Large Azimuthal Angles Research Articles

New techniques for initial alignment of strapdown inertial navigation system

Some new techniques for initial alignment of strapdown inertial navigation system are proposed in this paper. A new solution for the precise azimuth alignment is given in detail. A new prefilter, which consists of an IIR filter and a Kalman filter using hidden Markov model, is designed to attenuate the influence of sensor noise and outer disturbance. Navigation algorithm in alignment is modified to feedback continuously for the closed-loop system. It is shown that the initial estimated variance setting of azimuth angle error can influence the speed of initial alignment significantly. At the beginning of alignment, Kalman filter must make a very conservative guess at the initial value of azimuth angle error to get a high convergent speed of the azimuth angle. It is pointed out that the low signal to noise ratio makes the ordinary setting of the estimated azimuth variance slow down the convergent speed of the azimuth angle. Also is shown that the large azimuth angle error problem can be solved well by our solution. The feasibility of these new techniques is verified by simulation and experiment.

Two-particle azimuthal angle correlations and azimuthal charge balance function in relativistic heavy ion collisions

The two-particle azimuthal angle correlation (TPAC) and azimuthal charge balance function (ACBF) are used to study the anisotropic expansion in relativistic heavy ion collisions. It is demonstrated by the relativistic quantum molecular dynamics (RQMD) model and a multi-phase transport (AMPT) model that the small-angle correlation in TPAC indeed presents anisotropic expansion, and the large-angle (or back-to-back) correlation is mainly due to global momentum conservations. The AMPT model reproduces the observed TPAC, but the RQMD model fails to reproduce the strong correlations in both small and large azimuthal angles. The width of ACBF from RQMD and AMPT models decreases from peripheral to central collisions, consistent with experimental data, but in contrast to the expectation from thermal model calculations. The ACBF is insensitive to anisotropic expansion. It is a probe for the mechanism of hadronization, similar to the charge balance function in rapidity.

Advanced DVI for ECC direct bypass mitigation

An ECC direct bypass fraction during a late reflood phase of a LBLOCA is strongly dependent on the characteristics of the cross flow and the geometrical configuration of a DVI in the downcomer of a pressurized light water reactor. The important design parameters of a DVI are the elevation, the azimuthal angle, and the separator to prevent a steam–water interaction. An ECC sub-channel to separate or to isolate an ECC water from a high-speed cross flow is one of the important design features to mitigate the ECC bypass phenomena. A dual core barrel cylinder as an ECC flow separator is located between a reactor vessel and a core barrel outer wall in the downcomer annulus. A new narrow gap between the core barrel and the additional dual core barrel plays the role of a downward ECC flow channel or an ECC flow separator in a high-speed cross flow field of the downcomer annulus. The flow zone around a broken cold leg in the downcomer annulus has the role of a high ECC direct bypass due to a strong suction force while the wake zone of a hot leg has the role of an ECC penetration. Thus, the relative azimuthal angle of the DVI nozzle from the broken cold leg is an important design parameter. A large azimuthal angle from a cold leg to a hot leg needs to avoid a high suction flow zone when an ECC water is being injected. The other enhancing mechanism of an ECC penetration is a grooved core barrel which has small rectangular-shaped grooves vertically arranged on the core barrel wall of the reactor vessel downcomer annulus. These grooves have the role for a generation of a vortex induced by a high-speed cross flow. Since the stagnant flow in a lateral direction and rotational vortex provides the pulling force of an ECC drop or film to flow down into the lower downcomer annulus by gravity, the ECC direct bypass fraction is reduced when compared to the current design of a smoothed wall. An open channel of grooves generates a stagnant vortex, while a closed channel of grooves creates an isolated ECC downward flow channel from a high-speed lateral flow. In this study, new design concepts for a dual core barrel cylinder, grooved core barrel, and a reallocation of the DVI azimuthal angle are proposed and tested by using an air–water 1/5 scaled air–water test facility. The ECC direct bypass reduction performances of the new design concepts have been compared with that of the standard type of a DVI injection. The azimuthal angle of the DVI nozzle from a broken cold leg varies from −15° to +52° toward a hot leg. The test results show that the azimuthal injection angle is an effective parameter to reduce the ECC direct bypass fraction. The elevation of the DVI nozzle is also an important parameter to reduce the ECC direct bypass fraction. The most effective design for reducing the ECC direct bypass fraction is a dual core barrel. The reduction fraction when compared to the standard DVI is about −30% for the dual core barrel while it is −15% for the grooved core barrel.

