179 research outputs found
High Energy High Repetition Rate P-P Lasers.
A technique for obtaining of the repetitively pulsed operating regime in high-power wide-aperture lasers is proposed and experimentally realized. In this regime, the laser emits a train of pulses with duration of 100–150 ns and a pulse repetition rate of several tens of kilohertz. The main properties of the pulsed regime are theoretically analyzed and the proposed technique is tested in detail employing a test-bench gas-dynamic laser. The results of the test confirmed the conclusions of the theoretical analysis. The possibility of a repetitively pulsed regime in high-power wide-aperture lasers realization without significant reduction in the average output power is experimentally demonstrated
The ethical paradox and the problem of universal moral groundings
В статье рассмотрена этическая сторона этнического парадокса современности. Культурная граница рассматривается как область сопряжения универсальной формы и конкретно-исторического содержания морали.The article considers the ethics of ethnic paradox of modernity. Cultural boundary is considered as an area of conjugation of the universal form and the particular content of morality.Статья подготовлена при поддержке РГНФ, проект 14-26-20001 а(м) «Самопонимание этнокультурной идентичности в титульном этносе и сопряженной диаспоре (на примере исследования русской и армянской молодежи Армении и России)
Multiply Charged Ions and Their Effective Applications
The creation of high-power lasers has opened a new era in the development of basic research and cutting-edge technologies in various fields of practical application. All this is, first of all, due to the unique properties of laser sources of high-power coherent radiation. They include: a) high monochromaticity (i.e. a small width of the emission line), which offers new opportunities in high-resolution spectroscopy; b) high spatial and temporal coherence (i.e. the occurrence of light oscillations in a coordinated manner, resulting thereby in a distinct interference pattern), which gives a strong impetus to the development of holography and optical information processing methods; c) a relatively high specific energy that can be emitted by the laser, d) a possibility of varying the length of time during which the energy stored in the laser can be emitted in a wide range of durations: from continuous to femtoseconds; e) a possibility of variations in the temporal structure of radiation from tens of Hz up to tens of GHz; and f) a small divergence, which enables tight focusing. Due to these properties, the laser power density, which can affect the substance, reaches a giant value on the order of 1020 W/cm–2. Consequently, it is possible to expose a substance to radiation whose power density exceeds all known today values characterizing natural and artificial sources. This fantastic opportunity has been thoroughly investigated in the recent decades by scientists from different countries. Clearly, by gradually increasing the laser energy and reducing the length of time during which that energy is emitted, it is possible to observe several stages of an interaction like this
ПРОВОДЯЩИЙ КАНАЛ ДЛЯ ТРАНСМИССИИ ЭНЕРГИИ
Laser spark obtained by using a conical optics is much more appropriate to form conducting channels in atmosphere. Only two types of lasers are actively considered to be used in forming high-conductivity channels in atmosphere, controlled by laser spark: pulsed sub-microsecond gas and chemical lasers (CO2, DF) and short pulse solid-state and UV lasers. Main advantage of short pulse lasers is their ability in forming of super long ionized channels with a characteristic diameter of ~100 µ in atmosphere along the beam propagation direction. At estimated electron densities below 10 ⋅ 16 cm–3 in these filaments and laser wavelengths in the range of 0,5–1,0 mm, the plasma barely absorbs laser radiation. In this case, the length of the track composed of many filaments is determined by the laser intensity and may reach many kilometers at a femtosecond pulse energy of ~100 mJ. However, these lasers could not be used to form high-conductivity long channels in atmosphere. The ohmic resistance of this type a conducting channels turned out to be very high, and the gas in the channels could not be strongly heated (< 1 J). An electric breakdown controlled by radiation of femtosecond solid-state laser was implemented in only at a length of 3 m with a voltage of 2 MV across the discharge gap (670 kV/m).Not so long ago scientific group from P. N. Lebedev has improved that result, the discharge gap – 1 m had been broken under KrF laser irradiation when switching high-voltage (up to 390 kV/m) electric discharge by 100-ns UV pulses. Our previous result – 16 m long conducting channel controlled by a laser spark at the voltage – 3 MV – was obtained more than 20 years ago in Russia and Japan by using pulsed CO2 laser with energy – 0,5 kJ. An average electric field strength was < 190 kV/m. It is still too much for efficient applications.Лазерный разряд, полученный при помощи конической оптики, является наиболее подходящим для образования проводящих каналов в атмосфере. Чаще всего рассматриваются только два типа лазеров для формирования высокопроводящих каналов в атмосфере, управляемых лазерным разрядом: импульсные субмикросекундные газовохимический лазеры (CO2, DF) и короткоимпульсные твердотельные ультрафиолетовые лазеры.Основное преимущество короткоимпульсного лазера заключается в его способности формировать сверхдлинные ионизированные каналы с характерным диаметром ~100 мкм в атмосфере по направлению распространения луча. При расчётной плотности электронов ниже 10 ⋅ 16 см–3 в этих нитях при длине волны лазера в диапазоне 0,5–1,0 мм плазма слабо абсорбирует лазерное излучение. В данном случае длина пути, образуемого многими нитями и определяемая интенсивностью лазерного излучения, может исчисляться многими километрами при энергии фемтосекундного импульса, равной ~100 мДж. Однако такие лазеры не могут применяться для создания высокопроводимых длинных каналов в атмосфере. Активное сопротивление данного типа проводящих каналов оказывается очень высоким, и невозможно добиться сильного нагревания газа в этих каналах (<1 Дж). Электрический пробой, управляемый излучением фемтосекундного твердотельного лазера, обеспечивается только при длине 3 м и напряжении 2 MВ в искровом промежутке (670 кВ/м).Недавно научная группа из института имени П. Н. Лебедева улучшила этот результат. При этом искровой промежуток 1 м был пробит лазерным излучением KrF посредством переключения высоковольтного (до 390 кВ/м) энергетического разряда УФ импульсами длительностью 100 наносекунд. Наш предыдущий результат – это проводящий канал длиной в 16 м, контролируемый лазерным разрядом при напряжении 3 MВ, был получен более 20 лет тому назад в России и в Японии с использованием импульсного CO2-лазера с энергией, равной 0,5 кДж. Средняя напряженность электрического поля составляла < 190 кВ/м. Таким образом, предстоит еще много сделать, чтобы добиться эффективного применения
