bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of Alloying Process on Inclusions in Fe-9Cr Alloy Reinforced with Y2O3 Nanoparticles
Authors: Qiu Guo Xing , Qu Le Xin , Wang Dong Wei , Zhan Dong Ping , Jiang Zhou Hua , Zhang Hui Shu
Published: May 2020

The effects of the alloying sequence and refining time on the inclusions in Fe–9Cr alloy reinforced with Y2O3 nanoparticles were investigated. The size and number of inclusions in the alloys were determined via optical microscopy, and their morphology and composition were determined via scanning electron microscopy. The Y2O3 mainly acted as a nucleating agent in the Si–Mn+Y2O3+Ti alloying process, promoting the precipitation of other oxides, which was beneficial for the formation of Y–Ti–O particles. In contrast, no Y–Ti inclusions were formed when the Si–Mn+Ti+Y2O3 alloying process was employed. In addition, the inclusions in the alloy tended to stabilize after refinement for 5–10 min. This study offers a general pathway for the manufacture of oxide dispersion strengthened steel via a smelting process.
Ultrasonic Preparation of Submicron Low Melting Point Alloy Powder
Authors: Shu Qing Qing , Shi Jing Tao , Liu Jing , Deng Zhong Shan
Published: May 2020

In order to study the preparation of low-melting alloy powder in phase change materials, three sets of control experiments were set up in this paper. To explore the effects of ultrasonic oscillation, ultrasonic atomization technology and rapid cooling had an effect on the particle size, surface morphology and powder shape of ultrasonic powder making. In the experiment, ultrasonic atomization, rapidly cooling ultrasonic atomization, and ultrasonic vibration generated powder were tested. The results showed that the surface of fog droplets generated by ultrasonic atomization was smooth, with distinct particles. The powder diameter was large, ranging from 20-60 μm. The surface of the powder obtained by ultrasonic shock existed an aggregation phenomenon. The powder diameter was small ranging from 5-10 μm. The ultrasonic atomized powder obtained by rapid cooling was mostly spherical with a smooth surface. After the screening, spherical powder with a diameter of 15-25 μm and the smooth surface could be obtained. The results showed that the particle diameter is small and uniform, while the uneven surface was difficult to eliminate. The experimental conditions of rapid cooling were favorable for the smoothness of the particle surface and the roundness of powder shape. Spherical powder with a diameter of 15-25 μm can be obtained by screening the rapidly cooled powder after ultrasonic atomization. Different experimental conditions and technological approach can produce high-performance low melting point alloy powder.
Microstructure and Mechanical Properties of a Novel Ti-6.5Al-2Sn-4Zr-1.5Mo-2Nb-0.25Fe-0.2Si High-Temperature Titanium Alloy
Authors: Zhao Ming Yu , Song Xiao Yun , Zhang Wen Jing , Diao Yu Wei , Ye Wen Jun , Hui Song Xiao
Published: May 2020

The Ti-6.5Al-2Sn-4Zr-1.5Mo-2Nb-0.25Fe-0.2Si (wt%) alloy is a novel two-phase high temperature alloy for short-term application. The effects of different heat treatments on the microstructure and mechanical properties were investigated through electron probe microanalysis (EPMA), optical microcopy (OM), scanning electron microscope (SEM), electron backscattered diffraction (EBSD) and tensile tests at room temperature and 650°C. Subjected to the annealing treatment at α+β region (1010 °C/2 h, FC to 990 °C+990 °C/2 h, AC), the microstructure was composed of bimodal structure, which consists of equiaxed primary α (αp) phase and lamellar transformed β (βt) structure. As a strong β stabilizer, the content of Fe in α phase is much less than that in β phase. Annealing at β region (1040 °C/2 h, AC) resulted in the formation of widmannstatten structure, consisting of coarse raw β grain and secondary α phase precipitated on the β grain. With respect to the tensile property, different heat-treated alloys obtained similar strength. However, widmannstatten structure was characterized by lower plasticity, with the elongation only half that of bimodal structure. The fracture characteristics at room temperature for the alloy with bimodal structure and widmannstatten structure are dominated by ductile fracture and cleavage fracture, respectively.
Effect of Cu Content on Ageing Behavior for AA3104-H19 Can Body Sheet
Authors: Yang Yang , Zhao Pi Zhi , Xiao Xiang , Zheng Xiao Bing
Published: May 2020

AA3104 ingots with different Cu content (0.1wt.%, 0.2wt.% and 0.3wt.%) were prepared by DC casting, and then the ingots were processed to 0.26mm sheets with the method of making AA3104 can be body sheet. The AA3104-H19 sheets were aged at 180°C and the aging strengthen effect were found in the 0.2wt.%Cu and 0.3wt.%Cu alloys. Optical micrograph (OM), X-ray diffraction, high resolution transmission electron microscope were used on the sheets after different ageing time. Rod like coherency precipitates with the length about 5-10nm and the thickness about 2-3nm which were parallel to the [111] plane of the matrix was precipitated at peak aging (180°C-2h). According to the result of the thermodynamic phase diagram calculation, the precipitates should be S-Al2CuMg phase, but the structure of the precipitates were different from the precipitates reported in 2XXX alloy.
In Situ Observation on the Deformation Behavior of Primary α-Ti in a Textured Ti-6Al-4V
Authors: Liu Yun Xi , Chen Wei , Li Zhi Qiang , Liu Liang Liang , Liu Dong
Published: May 2020

