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991.
Soo Ho Kim Kwang Hoon Lee Baek Seok Seong Gyeung-Ho Kim Jong Sung Kim Young Soo Yoon 《Korean Journal of Chemical Engineering》2006,23(6):961-964
Recently, lithium titanium oxide material has gained renewed interest in electrodes for lithium ion rechargeable batteries.
We investigated the influence of excess Li on the structural characteristics of lithium titanium oxide synthesized by the
conventional powder calcination method, considering the potential for mass production. The lithium excess ratio is controlled
by using different weight of Li2CO3 powder during calcination. X-ray diffraction (XRD) measurement for the synthesized powder showed that the lithium titanium
oxide material with excess lithium content had a spinel crystal structure as well as a different crystal one. In addition,
high resolution transmission electron microscopy (HRTEM) and field emission scanning electron microscopy (FESEM) measurement
revealed that the lithium titanium oxide powders with a lithium excess ratio of 5–20% exhibited a two phase formation. Inductively
coupled plasma — atomic emission spectrometer (ICP-AES) and energy dispersive x-ray spectroscopy (EDX) measurements were used
to analyze composition of the lithium titanium oxide powder. These results suggested that the conventional calcination method,
considering the potential for mass production, formed two phases according to the Li excess amount in initial raw materials. 相似文献
992.
Seong Kyu Cheon Min Ho Park Seong Su Jeong Ho Ik Jun Tae Hoon Kim 《Integrated ferroelectrics》2019,195(1):81-90
AbstractIn this paper, a piezoelectric small robot was proposed and experimented. The piezoelectric bender of the actuator was composed of trapezoid ceramics which were attached on both surfaces of the elastic body. And an X-shaped structure was composed of four piezoelectric ceramic benders. When AC voltages which have different duty ratio were applied to the four benders, the motion of straight line according to a stick slip of the bender tips was obtained. A FEA simulation was used to analyze the motion of straight line. The output characteristics of the prototype actuator which was fabricated based on the analysis data were measured. 相似文献
993.
Tae Hoon Kim Seong Su Jeong Min Ho Park Ho Ik Jun Seong Kyu Cheon 《Integrated ferroelectrics》2019,195(1):91-99
AbstractT-shaped ambulatory piezoelectric actuator which can be used for various purposes such as lifesaving and environmental monitoring was proposed. The actuator consists of eight piezoelectric benders, t-shaped stator, and four legs, and it is very simple in structure and has the advantages of being easily manufactured and downsizing. It is also driven by four legs and can be moved forward and backward. The piezoelectric bender was composed of a carbon body and a ceramic plate. Vibration motions of the piezoelectric benders in x and z axes were transfer to the legs and the elliptical displacements at the ends of the legs were obtained by combination of the phase difference of 90 degrees. Characteristics of the actuators were simulated by finite element analysis, and the optimized prototype actuator was fabricated and experimented. 相似文献
994.
Min Han Ki Choi Gi Seob Jung Jong An Yang In Young 《Journal of Mechanical Science and Technology》2003,17(7):958-965
Structural integrity of either a passenger car or a light truck is one of the basic requirements for a full vehicle engineering
and development program. The results of the vehicle product performance are measured in terms of ride and handling, durability,
noise/vibration/harshness (NVH), crashworthiness and occupant safety. The level of performance of a vehicle directly affects
the marketability, profitability and, most importantly, the future of the automobile manufacturer. In this study, we used
the virtual proving ground (VPG) approach for obtaining the dynamic characteristics. The VPG approach uses a nonlinear dynamic
finite element code (LS-DYNA3D) which expands the application boundary outside the classic linear static assumptions. The
VPG approach also uses realistic boundary conditions of tire/road surface interactions. To verify the predicted dynamic results,
a single lane change test has been performed. The prediction results were compared with the experimental results, and the
feasibility of the integrated CAE analysis methodology was verified. 相似文献
995.
This study is concerned with the general solution of the field intensity factors and energy release rate for a Griffith crack
in a piezoelectric ceramic of finite radius under combined anti-plane mechanical and in-plane electrical loading. Both electrically
continuous and impermeable crack surface conditions are considered. Employing Mellin transforms and Fourier series, the problem
is reduced to dual integral forms. The solution to the resulting expressions is expressed in terms of Fredholm integral equation
of the second kind. The solutions are provided to study the influence of the crack length, the crack surface boundary conditions
on the intensity factors and the energy release rate. 相似文献
996.
