bluuebunny/crossref_metadata_2025 huggingface dataset:
Potato Market and Consumption
Authors: Pllana Mustafe , Merovci Nazim , Jashari Melihate , Tmava Aida , Shaqiri Fisnik
Published: June 2018

Potato, or as it is called the “bread of the poor”, is a traditional product and the fourth world's largest consumption culture after rice, wheat, and maize. Potato contains vitamin B6 (32%), starch (26%), copper (22%), vitamin C (22%), magnesium (19%), phosphorus (17%), fiber (15%), pantothenic acid (13%), and other ingredients. Americans eat on average 35 kg of frozen potatoes per year: 19 kg of fresh potatoes; 8 kg of potato chips; and 6 kg of dehydrated potato products. The global monthly consumption of potato per capita is 31.3 kg. A greater consumption per capita is in Europe with 87.8 kg/capita. Residents of cold countries of Eastern Europe are the biggest consumers of potatoes in the world. China is the largest producer in the world (75mil / year), but it is not the largest consumer per capita. The volume of international potato trade is smaller than the volume of production. Only 6% of potato production reaches trade market worldwide. Trade in processed potatoes is increased, and with higher rates exceed fresh potato trade. It passes from fresh consumption to processed consumption. Developed countries are those which provide markets with these processed products, earning high rate of profits. Processed potatoes make up 64 percent of total US potato consuming. Kosovo has a great potential to produce potatoes, but there are some obstacles such as small domestic consumption and the market in general. In this article, the factors that affect consumption are explored, which as a consequence increase the production.
O comportamento dos custos das indústrias do estado de Santa Catarina com ênfase nos Sticky costs
Authors: Fazoli Julio Cesar , Reis Luiza Santangelo , Borgert Altair
Published: June 2018

O presente trabalho objetivou identificar o comportamento dos custos do setor industrial do estado de Santa Catarina com ênfase nos Sticky costs. O trabalho analisou o comportamento sob duas óticas: a do setor industrial como um todo e, em um segundo momento, segmentado por setores. O objetivo desse tratamento foi compreender o comportamento dos custos de cada setor industrial de forma individualizada, haja vista que a composição dos custos industriais dos produtos comercializados está diretamente relacionada a fatores específicos de cada segmento. Com base nos resultados, pode-se inferir que os custos das indústrias catarinenses aumentam em 0,7781% diante do incremento de 1% sobre suas receitas líquidas de vendas, enquanto que, perante contrações das receitas de mesma magnitude, os custos apresentam redução de 0,7632%. Por outro lado, com a análise individualizada por setor, pode-se inferir que alguns segmentos possuem comportamento simétrico dos seus custos, enquanto em outros foram verificados comportamento Anti-sticky.
Comparison of Simplified and Advanced Design of Steel Structures in Fire
Authors: Kolšek Jerneja , Rebec Andrej
Published: June 2018

This paper presents the possible deviations between “realistic” (performance-based) calculations of fire resistance of steel structures and corresponding calculations made by one of the often used simplified (prescriptive) procedures of EN 1993-1-2 i.e. the method of critical temperature (MCT). The comparison is done for a case of an assembly consisting of a steel beam and a steel girder connected to each other by a bolted fin-plate connection. For such structure the MCT method suggests that the structural fire resistance is 50 minutes. However, the realistic fire resistance calculated by an advanced performance-based procedure is evaluated to 44 minutes. Although the discrepancy between the results of both methods is not significant in the presented case, this finding implies that MCT can be on the unsafe side for some cases. More future debates and clarifications are therefore encouraged regarding the actual limits of the applicability of the simplified procedures.
The Influence of «DORLUK» Impregnation on Physical and Mechanical Characteristics of Asphalt Pavements
Authors: Yadykina Valentina V. , Trautvain Anna , Akimov Andrey , Yakovlev Evgeniy
Published: June 2018

The article shows results of the influence of "DORLUK" impregnation on physical and mechanical characteristics of asphalt concrete pavement. "DORLUK" impregnation is produced by "Scientific-Production Enterprise" Plant Innovation Industrial Equipment" ("SPE "PIIE"). The impregnation was tested on the section of road «1P-193 from Voronezh to Tambov». The research of the additive’s effectiveness was carried out according to the following characteristics of asphalt-concrete samples: density, water saturation, water resistance, water permeability, fatigue strength. According to the findings the application of the "DORLUK" impregnation results in a significant decrease in the water saturation of asphalt concrete samples by 36%, and also in water permeability decrease under the pressure by 3-4 min. Reducing the water saturation and water permeability of asphalt concrete with impregnation will reduce the negative impact of water on the strength characteristics of asphalt concrete. It is important to note that the impregnation has no negative effect on the fatigue strength of asphalt concrete samples, since the amount of cycles of samples with impregnation and without it is the same.
The Effect of Blockage Ratio on Fluid Flow and Heat Transfer around a Confined Square Cylinder under the Effect Thermal Buoyancy
Authors: Laidoudi Houssem
Published: June 2018

