• Journal of Pharmaceutical Investigation
• /
• v.27 no.4
• /
• pp.287-293
• /
• 1997

To make a stable o/w emulsion, the effects of egg lecithin as an emulsifier and polyvinylpyrrolidone (PVP) as an auxiliary emulsifier on the physical stability of emulsion were investigated. The oil-in-water emulsion system was manufactured by microfluidizer and evaluated the physical stability. Average particle size and size distribution of emulsion was measured by dynamic light scattering analyzer and interfacial tension was measured. From the interfacial tension tested, critical micelle concentration of the egg lecithin was 0.1 %w/v and optimal concentration for the preparation of emulsion was 1.0 %w/v. The mean particle size was about $0.2\;{\mu}m$ which was suitable for injections. The short-term accelerated stability studies were conducted by centrifugation, freeze-thaw method and shaking of the emulsion samples. The addition of PVP was caused the reduction in the particle size and improved the physical stability of emulsion. These results suggested that a mixed interfacial film comprising the egg lecithin and PVP was formed at the o/w interface and it was effective in preventing phase separation under thermic or mechanical stress. We used antineoplaston A10 (A10) as a model drug which is peptide and amino acid derivative having a action to the living organism against the development of neoplastic growth by a nonimmunological progress. It has a poor solubility in water and there may be a difficulty in formulation of A10. Emulsion formulation study about A10 was performed. Solubility of A10 in emulsion was about five times as high as that in water. From the results of solubility and partition coefficient, almost A10 molecules in o/w emulsion exist in the interface between oil and water.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.993-994
• /
• 2008

Electrochromic (EC) devices are capable of reversibly changing their optical properties upon charge injection and extraction induced by the external voltage. The characteristics of the EC device, such as low power consumption, high coloration efficiency, and memory effects under open circuit status, make them suitable for use in a variety of applications including smart windows and electronic papers. Coloration due to reduction or oxidation of redox chromophores can be used for EC devices (e-paper), but the switching time is slow (second level). Recently, with increasing demand for the low cost, lightweight flat panel display with paper-like readability (electronic paper), an EC display technology based on dye-modified $TiO_2$ nanoparticle electrode was developed. A well known organic dye molecule, viologen, was adsorbed on the surface of a mesoporous $TiO_2$ nanoparticle film to form the EC electrode. On the other hand, ZnO is a wide bandgap II-VI semiconductor which has been applied in many fields such as UV lasers, field effect transistors and transparent conductors. The bandgap of the bulk ZnO is about 3.37 eV, which is close to that of the $TiO_2$ (3.4 eV). As a traditional transparent conductor, ZnO has excellent electron transport properties, even in ZnO nanoparticle films. In the past few years, one-dimension (1D) nanostructures of ZnO have attracted extensive research interest. In particular, 1D ZnO nanowires renders much better electron transportation capability by providing a direct conduction path for electron transport and greatly reducing the number of grain boundaries. These unique advantages make ZnO nanowires a promising matrix electrode for EC dye molecule loading. ZnO nanowires grow vertically from the substrate and form a dense array (Fig. 1). The ZnO nanowires show regular hexagonal cross section and the average diameter of the ZnO nanowires is about 100 nm. The cross-section image of the ZnO nanowires array (Fig. 1) indicates that the length of the ZnO nanowires is about $6\;{\mu}m$. From one on/off cycle of the ZnO EC cell (Fig. 2). We can see that, the switching time of a ZnO nanowire electrode EC cell with an active area of $1\;{\times}\;1\;cm^2$ is 170 ms and 142 ms for coloration and bleaching, respectively. The coloration and bleaching time is faster compared to the $TiO_2$ mesoporous EC devices with both coloration and bleaching time of about 250 ms for a device with an active area of $2.5\;cm^2$. With further optimization, it is possible that the response time can reach ten(s) of millisecond, i.e. capable of displaying video. Fig. 3 shows a prototype with two different transmittance states. It can be seen that good contrast was obtained. The retention was at least a few hours for these prototypes. Being an oxide, ZnO is oxidation resistant, i.e. it is more durable for field emission cathode. ZnO nanotetropods were also applied to realize the first prototype triode field emission device, making use of scattered surface-conduction electrons for field emission (Fig. 4). The device has a high efficiency (field emitted electron to total electron ratio) of about 60%. With this high efficiency, we were able to fabricate some prototype displays (Fig. 5 showing some alphanumerical symbols). ZnO tetrapods have four legs, which guarantees that there is one leg always pointing upward, even using screen printing method to fabricate the cathode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2008.11a
• /
• pp.430-430
• /
• 2008

