SNR bounds of FSO links and its evaluation for selected beams

We formulate the signal-to-noise ratio (SNR) for free-space optical links. Upon inserting typical operating parameters, it is seen that SNR well approximates to the inverse of aperture averaged scintillation parameter. By adopting a common source beam power of 10 mW, we select three different source sizes of Gaussian, annular Gaussian (AG), and cosh-Gaussian beams. We then evaluate the SNR of these beams. Our results indicate that when fixed aperture opening is used, fully and partially coherent beams yield almost the same SNR performance. On the other hand, however, focusing and lowering wavelength of operation appear to be quite instrumental in improving the SNR performance. In this context, medium-sized AGB seems to exhibit the best performance.     

Auto-tuning Similarity Search Algorithms on Multi-core Architectures

In recent times, large high-dimensional datasets have become ubiquitous. Video and image repositories, financial, and sensor data are just a few examples of such datasets in practice. Many applications that use such datasets require the retrieval of data items similar to a given query item, or the nearest neighbors (NN or $k$ -NN) of a given item. Another common query is the retrieval of multiple sets of nearest neighbors, i.e., multi $k$ -NN, for different query items on the same data. With commodity multi-core CPUs becoming more and more widespread at lower costs, developing parallel algorithms for these search problems has become increasingly important. While the core nearest neighbor search problem is relatively easy to parallelize, it is challenging to tune it for optimality. This is due to the fact that the various performance-specific algorithmic parameters, or “tuning knobs”, are inter-related and also depend on the data and query workloads. In this paper, we present (1) a detailed study of the various tuning knobs and their contributions on increasing the query throughput for parallelized versions of the two most common classes of high-dimensional multi-NN search algorithms: linear scan and tree traversal, and (2) an offline auto-tuner for setting these knobs by iteratively measuring actual query execution times for a given workload and dataset. We show experimentally that our auto-tuner reaches near-optimal performance and significantly outperforms un-tuned versions of parallel multi-NN algorithms for real video repository data on a variety of multi-core platforms.     

5G双频组网策略研究与应用

2.6 GHz和4.9 GHz双频组网中,用户驻留策略取决于4.9 GHz小区的建设用途,根据不同需求有不同的策略和配置方案.本文基于实际网络经验,结合用户体验和业务需求,提出了5G双频网策略的配置建议.     

Nitric Oxide Signalling in Descending Vasa Recta after Hypoxia/Re-Oxygenation

Reduced renal medullary oxygen supply is a key factor in the pathogenesis of acute kidney injury (AKI). As the medulla exclusively receives blood through descending vasa recta (DVR), dilating these microvessels after AKI may help in renoprotection by restoring renal medullary blood flow. We stimulated the NO-sGC-cGMP signalling pathway in DVR at three different levels before and after hypoxia/re-oxygenation (H/R). Rat DVR were isolated and perfused under isobaric conditions. The phosphodiesterase 5 (PDE5) inhibitor sildenafil (10⁻⁶ mol/L) impaired cGMP degradation and dilated DVR pre-constricted with angiotensin II (Ang II, 10⁻⁶ mol/L). Dilations by the soluble guanylyl cyclase (sGC) activator BAY 60-2770 as well as the nitric oxide donor sodium nitroprusside (SNP, 10⁻³ mol/L) were equally effective. Hypoxia (0.1% O₂) augmented DVR constriction by Ang II, thus potentially aggravating tissue hypoxia. H/R left DVR unresponsive to sildenafil, yet sGC activation by BAY 60-2770 effectively dilated DVR. Dilation to SNP under H/R is delayed. In conclusion, H/R renders PDE5 inhibition ineffective in dilating the crucial vessels supplying the area at risk for hypoxic damage. Stimulating sGC appears to be the most effective in restoring renal medullary blood flow after H/R and may prove to be the best target for maintaining oxygenation to this vulnerable area of the kidney.     