2D simulation is carried out to determine exactly the effect of blockage ratio on the flow and mixed convection heat transfer characteristics of Newtonian fluid across a square cylinder confined in horizontal channel, the numerical study is investigated in the range of these conditions:Re= 10 to 30,Ri= 0 to 1 and blockage ratioβ= 1/10 to 1/2. The flow structure and temperature field are visualized in terms of streamlines and isotherm contours. The total drag coefficient and average Nusselt number are also reported to show the combined effects of thermal buoyancy, Reynolds number and blockage ratio on the hydrodynamic flow forces and heat transfer rate. The obtained results showed that the effect of thermal buoyancy on fluid flow and heat transfer becomes more pronounced by decreasing the blockage ratio.
Thermodynamics Analysis of MHD Casson Fluid Slip Flow in a Porous Microchannel with Thermal Radiation
Authors: Shashikumar N.S. , Prasannakumara B.C. , Gireesha Bijjanal Jayanna , Makinde Oluwole Daniel
Published: June 2018

The heat transfer and entropy generation in a MHD flow of Casson fluid through a porous microchannel with thermal radiation were investigated numerically. Combined effects of suction/injection, hydrodynamic slip, magnetic field and convective boundary condition on the heat transfer and entropy generation are studied. The dimensionless equations are solved numerically by using fourth-fifth-order Runge–Kutta integration method along with shooting technique. Moreover, influences of pertinent parameters on velocity, temperature and entropy generation were discussed in detail and illustrated graphically. Based on numerical results, we can see that, entropy generation rate increases with an increase in radiation parameter and Biot number. As Hartmann number increases, the entropy generation decreases at the both cooled and heated plates and increases at the centerline region of the microchannel.
The Effect of Reynolds and Prandtl Number on Flow inside of Plan Channel of Waved Bottom Wall under Mixed Convection
Authors: Laidoudi Houssem , Bouzit Mohamed
Published: June 2018

2D simulations of incompressible fluid in plan channel of waved bottom wall is carried out in this paper to understand and to determine correctly the effects of the Reynolds, Prandtl and Richardson numbers on the fluid flow and heat transfer of waved channel wall. The governing equations involving continuity, momentum and energy are solved numerically based on commercial code which called ANSYS-CFX. The results are presented and discussed for the range of following conditions as:Re= 60 to 250,Pr= 0.7 to 30,Ri= 0 to 1 at fixed value of blockage ratio. The numerical results showed that increase in Richardson number and/ or Prantl number For Reynolds number limited between 60 and 200 increases tightly the heat transfer rate. For the value 250 of Reynolds number increase in the buoyancy strength reduces the value of heat transfer rate.
Numerical Approach at Flat Plate for Predicting the Film Cooling Effectiveness Part B: Effect Injection Angle
Authors: Kebir Farouk , Khorsi Azzeddine
Published: June 2018

In order to improve the cooling effectiveness of the film, a numerical study was conducted to study the effects of different film-cooled angles on surface heat transfer. In this work CFD simulation has revealed the difference of injection angles ranging from 35°,45°,55°,65° and 90° with different blowing, where the low blowing ratios are represented by M = 0.5, and the high blowing ratios by M = 1.0 and 1.5. And the turbulence closure is done with the help of the k - ω shear stress transport (SST) turbulence model. It is found that the stream-wise variations in the angles of the holes do not really provide a significant change in the adiabatic film cooling effectiveness results. On the other hand, the results indicate that the hole of angles 35°and 45° improved the centerline and laterally averaged adiabatic effectiveness, and the effectiveness decrease particularly at high blowing ratios.
Luminosity Correction Using Statistical Features on Retinal Images
Authors: Wan Mustapa Wan Azani , Yazid Haniza , Abdul Kader Mohamed Mydin M.
Published: June 2018

Retinal fundus image is important for the ophthalmologist to identify and detect many vision-related diseases, such as diabetes and hypertension. From an acquisition process, retinal images often have low gray level contrast and low dynamic range. This problem may seriously affect the diagnostic process and its outcome, especially if an automatic computer-based procedure is used to derive diagnostic parameters. In this paper, a new proposed method based on statistical information such as mean and standard deviation was studied. The combination of local and global technique was successful to detect the luminosity region. Then, a simple correction intensity equation was proposed in order to replace the problem intensity. The results of the numerical simulation (SNR = 2.347 and GCF = 4.581) indicate that the proposed method effective to enhance the luminosity region. Implications of the results and future research directions are also presented. Keywords: Detection, Luminosity, Retinal, Statistical.
Hybrid Metaheuristics for Solving the Blocking Flowshop Scheduling Problem
Authors: Lebbar Ghita , El Barkany Abdellah , Jabri Abdelouahhab , El Abbassi Ikram
Published: June 2018

This paper suggests two evolutionary optimization approaches for solving the blocking flow shop scheduling problem with the maximum completion time (makespan) criterion, namely the genetic algorithm (GA) and the simulated annealing genetic algorithms (SAGA) that combines the simulated annealing (SA) with the (GA), respectively. The considered problem and the proposed algorithms have some parameters to be adjusted through a design of experiments with exorbitant runs. In fact, a Taguchi method is presented to study the parameterization problem empirically. The performance of the proposed algorithms is evaluated by applying it to Taillard’s well-known benchmark problem, the experiment results show that the SA combined with GA method is advanced to the GA and to the compared algorithms proposed in the literature in minimizing makespan criterion. Ultimately, new known upper bounds for Taillard’s instances are reported for this problem, which can be used thereafter as a basis of benchmark in eventual investigations.
Experimental Investigation of Mechanical Behavior of a Polyamide before and after Constrained Groove Pressing Process
Authors: Bennouna Mohammed Salah , Aour Benaoumeur , Bouaksa Fatiha , Hamzaoui Saad
Published: June 2018

