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Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

Ali ALSALEH, Hamid M. SEDIGHI, Hassen M. OUAKAD

《结构与土木工程前沿（英文）》 2020年 第14卷 第4期   页码 1024-1032 doi: 10.1007/s11709-020-0647-y

摘要： The current work experimentally explores and then theoretically examines the lateral vibrations of an unbalanced Jeffcott rotor-system working at several unbalance conditions. To this end, three conditions of eccentric masses are considered by using a Bently Nevada RK-4 rotor kit. Measurements of the steady-state as well as the startup data at rigid and flexible rotor states are captured by conducting a setup that mimics the vibration monitoring industrial practices. The linear governing equation of the considered rotor is extracted by adopting the Lagrange method on the basis of rigid rotor assumptions to theoretically predict the lateral vibrations. The dynamic features of the rotor system such as the linearized bearing induced stiffness are exclusively acquired from startup data. It is demonstrated that, with an error of less than 5%, the proposed two-degrees-of-freedom model can predict the flexural vibrations at rigid condition. While at flexible condition, it fails to accurately predict the dynamic response. In contrast to the other works where nonlinear mathematical models with some complexities are proposed to mathematically model the real systems, the present study illustrates the applicability of employing simple models to predict the dynamic response of a real rotor-system with an acceptable accuracy.

关键词： rotor-dynamics     Jeffcott rotor     lateral vibrations     Lagrange method     system-equivalent stiffness     sleeve bearings     oil film induced stiffness    

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A review on different theoretical models of electrocaloric effect for refrigeration

《能源前沿（英文）》 2023年 第17卷 第4期   页码 478-503 doi: 10.1007/s11708-023-0884-6

摘要： The performance parameters for characterizing the electrocaloric effect are isothermal entropy change and the adiabatic temperature change, respectively. This paper reviews the electrocaloric effect of ferroelectric materials based on different theoretical models. First, it provides four different calculation scales (the first-principle-based effective Hamiltonian, the Landau-Devonshire thermodynamic theory, phase-field simulation, and finite element analysis) to explain the basic theory of calculating the electrocaloric effect. Then, it comprehensively reviews the recent progress of these methods in regulating the electrocaloric effect and the generation mechanism of the electrocaloric effect. Finally, it summarizes and anticipates the exploration of more novel electrocaloric materials based on the framework constructed by the different computational methods.

关键词： electrocaloric effect     effective Hamiltonian     phase-field modeling     different theoretical models    

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NOx removal by non-thermal plasma reduction: experimental and theoretical investigations

《化学科学与工程前沿（英文）》 2022年 第16卷 第10期   页码 1476-1484 doi: 10.1007/s11705-022-2165-z

摘要： Green and efficient NOx removal at low temperature is still desired. NOx removal via non-thermal plasma (NTP) reduction is one of such technique. This work presents the experimental and theoretical study on the NOx removal via NTP reduction (NTPRD) in dielectric barrier discharge reactor (DBD). The effect of O2 molar fraction on NOx species in the outlet of DBD, and effects of NH3/NO molar ratio and discharge power of DBD on NOx removal efficiency are investigated. Results indicate that anaerobic condition and higher discharge power is beneficial to direct removal of NOx, and the NOx removal efficiency can be up to 98.5% under the optimal operating conditions. It is also found that adding NH3 is favorable for the reduction of NOx to N2 at lower discharge power. In addition, the NOx removal mechanism and energy consumption analysis for the NTPRD process are also studied. It is found that the reduced active species ( N∗, N−, N+, N2∗, NH2+, etc.) generated in the NTPRD process play important roles for the reduction of NOx to N2. Our work paves a novel pathway for NOx removal from anaerobic gas in industrial application.

