BiFeO3 Thickness Dependence of the Exchange Bias in Polycrystalline BiFeO3/NiFe Bilayers

Xiaobo Xue,Biao You,Wenbing Rui,Wei Zhang,Jun Du,Xueyong Yuan,Qingyu Xu 한국물리학회 2013 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.62 No.12

A clear exchange bias has been observed at room temperature in a series of BiFeO3(t)/NiFe(3.6nm) bilayers, in which the BiFeO3 layers are single-phase polycrystalline with t varied from 8 nmto 240 nm. With increasing t, both the exchange bias field (HE) and the coercivity (HC) increasesharply and approach maxima when t is about 40 nm, which is close to one half the spin cycloidalmodulation period (64 nm) of the bulk BiFeO3 material. The oscillatory variations of HE and HCwith the BiFeO3 layer thickness suggest that the cycloidal spin structure may exist in polycrystallineBiFeO3 thin films. The angular dependence of the exchange bias exhibits collinear unidirectionaland uniaxial anisotropies in the present BiFeO3/NiFe bilayers.

Precursor and dispersion effects of active species on the activity of Mn-Ce-Ti catalysts for NO abatement

Xiaobo Wang,Jie Zhou,Caojian Jiang,Jia Wang,Keting Gui,Hywel Rhys Thomas 한국화학공학회 2019 Korean Journal of Chemical Engineering Vol.36 No.12

Mn-Ce-Ti catalysts were prepared by different precursors (including manganese nitrate, manganese acetate, and manganese chloride) and used for selective catalytic reduction (SCR) of NO with ammonia. The relationships among the structure, physicochemical properties, and catalytic activity were explored by N2 adsorption/desorption, X-ray diffraction (XRD), H2-temperature programmed reduction (H2-TPR), NH3-temperature programmed desorption (NH3TPD), X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HR-TEM), scanning electron microprobe (SEM) and energy dispersive spectroscopy (EDS) techniques. The results show that the different Mn precursors play important roles in the catalytic activity. The Mn-Ce-Ti(N) catalyst synthesized by manganese nitrate precursor exhibits the best catalytic activity, while the Mn-Ce-Ti(C) and Mn-Ce-Ti(Cl) catalyst prepared by manganese acetate and manganese chloride, respectively, exhibit relatively low catalytic activity. The manganese nitrate precursor could promote the specific surface area and redox ability, enhance the amounts of Brønsted and Lewis acid sites, and enrich the surface active species such as Mn4+, Ce3+ and surface chemisorbed oxygen of the catalyst, all of which will contribute to the SCR performance. Moreover, the Mn-Ce-Ti(N) catalyst possesses highly dispersed and uniform surface active species, which will result in the optimal physicochemical properties and superior catalytic performance.

Reconfigurable Flight Control System Design for Blended Wing Body UAV Based on Control Allocation

Xiaobo Qu,Jingping Shi,Haijun Zhou,Ling Zuo,Yongxi Lyu 제어로봇시스템학회 2018 제어로봇시스템학회 국제학술대회 논문집 Vol.2018 No.10

The aircraft control surface fault reconfigurable scheme based on control allocation is an active approach to achieve fault-tolerant in flight control. It has obvious advantages such as the structure and parameters of the control law does not need to be redesigned as deflector failures occurs. The attainable moment subset and allocation efficiency with typical control allocation algorithms are evaluated. A modular scheme reconfigurable flight control system (FCS) of a miniature tailless Blended Wing Body UAV is studied by utilizing weighted pseudo-inverse, direct control, and fixed-point control allocation methods. The performance of the reconfigurable FCS is tested and verified with the simulation including typical failure modes such as deflector floating, loss-of-effectiveness and lock-in-place. Results validate that the reconfigurable FCS based on control allocation has preferable ability to handle deflector failures, improve the safety and reliability of aircraft. And the modular scheme proposed in the article demonstrates a good application prospect in the field of aviation and aerospace engineering.

