Facile fabrication of mesoporous TiO2 electrodes for dye solar cells: chemical modification and repetitive coating

A chemical dispersing technique for preparing a coating paste of TiO₂ nanoparticles is disclosed to fabricate mesoporous electrodes for dye-sensitized TiO₂ solar cells. The suspension of TiO₂ (P-25) powder was stirred in aqueous nitric acid at 80°C, and then evaporated to dryness, giving the nitric acid-adsorbed P-25 powder. The coating paste was obtained by mixing the nitric acid-adsorbed P-25 with PEG (M_w 20,000) as a porosity-controlling agent and cellulosic polymer as a thickener. The mesoporous TiO₂ films were fabricated on conducting glasses by repetitive coating and calcined at 500°C (30 min). The TiO₂ film obtained by the five times repetitive coating (20 μm thickness) resulted in the 1.4 times higher energy conversion efficiency of the dye-sensitized solar cells than that of the one time coating TiO₂ film (V_oc=690 mV, J_sc=12.2 mA/cm², the fill FACTOR=0.71 and η=6.0%).     

低吸附耐高矿化度滑溜水体系研制与现场应用

为降低压裂用滑溜水对储层的吸附伤害和实现产出水直接配制,提高回收再利用率,基于耐高矿化度、低吸附的要求,通过引入极性阳离子片段设计并制备了一种高耐盐低吸附降阻剂NY,将NY与助排剂、黏土稳定剂等添加剂复配得到滑溜水体系,对滑溜水配方进行了优化,评价了滑溜水的综合性能,并在四川盆地页岩区块进行了现场应用。结果表明,降阻剂NY的耐盐降阻性能良好,在高矿化度(≤300 g/L)下的降阻率大于70%,并与各添加剂的配伍性良好。滑溜水的耐盐降阻性能良好,在矿化度为0～300 g/L的条件下,滑溜水体系的起黏时间均小于60 s,表观黏度为1～3 mPa·s,表面张力均小于30 mN/m,防膨率均大于80%,页岩吸附量≤3.66 mg/g,各项指标均满足行业标准与现场压裂需求。现场实施8口井,施工成功率100%,产出水重复利用率100%。与普通耐盐滑溜水相比,该滑溜水吸附性和对储层的伤害低,液体综合成本降低17%,单井产量提升44%,现场应用效果显著。图4表7参21     

Synthesis of optical quality ZnO nanowires utilizing ultrasonic spray pyrolysis

ZnO nanowires were grown by an ultrasonic spray pyrolysis technique. The aspect ratio and size of the wire were dependent mainly on the pH value of a precursor solution and the growth temperature. By high-resolution transmission electron microscopic analysis and photoluminescence measurements, it was confirmed that the nanowires are monocrystalline with good optical quality.     

Self-flux synthesis and photoluminescent properties of LiAl5O8

Pure-phase LiAl₅O₈ was selected as an oxide ceramic red phosphor material without dopants (color centers) and was synthesized using a self-flux method. The LiAl₅O₈ was formed by heating a powder mixture consisting of γ-Al₂O₃:Li₂SO₄ = 1:2 (molar ratio) at over 1100 °C for 1 h. Photoluminescence (PL) properties for the synthesized LiAl₅O₈ were investigated. The maximum intensity of the excitation spectrum for the photoluminescent emission of LiAl₅O₈ synthesized was at 274 nm. The peak intensity of the emission spectrum was at a wavelength of 667 nm (red color). The intensity of the peak emission spectrum increased with the heating temperature, i.e., the maximum peak intensity of the red emission spectrum was detected for the LiAl₅O₈ synthesized by heating at 1500 °C for 1 h.     

Standardized evaluation of chemical compositions of LiTaO3 single crystals for SAW devices using the LFB ultrasonic material characterization system

The line-focus-beam ultrasonic material characterization (LIFB-UMC) system is applied to compare and evaluate tolerances provided independently for the Curie temperature T/sub C/ and lattice constant /spl alpha/ to evaluate commercial LiTaO/sub 3/ single crystals by measuring the Rayleigh-type leaky surface acoustic wave (LSAW) velocities V/sub LSAW/. The relationships between VLSAW, and T/sub C/ and /spl alpha/ measured by individual manufacturers were obtained experimentally using 42/spl deg/YX-LiTaO/sub 3/ wafers as specimens from three crystal manufacturers. In addition, the relationship between VLSAW and SH-type SAW velocities V/sub SAW/ that are actually used for the SAW device wafers was obtained through calculations, using the chemical composition dependences of the acoustical physical constants for LiTaO/sub 3/ crystals reported previously. The result of a comparison between the T/sub C/ tolerance of /spl plusmn/3/spl deg/C and the /spl alpha/ tolerance of /spl plusmn/0.00002 nm through the common scale of VLSAW or VSAW demonstrated that the /spl alpha/ tolerance is 1.6 times larger than the T/sub C/ tolerance. Furthermore, we performed a standardized comparison of statistical data of T/sub C/ and /spl alpha/ for LiTaO/sub 3/ crystals grown by two manufacturers during 1999 and 2000, using VLSAW. The results clarified the differences of the average chemical compositions and of the chemical composition distributions among the crystal ingots between the two manufacturers. A guideline for the standardized evaluation procedure has been established for the SAW-device wafer specifications by the LFB-UMC system.     

