Efficiency Of Subsystem Research Articles

On the exergy efficiency of CO2 capture: The relation between sub-process and overall efficiencies

A generic exergy targeting tool for gas separation processes is developed, which is applicable to any defined boundary conditions for incoming feed gas as well as delivered separation products. Whereas targeting tools in the literature so far are mostly simplified and limited to post-combustion related cases and isothermal and isobaric conditions, the present approach is based on a rigorous exergy methodology, which enables exergy targeting for a broad spectrum of boundary conditions.Understanding the causes behind thermodynamic losses throughout the process is a prerequisite for improving energy efficiency. In this respect, exergy analysis provides a powerful tool, which enables the identification and quantification of irreversibilities and thereby exergy losses. The methodology is used to show that common separation processes can be attributed with negative minimum separation work, since a corresponding reversible separation process would yield an exergy output in addition to providing the specified product streams.CO2 capture involves considerable energy demand caused by the various processing steps. The exergy balance of a CO2 capture process can in turn be applied to determine the exergy efficiency for each sub-process as well as for the overall process. Exergy efficiency criteria can be formulated in different ways, and in the present work it will be evaluated primarily against the minimum theoretical exergy requirement, that is, the performance theoretically achievable for a reversible process.Through a quantitative example based on published literature on CO2 separation from syngas, it is shown that a process may still require a substantial amount of exergy input despite having a negative minimum separation work, which in turn results in a negative exergy efficiency. A relation between sub-system exergy efficiency and overall system exergy efficiency is derived on a general basis. For the numerical example of CO2 capture from syngas, the derived relation shows consistency and is able to reproduce the total process efficiency also when one of the sub-processes, CO2 separation, has a negative exergy efficiency. Exergy efficiency results are finally compared with corresponding results based on a well-established rational exergy efficiency.Despite different values and even signs for the separation sub-process efficiency, it is still shown that there are no contradictions between the two efficiency criteria when used consistently, since they give identical total exergy efficiency when applied to the control volume of the combined CO2 separation and compression process, and since identical results are obtained also when expressing the total exergy efficiency as a linear combination of the two sub-process efficiencies, one of which has a negative sign.

Performance evaluation of Chinese research universities: A parallel interactive network DEA approach with shared and fixed sum inputs

In recent years, Chinese government and universities have been striving to improve the quality of higher education according to the continuously updated university performance evaluation. The university performance evaluation has played an important role in education reform. As an essential function of university, the research activities show some particular features in China. On the one hand, scientific research activities have parallel interactive network structures. On the other hand, university, as centrally governed institution, faces limited financial support, implying a fixed-sum constraint on government grant funding. However, previous studies have not developed an appropriate method to address the above features, which may lead to biased empirical results. In order to fill the gap of previous studies, this paper intends to provide a novel data envelopment analysis (DEA) approach by considering the shared fixed-sum input in the network DEA model. We first divide the scientific research activity into two sub-systems which interact with each other, and the government grant funding as a shared fixed-sum input is consumed for the two sub-systems. Then, considering the effect of shared fixed-sum input on performance, the minimum amount of input adjustments is calculated to identify the common equilibrium efficient frontier, and the total efficiency is obtained by weighting the sum of sub-system efficiency. Finally, our models are empirically applied to assess the performance of Chinese universities. The main findings show that the overall efficiency of Chinese research universities varies widely, and then some meaningful recommendations for central policymakers are proposed.

Agent-based modelling and simulation for life-cycle airport flight planning and scheduling

ABSTRACT The airport flight planning and scheduling (AFPS) process involves many sub-systems in airport management, including flight arrival prediction, flight landing prioritisation, flight route scheduling, flight departure prioritisation and airport big-data planning. Existing literature has mainly focused on advancing the efficiency of specific sub-system(s) of AFPS. Therefore, there is a call to investigate the AFPS comprehensively and improve its performance systematically, instead of solely enhancing partial sub-system(s) in an airport. This paper proposes a life cycle analysis (LCA) framework to describe the “life cycle” that how an aircraft interacts with the AFPS system of an airport. The agent-based modelling and simulation technique is used to simulate the AFPS system under the LCA framework by treating each aircraft as a passive agent following the orders from the AFPS system. We demonstrate that the naive first-in-first-out principle can be modified to some simple prioritising rules to significantly reduce the overall delay (including importance-weighted delay) and processing time of flights, as well as to increase the number of departed aircraft. Hence, the produced agent-based model allows us to improve AFPS performance by optimising multiple sub-systems simultaneously.

