Global ETD Search

21	Bezeztrátová komprese obrazu / Lossless Image Compression Vondrášek, Petr January 2011 (has links) The aim of this master's thesis was to design, develop and test a method for lossless image compression. The theoretical part includes a description of selected exiting methods such as RLE, MTF, adaptive arithmetic coding, color models used in LOCO-I and JPEG 2000, predictors MED, GAP and laplacian pyramid. The conclusion includes a comparison of various combinations of chosen approaches and overall efficiency compared with PNG and JPEG-LS.
22	Universal homophonic coding Stevens, Charles Cater 11 1900 (has links) Redundancy in plaintext is a fertile source of attack in any encryption system. Compression before encryption reduces the redundancy in the plaintext, but this does not make a cipher more secure. The cipher text is still susceptible to known-plaintext and chosen-plaintext attacks. The aim of homophonic coding is to convert a plaintext source into a random sequence by randomly mapping each source symbol into one of a set of homophones. Each homophone is then encoded by a source coder after which it can be encrypted with a cryptographic system. The security of homophonic coding falls into the class of unconditionally secure ciphers. The main advantage of homophonic coding over pure source coding is that it provides security both against known-plaintext and chosen-plaintext attacks, whereas source coding merely protects against a ciphertext-only attack. The aim of this dissertation is to investigate the implementation of an adaptive homophonic coder based on an arithmetic coder. This type of homophonic coding is termed universal, as it is not dependent on the source statistics. / Computer Science / M.Sc. (Computer Science) Arithmetic coding Adaptive models Cryptography Data compression Homophonic coding Homophonic substitution Modelling randomness Statistical testing Secrecy Unconditional scurity 005.82 Data compression (Computer science) Computer security Data encryption (Computer science) Cryptography (Computer science) Ciphers -- Computer science Homophonic coding
23	Universal homophonic coding Stevens, Charles Cater 11 1900 (has links) Redundancy in plaintext is a fertile source of attack in any encryption system. Compression before encryption reduces the redundancy in the plaintext, but this does not make a cipher more secure. The cipher text is still susceptible to known-plaintext and chosen-plaintext attacks. The aim of homophonic coding is to convert a plaintext source into a random sequence by randomly mapping each source symbol into one of a set of homophones. Each homophone is then encoded by a source coder after which it can be encrypted with a cryptographic system. The security of homophonic coding falls into the class of unconditionally secure ciphers. The main advantage of homophonic coding over pure source coding is that it provides security both against known-plaintext and chosen-plaintext attacks, whereas source coding merely protects against a ciphertext-only attack. The aim of this dissertation is to investigate the implementation of an adaptive homophonic coder based on an arithmetic coder. This type of homophonic coding is termed universal, as it is not dependent on the source statistics. / Computer Science / M.Sc. (Computer Science) Arithmetic coding Adaptive models Cryptography Data compression Homophonic coding Homophonic substitution Modelling randomness Statistical testing Secrecy Unconditional scurity 005.82 Data compression (Computer science) Computer security Data encryption (Computer science) Cryptography (Computer science) Ciphers -- Computer science Homophonic coding
24	Komprese dat / Data compression Krejčí, Michal January 2009 (has links) This thesis deals with lossless and losing methods of data compressions and their possible applications in the measurement engineering. In the first part of the thesis there is a theoretical elaboration which informs the reader about the basic terminology, the reasons of data compression, the usage of data compression in standard practice and the division of compression algorithms. The practical part of thesis deals with the realization of the compress algorithms in Matlab and LabWindows/CVI.
25	Komprese obrazu pomocí vlnkové transformace / Image Compression Using the Wavelet Transform Urbánek, Pavel January 2013 (has links) This thesis is focused on subject of image compression using wavelet transform. The first part of this document provides reader with information about image compression, presents well known contemporary algorithms and looks into details of wavelet compression and following encoding schemes. Both JPEG and JPEG 2000 standards are introduced. Second part of this document analyzes and describes implementation of image compression tool including inovations and optimalizations. The third part is dedicated to comparison and evaluation of achievements.
26	A 64-channel back-gate adapted ultra-low-voltage spike-aware neural recording front-end with on-chip lossless/near-lossless compression engine and 3.3V stimulator in 22nm FDSOI Schüffny, Franz Marcus, Zeinolabedin, Seyed Mohammad Ali, George, Richard, Guo, Liyuan, Weiße, Annika, Uhlig, Johannes, Meyer, Julian, Dixius, Andreas, Hänzsche, Stefan, Berthel, Marc, Scholze, Stefan, Höppner, Sebastian, Mayr, Christian 21 February 2024 (has links) In neural implants and biohybrid research systems, the integration of electrode recording and stimulation front-ends with pre-processing circuitry promises a drastic increase in real-time capabilities [1,6]. In our proposed neural recording system, constant sampling with a bandwidth of 9.8kHz yields 6.73μV input-referred noise (IRN) at a power-per-channel of 0.34μW for the time-continuous ΔΣ−modulator, and 0.52μW for the digital filters and spike detectors. We introduce dynamic current/bandwidth selection at the ΔΣ and digital filter to reduce recording bandwidth at the absence of spikes (i.e. local field potentials). This is controlled by a two-level spike detection and adjusted by adaptive threshold estimation (ATE). Dynamic bandwidth selection reduces power by 53.7%, increasing the available channel count at a low heat dissipation. Adaptive back-gate voltage tuning (ABGVT) compensates for PVT variation in subthreshold circuits. This allows 1.8V input/output (IO) devices to operate at 0.4V supply voltage robustly. The proposed 64-channel neural recording system moreover includes a 16-channel adaptive compression engine (ACE) and an 8-channel on-chip current stimulator at 3.3V. The stimulator supports field-shaping approaches, promising increased selectivity in future research. info:eu-repo/classification/ddc/530 ddc:530

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