Operation of propeller motors composed of ship electric propulsion systems with semiconductor converters

The calculations of transient processes in ship electric propulsion systems (EPS) with semiconductor converters (SC) show that when the inverter transistors are locked, overvoltage occurs that may break through the insulation of propeller motors (PM). A feature of this overvoltage is its short duration and large value. Pulsed overvoltage of small duration and the EPS value of dozens or more kilovolts may occur in the circuits of the inverter supplying the PM winding. The main cause of overvoltage is the EPS self-induction resulting from rapid current reduction in circuits with inductances, including in motor windings, when the inverter transistors are locked. The paper presents the results of mathematical modeling of the processes arising when the inverter transistors functioning as part of the frequency converter are locked. The results of the analysis confirmed the possibility of overvoltage on the PM winding, which should be taken into account when designing the EPS and selecting equipment.

Theorizing Virtuality in Enterprise Social Systems

This chapter has built on research on today's modern organizations to lay the foundations for a comprehensive and systematic theorization of enterprise social systems. Theorizing virtuality marks a fundamental transformation in space-time parameters in communications. This is especially so in the context of rapid current advancements in IT such as cloud computing, as well as numerous other technological fronts. Current IT trends show that increased spatio-temporal plasticity heightens the effectiveness and the efficiency of modern enterprise social systems. In particular, subject-oriented asynchronous communications experience greater inferred plasticity and event-oriented synchronous communications experience greater referred plasticity. Finally, enterprise social systems vary in their degree of virtuality based on the perspective of the relevant stakeholder group considered.

Dynamic Improvement with a Feedforward Control Strategy of Bidirectional DC-DC Converter for Battery Charging and Discharging

With the increasing importance of power accumulator batteries in electric vehicles, the accurate characteristics of power accumulator batteries have an important role. In order to evaluate the power accumulator battery, battery charging and discharging is indispensable. In this article, a H-bridge bidirectional DC-DC converter is presented which can charge and discharge the battery with different voltage levels and one of the merits of this topology is that a wide output voltage range can be easily achieved. In the control part, a proportional-integral (PI) control strategy is adopted to ensure a stable and reliable operation of the converter. Furthermore, compared with the PI control strategy, a duty ratio feedforward control is utilized to obtain the rapid current dynamic response. In this article, firstly, the system configuration for battery charging and discharging is introduced, then the operating principles and mathematical model of the DC-DC converter are analyzed and derived. Secondly, for bidirectional DC-DC converters, the PI control method and duty ratio feedforward control method are put forward and designed. Finally, the simulation model is established based on PSIM software and the experiment platform is also built in lab. The results of the simulation and experiment research show that the H-bridge bidirectional DC-DC converter can operate reliably and stably during the charging, discharging and power flow reverse modes. In addition, the dynamic response of the charging and discharging current can also be further improved by introducing the duty ratio feedforward control method.

The Microstructure Evolution and Mechanical Properties of TiBw/TA15 Composite with Network Structure Prepared by Rapid Current Assisted Sintering

TiBw/TA15 (TA15 alloy reinforced by TiB whiskers) composites with network microstructures were successfully prepared by current-assisted sintering at 1100 °C for 10 min. The influence of the sintering parameters on the microstructures of obtained composites was investigated. The sintering temperature was the main factor affecting the average aspect ratio of TiBw, and the average diameter of TiBw could be controlled for various sintering conditions. Yield strength, ultimate compressive strength, and plastic strain at ambient temperature are 1172.5 MPa, 1818.4 MPa, and 22.4% for the TiBw/TA15 composites, respectively. Moreover, yield strength of the composites at 600 °C is 616.3 MPa, which is 26.1% higher than that of the TA15 titanium alloy. The effect of the TiBw on the microstructure evolution for the alloy matrix was discussed in detail. The strengthening mechanism of the TiBw/TA15 composites with network microstructure was attributed to the microstructure modification induced by TiBw, load bearing effect, and dislocation strengthening effect of the TiBw.

