Performance Of Operation Research Articles

Area-Efficient 1T-2D-2MTJ SOT-MRAM Cell for High Read Performance

This brief proposes a compact spin-orbit torque magnetic random-access memory (SOT-MRAM) cell structure with high read performance for embedded nonvolatile memory (eNVM) applications. The memory cell is composed of one transistor, two Schottky diodes, two magnetic tunnel junctions (MTJs) and one shared heavy metal (HM) layer, which can be abbreviated as 1T-2D-2MTJ cell. The two MTJs are stacked on the same HM layer for smaller area overhead and configured to be complementary with the magnetization of their pinned layers in the opposite direction to double the read sense margin. The write operation is also simplified since a current through the HM layer changes the resistances of both MTJs simultaneously. The evaluations include the micromagnetic simulation of the SOT device, the analysis of PVT variations for the read operation on bit-cell level, the estimation of bit-cell area and the simulations of performance and power consumption on array level. The results show that the proposed SOT-MRAM improves the performance and reliability of the read operation and achieves 75% (50%) reduction in bit-cell area compared to 4T-2MTJ SOT-MRAM (2T-2MTJ STT-MRAM), 83.0% reduction in write power consumption and 91.1% reduction in write latency compared to 2T-2MTJ STT-MRAM.

A High Step-Up Integrated Buck-Boost-Zeta Converter Using Three-Winding Coupled Inductor With Current Sharing Considered

This paper proposes a high-gain Buck-Boost-Zeta converter with three-winding coupled inductor, which is generated by differentially connecting the Buck-Boost converter and the Zeta converter and integrating the coupled inductor multiplier cell. An active switched-inductor is obtained at the input side by differential connection, which is used as the primary winding of the three-winding coupled inductor, and the multiplier cell is composed of the secondary winding and diode-capacitor. The diode-capacitor circuit in the topology is multiplexed as a passive clamp branch to absorb the leakage energy and the ZCS turn-on of the switches is achieved. Therefore, the proposed converter achieves higher voltage gain and lower switch voltage stress. At the same time, the proposed converter retains the continuous output current characteristic of the Zeta converter. The operation principles and performances of the proposed converter are analyzed in detail. Meanwhile, the imbalance currents of the primary windings caused by the leakage inductance error is analyzed and the coupled inductor current sharing method is given, which effectively alleviates the current pulsation of the primary winding. A 400W experimental prototype is built to verify the theoretical analysis.

IOT based Manhole Detection and Monitoring System

Abstract: With the increasing Urban population, the need for Internet of Things (IoT) based smart city applications, such as monitoring manhole covers (MC), becomes crucial. However, current MC monitoring systems lack full automation, have a short lifespan, and face design challenges from an IoT device perspective. In this study, we explore the use of compressive sensing (CS) to reduce power consumption in the analog-to-digital converter (ADC) of an IoT-based MC monitoring system, aiming to extend its lifetime. We propose two low-power analog chaotic oscillators as an alternative to the digital pseudo-random number generator (PRNG) commonly used in CS-based ADC's. The proposed systems are validated through temperature measurements, showing promising results. This research addresses circuit design challenges and improves system performance for long-term and efficient operation of IoT-based MC monitoring systems.

Service level And Logistic Performance: An Implementation Of Sustainable Quality Assessment

The study aimed to uncover the impact of quality assessment with the instruments of ISO 9001at major hub of logistics companies in Indonesia which divided into three major regions, western region, middle region and northern region of Indonesia. The implementation of ISO used three different variables as components and parameters of assessment which consist of continuous improvement, satisfaction of users and prevention of nonconformities. The methods were used by interviewing and deployment of structured questionnaires to related parties which directly engaged on quality assessment process in daily assignments. The result showed that the implementation of quality instruments such ISO 9001 affecting significantly the quality delivered to users and customers as well as the performance of overall operation held by the logistics companies. The result also showed that the quality of service was not only could be undertaken by two variables but also could be done with more variables that have not been explored. The opportunity of improvement had been implemented by logistics companies through giving optimum services to users and customers.

