• Bulletin of the Korean Chemical Society
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• v.23 no.8
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• pp.1067-1072
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• 2002

A new polystyrene-divinylbenzene resin containing 2-(2-thiazolylazo)-5-dimethylamino-phenol (TAM) functional groups has been synthesized and its sorption behavior for nineteen metal ions, including Zr(Ⅳ),Hf(Ⅳ) and U(Ⅵ) has been investigated by batch and column methods. The chelating resin showed high sorption affinity for Zr(Ⅳ) at pH 1-5 and U(Ⅵ) at pH 4. Some parameters affecting the sorption of the metal ions have been detailed. The breakthrough and overall capacities were measured under optimized conditions. The overall capacities of Zr(Ⅳ), Th(Ⅳ) and U(Ⅵ), which showed higher than the other metal ions, were 0.90,0.84 and 0.80 mmol/g, respectively. The elution order of metal ions at pH 4 was evaluated as Zr(Ⅳ) > Th(Ⅳ) > U(Ⅵ) > Cu(Ⅱ) > Hf(Ⅳ) > W(Ⅵ) > Mo(Ⅵ) > In(Ⅲ) > Sn(Ⅳ) > Cr(Ⅲ) > V(Ⅴ) > Fe(Ⅲ). Quantitative recovery of most metal ions except Zr(Ⅳ) was achieved using 2M HNO3. Desorption and recovery of Zr(Ⅳ) was successfully performed with 2 M HClO4 and 2 M HCl.

• Journal of Acupuncture Research
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• v.28 no.2
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• pp.107-116
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• 2011

Objectives : This study was performed to investigate the effects of fixed-intensity and varied-intensity electroacupuncture on heart rate variability in healthy people with stress task. Methods : Forty healthy subjects were randomly assigned to either group A or group B or C. Group A received fixed-intensity electroacupuncture(F-EA) at $ST_{36}$ and $ST_{37}$. After 1 week wash out period to prevent overlapping residual effects, they received varied-intensity electroacupuncture(V-EA) in which the intensity was changed every two minutes based on individual heart rate variability at the same points. Group B received the treatments in reverse order. Group C received no intervention as a control group. Results : Control group showed a significant increase of LF and LF/HF during the 2nd working memory task, while both F-EA and V-EA did not. In addition, V-EA showed a significant increase of HF during 2nd rest while F-EA did not. Conclusions : These results suggest that F-EA and V-EA can inhibit sympathetic activation more than control group and that V-EA can enhance parasympathetic activation more than F-EA.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.2
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• pp.333-338
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• 2008

In this paper, a new NMOS current-mirror type bridge rectifier for driving RFID chips, whose minimum input voltage required to obtain the effective DC output voltage is low enough and whose power dissipation can be reduced than that of conventional one, is proposed. The designed rectifier is able to supply high enough and well-rectified DC voltages to drive RFID transponder chips for the frequency range of 13.56 MHz HF(for ISO 18000-3), 915 MHz UHF(fur ISO 18000-6), and 2.45 GHz microwave(for ISO 18000-4). Output characteristics of the proposed rectifier are analyzed with the high frequency equivalent circuit. And the circuitry method for effective reducing of the gate leakage current due to the increasing of operating frequency is also proposed theoretically. Using this method, the power consumption of $100\;{\mu}W$ and the DC output voltage of 2.13V for 3V peak-to-peak input voltage and $45\;K{\Omega}$ load resistance are obtained. Compared to conventional one, the proposed rectifier operates in more stable and shows superior characteristics in UHF and microwave frequencies.

• Bulletin of the Korean Chemical Society
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• v.27 no.5
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• pp.759-761
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• 2006

The compound B(C6F5)3 and its variations have been widely employed as alkyl carbanion abstracting reagents to produce metallocene cations for olefin polymerization.1-3 Weakly coordinating anions containing boron can greatly improve the activity of metallocene catalysts used in industrial olefin polymerization4 and thus group IV and V metallocene complexes of the organohydroborate anions have been intensively investigated.5 Recently, many organohydroborate metallocene complexes have been reported by Shore and co-workers.6-8 A common structural feature of those complexes is the three-center two electron M-H-B bond, like that observed in transition metal tetrahydroborate complexes but the reactivity and fluxional behavior of organohydroborate complexes are unlike those of the tetrahydroborate analogues.6 Although many of those metallocenes have been synthesized, few complexes could be used in the olefin polymerization and then this laboratory has been involved in the chemistry of the cyclic organohydroborate anions, and their group IV metallocene derivatives for the catalyst.9 Described here is recent work that led to the preparation of a novel cyclic organohydroborate hafnocene complex (h5-C5H5)2Hf ？(μ-H)2BC8H14 ,Cl. The hafnocene complex contains the three-center two electron bond Hf-H-B10 in which the hydride abstraction for olefin polymerization may occur.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.08a
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• pp.284-284
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• 2011

