bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends and Development of Precast Concrete Closed Spandrel Arch Bridge Systems
Authors: Tan Geem Eng , Ong Tai Boon , Chong Yong Ong
Published: October 2015

Arch bridges which have existed since thousands years ago showed surprising durability. Due to the aesthetic value of arch bridges, it is widely used as crossing over valleys and rivers nowadays. Closed spandrel arch bridge is one type of arch bridges that has been developed using precast concrete technology since 1965. Currently, the available Precast Concrete Arch Bridge Systems are BEBO arch, Matiere arch, CON/SPAN arch, TechSpan arch, NUCON arch, Concrete-Filled FRP Tube arch, Flexi-Arch, Rivo CS-P Series arch and Pearl Chain arch. In this paper, development of the Precast Concrete Closed Spandrel Arch Bridge System is reviewed. The advantanges of precast closed spandrel arch bridge system will also be briefly presented. Comparisons in terms of arch sections, moulding, handling, transporting and installing among different Precast Concrete Closed Spandrel Arch Bridge Systems are also highlighted.
Impact of Ageing and the Stability of Adhesion Additive on Moisture Susceptibility and Adhesion
Authors: Valentova Tereza , Altman Jan , Valentin Jan , Hamzah Meor Othman
Published: October 2015

Asphalt mix durability is one of the most important aspects if looking on longer lifetime of pavement structures. It is influenced by several factors whereas one of the most important is moisture susceptibility and the quality of adhesion between bitumen binder and aggregateparticles. If the coating by the bitumen is not fully provided or is affected by strongly hydrophilic aggregate type which easier creates bonds with more polar water then it is immediately attacking the aggregate surface and leads to stripping effects – ongoing loss of bitumen-aggregate bonds, mix cohesion problems, etc. With respect to improve adhesion quality different additives (surfactants) are used, whereas two factors might be critical for them: 1) thermal stability of the additive used in bitumen stored for several days at elevated temperatures; 2) bitumen ageing and the effect on additive activity. Both aspects have been studied as a key objective of an ongoing research looking fora suitable laboratory procedure for simulating the thermal stability and assess the remaining activity of the additive. Further asphalt ageing impact on moisture susceptibility is evaluated by changed ratios of indirect tensile strength values for unaged and differently aged test specimens. Results for one type of mix and different aggregates with application of straight-run bitumen 50/70 and 4 different types of adhesion promoters are summarized in the paper.
Life Cycle Assessment for Pavement Sustainable Development: Critical Review
Authors: Babashamsi Peyman , Md Yusoff Nur Izzi , Ceylan Halil , Md Nor Nor Ghani
Published: October 2015

Certainly, one of the most cost effective and comprehensive infrastructure assets of the build environment is road infrastructure. The environmental impacts of this asset during its life-cycle drive researchers to create a foundational framework to quantify these effects. Life cycle assessment (LCA), a method for the assessment of all modules in a life cycle, has been examined to evaluate all the environmental modules and components of road projects due to constraints of environmental assessments. The enthusiasm for enhancing the sustainable development of basic infrastructure leads to quick expansion on pavement life cycle assessment. An audit of applicable published LCA studies has recognized that environmental modules, such as the usage module (rolling resistance of pavement, carbonation, and albedo), end of life (EOL) module, and components such as traffic congestion during the construction module are not regarded in most of the articles. These modules potentially have the same environmental impact as other regularly considered modules such as materials, transportation, and construction. The goal of this study is to recognize shortfalls in the fields that bolster pavement LCA, to prepare a comprehensive and straight forward methodology, and to provide a basis on which related studies can move forward
Physical and Rheological Properties of Aged Bitumen Rejuvenated with Waste Engine Oil
Authors: Arshad Ahmad Kamil , Kamaluddin Noor Azreena , Hashim Wardati , Ahmad Roslan Siti Rosyani
Published: October 2015

Age hardening of bitumen is one of the factors affecting the durability of asphaltic concrete pavements. As the bitumen ages, its viscosity increases and it becomes more stiff and brittle. Recycling agents have been used to restore or soften the aged bitumen properties to a consistency level appropriate for use in the recycling process of deteriorated pavements. This paper details a study on the use of Waste Engine Oil (WEO) from vehicles as a recycling agent for aged bitumen. The study focused on the rheological properties evaluation of virgin bitumen, aged bitumen and blended bitumen (50% of fresh bitumen + 50% of aged bitumen) mixed with waste engine oil as additive (with 0%, 3%, 6% and 9%). The aged bitumen was prepared through the process of Rolled Thin Oven Test (RTFOT) and Pressure Aging Vessel (PAV) test to simulate the aging process. The virgin bitumen, the aged bitumen, and the blended bitumen mixed with various proportions of WEO were then tested to determine their physical characteristics. Penetration, softening point, viscosity and dynamic shear rheometer (DSR) tests were conducted in order to determine rheological properties of the bitumen samples prepared. The penetration value of blended bitumen added with WEO increased with the addition of WEO. The softening point decrease with the percentage increased in WEO of the blended bitumen. The viscosity for the blended bitumen added with WEO decreases with the increase in the percentage of WEO added. The DSR results showed that the increase in the amount of WEO in blended bitumen decrease the G*/sin δ parameter. For the particular bitumen and WEO used, the optimum percentage of WEO is 6% by the total weight of bitumen as it complies with the Public Works Department of Malaysia’s specification requirements. This study suggests that WEO has ability to counteract the stiffening of aged bitumen and restore the aged bitumen to that of virgin bitumen. As the composition and performance of bitumen and WEO may be different from those used in this study, it is recommended that a detailed evaluation is carried out for the bitumen and WEO to be used in asphalt recycling.
Time Gap Evaluation due to the Existence of Heavy Vehicles on Urban Expressways
Authors: Hashim Wardati , Arshad Ahmad Kamil , Mustafa Masria , Kamaluddin Noor Azreena
Published: October 2015

