Application of the response surface methodology for optimizing the adsorptive removal of chromate using a magnetic crosslinked chitosan nanocomposite

Experimental design was used to optimize the adsorptive removal of chromate using a synthesized crosslinked chitosan with a magnetic NiFe₂O₄ core. In this regard, the response surface methodology which is based on central composite design, was used to determine the relation between the parameters influencing the adsorption efficiency. The statistical parameters of the resulting model were R² = 0.9922, and F-value = 164.48. As a final step, a nonlinear optimization was performed and the respective optimal values for pH, amount of the adsorbent, initial concentration of the pollutant, and contact time were determined as 4, 0.8 g L⁻¹, 150 ppm, and 25 min, and the predicted removal efficiency at a 95% confidence level was determined as 100.8 ± 1.8%, which was in good agreement with the experimental value (i.e., 95.5 ± 5.7%). © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47077.     

Experimental Study of CMC Evaluation in Single and Mixed Surfactant Systems, Using the UV–Vis Spectroscopic Method

In this study, the critical micellar concentration (CMC) of anionic, cationic and nonionic surfactants was determined using the UV–Vis spectroscopic method. Sodium lauryl sulfate (SDS) as anionic, hexadecyl-trimethyl-ammonium bromide as cationic, tert-octylphenol ethoxylates TOPEON (with N = 9.5, 7.5 and 35) and lauryl alcohol ethoxylate (23EO) as nonionic surfactants have been used. Concentration of surfactants varies both from below and above the CMC value in the pyrene solution. In addition, the amount of the CMC was determined using the values from the data obtained from the graph of absorbance versus concentration of surfactants. A comparative study was conducted between the results of the present study and the literature which shows a good agreement, in particular for TOPEO9.5 and LAEO23. Furthermore, the CMC value of SDS (as an ionic surfactant) in the presence of nonionic surfactants was also examined. The result reveals that with addition of small amount of nonionic surfactant to the anionic SDS surfactant, a decline in the CMC value of the anionic–nonionic system relative to the CMC of pure anionic surfactant was observed. In addition and for the first time, the effect of UV irradiation on the size of the micelle formations was studied. It was found that UV irradiation causes the formation of smaller micelles which is of prime concern in membrane technology.     

Progress in stability of organic solar cells exposed to air

In this paper, the stability of small-molecule organic solar cells based on copper phthalocyanine (CuPc) and fullerene (C₆₀) is investigated. The use of silver instead of aluminum as the metal electrode in these solar cells, with smaller grain size and grain boundaries as well as with more uniform grain size distribution in the film, results in significant improvement in the lifetime of the devices. The substantial role of silver in the protection of the cells against permeation of oxygen and/or water molecules into the organic thin films is confirmed. Substitution of a thin buffer layer (70 Å) of bathophenanthroline (Bphen) for bathocuproine (BCP), sandwiched between C₆₀ and the cathode, makes considerable progress in the lifetime of the device.     

Optical Nondestructive Evaluation for Structures

Abstract

This paper presents a new technique for evaluation of engineering structures, using optical measurement and probabilistic advancing cross-diagnosis. Its application is first computersimulated, and then it is tested in the laboratory. With the cooperation of the U.S. Federal Highway Administration, a recently developed coherent laser radar system was used to measure structural deformation. The data are treated to reduce noise and used to derive multiple features for reliable diagnosis. Both the simulation and laboratory test results show consistent effectiveness of the proposed technique, indicating a promising direction of nondestructive evaluation combining optical and computer technology.     

The novel,one step and facile synthesis of ZnO nanoparticles using heteropolyoxometalates and their photoluminescence behavior

A novel and facile wet chemical method is presented to synthesize zinc oxide nanoparticles (NPs) under ambient atmosphere and temperature. Keggin type heteropolyoxometalate (H₃[PW₁₂O₄₀]) was used as stabilizer and the effect of stirring time and amount of H₃[PW₁₂O₄₀] (HPW) were studied. XRD and TEM techniques were applied for the morphological and structural characterizations of NPs. Size of nanoparticles were determined using TEM, Scherrer’s formula as well as effective mass approximation. The results of these three methods are in good agreements and revealed single hexagonal zincite type crystalline with average particle size in the range of 3–15 nm. Photoluminescence behavior of the prepared sample shows a strong orange to red emission centred at about 620–635 nm, a green emission at around 550 nm and broad UV emission at around 400 nm.     