Study on the Stability of Tunnel in Weak Surrounding Rock considering Initial Support Parameters and Excavation Method

Xiaobo Zhang,Diao Zhang,Yao Rong,Yongli Ma,Chi Yao,Yang Sun 대한토목학회 2024 KSCE Journal of Civil Engineering Vol.28 No.6

The deformation control of surrounding rock is a crucial aspect in the design and construction of tunnels that traverse weak geological formations. This study developed a three-dimensional numerical model of tunnel excavation that accounts for the hysteresis of initial support, based on a highway tunnel under construction in Ganzhou, China. The rationality of the numerical model was verified through on-site measurements, and orthogonal tests were conducted to analyze the impact of construction parameters on the deformation of surrounding rock. The research findings indicate that the pipe-roof can be divided into four longitudinal sections according to the distribution of stress state: the tension section ahead of the entrance casing arch, the compression section behind the tunnel face, the tension section ahead of the tunnel face, and the compression section at the rear end of the pipe-roof. The grouting reinforcement can restrict the generation and development of plastic zone in the arch of surrounding rocks, which reduce the vault settlement significantly. The primary and secondary order of the impact on tunnel vault settlement, side wall convergence and surface uplift are excavation method, pipe-roof grouting radius, initial support thickness, pipe-roof layout range.

Flash-aware Virtual Memory System for Consumer Electronics

Xiaobo Ji,Fan Zeng 보안공학연구지원센터 2015 International Journal of Multimedia and Ubiquitous Vol.10 No.8

In this paper, an efficient flash-aware virtual memory system called FVMS is proposed for consumer electronics equipped with flash memory as secondary storage media. It introduces: 1) a redesigned read-ahead algorithm to delay the execution of page replacement algorithm, 2) a flash-aware page replacement algorithm considering access frequency, recent access time, and asymmetric I/O operation costs to reduce the number of flash page write operations and prevent serious degradation of page hit ratio, and 3) an efficient garbage collection policy taking into consideration the number of valid pages within each block and the number of erase operations on each block in order to reduce the cleaning cost and improve the degree of wear leveling. Experimental results show that the proposed FVMS outperforms existing virtual memory systems for flash memory in terms of energy consumption and the degree of wear leveling.

Research on Protection and Inheritance Strategy of Endangered Traditional Ceramic Crafts in Southern Fujian Folklore

Xiaobo Lian,Qingnian Zhang,Linping Zhou,Yuntao Huang,Zhouqing Liu KOREA INSTITUTE FOR HUMANITIES AND SOCIAL SCIENCES 2024 Journal of Arts and Cultural Studies(ACS) Vol.3 No.1

Background: In recent years, China's established many institutions and introduced reform programs to protect cultural heritage. Purpose:This research analyzes the protection status and development mode of endangered traditional ceramics in southern Fujian to better protect the endangered traditional ceramic technology in southern Fujian. It further researches ceramic process protection and inheritance development strategy. Methods: The attitudes of relevant national organizations towards protecting endangered traditional crafts are analyzed in the ceramic factory areas around Chaoshan and Foshan. The Dehua white porcelain, Jingdezhen porcelain mothers, and Foshan Shiwan dolls are compared through comparative research and literature to study various methods for protecting endangered traditional crafts. Further analyses on the strategies for the protection and development of the inheritance of endangered traditional ceramic crafts in the folklore of southern Fujian are also performed. Results: This article analyzes the protection and inheritance strategies of traditional ceramic crafts endangered in southern Fujian. It summarizes the three inheritance strategies of supporting inheritance talents, improving the protection mechanism, and establishing the protection and inheritance of traditional ceramic crafts on campus. Conclusion: The study of ceramic process protection strategy can summarize three points. First, to strengthen the precision support; second, to improve the inheritance and protection mechanism; and third, to establish research on the protection and inheritance of traditional ceramic processes.

Towards an Innovation-driven Nation

Xiaobo Wu,Jing Li 과학기술정책연구원 2015 STI Policy Review Vol.6 No.1

The rise of latecomer countries across the world directs academic attention to their catching-up and innovation processof seizing technological opportunities and combining internal and external knowledge. Different from the developed economies as well as the newly industrialized economies, China presents a special innovation environment, wherein its technology regime, market opportunities, and institutions are complex and the globalization trend affects competition in a broader way. In thiscontext, we clarify and extend the framework of “secondary innovation”. This framework describes the dynamics of those with relatively poor resources and capabilities in their efforts to capture the values of mature/emerging technology or business models by acquiringthem from across borders and then adapting to catching-up contexts. Such processes, differentiated from original innovation that involves the whole process from R&D to commercialization, has become a prevailing regime during paradigm shifts. In particular, unlike the traditional catch-up literature that focuses more on technology, the secondary innovation framework inclusively contains both technology and business model innovation, and puts forward the co-evolution between the two elements, which is more applicable to China’s context. In accordance, we also provide implications towards fulfilling the goal of building an innovation-driven nation.

