Simple Fall Criteria for MEMS Sensors: Data Analysis and Sensor Concept

This paper presents a new and simple fall detection concept based on detailed experimental data of human falling and the activities of daily living (ADLs). Establishing appropriate fall algorithms compatible with MEMS sensors requires detailed data on falls and ADLs that indicate clearly the variations of the kinematics at the possible sensor node location on the human body, such as hip, head, and chest. Currently, there is a lack of data on the exact direction and magnitude of each acceleration component associated with these node locations. This is crucial for MEMS structures, which have inertia elements very close to the substrate and are capacitively biased, and hence, are very sensitive to the direction of motion whether it is toward or away from the substrate. This work presents detailed data of the acceleration components on various locations on the human body during various kinds of falls and ADLs. A two-degree-of-freedom model is used to help interpret the experimental data. An algorithm for fall detection based on MEMS switches is then established. A new sensing concept based on the algorithm is proposed. The concept is based on employing several inertia sensors, which are triggered simultaneously, as electrical switches connected in series, upon receiving a true fall signal. In the case of everyday life activities, some or no switches will be triggered resulting in an open circuit configuration, thereby preventing false positive. Lumped-parameter model is presented for the device and preliminary simulation results are presented illustrating the new device concept

Jump and pull-in dynamics of an electrically actuated bistable MEMS device

This study analyzes a theoretical bistable MEMS device, which exhibits a considerable versatility of behavior. After exploring the coexistence of attractors, we focus on each rest position, and investigate the final outcome, when the electrodynamic voltage is suddenly applied. Our aim is to describe the parameter range where each attractor may practically be observed under realistic conditions, when an electric load is suddenly applied. Since disturbances are inevitably encountered in experiments and practice, a dynamical integrity analysis is performed in order to take them into account. We build the integrity charts, which examine the practical vulnerability of each attractor. A small integrity enhances the sensitivity of the system to disturbances, leading in practice either to jump or to dynamic pull-in. Accordingly, the parameter range where the device, subjected to a suddenly applied load, can operate in safe conditions with a certain attractor is smaller, and sometimes considerably smaller, than in the theoretical predictions. While we refer to a particular case-study, the approach is very general

The Effect of Time-Delay Feedback Controller on an Electrically Actuated Resonator

This paper presents a study of the effect of a time-delay feedback controller on the dynamics of a Microelectromechanical systems (MEMS) capacitor actuated by DC and AC voltages. It is shown that negative time-delay feedback control gain can lead to an unstable system, even if AC voltage is relatively small compared to DC voltage. Perturbation method is utilized to present analytically the nonlinear dynamic characteristics of the MEMS capacitor. Agreements among the results of a shooting technique, long-time integration, basin of attraction analysis with the perturbation method are achieved

Magnetoelastic Beam with Extended Polymer For Low Frequency Vibration Energy Harvesting

Ambient energy in the form of mechanical kinetic energy is mostly considered waste energy. The process of scavenging and storing such energy is known as energy harvesting. Energy harvesting from mechanical vibration is performed using resonant energy harvesters (EH) with two major goals: enhancing the power scavenged at low frequency sources of vibrations, and increasing the efficiency of scavenging energy by increasing the bandwidth near the resonant frequency. Toward such goals, we propose a piezoelectric EH of a composite cantilever beam with a tip magnet facing another magnet at a distance. The composite cantilever consists of a piezoelectric bimorph with an extended polymer material. With the effect of the nonlinearity of the magnetic force, higher amplitude can be achieved because of the generated bi-stability oscillations of the cantilever beam under harmonic excitation. The contribution of the this paper is to demonstrate lowering the achieved resonant frequency down to 17 Hz compared to 100 Hz for the piezoelectric bimorph beam without the extended polymer. Depending on the magnetic distance, the beam responses are divided to mono and bi-stable regions, for which we investigate static and dynamic behaviors. The dynamics of the system and the frequency and voltage responses of the beam are obtained using the shooting metho

AN EFFICIENT REDUCED-ORDER MODEL FOR THE NONLINEAR DYNAMICS OF CARBON NANOTUBES

ABSTRACT Because of the inherent nonlinearities involving the behavior of CNTs when excited by electrostatic forces, modeling and simulating their behavior is challenging. The complicated form of the electrostatic force describing the interaction of their cylindrical shape, forming upper electrodes, to lower electrodes poises serious computational challenges. This presents an obstacle against applying and using several nonlinear dynamics tools that typically used to analyze the behavior of complicated nonlinear systems, such as shooting, continuation, and integrity analysis techniques. This works presents an attempt to resolve this issue. We present an investigation of the nonlinear dynamics of carbon nanotubes when actuated by large electrostatic forces. We study expanding the complicated form of the electrostatic force into enough number of terms of the Taylor series. We plot and compare the expanded form of the electrostatic force to the exact form and found that at least twenty terms are needed to capture accurately the strong nonlinear form of the force over the full range of motion. Then, we utilize this form along with an Euler-Bernoulli beam model to study the static and dynamic behavior of CNTs. The geometric nonlinearity and the nonlinear electrostatic force are considered. An efficient reduced-order model (ROM) based on the Galerkin method is developed and utilized to simulate the static and dynamic responses of the CNTs. We found that the use of the new expanded form of the electrostatic force enables avoiding the cumbersome evaluation of the spatial integrals involving the electrostatic force during the modal projection procedure in the Galerkin method, which needs to be done at every time step. Hence, the new method proves to be much more efficient computationally

