Stop Operation Research Articles

A Consensus Study: Generational Differences in Neurosurgeons' Perception of Retirement and Practice Limits

Concerns about the changing demographics in the United States and the aging of the neurosurgical workforce exist. Both the importance and inherent risk of surgical responsibilities suggest that thought be given to whether workloads should change later in surgeons' careers. We sought to assess current neurosurgeons' expectations concerning their late-stage careers. A survey was sent to 3317 U.S. board-certified neurosurgeons. It was designed to assess surgeons' perceptions of call and operative responsibilities in the later stages of their careers. Statistical analyses were completed in R version 3.6.1, with an alpha set to 0.05. Six-hundred and fifty-nine neurosurgeons completed the questionnaire. Seventy-seven percent believed that the call burden should decrease later in practice, and 66% planned to decrease their own call burden later in their career. The most common age range for planned retirement was 65 to 69 years (36%), followed by 70+ years (33%). Most (67%) believed that there should not be a mandatory age to stop operating. More recent year of residency completion was negatively associated with the belief that call burden should decrease at older age groups and positively associated with support for a mandatory age to stop operating as well as an earlier retirement age. This study suggests that neurosurgeons have differing views on how workloads should change later in their careers. Younger neurosurgeons support an earlier decrease in workload or even a policy-mandated stop to operating after a certain age. These results may give insight into future trends and turnover in neurosurgery and provide a valuable tool to help practices anticipate workforce changes.

Variable Speed Drives in Electric Elevator Systems: A Review

Due to the industrial development and the growing modernity, the elevator systems have become indispensable in many multi-story buildings. When electrical elevators are employed to transport people, riding comfort becomes a very important issue, especially when high-speed elevators are used in high-rise buildings. The elevator systems should provide a good stop accuracy and excellent levels of ride comfort. Passengers experience some problems that affect their comfort such as vibration and jerk that occur when travelling between elevator floors especially when starting and stopping the cabin. To minimize the effects of these problems, the cabin must be driven in such a way as to ensure smooth operation and smooth starting and stopping. Therefore, there is a need to control the voltage and frequency of the electric motor that drives the elevator cabin.This paper introduces a look at the different types of variable speed drives and how they’re used in electric elevator systems, discussing current systems as well as recent development in the field. Therefore, a variable-speed design that provides smooth movement is needed to include a smooth ride, accurate leveling, and a large number of start and stop operations First, some basic principles in driving systems, such as load curves and driving speed/torque, as well as their relationship to stability, are discussed; reference curve generation; speed curve profiling of the elevator system to achieve smooth transmission. The latest study in this topic reached the implementation of an elevator prototype driven by permanent magnet linear synchronous motor (PMSLM) loaded by 24kg. The motor was controlled by voltage frequency drive (VFD) programmed with offline S-curve to get a smooth start and smooth stop for the elevator cabin and constant travel speed with the least jerk possible, estimated by 88% compared the that without using the driver.

Analysis, design and reconstruction of a VRP model in a collapsed distribution network using simulation and optimization

One of the main characteristics of real transportation problems is not only the complexity of designing their models but also the characterization of the elements that make up the supply chain. A more detailed study will certainly provide more information about the system. However, the use of regular networks for the development of models can remove key characteristics needed for correct decision making, so we propose the characterization of transport models through the conceptualization of complex networks.The methodology proposes a mechanism for the reconstruction of the network when the distribution network is under attack, and any of its nodes or arcs stop operating; making it very hard to find a solution to the vehicle routing problem. In this way by reconstructing the route and the cost matrix it is possible to obtain feasible routes.The purpose of this research is to show how the proposed methodology can be applied.

Incorporating Practical Degree of Saturation in Capacity Estimation of On-Street, Mid-Block, Off-Line Bus Stops

The effectiveness of an on-street bus facility depends on the general traffic that shares the lane used by buses. The Transit Capacity and Quality of Service Manual (TCQSM) methodology was used to estimate facility bus capacity based on critical stop operation. Hisham et al. provided an improved understanding of performance of an on-street, mid-block, off-line bus stop by relating bus stop capacity to the adjacent lane traffic flow rate. Using the TCQSM methodology, bus stop capacity was determined by adopting an estimated operation margin that relates to a design bus stop failure rate. However, failure rate is theoretically ambiguous and difficult to quantify in practice, particularly under high volume traffic conditions. In contrast, degree of saturation is a direct measure of operating conditions experienced by buses using the stop, and by the adjacent lane general traffic, so it directly affects approach delay and queuing. The aim of this study was to better understand performance at on-street, mid-block, off-line bus stops by considering degrees of saturation of loading areas and the adjacent lane rather than design failure rate according to the TCQSM methodology, and to ensure that waiting times upstream of bus stops are kept to acceptable levels by determining bus stop maximum working capacity.

