On-site Operation Research Articles

Comparative analysis of cold in-place recycling for roadway maintenance and rehabilitation from the perspectives of technical-cost-environmental nexus

Cold-in-place recycling (CIR) is a sustainable road pavement maintenance technology for its on-site operation and complete reuse of reclaimed asphalt pavement. However, its sustainable performance has not been thoroughly investigated. This study aims to systematically assess and compare CIR against three alternative maintenance technologies from technical, cost and environmental perspectives, specially taking into account different numbers of repaired layers. The technical improvement in full-depth loading resistance is evaluated using a newly developed multi-sequenced repeated load (MSRL) test. Environmental impacts are assessed through life cycle assessment (LCA), while cost analysis is conducted using life cycle cost analysis (LCCA), with consistent system boundary applied. Additionally, a nexus analysis is performed using a modified Boston Consulting Group (BCG) matrix to comprehensively examine the sustainable performance of different treatments and further explore the synergies and trade-offs among various assessment aspects. The multi-dimensional sustainable assessment results reveal the influence factors in each perspective. Final BCG matrix shows that CIR can achieve the comparable technical performance to the conventional maintenance treatment, while reducing GHG emissions by 60.8% and cost by 45.8%. The methodology and findings of this study are expected to provide helpful insights for decision-makers in reducing negative impacts and promoting integrated management for sustainability.

Transfer, elimination and accumulation of antibiotic resistance genes in decentralized household wastewater treatment facility treating total wastewater from residential complex

The fate and behavior of antibiotic resistance genes (ARGs) in decentralized household wastewater treatment facilities (DHWWTFs) are unclear. In this study, targeting on a representative DHWWTF that receive all wastewater from a residential complex having 150 households, the transfer, elimination and accumulation of tetG, tetM, sul1, sul2 and intl1 were quantitively studied through real-time PCR-based quantification, mass balance evaluation and the existing state analysis based on size fractionation. Significant abundance changes of the genes were observed in involved biological reactions and the sedimentation process due to microbial growth and decomposition as well as the accumulation of the genes to sludge. tetG and sul1 increased in their fluxes against respective input in the influent. Although substantial portions of the increased genes were found in excess sludge compared to the flux of genes in the influent, those remaining in the discharge were still high, with an average about 3.4 × 1014 copies/d. The abundance of all four genes (tetG, tetM, sul1and sul2) in both water and sludge phases showed a general trend of reduction as sludge accumulated gradually in its storage tank within two months after desludging. Classification of ARGs based on particle sizes (>250 μm, 125–250 μm, 75–125 μm, 25–75 μm, 3–25 μm, <3 μm) indicated that while the major part of ARGs were distributed in particles with larger sizes (125–250 μm), ARGs in smaller particles (3–25 μm) and free ARGs (<3 μm) still existed, which may pose a greater threat to water environment due to their poor settleability. The results of this study can benefit the optimization of on-site maintenance and operation of decentralized wastewater treatment facility for elimination of the transfer of ARGs.

Research on Operational Status Monitoring Technology of the Secondary Circuit of Intelligent Substation Based on Virtual Circuit Visualization

With the promotion and construction of intelligent substations, how to reliably monitor the operation status of the intelligent components and related circuits of the secondary circuit equipment has become a difficult problem to which needs to be paid attention in the optimization operation and relay protection of the power system. This article proposes an intelligent substation secondary circuit operation status monitoring technology, which visualizes the design of SCD files. At the same time, the entropy weight method and grey correlation analysis method are introduced into the monitoring system to improve the work efficiency of on-site operation and maintenance personnel and promote the development of substation intelligence.

