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Search Results: 1 - 10 of 328028 matches for " S. Hasan "
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Bi-Criteria Optimization Technique in Stochastic System Maintenance Allocation Problem  [PDF]
Irfan Ali, S. Suhaib Hasan
American Journal of Operations Research (AJOR) , 2013, DOI: 10.4236/ajor.2013.31002

In this paper, the problem of optimum allocation of repairable and replaceable components in a system is formulated as a Bi-objective stochastic non linear programming problem. The system maintenance time and cost are random variable and has gamma and normal distribution respectively. A Bi-criteria optimization technique, weighted Tchebycheff is used to obtain the optimum allocation for a system. A numerical example is also presented to illustrate the computational details.

Fast Handoff for 802.11 Wireless Network  [PDF]
Obay H. Sabrie, Hasan S. Hasan, Rosli Salleh
Communications and Network (CN) , 2011, DOI: 10.4236/cn.2011.34029
Abstract: Whenever the mobile station moves from the range of one access point and comes to the range of another access point a handoff process is occurred. This process takes a long time when using the IEEE 802.11 standard handoff and this delay affect the real time and multimedia applications. This paper provides a layer 2 handoff process for the IEEE 802.11 that is able to eliminate the scanning delay and reduce the total handoff delay.
Mass segregation in diverse environments
Priya Hasan,S N Hasan
Physics , 2011, DOI: 10.1111/j.1365-2966.2011.18305.x
Abstract: In this paper, using 2MASS photometry, we study the mass functions $\phi(M) = dN/dM \propto M^{-\alpha}$ of a sample of nine clusters of ages varying from 4 Myr--1.2 Gyr and Galactocentric distances from 6--12 kpc. We look for evidence of mass segregation in these clusters by tracing the variation in the value of $\alpha$ in different regions of the cluster as a function of the parameter $\tau = t_{age}/t_{relax}$ (where $t_{age}$ is the age of the cluster and $t_{relax}$ is the relaxation time of the cluster), Galactocentric distance, age and size of the cluster. The value of $\alpha$ value increases with age and $\tau$ and fits straight lines with slopes $m$ and y-intercepts $c$ given by $m=0.40\pm0.03$, $c=-1.86\pm0.27$ and $m=0.01\pm0.001$, $c=-0.85\pm0.02$, respectively and is a clear indicator of the dynamical processes involved. The confidence level of the Pearson's product-moment correlation of $\alpha$ with age is 0.76 with p=0.002 and with $\tau$ is 0.71 with p=0.007. The value of $\alpha$ also increases with Galactocentric distance, indicating the presence of a larger relative number of low mass stars in clusters at larger Galactocentric distances. We find two clusters, viz. IC 1805 and NGC 1893, with evidence of primordial or early dynamical mass segregation. Implications of primordial mass segregation on the formation of massive stars and recent results supporting early dynamical mass segregation are discussed.
Two Slot MIMO Configuration for Cooperative Sensor Network  [PDF]
Ibrahim Mansour, Jamal S. Rahhal, Hasan Farahneh
Int'l J. of Communications, Network and System Sciences (IJCNS) , 2010, DOI: 10.4236/ijcns.2010.39100
Abstract: Sensor networks are used in various applications. Sensors acquire samples of physical data and send them to a destination node in different topologies. Multiple Input Multiple Output (MIMO) systems showed good utilization of channel characteristics. In MIMO Sensor Network, multiple signals are transmitted from the sensors and multiple sensors are used as receiving nodes. This provides each sensor multiple copies of the transmitted signal and hence, array processing techniques helps in reducing the effects of noise. In this paper we devise the use of MIMO sensor network and array decision techniques to reduce the noise effect. The proposed system uses a transmission time diversity to form the MIMO system. If the number of sensors is large then groups of sensors will form the MIMO system and benefited from the diversity to reduce the required transmitted power from each sensor. Enhancing the BER reduce the required transmitted power which results in longer battery life for sensor nodes. Simulation results showed an overall gain in SNR that reaches 11dB in some sensor network scenarios. This gain in SNR led to the opportunity of reducing the transmitted power by similar amount and hence, longer battery life is obtained.
