Medium Speed Research Articles

Coordinated adaptive cruise control with integration of driving behaviors based on prediction for surrounding vehicles status

The adaptive cruise is an important vehicle control process for unmanned vehicles. This paper studies coordinated adaptive cruise control (ACC) of energy-saving in an intelligent networked environment, aiming to integrate control for common driving behaviors (cruising, following, lane-changing) by hierarchical control. The decision-making layer for integrating three driving behaviors is designed to improve the economy and passing time. Respectively, cruising strategy is optimized by considering efficient working area of motor; following strategy is constructed by dynamically adjusting the following distance with the state changes of the surrounding vehicles; lane-changing strategy is developed by considering the motor working efficiency of target speed. To improve the predictability of decision-making, non-linear autoregressive neural network (NARX) is introduced to predict the surrounding vehicle state. Furthermore, receiving the control reference from the decision layer, the controller is designed to realizes the tracking control of vehicle speed and following distance based on model predictive control (MPC), which is co-optimized for tracking, economy, and comfort. Eventually, the effectiveness of the coordinated ACC control is verified based on the hardware in the loop (HiL) test. The experiment results show that the vehicles with coordinated ACC can shorten the passing time and reduce the driving energy consumption to a certain extent, especially in the medium and low speed conditions.

Research on global optimization mechanism of intelligent compaction parameters of soil subgrade based on difference method

The global optimization mechanism plays a crucial role in enhancing construction efficiency and ensuring construction quality of soil subgrade such as building foundation or roadbed, within the context of intelligent compaction technology. There are three parts in the global optimization mechanism, which are determining the optimal work parameters, judging the compaction quality, and the feedback adjustment method. To establish a global optimization mechanism for intelligent compaction of subgrade soil, this paper developed a numerical simulation model for subgrade intelligent compaction, defined the necessary numerical simulation conditions for the global optimization mechanism of intelligent compaction. In this way, it provides a source of data for the establishment of global optimization mechanisms. Furthermore, the optimal working parameters are determined by the method of multivariate nonlinear fitting and calculating its extreme value. Meanwhile, an intelligent compaction quality judgment mechanism is established. Additionally, a feedback adjustment method for intelligent compaction was developed using the difference method to form a comprehensive global optimization mechanism. Finally, the intelligent compaction's global optimization mechanism has been validated through field experiments. The results of this study demonstrate that the boundary between low speed and medium speed rolling is 1.7 m/s. The optimal number of rolling passes is four and the ideal rolling speed ranges from 1.2 to 1.3 m/s when initial compaction degree reaches between 80 % and 90 %. The compaction degree, CMV (Compaction Meter Value) and AICV (Acceleration Intelligent Compaction Value) all exhibit a decreasing trend of subgrade compaction quality with increasing rolling speed, and the rate of decrease gradually accelerates.

DIRECT TORQUE CONTROL SCHEME FOR LESS HARMONIC CURRENTS AND TORQUE RIPPLES FOR DUAL STAR INDUCTION MOTOR

Multi-phase machine drives are widely used in high-power applications such as naval propulsion and railway traction. In the control context, direct torque control (DTC), based on the large voltage vectors, is the most used control for a dual-star induction motor. However, these techniques suffer from steady-state errors and torque ripples. Therefore, the stator phase currents have a non-sinusoidal waveform, which leads to high losses and reduces the drive efficiency of the system caused by considerable harmonic currents. This paper presents a modified direct torque control (MDTC) based on two steps to select the appropriate vector to supply the dual star induction motor (DSIM) and effectively reduce the harmonic currents. Moreover, this paper deals with a comparative study of 3-level, 5-level, and modified 5-level torque regulators to reduce the steady-state error and torque ripple. In addition, a PI controller is incorporated for the modified five-level torque regulator to reduce the torque error at low, medium, and high speeds. Moreover, an investigation of switching and core losses has been done for the DSIM drive. Finally, validation results have been presented to prove the effectiveness of developed direct torque control of the dual star induction motor (DSIM) under different operating conditions.

