Performance analysis of relay-aided wireless communication systems

Relay-aided networks have been proved to be cost-efficient solutions for wireless communications in respect of high data rates, enhanced spectrum efficiency and improved signal coverage. In the past decade, relaying techniques have been written into standards of modern wireless communications and significantly improve the quality of service (QoS) in wireless communications. In order to satisfy exponentially increased demands for data rates and wireless connectivities, various novel techniques for wireless communications have been proposed in recent years, which have brought significant challenges for the performance analysis of relaying networks. For the purpose of more practical investigations into relaying systems, researchers should not only analyse the relays employing novel techniques but also attach more importance to complex environments of wireless communications. With these objectives in mind, in this thesis, in-depth investigations into system performance for relay-assisted wireless communications are detailed. Firstly, the theoretic reliability of dual-hop amplify-and-forward (AF) systems over generalised η-μ and κ-μ fading channels are investigated using Gallager’s error exponents. These two versatile channel models can encompass a number of popular fading channels such as Rayleigh, Rician, Nakagami-m, Hoyt and one-sided Gaussian fading channels. We derive new analytical expressions for the probability distribution function (pdf) of the end-to-end signal-to-noise-ratio (SNR) of the system. These analytical expressions are then applied to analyse the system performance through the study of Gallager’s exponents, which are classical tight bounds of error exponents and present the trade-off between the practical information rate and the reliability of communication. Two types of Gallager’s exponents, namely the random coding error exponent (RCEE) and the expurgated error exponent, are studied. Based on the newly derived analytical expressions, we provide an efficient method to compute the required codeword length to achieve a predefined upper bound of error probability. In addition, the analytical expressions are derived for the cut-off rate and ergodic capacity of the system. Moreover, simplified expressions are presented at the high SNR regime. Secondly, the performance of a dual-hop amplify-and-forward (AF) multi-antenna relaying system over complex Gaussian channels is investigated. Three classical receiving strategies, i.e. the maximal-ratio combining (MRC), zero-forcing (ZF) and minimum mean square error (MMSE) are employed in the relay to mitigate the impact of co-channel interference (CCI), which follows the Poisson point process (PPP). We derive the exact analytical expressions of the capacities for this system in the infinite-area interference environment and the asymptotic analytical expressions for the lower bounds of capacities in the limited-area interference scenario. By computing the numerical results and the Monte Carlo simulation, we can observe the effect of relay processing schemes under different interference regimes. In the end, the non-orthogonal multiple access (NOMA) technique is introduced to relaying systems, which exploits multiplexing in the power domain. Order statistics are applied in this part to analyse the performances of ordered users. The randomness of both channel fading and path loss are taken into consideration. In addition to the exact analytical expressions, asymptotic expressions at high-SNR regimes are provided, which clearly show the effects of NOMA techniques using at relaying systems

Dry Powder Coating of Pharmaceutical Pellets with a Novel Rotary Fluidized Bed

The conventional coating of pharmaceutical pellets is achieved by liquid-based coating techniques using a fluidized bed or a pan coater. However, many restrictions and drawbacks such as long processing time and large energy consumption exist in the above method. Dry powder coating technique is a novel solventless coating technique that is able to mitigate the problems of liquid-based coating. In this study, a newly invented coating apparatus called rotary fluidized bed (RFB), was applied for the coating of pharmaceutical pellets by a dry powder coating process. The RFB has a unique structure where the hot fluidizing air is further aided by the rotation to ensure a uniform coating. Results of SEM micrographs indicated the piroxicam pellets formed continuous and dense coating film in the RFB. In-vitro drug release tests confirmed that the dry powder coated pellets successfully achieved immediate release, sustained release and delayed release with Eudragit® EPO, Eudragit® RS/RL and Acryl-EZE, respectively. The optimal operation conditions were as follows: curing temperature 2 h, curing temperature 50 oC, RFB rotating speed ~20 rpm, liquid plasticizer spraying rate ~0.25 g/min and fluidizing air flowrate ~35 L/min. The RFB demonstrated a comparable film formation quality and coating efficiency with the pan coater, while superior to the fluidized bed. For the more difficult-to-coat micronized pellets (0.1-0.3mm), the RFB presented better applicable potential than the other two apparatus. In conclusion, the RFB is a promising dry powder coating apparatus for pharmaceutical pellets coating

