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Shabri A.,University of Technology Malaysia | Suhartono,Sepuluh Nopember Institute of Technology
Hydrological Sciences Journal | Year: 2012

This paper investigates the ability of a least-squares support vector machine (LSSVM) model to improve the accuracy of streamflow forecasting. Cross-validation and grid-search methods are used to automatically determine the LSSVM parameters in the forecasting process. To assess the effectiveness of this model, monthly streamflow records from two stations, Tg Tulang and Tg Rambutan of the Kinta River in Perak, Peninsular Malaysia, were used as case studies. The performance of the LSSVM model is compared with the conventional statistical autoregressive integrated moving average (ARIMA), the artificial neural network (ANN) and support vector machine (SVM) models using various statistical measures. The results of the comparison indicate that the LSSVM model is a useful tool and a promising new method for streamflow forecasting.Editor D. Koutsoyiannis; Associate editor L. SeeCitation Shabri, A. and Suhartono, 2012. Streamflow forecasting using least-squares support vector machines. Hydrological Sciences Journal, 57 (7), 1275-1293. © 2012 Copyright 2012 IAHS Press. Source

Plack C.J.,University of Manchester | Arifianto D.,Sepuluh Nopember Institute of Technology
Journal of the Acoustical Society of America | Year: 2010

On- and off-frequency compression at the 4000- and 8000-Hz cochlear places were estimated using a new version of the additivity of forward masking (AFM) technique, that measures the effects of combining two non-overlapping forward maskers. Instead of measuring signal thresholds to estimate compression of the signal as in the original AFM technique, the decrease in masker threshold in the combined-masker condition compared to the individual-masker conditions is used to estimate compression of the masker at the signal place. By varying masker frequency it is possible to estimate off-frequency compression. The maskers were 500-Hz-wide bands of noise, and the signal was a brief pure tone. Compression at different levels was estimated using different overall signal levels, or different masker-signal intervals. It was shown that the new AFM technique and the original AFM technique produce consistent results. Considerable compression was observed for maskers well below the signal frequency, suggesting that the assumption of off-frequency linearity used in other techniques may not be valid. Reducing the duration of the first masker from 200 to 20 ms reduced the compression exponent in some cases, suggesting a possible influence of olivocochlear efferent activity. © 2010 Acoustical Society of America. Source

Darmawan M.S.,Sepuluh Nopember Institute of Technology
Magazine of Concrete Research | Year: 2010

Different types of corrosion may arise in steel reinforcement, such as general corrosion, pitting corrosion, hydrogen embrittlement, stress corrosion cracking and corrosion fatigue. However, corrosion of steel reinforcement in reinforced concrete (RC) structures can be classified into two categories: general (uniform) corrosion and pitting (localised) corrosion. In general, concrete researchers use uniform corrosion to study the effect of corrosion on RC structures. This approach is not accurate for concrete structures subjected to chloride attack, which usually experiences pitting corrosion. This paper describes an accelerated corrosion test used to obtain statistical parameters of maximum pit-depths distribution of corroded steel in a RC structure. Using probabilistic analysis, these statistical parameters are combined with statistical parameters of RC beams (i.e. beam dimensions, concrete strength, steel yield strength, cover thickness, workmanship quality, in situ strength factor, model error for flexure and shear and also corrosion rate) to determine the effect of corrosion on flexural and shear strength of RC beams. Using the proposed pitting corrosion model improves service life prediction of RC structures in a chloride environment. © 2010 Thomas Telford Ltd. Source

Semin,Sepuluh Nopember Institute of Technology
International Review of Mechanical Engineering | Year: 2012

In this article, previous work on the application of injector on CNG engines is reviewed. In the review of injector, the spray characteristics, the gas jet structure, the effect of injector nozzle geometry on fuel-air mixing, injector nozzle coefficients of discharge, injector nozzle spray tip penetration and cone angle as well as injector nozzle orifice shapes are outlined. Fuel-air mixing increases as the orifice diameter decreases. This can be a significant advantage for small orifice nozzles. However, multiple orifices are required to meet the desired mass flow rate as orifice diameter decreases. © 2012 Praise Worthy Prize S.r.l. - All right reserved. Source

Cahyadi M.N.,Hokkaido University | Cahyadi M.N.,Sepuluh Nopember Institute of Technology | Heki K.,Hokkaido University
Journal of Geophysical Research: Space Physics | Year: 2013

We studied ionospheric disturbances associated with the two large earthquakes in Sumatra, Indonesia, namely, the 2007 Bengkulu and the 2005 Nias earthquakes, by measuring the total electron contents (TEC) using a regional network of global positioning system (GPS) receivers. We first focus on coseismic ionospheric disturbances (CIDs) of the Bengkulu earthquake (M w 8.5). They appeared 11-16 min after the earthquake and propagated northward as fast as ~0.7 km/s, consistent with the sound speed at the ionospheric F layer height. Resonant oscillation of TEC with a frequency of ~5 mHz continued for at least 30 min after the earthquake. The largest aftershock (Mw 7.9) also showed clear CIDs similar to the main shock. A CID propagating with the Rayleigh wave velocity was not observed, possibly because the station distribution did not favor the radiation pattern of the surface waves. This earthquake, which occurred during a period of quiet geomagnetic activity, also showed clear preseismic TEC anomalies similar to those before the 2011 Tohoku-Oki earthquake. The positive and negative anomalies started 30-60 min before the earthquake to the north and the south of the fault region, respectively. On the other hand, we did not find any long-term TEC anomalies within 4-5 days before the earthquake. Co- and preseismic ionospheric anomalies of the 2005 Nias earthquake (Mw 8.6) were, however, masked by strong plasma bubble signatures, and we could not even discuss the presence or absence of CIDs and preseismic TEC changes for this earthquake. Key Points Bengkulu 2007 and Nias 2005 earthquake ©2013. American Geophysical Union. All Rights Reserved. Source

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