Environmental benefits of a hybrid system for algal biomass production, harvesting and nutrient recovery under a life-cycle assessment

Biofilm reactors (BRs) are being studied as a means to optimize microalgae biomass production and overcome harvesting bottlenecks. This has led to the development of hybrid systems (HS), which combine BRs with conventional systems. However, for this technology to be implemented on a large scale, environmental viability must be ensured for its various configurations. To this end, a study was conducted using two life cycle assessments (LCAs) based on primary data. The study evaluated different support materials (cotton, nylon, and polyester) and investigated the impact of coupling a BR to a high-rate pond (HRP) during domestic wastewater treatment for biomass production and harvesting. The LCAs were conducted by SimaPro® software using the ReCiPe 2016 midpoint and endpoint methods. Results of the environmental performance of the BR operation with different support materials revealed that the production of fabrics was not the most impactful stage, except for cotton, in which this stage was responsible for >90 % of the environmental impacts in the Land use, Freshwater ecotoxicity and Marine ecotoxicity categories. The environmental impact contribution of the production stage of nylon and polyester fabrics in all categories did not exceed 26 %. Despite requiring more energy and support material, the hybrid system showed a reduction of around 28 % across all environmental categories compared to a system consisting only of a HRP and settling tank (ST). This is due to the HS's higher biomass recovery efficiency. Additionally, increasing the number or surface area of BRs to encourage attached growth is a strategy that can lower environmental impacts by approximately 40 %. Therefore, the HS, composed of an HRP and a BR, proved to be a promising alternative for wastewater treatment and algal biomass production and harvesting.

Low-cost materials as vehicles for pesticides in aquatic media: a review of the current status of different biosorbents employed, optimization by RSM approach.

Water contamination by pesticides is increasing dramatically due to population growth and the extensive use of pesticides in agriculture, leading to grave environmental and health concerns. Thus, efficient processes and the design and development of effective treatment technologies are required due to the enormous demand for fresh water. The adsorption approach has been widely used to remove organic contaminants such as pesticides because of its performance, less expense, high selectivity, and simplicity of operation compared to other treatment technologies. Among alternative adsorbents, biomaterials abundantly available for pesticide sorption from water resources have attracted the attention of researchers worldwide. The main objective of this review article is to (i) present studies on a wide range of raw or chemically modified biomaterials potentially effective in removing pesticides from aqueous media; (ii) indicating the effectiveness of biosorbents as green and low-cost materials for removing pesticides from wastewater; and (iii) furthermore, report the application of response surface methodology (RSM) for modeling and optimizing adsorption.

Degradation Analysis of SOFC Performance for Long-Term Operation with High Fuel Utilization (2)

Three types of SOFC stacks have been operated in a NEDO’s project from FY2020 to FY2024 in order to clarify the technical issues for high efficiency and toughness of SOFC stacks and establish the methods for advanced degradation diagnosis of SOFC stacks. Long-term durability tests of two types of SOFC stacks as flatten-tubular type and planar type have been conducted toward 20,000 h under the high fuel utilization at 80 and 85 %, respectively close to the operational limits of the stacks. In addition, the degradation factors of SOFCs were analyzed by using the electrode polarization model developed by CRIEPI. As a result, cathode overvoltage and IR loss were the major degradation factors in the durability tests over 10,000 h.

Self-Standing, Ultrasonic Spray-Deposited Membranes for Fuel Cells.

The polymer electrolyte membrane and its contact with electrodes has a significant effect on the performance of fuel and electrolysis cells but the choice of commercially available membranes is limited. In this study, membranes for direct methanol fuel cells (DMFCs) were made by ultrasonic spray deposition from commercial Nafion solution; the effect of the drying temperature and presence of high boiling solvents on the membrane properties was then analyzed. When choosing suitable conditions, membranes with similar conductivity, water uptake, and higher crystallinity than comparable commercial membranes can be obtained. These show similar or superior performance in DMFC operation compared to commercial Nafion 115. Furthermore, they exhibit low permeability for hydrogen, which makes them attractive for electrolysis or hydrogen fuel cells. The findings from our work will allow for the adjustment of membrane properties to the specific requirements of fuel cells or water electrolysis, as well as the inclusion of additional functional components for composite membranes.

Mental workload assessments of aerial photography missions performed by novice unmanned aerial vehicle operators.

Mental workload is one of the important variables in understanding human performance in drone operation. To test the effects of gender, age group, flight route, and altitude on the flight performance and mental workload of the novice drone operators. Ten male and ten female participants without prior drone operating experience joined. They were split into two age groups. After attending a training, the participants operated a drone to perform photo taking missions under flight route and altitude conditions. The weighted NASA Task Load Index (TLX), Modified Cooper-Harper (MCH) scale, heart rate, and interbeat interval were measured to assess the mental workload of the participants. Flight time to complete the mission was adopted to indicate flight performance. The effect of age group was significant (p < 0.05) on flight time, weighted TLX score, and MCH score. Flight route and altitude were not significant on the two subjective ratings and two cardiac measures. The flight performance of younger participants was significantly better than that of their older counterpart. The effects of both the flight route and altitude on the perceived mental workload of the drone operators were insignificant. Both the weighted NASA TLX and MCH scales were appropriate in measuring the mental workload of the novice drone operators.

