Search results for: resonant transistor tunnels

Authors: Ali Mohammadi

Abstract:

Forming and equipping the surveyors team for construction projects such as dams, roads, and tunnels is always one of the first challenges and hiring surveyors who are proficient in reading maps and controlling structures, purchasing appropriate surveying equipment that the employer can find Also, using methods that can save time, in the bigger the project, the more these challenges show themselves. Finding a surveyor engineer who can lead the teams and train surveyors of the collection and buy TOTAL STATION according to the company's budget and the surveyors' ability to use them and the time available to each team In the following, we will introduce a surveying app and examine how to use it, which shows how useful it can be for surveyors in projects.

Keywords: DTM CUTFILL, datatransfer, section, tunnel, traverse

Procedia PDF Downloads 81

Authors: Wei Yao

Abstract:

A steerable and flexible drill is needed in orthopaedic surgery. For example, osteoarthritis is a common condition affecting millions of people for which joint replacement is an effective treatment which improves the quality and duration of life in elderly sufferers. Conventional surgery is not very accurate. Computer navigation and robotics can help increase the accuracy. For example, In Total Hip Arthroplasty (THA), robotic surgery is currently practiced mainly on acetabular side helping cup positioning and orientation. However, femoral stem positioning mostly uses hand-rasping method rather than robots for accurate positioning. The other case for using a flexible drill in surgery is Anterior Cruciate Ligament (ACL) Reconstruction. The majority of ACL Reconstruction failures are primarily caused by technical mistakes and surgical errors resulting from drilling the anatomical bone tunnels required to accommodate the ligament graft. The proposed new steerable drill system will perform orthopedic surgery through curved tunneling leading to better accuracy and patient outcomes. It may reduce intra-operative fractures, dislocations, early failure and leg length discrepancy by making possible a new level of precision. This technology is based on a robotically assisted, steerable, hand-held flexible drill, with a drill-tip tracking device and a multi-modality navigation system. The critical differentiator is that this robotically assisted surgical technology now allows the surgeon to prepare 'patient specific' and more anatomically correct 'curved' bone tunnels during orthopedic surgery rather than drilling straight holes as occurs currently with existing surgical tools. The flexible and steerable drill and its navigation system for femoral milling in total hip arthroplasty had been tested on sawbones to evaluate the accuracy of the positioning and orientation of femoral stem relative to the pre-operative plan. The data show the accuracy of the navigation system is better than traditional hand-rasping method.

Keywords: navigation, robotic orthopedic surgery, steerable drill, tracking

Procedia PDF Downloads 167

Authors: Ryan Brisbin, Hassan Harb, Justin Debow, Hrant Hratchian, Ryan Baxter

Abstract:

Donor-Acceptor (DA) frameworks are crucial parts of any technology requiring charge transport. This type of behavior is ubiquitous across technologies from semi conductors to solar panels. Currently, most DA systems involve metallic components, but progressive research is being pursued to design fully organic DA systems to be used as both organic semi-conductors and light emitting diodes. These systems are currently comprised of conductive polymers and salts. However, little is known about the effect of various physical aspects (size, torsional angle, electron density) have on the act of reversible charge transfer. Herein, the effect of torsional angle on reductive stability in bis(imino)pyridines is analyzed using a combination of single crystal analysis and electro-chemical peak current ratios from cyclic voltammetry. The computed free energies of reduction and electron attachment points were also investigated through density functional theory and natural ionization orbital theory to gain greater understanding of the global effect torsional angles have on electron transfer in bis(imino)pyridines. Findings indicated that torsional angles are a multi-variable parameter affected by both local steric constraints and resonant electronic contributions. Local steric impacted torsional angles demonstrated a negligible effect on electrochemical reversibility, while resonant affected torsional angles were observed to significantly alter the electrochemical reversibility.

Keywords: cyclic voltammetry, bis(imino)pyridines, structure-activity relationship, torsional angles

Procedia PDF Downloads 237

Authors: Chun-Wei Huang, Jyh-Cherng Gu, Ming-Ta Yang

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Non-synchronous breakage or line failure in power systems with light or no loads can lead to core saturation in transformers or potential transformers. This can cause component and capacitance matching resulting in the formation of resonant circuits, which trigger ferroresonance. This study employed a wavelet transform for the detection of ferroresonance. Simulation results demonstrate the efficacy of the proposed method.

