Impulse Duration Research Articles

APPLICATION OF INTENSIVE LIGHT RADIATION IN THE PATIENT WITH ERYTHEMATOTELANGIECTATIC ROSACEA

We present a description of the clinical case of a patient with an erythematotelangiectatic type of rosacea. Rosacea is a chronic recurrent dermatosis, characterized by skin lesions of the face in the form of erythema and papulopustular elements, which has polyethological origin. The disease occurs more frequently in women aged 30-50 years who have a certain genetic predisposition to transient reddening of the skin of the face or less often of the neck and the decollete zone. It is believed that the dermatosis is more likely to affect the I and II phototypes, but the disease can occur in any skin phototype. The patient came to the clinic with complaints about rashes in the chin and nasolabial triangle, flushing of the face, accompanied by tingling and burning. The patient turned to the clinic with complaints about rashes in the chin and nasolabial triangle, flushing of the face, accompanied by tingling and burning. She never consulted a dermatologist before. A diagnosis was made: “erythematotelangiectatic type of rosacea” (according to the classification proposed by the USA National Rosacea Society, stage I — persistent erythema and telangiectasia). Using the scale of diagnostic evaluation of rosacea, it was evaluated at 12 points. There are many approaches to the treatment of rosacea. Drug therapy is divided into systemic, external and complex. Systemic therapy has a number of side effects, so for light and medium-to- severe rosacea, only external therapy is more often prescribed. Because of the presence of pathologically altered vessels, the low efficacy of metronidazole, the patient was assigned a course of phototherapy with intense incoherent pulsating light at standard parameters. There was a significant improvement after two procedures, but vessels smaller than 0.4 mm remained intact, so the duration of the first pulse was increased in order to influence small- caliber vessels. Individual selection of parameters (duration of the first impulse and fluence) was made based on the dermatoscopic picture and patient’s phototype, which resulted in a significant clinical effect and persistent remission. Using the scale of diagnostic evaluation of rosacea it was evaluated at 1 point after treatment. This clinical case demonstrates the effectiveness of phototherapy with intense incoherent pulsating light with individual selection of the duration of the first pulse and energy density in patients with erythematotelangiectatic rosacea. In IPL-treatment schemes, it is desirable to select individual parameters for the duration of the first pulse and the energy density, based on the features of the dermatoscopic picture and skin phototype of each individual patient.

Material properties of the brain in injury-relevant conditions - Experiments and computational modeling.

Material properties of the brain have been extensively studied but remain poorly characterized. The vast variations in constitutive models and material constants are well documented. However, no study exists to translate the variations into disparities in impact-induced brain strains most relevant to brain injury. Here, we reviewed a subset of injury-relevant brain material properties either characterized in experiments or adopted in recent head injury models. To highlight how variations in measured brain material properties manifested in simulated brain strains, we selected six experiments that have provided a complete set of brain material model and constants to implement a common head injury model. Responses resulting from two extreme events representing a high-rate cadaveric head impact and a low-rate in vivo head rotation, respectively, varied substantially. We hypothesized, and further confirmed, that the time-varying shear moduli at the appropriate time scales (e.g., ~5 ms and ~40 ms corresponding to the impulse durations of the major acceleration peaks for the two impacts, respectively), rather than the initial or long-term shear moduli, were the most indicative of impact-induced brain strains. These results underscored the need to implement measured brain material properties into an actual head injury model for evaluation. They may also provide guidelines to better characterize brain material properties in future experiments and head injury models. Finally, our finding provided a practical solution to satisfy head injury model validation requirements at both ends of the impact severity spectrum. This would improve the confidence in model simulation performance across a range of time scales relevant to concussion and sub-concussion in the real-world.

