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71.
Formation of a Surficial Bifunctional Nanolayer on Nb2O5 for Ultrastable Electrodes for Lithium‐Ion Battery 下载免费PDF全文
Jun Young Cheong Chanhoon Kim Ji‐Won Jung Ki Ro Yoon Su‐Ho Cho Doo‐Young Youn Hye‐Yeon Jang Il‐Doo Kim 《Small (Weinheim an der Bergstrasse, Germany)》2017,13(19)
Safe and long cycle life electrode materials for lithium‐ion batteries are significantly important to meet the increasing demands of rechargeable batteries. Niobium pentoxide (Nb2O5) is one of the highly promising candidates for stable electrodes due to its safety and minimal volume expansion. Nevertheless, pulverization and low conductivity of Nb2O5 have remained as inherent challenges for its practical use as viable electrodes. A highly facile method is proposed to improve the overall cycle retention of Nb2O5 microparticles by ammonia (NH3) gas‐driven nitridation. After nitridation, an ultrathin surficial layer (2 nm) is formed on the Nb2O5, acting as a bifunctional nanolayer that allows facile lithium (Li)‐ion transport (10–100 times higher Li diffusivity compared with pristine Nb2O5 microparticles) and further prevents the pulverization of Nb2O5. With the subsequent decoration of silver (Ag) nanoparticles (NPs), the low electric conductivity of nitridated Nb2O5 is also significantly improved. Cycle retention is greatly improved for nitridated Nb2O5 (96.7%) compared with Nb2O5 (64.7%) for 500 cycles. Ag‐decorated, nitridated Nb2O5 microparticles and nitridated Nb2O5 microparticles exhibit ultrastable cycling for 3000 cycles at high current density (3000 mA g?1), which highlights the importance of the surficial nanolayer in improving overall electrochemical performances, in addition to conductive NPs. 相似文献
72.
To improve the steady state estimation error due to mismatched uncertainty, a variable structure observer for mismatched uncertain dynamical systems is proposed by using the generalised matrix inverse. Simulation results show that the estimation error is largely decreasing using the proposed observer.<> 相似文献
73.
Characteristics of airborne bacteria and fungi were surveyed in the public buildings regulated in Korea, with the six-stage cascade impactor. The total concentrations of airborne bacteria and fungi were averaged to 404 and 382 cfu m−3 in hospital, 931 and 536 cfu m−3 in kindergarten, 294 and 334 cfu m−3 in elderly welfare facility, and 586 and 371 cfu m−3 in postpartum nurse center. Mean respirable concentrations of airborne bacteria and fungi were 194 and 292 cfu m−3 in hospital, 358 and 347 cfu m−3 in kindergarten, 134 and 266 cfu m−3 in elderly welfare facility, and 254 and 289 cfu m−3 in postpartum nurse center, respectively. Based on this results, total and respirable concentrations of airborne bacteria and fungi were significantly highest in kindergarten and lowest in elderly welfare facility (p<0.05). The ratios of indoor and outdoor concentration for airborne bacteria and fungi were below 1.0 in all the investigated public buildings regardless of size distribution. The dominant genera identified in the public buildings were Staphylococcus spp., Micrococcus spp., Corynebacterium spp., and Bacillus spp., for airborne bacteria and Penicillium spp., Cladosporium spp., and Aspergillus spp., for airborne fungi, respectively. Size distributions of airborne bacteria and fungi in terms of the dominant genera were not observed consistently except for Staphylococcus spp., which was detected mainly on the first stage (>7.0 μm) and second stage(4.7–7.0 μm), and Penicillium spp., and Cladosporium spp., showing the highest collection rate at stage 3 (3.3–4.7 μm) regardless of the kind of the public buildings. 相似文献
74.
A convenient crosslinking method for sulfonated poly(ether ether ketone) membranes via friedel–crafts reaction using 1,6‐dibromohexane and aluminum trichloride 下载免费PDF全文
In this study, sulfonated poly(ether ether ketone) (SPEEK) was very efficiently crosslinked via a Friedel–Craft reaction using 1,6‐dibromohexane and AlCl3. The resulting crosslinked SPEEK (c‐SPEEK) membranes exhibited improved dimensional stability, thermal and chemical stability, and mechanical strength with slight reduction in the elongation. The methanol permeability was reduced by approximately two orders of magnitude by the crosslinking reaction. The proton conductivities of c‐SPEEK membranes were greater than Nafion‐212 in the temperature range of 30–90°C. Overall, this new crosslinking method can be conveniently and efficiently applicable to most aromatic hydrocarbon polymer membranes. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40695. 相似文献
75.
