Maximizing SNR in improper complex noise and applications to CDMA

The optimum linear time-invariant (LTI) filter that maximizes the signal-to-noise ratio (SNR) is, in general, the solution to an integral equation. This is the well-known matched filter. With regards to the detection of bandpass signals, we present the full form of the integral equation using the complex baseband representation of signals. The correct form of the complex integral equation includes, in addition to the autocorrelation function, a pseudoautocorrelation function which vanishes for most applications. However, in the presence of improper complex noise, overlooking the pseudoautocorrelation leads to a “nonoptimal” filter. To illustrate the concept, we apply the theory to a direct-sequence code-division multi-access (DS-CDMA) system in which improper complex noise arises. In the application, we derive the SNR maximizing filter and the nonoptimal filter and compare their near-far resistances     

The dendritic growth of γ′ precipitates and grain

The growth pattern of γ precipitates in the grains and at the grain boundaries has been investigated in a Ni-24Co-4Al-4Ti-5Cr-5Mo (weight percent) alloy of very small lattice misfit between the precipitate and the matrix phases under varying heat-treatment conditions. When aged at temperatures lower than the solvus temperature (T _s = 1150 °C) by more than 30 °C after direct cooling from the solution-treatment temperature, the nucleation density is high. In this condition, the supersaturation is quickly removed because of the overlapping diffusion fields and the precipitates undergo Ostwald ripening from the early stage. The precipitates then have an equilibrium shape of spheres in the grains and truncated spheres at nearly straight grain boundaries. The precipitates at the grain boundaries are coherent with one of the grains, and their number density is not much larger than that in the grains, apparently because of a large contact angle (about 150 deg) with the grain boundary. Quenching the alloy after the solution treatment and aging at any temperature also produce high precipitate number density and equilibrium shapes. When aged at temperatures just belowT _s (above 1140 °C), the nucleation density is low, the precipitates grow dendritically in the grains, and the grain boundaries become serrated. The observed dendritic growth characteristics do not quantitatively agree with the predictions of Mullins and Sekerka theory, but the discrepancy may be due to the uncertainties in both the observed and calculated quantities. By deeply etching the matrix, it is shown that the grain boundary serration is produced by the precipitates growing preferentially in the direction of the incoherent boundary because of the rapid solute diffusion along the grain boundary. The dendritic growth and grain boundary serration can be obtained also by slowly cooling through the temperature range just belowT _s.     

High-temperature polyimide nanofoams for microelectronic applications

Foamed polyimides have been developed in order to obtain thin film dielectric layers with very low dielectric constants for use in microelectronic devices. In these systems the pore sizes are in the nanometer range, thus, the term ‘nanofoam’. The polyimide foams are prepared from block copolymers consisting of thermally stable and thermally labile blocks, the latter being the dispersed phase. Foam formation is effected by thermolysis of the thermally labile block, leaving pores of the size and shape corresponding to the initial copolymer morphology. Nanofoams prepared from a number of polyimides as matrix materials were investigated as well as from a number of thermally labile polymers. The foams were characterized by a variety of experiments including TEM, SAXS, WAXD, DMTA, density measurements, refractive index measurements and dielectric constant measurements. Thin film foams, with high thermal stability and low dielectric constants approaching 2.0, can be prepared using the copolymer/nanofoam approach.     

Integrated modelling under uncertainty in watershed-level assessment and management.

Uncertainty in water quality model predictions is inevitably high due to natural stochasticity, model uncertainty, and parameter uncertainty. An integrated modelling system (modified-BASINS) under uncertainty is described and demonstrated for use in receiving-water quality prediction and watershed management. A Monte Carlo simulation was used to investigate the effect of various uncertainty types on output prediction. Without pollution control measures in the watershed, the concentrations of total nitrogen (T-N) and total phosphorus (T-P) in the Hwaong Reservoir, considering three uncertainty types, would be less than about 4.4 and 0.23 mg L(-1), respectively, in 2012, with 90% confidence. The effects of two watershed management practices, wastewater treatment plants (WWTP) and constructed wetlands (WETLAND), were evaluated. The combined scenario (WWTP + WETLAND) was the most effective at improving reservoir water quality, bringing concentrations of T-N and T-P in the Hwaong Reservoir to less than 3.4 and 0.14 mg L(-1), 24 and 41% improvements, respectively, with 90% confidence. Overall, the Monte Carlo simulation in the integrated modelling system was practical for estimating uncertainty and reliable in water quality prediction. The approach described here may allow decisions to be made based on the probability and level of risk, and its application is recommended.     