Raman Spectroscopy as an Assay to Disentangle Zinc Oxide Carbon Nanotube Composites for Optimized Uric Acid Detection

Refluxed zinc oxide (ZnO) nanoparticles (NPs) were prepared and attached to carboxylic acid functionalized multi-walled carbon nanotubes (COOH-MWNTs) via sonication. Practical optimization of electrocatalysts using sonication to disentangle a carbon nanotube composite for monitoring uric acid (UA) is shown. Monitoring UA is important for the management of medical disorders. Selection of sonication time is a crucial step in producing the desired composite. We report, for the first time, the practical use of Raman spectroscopy to tune the sonication involved in tethering ZnO NPs to the multi-walled carbon nanotube (MWNT) surface. Maximum current for detecting UA, using chronoamperometry and cyclic voltammetry, correlated with the highest sp2-hybridized carbon signal, as seen in the integrated Raman G band peak areas denoting maximum COOH-MWNT disentanglement. An array of ZnO/COOH-MWNT composites were prepared ranging from 60 to 240 min sonication times. Optimum sonication (150 min) corresponded with both maximum measured current and MWNT disentanglement. The sensor was able to quantitatively and selectively measure UA at clinically relevant concentrations (100–900 μM) with rapid current response time (< 5 s).

Theorizing Virtuality in Enterprise Social Systems

This chapter has built on research on today's modern organizations to lay the foundations for a comprehensive and systematic theorization of enterprise social systems. Theorizing virtuality marks a fundamental transformation in space-time parameters in communications. This is especially so in the context of rapid current advancements in IT such as cloud computing, as well as numerous other technological fronts. Current IT trends show that increased spatio-temporal plasticity heightens the effectiveness and the efficiency of modern enterprise social systems. In particular, subject-oriented asynchronous communications experience greater inferred plasticity and event-oriented synchronous communications experience greater referred plasticity. Finally, enterprise social systems vary in their degree of virtuality based on the perspective of the relevant stakeholder group considered.

Managing Virtuality in Enterprise Social Systems

This study has built on research on today's modern organizations with cloud computing to lay the foundations for a comprehensive and systematic theorization of Enterprise Social Systems. The trend toward virtuality marks a fundamental transformation in space-time parameters in communications. This is especially so in the context of rapid current advancements in IT such as cloud computing, as well as numerous other technological fronts. Current IT trends show that increased spatio-temporal plasticity heightens the effectiveness and the efficiency of predominantly Enterprise Social Systems in the cloud computing environment. In particular, subject oriented asynchronous communications experience greater inferred plasticity and event oriented synchronous communications experience greater referred plasticity. Finally, Enterprise Social Systems vary in their degree of virtuality based on the perspective of the relevant stakeholder group considered.

Role of domain calcium in purinergic P2X2 receptor channel desensitization

Activation of P2X2 receptor channels (P2X2Rs) is characterized by a rapid current growth accompanied by a decay of current during sustained ATP application, a phenomenon known as receptor desensitization. Using rat, mouse, and human receptors, we show here that two processes contribute to receptor desensitization: bath calcium-independent desensitization and calcium-dependent desensitization. Calcium-independent desensitization is minor and comparable during repetitive agonist application in cells expressing the full size of the receptor but is pronounced in cells expressing shorter versions of receptors, indicating a role of the COOH terminus in control of receptor desensitization. Calcium-dependent desensitization is substantial during initial agonist application and progressively increases during repetitive agonist application in bath ATP and calcium concentration-dependent manners. Experiments with substitution of bath Na+ with N-methyl-d-glucamine (NMDG+), a large organic cation, indicate that receptor pore dilation is a calcium-independent process in contrast to receptor desensitization. A decrease in the driving force for calcium by changing the holding potential from −60 to +120 mV further indicates that calcium influx through the channel pores at least partially accounts for receptor desensitization. Experiments with various receptor chimeras also indicate that the transmembrane and/or intracellular domains of P2X2R are required for development of calcium-dependent desensitization and that a decrease in the amplitude of current slows receptor desensitization. Simultaneous calcium and current recording shows development of calcium-dependent desensitization without an increase in global intracellular calcium concentrations. Combined with experiments with clamping intrapipette concentrations of calcium at various levels, these experiments indicate that domain calcium is sufficient to establish calcium-dependent receptor desensitization in experiments with whole-cell recordings.

The Chopping Voltage Regulation System Based on PLC Control

For the output voltage of traditional regulators have problems of unstable and unreliability. The chopping control system based on PLC control is designed. This paper takes the PLC intelligent processor as core of the system and uses IGBT constitute chopping circuit. Voltage signal possessed by fuzzy PID export PWM wave to control IGBT opened and closed achieve voltage regulation. The experiment result shows that the system has advantages of simple circuit, rapid current control, and high level automation.