Research of Turbine Oil Varnish in Generator Unit

In recent years, due to the fact that thermal power generating units have been deeply involved in the peak shaving work of the power grid, the frequent start and stop operations of the units and rapid load-carrying operations have made the operating conditions of the units very bad. In large-scale thermal power generation units, shutdown accidents caused by varnish failures are becoming more common. Take the serious varnish failure of Unit 3 in a domestic power plant as a case for analysis. The steam turbine oil after the varnish is formed is fully analyzed and tested and the metal ion content test is carried out. The changes in the physical indicators of the steam turbine oil during the formation of the varnish are studied to determine the influence of the steam turbine oil on the physical indicators of the steam turbine oil during the formation of the steam turbine oil. The operation and maintenance personnel can detect the varnish in advance through the daily sampling and analysis of the steam turbine oil, and timely take treatment measures to remove the varnish components in the oil to ensure the safe and stable operation of the unit. This article summarizes the reason for the formation of varnish and the detection method of varnish. It is of great significance to effectively discover and control the production of varnish during the operation of the generator set, to study the formation mechanism of varnish and to find an effective method to remove varnish. This article also introduces the commonly used paint film treatment methods for the convenience of electric power technicians.

Study of Pressure Pulsations in a Francis Turbine Designed for Frequent Start-Stop

Abstract The energy market aims for high flexibility that allows guaranteed power to the consumers with minimum carbon footprint. Over the last three decades, hydropower has been a reliable and an efficient option to meet the fluctuating energy demand as it allows high-ramping rate and quick start-stop. However, such critical operations bring certain challenges for hydro turbines, i.e., high-amplitude stochastic loading and the fatigue. Credible investigation of unsteady pressure pulsations and their signature is important to understand the consequences. The present work aims to study pressure pulsations in a model Francis turbine, which is designed for the frequent start–stop operations. A total of 112 numerical simulations, across the hill diagram, are conducted. Pressure pulsations in the vaneless space, blade channels, and draft tube are investigated. The results show distinct patterns of rotor-stator interaction frequencies in the turbine. In the regions of high rotational speed and low flow rate, stochastic pulsations are predominant.

Hotel Marketing Strategy in Biak Papua to Survive During the Covid-19 Pandemic

The pandemic has paralyzed global tourism. In Biak Papua, the impact of the pandemic on the tourism industry is enormous. Almost all hotels stop operating, even if one is open, that also opens up for the quarantine of Covid sufferers. This article examines the condition of hotels in Biak and the survival marketing strategies adopted during the outbreak. This research uses a descriptive qualitative approach using in-depth interviews and literature studies on books, scientific journals, and online news. This study focuses on Basana Inn and Manna Inn, on the grounds of the level of representation of the Jasmine Hotel and customer types. The research results show that the impact of the pandemic has resulted in almost empty hotel occupancy. The strategy carried out is almost the same, namely by terminating employees permanently and temporarily, limiting the use of hotel facilities, spending efficiency, selling non-room products online, and refusing to refund bookings by changing visit schedules. During the Covid 19 pandemic, a marketing strategy is very important to do. In obtaining optimal results, strategies in marketing are carried out which have a very broad scope, including analytical strategies to face competition, price strategies, product strategies, service strategies and so on. The Covid 19 outbreak has given service companies a sense of worry or discomfort, especially the Basana Inn Hotel which is engaged in accommodation services. Seeing the results of the identification of problems in this study, researchers are interested in researching the title "Hotel Marketing Strategies in Biak Papua to Survive the Covid-19 Pandemic." The purpose of this research is to find out and analyze the most appropriate strategy in the Covid 19 Pandemic situation.

