Doppler-shift compensation in the Taiwanese leaf-nosed bat (Hipposideros terasensis) recorded with a telemetry microphone system during flight

Biosonar behavior was examined in Taiwanese leaf-nosed bats (Hipposideros terasensis; CF-FM bats) during flight. Echolocation sounds were recorded using a telemetry microphone mounted on the bat's head. Flight speed and three-dimensional trajectory of the bat were reconstructed from images taken with a dual high-speed video camera system. Bats were observed to change the intensity and emission rate of pulses depending on the distance from the landing site. Frequencies of the dominant second harmonic constant frequency component (CF2) of calls estimated from the bats' flight speed agreed strongly with observed values. Taiwanese leaf-nosed bats changed CF2 frequencies depending on flight speed, which caused the CF2 frequencies of the Doppler-shifted echoes to remain constant. Pulse frequencies were also estimated using echoes returning directly ahead of the bat and from its sides for two different flight conditions: landing and U-turn. Bats in flight may periodically alter their attended angles from the front to the side when emitting echolocation pulses.     

Doppler-shift attenuation measurements on Mg by (α, α') and (p,p') reactions

The (α, α') and (p, p') reactions have been used to populate states in ²⁴Mg in order to measure lifetimes of ten states by the Doppler-shift attenuation method. The shifted γ-rays were observed by a planar 5.6 cm³ Ge(Li) detector at 90° to the beam at the target in coincidence with the scattered particles observed in either of two particle detectors located symmetrically with respect to the beam. A computer coupled dual two-parameter arrangement permitted concurrent measurements for all states appreciably populated. The present measured transition probabilities are compared with predictions from a truncated j-j coupling shell-model calculation.     

Vocal control of acoustic information for sonar discriminations by the echolocating bat, Eptesicus fuscus

This study aimed to determine whether bats using frequency modulated (FM) echolocation signals adapt the features of their vocalizations to the perceptual demands of a particular sonar task. Quantitative measures were obtained from the vocal signals produced by echolocating bats (Eptesicus fuscus) that were trained to perform in two distinct perceptual tasks, echo delay and Doppler-shift discriminations. In both perceptual tasks, the bats learned to discriminate electronically manipulated playback signals of their own echolocation sounds, which simulated echoes from sonar targets. Both tasks utilized a single-channel electronic target simulator and tested the bat's in a two-alternative forced choice procedure. The results of this study demonstrate changes in the features of the FM bats' sonar sounds with echolocation task demands, lending support to the notion that this animal actively controls the echo information that guides its behavior.     

Transformation of external-ear spectral cues into perceived delays by the big brown bat,Eptesicus fuscus

The external-ear transfer function for big brown bats (Eptesicus fuscus) contains two prominent notches that vary from 30 to 55 kHz and from 70 to 100 kHz, respectively, as sound-source elevation moves from -40 to +10 degrees. These notches resemble a higher-frequency version of external-ear cues for vertical localization in humans and other mammals. However, they also resemble interference notches created in echoes when reflected sounds overlap at short time separations of 30-50 micros. Psychophysical experiments have shown that bats actually perceive small time separations from interference notches, and here we used the same technique to test whether external-ear notches are recognized as a corresponding time separation, too. The bats' performance reveals the elevation dependence of a time-separation estimate at 25-45 micros in perceived delay. Convergence of target-shape and external-ear cues onto echo spectra creates ambiguity about whether a particular notch relates to the object or to its location, which the bat could resolve by ignoring the presence of notches at external-ear frequencies. Instead, the bat registers the frequencies of notches caused by the external ear along with notches caused by the target's structure and employs spectrogram correlation and transformation (SCAT) to convert them all into a family of delay estimates that includes elevation.     

Stabilization of perceived echo amplitudes in echolocating bats. II. The acoustic behavior of the big brown bat, Eptesicus fuscus, when tracking moving prey.

