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990 results on '"Liu, Jicheng"'

301. Preparation of low-temperature composite phase change materials (C-PCMs) from modified blast furnace slag (MBFS)

Author

Shuo Liu, Manman Lu, Yuanbo Zhang, Liu Jicheng, Tao Jiang, and Su Zijian

Subjects
Materials science, Composite number, 0211 other engineering and technologies, 020101 civil engineering, 02 engineering and technology, Building and Construction, Thermal energy storage, 0201 civil engineering, Adsorption, Volume (thermodynamics), Ground granulated blast-furnace slag, Latent heat, 021105 building & construction, Thermal, General Materials Science, Composite material, Porosity, Civil and Structural Engineering
Abstract

As widely used in building materials, blast furnace slag (BFS) has the potential to prepare composite phase change materials (C-PCMs), which can be applied in thermal energy storage field. However, the defects of insufficient porosity and small pore volume of the BFS have severely limited the PCMs adsorption capacity. In this study, the BFS was modified by Ca(OH)2 to improve the PCMs adsorption capacity. The results showed that the porous structure of BFS was significantly improved after modification. And the apertures of BFS were distinctly enlarged and vast irregular slit-shaped pores emerged, which significantly increased the paraffin adsorption capacity. The MBFS could hold about 26.4% paraffin when 10% Ca(OH)2 was added as modifier, which was almost double compared with the BFS. The melting temperature and latent heat of paraffin/MBFS C-PCMs were determined as 51.9 °C and 36.4 J/g. And the prepared C-PCMs could maintain good thermal reliability even after 100 thermal cycles, which presented a potential application in the thermal energy storage fields like building energy conservation and solar energy storage.

Published
2020

303. Least Squares Based Iterative Parameter Estimation Algorithm for State Space Model with Time-Delay

Author

Gu Ya, Ding Wei, Liu Jicheng, and Chou Yongxin

Subjects
0209 industrial biotechnology, State-space representation, Computer science, Estimation theory, 020206 networking & telecommunications, 02 engineering and technology, Shift operator, Least squares, Linear map, Identification (information), 020901 industrial engineering & automation, 0202 electrical engineering, electronic engineering, information engineering, State space, Representation (mathematics), Algorithm
Abstract

This paper researches parameter estimation problem for state space systems with time-delay. Combing the linear transformation and the property of the shift operator, the state space model with time-delay can be equivalent to the input-output representation and then can be transformed into the identification model. The least squares based iterative parameter estimation algorithm is raised to identify the system with time-delay and makes full use of all data at each iteration and thus can generate highly accurate parameter estimates. Finally, the example is provided to validate the proposed theorems.

Published
2018

304. Weak order in averaging principle for two-time-scale stochastic partial differential equations

Author

Fu, Hongbo, Wan, Li, Liu, Jicheng, and Liu, Xianming

Subjects
Probability (math.PR), FOS: Mathematics, Mathematics - Probability
Abstract

This work is devoted to averaging principle of a two-time-scale stochastic partial differential equation on a bounded interval $[0, l]$, where both the fast and slow components are directly perturbed by additive noises. Under some regular conditions on drift coefficients, it is proved that the rate of weak convergence for the slow variable to the averaged dynamics is of order $1-\varepsilon$ for arbitrarily small $\varepsilon>0$. The proof is based on an asymptotic expansion of solutions to Kolmogorov equations associated with the multiple-time-scale system.

Published
2018

305. Preparation and Characterization of NaNO3/BFS Composite Phase Change Materials

Author

Liu Jicheng, Manman Lu, Yuanbo Zhang, Su Zijian, Guanghui Li, Liu Bingbing, and Tao Jiang

Subjects
Materials science, Structural material, Operating temperature, Ground granulated blast-furnace slag, Composite number, Nano, Sintering, Composite material, Atmospheric temperature range, Durability
Abstract

Blast furnace slag (BFS), one kind of typical solid waste in the steel industry, was used as structural materials to synthesize NaNO3/BFS composite phase change materials (C-PCMs) by mixing and sintering method. NaNO3 in the composites functioned as phase change materials (PCMs) and BFS as structural skeleton to maintain a stable external form. In this study, the prepared C-PCMs could remain in the solid state without salt leakage even if operating temperature exceeded the melting temperature of NaNO3. The composition and structure of BFS and the prepared composites were characterized by XRD, FTIR, SEM and TG-DSC analyses. The results showed that NaNO3 was well incorporated in the pores of BFS. The melting temperature and latent heat of the final composites were 300.5 °C and 65.53 J/g, respectively. The product also had good thermal storage performance and durability even after 100 thermal cycles. The energy density of the product was calculated as high as 468.03 J/g for an temperature range of 50–400 °C.

