Особенности контактного разрушения льда

The formation of an intermediate layer under hydrostatic compression at a shear appearing due to the action of converging and diverging fronts of stress momentums (pulses) is considered. Continuous monitoring of deformational changes in the structure of ice was carried out using acoustic methods. The features of contact ice breaking in the diverging fronts of stress pulses are considered by the example of the slow impact of a rigid spherical indenter on an ice plate simulating half-space. Using the piezoelectric accelerometer, an oscillogram of the impact was recorded and a generalized dependence of the reduced stress on the reduced instantaneous velocity of the impact (semi-cubic parabola) was obtained. It is established that under conditions of the experiment (smooth convex indenter surface and icy half-space) a thin intermediate layer is formed, the properties of which determine the physical similarity in the family of curves «instantaneous force-instantaneous velocity». A rheological model with due regard for the change in the microstructure of ice during the impact is proposed. Quantitative determinations of the deformation changes in structure of solid ice samples were performed under intensive plastic deformation in a matrix with a profile similar to the Laval nozzle. The deformations created by the piston caused forced vibrations in the ice. The working surface of the piston in the form of an ellipsoid together with the smooth walls of the matrix and the reverse cone created conditions for parametric resonance and the formation of fronts of highfrequency stress pulses. Under influence of these pulses, zones with a superplastic fine-crystalline structure of ice (cumulative effect) were formed in ice. In the outlet cylindrical channel, a flow around an obstacle of the ice with the structure of an intermediate layer (dynamic viscosity 20 MPa s) and the distribution of velocities of motion over the channel cross section were studied. The obtained results can be used to simulate the processes of contact destruction of deep rocks by a support or an ice-resistant platform loaded with an ice field.Проанализированы закономерности эволюции структуры пресноводного льда в условиях гидростатического сжатия при сдвиге под действием сходящихся и расходящихся фронтов импульсов напряжений. Исследовано обтекание льдом препятствия, распределение скоростей в цилиндрическом канале, формирование промежуточного слоя вблизи поверхности шарового индентора при медленном ударе. Количественно определены деформационные изменения структуры льда непосредственно в процессе контактного разрушения

Физическое моделирование режимов движения ледников

Modes of «dry friction» at glacier-bedrock interface (ice sliding and flow) were simulated under uniform compression with different combinations of mechanical and thermodynamic factors. Effect of ice structure in the intermediate layer was considered in terms of strength of ice adhesion to complex-shaped substrate for typical cases: at frictional contact of ice frozen to the walls of the cylindrical matrix; when ice was pressing-through a confusor (with contraction ratio = 30); extruding the ice in a plastic state through a pipe. For these tests, а collapsible matrix was used. It consists of three sections: the feed cylinder, the convergent channel (confuser) and the forming pipe. Changes of ice during severe plastic deformation were monitored by acoustic emission in the range from 10 Hz to 25 kHz. Relationship between the size of moving structural elements, their natural resonant frequency, density and acoustic capacitance was applied. A theoretical model was verified. Correlation of amplitude-frequency spectra of acoustic emission at the frictional contact with the acoustic spectrum of natural oscillations of the glaciers from distant sources was confirmed. The results can be applied to remote sensing studies of ice movement modes at the glacier bedrock.Воспроизведены основные режимы движения ледников по сухому ложу – скольжение и течение, включая образование промежуточного слоя. Выявлен эффект формирования спиралевидной структуры льда в условиях высокого гидростатического давления. Теоретическая модель отражает суть физических процессов интенсивной пластической деформации в пресноводном льду, к которой относится и рекристаллизация. Определены структура, физико-механические, прочностные и акустические характеристики льда в промежуточном слое, рассмотрено также их влияние на режим скольжения. Разработанный акустико-механический метод может быть применён для дистанционного изучения режимов движения ледников по ложу

Evaluation of the resulting quality level index for interregional passenger automobile transport