Keywords: ferroresonance, wavelet transform, intelligent electronic device, transformer

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Authors: Simran Baweja, Bhavika Kalal, Surajit Maity

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Photoinduced tautomerization reactions have been the centre of attention among the scientific community over the past several decades because of their significance in various biological systems. 7-azaindole (7AI) is considered a model system for DNA base pairing and to understand the role of such tautomerization reactions in mutations. To the best of our knowledge, extensive studies have been carried out on 7-azaindole and its solvent clusters exhibiting proton/ hydrogen transfer in both solution as well as gas phases. Derivatives of the above molecule, like 2,7- and 2,6-diazaindoles are proposed to have even better photophysical properties due to the presence of -aza group on the 2nd position. However, there are studies in the solution phase that suggest the relevance of these molecules, but there are no experimental studies reported in the gas phase yet. In our current investigation, we present the first gas phase spectroscopic data of 2,7-diazaindole (2,7-DAI) and its solvent cluster (2,7-DAI-H2O). In this, we have employed state-of-the-art laser spectroscopic methods such as fluorescence excitation (LIF), dispersed fluorescence (DF), resonant two-photon ionization-time of flight mass spectrometry (2C-R2PI), photoionization efficiency spectroscopy (PIE), IR-UV double resonance spectroscopy, i.e., fluorescence-dip infrared spectroscopy (FDIR) and resonant ion-dip infrared spectroscopy (IDIR) to understand the electronic structure of the molecule. The origin band corresponding to the S1 ← S0 transition of the bare 2,7-DAI is found to be positioned at 33910 cm-1, whereas the origin band corresponding to S1 ← S0 transition of the 2,7-DAI-H2O is positioned at 33074 cm-1. The red-shifted transition in the case of solvent cluster suggests the enhanced feasibility of excited state hydrogen/ proton transfer. The ionization potential for the 2,7-DAI molecule is found to be 8.92 eV which is significantly higher than the previously reported 7AI (8.11 eV) molecule, making it a comparatively complex molecule to study. The ionization potential is reduced by 0.14 eV in the case of 2,7-DAI-H2O (8.78 eV) cluster compared to that of 2,7-DAI. Moreover, on comparison with the available literature values of 7AI, we found the origin band of 2,7-DAI and 2,7-DAI-H2O to be red-shifted by -729 and -280 cm-1 respectively. The ground and excited state N-H stretching frequencies of the 27DAI molecule were determined using fluorescence-dip infrared spectra (FDIR) and resonant ion dip infrared spectroscopy (IDIR), obtained at 3523 and 3467 cm-1, respectively. The lower value of vNH in the electronically excited state of 27DAI implies the higher acidity of the group compared to the ground state. Moreover, we have done extensive computational analysis, which suggests that the energy barrier in the excited state reduces significantly as we increase the number of catalytic solvent molecules (S= H2O, NH3) as well as the polarity of solvent molecules. We found that the ammonia molecule is a better candidate for hydrogen transfer compared to water because of its higher gas-phase basicity. Further studies are underway to understand the excited state dynamics and photochemistry of such N-rich chromophores.

Keywords: excited state hydrogen transfer, supersonic expansion, gas phase spectroscopy, IR-UV double resonance spectroscopy, laser induced fluorescence, photoionization efficiency spectroscopy

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Authors: Ali Mohammadi

Abstract:

The basis for the construction of any project is a map, a map where the surveyor can determine the coordinates of the points on the ground by using the coordinates and using the total station, projects such as dams, roads, tunnels and pipelines, if the base points are determined using GPS prepared can create challenges for the surveyor to control. First, we will examine some map projection on which the maps are designed, and a summary of their differences and the challenges that surveyors face in order to control them, because in order to build projects, we need real lengths and angles, so we have to use coordinates that provide us with the results of the calculations. We will examine some examples to understand the concept of localization so that the surveyor knows if he is facing a challenge or not and if he is faced with this challenge, how should he solve this problem.