A new inclining flight mode and oblique takeoff technique for a tiltrotor aircraft

A new tiltrotor inclining flight mode is presented in the study. Based on this mode, an optimized tiltrotor oblique takeoff technique is designed to improve the flight performance and efficiency in tiltrotor's takeoff operation. First, the proposed inclining flight mode is built through the dynamics analysis of the tiltrotor and related maneuver design and that makes the tiltrotor able to fly along an oblique path with its body line parallel to the flying direction. Then, with this new mode, a tiltrotor oblique takeoff technique and related control program are devised. Third, the shape of takeoff path in the oblique takeoff operation is studied, and an optimized oblique curved path is introduced to further improve the tiltrotor flight performance and efficiency. Simulations are conducted to investigate the effectiveness of the designed inclining flight mode and implemented oblique takeoff procedure in a set of different takeoff paths. It is found that the tiltrotor's flight performance and efficiency are significantly improved in terms of both required takeoff time and energy consumption. Finally, flight tests corresponding to the simulation work are conducted, that prove the effectiveness of the newly designed inclining flight mode and oblique takeoff technique.

Transformation in the system of residual number classes from one system of modules to another

The purpose of the study. The purpose of the study is an analytical consideration of the system of residual classes for the implementation of the operation of converting numbers from one system of residual classes to another. Method. System analysis, number theory, and the Chinese remainder theorem are tools of the research methodology. The method uses the representation of the number both by its remainders and in the polyadic code. The methodology is based on determining the positional characteristics for this module on the basis of the received positional characteristics for the remaining modules of the original system, with the subsequent construction on their basis of the residuals for the modules of the sought system. The proposed method is algorithmically simple. The results. The theoretical substantiation of the considered approach to obtain an effective solution of the non-modular transformation operation in the system of residual classes for the transition from the representation of a number by one system of modules to its representation by another system of modules is performed. It is shown that the proposed method provides the desired result. On the basis of the proposed approach, an increase in the performance of the conversion operation is achieved. Scientific novelty. The theoretical justification of the presented approach to the solution of the non-modular transformation operation in the system of residual classes for the transition from the representation of a number in one system of modules to its representation in another system of modules is proposed. It seems appropriate to apply the proposed approach as a prospective direction of research of complex operations in the system of residual classes. Practical significance. It follows from the importance of theoretical conclusions and obtained research results.It is based on the fact that there is a reasonably simple and effective approach to solving the problem of performing a non-modular conversion operation in the system of residual classes for the transition from the representation of a number in one system of modules to its representation in another system of modules. The considered solutions have high speed and can be effective in the development of modular computing structures for promising information technologies.

Development of a custom-made 2.8 T permanent-magnet dipole photon source for the ROCK beamline at SOLEIL.

In August 2021, the SOLEIL storage ring was restarted after the summer shutdown with a new bending magnet made entirely of permanent magnets. Producing a magnetic field of 2.8 T, it replaced one of the 32 electromagnetic dipoles (magnetic field of 1.7 T) of the ring to allow the ROCK beamline to exploit more intense photon fluxes in the hard X-ray range, thus improving the time resolution performances of the beamline for experiments carried out above 20 keV. The reduction of the new dipole magnetic gap required to produce the higher field has led to the construction and installation of a new vacuum vessel. The realization of the new dipole with permanent magnets was a technological feat due to the very strong magnetic forces. The permanent-magnet assembly required dedicated tools to be designed and constructed. Thanks to accurate magnetic measurements, a precise modelization of the new dipole was performed to identify its effects on the electron beam dynamics. The first measurements carried out on the ROCK beamline have highlighted the expected increase in photon flux, and the operation performances remain unchanged for the other beamlines. Here, the major developments and results of this innovative project are described in terms of technology, electron beam dynamics and photon beam performance on the ROCK beamline.

Study on the heat transfer with regard to an off-grid vending machine having a low impact on the environment

Following the current trend of energy economy, the article’s team designed a vending machine made of sandwich panels, in order to minimize the heat transfer from the environment to the chilled volume. The heat inputs calculation was based on the data provided in the sandwich panels’ technical sheets. In this paper, the real performance in operation was monitored, resulting in a deviation between 2.27 and 5.37% of the theoretical values for the global heat transfer coefficient. Furthermore, the TEWI coefficient (Total Equivalent Warming Impact) was evaluated to highlight the energy efficiency of the equipment, operating with refrigerant R290. Thereby, the authors emphasize the importance of the transition to natural refrigerants.

