Parallel Compression Research Articles

Caracterização tecnológica da madeira de Eucalyptus benthamii Maiden et Cambage

The knowledge about the technological properties of the wood enables the achievement of tools that assist in the adequate use of this material. Therefore, the aim of this study was accomplish the technological characterization of Eucalyptus benthamii wood for potential uses. For this, it was used six trees of the forestry plantation implanted in the Guatambu city, Santa Catarina State, Brazil. For the physical characterization of the wood, discs were obtained at three different positions of the trunk of each tree, determining the basic density and retractibility. The test pieces to the mechanical tests of parallel compression to the fibers, dynamic bending, static bending and Janka hardness were obtained from discs removed of the logs. The average basic density was 0.549 g cm-3, while the retractibility parameters were similar to those of genus eucalyptus, with an average anisotropy coefficient of 1.9, indicating that it is a specie unstable dimensionally. The results obtained from the mechanical tests show that the Eucalyptus benthamii wood has less resistant to mechanical stress, limiting its use for this purpose. Therefore, the application of this species for purposes applying mechanical stress is limited, making it necessary carrying out studies about the other properties of this wood.

Microstructure and Rheological Properties of Semi-Solid 7075 Slurries Using SEED Rheocasting Process

The SEED rheocasting process was used to produce semisolid slurries of high strength 7075 aluminum wrought alloys. The effects of the SEED processing parameters on the microstructure of semisolid slurries were studied. The impact of grain refinement on the grain morphology and size was investigated. The rheological properties of semisolid 7075 alloys were characterized at different solid fractions using a parallel plate compression viscometer. Results indicated that the grain refinement could greatly improve the globularity of α-Al grains and rheoformability. The relationships between viscosity and shear rate at different solid fractions in the transient state for both unrefined and refined semisolid slurries were evaluated and discussed.

Características anatómicas y propiedades mecánicas de la madera de Oecopetalum mexicanum Greenm. & C.H. Thomps. (Icacinaceae) de la sierra de Misantla, Veracruz, México

Se describe por primera vez la anatomía de la madera de Oecopetalum mexicanum ( cachichín ) Greenm. & C.H. Thomps., la cual es una especie que crece en los bosques y ecosistemas de café de la sierra de Misantla, Veracruz, México. Con el fin de conocer sus posibles usos, se determinaron las propiedades mecánicas en flexión, del tipo: esfuerzo en el límite de proporcionalidad, trabajo unitario en el límite de proporcionalidad, módulo de elasticidad, módulo de ruptura y trabajo unitario a carga máxima; en compresión paralela a la fibra, como lo fue el esfuerzo máximo, esfuerzo en el límite de proporcionalidad y módulo de elasticidad. Todo ello, en su madera en condición verde. Se investigó también la densidad relativa básica de cada muestra, así como el diámetro, la distribución y densidad de los vasos, la abundancia y distribución del parénquima axial y radial. A partir de macerados, se identificó el tamaño de los elementos de vaso, tamaño de las fibras y contenidos celulares. La descripción anatómica se basó en la IAWA List of microscopic features for hardwood Identification (IAWA 1989) . Los resultados obtenidos a la fecha indican que la madera del cachichín tiene resistencia similar a la del pino y, en algunas propiedades, incluso lo supera. Por lo tanto, es apta para la construcción, siempre y cuando se utilice todo el tronco y solo cuando sea posible aserrarla, se usarán piezas prismáticas aserradas.

