A memory-based high-speed digital delay line with a largeadjustable length

The digital delay line concept is based on a dynamic three-transistor cell memory, with pointer access and offers high operating frequency, large maximum length, and low power dissipation. The adjustable delay requires only a small overhead for control logic. An experimental chip with 60 K transistors, which utilizes this concept, has been built in a 1.5-μm CMOS technology. The adjustable delay ranges from 1 to 4096 clock cycles for a 4-bit-wide data word. Correct operation of the chip has been verified for clock frequencies in the range of 3 kHz to 30 MHz. Therefore the circuit is suitable for audio as well as video applications     

Fan-less heat exchanger concept for CO2 heat pump systems

A novel system for space heating has been developed taking advantage of the favourable characteristics of the transcritical CO₂ cycle, where heat is rejected by cooling of supercritical gas at gliding temperature. By a proper design of a counter flow heat exchanger it is possible to heat air to high temperatures and thereby giving the driving force for circulation of air through the heat exchanger, in consequence without using a fan. A concept without a fan, here called a fan-less concept, would give several advantages; no noise, no power consumption for the fan and increased comfort with reduced air draft in the room. The concept may also be used for heat rejection in systems for light commercial applications or other applications where fan assisted heat rejection concepts are used today.

An experimental study of a CO₂ to air heat exchanger has been performed. The heat exchanger was made of a vertically finned aluminium profile. Tubes for CO₂ were mounted in the base of the profile. CO₂ at supercritical pressure flowing downwards through the profile was heating air flowing in the channels formed by the fins of the profile. In this way a perfect counter flow heat exchange was obtained. The prototype heat exchanger was 2000 mm high and 190 mm wide, with 45 mm deep fins.

A simulation model was developed and verified to give good accordance with the experimental data. The model was then used to study how different design parameters influence the efficiency of the heat exchanger. By altering the number of fins and the fin thickness of the tested profile, the heat output at a given condition could be increased to almost double, meaning that the initial design was relatively far from optimal.

With the original heat exchanger profile design concept a heat exchanger with height, width and depth of, respectively 2000, 750 and 200 mm, would be required in order to achieve a heat output of 2500 W if the constraints for assumed acceptable efficiency was applied. If a heat exchanger with less height is preferred, the width will have to be increased in order to maintain about the same front area, width times height. Ideas have also been introduced for how to improve both the compactness and efficiency of the heat exchanger by introducing a compact counter flow heat exchanger in the lower part of the air flow channel. It is concluded that the new concept looks promising for use as the indoor heat exchanger in an air-to-air heat pump or as a gascooler for heat rejection in small commercial equipment, when using CO₂ as refrigerant.     

Incidents/accidents classification and reporting in Statoil

Based on requirements in the new petroleum regulations from Norwegian Petroleum Directorate (NPD) and the realisation of a need to improve and rationalise the routines for reporting and follow up of incidents, Statoil Exploration & Production Norway (Statoil E&P Norway) has formulated a new strategy and process for handling of incidents/accidents. The following past experiences serve as basis for the changes made to incident reporting in Statoil E&P Norway; too much resources were spent on a comprehensive handling and analysis of a vast amount of incidents with less importance for the safety level, taking the focus away from the more severe and important issues at hand, the assessment of "Risk Factor", i.e. the combination of recurrence frequency and consequence, was difficult to use. The high degree of subjectivity involved in the determination of the "Risk Factor" (in particular the estimation of the recurrence frequency) resulted in poor data quality and lack of consistency in the data material. The new system for categorisation and handling of undesirable incidents was established in January 2002. The intention was to get a higher degree of focus on serious incidents (injuries, damages, loss and near misses), with a thorough handling and follow-up. This is reflected throughout the handling of the serious incidents, all the way from immediate notification of the incident, through investigation and follow-up of corrective and preventive actions. Simultaneously, it was also an objective to rationalise/simplify the handling of less serious incidents. These incidents are, however, subjected to analyses twice a year in order to utilize the learning opportunity that they also provide. A year after the introduction of this new system for categorisation and follow-up of undesirable incidents, Statoil's experiences are predominantly good; the intention to get a higher degree of focus on serious incidents (injuries, damages, loss and near misses), has been met, the data quality for the more serious incidents (5% of the total number of incidents registered) has improved, the improved handling of incidents has contributed to more reliable and accurate HSE indicators at a corporate level, more user friendly codes in place for incident registration (based on MTO methodology), the revised matrix gives distinct criteria with respect to which investigation level to be initiated for a specific incident. All activities related to handling of undesirable incidents have been summarised and illustrated on a two-sided plastic form, incorporating both the categorisation matrix and the activity flowchart (see Figs. 1 and 4).     

BIO‐MOLECULAR EVENT EXTRACTION WITH MARKOV LOGIC

This article presents a novel approach to event extraction from biological text using Markov Logic. It can be described by three design decisions: (1) instead of building a pipeline using local classifiers, we design and learn a joint probabilistic model over events in a sentence; (2) instead of developing specific inference and learning algorithms for our joint model, we apply Markov Logic, a general purpose Statistical Relation Learning language, for this task; (3) we represent events as relations over the token indices of a sentence, as opposed to structures that relate event entities to gene or protein mentions. In this article, we extend our original work by providing an error analysis for binding events. Moreover, we investigate the impact of different loss functions to precision, recall and F‐measure. Finally, we show how to extract events of different types that share the same event clue. This extension allowed us to improve our performance our performance even further, leading to the third best scores for task 1 (in close range to the second place) and the best results for task 2 with a 14% point margin.     

