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coefficient Inequalities for p-Valent Functions

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Analysis in Theory and Applications 2018年第2期34卷 112-126页

作者： T.Panigrahi R.N.Mohapatra Department of Mathematics School of Applied SciencesKIIT Department of Mathematics University of Central Florida

In the present paper, the authors introduce a new subclass of p-valent analytic functions with complex order defined on the open unit disk U={z:z∈C and |z|<1} and obtain coefficient inequalities for the functions in ... 详细信息

In the present paper, the authors introduce a new subclass of p-valent analytic functions with complex order defined on the open unit disk U={z:z∈C and |z|coefficient inequalities for the functions in these class. Application of these results for the functions defined by the convolution are also obtained.

关键词： p-valent function subordination coefficient inequalities convolution

Effect of the drag coefficient on a typhoon wave model

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Journal of Oceanology and Limnology 2019年第6期37卷 1795-1804页

作者： WANG Zhifeng GONG Yijie CUI Junnan DONG Sheng WU Kejian Ocean University of China

The effect of the drag coefficient on a typhoon wave model is investigated.Drag coefficients for Pingtan Island are derived from the progress of nine typhoons using COARE 3.0 software.The wind parameters are obtained using the Weather Research and Forecasting model.The simulation of wind agrees well with observations.Typhoon wave fields are then simulated using the third-generation wave model SWAN.The wave model includes exponential and linear growths of the wind input,which determine the wave-growth mode.A triple triangular mesh is adopted with spatial resolution as fine as 100 m nearshore.The SWAN model performs better when using the new drag coefficient rather than the original coefficient.

关键词： drag coefficient typhoon wind typhoon wave numerical simulation

Experimental study on discharge coefficient of a gear-shaped weir

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Water Science and Engineering 2018年第3期11卷 258-264页

作者： Jing Zhang Qian Chang Qing-hua Zhang Shu-ning Li College of Water Conservancy and Civil Engineering Shandong Agricultural University River Management Bureau Huaihe River Commission of the Ministry of Water Resources

This study focused on hydraulic characteristics around a gear-shaped weir in a straight channel. Systematic experiments were carried out for weirs with two different gear heights and eight groups of geometrical parameters. The impacts of various geometrical parameters of gear-shaped weirs on the discharge capacity were investigated. The following conclusions are drawn from the experimental study:(1) The discharge coefficient(m_c) was influenced by the size of the gear: at a constant discharge, the weir with larger values of a/b(a is the width of the gear, and b is the width between the two neighboring gears) and a/c(c is the height of the gear) had a smaller value of m_c. The discharge capacity of the gear-shaped weir was influenced by the water depth in the weir.(2) For type C1 with a gear height of 0.01 m, when the discharge was less than 60m^3/h and H_1=P 1.0, m_c slowly decreased with the increases of the discharge and H_1=P for a=b 1.0 and a=c 1.0, and slowly increased with the discharge and H_1=P for a=b > 1.0 and a=c > 1.0.(3) A formula of m_cfor gear-shaped weirs was established based on the principle of weir flow, with consideration of the water depth in the weir, the weir height and width, and the height of the gear.

关键词： Experimental study Discharge coefficient Discharge capacity Gear-shaped weir Geometrical parameter

Effect of spatial scale on runoff coefficient: Evidence from the Ethiopian highlands

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International Soil and Water Conservation Research 2018年第4期6卷 289-296页

作者： Tesfaye Mebrate Lemma Gizaw Desta Gessesse Asfaw Kebede Kassa Desalegn Chemeda Edossa Debre Berhan University Debre BerhanEthiopia Water and Land Resources Center Addis AbabaEthiopia Haramaya Institute of Technology HaramayaEthiopia South-Man Engineering ManitobaWinnipegCanada

The runoff coefficient (RC) is the ratio between the runoff and rainfall amounts and is scale dependent, which is due in part to the heterogeneity of watershed characteristics. This study quantified the spatial scale effects on runoff using long-term rainfall-runoff data on runoff plots and small watersheds. Effect of spatial scale on RC was studied for 12 runoff plots (2m by 15m) and three small watersheds (113-477 ha) in the highlands of Ethiopia using a total of 4397 and 13,92515-day cumulative pairs of rainfall and runoff data at watershed and runoff plot scales, respectively. The observed average RC of runoff plots was extrapolated based on the extent of representation of a particular watershed in terms of slope, land use, cover and soil type. The weighted RC of plots was then compared with the observed RC of the watershed to determine a scale factor for extrapolation. A decrease in RC from plot to the watershed was observed in Anjeni and Andit Tid watersheds, while an increase in RC in Maybar watershed illustrates the role of specific watershed conditions in determining the scale effect. This, in turn, suggests that the variation in scale factor is not well explained by the difference in the area alone. The scale effect of runoff generation was better explained by extrapolating the RC based on the representation of different watershed characteristics. Thus, extrapolation exercises in runoff modeling and scaling efforts of soil and water conservation practices should consider the scale effect cautiously.

