Accurate High-speed Assembly of Optical Components in Optical Scanning Systems using UV-curing Adhesives: A Positional and Stability Study

In the miniaturized designs of optical scanning systems, UV-curing adhesives have been substituted for screws and bolts. The assembly of delicate optical components enforces stringent requirements on positional accuracy and stability after temperature and humidity cycle testing. The influence of the UV-curing adhesive is mainly determined by its polymerization shrinkage (typically more than 6%). With low amounts of Aerosil® fillers (5% by weight), shrinkage values of 3% can be attained. Optimized adhesive constructions lead to close positional tolerances (0.5 μm) and angular displacements (0.1 mrad).     

Effect of Multi-Wall Carbon Nanotubes on the Mechanical Properties of Natural Rubber

Multi-walled carbon nanotubes (MWNTs) were used to prepare natural rubber (NR) nanocomposites. Our first efforts to achieve nanostructures in MWNTs/NR nanocomposites were formed by incorporating carbon nanotubes in a polymer solution and subsequently evaporating the solvent. Using this technique, nanotubes can be dispersed homogeneously in the NR matrix in an attempt to increase the mechanical properties of these nanocomposites. The properties of the nanocomposites such as tensile strength, tensile modulus, elongation at break and hardness were studied. Mechanical test results show an increase in the initial modulus for up to 12 times in relation to pure NR. In addition to mechanical testing, the dispersion state of the MWNTs into NR studied by Transmission Electron Microscopy (TEM) in order to understand the morphology of the resulting system     

Piezoelectric properties of zinc oxide/iron oxide filled polyvinylidene fluoride nanocomposite fibers

Piezoelectric nanogenerators (PENG) with flexible and simple design have pronounced significance in fabricating sustainable devices for self-powering electronics. This study demonstrates the fabrication of electrospun nanocomposite fibers from polyvinylidene fluoride (PVDF) filled zinc oxide (ZnO)/iron oxide (FeO) nanomaterials. The nanocomposite fiber based flexible PENG shows piezoelectric output voltage of 5.9 V when 3 wt% of ZnO/FeO hybrid nanomaterial is introduced, which is 29.5 times higher than the neat PVDF. No apparent decline in output voltage is observed for almost 2000 s attributed to the outstanding durability. This higher piezoelectric output performance is correlated with the β-phase transformation studies from the Fourier transformation infrared spectroscopy and the crystallinity studies from the differential scanning calorimetry. Both these studies show respective enhancement of 3.79 and 2.16% in the β-phase crystallinity values of PVDF-ZnO/FeO 3 wt% composite. Higher dielectric constant value obtained for the same composite (three times higher than the neat PVDF) confirms the increased energy storage efficiency as well. Thus the proposed soft and flexible PENG is a promising mechanical energy harvester, and its good dielectric properties reveals the ability to use this material as good power sources for wearable and flexible electronic devices.

     

Collaborative Localization for Multi-Robot System with Fault Detection and Exclusion Based on the Kullback-Leibler Divergence

Multi-robot system attracted attention in various applications in order to replace the human operators. To achieve the intended goal, one of the main challenges of this system is to ensure the integrity of localization by adding a sensor fault diagnosis step to the localization task. In this paper, we present a framework able, in addition of localizing a group of robots, to detect and exclude the faulty sensors from the group with an optimized thresholding method. The estimator has the informational form of the Kalman Filter (KF) namely Information Filter (IF). A residual test based on the Kullback-Leibler divergence (KLD) between the predicted and the corrected distributions of the IF is developed. It is generated from two tests: the first acts on the means and the second deals with the covariance matrices. Thresholding using entropy based criterion and Receiver Operating Characteristics (ROC) curve are discussed. Finally, the validation of this framework is studied on real experimental data from a group of robots.     

Micellar Properties of Surface Active Ionic Liquid Lauryl Isoquinolinium Bromide and Anionic Polyelectrolyte Poly(Acrylic Acid Sodium Salt) in Aqueous Solution

The complex formation between anionic polyelectrolyte poly(acrylic acid sodium salt) [NaPAA] and surface active ionic liquid (SAIL) lauryl isoquinolinium bromide [C₁₂iQuin][Br] in aqueous media has been investigated by surface tension, isothermal titration calorimetry (ITC), and conductance. The self‐assembled structures have been characterized using dynamic light scattering (DLS) and turbidity measurements. A range of surface parameters have been calculated from tensiometric measurements including critical micelle concentration (CMC), surface excess concentration (Γ_cmc), surface pressure at the interface (Π_cmc), minimum area occupied at air–solvent interface (A_min), adsorption efficiency (pC₂₀), and surface tension at the CMC (γ_cmc). The thermodynamic parameters, i.e., standard enthalpy of micellization , standard free energy of micellization (), and standard entropy of micellization () have also been evaluated. Four different stages of transitions, corresponding to the progressive formation of NaPAA–[C₁₂iQuin][Br] complex (C₁)_, critical aggregation concentration (CAC), critical saturation concentration (C₃) and CMC have been observed owing to strong electrostatic and hydrophobic interactions. The results obtained from DLS and turbidity measurements show that size of the aggregates first decreases and then increases in the presence of polyelectrolyte. The binding isotherms obtained using isothermal titration calorimetry (ITC) show the concentration dependence as well as the highly cooperative nature of interactions corresponding to formation of polyelectrolyte–SAIL complexes.     

The performance of SAS-super-180 air sampler and settle plates for assessing viable fungal particles in the air of dry-cured meat production facility

Performances of SAS-super-180 air sampler and settle plates were investigated for the assessment of airborne fungal food contamination. Air samples were taken from processing rooms of a dry-cured production facility and outdoors. Fungal colonies and numbers of species were counted and compared. Quantitatively, the air sampler showed higher numbers of species and mean CFU/plate compared to settle plates. Qualitatively, the two methods showed similar dominating fungal genera and species associated with dry-cured meat products. The study showed settle plates could provide important qualitative information for food processing plants where airborne fungi associated with food products are the targets.     

Dielectric relaxation and conduction mechanism of complex perovskite Ca0.90Sr0.10Cu3Ti3.95Zn0.05O12 ceramic

In this work, Sr and Zn co-doped calcium copper titanate having nominal formula Ca_0.90Sr_0.10Cu₃Ti_3.95Zn_0.05O₁₂ has been synthesized and systematically studied for structure, dielectric and electrical properties. The phase purity of the prepared composition has been confirmed by X-ray diffraction (XRD) pattern and various structural parameters are presented here with Rietveld refinement data. The Scanning electron microscopy (SEM) image revealed the presence of homogeneous fine-grained microstructure investigated in the prepared ceramic. The impedance data well fitted with 2 R-CPE model confirmed the non-ideality of the system. Dielectric studies have shown the existence of two relaxation processes in low and high frequency domains. Low frequency dielectric response proposed as a combination of Maxwell-Wagner relaxation and intrinsic defect (V_o⁺⁺) while high frequency behavior has been interpreted in terms of polaronic relaxation caused by hopping process of an electron between Ti³⁺ and Ti⁴⁺ states. The frequency dependent behavior of conductivity has been well fitted to Dong’s model and interpreted in term of Overlapping Large Polaron Tunneling (OLPT) mechanism. The various parameters; relaxation angular frequency (ω₁) of Debye process, ionic hopping frequency (ω₂₎, dc conductivity (σ_o), cole- cole parameter (α) and frequency exponent (s) have been determined by Dong’s Model fitting.