Article 25 as an Alternate Way to Resolve the Crisis of the WTO Dispute Settlement Mechanism: A Chinese Perspective

The primary purpose of this research is to propose the solution to the current crisis of the WTO dispute settlement system focusing on Article 25 of the WTO Agreement. The Dispute Settlement Understanding is one of the significant successes of the WTO. Recent years, however, have witnessed the difficulties and challenges facing the multilateral trading system along with rising anti-globalization and trade protectionism. The Appellate Body (AB) has been experiencing an unprecedented crisis of dysfunction mainly due to the US’s boycott of appointing the new members. The WTO Members, including China, have thus proposed various reforms in response to the crisis. However, they have not touched the core demands of the US. Because of the imminent crisis that the AB is about to stop operating, China should take urgent action with other WTO members, consider launching a majority voting program, design and use alternative appeal arbitration, and combine international rules with domestic deepening reforms.

Failure Investigation of Repetitive Crack on MW-701D Gas Turbine Exhaust Manifold

A gas turbine power plant is the best choice for peak load conditions in power generation. As we know using gas turbine need less time to start and stop operation than a coal-fired power plant. In East Java, Indonesia has 9unit Gas Turbine Power Plant, which usually operates in peak load conditions. In this paper, a study will carry out an investigation based on maintenance data history which since 2010 founded repeatedly crack in the exhaust manifold. Failure Investigation in the exhaust manifold has been carried so that repetitive crack can be handled in the future. The crack location was mapped to found the root cause of failure. Fuel consumption and operation condition was analyzed to find the cause of the crack. Analysis with fluent software found that streamline of flue gas makes a turbulency in the spotted area. Material selection and design no free expansion in the exhaust manifold increase possibility of failure.

Artificial Neural Network Hysteresis Operators for the Identification of Hammerstein Hysteretic Systems

Abstract This paper introduces explicit neural representations of fundamental hysteresis operators such as the play and stop operators. The hysteresis neurons are represented by recurrent artificial neural networks (ANN) using classical activation functions and are trained with gradient-based learning algorithms. The hysteresis neurons are combined into a single ANN hysteretic layer which, from a mathematical point of view, is equivalent to a classical Prandtl-Ishlinskii model expression, but has all the advantages of ANNs. One such benefit is the flexibility it offers to be combined with other ANN layers to obtain various complex model structures. In this paper, this is illustrated by combining it with a linear recurrent neural network to obtain a Hammerstein model structure, which is often considered for the characterization of systems driven by a class of smart material-based actuators. The input nonlinearity in the Hammerstein model is represented by a Prandtl-Ishlinskii ANN hysteretic layer while the linear dynamics are captured using a linear recurrent ANN representing a single-input multiple-output linear time-invariant state-space model. The identification approach of the Hammerstein model with a hysteretic layer is illustrated both numerically and experimentally.

The relationship between stress of plate-fin structures and emergency stop operation process in LNG heat exchanger

For insuring the safe operation of LNG heat exchanger in the Emergency Stop Operation Process (ESOP), a numerical method is proposed to investigate the stress of Plate-Fin Structures (PFS) in that. The relationship between stress of PFS and ESOP is analyzed in LNG heat exchanger. The results will be obtained that the maximum equivalent stress of PFS is greater at the initial stage of ESOP than that at the last stage when the HMR pressure is more than 5 MPa. The maximum equivalent stress increases with the equilibrium temperature when is greater than 180 K and reaches peak value at the last stage of ESOP. The maximum equivalent stress is larger at the last stage of ESOP than the other stage and increases with the equilibrium pressure. When the temperature difference is more than 5 K in the ESOP, the influence of that is obvious for the stress of PFS. In the ESOP, the equilibrium temperature and temperature difference should be controlled within 240 K and 5 K, respectively.

