Mehdi Habibi

Fabrication, characterization of two nano-composite CuO-ZnO working electrodes for dye-sensitized solar cell.

Two kind of CuO-ZnO nanocomposite working electrodes were synthesized by sol-gel technology and applied in dye-sensitized solar cells (DSSCs). Their characteristics were studied by field emission scanning electron microscopy (FESEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectrum (DRS). CuO-ZnO nanocomposite thin films were prepared doctor blade technique on the fluorine-doped tin oxide (FTO) and used as working electrodes in dye sensitized solar cells (DSSC). Their photovoltaic behavior were compared with standard using D35 dye and an electrolyte containing [Co(bpy)3](PF6)2, [Co(pby)3](PF6)3, LiClO4, and 4-tert-butylpyridine (TBP). The ranges of short-circuit current (JSC) from 0.18 to 0.21 (mA/cm(2)), open-circuit voltage (VOC) from 0.24 to 0.55V, and fill factor from 0.34 to 0.39 were obtained for the DSSCs made using the working electrodes. The efficiency of the working electrodes after the addition of TBL was more than doubled. The light scattering and carrier transport properties of these composites promote the performance of dye-sensitized solar cells (DSSCs).

Dye-sensitized solar cell characteristics of nanocomposite zinc ferrite working electrode: effect of composite precursors and titania as a blocking layer on photovoltaic performance.

This research investigates the performance of a zinc ferrite (ZF) as working electrodes in a dye-sensitized solar cell (DSSC). This ZF working electrode was prepared by sol-gel and thermal decomposition of four different precursors including: zinc acetate dihydrate (Zn(CH3COO)2·2H2O), ferric nitrate nonahydrate (Fe(NO3)3·9H2O), iron(III) acetate; Fe(C2H3O2)3, and zinc nitrate hexahydrate, Zn(NO3)2·6H2O. The effects of annealing temperature and precursors on the structural, morphological, and optical properties were investigated. The field emission scanning electron microscope images (FESEM) and scanning electron microscopy (SEM) show that ZFe films are polycrystalline in nature and homogeneous with densely packed grains. Nanoporous zinc ferrite coatings were prepared by doctor blade technique on the fluorine-doped tin oxide (FTO) and used as working electrodes in DSSC. In all DSSCs, platinized FTO and [Co(bpy)3](2+/3+) in 3-methoxy proponitrile were used as counter electrode and redox mediator system respectively. Comparing the fill factors of four different zinc ferrite nanocomposites, the highest fill factor was for ZnFe2O4-TBL sample. Cell fabricated with ZnFeA working electrode shows relatively higher Jsc.

Novel nanostructure zinc zirconate, zinc oxide or zirconium oxide pastes coated on fluorine doped tin oxide thin film as photoelectrochemical working electrodes for dye-sensitized solar cell.

Zinc zirconate (ZnZrO(3)) (ZZ), zinc oxide (ZnO) (ZO) and zirconium oxide (ZrO(2)) (ZRO) nano-particles were synthesized by simple sol-gel method. ZZ, ZO and ZRO nano-particles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD) and UV-Vis diffuse reflectance spectrum (DRS). Nanoporous ZZ, ZO and ZRO thin films were prepared doctor blade technique on the fluorine-doped tin oxide (FTO) and used as working electrodes in dye sensitized solar cells (DSSC). Their photovoltaic behavior were compared with standard using D35 dye and an electrolyte containing [Co(bpy)(3)](PF(6))(2), [Co(pby)(3)](PF(6))(3), LiClO(4), and 4-tert-butylpyridine (TBP). The properties of DSSC have been studied by measuring their short-circuit photocurrent density (Jsc), open-circuit voltage (VOC) and fill factor (ff). The application of ZnZrO(3) as working electrode produces a significant improvement in the fill factor (ff) of the dye-sensitized solar cells (ff=56%) compared to ZnO working electrode (ff=40%) under the same condition.

Real time fractal image coder based on characteristic vector matching

Fractal coding algorithm has many applications including image compression. In this paper a classification scheme is presented which allows the hardware implementation of the fractal coder. High speed and low power consumption are the goal of the suggested design. The introduced method is based on binary classification of domain and range blocks. The proposed technique increases the processing speed and reduces the power consumption while the qualities of the reconstructed images are comparable with those of the available software techniques. In order to show the functionality of the proposed algorithm, the architecture was implemented on a FPGA chip. The application of the proposed hardware is shown in image compression. The resulted compression ratios, PSNR error, gate count, compression speed and power consumption are compared with the existing designs. Other applications of the proposed design are feasible in certain fields such as mass-volume database coding and also in video coders block matching schemes.

A novel adaptive Gaussian restoration filter for reducing periodic noises in digital image

Digital images can suffer from periodic noise, resulting in the appearance of repetitive patterns on the image data and quality degradation. In order to effectively reduce the periodic noise effects, a novel adaptive Gaussian notch filter is proposed in this paper. In the presented method, the frequency regions that correspond to noise are determined by applying a segmentation algorithm on the spectral band of the noisy image using an adaptive threshold. Then, a region growing algorithm tries to determine the bandwidth of each periodic noise component separately. Subsequently, proper Gaussian notch filters are used to decrease the periodic noises only at the contaminated noise frequencies. The proposed filter and some other well-known filters including the frequency domain mean and median filters and also the traditional Gaussian notch filter are compared to evaluate the effectiveness of the approach. The results in different conditions show that the proposed filter gains higher performance both visually and quantitatively with lower computational cost. Furthermore, compared with the other methods, the proposed filter does not need any tuning and parameter adjustments.