997.
Topology control is one of the important techniques in wireless multi-hop networks to preserve connectivity and extend the network lifetime. This is more significant in ZigBee, since the address assignment scheme is tightly coupled with topology construction. For example, there can be orphan nodes that cannot receive the network address and isolated from the network due to predefined network configurations. In this paper, we propose a distributed topology construction algorithm that controls the association time of each node in order to solve the orphan node problem in ZigBee as well as construct an efficient routing tree topology. The main idea of the distributed topology construction algorithm is to construct primary backbone nodes by propagating the invitation packets and controlling the association time based on the link quality. Since the dynamically selected primary nodes are spread throughout the network, they can provide backbone to accept the association requests from the remaining secondary nodes which are majority in a network. In the performance evaluation, we show that the proposed topology construction algorithm effectively solves the orphan node problem regardless of network density as well as provides efficient tree routing cost comparable to the approximation algorithm for degree constrained minimum routing cost tree (DC-MRCT) problem. 相似文献
998.
Hong?Jip?Kim Suk?Ho?Chung Chae?Hoon?SohnEmail author 《Journal of Mechanical Science and Technology》2004,18(5):838-846
Minimum ignition energies of hydrogen/air and methane/air mixtures have been investigated numerically by solving unsteady
one-dimensional conservation equations with detailed chemical kinetic mechanisms. Initial kernel size needed for numerical
calculation is a sensitive function of initial pressure of a mixture and should be estimated properly to obtain quantitative
agreement with experimental results. A simple macroscopic model to determine minimum ignition energy has been proposed, where
the initial kernel size is correlated with the quenching distance of a mixture and evaluated from the quenching distance determined
from experiment. The simulation predicts minimum ignition energies of two sample mixtures successfully which are in a good
agreement with the experimental data for the ranges of pressure and equivalence ratio. 相似文献
999.
Petra A. de Jong Pascal van Hattum Jan Rouwendal Aleid E. Brouwer 《Housing Studies》2018,33(7):1014-1037
AbstractTo date most prognoses of older adults in the housing market have been based on average housing preferences and average housing market behaviour of all persons in a certain age cohort. Due to socialcultural and social-economic dynamics, the relationship between age and housing is expected to change for successive cohorts. This study sets out to improve housing preferences estimates by recognizing the growing differentiation among older adults. This heterogeneity is analysed by differentiating older adults on their lifestyles (operationalized as values), using latent class analysis as a clustering technique. These analyses result in older adults being classified into five segments on the basis of their viewpoints, motivations and attitude. Next, for each lifestyle segment a separate discrete choice model is estimated, offering insight in the relative importance that these segments give to various housing attributes. The findings demonstrate advantages over a traditional, single model approach and can be helpful in formulating contemporary housing policy. 相似文献
1000.
Wu Bin Ying Da Som Moon Min Woo Lee Na Yeong Ko Nho Hoon Kwak Bumjae Lee Jin Zhu Ruoyu Zhang 《应用聚合物科学杂志》2018,135(5)
To simultaneously improve the fracture toughness and heat resistance of a cured toughened epoxy resin along with a reduction in its viscosity during the mixing process, two novel polysulfone‐type polymers are synthesized via azide–alkyne polymerization for use as toughening agents. The epoxy resin toughened with these polymers by in situ azide–alkyne polymerization during the cure process, which shows excellent processibility and based on the significantly lower viscosity (61 and 62 cP) during epoxy mixing process than that of commonly commercial polyethersulfone (PES, 127,612 cP). The novel polysulfone‐type polymer toughened epoxy resin showed the advantage in excellent fracture toughness than the PES toughened epoxy. In addition, the glass transition temperature of the novel polysulfone‐type polymer toughened epoxy resin is similar to that of the neat one (~230 °C) and does not decrease, which implies excellent heat resistance of the toughened epoxy. These phenomena can be attributed to the formation of semi‐interpenetrating polymer networks comprising the epoxy network and the linear polysulfone‐type polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45790. 相似文献