Tech Science Press
Not a member yet
3972 research outputs found
Sort by
Using a Musculoskeletal Mathematical Model to Analyze Fatigue of the Muscles in the Lower Limbs during Different Motions
No full textUnder the aim of finding effective rehabilitation solutions, the difference between the extents of fatigue of each muscle used in different motions are compared. Previous research suggested methods for estimating muscle torque and muscle tension on the basis of a musculoskeletal model. As a result, it has become possible to quantitatively identify the extent of fatigue in each muscle during motion. Therefore, to evaluate muscle fatigue more quantitatively, driving power and angular momentum are focused on. Based on the driving torque of joints and the muscle torque calculated by using a three-dimensional musculoskeletal model, a method for calculating the driving power of joints and the angular momentum of a muscle is proposed. This method is applied to analysis of different motions. Moreover, fatigue of muscles is quantitatively analyzed on the basis of driving power and angular momentum
Online Group Recommendation with Local Optimization
No full textThere are some scenarios that need group recommendation such as watching a movie or a TV series, selecting a tourist destination, or having dinner together. Approaches in this domain can be divided into two categories: Creating group profiles and aggregating individual recommender list. Yet none of the above methods can handle the online group recommendation both efficiently and accurately and these methods either strongly limited by their application environment, or bring bias towards those users having limited connections with this group. In this work, we propose a local optimization framework, using sub-group profiles to compute the item relevance. Such method can captures and removes the bias existed in the traditional group recommendation algorithms in a certain degree. It can then be used to derive single-user recommendation. We also propose an approach to overcome the problem caused by dynamic change or user updating about his social network, which detects the target user’s group by analyzing the link types between he and his neighbours, and then use the group information to generate his recommendations. Experimental analysis for group and personal recommendation on three different sizes of MovieLens datasets show fairly good results, our method consistently outperform several state-of-the-arts in efficiency. And we also provide the explanations behind the phenomena during the experiments
A New Interface Identification Technique Based on Absolute Density Gradient for Violent Flows
No full textAn identification technique for sharp interface and penetrated isolated particles is developed for simulating two-dimensional, incompressible and immiscible two-phase flows using meshless particle methods in this paper. This technique is based on the numerically computed density gradient of fluid particles and is suitable for capturing large interface deformation and even topological changes such as merging and breaking up of phases. A number of assumed particle configurations will be examined using the technique, including these with different level of randomness of particle distribution. The tests will show that the new technique can correctly identify almost all the interface and isolated particles, and also show that it is better than other existing popular methods tested
Modeling and Analysis of Global and Diffuse Solar Irradiation Components Using the Satellite Estimation Method of HELIOSAT
No full textIt is very important to determine the daily horizontal global, diffuse and beam irradiations correctly in planning energy systems, in cost analysis, in the atmosphere, and in the productivity evaluations. Besides, the knowledge of accurate solar irradiation is the most important component of the essential climate variables according to the Global Climate Observing System (GCOS) in August 2010. It is known that the changes of these irradiation parameters directly affect our atmosphere and cloud formation processes. Turkey is one of the countries, which has high solar energy potential by reason of its climatic and regional factors. Especially, Konya and Karaman regions (in Central Anatolia Region) are seen as the most efficient area in where the solar energy systems will be processed. Because of this reason that region has been designated as an Energy Specialized Industrial Zone (ESIZ) in Turkey. Solar energy inputs must carefully be determined in this region where the systems will be installed with respect to the climate and energy efficiency. In this work aims to understand the components of daily solar irradiation on a horizontal surface in selected region are analyzed by using the HELIOSAT method by setting satellite images. Results have been determined by comparing with ground measured data and method were analyzed by using statistical errors. According to the seven-year data, the accuracy of the daily global and diffuse solar irradiations estimation was found acceptable levels. Nevertheless, the estimated results reveal that this method can easily be adapted to any point in the world resembles with the Central Anatolia Region climate type. Especially, the obtained results are significant for the simulation studies such as solar PV power plants performance, payback time, and cost of energy analysis. Also, these results can be used to increase the performance of the solar energy system and to determine long-term a road map for climate change studies
Three Phase Composite Cylinder Assemblage Model for Analyzing the Elastic Behavior of MWCNT-Reinforced Polymers
