Judul: Hubungan antara Tomogram Berbasis Kecepatan Gelombang Bunyi dengan Tomogram Berbasis Impedansi Listrik pada Kayu Terduga Gaharu
Abstrak: Pengujian yang bersifat nondestruktif (NDT) yang sedang berkembang saat ini yaitu penggunaan teknologi untuk mengevaluasi kualitas kayu dan kesehatan kayu pohon berdiri dengan metode berbasis gelombang bunyi yaitu sonic tomography dan dengan metode berbasis impedansi listrik yaitu electrical impedance tomography. Suatu penelitian telah dilakukan untuk menduga keberadaan gaharu pada batang pohon A. malaccensis menggunakan alat PiCUS® Tomograph. Tujuan penelitian ini adalah mengidentifikasi dan mengevaluasi hasil tomogram berbasis impedansi listrik pada kayu terduga gaharu serta mengetahui hubungan antara tomogram berbasis kecepatan gelombang bunyi dengan tomogram berbasis impedansi listrik. Pada penelitian ini, dilakukan pengukuran kecepatan rambat bunyi dan impedansi listrik dilakukan pada lima batang pohon contoh kayu gaharu yang telah diinokulasi jamur, masing-masing pada ketinggian 20 cm, 120 cm dan 220 cm dari permukaan tanah. Pengolahan data image-J digunakan untuk menentukan nilai resistivitas berdasarkan tomogram warna yang dihasilkan. Hasil penelitian menunjukkan bahwa rataan resistivitas yaitu berkisar dari 175 Ωm dan kecepatan gelombang bunyi adalah 886 m/detik. Pada penelitian ini, nilai kecepatan gelombang bunyi pada sonic tomography dan nilai resistivitas pada electrical impedance tomography belum menunjukkan hubungan yang signifikan.
Keyword: sonic tomography, electrical impedance tomography, gaharu

Judul: Reliability of Sonic Tomography Technology as Detector of Gaharu in Aquilaria microcarpa Baill.
Abstrak: Gaharu or agarwood is known as valuable products of non timber forest products (NTFP’s). Due to its economic value, the product has been subjected to over exploitation practice in Indonesia's natural forests. Therefore, some gaharu producing trees have been classified as endangered species and included into Appendix II of CITES (convention on international trade for endangered species). Traditional harvesting practice of gaharu has been insisted to fell the trees without any reliable techniques in predicting the presence of gaharu. A study was conducted to evaluate the reliability of sonic tomography technology (Picus® Sonic Tomography) in detecting the presence of gaharu within A. microcarpa trees. Thirty five of A. microcarpa with ≥ 15 cm diameter at an experimental forest area in Carita, Banten Province were selected as sample trees. Four to six transducers of Picus® Sonic Tomography were mounted circularly on the stem of sample trees at 20 cm, 130 cm, and 200 cm height from the ground (as measuring points). The transducers were connected to the software system which could record any sonic wave velocities data of each sample trees, then converted those data to be color gradation images. The result showed that sonic wave velocities within sample trees were ranged from 400 to 900 m.s-1 with average value of 700 m.s-1. There was no significant difference of sonic wave velocity among measuring points. It was also found that sample trees with high sonic velocity tend to reveal dark color of tomography image (dark brown), meanwhile the lower value of sonic velocity denoted light color (green-violet-blue). In addition as such, gaharu containing sample trees tend to reveal light color image (sonic wave velocity around 750 m.s-1), low moisture content and high density. These findings were then proven by visual observation on the felled sample tree. In concluding, sonic tomography technology shows sufficient reliability to detect the presence of gaharu in the tree.
Keyword: Agarwood, Aquilaria microcarpa, sonic tomography, sonic wave velocity

Judul: A Continuous Vaccination Strategy in the SVIR Epidemic Model
Abstrak: Vaccination is conducted to minimize the spread of a disease. The vaccination is usually done several times within a fixed time interval. In the SVIR model, it is assumed that individuals do not get immediate immunity following a vaccination program. So according to process of vaccination on SVIR model, there are two strategies, i.e. the continuous vaccination strategy (CVS) and the pulse vaccination strategy (PVS). In this study, only the CVS strategy in epidemic model SVIR is considered. Results of the study indicate that dynamics of the CVS system depends on the basic reproductive number. If the basic reproductive number is less than one, then the disease-free fixed point is asymptotically stable. It means that the disease will eventually disappear from the population. Conversely, if the basic reproductive number is greater than one, then the endemic fixed point is asymptotically stable, which means that the disease will remain exist in the population. Simulation result shows that the vaccination would minimize the spread of disease by reducing the basic reproductive number. If the time for the vaccinated recipients to obtain the immunity, as well as a possibility of vaccinated recipients to be infected are neglected, then the disease will be eradicated. This condition is called an over-evaluating effect of vaccination.
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