A New Wideband Circularly Polarized Dielectric Resonator Antenna

A wideband and compact circularly polarized (CP) C-shaped dielectric resonator antenna (DRA) is presented. The proposed C-shaped DR is excited by a simple stripe line connected to a coplanar waveguide (CPW) feeding line. The C-shaped DRA is circularly polarized with 19% axial ratio (AR) bandwidth. It is found that the CP bandwidth can be expanded by using a narrow short circuit strip. The final design achieves CP with 50% AR bandwidth. The proposed circularly polarized DRA (CPDRA) with good radiation characteristics offers an impedance bandwidth of 58% between 3.45 and 6.26 GHz for VSWR ≤ 2. The proposed DRA is fabricated and tested. Very good agreement between simulated and measured results is obtained

Characterization of LUSI Mud as Geopolymer Raw Material

The mud of mud volcano samples were collected from an eruption site named ‘LUSI’ (Lumpur “mud” –Sidoarjo), East Java, Indonesia for characterization. Analysis showed that, the major constituents of mud are SiO2 and Al2O3 which are higher than those in fly ash. The particle of mud has a flake-shaped particle and the overall particle size is dominated by particles between 2.5μm – 25.0μm. The results of XRD shows that mud of mud volcano have a characteristic of structurally disordered compounds, and a set of peaks corresponding to minor crystalline phases such as quartz, feldspars, and kaolinite. FTIR adsorption bands of the raw material of mud have the chemical bonding between bands 1-5

Kesan penggunaan koswer multimedia animasi visual terhadap pencapaian pelajar dalam mata pelajaran matematik

Ramai pelajar yang bermasalah dalam topik Pelan dan Dongakan. Ini kerana pelajar sukar untuk membayangkan objek yang tersembunyi melalui proses pengajaran dan pembelajaran (P&P) secara konvensional. Penyelidik telah membangunkan satu koswer multimedia animasi visual dalam topik Pelan dan Dongakan dengan menerapkan kesemua elemen-elemen yang dapat membantu meningkatkan kemahiran visual iaitu elemen animasi, video, audio, grafik dan teks. Seterusnya, kajian kuasi eksperimental ini turut dijalankan bertujuan untuk mengetahui kesan penggunaan koswer multimedia animasi visual terhadap pencapaian pelajar bagi mata pelajaran Matematik di sekolah menengah. Ujian Pra dan Ujian Pos digunakan untuk melihat perbezaan pencapaian yang signifikan selepas menggunakan koswer multimedia animasi visual yang menggunakan teori Kognitif Visual Wiley. Responden yang terlibat dalam kajian ini ialah seramai 40 orang pelajar Tingkatan Lima yang dibahagikan kepada dua kumpulan iaitu kumpulan rawatan dan kumpulan kawalan yang dipilih daripada sebuah sekolah di daerah Batu Pahat, Johor. Hasil analisis menunjukkan peningkatan skor min markah bagi pelajar kumpulan rawatan. Hasil analisis ujian-t (paired-sample-t-test) membuktikan bahawa wujudnya perbezaan skor min markah yang signifikan di antara markah ujian pra dan markah ujian pos bagi kumpulan rawatan. Oleh itu, terdapat perbezaan yang signifikan di antara skor min markah ujian pra dan ujian pos bagi pelajar kumpulan rawatan selepas menggunakan koswer multimedia animasi visual. Manakala instrumen soal selidik yang digunakan untuk melihat tahap penerimaan pelajar selepas menggunakan koswer multimedia animasi visual berdasarkan tiga aspek iaitu aspek isi kandungan, aspek interaksi dan aspek persembahan telah memeperolehi skor min yang tinggi bagi ketiga-tiga aspek tersebut. Dapatan kajian ini menggambarkan penggunaan koswer multimedia animasi visual dapat membantu meningkatkan pencapaian Matematik di dalam bilik darjah terutama yang tidak melibatkan pengiraan

Analysis of Pressure Effects for Current Density and Electric Field Performance of Gas Insulations

Gas insulation had been used widely in high voltage industry as a dielectric component. According to the arrangement of gas particles that far apart from each other, lead to the movement of gas particles react fast with high temperature and pressure. Hence when breakdown occurred in a system, it will quickly protect the system by diminished the sparks to avoid flashover occurred. The intention of this research is to determine relationship between current density and electric field of gas insulations that have been used in the insulator. HV experimental test has been conducted, to obtain breakdown voltage of air to use as applied voltage in the simulation for breakdown purpose of three insulation gasses, which are Sulphur Hexafluoride (SF6), Octafluoropropane (C3F8), and Nitrogen (N2). Physical properties such as thermal conductivity, electrical conductivity, and temperature of each gasses are require to identify value of current density and electric field of each insulation gasses. Furthermore, two pressure spots were placed symmetrically between two electrodes in the insulator. Based on simulation’s results, C3F8 is the best gas insulation because in normal condition and when presence of pressures it had lowest current density compared to SF6 and N2. Thus, C3F8 had the highest value of electric field among the insulation gasses. Electrical insulator is an internal electrical charger that cannot move freely and its contrast with semiconductors and conductors that can conduct electrical current easily. When the insulating material was used to avoid electrical discharges, it’s called insulation. High voltage insulation has been used widely in industry at electrical equipment such as switchgear and circuit breaker. The importance of applied high voltage in the electrical equipment is to prevent it from damage when faulty or breakdown occurs. From the results that have been obtained, the best gas insulation can be applied in the insulator as a protective component in electrical industry

Low sidelobe and wideband characteristics of density tapered arrays for 5G mobile systems

Conventional mobile base station antennas are composed of equally spaced linear array antennas. In order to achieve low side lobe characteristics, excitation coefficients for array elements are determined by a feeding network. Because of complexity of the feeding network, applicable frequency range is limited. In 5G mobile system, multi frequency band operation is requested. For achieving low sidelobe and wide frequency characteristics, a density tapered array configuration is promising. Because of uniform excitation coefficients, feed network has no frequency dependence and wide frequency range application is expected. In this paper, abilities and design method of low sidelobe characteristics are investigated. By density tapering, sidelobe levels are reduced from-13dB to -16dB. As for wide band characteristics, low sidelobe characteristics are maintained during 28GHz to 56GHz operations. Usefulness of a density tapered array is numerically clarified

A novel green antenna phase-shift system with data acquisition boards

A novel green phase shifter system is proposed in this research. The system is developed by a combination of reconfigurable beam steering antennas and data acquisition (DAQ) boards. A combination of two reconfigurable beam steering antennas, located side-by-side, forms a spatial configuration structure with a fabricated ‘green’ element plank of rice husk placed in between. The concept of a spatial configuration technique has been ‘mutated’ by shifting the structure of spiral feed line and aperture slots of first beam steering antenna by as much as 45 ◦ . The PIN diode switches connected to the DAQ boards enable the intelligent capability of the spatial antennas. The activation of certain degree radiation patterns of either the first beam steering antenna or the second beam steering antenna depends on the memory of the DAQ boards — Beam Manager. When an intruder comes from the cardinal angles of 0◦/ 360◦, 90◦, 180◦, or 270◦, its range and angles’ location will be automatically detected by the first antenna through the output ports of the 1st DAQ: P1.0, P1.1, P1.2, and P1.3. The second antenna is then activated by the output ports of the 2nd DAQ: P2.0 up to P2.3, to adaptively maneuver the beam towards four different ordinal directions of 45◦, 135◦, 225◦, and 315◦