12,226 research outputs found
Architecture and Circuit Design Optimization for Compute-In-Memory
The objective of the proposed research is to optimize computing-in-memory (CIM) design for accelerating Deep Neural Network (DNN) algorithms. As compute peripheries such as analog-to-digital converter (ADC) introduce significant overhead in CIM inference design, the research first focuses on the circuit optimization for inference acceleration and proposes a resistive random access memory (RRAM) based ADC-free in-memory compute scheme. We comprehensively explore the trade-offs involving different types of ADCs and investigate a new ADC design especially suited for the CIM, which performs the analog shift-add for multiple weight significance bits, improving the throughput and energy efficiency under similar area constraints. Furthermore, we prototype an ADC-free CIM inference chip design with a fully-analog data processing manner between sub-arrays, which can significantly improve the hardware performance over the conventional CIM designs and achieve near-software classification accuracy on ImageNet and CIFAR-10/-100 dataset. Secondly, the research focuses on hardware support for CIM on-chip training. To maximize hardware reuse of CIM weight stationary dataflow, we propose the CIM training architectures with the transpose weight mapping strategy. The cell design and periphery circuitry are modified to efficiently support bi-directional compute. A novel solution of signed number multiplication is also proposed to handle the negative input in backpropagation. Finally, we propose an SRAM-based CIM training architecture and comprehensively explore the system-level hardware performance for DNN on-chip training based on silicon measurement results.Ph.D
Laser Technologies for Applications in Quantum Information Science
Scientific progress in experimental physics is inevitably dependent on continuing advances in the underlying technologies. Laser technologies enable controlled coherent and dissipative atom-light interactions and micro-optical technologies allow for the implementation of versatile optical systems not accessible with standard optics.
This thesis reports on important advances in both technologies with targeted applications ranging from Rydberg-state mediated quantum simulation and computation with individual atoms in arrays of optical tweezers to high-resolution spectroscopy of highly-charged ions.
A wide range of advances in laser technologies are reported: The long-term stability and maintainability of external-cavity diode laser systems is improved significantly by introducing a mechanically adjustable lens mount. Tapered-amplifier modules based on a similar lens mount are developed. The diode laser systems are complemented by digital controllers for laser frequency and intensity stabilisation. The controllers offer a bandwidth of up to 1.25 MHz and a noise performance set by the commercial STEMlab platform. In addition, shot-noise limited photodetectors optimised for intensity stabilisation and Pound-Drever-Hall frequency stabilisation as well as a fiber based detector for beat notes in the MHz-regime are developed. The capabilities of the presented techniques are demonstrated by analysing the performance of a laser system used for laser cooling of Rb85 at a wavelength of 780 nm. A reference laser system is stabilised to a spectroscopic reference provided by modulation transfer spectroscopy. This spectroscopy scheme is analysed finding optimal operation at high modulation indices. A suitable signal is generated with a compact and cost-efficient module. A scheme for laser offset-frequency stabilisation based on an optical phase-locked loop is realised. All frequency locks derived from the reference laser system offer a Lorentzian linewidth of 60 kHz (FWHM) in combination with a long-term stability of 130 kHz peak-to-peak within 10 days. Intensity stabilisation based on acousto-optic modulators in combination with the digital controller allows for real-time intensity control on microsecond time scales complemented by a sample and hold feature with a response time of 150 ns.
High demands on the spectral properties of the laser systems are put forward for the coherent excitation of quantum states. In this thesis, the performance of active frequency stabilisation is enhanced by introducing a novel current modulation technique for diode lasers. A flat response from DC to 100 MHz and a phase lag below 90° up to 25 MHz are achieved extending the bandwidth available for laserfrequency stabilisation. Applying this technique in combination with a fast proportional-derivative controller, two laser fields with a relative phase noise of 42 mrad for driving rubidium ground state transitions are realised. A laser system for coherent Rydberg excitation via a two-photon scheme provides light at 780 nm and at 480 nm via frequency-doubling from 960 nm. An output power of 0.6 W at 480 nm from a single-mode optical fiber is obtained . The frequencies of both laser systems are stabilised to a high-finesse reference cavity resulting in a linewidth of 1.02 kHz (FWHM) at 960 nm. Numerical simulations quantify the effect of the finite linewidth on the coherence of Rydberg Rabi-oscillations. A laser system similar to the 480 nm Rydberg system is developed for spectroscopy on highly charged bismuth.
