Equation-of-state calculations of chemical reaction equilibrium in nonideal systems

In order to calculate accurately chemical-reaction equilibria of a system over a wide range of temperatures and pressures, one must account for the non-idealities of the system. In this work, a method is developed to predict accurately chemical-reaction equilibria and phase equilibria of a system using an equation of state to account for the nonidealities. The general formalism for a multicomponent system with multiple reactions is presented. Three widely used cubic equations of state are used to calculate the physical properties of the species. The proposed method is applied to the water-gas shift reaction, to the decomposition of methylcyclohexane, and to the reaction of carbon monoxide with hydrogen sulfide over a wide range of temperatures and pressures.     

An approach to the dynamic modelling of manufacturing systems

Because of their complexity manufacturing systems are difficult to model. However, modelling is very often required in order to study the behaviour of the system. In this paper an approach is described, where an analogy is drawn between the behaviour of a manufacturing and a mechanical system. Manufacturing systems have to respond to a dynamic demand, namely, a demand that changes over time. Flexibility of a manufacturing system can be thought of as the ability and the rapidness with which the system responds to the dynamic demand. This resembles the behaviour of a mechanical system under the excitation of a force that changes over time. The paper attempts to establish a modelling method based on this analogy and uses this method in the study of a real industrial system.     

A digital hardware correlation system for fast ultrasonic data acquisition in peak power limited applications

The theoretical and experimental evaluation of a digital hardware correlation system for low-power ultrasonic applications is presented. The system, which incorporates dual Golay code matched filtering, is capable of 20-MHz processing rates with a signal-to-noise-ratio enhancement (SNRE) of 23 dB over a conventional pulse-echo system operating at the same peak power levels. The effects of digitization have been investigated, and a TTL (transistor transistor logic)-based hardware correlator has been developed. For many applications, low-voltage driving followed by differential detection is sufficient, permitting the system to be used in a number of power-limited environments. Sample tests conducted on three different transducers have demonstrated that the system is operational over a wide variety of probe configurations.     

Plasma Modes of Low-Dimensional Electron Systems over a Helium Film

The dispersion laws for collective modes in low-dimensional electron systems over a superfluid helium film covering a metal substrate are evaluated within the many-body multisubband formalism. In contrast to the electron system over bulk helium, the longitudinal mode is acoustic-like. The transversal mode is optical-like with a gap given by the one-electron spectroscopic intersubband frequency. We found that the effect of depolarization shift is supressed in the quasi-two-dimensional system.     

Isochronous dynamical systems

This is a terse review of recent results on isochronous dynamical systems, namely systems of (first-order, generally nonlinear) ordinary differential equations (ODEs) featuring an open set of initial data (which might coincide with the entire set of all initial data), from which emerge solutions all of which are completely periodic (i.e. periodic in all their components) with a fixed period (independent of the initial data, provided they are within the isochrony region). A leitmotif of this presentation is that 'isochronous systems are not rare'. Indeed, it is shown how any (autonomous) dynamical system can be modified or extended so that the new (also autonomous) system thereby obtained is isochronous with an arbitrarily assigned period T, while its dynamics, over time intervals much shorter than the period T, mimics closely that of the original system, or even, over an arbitrarily large fraction of its period T, coincides exactly with that of the original system. It is pointed out that this fact raises the issue of developing criteria providing, for a dynamical system, some kind of measure associated with a finite time scale of the complexity of its behaviour (while the current, standard definitions of integrable versus chaotic dynamical systems are related to the behaviour of a system over infinite time).     

