Ahmad Faris Ismail

Stability and thermal conductivity enhancement of carbon nanotube nanofluid using gum arabic

This experimental study reports on the stability and thermal conductivity enhancement of carbon nanotubes (CNTs) nanofluids with and without gum arabic (GA). The stability of CNT in the presence of GA dispersant in water is systematically investigated by taking into account the combined effect of various parameters, such as sonication time, temperature, dispersant and particle concentration. The concentrations of CNT and GA have been varied from 0.01 to 0.1 wt% and from 0.25 to 5 wt%, respectively, and the sonication time has been varied in between 1 and 24 h. The stability of nanofluid is measured in terms of CNT concentration as a function of sediment time using UV-Vis spectrophotometer. Thermal conductivity of CNT nanofluids is measured using KD-2 prothermal conductivity meter from 25 to 60°C. Optimum GA concentration is obtained for the entire range of CNT concentration and 1–2.5 wt% of GA is found to be sufficient to stabilise all CNT range in water. Rapid sedimentation of CNTs is observed at higher GA concentration and sonication time. CNT in aqueous suspensions show strong tendency to aggregation and networking into clusters. Stability and thermal conductivity enhancement of CNT nanofluids have been presented to provide a heat transport medium capable of achieving high heat conductivity. Increase in CNT concentrations resulted in the non-linear thermal conductivity enhancement. More than 100–250% enhancement in thermal conductivity is observed for the range of CNT concentration and temperature.

Numerical modelling of a multi-stage solar still

Abstract This paper reports the development of a mathematical model to predict the productivity and the thermal characteristics of a multistage solar still with an expansion nozzle and heat recovery in each stage of the still. Furthermore, this model is used to conduct a parametric investigation of the proposed solar still. A cost analysis is performed to shed some light on the potential of utilizing the proposed still for production of drinking water. It was found that making use of an expansion nozzle and heat recovery techniques in the proposed solar still tend to enhance the productivity of the still and the distillation efficiency. The daily solar still productivity can be up to 9 kg/m 2 , and the distillation efficiency is 87%. The unit cost for distilled water of this still is

Enhanced user authentication through typing biometrics with artificial neural networks and k-nearest neighbor algorithm

25.6/1000 gallons.

Handoff latency analysis of mobile IPv6 protocol variations

The emergence of global network access has promoted increased chances of malicious attack and intrusion. Password authentication has been known as the most commonly safeguard measure against these intrusions. Common it is, but the security measures that it provides have always been questionable. Thus, it gives rise to the need for a more secure and reliable authentication method in accessing computer systems. This paper proposes the design and development of a real time enhanced password security system through typing biometrics. Typing biometrics deals with the analysis of the unique habitual typing rhythms of individuals. The paper depicts the use of time latency between keystrokes to create typing patterns for individuals. Time latencies are extracted and classified accordingly; they are then used to recognize authentic users and reject imposters. The performance of both artificial neural networks and k-nearest neighbors as possible classifiers for this purpose were studied.

Theoretical and Experimental Investigation of a Novel Multistage Evacuated Solar Still

Mobile Ipv6 (MIPv6) is a protocol proposed for the future all-IP mobile Internet access. The goal of MIPv6 is to provide uninterrupted network connectivity while moving between different domains or access points. To date, there are various technologies under development for enhancing and optimizing the existing MIPv6 protocol. Using three simulated scenarios, this paper compares the effects of these variations on the handoff latency. The first simulation scenario studies the latency of linear movement of mobile nodes; and the second scenario studies the latency of ping-pong (continuous changing of domains) movement of mobile nodes; the third scenario studies latency, handoff success and effect of signaling load on handoffs by gradually increasing from 5 nodes to 50 nodes. The experimental scenarios were simulated in an open source Network Simulator 2 (ns-2). This paper also discusses the deployment challenges and proposes the most suitable variation of the Mobile IPv6 protocol for reducing handoff latency.

Application of CNT nanofluids in a turbulent flow heat exchanger

Solar desalination is an ideal source of fresh water for both drinking and agriculture. A lot of research was conducted on solar desalination systems, but most of the available systems have low production, are expensive, and are not reliable for long term use. In this work a new multistage evacuated solar desalination system was proposed and designed.The objective of this work is to increase the productivity and improve the low efficiency of the traditional solar desalination systems. The new system works by virtue of the higher evaporation rate under vacuum condition inside the solar still. A model for the system was developed and used to optimize the system design. The new model was subjected to a Finite Element Analysis (FEA) structural analysis using MSC/NASTRAN™ FEA software. A Computational Fluid Dynamics (CFD) simulation of the evaporation and condensation process inside one stage of the new solar still was conducted using FLUENT™ software. The system prototype was fabricated and tested at the actual outdoor ambient conditions for a period of 3 months. The productivity of this new system was found to be 14.2 kg/m2/day, which is about threefold of the maximum productivity of the basin type solar still. The cost of produced still water is estimated as 0.20 US

High Altitude Platform for Wireless Communications and Other Services

/gal. The results show that the multi-stage evacuated solar still might be a good option as a solar desalination system.

Dynamic keystroke analysis using AR model

Nanofluids have received much attention since its discovery owing to its enhanced thermal conductivity and heat transfer characteristics which makes them a promising coolant in heat transfer application. In this study, the enhancement in heat transfer of carbon nanotube (CNT) nanofluids under turbulent flow conditions is investigated experimentally. The CNT concentration was varied from 0.051 to 0.085 wt%, respectively. The nanofluid suspension was stabilised by gum arabic through a process of homogenisation and water bath sonication at 25 °C. The flow rate of cold fluid (water) is varied from 1.7 to 3 L/min, while flow rate of the hot fluid is varied between 2 and 3.5 L/min. Thermal conductivity, density, and viscosity of the nanofluids are also measured as a function of temperature and CNT concentration. The experimental results were validated with theoretical correlations for turbulent flow available in the literature. Results showed an enhancement in heat transfer between 9% and 67% as a function of temperature and CNT concentration.

Experimental and numerical investigation of heat transfer in CNT nanofluids

High altitude platform stations (HAPs) is a new and promising technology which can serve a large number of users at low-cost and quick access to modern wireless communication services. This paper reviews on the system structure, the advantages of HAPs over terrestrial and satellite architectures and possible communications applications of HAPs. It also present an overview about some underway HAPs projects worldwide. Finally, it focuses on the technical challenges and critical issues of energy source, platform station keeping, modulation, coding, antennas design, propagation, diversity, interference and handoff issues.

Duststorm measurements for the prediction of attenuation on microwave signals in Sudan

The design and development of a pressure sensor based typing biometrics authentication system (BAS) is discussed in this paper. The dynamic keystroke, represented by its time duration and force generates a waveform, which when concatenated results in a users typing pattern for the typed password. The design of the BAS is in two stages, whereby the hardware comprising the pressure sensor and the associated data acquisition system (DAS) is first implemented. The system DAS has been designed using LabVIEW software. Furthermore several data preprocessing techniques have been used to improve the quality of the acquired waveforms. The second stage involves a classifier to authenticate the users. This paper discusses a new data classifier technique based on autoregressive signal modeling (AR), which has been developed so as to correctly identify and authenticate the users of the system. Some experiments have been conducted to show the validity of the overall BAS performance. The results obtained have shown that this proposed system is reliable with many potential applications for computer security.