Advanced optical technologies are also at the heart of the micro-optical generation of tweezer arrays that offer unprecedented scalability of the system size. By using an optimised lens system in combination with an automatic evaluation routine, a tweezer array with several thousand sites and trap waists below 1 ÎĽm is demonstrated. A similar performance is achieved with a microlens array produced in an additive manufacturing process. The microlens design is optimised for the manufacturing process. Furthermore, scattering rates in dipole traps due to suppressed resonant light are analysed proving the feasibility of dipole trap generation using tapered amplifier systems
Design of efficient reversible floating-point arithmetic unit on field programmable gate array platform and its performance analysis
The reversible logic gates are used to improve the power dissipation in modern computer applications. The floating-point numbers with reversible features are added advantage to performing complex algorithms with high-performance computations. This manuscript implements an efficient reversible floating-point arithmetic (RFPA) unit, and its performance metrics are realized in detail. The RFP adder/subtractor (A/S), RFP multiplier, and RFP divider units are designed as a part of the RFP arithmetic unit. The RFPA unit is designed by considering basic reversible gates. The mantissa part of the RFP multiplier is created using a 24x24 Wallace tree multiplier. In contrast, the reciprocal unit of the RFP divider is designed using Newton Raphson’s method. The RFPA unit and its submodules are executed in parallel by utilizing one clock cycle individually. The RFPA unit and its submodules are synthesized separately on the Vivado IDE environment and obtained the implementation results on Artix-7 field programmable gate array (FPGA). The RFPA unit utilizes only 18.44% slice look-up tables (LUTs) by consuming the 0.891 W total power on Artix-7 FPGA. The RFPA unit sub-models are compared with existing approaches with better performance metrics and chip resource utilization improvements
Development and testing of an FPGA-controlled switched-integrator current amplifier for use in scanning tunnelling microscopy
The scanning tunnelling microscope (STM) is a very powerful analytic tool capable of achieving atomic resolution. Unfortunately, the STM is restricted to samples that are sufficiently conductive to allow adequate tunneling current for feedback control. The amplifier used to measure the tunneling current is the critical limiting component. If the amplifier could be made more sensitive, the STM could be operated at lower tunneling currents allowing lower conductivity samples to be studied. Most amplifiers used in STM employ a resistor feedback design, which become unstable at high gain necessitating a tradeoff between gain and bandwidth. One way to circumvent that stability problem is to use a capacitor feedback design (switched
integrator), which does not exhibit the same stability problem. This comes at the expense of added complexity because the output is the integral of the current and needs to be periodically reset. In this project, a switched-integrator current amplifier is constructed and explored. It consisted of an analog switched integrator controlled by a field-programmable-gate-array (FPGA) with a 16-bit analog-to-digital converter and an 18-bit digital-to-analog converter. A viable prototype was created which allowed for the exploration of the gain, phase, and time delay of such systems. This exploration helped further characterize the important design considerations and trade-offs necessary for such a system. A design sequence is proposed that allows for optimal planning based on the desired tunneling current and system bandwidth
Diagnostics of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin films
This thesis is devoted to the investigation of ion generation and fluxes from cathodic arc spots for a better understanding of energetic deposition of thin film. The ion generation is related to the arc spot properties, and ion fluxes influence the film deposition. Significantly, the cathodic arc has the explosion characteristic for the ignition process, which is the generation process of ions. Thus, it is not easy to observe the spot characteristics, and some fundamental questions related to cathodic arc spot motion are still open. The multiply charged ions produced from the arc spot ignition process have a higher ion potential energy than ions of other deposition techniques; therefore, consideration of the effect of ion potential energy on film growth is required for the cathodic arc technique.
The first part of this thesis deals with fundamental arc spot characteristics, especially the trend of spot motion in a magnetically steered arc source placed in vacuum or in a reactive gas atmosphere. This is investigated with a streak camera having high spatial and temporal resolutions. To answer the fundamental question of whether the spots have characteristic times, such as a 'periodic spot lifetime' or a 'the periodic characteristic time between spot ignitions”, the streak images were analyzed by fast Fourier transformation (FFT). It was found that the power spectrum of the arc spot fluctuations does not show any specific frequencies, which means the arc spot ignition process can be described by a fractal model, and the spectral slope in the log-log power-frequency diagram has a tendency to be reduced in the presence of a compound (for example oxide or nitride) layer on the cathode surface. Through the fractal analysis and measurements of optical emission spectroscopy, the fundamental limitation of the temporal resolution for the optical emission method is determined and considered.