The tensile deformation process and dislocation behavior of primary α-Ti of Ti-6Al-4V were studied by the in-situ tensile test combined with EBSD (electron backscatter diffraction). The initiation, evolution and distribution of dislocation slips at different strains were discussed. The results showed that the microtexture of the material had a significant influence on slip behavior. Typically, basal and prismatic  slips initiated first, but the dominant slip type was related to the local texture characteristics. Sometimes, the basal and prismatic  slips could still initiate when their Schmid factors were relatively low, while the pyramidal slips usually need a higher Schmid factor to initiate. With the increase of strain, the second slip system inside one grain was activated to accommodate the plastic deformation. When the deformation was localized in a specific microtextured region, basal  slips were dominant, but eventually the crack initiated from the  slip bands inside the grain.
Microstructures and Phase Formation of Refractory MoNbTaVZr High Entropy Alloy
Authors: Wang Hao Yu , Wang Zi Yue , Nong Zhi Sheng , Wang Ji Jie , Man Tian Nan , Zhu Jing Chuan
Published: May 2020

Microstructures, component distribution and mechanical properties of a refractory high entropy alloy MoNbTaVZr were investigated by scanning electron microscope, X-ray diffractometer and universal testing machine, and the formation rule of second phases in as-cast alloy was discussed by the results of first principle calculations. The results show that as-cast MoNbTaVZr alloy is composed of two solid solutions with body centered cubic structure, together with Mo2Zr and an unknown phase. The chemical compositions of dendritic regions are relatively uniform, while Zr and V elements are rich in interdendritic regions. There is a short yielding phase when as-cast alloy was operated by the compression. According to calculations, the C15 Mo2Zr Laves phase with the strongest formation ability and highest structural stability would be formed preferentially in MoNbTaVZr refractory high entropy alloy.
Effect of RE Addition on the Solidified Process and Microstructure of Al-7Si-0.3Mg Alloys
Authors: Li Long Fei , Li Da Quan , Hu Xiao Gang , Feng Jian , Zhang Yong Zhong , Kang Yong Lin
Published: May 2020

The solidification process and microstructure of Al-7Si-0.3Mg alloy with different rare earth (RE) additions have been studied by using thermal analysis, optical microscopy (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results showed that the addition of RE enhanced the liquidus temperature and decreased the growth temperature of eutectic Si, which lead to obvious increase in solidification interval of the studied alloy. In addition, the grain size of primary α-Al had no obvious change, and the mean area of eutectic Si particles decreased with increasing RE content to 1.6 wt.%. The RE-rich compounds with different compositions were obtained with increasing RE concentration in Al-7Si-0.3Mg alloys. The method of phase diagram calculation helps to clarify the formation and growth mechamism of different RE-rich phases during solidification.
Accelerated Transformation of Hot Deformed Austenite in SCM435 Steel
Authors: Yang Huan , Yu Wei , Chang Wen Gao , Man Zeng Qiang , Cao Yun Fei
Published: May 2020

The element chromium and molybdenum delays the γ→α phase transition, while the deformation energy storage and high temperature diffusion can promote the γ→α phase transition process. The phase change of alloy structural steel SCM435 under different deformation temperature and cooling path after heating and holding at 1050°C was measured by a thermal simulator. The microstructure and hardness of the steel under various rolling processes were studied by using SEM and micro-hardness tests. The low deformation temperature (800~720°C) and the slow post-rolling cooling speed (1~0.3°C/s) were favorable for the γ→α phase change, where the phase microstructure showed the low hardness. As the isothermal temperature decreases, the microstructure changes from Pearlite (P)+ Ferrite (F) to P+ F + Martensite(M). The lower the isothermal temperature, the higher the martensite content in the structure, and the higher the hardness was. Both the low temperature deformation and 660°C isothermal treatment could quickly accelerate the γ→α transformation of SCM435. The fastest transformation temperature in this case for pearlite of SCM435 was 660°C, and the phase transition ended within 300s, which significantly shortened the time compared with the isothermal time in the low temperature zone.
Effects of Final Cooling Temperature on Microstructure Transformation and Properties of Q550 Low Carbon Bainite Steel
Authors: Man Zeng Qiang , Yu Wei , Yang Huan , Chang Wen Gao , Cao Yun Fei
Published: May 2020

The mechanical properties of low carbon bainite steel are closely related to the microstructure and proportion after phase transformation. The microstructure of the deformed austenite of low carbon bainite steel after isothermal transformation and continuous cooling transformation was studied by thermal simulation test. The metallographic structure was observed by optical microscopy (OM) and scanning electron microscopy (SEM). The metallographic and microhardness were used to judge the microstructure type, and the CCT (continuous cooling transformation) curve and TTT (time-temperature-transformation) curve of the test steel were drawn. It was found that at 700-430 °C isothermal, undergo a variety of medium-temperature microstructure transformations appeared for the test steels, such as ferrite, pearlite, granular bainite and lath bainite. The cooling rate and final cooling temperature have great influence on the type and performance of the final microstructure. The final cooling temperature was controlled at about 515°C. The mixed microstructures of granular bainite (GB) and fine martensite-austenite (M-A) island, a small amount of acicular ferrite and lath bainite were obtained. The yield and tensile strengths of this type of microstructure reached 639 MPa and 750 MPa respectively, the shrinkage rate reached 17%, and the better low-temperature impact performance was realized.
Reliability Prediction of Variable Amplitude Corrosion Fatigue Life of TP140 Casing Steel
Authors: Cui Lu , Bian Kai Zhou , Kang Wen Quan , Zhang Yu Feng , Li Zhen
Published: May 2020

