bluuebunny/crossref_metadata_2025 huggingface dataset:
Influence of Temperature on Stress Distribution in Bainitic Steels - Application to 16 MND5-A508 Pressure Vessel Steel
Authors: Ouahab Razane , Pesci Raphaël , Berveiller Sophie , Patoor Etienne
Published: March 2011

In this study, the internal stress evolution of the ferrite phase of 16MND5-A508 has been determined using X-Ray Diffraction (XRD). The results of in situ tests combined with XRD analyses and performed at different temperatures (-150°C and 22°C) exhibit a difference of about 200MPa between the macroscopic stress and the ferrite one. The stress state in the cementite is determined by a mixture law; it reaches very high values up to 9000MPa. These results highlight the need to analyze the stress directly in the cementite phase by using appropriate tools, since its volume fraction does not allow it using XRD.
Experimental Analysis of Shot Peening on Carburized or Carbonitrided Parts
Authors: Renaud Pierre , Bristiel Philippe , Barrallier Laurent , Desvignes Marc , Kubler Regis
Published: March 2011

This experimental study focuses on the influence of shot peening on parts initially treated by carburizing or carbonitriding. Experimental investigations have been carried out: optical observations of the microstructures, in-depth hardness measurement, X-ray diffraction analysis of residual stresses. A comparison is made between the carburizing anad the carbonitriding treatments.
Approach by Simulation of Residual Stress Generated by Shot-Peening and Their Stability during Fatigue Cycling
Authors: Michaud H. , Sprauel Jean Michel , Braham Chedly
Published: March 2011

ASCOMETAL produces alloy steels used for spring (leaf or coil), where the weak fatigue points are on the surface which is reinforced by shot-peening. So, the fatigue optimization with the steel grade needs a perfect knowledge of the material answer after shot-peening. For that reason, an analytical model has been developed where low cycle fatigue behaviour and all the usual process parameters are integrated (especially the impact position, and the covering-rate). Moreover, through a Monte-Carlos approach, the model permits to analyse the effect of scattering elements like impact speeds, ball sizes, or material fatigue behaviour. With this model several key process parameters have been analysed and validated with residual stress profiles evaluated by X-ray diffraction. So, for spring leaf, the effect of an applied load during shot-peening or shakedown during bending fatigue is described.
Analysis and Prediction of Residual Stresses in Nitrided Tool Steel
Authors: Podgornik Bojan , Leskovšek Vojteh , Kovačič Miha , Vižintin Joze
Published: March 2011

Plasma nitriding is a thermo-chemical process of high importance for engineering components, which through generation of near-surface compressive residual stresses significantly improves wear and fatigue resistance. A precise knowledge of the level and distribution of residual stresses that exist in surface engineered components is necessary for accurate prediction of a component’s fatigue resistance. However, measurement of residual stress is not always possible, especially in the case of industrial tools and dies. Therefore, other methods for residual stress evaluation and prediction are required by industry. Results of this investigation show that residual stress level and depth in plasma nitrided tool steel increase by nitriding time and temperature. On the other hand, experimental data show that residual steel distribution in plasma nitrided tool steels can be determined on the basis of microhardness depth distribution.
Residual Stress Fields after Heat Treatment in Cladded Steel of Process Vessels
Authors: Marques Maria José , Batista António Castanhola , Rebelo-Kornmeier Joana , Hofmann Michael , Nobre Joao P. , Loureiro Altino
Published: March 2011

The influence of the heat treatment on the residual stress fields of weld cladded samples is discussed in this paper. The samples were elaborated from carbon steel plates, cladded in one of the faces with stainless steel filler metals by submerged arc welding. After the cladding process some of the samples were submitted to heat treatments with different parameters: one at 620° C for a holding time of 1 hour and the other at 540° C for a period of ten hours. The in‑depth residual stress profiles were determined by neutron diffraction. The results shown that the sample treated to 620 °C, presented the highest residual stress relaxation. The corresponding heat treatment has the industrial benefit to be shorter than the other heat treatment.
Residual Stress Development during Nitriding of Steels
Authors: Jegou Sebastien , Barrallier Laurent , Kubler Regis
Published: March 2011

Nitriding is a well-established thermochemical surface treatment of carbon micro-alloyed steels aiming enhancing surface properties such as fatigue, wear and corrosion resistances. The idea is taking benefits from the high hardening level due to a fine nitride precipitation and also the compressive residual stress state. Due to some complex interactions of phenomena during nitriding, the last has not been completely explained yet. When interest is focused on stress depth gradient and time evolution, difficulties find origins in pronounced heterogeneities whether it is the chemical gradient due to nitrogen diffusion, the resulting gradient of microstructure or the gradient of volumetric misfits. Relaxation of residual stresses is so usually described using a thermally controlled creep phenomenon due to the couple of diffusion and stress, but depend on phenomenological descriptions. A key point is also disregard that is the diffusion of carbon and its redistribution across the nitrided surface during the treatment. Based on experimental characterizations of model carbon iron-based alloys, the role of phase transformations, especially carbides, is explored in order to give better understandings of the residual stress development during nitriding.
Retained Austenite and Residual Stress Evolution in Carbonitrided Shot-Peened Steel
Authors: Van Wijk S. , François Manuel , Sura E. , Frabolot M.
Published: March 2011

