Repetitive Operation Research Articles

Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression

Performance characteristics of an excimer laser (XeCl) with single-stage magnetic pulse compression suitable for material processing applications are presented here. The laser incorporates in-built compact gas circulation and gas cooling to ensure fresh gas mixture between the electrodes for repetitive operation. A magnetically coupled tangential blower is used for gas circulation inside the laser chamber for repetitive operation. The exciter consists of C–C energy transfer circuit and thyratron is used as a high-voltage main switch with single-stage magnetic pulse compression (MPC) between thyratron and the laser electrodes. Low inductance of the laser head and uniform and intense pre-ionization are the main features of the electric circuit used in the laser. A 250 ns rise time voltage pulse was compressed to 100 ns duration with a single-stage magnetic pulse compressor using Ni–Zn ferrite cores. The laser can generate about 150 mJ at ∼100 Hz rep-rate reliably from a discharge volume of 100 cm 3. 2D spatial laser beam profile generated is presented here. The profile shows that the laser beam is completely filled with flat-top which is suitable for material processing applications. The SEM image of the microhole generated on copper target is presented here.

The investigation and improvement of the lifetime of high voltage ceramic capacitor under repetitive frequency operation

The lifetime tests for High Voltage Ceramic Capacitors (HVCC) were investigated under repetitive frequency operation at 25 Hz and three kinds of failure modes were summarized. The significant innovation of this paper is testing HVCC, made in the laboratory, under repetitive pulses and proposing several effective improvement methods. The results show that the lifetime of HVCC meets inverse power-law with the applied voltage and the voltage acceleration factor is about 5.8. Failure modes of HVCC are inner breakdown of ceramic dielectric, interface breakdown of ceramic-epoxy and abscission of brass terminals. The inner breakdown is in connection with abrupt destructive discharge under much higher stress while the interface breakdown is related to interface delamination and development of electrical trees in relatively low strength. The third failure mode is always caused by high current density. Based on the failure modes, several methods were taken to improve the performance of HVCC, which included coating semiconductor at the edge of silver layers, adding coupling agent to ceramic-epoxy interface and improving the structure of brass terminals. The lifetime of HVCC under repetitive frequency operation has been extended greatly from 103 shots to more than 105 shots after the investigation and improvement.

Modelling and simulation of complex repetitive construction operations

In an effort to improve productivity and optimise resource use, a simplified activity-on-arrow (AOA) approach is used in this paper to model and simulate real-world repetitive construction operations of high-rise buildings. The objective of the paper is to use simulation to find the optimum combination of construction resources to improve construction productivity and minimise operational cost. In order to achieve the goals of the study, a simulation model for typical floor finishes activities of a high-rise building project was developed. The model was validated through a predefined construction operation. Several model runs were then conducted using different resource combinations. The results were tabulated to arrive at the optimum combination that improves productivity and reduces the operational cost. In addition, the developed model was used to experiment with different resource alternatives and overtime options for one floor and for repetitive floors in order to arrive at the best resource alternatives that provide the optimum solution. The potential of using this approach for resource optimisation of large infrastructure networks is investigated, and possible future extensions to the present study are discussed.

Modelling and simulation of complex repetitive construction operations

Modelling and simulation of complex repetitive construction operations

Demonstration of Rapid Electrical Recovery in Repetitive Operation of a Counter-Facing Plasma-Focus Device

Demonstration of Rapid Electrical Recovery in Repetitive Operation of a Counter-Facing Plasma-Focus Device

