Randomized Algorithms for Tracking Distributed Count, Frequencies, and Ranks

We show that randomization can lead to significant improvements for a few fundamental problems in distributed tracking. Our basis is the {\em count-tracking} problem, where there are $k$ players, each holding a counter $n_i$ that gets incremented over time, and the goal is to track an \eps-approximation of their sum $n=\sum_i n_i$ continuously at all times, using minimum communication. While the deterministic communication complexity of the problem is \Theta(k/\eps \cdot \log N), where $N$ is the final value of $n$ when the tracking finishes, we show that with randomization, the communication cost can be reduced to \Theta(\sqrt{k}/\eps \cdot \log N). Our algorithm is simple and uses only O(1) space at each player, while the lower bound holds even assuming each player has infinite computing power. Then, we extend our techniques to two related distributed tracking problems: {\em frequency-tracking} and {\em rank-tracking}, and obtain similar improvements over previous deterministic algorithms. Both problems are of central importance in large data monitoring and analysis, and have been extensively studied in the literature.Comment: 19 pages, 1 figur

Fabrication of binder-free ultrafine WC-6CO composites by coupled multi-physical fields activation technology

A novel sintering method, named as coupled multi-physical fields activation technology, has been introduced for the forming of various material powder systems. Compared with the conventional ones, this technique presents more advantages: lower sintering temperature, shorter forming time, and remarkable inhibition of the grains coarsening. In the study, the cylinders of Φ4.0mm×4.0mm had been formed with ultrafine WC-6Co powders. The relative properties of sintered WC-6Co cemented carbides, such as hardness and the microstructures, had been obtained. The study has shown that a relative density, 97.80%, of the formed samples, could been achieved when the case of temperature 850℃, heating rate 50℃/s, pressure 75MPa and Electro-heating loop 6 times, were used. More importantly, the circumscription for the growth of grain size of WC, attributed to the effect of electrical field, renders coupled multi-physical fields activation technology applicable for getting WC-6Co cemented carbides with fine grain size and good properties

Dithiolopyrrolone Natural Products : Isolation, Synthesis and Biosynthesis

Peer reviewedPublisher PD

Effect of particle size on densification of copper powder during electric-field activated sintering for micro-scale forming

A novel Micro-forming technology, called electric-field activated sintering for micro-scale forming (Micro-FAST), was introduced for the forming of micro-components. The effect of particle size on densification is revealed for copper powder being sintered under the influence from electrical field and force-field during forming of micro-components. Three kinds of copper powders of different particle sizes ((i) average particle size of 0.5μm; (ii) average particle size of 30μm and (iii) the mixture powders with 20% weight of 30μm and 80% weight of 0.5μm) with no binder were used for the experiments. The results show that the density of the compact sintered with mixed copper powders is the largest due to more volume of liquid phase was formed in the particle's contacts. The result being in correspondence with the analytical results of computer simulation. The new understanding developed would help to better quality control during the sintering of micro-components

Sintering kinetics of the powder during fields-activated micro-forming and sintering (Micro-FAST) of copper micro-gears

Forming of micro-components from powder with fields-activated sintering technology (FAST) renders different forming and sintering mechanisms, comparing to that occurring during the forming of macro-sized components with a similar technology. Establishing a good understanding of these mechanisms would help process design and control aiming at achieving desired quality of the components to be formed. This paper presents a study and the results on the sintering kinetics of the powder during Micro-FAST for the fabrication of micro-gears (the module is 0.2 and the pitch diameter 1.6 mm) from copper powder. The results showed that the densification of copper powder is related largely to the bulk plastic-deformations of the particles and the melting of the particles at contact interfaces. Particularly, it is revealed that plastic deformations of the copper particles mainly occurred at approximately 340 °C and melting of the particle-interfaces at approximately 640 °C. Differently, in a densification process with a traditional powder sintering method, grain growth and neck growth would, normally, be two dominant mechanisms that achieve the densification of powder

A new densification mechanism of copper powder sintered under an electrical field

A new sintering mechanism is revealed for copper powder sintered under the influence of an electrical field and a force field during the formation of microcomponents. Analysis of the microstructure and grain boundary evolution of the sintered samples showed that the disappearance of the interface at contact areas between particles is a continuous process which involves new grain formation and grain refinement during this innovative microsintering process. The densification process is therefore different from what is known in a conventional powder sintering process

The Construction of a Community Long-term Care Model for Home-based Elderly Individuals

With rapidly aging populations, family care functions can become weakened, and community health services often lack unified standards. A standardized and professional community home-based long-term care model (CHLCM) for the elderly is urgently needed in many regions of China and in other countries. Here, we explored the indicators of the need for a CHLCM among elderly individuals, and we constructed a CHLCM. We created and distributed a questionnaire regarding the requirement of long-term care services, based on a literature review. The two-rounds Delphi method was used, involving 20 experts who were randomly selected from among the medical universities, community health service centers, and nursing homes in Nanning, Guangxi, China. The experts’ enthusiasm rates in the questionnaire’s two rounds were 95% and 100%, respectively. The authentic coefficient of the experts’ consulting was 0.857, and that of the experts’ academic level was 0.835; the judgement coefficient was 0.880 and the familiar coefficient was 0.855. The CHLCM includes service content and an evaluation. The coordination coefficients for the two primary, eight secondary, and 29 tertiary indicators were 0.200, 0.386, and 0.184, respectively (p<0.05). The experts’ enthusiasm and authority were high. The coordination of the experts’ agreement was sufficient, and the analysis results were reliable. The CHLCM includes 29 items that provide a foundation and references for the formulation of concrete indicators and subsequent research