State and parameter estimation approach to monitoring AGR nuclear core

This work concerns with the problem of monitoring an Advanced Gas-cooled Nuclear Reactor (AGR) core. This plant (figure 1) makes use of the heat given by the nuclear efficient reaction to produce electricity by means of steam turbines. These are driven by steam, which is heated, from the AGR gas using a heat exchanger. One of the advantages of a gas cooled reactor is the high temperature that the gas can achieve so that when it is used in conjunction with the heat exchanger and steamed turbine the thermal efficiency is very high

Condition monitoring of an advanced gas-cooled nuclear reactor core

A critical component of an advanced gas-cooled reactor station is the graphite core. As a station ages, the graphite bricks that comprise the core can distort and may eventually crack. Since the core cannot be replaced, the core integrity ultimately determines the station life. Monitoring these distortions is usually restricted to the routine outages, which occur every few years, as this is the only time that the reactor core can be accessed by external sensing equipment. This paper presents a monitoring module based on model-based techniques using measurements obtained during the refuelling process. A fault detection and isolation filter based on unknown input observer techniques is developed. The role of this filter is to estimate the friction force produced by the interaction between the wall of the fuel channel and the fuel assembly supporting brushes. This allows an estimate to be made of the shape of the graphite bricks that comprise the core and, therefore, to monitor any distortion on them

Protein Losses and Urea Nitrogen Underestimate Total Nitrogen Losses in Peritoneal Dialysis and Hemodialysis Patients

Objective: Muscle wasting is associated with increased mortality and is commonly reported in dialysis patients. Hemodialysis (HD) and peritoneal dialysis (PD) treatments lead to protein losses in effluent dialysate. We wished to determine whether changes in current dialysis practice had increased therapy-associated nitrogen losses. / Design: Cross-sectional cohort study. / Methods: Measurement of total protein, urea and total nitrogen in effluent dialysate from 24-hour collections from PD patients, and during haemodiafiltration (HDF) and haemodialysis (HD) sessions. / Subjects: One hundred eight adult dialysis patients. / Intervention: Peritoneal dialysis, high-flux haemodialysis and haemodiafiltration. / Main Outcome Measure: Total nitrogen and protein losses. / Results: Dialysate protein losses were measured in 68 PD and 40 HD patients. Sessional losses of urea (13.9 [9.2-21.1] vs. 4.8 [2.8-7.8] g); protein (8.6 [7.2-11.1] vs. 6.7 [3.9-11.1] g); and nitrogen (11.5 [8.7-17.7] vs. 4.9 [2.6-9.5] g) were all greater for HD than PD, P < .001. Protein-derived nitrogen was 71.9 (54.4-110.4) g for HD and 30.8 (16.1-59.6) g for PD. Weekly protein losses were lower with HD 25.9 (21.5-33.4) versus 46.6 (27-77.6) g/week, but nitrogen losses were similar. We found no difference between high-flux HD and HDF: urea (13.5 [8.8-20.6] vs. 15.3 [10.5-25.5] g); protein (8.8 [7.3-12.2] vs. 7.6 [5.8-9.0] g); and total nitrogen (11.6 [8.3-17.3] vs. 10.8 [8.9-22.5] g). Urea nitrogen (UN) only accounted for 45.1 (38.3-51.0)% PD and 63.0 (55.3-62.4)% HD of total nitrogen losses. / Conclusion: Although sessional losses of protein and UN were greater with HD, weekly losses were similar between modalities. We found no differences between HD and HDF. However, total nitrogen losses were much greater than the combination of protein and UN, suggesting greater nutritional losses with dialysis than previously reported

High-sensitivity noncontact atomic force microscope/scanning tunneling microscope (nc AFM/STM) operating at subangstrom oscillation amplitudes for atomic resolution imaging and force spectroscopy

