bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of UDC Casting on Hot Deformation Behavior and Properties of 2A14 Aluminum Alloy
Authors: Qiu Yang , Zhang Zhi Feng , Zhao Hao Dong , Li Bao , Chen Chun Sheng
Published: February 2019

Uniform direct chill (UDC) casting is coupled annular electromagnetic stirring and intercooling, having been utilized for the preparation of large-sized aluminum alloy billet. In this paper, the UDC casting was applied to 2A14 aluminum alloy billets with a diameter of 584 mm. Hot compression tests, cogging and ring rolling procedures were carried out for the billets, respectively. The results show that during the deformation temperature of 420 °C and the strain rate of 0.01 s−1 to 10 s−1, the flow stresses of different positions are higher and more stable in the UDC casting billet than in the normal direct chill (NDC) casting billet. The dislocation glide is the dominant deformation mechanism of 2A14 aluminum alloy. Meanwhile, the UDC casting significantly improves the mechanical properties of the rolled rings in tangential and axial directions compared with the NDC casting.
Corrosion Behavior and Oxide Films of New Zirconium Cladding Corroded at Different Conditions
Authors: Liao Jing Jing , Yang Zhong Bo , Qiu Shao Yu , Li Zheng Cao , Peng Qian
Published: February 2019

Zirconium alloys are mostly served as the cladding materials in water reactors. Corrosion is one of the concerning problems in zirconium utilization. Transition of corrosion occurs every 2~3 μm in thickness, but its mechanism is not confirmed. To study the influence of water chemistry and the mechanism behind transition, a new type of zirconium cladding was tested for three corrosion conditions: the pure water, LiOH solution, LiOH/H3BO3 solution at 360°C/18.6MPa. For all cases, Zr-0.5Sn-0.15Nb-0.5Fe-0.2V cladding had a lower corrosion rate and a longer transition time than N36 cladding. The corrosion results showed that the corrosion rate was the highest and the transition time was the shortest in LiOH solution. Oxide phase information on the oxidized surface was obtained by Raman study. Tetragonal zirconia, embedded in the surface, was found at the beginning of corrosion. As the corrosion time increased, tetragonal phase stress was almost released and the content of tetragonal phase was also decreased to zero at the transition point. Stable tetragonal phase was found on the samples corroded in pure water. However, in LiOH solution, it was eliminated the quickest. The acceleration of transition in LiOH solution is partly resulted from the fast transformation of tetragonal phase. The reason for the longer transition time in N2 cladding can be directly attributed to the smaller decrease of the tetragonal phase.
Properties of PP Wood-Plastic Composites with Biocompatibility Additives
Authors: Liu Shan Shan , Ge He Yi , Zou Yu , Chen Juan
Published: February 2019

Maleic anhydride grafted polypropylene compatibilizer (MAPP) and chitosan (CS) were mixed and used as a compound coupling agent to modify the PP matrix. 5 wt% NaOH and 10 wt% NaOH aqueous solution were used to treat corn stalk fiber (CSF), respectively. The effect of the complex coupling agent and the alkali treatment on the mechanical properties of CSF/PP composite was investigated. Morphological observation of the fracture surfaces was accepted to confirm CSF dispersion and wetting with the help of SEM. The results of the water absorption further demonstrated the binding of the interface between the CSF and the PP matrix. The wetting of the CSF in the PP was improved with the addition of the complex compatibilizer (5% MAPP + 5% CS). The formation of chemical bonding between the fiber and the matrix resulted in enhancing the interfacial compatibility between them. Compared with the pure PP, the flexural strength of 15-UT-5MAPPCS (63.14 MPa) and 15-UT-5MAPPCS (69.35 MPa) increased by 22.5% and 34.5%, respectively. The complex compatibilizer can replace alkaline treatment process to improve the mechanical properties of the composite.
Preparation and Properties of Reflective Heating Polyethylene Terephthalate Fiber
Authors: Huang Jia Peng , Tang Lian , Zhang Sheng Ming , Li Jian Wu , Wang Chao Sheng
Published: February 2019

Reflective heating polyester fiber is the fiber prepared by adding nanoparticle with reflecting infrared radiation into the polyester. The human body loses 60% of the total heat by heat radiation, but reflective heating fiber can reflect the body's infrared radiation back to the human body to minimize the loss of heat. In this paper, the purchased GTO powder is modified by silane coupling agent KH560, which is added into PET as a reflective heating powder, and PET fiber containing different content of GTO(0.3wt%,0.6wt%,0.9wt%) is prepared through adding masterbatch method. The particle size test shows that the average size of GTO powder modified by KH560 is about 180nm and the distribution is narrow, which meets the basic requirements of spinning. Through the SEM analysis of PET fibers cross-section, it is found that the GTO powder modified by KH560 were dispersed well in the PET substrate. The results of DSC and mechanical tests show that the fiber with 0.6wt% content of GTO powder have the improved elongation and the crystallinity degree. For the infrared thermal imaging and UV-VIS-NIR tests of the fabric, with the increase of the proportion of powder the infrared emissivity and reflectivity of the fabric increased, the warmth retention is also improved.
Effect of SiC Additions on Microstructure Evolution and Mechanical Properties of W-Based Composite Prepared by Arc-Melting
Authors: Kang Ke Jia , Fan Peng , Zhang Jian , Luo Qiang Guo , Shen Qiang , Zhang Lian Meng
Published: February 2019

