Present status of the theory of electron beam instabilities in storage rings

The coherent beam instabilities in circular accelerators are explained in terms of simple concepts of feedback devices. The notion of coupling impedance is introduced and interpreted by means of engineering circuit analysis. The condition of stability for the coherent motion is given in terms of the coupling impedance and accelerator and beam parameters.     

一个在中国工作的欧洲建筑师

总之,在中国的建筑执业经历对我来说,既是刺激的又是失望的。刺激是因为我们在一次次将新的中国文化与住宅综合体的城市设计相结合的尝试中起了重要作用;失望是我们看来,中国效尤了西方失败的先例,坚持认为这种信念是次要的,虽然城市文化在千百年来代表了中国最高的、最悠久的传统。为了与西方消费主义的新殖民主义对抗,我们需要借助体现传统中国文明的现代建筑。只有借助不同伟大传统之间的对话,才能产生新的优秀的城市建筑。     

Characterization of solid embeddable reference electrodes for corrosion monitoring in reinforced concrete structures

Metal-metal oxide (MMO), graphite and laboratory-made Ag/AgCl electrodes were electrochemically characterized to be used as reference electrodes embedded in concrete structures. Electrodes were studied in both, aqueous solutions of pH ranging from 7 to 13.5 and embedded into cement mortars; and the electrochemical studies were carried out in the absence and presence of chloride ions. Potential evolution, polarization behaviour, galvanostatic pulse response and impedance characteristics of the electrodes were carried out in aqueous solutions. Besides, the electrochemical stability of the electrodes embedded in mortar was studied for an exposure period of 2 years. It was found that the MMO pseudo-reference electrode is pH-sensitive, the graphite pseudo-reference electrode is oxygen sensitive and the Ag/AgCl pseudo-reference electrode is chloride sensitive. In spite of the fact that any of them can be used to determine the corrosion rates of rebars because they do not depend on the absolute potential and/or the long-term stability of the reference electrode when using traditional electrochemical techniques, long-term drifts in the electrode potentials may lead to misinterpretations of the rebar state. In this context graphite electrodes are recommended because they provide conservative results regarding the active/passive state of the rebars.     

Different design scenarios related to an open loop groundwater heat pump in a large building: Impact on subsurface and primary energy consumption

A multidisciplinary methodology is proposed for analyzing opportunities to use existing boreholes and an open-loop groundwater heat pump to provide summer cooling needs for large university buildings in Turin (NW Italy). The approach starts from a model of the buildings to determine the time profile of the cooling load. This curve is then coupled with a model of the off-design behaviour of the heat pump, which allows calculation of its energy performance (coefficient of performance, electricity consumption, etc.) as well as profiles of water discharge to the aquifer in terms of mass flow rate and temperature.Covering the peak energy needs of the buildings requires a variable amount of groundwater during the day. This could be provided varying the withdrawals from the aquifer but, as possible alternatives, two storage system solutions are examined: (1) chilled water storage and (2) groundwater storage. Simulations show that in both cases the use of storage systems produces environmental advantages, as the extent of the thermal plume reduces significantly. Moreover, chilled water storage presents a benefit in terms of reduced total primary energy consumption. The additional costs incurred by storage systems could necessitate public funding as well as system optimization.     

A comparison of two Crame/spl acute/r-Rao bounds for nonlinear filtering with P/sub d/<1

The paper presents a comparative study of two recently reported Crame/spl acute/r-Rao lower bounds (CRLBs) for nonlinear filtering, both applicable when the probability of detection is less than unity. The first bound is the information reduction factor CRLB; the second is the enumeration method CRLB. The enumeration method is accurate but computationally expensive. We prove in the paper that the information reduction factor bound is overoptimistic, being always less than the enumeration CRLB. The theory is illustrated by two target tracking applications: ballistic object tracking and bearings-only tracking. The simulations studies confirm the theory and reveal that the information reduction factor CRLB rapidly approaches the enumeration CRLB as the scan number increases.     

Wheel-flat diagnostic tool via wavelet transform

The detection and acknowledgement of signatures, for condition monitoring and fault diagnostics by wavelet transform, deserves increased attention, due to its property of variable time–frequency resolution, which overcomes limitations of classical time–frequency approaches.In the paper, a diagnostic tool is presented, based on the wavelet transform, able to detect and to quantify the wheel-flat defect of a test train at different speeds and to measure the train speed with proper accuracy. The designed diagnostic tool minimises the hardware requirements, since only one accelerometer is needed, and provides results in real time.The results, achieved by an exhaustive experimental campaign, permit to validate the effectiveness of the diagnostic tool and to demonstrate the advantages of wavelet-based detection of signatures.