Advanced Industrial Tools of Ergonomics Based on Industry 4.0 Concept

Over the years approach focusing in ergonomics has changed. We still talk about identification - analysis - elimination of the risks on the workplaces. But differences are at the possibilities of modern ergonomics, movement of science and technical possibilities. The options of using a mobile applications, Internet of Things, data gathering and their real time evaluation and their sharing. We present those solutions that combine traditional knowledge and modern technologies. The results are innovative and advanced ergonomic tools based on Industry 4.0 concept. Electronic tools are a new direction in ergonomics. With the support of mobile applications we see a way to create healthy conditions at work for production and also non-production workers, assembly and logistics. At the beginning of 20-th century, majority of us had no idea what the ergonomics is, how many risks occur during our job that they are connected with the health of employees and have not known that special methods and tools for their identification, analysis, evaluation and identification are developed. With the growing development of society we got to stadium when, luckily, majority of companies – employers even know the meaning of ergonomics or work risks, about risks at their workplaces and establish their evaluation and try to eliminate them. We have many methods and tools of modern ergonomics which enable us to realize analysis and optimization of employee's work to their benefit. Considering experience we can surely claim that we know the main problem of these days. It is requisite to realize ergonomic evaluation perfectly, extensively and mainly quickly. Slowness of some solutions discourages managers and directors and makes effective improving of work conditions impossible. The idea of mobile application developing which works as a screening tool came with demands from big companies that have dozens of workplaces and cannot identify work risks by themselves. Ceit ERgonomics Analysis Application, which is described in article, is output of our own research and development. It is a mobile application developed in CEIT Company in collaboration with the University of Žilina and Slovak ergonomic association. It is a screening evaluation of space conditions and work positions of workers at potentially risky workplaces. It is developed at the base of legislation and technical norms, at our own platform, with the support of virtual and augmented reality. The main goal of evaluation by the CERAA usage is to find out if the workplace is risky from the ergonomic view. It is an innovative way of applied augmented reality tools during the ergonomic evaluation of chosen workplaces. Nowadays, the new submodules are being developed. They will identify risks at administrative workplaces, submodule which will evaluate working with loads and other that will evaluate repetitive operations. CERAA is used in several industrial companies in Slovakia and Czech Republic from the second half of 2016.

Development of Marx generator type pulsed power system with MOSFETs and underwater pulsed electric discharge

We have developed a ten stages Marx generator type pulsed power system with MOSFETs. The operation principle of the circuit has been clarified, and the experimental results have confirmed the operation of the developed circuit. In the case of ten stages system, the repetitive operation is verified at the frequency of 1 kHz, and the output voltage of 9.4 kV was obtained. The current was calculated as 36 A, and increasing of the current flowed in the system was achieved. The experiment of the underwater pulsed electrical discharge is performed, and the occurrence of the underwater pulsed electric discharge was confirmed.

Performance Evaluations for OpenMP Accelerated Training Of Separable Image Filter

One of the widespread image processing applications is image filtering with two dimensional convolution. Determining the weights of image filters are of importance for the success of filtering operation. Heuristic algorithms such as genetic algorithms provide an efficient way of training these types of filters. Due to the high computational cost of repetitive image filtering operations, this process may take hours to implement using single core computing. OpenMP (Open Multi Processing) provides an efficient library for utilizing the computing power of multicore processors. In this study, OpenMP accelerated training of separable filters that are a subclass of convolution filters has been implemented based on genetic algorithms. Comparative speed-up results for various sizes of images using various sizes of filtering kernels were presented. Also the effect of population size of genetic algorithm and the number of working cores have been investigated.

A Novel Boil-Off Gas Re-Liquefaction Using a Spray Recondenser for Liquefied Natural-Gas Bunkering Operations

This study presents the design of a novel boil-off gas (BOG) re-liquefaction technology using a BOG recondenser system. The BOG recondenser system targets the liquefied natural gas (LNG) bunkering operation, in which the BOG phase transition occurs in a pressure vessel instead of a heat exchanger. The BOG that is generated during LNG bunkering operation is characterized as an intermittent flow with various peak loads. The system was designed to temporarily store the transient BOG inflow, condense it with subcooled LNG and store the condensed liquid. The superiority of the system was verified by comparing it with the most extensively employed conventional re-liquefaction system in terms of consumption energy and via an exergy analysis. Static simulations were conducted for three compositions; the results indicated that the proposed system provided 0 to 6.9% higher efficiencies. The exergy analysis indicates that the useful work of the conventional system is 24.9%, and the useful work of the proposed system is 26.0%. Process dynamic simulations of six cases were also performed to verify the behaviour of the BOG recondenser system. The results show that the pressure of the holdup in the recondenser vessel increased during the BOG inflow mode and decreased during the initialization mode. The maximum pressure of one of the bunkering cases was 3.45 bar. The system encountered a challenge during repetitive operations due to overpressurizing of the BOG recondenser vessel.