被动型氢原子钟吸气剂泵的应用研究

描述了上海天文台在2008年为提高被动型氢原子钟真空系统的可靠性所研制的由非蒸散型吸气剂泵和小离子泵组成的复合泵的实验过程,吸气剂泵在室温下吸收2.1MPa.l的H2气后仍可达到3.2×10-5Pa的真空度,2l/s的离子泵电流工作在0.30μA,证明了复合泵可以维持氢钟13年以上的正常工作。经过再激活固定了激活工艺,吸气剂最终吸氢6.0 MPa.l仍没有饱和,证明了吸气剂的强大吸氢能力。至今复合泵已成功应用在4台被动型氢钟上。     

Measurement-device-independent quantum key distribution: from idea towards application

We assess the overall performance of our quantum key distribution (QKD) system implementing the measurement-device-independent (MDI) protocol using components with varying capabilities such as different single-photon detectors and qubit preparation hardware. We experimentally show that superconducting nanowire single-photon detectors allow QKD over a channel featuring 60 dB loss, and QKD with more than 600 bits of secret key per second (not considering finite key effects) over a 16 dB loss channel. This corresponds to 300 and 80 km of standard telecommunication fiber, respectively. We also demonstrate that the integration of our QKD system into FPGA-based hardware (instead of state-of-the-art arbitrary waveform generators) does not impact on its performance. Our investigation allows us to acquire an improved understanding of the trade-offs between complexity, cost and system performance, which is required for future customization of MDI-QKD. Given that our system can be operated outside the laboratory over deployed fiber, we conclude that MDI-QKD is a promising approach to information-theoretic secure key distribution.     

Feed-forward linearisation technique for impulse radar ultra-wideband over fibre

The authors present the linearisation of impulse radar ultra-wideband (IR-UWB) transmission system over fibre. The radio frequency signal of IR-UWB is transmitted over 50 km of the single mode fibre (SMF) using external Mach Zehnder modulator (MZM), amplified, linearised and detected by photodetector receiver. For improving the linearity and suppressing the four-wave mixing (FWM) caused by semiconductor optical amplifier (SOA) and 50 km SMF, the system uses feed-forward technique. Link performance was evaluated for two IR-UWB signals to suppress the FWM. The theoretical simulation results demonstrate a distortion cancellation that is produced by SOA of better than 25 dB over 1550 nm single mode optical fibre cable. In addition, the characteristic transmission of UWB pulse radio through 50 km single mode radio over fibre (RoF) system, such as BER measurements to evaluate the performance of the UWB with respect to different laser power output level, is investigated. This technique has been used to successfully transmit indirectly modulated data using laser diode at 10 GB/s light-wave transmission system.     

RESILIENCE IN GERMAN TECHNOLOGY POLICY: INNOVATION THROUGH INSTITUTIONAL SYMBIOTIC TENSION

This paper reports on a detailed institutional study of the German technology transfer system using material from a survey of practitioners and observations of the system over a one-year period. The purpose of this research was to understand the dynamic within the German system that, despite heavy criticism over the past 10-15 years, has proved remarkably resilient, competitive and capable of change.2 It is argued that the dynamism lies within the funding and the institutional structures of the system which allow competition to exist alongside collaboration and networking, thus incorporating the best of a ''market based'' technology transfer system with the advantages of regulation and co-ordination. These inherent, but contradictory pressures are termed ''symbiotic tension'' - it is argued that this is key to understanding the resilience of the system.     

Competition and Collaboration in German Technology Transfer

This paper reports on a detailed institutional study of theGerman technology transfer system using material from a surveyof practitioners and observations of the system over a 2 yearperiod. The purpose of this research was to understand the dynamicswithin the system which, despite heavy criticism over the past10–15 years, has proved remarkably resilient, competitiveand capable of change. It is argued that the dynamism lies withinthe funding and the institutional structures of the system whichallow competition to exist alongside collaboration and networking,thus incorporating the best of a ‘market-based’technology transfer system with the advantages of regulationand coordination. These inherent, but contradictory, pressuresare termed ‘symbiotic tension’: it is argued thatthis is key to understanding the resilience of the system.     