In this study, the W-Si-C multi-phase composites were fabricated by an arc melting method. With addition of SiC, the grain size of W is obviously reduced, and the small angle misorientation becomes dominate, which is beneficial for the improvement of deformability. The effects of SiC additions (from 0.5 to 3wt%) on the microstructure and mechanical properties are mainly investigated. With 1 wt% SiC addition, the flexural strength reaches the highest value. The self-generation of W5Si3 may enhance the strength and ductility, but too much W5Si3 exists as brittle BP (Brittle to Plastic) microstructure. The highest flexural strength is obtained at approximately 1 vol% W5Si3.
Microstructures and Properties of Spinning for Silicon Carbide Particle Reinforced Aluminum Composite
Authors: Wu Hai Bao , Li Ji Zhen , Li De Fu , Liu De Gui , Chai Guo Qiang
Published: February 2019

In this paper, 15% SiCp/2009A1 composites were subjected to multi-pass hot spinning experiments. The principle of the microstructure and properties of the materials was studied with the increase of thinning rate. The microstructures, interfaces, precipitates and their properties of the tube, which were in the states of spinning, spinning and solution heat treatment were analyzed and discussed.The research shows that it is possible to prepare spinning pipe with good shape and smooth surface by taking use of the spinning process of this paper. During the power spinning process, the force of the rotary wheel to the pipe causes the billet to produce two-way deformation, and the axial and tangential grains are obviously elongated and the flow line is formed.There are mainly Al, SiC, CuAl2and Mg2Si phases in the tube, and the spinning deformation does not change the phase composition of the composites, but the SiC distribution can be more uniform and the oxide film on the surface of the aluminum particles is broken, as a result that the oxygen element will cluster at the interface.The solution heat treatment after spinning can greatly improve the yield strength and tensile strength of SiC/Al composites with a slight decrease in plasticity. The spinning process used in this paper can not only form a composite pipe with a smaller diameter and thinner wall thickness, but it can still be applied when the diameter of the pipe blank becomes larger and the wall thickness becomes thicker.Through the research on spinning process and microstructure, the feasibility of spinning process for preparing aluminum matrix composites pipes was explored, which provided technical and theoretical support for the preparation and processing of Particulate reinforced aluminum matrix composites (PRAMCs) pipes for aviation and aerospace applications.
Preparation and Characterization of Ni/ZrCoCe Stack Getter Films
Authors: Yuan Peng , Sui Yao Zong , Zhang Xiao , Liu Hao , Wei Feng , Xu Yao Hua
Published: February 2019

In order to improve the oxidation resistance of the ZrCoCe getter, highly porous Ni/ZrCoCe stack getter films were grown by the magnetron sputtering method. Scanning electron microscope (SEM) analysis indicate that the Ni/ZrCoCe stack film is composed of isolated columns. The film surface with cauliflower-like topography is formed among finely packed nanocrystals. Gas sorption investigation shows that the Ni/ZrCoCe stack film can be activated at 300 °C for 30 min and exhibits more favorable sorption capability than ZrCoCe bi-layered film. XPS results show that the Ni protective layer can play an important role in protecting the ZrCoCe film against oxidation. It can also improve the surface dissociation and diffusion of H2.
Magnetic Anisotropy in [Pt/Co]4/MgO/[Co/Pt]2 Multilayers
Authors: Li Qian , Li Lei , Zhou Wei , Chen Jun , Zhang Si Yuan , Cai Jian Hua
Published: February 2019

A serial of [Pt/Co]4/MgO/[Co/Pt]2multilayers were prepared by magnetron sputtering in this study and Antiferromagnetic (AF) interlayer coupling was observed with increasing MgO spacer thickness. Perpendicular magnetic anisotropy of soft layer in [Pt/Co]4/MgO/[Co/Pt]2multilayers were measured by Extraordinary Hall Effect (EHE). The direction of the magnetic field was parallel to the direction of the current. The results revealed that perpendicular magnetic anisotropy constant Kuoscillates with the thickness of MgO layer which is between 1.3 to 3.3 nm. The period of this oscillation is about 0.43 nm. This is very close to the monolayer (100) MgO. With increasing MgO spacer, the periodic variation of interface between [Pt/Co]nand MgO layer may be one of the reasons for this oscillation behavior of Ku.
Development and Potential Application of Advanced Functional Materials in the Oil Field
Authors: Zhao Gu Fan , Di Wei Na , Wang Rui Yao
Published: February 2019

The oil and gas industry places higher demands for new technologies and new materials. Advanced functional materials show broad application prospects in the oil field. Technological advances in the oil and gas sector are inseparable from the development and application of advanced functional materials. Through literature research, patent search analysis, expert consultation, some advanced functional materials with potential application in the oil field are sorted out, in order to provide inspiration and new ideas for improving the development of the oil and gas drilling technology. The nanomaterials dispersion and nanocomposites films are two of the most accessible ways to apply nanomaterials in the oil field. The cellulose nanofibers (CNF) and the diamond-like carbon (DLC) nanocomposites films would provide inspiration for the oil field chemistry and protection of downhole tools. The application of CNF and DLC nanocomposites could provide innovative ideas, research and foundation for the future development of the oil and gas drilling technology, and contribute to achieving a major technological breakthrough and improve the overall level of the oil and gas drilling technology.
Technical Study on Preparation of Co/C Composite Nanofibers via Electrospinning
Authors: Zhang Sa , Wang Jian Jiang , Zhao Fang
Published: February 2019