Stochastic financial analysis of diesel generation extension vs investment in hybrid photovoltaic-diesel-battery in a microgrid in the Amazon indigenous community

Due to environmental, operational, and regional restrictions, Brazil still has a lot of communities that do not have an integrated electricity supply, however, the government aims to promote universal access to electricity in the country. In this way, diesel oil generators are the main electricity source for these isolated indigenous communities, but in the generation expansion planning, renewable energy sources are an important way to promote a more sustainable generation in these Amazon regions. This article aims to present an economic analysis based on a Cost-Effectiveness Analysis and Cost-Benefit Analysis, using the Monte Carlo Simulation that compares the extension of the diesel capacity versus a PV-diesel-battery (PVDB) system in the Maruwai indigenous community that is located in the state of Roraima (Brazil). The photovoltaic system and the battery storage system are considered an alternative instead of repowering the electricity supply of the increase in on-site diesel generator operation. The results show that the diesel breakeven price is far below the current diesel oil spot price, which indicates that the hybrid system with photovoltaic cells and batteries is more economically feasible. In turn, the stochastic analysis, the results indicate that the hybrid PVDB system is economically attractive, but needs political incentives to mitigate the uncertainties about the average return for the investor.

Flow field distribution and structural strength performance evaluation of fixed offshore wind turbine based on digital twin technology

Due to the adverse impact of the offshore environment, the cost of on-site monitoring, operation and maintenance of offshore wind turbines is greatly increased. Here, a digital twin (DT) method based on digital model and computational fluid dynamics (CFD) simulation database is proposed, which is used to rapidly predict and synchronously display the distribution of the wake field, structural deformation and stress of fixed OWTs. First, a large number of data have been calculated by using CFD method. Second, the three-dimensional finite element model is reduced to a digital model by the proper orthogonal decomposition method, all data is stored in a multi-source heterogeneous database. Furthermore, the anisotropic inverse distance weighted interpolation and particle swarm optimization algorithm methods are used to obtain uncalculated data results and supplement database. Then the Bayesian regularization-back propagation neural network method is developed to correct the data with large errors. The results show that the learning error of the flow field and structural strength is less than 10% and 4% compared with the CFD method, respectively. This study could provide a rapid monitoring engineering reference for the safety assessment of turbine flow field distribution and structural strength.

Selectivity enhancement by the presence of HOF + CNT composite membranes investigated by non-equilibrium molecular dynamics

Hydrogen purification through membrane separation offers convenience and suitability for on-site operation, especially in automotive fuel cells that utilize reformed methanol as a hydrogen source. In this study, the molecular dynamics simulation method was employed to investigate the micro-separation mechanism of hydrogen purification using multi-walled carbon nanotubes (MWNTs) and hydrogen-bonded organic frameworks (HOFs) as membrane materials. Novel composite membranes combining different HOF and MWNT materials were designed to enhance the interaction energy with CO2. The results demonstrated that these composite membranes exhibited higher selectivity in the separation of H2/CO2 gas mixtures, achieving higher hydrogen permeability compared with individual HOF and MWNT membranes. Notably, the PhTCz1 + CNT, UPC-H4a + CNT, and TCPP-1,3-DPP + CNT-3 composite membranes demonstrated 100 % CO2 retention and reached a maximum flux hydrogen of 4.782 × 105 GPU, which was higher than traditional membranes by 6 orders of magnitude. Furthermore, the PhTCz1 + CNT-3 composite membrane had a significant ability to simultaneously intercept CO2 and CO. The MD calculation results show that this newly synthesized HOF + CNT composite membrane material can provide high permeability as well as ultrahigh selectivity simultaneously, making it a prospective H2 separation membrane with superior performance.