In order to improve transport services for the population, it is necessary to study and analyze the information on the quality of transport services on the basis of gained experience and wishes of the passengers. This paper, basing on the normative and technical documentation and expert assessments, provides the rationale for the selection of quality indicators for interregional passenger automobile transport. Quality evaluation indexes are supposed to be simple for calculation and use; quality indexes are supposed to be formed in the way to judge the participation of carriers in the improvement of the quality of the transport process, i. e. to separate the qualities, which depend and do not depend on their activities. Indexes, developed on the basis of the standards' requirements are used in this paper. Such approach in the management of interregional passenger transport can contribute to the quality improvement of interregional automobile transport services provided to the population. The results of statistical data processing of passengers' questionnaires are also given here. The transport quality indexes were quantified through the passengers' answers ranking, the evaluation of the interregional passenger automobile transport quality was carried out on the example of the Ulyanovsk State Technical University. © Published under licence by IOP Publishing Ltd

Лечение фибрилляции предсердий на догоспитальном этапе: клинико-экономические аспекты

Objective: to retrospectively study the results of emergency medical care for patients with uncomplicated attacks of atrial fibrillation and to provide a clinical and economic assessment of their prehospital management tactics. Material and methods. A comparative retrospective study was conducted to examine the results of emergency medical care rendered to 1200 patients with uncomplicated atrial fibrillation attacks lasting as long as 24 hours. Ambulance call and outpatient cards and inpatient case reports were used. A clinical and economic assessment of the prehospital management tactics for the patients was made. Results. The prehospital therapy of atrial fibrillation was found to be ineffective in the first hour of observation. In more than 90% of cases, an atrial fibrillation attack was eliminated by the end of the first 24 hours regardless of which antiarrhythmic agent had been used. Conclusion. The proposed prehos-pital management tactics for patients with uncomplicated atrial fibrillation attacks lasting as long as 24 hours make it possible to decrease the length of stay of a called ambulance team and to enhance its efficiency, without reducing the clinical effect of performed antiarrhythmic therapy. Key words: atrial fibrillation, emergency medical care, prehospi-tal stage, clinical and economic analysis.Цель исследования — провести ретроспективное изучение результатов оказания неотложной медицинской помощи больным с неосложненными приступами фибрилляции предсердий и дать клинико-экономическую оценку тактики их ведения на догоспитальном этапе. Материал и методы: проведено сравнительное ретроспективное изучение результатов оказания неотложной медицинской помощи 1200 больным с неосложненными приступами фибрилляции предсердий длительностью до 24 ч. Использованы карты вызовов бригад скорой помощи, амбулаторные карты поликлиник, истории болезни стационаров. Дана клинико-экономическая оценка тактики ведения больных на догоспитальном этапе. Результаты. Установлено, что терапия фибрилляции предсердий на догоспитальном этапе малоэффективна в первый час наблюдения. Более чем в 90% случаев приступ фибрилляции предсердий был устранен к концу первых суток независимо от примененного антиаритмического препарата. Заключение. Предлагаемая тактика ведения больных на догоспитальном этапе с неосложненными приступами фибрилляции предсердий длительностью до 24 часов позволяет при снижении экономических затрат, не снижая клинического эффекта от проводимой антиаритмической терапии, сократить время пребывания бригады скорой медицинской помощи на вызове, повысить ее оперативность. Ключевые слова: фибрилляция предсердий, неотложная медицинская помощь, догоспитальный этап, клинико-экономический анализ

Особенности оказания неотложной медицинской помощи больным с фибрилляцией предсердий на догоспитальном этапе: клинико-экономические аспекты

