Threshold computation for fault detection in linear discrete‐time Markov jump systems

This paper proposes a threshold computation scheme for an observer‐based fault detection (FD) in linear discrete‐time Markovian jump systems. An observer‐based FD scheme typically consists of two stages known as residual generation and residual evaluation. Even information of faults is contained inside a residual signal, a decision of faults occurrence is consequently made by a residual evaluation stage, which consists of residual evaluation function and threshold setting. For this reason, a successful FD strongly depends on a threshold setting for a given residual evaluation function. In this paper, Kalman filter (KF) is used as a residual generator. Based on an accessibility of Markov chain to KF, two types of residual generations are considered, namely mode‐dependent and mode‐independent residual generation. After that threshold is computed in a residual evaluation stage such that a maximum fault detection rate is achieved, for a given false alarm rate. Without any knowledge of a probability density function of residual signal before and after fault occurrence, a threshold is computed by using an estimation of residual evaluation function variance in a fault‐free case. Finally, a detection performance is demonstrated by a numerical example. Copyright © 2013 John Wiley & Sons, Ltd.     

Handling the Temperature Effect in Vibration Monitoring: Two Subspace-Based Analytical Approaches

The dynamics of most civil engineering structures is affected by the ambient temperature. This raises the issue of discriminating changes in modal parameters due to damage from those due to such effects. A statistical parametric damage detection algorithm based on a null space residual associated with output-only subspace identification and a χ2 test built on that residual has been designed by some of the writers. The purpose of this paper is to propose two extensions of this detection method which account for the temperature effect. The first extension uses a thermal model for deriving a temperature-adjusted null space. The second extension exploits the thermal model together with a statistical nuisance rejection technique. Both methods are illustrated on a laboratory test case within a climatic chamber.     

The taxation of UK oil and gas production: Why the windfalls got away

Starting with evidence that United Kingdom Continental Shelf oil and gas companies have benefitted very disproportionately from the recent period of extraordinarily high oil prices, this paper traces the history of this weakness in the UK’s petroleum fiscal regime. Evidence is provided that the progressive relaxations in the UK’s petroleum fiscal regime in 1983, 1987–1988 and 1993 were: largely unnecessary to stimulate the development of new, smaller, ‘marginal’ fields; misguided in their assumption that such fields were more costly to develop than earlier counterparts or larger contemporary fields; and impotent compared with the effects of oil price movements. The paper concludes with a conceptualisation which illuminates why these failures of policy were not just random: they emerged from the UK’s ‘non-proprietorial’ stance with respect to the country’s oil and gas resources, a stance which assumes responsibility for oil company profitability and vainly tries to counter market forces at the expense of government revenues.     

Implementation of a learning Kohonen neuron based on a newmultilevel storage technique

A compact implementation of a fully parallel Kohonen network with learning capabilities is described. Implementation issues concerning general neural networks are briefly explored, and an original mixed analog and digital technique for storing discrete voltages on a capacitor is presented. The limitations are discussed, and measurements on the storage dynamics are reported, showing that 8 b of resolution can be achieved. This technique is applied to the realization of a neuron dedicated to Kohonen maps. This neuron has been implemented in a standard 2-μm CMOS technology, and the synaptic functions are very dense. The implementation uses a standard 8-b integer arithmetic. Efficient and consistent encoding of the information, dynamic storage, and the adaptation of the synaptic weights and the synaptic multipliers use simple circuitry, thus leading to a low number of transistors     

Analysis of gross error rates in operation of commercial nuclear power stations

Experience in operation of US commercial nuclear power plants is reviewed over a 25-moth period. The reports accumulated in that period on events of human error and component failure are examined to evaluate gross operator error rates. The impact of such errors on plant operation and safety is examined through the use of proper taxonomies of error, tasks and failures. Four categories of human errors are considered; namely, operator, maintenance, installation and administrative. The computed error rates are used to examine appropriate operator models for evaluation of operator reliability. Human error rates are found to be significant to a varying degree in both BWR and PWR. This emphasizes the import of considering human factors in safety and reliability analysis of nuclear systems. The results also indicate that human errors, and especially operator errors, do indeed follow the exponential reliability model.     