고밀도 배터리 충방전 시스템을 위한 낮은 높이를 갖는 500W급 양방향 DC-DC 컨버터

This study proposes a new bidirectional low DC-DC converter without a fan with a low height of 25 mm for direct connection between a battery and a bidirectional low DC-DC converter(BLDC). To implement the proposed BLDC, dual active bridge(DAB) converter and two interleaving buck converter are adopted. For BLDC with low height and high efficiency, the transformer of the DAB converter is separated into two series on the primary side and two parallel structures on the secondary side. Inputs and outputs are connected in parallel and interleaving control is applied in two interleaving buck converters. Finally, double heat sink structure is adopted for high heat dissipation performance. A prototype of 500 W with an input voltage of 650 V and an output voltage of 1–5 V is manufactured to verify the performance of operation, efficiency, and temperature in steady and transient states.

Load-Aware Greedy Dynamic CoMP Clustering Mechanism for DPS CoMP in 5G Networks

Cooperative communications offered by the Coordinated Multipoint (CoMP) technique have been introduced and become an important technique in the 5G mobile networks to support very high system capacity and improve the end-user service quality, especially for the cell-edge users via the dynamic coordination of transceivers at different geographical sites. One major issue driving the performance of CoMP operation is the decision on the coopering clusters or the cluster formation strategies. In this work, an approach of CoMP clustering has been studied and proposed, the so-called load-aware greedy dynamic CoMP clustering mechanism. Our proposed CoMP clustering technique is deployed on top of the actual traffic-based load-aware Dynamic Point Selection CoMP (DPS CoMP) mechanism, which is our previously proposed mechanism. The approach is aimed at maximizing spectral efficiency with appropriate cell coordination based on well-balancing cell loads within the coordinating area of the 5G networks. System performance is numerically studied and observed for the 5G Non-Orthogonal Multiple Access (NOMA) systems embedded with our proposed mechanisms for the realistic scenarios, i.e., homogeneous network and Heterogeneous Network (HetNet) cases. Numerical results illustrate the benefit brought by our approaches in comparison with others CoMP clustering techniques as well as the potential for further improvement.

Performance improvement of a pump running as turbine for energy recovery considering the effects of polymer additives: An experimental study

Employing pumps as turbines (PAT) has proven to be a cost-effective and efficient method for producing clean electricity in various engineering applications. PATs are now being considered for use in pumped hydro storage plants (PHS) instead of using a series of separate pumps and turbines and also in oil, petrochemical, and refinery industries as pressure energy recovery. Therefore, it is highly desirable to improve the hydraulic and mechanical characteristics of PATs in such applications. In this study, the effects of polymer additives as drag reducing agents on the performance of a centrifugal pump running as turbine mode is experimentally investigated. Reducing the friction drag within a turbulent flow using additives such as long-chain flexible polymers has attracted considerable attention from an energy-saving perspective. For this purpose, a test rig including the feed pump and the main pump has been set up where aqueous solutions of polyacrylamide with concentrations of 150, 300, and 450 ppm are used as working fluid. In order to compare the turbine mode with the pump mode, the pump performance in direct operation is also evaluated. The findings reveal that compared to tap water, using polymer solutions increases the efficiency and output power of the PAT, which even further improves with increasing polymer concentration. In the turbine mode, the highest increase in efficiency occurred at 450 ppm, which represented an increase of 7.61%. On the other hand, in the pump mode, the maximum improvement in pump efficiency (8.30%) has been recorded when the 150 ppm solution is used instead of tap water. By increasing the flow rate of polymeric solutions, the percentage of increase in the pump’s efficiency, compared to tap water, is ascending. Conversely, the percentage of increase in the PAT’s efficiency declines as the flow rate of polymeric working fluid passing the turbine is increased. The degradation of the utilized polymer in solutions leads to a decrease in output power and efficiency of the PAT compared to its fresh state. Nevertheless, the PAT efficiency and generated power in the degraded condition of the solution are still higher than what can be achieved in presence of tap water as the working fluid. The results of this study generally show that the use of working fluids with viscoelastic properties, which contain additive polymers, significantly improves the performance of reverse and direct pumps. As such, it can be used as an alternative working fluid in the industries mentioned above.

