163 results on '"Wan, Kai"'
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52. Recovery of anammox process performance after substrate inhibition: Reactor performance, sludge morphology, and microbial community.
- Author
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Wan, Kai, Yu, Ye, Hu, Jinggang, Liu, Xuemei, Deng, Xiangyi, Yu, Junxia, Chi, Ruan, and Xiao, Chunqiao
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FILAMENTOUS bacteria , *HETEROTROPHIC bacteria , *MICROBIAL communities , *MORPHOLOGY , *CANDIDATUS , *GRANULATION , *NUCLEAR reactors - Abstract
[Display omitted] • Increasing the substrate concentration helped to improve the reactor tolerance. • In the P2 phase, side reactions impeded the removal of NO 2 –-N. • Filamentous bacteria, Ca and P synergistically promoted sludge granulation. • Anammox bacteria were reciprocal symbiosis with some heterotrophic bacteria. Most of the current studies have focused on the inhibition of anaerobic ammonium oxidation (anammox) by substrates, however, little attention has been paid to the recovery process of the reactor after inhibition. Therefore, we investigated the changes in reactor performance, granular sludge structure, and microbial community during the recovery phase after being inhibited by a high nitrogen load for 15 d. The nitrogen removal rate of the reactor was restored to pre-inhibition levels after 75 d of recovery, and the stoichiometric ratio converged to the theoretical value. The surface of the granular sludge developed into a broccoli-like structure, and the Ca and P contents of the granules increased from 6.88% and 4.39% to 24.42% and 13.88%, respectively. The abundance of the anammox bacterium Candidatus brocadia increased from 5.86% to 12.10%, and network analysis indicated that SMA102 and SBR1031 were positively correlated with the occurrence of Candidatus brocadia. [ABSTRACT FROM AUTHOR]
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- 2022
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53. Transition Metal Complexes of an (S,S)-1,2-Diphenylethylamine-Functionalized N-Heterocyclic Carbene: A New Member of the Asymmetric NHC Ligand Family.
- Author
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Wan, Kai Y., Lough, Alan J., and Morris, Robert H.
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PHENETHYLAMINES , *TRANSITION metals , *HETEROCYCLIC compounds , *CARBENES , *LIGANDS (Chemistry) , *METAL complexes - Abstract
By a simple SN2 reaction between N-methylimidazole and a chiral sulfamidate, the first proligand of a new class of enantiopure NHC-CHPh-CHPh-NH2 ligands can be prepared in high yield. This proligand, with the molecular formula [(S,S)-H2NCHPhCHPh-NC3H3N-CH3](PF6), when reacted with a slight excess of lithium or potassium bis(trimethylsilyl)amide, produces the corresponding NHC-CHPh-CHPh-NH2 ligand, "kaibene". In the presence of the silver(I) starting material AgPF6 or AgI, two Ag(kaibene)2X complexes (X = PF6 or I) and one helical kaibene silver polymer, [Ag(kaibene)]n(PF6)n, can be prepared. Using the suitable silver complex, we successfully transferred kaibene to ruthenium(II), iridium(I), and nickel(II). The ruthenium complex [Ru(p-cymene)(kaibene)(Cl)]PF6 with a base in THF is a moderately active catalyst at 50 °C and 25 bar of H2 for the hydrogenation of acetophenone but with no enantioselectivity. [ABSTRACT FROM AUTHOR]
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- 2016
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54. Barotropic current fluctuations coupled with sea level drawdown in Yellow and Bohai Seas.
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Wan, Kai, Bao, Xianwen, Wang, Yi, Wan, Xiuquan, Li, Haoqian, and Liu, Ke
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OCEAN currents , *SEA level , *ACOUSTIC Doppler current profiler , *BAROTROPIC equation , *CURRENT fluctuations - Abstract
Sub-tidal barotropic current variations coupled with residual sea level fluctuation in the Bohai and Yellow Seas during wintertime are addressed in this study. The temporal evolution and spatial distribution of current fluctuation are investigated using moored acoustic Doppler current profiler data in a three-dimensional numerical model. It is found that a southward current followed by a northward current occurred in the northern Yellow Sea during the fluctuation, concurrent with a significant outflow followed by inflow through the Bohai Strait. The process is consistent from surface to bottom and is coupled with remarkable residual sea level fluctuation. This quasi three-day fluctuation with amplitude 0.2-0.3 m/s leads to 1 m/1.2 m drawdown in the northern Yellow and Bohai Seas, respectively, strongly influencing water exchange between those seas. Because this a prominent feature in the seas, it is necessary to evaluate its effect on fluctuation during winter in future studies, in particular, the northward current during the recovery phase of sea level in the Bohai and Yellow Seas regarding seasonal variation. [ABSTRACT FROM AUTHOR]
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- 2015
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55. Insights into the Asymmetric Heterogeneous Catalysis in Porous Organic Polymers: Constructing A TADDOL-Embedded Chiral Catalyst for Studying the Structure-Activity Relationship.
- Author
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Wan-Kai An, Man-Yi Han, Chang-An Wang, Si-Min Yu, Yuan Zhang, Shi Bai, and Wei Wang
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POLYMERS , *MACROMOLECULES , *CATALYSIS , *CATALYSTS , *CHIRALITY - Abstract
Construction of porous organic polymers (POPs) as asymmetric catalysts remains as an important but challenging task. Herein, we exploit the 'bottom-up' strategy to facilely synthesize an α,α,α′,α′-tetraaryl-1,3-dioxolane-4,5-dimethanol (TADDOL)-based chiral porous polymer ( TADDOL- CPP) for highly efficient asymmetric catalysis. Constructed through the covalent linkages among the three-dimensional rigid monomers, TADDOL- CPP possesses hierarchical porous structure, high Brunauer-Emmett-Teller (BET) surface area, together with abundant and uniformly-distributed chiral sites. In the presence of [Ti(O iPr)4], TADDOL- CPP acts as a highly efficient and recyclable catalyst in the asymmetric addition of diethylzinc (Et2Zn) to aromatic aldehydes. Based on the direct observation of the key intermediates, the reaction mechanism has been revealed by solid-state 13C magic-angle spinning (MAS) NMR spectroscopy. In combination with the catalytic testing results, characterization on the working catalyst provides further information for understanding the structure-activity relationship. We suggest that the catalytic activity of TADDOL- CPP is largely affected by the structural rigidity, cooperative catalysis, local chiral environment, and hierarchical porous framework. We expect that the information obtained herein will benefit to the designed synthesis of robust POP catalysts toward practical applications. [ABSTRACT FROM AUTHOR]
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- 2014
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56. Mechanical instability of a solid inclusion in a soft matrix due to indentation.
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Liu, Shengchen and Wan, Kai-tak
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FINITE element method , *ELASTIC deformation , *INDENTATION (Materials science) - Abstract
A solid inclusion is embedded at a depth in a hyperelastic soft matrix resting on a rigid substrate. External compression is applied via an indenter vertical to the substrate, but the loading axis is misaligned with the inclusion. In case of large offset distance, the inclusion dodges the advancing indenter by moving laterally. For small offset, the inclusion moves vertically downward initially but turns abruptly sideways once the indenter reaches a critical depth. The unique behavior of gel under large elastic deformation is investigated by finite element analysis. Southwell subcritical extrapolation method is used to estimate the maximum indentation depth before a lateral displacement of the inclusion becomes inevitable. • An inclusion is embedded in a soft matrix. • Indentation axis is slightly misaligned with the inclusion. • Once indenter reaches a critical depth, inclusion experiences an unstable lateral motion. • Initial nearly symmetric stress field thus becomes asymmetric. [ABSTRACT FROM AUTHOR]
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- 2022
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57. Parameter Estimation of the Weibull Probability Distribution.
