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Artykuły w czasopismach na temat "Compression"
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GROSU-BULARDA, Andreea, Razvan Nicolae TEODOREANU, Andra-Luana LAZARESCU, Marius POPESCU, Florin-Vlad HODEA, Flavia Francesca LITA, Alexandru STOIAN, Cristian VANCEA, Liviu Petre COJOCARU, and Ioan LASCAR. "Nerve compression due to benign tumors or ganglion cysts in the upper limb – case series." Romanian Journal of Medical Practice 16, no. 4 (December 31, 2021): 501–8. http://dx.doi.org/10.37897/rjmp.2021.4.19.
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Tumor nerve compressions in the upper limb are relatively rare, usually involving ganglion cysts and benign tumors. We present a case series of five patients with peripheral nerve compression in the upper limb due to tumor or cystic masses- ulnar nerve compression in the Guyon’s tunnel due to a ganglion cyst, large median nerve schwannoma compressing anterior interosseous nerve and median nerve, voluminous lipoma compressing median nerve in the proximal forearm, superficial branch of radial nerve compression by a synovial cyst and elbow region lipoma compressing radial nerve. In the beginning, those benign lesions are asymptomatic but, as they continue to grow adjacent to a peripheral nerve clinical manifestations appear progressively as compressive neuropathies. After a preoperative imagistic analysis, tumor resection with careful dissection, in order to preserve the neurovascular structures, is the elective surgical procedure in order to obtain an optimal functional recovery.
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Ma, Wei Hua, and Hong Zhen Kang. "Experimental Study on Compressive Behavior of CFRP Confined Concrete Columns." Advanced Materials Research 446-449 (January 2012): 3725–29. http://dx.doi.org/10.4028/www.scientific.net/amr.446-449.3725.
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Compressive tests of 30 concrete column specimens with three concrete strength grades are carried out in this paper to study ultimate compressive strength of specimens. The specimens are divided into three groups, that is, unconfined, confined by CFRP with no initial compression and confined by CFRP with various initial compressions. The different initial compressions’ influence on ultimate stresses and strains are investigated. The decrease of CFRP reinforcing effect due to pre-compression are analyzed. The research results provide experimental datum for reinforced design of existing concrete columns.
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Isechi, Kohei. "Light Field Compression for Compressive 3D Display." International Journal of Machine Learning and Computing 9, no. 2 (April 2019): 208–12. http://dx.doi.org/10.18178/ijmlc.2019.9.2.788.
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Ko, Yousun, Alex Chadwick, Daniel Bates, and Robert Mullins. "Lane Compression." ACM Transactions on Embedded Computing Systems 20, no. 2 (March 2021): 1–26. http://dx.doi.org/10.1145/3431815.
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This article presents Lane Compression, a lightweight lossless compression technique for machine learning that is based on a detailed study of the statistical properties of machine learning data. The proposed technique profiles machine learning data gathered ahead of run-time and partitions values bit-wise into different lanes with more distinctive statistical characteristics. Then the most appropriate compression technique is chosen for each lane out of a small number of low-cost compression techniques. Lane Compression’s compute and memory requirements are very low and yet it achieves a compression rate comparable to or better than Huffman coding. We evaluate and analyse Lane Compression on a wide range of machine learning networks for both inference and re-training. We also demonstrate the profiling prior to run-time and the ability to configure the hardware based on the profiling guarantee robust performance across different models and datasets. Hardware implementations are described and the scheme’s simplicity makes it suitable for compressing both on-chip and off-chip traffic.
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P, Srividya. "Optimization of Lossless Compression Algorithms using Multithreading." Journal of Information Technology and Sciences 9, no. 1 (March 2, 2023): 36–42. http://dx.doi.org/10.46610/joits.2022.v09i01.005.
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The process of reducing the number of bits required to characterize data is referred to as compression. The advantages of compression include a reduction in the time taken to transfer data from one point to another, and a reduction in the cost required for the storage space and network bandwidth. There are two types of compression algorithms namely lossy compression algorithm and lossless compression algorithm. Lossy algorithms find utility in compressing audio and video signals whereas lossless algorithms are used in compressing text messages. The advent of the internet and its worldwide usage has not only raised the utility but also the storage of text, audio and video files. These multimedia files demand more storage space as compared to traditional files. This has given rise to the requirement for an efficient compression algorithm. There is a considerable improvement in the computing performance of the machines due to the advent of the multi-core processor. However, this multi-core architecture is not used by compression algorithms. This paper shows the implementation of lossless compression algorithms namely the Lempel-Ziv-Markov Algorithm, BZip2 and ZLIB algorithms using the concept of multithreading. The results obtained prove that the ZLIB algorithm proves to be more efficient in terms of the time taken to compress and decompress the text. The comparison is done for both compressions without multithreading and compression with multi-threading.
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P, Srividya. "Optimization of Lossless Compression Algorithms using Multithreading." Journal of Information Technology and Sciences 9, no. 1 (March 1, 2023): 36–42. http://dx.doi.org/10.46610/joits.2023.v09i01.005.
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The process of reducing the number of bits required to characterize data is referred to as compression. The advantages of compression include a reduction in the time taken to transfer data from one point to another, and a reduction in the cost required for the storage space and network bandwidth. There are two types of compression algorithms namely lossy compression algorithm and lossless compression algorithm. Lossy algorithms find utility in compressing audio and video signals whereas lossless algorithms are used in compressing text messages. The advent of the internet and its worldwide usage has not only raised the utility but also the storage of text, audio and video files. These multimedia files demand more storage space as compared to traditional files. This has given rise to the requirement for an efficient compression algorithm. There is a considerable improvement in the computing performance of the machines due to the advent of the multi-core processor. However, this multi-core architecture is not used by compression algorithms. This paper shows the implementation of lossless compression algorithms namely the Lempel-Ziv-Markov Algorithm, BZip2 and ZLIB algorithms using the concept of multithreading. The results obtained prove that the ZLIB algorithm proves to be more efficient in terms of the time taken to compress and decompress the text. The comparison is done for both compressions without multithreading and compression with multi-threading.
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Guerra, Aníbal, Jaime Lotero, José Édinson Aedo, and Sebastián Isaza. "Tackling the Challenges of FASTQ Referential Compression." Bioinformatics and Biology Insights 13 (January 2019): 117793221882137. http://dx.doi.org/10.1177/1177932218821373.
