Linear intermode conversion of electromagnetic wave energy in a magnetically soft gyrotropic material

The excitation of axial radio-frequency (rf) magnetic induction by an axial rf current is observed in a conductor with circular magnetic anisotropy when a weak magnetizing field is applied. The conductor is an amorphous cobalt-based wire, which exhibits azimuthal magnetic anisotropy. It serves as the central conductor in a coaxial line. The axial rf magnetic induction produces an emf in an induction coil coaxial to the conductor. The induction coil is part of a matched receiving circuit. The power conversion coefficient is as high as tens of percent. The measurements demonstrate the high sensitivity of the conversion coefficient to an external field. The theory of ferromagnetic resonance faithfully describes the results of the observations. Zh. Tekh. Fiz. 69, 58–63 (March 1999)     

Optical frequency conversion by a rotating molecular wave plate

We demonstrate efficient four-wave mixing in low-pressure molecular deuterium without the need for phase matching. We use two laser fields with opposite circular polarizations to produce a strong excitation of a rovibrational transition at a frequency of 3167 cm(-1) . The coherent molecular motion, in turn, modulates a third laser field (also circularly polarized) and results in highly efficient single-sideband conversion.     

Effect of the polarization of the electromagnetic wave on wave energy absorption caused by the linear transformation of waves

The paper deals with the experimental verification of the effect of the polarization of the electromagnetic wave on the linear transformation of waves in an inhomogeneous magnetoactive plasma. Experiments were carried out in magnetic field satisfying condition _ce/>1, where _ce, are the electron cyclotron frequency and the frequency of the electromagnetic wave. The expressive dependence of the electromagnetic wave energy absorption on its polarization found experimentally is in excellent agreement with the theory.The authors wish to thank the director of the Institute of Plasma Physics Dr. J. Váa for his interest in this work and to Drs. R. Klíma, V. Kopecký and J. atlov for many valuable discussions and comments.     

Extracting microwave energy from a cavity by mode conversion at a coupling window

A study is made of the production of high power nanosecond rf pulses by extracting microwave energy from an oversized cavity by means of conversion, at a coupling window, of the high-Q working mode to an auxiliary mode which is strongly coupled to an external load. It is shown that microwave rf pulse compressors with copper storage cavities and energy extraction by mode conversion at a coupling window can provide gains of 5–13 dB with output signal durations of 20–150 ns and peak powers of 5–10 MW in the 3-cm band and 50–100 MW in the 10-cm band. Rf pulses lasting 30 ns with peak powers of 0.5 MW have been obtained experimentally at a frequency of 9.4 GHz with a gain of 9 dB. Zh. Tekh. Fiz. 68, 92–96 (July 1998)     

State-of-the-art surface acoustic wave linear motor and its future applications

Two merits of the surface acoustic wave (SAW) device are its high energy density and small size. However, the driving frequency is around 10 MHz or higher. In spite of the difficulties involved with high frequency, the high energy density is attractive for actuator applications. The SAW linear motor's no load speed and maximum output force were 1.1 m/s and 3.5 N using a silicon slider. The silicon slider dimensions were 4 x 4 x 0.3 mm3. We made a lot of 30 microns diameter projections on the silicon surface. The acceleration was 1000 m/s2. The SAW motor is expected to be a high speed, quick response, high resolution microactuator, and much more. High driving voltage was a problem. Our newly designed electrode proved that the driving voltage was reduced to less than 10 V to excite the traveling wave. For actual applications, the SAW device will be placed in a slider. This design is effective in terms of performance and cost. The nanotribology of the SAW motor is also an important and interesting subject.     

具有聚电解质层圆柱形纳米通道中的电动能量转换效率

柔性纳米通道是在刚性纳米通道壁面处添加一层带某种电荷的聚电解质层或固定电荷层的纳米通道. 本文在低Zeta势近似下, 通过解析求解电势满足的线性化Poisson-Boltzmann方程和速度满足的Cauchy动量方程, 给出了圆柱形柔性纳米通道中电解质溶液的流向势和电动能量转换效率的解析解. 在表面Zeta势取值相同, 且管径相同(聚电解质层厚度远小于管径前提下)的情形下, 将圆柱形柔性纳米通道和刚性纳米通道中电解质溶液的流向势和电动转换效率进行了比较. 结果表明, 柔性纳米通道中的流向势和转换效率明显高于刚性通道中的流向势和转换效率. 在本文选取的参数范围内, 柔性纳米通道中的电动转换效率比刚性纳米通道中的转换效率提高1.5-3倍.     

