An interesting new record of the almost unknown brachypterous phaneropterine katydid Xenicola dohrni (Orthoptera: Tettigoniidae) from Argentina, and its high-ultrasound male-female communication.

In this study,a wavelet decomposition based method is proposed for determining the modulation type of the incoming signal to the receiver which is one of the important problems in intelligent communication systems. In this method, it is aimed to design the transmitted signal for determining the type of Mary FSK modulated signal and to detect the energy in each frequency band by using Discrete Wavelet Transform (DWT). For this, standard deviations in the lower bands are as features. In order to evaluate the performance of the classifier, simulation studies have been performed at different signal-to-noise ratio (SNR) levels. When the results for different frequency settings, i.e. carrier frequency and frequency range, it is seen that the classifier using the K-means clustering algorithm has a higher correct classification performance than the results reported in the literature when the suitable carrier frequency and frequency range are selected.

Military communication systems have recently been developed for operation in tactical areas using carrier telephone channels on spiral-4 cable. This is part of an extensive program intended to increase the flexibility of the military communications network. Good transmission performance under all environmental conditions has been stressed. These projects make use of a new type of spiral-4 cable. The cable is to be laid in 1/4-mile lengths with or without loading coils at the junetions. A 4-channel telephone system using the carrier frequency range from 4 to 20 kc has been designed for operation on the loaded cable for distances of 100 miles with repeaters at about 25-mile intervals. A 12-channel telephone system using the carrier frequency range from 12 to 68 kc has also been designed for operation on the nonloaded cable for distances of 200 miles with main repeaters at about 40-mile intervals and with "power-over-the-cable" repeaters at about 6-mile intervals. These new lowloss channels make possible the use of multilink connections and the ultimate establishment of a comprehensive military communication network. The circuits have been developed for great reliability, with simple operating procedures, automatic alarms, good maintenance practices, and great flexibility as to usage.

Military communication systems have recently been developed for operation in tactical areas using carrier telephone channels on spiral-4 cable. This is part of an extensive program intended to increase the flexibility of the military communications network. Good transmission performance under all environmental conditions has been stressed. These projects make use of a new type of spiral-4 cable. The cable is to be laid in 1/4-mile lengths with or without loading coils at the junctions. A 4-channel telephone system using the carrier frequency range from 4 to 20 kc has been designed for operation on the loaded cable for distances of 100 miles with repeaters at about 25-mile intervals. A 12-channel telephone system using the carrier frequency range from 12 to 68 kc has also been designed for operation on the nonloaded cable for distances of 200 miles with main repeaters at about 40-mile intervals and with ?power-over-the-cable? repeaters at about 6-mile intervals. These new low-loss channels make possible the use of multilink connections and the ultimate establishment of a comprehensive military communication network. The circuits have been developed for great reliability, with simple operating procedures, automatic alarms, good maintenance practices, and great flexibility as to usage.

Terrestrial communication systems require reliable wireless links for mobile to base connectivity beyond the line of sight where both ends of the link have antennas in close proximity to the ground. Frequency selection will partially determine the performance of a mobile terrestrial communications system in an intense multipath environment. This paper is part of an experimental effort to examine many aspects of RF propagation and radio hardware issues and focuses on the effects of rolling terrain, trees, and buildings on radio performance over a wide range of unmodulated carrier frequencies. Experimental data were collected using the unmanned ground vehicle technology test bed (UGV TTB) and other transmitter/receiver test fixtures. Experimental data were analyzed to determine the sensitivities of propagation mechanisms to carrier frequency. The experimental/analytical results along with bandwidth requirements and legal constraints indicate suitable ranges of carrier frequencies for terrestrial communication systems.

This paper presents an experimental procedure to determine the acoustic and vibration behavior of an inverter-fed induction motor based on measurements of the current spectrum, acoustic noise spectrum, overall noise in dB, and overall A-weighted noise in dBA. Measurements are carried out on space-vector modulated 8-hp and 3-hp induction motor drives over a range of carrier frequencies at different modulation frequencies. The experimental data help to distinguish between regions of high and low acoustic noise levels. The measurements also bring out the impact of carrier frequency on the acoustic noise. The sensitivity of the overall noise to carrier frequency is indicative of the relative dominance of the high-frequency electromagnetic noise over mechanical and aerodynamic components of noise. Based on the measured current and acoustic noise spectra, the ratio of dynamic deflection on the stator surface to the product of fundamental and harmonic current amplitudes is obtained at each operating point. The variation of this ratio of deflection to current product with carrier frequency indicates the resonant frequency clearly and also gives a measure of the amplification of vibration at frequencies close to the resonant frequency. This ratio is useful to predict the magnitude of acoustic noise corresponding to significant time-harmonic currents flowing in the stator winding.