Big brown bats, Eptesicus fuscus, can be trained to use echolocation to track a small microphone with a food reward attached when it is moved rapidly toward them. This situation mimics prey interception in the wild while allowing very precise recording of the sonar pulses emitted during tracking behavior. The results show that E. fuscus intensity compensates, reducing emitted intensity by 6 dB per halving of target range so that the intensity incident upon the target is constant and echo intensity increases by 6 dB per halving of range. This increase in echo intensity is effectively canceled by the reduction in auditory sensitivity due to automatic gain control (AGC) of 6 to 7 dB per halving of range. Intensity compensation behavior and AGC therefore form a dual-component, symmetrical system that stabilizes perceived echo amplitudes during target approach. The same system is present in the fishing bat, Noctilio leporinus, suggesting that it may be widespread in echolocating bats. Correlation analysis shows that, despite large changes in the duration of the pulses emitted by E. fuscus during an approach, the pulse frequency structure is such that the spatial image of the target perceived along the range axis is highly stable. Pulse duration is not reduced in the manner theoretically necessary to eliminate potential echo distortion effects due to AGC, but is reduced in such a way that this distortion is insignificant. During the terminal buzz, a high degree of temporal overlap (relative to pulse duration) occurs between emitted pulse and returning echo.     

Spectral cues and perception of the vertical position of targets by the big brown bat, Eptesicus fuscus

Big brown bats (Eptesicus fuscus) were trained to discriminate between vertical angles subtended by paired beads suspended from fishing line. Bats were rewarded for choosing the smaller of the two angles presented. The difference between the angles was changed systematically using a transformed up-down procedure and the bats' ability to detect the difference was measured at different vertical locations. When the beads were centered at +20 degrees (above the horizon), at 0 degree (the horizon), and at -20 degrees (below the horizon), vertical angle acuity (VAA) was maintained between 2.9 degrees and 4.1 degrees. At more extreme vertical positions both bats showed loss of acuity; when the beads were centered around -40 degrees, VAA was 6.7 degrees or 8.3 degrees and at +40, VAA was worse than 21 degrees (the largest difference tested). When the tragi of both ears were bent down and glued to the side of the face, bats showed severe loss of acuity for beads centered at -20 degrees (VAA 18.3 degrees and 20.1 degrees), but maintained their angle acuity for beads centered at +20 degrees (VAA 3.8 degrees and 4.9 degrees). The results are consistent with the spectral cues created by the filtering of the external ear.     

Source motion detection, estimation, and compensation for underwater acoustics inversion by wideband ambiguity lag-Doppler filtering

Acoustic channel properties in a shallow water environment with moving source and receiver are difficult to investigate. In fact, when the source-receiver relative position changes, the underwater environment causes multipath and Doppler scale changes on the transmitted signal over low-to-medium frequencies (300 Hz-20 kHz). This is the result of a combination of multiple paths propagation, source and receiver motions, as well as sea surface motion or water column fast changes. This paper investigates underwater acoustic channel properties in a shallow water (up to 150 m depth) and moving source-receiver conditions using extracted time-scale features of the propagation channel model for low-to-medium frequencies. An average impulse response of one transmission is estimated using the physical characteristics of propagation and the wideband ambiguity plane. Since a different Doppler scale should be considered for each propagating signal, a time-warping filtering method is proposed to estimate the channel time delay and Doppler scale attributes for each propagating path. The proposed method enables the estimation of motion-compensated impulse responses, where different Doppler scaling factors are considered for the different time delays. It was validated for channel profiles using real data from the BASE'07 experiment conducted by the North Atlantic Treaty Organization Undersea Research Center in the shallow water environment of the Malta Plateau, South Sicily. This paper provides a contribution to many field applications including passive ocean tomography with unknown natural sources position and movement. Another example is active ocean tomography where sources motion enables to rapidly cover one operational area for rapid environmental assessment and hydrophones may be drifting in order to avoid additional flow noise.     

Random crystal field effect on hysteresis loops and compensation behavior of mixed spin-(1, 3/2) Ising system

Magnetic hysteresis and compensation behavior of a mixed spin-(1, 3/2) Ising model on a square lattice are investigated in the framework of effective field theory based on a probability distribution technique. The effect of random crystal field, ferromagnetic and ferrimagnetic exchange interaction on hysteresis loops and compensation phenomenon are discussed. A number of characteristic phenomena have been reported such as the observation of triple hysteresis loops at low temperatures and for negative values of random crystal field. Critical and double compensation temperatures have been also found. The obtained results are also compared to some previous works.     