Digital technologies for enhancing crane safety in construction: a combined quantitative and qualitative analysis

A digital-enabled safety management approach is increasingly crucial for crane operations, which are common yet highly hazardous activities sensitive to environmental dynamics on construction sites. However, there exists a knowledge gap regarding the current status and developmental trajectory of this approach. Therefore, this paper aims to provide a comprehensive overview of digital technologies for enhancing crane safety, drawing insights from articles published between 2008 and 2021. Special emphasis is placed on the sensing devices currently in use for gathering “man-machine-environment” data, as well as the communication networks, data processing algorithms, and intuitive visualization platforms employed. Through qualitative and quantitative analysis of the literature, it is evident that while notable advancements have been made in digital-enabled crane safety management, these achievements remain largely confined to the experimentation stage. Consequently, a framework is proposed in this study to facilitate the practical implementation of digital-enabled crane safety management. Furthermore, recommendations for future research directions are presented. This comprehensive review offers valuable guidance for ensuring safe crane operations in the construction industry

Measurement of the complex polar magneto-optical Kerr effect using weak measurement

Polar magneto-optical Kerr effect (PMOKE) is one of the most widely being applied magneto-optical Kerr effects (MOKE) due to the induced complex MOKE signal, consisting of the Kerr rotation angle and the ellipticity, is very sensitive to the magnetization component perpendicular to the magnetic surface. However, the Kerr rotation angle and the ellipticity invariably coexist and pose a challenge in their separation. This dual presence plays a pivotal role in defining the light intensity detected, ultimately restricting the advancements in the measurement precision. In this paper, we propose a weak measurement (WM) scheme to measure the complex MOKE in the pure polar configuration. Unlike the traditional MOKE or WM method using a quarter-wave-plate to measure the Kerr rotation angle and the ellipticity separately, we realize the simultaneous measurement of these two parameters in a single WM process using two new pointers, which possesses a larger linear response region compared with the previous amplified shift pointer. The measurement precision for the complex PMOKE angle reaches to $10^{-4}$ deg in our experiment. Besides, the complex magneto-optical constant Q is also calculated. This work is of great significance for the measurement of the complex PMOKE with high efficiency, ultra-precision, low cost, and is an important attempt to obtain complex physical quantities using WM

Research on Traffic Signal Timing Method Based on Ant Colony Algorithm and Fuzzy Control Theory

The number of private cars has a blowout growth with the development of economics, which leads to the existing limited traffic resources cannot meet the normal traffic demand. The emergence of intelligent traffic has improved this phenomenon. Using intelligent traffic technology to conduct intersection vehicles can alleviate the congestion effectively. Traffic signal timing method plays an important role in intelligent traffic research. An independent intersection dynamic timing method combined with fuzzy control theory and improved ant colony algorithm is proposed in this paper. According to the characteristics of traffic flow distribution, the timing period is obtained with the improved webster algorithm. Through the optimal solution obtained by ant colony algorithm and the added delay of traffic signal calculated by fuzzy control method, the dynamic timing period of the traffic signal is obtained. The validity of the proposed method is proved by comparing with the original time period and the traditional algorithm

