bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Heat Treatment Method on Grain-Refining during Warm Deformation of Medium Carbon Steel
Authors: Fan Bo Wen , Wang Jian Min , Rao Guang
Published: December 2016

The microstructure evolution and grain-refining mechanism in the process of ultrafine grain preparation with combination of different heat treatments and warm deformation were studied. 5140 steel，medium carbon low alloy steel, was used in this experimental and divided into three groups, which is one time quenching state, three times cyclic quenching state and original state without any heart treatment as the control group. All the samples of above three groups hold at 600°C for 5 min, then warm deformation was carried out immediately in YJ-450 Four-Pillar Hydraulic Machine. The deformation amount of above samples is controlled beyond 50%. The result shows that microstructure of the medium carbon steel samples after once quenching treatment and three times cyclic quenching treatments was significantly refined after warm deformation. The grain-refining mechanism of supersaturated single-phase ferrite in warm deformation is that new dislocation boundaries are produced continuously through dislocation cross-slip, which segments and refines the original grains. The grain size of three times quenching state after warm deformation is obviously finer than the grain size of one time quenching state after warm deformation under the same condition. And quenching times is a very significant factor to the extent of fining grain after warm deformation. Through three times cyclic quenching treatments and warm deformation, the size of grains has reached nano-scale.
Micro-Strength Analysis of Sand Mold for Casting Based on Bonded-Particle Model
Authors: Zhu Fu Xian , Shan Zhong De , Liu Fen
Published: December 2016

The micro-strength of sand mold is analyzed based on bonded-particle model (BPM) due to the reason that the strength of sand mold largely influences the final casting properties. In this study, the stress and the strength as well as the stiffness parameters of the binding bridge between the sands are obtained firstly by establishing the equivalent micro-beam model of the binding bridge between the sands. Then, the tensile strength formula of Sand Mold is derived according to the idea packing shape of particle, which is then used for discussing the relationship between the tensile strength with the sand mesh and the mass fraction of binder. At last, the effects of the sand mesh and mass fraction of binder on the tensile strength of the Sand Mold are analyzed quantitatively, which shows the great agreement with the macroscopic experimental results of the sand mold strength.
Effect of in Addition to Zn-5Al Solder on Microstructure and Properties of Solder Joints
Authors: Kostolný Igor , Koleňák Roman
Published: December 2016

The effect of In addition to Zn-5Al on the interfacial reaction behaviors and mechanical properties of solder joints were investigated. It was found that addition of In decreasing the melting point of Zn-5Al solder. The segregation of In on grain boundary was observed. CuZn5 and Cu5Zn8 intermetallic phases were observed at joint interface. Segregation of In on grain boundary caused a significant decrease of strength of the Zn-5Al-In solder compared to Zn-5Al. Addition of 1% In to Zn-5Al solder resulted in a reduction of shear strength of 14 MPa. The interfacial microstructure, shear strength and fracture surfaces of Zn-5Al/Cu and Zn-5Al-1In/Cu solder joints were studied.
Annealing Effect for Cold Rolling 6016 Aluminum Alloy Sheet
Authors: Li Jiu Hui , He Dong Ye , Zheng Xuan Tao , Ding Gao Liang
Published: December 2016

In aluminum alloy sheet metal forming process, annealing treatment can improve the mechanical properties. The tensile test for different temperatures of 400°C, 450°C, 500°C, 550°C respectively have been carried out from 1h to 12h.The result revealed that the ductility increased with the increase of annealing temperature. It is found that the annealing treatment at 500°C for 6 h can get a good property. Furthermore, the result of tensile test showed that the yield strength increased from 130MPa before cold rolling to 190MPa after annealed, and the elongation of the sheet increased to 28.6%. The result of stamping test veriﬁed that the limiting draw ratio (LDR) increased after annealing treatment from 1.15 to 1.56. The value of blank holder force for the cylindrical cup is becoming smaller after the annealing treatment. The microstructure investigations on experimental aluminum alloys after long-time annealing and cold rolling conditions were presented. The changes of the main structural contituents have been obviously observed, which improved the formability of the alloys.
Analysis of the Properties of Mechanical Materials and Parts Based on ANSYS Software
Authors: Yang Ze , Li Jian Yong , Zhang Yan Ping , Li Hai Lian , Gao Xing Hua
Published: December 2016

In view of the significant role of material science in industrial production, the analysis and research on mechanical properties of materials and parts are of great significance to equipment production and machining. This paper, based on the finite element analysis of ANSYS software, will carry out the exploration and research on characteristics of material fatigue damage within mechanical materials and parts in a degree. Then, the general laws of material fatigue properties will be concluded from theoretical analysis, drawing of curve and equal-life curve as well as some comparisons between materials and parts. Finally, the correctness will be tested with the help of ANSYS software, which is an excellent finite element analysis software with abilities of modeling and simulation. Meanwhile, the whole process can provide somewhat valuable references and citations for practical applications, teachings, researches and academic conferences on material fatigue damage theory.
Zone Partitioning Sequential Calculation Method for Three-Dimensional Phase-Field Material Simulation during Directional Solidification
Authors: Feng Li , Hu Hai Huang , Jia Bei Bei , Wang Gang Gang , Zhu Chang Sheng , Xiao Rong Zhen
Published: December 2016