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The exponential growth of genomic data has recently motivated the development of compression algorithms to tackle the storage capacity limitations in bioinformatics centers. Referential compressors could theoretically achieve a much higher compression than their non-referential counterparts; however, the latest tools have not been able to harness such potential yet. To reach such goal, an efficient encoding model to represent the differences between the input and the reference is needed. In this article, we introduce a novel approach for referential compression of FASTQ files. The core of our compression scheme consists of a referential compressor based on the combination of local alignments with binary encoding optimized for long reads. Here we present the algorithms and performance tests developed for our reads compression algorithm, named UdeACompress. Our compressor achieved the best results when compressing long reads and competitive compression ratios for shorter reads when compared to the best programs in the state of the art. As an added value, it also showed reasonable execution times and memory consumption, in comparison with similar tools.
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Wang, Hong Yun, and Hui Qiang Zheng. "Shear and Squeeze Rheometry of Magnetorheological Fluids." Advanced Materials Research 305 (July 2011): 344–47. http://dx.doi.org/10.4028/www.scientific.net/amr.305.344.
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The mechanical properties of a magnetorheological (MR) fluid in shearing, compression and shearing after compression have been studied in the magnetic field which is generated by a coil carrying different magnitudes of DC electrical current on a self-constructed test system. The relations of compression stress versus compression strain, yield stress versus compression stress were studied under different magnetic fields. The compressing tests showed that the MR fluid is very stiff at small compressive strains lower than 0.13. The shear yield stress of MR fluids after compression was much stronger than that of uncompressed MR fluids under the same magnetic field. The enhanced shear yield stress of MR fluids can be utilized to design the MR clutch and brake for new structure and will make MR fluids technology attractive for many applications.
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Yedukondalu, G., Sajjan Patnaik, P. Lakshmi Venkatesh, and S. Siva Jagadeesh. "Chest compression with 2-DOF parallel manipulator for cardiopulmonary resuscitation." International Journal of Engineering & Technology 7, no. 2.8 (March 19, 2018): 211. http://dx.doi.org/10.14419/ijet.v7i2.8.10411.
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Chest compression process is used for recovering patients who met with a cardiac arrest in emergency situations. Chest compression is the only possibility of rescuing patients during cardiopulmonary resuscitation (CPR). It is hard to achieve the exact chest compression’s depth and rate even by experienced professionals as per the CPR guideline. A 2-DOF 2-RRR translational parallel manipulator was designed for delivering chest compressions. The kinematic analysis is carried out analytically.The workspace of the manipulator is examined in consideration of physical constraints imposed by joints. Finally, the manipulator operates with exact compression depth and rate during CPR.
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Mishra, Amit Kumar. "Versatile Video Coding (VVC) Standard: Overview and Applications." Turkish Journal of Computer and Mathematics Education (TURCOMAT) 10, no. 2 (September 10, 2019): 975–81. http://dx.doi.org/10.17762/turcomat.v10i2.13578.
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Information security includes picture and video compression and encryption since compressed data is more secure than uncompressed imagery. Another point is that handling data of smaller sizes is simple. Therefore, efficient, secure, and simple data transport methods are created through effective data compression technology. Consequently, there are two different sorts of compression algorithm techniques: lossy compressions and lossless compressions. Any type of data format, including text, audio, video, and picture files, may leverage these technologies. In this procedure, the Least Significant Bit technique is used to encrypt each frame of the video file format to be able to increase security. The primary goals of this procedure are to safeguard the data by encrypting the frames and compressing the video file. Using PSNR to enhance process throughput would also enhance data transmission security while reducing data loss.
Rozprawy doktorskie na temat "Compression"
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Hawary, Fatma. "Light field image compression and compressive acquisition." Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S082.
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En capturant une scène à partir de plusieurs points de vue, un champ de lumière fournit une représentation riche de la géométrie de la scène, ce qui permet une variété de nouvelles applications de post-capture ainsi que des expériences immersives. L'objectif de cette thèse est d'étudier la compressibilité des contenus de type champ de lumière afin de proposer de nouvelles solutions pour une imagerie de champs lumière à plus haute résolution. Deux aspects principaux ont été étudiés à travers ce travail. Les performances en compression sur les champs lumière des schémas de codage actuels étant encore limitées, il est nécessaire d'introduire des approches plus adaptées aux structures des champs de lumière. Nous proposons un schéma de compression comportant deux couches de codage. Une première couche encode uniquement un sous-ensemble de vues d’un champ de lumière et reconstruit les vues restantes via une méthode basée sur la parcimonie. Un codage résiduel améliore ensuite la qualité finale du champ de lumière décodé. Avec les moyens actuels de capture et de stockage, l’acquisition d’un champ de lumière à très haute résolution spatiale et angulaire reste impossible, une alternative consiste à reconstruire le champ de lumière avec une large résolution à partir d’un sous-ensemble d’échantillons acquis. Nous proposons une méthode de reconstruction automatique pour restaurer un champ de lumière échantillonné. L’approche utilise la parcimonie du champs de lumière dans le domaine de Fourier. Aucune estimation de la géométrie de la scène n'est nécessaire, et une reconstruction précise est obtenue même avec un échantillonnage assez réduit. Une étude supplémentaire du schéma complet, comprenant les deux approches proposées est menée afin de mesurer la distorsion introduite par les différents traitements. Les résultats montrent des performances comparables aux méthodes de synthèse de vues basées sur la l’estimation de profondeur<br>By capturing a scene from several points of view, a light field provides a rich representation of the scene geometry that brings a variety of novel post-capture applications and enables immersive experiences. The objective of this thesis is to study the compressibility of light field contents in order to propose novel solutions for higher-resolution light field imaging. Two main aspects were studied through this work. The compression performance on light fields of the actual coding schemes still being limited, there is need to introduce more adapted approaches to better describe the light field structures. We propose a scalable coding scheme that encodes only a subset of light field views and reconstruct the remaining views via a sparsity-based method. A residual coding provides an enhancement to the final quality of the decoded light field. Acquiring very large-scale light fields is still not feasible with the actual capture and storage facilities, a possible alternative is to reconstruct the densely sampled light field from a subset of acquired samples. We propose an automatic reconstruction method to recover a compressively sampled light field, that exploits its sparsity in the Fourier domain. No geometry estimation is needed, and an accurate reconstruction is achieved even with very low number of captured samples. A further study is conducted for the full scheme including a compressive sensing of a light field and its transmission via the proposed coding approach. The distortion introduced by the different processing is measured. The results show comparable performances to depth-based view synthesis methods
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Yell, M. D. "Steam compression in the single screw compressor." Thesis, University of Leeds, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372575.
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Nóbrega, Fernando Antônio Asevêdo. "Sumarização Automática de Atualização para a língua portuguesa." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/55/55134/tde-30072018-090806/.