Investigation of the Accuracy of the Height Dimensions of Forgings for Cold Volumetric Stamping Processes by the Computational and Analytical Method

In mechanical engineering, product quality indicators are inextricably linked with the accuracy of machining parts. The dimensions, shape and location of the surfaces obtained during processing determine the actual gaps and tightnesses in the joints of machine parts, and consequently, the technical parameters that affect the quality, reliability and economic performance of production and operation. Very often in practice, the achievable accuracy of processing, including cold volumetric stamping (HOS), is judged by the accuracy tables contained in special reference literature. Such tables contain indicative data on achievable accuracy for various technological operations, obtained by systematization of direct long-term observations in production conditions. However, the peculiarities of individual operations do not allow us to give a conclusion about the accuracy of stamping by analogy with other operations, since there is no comprehensive similarity between them. In particular, the sizes and shape of the initial blanks differ, mechanical the properties of their material, the friction conditions in the die cavity, the characteristics of the press used and other technological factors. Thus, taking into account the listed circumstances, in each specific case it is necessary to calculate the accuracy of processing, which should have the ultimate goal not only to obtain a numerical result, but first of all to disclose the mechanisms of accuracy control. The calculation of the processing accuracy should be carried out taking into account the methods of obtaining dimensions and methods of setting up the technological system. The article is devoted to the computational and analytical method for calculating the forging accuracy based on the application of the theory of parametric sensitivity.

Study on the 4-channel micro-monolithic design with geometry control for reversible solid oxide cell

Reversible solid oxide cell (R-SOC) has been attracting considerable attention as a technology capable of power generation and CO2 electrolysis. In addition to new material development, innovation in structural design is also a decisive factor. In this study, a 4-channel micro-monolithic design, in the form of a tear-drop inner channel structure, was successfully developed. The micro-monolith obtained includes plurality of micro-channels growing from multiple directions and spongy active regions near the exterior surface. Uniquely, the irregular tear-drop inner channels further increase the proportion of the electrochemically active region to the overall circumference, achieving more efficient utilization of the geometric surface area. Such micro-structured cells with Ni-YSZ/YSZ/YSZ-LSM materials exhibited effective performance in the reversible operation of R-SOC. A superior performance of 1.20 W·cm−2 at 800 ℃ for H2 fuel cell was demonstrated. Similarly, during the electrolysis of CO2, current density recorded by the cells reached 1.20 A·cm−2 at 1.5 V and 800 ℃, which is competitive compared with the values of the previous design investigations. Relatively low diffusion polarization shown in electrochemical impedance spectroscopy (EIS) suggests that this is due to the very gas transfer resistance in the fuel electrode. This novel multi-channel micro-monolithic structure shows a potential to substitute the conventional tubular counterpart.

Robust Optimal Control for Wastewater Treatment Process With Uncertain Time Delays

To achieve the excellent operational performance of the wastewater treatment process, optimal control has been considered a reliable method. However, there is a time-delay response of the operation performances to the process variables, leading to uncertainties of operational optimal objectives. It is difficult to obtain the optimal set-points due to the uncertain operational optimal objectives. Therefore, a kernel-density-estimation-based robust optimal control (KDE-ROC) method is proposed. First, a data-driven prediction strategy is developed to construct the uncertain operational optimal objectives. Based on the time-delay intervals, the uncertainties between process variables and operational optimal objectives are expressed. Second, a kernel-density-estimation-based robust optimization algorithm is designed to solve the uncertain operational optimal objectives. Then, the optimal set-points of process variables are obtained depending on the robustness index to reduce the influence of uncertainties. Third, an adaptive neural network controller is developed to track the optimal set-points of process variables. Finally, the proposed KDE-ROC is applied in benchmark simulation model No.1. In the experimental results, the optimal control performance of KDE-ROC is compared with some effective optimal control strategies to demonstrate its effectiveness.

Enhancement of dynamic properties for a gas foil bearing using structural components made of shape memory alloys – experimental study

Bearings are commonly employed in various types of rotating machineries. Their properties indisputably influence the overall performance and time of maintenance-free operation of the mechanical systems in which they are used to support the shafts. Consequently, much effort is considered to provide reliable bearings’ solution and develop new methods and technical tools for measurement and possibly modification of the operational characteristics of the above-mentioned parts. In reference, the concept of a smart bearing is developed as providing the means for real-time passive and active control of the bearings’ behavior as well as different types of smart materials are used to enhance their characteristics. The current study deals with an applications of structural components made of shape memory alloys to gas foil bearings (GFB). The paper presents and discusses the results of experimental tests conducted for the bearing’s prototype to characterize the efficiency of thermally-induced modifications of geometric properties of one of the crucial parts of the investigated GFB.