Judul: Acoustical Study Of Fluid Mud
Abstrak: Laboratory and field experiments were performed to investigate fluid mud properties by acoustic reflection technique using 192 KHz and 1.0 MHz transceivers. with the return signals sampled at 30 KHz and digitized with 12 bit resolution. Lab- oratory experiments were carried out in a cylindrical tank using sample of fluid mud collected from the Chesapeake Bay; field experiments were carried out in Battery Park, Delaware Bay and included in situ acoustic measurements as well as collection of bottom samples using a modified gravity corer. Acoustic measurements were taken in the laboratory on the simulated fluid mud to determine the relationship between bulk density and acoustic backscatter- ing, by allowing the fluid mud to settle. Laboratory measurements shows that sound attenuation was increased as a result of fluid mud compaction, approximately about 28 dB/m for the 192 KHz and 120 dB/m for the 1.0 MHz at the end of the compaction experiments (fluid mud thickness: 15 cm). The frequency depen- dance attenuation (f") of fluid mud is also increased as fluid mud compacted: at the end of compaction, the power value obtained was 0.9. Bulk density obtained and its corresponding acoustic backscattering show no clear relationship as a result of cancellation effect between bulk density (p) and sound speed (c).
Keyword: Acoustic system, Acoustic technique, Density, Bogor Agricultural University

Judul: Determining The Dense Soil Depth Using Acoustic Wave
Abstrak: Determining the dense soil depth using acoustic wave is one of the attempts of non-destructive detection method development. This method is applied since the ultrasonic wave detection has been widely conducted and applied in other fields, besides agriculture. The particular purpose of the research is to determine the amplitude of the acoustic waves received as the bouncing effect or the propagation on soil by the cultivating treatment on the dense soil depth. The research tools and materials applied is a sample soil of Latosol, which is connected through circuit of a series of signal generator used as the sinusoidal signal generator, and processed to transmitter speakers in several frequencies. Op-amp circuit functions as the amplifier and the audio waves stabilizer gained by receiver speakers, and they are connected to oscilloscope to visualize the results. Op-amp circuit with bigger amplified level, equipped with a filter circuit, and uses the appropriate power on the transmitter speakers circuit will cause the intensified waves transmitted according to the expected results. The use of the same kind of speakers eases the research to produce results as needed. The research is conducted at 30 % of water content by the speaker position forming 300 angles with bulk density of 1.0 gram/cm3 and 1.3 gram/cm3 in the cultivation layer of 0, 5, 10, 15, and 20 cm. In the treatment of cultivation layer thickness is known that the denser or thicker cultivation layer the smaller receiver of the audio wave amplitude. In the estimation of the dense soil depth using audio waves, it is seen that the audio wave amplitude value received will be smaller in the increase of cultivated soil layer. The making of the instrument is adjusted with the result of the previous research. The noise influences the sound waves produced and transmitted, and also the amplitude waves received. The noise covers the transmitted sound waves so that the sound waves is not detected by the oscilloscope.
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Judul: Closed Knight’s Tour pada Papan Catur Berbentuk Persegi Panjang dengan Ukuran Maksimal 8 × 8
Abstrak: Closed Knight’s Tour merupakan langkah kuda yang mengunjungi setiap kotak pada papan catur tepat satu kali dengan langkah kuda berawal dan berakhir pada kotak yang sama. Graf yang terbentuk dari closed knight’s tour dinotasikan sebagai graf G(m,n), dengan m adalah banyaknya baris dan n adalah banyaknya kolom. Graf tersebut memuat Hamiltonian cycle. Sebuah graf terhubung G adalah graf bipartite jika dan hanya jika graf tersebut tidak memiliki cycle dengan panjang ganjil. Papan catur yang memenuhi syarat cukup untuk memiliki closed knight’s tour adalah papan catur berukuran 5 × 6, 5 × 8, 6 × 6, 6 × 7, 6 × 8, 7 × 8, dan 8 × 8.
Keyword: bipartite, closed knight’s tour, hamiltonian cycle, knight’s tour, teori graf