INFLUÊNCIA DA TEMPERATURA NA RESISTÊNCIA E NO MÓDULO DE ELASTICIDADE EM MADEIRA DE HÍBRIDOS DE EUCALIPTOS

O trabalho trata da influência da temperatura, em um intervalo de 20ºC a 24ºC, nas propriedades físicas da madeira: umidade e massa específica e mecânicas: resistência e módulo de elasticidade à compressão paralela às fibras. O programa experimental foi realizado com 78 corpos de prova, de híbridos de Eucalyptus grandis com Eucalyptus urophylla, com massa específica aparente média de 671 kg/m3 e teor de umidade de 11,14%. Foram seguidos os procedimentos dos ensaios prescritos pela NBR 7190. Os resultados mostram uma diminuição linear do teor de umidade com o aumento da temperatura até 160°C. Destacam-se duas retas, a primeira de 20°C até 65°C com pequeno decréscimo do teor de umidade, chegando a 4% e a segunda de 65°C até 160°C com perda mais acentuada chegando a 0% de teor de umidade. Acima de 160°C, não apresentando mais umidade, a madeira perde apenas material orgânico, chegando a 20% de perda de massa quando atinge uma temperatura de 240°C. A massa específica praticamente permanece constante até a temperatura de 100ºC. A partir da temperatura de 100ºC até 240ºC a massa específica decresce linearmente chegando a 20%. A resistência à compressão paralela às fibras aumenta linearmente com a temperatura, chegando a 19% na temperatura de 100°C e, após esta temperatura, o comportamento se inverte com decréscimo linear até a temperatura de 180ºC. A partir de 180ºC, a queda de resistência é acentuada, chegando, na temperatura de 240ºC, a 32% menor do que a resistência na temperatura de 20ºC. O módulo de elasticidade diminui, apenas aumenta a temperatura. Até 120ºC existe uma diminuição linear não muito acentuada, em torno de 8%. Já de 120ºC até 200ºC a diminuição também é linear, porém, bastante acentuada chegando a 38%.

Performance comparison of sequential and parallel compression applications for DNA raw data

We present an experimental performance comparison of lossless compression programs for DNA raw data in FASTQ format files. General-purpose (PBZIP2, P7ZIP and PIGZ) and domain-specific compressors (SCALCE, QUIP, FASTQZ and DSRC) were analyzed in terms of compression ratio, execution speed, parallel scalability and memory consumption. Results showed that domain-specific tools increased the compression ratios up to 70 %, while reducing the runtime of general-purpose tools up to $$7\times $$ during compression and up to $$3\times $$ during decompression. Parallelism scaled performance up to $$13\times $$ when using 20 threads. Our analysis indicates that QUIP, DSRC and PBZIP2 are the best tools in their respective categories, with acceptable memory requirements. Nevertheless, the end user must consider the features of available hardware and define the priorities among its optimization objectives (compression ratio, runtime during compression or decompression, scalability, etc.) to properly select the best application for each particular scenario.

Data Compression for Climate Data

The different rates of increase for computational power and storage capabilities of supercomputers turn data storage into a technical and economical problem. Because storage capabilities are lagging behind, investments and operational costs for storage systems have increased to keep up with the supercomputers' I/O requirements. One promising approach is to reduce the amount of data that is stored. In this paper, we take a look at the impact of compression on performance and costs of high performance systems. To this end, we analyze the applicability of compression on all layers of the I/O stack, that is, main memory, network and storage. Based on the Mistral system of the German Climate Computing Center Deutsches Klimarechenzentrum, DKRZ, we illustrate potential performance improvements and cost savings. Making use of compression on a large scale can decrease investments and operational costs by 50% without negatively impacting performance. Additionally, we present ongoing work for supporting enhanced adaptive compression in the parallel distributed file system Lustre and application-specific compression.

Improving the permeability of Douglas-fir (Pseudotsuga menziesii) containing compression wood by Physisporinus vitreus and Xylaria longipes

The bioincising impact of Physisporinus vitreus and Xylaria longipes on the porous structure, and permeability of Douglas-fir containing compression wood was investigated. Fungal cultivation was carried out at 25°C and 85% relative humidity in an incubator for three time periods, namely, 15, 30 and 45 days. Safranin solution was injected into wood specimens to evaluate liquid permeability whereas air permeability was measured by the falling-water method. Wood exposure to both fungi enhanced permeability by increasing incubation period. However, the parallel compression strength of wood reduced. Microscopic imagery revealed degradation of bordered pits, bore-hole formation through tracheid walls as well as ray damage which are thought to be main reasons for improvements in air and liquid permeability. No pronounced differences were found between the fungi in their effects on permeability. Parenchyma rays were also shown to play an important role in the radial permeability of Douglas-fir compression wood.