Using multi plasma enhanced chemical vapor deposition system (Multi-PECVD), p-a-Si:H deposition layer as a $p^+$ region which was annealed by laser (Q-switched fiber laser, $\lambda$ = 1064 nm) on an n-type single crystalline Si (100) plane circle wafer was prepared as new doping method for single crystalline interdigitated back contact (IBC) solar cells. As lots of earlier studies implemented, most cases dealt with the excimer (excited dimer) laserannealing or crystallization of boron with the ultraviolet wavelength range and $10^{-9}$ sec pulse duration. In this study, the Q-switched fiber laser which has higher power, longer wavelength of infrared range ($\lambda$ = 1064 nm) and longer pulse duration of $10^{-8}$ sec than excimer laser was introduced for uniformly deposited p-a-Si:H layer to be annealed and to make sheet resistance expectable as an important process for IBC solar cell $p^+$ layer on a polished n-type Si circle wafer. A $525{\mu}m$ thick n-type Si semiconductor circle wafer of (100) plane which was dipped in a buffered hydrofluoric acid solution for 30 seconds was mounted on the Multi-PECVD system for p-a-Si:H deposition layer with the ratio of $SiH_4:H_2:B_2H_6$ = 30:120:30, at $200^{\circ}C$, 50 W power, 0.2 Torr pressure for 20 minutes. 15 mm $\times$ 15 mm size laser cut samples were annealed by fiber laser with different sets of power levels and frequencies. By comparing the results of lifetime measurement and sheet resistance relation, the laser condition set of 50 mm/s of mark speed, 160 kHz of period, 21 % of power level with continuous wave mode of scanner lens showed the features of small difference of lifetime and lowering sheet resistance than before the fiber laser treatment with not much surface damages. Diode level device was made to confirm these experimental results by measuring C-V, I-V characteristics. Uniform and expectable boron doped layer can play an important role to predict the efficiency during the fabricating process of IBC solar cells.

• Journal of the Institute of Electronics and Information Engineers
• /
• v.51 no.10
• /
• pp.57-63
• /
• 2014

This paper proposes an architecture of $3^{rd}$ order SDM(Sigma-Delta Modulator) with delayed feed-forward path in order to reduce the power consumption and area. The proposed SDM improve the architecture of conventional $3^{rd}$ order SDM which consists of two integrators. The proposed architecture can increase the coefficient values of first stage doubly by inserting the delayed feed-forward path. Accordingly, compared with the conventional architecture, the capacitor value($C_I$) of first integrator is reduced by half. Thus, because the load capacitance of first integrator became the half of original value, the output current of first op-amp is reduced as 51% and the capacitance area of first integrator is reduced as 48%. Therefore, the proposed method can optimize the power and the area. The proposed architecture in this paper is simulated under conditions which are supply voltage of 1.8V, input signal 1Vpp/1KHz, signal bandwidth of 24KHz and sampling frequency of 2.8224MHz in the 0.18um CMOS process. The simulation results are SNR(Signal to Noise Ratio) of 88.9dB and ENOB(Effective Number of Bits) of 14-bits. The total power consumption of the proposed SDM is $180{\mu}W$.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.11
• /
• pp.1999-2010
• /
• 1992

The fixed slab analogy device which can measure stress intensity factors(S.I.F) experimentally by slab analogy theory is developed in this paper. The margin of errors resulted from the new testing apparatus are between 0.02% and 8.25%. Therefore, it is assured that this one can be effectively used for the more accurate measurement of S.I.F.( $k_{I}$, $k_{I I}$) than conventional apparatus. The pitch of master grating used in this experiment is 0.1mm It is known that the ratio of the distance from crack tip to the crack length on obtaining the accurate stress intensity factor is between 0.4 and 0.7. The optimum curvature radius of slab is about 125mm. The thickness of slab(plate) used in the fixed slab analogy device is 0.05mm(P.V.C. ; E = 64 MN/ $m^{2}$, .nu.=0.38), which is proved to be suitable for the test. The optimum material for the frame(slab`s external boundary) is a alloy tool steel(SKS 5) plate and its thickness is 1mm. In this research, the rigid cracks are directly bonded to the slab surface by cyanoacrylate adhesive for the easiness of slab making and conformity to the practical crack figure. The material of rigid crack is thin steel plate. It is expected that the developed method can be used effectively for the analysis of $k_{I}$ and $k_{I I}$ of arbitrary shaped or distributed cracks.cks.

