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: Desain dan kinerja unit pemotongan serasah tebu dengan menggunakan pisau tipe reel
Abstrak: The problem of sugarcane trash after harvesting is experienced by the world's sugarcane plantations, including those in Indonesia. Large amount of sugarcane trash left in the field makes difficulties in soil management and plant maintenance. Current practice done by the sugarcane plantations was “burning before soil tillage”. However, the practice of burning cause unwanted impact to the environment and human health. Meanwhile, sugarcane trash still rich of nutrients for the land. Widely studied and has been proven that many sugarcane trash is very useful to increase the soil fertility. The trash size is still long so that it should be reduced to improve composting process. A prototype of reel type trash chopper has been designed and constructed with dimensions of 240 cm width, 268 cm length, and 133 cm height. The prototype was tested on 4 levels of reel rotational speeds (400, 450, 500, and 550 rpm) and 4 levels of trash densities (8, 16, 24, and 32 kg/m3). During the tests, cutting torque and rotational speed of the reel were measured using a torque-meter and a digital tachometer. The output of trash chopping were measured to know the quality of the chopping procces. The prototype chopped up sugarcane trash of about 1.7 - 3.2 cm length, with chopping capacity of 398 kg/hour. Results of the tests showed that cutting torque was in the range of 1.75 to 4.03 kg.m with the average of 2.88 kg.m, and average cutting power was 1.87 hp. Higher trash density caused a higher cutting torque and cutting power, while higher rotational speed caused a lower cutting torque and a higher cutting power. The highest cutting torque was 4.03 kg.m, when chopped sugarcane trash of 32 kg/m3 in trash density on 400 rotational speed. Increasing the rotational speed caused a shorter trash size.
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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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