Ultrasonic visualization and quantitative analysis of internal defects in RTV coatings

Room temperature vulcanised (RTV) silicone rubber coatings effectively enhance the insulation properties of electrical equipment. However, RTV coatings are prone to internal defects caused by the coating process and the effects of aging during service, which can lead to debonding of the coatings. Internal debonding defects are challenging to detect and can ultimately lead to accidents due to a reduction in the insulation capacity of the equipment. To visualize the internal defect morphology of RTV coatings and quantify the defect size, an ultrasonic pulse-echo-based method for detecting and imaging debonding defects is proposed. The method involves the development of a finite element model to investigate how ultrasonic waves propagate in RTV coatings and the influence of ultrasonic probes and inspection conditions on defect echoes. Furthermore, an ultrasonic detection system specifically designed for RTV coating debonding defects is constructed. This system utilizes wavelet packets in the time-frequency domain to analyze the echo signals in both normal and defective regions. The three-dimensional reconstruction of the debonding defect morphology is accomplished by integrating ultrasonic echo amplitude and position information. Finally, the size of the debonding defects is quantified using an adaptive threshold segmentation method. The findings indicate that ultrasound waves reflected in RTV materials propagate as spherical waves, with the acoustic energy primarily concentrated near the acoustic axis. As the propagation distance increases, the sound beam disperses along the axis and extends beyond the transducer, resulting in a decrease in the sound field's directionality. The developed visual reconstruction method in this study offers the capability of three-dimensional visualization for defects present within RTV coatings, including their length, width, and depth. The accurate determination of defect size is achieved through the utilization of the adaptive threshold segmentation method, yielding an average error rate of 5.7 % across different defect types. In comparison, the maximal interclass variance method (OTSU) and the fuzzy C-means (FCM) method produced results with error rates of 9.8 % and 7.9 %, respectively. The research presented in this paper enables precise assessment of debonding defect severity and establishes a reliable foundation for on-site inspection, operation, and maintenance of RTV coatings.

Development of complete sets of equipment for new intelligent carbon extruder

A complete set of equipment for a new type of intelligent carbon extrusion machine was developed in this paper. This equipment starts from batching and kneading, and then sends materials to the extruder chamber for stamping, pre-pressing, and extrusion. According to customer requirements, the extruded products are sized using a speed-measuring device, cut using an intelligent sizing device, and automatically marked. Finally, the material slot is moved and flipped to the quality detection system for quality detection and recording. Through on-site operation and production, the complete set of equipment for this new intelligent carbon extrusion machine meets user requirements.

CASE STUDY OF THE ESTABLISHMENT OF MAINTENANCE MECHANISM OF INJECTION MACHINE

Maintaining the normal operation of machinery and equipment in order to reduce the failure rate and increase the utilization rate is one of the most important tasks of on-site management. This research is mainly based on the establishment of relevant equipment inspection and maintenance specifications, the establishment of tables, and the promotion to on-site practical explanation, operation drills, and introduction and implementation. And use the DMAIC process of Six-Sigma to verify the improvement process. Before the equipment maintenance mechanism is introduced, the utilization rate, downtime, and number of failures were about 64.9%, 1603 min/month, and 16.7 times/month, respectively. After about half year implementation of the maintenance mechanism, its utilization rate, downtime, and number of failures were 76.13%, 250 min/month, and 3.5 times/month, respectively. Which has a significant improvement. Furthermore, in terms of tangible aspects, there are obvious improvements in increasing the utilization rate, reducing the number of failures, shortening the downtime, reduce manpower need, and raw material consumption. In the intangible aspect, the operator thus feels the cleanliness of the equipment is improved, the normal operation to reduce workload, and the work in a happy mood.

Application of a Phase Resolved Partial Discharge Pattern Analysis for Acoustic Emission Method in High Voltage Insulation Systems Diagnostics

An alternative method for analysis of acoustic emission (AE) signals generated by partial discharges (PD), based on a correlation between voltage phase run and AE pulses, so called phase resolved PD pattern (PRPD), is presented in the paper. PRPD pattern is a well-known analysis tool commonly used in such PD diagnostic methods as conventional electrical and UHF ones. Moreover, it yields various signal analysis abilities and allows a direct correlation indication between measurement results achieved using different methods. An original PRPD measurement methodology applied for AE method as well as some exemplary measurement results and further data analysis capabilities are presented in the paper. Also a comparative analysis of PRPD patterns achieved using various measurement methods and different PD source configurations have been investigated. All presented experiments were done under laboratory conditions using PD model sources immersed in the insulation oil. The main purpose of the presented research is to indicate an all-embracing analytical tool that yields an ability to direct comparison (qualitative as well as quantitative) of the AE measurement results with other commonly applied PD measurement methods. The presented results give a solid fundamental for further research work concerning a direct correlation method for AE and other described in the paper diagnostic techniques, mainly in order to continue PD phenomena analysis and assessment in real life high voltage apparatus insulation systems under normal onsite operation conditions.