Carbonitriding followed by shot peening is an important industrial process to improve the mechanical properties of components, especially by producing compressive residual stresses. In addition, a high hardness and strength produced by this process enhances the surface properties and leads also a high resistance to fatigue. In this study, shot peening with different parameters have been employed to treat the carbonitrided specimens. The measurements of residual stress and residual austenite were performed by X-ray diffraction. It is shown, with a simple eigenstrain model, that residual austenite transformation under shot impact contributes to a significant fraction of residual stresses. When the material (750 HV) is peened with 800 HV shot, it represents about 50%, the remaining is due to plasticity. When it is peened with 640HV shot, 100% of residual stresses can be explained by austenite transformation.
Bridging Gaps in Surface Zone Residual Stress Analysis Using Complementary Probes for Strain Depth Profiling
Authors: Fuß Tillman , Wimpory Robert C. , Klaus M. , Genzel C.
Published: March 2011

Residual stress depth profiling can be performed by means of non-destructive diffraction methods as well as semi destructive mechanical techniques like the hole drilling method. By none of these methods is it possible to cover the complete depth range being affected by residual stress fields which extend from the surface into the volume of the material. In this paper it is demonstrated that the combined application of surface sensitive X-ray methods and neutron diffraction used normally for bulk stress analysis allows for the study of residual stress gradients generated by mechanical surface treatment. Furthermore, it is shown that the hole drilling method can bridge the information gap between X-ray and neutron diffraction.
On the Measurement of Residual Stress in Induction Hardened Parts
Authors: Savaria Vincent , Hoseini Majid , Bridier Florent , Bocher Philippe , Arkinson Patrick
Published: March 2011

It is well known that induction surface heating followed by rapid quenching generally increases the fatigue life of steel components subjected to bending loads by significantly postponing the micro-crack nucleation and propagation processes. The phase transformation volume change combined with severe thermal gradients leave a hard surface layer under relatively high and deep compressive residual stresses. In this paper, residual stress measurements are done on induction hardened AMS6414 martensitic steel (aerospace grade of AISI4340) cylinders using two techniques: the so-called contour method and X-ray diffraction. For both methods, induction hardened parts raise many challenges. The contour method hardly describes high stress gradients near the surface while the diffraction technique accuracy appears limited considering the strong microstructural variation and the high depth of the stresses to be measured. For the contour method, a CMM and an optical pen using the confocal chromatic imaging principle were used to measure the surface after precision WEDM cutting. The effect of data filtering and smoothing on the calculated stresses are discussed. For X-ray analysis, the effect of stress relaxation during layer removal and analysis technique is explained. The difference between the residual stress measurements done with the two techniques is discussed with emphasis on both the surface and the in-depth measurements.
Current Status of Engineering Materials Diffractometer at J-PARC
Authors: Harjo Stefanus , Ito Takayoshi , Aizawa Kazuya , Arima Hiroshi , Abe Jun , Moriai Atsushi , Iwahashi Takaaki , Kamiyama Takashi
Published: March 2011

The Engineering Materials Diffractometer “TAKUMI” is designed and has been constructed at Materials & Life Science Facility (MLF) of Japan Proton Accelerator Research Complex (J-PARC) to conduct various kinds of studies on materials science and engineering and to promote industrial applications, related with strain measurements. The commissioning of TAKUMI has been started from September 2008, and several user programs have been done. In the commissioning, a resolution Δd/d at high resolution mode (with incident beam collimation) of less than 0.2% was achieved in a diffraction experiment using 2 mm diameter thick annealed piano wire. The d-range measured by TAKUMI with single pulse frame, i.e. standard operation, was confirmed to be 0.05 nm to 0.27 nm, showing that the optimum range for materials research is covered by this machine. TAKUMI adopted an event mode data recording method. It was found that the recording method is very useful to manipulate data as we like, for instance, detector range, time of flight binning width and time resolved data, even after the experiment has been finished.
Comparison of Curvature and X-Ray Methods for Measuring of Residual Stresses in Hard PVD Coatings
Authors: Lille Harri , Kõo Jakub , Gregor Andre , Ryabchikov Alexander , Sergejev Fjodor , Traksmaa Rainer , Kulu Priit
Published: March 2011

Physical Vapour Deposition and PVD coatings are designed for several applications, from industrial to biomedical. Residual stresses, arising during coating deposition, have important effect on the coating’s service life as their influence to the mechanical and tribological properties. Our aim was to investigate the residual stresses in five different PVD coatings (TiN, TiCN, TiAlN, TiAlN, nc-(AlTi) N/α -Si3N4) (presence of the Ti as adhesion layer) by the layer growing curvature method and the X-ray diffraction techniques using a plate and a strip as the substrate. Residual stresses were compressive and very large (2.98 - 7.24) GPa in all coatings and comparable in TiN, TiAlN, TiAlN coatings in the case of both methods. The magnitude of residual stresses is influenced by intrinsic strain in the case of layer growth rather than by thermal stress.
In-Situ Neutron Diffraction Study of the Deformation Behaviour of Two High-Manganese Austenitic Steels
Authors: Peng Ru Lin , Liu Xiao Peng , Wang Yan Dong , Zhang Shu Yan , Shen Yong Feng , Johansson Sten
Published: March 2011

