Time Dependent Performance Analysis of Wireless Networks

Many wireless networks are subject to frequent changes in a combination of network topology, traffic demand, and link capacity, such that nonstationary/transient conditions always exist in packet-level network behavior. Although there are extensive studies on the steady-state performance of wireless networks, little work exists on the systematic study of their packet-level time varying behavior. However, it is increasingly noted that wireless networks must not only perform well in steady state, but must also have acceptable performance under nonstationary/transient conditions. Furthermore, numerous applications in today's wireless networks are very critical to the real-time performance of delay, packet delivery ratio, etc, such as safety applications in vehicular networks and military applications in mobile ad hoc networks. Thus, there exists a need for techniques to analyze the time dependent performance of wireless networks. In this dissertation, we develop a performance modeling framework incorporating queuing and stochastic modeling techniques to efficiently evaluate packet-level time dependent performance of vehicular networks (single-hop) and mobile ad hoc networks (multi-hop). For vehicular networks, we consider the dynamic behavior of IEEE 802.11p MAC protocol due to node mobility and model the network hearability as a time varying adjacency matrix. For mobile ad hoc networks, we focus on the dynamic behavior of network layer performance due to rerouting and model the network connectivity as a time varying adjacency matrix. In both types of networks, node queues are modeled by the same fluid flow technique, which follows flow conservation principle to construct differential equations from a pointwise mapping of the steady-state queueing relationships. Numerical results confirm that fluid-flow based performance models are able to respond to the ongoing nonstationary/transient conditions of wireless networks promptly and accurately. Moreover, compared to the computation time of standard discrete event simulator, fluid-flow based model is shown to be a more scalable evaluation tool. In general, our proposed performance model can be used to explore network design alternatives or to get a quick estimate on the performance variation in response to some dynamic changes in network conditions

Wireless Sensor Networks for Smart Communications

(First paragraph) In the first edition of the special issue titled “Wireless Sensor Networks for Smart Communications”, a total of 22 manuscripts were received and 6 of these were accepted. This issue demonstrated that network congestion, user mobility, and adjacent spectrum interference are the main reasons for the degradation ofcommunication quality inWireless Sensor Networks (WSNs)

Perturbed stochastic fractal search for solar PV parameter estimation

Following the widespread use of solar energy all over the world, the design of high quality photovoltaic (PV) cells has attracted strong research interests. To properly evaluate, control and optimize solar PV systems, it is crucial to establish a reliable and accurate model, which is a challenging task due to the presence of non-linearity and multi-modality in the PV systems. In this work, a new meta-heuristic algorithm (MHA), called perturbed stochastic fractal search (pSFS), is proposed to estimate the PV parameters in an optimization framework. The novelty lies in two aspects: (i) employ its own searching operators, i.e., diffusion and updating, to achieve a balance between the global exploration and the local exploitation; and (ii) incorporate a chaotic elitist perturbation strategy to improve the searching performance. To examine the effectiveness of pSFS, this method is applied to solve three PV estimation problems for different PV models, including single diode, double diode and PV modules. Experimental results and statistical analysis show that the proposed pSFS has improved estimation accuracy and robustness compared with several other algorithms recently developed

Research progress in surface plasmon resonance technology in exosome characterization and identification

Exosomes are lipid bilayer membrane vesicles that are widely distributed in peripheral blood， saliva， urine， ascites and other fluids. A variety of tumor-related genes in exosomes are involved in the information exchange between cancer cells and normal cells， as well as the process of tumor cell proliferation and metastasis， play an important role in tumor development， and are potential biomarkers for tumor liquid biopsy. In recent years， surface plasmon resonance （SPR） is considered to have great application potential in the characterization of exosomes due to its high sensitivity， small sample size required for testing， short detection time and low background interference， etc. In this article， the basic principle of SPR and the application prospect of SPR-based biosensing platform in exosomes characterization were mainly illustrated

Skeletal Muscle Regeneration on Protein-Grafted and Microchannel-Patterned Scaffold for Hypopharyngeal Tissue Engineering

In the field of tissue engineering, polymeric materials with high biocompatibility like polylactic acid and polyglycolic acid have been widely used for fabricating living constructs. For hypopharynx tissue engineering, skeletal muscle is one important functional part of the whole organ, which assembles the unidirectionally aligned myotubes. In this study, a polyurethane (PU) scaffold with microchannel patterns was used to provide aligning guidance for the seeded human myoblasts. Due to the low hydrophilicity of PU, the scaffold was grafted with silk fibroin (PU-SF) or gelatin (PU-Gel) to improve its cell adhesion properties. Scaffolds were observed to degrade slowly over time, and their mechanical properties and hydrophilicities were improved through the surface grafting. Also, the myoblasts seeded on PU-SF had the higher proliferative rate and better differentiation compared with those on the control or PU-Gel. Our results demonstrate that polyurethane scaffolds seeded with myoblasts hold promise to guide hypopharynx muscle regeneration