Two-Dimensional Lamellar Phase of Poly(styrene sulfonate) Adsorbed onto an Oppositely Charged Lipid Monolayer

Polystyrene sulfonate (PSS 77 kDa) adsorbed onto oppositely charged dioctadecyldimethylammonium bromide (DODA) monolayers at the air/water interface is investigated with X-ray reflectivity and grazing incidence diffraction. The alkyl tails of DODA in the condensed phase form an oblique lattice with large tilts and intermediate azimuth angle. On PSS adsorption, the alkyl tail structure is maintained; only the tilt angle changes. Bragg peaks caused by flatly adsorbed, aligned PSS chains are observed, when DODA is in the fluid and also when it is in the condensed phase. The two-dimensional lamellar phase is only found at intermediate PSS bulk concentrations (0.001-1 mmol/L). In this phase, the PSS coverage can be varied by a factor of 3, depending on DODA molecular area and polymer bulk concentration. Charge compensation in the lamellar phase is almost achieved at 1 mmol/L. At larger bulk concentrations, PSS adsorbs flatly yet without chain alignment. Presumably, a necessary condition for a two-dimensional lamellar phase is a pronounced electrostatic force which causes a large persistence length as well as repulsion between the aligned chains.

Numerical Simulation for Orientation of Thin Disk Particles in a Newtonian Flow through a L-Shape Channel

Orientation evolution of thin disk particles, such as talc and mica, in a Newtonian flow through a L-shape channel was numerically simulated by decoupling flow kinematics with particle orientation using the Jeffery equation to obtain the knowledge of the processing of thin micro-particle reinforced composites: (1) periodic flip-over of a thin disk particle moving near the channel wall can be clearly observed for large initial azimuthal angle: (2) when a thin disk particle rounds the corner of a L-shape channel, a disk particle tends to align in the direction perpendicular to the flow plane as it approaches alignment along the streamline.

Oriented and thermal crystallization of poly(ethylene terephthalate)

The oriented and thermal crystallization of amorphous poly(ethylene terephthalate) (PET) films was investigated in terms of the morphological aspects. When the amorphous PET films were stretched up to the desired draw ratios in a hot water bath at 62, 72, and 80 °C, the birefringence of the specimens increased with increasing draw ratio (λ). This tendency becomes most significant when the specimen was drawn in the bath at 62 °C. The storage modulus of the specimen drawn at 62 °C was higher than those of the specimens drawn at 72 and 80 °C. The exothermic peak in the DSC curves was observed clearly for the specimen drawn up to λ=4 in the hot water bath at 80 °C, while the peak did not appear for the specimen drawn up to λ=4 at 62 °C. Under an Hv polarization condition, light scattering patterns from the specimens drawn in the hot water bath showed four lobes at small azimuthal angles and four sharp streaks at large azimuthal angles. Such a profile was independent of the drawing temperatures from 62 to 80 °C. Based on the observed Hv patterns, a model was proposed by assuming the existence of a row-nucleated sheaf-like structure whose rows were preferentially oriented at a particular angle with respect to the stretching direction. The patterns calculated by using the above model were rather close to the patterns observed. This agreement implies that row-nucleated sheaf-like texture arises with lamellar overgrowth.

Erratum: Diffractive exclusive photon production in DIS at DESY HERA [Phys. Rev. D58, 114001 (1998)

We demonstrate that perturbative QCD allows one to calculate the absolute cross section of diffractive exclusive production of photons at large $Q^2$ at HERA, while the aligned jet model allows one to estimate the cross section for intermediate $Q^2 \sim 2 GeV^2$. Furthermore, we find that the imaginary part of the amplitude for the production of real photons is larger than the imaginary part of the corresponding DIS amplitude by about a factor of 2, leading to the prediction of a significant counting rate for the current generation of experiments at HERA. We also find a large azimuthal angle asymmetry in $ep$ scattering for HERA kinematics which allows one to directly measure the real part of the DVCS amplitude and hence the nondiagonal parton distributions.