Time gap is important for road user to make decision relative to the lad vehicle at a roadway segment. Theoretically, if the gap is larger than reaction time, drivers would maintain the safe following distance from the vehicle in front or else the probability of vehicle collusion is considerably high. In expressways, gap is important for the purpose of lane changing and overtaking. Due to high allowable speed on expressways, time gap might be affected, especially with the consideration of heavy vehicle existence. This paper attempts to statistically justify any significance correlation between speed and time gap in relative to critical gap acceptance pertaining to the heavy vehicles and cars interaction on urban expressways. Extensive data was collected through video recording before being abstracted and processed by utilizing the TRAIS software. Then, statistical analysis in relative to the speed and time gap for various vehicles interactions are presented. The results showed there is a significant correlation between speed and time gap for all vehicles interaction. When cars following other cars at allowable average speed, the time gap is relatively low leading to a lower critical gap acceptance as compared to the situation with the existence of heavy vehicles.
Seismic Microzonation for Denizli Metropolitan Area, Turkey
Authors: Aydin Ali , Akyol Erdal , Gungor Mahmud , Soyatik Nuray , Tasdelen Suat
Published: October 2015

This study presents microzonation of the Denizli city center, is about 225 km2. It is mainly rely on t seismic velocities of the tested soil. For seismic microzonation area of has been selected as the study area. Seismic refraction methods have been used to generate two-dimensional profiles at 310 locations. These p and s wave velocities are used to estimate boundaries of the velocities at every 2 and 5 m intervals up to a depth of 60 m. The results are satisfactory for urban planning and it can successfully be used in urban areas. The municipal authority may be considered to use the results for land use studies.
Effect of Ni/Co Ratio on Bimetallic Oxide Supported Silica Catalyst in CO2 Methanation
Authors: Md Ali Siti Aminah , Ku Hamid Ku Halim , Ismail Kamariah Noor
Published: October 2015

Five series of silica supported bimetallic oxide (NiCo/SiO2) catalysts have been synthesized through successive reverse co-precipitation and wet impregnation methods at different metal loadings (i.e. 80Ni20Co/SiO2,, 60Ni40Co/SiO2,50Ni50Co/SiO2,40Ni60Co/SiO2,20Ni80Co/SiO2). The catalytic performance of these catalysts were tested for the CO2methanation catalysis using microactivity fixed bed reactor. Nickel rich catalyst (80Ni20Co/SiO2) exhibited the highest catalytic activity in the CO2methanation with 47.1% of CO2conversion. Meanwhile, the CH4selectivity and yield was found to be at 99.9% and 27%, respectively.
Iron and Manganese Removal from Groundwater Using High Quality Limestone
Authors: Akbar Nor Azliza , Abdul Aziz Hamidi , Adlan Mohd Nordin
Published: October 2015

Several techniques are used for iron and manganese removal from groundwater. Among these treatments, adsorption has been proven to be a very effective in metal removal for groundwater treatment. Thus, limestone has been proposed as adsorption media because of its low cost. In this study, the mineral contents of limestone were detected using X-ray fluorescence (XRF). XRF results showed that limestone contains 97.93% CaCO3, 0.87% MgO, and 1.2% other elements. Groundwater sample was obtained from USM borehole located at 5° 08’ 50.5”N and 100° 29’ 34.7”E. A batch study was carried out for various dosages of limestone media (5–50 g) in 200 mL of groundwater sample. The highest iron and manganese removal was more than 90% and 70%, respectively, at optimum dosage of 40 g/200 mL sample. Adsorption data were modeled using Langmuir and Freundlich adsorption isotherms. The batch study result shows that monolayer Langmuir isotherm fitted the experimental data better than the Freundlich isotherm. The correlation coefficient (R2) in the Langmuir isotherm for both metals were 0.84 and 0.97, whereas 0.83 and 0.23 in the Freundlich isotherm, respectively. Based on the present results, application of limestone as adsorbent media can be a good alternative of groundwater treatment because of the low cost of the media. Thus, the use of limestone could help to overcome the excessive iron and manganese problem in water treatment plants.
Oxygen Uptake by Biological Processes inside Oxidation Ditch
Authors: Saad Noor Aida , Abdul Aziz Hamidi , Abdullah Mohd Zulkifly , Zubair Mohamed , Mohd Remy Rozainy M.A.Z.
Published: October 2015

Abstract. In order to provide a better understanding of the Orbal Biological System (OBS), as one type of a modified oxidation ditch, the research aims to develop a preliminary process model to visualize the oxygen uptake by biological processes inside the oxidation ditch. Fundamentally, the model can be used as initial study to get a clearer picture of the oxygen utilization rate inside the ditch. Based on the results, the outer channel takes the highest portion of the overall oxygen consumption which is 66 % compare to the middle channel with only 14 % and followed by the inner channel with 20 %. However, simplifying assumptions made for the preliminary process model development (e.g. constant values of HRT throughout each channel) may affect the accuracy of describing the real conditions of the system.
Pharmaceutical Removal from Synthetic Wastewater Using Heterogeneous - Photocatalyst
Authors: Lee Chee Mei , Palaniandy Puganeshwary , Zaman Nastaein Qamaruz , Adlan Mohd Nordin
Published: October 2015

