检索结果-南通市图书馆

An Exact Solution for Heat Transfer of a Jet Co-Axially impinging on a Rotating Disk and its Comparisons with Stagnation Point Experiments

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2002年第1期11卷 53-59页

作者： i.v. shevchuk (institute of Engineering Thermophysics, Ukrainian National Academy of Sciences, 2a, Zhelyabov St., Ki.v. 03057, Ukraine. E-mail: ivshevch@i.com.ua) institute of Engineering Thermophysics Ukrainian National Academy of Sciences Ukraine

An exact solution of laminar heat transfer problem for a uniform flow perpendicular to a rotating disk was obtained. Radial velocity at the outer edge of the boundary layer increases linearly in the radial direction, while the temperature difference between the disk and outer flow follows a power law. The problem is solved using self-similar velocity and temperature profiles. Nusselt numbers were computed for the Prandtl numbers Pr=1 and 0.71 at different values of parameters affecting flow and heat transfer. Special flow regime was identified where rotating disk heat transfer is determined only by peculiarities of the impinging flow. Results of predictions agree well with known experiments in the vicinity of the stagnation point.

关键词： impinging jet rotating disk Nusselt number laminar flow heat transfer boundary layer exact solution

Simulation of Heat Transfer and Hydrodynamics over a Free Rotating Disk Using an improved Radial velocity Profile

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 1999年第4期8卷 243-249页

作者： i.v. shevchuk (institute of Engineering Thermophysics, Ukrainian National Academy of Sciences, 2a, Zhelyabov St., Ki.v. 03057, Ukraine) institute of Engineering Thermophysics Ukrainian National Academy of Sciences Kiev Ukraine

The paper presents results of simulation of turbulent heat transfer and hydrodynamics over a free rotating disk using an integral method based on power-law velocity and temperature profiles and three different laws for the tangent of the flow swirl angle tan. it appeared that a quadratic correlation of tan is the most proper one for a free rotating disk. Resulting equation for the Nusselt number is in a better agreement with experimental data of different authors than known Dorfman formula.

关键词： rotating disk boundary layer integral method Nusselt number tangent of the flow swirl angle velocity profile temperature profile.

Heat Transfer and Fluid Flow over a Single Disk in a Fluid Rotating as a Rigid Body

在线全文

学校读者我要写书评

暂无评论

Journal of Thermal Science 2004年第3期13卷 279-282页

作者： igor v. shevchuk Matthias H. BUSCHMANN institute of Engineering Thermophysics Ukrainian National Academy of Sciences 2a Zhelyabov St. Kiev 03057 UkraineInstitute of Fluid Mechanics Dresden University of Technology 01062 Dresden Germany

Laminar heat transfer problem is analyzed for a disk rotating with the angular speed ωin a co-rotating fluid (with the angular speed Ω). The fluid is swirled in accordance with a forced-vortex law, it rotates as a solid body at β= Ω/ω= const. Radial variation of the disk’s surface temperature follows a power law. An exact numerical solution of the problem is obtained basing on the self-similar profiles of the local temperature of fluid, its static pressure and velocity components. Numerical computations were done at the Prandtl numbers Pr = 1(?)0.71. it is shown that with increasing βboth radial and tangential components of shear stresses decrease, and to zero value at β= 1. Nusselt number is practically constant at β= 0(?) 0.3 (and even has a point of a maximum in this region); Nu decrease noticeably for larger βvalues.

关键词： rotating disk heat transfer fluid flow Nusselt number swirl.

Study of oxidative desulphurization process of coal with different metamorphism degrees

在线全文

学校读者我要写书评

暂无评论

燃料化学学报 2012年第2期40卷 129-137页

作者： S PYSHYEv v GUNKA Y PRYSiAZHNYi K shevchuk A PATTEK-JANCZYK institute of Chemistry and Chemical Technology Lviv Polytecnic National University St. Bandery 12 79013 Lviv Ukraine State Higher vocational School in Tarnow Mickiewicza 8 33-100 Tarnow Poland

The oxidative desulphurization process of coal with different metamorphism degrees treated by an air-steam mixture has been *** has been shown that the pyrite present in black coal and anthracite is oxidized with the sulphur dioxide formation,and the process chemical mechanism does not depend on the quality of organic *** medium-metamorphized coal,capable of turning into a plastic state and cake in the range of i.v.stigated temperatures(350～450 ℃),is desulphurized with the greatest *** chemical mechanism dealing with the transformations of pyritic sulphur present in brown coal differs from similar processes taking place in black coal and anthracite,because FeS2 is converted with hydrogen sulphide formation at desulphurization.

