Structure-property relationship and shape memory effect of polyurethane copolymer cross-linked with pentaerythritol     

Tae Keun Cho  Mi Hwa Chong  Byoung Chul Chun  Hye Ran Kim  Yong-Chan Chung 《Fibers and Polymers》2007,8(1):7-12

Polyurethane block copolymers chemically cross-linked by pentaerythritol, a four-way cross-linker, are tested for the shape memory effect. One of the copolymers shows higher shape recovery than any other shape memory copolymer synthesized by us so far. The copolymer maintains a surprising 94 % shape recovery after the third cyclic test. The four-way cross-linking by pentaerythritol and interaction between hard segments are mainly responsible for the very high shape recovery. Tensile mechanical properties also significantly improve by cross-linking. Glass transition temperature (T _g ) slightly increases with cross-linking content. Other characterization such molecular weight, IR, and X-ray diffraction is also carried out to understand the arrangement of copolymer chains.  相似文献   

A new color index for vegetation segmentation and classification     

Lee  Moon-Kyu  Golzarian  Mahmood Reza  Kim  Inki 《Precision Agriculture》2021,22(1):179-204

Color vegetation indices enable various precision agriculture applications by transforming a 3D-color image into its 1D-grayscale counterpart, such that the color of vegetation pixels can be accentuated, while those of nonvegetation pixels are attenuated. The quality of the transformation is essential to the outcomes of computational analyses to follow. The objective of this article is to propose a new vegetation index, the Elliptical Color Index (ECI), which leverages the quadratic discriminant analysis of 3D-color images along a normalized red (r)—green (g) plane. The proposed index is defined as an ellipse function of r and g variables with a shape parameter. For comparison, the ECI’s performance was evaluated along with six other indices, by using 240 color images as a test sample captured from four vegetation species under different illumination and background conditions, together with the corresponding ground-truth patterns. For comparative analysis, the receiver operating characteristic (ROC) and the precision–recall (PR) curves helped quantify the overall performance of vegetation segmentation across all of the vegetation indices evaluated. For a practical appraisal of vegetation segmentation outcomes, this paper applied Gaussian filtering, and then the thresholding method of Otsu, to the grayscale images transformed by each of the indices. Overall, the test results confirmed that ECI outperforms the other indices, in terms of the area under the curves of ROC and PR, as well as other performance metrics, including total error, precision, and F-score.

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Application of microbially induced calcite precipitation to prevent soil loss by rainfall: effect of particle size and organic matter content     

Chung  Hyeonyong  Kim  Sang Hyun  Nam  Kyoungphile 《Journal of Soils and Sediments》2021,21(8):2744-2754

Journal of Soils and Sediments - Soil loss by rainfall is a serious problem in civil and environmental engineering. In this study, microbially induced calcite precipitation (MICP) was applied to...  相似文献   

Electrokinetic remediation of heavy metal-contaminated soils: performance comparison between one- and two-dimensional electrode configurations     

Kim  Soon-Oh  Jeong  Jin Young  Lee  Woo-Chun  Yun  Seong-Taek  Jo  Ho Young 《Journal of Soils and Sediments》2021,21(8):2755-2769

Journal of Soils and Sediments - Electrokinetic (EK) soil remediation is significantly affected by the electrode configurations. Therefore, this study was conducted to compare the performance of...  相似文献   

Fluorescence and NIR spectroscopic study on the water interaction in polycarbonate film     

Min Sun Kim  Chong Sook Paik Sung 《Fibers and Polymers》2008,9(2):171-175

Water interactions in polycarbonate films have been studied using fluorescence and NIR Fourier transform spectroscopy. During water sorption process, the fluorescence emission spectra showed sensitive changes with the peak at 332 nm red shifted by 18 nm with water sorption. This red-shifted peak could be due to phenyl-2-phenoxybezoate, which is one of two major thermal degradation products in polycarbonate. In the spectra of phenyl-2-phenoxybenzoate in dimethyl formamide solution, a progressive red shift was also observed with the water addition. By using the NIR spectra, hydrogen-bonding interactions of the sorbed water with polycarbonate were investigated. It was found that water can be analyzed as free water S₀ or single hydrogen bonded water, S₁ while double hydrogen bonded water was negligible. During water immersion, most water species which are present as S₀ species decrease slightly, with a small increase in S₁ species. During desorption, S₀ species decrease sharply, while S1 species is reduced gradually. Two examples of S₁ structure in water-sorbed polycarbonate are proposed.  相似文献   

Effect of glycerol cross-linking and PDI on the shape memory effect and mechanical properties of polyurethane     