Spot diffusing angle diversity MC-CDMA optical wireless system

Multi-carrier code division multiple access (MC-CDMA) combines some of the desirable features of orthogonal frequency-division multiplexing (OFDM) and CDMA in that it offers multi-user capabilities at a reduced channel rate. The authors report the analysis of a MC-CDMA system over the bandlimited optical wireless (OW) channel. Furthermore, the authors evaluate the performance when a line strip multibeam system (LSMS) is used in conjunction with an angle diversity receiver in the OW MC-CDMA system. The results indicate that at a bit error rate of 10^-4 a 7 and 10 dB signal-to-noise ratio (SNR) improvements are obtained through the use of MC-CDMA in a 4-user system when compared to a single-user OW on?off keying system and a 4-user OW CDMA system, respectively. This improvement is obtained by enabling multi-user communication. The performance degrades gradually with increase in the number of users. The use of LSMS and angle diversity offers a more uniform SNR over a given indoor geometry compared to a conventional diffuse OW system (CDS). Results are reported for an angle diversity LSMS MC-CDMA system and are compared to the CDS MC-CDMA system.     

Reliability measures for dynamic multistate nonrepairable systems and their applications to system performance evaluation

The main focus of this paper is on the development of reliability measures for dynamic multistate systems which have M + 1 discrete states of working efficiency. In traditional reliability models for binary systems, one measure that is commonly used is the probability of success at some time t. For multistate systems, we can extend this definition and define the reliability of a multistate system to be the probability that the system still functions at some intermediate state k, 0 ≤ k ≤ M or higher at time t. To develop the reliability measures for multistate systems, we assume that the degradation of the multistate systems follows a Markov process and that the system can directly degrade into any lower state. The other focus of this paper is on the evaluation of multistate systems for system design. For traditional binary reliability evaluation, the better system at time t is the one that has a greater value of the area created by the integration over time of the expected value of the state of the system from time 0 to time t. This integration is also related to a customer's experience with the system over the period under consideration. For binary systems, the expected value of the state of the system at any time is equal to the probability of success at the time under consideration. Similarly, one way to evaluate multistate systems is to calculate some accumulated value which is the integration of the expected value of the state of the system from time 0 to time t. Another way to evaluate multistate systems is to estimate how much benefit the customer can receive through using the system. To obtain this measure, we include a customer's utility function over time, and develop a model that can calculate a customer's expected total utility for their experience with the system. A better system should give the customer a high total utility over time and then these measures can be used in system design and evaluation.     

Real-time measurement and control of an industrial system over a standard network: implementation of a prototype for educational purposes

This paper deals with a real-time distributed architecture based on the reservation protocol (RSVP). After some discussion of the RSVP, the prototype for real-time measurement and control of an industrial system over a standard computer network for educational purposes is described. The performance of the RSVP-based system is then analyzed and compared with an ordinary RSVP-less system.     

A Digital Integrated Circuit Radiosonde System

An integrated circuit radiosonde system was constructed and tested, with results indicating an improvement over the existing methods. This work deals with establishing the parameters. circuit design, construction, and testing of such a system. Sampling, pulse width modulation, time multiplexing, and pulse width to digital conversion are discussed. Further improvements for a follow-on system are delineated.     

Design analysis of a solid nitrogen cooled “permanent” high-temperature superconducting magnet system

Potential performance advantages of a solid nitrogen cooled “permanent” high-temperature superconducting (SN2/HTS) magnet system over a liquid helium cooled low-temperature superconducting (LHe/LTS) system are explored. The SN2/HTS system design includes a second solid heat capacitor that cools a radiation shield. Recooling of the heat capacitors is performed with a demountable cryocooler. The SN2/HTS system offers both enhanced stability and improved portability over a LHe/LTS system.Design codes are constructed to compare the SN2/HTS system design with a LHe/LTS design for a general permanent superconducting magnet system employing a room temperature bore. The codes predict the system volume and mass that should be expected for a given set of design requirements, i.e. field strength and bore size, and a given set of conductor properties. The results indicate that present HTS conductor critical current and index are not yet sufficient for producing SN2/HTS systems of a size that is comparable with that expected for a LHe/LTS system; however, the conductor properties of Bi2223/Ag have been consistently improving, and new HTS conductors are expected to be developed in the near future. The codes are used to determine the minimum Bi2223/Ag conductor performance required for a SN2/HTS system to be competitive with a LHe/LTS system.     

