. Verification of the model's adequacy has proved that the model is adequate for machines with average effective pressure and a wide range of fuel grades. There has been given the possibility of using the obtained model to estimate the wear value at different values of parametric factors

scholarly journals The Impact of Peer Assessment on Academic Performance: A Meta-analysis of Control Group Studies

2019 ◽  
Vol 32 (2) ◽  
pp. 481-509 ◽  
Author(s):  
Kit S. Double ◽  
Joshua A. McGrane ◽  
Therese N. Hopfenbeck
Keyword(s):  
Academic Performance ◽  
Peer Assessment ◽  
Meta Analysis ◽  
Experimental Studies ◽  
Teacher Assessment ◽  
Medium Effect ◽  
Practice Research ◽  
Control Group ◽  
Wide Range ◽  
The Impact

AbstractPeer assessment has been the subject of considerable research interest over the last three decades, with numerous educational researchers advocating for the integration of peer assessment into schools and instructional practice. Research synthesis in this area has, however, largely relied on narrative reviews to evaluate the efficacy of peer assessment. Here, we present a meta-analysis (54 studies, k = 141) of experimental and quasi-experimental studies that evaluated the effect of peer assessment on academic performance in primary, secondary, or tertiary students across subjects and domains. An overall small to medium effect of peer assessment on academic performance was found (g = 0.31, p < .001). The results suggest that peer assessment improves academic performance compared with no assessment (g = 0.31, p = .004) and teacher assessment (g = 0.28, p = .007), but was not significantly different in its effect from self-assessment (g = 0.23, p = .209). Additionally, meta-regressions examined the moderating effects of several feedback and educational characteristics (e.g., online vs offline, frequency, education level). Results suggested that the effectiveness of peer assessment was remarkably robust across a wide range of contexts. These findings provide support for peer assessment as a formative practice and suggest several implications for the implementation of peer assessment into the classroom.

scholarly journals The Impact of Hemodynamic Reflex Compensation Following Myocardial Infarction on Subsequent Ventricular Remodeling

2019 ◽  
Vol 141 (9) ◽  
Author(s):  
Colleen M. Witzenburg ◽  
Jeffrey W. Holmes
Keyword(s):  
Myocardial Infarction ◽  
Ventricular Remodeling ◽  
Experimental Studies ◽  
Left Ventricular ◽  
Published Data ◽  
Compensatory Mechanisms ◽  
Compensatory Response ◽  
Wide Range ◽  
Reflex Compensation ◽  
The Impact

Patients who survive a myocardial infarction (MI) are at high risk for ventricular dilation and heart failure. While infarct size is an important determinant of post-MI remodeling, different patients with the same size infarct often display different levels of left ventricular (LV) dilation. The acute physiologic response to MI involves reflex compensation, whereby increases in heart rate (HR), arterial resistance, venoconstriction, and contractility of the surviving myocardium act to maintain mean arterial pressure (MAP). We hypothesized that variability in reflex compensation might underlie some of the reported variability in post-MI remodeling, a hypothesis that is difficult to test using experimental data alone because some reflex responses are difficult or impossible to measure directly. We, therefore, employed a computational model to estimate the balance of compensatory mechanisms from experimentally reported hemodynamic data. We found a strikingly wide range of compensatory reflex profiles in response to MI in dogs and verified that pharmacologic blockade of sympathetic and parasympathetic reflexes nearly abolished this variability. Then, using a previously published model of postinfarction remodeling, we showed that observed variability in compensation translated to variability in predicted LV dilation consistent with published data. Treatment with a vasodilator shifted the compensatory response away from arterial and venous vasoconstriction and toward increased HR and myocardial contractility. Importantly, this shift reduced predicted dilation, a prediction that matched prior experimental studies. Thus, postinfarction reflex compensation could represent both a source of individual variability in the extent of LV remodeling and a target for therapies aimed at reducing that remodeling.

scholarly journals Experimental justification of laser therapy efficiency of men's infertility

2017 ◽  
Vol 7 (4) ◽  
pp. 44-53 ◽  
Author(s):  
Sergej V Moskvin ◽  
Sergej Ju Borovets ◽  
Viktor A Toropov
Keyword(s):  
Laser Therapy ◽  
High Efficiency ◽  
Experimental Studies ◽  
Low Level Laser Therapy ◽  
Low Level ◽  
Low Level Laser ◽  
Level Laser ◽  
Wide Range ◽  
Experimental Justification ◽  
The Impact

