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The present work proposes a Monte Carlo Simulation (MCS) to obtain availability projections for Hydroelectric Power Plants (HPP), based mainly on regulatory aspects involving the Availability Factor (AFA). The main purpose of the simulation is to generate scenarios to obtain statistics for risk analysis and decision-making in relation to the HPP. The proposed methodology consists of two steps, firstly, the optimization of the maintenance schedule of the hydroelectric plant is carried out, in order to allocate the mandatory maintenance in the simulation horizon. Then, for the MCS, scenarios of forced shutdowns of the Generating Units (GU) will be generated, which directly influence the operation and, consequently, the availability of the HPP. The scenarios will be inserted into an operation optimization model, which considers the impact of forced shutdown samples on the MCS. The proposed modeling was applied using real data from the Santo Antônio HPP, which is one of the largest hydroelectric plants in Brazil.

In order to ensure the reliable power supply of the local load in the micro-grid (MG), a seamless switching control technology (SSCT) suitable for grid-connected converter (GCC) is proposed. This technology includes silicon-controlled rectifiers (SCR) forced shutdown control strategy (SCR-FSCS) and three-loop control strategy (TLCS). The SCR-SSCT adjusts the load voltage in real time to form a back voltage at the grid-connected inductor, which greatly reduces the SCR shutdown time and ensures the reliability of local load power supply. The TLCS can easily realize the switching between the current source mode and the voltage source mode of the GCC. An experimental platform is established to carry out the relevant experiments. The experimental results show the rationality and effectiveness of the theoretical analysis and the proposed control technology.

Diesel generator sets are commonly used as power sources in transportation due to their versatility and cost-effectiveness. During the shutdown process, the diesel engine’s cylinder compression pressure would cause forced vibration in the driveline system through the crank linkage mechanism, resulting in unsteady loads that pose a threat to the bearing life. To address this issue, a coupling forward design method is proposed that takes into account the impact of unsteady loads on bearing life. An experiment was conducted on a 16V280 diesel generator set shutdown process, and a driveline dynamic model was established. The cumulative damage value that connects unsteady loads and bearing life was introduced to quantify the effect of unsteady loads on the bearing life during the shutdown process. The unsteady loads included torque fluctuation and collision forces. The results showed that reducing the driveline key gap and increasing the coupling stiffness can decrease the combined load on bearings and improve bearing life. A large stiffness coupling was designed to achieve shutdown smoothness and a 43.19% reduction in bearing life damage, confirming the design method’s feasibility concerning bearing life.

In view of the characteristic of large transformer load fluctuations, a feedforward fuzzy control strategy using the startup and shutdown of cooler groups as the executive means is proposed to meet the transformer temperature control requirements. Based on the research on the mechanism of oil-immersed forced oil circulation air-cooled (OFAF) coolers, fuzzy control rules are summarized to realize the closed-loop regulation of transformer oil temperature. Meanwhile, feedforward control is used to compensate for the impact of transformer power disturbances on oil temperature. A simulation control model of the OFAF cooler is built on the Simulink platform, which verifies the feasibility and effectiveness of the feedforward fuzzy control strategy for the transformer OFAF cooler. Furthermore, by comparing the results under two control execution modes, the advantages of using the startup and shutdown of cooler groups as the executive means are analyzed.

The availability (readiness) of a Steam Power Plant (PLTU) is an important factor, since one income from a Power Plant is based on its readiness reflected in the EAF (Equivalent Availibility Factor). Factor opposite to Availibility is Outage. Outage occurs when a unit is out of sync to a network and not in a Reserve Shutdown state.

National Nuclear Energy Agency has planned to convert the Bandung TRIGA reactor by replacing the rod-type into plate-type fuel elements. The calculation results show that Bandung TRIGA Plate reactor with 2000 kW power requires forced convection cooling system. According to the calculation results using the Coolod-N2 computer program the minimum required cooling flow rate is 70 kg/s. Consequently, it is necessary to modify the reactor primary cooling system. In this modification required a flapper valve design that can a double function. The valve closed when the primary pump is powered and the flow rate on the primary coolant is 70 kg/s. However, when the pump is off because of the power outages and the reactor will scram, so the flapper valve will open. The residual heat in the reactor core will be cooled by natural convection. There is reversal flow from a downward to an upward cooling direction, and the upward natural convection heat removal throughout the flapper valve. In addition, the reactor also will scram if the cooling flow rate drops below 85% of 70 kg/s. The flapper valve is equipped with a ballast pendulum to open the flapper valve. The pendulum load must be greater than the flapper valve force plus the pump force due to forced flow. The flapper valve will open, if the flow rate is smaller than 85% of the required flow. Conversely, the flapper valve load must be smaller than the amount of flapper valve force and flow due to the pumps attractiveness, so that the flapper valve can be closed tightly and the reactor can operate with a forced convection flow. The design of natural convection flapper valve considers the following of a reliable, a work based on passive systems, a simple, an easy to make, an easy maintenance and it can be observed from the top of the reactor tank deck. As a redundancy, the operation of natural convection a flapper valve is added by mechanical operation, so the operation of the valve is truly reliable.