Teaching strategies of distance teaching applied in design discipline

ABSTRACT COVID-19 has forced many universities to adopt online teaching. However, the design discipline attaches great importance to on-site operation and face-to-face design discussions, causing teachers to face major challenges in the implementation of distance teaching. The purpose of this study is to investigate the suitability and teaching strategies for distance teaching in designing courses (“design theory”, “design practice”, and “hybrid design”). The participants were 312 college students from 1st to 4th grade (above). The questionnaire is based on the “presence” that distance teaching focuses on, including: (1) “cognitive presence”, (2) “social presence”, and (3) “teaching presence”. Each indicator corresponds to the Motivated Strategies for Learning Questionnaire (MSLQ). The results of the study found: (1) “Creating a communication environment” and “real interactive feeling” are the most important elements, (2) A “hybrid design” course is more suitable for distance teaching design than other design courses, (3) The element of “hard requirements” is particularly prominent in the “design practice” course, and (4) Distance teaching needs to strengthen “social presence”. These results could provide a reference teaching planning template for the design department’s distance courses, assist teachers in curriculum planning and adjustment so that the design department can improve the existing distance predicament.

The Design of Electric Fire Engine

The electric fire engine is based on the single chip microcomputer as the control core. In order to better realize the fire extinguishing function, the latest electric fire engine has added the tracking module, wireless transceiver module, etc., to realize the intelligent fire engine to detect the fire source and extinguish the flame. This design combines the principle of single chip microcomputer with the hardware and software circuit program to realize the function of automatic tracking and fire extinguishing, without the fire personnel risking their lives to carry out on-site operation. This kind of electric intelligent fire truck adds some practical small functions, brings us a lot of convenience, can better serve human beings. The main model of this design is a small toy car model with universal wheel and motor control wheel. The chassis is installed with a variety of sensors with different functions to achieve the purpose of moving forward and backward, steering and avoiding obstacles and eventually extinguishing the fire source. At the same time, the car can also realize wireless remote control. By comparing the shortcomings of the traditional fire truck, some improvements are made, the circuit diagram of intelligent control is designed, and the method of wireless control car for fire fighting is explored with the combination of practice and thinking, so as to further improve the fire truck and make it intelligent. The main purpose of this design is to reduce the fire casualties and improve the need for fire personnel to take the risk of life operation of the traditional fire truck function. Its advantages are automatic tracking, avoidance of obstacles, wireless control, measuring the source of fire.

Rapid detection of bacterial load in food samples using disposable respirometric sensor sachets

We describe a new sensor platform for simple on-site analysis of total aerobic viable counts (TVCs) in food samples, which uses disposable sealable plastic sachets with phosphorescent oxygen sensor inserts and liquid growth media. Food samples are collected, placed directly in the sachets, which are then sealed and incubated at 30 °C while monitoring (hourly or endpoint) sensor signals non-invasively with a commercial handheld reader FirestingO2. The growth of microbiota produces characteristic respiration profiles, from which sample initial TVC load is quantified: the Threshold Time (TT, in hours), when the sensor signal reaches the set signal threshold, is determined and calibration equation is applied to it to calculate sample TVC load. The initial calibration equation, which provides the conversion of measured TT values (hours) into TVC, was generated with pure Escherichia coli culture: log(CFU/g) = 8.30–0.60 *TT25 ° for signal threshold of 25 degrees phase. Another calibration equation, which provides a better representation of whole food microbiota, was generated with a panel of 90 different food samples: log(CFU/g) = 8.53–0.60 *TT25°. This simple sensor system shows good correlation with traditional plate counting TVC method (ISO 4833) and suitability for autonomous on-site or in-field operation. Time to result of 1–6 h provided by the sensor sachet system is more than seven time faster than for the standard method.