The GNAQ T96S Mutation Affects Cell Signaling and Enhances the Oncogenic Properties of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC), the most common malignant tumor in the liver, grows and metastasizes rapidly. Despite advances in treatment modalities, the five-year survival rate of HCC remains less than 30%. We sought genetic mutations that may affect the oncogenic properties of HCC, using The Cancer Genome Atlas (TCGA) data analysis. We found that the GNAQ T96S mutation (threonine 96 to serine alteration of the Gαq protein) was present in 12 out of 373 HCC patients (3.2%). To examine the effect of the GNAQ T96S mutation on HCC, we transfected the SK-Hep-1 cell line with the wild-type or the mutant GNAQ T96S expression vector. Transfection with the wild-type GNAQ expression vector enhanced anchorage-independent growth, migration, and the MAPK pathways in the SK-Hep-1 cells compared to control vector transfection. Moreover, cell proliferation, anchorage-independent growth, migration, and the MAPK pathways were further enhanced in the SK-Hep-1 cells transfected with the GNAQ T96S expression vector compared to the wild-type GNAQ-transfected cells. In silico structural analysis shows that the substitution of the GNAQ amino acid threonine 96 with a serine may destabilize the interaction between the regulator of G protein signaling (RGS) protein and GNAQ. This may reduce the inhibitory effect of RGS on GNAQ signaling, enhancing the GNAQ signaling pathway. Single nucleotide polymorphism (SNP) genotyping analysis for Korean HCC patients shows that the GNAQ T96S mutation was found in only one of the 456 patients (0.22%). Our data suggest that the GNAQ T96S hotspot mutation may play an oncogenic role in HCC by potentiating the GNAQ signal transduction pathway.     

Biocompatibility of surface treated pure titanium and titanium alloy by<Emphasis Type="Italic">in vivo</Emphasis> and<Emphasis Type="Italic">in vitro</Emphasis> test

In the present study, commercial pure Ti and Ti-6Al-4V alloy specimens with and without alkali and heat treatments were implanted in the abdominal connective tissue of mice. Conventional stainless steel 316L was also implanted for comparison. After three months, their biocompatibility was evaluated byin vitro andin vivo experiments. Surface structural changes of specimens due to the alkali treatment and soaking in Hank’s solution were analyzed by XRD, SEM, XPS and AES. An apatite layer, which accelerates the connection with bone, was formed more easily on the alkali treated specimens than the non-treated specimens. The number of macrophages, which is known to increase as the inflammatory reaction proceeds, was much lower for the alkali and heat treated specimens than for the others. The average thickness of the fibrous capsule formed around the implant was much thinner for the alkali and heat treated specimens than for the others.     

Fabrication of Biodegradable Polyurethane Foam Scaffolds with Customized Shapes and Controlled Mechanical Properties by Gas Foaming Technique

Poly(ε-caprolactone) (PCL)-based polyurethane (PU) foam scaffolds with different mechanical properties are fabricated using a gas foaming technique to use as porous substitutes for ear or bone with cartilage. PCL diol or triol is used as a polyol in PU foam for biocompatibility and biodegradation, with an aqueous gelatin solution as a blowing agent. The highly porous inner and outer structures of the scaffolds are developed by employing a silicone surfactant and sulfuric acid, respectively. The PU scaffolds prepared by PCL diol show ductile and flexible properties, whereas the PU scaffolds prepared by PCL triol exhibit high compression strength. In vitro test reveals the low toxicity of the PU scaffolds and the high ALP activity of MC3T3-E1 cells in the PU scaffold prepared by PCL triol. By taking advantage of the difference in mechanical properties, customized PU scaffolds with ear or bone shapes are fabricated using a silicone mold. The PU scaffolds with two compartments of PCL diol and triol (corresponding to cartilage and bone, respectively) are fabricated as a substitute for bone with cartilage. It is believed that the PU scaffolds with highly porous structure and controlled mechanical properties have wide potential application for tissue engineering.     

An Incremental Roll Forming Process for Manufacturing Doubly Curved Sheets from General Quadrilateral Sheet Blanks with Enhanced Process Features

In order to manufacture a doubly curved sheet metal effectively, a flexible incremental roll forming process has been developed by adopting the advantages of the incremental forming process and the roll forming process by combining inherent flexibility of the incremental forming process and continuous deformation of the roll forming process. In the proposed roll forming system, a newly designed gripper system is attached in order to achieve automation and more precision manufacturing of the required sheet intended double curvature. The forming method has been further enhanced to form general quadrilateral blanks (including a square, a rectangle, a symmetrical trapezoid and an asymmetrical trapezoid, etc.) into doubly curved shapes by controlling the forming schedule developed by various experiments.