Inrush Current Based on Fast Fourier Transform

Advances in technology have caused the use of electricity to increase rapidly. With advances in technology, this is followed by the use of increasingly efficient electrical components or equipment. This more efficient electrical equipment causes the impedance of the component to be smaller, causing a surge in current when it is turned on. This current surge, if not followed by appropriate safety precautions, will be damage other components. Each load has different waveform characteristics and current transient peaks. For this reason, it is necessary to analyze the transient condition of a load to overcome this. This paper will explain the characteristics of the inrush current of the load due to ignition. There are three loads used in this study, namely resistive, capacitive and inductive loads. Then the use of this load is simulated by giving different ignition angle values, namely 0, 60, and 90 degrees. The analysis used is the Fast Fourier Transform (FFT) method which is a derivative of the Discrete Fourier Transform. The inrush current spectrum in this simulation is simulated using Simulink MATLAB with switching system modeling using TRIAC. This inrush current simulation data collection uses a sampling frequency of 100 Khz and will be analyzed in the first of 5 cycles. For each load in this paper, the harmonic values for each ignition angle will be presented. The simulation results show that the inrush current is caused by the ignition angle value used and because of components that can deviate energy such as inductors and capacitors as well as components which at the time of starting have a low impedance value such as incandescent lamps. The simulation also shows that the use of switching components for setting the ignition angle causes an increase in the value of Total Harmonic Distortion (THD) but the peak current in the first cycle when the ignition angle is set decreases.

Simulation System for PeLUIt 150 MW Nuclear Reactor by using vPower

In developing the PeLUIt 150 MW nuclear power plant based on the High Temperature Gas-cooled Reactor (HTGR) technology, with the helium-coolant and output thermal power of 150 MW, the PeLUIt simulator is also developed for training the operators and educating other technical personnel. Referred to the balance of plant (BOP) design of the PeLUIt, the simulator utilized the vPower simulation platform to simulate the secondary loop for power generation with a water-steam Rankine cycle. The paper focuses on developing the secondary loop’s main components: steam generator, steam turbine, condenser, deaerator, and feedwater pump. The reactor module in the primary loop is simplified as a heat source with 150 MW output. The steam generator that connects the primary and secondary loops is modeled with the heat exchanger module by transferring heat from helium to water/steam. Meanwhile, pressure and flow parameters can also be simulated for both helium and water/steam flows in steady-state and transient operating conditions. The steady-state simulation results are almost the same as the design data. The differences in the main steam temperature, feedwater pressure, and feedwater temperature, are 0.03%, 0.53%, and 0.02%, respectively. Meanwhile, the transient condition carried out in the loss of coolant accident showed a decrease in flowrate of 43.31 kg/s and an increase in temperature of feedwater and main-steam of 52.32 and 15.38 °C, respectively. In addition, there was a pressure drop of around 10.37 (feedwater) and 10.16 MPa (main-steam).

Teaching power system stabilizer and proportional-integral-derivative impacts on transient condition in synchronous generator

Understanding the concepts based on problem solving is not an easy methodology in teaching the impact of power systems stabilizer (PSS) on transient synchronous generator using MATLAB capability. Experiments conducted in simulating sessions play an important role in this teaching. This simulation can simulate power system stability behavior with reasonable accuracy in less time. This transient phenomenon of a power system utilizing synchronous generator and modelling by fully three-phase model with changes in stator flux linkages neglected is analyzed by employed single machine infinite bus taken to the power system. Whereas a power system stabilizer which consist of a wash-out circuit, two stages of compensation, a filter unit, and a limiter, is applied to control voltage and frequency of power systems in transient condition. Proportional-integral-derivative (PID) controller tuned by Ziegler-Nichols’s method is cascaded to conventional PSS in order to enhance the response time of system while providing a better result in damping for oscillation. This gives the clear idea about PSS and PID controller impacts on transient synchronous generator and its enhancement to the students of electrical engineering program, Institut Teknologi Nasional Yogyakarta.

