Search Results (5,807)

Digitalization has become more and more important for economic activities and economic development. E-commerce, as a part of local and international trade, is of increasing importance and is highly correlated with technological progress and innovation. Our research investigates the relevance of selected drivers that could explain the latest e-commerce adoption at global level. In our analysis, we used the UNCTAD B2C E-commerce Index (2014–2020, yearly data, covering 133 countries, 931 observations) which can be considered relevant to express an economy’s readiness to support e-commerce. E-commerce adoption is assessed in our research by the following six factors: (i) wealth, economic freedom, and economic development; (ii) access and sophistication of the financial sector; (iii) education; (iv) regulations; (v) development of ICT infrastructure; and (vi) frontier drivers (such as AI, cryptocurrencies, and blockchain technologies). In our research, we used a panel data analysis framework using hard data provided by different databases (UNCTAD, World Bank, etc.). The results we obtained confirmed that developed countries with a higher income level are higher adopters of e-commerce, financial development and the accessibility of financial services significantly help e-commerce adoption, a regulatory system (particularly economic freedom and property rights) strongly supports e-commerce adoption, education has a positive impact on e-commerce adoption, ICT infrastructure increases the adoption of e-commerce and the readiness and use of AI, and frontier technologies generate an increased adoption of e-commerce. The results we obtained are consistent with the findings of similar studies (most of them using different research methodologies) and opens the ground for interesting discussions and further research developments. The novelty of our research consists in the exhaustive perspective on e-commerce adoption drivers (including frontier technologies such as AI or blockchain) based on hard country data collected from various sources for a consistent panel of countries and a relevant number of years, providing an alternative approach to the mainstream studies on e-commerce adoption that process data from surveys, interviews, or focus groups. Full article

The physics-informed neural network (PINN) is an effective alternative method for solving differential equations that do not require grid partitioning, making it easy to implement. In this study, using automatic differentiation techniques, the PINN method is employed to solve differential equations by embedding prior physical information, such as boundary and initial conditions, into the loss function. The differential equation solution is obtained by minimizing the loss function. The PINN method is trained using the Adam algorithm, taking the differential equations of motion in structural dynamics as an example. The time sample set generated by the Sobol sequence is used as the input, while the displacement is considered the output. The initial conditions are incorporated into the loss function as penalty terms using automatic differentiation techniques. The effectiveness of the proposed method is validated through the numerical analysis of a two-degree-of-freedom system, a four-story frame structure, and a cantilever beam. The study also explores the impact of the input samples, the activation functions, the weight coefficients of the loss function, and the width and depth of the neural network on the PINN predictions. The results demonstrate that the PINN method effectively solves the differential equations of motion of damped systems. It is a general approach for solving differential equations of motion. Full article

In recent years, with the widespread application of indoor inspection robots, high-precision, robust environmental perception has become essential for robotic mapping. Addressing the issues of visual–inertial estimation inaccuracies due to redundant pose degrees of freedom and accelerometer drift during the planar motion of mobile robots in indoor environments, we propose a visual SLAM perception method that integrates wheel odometry information. First, the robot’s body pose is parameterized in SE(2) and the corresponding camera pose is parameterized in SE(3). On this basis, we derive the visual constraint residuals and their Jacobian matrices for reprojection observations using the camera projection model. We employ the concept of pre-integration to derive pose-constraint residuals and their Jacobian matrices and utilize marginalization theory to derive the relative pose residuals and their Jacobians for loop closure constraints. This approach solves the nonlinear optimization problem to obtain the optimal pose and landmark points of the ground-moving robot. A comparison with the ORBSLAM3 algorithm reveals that, in the recorded indoor environment datasets, the proposed algorithm demonstrates significantly higher perception accuracy, with root mean square error (RMSE) improvements of 89.2% in translation and 98.5% in rotation for absolute trajectory error (ATE). The overall trajectory localization accuracy ranges between 5 and 17 cm, validating the effectiveness of the proposed algorithm. These findings can be applied to preliminary mapping for the autonomous navigation of indoor mobile robots and serve as a basis for path planning based on the mapping results. Full article

Laser-based powder bed fusion of metals (PBF-LB/M) is a widely used additive manufacturing process characterized by a high degree of design freedom. As a result, near fully dense complex components can be produced in near-net shape by PBF-LB/M. Recently, the PBF-LB/M process was found to be a promising candidate to overcome challenges related to conventional machining of the Fe₆₄Ni₃₆ Invar alloy being well known for a low coefficient of thermal expansion (CTE). In this context, a correlation between process-induced porosity and the CTE was presumed in several studies. Therefore, the present study investigates whether the unique thermal properties of the PBF-LB/M-processed Fe₆₄Ni₃₆ Invar alloy can be tailored by the selective integration of defects. For this purpose, a full-factorial experimental design, representing by far the largest processing window in the literature, was considered, correlating the thermal expansion properties with porosity and hardness. Furthermore, the microstructure and mechanical properties were investigated by scanning electron microscopy and quasi-static tensile tests. Results by means of statistical analysis reveal that a systematic correlation between porosity and CTE properties could not be determined. However, by using specific process parameter combinations, the microstructure changed from a fine-grained fan-like structure to a coarse columnar structure. Full article

