Fabrication of moth eye structures via charged nanoparticle lithography with size and density control

We have developed and demonstrated an effective method for fabricating the moth eye structures formed by charged nanoparticle lithography (cNPL). We attached high-density gold nanoparticles (Au NPs) to GaN without aggregation by making the surface of Au NPs negatively charged and GaN positively charged. Au NPs were effectively used as an etching mask, and the moth eye structures of GaN were formed by inductively coupled plasma reactive ion etching. The moth eye structures with various sizes and densities were fabricated by the cNPL, and the moth eye structures reduced the reflectance. The cNPL, as a simple technique with size and density control, will provide high potential to optical device applications.     

Advances in J‐integral estimation of circumferentially surface cracked pipes

This paper describes enhanced J‐integral estimation schemes for pipes with circumferential semi‐elliptical cracks subjected to tensile loading, global bending and internal pressure. These schemes are given in two different forms to cover the wide ranges of geometries and material parameters; the modified GE/EPRI method and the modified reference stress method. In the former method, new plastic influence functions for fully plastic J‐integral estimation are developed based on extensive three‐dimensional finite element calculations. In the latter method, new optimized reference loads are suggested and utilized to predict the J values. To verify the feasibility of these two schemes, J‐integral values obtained from further detailed FE analyses are compared to those from the proposed schemes. Because the estimated J‐integrals agree fairly well with the detailed FE analysis results, the new solutions can be applied for accurate structural integrity assessment of different size pipes with a circumferential surface crack.     

Corrosion characteristics of anodized Ti–(10–40wt%)Hf alloys for metallic biomaterials use

The effect of anodizing on corrosion resistance of Ti–xHf alloys has been investigated. Ti–xHf alloys were prepared and anodized at 120, 170 and 220 V in 1 M H₃PO₄ solution, and crystallized at 300 and 500°C. Corrosion experiments were carried out using a potentiostat in 0.15 M NaCl solution at 36.5 ± 1°C. The Ti–xHf alloys exhibited the α′ and anatase phases. The pore size on the anodized surface increases as the applied voltage is increased, whereas the pore size decreases as the Hf content is increased. The anodized Ti–xHf alloys exhibited better corrosion resistance than non-anodized Ti–xHf alloys.     

Dependence of porosity, charge recombination kinetics and photovoltaic performance on annealing condition of TiO2 films

Effect of annealing temperature, time of nanocrystalline TiO2 film on porosity, electron transport/recombination and photovoltaic performance on dyesensitized solar cell (DSSC) had been investigated in this article. Photocurrent density was slightly higher as annealing at 550℃ compared to those of annealing at 450℃ and 500℃ under the given annealing time of 60 min, which was correlated with the amount of adsorbed dye. Thermogravimetric analysis showed there was a more weight loss between 500℃ and 550℃, which revealed there were more sites for dye adsorption. Given the annealing temperature of 550℃, as annealing time varied from 60 to 90 and 120 min, results showed that the average size of pore and surface area decreased with longer annealing time, which deteriorated photocurrent density due to less dye loading. Electron diffusion rate remained almost unchanged regardless of annealing condition.However, electron recombination was influenced by annealing condition, it became slower with the increase of the annealing temperature under the given annealing time. In the contray, the electron recombination developed faster for the longer annealing time at a given annealing temperature. These results suggested that heat treatment of TiO2 film at 550℃ for 60 min in air would be the optimal annealing condition to achieve high efficiency DSSC.     

Flux Optimization During Tapping in BOF Process

An integrated Plate Mill has started it’s operation on July 7, 2010 in Gwangyang Steelworks, POSCO. The production capability is about 2.5 million tons per year and the main stream consists of Blast Furnace, Hot metal pretreatment (KR), Converter, Bubbling Station, RH/VTD and Continuous Casting. Particularly, it is possible to control sulfur concentration at excellent level in BOF without any further treatment in LF or VTD, which is attained by unique KR process and scrap usage strategy in BOF. In this paper, desulfurization efficiency and steel cleanliness was introduced by optimizing flux amount during tapping in BOF process. In addition, the effect of the flux addition on the refractory of ladle was investigated based on EPMA analyses with the viewpoint of phase diagram. The cleanliness of each sample was examined using optical emission spectrometry and oxygen nitrogen determinator.     

