Judul: Cutting power and cutting quality of sugarcane stumps on several blade shapes and cutting pitchs
Abstrak: A study was conducted in order to get an optimum cutting blade design for sugarcane stump cutting. A test apparatus consisting of a rotary cutting unit, sugarcane stump holder-driver was used for the experiments. Three types of blade tip design were tested, and then cutting power and cutting quality were measured in the experiments. A blade tip design with gradual increase of radius from 30 cm to 30.6 cm was proposed, and compared to two other conventional blade tip designs. The rotary cutting unit with 8 blades was inclined 45o from horizontal and rotated at 550 rpm. The cutting radius was 30 cm. The cane was held vertically and moved to the cutting unit at forward speed of 0.3 m/s and 0.5 m/s. Test results showed that there was no significant difference of cutting power among the three types of tested blade. However, bigger cutting pitch produced a bigger cutting power than that of smaller cutting pitch. The average cutting power at forward speed of 0.3 m/s and 0.5 m/s was 76 Watt and 94 Watt respectively. The blade with gradual increase of radius produced the best cutting quality.
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Judul: Design and Working Performance of Sugar Cane Stubble Shaver Powered by Four Wheel Tractor
Abstrak: Cutting of sugar cane stubbles is an important activity in ratoon sugar cane production system. Stubble shaver powered by four wheel tractor, has been used in several sugar plantation in Indonesia. However, there were some problems encountered the application such as high power consumption; excessive blade tip wear; and low cutting quality of the stalks. The objectives of this research were: 1) to design a stubble shaver powered by PTO of four wheel tractor and 2) to analyze the influences of blade tip design, forward speed, rotation speed and tilt angle of the rotary cutting unit on cutting power and cutting quality. A sugar cane stubble shaver consisting of a rotary cutting unit with 8 blades rotated by tractor PTO, was designed and constructed. The prototype was tested to measure its working performance. The test was conducted using two types of blade tip design, on two levels of working speed (0.3 and 0.5 m s-1), two levels of rotational speed (500 and 850 rpm), and two levels of blade tilt angle (45o and 60o). The test result showed that the blade tip design with increased tip radius provided a lower working torque than the conventional blade tip design with constant tip radius. The lowest working torque was provided by operating condition of working speed of 0.5 m s-1, blade rotating speed of 850 rpm and tilt angle of 60o. The average working torque on that condition was 22.46 Nm. However, 0.3 m s-1 working speed, at 850 rpm rotating speed and 45o tilt angle provided a better stubble cutting quality than the other working condition.
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Judul: Peranan leukosit dalam sistem imun ikan teleost
Abstrak: Menurut Lagler, Bardach, Miller dan Passino (1977) leukosit merupakan salah satu jenis sel darah. Leukosit ikan terbagi menjadi leukosit granular dan leukosit agra nular. Selanjutnya leukosit granular terdiri dari eosin ofil, basofil dan neutrofil, sedangkan leukosit agranul- ar terdiri dari monosit, limfosit dan trombosit. Dalam keadaan normal leukosit ikan jumlahnya berkisar antara 3 20.000-150.000 butir tiap mm (Lagler et al, 1977). Eosinofil dan basofil Atlantic salmon dapat ditemu- kan dalam darah perifer dan limpa. Namun jumlah terba- nyak ditemukan dalam pronefros (Anderson, 1974). Keada- an demikian juga ditemukan pada neutrofil trout (Ander- son, 1974), plaice (Ellis, 1988b) dan carp (Suzuki dan Hibiya, 1988). Selanjutnya limfosit teleost dapat dite- mukan dalam pronefros (Anderson, 1974; Ellis, 1988b), timus (Anderson, 1974), darah perifer (Conroy, 1972) dan limpa (Anderson, 1974). Sedangkan makrofag dapat ditemu kan dalam jumlah sedikit pada limpa dan darah perifer (Conroy, 1972) dan dalam jumlah banyak pada pronefros (Anderson, 1974). Fagositosis bakteri oleh eosinofil telah dilaporkan pada goldfish (Rijkers, 1980) dan carp (Pliszka, 1939 da lam Rijkers, 1980). Sedangkan Bell (1976) melaporkan fagositosis bakteri oleh neutrofil. Makrofag ikan dila- porkan mampu memfagositosis bakteri (Anderson, 1974; Bell, 1976; McArthur dan Fletcher, 1985), partikel kar- bon (Anderson, 1974) dan runtuhan sel (Klontz et al, 1966 dalam McArthur dan Fletcher, 1985). Selanjutnya te lah dilaporkan pula bahwa trombosit ikan mempunyai sifat fagositik (Yokohama, 1960; Fange, 1968; Ferguson, 1976 dalam Rijkers, 1980). Sedangkan limfosit ikan berperan dalam respon imun yang diperantarai sel dan respon imun humoral (Rijkers, 1980; Ellis, 1988b). Respon imun ikan dipengaruhi oleh beberapa faktor, yaitu: suhu (Ellis, 1982; Rijkers, 1980), polutan (Rij kers, 1980; Ellis, 1988a), penyinərən (Rijkers, 1980), makanan (Ellis, 1988a) dan antibiotik (Rijkers, 1980)….
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