检索结果-南通市图书馆

Streamwise vortex generation by the rod

在线全文

学校读者我要写书评

暂无评论

Chinese Journal of Aeronautics 2019年第8期32卷 1903-1911页

作者： Ryszard SZWABA Pawel FLASZYNSKI piotr DOERFFER Department of Experimental Aerodynamics Institute of Fluid Flow Machinery Polish Academy of Sciences

The technology development related to aerodynamics is leading to ever increasing loads of wings, airfoils and turbine and compressor blades. The increase in aerodynamic forces is often leading to flow separation and depreciation of the aerodynamic performance of flying objects or propulsion systems. Flow control methods are required to avoid these negative effects. In the recent two decades the flow control by means of air-jet vortex generators has been also intensively investigated. In this method a streamwise vortex is introduced by an oblique jet. The necessity to supply air by a pipe system may be considered a disadvantage. In order to eliminate this feature, it has been proposed to put out a rod instead of a jet. It has been shown that the application of a rod can introduce the same effect as a jet, as long as the streamwise vortex generation is concerned and appropriate dimensions are used. The present paper focuses on the influence of rod vortex generators on a flow pattern downstream. The results presented here concern experimental and numerical investigations and provide guidelines for the design of a new flow control method dedicated mainly to external flows.

关键词： Air-jet vortex generator Boundary layer Flow control Rod vortex generator Streamwise vortices

Conductivity improvement of Ce_(0.8)Gd_(0.2)O_(1.9) solid electrolyte

在线全文

学校读者我要写书评

暂无评论

Journal of Rare Earths 2009年第4期27卷 655-660页

作者： Sebastian Molin Maria Gazda piotr Jasinski Faculty of Electronics Telecommunications and Informatics Gdansk University of Technology ul.Narutowicza 11/12 80-952 Gdansk Poland Faculty of Applied Physics and Mathematics Gdansk University of Technology ul.Narutowicza 11/12 80-952 Gdansk Poland

Solid oxide fuel cells based on doped cefia electrolytes offer operating temperatures of -600℃. During recent years much atten- tion was aimed at successful powder preparation with high sinter activity and high conductivity. The properties of ceria electrolyte are very sensitive to impurities introduced during powder and electrolyte fabrication. One of the most successful and commercially available processes for the production of clean powders is based on the addition of several percent metallic cations that will react with impurities and segregate into the triple points of grain boundaries. In this work the results obtained from doping of CGO20 by 2% Ca and prepared by different routes were presented. The way of introducing Ca seemed to play an important role.

关键词： rare earth solid elecllolyte electrical properties impedance spectroscopy fuel cell solid oxide fuel cells (SOFC)

Subinguinal microsurgical varicocelectomy is safe and effective in a solitary testicle

在线全文

学校读者我要写书评

暂无评论

Asian Journal of Andrology 2020年第1期22卷 120-121页

作者： piotr Dobronski Karolina Dobronska Lukasz Kupis piotr Radziszewski Department of Urology Medical University of WarsawWarsaw 02-005Poland First Department of Anesthesiology and Intensive Care Medical University of WarsawWarsaw 02-005Poland

Dear Editor,Varicocele is a common cause of male infertility,but in the course of a diagnostic infertility workup,other underlying problems are often *** to two-thirds of patients with nonidiopathic male infertility h... 详细信息

关键词： infertility patients surgical

Analytical and numerical method assessing the risk of sinkholes formation in mining areas

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

International Journal of Mining Science and Technology 2015年第1期25卷 85-89页

作者： piotr Strzalkowski Krzysztof Tomiczek Faculty of Mining and Geology Silesian University of Technology