Keywords: UTM, scale factor, cartesian, traverse

Procedia PDF Downloads 81

Authors: Hamid Fallah

Abstract:

Creating surveying stations is the first thing that a surveyor learns; they can use it for control and implementation in projects such as buildings, roads, tunnels, monitoring, etc., whatever is related to the preparation of maps. In this article, the method of calculation through the traverse table and by checking several examples of errors of several publishers of surveying books in the calculations of this table, we also control the results of several software in a simple way. Surveyors measure angles and lengths in creating surveying stations, so the most important task of a surveyor is to be able to correctly remove the error of angles and lengths from the calculations and to determine whether the amount of error is within the permissible limit for delete it or not.

Keywords: UTM, localization, scale factor, cartesian, traverse

Procedia PDF Downloads 82

Authors: Nuruddin Mohammod Zahangir, Syed Tanvir Ahmady, Firoz Ahmed, Mainul Kabir, Tamjid Mohammad Najmus Sakib Khan, Nazmul Hossain, Niaz Ahmed, Madhava Janardhan Naik

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The management of combined Coronary Artery Disease and Peripheral Vascular Disease is a challenge and brings with it numerous clinical dilemmas.The 56 year old gentleman presented to our department with significant triple vessel disease with occluded lower end of aorta just before bifurcation and bilateral superficial femoral arteries. Operation was done on 11.03.14. The The Left Internal Mammary Artery (LIMA) and the Right Internal Mammary Artery (RIMA) were harvested in skeletonized manner. The free RIMA was then anastomosed with LIMA to make LIMA-RIMA Y. Cardio Pulmonary Bypass was then established and coronary artery bypass grafts performed. LIMA was anastomosed to the Left Anterior Descending artery. RIMA was anastomosed to Posterior Descending Artery, 1st and 2nd Obtuse Marginal arteries in a sequential manner. Abdomen was opened by midline incision. The infrarenal aorta exposed and was found to be severely diseased. A Vascular Clamp was applied infrarenally, aortotomy done and limited endarterectomy performed. An end-to-side anastomosis was done with upper end of PTFE synthetic Y-graft (14/7 mm) to the infarenal Aorta and the Clamp released. Good flow noted in both limbs of the graft. Patient was then slowly weaned off from Cardio Pulmonary Bypass without difficulty. The distal two limbs of the Y graft were passed to the groin through retroperitoneal tunnels and anastomosed end-to-side with the common femoral arteries. Saphenous vein was interposed between common femoral and popliteal arteries bilaterally through subfascial tunnels in both thigh. On 12th postoperative day he was discharged from hospital in good general condition. Follow up after 3 months of operation the patient is doing good and free of chest pain and claudication pain.

Keywords: total arterial, coronary revascularization, aorto-bifemoral bypass, bifemoro-bipopliteal bypass

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Authors: Petr Vaculik

Abstract:

The newest semiconductor devices on the market are MOSFET transistors based on the silicon carbide – SiC. This material has exclusive features thanks to which it becomes a better switch than Si – silicon semiconductor switch. There are some special features that need to be understood to enable the device’s use to its full potential. The advantages and differences of SiC MOSFETs in comparison with Si IGBT transistors have been described in first part of this article. Second part describes driver for SiC MOSFET transistor and last part of article represents SiC MOSFET in the application of buck converter (step-down) and design of simple RC snubber.

Keywords: SiC, Si, MOSFET, IGBT, SBD, RC snubber

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Authors: Lekshmi Vijayan, K. Shreekrishna Kumar

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We demonstrated an organic field effect transistor based photodetector using phthalocyanine as the active material that exhibited high photosensitivity under varying light wavelengths. The thermally grown SiO₂ layer on silicon wafer act as a substrate. The critical parameters, such as photosensitivity, responsivity and detectivity, are comparatively high and were 3.09, 0.98AW⁻¹ and 4.86 × 10¹⁰ Jones, respectively, under a bias of 5 V and a monochromatic illumination intensity of 4mW cm⁻². The photodetector has a linear I-V curve with a low dark current. On comparing photoresponse of copper phthalocyanine at four different wavelengths, 560 nm shows better photoresponse and the highest value of photosensitivity is also obtained.

