IIUM Engineering Journal
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Comprehensive Downtime Prediction in Next-Generation Internet
Get PDFThe benchmark for the reliability quality of networks depends mainly on the accuracy and comprehensiveness of the reliability parameters. Downtime prediction of a communication system is crucial for the quality of service (QoS) offered to the end-user. Markov model enables analytical calculation of average single figure cumulative downtime over one year. The single average approach, generally, does not adequately describe the wide range of service performance that is likely to be experienced in communications systems due to the random nature of the failure. Therefore, it would be more appropriate to add downtime distribution obtained from network availability models to predict the expected cumulative downtime and other performance parameters among a large number of system populations. The distribution approach provides more comprehensive information about the behavior of the individual systems. Laplace-Stieltjes transform enables analytical solutions for simple network architectures, i.e. the simplex system and the parallel system. This paper uses simulations to determine reliability parameters for complex architecture such as the Multiprotocol Label Switching (MPLS) backbone planned for next-generation Internet. In addition to the single figure downtime, simulations provide other reliability parameters such as probability of zero downtime. The paper also considers the downtime distribution among a population of equally designed systems.Key Words: Reliability, availability, downtime, Multiprotocol label switchin
Fuzzy Logic Based Controller for Maintaining Human Comfort within Intelligent Building System
Get PDFThis paper presents an intelligent control approach for air handling unit (AHU) which is an integral part of heat, ventilation, and air conditioning (HVAC) system. In the past years various control design for HVAC have been proposed as this system remarkably consumes very high energy. But most of the proposed designs were focused on the control flow of heat-transfer medium such as chilled or heated water while the importance of the efficient mixture of outdoor and indoor enthalpies is sometimes ignored. These enthalpies invariably determine the best strategy to overcome thermal load in a controlled environment to satisfy human comfort, hence a control design strategy must be able to efficiently regulate the flow and mixture of outdoor and indoor enthalpies by a proper control of AHU dampers and fans. This approach requires sensors to measure temperature and relative humidity of both outdoor and indoor environments. However, unpredictable level of disturbances coming from many sources including heat generated by occupants, electrical items and air leaking and the continuous changes of outdoor enthalpy makes it difficult to model the process. Consequently, conventional controllers are not suitable, hence the use of fuzzy logic controller (FLC) is proposed in this paper. This proposed controller operates in a master and slave control loop so as to control the AHU dampers and fans with adjustable output membership function whilst at the same time a scaling-factor method is used to drive the master operation. To implement the proposed system, a small scale prototype has been designed and fabricated. This prototype is an AHU model which consists of ductwork, temperature and humidity sensors, dampers, air cooling and heating systems. A small box is used as a conditioning space in which a room temperature is measured. The control algorithm is programmed using National Instrument (NI) LabVIEW and executed using NI FieldPoint. Experimental results reveal that proper control of AHU dampers and fans is an effective and practical means to satisfy human comfort with minimum energy consumption.Keywords: Human comfort, Intelligent control, Air handling unit, Adaptive fuzzy logic contro
A COMPARISON BETWEEN SINGLE LINKAGE AND COMPLETE LINKAGE IN AGGLOMERATIVE HIERARCHICAL CLUSTER ANALYSIS FOR IDENTIFYING TOURISTS SEGMENTS
Get PDFCluster Analysis is a multivariate method in statistics. Agglomerative Hierarchical Cluster Analysis is one of approaches in Cluster Analysis. There are two linkage methods in Agglomerative Hierarchical Cluster Analysis which are Single Linkage and Complete Linkage. The purpose of this study is to compare between Single Linkage and Complete Linkage in Agglomerative Hierarchical Cluster Analysis. The comparison of performances between these linkage methods was shown by using Kruskal-Wallis test. The result of the comparison used for segmenting tourists of Kapas Island. The statistical software SPSS has been applied to analyze data of this research. The result from Kruskal-Wallis test shows Complete Linkage is more useful in identifying tourists segments. Keywords : Agglomerative Hierarchical Cluster Analysis, Single Linkage, Complete Linkage, Kruskal-Wallis test, tourist