Voids, which have not been liquidated and associated with shallow mining excavations, pose a serious threat of potential formation of sinkholes. This threat is connected with the loss of stability of voids that had been formed as a result of mining operations in the deeper strata. Taking into account the impact of lower coal seams mining on shallow excavations and based on the example of a region that had been intensely exploited, this paper proposes a methodology for analysing the stability of shallow mine voids in the rock mass. Deformations in the excavation region were calculated by using FLAC2D computer pro- gram and assigning the Coulomb-Mohr model to the rock mass. Based on the numerical analysis, this paper evaluated the stability of the void in the event of a roof support fall. The results indicate the like- lihood of void formation. Based on the Budryk-Knotbe theory, the deformations of rock mass and sand- stone strata in the roof of the void, which had been caused by mining exploitation in consecutive years, were calculated. The results of numerical calculations and analyses were compared with the limit defor- mations values of sandstone in tension. It is concluded that the exploitations cause the void to break down. The proposed method can forecast the discontinuous deformations threats in the areas that have undergone shallow undermining exploitation and the areas of underground urban.

关键词： Mining exploitationDiscontinued deformationsSinkholesStabilityRisk of sinkhole formationTensile deformations of rocks

DIRECTIONAL DO-NOTHING CONDITION FOR THE NAVIER-STOKES EQUATIONS

在线全文

学校读者我要写书评

暂无评论

Journal of Computational Mathematics 2014年第5期32卷 507-521页

作者： Malte Braack piotr Boguslaw Mucha Mathematisches Seminar Christian-Albrechts-Universitat zu Kiel Ludewig-Meyn-Str. 4 D-24098 Kiel Germany Institute of Applied Mathematics and Mechanics University of Warsaw ul Banacha 2 02-097 Warszawa Poland

The numerical solution of flow problems usually requires bounded domains although the physical problem may take place in an unbounded or substantially larger domain. In this case, artificial boundaries are necessary. A well established artificial boundary condition for the Navier-Stokes equations diseretized by finite elements is the “do-nothing” condition. The reason for this is the fact that this condition appears automatically in the variational formulation after partial integration of the viscous term and the pressure gradient. This condition is one of the most established outflow conditions for Navier-Stokes but there are very few analytical insight into this boundary condition. We address the question of existence and stability of weak solutions for the Navier-Stokes equations with a “directional do-nothing” condition. In contrast to the usual “do-nothing” condition this boundary condition has enhanced stability properties. In the case of pure outflow, the condition is equivalent to the original one, whereas in the case of inflow a dissipative effect appears. We show existence of weak solutions and illustrate the effect of this boundary condition by computation of steady and non-steady flows.

关键词： Boundary conditions Navier-Stokes Outflow condition Existence.

Improving Fault Detection in Modified Code-A Study from the Telecommunication Industry

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Computer Science & Technology 2007年第3期22卷 397-409页

作者： piotr Tomaszewski Lars Lundberg Hkan Grahn School of Engineering Blekinge Institute of Technology SE-372 25 RonnebySweden

Many software systems are developed in a number of consecutive releases. In each release not only new code is added but also existing code is often modified. In this study we show that the modified code can be an important source of faults. Faults are widely recognized as one of the major cost drivers in software projects. Therefore, we look for methods that improve the fault detection in the modified code. We propose and evaluate a number of prediction models that increase the efficiency of fault detection. To build and evaluate our models we use data collected from two large telecommunication systems produced by Ericsson. We evaluate the performance of our models by applying them both to a different release of the system than the one they are built on and to a different system. The performance of our models is compared to the performance of the theoretical best model, a simple model based on size, as well as to analyzing the code in a random order （not using any model）. We find that the use of our models provides a significant improvement over not using any model at all and over using a simple model based on the class size. The gain offered by our models corresponds to 38-57% of the theoretical maximum gain.

