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81.
Wonihl?ChoEmail author Seung-Ho?Lee Youngsoon?Baek Seong-Min?Lee Young?Tai?Kho 《Korean Journal of Chemical Engineering》2003,20(2):230-234
Catalytic combustion for applying heat shrink sleeves (HSS) to a pipeline in KOGAS was investigated. We used a low temperature
catalytic combustor in order to place HSS in the conduit. The surface temperature of the catalytic combustor maintained the
conditions at which HSS can become well-adhesive at the conduit. Therefore, the automatic HSS construction provided the chance
to establish gas pipeline safety by an automatic catalytic combustor device. 相似文献
82.
In a fin-tube heat exchanger the contact between fin collar and tube surface is obtained through mechanical expansion of tubes. Since the interfaces between the tubes and fins consist partially of metal-to-metal contact and partially of air, the features of heat transfer through the contact interfaces have not been fully investigated. The present study aims at the development of a new tool including an experiment and a numerical calculation for the estimation of the thermal contact conductance between the fin collar and tube surface, and pursues the evaluation of the factors affecting the thermal contact conductance in a fin-tube heat exchanger. Heat exchangers fabricated for the current study have been put to the test for heat balance in a vacuum chamber with water as an internal fluid. And a finite difference numerical scheme has been used for the data reduction of the experimental data to evaluate the thermal contact conductance. Fin-tube heat exchangers employed in the current research are of tube diameter of 7 mm with different tube expansion ratios, fin spacings, and fin types. The results of the present study imply that these parameters as well as hydrophilic fin coating have a significant effect on the thermal contact conductance. It has been discovered that the portion of the thermal contact resistance is not negligible compared with the total thermal resistance in a fin-tube heat exchanger, and this means that in order to reduce the thermal contact resistance thoughtful care should be taken in fabricating heat exchangers. 相似文献
83.
Physicochemical characterization of diclofenac sodium-loaded poloxamer gel as a rectal delivery system with fast absorption 总被引:1,自引:0,他引:1
Yong CS Sah H Jahng Y Chang HW Son JK Lee SH Jeong TC Rhee JD Baek SH Kim CK Choi HG 《Drug development and industrial pharmacy》2003,29(5):545-553
Rectal poloxamer gel systems composed of poloxamers and bioadhesive polymers were easy to administer to the anus and were mucoadhesive to the rectal tissues without leakage after the dose. However, a poloxamer gel containing diclofenac sodium could not be developed using bioadhesive polymers, since the drug was precipitated in this preparation. To develop a poloxamer gel using sodium chloride instead of bioadhesive polymers, the physicochemical properties such as gelation temperature, gel strength, and bioadhesive force of various formulations composed of diclofenac sodium, poloxamers, and sodium chloride were investigated. Furthermore, the pharmacokinetic study of diclofenac sodium delivered by the poloxamer gel was performed. Diclofenac sodium significantly increased the gelation temperature and weakened the gel strength and bioadhesive force, while sodium chloride did the opposite. The poloxamer gels with less than 1.0% sodium chloride, in which the drug was not precipitated, were inserted into the rectum without difficulty and leakage, and were retained in the rectum of rats for at least 6 hr. Furthermore, poloxamer gel gave significantly higher initial plasma concentrations and faster Tmax of diclofenac sodium than did solid suppository, indicating that drug from poloxamer gel could be absorbed faster than that from the solid one in rats. Our results suggested that a rectal poloxamer gel system with sodium chloride and poloxamers was a more physically stable, convenient, and effective rectal dosage form for diclofenac sodium. 相似文献
84.
