• 대한기계학회논문집B
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• 제20권7호
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• pp.2267-2276
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• 1996

공정산업분야 및 분무연소분야에서 많이 사용되고 있는 2유체 분무기에서 출구 초음속유동의 가시화와 하류의 가스압력 측정 결과로부터 다음과 같은 결론을 얻었다. 1) 과소팽창 또는 과대팽창 초음속노즐 유동에서 출구 Mach수가 일정한 경우, 유동이 박리하지 않는다면 가스의 정체압력(유량)이 증가함에 따라 노즐출구에서 충돌정체점까지의 길이와 초음속 유동영역의 길이는 증가한다. 2) 스피팅 현상은 액체공급관 출구의 흡인압력은 분사가스압력이 증가함에 따라 단조증가하지만 분사가스압력이 0.5MPa이상이 되면 증감현상이 커지며 돌출형 노즐에서 유동박리시 급격히 증가한 다음 거의 일정하게 유지된다. 4) 액체공급관 하류축상의 압력변화는 출구의 음압에서 충돌정체점까지 상승한 다음 급강하하고 충격파 세포상의 구조에 따라 진동하면서 대기압에 도달한다.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1824-1827
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• 2005

For application to micro fluid control systems such as ${\mu}TAS$ (Micro Total Analysis Systems) and DDS (Drug Delivery Systems), it is very significant to handle precise and minute flow rates with low pressure pulsation. In this study, a novel valveless piezoelectric pump using peristaltic motion with three disk type PZT actuators is presented. The newly devised pump with an effective size of $70mm{\times}60mm{\times}55mm$ has three actuator layers connected in series from inlet to outlet. The PZT actuator has a maximum displacement of 240 ${\mu}m$ and a maximum force of 1.6 N. When the driving voltage for PZT actuators is sequentially applied with a certain phase shift, the pumping is performed by peristaltic motion of liquid volume. The working fluid is shut off without the driving voltage. Three methods for sequential driving are proposed and experimentally investigated. First and second methods utilize an intermittent sinusoidal waveform with phase shift of $90{\circ}\;and\;120^{\circ}$, respectively. Third method uses a rectangular waveform with phase shift of $90^{\circ}$. A controller with multi-phase shifter is designed and fabricated. Then, frequency and voltage-flow rate characteristics and load pressure-flow rate characteristics are experimentally investigated to verify the validity of the developed pump.

• 한국재료학회지
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• 제13권11호
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• pp.737-741
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• 2003

Polycrystalline $Ti_{l-x}$ $Co_{x}$ $O_2$thin films on $SiO_2$ (200 nm)/Si (100) substrates were prepared using liquid-delivery metalorganic chemical vapor deposition. Microstructures and ferromagnetic properties were investigated as a function of doped Co concentration. Ferromagnetic behaviors of polycrystalline films were observed at room temperature, and the magnetic and structural properties strongly depended on the Co distribution, which varied widely with doped Co concentration. The annealed $Ti_{l-x}$ $Co_{x}$ $O_2$thin films with $x\leq$0.05 showed a homogeneous structure without any clusters, and pure ferromagnetic properties of thin films are only attributed to the X$l-x_{l-x}$ $Co_{x}$X$O_2$phases. On the other hand, in case of thin films above x = 0.05, Co-rich clusters formed in a homogeneous $Ti_{l-x}$ $Co_{x}$ $O_2$phase, and the overall ferromagnetic (FM) properties depended on both FMTCO and FMCo. Co-rich clusters with about 10-150 nm size decreased the value of Mr (the remanent magnetization) and increased the saturation magnetic field.

• Journal of Pharmaceutical Investigation
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• 제33권2호
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• pp.121-127
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• 2003

The objective of this study was to solidify the simvastatin self-microemulsifying drug delivery system (SMEDDS) and to improve the encapsulation efficiency of solidified alginate beads using sodium alginate. Typical simvastatin SMEDDS was composed of various oils, surfactants and cosurfactants. Also solidified-alginate beads was prepared by crosslinking liquid emulsion mixtures containing sodium alginate and other excipients (cetylpyridinum chloride (CP-Cl), hydroxypropyl methylcellulose, starch and so on). in $CaCl_2$ solution, it has been investigated that the drug release pattern and encapsulation efficiency were varied with the ratio of cationic lipid (CP-Cl). Solidified sodium alginate beads containing simvastatin SMEDDS were redispersed into media without re-aggregation. Oil droplet size of redispersed solidified-beads in media produced smaller than the initial size. The density of beads and drug loading amount were increased with increasing cationic lipid content. These systems have advantages of storage stability and predictability of drug release rate.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.135-136
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• 2006

Bismuth titanate ($Bi_4Ti_3O_{12}$, BIT) thin film has been studied intensively in the past decade due to its large remanent polarization, low crystallization temperature, and high Curie temperature. Substitution of various trivalent rare-earth cations (such as $La^{3+}$, $Nd^{3+}$, $Sm^{3+}$ and $Pr^{3+}$) in the BIT structure is known to improve its ferroelectric properties, such as remanent polarization and fatigue characteristics. Among them, neodymuim-substituted bismuth titanate, ((Bi, Nd)$_4Ti_3O_{12}$, BNT) has been receiving much attention due to its larger ferroelectricity. In this study, Ferroelectric $Bi_{3.3}Nd_{0.7}Ti_3O_{12}$ thin films were successfully fabricated by liquid delivery MOCVD process onto Pt(111)/Ti/$SiO_2$/Si(l00) substrates. Fabricated polycrystailine BNT thin films were found to be random orientations, which were confirmed by X-ray diffraction and scanning electron microscope analyses. The remanent polarization of these films increased with increase in annealing temperature. And the film also demonstrated fatigue-free behavior up to $10^{11}$ read/write switching cycles. These results indicate that the randomly oriented BNT thin film is a promising candidate among ferroelectric materials useful for lead-free nonvolatile ferroelectric random access memory applications.

