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"The utilization of bricks made of styrofoam is expectedly able to be a soundproof for noise control and as a preventive action to reduce the steadily increasing prevalence of hearing loss. This study aimed to assess the use of sound absorption material in which styrofoam was utilized to reduce the noise exposure. In this study, fine aggregates (sand and styrofoam) were made with a mixture of cement with a composition of 1:4 and 1:6, also the addition of polystyrene waste with a percentage of 0%, 20%, 40%, 60%, and 80%. Determination of acoustical property of the mixture was done by testing the sound absorption coefficient using Four Microphones Impedance Tube (ISO 140-3). The results showed that the highest value of absorption coefficient was at a frequency of 800 Hz with an additional 80% styrofoam for the composition of 1:4 at 0.4100 dB and at a frequency of 800 Hz with an additional 40% styrofoam for the composition of 1:6 at 0.5870 dB."

"Rugi-rugi (losses) pada saat terbentuknya pasangan elektron-hole (e-h pairs) di dalam solar cell adalah timbulnya transmission-loss dan termalizationloss. Aplikasi konsep up & down conversion dibahas pada Tesis ini untuk mengurangi rugi ? rugi tersebut sehingga perbaikan efisiensi solar cell bias dicapai. Proses up-conversion melibatkan energi photon yang rendah dikonversi menghasilkan energi photon yang lebih tinggi untuk mengurangi transmission loss. Down-conversion melibatkan energi photon yang tinggi dikonversi menjadi energi photon yang lebih rendah untuk mengurangi thermalization loss. Dalam riset ini dilakukan analisa dan simulasi terhadap aplikasi konsep up/down-conversion untuk mendapatkan perbaikan efisiensi pada solar cell. Dengan menggunakan simulator PC1D 5.9, sumber cahaya sekunder (secondary light source) diberikan dengan asumsi sebagai proses luminescence oleh up/downconverter masing ? masing dari rear surface dan front surface sesuai dengan prinsip konversi photon pada aplikasi tersebut. Simulasi dilakukan dengan memberikan variasi spektrum cahaya secara transien pada cahaya sekunder dan variasi intensitas cahaya dengan batasan maksimum terrestrial sun 0,1 W/cm2. Efisiensi maksimum didapat sebesar 18,71% untuk aplikasi up-converter, dan 20,18% untuk aplikasi down-converter dengan kondisi matahari tak terkonsentrasi. Hasil simulasi konsep up/down-conversion tersebut menunjukkan dapat mengurangi rugi ? rugi pada solar cell dan memperbaiki efisiensi untuk disain solar cell, dan dapat diaplikasikan untuk jenis solar cell konvensional yang ada sekarang. ......The losses appeared when electron-hole pairs are formed in solar cell indicated as transmission and thermalization loss. The application of up/downconversion concept is discussed in this Thesis, in order to reduce both loss, so the efficiency of solar cell can be improve. Up-conversion process involving two low energy photons converted into higher energy photon for reducing transmission loss. Down-conversion involving high energy photons converted into two lower energy photons for reducing thermalization loss. In this research has been analyzed and simulated about up/downconversion concept to achieved an improvement of solar cell efficiency. By using PC1D 5.9, a secondary light source is provided and it assumed as a luminescence from up/down-converter, which is directly emited from front and rear surface according to each conversion process. The variation of secondary light intensity is given in this simulation with the maximum limits 0,1 W/cm2 of terrestrial sun. Maximum efficiency obtained was 18.71% for the up-converter applications, and 20.18% for the down-converter applications with unconcentrated sun. The Results of applied up / down-conversion show can reduce losses in the solar cell and improve efficiency for solar cell design, and it can be applied also to the conventional solar cell."

"The book provides readers with a snapshot of recent research and industrial trends in field of industrial acoustics and vibration. Each chapter, accepted after a rigorous peer-review process, reports on a selected, original piece of work presented and discussed at the Second International Conference on Acoustics and Vibration (ICAV2018), which was organized by the Tunisian Association of Industrial Acoustics and Vibration (ATAVI) and held March 19-21, in Hammamet, Tunisia. The contributions cover advances in both theory and practice in a variety of subfields, such as: smart materials and structures; fluid-structure interaction; structural acoustics as well as computational vibro-acoustics and numerical methods. Further topics include: engines control, noise identification, robust design, flow-induced vibration and many others. This book provides a valuable resource for both academics and professionals dealing with diverse issues in applied mechanics. By combining advanced theories with industrial issues, it is expected to facilitate communication and collaboration between different groups of researchers and technology users."