Zone conditional assessment of flame-generated turbulence with DNS database of a turbulent premixed flame

Zone conditional two-fluid equations are derived and validated against a DNS database for a turbulent premixed flame. The conditional statistics of major flow variables are investigated to understand the mechanism of flame-generated turbulence. The flow field in the burned region shows substantially increased, highly anisotropic turbulence to conserve mass through a flamelet surface. The transverse component may be larger than the axial component for a distributed pdf of the flamelet orientation angle in the middle of the flame brush. The opposite occurs due to redistribution of turbulent kinetic energy and flamelet orientation mostly normal with respect to the mean flow at the end of the flame brush. The major source or sink terms of turbulent kinetic energy are the interfacial transfer by the mean reaction rate and the work terms induced by fluctuating pressure and velocity on the flame surface. Ad hoc modeling of some interfacial terms may be required for further application of the two-fluid model for modeling turbulence in turbulent premixed combustion simulations.     

叶片组轴向模态共振失效的理论与实验研究

为了找出叶片的失效机理及解决的办法，利用金相、扫描电镜等分析手段，从宏观和微观的角度对叶片及断口进行了观察和分析；用三维有限元法和实验方法对其振动特性进行了研究。分析得出：造成叶片开裂是由于叶片组第2类轴向振动模态和喷嘴叶栅出口气流不均匀引起的激振力频率发生共振，导致叶片高周疲劳造成的。叶根齿表面加工粗糙是裂纹起裂的一个重要诱发因素。采用不改变叶型，仅调整叶片组中的叶片数，成功地实现了叶片的改型设计。该研究表明：叶片组的第2类轴向振动模态同喷嘴激振力共振是危险的，应该避免。调整叶片组中的叶片数是调整叶片组轴向固有振动模态的一个有效方法。图6表3参5     

EFFECT of HEAT TREATMENT ON FIRMNESS of APPLES and APPLE SLICES

Effects of heat treatment on firmness of apples (Golden Delicious, McIntosh and Delicious) and apple slices were studied. Heat treatment (45C, for 1.75 h) of Golden Delicious and Delicious apples significantly increased their firmness, but no significant increase was observed for the McIntosh cultivar. After storage for 7 days at 2C, the treated apples were firmer than those stored at 10, 18, and 25C. Apple slices prepared from the heat treated apples were also firmer at 21 days storage than those prepared from nontreated apples: differences ranging from 12% for McIntosh to 48% for Delicious. This beneficial firming effect of heat treatment might have application in producing high quality minimally processed slices from Golden Delicious and Delicious apple cultivars.     

EFFECT of PLASTICIZER LEVEL and TEMPERATURE ON WATER VAPOR TRANSMISSION of CELLULOSE-BASED EDIBLE FILMS1

This study was conducted to determine water sorption isotherms of cellulose-based films made from methyl cellulose (MC) and hydroxypropyl cellulose (HPC), and to evaluate the effect of plasticizer concentration and temperature on water vapor permeability coefficient in those films. the equilibrium moisture contents of MC film and HPC film increased slowly with an increase in water activity (a_w) up to 0.75, but increased greatly after 0.75 a_w. the water vapor permeability coefficient of HPC film increased as the concentration of polyethylene glycol (PEG) increased; however, the water vapor permeability coefficient of MC film which contained 0.22 ml PEG/g cellulose was lower than of films which contained no or higher PEG. an Arrhenius-type relationship was fitted to examine temperature dependence of water vapor permeability coefficients of cellulose films. the edible films studied exhibited relatively low activation energies (14.56–16.43 kJ/mol) compared with typical food packaging materials.     

Cryostabilization of Functional Properties of Pre-Rigor and Post-rigor Beef by Dextrose Polymer and/or Phosphates

Cryostabilization of functional properties of pre-rigor and post-rigor beef throughout 5 mo frozen storage was investigated as affected by the addition of 8% neutralized high molecular weight dextrose polymer (polydextrose), alone or in combination with 0.5% phosphates (a 1:l mixture of sodium tripolyphosphate and tetrasodium pyrophos-phate). Pre-rigor meat to which polydextrose had been added prior to freezing was nearly equivalent in functional properties after 5 mo frozen storage to fresh, pre-rigor meat. Addition of the same level of phosphates plus polydextrose to nontreated muscle (control) after 5 mo frozen storage resulted in higher values for most measured indices of functionality. The effect was almost totally attributable to addition of the phosphates. However, addition of phosphate did not appear to increase the protein cryoprotective effect.