关键词： ${\rm{NO}}_x $ removal     NTP reduction     mechanism     energy consumption    

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Flexural-torsional buckling behavior of aluminum alloy beams

Xiaonong GUO,Zhe XIONG,Zuyan SHEN

《结构与土木工程前沿（英文）》 2015年 第9卷 第2期   页码 163-175 doi: 10.1007/s11709-014-0272-8

摘要： This paper presents an investigation on the flexural-torsional buckling behavior of aluminum alloy beams (AAB). First, based on the tests of 14 aluminum alloy beams under concentrated loads, the failure pattern, load-deformation curves, bearing capacity and flexural-torsional buckling factor are studied. It is found that all the beam specimens collapsed in the flexural-torsional buckling with excessive deformation pattern. Moreover, the span, loading location and slenderness ratio influence the flexural-torsional buckling capacity of beams significantly. Secondly, besides the experiments, a finite element method (FEM) analysis on the flexural-torsional buckling behavior of AAB is also conducted. The main parameters in the FEM analysis are initial imperfection, material property, cross-section and loading scheme. According to the analytical results, it is indicated that the FEM is reasonable to capture mechanical behavior of AAB. Finally, on the basis of the experimental and analytical results, theoretical formulae to estimate the flexural-torsional buckling capacity of AAB are proposed, which could improve the application of present codes for AAB.

关键词： flexural-torsional buckling     aluminum alloy beams (AAB)     finite element method (FEM)     theoretical formula    

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Thermal transport properties of monolayer phosphorene: a mini-review of theoretical studies

Guangzhao QIN, Ming HU

《能源前沿（英文）》 2018年 第12卷 第1期   页码 87-96 doi: 10.1007/s11708-018-0513-y

摘要： Phosphorene, a two-dimensional (2D) elemental semiconductor with a high carrier mobility and intrinsic direct band gap, possesses fascinating chemical and physical properties distinctively different from other 2D materials. Its rapidly growing applications in nano-/opto-electronics and thermoelectrics call for fundamental understanding of the thermal transport properties. Considering the fact that there have been so many studies on the thermal transport in phosphorene, it is on emerging demand to have a review on the progress of previous studies and give an outlook on future work. In this mini-review, the unique thermal transport properties of phosphorene induced by the hinge-like structure are examined. There exists a huge deviation in the reported thermal conductivity of phosphorene in literature. Besides, the mechanism underlying the deviation is discussed by reviewing the effect of different functionals and cutoff distance in calculating the thermal transport properties of phosphorene. It is found that the (vdW) interactions play a key role in the formation of resonant bonding, which leads to long-ranged interactions. Taking into account of the vdW interactions and including the long-ranged interactions caused by the resonant bonding with large cutoff distance are important for getting the accurate and converged thermal conductivity of phosphorene. Moreover, a fundamental insight into the thermal transport is provided based on the review of resonant bonding in phosphorene. This mini-review summarizes the progress of the thermal transport in phosphorene and gives an outlook on future horizons, which would benefit the design of phosphorene based nano-electronics.

关键词： thermal transport     phosphorene     resonant bonding    

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Prediction of the theoretical and semi-empirical model of ambient temperature

Foued CHABANE,Noureddine MOUMMI,Abdelhafid BRIMA,Abdelhafid MOUMMI

《能源前沿（英文）》 2016年 第10卷 第3期   页码 268-276 doi: 10.1007/s11708-016-0413-y

摘要： It is well known that the ambient temperature is a sensitive parameter which has a great effect on biology, technology, geology and even on human behavior. A prediction is a statement about an uncertain event. It is often, but not always, based upon experience or knowledge. Although guaranteed accurate information about the future is in many cases impossible, prediction can be useful to assist in making plans about possible developments. As a result, temperature profiles can be developed which accurately represent the expected ambient temperature exposure that this environment experiences during measurement. The ambient temperature over time is modeled based on the previous and data and using a Lagrange interpolation. To observe the comprehensive variation of ambient temperature the profile must be determined numerically. The model proposed in this paper can provide an acceptable way to measure the change in ambient temperature.

