Assessing Well Drilling Disturbance Effects on Offshore Foundation Piles in Clay

It is widely recognized that hydrocarbon well drilling from offshore platforms affects the surrounding ground. In clays, the level of disturbance can be severe when sections of open well collapse during drilling, impeding fluid return to the seabed (termed “packing-off”), and drilling fluid pressure is increased in order to obtain a breakthrough return path for the fluid. Significant swelling and hydraulic fracturing can take place in the surrounding soil mass. With time the excess pore pressures will dissipate and could cause increases in pore pressures far from the wells, potentially affecting areas occupied by the platform’s foundation piles. There is no established procedure to quantify the impact of such processes on foundation performance. This paper presents a numerical approach that involves a series of finite-element analyses in which drilling disturbance is treated as an idealized fluid injection process. The entry of pressurized drilling water into progressively enlarging fractured disturbed zones, and hence into the surrounding soil mass, is simulated with two- and three-dimensional nonlinear finite-element (FE) models, without modeling the actual hydraulic fracturing processes. The analyses make use of key observations made in the field at a piled offshore platform. The FE analyses predict marginal foundation capacity reductions, as well as significant global vertical and horizontal movements developing around the piles. It is demonstrated that the ground movement predictions are heavily influenced by the degree of geometric idealization.     

Antiproton therapy

Radiotherapy is one of the most important means we have for the treatment of localised tumours. It is therefore essential to optimize the technique, and a lot of effort goes into this endeavour. Since the proposal by Wilson in 1946 [R.R. Wilson, Radiology use of fast protons, Radiology 47 (1946) 487.] that proton beams might be better than photon beams at inactivating cancer cells, hadron therapy has been developed in parallel with photon therapy and a substantial knowledge has been gained on the effects of pions, protons and heavy ions (mostly carbon ions). Here we discuss the recent measurements by the CERN ACE collaboration of the biological effects of antiprotons, and argue that these particles very likely are the optimal agents for radiotherapy.     

Location Awareness—Improving Distributed Multimedia Communication

Multimedia creation and consumption is highly intensive and makes up the majority of Internet traffic nowadays. End-users are able to share their digital content with each other and to build communities based on interests, which often differ drastically according to location. Distributing these media using a central server can be quite expensive for a content provider. Distributed (peer-to-peer like) systems share costs evenly among participants. Thus, distributed multimedia systems will be more important in the future. The global distribution of end-users aggravates high-quality delivery of multimedia content. In this paper, we argue that geographical location-awareness greatly helps distributed multimedia communication. It increases the quality of multimedia content delivery and at the same time satisfies the growing need for more personalized, location-based services. In this paper, as a proof of concept, we introduce an overlay structure for distributed multimedia systems (and similar systems), which is location-aware and uses the locations of its nodes to optimize node-to-node communication for performance and delay. At the same time, the system enables location-based services.     

Infrared sensing of full penetration state in gas tungsten arc welding

The objective of this study is to present an applicable top-side infrared sensing technique for the prospective closed-loop control of weld penetration in gas tungsten arc welding (GTAW). A model is developed to calculate the full penetration state, which is specified by the back-side bead width, from the sensed infrared images. To ensure the model validity in the prospective closed-loop control, the experiments, which generate the data for the model identification, are conducted under the experimental conditions that will be encountered during practical closed-loop control of the welding process. The heat transfer condition and electrode tip angle may vary during welding or from case to case. Also, the control variables which are used to adjust the weld process in order to reach the required weld penetration will also change. In many cases, the current can be employed as an on-line adjustable control variable because of the implementation ease, when the welding speed and arc length are maintained at the preset values. Thus, different currents, workpiece sizes, and electrode tip angles are arranged in the experiments to emulate the possible current adjustments, case to case heat transfer variations, and electrode wear. The infrared characteristics of the effects of these parameters are extracted to regress the full penetration state. Finally, the back-side weld width (the full penetration state) is calculated using the resultant model from the sensed infrared data.     

A direct method for BBD matrix inversion

Published in Kibernetika i Sistemnyi Analiz, No. 2, pp. 51–64, March–April, 1994.     

Hydro-abrasive erosion of refractory ceramics

The paper discusses the material removal process in refractory ceramics eroded by hydro-abrasive jets. In particular, bauxite, sintered magnesia, and magnesia chromite are eroded. The influence of abrasive particle velocity, local exposure time, abrasive mass-flow rate, and abrasive type is investigated. Erosion depth, specific erosion rate, and geometry of the generated cavities are measured and analysed. For particle velocity as well as for local exposure time, threshold conditions are identified. At low erosion intensity, target material properties and abrasive type do not affect the material removal process notably. From optical and SEM-microscopy it is further found that the material removal mode changes with the progression of the erosion process. In the upper region of the eroded kerf, the dominating material removal mode is the simultaneous cutting of matrix and inclusion grains (transgranular). In the lower range, the erosion process is characterised by the removal of the binding matrix followed by washing off the inclusion grains (intergranular). The balance between both modes depends on the energy delivered to the erosion site. These observations are explained by assuming a continuous loss in kinetic energy of the abrasive particles during HAE. Some features of non-linear fracture are noticed and suggestions are made how to use non-linear fracture parameters to evaluate erosion resistance.     

Monitoring the depth of abrasive waterjet penetration

In order to control the uniformity of the abrasive waterjet penetration into the workpiece, it is necessary to devise a monitoring methodology that can indirectly monitor the depth of abrasive waterjet penetration. It was shown that the workpiece normal force generated by an abrasive waterjet could be used as the indicator of the depth of jet penetration, and that a force-feedback control holds promise as an effective way to regulate the depth of jet penetration. The effects of different abrasive waterjet process variables on both the depth of cut and the workpiece normal force are discussed.     

Nonseparable two- and three-dimensional wavelets

We present two- and three-dimensional nonseparable wavelets. They are obtained from discrete-time bases by iterating filter banks. We consider three sampling lattices: quincunx, separable by two in two dimensions, and FCO. The design methods are based either on cascade structures or on the McClellan transformation in the quincunx case. We give a few design examples. In particular, the first example of an orthonormal 2-D wavelet basis with symmetries is constructed