In-situ neutron diffraction experiments under tensile loading were carried out to study the micromechanical behaviour of two iron-manganese based steels, a TWIP (twinning induced plasticity) steel with 30 wt% Mn and a TRIP steel (transformation induced plasticity) with 20 wt% Mn. The former was loaded to 31.3% strain and the latter to 20% strain. The 30 wt.% Mn steel had a fully austenitic microstructure which remained stable over the loading range studied, while stress induced austenite to α´- and ε-martensite transformations occur in the 20 wt.% Mn steel which initially contained an α´-martensite in addition to the austenite. The evolution of lattice strains under tensile loading differs between the two steels, reflected their different plastic deformation mechanisms. A stronger grain-orientation dependent behaviour is observed during deformation for the 20 wt.% Mn in contrast to the 30wt.% Mn steel.
Measurement of Residual Stresses in Surface Treated Stainless Steel Groove Welds
Authors: Goudar D.M. , Turski Mark , Clitheroe Suzanne , Kingston Ed J. , Gill Chris , Withers Philip J. , Smith David John
Published: March 2011

This paper examines the extent to which mechanical shot peening (MSP), ultrasonic impact treatment (UIT) and laser shock peening (LSP) can affect the tensile residual stresses in the fusion zone caused by welding for a 10mm multi-pass 'V' groove weld within a 20 mm thick 304L stainless steel plate. Stresses are measured by deep hole drilling, neutron diffraction and incremental center hole drilling. For the UIT and LSP treated samples, the tensile stresses present in the as-welded plate are reversed to compressive stresses to a depth in excess of 2-4mm. For MSP the affected depth is much less (~0.5mm). The depth of these compressive stresses is similar to those measured in 20 mm thick parent plate test coupons.
Stability and Relaxation of Welding Residual Stresses
Authors: Farajian Majid , Nitschke-Pagel Thomas , Dilger Klaus
Published: March 2011

Residual stress relaxation of butt-welded small scale steel specimens under static and cyclic mechanical loading was investigated. The experiments were carried out on different types of steel with yield strengths between 300 and 1200MPa. The x-ray and neutron diffraction techniques were applied for the residual stresses analysis. The maximum values of initial residual stresses were measured at the weld bead centerline and were not as frequently assumed as high as the yield strength of the material. From fatigue point of view the internal stresses at the weld toe are of importance. It was observed that only a fraction of maximum residual stress accommodated in the weld bead centerline, is available at the weld toe. Under static tensile and compressive loading by increasing the load level the residual stress field relaxes continuously. The relaxation sets in with delay under compression since the tensile residual stresses should be first overcome. Under cyclic loading, once the first relaxation takes place further cyclic relaxation is either not considerable or continues moderately depending on loading conditions. In high cycle fatigue the residual stresses are stable until 2x106 cycles. In low cycle fatigue however the variation of the residual stresses continues until failure. This variation is partly related to crack initiation and propagation. The von Misses failure criterion with the local yield strength as material resistance against plastic deformation was able to describe the relaxation of surface welding residual stresses in low cycle fatigue.
Numerical Investigation of the Influence of Microstructure on the Residual Stress Distribution and Distortion in DP600 Welds
Authors: Pazooki A.M.Akbari , Hermans M.J.M. , Richardson I.M.
Published: March 2011

Dual phase steel consists of martensite embedded in a ferrite matrix. The material experiences high heating and cooling rates during welding, which alter the microstructure significantly. In this work the effects of solid state phase transformations on the prediction of residual stresses and distortion during welding of DP600 steel is investigated. Phase fractions have been calculated implicitly using continuous cooling time (CCT) diagrams. The results of the model are compared with experimental measurements for bead-on-plate welds made on DP600 sheets. It is found that the volume changes and the increase of the strength due to the martensitic transformation have both a significant effect on the residual stress and distortion level although in opposite directions. Martensitic phase transformations in DP600 steel tend to reduce tensile residual stresses in the weld metal.
Mechanical Property of Duplex Stainless Steel with Nanostructured Layer by Surface Mechanical Attrition Treatment
Authors: Chen Liu , Xu Xiao Lei
Published: March 2011

A grain size gradient layer material was produced by means of surface mechanical attrition treatment on a UNS S32304 duplex stainless steel. In this study, the mechanical property was characterized by tensile test, while microstructure was investigated by transmission electron microscopy, scanning electron microscopy and electron backscatter diffraction. The deformed layer enhanced both the yield strength and maximum strength with large ductility retained, as revealed by tensile test that the yield stress of 30 minutes processed sample was 702 MPa as compared with 454 MPa of as-annealed sample. The elongation to failure, however, decreased from 0.41 to 0.27.
Constitutive Model for Large Plastic Deformation of Nanocrystalline Materials
Authors: Jiang Hua , Zhou Jian Qiu , Zhu Rong Tao
Published: March 2011

A constitutive model was presented for nanocrystalline metallic materials that can experience large plastic deformation with shear band. The model was composed of two parts for different deformation stage: hardening stage and softening stage. In the hardening stage, the phase mixture model was used, and in the softening stage, a shear band deformation mechanism was proposed. Based on the model presented, numerical simulations were carried out to prove that the predications kept in good agreement with experimental data.
Effect of Grain Size Distribution on the Local Mechanical Behavior of Nanocrystalline Materials
Authors: Liu Ying Guang , Zhou Jian Qiu
Published: March 2011

