5,631 research outputs found
Hierarchical Cache-Aided Linear Function Retrieval with Security and Privacy Constraints
The hierarchical caching system where a server connects with multiple mirror
sites, each connecting with a distinct set of users, and both the mirror sites
and users are equipped with caching memories has been widely studied. However
all the existing works focus on single file retrieval, i.e., each user requests
one file, and ignore the security and privacy threats in communications. In
this paper we investigate the linear function retrieval problem for
hierarchical caching systems with content security and demand privacy, i.e.,
each user requests a linear combination of files, and meanwhile the files in
the library are protected against wiretappers and users' demands are kept
unknown to other users and unconnected mirror sites. First we propose a new
combination structure named hierarchical placement delivery array (HPDA), which
characterizes the data placement and delivery strategy of a coded caching
scheme. Then we construct two classes of HPDAs. Consequently two classes of
schemes with or without security and privacy are obtained respectively where
the first dedicates to minimizing the transmission load for the first hop and
can achieve the optimal transmission load for the first hop if ignoring the
security and privacy constraints; the second has more flexible parameters on
the memory sizes and a lower subpacketization compared with the first one, and
achieves a tradeoff between subpacketization and transmission loads.Comment: arXiv admin note: substantial text overlap with arXiv:2205.0023
Approaches to the Total Synthesis of Puupehenone-Type Marine Natural Products
Puupehenones have been isolated from the marine sponge Chondrosia chucalla, which belong to a growing family of natural products with more than 100 members. These marine natural products have attracted increasing attention mainly due to their wide variety of biological activities such as antitumor, antiviral, and anti-HIV, and thus offer promising opportunities for new drug development. This chapter covers the approaches to the total synthesis of puupehenone-type marine natural products including puupehenol, puupehenone, puupehedione, and halopuupehenones. The routes begin with the construction of their basic skeletons, followed by the modification of their C- and D-rings. The contents are divided into two sections in terms of the key strategies employed to construct the basic skeleton. One is the convergent synthesis route with two synthons coupled by nucleophilic or electrophilic reaction, and the other is the linear synthesis route with polyene series cyclization as a key reaction
Coded Caching Scheme for Partially Connected Linear Networks Via Multi-antenna Placement Delivery Array
In this paper, we study the coded caching scheme for the
partially connected linear network, where
there are files each of which has an equal size, transmitters and
users; each user and transmitter caches at most and
files respectively; each user cyclically communicates with
transmitters. The goal is to design caching and delivery schemes to reduce the
transmission latency measured by the metric normalized delivery time (NDT). By
delicately designing the data placement of the transmitters and users according
to the topology, we show that a combinatorial structure called multiple-antenna
placement delivery array (MAPDA), which was originally proposed for the
multiple-input single-output broadcast channels, can be also used to design
schemes for the partially connected linear network. Then, based on existing
MAPDAs and our constructing approach, we propose new schemes that achieve the
optimal NDT when and smaller NDT than that
of the existing schemes when (,
) or (). Moreover, our schemes operate in one-shot
linear delivery and significantly reduce the subpacketizations compared to the
existing scheme, which implies that our schemes have a wider range of
applications and lower complexity of implementation.Comment: 13 page
GENERATION OF CRACKS IN HIGHWAY EMBANKMENT ON BLACK COTTON SOIL
This research revealed the crack generation of the highway embankment from the water losing shrinkage of the wet black cotton soil (BCS), which is a type of soil with high swell-shrink potential. The road seepage meter was used to test the permeability of filling materials, which was used to replace BCS. The moisture content and embankment deflection of BCS foundation were measured after the rainy season. Based on the coupled consolidation theory for unsaturated soil, the change in additional tension stress of the embankment induced by water loss shrinkage of BCS was simulated by Abaqus. The results indicated that the rainfall seeped into the foundation through highly permeable refill materials to result in BCS expansion and decrease the embankment strength. After the rainy season, the additional tensile stress caused by water loss shrinkage of BCS induces cracking of highway embankment, and the maximum cracking depth often appears at the shoulder of highway. The deep and wide cracks are easy to appear in the low embankment constructed on a thick BCS foundation under strong evaporation
P2T: Pyramid Pooling Transformer for Scene Understanding
This paper jointly resolves two problems in vision transformer: i) the
computation of Multi-Head Self-Attention (MHSA) has high computational/space
complexity; ii) recent vision transformer networks are overly tuned for image
classification, ignoring the difference between image classification (simple
scenarios, more similar to NLP) and downstream scene understanding tasks
(complicated scenarios, rich structural and contextual information). To this
end, we note that pyramid pooling has been demonstrated to be effective in
various vision tasks owing to its powerful ability in context abstraction, and
its natural property of spatial invariance is also suitable to address the loss
of structural information (problem ii)). Hence, we propose to adapt pyramid
pooling to MHSA for alleviating its high requirement on computational resources
(problem i)). In this way, this pooling-based MHSA can well address the above
two problems and is thus flexible and powerful for downstream scene
understanding tasks. Plugged with our pooling-based MHSA, we build a
downstream-task-oriented transformer network, dubbed Pyramid Pooling
Transformer (P2T). Extensive experiments demonstrate that, when applied P2T as
the backbone network, it shows substantial superiority in various downstream
scene understanding tasks such as semantic segmentation, object detection,
instance segmentation, and visual saliency detection, compared to previous CNN-
and transformer-based networks. The code will be released at
https://github.com/yuhuan-wu/P2T
Bis[1,3-bis(1-methyl-1H-benzimidazol-2-yl)-2-oxapropane]cadmium dipicrate acetonitrile sesquisolvate 0.25-hydrate
In the title compound, [Cd(C18H18N4O)2](C6H2N3O7)2·1.5CH3CN·0.25H2O, the CdII ion is coordinated by four N atoms and two O atoms from two tridentate 1,3-bis(1-methyl-1H-benzimidazol-2-yl)-2-oxopropane ligands in a distorted octahedral coordination environment. The lengths of the chemically equivalent Cd—O bonds [2.4850 (16) and 2.5488 (16)Å] are signiificantly different. One of the picrate anions is disordered over two sets of sites, with refined occupancies of 0.504 (15) and 0.496 (15). A 0.5-occupancy acetonitrile solvent molecule is disordered over two sites with equal occupancies. The H atoms of a 0.25-occupancy solvent water molecule were neither located nor included in the refinement
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