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Pang, Wan-Kai
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WEIBULL distribution , *MARKOV processes , *PARAMETER estimation , *ESTIMATION theory , *BAYESIAN analysis , *MATHEMATICAL physics - Abstract
The Weibull distribution plays an important role in modelling failure distribution in reliability studies . The reliability of a product or a system is the probability that the product or the system will still function for a specified time period. Parameter estimation for the parameter of the Weibull distribution has been studied by other researchers in the past and a number of optimization methods have been proposed. In this paper, we use the Markov Chain Monte Carlo (MCMC) techniques to estimate the Weibull parameter. The method is quite successful and the major advantage of this method is that it is free from any restrictions. Inference for any quantity of interest is easy to carry out. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]
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- 2004
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58. Adhesion Map for Thin Membranes.
- Author
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Guangxu Li and Wan, Kai-tak
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MECHANICAL properties of thin films , *SURFACE forces , *ADHESION , *BIOLOGICAL membranes , *DEFORMATIONS (Mechanics) , *PHYSIOLOGY - Abstract
A new Tabor's parameter ? is defined for adhesion-delamination of thin membranes. A small ? corresponds to a thick, small, and stiff membrane under the influence of a long-range weak surface force, as in the Derjaguin-Muller-Toporov (DMT) limit. A large ? corresponds to a thin, large, and flexible membrane under the influence of a short-range strong surface force, as in the Johnson-Kendall-Roberts (JKR) limit. A new adhesion map based on ? is drawn to summarize the "pull-off" events and the delamination trajectory for membranes under mixed stretching-bending deformation. Maps are generated for one- and two-dimensional membranes clamped at the edge. [ABSTRACT FROM AUTHOR]
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- 2014
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59. Aggregation of Electrochemically Active Conjugated Organic Molecules and Its Impact on Aqueous Organic Redox Flow Batteries.
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Xiang, Zhipeng, Li, Wenjin, Wan, Kai, Fu, Zhiyong, and Liang, Zhenxing
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FLOW batteries , *OXIDATION-reduction reaction , *MOLECULES , *OXIDATION states , *ELECTROCHEMISTRY - Abstract
Molecule aggregation in solution is acknowledged to be universal and can regulate the molecule's physiochemical properties, which however has been rarely investigated in electrochemistry. Herein, an electrochemical method is developed to quantitatively study the aggregation behavior of the target molecule methyl viologen dichloride. It is found that the oxidation state dicationic ions stay discrete, while the singly‐reduced state monoradicals yield a concentration‐dependent aggregation behavior. As a result, the molecule's energy level and its redox potential can be effectively regulated. This work does not only provide a method to investigate the molecular aggregation, but also demonstrates the feasibility to tune redox flow battery's performance by regulating the aggregation behavior. [ABSTRACT FROM AUTHOR]
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- 2023
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60. Aggregation of Electrochemically Active Conjugated Organic Molecules and Its Impact on Aqueous Organic Redox Flow Batteries.
- Author
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Xiang, Zhipeng, Li, Wenjin, Wan, Kai, Fu, Zhiyong, and Liang, Zhenxing
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FLOW batteries , *OXIDATION-reduction reaction , *MOLECULES , *OXIDATION states , *ELECTROCHEMISTRY - Abstract
Molecule aggregation in solution is acknowledged to be universal and can regulate the molecule's physiochemical properties, which however has been rarely investigated in electrochemistry. Herein, an electrochemical method is developed to quantitatively study the aggregation behavior of the target molecule methyl viologen dichloride. It is found that the oxidation state dicationic ions stay discrete, while the singly‐reduced state monoradicals yield a concentration‐dependent aggregation behavior. As a result, the molecule's energy level and its redox potential can be effectively regulated. This work does not only provide a method to investigate the molecular aggregation, but also demonstrates the feasibility to tune redox flow battery's performance by regulating the aggregation behavior. [ABSTRACT FROM AUTHOR]
- Published
- 2023
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61. Carbon Dioxide Flux from Rice Paddy Soils in Central China: Effects of Intermittent Flooding and Draining Cycles.
- Author
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Liu, Yi, Wan, Kai-yuan, Tao, Yong, Li, Zhi-guo, Zhang, Guo-shi, Li, Shuang-lai, and Chen, Fang
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PADDY fields , *SOIL composition , *CARBON dioxide , *FLOODS , *DRAINAGE , *EMISSIONS (Air pollution) , *AGRICULTURAL ecology , *SOIL pollution - Abstract
A field experiment was conducted to (i) examine the diurnal and seasonal soil carbon dioxide (CO2) fluxes pattern in rice paddy fields in central China and (ii) assess the role of floodwater in controlling the emissions of CO2 from soil and floodwater in intermittently draining rice paddy soil. The soil CO2 flux rates ranged from −0.45 to 8.62 µmol.m−2.s−1 during the rice-growing season. The net effluxes of CO2 from the paddy soil were lower when the paddy was flooded than when it was drained. The CO2 emissions for the drained conditions showed distinct diurnal variation with a maximum efflux observed in the afternoon. When the paddy was flooded, daytime soil CO2 fluxes reversed with a peak negative efflux just after midday. In draining/flooding alternating periods, a sudden pulse-like event of rapidly increasing CO2 efflux occurred in response to re-flooding after draining. Correlation analysis showed a negative relation between soil CO2 flux and temperature under flooded conditions, but a positive relation was found under drained conditions. The results showed that draining and flooding cycles play a vital role in controlling CO2 emissions from paddy soils. [ABSTRACT FROM AUTHOR]
- Published
- 2013
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62. Exponential stability of numerical solutions for a class of stochastic age-dependent capital system with Poisson jumps
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Zhang, Qi-min, Pang, Wan-kai, and Leung, Ping-kei
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NUMERICAL solutions to stochastic differential equations , *APPROXIMATION theory , *POISSON processes , *MATHEMATICAL inequalities , *ERROR analysis in mathematics , *STOCHASTIC convergence , *JUMP processes - Abstract
Abstract: Recently, numerical solutions of stochastic differential equations have received a great deal of attention. Numerical approximation schemes are invaluable tools for exploring their properties. In this paper, we introduce a class of stochastic age-dependent (vintage) capital system with Poisson jumps. We also give the discrete approximate solution with an implicit Euler scheme in time discretization. Using Gronwall’s lemma and Barkholder–Davis–Gundy’s inequality, some criteria are obtained for the exponential stability of numerical solutions to the stochastic age-dependent capital system with Poisson jumps. It is proved that the numerical approximation solutions converge to the analytic solutions of the equations under the given conditions, where information on the order of approximation is provided. These error bounds imply strong convergence as the timestep tends to zero. A numerical example is used to illustrate the theoretical results. [Copyright &y& Elsevier]
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- 2011
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63. “Pull-in” of a pre-stressed thin film by an electrostatic potential: A 1-D rectangular bridge and a 2-D circular diaphragm
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Duan, Gang and Wan, Kai-tak
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STRAINS & stresses (Mechanics) , *MECHANICAL properties of thin films , *ELECTROSTATICS , *DIAPHRAGMS (Structural engineering) , *MATERIALS compression testing , *FINITE element method , *MICROELECTROMECHANICAL systems , *CONTACT mechanics - Abstract
Abstract: A one-dimensional (1-D) rectangular pre-stressed thin film clamped at two opposite ends is actuated by an electrostatic voltage applied to a pad directly underneath. The pre-stress is allowed to be either tensile or compressive in nature. At a critical applied voltage, the film becomes unstable and makes direct contact with the pad, leading to “pull-in”. An elastic model is constructed to account for the phenomenon over ranges of film–pad gap and residual stress. The results compare favorably with finite element analysis (FEA) in literature and experimental data, and possess distinct advantages over other available closed-form solutions. The model is further extended to a two-dimensional (2-D) axisymmetric diaphragm clamped at the periphery. Interrelationship between bridge–pad gap, residual membrane stress, critical voltage, and pull-in central deflection is derived such that new design criteria can be derived for micro-/nano-electromechanical devices. Implications for nano-structures are also discussed. [Copyright &y& Elsevier]
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- 2010
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64. Convergence of numerical solutions to stochastic age-structured population equations with diffusions and Markovian switching
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Ronghua, Li, Wan-kai, Pang, and Ping-kei, Leung
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STOCHASTIC convergence , *NUMERICAL solutions to stochastic differential equations , *AGE-structured populations , *DIFFUSION processes , *MARKOV processes , *NONLINEAR theories , *NUMERICAL analysis , *APPROXIMATION theory - Abstract
Abstract: In this paper, it is considered for a class of stochastic age-structured population equations with diffusions and Markovian switching. Most kind of equations are nonlinear and cannot be solved explicitly, so the construction of efficient computational methods is of great importance. The main aim of this paper is to develop a numerical scheme and investigate the convergence of numerical approximation. An example is given for illustration. [Copyright &y& Elsevier]
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- 2010
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65. Exponential stability of numerical solutions to stochastic delay Hopfield neural networks
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Ronghua, Li, Wan-kai, Pang, and Ping-kei, Leung
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ARTIFICIAL neural networks , *TIME delay systems , *EXPONENTIAL functions , *STOCHASTIC processes , *EULER method , *NUMERICAL analysis - Abstract
Abstract: The main aim of this paper is to investigate the exponential stability of the Euler method and the semi-implicit Euler method for stochastic delay Hopfield neural networks. The definition of MS-stability and GMS-stability of these two numerical methods is introduced. Under the conditions which guarantee the stability of the analytical solution, the Euler scheme is proved to be MS-stable and the semi-implicit scheme is to be MS-stable and GMS-stable. An example is given for illustration. [Copyright &y& Elsevier]
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- 2010
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66. Nutrient Elements in Leaves of Rare and Endangered Species in Wuhan Botanical Garden, China.
