Adaptive Kalman filter for MEMS IMU data fusion using enhanced covariance scaling

MEMS (micro-electro-mechanical-system) IMU (inertial measurement unit) sensors are characteristically noisy and this presents a serious problem to their effective use. The Kalman filter assumes zero-mean Gaussian process and measurement noise variables, and then recursively computes optimal state estimates. However, establishing the exact noise statistics is a non-trivial task. Additionally, this noise often varies widely in operation. Addressing this challenge is the focus of adaptive Kalman filtering techniques. In the covariance scaling method, the process and measurement noise covariance matrices Q and R are uniformly scaled by a scalar-quantity attenuating window. This study proposes a new approach where individual elements of Q and R are scaled element-wise to ensure more granular adaptation of noise components and hence improve accuracy. In addition, the scaling is performed over a smoothly decreasing window to balance aggressiveness of response and stability in steady state. Experimental results show that the root mean square errors for both pith and roll axes are significantly reduced compared to the conventional noise adaptation method, albeit at a slightly higher computational cost. Specifically, the root mean square pitch errors are 1.1? under acceleration and 2.1? under rotation, which are significantly less than the corresponding errors of the adaptive complementary filter and conventional covariance scaling-based adaptive Kalman filter tested under the same conditions.     

Theoretical bounds for the bit error rate for SAC OCDMA balanced detectors with multiple photodiodes

Photonic Network Communications - In this paper, we derive the theoretical lower and upper bounds for bit error rate (BER) for spectral amplitude coding OCDMA balanced detector (BD) employing...     

Iterative Bayesian Monte Carlo for nuclear data evaluation

In this work, we explore the use of an iterative Bayesian Monte Carlo（i BMC） method for nuclear data evaluation within a TALYS Evaluated Nuclear Data Library（TENDL） framework. The goal is to probe the model and parameter space of the TALYS code system to find the optimal model and parameter sets that reproduces selected experimental data. The method involves the simultaneous variation of many nuclear reaction models as well as their parameters included in the TALYS code. The’best’ model set with...     

Study the effect of recycled pressurized air on oxygen transfer design parameters in sequencing batch reactor technology

Aeration process consumes more than 60% of the total energy required for wastewater treatment. The present study aims to save power consumption within wastewater treatment aeration process through recycling of the air flow. A new technique of aeration is used to increase oxygen transfer efficiency via exploiting recycled pressurized air. A pilot plant has been constructed to study the effect of using recycled pressurized air within sequencing batch reactor (SBR) model. The results showed that the new technique comparing with the conventional SBR model improved Standard oxygen transfer rate (SORT), Standard oxygen transfer efficiency (SOTE) and Standard aeration efficiency (SAE). In particular, the new technique enhanced (SAE) with 10 and 4% at gauge pressure values 0.5 atm. and 2 atm. respectively. On the other hand, intermittent aeration enhanced (SAE) with 15 and 5% at gauge pressure values 0.5 atm. and 2 atm. respectively.     

ANALYSIS OF USED OIL BY IR-SFECTROSCOPIC AND SYNTHESIS OF DISPERSIONS OF A HIGHLY BASIC PETROLEUM CALCIUM SULFONATE ADDITIVE

ABSTRACT

Infrared absorptions of TLC subtractions of used motor oil, original oil, base oil and the additive, indicate the transformation of the polar and nonpolar components by further oxidation and oxidative degradation of carbonyl compounds into acids, esters and peroxides. Organic nitrates and nitro compounds were also detected after 2000Km and 3000Km service. The effects of basic calcium sulfonate additives, starting with used oil l000Km, 2000Km, 3000Km service, vacuum distillates of used oils and base oil, were studied. It has been found that the dispersant properties of these sulfonates are profoundly influenced by their structure. The alkalinity of the calcium sulfonate additive was determined by spectroscopic-IR method.     

