A tutorial on particle filters for online nonlinear/non-GaussianBayesian tracking

Increasingly, for many application areas, it is becoming important to include elements of nonlinearity and non-Gaussianity in order to model accurately the underlying dynamics of a physical system. Moreover, it is typically crucial to process data on-line as it arrives, both from the point of view of storage costs as well as for rapid adaptation to changing signal characteristics. In this paper, we review both optimal and suboptimal Bayesian algorithms for nonlinear/non-Gaussian tracking problems, with a focus on particle filters. Particle filters are sequential Monte Carlo methods based on point mass (or "particle") representations of probability densities, which can be applied to any state-space model and which generalize the traditional Kalman filtering methods. Several variants of the particle filter such as SIR, ASIR, and RPF are introduced within a generic framework of the sequential importance sampling (SIS) algorithm. These are discussed and compared with the standard EKF through an illustrative example     

Cache coherence requirements for interprocess rendezvous

Multiprocessors in which a shared bus is used by the processor to communicate with common memory are an emerging class of machines where there is a need to support parallel programming languages. A language construct that is found in a number of parallel programming languages to support synchronization and communication in the interprocess rendezvous. Shared-bus multiprocessor require a protocol to keep the date in their caches coherent. There are two major categories of these protocols: invalidation and write-boadcast. This paper examines the requirements for cache coherence protocols to support efficient interprocessor rendezvous. The approach taken is to examine the memory referencing patterns to the run-time data structures during rendezvous execution. The appropriate coherence protocol is shown to be a function of the processor scheduling strategy used by the run-time system at synchronzation points during the rendezvous. When processes migrate freely as a result of the scheduling strategy, invalidation protocols are found to be more efficient. When migration is restricted by the scheduler, write-broadcast protocols are more efficient.     

The intergranular embrittlement of Cu-AI-Ni β-phase alloys

Intergranular embrittlement in the Cu-Al-Ni -phase alloys has been investigated. Results of various experiments, which included an Auger electron spectroscopic analysis of freshly fractured grain boundary surfaces, lead to the conclusion that impurities do not play any significant role in the intergranular embrittlement of these alloys.     

Passive dissolution of hydrogen gas into groundwater using hollow-fiber membranes

A new hollow-fiber membrane remediation system has recently been developed to passively supply groundwater with dissolved hydrogen (H2) to stimulate the biodegradation of chlorinated solvents. Understanding the mass transfer behavior of membranes under conditions of creeping flow is critical for the design of such systems. Therefore, the objectives of this research were to evaluate the gas transfer behavior of hollow-fiber membranes under conditions typical of groundwater flow and to assess the effect of membrane configuration on gas transfer performance. Membrane gas transfer was evaluated using laboratory-scale glass columns operated at low flow velocities (8.6-12,973 cm/d). H2 was supplied to the inside of the membrane fibers while water flowed on the outside and normal to the fibers (i.e. cross-flow). Membrane configuration (single fiber and fabric) and membrane spacing for the fabric modules did not affect gas transfer performance. Therefore, the results from all of the experiments were combined to obtain the following dimensionless Sherwood number (Sh) correlation expressed as a function of Reynolds number (Re) and Schmidt number (Sc): Sh = 0.824Re(0.39)Sc(0.33) (0.0004相似文献   

On-line inspection of filter media for process and product improvement

Detecting, visualizing, identifying and reporting filter media defects during manufacture benefits not only roll-goods and media producers, but also cartridge manufacturers and end users. However, many still rely on end-of-roll sampling to detect such defects. Todd Clapp, Cognex Corp, USA, explains why on-line web inspection systems should be an essential part of the filter media manufacturing process.     

A new class of bookshelf bistable siloxane modified ferroelectric LC materials with electrical repairability in an LCoS configuration

Abstract— Investigation of siloxane‐based ferroelectric liquid crystals (Si‐FLCs) has revealed chevron‐free long‐term bistable behavior and, unusually, an easy regeneration of bistable performance after damage (e.g., by mechanical shock). The properties are intrinsically related to the chemical structure of the oligosiloxane materials. The phenomena result from the coupling of siloxane and organic moieties that causes nano‐phase segregation, which essentially reduces the correlation of tilting from adjacent layers and also generates weak anchoring by decoupling the bulk structure from the strong surface anchoring. A method of regenerating a condition with bistable performance by an electric field (without mechanical and heat treatment) is established. An in‐house Si‐FLC over a silicon (Si‐FLCoS) device is demonstrated, which exhibits good memory effects without chevron defects and a repair function for regenerating bistability in case of damage.     

Evaluation of polyethylene hollow-fiber membranes for hydrogen delivery to support reductive dechlorination in a soil column

Engineered systems are often needed to supply an electron donor, such as hydrogen (H(2)), to the subsurface to stimulate the biological dehalogenation of perchloroethene (PCE) to ethene. A column study was performed to evaluate the ability of gas permeable hollow-fiber membranes to supply H(2) directly to PCE-contaminated groundwater to facilitate bioremediation. Two glass columns were packed with soil obtained from a trichloroethene-contaminated site at Cape Canaveral, Florida, and were fed a minimal medium spiked with PCE (7 microM) for 391 days. The columns were operated in parallel, with one column receiving H(2) via polyethylene hollow-fiber membranes (lumen H(2) pressure of approximately 1atm) and a control column receiving no H(2). PCE was initially dechlorinated at a similar rate and to a similar extent in both columns, likely due to the presence of soil organic matter that was able to support dechlorination. After 265 days of operation, dechlorination performance declined in the control column and the benefits of membrane-supplied H(2) became evident. Although the membrane-supplied H(2) effectively stimulated PCE dechlorination at the end of the experiment (days 359-391), the system was inefficient in that only 5% of the supplied H(2) was used for dechlorination. Most of the remainder was used to support methanogenesis (94%). Despite the dominance of methanogens, nearly complete dechlorination of PCE to ethene was observed in the H(2)-fed column. In addition to the inefficient use of H(2), operational problems included excessive foulant accumulation on the outside of the membrane fibers and water condensation inside the fibers. Use of alternative membrane materials and changes to the operating approach (e.g. pulsing or supplying H(2) at low partial pressures) may help to overcome these problems so that this technology can provide effective and stable remediation of aquifers contaminated with chlorinated ethenes.     

Attention! Cosmopolitans ahead – They may not be as creative as they think!

Research on cosmopolitanism and creativity has received significant attention in recent years; however, the connections between these constructs are still ill‐defined. This study uses the creative cognition model to explore the relationship between cosmopolitanism and creativity using both self‐report and expert ratings of a qualitative task. Quantitative data support the assertion that cosmopolitanism is significantly and positively related to self‐expectations of creativity and creative work involvement. However, creative performance on a productive solutions task coded by creativity experts failed to replicate the self‐reported findings. We describe the practical and theoretical implications of these results for future research into cosmopolitanism and creativity.