Efficiency evaluation of higher education systems in China: A double frontier parallel DEA model

Higher education plays a crucial role in socioeconomic development. This paper proposes a double frontier parallel data envelopment analysis model to evaluate the performance of Chinese higher education systems. Such a system can be divided into a higher ordinary education subsystem and a higher vocational education subsystem. The presented approach comprehensively measures higher education system performance in terms of optimistic and pessimistic aspects. Using the presented approach, we estimate the overall and subsystem efficiencies simultaneously. We use this new technique to study the efficiencies of 30 provincial higher education systems in China during 2015–2017. Our crucial findings are as follows. (1) The presented model has more ranking discrimination power than the traditional optimistic and pessimistic models. (2) Jiangsu, Shaanxi, and Shandong obtain high average system efficiencies. (3) The inefficiency of higher education systems stem from both the higher ordinary education subsystem and higher vocational education subsystem. (4) The western area of China has the lowest average system efficiency and average subsystem efficiencies.

Strategy for the formation of innovative campuses is the basis for building a smart city in the context of digitalization

The paper is aimed at substantiating strategic alternatives for the formation of a campus functioning model based on an innovative approach, at studying and analyzing the functions of a planned campus as the core of an urban innovation system, an innovation institute and an educational organization of higher education. The paper updates the idea of promoting the smart education paradigm in Russia. The given paradigm is based on self-directed, motivated, flexible, resource-enriched, technological education that brings together smart learners, smart teachers and smart environments, including both formal and non-formal learning. It also involves a personalized approach to learners with the goal of acquiring necessary knowledge, skills, abilities, and competencies. In other words, the arrangement of university complexes should inspire scientists to new promising discoveries, and instill an attentive attitude to the environment in students. The relevance of the study is conditioned by the need of improving the efficiency of innovation cycle subsystems: support and dissemination of knowledge, production of new knowledge, commercialization and practical application. The conclusion that the campus mission is to develop every subject of interaction, create conditions for achieving the aims of the state, society, business, employees and students of the campus is made and justified in the paper.

Thermo-economic analysis of the integrated system of thermal power plant and liquid air energy storage

In the context of the rapid development of renewable energy, load regulation of the power grid has become a vital issue, and many researches on load regulation by thermal power plants (TPP) have been conducted. As a promising large-scale energy storage technology, the liquid air energy storage (LAES) system has significant advantages such as clean, low investment cost, and no geographical restrictions. In this paper, a coupled system combined by TPP and LAES system (TPP-LAES) is proposed, and technical and economic analysis are carried out to obtain the best configuration of the integrated system and verify its economic benefits. Technical analysis results demonstrate that the maximum round trip efficiency (RTE) of the LAES subsystem can reach 93.74 % when the extraction pressure is 242.00 bar. The RTE of the LAES subsystem of the optimal configuration is 58.31 %, at which the extraction pressure is 8.55 bar. The comprehensive efficiency of the optimal TPP-LAES integrated system is 40.86 %, which is about 1 % higher than the standalone LAES system. The energy storage density is 95.80 kWh/m3, and the net output power is 79.30 MW, exhibiting excellent system performance. The economic analysis results reveal that the initial investment cost of the TPP-LAES integrated system is 67.17 % of that of the standalone LAES system, and the levelized cost of storage (LCOS) is 154.30 USD/MWh, 24.63 % lower than that of the standalone LAES system, with outstanding economic benefits.