In this paper an experimental investigation of mechanical behavior of a thermoplastic polymer (polyamide PA 66) processed by constrained groove pressing (CGP) using several passes is presented. To this end, corrugating and straightening tools are designed and manufactured. The effects of the number of passes and the hold time on the mechanical behavior of the polyamide have been highlighted. The obtained results show that the material properties and the microstructure are significantly altered under CGP process. It has been found that the microhardness and the tensile properties have been progressed accordingly to the number of cycles, especially when the samples are processed using a hold time of five minutes. Hence, it can be concluded that this latter plays a very important role on the reorientation and stabilization of the microstructure when the processed material is a polymer.
Future Dielectric Materials for CNT Interconnects - Possibilities and Challenges
Authors: Sathyakam P. Uma , Mallick Partha S.
Published: June 2018

Carbon nanotube (CNT) interconnects are emerging as the ultimate choice for next generation ultra large scale integrated (ULSI) circuits. Significant progress in precise growth of aligned CNTs and integration of multiwalled CNT interconnects into a test chip make them promising candidates for future nanoelectronic chips. Tremendous research efforts were made on silicon based ultra-low-k dielectrics for Cu interconnects, but, the most recent advancements in polymer based composites as dielectric materials open up fresh challenges in the use of low-k dielectrics for CNT interconnects. This paper reviews the emerging polymer composites like Boron Nitride Nanotubes, Graphene/Polyimide composites, Metal Organic Frameworks and small diameter CNTs. Many reviews are already exists on the synthesis, fabrication, dielectric, mechanical, chemical and thermal properties of these materials. In this review, we have explained the specific properties of these materials and the necessities for integrating them into CNT interconnects to meet the requirements of future IC designers.Keywords: low-k dielectric materials, ultra low-k dielectrics, carbon nanotubes, interconnects, dielectric constant,
An Efficient Method to Completely Remove Catalyst Particles from HiPCO Single Walled Carbon Nanotubes
Authors: Godwin M. Anto , Allannavar Aparna Basavaraja , Joshi Sarika , Reddy Gadhadar , Abhishek S.S. , Bradley Robert Kelley
Published: June 2018

An efficient, economic and easy method for removing 99% of catalyst particle from high pressure carbon monoxide (HiPCO) single walled carbon nanotubes (SWCNT) is reported. The experiment is carried out at low temperature followed by acid treatment. The process exploited here is oxidation of the carbon impurities to gaseous phase as CO2 and removal of oxidized catalyst debris using acid treatment. Stability of SWCNT at these temperatures does not allow any damage to the nanotubes, however, some damage is observed which can be attributed to the oxidation of catalyst particles and their removal. The purified sample showed very less/no amount of amorphous carbon and catalyst impurities. Characterization of the material was carried out using Raman spectroscopy, Thermogravimetric analysis (TGA), Scanning electron microscopy (SEM), Transmission electron microscope (TEM) and Energy Dispersive Spectroscopy (EDAX). The resultant SWCNT were found to be highly pure. EDAX spectroscopy showed that the purified sample had only 0.5wt% of catalyst impurities whereas the as prepared once have 9.09wt%, also, TGA curve of the treated sample showed a very significant increase in the oxidation temperature indicating less defect and less catalyst content in the sample. The non- carbonaceous residue after purification is about 0.3%. highly efficient purification of SWCNT using the proposed method. This work provides a basis on removing the catalyst particles completely.
Fabrication and Compressive Properties of Titanium Foam for Bone Implant Applications
Authors: Li Zeng Feng , Wu Chen , Chen Gang , Tan Ping , Zhao Shao Yang , Ge Yuan , Yin Jin Gou
Published: June 2018

In order to meet the requirements for the purpose of biological implant materials, analyzes the matching requirements of the compatibility and mechanical properties of titanium foam biological; by powder metallurgy method, using TiH2 powder as raw material, using ammonium bicarbonate as pore forming agent, preparation of titanium foam. The influences of pore forming agent content and particle size, sintering temperature and holding time on the pore structure, pore distribution, pore size and compressive properties of foam titanium were discussed in detail. The results show that with the increase of the sintering temperature and prolonging holding time, titanium foam compressive yield strength and modulus increased; with the increase of the content of pore forming agent, titanium foam compression yield strength and Young's modulus decreased. The preparation of a porosity of 48% ~ 77%, pore size between 300 ~ 500 m, foam pore structure and pore size in micron level through three-dimensional pore, pore size of bio materials meet the requirements. The compressive strength is 98~186MPa, and the young's modulus is 1.6 ~ 6.8 GPa, which matches the strength and the modulus of elasticity of biological implants.
Physical and Tensile Properties of NiTi Alloy by Selective Electron Beam Melting
Authors: Hayat Muhammad Dilawer , Chen Gang , Liu Nan , Khan Shifaz , Tang Hui Ping , Cao Peng
Published: June 2018