P-Codec: Parallel Compressed File Decompression Algorithm for Hadoop

The increasing amount and size of data being handled by data analytic applications running on Hadoop has created a need for faster data processing. One of the effective methods for handling big data sizes is compression. Data compression not only makes network I/O processing faster, but also provides better utilization of resources. However, this approach defeats one of Hadoop’s main purposes, which is the parallelism of map and reduce tasks. The number of map tasks created is determined by the size of the file, so by compressing a large file, the number of mappers is reduced which in turn decreases parallelism. Consequently, standard Hadoop takes longer times to process. In this paper, we propose the design and implementation of a Parallel Compressed File Decompressor (P-Codec) that improves the performance of Hadoop when processing compressed data. P-Codec includes two modules; the first module decompresses data upon retrieval by a data node during the phase of uploading the data to the Hadoop Distributed File System (HDFS). This process reduces the runtime of a job by removing the burden of decompression during the MapReduce phase. The second P-Codec module is a decompressed map task divider that increases parallelism by dynamically changing the map task split sizes based on the size of the final decompressed block. Our experimental results using five different MapReduce benchmarks show an average improvement of approximately 80% compared to standard Hadoop.

Advanced exergy analysis of a R744 booster refrigeration system with parallel compression

In this paper, the advanced exergy analysis was applied to a R744 booster refrigeration system with parallel compression taking into account the design external temperatures of 25 °C and 35 °C, as well as the operating conditions of a conventional European supermarket. The global efficiencies of all the chosen compressors were extrapolated from some manufactures' data and appropriated optimization procedures of the performance of the investigated solution were implemented.According to the results associated with the conventional exergy evaluation, the gas cooler/condenser, the HS (high stage) compressor and the MT (medium temperature) display cabinet exhibited the highest enhancement potential. The further splitting of their corresponding exergy destruction rates into their different parts and the following assessment of the interactions among the components allowed figuring out the real achievable improvements. The avoidable irreversibilities of the HS compressor and that of the MT evaporator were mainly and completely endogenous, respectively. On the other hand, the gas cooler/condenser could be predominantly improved by decreasing the inefficiencies of the MT evaporator. As regards the auxiliary compressor, large enhancements were attainable through the drop in the irreversibilities occurring in the remaining components.

Longitudinal parallel compression suture to control postopartum hemorrhage due to placenta previa and accrete

ObjectiveTo assess the efficacy and safety of longitudinal parallel compression suture to control heavy postpartum hemorrhage (PPH) in patients with placenta previa/accreta. Materials and MethodsFifteen women received a longitudinal parallel compression suture to stop life-threatening PPH due to placenta previa with or without accreta during cesarean section. The suture apposed the anterior and posterior walls of the lower uterine segment together using an absorbable thread A 70-mm round needle with a Number-1 absorbable thread was used. The point of needle entry was 1 cm above the upper margin of the cervix and 1 cm from the right lateral border of the lower segment of the anterior wall. The suture was threaded through the uterine cavity to the serosa of the posterior wall. Then, it was directed upward and threaded from the posterior to the anterior wall at ∼1–2 cm above the upper boundary of the lower uterine segment and 3-cm medial to the right margin of the uterus. Both ends of the suture were tied on the anterior aspect of uterus. The left side was sutured in the same way. ResultsThe success rate of the procedure was 86.7% (13/15). Two of 15 cases were concurrently administered gauze packing and achieved satisfactory hemostasis. All patients resumed a normal menstrual flow, and no postoperative anatomical or physiological abnormalities related to the suture were observed. Three women achieved further pregnancies after the procedure. ConclusionLongitudinal parallel compression suture is a safe, easy, effective, practical, and conservative surgical technique to stop intractable PPH from the lower uterine segment, particularly in women who have a cesarean scar and placenta previa/accreta.

Hygro-mechanical behavior of thermally treated beech subjected to compression loads

The physical and mechanical properties of beech wood (Fagus sylvatica L.) were determined after industrial thermal treatment in a steam atmosphere. Parallel clear uniaxial compression specimens (20×20×20mm) were made from control and thermally treated wood, conditioned in a series from an oven dry to saturated atmosphere (20°C) and compression loaded parallel and transverse to the grain. The reduced density of thermally treated beech was reflected in the decreased stiffness and, especially, strength of wood transverse to the grain. No impact of thermal treatment on the longitudinal compression strength of wood was confirmed. Lower hygroscopicity was additionally detected with thermo-modified wood, whereas the relationship between wood moisture content and stiffness (MOE/MOE0), as well as strength (σ/σ0), along and transverse to the grain of the beech wood remained identical.