Model studies of THz-range generation by down-conversion in GaSe and GaSeS crystals
Model study of not phase matched and phase matched optical rectification or down-conversion of Ti:Sapphire laser pulses at 950 nm into THz and far-IRrange in pure and S-doped GaSe single crystals is carried out. First, the ordinary and extraordinary wave dispersions of the GaSe refractive indices were measured by terahertz time-domain spectroscopy (THz-TDS). Measured data were approximated in the form of Sellmeier dispersion equations for 0.62 - 2000 [mu]m range with using available shorter wave data
РАЗРАБОТКА СТРАТЕГИИ ВЕНЧУРНОЙ ИННОВАЦИОННОЙ КОМПАНИИ
Innovative companies, venture companies included, serve as locomotives of the growth of national economics. However, they are formed and operate under conditions of uncertain external and internal environment; therefore, certain strategic issues of their development can not beaddressed proceeding from traditional methods based on cash-flow discounting models. Best venture innovative company development strategy may be worked on the basis of the strategic capabilities method in conjunction with the theory of games and the real options approach. This is an incessant innovation method that unites approaches based on external and internal environment factors.Инновационные компании, в том числе венчурные, являясь локомотивом роста современных национальных экономик, создаются и развиваются в условиях неопределенности внешней и внутренней среды. Решить целый ряд стратегических вопросов развития этих компаний традиционными методами, базирующимися на моделях дисконтирования потоков денежных средств, невозможно. Наилучшей теоретической основой построения новой концепции стратегического управления венчурной инновационной компанией является метод динамических способностей в сочетании с теорией игр и с методом реальных опционов. Этот метод, объединивший внешний подход с внутренним, представляет собой путь непрерывных инноваций
Mass Transfer Mechanism in Real Crystals by Pulsed Laser Irradiation
The dynamic processes in the surface layers of metals subjected activity of a
pulsing laser irradiation, which destroyed not the crystalline structure in
details surveyed. The procedure of calculation of a dislocation density
generated in bulk of metal during the relaxation processes and at repeated
pulse laser action is presented. The results of evaluations coincide with high
accuracy with transmission electron microscopy dates. The
dislocation-interstitial mechanism of laser-stimulated mass-transfer in real
crystals is presented on the basis of the ideas of the interaction of structure
defects in dynamically deforming medium. The good compliance of theoretical and
experimental results approves a defining role of the presented mechanism of
mass transfer at pulse laser action on metals. The possible implementation this
dislocation-interstitial mechanism of mass transfer in metals to other cases of
pulsing influences is justifiedComment: 10 pages, 2 figures, Late
On the universality of the Discrete Nonlinear Schroedinger Equation
We address the universal applicability of the discrete nonlinear Schroedinger
equation. By employing an original but general top-down/bottom-up procedure
based on symmetry analysis to the case of optical lattices, we derive the most
widely applicable and the simplest possible model, revealing that the discrete
nonlinear Schroedinger equation is ``universally'' fit to describe light
propagation even in discrete tensorial nonlinear systems and in the presence of
nonparaxial and vectorial effects.Comment: 6 Pages, to appear in Phys. Rev.
The only known cyclopygid–‘atheloptic’ trilobite fauna from North America: the upper Ordovician fauna of the Pyle Mountain Argillite and its palaeoenvironmental significance
The trilobite fauna of the upper Ordovician (middle Katian) Pyle Mountain Argillite comprises a mixture of abundant mesopelagic cyclopygids and other pelagic taxa and a benthic fauna dominated by trilobites lacking eyes. Such faunas were widespread in deep water environments around Gondwana and terranes derived from that continent throughout Ordovician time but this is the only known record of such a fauna from North America and thus from Laurentia. It probably reflects a major sea level rise (the ‘Linearis drowning events’) as does the development of coeval cyclopygid-dominated deep water trilobite faunas in terranes that were marginal to Laurentia and are now preserved in Ireland and Scotland. The Pyle Mountain Argillite trilobite fauna occurs with a deep water Foliomena brachiopod fauna and comprises 22 species. Pelagic trilobites (mostly cyclopygids) constitute 36% of the preserved sclerites, and 45% of the fauna is the remains of trilobites lacking eyes, including one new species, Dindymene whittingtoni sp. nov. Three species of cyclopygid are present, belonging in Cyclopyge, Symphysops and Microparia (Heterocyclopyge). Cyclopygids are widely thought to have been stratified in the water column in life and thus their taxonomic diversity reflects the relative depths of the sea-beds on which their remains accumulated. A tabulation of middle and upper Katian cyclopygid-bearing faunas from several palaeoplates and terranes arranged on the basis of increasing numbers of cyclopygid genera allows an assessment of the relative depth ranges of the associated benthic taxa. The Pyle Mountain Argillite fauna lies towards the deeper end of this depth spectrum
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