NiTi is characterized as a shape memory alloy that has found interesting applications from aerospace to biomedical engineering. The use of NiTi in biomedical applications is due to its excellent biocompatibility, shape memory and pseudoelastic properties. These properties make NiTi an excellent candidate for many functional designs in biomedical fields. However, difficulties in manufacturing and processing of this alloy are significant hindrance to widespread applications. Advances in additive manufacturing (AM) such as selective laser and electron beam techniques have provided opportunities in manufacturing complex shaped NiTi parts. In this research paper, we demonstrate manufacturing of NiTi parts using a selective electron beam melting (SEBM) technique. Complete evaluation of physical, chemical and mechanical properties was carried out to determine the suitability of SEBM process. Differential scanning calorimeter (DSC), X-ray diffraction (XRD), and metallographic analyses were employed for the thermal and structural characterizations. The obtained results suggest that it is imperative to, and challenging to control the additive manufacturing process in order to obtain the desired microstructures and avoid unwanted texture. An exhaustive heat treatment of the samples after SEBM process might also be necessary.
Microstructure and Mechanical Properties of Ti-5Al-2.5Fe Alloy Produced by Powder Forging
Authors: Jia Ming Tu , Blanchard Clément , Bolzoni Leandro
Published: June 2018

Blended elemental powder metallurgy is a cost effective approach to produce near net shape titanium alloy parts; however, the residual pores remaining in sintered parts are detrimental to the mechanical properties. In this study, elemental powders (Ti, Al and Fe) were used to produce the Ti-5Al-2Fe alloy by a powder forging process, involving cold compaction, vacuum sintering, forging and heat treatment. The residual pores of the sintered parts were removed completely by forging at the temperature of 1250oC. The effect of solution and aging and mill annealing heat treatments on the mechanical properties of the forged Ti-5Al-2Fe parts were studied. It is found that the ductility of the forged Ti-5Al-2Fe parts is improved significantly by both solution and aging treatment and mill annealing, without decreasing their ultimate tensile strength, which sits around 1000 MPa. The enhancement of the mechanical behaviour is justified via understanding the evolution of the residual porosity and of the microstructural features of the materials.
High-Strength Concrete Made of Nonferrous-Metals Industry Waste
Authors: Umnova Elena V. , Ylesin Mikhail A. , Mashin Nikolay A. , Karmanovskaya Natalya V.
Published: June 2018

The use of calcium polysulfide sealer, which can be obtained by dilution of sulphur in lime suspension heated to 95 оС, when producing concrete of high specific weight provides improvement of its strength while being compressed by 30-50%. In doing so, up to 50% portland cement in the composition of binding one can be replaced with metallurgic ferriferrous slag or ferriferous stubs.
Use of the Piles of Effective Type in Geotechnical Construction
Authors: Sokolov Nikolai S.
Published: June 2018

Modern geotechnical construction has a wide range of technologies in its toolkit. Use of the Piles, manufactured with the help of different available technologies, represents one of the ways of the underground structures utilization at the objects zero level construction. The following basics shall be observed during zero cycle design and construction: 1) interactivity; 2) engineering viability; and cost efficiency. First principle suppose that interactivity utilization at the design is compulsory. This means: “initial design – test area – revised design”. It is necessary to adhere to the second principle for each of the elements of the formula given above. To ensure this, there are considered three and more Piles types (Bored Piles and Inclined Piles) in the initial design. It was determined that use of the Inclined Piles with multi point widening manufactured according to the Electric-Discharge Technology (EDT) is more preferable in comparison with the other Piles types. In effect, being Inclined Piles with the adjustable Holding Power, they have competitive advantages versus any other Pile. Therefore, use of the EDT Inclined Piles in the geotechnical construction after the interactive design has engineering viability and is a cost efficient way of underground structures construction.
Preparation and Catalytic Performance of Ni-Cu-B/TNTs Electrode by Cyclic Voltammetry Electrodeposition for Methanol Electro-Oxidation
Authors: Hou Guang Ya , Fang Guo  Liang , Tang Yi Ping , Wu Lian Kui , Cao Hua Zhen , Zheng Guo Qu
Published: June 2018

Orderly TiO2 nanotube arrays (TNTs) with high surface area became a prospective catalyst support. TNTs were obtained by anodizing Ti plate, and then the Ni-Cu-B/TNTs electrodes were prepared by cyclic voltammetry electrodeposition (CVE) method. SEM, EDS and electrochemical testing were used to investigate the microstructure and catalytic performance Ni-Cu-B/TNTs electrodes for methanol electro-oxidation. Effects of electrodeposition time, CVE scanning rate and times on the methanol electrooxidation were studied. The results show the shape of Ni-Cu-B particles on surface change from fusiform-like to spherical with an increasing of deposition temperature. The peak current density initially increased and then decreased with increasing electrodeposition time, rate and number of CVE scanning. The Ni-Cu-B/ TNTs electrode prepared by 30 cyclic times in 30°C at-0.8~0.2V and the scan rate of 20mV s-1 appear the best electrocatalytic activity for methanol oxidation. After cycled 1300 times for methanol oxidation, the peak current density decreased by 12%, indicating excellent long term stability of Ni-Cu-B/TNTs electrode.
Effect of Regenerated-Foundry Sand on the Mechanical Properties of Core
Authors: Kang Bu Yoon , Kim Kyeong Ho , Park Dae Won , Lee Man Sig
Published: June 2018

