Forward Resistance Research Articles

DEM parameters of slope cultivated purple soil in Southwest China and interaction mechanism between very narrow tine

The establishment of discrete element method (DEM) model for simulating the behavior of viscous soil can significantly contribute to the development of agricultural machinery, particularly in hilly areas worldwide. There is limited research on the parameter calibration of the DEM for purple soil in the Southwest China and its interaction mechanism between very narrow tine. Piling up test, rotating drum test and design-expert 12.0 software were used to design Plackett–Burman test, steepest climb test and Box–Behnken test successively. Combined with soil intrinsic parameter measurement test, soil simulation parameter calibration and optimization were completed. Based on the optimized DEM simulation parameters, the average relative errors of static repose angle and dynamic repose angle were 1.934 and 2.289%, respectively. The accuracy of parameter calibration results of DEM simulation was proved. Three kinds of very narrow tines were designed and processed. The interaction model and mechanism between soil-touch parts and soil was established. The average relative errors between the DEM simulation results of the forward resistance and disturbance area of the three soil-touch parts and the soil bin test results were 7.22% and 11.24%, respectively, which further proved that the calibration results of DEM parameters of purple soil and the interaction model with the soil-touch parts in this study were reliable. The physical and interaction parameters of slope cultivated purple soil in Southwest China were determined based on static-dynamic repose angle, providing more accurate parameters for study of soil-touch parts.

Optimization of Operation Parameters and Performance Prediction of Paddy Field Grader Based on a GA-BP Neural Network

Paddy field leveling is an essential step before rice transplanting. During the operation of a paddy field grader, a common issue is the wrapping of rice straw around the blades, resulting in a low rice straw burial rate. This study focused on analyzing the operating parameters of a disc spring–tooth-combined paddy field grader. A soil–straw mechanism simulation model was created using EDEM 2021 software to simulate the field operation status. Firstly, the single-factor test was carried out, with the working speed, the working depth of the disc cutter roller, and the rotation speed of the cutter roller as the factors and the straw-buried rate (SBR) and the machine forward resistance (MFR) as the test indexes, and the parameter range was optimized. The parameters were optimized by the response surface method (RSM) and machine learning algorithms. The results indicated that the genetic algorithm–back propagation (GA-BP) neural network outperformed other optimization models in terms of prediction accuracy and stability. By utilizing the GA-BP regression model and RSM model for regression fitting, two sets of optimal parameter combinations were obtained. Verification experiments were carried out using two sets of parameter combinations. Taking the average of the experimental results, the simulation results showed that the straw burial rate was 93.47% and the forward resistance was 6487 N for the parameter combinations of RSM, and the straw burial rate was 94.86% and the forward resistance was 6352 N for the parameter combinations of GA-BP; the field experiments showed that the straw burial rate was 92.86% and the forward resistance was 6518 N for the parameter combinations of RSM, and the straw burial rate was 95.17% and the forward resistance was 6249 N for the parameter combinations of GA-BP. The results demonstrated that the GA-BP prediction model exhibited better predictive capabilities compared to the traditional RSM, providing more accurate predictions of the paddy field grader’s field operation performance.

Development of novel thermal diode inspired by the structure of venous valve

To increase the unidirectional heat transfer capability of a thermal diode, a novel thermal diode with unidirectional movable valves as vapor channel is proposed based on the structure of venous valves. The thermal performance of this bionic thermal diode was experimentally investigated under different working conditions. The results demonstrate that the bionic thermal diode exhibits a high thermal rectification ratio and strong stability. The best thermal rectification ratio is 10.79, with a forward thermal resistance of 0.26 °C/W and a reverse thermal resistance of 2.86 °C/W, at a heating power of 15 W and a filling ratio of 15 %. The temperature distribution indicated that, under the reverse heat transfer mode, the vapor was obstructed at the first valve, leading to the high thermal resistance of thermal diode. Additionally, the effect of inclined angle on the thermal performance of thermal diode was also investigated. This study provides a novel approach for the design of thermal diodes.

