Papers by Keyword: Polarity

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Authors: Toshihide Ide, Mitsuaki Shimizu, Xu-Qiang Shen, Shinji Hara, Hajime Okumura, Toshio Nemoto
1459
Authors: B.S. Negi
Abstract: Stainless steels (SS) possess excellent corrosion, creep and high temperature oxidation resistance and are invariably used in refinery for construction of heater tubes, tube supports, Heat exchanger bundles, piping and internal lining of pressure vessels. Ferritic stainless steel type 405 is used for column strip-lining, martensitic stainless steel type 410 is used for column trays and heater tubes and austenitic stainless steel family is used very extensively for lining, piping, heat exchanger, heater tubes and tube supports. On-stream and turnaround condition monitoring of plant and equipment are carried out for health assessment and mitigation of premature failure. However, catastrophic failures of stainless steel due to stress corrosion cracking, thermal fatigue and stress relaxation cracking are encountered in addition to bulging and cracking of strip-lining. Field repairs of these components are required to be done. Stainless steels are difficult to weld due to low thermal conductivity, higher coefficient of thermal expansion, fissuring and solidification cracking problem during welding. Lower heat input and fast cooling facilitate the welding process. Welding of service exposed stainless steels is more challenging, as it has already undergone metallurgical degradation. Welding of stainless steels is carried out using TIG and SMAW process with matching electrode after establishing the welding specification procedures and welders qualification. Field repairs of stainless steels components are also attempted with original procedures and in case of difficulties, a buttering layer of inconel (ERNiCr3) or ER 309Mo is provided on the welding surface before using matching electrodes. Quality assurance of weld joint is ensured by stage-wise inspection and non-destructive testing. Dye penetrant test of root run and radiographic examination of final weld joint are most common. Post weld heat treatment is done as per code requirement. This Paper highlights three case studies on field repairs of stainless steel components in refinery. 1. Welding procedure followed for repair of bulged and cracked SS 316 strip-lining and cladding on carbon steel backing material. It is a dissimilar welding of SS 316L with degraded carbon steel. 2. Field welding of SS 347 Piping components, which has undergone thermal relaxation cracking at fillet joints. 3. Welding repair of SS 310 cast heater tube support conforming to A 297 Gr HK 40. The Paper also presents brief failure analysis with reasons and remedies.
375
Authors: Rui Ren, Bao Xiang Deng
Abstract: In this paper, the column chromatography technology on the separation of components of polypropylene fiber spin-finishes was studied. After determining the optimum separation condition, the column chromatography was used to separate and quantitatively analyze the main components of polypropylene fiber spin-finishes. The results showed this spin-finishes was mainly made up of four components, of which A: 1.85 %; B: 44.81 %; C: 27.58 %; D: 25.76 % by weight respectively.
2013
Authors: Sang Beom Kang, W.Alan Doolittle, Stuart R. Stock, April S. Brown
1499
Authors: Tomoaki Hatayama, Hidenori Koketsu, Hiroshi Yano, Takashi Fuyuki
Abstract: Relationship between the chemical reactivity and the orientation of SiC substrates was investigated. Thermal etching of 4H-SiC in the mixed gas of oxygen and chlorine was carried out as the chemical reaction. The etching rate did not change monotonously with the increase of the off angle in 4H-SiC (000-1) C substrate. By the use of such tendency in the thermal etching, the three dimensional structure with the specific pyramidal plane was able to be obtained.
869
Authors: Li Gong Yang, Bo Deng
Abstract: Text sentiment analysis is a new branch of computational linguistics which is widely concerned. In this paper, we present an approach to determine polarity of sentiment word based on context of sentence. We first change the context of sentence to semantic pattern vector, calculate the between different sentences, then compare sentences context indirectly by comparing similarity of their pattern vector, next we annotate polarity of sentiment word according to comparing result. Experiment shows that when the context of two sentences have high similarity, it is likely to have high precision in recognizing polarity of sentiment word. Our study shows it's feasible to use semantic pattern vector in representing context and judging polarity of sentiment words.
2340
Authors: Wen Li Zheng, Wei Yang
Abstract: A comparative study worked on crystal morphology and luminescence characteristic by hydrothermal method with mineralizer of 3 mol /L KOH, fill factor of 35%, under the condition of three kinds of mineralizers which included 3 mol /L KOH in sample 1, 3 mol /L KOH and 1 mol /L LiOH in sample 2, 3 mol /L KOH and CaO: Zn ( OH) 2 = 2% (amount of substance percentage). Nonpolar ZnO crystals were synthesized by adding proper proportion of CaO or LiOH,the speed of growth along c-axic was weakened obviously. The obtained ZnO crystals exposed more areas on the positive polar face c { 0001}. meanwhile,it exposed negative polar-c {000},positive pyramidal face + p { 101},negative pyramidal face-p {10} and hexagonal faces m {1010}. Only KOH or LiOH auxiliarily added,the emission spectrum was only visible light,no UV light from band edge transition, indicating that the crystal defects luminous center are numerous. A strong UV band emitting from band edge transition was in luminescent spectrumn of the prepared crystals by adding CaO,which indicated a decrease in defects luminous center.
302
Authors: Yeon Ki Hong, Hyoung Wook Lee, Sung Min Bae
Abstract: Acrylic acid and its derivatives are raw materials for polymeric, paint additives, adhesive, textile and leather treating products. The increasing demand of acrylic acid is great attention for its recovery from dilute aqueous solutions. With this aim, the amine based extraction of acrylic acid from its aqueous solutions in polar diluents was investigated. In the extraction, the tri-n-octylamine in polar diluents was found to provide higher extraction efficiency than that in nonpolar diluents. It was presumed that the acid-amine complex formation is difficult and the low solubility of acid-amine complex is low in nonpolar diluents. Higher extraction efficiency for acrylic acid was obtained with the polarity of active diluents due to higher solubility for acid-amine complex with polarity of diluents.
2801
Authors: Daisuke Shiba, Eiji Yamasue, Keiichi N. Ishihara, Hideyuki Okumura
Abstract: Mechanochemical (MC) processes are often modified to a large extent with use of process control agents (PCAs). An appropriate PCA is, however, chosen semi-empirically for any MC process such as ball-milling. In this study, milling period and medium, PCA kinds and amount, and powder kinds, are altered as major parameters to systematically and mechanistically investigate the effect of PCAs on powder milling and the related phenomena. The model systems selected are TiO2 and ZnO powders with various PCAs including alkanes, alcohols, water, and a few ionic liquids. According to X-ray line broadening analyses the viscosity and the structure of PCA molecules strongly affect the MC process. In addition, the MC process for harder TiO2 is quite different from ZnO, and oxygen-derived polarity of PCA molecules would cause major difference on the milling behavior. Various parameters controlling the MC process will be discussed.
2665
Authors: Yuji Yamamoto, S. Harada, Kazuaki Seki, Atsushi Horio, Takato Mitsuhashi, Toru Ujihara
Abstract: We investigated the dislocation behaviors during the solution growth on Si-face and C-face off-axis 4H-SiC seed crystals by using synchrotron X-ray topography. On Si-face, almost all threading screw dislocations (TSDs) and threading edge dislocations (TEDs) are converted into Frank-type defects and basal plane dislocations (BPDs), respectively. On the other hand, on C-face, TSDs were hardly converted. Some of TEDs were converted to BPDs and BPD-TED reconversion was often occurred. Therefore, to reduce density of threading dislocations in the grown crystal, it is better to use Si-face off-axis seed crystal.
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