HRVanalysis: A Free Software for Analyzing Cardiac Autonomic Activity.

Since the pioneering studies of the 1960s, heart rate variability (HRV) has become an increasingly used non-invasive tool for examining cardiac autonomic functions and dysfunctions in various populations and conditions. Many calculation methods have been developed to address these issues, each with their strengths and weaknesses. Although, its interpretation may remain difficult, this technique provides, from a non-invasive approach, reliable physiological information that was previously inaccessible, in many fields including death and health prediction, training and overtraining, cardiac and respiratory rehabilitation, sleep-disordered breathing, large cohort follow-ups, children's autonomic status, anesthesia, or neurophysiological studies. In this context, we developed HRVanalysis, a software to analyse HRV, used and improved for over 20 years and, thus, designed to meet laboratory requirements. The main strength of HRVanalysis is its wide application scope. In addition to standard analysis over short and long periods of RR intervals, the software allows time-frequency analysis using wavelet transform as well as analysis of autonomic nervous system status on surrounding scored events and on preselected labeled areas. Moreover, the interface is designed for easy study of large cohorts, including batch mode signal processing to avoid running repetitive operations. Results are displayed as figures or saved in TXT files directly employable in statistical softwares. Recordings can arise from RR or EKG files of different types such as cardiofrequencemeters, holters EKG, polygraphs, and data acquisition systems. HRVanalysis can be downloaded freely from the Web page at: https://anslabtools.univ-st-etienne.fr HRVanalysis is meticulously maintained and developed for in-house laboratory use. In this article, after a brief description of the context, we present an overall view of HRV analysis and we describe the methodological approach of the different techniques provided by the software.

A theoretical framework for evaluating mental workload resources in human systems design for manufacturing operations

As the nature of manufacturing work is changing, requiring more cognitive demands, there is a need to develop system models for measuring and predicting human performance in repetitive task operations. This paper presents a theoretical framework, which provides a systematic approach for measuring mental workload using a combination of analytical and empirical techniques: human performance modeling with a computer simulation and mathematical modeling, along with physiological, subjective and performance measures. For this study, the Air Force MATB, which is a re-development of the NASA simulation tool, was used to model multitasking in a controlled environment to validate the theoretical framework. The independent variable of task complexity was measured, in the modeling of resource demands for a cleaning-inspection process and a final inspection process, using three dependent variables (subjective, physiological and performance measures) with a total of four responses (NASA-TLX, Workload Profile, fixation duration and human error probability). The results indicate no significant difference among the response variables for each task complexity level, indicating the model accurately represents the operator's workload. Additional analysis shows accurate predication from the model in analyzing workload peaks. Relevance to industryThis theoretical framework is designed to evaluate operator mental workload utilization in the manufacturing domain. This is important because manufacturing work is changing by requiring more multitasking roles, which increases cognitive demand. Therefore, the industry needs models that can predict operator performance and mental workload for improved productivity.

A high-power subterahertz surface wave oscillator with separated overmoded slow wave structures**Project supported by the National Natural Science Foundation of China (Grant No. 61231003).

A megawatt-level subterahertz surface wave oscillator (SWO) is proposed to obtain high conversion efficiency by using separated overmoded slow wave structures (SWSs). Aiming at the repetitive operation and practical applications, the device driven by electron beam with modest energy and current is theoretically analyzed and verified. Then, the functions of the two SWS sections and the effect of the drift tube are investigated by using a particle-in-cell code to reveal how the proposed device achieves high efficiency. The mode analysis of the beam-wave interaction region in the device is also carried out, and the results indicate that multi-modes participate in the premodulation of the electron beam in the first SWS section, while the TM01 mode surface wave is successfully and dominantly excited and amplified in the second SWS section. Finally, a typical simulation result demonstrates that at a beam energy of 313 keV, beam current of 1.13 kA, and guiding magnetic field of above 3.5 T, a high-power subterahertz wave is obtained with an output power of about 70 MW at frequency 146.3 GHz, corresponding to the conversion efficiency of 20%. Compared with the results of the previous subterahertz overmoded SWOs with integral SWS and similar beam parameters, the efficiency increases almost 50% in the proposed device.

