Browsing by Author "Wang, Yu"
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Item Embargo Diagnostic features emerging in near-infrared reflectance spectroscopy for low petroleum hydrocarbon pollution after spectral subtraction(Elsevier, 2024-04-19) Lou, Qijia; Lei, Mei; Wang, Yu; Wang, Shaobin; Guo, Guanghui; Xiong, Wencheng; Jiang, Ying; Ju, Tienan; Zhao, Xiaofeng; Coulon, FredericDiagnostic features in near-infrared reflectance spectroscopy (NIRS) are the foundation of knowledge-based approach of petroleum hydrocarbon determination. However, a significant challenge arises when analyzing samples with low levels of petroleum hydrocarbon pollution, as they often lack distinctive diagnostic features in their sample NIRS spectra, limiting the effectiveness of this approach. To address this issue, we have developed a technical workflow for diagnostic spectrum construction and parameterization based on spectral subtraction. This method was applied on a set of NIRS spectra from soil samples that were contaminated with petroleum hydrocarbons (ranged between 178 and 1716 mg/kg of total petroleum hydrocarbon). Then two diagnostic features for low-level petroleum hydrocarbon pollution were found: (1) An overall downward concave emerged on diagnostic spectrum within both 2290–2370 nm and 1700–1780 nm for all low pollution levels even below 200 mg/kg; (2) An indicative pattern of asymmetric “W-shaped” double absorption valley occurred for those exceeding 1000 mg/kg, and its valleys located near 2310 nm, 2348 nm or 1727 nm, 1762 nm stably. These two features on diagnostic spectrum could be parameterized to detect, and the detection limit was at least about 10–50 times lower than that based on sample spectrum. These findings update our understanding on the detectability of spectral response from low petroleum hydrocarbon pollution, and widely extend the application of knowledge-based NIRS approach in either field detection or remote sensing identification for environmental management.Item Open Access Giant electric energy density in epitaxial lead-free thin films with coexistence of ferroelectrics and antiferroelectrics(Wiley, 2015-04-11) Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Scott, James F.; Zeng, Xierong; Huang, HaitaoFerroelectrics/antiferroelectrics with high dielectric breakdown strength have the potential to store a great amount of electrical energy, attractive for many modern applications in electronic devices and systems. Here we demonstrate that a giant electric energy density (154 J×cm-3, 3 times the highest value of lead-based systems and 5 times the value of the best dielectric/ferroelectric polymer), together with the excellent fatigue-free property, good thermal stability and high efficiency, is realized in pulsed laser deposited (Bi1/2Na1/2)0.9118La0.02Ba0.0582(Ti0.97Zr0.03)O3 (BNLBTZ) epitaxial lead-free relaxor thin films with the coexistence of ferroelectric (FE) and antiferroelectric (AFE) phases. This is endowed by high epitaxial quality, great relaxor dispersion and the coexistence of the FE/AFE phases near the morphotropic phase boundary (MPB). The giant energy storage effect of the BNLBTZ lead-free relaxor thin films may make a great impact on the modern energy storage technology.Item Open Access High dielectric tunability, electrostriction strain and electrocaloric strength at a tricritical point of tetragonal, rhombohedral and pseudocubic phases(Elsevier, 2015-06-16) Peng, Biaolin; Zhang, Qi; Li, Tieyu; Ke, Shanming; Ye, Mao; Wang, Yu; Niu, Hanben; Zeng, Xierong; Fan, Huiqing; Huang, HaitaoA relaxor ferroelectric Pb(Ni1/3Nb2/3)0.5Zr0.15Ti0.35O3 (PNNZT) ceramic was reported, designed upon an idea that the composition is selected to near a tricritical point of tetragonal, rhombohedral and pseudocubic phases. High dielectric tunability of 67%, simultaneously with high electrostriction strain of 0.319% and high electrocaloric strength (ΔT/ΔE) of 32.5 mK cm/kV are achieved, which make it a promising multifunctional material for applications in dielectric tunable, precisely controlled and electric refrigeration devices. This is endowed by the low energy barrier among the transitions of phases and strong relaxor ferroelectric activities around the tricritical point. This work provides a guide for the design of multifunctional ferroelectric materials and can promote the development of other multifunctional ferroic materials.Item Open Access Large Energy Storage Density and High Thermal Stability in a Highly Textured (111)-Oriented Pb0.8Ba0.2ZrO3 Relaxor Thin Film with the Coexistence of Antiferroelectric and Ferroelectric Phases(American Chemical Society, 2015-05-21) Peng, Biaolin; Zhang, Qi; Li, Xing; Sun, Tieyu; Fan, Huiqing; Ke, Shanming; Ye, Mao; Wang, Yu; Lu, Wei; Niu, Hanben; Zeng, Xierong; Huang, HaitaoA highly textured (111)-oriented Pb0.8Ba0.2ZrO3 (PBZ) relaxor thin film with the coexistence of antiferroelectric (AFE) and ferroelectric (FE) phases was prepared on a Pt/TiOx/SiO2/Si(100) substrate by using a sol-gel method. A large recoverable energy storage density of 40.18 J/cm3 along with an efficiency of 64.1% was achieved at room temperature. Over a wide temperature range of 250 K (from room temperature to 523 K), the variation of the energy density is within 5%, indicating a high thermal stability. The high energy storage performance was endowed by a large dielectric breakdown strength, great relaxor dispersion, highly textured orientation, and the coexistence of FE and AFE phases. The PBZ thin film is believed to be an attractive material for applications in energy storage systems over a wide temperature range (Graph Presented).Item Open Access New non-destructive method for testing the strength of cement mortar material based on vibration frequency of steel bar: Theory and experiment(Elsevier, 