CFD-FEA ANALYSIS OF HYDRAULIC SHOCK ABSORBER VALVE BEHAVIOR

Shams, M.,Ebrahimi, R.,Raoufi, A.,Jafari, B.J. The Korean Society of Automotive Engineers 2007 International journal of automotive technology Vol.8 No.5

In this study, a Coupled Computational Fluid Dynamics(CFD) and Finite Element Analysis(FEA) method are used to predict and evaluate the performance of an automotive shock absorber. Averaged Navier-Stokes equations are solved by the SIMPLE method and the RNG $k-\varepsilon$ is used to model turbulence. CFD analysis is carried out for different intake valve deflections and piston velocities. The force exerted on the valve in each valve deflection is obtained. The valve deflection-force relationship is investigated by the FEA method. The force exerted on the valve in each piston velocity is obtained with a combination of CFD and FEA results. Numerical results are compared with the experimental data and have shown agreement. Dependence of valve deflection as a function of piston velocity is investigated. Effects of hydraulic oil temperature change on valve behavior are also studied.

T-NEIGHBORHOODS IN VARIOUS CLASSES OF ANALYTIC FUNCTIONS

Shams, Saeid,Ebadian, Ali,Sayadiazar, Mahta,Sokol, Janusz Korean Mathematical Society 2014 대한수학회보 Vol.51 No.3

Let $\mathcal{A}$ be the class of analytic functions f in the open unit disk $\mathbb{U}$={z : ${\mid}z{\mid}$ < 1} with the normalization conditions $f(0)=f^{\prime}(0)-1=0$. If $f(z)=z+\sum_{n=2}^{\infty}a_nz^n$ and ${\delta}$ > 0 are given, then the $T_{\delta}$-neighborhood of the function f is defined as $$TN_{\delta}(f)\{g(z)=z+\sum_{n=2}^{\infty}b_nz^n{\in}\mathcal{A}:\sum_{n=2}^{\infty}T_n{\mid}a_n-b_n{\mid}{\leq}{\delta}\}$$, where $T=\{T_n\}_{n=2}^{\infty}$ is a sequence of positive numbers. In the present paper we investigate some problems concerning $T_{\delta}$-neighborhoods of function in various classes of analytic functions with $T=\{2^{-n}/n^2\}_{n=2}^{\infty}$. We also find bounds for $^{\delta}^*_T(A,B)$ defined by $$^{\delta}^*_T(A,B)=jnf\{{\delta}>0:B{\subset}TN_{\delta}(f)\;for\;all\;f{\in}A\}$$ where A, B are given subsets of $\mathcal{A}$.

Numerical Investigation of Different Flow Regimes for Square Cylinders in Staggered Configuration

Shams Ul Islam,Ghazala Nazeer,Sehrish Hassan Shigri 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.5

The present numerical investigation deals with the flow across two square cylinders placed in staggered alignment at fixed Reynolds number (Re) of 160 and varying gap spacings (g*) from 0 to 6. Numerical computations are conducted by employing the two-dimensional single-relaxation-time lattice Boltzmann method (SRT-LBM). The complex phenomena of vortex shedding are explored for different g* and outcomes are presented as vorticity snapshots, time-history analysis of drag and lift coefficients (CD and CL) and power spectra analysis of CL. Five flow patterns are observed which are named as: single bluff body flow, quasi periodic flow, chaotic flow, in-phase/anti-phase modulated flow and synchronized flow. The fluid forces are irregular for all flow pattern except for synchronized flow where lift is periodic due to synchronization of flow. It is observed that presence of an upstream cylinder in the near vicinity of downstream cylinder increases the drag at small gap spacing and vice versa.

