Judul: Sistem antrian M/G/I, M/M/I dan M/D/I
Abstrak: Sistem antrian yang dipelajari dalam karya ilmiah ini adalah sistem antrian M/G/1 tanpa waktu libur server dan dengan waktu libur server. M menyatakan pola kedatangan bersifat markov (proses kedatangan costumer menyebar Poisson dan waktu antar kedatangan menyebar exponensial), G menyatakan pola pelayanan bersifat umum (General) dan 1 menyatakan banyaknya server. Disiplin pelayanan yang digunakan adalah FIFO (First In First Out) dan kapasitas sistem tak terbatas, artinya tidak ada batasan untuk jumlah costumer yang masuk. Tujuan dari karya ilmiah ini adalah mempelajari penentuan nilai rata-rata dari banyaknya costumer di sistem, nilai rata-rata panjang antrian dan nilai rata-rata dari waktu antrian pada sistem antrian M/G/1 tanpa waktu libur server dan dengan waktu libur server. Diperoleh bahwa nilai rata-rata dari banyaknya costumer di sistem baik pada sistem antrian M/G/1 dengan waktu libur server ataupun tanpa waktu libur server meningkat secara linear sesuai dengan ragam dari waktu pelayanan. Nilai rata-rata dari banyaknya costumer sistem antrian M/G/1 dengan waktu libur server lebih banyak daripada nilai rata-rata dari banyaknya costumer pada sistem antrian M/G/1 tanpa waktu libur server. Begitu juga dengan nilai rata-rata dari panjang antrian dan waktu antriannya.
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Judul: Antrian bertipe M/G/I/N dengan server yang memiliki waktu pelayanan dan waktu libur
Abstrak: Masalah yang diamati adalah sebuah antrian bertipe M/G/1/N dengan server yang memiliki waktu libur dan waktu pelayanan. Masalah ini banyak terjadi terutama pada sistem produksi, sistem komputer dan komunikasi dimana server memiliki waktu libur sebagai akibat harus menjalankan perawatan (pada mesin produksi), atau harus melayani konsumen sekunder maupun harus mengerjakan pekerjaan yang lain. Fokus dari permasalahan adalah ingin mengevaluasi kinerja server sehingga dapat dilakukan efisiensi. Dengan memperoleh sebaran panjang antrian maka diharapkan dapat dilakukan penilaian terhadap kinerja server . Melalui beberapa langkah matematis, dapat disimpulkan bahwa peluang ada j costumer di sistem bergantung pada : (i)Peluang pada steady-state bahwa ada j costumer di sistem setelah kepergian seorang costumer akibat selesai dilayani ; (ii)Peluang bahwa ada costumer yang datang selama waktu libur server ; (iii)Laju kedatangan costumer ; (iv)Nilai harapan waktu libur dan waktu pelayanan; (v)Peluang tidak ada costumer di sistem setelah kepergian seorang costumer.
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Judul: Pengaruh Jumlah Bahan Pretanning dan Minyak Biji Karet (Hevea brasiliensis) Terhadap Mutu Kulit Samoa. Di
Abstrak: Animal hides or skins are the most valuable by product of the meat industry. Most of those hides are converted into leather by leather tanning process. Chrome based tanning is the most popular tanning process. At the chrome based tanning process, a lot of amount chrome are throw away into the environment that make a significant effect to the biological and ecological environment damaged. Due to concerns over the use and disposal of chromed tanned leather, the leather industry is now facing increasing scrutiny over its use of chrome as tanning agent. The use of non-chrome tannages has gradually become pre-eminent to producing leather, particularly in the European automotive leather markets. Chamois leather is one of leather product. It is produced from animal hides/skins by oil tanning process, usually with fish oil. High price and odour problems to the chamois leather that produced using fish oil motivate to do some research to solve that problems. Rubber seed oil is an oil that predicted can substitute fish oil. Pretanning process is needed to increase the oil penetration and protects the pelt from putrefying during oxidation periods (Khrisnan et al., 2005). Relugan GT 50 is the agent that used on this research. Relugan GT 50 is an aldehyde tanning agent, produced by BASF. This research was aimed to find out the effects of Relugan GT 50 concentration (offer) and rubber seeds (Hevea brasiliensis) oil to the chamois leather’s quality. Beside that, this research is also aimed to decide the best combination of the factors to produce chamois leather also to know the chamois leather characteristics. The preliminary research was carried out by analyzing the rubber seed’s kernel and eggshell as well as physico-chemical properties of the rubber seed oil. The main research was done by tanning the skin with Relugan GT 50 in concentrations of 1.5, 3.0 and 4.5% followed by rubber seed oil concentrations of 10, 20, and 30%. The experimental design used was completely randomize factorial design. The preliminary research shows that rubber seed’s kernel was 49% and rubber seed’s eggshell was 51%. The rubber seed’s oil characterstics were density of 0.94 (g/cm3), viscosity of 48,4 centistokes, colour of 2713 PtCo units, inodine value 113 g iod/ 100 g, peroxide value of 24 miliequivalent/1000 gram oil, acid value of 15 mg KOH/g oil and FFA content of 5.8%. The research shows that Relugan GT 50 concentration significantly affected shrinkage temperature (Ts) and pH; rubber seed oil concentration significantly affect the organoleptic properties of the leather. The optimum conditions for the tanning were Relugan GT of 3.0% concentration and 10% rubber seeds oil. The physical properties of the leather were shrinkage temperature of 75oC, thickness of 0.92 mm, tensile strength of 21.50 N/mm2, elongation at break of 144%, tear strength of 55.77 N/mm, water absorption of 266% (2 hours) and 299% (24 hours). The chemical properties were oil content of 2.5%, ash content of 1.2% and pH of 8. The organoleptic properties were softness of 7–8, colour of 8-9, and odour of 8-9.
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