Physics, Engineering and Material Science

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    Kesan luluhawa terhadap kekuatan ricih syal lempung dalam penentuan parameter kestabilan cerun
    (Universiti Teknologi Malaysia, 2017) Idrus Muhamad Alatas
    Syal lempung dalam keadaan semula jadi merupakan batuan lempung yang memiliki kekuatan ricih yang tinggi. Syal lempung yang terdedah kepada atmosfera dan hidrosfera menyebabkan kekuatan ricih berkurang dengan ketara. Perkara ini menyebabkan banyak kegagalan cerun berlaku di tanah syal lempung yang mana kaedah piawai untuk permasalahan tersebut masih belum ada. Oleh itu, kajian ini bertujuan menyiasat pengaruh luluhawa terhadap indeks dan ciri-ciri fizikal syal lempung serta penurunan kekuatan ricih puncak dan kekuatan ricih baki. Kajian ini juga bertujuan membangunkan kaedah yang tepat untuk menentukan dan mengaplikasikan parameter kekuatan ricih yang masih belum ada untuk permasalahan kestabilan cerun syal lempung. Pengambilan sampel tak terganggu syal lempung diperolehi daripada ujian galian dengan menggunakan acuan teras terbelah yang belum pernah digunakan. Sampel diuji di makmal untuk menentukan kekuatan ricih baki dan kemudiannya digunakan untuk menilai keadaan kes cerun di tapak pembinaan. Dua jenis hasil ujian ialah kekuatan ricih baki tanpa pelepasan tegasan dan kekuatan ricih baki dengan pelepasan tegasan. Pada kes cerun yang belum berlaku kegagalan, analisis kestabilan cerun menggunakan parameter kekuatan ricih yang sudah dipengaruhi luluhawa memberikan kejelekitan (c) antara 31% hingga 49%, manakala sudut geseran dalam (f) adalah antara 81% hingga 98% daripada keadaan semulajadi. Manakala pada kes cerun yang telah berlaku kegagalan, akan tetapi tidak berlaku penggalian, analisis kestabilan cerun yang menggunakan kekuatan ricih baki tanpa pelepasan tegasan memberikan hasil dengan kejelekitan baki (crp) adalah 21% hingga 28% dari kejelekitan puncak dan sudut geseran dalam (frp) adalah 32% hingga 45% dari sudut geseran dalam puncaknya. Pada kes cerun yang telah berlaku kegagalan, tetapi berlaku penggalian serta penimbunan semula, analisis kestabilan cerun menggunakan kekuatan ricih baki dengan pelepasan tegasan, kejelekitan baki (crf) adalah 2% hingga 9% dari kejelekitan puncak dan sudut geseran dalam (frf) adalah 19% hingga 24% dari sudut geseran dalam puncaknya. Hasil ujian kekuatan ricih baki yang diperolehi di makmal disahkan dengan penentuan kekuatan ricih baki yang berlaku pada kes kegagalan cerun di jalan tol Semarang Bawen STA 19+250. Analisis balik dengan kaedah elemen terhingga (FEM) dan kaedah had keseimbangan (LEM) telah mengesahkan bahawa ujian kekuatan ricih baki yang diperoleh di makmal dengan kaedah yang disyorkan telah membuktikan hasil yang cemerlang. Kajian ini mencadangkan ujian kekuatan ricih melalui proses luluhawa di makmal adalah sesuai untuk kejuruteraan rekabentuk rancangan kestabilan cerun pada tanah syal lempung di masa hadapan.
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    Task oriented feature extraction for complex human activity recognition
    (Universiti Teknologi Malaysia, 2022) Mohammed Mobark Salem Wahdeen
    Human Activities Recognition (HAR) using mobile phone devices provides valuable contextaware information about the type of activities individuals perform within a time interval. HAR leverages sensory data available on today's sensor-rich, cheap, and portable mobile phones. It enables mobile phones to provide personalized support for many healthcare and well-being applications. It also has significant contributions to robotic, homeland security and smart environments. However, current recognition systems based on mobile phone sensors have observable issues in recognizing composite activities that occur concurrently or interleave i.e., complex activities, limiting their use in real-world applications. In those activities, the existence and variations of each activity as well as the order and length may vary. In this research, the issues of low recognition accuracy and high computing cost of complex human activities using mobile phone sensors are addressed. The composition and variations of human activity are examined as factors that impact the complexity of activity recognition. This research proposes to increase the quality of extracted features to increase the recognition accuracy with less resource consumption. It proposes extracting the wrist velocity as a feature for recognizing the performing arm’s complex activity. The wrist velocity feature is task oriented. Using the task-oriented wrist velocity feature will help to reduce recognition errors and therefore increase recognition accuracy. For this purpose, an extraction method for the wrist velocity feature is developed. In addition, the developed method is applied to recognize complex human activities using the Complex Activity Recognizer through Wrist velocity system (CARWV). Firstly, the extraction method begins by integrating the accelerometer and gyroscope data of the smartphone, which is placed on the upper arm and forearm. The integrated data is used to calculate the rotational angles of the upper arm and forearm. Then, the calculated rotational angles and lengths of the upper arm and forearm are used to calculate the position and the velocity of the wrist while performing the activity. Secondly, in the proposed recognition system (CARWV), the complex activity is broken into tasks that are represented by basic arm movements. The wrist velocity while performing the basic arm movements is extracted. The decision tree classifier is used to recognize the basic arm movements through the extracted feature. Then, the existing and order of recognized basic arm movements in the complex activity are used as features for recognizing the complex activity by measuring the similarity using the distance metric. The experiments demonstrate the validity of the task-oriented property of the extracted feature. The experiments also show increased recognition accuracy when using the proposed system up to 86% over performance for the state-of-the-art works, with 13 sec execution time and 31264 kb allocated memory in a notebook computer with Core i7 processor and 8GM memory. This study can facilitate future research in other fields where performance and limited resources are critical quality factors such as robotics and Wireless Sensor Networks (WSN).
