Enhancing Hybrid OSS Development Through Agile Methods and High Media Synchronicity

Open source software (OSS) is increasingly being developed by hybrid teams that consist of a mix of company employees and volunteer developers. While hybrid OSS teams are becoming more prevalent, they also face unique challenges due to the involvement of different constituents. To address those challenges, this paper develops and validates a new organizing model. Specifically, the paper draws on media synchronicity theory (MST) to theorize that hybrid OSS teams would benefit from adopting an organizing model that involves practicing agile methods and using communication tools with multiple symbols sets and high transmission velocity. The paper also extends MST by conceptualizing the theory's key concept of communication convergence as consisting of two distinct dimensions: affective and cognitive convergence. Using primary survey data from hybrid OSS teams, the paper presents empirical evidence that such an organizing model can enhance those teams' affective convergence and cognitive convergence and, in turn, their development productivity and the quality of the software. In addition, the results show that affective convergence has a stronger impact on hybrid OSS teams' performance than cognitive convergence.

Application of Nondestructive Testing Technologies in Preserving Historic Trees and Ancient Timber Structures in China

In China, preserving historic trees and ancient timber structures has attracted more attention from researchers and institutions. Nondestructive testing (NDT) technology has gained momentum in the application and research in recent years. This paper presents some examples of the application of NDT techniques in the protection of historic trees and ancient timber structures in China. A total of nine NDT techniques were applied, including five techniques of visual inspection, sounding, Resistograph, stress wave transmission velocity, stress wave tomography for both historic trees and ancient timber structures, two techniques of the pulling-test and ground-penetrating radar (GPR) for historic trees alone, and two techniques of acoustic emission (AE) and digital imaging for ancient timber structures. Based on field testing, there is a very good detecting effect for visual inspection and Resistograph, but sounding works unsatisfactorily. The stress wave transmission velocity is found to be excellent in screening for the internal defects of historic tree trunks, but performs badly in screening for the internal defects within the wood members of ancient timber structures. AE is less successful but digital imaging performs well in long-term monitoring and damage warning of wood structures. The stress wave tomography successfully obtains images of internal defects inside tree trunks. The anchorage of some historic trees cannot be quantitatively evaluated with the pulling test if the tree is too large. GPR’s resolution and accuracy are very low, which limit its application. Theoretical research on NDT and promotion of NDT technology are still an essential part of the work in the future.

Historical and genomic data reveal the influencing factors on global transmission velocity of plague during the Third Pandemic

Quantitative knowledge about which natural and anthropogenic factors influence the global spread of plague remains sparse. We estimated the worldwide spreading velocity of plague during the Third Pandemic, using more than 200 years of extensive human plague case records and genomic data, and analyzed the association of spatiotemporal environmental factors with spreading velocity. Here, we show that two lineages, 2.MED and 1.ORI3, spread significantly faster than others, possibly reflecting differences among strains in transmission mechanisms and virulence. Plague spread fastest in regions with low population density and high proportion of pasture- or forestland, findings that should be taken into account for effective plague monitoring and control. Temperature exhibited a nonlinear, U-shaped association with spread speed, with a minimum around 20 °C, while precipitation showed a positive association. Our results suggest that global warming may accelerate plague spread in warm, tropical regions and that the projected increased precipitation in the Northern Hemisphere may increase plague spread in relevant regions.

Comparison of Ordinary Pores with Internal Cured Pores Produced by Superabsorbent Polymers

Porous cementitious mixtures were prepared with two different spherical particles: expanded polystyrene (EPS) and superabsorbent polymer (SAP). The effect of EPS and SAP on the compressive strength, ultrasonic transmission, internal relative humidity and hydration degree under different volume fraction were studied. Results indicated that SAP matrix possessed much higher compressive strength (30-60%, 28d), ultrasonic transmission velocity, internal humidity (11-13%RH, 28d) and hydration degree (13-21%, 28d) than EPS matrix, which indicated that the desorption of SAP accelerated the hydration and increased the compactness of the surrounding cement paste. The internal cured pores left by SAP might have been strengthened which was different from ordinary pores produced by EPS.

Research on Fluid Transmission Performance of Propellant Acquisition Vane Under Microgravity Environment

Propellant acquisition vane (PAV) is a key part of vane type surface tension tank (STT) and is mostly used to transmit fluid under microgravity environment, its transmission performance will determine fluid management of STT. In present paper, a ribbon type PAV with hems on both sides is conceptually designed, and its transmission performance has been analyzed based on four configuration parameters of its section form, which are flat part breadth, hems’ height, hems’ angle and separation distance between PAV and inner wall of STT. The laws of the effects of four configuration parameters on PAV’s transmission performance have been obtained and a set of most optimized configuration parameters has been given. Then transmission performance of the PAV whose configuration parameters of section form are the set of optimized parameters has been studied in-depth. Our results revealed that the optimized PAV is able to meet orbital demand of gas-free propellant completely during the end of STT’s life under harsh microgravity environment. On the basis of analyzed laws, microgravity environment has been conducted by the hundred meters drop tower tests, so the model test system with PAV is established and the campaigns have as objective to test the PAV’s fluid transmission performance under axial and lateral acceleration conditions. All these analyses and tests have been successfully conducted to demonstrate fluid transmission performance of such a PAV. According to present research, PAV with different section forms influences fluid transmission performance of STT remarkably. Thus, it is an effective way to control liquid transmission velocity by reasonably design of section form of PAV. Present research can not only provide a guideline for optimized design of new-style vane type fluid management assembly, but also present a new way for liquid control in space environment.

Effect of Pre-reacted Glass-ionomer Filler Extraction Solution on Demineralization of Bovine Enamel

SUMMARY Objective To determine the effect of pre-reacted glass-ionomer (PRG) filler extraction solution on the demineralization of bovine enamel by measuring changes in the ultrasound transmission velocity. Methods The specimens were prepared by cutting bovine teeth into enamel blocks. The specimens were immersed in buffered lactic acid solution for 10 minutes twice a day, and then stored in artificial saliva. Other specimens were stored in PRG filler extraction solution for 10 minutes, followed by 10-minute immersion in the buffered lactic acid solution twice a day. The propagation time of longitudinal ultrasonic waves was measured by a pulser receiver. Six specimens were used for each condition, and analyses of variance followed by Tukey tests (α=0.05) were done. Results No changes in sonic velocity were found for specimens stored in the PRG filler extraction solution, indicating that the PRG extraction solution had an effect on inhibiting the demineralization of bovine enamel. Conclusions The results obtained with the use of an ultrasound measurement technique suggested that PRG filler extraction solution has the ability to prevent demineralization of enamel.