Stable operation process of earthquake early warning system based on machine learning: trial test and management perspective

Earthquake Early Warning (EEW) is an alert system, based on seismic wave propagation theory, to reduce human casualties. EEW systems mainly utilize technologies through both network-based and on-site methods. The network-based method estimates the hypocenter and magnitude of an earthquake using data from multiple seismic stations, while the on-site method predicts the intensity measures from a single seismic station. Therefore, the on-site method reduces the lead time compared to the network-based method but is less accurate. To increase the accuracy of on-site EEW, our system was designed with a hybrid method, which included machine learning algorithms. At this time, machine learning was used to increase the accuracy of the initial P-wave identification rate. Additionally, a new approach using a nearby seismic station, called the 1+ α method, was proposed to reduce false alarms. In this study, an on-site EEW trial operation was performed to evaluate its performance. The warning cases for small and large events were reviewed and the possibility of stable alert decisions was confirmed.

Durability of humidity-based ventilation components after 13 years of operation in French residential buildings – Assessment of components performance in laboratory

Humidity-based DCV systems have been widely used in France for 35 years and are considered as a reference system, including for low-energy residential buildings. The on-going “Performance 2” project delivers feedback from 13 years of on-site operation in twenty-two social housing apartments. The initial project was a large-scale monitoring on thirty new occupied apartments in two buildings in France equipped with this DCV system, which extended from 2007 to 2009. Thirteen years later the buildings are re-visited, and the monitoring system is turned back on with the intention to assess the ventilation system performance after a prolonged in-situ functioning period. Then, the components have been collected and tested in laboratory facilities: as collected, after cleaning, and finally after a light rehabilitation. Despite largely insufficient levels of maintenance, 100 % of the exhaust units and air inlets not purposely degraded by the occupant, still reacted as expected to humidity. A good relationship was found between the visual maintenance level and the limitation of maximum airflow for each Air Terminal Device (ATD): an average limitation of −10.6 m3/h has been evaluated for ATDs presenting a “Bad” level of maintenance whereas the average limitation was only −2.2 m3/h for ATDs showing a “Good” maintenance state. Finally, after cleaning and refurbishing, but without touching the hygroscopic sensor/actuator, the ATDs still meet the specifications and are very close to their original characteristics.

Enabling Next-Generation Industrial Networks with Industrial PON

Traditional industrial networks primarily focus on onsite device operation and worker safety. They do not engage in the ongoing digital transformation with remote control machinery and big data processing. The next-generation of industrial networks is expected to offer high-speed connectivity, intelligent management, and flexible architecture to adapt to technology advances and business competitions. Data from the environment, machinery, and offices should be collected and analyzed to support automated procedures related to an industry. In this article, a network architecture based on the passive optical network (PON) technology, the so-called industrial PON, is proposed to enable the next-generation industrial networks. It manages the network resource via a three-layer structure. Recent industrial PON implementations deployed by a Tier 1 operator are investigated in detail to evaluate the solution feasibility and network performance. Results demonstrate that the industrial PON can connect various business assets, provide data exchange to automate industrial processes, and manage the business to improve production efficiency.

태양광 연계 에너지저장장치 내부 환경 특성 분석

This paper analyzed internal environmental impact of energy storage device facilities connected to the photovoltaic power generation system. The use of energy storage system is increasing for demanding in new renewable energy (photovoltaic power, wind power, etc.) and adjusting frequency regulation(FR) in system operation.BRSince fires are concentrated in energy storage systems for connection with renewable energy, it is necessary to find the cause of the fire through analysis of the on-site installation environment and operation. This paper analyzes the internal environmental characteristics of energy storage systems connected to photovoltaic power generation and proposes a safety plan.

