Sulfate Attack on Cement-Stabilized Sand

A 3.5-km (2.2 mi) section of a road in Georgia developed unexpected transverse bumps within 6 months after construction. The source of the bumps appeared to be expansion within the cement-stabilized base course. Laboratory examination of samples from areas showing distress revealed the presence of ettringite, a calcium sulfoaluminate the formation of which can be accompanied by severe expansion. This expansive material was the probable cause of the volume changes causing the transverse bumps. The calcium and alumina needed to form ettringite were available from the portland cement and the stabilized soil's clay minerals. The source of the sulfur was identified as the well water that was mixed with the cement-stabilized base. Sulfate attack of cement-stabilized soils is a relatively infrequent problem, but it is highly destructive when it occurs. Currently, there are no firm criteria for identifying when sulfate attack of a cement-stabilized soil is a potential problem nor are there established methods of preventing the attack.     

Location expression standards for ITS: Testing the LRMS Cross Street Profile

Location can be expressed in a number of ways: coordinates, street addresses, landmark references, linear references, grid references, etc. The Cross Streets Profile is part of a location messaging specification developed for use in Intelligent Transportation Systems (ITS). It describes a location essentially in terms of street names. This paper presents an evaluation of the Cross Streets Profile based upon lab and field tests using commercial street network databases in the County of Santa Barbara. Results vary widely, depending upon database quality which in turn is dependent on geography (major streets vs minor streets, rural vs urban). Success rates can be improved with intelligent algorithms. Future directions to improve the quality of location messaging are discussed.     

A lightweight web-based vulnerability scanner for small-scale computer network security assessment

There appears to be a common perception amongst average computer users pointing towards a global lack of trust when using the Internet. The resolution of this lack of trust relating to the use of the Internet, particularly orientated towards its commercial use and online purchasing, requires partly from website developers to create and maintain web applications that are robust and provide a certain degree of resilience to attack from outside threats. This project intends to contribute to this particular aspect by providing site developers and system testers, as well as simple site users, with a tool for reconnaissance, vulnerability scanning and remote network mapping that is easily accessible and useable due to its web-based and visual, event-driven interface. It is anticipated that the cumbersome task of learning to use a number of command line tools and their exact functionality and parameters can be avoided through this and similar developments, and hence that this will potentially widen the access to security testing, particularly to small and medium businesses.     

Optimization of decision networks in structured task environments

This paper considers the problem of determining the optimal distributed decision strategy for a team of decision-makers (DMs) arranged in an arbitrary acyclic organizational structure and controlling a complex structured process. Each DM has access to uncertain and partial information about the task environment and can control only a portion of it. We present an influence diagram model of the joint task-organization system and formulate the optimal team strategy in terms of a set of coupled hypothesis testing tasks at DMs. Specifically, we show that the scope of a local decision task is determined by the interaction of the task structure (what can be measured) and of the information access structure of the organization (who can measure what); while the control structure (who can influence what event) has an impact on the locally perceived costs associated with the decision options available. Theoretical results are illustrated via a numerical example, and connections to existing decision models are discussed     

A finite element model of the stress field in a star-shaped inclusion

The elastic stress field in the neighborhood of an inclusion in the shape of a five-pointed star embedded in a homogeneous matrix subject to a remote uniaxial strain is determined using the finite element method in both plane stress and plane strain. The results do not support a recent preliminary analytical result that both the individual stress components and the effective stress distribution inside the inclusion should be uniform.     

Design and control of RUPERT: a device for robotic upper extremity repetitive therapy.