Optimization of fluid-structure systems by eigenvalues gap separation with sensitivity analysis

The design optimization process is frequently accompanied by repetitive time-consuming operations, through the design analysis with a few modifications in its parameters, until the required system is encountered. Whenever possible, it is more convenient to use the sensitivity analysis during the optimization, which permits a fast evaluation of the model performance without doing a completely new analysis. In this work, one methodology for obtaining dynamic optimal structural shape through parameters changing was developed for coupled fluid-structure systems, which took advantage of the modal sensitivity analysis and available nonlinear programming tools. The objective of this work is to maximize the gap between two adjacent eigenvalues in coupled fluid-structure systems, in order to avoid the resonance phenomena at a specific natural frequency interval, taking the height of the cross-section of the beam structural elements as design variables with some dimensional constraints and a constant structural volume. The sequential quadratic programming algorithm was used for solving the constrained nonlinear optimization problem, and the modal sensitivity analysis was considered for the modal prediction of the modified design, as well as for the gradient evaluation of the objective function and system's constraints, throughout the optimization. The study was verified in two-dimensional coupled fluid-structure systems, where the structural system is modeled as a beam. The implemented methodology can be applied to avoid resonant situations or to improve the vibroacoustic comfort, for example, in cabins and reservoirs.

Dynamics of Laser Triggered, Gas-Insulated Spark Gaps During Repetitive Operation

The Electra pulsed power system at the U.S. Naval Research Laboratory uses laser triggered SF6 gas-insulated spark gaps to transfer energy to a high power electron beam diode. These 1-MV spark gaps have a charge transfer of 10 mC per shot operating at 5 pules per second (pps) utilizing electrodes with the potential durability of 300 000 pulses. During continuous repetitive switch operation, after a few thousand shots intermittent nonfire events occur with greater frequency approaching 100 000 shots. The nonfire events and the lack of reproducibility and reliability reduce the potential applications for laser triggered spark gaps. Therefore, the temporal evolution and the spatial evolution of the switch dynamics have been examined. Gated camera images, streak camera images, and interferometry are used to characterize the dynamics of single shots to directly compare to the dynamics during continuous operation. The streak camera images indicate that the switch dynamics are dependent on the repetition rate. For single shots and 1 pps operation (9000 continuous shots), no misfires (mistimings or nonfires) are observed in the switch. This observation is concomitant with a consistent and reproducible breakdown position and breakdown dynamics. At 5 pps, the variations in the laser breakdown position (preferentially toward cathode) and the laser breakdown emission intensity are observed. After several thousands of continuous shots, nonfire events are detected in small groups, before normal operation resumes. A temperature differential of at least 22.2 K (40 F) between the SF6 gas at the top of the housing and the bottom of the spark gap housing is observed. The onset of nonfire events is correlated with the hydrodynamic changes, from increased temperature, of the SF6 gas flow within the spark gap. A redesign of the spark gap along with adequate cooling to reduce the hydrodynamic flow and forces of the insulating SF6 gas would mitigate if not eliminate nonfire events.