The influence of particle oxidation catalyst (POC) mode on emissions reduction of a turbo-charging non-road diesel under wide operating conditions

In the present study, the influence of particle oxidation catalyst (POC) on emissions reduction of a non-road diesel engine is experimentally investigated under wide operating conditions. First, the diesel engine with four POC-aftertreatments (other reactors are kept unchanged) is tested under eight operating conditions non-road steady cycle (NRSC). Then, the diesel engine emissions with best POC-aftertreatment combination and without aftertreatment are comparatively tested under universal conditions. The experiments show that under NRSC, POC-3 which has Pt catalysts with Al2O3 support, asymmetrical channels layout and closed outlet form structure has the best overall exhaust purification, especially for nitrogen oxides (NOx) and particulate matter (PM). The PM conversions efficiency of POC-1, POC-2, POC-3 and POC-4 is 15.3%, 51.7%, 60.9% and 58.8%, respectively under NRSC. The contribution rates of emissions analysis results under NRSC indicated that a single POC mode cannot cover the whole engine operating range. Under universal characteristic test, the brake specific fuel consumption (BSFC) of original engine is a little lower than that of POC-3 in the whole engine operating conditions due to higher exhaust back pressure of POC-3. The engine with POC-3 has very good exhaust conversion efficiencies, the average conversion efficiency of NOx, PM, carbon monoxide (CO), and hydrocarbons (HC) is 96.1%, 51.9%, 77.8%, and 95.6%, respectively. The PM capture efficiency of POC-3 at low load of whole speed range and all load of medium speed are more than 50% compared to other operating conditions. There is little effect on carbon dioxide (CO2) emissions by POC.

Effects of Methanol–Ammonia Blending Ratio on Performance and Emission Characteristics of a Compression Ignition Engine

Sustainable ammonia is one of the leading candidates in the search for alternative clean fuels for marine applications. This paper aims to build a simulation model of a six-cylinder, four-stroke diesel engine to investigate the effects of increasing the ammonia proportion in methanol–ammonia fuel blends on engine performance and emissions. In the present study, the conditions of different speeds and different proportions of ammonia in fuel blends are investigated. The results show that the average effective pressure, brake power, and brake torque increase by about 5% with an increased ammonia substitution ratio. In terms of economic performance, the changes under medium and low speed conditions are not obvious. However, the change in high speed conditions is significant. The brake specific fuel consumption (BSFC) is reduced by 6.6%, and the brake thermal efficiency (BTE) is increased by 4%. It is found that the performance of the engine is best at medium speed. The best performance is achieved with higher efficiency and lower emissions. The present results can provide guidance for the optimization of ammonia–methanol blends and their applications in engines.

Field-Measurement of Surface Wind and Sediment Transport Patterns in a Coastal Dune Environment, Case Study of Cala Tirant (Menorca, Spain)

Blowouts are integral features of coastal dune fields. Their presence enhances both geomorphological and ecological diversity and enables the movement of sand by wind. Their role as a ‘transport corridor’ may be, however, considered negative from a coastal management perspective in heavily touristic areas, where the existence of blowouts close to the foredune can enhance the loss of sediment from the beach. This paper investigated the relationship between airflow dynamics and patterns of sediment transport from the beach to established dunes through a trough blowout located on the foredune. Seven three-cup anemometers were used to measure wind speed and direction over a 24 h sampling period at a frequency of 1 min under onshore (parallel to the blowout axis) medium and high wind speeds (max of 17.9 ms−1). To measure sediment transport, a total of 12 vertical sand traps were located at three positions along the length of the deflation basin. The results indicated that small amounts of sediments went into the blowout from the beach and that the highest rates of sediment remobilization took place within the deflation basin. These results highlight two processes: (a) flow channelization induced by the blowout topography caused an increase in wind speed and sediment transport toward the depositional lobe, and (b) the presence of embryo dunes and herbaceous vegetation at the beach–blowout boundary effectively reduced the amount of sediment transport from the beach to the landform. The results confirmed the significant role that vegetation plays in controlling sediment movement and conserving the beach–dune system.