A simplified model of the thermohydraulic behaviour of a linear collector network for the conversion of the solar energy

Summary A model has been set up to describe the thermohydraulic behaviour of a solar power plant in a quasi-steady-state approach; the simplifying assumptions have been proved to be correct. The model has been solved to determine the optimum sizes of the thermal accumulator.

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Riassunto è stato messo a punto un modello quasi stazionario per la descrizione del comportamento termoidraulico di un impianto per la conversione dell'energia solare. è stata verificata la correttezza delle ipotesi semplificative. Il modello è stato integrato per determinare le dimensioni ottimali dell'accumulatore termico.

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Резюме Предлагается модель для описания термогидравлического поведения солнечной силовой установки в квазистационарном приближении. Проведена проверка упрощающих предположений, лежащих в основе модели. Решение этой модели позволяет определить оптимальные размеры термического аккумулятора.

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Work performed in the framework of activities of P.F.E.-CNR.     

Heating by an electron Bernstein wave in a spherical tokamak plasma via mode conversion

The first successful high power heating of a high dielectric constant spherical tokamak plasma by an electron Bernstein wave (EBW) is reported. An EBW was excited by mode conversion (MC) of an mode cyclotron wave injected from the low magnetic field side of the TST-2 spherical tokamak. Evidence of electron heating was observed as increases in the stored energy and soft x-ray emission. The increased emission was concentrated in the plasma core region. A heating efficiency of over 50% was achieved, when the density gradient in the MC region was sufficiently steep.     

How to lasso a plane gravitational wave

Beginning with the stress-energy tensor of an elastic string this paper derives a relativistic string and its form in a parallel transported Fermi frame including its reduction to a Cosserat string in the Newtonian limit. In a Fermi frame gravitational curvature is seen to induce three dominant relative acceleration terms dependent on: position, velocity and position, strain and position, respectively. An example of a string arranged in an axially flowing ring (a lasso) is shown to have a set of natural frequencies that can be parametrically excited by a monochromatic plane gravitational wave. The lasso also exhibits, in common with spinning particles, oscillations about geodesic motion in proportion to spin magnitude and wave amplitude when the spin axis lies in the gravitational wave front.     

Allotropic conversion of carbon-related films by using energy beams

Energy beams, such as ion and laser beams, were employed to convert carbon allotropes into other ones at a specified position because these energy sources can be controlled precisely in time and space. The ion beam deposition technique employing mass-separated ions proved effective in studying the nucleation process by changing several growth parameters (ion species, incident energies, and substrate temperatures). Immersed nanosized diamonds were found in an sp ³-rich amorphous film prepared with 100-eV ¹²C⁺ ions at room temperature. Surrounding these nanodiamonds, regularly arrayed small bumps, “petals,” were formed around the periphery of bald circles upon cooling. Ar-ion laser illumination is effective in designing the array of high luminescent points on a C₆₀ film by careful control of the laser power, and the combination of a micro-Raman spectrometer with a piezoscanning system provides one with a tool for 2-dimensional processing of photosensitive materials. Simultaneous bombardment during C₆₀ evaporation results in an interesting pattern formation specific to the simultaneous treatment. The dependence of the surface nanoscale pattern on the ion energy and the substrate temperatures provides one with a new tool for designing nanoscale functional materials. As an extreme, the appearance of hexagonal diamonds was detected with disordered carbon and graphite under the condition of there being a high ratio between the Ne ion beam and the C₆₀ thermal beam.     

Surface-to-volume wave conversion in shallow water with a corrugated bottom

Acoustic transmission between points onshore or in very shallow water and points in deep water is strongly influenced by the shear rigidity of marine sediments, which control the parameters and the very existence of seismoacoustic surface waves. Previously, it was found that coupling between acoustic modes and the seismoacoustic surface waves is normally weak, although not negligible in the case of a gently sloping seafloor and soft sediments. In this paper, the previous work is extended by accounting for the small-scale roughness of the seafloor. The significant role of roughness in coupling between volume and surface waves is demonstrated. The combined effect of bottom topography, roughness, and wave attenuation in soft marine sediments on the sound propagation between points in shallow and deep water is discussed. Published in Russian in Akusticheskiĭ Zhurnal, 2008, Vol. 54, No. 3, pp. 400–407. The article was translated by the author.     

Dzyaloshinskii–Moriya interaction: How to measure its sign in weak ferromagnets?