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    Ergonomic design parameters for Malaysian car driver seating position
    (Universiti Teknologi Malaysia, 2017) Rashid, Zuli'zam
    A key element in an ergonomically designed driver workspace of a car is the correct identification of seating position and posture accommodation. Current practice by the automotive Original Equipment Manufacturer (OEM) is to utilize the Society of Automotive Engineering (SAE) standard practice and guidelines in the design process. However, it was found that utilizing such guidelines which were developed based on the American population, do not fit well with the anthropometry and stature of the Malaysian population. This research seeks to address this issue by reviewing the existing standard practices of Design Package and Ergonomic for seating position and accommodation used by a Malaysian automotive manufacturer, Perusahaan Otomobil Nasional (PROTON), and to subsequently propose a new design parameters which better fit the Malaysian population. In the first stage, 210 respondents participated in the anthropometry measurement study to determine the range of sizes for the Malaysian population. In addition, 62 respondents were involved for the driver seating position and accommodation study in the vehicle driver workspace buck mock-up survey and measurements. The results have shown that the Malaysian population are generally shorter if compared with the SAE J833 standard specification, especially for the lower body segments. From the accommodation study, it was found that the Malaysian driver preferred to seat forward, which is probably due to the shorter limb dimensions in the thigh length, buttock length, knee length and foot length. In second stage, questionnaire survey and measurement were used to develop a new design parameters and standards for driver seating positioning and accommodation model based on the Malaysian population. Statistical regression analysis was used to assist in this design parameters development. The statistical model developed was validated by comparing the calculated value of Seating Reference Point of X axis (SgRPx) with actual measurement values measured during respondents sitting in the mock-up. The result shows the difference between the calculated and measured values was within 10 %, indicating that the equation is acceptable. The findings of research are expected to enhance and improve the design guidelines / standard reference for the local automotive industry
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    Laminar flow heat transfer enhancement in multy-start spirally corrugated tubes
    (Universiti Teknologi Malaysia, 2016) Zaid Sattar Kareem
    Heat transfer plays an important role in many aspects of human life, especially the forced convection type. Hence, it has become very important to invest resources and efforts in this vital field to make some difference. Recently, the trend of using compact heat transport devices is of great interest to obtain an efficient, low cost and small size product which requires less production time with fewer efforts. Employing of artificial roughness, such as corrugation, for heat transfer enhancement in heat exchanger and other industrial thermal devices have shown promising results, with good performance reliability at lower cost. Therefore, the current study aimed to investigate experimentally and numerically the heat transfer enhancement and pressure drop increase in tubes with a superior type of corrugation i.e. the spiral corrugation. The flow of ionised water as working fluid in tubes at low Reynolds number was constructed to investigate the laminar flow regime of 100= Re=1300. Five spirally corrugated tubes and one smooth tube under constant wall heat flux boundary condition with various thermo-physical properties was investigated through experimental test and computational fluid dynamics simulation. Different corrugation parameters, such as corrugation height to diameter and corrugation pitch to diameter ratios were studied in different corrugated tube sizes. The results showed that the severity index, which combines the effect of both corrugation height and pitch, has great effects on heat transfer rate, friction factor, and thermal performance of the flow inside spirally corrugated tubes. The heat transfer enhancement was in the range of 1.3-2 compared to a smooth tube, accompanied with an increase in friction factor in the range 1.1-1.9. The thermal performance range was found to be improved by 1.2-2.08 times. The heat transfer and friction factor correlation are proposed
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    Superaugmentation and stability augmentation control system for unmanned aerial vehicle
    (Universiti Teknologi Malaysia, 2017) Yasser Abdullah Mahjoub Nogoud
    It is always a challenge to compromise between stability and controllability in the design of an aircraft. The challenge is becoming bigger in designing a flight control system of a small, light weight and low speed unmanned aerial vehicle (UAV). This type of UAV is facing a higher degree of difficulty because of its constraints in stability margin due to the limitation of the centre of gravity locations and experiencing more problems in control system when flying in air turbulence (severe wind gust or crosswind). This research work is focused on analysis, design and simulation of a robust flight control system (FCS) for a small UAV to make it capable of flying in severe gusty conditions. A combination of the variable stability technique along with advanced flying and handling qualities (FHQ) requirements are used to reduce the gust effect on the aircraft. A low-speed UTM-UAV is used as a testbed for this research. A mathematical model for the aircraft including gust velocity components was formulated based on a combination of experimental wind tunnel with theoretical and empirical methods to estimate the aerodynamics coefficient, thus stability and control derivatives. A linearized longitudinal and lateral-directional equations of motion of the aircraft in the state-space form were developed and validated against a non-linear model. Matlab/Simulink simulation algorithm was developed to analyse and evaluate the dynamic behaviour of the UAV at different speeds and CG locations. The simulation results show that the selection of particular stability and control derivatives has a significant influence on the FHQ level of the aircraft gust response for a small UAV. The superaugmentation FCS that consisted of stability augmentation system (SAS) and command stability augmentation system (CSAS) was developed to improve the dynamic characteristics of the longitudinal aircraft. A simulation result shows that the superaugmented aircraft is capable of operating in severe gust environments than augmented aircraft, and puts less strain on the elevator activity in both extreme and calm weather conditions. A comparison of superaugmented aircraft to augmented aircraft shows a significant reduction (70-80%) in undesirable pitch motion caused by a vertical gust in which, that level 1 flight phase Cat.C can be achieved.