Based on the constant amplitude CF test of oil well tube material TP140small specimen, the procedures of predicting the variable amplitude corrosion fatigue (VACF) life of given reliability of TP140 were developed. Through the multi-sample sinusoidal loading constant amplitude CF life texts, the reliability distribution of CF life was analyzed. The CF life prediction of the specified reliability was obtained under 4 different stress levels, and the corresponding P-S-N curve expressions were obtained. Using VACF loading block spectrum and P-S-N curve expressions, the VACF life was calculated without considering the loading sequence effect. Furthermore, 5 VACF life tests were carried out using the same loading block spectrum. The VACF life with reliability was predicted by the principle of reliability and statistics. VACF life was calculated and compared with the predicted life. Test results and analysis show that the predicted results agree well with the experimental results, and CF life of TP140 casing steel follows a lognormal distribution at the given equivalent stress level, which has been substantiated.
Comparative Study on Hydrogen Embrittlement Susceptibility in Heat-Affected Zone of TP321 Stainless Steel
Authors: Xu Xiu Qing , Niu Jing , Li Cheng Zheng , Huang Hang Juan , Yin Cheng Xian
Published: May 2020

TP321 stainless steel is widely used in hydrogenation refining pipes owing to its excellent performance of creep stress resistance and high-temperature resistance. In this study, thermal simulation tests were carried out on the welding heat-affected zone (HAZ) of TP321 stainless steel at temperatures of 1300 °C, 1100 °C, and 850°C using a Gleeble 3800 testing machine. Slow strain tensile tests were conducted under the condition of electrolytic hydrogen charging (EHC) and the metallographic microstructure of cracks as well as the morphology of fractures were analyzed in detail. The result shows that hydrogen can change the fracture mode of tensile specimen and the cracks initiated from and near the specimen surface after EHC. Hydrogen significantly decreases the plastic deformation capability of HAZ in TP321 stainless steel. The reduction of area after the fracture decreases by 58%, 41%, and 45% for HAZ at 1300 °C, 1100 °C, and 850 °C, respectively. The existence of δ ferrite was considered to be the main reason for the aggravation of hydrogen-induced plasticity loss.
Effect of Tempering Temperature on Microstructure and Properties of Low Carbon High Silicon Alloy Steel Treated by Q-P-T Process
Authors: Wei Jun Hu , Ran Xu , Ying Han
Published: May 2020

The mechanical properties and microstructure of low-carbon high-silicon alloy steel were examined under various tempering temperatures using the quenching, partitioning and tempering (Q–P–T) process. The performance changed with the variation in tempering temperature. The results show that the microstructure of low carbon high silicon alloy steel treated by Q-P-T process was mainly ferrite, martensite, carbide-free bainite and film-like retained austenite. This alloys exhibited good mechanical properties at tempering temperature of 300 °C. The product of strength and elongation were 33.7 GPa%. Specifically, the Ultimate tensile strength were 1508 MPa, the yield strength were 1048 MPa, and the elongation were 22.4%. At this temperature of 300 °C, the volume fraction of retained austenite reached 10.4%.
Application Feasibility Study of High Strength Pipeline Steel to Rig Derrick and Substructure
Authors: Li Fang Po , Zhang Zhi Wei , Zhang Bin
Published: May 2020

Derrick and substructure is one of rig’s core equipment components, and it is also the most important weight component of rig. The working environment of derrick and substructure is very serious, whose material should has high strength, excellent plasticity, toughness and weldability property. In this paper, the chemical composition, micro-structure, tensile property, impact property, hardness and weldability of high strength pipeline steel with strength grades of X70 (485MPa)~ X100(690MPa) were systematically analyzed. The analysis and study of the service environment of rig derrick and substructure as well as the technical requirements of the material, showed that the performance of high strength pipeline steel was obviously better than that of the same grade high strength low alloy structural steel used in rig derrick and substructure at present, and it can fully meet the technical requirement of rig derrick and substructure. The application of high strength pipeline steel to rig derrick and substructure will improve the service property, optimize the design , and fully ensure the service safety of rig derrick and substructure.
Preparation and Property of Waterborne Polyurethane/Cellulose Nanofiber Nanocomposite Films
Authors: Lin Yu Zhe , Zeng Jia Min , Ma Jing Hong , Gong Jing Hua
Published: May 2020

Waterborne polyurethane (WPU) is a new type of polyurethane system, which using water instead of organic solvent as dispersing medium. Because of its non-toxicity and environmental safety, WPU is considered as the development direction of coatings and adhesives. However, the mechanical properties of WPU are worse than that of solvent-based polyurethane, therefore, the modification of WPU has received increasingly attention. Meanwhile numerous evidences demonstrate the excellent properties of cellulose nanofibers (CNFs) such as high aspect ratio, low weight and outstanding mechanical strength. Therefore, there is a high expectation for CNFs to be introduced into WPU as reinforcing filler. In this work, a series of CNFs/WPU nanocomposite films were prepared by solution blending. The structure, morphology, thermal behavior and mechanical properties were investigated. SEM results showed that CNFs were evenly dispersed in the WPU matrix. Tensile tests indicated that the modulus and tensile strength of CNFs/WPU nanocomposite films were improved compared with the neat film. While the break elongation of the nanocomposite films decreased with the increase of CNFs content. The synergistic interaction between CNFs and WPU matrix plays an important role in the enhancement of mechanical properties.
Functionalization of MWNTs and its Influence on Thermal Performance of Modified Diphenyl Ether Polyimide Films
Authors: Fang Xue , Su Gui Ming , Jiang Hai Jian , Ma Yu Liang , Song Mei Hui , Zhang Xiao Chen , Chen Ming Yue
Published: May 2020

