Statistical analysis of positioning error of a CNC milling machine

The characteristics of the positioning error of a NC milling machine were studied through statistical analysis. It was found that (1) the mean of the error is significantly affected by the table position, (2) the variances of the error at different table positions are from the same population, and (3) the effect of the feedrate on positioning error is not significant. Also, a software correction technique was applied and workpiece error was decreased by 40%.     

RImCom: Raster-order Image Compressor for Embedded Video Applications

This paper presents a real-time, rate controlled, end-to-end (encoder and decoder) hardware solution for memory compression of raster-order video streams—named RImCom (short for Raster-order Image Compression). RImCom offers up to 3x compression that is either lossless or lossy at very reasonable PSNR values. The 180 nm ASIC implementation of RImCom achieves 28 fps at Ultra-HD resolution in the slow corner of synthesis. RImCom can match the fps of the state-of-the-art in the literature with 20 % less area or can achieve twice the fps with 55 % more area. Our FPGA implementation is the only end-to-end FPGA solution in the literature to achieve to this day over 60 fps at Full-HD resolution and to offer rate control. This work was motivated by video processing applications that require the previous frame(s) besides the current frame. When processing HD video streams, even when only one previous frame is required besides the current frame, a significant size and bandwidth of memory is needed. If the current frame is compressed on-the-fly with RImCom or a similar solution and stored on DRAM, and the previous frame is read from DRAM and decompressed with a small IP block, then the overall system cost, power consumption, and electromagnetic radiation are reduced.     

Accounting for time-dependent covariates in driving simulator studies

Driving involves multiple cognitive processes that are influenced by a dynamic external environment and internal feedback loops. These processes are typically studied in a simulator environment to capture time-dependent driver performance measures. The primary objective of this research is to show that data analysis techniques that ignore or improperly treat time-dependent covariates will lead to erroneous estimates and conclusions. This is demonstrated with a driving simulator study that was used to test whether a significant decrease in performance occurs in the presence of auditory and visual distractions. A total of 28 drivers participated in a 2 (age)?×?7 (strategy) repeated measures experiment. The response variable—accelerator release time—was analysed with and without consideration of time-dependent covariates. Using the inverse headway distance as a time-dependent covariate corrected logically inconsistent results obtained when the covariate was ignored. This indicates that ignoring covariates can actually lead to inappropriate design or policy implications.     

Platinum nanoparticles decorated carbon nanofiber hybrids as highly active electrocatalysts for polymer electrolyte membrane fuel cells

Increasing the efficiency of electrocatalyst is the key demand for the polymer electrolyte membrane fuel cells (PEMFC). To address the activity and performance challenges of commercial electrocatalyst, Pt/C, we introduce a new hybrid catalyst support for Pt nanoparticles. In this regard, combining or mixing specific type of carbon-based supports is a feasible strategy to increase catalyst utilization and performance. In the current study, Pt nanoparticles (NPs) were decorated on a new hybrid network, comprising of carbon nanofiber (CNF) and carbon black (CB), by means of a facile and efficient microwave (MW) assisted reduction method. All synthesized electrocatalysts were characterized to elucidate chemical and morphological structures. Then, the hybrid electrocatalysts were utilized as hydrogen oxidation reaction (HOR) and oxygen reduction reaction (ORR) electrocatalysts and their electrocatalytic activities were investigated by using cyclic voltammetry (CV) and linear sweep voltammetry (LSV), respectively. We found that the hybridization of CNF with CB substantially improved not only the electrocatalytic activity but also the fuel cell performance, which can be attributed to a consecutive conductive network, in which CB acts as a spacer, and synergistic effects between the CNF and CB. The hybrid electrocatalyst (Pt/CNF-CB with 50:50 wt%) showed a superior activity toward HOR and ORR while also offering exceptional fuel cell performance. That hybrid possessed the highest electrochemically active surface area (ECSA) compared with Pt/CNF and Pt/CB. In addition, the mass activity (at 0.80 V vs RHE) of the Pt/CNF-CB (50:50 wt%) is about 3.3 and 3.5 times higher than that of Pt/CNF and Pt/CB, respectively. Furthermore, that hybrid electrocatalyst exhibited enhanced fuel cell performance with 907 mW.cm⁻¹ maximum power density. This work demonstrated that the CNF-CB supported Pt nanoparticles as electrocatalysts are extremely promising for fuel cell reactions.     

