Hough forests for object detection, tracking, and action recognition

Abstract—The paper introduces Hough forests, which are random forests adapted to perform a generalized Hough transform in an efficient way. Compared to previous Hough-based systems such as implicit shape models, Hough forests improve the performance of the generalized Hough transform for object detection on a categorical level. At the same time, their flexibility permits extensions of the Hough transform to new domains such as object tracking and action recognition. Hough forests can be regarded as task-adapted codebooks of local appearance that allow fast supervised training and fast matching at test time. They achieve high detection accuracy since the entries of such codebooks are optimized to cast Hough votes with small variance and since their efficiency permits dense sampling of local image patches or video cuboids during detection. The efficacy of Hough forests for a set of computer vision tasks is validated through experiments on a large set of publicly available benchmark data sets and comparisons with the state-of-the-art.     

Effect of flow history on poly(vinylidine fluoride) crystalline phase transformation

This study was devoted to the effect of extensional flow during film extrusion on the formation of the β‐crystalline phase and on the piezoelectric properties of the extruded poly(vinylidine fluoride) (PVDF) films after cold drawing. The PVDF films were extruded at different draw ratios with two different dies, a conventional slit die and a two‐channel die, of which the latter was capable of applying high extensional flow to the PVDF melt. The PVDF films prepared with the two‐channel die were drawn at different temperatures, strain rates, and strains. The optimum stretching conditions for the achievement of the maximum β‐phase content were determined as follows: temperature = 90°C, strain = 500%, and strain rate = 0.083 s^?1. The samples prepared from the dies were then drawn under optimum stretching conditions, and their β‐phase content and piezoelectric strain coefficient (d₃₃) values were compared at equal draw ratios. Measured by the Fourier transform infrared technique, a maximum of 82% β‐phase content was obtained for the samples prepared with the two‐channel die, which was 7% higher than that of the samples prepared by the slit die. The d₃₃ value of the two‐channel die was 35 pC/N, which was also 5 pC/N higher than that of the samples prepared with the slit die. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

MATHEMATICAL AND EXPERIMENTAL INVESTIGATION ON NOX RECOVERY IN FLUIDIZED BED ADSORBERS FOR EXHAUST GASES OF NITRIC ACID PLANTS

A mathematical model for sorption of NOx from exhaust gas of nitric acid plants by activated carbon (AC) in a fluidized bed is proposed based on two-phase flow theory of fluidization. To solve the proposed model a computer program has been developed. The output of this program reveals the effects of various parameters such as temperature, inlet gas velocity, particle diameter, and inlet gas concentration on the rate of adsorption. To evaluate the proposed model, a pilot-scale plant was erected and the obtained experimental data were compared with the values predicted by the model. A good agreement is observed between these values. Once the validity of the proposed model is checked, it could be used for obtaining the optimum operating condition for this type of bed.     

Low-delay video control in a personal area network for augmented reality

A personal area network (PAN) is a feature of an augmented reality system, transmitting modified video for real-time display. Low-delay communication of encoded video over a Bluetooth wireless PAN is achieved in favourable channel conditions by a combination of dynamic packetisation of video slices together with centralised and predictive rate control. The result is minimised packet delay (below 0.05 s) and high-quality 40 dB video, with packet loss limited to 4 from radio frequency noise. Where channel conditions result in error bursts, dynamic rate change is introduced to reduce the need for packet retransmission and improve power efficiency.     

Kramers-Kronig-constrained variational dielectric fitting and the reflectance of a thin film on a substrate

A test was made of the ability of Kramers-Kronig-constrained variational dielectric fitting to extract the optical conductivity of a thin film from reflectance data containing structure due to both thin film and substrate. The reflectance of a series of well-characterized thin films of SrRu(x)Mg(1-x)O(3) and SrRu(x)O(3) with a variety of thicknesses (approximately 56-300 nm) and dc resistivities (approximately 250-2200 micro Omega cm) was measured. The low frequency values of the extracted optical conductivities agree with the dc measurements, however, removal of features due to the substrate improves with increasing film thickness.     

Preparation and characterizations of V2AlC-Al2O3 composite produced via spark plasma sintering

A 2:1:1 MAX phase, V₂AlC, composited with Al₂O₃ is prepared using spark plasma sintering (SPS). To obtain a sample with suitable physical and mechanical properties, an especial current rate regime is carried out for SPS. Different final temperatures of the synthesis (1000, 1200, 1400, and 1500°C) are considered (named S1000, S1200, S1400, and S1500, respectively). Phase analysis, physical and mechanical properties characterizations, and morphology of the samples are performed to determine the quality of the samples. The best characterizations belong to the samples of S1400 and S1500. Bending strengths about 325 and 316 MPa are obtained for the samples of S1400 and S1500, respectively. Regarding the total MAX phases formation and strength, the optimum sample is S1400. However, regarding bulk density, wear resistance, and hardness, S1500 has an advantage over the S1400. The advantages of S1500, as well as its larger grain size, are attributed to the better sintering of Al₂O₃.     

A 2.6-GHz/5.2-GHz frequency synthesizer in 0.4-μm CMOStechnology

This paper describes the design of a CMOS frequency synthesizer targeting wireless local-area network applications in the 5-GHz range. Based on an integer-N architecture, the synthesizer produces a 5.2-GHz output as well as the quadrature phases of a 2.6-GHz carrier. Fabricated in a 0.4-μm digital CMOS technology, the circuit provides a channel spacing of 23.5 MHz at 5.2 GHz while exhibiting a phase noise of -115 dBc/Hz at 2.6 GHz and -100 dBc/Hz at 5.2 GHz (both at 10-MHz offset). The reference sidebands are at -53 dBc at 2.6 GHz, and the power dissipation from a 2.6-V supply is 47 mW     

Fatigue of additively manufactured 316L stainless steel: The influence of porosity and surface roughness

The fatigue behaviour of additively manufactured (AM) 316L stainless steel is investigated with the main emphasis on internal porosity and surface roughness. A transition between two cases of failure are found: failure from defects in the surface region and failure from the internal defects. At low applied load level (and consequently a high number of cycles to failure), fatigue is initiating from defects in the surface region, while for high load levels, fatigue is initiating from internal defects. Porosities captured by X‐ray computed tomography (XCT) are compared with the defects initiating fatigue cracks, obtained from fractography. The fatigue data are synthesised using stress intensity factor (SIF) of the internal and surface defects on the fracture surface.     

Low temperature synthesis of Titanium diboride by carbothermal method

Titanium diboride powders have been synthesized by means of carbothermal reduction method utilizing Titanium oxide, Boric acid and Graphite. The effect of mechanical activation of mixed raw materials and the use of additional Boric acid on the final phases have been studied. The resultant powders were characterized by X-ray diffraction (XRD) analyzer and Field Emission Scanning Electron Microscope (FESEM). XRD patterns showed that TiB₂, TiC and C phases after heat treatment at stoichiometric ratio of reactants. By increasing the milling time, the unwanted phases such as C and TiC will be reduced. Pure TiB₂ could be synthesized with mechanical activation of raw materials for 24?h at non-stoichiometric ratio (using additional Boric acid) and heat treatment at low temperature of 1380?°C. In this condition, Titanium diboride could be achieved with residual carbon of 0.92 0.09wt% and mean average particle size of 3.28µm. Thermal analysis (TGA-DTA) was used to determine the reaction progress and mechanism. Results revealed that the intermediate phase, TiBO₃, played an important role in getting to lower temperature synthesis. This phase was identified after mechanical milling of raw materials and heat treatment at temperature of 1250?°C.