Study of the degradation and recyclability of polyethylene and polypropylene present in the marine environment

Polypropylene (PP) and polyethylene (PE) are two of the most widely used polymers in the world, and consequently the main polymer waste that contributes to the pollution of the oceans. Because they are considered inert to degradation, such waste becomes a threat to marine life. In this study, it was possible to collect data on the recyclability of PP and PE waste collected from the Great Pacific Garbage Patch. First, the degradation conditions suffered by these materials were evaluated. The Fourier transform infrared spectroscopy assays presented different levels of carbonyl in different layers below the surface of each material and scanning electron microscopy tests showed cracks and microorganisms. The mechanical and rheological properties were evaluated in order to evaluate the recyclability of samples exposed to the marine environment. From the study, it can be concluded that, despite the levels of degradation of the samples, it is possible to obtain satisfactory properties for mechanically recycled products. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48215.     

Preventing Environmental Contamination by Nonionic Surfactants and Nickel

Protecting the environment from contamination by heavy metals and nonionic surfactants, the sorption of oxyethylated alcohols OS-20, alkylmonoethers ALM-10 and nickel has been investigated, on the hydrogen form of Purolite C 106 cation exchanger. The problem is that nonionic surfactant is not removed by conventional ion exchange. Sorption isotherms were measured, coefficients for intraparticle diffusion were calculated. The sorption of nonionic surfactant from the solution, containing 10 mmol/l, amounts to 400 mg/g for OS-20 and 500 mg/g for ALM-10. The presence of nickel has no appreciable effect on the rate of intraparticle diffusion and the equilibrium sorption of surfactant. The sorption of nickel takes place in the form of both free cations and cations bonded with surfactant.

The sorption of nonionic surfactant and nickel in Purolite C 106 cation exchanger was found to be suitable for the simultaneous removal of both contaminants in order to reuse the water, recovered from nickel plating rinsewater, preventing the contamination of environment.     

Adaptive lossless image coding using least squares optimization with edge-look-ahead

In predictive image coding, the least squares (LS)-based adaptive predictor is noted as an efficient method to improve prediction result around edges. However pixel-by-pixel optimization of the predictor coefficients leads to a high coding complexity. To reduce computational complexity, we activate the LS optimization process only when the coding pixel is around an edge or when the prediction error is large. We propose a simple yet effective edge detector using only causal pixels. The system can look ahead to determine if the coding pixel is around an edge and initiate the LS adaptation to prevent the occurrence of a large prediction error. Our experiments show that the proposed approach can achieve a noticeable reduction in complexity with only a minor degradation in the prediction results.     

Manganese Functionalized Silicate Nanoparticles as a Fenton‐Type Catalyst for Water Purification by Advanced Oxidation Processes (AOP)

Wet hydrogen peroxide catalytic oxidation (WHPCO) is one of the most important industrially applicable advanced oxidation processes (AOPs) for the decomposition of organic pollutants in water. It is demonstrated that manganese functionalized silicate nanoparticles with interparticle porosity act as a superior Fenton‐type nanocatalyst in WHPCO as they can decompose 80% of a test organic compound in 30 minutes at neutral pH and room temperature. By using X‐ray absorption spectroscopic techniques it is also shown that the superior activity of the nanocatalyst can be attributed uniquely to framework manganese, which decomposes H₂O₂ to reactive hydroxyls and, unlike manganese in Mn₃O₄ or Mn₂O₃ nanoparticles, does not promote the simultaneous decomposition of hydrogen peroxide. The presented material thus introduces a new family of Fenton nanocatalysts, which are environmentally friendly, cost‐effective, and possess superior efficiency for the decomposition of H₂O₂ to reactive hydroxyls (AOP), which in turn readily decompose organic pollutants dissolved in water.     

