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111.
We study a set of problems related to efficient battery energy utilization for monitoring applications in a wireless sensor
network with the goal to increase the sensor network lifetime. We study several generalizations of a basic problem called
Set k-Cover. The problem can be described as follows: we are given a set of sensors, and a set of targets to be monitored. Each
target can be monitored by a subset of the sensors. To increase the lifetime of the sensor network, we would like to partition
the sensors into k sets (or time-slots), and activate each set of sensors in a different time-slot, thus extending the battery life of the sensors
by a factor of k. The goal is to find a partitioning that maximizes the total coverage of the targets for a given k. This problem is known to be NP-hard. We develop an improved approximation algorithm for this problem using a reduction to Max k-Cut. Moreover, we are able to demonstrate that this algorithm is efficient, and yields almost optimal solutions in practice. 相似文献
112.
There is an increasing interest in solving temporal planning problems. Identification and propagation of mutual exclusion
relations between actions can significantly enhance the efficiency of a planner. Current definitions of mutually exclusive
actions severely restrict their concurrency. In this paper, we report on thirteen groups of permanently mutually exclusive
PDDL 2.1, Level 3 actions. We report on sixteen types of potentially-conflicting interactions between two actions where concurrency
may be maximized by adjusting starting time of one of the two actions. We discuss several examples where actions can overlap
despite conflicting preconditions and/or effects. The processes executing these actions are mostly independent. We report
on a new domain-rewriting technique called “baiting” in order to improve the concurrency in temporal plans. Baiting actions
lure a temporal planner into improving concurrency. The technique involves splitting user-identified operators. We report
on three types of baiting (standard, double and nested) and show their suitability for various types of action interactions.
Baiting requires minimal modification to the planning code. Baiting does not increase the branching in search trees. Baiting
does not affect the soundness and completeness of a temporal planner. Our empirical evaluation shows that the makespans of
plans generated by efficient planner Sapa with baited domain are significantly lower than makespans of plans generated without
baiting. 相似文献
113.
Abdul Quamar Amol Deshpande Jimmy Lin 《The VLDB Journal The International Journal on Very Large Data Bases》2016,25(2):125-150
There is an increasing interest in executing complex analyses over large graphs, many of which require processing a large number of multi-hop neighborhoods or subgraphs. Examples include ego network analysis, motif counting, finding social circles, personalized recommendations, link prediction, anomaly detection, analyzing influence cascades, and others. These tasks are not well served by existing vertex-centric graph processing frameworks, where user programs are only able to directly access the state of a single vertex at a time, resulting in high communication, scheduling, and memory overheads in executing such tasks. Further, most existing graph processing frameworks ignore the challenges in extracting the relevant portions of the graph that an analysis task is interested in, and loading those onto distributed memory. This paper introduces NScale, a novel end-to-end graph processing framework that enables the distributed execution of complex subgraph-centric analytics over large-scale graphs in the cloud. NScale enables users to write programs at the level of subgraphs rather than at the level of vertices. Unlike most previous graph processing frameworks, which apply the user program to the entire graph, NScale allows users to declaratively specify subgraphs of interest. Our framework includes a novel graph extraction and packing (GEP) module that utilizes a cost-based optimizer to partition and pack the subgraphs of interest into memory on as few machines as possible. The distributed execution engine then takes over and runs the user program in parallel on those subgraphs, restricting the scope of the execution appropriately, and utilizes novel techniques to minimize memory consumption by exploiting overlaps among the subgraphs. We present a comprehensive empirical evaluation comparing against three state-of-the-art systems, namely Giraph, GraphLab, and GraphX, on several real-world datasets and a variety of analysis tasks. Our experimental results show orders-of-magnitude improvements in performance and drastic reductions in the cost of analytics compared to vertex-centric approaches. 相似文献
114.