关键词： fault prediction metrics testing and debugging

The influence of environmental factors on the carbon dioxide flux across the water–air interface of reservoirs in south-eastern Poland

在线全文

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2017年第6期29卷 290-299页

作者： Renata Gruca-Rokosz Lilianna Bartoszek piotr Koszelnik Faculty of Civil and Environmental Engineering and Architecture Rzeszdw University of TechnologyRzeszowPoland

Studies concerning the emission of carbon dioxide （CO2） were carried out in 2009-2012 for six reservoirs located in four provinces of south-eastern Poland. The CO2 flux across the water-air interface was measured using the ＂static chamber＂ method. The measured fluxes of CO2 （FCO2） ranged from -30.64 to 183.78 mmol/m2/day, and the average values varied in the range from -3.52 to 82.11 mmol/m2/day. In most of the cases, emission of CO2 to the atmosphere was observed. The obtained values of CO2 fluxes were comparable to values typical for other temperate reservoirs. Analysis of the influence of selected envi- ronmental factors on the FCO2 showed that it depends on parameters characterizing both the sediments and surface water. The CO2 flux at the water-air interface was positively correlated with parameters of bottom sediments such as porosity, content of organic carbon and total nitrogen; and negatively with pH value and 51℃ of organic carbon. In the case of the parameters characterizing surface water, positive dependences on the concen- trations of nitrate and total nitrogen, and negative relationships with water temperature and chlorophyll a concentrations, were found.

关键词： Carbon dioxideGreenhouse gasesReservoirSediment

A statistical analysis of geomechanical data and its effect on rock mass numerical modeling:a case study

在线全文

学校读者我要写书评

暂无评论

International Journal of Coal Science & Technology 2021年第3期8卷 312-323页

作者： piotr Malkowski Zbigniew Niedbalski Tafida Balarabe Faculty of Mining and Geoengineering AGH University of Science and Technologyal.Mickiewicza 3030-059 KrakówPoland Revoult Ltd al.Jana PawlaⅡ43a31-864 KrakówPoland

Geomechanical data are never sufficient in quantity or adequately precise and accurate for design purposes in mining and civil *** objective of this paper is to show the variability of rock properties at the sampled point in the roadway's roof,and then,how the statistical processing of the available geomechanical data can affect the results of numerical modelling of the roadway's *** cases were applied in the numerical analysis,using average values(the most common in geomechanical data analysis),average minus standard deviation,median,and average value minus statistical *** study show that different approach to the same geomechanical data set can change the modelling results *** case shows that average minus standard deviation is the most conservative and least *** gives the displacements and yielded elements zone in four times broader range comparing to the average values scenario,which is the least conservative *** two other cases need to be studied *** results obtained from them are placed between most favorable and most adverse *** the average values corrected by statistical error for the numerical analysis seems to be the best ***,the confidence level can be adjusted depending on the object importance and the assumed risk level.

关键词： Statistical analysis Geotechnical data Laboratory tests on rocks Numerical modelling

Impact of environmental factors on the sampling rate ofβ-blockers and sulfonamides from water by a carbon nanotube-passive sampler

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Environmental Sciences 2021年第3期33卷 413-427页

作者： Klaudia Godlewska Aleksandra Jakubus piotr Stepnowski Monika Paszkiewicz Department of Environmental Analysis Faculty of ChemistryUniversity of Gdanskul.Wita Stwosza 63Gdansk 80-308Poland

Passive techniques are a constantly evolving approach to the long-term monitoring of micropollutants,including pharmaceuticals,in the aquatic *** paper presents,for the first time,the calibration results of a new CNTs-PSDs(carbon nanotubes used as a sorbent in passive sampling devices)with an examination of the effect of donor phase salinity,water pH and the concentration of dissolved humic acids(DHAs),using both ultrapure and environmental *** rates(R_(s))were determined for the developed kinetic *** has been observed that the impact of the examined environmental factors on the R_(s) values strictly depends on the type of the *** the case ofβ-blockers,the only environmental parameter affecting their uptake rate was the salinity of water.A certain relationship was noted,namely the higher the salt concentration in water,the lower the Rs values ofβ-*** the case of sulfonamides,water salinity,water pH 7-9 and DHAs concentration decreased the uptake rate of these compounds by *** determined Rs values differed in particular when the values obtained from the experiments carried out using ultrapure water and environmental waters were *** general conclusion is that the calibration of novel CNTs-PSDs should be carried out under physicochemical conditions of the aquatic phase that are similar to the environmental matrix.

关键词： Carbon nanotubes Passive sampling Pharmaceuticals Sampling rates(R_s)