Study of cellulose particle motion effect on impulse breakdown in transformer oil

This paper conducts experimental research and theoretical analysis on the effect of cellulose particle motion on impulse breakdown in transformer oil. In the experiment, the spherically capped electrodes immersed in the bulk of the transformer oil are used to form a quasi-uniform electric field. The breakdown tests are carried out and the breakdown voltages for three cellulose contamination levels oil under four types of impulses, 1.4/50μs, 14/220μs, 80/850 μs and 240/2400 μs, are obtained. The experimental results show that both the impulse waveshape and cellulose contamination level have an effect on the breakdown of transformer oil. Longer impulse duration or higher cellulose contamination level of transformer oil can lead to the decrease of impulse breakdown voltage. Specifically, the effect of the high level cellulose contamination for U50% becomes much more significant under long-duration impulses. To verify the findings above, a numerical model is introduced for the cellulose particle dynamics in the transformer oil under these four kinds of impulses. Notably, the calculation result indicates the particles can accelerate with the action of the impulse, and particles can aggregate in concentrated area of the electric field in the oil gap with the action of the long-duration impulse. It is concluded that the particle motion can play a catalytic role in the impulse breakdown of the oil gap.

Analysis of Elastic Wave Parameters in the Elements of the "Striker – Gasket – Reinforced Concrete Beam" System

Application of automated monitoring systems ensures the deformation safety of structures. Such deformation control systems are supplemented with the tools, which allow evaluation of the criticality of the structure state on the basis of vibration measurements. These are acoustic emission registration systems and shock wave diagnostics systems.The results obtained in this study are directly related to the shock-wave vibrodiagnostics of reinforced concrete structures. Particular attention is given to vibrodiagnostics in a "spare mode", which causes no inelastic deformation to appear in the elements of the examined structure.The objective of this work is to find local impact parameters for excitation of mechanical oscillations of a desired spectrum in the structure and to excite an elastic wave with required wavefront characteristics. One of the main impact parameters determining these characteristics is the pulse duration. Based on the results of the numerical experiment performed on the basis of a mathematical model of dynamic elastic interaction of the elements of the "striker – gasket – reinforced concrete beam" system, the duration of the impulse action on the beam was determined depending on various factors. Thus, within a specified range of these factors the greatest interval of impulse duration is obtained under variation of the striker velocity within the interval from 0.1 ms to 3 ms. Assuming that the impulse duration defines one of the main wave frequencies of vibrations one may conclude that frequencies will vary in the range from 300Hz to 10000Hz.

Acceleration of Mass Transfer under Dynamic Loading

Under dynamic loading, the interaction of unloading waves with each other and with the faces causes the deformation of the sample due to the formation of standing waves, at the nodes of which the localized- deformation bands arise (if the high-speed tension does not exceed the spall strength, so the material in the zone of interference of unloading waves preserves its continuity). A consequence of deformation localization is the mass transfer of atoms and the doping phase particles to nascent localized-deformation bands. The duration of stress oscillations in standing waves in the ultrasonic frequency range exceeds the duration of the initial impulse by at least two orders of magnitude, which ensures an increase in the distance traveled by atoms and dispersed particles during deformation in standing waves.

Effect of changing of the parameters of the cable network of monitoring systems of high-rise buildings on the basis of string converters on their operability

The article is devoted to the problem of improving the reliability of monitoring systems for the technical conditions of high-rise buildings. The improvement is based on string sensors with an impulsed excitation method ensuring the maximum signal-to-noise ratio at their output. The influence of the parameters of the monitoring system on the shape of the excitation impulses of the string, and, consequently, on the amplitude of the string vibration of the string converter is also considered in the article. It has been experimentally proved that the parameters of the excitation impulses of the string converters. The article presents the results of the experiments showing the effect of the fronts duration of the excitation impulses on the amplitude of the oscillations of the strings. The influence of the fronts duration of the excitation impulse with the frontal lengths up to 0.5 ms is studied at the excitation impulse duration not exceeding 0.5 times the duration of natural oscillation periods of the string. The experimental data are compared with the theoretical ones and hypotheses explaining their difference are advanced. The article suggests some methods of reducing the influence of the cable-switching equipment system parameters on the amplitude of string oscillations. The possibilities of improving the reliability of the systems developed on the basis of string sensors with an impulsed excitation method and used for monitoring the technical conditions of the high-rise buildings are proposed.