Complex dendritic structures can be simulated directly by phase field method. However, phase field method needs a very fine mesh computing and memory requirements. A new calculation method named zone partitioning sequential calculation method is proposed to expand the simulation area of phase field method. The simulation area can be divided into several parts, and the parts can be calculated one by one in a certain order by the new method. This new method can reduce the computing and memory requirements of single calculation, because a part of the simulation area is less than the whole simulation area. Although this method could make error in the interface of different parts of the simulation area when the grains go through the interface, but the error has less effect on the grain growth. By using phase field method, coupled with zone partitioning sequential calculation method, the simulation of the directional solidification process of Al-Cu binary alloy is operated. The results show that the new method can be applied to phase field simulation of binary alloy solidification in a large area. The simulation results have certain accuracy and reliability.
Investigation on Process and Welded Joint Mechanical Properties of Bainitic Steel Rail Flash Butt Welding
Authors: Zhang Qi , Li Li , Ding Wei , Song Hong Tu , Gao Zhen Kun
Published: December 2016

Combine with the characteristics of bainitic rail U20Mn2SiCrNiMo, the flash butt welding process that suitable bainitic rail is optimized for improving bainitic joints’ performance basing on the mature technology of pearlitic rail flash butt welding, through approaches of lower heat input appropriate and matched upset forging length parameters, et.. In the post welding treatment, controlling the heating process strictly and using slow cooling measures are done to further optimize the properties of the welded joints. Then the performance tests are done on the bainitic rail joints welded with optimized welding and post welding process. The study results approve that the qualified bainitic rail joints can be obtained through appropriate flash butt welding process. Tensile strength and impact energy of bainitic joints are superior to pearlitic rail joints, but the elongation is reverse. The impact fracture of bainitic rail flash welded joints appear more defects such as hot cracks and silicate inclusions than pearlitic joints. Compared with parent metal, both types of the rail joints appear higher strength, but lower elongation and impact energy. The decreased percentage of bainitic rail joints compared with their parents is larger than pearlitic joints.
Experimental Verification of Scrub and Impact Resistance of the Epoxy Coatings Filled with the Finely Milled Waste Glass
Authors: Hodul Jakub , Hodná Jana , Drochytka Rostislav
Published: December 2016

The main aim of the research is to examine the possibility to replace the primary materials, glass flakes and mildly ground siliceous sand that are the most commonly used fillers in majority polymer coatings today, with special types of finely milled waste glass. During the experimental testing, carried out for the purpose of the research into the chosen progressive polymer protective materials (protective coating premium (PC-P) with higher long-term durability, protective coating economy (PC-E) and floor coating economy (FC-E)), some mechanical attributes of the developing epoxy coatings were tested. Impact resistance and scrub resistance are tested with the developing epoxy coatings containing secondary raw materials. These tests dealing with mechanical resistance and they are two of the most testing attributes of the epoxy polymer coatings. Based on the evaluation of the test results of performed tests the possibility of replacing the commonly used fillers by special types of finely milled waste glass is assessed.
Improved Out-Coupling Emission of Organic Light-Emitting Diodes by Employing Ag-Thin-Film or Al2O3-Thin-Film Longitudinal Wave Guides
Authors: Lin Yang , Liu Shi Qi , Li Wei Ling , Chen Guo , Wei Bin
Published: December 2016

We improved the current efficiencies of Organic Light-emitting diodes from 50 cd/A to 77.7 and 65.4 cd/A by employing Ag-thin-film and Al2O3-thin-film longitudinal wave guides with the same device structures, respectively, which was attributed to the recycle use of the internal mode because the reflection of the thin-film longitude wave guides. In addition, the introduction of these wave guides exported slight influence on the spectra which was resulted from mode selection by the micro-cavity consisting of ITO and organic layers.
Synthesis and Characterization of Silica Aerogel Materials Doped with TiO2 Powder for Thermal Insulation
Authors: Liu Guang Wu , Liu Yan Gang
Published: December 2016

Super insulation and hydrophobic silica-based aerogels doped with TiO2 powder (8wt %) were successfully synthesized by using cost effective processing from Tetraeth oxysilane (TEOS). After aging and washing of wet gel, surface modification were modified using trimethylchlorosilane (TMCS) via one-step solvent exchange and surface modification. And the proper molar ratio of TMCS to pore water is 0.02. The microstructure and morphology of the ultralow density silica aerogels were characterized by the specific surface area, SBET, SEM, and the pore size distribution techniques. From the results, the obtained aerogel doped with TiO2 powder exhibited excellent physical properties with less than 10% volume shrinkage, extremely high specific surface area (652 m2/g) and super hydrophobicity (contact angle of~145°). It should be noted that TiO2 powders are physically embedded by SiO2 aerogel, and there is an obvious Ti–O–Ti and Si–O–Si bonding group based on structural analysis. The thermal properties of silica aerogel were determined using the Hot Disk device, composite aerogel exhibited thermal conductivities of 0.0426 W/m·K at 700°C, TiO2 powders effectively suppressed the intensified thermal radiations at high temperatures to achieve ultralow thermal conductivities. These results have important implications for designing novel structure of porous materials of high performance for silica aerogels.
Chromium (VI) Adsorption Study Using Bio-Adsorbent Material Derived from Tamarind-Seed Testa
Authors: Setthayanond Jantip , Sae-Bae Porntip , Chaiyapongputti Podjanalak , Lim Phussadee
Published: December 2016