In this paper, we treated MWNTs by Fendon oxidation method and mixed acid method, finding the factors of functionalized effect affecting MWNTs. And added MWNTs treated to PI matrix for the study of the impact of MWNTs treated on thermal properties of the films. We using 3,3/,4,4/-diphenyl ether tetraacid dianhydride (ODPA) and 4,4'-diamino diphenyl ether (ODA) as raw material, mixing functional MWNTs and monomer by situ polymerization, then MWNTs / PAA hybrid glue was prepared. The molecular weight and distribution of the polyamic acid were measured by gel permeation chromatography (GPC), and the effects of different addition amounts on the product were examined. The PI/MWNTs films were prepared using an automatic film applicator, and finally the PI films were obtained by thermal imidization. The thermal behavior of the imidization process of the product was determined by differential scanning calorimetry (DSC) and thermogravimetric analysis (TG). The results showed that the PAA film has thermodynamic behavior at 150 ° C and 280 ° C approximately, which could be regarded as the kinetic interruption temperature of the imidization reaction. The dehydration cyclization reaction mainly occured in these two temperature ranges, moreover, the addition of MWNTs had no significant effect on the thermal decomposition temperature of the material which doping amount that does not affect the mechanical strength.
Manufactory and Properties of Poly(p-Phenylenebenzobisoxazole) Aerogels Prepared by a Simple Freeze-Drying Procedure
Authors: Wei Yu Nong , Li Guang , Yang Sheng Lin , Jin Jun Hong
Published: May 2020

Aerogels based on organic high performance fibers have been attracted great attention due to its excellent thermal and mechanical properties. Here, PBO nanofiber aerogel were prepared from the super-fiber PBO through a top-down process with a sol-gel process and a simple freeze-drying process, followed by thermal cross-linking. The prepared aerogel has a small volume shrinkage, a high specific surface area of 168.9 m2 /g and a small pore diameter of 1.356 nm. Because of its 3D porous structure, it results in a low density of 6 to 30 mg/cm3 and a high porosity (98%). The aerogel retains the molecular structure of PBO at the same time, which gives it initial thermal decomposition temperature up to 500 °C and a superior fire-retardant capability. PBO aerogel possesses good compressive properties with a yield stress of 0.44MPa at 80% strain and an elasticity modulus of 1.98 MPa which is higher than SiO2 and cellulose aerogel reported.
Research on Strong Spinning Process of GH4169 Alloy
Authors: Wu Hai Bao , Li Ji Zhen , Liu De Gui , Liu Jun Sheng
Published: May 2020

In this paper, the basic technology of spin forming process was carried out on the GH4169 alloy sheet by heating and strong spinning. The spheroidal spinability test method was used to study the spinability of the alloy. The effects of the strong spinning process parameters on the ultimate thinning rate, diameter expansion and fracture behavior of GH4169 alloy were analyzed. The research results showed that when the temperature was higher than 800 °C, the ultimate thinning rate of GH4169 alloy was above 80%. At the same time, with the increase of feed rate, the ultimate thinning rate of GH4169 alloy decreased. When the feed rate of the rotary wheel was lower than 200 mm•min-1, the ultimate thinning rate of GH4169 alloy was maintained above 80%. The radius of rotary wheel was strongly influence GH4169 alloy ductility which was confirmed by the picture of fracture. This basic research provides the experimental basis and process guidance for the practical use of GH4169 and other high-temperature alloy sheets to produce high-precision and high-performance spinning parts, which has significant application value.
Preparation of Silver Nanoparticles-Loaded Gel Fibers Based on Microfluidic Method and its Application as SERS Substrates
Authors: Li Wan Ying , Li Jia Hao , Ma Jing Hong , Gong Jing Hua
Published: May 2020

Surface-enhanced Raman scattering (SERS) spectroscopy technology has broad application prospects in food safety, environmental monitoring, surface science and material analysis because of the characteristics of ultra-high sensitivity and non-destructive testing. However, there are still some challenges in the preparation of SERS substrates. As SERS substrates, the common colloidal noble metal nanoparticles usually show low storage stability and poor repeatability of analytical results. In order to overcome these limitations, a coaxial microfluidic spinning device was designed to prepare flexible SERS substrates in this paper. Based on the microfluidic spinning and subsequent in-situ reduction reaction of AgNO3, novel gel fibers uniformly loaded with AgNPs were successfully prepared. The effects of the concentration of AgNO3 solution and UV irradiation duration on the formation of AgNPs were investigated. Transmission electron microscopy (TEM) showed that the average particle size was about 2.7 nm. The gel fibers loaded with AgNPs were used as SERS substrates to detect 4-mercaptobenzoic acid (4-MBA), which showed obvious Raman enhancement effect and good repeatability. The relative standard deviation of 10 test results was 4.75%, and the detection line range was 10-14-10-5 mol·L-1.
Effect of the Addition of Short Carbon Fiber on Thermal Insulation Properties of ZrB2- SiC Hot-Pressed Ceramics
Authors: He Lin Kai , Sun You Hong , Liu Mei Jun , Meng Qing Nan
Published: May 2020