The effect of charge compensation by means of Na+ ions on the luminescence behavior of Sm3+-doped CaAl4O7 phosphor

Results of structural and spectroscopic measurements of Sm³⁺ doped calcium aluminates: Ca_1?xSm_xAl₄O₇ and Ca_1?2xSm_xNa_xAl₄O₇ (x=0.0005, 0.002, 0.01, 0.02, 0.03, 0.05) obtained by the modified Pechini method are presented. All samples yield intense orange–red emission under violet excitation (404.5 nm). Narrow bands corresponding to characteristic f–f intraconfigurational transition of Sm³⁺ in excitation and emission spectra were observed. The influences of the concentration of Sm³⁺ as well as charge compensation by co-doping with Na⁺ ions on the luminescent properties of the phosphor were investigated. Detailed analysis of the emission spectra of Sm³⁺ doped and Sm³⁺,Na⁺ co-doped CaAl₄O₇ powders proved that activator ions substitute Ca²⁺ in the host. Co-doping with Na⁺ ions enhanced greatly the intensity of the luminescence. Concentration dependencies of the intensity of luminescence and its decay kinetics proved the emission quenching at higher dopant contents due to cross-relaxation processes between Sm³⁺ ions. Fitting of the ⁴G_5/2 state fluorescence decay to the Inokuti–Hirayama model indicated dipole–dipole interaction as the dominant mechanism of the cross-relaxation processes.     

Study on the 4×10 Gb/s,400 km dispersion compensation by chirped optical fiber grating

In this paper, the dispersion compensation for 4×10 Gb/s, 400 km G.652 fiber by chirped optical fiberBragg grating (FBG)is introduced.For the first time,we have measured and compensated the polarizationmode dispersion(PMD)of FBG, which in each channel is less than 1.1 ps.When the bit crror rate(BER)is 10~(-10)and the bit error is zero, the transmission power penalty of each channel is less than 2 dB, andthe best, result is negative which means that the receiver sensitivity is increased after transmission.     

Microstructure, hardness, and electrical behavior of Y-doped CaZrO3 films prepared by chemical solution deposition

CaZr_0.9Y_0.1O_3???δ films were fabricated by chemical solution deposition on single-crystalline YSZ (ZrO₂ doped by 10 mol% of Y₂O₃) substrates. Mechanical hardness and morphology of the films were studied using nano-indentation and atomic force microscopy techniques. Grain microstructure of the films has been shown to depend upon thermal treatment duration and film thickness. Thin films with grains a few times greater than the film thickness have been obtained. It has been shown that thickness of films can be evaluated by comparing of the indentation curves for the clean and coated by the film substrates. Mechanical hardness of the film has been found to be sensitive to the film grain microstructure. Electrical behavior of CaZr_0.9Y_0.1O_3???δ films studied by impedance spectroscopy strongly depends on the film microstructure.     

Microstructure, hydrogenation and optical behavior of Mg-Ni multilayer films deposited by magnetron sputtering

Mg-Ni multilayer films with sequential Mg and Ni layers were prepared by direct current magnetron sputtering. The substrate temperature influences the microstructure of the films greatly. The film deposited at 298 K exhibits multilayered structure, while the film shows nanocrystalline/amorphous composite structure at the deposition temperature of 473 K. The optical properties between hydrogenation/dehydrogenation states of the films were performed using spectrophotometer in visible light region. The film deposited at 473 K can switch from mirror-like metallic state towards brownish yellow transparent state under 0.6 MPa H₂ at 298 K, and the optical transmittance modulation reaches up to 20% both at a wavelength of 770 nm and IR region, while the film deposited at 298 K exhibits low optical change, and the optical switching behavior can hardly be found. The extra free energy stored in the boundary of the nanocrystallines benefits the formation of magnesium-based hydride, resulting in the enhancement of the optical switching properties of the Mg-Ni film deposited at 473 K.     