Aluminum nitride (AlN) films were deposited using pulsed laser deposition (PLD) onto sapphire (0001) substrates with varying processing conditions (temperature, pressure, and laser fluence). We have studied the dependence of optical properties, structural properties and their correlations for these AlN films. The optical transmission spectra of the produced films were measured, and a numerical procedure was applied to accurately determine the optical constants for films of non-uniform thickness. The microstructure and texture of the films were studied using various X-ray diffraction techniques. The real part of the refractive index was found to not vary significantly with processing parameters, but absorption was found to be strongly dependent on the deposition temperature and the nitrogen pressure in the deposition chamber. We report that low optical absorption, textured polycrystalline AlN films can be produced by PLD on sapphire substrates at both low and high laser fluence using a background nitrogen pressure of 6.0 × 10− 2 Pa (4.5 × 10− 4 Torr) of 99.9% purity. 相似文献
85.
Young‐Hwan Lee Baek Ho Jung Tapan K. Sarkar Mengtao Yuan Zhong Ji Seong‐Ook Park 《ETRI Journal》2007,29(1):8-17
In this paper, we present a time domain combined field integral equation formulation (TD‐CFIE) to analyze the transient electromagnetic response from dielectric objects. The solution method is based on the method of moments which involves separate spatial and temporal testing procedures. A set of the RWG functions is used for spatial expansion of the equivalent electric and magnetic current densities, and a combination of RWG and its orthogonal component is used for spatial testing. The time domain unknowns are approximated by a set of orthonormal basis functions derived from the Laguerre polynomials. These basis functions are also used for temporal testing. Use of this temporal expansion function characterizing the time variable makes it possible to handle the time derivative terms in the integral equation and decouples the space‐time continuum in an analytic fashion. Numerical results computed by the proposed formulation are compared with the solutions of the frequency domain combined field integral equation. 相似文献
86.
Chang-Kyun Oh Yun-Jae Kim Jong-Hyun Baek Woo-sik Kim 《International Journal of Fracture》2007,143(2):119-133
The present paper proposes ductile failure criteria in terms of true fracture strain (the equivalent strain to fracture) as
a function of the stress triaxiality (defined by the ratio of the hydrostatic stress to the equivalent stress) for the API
X65 steel. To determine the stress-modified fracture strain, smooth and notched tensile bars with four different notch radii
are tested, from which true fracture strains are determined as a function of the notch radius. Then detailed elastic–plastic,
large strain finite element analyses are performed to estimate variations of stress triaxiality in the tensile bars, which
leads to true fracture strains as a function of the stress triaxiality, by combining them with experimental results. Two different
failure criteria are proposed, one based on local stress and strain information at the site where failure initiation is likely
to take place, and the other based on averaged stress and strain information over the ligament where ductile fracture is expected.
As a case study, ligament failures of API X65 pipes with a gouge are predicted and compared with experimental data. 相似文献
87.
Wi‐Fi based hotspots offer mobile users broadband wireless Internet connectivity in public work spaces and corporate/university campuses. Despite the aggressive deployment of these hotspots in recent years, high‐speed wireless Internet access remains restricted to small geographical areas due to the limited physical coverage of wireless LANs. On the other hand, despite their lower throughput, cellular networks have a significantly wider coverage and are thus much more available. Recognizing that 2.5G or 3G cellular networks can effectively complement wireless LANs, we set out to develop a vertical handoff system that allows mobile users to seamlessly fall back to such cellular networks as the general packet radio service (GPRS) or 3G whenever wireless LAN connectivity is not available. The resulting handoff mechanism allows a network connection of a mobile node to operate over multiple wireless access networks in a way that is transparent to end user applications. In this paper, we present the design, implementation, and evaluation of a fully operational vertical handoff system, called OmniCon, which enables mobile nodes to automatically switch between wireless LAN and GPRS, based on wireless LAN availability, by introducing a simple extension to the existing Mobile IP implementation. We discuss the design issues in the proposed vertical handoff system for heterogeneous networks, including connection setup problems due to network address translation, and the disparity in link characteristics between wireless LANs and GPRS. A detailed performance evaluation study of the OmniCon prototype demonstrates its ability to migrate active network connections between these two wireless technologies with low handoff latency and close to zero packet loss. Copyright © 2006 John Wiley & Sons, Ltd. 相似文献
88.
