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Wangjing is a large residential cluster located at the intersection of the Fourth Ring Road and the airport expressway in the northeast part of Beijing. The area is a “suburb” according to official statistics and academic accounts, which often classify urban areas beyond the historical old city as suburbs. Due to its proximity to the airport and major expressways, Wangjing has developed quickly since the late 1990s. As more high-rise luxury apartment buildings get built, the area's population has reached 150,000 as of 2010, including more than 30,000 foreign expatriates living here amid Chinese urban professionals. Across the airport expressway from Wangjing is the 798 Factory, a hip arts quarter developed within a former electronics factory built in the 1950s. Looking for large studio space, a few artists moved into the Bauhaus-style workshops here in the late 1990s, and quickly bookstores, coffee shops, and galleries followed suit. By 2005, the 798 Factory had become the center of the contemporary Chinese art scene and home to many prestigious international galleries. Outside the factory compound is a working-class neighborhood developed in the 1950s to house workers at the nearby factories and their families. The living conditions here have not changed much for decades, with some families still sharing common kitchens and bathrooms with their neighbors in dilapidated apartment buildings. To the west side of Wangjing, after about a 15-minute drive along the Fourth Ring Road, one reaches the Olympic Park, a brand-new area of parks, stadiums, five-star hotels, golf courses, and exclusive gated communities of villas – all developed in the short period before the 2008 Beijing Olympics. Beyond the Fifth Ring Road, one can see many “urban villages,” former agricultural villages that have become populated by migrant workers with low-paid jobs – taxi drivers, construction workers, waiters, nannies, security guards, and street vendors. Unable to afford to live in the central city, migrant workers rent rooms from local peasants at the city's edge. Many of these villages are to be demolished soon to make space for commercial property development, and the migrant worker tenants will have to move to another village farther away from the city.

The purpose of this paper is to propose a novel jump control method based on Two Mass Spring Damp Inverted Pendulum (TMS-DIP) model, which makes the third generation of hydraulic driven wheel-legged robot prototype (WLR-3P) achieve stable jumping.

First, according to the configuration of the WLR, a TMS-DIP model is proposed to simplify the dynamic model of the robot. Then the jumping process is divided into four stages: thrust, ascent, descent and compression, and each stage is modeled and solved independently based on TMS-DIP model. Through WLR-3P kinematics, the trajectory of the upper and lower centroids of the TMS-DIP model can be mapped to the joint space of the robot. The corresponding control strategies are proposed for jumping height, landing buffer, jumping attitude and robotic balance, so as to realize the stable jump control of the WLR.

The TMS-DIP model proposed in this paper can simplify the WLR dynamic model and provide a simple and effective tool for the jumping trajectory planning of the robot. The proposed approach is suitable for hydraulic WLR jumping control. The performance of the proposed wheel-legged jump method was verified by experiments on WLR-3P.

This work provides an effective model (TMS-DIP) for the jump control of WLR-3P. The results showed that the number of landing shock (twice) and the pitch angle fluctuation range (0.44 rad) of center of mass of the jump control method based on TMS-DIP model are smaller than those based on spring-loaded inverted pendulum model. Therefore, the TMS-DIP model makes the jumping process of WLR more stable and gentler.

This paper aims to propose a method to solve the problem of localization and mapping of a two-wheeled inverted pendulum (TWIP) robot on the ground using the Stereo–inertial measurement unit (IMU) system. This method reparametrizes the pose according to the motion characteristics of TWIP and considers the impact of uneven ground on vision and IMU, which is more adaptable to the real environment.

When TWIP moves, it is constrained by the ground and swings back and forth to maintain balance. Therefore, the authors parameterize the robot pose as SE(2) pose plus pitch according to the motion characteristics of TWIP. However, the authors do not omit disturbances in other directions but perform error modeling, which is integrated into the visual constraints and IMU pre-integration constraints as an error term. Finally, the authors analyze the influence of the error term on the vision and IMU constraints during the optimization process. Compared to traditional algorithms, the algorithm is simpler and better adapt to the real environment.

