Phase behavior,density, and crystallization of polyethylene in n‐pentane and in n‐pentane/CO2 at high pressures

The phase behavior and volumetric properties of polyethylene (PE) in solutions of n‐pentane and n‐pentane/CO₂ were studied in a temperature (T) range of 370–440 K at pressures up to 60 MPa. Measurements were conducted with a variable‐volume view‐cell system equipped with optical sensors to monitor the changes in the transmitted light intensity as the P or the T of the system was changed. Lower‐critical‐solution‐temperature‐type behavior was observed for all of the liquid–liquid (L–L) phase boundaries, which shifted to higher pressures in solutions containing CO₂. The solid–fluid (S–F) phase boundaries were investigated over a P range of 8–54 MPa and took place in a narrow T range, from 374 to 378 K in this P interval. The S–F phase boundary showed a unique feature in that the demixing temperatures showed both increasing and decreasing trends with P depending on the P range. This was observed in both the PE/n‐pentane and PE/n‐pentane/CO₂ mixtures. The density of these solutions were measured as a function of P at selected temperatures or as a function of T at selected pressures that corresponded to the paths followed in approaching the phase boundaries (S–F or L–L) starting from a homogeneous one‐phase condition. The data showed a smooth variation of the overall mixture density along these paths. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 2201–2209, 2003     

Use of Warranties on Highway Projects: A Real Option Perspective

Since the introduction of warranty provisions in federal highway jobs, more and more state departments of transportation (DOTs) have considered the use of such provisions to protect their initial investment. This paper describes the pros and cons of warranty contracting in highway construction based on a survey of warranty practices in the United States. In particular, the need for state DOTs to buy a warranty for a well-built project is questioned. As an alternative, this paper introduces the warranty option, which gives the DOT the right to buy a warranty only if it becomes necessary at the end of construction. This option is exercised if the performance on site warrants it. This paper describes the mechanics of the warranty option and its advantages over the conventional warranty. A bid evaluation model is also developed for the warranty option approach.     

Films formed from polystyrene latex/clay composites: A fluorescence study

This study reports a steady-state fluorescence (SSF) technique for studying film formation from surfactant-free polystyrene (PS) latex and Na-montmorillonite (SNaM) composites. The composite films were prepared from pyrene (P)-labeled PS particles and SNaM clay at room temperature and annealed at elevated temperatures in 10-min intervals above glass transition temperature (t₃) of polystyrene. During the annealing processes, the transparency of the film improved considerably. Scattered light (I_s) and fluorescence intensity (I_p) from P were measured after each annealing step to monitor the stages of film formation. Evolution of transparency of composite films was monitored by using photon transmission intensity, I_tr. Scanning electron microscopy (SEM) was used to detect the variation in physical structure of annealed composite films. Minimum film formation temperature, T_q, and healing temperatures, T_h, were determined. Void closure and interdiffusion stages were modeled and related activation energies were determined. It was observed that both activation energies increased as the percent of SNaM was increased in composite films.     

Generic visual analysis for multi- and hyperspectral image data

Multi- and hyperspectral imaging and data analysis has been investigated in the last decades in the context of various fields of application like remote sensing or microscopic spectroscopy. However, recent developments in sensor technology and a growing number of application areas require a more generic view on data analysis, that clearly expands the current, domain-specific approaches. In this context, we address the problem of interactive exploration of multi- and hyperspectral data, consisting of (semi-)automatic data analysis and scientific visualization in a comprehensive fashion. In this paper, we propose an approach that enables a generic interactive exploration and easy segmentation of multi- and hyperspectral data, based on characterizing spectra of an individual dataset, the so-called endmembers. Using the concepts of existing endmember extraction algorithms, we derive a visual analysis system, where the characteristic spectra initially identified serve as input to interactively tailor a problem-specific visual analysis by means of visual exploration. An optional outlier detection improves the robustness of the endmember detection and analysis. An adequate system feedback of the costly unmixing procedure for the spectral data with respect to the current set of endmembers is ensured by a novel technique for progressive unmixing and view update which is applied at user modification. The progressive unmixing is based on an efficient prediction scheme applied to previous unmixing results. We present a detailed evaluation of our system in terms of confocal Raman microscopy, common multispectral imaging and remote sensing.     