关键词： ambient temperature     environment     correlation     theoretical model     semi-empirical    

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Theoretical and technological exploration of deep

Heping XIE, Yang JU, Shihua REN, Feng GAO, Jianzhong LIU, Yan ZHU

《能源前沿（英文）》 2019年 第13卷 第4期   页码 603-611 doi: 10.1007/s11708-019-0643-x

摘要： Mining industries worldwide have inevitably resorted to exploiting resources from the deep underground. However, traditional mining methods can cause various problems, e.g., considerable mining difficulty, environmental degradations, and frequent disastrous accidents. To exploit deep resources in the future, the concept of mining must be reconsidered and innovative new theories, methods, and technologies must be applied. To effectively acquire coal resources deeper than 2000 m, new theoretical and technological concepts about deep fluidized mining are required. The limits of mining depth need to be broken to acquire deep-coal resources in an environmentally friendly, safe, and efficient manner. This is characterized by ‘There are no coal on the ground and no men in the coal mine’. First, this paper systematically explains deep fluidized coal mining. Then, it presents a new theoretical concept, including the theories of mining-induced rock mechanics, three-field visualization, multi-physics coupling for transformation, and mining, transformation and transport. It also presents key technological concepts, including those of intelligent, unmanned, and fluidized mining. Finally, this paper presents a strategic roadmap for deep fluidized coal mining. In summary, this paper develops new theoretical and technological systems for accomplishing groundbreaking innovations in mining technologies of coal resources in the deep underground.

关键词： coal resource     deep in situ     fluidized mining     theoretical system     key technologies     strategic roadmap    

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Theoretical analysis and experimental investigation of valveless piezoelectric pump with unsymmetrical

ZHANG Jianhui, LU Jizhuang, XIA Qixiao, LI Hong

《机械工程前沿（英文）》 2007年 第2卷 第1期   页码 13-19 doi: 10.1007/s11465-007-0002-1

摘要： A novel valveless piezoelectric pump with unsymmetrical ridges is presented at first. It ingeniously utilizes the inner space of its chamber by developing its chamber bottom into unsymmetrical ridges along the direction of the inlet and outlet of the pump. Hence, a series of cuneiform channels are asymmetrically and alternately formed between the unsymmetrical ridges and the piezoelectric vibrator, which enables the pump to form a one-way flow instead of the function of the traditional diffuse or nozzle elements fitted outside the chamber. Then, by analyzing the vibration of the piezoelectric vibrator, the vibration deformation function and the equation of volume change are established. Meanwhile, the theoretical equation of the pump flow rate is established. Finally, a real valveless piezoelectric pump with unsymmetrical ridges is manufactured, and the flow rate of the pump is measured through experiments. It is proved that the theory is rational and correct by comparing the experimental flow rate and the theoretical flow rate. In addition, for calculating the theoretical flow rate, the positive and converse flow resistance coefficients of unsymmetrical ridges are measured through experiments, when one slope angle of the unsymmetrical ridges is 90º and another is changing from 20º to 60º, respectively.

关键词： unsymmetrical     theoretical flow     theoretical equation     pump flow     converse flow    

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Experimental study on flexural behavior of ECC/RC composite beams with U-shaped ECC permanent formwork

Zhi QIAO, Zuanfeng PAN, Weichen XUE, Shaoping MENG

《结构与土木工程前沿（英文）》 2019年 第13卷 第5期   页码 1271-1287 doi: 10.1007/s11709-019-0556-0

摘要： To enhance the durability of a reinforced concrete structure, engineered cementitious composite (ECC), which exhibits high tensile ductility and good crack control ability, is considered a promising alternative to conventional concrete. However, broad application of ECC is hindered by its high cost. This paper presents a new means to address this issue by introducing a composite beam with a U-shaped ECC permanent formwork and infill concrete. The flexural performance of the ECC/RC composite beam has been investigated experimentally with eight specimens. According to the test results, the failure of a composite beam with a U-shaped ECC formwork is initiated by the crushing of compressive concrete rather than debonding, even if the surface between the ECC and the concrete is smooth as-finished. Under the same reinforcement configurations, ECC/RC composite beams exhibit increases in flexural performance in terms of ductility, load-carrying capacity, and damage tolerance compared with the counterpart ordinary RC beam. Furthermore, a theoretical model based on the strip method is proposed to predict the moment-curvature responses of ECC/RC composite beams, and a simplified method based on the equivalent rectangular stress distribution approach has also evolved. The theoretical results are found to be in good agreement with the test data.

关键词： engineered cementitious composite (ECC)     durability     ECC/RC composite beam     permanent formwork     flexural performance     theoretical method    

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Mechanism insight into the formation of HS from thiophene pyrolysis: A theoretical study

《环境科学与工程前沿（英文）》 2021年 第15卷 第6期 doi: 10.1007/s11783-021-1404-8

摘要：

• Possible formation pathways of H2S were revealed in thiophene pyrolysis.