2020-09-30) Shi, Hao; Song, Lei; Chen, Wenlong; Zhang, Houquan; Wang, Guozhu; Yuan, Guotao; Zhang, Wenliang; Chen, Guiwu; Wang, Yu; Lin, GangTimely and accurately obtaining the strength of pouring material, e.g., concrete, cement mortar, is of great significance for engineering construction. In this paper, a non-destructive, economical and accurate strength detection method that suites for on-site using is proposed for the steel bar cement mortar material. The method based on the relationship between the vibration frequency of the steel bar and the properties of the mortar material, which is obtained by solving the Euler-Bernoulli beam problem. Both Particle Flow Code (PFC) software simulation (calibrated) and Split Hopkinson pressure Bar experiment on test samples of cement mortar and steel bar were performed to verify the theoretically obtained relationship. Studies on samples of various aggregate ratio further confirmed such correspondence. Results show that the dynamic stiffness of the cement mortar material dominates the calculation of the vibration frequency of steel bar, while the combined effect of the density, length, elastic modulus, inertia moment of the steel bar can be safely ignored. A single-valued mapping relation exists in between the dynamic stiffness coefficient and the Uniaxial Compressive Strength (UCS) of the cement mortar sample, i.e., increased dynamic stiffness coefficient with increasing UCS. Both experimental and predicted results showed a linear relationship between the vibration frequency of the steel bar and the strength of the mortar material. Fitted linear relations were proposed with coefficients depending on sample size and aggregate ratio and might serve as a good indicator for the strength of the mortar material. Further studies on the effect of internal defects of the mortar materials as well as on samples of more size and aggregate ratio are required to make the proposed method a practical toolItem Open Access Permanent-magnet flux-switching integrated starter generator with different rotor configurations for cogging torque and torque ripple mitigations(IEEE Institute of Electrical and Electronics, 2011-05-18T00:00:00Z) Fei, Wei-Zhong; Luk, Patrick Chi-Kwong; Shen, Jian-Xin; Xia, Bin; Wang, YuThis paper investigates the cogging torque and torque ripple features of a permanent-magnet flux-switching integrated starter generator. The effects of the rotor pole arc width on the cogging torque, torque ripple, and output torque are first established using finite-element analysis (FEA). Three torque ripple reduction techniques based on the optimization of three different rotor pole configurations, namely, uniform, step skewed, and axial pairing, are then proposed. The torque characteristics of each rotor configuration at varying load currents and phase angles are studied in detail. A prototype machine with a common stator and the three optimized rotor configurations are built for experimental validation. Both the FEA results and the experimental tests show that the step skewed and axial pairing techniques can alleviate the cogging torque significantly, but the latter is less effective than the former in reducing the overall torque ripple.Item Open Access Using network science to disentangle supply networks: a case study in aerospace industry(Cranfield University, 2014-07) Wang, Yu; Brintrup, Alexandra; Tiwari, AshutoshSupply chains in the aerospace sector are becoming more complex than ever before, frequently causing delays on the production process. Complexity gave rise to the term “supply networks”, changing the way we view supply chains from a structural point of view. Structural properties are important to investigate as they help define robustness and efficiency of systems. Although complexity in structure is suspected by previous researchers who studied these networks, empirical data to characterise what complexity means, and how it effects properties of networks has been largely absent from literature. If empirical data is available, network science can be used to understand structural properties of such complex supply networks. Network science is a suitable Mathematical tool for analysing the complex relationships and collaborations in the network and summarizing the properties of network from a fundamental, structural perspective. In this report, the author will apply network science to analyse the structure of the Airbus supply network. Due to the lack of aerospace supply chain data, firstly an empirical database is built. Analysis then focuses on the real structure of Airbus supply network and identification of key firms or communities under two scenarios: a non-weighted network in which the value of link is either 1 or 0, and a weighted network in which the value of link presents the strength of relationships among firms. While the weighted network indicates more informed features of the supply network structure by considering the weight of relationships, the non-weighted network can help us understand fundamental patterns that determine the structure of the connections in the network. The analysis indicates the Airbus supply network carries a power law distribution, which means most resources are dominated by few firms, and the network is robust to random firm failure but vulnerable to hub failure. The network contains communities with strong relationships between them.These communities do not only belong to the same industry and same region but have emerged as the result of an interaction between the two effects. Some key firms in the network own significant power of control the supply chain and fiancial resources, occupying key positions that bridge communities in the network.The study presents key structural features of a large scale network using empirical data and act as a case example for using network science based analysis in supply chains.