Study on Environment Perception and Automatic Navigation Technology for the Automatic Parking System

The traffic accidents, traffic jams and parking problems come to appear, and have caused more and more concerns of people. The automatic parking system can help us a lot to solve these problems. The automatic parking system in this paper includes two sections, environment perception and automatic controller. The median filter and least square method are used to process the laser sensor data. Then, feasible parking space can be displayed by using K-means clustering method. The Matlab fuzzy GUI is used to establish the fuzzy controller. The kinematics equation of car is utilized to simulate the automatic vertical parking in the Matlab/simulation with the different initial path angles. Experiment results show that the environmental perception method has perfect performance and the controlling algorithm of the automatic parking system has good feasibility.

Dielectric response of ANb_(2)O_(6)(A = Zn, Co, Mn, Ni) columbite niobates: From microwave to terahertz

In the upcoming 6-generation(6G)revolution,the achievement of low power consumption has become a key objective in research concerning terahertz devices.As an important component of passive devices,there are very few low-loss dielectric ceramics in the terahertz range.To elucidate the mechanism of loss and promote the application of microwave dielectric ceramics for future 6G technology(covering microwave and terahertz frequencies),the terahertz responses of ANb_(2)O_(6)(A=Zn,Co,Mn,and Ni)columbite niobates were studied.The influences of magnetic loss on the Qxf values in the microwave range with different transition metal ions in the A-site were reasonably analyzed.Moreover,due to the weakened magnetic relaxation properties in the terahertz range,the samples all exhibited low loss and approximate transparency,especially for MnNb_(2)O_(6) and NiNb_(2)O_(6)(tano<0.01 and absorption coefficient<10 cm^(-1) below 1.2 THz),which subverted the definition of traditional low-loss microwave dielectric ceramics.Ultimately,based on Mie theory,we designed a prototypical broadband metamaterial reflector to validate the applicability of the ANb_(2)O_(6) system in the terahertz band,which is highly important for the development of terahertz ceramic-based passive devices.

Circular dichroism-like response of terahertz wave caused by phase manipulation via all-silicon metasurface

Chiral metasurfaces based on asymmetric meta-atoms have achieved artificial circular dichroism(CD),spin-dependent wavefront control,near-field imaging,and other spin-related electromagnetic control.In this paper,we propose and experimentally verify a scheme for achieving high-efficiency chiral response similar to CD of terahertz(THz)wave via phase manipulation.By introducing the geometric phase and dynamic phase in an all-silicon metasurface,the spin-decoupled terahertz transmission is obtained.The giant circular dichroism-like effect in the transmission spectrum is observed by using a random phase distribution for one of the circular polarization components.More importantly,the effect can be adjusted when we change the area of the metasurface illuminated by an incident terahertz beam.In addition,we also demonstrate the spin-dependent arbitrary wavefront control of the transmitted terahertz wave,in which one of the circularly polarized components is scattered,while the other forms a focused vortex beam.Simulated and experimental results show that this method provides a new idea for spin selective control of THz waves.

Trade-off evaluation using carbon dioxide equivalent and hazard index of a paddy soil with application of organic liquid fertilizer

Dear Editor,Rice is an important staple food crop in Asia,but the anaerobic soil conditions in rice fields cause emission of the potent greenhouse gas,methane(CH)(Le Mer and Roger,2001),and promote the accumulation of arsenic(As)in the grain(Le Mer and Roger,2001;Khanam et al.,2020).To facilitate sustainable agriculture,using wastewater as an organic fertilizer is essential for reducing wastewater treatment-associated energy consumption and the recycling of wastewater nutrients(Zou et al.,2009).

Optical rectification in 4H-SiC:paving the way to generate strong terahertz fields with ultra-wide bandwidth

The 4H-SiC crystal is found to have great potential in terahertz generation via nonlinear optical frequency conversion due to its extremely high optical damage threshold,wide transparent range,etc.In this paper,optical rectification(OR)with tilted-pulse-front(TPF)setting based on the 4H-SiC crystal is proposed.The theory accounts for the optimization of incident pulse pre-chirping in the TPF OR process under high-intensity femtosecond laser pumping.Compared with the currently recognized LiNbO3-based TPF OR,which generates a single-cycle terahertz pulse within 3 THz,4HSiC demonstrates a significant advantage in producing ultra-widely tunable(up to over 14 THz,TPF angle 31◦–38◦)terahertz waves with high efficiency(~10–2)and strong field(~MV/cm).Besides,the spectrum characteristics,as well as the evolution from single-to multi-cycle terahertz pulses can be modulated flexibly by pre-chirping.The simulation results show that 4H-SiC enables terahertz frequency extending to an unprecedent range by OR,which has extremely important potential in strong-field terahertz applications.

Molecular diversity of arbuscular mycorrhizal fungi at a large-scale antimony mining area in southern China

Arbuscular mycorrhizal fungi （AMF） have great potential for assisting heavy metal hyperaccumulators in the remediation of contaminated soils. However, little information is available about the community composition of AMF under natural conditions in soils contaminated by antimony （Sb）. The objective of this study was to investigate the characteristics of AMF molecular diversity, and to explore the effects of Sb content and soil properties on the AMF community structure in an Sb mining area. Four Sb mine spoils and one adjacent reference area were selected from around the Xikuangshan mine in southern China. The association of AMF molecular diversity and community composition with the rhizosphere soils of the dominant plant species was studied by Polymerase Chain Reaction-Denaturing Gradient Gel Electrophoresis （PCR-DGGE）. Results from all five studied sites showed that the diversity of AMF decreased with increasing Sb concentration. Principal component analysis （PC_A） indicated that the AMF community structure was markedly different among these groups. Further redundancy analysis （RDA） showed that Sb contamination was the dominating factor influencing the AMF community structure in the Sb mine area. However, the multivariate analysis showed that, apart from the soil Sb content, extractable nitrogen content and organic matter content also attributed to AMF sequence distribution type. Some AMF sequences were only found in the highly contaminated area and these might be ideal candidates for improving phytoremediation efficiency in Sb mining regions. Gene sequencing analysis revealed that most species were affiliated with Gloraus, suggesting that Glomus was the dominant AMF genus in the studied Sb mining area.

Microfluidic integrated metamaterials for active terahertz photonics

A depletion layer played by aqueous organic liquids flowing in a platform of microfluidic integrated metamaterials is experimentally used to actively modulate terahertz(THz)waves.The polar configuration of water molecules in a depletion layer gives rise to a damping of THz waves.The parallel coupling of the damping effect induced by a depletion layer with the resonant response by metamaterials leads to an excellent modulation depth approaching 90%in intensity and a great difference over 210°in phase shift.Also,a tunability of slow-light effect is displayed.Joint time-frequency analysis performed by the continuous wavelet transforms reveals the consumed energy with varying water content,indicating a smaller moment of inertia related to a shortened relaxation time of the depletion layer.This work,as part of THz aqueous photonics,diametrically highlights the availability of water in THz devices,paving an alternative way of studying THz wave–liquid interactions and developing active THz photonics.