Browsing by Author "Li, Y."
Now showing 1 - 6 of 6
- Results Per Page
- Sort Options
Item Beyond Quantum Confinement: Excitonic Nonlocality in Halide Perovskite Nanoparticles with Mie Resonances(Royal Society of Chemistry) Berestennikov, A. S.; Li, Y.; Iorsh, I. V.; Zakhidov, Anvar A.; Rogach, A. L.; Makarov, S. V.; Zakhidov, Anvar A.Halide perovskite nanoparticles have demonstrated pronounced quantum confinement properties for nanometer-scale sizes and strong Mie resonances for 10 2 nm sizes. Here we studied the intermediate sizes where the nonlocal response of the exciton affects the spectral properties of Mie modes. The mechanism of this effect is associated with the fact that excitons in nanoparticles have an additional kinetic energy that is proportional to k 2 , where k is the wavenumber. Therefore, they possess higher energy than in the case of static excitons. The obtained experimental and theoretical results for MAPbBr 3 nanoparticles of various sizes (2-200 nm) show that for particle radii comparable with the Bohr radius of the exciton (a few nanometers in perovskites), the blue-shift of the photoluminescence, scattering, and absorption cross-section peaks related to quantum confinement should be dominating due to the weakness of Mie resonances for such small sizes. On the other hand, for larger sizes (more than 50-100 nm), the influence of Mie modes increases, and the blue shift remains despite the fact that the effect of quantum confinement becomes much weaker. ©2019 The Royal Society of Chemistry.Item Constraint Handling in ESC Control Strategies with Application to HVAC Systems(Institute of Electrical and Electronics Engineers Inc.) Dong, L.; Li, Y.; Salsbury, T. I.; House, J. M.; 0000-0001-5025-0313 (Li, Y); 46216170 (Li, Y); Dong, Liujia; Li, YaoyuWhen applying ESC to a complex system, internal variables within the system may be subject to constraints that cannot be handled explicitly by limiting the range of the variable(s) manipulated by ESC. This is particularly evident in HVAC systems where ESC is often used to minimize energy use but where internal variables need to be constrained to satisfy comfort requirements. To address this problem, the paper proposes the use of penalty functions that are incorporated in the objective function. This approach is generally applicable because mathematical information about the relationship between the constrained variables and the ESC manipulated variables is not required. The paper describes the application of penalty functions to two types of HVAC systems: variable refrigerant flow (VRF) systems; and roof-top air-conditioners. Different penalty function formulations are described and results are shown from tests on detailed simulation models. © 2018 AACC.Item Marginal Gains to Maximize Content Spread in Social Networks(Institute of Electrical and Electronics Engineers Inc., 2019-05-06) Yang, W.; Ma, J.; Li, Y.; Yan, R.; Yuan, Jing; Wu, Weili; Li, D.; 56851698 (Wu, W); Yuan, Jing; Wu, WeiliThe growing importance of social network for sharing and spreading various contents is leading to the changes in the way of information diffusion. To what extent can social content be diffused highly depends on the size of seed nodes and connectivity of the network. If the seed set is predetermined, then the best way to maximize the content spread is to add connectivities among the users. The existing work shows the content spread maximization problem to be NP-hard. One of the difficulties of designing an effective and efficient algorithm for the content spread maximization problem lies in that the objective function we aim to maximize lacks submodularity. In our work, we formulate the maximize content spread problem from an incremental marginal gain perspective. Although the objective function we derive is not submodular, both submodular lower and upper bounds are constructed and proved. Therefore, we apply the sandwich framework and devise a marginal increment-based algorithm (MIS) that guarantees a data-dependent factor. Furthermore, a novel scalable content spread maximization algorithm influence ranking and fast adjustment (IRFA), which is based on the influence ranking of a single node and fast adjustment with each boosting step in the network, is proposed. Through extensive experiments, we demonstrate that both MIS and IRFA algorithms are effective and outperform other edge selection strategies.Item Power Splitting-Based SWIPT with Dual-Hop DF Relaying in the Presence