Cataloged from PDF version of article.We describe a new, highly sensitive noncontact atomic force microscope/scanning tunneling microscope (STM) operating in ultrahigh vacuum (UHV) with subangstrom oscillation amplitudes for atomic resolution imaging and force-distance spectroscopy. A novel fiber interferometer with similar to4x10(-4) A/rootHz noise level is employed to detect cantilever displacements. Subangstrom oscillation amplitude is applied to the lever at a frequency well below the resonance and changes in the oscillation amplitude due to tip-sample force interactions are measured with a lock-in amplifier. Quantitative force gradient images can be obtained simultaneously with the STM topography. Employment of subangstrom oscillation amplitudes lets us perform force-distance measurements, which reveal very short-range force interactions, consistent with the theory. Performance of the microscope is demonstrated with quantitative atomic resolution images of Si(111)(7x7) and force-distance curves showing short interaction range, all obtained with <0.25 Angstrom lever oscillation amplitude. Our technique is not limited to UHV only and operation under liquids and air is feasible. (C) 2003 American Institute of Physics

State-dependent Riccati equation control with predicted trajectory

A modified State-Dependent Riccati Equation method is used which takes into account future variations in the system model dynamics. The system in the state dependent coefficient form, together with the prediction of the future trajectory, may be considered to be approximated by known time-varying system. For such a system the optimal control solution may be obtained for a discrete time system by solving the Riccati Difference Equation. The minimisation of the cost function for a predicted time-varying system is achieved by considering the prediction horizon as a combination of infinite and finite horizon parts. The infinite part is minimised by solving the Algebraic Riccati Equation and the finite part by the Riccati Difference Equation. The number of future prediction steps depends upon the problem and is a fixed variable chosen during the controller design. A comparison of results is provided with other design methods, which indicates that there is considerable potential for the technique

Local linear stability analysis of cyclone separators

Local linear stability analysis is applied to the flow inside a cyclone separator to investigate the unsteady precession of the vortex core. The results of the stability analysis are compared with experimental measurements of the vortex oscillations using high-speed photography with particle seeding and hot-wire anemometry. The experiments reveal distinct spatial variation in the oscillation behaviour within the cyclone. The unsteady motion is focused at each end of the device, at both the narrow cone tip and just below the exhaust duct at the top of the cone, which is known as a vortex finder. The local stability analysis shows that an absolute instability is present throughout the flow for some non-zero azimuthal wavenumbers. The unsteady flow is observed to be driven by coupling between the shear layer and inertial waves confined within the vortex core. Comparison of the stability analysis with experiments shows the same frequency and mode shape behaviour and suggests that the local analysis accurately predicts the unstable modes of the system. The precessing vortex core is responsible for a narrow-band acoustic noise. Comparisons are also drawn with acoustic measurements made on cyclones in which the system is defined by key non-dimensional parameters, such as the swirl number and outlet diameter ratio. The results in this study demonstrate the applicability of local stability analysis to a complex swirling system and yield credible details about the underlying mechanisms of the unstable flow inside the cyclone.Dyson Lt

Closed loop identification of systems within cascade connected control strategies

A brief review of the background to the Phase-Locked Loop (PLL) method of non-parametric system identification is presented. This introduces the idea of performing the non-parametric identification for any point on the frequency response curve of a process. The PLL identification method is then extended to perform the non-parametric identification of the component parts of a cascade connected control system. An advantage of the method is that the non-parametric identification is performed with the cascade control system connected in closed loop. An example demonstrating the identification method is given

The relationship between the insulin-like growth factor-1 axis, weight loss, an inflammation-based score and survival in patients with inoperable non-small cell lung cancer