Comparative retrospective study of emergency care rendering results for 1200 patients with uncomplicated fibrillation attacks was carried out and their management tactics clinic-economic assessment at a pre-admission stage was done. It has been found that therapy for atrial fibrillation is unproductive in the first hour of observation at a pre-admission stage. Atrial fibrillation attack was eliminated to the end of the first day regardless of used antiarrhythmic preparation in more than 90% of the cases. Proposed management tactics for patients with uncomplicated atrial fibrillation attacks until 24 hours of duration at a pre-admission stage allows by cost lowering and clinical effect of conducting antiarrhythmic therapy maintenance to shorten an emergency team stay time and increase its operative turnover.Проведено сравнительное ретроспективное изучение результатов оказания неотложной медицинской помощи 1 200 больным с неосложненными приступами фибрилляции предсердий и дана клинико-экономическая оценка тактики их ведения на догоспитальном этапе. Установлено, что терапия фибрилляции предсердий на догоспитальном этапе малоэффективна в первый час наблюдения. Более чем в 90% случаев приступ фибрилляции предсердий был устранен к концу первых суток независимо от примененного антиаритмического препарата. Предлагаемая тактика ведения больных на догоспитальном этапе с неосложненными приступами фибрилляции предсердий длительностью до 24 ч позволяет при снижении экономических затрат, не снижая клинического эффекта от проводимой антиаритмической терапии, сократить время пребывания бригады скорой медицинской помощи на вызове, повысить ее оперативность

Волновые структуры в ледяном поле и их влияние на прочность солёного льда

The heterogeneity of the strength of the ice field of the dynamic type of formation with an area of 800 m2 was investigated in time and space. It is shown that stationary periodic wave structures are formed in a closed volume of an ice field lying on the surface of a liquid in a rectangular basin. In a case of absence of any external influences, the dominant source of elastic waves in the ice is the coherent radiation of them on freezing of water, i.e. the ice field itself. Another wave structures, i.e. standing waves, form secondary ice textures in the ice field with diminished strength. Local hardness of ice was chosen as the criterion of strength. The recurrence of local hardness values as a function of coordinates of the measurement points in the longitudinal and transverse profiles of the ice field was determined. The hardness values vary from 40 to 60% with an axial force measurement error of 5%. The experimental relations are approximated by periodic curves, in which the maxima and minima of local hardness correlate with the nodes and antinodes of standing waves, respectively. The decrease in local ice hardness in the secondary textures is explained by high-frequency dynamic metamorphism. The wavelengths corresponding to bending-gravitational and longitudinal waves are identified, with the interference of which stationary periodic wave structures are formed. A similar regularity of changes in local hardness was revealed also in a river ice. The results obtained allow us to consider nonlinear wave phenomena as one of the factors controlling the spatial-temporal variability of the ice strength characteristics.Установлено, что в ледяном поле динамического типа формирования под действием стоячих волн образуются стационарные периодические волновые структуры. Определены масштабы таких структур. Изменение локальной твёрдости объясняется высокочастотным динамическим метаморфизмом льда в зонах пучностей стоячих волн. Показано, что источником упругих колебаний может быть когерентное излучение упругих волн при замораживании воды. Формирование аналогичных волновых структур в природном льде подтверждено полевыми измерениями твёрдости в речном ледяном покрове. Нелинейные волновые явления рассматриваются как один из факторов пространственно-временнóй изменчивости прочностных характеристик льда

COMPUTER SIMULATION TECHNOLOGIES IN RECONSTRUCTIVE AND RESTORATIVE SURGERY OF THE MIDFACE

The technique of computer-aided planning of surgical intervention in patients with trauma of the midface, to effectively carry out surgical procedures in the field of anatomical structures of the orbit and ethmoid labyrinth. The developed method allows to reduce the invasiveness of surgical intervention, to reduce the number of postoperative complications, shorten the rehabilitation period

Measurement of the e+e−→K+K−π+π−e^+e^- \to K^+K^-\pi^+\pi^- cross section with the CMD-3 detector at the VEPP-2000 collider

The process $e^+e^- \to K^+K^-\pi^+\pi^-$ has been studied in the center-of-mass energy range from 1500 to 2000\,MeV using a data sample of 23 pb$^{-1}$ collected with the CMD-3 detector at the VEPP-2000 $e^+e^-$ collider. Using about 24000 selected events, the $e^+e^- \to K^+K^-\pi^+\pi^-$ cross section has been measured with a systematic uncertainty decreasing from 11.7\% at 1500-1600\,MeV to 6.1\% above 1800\,MeV. A preliminary study of $K^+K^-\pi^+\pi^-$ production dynamics has been performed