Particle-based simulation of the interaction between fluid and knitwear

We present a particle-based method to simulate and visualize the interaction of knitwear with fluids. The knitwear is modeled using spring-mass systems and the fluid is modeled using the smoothed particle hydrodynamics method. Two-way coupling is achieved by considering surface tension, capillary, and interparticle forces between the fluid and knitwear. The simulation of fluid and knitwear particles is performed on the graphics processing unit. Photorealistic rendering of knitwear and fluid is achieved by using a hardware-accelerated rasterization-based rendering technique. Our method is able to simulate and visualize the macro- and microstructure of free-form knitwear and reflective and refractive characteristics of the fluid surface.     

Electrically controlled release of 5-fluorouracil from conductive gelatin methacryloyl-based hydrogels

Herein, electro-responsive hydrogels were obtained by incorporation of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT/PSS) into the gelatin methacryloyl (GelMA) by using photopolymerization technique. Hydrogels were characterized by FTIR and scanning electron microscopy analyses. Cytotoxicity tests were performed by L929 cell lines to determine cell compatibility. Swelling tests were conducted to investigate the water uptake capacity of hydrogels. 5-fluorouracil (5-FU) was selected as a model drug as it is known as a topical drug for some skin cancer type treatment. The release of 5-FU from the hydrogel was provided in efficient and controlled manner at simulated skin cancer (pH = 5.5) and under 0 and 1.5 V. The simulated drug delivery experiments conducted in vitro revealed that the drug releasing amount was higher when voltage is applied to the hydrogels. All results visualized that the obtained GelMA-based PEDOT/PSS hydrogels with enhanced electrical properties could be a potential candidate as an electrically sensitive drug carrier for treatment of skin cancer in the future applications. © 2018 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 46914.     

Arduino-based slider setup for gas–liquid mass transfer investigations: Experiments and CFD simulations

The implementation of traditional sensors is a drawback when investigating mass transfer phenomena within microstructured devices, since they disturb the flow and reactor characteristics. An Arduino based slider setup is developed, which is equipped with a computer-vision system to track gas–liquid slug flow. This setup is combined with an optical analytical method allowing to compare experimental results against CFD simulations and investigate the entire lifetime of a single liquid slug with high spatial and temporal resolution. Volumetric mass transfer coefficients are measured and compared with data from literature and the mass transfer contribution of the liquid film is discussed.     

Curing cycle modification for RTM6 to reduce hydrostatic residual tensile stress in 3D woven composites

Triaxial residual tensile stresses resulting after cooling a 3D woven composite from the curing temperature cause cracking in the resin pockets for weave architectures that have high through‐the‐thickness constraint. We show how curing cycle modifications can reduce the hydrostatic tensile stress generated by thermal mismatch during cooling of Hexcel RTM6 epoxy resin constrained in a quartz tube which simulates extreme constraint in a composite. The modified curing schedule consists of a high temperature cure to just before the glass transition, a lower temperature hold that takes the resin through the glass transition thereby freezing in the zero stress state, followed by high temperature cure to bring the resin to full conversion. We show that this process is sensitive to heating rates and can reduce the zero stress state of non‐toughened RTM6 resin to a temperature similar to a commercial rubber‐toughened resin, Cycom PR520. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43373.     

Size and expansion ratio analysis of micro nozzle gas flow

Size and expansion ratio effects on the flowfield are investigated for micro converging-diverging nozzles. Numerical computations are conducted by using two dimensional augmented Burnett equations and Navier-Stokes equations that were derived from the Boltzmann equation. The Maxwell-Smoluchowski slip boundary condition is used for adiabatic walls, and Steger-Warming flux vector splitting scheme is applied to the convective inviscid flux terms. The results from the augmented Burnett equation are compared with Navier-Stokes and Direct Simulation Monte Carlo (DSMC) results. Then, nozzle-size analysis is conducted for between 2 µm and 100 µm throat width. Influence of the Knudsen number is investigated, and temperature and Mach number variations are presented. In addition, the influence of the expansion ratio is studied with three (1.7:1, 3.4:1, and 6.8:1) different configurations. The results are compared with each other and an experimental data in the literature.