Reflection-High Energy Electron Diffraction Study of Si(100) Homoepitaxy by Femtosecond Pulsed Laser Deposition

The dynamics of femtosecond pulsed laser deposition (fsPLD) of Si(!00)-1 x I and Si(!00)-2x I homoepitaxy are studied by in situ reflection high-energy electron diffraction (RHEED) and ex situ atomic force microscopy (AFM). The effects of substrate temperature, laser fluence and the pressure of a passive gas on the Si(!00)-1 x I growth mode are discussed. It is shown that films grow following the Volmer-Weber (3D) growth mode. The substrate temperature largely affects the morphology of the grown film. Below ~ 400 °C (at laser fluence of~ 1.9 J/cm2), randomly oriented 3D clusters are grown. This is shown as the disappearance of the RHEED elastic peaks, leaving just a diffused pattern. Above that temperature (at the same laser fluence), on the other hand, transmission patterns are obtained, owing to the formation of crystalline 3D clusters. For a constant temperature, the laser fluence is also seen to affect the growth mode. Below ~ 0.8 J/cm2(for deposition at~ 430 °C), RHEED elastic peaks disappear due to the loss of long range order, while above that value transmission patterns (due to the growth of crystalline 3D clusters) are obtained. In order to emphasize the dependence of the growth dynamics on the surface reconstruction, fsPLD of Si/Si(I00)-2x 1 is also studied. Under the studied conditions, films grow by step-flow, which is seen as no change in the RHEED pattern. The average terrace width, as measured by the specular beam splitting, is seen to remain unchanged during deposition. Under the current experimental conditions, no RHEED oscillations (indicating layer-by-layer growth) are seen. Finally, the dependence of the growth dynamics on the laser pulse duration is obtained by comparing the results of fsPLD to those of nsPLD. With nsPLD, polycrystalline films are grown, as indicated by the ring RHEED pattern

Fuzzy logic traffic signal controller enhancement based on aggressive driver behavior classification

The rise in population worldwide and especially in Egypt, together with the increase in the number of vehicles present serious complications regarding traffic congestion and road safety. The elementary solution towards improving congestion is to expand road capacities by building new lanes. This, however, requires time and effort and therefore new methodologies are being implemented. Intelligent transportation systems (ITS) try to approach traffic congestion through the application of computational and engineering techniques. Traffic signal control is a branch of intelligent transportation systems which focuses on improving traffic signal conditions. A traffic signal controllers’ main objective is to improve this assignment in a way which reduces delays. This research proposes a new approach to enhancing traffic signal control and reducing delays of a single intersection, through the integration of an aggressive driving behavior classifier. Previous approaches dealt with traffic control and driver behavior separately, and therefore their successful integration is a new challenging area in the field. Multiple experiment sets were conducted to provide an indication to the effectiveness of our approach. Firstly, an aggressive driver behavior classifier using feed-forward neural network was successfully built utilizing Virginia Tech 100-car naturalistic driving study data. Its performance was compared against long short-term memory recurrent neural networks and support vector machines, and it resulted in better performance as shown by the area under the curve. To the best of our knowledge, this classifier is the first of its kind to be built on this 100-car study data. Secondly, a representation of aggressive driving behavior was constructed in the simulated environment, based on real life data and statistics. Finally, Mamdani’s fuzzy logic controller was modified to accommodate for the integration of the aggressive behavior classifier. The integration results were encouraging and yielded significant improvements at higher traffic flow volumes when compared against the built Mamdani’s controller. The results are promising and provide an initial step towards the integration of driver behavior classification and traffic signal control

Self-Assembly and Characterization of Germanium Quantum Dots on Silicon by Pulsed Laser Deposition

