ALBERT

Description: Due to their design, hollow cavity and filled sodium, hollow head and sodium filled engine valves (HHSVs) have superior performance to traditional solid valves in terms of mass and temperature reduction. This paper presents a new manufacturing method for 42Cr9Si2 steel hollow head and sodium filled valves. An inertia friction welding process parameter optimization was conducted to obtain a suitable process parameter range. The fatigue strength of 42Cr9Si2 steel at elevated temperatures was evaluated by rotating bending fatigue test with material specimens. Performance evaluation tests for real valve components were then carried out using a bespoke bench-top apparatus, as well as a stress evaluation utilizing a finite element method. It was proved that the optimized friction welding parameters of HHSV can achieve good welding quality and performance, and the HHSV specimen successfully survived defined durability tests proving the viability of this new method. The wear resistance of the HHSV specimens was evaluated and the corresponding wear mechanisms were found to be those classically defined in automotive valve wear.

Description: Adding fibers is highly effective to enhance the deflection and ductility of fiber-reinforced polymer (FRP)-reinforced beams. In this study, the stress and strain conditions of FRP-reinforced lightweight aggregate concrete (LWC) beams with and without fibers at ultimate load level were specified. Based on the sectional analyses, alternative equations to predict the balanced reinforcement ratio and flexural capacity for beams failed by balanced failure and concrete crushing were established. A rational equation for estimating the short-term stiffness of FRP–LWC beams at service-load levels was suggested based on Zhu’s model. In addition, the contribution of the steel fibers on the short-term stiffness was quantified incorporating the effects of FRP reinforcement ratio. The proposed short-term stiffness model was validated with measured deflections from an experimental database for fiber-reinforced normal weight concrete (FNWC) beams reinforced with FRP bars. Furthermore, six glass fiber-reinforced polymer (GFRP)-reinforced LWC beams with and without steel fibers were tested under four-point bending. Based on the test results, the proposed models and procedures according to current design codes ACI 440.1R, ISIS-M03, GB 50608, and CSA S806 were linked together by comparing their predictions. The results showed that increasing the reinforcement ratio and adding steel fibers decreased the strain of the FRP bars. The flexural capacity of the LWC beams with and without steel fibers was generally underestimated by the design codes, while the proposed model provided accurate ultimate moment predictions. Moreover, the proposed short-term stiffness model yielded reasonable estimations of deflection for both steel fiber-reinforced lightweight aggregate concrete (SFLWC) and FNWC beams.

Description: This paper presents a novel indoor topological localization method based on mobile phone videos. Conventional methods suffer from indoor dynamic environmental changes and scene ambiguity. The proposed Visual Landmark Sequence-based Indoor Localization (VLSIL) method is capable of addressing problems by taking steady indoor objects as landmarks. Unlike many feature or appearance matching-based localization methods, our method utilizes highly abstracted landmark sematic information to represent locations and thus is invariant to illumination changes, temporal variations, and occlusions. We match consistently detected landmarks against the topological map based on the occurrence order in the videos. The proposed approach contains two components: a convolutional neural network (CNN)-based landmark detector and a topological matching algorithm. The proposed detector is capable of reliably and accurately detecting landmarks. The other part is the matching algorithm built on the second order hidden Markov model and it can successfully handle the environmental ambiguity by fusing sematic and connectivity information of landmarks. To evaluate the method, we conduct extensive experiments on the real world dataset collected in two indoor environments, and the results show that our deep neural network-based indoor landmark detector accurately detects all landmarks and is expected to be utilized in similar environments without retraining and that VLSIL can effectively localize indoor landmarks.

Description: To address the low performance of health care service delivery in the half-market system, the Chinese government has begun to advocate the medical alliance (MA) recently. Instead of strict regulations on the procedure of diagnosis and treatment, flexible resource sharing among medical institutions of different grades inside each MA is encouraged. By now, many attempts have been made for MA establishment from different perspectives, but there is no effective model maturely developed. For the promotion of the spatial accessibility to medical services at different levels, it is important to organize the hierarchial medial services according to the distributions of different grades of health care facilities in a city. With the city proper of Tianjin as the study case, we explored the optimal establishment of MAs using the geographic information system (GIS). By means of the Voronoi Diagrams, the service regions of different medical institutions were precisely defined and the organizational structure of hierarchical medical services in MAs was determined. Through interpolation analysis, accessibility to different levels of medical services was measured, and on this basis, discussions were conducted on the service efficiency of the MAs. According to the results from Tianjin, (1) under the proposed organizational model for MAs, the fit of the service regions of the first grade and the other two higher grades of medical institutions was good. but the fit of the second and the third grade medical institutions was insufficient. (2) Although the overall service efficiency was excellent, there were still deficiencies in a number of the MAs. (3) Increasing the number of second and third grade medical institutions in specific regions near the city’s edge, as well as the number of first grade institutions, could further improve the performance of hierarchical medical services.

Description: There is an urgent need to monitor the structural state of composite bolted joints while still remaining in service; however, there are many difficulties in analyzing their strength and failure modes. In this paper, a built-in distributed eddy current (EC) sensor network based on EC array sensing film is developed to monitor the hole-edge damages of composite bolted joints. The EC array sensing film is bonded onto the bolt and consists of one exciting coil and four separate sensing coils. Experiments are conducted on unidirectional composite specimens to validate the ability of the EC array sensing film to quantitatively track the damage that occurs at the hole edge and to investigate the performances of the EC array sensing films with different configurations of the exciting coil. Experimental results show that the induced voltage of sensing coil changes only if the damage appears on the laminate structure where that particular sensing coil is located, whereas the induced voltages of the other sensing coils on other laminate plates remain unchanged. Numerical simulation based on the finite element method is also carried out to investigate and explain the phenomena observed in the experiments and to analyze the distribution of the EC around the bolt hole. Both experimental and numerical simulation results demonstrate that the developed EC array sensing film can effectively identify not only whether there is damage at the hole edge but also the damage location within the thickness and quantitative size.

Description: The contemporary sustainable development imperative sees enterprises seeking competitive advantages in innovation networks, the distinguishing features of which are continuous interaction and knowledge flow between participants. As an informal governance mechanism, cooperative culture influences the stability and durability of the members’ interactions. Knowledge flow is a core network activity that is highly dependent on the cultural environment. The purpose of this paper is to explore whether innovation governance performance is affected by cooperative culture and knowledge flow. How do they play an influential role? We use structural equation modeling (SEM) to analyze the linear relationships among the three variables: cooperative culture, knowledge flow, and governance performance. The results suggest that knowledge flow has a mediating effect on the relationship between cooperative culture and governance performance. We also use fuzzy set qualitative comparative analysis (fsQCA) to explore how cooperative culture and knowledge flow combined can influence governance performance. The results indicate that different combinations of cooperative culture and knowledge flow lead to different levels of governance performance, with two paths leading to high governance performance, which are fit creation-oriented and compatible sharing-oriented paths. These findings have significant implications for improving innovation governance performance and their sustainable development.

Description: Flow-induced energy harvesting has attracted more and more attention among researchers in both fields of the wind and the fluid. Piezoelectric energy harvesters and triboelectric nanogenerators are exploited to obtain superior performance and sustainability, and the electromagnetic conversion has been continuously improved in the meantime. Aiming at different circumstances, researchers have designed, manufactured, and tested a variety of energy harvesters. In this paper, we analyze the state-of-the-art energy harvesting techniques and categorize them based on the working environment, application targets, and energy conversion mechanisms. The trend of research endeavors is analyzed, and the advantages, existing problems of energy harvesters, and corresponding solutions of energy harvesters are assessed.