131,593 research outputs found
Building block libraries and structural considerations in the self-assembly of polyoxometalate and polyoxothiometalate systems
Inorganic metal-oxide clusters form a class of compounds that are unique in their topological and electronic versatility and are becoming increasingly more important in a variety of applications. Namely, Polyoxometalates (POMs) have shown an unmatched range of physical properties and the ability to form structures that can bridge several length scales. The formation of these molecular clusters is often ambiguous and is governed by self-assembly processes that limit our ability to rationally design such molecules. However, recent years have shown that by considering new building block principles the design and discovery of novel complex clusters is aiding our understanding of this process. Now with current progress in thiometalate chemistry, specifically polyoxothiometalates (POTM), the field of inorganic molecular clusters has further diversified allowing for the targeted development of molecules with specific functionality. This chapter discusses the main differences between POM and POTM systems and how this affects synthetic methodologies and reactivities. We will illustrate how careful structural considerations can lead to the generation of novel building blocks and further deepen our understanding of complex systems
The Virtual Block Interface: A Flexible Alternative to the Conventional Virtual Memory Framework
Computers continue to diversify with respect to system designs, emerging
memory technologies, and application memory demands. Unfortunately, continually
adapting the conventional virtual memory framework to each possible system
configuration is challenging, and often results in performance loss or requires
non-trivial workarounds. To address these challenges, we propose a new virtual
memory framework, the Virtual Block Interface (VBI). We design VBI based on the
key idea that delegating memory management duties to hardware can reduce the
overheads and software complexity associated with virtual memory. VBI
introduces a set of variable-sized virtual blocks (VBs) to applications. Each
VB is a contiguous region of the globally-visible VBI address space, and an
application can allocate each semantically meaningful unit of information
(e.g., a data structure) in a separate VB. VBI decouples access protection from
memory allocation and address translation. While the OS controls which programs
have access to which VBs, dedicated hardware in the memory controller manages
the physical memory allocation and address translation of the VBs. This
approach enables several architectural optimizations to (1) efficiently and
flexibly cater to different and increasingly diverse system configurations, and
(2) eliminate key inefficiencies of conventional virtual memory. We demonstrate
the benefits of VBI with two important use cases: (1) reducing the overheads of
address translation (for both native execution and virtual machine
environments), as VBI reduces the number of translation requests and associated
memory accesses; and (2) two heterogeneous main memory architectures, where VBI
increases the effectiveness of managing fast memory regions. For both cases,
VBI significanttly improves performance over conventional virtual memory
Resummation of non-global logarithms and the BFKL equation
We consider a `color density matrix' in gauge theory. We argue that it
systematically resums large logarithms originating from wide-angle soft
radiation, sometimes referred to as non-global logarithms, to all logarithmic
orders. We calculate its anomalous dimension at leading- and next-to-leading
order. Combined with a conformal transformation known to relate this problem to
shockwave scattering in the Regge limit, this is used to rederive the
next-to-leading order Balitsky-Fadin-Kuraev-Lipatov equation (including its
nonlinear generalization, the so-called Balitsky-JIMWLK equation), finding
perfect agreement with the literature. Exponentiation of divergences to all
logarithmic orders is demonstrated. The possibility of obtaining the evolution
equation (and BFKL) to three-loop is discussed.Comment: 29 pages, 32 including appendix, 7 figures. v2 presentation improved
thanks to helpful refere
Development of a Collaborative Design Tool for Structural Analysis in an Immersive Virtual Environment
This paper contains the results of an on-going collaborative research effort by the departments of Architecture and Computer Science of Virginia Polytechnic Institute and State University, U.S.A., to develop a computer visualization application for the structural analysis of building structures. The VIRTUAL-SAP computer program is being developed by linking PC-SAP4 (Structural Analysis Program), and virtual environment software developed using the SVE (Simple Virtual Environment) library. VIRTUAL-SAP is intended for use as a collaborative design tool to facilitate the interaction between the architect, engineer, and contractor by providing an environment that they can walk-through and observe the consequences of design alterations. Therefore, this software can be used as an interactive computer-aided analysis of building systems
Tangible user interfaces : past, present and future directions
In the last two decades, Tangible User Interfaces (TUIs) have emerged as a new interface type that interlinks the digital and physical worlds. Drawing upon users' knowledge and skills of interaction with the real non-digital world, TUIs show a potential to enhance the way in which people interact with and leverage digital information. However, TUI research is still in its infancy and extensive research is required in or- der to fully understand the implications of tangible user interfaces, to develop technologies that further bridge the digital and the physical, and to guide TUI design with empirical knowledge. This paper examines the existing body of work on Tangible User In- terfaces. We start by sketching the history of tangible user interfaces, examining the intellectual origins of this field. We then present TUIs in a broader context, survey application domains, and review frame- works and taxonomies. We also discuss conceptual foundations of TUIs including perspectives from cognitive sciences, phycology, and philoso- phy. Methods and technologies for designing, building, and evaluating TUIs are also addressed. Finally, we discuss the strengths and limita- tions of TUIs and chart directions for future research
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