Top PDF Development of micro-electromechanical systems in GaN

Development of micro-electromechanical systems in GaN

Development of micro-electromechanical systems in GaN

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ABSTRACT: Micro-electromechanical Systems technology addresses to the most innovative features. MEMS based

ABSTRACT: Micro-electromechanical Systems technology addresses to the most innovative features. MEMS based

A general purpose 40 pin 89C51 development board with on board power supply circuit, and reset switch, power status LED and a general purpose switch and LED. The board is compatible with the AT89S51/52 and the P89V51RD2 microcontrollers. The P89V51RD2 allows serial programming and can be programmed directly with this board through a serial connection to a PC without the need for an additional external programmer. This board is perfect if you are just starting out with 89C51 programming and also if you want a reliable tried and tested board for building advanced projects based on it.
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Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

Strain relaxation in InGaN/GaN micro-pillars evidenced by high resolution cathodoluminescence hyperspectral imaging

In summary, the high resolution CL hyperspectral imag- ing technique has been used to investigate the strain relaxa- tion in InGaN/GaN MQW micro-pillars with diameters ranging from 2 to 150 lm. The epitaxial MQW material studied was optimized for fabricating LEDs emitting in the yellow-green and included electron reservoir layers. These CL maps measured the detailed distributions in the QW emission wavelength attributable to changes in strain, as well as to intrinsic QW inhomogeneities. Peak emission wavelengths as a function of position have been calculated using finite element strain simulations and solution of the Schro¨dinger equation with appropriately chosen piezoelec- tric fields. The significant blue-shifts observed at the edge of the pillars are due to the partial relaxation of compressive strain in the QWs. This blue-shift and its ring shape distribu- tion could be observed even when the pillar diameter is larger than 30 lm. With decreasing pillar size, the maximum blue-shift at the pillar edge and the ratio of this maximum blue-shift region to the whole pillar area, are both increased. Moreover, a significant global blue-shift persisting to the pil- lar centre is also observed for the small pillars. Simulated spectral shifts agree well with the experimental CL results when the strained nature of the GaN buffer layer is taken account. No previous studies, to our knowledge, have reported the comparisons between simulated spectral shifts and experimental measurements for such a wide range of pil- lar diameters. The results of this study are directly relevant to the further technological development of micro/nano-LED array devices, in particular predicting significant effects from strain relaxation for LED diameters below 30 lm.
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Study on ultra-high sensitivity piezoelectric effect of GaN micro/nano columns

Study on ultra-high sensitivity piezoelectric effect of GaN micro/nano columns

With the development of wearables and electronic skin in recent years, it is an urgent need to improve the perfor- mance of sensors and power supply devices while reduc- ing their sizes. So that high efficiency energy transduction methods, which can convert the human body activities into electric signal, are explored widely. Of varied meth- ods, piezoelectric effect has been studied a lot as one of the major branches of nanogenerators and nanosensors for its excellent performance. For example, ZnO nanow- ires have been proven to be very effective in collecting mechanical energy at the micro/nano scale, and they are also well tolerated, highly efficient, and biocompatible [1]. Earlier researches on the piezoelectric properties of ZnO nanowires were led by Wang’ group [2]. It is believed that due to the strong piezoelectric effect of ZnO, the contact potential between the nanowire and the silver gel changes when the stress is applied. Therefore, the I–V character- istics change accordingly. And they verified the theo- retical expectations by atomic force microscopy (AFM)
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A Feasibility Study on Embedded Micro Electromechanical Sensors and Systems (MEMS) for Monitoring Highway Structures

A Feasibility Study on Embedded Micro Electromechanical Sensors and Systems (MEMS) for Monitoring Highway Structures