Get PDFEvolution of computational modeling and simulation has given more emphasis on the research activities related to carbon nanotube (CNT) reinforced polymer composites recently. This paper presents the composite cylinder assemblage (CCA) approach based on continuum mechanics for investigating the elastic properties of a polymer resin reinforced by multi-walled carbon nanotubes (MWCNTs). A three-phase cylindrical representative volume element (RVE) model is employed based on CCA technique to elucidate the effects of inter layers, chirality, interspacing, volume fraction of MWCNT, interphase properties and temperature conditions on the elastic modulus of the composite. The interface region between CNT and polymer matrix is modeled as the third phase with varying material properties. The constitutive relations for each material system have been derived based on solid mechanics and proper interfacial traction continuity conditions are imposed. The predicted results from the CCA approach are in well agreement with RVE-based finite element model. The outcomes reveal that temperature softening effect becomes more pronounced at higher volume fractions of CNTs
The Interface Stress Field in the Elastic System Consisting of the Hollow Cylinder and Surrounding Elastic Medium Under 3D Non-axisymmetric Forced Vibration
Get PDFThe paper develops and employs analytical-numerical solution method for the study of the time-harmonic dynamic stress field in the system consisting of the hollow cylinder and surrounding elastic medium under the non-axisymmetric forced vibration of this system. It is assumed that in the interior of the hollow cylinder the point-located with respect to the cylinder axis, non-axisymmetric with respect to the circumferential direction and uniformly distributed time-harmonic forces act. Corresponding boundary value problem is solved by employing of the exponential Fourier transformation with respect to the axial coordinate and by employing of the Fourier series expansion of these transformations. Numerical results on the frequency response of the interface normal stresses are presented and discussed
A Cryptograph Domain Image Retrieval Method Based on Paillier Homomorphic Block Encryption
Get PDFWith the rapid development of information network, the computing resources and storage capacity of ordinary users cannot meet their needs of data processing. The emergence of cloud computing solves this problem but brings data security problems. How to manage and retrieve ciphertext data effectively becomes a challenging problem. To these problems, a new image retrieval method in ciphertext domain by block image encrypting based on Paillier homomophic cryptosystem is proposed in this paper. This can be described as follows: According to the Paillier encryption technology, the image owner encrypts the original image in blocks, obtains the image in ciphertext domain, then passes it to the third party server. The server calculates the difference histogram of the image in ciphertext domain according to the public key and establishes the index database. The user passes the retrieved image to the server. The server computes the differential histogram of the retrieved image by public key. Then, compares the similarity of it with the histogram in index database and selects larger similarity images in ciphertext and send them to the user. The user obtains the target image with the private key. The experimental results show that the method is feasible and simple
Symmetry Transformations and Exact Solutions of a Generalized Hyperelastic Rod Equation
Get PDFIn this paper, a nonlinear wave equation with variable coefficients is studied, interestingly, this equation can be used to describe the travelling waves propagating along the circular rod composed of a general compressible hyperelastic material with variable cross-sections and variable material densities. With the aid of Lou’s direct method1, the nonlinear wave equation with variable coefficients is reduced and two sets of symmetry transformations and exact solutions of the nonlinear wave equation are obtained. The corresponding numerical examples of exact solutions are presented by using different coefficients. Particularly, while the variable coefficients are taken as some special constants, the nonlinear wave equation with variable coefficients reduces to the one with constant coefficients, which can be used to describe the propagation of the travelling waves in general cylindrical rods composed of generally hyperelastic materials. Using the same method to solve the nonlinear wave equation, the validity and rationality of this method are verified
Event-Based Anomaly Detection for Non-Public Industrial Communication Protocols in SDN-Based Control Systems
Get PDFAs the main communication mediums in industrial control networks, industrial communication protocols are always vulnerable to extreme exploitations, and it is very difficult to take protective measures due to their serious privacy. Based on the SDN (Software Defined Network) technology, this paper proposes a novel event-based anomaly detection approach to identify misbehaviors using non-public industrial communication protocols, and this approach can be installed in SDN switches as a security software appliance in SDN-based control systems. Furthermore, aiming at the unknown protocol specification and message format, this approach first restructures the industrial communication sessions and merges the payloads from industrial communication packets. After that, the feature selection and event sequence extraction can be carried out by using the N-gram model and K-means algorithm. Based on the obtained event sequences, this approach finally trains an event-based HMM (Hidden Markov Model) to identify aberrant industrial communication behaviors. Experimental results clearly show that the proposed approach has obvious advantages of classification accuracy and detection efficiency
Improved Lossless Data Hiding for JPEG Images Based on Histogram Modification
Get PDFThis paper proposes a lossless and high payload data hiding scheme for JPEG images by histogram modification. The most in JPEG bitstream consists of a sequence of VLCs (variable length codes) and the appended bits. Each VLC has a corresponding RLV (run/length value) to record the AC/DC coefficients. To achieve lossless data hiding with high payload, we shift the histogram of VLCs and modify the DHT segment to embed data. Since we sort the histogram of VLCs in descending order, the filesize expansion is limited. The paper’s key contribution includes: Lossless data hiding, less filesize expansion in identical pay-load and higher embedding efficiency