of a Direct Link(Institute of Electrical and Electronics Engineers Inc.) Ye, Y.; Li, Y.; Zhou, F.; Al-Dhahir, Naofal; Zhang, H.; Al-Dhahir, NaofalThis letter investigates the outage performance of dual-hop decode and forward relay systems in the presence of a direct link between the source and the destination, where simultaneous wireless information and power transfer is exploited at the relay by using a static/dynamic power splitting (PS) scheme. An analytical expression for the outage probability is derived to determine the optimal static PS ratio. Moreover, we study the dynamic PS scheme and derive a closed-form expression for the optimal dynamic PS ratio to minimize the outage probability at a given target rate. Furthermore, an analytical expression for the outage probability with the optimal dynamic PS ratio is also presented. It is shown that a full diversity gain can be achieved in the investigated system with static/dynamic PS scheme, and that the dynamic PS scheme outperforms the static PS scheme. ©2018 IEEEItem Sequentially Bridged Graphene Sheets with High Strength, Toughness, and Electrical Conductivity(National Academy of Sciences) Wan, S.; Li, Y.; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Kotov, N. A.; Jiang, L.; Cheng, Q.; Baughman, Ray H.; Mu, Jiuke; Aliev, Ali E.; Fang, Shaoli; Baughman, Ray H.We here show that infiltrated bridging agents can convert inexpensively fabricated graphene platelet sheets into high-performance materials, thereby avoiding the need for a polymer matrix. Two types of bridging agents were investigated for interconnecting graphene sheets, which attach to sheets by either π–π bonding or covalent bonding. When applied alone, the π–π bonding agent is most effective. However, successive application of the optimized ratio of π–π bonding and covalent bonding agents provides graphene sheets with the highest strength, toughness, fatigue resistance, electrical conductivity, electromagnetic interference shielding efficiency, and resistance to ultrasonic dissolution. Raman spectroscopy measurements of stress transfer to graphene platelets allow us to decipher the mechanisms of property improvement. In addition, the degree of orientation of graphene platelets increases with increasing effectiveness of the bonding agents, and the interlayer spacing increases. Compared with other materials that are strong in all directions within a sheet, the realized tensile strength (945 MPa) of the resin-free graphene platelet sheets was higher than for carbon nanotube or graphene platelet composites, and comparable to that of commercially available carbon fiber composites. The toughness of these composites, containing the combination of π–π bonding and covalent bonding, was much higher than for these other materials having high strengths for all in-plane directions, thereby opening the path to materials design of layered nanocomposites using multiple types of quantitatively engineered chemical bonds between nanoscale building blocks.Item Using Tri-Relation Networks for Effective Software Fault-Proneness Prediction(Institute of Electrical and Electronics Engineers Inc., 2019-05-15) Li, Y.; Wong, W. Eric; Lee, Shou-Yu; Wotawa, F.; 0000-0002-1021-4753 (Wong, WE); 65810187 (Wong, WE); Wong, W. Eric; Lee, Shou-YuSoftware modules and developers are two core elements during the process of software development. Previous studies have shown that analyzing relations between 1) software modules; (2) developers; and (3) modules and developers, is critical to understand how they interact with each other, which ultimately affects software quality. Specifically, relations such as developer contribution relation, module dependency relation, and developer collaboration relation have been used independently or in pairs to build networks for software fault-proneness prediction. However, none of them investigate the joint effort of these three relations. Bearing this in mind, in this paper, we propose a tri-relation network, a weighted network that integrates developer contribution, module dependency, and developer collaboration relations to study their combined impact on software quality. Four network node centrality metrics are further derived from the proposed network to predict the fault-proneness of a given software module at the file level. Moreover, we have explored a mechanism to refine current networks in order to further improve the effectiveness of software fault-proneness prediction. © 2013 IEEE.