A study has been conducted to find out how much heat removal in the refueling process in AP1000 reactor. The background of this research is, operation at a Nuclear Power Plant is strongly tied to periodical fuel replacement to guarantee future operations. The replacement of fuel assembly can be done by one-third of core or a half of core refueling. After the reactor shutdown, the spent fuel assemblies still generate decay heat that must be removed to prevent from fuel damage cause of heat buildup. The process of heat removal can be done by natural and forced convection modes. The purpose of this study was to obtain the cooling times after shutdown so that the fuel assembly can be transferred to the spent fuel storage pool (SFSP) with natural convection mode, and how minimum flow rate was required for cooling the 7 days spent fuel assembly by forced convection cooling in the SFSP. The requirement in the cooling was no boiling occurred in the channel. The calculation was carried out by assuming the inlet coolant temperature of 30°C and by using COOLOD-N2 code. The calculation results showed that for the one-third of core refueling and for cooling with natural convection, it took 21 days after shutdown, the new spent fuel assemblies could be transferred to SFSP, while for the forced convection cooling required minimum flow rate of 15 kg/s in the SFSP. The calculation result on the hot channel showed the outlet coolant temperature of 101.88°C, the maximum temperature of the outer cladding and the center fuel meat of 104.63°C and 105.21°C, respectively. As for a half of core refueling and for cooling with natural convection, it took 42 days after shutdown, the new spent fuel assemblies could be transferred to SFSP, while for the forced convection cooling required minimum flow rate of 25 kg/s in the SFSP. Calculations on the hottest channel showed the outlet coolant temperature of 90.54°C, the maximum temperature of outer cladding and the center fuel meat of 93.16°C and 93.75°C, respectively.

Purpose The novel coronavirus, SARS-CoV-2, emerged from Wuhan, China, causing a pandemic. Access to outpatient psychiatric care was limited. We conducted a pilot study of telepsychiatry during a national shutdown. Adult patients with post-traumatic stress disorder (PTSD) participated via Zoom. Patient preference comparing televisits to face-to-face visits was assessed. Recent findings Telemedicine has emerged as new technological tool in the evolution of the patient-physician relationship, changing the way we interact. Physicians and patients now have access to the electronic medical record, remote point-of-care testing, and each other. The present epidemic allows us to test the limits of technology in combating limited access to care for patients with psychiatric illness. Summary Twenty (90% male) patients with PTSD participated. Most (90 %) were moderately to severely depressed, and 50% used medical cannabis and increased their dosage during the study period. Patients preferred face-to-face meetings for its ease of use (p < .01) and general satisfaction from therapy (p < .01). However, given continued outbreak-limiting access to care, most patients stated they would continue with telepsychiatry. While most patients preferred face-to-face visits, telepsychiatry can be used during times of outbreak-limiting access to care. Future research and development should be directed at improving technological ease of use.

Purpose. Development and justification of a method for limiting resonance vibrations during start-up and shutdown of vibrating machines by using cord-reinforced rubber air springs as elastic elements Methodology. Viscoelastic models of two systems are considered; the first includes a rubber-cord air spring filled with compressed air and connected to an additional air volume through an orifice plate; the second system incorporates a rubber-cord air spring filled with liquid and connected to a hydropneumatic accumulator through an orifice plate. For these viscoelastic systems, linearized equivalent dynamic diagrams have been presented and differential equations of motion have been formulated. A method of limiting resonance vibrations during the start-up and shutdown of vibrating machines is considered. The effectiveness of limiting the resonance vibrations and forces transmitted to the fixed support structures is studied using the example of a vibrating screen. The worst case is considered when resonance vibrations are of a steady nature. The amplitude-frequency response and coefficients have been obtained, which characterize the dynamic load transmission to the fixed support structures for various viscous resistance forces determined by the orifice plate parameters. Findings. Equivalent schematic diagrams of viscoelastic systems incorporating rubber-cord air springs and a mathematical model describing the forced vibrations have been developed, a method has been proposed for limiting vibrations and loads transmitted to the fixed support structures during start-up and shutdown of vibrating machines. The effectiveness of the proposed method has been justified. Originality. It has been scientifically justified that the use of rubber-cord air springs as elastic elements of vibrating machines allows effectively limiting resonance vibrations and dynamic loads transmitted to the structures of fixed supports. Practical value. This allows limiting resonance vibration amplitude of a vibrating screen and decreasing dynamic loads transmitted to the fixed support structures of vibrating machines.

This paper explains the impact of industrial shut down and land use change in Chaliyar river basin in Kerala, the southern state of India. The gradual migration of local labour for jobs abroad has made a remarkable impact on the land use in the local region. The large scale migration was chiefly the outcome of unemployment in the local region as a result of the shutdown of the rayon industry which was the only source of income to the local village community. Two parallel phenomena were observed since 2001: the migration pattern of labour force in the study area, and the changes in land use pattern. Given this background of the problem it is interesting to observe the land use changes through remote sensing during different time periods.