Compound Parabolic Collecting Reactor (CPCR) was designed and used for the heterogeneous-photocatalytic treatment process. Sunray was act as an economically and ecologically sensible light source. The photocatalytic degradation of paracetamol in the synthetic wastewater by using titanium dioxide (TiO2) was investigated. The experimental results show that the paracetamol removal rates were very high and nearly equal (97.2% to 99.7%) at pH 4-7 and TiO2 concentration of 0.5-1 g/L. This implies that the photocatalytic degradation rate of paracetamol is not affected by pH range in this study as the electrostatic interaction between the TiO2 and paracetamol is not able to be developed unless a wider range of pH is set. Furthermore, the concentration of TiO2 of 0.5 g/L is too high to treat the concentration of 10 mg/L of paracetamol. Further research is needed in order to identify the optimum pH condition and a suitable correlation of concentration between TiO2 and paracetamol. Finally, the results proved that the heterogeneous-photocatalyst treatment method which associated with the application of CPCR and solar energy is able to eliminate the paracetamol from the synthetic wastewater.
Natural Organic Matter and Disinfectant By-Products (DBPs) Formation Potential in Agriculture Area in Malaysia
Authors: Ibrahim Nurazim , Abdul Aziz Hamidi , Yusoff Mohd Suffian
Published: October 2015

Natural organic matter (NOM) in water reacts with chlorine or other disinfectants and form hazardous disinfectant by-products (DBPs). This study aimed to detect the presence of NOM in a conventional water distribution system using UV absorbance at 254 nm as a surrogate. Two water treatment plants were selected, namely, Jalan Baharu Water Treatment Plant (JBWTP) and Lubok Buntar Water Treatment Plant (LBWTP). Aside from determining the amount of NOM, the reduction of UV254after completing the series of treatments (coagulation, flocculation, sedimentation, filtration, and disinfection) was also observed. The presence of UV254in both raw water and treated water samples confirmed the presence of NOM. The concentration of UV254recorded at JBWTP and LBWTP were 0.14 and 0.13 cm−1, respectively. After the treatment processes, the concentration was reduced to 0.04 cm−1for JBWTP and 0.03 cm−1for LBWTP. These results indicated that the water supply in both plants contains DBP precursors and implied the possibility of DBP formation in the system. Moreover, the percentage reduction of UV254recorded were 69% and 75% for JBWTP and LBWTP, respectively.
Waste to Wealth: Recovery of Recyclable Items and Biodegradable Wastes from Night Markets at Seberang Perai Selatan, Penang
Authors: Kamaruddin Mohamad Anuar , Yusoff Mohd Suffian , Ahmad Abdul Hadi
Published: October 2015

This study evaluates the potential of recyclable items and biodegradable wastes recovered from selected locations of night markets across Seberang Perai Selatan district, Penang. Three different sizes of night market covering 9 study locations were evaluated based on waste types and the amount generated. By using the coning and quartering technique, it was observed that bigger sizes of night market had higher recyclable items potential. In particular, 177.41 kg/day of wastes discarded which equivalent to RM 104.05 worth of recyclable items. Small night market size was found to only generate 21.1 kg/day of wastes and equivalent to RM 13.55 worth of recyclable items. In terms of organics recovered, about 587 kg of wastes identified as brown organics. Meanwhile, it was recorded that green organics made up about 235 kg out of 822 kg total biodegradable wastes. This study demonstrates that night market has the potential for recovery of recyclable items and organic composting which can reduce the amount of solid waste being disposed at the landfills.
Multiple Regression Model Using Performance Indices for Storage Capacity of a Reservoir System in Johor Catchment
Authors: Saket Oskoui Issa , Abdullah Rozi , Montaseri Majid
Published: October 2015

Storage–yield–reliability (S–Y–R) relationship is useful in many areas of hydrology and water resources. With the availability of such a relationship, reservoir planning analysis can be implemented much more rapidly and at a much shorter time needed for sequential analysis applying time series data. Existing relationships have been developed mostly for over-year capacity without considering both reliability and vulnerability performance indices. Hence, in this study, streamflow data from Johor river was used to develop a predictive relationship for total (i.e. within-year plus over-year) storage capacity involving both reliability and vulnerability performance indices as for use during reservoir planning. The reservoir was analyzed using 1000 sequences of synthetic data having the same length as historical data involving both time-based reliability and vulnerability performance indices by modified SPA. The model was then calibrated based on the mean of 1000 simulation results. Subsequently, the performance of the model was observed by comparing the model’s results with simulation outcomes for study systems. It was found that the performance of the model was very good in reproducing, the total storage capacity.
AHP Based Thermal Comfort Assessment through Passive Design Allocation in Tropical School Offices
Authors: Chan Siew Chong
Published: October 2015