In this paper, we simply derive matrix inequality conditions on the terminal weighting matrices for linear discrete time-varying systems that guarantee non-increasing and non-decreasing monotonicities of the saddle-point value of a dynamic game. We show that the derived terminal inequality conditions ensure the closed-loop stability of the receding horizon H X control (RHHC). The stabilizing RHHC guarantees the H X norm bound of the closed-loop system. The derived terminal inequality conditions include most well-known existing terminal conditions for the closed-loop stability as special cases. The condition on the state weighting matrix is weakened so as to include even the zero matrix. The results for time-invariant systems are obtained correspondingly from those in the time-varying case. 相似文献
89.
Hye Jin Hwang Sang Woo Kim Yu Mi Baek Sung Hak Lee Hee Sun Hwang Jong Won Yun 《Korean Journal of Chemical Engineering》2009,26(1):115-126
We established the gene expression profiling in streptozotocin (STZ)-induced diabetic rat liver in response to hypoglycemic
fungal polysaccharides (EPS), using oligonucleotide microarray analysis. Differentially regulated genes showing higher fold
change than 2 were identified and categorized through hierarchical clustering analysis. Among the 835 genes analyzed, 244
were up-regulated, while 321 were down-regulated after diabetes induction. Interestingly, many gene expressions altered after
STZ-treatment mimicked a normal rat liver by EPS therapy. Most of these genes included genes involving cell structure and
motility, immunity and defense, lipid, fatty acid and steroid metabolism, protein metabolism and modification, and signal
transduction. More importantly, we found a total of 36 genes that showed significant fold changes in their expression that
have not previously been examined in the context of diabetes. To validate the microarray results, we further confirmed the
gene expression patterns by RT-PCR using four genes of interest (carboxylesterase 2, stearoyl-coenzyme A desaturase 1, insulin-like
growth factor 1, and insulin-like growth factor binding protein 2). Taken together, EPS acted as a potent regulator of gene
expression for a wide variety of genes in diabetic rat liver. 相似文献
90.
Eunyoung Lee Michelle Novais de Paula Sangki Baek Huynh Kim Khanh Ta Minh Tan Nguyen Taeck-Hyun Jeong Chong Jai Kim Yeon Jin Jang Han Choe 《International journal of molecular sciences》2021,22(12)
Human stem-cell factor (hSCF) stimulates the survival, proliferation, and differentiation of hematopoietic cells by binding to the c-Kit receptor. Various applications of hSCF require the efficient and reliable production of hSCF. hSCF exists in three forms: as two membrane-spanning proteins hSCF248 and hSCF229 and truncated soluble N-terminal protein hSCF164. hSCF164 is known to be insoluble when expressed in Escherichia coli cytoplasm, requiring a complex refolding procedure. The activity of hSCF248 has never been studied. Here, we investigated novel production methods for recombinant hSCF164 and hSCF248 without the refolding process. To increase the solubility of hSCF164, maltose-binding protein (MBP) and protein disulfide isomerase b’a’ domain (PDIb’a’) tags were attached to the N-terminus of hSCF164. These fusion proteins were overexpressed in soluble form in the Origami 2(DE3) E. coli strain. These solubilization effects were enhanced at a low temperature. His-hSCF248, the poly-His tagged form of hSCF248, was expressed in a highly soluble form without a solubilization tag protein, which was unexpected because His-hSCF248 contains a transmembrane domain. hSCF164 was purified using affinity and ion-exchange chromatography, and His-hSCF248 was purified by ion-exchange and gel filtration chromatography. The purified proteins stimulated the proliferation of TF-1 cells. Interestingly, the EC50 value of His-hSCF248 was 1 pg/mL, 100-fold lower than 9 ng/mL hSCF164. Additionally, His-hSCF248 decreased the doubling time, increased the proportion of S and G2/M stages in the cell cycle, and increased the c-Myc expression at a 1000-fold lower concentration than hSCF164. In conclusion, His-hSCF248 was expressed in a soluble form in E. coli and had stronger activity than hSCF164. The molecular chaperone, MBP, enabled the soluble overexpression of hSCF164. 相似文献