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1.
Won Seok Lyoo Han Do Ghim Hee‐Sam Kim Joon Ho Kim Sam Soo Kim Won Sik Yoon Jinwon Lee Sang‐Seob Lee 《应用聚合物科学杂志》2002,86(14):3667-3672
N‐Vinylcarbazole (VCZ) was solution‐polymerized in tetrahydrofuran (THF) at ?20, 0, and 20°C using the photoinitiation method; the effects of the amount of solvent, polymerization temperature, and photoinitiator concentration were investigated. On the whole, the experimental results corresponded to predicted ones. Low polymerization temperature using photoinitiation proved to be successful in obtaining poly(N‐vinylcarbazole) (PVCZ) of a high molecular weight with a smaller temperature rise during polymerization; nevertheless of free radical polymerization by 2,2′‐azobis(2,4‐dimethylvaleronitrile) (ADMVN). The photo‐solution polymerization rate of VCZ in THF was proportional to the 0.47 power of ADMVN concentration. The molecular weight was higher and the molecular weight distribution was narrower with PVCZ polymerized at lower temperatures. For PVCZ prepared in THF at ?20°C using a photoinitiator concentration of 0.00005 mol/mol of VCZ, a weight‐average molecular weight of 510,000 was obtained, with a polydispersity index of 1.73, and a degree of lightness converged to about 99%. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 3667–3672, 2002 相似文献
2.
Won Seok Lyoo Chan Sik Park Joon Ho Kim Han Do Ghim Ji Youl Lee Jinwon Lee Chul Joo Lee 《应用聚合物科学杂志》2003,88(3):832-839
Vinyl pivalate (VPi) was suspension‐polymerized to synthesize high molecular weight (HMW) poly(vinyl pivalate) (PVPi) with a high conversion above 95% for a precursor of syndiotacticity‐rich HMW poly(vinyl alcohol) (PVA). Also, the effects of the polymerization conditions on the conversion, molecular weight, and degree of branching (DB) of PVPi and PVA prepared by the saponification of PVPi were investigated. Bulk polymerization was slightly superior to suspension polymerization in increasing the molecular weight of PVA. On the other hand, the latter was absolutely superior to the former in increasing the conversion of the polymer, indicating that the suspension polymerization rate of VPi was faster than that of the bulk one. These effects could be explained by a kinetic order of a 2,2′‐azobis(2,4‐dimethylvaleronitrile) concentration calculated by the initial rate method. Suspension polymerization of VPi at 55°C by controlling various polymerization factors proved to be successful in preparing PVA of HMW [number‐average degree of polymerization (Pn): 8200–10,500], high syndiotactic diad content (58%), and very high yield (ultimate conversion of VPi into PVPi: 94–98%). In the case of the bulk polymerization of VPi at the same conditions, the maximum Pn and conversion of 10,700–11,800 and 32–43% were obtained, respectively. The DB was lower and the Pn was higher with PVA prepared from PVPi polymerized at lower initiator concentrations. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 832–839, 2003 相似文献
3.
Won Seok Lyoo Jeong Hyun Yeum Byung Chul Ji Han Do Ghim Sam Soo Kim Joon Ho Kim Ji Youl Lee Jinwon Lee 《应用聚合物科学杂志》2003,88(6):1482-1487
Water‐soluble high molecular weight (HMW) syndiotactic poly(vinyl alcohol) (s‐PVA) microfibrillar fibers were prepared by the saponification with various conditions such as amount of alkali solution, saponification temperature, and saponification concentration from copoly(vinyl pivalate (VPi)/vinyl acetate (VAc)) copolymerized using various VPi/VAc feed ratios. To produce s‐PVA microbrillar fibers having various water‐soluble temperatures for many industrial applications, the intrinsic viscosities, syndiotactic diad (S‐diad) contents, and degrees of saponification (DS)s of PVAs were finely controlled to 1.2–3.6 dL/g, 56.3–58.3%, and 91.4–98.3%, respectively. Through a series of experiments, it was found that the amount of alkali may alter the structure of the saponified polymers, primarily the DS, and the structural variation changes viscosity. That is, intrinsic viscosity was sharply decreased as the amount of alkali solution was increased. DS was increased with an increase in the amount of alkali solution. S‐diad content was increased with an increase in the VPi content. HMW s‐PVA microfibrillar fibers having S‐diad content of 56.3–58.3% prepared by the saponification of copoly(VPi/VAc) were completely soluble in water at 100°C. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 1482–1487, 2003 相似文献
4.
Krishnapuram R. Medasani S. Sung-Hwan Jung Young-Sik Choi Balasubramaniam R. 《Knowledge and Data Engineering, IEEE Transactions on》2004,16(10):1185-1199
A typical content-based image retrieval (CBIR) system would need to handle the vagueness in the user queries as well as the inherent uncertainty in image representation, similarity measure, and relevance feedback. We discuss how fuzzy set theory can be effectively used for this purpose and describe an image retrieval system called FIRST (fuzzy image retrieval system) which incorporates many of these ideas. FIRST can handle exemplar-based, graphical-sketch-based, as well as linguistic queries involving region labels, attributes, and spatial relations. FIRST uses fuzzy attributed relational graphs (FARGs) to represent images, where each node in the graph represents an image region and each edge represents a relation between two regions. The given query is converted to a FARG, and a low-complexity fuzzy graph matching algorithm is used to compare the query graph with the FARGs in the database. The use of an indexing scheme based on a leader clustering algorithm avoids an exhaustive search of the FARG database. We quantify the retrieval performance of the system in terms of several standard measures. 相似文献
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Chang-Min Suh Sang-Yeob Oh Young-Sik Pyun 《Journal of Mechanical Science and Technology》2010,24(5):1061-1066
This experimental studies were carried out in order to understand the effects of the PVD coating and the UNSM treatment of
HSS55 (high speed steel 55) during the production of the automotive inner pipe by the plastic deformation of S45C. The field
test and the SEM images revealed that the PVD coating is necessary in spite of the high compressive residual stresses which
were formed at the head of a punch pin. Upon the application of the AlCrN coating with the UNSM treatment the productivity
and reliability of a punch pin had improved more than about 2.6 times compared to that of the TiN coating without the UNSM
treatment. It is likely that the improvement is caused by the decreased stress concentration factor by the ‘wrapped in oxides’
inside of an abrasion pit. The abrasion pits were mostly generated within range of 5% ∼ 50% of the diameter ratio from the
end of a pin and reached the maximum value about 17% from the end of a pin. 相似文献
10.
Modern microprocessors achieve high application performance at an acceptable level of power dissipation. Reorder buffer is used for out-of-order instructions to be committed in-order. The reorder buffer plays a key role in modern microprocessors because performance improvement techniques highly rely on aggressive speculation to feed wider issue, out-of-order, and deep pipelines. In terms of power to performance trade-off, reorder buffer is particularly important. This is because enlarging the reorder buffer size achieves high performance but naive scaling of the conventional reorder buffer architecture can severely increase the complexity and power consumption. In this paper, we propose low-power reorder buffer techniques for contemporary microprocessors. First, the separated reorder buffer reduces power dissipation by deferred allocation and early release. The deferred allocation delays the SROB allocation of instructions until all their data dependencies are resolved. Then, the instructions are executed in program order and they are released faster from the SROB. The result of the instruction is written into rename buffers immediately after the execution completes. Then, the result values in the rename buffer are written into the architectural register file at the commit state. The proposed approaches in this paper provide higher resource utilization and low power consumption. 相似文献