Short carbon fibers reinforced ZrB2-SiC ceramics were prepared by hot pressing sintering process. The short carbon fibers with different volume fractions (0.2.4.6.8.10.20) were added for improving the thermal insulation properties of ZrB2-SiC ceramics. The experimental results showed that as the content of short carbon fiber increased, the thermal diffusivity decreased from 43.9m2/s to 32.9m2/s, the thermal conductivity decreased from 104.3 W/(m·K) to 72.9 W/(m·K) and thermal insulation performance reduced by 43.1%, respectively. The enhancement of the thermal insulation properties is mainly due to high interfacial thermal resistance of short carbon fiber and matrix.
Integrated Computation and Preparation Optimization of In Situ Ordered Porous Aluminum Filled Tubes
Authors: Wang Han , Tian Long Bo , Hao Hai
Published: May 2020

As a kind of structural and functional composite material, foam filled tubes have an application prospect in automobile industry because it meets the requirements of automobile light weight and safety performance. The traditional preparation method of foam filled tubes is ex-situ preparation and there is no metallurgical bonding between the ordered porous aluminum filler and the thin-walled tube. In this study, the in-situ ordered porous aluminum filled tubes were proposed and prepared by combining the additive manufacturing technique and infiltration casting technique. The sand preform fabricated by selective laser sintering technique was placed in the bottom of 6061 aluminum alloy thin-walled tube. ZL111 aluminum alloy was utilized to infiltrate the sand preform and expected to form a metallurgical bonding between the ordered porous aluminum filler and the thin-walled tube. The infiltration process of the in-situ ordered porous aluminum filled tube was optimized by integrated computation. The peak temperature of contact region on the thin-walled tube was obtained. The in-situ ordered porous aluminum filled tubes were successfully fabricated by utilizing the optimized parameters.
Preparation and Characterization of High Mobility Nb-Doped SnO2 Transparent Conducting Films
Authors: He Lin An , Luan Cai Na , Wang Di , Le Yong , Ma Jin
Published: May 2020

Metal organic chemical vapor deposition (MOCVD) was employed for the preparation of niobium (Nb)-doped SnO2 films on SiO2 glass substrates. The structure, optical and electrical properties of the Nb-doped SnO2 films were systemically studied. The X-ray diffraction results indicated that the polycrystalline rutile SnO2 films were obtained with a preferred SnO2 [110] growth direction. Among which, the 5.4 at.% Nb-doped SnO2 film showed the lowest resistivity of 1.0×10-3 Ω∙cm and the highest Hall mobility of 74 cm2∙V-1∙s-1. The average visible light transmittance of the 5.4 at.% Nb-doped SnO2 sample was more than 79%. The obtained Nb-doped SnO2 films exhibited low resistivity, high Hall mobility and good transparency, which might have wide applications in electric and photoelectric devices.
Improved Sublimation Resistance of Skutterudites by Silane Modified Ceramic-Based Coating
Authors: Fang Long Hui , Fan Jin Hui , Wang Wei An , Li Xiao Ya
Published: May 2020

The organic/inorganic hybrid sol was prepared by hydrolysis polymerization of methyl-triethoxysilane (MTES) with acidic silica sol. Zirconium silicate, zircon sand and refractory fiber were respectively added to the hybrid sol to increase the stability of the coating in high temperature service. P-type skutterudite(SKD) protective coating obtained by multi-layer coating and certain pretreatment. Protective effect was studied by observing the diffusion of antimony from the SKD into the coating. The results show that the coating has the advantages of simple process and high strength and high stability after aging. The sublimation of antimony is suppressed and it is expected to be applied to the protection of SKD in vacuum.
Preparation and Characterization of Low Dielectric Constant Films Using Silicon Sources
Authors: He Zhi Wei , Lin Hong Xiao , Li Chun Yan , Mahajan Ashok M. , Gupta Swati A. , Zhou Mei
Published: May 2020

Effect of various silicon sources, such as TEOS, MTES mixed with TEOS and 1,3,5-tris(triethoxymethyl) on SiO2 films was investigated. The synthesized solutions were used as silicon sources to prepare silica-like backbone films. The investigation showed that all precursors can able to produce the flat and uniform films. An FTIR spectrum confirmed the formation of SiO2 in film matrix. The results indicated that the internal microstructure of each film is different. The incorporation of less polar bonds such as F and C was carried out using various Si sources, while the introduction of these sources confirmed through FTIR spectra. Optical properties of the films were carried out by using ellipsometric porosometry (EP) measurement. The leakage current density for the films prepared by using TEOS, MTES and 135TTEB was observed to be 2.8 × 10-7 A/cm2, 2.9 × 10-8 A / cm2, and 4.1 × 10-6 A / cm2, respectively, at 1 MV/cm electric field strength by the IV curves obtained by semiconductor characterization after fabricating MIS devices. The calculated dielectric constants from RI of the deposited SiO2 films were 2.0, 1.9 and 2.5 respectively. When the microstructure of the precursor solution changed, the introduction of atomic morphology or terminal inerted group ratio changed the internal bridging mode of SiO2, and thereby significantly reduced the dielectric constant and improved insulation.
Green Synthesis of Tungsten Ditelluride and the Magnetoresistance Property
Authors: Cao Ming Xing , Ma Li Wen , Xi Xiao Li , Wang Zhi Hong
Published: May 2020

