Edge Part Research Articles

Selective edge modification in graphene and graphite by chemical oxidation.

The effect of edge structures in graphene sheets has been well investigated theoretically but most experimental demonstrations of the functionalization have been for the bulk structures because of only a few reports on chemical methods to modify the edges selectively. We herein report a chemical method using the Lemieux-von Rudloff reagent that selectively oxidizes only the edges of graphene sheets. The selective oxidation at the edges of the graphene sheet was confirmed by thermogravimetric analysis (TGA), Raman mapping measurements, and X-ray photoelectron spectroscopy (XPS). The TGA result of the oxidized graphite with different particle sizes showed a slight weight loss at approximately 350 degrees C (2.29% for the middle particles (35 microm)), which indicates thermal decomposition of the oxidized edge part. The Raman mapping measurement in the inner part of graphene sheets didn't detect any defects or translational symmetry breaking after the oxidation. The XPS data clearly showed that the total carbon atom content present as C--O, C==O, and O--C==C increased from 4.65 to 6.18% by the oxidation. Using the obtained edge-oxidized graphene as a starting material, various functionalizations of the edge structure are expected in the future.

Application of excite-probe techniques for determination of surface, bulk and nonlinear recombination rates in cubic SiC

Non-equilibrium carrier dynamics was studied in a free-standing 160 μm thick 3C-SiC wafer using time-resolved differential transmittivity (DT), differential reflectivity (DR), and light induced transient grating (LITG) techniques. To enable investigation of carrier recombination and diffusion features in the middle part of the wafer, a wedge-shaped strip was prepared by polishing out the most-defective part of the wafer on the substrate side. Measurements of DT and DR decay kinetics on both sides of the wedged sample and their numerical fitting provided bulk lifetimes of 180 ns in the middle part and 60 ns in the edge part (∼50 μm thick subsurface region). On the as-grown side, the surface recombination velocity was equal to 3 × 103 cm/s. Carrier diffusivity, determined by LITG technique, and recombination rate were found injection-dependent. The low-injection value of diffusion length, LD = 8 μm, was found the longest in the middle part of the wafer, while at high injections it decreased to 1 μm due to an impact of Auger recombination with a coefficient, C = (4 ± 1) × 10−32 cm6/s. The 2.7 times lower diffusion length value in the edge part was explained by an impact of point defects to the carrier lifetime and diffusivity.

Aeromechanical Optimization of a Winglet-Squealer Tip for an Axial Turbine

The possibility of reducing the over tip leakage loss of unshrouded axial turbine rotors has been investigated in an experiment using a linear cascade of turbine blades and by using CFD. A numerical optimization of a winglet-squealer geometry was performed. The optimization involved the structural analysis alongside the CFD. Significant effects of the tip design on the tip gap flow pattern, loss generation and mechanical deformation under centrifugal loads were found. The results of the optimization process were verified by low speed cascade testing. The measurements showed that the optimized winglet-squealer design had a lower loss than the flat tip at all of the tested tip gaps. At the same time, it offered a 37% reduction in the rate of change of the aerodynamic loss with the tip gap size. The optimized tip geometry was used to experimentally assess the effects of the opening of the tip cavity in the leading edge part of the blade and the inclination of the pressure side squealer from the radial direction. The opening of the cavity had a negligible effect on the aerodynamic performance of the cascade. The squealer lean resulted in a small reduction of the aerodynamic loss at all the tested tip gaps. It was shown that a careful consideration of the mechanical aspects of the winglet is required during the design process. Mechanically unconstrained designs could result in unacceptable deformation of the winglet due to centrifugal loads. An example winglet geometry is presented that produced a similar aerodynamic loss to that of the optimized tip but had a much worse mechanical performance. The mechanisms leading to the reduction of the tip leakage loss were identified. Using this knowledge, a simple method for designing the tip geometry of a shroudless turbine rotor is proposed. Numerical calculations indicated that the optimized low-speed winglet-squealer geometry maintained its aerodynamic superiority over the flat tip blade with the exit Mach number increased from 0.1 to 0.8.