Metal foundries use high quality sand in the casting process and produce vast amounts of used foundry sand (UFS). Thus, in order to make the best use of foundry sand in the casting process, it is essential to demonstrate an appropriate recycling method and verify the influence of regenerated foundry sand (RFS) on the mechanical properties of core. In this study, physical and chemical characterizations were conducted on the RFS and the physical properties of cores containing different proportions of RFS were investigated with respect to the flexural strength. The UFS produced in controlled conditions was recycled by a wet type method and the regular foundry sand was replaced with varying proportions of RFS by weight (0, 20, 40 and 60 wt. %). Although the gradation of RFS was analogous with the regular foundry sand, the flexural strength test indicated that the sand mixture with 20 wt. % replacement of regular foundry sand was appropriate for core making without a drastic decrease of flexural strength. The flexural strength decreased with the increase of RFS contents at replacement proportion more than 20 wt. %.
Research on Correlation between Insulation Performances and Damage Degree of Burned Cable
Authors: Yu Xin , Zhang Tao , Wang Jin Feng , Li Zhi Wei , Yi Lin , Li Yu Feng
Published: June 2018

In this paper, the insulation near the fault point of a breakdown 220 kV cable joint for burned cable, which kept burning for about one hour, was investigated. The relationship between insulation performance and damage degree of burned cable was analyzed by comprehensive test of material performance. Differential scanning calorimetry (DSC) test results showed that the shoulder peak temperature could reflect the heat history of the materials. There was a correlation between damage degree and the characteristic absorption peak of spectrum (IR) graph. The result of mechanical performance was different obviously. The results of broadband dielectric spectrum showed that the relative permittivity and dielectric loss factor for samples close to the fault point were smaller. By the microstructure observation of sample crystal distribution form, the above conclusions were proved. As a conclusion, DSC, IR, SEM and dielectric performance analysis results matched the real situation, showed that these methods was feasible and effective to judge the damage degree of burned cable.
Research on Water Content and Physicochemical Properties of Insulating Materials for Water-Soaked XLPE Cable
Authors: Li Zhi Wei , Pan Ze Hua , Li Cheng Lei , Gao Peng Fei , Liang Sa Jia , Gao Nai Kui , Jin Hai Yun
Published: June 2018

The buried environment of cross-linked polyethylene (XPLE) cable is relatively severe, and some ones are even immersed in water directly. In this paper, an XLPE cable was soaked in foul water to simulate the cable’s actual water area environment, lasting for three years. The water content in the insulation layers of water-soaked cable was measured by infrared spectrometer and moisture analyzer, and the crystal morphology and physicochemical properties of the insulation layers were investigated by differential Scanning Calorimeter (DSC), scanning electron microscopy (SEM) and tensile testing technology. The results showed that a small amount of water did enter into the cable insulation owing to the increasing of hydroxyl (-OH) content, and followed being verified by moisture analyzer. The degree of crystallinity of water-soaked cable insulating material is also increased, and the mechanical properties were deteriorated.
Optical Properties Evaluated According to the Different Thickness Sapphire under the Same Polishing Conditions
Authors: Chae Ji Hoon , Lim Hyung Yu , Cho Bum Rae
Published: June 2018

The sapphire substrate have a significant impact on reducing the light scattering loss and in accordance with the crystalline surface and can improve the light emission efficiency is the surface roughness of the sapphire LED is an important factor. When the CMP process after measuring the transmittance, haze, and surface roughness had a transmittance of 84% or more transmittance at all wavelengths, regardless of the thickness it was confirmed that the haze also has a low value, regardless of the thickness. Was confirmed that the surface roughness is greater the thicker the thickness of the sapphire it affects the pressure of the CMP polishing and then take a lot of importing a low surface roughness value of the thickness of the sapphire CMP process the surface roughness value.
Assessment of Resistance to Fragmentation of Crushed-Stone Aggregate for the Application in Road Engineering
Authors: Babiak Michał , Ratajczak Adrianna , Ratajczak Maria , Węgliński Szymon
Published: June 2018

A lot of research centres in the world deal with developing the reuse of waste technology. The processed waste is applied in many industries, especially in the infrastructure construction. The European standards allow to apply recycled materials in implementation of buildings and the road engineering. In most cases, the detailed classifications for recycled aggregates are the subject of domestic standards, in which this topic is studied and developed deeply (Germany, Austria). In Poland, at the stage of applying the recycled aggregate, contractors are forced to rely on German or Austrian guidelines. In many cases, the application of the recycled materials is based on the contractors’ experience or intuition. That is why each additional development expansion of the knowledge on the recycled aggregates is added value and is very helpful for designers and contractors. The paper presents the comparison of mechanical resistance to fragmentation in a Los Angeles abrasion machine of selected crushed-stone and recycled aggregates (crushed concrete rubble) from demolished road structures.
Synthesis and Characterization of Red Mud and Sawdust Based Geopolymer Composites as Potential Construction Material
Authors: Kong Ing , Khoo Kay Min , Buddrick Oliver , Baharuddin Abdul Aziz , Khalili Pooria
Published: June 2018

The aim of this study was to synthesize the geopolymer composites formed by two industrial wastes, namely red mud (RM) and saw dust (SD). SD was chemically treated with alkali for the removal of lignin and subsequently bleached, before forming composite with acid-modified RM. The composites were then characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetic analysis (TGA) and universal testing machine to study the morphology, chemical, thermal and mechanical properties. The FTIR spectrum showed that Si and Al from the raw materials played the major role in forming aluminosilicate geopolymer composites. The SEM images revealed that SD and RM particles aggregated to form fully condensed geopolymer matrices with high compressive strength of 8.3-138 MPa, which were comparable to Portland cement (compressive strength of 9-20.7 MPa).
Preparation of BTO@GO@PU Composite Membrane and its Application in Microwave Absorption Field
Authors: Yan Yong Jie , Ni Qing Qing
Published: June 2018

