NUMERICAL STUDY OF TURBULENCE DYNAMICS IN PLUNGING & SURGING BREAKING WAVES

KHAYYER ABBAS,YEGANEH-BAKHTIARY ABBAS,GHAHERI ABBAS,GOTOH HITOSHI,SAKAI TETSUO 한국수자원학회 2005 한국수자원학회 학술대회 Vol.2005 No.1

Ring-Shaped Lateral Bracing System for Steel Structures

Abbas Shamivand,Jalal Akbari 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.2

Buckling of compression members has a great impact on the reduction of energy dissipation capacity and ductility of the structural system such as concentrically braced frame systems (CBFs). As well, direct connection of tensile and compression members to beams and designation of the link beam as a fuse, and the formation of plastic hinges in the link beam in eccentrically braced systems (EBFs) endanger the safety of this type structural systems. This paper introduces a new ring-shaped lateral bracing system so-called the Shami lateral bracing system (SLBs) which removes the common tensile and compressive members along with their connections to the structure. As a substitute, SLBs introduces a new element with proper ductility and energy dissipation capacity and could be an appropriate alternative to the existing systems. Because of the high degree of statically indeterminacy of the proposed system, the structural stiffness does not lead to a steep reduction after the formation of the first plastic hinge. The performance of this lateral system is evaluated by numerical modeling, and the results show that the structures resist against the lateral loads with acceptable seismic performance. It seems that this system in comparison with CBF and EBF systems may not be cost-effective for bending of the ring, welding, etc., but from the seismic performance points of view, it has good performance.

Buckling analysis of tapered BDFGM nano-beam under variable axial compression resting on elastic medium

Abbas Heydari,Mahdi Shariati 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.66 No.6

The current study presents a new technique in the framework of the nonlocal elasticity theory for a comprehensive buckling analysis of Euler-Bernoulli nano-beams made up of bidirectional functionally graded material (BDFGM). The mechanical properties are considered by exponential and arbitrary variations for axial and transverse directions, respectively. The various circumstances including tapering, resting on two-parameter elastic foundation, step-wise or continuous variations of axial loading, various shapes of sections with various distribution laws of mechanical properties and various boundary conditions like the multi-span beams are taken into account. As far as we know, for the first time in the current work, the buckling analyses of BDFGM nano-beams are carried out under mentioned circumstances. The critical buckling loads and mode shapes are calculated by using energy method and a new technique based on calculus of variations and collocation method. Fast convergence and excellent agreement with the known data in literature, wherever possible, presents the efficiency of proposed technique. The effects of boundary conditions, material and taper constants, foundation moduli, variable axial compression and small-scale of nano-beam on the buckling loads and mode shapes are investigated. Moreover the analytical solutions, for the simpler cases are provided in appendices.

The Content and Necessity of the New International Order in the New International Environment

Abbas Maleki 한국중동학회 1991 韓國 中東 學會 論叢 Vol.12 No.1

Ultra-High Performance Concrete: Mechanical Performance, Durability, Sustainability and Implementation Challenges

Abbas, S.,Nehdi, M.L.,Saleem, M.A. Korea Concrete Institute 2016 International Journal of Concrete Structures and M Vol.10 No.3

In this study, an extensive literature review has been conducted on the material characterization of UHPC and its potential for large-scale field applicability. The successful production of ultra-high performance concrete (UHPC) depends on its material ingredients and mixture proportioning, which leads to denser and relatively more homogenous particle packing. A database was compiled from various research and field studies around the world on the mechanical and durability performance of UHPC. It is shown that UHPC provides a viable and long-term solution for improved sustainable construction owing to its ultrahigh strength properties, improved fatigue behavior and very low porosity, leading to excellent resistance against aggressive environments. The literature review revealed that the curing regimes and fiber dosage are the main factors that control the mechanical and durability properties of UHPC. Currently, the applications of UHPC in construction are very limited due to its higher initial cost, lack of contractor experience and the absence of widely accepted design provisions. However, sustained research progress in producing UHPC using locally available materials under normal curing conditions should reduce its material cost. Current challenges regarding the implementation of UHPC in full-scale structures are highlighted. This study strives to assist engineers, consultants, contractors and other construction industry stakeholders to better understand the unique characteristics and capabilities of UHPC, which should demystify this resilient and sustainable construction material.

Continuous-time Nonlinear Robust MPC for Offset-free Tracking of Piece-wise Constant Setpoints with Unknown Disturbance

Abbas Zamani,Hossein Bolandi 제어·로봇·시스템학회 2022 International Journal of Control, Automation, and Vol.20 No.4

This paper develops a novel robust tracking predictive controller for continuous-time nonlinear systems capable to deal with changing setpoints and unknown non-additive bounded disturbance. The sudden changes in a setpoint and/or existence of disturbance may lead to feasibility and stability issues if a stabilizing terminal constraint-based predictive controller is used. The robust tracking MPC presented in this paper extends the artificial reference-based nonlinear MPC for continuous-time systems and disturbance rejection. Closed-loop input-to-state stability and recursive feasibility of the optimization problem are guaranteed by tightening the terminal region, input constraint, and appropriate terminal cost function. An explicit formula that specifies the bound of sampling time interval is also introduced. We show that the proposed controller can reach an offset-free tracking if the disturbance is slowly time varying. However, in the case of non-slowly varying disturbance, a specific bound on tracking error will be guaranteed using an appropriate disturbance observation error based Lyapunov function. The satellite attitude control system simulation results are provided to show the efficiency of the proposed controller.