关键词： Runoff coefficient Spatial scale Rainfall-runoff relation Ethiopian highlands

Projected area and drag coefficient of high velocity irregular fragments that rotate or tumble

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Defence Technology（防务技术） 2017年第4期13卷 269-280页

作者： John F. Moxnes 0yvind Fr0 yland Ivar J. 0ye Tom I. Brate Eva Friis Gard 0degardstuen Tallak H. Risdal Norwegian Defence Research Establishment Land Systems Division P.O. Box 25 2027 Kjeller Norway Nammo Raufoss AS P.O. Box 162 2831 Raufoss Norway HPVisTech AS Bj0rnstadgutua 21 2092 Minnesund Norway

3 degrees of freedom(DOF)exterior ballistic computer models are used in fragment studies to calculate individual trajectories of each fragment based on drag coefficient and the projected(presented)area in the direction of velocity of center of mass.The expectation of a randomly distributed projected area is commonly used for fragments that tumble(random rotation)during flight.We forecast a model where the expected drag coefficient is dependent of shape and Mach number.Rotation or tumbling only affects the expected projected area.Models of projected areas during tumbling and rotation are presented.An examination of the data by Mc Cleskey(1988)indicates that the volume of the fragment to the power of2/3 is a better parameter to characterize the drag coefficient of the fragments than the maximum projected area.Hydrocode simulations are used to verify results and to study projected area and drag coefficient of fragments.

关键词： Fragments Form factor Mach number Drag coefficient Cauchy area Tumbling

Parametric study on smoothed particle hydrodynamics for accurate determination of drag coefficient for a circular cylinder

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Water Science and Engineering 2017年第2期10卷 143-153页

作者： Maziar Gholami Korzani Sergio A. Galindo-Torres Alexander Scheuermann David J. Williams School of Civil Engineering The University of Queensland St Lucia Brisbane QLD 4072 Australia School of Mathematics and Physics The University of Queensland St Lucia Brisbane QLD 4072 Australia

Simulations of two-dimensional(2D) flow past a circular cylinder with the smoothed particle hydrodynamics(SPH) method were conducted in order to accurately determine the drag coefficient. The fluid was modeled as a viscous liquid with weak compressibility. Boundary conditions,such as a no-slip solid wall, inflow and outflow, and periodic boundaries, were employed to resemble the physical problem. A sensitivity analysis, which has been rarely addressed in previous studies, was conducted on several SPH parameters. Hence, the effects of distinct parameters, such as the kernel choices and the domain dimensions, were investigated with the goal of obtaining highly accurate results. A range of Reynolds numbers(1-500) was simulated, and the results were compared with existing experimental data. It was observed that the domain dimensions and the resolution of SPH particles, in comparison to the obstacle size, affected the obtained drag coefficient significantly. Other parameters, such as the background pressure, influenced the transient condition, but did not influence the steady state at which the drag coefficient was determined.

关键词： Smoothed particle hydrodynamics Drag coefficient Reynolds number Sensitivity analysis Viscous flow

coefficient of Engine Flexibility as a Basis for the Assessment of Vehicle Tractive Performance

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Chinese Journal of Mechanical Engineering 2019年第3期32卷 189-197页

作者： Dariusz Szpica Faculty of Mechanical Engineering Bialystok University of Technology

The paper attempts to analyze full load characteristics of over 500 combustion engines. Using statistical tools, the author determined the value of the coefficient of flexibility. Engine flexibility is the capability of the engine to adapt to varying loads. Importantly, in the investigations, the author took into account the parameters calculated in the course of the investigations on a chassis dynamometer, i.e., actual, not taken from technical specifications of brand new vehicles. Different stages of operating wear allow a better characterization of the population. Subsequent utilization of the results in tractive calculations is more reliable. The engines were divided into in six groups, depending on the type of fuel system: fuel injected gasoline and turbocharged gasoline, spark ignition LPG, naturally aspirated diesel and turbocharged diesel. However, engines running on alternative fuels are characterized with a greater flexibility than the fuel injected base engines. Conformity of flexibility of fuel injected and LPG IV generation engines have been observed, which confirms the appropriateness of engine adaptation to alternative fueling. Gasoline engine supercharging allowed a reduction of the maximum engine speed of the maximum torque, which extends the range of analyzable speeds for flexibility and consequently, the flexibility as such.

