AlGaN thin films can be used in a variety of electronic applications because have a wide energy band-gap and it's tuneable in range (3.11 eV-6.4 eV). However, the deposition of AlGaN facing difficulties depositing at room temperature and required longer time deposition to achieved high quality of AlGaN thin films. Due to that, there not many attempts on discovering AlGaN thin film deposition using the sputtering technique. In this work, the co-sputtering process was used to deposit AlGaN thin films, and the impacts of nitrogen gas flow rate on the structural and morphological characteristics of AlGaN thin films were examined. AlGaN films were sputtered simultaneously on silicon (111) substrate at minimum time deposition and room temperature using GaN and Al target. The fabricated AlGaN thin films were characterized using X-ray diffraction (XRD), atomic force microscopy (AFM), and surface profilometer. The AlGaN crystal structures do not exist in the XRD result. The roughness of the AlGaN films with 50 sccm nitrogen flow was 1.19 nm, 1.41 nm for 25 sccm, and 4.91 nm for AlGaN with no nitrogen gas flow. Meanwhile, grain size readings have varied with different nitrogen gas fluxes. The profilometer shows that the thickness of AlGaN films was decreasing with the increase of nitrogen gas flow. The Co-sputtering technique may be considered a great approach to improving the deposition of AlGaN thin films at minimizing time and temperature.

Aluminium nitride (AlN) thin film is a very attractive material to be used in electronic devices, and the most popular AlN orientations that have been reported are AlN (100) and AlN (002) planes. To the best of our knowledge, still less comparison study between AlN (100) with AlN (002) orientation based on a structural relationship with the electrical properties. For that purpose, the c-axis (002) and a-axis (100) of AlN thin films are deposited by using conventional RF magnetron sputtering. Energy-dispersive spectroscopy (EDS) analysis shows that AlN (100) has a higher percentage of oxygen content than AlN (002). X-ray diffraction (XRD) reveals that (002)-oriented AlN has better crystallinity than (100)-oriented AlN. Besides, from atomic force microscope (AFM) analysis, (100)-oriented AlN shows a smaller grain size (35.97 nm) than that of (002)-oriented AlN (58.47 nm). By impedance analyser, (100)-oriented AlN thin film shows higher electrical conductivity by one order magnitude higher than (002)-oriented AlN thin film due to high dielectric permittivity, high dielectric loss, fast dielectric relaxation, and lower capacitance. Hence, this study has shown a clear comparison between AlN (100) and AlN (002) based on structural and electrical properties relationship.

A cylindrical micro-perforated panel (MPP) can be used to absorb the sound of a flow system in a circular duct of a vacuum cleaner. A cascaded cylindrical MPP is a special class type where two cylindrical MPPs are arranged in a series to improve sound attenuation. The manufacturing of MPP primarily involves the machining of micro-perforations, because small holes are not readily made using injection moulding due to the complexity of the die, flow control of the molten polymer through the small orifices and dimensional stability, making it unsuitable for mass production. This limitation can be overcome with the use of additive manufacturing (AM) technology, where the micro-perforations can be designed and manufactured, with relatively larger tolerances. Experimental validation ensures that the manufactured prototype in this study is performed according to design. Results show that the transmission loss of the model and the experimental outcomes agree. The cascaded arrangement of the cylindrical MPP results in a wider effective frequency range and an increased transmission loss. Parametric studies of the combined effects of the perforation diameter, perforation ratio and the depth of air cavity on the diameter of the duct and length ratio are conducted using a transfer matrix method. A case study is demonstrated here in the design. Moreover, an AM of cascaded cylindrical MPP is performed to attenuate peak noise at 1650 Hz, where the optimum parameters of the cascaded cylindrical MPP are obtained using a genetic algorithm. The manufactured cascaded cylindrical MPP is installed on a vacuum cleaner duct, and the measurement of sound power level shows a reduction of 4 dB(A).