A theoretical model based on self-consistent approximation is proposed to explore the effect of grain size distribution on the local mechanical response of nanocrystalline (nc) materials. The representative volume element (RVE) is composed of grains randomly distributed with a grain size distribution following a log-normal statistical function. The grain interior and grain boundary are taken as an integral object to sustain deformation mechanisms of grain-boundary sliding, grain-boundary diffusion and grain-interior plasticity. Local plastic strains and internal stresses, developing within the RVE, have been recorded and discussed.
Superelasticity and Shape Memory Behaviors of Ti-25 at. % Nb Alloy Processed by ECAP and Aging
Authors: Song Jie , Zhang Xiao Ning , Jiang Hong , Sun Xiao Gang , Xie Chao Ying
Published: March 2011

Microstructure and mechanical behavior of Ti-25at.% Nb shape memory alloy processed by equal-channel angular pressing (ECAP) at 823K have been investigated. The effect of multi-passes ECAP and aging on the martensitic transformation temperature, shape memory effect and superelastic recovery strains of Ti-25at.%Nb alloy have been analyzed. It is found that with the increase of the pass number of ECAP, the yield stress decreases gradually, but the strain hardening rate increase obviously. After one pass ECAP and 573K aging treatment, a perfect superelasticity is obtained when the tensile strain is no more than 2%. Aging at 573K for 1 hour after ECAP, the yield stress and flow stress increase sharply, the shape memory effect and superelasticity change little.
Tensile Properties and Dislocation Strengthening of Commercial Pure Titanium Processed by Equal-Channel Angular Pressing at Liquid Nitrogen Temperature
Authors: Cheng Xiao Nong , Xu Hong Xing , Xu Xiao Jing , Zhang Zeng Lei
Published: March 2011

Equal channel angular pressing (ECAP) of a quenched commercial pure titanium (CP-Ti) (grade 2) has been successfully performed at liquid nitrogen temperature with an imposed equivalent strain of about ∼0.5, and its microstructures, tensile properties and dislocation strengthening were investigated. High-resolution transmission electron microscopy (HRTEM) shows that the ECAPed CP-Ti presented a microstructure containing lattice distortions, dislocations, stacking defects and deformation twins. Tensile tests indicate that the ECAPed CP-Ti had yield strength of ~700 MPa (40 % higher than that of the unECAPed CP-Ti) and a high level of tensile ductility (~28%). X-ray diffractometer (XRD) data indicate that the ECAP processing not only broaden the XRD peaks significantly but also decreased texture considerably. The theoretical analysis by using Taylor equation based on the coherent diffraction domain size and the lattice micro-strain obtained from XRD line broadening analysis illustrates that ECAP-resulted dislocation made a strengthening contribution of about ~35.1 %.
Effects of ECAE and Aging on Phase Transformations and Superelasticity of a Ni-Rich TiNi SMA
Authors: Zhang Xiao Ning , Song Jie , Jiang Hong , Sun Xiao Gang , Xie Chao Ying
Published: March 2011

Effects of equal-channel angular extrusion (ECAE) process at 773K and heat treatment on phase transformations and superelasticity of a Ni-rich TiNi shape memory alloy were investigated by differential scanning calorimeter (DSC) measurement and cyclic tensile test. The R phase transformation of Ni-rich TiNi alloy was stimulated after ECAE processes and within a larger temperature range. The martensitic transformation start temperature Ms of Ni-rich TiNi alloy decreased sharply after ECAE processes at 773 K, then rapidly rose back after the specimen aging at 773K for 30min. Reasons for the changes of phase transformation behaviors have been discussed. ECAE processed TiNi samples exhibit better super-elasticity than solution treated one. With the increase passes of ECAE, the superelasticity becomes more stable, and a completely recoverable strain of 6% is obtained for TiNi sample after 8 passes ECAE.
Fatigue Property and Fatigue Cracks of Ultra-Fine Grained Copper Processed by Equal-Channel Angular Pressing
Authors: Wang Qing Juan , Du Zhong Ze , Liu Xiao Yan , Kunz Ludvík
Published: March 2011

The fatigue life, cyclic deformation behavior and microstructure of ultra-fine grained (UFG) copper produced by equal-channel angular pressing (ECAP) were tested and observed in present work. Development of surface relief and fracture surfaces were observed by means of scanning electron microscopy. The results show that the higher tensile strength UFG copper has lower ductility and its strain controlled cyclic properties are worse while comparing with those of lower strength CG counterpart. All the ECAP specimens display obvious cyclic softening behavior under the applied strain range. The cyclic softening ratio increases with increasing strain amplitude. The cyclic hysteresis loops of UFG Cu shows the tension and compression peak stresses decreased gradually with number of cycles. The formation of SBs and grain boundary sliding is the main factor causing crack nucleation as well as premature failure.
Shearing Patterns of AZ31 Mg Alloy Processed by Equal-Channel Angular Pressing via Various Route
Authors: Feng Xiao Ming , Ai Tao Tao
Published: March 2011