The results of indoor and outdoor experiments show that, for the TWIP robot, the method has better positioning accuracy and robustness compared with the state-of-the-art.

The algorithm in this paper is proposed for the localization and mapping of a TWIP robot. Different from the traditional positioning method on SE(3), this paper parameterizes the robot pose as SE(2) pose plus pitch according to the motion of TWIP and the motion disturbances in other directions are integrated into visual constraints and IMU pre-integration constraints as error terms, which simplifies the optimization parameters, better adapts to the real environment and improves the accuracy of positioning.

This study aims to investigate how the relationship factors, including equity, shared responsibility and relationship dependence leverage the value co-creation. The research studies the value co-creation process in a business-to-business (B2B) context between suppliers and customers and provides empirical evidence of the underlying effects.

Using social exchange theory, the research uses a mixed-method of in-depth interviews and questionnaire surveys. The sample of the survey has 123 business customers.

The findings suggest that equity not only positively affects but also mediates the effect of shared responsibility on value co-creation. The mediation effect is further moderated by the relationship dependence that buyers have on the seller.

The cross-sectional survey used cannot establish causality relationships. Although the goal was not to establish causality, it could limit the rigor of the study. The longitudinal design could be used in the future to better address this deficiency. While the paper is the initial step to analyze the factors influencing value co-creation empirically, more studies could examine other commonly discussed constructs.

This empirical study enriches the value co-creation literature by examining the antecedents’ detailed mechanism that facilitates value co-creation in a B2B context.

This paper aims to examine the precision loss of ball screw raceway under different operating conditions and geometry parameters.

Based on a new coefficient K’ introduced especially for ball screws to reflect the actual contact condition, the modified Archard theory is applied to ball screws to obtain wear volume of the ball-screw contacts. Thus, the axial precision loss can be defined as the ratio of the wear volume to the contact area. Meanwhile, a novel running bench and a precision-measuring system of ball screws are conducted. Precision variation is obtained and analyzed during the whole life running test, which agrees well with the theoretical values calculated in this paper.

For a given rotational speed, the increasing rate of the precision loss rate is high at low axial load and then becomes small with the increasing axial load, whereas for a given axial load, the precision loss rate is proportional to the rotational speed. Besides, the precision loss rate is reduced with the increasing contact angle between a ball and the screw raceway, and is proportional to the helix angle when the angle changes from 1 to 10 degrees.

The rotational speed used in this experiment is low and the ball screw is of no-load type, although results calculated by the model and Wei’s model seem close when the axial load is high, whether the model built in the paper is applicable to the condition of high rotational speed and preload still needs to be verified in the future work.

This study provides an accurate model to predict the precision loss of the screw raceway and estimate the remaining life of ball screws, which is significant for better performance of ball screws as well as the computer numerical control machine tools.

Previous studies on the wear of ball screws mainly focused on the drag torque analysis and mechanical efficiency estimation, and the experiment to verify their theoretical analysis was almost all limited to the test of drag torque or axial rigidity, which is neither sufficient nor persuasive. However, in this paper, the authors proposed a comprehensive wear prediction model which combines the modified Archard wear theory, Hertz contact theory and kinematic theory of ball screws. To the best of the authors’ knowledge, this kind of study has never been reported in the literature. In addition, for the lack of the test bench and high cost of the experiment, the whole life operation test, which is designed and conducted to confirm the model in this paper, has never been reported in literature either.

Current policies and research on carbon emissions focus on operational emission but overlook the importance of embodied and user-transport emissions in residential buildings. This study built a comprehensive framework to assess the impact of life-cycle carbon emissions on different in-building open public spaces (open roof, open vertical garden, and open ground floor) in affordable housing.