This study presents a development of simple expansion tube attach with micro-perforated cylindrical panel (MPCP) to improve the acoustic performance. A simulation based boundary element method (BEM) was carried out using PLM Simcenter 3D. The model was constructed in three dimensional in CAD NX Nastran 12 application and then meshing into small elements. The acoustic properties and boundary condition were defined for the simulation purpose. The model was then fabricated by 3D printer material and verified with the transmission loss measurement utilized the two-load method. In comparison, the transmission loss of simple expansion tube with and without MPCP show a good agreement of BEM analysis and experimental result. The addition of the MPCP inside the expansion tube improved the transmission loss by 2-10 dB in wider frequency band compared to the simple expansion tube. Finally, the air cavity depth of the expansion tube is varied to study it effect. Its showed that, the larger air cavity depth caused the transmission loss peak shift to a lower frequency range.

In this paper, the sound absorption coefficient for micro-perforated panel (MPP) is conducted to determine the acoustic properties of MPP. Two different kind of MPP with the same parameter is used. One is Nylon material and another one is Brass material. Both are fabricated by using 3D Printing technology and Laser Cut process respectively. The sound absorption coefficient of both 3D Printed Nylon MPP and Laser Cut Brass MPP is measured with two-microphone method by using Impedance Tube. The calculated sound absorption coefficient is done by using MATLAB software based on the Classic Maa model. The measured sound absorption coefficient is compared with the calculated result for both MPP. The comparison results show some deviation, like measured results produce a big dip, absorption peak frequency shifted towards higher frequency and wider absorption bandwidth observed when compared to the calculated result. In conclusion, it is found out hole imperfection effect is one of the reasons to the deviation produce between the compared result.

This paper describes boundary element method (BEM), experimental and optimization studies conducted to understand the potential of expansion tube coupled micro-perforated cylindrical panel (MPCP) to enhance the acoustic attenuation for in-duct noise control issues. Due to complex structure of the MPCP and for the correct prediction of acoustic attenuation, BEM is adopted on the basis of PLM Simcenter 3D software to compute the sound transmission loss (TL). As the MPCP is cylindrical in-shape with numbers of sub-milimeter holes, additive manufacturing based 3D printing was utilized for the model prototyping to reduce current design limitation and enabled fast fabrication. The TL measurement based two-load method is adopted for modal validation. Subsequently, a parametric studies of the MPCP concerning the perforation hole diameter, perforation ratio and depth of air space are carried out to investigate the acoustical performance. Optimization via response surface method (RSM) is used as it allows evaluating the effects of multiple parameters as required in this study. The model validation result shows that the error between the BEM and and measured values is relatively small and show a good agreement. The R-square value is 0.89. The finding from parametric study shows that a widen peak attenuation can be achieve by reducing the perforation hole diameter and one way to increase the transmission loss amplitude is by increasing the air cavity depth. Finally, the optimized MPCP model was adopted to the commercial vacuum cleaner for the verification. The sound pressure level (SPL) of the vacuum cleaner is significantly attenuated within the objective frequency of 1.7 kHz and its A-weighted SPL is reduced by 1.8 dB.

This paper reviews a various methods exploring the topic of unmanned aerial vehicles (UAV) autonomous precision landing, covering two types of commercial UAVs, multi-rotor and fixed-wing UAVs. Four general methods gain the most eminence for the autonomous precision landing, which generally known as visual processing landing, satellite navigations landing, ground station navigation landing, and arrestor recovery landing. The assessment of the landing accuracies of each method are assessed and compared, if the results are being made available in the reviewed research articles. We also discussed the recent breakthroughs in sensors, processor, and flight technologies that can further improve the accuracy of UAV autonomous precision landing.

This paper presented the theory, planning, control and method for Unmanned Aerial Vehicles performing precision landings on a moving platform. Unmanned Aerial Vehicles performing flight mission often having issues of its retrieving due to the landing sequence inaccuracy which may lead to crash. Thus, in this paper, by using adaptive method and image processing, the H480 hexacopter, equipped with a gimbaled camera detecting the moving platform attached to a ground rover using a pattern recognition algorithm. Using AprilTag as the unique pattern, the H480 follows the moving platform and moves via pitch and roll instructions while constantly descending towards the ground. In this paper, the system proposed the degree of pitch and roll changes with regards to the position of the AprilTag i.e., the further the tag location detected from the camera center, the higher the degree of movement, such that the tag will be forced to be in the center of the camera frame. The system divides a camera frame into an 11x11 matrix in which each cell within the matrix suggests different pitch and roll degrees for the H480 movement. As a result, the system manages to assist the landing process for the H480 to reach the moving platform successfully with less than 0.5m offset from the center of the target.