Equal-channel angular pressing (ECAP) is used to convert coarse grain into ultrafine grain (UFG). The characteristics of ECAP and the shearing patterns obtained when ECAP applied to metals are investigated. Then propose a series of procedures to verify the structure evolution of AZ31 Mg alloys after ECAP processing. The results indicate that parameters including route, die angular and pressing passes influence on the microstructure of the AZ31 Mg alloys. Route BC is the optimum processing route due to the largest slipping angular range.
Effects of Si/Al Molar Ratio on Morphology of Mullite Nanocomposite Synthesized from Kaolin
Authors: Chen Nan Chun , Wang Wei , Deng Ai Ping , Ao Han Mei , Li Quan Hong
Published: March 2011

Mullite nanocomposite was synthesized using kaolin with different Si/Al molar ratios in the range of 1.1- 4.31. The synthesized samples were analyzed and characterized using XRD and SEM techniques and effects of Si/Al molar ratio on mullite nanocrystal morphology have been investigated. SEM results showed that the mullite nanocomposite synthesized from kaolin with different Si/Al molar ratios had different morphologies and distribution patterns of particle size. It was found that the mullite nanocrystals with relatively homogenous grain-size distribution, low aspect ratio, and little agglomeration were produced from the precursors made from kaolin with a Si/Al ratio of 1.1-2.33 at calcination temperature of 1100-1250 oC.
Microstructures and Properties of Ultrafine Grained Iron by Rolling
Authors: Ding Yi , Jiang Jian Hua , Shan Ai Dang
Published: March 2011

Microstructures and properties of ultrafine grained (UFG) iron by different rolling processing are investigated. By applying the asymmetric rolling (ASR), the equiaxed UFG iron with the grain size of 0.9 μm has been obtained due to the shear strain induced by the mismatch of the two roll during ASR. With the same rolling reduction, the ASR processed iron shows higher yield strength than that of the symmetrically rolled one. When the ASR processed iron is further symmetrically rolled, the grain morphology maintains equiaxed and the grain size decreases to about 0.3 μm.
Microtexture Study of Warm-Rolled High Strength Interstitial-Free (IF) Steel Sheets
Authors: Jing Cai Nian , Wang Ming Gang , Liu Xi Jun , Tan Qi Zhong , Wang Zuo Cheng , Han Fu Tao
Published: March 2011

Interstitial-free (IF) steel has excellent deep-drawability and was used widely in automotive industry. High strength IF-steel is that some phosphorus was put in common IF-steel to improve its strength without destroying the deep-drawability [1]. Microstructure and grain boundary character strongly affect the deep-drawability of high strength IF-steel, it is an obligatory task to test those characters. The technique of Electron Backscatter Diffraction (EBSD) can reveal the microtexture and detailed orientation distribution of grains from a single EBSD map, as a powerful instrument, EBSD was used widely in materials research from last decade [2]. Many researches have been focused on the texture evolution and recrystallization phenomena of high strength IF-steels [3,4], but the microtexture and grain boundary characters of warm-rolled high strength IF-steels was not fully investigated. The present study was aimed at researching the microtexture characters of a commercial high strength IF-steels under different warm-rolled temperature using EBSD technique, the microstructure and grain boundary character were analyzed systemically, and the relationship between the microstructure and deep-drawability was discussed.
Consensus on Diagnosis and Empiric Antibiotic Therapy of Febrile Neutropenia
Authors: Giurici Nagua , Zanazzo Giulio
Published: March 2011

Controversial issues on the management of empiric therapy and diagnosis of febrile neutropenia (FN) were faced by a Consensus Group of the Italian Association of Pediatric Hematology-Oncology (AIEOP). In this paper we report the suggestions of the consensus process regarding the role of aminoglycosides, glycopeptides and oral antibiotics in empiric therapy of FN, the rules for changing or discontinuing the therapy as well as the timing of the blood cultures.
Guidelines for the Management of Bacterial and Fungal Infections during Chemotherapy for Pediatric Acute Leukemia or Solid Tumors: What Is Available in 2010?
Authors: Castagnola Elio , Caviglia Ilaria , Haupt Riccardo
Published: March 2011

Febrile episodes and infections represent important complications during antineoplastic chemotherapy for pediatric neoplastic diseases. In the last years many international association published guidelines for the management of these complications in adults, but no document of this type was prepared for children. One of the major causes of this situation is probably the very low number of pediatric clinical trials with adequate power and design. The paper summarizes guidelines provided for the management of infectious complications in adults with cancer by different international and will comment on how much they may be translated in the management of pediatric patients.
Trace formulae for perturbations of class $\boldsymbol{{\boldsymbol S}_m}$
Authors: Aleksandrov Alexei B. , Peller Vladimir V.
Published: March 2011

We offer a new approach to trace formulae for functions of perturbed self-adjoint operators. We establish most general trace formulae in the case of perturbation of Schatten–von Neumann class

{\boldsymbol S}_m

, where

m

is a positive integer. We consider several special cases of our general trace formulae. In particular, as a special case we obtain the trace formula for the

m

th operator Taylor polynomial. In the case

m=1

this corresponds to the Livshits–Krein trace formula, while in the case

m=2

this corresponds to the Koplienko trace formula. In the case of an arbitrary positive integer

m

, the trace formula for the

m

th operator Taylor polynomial was obtained recently in [25]. Our results allow us to essentially enlarge the class of functions, for which the trace formula obtained in [25] holds. Namely, we prove that it holds for functions in the Besov space