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O enorme volume de dados textuais disponível na web caracteriza-se como um cenário ideal para inúmeras aplicações do Processamento de Língua Natural, tal como a tarefa da Sumarização Automática de Atualização (SAA), que tem por objetivo a geração automática de resumos a partir de uma coleção textual admitindo-se que o leitor possui algum conhecimento prévio sobre os textos-fonte. Dessa forma, um bom resumo de atualização deve ser constituído pelas informações mais relevantes, novas e atualizadas com relação ao conhecimento prévio do leitor. Essa tarefa implica em diversos desafios, sobretudo nas etapas de seleção e síntese de conteúdo para o sumário. Embora existam inúmeras abordagens na literatura, com diferentes níveis de complexidade teórica e computacional, pouco dessas investigações fazem uso de algum conhecimento linguístico profundo, que pode auxiliar a identificação de conteúdo mais relevante e atualizado. Além disso, os métodos de sumarização comumente empregam uma abordagem de síntese extrativa, na qual algumas sentenças dos textos-fonte são selecionadas e organizadas para compor o sumário sem alteração de seu conteúdo. Tal abordagem pode limitar a informatividade do sumário, uma vez que alguns segmentos sentenciais podem conter informação redundante ou irrelevante ao leitor. Assim, esforços recentes foram direcionados à síntese compressiva, na qual alguns segmentos das sentenças selecionadas para o sumário são removidos previamente à inserção no sumário. Nesse cenário, este trabalho de doutorado teve por objetivo a investigação do uso de conhecimentos linguísticos, como a Teoria Discursiva Multidocumento (CST), Segmentação de Subtópicos e Reconhecimento de Entidades Nomeadas, em distintas abordagens de seleção de conteúdo por meio das sínteses extrativas e compressivas visando à produção de sumários de atualização mais informativos. Tendo a língua Portuguesa como principal objeto de estudo, foram organizados três novos córpus, o CSTNews-Update, que viabiliza experimentos de SAA, e o PCSC-Pares e G1-Pares, para o desenvolvimento/avaliação de métodos de Compressão Sentencial. Ressalta-se que os experimentos de sumarização foram também realizados para a língua inglesa. Após as experimentações, observou-se que a Segmentação de Subtópicos foi mais efetiva para a produção de sumários mais informativos, porém, em apenas poucas abordagens de seleção de conteúdo. Além disso, foram propostas algumas simplificações para o método DualSum por meio da distribuição de Subtópicos. Tais métodos apresentaram resultados muito satisfatórios com menor complexidade computacional. Visando a produção de sumários compressivos, desenvolveram-se inúmeros métodos de Compressão Sentencial por meio de algoritmos de Aprendizado de Máquina. O melhor método proposto apresentou resultados superiores a um trabalho do estado da arte, que faz uso de algoritmos de Deep Learning. Além dos resultados supracitados, ressalta-se que anteriormente a este trabalho, a maioria das investigações de Sumarização Automática para a língua Portuguesa foi direcionada à geração de sumários a partir de um (monodocumento) ou vários textos relacionados (multidocumento) por meio da síntese extrativa, sobretudo pela ausência se recursos que viabilizassem a expansão da área de Sumarização Automática para esse idioma. Assim, as contribuições deste trabalho engajam-se em três campos, nos métodos de SAA propostos com conhecimento linguísticos, nos métodos de Compressão Sentencial e nos recursos desenvolvidos para a língua Portuguesa.<br>The huge amount of data that is available online is the main motivation for many tasks of Natural Language Processing, as the Update Summarization (US) which aims to produce a summary from a collection of related texts under the assumption the user/reader has some previous knowledge about the texts subject. Thus, a good update summary must be produced with the most relevant, new and updated content in order to assist the user. This task presents many research challenges, mainly in the processes of content selection and synthesis of the summary. Although there are several approaches for US, most of them do not use of some linguistic information that may assist the identification relevant content for the summary/user. Furthermore, US methods frequently apply an extractive synthesis approach, in which the summary is produced by picking some sentences from the source texts without rewriting operations. Once some segments of the picked sentences may contain redundant or irrelevant content, this synthesis process can to reduce the summary informativeness. Thus, some recent efforts in this field have focused in the compressive synthesis approach, in which some sentences are compressed by deletion of tokens or rewriting operations before be inserted in the output summary. Given this background, this PhD research has investigated the use of some linguistic information, as the Cross Document Theory (CST), Subtopic Segmentation and Named Entity Recognition into distinct content selection approaches for US by use extractive and compressive synthesis process in order to produce more informative update summaries. Once we have focused on the Portuguese language, we have compiled three new resources for this language, the CSTNews-Update, which allows the investigation of US methods for this language, the PCST-Pairs and G1-Pairs, in which there are pairs of original and compressed sentences in order to produce methods of sentence compression. It is important to say we also have performed experiments for the English language, in which there are more resources. The results show the Subtopic Segmentation assists the production of better summaries, however, this have occurred just on some content selection approaches. Furthermore, we also have proposed a simplification for the method DualSum by use Subtopic Segments. These simplifications require low computation power than DualSum and they have presented very satisfactory results. Aiming the production of compressive summaries, we have proposed different compression methods by use machine learning techniques. Our better proposed method present quality similar to a state-of-art system, which is based on Deep Learning algorithms. Previously this investigation, most of the researches on the Automatic Summarization field for the Portuguese language was focused on previous traditional tasks, as the production of summaries from one and many texts that does not consider the user knowledge, by use extractive synthesis processes. Thus, beside our proposed US systems based on linguistic information, which were evaluated over English and Portuguese datasets, we have produced many Compressions Methods and three new resources that will assist the expansion of the Automatic Summarization field for the Portuguese Language.
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Blais, Pascal. "Pattern compression." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp03/MQ38737.pdf.
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SANCHEZ, FERNANDO ZEGARRA. "COMPRESSION IGNITION OF ETHANOL-POWERED IN RAPID COMPRESSION MACHINE." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2016. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=29324@1.