Keywords: photodetector, responsivity, photosensitivity, detectivity

Procedia PDF Downloads 178

Authors: Jin-Siang Shaw, Patricia Moya Caceres, Sheng-Xiang Xu

Abstract:

This paper aims to integrate the particle swarm optimization (PSO) method with the adaptive fuzzy sliding mode controller (AFSMC) to achieve vibration attenuation in a piezoelectric actuator subject to base excitation. The piezoelectric actuator is a complicated system made of ferroelectric materials and its performance can be affected by nonlinear hysteresis loop and unknown system parameters and external disturbances. In this study, an adaptive fuzzy sliding mode controller is proposed for the vibration control of the system, because the fuzzy sliding mode controller is designed to tackle the unknown parameters and external disturbance of the system, and the adaptive algorithm is aimed for fine-tuning this controller for error converging purpose. Particle swarm optimization method is used in order to find the optimal controller parameters for the piezoelectric actuator. PSO starts with a population of random possible solutions, called particles. The particles move through the search space with dynamically adjusted speed and direction that change according to their historical behavior, allowing the values of the particles to quickly converge towards the best solutions for the proposed problem. In this paper, an initial set of controller parameters is applied to the piezoelectric actuator which is subject to resonant base excitation with large amplitude vibration. The resulting vibration suppression is about 50%. Then PSO is applied to search for an optimal controller in the neighborhood of this initial controller. The performance of the optimal fuzzy sliding mode controller found by PSO indeed improves up to 97.8% vibration attenuation. Finally, adaptive version of fuzzy sliding mode controller is adopted for further improving vibration suppression. Simulation result verifies the performance of the adaptive controller with 99.98% vibration reduction. Namely the vibration of the piezoelectric actuator subject to resonant base excitation can be completely annihilated using this PSO based adaptive fuzzy sliding mode controller.

Keywords: adaptive fuzzy sliding mode controller, particle swarm optimization, piezoelectric actuator, vibration suppression

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Authors: A.N. Moulay Khatir, A. Guen-Bouazza, B. Bouazza

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SOI-Multifin-FET shows excellent transistor characteristics, ideal sub-threshold swing, low drain induced barrier lowering (DIBL) without pocket implantation and negligible body bias dependency. In this work, we analyzed this combination by a three-dimensional numerical device simulator to investigate the influence of fins number on corner effect by analyzing its electrical characteristics and potential distribution in the oxide and the silicon in the section perpendicular to the flow of the current for SOI-single-fin FET, three-fin and five-fin, and we provide a comparison with a Trigate SOI Multi-FinFET structure.

Keywords: SOI, FinFET, corner effect, dual-gate, tri-gate, Multi-Fin FET

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Authors: Azizi Cherifa, O. Benzaoui

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The thermal aspects in the design of power circuits often deserve as much attention as pure electric components aspects as the operating temperature has a direct influence on their static and dynamic characteristics. MOSFET is fundamental in the circuits, it is the most widely used device in the current production of semiconductor components using their honorable performance. The aim of this contribution is devoted to the effect of the temperature on the properties of MOSFETs. The study enables us to calculate the drain current as function of bias in both linear and saturated modes. The effect of temperature is evaluated using a numerical simulation, using the laws of mobility and saturation velocity of carriers as a function of temperature.

Keywords: temperature, MOSFET, mobility, transistor

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Authors: Samaniego Campoverde José Enrique, Rosero Muñoz Jorge Enrique, Luzcando Narea Lorena Elizabeth

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This paper presents a practical and theoretical model for the operation of the Tesla coil using digital signal processing. The research is based on the analysis of ten scientific papers exploring the development and operation of the Tesla coil. Starting from the Testa coil, several modifications were carried out on the Tesla coil, with the aim of amplifying the digital signal by making use of digital signal processing. To achieve this, an amplifier with a transistor and digital filters provided by MATLAB software were used, which were chosen according to the characteristics of the signals in question.

Keywords: tesla coil, digital signal process, equalizer, graphical environment

Procedia PDF Downloads 117

Authors: Ayanori Sugiyama, Takahisa Hanei, Yasuhide Higo

Abstract:

Domestic demand for the construction of tunnels has been increasing in recent years in Japan. To meet this demand, various construction materials and construction methods have been developed to attain higher strength, reduction of negative impact on the environment and improvement for working conditions. In this report, we would like to introduce the newly developed shotcrete with superior hardening properties which were tested through the actual machine scale and its workability and strength development were evaluated. As a result, this new tunnel construction method was found to achieve higher workability and quicker strength development in only a couple of minutes.