Co/C composite nanofibers are prepared through electrospinning. Effect of salt, Spinning humidity, receiving equipment and heat treatment on the formation, morphology and structure of composite fibers were investigated. The morphology of composite fibers was observed by scanning electron microscopy (SEM).It was found out that when the ambient humidity was high, the nanofibers were agglomerated into fiber bundles. When the roller receiving equipment was used, ordered nanofibers can be obtained. Only cobalt acetate-doped composite nanofibers maintained intact fiber morphology after pre-oxidation and carbonization. And Co2+ was completely reduced to face-centered cubic structured Co nanoparticle. The ideal preparation technology is as follows: the humidity at 30% or less, doping with organic salt of cobalt acetate.
Preparation of Pd@Gr Composite Materials and Research on Catalytic Performance
Authors: Leng Jin Feng , Wang Kang , Xia Chang Peng
Published: February 2019

In this work, the preparation of graphene by chemical oxidation reduction method and a series of chemical reactions to get graphene oxide, with the preparation of graphene composites by simply chemical reduction method for the preparation of palladium/graphene composites. Through the chemical reduction method, the small size of Pd nanoparticles is acquired by controlling the content of reducing agent. The Pd nanoparticles on graphene surface is 10nm size and evenly distributed. Pd2+ adsorption on graphene surface and in situ were partially reduced to Pd to Pd2+ nanoparticles by the reducibility of graphene. In the process, the graphene was reduced to graphene and the final compound was thinner and more transparent than the pre-experiment oxide. The oxygen-containing functional groups on the surface of the graphene have influence to the nucleation and growth of metal nanoparticles and KI can control the morphology and size of nanoparticles. The particle size and dispersion uniformity have great influence on the catalytic performance of composites, the smaller particles have better catalytic performance. Keywords:palladium, graphene composites, nanoparticles
Preparation and Antibacterial Properties of Silver Nanowires
Authors: Zhou Yi Han
Published: February 2019

Silver ions have superior bactericidal properties, and their bactericidal activity ranks second among all metals (mercury ranks first, toxic, not used now). Due to its unique physical and chemical properties, nano-silver has also received increasing attention from researchers, and its antibacterial properties are far superior to traditional silver ion bactericides, such as silver nitrate and silver sulfadiazine. But the properties and performance of nanosilver materials depend on their size and morphology.In this paper, the nano-silver line was prepared by the polyol method. By controlling the ratio of AgNO3and PVP, the concentration of NaCl and the acidity and alkalinity of the reaction solution, the effects of reaction time and reaction temperature on the morphology and diameter of the silver wire were investigated. The antibacterial properties of nanosilver were determined by the perforation inhibition method. The experimental results showed that as the reaction temperature increased, the silver particles in the product decreased significantly, the diameter of the silver wire tended to be uniform, but the diameter increased. Finally, the optimal reaction temperature for preparing the silver oxide wire by the polyol method was 150 °C, the reaction time was 10 hours, and the diameter of the silver wire was 100 nm to 200 nm. Based on the measurement of the antibacterial diameter of nano-silver with different morphologies on Escherichia coli and Staphylococcus aureus, it can be found that nano-silver with different morphologies has excellent antibacterial effect, and silver cube is superior to silver particles and nano-silver lines.
Effect of Nickel-Modified SiC Particles on Compressive Damage of SiCp / 7075 Composites
Authors: Wang Xiao Hong , Hu Qiao Gang , Zhong Shi Yu , Dang Teng , Wang Hai Lun , Lin Yuan Hua
Published: February 2019

The wettability between silicon carbide and aluminum is poor, silicon carbide is difficult to fuse or the distribution of silicon carbide is not uniform in the ingot when the SiCp / 7075 composite is prepared by melt casting.The surface modification of SiCp by nickel plating can significantly reduce the wetting angle of SiC/Al and improve the distribution uniformity of silicon carbide in SiCp / 7075. In this thesis, the thermal compression process 6.5% SiCp / 7075 reinforced by nickel-plated modified silicon carbide is simulated by DEFOEM-3D software.The influence of the shape and particle size of nickel-plated modified silicon carbide on its compressive damage has been highlighted, and the deformation characteristics of the SiC/Ni/Al interface layer in the thermal compression process have been discussed. The numerical simulation results show that the 6.5% SiCp / 7075 reinforced by spherical nickel-plated modified silicon carbide particles with a particle size of 15 μm has the smallest compression damage value of 0.0426, at this point the compression temperature is 400°C, the compression ratio is 15, and the compression rate is 0.03s-1. the hot compression test of 6.5% SiCp / 7075 reinforced by spherical nickel-plated modified silicon carbide particles with a particle size of 15 μm was performed by using the same compression parameters as the numerical simulation. After hot pressing, the sample had a smooth surface with few obvious cracks, which was consistent with the numerical simulation results. Key words: nickel-plating modification; silicon carbide particles; compressive damage; grain size; grain morphology
Phase Field Simulation for Abnormal Growth of Grains by the In-Homogeneous Grain Boundary Energy
Authors: Wu Yan , Qin Er Wei , Yu Qing
Published: February 2019

