Quantum transport, master equations, and exchange fluctuations

We investigate to which extent a many-body Bloch-Redfield master equation description of quantum transport is consistent with the exact generalized equilibrium conditions known as exchange fluctuation theorems. Thereby we identify a class of master equations for which this is the case. Beyond this class, we find deviations which exhibit characteristic scaling laws as functions of the dot-lead tunneling, the inter-dot tunneling, and the temperature. These deviations are accompanied by an increase of lead energy fluctuations inherent in the Bloch-Redfield equation beyond rotating-wave approximation. We illustrate our results with numerical data for a double quantum dot attached to four leads.Comment: 8 page

Mobile Process Landscaping by Example of Residential Trade and Industry

This case study describes the method of process landscaping by example of a project in which the business processes of a company from the residential trade and industry were analyzed regarding their mobile potential. This analysis was conducted with the aim to organize these processes more efficiently in order to realize cost savings. Therefore a verification was required, whether the use of mobility supporting technology is suitable to obtain this goal and which professional requirements such a solution needs to fulfil. For that purpose, it is shown how the initial situation was analyzed, which alternative solutions on the basis of mobility supporting technology were developed and how these alternatives were economically evaluated. Furthermore, it is shown how first restrictions for the software and system design were made on the basis of one alternative. The method of Mobile Process Landscaping refers to the stage of requirements engineering in the software process

Cache craftiness for fast multicore key-value storage

We present Masstree, a fast key-value database designed for SMP machines. Masstree keeps all data in memory. Its main data structure is a trie-like concatenation of B+-trees, each of which handles a fixed-length slice of a variable-length key. This structure effectively handles arbitrary-length possiblybinary keys, including keys with long shared prefixes. [superscript +]-tree fanout was chosen to minimize total DRAM delay when descending the tree and prefetching each tree node. Lookups use optimistic concurrency control, a read-copy-update-like technique, and do not write shared data structures; updates lock only affected nodes. Logging and checkpointing provide consistency and durability. Though some of these ideas appear elsewhere, Masstree is the first to combine them. We discuss design variants and their consequences. On a 16-core machine, with logging enabled and queries arriving over a network, Masstree executes more than six million simple queries per second. This performance is comparable to that of memcached, a non-persistent hash table server, and higher (often much higher) than that of VoltDB, MongoDB, and Redis.National Science Foundation (U.S.). (Award 0834415)National Science Foundation (U.S.). (Award 0915164)Quanta Computer (Firm

Damage Detection by Template Matching of Scattered Waves

A method based on template matching is presented to detect and locate damage in buildings following severe shaking by an earthquake. The templates are constructed by finite‐element simulations of a suite of damage scenarios, with the solutions evaluated at the location (and orientation) of each sensor in the structure. The damage detection is carried out by cross‐correlating the templates with recordings acquired from earthquakes. A dense distributed network of sensors is important for detecting anomalies in the presence of ambient noise. The cross correlation of the templates with themselves provides a measure of the resolution of the damage location