Since global environmental issues are widely discussed nowadays, a number of studies are being carried out to resolve the challenges of reducing energy usage in buildings, especially related to energy use to sustain the indoor thermal comfort level. Among the methodologies used, Analytical Hierarchy Process (AHP) is commonly used to study the problems with multiple influencing factors which consist of different degree of implications. In this study, this model is used to investigate the effectiveness and consistency of respondents’ feedback onto the utility of passive design features in office buildings in order to sustain the indoor thermal comfort levels besides depending on artificial cooling equipment. A number of 122 academic staff from 5 units of primary schools within urban areas in Seremban District was involved in the study. All the schools were equipped with passive design elements, but different types of mechanical ventilation systems were installed in particular schools. Questionnaires with Likert scales were distributed to assist the respondents rank their subjective opinions with objective numerical values. The outputs of rankings generated through AHP by the respondents in different schools were studied, and their validities were further analyzed with ANOVA tests to justify the consistency of the findings. The results showed that there is not much significant difference among the evaluated batches, and thus, model is potential to be further developed into a more comprehensive evaluation tool to link with unidentified environmental and physical factors which generate important design data for future building designers.
Photo- and Thermo-Induced Effects in Chalcogenide Glasses from Point of View of the Barrier-Cluster-Heating Model
Authors: Banik Ivan , Pavlendová Gabriela
Published: October 2015

The paper explains the nature of mid-gap absorption, amplification effect of photoluminescence (at mid-gap absorption), the mechanism of the ESR signal in chalcogenide glasses, as well as correlations between these phenomena, based on the barrier-cluster-heating model. It also discusses the mechanism of photo-induced structural changes, which play an important role in the application area.
Minority Carrier Lifetime Improvement of Multicrystalline Silicon Using Combined Saw Damage Gettering and Emitter Formation
Authors: Martins George , Bonilla Ruy S. , Burton Toby , MacDonald P. , Wilshaw Peter R.
Published: October 2015

In this work we use Saw Damage Gettering (SDG) in combination with emitter formation to improve the minority carrier lifetime of highly contaminated multi-crystalline silicon wafers. This process is applied to wafers from the bottom of ingots, commonly referred to as the “red zone”, which are currently discarded since their high concentration of impurities limits the efficiency of solar cells produced therefrom. SDG is a potentially simple technique designed to upgrade these wafers. In this technique, bulk impurities are dissolved via annealing. The wafers are then cooled which generates a super-saturation of impurities in solution. The system then relaxes through the formation of precipitates in the saw damaged region. SDG is shown to be enhanced when using a temperature dependent cooling rate which maximizes the flux of impurities to the saw damaged regions. In addition, these benefits were observed even after an additional gettering process occurring during an emitter formation procedure. The SDG annealing conditions required to achieve the maximum lifetime were altered by the introduction of the emitter formation process. The enhancement generated by the SDG process may be sufficient to enable red-zone wafers to be processed is the same manner as higher quality no-red zone wafer wafers without adversely affecting the resultant cell efficiency. Due to its simplicity, it is expected that SDG can easily be incorporated into current production methods.
Electronic Properties of Dislocations
Authors: Reiche Manfred , Kittler Martin , Pippel Eckhard , Kosina Hans , Lugstein Alois , Uebensee Hartmut
Published: October 2015

Dislocations are one-dimensional crystal defects. Their dimension characterize the defects as nanostructures (nanowires). Measurements on defined dislocation arrays proved numerous exceptional electronic properties. A model of dislocations as quantum wires is proposed. The formation of the quantum wire is a consequence of the high strain level on the dislocation core modi-fying locally the band structure.
Spatial Distribution of the Dislocation Trails in Silicon
Authors: Orlov V.I. , Yakimov E.B. , Yarykin Nikolai
Published: October 2015

Formation of the dislocation trails (DTs) left at the slip plane behind expanding dislocation half-loops is studied in Cz-Si plastically deformed at 600°C using the selective chemical etching and the EBIC and LBIC techniques which are sensitive to the defect recombination activity. It is found that the dislocation trails are qualitatively different for the half-loops expanded from the tensile and compressed surfaces of the bent sample. In the tensile part, DTs with the strongest recombination contrast are always revealed behind the 60oarm of the half-loops, while DTs are invisible (if exits at all) behind another arm and the bottom segment. The dissimilar behavior of two differently aligned 60° segments can be related to a different fine structure of their cores. The picture of dislocation trails is found to be different in the 1020 μm surface layer that is tentatively ascribed to the near-surface bending of dislocations. In the compressed part, the EBIC and LBIC contrasts are generally smaller and the noticeable DTs are only revealed in the middle part the half-loop. Presumable reasons for the effects are discussed.
Hydrogen-Vacancy Complexes and their Deep States in n-Type Silicon
Authors: Kolevatov Ilia L. , Herklotz Frank , Bobal Viktor , Svensson Bengt Gunnar , Monakhov Edouard V.
Published: October 2015

The evolution of irradiation-induced and hydrogen-related defects in n-type silicon in the temperature range 0 – 300 °C has been studied by deep level transient spectroscopy (DLTS) and minority carrier transient spectroscopy (MCTS). Implantation of a box-like profile of hydrogen was performed into the depletion region of a Schottky diode to undertake the DLTS and MCTS measurements. Proportionality between the formation of two hydrogen-related deep states and a decrease of the vacancy-oxygen center concentration was found together with the appearance of new hydrogen-related energy levels.
Carbon-Hydrogen Complexes in n- and p-Type SiGe-Alloys Studied by Laplace Deep Level Transient Spectroscopy
Authors: Stübner Ronald , Kolkovsky Vladimir , Weber Jörg , Abrosimov N.V.
Published: October 2015