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Wan, Kai-yuan, Chen, Fang, Tao, Yong, and Chen, Shu-sen
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BOTANICAL gardens , *HABITATS , *BIOTIC communities , *ECOSYSTEM management , *ENDANGERED species - Abstract
Characteristics of mineral elements in plants are often strongly influenced by species' abundance and heterogeneous habitats. Therefore, nutrient analysis, after excluding interference of habitat heterogeneity, would directly reflect genetic traits of species in the community. From another aspect, knowledge of responses of species to environmental variation would be helpful in the management of natural and man-made ecosystems, especially those containing rare and endangered plants conserved in gardens. We studied the characteristics of twelve nutrient elements in 90 species in Wuhan Botanical Garden (WBG) and provided explanations of their survival status. Concentrations of the 12 nutrients in the artificial garden were consistent with those in other natural communities in the subtropical zone of China. Features of nutrient-limited at the community level were also consistent with the regional characteristics (N:P ratio being 9.79 ± 3.22, as exhibiting N-limited). The Ca + Mg concentrations differed between evergreen and deciduous species. The 90 species were clustered into various functional nutrition groups. The artificial community of the garden was a “sick” one relative to natural ones with wholesome ecological functions. The proportion of element-pairs with significant correlations (P < 0.01 or P < 0.05) to total element-pairs was only 24.2%, being lower than that of species in the natural community, This suggests that the harmonious relationship among nutrient elements in these species was yet to be achieved. Correlation analysis between survival status of the 90 species and their foliar nutrient ratios were positive for nitrogen (N), phosphorus (P), potassium (K), iron (Fe), zinc (Zn), copper (Cu), and sodium (Na), but negative for calcium (Ca), magnesium (Mg), manganese (Mn), and aluminum (Al). Cluster analysis suggested that, among 23 species with the poorest survival status, 21 species had higher Ca and Mg, but lower N and P concentrations. [ABSTRACT FROM AUTHOR]
- Published
- 2009
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67. Hepatocyte growth factor enhances proteolysis and invasiveness of human nasopharyngeal cancer cells through activation of PI3K and JNK
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Zhou, Hong Yan, Wan, Kai Fung, Ip, Carman K.M., Wong, Chris K.C., Mak, Nai Ki, Lo, Kwok Wai, and Wong, Alice S.T.
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HEPATOCYTE growth factor , *PROTEOLYSIS , *CANCER cells , *CELL motility - Abstract
Abstract: The hepatocyte growth factor (HGF) receptor, Met, is frequently overexpressed in nasopharyngeal cancer (NPC). Here, we showed for the first time that human NPC cells with high Met expression were more sensitive to the cell motility and invasion effect of HGF. The downregulation of Met by small interfering RNA decreased tumor cell invasion/migration. HGF significantly increased matrix metalloproteinase-9 production. This was inhibited by blocking phosphatidylinositide 3-kinase (PI3K) and c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase 1/2 and p38 mitogen-activated protein kinase signaling pathways. We also demonstrated that PI3K induced activation of JNK, with Akt as a potential point of this cross-talk. These results provide new insights into the molecular mechanism responsible for NPC progression and metastasis. [Copyright &y& Elsevier]
- Published
- 2008
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68. Air quality services on climate time-scales for decision making: An empirical study of China.
- Author
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Wan, Kai, Shackley, Simon, Doherty, Ruth M., Shi, Zongbo, Zhang, Peiqun, Glenk, Klaus, Bo, Xin, Chang, Luyu, Feng, Zhiqiang, Hewitt, Chris D., Wang, Qian, Xu, Jianming, and Xu, Jun
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QUALITY of service , *DECISION making , *COMMERCIAL aeronautics , *SEASONS , *CHINA studies , *AIR quality , *AIR pollution - Abstract
The provision of climate services for assessing and governing environmental problems such as poor air quality requires interactions between scientists and decision-makers. Air quality information services in China mainly focus on the coming days to weeks. However, users may benefit from air quality information on climate time-scales—from months to decades; hereafter air quality climate services. We focused on key decision-makers and stakeholders that are users of air quality climate services and conducted five workshops with these identified users to ascertain their priorities for air quality climate services, and the reasoning behind these priorities. We also conducted a choice-based conjoint experiment via an online survey distributed amongst regional and local Climate Centres and Environmental Monitoring Centres to assess quantitatively the decision-makers' needs. The results from the workshops and the survey showed that the needs for air quality climate services by users in China mainly relate to seasonal forecasting of winter haze events (PM 2.5 levels and/or the meteorological conditions conducive to the dispersion of the air pollution); there is also some interest in long-term projections of haze under climate change and a growing interest in ozone pollution in summer. Spatial relevance is perceived to be important to regional and city-level stakeholders who prefer information on the city-level, whilst national-wide information is important for national government agencies. A high level of reliability of forecasts was needed for uptake. The findings on the needs for air quality climate services by potential users can support researchers and policy-makers in developing the scientific capacity and providing tailored and effective air quality climate services in China. • To understand decision-maker needs on air quality climate services, qualitative and quantitative methods were conducted, and the results were compared and combined. • Decision-makers and stakeholders expressed a strong interest for seasonal forecasting for winter haze. • They also expressed a moderate interest for seasonal forecasting for summer ozone pollution, and a modest interest for long-term projections of haze under climate change. • A high level of reliability of forecasts was needed for uptake while multiple sources of uncertainties were recognised. [ABSTRACT FROM AUTHOR]
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- 2021
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69. Developing a Sustainability Evaluation System in Taiwan to Support Infrastructure Investment Decisions.
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Lee, Wan-Kai, Lin, Chien-yuan, and Kuo, Fei-Yu
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SUSTAINABLE development , *ECONOMIC development , *DECISION making , *INFRASTRUCTURE (Economics) - Abstract
In order to improve the effectiveness of infrastructure investments toward sustainable development, a comprehensive evaluation system to support decision making is critically needed. This article takes Taiwan as the study area; a sustainability evaluation system is developed to support decision making in government funding allocation for different infrastructure investments. In addition to the system development, operation and application potentials of the proposed system are illustrated and discussed through the evaluation of a controversial freeway construction project in Taiwan. [ABSTRACT FROM AUTHOR]
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- 2008
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70. Applications of a distributed fiber optic crack sensor for concrete structures
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Wan, Kai Tai and Leung, Christopher K.Y.