A parametric model of a typical affordable housing building in Shanghai, China was constructed and 36 variations of open public spaces studied. Embodied, operational, and user-transport carbon emissions were quantified over 50 years.

The results show that the life-cycle carbon emissions decrease with the application of the open public space. In addition, the paper found that the carbon reduction due to user transport is seven times higher than the carbon increment due to construction and over long-term operation.

This paper provides quantitative evidence for carbon emissions and in-building open public spaces, and the authors suggest taking multiple aspects into account in addition to the structure of the building is crucial to sustainable building development.

In the era of mobile internet, the social Q&A community has built a large-scale and complex knowledge label network through its internal knowledge units, and the scale and structure of the network have changed over time. By analysing the structural characteristics and evolution rules of knowledge label networks, the main purpose of this study is to understand the internal mechanisms of the replacement of old and new knowledge and the expansion of knowledge element boundaries, so as to explore the realization path of knowledge management in the new era from the perspective of complex networks.

This paper uses distributed crawlers to capture 419,349 samples from the Zhihu platform. Each sample contains 33 characteristic dimensions, and the natural year is used as the sliding window to divide the whole. In this study, the global knowledge label network and 11 local knowledge label networks are first constructed. Then, the degree distribution analysis and central node exploration of the knowledge label network are carried out using the complex network method. Finally, the average shortest path and average clustering coefficient of the network are analysed by the time series method, and the ARIMA model is used to predict the evolution of the correlation coefficient.

The research results show that the dissimilation degree of the degree distribution of the knowledge label network has gradually decreased from 2011 to 2021, and the attention of users in the knowledge community has shown a trend of distraction and diversification over time. With the expansion of the scale of the knowledge label network and the transformation to an information network, the network sparsity is becoming more and more obvious, and the knowledge granularity of the Q&A community is being refined and diversified. The prediction of the correlation coefficient of the knowledge label network by the ARIMA model shows that the connection between the labels is lacking diversity and the opinion strengthening phenomenon tends to strengthen, which is more likely to form the “echo chamber effect”, resulting in mutual isolation and even opposition between different circles. The Q&A community is about to enter a mature stage, and the corresponding status of each label has been finalized. The future development trend of label networks will be reflected in the substitution between labels, and the specific structure will not change significantly.

The Q&A community model is the trend in Web 2.0 community development. This study proves the effectiveness of complex networks and time series prediction methods in knowledge label network mining in the Q&A community.

This study aims to identify the prominent topics, the distribution and association characteristics of topics and the topic evolutionary trends of Documentary Heritage Preservation and Conservation (DHPAC) research in China.

Keywords of relevant papers in China National Knowledge Infrastructure (CNKI) were extracted as the data source in this study. First, frequency and co-occurrence of keywords of the selected papers were obtained by using SATI. Second, co-word network indicators were calculated with the Pajek software. Then, VOSviewer was applied to optimize the visualization of the sub-communities. Finally, a topics evolution map of this research field was implemented by CorTexT.

The research topics of DHPAC research in China were unbalanced but distinct. Topics of DHPAC research in China possessed inconspicuous orientation and consistency. The core topics had less influence on the overall network. A research system had formed with archival conservation and ancient books conservation as the core research directions. Research in this field had formed four continuous evolutionary paths about ancient books conservation, salvage conservation, archival conservation and archives conservation technology science with topics fusion and differentiation coexisting. Attentions on “ancient books conservation”, “paper relics conservation”, “electronic record”, “digitization”, “minority”, “documents in the republic of China” had increased during the past two decades and new hot topics of DHPAC research kept appearing in China.

This study synthesized and analyzed the research results of DHPAC research in China from a more comprehensive perspective and revealed the topic structure and longitudinal evolution process intuitively with co-word analysis and social network analysis, which can assist researchers to improve research systematization, discover new research directions and seek cooperative research path.

Consideration needs to be given to the difference [that] the diversity of cities makes to theory.Robinson (2002, p. 549)