Carey G.H.,King's College |
Abdelhady A.L.,King Abdullah University of Science and Technology |
Ning Z.,University of Shanghai for Science and Technology |
Thon S.M.,Johns Hopkins University |
And 2 more authors.
Chemical Reviews | Year: 2015
Colloidal quantum dot research has led to significant advances in synthesis methods, in material and film processing techniques, and in characterization and optimization of optoelectronic properties. Studies of novel passivation strategies, including new or hybrid ligand systems, surface engineering, core/shell strategies, and self-healing surfaces, will reduce trap states, improve carrier transport, and reduce the extent of energy level pinning. Another route to improved electronic transport in quantum dot films will rely on densifying nanocrystal films through improved packing and, ideally ordering. Such films will eliminate diversity in path length and thus tortuosity in charge transport through the device. Significant studies have been performed on the electron-transporting component yet as the optoelectronic quality of the quantum dot solid improves, even greater enhancements will be required in both the electron- and hole-accepting layers to ensure optimal performance. Research will need to adjust existing systems or apply novel material solutions, while intensely studying the interfaces between the quantum dot film and electrodes to eliminate any potential losses. Finally, as single-junction quantum dot solar cells advance and improve, a renewed focus will be placed on multiple-junction integration, with the goal of creating high-efficiency devices through improved spectral utilization and minimal loss associated with photocarrier thermalization.
Wang Z.,Brunel University |
Shen B.,Donghua University |
Shu H.,Donghua University |
Wei G.,University of Shanghai for Science and Technology
IEEE Transactions on Automatic Control | Year: 2012
In this paper, the quantized H ∞ control problem is investigated for a class of nonlinear stochastic time-delay network-based systems with probabilistic data missing. A nonlinear stochastic system with state delays is employed to model the networked control systems where the measured output and the input signals are quantized by two logarithmic quantizers, respectively. Moreover, the data missing phenomena are modeled by introducing a diagonal matrix composed of Bernoulli distributed stochastic variables taking values of 1 and 0, which describes that the data from different sensors may be lost with different missing probabilities. Subsequently, a sufficient condition is first derived in virtue of the method of sector-bounded uncertainties, which guarantees that the closed-loop system is stochastically stable and the controlled output satisfies H ∞ performance constraint for all nonzero exogenous disturbances under the zero-initial condition. Then, the sufficient condition is decoupled into some inequalities for the convenience of practical verification. Based on that, quantized H ∞ controllers are designed successfully for some special classes of nonlinear stochastic time-delay systems by using Matlab linear matrix inequality toolbox. Finally, a numerical simulation example is exploited to show the effectiveness and applicability of the results derived. © 2011 IEEE.
Zhao B.,University of Shanghai for Science and Technology
Separation and Purification Technology | Year: 2012
Modeling the particle separation efficiency has been a topic of interest since the air cyclones was introduced for gas-particle separation in the fields of environmental science and chemical engineering. In this work, a new simple time-of-flight model is theoretically developed to predict the particle separation efficiency in cyclones. In this model, the equivalent volume method is employed to geometrically modify the cylindrical-conical type cyclone as a right cylindrical cyclone in order to overcome the nonuniform effect on the particle separation distance. Based on the analysis of the gas flow pattern and the particle dynamics in the cyclone separator, the differential equation for the time-of-flight model is established according to the principle of particle mass balance. The model can be finally expressed as a simple explicit function including the main cyclone dimensions and operating parameters, without the need for solving complex equation of mathematical physics. The influences of the short-circuit flow near the bottom of cyclone outlet duct and the exchange flow between outer and inner vortex flow are comprehensively considered to revise the effective residence time of gas flow, a key parameter in the present model. By comparisons with experimental data as well as other classical separation models for the cyclones with different geometrical configurations and operating conditions, the results show that the present model has a relatively high predicted accuracy with the mean squared error of 0.0158. It is demonstrated that the present model has considerable availability for predicting the particle separation efficiency for cyclone separators. © 2011 Elsevier B.V. All rights reserved.