Predicting the Financial Behavior of the Religious Organization Board in Indonesia

ABBAS, Djamila,ALI, Muhammad,NOHONG, Mursalim,SOBARSYAH, Muhammad Korea Distribution Science Association 2020 The Journal of Asian Finance, Economics and Busine Vol.7 No.12

The religious organization members have a unique take on the spiritual factors related to their daily life. The present study contributed to the lack of discussion investigating this particular pool of data's financial behavior. This article regressed several predictors of economic behavior, i.e., the locus of control, financial attitude, income, and religiosity, with 460 respondents. The results of the research are as follows: Financial attitude partially influences the financial behavior of Muhammadiyah committee members. Income partially influences the financial behavior of Muhammadiyah committee members. This research indicates that income is one of the factors that plays an essential role in determining the merits of improvement of the financial behavior of Muhammadiyah committee members. The higher the level of income received by Muhammadiyah members, the higher the desire to spend the money. Religiosity partially influences the financial behavior of the religious board of Muhammadiyah members in Indonesia. The higher the religiosity of Muhammadiyah committee members will encourage better financial management. Religiosity indicates how often individuals or Muhammadiyah members practice the religious sharia that they embrace. The findings of this study reveal that locus of control, financial attitude, income, and religiosity are the strong predictors of the board of the religious organization's financial behavior in Indonesia.

Design of a Fuzzy Logic-based MPPT Controller for a PV System Employing Sensorless Control of MRAS-based PMSM

Abbas Mahmood Oghor Anwer,Fuad Alhaj Omar,Ahmet Afsin Kulaksiz 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.11

The permanent magnet synchronous motors (PMSM) are widely employed in industrial, robotic, water pumping and HVAC applications due to their numerous benefits such as small size, high-energy efficiency, high performance, low inertia and the ability to operate in full load at low speeds. In case the PMSM drive system is supplied from photovoltaic (PV) modules, it can be a perfect match for water pumping or HVAC applications. In such a system, in order to extract full energy from PV modules, a maximum power point tracking (MPPT) algorithm must be employed. This article presents a PV system-fed PMSM drive system with sensorless speed control. The proposed system consists of two main parts. The first part deals with MPPT algorithm based on fuzzy logic controller and the second part deals with PMSM drive system with a sensorless speed estimator by using Model Reference Adaptive System (MRAS) approach to eliminate the use of an encoder. The operation of PMSM is accomplished by using the vector control method to obtain a similar dynamic of the DC motor. The overall system is modelled in Matlab/Simulink environment and simulation results are collected under various operating conditions.

Size-dependent damped vibration and buckling analyses of bidirectional functionally graded solid circular nano-plate with arbitrary thickness variation

Abbas Heydari 국제구조공학회 2018 Structural Engineering and Mechanics, An Int'l Jou Vol.68 No.2

For the first time, nonlocal damped vibration and buckling analyses of arbitrary tapered bidirectional functionally graded solid circular nano-plate (BDFGSCNP) are presented by employing modified spectral Ritz method. The energy method based on Love-Kirchhoff plate theory assumptions is applied to derive neutral equilibrium equation. The Eringen’s nonlocal continuum theory is taken into account to capture small-scale effects. The characteristic equations and corresponding first mode shapes are calculated by using a novel modified basis in spectral Ritz method. The modified basis is in terms of orthogonal shifted Chebyshev polynomials of the first kind to avoid employing adhesive functions in the spectral Ritz method. The fast convergence and compatibility with various conditions are advantages of the modified spectral Ritz method. A more accurate multivariable function is used to model two-directional variations of elasticity modulus and mass density. The effects of nanoscale, in-plane pre-load, distributed dashpot, arbitrary tapering, pinned and clamped boundary conditions on natural frequencies and buckling loads are investigated. Observing an excellent agreement between results of current work and outcomes of previously published works in literature, indicates the results’ accuracy in current work.

A novel approach for forming carbon nanorods on the surface of carbon felt electrode by catalytic etching for high-performance vanadium redox flow battery

Abbas, Saleem,Lee, Hyuck,Hwang, Jinyeon,Mehmood, Asad,Shin, Hyun-Jin,Mehboob, Sheeraz,Lee, Ju-Young,Ha, Heung Yong Elsevier 2018 Carbon Vol.128 No.-

<P><B>Abstract</B></P> <P>In this work a novel method is unfolded to modify carbon felts (CF) to substantially improve the performance of the electrodes for vanadium redox flow batteries (VRFBs). The carbon felt, a well-known electrode material for VRFB, is catalytically etched by cobalt oxide to form carbon nanorods on the surface of the fibers comprising the CF. Unlike conventional multistep processes to grow nano-structures on carbon felts, this method simply involves a thermal treatment of catalyst-loaded felt in air to produce well aligned nanorods on its fibers. The surface morphology is optimized by etching temperature, treatment time and catalyst type. The catalytically etched CF shows an improved surface wettability and an enlarged specific surface area about two times compared to pristine CF that lead to an improvement of kinetics towards vanadium redox reactions. When used as electrode in all-vanadium redox flow battery, the nanorod-structured CF shows around 35% higher charge/discharge rate capability at 150 mA cm<SUP>−2</SUP> and 80% retained-capacity compared to 48% in case of un-etched CF as confirmed by a long run test with a hundred cycles of charge/discharge operation at 50 mA cm<SUP>−2</SUP>.</P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>