An efficient,heterogeneous, reusable atom transfer radical polymerization catalyst

Melamine based porous polymer (MPP) was prepared as a template solid to incorporate Cu(I) cations into the framework through chelating with nitrogen groups of the melamine. The copper integrated porous material (Cu(I)@MPP) was used as a heterogeneous catalyst and displayed high activity in copper catalyzed atom transfer radical polymerization of methyl methacrylate. The characterization of the Cu(I)@MPP was performed using nitrogen adsorption experiments and wide‐angle X‐ray and Fourier transform infrared spectroscopies. The atomic absorption spectroscopy measurements confirmed that the catalyst is practically non‐leaching and Cu(I) was found to be below 20 ppb after each atom transfer radical polymerization. Moreover, the catalyst showed reusability without any significant change in its activity. © 2017 Society of Chemical Industry     

Electrochemical hydrogen storage characteristics of Mg1.5Al0.5−xZrxNi (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) alloys synthesized by mechanical alloying

Mg_1.5Al_0.5−xZr_xNi (x = 0, 0.1, 0.2, 0.3, 0.4, 0.5) type alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. X-ray diffraction studies showed that Zr facilitated the amorphization of Mg₂Ni phase, while Al retarded the amorphization of this phase. The increase in the Zr content was observed to bring about significant improvement in the discharge capacities at all the ball milling durations. The stepwise replacement of Al with Zr, however, caused considerable reduction in the initial discharge capacities of the alloys. Despite the adverse effect of Al on the initial discharge capacity, it prevented the rapid degradation of Mg₂Ni phase with the charge/discharge cycles. When the beneficial effects of Zr and Al were combined by designing Mg_1.5Al_0.5−xZr_xNi type alloys, Mg_1.5Al_0.2Zr_0.3Ni alloy was found to have the highest discharge capacity at almost all the charge/discharge cycle steps. Among the obtained capacity retaining rates, Mg_1.5Al_0.4Zr_0.1Ni alloy had the best performance. This alloy has kept at least 50% of its initial discharge capacity at 20th cycle. The analysis by the electrochemical impedance spectroscopy revealed that the charge transfer resistances of Al-rich alloys were low at high depth of discharges. This observation was attributed to the formation of the porous unstable Mg(OH)₂ layer due to the intercalation of Al₂O₃ layers, which have the high rate of solubility in strongly basic solutions, and thus the exposition of the underlying electrocatalytically active Ni sites.     

Robust Region-of-Attraction Estimation

We propose a method to compute invariant subsets of the region-of-attraction for asymptotically stable equilibrium points of polynomial dynamical systems with bounded parametric uncertainty. Parameter-independent Lyapunov functions are used to characterize invariant subsets of the robust region-of-attraction. A branch-and-bound type refinement procedure reduces the conservatism. We demonstrate the method on an example from the literature and uncertain controlled short-period aircraft dynamics.      

Factors Affecting International Construction

A construction company’s decision to expand into international markets must be based on a good understanding of the opportunities and threats associated with international business, as well as the development of company strengths relative to international activities. These factors were evaluated in this study by surveying the executives in charge of international construction of large United States based contractors. The information was collected by means of two rounds of a Delphi survey, the results of which were used as input in an analytic hierarchy process (AHP). The findings indicate that track record, specialist expertise, project management capability are the most important company strengths; loss of key personnel, shortage of financial resources, and inflation and currency fluctuations are the most important threats relative to international markets; and increased long term profitability, the ability to maintain shareholders’ returns, and the globalization and openness of the markets are the most important opportunities available in international works. This study is of relevance to practitioners as it systematically highlights the factors that affect international construction for the benefit of executives of medium-to-large size construction companies who are considering expanding into overseas markets. It is of relevance to researchers too as it demonstrates the successful use of the combined Delphi and AHP.     

Importance of early dialysis for acute renal failure after an open-heart surgery

Coronary artery disease is a major cause of death in patients with a renal dysfunction. Among the patients who undergo coronary artery bypass grafting, renal dysfunction is known to be a major predictor of in-hospital and out-of-hospital mortality. From 2004 to 2007, we performed elective open-heart surgeries on 2380 patients in whom there was no primary renal failure. Of those patients, only 185 in whom acute renal failure (ARF) was developed were included in the study. The patients were divided into 2 groups: a late dialysis group (n=90) and an early dialysis group (n=95). The mean age of the patients was 62.3±6.4 in the late dialysis group and 64.5±5.2 in the early dialysis group. There were 32 female and 58 male patients in the late dialysis group and 36 female and 59 male patients in the early dialysis group. Acute renal failure developed only in 185 patients out of 2380 open-heart surgery patients. The overall mortality in the 2380 open-heart surgery patients was 1.97%. Mortality among the ARF patients was 5.9%. However, there was no significant difference in hospital mortality between the 2 groups. Major complications, such as postoperative pneumonia, prolonged ventilation time, arrhythmia, the number of times postoperative hemodialysis was performed, development of chronic renal failure, time spent in the intensive care unit and the period of hospitalization, sepsis, and low cardiac output, were significantly higher in the late dialysis group. There was no difference in mortality between the 2 groups. Early dialysis for open-heart surgery patients who develop ARF postoperatively does not decrease mortality. However, it decreases morbidity, the amount of time spent in intensive care, and the period of hospitalization and thus reduces patient costs.     