Geometric centre tracking of tagged objects using a low power demodulation smart vision sensor

In this study, a modulated light detecting smart CMOS image sensor is presented. The design has the ability to sense asynchronous signals transmitted from electronic markers such as flashing light emitting diodes (LEDs) tagged on moving objects. The geometric centre of the detected region is returned as the output result. With the presented sensor, object localisation and position detection functions are simplified, performed at higher speeds in real time and power requirement is reduced. The sensor in-pixel processing filters out the background image data, detects the modulated marker regions and projects the extracted region on the two axes, while the geometric centre extraction units placed at each axis identify the coordinates assigned to the marker. The design presents less sensitivity to object texture compared with techniques based on edge extraction or binarisation. The sensor has been designed as a 64 × 64 pixel VLSI CMOS chip in the 0.35 ?m standard CMOS technology and analysed in the presence of mismatches and noise. Issues such as sensor array scalability, speed and power dissipation are also examined in this study and features of the sensor are reported and compared with some previous designs.

Asynchronous demodulation technique for use in vision sensor image classification and segmentation

This paper presents a novel technique for classification and segmentation of a multiple-object image scene. Each object in the scene is tagged by a flashing LED operating at a specific frequency. The vision sensor, based on this technique, demodulates the captured light signal, omits the background illumination, and performs classification by assigning a unique ID-tag to each region based on its flashing light frequency. The process is performed in-pixel by an asynchronous demodulation and frequency identification circuit, which is designed in a standard 0.6µm CMOS technology. Simulation results confirm the validity of the proposed structure. At a frame rate of 250 fps the power consumption is 2.6µW/pixel, which is relatively low compared with those of sensors with similar functionality. The structure is intended for use as a low power, inexpensive solution in robot visual position feedback and localization. Copyright

A Generalized Study of Coil-Core-Aspect Ratio Optimization for Noise Reduction and SNR Enhancement in Search Coil Magnetometers at Low Frequencies

Here, a generalized induction coil sensor model (more generalized than other models) has been considered at low frequencies (within 0.1-100 Hz), and the equivalent magnetic field of the coils thermal noise and the sensors signal-to-noise ratio (SNR) were calculated theoretically based on the dimensions and geometry of the coil winding and its core. In our suggested theoretical consideration, all involved parameters were considered and optimized without any assumption and constraint, while some authors in their latest reports, have been used some assumptions and constraints in their sensor calculations (such as holding constant the sensors volume and aspect ratio). Our calculations indicated that the equivalent magnetic field of the thermal noise can be minimized by the coil-to-core weight ratio. Moreover, it was found that the sensors SNR can be maximized with only a special value of core aspect ratio (length to diameter of core ratio). The obtained theoretical results were evaluated experimentally by fabricating a search coil magnetometer model, using the optimum parameters. The resonance frequency and the parasitic capacitance of the coil were measured. Moreover, the variations of the transfer function of the magnetometer, with respect to frequency, were studied. Thus, it was shown that, at low frequencies, our experimentally measured noise data exhibit better agreement with our suggested theoretical results with respect to the state of the art.

Facial emotion recognition method based on Pyramid Histogram of Oriented Gradient over three direction of head

Today Human Computer Interaction (HCI) is one of the most important topics in machine vision and image processing fields. Through features can get beneficial information about the variety of emotions and gestures which are produced by the movements of facial major parts. In this paper we presented the technique of Pyramid Histogram of Oriented Gradient for feature extraction and compare it with gabor filters. Six basic facial expressions plus the neutral pose are considered in the evaluations. The KNN and SVM techniques are used in the classification phase. Unlike most emotion detection approaches that focus on frontal face view this method concentrates on three views of the face and can easily be generalized to other poses and feelings. We have tested our algorithm on the Radboud faces database (RaFD) over three directions of head (frontal, 45 degree to the right and 45 degree to the left). Cohn-Kanade (CK+) and JAFFE are two other databases used in this work. The experiments using the proposed method demonstrate favorable results. In the best condition by using Pyramid Histogram Of Oriented Gradient plus KNN classification, the success rates were 100, 96.7, 98.1, 98.3 and 98.9 % for RaFD (frontal pose), RaFD (45 degree to the right), RaFD (45 degree to the left), JAFFE and CK+ databases respectively.

Analysis, Enhancement, and Sensitivity Improvement of the Correlation Image Sensor

The correlation image sensor (CIS) is used in a variety of applications which involve the extraction and measurement of low-amplitude-modulated light signals from background interferences. Many applications have been reported on measurement of ac magnetic flux, interferometry, eye gaze tracking, and indirect 3-D imaging using these sensors. In this paper, the performance of different derivatives of the CIS is analyzed, and some modification is applied to the CIS to significantly increase its sensitivity at higher frame rates and reduce its output error. The effect of undesired parameters, such as parasitic capacitances, device mismatches, charge transfers, random noise, and temperature variations, is studied, and modified architectures are proposed to reduce them. The maximum demodulation frequency is also shown to be increased compared to original CIS. The presented designs are compared with previous solutions under similar operating conditions using a 0.35-μm standard CMOS technology. It is shown that the designs can be used to detect lower modulated signal levels over a wider background dynamic range.