Load balancing techniques for lifetime maximizing in wireless sensor networks

Energy consumption has been the focus of many studies on Wireless Sensor Networks (WSN). It is well recognized that energy is a strictly limited resource in WSNs. This limitation constrains the operation of the sensor nodes and somehow compromises the long term network performance as well as network activities. Indeed, the purpose of all application scenarios is to have sensor nodes deployed, unattended, for several months or years.This paper presents the lifetime maximization problem in “many-to-one” and “mostly-off” wireless sensor networks. In such network pattern, all sensor nodes generate and send packets to a single sink via multi-hop transmissions. We noticed, in our previous experimental studies, that since the entire sensor data has to be forwarded to a base station via multi-hop routing, the traffic pattern is highly non-uniform, putting a high burden on the sensor nodes close to the base station.In this paper, we propose some strategies that balance the energy consumption of these nodes and ensure maximum network lifetime by balancing the traffic load as equally as possible. First, we formalize the network lifetime maximization problem then we derive an optimal load balancing solution. Subsequently, we propose a heuristic to approximate the optimal solution and we compare both optimal and heuristic solutions with most common strategies such as shortest-path and equiproportional routing. We conclude that through the results of this work, combining load balancing with transmission power control outperforms the traditional routing schemes in terms of network lifetime maximization.     

Analysis of phytohormones and phosphate solubilization in Photorhabdus spp.

Bacteria of the genus Photorhabdus are nematodes (Heterorhabditidae) symbiont and highly entomopathogenic in nature. Present study was concerned to investigate the effects of Photorhabdus temperata M1021 and Photorhabdus luminescens TT01 on plant morphology and physiology (‘Dongjin-beyo’ and ‘waitoc’). A significant (p<0.05) increase in the plant growth attributes including total plant length, root length, biomass, and chlorophyll contents were observed after treatment with culture extracts. Moreover indole-3-acetic acid (IAA) production by respective bacteria was confirmed by GCMS analysis. IAA production through tryptophan independent pathway was confirmed in P. temperata M1021 and P. luminescens TT01. Phosphate solubilization capability was also investigated by growing them on pikovskaya (PVK) agar as well as on PVK liquid medium with pH 7 at 28±2°C for 14 days. IAA production and phosphate solubilization capability of these bacteria could be the potential factors for plant growth promotion.     

Potential interference and rain attenuation at 21.4–22 GHz downlink broadcasting satellite signals

World Radio Conference WRC-1992 has allocated the frequency band 21.4–22.0?GHz to regions 1 and 3 to be utilised to carry direct broadcasting satellite (DBS) services. This high-frequency band is more susceptible to rain attenuation, leading to degradation of the signal quality. Moreover, this frequency band is assigned to two different services, i.e. satellite broadcasting and fixed mobile services at the same regions; hence, the impact of intersystem interference in a depredated signal is a critical issue in the DBS receiver. In this study, the effects of rain attenuation on the DBS downlink signals as well as the impact of the potential interference on the reception quality will be estimated. An interference scenario will be introduced to investigate the system performance in both propagation mechanisms of clear-sky and rain conditions.     

The synthetic control chart based on two sample variances for monitoring the covariance matrix

In this article, we propose a new statistic to control the covariance matrix of bivariate processes. This new statistic is based on the sample variances of the two quality characteristics, in short VMAX statistic. The points plotted on the chart correspond to the maximum of the values of these two variances. The reasons to consider the VMAX statistic instead of the generalized variance | S | are its faster detection of process changes and its better diagnostic feature, that is, with the VMAX statistic it is easier to identify the out‐of‐control variable. We study the synthetic chart based on the VMAX statistic. The proposed chart is always more efficient than the chart based on the generalized variance | S |. An example is presented to illustrate the application of the proposed chart. Copyright © 2008 John Wiley & Sons, Ltd.     

Crosstalk Stability Analysis in Multilayer Graphene Nanoribbon Interconnects

In this paper a time-domain response and Nyquist stability criterion to acquire dependence of degree of crosstalk relative stability based on transmission lines modeling (TLM) is investigated for coupled multilayer graphene nanoribbon (MLGNR) interconnects. This is the first instance that such an analysis has been presented for coupled MLGNR consisting of both capacitive and mutual-inductive couplings. The near-end and far-end outputs of coupled MLGNR individually are compared in two cases, with considering both couplings and without them (single MLGNR). It is observed that the near-end output of the system together with both couplings is more stable and at its far-end output, an induced voltage is created. By increasing capacitive coupling or decreasing inductive coupling, the near-end output becomes more stable. Also, the results of changes of length and width of each ribbon show that by increasing the length and decreasing the width, the coupled MLGNR interconnects become more stable.     

