THE INDONESIA-MALAYSIA-SINGAPORE GROWTH TRIANGLE (IMS-GT) AND ITS IMPACT ON THE FERRY TRANSPORTATION IN THE RIAU ISLANDS.

Master'sMASTER OF ART

Usefulness of Simple Diffusion Kurtosis Imaging for Head and Neck Tumors: An Early Clinical Study

Diffusion kurtosis (DK) imaging (DKI), a type of restricted diffusion-weighted imaging, has been reported to be useful for tumor diagnoses in clinical studies. We developed a software program to simultaneously create DK images with apparent diffusion coefficient (ADC) maps and conducted an initial clinical study. Multi-shot echo-planar diffusion-weighted images were obtained at b-values of 0, 400, and 800 sec/mm2 for simple DKI, and DK images were created simultaneously with the ADC map. The usefulness of the DK image and ADC map was evaluated using a pixel analysis of all pixels and a median analysis of the pixels of each case. Tumor and normal tissues differed significantly in both pixel and median analyses. In the pixel analysis, the area under the curve was 0.64 for the mean kurtosis (MK) value and 0.77 for the ADC value. In the median analysis, the MK value was 0.74, and the ADC value was 0.75. The MK and ADC values correlated moderately in the pixel analysis and strongly in the median analysis. Our simple DKI system created DK images simultaneously with ADC maps, and the obtained MK and ADC values were useful for differentiating head and neck tumors from normal tissue

Best Feed Positions and Radiation Patterns of Typical Multibeam Dielectric Lens Antenna

Multibeam base station antennas are introduced for 5G and 6G mobile communication systems. Considering higher frequency bands such as millimeter waves for 5G and terahertz for 6G, dielectric lens antennas become promising candidates due to their simple antenna configuration and excellent multibeam radiation characteristics. Therefore, it is important to identify the best multibeam antenna from the existing typical lens antennas. In this article, a shaped lens and some conventional lenses are considered. For the conventional types, the hyperbolic-planar, plano-convex, and spherical-convex are selected. As for the shaped lens, Abbe’s sine condition lens is selected. This research begins by finding the best feed position of four types of lenses. A MATLAB program is developed to find the smallest distance point for all focal region rays. Based on this point, the feed position is selected and multibeam radiation patterns of four lenses are obtained. It is shown that the spherical-convex lens can achieve the highest gain and the smallest beam shape degradation. High gain characteristics are obtained until a 35° beam shift. As for sidelobe characteristics, Abbe’s sine condition lens has the lowest sidelobe level. These properties are then clarified using amplitude and phase distribution on the aperture plane. Furthermore, focal region ray concentration changes by $F/D$ and refractive index are discussed for practical applications

Measured performance of high gain dielectric lens antenna in 300 GHz band

A dielectric lens antenna was designed at 270 GHz to achieve high gain performance. A plano-convex lens was designed using the geometrical optics theory. For primary radiators, a pyramidal horn antenna was proposed which can easily control the beamwidth to illuminate the lens with uniformity. The measured gain was 25.7 dBi at 270 GHz, and the measured half-power beamwidth (HPBW) was 7.4 degree