Judul: Kajian elektroda penangkap gas buang sepeda motor untuk penurunan kadar emisi pencemar lingkungan
Abstrak: Penggunaan sepeda motor dapat mempercepat dan mempermudah aktivitas, sekaligus menimbulkan dampak buruk terhadap lingkungan melalui gas buangnya. Beberapa senyawa yang dikandung oleh gas buang sepeda motor diantaranya co, no, dan so2. Jika konsentrasi ketiga senyawa tersebut melebihi batas ambang, maka akan berbahaya bagi kesehatan manusia. Salah satu upaya untuk mengurangi ketiga senyawa pencemar tersebut, yaitu dengan diletakkan elektroda penangkap gas yang telah dialiri arus listrik di belakang knalpot dengan modifikasi bahan elektrodanya. Berdasarkan hasil penelitian, bahan elektroda yang dapat menurunkan gas pencemar (co, no, dan so2) paling banyak ialah tembaga. Hal ini disebabkan tembaga memiliki rapat muatan yang paling tinggi sehingga menghasilkan medan listrik yang lebih besar. Saat dilakukan variasi tegangan, hanya konsentrasi so2 yang menurun. Pada tegangan 50 volt, nilai konsentrasi so2 adalah 260.59 ppm. Kemudian elektroda tersebut diberikan tegangan sebesar 100, 200, dan 400 volt secara bergantian selang waktu 2 menit dan nilai konsentrasi pun berubah menjadi 151.61 ppm, 81.276 ppm, dan 55.746 ppm. Hasil penelitian masih kurang optimal karena banyak faktor, salah satunya sistem pembuangan emisi kendaraan tidak ideal. Kemudian hasil xrd menunjukkan bahwa setiap bahan plat elektroda mengalami penurunan derajat kristalinitas. Dengan demikian, terdapat pengotor dari gas buang sepeda motor yang menyebabkan kekristalan plat menurun.
Keyword: gas pencemar, medan listrik, plat elektroda, sepeda motor

Judul: The Effect Synergy Co-doping Atoms Ni and C on Boron Nitride as a Catalytic Converter of CO Oxidation to CO2
Abstrak: Penggunaan kendaraan bermotor merupakan salah satu sumber utama pencemaran udara karena menghasilkan gas emisi CO yang berbahaya dan bersifat toksik. Diperlukan upaya untuk mengurangi gas emisi yang diproduksi oleh kendaraan bermotor yaitu dengan pemasangan konverter katalitik pada saluran pipa gas buang. Konverter katalitik dapat mengurangi gas emisi CO melalui reaksi oksidasi pada permukaan katalis yang akan mengubah gas emisi tersebut menjadi CO2. Penelitian ini berfokus pada studi berbasis komputasi menggunakan metode Density Functional Theory (DFT) dalam menjelaskan peranan permukaan katalis h-BN yang didoping dengan atom Ni dan C dengan dua macam permodelan. Peletakan doping yang berbeda dari masing-masing permodelan doping struktur h-BN dapat merubah sifat material tersebut, model I menjadi semikonduktor tipe-n karena terjadinya surplus elektron dan memiliki celah band gap sebesar 2 eV sedangkan model II menjadi semikonduktor tipe-p dengan celah band gap sebesar 3 eV. Model I memiliki potensi lebih baik terkait akvitias katalis karena jarak ikatan Ni-C yang lebih pendek dengan panjang 2,25 Å, sedangkan model II lebih stabil secara struktural dengan total energi yang lebih rendah sebesar -13.569,09 eV., The use of motor vehicles is one of the main sources of air pollution as it emits the hazardous and toxic gas CO. Efforts are needed to reduce the gas emissions produced by motor vehicles, namely by installing catalytic converters in the exhaust pipes. Catalytic converters can reduce CO gas emissions through oxidation reactions on the catalyst surface that convert the gas emissions into CO2. This research focuses on a computational-based study using the Density Functional Theory (DFT) method to explain the role of the h-BN catalyst surface with Ni and C atom-doped structures with two kinds of modeling. The different doping placement of each doping modeling of the h-BN structure can change the properties of the material, model I becomes an n-type semiconductor due to electron surplus and has a band gap of 2 eV while model II becomes a p-type semiconductor with a band gap of 3 eV. Model I has better potential regarding catalytic activity due to the shorter Ni-C bond distance of 2,25 Å in length, while model II is more structurally stable with a lower total energy of -13.569,09 eV.
Keyword: converter catalytic, DFT, h-BN, oxidation CO

Judul: Categorization in Macaca fascicularis.
Abstrak: Categorization is an ability to group individuals or events into different classes mediated by conceptualized mental images. There are several levels of categorization and within a taxonomy the levels are nested. At the most concrete level of categorization, all or most members of the category shared common physical attributes that differ from other categories. The higher the level of category, the fewer common attributes between members of the group. In addition to humans, the ability to categorize has also been proposed in animals. One example of categorization in animal is species discrimination. Using matching-tosample task, present experiment tested ability of the long-tailed macaque (Macaca fascicularis) in discriminating dichotomous-stimuli of different animals. The species has been shown to be able to see photos as representations of real object so I used facial photos of humans and animals for the stimuli. First, I tested their ability to classify humans and macaques into separate group. Second, I tested their ability to discriminate their conspecific from other macaques. And the last, I tested whether the subjects were able to discriminate non-human animals from humans. In all of these experiments I found that the subjects showed high performance in categorizing objects, even when I discarded details of visual informations, such as color and local shapes. The ability to identify objects with reduced representation of physical properties means the subjects were able to generalize attributes of members of the group. This would indicate that the subjects created a higher level abstraction. On the other hand, in discriminating intrageneric macaque species I found that they were able to extract uniqueness of each species. More over, I also found that the subjects were able to put photos of non-human animals that shared very few similarities in physical percepts into one group. I suggested that the subjects could create a more abstract concept based on non-percepts relations as a basis to put the objects into one category. Thus, I concluded that M. fascicularis were able to perform multiple levels of categorizations.
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