• Molecules and Cells
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• v.19 no.2
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• pp.239-245
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• 2005

Factor for inversion stimulation (FIS), the Escherichia coli protein, is a positive regulator of the transcription of genes that encode stable RNA species, such as rRNA and tRNA. Transcription of the rnpB gene encoding M1 RNA, the catalytic subunit of E. coli RNase P, rapidly declines under stringent conditions, as does that of other stable RNAs. There are multiple putative FIS binding sites upstream of the rnpB promoter. We tested whether FIS binds to these sites, and if so, how it affects rnpB transcription. In vitro binding assays revealed specific binding of FIS to multiple sites in the rnpB promoter region. Interestingly, FIS bound not only to the upstream region of the promoter, but also to the region from +4 to +18. FIS activated rnpB transcription in vitro, but the level of activation was much lower than that of the rrnB promoter for rRNA. We also examined the effects of FIS on rnpB transcription in vivo using isogenic $fis^+$ and $fis^-$ strains. rnpB transcription was higher in the $fis^-$ than the $fis^+$ cells during the transitions from lag to exponential phase, and from exponential to stationary phase.

• Membrane and Water Treatment
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• v.6 no.5
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• pp.423-437
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• 2015

Polyvinylidene fluoride/fullerene nanoparticle (PVDF/$C_{60}$) composite microfiltration (MF) membranes were fabricated by a non-solvent induced phase separation (NIPS) using N, N-dimethylacetamide (DMAc) as solvent and deionized water (DI) as coagulation solution. Polyvinylpyrrolidone (PVP) was added to the casting solution to form membrane pores. $C_{60}$ was added in increments of 0.2% from 0.0% to 1.0% to produce six different membrane types: one pristine PVDF membrane type with no $C_{60}$ added as control, and five composite membrane types with varying $C_{60}$ concentrations of 0.2, 0.4, 0.6, 0.8 and 1.0%, respectively. The mechanical strength, morphology, pore size and distribution, hydrophilicity, surface property, permeation performance, and fouling resistance of the six membranes types were characterized using respective analytical methods. The results indicate that membranes containing $C_{60}$ have higher surface porosity and pore density than the pristine membrane. The presence of numerous pores on the membrane caused weaker mechanical strength, but the water flux of the composite membranes increased in spite of their smaller size. Initial flux and surface roughness reached the maximum point among the composite membranes when the $C_{60}$ concentration was 0.6 wt.%.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.31 no.4C
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• pp.351-363
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• 2006

The 8-VSB modulation, the transmission standard for the terrestrial digital television(DTV) of the Advanced Television Systems Committee(ATSC), suffers from multipath fading because it conveys information on the amplitude. To solve this problem, decision feedback equalizers(DFE's) have been commonly used in terrestrial DTV receivers. However, under severe channels, such as a 0 dB ghost channel or a single frequency network (SFN) channel, the DFE shows unstable convergence due to the error propagation caused by decision errors. Instead of unstable time-domain DFE schemes, by proposing a frequency-domain direct-inversion equalization method, we try to guarantee stable equalization and achieve low symbol error rates. To secure the existence of a channel inverse, channel-matched filtering and noncausal filtering are carried out prior to equalization. Simulation results show that the proposed method performs much better than existing DFE schemes in terms of both the stability and the symbol error rate.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.10 s.89
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• pp.983-995
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• 2004

This paper introduces a pre-compensation filter for compensating dispersive and resonant properties experienced along the usage of non-ideal wideband antennas in impulse communication systems. It has been well blown that the transmitted impulse signal becomes deformed because of dispersive and resonant characteristics. Accordingly, in spite of using ideal template signal at the correlator in coherent receiver, these impairments degrade overall performance attributed to low level of coherence. To overcome this problem this paper exploits a realization technique of pre-compensation filter purposely installed at transmitter whose stability is automatically guaranteed because it has an inversion form of minimum-phase ARMA (Auto-Regressive Moving Average) system. The performance of proposed scheme will be shown in results from computer simulations to verify its affirmative impact on impulse communication system with regarding several distinctively shaped antennas.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.18 no.4
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• pp.1042-1058
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• 2024

Terahertz (THz) communication is becoming a key technology for future 6G wireless networks because of its ultra-wide band. However, the implementation of THz communication systems confronts formidable challenges, notably beam splitting effects and high computational complexity associated with them. Our primary objective is to design a hybrid precoder that minimizes the Euclidean distance from the fully digital precoder. The analog precoding part adopts the delay-phase alternating minimization (DP-AltMin) algorithm, which divides the analog precoder into phase shifters and time delayers. This effectively addresses the beam splitting effects within THz communication by incorporating time delays. The traditional digital precoding solution, however, needs matrix inversion in THz massive multiple-input multiple-output (MIMO) communication systems, resulting in significant computational complexity and complicating the design of the analog precoder. To address this issue, we exploit the characteristics of THz massive MIMO communication systems and construct the digital precoder as a product of scale factors and semi-unitary matrices. We utilize Schatten norm and Hölder's inequality to create semi-unitary matrices after initializing the scale factors depending on the power allocation. Finally, the analog precoder and digital precoder are alternately optimized to obtain the ultimate hybrid precoding scheme. Extensive numerical simulations have demonstrated that our proposed algorithm outperforms existing methods in mitigating the beam splitting issue, improving system performance, and exhibiting lower complexity. Furthermore, our approach exhibits a more favorable alignment with practical application requirements, underlying its practicality and efficiency.