Keywords: accelerator, shotcrete, tunnel, high-strength

Procedia PDF Downloads 318

Authors: Anwar H. Jarndal, Ahmed S. Elwakil

Abstract:

In this paper, a fraction-order model for pad parasitic effect of GaN HEMT on Si substrate is developed and validated. Open de-embedding structure is used to characterize and de-embed substrate loading parasitic effects. Unbiased device measurements are implemented to extract parasitic inductances and resistances. The model shows very good simulation for S-parameter measurements under different bias conditions. It has been found that this approach can improve the simulation of intrinsic part of the transistor, which is very important for small- and large-signal modeling process.

Keywords: fractional-order modeling, GaNHEMT, si-substrate, open de-embedding structure

Procedia PDF Downloads 356

Authors: J. Das, T. S. Mahule, V. V. Srinivasu

Abstract:

Electron spin resonance (ESR) study at 9.45 GHz and a field modulation frequency of 100Hz was performed on bulk polycrystalline samples of Mn:TM (Fe/Ni) and Mn:RE (Gd/Sm) co doped ZnO samples with composition Zn1-xMn:TM/RE)xO synthesised by solid state reaction route and sintered at 500 0C temperature. The room temperature microwave absorption data collected by sweeping the DC magnetic field from -500 to 9500 G for the Mn:Fe and Mn:Ni co doped ZnO samples exhibit a rarely reported non resonant low field absorption (NRLFA) in addition to a strong absorption at around 3350G, usually associated with ferromagnetic resonance (FMR) satisfying Larmor’s relation due to absorption in the full saturation state. Observed low field absorption is distinct to ferromagnetic resonance even at low temperature and shows hysteresis. Interestingly, it shows a phase opposite with respect to the main ESR signal of the samples, which indicates that the low field absorption has a minimum value at zero magnetic field whereas the ESR signal has a maximum value. The major resonance peak as well as the peak corresponding to low field absorption exhibit asymmetric nature indicating magnetic anisotropy in the sample normally associated with intrinsic ferromagnetism. Anisotropy parameter for Mn:Ni codoped ZnO sample is noticed to be quite higher. The g values also support the presence of oxygen vacancies and clusters in the samples. These samples have shown room temperature ferromagnetism in the SQUID measurement. However, in rare earth (RE) co doped samples (Zn1-x (Mn: Gd/Sm)xO), which show paramagnetic behavior at room temperature, the low field microwave signals are not observed. As microwave currents due to itinerary electrons can lead to ohmic losses inside the sample, we speculate that more delocalized 3d electrons contributed from the TM dopants facilitate such microwave currents leading to the loss and hence absorption at the low field which is also supported by the increase in current with increased micro wave power. Besides, since Fe and Ni has intrinsic spin polarization with polarisability of around 45%, doping of Fe and Ni is expected to enhance the spin polarization related effect in ZnO. We emphasize that in this case Fe and Ni doping contribute to polarized current which interacts with the magnetization (spin) vector and get scattered giving rise to the absorption loss.

Keywords: co-doping, electron spin resonance, hysteresis, non-resonant microwave absorption

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Authors: Djelloul Chafia, Demagh Rafik, Kareche Toufik

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Human activities, made without precautions, accelerate the degradation of the soil structure and reduces its resistance. Operations, such as tunnel construction may exercise an influence more or less permanent on the grounds which surrounded them, these structures alter soil it is necessary to predict their impacts by suitable measures. This research is a numerical analysis that deals the risks and effects due to the weakening of the soil after digging two parallel vertical circular tunnels in urban areas, and suggests forecasting techniques based essentially on the organization of underground space. The simulations are performed using the finite-difference code FLAC in a two-dimensional case and with an elasto-plastic behavior of the soil.