Three experimental techniques sensitive to the sign of the Dzyaloshinskii-Moriya interaction are discussed: neutron diffraction, Mössbauer γ-ray diffraction, and resonant x-ray scattering. Classical examples of hematite (α-Fe₂O₃) and MnCO₃ crystals are considered in detail.     

Generation of a single normal wave by a vertical linear array in the water layer

The possibility of the acoustic energy emission into a single normal wave by a vertical linear array in a homogeneous water layer is considered for the case of the array aperture being smaller than the layer thickness.     

Frequency intermittency and energy pumping by linear attachments

The present paper considers the problem of realizing an effective targeted energy pumping from a linear oscillator to a set of ungrounded linear resonators attached to it. Theoretical as well as numerical results demonstrate the efficacy of using a complex attachment as a passive absorber of broadband energy injected into the primary structure. The paper unveils also the existence of an instantaneous frequency associated with the master response characterized by intermittency: a rather surprising result for a linear autonomous system. Comparison with nonlinear energy sinks demonstrates that the two systems have some analogies in this respect and that the linear complex attachment is a very efficient energy trap.     

Thermal regimes in a primary fluid heated by solar energy in a linear collector

Summary The steady-state heat transfer equation has been solved for the determination of temperature profiles in a diathermic oil flowing through a linear boiler placed on the focal line of cylindrical parabolic solar concentrators. Finite-difference methods have been employed to solve the equation, by assuming Nikuradse velocity profiles and available experimental data to supply boundary conditions and to estimate equation parameters. A set of solutions for several physical and geometrical situations is shown and discussed in order to give useful indications on the design of solar power plant.

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Riassunto Si risolve l'equazione del calore in regime stazionario per la determinazione dei profili di temperatura in un olio diatermico che scorre in una caldaia lineare posta sull'asse focale di un concentratore cilindrico parabolico solare. Per risolvere l'equazione si sono impiegati metodi alle differenze finite, assumendo profili di velocità di Nikuradse e i dati sperimentali disponibili per fornire le condizioni al contorno e per stimare i parametri dell'equazione. Si mostra e si discute una serie di soluzioni per parecchie situazioni fisiche e geometriche, così da fornire utili indicazioni sul progetto di una centrale solare.

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Резюме Решаются уравнения сохранения энергии для определения переходного поведения солнечной силовой установки. Используя типичные параметры установки и имеющиеся экспериментальные данные, указанные уравнения решаются с помощью метода конечных разностей. Рассматриваются различные физические и геометрические конфнгурации. Анализируются полученные результаты и делаются указания, касающиеся проекта солнечной силовой установки.

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To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

利用电磁左手材料调控电磁波的偏振反转

通过各向异性的电磁介质板的反射,电磁波的偏振状态可以被任意地调节,在特定的条件下甚至可以完全反转.本文在微波测量系统的基础上设计了一个测量偏振反转的实验,在特定的频率观测到了偏振反转的极大值.另外还提出了一个提高偏振反转率的方案并通过实验验证了其有效性.通过转移矩阵方法计算得到了偏振反转的理论结果并与实验结果进行了对比.     

Approximation of the three-dimensional linear water wave equations by a set of two-dimensional equations

Summary It is shown how the linear three-dimensional equations for surface water waves over a bottom of slowly varying depth may be approximated by a set of two-dimensional equations, the first of which is a simple extension of the equation derived by Berkhoff. Although the equation coefficients and the set structure are not simple, however this kind of approach does provide a new tool for the numerical solution of certain three-dimensional problems, for which, at present, other alternative approaches do not exist.

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Riassunto Si mostra come le equazioni lineari tridimensionali per onde marine di superficie su di un fondo lentamente variabile possano essere approssimate da un sistema di equazioni bidimensionali, di cui la prima è una semplice estensione dell’equazione derivata da Berkhoff. Benché i coefficienti delle, equazioni e la struttura del sistema non siano semplici, pure questo tipo di approccio rappresenta uno strumento nuovo per la soluzione di certi problemi tridimensionali, per i quali, al momento, non esistono altri approcci alternativi.

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Резюме Показывается, как линейные трехмерные уравнения для поверхностных водяных волн могут быть аппроксимированы системой двумерных уравнений, первое из которых представляет простое обобщение уравнения, выведенного ъеркоффом. Хотя коэффициенты уравнения и структура системы не являются простыми, однако этот подход дает новый метод для численного решения некоторых трехмерных проблем, для которых в настоящее время не существует друтих альтернативных приближений.