• Advances in materials Research
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• v.13 no.3
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• pp.243-251
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• 2024

The asymmetric polylactic acid (PLA) membrane was prepared via phase inversion method using non-solvent induced separation (NIPS) technique. This study aims to synthesized as well as to characterize the PLA membrane and evaluating the membrane performance on water flux and permeability. In addition, this research also studied the removal performance of methylene blue dye. The polymer solution has been prepared using 12 wt.% of PLA and dissolved in 88 wt.% of Dimethylacetamide (DMAc) as a solvent. Then, the cast film was immersed in different ratio of coagulant bath medium (distilled water: methanol: ethanol) ranging from 100:0:0, 75:25:0, 75:0:25 and 75:12.5:12.5, respectively). Several characterizations were performed which include, membrane contact angle and membrane porosity. Performance PLA membranes were determined in terms of water flux and permeability at 1 bar transmembrane pressure using dead-end permeation cell. Finally, methylene blue (MB) removal efficiency was tested at the same transmembrane pressure. The findings revealed that the increase of alcohol concentration in coagulant bath resulted in higher porosity and lower contact angle. In short, MB dye rejection efficiency is also closely related to the amount of alcohol ratio used in coagulant baths. Increases in concentration of methanol and ethanol in coagulant bath medium increases the membrane porosity thus increased in efficiency of methylene blue rejection.

• Nuclear Engineering and Technology
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• v.44 no.3
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• pp.237-248
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• 2012

Corium behavior in the lower plenum of the reactor vessel during a severe accident is very important, as this affects a failure mechanism of the lower head vessel and a thermal load to the outer reactor vessel under the IVR-ERVC (In-Vessel corium Retention through External Reactor Vessel Cooling) condition. This paper discusses the state of the art and technical issues on corium behavior in the lower plenum, such as initial corium pool formation characteristics and its transient behavior, natural convection heat transfer in various geometries, natural convection heat transfer with a phase change of melting and solidification, and corium interaction with a lower head vessel including penetrations of the ICI (In-Core Instrumentation) nozzle are discussed. It is recommended that more detailed analysis and experiments are necessary to solve the uncertainties of corium behavior in the lower plenum of the reactor vessel.

• Journal of the Korean Society of Industry Convergence
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• v.4 no.1
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• pp.61-69
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• 2001

Polycarbonate(PC) membranes for oxygen enrichment from air were prepared by the wet phase inversion method. In order to improve oxygen separation performances of the PC membrane, the effect of the added ethanol(nonsolvent) and $CuCl_2$(metal salt) concentration in the casting solution on morphology, oxygen permeability ami $O_2/N_2$ separation factor of the membrane was studied. In addition, tensile strength and elongation at break of the membrane were investigated. An asymmetric membrane with a dense top layer and a porous sublayer was obtained. The thickness of the dense top layer decreased with increasing amount of nonsolvent additive. Compared with pure PC membrane without additive(metal salt), the oxygen permeability and $O_2/N_2$ separation factor of the $PC/CuCl_2$ membrane are significantly improved. The oxygen permeability and $O_2/N_2$ separation factor is $5.25{\times}10^{-9}cm^3(STP){\cdot}cm/cm^2{\cdot}sec{\cdot}cmHg$ and 4.5, respectively. This improvement might be due to good interaction between metal salt and oxygen.

• Journal of Adhesion and Interface
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• v.11 no.1
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• pp.9-14
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• 2010

O/W emulsions were prepared with the phase inversion emulsification methods. The emulsifiers were used the UNIQ-1 (isopropylamine alkyl aryl sulphonate) and UNIQ-2 (alkoxylated glycol ether). Investigated effect that HLB value, agitator velocity and manufacture temperature get in mean particle size of emulsions. Mean particle size receives much effect of HLB value. Also, estimated stability about storage temperature and light. Emulsion's mean particle size was 193 nm lastly, reduced VOC amount used 90% than existing alkyd resin.

• KSBB Journal
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• v.29 no.5
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• pp.385-391
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• 2014

In this study, the emulsion dispersion stability of optimizing storage temperature was investigated. The system was based on oil/water (O/W) emulsions. In order to evaluate the stability, mean diameter of droplet was measured as a function of temperature with various mixed hydrophilic lipophilic balance (HLB). In addition, the correlations between phase inversion temperature (PIT) and the optimum storage temperature were probed. In this system, majority of the smallest droplet was shown at temperature of $20^{\circ}C$ below PIT. Whether the temperature was increased or decreased from the optimum, size of the droplet increased. According to the mixed HLB, the particle size and optimum storage temperature were also affected. As the concentrations of surfactant were increased, the size of particle decreased with lower optimum temperature for storage. If the surfactant (4 wt%) were mixed with HLB, the optimum storage temperature was $21^{\circ}C$ for maintaining the size of smallest droplet at 108.3 nm in diameter. At above optimum condition, increased size of particle was observed approximately 4 % increases from 108.2 nm to 112.3 nm after 600 hours. The size of particle in emulsion was maintained stably without any considerable effect of Ostwald ripening phenomena at the optimum storage temperature with low polydispersity index.