Cycle Operation Research Articles

Method for expert evaluation of the technical con-dition of the cylinder-piston group of automotive engines after hydrolock

Problem: The study examines the thermogasdynamic process within an internal combustion engine cylinder during cold cranking mode while measuring compression. Analysis of various models and comparison of known data revealed unresolved challenges in constructing mathematical models of the engine operating cycle. The vast majority of practical data and recommendations for compression measurement in a cylinder are based on empirical knowledge, numerous experiments, and tests. Consequently, there arises a need for computational models of the compression measurement process and their theoretical justification, particularly in cases where engine damage occurs during hydrolock in a cylinder. Methodology. To address the identified issues, a mathematical model of the thermogasdynamic process within the cylinder during cold cranking while measuring compression was developed. Originality. Unlike existing models, this model describes the processes in the cylinder step by step, considering the real nature of intake-exhaust processes, air leakage through part interfaces, and heat exchange with the walls. Through modeling, the main patterns of compression changes depending on the modes and the nature of damage to associated parts of the valve mechanism and the cylinder-piston group were identified, including deformation of the connecting rod during hydraulic lock due to liquid entering the cylinder. Practical value. Based on the study results, it was concluded that the model's properties make it effectively applicable in diagnosing and monitoring the technical condition of automotive engines during operation.

Peran Kepemilikan Manajerial dalam Hubungan Antara Tingkat Utang, Siklus Operasi, dan Ukuran Perusahaan Terhadap Persistensi Laba

This research aims to analyze the effect of debt level, operating cycle, and firm size on earnings persistence with managerial ownership as a moderating variable in consumer goods companies listed on the Indonesia Stock Exchange in 2020 – 2022. The data used in this study are data secondary with the sampling technique using purposive sampling based on certain criteria so that 53 companies were selected as research samples. Data analysis used multiple linear regression analysis using SPSS 25. The result showed that debt level and operating cycle had an effect on earnings persistence, while firm size had no effect on earnings persistence. Debt level, operating cycle, and firm size moderated by managerial ownership have no effect on earnings persistence.

Plastic zone and surrounding strain analysis in a lined cavern for compressed air energy storage subjected to cyclic high internal gas pressure and temperature

In the context of compressed air energy storage (CAES) technology, the strategic excavation of hard rock caverns is pivotal for overcoming geological challenges and advancing CAES deployment. This study adopts a circular profile for the cavern and investigates the impact of variables such as cavern diameter and depth. Considering the influence of cyclic internal gas pressure, temperature fluctuations, and potential leakage on the cavern, a thermo-hydro-mechanical coupled numerical model is developed using Comsol software. This model, grounded in classic elastoplastic constitutive relations, aligns with the conditions of a proposed project. It facilitates the computation of the plastic zone and surrounding strain for both the cavern lining and adjacent rock, post-excavation and throughout a typical ‘charging-storage-discharging-storage’ operational cycle. Through detailed analysis, the study delineates the variations and characteristics of the plastic zone and surrounding strain, thereby providing a solid foundation for a comprehensive examination of cavern stability, and the design of linings and sealing mechanisms.

Ion‐Impregnated Intermediate Layer for Enhancing Triboelectric Nanogenerator Performance

AbstractThe triboelectric nanogenerator (TENG) is gaining recognition as a highly promising, eco‐friendly self‐powered device for the growth of the Internet of Things (IoT). To improve the performance of TENGs, diverse materials are employed as interlayers. However, challenges related to cost and stability persist. Herein, a strategy that incorporates ion‐containing electrolyte polymers as interlayers is presented. This approach effectively mitigates charge decay and maximizes TENG efficiency by leveraging the high charge capacitance of the ionic electric double layer (iEDL). The incorporation of iEDL into TENG results in an approximate tenfold increase in current density (10–92 mA m−2) and a 13‐fold increase in power density (2–26 W m−2). The robust energy generation capabilities of iEDL‐TENG enable the operation of 100 LED lights and the charging of a 470 µF capacitor. Furthermore, the demonstrated device exhibits significant stability across 10,000 operational cycles and effectively maintains its performance when subjected to external physical forces such as blade‐induced cuts, penetrating wounds, and severe crumpling.

