Persulfate-Based Advanced Oxidation Process for Chlorpyrifos Degradation: Mechanism, Kinetics, and Toxicity Assessment.

Persulfate-based advanced oxidation process has been proven to be a promising method for the toxic pesticide chlorpyrifos (CPY) degradation in wastewater treatment. However, due to the limitation for the short-lived intermediates detection, a comprehensive understanding for the degradation pathway remains unclear. To address this issue, density functional theory was used to analyze the degradation mechanism of CPY at the M06-2X/6-311++G(3df,3pd)//M06-2X/6-31+G(d,p) level, and computational toxicology methods were employed to explore the toxicity of CPY and its degradation products. Results show that hydroxyl radicals (·OH) and sulfate radicals (SO4•-) initiate the degradation reactions by adding to the P=S bond and abstracting the H atom on the ethyl group, rather than undergoing α-elimination of the pyridine ring in the persulfate oxidation process. Moreover, the addition products were attracted and degraded by breaking the P-O bond, while the abstraction products were degraded through dealkylation reactions. The transformation products, including 3,5,6-trichloro-2-pyridynol, O,O-diethyl phosphorothioate, chlorpyrifos oxon, and acetaldehyde, obtained through theoretical calculations have been detected in previous experimental studies. The reaction rate constants of CPY with ·OH and SO4•- were 6.32 × 108 and 9.14 × 108 M-1·s-1 at room temperature, respectively, which was consistent with the experimental values of 4.42 × 109 and 4.5 × 109 M-1 s-1. Toxicity evaluation results indicated that the acute and chronic toxicity to aquatic organisms gradually decreased during the degradation process. However, some products still possess toxic or highly toxic levels, which may pose risks to human health. These research findings contribute to understanding the transformation behavior and risk assessment of CPY in practical wastewater treatment.

Time-optimal trajectory planning based on event-trigger and conditional proportional control.

Trajectory planning is an important issue for manipulators and robots. To get a optimal trajectory, many constraints including actuators specifications, motion range of joints, workspace limitations, etc, and many objectives including the shortest time, the shortest distance, the lowest energy consumption, the minimum oscillations, obstacles-avoiding, etc, should be considered both. In this paper, firstly, the forward kinematics and inverse kinematics of a five axis manipulator are deduced. And, a simple method to choose one appropriate solution from multi solutions of inverse kinematics is proposed. Secondly, an easy-implemented optimization method of trajectory planning is proposed based on seventh order polynomial interpolation, event-trigger mechanism and conditional proportional control (P control). The proposed optimization method can capture the time optimal trajectory, and the actuators specifications including velocity, acceleration of motor can be guaranteed as well. Thirdly, comparative simulations and experiments validate the effectiveness and efficiency of proposed optimization method. The research provides an insight for the application of trajectory optimization on the micro controller with low computing capability and high real-time performance requirement.

Design and simulation analysis of a bionic ostrich robot.

To look for the reason why the biped animal in nature can run with such high speed and to design a bionic biped prototype which can behave the high speed running and jumping ability, this paper takes the fastest bipedal animal in nature: ostrich as the research subject. Firstly, the body structure and motion characteristics of ostrich are investigated. Secondly, a simple mechanical structure of bionic ostrich robot is designed based on the above biological investigated results. The robot is under-actuated with one actuator each leg, with a spring on the tarsometatarsus and a torsion spring on the metatarsophalangeal joint at the foot end. And then the mechanical design of leg structure is optimized. Finally, the high-speed running and jumping running gait is planned, and comparative simulations are implemented with different design requirements among pure rigid and rigid-flexible coupling scheme, which are rigid, only with spring, only with torsion spring, and with spring and torsion spring both, in detail. Simulation results show that the rigid-flexible coupling design scheme and whole body motion coordination can achieve better high speed performance. It provides an insight for the design and control of legged robots.

Research on Position and Torque Loading System with Velocity-Sensitive and Adaptive Robust Control.

In this paper, the research emphasis focuses on the tracking precision of position loading and torque loading systems with velocity-sensitive and adaptive robust control. Compared with conventional PID control, the improved PID control based on velocity-sensitive fully manifests its superiority to position loading. By contrast, we analyzed the possible influence for the control difference of conventional PID and velocity-sensitive with PID. Furthermore, for the purpose of accurate torque loading, a mathematical model was established through dynamics analysis and the adaptive robust controller, where the adaptive robust control algorithm is designed to generate the reference position trajectory for the servo system in the upper controller while closed-loop position tracking is performed in the underlying controller, was built based on a state space equation. In the end, an experimental platform was built to verify the feasibility and advantages of the position and torque loading system with the velocity-sensitive and adaptive robust control.