Delirium in neurological practice

Delirium is an acute, usually reversible, fluctuating impairment of the level of consciousness, attention, and cognitive activity resulted from impaired brain metabolism due to a wide range of various neurological and non-neurological diseases, the effects of drugs and other substances. The main manifestations of delirium are acute changes in consciousness, disturbance of attention, perception, often with the development of hallucinations, emotion, sleep-wake cycle, psychomotor and autonomic activity. Delirium is divided into hypoactive and hyperactive subtypes depending on the severity of psychomotor and emotional disturbances. Patients with acute stroke are also often susceptible to episodes of delirium at the risk factors such as age, pre-existing cognitive impairment, pneumonia, urinary tract infections, and right hemispheric stroke. The pathophysiology of delirium has been less known, but there is evidence of the role of cholinergic deficiency. Delirium is a transient condition, but it needs treatment to prevent the development of complications since it is usually associated with poor functional outcomes, longer hospitalization and higher mortality. The strategy for the treatment of patients with delirium should be directed to early identification of its symptoms, elimination of modifiable risk factors and metabolic causes. In patients with severe symptoms of agitation and hallucinations, short-term prescription of antipsychotics for their relief is possible.

Update on Neonatal Isolated Hyperthyrotropinemia: A Systematic Review

The purpose of this paper was to systematically summarize the published literature on neonatal isolated hyperthyrotropinemia (HTT), with a focus on prevalence, L-T4 management, re-evaluation of thyroid function during infancy or childhood, etiology including genetic variation, thyroid imaging tests, and developmental outcome. Electronic and manual searches were conducted for relevant publications, and a total of 46 articles were included in this systematic review. The overall prevalence of neonatal HTT was estimated at 0.06%. The occurrence of abnormal imaging tests was found to be higher in the persistent than in the transient condition. A continuous spectrum of thyroid impairment severity can occur because of genetic factors, environmental factors, or a combination of the two. Excessive or insufficient iodine levels were found in 46% and 16% of infants, respectively. Thirty-five different genetic variants have been found in three genes in 37 patients with neonatal HTT of different ethnic backgrounds extracted from studies with variable design. In general, genetic variants reported in the TSHR gene, the most auspicious candidate gene for HTT, may explain the phenotype of the patients. Many practitioners elect to treat infants with HTT to prevent any possible adverse developmental effects. Most patients with thyroid abnormalities and/or carrying monoallelic or biallelic genetic variants have received L-T4 treatment. For all those neonates on treatment with L-T4, it is essential to ensure follow-up until 2 or 3 years of age and to conduct medically supervised trial-off therapy when warranted. TSH levels were found to be elevated following cessation of therapy in 44% of children. Withdrawal of treatment was judged as unsuccessful, and medication was restarted, in 78% of cases. Finally, data extracted from nine studies showed that none of the 94 included patients proved to have a poor developmental outcome (0/94). Among subjects presenting with normal cognitive performance, 82% of cases have received L-T4 therapy. Until now, the precise neurodevelopmental risks posed by mild disease remain uncertain.

Den konstanta oron

In the last decade, poor mental health among children and young people has been a recurrent topic of discussion in Swedish media. These discus­sions have predominately been characterized by both a dystopic tone and a presentism that, combined, has led to a framing of the situation as worse than ever and in need of immediate solutions. Based on an analysis of articles in Swedish daily newspapers from 1968 to 2008, we show in this article that alarming articles on the mental health of Swedish children and young people have, in fact, appeared frequently throughout these four decades and that these articles, regardless of year of publication, presented similar statistics over how many children and young people suffered from poor mental health. Alarms and concerns about the poor mental health of children and young people thus have a longer history than what is often claimed by contemporary actors. Nevertheless, we could also discern several important shifts over the years. In the early decades, the discussions revolved around the concepts of psychological disorders and psychological problems, while poor mental health became central during the latter part of the time period. However, more specific psychological and psychiatric terms, such as anxiety and psychosomatic symptoms, were more stable and did not really change to any significant extent over the years. Moreover, the set of actors involved in the discussion expanded and diversified over time, with civil society organizations in particular taking a more prominent place. To conclude, we argue that the consensus and consistency among the actors over time may be due to how the issue was framed in quantitative, descriptive and epide­miological terms, as this avoided any theoretically charged debates over the etiology and categorization of disorders, a question that has otherwise had a quite turbulent history in child psychiatry and psychology and which has divided experts and professionals. The discussions have also offered certain self-understandings to the public, including a normalizing conception of poor mental health presenting such problems as a transient condition that could possibly afflict any child or young person.