Effect of ethylene carbonate on properties of PVP-CsAlO2-LiClO4 solid polymer electrolytes

ABSTRACT

Solid polymer electrolytes (SPEs) have been widely studied due to its extensive applications in high energy rechargeable batteries, supercapacitors, fuel cells, photoelectrochemical and electrochromic displays. Herein, SPEs based on polyvinyl pyrrolidone (PVP) doped with cesium aluminate (CsAlO₂) nanoparticles (NPs), lithium perchlorate (LiClO₄) as an electrolyte and varying amounts viz., 2, 4, 6 and 8 wt.% of ethylene carbonate (EC) as plasticizer have been fabricated by solution intercalation technique. The structural features of PVP-CsAlO₂-LiClO₄-EC SPEs have been studied by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. The morphology of PVP-CsAlO₂-LiClO₄-EC SPEs has been examined by scanning electron microscopy (SEM). The thermal properties of the SPEs were characterized by the thermogravimetric analyzer (TGA) and differential scanning calorimeter (DSC) techniques. The TGA and DSC results revealed that a significant reduction in thermal stability and glass transition temperature (T_g) of PVP with an increase in EC content in SPE films. The optoelectrical properties of PVP-CsAlO₂-LiClO₄-EC SPE films have been evaluated using UV–visible spectroscopy. The band gap energy (E_g) was found to decrease with an increase in EC content, exhibiting a minimum of 4.23 eV for PVP-8 wt.% CsAlO₂-15 wt.% LiClO₄-8 wt.% EC. This could be ascribed to the formation of localized states and increased degree of disorder in the PVP-CsAlO₂-LiClO₄ SPE films. The integrated plasticizers increase the values of refractive index (RI), optical conductivity, and dielectric constants of PVP-CsAlO₂-LiClO₄ SPE films. The AC conductivity of the SPEs has been evaluated at room temperature using digital LCR meter in the frequency range 100 Hz – 5 MHz. The conductivity strongly depends on CsAlO₂ NPs and EC plasticizer content in SPEs.     

The role of Cr3+ ions substitution on structural,magnetic and dielectric modulus of manganese zinc nanoferrites

Polycrystalline manganese-zinc nanoferrites doped with Cr are produced by citrate–nitrate combustion method. Comprehensive analysis for the, Mn_0.8Zn_0.2Cr_xFe_2?xO₄; (0 ≤ x ≤ 0.1, step 0.02) nanoferrites was also performed using XRD, FTIR, HRTEM, magnetic and dielectric measurements. The structural, magnetic, and dielectric properties have been explained on the base of the entire cation distribution when Cr ions are added on the expense of Fe. VSM plots show narrow hysteresis loops, which infer that the investigated nanoferrites behave as super-paramagnetic materials. Cole-Cole plots proved that the conductivity is basically due to the grain boundary at low frequencies, and the bulk grains at high frequencies. The composition dependence of ε′, tanδ, and σ_ac manifests that the nanoferrite with x=0.04 is the optimized content. Summarizing the results, soft nanoferrite Mn_0.8Zn_0.2Cr_0.04Fe_1.96O₄ displayed distinctive features, which elect it for multilateral applications; especially for magnetic recording and computer memories.     

Vancomycin-induced acute interstitial nephritis

OBJECTIVE: To report a case of acute interstitial nephritis (AIN) related to administration of vancomycin for the treatment of Staphylococcus aureus sternal wound infection, osteomyelitis, and infective endocarditis. CASE SUMMARY: Reports in the literature regarding vancomycin-induced AIN are scarce. We describe the fifth known case of AIN, in a 64-year-old white man who developed fever, maculopapular rash, acute renal failure, eosinophilia, and eosinophiluria after approximately 1 month of vancomycin treatment. The results of the renal biopsy were consistent with an allergic drug reaction. Four months after his initial episode of AIN, the patient was rechallenged with vancomycin for the treatment of S. aureus septic arthritis. One day after initiation of vancomycin, serum eosinophils started to rise, his urine tested positive for eosinophils, but his serum creatinine remained stable. CONCLUSIONS: Our case report and others from the literature suggest vancomycin causes allergic AIN. Clinicians should be aware of this adverse effect in an era of increasing use of vancomycin for treatment of resistant gram-positive organisms.     

Operational data analysis of MSF desalination plants. A case study of Jeddah I

Monthly operation and maintenance reports of the oldest large MSF plant in Saudi Arabia, Jeddah I, are analyzed to extract information or generic operation and design problems and to seek means for the mitigation of such problems. The accumulated records are quantified to provide estimates of equipment failure rates. Three systems are found to be the major contributors to plant outage namely, make-up water, brine recycle and sea water intake systems. Root causes of the plant unscheduled shutdowns or reductions in water production are assessed to examine generic reasons for deviations of MSF systems from standard expected performance.