Finite element analysis and verification of laser marking on eggshell

The first aim of the study was to establish the temperature model of the eggshell by the finite element analysis software ANSYS and realize the eggshell temperature field based on the laser marking processing. The eggshell surface which created the meshing model, set the parameters with the ANSYS Parameter Design Language and simulated that the Gaussian distributed laser beam acted on the surface were established. In addition, marking characters made use of the CO₂ laser processing system on the brittle eggshell to analyze whether laser beams caused damage to the inner of the eggshell. According to the results of the comparison between the simulation by ANSYS and the experiment of laser marking, it is revealed that the heat-affected area by laser marking is similar to that of the simulation.     

Magnetohydrodynamically enhanced heat transfer in a liquid metal system

The phenomena of liquid metal flow under the influence of magnetic and electric fields are important in the development and design of nuclear and metallurgical plants, such as the blanket cooling systems of fusion or fast breeder reactors and electromagnetic stirring devices. In this study, a computer code that models recirculating flows in two dimensions using a k − ε turbulence model is expanded to include the magnetohydrodynamic (MHD) effects of applied electric and magnetic fields. This modified code is then used to examine the effect of MHD stirring on the heat transfer characteristics of a liquid metal cooling system. Using liquid sodium properties, various thermophysical properties are investigated. The results indicate that a significant increase in the rate of heat transfer is obtainable when the heat transfer system is operated in the presence of MHD stirring.     

Catalyst layer-free carbon-coated steel—An easy route to bipolar plates of polymer electrolyte membrane fuel cells: Characterization on structure and electrochemistry

Stainless steel coated with carbon by CVD process has been evaluated as a low-cost and small-volume substitute for graphite bipolar plate in polymer electrolyte membrane fuel cell (PEMFC). Carbon film was grown at 690–930 °C under gas-mixture of C₂H₂–H₂. Scanning electron microscopy and X-ray diffractometry were used to characterize surface morphology and crystal structure of resultant carbon films, which were found to depend much on reaction temperature. Interfacial contact resistance (ICR), hydrophobicity and chemical stability of obtained specimens were measured to compare with commercial highly oriented pyrolytic graphite (HOPG). All carbon films investigated in this study show improved ICR and hydrophobicity of SUS304 substrate to the level of HOPG. Amorphous carbon layer with continuous film structure prepared at 810 °C shows the best protection of SUS304 substrate against the attack of H_(aq)⁺ (anodic side) and the best resistance of the coated carbon from gasification (cathodic side) in the simulated PEMFC environment.     

Surface oxidation of molten Sn(Ag,Ni, In,Cu) alloys

The surface oxidations of molten Sn(Ag, Ni, In, Cu) alloys are studied. We conclude that the microstructure (phase and density) of the surface oxide layer is the key factor for the surface oxidation formation. Also, we found that the microstructure (phase and density) of the Sn surface oxide layer is highly influenced by the additives in the solder alloys, which can be roughly anticipated from the additives’ electromagnetic field values and Gibbs free energies of oxide formation. The detailed effect (either retarding or enhancing) of the additives on the surface oxidation is discussed in this paper.     

One‐Step,Room‐Temperature Synthesis of Glutathione‐Capped Iron‐Oxide Nanoparticles and their Application in In Vivo T1‐Weighted Magnetic Resonance Imaging

The room‐temperature, aqueous‐phase synthesis of iron‐oxide nanoparticles (IO NPs) with glutathione (GSH) is reported. The simple, one‐step reduction involves GSH as a capping agent and tetrakis(hydroxymethyl)phosphonium chloride (THPC) as the reducing agent; GSH is an anti‐oxidant that is abundant in the human body while THPC is commonly used in the synthesis of noble‐metal clusters. Due to their low magnetization and good water‐dispersibility, the resulting GSH‐IO NPs, which are 3.72 ± 0.12 nm in diameter, exhibit a low r₂ relaxivity (8.28 mm ^?1s^?1) and r₂/r₁ ratio (2.28)—both of which are critical for T₁ contrast agents. This, together with the excellent biocompatibility, makes these NPs an ideal candidate to be a T₁ contrast agent. Its capability in cellular imaging is illustrated by the high signal intensity in the T₁‐weighted magnetic resonance imaging (MRI) of treated HeLa cells. Surprisingly, the GSH‐IO NPs escape ingestion by the hepatic reticuloendothelial system, enabling strong vascular enhancement at the internal carotid artery and superior sagittal sinus, where detection of the thrombus is critical for diagnosing a stroke. Moreover, serial T₁‐ and T₂‐weighted time‐dependent MR images are resolved for a rat's kidneys, unveiling detailed cortical‐medullary anatomy and renal physiological functions. The newly developed GSH‐IO NPs thus open a new dimension in efforts towards high‐performance, long‐circulating MRI contrast agents that have biotargeting potential.     

