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Appl. Sci., Volume 2, Issue 3 (September 2012), Pages 566-681

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Research

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Open AccessArticle Determination of Morphological Parameters of Supported Gold Nanoparticles: Comparison of AFM Combined with Optical Spectroscopy and Theoretical Modeling versus TEM
Appl. Sci. 2012, 2(3), 566-583; doi:10.3390/app2030566
Received: 25 April 2012 / Revised: 11 June 2012 / Accepted: 15 June 2012 / Published: 2 July 2012
Cited by 2 | PDF Full-text (826 KB) | HTML Full-text | XML Full-text
Abstract
The morphology of small gold particles prepared by Volmer–Weber growth on sapphire substrates have been investigated by two different characterization techniques. First, by non-extensive atomic force microscopy (AFM) in combination with optical spectroscopy and modeling of the optical properties using a theoretical model,
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The morphology of small gold particles prepared by Volmer–Weber growth on sapphire substrates have been investigated by two different characterization techniques. First, by non-extensive atomic force microscopy (AFM) in combination with optical spectroscopy and modeling of the optical properties using a theoretical model, recently developed in our group. Second, by extensive transmission electron microscopy (TEM). Comparing the results obtained with both techniques demonstrate that for small gold nanoparticles within the quasistatic limit, the morphological properties can be precisely determined by an appropriate theoretical modeling of the optical properties in combination with simple AFM measurements. The apparent mean axial ratio of the nanoparticles, i.e., the axial ratio that corresponds to the center frequency of the ensemble plasmon resonance, is obtained easily from the extinction spectrum. The mean size is determined by the nanoparticle number density and the amount of deposited material, measured by AFM and a quartz micro balance, respectively. To extract the most probable axial ratio of the nanoparticle ensemble, i.e., the axial ratio that corresponds to the most probable nanoparticle size in the ensemble, we apply the new theoretical model, which allows to extract the functional dependence of the nanoparticle shape on its size. The morphological parameters obtained with this procedure will be afterwards compared to extensive TEM measurements. The results obtained with both techniques yield excellent agreement. For example, the lateral dimensions of the nanoparticles after deposition of 15.2 × 1015 atoms/cm2 of gold has been compared. While a mean lateral diameter of (13 ± 2) nm has been extracted from AFM, optical spectroscopy and modeling, a value of (12 ± 2) nm is derived from TEM. The consistency of the results demonstrate the precision of our new model. Moreover, since our theoretical model allows to extract the functional dependence of the nanoparticle size and shape, a relatively simple analysis is sufficient for a full characterization of small noble metal nanoparticles. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessArticle Assessment of Heavy Metal Contamination of Agricultural Soil around Dhaka Export Processing Zone (DEPZ), Bangladesh: Implication of Seasonal Variation and Indices
Appl. Sci. 2012, 2(3), 584-601; doi:10.3390/app2030584
Received: 20 April 2012 / Revised: 11 June 2012 / Accepted: 12 June 2012 / Published: 2 July 2012
Cited by 27 | PDF Full-text (1394 KB) | HTML Full-text | XML Full-text
Abstract
Intense urbanization, large scale industrialization and unprecedented population growth in the last few decades have been responsible for lowering environmental quality. Soil contamination with metals is a serious concern due to their toxicity and ability to accumulate in the biota. The present work
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Intense urbanization, large scale industrialization and unprecedented population growth in the last few decades have been responsible for lowering environmental quality. Soil contamination with metals is a serious concern due to their toxicity and ability to accumulate in the biota. The present work assessed the heavy metal contamination of agricultural soil in the close vicinity of the Dhaka Export Processing Zone (DEPZ) in both dry and wet seasons using different indices viz., index of geoaccumulation (Igeo), contamination factor ( ), degree of contamination ( ), modified degree of contamination (mCd) and pollution load index (PLI). Samples were collected from the surface