Theoretical Prediction of Experimental Jump and Pull-In Dynamics in a MEMS Sensor

The present research study deals with an electrically actuated MEMS device. An experimental investigation is performed, via frequency sweeps in a neighbourhood of the first natural frequency. Resonant behavior is explored, with special attention devoted to jump and pull-in dynamics. A theoretical single degree-of-freedom spring-mass model is derived. Classical numerical simulations are observed to properly predict the main nonlinear features. Nevertheless, some discrepancies arise, which are particularly visible in the resonant branch. They mainly concern the practical range of existence of each attractor and the final outcome after its disappearance. These differences are likely due to disturbances, which are unavoidable in practice, but have not been included in the model. To take disturbances into account, in addition to the classical local investigations, we consider the global dynamics and explore the robustness of the obtained results by performing a dynamical integrity analysis. Our aim is that of developing an applicable confident estimate of the system response. Integrity profiles and integrity charts are built to detect the parameter range where reliability is practically strong and where it becomes weak. Integrity curves exactly follow the experimental data. They inform about the practical range of actuality. We discuss the combined use of integrity charts in the engineering design. Although we refer to a particular case-study, the approach is very general

Ocular Manifestations in Rheumatoid Arthritis: A Descriptive Cross-Sectional Study from Iraq

Background: Ocular involvement.is one of the most important extra articular manifestation of rheumatoid arthritis (RA) Objective: To evaluate the ocular manifestations in patients with RA. Patients and Methods: A cross sectional study was conducted on (103) patients with RA diagnosed according to either 1987 revised American College of Rheumatology (ACR) criteria or the 2010 ACR /European League Against Rheumatism (EULAR) criteria for diagnosis of RA. Baseline demographic and clinical characteristics of patients were recorded. Ocular manifestations were assessed in all patients. Results: A total of 103 patients with RA enrolled in this study, the mean age was 41.5 years with a female to male ratio of 7.6: 1. A positive serum for rheumatoid factor was obtained in 72.8% of patients, and a positive anti-cyclic citrullinated peptide antibody (ACPA) was obtained in 69.9% of patients. Dry eyes were the most frequently identifiable ocular manifestation (27.2%), followed by drug induced ocular disease (12.6%), in this category, posterior subcapsular cataract ranked first (8.7%), followed by blepharitis (3.9%). The occurrence of ocular inflammatory diseases was 8.7%, among this category of ocular diseases, conjunctivitis was at the top of the list (5.8%). A significant correlation was found between ocular dryness with RF, ACPA, high disease activity and treatment with biological drugs. Conclusions: The prevalence of ocular findings in patients with RA was 57.2%. The commonest was ocular dryness followed by posterior subcapsular cataract, other types of cataract, conjunctivitis, blepharitis, uveitis, episcleritis, keratitis and scleromalacia. Ocular dryness had a significant correlation with RF, ACPA, high disease activity and treatment with biological drugs but there was no correlation of these predictors with drug induce ocular disease or inflammatory ocular disease. There was no significant correlation between ocular manifestation with age, gender, functional class and disease duration. Keywords: Rheumatoid arthritis, Ocular manifestations, Dry eyes, Drug induced ocular manifestations, Ocular inflammatory diseases

Haemostasis in Open Carpal Tunnel Release: Tourniquet vs Local Anaesthetic and Adrenaline

Open carpal tunnel release is one of the commonest performed procedures in hand surgery. We performed a prospective randomised control trial to compare the efficacy and patient satisfaction of the traditional arm tourniquet versus infiltration of adrenaline and local anaesthetic solution to achieve haemostasis during the procedure. Using a combination of objective and subjective measures we concluded that infiltration of local anaesthetic and adrenaline not only provided adequate haemostasis but also provided a significantly more tolerable experience for the patient during the procedure

Haemostasis in Open Carpal Tunnel Release: Tourniquet vs Local Anaesthetic and Adrenaline

Open carpal tunnel release is one of the commonest performed procedures in hand surgery. We performed a prospective randomised control trial to compare the efficacy and patient satisfaction of the traditional arm tourniquet versus infiltration of adrenaline and local anaesthetic solution to achieve haemostasis during the procedure. Using a combination of objective and subjective measures we concluded that infiltration of local anaesthetic and adrenaline not only provided adequate haemostasis but also provided a significantly more tolerable experience for the patient during the procedure

First molecular analysis of rabies virus in Qatar and clinical cases imported into Qatar, a case report

Identifying the origin of the rabies virus (RABV) infection may have significant implications for control measures. Here, we identified the source of a RABV infection of two Nepalese migrants in Qatar by comparing their RABV genomes with RABV genomes isolated from the brains of a RABV infected camel and fox from Qatar