65 research outputs found
A Parametric Study on Free Vibration of Multi-perforated Rectangular Plates
AbstractThis work involves study of the first three natural frequencies of the perforated plates. The effect of the parameters which influence them have been studied. The parameters considered are the shape of perforations, pattern of the perforations, aspect ratio of the plate, dimensions of the plate, ligament efficiency and the mass remnant ratio (MRR). The study is focused on the effect of the most influencing parameter on the free vibrations
Familial Progressive Hyperpigmentation: A Case Report
Familial progressive hyperpigmentation (FPH) is a rare genodermatosis characterized by hyperpigmented patches in the skin and mucous membranes, present in early infancy, and increase in size and number with age. The genetic basis for FPH remains unknown. We report an unusual case of familial progressive hypermelanosis in a 17-year-old male patient with family history, who presented with a peculiar progressive oral pigmentation disorder. Diagnosis was confirmed by a series of hematological, biochemical, and histopathological investigations. Our paper stresses the need for the dentist to be aware of the systemic conditions that can also manifest in the oral cavity
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Capturing Skill State in Curriculum Learning for Human Skill Acquisition
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Phase Equilibria Calculations of Polyethylene Solutions from SAFT-Type Equations of State
A Modular Design for Distributed Measurement of Human–Robot Interaction Forces in Wearable Devices
Measurement of interaction forces distributed across the attachment interface in wearable devices is critical for understanding ergonomic physical human–robot interaction (pHRI). The main challenges in sensorization of pHRI interfaces are (i) capturing the fine nature of force transmission from compliant human tissue onto rigid surfaces in the wearable device and (ii) utilizing a low-cost and easily implementable design that can be adapted for a variety of human interfaces. This paper addresses both challenges and presents a modular sensing panel that uses force-sensing resistors (FSRs) combined with robust electrical and mechanical integration principles that result in a reliable solution for distributed load measurement. The design is demonstrated through an upper-arm cuff, which uses 24 sensing panels, in conjunction with the Harmony exoskeleton. Validation of the design with controlled loading of the sensorized cuff proves the viability of FSRs in an interface sensing solution. Preliminary experiments with a human subject highlight the value of distributed interface force measurement in recognizing the factors that influence ergonomic pHRI and elucidating their effects. The modular design and low cost of the sensing panel lend themselves to extension of this approach for studying ergonomics in a variety of wearable applications with the goal of achieving safe, comfortable, and effective human–robot interaction
The fluid structures for soft-sphere potentials via the zero-separation theorems on molecular distribution functions
10 pags., 10 figs., 5 tabs.We present a class of closures specifically designed to satisfy the zero-separation theorems for the correlation functions y(r) (the cavity function), γ(r) = h(r) - C(r) (the indirect correlation), and B(r) (the bridge function) at coincidence r=0 for soft-sphere pair potentials. The rationale is to ensure the correct behavior of these correlation functions inside the core r<σ. Since the coincidence theorems implicate the thermodynamic properties of the bulk fluid: the isothermal compressibility, the internal energy and the chemical potentials, we can hopefully enforce consistency between the structure and thermodynamic properties. We solve the Ornstein-Zernike equation for the Lennard-Jones molecules where plentiful Monte Carlo data are available for testing. It turns out that not only consistency is achieved, we also obtain accurate structures: the pair correlation function g(r), the cavity function, and the bridge function for wide ranges of fluid states (0.72<T*<1.5, p*<0.9). Comparison with MC data attests to the accuracy. The closure of the zero-separation type (ZSEP), is sufficiently robust and flexible to ensure not only fulfillment of the zero-separation theorems but also pressure consistency. Success with the Lennard-Jones potential implies its applicability to other similar soft-sphere potentials. © 1996 American Institute of Physics.E.L. acknowledges support from the Spanish Direccion General de Investigacion
Cientıfica y Tecnica under Grant No. PB94-0112
Phase behavior applications of SAFT based equations of state—from associating fluids to polydisperse, polar copolymers
Prediction of the thermodynamic properties of associating polyatomic fluids
Thermodynamic properties of associating polyatomic fluids are studied using molecular simulation and theory. The overall goal of this study was to develop a theory to predict the properties of fluid mixtures with intermolecular and intramolecular association.
Intermolecular association is well understood mainly due to a theory developed by Wertheim for spherical associating molecules. In this work we performed the first tests of Wertheim's theory and its extensions for a wide variety of model fluids. Predictions from Wertheim's theory for associating hard sphere (HS) and Lennard Jones (LJ) molecules with four bonding sites were tested against simulation results. We found that the first order perturbation form of Wertheim's theory is in good agreement with simulation results. The theory was also tested for associating diatomic, triatomic, and longer chain molecules. The approximations used to simplify the theory are explained and we show how a spherical reference can be used to predict the properties of an associating chain fluid.
A hard chain equation of state was previously obtained by extending Wertheim's theory to mixtures. In this work, a new chain equation of state is derived which predicts properties in much better agreement with molecular simulation, especially for long chains (8 segments). The chain equation of state was also extended to LJ chains and mixtures of LJ chains. The results from this extension are in good agreement with simulation results.
Prior to this work, no theory could accurately predict the properties of intramolecularly associating fluids. Such a theory is essential to the prediction of the properties of associating polymer solutions. A theory for intramolecular association in the absence of intermolecular association was developed. This theory is in good agreement with simulation results for tetramers with association sites on the terminal segments which can only bond intramolecularly. To develop a theory for the competition between inter and intramolecular association we combined Wertheim's theory for intermolecular association with our theory for intramolecular association. This combined theory gives good agreement with simulation results for tetramers with association sites that can bond intermolecularly and intramolecularly. The theory also explains some of the anomalous behavior of these systems
Prediction of the thermodynamic properties of complex polyatomic hydrogen bonding fluids
A novel inverse kinematics method for upper-limb exoskeleton under joint coordination constraints
In this study, we address the inverse kinematics problem for an upper-limb exoskeleton by presenting a novel method that guarantees the satisfaction of joint-space constraints, and solves closed-chain mechanisms in a serial robot configuration. Starting from the conventional differential kinematics method based on the inversion of the Jacobian matrix, we describe and test two improved algorithms based on the Projected-Gradient method, that take into account joint-space equality constraints. We use the Harmony exoskeleton as a platform to demonstrate the method. Specifically, we address the joint constraints that the robot maintains in order to match anatomical shoulder movement and the closed-chain mechanisms used for the robot's joint control. Results show good performances of the proposed algorithms, which are confirmed by the ability of the robot to follow the desired task-space trajectory while ensuring the fulfilment of joint-space constraints, with a maximum error of about 0.05 degrees
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