• Korean Journal of Materials Research
• /
• v.20 no.12
• /
• pp.669-675
• /
• 2010

One of the greatest challenges for our society is providing powerful electrochemical energy conversion and storage devices. Rechargeable lithium-ion batteries and fuel cells are among the most promising candidates in terms of energy and power density. As the starting material, $TiCl_4{\cdot}YCl_3$ solution and dispersing agent (HCP) were mixed and synthesized using ammonia as the precipitation agent, in order to prepare the nano size Y doped spherical $TiO_2$ precursor. Then, the $Li_4Ti_5O_{12}$ was synthesized using solid state reaction method through the stoichiometric mixture of Y doped spherical $TiO_2$ precursor and LiOH. The Ti mole increased the concentration of the spherical particle size due to the addition of HPC with a similar particle size distribution in a well in which $Li_4Ti_5O_{12}$ spherical particles could be obtained. The optimal synthesis conditions and the molar ratio of the Ti 0.05 mol reaction at $50^{\circ}C$ for 30 minutes and at $850^{\circ}C$ for 6 hours heat treatment time were optimized. $Li_4Ti_5O_{12}$ was prepared by the above conditions as a working electrode after generating the Coin cell; then, electrochemical properties were evaluated when the voltage range of 1.5V was flat, the initial capacity was 141 mAh/g, and cycle retention rate was 86%; also, redox reactions between 1.5 and 1.7V, which arose from the insertion and deintercalation of 0.005 mole of Y doping is not a case of doping because the C-rate characteristics were significantly better.

• Transactions of the Korean hydrogen and new energy society
• /
• v.22 no.1
• /
• pp.1-12
• /
• 2011

To improve the mechanical properties, such as durabilities and antioxidative characteristics, the covalently cross-linked (CL-) SPEEK (sulfonated polyether ether ketone)/Cs-substituted HPA (heteropoly acid) organic-inorganic composite membranes (CL-SPEEK/Cs-HPAs), have been intensively investigated. The composite membrane were prepared by blending cesium-substituted HPAs (Cs-HPAs), including tungstophosphoric acid (TPA), molybdophosphoric acid (MoPA), and tungstosilicic acid (TSiA) with cross-linking agent content of 0.01 mL. And composite electrolytes composed of Cs-HPAs, prepared by immersion (imm.) and titration (titr.) methods to increase the stability of HPAs in water, were applied to polymer electrolyte membrane electrolysis (PEME). As a result, the proton conductivity of Cs-substituted composite membranes increased rapidly over $60^{\circ}C$ but mechanical properties, such as tensile strength, decreased in accordance with added Cs content. The bleeding-out of Cs-TPA membranes by titration method (50 vol.% Cs) decreased steadily to 2.15%. In the oxidative stability test by Fenton solution, the durability of membranes with Cs-HPA significantly increased. In case of CL-SPEEK/ Cs-TPA membrane, duration time increased more than 1200 hours. It is expected that even though CL-SPEEK/Cs-MoPA membrane shows the high proton conductivity, electrocatalytic activity and cell voltage of 1.80 V for water electrolysis, the CL-SPEEK/Cs-TPA (imm.) is more suitable as an alternative membrane in real system with the satisfactory proton conductivity, mechanical properties, anti-oxidative stability and cell voltage of 1.89 V.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.21 no.1
• /
• pp.54-59
• /
• 1992

The characteristics of endogenous and exogenous ${\beta}-galactosidase\;({\beta}-Galase)$ produced from L. acidophilus were investigated as one of the serial studies on the fermentation of Chinese cabbage kimchi using L. acidophilus. Apparent molecular weight of endogenous and exogenous of the ${\beta}-Galase$ were investigated to be 550,000 and 740,000 daltons by the method of gel filtration and Km values of the both enzymes were 1.67mg/ml, 1.33mg/ml and $V_{max}$ were $8.5\;{\mu}\;mol/mg/30min.$, $2.65\;{\mu}\;mol/ml/30min.$, respectively. The optimum pH of the enzymes were 7 and 8, respectively. The optimum temperatures and salt concentrations of the both enzyme were the same and appeared to $30^{\circ}C$and$4{\sim}5%$, respectively. The activities of the endogenous and exogenous ${\beta}-Galase$ were decreased by increasing of temperature from $60^{\circ}C$to$90^{\circ}C$ and the decreasing rate of the enzyme activities on the processing of the heating times showed high at first 2 minutes of heating.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.33 no.6
• /
• pp.475-482
• /
• 2020

