64 research outputs found
Ontology-based recommender system for a learning sequence in programming languages
The same learning process in educational systems could be boring and time consuming for some learners. This problem arises from the lack of personalized learning sequence for learners with different knowledge level. Recommender systems play an important role in assisting the learners to find suitable learning materials and personalized learning sequence. Use of ontology for knowledge representation in knowledge-based recommender systems would facilitate sharing, reuse and common terminology. Since programming concepts have logical relationships among together so, traditional education systems are more stressful and very time-consuming. This paper aims to propose an ontology-based recommender system to present a Personalized Learning Sequence in Programming (PLSP) domain which is depended to learner's knowledge level. A recommender module and, the knowledge base module are integrated together in the proposed framework. The recommender module as the main module in the framework, has three stages which is working based on semantic rules and ontology representation. Evaluation of the system was carried out by comparing the non-recommender system (web-based search) using 32 ICT respondents. Results demonstrate that the participants who used the proposed system spent 1119 seconds to find the suitable learning path in comparison to those who used a non-recommender system (3480 seconds) in the same learning material. It means that learners who follow learning path with PLSP, are more suitable for them. Furthermore, the average mean value of usability test is 4.47, (5 maximum scale) which indicates that the system proved to be useful, was easy to use, and satisfied the users
Optimization of UV-photografting factors in preparation of polyacrylic-polyethersulfone forward osmosis membrane using response surface methodology
Commercial nanofiltration polyethersulfone (NF2) membrane was modified via ultraviolet (UV) photografting to prepare a high-performance forward osmosis (FO) membrane. The optimized condition of grafting parameters was obtained using central composite design (CCD) and response surface methodology (RSM). UV-photografting time and acrylic acid (AA) monomer concentration were the considered variables, while the two RSM responses were water permeate flux and reverse salt diffusion flux (RSD). Quadratic models were established between the responses and the independent parameters using analysis of variance (ANOVA). The membranes were characterized with functional group, morphology and surface roughness. The obtained optimum conditions were 2.81min grafting time and 27.85g/L AA monomer concentration. Under these conditions, a maximum water permeate flux of 1.52±0.04L/m2·h was achieved with an RSD value of 10.09±0.36g/m2·h. The optimized membrane exhibited a higher water flux compared to the unmodified NF2 membrane without any significant change of the RSD value
Factorial design in optimizing parameters for thermoresponsive ionic liquids as draw solution
This study aims to optimize the operating conditions of the forward osmosis (FO) process by introducing thermo-responsive ionic liquids (TRILs) namely 1-butyl-3-methylimidazolium tetrafluoroborate ([Bmim][BF4]) as a draw solution for seawater desalination applications. The influence of the operation parameters, such as the feed and draw flowrate (60â300 ml/min), draw solution concentration (0.6â3.0 M), temperature (25â50 °C), and type of flow with feed concentration using artificial seawater (0.6 M NaCl). The interaction between parameters has been specified using fractional factorial design (FrFD). The draw solution concentration and the interactions between draw and feed flowrate were the most significant factors in achieving high water flux 5.1 LMH. Besides that, the draw flowrate and the interaction of both draw and feed flowrate give high significance toward adverse effects (such as concentration polarization), which is good to obtain low reverse salt at 1.3 gMH. Use the desirability function (DF) to obtain the highest water flux of 5.04 LMH and the lowest reverse salt flux of 1.71 gMH, with a desirability of 0.95. The optimal condition for FO performance is 300 ml/min feed and draw flowrate with 3.0 M draw solution at 25 °C and co-current flow
Characterization of Enzyme Produced from Pseudomonas Putida for BTX (Benzene, Toluene & Xylene) Treatment in Petrochemical Industry Wastewater System
One of the big challenges in petrochemical industries is waste management. Currently, huge money was spending on the disposal of the waste. Industries are trying hard to find an alternative method to reduce the cost and improve the effectiveness of current waste management including treatment efficiency. Most of petrochemical wastes are containing benzene, toluene and xylene (BTX) which are very harmful to environment and living organisms. Common method used to separate the BTX from the waste are by using liquid-liquid and stripping process. One of the alternative to treat BTX is biological treatment method that used the natural capability of microorganisms to degrade to less harmful product is been applied. Some of examples
are Pseudomonas Putida. (P. putida), Rhizobium, and Agrobacterium. P. putida is selected in this study for the
biological treatment of BTX in petrochemical wastewater because it can produce an enzyme that has the
capability of breakdown the aromatic hydrocarbon to carbon dioxide (CO2) and water (H2O). The main
objective of this study is to produce and extract the enzymes produce, characterised the enzymes. This study also
to investigate the effect of different concentration on the treatment as well as the growth of the bacteria.
The enzyme is purified using salt precipitation and analysed using SDS_PAGE technique. UV-Vis is used to study the growth of the bacteria in the culture stock by measuring its optical density. The concentration of BTX was
varied to determine the effect of the concentration on the percentage removal and the growth of P. putida.