The phase field models have been built to study the influence of the nonuniform grain boundary energy for abnormal growth of grains in the AZ31 magnesium alloy in the real time and space. The simulated results show that if the grains of a certain orientation with low grain boundary energy in the AZ31 Mg alloy, abnormal grain growth will occur after annealing treatment, and only if the local low grain boundary energy is less than 0.98σ0, can the certain grains grow abnormally in the microstructure.
Creep Properties and Microstructural Evolution at 760°C/785MPa of a Re-Containing Single Crystal Superalloy
Authors: Zhao Yun Song , Liu Yan Fei , Zhao Jing Xuan , Zhang Xiao Tie , Yang Yan , Chen Hao , Jiang Hua , Luo Yu Shi
Published: February 2019

Intermediate temperature creep properties are considered a key indicator of single crystal superalloys used for turbine blades of aircraft engines. The interrupted and ruptured creep tests were carried out in a second generation single crystal superalloy under the conditions of 760°C/785MPa. The creep rupture life as well as minimum creep rate were also in the same level of those in CMSX-4 and PWA1484. The microstructural evolution at different creep stages were analyzed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The results showed the γ’ phases kept the cuboid morphology mostly until the creep rupture, and super lattice stacking faults (SSFs) extended along [-1 1 0] and [-1-1 0] orientations within the γ’ precipitate were the typical dislocation configuration.
Effect of Type B Steel Sleeve Rehabilitate Girth Weld Defect on the Microstructure and Property of X80 Pipeline
Authors: Ma Wei Feng , Ren Jun Jie , Zhou Hui Ping , Wang Ke , Luo Jin Heng , Zhao Xin Wei , Huo Chun Yong
Published: February 2019

In recent years, accident caused by girth weld defects is relatively common. The failure mode of girth weld is mostly fracture. It is an effective way to avoid the failure accident of girth weld to find the hidden trouble of girth weld and repair it in time before the failure. The type B steel sleeve is an effective method to repair the girth weld defects. However, quite few works have been carried out on the reliability verification and engineering practice of repairing the X80 pipeline girth welds. Therefore, it is necessary to carry out full-size physical test for engineering and obtain the influence law of welding operation on main pipeline performance, with the aim of reliability of repair quality and service after repair. In the present work, the reliability study of repairing with type B steel sleeve on X80 pipe girth weld defects was verified. The results show that the bearing capacity of the type B sleeve can effectively guarantee the safe operation of the pipeline in the case of leakage from the girth weld. But there are obvious influence on the material properties of the outer surface of the main pipe due to the welding heat. Effects from longitudinal weld seam is smaller than effects from fillet weld. Grain roughening occurred in heat affected zone of fillet weld which results in that the hardness of the main pipe under the fillet weld increased and the yield strength was reduced by 5.5%. Surface cracking occurs during bending test. There is a certain service risk and it should be used under more frequent monitoring than usual.
Study on Welding Techniques of 316L Lined Bimetallic Pipe
Authors: Li Fa Gen , Li Xun Ji , Li Wei Wei , Li Xian Ming , Chang Ze Liang , Feng Quan
Published: February 2019

It is well known that welding technique was often a knotty problem for bimetallic lined steel pipes to use widely. A number of failures in secession of weld cracking and weld corrosion had been observed in oil fields in recent years, which seriously disrupted the order of oil and gas production. To solve welding problems of 316L bimetallic lined pipes, works outcome about failure analysis and welding process research were presented in this paper. Failure analysis results confirmed that Welding defects, high hardness regions was the main reasons about failure problems of weld crack while structure design defects of seal weld and bad back-protection effects of flux-cored wire resulted in weld corrosion. Welding defects in the regions of seal weld became the failure source while the high hardness both in the region of seal weld and weld joint formed the crack propagation channel, and therefore both initially contributed to weld cracking. Additionally owing to the structure design of seal weld, liner layer would be heated over and over again during the period of seal weld and then it was not enough to protect CRA layers from being damaged during the period of girth weld. As a result the corrosion resistance in the welding area was reduced to become a weak area. On the basis of failure analysis, further research work was carried out to improve welding performance. Seal weld structure and girth weld process was improved. The difference of welding wires and welding process was analyzed, and their defects were described separately. Results showed that the welding performance welding by ERNiCrMo-3 and supporting technology was more reliable than ATS-F309L and supporting technology, whether seal weld or butt welding. The distribution and value of the hardness could be effectively controlled; Moreover, corrosion resistance performance was also better. Therefore, the seal weld and girth weld conducted by ERNiCrMo-3 and supporting technology was feasible.
Radiofrequency Ablation for Lung Carcinomas: A Retrospective Review of a High-Risk Patient Population at a Community Hospital
Authors: Cornish Nathan A. , Kantharia Sarah , Oselkin Martin , Portnow Leah , Shah Jay , Brichkov Igor , Shaw Jason , Harris Loren , Homel Peter , Sarkar Debkumar , Mobley David , Honig Shaun , Sobolevsky Sergei
Published: February 2019