B_{\infty1}^m(\Bbb R)

.
Size dependence of volume and surface nucleation rates for homogeneous freezing of supercooled water droplets
Authors: Kuhn T. , Earle M. E. , Khalizov A. F. , Sloan J. J.
Published: March 2011

Abstract. The relative roles of volume and surface nucleation were investigated for the homogeneous freezing of pure water droplets. Experiments were carried out in a cryogenic laminar aerosol flow tube using supercooled water aerosols with maximum volume densities at radii between 1 and 3 μm. Temperature- and size-dependent values of volume- and surface-based homogeneous nucleation rates between 234.8 and 236.2 K were derived using a microphysical model and aerosol phase compositions and size distributions determined from infrared extinction measurements in the flow tube. The results show that the contribution from nucleation at the droplet surface increases with decreasing droplet radius and dominates over nucleation in the bulk droplet volume for droplets with radii smaller than approximately 5 μm. This is interpreted in terms of a lowered free energy of ice germ formation in the surface-based process. The implications of surface nucleation for the parameterization of homogeneous ice nucleation in numerical models are considered.
THEMIS observations of double-onset substorms and their association with IMF variations
Authors: Cheng C.-C. , Russell C. T. , Angelopoulos V. , Mann I. R. , Glassmeier K.-H. , Baumjohann W.
Published: March 2011

Abstract. On 16 July 2008, two pairs of consecutive bursts of Pi2 pulsations were recorded simultaneously across the THEMIS ground-based observatory system. Wavelet transformation reveals that for each high-latitude pair, the dominant frequency of the first burst is higher than that of the second. But at low latitudes, the dominant frequency does not change. It is suggested that both pairs result from fast magnetospheric cavity waves with the second burst also containing shear Alfvén waves. INTERMAGNET magnetograms at auroral latitudes showed magnetic variations affected by two recurrent electrojets for each pair. The ground-based magnetometers and those at geostationary orbit sensed magnetic perturbations consistent with the formation of the substorm current wedge. Four consecutive enhancements of energetic electron and ion fluxes detected by the THEMIS probes in the dayside magnetosphere appeared in the later afternoon and then in the early afternoon. The horizontal magnetic variation vectors had vortex patterns similar to those induced by the upward and downward field-aligned currents during substorm times. The hodogram at mid-L stations had a polarization pattern similar to the one induced by the substorm current wedge for each Pi2 burst. The mapping of ground Pi2 onset timing to the interplanetary magnetic field (IMF) observations shows that they appear under two cycles of north-to-south and then north variation. CLUSTER 4 in the south lobe observed wave-like magnetic fluctuations, probably driven by near-Earth reconnection, similar to those on the ground. These two observations are consistent with the link of double-onset substorms to magnetotail reconnection externally triggered by IMF variations.
Dissolved and particulate primary production along a longitudinal gradient in the Mediterranean Sea
Authors: López-Sandoval D. C. , Fernández A. , Marañón E.
Published: March 2011

Abstract. We have determined the photosynthetic production of dissolved (DOCp) and particulate organic carbon (POCp) along a longitudinal transect in the Mediterranean Sea during the summer stratification period. The euphotic layer-integrated rates of DOCp and POCp ranged between approximately 50–130 and 95–210 mgC m−2 d−1, respectively, and showed an east to west increasing trend. For the whole transect, the relative contribution of DOCp to total, euphotic layer-integrated primary production (percentage of extracellular release, PER) averaged ~37% and did not show any clear longitudinal pattern. In spite of the relatively high PER values, the measured DOCp rates were much lower than the estimated bacterial carbon demand, suggesting a small degree of coupling between phytoplankton exudation and bacterial metabolism. Our results, when compared with previous measurements obtained with the same methods in several ecosystems of contrasting productivity, support the view that the relative importance of DOCp increases under strong nutrient limitation.
An analyses of long-term precipitation variability based on entropy over Xinjiang, northwestern China
Authors: Zhao C. , Ding Y. , Ye B. , Yao S. , Zhao Q. , Wang Z. , Wang Y.
Published: March 2011

Abstract. Precipitation is one of important supply of water resources in arid and semiarid region of northwestern China, plays the vital role to maintain the fragile ecosystem. The entropy method was employed to detect the spatial variability of precipitation over monthly, seasonal and annual timescales in Xinjiang. The spatial distribution of precipitation variability was significantly affected by topography, and was zonal on annual, seasonal and monthly. The non-parametric Mann-kendall test was used to analyze the change point of trend. A precipitation concentration index has been developed categorize the variability of annual precipitation. The summer variability contributed less than that of other seasons to the annual variability. There is a great difference in the contribution of the different monthly variabilities to the annual mean variability in different years. Overall, the variability of precipitation was shown increase north of Xinjiang, especially in mountainous regions where the increase was statistically (P = 0.05) significant. South of the Xinjiang, the variability increased only slightly, consistent with the distribution of precipitation.
Time-predictable model applicability for earthquake occurrence in northeast India and vicinity
Authors: Panthi A. , Shanker D. , Singh H. N. , Kumar A. , Paudyal H.
Published: March 2011