Self-assembled Ge quantum dots (QD) are grown on Si(100)-(2×1) by pulsed laser deposition (PLD). In situ reflection-high energy electron diffraction (RHEED) and post-deposition atomic force microscopy (AFM) are used to study the growth dynamics and morphology of the QDs. Several films of different thicknesses were grown at a substrate temperature of 400°C using a Q-switched Nd:YAG laser (λ = 1064 mu, 40 ns pulse width, 23 J/cm2 fluence, and 10 Hz repetition rate). At low film thicknesses, but clusters that are faceted by different planes, depending on their height, are observed after the completion of the wetting layer. With increasing film thickness, the size of the clusters grows, and they gradually lose their facetation and become more rounded. With further thickness increase, the shape of these clusters becomes dome-like with some pyramids observed among the majority of domes. The effect of the laser fluence on the morphology of the grown clusters was studied. The cluster density was found to increase dramatically while the average cluster size decreased with the increase in the laser fluence. For a laser fluence of 70 J/cm2, dome-shaped clusters that are smaller than the large huts formed at 23 J/cm2 were observed. At a substrate temperature of 150°C, misoriented three-dimensional (3D) clusters formed producing only a RHEED background. At 400 and 500°C, huts and a lower density of domes formed, respectively. Above 600°C, 3D clusters formed on top of a discontinuous textured layer. As an application, pulsed laser deposition is used to fabricate multilayered Ge quantum-dot photodetector on Si(100). Forty successive Ge quantum dot layers, each covered with a thin Si layer, were deposited. Deposition and growth are monitored by in situ reflection-high energy electron diffraction and the morphology is further studied by ex situ atomic force microscopy. The difference in the current values in dark and illumination conditions was used to measure the device sensitivity to radiation. Spectral responsivity measurements reveal a peak around 2 μm, with responsivity that increases three orders of magnitude as bias increases from 0.5 to 3.5 V. The effects of laser-induced electronic excitations on the self-assembly of Ge quantum dots on Si(100)-2×1 grown by pulsed laser deposition are also studied. Electronic excitations, due to laser irradiation of the Si substrate and the Ge film during growth, are shown to decrease the roughness of films grown at a substrate temperature of ∼120°C. At this temperature, the grown films are nonepitaxial. However, electronic excitation results in the formation of an epitaxial wetting layer and crystalline Ge quantum dots at ∼260°C, a temperature at which no crystalline quantum dots form without excitation under the same deposition conditions. Finally, the very early stages of formation of Ge but clusters on Si(100) has been studied by UHV STM. Growth starts by the formation of a very low density of asymmetric huts with high aspect ratios. Further deposition results in a higher density of clusters characterized by their narrow size and height distributions. These clusters are almost of the same lateral size as those deposited at lower thicknesses

Chest Wall Tumors: A Spectrum of Different Pathologies and Outcomes of Reconstruction Techniques

Background: Chest wall resection and further reconstruction for tumors represent a challenging concept for surgeons. Thanks to the evolving reconstruction techniques, good results were obtained after extensive resection and reconstruction. Patients and methods: This prospective cohort study was conducted at our University Hospitals throughout 5 years. A total of 43 eligible cases with chest wall tumors were included. All cases were subjected to a multidisciplinary team approach, complete history taking, physical examination, radiological evaluation, and biopsy. The details of surgical techniques, complications, and follow up parameters were included. Results: The mean age of the included cases was 29.45 years. We included a total of 24 males (55.8%). Fibromatosis was the commonest encountered pathology (27.9%), followed by chondrosarcoma (25.5%), and osteosarcoma (21%). Regarding the method of reconstruction, polypropylene mesh was used in 46.5% of cases, followed by direct closure (30.2%). Ten cases were managed by Methyl Methacrylate within the proline mesh (23.3%), while superimposed muscle flap was performed in only 2 cases (4.6%). Post-operatively, bleeding was encountered in 5 cases collectively (11.6%), while wound infection occurred in 11.6% of cases. Pulmonary complications included pneumonia (2.3%) and atelectasis (11.6%). Furthermore, chest wall instability was present in (11.6%) of cases. On follow up, recurrence was diagnosed in (9.3%) of cases (n = 4). Conclusion: Surgical intervention is very effective if tailored to every patient as per team paln. A multidisciplinary team approach is extremely important especially if an extensive demolition is required. Indeed, radical wide en-bloc resection can achieve satisfactory results provided that the extent of resection is not influenced by any anticipated reconstruction problems

Design and Implementation of Inferential (IQ) Model to Predict i-C4 Percentage and to Save Fuel Gas Consumption in Gas Train De-Propaniser Tower

The main goal of this paper is to present the effect of using reflux to feed ratio as an independent variable in designing a Model-Base Inferential IQ to predict the i-C4 percentage in the top of a DE-Propaniser tower. The addition of this variable is a modification of an existing inferential IQ model with a design, which only uses the De-Propaniser tower top temperature and pressure as independent variables, and has resulted in significant improvements in the prediction of i-C4 percentage, operation and economics of the tower operation

