This study aims to determine the level of sound attenuation of Styrofoam material. This research is using a noise meter application Decibel X: dB Sound Level Meter and a sound generator as a sound source. Styrofoam as an acoustic material with a thickness of 1 cm; 1.5 cm; 2 cm; 2.5 cm ; 3 cm; 3.5 cm and 4 cm. The average absorption coefficient obtained in this study with a material thickness of 1 cm is 0.023. Then the average absorption coefficient at a thickness of 1.5 cm is 0.031. While the average absorption coefficient at a material thickness of 2 cm is 0.040. Furthermore, the average sound absorption coefficient at a thickness of 2.5 cm and 3 cm has the same value, namely 0.039. Then, the average sound absorption coefficient at a thickness of 3.5 cm and 4 cm also has the same value, which is 0.038. Based on the research that has been done, it can be concluded that sound absorption at frequencies below 1000 Hz occurs significant sound absorption. At frequencies of 200 Hz, 400 Hz, 600 Hz and 800 Hz, the average sound absorption increases from 1 cm to 3.5 cm of Styrofoam thickness. While the thickness of Styrofoam 4 cm on average did not show a significant increase in sound absorption. Styrofoam thickness of 4 cm can effectively absorb sound at a frequency of 1000 Hz only.
Abstract-A depth experience and knowledge are needed in analyzing the prediction of seawater intrusion. We report here a physical modelling for monitoring the model scale of seawater intrusion. The model used in this research is glass basin consists of two parts; soil and seawater. The intrusion of seawater into soil in the glass basin is modelled. The results of 2-D inversion by using software Res2DInv32 showed that the monitoring of seawater intrusion, in soil model scale, can be detected by using Schlumberger configuration resistivity method. The watering process of freshwater into soil caused the electric resistivity value decreased. This phenomenon can be seen from the transition of the resistivity pseudo section before and after the watering process using different cummulative volume of freshwater in different soil. After being intruded by the seawater, the measured soil resistivity is 2.22 Ωm -5.69 Ωm which means that the soil had been intruded. Kata Kunci-metode geolistrik, intrusi air laut Keywords-geoelectrical method, seawater intrusion Abstrak
Indonesia merupakan negara yang mempunyai sumber daya mineral melimpah diantaranya adalah pasir besi, stronsium, dan keramik porselin. Bahanbahan tersebut sering digunakan sebagai bahan baku dalam komponen elektronik. Material keramik dari lempung dimanfaatkan sebagai dielektrik sedangkan stronsium dan pasir besi sebagai bahan ferit. Stronsium memiliki sifat yang ringan, tahan terhadap suhu tinggi, serta tidak mudah rapuh. Selain itu stronsium memiliki permitivitas listrik yang tinggi yang cocok digunakan sebagai bahan dielektrik pengisi kapasitor. Bahan dielektrik yang dapat menyimpan energi tinggi adalah bahan dielektrik berbentuk keramik. Keramik porselin alumina memiliki rumus kimia(Al2O3). Tujuan penelitian ini adalah untuk meningkatkan struktur dielektrik pada kapasitor dengan komposit stronsium ferit-keramik porselin alumina. Untuk meningkatkan kualitas dari dielektrik maka dibuat komposit dari Sr ferit dan keramik alumina. Sehingga bahan dielektrik lebih ringan, tahan terhadap korosi, dapat menyimpan energi lebih banyak. Dielektrik dibuat dengan komposit stronsium ferit dan keramik porselin alumina dan perekat menggunakan PVA. Stronsium ferit disintesis dengan bahan baku utama stronsium oksida dan pasir besi. Bahan keramik diambil dari bahan-bahan alam lempung. Pembuatan komposit dengan variasi stronsium ferit dan keramik 0:20 gram, 5:15 gram, 10:10 gram, dan 15 : 5 gram. Pencetakan dilakukan menggunakan pompa hidraulik bertekanan 4 ton diameter cetakan 4 cm. Sintering dilakukan dengan menggunakan furnace pada temperatur 250oC. Karakterisai yang dilakukan adalah uji kuat tekan, uji kapasitansi, dan uji Microscopy dengan menggunakan SEM. Hasil uji kuat tekan menunjukkan semakin meningkat seiring dengan bertambahnya stronsium ferit dan tertinggi dengan variasi stronsium ferit massa 15 gram adalah 34,7 x 102 kg. Uji kapasitansi menggunakan plat aluminium diperoleh nilai kapasitansi tertinggi pada variasi massa stronsium ferit 5 gram yaitu 11.5 nF yang dialiri arus AC 7 V. Struktur permukaan menunjukkan penambahan stronsium ferit pada komposit dielektrik adalah heterogen.
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