Improvement of sinterability of gadolinia-doped ceria via a high-energy ball milling process

High-energy ball milling process has been applied to gadolinia-doped ceria system. The sinterability of gadolinia-doped ceria was significantly enhanced by the high-energy ball milling process. A comparison was also made of the sintering behavior of milled powders doped with gallia as a sintering aid. Dense Ce_0.8Gd_0.2O_1.9 ceramics with 97% of the theoretical density could be obtained by sintering the milled mixture with 0.5 mol% Ga₂O₃ addition at 1,250 °C for 5 h.     

Standardization of a shear test method for lead-free solder paste chip joints

The electronics industry is moving to replace Pb-based solder with Pb-free solder because of the growing environmental regulations governing the use of lead. Solder joints made from Pb-free solder paste do not yet have an evaluation method to classify its mechanical properties such as shear strength. In this study, we reflowed solder joints from Sn–3.0Ag–0.5Cu solder paste. To standardize the shear test method, we measured the shear strength of the solder joint of a 2012 ceramic chip at a shear rate of 3–60 mm/min and a shear height of 10–380 μm using different shaped shear jigs. We statistically analyzed the optimum number of shear tests by calculating the accumulative average value, standard deviation, and width of the confidence interval. The fracture surface was examined by scanning electron microscope and discussed in terms of the shear conditions.     

Suppression of IEEE 802.11a interference using SVD-based algorithm for DS-UWB systems in wireless multipath channels

IEEE 802.11a systems which operate around 5 GHz and overlap the band of UWB signals will interfere with UWB systems significantly. In this letter, a novel narrow-band interference (NBI) suppression technique based on the singular value decomposition (SVD) algorithm is proposed in direct sequence ultra-wideband (DS-UWB) systems in wireless multipath channels. SVD is used to approximate the interference which then is subtracted from the received signals. In contrast to the conventional suppression methods such as the notch filter and the maximal-ratio combining partial RAKE (MRC PRAKE) receiver, our proposed technique is simple and robust, the hardware complexity of the receiver can be reduced greatly.     

Enzyme-amplified electrochemical detection of DNA using electrocatalysis of ferrocenyl-tethered dendrimer

We have developed a sandwich-type enzyme-linked DNA sensor as a new electrochemical method to detect DNA hybridization. A partially ferrocenyl-tethered poly(amidoamine) dendrimer (Fc-D) was used as an electrocatalyst to enhance the electronic signals of DNA detection as well as a building block to immobilize capture probes. Fc-D was immobilized on a carboxylic acid-terminated self-assembled monolayer (SAM) by covalent coupling of unreacted amine in Fc-D to the acid. Thiolated capture probe was attached to the remaining amine groups of Fc-D on the SAM via a bifunctional linker. The target DNA was hybridized with the capture probe, and an extension in the DNA of the target was then hybridized with a biotinylated detection probe. Avidin-conjugated alkaline phosphatase was bound to the detection probe and allowed to generate the electroactive label, p-aminophenol, from p-aminophenyl phosphate enzymatically. p-Aminophenol diffuses into the Fc-D layer and is then electrocatalytically oxidized by the electronic mediation of the immobilized Fc-D, which leads to a great enhancement in signal. Consequently, the amount of hybridized target can be estimated using the intensity of electrocatalytic current. This DNA sensor exhibits a detection limit of 20 fmol. Our method was also successfully applied to the sequence-selective discrimination between perfectly matched and single-base mismatched target oligonucleotides.     

A goal programming model as an aid in facility location analysis

This paper presents an application of goal programming as an aid in facility location analysis. Specifically, this paper illustrates the use of a goal programming model to resolve a site location problem. The results of this study show that the goal programming model presented can be used to improve the site selection process over existing models. This is accomplished by allowing consideration of substitutable resources that exist in the decision environment.     