Performance Evaluation of Complex Wavelet Packet Modulation (CWPM) System over Multipath Rayleigh Fading Channel  [PDF]
Hikmat N. Abdullah, Fadhil S. Hasan
Journal of Signal and Information Processing (JSIP) , 2012, DOI: 10.4236/jsip.2012.33045
Abstract: In this paper a novel multicarrier modulation system called Complex Wavelet Packet Modulation (CWPM) has been proposed. It is based on using the Complex Wavelet Transform (CWT) together with the Wavelet Packet Modulation (WPM). The proposed system has been tested for communication over flat and frequency selective Rayleigh fading channels and its performance has been compared with some other multicarrier systems. The simulation results show that the performance of the proposed CWPM system has the best performance in all types of channel considered as compared with OFDM, Slantlet based OFDM, FRAT based OFDM and WPM systems. Furthermore, the proposed scheme has less PAPR as compared with the traditional WPM multicarrier system.
Performance of cryogenically treated CBN inserts on difficult to cut materials during turning
S. Thamizhmanii,S. Hasan
Journal of Achievements in Materials and Manufacturing Engineering , 2012,
Abstract: Machining of materials is recognized as removing unwanted materials by using different cutting inserts. In this research, cutting inserts used are CBN inserts and treated cryogenically at -196°C in liquid nitrogen chamber. The inserts are subjected to 30 hours of treatment in controlled atmosphere. The materials used are Titanium and AISI 440 C hard Martensitic Stainless steel. The cutting parameters are cutting velocity 30, 40 and 50 m/min with feed rate of 0.05, 0.10 and 0.15 mm/rev and depth of cut of 0.05, 0.75 and 1.00 mm. The performance evaluated was tool wear, surface roughness. Cryogenically treated CBN inserts produced less tool wear on titanium than AISI 440 C Martensitic stainless steel. The roughness produced was low at high cutting speed with low feed rate. Flank wear was not progressive and varied. In turning AISI 440 C stainless steel, built up edge formed in all cutting speed which is a common phenomena and lead to crater wear formation. The chips produced were saw tooth chips by both materials.
Analyses of roughness, forces and wear in turning gray cast iron
S. Thamizhmanii,S. Hasan
Journal of Achievements in Materials and Manufacturing Engineering , 2006,
Abstract: Purpose: Purpose of this research was to analyze the surface roughness, cutting tool forces and tool wear in machining casted gray iron.Design/methodology/approach: The methodology adopted was turning process from other machining process. The turning is the widely employed manufacturing process. The tests were conducted by designing various cutting speed, feed and a constant depth of cut. In turning casted gray iron, flank wear, crater wear and built up edge are the common phenomenon.Findings: from the tests were the formation of flank wear, crater wear while machining the casted gray iron. Further research is possible in the direction measuring the residual stresses and the vibration of the cutting tool.Research limitations/implications: There are some limitations in carrying the tests namely vibration of the tool, tool wear and length of work piece. The constraint in measuring depth of crater wear was due to non availability of technology devices and equipments. However, the length of crater wear was measured for analyzes.Originality/value: The value of the work lies in the utility of the results obtained to researchers and users of the casted gray iron material for their components.
A review on an employee empowerment in TQM practice
S. Thamizhmanii,S. Hasan
Journal of Achievements in Materials and Manufacturing Engineering , 2010,
Abstract: Purpose: This paper discusses the issues of employee’s empowerment, their training needs, suggestions and other issues related to it. Total quality management (TQM) is a management technique adopted by the most manufacturing organizations. TQM in general is viewed as organization set up which will help to manufacture products at lowest cost by the following various management techniques through continuous improvement. Employee empowerment is providing decision making powers to a team or an individual.Design/methodology/approach: Employee empowerment is providing decision making powers for a team or individual.Findings: Employee empowerment is good for an organization and employee is empowered to make specific decision for the interest of the organization. Empowerment helps to play a wider role in an organization as a process owner.Research limitations/implications: This is a conceptual study, and hence, there is no hypothesis tested as an empirical study. It does provide a good foundation for future research.Originality/value: The paper is a conceptual design and more elaborative requirements can be done. This is an input to create awareness among the organizations.