Snake robots have broad application potential, but their motion-control and motion-planning problems are extremely challenging due to the high redundancy of degrees of freedom (DoFs), and the lack of complete system tools further hinders the research of snake robots. In this paper, a coordinate system and a kinematic model were established based on the D-H method for snake robots. The rhythm-generation model for multimodal motion gait and a novel sliding-window five-point interpolation-derivative model were proposed based on a bio-inspired central pattern generator (CPG) model. A prototype and simulator were constructed based on the designed snake robot models to achieve the multimodal motion gait for the snake robot and improve its environmental adaptability. Furthermore, a novel structure–drive–perception–control integration snake robot system (SnakeSys) was built based on the robot-operating system (ROS). Finally, the effectiveness, feasibility, and accuracy of the kinematic model and control model in motion control and information perception were verified through simulations and experiments. We open sourced SnakeSys so that relevant researchers or developers can directly utilize or further develop it. Full article

The Daitokuji Old Collection’s 500 Luohans Paintings 五百羅漢圖, painted by Southern Song Mingzhou 明州 artists Lin Tinggui 林庭珪 and Zhou Jichang 周季常, have become a focal point in recent studies on the Chinese Buddhist material culture of the Song Dynasty. Among the 500 Luohans series, five paintings are related to the ancient Indian legend of Emperor Aśoka’s creation of 84,000 stupas. These paintings include “Building a Stupa” (No.78), “King Aśoka Stupa Emitting Light” (No.79), “Precious Stupa on the Rock” (No.80), and “Miracle of Light-Emitting Relics” (No.81), which are currently housed in the Daitokuji 大德寺 in Kyoto, Japan, and “Luohans Watching the Relics’ Light” (B5), which is housed in the Museum of Fine Arts in Boston, the US. However, the way in which the “King Aśoka Stupa” 阿育王塔 and “Relics’ Light” 舍利光 series were integrated into the overall visual narrative of the 500 Luohans in the Daitokuji and Boston collections, as well as the profound meanings and social-cultural contexts embedded in these images, have been rarely studied in depth. The introduction of the miraculous relics theme into the Daitokuji Old Collection’s 500 Luohans Paintings originates from an earlier version by the monk Fa Neng. However, Fa Neng’s version recorded by the Northern Song literati Qin Guan 秦觀 does not mention the King Aśoka Stupa. The artists had considerable freedom in depicting miraculous relic phenomena and King Aśoka Stupa. The specific details of King Aśoka Stupa’s background in Tiantai Mountain 天台山, such as rock bridges, waterfalls, and rock caves, as well as the craftsmanship of King Aśoka Stupa, reflect particular contemporary ideas. The vivid depictions of the “King Aśoka Stupa” and “Relics’ Light” in the Daitokuji Present Collection and the Boston Collection of the 500 Luohans may indicate a close connection between the creation of these images and the fervent Relics Worship at King Aśoka Temple 阿育王寺 in Mingzhou during Southern Song. This paper synthesizes these images, ancient Chinese and Japanese manuscripts, and fieldwork insights to interpret the sources and significance of these images. Full article

While floating wind lidars provide reliable and cost-effective measurements, these measurements may be inaccurate due to the motion of the installation platforms. Prior studies have not distinguished between systematic errors associated with lidars and errors resulting from motion. This study will fill this gap by examining the impact of platform motion on two types of profiling wind lidar systems: the pulsed WindCube V1 (Leosphere) and the continuous-wave ZephIR 300 (Natural Power). On a moving hexapod platform, both systems were subjected to 50 controlled sinusoidal motion cases in different degrees of freedom. Two reference lidars were placed at a distance of five meters from the platform as reference lidars. Motion-induced errors in mean wind speed and turbulence intensity estimation by lidars are analyzed. Additionally, the effectiveness of a motion correction approach in reducing these errors across various scenarios is evaluated. The results indicate that presence of rotational motion leads to higher turbulence intensity (TI) estimation by moving lidars. The absolute percentage error between lidars is the highest when lidars are exposed to yaw and heave motion and is the lowest when exposed to surge motion. The correlation between lidars, though it is the lowest in the presence of pitch, yaw, and heave motion. Furthermore, applying motion compensation can compensate the correlation drop and erroneous TI estimation. Full article