Electronic and structural study of Pt-modified Au vicinal surfaces: a model system for Pt-Au catalysts.

Two single crystalline surfaces of Au vicinal to the (111) plane were modified with Pt and studied using scanning tunneling microscopy (STM) and X-ray photoemission spectroscopy (XPS) in ultra-high vacuum environment. The vicinal surfaces studied are Au(332) and Au(887) and different Pt coverage (θPt) were deposited on each surface. From STM images we determine that Pt deposits on both surfaces as nanoislands with heights ranging from 1 ML to 3 ML depending on θPt. On both surfaces the early growth of Pt ad-islands occurs at the lower part of the step edge, with Pt ad-atoms being incorporated into the steps in some cases. XPS results indicate that partial alloying of Pt occurs at the interface at room temperature and at all coverage, as suggested by the negative chemical shift of Pt 4f core line, indicating an upward shift of the d-band center of the alloyed Pt. Also, the existence of a segregated Pt phase especially at higher coverage is detected by XPS. Sample annealing indicates that the temperature rise promotes a further incorporation of Pt atoms into the Au substrate as supported by STM and XPS results. Additionally, the catalytic activity of different PtAu systems reported in the literature for some electrochemical reactions is discussed considering our findings.

The effect of thermal processing parameters on the microstructure of extruded and sintered TiO2 ceramics

There are no investigations concerning the microstructural homogeneity in cross section of extruded and sintered samples found in literature. In this work TiO2 ceramics obtained by extrusion technology is investigated. Samples were sintered under three different sintering conditions: A) 1100→850 °C, B) 1100 °C and C) 1100→1450 °C. Two step sintering at 1100 − 850 °C leads to the formation of denser microstructure (77.2 % of TD) compared to single step sintering at 1100 °C (75.4 % of TD). After thermal treatment there are differences between microstructure in middle and edge part of all samples. Microstructure of samples after each sintering condition is different. Needle-shaped and irregularly shaped grains and bimodal porosity can be found in SEM investigations.

Mechanical properties of worsted fabrics for emotional garment to the rapier loom characteristics

This study examined the mechanical properties of worsted fabrics woven using various rapier weaving looms. For this purpose, the warp and weft yarn tensions during weaving were measured on the three types of rapier looms, and the fabric mechanical property changes due to the warp and weft tension differences were measured and analyzed according to the fabric position and particular rapier loom using the KES-FB system. The warp tension variation along the loom width direction in P-GTX loom showed the lowest value compared to FAST and THEMA looms. The warp tensions on the central part of the three types of looms were much higher than those on the left and right sides of the looms. The extensibility and bending rigidity of the fabric woven by P-GTX rapier loom showed lower values than those of FAST and THEMA looms, which appears to have originated from the low warp and weft weaving tensions of P-GTX rapier loom. On the other hand, the compressional property and shear modulus showed compromised results due to lateral deformation by compression and constraint deformation of the warp and weft by shear. The friction coefficient of the fabric surface woven by FAST loom showed the lowest value due to the flatter surface by the high warp tension. The mechanical properties of the fabric loaded by a high warp tension on the central part of the loom were also affected by the high weft yarn crimp due to the wider spacing between warp yarns by the higher warp tension during weaving, which makes the surface of the central part of the fabric flatter and smoother than the edge part of the fabric.

Twisted Wire Stent Technique for Delayed Sternal Closure After Congenital Heart Operations

After congenital heart operations, keeping the sternal edges wide open may require sternal stenting in some extreme cases in which delayed sternal closure is necessary after operation, because sternal edges may compromise cardiac function as a result of the elasticity of the thoracic cage. We describe an easy and safe way for sternal stenting using conventional sternal steel wires.