Hard elastic behavior in polyurethane foams

Hard elastic behavior is characterized by high porosity and high recoverability from large strain, and initial Hookean elasticity was discovered in polyurethane foams containing styrene–acrylonitrile (SAN) copolymer particles. The presence of SAN particles introduces a heterogeneous morphology, and when the foam was strained in the SEM, it was observed that the struts became highly porous with profuse voiding nucleated by the SAN particles. It was found that these flexible polyurethane foams had a similar morphological structure in the strained struts as did the typical hard elastic materials. The phenomenon of stress depression, when foam specimens under stress were subjected to nonswelling liquids, was utilized to probe the role of surface stress in these hard elastic foams. An analytic methodology established for other highly porous hard elastic materials based on stress depression was utilized to obtain the average distance between voids in the struts. The calculated values were in good agreement with direct scanning electron microscopy observations, confirming that voiding initiated at the boundaries of SAN particles.     

Effect of scaffold end frame carrying strategies on worker stepping response, postural stability, and perceived task difficulty

OBJECTIVE: This study determined the most favorable strategy for carrying scaffold end frames while minimizing the risk of injuries from being struck by an object, falling, and overexertion. BACKGROUND: Scaffold erectors are at risk of high exposure to the aforementioned hazards associated with the dynamic human-scaffolding interface and work environments. Identifying an optimal work strategy can help reduce risk of injuries to the worker. METHOD: Three carrying methods, four types of work surfaces, two weights of scaffold frames, and three directions of stepping movement were tested in a laboratory with 18 construction workers. RESULTS: The effects of carrying method on postural instability and task difficulty rating were significant for handling the 22-kg end frame. Response time, postural instability, and perceived task difficulty rating were significantly reduced when the 9-kg end frame was used as compared with the 22-kg frame. CONCLUSION: The symmetric side-carrying method was the best option for handling 22-kg scaffold end frames. A 9-kg end frame (e.g., made of reinforced lightweight materials) has the potential to reduce injury risk among scaffold handlers during their scaffold erection and dismantlingjobs. APPLICATION: Scaffold erectors may want to adopt the symmetric side-carrying method as the primary technique for handling the 22-kg scaffold end frame, which is currently the one most used in the industry.     

Conductive SnO2/Sb powder: preparation and optical properties

Preparation of an SnO₂ semiconducting powder doped with antimony (x=2.38 mol%) was achieved by co-precipitation. The unit cell parameters of the doped SnO₂ powders were measured and their changes with dopant concentration were determined. Four-point sheet resistance measurements, together with optical and infrared spectra of the powder were taken in order to obtain a highly-conducting, low-emitting powder which could be used for antistatic paint preparation. Evolution of the phonon bands corresponding to Sn-O stretching modes as a function of dopant concentration were followed, and a model calculation based on an extended four-parametric Kurosawa relation was applied to the reflection spectra of differently doped powders. It was found that the frequency of the plasma oscillations shifts with dopant concentration, and the intensity of the reflectivity peaks was correlated with plasmon-phonon interactions. An additional negative reflection peak in the range 1100 to 1200 cm^–1 was found in the reflection spectra of highly doped powders and was attributed to the coupled modes between the plasma oscillations and one of the phonon combinational or overtone modes of SnO₂.     

New estimates of the determinants of urban crime

The Annals of Regional Science - New tests of the utility maximizing model of criminal behavior, first proposed by Becker, are performed. These tests use newer data than has previously been...     

Least-Squares-Based Switching Structure for Lossless Image Coding

Many coding methods are more efficient with some images than others. In particular, run-length coding is very useful for coding areas of little changes. Adaptive predictive coding achieves high coding efficiency for fast changing areas like edges. In this paper, we propose a switching coding scheme that will combine the advantages of both run-length and adaptive linear predictive coding. For pixels in slowly varying areas, run-length coding is used; otherwise least-squares (LS)-adaptive predictive coding is used. Instead of performing LS adaptation in a pixel-by-pixel manner, we adapt the predictor coefficients only when an edge is detected so that the computational complexity can be significantly reduced. For this, we use a simple yet effective edge detector using only causal pixels. This way, the proposed system can look ahead to determine if the coding pixel is around an edge and initiate the LS adaptation in advance to prevent the occurrence of a large prediction error. With the proposed switching structure, very good prediction results can be obtained in both slowly varying areas and pixels around boundaries. Furthermore, only causal pixels are used for estimating the coding pixels in the proposed encoder; no additional side information needs to be transmitted. Extensive experiments as well as comparisons to existing state-of-the-art predictors and coders will be given to demonstrate its usefulness.