Judul: Synthesis of Neutron Radiation Shields Based on Concrete With filler Palm Fiber and Coconut Shell Powder.
Abstrak: Radiasi neutron merupakan radiasi pengion yang memiliki daya tembus yang tinggi, sehingga diperlukan perisai radiasi untuk mengurangi bahaya radiasi neutron. Telah dilakukan sintesis beton dengan filler serat ijuk dan serbuk batok kelapa sebagai perisai radiasi neutron. Bahan perisai radiasi dibuat dengan menggunakan pasir lukulo, semen, kapur, split, air dan penambahan filler serat ijuk dan serbuk batok kelapa sebesar 5%, 10%, dan 20%. Eksperimen ini menggunakan Energy-dispersive X-ray spectroscopy (EDS) untuk analisis unsur. Pengujian serapan neutron menggunakan teknik radiografi neutron dengan metode film menunjukkan bahwa nilai tampang lintang makroskopik (Ʃ) memiliki karakteristik fungsi eksponensial terhadap tebal perisai beton untuk filler serat ijuk 5% yaitu 0,2538 cm-1, filler serat ijuk 10% yaitu 0,2604 cm-1, filler serat ijuk 20% yaitu 0,2754 cm-1, filler serbuk batok kelapa 5% yaitu 0,214 cm-1, filler serbuk batok kelapa 10% yaitu 0,2179 cm-1, filler serbuk batok kelapa 20% yaitu 0,2408 cm-1. Nilai tampang lintang makroskopik (Ʃ) meningkat seiring bertambahnya kadar filler., Neutron radiation is ionizing radiation that has high penetrating power, so radiation shielding is needed to reduce the danger of neutron radiation. Concrete synthesis has been carried out using palm fiber filler and coconut shell powder as a shield for neutron radiation. Radiation shielding material was made by using lukulo sand, cement, lime, split, water, and the addition of 5%, 10%, and 20% of filler fibers and coconut shell powder. The experiment used Energy-dispersive Xray spectroscopy (EDS) for elemental analysis. The neutron absorption test using the neutron radiography technique with the film method showed that the value of the macroscopic cross section had a characteristic exponential function of the thickness of the concrete shield for 5% palm fiber filler, namely 0,2538 cm-1, 10% palm fiber filler that was 0,2604 cm-1, palm fiber filler 20% is 0,2754 cm-1, coconut shell powder filler is 5% that was 0,214 cm-1, 10% coconut shell powder filler was 0,2179 cm-1, coconut shell powder filler 20% was 0,2408 cm-1. The value of the macroscopic cross section rose as filler content increasing.
Keyword: Beton, perisai radiasi neutron, serat ijuk, serbuk batok kelapa, tampang lintang makroskopik, Coconut shell powder, concrete, macroscopic cross section, neutron radiation shielding, palm fiber

Judul: Synthesis of Neutron Radiation Shields Based on Concrete With Variations of Sand Types
Abstrak: ABSTRACT VENANDA AGUSTINA. Synthesis of Neutron Radiation Shields Based on Concrete With Variations of Sand Types. Supervised by MOHAMMAD NUR INDRO, DJAMIL HUSIN and IWAN SUMIRAT. Neutron radiation is ionizing radiation which has a high penetrating power. So a radiation shield is needed to reduce the danger from neutron radiation. In this study, a neutron radiation shield was made from concrete with 3 different types of sand, namely lukulo sand, white bangka sand and black bangka sand. Concrete as a shield for neutron radiation is tested for its absorption ability using the film method. This experiment also uses Energy-dispersive X-ray spectroscopy (EDS) for elemental analysis. The test results show that the white bangka sand concrete has a good performance as a neutron radiation shield because it has a high attenuation coefficient and a high neutron cross-section. The linear attenuation coefficient of lukulo sand concrete, white bangka sand concrete and black bangka sand concrete were 0.182 cm-1, 0.548 cm-1 and 0.430 cm-1, respectively. The cross-section of the largest neutron is owned by the white bangka sand, then the black bangka sand and lukulo sand. Keywords: Attenuation coefficient, Concrete, Film method, Neutron radiation, Neutron radiation shielding, Radiasi neutron merupakan radiasi pengion yang memiliki daya tembus yang tinggi. Sehingga diperlukan perisai radiasi untuk mengurangi bahaya dari radiasi neutron. Pada penelitian ini dibuat perisai radiasi neutron dari beton dengan 3 jenis pasir berbeda yaitu pasir lukulo, pasir putih bangka dan pasir hitam bangka. Beton sebagai perisai radiasi neutron di uji kemampuan serapannya dengan menggunakan metode film. Eksperimen ini juga menggunakan Energy-dispersive X-ray spectroscopy (EDS) untuk analisis unsur. Hasil pengujian menunjukan bahwa beton dari pasir putih bangka memiliki kinerja yang baik sebagai perisai radiasi neutron karena memiliki nilai koefisien atenuasi yang tinggi serta tampang lintang neutron yang tinggi. Koefisien atenuasi linear dari beton pasir lukulo, beton pasir putih bangka dan beton pasir hitam bangka berturut-turut yaitu 0.182 cm-1, 0.548 cm-1 dan 0.430 cm-1. Tampang lintang neutron dari yang terbesar dimiliki pasir putih bangka, kemudian pasir hitam bangka dan pasir lukulo. Kata kunci: Beton, Koefisien atenuasi, Metode film, Perisai radiasi neutron, Radiasi neutron, Neutron radiation is ionizing radiation which has a high penetrating power. So a radiation shield is needed to reduce the danger from neutron radiation. In this study, a neutron radiation shield was made from concrete with 3 different types of sand, namely lukulo sand, white bangka sand and black bangka sand. Concrete as a shield for neutron radiation is tested for its absorption ability using the film method. This experiment also uses Energy-dispersive X-ray spectroscopy (EDS) for elemental analysis. The test results show that the white bangka sand concrete has a good performance as a neutron radiation shield because it has a high attenuation coefficient and a high neutron cross-section. The linear attenuation coefficient of lukulo sand concrete, white bangka sand concrete and black bangka sand concrete were 0.182 cm-1, 0.548 cm-1 and 0.430 cm-1, respectively. The cross-section of the largest neutron is owned by the white bangka sand, then the black bangka sand and lukulo sand. Keywords: Attenuation coefficient, Concrete, Film method, Neutron radiation,
Keyword: Attenuation coefficient, Concrete, Film method, Neutron radiation, Neutron radiation shielding

Judul: Bifurkasi Hopf pada Model Siklus Bisnis Kaldor Kalecki tanpa dan dengan Waktu Tunda
Abstrak: Business cycle model is one of dynamical system models in economic. One of the business cycles model is Kaldor-Kalecki model. Kaldor-Kalecki business cycle model that is written in delayed defferential equations, is a business cycle model that involves gross product and capital stock of a company. In this paper Kaldor-Kalecki business cycle model is analyzed using both nondelay and delay in time of capital stock. By Taylor expansion for the time delayed model, an analysis of stability around the fixed points has been done. Furthermore, by using Hopf bifurcation theorem, it can be shown that there exists periodic orbits and limit cycle. In the nondelayed model, changing the parameter of goods market could lead to the occurrence of Hopf bifurcation and the existence of limit cycle. Similarly, for the delayed model, it has been shown that changing the time delay parameter may result in the occurrence of Hopf bifurcation and limit cycle.
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