The three-dimensional (3D) millimeter-wave (MMW) image is a big data with redundant information that not only blurs the image but also increases the computational load on the denoising procedure. To address this problem, we propose an intensity-density associative clustering method which mainly consists of two phases. Specifically, an intensity-based clustering algorithm, e.g., K-Means, is firstly applied on the amplitude of the image data and initially achieves denoising and data compression. Then, a density-based spatial clustering algorithm, e.g., DBSCAN, is used to further extract object information. Due to the label transferring from the retained amplitude, only valid image data can forward spatial information to DBSCAN, and as a result, the computational load on DBSCAN decreases. Also, a multithreaded parallel computing framework is developed to exploit the distributed multicore processing for its implementation. Therefore, the proposed method can be well-adapted for 3D MMW image data in a computational efficient way. Simulations and experimental results confirm the effectiveness of our method that has good efficiency on big MMW image data with respect to the noise suppression and object information extraction.

.This paper presents a hybrid porous-core flexible photonic crystal fiber (PCF), which has the potential for low-loss guidance of broadband terahertz (THz) waves at low THz bands. Here, the cyclic olefin polymer TOPAS is used for the main material to increase the flexibility of PCF. The central hybrid porous-core area contains a circular and hexagonal design, which reduces the loss of PCF. Simulation results show that the proposed fiber has a very low confinement loss of 3.47  ×  10  −  6  dB  /  cm at 500 GHz operating frequency. The bending loss at a bending radius of 1 cm is as low as 3.2  ×  10  −  4  dB  /  cm. The negligible modal loss facilitates the flexible application to THz systems. Moreover, the fabrication of the proposed PCF design is compatible with widely used methods and technologies, including stacking and drawing, extrusion and drilling. This newly proposed hybrid design of the porous-core region can be considered as an improved version in the research of THz porous-core waveguides.