Performance assessment and diagnosis of refinery control loops

This paper discusses the application of control loop performance assessment (Desborough and Harris, 1992) in a refinery setting. In a large process it is not feasible to tailor the parameters of the algorithm to every individual control loop. A procedure is illustrated for selecting default values which make it possible to implement the technology on a refinery-wide scale. For instance, it is shown that the prediction horizon perameter in the CLPA algorithm can be set so that the analysis is sensitive to the persistent signals that cause loss of performance. Default values are suggested for refinery applications.A frequent cause of loss of performance in a control loop is a persistent oscillation due to a valve nonlinearity or a tuning fault. The paper presents an operational signatures in the form of an estimate of the closed loop impulse response that suggest the causes of such oscillations

Fatigue behavior of flexhoses and bellows due to flow-induced vibrations

The analysis and results developed in a fresh approach to calculate flow induced vibration response of a flexible flow passage are summarized. The vibration results are further examined in the frequency domain to obtain dominant frequency information. A cumulative damage analysis due to cyclic strains is performed to obtain the number of cycles to failure for a metallic bellows of particular specifications under a variety of operational conditions. Sample plots of time and frequency domain responses are included. The complex listing of a computer program is provided. The program successively executes each of the analyses needed to calculate the vibration response, the frequency response, the cyclic strains and the number of cycles to failure. The program prompts the user for necessary input information. Sample data from the program is provided. The fatigue life results obtained by the computer model lie within an acceptable range of previously measured available data

A change in the NICE guidelines on antibiotic prophylaxis

Since 2008, NICE clinical guidelines have stated: ‘Antibiotic prophylaxis against infective endocarditis is not recommended for people undergoing dental procedures’. This put UK guidance at odds with guidance in the rest of the world, where antibiotic prophylaxis is recommended for patients at high-risk of infective endocarditis undergoing invasive dental procedures. Many dentists also felt this wording prohibited the use of antibiotic prophylaxis, regardless of the wishes of the patient or their personal risk of infective endocarditis and made it difficult for them to use their clinical judgment to deliver individualised care in the best interests of their patients. NICE have now changed this guidance to ‘Antibiotic prophylaxis against infective endocarditis is not recommended routinely for people undergoing dental procedures.’ This article examines the implications of this small but important change

<i>Schistosoma mansoni</i> cercariae experience influx of macromolecules during skin penetration

We have observed that when cercariae penetrate the skin of mice, there is influx into their tissues of Lucifer Yellow and certain labelled molecules of up to 20 kDa molecular weight. This observation was made using a variety of fluorescent membrane-impermeant compounds injected into the skin before the application of cercariae. This unexpected phenomenon was investigated further by transforming cercariae in vitro in the presence of the membrane-impermeant compounds and examining the distribution by microscopy. In schistosomula derived from this procedure, the nephridiopore and surface membrane were labelled while the pre- and post-acetabular glands were not labelled. The region associated with the oesophagus within the pharyngeal muscle clearly contained the fluorescent molecules, as did the region adjacent to the excretory tubules and the germinal mass. We used cercariae stained with carmine to aid identification of regions labelled with Lucifer Yellow. Although the mechanism of this influx is unclear, the observation is significant. From it, we can suggest an hypothesis that, during skin penetration, exposure of internal tissues of the parasite to external macromolecules represents a novel host-parasite interfac

The use of information in online healthcare provider choice

In order to evaluate and facilitate the provision of health information online, we must first understand how it is perceived by those who use it. Two important considerations in research on patients’ information use in online healthcare provider choice are the need for a conceptual framework for studying information types and methods for studying information use. Therefore, our first contribution lies in using Donabedian's structure-process-outcome model of healthcare quality to identify specific patterns of preference and information use in online healthcare provider choice, and differences in information use between two healthcare provider types. Our second contribution lies in identifying differences in results between data collection methods (importance rating/selection, concurrent self-report of online information use and retrospective information use) in relation to choice tasks. In a mixed-methods design, provider type (primary and secondary care) was systematically varied during participants’ use of the infomediary NHS Choices. Participants preferred process topics over structure topics, in contrast with the results of concurrent and retrospective self-report. We conclude that the differences in results between the types of data collection method reflect underlying differences in choice task. Future research should address the use of novel infomediary user-interfaces, and infomediaries in relation to the use of other information sources and (e-)health literacy

A Test System Model for Stability Studies of UK Power Grid

The paper presents a test system model to study the effect of variable wind power output on the stability of future power systems. The test system is built upon a future UK transmission system model and it contains different types of generators, HVDC transmission lines, and interconnections. A poorly damped inter-area mode is present in the test system that closely resembles the Scotland-England inter-area mode existing in the UK transmission system. The study system will help to analyze the impact of increased variability in power system operating conditions on the oscillatory mode. © 2013 IEEE

High yield fusion in a Staged Z-pinch

We simulate fusion in a Z-pinch; where the load is a xenon-plasma liner imploding onto a deuterium-tritium plasma target and the driver is a 2 MJ, 17 MA, 95 ns risetime pulser. The implosion system is modeled using the dynamic, 2-1/2 D, radiation-MHD code, MACH2. During implosion a shock forms in the Xe liner, transporting current and energy radially inward. After collision with the DT, a secondary shock forms pre-heating the DT to several hundred eV. Adiabatic compression leads subsequently to a fusion burn, as the target is surrounded by a flux-compressed, intense, azimuthal-magnetic field. The intense-magnetic field confines fusion $\alpha$-particles, providing an additional source of ion heating that leads to target ignition. The target remains stable up to the time of ignition. Predictions are for a neutron yield of $3.0\times 10^{19}$ and a thermonuclear energy of 84 MJ, that is, 42 times greater than the initial, capacitor-stored energy

Kerrville Ponding Dam, Guadalupe River, Texas

Kerrville Ponding Dam is a relatively small channel dam in the Guadalupe River in Kerrville, Texas. The dam is 22 feet (6.7M) high and 600 feet (183M) long and provides a water supply for the City of Kerrville. The dam was constructed during 1979-1980. Seepage problems in the abutments were observed during the initial filling of the reservoir. Some minor corrections to the problems were made at that time. In June 1981, after a moderate flood flow passed over the dam, additional seepage problems occurred. The downstream slope protection was displaced to the extent that cracks appeared in the concrete. This damage lead to a more significant amount of repair. On December 31, 1984 the dam was overtopped by a flood to a depth of 10.5 feet (3.2M) above the spillway elevation. The dam suffered severe damage including loss of a portion of the concrete cap and significant erosion of the clay core over approximately one-third of the length of the dam, and seepage related damage at both the abutment areas. Figure 1 shows the conditions of the structure in January 1985. The dam suffered a “Type 1 Accident” as defined according to International Commission on Large Dams (ICOLD)