关键词： Vehicle Tractive performance Flexibility coefficient Engine characteristics

TESTING DRAG coefficient APPROACHES BY USING THE BUOY DATA COLLECTED IN MODERATE TO HIGH WIND UNDER FOLLOWING,CROSSING AND OPPOSING SWELL CONDITIONS

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Journal of Tropical Meteorology 2019年第3期25卷 336-343页

作者：彭文武高志球李煜斌张荣智童兵吴彬贵何宜军 Jiangsu Key Laboratory of Agriculture Meteorology School of Applied MeteorologyNanjing University of Information Science and TechnologyNanjing 210044 China School of Atmospheric Physics Nanjing University of Information Science and TechnologyNanjing 210044 China Meteorological Center of East China Regional Air Traffic Management Bureau of Civil Aviation of China Shanghai 201105 China Tianjin Institute of Meteorological Science Tianjin 300074 China Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters School of OceanographyNanjing University of Information Science and TechnologyNanjing 210044 China

Hurricane intensity and track are strongly affected by air-sea interactions. Classified as following swells,crossing swells, and opposing swells, the observed wave height was parameterized by using the 10-m wind speed collected on 5 buoys by the National Buoy Data Center during 13 hurricane events. The path information of these 13 hurricanes was obtained from the National Hurricane Center Best Track(NHC-BT). Results show that the wave height increases exponentially with the 10-m wind speed, and the wave height reaches the maximum value, 11.2 m(8.1 m),when 10-m wind speed is 40 m s-1 under the following and crossing(opposing) swell conditions. We find that the wave steepness(the ratio of wave height to wave length) is proportional to the-2/3 power of the wave age(the ratio of wave phase velocity to 10-m wind speed). The parameterizations of friction velocity and drag coefficient are tested using the buoy data collected in moderate to high wind under following, crossing and opposing swell conditions. A wave age dependent equation for drag coefficient is found more accurate and recommended for future usage in numerical models.Furthermore, these algorithms also suggest that wind-swell orientation needs to be considered to retrieve accurate surface drag under high winds and strong swells.

关键词： drag coefficient high wind wave height wave age swell

Impact of Temperature on Absorption coefficient of Pure Seawater in the Blue Wavelengths Inferred from Satellite and In Situ Measurements

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Journal of Remote Sensing 2021年第1期2021卷 289-301页

作者： Guomei Wei Zhongping Lee Xiuling Wu Xiaolong Yu Shaoling Shang Ricardo Letelier State Key Laboratory of Marine Environmental Science College of Ocean and Earth SciencesXiamen UniversityXiamen 361102China Research and Development Center for Ocean Observation Technologies Xiamen UniversityXiamen 361102China School for the Environment University of Massachusetts BostonBostonMA 02125USA College of Earth Ocean&Atmospheric SciencesOregon State UniversityCorvallisOR 97331USA

There has been a long history of interest on how(if)the absorption coefficient of“pure”fresh water(a_(fw)(λ))and“pure”seawater(a_(sw)(λ))changes with temperature(T),yet the impact of T reported in the literature differs significantly in the blue domain.Unlike the previous studies based on laboratory measurements,we took an approach based on~18 years(2002–2020)of MODIS ocean color and temperature measurements in the oligotrophic oceans,along with field measured chlorophyll concentration and phytoplankton absorption coefficient,to examine the relationship between T and the total absorption coefficient(a(λ))at 412 and 443 nm.We found that the values of a(412)and a(443)in the summer are nearly flat(slightly decreasing)for the observed T range of~19–27℃.Since there are no detectable changes of chlorophyll during this period,the results suggest that T has a negligible impact on a_(sw)(412) and a_(sw)(443)in this T range.As a complement,the impact of salinity on a_(fw)(λ) was also evaluated using three independent determinations of a_(sw)(λ) and a_(fw)(λ),where good agreements were found from these observations.

关键词： salinity ocean coefficient