Utility‐based probabilistic call admission control for complete fairness in wireless networks

Resource reservation or the other prioritization strategies adopted by Call Admission Control (CAC) schemes in wireless networks lead to unfair resource allocation to users belonging to different service classes (SCs) due to high divergence among the respective call blocking probabilities (CBPs). In this paper, we propose dynamic optimization of probabilistic CAC (P‐CAC) schemes to assure CAC fairness among users of different SCs in wireless networks. The approach is based on users utility combined with fairness optimization, aiming at dynamically determining the probability value in the P‐CAC scheme. This optimal probability is adjusted to network ongoing traffic, CBPs of each SC, prioritization levels characterizing the SCs supported, and the users risk aversion, which reflects their behavior toward the perceived QoS. The existence and uniqueness of the optimal probability that leads to absolute fairness among the users of a wireless network are proven. Copyright © 2012 John Wiley & Sons, Ltd.     

Characteristics of large‐scale nanohole arrays for thin‐silicon photovoltaics

Nanostructured crystalline silicon is promising for thin‐silicon photovoltaic devices because of reduced material usage and wafer quality constraint. This paper presents the optical and photovoltaic characteristics of silicon nanohole (SiNH) arrays fabricated using polystyrene nanosphere lithography and reactive‐ion etching (RIE) techniques for large‐area processes. A post‐RIE damage removal etching is subsequently introduced to mitigate the surface recombination issues and also suppress the surface reflection due to modifications in the nanohole sidewall profile, resulting in a 19% increase in the power conversion efficiency. We show that the damage removal etching treatment can effectively recover the carrier lifetime and dark current–voltage characteristics of SiNH solar cells to resemble the planar counterpart without RIE damages. Furthermore, the reflectance spectra exhibit broadband and omnidirectional anti‐reflective properties, where an AM1.5 G spectrum‐weighted reflectance achieves 4.7% for SiNH arrays. Finally, a three‐dimensional optical modeling has also been established to investigate the dimension and wafer thickness dependence of light absorption. We conclude that the SiNH arrays reveal great potential for efficient light harvesting in thin‐silicon photovoltaics with a 95% material reduction compared to a typical cell thickness of 200 µm. Copyright © 2012 John Wiley & Sons, Ltd.     

Evaluation of simulated transfer functions of concrete plate derived by impact-echo method

In this study, the simulated transfer function of a concrete plate was obtained solely from displacement waveform in an impact-echo test. In the simulated transfer function, the amplitude corresponding to the modal vibration at thickness direction, called the thickness-amplitude, can be consistent during various tests on the same location. An empirical formula was obtained by numerical simulation to predict the thickness-amplitude for given thickness, impact–receiver distance, and P-wave speed. The formula was confirmed experimentally using plates made from various mixed materials with various thicknesses. The differences between the experimental and predicted thickness-amplitude are mostly within 10%. The formula has the potential for quantitative evaluation of the bond between concrete and the substrate layer.     

Efficient algorithms for mining closed itemsets and their lattice structure

The set of frequent closed itemsets uniquely determines the exact frequency of all itemsets, yet it can be orders of magnitude smaller than the set of all frequent itemsets. In this paper, we present CHARM, an efficient algorithm for mining all frequent closed itemsets. It enumerates closed sets using a dual itemset-tidset search tree, using an efficient hybrid search that skips many levels. It also uses a technique called diffsets to reduce the memory footprint of intermediate computations. Finally, it uses a fast hash-based approach to remove any "nonclosed" sets found during computation. We also present CHARM-L, an algorithm that outputs the closed itemset lattice, which is very useful for rule generation and visualization. An extensive experimental evaluation on a number of real and synthetic databases shows that CHARM is a state-of-the-art algorithm that outperforms previous methods. Further, CHARM-L explicitly generates the frequent closed itemset lattice.     

ESD protection design for 1- to 10-GHz distributed amplifier in CMOS technology

Two distributed electrostatic discharge (ESD) protection schemes are presented and applied to protect distributed amplifiers (DAs) against ESD stresses. Fabricated in a standard 0.25-/spl mu/m CMOS process, the DA with the first protection scheme of the equal-sized distributed ESD (ES-DESD) protection scheme, contributing an extra 300 fF parasitic capacitance to the circuit, can sustain the human-body model (HBM) ESD level of 5.5 kV and machine-model (MM) ESD level of 325 V and exhibits the flat-gain of 4.7 /spl plusmn/ 1 dB from 1 to 10 GHz. With the same amount of parasitic capacitance, the DA with the second protection scheme of the decreasing-sized distributed ESD (DS-DESD) protection scheme achieves better ESD robustness, where the HBM ESD level over 8 kV and MM ESD level is 575 V, and has the flat-gain of 4.9 /spl plusmn/ 1.1 dB over the 1 to 9.2-GHz band. With these two proposed ESD protection schemes, the broad-band RF performances and high ESD robustness of the DA can be successfully codesigned to meet the application specifications.