Abstract. Northeast India and its vicinity is one of the seismically most active regions in the world, where a few large and several moderate earthquakes have occurred in the past. In this study the region of northeast India has been considered for an earthquake generation model using earthquake data as reported by earthquake catalogues National Geophysical Data Centre, National Earthquake Information Centre, United States Geological Survey and from book prepared by Gupta et al. (1986) for the period 1906–2008. The events having a surface wave magnitude of Ms≥5.5 were considered for statistical analysis. In this region, nineteen seismogenic sources were identified by the observation of clustering of earthquakes. It is observed that the time interval between the two consecutive mainshocks depends upon the preceding mainshock magnitude (Mp) and not on the following mainshock (Mf). This result corroborates the validity of time-predictable model in northeast India and its adjoining regions. A linear relation between the logarithm of repeat time (T) of two consecutive events and the magnitude of the preceding mainshock is established in the form LogT = cMp+a, where "c" is a positive slope of line and "a" is function of minimum magnitude of the earthquake considered. The values of the parameters "c" and "a" are estimated to be 0.21 and 0.35 in northeast India and its adjoining regions. The less value of c than the average implies that the earthquake occurrence in this region is different from those of plate boundaries. The result derived can be used for long term seismic hazard estimation in the delineated seismogenic regions.
Multifractal analysis of oceanic chlorophyll maps remotely sensed from space
Authors: de Montera L. , Jouini M. , Verrier S. , Thiria S. , Crepon M.
Published: March 2011

Abstract. Phytoplankton patchiness has been investigated with multifractal analysis techniques. We analyzed oceanic chlorophyll maps, measured by the SeaWiFS orbiting sensor, which are considered to be good proxies for phytoplankton. The study area is the Senegalo-Mauritanian upwelling region, because it has a low cloud cover and high chlorophyll concentrations. Multifractal properties are observed, from the sub-mesoscale up to the mesoscale, and are found to be consistent with the Corssin-Obukhov scale law of passive scalars. This result indicates that, in this specific region and within this scale range, turbulent mixing would be the dominant effect leading to the observed variability of phytoplankton fields. Finally, it is shown that multifractal patchiness can be responsible for significant biases in the nonlinear source and sink terms involved in biogeochemical numerical models.
Cellular Signal Transduction Pathways by Leptin in Colorectal Cancer Tissue: Preliminary Results
Authors: Nowakowska-Zajdel Ewa , Mazurek Urszula , Stachowicz Malgorzata , Niedworok Elzbieta , Fatyga Edyta , Muc-Wierzgoń Małgorzata
Published: March 2011

The aim of the study was to analyse genes typing with the use of the oligonucleotide microarray technique (HG-U133A, Affymetrix) differentiating colorectal cancer tissues from tissues assessed histopathologically as healthy ones among a panel of 91 mRNA of genes encoding proteins involved in activation of cellular signal transduction pathways by leptin. Frozen tumor specimens from 11 colon cancer patients in various stages of clinical progression of the disease in an I–IV stage scale according to the TNM staging were used in molecular tests. Among the genes participating in the cascade of signal transfer in cell activated by leptin, the following ones: AKT1, STAT3, MCL1 were qualified as differentiating stage I and II and VEGFC, CCNDI the encoding genes respectively as differentiating III and IV stage neoplasm. It is necessary to extend studies of analysis of cellular signal transduction pathways by leptin in colorectal cancer initiation and transformation processes.
Decentralized adaptive output‐feedback control for stochastic interconnected systems with stochastic unmodeled dynamic interactions
Authors: Yu Xin , Xie Xue‐Jun , Wu Yu‐Qiang
Published: March 2011

In this paper, we consider the problem of decentralized adaptive output‐feedback regulation for stochastic nonlinear interconnected systems with unknown virtual control coefficients, stochastic unmodeled dynamic interactions. The main contributions of the paper are as follows: (1) This paper presents the first result on decentralized output‐feedback control for stochastic nonlinear systems with unknown virtual control coefficients; (2) For stochastic interconnected systems with stochastic integral input‐to‐state stable unmodeled dynamics, and more general nonlinear uncertain interconnections which depend upon the outputs of subsystems and the stochastic unmodeled dynamics, a decentralized output‐feedback controller is designed to drive the outputs and states to the origin almost surely. Copyright © 2011 John Wiley & Sons, Ltd.
Process fault prognosis using a fuzzy‐adaptive unscented Kalman predictor
Authors: Tian Xuemin , Cao Yu Ping , Chen Sheng
Published: March 2011

By monitoring the future process status via information prediction, process fault prognosis is able to give an early alarm and therefore prevent faults, when the faults are still in their early stages. A fuzzy‐adaptive unscented Kalman filter (FAUKF)‐based predictor is proposed to improve the tracking and forecasting capability for process fault prognosis. The predictor combines the strong tracking concept and fuzzy logic idea. Similar to the standard adaptive unscented Kalman filter (AUKF) that employs an adaptive parameter to correct the estimation error covariance, a Takagi–Sugeno fuzzy logic system is designed to provide a better adaptive parameter for smoothing this regulation. Compared with the standard AUKF, the proposed FAUKF has the same strong tracking ability but does not suffer from the drawback of serious tracking fluctuation. Two simulation examples demonstrate the effectiveness of the proposed predictor. Copyright © 2011 John Wiley & Sons, Ltd.
Porous Titanium Coatings Through Electrophoretic Deposition of TiH2 Suspensions
Authors: Braem Annabel , Mattheys Tina , Neirinck Bram , Schrooten Jan , Van der Biest Omer , Vleugels Jef
Published: March 2011

