During the last decades, electronic textual information has become the world's largest and most important information source. Daily newspapers, books, scientific and governmental publications, blogs and private messages have grown into a wellspring of endless information and knowledge. Since neither existing nor new information can be read in its entirety, we rely increasingly on computers to extract and visualize meaningful or interesting topics and documents from this huge information reservoir. In this paper, we extend, improve and combine existing individual approaches into an overall framework that supports topologi-cal analysis of high dimensional document point clouds given by the well-known tf-idf document-term weighting method. We show that traditional distance-based approaches fail in very high dimensional spaces, and we describe an improved two-stage method for topology-based projections from the original high dimensional information space to both two dimensional (2-D) and three dimensional (3-D) visualizations. To demonstrate the accuracy and usability of this framework, we compare it to methods introduced recently and apply it to complex document and patent collections.
In this paper, we propose a masked photocathode inside a photoinjector for generating high brightness electron beam. Instead of mounting the photocathode onto an electrode, an electrode with small hole is used as a mask to shield the photocathode from the accelerating vacuum chamber. Using such a masked photocathode will make the replacement of photocathode material easy by rotating the photocathode behind the electrode into the hole. Furthermore, this helps reduce the dark current or secondary electron emission from the photocathode material. The masked photocathode also provides transverse cut-off to a Gaussian laser beam that reduces electron beam emittance growth from nonlinear space-charge effects.
U .1 Presented at the IUPAC Meeting, Tokyo, Japan, September 1 - 11, 1977 LBL-6934 c.1 tAt-90ft ACTIVE SITES FOR HYDROCARBON CATALYSIS ON METAL SURFACES G. A. Somorjai October 18, 1977 Prepared for the U. S. Department of Energy under Contract W-740S-ENG-48 For Reference Not to be taken from this room
The characteristics of new prototype high gain photomultipliers having two microchannel plates in cascade for electron multiplication have been investigated. Measurements are given of the gain, dark current, quantum efficiency, anode pulse linearity, electron transit time, single and multiphotoelectron time spreads, and pulse height resolution of LEP PM137 8/II and PM137 7/I photomultipliers. The gain as a function of transverse magnetic field has been measured and is discussed. Emphasis is put on the determination of optimum photomultiplier operating conditions, particularly with respect to their pulse height resolution capability. Photomultiplier characteristics as a function of input pulse repetition frequency have been also investigated and discussed.
LBNL-42098 ~R~EST BERKELEY ~RLA~Da NA~IO~AL. L.AWFUZP4CE LABn RATa RY CFDSimulationof Infiltration Heat Recovery C.R.Buchananand M.H.Sherman EnvironmentalEnergy TechnologiesDivision July 1998
Two high-purity germanium coaxial detectors, having opposite electrode configurations from one another, but fabricated from the same germanium crystal, were irradiated simultaneously with fast neutrons from an unmoderated 252Cf source. Both detectors were 42 mm diam. The detector having the conventional electrode configuration was about 28 times more sensitive to radiation damage than was the dete...
Two short (4 and 6 day) recording periods at The Geysers geothermal field provided useful data on two large refraction explosions and numerous microearthquakes. The vapor‐dominated reservoir appears to be characterized by regionally anomalous high P‐ and S‐wave velocities and low attenuation, but the anomaly seems to decrease, possibly reversing, with depth. Microearthquakes occur in a diffuse pattern, with no indication of dominant throughgoing faults and an absence of activity in the main production zone. Mechanisms are generally consistent with northeast‐southwest compression. Occurrence rates indicate a slightly high incidence of smaller magnitude shocks. It is possible that the microearthquake activity is related to an expanding steam zone. While the present anomalies appear to delineate the reservoir, it is not certain that they would have been detectable during exploration prior to large‐scale exploitation of the field.