Mistuning Effects on Aero-elastic Stability of Contra-Rotating Turbine Blades

Xiaobo Zhang,Yanrong Wang 한국항공우주학회 2019 International Journal of Aeronautical and Space Sc Vol.20 No.1

The aero-elasticity of contra-rotating turbine blades has been evaluated by employing the energy method and the aero-elastic eigenvalue method, which is different from the normal turbine blades with HPT wake impinging on the LPT directly. The effects of two different intentional mistuning patterns and random mistuning with standard deviation from 0.1 to 1% on aeroelastic stability of the low-pressure turbine (LPT) blades have been investigated by use of the eigenvaluemethod. Studies show that the best stabilized effect can be obtained with a specific distribution of mistuning amount for alternate and sinusoidal patterns. The random mistuning can improve the stability of tuned system with the increase of the standard deviation. But when the standard deviation is greater than 0.6%, the improving effect is invariable. For the mistuned system, the random mistuning decreases the stability of the intentional mistuned system and the optimal mistuning pattern has been changed. Additionally, when the standard deviation of the random mistuning is fixed, the mistuning amount has a more significant effect on the alternate mistuning than the sinusoidal mistuning.

Urban Flood Resilience Assessment Based on VIKOR-GRA: A Case Study in Chongqing, China

Xiaobo Chen,Zupei Guo,Hengyu Zhou,Xikun Qian,Xuesheng Zhang 대한토목학회 2022 KSCE JOURNAL OF CIVIL ENGINEERING Vol.26 No.9

Flooding has been considered as one of the major challenges of urban hazards resilience assessment. Improving urban flood risk resilience has become a critical issue for city management. However, urban flood assessment models on the resilience perspective are rare. Meanwhile, in the perspective of resilience, the existing studies using the TOPSIS (Technique for Order Preference by Similarity to an Ideal Solution) assessment method for disaster assessment lack consideration of evaluation scenarios located in the midpoint of positive and negative ideal solutions. To address these issues, this study establishes an urban flood disaster resilience assessment model, selects indicators according to the TOSE (Technical, Organizational, Social and Economic) framework, ranks cities through the VIKOR-GRA (VlseKriterijumska Optimizacija I Kompromisno Resenje, Grey Relational Analysis) method, and proposes measures to improve urban disaster resilience through the resilience assessment. Chongqing is taken as an example in this study to verify the feasibility and effectiveness of the proposed model, and practical management opinions are presented to improve flood resilience in these cities. Through the analysis of actual cases, it can be seen that the model has good applicability and can better reflect the actual situation. The knowledge of flood resilience assessment methods is of particular value to policy makers, researchers and industry professionals in assessing potential risks and recognizing the importance of flood prevention mechanisms.

Ga Content and Thickness Inhomogeneity Effects on Cu(In, Ga)Se2 Solar Modules

Xiaobo Zhu,Tzu-Huan Cheng,Chee-Wee Liu 대한금속·재료학회 2016 ELECTRONIC MATERIALS LETTERS Vol.12 No.4

The fluctuation of Ga content and absorption layer thickness of Cu(In,Ga)Se2 (CIGS) solar modules is investigated by 3-dimensional numericalsimulation. The band gap of CIGS is increased by the increasing Gacontent, and the residual compressive strain. Strain effect worsens thedegradation of the power conversion efficiency of CIGS module in additionto Ga fluctuation. The intracell Ga fluctuation degrades the open circuitvoltage due to the minimum open circuit voltage in the parallelconfiguration, and also affects the short circuit current due to the Gadependentlight absorption. The intercell Ga fluctuation leads to a moresignificant degradation for CIGS solar module efficiency than the intracellGa fluctuation due to the additional degradation of the fill factor. Thethickness fluctuation has a small effect on open circuit voltage, but causesstrong degradation of short circuit current and fill factor, which leads to amore significant degradation on power conversion efficiency than Gafluctuation to the same fluctuation percentage. In reality, the thickness canbe tightly controlled within the fluctuation of 5% or less.