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111.
This paper deals with a time-dependent analysis of reinforced concrete (RC) frame structures considering the construction sequences. Because of the non-mechanical deformations induced by the time-dependent deformations of concrete, concrete structures usually present different behaviors when the construction sequences are changed, despite having the same structural configurations. Therefore, the time-dependent effects of concrete such as creep and shrinkage must be taken into consideration to simulate the actual behavior of RC frame structures. The material nonlinearity including the cracking of concrete is taken into consideration, and geometric nonlinearity due to the P-Δ effect is also taken into account by using the initial stress matrix. In addition, the creep deformation of concrete is described in accordance with a first-order algorithm based on the expansion of a degenerated kernel of the compliance function. Finally, correlation studies with previous numerical results and experimental data are conducted to verify the validity of the proposed model. An analysis of a 10-story RC frame structure is carried out to assess the differences in structural responses according to the construction sequences. 相似文献
112.
The c-axis preferred orientation of ZnO film is the most important factor for its successful application in piezoelectric devices. The effects of surface roughness of the substrate on the c-axis preferred orientation of ZnO thin films, deposited by radio frequency magnetron sputtering, were investigated. During sputtering, the oxygen content in the argon environment used was varied from 0 to 70% at a total sputtering pressure of 10 mTorr. Very smooth Si, smooth evaporated Au/Si, smooth evaporated-Al/Si, and rough sputtered-Al/Si were used as substrates. Their r.m.s. roughnesses, as measured by atomic force microscopy, were 1.27, 17.1, 21.1 and 65-118 Å, respectively. The crystalline structure and the angular spread of the (0 0* 2) plane normal to the ZnO films were determined using X-ray diffraction and X-ray rocking curves, respectively. The crystallinity and the preferred c-axis orientation of the ZnO films were strongly dependent on the surface roughness of the substrates rather than on the oxygen content of the working environment or on the chemical nature of the substrate. 相似文献
113.
Ik Seon Kwon Tekalign Terfa Debela In Hye Kwak Yun Chang Park Jaemin Seo Ju Yong Shim Seung Jo Yoo Jin‐Gyu Kim Jeunghee Park Hong Seok Kang 《Small (Weinheim an der Bergstrasse, Germany)》2020,16(13)
2D MoS2 nanostructures have recently attracted considerable attention because of their outstanding electrocatalytic properties. The synthesis of unique Co–Ru–MoS2 hybrid nanosheets with excellent catalytic activity toward overall water splitting in alkaline solution is reported. 1T′ phase MoS2 nanosheets are doped homogeneously with Co atoms and decorated with Ru nanoparticles. The catalytic performance of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) is characterized by low overpotentials of 52 and 308 mV at 10 mA cm?2 and Tafel slopes of 55 and 50 mV decade?1 in 1.0 m KOH, respectively. Analysis of X‐ray photoelectron and absorption spectra of the catalysts show that the MoS2 well retained its metallic 1T′ phase, which guarantees good electrical conductivity during the reaction. The Gibbs free energy calculation for the reaction pathway in alkaline electrolyte confirms that the Ru nanoparticles on the Co‐doped MoS2 greatly enhance the HER activity. Water adsorption and dissociation take place favorably on the Ru, and the doped Co further catalyzes HER by making the reaction intermediates more favorable. The high OER performance is attributed to the catalytically active RuO2 nanoparticles that are produced via oxidation of Ru nanoparticles. 相似文献
114.
In this letter, we propose a cognitive ultra‐wideband radio scheme which is based on a modified chirp waveform. Therefore, it requires only time domain processing in the cognitive radio systems and reduces system complexity and power consumption. 相似文献
115.
Recently, wireless multimedia sensor networks (WMSNs) have emerged as one of the most important technologies, driven by the
development of powerful multimedia device such as CMOS. WMSNs require several factors such as resource constraints, specific
QoS, high bandwidth and so on. In this paper, we propose a hierarchical heterogeneous network model based routing protocol
for WMSNs. In our proposal, proposed network model is classified into monitoring class, delivery class and aggregation class.