Enzymes detected or purified in this study was benzene reductase. Other expected enzymes were not able to be
purified or analysed. It was found that in this experimental study, the removal of benzene is at 74% to 80%. The
removal of toluene is at 62% to 75%. The removal of xylene is at 23% to 42%. Increasing the concentration of contaminants will reduce the removal capabilities
A Measurement of Time-Averaged Aerosol Optical Depth using Air-Showers Observed in Stereo by HiRes
Air fluorescence measurements of cosmic ray energy must be corrected for
attenuation of the atmosphere. In this paper we show that the air-showers
themselves can yield a measurement of the aerosol attenuation in terms of
optical depth, time-averaged over extended periods. Although the technique
lacks statistical power to make the critical hourly measurements that only
specialized active instruments can achieve, we note the technique does not
depend on absolute calibration of the detector hardware, and requires no
additional equipment beyond the fluorescence detectors that observe the air
showers. This paper describes the technique, and presents results based on
analysis of 1258 air-showers observed in stereo by the High Resolution Fly's
Eye over a four year span.Comment: 7 pages, 3 figures, accepted for publication by Astroparticle Physics
Journa
Search for Point Sources of Ultra-High Energy Cosmic Rays Above 40 EeV Using a Maximum Likelihood Ratio Test
We present the results of a search for cosmic ray point sources at energies
above 40 EeV in the combined data sets recorded by the AGASA and HiRes stereo
experiments. The analysis is based on a maximum likelihood ratio test using the
probability density function for each event rather than requiring an a priori
choice of a fixed angular bin size. No statistically significant clustering of
events consistent with a point source is found.Comment: 7 pages, 7 figures. Accepted for publication in The Astrophysical
Journa
Search for Correlations between HiRes Stereo Events and Active Galactic Nuclei
We have searched for correlations between the pointing directions of
ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye
experiment and Active Galactic Nuclei (AGN) visible from its northern
hemisphere location. No correlations, other than random correlations, have been
found. We report our results using search parameters prescribed by the Pierre
Auger collaboration. Using these parameters, the Auger collaboration concludes
that a positive correlation exists for sources visible to their southern
hemisphere location. We also describe results using two methods for determining
the chance probability of correlations: one in which a hypothesis is formed
from scanning one half of the data and tested on the second half, and another
which involves a scan over the entire data set. The most significant
correlation found occurred with a chance probability of 24%.Comment: 13 pages, 1 table, 5 figure
An upper limit on the electron-neutrino flux from the HiRes detector
Air-fluorescence detectors such as the High Resolution Fly's Eye (HiRes)
detector are very sensitive to upward-going, Earth-skimming ultrahigh energy
electron-neutrino-induced showers. This is due to the relatively large
interaction cross sections of these high-energy neutrinos and to the
Landau-Pomeranchuk-Migdal (LPM) effect. The LPM effect causes a significant
decrease in the cross sections for bremsstrahlung and pair production, allowing
charged-current electron-neutrino-induced showers occurring deep in the Earth's
crust to be detectable as they exit the Earth into the atmosphere. A search for
upward-going neutrino-induced showers in the HiRes-II monocular dataset has
yielded a null result. From an LPM calculation of the energy spectrum of
charged particles as a function of primary energy and depth for
electron-induced showers in rock, we calculate the shape of the resulting
profile of these showers in air. We describe a full detector Monte Carlo
simulation to determine the detector response to upward-going
electron-neutrino-induced cascades and present an upper limit on the flux of
electron-neutrinos.Comment: 13 pages, 3 figures. submitted to Astrophysical Journa
A Likelihood Method for Measuring the Ultrahigh Energy Cosmic Ray Composition
Air fluorescence detectors traditionally determine the dominant chemical
composit ion of the ultrahigh energy cosmic ray flux by comparing the averaged
slant depth of the shower maximum, , as a function of energy to the
slant depths expect ed for various hypothesized primaries. In this paper, we
present a method to make a direct measurement of the expected mean number of
protons and iron by comparing the shap es of the expected
distributions to the distribution for data. The advantages of this method
includes the use of information of the full distribution and its ability to
calculate a flux for various cosmic ray compositi ons. The same method can be
expanded to marginalize uncertainties due to choice of spectra, hadronic models
and atmospheric parameters. We demonstrate the technique with independent
simulated data samples from a parent sample of protons and iron. We accurately
predict the number of protons and iron in the parent sample and show that the
uncertainties are meaningful.Comment: 11 figures, 22 pages, accepted by Astroparticle Physic
A Study of the Composition of Ultra High Energy Cosmic Rays Using the High Resolution Fly's Eye
The composition of Ultra High Energy Cosmic Rays (UHECR) is measured with the
High Resolution Fly's Eye cosmic ray observatory (HiRes) data using the Xmax
technique. Data were collected in stereo between 1999 November and 2001
September. The data are reconstructed with well-determined geometry.
Measurements of the atmospheric transmission are incorporated in the
reconstruction. The detector resolution is found to be 30 g cm^-2 in Xmax and
13% in Energy. The Xmax elongation rate between 10^18.0 eV and 10^19.4 eV is
measured to be 54.5 +/- 6.5 (stat) +/- 4.5 (sys) g cm^-2 per decade. This is
compared to predictions using the QGSJet01 and SIBYLL 2.1 hadronic interaction
models for both protons and iron nuclei. CORSIKA-generated Extensive Air
Showers (EAS) are incorporated directly into a detailed detector Monte Carlo
program. The elongation rate and the Xmax distribution widths are consistent
with a constant or slowly changing and predominantly light composition. A
simple model containing only protons and iron nuclei is compared to QGSJet and
SIBYLL. The best agreement between the model and the data is at 80% protons for
QGSJet and 60% protons for SIBYLL.Comment: 52 pages, 27 figures. Revised Fig. 10 caption, improved Fig. 23,
resubmitted to ApJ. (Previously revised to address referee's comments.)
(Originally 37 pages, 13 figures. Submitted to ApJ
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