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Three new types of acoustic insulation facilities, namely, full-enclosed (FEAB), bilateral-inverted-L-shaped (BILSAB), and inverted-L-shaped (ILSAB) acoustic barriers, are gradually receiving application along high-speed railways. A moving high-speed train (HST) may induce a nonlinear aerodynamic impact on the acoustic barrier. The HST may also experience a rapid change in its aerodynamic loads, reducing its stability and causing discomfort to passengers. Hence, nonlinear aerodynamic effects of three new types of high-speed railway acoustic insulation facilities when an HST passes by are compared based on model experiments and improved delayed detached eddy simulations (IDDES). Results show that: (i) When a HST runs at 350 km/h, the coefficient of pressure difference on the FEAB is 5.64 and 8.78 times higher than in the BILSAB and ILSAB, respectively. (ii) The amplitude of drag force coefficient of the head car when entering the FEAB is 2.80 and 2.95 times that of the BILSAB and ILSAB, respectively. The amplitude of lift coefficient of the tail car when running through the BILSAB is 1.27 and 1.37 times that of the FEAB and ILSAB. The amplitude of side force coefficient of the tail car when running through the ILSAB is 1.18 and 1.24 times that of the FEAB and BILSAB. (iii) For the tail car, the standard deviation of Cx when running inside the FEAB is 2.18 and 2.15 times that of the BILSAB and ILSAB, respectively. The standard deviation of Cy when running inside the FEAB is 1.42 and 1.51 times that of the BILSAB and ILSAB, respectively. The standard deviation of Cy when running inside the FEAB is 1.48 and 1.15 times that of the BILSAB and ILSAB, respectively. The results of this research may provide reference value for optimizing the structural patterns and improving the train's operating stability. [ABSTRACT FROM AUTHOR]

Competition in digital game-based learning (DGBL) is tantamount to a double-edged sword, because it not only improves students' learning performance, but may also cause them psychological stress. Therefore, researchers focus on collaboration, for it can mitigate the negative effect of competition. However, studies on the correlations among competition, collaboration, and learning performance in DGBL remain wanting so far. To remedy this deficiency, this study developed a question bank practice game which offers a situation of intergroup competition with intragroup collaboration, and devised a research model to investigate the correlations among competition, collaboration, and learning performance in DGBL. The research findings of this study indicated that: (1) perceived competition is a factor more significant than perceived collaboration behind learning performance, in which perceived competition directly affects perceived collaboration; (2) perceived competition not only directly affects behavioral intention, but also indirectly influences it via perceived enjoyment, whereas perceived collaboration simply has indirect influence on behavioral intention through perceived usefulness; and (3) behavioral intention directly influences learning performance. These research findings showed that the combination of competition and collaboration indeed influences students' learning performance in DGBL, and competition occupies the most crucial role. This is because the pleasure brought by competition strongly prompts students to engage in DGBL, which in turn influences their learning performance in DGBL. Meanwhile, competition also facilitates students' collaboration, from which they benefit personally in terms of learning. [ABSTRACT FROM AUTHOR]

Classroom community in higher education benefits students' learning because it can soothe students' anxiety about isolation. However, only a small number of studies investigated the key factors behind the cohesion of a classroom community. It is a vital issue because previous studies have pointed out that cohesion is crucial for the survival of a community. Against this background, this study developed a research model that incorporates social presence and social capital, so as to identify the decisive factors behind the cohesion of a classroom community. Our research findings demonstrated that social presence plays a pivotal role in affecting the cohesion of a classroom community. The former not only directly influenced the latter, but also affected it indirectly via structural and relational social capital. This result implies that increasing the interaction among community members (e.g. engaging them in discussion rather than allowing them to ignore read messages) is the first priority if we are going to alleviate students' anxiety about isolation with classroom community. As students' interaction increases, their social ties and mutual trust will become stronger, and their cohesion will be strengthened as well. [ABSTRACT FROM AUTHOR]

