| Nama Pengarang | : | Ali Arman Lubis, Diana A. Barus, dan Rina Sri W. Simanjuntak |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 77-82 |
| Abstraksi Narasi | : | Concentration and distribution of natural radionuclides (...U, ...Th, ...Ra dan ...K) and anthropogenic ...Cs have been analyzed in soil samples from Taman Nasional Gunung Leuser (TNGL) using gamma spectrometry. Soil samples were collected from 25 locations and the depth of 20 cm using core sampler of 7,8 cm diameter. The mean activites of ...U, ...Th, ...Ra, ...K and ...Cs are (57,99...6,31), (55,08...4,16), (34,59...3,18), (260,79...46,45) and (2,23...0,31) Bq/kg, respectively, and the dose rate is 72,49 nGrey/hour. |
| Nama Pengarang | : | Ruth Melliawati |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 55-60 |
| Abstraksi Narasi | : | Fermentation process by Acetobacter sp. RMG-1using coconut water or pineapple extract as medium yields acetic acid and cellulose. Total concentration of acetic acid obtained was 2,23 mg/ml in the fermentation performed for 168 hours using coconut water and 8,35 mg/ml in the fermentation performed for 96 hours using pineapple extract. The highest acetic acid concentration of 24,79 mg/ml in the fermentation using coconut water was reached after 96 hours, while in the fementation using pineapple extract the highest acetic acid concentration of 4,41 mg/ml was reached after 24 hours. The average production of cellulose in the coconut water medium was 10,02 gram (wet) or equivalent to 1,95 gram dry weight, while in the pineapple extract medium was 11,32 gram (wet) or equivalent to 1,95 gram dry weight. The results of this work showed that acetic acid concentration in coconut water fermentation was higher than in the pineapple extract medium, but cellulose production was higher in pineapple extract medium. |
| Nama Pengarang | : | Rudhito, M. Andy |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 61-70 |
| Abstraksi Narasi | : | We discuss the interpretation of some matrix max-plus algebra R... operations and concepts in graph theory. We show that every matrix A ... R ... corresponds to weighted directed graph and conversely. A formula for the maximum mean weight of the elementary circuit in the presedence graph of A is ....(A) = ......trace(A...) . If matrix A ... R... is irreducible, then A has a unique max-plus algebra eigen value ...(a). |
| Nama Pengarang | : | RMJT Soehakso |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 40-50 |
| Abstraksi Narasi | : | Using examples from quantification theory, the construction of BETH`S semantic tableau is discused in detail. The "semantic" qualification refers to the use of the semantical notions "truth" and "falsity". However, rearrangement of the formulae appearing in the tableau gives a formal proof of the conclusion using step by step inferences starting with the premisses. Moreover, since to each step there corresponds a mechanical derivation rule, the tableau can be transformed into a purely syntactical derivation relying only on the typographical structure of the expressions. BETH also presents an outline of a procedure by which the method can be applied to the axiomatics of mathematical theories. The result of the procedure turns out to be fully in accordance with the celebrated theorem of LOWENHEIM-SKOLEM-GODEL. |
| Nama Pengarang | : | Budi Sugiharto |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 19-26 |
| Abstraksi Narasi | : | Coaldozer is one of the heavy equipments used coal exploitation. Special attention must be given to the coaldozer steering system, because it is usually subected to heavy work. The hydraulic system is the best for this steering, since it can move slowly, has high pressure and can be operated more easily. |
| Nama Pengarang | : | Linggo Sumarno |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 27-39 |
| Abstraksi Narasi | : | In a signal transmission through a medium, additional unwanted signals such as random noise contaminated with the transmitted signal are frequently encontered. If the random noise contents are small, the transmitted signal can be identified easily. However, if they are quite big, the transmitted signal will be very difficult to identify. To overcome this problem, two kinds of random noise filter using Fast Fourier Transform (FFT), which perform processing in the frequency domain, have been designed. The first one is a filter with filter-parameter varying according to the peak of the original signal detected in the frequency domain, whereas the second one is a filter with filter-parameter varying according to the peak of random noise in the frequency domain. A simulation of the above filters has been carried out. It is shown that a badly contaminated signal with random noise can be recovered, so that the original signal can be identified. |
| Nama Pengarang | : | L. Wilardjo |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 62-70 |
| Abstraksi Narasi | : | Wangsness` "recipe" to obtain the field components of guided microwaves in rectangular waveguides, both in the transverse-electric (TE) and transverse-magnetic (TM) modes, is given. So are the TE and TM-mode field components of microwaves in cylindrical waveguides, following the forms given by Paris and Hurd. Then it is shown through derivation, that includes solving Helmholtz` partial differential equation in cylidrical coordinate system, that the Wangsness` "recipe" can be used to get these TE and TM-mode field components of guided microwaves in cylindrical waveguides. Notes are also given on the approximation and the boundary conditions used, and on the application of the latters to determinecylindrical waveguide parameters such as cut-off frequency, inside-the-guide wavelength, phase velocity, etc. |
| Nama Pengarang | : | Y.B. Lukiyanto |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 7-18 |
| Abstraksi Narasi | : | The cross-flow spray washer cooling (SWC) is a direct-contact heat exchanger between cooling and cooled fluid, which are cold water and air respectively. The cold water is sprayed from the top of the SWC, while the air to be cooled is flowed horizontally through the falling water, washing away dusts from the passing air. Like other kinds of heat exchanger, theSWC has its own typical characteristics. The objective of this research is to find out those particular characteristics of the SWC, and to utilize the optimum of its ideasl point of heat transfer. |
| Nama Pengarang | : | Sri Agustini Sulandari |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 71-80 |
| Abstraksi Narasi | : | Holographic interferometry is an accurate method of measuring a very small displacement, i.e. in micrometer (10^6 m or lee) orde. By using this method, fringe patterns are obtained from the interference of light rays scattered from pairs of corresponding points on the illuminated object surfaces before and after the displacement has occurred. Due to its superiority this method is very suitable for length measurements in the rays wave length orde, e.g. the measurement of surface deformation, oscillation amplitude and structure dispalcement in micrometer orde. This paper discusses the holographic recording process of deformation or oscillation being executed, as well as the holographic reconstruction process, and the analysis of the recorded fringe patterns on photographic film. |
| Nama Pengarang | : | R. Soemantri |
| Nama Majalah/Jurnal | : | Sigma Jurnal Sains dan Teknologi |
| Volume / Nomor Edisi | : | - |
| Nomor Halaman | : | 51-61 |
| Abstraksi Narasi | : | Continuous nowhere differentiable functions are usually constructed by uniformly convergent series of continuous periodic functions. This paper discusses a construction by contraction mappings on the space of fractals. |
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