Boosting for Generic 2D/3D Object Recognition

Generic object recognition is an important function of the human visual system. For an artificial vision system to be able to emulate the human perception abilities, it should also be able to perform generic object recognition. In this thesis, we address the generic object recognition problem and present different approaches and models which tackle different aspects of this difficult problem. First, we present a model for generic 2D object recognition from complex 2D images. The model exploits only appearance-based information, in the form of a combination of texture and color cues, for binary classification of 2D object classes. Learning is accomplished in a weakly supervised manner using Boosting. However, we live in a 3D world and the ability to recognize 3D objects is very important for any vision system. Therefore, we present a model for generic recognition of 3D objects from range images. Our model makes use of a combination of simple local shape descriptors extracted from range images for recognizing 3D object categories, as shape is an important information provided by range images. Moreover, we present a novel dataset for generic object recognition that provides 2D and range images about different object classes using a Time-of-Flight (ToF) camera. As the surrounding world contains thousands of different object categories, recognizing many different object classes is important as well. Therefore, we extend our generic 3D object recognition model to deal with the multi-class learning and recognition task. Moreover, we extend the multi-class recognition model by introducing a novel model which uses a combination of appearance-based information extracted from 2D images and range-based (shape) information extracted from range images for multi-class generic 3D object recognition and promising results are obtained

Quantum Dot Infrared Photodetector Fabricated by Pulsed Laser Deposition Technique

Pulsed laser deposition is used to fabricate multilayered Ge quantum-dot photodetector on Si(100). Growth was studied by reflection high-energy electron diffraction and atomic force microscopy. The difference in the current values in dark and illumination conditions was used to measure the device sensitivity to radiation. Spectral responsivity measurements reveal a peak around 2 μm, with responsity that increases three orders of magnitude as bias increases from 0.5 to 3.5 V

An enhanced DC-link voltage response for wind-driven doubly fed induction generator using adaptive fuzzy extended state observer and sliding mode control

This paper presents an enhancement method to improve the performance of the DC-link voltage loop regulation in a Doubly-Fed Induction Generator (DFIG)- based wind energy converter. An intelligent, combined control approach based on a metaheuristics-tuned Second-Order Sliding Mode (SOSM) controller and an adaptive fuzzy-scheduled Extended State Observer (ESO) is proposed and successfully applied. The proposed fuzzy gains-scheduling mechanism is performed to adaptively tune and update the bandwidth of the ESO while disturbances occur. Besides common time-domain performance indexes, bounded limitations on the effective parameters of the designed Super Twisting (STA)-based SOSM controllers are set thanks to the Lyapunov theory and used as nonlinear constraints for the formulated hard optimization control problem. A set of advanced metaheuristics, such as Thermal Exchange Optimization (TEO), Particle Swarm Optimization (PSO), Genetic Algorithm (GA), Harmony Search Algorithm (HSA), Water Cycle Algorithm (WCA), and Grasshopper Optimization Algorithm (GOA), is considered to solve the constrained optimization problem. Demonstrative simulation results are carried out to show the superiority and effectiveness of the proposed control scheme in terms of grid disturbances rejection, closed-loop tracking performance, and robustness against the chattering phenomenon. Several comparisons to our related works, i.e., approaches based on TEO-tuned PI controller, TEO-tuned STA-SOSM controller, and STA-SOSM controller-based linear observer, are presented and discussed

The Effect of Cinnamon versus Atorvastatin on the Submandibular Salivary Gland of Hypercholesterolemic Albino Rats (Histological, Immunohistochemical and Ultrastructural study)

Hypercholesterolemia refers to elevated cholesterol levels in the blood, and statin family compounds are essential synthetic medications for treating this condition. Plant extracts, such as cinnamon, were used to treat various diseases, researchs showing that cinnamon significantly reduces blood triglycerides and total cholesterol while increasing HDL cholesterol levels. Objectives: The present study's goal was to compare the effect of Cinnamon versus Atorvastatin on the submandibular salivary gland of hypercholesterolemic albino rats. Materials and Methods: There were two groups of twenty-eight male albino rats. (1) Control group: rats were kept on a normal diet, (2) Experimental groups: Hypercholesterolemic group: rats fed with hypercholesterolemic rich diet for 4 months, Atorvastatin and Cinnamon groups: rats were given Atorvastatin tablets and Cinnamon powder at the beginning of the third month with a dose of 10 mg/kg BW. and 6mg \ Kg. B.W. respectively. Sections 5 mm thick of the submandibular salivary glands were examined histologically, ultra-structurally, and immunologically through assessment of anti-Caspase Ⅲ immune antibody. Results: The group with high cholesterol showed marked degenerative changes in parenchymal elements of the submandibular salivary gland, while the Atorvastatin and Cinnamon groups showed a marked enhancing effect in the histological structure of the rat’s submandibular gland. Conclusion: Administration of Atorvastatin as a synthetic line of treatment for hypercholesterolemia positively affected submandibular gland tissue and the cholesterol level in the blood. As a natural herbal line of treatment Cinnamon enhanced the histological and ultrastructure picture of the submandibular gland, level of caspase III in addition to blood cholesterol levels in hypercholesteraemic rat