• Journal of Life Science
• /
• v.15 no.4 s.71
• /
• pp.553-560
• /
• 2005

The stf (Salmonella typhimurium fimbriae) operon consisting of stfA(CDEFG assumes to encode putative fimbriae. The complete stf operon is existed in S. typhimurium and S. choleraesuis, whereas it is absent in S. typhi. Analyses of the amino acid residues between major subunit StfA of the Stf fimbriae and those of known other fimbriaes suggested that Stf belongs to class I type fimbriae. Through comparison of StfD chaperone with the other fimbrial chaperones, and of C-terminus in subunits of Stf fimbriae, it belongs to FGS (with a short Fl-G1 loop) subfamily. In order to investigate the expression of stf operon, we have constructed a Salmonella strain containing a chromosomal stfA::lacZYA transcriptional fusion, resulting in S. typhimurium $_X8532$. The strain $_X8532$ lacked the expression of \beta-galactosidase$ under normal culture conditions. However, with longer incubation time of the S. typhimurium $_X8532$, we have isolated 21 individual strains exhibiting $Lac^+$ phenotype. $Lac^+$ phenotype was appeared as approximately 0.03 frequency per generation. All isolates expressed lacZ constitutively in the various environmental conditions. Various global regulatory proteins including RpoS, OmpR, and CpxR were not involved in the regulation of the stf operon. A S. typhimurium $_X8661$ mutant lacking stfAC function attenuated 6.7 folds more than that of wild type $_X3761$ in the mouse virulence test, suggesting in the somehow involved in the Salmonella pathogenesis.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.2C
• /
• pp.206-212
• /
• 2004

In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. STBC(Space-Time Block Coding) has been proposed as a simple diversity scheme using two transmit antennas. Also ST-OFDM(Space-Time Block Coded OFDM) and SF-OFDM(Space-Frequency Block Coded OFDM) transmission scheme, that the STBC is applied to the OFDM, has been proposed. In this paper, we propose STF-OFDM transmission scheme that to coded in time, space and frequency domain. The STF-OFDM transmission scheme that we propose in this paper is the way to improve a performance of conventional ST-OFDM, by using frequency diversity.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.7C
• /
• pp.954-961
• /
• 2004

In this paper, we propose a STF(Space-Time-Frequency) coded OFDM(Orthogonal Frequency Division Multiplexing) transmission scheme as an attractive solution for high bit rate data transmission in a multipath fading environment. The STF-OFDM transmission scheme that we propose in this paper is a simple transmission cheme for achieving frequency diversity gain with low complexity. Using preceding in frequency domain, we obtain frequency diversity gain and improve the SER performance of conventional ST-OFDM. The preceding scheme proposed in this paper is a very simple method that can be encoded and decoded with low complexity.

• Proceedings of the Botanical Society of Korea Conference
• /
• 1996.07a
• /
• pp.40-47
• /
• 1996

The promoters of a variety of plant genes are characterized by the presence of TGACG motif-containing sequences. These genes often exhibit quite diverse expression characteristics and in many case the TGACG-motif has been demonstrated to be essential for expression. Here we report the isolation and characterization of a soybean cDNA that encodes a novel basic/leucine zipper (bZIP) protein, STF1, that specifically interacts with Hex (TGACGTGG) and CRE (TGACGTCA) sequences. This protein contains a bZIP motif at C-teminus and an acidic domain at N-terminus. DNA binding specificities, heterodimer formation, and expression characteristics of STF1 were compared with a soybean TGA1 protein, STGA1. The soybean STF1 interacts with TGACG-sequences containing an ACGT core, while STGA1 requires TGACG as a sufficient binding sequence. The flanking sequences to the TGACG motif affected DNA binding of STF1 siginificantly. The STF1 mRNA is found mainly in dark grown soybean seedling with higher expression in apical and elongating hypocotyl, while STGA1 mRNA is highly abundant in roots of light grown plants. Furthermore, we demonstrate that STF1 heterodimerzes with G-box binding factorss (GBFs) which was not observed with TGA1. The fact that STF1 possesses both distinct DNA binding speficities and heterodimerization properties suggest that STF1 belongs to a new family of plant bZIP proteins which recognize the Hex/CRE motif.

• Tunnel and Underground Space
• /
• v.32 no.4
• /
• pp.272-284
• /
• 2022

This study conducted tunnel blasting to evaluate the blasting effect of a shear thickening fluid-based blasting stemming material and a sealed plug device under development. STF single stemming and STF stemming materials were combined with plugs to a tunnel blasting to which the SAV-Cut method was applied, and the advanced rate and fragmentation of tunnel blasting muck pile were compared when sand stemming was used. Tunnel advanced rate was evaluated using a 3D laser scanner. When the STF stemming material and STF stemming material with the plug were compared to the sand stemming material, it increased by 5.7 and 5.36%, respectively. As a result of evaluation of the fragmentation of tunnel blasting muck pile, it was the best when the STF stemming material was applied, and it decreased by about 61% compared to the case of sand stemming blasting. However, no significant improvement in blasting effect was observed with the application of plug devices.