Barium titanate/graphene oxide/polyurethane (BTO@GO@PU) composite membranes for microwave absorption were designed and fabricated by mechanical-blending of BTO and GO in PU medium, followed by mold formation. The cross section morphology of the BTO@GO@PU membrane indicated that the BTO nanoparticles with 450 nm average diameter are successfully incorporated into the PU matrix. Mechanical tensile measurement showed that, as the amount of BTO nanoparticles increased from 5 wt% to 20 wt%, the elastic modulus of the corresponding membrane increased up to 23.0 MPa elongation with the elongation above 450 %. Microwave absorption property of the BTO@GO@PU membranes were evaluated by measuring its reflection loss in the frequency range of 0.1-18 GHz. With the addition of BTO up to 20 wt%, the maximum absorptivity of the composite reached up to 51 %. This is attributed to the dielectric loss of BTO nanoparticles.
Performance and Evaluation of Low Cost Sugarcane Bagasse - Polypropylene Biocomposites as Candidate Material for Automotive Parcel Tray
Authors: Anggono Juliana , Sugondo Suwandi , Alim Rassy , Purwaningsih Hariyati , Wibawa Aria
Published: June 2018

Many auto manufacturers such as Mercedes Benz, Toyota and DaimlerChrysler have already embraced natural fiber composites into both interior and exterior parts and are looking to expand the uses of this composites. They have to balance the changing public demands of greater comfort, better driving performances, and higher safety standards with the environmental requirements. Based on the preliminary study using 20 to 30 wt.% NaOH treated sugarcane bagasse fibers to make biocomposites with polypropylene matrix, the tensile strength obtained was variably, in the range between 8.31 to 20.59 MPa. A further study was required to improve the strength of the composites in comparison with the specified flexural strength required by the industry for automotive parcel tray. The sugarcane bagasse fibers obtained from the sugar mill were used and alkali treated with 10% v/v NaOH at various soaking time of 2, 4, and 6 hours. Biocomposite samples were prepared from 25/75 wt.% ratio sugarcane fibers/polypropylene (PP). The highest tensile strength of 14.35 MPa was obtained from the samples with sugarcane fibers receiving two-hour alkali treatment. However, the highest flexural strength (37.78 MPa) was gained on the samples made from sugarcane fibers with 4 hours alkali treatment. This value has met the strength specification of two materials for current parcel trays which were made from monomaterial of polypropylene and woodboard composite which their flexural strengths were 35.6 MPa and 37.57 MPa, respectively. Structural studies using scanning electron microscopy (SEM) on the fracture surface of tensile tested samples show two different orientations of bagasse fibres in PP matrix, i.e. a group was in longitudinal orientation and other in transversal orientation.
Understanding the Chemistry in Silicon Carbide Chemical Vapor Deposition
Authors: Danielsson Örjan
Published: June 2018

Understanding the chemistry in CVD of SiC is important to be able to control, improve and scale up the process to become industrially competitive. A thorough understanding have so far been difficult to achieve due to the complex nature of the process. Through modeling tools, and a systematic approach when constructing the chemical models, new insights to the SiC CVD chemistry can be obtained. Using a general model that is independent on the choice of precursors and reactor configuration, and by coupling modeling results to experimental findings, we here show that SiCl2 and SiH2 previously suggested as the main silicon bearing growth species in the chlorinated and standard chemistries, respectively, does not contribute significantly to the SiC growth, and that the main active species are C2H2, CH3, Si, and SiCl.
Reduction of Surface and PL Defects on n-Type 4H-SiC Epitaxial Films Grown Using a High Speed Wafer Rotation Vertical CVD Tool
Authors: Daigo Yoshiaki , Ishiguro Akio , Ishii Shigeaki , Ito Hideki
Published: June 2018

4H-SiC homo-epitaxial films were grown using a high speed wafer rotation vertical CVD tool, and effects of wafer rotation speed during initial temperature ramping before epitaxial growth were investigated. Also, the effects of conditions during growth of the highly doped buffer layer on both surface and PL defect densities were investigated. It was found that the wafer rotation speed during the temperature ramping has a large influence on the surface defect density of the films. Especially, triangles generated from small pits were considerably reduced in the samples grown at a higher wafer rotation speed during the temperature ramping. The phenomena could be explained as a result of suppressed interfacial reaction between down-falls (DFs) and the wafer surface. Additionally, it was found that the density of basal plane dislocations (BPDs) on a drift layer is remarkably reduced by adjusting the C/Si ratio during growth of the buffer layer grown prior to the drift layer. By applying higher wafer rotation speed during the temperature ramping and optimizing the C/Si ratio for the growth of the buffer layer, a total defect density of 0.75 cm-2 on the film, which includes DFs, triangles, DF-triangles, stacking faults (SFs) and BPDs, was achieved.
In Situ Synchrotron X-Ray Topography Observation of Double-Ended Frank-Read Sources in PVT-Grown 4H-SiC Wafers
Authors: Yang Yu , Guo Jian Qiu , Raghothamachar Balaji , Dudley Michael , Weit Swetlana , Danilewsky Andreas N. , McNally Patrick J. , Tanner Brian R.
Published: June 2018

