Digital natives’ intention to interact with social media: Value systems and gender

Social media research focuses predominantly on the link between attitude, behaviour and intention, and rarely takes value systems into account. Values are expected, through intervening variables, to affect intention directly or indirectly. Starting from the Theory of Trying, the aim of this study is to investigate how value systems affect digital natives’ intention to interact with social media. By using Fuzzy Set Qualitative Comparative Analysis (fsQCA), an empirical analysis involving data from 116 social media users is carried out to examine how global and domain-specific values, attitude towards trying and gender affect the intention to interact. The results of a configurational analysis show that gender appears to affect many of the configurations leading to the outcome of interest. There are two configurations in which, regardless of gender, global values, domain-specific values and attitude towards trying cause the outcome. The findings indicate that there is no single condition necessary to ensure the outcome, but there are several different configurations of the conditions lead to outcome of interest.     

Analysis of Thermoelastic Crack Problems Using Green–Lindsay Theory

A boundary element method using the Laplace transform in time domain is presented for the analysis of fracture mechanics under thermal shock using the Green and Lindsay (GL) theory of thermoelasticity. The dynamic thermoelastic model of Green and Lindsay is selected to show the effect of thermal wave propagation at finite speed on crack tip stress intensity factor evaluation. The singular behavior of the temperature and displacement fields in the vicinity of the crack tip is modeled by the quarter-point elements. Thermal dynamic stress intensity factor for mode I is evaluated from computed nodal values, using the well-known displacement and traction formulas. The accuracy of the method is investigated through comparison of the results with the available data in literature. Condition where the inertia term plays important role is discussed and variations of dynamic stress intensity factor is investigated. Different relaxation times are chosen to briefly show their effects on stress intensity factor in the Green and Lindsay theory.     

A new hybrid for improvement of auto-regressive integrated moving average models applying particle swarm optimization

A time series forecasting is an active research applied significantly in a variety of economics areas. Over the past three decades an auto-regressive integrated moving average (ARIMA) model, as one of the most important time series models, has been applied in financial markets forecasting. Recent researches in time series forecasting ARIMA models indicate some basic limitations which detract from their popularities for financial time series forecasting: One limitation of an ARIMA model is that it requires a large amount of historical data to generate an accurate result. Both theoretical and empirical findings suggest that combining different time series models may be an effective method of improving the predictive performances of data especially when the models in the ensemble are quite different. The main purpose of present paper is to combine the ARIMA model with the particle swarm optimization (PSO) model in order to improve and generate more accurate forecasting results. Under small data information, combining the PSO and ARIMA models performs better performance results compared to an ARIMA model itself. The proposed model is robust and it may be used as an alternative forecasting tool in economics areas.     

Data uploading time estimation for CUBIC TCP in long distance networks

CUBIC is a TCP-friendly algorithm that uses a cubic curve, independent of the round-trip time, to rapidly recover from a packet loss. New releases of Linux use CUBIC for the TCP protocol. In this paper, we show that if the socket buffer size of a sender TCP is small compared with the bandwidth-delay product, Linux TCP window size drops to almost zero every time a packet loss occurs. Using this fact, we estimate data uploading time in long distance networks with packet loss. Also we discuss the improvement of the uploading time by increasing cumulative socket buffer size in two ways: large buffer size or parallel connections.     

Reinforcement learning movement path for multiple mobile sinks in wireless sensor networks

Mobile sink nodes play a very active role in wireless sensor network (WSN) routing. Because hiring these nodes can decrease the energy consumption of each node, end-to-end delay, and network latency significantly. Therefore, mobile sinks can soar the network lifetime dramatically. Generally, there are three movement paths for a mobile sink, which are as follows: (1) Random/stochastic, (2) controlled, and (3) fixed/ predictable/predefined paths. In this paper, a novel movement path is introduced as a fourth category of movement paths for mobile sinks. This path is based on deep learning, so a mobile sink node can go to the appropriate region that has more data at a suitable time. Thereupon, WSN routing can improve very much in terms of end-to-end delay, network latency, network lifetime, delivery ratio, and energy efficiency. The new proposed routing suggests a reinforcement learning movement path (RLMP) for multiple mobile sinks. The network in the proposed work consists of a couple of regions; each region can be employed for a special purpose, so this method is hired for any application and any size of the network. All simulations in this paper are done by network simulator 3 (NS-3). The experimental results clearly show that the RLMP overcomes other approaches by at least 32.48% in the network lifetime benchmark.     