Figure 10. Crossbow base station (Crossbow Technology, Inc. 2007) Crossbow has a large selection of different types of sensor systems. This versatility is an advantage in SHM. There are many different attributes that need to be measured in a structure and this system has the capability to measure many of the structure’s properties, while keeping all of the sensors on the same network. Individuals monitoring the roads or structure will be able to access real-time data remotely. As more research and development is done, it’s possible that the size of these sensors will become smaller, which will allow for many other applications. Sensicast
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Modelling and parameter identification of electromechanical systems for energy harvesting and sensing

Modelling and parameter identification of electromechanical systems for energy harvesting and sensing

Electromechanical systems are a fundamental component of a wide class of devices, such as actu- ators, sensors, controllers, motors and transducers. Several recent scientific researches about elec- tromechanical systems are also focused on energy harvesting technologies with the aim to convert mechanical vibrations into electrical energy, thereby facilitating the development of small electronic autonomous apparatuses [20, 29]. To achieve this result, several prototypes have been built in the last years based on thermoelectric, electromagnetic, pyroelectric, triboelectric and piezoelectric effects [44]. The length of these devices range from the nanoscale to the microscale, up to the macroscale. In this framework, advanced modelling and experimental characterization of the dy- namic response are important to enhance the electromechanical systems performances. A reliable modelling is one of the main task in order to predict the response of complex intelligent materials and structures, given external loads and boundary conditions [13]. Furthermore, the continuous growth of the complexity in smart, micro and nano electromechanical devices calls for multiphysics and multiscale numerical simulations [45, 46, 47]. At the same time, experimental data are essen- tial to assess the reliability of the model predictions. Given the model and the experimental data, dynamic system identification can be accomplished.
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Micro Transportation Systems: A Review

Micro Transportation Systems: A Review

In solid-based transportation systems, objects directly con- tact with the solid actuators to receive the motion. Much work on these systems has been reported. In 2-D trans- portation system based on ciliary motion, objects were elevated and moved by the ciliary type thermal actuator arrays [7-14] or by permalloy magnetic actuator arrays [15] underneath. In array-driven ultrasonic micro-actua- tors [16], objects were conveyed by ultrasonic swing of the pillars array beneath. XY-plane transportation systems based on surface acoustic waves in piezoelectric substrate [17,18], 2-D micro conveyor based on electrostatic ac- tuator [19,20], inchworm motors with bidirectional XY electrostatic actuators [21,22] or transportation system based on vibrations of a slider combined with wedge me- chanism [23], etc.
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PSS for various electromechanical

PSS for various electromechanical

Abstract— Power systems stabilizers (PSS) are very effective for damping oscillation due to occurring disturbances and keeping synchronism in excitation circuits of synchronous generators. Design and tuning of PSS are crucial issues for researchers involved in the development of power systems control . It is because of inaccurate setting of PSS that not only it causes damping oscillations but it also contributes to the amplification of instability leading to the loss of synchronism. In this paper, an optimum PSS is designed using a novel method called combinatorial discrete and continuous action reinforcement learning automata (CDCARLA). The proposed method is implemented for a single machine-infinite bus (SMIB) and it is compared with an IEEE standard PSS. Simulation results show that the proposed PSS has a significantly better performance as well as satisfactory robustness compared to the standard PSS. The advantage of CDCARLA is that it does not need system dynamics or any other information on power system. It can be said that, this method utlizes nonlinear features of power system. The CDCARLA method can be considered as one of the automatic design techniques using PSS.
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Electromechanical Actuator Development for Integrated Chatter Prediction on High Speed Machining Centers

Electromechanical Actuator Development for Integrated Chatter Prediction on High Speed Machining Centers

Researchers at the National Institute of Standards and Technology (NIST) [5] have devised a passive actuation technique to enable automated prediction of machine tool chatter (Figure 2.7). Their implementation of this technique uses a permanent magnet (PM) to create force excitations on the machine structure. The PM is situated near the tip of the rotating tool to impart magnetic forces as each tooth passes. This creates a train of synchronous excitation forces as the spindle speed is ramped from rest to its maximum speed. This approach simulates the swept sine force profile of an electromechanical shaker, but has the advantage of avoiding mass-loading the tool/spindle/machine structure. The NIST PM implementation also promises the advantage of relatively easy setup and application since no special skills or testing expertise are required. This excitation method is especially beneficial when compared to the impact hammer method for testing tools with longer overhangs where it is particularly difficult to make a clean hit and avoid multiple impacts. Impact hammer testing is discussed in detail in section 3.2.
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Modal Analysis of Micro-Electromechanical Systems