Exploring Resistance Reduction of Subsoiling Through Sandfish (Scincus scincus) Inspired Sinusoidal Locomotion

Highlights Biomimetic design, inspired by sandfish locomotion, decreased subsoiling resistance. Penetration tests and simulations showed bioinspired tines outperforming traditional ones in resistance reduction. DEM-MBD co-simulation effectively modeled the sandfish's movement, revealing the mechanisms of soil interactions. Simulations confirmed that sinusoidal subsoiler movement significantly reduced soil resistance. Abstract. This study addresses the issue of high resistance and low efficiency in subsoiling operations by employing a novel method inspired by the unique locomotion of the sandfish (scincus scincus), aimed at reducing forward resistance. The unparalleled adaptability of the sandfish in navigating granular media, such as desert sand, offers valuable insights for enhancing agricultural machinery. This research employs sandfish’s movement principles to propose innovative strategies for improving subsoiling efficiency. A sandfish inspired prototype, created through reverse engineering, served as the basis for the analysis. The models of both traditional (T-S) and bioinspired (B-S) subsoiler tines for comparative assessment were developed. The EDEM simulation model’s performance was calibrated using soil penetration tests and integrated with multibody dynamics (MBD) to analyze the sandfish’s variable locomotion in sandy soil. The impact of linear and sinusoidal locomotion at velocities of 0.8 m/s, 1.0 m/s, and 1.2 m/s on resistance and soil disturbance were investigated and contrasted. The congruence between measured and simulated resistance-depth curves for T-S and B-S models was desirable, with maximum resistance errors of 2.54% and 2.47%, respectively, confirming the simulation model’s accuracy in predicting mechanical interactions. A comparison of characteristic angles validated the close correlation between simulated and actual sandfish locomotion in soil. Stress analysis during soil locomotion of the sandfish head indicated a 25.1% reduction in resistance with sinusoidal motion compared to linear motion. At the specified velocities, sinusoidal locomotion of the subsoiler tine showed resistance reductions of 6.75%, 7.39%, and 9.40%, respectively, relative to linear locomotion. The mechanism of resistance reduction in sinusoidal locomotion was further verified through soil compression force analysis, supporting the adoption of sandfish-inspired sinusoidal behavior as an innovative approach to enhance efficiency in agricultural practices. Keywords: Bioinspired design, DEM-MBD simulation, Sandfish (Scincus scincus), Sinusoidal locomotion, Subsoiling.

Producing electricity on board a ship in motion or stationary using photovoltaic panels

A very important pillar for the world economy is the transport sector. Nowadays, about 80% of freight transport has been done by sea. Besides the recognized economic efficiency, ships are, unfortunately, an important sources of marine environment pollution. It is well known that the IMO is permanently concerned in maritime safety and many measures have been shown to be successful in reducing ship-sourced pollution. But it is not enough, new solutions must be found, and the answer can come from the direction of green energies (electricity produced from renewable sources). On board ships can be used as renewable energy sources wind energy or solar energy. Solar energy is easier to use because photovoltaic panels can be mounted on board the ship to produce electricity (however, provided that the photovoltaic panels do not increase the ship's forward resistance or reduce its manoeuvrability). Studies have shown that offshore wind energy is much more efficient than a ship-mounted wind turbine because an on-board wind turbine greatly reduces a ship's speed and manoeuvrability. The authors of the paper proposed to study the production of electrical energy obtained with the help of photovoltaic panels on board a ship in motion and stationary. The ship marched in the Mediterranean Sea for two months.

Optimization and test of ginger-shaking and harvesting device based on EDEM software

Considering the challenges posed by the elevated excavation resistance and substantial soil content of ginger blocks, a specialized digging and harvesting device was designed. The device primarily consists of a digging shovel, shaking fence, hydraulic cylinder, lifting arm and other devices. The mechanical characteristics of the digging device and the mechanism of soil crushing were analysed, and the key factors affecting excavation resistance and soil crushing were determined as follows: forward speed Vm, shaking soil frequency f, shovel surface tilt angle ɑ, shaking fence tilt angle β. To determine the influence rules of key factors on excavation resistance and soil flow, a ginger virtual simulation model of EDEM was constructed. Through the utilization of a target optimization method, an improved parameter combination for evaluating the performance of the ginger harvest operation was established. The optimized parameters were as follows: forward speed of 0.35 m/s, shaking soil frequency of 4.0 Hz, shaking fence inclination at 26.0°, and digging shovel inclination at 9.0°. The field test results show that the ginger harvest effect was good, the ginger block contained fewer impurities such as soil, the harvester operation was stable, and there was no congestion and rollover phenomenon. The forward resistance of the excavation harvesting device was found to be 1368.8 N, the soil content was 4.6 %, and the relative error with the expected result was 7.30 %, thereby meeting the requirements of ginger harvesting and the use requirements of users.