Dielectric behavior of alumina thin film under high DC electric field prepared by sol–gel method

Dielectric behavior of aluminum oxide (Al2O3) thin film under high DC electric field is presented and discussed. Aluminum oxide thin films were prepared starting from aluminum isopropoxide as a precursor via a wet chemistry route. Silicon substrates and silica glass substrates were used to deposit the films via spin-coating technique. The deposited films were then annealed under 450°C–700°C for 2–3 h. Dense, crack-free and uniform films were obtained. The thickness of the films is in the range of 200–800 nm. The films obtained are in amorphous state as revealed by the X-ray diffraction patterns. Voltage–Current (V–I) characteristics of the films were used to study the dielectric behavior of the films. Very low leakage current density J under high DC electric field E can be obtained. The breakdown electric field of the films is around 1.2 MV/cm. The V–I characteristics of the films are slightly nonlinear. With platinum as bottom electrode and gold as top electrode, successive breakdown phenomena of the films under high DC electric field were observed. Each breakdown event of the film corresponds to a sharp spike at the V–I plot of the sample. The shape of the breakdown spots of the films are in crater-like with a breakdown channel of diameter around a few micrometers as revealed by SEM images. The top gold electrode at the breakdown spots either splashed out or ripped off from the breakdown spots, which isolated the breakdown spots from rest of the electrode, and made the successive breakdown of the sample possible. The breakdown spots of the sample are concentrated at the edge of the electrode with proportional spacing, which can be easily understood as the edge effect of the parallel capacitor configuration, while the uniform distribution of the breakdown spots signifies that the uniformity of the films thus prepared are satisfied. Breakdown spots apart from the electrode edge can also be observed. Most of such spots associated with ripped-off gold film electrode in large area. We suppose such breakdown took place at higher electric field after the successive breakdown at the electrode edge and the isolation of the edge part from rest of the sample. Higher energy is needed to tear off larger section of the electrode. The breakdown characteristics of the films reported in this work are useful for the further study to enhance the breakdown strength of the film.

항공기 날개 앞전의 레이더흡수구조 최적화

In this paper, objective functions are defined for optimization of radar absorbing structures (RAS) on the aircraft wing leading edge. RAS is regarded as a single layer structure made of dielectrics. Design variables are the real and imaginary parts of complex permittivity. Reflection coefficient(RC) and radar cross section(RCS) are used in the objective function respectively. Transmission line theory is employed to calculate the RC. The RCS is evaluated by using physical optics(PO) for a leading edge part model. Genetic algorithm(GA) is used to perform optimization procedures. The radar absorbing performance of designed RAS is assessed by the RCS of a wing which has RAS on the leading edge.

The strength of binary junctions in hexagonal close-packed crystals

A comparative study of non-coplanar binary dislocation junctions in magnesium (Mg) and beryllium (Be) is presented to examine the effects of elastic properties and active Burgers vectors on junction formation and destruction in hexagonal close-packed (hcp) crystals via discrete dislocation dynamics simulations. Two junction configurations formed at intersecting prismatic (011¯0)/basal(0001) planes and type-II pyramidal (2¯112)/prismatic(011¯0) planes are studied using Burgers vectors of varying magnitudes. The equilibrium junctions are created from two intersecting straight gliding dislocations, and their subsequent strengths are evaluated under uniform applied stresses. The relative junction strengths between Mg and Be are consistent with their relative elastic stiffness, i.e., the modulus of elasticity for Mg is approximately one order of magnitude smaller than that of Be, and their junction strengths are similarly one order of magnitude apart. In general, the yield surfaces for junctions in Be are larger than those in Mg after normalization with the respective elastic moduli and Poisson’s ratios. All yield surfaces exhibit a strong symmetry. However, the size and shape of the yield surfaces depend on the slip systems, especially the active Burgers vectors. The yield surfaces of hcp crystals can resemble those of face-centered cubic or body-centered cubic crystals when the active Burgers vectors of the dislocations involved in the junction are of type 〈a〉, namely 13〈112¯0〉, and are distinct when Burgers vectors of different types are used: for instance, a type 〈a+c〉, namely 13〈112¯3¯〉, interacting with a type 〈a〉. It was also found that junctions with more edge part exhibit more elongated yield surfaces than those with more screw part, and slip systems involved with 〈a〉 Burgers vectors result in smaller yield surfaces. These results demonstrate that junction strengths for hcp crystals are largely determined by elastic properties and Burgers vectors. The work aims to assess the effects of intrinsic material properties and dislocation slip systems on the strength of different binary dislocation junctions for general hcp structures.

