Home About us Contact
|
Home About us Contact | ||
|
|
||
Practical Design (practical + design)
Selected AbstractsGeneration of quantum-entangled twin photons by waveguide nonlinear-optic devicesLASER & PHOTONICS REVIEWS, Issue 4 2009T. Suhara Abstract This paper reviews the quasi-phase-matched (QPM) waveguide nonlinear-optic device technologies for generation of quantum-entangled twin photons indispensable for quantum-information techniques. After a brief introduction to the concept of entanglement, quantum theory analysis of twin-photon generation (TPG) is outlined to clarify the properties of twin photons. Then, methods for entangled-photon generation are discussed. Practical design and theoretical performances of LiNbO3 waveguide QPM TPG devices, as well as the fabrication techniques, are described. Finally, experimental demonstrations of polarization-entangled twin-photon generation by waveguide Type-I and Type-II QPM TPG devices are presented. [source] Experimental research of boiling heat transfer of smooth and screwed tubeHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 2 2007Maode Li Abstract In this paper, based on the analog theory of heat transfer research, we performed an analog experiment on boiling heat transfer in smooth tube and screwed tubes. These are widely used in the high pressure generator of lithium bromide absorption refrigeration. From the experimental research, we obtained a series of results on the boiling heat transfer of a single smooth tube and three screwed tubes. The working condition is near the zone of bubble boiling and the overheat wall temperature ranges from 2,7 °C, with a fluid medium of pure water and salt water solution. These results agreed well with the known results, and are significant for the practical design and application of a high pressure generator of lithium bromide absorption for refrigeration. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 36(2): 74,84, 2007; Published online in Wiley InterScience (www.interscience. wiley.com). DOI 10.1002/htj.20145 [source] Second-order analysis and design of steel structures allowing for member and frame imperfectionsINTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN ENGINEERING, Issue 5 2005J. X. Gu Abstract Conventional linear analysis is deficient in handling the design of slender frames since the effective length and other non-linear effects are difficult to assess accurately. Some proposed non-linear analyses cannot be directly employed for practical design since they are unable to re-produce the buckling curves of the basic structural element, a simple column under axial force, by a single element per member. This paper describes an advanced element, using the same physical significance as the advanced and second-order analysis proposed by a number of researchers and the BS5950(2000) and AS4100 (1995), for practical design of slender steel frames. The proposed element captures the physical behaviour of a structural member that the buckling strength of the member can be predicted using a single element per member and without assuming any effective length. Copyright © 2004 John Wiley & Sons, Ltd. [source] Survey of quantitative feedback theory (QFT),INTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 10 2001Isaac Horowitz QFT is an engineering design theory devoted to the practical design of feedback control systems. The foundation of QFT is that feedback is needed in control only when plant (P), parameter and/or disturbance (D) uncertainties (sets ,,={P}, ,,={D}) exceed the acceptable (A) system performance uncertainty (set ,,={A}). The principal properties of QFT are as follows. (1) The amount of feedback needed is tuned to the (,,, ,,, ,,) sets. If ,, ,exceeds' (,,, ,,), feedback is not needed at all. (2) The simplest modelling is used: (a) command, disturbance and sensor noise inputs, and (b) the available sensing points and the defined outputs. No special controllability test is needed in either linear or non-linear plants. It is inherent in the design procedure. There is no observability problem because uncertainty is included. The number of independent sensors determines the number of independent loop transmissions (Li), the functions which provide the benefits of feedback. (3) The simplest mathematical tools have been found most use ful,primarily frequency response. The uncertainties are expressed as sets in the complex plane. The need for the larger ,,, ,, sets to be squeezed into the smaller ,, set results in bounds on the Li(j,) in the complex plane. In the more complex systems a key problem is the division of the ,feedback burden' among the available