Full-feedback contention window adaption for IEEE 802.11 WLANs

Backoff mechanism is a key component of contention-based medium access control（MAC） layer protocol.It has been shown that the backoff mechanism of IEEE 802.11 standard may be very inefficient especially when the network is congested.Numbers of methods have been proposed to tune the contention window（CW） with the aim to achieve the optimal throughput in IEEE 802.11 WLANs.However,the mechanisms do not specifically address proper settings for the variable packet length influence and CW diverging problem.This paper proposes a novel four-way handshaking full-feedback backoff algorithm named adoptive contention window backoff（ACWB） to overcome these drawbacks.The performance of the proposed algorithm is investigated through analysis and simulation.Simulation results demonstrate that the ACWB algorithm provides a remarkable performance improvement in terms of short-term fairness,packet delay and delay jitter,while maintaining an optimal throughput close to the theoretical throughput limit of the IEEE 802.11 distributed coordination function（DCF） access scheme.

Root length density distribution and associated soil water dynamics for tomato plants under furrow irrigation in a solar greenhouse

Furrow irrigation is a traditional widely-used irrigation method in the world. Understanding the dynamics of soil water distribution is essential to developing effective furrow irrigation strategies, especially in water-limited regions. The objectives of this study are to analyze root length density distribution and to explore soil water dynamics by simulating soil water content using a HYDRUS-2D model with consideration of root water uptake for furrow irrigated tomato plants in a solar greenhouse in Northwest China. Soil water contents were also in-situ observed by the ECH_2O sensors from 4 June to 19 June and from 21 June to 4 July, 2012. Results showed that the root length density of tomato plants was concentrated in the 0–50 cm soil layers, and radiated 0–18 cm toward the furrow and 0–30 cm along the bed axis. Soil water content values simulated by the HYDRUS-2D model agreed well with those observed by the ECH_2O sensors, with regression coefficient of 0.988, coefficient of determination of 0.89, and index of agreement of 0.97. The HYDRUS-2D model with the calibrated parameters was then applied to explore the optimal irrigation scheduling. Infrequent irrigation with a large amount of water for each irrigation event could result in 10%–18% of the irrigation water losses. Thus we recommend high irrigation frequency with a low amount of water for each irrigation event in greenhouses for arid region. The maximum high irrigation amount and the suitable irrigation interval required to avoid plant water stress and drainage water were 34 mm and 6 days, respectively, for given daily average transpiration rate of 4.0 mm/d. To sum up, the HYDRUS-2D model with consideration of root water uptake can be used to improve irrigation scheduling for furrow irrigated tomato plants in greenhouses in arid regions.

Hydration Mechanism of Cement-based Materials with Different Si-rich Mineral Admixtures

Early hydration mechanism of cement-based materials with silica fume, nano-SiO2 and silica sol of different contents was investigated, and the detailed effect of these Si-rich mineral admixtures in three stages of early hydration（NG, I, D） using kinetics model was focused. The results showed that silica fume, nano-SiO2, and silica sol have significant effect on kinetic parameters n, k1, k2 and k3, the fineness and existing form of SiO2 particles in these Si-rich mineral admixtures are two important factors to affect the hydration process and on the parameters. Through integrated use of methods of hydration heat-Krstulovic-Dabic Modelsynthetical thermal analysis, data of hydration heat were collected, hydration degree was characterized, as well as the resulting crystallization behavior of early hydration, to build a numerical relationship between parameter n and CH contents that n decreases with increasing CH, and thus, a direct connection between hydration heat release behavior and crystallization behavior has been established.

Deconstructing Socially Constructed Subtle Prejudices During the First Wave of Covid-19 Pandemic Among Immigrant Population in Finland

The research work is based on random web-based open survey from targeted immigrant’s social media groups targeting 30 eligible male and female immigrants living in Finland during the first wave of coronavirus pandemic.The data were collected through online data collection tools to comply with the safety guidelines during the survey period.The analysis of gathered information illuminates the subtle alienation of immigrants through the information and communication channels,and deconstructs the Finnish government interventions in the midst of a pandemic through the socially constructed lenses of inclusion and justice in Finland.The survey reveals the knowledge,attitudes,and perceptions held by and of immigrants by the immigrants towards the authorities in Finland.Grounded theory is applied to qualitatively analyze data.The analysis is anchored on the stereotype content model to reveal the subtle historical and systemic alienation through information and communication channels.The theory of prejudice and the theory of symbolic racism are complimentarily used to deconstruct the injustice meted against the immigrants resulting in alienation through official authority practices and socially constructed disguises of inclusivity and justice by the Finnish society.

What will I be like at eighty? How human values contribute to expected real and ideal self-images in old age in a Germanic/Austrian cultural context

According to Grawe’s Consistency Theory, congruence between an individual’s aims and reality is fundamental for psychological health. We examined the real and ideal self-images of N = 440 participants in a Germanic/Austrian cultural context as perceived in presence and as anticipated for an age of 80 years and examined their relationship to value orientations as a coping resource. From adjective ratings on the Semantic Differential for the real self-image at presence, two dimensions were extracted, one representing Warmth (W) and one representing Competence (C) in the sense of the Stereotype Content Model. Cluster analysis yielded one type of respondents with a cautiously optimistic, and one with a moderately pessimistic view of the present and the future. A third cluster devalued W and C in favor of Religiosity and Conservatism and had the highest degree of congruence between real and ideal self-images. Thus, hypotheses with regard to Religiosity and Conservatism as coping resources were confirmed.

Joint model of user check-in activities for point-of-interest recommendation

With the rapid development of location-based networks, point-of-interest（POI） recommendation has become an important means to help people discover interesting and attractive locations, especially when users travel out of town. However, because users only check-in interaction is highly sparse, which creates a big challenge for POI recommendation. To tackle this challenge, we propose a joint probabilistic generative model called geographical temporal social content popularity（GTSCP） to imitate user check-in activities in a process of decision making, which effectively integrates the geographical influence, temporal effect, social correlation, content information and popularity impact factors to overcome the data sparsity, especially for out-of-town users. Our proposed the GTSCP supports two recommendation scenarios in a joint model, i.e., home-town recommendation and out-of-town recommendation. Experimental results show that GTSCP achieves significantly superior recommendation quality compared to other state-of-the-art POI recommendation techniques.