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OPTICAL fiber detectors , *CRACKING of concrete , *CONCRETE defects , *PERFORMANCE standards - Abstract
Abstract: The degradation of concrete structures is always accompanied by the formation of cracks. If cracks are detected at an early stage before significant degradation occurs, life of the structure can be extended by the performance of relatively low cost but timely maintenance measures. To detect and monitor cracking in concrete structures, where the crack locations are often not known in a-priori, a distributed optical crack sensor based on OTDR measurement of bend loss has been developed. In this paper, the sensing principle will be discussed and the fabrication of sensors for surface attachment and internal embedment is described. Experimental results are shown to demonstrate that the optical power loss versus crack opening relation at a particular point of bend loss is independent of the number of bends along the fiber. Then, the monitoring of single and multiple cracks under quasi-static loading is illustrated, followed by the detection of cracks under restrained dimensional change (caused by shrinkage or thermal effects). Finally, the sensor performance under cyclic loading is studied. Based on the test results, the potential of the sensor for practical applications is demonstrated. [Copyright &y& Elsevier]
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- 2007
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71. Fiber optic sensor for the monitoring of mixed mode cracks in structures
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Wan, Kai Tai and Leung, Christopher K.Y.
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OPTICAL detectors , *FIBER optics , *REMOTE sensing , *CRACKING of concrete - Abstract
Abstract: Cracks in structures may open in mixed mode under general loading conditions. In other words, there are both opening and shearing displacements along the crack. In our former work, a distributed fiber optic sensor has been developed for the detection and monitoring of purely opening cracks (or Mode I cracks). The sensing principle is based on the bending loss of an optical fiber intersecting the opening crack at an angle other than 90°. In the present work, the sensing concept is extended to the monitoring of mixed mode cracks. To obtain both the opening and shear displacements at the crack, two independent measurements are required. Based on theoretical simulation, the feasibility of various sensing strategies, including the use of two wavelengths and two fibers, are first investigated to identify the most promising approach. A method to solve the inverse problem of obtaining the crack displacements from the measured signal losses is then derived. Experiments are performed under controlled crack opening/shearing history to verify the sensing approach. Good agreement between derived opening/shearing displacements and imposed displacements has been obtained. [Copyright &y& Elsevier]
- Published
- 2007
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72. A bending-to-stretching analysis of the blister test in the presence of tensile residual stress
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Guo, Shu, Wan, Kai-Tak, and Dillard, David A.
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RESIDUAL stresses , *STRENGTH of materials , *THIN films , *FRACTURE mechanics - Abstract
Abstract: The adhesion of films and coatings to rigid substrates is often measured using blister geometries, which are loaded either by an applied pressure or a central shaft. The measurement will be affected if there are residual stresses that make a contribution to the energy release rate. This effect is investigated using analytical solutions based on the principle of virtual displacements. A geometrically nonlinear finite element analysis is conducted for comparison. Furthermore, the relationships among strain energy release rate, load, deflection, and fracture radius are discussed in detail. Both analytical solutions and numerical results reveal that uniform tensile residual stresses reduce a specimen’s deflection if it experiences plate behavior under small loads. However, this effect becomes negligible when membrane stresses induced by the loading become dominant. [Copyright &y& Elsevier]
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- 2005
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73. Derivation of the strain energy release rate G from first principles for the pressurized blister test
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Arjun, Anup and Wan, Kai-Tak
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STRAINS & stresses (Mechanics) , *FORCE & energy , *NUMERICAL analysis , *METHODOLOGY , *DYNAMIC testing of materials - Abstract
The strain energy release rate, G, is derived from first principles and is shown to be consistent with the exact numerical solution by Cotterell and Chen (Int. J. Fract. 86 (1997) 191). Comparison with the classical Rayleigh–Ritz energy method and other published methods shows that the gradual change in blister profile over the entire loading process must be considered for the correct G to be calculated. [Copyright &y& Elsevier]
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- 2005
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74. A theoretical and numerical study of thin film delamination using the pull-off test
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Sun, Zuo, Wan, Kai-Tak, and Dillard, David A.
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STRAIN hardening , *STRAINS & stresses (Mechanics) , *METAL fractures , *HARDENABILITY of metals - Abstract
An accurate closed-form analytical solution for the strain energy release rate for a thin rectangular film loaded by a central line force using the pull-off test is derived in the presence of a tensile residual stress. The theoretical constitutive relation and the strain energy release rate agree very well with two-dimensional nonlinear finite element analysis for the entire deformation regime ranging from bending plate to stretching membrane. Fracture modes for this pull-off test are also investigated based upon the finite element analysis, offering additional insights to the interfacial delamination. [Copyright &y& Elsevier]
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- 2004
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75. A theoretical and numerical study of a thin clamped circular film under an external load in the presence of a tensile residual stress
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Wan, Kai-Tak, Guo, Shu, and Dillard, David A.
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THIN films , *RESIDUAL stresses - Abstract
Tensile residual stress in a plate or membrane clamped at the perimeter can be measured by either applying a uniform hydrostatic pressure or a central load via a cylindrical punch (with several different loading configurations). Analytical constitutive relations are derived here based on an average membrane stress approximation and are compared to finite element analysis results. The thickness and flexural rigidity of the film are not confined to a small range but will span a wide spectrum. The elastic responses of the blistering films are shown to be linear when the film is thick, relatively rigid, or subjected to a large residual stress, and cubic when the film is thin, flexible, or under a small residual stress. The linear-to-cubic transition is formulated. [Copyright &y& Elsevier]
- Published
- 2003
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76. Constitutive equation for elastic indentation of a thin-walled bio-mimetic microcapsule by an atomic force microscope tip
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Wan, Kai-tak, Chan, Vincent, and Dillard, David A.
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ARTIFICIAL cells , *ATOMIC force microscopy , *BENDING moment - Abstract
A new theoretical model is presented for the mechanical response of a thin-walled bio-mimetic microcapsule upon indentation using an atomic force microscope. The membrane is strained by both bending moments and membrane stress in the presence of a tensile pre-stress. When the intrinsic membrane stress is large compared to the local stress around the indentation dimple, the constitutive relation is linear; and when it is small, a cubic relation is deduced. The new theory is rigorously compared to the existing models of: (i) membrane under pure bending by Boulbitch; and (ii) membrane under pure stretching by Yao et al., which are shown to be two limiting cases of our general solution. Published experimental data in literature show that AFM measurement always involves deformation mode of mixed bending and stretching. [Copyright &y& Elsevier]
- Published
- 2003
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77. Mechanical integrity and adhesion of thin films for applications in electronics packaging and cell biology
- Author
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Duan, Jin, Wan, Kai-tak, and Chian, Kerm-sin
- Subjects
- *
THIN films , *TRIBOLOGY - Abstract
A new theoretical model was developed for a pull-off adhesion test using an axisymmetric flat punch and a rectangular flat punch adhered to a thin polymer film interface. An elastic solution was derived to portray the mechanical integrity of the thin film. A mechanical energy release rate was calculated numerically. As the punch was pulled away from the adhered film, the film deformed under mixed bending and stretching. Both stiffness and thickness of the film were allowed to vary. The derived solid-film ‘pull-off’ events sharply contrast with the abrupt pull-off in solid–solid adhesion as predicted by the classical JKR theory. [Copyright &y& Elsevier]
