Autonomous Exploration Method of Unmanned Ground Vehicles Based on an Incremental B-Spline Probability Roadmap.

Autonomous exploration in unknown environments is a fundamental problem for the practical application of unmanned ground vehicles (UGVs). However, existing exploration methods face difficulties when directly applied to UGVs due to limited sensory coverage, conservative exploration strategies, inappropriate decision frequencies, and the non-holonomic constraints of wheeled vehicles. In this paper, we present IB-PRM, a hierarchical planning method that combines Incremental B-splines with a probabilistic roadmap, which can support rapid exploration by a UGV in complex unknown environments. We define a new frontier structure that includes both information-gain guidance and a B-spline curve segment with different arrival orientations to satisfy the non-holonomic constraint characteristics of UGVs. We construct and maintain local and global graphs to generate and store filtered frontiers. By jointly solving the Traveling Salesman Problem (TSP) using these frontiers, we obtain the optimal global path traversing feasible frontiers. Finally, we optimize the global path based on the Time Elastic Band (TEB) algorithm to obtain a smooth, continuous, and feasible local trajectory. We conducted comparative experiments with existing advanced exploration methods in simulation environments of different scenarios, and the experimental results demonstrate that our method can effectively improve the efficiency of UGV exploration.

Gaze Point Tracking Based on a Robotic Body-Head-Eye Coordination Method.

When the magnitude of a gaze is too large, human beings change the orientation of their head or body to assist their eyes in tracking targets because saccade alone is insufficient to keep a target at the center region of the retina. To make a robot gaze at targets rapidly and stably (as a human does), it is necessary to design a body-head-eye coordinated motion control strategy. A robot system equipped with eyes and a head is designed in this paper. Gaze point tracking problems are divided into two sub-problems: in situ gaze point tracking and approaching gaze point tracking. In the in situ gaze tracking state, the desired positions of the eye, head and body are calculated on the basis of minimizing resource consumption and maximizing stability. In the approaching gaze point tracking state, the robot is expected to approach the object at a zero angle. In the process of tracking, the three-dimensional (3D) coordinates of the object are obtained by the bionic eye and then converted to the head coordinate system and the mobile robot coordinate system. The desired positions of the head, eyes and body are obtained according to the object's 3D coordinates. Then, using sophisticated motor control methods, the head, eyes and body are controlled to the desired position. This method avoids the complex process of adjusting control parameters and does not require the design of complex control algorithms. Based on this strategy, in situ gaze point tracking and approaching gaze point tracking experiments are performed by the robot. The experimental results show that body-head-eye coordination gaze point tracking based on the 3D coordinates of an object is feasible. This paper provides a new method that differs from the traditional two-dimensional image-based method for robotic body-head-eye gaze point tracking.

Novel tetrahydrofuran derivatives from Trigonostemon howii with their potential anti-HIV-1 activities.

A novel tetrahydrofuran derivative, trigonohowine (1), together with five known tetrahydrofuran derivatives (2-6), were isolated from the stems and leaves of Trigonostemon howii. The structure of 1 was elucidated by extensive spectroscopic methods and the known compounds were identified by comparisons with the data reported in literature. Among them, trigonohowine (1) represents the first example of a new type of tetrahydrofuran derivative, possessing an unprecedented carbon skeleton containing 23 carbon atoms on the carbon skeleton and the known compouds (2-6) are rare tetrahydrofuran derivatives in the plant kingdom with various carbon skeletons. All isolated compounds were evaluated for their anti-HIV-1 activities. Compounds 1-6 showed significant anti-HIV-1 activities with EC50 ranged from 0.08 to 1.03 µM. These findings suggest that the discoveries of these tetrahydrofuran derivatives with significant anti-HIV-1 activities isolated from T. howii could be of great importance to the development of new anti-HIV agents.

Cytotoxic dihydrobenzofuran neolignans from Mappianthus iodoies.

Three new dihydrobenzofuran neolignans, mappiodoinins A-C (1-3), together with nine known analogues (4 -12) were isolated from the stems and leaves of Mappianthus iodoies. Their structures with the absolute configurations were elucidated by extensive spectroscopic methods. This is the first time to find dihydrobenzofuran neolignans from the genus Mappianthus. All isolated compounds were evaluated for their cytotoxicities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW-480 in vitro. Neolignans 1-12 showed significant cytotoxic effects against various human cancer cell lines with IC50 values ranging from 0.16 to 18.62 µM.

Development of a 3-DOF Angle Sensor Based on a Single Laser Interference Probe.

The development of high-precision satellites has increased the demand for ultraprecision three-degrees-of-freedom (3-DOF) angle measurements for detecting structural deformation. The required instrument should simultaneously measure pitch, yaw, and roll angles using a single reference point. This paper proposes a 3-DOF angle measurement method based on the wavefront interference principle, and a mathematical model and its decoupling algorithm were built. Then, an angle-sensing probe with an extremely simple structure was designed and constructed. Finally, a series of experiments were performed to verify the method's feasibility. The experiment results showed that the roll, pitch, and yaw measurement resolution of the probe was better than 10, 1, and 1 µrad, respectively, providing a high-performance 3-DOF angle measurement with a single probe. The short-term stabilities of roll, pitch, and yaw were better than 22, 1.7, and 2.0 µrad, respectively.

A new abietane diterpenoid from the roots of Tripterygium regelii.

A new abietane diterpenoid, tripterregeline A (1), together with six known diterpenoids (2-7), were isolated from the roots of Tripterygium regelii. The structure of 1 was elucidated by extensive spectroscopic methods and the known compounds were identified by comparison with data reported in the literature. All isolated compounds were evaluated for their cytotoxicities against five human cancer cell lines: HL-60, SMMC-7721, A-549, MCF-7 and SW480 in vitro. Compounds 1-7 showed significant inhibitory effects against various human cancer cell lines with IC50 values ranging from 0.58 to 21.06 µM.