Trajetórias da infraestrutura no Brasil. Concepções, operacionalizações e marcos conceituais em perspectiva

Abstract Incompatibilities arising from the implementation of infrastructures over consolidated territorial dynamics are recurrent. Based on this axiom, the objective is to investigate the involvement of infrastructure planning in such incompatibilities. Methodologically, the analysis is based on theoretical schools that relate infrastructure and the city and uses studies on new infrastructures or interventions in existing infrastructures. The text provides a brief review of historical infrastructural patterns, addresses priorities in their conceptions, and studies their operational cycles. From this framework, it was possible to formulate the argument that, in Brazil, infrastructure is designed to (re)structure sectors, and when implemented, it (de)structures places. This argument motivated the investigation of new conceptual frameworks that allowed us to advocate that the design of infrastructures should be based on territorial evidence.

Modeling and experimental evaluation of the stepping characteristic on a walking-type piezoelectric actuator

Aiming at the suppression of backward motion, a walking-type piezoelectric actuator was developed in this paper. Two walking modes of ellipse-shaped walking and rhombus-shaped walking were discussed. The dynamic models in the x and y direction were established to simulate the stepping characteristics of two walking modes. The simulated results depicted that the actuator was able to achieve stepping displacement free of backward motion. A prototype was fabricated, and a series of experiments were conducted. The experiments indicated that, under two walking modes, there was a backward displacement in each operating cycle due to assembly errors. To suppress backward motion, a solution to compensate for the assembly errors by varying the bias voltage difference between two stators was proposed. After correcting the assembly errors, the backward displacements were almost eliminated and reduced by 71.4% from 0.28 to 0.08 μm and 68.1% from 0.22 to 0.07 μm, respectively under the ellipse-shaped walking mode and rhombus-shaped walking mode, which proved the effectiveness of the proposed actuator.

Characteristics of particle formation in O3-UBAC filter and effects of operational parameter on particles

The ozone oxidation and up-flow biological activated carbon (O3-UBAC) process has been recognized for its ability to extend the operating cycle of biological activated carbon (BAC) filters by expanding the carbon layer and maintaining a dynamic balance of the carbon biofilm. However, the primary focus of O3-UBAC is the removal of organic pollutants, often overlooking the treatment of particles. To address this gap, a pilot-scale study was conducted using sedimentation basin effluent samples from a drinking water treatment plant (DWTP), which were added into BAC columns. The study aimed to investigate the seasonal variation of effluent particles during the UBAC operating cycle, including particle counts, size distribution, and mass composition. Based on particle characteristics and the combined effects of adsorption and biodegradation, the UBAC operation cycle was divided into three periods. Results revealed that hydraulic impacts and biofilm desorption on carbon could increase the proportion of particles >5 μm in effluent. Pre-ozonation demonstrated significant effects on particle counts and Heterotrophic Plate Count (HPC) levels (p < 0.05), with the addition of 1 mg/L O3 resulting in a reduction in particle counts in the effluent. Moreover, particle removal could be achieved by adjusting the upward flow velocity, necessitating comprehensive consideration of pollutants. Furthermore, microbial community analysis under optimal operating conditions unveiled significant changes in the microbial diversity of UBAC-treated water particles. Although the influent and effluent exhibited similarities at different phylum levels, the dominant bacteria differed significantly at various levels.

Design and behaviour estimate of a novel solar and fuel cell complementary driven supercritical-CO2 cycle thermal system

Solar-integrated fuel cell systems are widely regarded as an effective means of saving energy and reducing emissions, given their ability to decrease reliance on fossil fuels. However, solar thermal power systems are intermittent, whereas fuel cell waste heat power generation has continuous power output. The paper proposes a novel solar and molten carbonate fuel cell complementary driven supercritical-CO2 cycle system. The performance of multi-energy complementary driven supercritical-CO2 cycle and system operation mode conversion is being investigated. The complementary operation mode ensures the continuous output of the proposed system through the switching of the solar module and the fuel cell module. The result indicates that the fuel cell module operates for 23.5 % of the time in a year, resulting in a reduction of the storage tank volume by 14,723 m3 and a decrease of the fixed heliostat area by 108,237 m2. The efficiency of the supercritical-CO2 cycle individually is 43.1 %, and with the addition of the waste heat utilization subsystem, the cycle efficiency of the proposed system reaches 50.89 %. Furthermore, the levelized cost of electricity for the proposed system is 0.1861$/kWh, and the research results can serve as a reference for the design of complementary energy systems.

