| Nama Pengarang | : | PK. Purwadi |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 63-71 |
| Abstraksi Narasi | : | The aim of this research is to find out the temperature distribution in a process of heat transfer involving phase changes. The research was carried out by using vegetable oil flowing in vertical plates. The plate wall temperature is below the vegetable oil freezing temperature. The study was done by varying the oil flow rate at 500 ml/minute, 700 ml/minute, and 1000 ml/minute. The appropriate mathematical model was chosen based on the one-dimensional heat diffusion equation. The results of the research show that (1) the maximum deviation of the laboratory experiment from the numeric computation is less than 20%; (2) the explicit method cannot be applied, whereas the implicit and Crank Nicolson methods yield similar outcomes. |
| Nama Pengarang | : | Lusia Krismiyati Budiasih |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 1-9 |
| Abstraksi Narasi | : | Bell number (Bn), the number of ways a set of n elements can be partitioned into nonempty subsets, can be evaluated both deterministically and probabilistically. From deterministic aspect, it can be defined by the sum of the n Stirling number of the second kind or using Dobinski`s formula. From a probabilistic perspective, the series on the Dobinski`s formula represents the n pangkat th moment of the Poisson distribution with mean 1. |
| Nama Pengarang | : | DS. Bambang Soelistijanto |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 51-61 |
| Abstraksi Narasi | : | Network security has become the main issues in network computings. Firewall system is one of the most popular methods in network security system. A firewall is a components or a set of components that restricts access between a protected network and the internet, or between sets of networks. Unfortunately, building a protected network needs a lot of money, while in many cases the security throughput still cannot cope with the administrator`s needs. One method in network security is building a bastian host (host based security). A bastion host is a computer that must be highly secured in secure or non-secure networks. TCP port has become one of the important things on low-level protocol details that an attacker usually uses to establish connection to an attacked host. In TCP/IP networks, a port represents an endpoint in the establishment of a connection between computers. By knowing the status of TCP port, the security level of the protected host can be detected quickly. |
| Nama Pengarang | : | Tjandrawati, M.M. Yetty, DS. Bambang Soelistijanto, Lusia Kismiati Budiasih, PK Purwadi, Joni Agustian, Spillane, James J., Santoso, Mardi, Ridowati Gunawan, Henry P. Panggabean, H. Harsoyono, Antonio Sergio B. Sombra |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 17-27 |
| Abstraksi Narasi | : | Butylhidroxsianisol (BHA) which belongs to synthetic antioxidant class has been widely used in food and medicine productions. The regulation concerning BHA applications has been established since its carcinogenic effects were revealed. The aim of this study is to analyse both qualitatively and quantitatively the BHA presence in some cooking oils using High Performance Liquid Chromatography (HPLC) method. BHA samples were obtained by extraction process of cooking oil using hexane saturated with acetonitrile (1:1). BHA contents were subsequently determined using HPLC-UV 280nm. Standard solution series of BHA of 20, 40, 60, 80, and 100 ppm were injected and BHA characteristic peaks were displayed at retention time of 15 minutes. The results of four samples of analysed cooking oil show that two samples are suspected of having BHA content as indicated in their chromatogram profiles. |
| Nama Pengarang | : | Reny Kusumastuti |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 109-115 |
| Abstraksi Narasi | : | Endosulfan is a commonly used cyclodiene organochlorine pesticide. This study explores the effects of endosulfan on retinyl in sera, body weight, relative liver weight (the liver to body weight ratio), and histopathological apperance of the liver. Two-month-old male Wistar strain rats were divided into four groups. The treatment grups received endosulfan orally at a rate of 0.6 (group II), 1.2 (group III) and 2.4 (group IV) mg/kg body weght/day for 60 days, whereas control animals (group I) received sterile water. Retinyl palmitate levels in sera were analzes on the day before treatment, on 30 and 60 days after the first treatment. Body weight were also measured at 0, 20, 40 and 60 days after first treatment. Histopathological appearance of the livers and relative liver weights were analyzed after necropsy. Variance analysis shows that the treatment of endosulfan did not significantly (p>0.05) influence changes in retinyl palmitate serum levels, but endosulfan supplementation significantly (p |
| Nama Pengarang | : | A. Bayu Primawan |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 185-191 |
