Design of a novel compact modified‐circular printed antenna for high data rate wireless sensor networks

This paper presents a novel compact circular patch Ultrawideband (UWB) antenna for sensor node applications. The microstrip‐fed low‐profile antenna comprises an elliptical ring slot, two crescent‐shaped slots and two dumbbell‐shaped slots in feedline. The antenna miniaturization is achieved by a novel combination of an elliptical ring slot, two crescent‐shaped slots in circular patch. The proposed prototype has been fabricated on inexpensive FR4 substrate and the relative permittivity is (ε_r = 4.3) with 1.6 mm thickness. The overall size of the proposed miniaturized antenna is about (0.1 λ_r × 0.15 λ_r), where λ_r is the resonating wavelength of the lowest UWB frequency (ie, 3.1 GHz). The measured radiation performances of the proposed antenna are nearly an omnidirectional pattern in H‐plane and bidirectional pattern in E‐plane for all the frequencies in the whole UWB band. The development process of the antenna, radiation properties and group delay is completely analyzed and discussed.     

The role of contact stresses and wall friction on fluidization

Fluidization and defluidization experiments, where we increased the gas superficial velocity in small increments and then decreased it, were performed in tubes of different diameters to probe the role of wall friction on pressure drop and bed height. Such experiments, covering the regimes of packed bed, stable bed expansion and bubbling bed, were carried out for several different particles. The compressive yield strength of the particle assemblies at various volume fractions was determined by measuring the height of fully defluidized beds at various mass loading levels. The systematic effect of the tube diameter on pressure drop and bed height hysteresis could be rationalized in terms of a one-dimensional model that accounted for the effect of wall friction and path-dependent contact stresses in the particle phase. Bubbling seemed to set in when the yield stress in the particle assembly could be overcome by the inherent fluctuations. Our experiments, which focused primarily on gas velocities below the minimum bubbling conditions, did not reveal any dramatic change across the Geldart A-B boundary. This is consistent with the original observation by Geldart (Powder Technol. 7 (1973) 285). The distinct difference between beds of group A and B particles in the gently bubbling regime reported by Cody et al. (Powder Technol. 87 (1996) 211) is thus likely to be due to changes in the dynamics of the bubbles, as we observed no striking difference between these beds at gas velocities below minimum bubbling conditions.     

Flexural Behaviour of Fibre‐Reinforced Syntactic Foams

Summary: Syntactic foams containing 0.9, 1.76, 2.54, 3.54 and 4.5 vol.‐% of E‐glass fibres in the form of chopped strands were processed and subjected to three‐point bending tests. The results showed that introduction of chopped strand fibres into the syntactic foam system increased the flexural strength. The values increased with the amount of fibres in the foam system except for the one containing 3.5 vol.‐% of fibres, which showed a lower value than other fibre‐reinforced systems, thereby deviating from the trend. This exception was attributed to the difference in processing route adopted for this particular fibre‐bearing foam. However, in general, the incorporation of chopped strand fibres improved the flexural behaviour of the syntactic foam system without much variation in density, thus making reinforced syntactic foams to act as better and improved core materials for sandwich applications.

Fibre‐debonding and protuberance, and river pattern in a failed sample.     

On the Relationship Between Cyclic Deformation Behavior and Slip Mode in 316LN Stainless Steel with Varying Nitrogen Content

The relationship between cyclic deformation, slip-mode and dislocation structures is investigated in 316LN stainless steel (with 0.07–0.22 wt% Nitrogen) subjected to low cycle fatigue at temperatures in the range 300–873 K and at a 0.6 % strain amplitude. Irrespective of the nitrogen content, cyclic softening/saturation occupied a large fraction of fatigue life at temperatures <773 K. The end-of-life dislocation structures (e.g. dislocation cells, planar slip-bands) characterizing the cyclic softening/saturation belong to wavy/mixed/planar slip-modes of deformation. On the other hand at temperatures ≥773 K, similar dislocation structures are noticed to be associated with significant cyclic strengthening with limited softening. The differences in the above deformation behavior is found to be controlled not by the nature of slip-mode but by the consequences of dynamic strain aging occurrence (e.g. significant cyclic strengthening and pronounced serrations) which are noticed to vary in the temperature range 573–873 K. Maximum fatigue life is observed at 0.11–0.14 wt% N that induced mixed mode of deformation.     