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PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO<br>COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>PROGRAMA DE EXCELENCIA ACADEMICA<br>Com o passar do tempo, a humanidade tem uma maior dependência na geração de energia, utilizada para promoção de conforto, transporte e outros. Com a finalidade de resolver este aumento de demanda, novas fontes eficientes, de preferência renováveis, estão sendo pesquisadas. O transporte é uma das atividades que tem maior dependência dos combustíveis fósseis, além de ser também um dos maiores geradores de gases de efeito estufa. É por isso, que em diversas partes do mundo, o homem pesquisa novas fontes de energia renováveis que possam ser substitutas dos atuais tradicionais usados no transporte. Sabe-se, que os motores Diesel são mais eficientes com relação aos motores Otto. Devido a este fato, há mais 30 anos pesquisam-se e desenvolvem-se sistemas de ignição por compressão, movidos com combustíveis renováveis, o qual permita a diminuição da dependência dos combustíveis fósseis e garanta a redução de gases de efeito estufa. O etanol é um candidato para substituir o oleo Diesel, mas tem que se levar em conta algumas alterações (aumento da relação de compressão, adição de melhoradores da autoignição, etc.) antes de ser utilizado nos motores Diesel. Com base nisto, a presente tese apresenta uma nova proposta, utilizar como melhorador da autoignição do etanol o n-butanol. Para tal propósito se desenvolveu diversos testes com diversas relações de compressão, percentuais em massa de aditivo na mistura de etanol e diversos avanços da injeção. Os testes foram realizados em uma máquina de compressão rápida (MCR) com misturas de etanol e polietilenoglicol 400 e 600, n-butanol, além dos testes refenciais com óleo Disel e ED95. Os resultados mostram que o n-butanol, com uma participação de 10 por cento na mistura, pode ser utilizado como melhorador da autoignição do etanol em sistemas de ignição por compressão.<br>Over time, humanity has developed a greater reliance inpower generation, used to promoter comfort, transport and others. In order to address this increased demand new efficient sources are being searched, in preference, renewable sources. Transportation is one of the activities that have greater reliance on fossil fuels as well as being one of the largest generators of greenhouse gases. Therefore, in many parts of the world men are engaged in the search of new renewable energy sources that can substitute the current one used in transport. It is known that diesel engines are more efficient in comparison to the Otto engime. Due to this fact, for more than 30 years research has been conducted in order to develop ignition systems by compression, powered with renewable fuels, which reduces the dependence on fossil fuels and the emission of greenhouse gases. Ethanol is a viable candidate to replace diesel oil, but some improvements have to be accounted for before it s used in diesel engines, improvements such as the increase in compression ratio, adding auto-ignition improves, etc. Based on the facts presented, this thesis offers a new proposal, the use of n-butanol as an auto-ignition improver for ethanol. For this purpose several tests have been executed with various compression ratios, mass percentage of additive in the mixture off ethanol and many start of injections. The tests were performed in a rapid compression machine (RCM) with mixtures of ethanol and polyethylene glycol 400 and 600, and n-butanol inaddition to the reference test with diesel oil and ED95. The results show that n-butanol with a 10 per cent share of the mixture, can be used as an auto ignition improver for ethanol in compression ignition systems.
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Agostini, Luciano Volcan. "Projeto de arquiteturas integradas para a compressão de imagens JPEG." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2002. http://hdl.handle.net/10183/11431.
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Esta dissertação apresenta o desenvolvimento de arquiteturas para a compressão JPEG, onde são apresentadas arquiteturas de um compressor JPEG para imagens em tons de cinza, de um compressor JPEG para imagens coloridas e de um conversor de espaço de cores de RGB para YCbCr. As arquiteturas desenvolvidas são detalhadamente apresentadas, tendo sido completamente descritas em VHDL, com sua síntese direcionada para FPGAs da família Flex10KE da Altera. A arquitetura integrada do compressor JPEG para imagens em tons de cinza possui uma latência mínima de 237 ciclos de clock e processa uma imagem de 640x480 pixels em 18,5ms, permitindo uma taxa de processamento de 54 imagens por segundo. As estimativas realizadas em torno da taxa de compressão obtida indicam que ela seria de aproximadamente 6,2 vezes ou de 84 %. A arquitetura integrada do compressor JPEG para imagens coloridas foi gerada a partir de adaptações na arquitetura do compressor para imagens em tons de cinza. Esta arquitetura também possui a latência mínima de 237 ciclos de clock, sendo capaz de processar uma imagem coloria de 640 x 480 pixels em 54,4ms, permitindo uma taxa de processamento de 18,4 imagens por segundo. A taxa de compressão obtida, segundo estimativas, seria de aproximadamente 14,4 vezes ou de 93 %. A arquitetura para o conversor de espaço de cores de RBG para YCbCr possui uma latência de 6 ciclos de clock e é capaz de processar uma imagem colorida de 640x480 pixels em 84,6ms, o que permite uma taxa de processamento de 11,8 imagens por segundo. Esta arquitetura não chegou a ser integrada com a arquitetura do compressor de imagens coloridas, mas algumas sugestões e estimativas foram realizadas nesta direção.<br>This dissertation presents the design of architectures for JPEG image compression. Architectures for a gray scale images JPEG compressor that were developed are herein presented. This work also addresses a color images JPEG compressor and a color space converter. The designed architectures are described in detail and they were completely described in VHDL, with synthesis directed for Altera Flex10KE family of FPGAs. The integrated architecture for gray scale images JPEG compressor has a minimum latency of 237 clock cycles and it processes an image of 640x480 pixels in 18,5ms, allowing a processing rate of 54 images per second. The compression rate, according to estimates, would be of 6,2 times or 84%, in percentage of bits compression. The integrated architecture for color images JPEG compression was generated starting from incremental changes in the architecture of gray scale images compressor. This architecture also has the minimum latency of 237 clock cycles and it can process a color image of 640 x 480 pixels in 54,4ms, allowing a processing rate of 18,4 images per second. The compression rate, according to estimates, would be of 14,4 times or 93%, in percentage of bits compression. The architecture for space color conversor from RBG to YCbCr has a latency of 6 clock cycles and it is able to process a color image of 640 x 480 pixels in 84,6ms, allowing a processing rate of 11,8 images per second. This architecture was finally not integrated with the color images compressor architecture, but some suggestions, alternatives and estimates were made in this direction.
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Khan, Jobaidur Rahman. "Fog Cooling, Wet Compression and Droplet Dynamics In Gas Turbine Compressors." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/908.
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During hot days, gas turbine power output deteriorates significantly. Among various means to augment gas turbine output, inlet air fog cooling is considered as the simplest and most costeffective method. During fog cooling, water is atomized to micro-scaled droplets and introduced into the inlet airflow. In addition to cooling the inlet air, overspray can further enhance output power by intercooling the compressor. However, there are concerns that the water droplets might damage the compressor blades and increased mass might cause potential compressor operation instability due to reduced safety margin. Furthermore, the two-phase flow thermodynamics during wet compression in a rotating system has not been fully established, so continued research and development in wet compression theory and prediction model are required. The objective of this research is to improve existing wet compression theory and associated models to accurately predict the compressor and the entire gas turbine system performance for the application of gas turbine inlet fog cooling. The following achievements have been accomplished: (a) At the system level, a global gas turbine inlet fog cooling theory and algorithm have been developed and a system performance code, FogGT, has been written according to the developed theory. (b) At the component level, a stage-stacking wet compression theory in the compressor has been developed with known airfoil configurations. (c) Both equilibrium and non-equilibrium water droplet thermal-fluid dynamic models have been developed including droplet drag forces, evaporation rate, breakup and coalescence. A liquid erosion model has also been developed and incorporated. (d) Model for using computational fluid dynamics (CFD) code has been developed to simulate multiphase wet compression in the rotating compressor stage. In addition, with the continued increase in volatility of natural gas prices as well as concerns regarding national energy security, this research has also investigated employing inlet fogging to gas turbine system fired with alternative fuels such as low calorific value synthetic gases. The key results include discovering that the saturated fogging can reduce compressor power consumption, but overspray, against conventional intuition, actually increases compressor power. Nevertheless, inlet fogging does increase overall net power output.