| Abstraksi Narasi | : | Intranet technology as an application of Internet Protocal within a Local Area Network (LAN) has been utilized to deliver voice using Voice over Internet Protocal technology. A LAN-based PBX system combines different circuit-switching networks into a single packet-switching network. Designing a LAN-based PBX system is started by line and port calculation to determine the number of computer hardwares, i.e. the server and gateway. The next step is to design the interest network within the local IP numberinga and the setup scenario of call and connection numbering for the telephone handset or users. |
| Nama Pengarang | : | Hanoch J. Sohilait |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 135-139 |
| Abstraksi Narasi | : | The synthesis of ester formate compounds from eugenol and methyleugenol has been achieved through conversion of allyl group to ester group. The addotion reaction of methyleugenol with formic acid yields 1-(3.4-dimethoxyphenyl)-2-propyl formate (56,17%), and the addition reaction of eugenol with formic acid produces two compounds of eugenyl formate (55.47%), namely 1-(4-hydroxy-3-methoxyphenyl)-2-propyl formate and 1-(4-hidroxy-3-methoxphenyl)-1 propyl formate. The structure elucidations of these products were analyzed using FTIR, pang 1 H-NMR, pangkat 13C-NMR, and MS. |
| Nama Pengarang | : | Damar Wijaya |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 171-183 |
| Abstraksi Narasi | : | The mobile communication market has been going through a remarkable increase in the volume of demand as well as in the quality requirements. The limited resource is the available freaquency spectrum. In GSM networks, frequency reuse has been the basic tool for optimising the spectrum management. This method is sometimes insufficient for the most congested networks in the urban area. Frequency Hopping (FH) is one of the methods that allow one to expand the available capacity of mobile networks or to improve the quality of service. Frequency hopping is a technique to ensure the secrecy of the communication and combat jamming. It has been included in GSM specification to deal with two specific problems, which affect transmission quality, namely multipath fading and interference. Moreover, it will significantly increase system capacity. The process to cope with multipath fading is referred as Frequency Diversity, and the effect of interference handling is called interference Averaging. Implementataion of frequency hopping technique in the mature GSM network causes a significant improvement in some parameters of signal quality and system capacity such as reduction of frame erasure rate from 25% to 6%, reduction of dropped call from 2,6% to 2,4% and tighter frequency reuse factor from 4/12 to 2/6 - 3C(FH). |
| Nama Pengarang | : | I Gusti Ketut Puja , Mudjijana, Tjipto Suyitno |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 151-162 |
| Abstraksi Narasi | : | The object of this study is to investigate the effects of testing temperature on fatigue endurance of nitrided-low carbon steel shaft. Materials were machined to form fatigue specimens according to ASTM E466 standard. Nitriding process of the tasted materials was conducted by nitrogen ion implantation method using ion accelerator in P3TM BATAN Yogyakarta. The fatigue endurance test was conducted on specimen with and wthithout implantation. The ion implantation specimen is tested with rotary bending machine for fatigue endurance using three variations of testing temperature. The results of study show that nitriding process with nitrogen ion implantation changes materials hardness, surface coarse and fatigue endurance. The micro structure observation with SEM shows that a white layer of 1.92 Myu-m iron-nitride is formed on steel shaft surface, crystal granules become clearer than the original phase, and the surface coarse is lower. The fatigue endurance of nitrided steel shaft becomes better in terms of presence of fatigue endurance limit of about 18%. In the nitrided steel shaft, the increase in test temperature up to 300 derajad Celcius increases the fatigue endurance. |
| Nama Pengarang | : | Kadarwati Budihardjo, Etty Sumiatl |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 117-125 |
| Abstraksi Narasi | : | The aim of this study is to find out the best kind, dosage, and spraying time of various plant growth regulators on Gondol tomato cultivar. The research was conducted at the experimental garden of the Research Institute for Vegetable in Lembang by applying a Factorial Rendomized Block Design to test 21 treatment combinations with 3 replications. The first factor is three intervals of spraying time of plant growth regulators, and the second factor is three levels of dosage (0.1, 1.5 and 2.5 mill pangkat -1 respectively) of Dekamon and Nasuleaf plant growth regulators and the control. Results of this experiment shows that foliar feeding with 1.5 days after transplant is the best treatment for Gondol tomato cultivar, in terms of the quality and storange life of tomato fruit produced. |
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