The second part of this thesis considers cathodic arc’s application aspects: the energetic deposition of thin films and coatings. Most studies related to energetic deposition have previously investigated the effects of ion kinetic energy on film deposition; however, this thesis focuses on the effects of ion potential energy on film growth. To investigate the effect of ion potential energy on film growth, plasma diagnostic by energy-resolved mass spectrometry and deposited film characterization by XRD, XRR, AFM, profilometry and SEM were carried out. The ion potential energy influences the preferential direction of film growth or a polycrystalline growth in the case of aluminum deposition. This result could be a starting point for further research into the effect of ion potential energy on film deposition
High Voltage DC-biased Oil Type Medium Frequency Transformer; A Green Solution for Series DC Wind Park Concept
The electric energy generated by remote offshore wind parks is transported to the consumers using high voltage submarine cables. On the generation site, such transmissions are realized today by collecting the energy produced by several wind turbines in a bulky and expensive transformer placed on a dedicated platform. An alternative solution has been proposed recently, which allows to reduce the installation and maintenance costs by eliminating such a platform. It is suggested to equip each wind turbine in the wind park by an individual DC/DC converter and connect them in series to reach the DC voltage level required for an efficient HVDC energy transportation to the shore. The DC/DC converter is supposed to be a Dual Active Bridge (DAB) converter, which can be made reasonably small to be placed on the wind turbine tower or even in its nacelle. The key element of the converter defining its size and mass is a special transformer, which operates at voltages comprising a high (switching) frequency component superimposed on a high DC offset voltage. DC insulation design of such a transformer and investigation of the effects of a high DC insulation level on the other electromagnetic properties of the transformer is the subject of the present research.In order to verify the concept a prototype of the transformer was built, and its evaluation presented. The unit has been manufactured for the rated power of 50 kW and rated voltages 0.4/5 kV including DC offset of 125 kV and square-shaped oscillations with the frequency of 5 kHz. The magnetic system was made of ferrite material and consisted of 10 shell-type core segments. The magnetic properties have been verified by measuring magnetization and losses at various frequencies in the range 1-10 kHz to cover the operational range of the DAB. The types and dimensions of the windings and their conductors were chosen to minimize the proximity and eddy current effects at higher frequencies. To reduce the size of the transformer and to allow for its efficient cooling, the active part was immersed in oil and cellulose-based materials (paper and pressboard) were used to build the high voltage insulation system. The principles for dimensioning the insulation of the transformer are discussed. The criteria used for selecting insulating distances were based on the consideration of the electric field strength obtained from FEM simulations and using the non-linear Maxwell-Wagner model accounting for local variations of the electric field caused by accumulation of interfacial charges induced by DC stresses. The properties of the materials needed for the calculations were obtained by measuring their dielectric constants and electric conductivities. The methodology used for the measurements conducted for conventional mineral oil and eco-friendly biodegradable transformer oils and, respectively, for oil-impregnated paper/pressboard, is presented. The methodologies used for obtaining parameters of the built transformer prototype needed for its integration in the power electric circuit of the DAB are introduced. A method developed for accurate calculations of the leakage inductance for the shell-type multi core transformers with circular windings is described. Two innovative methods for evaluations of parasitic capacitances based on high frequency equivalent circuits of the transformer are presented. The results of their verifications against performed Frequency Response Analysis measurements and FEM calculations as well as their accuracy are discussed.Thermal performance of the developed transformer prototype is analysed based on the results of computer simulations of heat transfer in its active part under rated load. Identified hot spots and solutions for their elimination are presented.Finally, the expected dimensions, weight, and efficiency of an actual DC/DC converter with the rated parameters corresponding to a 6 MW, 1.8 kV real wind turbine having a 250 kV offset DC voltage are estimated assuming that the developed transformer prototype is scalable. It is shown that the proposed solution allows for installing the full-scale converter having 2.2 Tons in weight and 1.8 m3 in volume on the bottom of the wind turbine’s tower
Narrative Potential of Menus in Video Games
openNei videogiochi, il menu principale è la casella degli strumenti del giocatore. Lo scopo del menu principale di un videogioco si trova anche nella nostra realtà per cose come una borsa personale o una casa. La struttura e il contenuto di questi oggetti raccontano la vita di una persona. Queste sono cassette degli attrezzi che descrivono gli obiettivi, le azioni e gli elementi importanti di come uno sceglie vivere la sua vita. Comparativamente, il layout e il contenuto del menu principale raccontano la storia del giocatore nel gioco. Il menu principale può anticipare la narrazione e può indicizzare l'interazione con il mondo di gioco. Dimostra i controlli di base del gioco e la logica dell'interfaccia. Per questi motivi, il menu principale può essere considerato l'offerta principale del gioco. Questo estratto è legato a una tesi finale che esaminerà le narrazioni, l'importanza e la presenza di come i menu principali sono organizzati, presentati e utilizzati.