Algorithm for the Optimal Design of a Fault-Tolerant Aircraft Power Transmission Network

Aircraft manufacturers aim to decrease the fuel consumption based on reducing weight and increasing the subsystem efficiency. Hence, the electric power system (EPS) acquires great relevance because it must be efficient and lightweight. Any change in the EPS must not affect the aircraft’s electrical safety, which under a traditional decentralized EPS strategy is ensured by redundancy. Recently, several decentralized EPS strategies based on the introduction of multiport power converters have arisen. Such strategies meet the established safety goals since the aforementioned devices make it possible to recalculate the path to continue powering the loads in case of failure. However, the literature does not address how to connect such multiport power converters. The main contribution of this article is to present a low-complexity algorithm that minimizing the redundancy of wiring, provides a fault-tolerant power transmission network. This is done under a decentralized EPS strategy where multiport power converters are used. The proposed strategy is evaluated on Boeing 787 aircraft, where we compare the length of the cables both under a traditional decentralized network configuration (where the redundancy option is used to ensure the safety of operation) and in the network provided by our algorithm. A saving of 66.6% is obtained.

Assessing city sustainable development—Residents' quality of life from the perspective of sustainable development goals and spatiotemporal evolution

AbstractScientific evaluation of the sustainable development efficiency of China's large and medium‐sized cities has far‐reaching significance to how to improve the well‐being of residents and improve the level of sustainable development. This research uses the parallel two‐stage SBM dynamic (PT‐DSBM) model to evaluate the sustainable development efficiency of 33 cities in eastern, central, and western China. The innovation of this article is divided into two points. First of all, the PT‐DSBM model is used to subdivide the sustainable development system into social, economic, and ecological subsystems and closely integrates it with residents' QOL, which further reveals the inherent mechanism of the sustainable development system. Second, the spatiotemporal evolution can further reveal the spatiotemporal changes of sustainable development and residents' QOL within the scope of this investigation. The results show the following. (1) The overall efficiency of urban sustainable development in China is high in the east and west and low in the central. (2) The social subsystem efficiency in western cities exhibits outstanding performance, eastern cities perform better in economic and ecological sustainable subsystems, while the efficiency of residents' QOL remains at a high level in the sample cities as a whole. (3) In the study of spatiotemporal evolution, the concentration of urban sustainable development decreases with time evolution. Finally, this research gives suggestions on social security, stakeholder engagement, and environmental policies.

Design, Modelling, and Thermodynamic Analysis of a Novel Marine Power System Based on Methanol Solid Oxide Fuel Cells, Integrated Proton Exchange Membrane Fuel Cells, and Combined Heat and Power Production

A novel maritime power system that uses methanol solid oxide fuel cells (SOFCs) to power marine vessels in an eco-friendly manner is proposed. The SOFCs, gas turbine (GT), steam Rankine cycle (SRC), proton exchange membrane fuel cells (PEMFCs), and organic Rankine cycle (ORC) were integrated together to generate useful energy and harvest wasted heat. The system supplies the exhaust heat from the SOFCs to the methanol dissociation unit for hydrogen production, whereas the heat exchangers and SRC recover the remaining waste heat to produce useful electricity. Mathematical models were established, and the thermodynamic efficiencies of the system were evaluated. The first and second laws of thermodynamics were used to construct the dynamic behavior of the system. Furthermore, the exergy destruction of all the subsystems was estimated. The thermodynamic performances of the main subsystem and entire system were evaluated to be 77.75% and 44.71% for the energy and exergy efficiencies, respectively. With a hydrogen distribution ratio of β = 0.12, the PEMFCs can generate 432.893 kW for the propulsion plant of the target vessel. This is also important for the rapid adaptation of the vessel’s needs for power generation, especially during start-up and maneuvering. A comprehensive parametric analysis was performed to examine the influence of changing current densities in the SOFCs, as well as the influence of the hydrogen distribution ratio and hydrogen storage ratio on the operational performance of the proposed systems. Increasing the hydrogen storage ratio (φ = 0–0.5) reduces the PEMFCs power output, but the energy efficiency and exergy efficiency of the PEMFC-ORC subsystem increased by 2.29% and 1.39%, respectively.