CAPTAIN P. P. ECKERSLEY addressed the British Institute of Radio Engineers at its meeting on April 18 on “The Future of Radio Communication”. He dealt at some length with the limitation of communication channels available, for the whole of Europe for example, without mutual interference, and explained that, although the number of possible frequencies available might be infinite, the useful range is not. He said that the service range of transmission might be said to be proportional to its wavelength, so that very high frequency transmissions have a very small reliable service area. If the band width occupied by a transmission could be reduced, the number of channels could be increased in the same proportion. Examples of narrow band transmissions cited included single sideband, suppressed carrier (for wired transmissions) and restricted modulation frequencies, and he mentioned an American invention by which an intelligible modulation range of 200-3,000 c./s. can be transformed at the transmitter to a range of from zero to a few hundred cycles a second, thus reducing the sideband frequency width to be accommodated, and providing further channels in a given range of carrier frequencies ; the signal is retransformed at the receiver. Captain Eckersley still believes, in spite of theories to the contrary, that sidebands were real.

1. Phonotaxis was investigated in two cicada species: Cystosoma saundersii and Cyclochila australasiae. Females were placed on a stick within a flight cage and presented with artificially generated calling songs. These model calling songs had a range of carrier frequencies, but their temporal parameters were similar to those of the natural calling song. They were broadcast at intensities 30 to 40 dB above the physiological threshold for each frequency. 2. Phonotaxis of female Cystosoma saundersii was restricted to a 45 minute period just after sunset, and was highly directional. Between 60 and 70% of flights made during trials in which a model calling song was broadcast were directed towards the loudspeaker at both frequencies tested. 3. Phonotaxis of female Cyclochila australasiae occurred throughout the evening, and showed no directional preference toward the loudspeaker. The mean number of flights per trial period was significantly greater in trials during which a model calling song was broadcast than in control trials during which no model calling song was broadcast. There was no significant difference in the mean number of flights per trial with different carrier frequencies. 4. In female cicadas, acoustic signals of the males are preferentially graded by the tuned auditory system; phonotactic decisions are then made on the basis of relative intensity without active discrimination between frequencies.

Variable carrier single rate deadbeat control method for low carrier frequency was proposed. In the large capacity inverter system, the carrier frequency range is limited to relatively lower frequency range, the trade off between the control accuracy and the efficiency should be considered. Digital hysteresis control was applied to the inductor current, suitable carrier frequency was adopted in every carrier period, the control accuracy could kept in the tolerable range with low carrier frequency. 2.4MHz multi-sampling method and space vector modulation was also applied to improve the characteristics.

The properties of some ferrites and other magnetic materials in the carrier frequency range are compared and an indication is given of the field of application of ferrites.In transformer design, insertion loss and return loss are examined in relation to the reluctivity of core materials, and it is shown that ferrites have advantages in the frequency range above 30kc/s. Examples are given of a ferrite-cored transformer in the input network of a 0·3–12Mc/s coaxial-line amplifier, a hybrid coil for the measurement of return loss in the range 1–100Mc/s, and a 5kW transformer for 4–28Mc/s. The design of inductors for carrier frequencies falls into three main classes. In one class very high stability may be obtained with high Q-factor. In the second class, very high Q-factor is combined with high stability. In the third class adequate performance is accompanied by very small size.

Using the normal waves method allows us to analyze decameter radio paths quite effectively. The practical application of the algorithm of HF propagation forecast developed in ISTP RAS demonstrate the effectiveness of that approach. As a part of the normal waves method, the electromagnetic field in Earth-ionosphere waveguide is represented as infinite series of the eigenfunctions of the radial operator. However, we use only the so-called group of weak decaying waves for numerical calculations. Using this approach leads to necessity to use carrier frequencies of a signal higher than a minimal critical frequency along a propagation path. Thus, there are always a number of normal wave when the signal cease to reflect off the ionosphere. The number of normal waves in the weak decaying waves group becomes infinite if the critical frequency is lesser than the critical frequency of the path. In this case, the real parts of the spectral parameter form a sequence converging to zero. It corresponds to the physical presence of the propagation angle close to the vertical. The imaginary parts of the spectral parameter increase with the number of normal wave due to an ionosphere absorption rather than propagation through the ionosphere barrier. In this case, the previously used algorithm is not applicable. This paper presents a modification of the normal waves method which allows one to solve problems of the spectrum calculation of the radial operator. A numerical algorithm of a field calculation for carrier frequencies in range 2-30 MHz is developed. To take into account the effect of ionospheric irregularities on the propagation characteristics of radio waves in the Earth-ionosphere waveguide we use the method of cross-sections for the construction of the basis transformation matrix from one waveguide section to the other. We show that it is better to use the numerical value of the spectral parameter instead of the previously used normal wave number as the adiabatic invariant.