Liquefaction of municipal waste plastics in VGO over acidic and non-acidic catalysts

Co-processing of municipal waste plastics (MWP) with vacuum gas oil (VGO) over HZSM-5, DHC-8 (commercial silica-alumina catalyst) and cobalt loaded active carbon catalyst has been comparatively studied. Co-processing experiments were carried out under hydrogen atmosphere at temperatures between 425 and 450 °C. The composition, sulphur and chlorine amount of liquid products were determined. The product distribution and the composition of liquids were changed depending upon the temperature and the catalyst type. As expected temperature led to increase in cracking activity of catalysts. DHC-8 and HZSM-5 showed substantially different activities in co-processing due to the difference in their acidity. HZSM-5 gave highest gas yield at all temperatures and highest liquid yield (38.3) at low temperature. Although Co-AC was a neutral catalyst, it showed the cracking activity as well as HZSM-5 and more than DHC-8. No chlorine compound was observed in liquid products. The sulphur amount in liquid products varied with the catalyst type. Although HZSM-5 showed good cracking activity at low temperatures, it gave the liquid product containing highest sulphur amount. By considering both the quantity and quality of liquid fuel obtained from co-processing, it may be concluded that Co-AC gave the best result in the co-processing of the MWP/VGO blend. To observe the effect of metal type loaded on active carbon on catalyst activity, a series of co-processing experiments was also carried out.     

Sensitivity Analyses and Sensitivity Coefficients of Standardized Daily ASCE-Penman-Monteith Equation

The sensitivity of the standardized ASCE grass-reference Penman-Monteith evapotranspiration (ASCE-PM ETo) equation to climate variables in different regions has not yet been studied. Sensitivity analyses for the standardized daily form of the ASCE-PM equation were conducted on wind speed at 2?m height (U2), maximum and minimum air temperatures (Tmax and Tmin), vapor pressure deficit (VPD), and solar radiation (Rs) in the following regions of the United States: semiarid (Scottsbluff, Nebraska, and Bushland, Texas), a Mediterranean-type climate (Santa Barbara, California), coastal humid (Fort Pierce, Florida), inland humid and semihumid (Rockport, Missouri, and Clay Center, Nebraska), and an island (Twitchell Island, California). The sensitivity coefficients were derived for each variable on a daily basis. In general, ETo was most sensitive to VPD at all locations, while sensitivity of ETo to the same variable showed significant variation from one location to another and at the same location within the year. After VPD, ETo was most sensitive to U2 in semiarid regions (Scottsbluff, Clay Center, and Bushland) during the summer months. The Rs was the dominant driving force of ETo at humid locations (Fort Pierce and Rockport) during the summer months. At Santa Barbara, the sensitivity of ETo to U2 was minimal during the summer months. At Bushland, Scottsbluff, and Twitchell Island, ETo was more sensitive to Tmax than Rs in summer months, whereas it was equally sensitive to Tmax and Rs at Clay Center. The ETo was not sensitive to Tmin at any of the locations. The change in ETo was linearly related to change in climate variables (with r2 ≥ 0.96 in most cases), with the exception of Tmin, at all sites. Increase in ETo with respect to increase in climate variable changed considerably by month. On an annual average, a 1°C increase in Tmax resulted in 0.11, 0.06, 0.16, 0.07, 0.11, 0.08, and 0.10?mm increases in ETo at Scottsbluff, Santa Barbara, Bushland, Fort Pierce, Twitchell Island, Rockport, and Clay Center. A 1?m?s?1 increase in U2 resulted in 0.42, 0.18, 0.37, 0.28, 0.31, 0.20, and 0.26?mm increases in ETo at the same locations. A unit increase in Tmax resulted in the largest increase in ETo at Bushland, and a unit increase in Rs caused the largest increases in ETo at Fort Pierce. A 1?MJ?m?2?d?1 increase in Rs resulted in 0.05, 0.08, 0.06, 0.11, 0.05, 0.06, and 0.06?mm increases in ETo at the same locations. A 0.4?kPa increase in VPD resulted in 1.13, 0.54, 1.29, 0.57, 1.04, 1.10, and 1.22?mm increases in ETo at the same locations. The U2 had the most effect on ETo at Scottsbluff and Bushland, the two locations where dry and strong winds are common during the growing season. The sensitivity coefficient for Rs was higher during the summer months and lower during the winter months, and the opposite was observed for VPD (except for Twitchell Island). The decrease of the sensitivity coefficients for Rs corresponding to an increase in the sensitivity coefficient for VPD is due to a decrease in the energy term in favor of the increase in significance of the aerodynamic term of the standardized ASCE-PM equation in summer versus winter months. Because the ASCE-PM and the Food and Agriculture Organization paper number 56 Penman-Monteith (FAO56-PM) equations are identical when applied on a daily time step, the results of the sensitivity analyses and sensitivity coefficients of this study should be directly applicable to the FAO56-PM equation.     