关键词： Density functional theory     Waste rubber     Thiophene     H2S     Pyrolysis    

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enhancement in high acidity using di-(2-ethylhexyl)phosphoric acid with [Cl] present: an experimental and theoretical

《化学科学与工程前沿（英文）》 2023年 第17卷 第1期   页码 56-67 doi: 10.1007/s11705-022-2185-8

摘要： Separation of vanadium from black shale leaching solution at low pH is very meaningful, which can effectively avoid the generation of alkali neutralization slag and the resulting vanadium loss. In this study, coordination mechanism of vanadium in acid leaching solution at low pH was investigated with the intervention of chloride ions. Under the conditions of pH 0.8, di-(2-ethylhexyl)phosphoric acid concentration of 20%, phase ratio of 1:2, and extraction time of 8 min, the vanadium extraction could reach 80.00%. The Fourier transform infrared and electrospray ionization results reveal that, despite the fact that the chloride ion in the leachate could significantly promote vanadium extraction, the chloride ion does not enter the organic phase, indicating an intriguing phenomenon. Among Cl−–V, SO42−–V, and H2O–V, the V–Cl bond is longer and the potential difference between coordinate ions and vanadium is smaller. Therefore, VO2+ gets easily desorbed with chloride ions and enter the organic phase. At the same time, the hydrogen ions of di-(2-ethylhexyl)phosphoric acid also enter the water phase more easily, which reduces the pH required for the extraction reaction.

关键词： vanadium     black shale     solvent extraction     high acidity extraction    

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Governance approach to China’s environmental challenges: Towards a theoretical synthesis

QI Ye, XUE Lan, ZHANG Lingyun

《环境科学与工程前沿（英文）》 2007年 第1卷 第4期   页码 385-400 doi: 10.1007/s11783-007-0066-5

摘要： This paper reviewed recent research in environmental governance as a response to environmental challenges at various spatial, temporal and administrative scales. It documented the shift of approach from regulation to governance, and attempted to provide a comprehensive understanding why and how the transformation occurred. It also described major factors and forces of environmental governance, and discussed research advance in environmental governance theory. Finally, this paper summarized recent research findings on environmental governance in China, and listed policy recommendation for enhancing the governance.

关键词： environmental governance     approach     temporal     regulation     various    

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Konjac glucomannan and xanthan gum as compression coat for colonic drug delivery: experimental and theoretical

Kang WANG, Jiangyang FAN, Yanjun LIU, Zhimin HE,

《化学科学与工程前沿（英文）》 2010年 第4卷 第1期   页码 102-108 doi: 10.1007/s11705-009-0299-x

摘要： Compression coated tablets for oral colon specific delivery systems were developed with a mixture polysaccharide of konjac glucomannan (KGM) and xanthan gum (XG) as the compression coat. Diffusion of cimetidine from compression coated tablets was investigated by release experiment . 0.22U/mL -mannanase was applied in the mimic colon solution. The structure of the mixture polysaccharide was studied by an atomic force microscope (AFM). The experimental results indicate that a KGM70 tablet with a 0.4g coat is of good design, due to a less than 5% drug loss in the mimic upper gastrointestinal solution by the synergistic interaction between XG and KGM, and due to about 50% cumulative release in the mimic colon solution by degradation after 24 hours. The release mechanism and model are discussed based on different periods of drug release including the delay of the drug, the constant release without an enzyme and the delay of degradation. Under hydrolysis by -mannanase, drug release from the tablet with KGM coat shows an exponential increase, while that from the dosage with the mixture polysaccharide coat is an approximately zero-order process in which the constant release rate relates to the release velocity of a non-degraded system, the content of KGM within the coat and the average molecular weight ratio of KGM to XG. It was found that XG was the framework of the polysaccharide mixtures by AFM, which is similar to the analysis results from experiments on drug release.
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A review of recent experimental investigations and theoretical analyses for pulsating heat pipes