공정변수간의 교호작용을 고려한 모서리 접합두께 및 처짐량 예측 회귀식 도출

The thickness and deflection of melting parts of the glass edge reach the biggest effect on the intensity and thermal insulation performance. During the sealing process using a hydrogen mixed gas torch, the thickness and the deflection effect of the edge part are affected by process parameters. In order to analyze the correlative relationship of the thickness prediction and the deflection of the edge part according to the process parameters, data was obtained by conducting sealing experiments. The main effects and interaction effects of process parameters for the thickness and the shape of the glass edge parts were analyzed through the design of experiment. A mathematical experiment equation that can predict the thickness and deflection of the edge part according to the process parameters was developed by conducting multiple regression equations.

Conjugate calculation of a film-cooled blade for improvement of the leading edge cooling configuration

Great efforts are still put into the design process of advanced film-cooling configurations. In particular, the vanes and blades of turbine front stages have to be cooled extensively for a safe operation. The conjugate calculation technique is used for the three-dimensional thermal load prediction of a film-cooled test blade of a modern gas turbine. Thus, it becomes possible to take into account the interaction of internal flows, external flow, and heat transfer without the prescription of heat transfer coefficients. The focus of the investigation is laid on the leading edge part of the blade. The numerical model consists of all internal flow passages and cooling hole rows at the leading edge. Furthermore, the radial gap flow is also part of the model. The comparison with thermal pyrometer measurements shows that with respect to regions with high thermal load a qualitatively and quantitatively good agreement of the conjugate results and the measurements can be found. In particular, the region in the vicinity of the mid-span section is exposed to a higher thermal load, which requires further improvement of the cooling arrangement. Altogether the achieved results demonstrate that the conjugate calculation technique is applicable for reasonable prediction of three-dimensional thermal load of complex cooling configurations for blades.

Spatial distribution and nutritional requirements of the endosymbiont-bearing bivalve Loripes lacteus (sensu Poli, 1791) in a Mediterranean Nanozostera noltii (Hornemann) meadow

Sulphur-oxidising endosymbiont-bearing bivalves often inhabit seagrass meadows, where they can control sulphide levels and variably contribute to carbon cycling, by feeding on endosymbiotic bacteria and/or on particulate organic matter from the water column. The patterns of variability in their feeding mode and their spatial distribution within the seagrass meadows are however poorly studied. Seagrass beds form naturally patchy habitats with seagrass-sand edges that may have variable effects on different organisms. The present study aims at understanding differences in feeding mode and abundance of the endosymbiont-bearing bivalve Loripes lacteus (sensu Poli, 1791) as well as the physiological conditions of its endosymbiotic populations between edge and inner portion of meadows of the eelgrass Nanozostera noltii (Hornemann). In July 2010, Loripes specimens were sampled in 4 eelgrass patches at 2 different locations in the Thau lagoon, South of France. There was a clear negative edge effect on the abundance of small individuals of Loripes, while large individuals were homogeneously distributed between edge and inner part of the meadow. Although Loripes isotopic signatures (δ13C and δ15N) were always closer to those of its symbiotic bacteria than to those of suspension-feeding bivalves, eelgrass edge enhanced mixotrophic behaviour of small animals, which assimilated less bacterial carbon and nitrogen at the edge than in the inner part of the eelgrass meadow. No differences related to eelgrass edges were instead found for the bacterial populations harboured by Loripes. Rather, flow cytometry revealed large variability at small spatial scales. Although bacteria were always important for the nutrition of Loripes, these findings showed that seagrass edges may contribute to regulate feeding mode and population structure of Loripes, which may have implications for seagrass functioning.