Zhao B.,University of Shanghai for Science and Technology |
Su Y.,Donghua University
Renewable and Sustainable Energy Reviews | Year: 2014
Global warming caused by anthropogenic CO2 emission has been one of the most important issues in the fields of science, environment and even international economics and politics. To control and reduce CO2 emissions, intensive carbon dioxide capture and storage (CCS) technologies have been comprehensively developed for sequestration of CO2 especially from combustion flue gas. Microalgae-based CO2 biological fixation is regarded as a potential way to not only reduce CO2 emission but also achieve energy utilization of microalgal biomass. However, in this approach culture process of microalgae plays an important role as it is directly related to the mechanism of microalgal-CO2 fixation and characteristics of microalgal biomass production. The aim of this work is to present a state-of-the-art review on the process effect, especially on the effects of photobiochemical process, microalgal species, physicochemical process and hydrodynamic process on the performance of microalgal-CO2 fixation and biomass production. Also, the perspectives are proposed in order to provide a positive reference on developing its fundamental research and key technology. © 2013 Elsevier Ltd.
Fang L.,University of Shanghai for Science and Technology |
Jia H.,University of Shanghai for Science and Technology
Optics Express | Year: 2014
Two parallel combinative long-period fiber gratings (LPFGs) can convert the fundamental core mode LP01 in a single-mode fiber (SMF) into one desired higher order core mode LP0m in a few-mode fiber (FMF), in the process of which one specific cladding mode acts as a medium coupled from one fiber to another. Different LP0m modes can be obtained by controlling the grating period of LPFG in FMF to meet the phase matching condition. In this article we focus on the design and analyses of LP02 and LP 03 mode add/drop multiplexers (MADMs). This device has some advantages of facile and good scalability, and particularly, of eliminating coupling interferences for the ahead multiplexed modes by the posterior MADMs or couplers. Furthermore, the conversion rate of mode power theoretically can approach as much as 98% and the 3dB bandwidth can reach 10nm or more. © 2014 Optical Society of America.
Ji Y.,University of Shanghai for Science and Technology
Materials Letters | Year: 2013
A novel method to fabricate TiO2 nanorod arrays on a flat Ti foil substrate was developed. High density titania nanorods had been produced via sintering NaOH solution coated Ti foil at 800 C. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and infrared spectrum (FTIR) were applied to characterize the obtained products. The titania nanorod arrays showed a mainly rutile phase with approximately 500 nm in width, and 5 μm in thickness. The growth process of TiO2 nanorod arrays at different temperature was systematically investigated. Meanwhile, the effect of surface wetness on the structure of titania nanorod arrays was also studied. It was found that the co-existence of water and alkali played important roles in the growth of titania nanorod arrays. © 2013 Elsevier B.V.
Yuan X.,University of Shanghai for Science and Technology
IEEE Transactions on Wireless Communications | Year: 2014
Recently, much research interest has been focused on the design of efficient communication mechanisms for multiple-input-multiple-output (MIMO) multiway relay channels (mRCs). In this paper, we investigate achievable degrees of freedom (DoFs) of the MIMO mRC with L clusters and K users per cluster, where each user is equipped with M antennas and the relay with N antennas. Our analysis is focused on a new data exchange model, termed clustered full data exchange, i.e., each user in a cluster wants to learn the messages of all the other users in the same cluster. Novel signal alignment techniques are developed to jointly and systematically construct the beamforming matrices at the users and the relay for efficient implementation of physical-layer network coding. Based on this, we derive an achievable DoF of the MIMO mRC with an arbitrary network configuration of L and K, as well as with an arbitrary antenna configuration of M and N. We show that our proposed scheme achieves the DoF capacity when M/N \leq 1/(LK-1) and M/N\geq((K-1)L+1)/KL. The DoF results derived in this paper can serve as fundamental benchmarks in evaluating the performance of practical communication systems over MIMO mRCs and provide guidance and insights into the design of wireless relay networks. © 2002-2012 IEEE.