Feasibility Study of Exhaust Energy Recovery System for Mobile Carbon Capture Operations in Commercial Engines through 1D Simulation

The global proportion of eco-friendly vehicles continues to increase; however, regarding hybrid vehicles, the vehicle powertrains in most countries include internal combustion engines. Therefore, research on reducing the carbon emissions from internal combustion engines must be conducted. Carbon capture technology must be developed for e-fuel, which has recently attracted attention, to achieve carbon neutrality. In this study, a turbo compound system capable of recovering waste exhaust gas energy was selected as the most appropriate energy supply system to operate a mobile carbon capture system. The feasibility was reviewed by analyzing the turbo compound speed, pressure drop, power generation, etc., using a one-dimensional simulation method. The maximum power generation of the configured turbo compound system was approximately 9 kW, and approximately 1–3 kW of energy could be recovered under medium speed and load conditions, which are the optimal operating conditions for a test engine with the displacement of a 4 L.

Experimental and numerical analysis study on the low and medium speed bird strike

The bird impact process of civil aircraft mostly occurs in the takeoff and landing phases. The movement speed of the aircraft in these phases belong to the category of low and medium speed, and the bird will not disintegrate in this velocity range. The speed and direction of the bird after impacting with the air intake directly affects the damage to the aero-engine. According to the preliminary experimental data, we developed a bird strike trajectory prediction model based on the quasi-linear viscoelastic model. This model reproduced the trajectory change law in the low and medium speed bird impact experiment combining with the simulation analysis under multiple conditions. We designed a simulated air intake model for the real air intake structure characteristics, and processed the simulated air intake parts based on this model. The accuracy of the model was further verified by comparing the simulated and experimental bird impact trajectories, and a predictive modeling method was obtained for the simulation of low and medium speed bird impact trajectories.

РАСЧЁТ КОМБИНИРОВАННОЙ КОНСТРУКЦИИ ЖИДКОСТНОКОЛЬЦЕВОГО ВАКУУМНОГО НАСОСА

Liquid ring vacuum pumps are widely used in many areas of the agro-industrial complex, in particular for milking processes, storage of plant materials, their drying and extraction, as well as pneumatic transport. It has been revealed that one of the main disadvantages of liquid ring vacuum pumps - low efficiency (25-50%) is often caused by hydraulic losses during rotation of the liquid ring on a stationary body, as well as inaccurate physical prerequisites in the equations describing the movement of the liquid ring - a two-phase turbulent flow in the working pump cavity. As a consequence, the pump engineering calculation method leads to overestimated performance characteristics at the design stage. In this regard, a combined design of a liquid ring vacuum pump with a rotating casing has been proposed, in which rotation can be transmitted from the impeller blades to the casing blades (in the case of low and medium speed pump size), through involute engagement, or from the casing blades to the impeller blades (in in case of high and especially high speed of action). The basis for calculating the liquid ring is the continuity equation, the stability condition of the liquid ring and the threshold for the occurrence of cavitation phenomena, as well as a coefficient characterizing the drop in speed for turbulent motion in a bladeless space in areas (suction, maximum, compression, discharge). In this case, the mechanism of movement of the liquid ring in the working cavity of the pump is represented by physical processes in the form of the interaction of two power flows: the hydraulic flow of the working fluid and the thermodynamic flow of the gaseous medium. When calculating the main operating parameter of the pump - the actual speed of action - the evaporation of liquid droplets due to changes in the temperature of the liquid ring was taken into account. The forces acting on the rotating wheel and the rotating body of the combined design of a liquid ring vacuum pump are determined analytically.

