Relative Phase Change Research Articles

Stochastic amplitude fluctuation in coherent OTDR and a new technique for its reduction by stimulating synchronous optical frequency hopping

The dynamic range of optical time-domain reflectometry (OTDR) can be extended by employing self-heterodyne coherent detection. However, with coherent detection OTDR (C-OTDR) there is a problem of amplitude fluctuation in the C-OTDR trace caused by (1) the fading noise resulting from the interference between the Rayleigh backscattered lights, (2) the polarization dependent fluctuation of the optical detection efficiency, and (3) the heterodyne detection efficiency fluctuation due to the relative phase change between the Rayleigh backscattered signals and the local oscillator (LO). This paper provides a stochastic description of the amplitude fluctuation using probability density functions and the calculated amplitude fluctuation with M integrations when reduction techniques are applied. We have found theoretically that it is difficult to reduce the amplitude fluctuation effectively by the optical frequency domain integration technique using the asynchronous optical frequency hopping of the source. This is because of an inclination increase in the C-OTDR trace which reduces the measurement accuracy. We propose a synchronous optical frequency hopping technique in which an RF current pulse is induced in the drive current of the laser diode (LD) during the LD temperature change. This effectively reduces the amplitude fluctuation without any increase in the inclination. The amplitude fluctuation for a 1 /spl mu/s pulse width is reduced experimentally to 1/7 that with the LD temperature stabilized. For 100 and 30 ns pulse widths, it is reduced to 1/11 of that with the LD temperature stabilized. These experimental results are in good agreement with the calculated ones.

Dynamical Patterns in the Development of Clapping

The development of a complex rhythmical behavior-clapping-is modeled using a formal, explicit model of coupled oscillator dynamics. Even though this behavior manifests a good deal of nonstationarity and high variability within and across subjects, results indicate that these properties may be dynamically modeled quantitatively as well as qualitatively. Results suggest that clapping goes through a less stable period of relative coordination between 3 and 7 years before more stable absolute coordination is achieved. Nevertheless, in that the clapping behavior is affected in highly predictable ways by inertial loading of the limbs, the same underlying dynamic seems responsible for the coordination of both the younger and older children. Developmentally, the behavior of the coordination variable (relative phase) changes from a nonconstant magnitude in younger clappers to a constant magnitude in older clappers. These results suggest that development of proficiency in rhythmic motor skills displays developmental changes that can be understood well in dynamical terms.

Experimental observation of coherent millimeter wave radiation in a folded waveguide employed with a gyrating electron beam.

The first experimental observation of a strong millimeter wave radiation from a gyrating electron beam propagating through an H-plane bend rectangular folded waveguide is reported. Measurements of power, frequency, and relative phase change of both forward- and backward-wave radiations verified that the oscillation originated from an absolute instability near a stop band of the second space harmonic. A high power radiation of 5.5 kW which corresponds to an electronic efficiency of 24% was observed at 32.8 GHz.

Double security level in a telecommunication system based on phase coding and false data transmission

A new communication system exhibiting a double security level is demonstrated. Information coding is based on relative phase changes between consecutive time intervals of the light emitted from a highly coherent CW source. An imbalanced Mach-Zehnder interferometer whose time delay matches the intervals duration is used to decode the data. The first security level is related to the constant optical power in the transmission link. To further enhance the security, a low coherent source is used to send false data down the transmission link. Common mode rejection is used to separate the real signal from the false signal. This system provides a high signal-to-noise ratio as well as a low crosstalk in a wavelength division multiplexing network.

Electron Phase Counting Micromagnetometry Using a Differential Phase Contrast/Interference Scanning Transmission Electron Microscope

A new method of micromagnetometry, electron phase counting (EPC), using a scanning transmission electron microscope with differential phase contrast and interference imaging modes has been proposed and tested. By counting the relative phase changes occurring in a pair of mutually coherent fine probes as they are moved from an observation point to a nearby reference point, integrated magnetic flux density at the observation point can be quantified without recourse to instrumental signal intensity calibration. Its feasibility for practical micromagnetometry has been confirmed by the successful application of two different EPC procedures to a NiFe alloy film.

Sensitive detection of magnetic field distribution using scanning interference electron microscope (invited) (abstract)

We have implemented interference imaging mode as well as Lorentz imaging mode on a scanning transmission electron microscope (HITACHI HF-2000 with a scanning option; 200 kV accelerating voltage). In the interference mode, a pair of mutually coherent fine probes scan simultaneously across the region of magnetic induction. By monitoring the relative phase change occurring in the probe pair, the variation of the magnetic flux bound by the probe trajectories can be sensed by the universal unit of e/h (−‖e‖: electron charge and h: Planck’s constant). The combined use of this imaging mode with the Lorentz mode which is based on the detection of the probe deflection by Lorentz force facilitates detailed analyses of fringing field around magnetic materials and magnetic induction inside magnetic films. The microscope described above is particularly suited for the study of magnetic storage devices whose microscopic magnetic properties are drawing much attention recently. We show here the results of its application to the observation of field distributions near the MR (magnetoresistive) heads and induction distributions associated with high density longitudinal and perpendicular recording media.