• Explosives and Blasting
• /
• v.41 no.3
• /
• pp.1-12
• /
• 2023

A basic assessment of techniques to mitigate the risk of blast shock waves from proximity explosions was conducted. Common existing techniques include using mitigant materials to form barriers around the explosive or in the direction of propagation of the shock wave. Various explosive energy dissipation mechanisms have been proposed, and research on blast shock wave mitigation utilizing impedance differences has drawn considerable interest. In this study, shear thickening fluid (STF) was applied as a blast mitigation material to evaluate the effectiveness of STF mitigation material on explosion shock wave mitigation through explosion experiments and numerical analysis. As a result, the effectiveness of the STF mitigant material in reducing the explosion shock pressure was verified.

• International Journal of Aeronautical and Space Sciences
• /
• v.14 no.2
• /
• pp.140-145
• /
• 2013

The development of high performance fabrics have advanced body armor technology and improved ballistic performance while maintaining flexibility. Utilization of the shear thickening phenomenon exhibited by Shear Thickening Fluids (STF) has allowed further enhancement without hindering flexibility of the fabric through a process of impregnation. The effect of STF impregnation on the ballistic performance of fabrics has been studied for impact velocities below 700 m/s. Studies of STF-impregnated fabrics for high velocity impacts, which would provide a transition to significantly higher velocity ranges, are lacking. This study aims to investigate the effect of STF impregnation on the high velocity impact characteristics of Kevlar fabric by effectively dispersing silica nanoparticles in a suspension, impregnating Kevlar fabrics, and performing high velocity impact experiments with projectile velocities in the range of 1 km/s to compare the post impact characteristics between neat Kevlar and impregnated Kevlar fabrics. 100 nm diameter silica nanoparticles were dispersed using a homogenizer and sonicator in a solution of polyethylene glycol (PEG) and diluted with methanol for effective impregnation to Kevlar fabric, and the methanol was evaporated in a heat oven. High velocity impact of STF-impregnated Kevlar fabric revealed differences in the post impact rear formation compared to neat Kevlar.

• Composites Research
• /
• v.29 no.1
• /
• pp.24-32
• /
• 2016

Ballistic impact analyses have been performed with the Kevlar fabric impregnated with STF(shear thickening fluid). Multi-layer laminates modeled with 3D isoparametric shell elements were used for the performance analysis and their results are compared with experimental results. Both experiments and numerical analyses have been done to verify the usefulness of STF to enhance the impact resistance performance. The results showed that STF increases friction within a bundle of fiber, and this phenomena is more apparent in the velocity range of under near 450 m/s. In this research, it is emphasized that FEA analyses of STF impregnated Kevlar fabric laminate were successfully conducted using shell elements. Moreover, the effectiveness of the technique and accuracy were verified through the comparison with reliable experimental data.

• Composites Research
• /
• v.20 no.3
• /
• pp.17-24
• /
• 2007

In this study, the failure modes by ballistic impacts were studied both for a neat Kevlar woven fabric and a Kevlar liquid armor impregnated with shear thickening fluid (STF) containing silica particles. These two materials showed quite different failure modes macroscopically in ballistic impacts tests used by Cal.22 FSP and 9mm FMJ bullet. Yarn pull-out for the neat Kevlar woven fabric and yarn fracture occurred partially through all plies from 1st ply to last one for the STF-Kevlar are an important energy absorption mechanisms. The results observed by S.E.M showed commonly fiber damage which are torn skin in the longitudinal fiber direction, fiber split axially and fiber fracture for two materials. The reasons why STF-kevlar liquid armor material exhibits excellent ballistic performance are as follow: firstly the increased friction forces between yarn-yarn and fabric-fabric covered with silica particles and secondary the evolution of shear thickening phenomenmon resulting in suppression of yarn mobility.

• The Journal of Korean Association of Computer Education
• /
• v.7 no.5
• /
• pp.101-110
• /
• 2004

The multimedia community needs an environmental data representation and interchange mechanism which not only satisfies the requirements of today's systems, but can be extended to meet future data sharing needs. This mechanism must allow for the standard representation of, and access to data. The SEDRIS STF(SEDRIS Transmittal Format)provides environment data users and producers with a clearly defined interchange specification. In this paper I develop data converter commercial data(3DS MAX) format to standard interchange format and vice verse without losing semantic of information content using SEDRIS standard interchange format.