Design and research of a valve-based piezoelectric pump with low forward resistance and high reverse shutoff

This paper proposes, designs, manufactures and experimentally studies a wedge valve piezoelectric pump driven by a double displacement amplifier vibrator (DDAV). A novel wedge valve is designed, manufactured and analyzed, and the static performance of the wedge valve is tested. The test results show that it has less forward resistance and high reverse shutoff. The DDAV and pump body are designed, and the test experimental platform is built. Results indicate that the static opening pressure of the wedge valve is 0.27 kPa, and the reverse shutoff pressure can reach 200 kPa. When the driving voltage is 700 Vpp and the driving frequency is 425 Hz, the maximum flow rate is 491.2 ml min−1 and the maximum output pressure is 160 kPa.

An Anonymous Authentication Scheme Based on Chinese Residue Theorem in Wireless Body Area Networks

Considering the resource limitations of low-cost wireless sensors, there is a growing inclination to utilize cryptographic primitives that are optimized for efficiency, such as symmetric key encryption/decryption and hash functions, when designing authentication schemes. However, designing a lightweight authentication scheme that can meet various security requirements poses a significant challenge. In recent years, numerous lightweight authentication schemes have been proposed in order to address these security needs. Nevertheless, recent research has revealed that many of these schemes exhibit security vulnerabilities and design deficiencies, including challenges related to asynchronization and impractical gateway-node search operations. Due to the inadequate security of existing schemes, this study introduces a novel privacy-preserving authentication scheme that aims to provide adaptive resilience against desynchronization attacks in wireless body area networks (WBANs). The proposed scheme utilizes lightweight cryptographic modules to optimize efficiency. To ensure user anonymity, the Chinese Remainder Theorem technique is employed, whereas forward secrecy and resistance to desynchronization attacks are achieved through the use of one-way hash chains and serial numbers, respectively. Through extensive analysis and comparisons, the proposed scheme is demonstrated to strike a fine balance between security and efficiency.

Low-frequency noise in Au-decorated graphene–Si Schottky barrier diode at selected ambient gases

We report results of the current–voltage characteristics and low-frequency noise in Au nanoparticle (AuNP)-decorated graphene–Si Schottky barrier diodes. Measurements were conducted in ambient air with addition of either of two organic vapors, tetrahydrofuran [(CH2)4O; THF] and chloroform (CHCl3), as also during yellow light illumination (592 nm), close to the measured particle plasmon polariton frequency of the Au nanoparticle layer. We observed a shift of the DC characteristics at forward voltages (forward resistance region) when tetrahydrofuran vapor was admitted (in a Au-decorated graphene–Si Schottky diode), and a tiny shift under yellow irradiation when chloroform was added (in not decorated graphene–Si Schottky diode). Significantly larger difference in the low-frequency noise was observed for the two gases during yellow light irradiation, compared with no illumination. The noise intensity was suppressed by AuNPs when compared with noise in graphene–Si Schottky diode without an AuNP layer. We conclude that flicker noise generated in the investigated Au-decorated Schottky diodes can be utilized for gas detection.

Design and thermal performance of thermal diode based on the asymmetric flow resistance in vapor channel

To reduce the cost of the thermal diodes and increase its unidirectional heat transfer reliability, a thermal diode with tesla valve structure is proposed and its thermal performance is experimentally investigated. The relation between the structure parameters (including branch angleα, channel depth d, number of unit n and number of channel N) and the fluid flow performance of tesla vapor channel is studied by numerical simulation. According to the simulation results, the parameters of α = 30°, d = 1.5 mm, n = 16 and N = 4 were chosen for the vapor channel in thermal diode. Experimental results show that the reverse thermal resistance is larger than the forward thermal resistance under the wide range of working conditions, indicating the good unidirectional heat transport capacity of the proposed thermal diode. The maximum ratio of reverse thermal resistance to forward thermal resistance K reaches around 3.02 under the filling ratio of 24% and the heating power of 7 W.