(Invited) Highly Functional Graphene Nano-Electromechanical (GNEM) Devices for Advanced Switch and Sensor Applications

Graphene, as a monolayer of graphite, has an ultra-high Young’s modulus of ~1 TPa, which makes it a promising candidate for Nano-Electromechanical (NEM) devices. The graphene NEM switches is expected to show minimized electrical leakage, sharp switching response, low actuation voltage, and high on/off ratio. A simple bottom-up procedure using a polymer sacrificial spacer is utilized to fabricate graphene electromechanical contact switch devices. Low pull-in voltage of below 5 V is achieved with good consistency [1], which is compatible with the conventional complementary metal-oxide-semiconductor circuit requirements. In addition, the formation of carbon-gold bonds at the contact position is proposed as another important mechanism for the irreversible switch other than the well-known irreversible static friction. In order to overcome the stiction issue and realize repetitive switching operations, we exploited a natural chromium oxide layer formed on the chromium electrode. We fabricated a doubly-clamped beam and cantilever graphene nanoelectromechanical switches with a local top actuation electrode. The low pull-in voltage below 5 V was realized in both of the switches. The naturally formed chromium oxide at the graphene-electrode contact interface prevents the formation of chemical bonds between graphene and metal, resulting in reversible switching operation successfully. Thanks to highly-stable SP2 bonds in a 2D honeycomb lattice, graphene exhibits an extremely suppressed electrical noise, making it possible to realize extremly-sensitive sensor. For the physisorbed CO2 molecules - graphene vdW complexes, we found it is possible to tune the vdW interaction with external electric fields. The field-dependent charge transfer in the CO2−graphene complex was unveiled along with small variations in the equilibrium CO2−graphene distance and the O−C−O bonding angle. By reversing the substrate bias polarity, the charge transfer direction also switched, signifying the role of physisorbed CO2molecules can be altered electrically between donor and acceptor. The range of such electrical tunability was found inherent in individual molecular species [2]. In recent years, direct milling of graphene by Helium ion beam (HIB) has been actively explored. The main advantages of HIB milling over typical gallium focused ion beam (FIB) milling are: high resolution and less damage to the graphene. This HIB milling can be actively explored to carve the suspended graphene into a very narrow beam, which will help to realize narrower suspended graphene beams, which can’t be realized with the standard electron beam lithography technique. Towards this direction, gas field ionization source (GFIS) system with Helium and Nitrogen beams is introduced. In order to use HIB milling, a suspended monolayer graphene beam device was first fabricated without a top gate. These devices were used for the further HIB milling. We successfully patterned a 60-nm-long and 15-nm wide suspended graphene beam. As the next step to utilize our unique graphene nano-electro-mechanical systems (NEMS) to realize a well challenging application, the NEMS sensor devices were explored to realize individual CO2 molecule detection. Detection of a single molecule’s adsorption and desorption, which determines the ultimate resolution of gas sensing, has rarely been achieved with conventional solid-state sensor devices. A doubly clamped bilayer graphene beam was first fabricated and then by applying a voltage to the lower gold electrode the graphene beam was electrostatically pulled down. It was found that despite the negligible charge transfer from a single very poor doping CO2 physisorbed molecule, it strongly affects the electronic transport in suspended graphene beam by inducing charged impurity, which can shut down part of conduction of the graphene channel with Coulomb impurity scattering. We detected each individual physisorption of CO2molecule as a step-wise resistance change with a quantized interval for the graphene channel [3].

Porous‐Resin‐Supported Calcium Sulfate Materials for Thermal Energy Storage

AbstractA new porous‐resin‐supported calcium sulfate (CaSO4‐PSM) material with high‐density and high reactivity for chemical heat storage is developed and characterized. The newly developed CaSO4‐PSM exhibits a higher reactivity than normal CaSO4. Furthermore, the particle diameter is an important factor for the development of new chemical thermal energy storage (CTES) material. CaSO4‐PSM exhibits good performance in the hydration and dehydration processes when used as a CTES material. The hydration reaction rate of the particle with a diameter of 75 μm is 13.3 times of that of 750 μm, whereas, the dehydration reaction velocity is approximately 1.5 times higher. This finding is due to more abundant favorable pore channels for vapor transport and a larger specific surface area. Aggregation of the CaSO4 particles before and after repetitive operations can be eliminated, and a good durability of the new porous supported thermal energy storage material of CaSO4 can be obtained.

