Judul: Surface Characteristics of Scots Pine (Pine sylvestris L.) Chemically Modified by Citric Acid Sorbitol and Softener
Abstrak: Penggunaan kayu sebagai bahan baku produk eksterior harus memiliki keawetan yang baik. Kayu pinus scots memiliki keawetan yang rendah, sehingga keawetannya perlu ditingkatkan melalui modifikasi kayu. Penelitian ini bertujuan untuk mengetahui pengaruh modifikasi kimia menggunakan asam sitrat-sorbitol atau CAS (dengan beberapa rasio molar dan konsentrasi larutan) dan softener terhadap karakteristik permukaan kayu pinus scots sebelum dan setelah uji kubur selama 4 bulan, 8 bulan, dan 12 bulan. Pengujian karakteristik permukaan meliputi uji kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat. Hasil penelitian menunjukkan bahwa nilai kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat meningkat seiring dengan semakin lamanya waktu uji kubur. Kayu dengan perlakuan CAS 1:1_20% menghasilkan nilai keterbasahan dan daya lekat cat tertinggi. Peningkatan rasio molar dan konsentrasi asam sitrat dapat menurunkan nilai kekasaran permukaan, energi bebas permukaan, keterbasahan, dan daya lekat cat pada kayu. Cat alkid menghasilkan nilai keterbasahan dan daya lekat cat lebih baik dibandingkan cat akrilik., The used of wood as a raw material for exterior products must have good durability. Scots pine (Pinus sylvestris L.) wood has low durability, hence its durability needed to be increase by a wood modification. This study aimed to determine the effect of chemical modification using citric acid-sorbitol or CAS (with several molar ratios and solution concentrations) and softener on the surface characteristics of scots pine wood before and after graveyard test for 4 months, 8 months, and 12 months. The surface characteristics studied were surface roughness, surface free energy (SFE), wettability, and bonding quality. The results show that the values of surface roughness, surface free energy, wettability, and bonding quality increased as the longer of the graveyard test. CAS 1:1_20% wood treated resulted in the highest wettability and bonding quality values. Increasing the molar ratio and concentration of citric acid could reduce the value of surface roughness, SFE, wettability, and bonding quality. Alkyd paint produced better wettability and bonding quality than acrylic paints.
Keyword: citric acid sorbitol, graveyard test, scots pine, softener, surface characteristics

Judul: Surface Characteristics of Modified Scots Pine by DMDHEU (Dimethylol Dihydroxy Ethylene Urea) and Phenol Formaldehyde
Abstrak: Karakteristik permukaan kayu merupakan salah satu sifat yang mempengaruhi kualitas permukaan kayu terutama pada proses finishing. Kualitas kayu scots pine dapat ditingkatkan dengan teknik modifikasi kimia menggunakan Dimetilol Dihidroksi Etilen Urea (DMDHEU) dan Fenol Formaldehida (PF). Penelitian ini bertujuan mengevaluasi karakteristik permukaan kayu scots pine hasil modifikasi (PF resin, PF resin dengan bio-oil (PFO), DMDHEU resin (D), turunan DMDHEU resin bebas formaldehida (DE), DMDHEU resin dengan softener (DS), dan DMDHEU resin termodifikasi (MD)) setelah uji kubur selama 4, 8, dan 12 bulan. Modifikasi kayu menggunakan metode impregnasi. Hasil penelitian menunjukkan bahwa modifikasi kimia dan lama uji kubur berpengaruh terhadap karakteristik permukaan kayu. Nilai kekasaran permukaan, energi bebas permukaan (Surface Free Energy-SFE), keterbasahan, dan daya lekat cat meningkat seiring lama waktu uji kubur. Hasil uji SFE sebelum uji kubur memiliki nilai komponen polar yang lebih rendah, sedangkan setelah uji kubur nilai komponen polar meningkat dan lebih tinggi dibandingkan komponen dispersi. Nilai keterbasahan paling tinggi pada perlakuan DE dan nilai terendah pada perlakuan PF. Daya lekat cat alkid memiliki kualitas yang lebih baik dibandingkan dengan daya lekat cat akrilik., Wood surface characteristics are one of the properties that affect the surface quality, especially the finishing process. The quality of scots pine wood can be improved by chemical modification of using Dimethylol Dihydroxy Ethylene Urea (DMDHEU) and Phenol Formaldehyde (PF). This study aimed to evaluate the surface characteristics of scots pine chemically modified by PF, PF with bio-oil (PFO), DMDHEU (D), DMDHEU derivative of formaldehyde-free resin (DE), DMDHEU with softener (DS), and modified-DMDHEU (MD) after 4, 8, and 12 months graveyard tests. The wood modification method was impregnation. The results showed that chemical modification treatment and graveyard test affected the wood surface characteristic. The values of roughness, surface free energy (SFE), wettability, and bonding quality increased as longer period of the graveyard test. The SFE value before the graveyard test was a lower polar component, while after the graveyard test increased to be higher than the dispersion component. The wettability value of the DE treatment was higher than the other treatments, meanwhile the wettability of the PF treatment was the lowest. Alkyd paint had better bonding quality than acrylic paint.
Keyword: DMDHEU, graveyard test, PF, scots pine, surface characteristics

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model