As a new type of unsaturated linear magnetoresistive materials, tungsten ditelluride series material has potential applications in the fields of strong magnetic detection, information recording and magnetic storage devices. The current development concepts of “green materials”, “green chemical technology” and “environmentally friendly technology” require us to pursue the non-toxic, low-emission and non-emission in material synthesis technology. At the same time, the prepared products show excellent performance and high versatility and efficiency. According to our previous work, the study attempts to use a low-volatile amine solvent as a pretreatment raw material to synthesize a tungsten germanium-based linear magnetoresistive material by hydrothermal/solvothermal method and self-fluxing method. The obtained materials were subjected to XRD, Raman, SEM and Magnetoresistance. Experimental results show that when the mass ratio of W and Te is 1:4, the prepared material is pure phase and the sample is the layered structure. The Magnetoresistance Property points out that the maximum value is about 190 %, which appears in the condition of 10 K and 7 T. Those test projects include phase, structure and morphology characteristics, and provide technical parameters and methods for the development of green synthesis and potential applications of tungsten ditelluride series linear magnetoresistive materials.
Impact of Remittances on Estate Sector Poverty: A Study on the Tea Estate Sector in Badulla District
Authors: Dharmadasa R.A.P.I.S. , Weerahewa J. , Samarathunga P.A.
Published: May 2020

Availability of external employment and resulting migration play an important role in poverty reduction in the rural areas of developing countries. Estate sector continues to play a major role in the tea industry of Sri Lanka. As fine plucking is still considered to be important to maintain the quality of the final product, shrinkage of residential work force due to out-migration of skilled laborers from formerly residential work is identified as a major problem faced by the industry. From the household perspectives, remittances from migrated members would increase household income and ultimately affect the poverty level of the estate households. Therefore, this study was conducted to investigate the impact of labor migration on poverty in estate sector in Badulla District. Assuming that the remittances are a potential substitute for household earnings within the estate, counterfactual scenarios were built to understand what household poverty would have been in the absence of migration and remittances. Results reveal that poverty incidence, depth of poverty and severity of poverty of households are reduced by 13.19%, 3.81% and 1.37% respectively due to migration and remittances. Hence, the study concludes that labor migration is an important upward driver for households in tea estates to move out of poverty. Identifying skill levels of residential workers and a remuneration policy to encourage retention of high skilled workers to continue work in the estates can be recommended. This may help to have extra income for worker households and increase the labor productivity in the estates.
Ha-Joon Chang, Economics: The User’s Guide
Authors: Kumara Thusitha
Published: May 2020

No Abstract available.
Nexus between Awareness of Recommendations and Income from Rubber Cultivation: A Structural Equation Model
Authors: Balasooriya B.M.C.D. , Edirisinghe J.C. , Seneviratne P.
Published: May 2020

Rubber cultivation provides an important source of income for many small farmers in rural areas. In addition, it is a vital source of foreign exchange earnings to the country. However, in the present day rubber is less profitable due to a slump in prices. Cyclical fluctuation in rubber prices is a stylized fact. Therefore, one strategy to keep small farmers in rubber cultivation is to enhance productivity and thereby their income. It is hypothesized that productivity increases can be brought about by improved extension, which creates awareness of recommended technologies and practices in rubber cultivation. With this background, this research studied whether ‘Awareness’ has an impact on productivity and through that on farm income. For this data were collected from a sample of 206 smallholder rubber farmers from Kegalle District, which is one of the major rubber growing districts in Sri Lanka. The Structural Equation Model constructed show that there is a considerable impact by awareness on relevant technologies in improving farmer productivity. But the indirect effect of awareness on farm income through productivity is weak in the sample of data analyzed. Thus, policies geared towards increases in productivity should be coupled with policies related to the marketing of rubber for the small farmers to truly benefit and survive the price shock.
The Effect of Fertilizer Subsidy on Small-Scale Paddy Production in Sri Lanka: A Case in Hinguraggoda Divisional Secretariat Division in Polonnaruwa District
Authors: Ranathilaka M.B. , Arachchi I.A.J.I.
Published: May 2020

At present, the expenditure on fertilizer subsidy has become a heavy burden on the budget in Sri Lanka. The studies which attempted to analyze the impact of fertilizer subsidy on the productivity of paddy farming also provide rather mixed results. Thus, the present study aims to identify the effects of government fertilizer subsidy policy on the productivity of small-scale paddy farming in Sri Lanka by employing the econometric model developed by Hu and Antle (1993). The primary data for the study were drawn from a field survey conducted in the Hinguraggoda Divisinal Secretariat division in Polonnaruwa district. The results revealed that fertilizer subsidy has a positive impact on the productivity of paddy farming, but with decidedly less responsiveness (highly inelastic) indicating the need for agricultural policy priorities to enhance the positive responsiveness of fertilizer subsidy on farm productivity. The results further revealed a positive relationship between the level of farmer education and the productivity of a paddy farm. The study suggests the need of farm-level experiments (soil analysis, technological adaptations, water management techniques, type of adaptable paddy varieties, and extension inputs) to enhance the positive responsiveness of fertilizer subsidy policy on small-scale paddy farm productivity in Sri Lanka.
Expanding the Production Possibility Frontier of Sri Lanka: A Historical Economic Perspective on Technological Progress
Authors: Kumara P.H.T.
Published: May 2020