A single-period perishable inventory model where deterioration begins at a random point in time

This paper develops a single-period inventory model where the stock begins to deteriorate at a random point in time within the period. Once this deterioration begins, the selling price can be adjusted once at that point. Optimum order size and pricing policies are determined for such an inventory model through a numerical illustration.     

Application of MIKE SHE modelling system to set up a detailed water balance computation

Estimation of total water balance is a substantial issue for watershed modelling in order to simulate the major components of the hydrological cycle to determine the stress of different anthropogenic activities on the available water resources within a catchment. In this context, the fully distributed physically based MIKE SHE modelling system was used to simulate the individual hydrological components of the total water balance for the Paya Indah Wetlands (PIW) watershed in the west of Peninsular Malaysia. Results reveal that the overall water balance is predominantly controlled by climate variables. Application of the model to the PIW watershed provides detailed estimation of the total water balance for a first‐order catchment in which actual evapotranspiration (ET) represents approximately 65 and 58%, while overland flow (OL) to the PIW lake system represents 12.38 and 12.3% of the total rainfall during the calibration and validation periods, respectively. The difference of the inflow and outflow was taken as storage in depth. Overall, the model gives a reasonable output of total error of less than 1% of the total rainfall, which in turn indicates that the interaction among components is satisfactorily sustained.     

A cross industry comparison of inter-organisational systems implementation activities

The Inter-organisational systems (IOS) Motivation Model (IMM) has recently been proposed as a theory that explains variations in IOS implementation processes initiated by organisations. The IMM classifies IOS adoption projects (regardless of the underlying technology used) into four generic motivation scenarios and explains different implementation processes for each motivation scenario. The theory was tested in the Australian pharmaceutical industry where it received broad support. In order to enhance its generality, in this study we explore the applicability of part of the IMM theory to a different industry context by addressing the research objective that organisations with the same motive for implementing an IOS initiate the same implementation activities regardless of differences in the industry contexts within which they operate. We have used a multiple case study approach and compared the implementation of a proprietary in-house built e-ordering system in a large Australian pharmaceutical manufacturing company with that of a web-based EDI system used by a large automotive manufacturing company using IMM as a theoretical lens. The empirical results indicate a striking similarity in the implementation processes of these two different IOS applications; this can largely be explained using the IMM theory. Furthermore, the differences in industry contexts do not appear to have a direct influence on the activities associated with implementing these systems.     

Molecular Characterization of α- and β-Thalassaemia among Malay Patients

Both α- and β-thalassaemia syndromes are public health problems in the multi-ethnic population of Malaysia. To molecularly characterise the α- and β-thalassaemia deletions and mutations among Malays from Penang, Gap-PCR and multiplexed amplification refractory mutation systems were used to study 13 α-thalassaemia determinants and 20 β-thalassaemia mutations in 28 and 40 unrelated Malays, respectively. Four α-thalassaemia deletions and mutations were demonstrated. −−^SEA deletion and α^CSα accounted for more than 70% of the α-thalassaemia alleles. Out of the 20 β-thalassaemia alleles studied, nine different β-thalassaemia mutations were identified of which β^E accounted for more than 40%. We concluded that the highest prevalence of (α- and β-thalassaemia alleles in the Malays from Penang are −−^SEA deletion and β^E mutation, respectively.     

An optimal production run for an imperfect production process with allowable shortages and time-varying fraction defective rate

The effects of an imperfect production process on the optimal production run by assuming that an elapsed time until the process shift is exponentially distributed have been studied. This problem was extended by assuming that the elapsed time until the process shift is arbitrarily distributed. The models, however, do not allow for shortages. This work has been generalized by assuming that shortages were allowed. The common assumption of all the above-mentioned models is that a fixed percentage of defective items are produced during the out-of-control period. This assumption may not be applicable in many industrial situations. Intuitively, the percentage of defective rate should increase with an increase in the duration of the out-of-control period. In fact, other research has considered an imperfect production process model with a variable rate of defective units produced when the process is in an out-of-control state. The defective rate is assumed to be a function of detection delay. The main purpose of this paper is to further generalize earlier work by introducing a time-varying percentage defective rate. This paper develops a model to determine the optimal production run for a deteriorating production system, with allowable shortages, and time-varying fraction defective rate. However, the elapsed time until the production process shift is assumed to be exponentially distributed. A unique optimal production run is found that minimizes the total expected cost. A numerical example is provided to illustrate the application of the model and to prove the convexity of the total cost function. A sensitivity analysis is also conducted to study the effects of various model parameters on the optimal production run and the total cost.