Modal Analysis of Micro-Electromechanical Systems

In the present study, effects of ambient pressures, effects of this pressure over gap heights of a micro cantilevers array and effects of substrate materials are studied. Modal Analysis and Transient Analysis are performed in Ansys Workbench to obtain the natural frequencies of the MC Array and FRF curves for two models having difference in their substrate materials. These natural frequencies provided with a direct comparison of sensitivity of two models while FRF curves are analyzed to obtain damping ratios and quality factors of both models. A comparison of damping ratios and quality factor has been made between two models to check for the more sensitive model on these ambient pressures.
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On-chip GaN-based dual-color micro-LED arrays and their application in visible light communication

On-chip GaN-based dual-color micro-LED arrays and their application in visible light communication

The interest in gallium nitride (GaN)-based micron-sized light emitting diodes (micro-LEDs), of lateral dimension smaller than 100 µm, has increased dramatically in recent years [1]. GaN-based micro-LEDs offer exceptional brightness, contrast, fast response time, long operation lifetime, and low power consumption, which have facilitated their application in several fields, such as microdisplays [2–4], visible light communication (VLC) [5,6], fluorescence sensing [7], and optoelectronic tweezing [8]. Despite the huge success of monochromatic GaN-based micro LED with different configurations for the aforementioned applications, a general thread common to many applications is the desire for different color micro-emitters on a single chip platform. Multi-color emission can be achieved by using color converters to downshift the GaN-based micro-LED blue emission to longer wavelengths. However, due to the color converters’ lower efficiency, slow response time, and short lifespan, this solution is unsuitable for many applications [3]. Although possible [9–11], the growth of highly efficient inorganic red, green, and blue emitting materials on a single wafer is still in its early stages and is extremely challenging. As, currently, highly efficient blue and green emitting LED structures are GaN-based, while efficient red emitters are aluminum gallium indium phosphide-based [12]. An alternative is to fabricate blue, green, and red emitting micro-LEDs on their respective growth wafers and then transfer the three different color emitting micro-LEDs onto a common substrate. Conventional assembly techniques, relying on robotic systems for placement of materials mechanically diced from a source wafer onto a common platform, are incapable of handling ultrasmall micro-LEDs
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Planar micro- and nano-patterning of GaN light-emitting diodes : guidelines and limitations

Planar micro- and nano-patterning of GaN light-emitting diodes : guidelines and limitations

eV , e is the elementary charge and V the voltage applied to the diode. It should be noted that this voltage V is actually a bit lower than the voltage applied to a real device because the contact resistivities are ignored. Spa- tial variation of V due to the resistivity of the spreading layer is assumed to be negligible for very small patterns as considered here. Planar approaches can typically be understood by simply assuming a patterned p-contact area. This is even true for techniques (such as localized plasma-treatment) that change the electrical properties of the p-GaN because the present understanding is that the p-GaN is only affected in a very thin layer (an order of magnitude thinner than the p-GaN thickness) directly at the top-surface 9 .
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Active-matrix GaN micro light-emitting diode display with unprecedented brightness

Active-matrix GaN micro light-emitting diode display with unprecedented brightness

High brightness CMOS-controlled microdisplays can be made on the basis of GaN flip-chip micro-LEDs. Limiting factors to the achievable luminance include the current handling capability of the control electronics, the current distribution within the LED structure and thermal management. In particular, it is demonstrated that careful LED design toward optimal current distribution in the n-GaN layer is crucial for obtaining the highest possible display luminance. These design considerations may have impact on the fill-factor, pixel size, and resolution. Furthermore, we show that in high-brightness dc and pulsed operation an electrical crosstalk occurs, which is caused by a nonthermal increase of differential resistance and may be linked to current crowding.
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Design, fabrication and application of GaN-based micro-LED arrays with individual addressing by n-electrodes