A consistent formulation for imposing packaging constraints in shape optimization using Vertex Morphing parametrization

This paper aims at imposing no-penetration condition over arbitrary surfaces which act as bounding surfaces, also known as packaging constraints, on the design surface of shape optimization problem. We use Vertex Morphing technique for the shape parametrization. Vertex Morphing is a consistent surface control approach for node-based shape optimization. The suitability of this technique has been assessed and demonstrated for a wide range of engineering applications without geometric shape constraints. In this contribution, a consistent formulation is presented for the implementation of numerous point-wise geometric constraints in four main steps. First, a potential contact between optimization surface points and the bounding surface is identified via the so-called gap function. Second, the shape gradients of objective functions and active constraints are mapped onto the Vertex Morphing’s control space, where the optimization problem is formulated. Third, the linear least squares method is used to project the steepest-descent search direction onto the subspace tangent to the mapped active constraints. Finally, the feasible design update is mapped onto the geometry space. To verify the perfect consistency between the geometry space (where the constraints are formulated) and the control space (where the optimization problem is solved) two applications of CFD shape optimization in the automotive industry are presented.     

An improved teaching‐learning–based optimization for design of frequency reconfigurable antennas

This paper proposes an improved teaching‐learning–based optimization (ITLBO) for the electromagnetics and antenna community. The basic TLBO was applied to many different problems with consistent success. For improving the algorithm performance, in the learner phase, each group of two learners is replaced by three‐member groups. Furthermore, two new phases are added to the algorithm. The first phase involves selection of several better learners for teaching subjects to randomly selected weaker learners. The second phase is a mutation operation. The presented algorithm with these changes simulates a classroom more realistically and avoids being trapped in local optima. First, the ITLBO is evaluated to optimize seven benchmark functions and is shown to be faster and better. In addition, a frequency reconfigurable antenna design is considered as a practical problem and Taguchi's method is applied for adjusting the control parameters of the algorithm. Comparisons of the performance of this algorithm with those of the TLBO, two other improved versions of TLBO (I‐TLBO and improved TLBO with learning experience of other learners [LETLBO]) and genetic algorithms demonstrate the higher efficiency for this algorithm in electromagnetic problems. A prototype of the proposed antenna is fabricated, and the simulation and measurement results agree well.     

HOW TO MAKE THE HILL CIPHER SECURE

ABSTRACT

This paper presents a symmetric cipher that is actually a variation of the Hill cipher. The new scheme makes use of “random” permutations of columns and rows of a matrix to form a “different” key for each data encryption. The cipher has matrix products and permutations as the only operations which may be performed “efficiently” by primitive operators, when the system parameters are carefully chosen.     

An elastic plastic damage formulation for concrete: Application to elementary tests and comparison with an isotropic damage model

Pure elastic damage models or pure elastic plastic constitutive laws are not totally satisfactory to describe the behaviour of concrete. They indeed fail to reproduce the unloading slopes during cyclic loading which define experimentally the value of the damage in the material. When coupled effects are considered, in particular in hydro-mechanical problems, the capability of numerical models to reproduce the unloading behaviour is essential, because an accurate value of the damage, which controls the material permeability, is needed. In the context of very large size calculations that are needed for 3D massive structures heavily reinforced and pre-stressed (such as containment vessels), constitutive relations ought also to be as simple as possible. Here an elastic plastic damage formulation is proposed to circumvent the disadvantages of pure plastic and pure damage approaches. It is based on an isotropic damage model combined with a hardening yield plastic surface in order to reach a compromise as far as simplicity is concerned. Three elementary tests are first considered for validation. A tension test, a cyclic compression test and triaxial tests illustrate the improvements achieved by the coupled law compared to a simple damage model (plastic strains, change of volumetric behaviour, decrease in the elastic slope under hydrostatic pressures). Finally, one structural application is also considered: a concrete column wrapped in a steel tube.