Visual interfaces for the digital simulation system of the IPR-R1 Triga nuclear research reactor

Nuclear Technology Development Center (CDTN) offers the Training Course for Research Reactor Operator (Ctorp). This course is offered since 1974 and about 250 nuclear professionals were certificated by CDTN. Thus, a digital simulation system for the IPR-R1 Triga research reactor was developed to be a tool for teaching, training and recycling professionals. The simulator was developed using the LabVIEW® (Laboratory Virtual Instruments Engineering Workbench), with support calculation software, where mathematical models and graphical interface configurations form a friendly platform, which allows the trainee to be identified with the physical systems of the research reactor. A simplified modeling of the main physical phenomena related to the operation of the reactor and the reactivity control systems, reactor cooling and reactor protection was used. The digital simulator allows an HMI (Human-Machine Interaction) by manipulating system variables and monitoring trends in quantities during the operation of the reactor, showing an interactive tool for teaching, training and recycling for professionals in the IPR-R1 Triga nuclear research, allowing simulations of the start, power and stop operations. This paper presents the design and results of the user visual interfaces developed for the reactor operation simulator. This is the equivalent part of structured text programming and, therefore, the most significant part of the developed simulator.

Computer Simulator for the Research Reactor IPEN/MB-01

A computer simulator for the Nuclear Research Reactor IPEN / MB-01 was developed to be a tool for teaching, training and recycling professionals. The simulator was developed on a SCADA platform (Supervision and Data Acquisition System) with support calculation software, where mathematical models and graphical interface configurations form a friendly platform, which allows the trainee to be identified with the physical systems of the research reactor. A simplified modeling of the main physical phenomena related to the operation of the reactor and the reactivity control systems, reactor cooling and reactor protection was used. The Simulator allows an HMI (Human-Machine Interaction) by manipulating system variables and monitoring trends in quantities during the operation of the reactor, showing an interactive tool for teaching, training and recycling for professionals in the Nuclear Reactor IPEN / MB -01, allowing simulations of the start, power and stop operations.

Analysis of vulnerability of fuel supply systems in gas-consuming regions due to failure of critical gas industry facilities

The paper proposes a new approach to the analysis of the vulnerability of fuel supply to regions that consume natural gas when critical facilities (CFs) of the gas industry stop operating. The feature distinguishing this approach from the known ones is that it simultaneously considers indices of a natural gas share in the structure of regional fuel and energy balance and configuration of the main gas pipeline network that serves the regions. This approach involves specialized multi-iterative studies, which have made it possible for the first time to identify the gas industry facilities that are critical for gas supply to the regions. Investigation of various shutdown options for these facilities determines the regions, which are most susceptible to natural gas shortages in the event of emergencies in the gas industry.The list of such regions is ranked according to the degree of vulnerability of fuel supply systems. Findings indicate that the vulnerability of these systems in about 70% of all gas-consuming regions in Russia upon a shutdown of specific critical gas facilities is 5% or more. At the same time, for some of these regions, failure of any CF can cause a 100% gas shortage. The principles for the formation of a ranked list of the gas transmission network CFs are presented on the example of Russia. The ranking is performed by the value of the total gas shortage for consumers, which may arise when a particular facility in the gas transmission network stops operating. Critical facilities of gas transmission network are compared by the number of regions, which may suffer from a gas shortage in the event of the shutdown of these facilities.The study shows that when 28 such facilities (out of the 193 identified) cease to operate (one at a time), significant gas shortages can simultaneously occur in several regions. Results suggest that the presented method can be used in planning invariant measures to reduce the vulnerability of fuel supply systems in the regions consuming gas.

Design and Implementation of an Elevator Power Failure Warning System

The elevator power failure is a serious safety accident and needs to be detected in time. Therefore, it is essential to monitor this situation via up-to-date technology. A novel warning system is proposed for the accident of the elevator power failure. Firstly, the data collector based on STM32 microcontroller is designed for collecting the elevator operation data from the Controller Area Network (CAN) bus interface of the elevator. Then these data are sent to the remote monitoring platform via the NB-IoT module. The platform extracts various operating signals of the elevator from the CAN bus data, such as door opening and closing signals, internal stroke signals, and stopping operation signals. Therefore, the warning system can further determine whether there is a power outage or the elevator is trapped.

