Judul: Rancang Bangun dan Uji Kinerja Alat Pengutip Brondolan Sawit
Abstrak: Prototipe alat pengutip brondolan sawit telah didesain dan dibuat. Tujuan penelitian ini adalah untuk mendapatkan desain, prototipe, dan data kinerja maksimal dari alat pengutip brondolan sawit untuk diaplikasikan di kebun sawit. Komponennya terdiri dari pengutip, rangka, roller, handle dan penampung brondolan yang terkutip. Desain prototipe alat dibuat dengan mempertimbangkan faktor karakteristik brondolan sawit dan kondisi lahan sawit di Indonesia, agar nantinya alat bekerja dengan baik sesuai tujuan pembuatan. Hasil analisis struktural, pemilihan dan perencanaan bahan pada rangka juga dilakukan, digunakan besi siku dengan bahan SC45 yang memiliki tegangan izin (σb) = 58 kg/mm² lebih besar daripada tegangan geser dan tegangan bending yang diterima oleh bahan. Hasil simulasi beban statis menggunakan Software SolidWorks menunjukkan bahwa bahan dan dimensi pada komponen rangka utama masih aman karena tegangan maksimum yang diterima oleh bahan lebih kecil dari tegangan izin bahan. Kekurangan terdapat pada besar kecepatan putar (rpm) pengutip yang tidak bisa dikontrol karena sumber daya bukan dari putaran motor melainkan dari dorongan manusia. Hasil menunjukkan bahwa efisiensi pengutipan tertinggi sebesar 73%, losses sebesar 27%. Kapasitas lapang pengutipan alat ini sebesar 0.26 kg/menit atau 16.18 kg/jam.
Keyword: alat pengutip, brondolan sawit, desain, uji kinerja

Judul: Desain dan Kinerja Kolektor Brondolan Sawit yang Efektif Berbasis Spiral Baja Berlapis Silicone Rubber
Abstrak: Buah sawit yang lepas dari tandannya (brondolan) mencapai 12.5%-75%, yang biasanya dipungut dengan tangan. Untuk mempercepat pengutipannya diperlukan alat bantu yang lebih cepat dan efektif. Penelitian ini bertujuan untuk mendesain dan menguji kinerja prototipe kolektor brondolan sawit tipe roller dan tipe plat datar dilengkapi pin-pin spiral baja berlapis silicone rubber. Prototipe ini dirancang agar 1) memiliki kapasitas yang lebih besar dari cara pungut dengan tangan, 2) efektif dalam mengutip brondolan, 3) tidak merusak brondolan, 4) dan hasil pengutipan bersih dari kotoran. Kolektor ini menggunakan prinsip pin-pin spiral baja yang menjepit buah dan mengumpulkannya pada wadah. Pin-pin penjepit tersebut dipasang berderet dengan jarak antar pin yang optimum pada plat berbentuk silinder atau plat datar. Ada dua tipe kolektor yang didesain dan dicoba, yaitu tipe roller dan tipe plat datar. Hasil uji menunjukkan bahwa kolektor tipe plat datar memiliki kapasitas pengutipan yang paling tinggi (2.94 kg/menit), sementara kapasitas kolektor tipe roller sebesar 2.61 kg/menit dan pungut dengan tangan berkapasitas 1.88 kg/menit. Efektivitas pengutipan kolektor tipe roller rata-rata 40.3% di lahan yang tertutup rerumputan, 63% di lahan yang bersih dari rerumputan, dan 76.3% di lahan yang datar tanpa rerumputan. Pengutipan menggunakan kedua jenis kolektor tersebut mengakibatkan 5-7% buah yang luka tergores. Kontaminan yang ikut terbawa dalam satu kali pengutipan sebanyak 60-80 g. The oil palm loose fruits reaches 12.5%-75% of the total fruits, which are usually collected by hand. To accelerate the work, required a faster and more effective tool to collect the loose fruits. The research aims to design and test the performance of a roller type and a flat plate type loose fruits collectors equipped with silicone rubber coated steel spiral pins. These collectors were designed to be: a) having a higher collection capacity the way collected by hand, b) more effectively picking up fruits, c) does not damage the fruits, and d) does not take contaminant. The collector uses the principles of steel spiral pins that clamp the fruit and collect them on the container. The clamp pins are installed with the optimum spacing on a cylinders or on a flat plate. There are two types of collectors designed and tested in the field, namely roller type and flat plate type. The test results show that the flat plate type collector has the highest collecting capacity (2.94 kg/min), while the roller type collector capacity is 2.61 kg/min and collected by hand with a capacity of 1.88 kg/min. The average effectiveness of the roller-type collector is 40.3% in the grass-covered land, 63% on the clean land, and 76.3% on flat-clean land. The fruits collection using both types of collectors resulted in 5-7% of the injured fruit. The contaminants are carried over by the collector as much as 60-80 g in each collecting process.
Keyword: collector, design, loose fruits, roller, steel spiral, brondolan sawit, desain, kolektor, roller, spiral baja

Judul: Model’s Dynamics for Lymphocytes Recovery on the HIV presence with Protease Inhibitor Therapy.
Abstrak: HIV is a member of retrovirus that especially attacks lymphocytes or white blood cells, known as CD4+ T cells. New T cells created from sources within the body such as the thymus and by proliferation of existing T cells. In this paper, influence of protease inhibitor therapy in HIV dynamics will be analyzed. The influence can be categoried in three models, which are model HIV without drug therapy, model HIV with protease inhibitor and model T cell recovery. In the models, three parameters which are uninfected cells population, infected cells population and virus population are studied. From HIV without drug therapy model it is obtained two types fixed point which are uninfected fixed point and infected fixed point. The stability of fixed point depends on basic reproduction number which is influenceed by the total number of virus produced by a cell during its lifetime. From HIV with protease inhibitor therapy model it is obtained two type fixed points. The stability of fixed point depends on basic reproduction number. Other than influenceed by the total number of virus produced by a cell during its lifetime, basic reproduction number of this model also affected by the effectiveness of a protease inhibitor. Basic reproduction number of this model is smaller than that of model HIV without drug therapy. In the model T cell recovery, new T cells created only from sources within the body, and T cells can be invulnerable to HIV infection after the therapy. From the model it is obtained only one fixed point that is uninfected fixed point. The stability of fixed point depends on basic reproduction number. The total number of virus produced by a cell during its lifetime and the effectiveness of a protease inhibitor determine the basic reproduction number. Basic reproduction number of this model is smallest than that of other models.
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