Low-cost, high-efficiency, and high-speed SiGe phototransistors in commercial BiCMOS

We present a new approach to obtain low-cost and high-performance SiGe phototransistors in a commercial BiCMOS process. Photoresponsivity of 2.7 A/W was obtained for 850-nm detection due to the transistor gain, corresponding to 393% quantum efficiency. Responsivities of 0.13 A/W and 0.07mA/W were achieved for 1060 and 1310 nm with SiGe absorption. With V/sub ce/=2 V, we measure a -3-dB bandwidth of up to 5.3 GHz for phototransistors with a 4-/spl mu/m/sup 2/ active area and 2.0 GHz for phototransistors with 60-/spl mu/m/sup 2/ active area and finger contacts. This high-efficiency and high-speed phototransistor is an enabling device for monolithic receiver integration.     

Materials science and metallurgy of the Caribbean steel drum Part I Fabrication, deformation phenomena and acoustic fundamentals

Steel-drum fabrication, especially the sinking of the drum head (also referred to as the pan) by hand with a hammer, has been examined in detail utilizing light metallography (LM) and transmission electron microscopy (TEM) to characterize residual microstructures corresponding to reductions in thickness of up to 50 % at the bottom of the drum head. Dislocation densities in the low-carbon (0.01–0.05 wt % C), ferritic steels can exceed 10¹⁰ cm^-2. Simulations of simple, ideal, free circular notes utilizing 316 stainless-steel plates (0.05 wt % C), cold rolled to reductions up to 40%, revealed that deformation (per cent cold reduction) has an important effect on the acoustic spectrum, especially harmonic spectra. Harmonic-node splitting was observed for thin circular plates (0.076 cm thick); the frequency difference was 60 Hz at 20% cold reduction and 160 Hz at 40% cold reduction. These dispersion effects, due to deformation-induced microstructures, as well as irregularities in the note geometries and thicknesses, point to the complex and non-linear acoustic features that contribute to the unique sounds of the Caribbean steel drum.     

RFID privacy: an overview of problems and proposed solutions

As organizations aggressively deploy radio frequency identification systems, activists are increasingly concerned about RFID's potential to invade user privacy. This overview highlights potential threats and how they might be addressed using both technology and public policy.     

Analysis of intrachip electrical and optical fanout

We examine the benefits of electrical isolation in intrachip optical signaling. We calculate the delay and energy metrics of an optical interconnect with fanout driving an electrical load. By examining fanout and including load drivers into delay equations, we make a shift from the general trend of looking at optical interconnects as a replacement for long parasitic wires. Our calculations show that optical fanout provides a large improvement in an Etau2 (energy delay squared) metric and improves performance even at very short intrachip distances. The break-even length corresponds to the wiring length of 250 minimum-size inverters that are compactly laid out. These results provide a compelling reason to further examine the implementation of optical interconnects.     

Dietary sitostanol and campestanol: Accumulation in the blood of humans with sitosterolemia and xanthomatosis and in rat tissues

Dietary sitostanol has a hypocholesterolemic effect because it decreases the absorption of cholesterol. However, its effects on the sitostanol concentrations in the blood and tissues are relatively unknown, especially in patients with sitosterolemia and xanthomatosis. These patients hyperabsorb all sterols and fail to excrete ingested sitosterol and other plant sterols as normal people do. The goal of the present study was to examine the absorbability of dietary sitostanol in humans and animals and its potential long-term effect. Two patients with sitosterolemia were fed the margarine Benecol (McNeill Nutritionals, Ft. Washington, PA), which is enriched in sitostanol and campestanol, for 7–18 wk. Their plasma cholesterol levels decreased from 180 to 167 mg/dL and 153 to 113 mg/dL, respectively. Campesterol and sitosterol also decreased. However, their plasma sitostanol levels increased from 1.6 to 10.1 mg/dL and from 2.8 to 7.9 mg/dL, respectively. Plasma campestanol also increased. After Benecol withdrawal, the decline in plasma of both sitostanol and campestanol was very sluggish. In an animal study, two groups of rats were fed high-cholesterol diets with and without sitostanol for 4 wk. As expected, plasma and liver cholesterol levels decreased 18 and 53%, respectively. The sitostanol in plasma increased fourfold, and sitostanol increased threefold in skeletal muscle and twofold in heart muscle. Campestanol also increased significantly in both plasma and tissues. Our data indicate that dietary sitostanol and campestanol are absorbed by patients with sitosterolemia and xanthomatosis and also by rats. The absorbed plant stanols were deposited in rat tissues. Once absorbed by sitosterolemic patients, the prolonged retention of sitostanol and campestanol in plasma might increase their atherogenic potential.     