АНАЛИЗ ФУНКЦИОНИРОВАНИЯ ПОДСИСТЕМЫ КОНТРОЛЯ УТЕЧЕК ИНФОРМАЦИИ АВТОМАТИЗИРОВАННОЙ СИСТЕМЫ В ЗАЩИЩЕННОМ ИСПОЛНЕНИИ

The aim of the study is to increase the efficiency of the information leak control sub-system of a protected automated system based on the rational redistribution of resources.
 The article is devoted to solving a specific scientific problem to analyse the information leak control subsystem of a protected automated system.
 The research method is analysing the architectures of the information leak prevention system and the information security monitoring centre, highlighting the architecture short-comings. Subsequently, the architecture synthesis of the information leak prevention system and the information security monitoring centre is presented; also the formal statement of the problem is described. 
 The novelty of this study lies in developing a model and methodology for evaluating the efficiency of the information leak control subsystem of a protected automated system.
 As an analysis result of operating the information leak control subsystem of a protected automated system, a number of short-comings are identified and a method for solving them is presented. 
 Thus, to solve the problem, parameters are introduced and determining their optimality minimises information leakage of a protected automated system

Exploring the environmental efficiency of airlines through a parallel RAM approach.

Air pollution in the aviation industry is becoming increasingly severe worldwide, along with rapid economic development. Therefore, it is significant to pay close attention to airlines worldwide. Usually, the airlines contain passenger transportation and freight transportation on the operating move. This paper proposes a parallel range adjusted measure (PRAM) to comprehensively measure and evaluate the environmental efficiency of 18 airlines from 2014 to 2019. Different from existing models, the model can handle shared inputs, shared desirable outputs, and shared undesirable outputs simultaneously. We build a shared resource decomposition procedure to perform a comparative analysis of the highest subsystem efficiency, and the sensitivity analysis proves the validity of the results. The main findings are as follows: 1. The optimal efficiency can be achieved by most of the 18 airlines when sharing resources; 2. Operating costs in the freight system should be increased to achieve optimal efficiency; 3. Asian airlines show higher efficiency than the airlines in Europe.

Development And Research of A Two-Contour Solar System In The Lorawan Network

This article examines the mechanism for researching and improving the energy efficiency of a solar water heating system (SWH) in a building located in Kazakhstan. In this paper, we use data collected from LoRaWAN to obtain information about various environmental and operational aspects of the system under consideration, which determine the possibilities for improving the efficiency of various SWH subsystems and develop management strategies for the effective operation of the entire system. With the help of data collected by IoT, such as water consumption, the schedule of the heat pump and water pump, the availability of solar energy and electricity consumption, we conduct a comprehensive energy audit to analyze the efficiency of subsystems, as well as the performance of the system as a whole. Based on the findings obtained from the data analysis, appropriate management strategies are developed for various subsystems in order to increase the efficiency of the entire system and reduce the operating costs of SWH.

The calculation of the regulated number of remote sensors of gas analyzers surrounding rectangular outdoor facilities at oil refineries

Introduction. The authors emphasize the importance of pre-explosive concentration sensors, that ensure the required fire safety (FS) at fire/explosion hazardous facilities of oil refineries. The authors substantiate the importance of maintenance procedures for first-level alarming devices that are part of automated process control systems (APCS) installed around outdoor facilities of refineries.Theoretical fundamentals. The authors argue that two counter-running subprocesses (destructive and creative (restorative)), that ensure fire safety, can describe a decrease in the efficiency of APCS subsystems in the FS monitoring, as well as their restoration at refinery facilities. The proper maintenance of gas detectors is presented as a discrete creative subprocess. The authors demonstrate a relation between the spatial location of sensors of stationary gas analyzers and the computability of their number, depending on the outdoor facility perimeter.Research results. To mathematically describe the maintenance procedure applied to stationary gas analyzers, the authors assess the dependence between the number of remote detectors, the perimeter of the rectangular outdoor unit, around which they are installed at a refinery, and the prescribed distance between the sensors.Conclusion. This assessment conveys the features of installation of gas detectors of any type depending on their classification based on physical methods of analysis. A conclusion is drawn that the perimeter data can help to calculate the number of rows for the installation of devices, the length of each row, the prescribed number of gas detectors in each row.