layer of soil and analyzed by Atomic Absorption Spectrophotometer (AAS). The trend of metals according to average concentration during the dry and wet seasons was As > Fe > Hg > Mn > Zn > Cu > Cr > Ni > Pb > Cd and As > Fe > Mn > Zn > Hg > Cu > Ni > Cr > Pb > Cd, respectively. Because of seasonal rainfall, dilution and other run-off during the wet season, metals from the upper layer of soil were flushed out to some extent and hence all the indices values were lower in this season compared to that of the dry season. Igeo results revealed that the study area was strongly and moderately contaminated with As and Hg in the dry and wet seasons respectively. According to , soil was classified as moderately contaminated with Zn, Cr, Pb and Ni, considerably contaminated with Cu and highly contaminated with As and Hg. The general trend of the mean was Hg > As > Cu > Zn > Ni > Cr > Pb > Fe > Mn > Cd and As > Hg > Cu > Cd > Zn > Ni >Pb > Fe > Mn in dry and wet seasons, respectively. The mCf values in the dry and wet seasons were 575.13 and 244.44 respectively indicating an ultra high degree of contamination. The Cd values in both seasons were associated with a very high degree of contamination. PLI results indicated immediate intervention to ameliorate pollution in both seasons. The main sources of metals included effluents from wastewater treatment plants, treated and untreated wastewater from surrounding industrial establishments as well as agricultural activities. Protecting the agricultural soil is a formidable challenge in the study area, which requires modernization of industries, thereby improving the recovery and recycling of wastewater. Indices analysis presented in the present work could serve as a landmark for contemporary research in toxicology. Full article
Open AccessArticle Numerical Observation of the Jet Flight Patterns of Linear Shaped Charges
Appl. Sci. 2012, 2(3), 629-640; doi:10.3390/app2030629
Received: 1 June 2012 / Revised: 27 June 2012 / Accepted: 2 July 2012 / Published: 6 July 2012
Cited by 2 | PDF Full-text (6960 KB) | HTML Full-text | XML Full-text
Abstract
Linear Shaped Charges (LSCs) have been assumed to function in the same manner as Conical Shaped Charges (CSCs) in the published literature that describes a metallic jet process for penetration. However, based on the facts that the LSC liner is composed of flat
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Linear Shaped Charges (LSCs) have been assumed to function in the same manner as Conical Shaped Charges (CSCs) in the published literature that describes a metallic jet process for penetration. However, based on the facts that the LSC liner is composed of flat surfaces instead of the curved cone shaped liner of a CSC and the LSC detonation propagation is perpendicular to the penetrator projection direction, the approach to investigate the penetrator formation process of LSCs should be examined from a different perspective. Because there are fundamental differences between CSCs and LSCs in the formation of a jet, the cutting performances would be under different regimes. As a preliminary investigation, in this paper, we report a numerical observation of the LSC jetting properties using AUTODYN®. Full article
Open AccessArticle Continuous Process for Biodiesel Production in Packed Bed Reactor from Waste Frying Oil Using Potassium Hydroxide Supported on Jatropha curcas Fruit Shell as Solid Catalyst
Appl. Sci. 2012, 2(3), 641-653; doi:10.3390/app2030641
Received: 31 July 2012 / Revised: 24 August 2012 / Accepted: 24 August 2012 / Published: 29 August 2012
Cited by 8 | PDF Full-text (1481 KB) | HTML Full-text | XML Full-text
Abstract
The transesterification of waste frying oil (WFO) with methanol in the presence of potassium hydroxide catalyst supported on Jatropha curcas fruit shell activated carbon (KOH/JS) was studied. The catalyst systems were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller
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The transesterification of waste frying oil (WFO) with methanol in the presence of potassium hydroxide catalyst supported on Jatropha curcas fruit shell activated carbon (KOH/JS) was studied. The catalyst systems were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and the Brunauer–Emmett–Teller (BET) method. The effects of reaction variables such as residence time, reaction temperature, methanol/oil molar ratio and catalyst bed height in packed bed reactor (PBR) on the yield of biodiesel were investigated. SEM images showed that KOH was well distributed on the catalyst support. The optimum conditions for achieving the conversion yield of 86.7% consisted of a residence time of 2 h, reaction temperature of 60 °C, methanol/oil molar ratio of 16 and catalyst bed height of 250 mm. KOH/JS could be used repeatedly five times without any activation treatment, and no significant activity loss was observed. The results confirmed that KOH/JS catalyst had a great potential to be used for industrial application in the transesterification of WFO. The fuel properties of biodiesel were also determined. Full article