In this research, the chromium (VI) adsorption in potassium chromate (K2CrO4) and potassium dichromate (K2Cr2O7) was studied with the low-cost adsorbent derived from sweet tamarind seeds obtained from the food processing industry in Thailand. The tamarind-seed testa was prepared by decoloring the tamarind-seed husks in boiling water and 1% NaOH solution followed by bleaching in H2O2 solution. The major components found in the tamarind-seed testa were alkali hydrolysable, low molecular-weight carbohydrates. The study found that the adsorbent material derived from tamarind–seed testa could well adsorb chromium ions in both chromium compound solutions at pH 2. The adsorption took place rapidly within the first 4 hours and then gradually declined until reaching adsorption equilibrium in 12 hours. Adsorption of chromium (VI) from potassium chromate solution was superior to that from potassium dichromate. Chromium adsorption at pH 2 fitted well with Langmuir and Freundlich isotherms. The adsorption mechanism in both solutions was a monolayer chemical adsorption rather than multilayer physical adsorption. The adsorbent could almost completely remove chromium in potassium chromate (90% removal) while it could remove 57% chromium from potassium dichromate solution when the initial chromium concentration of 100 mg/l was employed.
Separation of Non-Natural Carboxyl Amino Acid Enantiomers by Capillary Electrophoresis with CM-β-Cyclodextrins as Chiral Selective Reagent
Authors: Li Bao Hui , Li Xiao Yan , Yang Xiao Dan
Published: December 2016

A method was built to separate three kinds of enantiomers of non-natural carboxyl amino acid with CE while CM-β-CDacted as chiral selective reagent. Several different β-CD derivatives were used as the chiral separation agent, and it was proved that CM-β-CDhad the advantage of chiral selectivity for carboxyl amino acids. Three kinds of enantiomers of carboxyl amino acids were separated by CE in a 50 μm i.d.×60 cm (effective length 45 cm) fused-silica capillary at 20 kV voltages and 10 mM NaH2PO4 solution served as running buffer solution with 10 mM CM-β-CDserving as selective reagent. The optimum detection wavelength was 214nm.
The Effect of Modifying Agents on the Mechanical Properties of Straw Flour/Waste Plastic Composite Materials
Authors: Ge Zheng Hao , Si Dan Ge , Lan Yun Li , Shi Mei Nong
Published: December 2016

Though there has been a large number of studies concerning the modification of wood plastic composite materials, there is still more to be done. This report aims to study the effect of the coupling agents (PP-g-MAH, silane, titanate) and compatibilizer(SBS) on the mechanical properties of straw flour/waste plastic composites. Straw flour, waste plastic, modifying agents and other additives were mixed evenly in a high speed mixing machine. And the mixed materials were compounded into the pelllets using the twin-screw extruder. Then the test specimens were prepared by the injection molding. The influence of 4% coupling agent (PP-g-MAH, silane, titanate) on the mechanical properties of straw flour/waste plastic composites was researched, and the most suitable coupling agent to the composites was obtained. In order to increase the toughness of the composite materials and to furthermore improve the comprehensive mechanical properties, the WPCs with different contents styrene butadiene styrene (SBS) were investigated. The experimental results showed that the coupling agent PP-g-MAH and the content was 4%, the mechanical properties of the composite materials were better; when SBS content was 5%, the maximum increases of tensile strength, flexural strength and impact strength of SBS modified WPCs were by 14.34%, 20.75%, 34.38% compared to those of neat WPCs respectively.
Optimization of Esterification and Transesterification Reactions for Biodiesel Production from Crude Coconut Oil Using RSM Techniques
Authors: Pimngern Natta , Punsuvon Vittaya
Published: December 2016

Crude coconut oil with high free fatty acid (FFA) content was used as a raw material to produce biodiesel. In this work, the esterification followed by transesterification of crude coconut oil with methanol is studied. The response surface methodology (RSM) with 5-level-3-factor central composite design (CCD) was applied to study the effect of different factors on the FFA content of esterification and the percentage of fatty acid methyl ester (FAME) conversion of transesterification. The FAME conversion was detected by proton magnetic resonance (1H-NMR) spectrometer. As a result, the optimum conditions for esterification were 6:1 of methanol-to-oil molar ratio, 0.75wt% of sulfuric acid (H2SO4) concentration and 90 min of reaction time. The optimum conditions for transesterification were 8.23:1 of methanol-to-oil molar ratio, 0.75wt% of sodium hydroxide (NaOH) concentration and 80 min of reaction time. Quadratic model equations were obtained describing the relationships between dependents and independent variables to minimize the FFA content and maximize the FAME conversion. Fuel properties of the crude coconut oil biodiesel were also examined followed ASTM and EN standards. The results showed that all properties met well with both standards.
Isolation, Identification, and Characterization of Lambda-Cyhalothrin Pesticide Degrading Bacterium ZC-5
Authors: Zhang Rong Hu , Zhou Zhen Hua , Feng Jian Cheng
Published: December 2016