Male infertility is a multifactorial syndrome, which includes a wide range of disorders. It is a symptom of many different pathological conditions affecting both the reproductive and other body systems: endocrine, nervous, blood-vascular, and immune systems. Low level laser therapy is a method of modern physiotherapy, in which the impact is carried out by low-intensity laser irradiation (LILI). It is widely used in all areas of modern medicine, due to its high efficiency, simplicity of use, the absence of contraindications and side effects. The results of russian and foreign experimental studies on the article subject were analyzed. A definite conclusion is drawn that low level laser therapy should be used as much as possible in the complex treatment of men with infertility, since the effectiveness of the method is not just high, but often has no alternatives. At the same time, the available low level laser therapy techniques should be widely used: locally, rectally, laser acupuncture, ILBI (intravenous laser blood irradiation), on the projection of various organs, paravertebrally, etc. All parameters of laser action should be set (wavelength; mode of operation; frequency for pulsed lasers; power; power density, determined by the method of exposure; exposure, localization), which are specified by the relevant regulatory documents and clinical recommendations. (For citation: Moskvin SV, Borovets SJu, Toropov VA. Experimental justification of laser therapy efficiency of men's infertility. Urologicheskie vedomosti. 2017;7(4):44-53. doi: 10.17816/uroved7444-53).

scholarly journals Bayesian Modeling of Wood-Age Offsets in Cremated Bone

Radiocarbon ◽  
2020 ◽  
Vol 62 (2) ◽  
pp. 379-401
Author(s):  
Helene Agerskov Rose ◽  
John Meadows ◽  
Mogens Bo Henriksen
Keyword(s):  
Exponential Distribution ◽  
Empirical Data ◽  
Bayesian Modeling ◽  
Experimental Studies ◽  
Carbon Exchange ◽  
Calendar Date ◽  
Wood Age ◽  
Wide Range ◽  
The Impact ◽  
Bone Apatite

ABSTRACTExperimental studies have shown that significant carbon exchange occurs between bone-apatite and the pyre atmosphere during cremation, which can cause a calendar date offset between the radiocarbon (14C) event and the date of cremation. There are limited empirical data available to assess the magnitude of such wood-age offsets, but the aim of this paper is to test if they can be modeled statistically. We present new 14C dates on modern bone cremated in realistic open-air experiments and on archaeological samples of cremated bone and associated organic material. Experimental results demonstrate a wide range of carbon exchange with a mean of 58.6 ± 14.8%. Archaeological results indicate that the wood-age offsets have an approximately exponential distribution. We test whether the default Charcoal Outlier_Model in OxCal v4.3, developed to reduce the impact of wood-age offsets in dates of charcoal, is appropriate for cremated bone, but find that it slightly underestimates apparent offsets. To counter the intrinsic age of both pyre fuel and unburned bio-apatite, we instead propose a bespoke Cremation Outlier_Model, which combines an exponential distribution of calendar age offsets with a minimum offset, and provides better estimates of the actual dates of cremations.

On the Effect of Trailing Edge Under-Filing on the Apparent Slip Factor of Centrifugal Impellers

2019 ◽  
Author(s):  
Oliver Litfin ◽  
Antonio Delgado
Keyword(s):  
Flow Regime ◽  
Separated Flow ◽  
Wake Flow ◽  
Flow Structures ◽  
Trailing Edge ◽  
Apparent Slip ◽  
Slip Factor ◽  
Wide Range ◽  
The Impact ◽  
Insight Into

Abstract The trailing edge flow in a centrifugal impeller is of great importance as it determines the exit flow velocity triangle and therefore the work transferred to the fluid. The present study deals with the impact of trailing edge under-filing on the impeller exit flow and the resulting slip factor. Different under-filed trailing edge shapes are investigated by means of numerical simulations. 2D-RANS simulations are performed for a wide range of blade angles. For the default cut-off trailing edge configuration an attached and a separated flow regime around the blade trailing edge can be distinguished, mainly depending on the blade exit angle. The occurrence of the separated flow regime is associated with a significant change in performance, mainly due to the reduced flow deflection at the impeller exit. Under-filing of the trailing edge leads to less apparent slip for blade angles up to 40 degrees. This can be attributed to the fact that under-filing prevents the attached flow regime occurring in case of the default trailing edge. Additional DES simulations provide deeper insight into the detailed flow structures involved in this phenomena and reveal the turbulent flow structures in the trailing edge and wake flow. The obtained results provide a deep insight into trailing edge flows in centrifugal pump impellers and help to get a better understanding of the phenomena involved. Moreover, the results can provide an explanation to the often observed deviation of the apparent impeller slip from the theoretical slip predicted by slip factor models.

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