Efficiency increase in carbon dioxide refrigeration technology with parallel compression

In this article, we will review the comparison between a CO2 refrigeration system with a parallel compressor and a conventional carbon dioxide refrigeration machine. In order to carry out the comparison, a numerical model has been generated showing a good correlation to experimental data obtained with a fully instrumented test rig machine. We can determine under which conditions an increase in the energy efficiency ratio (EER) of 10% and more can be expected with a parallel compression system. The results will help users to decide upon economically viable refrigeration systems, depending on the operational conditions of the machine. In usual operating conditions, the achievable increase in the EER by the parallel compressor has been determined; furthermore, it showed that a low evaporation temperature and a high temperature at the outlet of the gas cooler have a positive effect on the parallel compression circuit. With respect to the intermediate pressure, an optimum can be specified at low evaporation temperatures.

Experimental analysis of the R744 vapour compression rack equipped with the multi-ejector expansion work recovery module

A test facility for the experimental investigation of the R744 vapour compression rack equipped with a multi-ejector expansion work recovery module was designed and manufactured. A comparison of the R744 multi-ejector refrigeration system with the R744 parallel compression system at the same test facility was carried out based on the energy performance characteristics of refrigeration capacity, power consumption, COP, and exergy efficiency. Apart from the system performance comparison, the influence of the pressure level in the flash tank on the system performance for the two alternatives was analysed. The experimental results indicate COP and exergy efficiency improvements of the multi-ejector refrigeration system up to 7% and 13.7%, respectively. The highest values of COP and exergy efficiency were obtained by a multi-ejector refrigeration system with the tank pressure lift close to the maximum value possible to operate the multi-ejector expansion module. The values of the effective compressor efficiencies were significantly different, depending on the operation module (cooling load and heat rejection conditions).

Energy and environmental performance assessment of R744 booster supermarket refrigeration systems operating in warm climates

This paper presents a theoretical comparison among different commercial refrigeration systems in terms of annual energy consumption and environmental impact. Eight configurations were studied: a R744/R134a cascade refrigeration system (baseline), a conventional and an improved R744 booster system, two R744 booster solutions with dedicated mechanical subcooling, a R744 booster with parallel compression and two solutions which combined the parallel compression and the mechanical subcooling. The evaluation was based on the weather data in Valencia (Spain) and in Athens (Greece), as well as on the running modes of a conventional European supermarket. A transition zone, which occurred between subcritical and transcritical operations, was adopted.The results showed that all the enhanced configurations may achieve a comparable energy saving to the one of the baseline in both the selected locations. Furthermore, they allow reducing the Total Equivalent Warming Impact (TEWI) by at least 9.6% beside the cascade solution.

L1k-t ESPIRiT: Accelerating Dynamic MRI Using Efficient Auto-Calibrated Parallel Imaging and Compressed Sensing Reconstruction

L1k-t ESPIRiT: Accelerating Dynamic MRI Using Efficient Auto-Calibrated Parallel Imaging and Compressed Sensing Reconstruction

ANÁLISE DA DEFORMAÇÃO RESIDUAL LONGITUDINAL E SUA RELAÇÃO COM PROPRIEDADES TECNOLÓGICAS DA MADEIRA DE ACÁCIA-NEGRA

RESUMOA madeira de acácia-negra tem sido utilizada em nichos que conferem pouco valor agregado à esse material. Diante disso, este trabalho teve como objetivo analisar as deformações residuais longitudinais (DRL) e suas relações com propriedades da madeira de Acacia mearnsii. Para tanto, foram selecionadas 60 árvores em plantios com idades distintas (4 e 7 anos) no Município de Piratini, RS. As características de crescimento avaliadas consistiram em diâmetro à altura do peito (1,3 m; DAP), espessura de casca (EP) e altura comercial (h). As propriedades físicas avaliadas massa específica básica (ρ) e teorde umidade à base seca (Tu). Já o tempo de propagação de onda ultrassonora foi determinado em conformidade com o procedimento NBR 15521. As propriedades mecânicas foram o módulo de elasticidade dinâmico (Ed), bem como as propriedades descritas no procedimento normativo D143-94, através dos ensaios de flexão estática, compressão paralela às fibras e Dureza Janka. ADRLesuas relações com as propriedades da madeira mostraram-se semelhantes aos resultados encontrados na literatura para a madeira de espécies do gênero Eucalyptus. No entanto, em magnitude, tais níveis se mostraram sensivelmente menores, conferindo à madeira de acácia-negra no que se refere a esse parâmetro de qualidade, indicação para a confecção de produtos sólidos.

