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131.
Reliability-based design optimization of problems with correlated input variables using a Gaussian Copula 总被引:4,自引:2,他引:2
The reliability-based design optimization (RBDO) using performance measure approach for problems with correlated input variables
requires a transformation from the correlated input random variables into independent standard normal variables. For the transformation
with correlated input variables, the two most representative transformations, the Rosenblatt and Nataf transformations, are
investigated. The Rosenblatt transformation requires a joint cumulative distribution function (CDF). Thus, the Rosenblatt
transformation can be used only if the joint CDF is given or input variables are independent. In the Nataf transformation,
the joint CDF is approximated using the Gaussian copula, marginal CDFs, and covariance of the input correlated variables.
Using the generated CDF, the correlated input variables are transformed into correlated normal variables and then the correlated
normal variables are transformed into independent standard normal variables through a linear transformation. Thus, the Nataf
transformation can accurately estimates joint normal and some lognormal CDFs of the input variable that cover broad engineering
applications. This paper develops a PMA-based RBDO method for problems with correlated random input variables using the Gaussian
copula. Several numerical examples show that the correlated random input variables significantly affect RBDO results. 相似文献
132.
Y. H. Bae A. I. Lyakhov V. M. Vishnevsky K. J. Kim B. D. Choi 《Automation and Remote Control》2008,69(3):529-543
In this paper, we estimate characteristics of the IEEE 802.11 DCF (Distributed Coordination Function) in non-saturation mode. We take into account two significant features inherent to the non-saturated 802.11 DCF: (i) the possibility of asynchronous transmission performed without preceding backoff for the first packet arriving at the idle staion; and (ii) so-called post backoff meaning that a station must perform a backoff once after any of its transmissions even if its queue becomes empty. We derive the probability generating function (PGF) of Head-of-Line delay (HoL-delay). Our method to find PGF of HoL-delay is quite intuitive and straightforward. Also, we obtain the packet loss probability and non-saturation throughput. Numerical results show that these two features inherent to the non-saturated 802.11 DCF influence on the performance measures of DCF such as delay considerably and it should be taken into account for accurate modeling of DCF. 相似文献
133.
Summary A new thermotropic side-chain liquid crystalline polymers based on poly (dipropargylamine) backbone were prepared by metathesis
polymerization with transition metal catalysts. It was found that the MoCl5-EtAlCl2 catalyst system were very effective for the cyclopolymerization of presently investigated monomers. Resulting polymers were
soluble in common organic solvents such as THF, chloroform, etc. The number-average molecular weight (
) values of the polymers were in the range of 6.49x103–11.6x103, relative to polystyrene standard by GPC.
Thermal properties of the monomers and the polymers synthesized were examined by differential scanning calorimetry (DSC) and
cross-polarized optical microscopy. Both monomer and polymer displayed enantiotropic liquid crystallinity showing the reversible
phase transition. 相似文献
134.
Seok Woo Choi Dong Yong Kim Hyong Kap Kim 《Analog Integrated Circuits and Signal Processing》1994,6(2):95-103
A modified low-pass filter functions are proposed. A modified inverse Chebyshev function possesses progressively diminishing ripples in the stopband whereas the modified Chebyshev function exhibits ripples diminishing toward = 0 in the passband.Both are realizable in the doubly-terminated ladder structures for the ordern even or odd, thus lending themselves amenable to high-quality activeRC or switched capacitor filters through the simulation techniques. 相似文献
135.
Chung-In Um In-Han Kim Yeon-Mu Choi Thomas F. George 《Journal of Low Temperature Physics》1994,95(3-4):547-578
The temperature variations of the diffusion coefficientD(T), thermal diffusion ratio k
T
(T) and thermal conductivity (T) in a dilute solution of3He atom in two-dimensional liquid helium are evaluated explicitly by solving the kinetic equations via phonon-phonon, phonon-roton, roton-roton, impurityelementary excitation and impurity-impurity scatterings. In the low-temperature region, the main contributions toD(T) and (T) come from the interactions between phonons and impurities, while in the high-temperature region the interactions between impurities and whole elementary excitations contribute more strongly toD(T) and (T) than those of only elementary excitations. For a dilute solution, the thermal diffusion ratio k
T
(T), neglecting the internal mass counterflow, is much smaller than the effective thermal diffusion ratio k
T
*
(T), which is a function of thermostatic properties. The effective thermal conductivity eff is much larger than the thermal conductivity and has different temperature dependence from the thermal conductivity. The behaviors of the two-dimensional diffusion coefficient and thermal conductivity are much like the bulk case, where they exhibit exponential decay with increasing temperature, although they are much smaller than those of the bulk case. 相似文献
136.
137.