ACES

Many modern smart building applications are supported by wireless sensors to sense physical parameters, given the flexibility they offer and the reduced cost of deployment. However, most wireless sensors are powered by batteries today, and large deployments are inhibited by the requirement of periodic battery replacement. Energy harvesting sensors provide an attractive alternative, but they need to provide adequate quality of service to applications given the uncertainty of energy availability. We propose ACES, which uses reinforcement learning to maximize sensing quality of energy harvesting sensors for periodic and event-driven indoor sensing with available energy. Our custom-built sensor platform uses a supercapacitor to store energy and Bluetooth Low Energy to relay sensors data. Using simulations and real deployments, we use the data collected to continually adapt the sensing of each node to changing environmental patterns and transfer learning to reduce the training time in real deployments. In our 60-node deployment lasting 2 weeks, nodes stop operations only 0.1% of the time, and collection of data is comparable with current battery-powered nodes. We show that ACES reduces the node duty-cycle period by an average of 33% compared to three prior reinforcement learning techniques while continuously learning environmental changes over time.

ANALISIS KINERJA MESIN CREPER LINE A DENGAN METODE OVERALL EQUIPMENT EFFECTIVENESS (OEE) DI PT BATANGHARI TEMBESI

PT Batanghari Tembesi is a company that produces crumb rubber which will later be exported to various foreign companies. In the production process will not be separated from problems related to the effectiveness of the machine / equipment. Machines often experience damage or interference that can lead to wasted production time and decreased production levels. Therefore, effective and efficient steps in maintaining machinery / equipment are needed to overcome and prevent these problems. Overall Equipment Effectiveness (OEE) is a method of measuring the performance and effectiveness of machines / equipment used in the production process. In this OEE method there are three elements that are measured, namely Availability, Perfomance Rate, and Quality Rate. The object examined in this study is the PT Batanghari Tembesi creper line A machine because this machine is the most frequently damaged. Based on the calculation results, obtained the OEE value on the creper machine line A is 86.01%. Availabilty on the creper line A machine is 94.45%. Performance Efficiency on the creper line A machine is 91.05%, and the Quality Rate is 100%. Based on the analysis of observations there are four main factors that influence the performance and effectiveness of the machine, namely humans who are less careful and have not followed work procedures properly, machines that have not been properly treated, work methods that have not applied inspections of materials that will enter the production process and the environment (external), which is a power outage that makes the engine stop operating. While for the calculation of the value of each factor of the six big losses, it is found that the two biggest dominant factors (affecting the level of machine effectiveness) are breakdown time and reduced speed losses.

A case study on particulate emissions from a gasoline plug-in hybrid electric vehicle during engine warm-up, taking into account start–stop operation

Concerning the discussions about emissions caused by individual mobility, it is foreseeable that future vehicle concepts will increasingly be based on hybrid powertrains. These systems lead to more complex operating scenarios, which have a significant influence on the resulting emissions of the engine. This work shows a case study and the results in the operation and emission behavior of a plug-in hybrid electric vehicle with a direct injection gasoline engine when operated in an internationally recognized driving cycle. The vehicle’s exhaust aftertreatment system consists of a three-way catalytic converter; a particulate filter is not installed. The emissions are analyzed with a focus on particulate number emissions (from soot), especially during the warm-up phase and the frequent start–stop events (in total, there are 12 internal combustion engine operating phases), which are typical for hybrid vehicles. The results show that approximately 50% of the emitted particulates have a smaller size, 23 nm (a very high number of particulates with a mean size of 10 to 15 nm are present), which are currently not regulated, but are expected to have a high risk of adverse health effects.

Research on the proportional-integral-derivative synchronous control method of the marine spherical isolation plug in the rotation process

The emergency pipeline repair technology is crucial to the maintenance and safety of pipelines under the emergency condition. In the offshore industry, the marine spherical isolation plug, a novel active plug device, is a significant emergency repair equipment of the hot tapping and line stop operation. In this article, the structure scheme and operation process of the marine spherical isolation plug are designed. A mathematic model is extracted from the proposed structure, and then the coordinates of the center of the spherical plug head is calculated using the D–H method. The displacements of the inserting hydraulic cylinder and the rotation hydraulic cylinder are investigated to provide the remote control data for the upper computer controller during the torsion process of the plug head. Moreover, a proportional-integral-derivative (PID) synchronous control method simulated by MATLAB is presented to reduce the rotation error of the plug head. To discuss the control strategy, a numerical model using ADAMS software is built. The results show that the error of the PID synchronous control method is more precise than that of the signal step-by-step control method; the number of steps of 90 is recommended in the actual operation. This article will provide theoretical guidance for the optimization design of the marine spherical isolation plug system.

