Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a fixed subset of atoms; the second assigns each a fixed subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently—those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 100,000,000 atoms on several parallel supercomputers--the nCUBE 2, Intel iPSC/860 and Paragon, and Cray T3D. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and a 1840-node Intel Paragon performs up to 165 faster than a single Cray C9O processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

Fast parallel algorithms for short-range molecular dynamics

Searchable symmetric encryption (SSE) allows a party to outsource the storage of its data to another party (a server) in a private manner, while maintaining the ability to selectively search over it. This problem has been the focus of active research in recent years. In this paper we show two solutions to SSE that simultaneously enjoy the following properties: Both solutions are more efficient than all previous constant-round schemes. In particular, the work performed by the server per returned document is constant as opposed to linear in the size of the data. Both solutions enjoy stronger security guarantees than previous constant-round schemes. In fact, we point out subtle but serious problems with previous notions of security for SSE, and show how to design constructions which avoid these pitfalls. Further, our second solution also achieves what we call adaptive SSE security, where queries to the server can be chosen adaptively (by the adversary) during the execution of the search; this notion is both important in practice and has not been previously considered.Surprisingly, despite being more secure and more efficient, our SSE schemes are remarkably simple. We consider the simplicity of both solutions as an important step towards the deployment of SSE technologies.As an additional contribution, we also consider multi-user SSE. All prior work on SSE studied the setting where only the owner of the data is capable of submitting search queries. We consider the natural extension where an arbitrary group of parties other than the owner can submit search queries. We formally define SSE in the multi-user setting, and present an efficient construction that achieves better performance than simply using access control mechanisms.

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Searchable symmetric encryption: improved definitions and efficient constructions

We consider the problem of building a secure cloud storage service on top of a public cloud infrastructure where the service provider is not completely trusted by the customer We describe, at a high level, several architectures that combine recent and non-standard cryptographic primitives in order to achieve our goal We survey the benefits such an architecture would provide to both customers and service providers and give an overview of recent advances in cryptography motivated specifically by cloud storage

/pdf/cryptographic-cloud-storage-3uxa4mufav.pdf

Cryptographic cloud storage

Searchable symmetric encryption SSE allows a party to outsource the storage of his data to another party in a private manner, while maintaining the ability to selectively search over it. This problem has been the focus of active research and several security definitions and constructions have been proposed. In this paper we begin by reviewing existing notions of security and propose new and stronger security definitions. We then present two constructions that we show secure under our new definitions. Interestingly, in addition to satisfying stronger security guarantees, our constructions are more efficient than all previous constructions.Further, prior work on SSE only considered the setting where only the owner of the data is capable of submitting search queries. We consider the natural extension where an arbitrary group of parties other than the owner can submit search queries. We formally define SSE in this multi-user setting, and present an efficient construction.

/pdf/searchable-symmetric-encryption-improved-definitions-and-1ghaqvyi64.pdf

Searchable symmetric encryption: Improved definitions and efficient constructions

Get the phase diagram information you need at a price you can afford. Key Features: Peer reviewed by the Japanese Committee for Alloy Phase Diagrams. Updated through April 2000. Total number of diagrams = 2,332 (605 are new of greatly revised diagrams; among these 171 are not in Binary Alloy Phase Diagrams, 2nd Edition). Approximately 600 crystal structure tables of systems for which phase diagrams are unknown. You've been asking for a simple book containing just binary phase diagrams and crystal structure data. Desk Handbook: Phase Diagrams for Binary Alloys meets this need, and it presents the most current information. Updates the previous print compilation of binary phase diagrams by 10 years. Presents diagrams in consistent size. Shows the principal axis in atomic per cent, with a secondary axis in weight per cent. Includes an introductory article on phase diagrams and their use. Gives reference to the original literature source. This volume is the latest outgrowth of the phase diagram activity in which ASM International has been involved since 1978.

Desk handbook phase diagrams for binary alloys

Phosphor-converted white light-emitting diodes (pc-WLEDs) are efficient light sources used in lighting, high-tech displays, and electronic devices. One of the most significant challenges of pc-WLEDs is the thermal quenching, in which the phosphor suffers from emission loss with increasing temperature during high-power LED operation. Here, we report a blue-emitting Na3–2xSc2(PO4)3:xEu2+ phosphor (λem = 453 nm) that does not exhibit thermal quenching even up to 200 °C. This phenomenon of zero thermal quenching originates from the ability of the phosphor to compensate the emission losses and therefore sustain the luminescence with increasing temperature. The findings are explained by polymorphic modification and possible energy transfer from electron–hole pairs at the thermally activated defect levels to the Eu2+ 5d-band with increasing temperature. Our results could initiate the exploration of phosphors with zero thermal quenching for high-power LED applications. A blue-emitting phosphor without thermal quenching is reported. The emission losses at high temperatures are compensated by a counter mechanism, originating in energy transfer between electron–hole pairs and thermally activated defect levels.

A zero-thermal-quenching phosphor

In a public key encryption, we may want to enable someone to test whether something is a keyword in a given document without leaking anything else about the document. An email gateway, for example, may be desired to test whether the email contains a keyword “urgent” so that it could route the email accordingly, without leaking any content to the gateway. This mechanism was referred as public key encryption with keyword search [4]. Similarly, a user may want to enable an email gateway to search keywords conjunctively, such as “urgent” email from “Bob” about “finance”, without leaking anything else about the email. We refer to this mechanism as public key encryption with conjunctive field keyword search. In this paper, we define the security model of this mechanism and propose two efficient schemes whose security is proved in the random oracle model.

Public key encryption with conjunctive field keyword search

Silicon nanowire biosensors for detection of cardiac troponin I (cTnI) with high sensitivity.

We have fabricated n-channel junctionless nanowire transistors with gate lengths in the range of 20–250 nm, and have compared their electrical performances with conventional inversion-mode nanowire transistors. The junctionless tri-gate transistor with a gate length of 20 nm showed excellent electrical characteristics with a high Ion/Ioff ratio (>106), good subthreshold slope (∼79 mV/dec), and low drain-induced barrier lowering (∼10 mV/V). The simpler fabrication process without junction formation results in improved short-channel characteristics compared to the inversion-mode devices, and also makes the junctionless nanowire transistor a promising candidate for sub 22-nm technology nodes.

Kihyun Kim

Papers

A zero-thermal-quenching phosphor

Public key encryption with conjunctive field keyword search

Silicon nanowire biosensors for detection of cardiac troponin I (cTnI) with high sensitivity.

Electrical characteristics of 20-nm junctionless Si nanowire transistors

Role of yttrium in activation of 〈c + a〉 slip in magnesium: An atomistic approach