Introduction: The level of living conditions in a developed country such as the United States of America, Japan or the United Kingdom is not anymore a secret for any of the Sri Lankans living in this information age. Moreover, no one in the 21st Century would reject to have that level of comfort in his or her life. Therefore, the central question that gets to one’s mind is that how they have achieved such development while we are struggling for it for decades even after independence. Alternatively, we can ask the same question, “how did they achieve that much of development while we are not having”? Answering this question is not an easy task. Even the shorted list of answers is so long, to name a few; effects of colonization, typical Sri Lankan culture, religion, corrupted political culture, bad institutions, and poor technological progress. Not to argue with the list, since it is not a complete one and the order can be different as one think. However, if we analyze it with world history, it suggests that the main culprit is the poor technological progress in the country during the past two centuries. Hence, the main objectives of this article are to answer the over raided question of “why Sri Lanka could not achieve the living conditions that the developed countries currently enjoying” and “how the future policy directions should be formulated to catch up the developed world” in a historical economic perfective.
Forecasting the Sri Lankan Population with the Gompertz and Verhulst Logistic Growth Models
Authors: Welagedara W.A.D.M. , Nawarathna Lakshika S. , Nawarathna Ruwan D.
Published: May 2020

Population growth is one of the major problems in the world. The population forecast is predicted by each and every country from an early age. Further, the population growth and the size of the country are major factors which affect its economy and policies. Hence, it has emphasized the importance of predicting the future population of Sri Lanka. Therefore, this study mainly focuses on proposing population growth models to predict the population growth of Sri Lanka. The Verhulst logistic growth model and the Gompertz growth model are used to predict the population of Sri Lanka using population data from the census population and the mid-year population, the birth rate and the death rate obtained from the Department of Registrar General of Sri Lanka from 1990 to 2018. The explicit solutions for each model are derived by using mathematical techniques of differentiation and integration. The carrying capacity; i.e., the maximum number of the population an environment can support, indefinitely was calculated using the two models. The percentages of Root Means Square Error (RMSE), Mean Absolute Percentage Deviation (MAPD) and Symmetric Mean Absolute Percentage Error (SMAPE) were calculated to measure the prediction accuracy between the actual data and the predicted data of the proposed models. Then the Sri Lankan population from 2019 to 2048 was predicted using the proposed models. Results show the prediction accuracy of Gompertz model to be higher compared to the one of Verhulst logistic growth model. This study provides a deep insight into the population prediction in Sri Lanka, a country with limited resources, and in an area teeming with conflicts.
The Degree of Financial Literacy as a Deterministic Factor in Investment Decisions: Evidence from Colombo Stock Exchange (CSE) of Sri Lanka
Authors: Weerawansa S.R.S.D.K. , Morage N.S.
Published: May 2020

Local retail investors at the CSE are not gaining the optimum benefits out of the market whereas, the foreign investors are gaining high profits through trading stocks. In addition, the financial literacy level of Sri Lankans is low compared to other countries. The main target of the researcher is to determine “The Impact of Behavioral Finance on Investment Decision-Making in the Stock Market and the Moderating Role of Financial Literacy: with special reference to local individual investors at the CSE of Sri Lanka”. The findings of the study revealed that a significant relationship exists between behavioral finance and investment decision-making. It was also established that financial literacy moderates the relationship between the independent variables and the dependent variable. The qualitative findings resulted in a final thematic analysis which gave rise to additional independent variables and moderating variables which were suggested for future research by the author.
Land Access, Livelihood Diversification and Migration of Rural Youth in Sri Lanka
Authors: Samaraweera W.G.R.L. , Dharmadasa R.A.P.I.S. , Weerahewa J. , Kumara P.H.T. , Fernando P.M.M.
Published: May 2020

Rural livelihood diversification and youth migration have potential impacts on Sri Lankan agricultural sector. Therefore, this study was designed to assess the impact of land access on rural youths’ choice of livelihood and their choice of migration. A nationally representative sample of rural youth was isolated and a multinomial logit model under random utility framework was estimated to assess the livelihood diversification. A probit model of migration outcome was estimated to assess the rural youth’s choice of migration in lieu of land access. Results revealed that land access is strongly associated with the livelihood choices of agriculture and urban salaried employment of rural youth. Being a female youth makes the choice of livelihood less likely to be in agriculture. Education acts as an upward driver in choosing urban salaried employment while educated youth tend not to choose agriculture. The tendency to migrate reduces with increased access to land. Therefore, land access is a crucial factor for rural youth to choose agricultural livelihoods alongside rural youth not to be migrated.
The Adoption of Computerized Accounting System (CAS) in Small and Medium Scale Enterprises (SMEs): With Special Reference to SMEs located in Matara District, Sri Lanka
Authors: Darshi G.A.N.
Published: May 2020

