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151.
152.
Blends of bisphenol-A polyarbonate (PC) and poly(ethylene terephthalate) (PET) has been investigated by differential scanning calorimetry and scanning electron microscopy. Blends were prepared by screw extrusion and solution casting with weight fractions of PC in the blends varying from 0.90 to 0.10. From the measured glass transition temperature (Tg) and apparent weight fractions of PC and PET dissolved in each phase, it appears that PET dissolves more in the PC-rich phase than does the PC in the PET-rich phase. The composition-dependent values of the Flory–Huggins polymer–polymer–interaction parameter were determined and found to be from 0.054 to 0.037 for extruded blends at 275°C and from 0.058 to 0.040 for solution casting at 25°C. The interaction parameter decreases with increasing PET concentration. This result is consistent with the values of the Tgs, the microscopy study, and the measured extrudate swell ratios which show that compatibility increases more in the PET-rich compositions than in the PC-rich compositions. The PC–PET blends are not microscopically miscible for all the blend compositions. 相似文献
153.
Politically-themed stocks mainly refer to stocks that benefit from the policies of politicians. This study gave the empirical analysis of the politically-themed stocks in the Republic of Korea and constructed politically-themed stock networks based on the Republic of Korea’s politically-themed stocks, derived mainly from politicians. To select politically-themed stocks, we calculated the daily politician sentiment index (PSI), which means politicians’ daily reputation using politicians’ search volume data and sentiment analysis results from politician-related text data. Additionally, we selected politically-themed stock candidates from politician-related search volume data. To measure causal relationships, we adopted entropy-based measures. We determined politically-themed stocks based on causal relationships from the rates of change of the PSI to their abnormal returns. To illustrate causal relationships between politically-themed stocks, we constructed politically-themed stock networks based on causal relationships using entropy-based approaches. Moreover, we experimented using politically-themed stocks in real-world situations from the schematized networks, focusing on politically-themed stock networks’ dynamic changes. We verified that the investment strategy using the PSI and politically-themed stocks that we selected could benchmark the main stock market indices such as the KOSPI and KOSDAQ around political events. 相似文献
154.
An efficient one-step method to prepare aryl-substituted carbazoles via tandem double or triple CC bond formations by multiple Suzuki couplings and CN bond formation by Cadogan cyclization has been developed. The developed method employs commercially available or easily preparable polybromonitrobenzenes and arylboronic acids as starting materials, tolerates various functional groups, and provides good yields. 相似文献
155.
This paper presents a simplified optical method for measuring the residual stresses by rapid cooling in thermosetting resin
strips. First, the fundamental equations for calculating the residual stress from the residual birefringence were obtained
by the linear photoviscoelastic theory. The specimens were then subjected to rapid cooling. After rapid cooling, the residual
stress was measured by two methods, the simplified optical method mentioned above and the well-known layer-removal method.
The effectiveness of the simplified optical method was discussed by comparing results of the two methods. 相似文献
156.
Silica/perfluoroalkyl methacrylate polymer (PHDFDMA) particles were prepared using various types of silica by polymerization
in supercritical carbon dioxide. There are three steps in the fabrication of inorganic/organic hybrid composites: silane treatment,
polymerization, and soxhlet extraction. After these steps, we observed the morphology of silica/PHDFDMA particles using field
emission scanning electron microscope and transmission electron microscope. From these analyses, we can confirm that the silica/PHDFDMA
core/shell particles were obtained when we used Ludox and silica gel as a silica template. On the other hand, core/shell particles
were not formed when using fused silica and precipitated silica. In addition, to confirm the amount of polymer on silica,
we performed an analysis using thermogravimetric analysis and electron probe micro-analyzer. In this case, PHDFDMA was approximately
20 wt.% on the silica gel and 40 wt.% on the Ludox, respectively. When using fused silica and precipitated silica as a template,
amount of PHDFDMA on silica was maximum 5 wt.% and over 40 wt.%, respectively. From these results, to obtain enough PHDFDMA
encapsulated silica particle, colloidal silica, Ludox is the best template in four different types of silica. 相似文献
157.