Protection method of traction power supply system for low and medium speed Maglev traffic based on fault traveling wave features

AbstractLow and medium speed magnetic levitation traffic with short power supply distance and complex grounding network structure, prone to power supply rail grounding faults. However, the existing fault location methods do not accurately locate the fault point, making it difficult for the protective device to act to cut off the fault. To address the above problems, this paper builds a dynamic simulation model of the low and medium speed magnetic levitation power supply rails to study the distribution characteristics of the fault traveling waves after a ground fault occurs in the power supply rails, and analyses the generation mechanism of the traveling wave spectrum through formula calculation. First, the difference in current between the positive and negative bus bars is analyzed to determine whether a ground fault has occurred. Second, the direction of the current difference between stations is compared to locate the faulty section. Finally, the fault distance is calculated from the frequency difference of the fault voltage at the double‐ended station. Through simulation, the method is validated to be unaffected by fault location, fault transition resistance, noise interference, and is applicable to short circuit faults caused by lightning strikes, and the ranging error always remains within 20 m. The method has strong robustness, can effectively solve the problem of protection misoperation and accurately locate the fault point. It is suitable for low and medium speed magnetic levitation transportation power supply rail ground fault.

Determination of the Effect of Epigallocatechin Gallate on Oxidative Stress, Apoptosis and Sperm Quality in Rabbit Semen

Objectives;In this study, it was aimed to determine the effect of Epigallocatechin gallate (EGCG) on the cryopreservation of rabbit semen. 
 Material and metod; For this purpose, semen was collected from six male New Zealand rabbits. Collected semen were divided into 5 groups as control, 25 µM, 50 µM, 100 µM and 200 µM. Semen samples were reconstituted and frozen after adding EGCG. Frozen straws were then thawed. 
 Results; After freezing and thawing, total motility, progressive motility, and rate of fast and medium speed sperm were significantly higher in the 50 µM group than in the other groups. Static sperm ratio was found to be lower in the 50 µM group than in the other groups. When the flow cytometry results were examined, there was no statistical difference between the groups in terms of the ratio of dead and live sperm. However, the rate of dead sperm with acrosome damage was found to be the lowest in the 50 µM group. High mitochondrial membrane potential sperm ratio was found higher in 50 µM and 100 µM groups compared to other groups (p

Research on the cushioning and energy absorption characteristics of gradient sinusoidal negative Poisson’s ratio honeycomb structures

In this study, we designed improved cellular materials (CMs) with good energy absorption capacities, proposing new types of CMs with negative Poisson ratios by introducing sinusoidal cell walls and three different gradients. The amplitude of the sinusoidal wall, cell periodicity, and cell wall thickness were modulated in three layers across the structure (denoted as AG-CM, PG-CM, and WTG-CM, respectively). The influence of the different gradient parameters on the dynamic response of the CMs was analysed. The finite element method was used to explicitly simulate the deformation behaviour, dynamic shock stress, and energy absorption characteristics of the proposed structures at different impact speeds and directions. The initial peak stress in the face of the impact of the CM with a reasonable gradient setting was lower than that of the non-gradient CM. In contrast, its energy absorption was higher than that of the non-gradient CM. WTG-CM exhibited the highest energy absorption for a low-speed impact (7 m/s). For a medium and high speed impacts (35 m/s and 70 m/s), AG-CM exhibited the highest energy absorption in the face of positive gradient impact, whereas WTG-CM exhibited the highest energy-absorbing energy when impacting against the gradient. Under similar impact rates, the energy absorption energy of the different CMs varied by 32.1%. For the same CM, the maximum difference in absorption energy between shock modes was 33.8%.

On the suitability of medium speed maglev transport systems: an analysis of perceptions in the transportation sector

Background: Medium speed maglev transport systems are considered a disruptive innovation. This complicates potential access to the transport market, which is dominated by conventional, traditional transport systems. Can maglev systems compete with them?
 Aim: Aimed specifically at transport professionals, the survey analyses current [2023] perceptions of maglev systems for passenger and freight transport. Are medium speed maglev systems suitable for the future of transport from the perspective of transport experts?
 Methods: International web survey of five hundred professionals in the transport sector. The focus is on application and suitability. It is not a technical comparison of systems.
 Results: Medium-speed maglev systems are considered to be competitive, and in some cases superior, to established transport systems in the same speed range. However, most international experts see the suitability of maglev systems primarily for specific applications, such as passenger transport between airports and city centers, or as a freight transport system for special logistics tasks.
 Conclusion: An innovation of maglev systems in well-defined applications seems reasonable and promising from an expert's point of view.