A deep level transient spectroscopy (DLTS) study on n- and p-type diluted Si1-xGex alloys (x=0, 0.011, 0.026, 0.046, and 0.070) is presented. Defect levels of several carbon-hydrogen (CH) complexes are observed. The high-resolution Laplace-DLTS technique allows us to detect configurations of defects which contain different numbers of Ge atoms in the first and second-nearest neighbourhood of the CH complexes. The electrical properties of the defects will be analysed and their origin will be discussed.
A Density Functional Study of Iron Segregation at ISFs and Σ5-(001) GBs in mc-Si
Authors: Al-Ani Oras A. , Goss J.P. , Cowern N.E.B. , Briddon Patrick R. , Al-Hadidi Meaad , Al-Hamadany Raied , Rayson M.J.
Published: October 2015

Removal of the dilaterous effects of iron in silicon is critical for the performance of multicrystalline silicon (mc-Si) solar cells, with internal gettering at extended defects including stacking faults and grain boundaries being one possibility. We present the results of a density function study of the behavoiur of iron at the intrinsic stacking fault and (001)–Σ 5 twist grain boundary, which both represent examples of fully bonded systems. Our results show iron is bound more strongly to the grain-boundary than the stacking fault, which we ascribe to a combination of Si-Fe chemistry and strain relaxation. However, we find that the binding energy of a single Fe atom to these extended defects is modest, and less than 0.5 eV.
Similarity of Atomic Configurations of Thermally Stable Positron-Sensitive Complexes Produced with 0.9-MeV Electrons and 15-MeV Protons in n–FZ–Si:P Crystals
Authors: Arutyunov Nikolai Yu. , Elsayed M. , Krause-Rehberg Reinhard , Emtsev Vadim V. , Oganesyan Gagik A. , Kozlovski Vitalii V.
Published: October 2015

We observed for the first time the thermally stable point positron-sensitive center of a vacancy type in n–FZ–Si (P) material irradiated at RT by ~ 0.9-MeV electrons. The center that emerges after isochronal annealing at Tanneal.≈ 260 – 280 oC is found to be similar to the vacancy-group-V-atom complex revealed in the same Si material irradiated by 15-MeV protons; the detecting of the centers by the positron trapping is finalized at Tanneal.≥ 520 oC. The annihilation gamma-quanta to be emitted from the positron trap gives rise to a characteristic positron lifetime τ2 (I2 ~ 38–19 %) ≤ 276 – 294 ps which is somewhat longer than the one predicted for unrelaxed single vacancy τV.≈ 254 – 261 ps. Our data suggested a configuration of the complex VopPVop, wherein the atom of phosphorus is tied to a split open vacancy volume 2Vop. It is argued that Vop volume detected by the positron trapping may be formed by extended semi-vacancy, Vs-ext , or by the relaxed inwards vacancy, Vinw , thus resulting in a distorted Vs-extPVs-ext or VinwPVinw configurations.
Interstitial Carbon in p-Type Copper-Doped Silicon
Authors: Yarykin Nikolai , Weber Jörg
Published: October 2015

The spectrum of defects produced by 5 MeV electron irradiation at room temperature in the oxygen-lean p-type silicon strongly contaminated with interstitial copper (Cui) is studied using the deep-level transient spectroscopy. It is observed that the interstitial carbon defects (Ci), which are abundant in irradiated copper-free samples, are not detected directly after irradiation. The phenomenon is attributed to the formation of a {Cui, Ci} complexes which exhibit no deep levels in the lower half of the band gap. The complexes are shown to dissociate under anneals at 300-340 K resulting in the appearance of the Ci species.
Characterization of Si Convertors of Beta-Radiation in the Scanning Electron Microscope
Authors: Polikarpov M.A. , Yakimov Eugene B.
Published: October 2015

The approach for imitation of beta radiation using the e-beam of scanning electron microscope (SEM) for semiconductor energy converter testing is proposed. It is based on the Monte-Carlo simulation of depth-dose dependence for beta-particles and a determination of collection probability from the EBIC measurements of collection efficiency dependence on beam energy. Experiments with the 63Ni radiation source confirm that such approach allows to predict the efficiency of semiconductor structures for radiation energy conversion to electric power.
Electrical Properties of Defects in Ga-Doped Ge Irradiated with Fast Electrons and Protons
Authors: Emtsev Vadim V. , Abrosimov Nikolay V. , Kozlovski Vitalii V. , Oganesyan Gagik A.
Published: October 2015

Electrical properties of radiation-produced defects in p-Ge irradiated with MeV electrons and protons are investigated. The dominant defects in electron-irradiated p-Ge were found to be neutral for the most part, whereas they are electrically active in proton-irradiated materials. Evidently, the reactions between impurity atoms and intrinsic point defects leading to formation of secondary Ga-related defects in electron-and proton-irradiated p-Ge appear to be distinct. Production rates of radiation defects in n-Ge and p-Ge are compared. A marked difference in the removal rates of shallow donor/acceptor impurity states, at least by an order-of-magnitude, is thought to be due to greatly enhanced annihilation of Frenkel pairs in p-type Ge.
Heat Flow and Defects in Semiconductors: beyond the Phonon Scattering Assumption
Authors: Estreicher Stefan K. , Gibbons T. Michael , Bebek M. Bahadir , Cardona Alexander L.
Published: October 2015