&lt;b&gt;Background &#38; aims:&lt;/b&gt; The involvement of a systemic inflammatory response, as evidenced by the Glasgow Prognostic Score (GPS), is associated with weight loss and poor outcome in patients with non-small cell lung cancer. There is good evidence that nutritional and functional decline in patients with advanced malignant disease is associated with catabolic changes in metabolism. However, defects in anabolism may also contribute towards nutritional decline in patients with cancer. The aim of the present study was to examine the relationship between IGF-1 and IGFBP-3, performance status, mGPS and survival in patients with inoperable NSCLC. &lt;b&gt;Methods:&lt;/b&gt; 56 patients with inoperable NSCLC were studied. The plasma concentrations of IGF-1, IGFBP-3 and leptin were measured using ELISA and RIA. &lt;b&gt;Results:&lt;/b&gt; The patients were predominantly male (61%), over 60 years old (80%), with advanced (stage III or IV) disease (98%), with a BMI≥20 (84%), an ECOG-ps of 0 or 1 (79%), a haemoglobin (59%) and white cell count (79%) in the reference range. On follow-up 43 patients died of their cancer. On univariate analysis, BMI (p&#60;0.05), Stage (p&#60;0.05), ECOG-ps (p&#60;0.05), haemoglobin (p&#60;0.05), white cell count (p&#60;0.05) and mGPS (p&#60;0.05) were associated with cancer specific survival. There was no association between age, sex, treatment, IGF-1, IGFBP-3, IGF-1:IGFBP-3 ratio, or leptin and cancer specific survival. With an increasing mGPS concentrations of haemoglobin (p&#60;0.005) and IGFBP-3 (p&#60;0.05) decreased. mGPS was not associated with either IGF-1(p&#62;0.20), or leptin (p&#62;0.20). &lt;b&gt;Conclusions:&lt;/b&gt; In summary, the results of this study suggest that anabolism (IGF-1 axis) does not play a significant role in the relationship between nutritional and functional decline, systemic inflammation and poor survival in patients with inoperable NSCLC

Direct measurement of interatomic force gradients using an ultra-low-amplitude atomic force microscope

Interatomic force gradients between a W tip and a 7 × 7 reconstructed Si(111) surface were measured using an off-resonance, ultra-low-amplitude atomic force microscope (AFM) technique. The amplitudes used were less than 1 Å (peak-to-peak), which allowed direct measurement of the interaction force gradients as a function of separation. The force gradient curves are shown to consist of an attractive van der Waals part and short-range attractive and repulsive interactions. The van der Waals background can be subtracted, leaving a short-range interaction with an energy parameter of 1.9-3.4 eV and an interaction length-scale of 0.54-1.26 Å, characteristic of a single atomic bond. This correlates well with our observation of single-atom resolved force gradient images. In general, the interaction is reversible up to the zero intercept of the force gradient (inflection point of the energy). Beyond this point hysteresis tends to be observed and the onset of inelastic deformation can be clearly discerned. An analysis of the atomic scale contact gives reasonable values for the interfacial energy, yield strength, and the energy per atom needed to initiate plastic deformation

The effect of increasing physical activity and/or omega-3 supplementation on fatigue in inflammatory bowel disease

Objective: Fatigue is frequently reported by patients with inflammatory bowel disease (IBD), irrespective of disease activity; however, evidence regarding fatigue management is limited. This study tested the effect of individualised advice to increase physical activity and/or omega-3 fatty acids supplementation, on IBD-related fatigue. Methods: A pilot study in patients with inactive IBD, utilising a randomised controlled 2x2 factorial design (four groups) compared baseline and post-intervention fatigque scores. Study interventions: individualised exercise advice (15 minute consultation) and/or supplementation (omega-3 fatty acids, 2970mg/day) for 12 weeks. Control interventions: general health discussion and/or placebo supplement. All patients received follow-up support. Primary outcome was fatigue measured by Functional Assessment of Chronic Illness Therapy-Fatigue (FACIT-F) scale score; secondary outcomes included change in Inflammatory Bowel Disease-Fatigue (IBD-F) scale score. Results: From n=656 screened patients, n=74 who met the selection criteria were randomised, n=60 commenced, and n=52 completed the study. Fatigue as tThe primary outcome fatigque, measured with FACIT-F, showed slight worsening in the omega-3 supplementation group (95%CI:-8.6-(-0.7);p=0.02), and no change in the exercise advice group (p=0.38). Reduced fatigue, measured by IBD-F score, was identified in the exercise group (95%CI:-3.8-(-0.2);p=0.03). One treatment-related adverse event (musculoskeletal pain) was reported with exercise. Conclusions: Advice to increase physical activity and omega-3 supplementation, singly or in combination, were shown to be safe and generally well-tolerated. There was no evidence of exercise-related adverse effects on gut-related symptoms, and some evidence of improvement in fatigue. The slight worsening of fatigue with omega-3 supplementation is unexplained. Regular moderate to -vigorous exercise may be a self-management option in IBD-related fatigue