Active learning assisted strategy of constructing hybrid models in repetitive operations of membrane filtration processes: Using case of mixture of bentonite clay and sodium alginate

Reliable prediction of the transmembrane pressure (TMP) in membrane filtration systems often encounters different challenges in practice, including process nonlinearity, cycle-to-cycle change, and multiple operating conditions. In this work, an active learning TMP model with the hybrid structure is developed to predict the short-term fouling formation. The advantages of the physical and empirical models are integrated into this hybrid model. For construction of the empirical model, the Gaussian process regression model (GPRM) is adopted to approximate the complex fouling mechanism with fouling propensity in the short-term period. It can be a useful complement to the physical model with inaccuracy. Moreover, GPRM can simultaneously provide the prediction variance. Using this appealing property, the hybrid TMP model can be updated in an active and efficient manner without introducing additional unnecessary data samples. Consequently, accurate hybrid TMP models for the repetitive operations of membrane filtration processes are established. The superiority of the proposed hybrid TMP models is demonstrated through simulation and short-term experiments. The experimental results show the hybrid TMP models have better prediction performance (with R2 values larger than 0.9) than the physical model (with R2 about 0.5).

Development of cooling technologies for SMES

A Superconducting Magnetic Energy Storage (SMES) system has good characteristics as energy storage equipment in electric power systems such as high efficiency, quick response and no deterioration in repetition operation. Since 1991, the Agency for National Resources and Energy Japan has carried out a national project to develop an SMES for power control in power systems. Moreover, SMES has been developed to bridge for instantaneous voltage dips since 2003. A field test of 5MVA SMES for bridging instantaneous voltage dips was carried out on an advanced large liquid crystal TV plant in Kameyama from July 2003. Before that, a 10MVA SMES system was working there. After the field test, the commercial SMES for instantaneous voltage dips is working there. In 2015, three commercial SMES units for bridging instantaneous voltage dips are operating in Japan. These SMESs are all equipped with metal superconducting coils. When considering cost-reduction, size-reduction, and maintenance of the SMES in the future, it is necessary to develop a SMES with a high-temperature superconductor and improve the efficiency of its cooling system. We have also developed and conducted operation tests of SMES with a Bi2212 oxide superconductor and high performance cryocooler which enable energy conservation operation by inverter control. In this paper, developed results on cooling systems and cryocooler for SMES are presented.

Thermal Properties of an Intense Relativistic Electron Beam Collector Under Repetitive Pulse Operation

With the increase in power and miniaturization in a size of repetitively operated high-power microwave (HPM) sources, such as relativistic backward-wave oscillators, the thermal control and cooling methods for a collector have the great effects on efficient operations of these devices. In this paper, the thermal properties of an intense relativistic electron beam collector under repetitive operation were studied. The bombardment area caused by energetic electrons was experimentally quantified, and the pulsed thermal loading for a 700-keV and 7-kA beam current was calculated. With an ANSYS multiphysics package, the typical results of temperature history of the collector under 10–100-Hz operation were presented. The dependence of peak temperatures on forced cooling conditions at different pulse repetition rates was also obtained. Comparison results show that the cooling process is influenced by collector thermophysical parameters, interface thickness, and convective factor of the forced water cooling. Finally, the hydraulic system necessary to achieve appropriate cooling fluid flow was discussed. These results may supply an efficient reference to the optimization and reasonable use of a repetitively operated beam collector in the HPM tubes.

A Magnetically Insulated Transmission Line Oscillator With Metal Array Cathode

An L-band magnetically insulated transmission line oscillator (MILO) with metal array cathode (MAC) is presented. Metal plates with different radii and thicknesses are periodically arranged in the longitudinal direction to act as emitters. To ensure stability of the tube, higher order mode depressed structure is applied. Experimental results reveal that MAC-MILO works steadily at the fundamental mode. High-power microwave at the same power level as the velvet cathode is generated by the MAC-MILO. The MAC has a much longer lifetime and a much lower outgassing rate compared with the velvet. This tube brings a promising approach to repetitive operation of the MILO.