Also we define two kinds of the routing path in order to ensure bandwidth and QoS. In simulation results, we illustrate the
performance of our proposal. 相似文献
116.
Hong Jae Yim Jae Hong Kim Sun-Jong Park Hyo-Gyoung Kwak 《Cement and Concrete Research》2012,42(11):1438-1446
Thermal damage in concrete usually induces contact-type defects, which result in degradation of the concrete's performance. This paper attempts to visualize the thermal damage in a multiscale, and characterizes the thermally damaged concrete using a nonlinear ultrasonic method. An impact-modulation method is used to obtain nonlinearity parameters, as a quantitative measure of contact-type defects, and shows better sensitivity than phase velocity variation as a linear ultrasonic method for thermally damaged concrete. The measured nonlinearity parameter is compared with the permeable pores, which reflect the occurrence of opening and pores in thermally damaged concrete. Degradation of concrete strength due to thermal damage is also assessed via the measurement. 相似文献
117.
Doh-Soon Kwak 《Expert systems with applications》2012,39(3):2590-2596
Due to the rapid development of information technologies, abundant data have become readily available. Data mining techniques have been used for process optimization in many manufacturing processes in automotive, LCD, semiconductor, and steel production, among others. However, a large amount of missing values occurs in the data set due to several causes (e.g., data discarded by gross measurement errors, measurement machine breakdown, routine maintenance, sampling inspection, and sensor failure), which frequently complicate the application of data mining to the data set. This study proposes a new procedure for optimizing processes called missing values-Patient Rule Induction Method (m-PRIM), which handles the missing-values problem systematically and yields considerable process improvement, even if a significant portion of the data set has missing values. A case study in a semiconductor manufacturing process is conducted to illustrate the proposed procedure. 相似文献
118.
All controlled radical polymerization (CRP) procedures rely on a dynamic and rapid equilibrium between dormant and active species. This equilibrium can be established through different mechanisms and all the resulting CRP processes have their own advantages and limitations. Therefore, it becomes interesting to investigate the possibility of combining CRP techniques to eliminate specific drawbacks of each individual procedure. Atom transfer radical polymerization (ATRP) with alkyl pseudohalides acting as initiators and chain transfer agents was developed for that purpose. The process relies on a dual mechanism involving both activation deactivation and reversible addition fragmentation chain transfer (RAFT). This peculiar characteristic of ATRP with alkyl pseudohalides acting as chain transfer agents made it possible to overcome some of the limitations typically associated with conventional ATRP and RAFT polymerization as well as to prepare new responsive materials. 相似文献
119.
Jae-Bok Seol Dierk Raabe P. Choi Hyung-Seok Park J.-H. Kwak Chan-Gyung Park 《Scripta materialia》2013,68(6):348-353
We study the structure and chemical composition of the κ-carbide formed as a result of isothermal transformation in an Fe–3.0Mn–5.5Al–0.3C alloy using transmission electron microscopy and atom probe tomography. Both methods reveal the evolution of κ-particle morphology as well as the partitioning of solutes. We propose that the κ-phase is formed by a eutectoid reaction associated with nucleation growth. The nucleation of κ-carbide is controlled by both the ordering of Al partitioned to austenite and the carbon diffusion at elevated temperatures. 相似文献
120.
Changsoo Jang Geun Sik Ahn Yung Joon Kim Dong Ok Kwak Seong Woon Booh Jae Ok Kim 《Electronics Packaging Manufacturing, IEEE Transactions on》2003,26(1):46-53
The joint structure of a transducer horn-holder assembly for a wire bonder was examined through finite element contact analysis. Three-dimensional modeling and analysis was carried out to survey the internal physics of this structure and to verify the accuracy of a proposed computation relative to measurement. After validation, a two-dimensional model was built to conduct parametric studies and improve the efficiency and speed of the computation. Several factors such as boundary conditions, modeling boundary, and mesh density, were considered to obtain consistency with the three-dimensional analysis. Arc angle and the position of each holder boss were chosen as design parameters. A designed computation approach was applied for efficiency in computation. As a result, a guideline for holder boss design was suggested, and the main factors and their influence on stress concentration in the transducer horn were surveyed. 相似文献