A unified approach to ranking in probabilistic databases 总被引:1,自引:0,他引:1
Jian Li Barna Saha Amol Deshpande 《The VLDB Journal The International Journal on Very Large Data Bases》2011,20(2):249-275
Ranking is a fundamental operation in data analysis and decision support and plays an even more crucial role if the dataset being explored exhibits uncertainty. This has led to much work in understanding how to rank the tuples in a probabilistic dataset in recent years. In this article, we present a unified approach to ranking and top-k query processing in probabilistic databases by viewing it as a multi-criterion optimization problem and by deriving a set of features that capture the key properties of a probabilistic dataset that dictate the ranked result. We contend that a single, specific ranking function may not suffice for probabilistic databases, and we instead propose two parameterized ranking functions, called PRF ω and PRF e, that generalize or can approximate many of the previously proposed ranking functions. We present novel generating functions-based algorithms for efficiently ranking large datasets according to these ranking functions, even if the datasets exhibit complex correlations modeled using probabilistic and/xor trees or Markov networks. We further propose that the parameters of the ranking function be learned from user preferences, and we develop an approach to learn those parameters. Finally, we present a comprehensive experimental study that illustrates the effectiveness of our parameterized ranking functions, especially PRF e, at approximating other ranking functions and the scalability of our proposed algorithms for exact or approximate ranking. 相似文献
115.
Prithviraj Sen Amol Deshpande Lise Getoor 《The VLDB Journal The International Journal on Very Large Data Bases》2009,18(5):1065-1090
Due to numerous applications producing noisy data, e.g., sensor data, experimental data, data from uncurated sources, information
extraction, etc., there has been a surge of interest in the development of probabilistic databases. Most probabilistic database
models proposed to date, however, fail to meet the challenges of real-world applications on two counts: (1) they often restrict
the kinds of uncertainty that the user can represent; and (2) the query processing algorithms often cannot scale up to the
needs of the application. In this work, we define a probabilistic database model, PrDB, that uses graphical models, a state-of-the-art probabilistic modeling technique developed within the statistics and machine
learning community, to model uncertain data. We show how this results in a rich, complex yet compact probabilistic database
model, which can capture the commonly occurring uncertainty models (tuple uncertainty, attribute uncertainty), more complex
models (correlated tuples and attributes) and allows compact representation (shared and schema-level correlations). In addition,
we show how query evaluation in PrDB translates into inference in an appropriately augmented graphical model. This allows us to easily use any of a myriad of
exact and approximate inference algorithms developed within the graphical modeling community. While probabilistic inference
provides a generic approach to solving queries, we show how the use of shared correlations, together with a novel inference
algorithm that we developed based on bisimulation, can speed query processing significantly. We present a comprehensive experimental
evaluation of the proposed techniques and show that even with a few shared correlations, significant speedups are possible. 相似文献
116.
A novel method of patterning surfaces with synthetic or biological polymers is demonstrated. It consists of using microcontact printing to pattern a gold surface with an adsorbate that imparts hydrophilicity; the remainder of the surface is covered with one that imparts hydrophobicity. 16-Mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol, respectively, have been used as the hydrophilic and hydrophobic adsorbates. This functionalized gold surface then serves as a template for patterning hydrophilic polymers and biomaterials, which are either spin-coated or drop-cast onto the surface. Using this methodology, it is shown by atomic force microscopy, scanning electron microscopy (SEM), and fluorescence microscopy that micron-scale patterns of a poly(ethylene)-block-poly(ethylene oxide) copolymer, poly-L-tryptophan, and bovine collagen can be fabricated, with these mimicking the MHDA patterns. For the block copolymer, it is found by atomic force microscopy that the heights of the polymer patterns decrease as their widths decrease. This is believed to be due to the inherent instability of tall, narrow polymer structures and the tendency of the polymer to minimize its exposed surface area. For poly-L-tryptophan, two different molecular weights of this polyamino acid have been studied, and different morphologies within the patterned regions are observed. While oligomeric poly-L-tryptophan (1,000-5,000 g/mol) gives smooth MHDA-covered patterns, the higher molecular weight (15,000-50,000 g/mol) yields fibrous ones. 相似文献
117.
Gas holdup, effective interfacial area and volumetric mass transfer coefficient were measured in two and three phase downflow bubble columns. The mass transfer data were obtained using the chemical method of sulfite oxidation, and the gas holdup was measured using the hydrostatic technique. Glass beads and Triton 114 were used to study the effects of solids and liquid surface tension on the gas holdup and the mass transfer parameters a and kLa. The gas holdup in three phase systems was measured for non-wettable (glass bead) and wettable (coal and shale particles) solids.