Diffractive exclusive photon production in DIS at DESY HERA

We demonstrate that perturbative QCD allows one to calculate the absolute cross section of diffractive exclusive production of photons at large $Q^2$ at HERA, while the aligned jet model allows one to estimate the cross section for intermediate $Q^2 \sim 2 GeV^2$. Furthermore, we find that the imaginary part of the amplitude for the production of real photons is larger than the imaginary part of the corresponding DIS amplitude by about a factor of 2, leading to the prediction of a significant counting rate for the current generation of experiments at HERA. We also find a large azimuthal angle asymmetry in $ep$ scattering for HERA kinematics which allows one to directly measure the real part of the DVCS amplitude and hence the nondiagonal parton distributions.

Azimuth angle variations of specular reflection echoes in the lower atmosphere observed with the MU radar

Abstract We studied azimuth angle variations of clear-air echoes in the troposphere and lower stratosphere, observed by steering the antenna beam of the MU radar into 12 positions, the azimuth angle being changed every 30 ° at a zenith angle of 6 °. Azimuth angle variations of the echo intensity were recognized in a large height range in the lower stratosphere, although they were also sometimes found in the troposphere, which was approximated by a fairly smooth sinusoidal curve, with one or two cycles in 360 ° azimuth angle. Moreover, their structure showed continuous progression with time and altitude. The range of variations was generally greater in the lower stratosphere, the ratio of the maximum to the minimum sometimes exceeding 15 dB. The large azimuth angle variations were associated with the aspect sensitivity of the echo power, suggesting that they were caused by the characteristics of specular reflection rather than the effects of localized turbulence scattering, and suggesting that the reflection surface was corrugated, probably the result of the effects of gravity waves. A numerical model qualitatively explained the fundamental behavior of the azimuth angle dependence of the echo power, it being assumed that the vertical displacement of the reflection surface showed sinusoidal variation caused by the dynamical effects of a monochromatic gravity wave.

Direction-dependent spectral sensitivity and interaural spectral difference in a dolphin: Evoked potential study

Sensitivity and interaural intensity difference (IID) dependence on sound frequency and direction was measured in an Amazon river dolphin Inia geoffrensis by recording the auditory nerve evoked response from the body surface. The maximal sensitivity in the horizontal plane was found when the sound direction was 5 degrees to 10 degrees ipsilateral to the recorded ear; the direction dependence of sensitivity was more pronounced at higher frequencies than at lower ones. The IID reached its peak at small azimuthal angles (7.5 degrees to 15 degrees) and higher sound frequencies (100 kHz), or at large azimuthal angles (30 degrees to 45 degrees) and lower sound frequencies (20 to 30 kHz). Each sound direction featured its specific pattern of spectral sensitivity and of interaural spectral difference. The interaural spectral difference fluctuated within a range of more than 20 dB depending on sound direction. The data indicate that interaural intensity as well as spectral difference may be cues for binaural localization of sound direction by dolphins.

Investigation of haem—protein coupling and structural heterogenity in myoglobin and haemoglobin by resonance Raman spectroscopy