Electrocardiographic artefacts mimicking atrial tachycardia resulted in unnecessary diagnostic and therapeutic measures

Shams Y-Hassan,Christer Sylvén 대한내과학회 2013 The Korean Journal of Internal Medicine Vol.28 No.2

Electrocardiographic (ECG) artefacts may closely simulate both supraventricular and ventricular tachycardias. We describe a case initially diagnosed as rapid atrial fibrillation, based on 12-lead surface ECG (especially the limb leads) and monitor tracing. The arrhythmia was resistant to beta blockers. Because of the at times apparently regular rhythm, an esophageal ECG recording was performed, and adenosine was administered. When the presumed atrial fibrillation terminated after sodium pentothal was administered while preparing for electrical cardioversion, the oesophageal ECG recordings and the ECGs during adenosine administration were reviewed. An ECG artefact diagnosis was suspected, and then confirmed,during relapse of the “arrhythmia,” with simple palpation of the radial pulse and cardiac auscultation.

Investigations of radiation shielding using Monte Carlo method and elastic properties of PbO-SiO2-B2O3-Na2O glasses

Shams A.M. Issa,Yasser B. Saddeek,H.O. Tekin,M.I. Sayyed,Khamies saber Shaaban 한국물리학회 2018 Current Applied Physics Vol.18 No.6

Several physical parameters such as the packing density (PD), oxygen molar volume (OMV), oxygen packing density (OPD) and the elastic moduli of the quaternary glass system xPbO-(30-x)SiO2-46.67B2O3-23.33Na2O (x = 0, 5, 10 and 15 mol%) have been evaluated. The elastic moduli were computed according to Makishima-Mackenzie model and Rocherulle model. The values of these moduli have been compared to their experimental values. Moreover, different shielding parameters such as mass attenuation coefficients (MAC), half value layer (HVL), mean free path (MFP), effective atomic numbers (EAN), effective electron densities (EED) and buildup factors have been evaluated using the WinXcom program in the energy range 0.015–15 MeV for the quaternary studied glass system. The MAC values have been compared with MCNPX (version 2.6.0) Monte Carlo code. Besides, mass stopping power (MSP) for proton, alpha and electron as well as the removal cross section for fast neutron (∑R) have been calculated. The results observed that the composition has the highest value of PbO (15 mol %) showed excellent nuclear radiation shielding and elastic properties.

Throughput Maximization by Optimal UAV Positioning in SDN-based Aerial Communication Network

Shams ur Rahman,Geon-Hwan Kim,You-ze Cho,Ajmal Khan 한국통신학회 2018 한국통신학회 학술대회논문집 Vol.2018 No.6

Mobile wireless ad-hoc network routing protocols comparison for real-time military application

Shams Al Ajraw,Bang Tran 대한공간정보학회 2024 Spatial Information Research Vol.32 No.1

Mobile wireless Ad-hoc has become more popular because it forms quickly, has an easy setup, and has easy extensibility. The mobile ad-hoc wireless networks can be further classified according to their applications as follows: Regular user ad-hoc networks are commercial communication that applies to vehicles to help avoid collisions and accidents and live connections to transfer data from car to car. Another application is disaster rescue ad-hoc networking, usually used when a normal infrastructure network is destroyed by storms, earthquakes, tsunamis, etc. Nowadays, a lot of applications, particularly those related to the military and emergency situations, rely on mobile ad hoc wireless networks, where security needs are more challenging to provide than in regular networks. We present the tactical network needs for the military. This platform attempts to assess the possible advantages of mobile ad hoc networks in tactical military applications. This work proposes route discovery using reactive (on-demand) routing protocols where nodes need to just transfer data. This eliminates the requirement for each node to store and maintain any routing tables. This study presents and contrasts the benefits and drawbacks of two fundamental mobile ad hoc routing systems (AODV and DSR). Both protocols are On-Demand routing techniques, and when data needs to be sent, the discovery phase begins. The results of the simulation, the AODV routing approach outperforms the DSV routing method under identical simulated conditions. Mobile wireless Ad-hoc has become more popular because it forms quickly, has an easy setup, and has easy extensibility. The mobile ad-hoc wireless networks can be further classified according to their applications as follows: Regular user ad-hoc networks are commercial communication that applies to vehicles to help avoid collisions and accidents and live connections to transfer data from car to car. Another application is disaster rescue ad-hoc networking, usually used when a normal infrastructure network is destroyed by storms, earthquakes, tsunamis, etc. Nowadays, a lot of applications, particularly those related to the military and emergency situations, rely on mobile ad hoc wireless networks, where security needs are more challenging to provide than in regular networks. We present the tactical network needs for the military. This platform attempts to assess the possible advantages of mobile ad hoc networks in tactical military applications. This work proposes route discovery using reactive (on-demand) routing protocols where nodes need to just transfer data. This eliminates the requirement for each node to store and maintain any routing tables. This study presents and contrasts the benefits and drawbacks of two fundamental mobile ad hoc routing systems (AODV and DSR). Both protocols are OnDemand routing techniques, and when data needs to be sent, the discovery phase begins. The results of the simulation, the AODV routing approach outperforms the DSV routing method under identical simulated conditions.