Study of the pH dependence of diffraction efficiency of phase holograms in dye sensitized dichromated gelatin

Dichromated gelatin is thought to be a good substitute for photographic emulsions in some uses. The results of a systematic study of the effect of the pH of the developer on the diffraction efficiency of volume holographic gratings recorded in dye sensitized dichromated gelatin are presented.     

Statistical Delay Fault Coverage Estimation for Synchronous Sequential Circuits

We present a technique to statistically estimate path-delay fault coverage for synchronous sequential circuits. We perform fault-free simulation using a multivalue algebra and accumulate signal transition statistics, from which we calculate controllabilities of all signals and sensitization probabilities for all gates and flip-flops. We use a rated clock testing model where all time frames operate at the rated clock. We obtain path observabilities either by enumerating paths in the all-paths method, or by a nonenumerative method considering only the longest paths. The path-delay fault detectability is the product of observabilities of signals on paths from primary inputs (PIs) or pseudo-primary inputs (PPIs) to primary outputs (POs) or pseudo-primary outputs (PPOs), and the controllability on the corresponding PI or PPI. We use the optimistic update rule of Bose et al. for updating latches during logic simulation. When compared with exact fault simulation, the average absolute deviation in our statistical fault coverage estimation technique is 1.23% and the very worst absolute deviation was 6.59%. On average, our method accelerates delay fault coverage computation four times over an exact path delay fault simulator.     

Jarosite characteristics and its utilisation potentials

During metallic zinc extraction from zinc sulphide or sulphide ore, huge quantity of jarosite is being released universally as solid residues. The jarosite mainly contains iron, sulphur, zinc, calcium, lead, cadmium and aluminium. Jarosite released from such industrial process is complex and its quality and quantity make the task more complex for safe disposal. Apart from water contamination, jarosite already accumulated and its increasing annual production is a major source of pollution for surrounding environment including soil, vegetation and aquatic life and hence its disposal leads to major concern because of the stringent environmental protection regulations. An attempt was made to evaluate the characteristics of Indian jarosite with an objectives to understand its potentials for recycling and utilising as raw materials for developing value added products. Sand and Coal Combustion Residues (CCRs) was used as an admixture to attain good workability and detoxify the toxic substance in the jarosite. Result revealed that jarosite is silty clay loam in texture having 63.48% silt sized and 32.35% clay sized particles. The particle size of jarosite (D90=16.21+/-0.20 microm) is finer than the CCRs (D90=19.72+/-0.18 microm). The jarosite is nonuniform in structure and shape as compared to the CCRs having spherical, hollow shaped and some of them are cenosphere in nature. The major mineral phase of jarosite is Potassium Iron Sulphate Hydroxide {KFe3(SO4)2(OH)6}and Iron Sulphate Hydrate {2 Fe2O3SO3 x 5 H2O}. In CCRs the dominant phases are quartz {SiO2}, mullite {3 Al2O3 x 2 SiO2} and hematite {Fe2O3}. The high electrical conductivity of jarosite (13.26+/-0.437 dS/m) indicates that the presence of cations and anions are predominant over CCRs (0.498+/-0.007 dS/m). The major portion of jarosite consists of iron (23.66+/-0.18%), sulphur (12.23+/-0.2%) and zinc (8.243+/-0.075%). But CCRs main constituents are silicon (27.41+/-0.74%), aluminium (15.167+/-0.376%) and iron (4.447+/-0.69%). The other constituents such as calcium, aluminium, silicon, lead, and manganese are also present in the range of 0.5 to 5%. Heavy metals such as copper, chromium, and cadmium are found higher in jarosite as compared to the CCRs. The statistically designed experimental trials revealed that the density, water absorption capacity and compressive strength of fired jarosite bricks are 1.51 gm/cm3, 17.46% and 43.4 kg/cm2 respectively with jarosite sand mixture in the ratio of 3:1 indicating the potentials in developing building materials.