Synthesis of the web-based CAD viewer for interference verification of injection moulds

This paper describes the development of a web-based interference examination system in mould design processes. Although several commercial computer-aided design (CAD) systems offer interference inspection functions, those systems are very expensive and inadequate to perform collaborative works over the Internet. In this paper an efficient and precise hybrid interference examination algorithm applicable to multilevel assemblies is studied for injection mould design processes. In order to design a collaborative system over the distributed environment, lightweight CAD files produced from the optimally transformed CAD data through ACIS kernel and InterOp are applied to develop a web-based interference verification system. Collaborators related to the development of a new product can verify the interference over the Internet without commercial CAD systems. The system reduces production cost, errors and lead-time to the market. The validity of the developed system is confirmed through case studies.     

A probability model of system downtime with implications for optimal warranty design

Traditional approaches toward modeling the availability of a system often do not formally take into account uncertainty over the parameter values of the model. Such models are then frequently criticized because the observed reliability of a system does not match that predicted by the model. This paper extends a recently published segregated failures model so that, rather than providing a single figure for the availability of a system, uncertainty over model parameter values is incorporated and a predictive probability distribution is given. This predictive distribution is generated in a practical way by displaying the uncertainties and dependencies of the parameters of the model through a Bayesian network (BN). Permitting uncertainty in the reliability model then allows the user to determine whether the predicted reliability was incorrect due to inherent variability in the system under study, or due to the use of an inappropriate model. Furthermore, it is demonstrated how the predictive distribution can be used when reliability predictions are employed within a formal decision‐theoretic framework. Use of the model is illustrated with the example of a high‐availability computer system with multiple recovery procedures. An BN is produced to display the relations between parameters of the model in this case and to generate a predictive probability distribution of the system's availability. This predictive distribution is then used to make two decisions under uncertainty concerning the offered warranty policies on the system: a qualitative decision and an optimization over a continuous decision space. Copyright © 2009 John Wiley & Sons, Ltd.     

Broadband ultrasound field mapping system using a wavelength tuned, optically scanned focused laser beam to address a Fabry Perot polymer film sensor

An optical system for rapidly mapping broad-band ultrasound fields with high spatial resolution has been developed. The transduction mechanism is based upon the detection of acoustically induced changes in the optical thickness of a thin polymer film acting as a Fabry Perot sensing interferometer (FPI). By using a PC-controlled galvanometer mirror to line-scan a focused laser beam over the surface of the FPI, and a wavelength-tuned phase bias control system to optimally set the FPI working point, a notional 1D ultrasound array was synthesized. This system enabled ultrasound fields to be mapped over an aperture of 40 mm, in 50-microm steps with an optically defined element size of 50 microm and an acquisition time of 50 ms per step. The sensor comprised a 38-microm polymer film FPI which was directly vacuum-deposited onto an impedance-matched polycarbonate backing stub. The -3 dB acoustic bandwidth of the sensor was 300 kHz to 28 MHz and the peak noise-equivalent-pressure was 10 kPa over a 20-MHz measurement bandwidth. To demonstrate the system, the outputs of various planar and focused pulsed ultrasound transducers with operating frequencies in the range 3.5 to 20 MHz were mapped. It is considered that this approach offers a practical and inexpensive alternative to piezoelectric-based arrays and scanning systems for rapid transducer field characterization and biomedical and industrial ultrasonic imaging applications.     

Performability of automated manufacturing systems with centralized material handling

We present a framework for performance evaluation of manufacturing systems subject to failure and repair. In particular, we determine the mean and variance of accumulated production over a specified time frame and show the usefulness of these results in system design and in evaluating operational policies for manufacturing systems. We extend this analysis for lead time as well. A detailed performability study is carried out for the generic model of a manufacturing system with centralized material handling. Several numerical results are presented, and the relevance of performability analysis in resolving system design issues is highlighted. Specific problems addressed include computing the distribution of total production over a shift period, determining the shift length necessary to deliver a given production target with a desired probability, and obtaining the distribution of Manufacturing Lead Time, all in the face of potential subsystem failures.