Sensitivity Analysis of Edge Sealing Process Parameters of Vacuum Glazing Panel

The edge sealing process of vacuum glazing panel manufacture is one that requires high reliability in order to maintain a vacuum state between two sheets of glass. In this study, a method of melting and sealing two sheets of glass using the hydrogen mixed gas torch during edge sealing was conducted. During melting and sealing, the deflection effect of the edge part is affected by process parameters such as flow rate of hydrogen mixed gas, moving speed of torch, and distance between the torch and the glass, among others. In order to analyze the correlative relationship of the shape prediction and the sealing shape of the edge part according to the process parameters, data was obtained by conducting sealing experiments and setting shape parameters for the lower melting part. A mathematical experiment equation that can predict the shape of the lower edge part according to the process parameters was developed by conducting nonlinear multiple regression analysis based on the data obtained for the shape parameters. In addition, sensitivity analysis according to the changes in the process parameters was carried out and the effects of the process parameters on the edge shape parameters were analyzed by using the developed mathematical equation.

Performance Assessment for LTE-Advanced Networks with Uniform Fractional Guard Channel over Soft Frequency Reuse Scheme

Dropping probability of handoff calls and blocking probability of new calls are two important Quality of Service (QoS) measures for LTE-Advanced networks. Applying QoS for Cell edge users in soft frequency reuse scheme in LTE system is a challenge as they already suffer from limited resources. Assigning some resources for handover calls may enhance dropping probability but this is in price of degradation in the blocking probability for new calls in cell-edge. Uniform Fractional Guard Channel (UFGC) is a call admission policy that provides QoS without reserving resources for handover calls. In this paper, the performance of Soft Frequency Reuse (SFR) in presence of Uniform Fractional Guard Channel (UFGC) will be investigated using queuing analysis. The mathematical model and performance metrics will be deduced in this assessment. The impact of UFGC will be evaluated in edge and core part separately. Then the optimal value for the parameter of UFGC will be obtained to minimize the blocking probability of new calls with the constraint on the upper bound on the dropping probability of handoff calls.

0420 実機ガスタービン第一段動翼を対象とした共役熱伝達解析(OS4-4 流体機械の研究開発とそれに関連した複雑流動現象,OS4 流体機械の研究開発とそれに関連した複雑流動現象)

Conjugate heat transfer simulations were conducted for the first stage rotor blade in an actual gas turbine and compared with experimental results. The objectives of this research are to validate prediction accuracy of temperature distribution on the rotor blade surface and find key factors to improve the prediction accuracy. These simulations were carried out at the similar condition as gas turbine operation. Temperature distributions predicted by the simulations reasonably agreed with those of the experiment near the rotor leading edge part. However, temperature distribution on the pressure side was different between the simulation and experiment. In the internal cooling flow passage, main stream leans toward one side of walls due to Coriolis force and the temperature on this side became lower than the experimental results. It is important for obtaining better prediction accuracy of heat transfer to solve the complex flow phenomena caused by several vortices generated by rotation, flow turning, or the rib-turbulator in the internal cooling flow region.

An Adaptive-regularized Image Super-resolution

摘要: 提出一种自适应正则化的图像超分辨率重建算法. 首先, 利用局部残差均值自适应地计算各低分辨率图像通道的权值参数矩阵, 可有效地利用各通道对应区域间的交叉信息; 其次, 利用正则项局部误差均值自适应地计算平衡正则项和保真项的正则化参数矩阵, 能较好地保持图像边缘纹理等信息.实验结果表明本文算法不但具有较高峰值信噪比(Peak signal to noise ratio, PSNR) 和结构相似度(Structural similarity, SSIM), 而且在边缘、纹理等细节区域具有更好的重建效果. 关键词: 超分辨率 / 最大后验估计 / 自适应正则化 / 邻域约束

A Long-term synoptic-scale climate study over Mariepskop, Mpumalanga, South Africa