Keywords: sol, weakening, degradation, prevention, tunnel

Procedia PDF Downloads 557

Authors: Entfellner Manuel, Wannenmacher Helmut, Reisenbauer Josef, Schubert Wulf

Abstract:

When tunnelling in overstressed weak rocks ("squeezing ground"), two basic design approaches are available: the resistance principle, and the yielding principle. The resistance principle relies on rigid support systems to withstand the ground pressure. Alternatively, the yielding principle prioritizes controlled deformation, allowing the ground to deform without compromising tunnel integrity. This paper highlights the beneficial factors of the yielding principle for conventionally excavated tunnels in overstressed weak rocks. Especially the application of a ductile shotcrete lining with yielding elements is analysed in detail. Construction costs, safety, short- and long-term stabilities are discussed.

Keywords: squeezing ground, yielding principle, yielding element, conventional tunneling

Procedia PDF Downloads 71

Authors: Mourad Hrizi

Abstract:

In this paper, we study the inverse problem of reconstructing an interior interface D appearing in the elliptic partial differential equation: Δu+χ(D)u=0 from the knowledge of the boundary measurements. This problem arises from a semiconductor transistor model. We propose a new shape reconstruction procedure that is based on the Kohn-Vogelius formulation and the topological sensitivity method. The inverse problem is formulated as a topology optimization one. A topological sensitivity analysis is derived from a function. The unknown subdomain D is reconstructed using a level-set curve of the topological gradient. Finally, we give several examples to show the viability of our proposed method.

Keywords: inverse problem, topological optimization, topological gradient, Kohn-Vogelius formulation

Procedia PDF Downloads 244

Authors: Shankha Sanyal, Archi Banerjee, Sayan Biswas, Sourya Sengupta, Sayan Nag, Ranjan Sengupta, Dipak Ghosh

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The term ‘gestalt’ has been widely used in the field of psychology which defined the perception of human mind to group any object not in part but as a 'unified' whole. Music, in general, is polyphonic - i.e. a combination of a number of pure tones (frequencies) mixed together in a manner that sounds harmonious. The study of human brain response due to different frequency groups of the acoustic signal can give us an excellent insight regarding the neural and functional architecture of brain functions. Hence, the study of music cognition using neuro-biosensors is becoming a rapidly emerging field of research. In this work, we have tried to analyze the effect of different frequency bands of music on the various frequency rhythms of human brain obtained from EEG data. Four widely popular Rabindrasangeet clips were subjected to Wavelet Transform method for extracting five resonant frequency bands from the original music signal. These frequency bands were initially analyzed with Detrended/Adaptive Fractal analysis (DFA/AFA) methods. A listening test was conducted on a pool of 100 respondents to assess the frequency band in which the music becomes non-recognizable. Next, these resonant frequency bands were presented to 20 subjects as auditory stimulus and EEG signals recorded simultaneously in 19 different locations of the brain. The recorded EEG signals were noise cleaned and subjected again to DFA/AFA technique on the alpha, theta and gamma frequency range. Thus, we obtained the scaling exponents from the two methods in alpha, theta and gamma EEG rhythms corresponding to different frequency bands of music. From the analysis of music signal, it is seen that loss of recognition is proportional to the loss of long range correlation in the signal. From the EEG signal analysis, we obtain frequency specific arousal based response in different lobes of brain as well as in specific EEG bands corresponding to musical stimuli. In this way, we look to identify a specific frequency band beyond which the music becomes non-recognizable and below which in spite of the absence of other bands the music is perceivable to the audience. This revelation can be of immense importance when it comes to the field of cognitive music therapy and researchers of creativity.

Keywords: AFA, DFA, EEG, gestalt in music, Hurst exponent

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Authors: Mehdi Saeidmanesh, Razali Ismail

Abstract:

Recently, Graphene Nanoribbon Field Effect Transistors (GNR FETs) attract a great deal of attention due to their better performance in comparison with conventional devices. In this paper, channel length Modulation (CLM) effect on the electrical characteristics of GNR FETs is analytically studied and modeled. To this end, the special distribution of the electric potential along the channel and current-voltage characteristic of the device is modeled. The obtained results of analytical model are compared to the experimental data of published works. As a result, it is observable that considering the effect of CLM, the current-voltage response of GNR FET is more realistic.

