Evolving Relationship between Oil and Corn under Structural Changes

This paper focuses on the better estimation of the correlation between oil and corn with Realized Beta GARCH model, the first moment Granger Causality test on the prices of oil and corn, and the second moment causality test on the volatilities and returns of oil and corn. Since the past decade has witnessed the ever-fast development in biofuel production and increasing volatilities in the markets, I further perform Bai and Perron Procedure to detect possible structural breaks from 2004 to 2014 and use impulse response functions to help draw insight into the changing causal relationships in the price levels. I find that the correlation between oil and corn nearly doubled during the financial crisis and then resumes back to the normal level about 0.2. However, the statistically significant causal relationship from oil prices to corn prices detected in the prior crisis period cannot be found later as a result of higher volatilities and nonexistent arbitrage. The second moment causality test on the volatilities confirms our hypothesis that knowing the information on the returns of oil at time t can help predict the volatilities of corn at time t+1.Bachelor of Scienc

Image processing based quantitative damage evaluation in composites with long pulse thermography

Pulsed thermography is a contactless and rapid non-destructive evaluation (NDE) technique that is widely used for the inspection of fibre reinforced plastic composites. However, pulsed thermography uses expensive and specialist equipment such high-energy flash lamps to generate heat into the sample, so that alternative thermal stimulation sources are needed. Long pulse thermography was recently developed as a cost-effective solution to enhance the defect detectability in composites by generating step-pulse heat into the test sample with inexpensive quartz halogen lamps and measuring the thermal response during the material cooling down. This paper provides a quantitative comparison of long pulse thermography with traditional pulsed thermography and step heating thermography in carbon fibre and glass fibre composites with flat-bottomed holes located at various depths. The three thermographic methods are processed with advanced thermal image algorithms such as absolute thermal contrast, thermographic signal reconstruction, phase Fourier analysis and principal component analysis in order to reduce thermal image artefacts. Experimental tests have shown that principal component analysis applied to long pulse thermography provides accurate imaging results over traditional pulsed thermography and step heating thermography. Hence, this inspection technique can be considered as an efficient and cost-effective thermographic method for low thermal conductivity and low thermal response rate materials. This work is carried out within the scope of EU H2020 funded EXTREME projec

Research on the Evaluation System of Scientific Research Ethics Based on AHP-Fuzzy Comprehensive Evaluation

Scientific research ethics is the value concept and code of conduct to be followed in scientific research, technological development and other scientific and technological activities. However, in recent years, some researchers have ignored ethical constraints in scientific research activities, resulting in more prominent ethical issues in scientific research. This study takes China Southern Power Grid Corporation as an example, based on ISO9000 standards, uses AHP-fuzzy comprehensive evaluation theory to establish a scientific research ethics evaluation system, aiming at improving the timeliness and targeting of scientific research ethics management

Analysis and Diagnosis of CBM Fractured Wells’ Productivity Damage in the Middle of Qinshui Basin, China

CBM differs from conventional reservoirs, which is easily damaged with complex factors. There were massive papers on CBM damage mechanism, but with fewer studies on pollution types and stimulating measures. This paper studies various factors on SHI Zhuang CBM field’s production from the perspective of geology, engineering and drainage, establishes typical production model to determine reservoir pollution types, and builds up well and layer selection standard for recovering potential reservoirs. The result proves that impacts on CBM wells productivity cannot be ignored because their damages are huge, such as subsided column, fracturing fluid soaking time, fracturing problems, pumping efficiency, drainage time interval, production efficiency, and liquid loading rates etc. Major factors’ determination and typical curves’ establishment offer references on reservoir diagnosis, which is of great significance on layer selecting stimulation of inefficient wells

Electric-field Control of Magnetism with Emergent Topological Hall Effect in SrRuO3 through Proton Evolution

