The LHAM log-structured history data access method

Numerous applications such as stock market or medical information systems require that both historical and current data be logically integrated into a temporal database. The underlying access method must support different forms of “time-travel” queries, the migration of old record versions onto inexpensive archive media, and high insertion and update rates. This paper presents an access method for transaction-time temporal data, called the log-structured history data access method (LHAM) that meets these demands. The basic principle of LHAM is to partition the data into successive components based on the timestamps of the record versions. Components are assigned to different levels of a storage hierarchy, and incoming data is continuously migrated through the hierarchy. The paper discusses the LHAM concepts, including concurrency control and recovery, our full-fledged LHAM implementation, and experimental performance results based on this implementation. A detailed comparison with the TSB-tree, both analytically and based on experiments with real implementations, shows that LHAM is highly superior in terms of insert performance, while query performance is in almost all cases at least as good as for the TSB-tree; in many cases it is much better. Received March 4, 1999 / Accepted September 28, 1999     

Performance funnels and tracking control

Tracking of an absolutely continuous reference signal (assumed bounded with essentially bounded derivative) is considered in the context of a class of non-linear, single-input, single-output, dynamical systems modelled by functional differential equations satisfying certain structural hypotheses (which, interpreted in the highly specialised case of linear systems, translate into assumptions of (i) relative degree one, (ii) positive high-frequency gain and (iii) stable zero dynamics). The control objective is evolution of the tracking error within a prespecified funnel, thereby guaranteeing prescribed transient performance and prescribed asymptotic tracking accuracy. This objective is achieved by a control which takes the form of linear error feedback with time-varying gain. The gain is generated by a non-linear feedback law in which the reciprocal of the distance of the tracking error to the funnel boundary plays a central role. In common with many established adaptive control methodologies, the overall feedback structure exploits an intrinsic high-gain property of the system, but differs from these methodologies in two fundamental respects: the funnel control gain is not dynamically generated and is not necessarily monotone. The main distinguishing feature of the present article vis à vis its various precursors is twofold: (a) non-linearities of a general nature can be tolerated in the input channel; (b) a more general formulation of prescribed transient behaviour is encompassed (including, for example, practical (M, μ)-stability wherein, for prescribed parameter values M > 1, μ > 0 and λ > 0, the tracking error e(·) is required to satisfy |e(t)| < max {Me ^?μt |e(0)|, λ} for all t ≥ 0).     

Tiled++: An Enhanced Tiled Hi-Res Display Wall

In recent years, high-resolution displays have become increasingly important to decision makers and scientists because large screens combined with a high pixel count facilitate content rich, simultaneous display of computer-generated imagery and high-definition video data from multiple sources. Tiled displays are attractive due to their extended screen real estate, scalability, and low cost. LCD panels are usually preferred over projectors because of their superior resolution. One of the drawbacks of LCD-based tiled displays is the fact that users sometimes get distracted by the screens' bezels, which cause discontinuities in rendered images, animations, or videos. Most conventional solutions either ignore the bezels and display all pixels, causing objects to become distorted, or eliminate the pixels that would normally fall under the bezels, causing pixels to be missing in the display of static images. In animations, the missing pixels will eventually reappear when the object moves, providing an experience that is similar to looking through a French window. In this paper, we present a new scalable approach that leads neither to discontinuities nor to significant loss of information. By projecting onto the bezels, we demonstrate that a combination of LCD-based tiled displays and projection significantly reduces the bezel problem. Our technique eliminates ambiguities that commonly occur on tiled displays in the fields of information visualization, visual data analysis, human-computer interaction, and scientific data display. It improves the usability of multimonitor systems by virtually eliminating the bezels. We describe a setup and provide results from an evaluation experiment conducted on a 3 times 3 and on a 10 times 5 tiled display wall.     

Novel surface acoustic wave (SAW)-driven closed PDMS flow chamber

In this article, we demonstrate a novel microfluidic flow chamber driven by surface acoustic waves. Our device is a closed loop channel with an integrated acoustic micropump without external fluidic connections that allows for the investigation of small fluid samples in a continuous flow. The fabrication of the channels is particularly simple and uses standard milling and PDMS molding. The micropump consists of gold electrodes deposited on a piezoelectric substrate employing photolithography. We show that the pump generates a pressure-driven Poiseuille flow, investigate the acoustic actuation mechanism, characterize the flow profile for different channel geometries, and evaluate the driving pressure, efficiency and response time of the acoustic micropump. The fast response time of our pump permits the generation of non-stationary flows. To demonstrate the versatility of the device, we have pumped a red blood cell suspension at a physiological rate of 60?beats/min.     

Viscose‐based porous carbon fibers: improving yield and porosity through optimization of the carbonization process by design of experiment

Journal of Porous Materials - In this study, the production of porous carbon fibers from viscose fibers was investigated. The effects of final carbonization temperature...     

Efficient Memory-Protected Integration of Add-On Software Subsystems in Small Embedded Automotive Applications

Current innovations in the automotive industry evolve mainly in the electronics and software domain. This leads to an increasing integration of additional software subsystems into already existing electronic control units (ECUs) to cope with the raised amount and complexity of present ECUs in modern high-end vehicles. This paper discusses different approaches which are required to integrate such add-on software subsystems in an isolated memory domain, and considers particularly the special needs of small embedded systems-including the limited hardware support. Special focus is brought to the efficient detection of malicious memory accesses, as well as the benefits of a thereupon possible and adaptable failure-handling strategy. All investigations are based on a developed memory-protection framework which has been tailored to the special needs of a sample vehicle dynamics control system. Its usage allows the combination of. integrating additional subsystems without reducing the main application's availability     

Thermoanalytical Screening of Nitrogen-Rich Substances

The thermal decomposition behaviour of approx. 60 nitrogen-rich substances on the basis of tetrazole and tetrazine structures was investigated by thermoanalytical methods. Decomposition mechanisms initiated by ring opening of the heterocycles could be established. Substituent effects on the exothermic decomposition characteristics of nitrogen-rich compounds are demonstrated.     

Burning Behaviour of Gas Generators with High Boron Content

Gas generators with high boron content of interest for ducted rockets were prepared and characterized. The parameters tested were:

• – combustion residue
• – pressure exponent
• – flow and temperature of the ejected boron particles
• – mechanical properties.

The results of the experments (optical bomb, high speed camera, two-color pyrometer, thermal analysis, tensile test) are presented and discussed.     

Simulation of operational behaviour of patchily regenerated, rigid gas cleaning filter media

Particle removal from hot process gases is frequently accomplished with regenerable ceramic filters. When regenerating such media periodically, the dust cake may be detached from parts of the filter surface while other regions remain intact (‘patchy cleaning’). The filtration process depends on how these patterns of incomplete regeneration evolve over a number of cycles, how they change the build-up of the new cake, and how they affect the pressure drop. A two-dimensional quasi stationary flow model is used to predict pressure drops as a function of regeneration efficiencies and regeneration patterns, taking into account the finite thickness and flow resistance of the medium itself. The effect of non-uniform cake build-up on the pressure rise during a filter cycle is also modelled for a partially regenerated filter. The calculations prove that the pressure drop rises faster for lower regeneration efficiencies and that also cycle times become briefer with lower regeneration efficiency. It can also be shown, that the regeneration pattern only influences the pressure drop curve at the very beginning of the filtration cycle but does not influence the filtration cycle times.