Purpose: The purpose of this study is to retrospectively evaluate the technical efficacy, safety, and treatment outcomes of percutaneous radiofrequency ablation (RFA) of lung tumors in patients not amenable to surgery at an urban community hospital. Materials and Methods: Informed consent and IRB approval was obtained. Eligible tumors were defined as those in patients deemed poor surgical candidates by multidisciplinary consensus or those refusing surgery. Response to treatment was assessed by computed tomography (CT) performed immediately postprocedure and regular intervals up to 36 months later. Complete response was measured as a 30% decrease in mean tumor diameter without evidence of contrast enhancement or tumor growth within the ablation zone as defined by the response evaluation in solid tumors. Patient demographics, technical success, postprocedure complications, and survival were assessed and compared with data available in literature. Results: Twenty-four patients with a total of 29 tumors underwent percutaneous CT guided RFA for biopsy-proven lung malignancies between 2010 and 2016. Complete response was achieved in 82% (14/17) of treated tumors in patients who complied with postprocedure imaging recommendations. Immediate postprocedure complications occurred following 27.6% (8/29) ablations with pneumothorax being the most common, 17.2% (6/29). Mean survival is 28.5 months (95% confidence interval: 19.7–37.3). Progressive disease was seen in 18% (3/17) patients. No immediate treatment mortality was found. No significant difference was found in survival in patients with multiple comorbidities as measured by the Charlson Comorbidity Index. Conclusions: RFA of lung tumors is a well-tolerated procedure with low incidence of minor complications, a good tumor response and survival benefit in selected patients in the community setting. This is a positive endorsement of the potential success of tumor RFA programs outside of the academic setting. In addition, patients with multiple comorbidities should still be considered candidates for RFA as no difference was seen in survival in patients with multiple medical comorbidities.
Multiple, Bilateral Renal Oncocytomas: An Uncommon Condition Managed with Percutaneous Cryoablation
Authors: Esposito Robert A. , Gordetsky Jennifer , Rais-Bahrami Soroush , Gunn Andrew J.
Published: February 2019

Multiple, bilateral renal oncocytomas are uncommon, and the management of this condition is poorly described. Here, we report a case of multiple, bilateral, biopsy-proven renal oncocytomas that were successfully managed using percutaneous cryoablation. This procedure may serve as a less invasive treatment for patients with multiple, bilateral renal oncocytomas when compared to radical or partial nephrectomy.
Urgent-Start Peritoneal Dialysis Catheter Placement: Comparative Study between Percutaneous Image-Guided versus Laparoscopic Techniques
Authors: Mahmoud Khalid , Moawad Sherif , Farrington Crystal , Massoud Moustafa , Gunn Andrew , Li Yufeng , Dai Chen , Hamed Basant Farouk , Almehmi Ammar , Abdel-Aal Ahmed Kamel
Published: February 2019

Objective: The objective of this study was to compare the outcomes and complications of percutaneous image-guided versus laparoscopic peritoneal dialysis (PD) catheter placement techniques in the urgent-start setting. Materials and Methods: The medical records of 273 patients who had their first PD catheter between November 2012 and May 2017 were retrospectively reviewed. Patients were divided into radiologic group (n = 26) and laparoscopic group (n = 16). Descriptive and Kaplan–Meier (KM) analysis were used to compare time to first complication, time to catheter removal, and patient survival between the two groups. Complication-free and catheter removal rates at 1, 3, and 12 months were estimated from KM analysis. Results: A total of 42 patients were included in the study. The baseline demographics were similar between the two groups. In the radiologic group, the estimated 1, 3, and 12 months' complication-free rate were 100%, 94%, and 67%, respectively, which was not significantly different from 93%, 85%, and 45%, respectively, in the laparoscopic group (P = 0.543). The rate of catheter complications was not significantly different between the radiologic group (50%) and the laparoscopic group (31%) (P = 0.3382). The catheter removal rate in the radiologic group was 8, 18%, and 38% at 1, 3, and 12 months, respectively, versus 0%, 8%, and 20%, respectively, in the laparoscopic group (P = 0.298). The overall patient survival between two groups was not significantly different (P = 0.116) with estimated patient mortality of 15.4% at 12 months in the radiologic group and no deaths in the laparoscopic group. Conclusion: Image-guided percutaneously placed PD catheters have a similar complication and removal rates compared to laparoscopically placed catheters in the urgent-start setting.
Percutaneous Transhepatic Biodegradable Stent Placement for Benign Anastomotic Biliary Strictures: Short-Term Outcomes of a Single-Institution Experience
Authors: Arabi Mohammad , Alrehaili Bassam , Salman Refaat , Qazi Shahbaz , Bashir Omar , Abdullah Khalid , Almoaiqel Mohammad
Published: February 2019

Purpose: The purpose of this study was to assess the safety and effectiveness of biodegradable stents in the management of benign anastomotic biliary strictures. Materials and Methods: This retrospective study included all consecutive adult patients who underwent percutaneous biodegradable stent insertion for benign anastomotic biliary strictures that were refractory to cholangioplasty or biliary drainage-dependent or preferred stent placement to avoid long-term tube dependence. Fourteen stents were used in 12 patients (9 males) with a mean age of 53 years (range: 23–72 years). Ten patients had liver transplant (7 – choledochocholedochal anastomosis and 3 – hepaticojejunal anastomosis). Two patients had primary sclerosing cholangitis with hepaticojejunal anastomosis. The mean time since surgery was 5.5 years (6 months–16 years). Ten patients had an average of three (range: 1–6) previous sessions of biliary dilatation. Two patients initially preferred stent placement to avoid long-term tube dependence. Results: Technical and clinical success was achieved in all cases. One patient died 2 months after stent insertion because of progressive liver cirrhosis. No re-intervention was required in 8 (72%) of the remaining 11 patients at a mean follow-up time of 234 days (96–539 days). Three liver transplant patients required re-intervention at a mean time of 287 days. There were one severe procedure-related complication (cholangitis and sepsis) and one mild complication (transient septicemia). Stent migration into the bowel occurred in one case a few days after insertion, but this required no re-intervention. No procedure-related mortality occurred. Conclusion: Biodegradable biliary stent may offer a safe and effective option to avoid tube dependence in patients with benign anastomotic biliary strictures.
Retrieval of aerosol properties from ceilometer and photometer
measurements: long-term evaluation with in-situ data and statistical
analysis at Montsec (southern Pyrenees)
Authors: Titos Gloria , Ealo Marina , Román Roberto , Cazorla Alberto , Sola Yolanda , Dubovik Oleg , Alastuey Andrés , Pandolfi Marco
Published: February 2019