Experimental Study of Blast Wave Mitigation in Open Cell Foams

In the present study, the experimental measurements have been conducted to investigate the blast wave mitigation in open cell natural rubber as well as synthetic (polyurethane) foams. The different blast strengths have been generated by exploding different quantity of explosive at 1.5 m standoff distance. The transmitted blast pressures through both foams have been recorded using a piezoelectric pressure sensor which was incorporated at the top surface of the composite plate. The modified blast wave parameters such as peak overpressure, positive phase duration, and impulse were investigated through both natural and synthetic foams at different blast pressure strengths. It was observed that the peak overpressure was significantly decreased, while positive phase duration and blast impulse were initially increased up to a certain extent, thereafter it was found to be decreased with increasing blast strengths. The results showed that a single layer of natural foam attributed 83 % peak overpressure mitigation, whereas double layer natural foam exhibited 90 % mitigation. Secondly, it was also found that natural rubber foam showed better performance in terms of impulse than that of synthetic foam.

RESEARCH OF IMPULSE PROPERTIES OF INDUM PHOSPHIDE

A theoretical research of the indium phosphide impulse properties has been carried out. The effect of the overshoot of the charge carriers drift velocity is analyzed. The influence of the electric field impulse parameters on the time and space distribution of the drift velocity was analyzed numerically. It is shown that the effect of the high electric field rectangular impulse on indium phosphide causes a short-term overshoot of the drift velocity. If the electric field is becoming stronger, the peak value of the drift velocity is getting higher but the duration of the overshoot is reducing. It is showing that the impulse duration does not affect the magnitude of the overshoot and the rate of relaxation processes. With increasing of the rectangular Impulse front duration peak values of high field overshoot are reducing. The impulse properties of indium phosphide and gallium arsenide were compared.

Reliability and failure analysis of SAC 105 and SAC 1205N lead-free solder alloys during drop test events

The purpose of this study is to establish a predictive fatigue life model for SAC 105 (Sn-1.0Ag-0.5Cu) and SAC 1205N (Sn-1.2Ag-0.5Cu with nickel) lead-free solder alloys. A simulation model approach was developed to investigate the stress and strain of the solder joint during drop tests. A Joint Electronic Device Engineering Council (JEDEC) Condition B drop test was simulated. This test is characterized by a 1500g peak acceleration for an impulse duration of 0.5ms. At the point of impact during the drop test, the deformation of the printed circuit board (PCB) via bending and mechanical shocks can cause joint cracks in the solder. To establish a predictive model for the 10% fatigue life of the lead-free solder joint under drop test conditions, the study was conducted in three main phases: material analysis of the lead-free solder alloy, the drop test model, and the 10% fatigue life analysis. Tensile tests of SAC 105 and SAC 1205N were used to examine the elastic and plastic behavior of the solder alloy mechanism. Simulations and drop tests were performed to investigate the failure of the microelectronic package resulting from the drop test. The predictive fatigue life models of SAC 105 and SAC 1205N were validated by the experimental results with satisfactory accuracy.

Simulation of dynamic of devices of systems of protection from defeat factors

Scientific article perspective. To estimat action of factors of defeat on the elements of protective constructions and military technique is possible: by model tests on polygons; by tests on the special laboratory stands and theoretical researches yet on the stage of planning with the use of calculation models of elements of constructions. The safety of elements of constructions exploitation depends on authenticity of information about its shock strength and stability.The intensive shock loading can reduce in destruction both a separate constructive part, and a construction as a whole. For the shock loading characteristic is: a short time of action in comparison with the least periods of eigentones of construction and and evocation of the considerable relative moving of elements of construction. Significant transitions are accompanied big dynamic and contact tensions, that negatively influences on durability. Consequently, for the estimation of dynamic properties of elements of constructions it is expedient to forecast their conduct at a blow.The purpose. The purpose of work is determination of reaction of the cored element of construction at the different methods of fixing of its ends on the action of shock impulse of small duration and large intensity. Also research of influence of geometrical parameters of bar is on the size of reaction on a blow.Essence of researches, used methods. The reaction of the cored element of construction on a blow is certain from the decision of differential equation of motion of bar on the basis of theory of transversal blow of S. P. Timoshenko. Initial conditions are accepted zero. Boundary conditions depended on the method of fixing of ends of bar. Moving of points of bar in the place of blow is calculated after the integral of Duhamel taking into account the first two forms of bend eigentones. A shock impulse is given with a semisinewave form.The obtained results and conclusions. As a result of work the certain moving of points of bars is in the place of blow at three methods of fixing of ends: joint doing all the washing, hard jamming and cantilever fastening. Influence of geometrical parameters of steel bar is analysed on the size of reaction on a blow. It is indicated on pointlessness of placing of cantilever bar in constructions which work at the action of the shock loading.

