Melt‐blowing thermoplastic polyurethane and polyether‐block‐amide elastomers: Effect of processing conditions and crystallization on web properties

Melt‐blown webs from ester and ether thermoplastic polyurethanes and polyether‐block‐amide (PEBA) elastomers were produced at different die‐to‐collector distances (DCD) to study the correlation between the polymer type and hardness, melt‐blowing process conditions, and web properties. An experimental set up was built to measure the air temperature and velocity profiles below and across the melt‐blowing die to correlate the fiber formation process and polymer crystallization behavior to process conditions and web properties. It was shown that air temperature and velocity profiles follow similar trends with increasing distance below the melt‐blowing die: both drop rapidly until reaching a plateau region approximately 5–6 cm below the die. Thereafter, they remain relatively constant with further increasing distance. It was found that crystallization onset and peak temperatures of all block copolymers in this study fall within this region of rapid velocity and temperature drop. This suggests that the polymers have already started to crystallize and solidify before reaching the collector, the extent of which depends on the crystallization kinetics of the polymer. The strong influence of the crystallization kinetics on web strength was clearly demonstrated in the PEBA series. In particular, the hardest grade produced the lowest web strength mainly because of its high crystallization rate and crystallization onset temperature. It is concluded that the melt‐blown web strength is strongly dependent on the degree of fiber‐to‐fiber adhesion within the web, which is determined by the amount of fiber solidification that occurs prior to the collector. The crystallization kinetics of the polymer and the distances traveled between the die and collector or the exposure time of the polymer melt to process and ambient air were shown to be critical in the amount of fiber solidification attained. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Multilevel statistical inference from functional near-infrared spectroscopy data during stroop interference

Functional near-infrared spectroscopy (fNIRS) is an emerging technique for monitoring the concentration changes of oxy- and deoxy-hemoglobin (oxy-Hb and deoxy-Hb) in the brain. An important consideration in fNIRS-based neuroimaging modality is to conduct group-level analysis from a set of time series measured from a group of subjects. We investigate the feasibility of multilevel statistical inference for fNIRS. As a case study, we search for hemodynamic activations in the prefrontal cortex during Stroop interference. Hierarchical general linear model (GLM) is used for making this multilevel analysis. Activation patterns both at the subject and group level are investigated on a comparative basis using various classical and Bayesian inference methods. All methods showed consistent left lateral prefrontal cortex activation for oxy-Hb during interference condition, while the effects were much less pronounced for deoxy-Hb. Our analysis showed that mixed effects or Bayesian models are more convenient for faithful analysis of fNIRS data. We arrived at two important conclusions. First, fNIRS has the capability to identify activations at the group level, and second, the mixed effects or Bayesian model is the appropriate mechanism to pass from subject to group-level inference.     

A Monolithic Phased Array Using 3-bit Distributed RF MEMS Phase Shifters

This paper presents a novel electronically scanning phased-array antenna with 128 switches monolithically implemented using RF microelectromechanical systems (MEMS) technology. The structure, which is designed at 15 GHz, consists of four linearly placed microstrip patch antennas, 3-bit distributed RF MEMS low-loss phase shifters, and a corporate feed network. MEMS switches and high-Q metal-air-metal capacitors are employed as loading elements in the phase shifter. The system is fabricated monolithically using an in-house surface micromachining process on a glass substrate and occupies an area of 6 cm times 5 cm. The measurement results show that the phase shifter can provide nearly 20deg/50deg/95deg phase shifts and their combinations at the expense of 1.5-dB average insertion loss at 15 GHz for eight combinations. It is also shown by measurements that the main beam can be steered to required directions by suitable settings of the RF MEMS phase shifters.     

Marination of deep-water pink shrimp with rosemary extract and the determination of its shelf-life

The effect of the antioxidant activity of rosemary extract on marinated deep-water pink shrimp (Parapenaeus longirostris Lucas, 1846) stored at 1 °C was investigated. Chemical, physical, instrumental, microbiological and sensory analyses were performed to investigate the quality changes and to determine the shelf-life of marinated shrimps. Chemical composition of the shrimp was determined and no significant difference (P > 0.05) was found between the control group (without rosemary extract) and the experimental group (with rosemary extract). Both groups contained 2% citric acid. There was no significant difference (P > 0.05) between the sensory analysis of control and experimental groups on storage days 0, 15, 30, 45 and 60 while rancidity was noted by the panelists in the control group on day 75. The TBA value of the control group reached the consumption limit on day 75 but it was still ‘very good’ for the experimental group. Although the bacterial load of both groups were lower than the consumption limits on storage day 75, TBA value limited the shelf-life of the control group but the experimental group was still of good quality for consumption after 75 days.     