Abstract. Given the need of accurate knowledge of aerosol microphysical and optical properties with height resolution, various algorithms combining vertically-resolved and column integrated aerosol information have been developed in the last years. Here we present new results of vertically-resolved extensive aerosol optical properties (backscattering, scattering and extinction) and volume concentrations retrieved with the GRASP (Generalized Retrieval of Aerosol and Surface Properties) algorithm over a 3 year-period. The range-corrected signal (RCS) at 1064 nm measured with a ceilometer and the aerosol optical depth (AOD) and sky radiances from a sun/sky photometer have been used as input for this algorithm. We perform a detailed evaluation of GRASP retrievals with simultaneous in-situ measurements performed at the same height, at the Montsec mountaintop observatory (MSA) in the Pre-Pyrenees (northeastern Spain). This is the first long-term evaluation of various outputs of this algorithm; previous evaluations focused only on the study of aerosol volume concentration for short-term periods. In general, our results show good agreement between techniques although GRASP inversions yield higher values than those measured in-situ. The statistical analysis of the extinction coefficient vertical profiles shows a clear seasonality as well as significant differences depending on the air-masses origin. The observed seasonal cycle is mainly modulated by a higher development of the atmospheric boundary layer (ABL) during warm months, which favors the transport of pollutants to MSA, and higher influence of regional and North-African episodes. On the other hand, in winter, MSA is frequently influenced by free troposphere conditions and venting periods, and therefore lower extinction coefficients that markedly decrease with height. This study shows the potentiality of implementing GRASP in ceilometers and lidars networks for obtaining aerosol optical properties and volume concentrations at multiple sites worldwide, which will definitely contribute to enhance the representativeness of aerosol vertical distribution as well as to provide useful information for satellite and global models evaluation.
Modeling anaerobic soil organic carbon decomposition in Arctic polygon tundra: insights into soil geochemical influences on carbon mineralization
Authors: Zheng Jianqiu , Thornton Peter E. , Painter Scott L. , Gu Baohua , Wullschleger Stan D. , Graham David E.
Published: February 2019

Abstract. Rapid warming of Arctic ecosystems exposes soil organic matter
(SOM) to accelerated microbial decomposition, potentially leading to
increased emissions of carbon dioxide (CO2) and methane
(CH4) that have a positive feedback on global warming. Current
estimates of the magnitude and form of carbon emissions from Earth system
models include significant uncertainties, partially due to the oversimplified
representation of geochemical constraints on microbial decomposition. Here, we
coupled modeling principles developed in different disciplines, including a
thermodynamically based microbial growth model for methanogenesis and iron
reduction, a pool-based model to represent upstream carbon transformations,
and a humic ion-binding model for dynamic pH simulation to build a more
versatile carbon decomposition model framework that can be applied to soils
under varying redox conditions. This new model framework was parameterized
and validated using synthesized anaerobic incubation data from permafrost-affected
soils along a gradient of fine-scale thermal and hydrological
variabilities across Arctic polygonal tundra. The model accurately simulated
anaerobic CO2 production and its temperature sensitivity using data
on labile carbon pools and fermentation rates as model constraints.
CH4 production is strongly influenced by water content, pH,
methanogen biomass, and presence of competing electron acceptors, resulting
in high variability in its temperature sensitivity. This work provides new
insights into the interactions of SOM pools, temperature increase, soil
geochemical feedbacks, and resulting CO2 and CH4
production. The proposed anaerobic carbon decomposition framework presented
here builds a mechanistic link between soil geochemistry and carbon
mineralization, making it applicable over a wide range of soils under
different environmental settings.
Gas transfer velocities of CO2 in subtropical monsoonal climate streams and small rivers
Authors: Li Siyue , Mao Rong , Ma Yongmei , Sarma Vedula V. S. S.
Published: February 2019

Abstract. CO2 outgassing from rivers is a critical component for evaluating
riverine carbon cycle, but it is poorly quantified largely due to limited
measurements and modeling of gas transfer velocity in subtropical streams and
rivers. We measured CO2 flux rates and calculated k and partial
pressure (pCO2) in 60 river networks of the Three Gorges
Reservoir (TGR) region, a typical area in the upper Yangtze River with
monsoonal climate and mountainous terrain. The determined k600 (gas
transfer velocity normalized to a Schmidt number of 600 (k600) at a
temperature of 20 ∘C) value (48.4±53.2 cm h−1) showed large variability
due to spatial variations in physical processes related to surface water turbulence.
Our flux-derived k values using chambers were comparable
with k values using the model derived from
flow velocities based on a subset of data. Unlike in open waters, e.g.,
lakes, k600 is more pertinent to flow velocity and water depth in the
studied river systems. Our results show that TGR river networks emitted
approx. 0.69 to 0.71 Tg CO2 (1 Tg =1012 g) during the monsoon
period using varying approaches such as chambers, derived k600 values
and models. This study suggests that incorporating scale-appropriate k
measurements into extensive pCO2 investigations is
required to refine basin-wide carbon budgets in subtropical streams and
small rivers. We concluded that the simple parameterization of k600 as a
function of morphological characteristics is site specific for
regions and watersheds and hence highly variable in rivers of the upper Yangtze.
k600 models should be developed for stream studies to evaluate the
contribution of these regions to atmospheric CO2.
Semantic Description and Complete Computer Characterization of Structural Geological Models
Authors: Zhan Xianglin , Liang Jiandong , Lu Cai , Hu Guangmin
Published: February 2019