High-Efficiency and Stable Colloidal One-Dimensional Core/Shell Nanorod Light-Emitting Diodes.

Anisotropic nanocrystals such as nanorods (NRs) display unique linearly polarized emission, which is expected to break the external quantum efficiency (EQE) limit of quantum dot-based light-emitting diodes (LEDs). However, the progress in achieving a higher EQE using NRs encounters several challenges, primarily involving a low photoluminescence quantum yield (PLQY) of NRs and imbalanced charge injection in NR-LEDs. In this work, we investigated NR-LEDs based on CdSe/CdZnS/ZnS rod-in-rod NRs with a high PLQY and higher linear polarization compared to those of dot-in-rod NRs. The balanced charge injection is achieved using ZnMgO nanoparticles as the electron transport layer and poly-TPD {poly[N,N'-bis(4-butylphenyl)-N,N'-bis(phenyl)benzidine]} as the hole transport layer. Therefore, the NR-LEDs exhibit a maximum EQE of 21.5% and a maximum luminance of >120 000 cd/m2 owing to the high level of in-plane transitions with a dipole moment of 90%. The NR-LEDs also have greatly inhibited droop in EQE under a high current density as well as outstanding operation lifetime and cycle stability.

Enzyme-powered soft robots: Harnessing biochemical reaction for locomotion

Enzymes have been known as “renewable resources” in cellular processes (in vivo) for more than a century, and are applied in a wide range of fields, including pharmaceuticals and food, particularly through in vitro approaches. This study explored using an enzymatic reaction as the power source for soft robots (here, robots fashioned from silicone). Soft robots powered by pneumatic pressure deform flexible materials in response to internal pressure changes, thereby inducing robot motion. Traditionally, the primary operational principle involved controlling internal pressure using a compressor, creating challenges related to device enlargement, weight, and electric power consumption. Here, as an alternative, we operated a pneumatically driven soft robot by applying the O2 gas generated from decomposition of H2O2 catalyzed by the ubiquitous enzyme catalase. The generation of O2 gas was influenced by the catalase concentration, H2O2 concentration, and the supply-rate of H2O2. Operational tests on a silicone-rubber soft arm suggested controllability of its velocity and number of operational cycles by modifying the enzymatic reaction conditions. Our findings demonstrate the utility of the catalase-catalyzed reaction as a power source for soft robots, thereby showcasing novel prospects for enzyme applications.

Continuous operation of nano-catalytic ozonation using membrane separation coupling system: Influence factors and mechanism

The application of nano-catalysts in improving the ozonation removal efficiency for refractory organic compounds has been extensively investigated. However, cost-effective nano-catalysts separation remains a challenge. In this study, membrane separation processes were employed to separate nano-MgO catalysts from an ozonation system. A continuous nano-catalytic ozonation membrane separation (nCOMS) coupling system was successfully constructed for treating quinoline. The results showed that long hydraulic retention time (HRT) and high nano-MgO dosage could improve the quinolone removal efficiency but shorten operation cycles. At the optimal operation conditions of HRT = 4 h and nano-MgO dosage = 0.2 g/L, the nCOMS system achieved a stable quinoline removal efficiency of 85.2% for 240 min running with a transmembrane pressure lower than 10 kPa. The quinoline removal efficiency contribution for ozonation, catalysis and membrane separation was 57.1%, 24.9% and 18.0%, respectively. Compared to ozonation membrane separation system, the fouling rate index of the nCOMS system increased by 60% under optimal conditions, but the irreversible fouling was reduced to 28%. In addition, the nCOMS system exhibited reduced adverse effects of coexisting natural organic matter (NOM) on quinoline removal and membrane fouling. In conclusion, the nCOMS system demonstrated higher quinoline removal efficiency, lower irreversible fouling, and reduced adverse effect of coexisting NOM, thereby signifying its potential for practical applications in advanced treatment of industrial wastewater.

