Md. Tawhidul Islam Khan

Performance analysis of mobile ad-hoc network routing protocols

Routing in ad-hoc networks is nontrivial due to highly dynamic environment. An Ad Hoc Protocol can also mean an improvised and often impromptu protocol established for a particular specific purpose for these reasons several routing protocols targeted at mobile ad-hoc networks are being proposed. DSDV, AODV, TORA, LAR, and DSR are the most prominent among them. This paper investigates and undertakes simulation based study of mobile ad-hoc network (MANET) routing protocols. All protocols are provided with identical traffic load and mobility patterns. We have considered TCP as transport protocol and FTP as traffic generator and NS2 as simulation tools.

EMG signals in co-activations of lower limb muscles for knee joint analysis

Integrity analysis of knee joint involves a detail study of several anatomical parts such as bones, cartilage, tendons etc. The disorderness or damage of these anatomical parts causes several knee diseases, like osteoarthritis (OA), which is generally found in an increasing tendency particularly, in an aged society. Although, the reasoning of OA in knee joint does not concentrated to the present paper, however, the influences of related muscular co-activities with knee flexor-extensor actions are figured out in the present research. Particularly, the muscle reflection action of two major skeletal muscles at knee are investigated with aging functions of participants. EMG signals have been collected from the Vastus lateralis and the Gastrocnemius for the dynamic movements (standing and sitting) of knee joint. Aged participants (around 60 years old) and young participants (around 20 years old) joined the experiments. Data have been collected from both legs, however, analysis is shown only for left leg in this paper. EMG sensors and the related devices for this sensing technique have been installed based on the instructions of Biometric Co. Ltd. The result shows that the voltage amplitudes of EMG signals vary largely with increasing ages and thus, the result focuses the postural effectiveness of muscular activities in the stability challenges of knee joint movements.

Real‐time acoustic blind signal separation system based on the spatio‐temporal gradient analysis

This paper presents an autonomous directivity microphone system for the blind source separation based on the newly proposed spatio‐temporal gradient algorithm. The blind source separation technique principally uses no a priori knowledge about parameters of convolution, filtering, nor mixing. In the simplest case of the blind source separation problems, the observed mixing signals are the linear combinations of unknown source signals which are mutually and statistically independent and contain zero mean. The proposed blind signal separation algorithm utilizes the linearity among the four signals: (1) the sound pressure, (2) x, (3) y, and (4) z‐directional particle velocities, all of which are governed by the wave equation and the equation of motion. The proposed method, therefore, has an ability to simplify the convoluted blind source separation problems into the instantaneous blind source separation problems over the spatio‐temporal gradient space. Several acoustical experiments have been performed with a...

A simple imaging technique attributed to the dynamic motion of knee joint

Imaging of human motion for different applications are becoming an interested area of biomedical research now a days. Therefore, several devices are already implemented for the purposes. However, maximum of those devices require many individual applicable accessories and transfer modes and thus the motion sensing equipment become complicated and extra burden to the applicants. Furthermore, most of the available motion sensors still need cable connections to the data transmission system although, very few wireless sensors are recently introducing with high costing. Particularly, for imaging the muscle activities of human body with EMG sensors for different human actions, several devices of sensors, connecting wires, data-logger etc. are necessary. All of these connections make extra obstacles in the experiment of human movements. Therefore, wireless sensing systems are demanded to invent. In the present paper a simple image processing technique by using a USB camera system has been explained for conducting the dynamic analysis of knee joint during its flexor-extensor effects. Particularly, the proposed imaging system is used in acquisition of angular position data of knee joint movements during standing and sitting conditions. The algorithm has been developed in the Intel Open Source Computer Vision Library (OpenCV) platform. The acquisition data of the proposed technique also compared with the goniometer system and found the reasonable acceptance of the proposed system.

EMG signals in muscular co-activations for dynamic analysis of knee joint

Integrity analysis of knee joint involves a detail study of several anatomical parts such as bones, cartilage, tendons etc. The disorderness or damage of these anatomical parts causes several knee diseases, like osteoarthritis (OA), which is generally found in an increasing tendency particularly, in an aged society. Although, the reasoning of OA in knee joint does not concentrated to the present paper, however, the influences of related muscular co-activities with knee flexor-extensor actions are figured out in the present research. Particularly, the muscle reflection action of two major skeletal muscles at knee are investigated with aging functions of participants. EMG signals have been collected from the Vastus medialis and the Gastrocnemius for the dynamic movements (standing and sitting) of knee joint. Aged participants (around 60 years old) and young participants (around 20 years old) joined the experiments. Data from both legs are collected simultaneously along with data of bone activities. EMG sensors and the related devices for this sensing technique have been installed based on the instructions of Biometric Co. Ltd. The result shows that the voltage amplitudes of EMG signals vary largely with increasing ages and thus, the result focuses the postural effectiveness of muscular activities in the stability challenges of knee joint movements.

Analysis of the local frequency spectrum for the chirp signal

In this article, the statistical moments of the local spectrum obtained from Gabor transform technique for the chirp signal are presented both analytically and numerically. The chirp signal estimation considering only ridge frequency component and electrically band limited frequency components is also discussed.

Active noise control‐like performance of a spherical reflector

The principle of cancellation of tonal noise by using a spherical reflector, the designing method of an appropriate reflector for canceling jet screech, the advantage of a spherical compared to a flat reflector for canceling a tonal noise, and a prospective application for an aircraft to protect the fuselage from acoustic fatigue are discussed. The thrust loss due to the new technique was also evaluated directly with a vertical wind tunnel. The change in the aerodynamic structure was optically observed by using a schlieren apparatus along with a high‐speed video camera. [Work supported by grant of JSPS, Japan.]

Multilayered spatio‐temporal gradient analysis for acoustic blind source separation

A novel blind source separation of a mixture of two or more voice signals has been proposed in the present paper. The separation system has been focused based on the spatio‐temporal gradient analysis. The proposed algorithm utilizes the linearity among the signals: sound pressure of source signals, the three‐dimensional (x, y, and z directional) particle velocity vector, and its gradient of the observed signals, all of which are governed by the equation of motion. Principally, as the mechanism of blind source separation uses no‐ priori information about the parameters of convolution, filtering as well as mixing of source signals, some simple assumptions such as the statistical independency of the linearly combined (mixed) observed signals containing zero mean as well as unit variance have been implied in the present separation algorithm. Therefore, the proposed method has successfully simplified the convoluted blind source separation problem into an instantaneous blind source separation problem over the s...