Abstract. A structural geological model is an important basis for the understanding of subsurface structures and exploration of mineral resources, especially petroleum reservoirs. In the field of geological modelling, the lack of a well-defined semantic level description and corresponding computer characterization method hinders its application. In this paper, we propose the semantic descriptions for structural geological models in order to facilitate computer based processing of geological semantics. A multi-level heterogeneous network is proposed to characterize the semantic description for this purpose. The semantic description of a structural geological model gives a complete description of structural units (called semantic entities) of structural models. Basic semantic entities include points, lines, interfaces, bodies, formations and advanced semantic entities include stratified structures/massive structures, planar structures, linear structures. Semantic relations represent the logical relationships among these semantic entities. The multi-level heterogeneous network contains complete information of structural geological models for both geometry and geology. Hence, it has a one-to-one correspondence with a structural geological model. In particular, we propose a bottom-up and top-down integrating structural modelling method based on semantic descriptions. This approach aims to address defects of the existing structural modelling methods that can only carry out bottom-up modelling. Because the addition of semantic information, it improves the adaptability of structural modelling to complex structures and enhances modelling efficiency.
Reasons Why Azerbaijani Students Choose Eskişehir in Turkey for Their Graduate Education
Authors: Güngör Semra Kıranlı , Musali Asiya
Published: February 2019

This research explored why graduate Azerbaijani education students chose to pursue their overseas education in Turkey, which factors they took into consideration, and what contributions this education will provide both them and their countries. The phenomenological model was utilized in the research. The research comprised 25 Azerbaijani students enrolled at the graduate-level in Eskişehir Osmangazi and Anadolu Universities in the 2017-2018 academic year. The interviews were coded with content analysis and formed themes and subthemes. The findings reflected that Azerbaijani students viewed Turkey as a ‘sister’ city and therefore preferred to study their overseas education there because of the common religion, language, and the cultural proximity. Moreover Eskişehir has suitable living conditions for the students due to a favorable economy.
Trabalho, sentidos e saúde mental: percepção de participantes em um projeto geração de renda
Authors: Santos Shirley Alves dos , Carnut Leonardo
Published: February 2019

Este estudo objetivou analisar os sentidos do trabalho para os participantes de uma pesquisa-ação denominada “Projeto Geração de Renda” na região metropolitana do Recife/PE com intuito de gerar reflexões em direção ao conceito de trabalho emancipado segundo os princípios da economia solidária. Tratou-se de uma pesquisa qualitativa, com entrevistas não-estruturadas de 8 sujeitos da pesquisa-ação realizada sob a perspectiva freireana de educação popular. Utilizou-se a análise do discurso de Gill, tomando-se como referencial o sentido do trabalho no contexto da Política de Saúde Mental. Observou-se que os sentidos encontrados no discurso dos participantes se baseiam em diferentes concepções, sobretudo no sentido do trabalho como sustento das necessidades da sobrevivência humana, e desta maneira, como potencialidade para a reprodução da vida. No entanto, estes sentidos estão no âmbito do trabalho protegido-terapêutico e distanciados do trabalho emancipado. O processo de reabilitação psicossocial para pessoas com experiência na loucura e na perspectiva do trabalho precisa ir além de geração de renda. Quando atrelada ao trabalho emancipado, pode-se pensar que promova a participação democrática e cidadã. Dessa forma, há um terreno fértil para a construção de novas relações consigo e com os outros, pautadas nos princípios do movimento da economia solidária.
Análise crítica do modelo BPSO-96 de QVT a partir da teoria da atividade de A. N. Leontiev
Authors: Pracidelli Flavia , Rossler João Henrique
Published: February 2019

Este artigo, fruto de uma dissertação de mestrado cuja metodologia adotada foi a pesquisa teórico-bibliográfica, discute criticamente o que se convencionou denominar como Qualidade de Vida no Trabalho (QVT), a partir da teoria da atividade de A. N. Leontiev, tendo como objeto específico de análise o modelo Biopsicossocial e Organizacional (BPSO-96) de QVT. Para isso, revisa o conceito e a história da QVT, bem como apresenta uma síntese das críticas a ela já apontadas por diversos autores. Na sequência, define e analisa o modelo BPSO-96. O intuito é contribuir com os estudos críticos da QVT, demonstrando que se trata de uma estratégia de gestão cujo objetivo velado é o aumento da produtividade do trabalhador, por meio de métodos que manipulam objetiva e subjetivamente os motivos da atividade de trabalho e obscurecem em sua consciência seu sentido alienado. Dessa forma, este artigo visa contribuir para o processo de tomada de consciência dos reais objetivos e consequências dos programas de QVT para a classe trabalhadora, mostrando que, apesar de seu discurso pseudo-humanista, esta estratégia de gestão atende prioritariamente aos interesses de maior produtividade da organização.
O Programa Nacional do Livro Didático e o processo de constituição de uma Didática da História para os Anos Iniciais
Authors: Sanches Tiago Costa
Published: February 2019