(This article belongs to the Special Issue Renewable Energy)
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Open AccessArticle Ab Initio Study of Lattice Site Occupancies in Binary Sigma Phases Using a Single-Site Mean Field Model
Appl. Sci. 2012, 2(3), 654-668; doi:10.3390/app2030654
Received: 3 July 2012 / Revised: 7 August 2012 / Accepted: 13 August 2012 / Published: 3 September 2012
Cited by 1 | PDF Full-text (2868 KB) | HTML Full-text | XML Full-text
Abstract
The site occupation of binary Fe-Cr, Co-Cr, Re-W and Fe-V sigma phases is studied in the present work with a first-principles-based single-site mean field theory. We show that the alloy components in these systems exhibit similar site preferences except for the Re-W system,
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The site occupation of binary Fe-Cr, Co-Cr, Re-W and Fe-V sigma phases is studied in the present work with a first-principles-based single-site mean field theory. We show that the alloy components in these systems exhibit similar site preferences except for the Re-W system, where the occupation of two sites is reversed in agreement with previously published works. In case of the FeV sigma phase, for which the size mismatch between the alloy components is large, we also include into our consideration the effect of local lattice relaxations. The obtained results are found in good agreement with the experimental data and previous theoretical studies. Full article
(This article belongs to the Special Issue Frank-Kasper Phases)

Review

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Open AccessReview Optical Current Sensors for High Power Systems: A Review
Appl. Sci. 2012, 2(3), 602-628; doi:10.3390/app2030602
Received: 23 May 2012 / Revised: 15 June 2012 / Accepted: 18 June 2012 / Published: 2 July 2012
Cited by 22 | PDF Full-text (1103 KB) | HTML Full-text | XML Full-text
Abstract
The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering
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The intrinsic advantages of optical sensor technology are very appealing for high voltage applications and can become a valuable asset in a new generation of smart grids. In this paper the authors present a review of optical sensors technologies for electrical current metering in high voltage applications. A brief historical overview is given together with a more detailed focus on recent developments. Technologies addressed include all fiber sensors, bulk magneto-optical sensors, piezoelectric transducers, magnetic force sensors and hybrid sensors. The physical principles and main advantages and disadvantages are discussed. Configurations and strategies to overcome common problems, such as interference from external currents and magnetic fields induced linear birefringence and others are discussed. The state-of-the-art is presented including commercial available systems. Full article
(This article belongs to the Special Issue Feature Papers)
Open AccessReview Non-Stoichiometry and Calphad Modeling of Frank-Kasper Phases
Appl. Sci. 2012, 2(3), 669-681; doi:10.3390/app2030669
Received: 24 July 2012 / Revised: 28 August 2012 / Accepted: 28 August 2012 / Published: 10 September 2012
Cited by 4 | PDF Full-text (230 KB) | HTML Full-text | XML Full-text
Abstract
One of the many singularities of Frank-Kasper phases is their ability to accommodate extremely large composition ranges by atom mixing on the different sites of the crystal structures. This phenomenon will be reviewed in the present paper with special emphasis on the experimental
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One of the many singularities of Frank-Kasper phases is their ability to accommodate extremely large composition ranges by atom mixing on the different sites of the crystal structures. This phenomenon will be reviewed in the present paper with special emphasis on the experimental demonstration of this phenomenon, the theoretical calculation of disordered structures and the modeling of these phases. Full article
(This article belongs to the Special Issue Frank-Kasper Phases)
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