It is universally accepted that defects in materials scatter thermal phonons, and that this scattering is the reason why defects reduce the flow of heat relative to the defect-free material. However, ab-initio molecular-dynamics simulations which include defect dynamics show that the interactions between thermal phonons and defects involve the coupling between bulk (delocalized) and defect-related (localized) oscillators. Defects introduce Spatially-Localized Modes (SLMs) which trap thermal phonons for dozens to hundreds of periods of oscillation, much longer than the lifetimes of bulk excitations of the same frequency. When a phonon traps in a SLM, momentum is lost and the decay of localized phonons does not depend on the origin of the excitation but on the availability of receiving modes. This strongly suggests that carefully selected interfaces and/or δ-layers can be used to predict and control the flow of heat.
Ge and GeSn Light Emitters on Si
Authors: Oehme Michael , Gollhofer Martin , Kostecki Konrad , Koerner Roman , Bechler Stefan , Widmann Daniel , Arguirov Tzanimir , Kittler Martin , Schulze Jörg
Published: October 2015

The heteroepitaxial growth of GeSn and Ge crystals on Si substrates are investigated for Si-based photonic applications. Light Emitting Diodes with emission wavelengths from 2,100 to 1,550 nm could be demonstrated with active intrinsic GeSn light emitting layers between Ge barriers. A clear shift of the direct band gap toward the infrared beyond 2 μm is measured. Emission intensity is increased compared to Ge Light Emitting Diodes. Room temperature lasing from electrically pumped n-type doped Ge edge emitting devices are demonstrated. The edge emitter is formed by cleaving Si-Ge waveguide heterodiodes, providing optical feedback through a Fabry-Pérot resonator. The electroluminescence spectra of the devices showed optical bleaching and intensity gain for wavelengths between 1,660 nm and 1,700 nm.
Electrical Characterization and Defect-Related Luminescence in Oxygen Implanted Silicon
Authors: Danilov D.V. , Vyvenko O.F. , Sobolev N.A. , Vdovin V.I. , Loshachenko A.S. , Shek E.I. , Aruev P.N. , Zabrodskiy V.V.
Published: October 2015

Defect structure, electrical properties and defect-related luminescence (DRL) of light emitting diodes (LED) with the active defect-rich region produced by oxygen implantation and a subsequent multistep annealing of silicon wafers were investigated. It was found that defect-rich regions possess an embedded positive charge in both n-and p-type of the samples whose origin was ascribed to oxygen precipitates (OP). The presence of that charge in the implanted region of p-based LED gave rise to the apparent conductivity type conversion and to a significant increase of free electron concentration in n-based LEDs. A significant difference in the shape and in the excitation dependence of luminescence spectra as well as in the properties of DLTS signals was found between p-and n-type samples. From an analysis of the obtained data the DRL band centered at 0.79 eV was ascribed to small OPs segregated at dislocations whose filling with the holes hinders optical transitions via dislocation-related states at 0.805 eV and the broad DRL band at energies higher than 0.81 eV was ascribed to large OPs.
Electrical Characterization of Defects Introduced in n-Type N-Doped 4H-SiC during Electron Beam Exposure
Authors: Omotoso Ezekiel , Meyer Walter Ernst , Auret Francois Danie , Martins Coelho Sergio Manuel , Ngoepe Phuti Ngako Mahloka
Published: October 2015

Deep level transient spectroscopy (DLTS) was used to characterize the defects introduced in n-type, N-doped, 4H-SiC while being exposed to electron beam evaporation conditions. This was done by heating a tungsten source using an electron beam current of 100 mA, which was not sufficient to evaporate tungsten. Two new defects were introduced during the exposure of 4H-SiC samples to electron beam deposition conditions (without metal deposition) after resistively evaporated nickel Schottky contacts. We established the identity of these defects by comparing their signatures to those of high energy particle irradiation induced defects of the same materials. The defect E0.42 had acceptor-like behaviour and could be attributed to be a silicon or carbon vacancy. The E0.71 had intrinsic nature and was linked to a carbon vacancy and/or carbon interstials.
Managing elephants in Sri Lanka: where we are and where we need to be
Authors: Fernando Prithiviraj
Published: October 2015

Asian elephants are ‘endangered’ but come into significant conflict with humans. Sri Lanka holds an important position in relation to Asian elephants, both in terms of species conservation and human-elephant conflict mitigation. Historical aspects of the two main conservation agencies and lack of coordination between them has prevented a landscape level holistic approach to conservation in general and elephants in particular. The primary objective of elephant management is human-elephant conflict mitigation and secondarily elephant conservation. Many human-elephant conflict mitigation activities are ineffective and in some cases cause its escalation and wider spread. Others are extremely detrimental to elephant conservation. Effective human-elephant conflict mitigation and elephant conservation requires a paradigm change. Elephant management needs to be based on science and evidence rather than outdated beliefs and false assumptions. Unless immediate and effective remedial measures are taken, human-elephant conflict will continue to escalate and the elephant population continue to decline. Ceylon Journal of Science (Bio. Sci.) 44 (1) : 1-11, 2015
An automated system for analyzing agarose and polyacrylamide gel images
Authors: Abeykoon A.M.K.W.K. , Dhanapala M.P.C.S. , Yapa R. D. , Sooriyapathirana S.D.S.S.
Published: October 2015

