Search

In this paper the influence of the deformation of the shapers of various stiffness on the vibration characteristics of the impact is estimated. In particular, the influence of the deformation on the high-frequency vibrations that appears during the operation of the shapers is also estimated. Both analytical and experimental results of measuring of deformation of shapers are presented. The structure of the model of the shock testing machine developed in Peter the Great St. Petersburg Polytechnic University is described in details. An algorithm for the analysis of vibration characteristics obtained during the tests on the model of an impact machine is presented. The results of studies of the characteristics of the materials which the shock pulse shapers are made of are presented. The life of the shapers made of various materials is estimated. Analytic and experimental dependences of the shaper deformation on the lifting height of the shock table are presented. Conclusions about the effect of shaper deformation on impact parameters are drawn.

It has been demonstrated that thermally poled regions of silicate glasses are capable of blocking penetration of silver ions into the glasses in the course of ion exchange processing. This allows using locally poled regions of the glass surface as thick dielectric masks in the formation of ion exchanged structures, like channel optical waveguides, in glass substrates. This approach provides easy multiplication of the structures and, being based on the thermal electric field imprinting of the masks, allows avoiding both lithography with the use of liquid chemicals and the influence of metal masks on the spatial distribution of the ions penetrating the glass in the ion exchange.

Thermal relaxation of the second harmonic generation (SHG) observed in thermally poled soda-lime silicate glass is studied. At least two relaxation processes could be distinguished. Determined activation energy of the fastest SHG relaxation process is equal to about 0.5 eV. This SHG relaxation occurs at temperatures essentially below ones, at which the thermally stimulated depolarization current (TSDC) measurements show the relaxation of the spatial charge formed in thermal poling of the glasses. This confirms that SHG in poled glasses is not mostly conditioned by the “frozen” spatial charge and electric field of this charge.

The influence of thermal poling and ion exchange on the rate of reactive ion etching of a soda-lime silicate glass in CF4-Ar plasma was studied. It is shown that the replacement of Na+ by Ag+ ions increases the durability of the glass etching while thermal poling of the glass increases the etching rate. The fastest etching was registered for the glasses poled using deposited metal film anodic electrode and using corona discharge in nitrogen atmosphere. Corona poling of the glass in atmospheric air instead of nitrogen essentially decreased the rate.

All industrial products including robots used for various works in arctic zone, can be exposed to various shock loads. In arctic conditions, such loads are: tectonical impacts, impacts from snow mass and other phenomena. To confirm the durability of products exposed to shock loads during exploitation, the impact tests ma products should be preliminary carried out. Such tests are performed in special equipment - shock machines. Shock machines are complex highly automated equipment. The development and production of machines of this type require advanced high technology and serious financial investments. Therefore, a deep understanding of operation principles of shock-testing machines, their design and methods of adjusting is very important. In the current paper the structures and designs of several types of developed shock machines are analyzed in details: single-shock machine, multiple-shock machine, machine with a pneumatic accelerator. Data on the development of a positional multi-motor pneumatic drive by the High School of Automatics and Robotics of Peter the Great St. Petersburg Polytechnic University are presented. The interface of the operation panel of the multiple shock machine is described according to operating modes, recording and processing the results of measuring the parameters of the shock pulse. Directions of research in the field of synthesis of shock machines for testing Arctic robotics are defined.

Over the past decades, signicant attention has been paid to biomedical applications of terahertz (THz) technology. Nowadays, THz spectroscopy and imaging allow for solving numerous demanding problems in biological, medical, food, plant and pharmaceutical sciences. Among all biomedical applications, a label-free diagnosis of malignant and benign neoplasms represents one of the most attractive branches of THz technology. Despite the attractiveness, the methods of THz diagnosis are still far from medical practice. In this review, we consider the modern research results in THz diagnosis of malignant and benign neoplasms, along with the topical research and engineering problems, which restrain the THz technology translation to clinics. We start from analysis of the common models of THz-wave { tissue interactions and the eects of tissue exposure to THz waves. Then, we discuss existing modalities of THz spectroscopic and imaging systems, which either have been already applied in medical imaging, or hold strong potential. We summarize the earlier-reported and the original results of THz measurements of neoplasms with dierent nosology and localization. We pay attention to the origin of contrast between healthy and pathological tissues in the THz spectra and images and discuss the prospective of THz technology in non-invasive, minimally-invasive and intraoperative diagnosis, as well as in aiding histology. Finally, we review the challenging problems of THz diagnosis, as well as attempts to solve them, which should bring the THz technology much closer to the medical practice. This review allows one to objectively uncover benets and weaknesses of the THz technology in diagnosis of malignant and benign neoplasms.

We measured thermal relaxation of the second order nonlinearity (SON) observed in a thermally-poled soda-lime silicate glass. It is shown that 50-min annealing of the glass at 400°C results in a complete SON degradation. Performed studies of thermo-stimulated depolarization current (TSDC) revealed that the poling-induced spatial electric charge relaxes above the glass transition temperature. This indicates that SON is not induced by this spatial charge.

