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Hoai Han Nguyen,Thi Thu Hien Nguyen,조영상 대한금속·재료학회 2022 대한금속·재료학회지 Vol.60 No.10
Silica fibers were fabricated by sol-gel reaction and an electrospinning process. A high voltage source of electricity was applied to the prepared spinning solution to form the fibers. Macroporous silica fibers were prepared using polystyrene (PS) nanospheres as templates after calcination. The pore size could be controlled by adjusting the diameter of the PS nanospheres in the spinning solution. PS nanospheres with different diameters (250, 430, 600, 870, and 1000 nm) were synthesized for this purpose using the dispersion polymerization method. Silica fibers have a hydrophilic surface. A coating film applied to the fibers showed superhydrophilicity, which is not suitable for adsorbing oil contaminant. Thus, silane coupling agents containing methyl groups were used to modify the surface of the porous fibers to obtain hydrophobic and water-repellent properties. The amount of oil adsorbed by the porous silica fibers modified with various kinds of coupling agent or PS nanospheres with different sizes was investigated, to determine their effects on oil adsorption. When the size of the macropores in the fibers increased, the amount of oil adsorption increased, because oil infiltration through the pores became easier. Small hydrophobic groups of the silane coupling agent, like methyl groups, were able to adsorb more oil compared to bulky functional groups. The measured oil adsorption capacity of the porous fibers was found to be larger than that of mesomacroporous silica particles, since the voids between the fibers might provide additional space for oil adsorption.
Nguyen Hoai-Han,Park So-Hyun,Tran Quang-Hai,Jeong Jae-Hun,Cho Young-Sang 한국세라믹학회 2024 한국세라믹학회지 Vol.61 No.1
This study focuses on the synthesis and surface modification of silica particles using round-bottom flask and Taylor-vortex reactors with varying stirring speeds and K2SiO3 concentrations. The successful surface modification with MTCS is confirmed through FT–IR analysis, indicating the covalent attachment of methyl groups on the silica surface. Oil adsorption capacity testing reveals the influence of reactor type and stirring speed on particle performance. The Taylor-vortex reactor consistently displays higher homogeneity and oil adsorption capacity at lower stirring speeds, thanks to controlled hydrodynamic conditions. The FT–IR analysis also highlights characteristic oscillations and cohesion of the –CH3 groups after MTCS treatment. The findings underscore the importance of reactor selection and parameter optimization in tailoring silica particles for specific applications. This study contributes valuable insights into silica particle synthesis and modification, with implications in materials science and environmental technologies.
A High-linearity Wideband Discrete-time Receiver for Software-defined Radio
Hoai-Nam Nguyen,D. M. A. N. B. Dissanayake,Seok-Kyun Han,Sang-Gug Lee 대한전자공학회 2018 Journal of semiconductor technology and science Vol.18 No.1
A discrete-time (DT) receiver for software-defined radio (SDR) applications is presented. The receiver chain includes a wideband LNA and high linearity current commutating passive mixers merged with baseband switched-capacitor filters (SCFs) in current mode to simplify analog circuitries and reduce power consumption. An RF transconductor (RF TA) with capacitive-peaking bandwidth extension technique is proposed for the mixers to maximize the operating frequency band of the receiver. Implemented in a 0.18 μm CMOS process, the proposed receiver achieves a maximum voltage conversion gain of 41.2 dB, minimum NF of 3.8 dB, in-band IIP3 of -9 dBm, and out-of-band IIP3 of -6 dBm, respectively. The receiver operates from 0.7 to 2.4 GHz while dissipating 28-34 mA current from 1.8 V supplies.
Nicotine in High Concentration Causes Contraction of Isolated Strips of Rabbit Corpus Cavernosum
Nguyen, Hoai Bac,Lee, Shin Young,Park, Soo Hyun,Han, Jun Hyun,Lee, Moo Yeol,Myung, Soon Chul The Korean Society of Pharmacology 2015 The Korean Journal of Physiology & Pharmacology Vol.19 No.3
It is well known that cigarette smoke can cause erectile dysfunction by affecting the penile vascular system. However, the exact effects of nicotine on the corpus cavernosum remains poorly understood. Nicotine has been reported to cause relaxation of the corpus cavernosum; it has also been reported to cause both contraction and relaxation. Therefore, high concentrations of nicotine were studied in strips from the rabbit corpus cavernosum to better understand its effects. The proximal penile corpus cavernosal strips from male rabbits weighing approximately 4 kg were used in organ bath studies. Nicotine in high concentrations ($10^{-5}{\sim}10^{-4}M$) produced dose-dependent contractions of the corpus cavernosal strips. The incubation with $10^{-5}M$ hexamethonium (nicotinic receptor antagonist) significantly inhibited the magnitude of the nicotine associated contractions. The nicotine-induced contractions were not only significantly inhibited by pretreatment with $10^{-5}M$ indomethacin (nonspecific cyclooxygenase inhibitor) and with $10^{-6}M$ NS-398 (selective cyclooxygenase inhibitor), but also with $10^{-6}M$ Y-27632 (Rho kinase inhibitor). Ozagrel (thromboxane $A_2$ synthase inhibitor) and SQ-29548 (highly selective TP receptor antagonist) pretreatments significantly reduced the nicotine-induced contractile amplitude of the strips. High concentrations of nicotine caused contraction of isolated rabbit corpus cavernosal strips. This contraction appeared to be mediated by activation of nicotinic receptors. Rho-kinase and cyclooxygenase pathways, especially cyclooxygenase-2 and thromboxane $A_2$, might play a pivotal role in the mechanism associated with nicotine-induced contraction of the rabbit corpus cavernosum.
A 41dB Gain Control Range 6<sup>th</sup>-Order Band-Pass Receiver Front-End Using CMOS Switched FTI
Han, Seon-Ho,Nguyen, Hoai-Nam,Kim, Ki-Su,Park, Mi-Jeong,Yeo, Ik-Soo,Kim, Cheon-Soo The Institute of Electronics and Information Engin 2016 Journal of semiconductor technology and science Vol.16 No.5
A 41dB gain control range $6^{th}$-order band-pass receiver front-end (RFE) using CMOS switched frequency translated impedance (FTI) is presented in a 40 nm CMOS technology. The RFE consists of a frequency tunable RF band-pass filter (BPF), IQ gm cells, and IQ TIAs. The RF BPF has wide gain control range preserving constant filter Q and pass band flatness due to proposed pre-distortion scheme. Also, the RF filter using CMOS switches in FTI blocks shows low clock leakage to signal nodes, and results in low common mode noise and stable operation. The baseband IQ signals are generated by combining baseband Gm cells which receives 8-phase signal outputs down-converted at last stage of FTIs in the RF BPF. The measured results of the RFE show 36.4 dB gain and 6.3 dB NF at maximum gain mode. The pass-band IIP3 and out-band IIP3@20 MHz offset are -10 dBm and +12.6 dBm at maximum gain mode, and +14 dBm and +20.5 dBm at minimum gain mode, respectively. With a 1.2 V power supply, the current consumption of the overall RFE is 40 mA at 500 MHz carrier frequency.