- Published
- 2003
- Full Text
- View/download PDF
78. Thermal induced modification of the contact mechanics of adhering liposomes on cationic substrate
- Author
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Chan, Vincent and Wan, Kai-Tak
- Subjects
- *
THERMOTROPISM , *PHOSPHOLIPIDS , *ELECTROSTATICS , *HEAT transfer - Abstract
The correlation between the mechanical property and the thermotropic transition of the phospholipid bilayer has been recently demonstrated (Chem. Phys. Lipids 110 (2001) 27). However, the role of thermal induced mechanical responses of phospholipid bilayer on the contact mechanics of liposome adhering on a cationic substrate has not been determined. In this study, confocal-reflectance interference contrast microscopy, phase contrast microscopy and contact mechanics modeling are applied to probe the adhesion mechanisms of liposomes in the presence of electrostatic interactions during the thermotropic transition of the lipid bilayer. When temperature increases from 23 to 49 °C at pH 7.4, the degree of liposome deformation (a/R) and adhesion energy of dipalmitoyl-sn-glycero-3-phosphocholine liposome increases by 10% and remains constant, respectively, on 3-amino-propyl-triethoxy-silane (APTES) modified substrate. The extents of increase in these two parameters are highly dependent on the physicochemical properties of the rigid substrate. At pH 4, the adhesion energies above and below the phase transition temperature (Tm) are increased by one order of magnitude due to the formation of the free silanol groups on APTES substrate. In hypotonic condition, the degree of vesicle deformation remains constant and the adhesion energy reduces by 20% during sample heating. Under all conditions, the adhesion energy of the adhering liposome spans a few orders of magnitude against the increase of liposome size as the surface area to volume ratio is maximized in smallest vesicle. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
79. Substrate-induced deformation and adhesion of phospholipid vesicles at the main phase transition
- Author
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Lai, Alvin Chi-keung, Wan, Kai-tak, and Chan, Vincent
- Subjects
- *
LIPOSOMES , *TRANSITION temperature , *PHASE transitions - Abstract
The physiochemical properties of phospholipid vesicle, e.g. permeability, elasticity, etc., are directly modulated by the chain-melting transition of the lipid bilayer. Currently, there is a lack of understanding in the relationship between thermotropic transition, mechanical deformation and adhesion strength for an adherent vesicle at temperature close to main phase transition temperature Tm. In this study, the contact mechanics of dimyristoyl-phosphatidylcholine (DMPC) vesicle at the main phase transition are probed by confocal reflectance interference contrast microscopy in combination with phase contrast microscopy. It is shown that DMPC vesicles strongly adhere on pure fused silica substrate at Tm and the degree of deformation as well as the adhesion energy is a decreasing function against the mid-plane diameter of the vesicles. Furthermore, an increase of osmotic pressure at the gel/liquid crystalline phase co-existence imposes insignificant changes in both the degree of deformation and adhesion energy of adherent vesicles when the lipid bilayer permeability is maximized. With the reverse of substrate charge, the mechanical deformation and adhesion strength for larger vesicles (mid-plane diameter >18 μm) are significantly reduced. By monitoring the parametric response of substrate-induced vesicle adhesion during main phase transition, it is shown that the degree of deformation and adhesion energy of adhering vesicle is increased and unchanged, respectively, against the increase of temperature. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
80. Inversion of confluent Vandermonde matrices
- Author
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Hou, Shui-Hung and Pang, Wan-Kai
- Subjects
- *
ALGORITHMS , *MATRICES (Mathematics) - Abstract
This paper is concerned with the inversion of confluent Vandermonde matrices. A novel and simple recursive algorithm for inverting confluent Vandermonde matrices is presented. The algorithm is suitable for classroom use in both numerical as well as symbolic computation. Examples are included to illustrate the proposed algorithm. [Copyright &y& Elsevier]
- Published
- 2002
- Full Text
- View/download PDF
81. Response to “Comment on ‘Adhesion-delamination mechanics of a presented rectangular film adhered onto a rigid substrate’ [J. Appl. Phys. 101, 024903 (2007)]”.
- Author
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Wan, Kai-Tak and Duan, Gang
- Subjects
- *
LETTERS to the editor , *PHYSICS - Abstract
A letter to the editor is presented in response to the article "Adhesion-delamination mechanics of a presented rectangular film adhered onto a rigid substrate."
- Published
- 2007
- Full Text
- View/download PDF
82. Distributed adaptive iterative learning control for 2D multi agent systems.
- Author
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Xu, Qingyuan, Mai, Qingquan, Wang, Boxian, Wan, Kai, and Wei, Yunshan
- Abstract
This letter addresses the output consensus problem for a class of two‐dimensional (2D) multi agent systems (MASs) described by Fornasini–Marchesini model. By transforming the 2D agent into a compact form, an adaptive variable, which adjusted by the tracking errors of itself and the neighbour agents, is designed to approximate the unknown varying coefficient. Then, based on the approximated coefficient and the iteration‐varying reference surfaces, the distributed adaptive iterative learning control strategy is obtained. The output consensus of the 2D multi agent is proved. Simulations are included to verify the effectiveness of the investigated distributed adaptive ILC for 2D MASs with random variations on initial condition and reference surface. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
83. Influence of Nitrogen Loading on the Performance of Partial Nitrification Processes and the Evolution of Microbial Communities.
- Author
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Liu, Xuemei, Xiao, Chunqiao, Hu, Jingang, Wan, Kai, Deng, Xiangyi, and Chi, Ruan
- Subjects
- *
NITROGEN cycle , *MICROBIAL communities , *NITRIFICATION , *AMMONIA-oxidizing bacteria , *DENITRIFYING bacteria , *NITROGEN - Abstract
Stable and efficient partial nitrification reaction and nitrite accumulation are essential for the operation of partial nitrification-anaerobic ammonia oxidation process. This paper investigated the changes in the performance of a partial nitrification bioreactor during the domestication process. After 40 days of domestication, the partial nitrification reaction remained stable, the nitrite accumulation rate (NAR) increased significantly to 85.7%, and the NO2--N/NH4+-N ratio stabilized at 1.25 ± 0.04. Both diversity indices (Simpson and Shannon) and richness indices (Ace and Chao1) tend to decrease with domestication. Nitrosomonas as a typical ammonia oxidizing bacterium it increased its relative abundance in the reactor from 0.02 ± 0.007% at P1 to 11.6 ± 2.2% at P2, and at P3 stage the denitrifying functional bacteria norank_f_AKYH76, Dokdonella and unclassified_f_Comamonadaceae reached 33.4 ± 12.5%, 18.8 ± 1.8%, and 10.1 ± 1.3%, respectively, and the increase in the relative abundance of these functional species was also consistent with the accumulation of nitrite nitrogen in the reactor. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
84. A novel identification method for all geometric errors of rotary axis based on boundaryless constraint optimization method.
- Author
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Peng, Weichao, Huang, Jianfeng, Wan, Kai, and Xia, Hongjian
- Subjects
- *
IDENTIFICATION , *MEASUREMENT errors , *LEAST squares , *CURVE fitting , *ERROR functions , *SENSITIVITY analysis - Abstract
• The relationship between moving bodies on the rotary table is presented based on kinematic theory. • Separately identification method for position independent geometric errors by double ball bar is presented. • A novel optimization identification method for identification of position dependent geometric errors is proposed. • The influence of installation errors on geometric errors identification is investigated based on sensitivity analysis. For the redundancy in definition of position independent geometric errors(PIGEs) and position dependent geometric errors(PDGEs), it is difficult to identify all geometric errors of rotational axis simultaneously. A novel identification method using boundaryless constraint optimization method(BCOM) is established to improve PIGEs and PDGEs identification accuracy of rotary axis. For PIGEs, the two different dimension errors are identified separately based on least square method through appropriate measurement direction by double ball bar(DBB), and thus decrease condition number of identification matrix. For PDGEs, the B-spline curve is applied to fit the geometric errors and the objective function has been established. Several measurement paths are conducted and geometric errors are figured out by iterations of objective function. Furthermore, setup errors of DBB are investigated and discussed based on the sensitivity analysis. Finally, Simulations and experiments are conducted and their results demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
85. Enhanced Control of the Fungus Gnat Bradysia odoriphaga (Diptera: Sciaridae) by Co-Application of Clothianidin and Hexaflumuron.
