On the credibility of manet simulations

Simulation is useful for evaluating protocol performance and operation. However, the lack of rigor with which it's applied threatens the credibility of the published research within the manet research community. Mobile ad hoc networks (manets) allow rapid deployment because they don't depend on a fixed infrastructure. Manet nodes can participate as the source, the destination, or an intermediate router. This flexibility is attractive for military applications, disaster-response situations, and academic environments where fixed net working infrastructures might not be available.     

Reliable eye-diagram analysis of data links via device macromodels

This paper addresses the impact of device macromodels on the accuracy of signal integrity and performance predictions for critical digital interconnecting systems. It exploits nonlinear parametric models for both single-ended and differential devices, including the effects of power supply fluctuations and receiver bit detection. The analysis demonstrates that the use of well-designed macromodels dramatically speeds up the simulation as well it preserves timing accuracy even for long bit sequences.     

PowerNap: an efficient power management scheme for mobile devices

We present PowerNap, an OS power management scheme, which can significantly improve the battery life of mobile devices. The key feature of PowerNap is the skipping of the periodic system timer ticks associated with the operating system. On an idle device, this modification increases the time between successive timer interrupts and enables us to put the processor/system into a more efficient low power state. This saves the energy consumed by workless timer interrupts and the excess energy consumed by the processor in less efficient low power states. PowerNap is tightly integrated with the kernel and is designed for optimal control of the latency and energy associated with transitioning in and out of the low power states. We describe an implementation of PowerNap and its impact on system software. Experiments with IBM's WatchPad verify the ability of PowerNap to extend battery life. An analytical model that quantifies the ability of the scheme to reduce power is also presented. The model is in good agreement with experimental results. We apply the model to small form-factor devices which use processors that have a PowerDown state. In such devices, PowerNap may extend battery life by more than 42 percent for small processor workloads and for background power levels below 10 mW.     

Pre-Processing of Integral Images for 3-D Displays

This paper seeks to explore a method to accurately correct geometric distortions caused during the capture of three-dimensional (3-D) integral images. Such distortions are rotational and scaling errors which, if not corrected, will cause banding and moire effects on the replayed image. The method for calculating the angle of deviation in the 3-D Integral Images is based on Hough Transform. It allows detection of the angle necessary for correction of the rotational error. Experiments have been conducted on a number of 3-D integral image samples and it has been found that the proposed method produces results with accuracy of 0.05 deg     

On-line estimation of kinetic parameters in anaerobic digestion using observer-based estimators and multiwavelength fluorometry.

Observer-based estimators (OBE) were used for estimation of state variables and kinetic parameters in an anaerobic digestion (AD) process. A simplified first-order model with time-varying kinetic parameters was used to design an OBE for kinetic parameter estimation. This approach was validated on a laboratory-scale anaerobic reactor equipped with a multiwavelength fluorometer for on-line measurements of COD and VFA concentrations in the reactor effluent. The proposed estimators provide continuous adjustment of kinetic parameters and can be used for predictions of state variables between samples acquisition and during sensor failure.     

Co-digestion of ruminal content and blood from slaughterhouse industries: influence of solid concentration and ammonium generation.

At the present time, organic solid wastes from industries and agricultural activities are considered to be promising substrates for biogas production via anaerobic digestion. Moreover solids stabilisation is required before reutilization or disposal. Slaughterhouses are among the most important industries in Uruguay and produce 150,000 tons of ruminal content (RC) and 30,000 tons of blood per year. In order to determine the influence of the solids and blood contents, the ammonia inhibition and the inoculum adaptation co-digestion batch tests were performed. A set of experiences with TS concentration of 2.5%, 5% and 7.5% and different ratios of RC/blood were carried out using an inoculum from an UASB reactor. In all experiences fast blood hydrolisation was observed. A higher methane production was detected in the experiences with higher TS content. However, the fraction of solids degradation was lower in these experiences. A plateau in the biogas production was found. The free ammonia level, which was above the reported inhibitory levels, could explain this behaviour. After the inhibition period the biogas production restarted probably due to the biomass acclimatisation to the ammonia. In order to determine the inoculum adaptation a new experiment was performed. The inoculum used was the sludge coming from the first set of experiences. Based upon batch tests a 3.5 m3 pilot reactor was designed and started up. Ammonia inhibition was avoided by the start-up strategy and in two weeks the biogas production was 3.5 m3/d. The VS stabilisation with a solid retention time of 20 days was of 43%. The pilot reactor working at steady state had a TS concentration of 3-4% with a ratio of RC/blood of 10:1 at the entrance.     