Nos percursos de constituição da Didática da História nos anos iniciais, diversas concepções de ensino aprendizagem da História pautaram os debates sobre o tema, conferindo a esta Didática um caráter epistemológico específico. Preocupada em investigar os processos de construção do conhecimento histórico, utilizando a epistemologia específica da História, a linha de pesquisa Educação Histórica, apresenta hoje uma possibilidade de se pensar a Didática da Histórica a partir da própria ciência de referência. O presente estudo contou com uma investigação empírica que, a partir da abordagem metodológica denominada Análise de Conteúdo e procurou investigar em guias de livro didático referente ao Programa Nacional do Livro Didático (PNLD) quais concepções de ensino aprendizagem balizaram sua construção e orientações. Deste estudo teórico e das análises, pode-se verificar alguns pressupostos e significados de uma Didática da História para os anos primeiros anos do Ensino Fundamental.
O que ensinam e como ensinam os Livros Didáticos de História para os adolescentes? Uma experiência de leitura crítica do Guia de Livros Didáticos de História – Anos Finais do Ensino Fundamental (PNLD 2017)
Authors: Moscato Daniela Casoni
Published: February 2019

Este texto é um relato de minha experiência de leitora crítica para o “Programa Nacional do Livro e do Material Didático (PNLD) de 2017” e de minha apresentação na mesa redonda do evento “Livro didático de história: conhecimento histórico e didática da história no mundo contemporâneo”, em 2017. Desta forma, trago neste artigo a descrição das etapas do trabalho que realizei e possíveis reflexões sobre o GUIA de História 2017. Como uma das três leitoras das resenhas das coleções aprovadas pela equipe avaliativa, realizei este trabalho seguindo os critérios de fichas de análise e de acordo com o meu lugar social: o de professora de História da rede pública de ensino. Escreverei desse mesmo lugar.
Metoda wizualizacji kształtu membrany wiotkiej pompy wspomagania serca
Authors: Sulej Wojciech , Murawski Krzysztof
Published: February 2019

W artykule przedstawiono metodę wizualizacji kształtu membrany wiotkiej pneumatycznej, pozaustrojowej pompy wspomagania pracy mięśnia sercowego. Celem badań było opracowanie techniki wyznaczania, w czasie rzeczywistym, nieregularnego widoku membrany. Widok tworzono na podstawie jednego obrazu membrany wykonanego nieruchomą kamerą wyposażoną w obiektyw o stałej ogniskowej ze stałą nastawą ostrości. Badania ukierunkowano na użycie technik rzeczywistości wirtualnej. Przyjęto, że metody wykorzystywane do tworzenia realistycznej, trójwymiarowej grafiki komputerowej, łącznie z autorską metodą wyznaczania odległości typu Depth from Defocus pozwolą osiągnąć założony cel. W artykule zawarto również wyniki uzyskane metodą wizualizacji kształtu membrany dla modelowych (znanych) kształtów membran
Analiza właściwości wybranych rozwiązań rozproszonych systemów plików
Authors: Kula Karolina , Markowski Marcin
Published: February 2019

W artykule przedstawiono analizę porównawczą trzech najpopularniejszych rozproszonych systemów plików: Ceph, LizardFS, GlusterFS. Głównym kryterium oceny badanych systemów była ich wydajność, rozumiana jako liczba operacji zapisu i odczytu w jednostce czasu oraz maksymalny transfer danych. Analizę oparto na wynikach licznych eksperymentów przeprowadzonych w opracowanym w tym celu stanowisku badawczym. Część badawczą poprzedzono przeglądem technologii oraz najpopularniejszych istniejących systemów tego typu. W pracy przedstawiono wyniki eksperymentów, ich analizę oraz praktyczne wnioski. In this paper we present a comparative analysis of three most popular distributed file systems: Ceph, LizardFS nad GlusterFS. The main evaluation criterion was the efficiency of systems, meant as the number of read and write operation per second and maximum data transfer rate. The analysis is based on results of many experiments conducted in experimental testbed, prepared for this purpose. Experimental part of the paper is preceded with a survey of technology related to most important distributed file systems. The results of experiments have been presented and analyzed, also some practical conclusions have been formulated.
USE OF SATISFACTION SURVEYS IN MOTIVATING EMPLOYEES
Authors: Bakonyi Jadwiga , Bilnik Sebastian
Published: February 2019

This article deals with the problem of employee satisfaction, particularly the determinant, which has an effect on it. A survey questionnaire, designed for the needs of this study was used as a research method. Satisfaction survey allows recognising different attitudes of employees thus enabling selection of more personalised motivating tools. This research shows that the satisfaction of employees is most of all influence by: the level of remuneration and possibility of Professional development. Demographic variables do not significantly influence on the level of employees satisfaction.
HUMAN CAPITAL IN INTERNATIONAL ORGANIZATIONS IN THE INFORMATION TECHNOLOGY INDUSTRY – RESULTS OF EMPIRICAL RESEARCH
Authors: Żelazna Anna , Socha Moinika
Published: February 2019

The most important asset of any organization is the people. Measures taken to improve the quality and safety of work, the atmosphere and relations between employees should be treated as an investment, since the long-term benefits of such activities can be seen in many respects. The aim of this paper is to present the results of empirical pilot studies conducted in IT corporations concerning the implementation of corporate social responsibility principles towards employees