Combustion Characteristics of Hydrogen-methane Hybrid Fuels

ABSTRACT As the development and increasingly widespread use of IGCC and zero emission energy system, the development of advanced combustion capabilities for gaseous hydrogen and hydrogen rich fuels in gas turbine applications is becoming an area of much great concern. The combustion characteristics of hydrogen rich fuel is very different from nature gas in aspects such as flame stability, flame temperature, combustor acoustics, pollutant emissions, combustor efficiency, and some other important quantities. However, few of these issues are clearly understood by far. The purpose of this paper is to compare in detail the combustion performance of hydrogen-methane hybrid fuels with various volumetric H 2 fractions ranging from 0% to 100%. Meanwhile, the comparison of pure H 2 , pure CH 4 , and 80%H 2 +20%CH 4 was the emphasis. 80%H 2 +20%CH 4 hybrid gas is selected expressly because its component is approximately equal to the outcome of a hydrogen production test bed of our laboratory, and it is considered by the team to be a potential transition fuel of gas turbines between nature gas and pure hydrogen. Detailed experimental measurements and numerical simulations were conducted using a coflow jet diffusion burner. It was found that in the extent of experiments, when under equal general power, the flame length of hydrogen contained fuels wasn't much shorter than methane, and didn't get shorter with the increase of H 2 fraction as expected. That was because the shortening tendency caused by the increase of H 2 fraction was counteracted partially by the increase of fuel velocity, results of which was the extending of flame length. Maximum temperature of H 2 flame was 1733K, which was 30K higher than 80%H 2 +20%CH 4 and 120K higher than CH 4. All of the highest temperatures of the three fuels were presented at the recirculation zone of the flame. Although it seemed that the flame of CH 4 had the longest dimension compared with H 2 contained fuels when observed through photos, the high temperature region of flames was getting longer when increasing H 2 fractions. Curves of temperature distribution predicted by all the four combustion models in FLUENT investigated here had a departure away from the experimental data. Among the models, Flamelet model was the one whose prediction was comparatively close to the experimental results. Flame of H 2 and 80%H 2 +20%CH 4 had a much better stability than flame of CH 4 , they could reach a so called recirculating flame phase and never been blew out in the extent of experiments. On the contrary, CH 4 flames were blew out easily soon after they were lifted up. Distribution of OH concentration at the root of flames showed that the flame boundary of H 2 and 80%H 2 +20%CH 4 was more clearly than CH 4. That is to say, at the root of the flame, combustion of H 2 was the most intensive one, 80%H 2 +20%CH 4 took the second place, while CH 4 was the least. NOx emissions didn't show a linear relationship with the volumetric fraction of H 2 , but showed an exponential uptrend instead. It presented a fairly consistent tendency with flame

Dynamic Rail Near-Surface Inspection of Multiphysical Coupled Electromagnetic and Thermography Sensing System

The effectiveness of railway fault inspection has remained challenging. Conventional techniques are still functionally limited and unable to meet the increasing demand of railway diagnosis. To mitigate the variety of rail fault detection problems, this article proposes a dynamic railway inspection system based on multiphysical coupled electromagnetic and thermography sensing. It further shows the development and construction of a new inverted L-type magnet yoke abreast with volumetric coil array. The novel structure can not only significantly enhance the sensitivity and detectability of the region of interest (ROI), but also effectively detect the subsurface defects with the compensation of coils array due to the coupled electromagnetic field. Furthermore, the theoretical analysis of the coupled physical fields has been derived and proved to be consistent with the numerical simulation results. A rail test sample with various defects is carried out to verify the feasibility of the proposed system. Additionally, a metric learning post-processing algorithm has been conducted for distilling eddy current signals and thermograms to improve the accuracy of the detection results. On-site experimental and contrast results with various levels of performance validation have demonstrated that the integrated system is well suited for dynamic rail inspection on near-surface cracks at speed of 1 km/h

How we learn social norms: a three-stage model for social norm learning

As social animals, humans are unique to make the world function well by developing, maintaining, and enforcing social norms. As a prerequisite among these norm-related processes, learning social norms can act as a basis that helps us quickly coordinate with others, which is beneficial to social inclusion when people enter into a new environment or experience certain sociocultural changes. Given the positive effects of learning social norms on social order and sociocultural adaptability in daily life, there is an urgent need to understand the underlying mechanisms of social norm learning. In this article, we review a set of works regarding social norms and highlight the specificity of social norm learning. We then propose an integrated model of social norm learning containing three stages, i.e., pre-learning, reinforcement learning, and internalization, map a potential brain network in processing social norm learning, and further discuss the potential influencing factors that modulate social norm learning. Finally, we outline a couple of future directions along this line, including theoretical (i.e., societal and individual differences in social norm learning), methodological (i.e., longitudinal research, experimental methods, neuroimaging studies), and practical issues