7-N-Substituted-3-oxadiazole Quinolones with Potent Antimalarial Activity Target the Cytochrome bc1 Complex.

The development of new antimalarials is required because of the threat of resistance to current antimalarial therapies. To discover new antimalarial chemotypes, we screened the Janssen Jumpstarter library against the P. falciparum asexual parasite and identified the 7-N-substituted-3-oxadiazole quinolone hit class. We established the structure-activity relationship and optimized the antimalarial potency. The optimized analog WJM228 (17) showed robust metabolic stability in vitro, although the aqueous solubility was limited. Forward genetic resistance studies uncovered that WJM228 targets the Qo site of cytochrome b (cyt b), an important component of the mitochondrial electron transport chain (ETC) that is essential for pyrimidine biosynthesis and an established antimalarial target. Profiling against drug-resistant parasites confirmed that WJM228 confers resistance to the Qo site but not Qi site mutations, and in a biosensor assay, it was shown to impact the ETC via inhibition of cyt b. Consistent with other cyt b targeted antimalarials, WJM228 prevented pre-erythrocytic parasite and male gamete development and reduced asexual parasitemia in a P. berghei mouse model of malaria. Correcting the limited aqueous solubility and the high susceptibility to cyt b Qo site resistant parasites found in the clinic will be major obstacles in the future development of the 3-oxadiazole quinolone antimalarial class.

Thickness Study of Ga2O3 Barrier Layer in p-Si/n-MgZnO:Er/Ga2O3/ZnO:In Diode

The p-Si/n-MgZnO:Er/Ga2O3/ZnO:In diodes with different Ga2O3 thicknesses were fabricated through spray pyrolysis deposition at 450 °C with aqueous solutions containing magnesium nitrate, zinc acetate, erbium acetate, gallium nitrate, and indium nitrate precursors. The effects of Ga2O3 layer thickness on the diode properties were investigated. For the deposited films, a combined tiny hexagonal slices and small blocks surface morphology was characterized by scanning electron microscopy for all samples. Diodes were formed after In and Ag deposition on the back side and top side, respectively. The current-voltage characteristics and luminescence spectra are studied. With the increasing of Ga2O3 thickness, the diode forward bias resistance increases while the reverse biased dark current shows the decrease-increase characters. The Er ion corresponded green light emission was characterized for the diode under reverse biased breakdown condition. The increased luminescent intensity with low turn-on current behaviors was characterized by the diode with a Ga2O3 thickness of 4.9 nm. With the diode electrical and luminescence analysis, the effect of the Ga2O3 barrier layer on the diode was discussed. The Ga2O3 barrier layer improves performance for rare earth-related light-emitting devices.

A new validated open-source numerical tool for the evaluation of the performance of wind-assisted ship propulsion systems

Wind propulsion is envisioned as one of the solutions for the decarbonisation of maritime transport, as it offers high efficiency in terms of primary energy comsumption. Many wind propulsion systems already exist at various development stages, but the uncertainties over their performance is a strong obstacle to their adoption by ship owners. This paper presents a general method for the assessment of steady and unsteady performances of wind- propelled ships with 6 degrees of freedom, as implemented in the open-source program xWASP_CN. Inspired by system-based modelling, the method consists in the independent modelling of the forces acting on the ship, as functions of the ship’s 6 degrees of freedom and environmental conditions. An original root-finding algorithm that leverages the specifics of the physical problem to find the steady equilibrium is presented. The method works either like a Power Prediction Program (PPP) or like a Velocity Prediction Program (VPP). As a PPP, the forward speed and course are fixed while the required propulsive power, leeway angle, heel, trim and sinkage are solved. As a VPP, only the course is fixed and the attained forward speed, leeway angle, heel, trim and sinkage are solved. This makes the method suitable for both hybrid propulsion and pure wind propulsion. The force models can be semi-empirical (usually requiring very little input data), based on preliminary experimental or numerical results (such as forward resistance curves, lift/drag coefficients and frequency-domain sea-keeping coefficients), or full-fledged flow solvers (e.g. potential theory, CFD). Thus the method is suitable for all design stages as each force can be modelled with several levels of accuracy depending on the input data available. Comparisons of an intermediate-level model with experiments on a 18-ft catamaran fitted with a Flettner rotor and a water turbine show good agreement for steady-state results.