Dynamics of movement coordination and tremor during gait in Parkinson's disease

Movement coordination, transition and stability aspects of gait in individuals with Parkinson's disease were investigated. Changes in movement coordination were evaluated by means of relative phase changes between upper and lower extremities and stability of patterns by means of the standard deviation of relative phase. Spectroscopic analysis of individual limb oscillators and of the relative phase between these oscillators was used to assess the contribution of lower and higher (e.g., tremor) frequency components on the coordination dynamics. Coordination changes in five patients and five age-matched controls were evaluated by means of accelerometry while movement velocity was manipulated as a control parameter on a motor-driven treadmill. Relative phase changes and stability features showed gradual changes in upper and lower extremity oscillations with walking velocity, a finding consistent with model predictions by Schöner et al. (1990) regarding gait changes in the quadrupedal walking mode. Parkinson's disease patients showed overall less adaptations in relative phase than the control group, especially those involving the upper extremities. Frequency analyses of relative phase also demonstrated that 1. (a) systematic scaling of walking velocity can affect the dominant frequency of Parkinsonian tremor, 2. (b) higher order frequency components in relative phase can play a functional, stabilizing role, and 3. (c) 1/ƒ scaling properties of the relative phase power spectrum can identify the higher degree of constraint on the coordination dynamics in Parkinson's disease.

Phase effects in forward masking of the compound action potential: a comparison of responses to stimulus and distortion frequencies

When a complex stimulus is presented, new frequencies (distortion products, DPs) are generated within the cochlea. The most intense DPs are lower in frequency than the stimulus tones (primaries). It is not clear whether the relative phase of stimuli is encoded by neural channels tuned to the primaries or by channels tuned to the DPs. We estimated the response of auditory nerve fibres tuned to each of these channels as a function of the relative phase of harmonic stimuli. The compound action potential (CAP) evoked by probes at the primary or distortion frequencies was masked by harmonic 2-tone maskers and cochlear generated DPs. The degree of masking reflected the response to the masker of fibres tuned to the probe. Changes in relative phase of the primaries resulted in a large modulation of the response of fibres tuned to the DPs. Except for a primary frequency ratio of 1:2, the response of fibres tuned to the primaries was only shallowly modulated by changes in relative phase. However, the level of response to the DPs was much lower than the response to the stimulus tones.

Relative Phase Alterations During Bimanual Skill Acquisition.

The purposes of the research reported here were (a) to examine changes in relative phase during the acquisition of a new coordination pattern and (b) to determine the effect of learning this pattern on the ability to perform other coordination patterns. Ten subjects practiced an upper limb coordination task that required a 90 degrees phase offset and different amplitudes for each arm. A gross approximation of the mean relative phase for the intended coordination pattern occurred quickly, but the attainment of stability occurred much more gradually. These results were accompanied by changes in pattern stability across practice and on various transfer tests. Learning of the new coordination pattern also affected the stability of the antiphase mode, but this effect was only temporary.

Flux line in a d-wave uperconductor

The structure of the core of a vortex line in a d ∞ 2− y 2 superconductor is studied within Bogoliubov-de Gennes theory. Three regions of the vortex are identified: (1) The inner core which supports localized fermionic excitations, (2) The outer core where d-wave and extended s-wave pairing coexist and the fermionic excitations are gapped, (3) The asymptotic region where the superconductor is in a d ∞ 2− y 2 state and low-energy quasi particles are present. The outer core is found to consist of four domains where the superconductor is in an s ± id state. The change in the relative phase is confined to domain walls where the relative phase changes by π.

Solubility parameter effects on microencapsulation in the presence of polyisobutylene

Abstract A nonsolvent/solvent evaporation method of microencapsulation using ethylcellulose and ion-exchange resin-drug complex was used to show that solubility parameters of the microencapsulation system affect the ability of polyisobutylene (PIB) to promote mononucleated microcapsules. Microencapsulations using solvent systems which had solubility parameters well within the PIB soluble region of a two-dimensional solubility parameter map produced nonaggregated microcapsules which exhibited similar morphological characteristics. Whereas multinucleated microcapsules were produced when solvent systems were used which had solubility parameters close to the region of insolubility for PIB. Further examination of solubility parameter maps of ethylcellulose as affected by polyisobutylene demonstrated that PIB altered the phase changes of ethylcellulose. The formation of two liquid phases induced by polyisobutylene can be used to explain how mononucleated microcapsules are produced using the adjunct polymer PIB. The use of a solubility parameter map for the coating polymer ethylcellulose, as affected by the adjunct polymer, polyisobutylene, can be used to choose solvent systems providing related phase changes and consequently similar microcapsule coats.

