Instruments and Experimental Techniques最新文献

The possibility of efficiently using the principle of pulse voltage multiplication in generators of powerful nanosecond pulses based on high-voltage blocks of shock-ionized dynistors is demonstrated. The electric circuit and design of a generator containing a coaxial cable with a characteristic impedance of 75 Ω and four modules with an operating voltage of 10 kV are described. The modules are switched on in a relay-race mode; each module includes a block of dynistors and a capacitor bank with a capacitance of 8.8 nF. The results of an experimental study of the generator are given. When the cable is connected to a 75-Ω resistor and the capacitors are charged to a voltage of 10 kV, the generator provides the formation of output voltage pulses with an amplitude of ~38 kV, a front-edge duration of ~4.5 ns, and a half-height duration of ~145 ns. The jitter of the output pulses does not exceed 2 ns. When connecting the cable to a spark gap, the generator is capable of operating in a wide range of spark-gap breakdown voltages, as well as in the idling mode, in which the voltage amplitude at the end of the cable reaches a value close to 80 kV. The possibility of scaling up the generator output parameters is shown.

The split-type ultra-high-pressure die with a prism-type cavity is studied by numerical simulation and destructive experiments, which is used for synthesizing super-hard materials and scientific research. The relationship between the split angle and cylinder stresses, stress characteristics, and ultimate pressure-bearing capacity is analyzed. In split-type dies, the divided bodies are pressed together, providing significantly improved massive and lateral support effects, which effectively minimize cylinder stress. The simulation results demonstrate that an increase in the split angle of the cylinder leads to a corresponding decrease in cylinder stress. The stresses in the radial split-type cylinder with a prism-shaped cavity are significantly lower compared to those in belt-type and tangential split-type cylinders. The inner wall of the split-type cylinder, which is flat, bears compressive stresses in the circumferential, radial, and axial directions, resulting in a stress condition that closely resembles the hydrostatic stress state, which is an optimal condition for tungsten carbide material. The pressure-bearing capacities have been verified through destructive experiments and the results indicate that the split-type dies are capable of bearing higher pressures. The split-type ultra-high-pressure die introduces a novel idea and approach to achieving a higher ultimate pressure-bearing capacity and a larger cavity.

Monitoring of methane from oil and natural gas operations is essential to mitigate environmental risks and promote sustainable practices. The method is an effective tool to detect methane presence and compute methane concentration under condition of low signal to noise ratio. The proposed adaptive time synchronous moving average (ATSMA) and pulse signal fusion of laser signal allow to reduce measurement noise. The proposed ATSMA method reduces the random noise level in terms of root mean square error by 10 times less than the established method. The harmonic ratio features and time–amplitude features improve taking into consideration the properties of the absorption signal and pulse allow to improve the methane estimation accuracy. The proposed method provides linear regression model (R² = 0.995) with one dependent variable (time–amplitude centroid area of the absorption pulse) for estimating methane concentration for the measured absorption signal.

An experimental setup has been developed to study interaction between fast neutrons with an energy above 1 MeV and low-Z nuclei with the emission of a ³H or ⁴He nucleus and an electron−positron pair. Its components are a position-sensitive neutron detector with a layer of nuclei under study and proportional chamber with sensitive dimensions of 50 × 50 mm², two position-sensitive silicon detectors with sensitive dimensions of 64 × 64 mm², and two scintillation detectors based on NaI crystals with a diameter of 42 mm, a height of 46 mm, and an energy resolution of ~4.5% for electrons. It is possible to study rare intranuclear processes with the emission of internal-conversion electron−positron pairs by performing spatial reconstruction of events and measuring the energy and exit angle of an electron and a positron.

A simple noncontact optical method for measuring the main parameters of weakly absorbing droplets in nonstationary aerosol flows with low time resolution is proposed. It allows simultaneous measurement of droplet sizes and their speeds and concentrations as a function of time.

The ¹⁰³Ru radionuclide has been produced using a reactor and identified with the aim of developing the ¹⁰³Ru/^103mRh generator. Methods for synthesis and distillation of highly volatile RuO₄ from metallic ruthenium and from solutions have been developed and tested. The effect of RuO₄ purification from concomitant radionuclides during distillation is shown. The feasibility of separating ruthenium and the target radioisotope ^103mRh by thermal distillation of RuO₄ has been demonstrated for the first time.