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Day, Benjamin Marc. "An Evaluation and Redesign of a Thermal Compression Evaporator." ScholarWorks@UNO, 2009. http://scholarworks.uno.edu/td/926.
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Evaporators separate liquids from solutions. For maximum efficiency, designers reduce the temperature difference between the heating and heated media using multiple-stage evaporators. This efficiency requires increased size and bulk. A vendor claimed its thermal compression evaporator achieved high efficiency with only two stages. It did not function as claimed. This project investigated the evaporator's design to identify its problems and propose an alternative design with a minimized footprint. The analysis showed theoretical flaws and design weaknesses in the evaporator, including violation of the first law of thermodynamics. An alternative thermal compressor design was created through computational fluid dynamics using spreadsheet methods developed in house, aided by the software product FLUENT. Detailed component sizing was done using the software product HYSYS. The proposed redesign achieved four to one efficiency with two stage thermal compression, using one half of the space of a traditional system of similar performance.
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Hernández-Cabronero, Miguel. "DNA Microarray Image Compression." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/297706.
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En los experimentos con DNA microarrays se genran dos imágenes monocromo, las cuales es conveniente almacenar para poder realizar análisis más precisos en un futuro. Por tanto, la compresión de imágenes surge como una herramienta particularmente útil para minimizar los costes asociados al almacenamiento y la transmisión de dichas imágenes. Esta tesis tiene por objetivo mejorar el estado del arte en la compresión de imágenes de DNA microarrays.
Como parte de esta tesis, se ha realizado una detallada investigación de las características de las imágenes de DNA microarray. Los resultados experimentales indican que los algoritmos de compresión no adaptados a este tipo de imágenes producen resultados más bien pobres debido a las características de estas imágenes. Analizando las entropías de primer orden y condicionales, se ha podido determinar un límite aproximado a la compresibilidad sin pérdida de estas imágenes. Aunque la compresión basada en contexto y en segmentación proporcionan mejoras modestas frente a algoritmos de compresión genéricos, parece necesario realizar avances rompedores en el campo de compresión de datos para superar los ratios 2:1 en la mayor parte de las imágenes.
Antes del comienzo de esta tesis se habían propuesto varios algoritmos de compresión sin pérdida con rendimientos cercanos al límite óptimo anteriormente mencionado. Sin embargo, ninguno es compatible con los estándares de compresión existentes. Por tanto, la disponibilidad de descompresores compatibles en plataformas futuras no está garantizado. Además, la adhesión a dichos estándares se require normalmente en escenarios clínicos. Para abordar estos problemos, se propone una transformada reversible compatible con el standard JPEG2000: la Histogram Swap Transform (HST). La HST mejora el rendimiento medio de JPEG2000 en todos los corpora entre 1.97% y 15.53%. Además, esta transformada puede aplicarse incurriendo en un sobrecoste de tiempo negligible. Con la HST, JPEG2000 se convierte en la alternativa estándard más competitiva a los compresores no estándard. Las similaridades entre imágenes del mismo corpus también se han estudiado para mejorar aún más los resultados de compresión de imágenes de DNA
microarrays. En concreto, se ha encontrado una agrupación óptima de las imágenes que maximiza la correlación dentro de los grupos. Dependiendo del corpus observado, pueden observarse resultados de correlación medios de entre 0.75 y 0.92. Los resultados experimentales obtenidos indican que las técnicas de decorrelación espectral pueden mejorar los resultados de compresión hasta en 0.6 bpp, si bien ninguna de las transformadas es efectiva para todos los corpora utilizados.
Por otro lado, los algoritmos de compresión con pérdida permiten obtener resultados de compresión arbitrarios a cambio de modificar las imágenes y, por tanto, de distorsionar subsiguientes procesos de análisis. Si la distorsión introducida es más pequeña que la variabilidad experimental inherente, dicha distorsión se considera generalmente aceptable. Por tanto, el uso de técnicas de compresión con pérdida está justificado. En esta tesis se propone una métrica de distorsión para imágenes de DNA microarrays capaz de predecir la cantidad de distorsión introducida en el análisis sin necesitar analizar las imágenes modificadas, diferenciando entre cambios importantes y no importantes.
Asimismo, aunque ya se habían propuesto algunos algoritmos de compresión con pérdida para estas imágenes antes del comienzo de la tesis, ninguno estaba específicamente diseñado para minimizar el impacto en los procesos de análisis para un bitrate prefijado. En esta tesis, se propone un compresor con pérdida (el Relative Quantizer (RQ) coder) que mejora los resultados de todos los métodos anteriormente publicados. Los resultados obtenidos sugieren que es posible comprimir con ratios superiores a 4.5:1 mientras se introducen distorsiones en el análisis inferiores a la mitad de la variabilidad experimental inherente. Además, se han propuesto algunas mejoras a dicho compresor, las cuales permiten realizar una codificación lossy-to-lossless (el Progressive RQ (PRQ) coder), pudiéndose así reconstruir una imagen comprimida con diferentes niveles de calidad. Cabe señalar que los resultados de compresión anteriormente mencionados se obtienen con una complejidad computacional ligeramente inferior a la del mejor compresor sin pérdida para imágenes de DNA microarrays.<br>In DNA microarray experiments, two grayscale images are produced. It is convenient to save these images for future, more accurate re-analysis. Thus, image compression emerges as a particularly useful tool to alleviate the associated storage and transmission costs. This dissertation aims at improving the state of the art of the compression of DNA microarray images.
A thorough investigation of the characteristics of DNA microarray images has been performed as a part of this work. Results indicate that algorithms not adapted to DNA microarray images typically attain only mediocre lossless compression results due to the image characteristics. By analyzing the first-order and conditional entropy present in these images, it is possible to determine approximate limits to their lossless compressibility. Even though context-based coding and segmentation provide modest improvements over generic-purpose algorithms, conceptual breakthroughs in data coding are arguably required to achieve compression ratios exceeding 2:1 for most images.