Teaching construction sciences with the integration of BIM to undergraduate architecture students

This study aims to test two hypotheses: teaching building information modeling (BIM) in relation to construction science provides students with a remarkable understanding of the nature of construction science (Hypothesis 1), and if the student has positive attitude toward the use of the BIM program, then efficiency by which construction science is taught by its means is improved (Hypothesis 2). Results and process of a case study with a novel teaching methodology were discussed in terms of the benefits of the students. A questionnaire study was conducted on the student group with which the case study was performed to test each student's attitude. Results were evaluated statistically. When BIM is integrated with the teaching of basic construction courses within architecture degree programs, the students understood the building system principles simply and effectively. As a result of the statistical analysis, the students find the applied method effective. Moreover, their attitude toward BIM affects the process.     

Platinum‐promoted fibrous silica Y zeolite with enhanced mass transfer as a highly selective catalyst for n‐dodecane hydroisomerization

A fibrous silica zeolite Y (HY@KCC‐1) catalyst with a high surface area of 568 m²/g and unique core‐shell morphology was successfully synthesized via a modified KCC‐1 synthesis method. Characterization of the catalysts was achieved with X‐ray powder diffraction (XRD), field emission scanning microscope (FESEM), N₂ adsorption/desorption, and 2,6‐dimethylpyridine adsorbed Fourier‐transform infrared spectroscopy (FTIR). The Pt/HY@KCC‐1 has displayed complete n‐dodecane conversion coupled with an incredibly enhanced isomer yield of 72% at 350°C, nearly two‐fold higher than that of unmodified Pt/HY catalyst. Remarkably, Pt/HY@KCC‐1 had an internal effectiveness factor (η) of unity and negligible internal diffusion limitation, thus suggesting its potential application in hydroisomerization of higher hydrocarbons for enhancing fuel properties.     

一个非洲人的观点

在非洲国家，上半个世纪城市化发展的速度如此之快，以至于它压倒了任何想要利用城市规划的方式对其进行控制与管理的企图。传统上，对城市增长与城市发展进行的管理与指导采用的首要方法取决于总体规划甚至是战略规划的构思与成果。     

Slurry analysis after lead collection on a sorbent and its determination by electrothermal atomic absorption spectrometry

In this study, in order to eliminate the drawbacks of elution step and to reach higher enrichment factors, a novel preconcentration/separation technique for the slurry analysis of sorbent loaded with lead prior to its determination by electrothermal atomic absorption spectrometry was described. For this purpose, at first, lead was collected on ethylene glycol dimethacrylate methacrylic acid copolymer (EGDMA-MA) treated with ammonium pyrolidine dithiocarbamate (APDC) by conventional batch technique. After separation of liquid phase, slurry of the sorbent was prepared and directly pipetted into graphite furnace of atomic absorption spectrophotometer. Optimum conditions for quantitative sorption and preparation of the slurry were investigated. A 100-fold enrichment factor could be easily reached.

The analyte element in certified sea-water and Bovine-liver samples was determined in the range of 95% confidence level. The proposed technique was fast and simple and the risks of contamination and analyte loss were low. Detection limit (3δ) for Pb was 1.67 μg l⁻¹.     

Estimating Drilling Parameters for Diamond Bit Drilling Operations Using Artificial Neural Networks

Diamond bit drilling is one of the most widely used and preferable drilling techniques because of its higher rate of penetration and core recovery in the hardest rocks, the ability to drill in any direction with less deviation, and the ability to drill with greater precision in coring and prospecting drilling. Conventional bit analysis techniques include mathematical methods such as specific energy and formation drillability. In this study, artificial neural network (ANN) analysis as opposed to conventional mathematical techniques is used to estimate major drilling parameters for diamond bit drilling, i.e., weight on bit, rotational speed, and bit type. The use of the proposed methodology is demonstrated using an ANN trained with information obtained from 45,000?m of diamond bit drilling operations conducted on several formations and locations in Turkey. The studied formations include shallow carbonates as well as sandstones in the Zonguldak hard coal basin. The neural network results are compared to those obtained from conventional methods such as specific energy analysis. It was observed that the proposed methodology provided satisfactory results both in relatively less documented and drilled formations as well as in well-known formations.