Marine Two-Headed Sphingolipid-Like Compound Rhizochalin Inhibits EGF-Induced Transformation of JB6 P<Superscript>+</Superscript> Cl41 Cells

Rhizochalin [(2R,3R,26R,27R)-2,27-diamino-3-hydroxy-26-[(2R,3R,4S,6R)-3,4,5-trihydroxy-6-(hydroxymethyl)tetrahydro-2H-pyran-2-yloxy]octacosan-11-one], an antimicrobial and cytotoxic marine two-headed sphingolipid-like natural product, isolated from the sponge Rhizochalina incrustata, and some related compounds were studied as anticarcinogenic and proapoptotic agents. The corresponding effects were tested on the mouse skin epidermal JB6 P⁺ Cl 41 cell line, its stable transfectants, THP-1, HeLa, and SNU-C4 human tumor cells using a variety of assessments, including cell viability (MTS), flow cytometry, anchorage-independent soft agar, and luciferase assays. At 5–10 μM concentrations, rhizochalin was effective as an inhibitor of the malignant transformation of JB6 P⁺ Cl 41 cells or colony formation of human tumor cells, which exerted its action, at least in part, through the induction of p53-dependent apoptosis. Structure–activity relationship study showed aglycon of rhizochalin to be the most active while peracetylated aglycon was the least active among the compounds studied.     

Low resistance and reflective Mg-doped indium oxide-Ag ohmic contacts for flip-chip light-emitting diodes

We have investigated an Mg-doped In/sub x/O/sub y/(MIO)-Ag scheme for the formation of high-quality ohmic contacts to p-type GaN for flip-chip light-emitting diodes (LEDs). The as-deposited sample shows nonlinear current-voltage (I--V) characteristics. However, annealing the contacts at temperatures of 330/spl deg/C-530/spl deg/C for 1 min in air ambient results in linear I--V behaviors, producing specific contact resistances of 10/sup -4/--10/sup -5/ /spl Omega//spl middot/cm/sup 2/. In addition, blue LEDs fabricated with the MIO-Ag contact layers give forward-bias voltages of 3.13-3.15 V at an injection current of 20 mA. It is further shown that LEDs made with the MIO-Ag contact layers give higher output power compared with that with the Ag contact layer. This result strongly indicates that the MIO-Ag can be a promising scheme for the realization of high brightness LEDs for solid-state lighting application.     

The interactions between Si/Co films and GaAs(001) substrates

Interfacial reactions of Si/Co films on (001) oriented GaAs substrate, in the temperature range 300–700°C for 30 min, have been investigated using a combination of x-ray diffraction, Auger electron spectroscopy, and transmission electron microscopy. Cobalt starts to react with GaAs and Si at 380°C by formation of Co₂GaAs, and Co₂Si phases, respectively. At 420°C, the entire layer of Co is consumed, and the layer structure is observed with the sequence Si/CoSi/CoGa(CoAs)/Co₂GaAs/GaAs. Contacts produced in this annealing regime are rectifying and the Schottky barrier heights increase from 0.69 eV(as-deposited state) up to 0.81 eV (420°C). In the subsequent reaction, CoSi grows at the expense of the decompositions of CoGa and CoAs at 460°C. In addition, the ternary phase also is decomposed and only the CoSi phase remains upon the GaAs surface at 600°C. Contacts produced at higher temperature regime (>460°C) have low barriers. The interface between CoSi and GaAs is stable up to 700°C. The results of interfacial reactions can be understood from the calculated Si−Co−Ga−As quaternary phase diagram.     

Project Management Process Maturity (PM)2 Model

This paper presents the project management process maturity (PM)2 model that determines and positions an organization’s relative project management level with other organizations. The comprehensive model follows a systematic approach to establish an organization’s current project management level. Each maturity level consists of major project management characteristics, factors, and processes. The model evolves from functionally driven organizational practices to project driven organization that incorporates continuous project learning. The (PM)2 model provides an orderly, disciplined process to achieve higher levels of project management maturity.     

Span ratios in bridges constructed using a balanced cantilever method

This paper introduces a relation to determine the span ratio between exterior and interior spans, which is required in the preliminary design stage of bridges constructed by balanced cantilever method. On the basis of the numerical results obtained by rigorous time-dependent analyses and by the simple equations introduced in the companion paper, the moment distribution along the spans and its variation with the construction sequence are reviewed, and a recommendation for a rational design is suggested. First, a relation for the initial tendon force is derived on the basis of an assumption that no vertical drift occurs at the far end of a cantilever beam due to the balanced condition between the self-weight and the cantilever tendons. In advance, the determination of an effective span ratio is followed with an assumption that the magnitude of maximum negative moment must be the same as that of the maximum positive moment along all of the spans. Finally, many rigorous time-dependent analyses are conducted to establish the validity of the introduced relations, and this paper shows that an effective span length ratio of the exterior span to the interior span ranges between 0.75 and 0.8.