Relation between space-time inversion and particle-antiparticle symmetry and the microscopic essence of special relativity

After analyzing the implication of investigations on the C, P and T transformations since 1956, we propose that there is a basic symmetry in particle physics. The combined space-time inversion is equivalent to particle-antiparticle transformation, denoted by ${\cal PT=C}$. It is shown that the relativistic quantum mechanics and quantum field theory do contain this invariance explicitly or implicitly. In particular, (a) the appearance of negative energy or negative probability density in single particle theory -- corresponding to the fact of existence of antiparticle, (b) spin- statistics connection, (c) CPT theorem, (d) the Feynman propagator are linked together via this symmetry. Furthermore, we try to derive the main results of special relativity, especially, (e) the mass-energy relation, (f) the Lorentz transformation by this one ``relativistic'' postulate and some ``nonrelativistic'' knowledge.Comment: 29 pages, Latex, 1 figur

Second language user support

Computer users rarely experience entirely trouble-free interaction. The natural variety ofindividuals ensures that no software systems yield constantly fluent interaction for allusers. In consequence, software designers often strive to ameliorate this situation bybuilding 'user support' into their systems. User support can take different forms but,conventionally, each aims to assist the needy end-user by means of facilities directly supporting the performance of certain operations, or through supply of information thatadvises the user on available system functionality.The present paper briefly characterises a range of user support facilities before describingone requirement in greater detail. This aspect considers the needs of users whose mother-tongue is not English, but who are obliged to use English-based information systems. Inthis context, 'helping the user' must reasonably extend beyond mere advice on systemoperation to selective elucidation of information content. We regard this move as alogical extension of the user support concept, by seeking to address specific interactionneeds in a target user population. An example of this approach is described through aninformation system, in the domain of civil engineering, for native Chinese speakers ofEnglish

Engineering properties of Singapore old alluvium

Ph.DDOCTOR OF PHILOSOPH

Electrical, optical and magnetic resonance studies of novel [pi]-conjugated polymers

Conductivity, optical properties including visible and infrared (IR) absorption and photoluminescence (PL), and magnetic resonance properties including electron spin resonance (ESR) and optically detected magnetic resonance (ODMR) have been studied in polydiethynylsilanes (PDES) and poly(2,5-dibutoxyparaphenyleneacetylene) (PDBOPA), which were recently synthesized by Dr. T. J. Barton\u27s group at the Ames Laboratory. PDES and PDBOPA blend and PDBOPA-based electroluminescent preliminary diodes which were fabricated by the author were also explored;The undoped one-dimensional gap of PDES polymers, which have average molecular weight from ~2 x 10[superscript]5 to 1 x 10[superscript]6, is 2.0 eV in both films and solutions; photoluminescence is barely observed. I[subscript]2 doping induces a single absorption band at ~1.05 eV in solutions and lightly doped films, but another at ~0.55 eV in heavily doped films. Both are correlated with strong IR-active vibrations associated with known lines in Raman scattering. The doping-induced ESR of the solutions is linear in the 1.05-eV peak, but only ~2% of the carriers yield an ESR, which is motionally narrowed. No double modulation light-induced ESR is detected. The results are discussed in relation to solitons, polarons, bipolarons, and A-B solitons;PDBOPA with average molecular weight ~5 x 10[superscript]4 is somehow passive to I[subscript]2 doping. Exposure to I[subscript]2 vapor at ~80°C increases the conductivity to ~5 x 10[superscript]-3 S/cm, but the I[subscript]2 rapidly evolves from the film at room temperature. The absorption onsets at 2.53 eV and peaks at 2.81 eV. The 2.71 eV-excited photoluminescence (PL) peaks at ~2.0 eV in films and solutions. In all cases, it is very intense and largely structureless. Three PL-enhancing ODMR features are observed: (i) a strong narrow (~15 G wide) resonance at g = 2.0025, attributed to intrachain polaron recombination; (ii) a ~1.2 kG wide triplet exciton powder pattern around g ~ 2, and (iii) the [delta]m[subscript] s = 2 transitions of these excitons at g ≅ 4.07. The results are discussed in relation to conformational defects resulting from the near cylindrical symmetry of the backbone acetylene units;The improving optical properties of dilute PDBOPA blend over pure PDBOPA including the strong enhancement of the PL quantum yield, reduced photoinduced degradation, a large blue shift of the PL peak and a partially resolved vibronic structure in the PL spectrum are discussed within the framework of dynamics of photo-excitation and decay. The PDBOPA based electroluminescent diodes have been successfully fabricated for the first time, although the quantum yield was low. Suggestions for improvements are briefly discussed. ftn*DOE Report IS-T-1559. This work was performed under contract No. W-7405-Eng-82 with the U.S. Department of Energy

Characterization of Wave Propagation in Thin Laminated Plates

This is an electronic version of an article published in Du, C., Ni, Q. & Natsuki, T. (2010). Characterization of Wave Propagation in Thin Laminated Plates. [Materials and Manufacturing Processes is available online at: http://www.informaworld.com/smpp/content~db=all?content=10.1080/10426910903426349The formulae including the in-plane stiffness and bending stiffness coefficients and coupling effect in out-plane were presented for analyzing characterization of wave propagation. Using the present formulae, the wave velocities can be calculated in any case of laminated plates including nonsymmetric lamination. In this study, the characteristics of wave propagation in thin laminated plates were investigated in detail. Five modes including symmetric modes and antisymmetric modes were obtained from the proposed formulae. For each mode, the wave velocities of laminated plates were investigated in different conditions such as plate thickness, stacking sequence, and vibrational frequency.ArticleMATERIALS AND MANUFACTURING PROCESSES. 25(4):259-263 (2010)journal articl

Carbon nanotube template-assisted synthesis of zinc ferrite nanochains

We synthesized zinc ferrite nanochains assembled from nanoparticles using a carbon nanotubes (CNTs) template method The resulting nanochains were systematically characterized with respect to crystal structure morphology elemental composition magnetic properties and specific surface area by X-ray diffraction (XRD) transmission electron microscopy (TEM) field emission scanning electron microscopy (FESEM) X-ray photoelectron spectroscopy (XPS) superconducting quantum interference device (SQUID) magnetometry and the N(2) adsorption method The morphology results showed that the zinc ferrite particles with diameters of 10-20 rim were structurally linked to form nanochains The magnetic property investigation indicated that the zinc ferrite nanochains exhibited ferromagnetic behavior and possessed a saturation magnetization of 45 4 emu g(-1) at 300K We addressed the growth mechanism by analyzing the experimental conditions and characterization results This method may be applicable to synthesizing other metal oxide nanochains as wellArticleMATERIALS CHEMISTRY AND PHYSICS. 124(2-3):1029-1033 (2010)journal articl