Simulation and verification of measurement system for deep-sea pressure and its small fluctuation pressure

Combined pressure measuring system (CPMS), which is mainly used for measuring deep-sea larger pressure and its small fluctuation pressure, is studied. First, the working principle of the CPMS is introduced. Second, the mathematical model of the CPMS is established. Third, the influence of the cross-sectional area of the piston, the equivalent mass of the piston, the diving speed, the cross-sectional diameter of the compensator piston, the air content of the liquid medium, and the small fluctuation pressure on the measurement performance of the CPMS is analyzed using the simulation model. Then, the design principle of the system is summarized. Finally, the test platform is built. The results show that the dynamic pressure is not more than 0.025 bar when the pressure change speed is 0.2 bar/s, the pressure is 2.8 × 10−3 bar under 20 bar, thereby verifying the validity and accuracy of the measurement method and providing theoretical basis and reference for the design and optimization of the measurement system.

Dinamica poluarii aerului atmosferic în Republica Moldova în contextul conventiilor de mediu

The paper presents calculation of emissions of pollutants from different categories of source according to UN framework Convention and LRTAP using EMEP EEA emission inventory guidebook/2013. For the period 1990-2017 has been found a trend of decrease of emissions into the atmosphere, generated primarily by the economic crisis and the changes and modernization especially in the field of thermal energy and transport. Decreasing of the emmisions content is approximatively 10-25% per yearuntil 2000 with a small fluctuation in griuth in recent years. The paper presents different approaches for assessment of emmisions as a result of use various sources.

Study on Small Fluctuation Stability in Air Cushion Surge Chamber Based on State Space Method

In this paper, on the basis of the state space method and actual system arrangement, the small fluctuation mathematical model of the water conveyance system with air cushion surge chamber (ACSC) was established. According to the basic equations of ACSC, the ideal gas state equation and the units constant output equation, the formula describing the stable cross-section area (SCSA) of ACSC was deduced, and the small fluctuation stability (SFS) of water conveyance system was analyzed. The corresponding results showed that the air chamber constant had a great influence on the SCSA of ACSC. When the air chamber constant became larger, the quality of the system small fluctuation went worse. The higher upstream water level and the lower initial air chamber height will lead to a smaller initial air chamber constant of ACSC, which is destructive for the stability of the system small fluctuation; As long as the equivalent air quality and air chamber volume are constant, good quality system small fluctuations could be obtained when the initial air chamber height is small and the area of ACSC is large.

Pressure-Assisted Sintering of Buried Thick Film Resistors in LTCC

In this work, the effect of the pressure-assisted sintering process on buried thick film resistors integrated in LTCC multilayer has been studied. Four commercial resistor pastes with sheet resistivities between 10 kΩ and 10 MΩ/cm were analyzed. First they were characterized by SEM/EDX, XRD and Laser diffraction to determine composition and particle distribution. The pastes consist of isolating particles and of Ruthenium based particles that are supposed to build the conductive phase. The pastes were screen printed on LTCC green tape (DP 951) and buried in four layer laminates. Sintering was done in two ways, pressureless (PLS) and also pressure-assisted (PAS). The pressureless sintered resistors showed electrical resistance values roughly in the range of the nominal sheet resistivity and only relatively small fluctuation within one sample. The PAS samples on the other hand showed significantly higher resistances and larger deviations. The microstructure of the sintered resistors was again investigated by SEM and XRD. It seems that the resistivity is determined by the ratio of the two Ruthenium phases RuO2 and Pb2Ru2O6.5, where RuO2 has the higher conductivity. Buried resistors cannot be trimmed by a laser to adjust the resistance. But we discovered that a refiring step will reduce and normalize the resistivity of the PAS resistors significantly.

Investigation on Type-4 and Type-11 Mixed Topology of LLC Resonant Converter

LLC resonant converter can adjust the output for a wide range of source and load with a small fluctuation of switching frequency, so it is used widely. This paper introduces all arrangements of LLC topological group, then proposes a new topology which is consist of Type-4 and Type-11 that used widely,in this paper we also give its calculate method of resonant frequency. Lastly we get gain characteristics of the topologies in the PSpice simulation environment and analyse the influence factors on adjustment ability in certain load range .

Study on Stability of Hydroelectric Generating Set Influenced by the Governor Parameters under Isolated Grid

In order to study on stability of hydroelectric generating set under isolated grid, taking hydraulic, mechanical, and electrical system into consideration to build the mathematical model. This paper has researched on the main governor parameters sensitivity in the small fluctuations transition process of complex hydropower station under isolated grid. According to the simulated results, KP or KI increases, or KD decreases appropriately, governor quality of small fluctuation transition process will be better. The influence caused by KD is the most obvious of the three.