The structural design, control system, and integrated biofeedback for a wearable exoskeletal robot for upper extremity stroke rehabilitation are presented. Assisted with clinical evaluation, designers, engineers, and scientists have built a device for robotic assisted upper extremity repetitive therapy (RUPERT). Intense, repetitive physical rehabilitation has been shown to be beneficial overcoming upper extremity deficits, but the therapy is labor intensive and expensive and difficult to evaluate quantitatively and objectively. The RUPERT is developed to provide a low cost, safe and easy-to-use, robotic-device to assist the patient and therapist to achieve more systematic therapy at home or in the clinic. The RUPERT has four actuated degrees-of-freedom driven by compliant and safe pneumatic muscles (PMs) on the shoulder, elbow, and wrist. They are programmed to actuate the device to extend the arm and move the arm in 3-D space. It is very important to note that gravity is not compensated and the daily tasks are practiced in a natural setting. Because the device is wearable and lightweight to increase portability, it can be worn standing or sitting providing therapy tasks that better mimic activities of daily living. The sensors feed back position and force information for quantitative evaluation of task performance. The device can also provide real-time, objective assessment of functional improvement. We have tested the device on stroke survivors performing two critical activities of daily living (ADL): reaching out and self feeding. The future improvement of the device involves increased degrees-of-freedom and interactive control to adapt to a user's physical conditions.     

A ground-based radar backscatter investigation in the percolation zone of the Greenland ice sheet

Satellite radar altimeters and scatterometers deployed over ice sheets experience backscatter from the surface and from within the snowpack, termed surface and volume backscatter respectively. In order to assess the errors in satellite altimeter measurements it is vital to know where the return is originating from in the snowpack. This return can vary spatially and temporally. Seasonal variations in the volume backscatter can be a major complicating factor in the radar return from the percolation zone. Ground-based step-frequency radar was deployed in the percolation zone of the Greenland Ice Sheet at ∼ 1945 m elevation (69 51N, 47 15W). Previous measurements in this area made by scientists from the Byrd Polar Research Centre and the University of Kansas, undertaken prior to summer melt events, have shown the strongest backscatter from ice features at around 1 m depth buried beneath the previous end-of-summer surface. In autumn 2004, radar measurements in the Ku band with bandwidths of 1 and 8 GHz were made alongside detailed stratigraphic observations within a 1 km² site. The radar results revealed no continuous reflecting horizons in the upper 3.5 m of the firn. Shallow cores and snowpits also indicated that there were no spatially continuous stratigraphic horizons across the study site. An average electromagnetic wave velocity of 2.11 ± 0.05 × 10⁸ m s^− 1 was determined for the upper metre of the firn. Surface and volume backscatter at vertical incidence were calculated using a standard model. The contribution of the surface backscatter to the total backscatter was on average 6 dB higher than that of the volume backscatter. However, at the higher 8 GHz bandwidth the strongest return frequently originated not from the surface but from within the upper 30 cm of the snowpack, most probably from thin ice layers. At 1 GHz bandwidth these ice layers were not always resolved; their return merged with the surface return, causing it to broaden, with the peak and leading edge moving down. Modelling using density and thickness measurements from shallow cores and snowpits showed that the backscatter from these shallow, thin ice layers could be stronger than the surface return owing to constructive interference from the top and base of the layers.     

Introduction to a special issue: the future of landscape characterisation,and the future character of landscape – between space,time, history,place and nature

Abstract

In any discussion of landscape characterisation the elephant in the room is the question of just what is landscape? Another way of putting this question is to simply ask: ‘How would you characterise landscape?’ What this implies is that there is a certain circularity in landscape characterisation because, through the very act of characterising landscape, one is also defining what one means by landscape. The European Landscape Convention’s definition of landscape as ‘an area, as perceived by people, whose character is the result of the action and interaction of natural and/or human factors’ suggests a similar circularity because the character of an area, as it results from the action of natural and/or human factors, is dependent upon human perception, which is presumably also, in addition, one of the human factors acting upon the landscape. This circularity, or ‘circulating reference’, to use Bruno Latour’s term, is fundamental to Denis Cosgrove’s analysis of the origin of the modern concept of landscape as scenic space, and his analysis, we would suggest, helps explain some of the questions raised in this special issue concerning landscape characterisation and the future character of landscape .