The mass transfer data obtained in the downflow bubble column were compared with the values published for upflow bubble columns. The results indicate that in the range of superficial gas velocities (0.002-0.025) m/s investigated, the values of the mass transfer coefficient were of the same order of magnitude as those observed in upflow systems, but the values of interfacial area were at least two fold greater. Also, the results showed that the operating variables and the physical properties had different influences on a and kLa in the downflow bubble column. Correlations for a and kLa for the downflow bubble column are proposed which predict the data with adequate accuracy in the range of operating conditions investigated. 相似文献
The mass transfer data obtained in the downflow bubble column were compared with the values published for upflow bubble columns. The results indicate that in the range of superficial gas velocities (0.002-0.025) m/s investigated, the values of the mass transfer coefficient were of the same order of magnitude as those observed in upflow systems, but the values of interfacial area were at least two fold greater. Also, the results showed that the operating variables and the physical properties had different influences on a and kLa in the downflow bubble column. Correlations for a and kLa for the downflow bubble column are proposed which predict the data with adequate accuracy in the range of operating conditions investigated. 相似文献
118.
Whole-cell sensing systems based on living genetically engineered bacteria are known to have high sensitivity, selectivity, and rapid response times. Although these systems have found applications in biomedical and environmental analyses, their limited shelf life and transportability still restrict their use for on-site monitoring of analytes. To that end, we have developed a new method for the long-term preservation, storage, and transport of whole-cell biosensing systems that is based on bacterial spores, a dormant form of life. Specifically, we have employed spore-forming bacteria such as Bacillus subtilis and Bacillus megaterium for development of luminescent sensing systems for two model analytes, namely, arsenic and zinc. These sensing cells were converted to spores, which can then be "revived" (germinated) at a later time to generate viable and metabolically active cells. Herein, we demonstrate that these spore-based sensing systems retained their analytical performance, in terms of detection limit, dynamic range, and reproducibility, after storage at room temperature for at least 6 and 8 months, respectively, as well as after three cycles where the cells alternated between being dormant or active, i.e., sporulation-germination cycles. The ability to cycle the sensing cells between active and dormant states prolongs the cell's lifetimes and increases their robustness and ruggedness, thus making them more amenable for field applications. In addition, the small size of spores allows for their easy transport and incorporation in miniaturized portable devices. Finally, we envision that this novel strategy could expand the use of whole-cell biosensors for on-site sensing not only in mild environments but also in harsh environments and locations where there is no easy access to a laboratory, e.g., in developing countries. 相似文献
119.
Bao Tram L. Hoang Stephen J. Fletcher Christopher A. Brosnan Amol B. Ghodke Narelle Manzie Neena Mitter 《International journal of molecular sciences》2022,23(12)
RNA interference (RNAi) is a powerful tool that is being increasingly utilized for crop protection against viruses, fungal pathogens, and insect pests. The non-transgenic approach of spray-induced gene silencing (SIGS), which relies on spray application of double-stranded RNA (dsRNA) to induce RNAi, has come to prominence due to its safety and environmental benefits in addition to its wide host range and high target specificity. However, along with promising results in recent studies, several factors limiting SIGS RNAi efficiency have been recognized in insects and plants. While sprayed dsRNA on the plant surface can produce a robust RNAi response in some chewing insects, plant uptake and systemic movement of dsRNA is required for delivery to many other target organisms. For example, pests such as sucking insects require the presence of dsRNA in vascular tissues, while many fungal pathogens are predominately located in internal plant tissues. Investigating the mechanisms by which sprayed dsRNA enters and moves through plant tissues and understanding the barriers that may hinder this process are essential for developing efficient ways to deliver dsRNA into plant systems. In this review, we assess current knowledge of the plant foliar and cellular uptake of dsRNA molecules. We will also identify major barriers to uptake, including leaf morphological features as well as environmental factors, and address methods to overcome these barriers. 相似文献
120.
Jaydeep B. Deshpande Govinda R. Navale Mahesh S. Dharne Amol A. Kulkarni 《化学工程与技术》2020,43(3):582-592
Continuous-flow separation and recovery of silver nanoparticles (AgNPs) using an annular centrifugal extractor (ACE) is demonstrated. Separation was achieved at the liquid-liquid interface based on the balance between centrifugal force and the solubility of the capping agent. A mathematical model is presented to understand the mechanism in greater detail. The separation of poly(vinylpyrrolidone) (PVP)-coated AgNPs in an ACE using a strong immiscible solvent was performed. The material accumulated at the interface was separated periodically without discontinuing the operation. The method is also suitable for separation of large particles or 1D/2D nanostructures even employing a single annular centrifugal extractor. Stable AgNPs were selected for a detailed antimicrobial activity study. 相似文献