Judul: Prototipe Dan Kinerja Sistem Penggerak Kendaraan Air Berbasis Getaran Struktur.
Abstrak: Beberapa karakteristik fisika-mekanika hewan yang ada dimuka bumi telah menginspirasi dalam pengembangan sistem penggerak baik di air, darat, maupun udara. Salah satu konsep bio-mimetik yang menjadi pusat perhatian adalah sistem pergerakan ikan di dalam air yang dapat digunakan untuk sistem penggerak kendaraan air. Tujuan umum dari penelitian ini adalah merancang sistem penggerak kendaraan air menggunakan getaran (resonansi) dari struktur berbentuk plat tipis dan menguji kinerja dari sistem tersebut pada sebuah model kendaraan air. Alat dan bahan yang digunakan terdiri dari beberapa bagian, yaitu pembuatan sistem kelistrikan, pembuatan mekanisme sistem penggerak, pembuatan model kendaraan air, dan perlengkapan uji kinerja. Rancangan terdiri dari dua jenis yakni rancangan fungsional dan rancangan struktural. Fungsi dan struktur utama dari sistem yang dibuat adalah sistem kelistrikan akan menghasilkan daya listrik DC variabel yang stabil, mekanisme crank and rocker akan mengubah gerak rotasi menjadi gerak bolak balik, rancangan kendaraan air yang dapat bergerak lurus ke depan, dan instrumen untuk menampilkan putaran motor listrik dan daya listrik yang digunakan. Pengukuran dan pengujian meliputi validasi mekanisme crank and rocker, kalibrasi alat ukur, perhitungan luasan basah dan bobot kendaraan air, perhitungan kecepatan maju, gaya dorong, dan putaran serta daya listrik terpakai. Rancangan acak kelompok (RAK) dianalisis menggunakan perangkat lunak IBM SPSS 20.0. Kendaraan air memiliki dimensi panjang, lebar, dan tinggi berturut-turut 100 cm, 50 cm, dan 30 cm dengan dua jenis luasan basah yakni 0.32 m2 (bobot 12.5 kg) dan 0.57 m2 (bobot 17.5 kg). Mekanisme crank and rocker dapat digunakan pada sistem penggerak. Ukuran batang hubung R1, R2, R3, dan R4 dengan posisi sumbu yang tepat berturut-turut adalah 80 mm, 20 mm, 90 mm, dan 50 mm dan sudah memenuhi kriteria Grashof. Berdasarkan hasil simulasi, frekuensi pribadi mode ke-2 untuk masing-masing plat berada pada putaran motor listrik 202 rpm, sedangkan berdasarkan uji langsung nilai frekuensi pribadi yang dihasilkan plat 1, plat 2, plat 3, dan plat 4 pada kondisi luasan basah 0.32 m2 berturut-turut 313, 243, 233, dan 250 rpm. Perbedaan tersebut diakibatkan oleh kedalaman plat yang tidak sama dengan simulasi sehingga tekanan air juga berbeda. Berdasarkan uji kinerja, kecepatan maju kendaraan air berkisar antara 0.07 – 0.38 m/s, gaya dorong yang dihasilkan masing-masing plat berkisar antara 0.01 – 0.19 N/kg bobot kendaraan air, konsumsi daya listrik yang digunakan berkisar antara 1.75 – 75.13 watt, daya mekanis yang dihasilkan berkisar antara 0.02 – 0.90 watt, dan efisiensi daya mekanis berkisar antara 0.35 – 5.21 %. Nilai efisiensi tertinggi dihasilkan pada sistem penggerak plat 1 (panjang 500 mm, lebar 30 mm, dan tebal 1 mm) untuk kedua kondisi luasan basah kendaraan air dan secara umum memiliki nilai rataan tiap parameter yang berbeda nyata dengan plat 4 (panjang 500 mm, lebar 60 mm, dan tebal 1 mm).
Keyword: getaran struktur, gaya dorong, kendaraan air, efisiensi daya

Judul: Rancang Bangun dan Kinerja Aerator Tipe Kincir dengan Sudu Bergerak
Abstrak: To reduce operating costs, the power efficiency of paddle wheel aerator needs to be improved. The purpose of this study was to design a paddle wheel aerator with movable blades to reduce its rotation power requirement and produce the best aeration performance. In this aerator design, paddles were driven to open and close on hinges using cam-rods mechanism, in which the paddles opened while scooping up water, and closed when paddles were above the water surface. The aerator was rotated using an electric motor. Performance tests were carried out on a test pond, on operating depths of 4 and 6 cm, with a combination of rotational speed of 115, 135, and 154 rpm. In the test, the electrical power requirements, and the performance of aeration, i.e.: water covering area, bursts length, and bursts wide were measured. The test results showed that the use of electric power could be reduced about 2-5 watts using the paddle wheel aerator with movable paddles, at operating depth of 4 cm at all rotational speeds tested. But at 6 cm operating depth, the use of the movable paddles type aerator could not reduce the need for electrical power. The resulting aeration performance of of the movable paddles aerator was relatively similar with that of the fixed blade aerator.
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Judul: Kajian Listeria monocytogenes pada Keju Gouda
Abstrak: Listeria monocytogenes is a foodborne pathogen, which has been associated with several outbreaks of human listeriosis especially in high risk groups. L. monocytogenes could present in Gouda cheeses because it was influenced by various factors, including unsatisfactory pasteurization treatment, contamination after heat treatment, improper sanitizing procedures and ability of this bacteria to forming biofilms. In addition, this bacteria could survive during the process of cheese making and ripening. The purpose of this study were to examine the presence of L. monocytogenes in Gouda cheeses and to provide an overview of Gouda cheese safety of in regards with L. monocytogenes. The samples of this study consisted of 15 local Gouda cheese and 15 imported Gouda cheese which were sold in supermarkets. The samples were taken with considering production code and expired date. The method to detect presence of L. monocytogenes which referred to the Bacteriological Analytical Manual, US Food and Drug Administration and Bergey's Manual of Determinative Bacteriology. The first step was enrichment of samples in Listeria enrichment broth, then isolated in oxford agar and identification step using catalase test, 3% KOH test, Gram stain, carbohydrate fermentation test (mannitol, rhamnose, xylose), motility test and CAMP test. The results of this study showed that L. monocytogenes was not found in 15 samples of local Gouda cheese (0%) and 15 samples of imported Gouda cheese (0%). The absence of L. monocytogenes in local and imported Gouda cheeses was related to combination of preservative factors in Gouda cheese such as pasteurization of milk as raw material for making of Gouda cheese, decrease in pH was caused by the addition of lactic acid bacteria starter cultures, and decline in water activity during the ripening process of Gouda cheeses. The combination of these preservative factors could inhibit the growth of L. monocytogenes could even inactivate L. monocytogenes. In addition, there was not contamination of L. monocytogenes after the pasteurization and during processing of milk to become cheeses. Another factor that could affect the absence of L. monocytogenes in Gouda cheese samples was the number of L. monocytogenes in the samples below the detection limit of conventional method which used in this study. The study could be concluded that all of samples of Gouda cheese were not found the existence of L. monocytogenes and relatively safe from contamination of L. monocytogenes and fulfilled the standard that determined by national standard of Indonesia 7388:2009 about Maximum Limit of Microbial Contamination in Food.
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