An investigation of the pH-activity relationships of Cex, a family 10 xylanase from Cellulomonas fimi: xylan inhibition and the influence of nitro-substituted aryl-beta-D-xylobiosides on xylanase activity

The kinetic parameters of Cex, a family 10 xylanase from Cellulomonas fimi, were determined at various pH levels using soluble birchwood xylan (BWX) as a natural polymeric substrate along with three other synthetic aryl-beta-D-xylobioside substrates. Using BWX, a high level of substrate inhibition was observed which increased with decreasing pH. In contrast, typical Michaelis-Menten-type profiles were obtained using the three aryl-beta-D-xylobiosides as substrates. The k(cat) values determined using o-nitrophenyl-beta-D-xylobioside did not change as the pH increased, whereas the k(cat) values obtained with BWX, phenyl-beta-D-xylobioside and p-nitrophenyl-beta-D-xylobioside decreased, suggesting that the presence of an ortho nitro group affects the activity displayed by Cex. These differences were not observed with XynB from Clostridium stercorarium F9, a member of the same family of xylanases as Cex. These results indicate that a careful evaluation is required when employing substituted aryl-beta-D-xylobiosides in the characterization of xylanases.     

Interactive segmentation of the cerebral lobes with fuzzy inference in 3T MR images.

Measurement of volume and surface area of the frontal, parietal, temporal and occipital lobes from magnetic resonance (MR) images shows promise as a method for use in diagnosis of dementia. This article presents a novel computer-aided system for automatically segmenting the cerebral lobes from 3T human brain MR images. Until now, the anatomical definition of cerebral lobes on the cerebral cortex is somewhat vague for use in automatic delineation of boundary lines, and there is no definition of cerebral lobes in the interior of the cerebrum. Therefore, we have developed a new method for defining cerebral lobes on the cerebral cortex and in the interior of the cerebrum. The proposed method determines the boundaries between the lobes by deforming initial surfaces. The initial surfaces are automatically determined based on user-given landmarks. They are smoothed and deformed so that the deforming boundaries run along the hourglass portion of the three-dimensional shape of the cerebrum with fuzzy rule-based active contour and surface models. The cerebrum is divided into the cerebral lobes according to the boundaries determined using this method. The reproducibility of our system with a given subject was assessed by examining the variability of volume and surface area in three healthy subjects, with measurements performed by three beginners and one expert user. The experimental results show that our system segments the cerebral lobes with high reproducibility.     

c-axis Superfluid Response and Quasiparticle Conductivity in Bi2Sr2CaCu2O8+δ and Bi2Sr2CuO6+δ

Josephson plasma resonance for underdoped Bi ₂ Sr ₂ CaCu ₂ O ₈₊ and Bi ₂ Sr ₂ CuO ₆₊ have been measured by sweeping the microwave, frequency continuously. The resonance enables us to determine the superfluid density and quasiparticle conductivity in the c-axis accurately. We show that the. superfluid response and the low energy excitations out of the condensate in the c-axis of these materials are very different from those in the ordinary Josephson multilayer tunnel junctions. The Josephson coupling energy in single layer Bi ₂ Sr ₂ CuO ₆₊ is more than 5000 times smaller than is predicted in interlayer tunneling model.     

Space charge behavior in polymer film based on increment of capacitance under AC high field

Polymer materials have excellent dielectric and insulation properties; however, those properties in AC high field region have not been known well. Recently we established an evaluation method of high‐field AC dissipation current waveform of polymer materials 1 . AC dissipation current waveforms of polyethylene and polypropylene films show nonlinear distortion in AC high‐field region. This nonlinearity was thought to be related to the behavior of AC space charge formation in the sample near electrodes. The properties of space charge formed under AC high field at power frequency seem to differ from those formed under DC high field. The measurement of AC space charge distribution is not so easy due to the resolution limit of the space charge measurement. We studied the dielectric properties of biaxially oriented polypropylene (BOPP) film under AC high field up to 120 °C. It was found that tan δ, AC dissipation current (Ixr), and unbalanced component of capacitive current (ΔIxc) increased when the temperature became higher. In particular, ΔIxc increased above some threshold field and was considered to be due to the AC space charge formation. This AC space charge layer near electrode is thought to be formed due to carrier injection under AC high‐field application. Usually, the carrier mobility becomes smaller on lowering the temperature. Most of the carriers injected from the electrode are trapped near the electrode in the sample film. But in the high‐temperature region, the carrier mobility becomes larger and the carrier injection starts to increase from lower field. Many more carriers are injected from the electrode. It is thought that some of the injected carriers are trapped inside the sample film; the others go through the sample to the opposite side. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(2): 8–16, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10018     

Chemorheology of an epoxy resin for pultrusion

The Williams-Landel-Ferry (W-L-F) equation was shown to describe the temperature dependence of the viscosity of a sulfonium accelerated, amine cured epoxy resin that had been formulated for pultrusion. The reference temperature and the viscosity at the reference temperature of the W-L-F equation were found to be simple functions of the resin advancement as determined by isothermal differential scanning calorimetry, A method is described of constructing the baseline for temperature-programmed differential scanning calorimetry analyses in which the heat capacity is changing due to reaction.