A highly efficient lambda-cyhalothrin-degrading bacterium, designated as strain ZC-5, was isolated from the activated sludge of a sewage aeration tank in a pesticide factory by enrichment acclimation and the streak plate method. Strain ZC-5 can grow on minimal medium with lambda-cyhalothrin as the sole source of carbon and nitrogen. After cultivation for 6 h to 24 h, the biomass of the bacterial strain significantly increased at the logarithmic phase. By contrast, the concentration of lambda-cyhalothrin rapidly decreased. The residual lambda-cyhalothrin presented a concentration of 250 mg/L and a degradation rate of 50%. Gas chromatography revealed that this strain can degrade 87.1% lambda-cyhalothrin (500 mg/L) in the culture within 2 days. Morphological analysis showed the Gram-negative strain as short rods. Physiological and biochemical characterizations, as well as phylogenetic analysis of the 16S rDNA sequence identified the bacterium to be an Achromobacter xylosoxidans strain. Results showed that this strain can provide a novel strategy to biodegrade the pesticide lambda-cyhalothrin.
The Effects of Preparation Methods on Iron Structures of Iron-Supported HZSM-5 and their Catalytic Performance for Methanol Dehydration
Authors: Pantupho Waenkaew , Neramittagapong Arthit , Osakoo Nuttawut , Wittayakun Jatuporn , Loiha Sirinuch
Published: December 2016

Iron-supported HZSM-5 catalysts were prepared by hydrothermal (Fe-HZSM-5_HYD) and impregnation methods (Fe/HZSM-5_IMP). The active species of binuclear-iron complex and iron-substituted zeolite framework, confirmed by EXAFS analysis, were observed on Fe/HZSM-5_IMP and Fe-HZSM-5_HYD, respectively. The catalysts were used for production of dimethyl ether (DME) by methanol dehydration at 200-350 °C using fixed bed flow reactor. Fe/HZSM-5_IMP showed higher catalytic conversion than Fe-HZSM-5_HYD. However, the Fe/HZSM-5_IMP catalyst was less selective to DME product and strongly deactivated for 24h. The deactivation might due to transformation of binuclear-iron to the a-iron site which was strong acidic strengh. The iron-substituted zeolite framework of Fe-HZSM-5_HYD showed high stability toward methanol dehydration. Moreover, the catalyst showed advantages of good selective to DME and low carbon deposition on surface. These results suggested that the iron-substituted zeolite framework structure could improve catalytic performance for mrthanol dehydration.
Research on the Interaction between Biomaterials of Human Serum and Dibazol by Fluorescence Spectroscopy
Authors: Wang Tian Hu , Luo Yin Sheng
Published: December 2016

The interaction of dibazol to serum was investigated by fluorescence and UV-vis spectroscopy. The fluorescence experiment results show that the fluorescence of human serum can be effectively induced by light wave. The maximum fluorescence intensity of serum is excited at 280 nm and the peak wavelength is about 334 nm. It can also be concluded that the fluorescence intensity gradually increase with the increasing excitation light wavelength. The range of the fluorescence spectroscopy of serum-dibazol system induced by excited at different wavelength is about 290 - 450 nm. The fluorescence intensity of the interaction system of dibazol-serum is significantly reduced, indicating that the fluorescence quenching of serum occurred strongly caused by dibazol and there is a new compound formed between dibazol and serum. The absorption spectra show that there is a large blue in the system of dibazol and serum, which reveal that there is a kind of new complex between dibazol and serum. It is very significance to study the interaction between dibazol and serum for understanding of drug’s toxicity and its distribution in the organism.
Granule Morphology of Supplementary Cementitious Materials under Different Cooling Conditions
Authors: Li Zai Bo , Zhao Xu Guang , Zhao San Yin , He Tu Sheng
Published: December 2016

Basic oxygen furnace slag (BOFS) , a mass supplementary cementitious materials, can be used as an active additive in building materials. The work present the result of granule morphology of two kinds of BOFS powder, cooled by water quenching (BOFS-W) and air splashing method(BOFS-A). Micrographs of two kinds of BOFS powder were observed with a scan electron microscope (SEM), then, length of major axis and minor axis of two-dimension projective outline of every granule in these SEM micrographs was measured manually and their ratio (RLB) was used to represent the granule sphericity. Each BOFS powder was divided into 6 parts with different granularity range. By means of measurement and statistical analysis, the average RLB value of granules with different granularity grade was obtained and the relation between size and sphericity of granule was explored. Result showed that BOFS-W is superior to BOFS-A in sphericity of granule. According to different granularity grade, statistical average values of RLB of BOFS-W and BOFS-A range 1.422-1.496 and 1.490-1.647, respectively. The difference of BOFS-W and BOFS-A on granule sphericity mainly is reflected in coarse granule.
The Domestic Research Situation of Crop Straws as Building Wall Materials and Thermal Insulation Materials
Authors: Xu De Feng , Tao Sheng Nan , Chen Li Mei , Cheng Shu Chao , Xiao Fei , Qinwei Li Fa
Published: December 2016