We present in-situ observations of the dynamical operation of multiple double-ended Frank-Read dislocation sources in a PVT-grown 4H-SiC wafer under thermal gradient stresses. The nucleation of these sources is facilitated by a specific configuration consisting of one basal plane dislocation (BPD) segment pinned by two threading edge dislocations (TEDs). This configuration is formed during PVT crystal growth by deflection of TEDs on to the basal planes by macrosteps and re-deflection of resulting BPDs back into TEDs. Under the influence of thermal gradient stresses induced by heating inside a double ellipsoidal mirror furnace, the pinned BPD segment glides and activates dislocation multiplication by the double Frank-Read source mechanism. A more intricate mechanism of swapping of TED pinning points between Frank-Read sources lying on same basal plane is identified, enabling one dislocation loop to effectively “pass through” the other dislocations on same basal plane.
Various Single Photon Sources Observed in SiC Pin Diodes
Authors: Tsunemi Hiroki , Honda Tomoya , Makino Takahiro , Onoda Shinobu , Sato Shin Ichiro , Hijikata Yasuto , Ohshima Takeshi
Published: June 2018

Luminescence centers formed in the vicinity of SiC surface are expected to be utilized as Single Photon Sources (SPSs) because of the high-brightness and the potential of electric control at room temperature. In order to gain more insight into the surface SPSs, 4H-SiC pin-diodes are fabricated and the surface SPSs formed in the pin diodes are investigated using a confocal laser scanning fluorescence microscope (CFM). Locations where the surface SPSs appear as well as photoluminescence spectra of the observed surface SPSs are presented. Antibunching characteristics of the surface SPSs are also investigated by the second order autocorrelation function measurement. We conclude that two different types of surface SPSs appear in the surface of 4H-SiC. The location dependence of the observed surface SPSs indicates that the oxide layer on 4H-SiC plays an important role in the formation of surface SPSs, whereas neither ion implantation nor donor ions had an effect. The peak wavelength of luminescence spectra widely varies depending on their locations, indicating lattice strain introduced by the oxide layer has the potential to affect the luminescence spectra.
Deep Level Defects in 4H-SiC Epitaxial Layers
Authors: Capan Ivana , Brodar Tomislav , Ohshima Takeshi , Sato Shin Ichiro , Makino Takahiro , Pastuovic Željko , Siegele Rainer , Snoj Luka , Radulović Vladimir , Coutinho José , Torres Vitor , Demmouche Kamel
Published: June 2018

We present a study of electrically active radiation-induced defects formed in 4H-SiC epitaxial layers following irradiation with fast neutrons, as well as 600 keV H+ and 2 MeV He++ ion implantations. We also look at electron emission energies and mechanisms of the carbon vacancy in 4H-SiC by means of first-principles modelling. Combining the relative stability of carbon vacancies at different sites with the relative amplitude of the observed Laplace-DLTS peaks, we were able to connect Z1 and Z2 to emissions from double negatively charged carbon vacancies located at the h- and k-sites, respectively.
Resistivity Increase in 6H-SiC Crystal Grown with Simple Modification in PVT Process
Authors: Choi Jung Woo , Park Jong Hwi , Seo Jung Doo , Kim Jung Gyu , Kyun Myung Ok , Ku Kap Ryeol , Kim Young Gon , Choi Su Hun , Lee Won Jae
Published: June 2018

6H-SiC single crystal was grown with simple modification in PVT process to investigate the aspect of resistivity change in crystal. The modified process consisted of a new initial step to get rid of impurities in the growth cell before the main growth of SiC crystal. The new step in the modified process was designed to consist of higher temperature than the growth temperature for sublimation of impurities. SiC crystal grown with using 2 times of impurities sublimation process (ISP) step exhibited lower variation of resistivity value on whole wafer than SiC grown using with 1 time. With implementation of new modified step in growth process, SiC single crystal with resistivity value above 103Ωcm could be obtained by simple PVT process and conventional low-purity SiC source material.
Effect of Electron Irradiation on Electrical and Electroluminescent Properties of n+p 4H-SiC Structures
Authors: Strel'chuk Anatoly M. , Kalyadin Anton E. , Lebedev Alexander A. , Kozlovski Vitalii V. , Romanov Leonid P. , Petrov Victor A.
Published: June 2018

A study of how electron irradiation affects the current-voltage (I-V) and electroluminescence (EL) characteristics of two types of 4H-SiC n+p structures with p-base and base doping to ~5∙1015 cm-3 is presented. The characteristics were measured prior to irradiation and after each of five stages of irradiation with 0.9 MeV electrons at doses in the range from 1∙1015 to 1.1∙1016 cm-2. The irradiation leads to an increase in the recombination current, decrease in the intensity of the edge EL (hνmax≈3.18 eV), and increase in the intensity of the infra-red (IR) EL (hνmax≈1.35 eV), which starts to predominate. Presumably, this indicates that the nonequilibrium carrier lifetime decreases and the concentration of acceptor type defects grows as a result of the irradiation. The IR EL, attributed to a complex defect containing a silicon vacancy, is of interest for development of single-photon sources of light.
Evaluation of the Effect of Ultraviolet Light Excitation during Characterization of Silicon Carbide Epitaxial Layers
Authors: Das Hrishikesh , Sunkari Swapna , Akdik Oener , Konstantinov Andrei , Gumaelius Krister , Svedberg Jan Olov , Allerstam Fredrik
Published: June 2018