Ionic substitution forms an essential pathway to manipulate the carrier density and crystalline symmetry of materials via ion-lattice-electron coupling, leading to a rich spectrum of electronic states in strongly correlated systems. Using the ferromagnetic metal SrRuO3 as a model system, we demonstrate an efficient and reversible control of both carrier density and crystalline symmetry through the ionic liquid gating induced protonation. The insertion of protons electron-dopes SrRuO3, leading to an exotic ferromagnetic to paramagnetic phase transition along with the increase of proton concentration. Intriguingly, we observe an emergent topological Hall effect at the boundary of the phase transition as the consequence of the newly-established Dzyaloshinskii-Moriya interaction owing to the breaking of inversion symmetry in protonated SrRuO3 with the proton compositional film-depth gradient. We envision that electric-field controlled protonation opens a novel strategy to design material functionalities

Reversible manipulation of the magnetic state in SrRuO3 through electric-field controlled proton evolution

Ionic substitution forms an essential pathway to manipulate the structural phase, carrier density and crystalline symmetry of materials via ion-electron-lattice coupling, leading to a rich spectrum of electronic states in strongly correlated systems. Using the ferromagnetic metal SrRuO3 as a model system, we demonstrate an efficient and reversible control of both structural and electronic phase transformations through the electric-field controlled proton evolution with ionic liquid gating. The insertion of protons results in a large structural expansion and increased carrier density, leading to an exotic ferromagnetic to paramagnetic phase transition. Importantly, we reveal a novel protonated compound of HSrRuO3 with paramagnetic metallic as ground state. We observe a topological Hall effect at the boundary of the phase transition due to the proton concentration gradient across the film-depth. We envision that electric-field controlled protonation opens up a pathway to explore novel electronic states and material functionalities in protonated material systems

Two new species of cavernicolous trechines from central Guizhou and northwestern Guangxi, China (Coleoptera: Carabidae: Trechinae)

Ma, Zijun, Huang, Sunbin, Tian, Mingyi (2020): Two new species of cavernicolous trechines from central Guizhou and northwestern Guangxi, China (Coleoptera: Carabidae: Trechinae). Zootaxa 4861 (4): 581-593, DOI: https://doi.org/10.11646/zootaxa.4861.4.

Discovery of a cavernicolous trechine species from the Sanwang Dong-Erwang Dong cave system, Wulong, Chongqing, southwestern China (Coleoptera Carabidae: Trechinae)

Chen, Mengzhen, Ma, Zijun, Tian, Mingyi (2019): Discovery of a cavernicolous trechine species from the Sanwang Dong-Erwang Dong cave system, Wulong, Chongqing, southwestern China (Coleoptera Carabidae: Trechinae). Zootaxa 4668 (1): 105-114, DOI: https://doi.org/10.11646/zootaxa.4668.1.

Finite-Time Attitude Control for Quadrotor with Input Constraints and Disturbances

This paper investigates the adaptive output feedback attitude control of a quadrotor. First, a nonsingular terminal sliding-mode variable and auxiliary variable are introduced into a closed-loop structure. Meanwhile, a fuzzy logic system is incorporated into an adaptive algorithm to compensate for the adverse influence caused by lumped disturbances including system uncertainty and external disturbances on the attitude adjustment performance of a quadrotor. Then, a novel finite-time output feedback controller equipped with the saturation suppression algorithm is designed. Rigorous proof shows that the design control strategy ensures the closed-loop system stability and guarantees the attitude of the spacecraft to track desired command signals in finite time. Simulation results are presented to illustrate the performance of the proposed control scheme

A Multiscale Method to Develop Three-Dimensional Anisotropic Constitutive Model for Soils

A multiscale method is presented to develop a constitutive model for anisotropic soils in a three-dimensional (3D) stress state. A fabric tensor and its evolution, which quantify the particle arrangement at the microscale, are adopted to describe the effects of the inherent and induced anisotropy on the mechanical behaviors at the macroscale. Using two steps of stress mapping, the deformation and failure of anisotropic soil under the 3D stress state are equivalent to those of isotropic soil under the triaxial compression stress state. A series of discrete element method (DEM) simulations are conducted to preliminarily verify this equivalence. Based on the above method, the obtained anisotropic yield surface is continuous and smooth. Then, a fabric evolution law is established according to the DEM simulation results. Compared with the rotational hardening law, the fabric evolution law can also make the yield surface rotate during the loading process, and it can grasp the microscopic mechanism of soil deformation. As an example, an anisotropic modified Cam-clay model is developed, and its performance validates the ability of the proposed method to account for the effect of soil anisotropy