A spatially hierarchical integration of close-range remote sensing, leaf structure and physiology assists in diagnosing spatiotemporal dimensions of field-scale ecosystem photosynthetic productivity

Xue, Wei,Ko, Jonghan,Werner, Christiane,Tenhunen, John Elsevier 2017 Agricultural and forest meteorology Vol.247 No.-

<P><B>Abstract</B></P> <P>There are great variations of inter-annual ecosystem photosynthetic productivity (GPP) in rice agricultural mosaic landscapes in Asian monsoon regions, consisting of relatively small land holdings. It is therefore of great importance to capture and interpret spatiotemporal aspects of per-field GPP. This goal, however, remains challenging partially due to absence of adequate methodology that applies ecophysiological data to broader spatial and temporal dimensions to explicitly quantify influences of environment change on per-field GPP. To accomplish the goal, field experiments were carried out at spatially adjacent flooding paddy (PD) and rainfed (RF) lowland rice (<I>Oryza sativa</I>) fields, taking year-round measurements in micrometeorological factors, leaf and canopy photosynthesis, and field reflectance with help from an unmanned aviation vehicle (UAV) system. A spatially hierarchical integration (PIXel based CANopy photosynthesis model, PIXCAN) that fuses measurements from leaf to canopy and field scales was then developed. Our results showed that the PIXCAN fusion could well capture and characterize spatial properties of per-field ecosystem GPP. Spatial variations (SV) of ecosystem carbon uptake capacity (GPP<SUB>max</SUB>) at the PD and RF fields decreased over the growing season. However, occurrence of prolonged non-precipitation period due to climate anormaly in mid-August led to severe constraints of GPP<SUB>max</SUB> and counter-seasonally strengthened SV that would decrease in the RF rice field, primarily due to drought impacts on light-harvesting efficiency and less to stomatal conductance. Collectively, we highlighted ecological implications of the integration applied at field niche in spatially hierarchical observation of ecosystem regulating/production provisions from leaf to landscape dimensions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> A spatially hierarchical integration (PIXCAN) links UAV remote sensing and at-surface measurements. </LI> <LI> Spatiotemporal variations of per-field photosynthetic productivity were captured and interpreted. </LI> <LI> Occurrence of prolonged non-rainfall period led to severe constraints of GPP<SUB>max</SUB> and significantly strengthened SV. </LI> <LI> Drought-stressed ecosystem GPP<SUB>max</SUB> primarily due to constrained light-harvesting efficiency and less to stomatal conductance. </LI> <LI> Ecological implications of the integration in spatially hierarchical observation of ecosystem GPP. </LI> </UL> </P>

EFFECTS OF COOPERATIVE VEHICLE INFRASTRUCTURE SYSTEM ON DRIVER’S VISUAL AND DRIVING PERFORMANCE BASED ON COGNITION PROCESS

Xuewei Li,Zhenlong Li,Xiaohua Zhao,Jian Rong,Yunlong Zhang 한국자동차공학회 2022 International journal of automotive technology Vol.23 No.5

This study explores the influence of cooperative vehicle infrastructure system (CVIS) on the driver’s visual and driving performance. Taking the work zone as an example, a driving simulation experiment involving 37 drivers has been conducted to collect driver’s eye movement and vehicle running data in the same scenario with and without CVIS information respectively. Next, the nonparametric test and grey relational analysis (GRA) have been used to compare the specific performance and to analyze the correlations among the multi-stage of driver’s information process. The results present that CVIS information has the potential to alleviate the driver’s tension and the difficulty of information perception. Meanwhile, the driver tends to search visual information more actively and complete the lane changing behavior earlier. Further analysis indicates that CVIS information can reduce the influence of mental workload on lane-changing decisions, and enhance the correlation between visual information processing and lane-changing decisions, as well as the effect of decision-making timing on the running state. Therefore, drivers’ speed control ability was improved and the traffic flow was smoother. The findings give an insight into the influence mechanism of the cooperative information on driving performance and provide a direction for a comprehensive assessment of CVIS based on human factors.