At present, the comprehensive utilization of crop straws exist the problem of the lower industrial utilization in Jilin Province, China. It’s well-known that the industrial conversion of crop straws are often used as the building wall materials and thermal insulation materials in our country. According to the above two questions, this paper elaborates the domestic research situation of crop straws that serve as building wall materials and thermal insulation materials, and summarizes the fabrication process, mechanical property and thermal performance of the crop straws as building wall materials and thermal insulation materials. Finally, the article puts forward three key problems of crop straws, which are used as the building wall materials and thermal insulation materials. I hope that this paper can provide valuable reference for speeding up the comprehensive utilization of crop straws in Jilin Province.
Smart Building Materials of BIM and RFID in LifeCycle Management of Steel Structure
Authors: Xie Yun Fei , Li Chun Xiang , Li Zhi Hui
Published: December 2016

With the development of economy, steel structure is more and more widely applied in China. With the deepening of sustainable development, the industrialization of construction become more and more hot in construction industry. Steel Structure is expected to be an important building material of industrialization. Obviously steel structure has been a main forms using in China. According to the characteristics of steel structure, smart material of BIM and RFID can be chosen as a new integration. This smart material can be used to solve the key technology of lifecycle management and information is shared, exchange with each other between participants during each stage.
FE Evaluation of Reinforced Concrete Bridge Decks with Glass-FRP Composite Bars
Authors: Huang Jian Wei , Davis Jonathan
Published: December 2016

In order to resolve the steel corrosion problem in bridge decks, glass fiber reinforced polymer (GFRP) has been recommended as a substitute to the conventional steel reinforcement in bridge decks. However, the use of GFRP bars in bridge decks is still limited by several concerns, including the long-term durability of GFRP bars in the concrete under sustained loadings. Literature review showed that the tensile strength reduction of the GFRP bar should be governed by the sustained stress level in the GFRP bar. In this regard, a GFRP reinforced concrete deck was simulated in this paper, aiming to investigate the sustained stress levels in the GFRP bars through three dimensional finite element (FE) modeling. Per AASHTO LRFD specifications, one lane loaded and two lane loaded cases were examined to identify the maximum tensile strains in the internal GFRP bars subjected to dead loads and HL-93 design loadings. The FE results showed that the maximum tensile stresses in GFRP bars under service loads were less than 1% of the GFRP design strength, which implied that the GFRP bars could have excellent long-term performance in real concrete bridge decks.
Uplift Model Analysis for Shallow Overlaying Slurry Shield Tunnel Based on Time-Varying Behavior of Cement Grouting Material
Authors: Haung Yu , Li Lin , Ni Jing , Chen Lei Biao
Published: December 2016

As a necessary and key procedure of shield technology, synchronous grouting affects ground layer deformation, and controls the tunnel uplift and ground subsidence, usually exerting negative influence on underground engineering construction and surrounding buildings. This paper establishes the 2D uplift model of the soil and lining by ABAQUS, based on a static buoyancy varying with solidification of grout and dynamic buoyancy produced by grouting pressure. The effect of buoyancy on lining is simulated in the lining and soil through a series of specific magnitude of interference fit. Effectiveness of the model is validated by comparison of data measurement of South Hongmei Rd. tunnel with predicted results for vertical displacement of ground surface. East line of South Hongmei Rd. tunnel with super large diameter is chosen for the simulation and central burial depths vary as a key parameter. The results show t4hat the differences between predictions and data measurement are limited, hence providing a basis of numerical analysis for the design and optimization of shallow slurry shield tunnel with super large diameter.
Prediction of Collapse Area of Construction Materials for Cooling Tower with Different Cut Height Due to the Blasting Demolition
Authors: Tao Tie Jun , Liu Lian Sheng , Chi En An , Zhao Ming Sheng
Published: December 2016

The effect of cut height on collapse area is simulated and analyzed by dynamic finite element software. Meanwhile, the simulated collapse processes of the cooling tower with different cut height were completed in a parallel study, the results of which are briefly introduced in this paper. The results show that: as the cut height increases, ground vibration on surrounding structures and collapse area of cooling tower decreases. At last, numerical simulation results were used in blasting project, which reduced hazard of collapse vibration and verify the scientific of this method.
Long-Term Behavior of Low-Heat Cement Concrete under Different Curing Temperatures
Authors: Mun Jae Sung , Yang Keun Hyeok , Kim Si Jun
Published: December 2016

The present study is to estimate long-term characteristics of low-heat cement-based ternary blended concrete prepared for reducing hydration heat in mass concrete. 15% modified fly ash and 5% limestone powder were added for partial replacement of the low-heat cement. To achieve the designed compressive strength of 42 MPa, water-to-binder ratios were determined to be 27.5, 30 and 32.5% for ambient curing temperatures of 5, 20 and 40°C, respectively. Test results showed that, with the decrease in curing temperature, the drying shrinkage strains tended to decrease, whereas creep strain increased.
The Bifurcation Diagram of Cubic Polynomial Vector Fields on CP1
Authors: Rousseau C.
Published: December 2016

In this paper we give the bifurcation diagram of the family of cubic vector fields z=, depending on the values of . The bifurcation diagram is in ℝ 4, but its conic structure allows describing it for parameter values in . There are two open simply connected regions of structurally stable vector fields separated by surfaces corresponding to bifurcations of homoclinic connections between two separatrices of the pole at infinity. These branch from the codimension 2 curve of double singular points. We also explain the bifurcation of homoclinic connection in terms of the description of Douady and Sentenac of polynomial vector fields.
Polynomial chaos and scaling limits of disordered systems
Authors: Caravenna Francesco , Sun Rongfeng , Zygouras Nikos
Published: December 2016