(Invited) Reverse Current Behavior and ADT Protocol for Start & Stop Operation of Bipolar Alkaline Water Electrolyzer

Introduction Water electrolysis is expected a key energy conversion system to introduce large-scale renewable electricity under power grid management. Here, less expensive large system is needed. Alkaline water electrolysis (AWE) systems are well-developed large system to combine hydropower generation, but fluctuated operation with start and stop operation is not considered for conventional systems. Therefore, improvement of durability to combine photovoltaic and/or wind turbine generation is significant issue. In this study, we have been investigated reverse current behavior of bipolar alkaline water electrolyzers and proposes accelerated durability test (ADT) protocol. Theoretical and Experimental Figure 1 shows configuration of bipolar alkaline water electrolyzer, principle of reverse current. An equivalent circuit to analyze reverse current is also shown in the figure. During electrolysis, surface Ni of anode oxidizes to Ni(III) and that of cathode reduces to Ni(0). They electronically connect on a bipolar plate and ionically connect through manifold to distribute electrolyte. In the equivalent circuit, electrochemical potential difference between anode and cathode on a bipolar plate correspond to electromotive force of Uk(t). The R 1 and R 2 correspond ionic resistances of branch and communicating tubes, respectively. Relationship among these parameters can describe as eq. 1 in Fig. 1 based on the Kirchhoff's laws, so reverse current would be estimated. In this study, we measured electrode potential and reverse current after 1 h water electrolysis at 0.6 Acm-2 for 2 to 4 cells stack bipolar electrolyzer using commercially available industrial anode and cathode (De Nora Permelec Ltd). The reverse current was measured ionic current through communicating tube with D. C. clamp meter.As bipolar electrolyzer evaluation, we measured electrode potential and reverse current after 1 h water electrolysis at 0.6 Acm-2 for 2 to 4 cells stack bipolar electrolyzer using the commercially available anode and cathode. Effective electrode size was 27 cm2. The reverse current was measured ionic current through communicating tube with D. C. clamp meter (KEW2510, Kyoritsu).As start & stop operation simulated ADT protocol, we propose the combination of constant current electrolysis, potential sweep, and chronoamperometry as the inset of illustration in Fig. 4, because constant current measurement is easier to get reproductivity in high current that need accurate iR correction for constant potential measurement and current control measurement never simulate stop operation. Results and discussion Figure 2 shows the setup of lab-scale electrolyzer and cell performances in the stacks. All cells showed almost the same performance. Figure 3 shows reverse currents and electrode potentials as a function of time for 2 to 4 cells stack electrolyzer. The longer cell stack had lager reverse current at initial period of stop operation. As the potential difference between anode and cathode decreased, the reverse current decreased. The anode potential significantly decreased certain time, and that for longer cell stack was shorter. For the 4 cells stack, the time for the BP2 was shorter than that for the BP1 and BP3. Simultaneously, the I 2 was larger than the I 1 and I 3. These behaviors could be explained with eq. 1 in the Fig. 1 with the same electromotive force of the U(t=0)s for initial period and time function of U(t)s with same surface condition for all cells at the end of electrolysis. Remarkable point is that the cathode potential of BP2 was higher than the anode, which is impossible with discharge of BP2 itself. This opposite potential of the BP2 would be forced by electromotive force of the BP1 and BP3.Figure 4 shows the anode potential at 10 mAcm-2 (E @10mAcm-2) of oxygen evolution reaction (OER) current during the ADT protocol with various minimum potential: E min. The all anodes significantly degraded for around 3-days test protocol, although DN851 was developed as an active and durable anode for conventional OER electrode. The degradation increased with decreases of the E min. Above 0 V vs. RHE of the E min, The E @10mAcm-2 increased after ca. 800 cycles of introduction period and reached around 1.69 V vs. RHE after 1900 cycles, although it increased from initial period and the increase continued around 2000 cycles for -0.3 V vs. RHE of the E min. From these experimental results, the E min of between 0 to 0.3 V vs. RHE might be suitable for the ADT protocol because of rapid degradation with robustness to the E min. Acknowledgements This study was based on results obtained from the Development of Fundamental Technology for Advancement of Water Electrolysis Hydrogen Production in Advancement of Hydrogen Technologies and Utilization Project commissioned by the New Energy and Industrial Technology Development Organization (NEDO). Figure 1