AbstractTo probe distortions of the haem group in myoglobin and haemoglobin resulting from ligand—haem and protein—haem interactions, the dispersion of the depolarization ratio and the resonance excitation profiles of the Raman line ν4 were analysed in terms of parameters describing intra‐ and intermanifold vibronic coupling between the Q and B states of the porphyrin macrocycle. These parameters depend linearly on symmetry classified normal distortions of the haem group. It is shown by group theoretical arguments that perturbations at the pyrrole nitrogens N(I) and N(III) of the haem cause B1g‐type distortions which increase with increasing tilt and bend angles of the proximal imidazole and the distal O2 ligand, respectively. Moreover, antisymmetric A2g‐type distortions are imposed via perturbations at the Cα atoms of pyrrole I and III when one of the ligands moves away from a position in which it eclipses the N(I)Fe2+N(III) line of the porphyrin. It is found that the influence of the proximal and distal ligand on the haem symmetry is different in myoglobin and haemoglobin. In oxymyoglobin the O2—haem interaction is responsible for the comparatively large B1g distortion at N(III). B1g distortions in oxyhaemoglobin and its isolated subunits are smaller then in oxymyoglobin. They are mainly caused by repulsive interactions between haem and proximal imidazole. A2g distortions at Cα(I) and Cα(III) are negligible in oxymyoglobin and small in deoxymyoglobin and deoxyhaemoglobin. They are comparatively strong, however, in oxyhaemoglobin and its isolated subunits, owing to the proximity and the large azimuthal angle of the proximal imidazole. In the isolated β‐chains of oxyhaemoglobin haem—protein coupling is more effective and causes larger B1g and A2g distortions than in the α‐chains. While the haem distortions investigated are independent of pH in the isolated α‐chain, they depend significantly on pH in the isolated β‐chain. This is caused by protonation of three titrable groups with pK = 5.8, 6.6 and 7.8, which were earlier assigned to His Eβ, His HC3β and His FG4β, respectively. In intact oxyHbA the allosteric coupling between these titrable groups and haem are modified by strengthening that of His HC3β and reducing that of His FG4β. Coupling between the former group and the haem is probably caused by the hydrogen bond between the penultimate Tyr HC2β and Val FG5β and steric interactions between Tyr HC2β and Cys F9β. Consequently, it is completely absent in the modified oxyhaemoglobin bis(maleimidomethyl) ether, in which the hydrogen bond between the penultimate Tyr HC2β and Val FG5β is ruptured.

The Panoramic Rheed Patterns

When applying the reflection high energy electron diffraction (RHEED) and reflection electron microscopy (REM) methods[1] on the study of crystal surfaces it is necessary to index the RHEED spots and recognize the azimuth of the electron beam direction. This can be difficult because the RHEED pattern, unlike the transmission electron diffraction (TED) pattern, is distorted by the inner potential of the specimen and only one half of the pattern is shown. We found that it is useful, at the beginning of working on a certain surface of a certain crystal, to record a panoramic RHEED pattern by rotating the crystal through a large azimuth angle. This produces a map which is similar to the Kikuchi maps[2] used in transmission electron microscopy (TEM).Two examples of these panoramic RHEED patterns, one from the Pt(111) [3] and the other from α-Al203 (0001) [4,5,6), are shown in Figs. 1 and 2.The transmission Kikuchi maps are recorded using a specimen of suitable thickness such that the Kikuchi lines are strong and the diffraction spots are practically invisible. On the contrary, in making the panoramic RHEED patterns (or RHEED maps) we have no control over the thickness of the specimen. The electron beam enters and exits the same surface of the crystal; therefore, the relative intensities of the Bragg diffracted spots and the Kikuchi lines are not adjustable. The only adjustment lies in choosing the accelerating voltage and the incidence angle of the electrons such that the RHEED pattern has relatively low diffuse scattering.

Critical assessment and modification of Robinson's method for the ellipsometric investigation of thin film materials

Local optical properties of thin film materials can be easily studied using an ellipsometric method devised by Robinson. We have modified the optical components and measuring technique and investigated some critical parameters limiting the accuracy of this method. The analysis of the state of polarization, i.e. azimuth and ellipticity, of the beam emerging from the sample is exclusively based on the measurement of azimuths. By means of modulating the beam azimuth with a Faraday cell and using either a lock-in technique or an X–Y oscilloscope display for detection a very sensitive measurement of the beam polarization is possible. We have evaluated the beam ellipticity both for small and large azimuthal angles, and have used the Poincaré sphere for the graphical representation of all measuring procedures. To eliminate depolarization by reflection all optical components, with emphasis on the wave plate and non-birefringent collimating lens, have been anti-reflection coated. Experimentally an absolute accuracy of 10 −2 degrees was achieved in the determination of ellipticity and azimuth.