A cumulative damage model for extremely low cycle fatigue cracking in steel structure

Xuewei Huang,Jun Zhao 국제구조공학회 2017 Structural Engineering and Mechanics, An Int'l Jou Vol.62 No.2

The purpose of this work is to predict ductile fracture of structural steel under extremely low cyclic loading experienced in earthquake. A cumulative damage model is proposed on the basis of an existing damage model originally aiming to predict fracture under monotonic loading. The cumulative damage model assumes that damage does not grow when stress triaxiality is below a threshold and fracture occurs when accumulated damage reach unit. The model was implemented in ABAQUS software. The cumulative damage model parameters for steel base metal, weld metal and heat affected zone were calibrated, respectively, through testing and finite element analyses of notched coupon specimens. The damage evolution law in the notched coupon specimens under different loads was compared. Finally, in order to examine the engineering applicability of the proposed model, the fracture performance of beam-column welded joints reported by previous researches was analyzed based on the cumulative damage model. The analysis results show that the cumulative damage model is able to successfully predict the cracking location, fracture process, the crack initiation life, and the total fatigue life of the joints.

Experimental and Fracture Model Study of Q690D Steel Under Various Stress Conditions

Xuewei Huang,Jianzhou Ge,Jun Zhao,Wei Zhao 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.2

The fracture failure of high-strength steel has an important relationship with the stress state. In order to predict the fracture failure of high-strength steel under diff erent stress conditions, based on the void growth model (VGM), a fracture model which comprehensively considers the eff ect of stress triaxiality and the Lode parameter on fracture failure is proposed and is called LVGM. A batch of Chinese Q690D high strength steel round rods and plate shaped specimens refl ecting diff erent stress states were processed, and the monotonic tensile tests, the scanning electron microscopy tests and the fi nite element calculation were carried out to study the crack initiation of the specimens. The microscopic mechanism of the fracture damage of the specimens was analyzed. Based on the fracture test results of the specimens and the corresponding fi nite element analysis, the LVGM parameters of the Q690D high strength steel were calibrated. Finally, the LVGM was used to predict the crack initiation and fracture failure process of the specimens with initial gap. The prediction results are in good agreement with the experimental results, and the LVGM has better prediction accuracy than the VGM.

On the Feasibility of Self-Correction of the Appellate Body’s Previous Decision: Lessons from China-Rare Earths

Xuewei Feng 이준국제법연구원 2015 China and WTO Review Vol.1 No.2

Small Signal Modeling, Analysis and Control of Naturally Clamped Soft-switching Current-fed Three-Phase Bidirectional DC/DC Converter

Xuewei Pan,Peng Wang,Quoc Nam Trinh,Akshay Kumar Rathore 전력전자학회 2015 ICPE(ISPE)논문집 Vol.2015 No.6

A small signal analysis and a closed loop control design of naturally commutated current-fed threephase isolated dc/dc converter are presented in this paper. State-space averaging technique is used to derive the small signal model. Based on the derived small signal model, a closed two-loop controller is designed and implemented on mixed signal (analog and digital) processor Cypress PSoC 5. A complete design procedure is presented. Simulation results using PSIM 9.0.4 and experimental waveforms from a 750W prototype with the designed controller are illustrated to verify the stability of the control system. Experimental results for step changes in load clearly show satisfactory transient performance of the converter and validate closed two-loop design.

Model-free Optimal Tracking Control for an Aircraft Skin Inspection Robot with Constrained-input and Input Time-delay via Integral Reinforcement Learning

Xuewei Wu,Congqing Wang 제어·로봇·시스템학회 2020 International Journal of Control, Automation, and Vol.18 No.1

This paper presents a model-free optimal tracking control algorithm for an aircraft skin inspection robot with constrained-input and input time-delay. To tackle the input time-delay problem, the original system is transformed into a delay-free system with constrained-input and unknown input coupling term. In order to overcome the optimal control problem subject to constrained-input,a discounted value function is employed. In general, it is known that the HJB equation does not admit a classical smooth solution. Moreover, since the input coupling term of the delay-free system is unknown, a model-free integral reinforcement learning(IRL) algorithm which only requires the system sampling data generated by arbitrary different control inputs and external disturbances is proposed. The model-free IRL method is implemented on an actor-critic neural network (NN) structure. A system sampling data set is utilized to learn the value function and control policy. Finally, the simulation verifies the effectiveness of the proposed algorithm.

