Abdul Ghaffar Abdul Rahman

Universitas Informatika dan Bisnis Indonesia

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Zhi Chao Ong

University of Malaya

Zubaidah Ismail

University of Malaya

Siamak Noroozi

Bournemouth University

Shin Yee Khoo

University of Malaya

Keen Kuan Kong

University of Malaya

Wen Tong Chong

University of Malaya

John Vinney

Bournemouth University

Philip Sewell

Bournemouth University

Bryce Dyer

Bournemouth University

Mihai Dupac

Bournemouth University

Cooperative Institutions

University of Malaya

International Islamic University Malaysia

Bournemouth University

Universiti Malaysia Pahang Al-Sultan Abdullah

Falmouth University

University of the West of England

University of Engineering and Technology Taxila

University of Engineering and Technology Lahore

Cardiff Metropolitan University

Universiti Teknologi MARA

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Numerical Methods - Numerical Integration & Dierentiation

Abdul Ghaffar Abdul Rahman

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Performance enhancement of bi-lateral lower-limb amputees in the latter phases of running events: an initial investigation

Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology (2012)

Siamak Noroozi Philip Sewell Abdul Ghaffar Abdul Rahman John Vinney Zhi Chao Ong

Current methods of evaluating the performance of a runner using an energy return prosthesis often rely on a physiological methodology, making the differentiation between the contributions from the biological and the prosthetic elements of the below-knee amputee athlete difficult. In this paper a series of mass and composite foot systems were used to evaluate the effect that gravity, mass, stiffness and inertia have on the dynamic characteristics of a prosthesis. It is demonstrated that if the natural characteristics of a system are identified and synchronised with the physiological gait behaviour of a runner, performance enhancement can occur, resulting in a faster take off speed and in storing extra energy in the system that can later be recovered. Therefore, a bi-lateral amputee athlete with near symmetrical gait can recover the stored energy during the steady state or latter phases of a running event.

10.1177/1754337112451959

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Citations (17)

Study of open crack in rotor shaft using changes in frequency response function phase

International Journal of Damage Mechanics (2012)

Abdul Ghaffar Abdul Rahman Zubaidah Ismail Siamak Noroozi Zhi Chao Ong

In recent years, significant efforts have been devoted to developing non-destructive techniques for damage identification in structures. This study investigated the effects of cracks and damages on the integrity of structures, with a view to detect, quantify, and determine their extents and locations. Previous works have used parameters, such as, changes in natural frequencies and mode shapes, as detectors. However, such parameters are not sensitive enough to detect early defects. In this paper, phase measurements are sought. Measurements of the acceleration frequency responses at different points on each rotor shaft were taken using a multi-channel frequency analyzer. The damage detection schemes used in this study depended on the changes in the phase of the measured acceleration frequency response functions. To study the changes of phases, it was interpreted in phase spectrum and Nyquist plot. Nyquist plot was used as it includes both real and imaginary parts of the amplitude and this was used to study phase shifts due to the presence of crack. The changes in phase depended on crack depth and how close the crack is to that mode shape node. Meanwhile, the changes in phase of lower eigenvectors were observed clearly. Thus, first mode shape was helpful in identifying the location of the crack. The vibration behavior of the rotor shaft was shown to be very sensitive to the crack depth, crack location and mode number. It is concluded that changes in phase as a function of crack depths and locations can be effective in crack detection methodology.

Phase angle (astronomy)

10.1177/1056789512466755

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Citations (19)

Modal analysis of composite prosthetic energy-storing-and-returning feet: an initial investigation

Proceedings of the Institution of Mechanical Engineers Part P Journal of Sports Engineering and Technology (2012)

Siamak Noroozi Philip Sewell Abdul Ghaffar Abdul Rahman John Vinney Zhi Chao Ong

The desire of individuals with a lower-limb amputation to participate in sports, coupled with the high demands of athletics, has resulted in the development of energy-storing-and-returning feet, capable of storing energy during stance and returning it to the individual in late stance to assist in forward propulsion. However, little attention has been paid to date to advance the understanding of their dynamic characteristics (natural frequencies, mode shapes and damping) during running. The evaluation of such parameters is now urgently required, as the use of energy-storing-and-returning feet is now being investigated through legal and justice systems to determine participation of amputee athletes using them at the Olympic Games. This paper presents a study of the dynamic characteristics of two commercially available Elite Blade composite feet (solid and split foot). A full modal analysis of the feet was conducted with varying masses attached to them, representing different body masses. The study showed that natural frequencies close to typical running step frequency can be achieved with simple control of the mass or stiffness. It was concluded that further study of the dynamic characteristics could result in a significant change in the design, development and the attitude towards the use of composite prosthetic feet. This initial study has highlighted the key questions that need to be answered to fully understand the dynamic characteristics and inform designers on how to tune a foot to match an amputee’s gait and body condition.