Teaching-Learning-Based Optimization with Learning Enthusiasm Mechanism and Its Application in Chemical Engineering

Teaching-learning-based optimization (TLBO) is a population-based metaheuristic search algorithm inspired by the teaching and learning process in a classroom. It has been successfully applied to many scientific and engineering applications in the past few years. In the basic TLBO and most of its variants, all the learners have the same probability of getting knowledge from others. However, in the real world, learners are different, and each learner’s learning enthusiasm is not the same, resulting in different probabilities of acquiring knowledge. Motivated by this phenomenon, this study introduces a learning enthusiasm mechanism into the basic TLBO and proposes a learning enthusiasm based TLBO (LebTLBO). In the LebTLBO, learners with good grades have high learning enthusiasm, and they have large probabilities of acquiring knowledge from others; by contrast, learners with bad grades have low learning enthusiasm, and they have relative small probabilities of acquiring knowledge from others. In addition, a poor student tutoring phase is introduced to improve the quality of the poor learners. The proposed method is evaluated on the CEC2014 benchmark functions, and the computational results demonstrate that it offers promising results compared with other efficient TLBO and non-TLBO algorithms. Finally, LebTLBO is applied to solve three optimal control problems in chemical engineering, and the competitive results show its potential for real-world problems

Coupling Coordination Relationship and Dynamic Response between Urbanization and Urban Resilience: Case of Yangtze River Delta

In the context of rapid urbanization, urban resilience, as a new way of thinking to seek solutions to urban risk crises, has become an important direction and a new development trend in the continued acceleration of urbanization. This study takes the Yangtze River Delta (YRD) as the study object, establishes a comprehensive evaluation index system of urbanization and urban resilience from a multi-dimensional perspective based on the improved entropy value method, and uses the coupling coordination degree (CCD) model, the kernel density estimation method, and the exploratory spatial data analysis (ESDA) method to investigate the spatio-temporal evolution trends of the CCD level of urbanization and urban resilience. Further, the dynamic response relationship of the coupling between the two systems is revealed by the PVAR model. The study results are shown as follows: (1) The urbanization level and the urban resilience level show a box-shaped clustering of overall urbanization values and urban resilience values, with a widening absolute gap between extreme value cities. (2) The kernel density estimates of CCD values for urbanization and urban resilience show an upward trend in the overall level of CCD, with regional integration replacing multi-level differentiation. (3) The level of CCD shows a continuous upward trend in terms of the spatial distribution characteristics of CCD, and the high-class area shows regional integration. (4) The spatial agglomeration trend of CCD continues to develop, reaching a region-wide hot spot agglomeration. (5) The PVAR model indicates that there is a dynamic response relationship between the urbanization system and the urban resilience system. Finally, based on the above research results, this study gives policy recommendations for the coordination and sustainable development of the urbanization system and the urban resilience system, providing some academic references for the relevant departments in the YRD to accelerate urbanization, enhance the urban resilience level, and promote regional integration

Fabrication and Irradiation Effect of Inverted Metamorphic Triple Junction GaInP/GaAs/InGaAs Solar Cells

Inverted metamorphic triple junction (IMM3J) GaInP/GaAs/InGaAs solar cells have the advantages of high efficiency, excellent radiation resistance, lightweight and flexible properties, especially suitable for space application. In this paper, we first fabricate the IMM3J GaInP/GaAs/InGaAs solar cell, which has a short circuit current density of 16.5 mA/cm2, an open circuit voltage of 3141.8 mV, a fill factor of 84.3%, and an efficiency of 32.2%. Then, the IMM3J solar cell is irradiated by 2 MeV protons with different fluences from 2 × 1011 cm−2 to 2 × 1012 cm−2. Finally, the output electrical properties of IMM3J solar cells at the beginning of life and end of life are analyzed by current-voltage characterization. The degradation behaviors of each subcell before and after irradiation can also be described by the external quantum efficiency and short circuit current density

Fabrication and Irradiation Effect of Inverted Metamorphic Triple Junction GaInP/GaAs/InGaAs Solar Cells

Inverted metamorphic triple junction (IMM3J) GaInP/GaAs/InGaAs solar cells have the advantages of high efficiency, excellent radiation resistance, lightweight and flexible properties, especially suitable for space application. In this paper, we first fabricate the IMM3J GaInP/GaAs/InGaAs solar cell, which has a short circuit current density of 16.5 mA/cm2, an open circuit voltage of 3141.8 mV, a fill factor of 84.3%, and an efficiency of 32.2%. Then, the IMM3J solar cell is irradiated by 2 MeV protons with different fluences from 2 × 1011 cm−2 to 2 × 1012 cm−2. Finally, the output electrical properties of IMM3J solar cells at the beginning of life and end of life are analyzed by current-voltage characterization. The degradation behaviors of each subcell before and after irradiation can also be described by the external quantum efficiency and short circuit current density