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Purpose The purpose of this paper is to adapt the design-based learning (DBL) approach for entrepreneurship education. Having in mind the aim to improve the innovative thinking competence of nascent entrepreneurs that operate at the fuzzy front end of innovation, the research identifies key characteristics of the co-design-based learning (Co-DBL) approach for nurturing entrepreneurs in the digital age. Design/methodology/approach The exploratory research is based on qualitative and quantitative analysis. To get feedback and to evaluate the progress of innovative thinking competence of Co-DBL participants, the pre- and post-co-design workshop surveys were administrated. The statistical analysis of the surveys was carried out to determine the effects of the Co-DBL. Findings The research has revealed key dimensions relevant to Co-DBL in entrepreneurial learning (features of the project, facilities for project activities, features of the teaching process, features of learning context and assessment) and found the corresponding characteristics. The results of the current study show the perspective of the suggested Co-DBL approach in entrepreneurial learning to improve creativity, analyticity, intuition and flexibility of thinking of nascent entrepreneurs. Originality/value This paper presents a new look at co-design that can be applied to entrepreneurship education to enhance innovative thinking, improve the ability of nascent entrepreneurs to identify and create opportunity and to tolerate ambiguity and conditions of uncertainty in the search and development of innovative solutions.

A critical aspect of product development is inclusion of input from future users/customers. This input is invaluable for identification of innovative product features and functionality due to chaos, lack of predictability and structure that dominate at the first stage of innovative product development process, so-called Fuzzy Front End. This paper reviews the innovative product development challenges and aims to perceive how early-stage prototypes in combination with storytelling can help to better utilize user input and improve product management at the early stage of the process. We organized experiment-driven innovative product development process, immersed three cross-disciplinary product teams in design research and suggested them to experience through rapid prototyping. Guided by empirical exploratory study and statistical analysis we explore the accuracy of user input when it is provided based on different product representations (such as sketches, mock-ups and minimum feature set products) with and without storytelling.

This paper discusses the results of a study aimed at gaining a deeper understanding of how the COVID-19 pandemic has changed the Russian tourism market and how local tourism enterprises respond to challenges caused by the COVID-19 pandemic. Summarizing their experience of doing business in crisis conditions can allow a more efficient response to similar crises in the future and contribute to a more resilient tourism sector in the aftermath of the pandemic. In order to meet the research objective, we combined various sources of operational statistical information about the state of the industry with the results of a survey conducted in the Nizhny Novgorod region and in-depth interviews with representatives of tourism enterprises. We found that Russian tourism enterprises have proved to be quite resilient by looking for additional opportunities, and paying special attention to staff development and team consolidation. However, there are problems faced by local tourism enterprises in obtaining state support. Therefore, tourism enterprises that rely on themselves and innovate to create services and products adjusted to new customer needs and preferences have a better chance to survive. In particular, the wider use of digital marketing instruments helps SMEs to propose a new value for customers aligned to the new requirements and trends in tourism, such as travel security, prevailing interest in individual and short-term trips for short distances, and the sharply increased demand for domestic tourism destinations.

The new multi-frequency process, which consists of three coupled nonlinear optical interactions: two parametric down-conversions and one up-conversion, in aperiodically poled nonlinear crystal is investigated. The spatial dynamics of wave intensities is studied in detail. The possibility of secondary simpliflcation of coupled equations for correct describing the dynamics of wave interactions is demonstrated. The optimal conditions for parametrical instability of the initial stage of wave interactions are found.

The intracavity second-harmonic generation of laser radiation in an active nonlinear crystal is studied. The spatial distributions of the intensity and power of laser radiation and its second harmonic are calculated by the method of numerical simulations as functions of the parameters of the resonator, active nonlinear crystal, and pump. The analysis is performed for a periodically poled Nd:Mg:LiNbO3 crystal taking diffraction into account.

Nonclassical light generation at self-frequency halving in periodically poled active nonlinear crystals is studied. The squeezing spectra of fundamental radiation and its subharmonic are investigated for a periodically poled Nd:Mg:LiNbO3 crystal.

The results of classical and quantum studies of the laser-radiation self-frequency conversion processes in periodically poled active nonlinear crystals are overviewed. The theoretical and experimental results of studying quasi-phase-matched self-frequency doubling and summation of the laser and pump frequencies in an active nonlinear periodically poled Nd:Mg:LiNbO3 crystal are presented. The possibility of producing frequency-and polarization-entangled states and the sub-Poisson field statistics through a consecutive nonlinear optical frequency conversion in periodically poled nonlinear crystals is considered.