- Author
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Wang, Yongqing, Wan, Kai, Wang, Ruifei, Wu, Jiyingzi, Hou, Ruiquan, Zhao, Kunyu, Zhang, Zhixiang, Chen, Jianjun, and Cheng, Dongmei
- Subjects
- *
MYCETOPHILIDAE , *CLOTHIANIDIN , *INSECT growth regulators , *DIPTERA , *INSECTICIDE resistance - Abstract
Simple Summary: The fungus gnat (Bradysia odoriphaga Yang and Zhang) is a major pest of chive (Allium tuberosum Rottl. ex Spreng) that can cause more than 50% yield losses during chive production in China. The neonicotinoid, neuroactive insecticide clothianidin has been widely used for chive gnat control; however, following intensive use of this compound, its effects on chive gnat have been markedly reduced, possibly due to the development of insecticide resistance. Hexaflumuron is an insect growth regulator which disrupts chitin synthesis during molting by inhibiting the incorporation of N-acetyl glucosamine monomers into the integument chitin of insects. The present study shows that co-drenching of clothianidin and hexaflumuron enhanced chive absorption of clothianidin, resulting in significant improvement in control of fungus gnat. Additionally, the terminal residues of clothianidin in chive were lower than the maximum residue limit in chive set by the Codex Alimentarius Commission, hence, the chive could be safe for consumption. The fungus gnat is a major pest of chive in China. Its control has been relied heavily on the application of clothianidin. Due to the intensive application, its control efficacy become reduced. The present study was intended to evaluate co-drenching of clothianidin with hexaflumuron on absorption and dissipation of clothianidin in chive plants and soils and determine the effect of such application on control efficacies. Chive production fields in Guangdong and Hubei Provinces were drenched with clothianidin alone and a mixture of clothianidin and hexaflumuron at low application rates. Concentrations of clothianidin in chive plants and soils were analyzed by HPLC. Results showed that co-application had higher control efficacies against the fungus gnat than clothianidin alone. The co-application enhanced clothianidin absorption and dissipation and extended the half-lives of clothianidin in chive. It was likely that hexaflumuron protected chive roots from larva damage, and healthy roots absorbed more clothianidin, resulting in the extension of the half-lives. Additionally, the terminal residues of clothianidin in chive after 14 days of application were lower than the maximum residue limit in chive set by the Codex Alimentarius Commission. This study for the first time documented that co-application of clothianidin and hexaflumuron improved chive plants in absorption and dissipation of clothianidin and enhanced fungus gnat control efficacies. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
86. MODELLING BINARY DATA: A GIBBS SAMPLING APPROACH.
- Author
-
Wan-Kai Pang
- Subjects
- *
LINEAR statistical models , *STATISTICAL sampling - Abstract
Examines a Gibbs sampling approach to modelling binary data. Estimation of the model parameters of a generalized linear model with random effects; Use of adaptive rejection sampling method proposed by Gilks and Wild; Adaptive rejection sampling algorithm.
- Published
- 1999
- Full Text
- View/download PDF
87. Cache-Aided General Linear Function Retrieval.
- Author
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Wan, Kai, Sun, Hua, Ji, Mingyue, Tuninetti, Daniela, and Caire, Giuseppe
- Subjects
- *
MULTICASTING (Computer networks) , *MEMORY - Abstract
Coded Caching, proposed by Maddah-Ali and Niesen (MAN), has the potential to reduce network traffic by pre-storing content in the users' local memories when the network is underutilized and transmitting coded multicast messages that simultaneously benefit many users at once during peak-hour times. This paper considers the linear function retrieval version of the original coded caching setting, where users are interested in retrieving a number of linear combinations of the data points stored at the server, as opposed to a single file. This extends the scope of the authors' past work that only considered the class of linear functions that operate element-wise over the files. On observing that the existing cache-aided scalar linear function retrieval scheme does not work in the proposed setting, this paper designs a novel coded caching scheme that outperforms uncoded caching schemes that either use unicast transmissions or let each user recover all files in the library. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
88. Automated detection of subthalamic nucleus in deep brain stimulation surgery for Parkinson's disease using microelectrode recordings and wavelet packet features.
- Author
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Karthick, P.A., Wan, Kai Rui, An Qi, Angela See, Dauwels, Justin, and King, Nicolas Kon Kam
- Subjects
- *
DEEP brain stimulation , *PARKINSON'S disease , *SUBTHALAMIC nucleus , *BRAIN stimulation , *BRAIN surgery , *SUPPORT vector machines - Abstract
• Microelectrode recordings performed during DBS surgery are stochastic and non-stationary, therefore, their interpretation is challenging. • Wavelet packet based features are explored to localize the pre-STN, STN and post-STN. • k - N N , support vector machine and random forest models are designed to detect the STN. • Proposed system achieves a maximum average accuracy of 85.01 % in the classification non-STN vs. STN with random forest. • Proposed method is a fast and reliable, therefore, it may facilitate real-time intraoperative STN identification. Deep brain stimulation (DBS) to the subthalamic nucleus (STN) is an effective neurosurgery that overcomes the motor system alternations of patients with advanced Parkinson's disease. The most challenging aspect of DBS surgery is the accurate identification of STN and its borders. In general, it is performed manually by a neurophysiologist using the microelectrode recordings (MERs). This process is subjective, and tedious and further, interpretation of MERs is difficult because of its inherent nonstationary variations. In this work, the wavelet-packet based features are proposed to automatically localize the STN and its subcortical structures using microelectrode recorded signals during DBS surgery. The study analyses 2904 MERs of 26 PD patients who underwent DBS implantation. The low and high order statistical parameters are extracted from the wavelet packet coefficients of MERs and used in the classifications, namely, non-STN vs. STN, pre-STN vs. STN and STN vs. post-STN. Most of the features are significantly different in STN and its subcortical regions, namely, pre-STN and post-STN. The proposed features achieve an average accuracy of 85 % in non-STN vs. STN, 87.2 % in pre-STN vs. STN and 77.7 % in STN vs. post-STN. The accuracy is improved by around 10 % in non-STN vs. STN and STN vs. post-STN when the transition error is 1 mm. The proposed features are found to be better than the wavelet features. The proposed approach could be a potential useful adjunct for the real-time rapid intraoperative identification of STN and its anatomical borders. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
89. An aquaporin and an aquaglyceroporin have roles in low temperature adaptation of mosquitoes (Anopheles sinensis)
- Author
-
Zhao, Yong‐Qiao, Tang, Yi‐Ying, Hu, Ju‐Ping, Huang, Yu‐Zheng, Wan, Kai, Zhang, Mei‐Hua, Li, Ju‐Lin, Zhu, Guo‐Ding, and Tang, Jian‐Xia
- Abstract
Mosquitoes (
Anopheles sinensis ), widely geographically distributed in Asia including China, are the primary vector of the malaria parasitePlasmodium vivax and other parasitic diseases such as Malayan filariasis.An. sinensis can survive through low winter temperatures. Aquaporin channels are found in all life forms, where they facilitate environmental adaptation by allowing rapid trans‐cellular movement of water (classical aquaporins) or water and solutes such as glycerol (aquaglyceroporins). Here, we identified and characterized 2 aquaporin (AQP) homologs inAn. sinensis : AsAQP2 (An. sinensis aquaglyceroporin) and AsAQP4 (An. sinensis aquaporin). When expressed in frog (Xenopus laevis ) oocytes, AsAQP2 transported water, glycerol, and urea; AsAQP4 transported only water. Water permeation through AsAQP2 and AsAQP4 was inhibited by mercuric chloride.AsAQP2 expression was slightly higher in adult female mosquitoes than in males, andAsAQP4 expression was significantly higher in adult males. The 2 AsAQPs were highly expressed in Malpighian tubules and midgut.AsAQP2 andAsAQP4 expression was up‐regulated by blood feeding compared with sugar feeding. At freezing point (0 °C), theAsAQP4 expression level increased andAn. sinensis survival time reduced compared with those at normal temperature (26 °C). At low temperature (8 °C), theAsAQP2 andAsAQP4 expression levels decreased and survival time was significantly longer compared with those at 26 °C. These results suggest that AsAQP2 and AsAQP4 have roles in water homeostasis during blood digestion and in low temperature adaptation ofA. sinensis . Together, our results show that the 2 AQPs are important for mosquito diuresis after blood feeding and when exposed to low temperatures. [ABSTRACT FROM AUTHOR]- Published