Inspired by recent work of Alberts, Khanin and Quastel, we formulate general conditions ensuring that a sequence of multi-linear polynomials of independent random variables (called
polynomial chaos
expansions) converges to a limiting random variable, given by a
Wiener chaos
expansion over the

d

-dimensional white noise. A key ingredient in our approach is a
Lindeberg principle
for polynomial chaos expansions, which extends earlier work of Mossel, O’Donnell and Oleszkiewicz. These results provide a unified framework to study the
continuum and weak disorder scaling limits
of statistical mechanics systems that are
disorder relevant
, including the disordered pinning model, the (long-range) directed polymer model in dimension 1 + 1, and the two-dimensional random field Ising model. This gives a new perspective in the study of disorder relevance, and leads to interesting new continuum models that warrant further studies.
Bernstein inequalities with nondoubling weights
Authors: Bondarenko Andrii , Tikhonov Sergey
Published: December 2016

We answer Totik's question on weighted Bernstein's inequalities by showing that

\|T_n'\|_{L_p(\omega)} \leq C(p,\omega)\, {n}\,\|T_n\|_{L_p(\omega)},\qquad 0 < p \leq \infty,

holds for all trigonometric polynomials

T_n

and certain nondoubling weights

\omega

. Moreover, we find necessary conditions on

\omega

for Bernstein's inequality to hold. We also prove weighted Markov, Remez, and Nikolskii inequalities for trigonometric and algebraic polynomials.
Curvature-dimension inequalities and Ricci lower bounds for sub-Riemannian manifolds with transverse symmetries
Authors: Baudoin Fabrice , Garofalo Nicola
Published: December 2016

Let

\mathbb M

be a smooth connected manifold endowed with a smooth measure

\mu

and a smooth locally subelliptic diffusion operator

L

satisfying

L1=0

, and which is symmetric with respect to

\mu

. Associated with

L

one has the
carré du champ

\Gamma

and a canonical distance

d

, with respect to which we suppose that

(\mathbb M,d)

be complete. We assume that

\mathbb M

is also equipped with another first-order differential bilinear form

\Gamma^Z

and we assume that

\Gamma

and

\Gamma^Z

satisfy the Hypothesis 1.1, 1.2 and 1.4 below. With these forms we introduce in (1.12) a generalization of the curvature-dimension inequality from Riemannian geometry (see Definition 1.3). In our main results we prove that, using solely (1.12), one can develop a theory which parallels the celebrated works of Yau, and Li–Yau on complete manifolds with Ricci curvature bounded from below. We also obtain an analogue of the Bonnet–Myers theorem. In Section 2 we construct large classes of sub-Riemannian manifolds with transverse symmetries which satisfy the generalized curvature-dimension inequality (1.12). Such classes include all Sasakian manifolds whose horizontal Webster–Tanaka–Ricci curvature is bounded from below, all Carnot groups with step two, and wide subclasses of principal bundles over Riemannian manifolds whose Ricci curvature is bounded from below.
Triple Massey products and Galois theory
Authors: Mináč Ján , Tân Nguyên Duy
Published: December 2016

We show that any triple Massey product with respect to prime 2 contains 0 whenever it is defined over any field. This extends the theorem of M. J. Hopkins and K. G. Wickelgren, from global fields to any fields. This is the first time when the vanishing of any

n

-Massey product for some prime

p

has been established for all fields. This leads to a strong restriction on the shape of relations in the maximal pro-2-quotients of absolute Galois groups, which was out of reach until now. We also develop an extension of Serre's transgression method to detect triple commutators in relations of pro-

p

-groups, where we do not require that all cup products vanish. We prove that all

n

-Massey products,

n \geq 3

, vanish for general Demushkin groups. We formulate and provide evidence for two conjectures related to the structure of absolute Galois groups of fields. In each case when these conjectures can be verified, they have some interesting concrete Galois theoretic consequences. They are also related to the Bloch–Kato conjecture.
Fourth-Year Medical School Course Load and Success as a Medical Intern
Authors: Richards Christopher J. , Mukamal Kenneth J. , DeMelo Nikki , Smith C. Christopher
Published: December 2016

Background 

The fourth year of medical school has come under recent scrutiny for its lack of structure, cost- and time-effectiveness, and quality of education it provides. Some have advocated for increasing clinical burden in the fourth year, while others have suggested it be abolished.

Objective 

To assess the relationship between fourth-year course load and success during internship.

Methods 

We reviewed transcripts of 78 internal medicine interns from 2011–2013 and compared the number of intensive courses (defined as subinternships, intensive care, surgical clerkships, and emergency medicine rotations) with multi-source performance evaluations from the internship. We assessed relative risk (RR) and 95% confidence interval (CI) of achieving excellent scores according to the number of intensive courses taken, using generalized estimating equations, adjusting for demographics, US Medical Licensing Examination (USMLE) Step 1 board scores, and other measures of medical school performance.