Near infrared spectroscopy to predict bitter pit development in different varieties of apples

Bitter pit is a physiological disorder in apples. Several major apple varieties are susceptible to this disorder that poses a great challenge to growers and the associated industry as it significantly reduces the produce utilization value and marketability. The current method of bitter pit detection is through visual assessment of symptoms. Near infrared (NIR) spectroscopy is a non-invasive technique that can be utilized towards detecting bitter pit development in fruits in pre-/non-symptomatic stages. Therefore, NIR spectra (935–2500 nm) of apples were collected from healthy and bitter pit Honeycrisp, Golden Delicious, and Granny Smith apples from a commercial orchard. The apples were stored in a controlled environment and spectral reflectance data were acquired at days 0, 7, 14, 35, and 63 after harvest. Chemical analysis was performed at the end of the storage period to estimate calcium, magnesium, and potassium content in the fruit peel. Partial least square regression (PLSR) was used to identify the apples as healthy or bitter pit using NIR-based spectral features. In addition, specific spectral features were selected by implementing two feature extraction methods: PLSR and stepwise discriminant analysis (SDA) on day 63 spectral dataset. The PLSR and SDA-based selected features from day 63 in Honeycrisp apples classified the same dataset with classification accuracies of about 100% with both methods. Regression analysis indicated a strong relationship between the PLSR-based spectral features and magnesium-to-calcium ratio in fruit peel in all three (Honeycrisp, Golden Delicious, and Granny Smith) apple varieties.     

Combining dependent bodies of evidence

Dempster’s combination rule can only be applied to independent bodies of evidence. One occurrence of dependence between two bodies of evidence is when they result from a common source. This paper proposes an improved method for combining dependent bodies of evidence which takes the significance of the common information sources into consideration. The method is based on the significance weighting operation and the “decombination” operation. A numerical example is illustrated to show the use and effectiveness of the proposed method.     

Hydrophilic Sparse Ionic Monolayer‐Protected Metal Nanoparticles: Highly Concentrated Nano‐Au and Nano‐Ag “Inks” that can be Sintered to Near‐Bulk Conductivity at 150 °C

Here, monolayer‐protected gold and silver nanoparticles with extremely high solvent dispersibility (over 200 mg mL^?1 in water and glycols) and low coalescence temperature (approximately 150 °C, measured by the percolation transition temperature T_p) are developed, to reach conductivities better than 1 × 10⁵ S cm^?1. These materials are suitable for inkjet and other forms of printing on substrates that may be solvent‐ and/or temperature‐sensitive, such as for plastic electronics, and as bus lines for solar and lighting panels. This is achieved using a new concept of the sparse ionic protection monolayer. The metal nanoparticles are initially protected by a two‐component mixed ligand shell comprising an ω‐functionalized ionic ligand and a labile ligand. These are selectively desorbed to give a sparse shell of the ω‐ionic ligands of ca. 25% coverage. Through a systematic study of different monolayer‐protected Au nanoparticles using FTIR spectroscopy, supported by XPS and DSC, it is shown that T_p is not determined by thermodynamic size melting or by surface area effects, as previously thought, but by the temperature when ca. 80% of the dense monolayer is eliminated. Therefore, T_p depends on the thermal stability and packing density of the shell, rather than the size of the metal core, while the solubility characteristics depend strongly on the exposed terminal group.     

Frequency warping for VTLN and speaker adaptation by linear transformation of standard MFCC

Vocal tract length normalization (VTLN) for standard filterbank-based Mel frequency cepstral coefficient (MFCC) features is usually implemented by warping the center frequencies of the Mel filterbank, and the warping factor is estimated using the maximum likelihood score (MLS) criterion. A linear transform (LT) equivalent for frequency warping (FW) would enable more efficient MLS estimation. We recently proposed a novel LT to perform FW for VTLN and model adaptation with standard MFCC features. In this paper, we present the mathematical derivation of the LT and give a compact formula to calculate it for any FW function. We also show that our LT is closely related to different LTs previously proposed for FW with cepstral features, and these LTs for FW are all shown to be numerically almost identical for the sine-log all-pass transform (SLAPT) warping functions. Our formula for the transformation matrix is, however, computationally simpler and, unlike other previous LT approaches to VTLN with MFCC features, no modification of the standard MFCC feature extraction scheme is required. In VTLN and speaker adaptive modeling (SAM) experiments with the DARPA resource management (RM1) database, the performance of the new LT was comparable to that of regular VTLN implemented by warping the Mel filterbank, when the MLS criterion was used for FW estimation. This demonstrates that the approximations involved do not lead to any performance degradation. Performance comparable to front end VTLN was also obtained with LT adaptation of HMM means in the back end, combined with mean bias and variance adaptation according to the maximum likelihood linear regression (MLLR) framework. The FW methods performed significantly better than standard MLLR for very limited adaptation data (1 utterance), and were equally effective with unsupervised parameter estimation. We also performed speaker adaptive training (SAT) with feature space LT denoted CLTFW. Global CLTFW SAT gave results comparable to SAM and VTLN. By estimating multiple CLTFW transforms using a regression tree, and including an additive bias, we obtained significantly improved results compared to VTLN, with increasing adaptation data.