Greenhouse gas emissions as influenced by wetland vegetation degradation along a moisture gradient on the eastern Qinghai-Tibet Plateau of North-West China

Vegetation loss and plant diversity decline in wetlands affect carbon and nitrogen cycling and consequently influence gas fluxes. Although extensive grazing by livestock and climate change have caused significant physical degradation of wetlands on the Qinghai-Tibet Plateau (QTP), and created a clear drainage gradient, the impact on greenhouse gas (GHG) emissions associated with this change has rarely been reported. A 3-year study (2013–2015) was conducted to examine the effect of vegetation change and seasonality on ecosystem respiration, methane (CH₄) and nitrous oxide (N₂O) fluxes in four classes of wetlands with distinct magnitudes of vegetation degradation: healthy vegetation (HV), slightly degraded (SD), moderately degraded, and heavily degraded (HD). We used the dark static chamber-chromatography method to measure the gas fluxes. Highly degraded wetlands were larger C and GHG sources than HV, despite lower methane emissions, due to the loss of gross primary production. SD and HD exhibited the highest cumulative mean annual ecosystem respiration and N₂O emissions, respectively. Ecosystem respiration and CH₄ fluxes were much higher during the growing seasons than in the non-growing seasons. Ecosystem respiration and N₂O fluxes were positively correlated with soil and air temperatures. This points at a potential effect of global warming on GHG emissions from the QTP wetlands. Top soil (0–20 cm) moisture content significantly correlated positively with CH₄ fluxes. Vegetation loss led to a reduced C uptake and increased global warming potential. Therefore, we recommend soil conservation measures and reduced livestock grazing in the wetlands in order to conserve their role as carbon sinks.     

Low-Cycle Fatigue Testing of High-Performance Concrete Bonded Overlay–Bridge Deck Slab Systems

Plain and fibrous latex modified concrete and microsilica concrete overlays with acceptable laboratory strength and durability characteristics were installed on a full-scale prototype bridge deck for field performance evaluation. After 1?year of exposure to drying shrinkage, temperature variations, and freeze–thaw cycles, no cracking or debonding were observed in the overlays. The bond strengths at 28?days and at 1?year were acceptable for all overlay types due to the excellent curing and surface preparation using water-jet blasting. The prototype bridge was then statically tested before and after applying low-cycle fatigue loading simulating AASHTO HS20 truck service load, overload, and ultimate load. Minor bond strength deterioration at the maximum negative moment region and slight bridge stiffness degradation were observed after each load case. Significant enhancement in the bridge stiffness was observed after installation of the overlays. Also, the overlay with synthetic fibers showed better crack bridging action than the overlay with steel fibers.     

Polypropylene/phosphazene nanotube nanocomposites: Thermal,mechanical, and flame retardation studies

In this study, flame retardant polypropylene (PP) nanocomposites with superior mechanical performance have been developed using amine-functionalized phosphazene nanotubes (APZS, 1–10 wt%) through melt-blending method. Polypropylene-graft-maleic anhydride was used as the compatibilizer to attain effective interaction between the nanofiller and the PP matrix. The characterization of amine-functionalized phosphazene nanotubes (APZS) using solid-state nuclear magnetic resonance (NMR), X-ray photoelectron spectroscopy, X-ray diffraction, fourier-transform infrared (FTIR), and transmission electron microscopy indicated successful amine functionalization, though structural changes were observed as compared to the unfunctionalized nanotubes. Owing to the covalent polymer-filler interfacial interactions and resulting in uniform filler dispersion, the nanocomposites exhibited significant enhancement in the tensile modulus up to 5 wt% APZS content (98% increment at 5 wt% content as compared to pure polymer). The addition of a small fraction of APZS (1 wt%) improved the impact strength of the nanocomposite by more than 180%. APZS acted as a weak nucleating agent for PP, thereby leading to enhanced degree of crystallinity (up to 5 wt% APZS content). The thermal stability of the nanocomposites was also enhanced with APZS content. The nanocomposites with 5 and 10 wt% APZS loading exhibited a V0 rating in UL-94 test, indicating that APZS introduced a robust flame retardancy behavior in the PP nanocomposites. The limiting oxygen index values also confirmed the findings from the UL-94 analysis. The developed nanocomposites exhibit high potential of use in a wide range of high temperature applications.