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31.
This study investigated the influence of the longitudinal airflow on the smoke propagation in a tunnel by large-eddy simulation, which is now widely applied to study the turbulent flow. The smoke movement characteristics were studied in detail, with varying the longitudinal airflow in the tunnel. Six fire scenarios have been simulated with Fire Dynamics Simulator (FDS) and the results of the longitudinal distribution of CO concentration, temperature distribution, interface height, stratification, and the efficiency of smoke extraction in the tunnel have been analyzed to evaluate the different fire cases. FDS predicted a CO concentration distribution compared to calculated values using the Hu model. Furthermore, the predicted maximum smoke temperatures are compared to those given by the Kurioka model. A reasonably good agreement has been obtained for both models. The obtained results showed that the increase of the forced airflow velocity has for results a loss of stratification and significant decrease in the efficiency of extraction.  相似文献   
32.
Afif  Mouna  Ayachi  Riadh  Said  Yahia  Atri  Mohamed 《Neural Processing Letters》2020,51(3):2827-2837
Neural Processing Letters - Recognizing indoor scene and objects and estimating their poses present a wide range of applications in robotic field. This task becomes more challenging especially in...  相似文献   
33.
The biogas production potential of different mixtures of cow manure (CM) and three-phase olive mill solid waste (3POMSW) at 37°C was evaluated. Results showed that 3POMSW produced more methane yield than CM. In the anaerobic co-digestion (AcoD) methane yield increased with increasing of 3POMSW content, the maximum methane yield was observed at 3POMSW:CM ratio of 3:1. Addition of an enzyme mixture (Celluclast, Pulpzyme HC, Sherazyme, Novozym 342, and Resinase A 2X) to the 1:1 mixture increased the quantity and quality of biogas production and reduced the retention time required to achieve a high rate of biodegradation. Therefore, AcoD with enzymes was an effective way to improve the methane yield of 3POMSW and CM.  相似文献   
34.
In this article, simulated annealing (SA), genetic algorithm (GA), and tabu search (TS) methods are employed separately and together for finding optimal radiant heater settings for obtaining a specific temperature profile on a design surface. Results show that all methods yield to very acceptable results for various desired temperature profiles but after different number of iterations. The GA and TS methods progress very rapidly before slowly stabilizing after a certain number of iterations, while the SA method progresses for longer periods. In addition, hybrid combinations of GA, SA, and TS proved to be better than separate ones.  相似文献   
35.
The aim of this work was to investigate the influence of two different drying methods, traditionally by sun and controlled temperatures of 45, 50, 60 and 70 °C and relative humidity of 20 and 30% on the chemical composition of Sepia officinalis. When compared to fresh samples, lipid content increased under both drying methods whereas protein levels significantly increased only under controlled conditions. Drying procedures increased the percentage of saturated fatty acids mainly in sun‐dried samples and at high temperature (70 °C). A significant decrease in the amount of polyunsaturated fatty acids was detected in sun‐dried samples. No significant differences were found between the levels of polyunsaturated fatty acids of fresh cuttlefish and those under controlled conditions. The highest value of malondialdehyde in mantles was observed in sun‐dried samples, while in tentacles the highest level was seen at 70 °C. The highest level of advanced oxidation protein products was noted in traditionally sun‐dried samples. The results obtained showed that 45–50 °C and 20–30% humidity conserved the value of proteins and lipids more than traditional drying. Results of this study may be suitable for developing a reliable industrial index.  相似文献   
36.
In injection molding, high pressure is required to completely replicate the mold geometry, due to the viscosity of thermoplastic polymers, the reduced thickness of the cavity, and the low mold temperature. The reduction of the drag required to fill a thin‐wall injection molding cavity can be promoted by inducing the strong slip of the polymer melt over the mold surface, which occurs within the first monolayer of macromolecules adsorbed at the wall. In this work, the effects of different laser‐induced periodic surface structures (LIPSS) topographies on the reduction of the melt flow resistance of polypropylene were characterized. Ultrafast laser processing of the mold surface was used to manufacture nano‐scale ripples with different orientation and morphology. Moreover, the effects of those injection molding parameters that mostly affect the interaction between the mold surface and the molten polymer were evaluated. The effect of LIPSS on the slip of the polymer melt was modeled to understand the effect of the different treatments on the pressure required to fill the thin‐wall cavity. The results show that LIPPS can be used to treat injection mold surfaces to promote the onset of wall slip, thus reducing the injection pressure up to 13%. POLYM. ENG. SCI., 59:1889–1896, 2019. © 2019 Society of Plastics Engineers  相似文献   
37.
Solar energy utilization for domestic hot water and house heating is investigated in this paper. The TRNSYS program is used for system simulation. The annual solar fraction of such a system is 0.80 in the West Bank. Solar heating can save up to 28% of the conventional annual heating cost.  相似文献   
38.
In this paper, we propose a new approach for block-based lossless image compression by defining a new semiparametric finite mixture model-based adaptive arithmetic coding. Conventional adaptive arithmetic encoders start encoding a sequence of symbols with a uniform distribution, and they update the frequency of each symbol by incrementing its count after it has been encoded. When encoding an image row by row or block by block, conventional adaptive arithmetic encoders provide the same compression results. In addition, images are normally non-stationary signals, which means that different areas in an image have different probability distributions, so conventional adaptive arithmetic encoders which provide probabilities for the whole image are not very efficient. In the proposed compression scheme, an image is divided into non-overlapping blocks of pixels, which are separately encoded with an appropriate statistical model. Hence, instead of starting to encode each block with a uniform distribution, we propose to start with a probability distribution which is modeled by a semiparametric mixture obtained from the distributions of its neighboring blocks. The semiparametric model parameters are estimated through maximum likelihood using the expectation–maximization algorithm in order to maximize the arithmetic coding efficiency. The results of comparative experiments show that we provide significant improvements over conventional adaptive arithmetic encoders and the state-of-the-art lossless image compression standards.  相似文献   
39.
Cross-layer strategies for resource allocation in wireless networks are essential to guaranty an efficient utilization of the scarce resource. In this paper, we present an efficient radio resource allocation scheme based on PHY/MAC cross layer design and QoS-guaranteed scheduling for multi-user (MU), multi-service (MS), multi-input multi-output (MIMO) concept, orthogonal frequency division multiple access (OFDMA) systems. It is about a downlink multimedia transmission chain in which the available resources as power and bandwidth, are dynamically allocated according to the system parameters. Among these parameters, we can mention the physical link elements such as channel state information, spectral efficiency and error code corrector rate, and MAC link variables, which correspond to the users QoS requirements and the queue status. Primarily, we use a jointly method which parametrizes these system parameters, according to the total power, and the bit error rate constraints. Secondly, we propose a QoS-guaranteed scheduling that shares the sub-carriers to the users. These users request several type of traffic under throughput threshold constraints. The main objective in this work is to adjust the average throughput per service of each user, according to their needs and likewise to satisfy a great number of connexions. Subsequently, we consider a model of moderated compartmentalization between various classes of services by partitioning the total bandwidth into several parts. Each class of service will occupy a part of the bandwidth and will be transmitted over a maximum number of sub-carriers. The simulation results show that the proposed strategy provides a more interesting performance improvement (in terms of average data rate and user satisfaction) than other existing resource allocation schemes, such as nonadaptive resource allocation strategy. The performances are also analyzed and compared for the two multi-service multi-user MIMO–OFDMA systems; with sub-carriers partitioning and without sub-carriers partitioning.  相似文献   
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