Classical studies of area summation measure contrast detection thresholds as a function of grating diameter. Unfortunately, (i) this approach is compromised by retinal inhomogeneity and (ii) it potentially confounds summation of signal with summation of internal noise. The Swiss cheese stimulus of T. S. Meese and R. J. Summers (2007) and the closely related Battenberg stimulus of T. S. Meese (2010) were designed to avoid these problems by keeping target diameter constant and modulating interdigitated checks of first-order carrier contrast within the stimulus region. This approach has revealed a contrast integration process with greater potency than the classical model of spatial probability summation. Here, we used Swiss cheese stimuli to investigate the spatial limits of contrast integration over a range of carrier frequencies (1-16 c/deg) and raised plaid modulator frequencies (0.25-32 cycles/check). Subthreshold summation for interdigitated carrier pairs remained strong (∼4 to 6 dB) up to 4 to 8 cycles/check. Our computational analysis of these results implied linear signal combination (following square-law transduction) over either (i) 12 carrier cycles or more or (ii) 1.27 deg or more. Our model has three stages of summation: short-range summation within linear receptive fields, medium-range integration to compute contrast energy for multiple patches of the image, and long-range pooling of the contrast integrators by probability summation. Our analysis legitimizes the inclusion of widespread integration of signal (and noise) within hierarchical image processing models. It also confirms the individual differences in the spatial extent of integration that emerge from our approach.

Characterization and calculation of losses in soft magnetic composites for motors with SVPWM excitation

A is generated by cross-correlating local copies of a global positioning system (GPS) signal with an ocean-reflected GPS signal, over a range of carrier frequencies and code delays. The shape of this waveform can be inverted to obtain estimates of the ocean surface roughness. To assess the accuracy of these retrievals, a stochastic model for the waveform time series measurements was developed in a previous publication. In this letter, this model is validated by comparing the predicted autocorrelation function of the waveform against the autocorrelation computed from experimental waveforms collected from an airborne receiver. A 1-ms coherent integration time was used at first. Then, blocks of these measurements were concatenated to produce equivalent integration times of up to 5 ms to compare the dependence of model predictions on integration time. Correlation time was estimated by fitting a model Gaussian function to the magnitude or the real part of the autocorrelation function. The magnitude and phase of the complex autocorrelation function from the model were also studied to show the location of the first null, and better explain cases in which the Gaussian function did not fit well. The autocorrelation is found to be weakly dependent upon the surface roughness, over a range of moderate wind speeds.

The study of intramolecular bifurcational dynamics of photoisomerization at an irradiation of a molecule by weak and enough long (much more in comparison with the period of considered vibrations of in the exited resonant electronic state of a molecule) light pulses is given. The dynamics is described using the results of the numerical solution of self-consistent Schrodinger equations for amplitudes of electronic states of molecule and Newton equation for isomerization coordinate. The examples of the and bifurcations of choice of one or another well of the double-well potential by isomerization oscillator are given. It is concluded that at reduction of duration of pulses of an irradiation resulting in irreversible isomerization, the range of carrier frequency without bifurcation values extends. This can be considered as the contribution to development of a general approach to assessing robustness in control of photochemical reactions

According to main challenges to aircraft protection against high power microwave (HPM), the formula of electromagnetic transmission rate and reflectivity both for the perpendicularly and parallely polarized incident field are modified and simplified, a shielded cockpit glass construction is designed by a new optimized method on genetic algorithm, and protective efficiency analysis on military aircraft’s cockpit against HPM is carried out on a virtual 3D plane, airborne equipments and pilot model with a scale of 1:1. The verification simulation tests show the optimized construction has good protective efficiency in the range of carrier frequencies between 1-20 GHz, and protective intensity does not exceed limits of relevant international standard.