Keywords: graphene nanoribbon, field effect transistors, short channel effects, channel length modulation

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Authors: Yih-Chien Chen, Yu-Cheng You

Abstract:

The microwave dielectric properties of La2MoO6 ceramics were investigated with a view to their application in mobile communication. La2MoO6 ceramics were prepared by the conventional solid-state method with various sintering conditions. The X-ray diffraction peaks of La2MoO6 ceramic did not vary significantly with sintering conditions. The average grain size of La2MoO6 ceramics increased as the temperature and time of sintering increased. A maximum density of 5.67 g/cm3, a dielectric constants (εr) of 14.1, a quality factor (Q×f) of 68,000 GHz, and a temperature coefficient of resonant frequency (τf) of -56 ppm/℃ were obtained when La2MoO6 ceramics that were sintered at 1300 ℃ for 4h.

Keywords: ceramics, sintering, microwave dielectric properties, La2MoO6

Procedia PDF Downloads 291

Authors: Vishwajit Ghatge, David Looper

Abstract:

Over the last few decades, oilfield service rolling equipment has significantly increased in weight, primarily because of emissions regulations, which require larger/heavier engines, larger cooling systems, and emissions after-treatment systems, in some cases, etc. Larger engines cause more vibration and shock loads, leading to failure of electronics and control systems. If the vibrating frequency of the engine matches the system frequency, high resonance is observed on structural parts and mounts. One such existing automated control equipment system comprising wire rope mounts used for mounting computers was designed approximately 12 years ago. This includes the use of an industrial- grade computer to control the system operation. The original computer had a smaller, lighter enclosure. After a few years, a newer computer version was introduced, which was 10 lbm heavier. Some failures of internal computer parts have been documented for cases in which the old mounts were used. Because of the added weight, there is a possibility of having the two brackets impact each other under off-road conditions, which causes a high shock input to the computer parts. This added failure mode requires validating the existing mount design to suit the new heavy-weight computer. This paper discusses the modal finite element method (FEM) analysis and experimental modal analysis conducted to study the effects of vibration on the wire rope mounts and the computer. The existing mount was modelled in ANSYS software, and resultant mode shapes and frequencies were obtained. The experimental modal analysis was conducted, and actual frequency responses were observed and recorded. Results clearly revealed that at resonance frequency, the brackets were colliding and potentially causing damage to computer parts. To solve this issue, spring mounts of different stiffness were modeled in ANSYS software, and the resonant frequency was determined. Increasing the stiffness of the system increased the resonant frequency zone away from the frequency window at which the engine showed heavy vibrations or resonance. After multiple iterations in ANSYS software, the stiffness of the spring mount was finalized, which was again experimentally validated.

Keywords: experimental modal analysis, FEM Modal Analysis, frequency, modal analysis, resonance, vibration

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Authors: N. Massoum, B. Bouazza

Abstract:

In this paper, we have developed a numerical simulation model to describe the electrical properties of GaInP MESFET with submicron gate (Lg = 0.5 µm). This model takes into account the three-dimensional (3D) distribution of the load in the short channel and the law effect of mobility as a function of electric field. Simulation software based on a stochastic method such as Monte Carlo has been established. The results are discussed and compared with those of the experiment. The result suggests experimentally that, in a very small gate length in our devices (smaller than 40 nm), short-channel tunneling explains the degradation of transistor performance, which was previously enhanced by velocity overshoot.

Keywords: Monte Carlo simulation, transient electron transport, MESFET device, simulation software

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Authors: A. boursali, A. Guen Bouazza, M. Khaouani, Z. Kourdi, B. Bouazza

Abstract:

This paper presents the design, development and characterization of the devices simulation for X-Band Radar applications. The effect of an InAlN/GaN structure on the RF performance High Electron Mobility Transistor (HEMT) device. Systematic investigations on the small signal as well as power performance as functions of the drain biases are presented. Were improved for X-band applications. The Power Added Efficiency (PAE) was achieved over 23% for X-band. The developed devices combine two InAlN/GaN HEMTs of 30nm gate periphery and exhibited the output power of over 50W. An InAlN/GaN HEMT with 30nm gate periphery was developed and exhibited the output power of over 120W.