Li(j,). Point-by-point frequency synthesis tremendously simplifies this problem. This is also true for highly uncertain non-linear and time-varying plants which are converted into rigorously equivalent linear time invariant plant sets and/or disturbance sets with respect to the acceptable output set ,,. Fixed point theory justifies the equivalence. (4) Design trade-offs are highly transparent in the frequency domain: between design complexity and cost of feedback (primarily bandwidth), sensor noise levels, plant saturation levels, number of sensors needed, relative sizes of ,,, ,, and cost of feedback. The designer sees the trade-offs between these factors as he proceeds and can decide according to their relative importance in his particular situation. QFT design techniques with these properties have been developed step by step for: (i) highly uncertain linear time invariant (LTI) SISO single- and multiple-loop systems, MIMO single-loop matrix and multiple-loop matrix systems; and (ii) non-linear and time-varying SISO and MIMO plants, and to a more limited extent for plants with distributed control inputs and sensors. QFT has also been developed for single- and multiple-loop dithered non-linear (adaptive) systems with LTI plants, and for a special class (FORE) of non-linear compensation. New techniques have been found for handling non-minimum-phase (NMP) MIMO plants, plants with both zeros and poles in the right half-plane and LTI plants with incidental hard non-linearities such as saturation. [source] An optimum design of deep-space downlinks affected by tropospheric attenuation,INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS AND NETWORKING, Issue 6 2009Emilio Matricciani Abstract In the paper, we propose an optimum design of deep-space downlinks made with 2 hops, at Ka band and above, in which each hop should be designed for providing half of the total noise-to-signal power ratio. We have derived this result from maximizing the ratio between the tropospheric attenuation in the 2-hop downlink and that in the 1-hop downlink. The design of the 1st hop (free-space) of the 2-hop downlink can reduce the spacecraft power, for the same antennas physical size, by increasing the carrier frequency from Ka band (32,GHz) to W band (80,GHz). This choice is not available in 1-hop downlink design because of the huge Earth tropospheric attenuation expected in the W frequency band. To show a practical design, we have applied the theory to compare 1-hop downlink design at 32,GHz to 2-hop downlink design that adopts 32 or 80,GHz in the 1st hop. The calculations refer to spacecrafts located at two astronomical units (300×106,km, about planet Mars) and to NASA and ESA receiving stations located in Goldstone (California), Cebreros (Madrid, Spain), Canberra and New Norcia (Australia). At 0.1% outage probability, in an average year or in the worst month, 1-hop downlinks show performance critical or close to fail, because of the large tropospheric attenuation (except at Goldstone), while 2-hop downlinks always work. Copyright © 2009 John Wiley & Sons, Ltd. [source] Experimental investigation into femtosecond fiber ring laser with passive mode lockingMICROWAVE AND OPTICAL TECHNOLOGY LETTERS, Issue 1 2009Xiaoping Xie Abstract A passively mode-locked Er3+ -doped fiber ring laser is experimentally investigated, with the emphasis on its practical design by considering the effects of ring cavity length, pumping light power, and optical amplification on the femtosecond optical pulses obtained. It is shown that the designed fiber ring laser can operate at the center wavelength of 1550 nm to produce a train of periodic optical pulses with full width at half maximum (FWHM) of 270 fs, repetition frequency of 20 MHz, and average output optical power of 146 ,W. The resulting femtosecond optical pulses are then amplified by using three kinds of Er3+ -doped optical fibers with different lengths and Er3+ -doped concentrations, respectively, while employing the same pumping laser. In the experiments, both the FWHM of amplified optical pulses and the amplifier gain are measured under different conditions. The optimization of optical pulse width is also carried out in terms of pumping light power. © 2008 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 63,67, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23985 [source] Tribological behavior of pure and graphite-filled polyimides under atmospheric conditionsPOLYMER ENGINEERING & SCIENCE, Issue 8 2003P. Samyn As the use of common engineering plastics in tribological systems is limited to low sliding velocities and low loads because of creep and insufficient temperature