A quantum theory of self-convers of the lasing frequency in active nonlinear crystals placed in a cavity is developed. The generation of nonclassical (quadrature squeezed) light upon self-doubling of the laser radiation frequency is studied in detail, with no limitations on the relations between the relaxation times of the inverse population and the polarization of the medium and the lifetime of a photon in the cavity. The fluctuation spectra of the quadrature components of the fields of the laser radiation and its second harmonic are studied in dependence on the pumping parameters and the parameters of the cavity. Numerical calculations are performed for a Nd:Mg:LiNbO 3 crystal with a regular domain structure. © 2003 MAIK "Nauka/Interperiodica".

A theory is developed to describe sequential quasi-synchronous wave interactions in an active non-linear medium with a regular domain structure inside a cavity. In particular, sequential processes of quasi-synchronous third-harmonic generation and quasi-synchronous parametric amplification that occur in a Nd:Mg:LiNbO3 crystal with a regular domain structure under low-frequency pumping are analyzed. The efficiency of these nonlinear optical processes is studied as a function of both the reflection coefficient of the exit mirror and the linear loss in the medium.

Recent results in the field of three-frequency wave interaction in homogeneous and inhomogeneous (periodically poled) active nonlinear crystals with quadratic nonlinearity are reviewed. The quasiphase-matched processes of self-frequency doubling, self-frequency halving, and frequency mixing of the pump and laser radiations are studied. The consecutive quasi-phase-matched processes of the third-harmonic generation and parametric amplification with low-frequency pumping in periodically poled active nonlinear crystals are also investigated. The analysis is carried out for the case of a periodically poled Nd:Mg:LiNbO3 crystal. Perspectives of using periodically poled active nonlinear crystals in laser devices with self-frequency conversion are discussed.

The theory of intracavity quasi-phase-matched self-frequency conversion in an active nonlinear periodically poled structure is developed. The processes of quasi-phase-matched self-frequency doubling, self-halving and mixing using the pump wave in a periodically poled Nd:Mg:LiNbO{sub 3} crystal are studied. The dependences of the efficiency of nonlinear optical conversion in these processes on the reflection coefficient of the output mirror and on linear losses in the medium are investigated. (nonlinear optical phenomena)

A brief review of recent advances in the studies of two coupled three-wave nonlinear optical processes with multiple frequencies, which possess a number of special properties compared to conventional three-wave processes, is presented. The consecutive interactions of co-propagating and counter-propagating light waves in a LiNbO3 crystal with a regular domain structure are considered. The energy exchange upon consecutive interactions of the waves with frequencies ω, 2ω and 3ω is analysed. The prospects of using consecutive nonlinear optical processes in quantum electronics and nonlinear optics are discussed.

The possibility exists for improving the present experimental constraint on the tensor coupling constant in radiative pion decay by at least a factor of six. The method emphasizes relative decay probabilities rather than absolute rates.

Theoretical and experimental investigations were made of frequency sweeping in a system formed by a highly stable cw master oscillator and a multipass pulsed slab amplifier. It is shown that in a four-pass small-signal amplification system the chirp of the amplified radiation does not exceed 7.7 kHz when the energy of the pump pulses is 36 J and the duration of these pulses is 300 μs.

Quasi-phase-matched second harmonic generation at 542 nm by self-frequency doubling laser radiation at 1084 nm and quasi-phase-matched sum-frequency generation at 464 nm by summing frequencies of laser radiation and of nonabsorbed fraction of diode laser pump radiation at 810 nm are experimentally achieved. These processes are realised in a Q-switched laser based on a periodically poled active nonlinear Nd : Mg : LiNbO3 crystal.

The primary sources of the amplitude and frequency fluctuations of a technical nature in the radiation from monolithic single-frequency traveling-wave ring lasers with semiconductor pumping have been studied. The spectral characteristics of the radiation from such lasers have been studied experimentally.

Various grades of steel have been tested for wear under different abrasive conditions. For carbon steels, owing to the increase in hardness and martensite content, wear intensity from Armco Fe to steel U8 decreases by 67%. Maximum wear resistance for dispersion-hardening steels of Cr3Ni3MoV type is achieved when V C = 4 , because of the formation of vanadium carbides. The non-stable austenitic steels with an optimal amount of strain-induced martensite exhibit good wear-resistant properties.

The dependences of the lasing threshold, of the output power, of the spectrum, and of the polarisation azimuth of the radiation from a ring Nd:YAG chip laser on the azimuth of the linear polarisation of the pump radiation were observed experimentally for the first time. An attempt was made to account qualitatively for the dependence of the lasing threshold of this laser on the azimuth of the pump radiation polarisation.

The spatial coherence of the radiation emitted by a single-frequency ring Nd : YAG chip laser with a diode pumping was determined. The maximum value of the degrees coherence was 0.99994±0.00003. The factors limiting the spatial coherence of the radiation of low-power diode-pumped solid-state lasers was discussed.