- 2024
- Full Text
- View/download PDF
90. Light‐Induced Vicinal Dichlorination of Alkenes Using FeCl3 as the Dichlorination Reagent.
- Author
-
Li, Minghao, Qiu, Ming, Ren, Yun‐Lai, Li, Hui, and An, Wan‐Kai
- Subjects
- *
ALKENES , *FERRIC chloride , *CHLORINATION , *WATER chlorination , *CHLORIDES , *WATER disinfection - Abstract
We report a ligand‐to‐metal charge‐transfer (LMCT) process that used ferric (III) chloride as efficient chlorination reagent to mediate the vicinal dichlorination of alkenes. Under 420 nm LED light, the easily available and safe ferric (III) chloride could facilitate various alkenes to transform as 1,2‐dichloride compounds with good to excellent yields (19 examples). The strategy showed a more economic protocol than CuCl2, and provided a significant reference for the light‐Induced dichlorination in industrial catalysis. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
91. Cathodic Electrodeposition of MOF Films Using Hydrogen Peroxide.
- Author
-
Xie, Sijie, Monnens, Wouter, Wan, Kai, Zhang, Wei, Guo, Wei, Xu, MaoWen, Vankelecom, Ivo F. J., Zhang, Xuan, and Fransaer, Jan
- Subjects
- *
ROSE bengal , *ELECTROPLATING , *METAL-organic frameworks , *METALS - Abstract
Metal–organic framework (MOF) films can be made by cathodic electrodeposition, where a Brønsted base is formed electrochemically which deprotonates the MOF linkers that are present in solution as undissociated/partially dissociated weak acids. However, the co‐deposition of metal and the narrow range of possible metal nodes limit the scope of this method. In this work, we propose the use of hydrogen peroxide (hydrogen peroxide assisted cathodic deposition or HPACD), to overcome these limitations. Electrochemical measurements indicate that in DMF, hydrogen peroxide is reduced to superoxide anions that deprotonate the carboxylic ligands. This single‐electron reduction happens at much higher potentials than all previous reported methods. This prevents the co‐deposition of metal and extends the range of possible metal nodes. Various pure MOF films (HKUST‐1, MIL‐53(Fe) and MOF‐5) were prepared via this approach. HPACD was also used for the preparation of patterned MOF films and of flexible Cu‐BTC coated paper membranes which reject 99.1 % of Rose Bengal from water with a permeance of 8.4 L m−2 h−1 bar−1. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
92. Cathodic Electrodeposition of MOF Films Using Hydrogen Peroxide.
- Author
-
Xie, Sijie, Monnens, Wouter, Wan, Kai, Zhang, Wei, Guo, Wei, Xu, MaoWen, Vankelecom, Ivo F. J., Zhang, Xuan, and Fransaer, Jan
- Subjects
- *
ROSE bengal , *ELECTROPLATING , *METAL-organic frameworks , *METALS - Abstract
Metal–organic framework (MOF) films can be made by cathodic electrodeposition, where a Brønsted base is formed electrochemically which deprotonates the MOF linkers that are present in solution as undissociated/partially dissociated weak acids. However, the co‐deposition of metal and the narrow range of possible metal nodes limit the scope of this method. In this work, we propose the use of hydrogen peroxide (hydrogen peroxide assisted cathodic deposition or HPACD), to overcome these limitations. Electrochemical measurements indicate that in DMF, hydrogen peroxide is reduced to superoxide anions that deprotonate the carboxylic ligands. This single‐electron reduction happens at much higher potentials than all previous reported methods. This prevents the co‐deposition of metal and extends the range of possible metal nodes. Various pure MOF films (HKUST‐1, MIL‐53(Fe) and MOF‐5) were prepared via this approach. HPACD was also used for the preparation of patterned MOF films and of flexible Cu‐BTC coated paper membranes which reject 99.1 % of Rose Bengal from water with a permeance of 8.4 L m−2 h−1 bar−1. [ABSTRACT FROM AUTHOR]
- Published
- 2021
- Full Text
- View/download PDF
93. Metasurfaces: Wireless Communications through a Simplified Architecture Based on Time‐Domain Digital Coding Metasurface (Adv. Mater. Technol. 7/2019).
- Author
-
Dai, Jun Yan, Tang, Wan Kai, Zhao, Jie, Li, Xiang, Cheng, Qiang, Ke, Jun Chen, Chen, Ming Zheng, Jin, Shi, and Cui, Tie Jun
- Subjects
- *
WIRELESS communications , *DIGITAL communications , *WIRELESS channels , *DATA transmission systems - Published
- 2019
- Full Text
- View/download PDF
94. Wireless Communications through a Simplified Architecture Based on Time‐Domain Digital Coding Metasurface.
- Author
-
Dai, Jun Yan, Tang, Wan Kai, Zhao, Jie, Li, Xiang, Cheng, Qiang, Ke, Jun Chen, Chen, Ming Zheng, Jin, Shi, and Cui, Tie Jun
- Subjects
- *
WIRELESS communications , *DIGITAL communications , *FREQUENCY shift keying , *TELECOMMUNICATION , *VARACTORS - Abstract
Tailoring the electromagnetic responses by metasurface greatly expands one's capabilities to manipulate light in a controlled manner. Either amplitude or phase of the incident wave can be altered during the light–matter interaction, and thus opens the possibility of information modulation without conventional analog or digital circuits. A prototype of quadrature phase‐shift keying (QPSK) wireless communication based on time‐domain digital coding metasurface, whose reflection properties can be varied within different time slots by changing the biasing voltages of varactor diodes in specially designed meta‐atoms, is developed here. As the information is transformed into binary bit streams and mapped to pulse sequences of the biasing voltage, the baseband digital signal is directly modulated to the carrier wave through the digital coding metasurface. Compared to the earlier version of binary frequency‐shift keying architecture based on digital coding metasurface, the proposed QPSK system has a much higher data‐transmission rate for wireless communications. A proof‐of‐concept experiment is conducted to prove the real‐time transmission ability of this system, where a video is delivered between the transmitter and receiver with high accuracy and date rate. The presented work is promising in the development of next‐generation wireless communication technologies. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
95. Hierarchical Porous Ni3S4 with Enriched High‐Valence Ni Sites as a Robust Electrocatalyst for Efficient Oxygen Evolution Reaction.
- Author
-
Wan, Kai, Luo, Jiangshui, Zhou, Chen, Zhang, Ting, Arbiol, Jordi, Lu, Xihong, Mao, Bing‐Wei, Zhang, Xuan, and Fransaer, Jan
- Subjects
- *
OXYGEN evolution reactions , *ELECTROCATALYSTS , *WATER efficiency , *ENERGY conversion , *CHARGE exchange , *ENERGY consumption - Abstract
Electrochemical water splitting is a common way to produce hydrogen gas, but the sluggish kinetics of the oxygen evolution reaction (OER) significantly limits the overall energy conversion efficiency of water splitting. In this work, a highly active and stable, meso–macro hierarchical porous Ni3S4 architecture, enriched in Ni3+ is designed as an advanced electrocatalyst for OER. The obtained Ni3S4 architectures exhibit a relatively low overpotential of 257 mV at 10 mA cm−2 and 300 mV at 50 mA cm−2. Additionally, this Ni3S4 catalyst has excellent long‐term stability (no degradation after 300 h at 50 mA cm−2). The outstanding OER performance is due to the high concentration of Ni3+ and the meso–macro hierarchical porous structure. The presence of Ni3+ enhances the chemisorption of OH−, which facilitates electron transfer to the surface during OER. The hierarchical porosity increases the number of exposed active sites, and facilitates mass transport. A water‐splitting electrolyzer using the prepared Ni3S4 as the anode catalyst and Pt/C as the cathode catalyst achieves a low cell voltage of 1.51 V at 10 mA cm−2. Therefore, this work provides a new strategy for the rational design of highly active OER electrocatalysts with high valence Ni3+ and hierarchical porous architectures. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