Upper limits to the mean annual optical efficiency of solar mono-tower systems

This study presents an analysis of the theoretical upper limits to the mean annual optical efficiency of the Light Collection and Concentration (LCC) subsystem of a solar tower system, which is the subsystem composed of the heliostat field and the active surfaces of the receiver that capture the concentrated solar radiation sent by the heliostat field to transform it into thermal energy. The “ideal” LCC subsystem is modelled gradually, by incrementally introducing into the model factors that limit the mean annual optical efficiency of any LCC subsystem and whose influence in the optical efficiency cannot be reduced to zero, starting with the cosine factor, followed by the atmospheric transmittance, and then by the product of the receiver intercept factor and a factor related to the shading of the heliostat field by the receiver. At each degree of complexity of the ideal LCC subsystem model, the optimal configuration of the “ideal” LCC subsystem that achieves the highest mean annual optical efficiency in terms of heliostat field shape and receiver size is identified for a selected range of latitudes, tower heights and heliostat field sizes or total mirror areas. Thus, the upper-limits of the mean annual optical efficiency of the LCC subsystem of solar towers are obtained as a function of the specified parameters. The results obtained show that at a latitude of 30° North, for tower heights between 200 and 300 meters and heliostat fields with mirror areas between 1.3km2 and 2.5km2, the upper limit of the mean annual optical efficiencies vary between 79.2% and 74.7%, with the highest upper limit corresponding to the combinations of the tallest towers and smallest heliostat fields. This strongly indicates that the mean annual optical efficiency of actual solar mono-tower systems of commercially realistic heliostat field sizes and tower heights will hardly reach 70% at any location on Earth.

Design and analysis of a new solar hydrogen plant for power, methane, ammonia and urea generation

In this paper, a solar power-based combined plant for power, hydrogen, methane, ammonia and urea production is proposed. A parabolic trough collector is utilized for the system prime mover. Moreover, steam Rankine cycle, organic Rankine cycle, hydrogen production and compression subsystem, ammonia, methane and urea production units, single-effect absorption cooling unit, and freshwater production plant are integrated together to develop the present system for better system performance and cost-effectiveness and reduced environmental impact. In order to analyze and evaluate the proposed multigeneration plant, thermodynamic, parametric and economic studies are performed. According to the assessment results, it is found that energetic and exergetic efficiencies of the present multigeneration plant are 66.12% and 61.56%, respectively. The comparisons of the subsystem and overall plant efficiencies show that the highest energetic and energetic efficiencies belong to freshwater production plant by 79.24% and 75.62%, respectively. In addition, the present parametric analysis indicates that an increase in the reference temperature, solar radiation intensity and working pressure of the solar process has a positive effect on the plant's performance. The cost analysis reveals that as the solar radiation intensity and the working pressure of the solar process increase, the hydrogen generation cost decreases. Furthermore, the hydrogen generation cost is achieved to be 1.94 $/kgH2 at 650 W/m2 of the solar radiation intensity, with other parameters remaining constant.

Measuring the performance of supply chain innovations

The issue of evaluating the performance of supply chain innovations in an organization in the current economic environment is studied in the paper. The proposed technique is used to compare several projected supply chain innovations and is based on a comprehensive evaluation using an integral coefficient and taking into account both financial and non-financial indicators, depending on the purpose and focus of suggested innovations. The presented approach was tested as part of the analysis of two supply chain innovations, using the example of the selected trading company. Based on the tasks that are planned to be solved with the use of corresponding supply chain innovations, the categories and indicators are identified for calculating the integral coefficient in order to measure the performance of supply chain innovation. The final analysis also takes into consideration the selected indicators for evaluating the efficiency of investments and functional subsystems of a supply chain to develop sound management decisions in the field of the company's logistic system transformation.

Exploring the effect of COVID-19 on airline environmental efficiency through an interval epsilon-based measure model.

COVID-19 has dealt an unprecedented blow to the aviation industry since 2020. This paper applies the interval epsilon-based measure (IEBM) model to evaluate the optimal quarterly environmental efficiency of 14 global airlines of passenger and cargo subsystems during 2018–2020. Then, the time series prediction method is applied to forecast the interval data of inputs and outputs from 2021 to 2022. Finally, we can calculate the quarterly efficiency. Thus, the future development trends of airlines can be predicted. The results show that (1) COVID-19 has hit the passenger subsystem harder, while the freight subsystem has become more efficient; (2) the efficiency of the freight subsystem has inevitably declined in the post-epidemic era; and (3) therefore, the airlines will have a “√” shaped recovery curve in the next few years.