Measurement of surface roughness and flank wear on hard martensitic stainless steel by CBN and PCBN cutting tools
S. Thamizhmanii,S. Hasan
Journal of Achievements in Materials and Manufacturing Engineering , 2008,
Abstract: Purpose: The experiments with different operating parameters using CBN and PCBN tools on hard AISI 440 C material were investigated in this paper.Design/methodology/approach: In this research AISI 440 C stainless was used under hard condition. The cutting tools are having three cutting edges and each edge repeated for 5 times. The test conducted by each cutting edge was termed as trail 1, 2, 3, 4 & 5. The length of cutting was 150 mm and each trail. The surface roughness and flank wear, crater wear and BUE were measured by SEM.Findings: The surface roughness was low by CBN at high turning cutting speed and the flank wear was high. The surface roughness was high by PCBN tool than CBN tool and flank wear recorded was low for PCBN tool than CBN tool. The chips produced were saw tooth in all operating parameters. The CBN tool was unable to withstand heat at cutting zone and hence more flank wear occurred. The PCBN tool sustained the temperature and less tool wear occurred. More crater wear formed on PCBN tools where as CBN tool produced less crater wear. The formation of crater wear on the rake face was due to rough surface of the saw tooth chips.Practical implications: The investigation results will provide useful information to applying CBN and PCBN cutting tools in hard turning stainless steels.Originality/value: Hard turning is a latest technology and possible to turn all hard materials. The hard turning produce net shaped products and reduces machining time, low cost per products, etc. The difficult to cut materials like stainless steels was turned by super hard cutting tools like CBN and PCBN to achieve good surface roughness, dimensional control and reduced tool wear.
Transition Frequencies and Negative Resistance of Inductively Terminated CMOS Buffer Cell and Application in MMW LC VCO
S. M. Rezaul Hasan
Active and Passive Electronic Components , 2010, DOI: 10.1155/2010/542406
Abstract: This paper investigates the transition frequencies ( ) of an inductively terminated CMOS source follower buffer for negative resistance behavior at which the effective shunt resistance looking into the source of the buffer cell changes sign. Possible limiting frequencies of oscillation are determined based on resonators formed by a grounded gate inductor and a parasitic capacitance at the gate of the negative resistance buffer cell. The range of frequencies of oscillation of this negative resistance buffer cell for variations in the different circuit parameters/elements is explored. Following this, a millimeter wave (MMW) oscillator is simulated using the IBM 130?nm CMOS process technology which can operate at 70?GHz. High-frequency MOSFET model was used for these simulations. The cell had an extremely low power dissipation of under 3?mW. Extensive Monte Carlo simulations were carried out for manufacturability analysis considering up to 50% variation in process and geometrical parameters, supply voltage, and ambient temperature. Noise analysis and a simulated estimate of the phase noise in an MMW LC VCO application is also reported. 1. Introduction Developing cost-effective advanced microwave communication systems using Millimeter wave (MMW) oscillators, or MMW voltage controlled oscillators (VCOs) on low-cost nanometric bulk CMOS process technologies is of immense interest in the semiconductor and circuit design research community. Design of MMW Oscillators and VCOs in III-V compound semiconductors and Si-Ge Heterojunction devices [1–4] has been reported for many years, but in recent times vast effort has been focused on CMOS MMW implementations [5–8]. In this regard, investigation of the high-frequency behavior and maximum possible oscillation frequency of CMOS negative resistance cell is crucial as CMOS devices have inherently lower unity-gain frequency ( ) compared to III-V compound semiconductor FET and Si-Ge HBT devices. Recently Veenstra and van der Heijden [9] proposed the maximum possible oscillation frequency of a negative resistance cell as , which is defined as a frequency where the effective negative resistance of the cell turns from negative to positive. The well known cross-coupled CMOS negative resistance cell has the disadvantage of a which is hard-limited by device size and bias drain. CMOS imitations of cross-coupled and other bipolar cells to overcome these limitations has been largely unsuccessful [7]. On the other hand, CMOS versions of Colpitts and Clapp (or Clapp-Gouriet) oscillators were found to have higher than a cross-coupled
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