Thuy-Duong Nguyen-Phan Myoung Bok Song Eui Jung Kim Eun Woo Shin 《Research on Chemical Intermediates》2010,36(6-7):613-619
One-dimensional titania nanomaterials were synthesized by soft chemical processes in an alkali medium. The effect of alkali-treatment temperature on the morphology, porosity, and crystalline phase of TiO2 nanomaterials was investigated. Nanotubes having an opening end were observed when aging the sample at 130 °C, while conducting the process at 180 °C resulted in nanoribbons with a high aspect ratio. Post-treatment at 300 °C led to the partial transformation from tubular structures into nanoparticles or ribbons into nanobelts. While the monoclinic sodium hexatitanate and anatase crystal had a tubular structure, nanoribbons and nanobelt TiO2 also showed the presence of hydrogen titanate and sodium trititanate. High surface areas were achieved in as-prepared nanotubes and nanoribbons, 456.5 and 72.1 m2/g, respectively, and a drastic reduction was obtained upon post-treatment at 300 °C to 72.1 and 19.2 m2/g, respectively. 相似文献
158.
Hooper J Sauer EL Arns S Woo TK Barriault L 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(47):14124-14130
We report herein a detailed investigation into the reaction mechanism for a sequential oxy-Cope/ene reaction under anionic conditions. With DFT calculations and ab initio molecular dynamics simulations, the observed diastereoselectivity is shown to be the result of an isomerization of the enolate olefin, which would evidently not occur under neutral conditions. The potential energy surface was thoroughly mapped out for the reaction pathways and the proposed mechanism confirmed the different product distributions observed under neutral and anionic oxy-Cope conditions. In addition, other possible pathways are shown to be higher in energy and experimental evidence is given that supports the olefin-isomerization pathway. 相似文献
159.
Gjergji Shore Woo‐Jin Yoo Dr. Chao‐Jun Li Prof. Michael G. Organ Prof. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(1):126-133
An effective multi‐component reaction (MCR) protocol has been developed for the construction of propargyl amines from aldehydes, amines and terminal alkynes by using microwave‐assisted continuous‐flow organic synthesis (MACOS). The process is catalysed by thin films of either copper or gold that achieve temperatures in excess of 900 °C when irradiated with low levels of microwave power. The process works equally well for premixed solutions of the three starting materials, or as three separate streams, which improves the combinatorial efficiency of the method. The process tolerates a wide variety of functional groups and heterocycles, and conversion over these diverse substrates ranges from 70–90 %. 相似文献
160.
Electrospinning fabrication and characterization of poly(vinyl alcohol)/montmorillonite/silver hybrid nanofibers for antibacterial applications 总被引:1,自引:0,他引:1
Jae Hyeung Park Mohammad Rezaul Karim In Kyo Kim In Woo Cheong Jong Won Kim Do Gyu Bae Jin Won Cho Jeong Hyun Yeum 《Colloid and polymer science》2010,288(1):115-121
Poly(vinyl alcohol) (PVA)/montmorillonite clay (MMT)/silver (Ag) nanoparticles have been electrospun for fabricating PVA/MMT/Ag
nanofiber in aqueous solutions. Since PVA is a water-soluble and biocompatible polymer, it is one of the best materials for
preparation of antibacterial nanofiber. MMT has been used as an inorganic filler to enhance properties of homopolymeric nanofiber.
The PVA/MMT/Ag nanofiber diameter increases with increasing contents of MMT clay and Ag nanoparticles. In preservation test,
the PVA/MMT/Ag nanofiber confirms an excellent antibacterial performance, elucidating for practical uses as a new preservative.
Moreover, the PVA/MMT/Ag nanofiber shows improved thermal properties. 相似文献