Brillouin/erbium fiber lasers

Brillouin/erbium fiber lasers (BEFLs) have been recently demonstrated as a novel mode of operation of a fiber laser. In a hybrid Brillouin/erbium fiber laser, the combination of two gain media, the gain from the erbium-doped fiber (EDF) and Brillouin gain in single-mode optical fibers allows a resonator to be constructed which supports a laser comb with ~10 GHz or ~0.1 nm line spacing at room temperature. In this paper, we present a detailed discussion of the operation of BEFLs. Single and multiple wavelength generation is discussed, and modeling of single wavelength operation is described     

Image compression using quadtree partitioned iterated functionsystems

Partitioned iterated function systems have been used to compress images, but in previous work, images have been partitioned into fixed size blocks. The authors present an image compression technique using variable block sizes based on quadtree partitioning. Experimental results show that it can achieve higher compression performance than the fixed-size partitioning technique     

Gouge initiation in high-velocity rocket sled testing

A model is presented which describes the formation of surface damage “gouging” on the rails that guide rocket sleds. An unbalanced sled can randomly cause a very shallow-angle, oblique impact between the sled shoe and the rail. This damage phenomenon has also been observed in high-velocity guns where the projectile is analogous to the moving sled shoe and the gun barrel is analogous to the stationary rail. At sufficiently high velocity, the oblique impact will produce a thin hot layer of soft material on the contact surfaces. Under the action of a normal moving load, the soft layer lends itself to an anti-symmetric deformation and the formation of a “hump” in front of the moving load. A gouge is formed when this hump is overrun by the sled shoe. The phenomenon is simulated numerically using the CTH strong shock physics code, and the results are in good agreement with experimental observation.     

Effects of O2 and N2 Gas Concentration on the Formation of Ho2O3 Gate Oxide on 4H-SiC Substrate

Silicon - In this paper, the impacts of flow concentration of oxynitridation on the structural and electrical performance of a high-κ Ho2O3 dielectric on n-type 4H-SiC were studied. The Ho2O3...     

Interfacial delamination investigation between copper bumps in 3D chip stacking package by using the modified virtual crack closure technique

In this study, the modified virtual crack closure technique (MVCCT) incorporated with the finite element method (FEM) is applied to investigate the delamination behavior between stacked copper bumps in 3D chip stacking packaging at package-level and board-level, and the energy release rate at the delamination front is evaluated as the criterion of the crack expansion. The package-level structure is firstly simulated to validate the dependability of MVCCT, and the results reveal that the delamination between copper bumps within specific size will not induce delamination expansion during thermal cycling condition, which show good agreement with experiment results. The mesh density and the delamination geometry effect analyses are also studied at package-level to ensure the reliable result of finite element analysis. The results show that the former has an insignificant effect on the energy release rate, while the later has a significant influence. Moreover, based on the simulation results at package-level structure, the further delamination behavior at board-level is investigated to predict potential failure mode different from the package-level structure. The results show higher energy release rate is induced and mixed fracture mode occurs.     

Aurones as modulators of ABCG2 and ABCB1: synthesis and structure-activity relationships

The ability of aurones to modulate the efflux activities of ABCG2 and ABCB1 was investigated by quantifying their effects on the accumulation of pheophorbide?A (PhA) in ABCG2-overexpressing MDA-MB-231/R cells and calcein?AM in ABCB1-overexpressing MDCKII/MDR1 cells. Key structural features for interactions at both ABCG2 and ABCB1 are a methoxylated ring?A, an intact exocyclic double bond, and the location of the carbonyl bond on ring?C. Modifications on rings?B and C were less critical and served primarily to moderate activity and selectivity for one or both transporters. These SAR trends were quantified by Free-Wilson analyses and are reflected in a pharmacophore model for PhA accumulation. Several compounds were found to be equipotent with fumitremorgin?C (FTC) in promoting PhA accumulation, and they also demonstrated strong affinities for ABCB1. These compounds were disubstituted on ring?B with methoxy or a combination of methoxy and hydroxy groups. Taken together, our findings highlight the versatility of the aurone template as a lead scaffold for the design of dual-targeting ABCG2 and ABCB1 modulators.     

Band alignment and enhanced breakdown field of simultaneously oxidized and nitrided Zr film on Si

The band alignment of ZrO₂/interfacial layer/Si structure fabricated by simultaneous oxidation and nitridation of sputtered Zr on Si in N₂O at 700°C for different durations has been established by using X-ray photoelectron spectroscopy. Valence band offset of ZrO₂/Si was found to be 4.75 eV, while the highest corresponding conduction offset of ZrO₂/interfacial layer was found to be 3.40 eV; owing to the combination of relatively larger bandgaps, it enhanced electrical breakdown field to 13.6 MV/cm at 10^-6 A/cm².     

Oxidation of sputtered Zr thin film on Si substrate

Oxidation of sputtered Zr thin film on Si substrate has been investigated by varying oxidation times (5–60 min) at 500 °C. Fourier transform infrared spectroscopy indicated the existence of ZrO₂ by showing spectra of Zr–O. Vibration mode of Si–O and Zr–O–Si are also detected for all samples oxidized at different duration. This suggested the existence of SiO _x and Zr _x Si _y O _z compounds and they might be located at interfacial layers (ILs) between ZrO₂ and Si. Cross-sectional image of high resolution transmission electron microscopy taken from 60-min oxidized sample showed that both ZrO₂ and IL thickness is ~3.5 nm. Time-of-flight secondary-ion-mass spectroscopy suggested that Zr _x Si _y O _z may be formed after oxidized for 15 min. The proposed IL is consisted of a mixture of Zr _x Si _y O _z and SiO _x . A physical model has been established to explain the observation. Electrical characterization shows that capacitance–voltage curves have small hysteresis and their flatband voltages are shifted to a negative bias. Effective dielectric constant values of the investigated oxides are in the range of 4.22–5.29. Leakage current density–breakdown voltage characteristic shows that 5-min oxidized sample has the lowest dielectric breakdown voltage if compared with the other samples.     

A Review on Die Attach Materials for SiC-Based High-Temperature Power Devices

Recently, high-temperature power devices have become a popular discussion topic because of their various potential applications in the automotive, down-hole oil and gas industries for well logging, aircraft, space exploration, nuclear environments, and radars. Devices for these applications are fabricated on silicon carbide-based semiconductor material. For these devices to perform effectively, an appropriate die attach material with specific requirements must be selected and employed correctly. This article presents a review of this topic, with a focus on the die attach materials operating at temperatures higher than 623 K (350 °C). Future challenges and prospects related to high-temperature die attach materials also are proposed at the end of this article.