The paper presents the design of a lightweight, wide-range, high-frequency measurement counter. This counter provides a measurement range of 1 Hz–250 MHz on one channel and 200 MHz–8 GHz on the other, enabling broad coverage across high-frequency applications. Measurement data is processed using a Kalman filtering algorithm in conjunction with a back propagation (BP) neural network compensation algorithm, which together enhance the stability and accuracy of the system. Within the input power range of ±12 dBm, the high-frequency channel achieves average relative error of 2.30 × 10^–8, while the low-frequency channel maintains average relative error of 2.22 × 10^–8. Compared to general-purpose frequency counters, the proposed system offers advantages in terms of low cost, compact size, reduced complexity, high accuracy, good stability, and practical usability, effectively meeting actual measurement needs. It has significant potential for applications in high-precision GNSS timing systems.

The ways to create two-phase hydrogen flowmeters in the range of mass or volume flow rates from approximately 0.2 to 2.5 kg/s or from ~10 to ~130 m³/h, counting by liquid, and flowmeters for liquefied natural gas (LNG) from ~5 to ~210 kg/s or from ~50 to ~2100 m³/h are offered. The principle of operation of flowmeters is based on a combination of void-fraction RF-sensors with a uniform electric field inside sensitive elements with different sensitivities to determine the average density of a two-phase mixture and conical narrowing devices to find the average flow velocity. The expediency of using gamma densitometers for two-phase LNG flowmeters at relatively large diameters DN ≥ 250 is shown. It is proposed how to minimize the problems inherent in such two-phase flowmeters taking the experience of creating analogues for helium into account. The differences between the approaches for the implementation of systems for hydrogen and LNG compared to analogues for two-phase helium due to the significant difference in their properties are considered. Specific technical solutions of two-phase hydrogen and LNG flowmeters with horizontal flow-through cryostats are presented, which are operable in the range of void fractions from 0 to ~0.9 with a relatively small total hydraulic resistance of the flowmeter path. The features of RF-sensor calibrations at different temperatures of cryogens are noted. Some disadvantages of previous approaches to determining the LNG flowrates are shown and the uncertainties of finding the flowrates of two-phase hydrogen and LNG flows are estimated.

The article offers ways to create two-phase helium flowmeters in the range of mass flow rates from approximately 5–6 to more than 1000 g/s. The principle of operation of flowmeters is based on a combination of capacitive void fraction sensors with a uniform electric field inside the sensing elements to determine the average density of the two-phase mixture and conical narrowing devices to find the average flow velocity. In this case, capacitive sensors with sensitive elements of both circular and annular cross sections, which significantly differ in their sensitivity, can be used. The features and problems inherent in two-phase flowmeters of this type are considered, which include, first of all, the influence of a variety of flow patterns on the characteristics of the narrowing device. Another problem is to consider the influence of the structure of a two-phase flow on the determination of its average density. One more problem is related to possible differences between the measured values of the pressure drops in the narrowing device and the expected values, which are estimated using a homogeneous model in one of the limiting cases of a two-phase flow. The ways of minimizing these problems are shown using a combination of individual technical solutions that have already been tested in practice. Specific technical variants of two-phase helium flowmeters, including a flow-through horizontal cryostat, are presented, which are operable in the entire range of the void fractions from 0 to 1 with a relatively small total hydraulic resistance of the flowmeter’s flow part. The differences between the new and previous technical solutions are shown. The uncertainties of determining the flow rate of two-phase helium flows are estimated.

The stick-slip piezoelectric actuators have the disadvantage of backward motion, which reduces the efficiency of the piezoelectric actuator and triggers problems such as abrasion of the driving foot and will seriously affect the life of the actuator. In this study, a new flexible mechanism with inertial block is proposed. The structural parameters and the trajectory of the driving foot are verified by the finite element method. A prototype of the piezoelectric actuator is fabricated and various experiments on the trajectory of the driving foot and the performance of the actuator are conducted. The experimental results show that the piezoelectric actuator can achieve smooth motion with a maximum motion speed of 5.54 μm/s at f = 1 Hz and U = 100 V with symmetry 0% sawtooth wave drive, while the maximum speed can reach 1278.81 μm/s at f = 3000 Hz and U = 100 V. The piezoelectric actuator can realize a maximum horizontal load of 50 g and a maximum vertical load of 1400 g. The results show that the new flexible mechanism and its driving method proposed in this study are practicable, which can effectively reduce the sliding friction in the rapid rise period and effectively increase the static friction in the slow fall period and can achieve smooth motion with high load capacity and driving frequency. It has certain significance for the performance improvement and market application of piezoelectric actuator.