Published
2018

338. Fungal bioremediation of soil co-contaminated with petroleum hydrocarbons and toxic metals.

Author

Li, Qianwei, Liu, Jicheng, and Gadd, Geoffrey Michael

Subjects
*FUNGAL remediation, *HEAVY metals, *PETROLEUM, *HYDROCARBONS, *EXTRACELLULAR enzymes, *PETROLEUM products
Abstract

Much research has been carried out on the bacterial bioremediation of soil contaminated with petroleum hydrocarbons and toxic metals but much less is known about the potential of fungi in sites that are co-contaminated with both classes of pollutants. This article documents the roles of fungi in soil polluted with both petroleum hydrocarbons and toxic metals as well as the mechanisms involved in the biotransformation of such substances. Soil characteristics (e.g., structural components, pH, and temperature) and intracellular or excreted extracellular enzymes and metabolites are crucial factors which affect the efficiency of combined pollutant transformations. At present, bioremediation of soil co-contaminated with petroleum hydrocarbons and toxic metals is mostly focused on the removal, detoxification, or degradation efficiency of single or composite pollutants of each type. Little research has been carried out on the metabolism of fungi in response to complex pollutant stress. To overcome current bottlenecks in understanding fungal bioremediation, the potential of new approaches, e.g., gradient diffusion film technology (DGT) and metabolomics, is also discussed. Key points: • Fungi play important roles in soil co-contaminated with TPH and toxic metals. • Soil characteristics, enzymes, and metabolites are major factors in bioremediation. • DGT and metabolomics can be applied to overcome current bottlenecks. [ABSTRACT FROM AUTHOR]

Published
2020
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339. Weak order in averaging principle for stochastic wave equations with a fast oscillation

Author

Fu, Hongbo, Wan, Li, Liu, Jicheng, and Liu, Xianming

Subjects
Probability (math.PR), FOS: Mathematics, Mathematics - Probability
Abstract

This article deals with the weak errors for averaging principle for a stochastic wave equation in a bounded interval $[0,L]$, perturbed by a oscillating term arising as the solution of a stochastic reaction-diffusion equation evolving with respect to the fast time. Under suitable conditions, it is proved that the rate of weak convergence to the averaged effective dynamics is of order $1$ via an asymptotic expansion approach., Comment: arXiv admin note: text overlap with arXiv:1701.07983

Published
2017
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340. Evaluation of value-added efficiency in energy storage industry value chain: Evidence from China

Author

Liu, Jicheng, Lu, Chaoran, Ma, Xuying, and Li, Yinghuan

Abstract

With the determination of carbon peak and neutrality targets, and the need for the construction of new power systems, it is crucial for the high-quality development of the energy storage industry. This study aims to scientifically and accurately study the current situation and problems of its value chain, and analyze its driving factors and improvement paths. To that end, we constructed an empirical study under a combination of “ Smiling Curve”, Principal Component Analysis and three-stage DEA-Malmquist model. We based on the “Smiling Curve” theory, with the main business profit rate of 168 listed enterprises in the energy storage industry from 2017 to 2021 as the sample variable, the smile pattern of the value chain of the value storage industry is studied. Further, PCA is used to explore the value-added driving factors of upstream, midstream and downstream listed companies. Finally, the three-stage DEA-Malmquist model is used to evaluate the static and dynamic efficiency of each link in the value chain, excluding the influence of environmental and random factors. The results demonstrate that the value chain presents an arc-shaped smile, and the overall value-added capacity has improved after 2019, but the midstream link is still weak. The main driving factors of value-added efficiency of energy storage enterprises in different links are quite different. Under the new development requirements, enterprises should actively seek value-added breakthroughs. In addition, the value-added efficiency of energy storage enterprises is more sensitive to the external environment, verifying the need to consider environmental and random factors.

Published
2024
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341. Fluctuation analysis of synchronized system.

Author

Li, Ge and Liu, Jicheng

Subjects
*CENTRAL limit theorem, *LIMIT theorems, *MARTINGALES (Mathematics)
Abstract

We study the limiting behavior of fluctuations of synchronized system with small noise around their averaged deterministic limit. There are three regimes depending on how fast the intensity of the noise goes to zero relative to coupling parameter. By simple transformations, the original synchronized system is equivalently converted into the slow–fast system, then we derive the central limit theorem of the slow variable by the martingale method. Therefore, the fluctuation properties corresponding to the original synchronized system are derived. [ABSTRACT FROM AUTHOR]

Published
2024
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343. Impact of customers' impatience on an M/M/1 queueing system subject to differentiated vacations with a waiting server.

Author

Suranga Sampath, M. I. G. and Liu, Jicheng

Subjects
PATIENCE, POISSON processes, BESSEL functions, CONTINUED fractions, VACATIONS
Abstract

Impatience behavior of an M/M/1 queueing system, which has differentiated server vacations, is considered. Arrivals follow a Poisson process, service is exponentially distributed, as are both vacation types. When the system is empty after waiting for a random period of time, the server takes a vacation and returns after a random duration. If there are still no customers in the system, server can go for a vacation of shorter duration. If the server is in a vacation state, arriving customers become impatient with an individual timer which is exponentially distributed. Explicit expressions for time-dependent probabilities of the system size are obtained in terms of the modified Bessel function of first kind by making use of Laplace transforms and probability generating function techniques along with continued fractions and the confluent hypergeometric function. Explicit expressions for the time-dependent mean and variance of the system size are also derived. Moreover, steady-state probabilities for the system size are derived from the transient state probabilities. Finally, a numerical example is presented to study the behavior of the system. [ABSTRACT FROM AUTHOR]

Published
2020
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