We investigate gravitational collapse of a spherically symmetric thin shell in the Einstein–Gauss–Bonnet (EGB) gravity. Under the recently proposed 4D limit, we find that the collapsing shell will be bounced back at a small radius, without forming a singularity. This bouncing behavior is similar to those of a test particle and a homogeneous spherical dust star, in accordance with the expectation that the Gauss–Bonnet term will modify the small scale behavior of the Einstein gravity. We analyze the causal structure of the dynamic spacetime that represents the bouncing process, finding that the thin shell has an oscillation behavior on the Penrose diagram, which means that the thin shell results in a novel type of black hole with respect to observers outside the event horizon that the collapse forms. We also find that the weak cosmic censorship conjecture holds in this model. Further implications of such a regular gravitational collapse are discussed. [ABSTRACT FROM AUTHOR]

Middle-aged adults have a stronger sense of urgency about health apps that not only enhance their health management but also help them administer self-treatment. However, middle-aged adults' attitudes toward health app usage have received surprisingly little scholarly attention, which has hampered the promotion of this kind of apps among them. To remedy this deficiency, this research specifically investigated this vital issue and presents findings contributory to promoting health apps. Our research findings indicated that (1) middle-aged adults with no health management habit tend to find health apps valuable and get a favorable impression about them, while those who already have the habit do not; (2) most middle-aged adults do not decide to use health apps out of sentimental reasons; and (3) middle-aged adults' confidence in using smartphones significantly influences their cognitive evaluation of health apps. In sum, these research findings suggested that middle-aged adults look at health apps in a non-affective manner, and their confidence in using smartphones facilitates their use of health apps. [ABSTRACT FROM AUTHOR]

To fully utilize the resources of heterogeneous cellular networks (HCNs), an effective approach that offloads users to the underloaded small cells from overloaded macrocells is widely advocated. However, this operation often leads to a bad result that the offloaded users achieve lower signal-to-interference-plus-noise-ratio (SINR) than these users in macrocells. Thus, some appropriate interference avoidance techniques should be adopted to partially alleviate the SINR degradation. For this, we consider the resource (frequency) partitioning that turns off some fraction of such resources in a macrocell. Naturally, an optimal offloading strategy should be closely coupled with resource partitioning, and in turn the optimal partition decides the offloading performance. In this paper, we propose a distributed association strategy with joint offloading and resource partitioning for HCNs. We reveal that load balancing, by itself, is insufficient, and additional resource partitioning is required to improve system performance. Meanwhile, we also show that, compared with the best power association and range extension association, the proposed scheme provides better association performance. [ABSTRACT FROM AUTHOR]

Computer supported cooperative learning (CSCL) has attained considerable attention in recent years, but most CSCL systems do not consider ways of supporting learners in finding appropriate learning companions. In this study, we propose an intelligent learning companion recommendation mechanism ( ILCRM) to deal with this problem. Specifically, ILCRM comprises three agents: (i) a candidate retrieval agent ( CRA), (ii) a candidate evaluation agent ( CEA), and (iii) a GA- based learning companion composition agent ( GLCCA). The CRA and CEA are used to search a series of learning companion candidates based on two criteria (expertise level and participation level), and the GLCCA is employed to compose an appropriate cooperative group in which group members could be able to help learners solve the problems they face. The experimental results show that the proposed approach obtains a near optimal learning companion recommendation, has a significantly low computational cost, and satisfies the specified demands. [ABSTRACT FROM AUTHOR]

Vocabulary is the foundation for students who learn a foreign language. Nevertheless, students may be bored by the painstaking process of rote learning. To this end, this study designed a handheld sensor-based vocabulary game based on a scaffolding strategy for improving students' motivation and achievement in vocabulary learning. On the one hand, such mobile technologies not only help students learn vocabulary anytime and anywhere, but also create embodied learning experiences by allowing students to control the avatar in the game with their hands. On the other hand, the scaffolding strategy adopted in this study serves as a complementary mechanism to help students learn vocabulary. To evaluate the effectiveness of the game, this study conducted a quasi-experiment by dividing the participating students into an experimental group and a control group. The former played the handheld sensor-based vocabulary game based on the scaffolding strategy, while the latter played the same game without the assistance of the scaffolding strategy. The research findings of this study showed that the handheld sensor-based vocabulary game significantly improved the low-achieving students' motivation and performance in vocabulary learning, but seemed to be less effective in helping them retain the vocabulary they learned through the game. [ABSTRACT FROM AUTHOR]