Computerized Accounting System (CAS) plays a prominent role in providing information accurately and quickly to meet the challenges of the ever-changing business environment. Developing countries, however, struggle and are reluctant towards adopting CAS in SMEs. In Sri Lanka whereas an emerging economy is existing, a few studies have attempted to study the reticence of adopting CAS in SME sector. SME sector is vital in developing economy as it generates employment, promotes the growth of Gross Domestic Product (GDP) and stimulates other economic activities. Even though SMEs engender many benefits, their persistence is threatened and need strategies to overwhelm the challenges in the competitive business environment in emerging economies. In line with the previous studies focused on the technological revolution and SMEs in developing countries, research findings reveal that SMEs have a poor accounting system and slower in using new technology. According to them, one key strategy is accountability via sound reporting practices. The study, therefore, examines the factors which affect to the adoption of CAS in SMEs in Sri Lanka. According to the literature, the various factors were identified and broadly classified under different categories. In this study, four factors are included in the research model as managers’ support, perceived usefulness, ability of bearing the cost and human resource proficiency. This study was conducted through the structured questionnaire survey method. Data was collected from 118 SMEs representing manufacturing, trading and services sectors in Matara District, Sri Lanka. The study used Partial Least Squares (PLS) path modeling to analyze the collected data. The study results disclosed that manager’s support and firm’s ability of bearing the cost have a positive and statistically significant relationship with adoption of CAS in SMEs. As per survey results, it has confirmed that there is a positive relationship between perceived usefulness and HR proficiency on adoption of CAS but it is not statistically significant.
The Curious Case of Hemoglobin DC Disease Masquerading as Sickle Cell Anemia
Authors: Hirani Samina , Gupta Supriya , Veillon Diana , Patan Shajadi , Master Samip , Mansour Richard
Published: May 2020

Hemoglobin D is a relatively rare disease first reported in 1951. We present the first reported case of Hemoglobin DC disease. This is a case of a Hemoglobinopathy with DC disease in a woman with a previous diagnosis of Hemoglobin SC disease. A 19-year-old woman presented to the Adult Hematology clinic at a tertiary care hospital in Northwest Louisiana for transition of care from Pediatric Hematology for a diagnosis of Hemoglobin SC disease diagnosed at the age 4. Historical data suggested no avascular necrosis, acute chest syndrome, and very few episodes of pain crisis. She has never taken hydroxyurea. Laboratory work showed persistently normal hemoglobin and white blood cell counts. All sickle cell preparations in the past were negative. Computerized tomography scan of the abdomen was reviewed and showed a spleen grossly normal in size and appearance. Given the incongruent clinical picture for sickle cell disease, repeat hemoglobinopathy evaluation with Capillary electrophoresis and confirmatory acid electrophoresis (to differentiate hemoglobins that co-migrate with Hemoglobin S) showed a probable double heterozygote for Hemoglobin D and C with suspected coexistent alpha thalassemia minor based on red blood cell indices. This case confirms the importance of the required confirmatory method to ensure a correct diagnosis since a misdiagnosis can lead to numerous adverse clinical or psychological effects for patients.
Вещественные кубики Сегре, квартики Игузы и квартики Куммера
Authors: Krasnov Vyacheslav Alekseevich
Published: May 2020

В работе доказываются свойства вещественных кубик Сегре. В частности, находятся топологические типы вещественных частей кубик Сегре, а также вещественных частей дополнений к плоскостям Сегре. Доказываются дифференциально-геометрические свойства вещественных частей вещественных кубик Сегре и квартик Куммера. Изучаются группы автоморфизмов вещественных кубик Сегре, в частности, их действие на вещественных частях этих кубик.
Библиография: 16 наименований.
Об арифметике модифицированных групп классов иделей
Authors: Lee Wan , Seo Soogil
Published: May 2020

Пусть $k$ - числовое поле и $S$, $T$ - множества точек поля $k$. Для любого простого $p$ мы определяем инвариант $\mathscr{G}=\mathscr{G}_p(k_\infty/k,S,T)$, связанный с группой Галуа максимального абелева расширения поля $k$, которое не разветвлено вне $S$ и вполне распадается в $T$. В основной теореме мы интерпретируем $\mathscr{G}$ в терминах другого арифметического объекта $\mathscr{U}$, затрагивающего различные группы единиц и использующего теорию родов, примененную к некоторым модулям, которые получены некоторыми техническими модификациями из групп иделей. Мы показываем, что эта интерпретация функториальна относительно $S$ и $T$ и, вследствие этого, приводит к интересным взаимосвязям арифметических объектов $\mathscr{G}$ и $\mathscr{U}$ при меняющихся $S$ и $T$. Наш подход и методы новы и отличны от классических методов теории родов для групп иделей. Преимущество новых методов на конечном уровне не только обобщает, но также усиливает некоторые известные результаты, затрагивающие максимальную $p$-абелеву проконечную группу Галуа поля $k$, не разветвленную вне $S$ и распадающуюся в $T$, в терминах арифметики некоторых единиц поля $k$. На бесконечном уровне наши методы связывают глубокую арифметику специальных единиц с арифметикой проконечных групп Галуа. Например, для специального выбора $S$ и $T$ инварианты $\mathscr{G}$ связаны с гипотезами Гросса (или Кузьмина-Гросса) и Леопольдта. Соответственно, функториальная интерпретация $\mathscr{G}$ при вариации $S$ и $T$ в специальных случаях включает интересные связи между гипотезами Гросса и Леопольдта, полученные более простым и конкретным образом. Как результат, мы высказываем предположение, что $\mathscr{G}$ конечен для всех конечных непересекающихся множеств $S$, $T$ над круговой $\mathbb{Z}_p$-башней поля $k$, что включает гипотезы Гросса и Леопольдта как специальные случаи.
Библиография: 23 наименования.