Adsorption and desorption behavior of NO on H-ZSM-5, Na-ZSM-5, and Na-A as studied by EPR

Nitric monoxide probe molecules are used to characterize the Lewis acid properties of sodium cations and aluminum defect centers in various zeolite materials. The adsorption-desorption behavior of NO probe molecules is studied at different temperatures for Na-A, Na-ZSM-5, H-ZSM-5, and silicalite. Adsorbed NO molecules form paramagnetic adsorption complexes with Lewis acid sites which can be examined by EPR transitions ((Delta)m(S)+/-1) at g approximately 2.0. Otherwise the desorption of NO into the gas phase can be monitored by the typical nine-line EPR spectrum ((Delta)m(J)+/-1) of the (2)Pi(3/2) state at g approximately 0.7776. This gas-phase signal is used to study the overall adsorption-desorption properties of the zeolites in the temperature range 150 K less than or approximately T less than or approximately 300 K. At lower temperatures the probe molecules are adsorbed at the Lewis acid sites inside the nanoporous materials and produce an intensive spectrum at T less than or approximately 110 K. But at intermediate temperatures 110 K less than or approximately T less than or approximately 150 K the NO molecules are adsorbed only for a few hundred picoseconds because the lifetime of the adsorption complexes is limited by the beginning desorption processes. The decreasing lifetime of the adsorption complex with rising temperature results in an increasing homogeneous line broadening of their EPR signals. An analysis of the line-broadening effects provides an opportunity for determining the specific desorption energies E(A)(H-ZSM-5)=(20.2+/-7.3) kJ/mol, E(A)(Na-ZSM-5)=(4.1+/-1.5) kJ/mol, and E(A)(Na-A)=(7.1+/-2.1) kJ/mol for NO probe molecules at sodium cations and aluminum defect centers just below the desorption temperature.     

多价抗衡离子诱导聚甲基丙烯酸N,N-二甲基氨基乙酯(PDMAEMA)刷构象转变的UCST行为

本文应用分子场理论,研究pH、[Fe(CN)_6]~(3-)诱导聚甲基丙烯酸N,N-二甲基氨基乙酯(PDMAEMA)刷的上临界溶解温度(UCST)构象转变与结构特性.理论模型考虑p H和[Fe(CN)_6]~(3-)对PDMAEMA刷体系的静电调控作用.研究发现,在不同[Fe(CN)_6]~(3-)浓度、不同p H条件下,PDMAEMA刷呈现了UCST构象转变行为.由于p H调节PDMAEMA单体质子化,[Fe(CN)_6]~(3-)通过与PDMAEMA带正电荷的单体结合,形成了在PDMAEMA链内以[Fe(CN)_6]~(3-)为中介的带电单体间的静电吸引结合.随着温度升高,[Fe(CN)_6]~(3-)与PDMAEMA带正电荷的单体结合被破坏,[Fe(CN)_6]~(3-)在链内凝聚导致的静电屏蔽效应减弱,PDMAEMA链内带电单体间的静电排斥增强,PDMAEMA刷的构象呈现了从塌缩到溶胀的UCST转变行为,并且在较高[Fe(CN)_6]~(3-)浓度条件下,PDMAEMA刷构象转变的UCST增高.在较低p H值条件下,较多的PDMAEMA单体被质子化,[Fe(CN)_6]~(3-)与PDMAEMA带正电单体的结合增强,PDMAEMA刷构象转变的UCST增大.基于pH和[Fe(CN)_6]~(3-)对PDMAEMA刷体系中的静电调控效应,可以预言,在较小p H和较大[Fe(CN)_6]~(3-)浓度条件下,PDMAEMA链在垂直培基表面沿着链方向形成结节状结构.这是由于以[Fe(CN)_6]~(3-)为中介的链内带电单体间的静电吸引作用增强,导致临近单体间汇聚结节.我们的理论结果符合实验观测,由此表明,pH调节PDMAEMA单体的带电状态,以及[Fe(CN)_6]~(3-)在PDMAEMA链内凝聚导致的静电屏蔽效应,决定着PDMAEMA刷的UCST构象转变和结构特性.     