The scanning of Silicon Carbide (SiC) epitaxy wafers for defects by ultraviolet (UV) laser or lamps is widely prevalent. In this work, we document the effects of UV light excitation on the SiC epitaxy material. An increase in background photoluminescence (PL) is observed after repeated scans. The effect of this increase on defect detection is shown. Optimal surface treatments to recover the material back to the original state are demonstrated. Further, some surface treatments are proposed which reduce the effect of the UV light excitation and prevent to a large extent the rise in background PL.
Depth Profiling of Carrier Lifetime in Thick 4H-SiC Epilayers Using Two-Photon Absorption
Authors: Mahadik Nadeemullah A. , Stahlbush Robert E. , Klein Paul B. , Khachatrian Ani , Buchner Stephen
Published: June 2018

Depth profiling of the ambipolar carrier lifetime was performed in n-type, 140mm thick silicon carbide (SiC) epilayer using excitation by two-photon absorption (TPA) with a pulsed 586nm laser, and confocal measurement of time resolved photoluminescence (TRPL) decay from the excited region. A depth resolution of ≈10mm was obtained. The PL decay curves were analyzed using a recently developed formalism that takes into account the TPA excitation, carrier diffusion and surface/interface recombination. The carrier lifetime decreases near the top surface of the epitaxial layer as well as near its interface with the substrate.
Improvement of Local Deep Level Transient Spectroscopy for Microscopic Evaluation of SiO2/4H-SiC Interfaces
Authors: Yamagishi Yuji , Cho Yasuo
Published: June 2018

We demonstrate our new local deep level spectroscopy system improved for more accurate analysis of trap states at SiO2/4H-SiC interfaces. Full waveforms of the local capacitance transient with the amplitude of attofarads and the time scale of microseconds were obtained and quantitatively analyzed. The local energy distribution of interface state density in the energy range of EC − Eit = 0.31–0.38 eV was obtained. Two-dimensional mapping of the interface states showed inhomogeneous contrasts with the lateral spatial scale of several hundreds of nanometers, suggesting that the physical origin of the trap states at SiO2/SiC interfaces is likely to be microscopically clustered.
THz Emission from SiC Natural Superlattice Diodes Induced by Strong Electrical Field
Authors: Sankin Vladimir Ilich , Andrianov Alexander V. , Petrov Alexey G. , Zachar'in A.O. , Nagalyuk Sergey , Shkrebiy Pavel P. , Lebedev Alexander A.
Published: June 2018

Recently the intense terahertz electroluminescence from monopolar n++–n– –n+ structures of 6H- and 8H-SiC of natural superlattices at helium temperatures due to Bloch oscillations was discovered. In the present work we present the THz emission spectra of bipolar n++–π–n+ structures (π is a high-resistance layer of p-type conductivity) of natural superlattices 4H-, 8H- and 15R-SiC at 7 K. The bipolar n++–π–n+ structures of 4H- and 8H-SiC were analogous to those of structures for which the negative differential conductivity effect was observed earlier for three polytypes (4H, 6H and 8H) at T=300 K. We demonstrate resemblance and differences of the spontaneous THz emission spectra for the monopolar and bipolar 4H-, 6H- 8H- and 15R-SiC natural superlattices caused by Bloch oscillations of electrons in the SiC natural superlattice.
Chemical Trend in Band Structure of 3d-Transition-Metal-Doped AlN Films
Authors: Tatemizo Nobuyuki , Imada Saki , Miura Yoshio , Nishio Koji , Isshiki Toshiyuki
Published: June 2018

Band structure calculations for radiofrequency-sputtered AlN-films doped with various 3d-transition-metals (TM: V, Cr, and Mn) were conducted to investigate the origin of the characteristic optical absorption structures. Experimentally evaluated crystal structures and lattice constants of the synthesized films were adopted for supercells. The model calculations showed that additional energy bands mainly consisting of 3d e and t states of TMs are formed in the band gap of AlN (6.2 eV), and that their potentials depend on the TM species. It was also shown that the Fermi levels of Cr- and Mn-doped AlN lie within the spin-up t band, while the Fermi level of V-doped AlN lies between the spin-up e and t bands. These findings imply that the materials have TM species-dependent, multiple absorption paths with lower energy than the band gap energy of AlN, resulting in optical absorption in the near-ultraviolet, visible, and infrared regions.
Metal/Semiconductor Contacts to Silicon Carbide: Physics and Technology
Authors: Roccaforte Fabrizio , Vivona Marilena , Greco Giuseppe , Lo Nigro Raffaella , Giannazzo Filippo , Rascunà Simone , Saggio Mario
Published: June 2018

The physics and technology of metal/semiconductor interfaces are key-points in the development of silicon carbide (SiC) based devices. Although in the last decade, the metal to 4H-SiC contacts, either Ohmic or Schottky type, have been extensively investigated with important achievements, these remain even now an intriguing topic since metal contacts are fundamental bricks of all electronic devices. Hence, their comprehension is at the base of the improvement of the performances of simple devices and complex systems. In this context, this paper aims to highlight some relevant aspects related to metal/semiconductor contacts to SiC, both on n-type and p-type, with an emphasis on the role of the barrier and on the carrier transport mechanisms at the interfaces.