Removal of lead (II) and nickel (II) ions from aqueous solution using activated carbon prepared from rapeseed oil cake by Na<Subscript>2</Subscript>CO<Subscript>3</Subscript> activation

In this study, rapeseed oil cake as a precursor was used to prepare activated carbons by chemical activation with sodium carbonate (Na₂CO₃) at 600 and 800 °C. The activated carbon with the highest surface area of 850 m² g^?1 was produced at 800 °C. The prepared activated carbons were mainly microporous. The activated carbon having the highest surface area was used as an adsorbent for the removal of lead (II) and nickel (II) ions from aqueous solutions. The effects of pH, contact time, and initial ion concentration on the adsorption capacity of the activated carbon were investigated. The kinetic data of adsorption process were studied using pseudo-first-order, pseudo-second-order kinetic models and intraparticle diffusion model. The experimental data were well adapted to the pseudo-second-order model for both tested ions. The adsorption data for both ions were well correlated with Langmuir isotherm. The maximum monolayer adsorption capacities of the activated carbon for the removal of lead (II) and nickel (II) ions were determined as 129.87 and 133.33 mg g^?1, respectively.     

基于相控外差干涉技术的纳米定位方法的研究

针对工业领域和计量界对定位精度要求的提高,提出了一种基于迈克尔逊干涉仪反向特性的定位控制方法。该方法采用相位锁定控制和外差干涉技术来完成位置测量和控制。在严格控制实验环境条件下,得到了步距值为5 nm的双向步进位移。步距值的不确定度为8×10-9 nm,位移重复性误差小于1 nm。该定位方法的测量尺寸可直接溯源至长度标准,并且采用光电步进相移法可克服压电陶瓷的非线性和蠕变的机械缺陷。该方法在系统环境控制条件下适用于毫米行程位移,可应用于纳米计量和超精密加工等领域。     

Dynamics of Nocturnal, Daytime, and Sum-of-Hourly Evapotranspiration and Other Surface Energy Fluxes over Nonstressed Maize Canopy

The magnitude and driving forces of nocturnal evaporative losses, ETcnight, and the interactions of other surface energy fluxes and microclimatic variables under various climatic, soil, and management conditions are not well understood. Such relationships are important for ecophysiological studies. This research attempts to investigate such relationships. Furthermore, ETcnight can be a sizable portion of the daily total evaporative losses. Most empirical equations, especially ones that use solar or net radiation to estimate daily evapotranspiration (ET), either ignore or poorly treat the contribution of ETcnight to the daily total ET. Neglecting ETcnight can lead to errors in determining the daily or the sum-of-hourly ETc (i.e., ETcSOH) and can also cause cumulative errors when making long-term water balance analyses. In this paper, the magnitudes, trends, and contribution to the nocturnal surface energy balance of various microclimatic variables (air temperature, Ta; vapor pressure deficit, VPD; relative humidity, RH; and wind speed at 3?m, u3) and surface energy fluxes (ETcnight; soil heat flux, G; sensible heat flux, H; and net radiation, Rn); were quantified and interpreted for a nonstressed and subsurface-drip-irrigated maize canopy. The effect of microclimatic variables and surface energy flux components on the Bowen ratio energy balance system (BREBS)-measured ETcnight and daytime evaporative loss, ETcday, were investigated in the growing season of 2005 (i.e., April 22–September 30) and 2006 (May 12–September 27). The nighttime evaporative losses were high early in the season during partial canopy closure because of increased surface soil evaporation and were also high later in the season during and after leaf aging, physiological maturity, and leaf senescence. The seasonal average nighttime evaporative losses for 2005 and 2006 were 0.19 and 0.11??mm/night, respectively. Losses of 0.50?mm or more occurred in 2005 and 2006 on eight and seven nights, respectively. The seasonal total ETcnight, ETcday, and ETcSOH in 2005 were 31, 612, and 642?mm, respectively. The ETc values in 2006 were 16, 533, and 547?mm, respectively. In both years, the percent ratio of ETcday to ETcSOH usually was more than 80–85%. ETcnight was affected primarily by u3, VPD, and Ta. A strong relationship between ETcnight and nighttime sensible heat was observed. Some of the largest ratios of ETcnight to ETcSOH occurred on rainy nights with strong winds. Because of strong winds, the ETcnight was high owing to the clear coupling among all energy exchanges within and above the canopy as a result of the mixing of the lower boundary layer of the microclimate. The results of this study showed that the ETcnight can be up to 5% of the ETcSOH, even for a subsurface-drip-irrigated maize canopy in which the soil surface is usually dry, thus, less evaporative losses potential compared with the surface or sprinkler-irrigated surfaces in which ETcnight would be expected to be considerably higher because of wetter surface conditions. ETcnight needs to be quantified for different vegetation surfaces and management practices, surface wetting, and climatic conditions to better account for nighttime water losses and better understand nighttime energy balance mechanisms.