Analysis of Rain Effects on Terrestrial Free Space Optics based on Data Measured in Tropical Climate
Get PDFFree Space Optics (FSO) shows a great alternative as the solution for last mile problem where fiber optics is unavailable due to deployment time and cost constraint. However, the feasibility of using FSO system as communication link very much depends on local weather. Since tropical region experiences heavy rainfall, rain with high intensity is expected to affect the FSO link severely. Few prediction models have been proposed by ITU-R based on France and Japan’s measurement. This paper has compared rain attenuation predicted by models and data measured in Malaysia over Free Space Optical links for one year period. Prediction models are clearly unable to predict attenuation measured in tropical climate. ABSTRAK: Wayarles optik menjadi alternatif sebagai satu penyelesaian kepada masalah kesesakan terutama diakhir sesuatu talian dimana ianya tidak dapat diselesaikan dengan menggunakan gentian fiber akibat daripada kekangan masa pemasangan dan masalah kewangan. Walaubagaimanapun, kejayaan untuk menggunakan wayarless optic ini amat bergantung kepada keadaan cuaca di sesuatu tempat. Di rantau tropika hujan lebat sentiasa dialami, oleh itu hujan dengan kepadatan tinggi adalah dijangkakan lebih memberi kesan kepada talian wayarles optic ini. Beberapa model yang telah dicadangkan oleh ITU-R berlandaskan kepada pengumpulan data yang dibuat di Perancis dan Jepun. Kertas kajian ini akan membandingkan antara model-model yang telah digunapakai dengan data yang dikumpulkan di Malaysia selama setahun. Jelasnya model yang telah digunapakai tidak dapat digunakan secara berkesan di rantau tropika.KEYWORDS: free space optics; rainfall rate; rain attenuatio
Iterative Spatial Sectoring: An Extention of Simpson’s Rule for Determining Area of Irregular Close Shape
Get PDFJust as the method for determining the properties of shapes like triangles, parallelogram, cuboids, and geometric figures like circle, and spheres have standard formulae, the determination of a function F(x) in many dimensions have formulae or standard methods. Complex 2D and 3D figures consisting of intricate merger of regular shapes have had their parameters determined through careful separation and determination of the properties of individual components that make up the figure. Moreover, the case of irregular close shapes mostly but not limited to 2D and 3D which abound in science and engineering have equally received attention resulting in lots of approximation method evolved over time. The Iterative spatial sectoring is a novel way of determining the area of 2D irregular close shape by expanding on the famours Simpson’s method for finding the area of a function F(x) whose definite integral is either tedious or impossible by standard approaches. ABSTRAK: Seperti beberapa kaedah yang ada yang sering kali digunakan untuk menentukan sifat-sifat bentuk seperti segi tiga, segi empat selari, kuboid, dan rajah geometrik seperti bulatan, dan sfera; semuanya mempunyai formula-formula yang standard, penentuan fungsi F(x). Bentuk kompleks dua dimensi, 2D dan tiga dimensi, 3D terdiri daripada penyatuan rumit bentuk-bentuk yang biasa dimana parameternya ditentukan melalui pengasingan yang cermat dan penentuan ciri-ciri komponen individu yang akhirnya membentukkannya. Walaupun begitu, dalam hal bentuk tertutup yang tak nalar, ia bukan hanya terhad kepada bentuk 2D dan 3D yang banyak terdapat dalam bidang sains dan kejuruteraan. Ia mendapat perhatian meluas dimana pelbagai kaedah penghampiran dihasilkan. Pensektoran ruang berlelar merupakan cara baru yang digunakan untuk menentukan keluasan bentuk 2D tak nalar yang bertutup dengan mengembangkan kaedah Simpson’s untuk mendapatkan keluasan dengan fungsi F(x) dimana kamirannya sama ada terlalu rumit ataupun di anggap mustahil mengikut cara biasa.KEYWORDS: function F(x); irregular shape; Simpson’s method; definite integral; iterative spatial sectorin
A Proposed Method for Improving the Performance of P-Type GaAs IMPATTs
Get PDFA special waveform is proposed and assumed to be the optimum waveform for p-type GaAs IMPATTs. This waveform is deduced after careful and extensive study of the performance of these devices. The results presented here indicate the superiority of the performance of the IMPATTs driven by the proposed waveform over that obtained when the same IMPATTs are driven by the conventional sinusoidal waveform. These results are obtained using a full-scale computer simulation program that takes fully into account all the physical effects pertinent to IMPATT operation. In this paper, it is indicated that the superiority of the proposed waveform is attributed to its ability to reduce the bad effects that usually degrade the IMPATT performance such as the space-charge effect and the drift-velocity dropping below saturation effect. The superiority is also attributed to the ability of the proposed waveform to improve the phase relationship between the terminal voltage and the induced current.Key Words: Computer-Aided Design, GaAs IMPATT, Microwave Engineerin