Prior to the start of this thesis, several lossless coding algorithms that have performance results close to the aforementioned limit were published. However, none of them is compliant with existing image compression standards. Hence, the availability of decoders in future platforms -a requisite for future re-analysis- is not guaranteed. Moreover, the adhesion to standards is usually a requisite in clinical scenarios. To address these problems, a fast reversible transform compatible with the JPEG2000 standard -the Histogram Swap Transform (HST)- is proposed. The HST improves the average compression performance of JPEG2000 for all tested image corpora, with gains ranging from 1.97% to 15.53%. Furthermore, this transform can be applied with only negligible time complexity overhead. With the HST, JPEG2000 becomes arguably the most competitive alternatives to microarray-specific, non-standard compressors. The similarities among sets of microarray images have also been studied as a means to improve the
compression performance of standard and microarray-specific algorithms. An optimal grouping of the images which maximizes the inter-group correlation is described. Average correlations between 0.75 and 0.92 are observed for the tested corpora. Thorough experimental results suggest that spectral decorrelation transforms can improve some lossless coding results by up to 0.6bpp, although no single transform is effective for all copora.
Lossy coding algorithms can yield almost arbitrary compression ratios at the cost of modifying the images and, thus, of distorting subsequent analysis processes. If the introduced distortion is smaller than the inherent experimental variability, it is usually considered acceptable. Hence, the use of lossy compression is justified on the assumption that the analysis distortion is assessed. In this work, a distortion metric for DNA microarray images is proposed to predict the extent of this distortion without needing a complete re-analysis of the modified images. Experimental results suggest that this metric is able to tell apart image changes that affect subsequent analysis from image modifications that do not. Although some lossy coding algorithms were previously described for this type of images, none of them is specifically designed to minimize the impact on subsequent analysis for a given target bitrate. In this dissertation, a lossy coder -the Relative Quantizer (RQ) coder- that improves upon the rate-
distortion results of previously published methods is proposed. Experiments suggest that compression ratios exceeding 4.5:1 can be achieved while introducing distortions smaller than half the inherent experimental variability. Furthermore, a lossy-to-lossless extension of this coder -the Progressive RQ (PRQ) coder- is also described. With the PRQ, images can be compressed once and then reconstructed
at different quality levels, including lossless reconstruction. In addition, the competitive rate-distortion results of the RQ and PRQ coders can be obtained with computational complexity slightly smaller than that of the best-performing lossless coder of DNA microarray images.
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Grün, Alexander. "Nonlinear pulse compression." Doctoral thesis, Universitat Politècnica de Catalunya, 2014. http://hdl.handle.net/10803/284879.
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In this thesis I investigate two methods for generating ultrashort laser pulses in spectral regions which are ordinarily difficult to achieve by the existing techniques. These pulses are specially attractive in the study of ultrafast (few femtosecond) atomic and molecular dynamics.
The first involves Optical Parametric Amplification (OPA) mediated by four-wave-mixing in gas and supports the generation of ultrashort pulses in the Near-InfraRed (NIR) to the Mid-InfraRed (MIR) spectral region. By combining pulses at a centre wavelength of 800 nm and their second harmonic in an argon-filled hollow-core fibre, we demonstrate near-infrared pulses, peaked at 1.4 µm, with 5 µJ energy and 45 fs duration at the fibre output. The four-wave-mixing process involved in the OPA is expected to lead carrier-envelope phase stable pulses which is of great importance for applications in extreme nonlinear optics. These NIR to MIR pulses can be used directly for nonlinear light-matter interactions making use of its long-wavelength characteristics.
The second method allows the compression of intense femtosecond pulses in the ultraviolet (UV) region by sum-frequency mixing two bandwidth limited NIR pulses in a noncollinear phasematching geometry under particular conditions of group-velocity mismatch. Specifically, the crystal has to be chosen such that the group velocities of the NIR pump pulses, v1 and v2 , and of the sum-frequency generated pulse, vSF, meet the following condition, v1 < vSF < v2. In case of strong energy exchange and an appropriate pre-delay between the pump waves, the leading edge of the faster pump pulse and the trailing edge of the slower one are depleted. This way the temporal overlap region of the pump pulses remains narrow resulting in the shortening of the upconverted pulse. The noncollinear beam geometry allows to control the relative group velocities while maintaining the phasematching condition. To ensure parallel wavefronts inside the crystal and that the sum-frequency generated pulses emerge untilted, pre-compensation of the NIR pulse-front tilts is essential. I show that these pulse-front tilts can be achieved using a very compact setup based on transmission gratings and a more complex setup based on prisms combined with telescopes. UV pulses as short as 32 fs (25 fs) have been generated by noncollinear nonlinear pulse compression in a type II phasematching BBO crystal, starting with NIR pulses of 74 fs (46 fs) duration. This is of interest, because there is no crystal that can be used for nonlinear pulse compression at wavelengths near 800 nm in a collinear geometry. Compared to state-of-the-art compression techniques based on self-phase modulation, pulse compression by sum-frequency generation is free of aperture limitation, and thus scalable in energy. Such femtosecond pulses in the visible and in the ultraviolet are strongly desired for studying ultrafast dynamics of a variety of (bio)molecular systems.<br>En esta tesis he investigado dos métodos para generar pulsos láser ultracortos en regiones espectrales que son típicamente difíciles de lograr con las técnicas existentes. Estos pulsos son especialmente atractivos en el estudio de la dinámica ultrarrápida (pocos femtosegundos) en átomos y moléculas. La primera técnica implica Amplificación Paramétrica Óptica (OPA) mediante mezcla de cuatro ondas en fase gaseosa y soporta la generación de pulsos ultracortos desde el Infrarrojo-Cercano (NIR) hasta la región espectral del Infrarrojo-Medio (MIR). Mediante la combinación de pulsos centrados a una longitud de onda de 800 nm y su segundo armónico en una fibra hueca rellena de argón, hemos demostrado a la salida de la fibra la generación de pulsos en el NIR, centrados a 1.4 µm, con 5 µJ de energía y 45 fs de duración. Se espera que el proceso de mezcla de cuatro ondas involucrado en el OPA lleve a pulsos con fase de la envolvente de la portadora estables, ya que es de gran importancia para aplicaciones en óptica extrema no lineal. Estos pulsos desde el NIR hasta el MIR se pueden utilizar directamente en interacciones no-lineales materia-radiación, haciendo uso de sus características de longitud de onda largas. El segundo método permite la compresión de pulsos intensos de femtosegundos en la región del ultravioleta (UV) mediante la mezcla de suma de frecuencias de dos pulsos en el NIR limitados en el ancho de banda en una geometría de ajuste de fases no-colineal bajo condiciones particulares de discrepancia de velocidades de grupo. Específicamente, el cristal debe ser elegido de tal manera que las velocidades de grupo de los pulsos de bombeo del NIR, v1 y v2, y la del pulso suma-de-frecuencias generado, vSF, cumplan la siguiente condición, v1 < vSF < v2. En el caso de un fuerte intercambio de energía y un pre-retardo adecuado entre las ondas de bombeo, el borde delantero del pulso de bombeo más rápido y el borde trasero del más lento se agotan. De esta manera la región de solapamiento temporal de los impulsos de bombeo permanece estrecha, resultando en el acortamiento del impulso generado. La geometría de haces no-colineales permite controlar las velocidades de grupo relativas mientras mantiene la condición de ajuste de fase. Para asegurar frentes de onda paralelos dentro del cristal y que los pulsos generados por suma de frecuencias se generen sin inclinación, es esencial la pre-compensación de la inclinación de los frente de onda de los pulsos NIR. En esta tesis se muestra que estas inclinaciones de los frentes de onda se pueden lograr utilizando una configuración muy compacta basada en rejillas de transmisión y una configuración más compleja basada en prismas combinados con telescopios. Pulsos en el UV tan cortos como 32 fs (25 fs) se han generado mediante compresión de pulsos no-lineal no-colineal en un cristal BBO de ajuste de fase tipo II, comenzando con pulsos en el NIR de 74 fs (46 fs) de duración. El interés de este método radica en la inexistencia de cristales que se puedan utilizar para la compresión de impulsos no-lineal a longitudes de onda entorno a 800 nm en una geometría colineal. En comparación con las técnicas de última generación de compresión basadas en la automodulación de fase, la compresión de pulsos por suma de frecuencias esta libre de restricciones en la apertura de los pulsos, y por lo tanto es expandible en energía. Tales pulsos de femtosegundos en el visible y en el ultravioleta son fuertemente deseados en el estudio de dinámica ultrarrápida de una gran variedad de sistemas (bio)moleculares.