Polyethylene glycol‐sugar composites as shape stabilized phase change materials for thermal energy storage

Polyethylene glycol (PEG)‐sugar composites have been investigated as cost effective shape‐stabilized phase change materials for thermal energy storage. PEGs form internal hydrogen bonds stabilizing their chains at solid state. However low molecular weight PEGs are liquid due to short chains as high molecular weight PEGs have too little concentration of hydroxyl groups. Therefore, glucose, fructose, and lactose are used as hydrogen bond source in this study. Consequently it is found that sugars stabilized PEGs up to 90% PEG constitution in solid state except for 90%PEG10,000/10% fructose blend. Fourier transform‐infrared (FT‐IR) analysis revealed considerable interactions between PEGs. The maximum changes in the spectra were observed in the OH stretching region as band broadening due to increasing hydrogen bonding interactions. Differential scanning calorimetry (DSC) analysis are used to determine phase change temperatures and enthalpy of the shape‐stabilized composites that are slightly lower than those of PEG precursors due to the interference effect of sugar in crystallization process. The enthalpies of the blends are 89%, 95%, and 94% of expected from 90%PEG/10% glucose blends, 93%, 94%, and 93% of expected from 90% PEG/10% fructose blends, and 99%, 96%, and 96% of expected from 90% PEG/10% lactose blends respectively when PEGs with 1,000; 6,000; and 10,000 g/mol average molecular weights are used respectively. The diameter of the spherulitic crystals of PEGs decreases with the addition of any of sugar derivatives and spherulites of the composites turns to semi‐amorphous solid structures at temperatures above melting point of PEG precursor. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers     

Coated particle fuel to improve safety, design, economics in water-cooled and gas-cooled reactors

In the context of Inert Matrix Fuels (IMF), coated particles (CP)s may play an important role to reduce the problems connected to the plutonium (Pu) and minor actinides stockpiles. In addition, the coatings of the fuel kernels made of different low and high-density ceramic layers allow a safe containment of fission products in operational, accidental and disposal conditions. Pu-based CPs embedded in a ceramic matrix (e.g. graphite, like in HTR fuel elements) can be judged as a special cercer type. There is a wide variety of different coatings and kernel compositions that has not yet been explored beyond the HTR development. Thus it can be expected that the CP technology can be applied to other reactor systems, too. For getting full benefit of the fission product retention capability of the CPs, not only the particle design but also the core geometry as well as power densities etc. have to be adopted to each specific requirement.     

Investigation of mechanical and creep properties of polypyrrole by depth-sensing indentation

In this study, we used depth-sensing indentation (DSI) technique to investigate some mechanical properties (reduced elastic modulus, indentation hardness, and creep) of polypyrrole (PPy) conducting polymer obtained with different support electrolyte concentration. The influence of support electrolyte concentration on these parameters was also determined. The order of doping degree of the samples was determined by cyclic voltammetry. The indentation load–displacement curves of the samples were obtained under different peak load levels with a 70 s holding time at maximum load. Reduced elastic modulus and hardness values were determined by analysis of these curves using the Feng–Ngan (F–N) and Tang–Ngan (T–N) methods, respectively. Both reduced elastic modulus (E _r) and indentation hardness (H) exhibited significant peak load dependence, i.e., indentation size effect (ISE). It was found that both E _r and H values decreased as the support electrolyte concentration was increased. This was explained by an increase in the free volume as the doping degree was raised. The creep behavior of the samples was monitored from the load holding segment of the load–unload curves. It was found that creep increases with the increasing support electrolyte concentration.