Results 

For each additional intensive course taken, the RR of obtaining an excellent score per intensive course was 1.05 (95% CI 1.03–1.07, P < .001), whereas the RR per nonintensive course taken was 0.99 (95% CI 0.98–1.00, P = .03). An association of intensive course work with increased risk of excellent performance was seen across multiple clinical competencies, including medical knowledge (RR 1.08, 95% CI 1.04–1.11); patient care (RR 1.07, 95% CI 1.04–1.10); and practice-based learning (RR 1.05, 95% CI 1.03–1.09).

Conclusions 

For this single institution's cohort of medical interns, increased exposure to intensive course work during the fourth year of medical school was associated with better clinical evaluations during internship.
Examining the Functioning and Reliability of the Family Medicine Milestones
Authors: Peabody Michael R. , O'Neill Thomas R. , Peterson Lars E.
Published: December 2016

Background 

The Family Medicine (FM) Milestones are a framework designed to assess development of residents in key dimensions of physician competency. Residency programs use the milestones in semiannual reviews of resident performance from entry toward graduation.

Objective 

To examine the functioning and reliability of the FM Milestones and to determine whether they measure the amount of a latent trait (eg, knowledge or ability) possessed by a resident or simply indicate where a resident falls along the training sequence.

Methods 

This study utilized the Rasch Partial Credit model to examine academic year 2014–2015 ratings for 10 563 residents from 476 residency programs (postgraduate year [PGY] 1 = 3639; PGY-2 = 3562; PGY-3 = 3351; PGY-4 = 11).

Results 

Reliability was exceptionally high at 0.99. Mean scores were 3.2 (SD = 1.3) for PGY-1; 5.0 (SD = 1.3) for PGY-2; 6.7 (SD = 1.2) for PGY-3; and 7.4 (SD = 1.0) for PGY-4. Keyform analysis showed a rating on 1 item was likely to be similar for all other items.

Conclusions 

Our findings suggest that FM Milestones seem to largely function as intended. Lack of spread in item difficulty and lack of variation in category probabilities show that FM Milestones do not measure the amount of a latent trait possessed by a resident, but rather describe where a resident falls along the training sequence. High reliability indicates residents are being rated in a stable manner as they progress through residency, and individual residents deviating from this rating structure warrant consideration by program leaders.
Traditional Music as the Sound of Space: Examples from Bosnia and Herzegovina
Authors: Toska Amra
Published: December 2016

The connection between the traditional music and its ambient through the existing physical space, a product of nature and human activity, is reflected in the social and musical behaviour (elements of style), acoustic phenomena and rules, and in the inner architecture or structure of the particular traditional musical expression.
Gong and Its Therapeutic Meaning
Authors: Pesek Albinca , Bratina Tomaž
Published: December 2016

The study, which was conducted utilising a sample of 129 users of sound baths with gongs in 2015 in Slovenia, has shown that all users define the effect of sound vibrations as healing and/or relaxing. They testified on achieving durable inner peace, on better physical and mental wellbeing, fresh impetus for work, desire for personal growth and other positive effects.
Linnaeus, Zoomusicology, Ecomusicology, and the Quest for Meaningful Categories
Authors: Sorce Keller Marcello
Published: December 2016

“Music” is not a scientific term. In the course of time, it has become like a big container, where sonic objects and practices that have nothing in common are put together. It carries so many historical and cultural connotations as to make it unfit for scholarly discourse about the social use of sound.
The Soundscape of Change: The Reculturalization of Savamala
Authors: Medić Ivana
Published: December 2016

In this article I analyze the reculturalization strategies implemented in Savamala, an urban quarter in central Belgrade. Recent years have witnessed many efforts to rebrand Belgrade as a safe, modern, cosmopolitan and tourist-friendly city. These initiatives transform the soundscape of Belgrade; sometimes the changes are byproducts of other developments, but sometimes, as I demonstrate using the example of Savamala, the changes in soundscape are done deliberately and with a clear purpose.
Defining Nostalgic Musicscape: Starogradska muzika in Skadarlija (Belgrade) as Sound Environment
Authors: Dumnić Marija
Published: December 2016

Skadarlija Street in Belgrade, officially called a “bohemian quarter” because of its numerous taverns, is characterized by the discourse of nostalgia. Performances of the starogradska muzika (“old urban music”) genre creat Skadarlija’s musicscape. This paper deals with process of construction and commodification of the sound environment, particularly examining the role of nostalgia therein.
Sounding the Alarm: An Introduction to Ecological Sound Art
Authors: Gilmurray Jonathan
Published: December 2016

In recent years, a number of sound artists have begun engaging with ecological issues through their work, forming a growing movement of ˝ecological sound art˝. This paper traces its development, examines its influences, and provides examples of the artists whose work is currently defining this important and timely new field.
Variability of winter and summer surface ozone in Mexico City on the intraseasonal timescale
Authors: Barrett Bradford S. , Raga Graciela B.
Published: December 2016