Static Bending Mechanical Properties of Prestressed Concrete Composite Slab with Removable Rectangular Steel-Tube Lattice Girders

In recent years, with the development of building technology, the Chinese construction industry has begun to gradually promote the prefabricated buildings to save on construction costs. Among them, composite slabs, as essential components of prefabricated buildings, have been widely used by designers mainly in favor of their low cost. However, is it possible to further reduce the cost without affecting the quality? Researchers think so if the operation cycle of support from the bottom of composite slabs can accelerate and the mechanical properties of their bottom plate can be optimized. To prove this hypothesis, researchers proposed a new type of prestressed concrete composite slab with removable rectangular steel-tube lattice girders (referred to as CDB composite slabs), whose bottom plate consists of a temporary structure composed of a prestressed concrete prefabricated plate and removable rectangular steel-tube lattice girders. Through static bending performance tests on three prefabricated bottom plates and one composite slab, researchers measured corresponding load-displacement curves, load-strain curves, crack development, and distribution, etc. The test results show that the top chord rectangular steel tubes connected to the bottom plate concrete through web reinforcement bars significantly improve the rigidity, crack resistance, and load-bearing capacity of the bottom plate and possess better ductility and out-of-plane stability. The number of supports at the bottom of the bottom plate is effectively reduced, with the maximum unsupported span reaching 4.8 m. Beyond 4.8 m, only one additional support is needed, and the maximum support span can be up to 9.0 m, which provides space for cost reduction. The cooperative load-bearing performance of the prefabricated bottom plate and the post-cast composite layer concrete is good. The top chord rectangular steel tubes are easy to dismantle and can be reused, which reduces the steel consumption by about 24% compared to that used for the same size of ordinary steel-tube lattice-girder concrete composite slabs. It can greatly decrease the cost. In conclusion, the results have shown that the new method researchers proposed here is practically applicable and also provides great space to save on financial costs.

The Impact of Firm Risk and the COVID-19 Crisis on Working Capital Management Strategies: Evidence from a Market Affected by Economic Uncertainty

The present study aims to investigate the impact of the COVID-19 crisis and firm risk on working capital management policies among manufacturing firms listed on the Tehran Stock Exchange (TSE). The study sample consists of 1200 observations and 200 companies listed on the TSE over a six-year period from 2016 to 2021; furthermore, the statistical method used to test the hypotheses is ordinary least squares (OLS). The results show that the COVID-19 pandemic has led managers to increase current assets to total assets ratio (CATAR), current ratio (CR), quick ratio (QR), net working capital (NWC), cash to current assets (CTCA) ratio, while it has caused a decrease in operational cycle (OC), days account receivables (DAR), and current liabilities to total assets ratio (CLTAR). Furthermore, we find that the higher the company’s risk, the more managers are motivated to embrace the working capital investment policy, net working capital, cash to current assets ratio, and cash conversion efficiency (CCE). In general, our findings indicate that during times of crisis, Iranian companies tend to adopt conservative working capital policies to ensure sufficient liquidity to respond appropriately to unforeseen events. In this study, the theory of liquidity preference aligns with the observed behavior of firms in response to the COVID-19 crisis and firm risk, where the emphasis on liquidity and short-term financial stability becomes paramount.

A theoretical framework for the analysis of an opposed piston linear engine design

