A hybrid localization approach in 3D wireless sensor network

Location information acquisition is crucial for many wireless sensor network (WSN) applications. While existing localization approaches mainly focus on 2D plane, the emerging 3D localization brings WSNs closer to reality with much enhanced accuracy. Two types of 3D localization algorithms are mainly used in localization application: the range-based localization and the range-free localization. The range-based localization algorithm has strict requirements on hardware and therefore is costly to implement in practice. The range-free localization algorithm reduces the hardware cost but at the expense of low localization accuracy. On addressing the shortage of both algorithms, in this paper, we develop a novel hybrid localization scheme, which utilizes the range-based attribute RSSI and the range-free attribute hopsize, to achieve accurate yet low-cost 3D localization. As anchor node deployment strategy plays an important role in improving the localization accuracy, an anchor node configuration scheme is also developed in this work by utilizing the MIS (maximal independent set) of a network. With proper anchor node configuration and propagation model selection, using simulations, we show that our proposed algorithm improves the localization accuracy by 38.9% compared with 3D DV-HOP and 52.7% compared with 3D centroid

Netest: a tool to measure the maximum burst size, available bandwidth and achievable throughput

Distinguishing available bandwidth and achievable throughput is essential for improving network applications' performance. Achievable throughput is the throughput considering a number of factors such as network protocol, host speed, network path, and TCP buffer space, where as available bandwidth only considers the network path. Without understanding this difference, trying to improve network applications' performance is like ''blind men feeling the elephant'' [4]. In this paper, we define and distinguish bandwidth and throughput, and debate which part of each is achievable and which is available. Also, we introduce and discuss a new concept - Maximum Burst Size that is crucial to the network performance and bandwidth sharing. A tool, netest, is introduced to help users to determine the available bandwidth, and provides information to achieve better throughput with fairness of sharing the available bandwidth, thus reducing misuse of the network

Study on Matching Ability Between Cement Particle Size and Permeability in the Process of Oil Reservoir Plugging

In order to satisfy the plugging demands of injecting the cement plugging agent into reservoirs with different radial depths, the technical studies of cement particle size optimization should be conducted. Through indoor experiment, the relationship between cement particle size and permeability was investigated by both macroscopic and microcosmic analysis. It is observed that the reservoirs which permeabilities are within 50~200mD are matching well with the cement agents which particle sizes are less than 5μm. And the permeabilities within 200~400mD are matching well with the cement agents which particle sizes are within 5~10μm, the permeabilities within 400~700mD are matching well with the cement agents which particle sizes are within 10~20μm, the permeabilities are above 700mD are matching well with the cement agents which particle sizes are more than 20μm. The plugging success rates of all the matching experiments are exceeding 90%. This research result is important to direct the plugging operation in the field.Key words: Plugging off and channeling prevention; Cement particle size; Permeability; Matching relationship; Experimental stud

Astrocytic LRP1 mediates brain Aβ clearance and impacts amyloid deposition

Accumulation and deposition of amyloid-β (Aβ) in the brain represent an early and perhaps necessary step in the pathogenesis of Alzheimer's disease (AD). Aβ accumulation leads to the formation of Aβ aggregates, which may directly and indirectly lead to eventual neurodegeneration. While Aβ production is accelerated in many familial forms of early-onset AD, increasing evidence indicates that impaired clearance of Aβ is more evident in late-onset AD. To uncover the mechanisms underlying impaired Aβ clearance in AD, we examined the role of low-density lipoprotein receptor-related protein 1 (LRP1) in astrocytes. Although LRP1 has been shown to play critical roles in brain Aβ metabolism in neurons and vascular mural cells, its role in astrocytes, the most abundant cell type in the brain responsible for maintaining neuronal homeostasis, remains unclear. Here, we show that astrocytic LRP1 plays a critical role in brain Aβ clearance. LRP1 knockdown in primary astrocytes resulted in decreased cellular Aβ uptake and degradation. In addition, silencing of LRP1 in astrocytes led to downregulation of several major Aβ-degrading enzymes, including matrix metalloproteases MMP2, MMP9, and insulin-degrading enzyme. More important, conditional knock-out of theLrp1gene in astrocytes in the background of APP/PS1 mice impaired brain Aβ clearance, exacerbated Aβ accumulation, and accelerated amyloid plaque deposition without affecting its production. Together, our results demonstrate that astrocytic LRP1 plays an important role in Aβ metabolism and that restoring LRP1 expression and function in the brain could be an effective strategy to facilitate Aβ clearance and counter amyloid pathology in AD.SIGNIFICANCE STATEMENTAstrocytes represent a major cell type regulating brain homeostasis; however, their roles in brain clearance of amyloid-β (Aβ) and underlying mechanism are not clear. In this study, we used both cellular models and conditional knock-out mouse models to address the role of a critical Aβ receptor, the low-density lipoprotein receptor-related protein 1 (LRP1) in astrocytes. We found that LRP1 in astrocytes plays a critical role in brain Aβ clearance by modulating several Aβ-degrading enzymes and cellular degradation pathways. Our results establish a critical role of astrocytic LRP1 in brain Aβ clearance and shed light on specific Aβ clearance pathways that may help to establish new targets for AD prevention and therapy.</jats:p

Sources of Value Gains in Minority Equity Investments by Private Equity Funds: Evidence from Block Share Acquisitions

Using a large sample of block share acquisitions made by private equity (PE) funds over the 1990 to 2006 period, we examine the sources of value gains in PE minority equity investments. We find that compared to non-PE acquirers, PE acquirers are more likely to place representatives with finance experience on a target’s board, particularly when the target performs poorly or when it has more pronounced agency problems. PE acquirers are also more likely to place representatives with experience in the target’s industry on the target’s board when the target has more complex operations (e.g., multiple segments or higher R&amp;D intensity). The targets in PE acquisitions, particularly those whose boards have representatives from PE acquirers, realize both higher abnormal announcement returns and better post-acquisition operating performance than do targets in other types of acquisitions. Target announcement abnormal returns and post-acquisition operating performance are also higher when PE-appointed directors have expertise in the target’s industry, when they sit on the boards of poorly performing targets, or when they sit on the boards of targets with higher R&amp;D intensity. Thes

Network characterization service (NCS

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