Natural frequency

Foot (prosody)

10.1177/1754337112439274

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Citations (22)

Similitude study of an in-service industrial piping system under high flow induced vibration

Journal of Mechanical Science and Technology (2017)

Yap Huey Tyng Zhi Chao Ong Keen Kuan Kong Zubaidah Ismail Abdul Ghaffar Abdul Rahman

Similitude

10.1007/s12206-017-0713-0

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Citations (7)

روایة ( الجوهرة والقبطان ) لزوینة الکلبانی دراسة فی جمالیات التشکیل الفنی سید أحمد عبد الرحمن محمد

مجــلة کلیة اللغة العربیة بأســیوط (2020)

Syed Ahmed Abdul Ghaffar Abdul Rahman

This novel comes within the framework of those few and perhaps rare novels in our Arab narrative literature, especially the Gulf, from it, which made the sea its main environment in which all its events and details revolve.Hence the importance of the novel (Al-Jawhara and Al-Qubtan), which proved its artistic and literary ability in its monitoring of the maritime and maritime history of the Arab Gulf region and its inhabitants in the previous time, and the relationship of this past to their present and future As for the artistic construction of this novel, it clearly depended on realism, as evidenced by its reliance on (history) of events, their time and place in days, months, and years, and also relied on the narrator's method of narrating these events and their precise details, until the reader seemed as if the narrator himself was part of The event and its structure cannot be separated from it, even though it is not actually involved in it on the ground, but its presence in it was indirectly fortunate

10.21608/jfla.2020.136587

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Effectiveness of Impact-Synchronous Time Averaging in determination of dynamic characteristics of a rotor dynamic system

Measurement (2010)

Abdul Ghaffar Abdul Rahman Zhi Chao Ong Zubaidah Ismail

Natural frequency

Helicopter rotor

10.1016/j.measurement.2010.09.005

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Citations (46)

Impact Force Identification by Using Modal Transformation Method for Automobile Test Rig

Applied Mechanics and Materials (2013)

Abdul Ghaffar Abdul Rahman Shin Yee Khoo Zubaidah Ismail Wen Tong Chong Siamak Noroozi

In the automobile industry, impact force is the main cause for material fatigue in lightweight vehicles. Bump-excited impact force is the most common case, which causes damage to vehicles and reduces the quality of the ride. Force identification is important to reflect the structure's health so that action such as structure modification can be taken before material fatigue. However, direct measurement by using force transducer is not practical due to difficulty in force sensor configuration. A methodology utilizing Operating Deflection Shape (ODS) analysis, Frequency Response Function (FRF) measurement and Modal Transformation Method (MTM) to evaluate the dynamic force is proposed here. This method is called indirect force measurement by using inverse technique. The performance of this approach was demonstrated via experiment. From the measured responses and measured dynamic characteristics of an automobile test rig, a real time mathematical manipulation can generate the systems input force. The force location is known in priori for impact excitation and therefore the inverse problem is well-posed. This method was tested using different force location with unique input force. It shows that high quality of curve fitting to extract the modal parameters such as damped natural frequency, modal damping and residue mode shape is essential to obtain a high accuracy force determination result.

Impact

Natural frequency

Force dynamics

10.4028/www.scientific.net/amm.471.102

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Citations (4)

Importance of Selecting a Suitable Analysis Frequency Range in Impact Force Identification for Automobile Test Rig

Applied Mechanics and Materials (2014)

Shin Yee Khoo Zhi Chao Ong Keen Kuan Kong Zubaidah Ismail Wen Tong Chong

In this study, the effectiveness of selecting a suitable analysis frequency range in impact force identification is highlighted. A methodology that utilizesOperating Deflection Shape (ODS) analysis, Modal Analysis (MA) and Modal Transformation Method (MTM) to evaluate the dynamic force in three cases of analysis frequency ranges was presented. These three cases are the over-estimated, even-estimated, and under-estimated cases, which consist of higher, similar andlower analysis frequency range respectively, compared to the actual excitation frequency range. The performance of this approach was demonstrated via experiment. A Perspex plate with four ground supports was used as the automobile test rig. By measuring the acceleration response and Frequency Response Function (FRF) of the test rig, the time history of unknown force was recovered by the proposed method where the impact location was known in advance. It showed that the force identification result for even-estimated case falls within acceptable range while the force identification result for over-estimated and under-estimated cases isnot acceptable

Impact

Frequency analysis

Response analysis

Identification

Natural frequency

10.4028/www.scientific.net/amm.663.88

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Analisis Perbandingan Perlin Noise Dan Simplex Noise Untuk Penciptaan Permukaan Daratan Pada Pembuatan Game

Konferensi Nasional Sistem Informasi (KNSI) 2018 (2018)

Wandi Wijaya Abdul Ghaffar Abdul Rahman

Procedural content generation merupakan salah satu cara untuk menciptakan objek atau perilaku yang bersifat acak serta otomatis, agar memiliki tampak yang berbeda dari objek lain. Content pada sebuah game seperti pembentukan permukaan daratan atau terrain dapat dibentuk secara unik menggunakan metode noise. Dalam sistem ini, noise yang akan digunakan adalah Perlin noise dan simplex noise. Kedua noise tersebut dikembangkan agar dapat membentuk suatu simulasi permukaan daratan yang menyerupai daratan, pegunungan, atau dasar laut. Hasil dari penelitian ini untuk mencari tahu tingkat efisiensi dan besarnya penggunaan beban komputasi di antara Perlin dan simplex noise. Metodologi yang digunakan terdiri dari proses studi literatur, analisa data, desain sistem, implementasi, dan pengujian sistem. Masin-masing noise memiliki bidang dimensi satu hingga dimensi tiga yang diuji berdasarkan input frekuensi noise, octave, persistence, lacunarity. Pengujian dilakukan dengan membandingkan penggunaan CPU, GPU, dan RAM komputer pada saat proses render masing-masing noise tersebut. Simplex noise yang berasal dari pengembangan Perlin noise tingkat lanjut memiliki tingkat efisiensi penggunaan CPU, GPU, dan RAM yang lebih baik daripada Perlin noise.

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