In-plane dynamic crushing of a novel arc-shaped reentrant structure

This study proposes a novel structure through bionic design, exhibiting a negative Poisson’s ratio, high stability, and energy absorption properties. The structural responses of both the conventional and novel honeycombs under dynamic impacts are obtained through simulation, characterizing their deformation modes and mechanical properties. The results show that the novel structure exhibits almost no localized densification, significantly reduced stress fluctuation, and a notable reduction in peak stress, differing significantly from the conventional structure. Furthermore, considering the NPR effect at medium and high speeds, the platform stress solution is derived, confirming the high stability of the novel honeycomb structure.

Friction and wear properties of a novel interface of ordered microporous Ni-based coating combined with MoS2 under complex working conditions

For realizing the function of friction reduction and wear resistance in one, this paper proposes a new type interface structure of ordered microporous Ni-based coating composite MoS2. When the micropore density is 19.63%, the new interface structure obtains the optimum tribological performance, and compared to matrix and traditional Ni based coating, the friction coefficient and wear rate of new structure can be reduced by more than 20% and 65% respectively. The cooperative interaction between the formed lubrication layer rich in MoS2 and hard Ni-based coating is the most important reason for imporving the friction reduction and wear resistance. The new friction interface can obtain stable and prominent tribological properties at wide load and low to medium speed.

Mechanical Properties of Composite Track Beam for Medium and Low Speed Maglev Transit

Traditional medium-low speed Maglev track separated beam structures have drawbacks such as large structural height and neglect of F-type rail stiffness. This study proposes a new integrated track beam for medium-low speed maglev transportation. Finite element analysis is employed to compare the strength, stiffness, and natural frequencies of the integrated track beam with the existing separated track beam. The influence of beam height on the overall mechanical performance of the integrated track beam is analyzed. The ultimate bearing capacity of the steel-concrete composite joint in the integrated track beam is investigated through full-scale model testing. The results demonstrate that the proposed integrated track beam exhibits a 28% increase in flexural stiffness. The mid-span deflection is reduced by 19.9% under static and live loads. The first-order vertical natural frequency increases by 13.6%. The main factor governing the minimum beam height of the integrated track beam is the deflection limit under static and live loads. The beam height can be optimized from 2.1 m to 1.6 m. The model testing reveals that the F-type rail is controlled by torsional stiffness and can withstand 1.3 times the design load. The ultimate bearing capacity of the steel-concrete composite joint is 4.5 times the design load, providing sufficient load reserves.

Numerical Analysis of Dual Fuel Combustion in a Medium Speed Marine Engine Supplied with Methane/Hydrogen Blends

Compression ignition engines will still be predominant in the naval sector: their high efficiency, high torque, and heavy weight perfectly suit the demands and architecture of ships. Nevertheless, recent emission legislations impose limitations to the pollutant emissions levels in this sector as well. In addition to post-treatment systems, it is necessary to reduce some pollutant species, and, therefore, the study of combustion strategies and new fuels can represent valid paths for limiting environmental harmful emissions such as CO2. The use of methane in dual fuel mode has already been implemented on existent vessels, but the progressive decarbonization will lead to the utilization of carbon-neutral or carbon-free fuels such as, in the last case, hydrogen. Thanks to its high reactivity nature, it can be helpful in the reduction of exhaust CH4. On the contrary, together with the high temperatures achieved by its oxidation, hydrogen could cause uncontrolled ignition of the premixed charge and high emissions of NOx. As a matter of fact, a source of ignition is still necessary to have better control on the whole combustion development. To this end, an optimal and specific injection strategy can help to overcome all the before-mentioned issues. In this study, three-dimensional numerical simulations have been performed with the ANSYS Forte® software (version 19.2) in an 8.8 L dual fuel engine cylinder supplied with methane, hydrogen, or hydrogen–methane blends with reference to experimental tests from the literature. A new kinetic mechanism has been used for the description of diesel fuel surrogate oxidation with a set of reactions specifically addressed for the low temperatures together with the GRIMECH 3.0 for CH4 and H2. This kinetics scheme allowed for the adequate reproduction of the ignition timing for the various mixtures used. Preliminary calculations with a one-dimensional commercial code were performed to retrieve the initial conditions of CFD calculations in the cylinder. The used approach demonstrated to be quite a reliable tool to predict the performance of a marine engine working under dual fuel mode with hydrogen-based blends at medium load. As a result, the system modelling shows that using hydrogen as fuel in the engine can achieve the same performance as diesel/natural gas, but when hydrogen totally replaces methane, CO2 is decreased up to 54% at the expense of the increase of about 76% of NOx emissions.

