No abstract

Extending research on voluntary turnover in the team setting, this study adopts a multilevel self-determination theoretical approach to examine the unique roles of individual and social-contextual motivational precursors, autonomy orientation and autonomy support, in reducing team member voluntary turnover. Analysis of multilevel time-lagged data collected from 817 employees on 115 teams indicates that psychological empowerment mediates the main effect of autonomy orientation and the interactive effect of autonomy support and its differentiation on a team member's voluntary turnover. The findings have meaningful implications for the turnover and self-determination literatures as well as for managers who endeavor to prevent voluntary turnover in teams.

System security monitoring has become more and more difficult with the ever-growing complexity and dynamicity of the Internet of Things (IoT). In this paper, we develop an Intelligent Maintenance and Lightweight Anomaly Detection System (IMLADS) for efficient security management of the IoT. Firstly, unlike the traditional system use static agents, we employ the mobile agent to perform data collection and analysis, which can automatically transfer to other nodes according to the pre-set monitoring task. The mobility is handled by the mobile agent running platform, which is irrelevant with the node or its operation system. Combined with this technology, we can greatly reduce the number of agents running in the system while increasing the system stability and scalability. Secondly, we design different methods for node level and system level security monitoring. For the node level security monitoring, we develop a lightweight data collection and analysis method which only occupy little local computing resources. For the system level security monitoring, we proposed a parameter calculation method based on sketch, whose computational complexity is constant and irrelevant with the system scale. Finally, we design agents to perform suitable response policies for system maintenance and abnormal behavior control based on the anomaly mining results. The experimental results based on the platform constructed show that the proposed method has lower computational complexity and higher detection accuracy. For the node level monitoring, the time complexity is reduced by 50% with high detection accuracy. For the system level monitoring, the time complexity is about 1 s for parameter calculation in a middle scale IoT network.

No abstract

The remarkable characteristics of the silent flight of owls provide infinite inspiration for the low-noise operation of the rotating impeller machinery. However, how the characteristics of owl wings, including the leading-edge serrations, trailing-edge serrations, and plumed surfaces, affect the aerodynamic noise has not been studied comprehensively. According to previous research, the noise reduction level of an airfoil with an extensive sinusoidal profile is limited to a certain degree. In this paper, as a new coupling element, the surface ridge of owl wings is added to the airfoils with leading-edge serrations. Based on the NACA0012 (National Advisory Committee for Aeronautics) airfoil, the bionic airfoils with sinusoidal, serrated, and iron-shaped leading-edge serrations and surface ridges are reconstructed and studied to reveal the noise reduction mechanism of the coupled elements. The hybrid numerical method of large eddy simulation combined with the acoustic analog equations is adopted to predict the far-field acoustic characteristics. The vortex dynamic method is used to exposit the noise reduction mechanism of biomimetic flow control. The results demonstrate that the airfoil with iron-shaped leading-edge serrations has the best effect of noise reduction. Relative to the original airfoil, the sound pressure level is reduced by 14.3 dB. The change of streamwise vortices caused by the biomimetic structures leads the regular large-scale tubular vortices to separate into smaller horseshoe vortices. In addition, the correlation coefficient of spanwise is reduced, and the change of time-averaged vorticity in the space field promotes the attenuation effect of sound source caused by sound pressure fluctuation radiation.

Ceramic nanofibrous nanostructure-based sponges have attracted significant attention due to ultrahigh porosity, low thermal conductivity, large specific area, and chemical stability. From the regulation of the fiber itself to the construction method of 3D networks, efforts are being made to improve the mechanical properties of ceramic sponges for practical applications. So far resilient compressibility has been realized in ceramic nanofibrousbased sponges via structural design, but they still show brittle fracture under a more complex stress state. Herein, we introduced a highly aligned and interwoven Si 3 N 4 nanofiber sponge, which exhibits superflexibility, large break elongation (>80%), large-strain reversible stretch (20%), and good resistance to tensile fatigue. The ceramic sponge also displays reversible compressibility up to 60% strain, puncture resistance, high air filtration efficiency (>99.8%), and low pressure drop (38% of cotton fiber), making the ceramic sponge a high-performance wearable respirator to protect us from harm due to PM 2.5 pollution and possible microorganisms.

Ion implantation is widely utilized in microelectromechanical systems (MEMS), applied for embedded lead, resistors, conductivity modifications and so forth. In order to achieve an expected device, the principle of ion implantation must be carefully examined. The elementary theory of ion implantation including implantation mechanism, projectile range and implantation-caused damage in the target were studied, which can be regarded as the guidance of ion implantation in MEMS device design and fabrication. Critical factors including implantations dose, energy and annealing conditions are examined by simulations and experiments. The implantation dose mainly determines the dopant concentration in the target substrate. The implantation energy is the key factor of the depth of the dopant elements. The annealing time mainly affects the repair degree of lattice damage and thus the activated elements’ ratio. These factors all together contribute to ions’ behavior in the substrates and characters of the devices. The results can be referred to in the MEMS design, especially piezoresistive devices.

To assess whether and to what extent the anti-poverty relocation and settlement program (APRSP) in China will be able to resolve the development dilemma of ecosystem conservation and human wellbeing, it is important to study the effects of policy on rural households in terms of the income generation from ecosystem services (ES). We constructed an index of dependence on ecosystem services (IDES) to evaluate the dependence of households’ net income generation on ecosystem services. Using data collected from South Shaanxi Province, we examined the effects of the relocation program on rural households’ IDES. We find that this relocation may benefit the ecosystem by significantly decreasing participants’ IDES. Relocation households have higher net incomes than non-relocation households from total ecosystem services, provisioning services, regulating services, and cultural services as well as socio-economic activities. There are significant differences in IDES between groups with different relocation and resettlement characteristics. The anti-poverty relocation program optimized the rural households’ income structure by increasing the proportion of income from socio-economic activities while reducing the proportion of income from ecosystem services. This study provides new evidence for evaluating eco-conservation and development policies by linking ecosystem services and human well-being at a micro scale. We also address the policy implications of our analysis for anti-poverty relocation programs.