Design, fabrication and application of GaN-based micro-LED arrays with individual addressing by n-electrodes

with complementary metal-oxide-semiconductor (CMOS) active ma- trix drivers, using flip-chip bonding [3], [7], [15]. Compared with the alternative matrix addressing scheme, the flexible control of individual elements is of great benefit for µ display and VLC applica- tions. However, in the conventional embodiment, there are also some drawbacks. In a conventional µ LED array, elements share a common n-electrode (cathode) with individually addressable p- electrodes (anodes). This configuration is shown in Fig. 1(a), and it is generally used because standard GaN LED epitaxial structures invariably have the p-side of the junction on top, which is ne- cessitated by the relatively low conductivity of p-doped GaN [16], in addition to several growth issues. In the configuration shown in Fig. 1(a), the n-type GaN layer functions as a shared conductive path for all µLED elements in the array. Therefore, different distances between the common n-electrode and the respective µLED elements lead to different series-resistance contributions from the n-type GaN. These differing series resistances result in non-uniform operating currents at the same applied voltage for each µLED element and, thus, poor optical element-to-element uniformity [14] and high crosstalk [17], which are undesirable in practical applications. Concerning the driver choice, this configuration also restricts the CMOS circuitry to designs based on p-type MOS (PMOS) transistors. It is well known that the mobility of majority carriers (holes) in PMOS transistors ( ≈ 450 cm 2 /(V · s)
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Design Optimization Methods for Complex Electromechanical Systems: Addressing User Preferences and Uncertainties.

Design Optimization Methods for Complex Electromechanical Systems: Addressing User Preferences and Uncertainties.

In recent years, there has been an increased focus on the use of Shape Memory Alloys (SMAs) in medical devices (including coronary stents [43] catheter guide wires [44], miniature forceps [45], eyeglass frames [46] etc.), energy absorption [47], and sensing applications [48]. These materials possess the unique ability to ‘memorize’ shapes through thermally induced phase transitions [49], making them potentially attractive for micro-actuation applications. Their material composition (e.g. Cu–Zn, Cu–Zn–Al, Cu–Al–Ni, Ni–Ti, Ni–Ti–Fe, Fe–Pt) largely determines critical mechanical properties including ductility, corrosion, and ‘memory’ properties of the alloy. Three SMA characteristics are associated with crystal reorientation during stress and temperature-induced phase changes: the pseudoelastic effect, the one-way effect, and the two-way effect [50], [49]. The pseudoelastic effect exhibits a reversible response to deformation by temperature and applied stress. The one-way effect is characterized by shape change upon loading, but no reorientation upon cooling. Once deformed, the ‘memorized’ shape is recovered when heated above the transition temperature. The two-way effect refers to shape change upon cooling and heating without external loading.
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CMOS-Electromechanical Systems Microsensor Resonator with High Q-Factor at Low Voltage

CMOS-Electromechanical Systems Microsensor Resonator with High Q-Factor at Low Voltage

Abstract— The paper presents a novel resonant-microsensor platform for chemical and biological sensing applications in gaseous and liquid environment. We report a thermally driven and piezoresistively sensed CMOS-microelectromechanical systems (MEMS) resonator with quality factor Q >15 000 and stopband rejection of 15 dB under CMOS-compatible bias voltage. Tha basic requirement of CMOS under the influence of this bias voltage. In addition, the combination of the bulk-mode resonator design and high- Q SiO 2 /polysilicon structural material leads to resonator Q >15 000, a key index for low-phase-noise oscillators
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Structured illumination for communications and bioscience using GaN micro-LED arrays interfaced to CMOS