Thermal expansion of benzene at high pressure determined by a calorimetric method,its behavior near melting

The piezothermal method was used to determine the thermal expansivity of benzene up to 4 kbar along 9 isothermal paths, in the range 250–350 K.It is shown that, in the solid phases, the thermal expansion is a function of volume only. This property which appears to be typical of the solid phase still holds in the premelting region. This suggests that premelting is concerned only with the evolution of the solid phase.     

Study of the mobility,surface area,and sintering behavior of agglomerates in the transition regime by tandem differential mobility analysis

The surface area of nanosized agglomerates is of great importance as the reactivity and health effects of such particles are highly dependent on surface area. Changes in surface area through sintering during nanoparticle synthesis processes are also of interest for precision control of synthesised particles. Unfortunately, information on particle surface area and surface area dynamics is not readily obtainable through traditional particle mobility sizing techniques. In this study, we have experimentally determined the mobility diameter of transition regime agglomerates with 3, 4, and 5 primary particles. Agglomerates were produced by spray drying well-characterised polystyrene latex particles with diameters of 55, 67, 76, and 99 nm. Tandem differential mobility analysis was used to determine agglomerate mobility diameter by selecting monodisperse agglomerates with the same number of primary particles in the first DMA, and subsequently completely sintering the agglomerates in a furnace aerosol reactor. The size distribution of the completely sintered particles was measured by an SMPS system, which allowed for the determination of the number of primary particles in the agglomerates. A simple power law regression was used to express mobility diameter as a function of primary particle size and the number of primary particles, and had an excellent correlation (R² = 0.9971) with the experimental data. A scaling exponent was determined from the experimental data to relate measured mobility diameter to surface area for agglomerates. Using this relationship, the sintering characteristics of agglomerates were also examined for varying furnace temperatures and residence times. The sintering data agreed well with the geometric sintering model (GSM) model proposed by Cho & Biswas (2006a) as well as with the model proposed Koch & Friedlander (1990) for sintering by viscous flow.     

Demonstration of PMD compensation by using a DSP-Based OPMDC prototype in a 43-Gb/s RZ-DQPSK, 1200 km DWDM transmission

This paper reports the DSP-based prototype compensator we have made to compensate the polarization mode dispersion (PMD) in fibers. It was tested in one channel of a 40 × 43-Gb/s DWDM DQPSK system, which is the commercial product line, either in the back-to-back case by using a PMD emulator, or in a 1200-km transmission testbed. The prototype showed a good performance under the tests of fast SOP and PSP rotation, DGD jump variation, and moderate knock on the testbed in a period as long as 12 h.     

Studies on ionic solvation behavior of ionic liquid (tetrabutylphosphonium tetrafluoroborate) in some liquid media by volumetric,viscometric, and acoustic measurements

Physicochemical properties such as density (ρ), viscosity (η), ultrasonic speed (u) of ionic liquid tetrabutylphosphonium tetrafluoroborate in acetonitrile, tetrahydrofuran, 1,3-dioxolane, and their binaries have been studied over the entire range of composition at 298.15°K. Apparent molar volumes (? _V ) and viscosity B-coefficients supplemented with the data of densities and viscosities, respectively, have been interpreted in terms of ion–solvent interactions. The limiting apparent molar volumes (? _V ⁰ ), experimental slopes (S _V ^? ) derived from the Masson equation, and viscosity A and B-coefficients analyzed by the Jones–Dole equation have also been interpreted. The adiabatic compressibility (β) has been evaluated using the ultrasonic speed (u) values. Thereafter, limiting apparent molar adiabatic compressibilities (? _K ⁰  ) have been evaluated and discussed for the same.

Bragg grating dispersion compensation: comments on ‘UV-written in-fibre Bragg gratings’ by I. Bennion,J. A. R. Williams,L. Zhang,K. Sugden,N. J. Doran

The design criteria for fibre Bragg grating dispersion compensation are discussed, and the use of local grating dispersion d2 φ/d2 by Bennion et al. [1] is shown to be overly restrictive. A more useful measure of compensation degradation is phase deviation from the desired quadratic frequency dependence. This revised version was published online in November 2006 with corrections to the Cover Date.