Advanced Method of Variable Refrigerant Flow (VRF) Systems Designing to Forecast Onsite Operation—Part 2: Phenomenological Simulation to Recoup Refrigeration Energy

This paper focuses on the application of speed-regulated compressors (SRCs) to cover changeable heat loads with high efficiency in conventional air conditioning systems (ACS) as well as in the more advanced variable refrigerant flow (VRF)-type outdoor and indoor ACS. In reality, an SRC is an oversized compressor, although it can operate efficiently at part loads. The higher the level of regulated loads (LRL) of the SRC, the more the compressor is oversized. It is preferable to reduce the size of the SRC by covering the peak loads and recouping the excessive refrigeration energy reserved at decreased actual loads within the range of regulated loads. Therefore, the range of changeable loads is chosen as the object to be narrowed by using the reserved refrigeration capacity. Thus, the general fundamental approach of dividing the overall heat load range of the ACS into the ranges with changeable and unchangeable loads, as previously developed by the authors, is applied for the range of primary changeable loads. Due to this innovative step, the principle of two-stage outdoor air conditioning according to changeable and unchangeable loads, also proposed by the authors, has been extended over the range of primary changeable loads to reduce the level of refrigeration capacity regulation and SRC size. To realize this, part of the changeable load range is offset by the reserved refrigeration capacity, leading to a reduction in the changeable load range and the SRC size by approximately 20% for temperate climatic conditions.

Wearable Device-Based Intelligent Patrol Inspection System Design and Implementation

The traditional on-site operation of power stations includes inspection and maintenance. However, it heavily relies on experience for maintenance. Most on-site operation and maintenance data are text records. On the one hand, the data processing is tedious for experience to affect the safe on-site operation. On the other hand, we usually cannot give full consideration to the value of maintenance experience, so that the corresponding efficiency is very low. Therefore, this paper proposes a wearable device based remote and intelligent patrol inspection system that uses the cloud video transmission mode of both public and private clouds to realize the video connection between the power stations and the remote diagnosis center and uses the wearable devices for real experience. In this way, the authors can simulate real operation guidance and safety supervision, etc. so as to realize the remote management patrol operations, improve the fault detection efficiency, and improve equipment reliability.

Advanced Method of Variable Refrigerant Flow (VRF) Systems Designing to Forecast On-Site Operation—Part 1: General Approaches and Criteria

All the energetic management and controlling strategies in ambient air conditioning systems (ACS) are aimed to match design load to current needs. This might be achieved by determining a rational value of design thermal load without overestimation that can minimize its deviation from the actual values. The application of variable refrigerant flow (VRF) systems with speed-regulated compressors (SRC) is considered as the most advanced trend in building air conditioning due to the ability of SRCs to cover changeable heat loads without lowering their efficiency. The level of load regulation by SRC is evaluated as the ratio of the load range, regulated by SCR, to the overall design load range. With this, the range of actual changeable loads is usually supposed to be covered by SRC entirely while keeping the rest, unregulated, and load range unchangeable. However, to confirm this, the rest load range behind the regulated one should be investigated to estimate the efficiency of SRC operation. Therefore, the approach to dividing the overall thermal load range of ambient air conditioning into the ranges of changeable and unchangeable loads to compare with those covered by SRC is used. From this approach, the method of rational designing and shearing a design refrigeration capacity in response to current loading, based on the principle of two-stage ambient air conditioning, has been widened on the VRF systems to estimate the efficiency of SCR application. This was realized by imposing the load ranges regulated by SRC onto the ranges of changeable and unchangeable loads within the overall range of actual loading. The proposed innovative criteria and indicators for rational shearing the load ranges to match current duties and load level evaluation can reveal the reserves for improving the efficiency of SRC compressor operation and the ACS of VRF type as a whole.