Does change in barometric pressure per given time at high altitude influence symptoms of acute mountain sickness on Mount Fuji? A pilot study

Background Acute mountain sickness (AMS) is a common, transient condition characterized primarily by headaches, and it can also be associated with fatigue, dizziness, and nausea with vomiting. The symptoms of AMS are most pronounced after the first night spent at a new altitude. At sea level, changes in barometric pressure per given time have been associated with migraine headaches. We sought to investigate whether changes in barometric pressure, subjective sleep quality index, and other candidates contributed to the risk of developing AMS on Mount Fuji in Japan. Method We surveyed 353 trekkers who stayed overnight at a mountain lodge before summitting Mount Fuji. We collected information regarding sex, age, sleeping altitude at the hut, and perceived sleep quality index including sleep time. AMS was assessed with the Lake Louise Scoring system. Barometric pressure and ambient temperature were collected at the 5th station (2305 m) and at the summit (3776 m). Result The overall prevalence of AMS in our cohort was 41.4% (Lake Louise Score ≥ 3 with headache, n=146). Using logistic regression, three factors were combined to generate a robust model for determining the risk of AMS (with or without AMS). These included (1) Δ barometric pressure during ascent per hour, (2) sleepiness on rising, and (3) sleep refreshment assessed by perceived sleep quality index. Conclusion These results suggest that climbers who stay overnight at the lodge should keep a better physical condition of sleep, and would pay attention to information of barometric pressure condition to decrease their risk of AMS at the summit of Mount Fuji. Our observatory data indicated that an overnight staying in half way up to the summit does not necessarily reduce the AMS risk in both sexes and irrespective of age, at least, until 3776 m elevation.

Modelling of Flow Behaviour and Rheological Properties of M2 Steel in Semisolid State

The present study develops a model to investigate time dependent behaviours of M2 steel in semisolid state during step-change in shear rate. The Couette flow of the semisolid material between two parallel plates is considered. The flow field is presented by momentum conservation equation. The non-Newtoniun behaviour of the semisolid material is expressed by the Herschel-Bulkley model. The agglomeration and de-agglomeration phenomena of the suspended particles in semisolid state under shear are represented introducing a time dependent structural parameter. The proposed model fitted well with existing work in a wide range of shear rates and could predict the flow and apparent viscosity of semisolid M2 steel. Finally, the work involves prediction of the flow field, rate of strain and apparent viscosity of the semisolid material under transient condition. It is observed that the time dependent viscosity is highly non-linear during step-change in shear rate. It is noticed that the structural parameter decreases as the shear rate is increased. Whereas, the apparent viscosity decreases with increasing shear rate but shows an undulation and after that gradually rises to a higher steady value as the plate velocity decreases suddenly.

Dynamic state estimation of multi-machine power system with UPFC using EKF algorithm

Estimation of dynamic state variables in a multi-machine power system connected with UPFC is presented in this paper, using Extended Kalman filter (EKF) algorithm. A two-generator test case is used to estimate the generator rotor angle and rotor speed. The DC link voltage of the UPFC is the additional state variable to be estimated. Dynamic mathematical modeling of the multi-machine system with UPFC is explained in this work. DSE is done under transient condition of three-phase fault.