Improving Efficiency of Heterogeneous Wi-Fi Networks with Joint Usage of TIM Segmentation and Restricted Access Window
In order to meet the rising demands for the Internet of Things technologies, Wi-Fi community has developed Wi-Fi HaLow. It extends Wi-Fi with new functionality supporting high number of autonomous devices with various power capabilities and traffic patterns. In the paper, we study the cooperation of such new mechanisms as TIM Segmentation and Restricted Access Window. TIM Segmentation reduces energy consumption for low-power devices retrieving data from the Access Point, while Restricted Access Window reduces contention and allows the Access Point to protect stations with different capabilities from interfering each other. We consider joint usage of these mechanisms in a heterogeneous network with a high number of low-power stations with rare traffic and several powered stations with saturated traffic. Specifically, for TIM Segmentation and Restricted Access Window we develop a simple and fairly accurate mathematical method to set up the parameters of the mechanisms in order to improve performance for both types of stations, i.e. to reduce power consumption for low-power stations and to increase throughput for the other ones.
The interaction and tunneling conductance between oppositely located ends of coaxial carbon nanotubes are studied by the example of two (11, 11) nanotubes with open ends terminated by hydrogen atoms. The Green function formalism is applied to determine the tunneling current through the nanotube ends as a function of the distance between the ends, relative orientation of the nanotubes and voltage applied. The energy favorable configuration of the coaxial nanotubes is obtained by the analysis of their interaction energy at different distances between the nanotube ends and angles of their relative rotation. Using these calculations, a general scheme of the force sensor based on the interaction between ends of coaxial nanotubes is proposed and the relation between the tunneling conductance and measured force is established for the considered nanotubes. The operational characteristics of this device as a magnetic field sensor based on measurements of the magnetic force acting on the coaxial nanotubes filled with magnetic endofullerenes are estimated.
The article presents the technology and different variants of manufacturing of chemical sensors, made on the basis of metal oxide semiconductors for use in the type of "electronic nose" devices. The prospects of using neural networks to detect gas mixtures.
The first World Climate Conference, which was sponsored by the World Meteorological Organization in Genève in 1979, triggered an international dialogue on global warming. From the 1997 United Nations-sponsored conference-during which the Kyoto Protocol was signed-through meetings in Copenhagen, Cancún, Durban, and most recently Doha (2012) and Warsaw (2013), worldwide attention to the issue of global warming and its impact on the world's economy has rapidly increased in intensity. The consensus of these debates and discussions, however, is less than clear. Optimistically, many geoscience researchers and members of the Intergovernmental Panel on Climate Change (IPCC) have supported CO2 emission reduction pledges while maintaining that a 2°C limit in increased temperature by the year 2100 is achievable through international coordination. Other observers postulate that established CO2 reduction commitments such as those agreed to at the Copenhagen United Nations Climate Change Conference (2009) are insufficient and cannot hold the global warming increase below 2°C. As experts theorize on precisely what impact global warming will have, developing nations have become particularly alarmed. The developed world will use energy to mitigate global warming effects, but developing countries are more exposed by geography and poverty to the most dangerous consequences of a global temperature rise and lack the economic means to adapt. The complex dynamics that result from this confluence of science and geopolitics gives rise to even more complicated issues for economists, financial planners, business leaders, and policy-makers. The Oxford Handbook of the Macroeconomics of Global Warming analyzes the economic impact of issues related to and resulting from global warming, specifically the implications of possible preventative measures, various policy changes, and adaptation efforts as well as the different consequences climate change will have on both developing and developed nations. This multi-disciplinary approach, which touches on issues of growth, employment, and development, elucidates for readers state-of-the-art research on the complex and far-reaching problem of global warming.
The article considers a choice of CAD system and SPICE-models for the circuit simulation of characteristics of the bipolar (BiJFET) analog integrated circuits (IC) at the exposure of the penetrating radiation (PR) and the low temperatures. The authors suggest a modified SPICE-model, which describes the nonmonotonic change of the peak drain current and the slope of the p-n junction FET (JFET) within the temperature range from –200ºС to 30ºС.
This paper desribes the history of a laser gyro, which originated from one of the fundamental physics area - optics of moving media, and in particular the Sagnac effect. The development of the ring laser gyro construction concepts from its first samples of minimal configuration to multi-frequency Zeeman modifications with nonplanar resonators is observed.The general trends in the inertial sensors market are presented.
In this paper development of a 2D indoor positioning system based on a wireless sensor network (WSN) technology (ZigBeePro protocol) to use for transmission power adjustable solutions is described. There was implemented real-time system with different positioning methods and algorithms: triangulation, fingerprinting, fingerprinting with K weighted nearest neighbor algorithm. There was also implemented median filter to make the raw data smoother. The important point in this study is to compare different methods for different physical areas. Experimental results in real environment showed the difference in accuracy for different methods for different areas. With the software it is possible to configure positioning system by changing weights for different nodes in K weighted nearest neighbor algorithm. The software developed for the coordinates estimation can help determination of the points in the real area with 0 m accuracy where it is possible to set up special control devices and guarantee location of the mobile device and where it is also possible to adjust transmission power after defining the position of the mobile device.
A scenario-based prognosis of the evolution of global power generation markets until 2040, which was developed using the Scaner model-and-information complex, was given. The perspective development of fuel markets, vital for the power generation industry, was considered, and an attempt to predict the demand, production, and prices of oil, gas, coal, and noncarbon resources across various regions of the world was made. The anticipated decline in the growth of the global demand for fossil fuels and their sufficiency with relatively low extraction expenses will maintain the fuel prices (the data hereinafter are given as per 2014 prices) lower than their peak values in 2012. The outrunning growth of demand for electric power is shown in comparison with other power resources by regions and large countries in the world. The conditions of interfuel competition in the electric power industry considering the changes in anticipated fuel prices and cost indicators for various power generation technologies were studied. For this purpose, the ratios of discounted costs of electric power production by new gas and coal TPPs and wind and solar power plants were estimated. It was proven that accounting the system effects (operation modes, necessary duplicating and reserving the power of electric power plants using renewable energy sources) notably reduces the competitiveness of the renewable power industry and is not always compensated by the expected lowering of its capital intensity and growth of fuel for TPPs. However, even with a moderate (in relation to other prognoses) growth of the role of power plants using renewable energy sources, they will triple electric power production. In this context, thermal power plants will preserve their leadership covering up to 60% of the global electric power production, approximately half using gas. Keywords: electric power, gas, coal, renewable power sources, power consumption, fuel extraction, fuel markets, interfuel competition, social efficiency, cost of electric power production