关键词： oxidative desulphurization organic matrix pyrite metamorphism degree sulphur

Whirl interaction of a Drill Bit with the Bore-Hole Bottom

在线全文

学校读者我要写书评

暂无评论

Modern Mechanical Engineering 2015年第3期5卷 41-60页

作者： Nabil W. Musa v. i. Gulyayev L. v. shevchuk Hasan Aldabas Department of Mechanical Engineering Philadelphia University Amman Jordan Department of Mathematics National Transport University Kyiv Ukraine

This paper deals with the theoretic simulation of a drill bit whirling under conditions of its contact interaction with the bore-hole bottom rock plane. The bit is considered to be an absolutely rigid ellipsoidal body with uneven surface. it is attached to the lower end of a rotating elastic drill string. in the perturbed state, the bit can roll without sliding on the bore-hole bottom, performing whirling vibrations (the model of dynamic equilibrium with pure rolling when maximum cohesive force does not exceed the ultimate Coulombic friction). To describe these motions, a nonholonomic dynamic model is proposed, constitutive partial differential equations are deduced. With their use, the whirling vibrations of oblong and oblate ellipsoidal bits are analyzed, the functions of cohesive (frictional) forces are calculated. it is shown that the system of elastic drill string and ellipsoidal bit can acquire stable or unstable whirl modes with approaching critical Eulerian values by the parameters of axial force, torque and angular velocity. The analogy of the found modes of motions with ones of the Celtic stones is established. it is shown that the ellipsoidal bits can stop their whirling vibrations and change directions of their circumferential motions in the same manner as the ellipsoidal Celtic stones do. As this takes place, the trajectories of the oblate ellipsoidal bits are characterized by more complicated paths and irregularities.

关键词： Deep Drilling Ellipsoidal Bits Nonholonomic Dynamics Celtic Stones instability Forward and Backward Whirling Motions

Study of impregnated cellulose thermal treatment process and properties of obtained active carbon

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

Chemical Reports 2019年第2期1卷 58-66页

作者： Nina K. Luneva Tatiana i. Ezovitova viacheslav v. shevchuk Alexander A. Ratko State Scientific institution “Institute of General and Inorganic Chemistry of National Academy of Sciences of Belarus” Minsk 220072 Belarus.

Single-stage process of obtaining active carbon by thermal processing of plant raw materials (mixture of different types of wood sawdust), impregnated with the mixture of phosphoric acid, urea and nitric acid salts has been developed. Active influence of impregnates on the process of carbonization and formation of carbon residue has been formed. it is established that carbon residue obtained in the interval of heating 20℃-(500℃-700℃), possesses high sorption activity to the vapors of organic compounds and has ion-exchange capacity. it has been showed that the value of carton residue depending on the impregnate used in the wood increases compared to the yield of non-treated initial raw materials by 3.1 times at 600℃ and by 4.2 times at 700℃.

关键词： impregnate thermal decomposition of wood porous sorbent specific surface activity by benzene iodine

Abnormalities of uterine cervix in women with inflammatory bowel disease

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

World Journal of Gastroenterology 2006年第38期12卷 6167-6171页

作者： Jyoti Bhatia Jason Bratcher Burton Korelitz Katherine vakher Shlomo Mannor Maria shevchuk Gworgia Panagopoulos Adam Ofer Ecaterina Tamas Panayota Kotsali Oana vele Division of Gastroenterology Department of Medicine and Departments of Obstetrics and Gynecology and Pathology Lenox Hill Hospital and New York University School of Medicine New York United States

AiM： To evaluate the prevalence of abnormalities of the uterine cervix in women with inflammatory bowel disease （iBD） when compared to healthy controls. METHODS： One hundred and sixteen patients with iBD [64 with Crohn＇s disease （CD） and 52 with ulcerative colitis （UC）] were matched to 116 healthy controls by age （＋/- 2 years） at the time of most recent papanicolaou （Pap） smear. Data collected consisted of age, race, marital status, number of pregnancies, abortions/miscarriages, duration and severity of iBD, Pap smear results within five years of enrollment, and treatment with immunosuppressive drugs. Pap smear results were categorized as normal or abnormal including atypical squamous cells of undetermined significance （ASCUS）, low-grade squamous intraepithelial lesion （LGSiL）, and high-grade squamous intraepithelial lesion （HGSiL）. RESULTS： The median age at the time of Pap smear was 46 （range： 17-74） years for the iBD group and matched controls （range： 19-72 years）. There were more Caucasian subjects than other ethnicities in the iBD patient group （P = 0.025）, as well as fewer abortions （P = 0.008）, but there was no significant difference regarding marital status. Eighteen percent of iBD patients had abnormal Pap smears compared to 5% of controls （P = 0.004）. Subgroup analysis of the iBD patients revealed no significant differences between CD and UC patients in age, ethnicity, marital status, number of abortions, disease severity, family history of iBD, or disease duration. No significant difference was observed in the number of abnormal Pap smears or the use of immunosuppressive medications between CD and UC patients CP = 0.793）. No definitive observation could be made regarding HPv status, as this was not routinely i.v.stigated during the timeframe of our study. CONCLUSiON： Diagnosis of iBD in women is related to an increased risk of abnormal Pap smear, while type of iBD and exposure to immunosuppressive medications are not. This has significant implicatio

关键词： inflammatory bowel disease Ulcerative colitis Crohn's disease Cervical cancer Pap smear

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

32通道毫米波被动成像系统

32通道毫米波被动成像系统