For electronic paper displays using electrophoresis, the response time and reflectivity of the image panel fabricated by filtering are analyzed. For the filtering process, a square wave and ramp wave are applied to white charged particles with a unique q/m value. We divide the sample panels into #1 to #4 according to the applied waveform in the filtering process. Step waves comprising two steps are used to drive the panel; therefore, we divide the driving conditions into D1~D4. The applied voltage at the first stage of the half cycle of the driving waveform moves the charged particles attached via the image force from the electrode, and the applied voltage at the second stage moves the floating charged particles by detaching. As mentioned, four types of driving conditions (D1 to D4) classified according to the half cycle of the driving waveform are applied to the samples #1 to #4), which are classified according to four types of filtering process. When driving condition D1 is applied to the four types of sample panels, the rise time of #1 is 1.59s, #2 is 1.706s, #3 is 1.853s, and #4 is 1.235s, resulting in #4 being relatively faster compared with other sample panels, and showing the same trend in other driving conditions. As a result, we confirm that applying the driving condition D1 causes abrupt movement of the white charged particles injected into the cell. When the same driving waveform (D1) is applied to each sample, reflectivities of 32.1% for #1, 31.4% for #2, 27.9% for #3, and 63.4% for #4 are measured. From the experiment, we confirm that the driving condition D1 (1s of 3.5 V, 9s of 3.0 V) and ramp wave #4 in filtering are desirable for good reflectivity and response time. Our research is expected to contribute to the improvement of the filtering process and optimization of the driving waveform.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.02a
• /
• pp.128-128
• /
• 2010

중적외선 영역은 장애물에 의해서 파장의 흡수가 거의 일어나지 않기 때문에 적외선 소자에서 널리 이용되고 있다. 현재 대부분의 중적외선 소자에는 HgCdTe (MCT)가 사용되고 있지만, 3성분계 화합물이 가지는 여러 문제를 가지고 있다. 반면에, 2성분계 화합물인 인듐안티모나이드 (InSb)는 중적외선 영역 ($3-5\;{\mu}m$) 파장 대에서 HgCdTe와 대등한 소자 특성을 나타냄과 동시에 낮은 기판 가격, 소자 제작의 용이성, 그리고 야전과 우주 공간에서 소자 동작의 안정성 때문에 HgCdTe를 대체할 물질로 주목을 받고 있다. InSb는 미국과 이스라엘과 같은 일부 선진국을 중심으로 연구가 되었지만, 국방 분야의 중요한 소자로 인식되었기 때문에 소자 제작에 관한 기술적인 내용은 국내에 많이 알려지지 않은 상태이다. 따라서 본 연구에서는 InSb 소자 제작의 기초연구로 절연막과 pn 접합 형성에 대한 연구를 수행하였다. 절연막의 특성을 알아보기 위해, InSb 기판위에 $SiO_2$와 $Si_3N_4$를 PECVD (Plasma Enhanced Chemical Vapor Deposition)로 증착을 하였다. 절연막의 계면 트랩 밀도는 77K에서 C-V (Capacitance-Voltage) 분석을 통하여 계산하였으며, Terman method 방법을 이용하였다.[1] $SiO_2$는 $120-200^{\circ}C$의 온도 영역에서 계면 트랩 밀도가 $4-5\;{\times}\;10^{11}cm^{-2}$범위를 가진 반면, $240^{\circ}C$의 경우 계면 트랩 밀도가 $21\;{\times}\;10^{11}cm^{-2}$로 크게 증가하였다. $Si_3N_4$는 $SiO_2$ 절연막에 비해서 3배 정도의 높은 계면 트랩 밀도 값을 나타내었으며. Remote PECVD 장비를 이용하여 $Si_3N_4$ 절연막에 관한 연구를 추가적으로 진행하여 $7-9\;{\times}\;10^{11}cm^{-2}$ 정도의 계면 트랩 밀도 값을 구할 수가 있었다. 따라서 InSb에 대한 절연막은 $200^{\circ}C$ 이하에서 증착된 $SiO_2$와 Remote PECVD로 증착 된 $Si_3N_4$가 적합하다고 할 수 있다. 절연막 연구와 더불어 InSb 소자의 pn 접합 연구를 진행하였다. n-InSb (100) 기판 ($n\;=\;0.2-0.85\;{\times}\;10^{15}cm^{-3}$ @77K)에 $Be^+$이온 주입하여 p층을 형성하여 제작 되었으며, 열처리 조건에 따른 소자의 특성을 관찰 하였다. $450^{\circ}C$에서 30초 동안 RTA (Rapid Thermal Annealing)공정을 진행한 샘플은 -0.1 V에서 $50\;{\mu}A$의 높은 암전류가 관찰되었으며, 열처리 조건을 60, 120, 180초로 변화하면서 소자의 특성 변화를 관찰하였다.