Performance Measurement for the Recycling Production System Using Cooperative Game Network Data Envelopment Analysis

Resources scarcity and environmental degradation have made sustainable resource utilization and environmental protection necessary worldwide. The development of the circular economy is considered an approach for more appropriate economic and environmental management. This work introduces a cooperative game network data envelopment analysis model for evaluating the implementation effect of recycling production systems from a closed loop and centralized control perspective. The factor efficiency analysis of the involved inputs and outputs is presented to provide guidance for the factor dominance of subsystem efficiencies. An application for assessing the circular economy of EU countries is provided to illustrate the validation of the proposed method. Our results show that the average performance of the production subsystem is superior to that of the recycling subsystem in EU countries. Furthermore, factor efficiency analysis reveals that the inefficient environmental treatment input is the culprit in worse performance of the recycling subsystem. A comparison of the proposed method with recent studies for circular economy performance evaluation is also included.

Efficiency and driving force assessment of an integrated urban water use and wastewater treatment system: Evidence from spatial panel data of the urban agglomeration on the middle reaches of the Yangtze River

With the rapid development of urban agglomerations, urban water use and wastewater environments have gradually constrained sustainable development and caused increasing concern. In this paper, we selected the urban agglomeration on the middle reaches of the Yangtze River (UAMRYZ) as a typical area. We proposed an integrated urban water use and wastewater treatment (UWUWT) system and its urban water use (UWU) subsystem and urban wastewater treatment (UWT) subsystem. Moreover, an integrated two-stage slacks-based measure (SBM) data envelopment analysis (DEA) model was used to evaluate the efficiency of the UWUWT system and its subsystem during 2010 to 2017. Additionally, the multiscale geographically weighted regression (MGWR) model was adopted to analyze the influence mechanism of each factor on the defined system. The results indicated that the tendency of UWU efficiency and UWUWT efficiency were similar and mainly showed the same trend with an ‘N’ shape in a time-dependent manner for the UAMRYZ and provinces, respectively. Furthermore, the UWU efficiency and UWUWT efficiency of each city showed strong spatiotemporal heterogeneity. The UWT efficiency of the UAMRYZ and its representative cities was stable in the region and always had a higher value. With continuous economic development and increased interregional foreign trade, the UWU subsystem efficiency and the UWUWT system efficiency had a significant increase for cities along the entire river in the Yangtze Basin. The regional differences of the overall UWU efficiency, UWT efficiency and UWUWT efficiency gradually decreased and the efficiency has gradually improved from 2010 to 2017. Attribution analysis showed that the secondary industry was the main constraining factor, while the water resource was the most acceleration factor for the UWUWT system in most areas and the UWT subsystem for all cities. Our study evaluated the specific insufficiencies of the defined system and supported regulatory policies.

Methods for assessing the efficiency of access control subsystems at informatization facilities of internal affairs bodies and aspects of their improvement

Objective. The purpose of the article is to analyse the existing methodology used to assess the efficiency of automated information security systems by studying open literature sources, international and industry standards of the Russian Federation on information security of automated systems, guidelines and orders of the Federal Service for Technical and Expert Control of Russia, as well as departmental orders, instructions and regulations on information security at informatization facilities of internal affairs bodies. The analysis results in identifying the advantages and disadvantages of the specified methodology, as well as the possibilities of its use when conducting a quantitative assessment of the efficiency of access control subsystems of information security systems at the informatization facilities of internal affairs bodies. Methods. To achieve this goal, the method for system analysis of approaches used to assess the efficiency of information security tools and systems has been applied. Results. The paper presents results of analysing the main approaches used to assess the efficiency of tools and systems for information security of automated systems. The paper determines the relationship between the efficiency indicator of access control subsystems of information security systems and the main disadvantage of their use in protected automated systems of internal affairs bodies. The paper substantiates main directions of improving the existing methodology, proposes methods and indicators for quantifying the efficiency of access control subsystems (including those modified on the basis of using new information and communication technologies) of information security systems in protected automated systems of internal affairs bodies. Conclusion. The results obtained can be used to quantify the security level of existing automated systems and those being developed at informatization facilities of internal affairs bodies.