Energy-Aware Georouting with Guaranteed Delivery in Wireless Sensor Networks with Obstacles

We propose, end-to-end (EtE), a novel EtE localized routing protocol for wireless sensor networks that is energy-efficient and guarantees delivery. To forward a packet, a node s in graph G computes the cost of the energy weighted shortest path (SP) between s and each of its neighbors in the forward direction towards the destination which minimizes the ratio of the cost of the SP to the progress (reduction in distance towards the destination). It then sends the message to the first node on the SP from s to x: say node x′. Node x′ restarts the same greedy routing process until the destination is reached or an obstacle is encountered and the routing fails. To recover from the latter scenario, local minima trap, our algorithm invokes an energy-aware Face routing that guarantees delivery. Our work is the first to optimize energy consumption of Face routing. It works as follows. First, it builds a connected dominating set from graph G, second it computes its Gabriel graph to obtain the planar graph G′. Face routing is invoked and applied to G′ only to determine which edges to follow in the recovery process. On each edge, greedy routing is applied. This two-phase (greedy–Face) EtE routing process reiterates until the final destination is reached. Simulation results show that EtE outperforms several existing geographical routing on energy consumption metric and delivery rate. Moreover, we prove that the computed path length and the total energy of the path are constant factors of the optimal for dense networks.

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Performance Analysis of Multiuser DS-CDMA in MIMO Systems Over Rayleigh Fading Channels

The performance of space-time transmit diversity is examined in a multiuser direct-sequence code-division multiple-access (DS-CDMA) system over fast- and slow-fading channels. The underlying space-time system employs transmit antennas and receive antennas at the mobile user and receiver base station, respectively. We consider the performance of the space-time multiuser system when using the linear decorrelator detector to combat the effect of multiuser interference. In our analysis, we derive a closed-form expression for the probability of bit error for both fast- and slow-fading channels. These theoretical results are shown to be very accurate when compared to system simulations. Both simulations and theoretical results prove that, regardless of the system load, the full diversity order of for fast-fading channels and for slow-fading channels is always maintained, and only a signal-to-noise ratio (SNR) loss is incurred. This SNR loss is proved to be a function of only the number of users (i.e., level of interference) and independent of the number of transmit and/or receive antennas. Using our theoretical results, we show that the loss in SNR from the single-user bound can be well approximated by , where represents the level of multiuser interference.     

CO2 Adsorption Isotherm on Modified Calcite,Quartz, and Kaolinite Surfaces: Surface Energy Analysis

Interaction of CO₂ with mineral surfaces is of increasing importance to the activities related to CO₂ sequestration and enhanced oil recovery. Adsorption/interaction of CO₂ with mineral powder surfaces is addressed using microcalorimetric method coupled with gas chromatograph as a detector. Calcite powder surface is modified with stearic acid (SA) and asphaltene, while the silicate mineral powder surfaces (quartz and kaolinite) are modified with N,N-dimethyldodecylamine (NN-DMDA) and asphaltene. Unmodified calcite in presence of humidity has shown to have the highest capacity for CO₂ adsorption among the tested minerals, where a reaction may occur at the calcite surface. The adsorption capacity of calcite is reduced upon modification with SA and asphaltene. Similar observation is also shown with the modified silicate minerals with asphaltene. In contrast, for the modified silicate with NN-DMDA, the adsorption capacity of CO₂ increased, which may be explained by the interaction of CO₂ with the amine group of NN-DMDA.     

LAD-CBM; new data processing tool for diagnosis and prognosis in condition-based maintenance

This paper investigates the application of a data mining technique called Logical Analysis of Data (LAD) to condition-based maintenance. The existing classification techniques are mainly based on statistical analysis and modeling approaches. This paper presents a classification technique based on combinatory and Boolean theory. It is shown that LAD is particularly suitable for detecting the state of equipment because of its new way of pre-processing noisy and missing data. A numerical example and an application are presented.     

What is Middle Maintenance Policy?

The main purpose of this paper is to propose several new maintenance policies that can be performed at suitable middle times for trivariate preventive maintenance scenarios. Firstly, characteristics and limitations for the approaches of whichever occurs first and whichever occurs last are analyzed, and their respective maintenance models, which are called first maintenance and last maintenance, are given directly. Secondly, a combined approach of first and last is employed and middle maintenance is proposed. Thirdly, the aforementioned policy is modified to be performed at discrete working cycles, using the method of overtime maintenance. Finally, a new approach of whichever occurs middle is proposed for modelings. We give the analyses of how to formulate the middle maintenances and obtain their expected maintenance cost rates, using the technique of cumulative damage models. Numerical examples are given to compare the optimal policies among first, last, and middle maintenances. Finally, a potential application of middle maintenance is provided for future studies. Copyright © 2015 John Wiley & Sons, Ltd.     

Improved algorithm for radial distribution networks load flow solution

The main aim of this paper is to present an improved method to solve load flow problem in balanced radial distribution systems with laterals. The method is efficient and easy to implement. Based on electric circuit laws, this method is iterative and allows the evaluation of both, voltage (rms) values and phase-angles. The phase-angles although of small values become necessary in the reactive energy optimisation problem. To solve the load flow in lines with laterals, a simple technique of determining nodes beyond each branch is given. Speed convergence was increased by an appropriate choice of initial voltages. The method requires a small number of iterations and less computational time. It has been used successfully in several line examples. The obtained results for voltage magnitudes and deviation-angles are found to be very close to those of previous works.     

Simulation of partially observed Markov decision process and dynamic quality improvement

Computer simulation is used to compare three quality policies. The first policy is ‘do-nothing’. The second is an appraisal policy. The third policy includes prevention that leads to process quality improvement. The simulation model is based on a Partially Observed Markov Decision Process (POMDP). The unobserved states of the process depend on the failure rate, λ. The observed process output is the number of conforming and nonconforming products. The process performance is measured by quality costs per unit. The simulation language used is SLAM II. The power of using computer simulation to model the dynamics of process quality improvement is discussed.     

A proposed enhanced scheme for the dynamic frequency hopping performance in the IEEE 802.22 standard

This paper presents an integrated scheme for the dynamic‐frequency‐hopping (DFH) technique provided in literature for the IEEE 802.22 standard supporting wireless regional area networks (WRANs). The performance of DFH is analyzed thoroughly for various channel models and for a multiple‐input multiple‐output systems. The core of this research is based on the coexistence of digital terrestrial TV broadcasting and the WRANs in the TV white space. The proposed technique aims at protecting the incumbent users from interfering with the cognitive broadband access in the TV spectrum. In order to achieve this, spectrum sensing is performed in the intended working channel in DFH while spectrum monitoring with an energy‐ratio (ER) algorithm is applied during the WRAN data transmission in the working channel. Hence, in the DFH‐ER algorithm, the reappearance of a digital terrestrial TV signal in a band occupied by the WRANs would be detected immediately. This will provide interference free performance for the licensed signal as well as reliable data transmission for the unlicensed ones. Both analyses and simulation results of the proposed DFH‐ER technique compared with the conventional DFH scenario exemplify the enhancement of the WRAN data transmission while protecting the digital terrestrial TV users. Copyright © 2016 John Wiley & Sons, Ltd.