Improved self‐balancing voltage five‐level ANPC converter and its control strategy

SummaryFive‐level active neutral‐point‐clamped (5L‐ANPC) converters have great practical potential in the field of medium and high voltage variable frequency speed regulation. However, the dynamic and static voltage imbalance of the series IGBTs may cause permanent damage to the device, which limits its popularization and application. In this paper, an improved self‐balancing voltage 5L‐ANPC topology (ISBV‐5L‐ANPC) is proposed to address such voltage balancing problem as series switches and high voltage leaps, which realizes dynamic and static voltage equalization by connecting the self‐balancing module consisting of an auxiliary capacitor to the bridge arm, so that it clamps the series switches. In this paper, the operation principle of ISBV‐5L‐ANPC is given in detail, and the control strategy of ISBV‐5L‐ANPC is proposed, and the key parameters in the topology are analyzed and designed. Finally, an ISBV‐5L‐ANPC prototype was built, and the effectiveness of the proposed topology and the feasibility of the control strategy are verified through the experimental results.

DETERMINATION OF PAPER LUMEN UNIFORMITY DIFFERENT CLASSES

In this paper, a study was made of the uniformity of the clearance of office papers of various classes and
 brands. The need for a detailed study of the structure of office paper is caused by a large number of defects that occur
 during the printing process. To obtain high-quality images at high and medium speeds of equipment and at minimal
 cost, it is necessary to know the structural properties of paper and be able to control them.
 Evaluation, study and characterization of the factors that are believed to influence the interaction between
 inkjet ink and the surface of office paper can be performed using the method of expert judgment. The article describes
 an expert method for determining the gap, based on the organoleptic perception of the paper gap by a group of people.
 In the process of work, paper samples with the best lumen performance were identified. The results obtained in
 the work can be applied in the practice of printing houses for the correct choice of material for printing. This method
 of assessing the level of paper quality allows the company to quickly respond to problems associated with printing and
 further processing of printed products.

Experimental and Simulation Research on the Vibration Characteristics of the Traction Motor of Medium and Low Speed Maglev Train under Electromagnetic Excitation

In a medium and low speed maglev train, the linear induction motor (LIM) is employed as the traction motor, during operation its vibration characteristics correlate with the dynamic performance and noise radiation characteristics of the train. This paper conducted tests and established a three-dimensional simulation model of the LIM in a medium and low speed maglev train, to study the motor vibration characteristics by comparative analysis between test and simulation. The analysis results showed that the electromagnetic excitation sources of the train appear in the high-frequency band, with the main characteristic frequencies of 497.33 Hz, 994.33 Hz, 1989.00 Hz, and 3977.67 Hz. The structural modal analysis and vibration harmonic response analysis of the motor showed that the 3rd, 8th, and 18th modal frequencies of the motor structure approximate the frequencies of the electromagnetic excitation sources. As a result, the motor generates resonance at 497.33 Hz and 994.33 Hz under that excitation. The validity of the simulation was confirmed by the corresponding tests. From the perspective of theory, experiment, and simulation, this research can contribute to the optimization of traction systems in the future design of medium and low speed maglev trains.