resistance, there is increasing interest in application of high-performance polymers such as polyimides, characterized by their ability to maintain favorable mechanical properties up to their melting point. However, for practical design, tribotesting remains necessary for determination of the material's performance under a given contact situation. In this article, two commercially available polyimides are tested at relatively high sliding velocities and contact pressures under atmospheric conditions of temperature and humidity. A consistent overview of tendencies in friction and wear for pure polyimides as a function of applied normal loads and sliding velocities is given. Addition of 15% by weight graphite powder as internal solid lubricant strongly influences friction and wear. Its behavior is compared with pure polyimide grades and differences are discussed in relation with experimental measured bulk-temperatures. A linear temperature law is derived as a function of pv-levels and a steady-state condition is found at different temperature levels, in accordance with thermal conductivity of the polymer bulks. In case of graphite additives, a steady state in temperature coincides with the regime condition of wear rate. [source] Practical assessment of project performance: the ,potential impact' approach,PUBLIC ADMINISTRATION & DEVELOPMENT, Issue 5 2000Michael Hubbard This article sets out an approach to assessing project performance, using ,potential impact' of the project. Its purpose is to assist project design and evaluation. In project design, potential impacts of alternative activities on the project objective are compared, in order to select activities with the greatest impact. In project evaluation, potential and actual impacts of a project are compared. Additional benefits of the approach are that it indicates ,value for money' of development assistance invested in projects, and easier tracing of reasons for underachievement in projects to weaknesses in their design or management. Limitations are that it relies on informed judgement of the planners or evaluators and the categories for rating performance may unavoidably be broad. It complements the logical framework approach by providing a practical design and evaluation tool. Copyright © 2000 John Wiley & Sons, Ltd. [source] Reconciling Economic Growth and Carbon Mitigation: Challenges and Policy Options in ChinaASIAN ECONOMIC POLICY REVIEW, Issue 1 2010Jing CAO C68; D58; H23; Q54 As the biggest carbon emitter in the world, China is facing tremendous pressure domestically and internationally. To promote the international efforts to tackle climate change, the Chinese government announced its 2020 carbon intensity target and is actively taking part in the international climate negotiations. In this paper, we review some of the climate burden-sharing proposals raised by Chinese scholars to shed some light on China's perspective on the post-Kyoto climate architecture. Then we summarize China's current pollution abatement policies and measures, and analyze some potential policy instruments for China to reconcile its future economic growth and carbon mitigation, as well as some practical design and enforcement issues to be considered for the near term. [source] Untersuchungen zum vertikalen Tragverhalten von SpundwändenBAUTECHNIK, Issue 8 2009Jürgen Grabe Univ.-Prof. Geotechnik; Bodenmechanik; Geotechnical Engineering; Soil Mechanics Abstract Spundwände werden im Wesentlichen auf Biegung infolge einer Belastung durch Erd- und Wasserdrücke beansprucht. Sie können aber auch zum Abtrag von Vertikallasten dienen. Das Tragverhalten von Spundwänden ist bei genauer Betrachtung äußerst komplex, da diesem eine räumlich und zeitlich gekoppelte Boden-Bauwerk-Interaktion zugrunde liegt. Für die praktische Bemessung muss das Tragverhalten daher stark idealisiert werden. Die Rechtfertigung der dafür notwendigen Modellvorstellungen sowie deren Vereinfachungen und Annnahmen sind, wie häufig in der Geotechnik, hauptsächlich durch Erfahrung begründet. Researching the vertical load bearing behaviour of sheet piles. Sheet pile walls are mainly used to carry loads caused by earth and water pressure via bending. In special cases these walls can be used to transfer vertical loads to the subsoil. The complex load bearing behaviour of sheet pile walls is caused by the sterical and temporal coupled soil structure interaction. For practical design the load bearing behaviour needs to be idealised. The apologies used to explain the model conceptions as well as their simplifications are, as usual in geotechnics, mainly motivated by operating experience. [source] | ||||||||||