Tilt Angle Measurement Based on Arrayed Eddy Current Sensors

Xuewei Chao,Yang Li,Jing Nie 한국자기학회 2016 Journal of Magnetics Vol.21 No.4

Eddy current (EC) sensor works based on the electromagnetic induction principle and has been widely applied in the industrial testing and evaluation due to its robustness and environmental adaptability. Meanwhile, tilt angle measurement is mainly based on the laser or visual method, which is strict with the measurement environment and not suitable for the industrial applications. In this paper, a novel tilt angle measurement method based on arrayed EC sensors is proposed. Both the simulation and experiments indicate that the measured error is approximately linear with tilt angle and the accuracy after compensation is 0.25°. In conclusion, this research cannot only broaden the scope of EC application, but also overcome the shortcomings of existing angle measurement methods.

Long-chain alcohols derived from the microalga Monoraphidium

Yang, Xuewei,Dai, Xin,Zhang, Rui,Shao, Cong,Geng, Shu,Chen, Guangyi,Liu, Xianhua,Wang, Guangyi Techno-Press 2013 Advances in energy research Vol.1 No.2

This study was to investigate the composition and characteristics of long-chained alcohols extracted from the algal strain Monoraphidium 3s35. The production of biomass was optimized using different cultivation methods. Under the aerated growth condition, this strain yielded up to 37.26% extracts of dry weight and $576mgL^{-1}$ biomass. The major compounds of the extracts are mainly long-chained alcohols (89.24%), with carbon chain length ranging from 12 to 20. Interestingly, or the long-chained alcohols, 3-(2-Methoxyethyl)-1-nonanol, 3,7,11,15-Tetramethyl-2-hexadecen-1-ol and oleyl alcohol accounted for 53.68%, 23.45%, and 12.11%, respectively. Because of their amphipathic nature, these long-chained alcohols have been widely used in bioenergy production and cosmetics industry. Furthermore, Monoraphidium 3s35 produced 9.73% of $C_{17}$ and $C_{20}$ alkanes, which can be used as an important supplement for the petrodiesel-like fuel.

Lactobacillus salivarius REN Counteracted Unfavorable 4-Nitroquinoline-1-Oxide-Induced Changes in Colonic Microflora of Rats

Ming Zhang,Xuewei Qiao,Liang Zhao,Lu Jiang,Fazheng Ren 한국미생물학회 2011 The journal of microbiology Vol.49 No.6

Probiotics and carcinogens both have a significant effect on the microfloral composition of the human intestine. The objective of this study was to investigate the impact of an important carcinogen, 4-Nitroquinoline-1- Oxide on colonic microflora and the efficacy of the probiotic Lactobacillus salivarius REN as an agent of counteracting these effects. Using denaturing gradient gel electrophoresis (DGGE) combined with redundancy analysis, we demonstrated that both 4-Nitroquinoline-1-Oxide and L. salivarius REN significantly altered the bacterial communities of rat colons. A total of 27 bacterial strains were identified as being affected by treatment with 4-Nitroquinoline-1-Oxide or L. salivarius REN using a t-value biplot combined with band sequencing. 4-Nitroquinoline-1-Oxide treatment increased the abundance of two potential pathogens (one Helicobacter strain and one Desulfovibrio strain), as well as reducing the abundance of two potentially beneficial strains (one Ruminococcaceae strain and one Rumen bacteria). The Helicobacter strain was initally detected in carcinogen-treated rat intestinal microflora, but L. salivarius REN treatment effectively suppressed the growth of the Helicobacter strain. These results suggested that L. salivarius REN may be a potential probiotic, efficiently acting against the initial infection with, and the growth of pathogenic bacteria.