Influence of the second phase on the room-temperature tensile and creep deformation mechanisms of α-β titanium alloys: Part I. Tensile deformation

The effects of α and β phase interactions on the room-temperature tensile and creep deformation behavior of α + β titanium alloys with Widmanst?tten microstructures were studied using Ti-6.0 wt pct Mn and Ti-8.1 wt pct V as the model two-phase alloy systems. This article, Part I, deals with tensile deformation. It was found that when the α phase is present as thin (<10-μm) plates in the α + β alloys, significant twinning occurs. No significant twinning was observed in single-phase alloys with the same chemistry and similar grain size. Additionally, the β phase of Ti-8.1 V deforms by stress-induced hexagonal martensite (α′), while only twinning occurs in the single-phase β alloy with the same chemistry. Twinning in the α phase in association with stress-induced martensite (SIM) in the β phase was observed for the first time in a two-phase titanium alloy. This behavior is explained in terms of a number of factors including elastic interaction stresses between the α and β phases, coherency between the α phase and hexagonal martensite, and β phase stability.     

Identification of the adverse effect of nitrate on the phosphate release rate and improvement of EBPR process models.

The adverse effect of nitrate on the phosphate release rate in the anaerobic phase was observed and was hardly explainable with conventional EBPR process models. Four possible mechanisms were proposed including substrate competition, reduced fermentation, parallel reaction and sequential reaction. Batch experiments were designed and conducted to identify the dominant mechanism. Results showed that the sequential reaction was the only possible mechanism where only denitrification occurred if any nitrate existed in the anaerobic phase. Then the phosphate release following after the nitrate was completely removed. Nitrate inhibition effect was added into the PHA storage rate to incorporate the sequential reaction in the conventional ASM3 plus EAWAG bio-P module (ASM3 + P). Nitrate inhibition coefficient, K(I,NO,PAO) was found to be as low as 0.05 mg/L. This correlated well with experimental observation where no also meant that the anaerobic compartment of a continuous flow reactor could be seriously affected by the residual nitrate contained in the sludge recycle flow. This phenomenon caused overestimation of the phosphate uptake rate and consequently underestimation of PO4(3-) -P concentration. This problem was resolved by incorporation of a nitrate inhibition term in the ASM3 + P for more accurate simulation of the EBPR process.     

Design of a retention tank: comparison of stormwater quality models with various levels of complexity.

Stormwater quality simulation models are useful tools for the design and management of sewer systems. Modelling results are highly sensitive to experimental data used for calibration. This sensitivity is examined for three modelling approaches of various complexities (site mean concentration approach, event mean concentration approach and build-up, washoff and transport modelling approach) applied to a typical case study (design of a dry detention tank), accounting for the variability of calibration data and their effect on simulation results. Calibrated models with different calibration data sets were used to simulate 3 years of rainfall with different retention tank specific volumes. Annual pollutant load interception efficiencies were determined. Simulations results revealed (i) that there is no advantage in using the EMC model compared to the SMC model and (ii) that the BWT model resulted in higher design ratios than those given by the SMC/hydraulic approach. For both EMC and BWT models, using an increasing number n of events for calibration leads to narrower confidence intervals for the design ratios. It is crucial for design ratios to account for successive storm events in chronological order and to account for the maximum allowable flow to be transferred to the downstream WWTP.     

An inventory analysis of rural pollution loads in China.

Rural pollution has attracted increasing attention over the past decade for its important consequences on surface and groundwater quality. This is particularly so in China due to the wide and effective control of industrial and municipal wastewater discharges over the past decade. Based on the discussion of rural activities in China, this paper develops a new method of inventory analysis through the definition of elementary unit (EU). This inventory analysis approach is then applied to estimate the total rural pollution loads of COD, TN and TP, as well as their spatial distributions in China. Further analysis is also conducted to investigate the correlations between rural pollution loads and agricultural production outputs, as well as population. It is found that China's agriculture is developing largely at the cost of environment quality, and a high population, as well as the increasing demand for agricultural products, is one of the dominant driving forces. The constructed EKC, which describes the relationship between rural pollution loads and agricultural income, also reveals that current agricultural development in China is mostly far from de-locked from the environmental problem.