Characterization of electromagnetic properties for durability performance and saturation in hardened cement mortar

Electromagnetic (EM) properties—dielectric constant and conductivity are changed with porosity and saturation in cement-based materials. In this paper, dielectric constant and conductivity are measured in cement mortar with 5 different mixture conditions considering saturation. For the same mixture proportions, durability tests including porosity, chloride diffusion, air permeability, sorptivity, and water diffusion are performed. Among the continuously measured EM properties within 5–20 GHz of frequency range for different saturation, results under 60% of saturation which shows stable results are selected and averaged as one value. The averaged measurements utilizing results under 60% of saturation are compared with those from durability tests.Through the normalization using the results of W/C 40% which shows best durability performances, changing ratios of durability characteristics are evaluated with normalized dielectric constant and conductivity. The behaviors of EM properties with different saturation and their relationships with durability performances are studied.     

Kinetic and morphological study of a magnesium ethoxide‐based Ziegler–Natta catalyst for propylene polymerization

BACKGROUND: Kinetic and morphological aspects of slurry propylene polymerization using a MgCl₂‐supported Ziegler–Natta catalyst synthesized from a Mg(OEt)₂ precursor are investigated in comparison with a ball‐milled Ziegler–Natta catalyst. RESULTS: The two types of catalyst show completely different polymerization profiles: mild activation and long‐standing activity with good replication of the catalyst particles for the Mg(OEt)₂‐based catalyst, and rapid activation and deactivation with severe fragmentation of the catalyst particles for the ball‐milled catalyst. The observed differences are discussed in relation to spatial distribution of TiCl₄ on the outermost part and inside of the catalyst particles. CONCLUSION: The Mg(OEt)₂‐based Ziegler–Natta catalyst is believed to show highly stable polymerization activity and good replication because of the uniform titanium distribution all over the catalyst particles. Copyright © 2008 Society of Chemical Industry     

Adaptive orthogonal signaling with diversity in a frequency-nonselective Rayleigh fading channel

Power and rate adaptations with diversity are considered for M-ary orthogonal signals in a frequency-nonselective Rayleigh fading channel. We derived the minimum required E~/sub b//N/sub 0/ for a given probability of error, the maximum average data rate, and the outage probability, when maximal-ratio combining is performed with an imperfect channel estimation. We analyzed the effects of channel estimation errors on the required E~/sub b//N/sub 0/ and outage probability, as a function of diversity order and adaptation methods. The relative benefits of rate and power control techniques are further presented in terms of channel estimation error, diversity order, and outage probability. The minimum required E~/sub b//N/sub 0/ with Reed-Solomon codes is also presented for comparison purposes.     

Relaxation-free harmonically mode-locked semiconductor-fiber ringlaser

A 10-Gb/s semiconductor-fiber ring laser is proposed and demonstrated. The performance of a harmonically mode-locked semiconductor-fiber ring laser was described in detail. A long cavity length configuration in semiconductor optical amplifier is found to eliminate the relaxation oscillation, and improved short-term amplitude stability. The laser output has a pulsewidth of 18.4 ps and a spectral width of 0.3 nm     

Sodium ramping in hemodialysis: a study of beneficial and adverse effects

Sodium ramping has been introduced as a technique to decrease side effects occurring during hemodialysis. We studied sodium ramping in 414 dialysis sessions in 23 patients by randomizing 2-week blocks of dialysis to either steady dialysate sodium of 140 mEq/L, linear sodium ramping during dialysis from 155 mEq/L to 140 mEq/ L, or stepwise ramping (sodium of 155 mEq/L for 3 hours and 140 mEq/L for 1 hour). We studied the number and severity of hypotensive and hypertensive episodes. A hypotensive episode was defined as an abrupt decline of systolic blood pressure of more than 50 mm Hg, a decrease in blood pressure accompanied by symptoms requiring intervention, or systolic blood pressure of less than 90 mm Hg even without symptoms. A hypertensive episode was defined as a sudden increase in systolic blood pressure of over 30 mm Hg. We also recorded other side effects (headache, cramps, nausea, vomiting, dizziness, thirst, fatigue, weight gain, and blood pressure) during, immediately after, and between dialysis sessions. There was no major difference between the two ramping protocols, but compared with standard dialysis, both decreased total number of side effects from 4.0 to 3.0 (P = 0.057); the number of hypotensive episodes decreased from 1.3 to 0.7 (P = 0.036). The lowest blood pressure was 114/66 mm Hg during control and 123/69 mm Hg during ramping (P < 0.0001). The frequency of cramps during dialysis decreased from 0.9 to 0.5 (P = 0.006). There was no difference in headache, nausea, or vomiting. The number of hypertensive episodes increased from 0.045 to 0.086 during ramping (P = 0.125). Of 23 patients, only five (22%) had a marked decrease in symptoms; two of the three most symptomatic patients showed no significant improvement. Between dialysis sessions, patients complained of more fatigue and thirst (P < 0.0001 and P = 0.0028, respectively), and interdialytic weight gain following ramping was 5.1% of body weight compared with 4.4% without ramping (P < 0.0001). Blood pressure also increased following ramping, from 143/79 mm Hg to 152/81 mm Hg (P = 0.001). Ramping can decrease the overall number of side effects, but increases interdialytic symptoms, weight gain, and hypertension. In most instances, it simply changes the time the side effects occur. Only 22% of patients have significant benefit. These patients can be identified only through trial and error, as no model of these patients can be created.     

Surface stress‐induced membrane biosensor based on double‐layer stable gold nanostructures for E. coli detection

The surface stress‐based biosensor has been applied in fast and sensitive identification of Escherichia coli (E. coli)with significance for public health, food, and water safety. However, the stable sensitive element of flexible biosensor based on surface stress is still crucial and challengeable. Here, the authors reported surface stress‐induced biosensors based on double‐layer stable gold nanostructures (D‐AuNS‐SSMB) for E. coli O157:H7 detection. Bacterial detection demonstrates the high stability of the biosensor. The resistance change of biosensor is linear to the logarithmic value of the E. coli O157:H7 concentrations ranging from 10³  to 10⁷  CFU/mL with a limit of detection (LOD) of 43 CFU/mL. The captured signals of D‐AuNS‐SSMB comes from surface stress generated by antigen–antibody binding. In addition, the biosensor exhibits good stability, reproducibility and specificity in detection of E. coli O157:H7 as well. This study provides a new preparation method of stable sensitive element for the E. coli detection.Inspec keywords: microorganisms, biosensors, gold, membranes, stress measurement, nanostructured materials, nanosensorsOther keywords: double‐layer stable gold nanostructures, D‐AuNS‐SSMB, bacterial detection, surface stress‐induced membrane biosensor, escherichia coli detection, water safety, stability, E. coli O157:H7 concentration detection, antigen–antibody binding, Au     

聚合物泥浆转变成水泥浆固井技术应用研究

介绍了ＭＣＴ技术波特兰水泥转化法和高炉矿渣化法的室内试验和现场应用试验，经综合分析认为，矿渣转化法有较大的技术优势具有提高固井质量，降低固井成本诸特点，有广泛的应用前景。     

富钒储氢钒镍合金的研制

介绍了采用铝热还原法制备富钒储氢钒镍合金的工艺及其影响因素。产品性能经测试符合用户要求。     

Performance of DS SS system under on-off wideband jamming

A performance analysis of a direct sequence spread spectrum (DS SS) system under a periodic on-off wideband jammer is presented. Closed-form results of system bit error rate (BER) are derived for all possible cases of jammer duty cycle