The intracavity self-frequency conversion of laser radiation in active nonlinear crystal is studied. The spatial distributions of intensities and powers of laser radiation and radiation with conversed frequency are calculated by the method of numerical simulations as functions of parameters of cavity, active nonlinear crystal and pump. The analysis is performed for periodically poled Nd:Mg:LiNbO 3 crystal taking diffraction into account.

We introduce the results of the study of quasi-phase matched processes of self-frequency conversion in periodically poled active nonlinear crystals. The processes of self-frequency doubling and self-frequency summing have been experimentally realized and studied in periodically poled Nd:Mg:LiNbO 3 crystals in CW and Q-switched regimes. The theory of self-frequency conversion has developed. The results of theory are in good agreement with experiments.

A method is proposed for the description of ring cavities with a nonplanar axial contour. This method makes it possible to find the stability regions and the characteristics of a Gaussian mode with general astigmatism, which is formed in such cavities. Numerical calculations are reported of the field characteristics and stability regions of a four-mirror ring cavity with a nonplanar axial contour.

We introduce the results of the study of intracavity quasi-phase-matched three-frequency wave interactions in active nonlinear periodically poled crystals. The process of self-frequency summing in periodically poled Nd:Mg:LiNbO 3 has been studied. Quasi-phase-matched sum-frequency generation at 0.464 μm by self-frequency summing of fundamental radiation at 1.084 μm and unabsorbed part of pump radiation of diode laser at 0.810 μm in periodically poled Nd:Mg:LiNbO 3 crystal has been realized experimentally.

We present results of theoretical and experimental study of the consecutive third harmonic generation in a periodically poled bulk LiNbO/sub 3/:Y crystal. It is shown theoretically that under certain conditions for nonlinear coefficients the energy of wave with frequency /spl omega/ in the consecutive considered interaction can be almost completely converted to the energy of wave with frequency 3/spl omega/.

We introduce the theory of intracavity quasi-phase-matched three-frequency wave interactions in active-nonlinear periodically poled medium, and in particular, self-frequency doubling and halving. The combination of laser oscillation of active ions with nonlinear optical properties of the host material provides an opportunity for creation laser with self- frequency conversion. Quasi-phase-matched second harmonic generation at 0.542 micrometer by self-frequency doubling of fundamental radiation laser radiation at 1.084 micrometer in periodically poled Nd:Mg:LiNbO3 crystal pumping by diode laser at 0.810 micrometer has been observed experimentally.© (2001) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We present results of theoretical and experimental investigations of frequency sweeping mechanisms of the narrowline diode-pumped monolithic ring Nd:YAG laser radiation in multipass pulsed slab amplifier. The obtained value of the maximal chirp in the four-pass slab amplifier does not exceed 7.7 kHz when energy of the pump pulses is 36 J and the duration of these pulses is 0.3 ms.

We present results of precise measurement of spatial coherence degree and depolarization degree of the single frequency diode-pumped monolithic ring Nd:YAG laser radiation. An analysis is made of the factors influencing the spatial coherence and depolarization of miniature lasers with longitudinal diode pumping.

The connection of rare decays to supersymmetric grand unification is highlighted, and a review of the status of rare decay experiments is given. Plans for future investigations of processes that violate lepton flavor are discussed. A new result from the MEGA experiment, a search for {mu}{sup +} {yields} e{sup +} {gamma}, is reported to be B.R. < 3.8 x 10{sup -11} with 90% confidence.

For the first time depolarization degree of the diode-pumped monolithic ring Nd3+:YAG laser has been measured. The obtained value of depolarization degree equals 3 (DOT) 10-3. It has been shown that the dominant mechanism of the intracavity losses and the output light depolarization is diffraction on random inhomogeneities of birefringence in the laser media.© (1996) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The intracavity summing of the frequencies of lasing (λ = 1.084 μm) and pump radiation from a 0.81-μm diode laser is performed in a periodically poled active nonlinear Nd:Mg:LiNbO3 crystal.

The possibility of the quasi-phase-matched generation of the second harmonic (λ = 0.542 μm) by self-doubling of the fundamental radiation frequency in an Nd:Mg:LiNbO3 crystal laser having a regular domain structure and pumped by a diode laser (λpump = 0.81 μm) was demonstrated.

Consecutive generation of the third harmonic (i.e. generation of radiation with the doubled frequency followed by frequency summation) radiation from a Q-switched Nd:YAG laser (λ = 1.064 μm) was observed in a Y:LiNbO3 crystal polarised periodically along the z axis. The modulation period of the nonlinear susceptibility was ~ 60 μm. The second and third harmonics of the radiation were generated respectively in the ninth and thirty-third quasi-phase-matching orders.

It is shown that a systematic error, associated with the anisotropic nature of natural fluctuations in a laser, is introduced in measurement of the degree of depolarisation of elliptically polarised laser radiation by a method based on its conversion into linearly polarised radiation.