Younés Abbassi Youcef Ait-Amirat Rachid Outbib 《International journal of systems science》2013,44(16):2873-2886
This paper mainly studies nonlinear feedback control applied to the nonlinear vehicle dynamics with varying velocity. The main objective of this study is the stabilisation of longitudinal, lateral and yaw angular vehicle velocities. To this end, a nonlinear vehicle model is developed which takes both the lateral and longitudinal vehicle dynamics into account. Based on this model, a method to build a nonlinear state feedback control is first designed by which the complexity of system structure can be simplified. The obtained system is then synthesised by the combined Lyapunov–LaSalle method. The simulation results show that the proposed control can improve stability and comfort of vehicle driving. Moreover, this paper presents a lemma which ensures the trajectory tracking and path-following problem for vehicle. It can also be exploited simultaneously to solve both the tracking and path-following control problems of the vehicle ride and driving stability. We also show how the results of the lemma can be applied to solve the path-following problem, in which the vehicle converges and follows a designed path. The effectiveness of the proposed lemma for trajectory tracking is clearly demonstrated by simulation results. 相似文献
76.
A series of pH‐responsive hydrogels were studied as potential drug carriers for the protection of insulin from the acidic environment of the stomach before releasing in the small intestine. Hydrogels based on poly(vinyl alcohol) networks grafted with acrylic acid or methacrylic acid were prepared by a two‐step process. Poly(vinyl alcohol) hydrogels were prepared by gamma ray irradiation (50 kGy) and then followed by grafting either acrylic acid or methacrylic acid onto these poly(vinyl alcohol) hydrogels with subsequent irradiation (5–20 kGy). These graft hydrogels showed pH‐sensitive swelling behavior and were used as carriers for the controlled release of insulin. The in vitro release of insulin was observed for the insulin‐loaded hydrogels in a simulated intestinal fluid (pH 6.8) but not in a simulated gastric fluid (pH 1.2). The release behavior of insulin in vivo in a rat model confirmed the effectiveness of the oral delivery of insulin to control the level of glucose. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 636–643, 2004 相似文献
77.
Sin?KimEmail author Min-Chan?Kim Kyung?Youn Kim 《Journal of Mechanical Science and Technology》2002,16(10):1320-1326
In a one-dimensional heat conduction domain with heated and insulated walls, an integral approach is proposed to estimate
time-dependent boundary heat flux without internal measurements. It is assumed that the expression of the heat flux is not
known a priori. Hence, the present inverse heat conduction problem is classified as a function estimation problem. The spatial
temperature distribution is approximated as a third-order polynomial of position, whose four coefficients are determined from
the heat fluxes and the temperatures at both ends at each measurement. After integrating the heat conduction equation over
spatial and time domain, respectively, a simple and non-iterative recursive equation to estimate the time-dependent boundary
heat flux is derived. Several examples are introduced to show the effectiveness of the present approach. 相似文献
78.
A new anionic conjugated polymer containing a fluorene group in the main chain was designed and synthesized from poly(2,7‐(9,9′‐dihexylfluorene)‐5,5′‐bibenzimidazole) (PFBI). The polymer showed strong blue emission with high quantum efficiency (0.64) at 450 nm in MeOH and the dramatic quenching effect by Methyl Viologen (MV2+). The fluorescence‐quenching effect results from the weak complex formation between an anionic polymer and electron acceptors such as bipyridinium derivatives. The linear Stern–Volmer constant (Ksv) was 3.7×105 M?1 for MV2+. The newly synthesized polymer is expected to show the applicability for biological and chemical sensors. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 900–904, 2004 相似文献
79.
Alper Sarıoğlan Ömer Tunç Savaşçı Ayşe Erdem-Şenatalar Vu Thu Ha Gilbert Sapaly Younès Ben Taârit 《Catalysis Letters》2007,118(1-2):123-128
MFI type inorganic carrier was used in two different cationic forms, hydrogen and calcium respectively. MFI-supported molybdenum
and rhenium catalysts were prepared. The activities of the catalysts were compared for the aromatization reaction of methane.
Higher activity values were attained with the catalysts supported on HZSM-5. Aromatics were also observed with the catalysts
supported on CaZSM-5, despite their deficiency in acid sites. Highly dispersed rhenium is expected to be formed with the use
of the inorganic carrier in calcium form. On the other hand, lower reaction rates were observed with rhenium supported on
CaZSM-5, in spite of the improved dispersion of the active rhenium species on this catalyst. This was interpreted in terms
of the critical role of the acid sites in the conversion of methane to aromatics, compared to the improved dispersion of the
active metal. 相似文献
80.
Jae Ho Yang Kun Woo Song Keon Sik Kim Youn Ho Jung 《Journal of Nuclear Materials》2006,353(3):202-208
A new fabrication process of UO2-W composite fuel has been studied in order to improve the thermal conductivity of the UO2 pellet by the addition of a small amount of W. A fabrication process was designed from the phase equilibria among tungsten, tungsten oxides and UO2. The conventionally sintered UO2 pellet which contains W particles is heat-treated in an oxidizing gas and then in a reducing gas. In the oxidizing heat-treatment W particles are oxidized and liquid tungsten oxide penetrates within the UO2 grain boundary, and in the reducing heat-treatment liquid oxide is transformed to solid tungsten which forms a continuous channel along the UO2 grain boundary. This developed technique can provide a continuous W channel covering UO2 grains for a UO2-W composite fuel even with a small amount of a metal phase - below 6 vol.%. The thermal diffusivity of the UO2-6 vol.%W cermet composite increases by about 80% when compared with that of a pure UO2 pellet. 相似文献