Mariepskop forms part of the northernmost edge of the Drakensberg Mountain range and is known for its complex topography associated with meso-scale atmospheric circulation, and therefore its numerous climatic zones. The mountain hosts a high biodiversity. The peak of Mariepskop lies at approximately 1900m Above Mean Sea Level (AMSL), which is higher than the surrounding escarpment to the east. Its foothills also extend well into the Lowveld at about 700 m AMSL. Mariepskop is therefore ideal for studying airflow exchange between the industrial Highveld and the Lowveld with its diversity of natural resources. It is also ideal for detecting global warming signals on altitudinal gradients extending from the Lowveld to altitudes above the Highveld escarpment. In this study long-term National Centre for Atmospheric Research / National Centre for Environmental Prediction (NCAR/NCEP) wind data at two atmospheric pressure levels (850 and 700 hPa), as well as near-surface temperature data, were obtained for the Mariepskop region for the summer (December-January-February: DJF (1981-2011 )) and winter (June-July-August: JJA (1980-2012)) seasons. The data was used to study synoptic wind flow across the mountain in the upper (700 hPa) and lower (800 hPa) atmosphere, as well as near-surface temperature gradients. During the summer season, east-south-easterly and south-easterly winds were found to be the most prominent. These winds are commonly associated with both continental and ridging anticyclonic conditions. During winter, the predominant wind direction at 850 hPa is south-easterly, which is also due to the influence of ridging anticyclones, while at 700 hPa the dominant winter wind direction becomes west-south-west, which is due to the more frequent eastward passing of cyclonic frontal systems across the Highveld towards the Lowveld. Long-term near-surface temperatures exhibit a weak increasing linear temperature trend for both seasons, which might be due to global warming.

“Occult” Melanocytes in Nail Matrix Melanoma

To the Editor: Although there is little need these days to encourage the further use of immunohistochemistry in the study of nevomelanocytic lesions, there is one group of such lesions in which its use is essential to ensure the correct diagnosis—pigmented lesions of the nail bed/matrix. Longitudinal melanonychia (melanonychia striata in longitudinem) is a not uncommon clinical problem that may result from a melanotic macule or nevus of the nail bed/matrix or from an early stage of subungual melanoma. Nail streaks are also common in dark-skinned people adding to the diagnostic confusion in this area. The pathologic findings may also be difficult to interpret with the distinction between a melanotic macule and an early acral lentiginous melanoma problematic. A 2-mm biopsy from the advancing edge of a melanoma may be particularly difficult to diagnose as there is often no cell crowding and the melanocytes are difficult to discern from adjacent keratinocytes.1 This has given rise to the use of the term “acral atypical melanocytic hyperplasia” for these indeterminate lesions.2 Immunohistochemistry stains (such as the melan A or MART-1, HMB45, and some of the newer “cocktails” with a red chromogen) highlight the melanocytes distinctly.3 In early melanomas, the dendrites are plumper and longer than melanotic macules, and the nuclei of melanocytes are larger and hyperchromatic. Pagetoid spread of melanocytes is highlighted by these immunohistochemical stains (Fig. 1). Furthermore, the older (central) area of the lesion is much more likely to be diagnostic than the newer (advancing edge) part of the lesion. The presence of inflammatory cells in the dermis favors melanoma over a macule, but one of us (D.W.) has seen cases of matrical melanoma, in which the infiltrate was sparse or nonexistent.FIGURE 1: Nail matrix melanoma. A, Melanocytes are difficult to discern in this hematoxylin and eosin preparation (original magnification ×100). B, Melanocytes, some plump, are easily recognized in this same case using a “Melanoma Cocktail” preparation with a red chromogen (original magnification ×100).Dermatopathology of the nail matrix is not for the faint-hearted or inexperienced.

A study on the micro-endmilling surface prediction model with non-dynamic errors

In this study, the surface prediction numerical model for micro-endmilling, including the non-dynamic errors of micro-endmilling such as tool geometric and set-up errors, was proposed. For verifying the proposed prediction numerical model, the inspection method of tool non-dynamic errors was proposed and applied to the verification experiments. In micro-endmilling, the geometry and manufacture error of micro tool and tool set-up error affect the quality of micro cutting process seriously compared to macro endmilling because the specific cutting energy and feed per tooth to tool radius are very large and commented errors works in combination. Therefore, for the numerical model for predicting the micro-endmilling surface, error variables such as tool dish, tool eccentricity, tilted edge part, and tool runout were applied to the proposed numerical model. Besides, it is very important that those errors are measured accurately. Finally, the numerical prediction model was verified by the micro cutting experiments applied the inspection method of tool non-dynamic errors.