Software-defined network aided lightweight group key management for resource-constrained Internet of Things devices

Software-Defined Network (SDN) and Network Function Virtualization (NFV) are key enablers for provisioning dynamic, virtual security services on demand. This article, presents a novel Group Key Management scheme for Low-Resource Devices (GKM-LRD) with SDN aided trusted key management server as a central server to provide key management service to groups formed in Internet of Things (IoT) applications. In addition to the group key management scheme, a lightweight packet key-based communication system is proposed to make the data traffic reliable. Packet keys are short sized keys acquiring the lifetime of a packet. Even though the key is short sized, the security strength comes from its short lifetime. The proposed GKM-LRD is evaluated in terms of computation load, communication load, storage and scalability in comparison with the existing group key management schemes. The computation load, communication load and storage load is reduced by 80%, 17.25% and 20% respectively in comparison with the existing system assuring the scheme as lightweight and applicable for IoT devices. The proposed packet key-based communication scheme is compared with an existing Diffie-Hellman based packet key system. The results show the system is comparatively lightweight with computation load reduced by 74.8%. The security analysis of the proposed scheme proves that the scheme ensures forward secrecy, backward secrecy and resistance to man-in-the-middle and replay attacks.

Optimization Design and Simulation Experiment of a Press Roller Based on a Lemniscate-Shaped Curve in Rice–Wheat Rotation Region of China

In order to solve the problems of high forward-resistance and serious soil adhesion in a rice–wheat rotation area, the smooth press roller of a wheat planter in a rice–wheat rotation area was selected as the research object. The low resistance and the adhesion structure of the press roller on a lemniscate-shaped curve were considered, and the geometric design method was adopted to modify the geometric structure of the smooth press roller. A simulation model of the roller–soil interaction was designed using the EDEM2020 software (DEM Solutions Ltd., Edinburgh, Scotland, UK), to investigate the behavior of soil adhering to the surface of the press roller, as well as the effects of the structure and the working parameters on soil adhesion and forward resistance. In addition, the numerical simulation method was combined with the central-plane composite response test scheme to perform the simulation test, using Design-Expert 10.0.4 software (Stat-Ease Inc., Minneapolis, MN, USA). In this test, the forward speed, the axial spacing, and the bulge height were taken as the test factors. On this basis, the working performance of the lemniscate curve type of the press roller was evaluated by establishing a response surface for soil adhesion and forward resistance. With the reduction in soil adhesion and the working resistance as constraints, the optimization was carried out under the condition of a forward speed of 7 km/h. Under a forward speed of 7 km/h, an axial spacing of 40.7–46.8 mm, and a bulge height of 9.3–11.5 mm, the soil adhesion was less than 70 g and the forward resistance was less than 50 N, meaning that the working performance of the lemniscate curve type of the press roller meets the requirements for actual production. In short, this research provides a new idea and reference for the application of a press roller in a rice–wheat rotation area.

Development of an improved and versatile 2D+t modelling methodology for planing crafts

The availability of accurate numerical tools for predicting the energy consumption of recreational crafts is pivotal in view of reducing the environmental impact on local waters. A computationally efficient digital twin capable of accurately predicting the boat resistance is thus required to account for the energy fluxes.In the study, an improved 3-DOF (Degree-of-freedom) 2D + t approach, aimed at predicting the forward resistance of a planing craft in waves and wind conditions is developed and validated. With respect to the existing literature models, a simplified methodology to account for diffraction forces is proposed, together with a novel approach for the estimation of the transom effects on drag and lift forces. A throughout comparison of model results with literature data of different planing hulls is presented, showing the potential of the proposed methodology.The developed model was applied to a 10 m flybridge test case, also including the effects of wind resistance. To this purpose, a dedicated CFD (Computational fluid dynamics) analysis of the freeboard aerodynamics has been attained and correlations for lift and drag coefficients are proposed. In addition, the potential of the proposed methodology is shown also in terms of passenger comfort by assessing the habitability under different wave conditions.

