Knee joint contact force is related to knee joint pain and related diseases such as osteoarthritis. Joint loading during gait even on an intact knee may cumulatively lead to the joint diseases. Previous studies on forward dynamics simulation suggest that knee joint angle is a key factor to alter knee joint contact force during walking. However, current literature has not shown the relationship between the quantities in actual human gait motion. In the present study, an open gait database was used to investigate the relationship between the quantities. Knee joint contact force and muscle forces were estimated using a musculoskeletal model, and the quantities in the early stance phase were analyzed. The knee joint contact force showed decreased correlation with decreasing knee flexion angle. The force of the muscles on the thigh also systematically changed with the knee flexion angle. Nevertheless, the knee joint contact force was larger for subjects whose knee flexion angle was less than 10° in the early stance phase. These results revealed a risk motion for larger joint contact forces. It is suggested that walking with a straighter leg can be a practical strategy to reduce knee joint contact force. A fully extended knee would change the gait mechanism and lead to a higher load on the knee.

In order to solve the spatial obstacle avoidance requirements of the boom jitter caused by the gradient projection method control in the self-motion of the hybrid light array high-altitude vehicle, which leads to the discontinuous motion trajectory and the multi-obstacle environment, this paper proposes a boom obstacle avoidance control method based on the improved gradient projection method. In order to suppress the jib jitter, a boom motion stability control algorithm was designed, and the improved gradient projection method was divided into two parts, which were controlled separately according to the proportion of the length of the telescoping arm to achieve stable movement. In terms of obstacle avoidance, the obstacle is modeled by the hyperquadric surface function, and the proximity between the boom and the obstacle is evaluated by using the pseudo-distance instead of the Euclidean distance, and the obstacle avoidance escape speed is introduced on this basis to effectively avoid collision. At the same time, the end position error reduction algorithm is added to reduce the end velocity and improve the trajectory tracking accuracy. Simulation and semi-physical experiments show that the algorithm can realize the smooth motion control of the boom and can effectively realize the obstacle avoidance of multiple obstacles in the complex environment.

In order to explore an efficient, accurate, and convenient finite element simulation method for laser peening forming, a square laser loading model was constructed by studying the loading feature unit of the circular spot superposition model, which can replace the circular spots overlay laser peening forming. and Finite element simulation was conducted on 7075 aluminum alloy flat plate model. In order to verify the rationality and effectiveness of the square finite element loading model and its finite element simulation method, a finite element model base on 7075 aluminum alloy flat plate was used as the object for simulation. The corresponding experiment of 7075 aluminum alloy flat plate laser peening forming was conducted, and the experimental results were compared with the finite element analysis results. The results indicate that the finite element simulation results comply with experimental laws in terms of stress and forming. After laser peening forming, both finite element simulation and experimental results show that high amplitude residual compressive stress is generated on the surface of the metal plate. Compared with the experimental results, the magnitude and overall trend of residual stress at different positions are consistent. And the free end offset of the upper surface of the formed metal plate obtained from finite element simulation and experiments, as well as the arch span and height of the surface contour curve in the forming area of the metal plate, are similar. This indicates that the constructed square laser loading model and its finite element simulation method are reasonable, effective and in accordance with experimental laws. Finally, the reasons for sheet metal forming under laser peening were attributed to the gradient plastic extension effect driven by the surface material of the substrate under the effect of laser shot peening.

The preference set-based design (PSD) method enhances design efficiency by providing an adjustment range that reflects the preferences of the designer in the quantitative design variables and performance. However, applying PSD in early design stages, where variables and performance are often qualitative or their relationships fluctuate probabilistically owing to individual differences (probabilistic objective function), is challenging. This study proposes a PSD method that addresses these issues using the rough set theory, which is suitable for handling such design problems. This approach derives if-then rules from data combining qualitative and quantitative design variables and performance. These rules are specified based on four PSD indicators and target either frequently occurring or high-importance data. The proposed method was validated on car evaluation data from a U.S. automobile market. The analysis resulted in decision rules incorporating both quantitative and qualitative design variables, as well as the characteristics of four indicators. This demonstrates the applicability of the proposed method to design problems with qualitative variables and performance or a probabilistic objective function. Additionally, a parameter study of indicator weights yielded diverse decision rules (Pareto optimal solutions) based on the weight ratio, highlighting the ability of the proposed method to generate design solutions aligned with specific characteristics of each indicator, further confirming its applicability to a wide range of design problems.

This paper focuses on the study of the turning of Austenitic Stainless Steel products manufactured with the Wire and arc direct energy deposition (DED-Arc) process by comparing the cutting process of two different samples, one manufactured with the DED-Arc methodology and the other by the hot rolling technique, for both oblique and orthogonal cutting. Focusing on the cutting forces aspect of the cutting procedure and the chip formation, these parameters were compared for both samples. Their differences are highlighted and discussed, mainly regarding their microstructure and possible influence on turning. Although the hot rolled samples presented higher values for the cutting forces for both cases, the profile of forces was stable as was the chip formed. The DED-Arc sample, on the other hand, presented not only a high degree of variability of cutting forces but also a periodic pattern of this kind of variation. Also, non-uniform was the chips formed and their evacuation. Those changes were discussed and explained to be mainly influenced by the dendritic microstructure and the anisotropic behavior of the DED-Arc SUS316L.

This research proposes feedforward control techniques aimed at reducing the seek time in hard disk drives (HDDs). These techniques utilize a sampled-data polynomial approach based on a triangular approximation first-order hold (triangle hold) with a non-zero initial value. In the first proposed method, we developed a sampled-data polynomial that allows for arbitrary initial values of the acceleration trajectory. In the second proposed method, to reduce computational load, we employ an approximate initial value for the acceleration trajectory in the sampled-data polynomial. These methods improve the seek time of the magnetic-head positioning control system in HDDs, primarily because the triangle hold offers a faster response compared to the traditional zero-order hold (ZOH). Moreover, these methods improve the seek time over the conventional method with the causal first-order hold (CFOH) because the triangle hold reduces the amplitude of transient vibrations. Validation results for the track-seek control of HDDs demonstrate that the proposed methods effectively reduce seek time compared to conventional methods.