Książki na temat "Compression"
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Salomon, David. Data Compression. New York, NY: Springer New York, 1998. http://dx.doi.org/10.1007/978-1-4757-2939-9.
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Salomon, David. Data Compression. Berlin, Heidelberg: Springer Berlin Heidelberg, 2000. http://dx.doi.org/10.1007/978-3-642-86092-8.
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Bell, Timothy C. Text compression. Englewood Cliffs, N.J: Prentice Hall, 1990.
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Great Britain. Health and Safety Executive., ed. Compression chambers. Sudbury: HSE Books, 1998.
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Alexander, Will. Compression & Purity. San Francisco, USA: City Lights Books, 2011.
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Mark, Nelson. The data compression book: Featuring fast, efficient data compresssion techniques in C. Redwood City, CA: M & T, 1991.
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Pearlman, William A. Wavelet Image Compression. Cham: Springer International Publishing, 2013. http://dx.doi.org/10.1007/978-3-031-02248-7.
Pełny tekst źródłaCzęści książek na temat "Compression"
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Slinko, Arkadii. "Compression." In Springer Undergraduate Mathematics Series, 235–55. Cham: Springer International Publishing, 2020. http://dx.doi.org/10.1007/978-3-030-44074-9_8.
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Domański, Marek, and Maciej Bartkowiak. "Compression." In The Colour Image Processing Handbook, 242–304. Boston, MA: Springer US, 1998. http://dx.doi.org/10.1007/978-1-4615-5779-1_13.
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Plattner, Hasso. "Compression." In A Course in In-Memory Data Management, 43–54. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-36524-9_7.
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Adeyeri, Joseph B. "Compression." In Selective Neck Dissection for Oral Cancer, 1–10. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-12127-7_63-1.
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Bhaduri, Amit. "Compression." In Mechanical Properties and Working of Metals and Alloys, 95–117. Singapore: Springer Singapore, 2018. http://dx.doi.org/10.1007/978-981-10-7209-3_2.
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Slinko, Arkadii. "Compression." In Springer Undergraduate Mathematics Series, 213–28. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-21951-6_8.
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Schreiber, William F. "Compression." In Fundamentals of Electronic Imaging Systems, 104–33. Berlin, Heidelberg: Springer Berlin Heidelberg, 1993. http://dx.doi.org/10.1007/978-3-642-77847-6_5.
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Kao, Ming-Yang. "Compression." In Encyclopedia of Algorithms, 183. Boston, MA: Springer US, 2008. http://dx.doi.org/10.1007/978-0-387-30162-4_85.
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Fitzjarrell, David, and Mary Mikell Spence. "Compression." In Oracle Exadata Survival Guide, 83–118. Berkeley, CA: Apress, 2013. http://dx.doi.org/10.1007/978-1-4302-6011-0_6.
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Schreiber, William F. "Compression." In Fundamentals of Electronic Imaging Systems, 104–33. Berlin, Heidelberg: Springer Berlin Heidelberg, 1991. http://dx.doi.org/10.1007/978-3-662-00743-3_5.
Pełny tekst źródłaStreszczenia konferencji na temat "Compression"
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Tang, Luyang, Yongqi Zhai, and Ronggang Wang. "Compression-Aware Tuning for Compressing Volumetric Radiance Fields." In 2024 IEEE International Conference on Image Processing (ICIP), 2250–56. IEEE, 2024. http://dx.doi.org/10.1109/icip51287.2024.10647954.
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Prior, Morgan E., Thomas J. Howard, Emily Light, Najib Ishaq, and Noah M. Daniels. "Generalized compression and compressive search of large datasets." In 2024 IEEE International Conference on Big Data (BigData), 5702–10. IEEE, 2024. https://doi.org/10.1109/bigdata62323.2024.10825508.
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Xue, Xianglian, Haiyan Jin, and Changjun Zhou. "Adaptive Compression-Encryption Scheme for Medical Image Based on Improved Compressive Sensing and Deoxyribonucleic Acid Coding-Compression." In 2024 IEEE International Conference on Bioinformatics and Biomedicine (BIBM), 7168–72. IEEE, 2024. https://doi.org/10.1109/bibm62325.2024.10822367.
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Wang, Weilan, Yu Mao, Tang Dongdong, Du Hongchao, Nan Guan, and Chun Jason Xue. "When Compression Meets Model Compression: Memory-Efficient Double Compression for Large Language Models." In Findings of the Association for Computational Linguistics: EMNLP 2024, 16973–83. Stroudsburg, PA, USA: Association for Computational Linguistics, 2024. http://dx.doi.org/10.18653/v1/2024.findings-emnlp.988.
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Choukse, Esha, Mattan Erez, and Alaa R. Alameldeen. "Compresso: Pragmatic Main Memory Compression." In 2018 51st Annual IEEE/ACM International Symposium on Microarchitecture (MICRO). IEEE, 2018. http://dx.doi.org/10.1109/micro.2018.00051.