Agarose or polyacrylamide gel electrophoresis is a common technique used to separate nucleic acids (DNA and RNA) according to their molecular weight, which generates images that can be analyzed automatically by a system. The separated DNA fragments of different molecular weights give a series of bands with positions in the gel image corresponding to their molecular weights. Automated image analysis of the gels removes much of the subjectivity of manual interpretation of band positions and sizes. In this paper, an automated system was designed for analyzing DNA bands using image and signal processing techniques. The proposed algorithm consists of four main steps: preprocessing to enhance the image, detecting lanes and bands, identifying band lengths and clustering; in which it can identify the similarities of the biological samples based on shared bands. The proposed technique eliminates defects due to noise and double bands in images. Ceylon Journal of Science (Bio. Sci.) 44 (1) : 45-54, 2015
Preharvest calcium chloride application improves postharvest keeping quality of tomato (Lycopersicon esculentum Mill.)
Authors: Daundasekera W. A. M. , Liyanage G. L. S. G. , Wijerathne R. Y. , Pieris R.
Published: October 2015

Developing fruits of local tomato cultivar ‘Rajitha’ were subjected to different preharvest calcium treatments in order to determine an effective means of extending the keeping quality of the commodity. Treatments were conducted with two calcium concentrations (3% and 5% w/v). There were two spraying protocols; single-application on fruit at 7 days after full bloom (DAFB) and multiple- application viz. weekly spraying starting from 7 DAFB until harvesting. Fruits were harvested at turning stage of colour development and allowed to reach red ripe stage under ambient conditions. Observations were made on the shelf life, titratable acidity (TA), total soluble solids (TSS) content, total calcium content in the outer pericarp and % weight loss during storage. Effect of calcium chloride treatment on susceptibility to fungal diseases was tested on fruits harvested at the ‘turning stage’ on wounded and non-wounded tissues. Rot development with respect to time was tested for both natural disease development and under artificial inoculation with fungal species isolated from tomato fruits. Calcium chloride treatment resulted in a 2.3 to 3.8-fold extension of shelf life of fruits compared to non-treated ones. Calcium treated fruits also exhibited a significantly higher firmness, total calcium content in the outer pericarp and TSS content but significantly lower fresh weight at harvest and a greater weight loss during storage under ambient temperature (27 ±2 0C). Calcium treatment has no consistent relationship with the % TA of fruit. Aspergillus niger and Rhizopus stolonifer were identified as the main postharvest fungal pathogens in tomato. Disease severity was less in Ca2+ treated fruits and the significance of this effect varied between pathogenic fungal species. Irrespective of the Ca2+ treatment, wounded fruits exhibited higher disease severity under natural conditions and also upon artificial inoculation. The extended shelf life in calcium-treated tomato appears to be through higher retention of firmness and retardation of skin colour development. Ceylon Journal of Science (Bio. Sci.) 44 (1) : 55-60, 2015
Prevalence of Hemolytic Anemia and Hemoglobinopathies among the Pregnant Women Attending a Tertiary Hospital in Central India
Authors: Balgir Ranbir S.
Published: October 2015

Anemia in pregnancy is one of the causes of maternal morbidity and, maternal and fetal mortality in India. Hemoglobin transports oxygen to different parts of the body. Any defect in hemoglobin structure leads to its adverse functions. Screening of pregnant women for hemoglobinopahties helps in early intervention for reducing morbidity and mortality. Although the prevalence of hemoglobinopathies especially of the sickle cell disorders is high in Madhya Pradesh but any study on pregnant women is lacking. This study had set the objectives to find the prevalence of anemia and hemoglobin disorders in pregnant women, and to determine the health status through hematological indices profile in central India. Hospital based a cross-sectional study showed 12.26% prevalence of hemoglobinopathies among 416 pregnant women, the sickle cell trait being 7.45%, followed by β-thalassemia trait (2.89%), hemoglobin E trait (0.24%), and sickle cell disease (1.68%). About 88% of the pregnant women were found free of hemoglobinopathies. Of the 9.13% pregnant women included in the study were suffering from sickle cell disorders. However, the overall 47.11% anemia was observed in pregnant women, ranging in between 45% to 66% and seemed to show a reduction in anemia after nutritional supplementations and improvement in maternal health care at antenatal check up due to accessibility to medical health facilities. A comparison of hematological indices of pregnant women afflicted with and without sickle cell disorders have revealed much reduced hemoglobin level, red blood cells count, mean corpuscular volume, hematocrit, and mean corpuscular hemoglobin; and raised leucocytosis in sickle cell disorder cases than among the normal pregnant women. A more vigorous and realistic campaign of prophylactic regime of supplementations for these pregnant women and child health care is suggested.
Sensitivity analysis of the potential impact of discrepancies in stratosphere–troposphere exchange on inferred sources and sinks of CO2
Authors: Deng F. , Jones D. B. A. , Walker T. W. , Keller M. , Bowman K. W. , Henze D. K. , Nassar R. , Kort E. A. , Wofsy S. C. , Walker K. A. , Bourassa A. E. , Degenstein D. A.
Published: October 2015