Liao J.,University of Shanghai for Science and Technology
Nature Structural and Molecular Biology | Year: 2016
Na+/Ca2+ exchangers use the Na+ electrochemical gradient across the plasma membrane to extrude intracellular Ca2+ and play a central role in Ca2+ homeostasis. Here, we elucidate their mechanisms of extracellular ion recognition and exchange through a structural analysis of the exchanger from Methanococcus jannaschii (NCX_Mj) bound to Na+, Ca2+ or Sr2+ in various occupancies and in an apo state. This analysis defines the binding mode and relative affinity of these ions, establishes the structural basis for the anticipated 3:1 Na+/Ca2+-exchange stoichiometry and reveals the conformational changes at the onset of the alternating-access transport mechanism. An independent analysis of the dynamics and conformational free-energy landscape of NCX_Mj in different ion-occupancy states, based on enhanced-sampling molecular dynamics simulations, demonstrates that the crystal structures reflect mechanistically relevant, interconverting conformations. These calculations also reveal the mechanism by which the outward-to-inward transition is controlled by the ion occupancy, thereby explaining the emergence of strictly coupled Na+/Ca2+ antiport. © 2016 Nature Publishing Group, a division of Macmillan Publishers Limited. All Rights Reserved.
Mao Q.,University of Shanghai for Science and Technology
Digital Signal Processing: A Review Journal | Year: 2014
A fast algorithm for matrix embedding steganography is proposed in this paper. Matrix embedding encodes the cover image and the secret message with an error correction code and modifies the cover image according to the coding result. The modification to the cover image is the coset leader of the error correction code, and it is computationally complex to find the coset leader. This paper proposes a fast algorithm to find the coset leader by using a lookup table algorithm. The proposed algorithm is suitable for matrix embedding steganography using Hamming code and random linear code. In our scheme, the syndrome of the coset is used to search for the coset leader in the standard array of the error correction code. For the Hamming code, we improved the parity check matrix of the code in order to make the syndrome indicate the coset leader by itself. Therefore, it is not necessary to search for the coset leader in a table. For the random linear code, this method is effective for most cosets, and we only memorize the coset leaders that cannot be identified by their syndromes. With this approach, the size of the table can be reduced significantly, and the computational complexity of embedding can be decreased. The proposed fast embedding algorithm has the same embedding efficiency as the conventional matrix embedding. Compared with the existing fast matrix embedding algorithms, the computational complexity of the proposed scheme is decreased significantly for the steganographic systems with low and medium embedding rates. © 2013 Elsevier Inc.
Yu D.G.,University of Shanghai for Science and Technology
International journal of nanomedicine | Year: 2011
The objective of this investigation was to develop a new type of solid dispersion in the form of core-sheath nanofibers using coaxial electrospinning for poorly water-soluble drugs. Different functional ingredients can be placed in various parts of core-sheath nanofibers to improve synergistically the dissolution and permeation properties of encapsulated drugs and to enable drugs to exert their actions. Using acyclovir as a model drug, polyvinylpyrrolidone as the hydrophilic filament-forming polymer matrix, sodium dodecyl sulfate as a transmembrane enhancer, and sucralose as a sweetener, core-sheath nanofibers were successfully prepared, with the sheath part consisting of polyvinylpyrrolidone, sodium dodecyl sulfate, and sucralose, and the core part composed of polyvinylpyrrolidone and acyclovir. The core-sheath nanofibers had an average diameter of 410 ± 94 nm with a uniform structure and smooth surface. Differential scanning calorimetry and x-ray diffraction results demonstrated that acyclovir, sodium dodecyl sulfate, and sucralose were well distributed in the polyvinylpyrrolidone matrix in an amorphous state due to favoring of second-order interactions. In vitro dissolution and permeation studies showed that the core-sheath nanofiber solid dispersions could rapidly release acyclovir within one minute, with an over six-fold increased permeation rate across the sublingual mucosa compared with that of crude acyclovir particles. The study reported here provides an example of the systematic design, preparation, characterization, and application of a novel type of solid dispersion consisting of multiple components and structural characteristics.