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Jahanian, Shahriar, and A. J. McPhate. "Approximate Residual Interface Compression in a Laminated Magnet." In ASME 1993 Design Technical Conferences. American Society of Mechanical Engineers, 1993. http://dx.doi.org/10.1115/detc1993-0072.
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Abstract Present design of large laminated magnets are based on effective modulus of elasticity for the plate stack that is invariant with interplate compression. Experimental results indicates this is not a valid assumption. This analysis considers the specific design used for compact electron storage ring dipole magnet at the Center for Advanced Micro Devices (CAMD) at Louisiana State University. An iterative technique, using FEM is developed to approximate the effective modulus throughout the magnet structure. This particular magnet is constructed from 1424 steel plates (1.5mm × 610mm × 780mm) by first compressing a 45° 2.93m raduis curvilinear stack to a specified preload and then welding straight and curved straps to the exterior of the stack. Release of the preload allowsexpansion of the stack and forces stretch of the straps, the resultant interplate compression is considerably different from the initial preload and varies throughout the magnet. The analysis technique introduced in this paper is a simplified approach to the interplate compression modeling and consists of the supeposition of two simple analysis; one with straps attached, one without straps attached. An iterative approach is used to incorporate the dependence of effective compressive modulus on the interplate compression. An estimate of the average modulus is assumed for the entire stack and residual compression is calculated. From this residual compression and from experimental data, a distribution of compressive modulus throughout the magnet is computed. From this computed distribution, a new estimate for the compressive modulus is made for each element of the model and the analysis iterated. The net results are the compressive modulus distribution throughout the magnet ia a form suitable in subsequent dynamic analysis.
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Yi Yang, Oscar C. Au, Lu Fang, Xing Wen, and Weiran Tang. "Reweighted Compressive Sampling for image compression." In 2009 Picture Coding Symposium (PCS). IEEE, 2009. http://dx.doi.org/10.1109/pcs.2009.5167354.
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Merino, L. M., and L. E. Mendoza. "Robust compression using Compressive Sensing (CS)." In 2010 IEEE ANDESCON. IEEE, 2010. http://dx.doi.org/10.1109/andescon.2010.5633063.
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Qin, Liang, and Jie Sun. "Model Compression for Data Compression: Neural Network Based Lossless Compressor Made Practical." In 2023 Data Compression Conference (DCC). IEEE, 2023. http://dx.doi.org/10.1109/dcc55655.2023.00013.
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Simons, Sarah, Ryan Cater, Klaus Brun, Grant Musgrove, and Rainer Kurz. "Measured Thermodynamic Effect of Wet Gas Compression." In ASME Turbo Expo 2018: Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/gt2018-75058.
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Significant work has been performed to qualify and quantify the effects of operating with wet gas in a centrifugal compressor system [1, 2]. Of particular interest is the sharp decrease in the isentropic efficiency of the machine when operating with process gas containing various liquid volume fractions. However, it is unknown how much of the performance losses are due to aerodynamic effects, such as blade profile and flow separation losses, rather than the basic thermodynamic effects of compressing a multiphase gas that has a higher density, integral wet-cooling, and contains small amounts of high-density droplets. Previous studies showed that the overall efficiency losses exceeded those expected from purely thermodynamic effects so aerodynamic effects have been principally blamed for the lower efficiency. However, no test data exists in the public domain that quantifies these losses and it is experimentally difficult to perform this type of testing in centrifugal compressor. Therefore, a series of tests was performed on a reciprocating compressor with power and efficiency recorded through dynamic pressure measurements obtained inside the compression cylinder, torque measured on the shaft, and enthalpy rise measurements obtained outside the cylinders. Using this approach one can eliminate (or differentiate) the aerodynamic effects of wet gas compression, such as valve losses, thus allowing the direct determination of the thermodynamic losses of wet gas compression. Specifically, when there is multi-phase flow entering the machinery, there is the thermodynamic effect of how a mixture of water and air behaves when being compressed [from a process perspective] and the aerodynamic effect of moisture encountering the blades of a centrifugal compressor [performance loss] or the valve passages of a reciprocating compressor [pressure loss]. Directly instrumenting the internals of a reciprocating compressor cylinder allows the evaluation of the thermodynamic performance of multi-phase compression separate from any aerodynamic penalties. This paper describes the tests performed in a reciprocating compressor open test loop operating with varying amounts of liquid volume fractions (LVFs) of water in the process gas (air). The data was reduced using Pressure-Volume card measurements inside and outside the cylinder, enthalpy rise, as well as torque to determine the impact of volume fraction on compression power and efficiency. Additionally, the valve losses, system efficiencies, and peak compression “spike” were evaluated in relations to the LVFs.
Raporty organizacyjne na temat "Compression"
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Bauer, Travis. NgramPPM: Compression Analytics without Compression. Office of Scientific and Technical Information (OSTI), September 2021. http://dx.doi.org/10.2172/1822127.
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Kriha, Kenneth, Guillaume Petitpas, Michael Melchionda, Herie Soto, Yanli Wang, and Zhili Feng. Compressor-less Hydrogen Refueling Station Using Thermal Compression. Office of Scientific and Technical Information (OSTI), February 2019. http://dx.doi.org/10.2172/1524866.
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Broerman, Eugene, Nathan Poerner, and Willard Shade. Linear Motor Reciprocating Compressor (LMRC) for Forecourt Hydrogen Compression. Office of Scientific and Technical Information (OSTI), November 2020. http://dx.doi.org/10.2172/1894346.
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Skone, Timothy J. CO2 Compression. Office of Scientific and Technical Information (OSTI), July 2012. http://dx.doi.org/10.2172/1509260.
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NETROLOGIC INC SAN DIEGO CA. Image Compression. Fort Belvoir, VA: Defense Technical Information Center, June 1990. http://dx.doi.org/10.21236/ada224242.
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Chandrasekaran, S. compression _UCMerced. Office of Scientific and Technical Information (OSTI), August 2024. http://dx.doi.org/10.2172/2438174.
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Pelletier, G. RObust Header Compression (ROHC): A Compression Profile for IP. RFC Editor, June 2004. http://dx.doi.org/10.17487/rfc3843.
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Johnson, Terry A., Anne Mallow, Robert C. Bowman, Barton D. Smith, Craig Jensen, and Lawrence Anovitz. Metal Hydride Compression. Office of Scientific and Technical Information (OSTI), October 2018. http://dx.doi.org/10.2172/1481555.
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Johnson, Terry A., Robert Bowman, Barton Smith, Lawrence Anovitz, and Craig Jensen. Metal Hydride Compression. Office of Scientific and Technical Information (OSTI), July 2017. http://dx.doi.org/10.2172/1373472.
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Degermark, M., B. Nordgren, and S. Pink. IP Header Compression. RFC Editor, February 1999. http://dx.doi.org/10.17487/rfc2507.
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