Xin TANG, Lili SHA, Hua ZHANG, Yonglin JU

《能源前沿（英文）》 2013年 第7卷 第2期   页码 161-173 doi: 10.1007/s11708-013-0250-1

摘要： Pulsating heat pipe (PHP), or oscillating heat pipe (OHP), a novel type of highly efficient heat transfer component, has been widely applied in many fields, such as in space-borne two-phase thermal control systems, in the cooling of electronic devices and in energy-saving technology, etc. In the present paper, the characteristics and working principles of the PHPs are introduced and the current researches in the field are described from the viewpoint of experimental tests, theoretical analyses as well as practical applications. Besides, it is found that the state-of-the-art experimental investigations on the PHPs are mainly focused on the flow visualization and the applications of nanofluids and other functional fluids, aiming at enhancing the heat transfer performance of the PHPs. In addition, it is also pointed out that the present theoretical analyses of the PHP are restricted by further development of two-phase flow theories, and are concentrated in the non-linear analyses. Numerical simulations are expected to be another research focus, in particular of the combination of the nanofluids and functional fluids.

关键词： pulsating heat pipe (PHP)     flow visualization     nanofluids     nonlinear analysis    

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煤层注水参数的数量化理论正交设计优化法的研究

秦书玉,秦伟瀚

《中国工程科学》 2003年 第5卷 第10期   页码 52-55

摘要：

应用正交设计优化煤层注水工艺参数的组合，对地质条件稳定的煤层是实现最佳注水效果的一种较好的方法。但是，对于地质条件不断变化的煤层，采用该方法，其效果不一定能满足注水工程要求。为此，针对地质因素为不稳定状态下的煤层及影响煤层注水的地质因素既有定性变量又有定量变量的特征，提出利用数量化理论与正交设计2种方法确定注水工艺参数的最优组合，并进行了工程试验优化研究。试验结果表明，此法节省注水试验工程量，接近实际工程要求。

关键词： 数量化理论     工艺参数     正交设计     煤层注水     试验研究    

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标题 作者 时间 类型 操作

Experimental and theoretical investigations of the lateral vibrations of an unbalanced Jeffcott rotor

Ali ALSALEH, Hamid M. SEDIGHI, Hassen M. OUAKAD

期刊论文

A review on different theoretical models of electrocaloric effect for refrigeration

期刊论文

NOx removal by non-thermal plasma reduction: experimental and theoretical investigations

期刊论文

Flexural-torsional buckling behavior of aluminum alloy beams

Xiaonong GUO,Zhe XIONG,Zuyan SHEN

期刊论文

Thermal transport properties of monolayer phosphorene: a mini-review of theoretical studies

Guangzhao QIN, Ming HU

期刊论文

Prediction of the theoretical and semi-empirical model of ambient temperature

Foued CHABANE,Noureddine MOUMMI,Abdelhafid BRIMA,Abdelhafid MOUMMI

期刊论文

Theoretical and technological exploration of deep

Heping XIE, Yang JU, Shihua REN, Feng GAO, Jianzhong LIU, Yan ZHU

期刊论文

Theoretical analysis and experimental investigation of valveless piezoelectric pump with unsymmetrical

ZHANG Jianhui, LU Jizhuang, XIA Qixiao, LI Hong

期刊论文

Experimental study on flexural behavior of ECC/RC composite beams with U-shaped ECC permanent formwork

Zhi QIAO, Zuanfeng PAN, Weichen XUE, Shaoping MENG

期刊论文

Mechanism insight into the formation of HS from thiophene pyrolysis: A theoretical study

期刊论文

enhancement in high acidity using di-(2-ethylhexyl)phosphoric acid with [Cl] present: an experimental and theoretical

期刊论文

Governance approach to China’s environmental challenges: Towards a theoretical synthesis

QI Ye, XUE Lan, ZHANG Lingyun

期刊论文

Konjac glucomannan and xanthan gum as compression coat for colonic drug delivery: experimental and theoretical

Kang WANG, Jiangyang FAN, Yanjun LIU, Zhimin HE,

期刊论文

A review of recent experimental investigations and theoretical analyses for pulsating heat pipes

Xin TANG, Lili SHA, Hua ZHANG, Yonglin JU

期刊论文

煤层注水参数的数量化理论正交设计优化法的研究

秦书玉,秦伟瀚

期刊论文