Abstract. Surface ozone concentrations in Mexico City frequently exceed the Mexican standard and have proven difficult to forecast due to changes in meteorological conditions at its tropical location. The Madden–Julian Oscillation (MJO) is largely responsible for intraseasonal variability in the tropics. Circulation patterns in the lower and upper troposphere and precipitation are associated with the oscillation as it progresses eastward around the planet. It is typically described by phases (labeled 1 through 8), which correspond to the broad longitudinal location of the active component of the oscillation with enhanced precipitation. In this study we evaluate the intraseasonal variability of winter and summer surface ozone concentrations in Mexico City, which was investigated over the period 1986–2014 to determine if there is a modulation by the MJO that would aid in the forecast of high-pollution episodes. Over 1 000 000 hourly observations of surface ozone from five stations around the metropolitan area were standardized and then binned by active phase of the MJO, with phase determined using the real-time multivariate MJO index. Highest winter ozone concentrations were found in Mexico City on days when the MJO was active and in phase 2 (over the Indian Ocean), and highest summer ozone concentrations were found on days when the MJO was active and in phase 6 (over the western Pacific Ocean). Lowest winter ozone concentrations were found during active MJO phase 8 (over the eastern Pacific Ocean), and lowest summer ozone concentrations were found during active MJO phase 1 (over the Atlantic Ocean). Anomalies of reanalysis-based cloud cover and UV-B radiation supported the observed variability in surface ozone in both summer and winter: MJO phases with highest ozone concentration had largest positive UV-B radiation anomalies and lowest cloud-cover fraction, while phases with lowest ozone concentration had largest negative UV-B radiation anomalies and highest cloud-cover fraction. Furthermore, geopotential height anomalies at 250 hPa favoring reduced cloudiness, and thus elevated surface ozone, were found in both seasons during MJO phases with above-normal ozone concentrations. Similar height anomalies at 250 hPa favoring enhanced cloudiness, and thus reduced surface ozone, were found in both seasons during MJO phases with below-normal ozone concentrations. These anomalies confirm a physical pathway for MJO modulation of surface ozone via modulation of the upper troposphere.
Widespread persistent polar stratospheric ice clouds in the Arctic
Authors: Voigt Christiane , Dörnbrack Andreas , Wirth Martin , Groß Silke M. , Baumann Robert , Ehard Benedikt , Pitts Michael C. , Poole Lamont R. , Sinnhuber Björn-Martin , Oelhaf Hermann
Published: December 2016

Abstract. Despite a general decline in ozone depleting substances in the stratosphere due to the multi-national commitment to substantially reduce the emissions of their precursors, the magnitude of Arctic polar ozone loss has not decreased in recent years. Thus new observations at cold conditions can help to enhance our knowledge of polar stratospheric cloud (PSC) formation and life cycle which is of relevance for Arctic ozone loss. In the unique winter 2015/16, cold and persistent areas with temperatures below the ice frost point Tice developed in the Arctic stratosphere, caused by reduced perturbations of the polar vortex through planetary waves. Due to these extreme conditions, unprecedented and widespread ice PSCs formed and persisted for more than a month in the Arctic. These ice PSCs were repeatedly detected by lidars on the CALIPSO satellite and on the high altitude long range research aircraft HALO. A new lower threshold of the backscatter ratio−1 of 0.3 for ice PSCs derived from high-resolution lidar measurements at 532 nm wavelength leads to enhanced ice PSC coverage compared to previous analysis. The ice PSCs were generally surrounded by nitric acid trihydrate (NAT) and supercooled ternary solution (STS) clouds. By combining optical PSC data and trajectory analysis, we investigate ice formation pathways. In addition to ice nucleation in STSm with meteoric dust, we find that ice nucleation on pre-existing NAT may play an important role in polar winter. Persistent synoptic-scale Arctic ice PSCs have not been observed so far. Hence, ice PSCs are a sensitive marker for cold stratospheric winter temperatures modulated by natural variability and climate change.
Hermann Karsten (1817–1908): a German naturalist in the Neotropics and the significance of his paleovertebrate collection
Authors: Carrillo-Briceño Jorge Domingo , Amson Eli , Zurita Alfredo , Sánchez-Villagra Marcelo Ricardo
Published: December 2016

Abstract. During the mid-19th century, the German naturalist Hermann Karsten conducted a 12-year exploration (1844–1856) in the territories of Ecuador, New Granada (now Colombia) and Venezuela, allowing him to produce important botanic, geographic and geologic descriptions with valuable information that permits us to refer to him as a pioneer in many of these topics. With his return to Europe, abundant geological, paleontological and living plant specimens were brought and housed in European museums and botanical gardens. The Karsten collection included an important invertebrate collection from the Cretaceous of the Andes of Colombia and Venezuela, which was studied and published by himself and the renowned German paleontologist Leopold von Buch, filling a large void in the knowledge about ancients faunas. H. Karsten's vertebrate collection was never illustrated or subjected to a detailed taxonomic study, being mentioned in scientific publications in a repetitive manner and with incorrect taxonomic and provenance information. More than 160 years after they were collected, we carried out a taxonomic revision of all H. Karsten's vertebrate specimens from Colombia and Venezuela, which are housed in the Museum of Natural History in Berlin. These specimens are represented by cranial and postcranial elements of megafauna, which include Megatheriidae, Mylodontidae and Glyptodontidae (Xenarthra), Toxodontidae (Notoungulata), Gomphotheriidae (Proboscidea), and many other indeterminate mammal remains. This revision is intended to clarify the taxonomy and provenance of the specimens, emphasizing the historical importance of this fossil collection and its significance for the paleontology of the region.