Structure pattern peculiarities and electrical characteristics of surface dielectric barrier discharge in air driven by impulse and sine high voltage

Structure patterns and electric characteristics of surface dielectric barrier discharges in air driven by periodic unipolar impulse voltage with ns front duration and sine voltage of the same frequency f = 15 kHz are presented. An influence of voltage impulse polarity, amplitude and impulse duration on discharge characteristics is shown to exist. The currents extracted from the surface discharge plasma layer by d.c. voltage of additional third electrode are found to depend on the waveform of the applied high voltage impulses.

New opportunities to improve the fuel supply system with a battery fuel system

The article shows the effect of increasing the injection pressure (up to p = 250 MPa) on the dynamics of the development of the fuel jet. An increase in the pressure in the accumulator led to a decrease in the angle of the boundary layer of the jet. A decrease in the oscillations of the boundary layer of the jet about its axis is shown. The greatest variations were recorded at рак = 50 MPa. Then, as the рак increases, the vibrations of the nucleus decrease and become practically imperceptible at 250 MPa. A method for controlling the shape of the differential injection characteristic by an electric pulse, which is applied to an electromagnet of the control valve of the electrohydraulic injector of battery fuel system, is provided. The impulse consists of the preliminary, the main and the following additional one. The duration of the preliminary impulse determines the amplitude of the initial stage of the injection characteristic, and the interval between the preliminary and main pulse is the amplitude between the initial and main stages of the injection characteristic. The interval between the main and additional electric pulses is selected in such a way that the subsequent stage of the injection characteristic begins after the termination of the main, but without an interval between them. By selecting the durations of the control electric pulses and the intervals between them, it is possible to obtain a predetermined shape of the differential injection characteristic from stepped to a characteristic with an inclined leading edge. In nozzles with two groups of holes (correction sprayer), the flow rate of the holes in the sub-head volume and on the locking cone is significantly different and depends on the position of the needle. This creates the prerequisites for correcting the fuel supply through the spray holes and, consequently, along the zones of the combustion chamber, taking into account the mode of operation of the diesel engine.

Overturning of rigid blocks for earthquake excitation

Overturning of rigid blocks on rigid foundations subjected to earthquakes in principle can be analyzed by simple replacement signals. The effect of a signal is generally characterized by its overturning curve. In this paper a new approach is presented, which is based on the overturning acceleration spectra (OAS). It is shown that an earthquake can be reasonably well represented for overturning by two parameters: the peak ground acceleration and the replacement impulse duration. In the paper the OAS of rigid blocks is presented for 100 different earthquake records. Based on the replacement impulse duration a simple design method is presented to predict the safety of rocking blocks.

Characteristics of the effect of an impulse supply voltage on the structure and characteristics of a surface discharge

Results of an experimental investigation of surface barrier discharge in a three-electrode system are presented. An analysis is done of the flow intensity of charged species extracted from the plasma layer of the surface discharge by the field of high dc potential of the third electrode. A high unipolar periodic impulse voltage of 15-kHz frequency, impulse duration from 0.5 to 45 ms, and 150-ns impulse-front duration is used to form the surface discharge. A It is revealed that the voltage-impulse duration has a significant effect on the intensity of charged species flow (extracted current), the character of the influence being dependent on the voltage-impulse polarity. The influence of voltage-impulse duration on the surface-discharge current is revealed as well. Pictures of the structure of surface discharge at the rise and the fall of the voltage impulse made by means of a high-speed camera are presented. The difference of the discharge structure for different polarities of voltage impulse is revealed. It is suggested that the surface-discharge characteristics are dependent on a combination of a number of factors, such as the parameters of the impulse voltage, volume charge in the gas gap, and the charge on the barrier surface, as well as the material and surface structure of the barrier.