Thermal poling of a multicomponent silicate glass was performed in air and in argon atmospheres at various voltages, and the temperature dependences of the depolarization currents (TSDC) in the poled glasses were studied. In addition, the concentration profiles of univalent and bivalent cations in subanodic regions of the poled glasses were measured with EDS and SIMS techniques. The difference in the displacements of bivalent ions at poling of the glasses in closed and open anode configurations allowed us to identify “frozen” spatial charge relaxation peaks observed in the TSDC measurements and to relate these peaks to hydrogen and bivalent metal ions relaxation.

The seismic situation in a number of rooms of the NRNU MEPhI, including the Laboratory Building, where the construction of the multifunctional laser complex ELF is planned, is studied. Estimations of seismic and vibrational noise at the main and isolated parts of the basement of the room that hosts the laser complex are obtained.

Two setups for manipulating (translocation, stretching, rotation) microscopic objects (with the dimensions from several nanometers to tens of micrometers) are developed based on optical trapping by femtosecond laser radiation. The possibility of single-cell translocation is shown. The possibility of destructing malignant cells as well as of cutting off a fragment from a malignant cell cluster due to the rapture of bonds is demonstrated in multiphoton absorption of femtosecond light pulses. The possibility of the holographic control to move several particles simultaneously is shown.

Terahertz (THz) waveguiding in sapphire shaped single crystal has been studied using the numerical simulations. The numerical finite-difference analysis has been implemented to characterize the dispersion and loss in the photonic crystalline waveguide containing hollow cylindrical channels, which form the hexagonal lattice. Observed results demonstrate the ability to guide the THz-waves in multi-mode regime in wide frequency range with the minimal power extinction coefficient of 0.02 dB/cm at 1.45 THz. This shows the prospectives of the shaped crystals for highly-efficient THz waveguiding.

Monte Carlo (MC) numerical simulation of light propagation in living tissue is widely used for characterization of optical coherence tomography (OCT) signals. Using MC simulation we obtained OCT images of skin with dysplastic nevus. Two various positions of skin nevus in depth were considered. Comparing these OCT simulation results with image of skin without nevus, we showed that OCT medical approach allows to detect dysplastic nevus at different stages of its life.

In this work, we have manufactured the experimental setup to study the modes of automated destruction of biological tissue in vitro. We have implemented the setup in microsurgical operations, which allows us to verify the modes of tissues destruction.

We have proposed a method for hyper-spectral fluorescent imaging based on acousto-optical filtering. The object of interest was pumped using ultraviolet radiation of mercury lamp equipped with monochromatic excitation filter with the window of transparency centered at 365 nm. Double TeO2-based acousto-optical filter, tunable in range from 430 to 780 nm and having 2 nm bandwidth of spectral transparency, was used in order to detect quasimonochromatic images of object fluorescence. Modulating of ultraviolet pump intensity was used in order to reduce an impact of non-fluorescent background on the sample fluorescent imaging. The technique for signal-to-noise ratio improvement, based on fluorescence intensity estimation via digital processing of modulated video sequence of fluorescent object, was introduced. We have implemented the proposed technique for the test sample studying and we have discussed its possible applications.

Biomedical applications of terahertz (THz) technology and, in particular, THz pulsed spectroscopy have attracted considerable interest in the scientific community. A lot of papers have been dedicated to studying the ability for human disease diagnosis, including the diagnosis of human skin cancers. In this paper we have studied the THz material parameters and THz dielectric properties of human skin and pathology in vivo, and THz pulsed spectroscopy has been utilized for this purpose. We have found a contrast between material parameters of basal cell carcinoma and healthy skin, and we have also compared the THz material parameters of dysplastic and non-dysplastic pigmentary nevi in order to study the ability for early melanoma diagnosis. Significant differences between the THz material parameters of healthy skin and pathology have been detected, thus, THz pulsed spectroscopy promises to be become an effective tool for non-invasive diagnosis of skin neoplasms.

We have analysed the clinical symptoms and the malignization signs of pigmented skin neoplasms. We have estimated the complex of clinical parameters which could be measured for the purpose of skin screening diagnostic via digital image processing. Allowable errors of clinical parameter characterization have been calculated, and the origin of these errors has been discussed. Proposed technique for automated screening of pigmentary skin neoplasms should become an effective tool for early skin diagnostics.

Optical coherent tomography (OCT) is a rapidly developing method of fundamental and applied research. Detection and processing of OCT images is a very important problem of applied physics and optical signal processing. In the present paper we are demonstrating the ability for effective wavelet-domain de-noising of OCT images. We are realizing an algorithm for wavelet-domain de-noising of OCT data and implementing it for the purpose of studying test samples and for in vivo nail tomography. High de-noising efficiency with no significant losses of information about the internal sample structure is observed.

Our research into photon echo (PE) and stimulated photon echo (SPE) in ytterbium vapour at the transition 0 ↔ 1 is summarized. We present the polarization properties of PE and SPE in pure gas, anisotropy of collision relaxation, collision-induced PE and collision-induced SPE.