Improved AntHocNet with Bidirectional Path Setup and Loop Avoidance

Shams ur Rahman(라프만 샴스 우르),Jae-Choong Nam(남재충),Ajmal Khan(아즈말 칸),You-Ze Cho(조유제) 한국통신학회 2017 韓國通信學會論文誌 Vol.42 No.1

Drag reduction on a square cylinder using multiple detached control cylinders

Shams-Ul-Islam,Raheela Manzoor,Umar Khan,Ghazala Nazeer,Sehrish Hassan 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.5

A two-dimensional numerical simulation for flow over a main cylinder with detached controlling cylinders placed at differentposition is performed through Lattice Boltzmann Method (LBM) to reduce fluid forces. For this study the Reynolds number (Re) isfixed at 160, while gap ratio between these cylinders are taken in the range from 0.5 to 8. The results yield in terms of vorticity, timeseriesanalysis of drag and lift coefficients, power spectra of lift coefficients and force statistics. Depending on gap spacing, flow isclassified into four different patterns, called as (i) single blender body, (ii) shear layer reattachment, (iii) fully developed flow and (iv)vortex suppression fully developed flow patterns. In comparison of all three configurations, it is examined that the maximum value ofCdmean and Strouhal number occurs for downstream configuration. Whereas, upstream and dual configuration play a vital role toreduce forces and to suppress vortex shedding. The maximum reduction found in mean drag coefficient for downstream, upstreamand for dual configuration is 8.3%, 51% and 50.8%, respectively. Whereas, the reduction in Clrms values for all three configurationsis 84.4%, 58.2% and 86.4% , respectively.

Numerical investigation of fluid flow past a square cylinder using upstream, downstream and dual splitter plates

Shams Ul Islam,Raheela Manzoor,Zhou Chao Ying,Mohammad Mehdi Rashdi,A. Khan 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.2

A two-dimensional numerical study is carried out to analyze the drag reduction and vortex shedding suppression behind a square cylinder in presence of splitter plate arranged in upstream, downstream and both upstream and downstream location at low Reynolds number (Re = 160). Computations are performed using a Single relaxation time lattice Boltzmann method (SRT-LBM). Firstly, the code is validated for flow past a single square cylinder. The obtained results are compared to those available in literature and found to be in good agreement. Numerical simulations are performed in the ranges of 1 ≤ L ≤ 4 and 0 ≤ g ≤ 7, where L and g are the length of splitter plate and gap spacing between the splitter plate and main square cylinder, respectively. The effect of these parameters on the vortex shedding frequency, time-trace analysis of drag and lift coefficients, power spectra analysis of lift coefficient, vorticity contours visualization and force exerted on the cylinder are quantified together with the observed flow patterns around the main cylinder and within the gap spacings. The observed results are also compared with a single square cylinder without splitter plate. We found that at some combinations of L and g, the mean drag coefficient and Strouhal number reach either its maximum or minimum value. It is found that the drag is reduced up to 62.2 %, 13.3 % and 70.2 % for upstream, downstream and dual splitter plates, respectively as compared to a single square cylinder (without splitter plate). In addition, in this paper we also discussed the applications of SRT-LBM for suppression of vortex shedding and reduction of the drag coefficients.