Ion sensitive field effect transistor (ISFET)는 용액 중의 각종 이온 농도를 측정하는 반도체 이온 센서이다. ISFET는 작은 소자 크기, 견고한 구조, 즉각적인 반응속도, 기존의 CMOS공정과 호환이 가능하다는 장점이 있다. ISFET의 기본 구조는 기존의 metal oxide semiconductor field effect transistor (MOSFET)에서 고안되었으며, ISFET는 기존의 MOSFET의 게이트 전극 부분이 기준전극과 전해질로 대체되어진 구조를 가지고 있다. ISFET소자의 pH 감지 메커니즘은 감지막의 표면에서 pH용액의 수소이온이 막의 표면에 속박되어 표면전위의 변화를 유발하는 것에 기인한다. 그 결과, 수소이온의 농도에 따라 ISFET의 문턱전압의 변화를 일으키게 되고 드레인 전류의 양 또한 달라지게 된다. 한편, ISFET의 좋은 pH감지특성과 높은 출력특성을 얻기 위하여 high-k물질들이 감지막으로써 지속적으로 연구되어져 왔다. 그 중 Al2O3와 HfO2는 높은 유전상수와 좋은 pH 감지능력으로 인하여 많은 연구가 이루어져온 물질이다. 하지만 HfO2는 높은 유전상수를 갖음에도 불구하고 화학용액에 대한 non-ideal 효과에 취약하다는 보고가 있다. 반면에 Al2O3의 유전상수는 HfO2보다 작지만 화학용액으로 인한 손상에 대하여 강한 immunity가 있는 재료이다. 본 연구에서는, 이러한 각각의 high-k 물질들의 단점을 보안하기 위하여 SiO2/HfO2/Al2O3(OHA) 적층막을 이용한 ISFET pH 센서를 제작하였으며 SOI 기판에서 구현되었다. SOI기판에서 OHA 적층막을 이용한 ISFET 제작이 이루어짐에 따라서 소자의 signal to noise 비율을 증대 시킬것으로 기대된다. 실제로 SOI-ISFET와 같이 제작된 SOI-MOSFET는 1.8${\times}$1010의 높은 on/off 전류 비율을을 보였으며 65 mV/dec의 subthreshold swing 값을 갖음으로써, 우수한 전기적 특성을 보이는 ISFET가 제작이 되었음을 확인 하였다. OHA 감지 적층막의 각 층은 양호한 계면상태, 높은 출력특성, 화학용액에 대한non-ideal 효과에 강한 immunity을 위하여 적층되었다. 결론적으로 SOI과 OHA 적층감지막을 이용하여 우수한 pH 감지 특성을 보이는 pH 센서가 제작되었다.

• Proceedings of the Korean Vacuum Society Conference
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• 2000.02a
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• pp.60-60
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• 2000

The adhesion interface formation between copper and poly(ethylene terephthalate)(PET), poly(methyl methacrylate)(PMMA) and Polyimide films was treated using Ion assisted reaction system to sequential sputter deposition by High-Frequency ion source. The ion beam modification system used a new type of low power HF ion thruster for space application as new low thruster electric propulsion system. Low power HF ion thruster with diameter 100mm gives the opportunity to obtain beams of Ar+ with currents 20~150 mA (current density 0.5~3.5 mA/cm2) and energy 200~2500eV at HF power level 10~150 W. Using Ar as a working gas it is possible to obtain thrust within 3~8 mN. Contact angles for untreated films were over 95$^{\circ}$ and 80 for Pet, 10o for PMMA and 12o for PI samples as a condition of ion assisted reaction at the ion dose of 10$\times$1016 ions/cm2, the ion beam potential of 1.2 keV and 4 ml/min for environmental gas flow rate. 900o peel tests yielded values of 15 to 35 for PET, 18 to 40 and 12 to 36 g/min. respectively. High resolution X-ray photoelectron spectrocopy is the Cls region for Cu metal on these polymer substrates showed increases in C=O-O groups for polymide, whereas PET and PMMA treated samples showed only C=O groups with increase the ion dose. Finally, unstable polymer surface can be changed from hydrophobic to hydrophilic formation such as C-O and C=O that were confirmed by the XPS analysis, conclusionally, the ion assisted reaction is very effective tools to attach reactive ion species to form functional groups on C-C bond chains of PET, PMMA and PI.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.20-29
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• 2018