LBNL is using pressurized bladders in its high field superconducting magnet program Magnet RD3; a 14 T race track dipole, has been assembled and pre-stressed using such a system. The bladder, placed between the coil pack and the iron yoke, can provide 70 MPa of pressure while compressing the coil pack and tensioning a 40 mm thick structural aluminum shell. Interference keys replace the bladder's functionality as they are deflated and removed leaving the shell in 140 MPa of tension. During cool down, stress in the shell increases to 250 MPa as a result of the difference in thermal expansion between the aluminum shell and the inner iron yoke. A number of strain gauges mounted onto the shell were used to monitor its strain during assembly, cool-down and testing. This technique ensures that the final and maximum stress in the shell is reached before the magnet is ever energized. The use of a structural shell and pressurized bladders has simplified magnet assembly considerably. In this paper we describe the bladder system and its use in the assembly of a 14 T Nb/sub 3/Sn magnet.
The protonation reactions of two ligands that play important roles in the TALSPEAK process for the separation of trivalent actinides from lanthanides, lactic acid, and diethylenetrinitropentaacetic acid (DTPA), have been studied at variable temperatures. The protonation constants at 10-70 degrees C were determined by titration potentiometry and the protonation enthalpies were determined at 25 degrees C by titration microcalorimetry. The protonation constants remain essentially unchanged (25-70 degrees C) within the experimental uncertainties, indicating that the effect of temperature on the protonation of lactate is insignificant. In contrast, the protonation constants of DTPA (logH's) generally decrease as the temperature is increased. Results from this study indicate that the effect of temperature on the protonation of DTPA could alter the speciation of metal ions (actinides and lanthanides) in the TALSPEAK system, since lower values of logH at higher temperatures suggest that the hydrogen ions would compete less strongly with the metal ions for the complexation of DTPA at higher temperatures.
Upon femtosecond laser irradiation, a bright, broadband photoluminescence is observed from graphene at frequencies well above the excitation frequency. Analyses show that it arises from radiative recombination of a broad distribution of nonequilibrium electrons and holes, generated by rapid scattering between photoexcited carriers within tens of femtoseconds after the optical excitation. Its highly unusual characteristics come from the unique electronic and structural properties of graphene.
We discuss how various aspects of Wilson loops in large-Ngauge theories are studied from the point of view of the AdS-CFT correspondence.
We have discovered what appear to be micrometeorites imbedded in seven late Pleistocene Alaskan mammoth tusks and a Siberian bison skull. The micrometeorites apparently shattered on impact leaving 2 to 5 mm hemispherical debris patterns surrounded by carbonized rings. Multiple impacts are observed on only one side of the tusks and skull consistent with the micrometeorites having come from a single direction. The impact sites are strongly magnetic indicating significant iron content. We analyzed several imbedded micrometeorite fragments from both tusks and skull with laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) and X-ray fluorescence (XRF). These analyses confirm the high iron content and indicate compositions highly enriched in nickel and depleted in titanium, unlike any natural terrestrial sources. In addition, electron microprobe (EMP) analyses of a Fe-Ni sulfide grain (tusk 2) show it contains between 3 and 20 weight percent Ni. Prompt gamma-ray activation analysis (PGAA) of a particle extracted from the bison skull indicates ~;;0.4 mg of iron, in agreement with a micrometeorite ~;;1 mm in diameter. In addition, scanning electron microscope (SEM) images and XRF analyses of the skull show possible entry channels containing Fe-rich material. The majority of tusks (5/7) have a calibrated weighted mean 14C age of 32.9 +- 1.8 ka BP, which coincides with the onset of significant declines <36 ka ago in Beringian bison, horse, brown bear, and mammoth populations, as well as in mammoth genetic diversity. It appears likely that the impacts and population declines are related events, although their precise nature remains to be determined.