Coarse‐to‐Fine Isometric Shape Correspondence by Tracking Symmetric Flips

We address the symmetric flip problem that is inherent to multi‐resolution isometric shape matching algorithms. To this effect, we extend our previous work which handles the dense isometric correspondence problem in the original 3D Euclidean space via coarse‐to‐fine combinatorial matching. The key idea is based on keeping track of all optimal solutions, which may be more than one due to symmetry especially at coarse levels, throughout denser levels of the shape matching process. We compare the resulting dense correspondence algorithm with state‐of‐the‐art techniques over several 3D shape benchmark datasets. The experiments show that our method, which is fast and scalable, is performance‐wise better than or on a par with the best performant algorithms existing in the literature for isometric (or nearly isometric) shape correspondence. Our key idea of tracking symmetric flips can be considered as a meta‐approach that can be applied to other multi‐resolution shape matching algorithms, as we also demonstrate by experiments.     

River: an intermediate language for stream processing

This paper presents both a calculus for stream processing, named Brooklet, and its realization as an intermediate language, named River. Because River is based on Brooklet, it has a formal semantics that enables reasoning about the correctness of source translations and optimizations. River builds on Brooklet by addressing the real‐world details that the calculus elides. We evaluated our system by implementing front‐ends for three streaming languages, and three important optimizations, and a back‐end for the System S distributed streaming runtime. Overall, we significantly lower the barrier to entry for new stream‐processing languages and thus grow the ecosystem of this crucial style of programming. Copyright © 2015 John Wiley & Sons, Ltd.     

Compatibility of a polycarboxylate-based superplasticiser with different set-controlling admixtures

The compatibility of specific combinations of chemical admixtures for cement pastes and mortars have been investigated. The consistency, setting time and compressive strength of cement pastes and mortars incorporating a polycarboxylate-based plasticizing admixture (PCA) with four different set-controlling admixtures (SCA); calcium formate (CF), tri-ethanolamine (TEA), mixture of calcium nitrite and nitrate salts (CNN blend) and sodium aluminate (SA) have been determined within the scope of this study. Fifty-two mortar and paste specimens with different amounts of PCA and SCA combinations have been prepared. Water/cement ratios of cement paste and mortar mixtures were 0.24 and 0.50, respectively. The paste mixtures have been prepared to determine the setting time data and the mortar mixtures have been used to determine the consistency and compressive strength values. Test results indicated that the PCA employed in this study, retards the setting time, improves consistency and reduces the early strength development of all paste and mortar mixtures at dosages greater than 0.4% by mass of cement. However, the use of different set-controlling admixtures in combination with PCA caused drastic changes in the performances of the mixtures depending on the type and amount of SCAs. It was concluded that, in order to reduce the setting time and increase the early strength of PCA incorporated mortars without causing consistency loss, the combination of PCA, and SCA should be optimized according to their types. A new 3D box-plot method has been used to determine the optimum admixture combinations for the desired properties. Maximum flow, shortest setting time and highest early strength criterion were the targets of the optimization. The most effective combination to obtain desired set acceleration and high early strength values was 1.8% PCA with 1.6% nitrite and nitrate salts based SCA by mass of cement. If consistency lost is in secondary importance, 1.8% PCA based plasticiser with 1% sodium aluminate based SCA may be an alternative combination. The proposed method can be used to optimize the targeted properties for a specific combination of cement, PCA and SCA.     

Ageing in the LHCb outer tracker: Aromatic hydrocarbons and wire cleaning

The LHCb Outer Tracker straw tubes have shown to suffer from gain loss after irradiation in the laboratory at moderate intensities. Under irradiation an insulating layer is formed on the anode wire. The ageing is caused by contamination of the counting gas due to outgassing of the plastifier di-isopropyl-naphthalene in araldite AY103-1 used at construction. This paper presents irradiation results with and without the plastifier, together with the mass spectra of the glue samples. In addition, the effects of wire heating and large currents are presented.