Despite the tendency of some modern scholars to mark Augustine as the father of religious coercion, the Second Vatican Council (1962–65) cites him as a principal source for freedom of conscience. This essay presents evidence from Augustine’s letters and anti-Donatist writings to show that he both upheld freedom of conscience and maintained a vital role for state force. The essay shows that far from simply providing a Christian justification for the use of state force against non-Catholics, Augustine most notably imposed the limits of Christian charity on a long history of state-sponsored religious persecution. Only by the charitable and paternal application of discipline by the state would many Donatists be truly free to follow their conscience. In this way, those persecuted for being in schism could attain freedom by coercion. Full article

Interventional radiologists mainly rely on visual feedback via imaging modalities to steer a needle toward a tumor during biopsy and ablation procedures. In the case of CT-guided procedures, there is a risk of exposure to hazardous X-ray-based ionizing radiation. Therefore, CT scans are usually not used continuously, which increases the chances of a misplacement of the needle and the need for reinsertion, leading to more tissue trauma. Interventionalists also encounter haptic feedback via needle–tissue interaction forces while steering a needle. These forces are useful but insufficient to clearly perceive and identify deep-tissue structures such as tumors. The objective of this paper was to investigate the effect of enhanced force feedback for sensing interaction forces and guiding the needle when applied individually and simultaneously during a virtual CT-guided needle insertion task. We also compared the enhanced haptic feedback to enhanced visual feedback. We hypothesized that enhancing the haptic feedback limits the time needed to reach the target accurately and reduces the number of CT scans, as the interventionalist depends more on real-time enhanced haptic feedback. To test the hypothesis, a simulation environment was developed to virtually steer a needle in five degrees of freedom (DoF) to reach a tumor target embedded in a liver model. Twelve participants performed in the experiment with different feedback conditions where we measured their performance in terms of the following: targeting accuracy, trajectory tracking, number of CT scans required, and the time needed to finish the task. The results suggest that the combination of enhanced haptic feedback for guidance and sensing needle–tissue interaction forces significantly reduce the number of scans and the duration required to finish the task by 32.1% and 46.9%, respectively, when compared to nonenhanced haptic feedback. The other feedback modalities significantly reduced the duration to finish the task by around 30% compared to nonenhanced haptic feedback. Full article

It is difficult for traditional aluminum alloy manufacturing technology to meet the requirements of large-scale and high-precision complex shape structural parts. Wire Arc additive manufacturing technology (WAAM) is an innovative production method that presents the unique advantages of high material utilization, a large degree of design freedom, fast prototyping speed, and low cast. As a result, WAAM is suitable for near-net forming of large-scale complex industrial production and has a wide range of applications in aerospace, automobile manufacturing, and marine engineering fields. In order to serve as a reference for the further development of WAAM technology, this paper provides an overview of the current developments in WAAM both from the digital control system and processing parameters in summary of the recent research progress. This work firstly summarized the principle of simulation layering and path planning and discussed the influence of relative technological parameters, such as current, wire feeding speed, welding speed, shielding gas, and so on. It can be seen that both the welding current and wire feeding speed are directly proportional to the heat input while the travel speed is inversely proportional to the heat input. This process regulation is an important means to improve the quality of deposited parts. This paper then summarized various methods including heat input, alloy composition, and heat treatment. The results showed that in the process of WAAM, it is necessary to control the appropriate heat input to achieve minimum heat accumulation and improve the performance of the deposited parts. To obtain higher mechanical properties (tensile strength has been increased by 28%–45%), aluminum matrix composites by WAAM have proved to be an effective method. The corresponding proper heat treatment can also increase the tensile strength of WAAM Al alloy by 104.3%. In addition, mechanical properties are always assessed to evaluate the quality of deposited parts. The mechanical properties including the tensile strength, yield strength, and hardness of the deposited parts under different processing conditions have been summarized to provide a reference for the quality evaluation of the deposition. Examples of industrial products fabricated by WAAM are also introduced. Finally, the application status of WAAM aluminum alloy is summarized and the corresponding future research direction is prospected. Full article

To research the dynamic response of a new type of dedicated transmission for a hybrid electric vehicle, a detailed dynamics model should be built. However, a model with too many degrees of freedom has a negative effect on controller design, which means the detailed model should be simplified. In this paper, two dynamic models are established. One is an original and detailed powertrain dynamics model (ODPDM), which can capture the transient response, and it is validated that the ODPDM can be used to accurately describe the real vehicle in some specific operating conditions. The other is a simplified torsional vibration dynamics model to study the torsional vibration characteristics of the hybrid electric vehicle. Compared with the full-order model, which is based on the ODPDM, the simplified model has a very similar vibration in low frequency. This study provides a basis for further vibration control of the hybrid powertrain during the process of a driving-mode switch. Full article