High contrast asymmetric Fabry–Perot electro-absorption modulator with zero phase change

By analyzing the exciton line shapes of quantum wells, we can determine the wavelengths and biases at which they exhibit large absorption changes and zero refractive index changes relative to zero bias. To use this effect, we placed GaAs/AlGaAs quantum wells in the intrinsic region of a reverse-biased p-i-n diode asymmetric Fabry–Perot modulator. We then developed a sample that could be post-growth processed to optimize all relevant parameters. We used computer simulation to determine the exact post-growth correction required and produced reflection modulators with 90% reflection change and zero relative phase change.

Time-delay Fizeau phase-conjugate interferometer

A time-delay Fizeau phase-conjugate interferometer is constructed by using a BaTiO(3) crystal in a degenerate four-wave-mixing configuration. The slow response time of BaTiO(3) is used to build a phase-conjugate mirror that functions as a holographic memory. An optical wave and its time-delayed version are stored inside the crystal sequentially while their phase-conjugate waves are generated simultaneously. Superposition of the two phase-conjugate waves produces an interferogram as a result of the relative phase change of the input waves. The simplicity and real-time operation of this technique lead to several advantages over the conventional holographic interferometry. The use of photorefractive crystal eliminates the darkroom process and reposition procedure. A higher accuracy can be achieved because the interfering waves are phase-conjugate waves. The principle of this technique is presented and the experimental results and its applications are discussed.

Displacement Damage Effects and Related Phase Changes of Ar-Ion-Irradiated BiSrCaCuO System Superconducting Thin Films

BiSrCaCuO thin films of 0.5 µm thickness containing mainly the high-Tc phase were irradiated with 100 keV Ar ions up to 5×1017 ions/cm2 at 10 K or 300 K. The irradiated thin films were considered to consist of a heavily damaged surface layer and an underlying partly displaced crystalline layer. The transition temperature Tc of the films decreased initially with increasing Ar ion dose and converged at about 63 K for doses larger than 1×1017 ions/cm2. By a subsequent annealing below 800°C, the Tc recovered up to 98 K. The relative X-ray diffraction intensity of the high-Tc phase reached a maximum upon annealing at 700∼730°C. During the annealing, the heavily damaged or amorphous surface layer recrystallizes and regrows into better quality high-Tc phase particles with concomitant formation of the thermodynamically stable Ca-free phase at this low temperature range.

Mesothermal gold mineralization in a Proterozoic greenstone belt; western Flin Flon Domain, Saskatchewan, Canada

The Flin Flon domain, Trans-Hudson orogen, Canada, is an example of a Proterozoic greenstone belt that hosts a large number of small mesothermal gold occurrences. The greenstone belt consists of tholeiitic to calc-alkaline volcanic rocks (Amisk Group; approximately 1900-1880 Ma) unconformably overlain by molasse-type sedimentary rocks (Missi Group; 1850-1840 Ma). The supracrustal rocks are intruded by gabbroic to granitic rocks ranging in age from synvolcanic to late tectonic (1890-1835 Ma). Metamorphic grade varies from prehnite-pumpellyite facies to amphibolite facies, and peak thermal conditions generally were attained locally during granitoid intrusion. Many of the shear zones and the dominant regional foliation developed during ductile deformation coeval with peak metamorphism. These shear zones were reactivated and mineralized under brittle-ductile conditions during postpeak metamorphic uplift.Mesothermal gold mineralization is hosted in quartz veins that developed at jogs or zones of competency contrasts along brittle-ductile shear zones, in all lithologies in the region. Alteration envelopes, which consist of quartz-carbonate-chlorite-albite-muscovite-pyrite, are usually less than a few meters wide and overprint regional metamorphic assemblages. The veins consist of milky-colored quartz and may also contain tourmaline, ankerite, chlorite, and muscovite. Pyrite and arsenopyrite are the dominant sulfides, and gold grade is proportional to the modal abundance of sulfides.The dominant fluids associated with gold mineralization were H 2 O-CO 2 -NaCl (0.6-14.7 wt % NaCl equiv) in composition, with generally uniform H 2 O/CO 2 phase ratios in a given plane or zone but variable phase ratios between zones. Oxygen isotope mineral pairs indicate temperature of mineralization of between 360 degrees and 420 degrees C, which, when combined with fluid inclusion density estimates, indicate that most of the gold mineralization occurred at a pressure of about 2 kbars. Rapid pressure release in dilatant zones with related phase separation and change in fluid composition and properties, and local fluid-wall rock interaction, are the likely gold-precipitation mechanisms.The O, H, S, C, and Sr isotope compositions of hydrothermal minerals in the shear zones indicate that the mineralizing fluids interacted extensively with Proterozoic metamorphic and igneous rocks similar in composition to those presently exposed at the surface, at high temperatures and at low water/rock ratios. The O and H isotope compositions are compatible with formation of the fluids from devolatilization reactions during prograde metamorphism at depth. The O isotope composition of barren quartz veins varies with the host rocks indicating that these fluids were either locally derived or interacted extensively with the immediate host rocks.An Rb-Sr isochron age of 1760 + or - 9 Ma on tourmaline and muscovite from the Rio deposit is similar to 40 Ar/ 39 Ar plateau ages for muscovites from the premetamorphic Laurel Lake deposit in the Flin Flon domain. This suggests that fluid advection through the Rio deposit was contemporaneous with the thermal event that affected Laurel Lake muscovites. These ages, along with an age from the Tartan Lake mesothermal deposit (1791 + or - 4 Ma) in the Flin Flon domain, indicate that fluid flow related to hydrothermal activity along the shear zones in the western Flin Flon domain occurred periodically over a period of about 30 Ma.These Proterozoic gold occurrences are similar to Archean mesothermal gold deposits in terms of geologic, structural, and tectonic setting, alteration and vein mineralogy, and fluid composition, pressure, and temperature. However, the limited extent of alteration, the low gold content, the isotopic systematics, and the lack of either S-type granites or mantle-derived lamprophyres suggest that the shear zones hosting the western Flin Flon domain occurrences sampled limited quantities of fluids and, thus, were not transcrustal features capable of hosting giant gold deposits.