Ti and its alloys show the excellent corrosion resistance to chloride environments, but they show less corrosion resistance in HCl, $H_2SO_4$, NaOH, $H_3PO_4$, and especially HF environments at high temperature and concentration. In this study, we used the commercially pure titanium and Ti-6Al-4V alloy, and evaluated the effect of the manufacturing process on the electrochemical properties. We used commercial products of rolled and forged materials, and made additive manufactured materials by DMT (Directed Metal Tooling) method. We annealed each specimen at $760^{\circ}C$ for one hour and then air cooled. We performed anodic polarization test, AC impedance measurement, and Mott-Schottky plot to evaluate the electrochemical properties. Despite of the difference of its microstructure of CP-Ti and Ti-6Al-4V alloys by the manufacturing process, the anodic polarization behavior was similar in 20% sulfuric acid. However, the addition of 0.1% hydrofluoric acid degraded the electrochemical properties. Among three kinds of the manufacturing process, the electrochemical properties of additive manufactured CP-Ti, and Ti-6Al-4V alloys were the lowest. It is noted that the test materials showed a Warburg impedance in HF acid environments.

• Journal of IKEEE
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• v.25 no.4
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• pp.770-773
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• 2021

In this paper, the retention characteristics of 3D NAND flash memory applied with tapering and ferroelectric (HfO₂) structure were analyzed after programming operation. Electrons trapped in nitride are affected by lateral charge migration over time. It was confirmed that more lateral charge migration occurred in the channel thickened by tapering of the trapped electrons. In addition, the Oxide-Nitride-Ferroelectric (ONF) structure has better lateral charge migration due to polarization, so the change in threshold voltage (V_th) is reduced compared to the Oxide-Nitride-Oxide (ONO) structure.

• Korean Circulation Journal
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• v.53 no.7
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• pp.483-496
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• 2023

Background and Objectives: Atrial fibrillation (AF) is associated with decreased cardiac resynchronization therapy (CRT) benefits compared to sinus rhythm (SR). Effective biventricular (BiV) pacing is a determinant of CRT success, but AF can interfere with adequate BiV pacing and affect clinical outcomes. We investigated the effect of device-detected AF on clinical outcomes and optimal BiV pacing in patients with heart failure (HF) treated with CRT. Methods: We retrospectively analyzed 174 patients who underwent CRT implantation between 2012 and 2019 at a tertiary center. The optimal BiV pacing percentage was defined as ≥98%. Device-detected AF was defined as an atrial high-rate episode ≥180 beats per minute lasting more than 6 minutes during the follow-up period. We stratified the patients without preexisting AF at pre-implantation into device-detected AF and no-AF groups. Results: A total of 120 patients did not show preexisting AF at pre-implantation, and 54 had AF. Among these 120 patients, 19 (15.8%) showed device-detected AF during a median follow-up of 25.1 months. The proportion of optimal BiV pacing was significantly lower in the device-detected AF group than in the no-AF group (42.1% vs. 75.2%, p=0.009). The devicedetected AF group had a higher incidence of HF hospitalization, cardiovascular death, and all-cause death than the no-AF group. The device-detected AF and previous AF groups showed no significant differences regarding the percentage of BiV pacing and clinical outcomes. Conclusions: For HF patients implanted with CRT, device-detected AF was associated with lower optimal BiV pacing and worse clinical outcomes than no-AF.

• Membrane and Water Treatment
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• v.1 no.3
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• pp.207-214
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• 2010

Approximately 80% of water used in urban areas reappears as municipal wastewater (MWW). Reclamation of MWW is an attractive proposition under the present scenario of water stressed cities in India. In this paper, we attempted to reclaim MWW using lab-scale hollow- fiber (HF) membrane modules for possible reuse in non-potable applications. Experiments were conducted to evaluate the efficiency of virgin HF ($M_1$) and modified HF ($M_2$) modules. The $M_2$ module consists of HF modified with a skin layer formed through interfacial polymerization of m-phenylenediamine with trimesoyl chloride (MPD-TMC). The molecular weight cut-off (MWCO) of $M_1$ was 44000 g/mol and that of $M_2$ 10000 -14000 g/mol on the basis of rejection of polyethylene glycol. The combination of $M_1$ and $M_2$ modules was able to reduce concentrations of most of the pollutants in sewage and improved the treated water quality to the acceptable limits for non potable reuse applications. It is found that about 98-99% of the initial flux is recovered by the backwashing process, which was approximately two times in a month when operated continuously.