Abstract. The upper troposphere and lower stratosphere (UTLS) represents a transition region between the more dynamically active troposphere and more stably stratified stratosphere. The region is characterized by strong gradients in the distribution of long-lived tracers, whose representation in models is sensitive to discrepancies in transport. We evaluate the GEOS-Chem model in the UTLS using carbon dioxide (CO2) and ozone (O3) observations from the HIAPER (The High-Performance Instrumented Airborne Platform for Environmental Research) Pole-to-Pole Observations (HIPPO) campaign in March 2010. GEOS-Chem CO2/O3 correlation suggests that there is a discrepancy in mixing across the tropopause in the model, which results in an overestimate of CO2 and an underestimate of O3 in the Arctic lower stratosphere. We assimilate stratospheric O3 data from the Optical Spectrograph and InfraRed Imager System (OSIRIS) and use the assimilated O3 fields together with the HIPPO CO2/O3 correlations to obtain an adjustment to the modeled CO2 profile in the Arctic UTLS (primarily between the 320 and 360 K isentropic surfaces). The HIPPO-derived adjustment corresponds to a sink of 0.60 Pg C for March–August 2010 in the Arctic. Imposing this adjustment results in a reduction in the CO2 sinks inferred from GOSAT observations for temperate North America, Europe, and tropical Asia of 19, 13, and 49 %, respectively. Conversely, the inversion increased the source of CO2 from tropical South America by 23 %. We find that the model also underestimates CO2 in the upper tropical and subtropical troposphere. Correcting for the underestimate in the model relative to HIPPO in the tropical upper troposphere leads to a reduction in the source from tropical South America by 77 %, and produces an estimated sink for tropical Asia that is only 19 % larger than the standard inversion (without the imposed source and sink). Globally, the inversion with the Arctic and tropical adjustment produces a sink of −6.64 Pg C, which is consistent with the estimate of −6.65 Pg C in the standard inversion. However, the standard inversion produces a stronger northern land sink by 0.98 Pg C to account for the CO2 overestimate in the high-latitude UTLS, suggesting that this UTLS discrepancy can impact the latitudinal distribution of the inferred sources and sinks. We find that doubling the model resolution from 4° × 5° to 2° × 2.5° enhances the CO2 vertical gradient in the high-latitude UTLS, and reduces the overestimate in CO2 in the extratropical lower stratosphere. Our results illustrate that discrepancies in the CO2 distribution in the UTLS can affect CO2 flux inversions and suggest the need for more careful evaluation of model errors in the UTLS.
Secondary formation of nitrated phenols: insights from observations during the Uintah Basin Winter Ozone Study (UBWOS) 2014
Authors: Yuan B. , Liggio J. , Wentzell J. , Li S.-M. , Stark H. , Roberts J. M. , Gilman J. , Lerner B. , Warneke C. , Li R. , Leithead A. , Osthoff H. D. , Wild R. , Brown S. S. , de Gouw J. A.
Published: October 2015

Abstract. We describe the results from online measurements of nitrated phenols using a time of flight chemical ionization mass spectrometer (ToF-CIMS) with acetate as reagent ion in an oil and gas production region in January and February of 2014. Strong diurnal profiles were observed for nitrated phenols, with concentration maxima at night. Based on known markers (CH4, NOx, CO2), primary emissions of nitrated phenols were not important in this study. A box model was used to simulate secondary formation of phenol, nitrophenol (NP) and dinitrophenols (DNP). The box model results indicate that oxidation of aromatics in the gas phase can explain the observed concentrations of NP and DNP in this study. Photolysis was the most efficient loss pathway for NP in the gas phase. We show that aqueous-phase reactions and heterogeneous reactions were minor sources of nitrated phenols in our study. This study demonstrates that the emergence of new ToF-CIMS (including PTR-TOF) techniques allows for the measurement of intermediate oxygenates at low levels and these measurements improve our understanding of the evolution of primary VOCs in the atmosphere.
New temperature and pressure retrieval algorithm for high-resolution infrared solar occultation spectroscopy: analysis and validation against ACE-FTS and COSMIC
Authors: Olsen K. S. , Toon G. C. , Boone C. D. , Strong K.
Published: October 2015

Abstract. Motivated by the initial selection of a high-resolution solar occultation Fourier transform spectrometer (FTS) to fly to Mars on the ExoMars Trace Gas Orbiter, we have been developing algorithms for retrieving volume mixing ratio vertical profiles of trace gases, the primary component of which is a new algorithm and software for retrieving vertical profiles of temperature and pressure from the spectra. In contrast to Earth-observing instruments, which can rely on accurate meteorological models, a priori information, and spacecraft position, Mars retrievals require a method with minimal reliance on such data. The temperature and pressure retrieval algorithms developed for this work were evaluated using Earth-observing spectra from the Atmospheric Chemistry Experiment (ACE) FTS, a solar occultation instrument in orbit since 2003, and the basis for the instrument selected for a Mars mission. ACE-FTS makes multiple measurements during an occultation, separated in altitude by 1.5–5 km, and we analyze 10 CO2 vibration-rotation bands at each altitude, each with a different usable altitude range. We describe the algorithms and present results of their application and their comparison to the ACE-FTS data products. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) provides vertical profiles of temperature up to 40 km with high vertical resolution. Using six satellites and GPS radio occultation, COSMIC's data product has excellent temporal and spatial coverage, allowing us to find coincident measurements with ACE with very tight criteria: less than 1.5 h and 150 km. We present an inter-comparison of temperature profiles retrieved from ACE-FTS using our algorithm, that of the ACE Science Team (v3.5), and from COSMIC. When our retrievals are compared to ACE-FTS v3.5, we find mean differences between −5 and +2 K, and that our retrieved profiles have no seasonal or zonal biases, but do have a warm bias in the stratosphere and a cold bias in the mesosphere. When compared to COSMIC, we do not observe a warm/cool bias and mean differences are between −4 and +1 K. COSMIC comparisons are restricted to below 40 km, where our retrievals have the best agreement with ACE-FTS v3.5. When comparing ACE-FTS v3.5 to COSMIC we observe a cold bias in COSMIC of 0.5 K, and mean differences are between −0.9 and +0.6 K.