The degradation of the critical current of impregnated Rutherford type Nb/sub 3/Sn cables was investigated as a function of the applied transverse load and magnetic field. The cable is made of modified jelly-roll-type strand material and has a keystone angle of 1.0 degrees . The voltage-current characteristics were determined for the magnetic field ranging from 2 to 11 T and transverse pressure up to 250 MPa on the cable surface. It was found that the 48-strand cable, made of strands with six elements in the matrix, showed a larger critical current degradation than the 26-strand cable with 36 elements per strand. The global degradation of the 48-strand cable was 63% at 150 MPa, and 40% at 150 MPa for the 26-strand cable. Microanalysis of the cross-section before and after compression is presented, showing significant permanent damage to the superconducting strands.<>
Lipid impregnated Millipore filter membranes, which model certain permeability characteristics of lipid bilayers, were used to examine the effect of ozone on membrane conductance. It was found that the conductance across a lipid impregnated filter membrane increased progressively upon exposure to a stream of oxygen delivering up to 5 ppm ozone to the aqueous compartment. The extent of this conductance increase depended on duration of ozone treatment (tenfold after 30 min), ozone concentration (linear dependence to at least 5 ppm), the bathing solution pH (the lower the pH is, the higher the conductance), lipid composition (unsaturation required), temperature, and the existence of a membrane barrier between ozone and the assay membrane (no penetration of ozone through a membrane). It was also found that the presence of α-tocopherol, or cholesterol as part of the lipid of the filter membrane diminished the conductance increases. Virtually complete protection occurred at about a 1% mole ratio of α-tocopherol/lecithin. Since saturated lipid impregnated filter membranes are relatively unaffected by ozone, it is concluded that reaction products of unsaturated lipids with ozone are responsible for the observed conductance increases.
FLOW-THROUGH POROUS ELECTRODES J(~mhes •D• Arthur Trainham III thes is) August 1979 TWO-WEEK LOAN copy This is a Library Circulating Copy wh may be borrowed two weeks. For a personal copy, call Tech. fo. Division, Ext. 6782. the Department
An historical review of the development of semiconductor detectors is presented. Detector physics, material requirements, and signal processing are discussed.
Electron clouds have been shown to trigger fast growing instabilities on proton beams circulating in the SPS [1], and a feedback system to control the instabilities is under active development [2]. We present the latest improvements to the Warp-Posinst simulation framework and feedback model, and its application to the self-consistent simulations of two consecutive bunches interacting with an electron cloud in the SPS.
The scintillation properties of cerium-doped oxyhalides following the general formula REOX (RE=Y, La, Gd, and Lu; X=F, Cl, Br, and I) are reported. These materials were synthesized under dry conditions as microcrystalline powders from conventional solid state reactions. The room temperature X-ray excited emission and scintillation decay curves were measured and analyzed for each material. Additionally, the hygroscopic nature of the oxychlorides and oxybromides was compared to that of their corresponding rare earth halides. The yttrium, lanthanum, and gadolinium oxychlorides, and all of the oxybromides and oxyiodides are found to be activated by Ce3+. GdOBr doped with 0.5% Ce3+ has the highest light output with a relative luminosity of about one-half that of LaBr3: Ce3+. It displays a single exponential decay of 30 ns.
In the push towards commercialization of extreme-ultraviolet lithography (EUVL), meeting the stringent requirements for line-edge roughness (LER) is increasingly challenging. For the 22-nm half-pitch node and below, the ITRS requires under 1.2 nm LER. Much of this LER is thought to arise from three significant contributors: LER on the mask absorber pattern, LER from the resist, and LER from mask roughness induced speckle. The physical mechanism behind the last contributor is becoming clearer, but how it is affected by the presence of aberrations is less well understood. Here, we conduct a full 2D aerial image simulation analysis of aberrations sensitivities of mask roughness induced LER for the first 37 fringe zernikes. These results serve as a guideline for future LER aberrations control. In examining how to mitigate mask roughness induced LER, we next consider an alternate illumination scheme whereby a traditional dipole's angular spectrum is extended in the direction parallel to the line-and-space mask absorber pattern to represent a 'strip'. While this illumination surprisingly provides merely minimal improvement to the LER as several alternate illumination schemes, overall imaging quality in terms of ILS, NILS, and contrast is improved. While the 22-nm half-pitch node can tolerate significant aberrations from a maskmore » roughness induced LER perspective, total aberration levels for the 16-nm half-pitch node need to be strictly capped at 0.25nm rms to meet the ITRS guidelines. An individual aberrations study for the first 37 fringe zernikes on the 16-nm half-pitch node at the 0.25nm rms level reveals a sensitivity to various forms of spherical aberrations (Z9 & Z25) and quadrafoil (Z28) in particular, under conventional crosspole illumination ({sigma} = 0.10). Compared to conventional dipole or crosspole illuminations, an extended dipole 'strip' illumination scheme offers a way to mitigate mask roughness induced LER, while still maintaining high imaging quality for critical mask levels at the 16-nm half-pitch node.« less