Defect-induced measurements of semi-organic ammonium hydrogen oxalate oxalic acid dihydrate single crystals using gamma irradiation

The structural, optical, mechanical and electrical properties of pure and 5—20-kGy gamma-irradiated semi-organic single crystals of ammonium hydrogen oxalate oxalic acid dihydrate (NH4H3(C4O8).2H2O) are presented. The crystals were synthesized at room temperature using facile solvent evaporation technique. Powder XRD measurements indicate gradual enhancement in crystallinity and lattice defect annihilation for low radiation dosage. Radiation-induced increase in optical band gap (4.01–4.16 eV) indicates high damage threshold of the crystals. Quenching of photoluminescence is attributed to the lowering of surface defect density with radiation. The influence of gamma radiation on the functional vibrations of the crystals is studied using FTIR-Raman spectroscopy. Vickers microhardness measurements show gradual enhancement in crystal hardness with the increase in radiation. An increase in forward resistance with irradiation is observed from I–V measurements and is attributed to high transparency of the crystals. These results indicate the viability of NH4H3(C4O8) 2H2O crystals in potential space optoelectronic applications.

Entropy Analysis of a Valveless Piezoelectric Pump With Hyperbolic Tubes

In order to solve the problems of large reflux and low output performance of the valveless piezoelectric pump with conical tubes, the valveless piezoelectric pump with hyperbolic tubes was proposed. However, the previous research only paid attention to the difference of forward and reverse flow resistance inside the tubes. For this reason, the prototypes of conical tube valveless piezoelectric pump and hyperbolic tubes valveless piezoelectric pump were fabricated in this paper. The maximum output flow rate of the valveless piezoelectric pump with hyperbolic tubes was 54 ml/min. Subsequently, the size and position of entropy production of the hyperbolic tube and the conical tube were numerically calculated based on entropy production theory in this paper. The results show that the entropy production rate of the hyperbolic tube was significantly lower than that of the conical tube, which is consistent with the experimental results. This research analyzed the energy loss inside the valveless piezoelectric pump by using the entropy generation theory, and provided a new design and research method for improving the output performance of the valveless piezoelectric pump in the future.

Design and study of an integral valve piezoelectric pump with a novel working mode.

In this paper, an integral valve is proposed by connecting the inlet cantilever valve and the outlet cantilever valve with a connecting post and a rubber circle plate structure. The integral valve changes the traditional inlet cantilever valve and outlet cantilever valve to work independently and realizes the joint response of the inlet cantilever valve and the outlet cantilever valve. The integral valve was designed, manufactured, and installed, and the performance of the static experimental test equipment of the valve and that of the experimental equipment of the piezoelectric pump were evaluated. The static performance of the integral valve was tested. In addition, the performance of the integral valve piezoelectric pump and the cantilever valve piezoelectric pump was tested and compared. The experimental results show that the integral valve piezoelectric pump reaches up to 270.2 ml/min at 210 Vrms, 45Hz; the pressure can reach 86.2 cmH2O at 40Hz. Compared to cantilever valves, integral valves have less forward flow resistance and better reverse shutoff. In particular, the pressure of the integral valve piezoelectric pump can be significantly improved compared to the cantilever valve piezoelectric pump. In terms of efficiency, the integrated valve piezoelectric pump will have better performance in the low-frequency region.

A zero bias highly efficient active diode circuit for piezoelectric energy harvester

This paper presents a MOS based active diode circuit for efficient rectification of piezoelectric energy harvester (PZEH). The active diode consists of a PMOS switch along with auto tuned control circuit to control the gate of the PMOS. The strength of gate voltage of the PMOS in conducting state has been improved to provide the low forward resistance at high current. In the on-state, the voltage drop across the active diode is 33 mV at diode current of 136 µA. The maximum reverse leakage current in the non conduction state of PMOS has been reduced from 18 µA of conventional MOS diode to 1.5 µA. The auto tuned control circuit does not require external bias. The active rectifier using proposed active diode used for ac to dc conversion of PZEH output has been presented in this paper. The circuit provides a power conversion efficiency of 94% which is 36% better than the conventional MOS based rectifier.