6 research outputs found
Cooperative Automotive Radars with Multi-Aperture Multiplexing MIMO Sparse Array Design
In this paper, a multi-aperture multiplexing multiple-input multiple-output (MAM-MIMO) sparse array is presented for cooperative automotive radars (CARs). The proposed sparse array composed of multiple subarrays can simultaneously cover a wide field-of-view (FOV) and achieve the required azimuth resolution at different ranges. To validate this idea, an optimization model for the MAM-MIMO sparse array is derived based on the example of CARs. This optimization model has been found by combining the peak-to-sidelobe ratio (PSLR) at all beams pointing within the constraints of different detection ranges. In addition, a hierarchical genetic algorithm based on the multi-objective decomposition method has been developed to obtain the optimized sparse array. The proposed method has been evaluated through both simulations and experiments. It is demonstrated that the optimized MAM-MIMO sparse array can effectively suppress sidelobes of its subarrays, yet with reasonably high azimuth resolutions and large FOVs
Pure Graphene Oxide Vertical pân Junction with Remarkable Rectification Effect
Graphene p-n junctions have important applications in the fields of optical interconnection and lowâpower integrated circuits. Most current research is based on the lateral p-n junction prepared by chemical doping and other methods. Here, we report a new type of pure graphene oxide (pGO) vertical p-n junctions which do not dope any other elements but only controls the oxygen content of GO. The IâV curve of the pGO vertical pân junction demonstrates a remarkable rectification effect. In addition, the pGO vertical pân junction shows stability of its rectification characteristic over long-term storage for six months when sealed and stored in a PE bag. Moreover, the pGO vertical pân junctions have obvious photoelectric response and various rectification effects with different thicknesses and an oxygen content of GO, humidity, and temperature. Hall effect test results show that rGO is an nâtype semiconductor; theoretical calculations and research show that GO is generally a pâtype semiconductor with a bandgap, thereby forming a pân junction. Our work provides a method for preparing undoped GO vertical pân junctions with advantages such as simplicity, convenience, and largeâscale industrial preparation. Our work demonstrates great potential for application in electronics and highly sensitive sensors
Pure Graphene Oxide Vertical pân Junction with Remarkable Rectification Effect
Graphene p-n junctions have important applications in the fields of optical interconnection and lowâpower integrated circuits. Most current research is based on the lateral p-n junction prepared by chemical doping and other methods. Here, we report a new type of pure graphene oxide (pGO) vertical p-n junctions which do not dope any other elements but only controls the oxygen content of GO. The IâV curve of the pGO vertical pân junction demonstrates a remarkable rectification effect. In addition, the pGO vertical pân junction shows stability of its rectification characteristic over long-term storage for six months when sealed and stored in a PE bag. Moreover, the pGO vertical pân junctions have obvious photoelectric response and various rectification effects with different thicknesses and an oxygen content of GO, humidity, and temperature. Hall effect test results show that rGO is an nâtype semiconductor; theoretical calculations and research show that GO is generally a pâtype semiconductor with a bandgap, thereby forming a pân junction. Our work provides a method for preparing undoped GO vertical pân junctions with advantages such as simplicity, convenience, and largeâscale industrial preparation. Our work demonstrates great potential for application in electronics and highly sensitive sensors
Sub-4 nm Nanodiamonds from Graphene-Oxide and Nitrated Polycyclic Aromatic Hydrocarbons at 423 K
Nanodiamonds are interesting materials from the point of view of their biocompatibility and their chemical, spectroscopic, and mechanical properties. Current synthetic methods for nanodiamonds involve harsh environments, which are potentially hazardous in addition to being expensive. We report a low-temperature (423 K) hydrothermal approach to form nanodiamonds by using graphene-oxide or nitrated polycyclic aromatic hydrocarbons (naphthalene, anthracene, phenanthrene, or pyrene) as a starting material. The reaction products contain single-crystalline or twinned nanodiamonds with average diameters in the 2???3 nm range. Theoretical calculations prove that, at the nanoscale, sub-4 nm nanodiamonds may adopt a structure that is more stable than graphene-oxide and nitrated polycyclic aromatic hydrocarbons. Our findings show that sp2 carbon in the polycyclic aromatic precursor can be converted to sp3 carbon under unexpectedly moderate temperature conditions by using nanoscale precursors and thus offer a low-temperature approach for the synthesis of sub-4 nm nanodiamonds