(1) Background: Sustainable development goal 5.6 calls for “universal access to sexual and reproductive health and reproductive rights” to fulfil sexual and reproductive practices. The capability approach helps refine the analysis of contraceptive use by going beyond the dichotomous view of contraceptive use as use/non-use to focus on women’s freedom to choose what they have good reason to value. Using the case of Burkina Faso, we probe more deeply into whether contraceptive use reflects real progress in women’s reproductive rights to realize the fertility projects they value. (2) Methods: We use PMA2020 data collected in Burkina Faso between December 2018 and January 2019. The survey included 3329 women with a participation rate of 97.7%. The PMA2020 female core questionnaire solicits information on fertility and contraceptive behavior, much like the DHS. We asked a series of specific questions about cognitive and psychosocial access relating to FP. We examined bivariate associations between our outcome measure “contraceptive behavior” and a set of independent variables. We also used logistic regression models to evaluate associations with endowments/conversion and capability factors and current functioning by focusing on overuse (i.e., use of contraceptives despite desiring pregnancy within the next 12 months). (3) Results: Women who said their ideal number of children was “up to God” had the highest level of overuse, which was also higher among women living in communities with medium acceptance of contraception and greater support for fertility. Women who have higher and middle levels of information tend to engage less in overuse than those with lower information levels. (4) Conclusions: We conclude that overuse (contraceptive use when desiring a child soon) may reveal a lack of rights, as it is associated with a lack of information about contraceptives and women’s inability to conceive an ideal number of children. Efforts should be made to enhance women’s level of contraceptive information. Full article

Urban secondary wilderness (USWs) is a near-natural place in cities and is an important link to reconnect humans with the natural world. Assessing the perceptual elements of USWs not only provides insight into public perceptions and preferences, but also helps to further explore its relevance to experiential values such as environmental restoration benefits. In this study, we selected three USWs cases located in Fuzhou, the capital city of Fujian Province, China, and constructed an evaluation system containing two types of dimensions and seventeen perceptual elements. Based on the public’s evaluation of the importance of and satisfaction with the perceived elements, we extracted the key perceived elements and analyzed their relationship with environmental restoration benefits. The results indicated that all three USWs cases scored over 4.9 on the Perceived Restoration Scale (PRS). Plants, Landscape color, Water, Landform, Climate, Freedom, and Naturalness are the key perceptual elements of the USWs, and the correlation coefficients between the satisfaction with the above seven perceptual elements and the scores of the PRS were all positive. In summary, USWs is an ideal place for residents to carry out restoration activities, and its key perceptual elements play a driving role. Full article

Delta robots are the most common parallel robots for manipulation tasks. In many industrial applications, they must be operated at reduced speed, or dwell times have to be included in the motion planning, to prevent frame vibrations. As a result, their full potential cannot be realized. Against this background, this publication is concerned with the mechanical design of an active dynamic balancing unit for the reduction of frame vibrations. In the first part of this publication, the main design requirements for an active dynamic balancing mechanism are discussed, followed by a presentation of possible mechanism designs. Subsequently, one the most promising mechanisms is described in detail and its kinematics and dynamics equations are derived. Finally, the dimensions of a prototype mechanism designed to experimentally validate the concept of active dynamic balancing are defined using the example of Suisui Bot, a low-cost Delta robot. Full article

Our study presents a novel design for a cable-driven robotic arm, emphasizing low cost, low inertia movement, and long-term cable durability. The robotic arm shares similar specifications with the UR5 robotic arm, featuring a total of six degrees of freedom (DOF) distributed in a 1:1:1:3 ratio at the arm base, shoulder, elbow, and wrist, respectively. The three DOF at the wrist joints are driven by a cable system, with heavy motors relocated from the end-effector to the shoulder base. This repositioning results in a lighter cable-actuated wrist (weighing 0.8 kg), which enhances safety during human interaction and reduces the torque requirements for the elbow and shoulder motors. Consequently, the overall cost and weight of the robotic arm are reduced, achieving a payload-to-body weight ratio of 5:8.4 kg. To ensure good positional repeatability, the shoulder and elbow joints, which influence longer moment arms, are designed with a direct-drive structure. To evaluate the design’s performance, tests were conducted on loading capability, cable durability, position repeatability, and manipulation. The tests demonstrated that the arm could manipulate a 5 kg payload with a positional repeatability error of less than 0.1 mm. Additionally, a novel cable tightener design was introduced, which served dual functions: conveniently tightening the cable and reducing the high-stress concentration near the cable locking end to minimize cable loosening. When subjected to an initial cable tension of 100 kg, this design retained approximately 80% of the load after 10 years at a room temperature of 24 °C. Full article