Keywords: InAlN/GaN, HEMT, RF analyses, PAE, X-Band, radar

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Authors: F. Bendahma, S. Bentata, S. Cherid, A. Zitouni, S. Terkhi, T. Lantri, Y. Sefir, Z. F. Meghoufel

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We examine the electronic transport properties in Al_xGa_1-xAs/GaAs superlattices. Using the transfer-matrix technique and the exact Airy function formalism, we investigate theoretically the effect of structural parameters on the electronic energy spectra of trimer thickness barrier (TTB). Our numerical calculations showed that the localization length of the states becomes more extended when the disorder is correlated (trimer case). We have also found that the resonant tunneling time (RTT) is of the order of several femtoseconds.

Keywords: electronic transport properties, structural parameters, superlattices, transfer-matrix technique

Procedia PDF Downloads 285

Authors: Oussema Tabbabi, Mondher Laabidi, Fethi Choubani, J. David

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This study presents a miniaturized antenna based on chiral metamaterials slotted ground plane. To decrease resonant frequency while keeping the antennas physical dimensions the same, we propose a two novel patch antennas with double Z and cross slots on the ground plane. The length of the each type of slot are also altered to investigate the effect on miniaturization performance. Resonance frequency reduction has been achieved nearly to 30% and 23% as well as size reduction of almost 28% and 22% for the double Z and the cross shape respectively.

Keywords: chiral metamaterials, miniaturized antenna, miniaturization, resonance frequency

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Authors: Emiliano Matta

Abstract:

Passive resonant vibration absorbers are among the most widely used dynamic control systems in civil engineering. They typically consist in a single-degree-of-freedom mechanical appendage of the main structure, tuned to one structural target mode through frequency and damping optimization. One classical scheme is the pendulum absorber, whose mass is constrained to move along a curved trajectory and is damped by viscous dashpots. Even though the principle is well known, the search for improved arrangements is still under way. In recent years this investigation inspired a type of bidirectional pendulum absorber (BPA), consisting of a mass constrained to move along an optimal three-dimensional (3D) concave surface. For such a BPA, the surface principal curvatures are designed to ensure a bidirectional tuning of the absorber to both principal modes of the main structure, while damping is produced either by horizontal viscous dashpots or by vertical friction dashpots, connecting the BPA to the main structure. In this paper, a variant of BPA is proposed, where damping originates from the variable tangential friction force which develops between the pendulum mass and the 3D surface as a result of a spatially-varying friction coefficient pattern. Namely, a friction coefficient is proposed that varies along the pendulum surface in proportion to the modulus of the 3D surface gradient. With such an assumption, the dissipative model of the absorber can be proven to be nonlinear homogeneous in the small displacement domain. The resulting homogeneous BPA (HBPA) has a fundamental advantage over conventional friction-type absorbers, because its equivalent damping ratio results independent on the amplitude of oscillations, and therefore its optimal performance does not depend on the excitation level. On the other hand, the HBPA is more compact than viscously damped BPAs because it does not need the installation of dampers. This paper presents the analytical model of the HBPA and an optimal methodology for its design. Numerical simulations of single- and multi-story building structures under wind and earthquake loads are presented to compare the HBPA with classical viscously damped BPAs. It is shown that the HBPA is a promising alternative to existing BPA types and that homogeneous tangential friction is an effective means to realize systems provided with amplitude-independent damping.

Keywords: amplitude-independent damping, homogeneous friction, pendulum nonlinear dynamics, structural control, vibration resonant absorbers

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Authors: Peng Li, Er-xiang Song

Abstract:

Numerical analysis of longitudinal tunnel seismic response due to spatial variation of earthquake ground motion is an important issue that cannot be ignored in the design and safety evaluation of tunnel structures. In this paper, numerical methods for analysis of tunnel longitudinal response under asynchronous seismic wave is extensively studied, including the improvement of the 1D time-domain finite element method, three dimensional numerical simulation technique for the site asynchronous earthquake response as well as the 3-D soil-tunnel structure interaction analysis. The study outcome will be beneficial to aid further research on the nonlinear meticulous numerical analysis and seismic response mechanism of tunnel structures under asynchronous earthquake motion.

Keywords: asynchronous input, longitudinal seismic response, tunnel structure, numerical simulation, traveling wave effect

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