Search Results (5)

This paper aimed to study soil organic carbon (SOC) sequestration under no-tillage (NT) and full inversion tillage (FIT) soil management systems as influenced by crop residue placement. A five-year piece of research was carried out in western Sicily, Italy, on an Opuntia ficus-indica orchard (C-CAM soil) located in a semi-arid Mediterranean climate. Barley was sown annually in the orchard inter-rows at 180 kg ha⁻¹. FIT and NT were compared in interaction with two barley residue managements: (i) removed (rem) and (ii) retained in the field (ret), laid in a split-plot design, with soil management as the main plot and residue management as the sub-plot. The main plot was arranged on two inter-rows, 108 m long and 5 m wide each, replicated three times. SOC (%) and carbon natural abundance (δ¹³C‰) were determined by using an EA-IRMS. The highest biomass turnover was achieved by FITret (0.85%) vs. NTret (0.46%). The distribution of SOC showed higher values for NT in the top 10 cm soil layer (6.3 g kg⁻¹ in NTret vs. 5.0 g kg⁻¹ in FITret) but lower carbon content in deeper layers. At a depth of 30 cm, FITret maintained 4.4 g kg⁻¹ of SOC, while NTret reached only 3.7 g kg⁻¹, confirming that tillage facilitates the transport and stabilization of carbon in deeper layers. Our results also suggested that when crop residues are left on the soil surface instead of being incorporated into the soil, this may limit the effectiveness of carbon sequestration. Under the experimental tested conditions, which include low susceptibility to erosion processes, the FIT system proved to be an optimal strategy to enhance SOC sequestration and improve the sustainability of agricultural systems in a semi-arid Mediterranean environment. Full article

Frontal plane ankle motion is important for balance in walking but is seldom controlled in robotic prostheses. This article describes the design, control and performance of a semi-active two-degree-of-freedom robotic prosthetic ankle. The mechanism uses a non-backdrivable wedge cam system based on rotating inclined planes, allowing actuation only during swing phases for low power, light weight and compactness. We present details of the mechanism and its kinematic and mechatronic control, and a benchtop investigation of the system’s speed and accuracy in ankle angle control. The two-axis ankle achieves angular reorientation movements spanning ±10 deg in any direction in less than 0.9 s. It achieves a plantarflexion/dorsiflexion error of 0.35 ± 0.27 deg and an inversion/eversion error of 0.29 ± 0.25 deg. Backdriven motion during walking tests is negligible. Strengths of the design include self-locking behavior for low power and simple kinematic control. Two-axis ankle angle control could enable applications such as balance augmentation, turning assistance, and wearable perturbation training. Full article

This paper proposes a general design method for cams based on the kinematics and dynamics of a mechanical system. According to the actuator’s trajectory, the cam profile is generated in reverse based on the kinematic model of the system. Firstly, the cam design’s optimising problem is converted into the execution trajectory’s optimisation to obtain the optimum operation trajectory according to the actuator’s requirements. Secondly, the relationship between the cam profile and the actuation trajectory is modelled based on the kinematics and dynamics of the mechanical system. Then, applying the cubic spline interpolation method, the cam profile is generated, and the error compensation methods are illustrated through numerical analysis. Finally, the validity of the presented design method is verified through experiments, which demonstrate the reliability of this method. Full article

This paper proposes a joint encryption and screen-cam robust watermarking scheme. This method combines the advantages of smartphone, encryption and watermarking technologies, thereby achieving watermark extraction with a smartphone, partial decryption and tracking leakage from sneak shots. We design a dual watermarking algorithm to achieve watermark detection from both encrypted and decrypted images. First, a watermark is embedded in the discrete Fourier transform (DFT) domain to enable leakage tracking. Then, a second watermark is generated based on QR (Quick response) code encoding and inverse DFT to achieve high watermark capacity and error correction ability, where the secret key for decryption is included in the watermark message. By hiding this message carrying the watermark for the encrypted image in the changes caused by embedding the first watermark, we can improve imperceptibility and will not affect the effectiveness of the proposed scheme. Finally, to enhance the robustness of watermark after encryption, a chaotic mapping-based segment encryption algorithm is proposed. In the process of watermark detection, to cope with perspective correction, a frame locating based algorithm is employed to achieve watermark synchronization from a recaptured picture of the encrypted image. Considering the severe quality degradation, we use a noise component and local statistic feature-based method to extract the message bits. The experimental results show that the proposed scheme is secure, and highly robust, to screen-cam the process for both before and after decryption. Additionally, after decryption, the proposed scheme also has high robustness against common image processing attacks. Full article

At present, there are few reports on the profiling mechanism that can achieve surface envelope profiling along the surface of a shaft whose radius is constantly changing. Existing profiling mechanisms cannot achieve this function. To this end, a novel deployable arc profiling mechanism is presented in this paper. The mechanism can realize centering deployment along the shaft with a changing radius. The radius of the deployable arc can be adapted to the continuous change of shaft radius, and its surface can always maintain the arc shape for surface envelope profiling. The mechanism is mainly composed of compound cams. Each cam contains multiple grooves, and each groove connects to an arc support linkage. The arc support linkage is controlled by the compound motion of cams in different layers. The pitch curve of each groove is designed by applying the method of relative motion and inverse solution and obtained various parameter equations of the mechanism. The feasibility of this mechanism is verified by analysis, experiment, and application test. The results show that the proposed deployable arc profiling mechanism can achieve the design purpose and the profiling accuracy is kept above 96.425%. Full article