Seung Gyo Jeong Jin Young Oh Lin Hao Jian Liu Woo Seok Choi 《Advanced functional materials》2023,33(38):2301770
Unexpected, yet useful functionalities emerge when two or more materials merge coherently. Artificial oxide superlattices realize atomic and crystal structures that are not available in nature, thus providing controllable correlated quantum phenomena. This review focuses on 4d and 5d perovskite oxide superlattices, in which the spin–orbit coupling plays a significant role compared with conventional 3d oxide superlattices. Modulations in crystal structures with octahedral distortion, phonon engineering, electronic structures, spin orderings, and dimensionality control are discussed for 4d oxide superlattices. Atomic and magnetic structures, Jeff = 1/2 pseudospin and charge fluctuations, and the integration of topology and correlation are discussed for 5d oxide superlattices. This review provides insights into how correlated quantum phenomena arise from the deliberate design of superlattice structures that give birth to novel functionalities. 相似文献
138.
Changmin Lee Youngjae Hong Dongho Kim Younghwan Lim Jang Wook Choi Sung-Yoon Chung 《Advanced functional materials》2023,33(44):2303763
Protons in aqueous electrolytes can perform as an additional type of charge carrier for insertion/extraction in addition to the primary carrier cations in aqueous rechargeable batteries. Despite many diverse claims regarding the effect of protons, mutually conflicting experimental results and their interpretations without direct evidence have been reported over the last decade. Systematic examinations and analyses are thus imperative to clarify the conditions of proton insertion in aqueous rechargeable batteries. Utilizing V2O5 as a model cathode and beaker-type cells with a sufficient amount of ZnSO4 aqueous electrolytes in this work, it is demonstrated that protons are inserted into the cathode prior to Zn-ions in low-pH conditions (pH ≤ 3.0). In stark contrast, the influence of protons on the discharge voltage and capacity is insignificant, when either the pH becomes higher (pH ≥ 4.0) or the electrolyte volume is considerably low in coin-type cells. Similar behavior of pH-dependent proton insertion is also verified in Na–, Mg–, and Al-ion electrolytes. Providing a resolution to the controversy regarding proton insertion, the present study emphasizes that the influence of protons substantially varies depending on the pH and relative volume of electrolytes in aqueous batteries. 相似文献
139.
Seonho Kim Ho Kyun Jung Puji Lestari Handayani Taehoon Kim Byung Mun Jung U Hyeok Choi 《Advanced functional materials》2023,33(13):2210916
For the development of all-solid-state lithium metal batteries (LMBs), a high-porous silica aerogel (SA)-reinforced single-Li+ conducting nanocomposite polymer electrolyte (NPE) is prepared via two-step selective functionalization. The mesoporous SA is introduced as a mechanical framework for NPE as well as a channel for fast lithium cation migration. Two types of monomers containing weak-binding imide anions and Li+ cations are synthesized and used to prepare NPEs, where these monomers are grafted in SA to produce SA-based NPEs (SANPEs) as ionomer-in-framework. This hybrid SANPE exhibits high ionic conductivities (≈10−3 S cm−1), high modulus (≈105 Pa), high lithium transference number (0.84), and wide electrochemical window (>4.8 V). The resultant SANPE in the lithium symmetric cell possesses long-term cyclic stability without short-circuiting over 800 h under 0.2 mA cm−2. Furthermore, the LiFePO4|SANPE|Li solid-state batteries present a high discharge capacity of 167 mAh g−1 at 0.1 C, good rate capability up to 1 C, wide operating temperatures (from −10 to 40 °C), and a stable cycling performance with 97% capacity retention and 100% coulombic efficiency after 75 cycles at 1 C and 25 °C. The SANPE demonstrates a new design principle for solid-state electrolytes, allowing for a perfect complex between inorganic silica and organic polymer, for high-energy-density LMBs. 相似文献
140.
Hardware security primitives, also known as physical unclonable functions (PUFs), perform innovative roles to extract the randomness unique to specific hardware. This paper proposes a novel hardware security primitive using a commercial off-the-shelf flash memory chip that is an intrinsic part of most commercial Internet of Things (IoT) devices. First, we define a hardware security source model to describe a hardware-based fixed random bit generator for use in security applications, such as cryptographic key generation. Then, we propose a hardware security primitive with flash memory by exploiting the variability of tunneling electrons in the floating gate. In accordance with the requirements for robustness against the environment, timing variations, and random errors, we developed an adaptive extraction algorithm for the flash PUF. Experimental results show that the proposed flash PUF successfully generates a fixed random response, where the uniqueness is 49.1%, steadiness is 3.8%, uniformity is 50.2%, and min-entropy per bit is 0.87. Thus, our approach can be applied to security applications with reliability and satisfy high-entropy requirements, such as cryptographic key generation for IoT devices. 相似文献