Fat oxidation in freeze-dried grouper during storage at different temperatures and moisture contents

The effects of moisture content levels and storage temperature on the lipid oxidation in freeze-dried grouper were studied. Three trends were observed in the changes of PV (peroxide value) depending on the moisture content and storage temperature. An exponential rise of PV was observed (p < 0.05) at lower temperatures (−20 °C and 5 °C for samples at moisture 5 g/100 g; and −20 °C for samples at moisture 20 g/100 g). At temperatures 25 °C for samples at moisture 5 g /100 g, and 5 and 25 °C for samples at 20 g moisture/100 g peaks of PV were observed (p < 0.05). At higher temperatures (40 °C for both moisture content levels) an exponential decay instead of increase were observed (p < 0.05). Moisture content levels had no significant effect (p > 0.05) on PV stored at temperature of −40 °C. The monolayer moisture for freeze-dried grouper was estimated as 6.2 g/100 g dry solids using BET-isotherm. Differential scanning calorimetry (DSC and modulated DSC) thermogram line showed two shifts (i.e. glass transition) and two endothermic peaks, one for melting of oil and another for decomposition. The validity of the water activity and glass transition concepts were evaluated. It is concluded that glass transition concept may be used to explain the process more adequately.     

Electro-Synthesis of Nano-Colloidal PANI/ND Composite for Enhancement of Corrosion-Protection Effect of PANI Coatings

The polyaniline/nanodiamond (PANI/ND) nanocomposite coating was prepared on mild steel via electrochemical polymerization using cyclic voltammetry technique. The ultrasonic irradiation was used for effectively dispersing ND particles in electropolymerization solution. The prepared nanocomposite films were found to be nano-colloidal, and very adherent with low porosity. The corrosion performance of the coatings was investigated in 0.5 M H₂SO₄ solution by electrochemical impedance spectroscopy and polarization methods. The obtained results showed that the presence of ND particles significantly enhanced the corrosion protection performance of the PANI films in 0.5 M H₂SO₄ corrosive medium. X-ray diffraction and FT-IR techniques confirmed the intercalation of the nanoparticles in PANI matrix.     

ST Logistics: Distributing Consumer Goods in China

This paper describes the experience gained from a research collaboration between a group of researchers at the National University of Singapore and logistics executives in Sembcorp Logistics (formerly ST Logistics), in the latter's effort to develop a marketing and strategic planning software tool to enhance its third party logistics (3PL) services in China. As China opened up its economy in the late 1980s, many Western consumer goods manufacturers set up plants or formed joint ventures in China in an attempt to capture this huge market. While the production process can be easily built on the existing technologies and can be efficient costwise, the distribution process is still a challenge because of the backward nature of the infrastructure and the bureaucratic roadblocks, resulting in very high supply chain transaction costs. Consequently, most manufacturers turn to third-party logistics providers (3PLs) who have the required logistics expertise to operate in China. One of the leading 3PLs in China is Shenzhen ST-Anda Logistics (ST-Anda), a joint venture between Sembcorp Logistics and China Merchant Holdings. It has an existing pan-China network of distribution centers. Recently, to improve services to their customers, ST-Anda started planning for the expansion of their logistics distribution network. An OR/MS modeling approach was taken to help them in this venture.     

Physical model for the power-law voltage and current acceleration of TDDB

As gate voltages scale in ultra-thin gate oxide CMOS and single carrier energy drops below the threshold required for defect generation, we postulate that multiple carrier induced defect generation becomes the dominant degradation mechanism resulting in a power-law voltage and local current acceleration of time-dependent dielectric breakdown (TDDB). Data from multiple technology nodes is presented to corroborate our hypothesis, which is also demonstrated to be consistent with literature reports from several different companies. To the best of our knowledge, this is the first time the power-law local gate current acceleration is proposed in contrast to earlier formulations based on total gate current.