Stability-Guaranteed and High Terrain Adaptability Static Gait for Quadruped Robots.

Stability is a prerequisite for legged robots to execute tasks and traverse rough terrains. To guarantee the stability of quadruped locomotion and improve the terrain adaptability of quadruped robots, a stability-guaranteed and high terrain adaptability static gait for quadruped robots is addressed. Firstly, three chosen stability-guaranteed static gaits: intermittent gait 1&2 and coordinated gait are investigated. In addition, then the static gait: intermittent gait 1, which is with the biggest stability margin, is chosen to do a further research about quadruped robots walking on rough terrains. Secondly, a position/force based impedance control is employed to achieve a compliant behavior of quadruped robots on rough terrains. Thirdly, an exploratory gait planning method on uneven terrains with touch sensing and an attitude-position adjustment strategy with terrain estimation are proposed to improve the terrain adaptability of quadruped robots. Finally, the proposed methods are validated by simulations.

Microscopic evaluation of traffic safety at signal coordinated intersections: A before-after study.

OBJECTIVE: This research aims to evaluate the safety impacts of signal coordination on signalized intersections and provide a scientific basis to design and improve signal control and management from a traffic safety perspective. METHODS: A kernel regression model is adopted to evaluate the safety performance of intersections before and after implementing the signal coordination strategy. By using this statistical method, the authors identify the nonlinear relationship between crash frequency and the crash's spatial location and examine the discrepancy of crash spatial distributions between the coordination and noncoordination conditions at disaggregated levels, such as time of day and crash type. A case study is presented with the use of Michigan crash data (2003-2007). RESULTS: The study finds that the (1) crash distribution on arterials tends to be spatially disperse when the signal coordination is in operation and (2) crash frequency at the approaches of intersections is increased with the use of signal coordination under the following conditions: Nonpeak hours, rear-end and sideswipe crashes, intersections with low speed limits, and both injury and property damage-only crashes. CONCLUSION: Signal coordination poses safety concerns in addition to its operational benefits for intersections.

Compliance control for a hydraulic bouncing system.

This paper is to reduce the contact impact, control the leg stiffness and bouncing height. Firstly, the combining position/force active compliance control was involved in the deceleration phase to decrease the impact force and improve the leg compliance capacity. Then a reasonable velocity control of cylinder was addressed to control the bouncing height to the given value in the acceleration phase. Due to the model uncertainties and disturbances in the deceleration and acceleration phase, a near inverse like controller with a proportional and differential control (PD) was added into the velocity control of acceleration phase to compensate the bouncing height control error. Finally, the effectiveness of proposed controller was validated by experiments. Experimental results showed the impact force could be reduced effectively and a significant bouncing height control performance could be achieved. The influences of initial energy, preload of spring and velocity of cylinder on the bouncing height were addressed as well.

[Effects of potato/soybean intercropping on photosynthetic characteristics and yield of three soybean varieties].

The potato/soybean intercropping trials using three soybean varieties including Zhonghuang 30 (early-maturing variety) , Jidou 17 (mid maturing variety) and Qihuang 34 (late maturing variety) with the sole cropping potato as control were carried out to determine the dynamic changes of leaf area index (LAI) of soybean, accumulation of dry matter, photosynthetic characteristics, yield and yield components. The results showed that the LAI, dry matter accumulation, net photosynthesis (Pn), transpiration rate (Tr) and stomatal conduction (g(s)) of soybean in all intercropping systems were lower than in monoculture because of the influence of intensified lower light during earlier growing stage, and the duration from planting to flowering was extended. When the potato was harvested, the LAI, dry matter accumulation, Pn, Tr and g(s) of soybean in all intercropping systems increased, especially for mid-maturing and late-maturing varieties, which became much closer to those in the monoculture. Compared with sole cropping, the pods per plant, seeds per plant and seeds per pod in intercropping system significantly decreased by 22.0%, 36.0% and 17.6% for early-maturing soybean, 5.1%, 13.1% and 8.9% for mid-maturing soybean, 5.7%, 7.6% and 2.1% for late-maturing soybean, respectively. The yields of mid-maturing and late-maturing varieties in intercropping systems were higher than that of the early-maturing, which increased by 92.4% and 163.4%, with the land equivalent ratio (LER) of 1.81 and 1.84, respectively. This suggested that mid-maturing and late-maturing soybean varieties were suitable for intercropping with the potato to improve photosynthetic efficiency, dry matter accumulation and yield of intercropping soybean.