Structured illumination for communications and bioscience using GaN micro-LED arrays interfaced to CMOS

Overview • Institute of Photonics overview • GaN micro-LEDs • Integration of micro-LEDs and CMOS drivers • Application #1: “Smart Lighting” indoor positioning • Application #2: Visible L[r]

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SMC-PID for Electromechanical Plant

SMC-PID for Electromechanical Plant

hyperbolic functions, and hysteresis-saturation functions. An ultimate roundedness of the error within some predetermined boundary layer is considered in these continuous functions . Some other studies have also been used to overcome chattering phenomena such as use of a first-order low-pass filter between the controller and the plant Sliding mode control has been widely studied in recent years and has started to play an important role in the application of control theory to practical problems . It has been successfully applied to underwater vehicles , automotive transmissions and engines, and power systems , induction motor, robots, electric drives , human neuromuscular process, and elevator velocity . Sliding mode control has also been applied to dc motors using simulations. In this paper, a real application is performed such that a sliding mode controller is designed using a PID sliding surface for the speed control of an electromechanical plant, a dc motor connected to a load via a shaft. The feasibility and effectiveness of the proposed sliding mode controller is experimentally demonstrated and the system is controlled using a computer. The results obtained from the present study are compared with the traditional PID control in dynamic responses of the closed-loop control system.
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Modelling and Control of Micro Environmental Systems

Modelling and Control of Micro Environmental Systems

The means o f measuring the airflow within the Lancaster chamber is via an Air V elocity Transducer (AVT), (ITA M odel 8455). The TSI air velocity transducers are precision instruments designed specifically to measure air velocity in fixed installations or test facilities. The air velocity transducer was chosen to measure the airflow in the Lancaster micro-environment chamber because o f its relative ease o f use and installation, along with the fact it has a very fast response to differing inputs and can measure low airflow rates to a high degree o f accuracy. Additionally, it is very portable and non-intrusive to the airflow and this allows easy measurement o f airflow at any point within the 3D airspace. The Leuven chamber uses a free running impeller, which has been shown to measure the airflow very accurately, especially at m edium to high ventilation rates (1500-6000m 3/hr); nonetheless, in this installation the decision was taken to use an airflow sensor that had a faster and more accurate response at low ventilation rates. The main drawback being the omni-direction o f this particular m odel, which can make it difficult to measure convective currents in certain locations within the chamber, however, the free running impeller would fair even w orse outside the outlet duct it is usually housed in. A second air velocity transducer has been added to allow measurements in different locations compared to the inlet and outlet. A lso, a mass balance o f airflow through the chamber is possible with a measurement at both inlet and outlet and a choice o f measurement location can be made for m odelling and control purposes.
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Electromechanical modelling of trapezoidal microstructures

Electromechanical modelling of trapezoidal microstructures

Higgins [5] gives an excellent overview of almost all of the m ost interesting papers w ritten on the torsion problem, covering a period from the m id 1800s to the 1940s. The methods mentioned include: the inverse method by Saint-Venant; the m ethod of images invented by Kelvin and applied by Hay [6]; and Lamé's m ethod applied by Clebesch. After the 1930s we start to see the emergence of more common m ethods that are in use today. Conformai m apping was used by Seth to solve the torsion problems of T and L shaped cross-sections in 1934 [7]. The same author then pubUshed a m ethod to calculate the torsion of regular polygons by using conformai m apping onto a circle [8]. By the 1940s it was becoming apparent that finding solutions for every possible type of cross- section w ould be difficult to do. In the torsion problems of T and L shaped cross-sections the mathematics is extremely complicated and not very applicable to other shapes. Finite Element Analysis (FEA) was first developed in 1943 by R. Courant [9], who utilised the Ritz m ethod [10,11] of numerical analysis and variational calculus to obtain approximate solutions to vibration systems. Shortly thereafter, a paper published in 1956 by Turner et al. [12] established the m odem day form of the finite element concept through the derivation of the stifihess matrix for the triangular element.
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