In the biomedical field, modification of titanium surfaces to improve the osteoinductive and antibacterial behavior is widely investigated. This functionalization can be further ameliorated by providing a porous coating with high loading capacity for bioactive materials and drug delivery carriers at the implant surface. In this work, a new powder metallurgical processing route used to deposit such porous pure titanium coatings on Ti based substrates is presented. The coatings were prepared by electrophoretic deposition (EPD) of TiH2 powder suspensions followed by dehydrogenation and sintering in vacuum. The use of hydrides allowed to lower the sintering temperature below that of the α–β transition of the Ti6Al4V substrate. Measurement of the tensile bond strength confirmed a strong adhesion of the porous coating. Deposition of powders with different grain sizes resulted in porous titanium coatings with varying thickness, pore morphology, and surface roughness. The possibility to extend this coating technique to complex shaped implants is highlighted.
Tailored Assembly of Carbon Nanotubes and Graphene
Authors: Lee Sun Hwa , Lee Duck Hyun , Lee Won Jun , Kim Sang Ouk
Published: March 2011

This Feature Article reviews recent progress in the tailored assembly of carbon nanotubes and graphene into three‐dimensional architectures with particular emphasis on our own research employing self‐assembly principles. Carbon nanotubes and graphene can be assembled into macroporous films, hollow spherical capsules, or hollow nanotubes, via directed assembly from solvent dispersion. This approach is cost‐effective and beneficial for large‐scale assembly, but pre‐requests stable dispersion in a solvent medium. Directed growth from a nanopatterned catalyst array is another promising approach, which enables the control of morphology and properties of graphitic materials as well as their assembly. In addition, the aforementioned two approaches can be synergistically integrated to generate a carbon hybrid assembly consisting of vertical carbon nanotubes grown on flexible graphene films. Tailored assembly relying on scalable self‐assembly principles offer viable routes that are scalable for mass production towards the ultimate utilization of graphitic carbon materials in nanoelectronics, displays, sensors, energy storage/conversion devices, and so on, including future flexible devices.
An Electrically Tuned Solid‐State Thermal Memory Based on Metal–Insulator Transition of Single‐Crystalline VO2 Nanobeams
Authors: Xie Rongguo , Bui Cong Tinh , Varghese Binni , Zhang Qingxin , Sow Chorng Haur , Li Baowen , Thong John T. L.
Published: March 2011

A solid‐state thermal memory that can store and retain thermal information with temperature states as input and output is demonstrated experimentally. A single‐crystal VO2 nanobeam is used, undergoing a metal–insulator transition at ∼340 K, to obtain a nonlinear and hysteresis response in temperature. It is shown that the application of a voltage bias can substantially tune the characteristics of the thermal memory, to an extent that the heat conduction can be increased ∼60%, and the output HIGH/LOW temperature difference can be amplified over two orders of magnitude compared to an unbiased device. The realization of a solid‐state thermal memory combined with an effective electrical control thus allows the development of practical thermal devices for nano‐ to macroscale thermal management.
Quantification of valve leakage rates
Authors: Meland E. , Thornhill N.F. , Lunde E. , Rasmussen M.
Published: March 2011

This article gives an overview of methods concerning the detection and quantification of internal leaks through valves. It also presents comparisons of the methods using new experimental data with emphasis on the spectral information in the signals. The first method utilizes known analytical relationships between acoustic emissions and fluid flow. The second method is a data‐driven comparative approach where an online signal from a leaking valve is compared with a set of saved reference signals from leaking valves. The work presents a new and improved way of leak estimation compared to what is practiced in the industry today, which will ultimately result in safer operations and reduced maintenance related costs. © 2011 American Institute of Chemical Engineers AIChE J, 2012
20 V stack of aqueous supercapacitors with carbon (−), titanium bipolar plates and CNT‐polypyrrole composite (+)
Authors: Zhou Xiaohang , Peng Chuang , Chen George Z.
Published: March 2011

A 20 V stack of 19 supercapacitors was fabricated from titanium bipolar plates (150 × 150 × 0.1 mm3) coated on each side with carbon nanotubes and polypyrrole composite (+) and pigment carbon black (−), and microporous polymeric separators containing aqueous KCl. Internal sealing of each cell in the stack was achieved by placing a silicone rubber washer between neighboring bipolar plates. The stack was tested by high voltage cyclic voltammetry, galvanostatic charging and discharging, and electrochemical impedance spectroscopy. It approached 25 kW/kg in maximum specific power and 3.64 Wh/kg in specific energy. Performance of the stack through intermittent charging‐discharging tests in a storage period of 10 months (still ongoing) remained fairly stable. For example, it exhibited almost zero decay in capacitance after 1000 continuous galvanostatic charging‐discharging cycles in the first month of storage (10 V), and less than 6% loss in the seventh month (19 V). © 2011 American Institute of Chemical Engineers AIChE J, 2012