Il menu principale è un elemento visivo e narrativo che è all'interno dell'interfaccia non limitato ad essere parte del codice di programmazione di un gioco. Gli obiettivi principali e lo scopo del gioco saranno presenti nel menu principale, indipendentemente se il giocatore sceglie di giocare il gioco come previsto. Quali sono le opzioni identificano gli elementi importanti del gioco. Dove e come gli elementi sono posizionati identificano la loro gerarchia e le relazioni. Come vengono utilizzate le opzioni, facendo riferimento all'input dell'utente, sono collegate all'hardware del gioco e a come il giocatore si muove all'interno del gioco. La forma del funzionamento del menu principale rifletterà e dimostrerà come viene utilizzato l'hardware e la logica dell'interfaccia. Queste considerazioni possono dimostrare come il menu principale funge da guida al gioco come offerta primaria dimostrando come giocare il gioco. Il menu principale come elemento visivo e narrativo si trova in tutti i giochi moderni, con alcune eccezioni, perché è parte integrante dell'interfaccia e della storia del gioco.
La mia tesi introdurrà la mia metodologia e lo stato dell'arte sui principali menu nel campo interdisciplinare degli studi di gioco. Gli studi di casi includeranno giochi digitali del franchise Pokémon, la saga di The Legend of Zelda, Animal Crossing e Katamari Damaci. Questo studio spera di portare consapevolezza allo studio del menu principale come più di una semplice interfaccia. Si tratta di un elemento narrativo importante di un gioco che dovrebbe essere un argomento ben studiato all'interno di studi di gioco. I videogiochi possono essere classificati in base al menu principale e l'interfaccia, aggiungendo ai generi tradizionali che vengono utilizzati. Può essere possibile che le recenti tendenze e cambiamenti nei videogiochi che vengono creati dalla tecnologia più recente non sono del tutto nuovi. Questi giochi potrebbero essere realizzando modi che i vecchi giochi erano originariamente destinati ad essere giocato.In videogames, the main menu is the player’s toolbox. The purpose of the main menu to a video game is also found in our reality to things such as a personal bag or a home. The structure and contents of these objects both tell a story of a person’s life. These are toolboxes that outline the goals, actions, and important elements of how one chooses to live his life. Comparatively, the layout and contents of the main menu tell the story of the player in the game. The main menu can anticipate narrative and it can index interaction with the game-world. It demonstrates the basic controls of the game and the interface’s logic. For these reasons, the main menu can be considered the game’s primary affordance. This abstract is related of a final thesis which will look at the narratives, importance, and presence of how main menus are organized, presented, and used.
The main menu is a visual and narrative element that is within the interface not limited to being part of a game’s programming code. The main objectives and purpose of play will be present in the main menu regardless if the player chooses to play the game as intended. What the options are identify the important elements of play. Where and how the elements are placed identify their hierarchy and relationships. How the options are used, referring to user input, are linked to the game’s hardware and how the player is moving within the game. The form of the main menu’s operation will reflect and demonstrate how the hardware is used and the interface’s logic. These considerations can prove how the main menu acts as a guide to the game as primary affordance by demonstrating how to play the game. The main menu as a visual and narrative element is found in all modern games, with some exceptions, because it is an integral part of the game's interface and story.
My thesis will introduce my methodology and the state of art about main menus in the interdisciplinary field of game studies. Case studies will include digital games from the Pokémon franchise, the saga of The Legend of Zelda, Animal Crossing, and Katamari Damaci. This study hopes to bring awareness to studying the main menu as more than just an interface. It is an important narrative element of a game that should be a well-studied topic within game studies. Videogames can be categorized based on main menu and interface, adding to the traditional genres that are used. It may be possible that recent trends and changes in videogames that are created from newer technology are not entirely new. These games could be realizing ways that older games were originally intended to be played
A Hardware-Based Configurable Algorithm for Eye Blink Signal Detection Using a Single-Channel BCI Headset
Eye blink artifacts in electroencephalographic (EEG) signals have been used in multiple applications as an effective method for human-computer interaction. Hence, an effective and low-cost blinking detection method would be an invaluable aid for the development of this technology. A configurable hardware algorithm, described using hardware description language, for eye blink detection based on EEG signals from a one-channel brain-computer interface (BCI) headset was developed and implemented, showing better performance in terms of effectiveness and detection time than manufacturer-provided software
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