Iso- and variothermal injection compression moulding of polymer micro- and nanostructures for optical and medical applications

The surfaces of medical and optical polymer products are being increasingly functionalized with micro- and nanostructures using mass replication methods like injection moulding. We compared the filling behaviour and replication quality of such structures using four different moulding processes with two polymers of different viscosity and wetting behaviour. For this purpose, we replicated three representative 2D and 3D micro- and nanostructures into polymethylmethacrylate and amorphous polyamide by isothermal and variothermal injection moulding with and without compression, respectively, using the same mould. The parallel compression phase reduced the internal pressure in the cavity, leading to fewer demoulding issues but without significant influence on the replication fidelity. Variothermal heating of the mould in combination with a polymer of low viscosity and good wetting behaviour was favourable especially for filling of high aspect-ratio structures. For microstructure replication, melt viscosity and no-flow temperature were clearly more relevant than wetting as flow resistance and frozen layer formation are the main reasons for incomplete filling at this length scale. In nanostructures, the capillary effect becomes increasingly dominant depending on the surface energy of the polymer.

Numerical optimization of a transcritical CO 2 /propylene cascaded refrigeration-heat pump system with economizer in HT cycle

Use of organic refrigerants such as Hydrochlorofluorocarbons and Chlorofluorocarbons have been criticized for their adverse impact on the Earth’s protective ozone layer and for their significant global warming potential (GWP). CO2 has been receiving great concern as an alternative refrigerant. Cascade refrigeration systems employing CO2 are used for low temperature applications. Being a low critical temperature fluid CO2 transcritical cascade systems offer low COP for a given application. Parallel compression economization is one of the promising cycle modifications to improve the COP of transcritical CO2 cascaded systems. In this paper, transcritical CO2/propylene cascade system with parallel compression economization in the HT cycle has been analysed for cooling/heating applications. An enhancement in COP of 9% has been predicted. Thermodynamic analysis on R744-R1270 cascade refrigeration system has been performed to determine the optimal value of the various design parameters of the system. The design parameters included are: gas cooler outlet temperature and intermediate temperature in the high temperature circuit and evaporator temperature and temperature difference in the cascade condenser in the low temperature circuit.

An intelligent water drop algorithm to identical parallel machine scheduling with controllable processing times: a just-in-time approach

Identical parallel machine scheduling problem with controllable processing times is investigated in this research. In such an area, our focus is mostly motivated by the adoption of just-in-time (JIT) philosophy with the objective of minimizing total weighted tardiness and earliness as well as job compressions/expansion cost simultaneously. Also the optimal set amounts of job compressions/expansion plus the job sequence are determined on each machine. It is assumed that the jobs processing times can vary within a given interval, i.e., it is permitted to compress or expand in return for compression/expansion cost. A mixed integer linear programming (MILP) model for the considered problem is firstly proposed and thereafter the optimal jobs set amounts of compression and expansion processing times in a known sequence are determined via parallel net benefit compression–net benefit expansion called PNBC–NBE heuristic. An intelligent water drop (IWD) algorithm, as a new swarm-based nature-inspired optimization one, is also adopted to solve this multi-criteria problem. A heuristic method besides three meta-heuristic algorithms is then employed to solve small- and medium- to large-size sample-generated instances. Computational results reveal that the proposed IWDNN outperforms the other techniques and is a trustable one which can solve such complicated problems with satisfactory consequences.

The pseudo-distance technique for parallel lossless compression of color-mapped images

Data compression is a challenging process with important practical applications. Specialized techniques for lossy and lossless data compression have been the subject of numerous investigations during last several decades. Previously, we studied the use of the pseudo-distance technique (PDT) in lossless compression of color-mapped images and its parallel implementation. In this paper we present a new technique (PDT2) to improve compression gain of PDT. We also present a parallelized implementation of the new technique, which results in substantial gains in compression time while providing the desired compression efficiency. We demonstrate that on non-dithered images PDT2 outperforms PDT by 22.4% and PNG by 29.3%. On dithered images, PDT2 achieves compression gains of 7.1% over PDT and 23.8% over PNG. We also show that the parallel implementation of PDT2, while compromising compression less than 0.3%, achieves near linear speedup and utilization of Intel Hyper-Threading technology on supported systems improves speedup on average 18%.