Judul: Electrical Properties of Gewang Wood (Corypha utan Lamk.)
Abstrak: Sifat kelistrikan merupakan salah satu hal yang penting untuk pengembangan produk dari suatu material termasuk kayu. Penelitian ini bertujuan untuk mengetahui sifat kelistrikan kayu gewang (Corypha utan Lamk.) yang berasal dari bagian dalam, tengah, dan tepi batang. Sifat kelistrikan kayu yang diteliti yaitu impedansi, kapasitansi, dan konduktansi menggunakan LCR Hi-tester dengan metode kapasitor plat sejajar. Hasil penelitian sifat fisis menunjukkan bahwa kadar air kayu gewang menurun dari bagian dalam hingga bagian tepi, sedangkan kerapatan dan berat jenisnya meningkat dari bagian dalam hingga bagian tepi batang. Nilai rata rata impedansi pada kayu gewang pada bagian dalam, tengah, tepi berkisar 1,686x10^5Ω - 1,873x10^5Ω. Nilai rata rata kapasitansi pada kayu gewang pada bagian dalam, tengah, tepi berkisar 3,961x10^(-9) F - 4,155x10^(-9) F. Nilai rata rata konstanta dielektrik pada kayu gewang pada bagian dalam, tengah, tepi berkisar 3,581x10^3- 3,807x10^3. Nilai rata rata konduktansi dielektrik pada kayu gewang pada bagian dalam, tengah, tepi berkisar 3,673x10^(-5) S - 3,884x10^(-5) S. Nilai rata rata konduktivitas pada kayu gewang pada bagian dalam, tengah, tepi berkisar 2,938x10^(-4) S/cm - 3,107x10^(-4) S/cm., Electrical properties are one of the important things for product development of a material including wood. This study aims to determine the electrical properties of gewang wood (Corypha utan Lamk.) originated from inner, middle, and outer part of the trunk. Electrical properties that were tested were impedance, capacitance, and conductance using LCR-Hitester with parallel plate method. The result showed that the moisture content of gewang stem decrease from inner to outer part, while the density and specific gravity increase from inner to outer part. The average of impedance value in the inner, middle, and outer part of the trunk ranged 1.686x10^5Ω - 1.873x10^5Ω. The average of capacitance value in the inner, middle, and outer part of the trunk ranged 3.961x10^(-9) F – 4.155x10^(-9) F. The average of dielectric constant value in the inner, middle, and outer part of the trunk ranged 3.581x10^3- 3.807x10^3. The average of conductance value in the inner, middle, and outer part of the trunk ranged 3.673x10^(-5) S – 3.884x10^(-5) S. The average of conductivity value in the inner, middle, and outer part of the trunk ranged 2.938x10^(-4) S/cm – 3.107x10^(-4) S/cm.
Keyword: Impedansi, Kayu Gewang, konduktivitas listrik, semikonduktor, Electrical conductivity, Gewang stem, impedance, semi-conductor

Judul: Characterization of Wood Orientation and Moisture Content  Based on Electrical Capacitance Technology
Abstrak: Kayu merupakan bahan dielektrik alami yang memiliki kemampuan untuk menyimpan muatan listrik. Sifat listrik yang dimiliki kayu berupa impedansi, konduktansi dan kapasitansi yang umumnya dipengaruhi oleh beberapa faktor seperti kadar air dan struktur anatomi. Sifat tersebut dapat memberikan manfaat dalam berbagai keperluan, namun pada kenyataannya sifat listrik kayu masih terbatas pemanfaatannya sehingga mendorong dilakukannya penelitian ini. Tujuan penelitian adalah menganalisis sifat kapasitansi listrik pada kayu berdasarkan perbedaan kadar air serta perbedaan orientasi penampang kayu. Pengambilan data kapasitansi listrik dilakukan saat kadar air target telah tercapai. Kadar air yang diukur adalah kadar air basah, kadar air titik jenuh serat, dan kadar air kering udara Data diambil menggunakan WIDER (Wood Species Identifier) yaitu teknologi yang dapat mengukur nilai kapasitansi yang dihasilkan oleh sensor dengan memanfaatkan sifat resistansi, konduktansi dan kapasitansi. Sensor tersebut terdiri dari pemancar gelombang (transmitter) dan penerima sinyal (receiver) untuk melihat distribusi aliran listrik di dalam material dengan mendeteksi variasi permitivitas dielektrik yang selanjutnya diterima oleh sistem akuisisi data yang akan memproses kapasitansi dan pengukuran medan listrik untuk selanjutnya diproses oleh sistem komputer. Hasil penelitian menunjukkan tidak terdapat pengaruh yang nyata berdasarkan orientasi bidang ortogonal terhadap nilai kapasitansi yang dihasilkan. Sementara itu, kondisi kadar air pada kayu memberikan pengaruh yang nyata terhadap nilai kapasitansi. Kadar air basah memberikan nilai kapasitansi listrik yang paling tinggi dibandingkan dengan kayu pada kondisi kadar air titik jenuh serat dan kering udara. Untuk kayu dengan kondisi kadar air titik jenuh serat nilai kapasitansi listrik yang dihasilkan lebih tinggi dibandingkan kayu kondisi kadar air kering udara. Selain itu, kayu dengan kerapatan yang tinggi akan menghasilkan nilai kapasitansi yang lebih tinggi dibandingkan dengan kayu yang memiliki kerapatan rendah. Perbedaan jenis kayu menghasilkan nilai kapasitansi listrik yang berbeda. Hal tersebut dapat dijelaskan karena berkaitan dengan struktur anatomi kayu terutama tebal dinding tiap jenis kayu yang berbeda. Kata kunci: Kapasitansi listrik, sifat dielektrik kayu, WIDER, medan listrik, kadar air kayu, orientasi bidang ortogonal, Wood is a natural dielectric material that has an ability to store electric charges. The electrical properties of wood are in the form of impedance, conductance, and capacitance, which are generally influenced by several factors such as moisture content and anatomical structure. These properties can be beneficial in various applications. However, the implementation technology of electrical properties of wood are still limited. This research aimed to analyze the capacitance properties of wood based on the differences in moisture content and wood orthogonal orientation. Data on electrical capacitance were collected once the target moisture content has been reached. The moisture content was measured as green moisture content, fiber saturation point, and air-dry moisture content by using WIDER (Wood Species Identifier), a technology created to measure the capacitance value produced by sensors by utilizing the properties of resistance, conductance, and capacitance. The sensor consists of a transmitter and receiver to examine the distribution within material by detecting the dielectric permittivity variation, which is then received by the data acquisition system to measure the capacitance and electric field for further processed by the computer system. The research results showed that there was no effect of orthogonal orientation on the capacitance value
Keyword: Kapasitansi listrik, sifat dielektrik kayu, WIDER, medan listrik, kadar  air kayu, orientasi bidang ortogonal

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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