Yong-Chan Chung  Woo Seok Kim  Tae Keun Cho  Byoung Chul Chun 《Fibers and Polymers》2008,9(4):388-392

A series of shape memory polyurethane (PU) copolymers synthesized from 1,4-phenyldiisocyanate (PDI), poly(tetramethyleneglycol) (PTMG), 1,4-butanediol (BD) as a chain extender, and glycerol as a cross-linking agent were tested for the mechanical properties and the shape memory effect at the temperature 20 °C above melting temperature (T _m), and were compared with other PUs synthesized from 4,4′-methylene-bis-phenyldiisocyanate (MDI), PTMG, and BD. Mechanical properties and shape memory effect were improved substantially by adopting both PDI and glycerol. Interestingly, enthalpy of melting and T _m were not affected by the glycerol content. Vibration and shock absorption ability was investigated by measuring both loss tan δ and storage modulus with dynamic mechanical analyzer (DMA).  相似文献   

Evaluation of water holding capacity and breadmaking properties for frozen dough containing ice structuring proteins from winter wheat     

Hua-Neng Xu  Weining Huang  Chunli Jia  Yangsoo Kim  Huiping Liu 《Journal of Cereal Science》2009

The effects of ice structuring proteins (ISPs) from white wheat and storage conditions on the water holding capacity (WHC) and breadmaking properties of frozen dough were investigated. The WHC of frozen dough was measured by centrifugation and the breadmaking properties were assessed as proofing time and bread specific volume. It was found that the prolonged frozen storage and freeze–thaw cycles decreased the WHC and breadmaking properties of dough. ISPs were highly effective in increasing the WHC of frozen dough and improving the breadmaking properties. There was a strong correlation between WHC and breadmaking properties (proofing time and bread specific volume) of frozen dough.  相似文献   

Copper metallization of poly(ethylene terephthalate) fabrics via intermediate polyaniline layers     

Nowoo Park  Il Won Kim  Jooyong Kim 《Fibers and Polymers》2009,10(3):310-314

Poly(ethylene terephthalate) fabrics were metallized through electroless plating of copper. The copper plating was performed on palladium-decorated polyaniline surfaces, and polyaniline was present as an intermediate layer on fabrics to facilitate palladium formation. Different oxidation states of polyaniline were tested in their efficacy in Pd (II) reduction and subsequent Cu plating. X-ray photoelectron spectroscopy was used to monitor the surface changes along the metallization procedure, and surface resistance was measure to probe the electrical properties of the metallized fabrics.  相似文献   

Synthesis and application of o,o′-dihydroxyazo dyes and their metal complexes     

Sang Bum Ahn  Jae Pil Kim  Woo Sub Shim 《Fibers and Polymers》2009,10(5):643-649

This paper presents the synthesis of metal complex acid dyes obtained from the reaction of o,o′-dihydroxyazo dyes and chromium and cobalt sulfate. The ¹H-NMR, FT-IR and UV/Visible Spectrophotometer, TLC (Thin Layer Chromatography) and ICP (Ion Chromatography) of the intermediates and the metal complexes were studied and compared. Their properties such as dyeing, fastness and toxicity on nylon were also assessed according to standard methods.  相似文献   

Application of the real fabric frictional speeds to the fabric sound analysis using water repellent fabrics     

Yoonjung Yang  Chunjeong Kim  Jangwoon Park  Heecheon You  Gilsoo Cho 《Fibers and Polymers》2009,10(4):557-561

This study aims to determine fabric frictional speeds between the arm and the trunk when people walk (1.3 m/s), jog (2.5 m/s) and run (4.5 m/s), and to apply the measured speeds to setting a sound generator for each motion to obtain fabric rustling sounds. By analyzing body motions captured by the Falcon motion analysis system and a camcorder, it was identified that the friction between the arm and trunk occurred within 10° of shoulder angle along the center line of the trunk in the sagittal plane and the maximum frictional speed occurred at the elbow within the shoulder friction range. The averages (SDs) of maximum frictional speed at the elbow were found 0.63 m/s (0.17) at walking, 1.1 m/s (0.25) at jogging, and 1.98 m/s (0.35) at running. The frictional sounds of three coated nylon fabrics were obtained using these predetermined speeds. We calculated sound characteristics such as the sound pressure levels (SPL) and Zwicker’s psychoacoustic parameter using 1/3 octave band analysis. The SPL values ranged from 74.2 dB at running to 79.0 dB at jogging, which was about the same noise level as in the busy street. The values of loudness (Z) at walking and jogging were higher than that at running, but the fluctuation strength (Z) increased in the order of walking, jogging, and running.  相似文献