The Production and Perception of Syllable Structure

Much research on speech over the years has focused on uncovering examples of the nonlinear relationship between acoustics and perception (e.g., so-called "categorical perception") and between articulation and acoustics [as described by Stevens's (1972) quantal theory]. In the present experiment we demonstrate that naturally occurring linear changes in articulation may also be perceived discontinuously. Specifically, linear changes in relative phase of glottal and oral movements are perceived as categorical changes in the location of syllable juncture. Thus, phase transitions observed during speech demarcate a change in syllabic organization.

Optimization of SAR distributions in liver and lung regions irradiated by the H-horn annular phased array hyperthermia system

The author discusses a type of annular phased array (APA) system-the H-horn APA. The phase and amplitude control of power deposition patterns for this system have been theoretically analyzed at a frequency of 200 MHz. The formulas for calculating the electric field (E-field) and specific absorption rate (SAR) for this APA system have been derived and can be applied to other types of APA systems. Models on computerized tomography (CT) scans from liver and lung regions have been used for predicting optimization of the E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the phase and amplitude control of SAR patterns results in a more selective and effective heating of tumors situated eccentrically and deeply within the body. The numerical results indicate that it is possible to shift the absorbed power patterns by electrically varying the phase and/or the amplitude of the sources and manually moving the positions of the horns. >

Theoretical Analysis of H-Horn Annular Phased Array System for Heating Deep-Seated Tumors

This paper discusses a type of annular phased array system--H-Horn APA. The phase and amplitude control of power deposition patterns for this system are theoretically analyzed at a frequency of 200 MHz. The formulas for calculating E-field and SAR for this APA system are derived, and can be applied to other type APA systems. Models of computerized tomography (CT) scans from liver and lung regions have been used, respectively, for predicting optimization of E-field and SAR patterns in the case of the relative phase and amplitude changes. It is shown that the techniques of the phase and amplitude control of SAR patterns result in more selectively and effectively heating of tumors situated eccentrically and deeply within bodies of patients. The APA hyperthermia described in this paper shows great promise, and it looks very useful for developing clinical applications.

Multilayer optical elements for generation and analysis of circularly polarized X-rays

Calculations of the relative phase changes of σ and π electric field components on Bragg reflection from and transmission through multilayers are presented. Large relative phase changes can be calculated in certain cases, which may lead to utility of multilayers as quarter-wave plates for generation and analysis of circularly polarized soft X-radiation. Similar behavior may be expected for perfect crystals in the hard X-ray range.

Novel investigations on thermogravimetric and differential thermal analyses of elemental, compound and mixed semiconductors

A systematic study was made of the relative stability and various phase changes which take place when elemental compound and mechanically mixed semiconductors are heated. These were chalcogens, calcogenides and mixtures of the two. The interest in the present investigation is due to the useful application of the prepared materials in the transistor, radar, rectifier and other electronic industries. Thermogravimetry and differential thermal analysis were carried out in air in the temperature range 20–830°. The results led to the conclusion that the degree of stability of the mechanically mixed semiconducting components is much higher than that of either elemental or compound semiconductors. The results were discussed on the basis of the electronegativity differences and oxygen affinities of the non-metallic components. The thermal stability ranges were evaluated in each case for the materials investigated, for their subsequent physical measurements and their suitability for the production of semiconducting devices.