Ali M. Hallal

Tremor Reduction at the Palm of a Parkinson’s Patient Using Dynamic Vibration Absorber

Parkinson’s patients suffer from severe tremor due to an abnormality in their central oscillator. Medications used to decrease involuntary antagonistic muscles contraction can threaten their life. However, mechanical vibration absorbers can be used as an alternative treatment. The objective of this study is to provide a dynamic modeling of the human hand that describes the biodynamic response of Parkinson’s patients and to design an effective tuned vibration absorber able to suppress their pathological tremor. The hand is modeled as a three degrees-of-freedom (DOF) system describing the flexion motion at the proximal joints on the horizontal plane. Resting tremor is modeled as dual harmonic excitation due to shoulder and elbow muscle activation operating at resonance frequencies. The performance of the single dynamic vibration absorber (DVA) is studied when attached to the forearm and compared with the dual DVA tuned at both excitation frequencies. Equations of motion are derived and solved using the complex transfer function of the non-Lagrangian system. The absorber’s systems are designed as a stainless steel alloy cantilevered beam with an attached copper mass. The dual DVA was the most efficient absorber which reduces 98.3%–99.5%, 97.0%–97.3% and 97.4%–97.5% of the Parkinson’s tremor amplitude at the shoulder, elbow and wrist joint.

Improvement in failure prediction algorithm for textile composites

This study presents an analytical modeling of the mechanical behavior of textile composites. The main objective of this study is to evaluate in-plane and out of plane ultimate strengths for different types of 2D and 3D fabric-reinforced polymer. The proposed analytical model consists of a homogenization method, a failure criterion, and a damaged stiffness model. An improved failure prediction algorithm is presented, which tends to enhance the prediction of ultimate strengths. It is shown that assuming a final failure of undulated yarns for a failure of 90% of subdivisions rather than 100%, alongside assigning a multi-failure mode for the failed subdivision rather than single failure mode is yielding much better results. The predicted elastic properties and ultimate strengths are compared to available experimental and numerical data, where a very good agreement is shown. The proposed model offers a reliable, simple, and easy to use analytical tool.

Biomechanical treatment for rest tremor of Parkinson's patient

Vibration absorbers are effective devices used to reduce the unwanted motion of a vibrating system. It is recently used to reduce the involuntary tremor of a Parkinsons patient. The absorber can be attached to the forearm of the patient hand. Such system can be excited at resonance frequencies reflecting the resting tremor due to the shoulder and elbow muscles activation. Two single absorbers are designed and tested numerically in reducing the involuntary tremor: the conventional absorber having its spring and damper connected in parallel and the elastic-damper absorber having its spring and damper connected in series. Both absorbers are designed to satisfy the tuning conditions at the fundamental frequency of the primary system with the same total mass. The conventional absorber causes 75.5-97.4%, 11.1-48.0% and 41.2-49.7% reduction at the shoulder, elbow and the wrist joints, respectively. However, the elastic-damper absorber causes 74.0-78.7%, 5.0-35.0% and 29.3- 45.8% at the same positions, respectively. The elastic-damper absorber can cause this reduction with a device of shorter length.

Analytical Modeling: Three Stages Homogenization Method

A small to moderate sized modern computer system employs advanced features such as fault-tolerance ( see Fault-tolerant systems), resource sharing and contention, concurrency an d synchronization, timeliness ( see Real-time systems), and degradable performance. When such a computer system i being designed and implemented, it becomes essential to answer “what-if” questions and carry out trade-o ff studies to choose between a set of contending design alternatives. The broad classes of measures that need to be valuated are:

Structural control and biomechanical tremor suppression: Comparison between different types of passive absorber

Active and semi-active control devices can be used as advanced and accurate controllers to reduce the undesired vibration of a structure. However, some of these controllers may have a complex design, especially for systems excited with multi-degree-of-freedom frequencies, which demand the use of high anti-fatigue material properties, and others that may require a large power source. So, improvements in the design of passive controllers are of high interest for researchers. These controllers have a very simple design and aim to counteract vibration with no power requirements. In this paper, six different passive controllers were designed to analyze and compare their performance. The performance is considered in terms of the percentage of reduction in the primary system’s displacement amplitude and the bandwidth of each designed passive controller. The system of interest is taken as the three-degree-of-freedom dynamic hand system reflecting the behavior of Parkinsonian patients. Four joint muscles operating at two resonance harmonic excitation frequencies are considered to produce movements. Each controller was attached to the forearm of the hand set in the horizontal plane to analyze their capability in reducing the rest tremor (3–7 Hz) at the proximal joint. The dual series elastic–viscous absorber is shown to be a very effective controller. It is formed from a series connection between an elastic absorber (mass–spring) and a viscous absorber (mass–dashpot). It causes about 80% reduction in tremor amplitude with 4 Hz wide frequency band at the shoulder, elbow and wrist joints. This range of operational frequency is close to that of healthy cases, 4.5 Hz.

In-plane permeability prediction model for non-crimp and 3D orthogonal fabrics

Abstract Permeability reflects the ease of flow inside a composite fabric. A predictive model has been developed to estimate the unidirectional permeability in both, the warp and weft directions, for a family of non-crimped and 3D orthogonal fabrics. The model is based on an analytical solution derived from previous studies, in which the microscopic permeability of unidirectional fiber bundles is estimated. The implementation of this model requires basic geometrical parameters of the fabric architecture. Those parameters include the dimension of the mesopores and architecture of the fiber bundles, which are determined from pictures taken for the fabric and from the textile data sheet. In addition, the average volume of mesopores and fiber bundles are calculated for different fiber volume fractions in the warp and weft directions. The model evaluates two contributions; the first one deals with the flow inside and in between the tows, while the second one figures out the flow deviations arising from the stitching yarns. The model uses effective radius and fiber volume fraction to evaluate permeability for the two flow contributions mentioned above. An experimental investigation validates the predictive model for five different fabrics and three different fiber volume fractions. Good agreement is found.

Finite element modeling of longitudinal permeability component of a stitched fabric

The following work aims to present a reliable numerical method for predicting the longitudinal permeability of a unidirectional (UD) stitched fabric. An experimental measurement of longitudinal permeability is done using a closed resin transfer mold (RTM) system. Concerning the Finite element modeling, an arrangement of the fiber bundles and a unit cell is proposed. The evaluation of numerical permeability is based on a main assumption. The assumption says that the permeability of the unit cell is mainly calculated from the flow passing through gaps (between the bundles). Thus we avoid the simulation on a real unit cell with micro flow throughout the fibers. The predicted numerical results were in good agreement with the experimental data.

Passive vibration absorber for tremor in hand of parkinsonian patients: Tuned vibration absorber for rest tremor

Parkinsons disease is characterized by involuntary movement of body parts resulting from antagonistic muscle contractions. In this paper, an effective passive vibration absorber is modeled to control the involuntary pathological rest tremor in the right hand of Parkinsons disease patient. The three-degree-of-freedom dynamic hand model capable to describe the flexion-extension planar motion at shoulder, elbow, and wrist joints in horizontal plane is designed. The passive tuned vibration absorber is modeled to suppress flexion motion of shoulder, elbow and wrist joints. Active inputs producing motion are considered at shoulder and elbow joints, and driven at resonance frequencies. The equations of motion for the dynamically coupled modeled hand system are derived. The responses are represented in time and frequency domains using the complex transfer function method. Optimum position of the absorber on the forearm is determined in terms of its effectiveness in reducing tremors amplitude.