| Nama Pengarang | : | Mungkasi, Sudi |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 39 - 46 |
| Abstraksi Narasi | : | The paper discusses the lyapunov- second method (the direct method) a method for studying the stability of a solution, which is very different from the lyapunov- frist method (the method of linearization). Lyapunov- second method is formulated from the principle for the stability of a mechanical sytem:"Amechanical sytem, whith is in a stte where its potential energy has an isolated minimum, is in a state of stable equilibbrium: Starting from this principle, ideas of stability were generalized. Defferential equition, which have not been characterize apriori by a potential energy or a quantity energy in general, are studied. To analyze the stability of trivial solution, the lyapunov- fungtion will be introduced. |
| Nama Pengarang | : | Mardi Santoso, Musbihatul Hidayah, Joseph J. Brophy |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 145-147 |
| Abstraksi Narasi | : | Indonesian tea tree oil was isolated from the fresh leaves of Melaleuca alternifolia by modified simultaneous distillation-extraction for six hours in 0.42% (w/w) yield. The oil was colorless, and its aroma similar to its leaves. Gas chromatography and gas chromatography/mass spectrometry analysis of the oil has identified nine monoterpene hydrocarbons, seven sesquiterpene hydrocarbons, seven oxygenated monoterpenes, and eight oxygenated sesquiterpenes. Terpinen-4-ol (46.51%), p-cymene (19.23%), and y-terpinene (6.77%) were found as the major components of the oil. |
| Nama Pengarang | : | Sulandari S. A. , Karyono dan A. B. Setio Utomo |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 127-133 |
| Abstraksi Narasi | : | An optogalvanic spectroscopy of neon and barium atoms in a Ba/Ne hollow cathode discharge lamp has been investigated usingh a pulsed tunable Piridin-1 + DCM dye laser which is pumped by a pulsed Nd: YAG laser. The wavelength covering of the dye laser is from 6266 A to 6719 A. The optogalvanic signal is detected on the wavelength of 6266,2 A, 6304,5 A, 6334,6 A, 6383,2 A, 6402,0 A, 6507,2 A, 6532,7 A, 6599,8 A, 6678,5 A, 6718,5 A for neon on a 3.0 mA of the current discharge, and 6603,81 A, 6638,30 A, 6653,48 A, 6666,11 A, 6694,58 A for barium atom on a 18.0 mA of the current discharge. On certain resonance transitions, the optogalvanic temporal signal depends on the various discharge current in the discharge lamp caused by the characteristic of the energy level involved in the transitions. |
| Nama Pengarang | : | M.Andy Rudhito |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 157-164 |
| Abstraksi Narasi | : | We discuss the solution of max-plus system of linear equations ....and an optimization problem related to this system. The greatest subsolution of .....exists and is given..... |
| Nama Pengarang | : | Vonny dan L. Hartanto Nugroho |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 171-177 |
| Abstraksi Narasi | : | Wild silk moth Attacus atlas (L.) is categorized as polyphagous insect, consuming different familia of plants such as keben, gempol, sirsak and mahoni. Previous researches reported that there was a difference in larval eating behaviour among these four foodplants. Larval A. atlas is more gluttonous in eating keben and has the shortest larval phase compared to other food plants. This research is aimed to investigate the comparison of epidermis surface conditions as the first contact place between larval and its food plant and the reason why keben leaf is more preferred than the other leaves as food plant based on the anatomical point of view. This research used Scanning Electron Microscopy to obtain epidermis surface texture. The results show that keben, which is the most preferred leaf, has soft structure, meaning that it has thin cell wall, bigger size of epidermal cells, and no trichomes. |
| Nama Pengarang | : | Linggo Sumarno dan Evy Harjanti |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 117-125 |
| Abstraksi Narasi | : | This research was carried out to recognize human speech using Kohonen neural network trained in an unsupervised manner. There are four Indonesian speech patterns to be recognized, namely: `Maju`, `Kiri`, and `Kanan`, which were recognized by the neural network after feature extraction based on speech coding. The simulation of the neural network yields recognition rate up to 78.75 % for untrained patterns. |
| Nama Pengarang | : | Supriyanto, Mudjijana, Tjipto Sujitno |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 91-99 |
| Abstraksi Narasi | : | The surface hardness of material can be improved through appropriate surface coating technique. There have been many various ways of surface coating to obtain optimum result. On way of surface coating is sputtering. Thin layer deposition of TiN + AIN (Titanium Nitride + Aluminium Nitride) material with Sputtering is a modern coating process for improving material properties. The objective of this research is to obtain optimum result on surface hardness and lifetime of high speed steel (HSS) cutting tools. Fourty pieces of (9.4x9.4x11)mm specimens are coated with TiN + AIN with variety in temperature, duration, and gas pressure ratio. Micro Vickers 10 gf is used to test the surface hardness. Initial hardness of the HSS materials is VHN 847.9. Optimum hardness of VHN 1756.2 is reached at 150 derajad C after 2 hour process at 3.10...: 3.10... kg/cm persegi pressure ratio of Ar : N2. HSS cutting tool with TiN + AIN deposition is used to cut 1 mm low carbon steel with 0.084 mmrev feeding speed and 35, 45, dan 48 m.min cutting speed. The result of the research shows that the cutting tool with TiN + AIN coating increases 107% in hardness and 80-100% in lifetime compared to those without the TiN + AIN coating. |
| Nama Pengarang | : | Damar Widjaja |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 107-115 |
| Abstraksi Narasi | : | It has been widely known that active element pattern of phased array antennas, as a result of one element which is excited and the others are terminated by matching loads, can be expressed in terms of scaterring matrix parameter of an array. In this paper, the relationship will be reversed, with the intention that the scattering parameter of all elements of the phased array can be obtained from the active element pattern. In addition, an active input impedance of all elements of the array that are fully excited can also be obtained from the active element array. |
| Nama Pengarang | : | Saifatur Rusli, Suparto |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 101-105 |
| Abstraksi Narasi | : | In general, reflection seismic method has capability to represent sub-surface in time domain. Seismic cross-section that depicts the formation of sub-surface ussually uses time domain in the TWT (Two Way Times) format. In the process of seismic data acquisition, seismic wave propagates in down-going and upgoing manner so that the obtained results from data processing are in the format of TWT seismic vs shot points. This paper describes the construction of depth-structure map of Kujung Formation in the East Java Sea as part of exploration activities of oil companies in Indonesia. Manual data is picked from seismic cross-section and crossed with the Vrms data of three wells in the exploration location. TWT shelf-edge map of Kujung Formation is divided into two parts and the results are crossed with velocity-structure map using Geoframe CPS-3 software, by which the depth-structure of Kujung Formation shelf-edge is obtained. One of the objectives of this map construction is to obtain more real visualization of sub-surface by using depth domain approach which can be used in exploration activities of oil companies in Indonesia. |
| Nama Pengarang | : | Herry Pribawanto Suryawan |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 165-170 |
| Abstraksi Narasi | : | The rational number system ... and the real number system ... are borth ordered fields. In ... there are Cauchy sequences which do not converge, in ... however all Cauchy sequences do converge. This property, which distinguishes ... from ... , is called completeness property. It will shown in this paper that there is essentially only one complete ordered field. The alternate form of completeness which involves the least upper bound (supremum) concept will be used in this discussion. |
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