Repetitive Impulse Withstand Performance of Metal–Oxide Varistors

This study focuses on the relationship between test current waveforms and impulse withstand capability of metal–oxide varistors (MOVs) (withstand energy, current density, and the number of withstand shots) in repetitive impulse application and discusses the mechanical and electrical failure mechanisms. The performance and relationship of withstand energy and withstand shots for conventional 2-ms rectangular waveform, 4/10- $\mu $ s, and newly introduced 10/350- $\mu $ s impulses are investigated. Notably, the 10/350- $\mu $ s waveform has aspects of both steep rise impulse and long duration impulse. In addition, the varistor voltage change after repetitive impulse applications for 10/350- $\mu $ s and 4/10- $\mu $ s waveforms is investigated. There is no direct relationship between varistor voltage drop and repetitive withstand shots. However, ${V}_{1 {\rm mA}}$ and ${V}_{0.01 {\rm mA}}$ changes indicate the degree of MOV damage caused by the impulses and are important factors to monitor progressive damage. Based on these findings, optimal MOV design is discussed.

The Thrombolytic Effect of Diagnostic Ultrasound-Induced Microbubble Cavitation in Acute Carotid Thromboembolism.

Acute ischemic stroke is often due to thromboembolism forming over ruptured atherosclerotic plaque in the carotid artery (CA). The presence of intraluminal CA thrombus is associated with a high risk of thromboembolic cerebral ischemic events. The cavitation induced by diagnostic ultrasound high mechanical index (MI) impulses applied locally during a commercially available intravenous microbubble infusion has dissolved intravascular thrombi, especially when using longer pulse durations. The beneficial effects of this in acute carotid thromboembolism is not known. An oversized balloon injury was created in the distal extracranial common CA of 38 porcine carotid arteries. After this, a 70% to 80% stenosis was created in the mid common CA proximal to the injury site using partial balloon inflation. Acute thrombotic CA occlusions were created just distal to the balloon catheter by injecting fresh autologous arterial thrombi. After angiographic documentation of occlusion, the common carotid thrombosis was treated with either diagnostic low MI imaging alone (0.2 MI; Philips S5-1) applied through a tissue mimicking phantom (TMP) or intermittent diagnostic high MI stable cavitation (SC)-inducing impulses with a longer pulse duration (0.8 MI; 20 microseconds' pulse duration) or inertial cavitation (IC) impulses (1.2 MI; 20 microseconds' pulse duration). All treatment times were for 30 minutes. Intravenous ultrasound contrast (2% Definity; Lantheus Medical) was infused during the treatment period. Angiographic recanalization in 4 intracranial and extracranial vessels downstream from the CA occlusion (auricular, ascending pharyngeal, buccinator, and maxillary) was assessed with both magnetic resonance 3-dimensional time-of-flight and phase contrast angiography. All magnetic resonance images were interpreted by an independent neuroradiologist using the thrombolysis in cerebral infarction (TICI) scoring system. By phase contrast angiography, at least mild recanalization (TICI 2a or higher) was seen in 64% of downstream vessels treated with SC impulses compared with 33% of IC treated and 29% of low MI alone treated downstream vessels (P = 0.001), whereas moderate or complete recanalization (TICI 2b or higher) was seen in 39% of SC treated vessels compared with 10% IC treated and 21% of low MI alone treated vessels (P = 0.001). High MI 20-microsecond pulse duration impulses during a commercial microbubble infusion can be used to recanalize acutely thrombosed carotid arteries and restore downstream flow without anticoagulants. However, this effect is only seen with SC-inducing impulses and not at higher mechanical indices, when a paradoxical reversal of the thrombolytic effect is observed. Diagnostic ultrasound-induced SC can be a nonsurgical method of dissolving CA thrombi and preventing thromboembolization.