An analysis is made of the possibility of determination of the width of a narrow-band emission spectrum of a laser by a modified heterodyne method. This method is based on the dependence of the maximum of the spectrum of beats on the delay time between interfering waves.

The degree of depolarisation of radiation from a single-frequency ring monolithic diode-pumped(chip) Nd3+:YAG laser was measured for the first time: its value was 3×10-3. The dominant mechanism of intracavity losses and of depolarisation of the output radiation was diffraction by random inhomogeneities of the birefringence of the active element.

We have investigated linear diode-pumped YAG lasers with matching optics provided by specially shaped gradient lenses for various choices of active-element length and output-mirror transmission coefficient. For these lasers we obtained single-frequency lasing on the lowest transverse mode at a power of 40 μW. The laser linewidth, which was measured by a heterodyne method was 10 kHz.

The delay time of the principal superradiance pulse is found theoretically for the cases when a longitudinal wide-band pump pulse is long on the time scale of the output radiation or when such a pump pulse travels along an active medium more slowly than the optical wave. A comparison is made of the delay times of the forward and reverse waves. A linearized semiclassical problem (one-dimensional case) with a random source is solved for the amplitude of the radiation field.

The isotopic composition of medical-biological objects (MBO) is studied by the method of laser mass spectrometry (LMS). It is found that anomalous fractionation of carbon, oxygen, silicon, sulfur, potassium, and calcium isotopes occurs in MBO. A correlation is established between the neutron binding energy of the isotopes and the anomalous fractionation of isotopes of some elements in MBO.

It is shown that the asymmetric nature of the radiation emitted by a self-terminating neon laser (? = 614.3 nm) is a consequence of the propagation of ionizing potential gradient waves that ensure the traveling nature of the excitation of a gas. A solution of the Maxwell-Bloch equations yields formulas relating the delay between the appearance of superradiance pulses from the opposite ends of a source to the velocity of propagation of these waves. Estimates obtained of the velocity of propagation of ionizing potential gradient waves in neon are in agreement with the available experimental data.

A study is made of the dynamics of a superradiance pulse in a transversely inhomogeneous active medium inside a tubular waveguide with dielectric walls. The problem is solved numerically in the approximation of a given field profile by expanding the radiation field in terms of the normal modes of the waveguide and the polarization and inversion of the medium in terms of basis functions dependent on the transverse coordinates. It is shown that an inhomogeneous transverse distribution of the field and of the initial inversion can suppress the appearance of oscillatory replicas (superradiant ringing) of the main superradiance field and also can result in incomplete utilization of the energy stored in the active medium because of coherent dephasing of the polarization of the medium in different parts of a transverse cross section of the waveguide.

It is shown that materials with different physical properties are characterized by different widths of the linear part of the dependence of the charge reaching the slit of a mass-spectrograph monitor on the number of laser pulses. This difference and the change in the ratio of singly and doubly charged ions in the analytic part of a mass spectrograph are determined by the shape of the craters formed as a result of the interaction of laser radiation with the investigated material.

A semiclassical method is used to study cooperative spontaneous radiation (superradiance) emitted from an excited medium in a thin dielectric waveguide subject to an allowance for the highest-Q normal wave in the waveguide (constant profile fields). A radiation pulse is described by a nonlinear equation which represents weakening of the interaction between matter and a field of constant profile in the case of a large-area pulse. This results in partial utilization of the stored energy, reduces the steepness of the edges of a pulse and its maximum intensity, and suppresses oscillation replicas.

Using laser mass-spectrometry elemental and isotopic studies of atherosclerotic plaques (atheromatosis, calcinosis) and adjacent tissues were performed. The studies have revealed changes in concentrations of various elements depending on the gravity of the disease (atheromatosis, calcinosis) and impaired natural distribution of calcium and silicon isotopes independent of the damage degree.

Laser mass-spectroscopic studies were carried out of element and isotope composition of sclerotic formations (patches) of large blood vessels on calcinosis and ateromatosis stage, as well as of the region adjoining the calcinosic formation of the vessel tissue. It was shown that the basis of the "patches" consists of carbon, nitrogen and oxygen. 13 elements of micromixtures were found. Changes were revealed of the content of some elements and anomalous disturbance of natural distribution of oxygen, silicon, magnesium and calcium isotopes depending on the stage of arteriosclerosis formation.

A solid-state laser was developed on the basis of a highly stable cw narrow-band monolithic YAG laser pumped by semi-conductor diode lasers, a system for shaping a pulse of given duration, and a multipass slab amplifier. The spectral and power characteristics of the YAG laser acting as a master oscillator were investigated. An interferometric study was made of the thermal distortions of the laser beam in the slab amplifier where the ray paths were zigzag-shaped. The signal from the master oscillator was amplified by a factor of 7×104 in the four-pass slab amplifier without distortion of the spatial characteristics of the laser beam.