While computer simulations have been shown to be effective with regard to supporting learning, little effort has been made to explore the factors that affect the intention to use such tools. This paper applies the technology acceptance model and examines two external variables, facilitating conditions and computer self-efficacy, testing a number of hypotheses. The results show that most of the hypotheses the authors developed before the study were supported by the data collected, and further reveal that perceived usefulness is the most important determinant of student intention to use a computer simulation, followed by attitude toward using and computer self-efficacy. Finally, both the implications and limitations of this study are discussed, and further research directions are proposed. [ABSTRACT FROM AUTHOR]

In heterogeneous cellular networks (HCNs), it is desirable that users in macrocells should be offloaded to small cells with less congested traffic. However, these offloaded users often have lower signal-to-interference-plus-noise-ratio (SINR) than them in macrocells. The degradation of SINR can be partially alleviated by adopting interference avoidance techniques, such as resource partitioning, whereby the macrocell lets some fraction of such resources be unavailable. Naturally, an optimal offloading scheme should be tightly coupled with resource partitioning; the optimal partition in turn decides the number of offloaded users. Moreover, in order to reduce the call blocking probability of users, we need to consider their quality of service (QoS) requirements. Thus, in this paper, we propose a distributed QoS-aware strategy with joint offloading and resource partitioning for HCNs. We reveal that load balancing, by itself, is insufficient, and additional resource partitioning should be considered to reduce the call blocking probability. Meanwhile, we also show that compared with the best power association and range expansion association, the proposed scheme has more obvious superiorities over call blocking probability. [ABSTRACT FROM AUTHOR]

The volatilization of stibnite (SbS) in nitrogen from 700 to 1000 °C was investigated by using thermogravimetric analysis. The results indicate that in inert atmosphere, stibnite can be volatilized most efficiently as SbS (g) at a linear rate below 850 °C, with activation energy of 137.18 kJ/mol, and the reaction rate constant can be expressed as k=206901exp(−16.5/ T). Stibnite can be decomposed into Sb and sulfur at temperature above 850 °C in a nitrogen atmosphere. However, in the presence of oxygen, stibnite is oxidized into Sb and SO gas at high temperature. Otherwise, Sb is oxidized quickly into antimony oxides such as SbO and SbO, while SbO can be volatilized efficiently at high temperature. [ABSTRACT FROM AUTHOR]

Mechanisms of arbuscular mycorrhiza (AM)-induced lower oxidative burst of host plants under drought stress (DS) are not elucidated. A noninvasive microtest technology (NMT) was used to investigate the effects of Funneliformis mosseae on net fluxes of root hydrogen peroxide (HO) and calcium ions (Ca) in 5-month-old Poncirus trifoliata, in combination with catalase (CAT) and superoxide dismutase (SOD) activities as well as tissue superoxide radical (O) and HO concentrations under DS and well-watered (WW) conditions. A 2-month DS (55 % maximum water holding capacity of growth substrates) significantly inhibited AM fungal root colonization, while AM symbiosis significantly increased plant biomass production, irrespective of water status. F. mosseae inoculation generally increased SOD and CAT activity but decreased O and HO concentrations in leaves and roots under WW and DS. Compared with non-AM seedlings, roots of AM seedlings had significantly higher net HO effluxes and net Ca influxes, especially in the meristem zone, but lower net HO efflux in the elongation zone. Net Ca influxes into roots were significantly positively correlated with root net HO effluxes but negatively with root HO concentrations. Results from this study suggest that AM-induced lower oxidative burst is related with higher antioxidant enzyme activities, root net HO effluxes, and Ca influxes under WW and DS. [ABSTRACT FROM AUTHOR]