Effect of Lithium Chloride (Licl) Dopant on The Performance of Catalysts for the Oxidative Coupling of Methane
Get PDFThe Effects of Weathering on Mechanical Properties of Glass Fiber Reinforced Plastics (Grp) Materials
Get PDFGlass fiber reinforced plastics composite is extensively used as a structural material for pools, oil pipes and tanks because it has good corrosion resistance properties. The effects of weathering on the mechanical properties of glass fiber reinforced plastics (GRP) in the Sultanate of Oman have been studied. The tensile and three point bend specimens were exposed to outdoor conditions (open atmosphere) in sunlight and tested for various intervals of time. It was observed that as the exposure time to sunlight, ultraviolet radiation and dust increases the mechanical properties of GRP materials decrease. The effects of relative humidity (%RH) on the mechanical properties were also studied. It was found that as the relative humidity increased in the atmosphere during the exposure time, the tensile strength, flexural strength and modulus of elasticity are lowered. This work has revealed that the decrease in the mechanical properties of GRP under weathering conditions is subjected to atmospheric conditions such as humidity, temperature, ultraviolet radiation and pollutant.Key Words: Weathering, Glass-Fiber Reinforced Plastics, Degradatio
DEVELOPMENT OF VIRTUAL ASSEMBLY LAYOUT WITH MODELING LANGUAGES APPROACH AND SIMULATION USING DELMIA™ QUEST®
Get PDFABSTRACT: The paper presented the development of virtual layout model with modeling languages approach. This research also explores the flexibility of the model configurations through the development process of database for storing and representing the virtual model. The concept and mechanisms of database development involves the use of eXtensible Markup Language (XML). The objectives of the research are therefore to obtain a basic understanding on how these modeling languages are used to develop virtual model, representing the simulation by using Delmia™ QUEST® and develop a database for share, store and future usage. Therefore, the generated simulation presents the feasibility of interchanging models using modeling language approach as an intermediate representation and provides an opportunity to improve simulation quality
Kinematic Analysis Of Tricept Parallel Manipulator
Get PDFParallel manipulators consist of fixed and moving platforms connected to each other with some actuated links. They have some significant advantages over their serial counterparts. While, they suffer from relatively small workspaces, complex kinematics relations and highly singular points within their workspaces. In this paper, forward kinematics of Tricept parallel manipulator is solved analytically and its workspace optimization is performed. This parallel manipulator has a complex degree of freedom, therefore leads to dimensional in-homogeneous Jacobian matrices. Thus, we divide some entries of the Jacobian by units of length, thereby producing a new Jacobian that is dimensionally homogeneous. Moreover, its workspace is parameterized using some design parameters. Then, using GA method, the workspace is optimized subjects to some geometric constraints. Finally, dexterity of the design is evaluated. Keywords- Kinematic, Workspace, Singularity, TriceptABSTRAK - Manipulator selari terdiri daripada platform tetap dan bergerak yang bersambung antara satu sama lain dengan beberapa pautan bergerak. Manipulator selari mempunyai beberapa kebaikan tertentu dibandingkan dengan yang bersamaan dengannya. Walaupun ia mempunyai ruang kerja yang sempit, hubungan kinematik kompleks dan titik tunggal tinggi dalam linkungan ruang kerjanya. Dalam kajian ini, kinematik ke hadapan manipulator selari Tricept diselesaikan secara analisa dan pengoptimuman ruang kerja dijalankan. Manipulator selari ini mempunyai darjah kebebasan yang kompleks, yang menyebabkan ia mendorong kepada kehomogenan dimensi matriks Jacobian. Catatan Jacobian dibahagikan kepada unit panjang, dimana ia menghasilkan Jacobian baru yang homogen dimensinya. Tambahan, ruang kerjanya diparameterkan dengan menggunakan beberapa parameter reka bentuk. Kemudian, dengan kaedah GA, ruang kerja mengoptimakan subjek kepada beberapa kekangan geometrik. Akhirnya, kecakatan reka bentuk dinilaikan.Keywords- Kinematic, Workspace, Singularity, Tricep