Traditional crank-based engines face limitations due to mechanical, thermal, and combustion inefficiencies. In contrast, the opposed piston design of a linear engine generator mitigates frictional losses by eliminating rotational motion and crankshaft linkages. Instead, electrical power is generated through the oscillation of a translator within a linear stator. However, the lack of geometric constraints in the free piston design leads to uncertainties regarding dead center positions, resulting in challenges such as misfire, stall, over-fueling, and rapid load changes.This study aims to fill this gap by reviewing existing modeling literature and advancing the fundamental understanding of opposed piston linear engines (OPLE) with springs through the development of an idealized, nondimensional model. A combination of analytical and numerical models was developed to better understand the behavior of the OPLE. The model introduces a streamlined symmetric analytical solution, succeeded by a broader general analytical resolution, with careful attention to the significant influence of thermodynamic effects at each phase, offering insights into the engine's dynamic performance. Limitations inherent to the analytical solutions are addressed by a numerical scheme utilizing the Runge-Kutta technique. This approach guarantees swift and dependable computational outcomes, which captures cyclic variation. The alternator model amalgamates both linear and sinusoidal work profiles, adjusting the magnetic work output in response to fluctuations in the compression ratio relative to the Top Dead Center (TDC) clearance distance. This adjustment dictates the generator load for each translator.The proposed model integrates the dynamics of a damped spring-mass system with thermodynamic expressions representing in-cylinder processes. Simplifications are made assuming perfect springs, ideal gases, instantaneous heat transfer, and an average friction force dependent on stroke length for work output. Selected cases are analyzed to elucidate the system's fundamental behavior, both within and outside the context of the Otto cycle, showcasing natural and forced stability over multiple operation cycles. Notably, enhancing the baseline cylinder pressure, or input heat relative to spring stiffness can elevate the work-to-heat ratio values. The attained work-to-heat ratio within compression ratio window of 16 is approximately 28 %. While this percentage may fluctuate in the context of general FPLE designs, the model developed for OPLE in this work plays a crucial role in maintaining the engine within this narrowly defined efficiency range, without compromising the potential performance demonstrated in this study. Differences in compression ratios provided intriguing insights into the dynamics of the translator and the in-cylinder thermodynamics of the interconnected system. Lower TDC clearance resulted in high translator displacement, velocity, and enhanced thermal efficiency.

Off-line chemical cleaning reduces the spatial heterogeneity of membrane fouling in full-scale membrane bioreactors: A case study

Full-scale membrane bioreactors (MBRs) are widely employed for wastewater treatment. Nevertheless, the spatial heterogeneity of membrane fouling within full-scale MBR modules has received limited attention, especially regarding the impact of off-line chemical cleaning on this spatial heterogeneity. This study, based on 192 hollow fiber samples collected from two full-scale MBRs, investigated the spatial fouling heterogeneity before and after off-line chemical cleaning. The membrane samples were categorized into different groups based on sampling locations, and statistical tools were employed to analyze spatial fouling heterogeneity. The results of foulant mass and filtration resistance of samples confirmed the presence of spatial fouling heterogeneity within the MBR modules after 5 months of operation. The off-line chemical cleaning removed organic foulants more effectively than inorganic foulants, and interestingly, it effectively reduced the spatial fouling heterogeneity. Computational fluid dynamics analysis in the cleaning tank and the chlorine concentration distribution indicated that chemical cleaning occurred without mass transfer or reaction limitations. We further offer insights into the reduction of spatial fouling heterogeneity by clarifying the fouling layer structure and the role of off-line chemical cleaning. Our findings suggest that with an appropriate cleaning strategy, the hollow fiber filtration performance can be rebalanced before a new operation cycle.

Deep learning-based digital twin for intelligent predictive maintenance of rapier loom

The rapier loom works in a complex environment and operates at high speeds. It is inevitable that its performance will deteriorate during the production process, which in turn will cause faults. The development of maintenance has undergone the transition from “regular maintenance” and “post-event maintenance” to “predictive maintenance”. In order to achieve the synergistic optimization goal of ensuring operational safety and reducing operational costs, a predictive maintenance method driven by the fusion of digital twin and deep learning is proposed based on the idea of “combining the real with the virtual and controlling the real”. Firstly, a digital twin system structure model of rapier weaving machine is constructed, and the overall architecture of digital twin is proposed according to the full operation cycle of rapier weaving machine. Then, the digital twin-driven process parameter evaluation and prediction and health state evaluation and prediction are investigated separately. In order to achieve the evaluation and prediction of process parameters to ensure the efficiency of weaving machine operation, the prediction method of IWOA optimized BP neural network driven by twin data is proposed and the model is updated and optimized based on the martingale distance approach. In order to achieve health state assessment and prediction, we use health index as an evaluation index to characterize the health condition of spindles, and use BiLSTM network to achieve prediction of remaining spindle life and then make maintenance decisions. The results show that there are greater advantages to combining deep learning and digital twin technology for intelligent predictive maintenance of rapier loom.