Saturated impulse for pulse-loaded rectangular plates with various boundary conditions

Saturated impulse refers to the critical value after which the deflection of the beam or plate under pulse loading will not increase with further applied load. This paper investigates this phenomenon for rectangular plates under rectangular pulse-loading with various symmetric boundary conditions, e.g. two opposite edges of the plate are fully clamped while the other two edges are simply supported or free. For rectangular plates with symmetric boundaries under rectangular pressure pulse, the saturated duration and saturated impulse are merely dictated by the deformation mechanism, not by the boundary conditions. Then the effects of the aspect ratio and the boundary condition on the saturation impulse for elastic-plastic plates are revealed through numerical simulation. Bilinear elastic-plastic rectangular plates, with fully clamped boundaries and simply supported boundaries, subjected to rectangular pulse-loading are taken as typical examples. Subsequently, the saturation phenomenon is summarized from square plates to rectangular plates. The correlation is made between the results obtained from elastic-plastic analysis and those predicted by the rigid-plastic approximation. Finally, based on numerical simulation, theoretically and practically meaningful empirical expressions on the saturation phenomenon are proposed to facilitate engineering designs.

Differences in head impulse test results due to analysis techniques.

Different analysis techniques are used to define vestibulo-ocular reflex (VOR) gain between eye and head angular velocity during the video head impulse test (vHIT). Comparisons would aid selection of gain techniques best related to head impulse characteristics and promote standardisation. Compare and contrast known methods of calculating vHIT VOR gain. We examined lateral canal vHIT responses recorded from 20 patients twice within 13 weeks of acute unilateral peripheral vestibular deficit onset. Ten patients were tested with an ICS Impulse system (GN Otometrics) and 10 with an EyeSeeCam (ESC) system (Interacoustics). Mean gain and variance were computed with area, average sample gain, and regression techniques over specific head angular velocity (HV) and acceleration (HA) intervals. Results for the same gain technique were not different between measurement systems. Area and average sample gain yielded equally lower variances than regression techniques. Gains computed over the whole impulse duration were larger than those computed for increasing HV. Gain over decreasing HV was associated with larger variances. Gains computed around peak HV were smaller than those computed around peak HA. The median gain over 50-70 ms was not different from gain around peak HV. However, depending on technique used, the gain over increasing HV was different from gain around peak HA. Conversion equations between gains obtained with standard ICS and ESC methods were computed. For low gains, the conversion was dominated by a constant that needed to be added to ESC gains to equal ICS gains. We recommend manufacturers standardize vHIT gain calculations using 2 techniques: area gain around peak HA and peak HV.

Study of parameters of a facility generating compressive plasma flows

The prosperity of plasma technologies stimulates making of a facility generating compressive plasma flows at the South Ural State University. The facility is a compact-geometry magnetoplasma compressor with the following parameters: stored energy up to 15 kJ, voltage of a bank from 3 to 5 kV; nitrogen, air, and other gases can serve as its operating gas. The investigation of parameters of the facility showed the following parameters of compressive plasma flows: impulse duration of up to 120 μs, discharge current of 50-120 kA, speed of plasma flow of 15-30 km/s. By contrast to the available facilities, the parameters of the developed facility can be adjusted in a wide range of voltage from 2 kV to 10 kV, its design permits generating CPF in horizontal and vertical positions.

Extended Duration Running and Impulse Loading Characteristics of an Acoustic Bearing with Enhanced Geometry

This paper presents performance during prolonged running of the acoustic bearing when PZTs are switched off and when they are switched on. The effect of active PZT on shaft’s displacements in X and Y directions is clearly demonstrated. Performance of the acoustic bearing was also assessed when an impulse force was applied to the running shaft at speed. Once again the benefits of having PZTs active are beyond doubt. The instability caused by the impulse force was rapidly mitigated as the bearing returned to its usual dynamics within around two second. In contrast, dynamics of the acoustic bearing operating with PZTs switched off was significantly disturbed and in the time of the test never returned to its status before application of the impulse force.