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Carbon capture is an important and effective approach to control the emission of CO2 from point sources such as fossil fuel power plants, industrial furnaces and cement plants into the atmosphere. For an efficient CO2 capture operation, many aspects of the CO2 capture steps need to be carefully considered. Currently the most mature CO2 capture technology is liquid amine scrubbing. Alternatively, solid sorbents can be used to effectively capture CO2 while alleviating the disadvantages associated with liquid amine sorbents. In this review, we critically assess solid metal oxide CO2 sorbents, especially oxides of group 1 (Li, Na and K) and group 2 (Mg, Ca, Sr and Ba) metals, for capturing CO2 at moderate to high temperatures. In particular, we focus on the recent advances in developing synthetic metal oxide sorbents, and the correlation between the design, synthetic approaches and their cyclic CO2 capture performance, which are characterised by CO2 uptake capacity, rate of carbonation and cyclic stability. The state-of-the-art, challenges, opportunities and future research directions for these metal oxide sorbents are discussed. By devoting more research effort to address the issues identified, there can be great potential to utilise Group 1 and 2 metal oxides as cost-effective, highly efficient sorbents for CO2 capture in a variety of carbon capture applications.

The millimeter-wave (mmWave) band will be used for the fifth-generation communication systems. In this paper, 60-GHz mmWave channel measurements and modeling are carried out for indoor office environments. The rotated directional antenna-based method and uniform virtual array-based method are adopted and compared to investigate the 60-GHz channel in a 3-D space, simultaneously covering azimuth and coelevation domains. The multipath component parameters including power, delay, azimuth, and elevation angles are estimated with the space-alternating generalized expectation–maximization estimation algorithm, and then processed with the K-means clustering algorithm. An extended Saleh–Valenzuela model with both delay and angular cluster features is used to characterize the measured channel, and the intercluster and intracluster parameters are extracted. We find that the azimuth departure angles are diverse and highly related to the antenna position and measurement environment, while the elevation departure angles are more related to the antenna height difference and confined in a relatively small direction range. The azimuth angle spread is much larger than the elevation angle spread either in global level or in cluster level. The results agree with the studies in the literature and channel models in IEEE standards.

The interuser interference between wireless body area networks worn by two moving persons in an indoor environment at 60 and 2.45 GHz is experimentally investigated. Both omnidirectional antennas (monopoles) and directional antennas (horns) were used in the measurements. The interference power-level variation and carrier-to-interference ratio (CIR) were measured and characterized. Median interference power-level reduction of nearly 20 dB was achieved in all measured channels by adopting 60-GHz radio transmissions compared to 2.45 GHz, both with omnidirectional on-body antennas. A further 20 dB of interference-level reduction was achieved at 60 GHz by adopting directional antennas confining the radiated wave along the body surface. Level crossing rates for interference power variation using omnidirectional antennas range from 2.7 to 7.2 $\text{s}^{-1}$ at 2.45 GHz and 32–64 $\text{s}^{-1}$ at 60 GHz for static to progressively more dynamic links, whereas the corresponding range using 60-GHz directional antennas is reduced to 39–54 $\text{s}^{-1}$ . The median improvement in the instantaneous CIR for the chest-head channel between 60 and 2.45 GHz was approximately 30 dB. The measured interference power level and CIR, in dB, were found to satisfactorily fit the normal distribution according to the normalized root-mean-square error-based fit metric.

Along with the gradual promotion of information education, the emerging information technology provides a broad and innovative platform for online learning services of Open University, and significantly advances the integration of the ideas of Ubiquitous learning (U-Learning) and blended learning. This research, based on the online courses of Open University, established a system of evaluation index for learning support services. Based upon the twenty-two online courses of the Open University of Guangdong (OUGD), an evaluation and analysis was conducted to explore the status quo and problem of the learning support services in these open universities. On this basis, combining with relevant research and empirical surveys this research found that the learning support services were moving along the trend towards personalization, ubiquitous and intelligence, which might provide a useful reference to the diverse development and innovative application of OCLSS in our country.

Variation of on-body millimetre-wave propagation channels with body movements has been studied experimentally. A statistical description of the propagation channel is presented, including path-loss probability distributions, level-crossing rates and average fade durations. The median path losses for the considered practical links with omnidirectional monopole antennas lied within the range of 55–88 dB. The signal variation was found to consist of two superimposed variations, in general: the long-term and short-term fadings, but was dominated by the much stronger long-term fading. The use of a simple two-state Markov process model to describe on-body communication links is also proposed and its limitations are discussed.