Achievement of high-current continuous-wave deuteron injector for linear IFMIF prototype accelerator (LIPAc)

The Linear IFMIF (International Fusion Materials Irradiation Facility) Prototype Accelerator (LIPAc) is aiming at demonstrating the low-energy section of a 40 MeV/125 mA IFMIF deuteron accelerator up to 9 MeV with a full beam current in continuous-wave operation. For such a high-power beam, the LIPAc injector is required to produce a beam current of 140 mA and 100 keV D+ beams. The injector commissioning to reach high beam current has been progressing at high duty cycle operation, then stable operation for many hours at a beam condition of 150 mA total extracted current. This result demonstrates that the LIPAc injector can meet the required performance for nominal 125 mA long pulse deuteron beam acceleration.

Performance investigation on dual bed adsorption chiller integrated with a partially covered N-PVT collector

The theoretical performance investigation of the adsorption chiller system integrated with a partially covered N-PVT Collector is mathematically modeled and presented in the paper. The study employs a MATLAB-Simulink integrated interface, and the silica gel-water combination serves as the working pair. The average weather conditions of Shiv Nadar Institute of Eminence for the month of May are taken into account the study. The investigation shows that solar energy integrated with an adsorption cooling system could efficiently provide a cooling effect. The results suggested that, due to the direct integration of the PVT with the chiller system, the influence of cycle operation is significant at the minimum and maximum solar radiation times. An optimization research for the optimal number of collectors for silica gel regeneration revealed that using N = 5 collectors results in an outlet hot water temperature range of 110 0C. During operation, the maximum adsorption capacity of 0.21 kg of water/Kg desiccant is obtained, for providing an adequate cooling effect. The system achieved a specific cooling power of between 50 and 200 W/kg during the process, and a coefficient of performance between 0.15 and 0.23.

Resource-constrained bridge maintenance optimization by harmonizing structural safety and maintenance duration

Bridges are progressively experiencing significant structural wear and challenges in their maintenance procedures. To address this issue, it's crucial to clarify the order of maintenance activities during the bridge maintenance process and the impact of maintenance resources on structural safety performance. This understanding allows for the precise establishment of a model that captures the changes in structural safety performance in relation to the bridge maintenance duration that are resource-constrained. This paper proposes a resource-constrained bridge maintenance optimization method where neither the structural safety performance loss nor the duration holds a dominant advantage. An Adjusted NSGA-II (Adj-NSGA-II) method is employed to determine the total structural safety performance loss and total duration throughout the bridge's operational cycle. The results show that the number of construction workers in the mathematical model proposed will have different degrees of influence on the change of the total construction duration under the similar total structural safety performance. The proposed method not only enhances the scientific management capabilities of decision-makers in bridge maintenance planning but also provides a framework that can be applied to maintain other structural forms.

Enhancing Operational Efficiency and Cash Flow through Supply Chain Optimization in the Oil and Gas Sector

The oil and gas industry continues to play a vital role in meeting the world&amp;#39;s energy needs. As renewable energy sources gain traction, there is an imperative to refine operational models, prioritizing sustainability, and cost-effectiveness. This study employs a comprehensive conceptual framework integrating critical analysis of business scenarios, product positioning, and market segmentation. The study adopts supply network optimization, encompassing demand forecasting, inventory management, transportation, production scheduling, cash flow management, and data analytics. The research evaluates three supply models: Satellite Manufacturing, Hub Manufacturing, and Contract Manufacturing. It employs scenario analysis to assess the impact of supply chain strategies on operating and cash cycles. The analysis reveals that Hub- based contract manufacturing is the most effective model. The research demonstrates that optimizing supply networks directly influences the operating and cash cycles of companies in the Oil and Gas industry. By reducing inventory levels, optimizing supplier payment terms, and streamlining production processes, organizations can achieve cost savings, improve efficiency, and enhance cash flow management. The study underscores the importance of thorough analysis and strategic decision-making in selecting supply chain models to enhance cost efficiency, operational effectiveness, and cash flow management. The study is limited to midstream and downstream services and may vary based on industry contexts. Future research could explore additional supply chain strategies across different sectors. This research contributes to the sustainable consumption and value co-creation literature by offering practical insights for businesses operating in the oil and gas industry or similar contexts. It provides a framework for optimizing supply chain models to improve cost efficiency and cash flow management, thereby enhancing overall business performance.