Potential Toxic Effect on Aquatic Fauna by the Dwarf Shrub Empetrum hermaphroditum

The common evergreen dwarf shrub Empetrum hermaphroditum has influence on the functioning of boreal terrestrial ecosystems in northern Sweden. The negative effects of E. hermaphroditum are partly attributed to the production of the dihydrostilbene, batatasin-III, which is released from leaves and litter by rain and snowmelt. In this study, we investigated whether batatasin-III is carried by runoff into streams and lakes during the snowmelt period and whether it is also potentially hazardous to aquatic fauna. Sampling of water from streams and a lake for which the surrounding terrestrial vegetation is dominated by E. hermaphroditum was done during the snowmelt period in May 1993 and in 1998, and analyzed for batatasin-III. Using 24- and 48-hr standard toxicity tests, we analyzed toxicity to brown trout (Salmo trutta) alevins and juvenile water fleas (Daphnia magna). Toxicity (proportion of dead individuals) to trout was tested at pH 6.5 and compared with that of a phenol within a range of concentrations. In the toxicity (proportion of immobilized individuals) test on D. magna, the interactive effect of pH (pH 5.5-7.0) was included. Concentration of batatasin-III was generally higher in 1998 than in 1993 and showed peak levels during snowmelt. Concentration in ephemeral runnels > the lake > streams running through clear-cuts dominated by E. hermaphroditum > control streams lacking adjacent E. hermaphroditum vegetation. The maximum concentration of batatasin-III found was 1.06 mg l(-1). The proportion of dead yolk sac alevins increased significantly (P < 0.001) with increasing concentrations of batatasin-III and time of exposure. After 24 hr, EC50 was 10 mg l(-1). It was 2 mg l(-1) after 48 hr. The effect of phenol was negligible, indicating a specific phytotoxic effect of the bibenzyl structure of batatasin-III. The proportion of mobile D. magna became significantly smaller (P < 0.001) with increasing concentrations of batatasin-III, with decreasing pH, and with increasing exposure time. EC50 varied between 7 and 17 mg l(-1) at pH 5.5 and 7.0, respectively. After 24 hr EC50 decreased and was 2.5 at pH 5.5 and 12 mg l(-1) at pH 7.0. The levels of batatasin-III found in the field samples were below the lowest EC50 in acute toxicity tests. However, in view of the interactive effect of pH and exposure time, this study suggests that this stable plant metabolite may impose a lethal effect on the aquatic fauna in small streams.     

Subpixel mapping of snow cover in forests by optical remote sensing

Forest represents a challenging problem for snow-cover mapping by optical satellite remote sensing. To investigate reflectance variability and to improve the mapping of snow in forested areas, a method for subpixel mapping of snow cover in forests (SnowFrac) has been developed. The SnowFrac method is based on linear spectral mixing modelling of snow, trees and snow-free ground. The focus has been on developing a physically based reflectance model which uses a forest-cover map as prior information. The method was tested in flat terrain covered by spruce, pine and birch forests, close to the Jotunheimen region of South Norway. Experiments were carried out using a completely snow-covered Landsat Thematic Mapper (TM) scene, aerial photos and in situ reflectance measurements. A detailed forest model was photogrammetrically derived from the aerial photos. Modelled and observed TM reflectances were compared. In the given situation, the results demonstrate that snow and individual tree species, in addition to cast shadows on the snow surface from single trees, are the most influencing factors on visible and near-infrared reflectance. Modelling of diffuse radiation reduced by surrounding trees slightly improve the results, indicating that this effect is less important. The best results are obtained for pine forest and mixed pine and birch forest. Future work will focus on deriving a simplified reflectance model suitable for operational snow-cover mapping in forests.     

Compositional Verification of a Multi-Agent System for One-to-Many Negotiation

Verification of multi-agent systems hardly occurs in design practice. One of the difficulties is that required properties for a multi-agent system usually refer to multi-agent behaviour which has nontrivial dynamics. To constrain these multi-agent behavioural dynamics, often a form of organisational structure is used, for example, for negotiating agents, by following strict protocols. The claim is that these negotiation protocols entail a structured process that is manageable with respect to analysis, design and execution of such a multi-agent system. In this paper this is shown by a case study: verification of a multi-agent system for one-to-many negotiation in the domain of load balancing of electricity use. A compositional verification method for multi-agent systems is applied that allows to (1) logically relate dynamic properties of the multi-agent system as a whole to dynamic properties of agents, and (2) logically relate dynamic properties of agents to properties of their subcomponents. Given that properties of these subcomponents can be verified by more standard methods, these logical relationships provide proofs of the dynamic properties of the multi-agent system as a whole.     

Modelling of Tool Workpiece Interactions—Coefficient of Restitution for Hammer Drilling of Concrete

Forschung im Ingenieurwesen - In product development of hammer drills simulation models and physical replacement models are used for validation purposes. These models require...