In this paper, by using a multiple-input multiple-output (MIMO) antenna array, a channel measurement campaign in outdoor environments is introduced. The measurement campaign captures the spatial characteristics of centimeter wave (cm-wave) propagation at the center frequency of 26 GHz . By using the parametric approach of the Space-Alternating Generalized Expectation-maximization (SAGE) algorithm, the channel characteristics in the delay and spatial domains are extracted, and compared with the channel model below 6 GHz. Our analysis shows that the channel dispersions in the delay and directional domains are smaller at the 26 GHz. Furthermore, single-user (SU)-MIMO and multi-user (MU)-MIMO channel matrix properties are investigated, and show that the MU-MIMO channel has good orthogonal property. It implies that MU-MIMO will be one promising MIMO technique in cm-wave band.

A novel low-profile high-gain, end-fire Yagi–Uda antenna array designed for an on-body communication link at 60 GHz is described. The antenna consists of four single Yagi antennas, which is composed of a driven dipole, 18 directors, and a reflector. Simulation and measurement in free space show a good agreement, and 15 dBi gain is achieved. Measurements with a body tissue phantom have been done to investigate the antenna's performance in close proximity to the human body. Results show that the reflection coefficient changes a little, whereas the radiation pattern in the H plane is affected. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:2728–2730, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26443

Measurements of on-body dynamic propagation channels have been performed at 60 GHz using dual-polarized scalar horns. The measured cumulative distribution functions (CDF) were compared to those reported previously with monopole antennas. The performances of horn and monopole antennas were compared in various on-body channels and it was found that omnidirectional low-gain antennas produce stronger path gain in some channels. It was concluded that polarization diversity is unlikely to provide a significant gain but the channel capacity may be improved by using several polarization channels in a multiple-input multiple output (MIMO) system.

Modeling and simulation are essential techniques for both engineering research and design. They enable many undertakings from early exploration of design concepts to understanding of complex phenomena. Body sensor networks (BSNs) are complex cyber-physical systems where resource-constrained networked computational systems must interact with highly dynamic and complex humans and their environment to achieve system goals of human health monitoring. Modeling and simulation in BSNs have so far been limited to just BSN components or looking at specific cyber-physical interaction issues. In this paper, we present BodySim, a multi-domain modeling framework that allows BSN designers and researchers to explore the cyber-physical issues in various systems scenarios by providing virtual human subject modeling capabilities and interfaces to virtual sensor models to allow experimentation and exploration in virtual space. We describe the architecture and our current instantiation of particular components for this framework. We also illustrate the kinds of explorations that can be done with this framework using our motivating applications in wireless communication and inertial sensing.

This paper reviews recent results on radiowave propagation measurements, models and electromagnetic analysis methods for 60 GHz body-area networking (BAN) applications. The viability of mm-wave BANs is discussed and established. The advantages of adopting a mm-wave band for body area networking over lower frequency microwave bands are discussed and quantified. Finally, a number of outstanding research challenges are identified.

Observability of 60 GHz wireless body area networks is being investigated, in the context of the maximum outdoor detection range for such a network. An off-body channel within a scattering environment has been characterized. By decomposing the detection channel into a free-space channel and a body-local environment channel, an observability estimation model is proposed based on the measured data.

Inter-user interference between two wireless body area networks at 60 GHz has been investigated. A series of data sets have been gathered in a laboratory environment for random realistic activities and body orientations, and have been subjected to statistical analysis. The characterization of interfering signal strength variations for several links and statistical parameters such as level crossing rate and average peak duration are presented.

Propagation between two antennas on a human body in millimeter-wave frequency band have been investigated empirically. Propagation characteristics of a number of on-body propagation channels were studied with two types of antennas: quarter-wavelength monopoles and rectangular horns, the first being representative of low-gain omnidirectional antennas and the latter being the high-gain directional antenna. The channel characteristics for the two types of the antennas were compared. The path gain of the links with the horn antennas was found to be higher the that for monopoles. However, the variability of the path gain was also much greater for some channels. The path gain variation with time was described by a two-scale statistical model in which short-term fading was found to follow approximately Cauchy-Lorentz probability distribution.

On-body communication is of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper reviews 60 GHz on-body communication and its benefits and challenges. Two novel low profile high gain, end-fire wearable antennas are then described. Measurements with an experimental phantom and real human body are presented. Results show antennas achieve good performance close to a phantom. Shadowing effects and polarisation issues for on-body communications at 60 GHz are discussed.

On-body communication is of increasing interest for a number of applications, such as medical-sensor networks, emergency-service workers, and personal communications. This paper reviews 60 GHz on-body communication and its benefits and challenges. Two novel low profile high gain, end-fire wearable antennas are then described. They are promising candidates for on-body channels at 60 GHz. The first one is a conventional printed Yagi array, which gives up to 17 dB gain and 6 GHz bandwidth. The other is a substrate integrated waveguide Yagi antenna which also gives 15 dB gain. Because these two antennas have different polarization, they can be used to investigate 60 GHz on-body channels in future work.

A novel substrate integrated waveguide (SIW) Yagi-Uda antenna for 60 GHz applications is presented. The proposed antenna has the merits of low profile and light weight and is suitable for direct integration with the SIW wireless front end. Simulated results are compared with measured data and good agreement is reported.