The Experts below are selected from a list of 8298 Experts worldwide ranked by ideXlab platform

Zhi-hua Wang - One of the best experts on this subject based on the ideXlab platform.

  • The Hysteresis Effect on surface-air temperature relationship and its implications to urban planning: An examination in Phoenix, Arizona, USA
    Landscape and Urban Planning, 2017
    Co-Authors: Jiyun Song, Zhi-hua Wang, Soe W. Myint, Chuyuan Wang
    Abstract:

    Abstract Urban areas, with massive built-up landscapes and manmade structures, have different patterns of local microclimate as compared to natural terrains. A better understanding of the surface-air temperature relationship in urban environments is of significant importance in interpreting urban climatic characteristics and solving related environmental problems via sustainable landscape planning strategies. In this study, we analyse the ground-based in-situ measurements as well as remotely sensed thermal dataset in Phoenix, AZ. Prominent Hysteresis Effect manifests in correlating diurnal cycles of surface and near-surface air temperatures. In particular, a peculiar pattern of “8-shaped” surface-air temperature Hysteresis is observed over concrete pavement especially in winters. Pearson’s r values, measuring the strength of surface-air temperature coupling, show strong correlation with incoming solar radiation and wind speed, but are relatively insensitive to humidity. The Hysteresis Effect diminishes at climatic scale, such that the remotely sensed surface temperature can be approximated as linearly correlated to the near-surface air temperature.

  • Revisiting the Hysteresis Effect in surface energy budgets
    Geophysical Research Letters, 2013
    Co-Authors: Ting Sun, Zhi-hua Wang
    Abstract:

    The Hysteresis Effect in diurnal cycles of net radiation Rn and ground heat flux G0 has been observed in many studies, while the governing mechanism remains vague. In this study, we link the phenomenology of Hysteresis loops to the wave phase difference between the diurnal evolutions of various terms in the surface energy balance. Rn and G0 are parameterized with the incoming solar radiation and the surface temperature as two control parameters of the surface energy partitioning. The theoretical analysis shows that the vertical water flux W and the scaled ratio math formula (net shortwave radiation to outgoing longwave radiation) play crucial roles in shaping Hysteresis loops of Rn and G0. Comparisons to field measurements indicate that Hysteresis loops for different land covers can be well captured by the theoretical model, which is also consistent with Camuffo-Bernadi formula. This study provides insight into the surface partitioning and temporal evolution of the energy budget at the land surface.

Carlos Levi - One of the best experts on this subject based on the ideXlab platform.

  • A Two-Dimensional Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder
    Journal of Offshore Mechanics and Arctic Engineering, 2011
    Co-Authors: Juan B. V. Wanderley, Sergio H. Sphaier, Carlos Levi
    Abstract:

    The Hysteresis Effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the two-dimensional Reynolds averaged Navier-Stokes equations. An upwind and total variation diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the Hysteresis Effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.

  • A Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder
    Volume 5: Polar and Arctic Sciences and Technology; CFD and VIV, 2009
    Co-Authors: Juan B. V. Wanderley, Sergio H. Sphaier, Carlos Levi
    Abstract:

    The Hysteresis Effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the Reynolds average Navier-Stokes equations. An upwind and Total Variation Diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the Hysteresis Effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.Copyright © 2009 by ASME

Jin-ho You - One of the best experts on this subject based on the ideXlab platform.

  • Parameter Identification and SOC Estimation of a Battery Under the Hysteresis Effect
    IEEE Transactions on Industrial Electronics, 2020
    Co-Authors: Minkyu Kwak, Bataa Lkhagvasuren, Jinsoo Park, Jin-ho You
    Abstract:

    This article concerns the estimation algorithms of battery's parameters and state of charge (SOC) and it is twofold. First, we present a simple variable length block wise least square estimation algorithm by considering locally linear SOC and open circuit voltage (OCV) relation on the run. The proposed algorithm can estimate accurately the parameters and follow the parameter changes. After estimating the battery parameters, SOC is directly computed from the combination of estimated parameters and SOC-OCV relation. This estimation scheme, which assumes Hysteresis Effect is negligible, is an online method. Second, if the Hysteresis Effect is considered in the model, we present an additional least square optimization problem to estimate SOC accurately. In this case, some parameters are tuned up in an offline way. Our approach compared with the extended Kalman filter based estimation method. The algorithms are validated by experiments with real data obtained from lab tests.

Juan B. V. Wanderley - One of the best experts on this subject based on the ideXlab platform.

  • A Two-Dimensional Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder
    Journal of Offshore Mechanics and Arctic Engineering, 2011
    Co-Authors: Juan B. V. Wanderley, Sergio H. Sphaier, Carlos Levi
    Abstract:

    The Hysteresis Effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the two-dimensional Reynolds averaged Navier-Stokes equations. An upwind and total variation diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the Hysteresis Effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.

  • A Numerical Investigation of the Hysteresis Effect on Vortex Induced Vibration on an Elastically Mounted Rigid Cylinder
    Volume 5: Polar and Arctic Sciences and Technology; CFD and VIV, 2009
    Co-Authors: Juan B. V. Wanderley, Sergio H. Sphaier, Carlos Levi
    Abstract:

    The Hysteresis Effect on the vortex induced vibration (VIV) on a circular cylinder is investigated by the numerical solution of the Reynolds average Navier-Stokes equations. An upwind and Total Variation Diminishing (TVD) conservative scheme is used to solve the governing equations written in curvilinear coordinates and the k-e turbulence model is used to simulate the turbulent flow in the wake of the body. The cylinder is supported by a spring and a damper and free to vibrate in the transverse direction. In previous work, numerical results for the amplitude of oscillation and vortex shedding frequency were compared to experimental data obtained from the literature to validate the code for VIV simulations. In the present work, results of practical interest are presented for the power absorbed by the system, phase angle, amplitude, frequency, and lift coefficient. The numerical results indicate that the Hysteresis Effect is observed only when the frequency of vortex shedding gets closer to the natural frequency of the structure in air.Copyright © 2009 by ASME

Qifei Wang - One of the best experts on this subject based on the ideXlab platform.

  • Tunable Hysteresis Effect for perovskite solar cells
    Energy & Environmental Science, 2017
    Co-Authors: Yaoguang Rong, Sandheep Ravishankar, Huawei Liu, Xiaomeng Hou, Yusong Sheng, Anyi Mei, Qifei Wang
    Abstract:

    Perovskite solar cells (PSCs) usually suffer from a Hysteresis Effect in current–voltage measurements, which leads to an inaccurate estimation of the device efficiency. Although ion migration, charge trapping/detrapping, and accumulation have been proposed as a basis for the Hysteresis, the origin of the Hysteresis has not been apparently unraveled. Herein we reported a tunable Hysteresis Effect based uniquely on open-circuit voltage variations in printable mesoscopic PSCs with a simplified triple-layer TiO2/ZrO2/carbon architecture. The electrons are collected by the compact TiO2/mesoporous TiO2 (c-TiO2/mp-TiO2) bilayer, and the holes are collected by the carbon layer. By adjusting the spray deposition cycles for the c-TiO2 layer and UV-ozone treatment, we achieved Hysteresis-normal, Hysteresis-free, and Hysteresis-inverted PSCs. Such unique trends of tunable Hysteresis are analyzed by considering the polarization of the TiO2/perovskite interface, which can accumulate positive charges reversibly. Successfully tuning of the Hysteresis Effect clarifies the critical importance of the c-TiO2/perovskite interface in controlling the hysteretic trends observed, providing important insights towards the understanding of this rapidly developing photovoltaic technology.