96. Light-induced holographic all-optical waveguide scheme based on photoisomerization.
- Author
-
Liang, Jianchu, Long, Dafeng, Liu, Tong, Wan, Kai, Gong, Weiping, Xu, Sililu, Qiang, Na, Huang, Kaijian, and Wei, Xiaohui
- Subjects
- *
PHOTOISOMERIZATION , *HOLOGRAPHIC gratings , *NONLINEAR optical spectroscopy , *LIGHT propagation , *ISOMERIZATION - Abstract
The all-optical waveguide theory based on photoisomerization nonlinear effects is systematically and deeply studied, and a nonlinear holographic all-optical waveguide scheme is proposed for the first time. It is found that the induction of a light with stronger isomerization activity on the material weakens the self-defocusing effects of the signal light. Especially, polarization states of both inducing light and signal light also unexpectedly affect propagation of signal light. Part of the theoretical results has been qualitatively confirmed by Z-scan experiments. The proposed holographic all-optical waveguide scheme means polarization information is applied in the all-optical waveguide besides intensity information. Compared with the traditional all-optical waveguide, the performance of holographic waveguide will be greatly improved, making the control of light more precise and easier. Such nonlinear waveguide scheme may find its application in the future all-optical net. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
97. MOF Material-Derived Bimetallic Sulfide Co x Ni y S for Electrocatalytic Oxidation of 5-Hydroxymethylfurfural.
- Author
-
Guo, Cong, Huo, Yunying, Zhang, Qiao, Wan, Kai, Yang, Guangxing, Liu, Zhiting, and Peng, Feng
- Subjects
- *
METAL catalysts , *BIOMASS chemicals , *BIOMASS conversion , *LAMINATED metals , *SUSTAINABLE chemistry , *STEAM reforming - Abstract
The electrocatalytic conversion of biomass into high-value-added chemicals is one of the effective methods of green chemistry. Conventional metal catalysts have disadvantages, such as low atomic utilization and small surface areas. Catalyst materials derived from metal–organic frameworks (MOFs) have received much attention due to their unique physicochemical properties. Here, an MOF-derived non-precious metal CoxNiyS electrocatalyst was applied to the oxidation of biomass-derivative 5-hydroxymethylfurfural (HMF). The HMF oxidation reaction activities were modulated by regulating the content of Co and Ni bimetals, showing a volcano curve with an increasing proportion of Co. When the Co:Ni ratio was 2:1, the HMF conversion rate reached 84.5%, and the yield of the main product, 2,5-furandicarboxylic acid (FDCA), was 54%. The XPS results showed that the presence of high-valent nickel species after electrolysis, which further proved the existence and reactivity of NiOOH, as well as the synergistic effect of Co and Ni promoted the conversion of HMF. Increasing the content of Ni could increase the activity of HMF electrochemical oxidation, and increasing the content of Co could reduce the increase in the anodic current. This study has important significance for designing better HMF electrochemical catalysts in the future. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
98. Adhesion-delamination mechanics of a prestressed rectangular film adhered onto a rigid substrate.
- Author
-
Wong, Ming-Fung, Duan, Gang, and Wan, Kai-Tak
- Subjects
- *
ADHESION , *DELAMINATION of composite materials , *MICROMECHANICS , *THIN films , *MICROELECTROMECHANICAL systems , *NANOSTRUCTURES , *MATERIALS science - Abstract
A prestressed rectangular film clamped at both ends delaminates from a rigid punch. Based on a thermodynamic energy balance, the delamination mechanics is derived to relate the simultaneous external tensile force applied to the punch, punch displacement, and contact area. Effects of the coupled tensile residual membrane stress and adhesion energy at the punch-film interface are investigated. A “pinch off” (stable shrinking of the contact area to a line) is predicted, contrasting the nonzero “pull-off” radius in a clamped circular film. The model is useful in understanding the behavior of various adhesion-delamination phenomena, especially in one dimensional capacitive microelectromechanical systems radio frequency switches, microstructure network, and nanostructures. [ABSTRACT FROM AUTHOR]
- Published
- 2007
- Full Text
- View/download PDF
99. Field retrieved photovoltaic backsheet survey from diverse climate zones: Analysis of degradation patterns and phenomena.
- Author
-
Wieser, Raymond J., Wang, Yu, Fairbrother, Andrew, Napoli, Sophie, Hauser, Adam W., Julien, Scott, Gu, Xiaohong, O'Brien, Gregory S., Wan, Kai-Tak, Ji, Liang, Kempe, Michael D., Boyce, Kenneth P., and Bruckman, Laura S.
- Subjects
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POLYMER degradation , *CLIMATIC zones , *FLUOROPOLYMERS , *FLUOROETHYLENE , *DIFFERENTIAL scanning calorimetry , *DIFLUOROETHYLENE , *MICROSCOPY , *ATTENUATED total reflectance - Abstract
Understanding the impact of climate stressors on photovoltaic (PV) backsheet degradation in real-use conditions is critical to improve the accelerated testing exposures, extend the backsheet lifetime, and increase the confidence in PV reliability. In this work, a total of 33 PV module backsheets were retrieved from six climatic zones worldwide with 2 - 28 years of exposure. These modules included five types of backsheet air-side materials (or outer layer): poly(vinylidene fluoride) (PVDF), poly(tetrafluoroethylene-co-hexafluoropropylene-co-vinylidene fluoride) (THV), poly(vinyl fluoride) (PVF), poly(ethylene terephthalate) (PET), and polyamide (PA). Attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR) was used to identify air-side materials. The degradation induced color change, gloss loss, and chemical material changes analyzed using optical microscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), colorimetry (yellowness index (YI)), and gloss measurements. PVDF, THV, and PVF air-side layer backsheets, in particular PVF, had minimal degradation in the air-side layer appearance and chemical structures after exposure in different climatic zones. The PET air-side backsheets exhibited obvious color increase (22.55 YI units after about 9 years exposure) and the PA/PA/PA backsheets showed large gloss loss (up to 76.4 %) relative to the unexposed backsheets. Severe cracks between cells that penetrated through the entire thickness of backsheets are observed on PA/PA/PA backsheets after 4-6 years of exposure in 6 climatic zones. The current indoor exposure standards were not sufficient to identify this degradation type. However, fluoropolymer based PV backsheets showed lower levels of degradation predictors and increased climatic resistance. Specific samples (PVF) showed little change from baseline after 28 years of outdoor exposure. • Retrieved module backsheet characterization. • Diverse climatic exposure. • Inhomogeneous backsheet degradation. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
100. Achieving Efficient Electrocatalytic Oxygen Evolution in Acidic Media on Yttrium Ruthenate Pyrochlore through Cobalt Incorporation.
- Author
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Han, Ning, Feng, Shihui, Liang, Yi, Wang, Jun, Zhang, Wei, Guo, Xiaolong, Ma, Qianru, Liu, Qiong, Guo, Wei, Zhou, Zhenyu, Xie, Sijie, Wan, Kai, Jiang, Yinzhu, Vlad, Alexandru, Guo, Yuzheng, Gaigneaux, Eric M., Zhang, Chi, Fransaer, Jan, and Zhang, Xuan
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HYDROGEN evolution reactions , *COBALT , *PYROCHLORE , *YTTRIUM , *OXYGEN evolution reactions , *CHEMICAL stability - Abstract
The development of electrocatalysts for the oxygen evolution reaction (OER) especially in acidic media remains the major challenge that still requires significant advances, both in material design and mechanistic exploration. In this study, the incorporation of cobalt in Y2‐xCoxRu2O7−δ results in an ultrahigh OER activity because of the charge redistribution at eg orbitals between Ru and Co atoms. The Y1.75Co0.25Ru2O7−δ electrocatalyst exhibits an extremely small overpotential of 275 mV in 0.5 m H2SO4 at the current density of 10 mA cm−2, which is smaller than that of parent Y2Ru2O7−δ (360 mV) and commercial RuO2 (286 mV) catalysts. The systematic investigation of the composition related to OER activity shows that the Co substitution will also bring other effective changes, such as reducing the bandgap, and creating oxygen vacancies, which result in fast OER charge transfer. Meanwhile, the strengthening of the bond hybridization between the d orbitals of metal (Y and Ru) and the 2p orbitals of O will intrinsically enhance the chemical stability. Finally, theoretical calculations indicate that cobalt substitution reduces the theoretical overpotential both through an adsorbate evolution mechanism and a lattice oxygen‐mediated mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2023
- Full Text
- View/download PDF
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