• KSBB Journal
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• 제31권4호
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• pp.208-213
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• 2016

Recently, numerous studies have utilized graphene in biomedical applications such as drug delivery, cancer therapy, and bioimaging. In this study, graphene was eco-friendly prepared by liquid phase exfoliation of graphite using plant extracts in water. Initially, 12 different plants or plant parts were screened for the characteristic graphene peak at near 268 nm using UV-Vis spectrophotometric analyses. The ability to form stable black graphene dispersion was highest using Xanthium strumarium extract. Transmission electron microscopy images showed that about 5 layer-graphene was produced from 1 g/L of graphite, while more than 5 layers were formed from 2 g/L of graphite. The optimum X. strumarium concentration for graphene production was 2 g/100 mL.

• Asian Pacific Journal of Cancer Prevention
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• 제15권5호
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• pp.2069-2074
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• 2014

Purpose: To appraise the frequency of cervical cytological abnormalities in a population at normal risk via analysing the archive records of cytology for the period of approximately 9,5 years, comparing them with patient demographic charecteristics, and discuss the results for women under age of 35. Materials and Methods: A total of 32,578 cases of Pap smears were retrieved and analysed from our archive included the Pap tests performed between January 2001 and April 2010 at the Early Cancer Screening, Diagnosing and Education Center by the consent of three pathologists via utilizing the Bethesda System Criteria 2001 and the results were compared with some demographical characteristics. Results: Our rate of the cervical cytological abnormality was 1.83%, with ASCUS in 1.18%, LSIL in 0.39, HSIL in 0.16%, AGUS in 0.07%, squamous cell carcinoma in 0.02%, and adenoarcinoma in 0.006%. Cytological abnormalities were detected mostly in those with higher age, lower parity, and premenopausal period whereas the smoking status was without influence. Bacterial vaginosis (5.6%) was the most frequent infectious finding (Candida albicans 2.7%; Actinomyces sp. 1.3%; and Trichomonas vaginalis 0.2%) detected on the smears. The rate of abnormal cervical cytology was 9.5% among the women aged between 30-34. Conclusions: Early detection of the cervical abnormalities by means of the regular cervical cancer screening programmes is useful to attenuate the incidence, mortality, and morbidity of cervical cancer. Our prevalence of the cytological abnormalities was much lower than the one in Western populations in general but very similar to those reported from other Islamic countries that may be explained by the conservative lifestyle and the lower prevalence of HPV in Turkey. A remarkable rate of abnormal cervical cytology of women aged 30-34 was pointed out in the present study.

• Journal of Biosystems Engineering
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• 제32권6호
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• pp.440-447
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• 2007

In this study, a biosensor was developed using an enzyme-linked immunosorbent assay (ELISA) to rapidly measure the fungicide iprovalicarb residues in agricultural products. The biosensor was designed to include micro-pumps and solenoid valves for fluid transport, a spectrophotometer cuvet as a reaction chamber, a photodiode with a light-emitting diode for optical density measurement, and a control microcomputer to implement assay. The rate of change in optical density of the cuvet was read as final signal output. Micro-pumps were evaluated to investigate their delivery capability, the highest values of the error and the coefficient of variation were 4.3% and 4.6% respectively. As the incubation period was reduced from 15 minutes to 11 minutes to shorten the total processing time, the sensor sensitivity was decreased as the antibody dilution ratio was reduced to a half. The maximum usable period of the coated cuvet was found to be two days with 1% error limit. To predict the concentration of the iprovalicarb residue in agricultural products, a linear calibration model was obtained with r-square values of 0.992 for potato and 0.985 for onion. In validation test for the samples of potatoes and onions against the high performance liquid chromatography, very high correlation values were obtained as 0.996 and 0.993 respectively. Using the cuvet immobilized with antigen, it took 21-minutes for the biosensor to complete the measuring process of the iprovalicarb residues.

• Journal of Pharmaceutical Investigation
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• 제39권5호
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• pp.359-366
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• 2009

In this study, paclitaxel-loaded lipid nanosuspension (PxLN) was prepared and the in vivo profiles after intravenous administration in rats were investigated. We compared the manufacturing processes depending on the temperature: PxLN-H for a hot homogenization process and PxLN-C for solidification of lipid-drug mixtures by liquid nitrogen. Both formulations showed submicron size distribution and the similar drug loading efficiency of about 70%. In vitro release of PxLNs and Taxol$^{(R)}$ performed by a dialysis diffusion method showed similar pattern for PxLN-H and Taxol$^{(R)}$, but the reduced release profile for PxLN-C. PxLN or Taxol$^{(R)}$ was intravenously administered to the rats at a dose of 5 mg/kg as paclitaxel. The drug in blood samples were assayed by the HPLC/MS/MS method. The AUC$_t$ of PxLN-H was 3.4-fold greater than that of Taxol$^{(R)}$. PxLN-H gave higher biodistribution in all tissues than did Taxol$^{(R)}$. In addition, it maintained the higher drug concentration for 12 h. This lipid nanosuspension might be a promising candidate for an alternative formulation for the parenteral delivery of poorly water-soluble paclitaxel.

• 대한화장품학회지
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• 제41권3호
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• pp.201-208
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• 2015

오가노겔은 반고형상이며 3차원의 네트워크 구조로 이루어진 친유성 용매로 이루어져 있다. 본 연구에서는 유상과 수상에서 모두 난용성 특징을 가진 제니스테인을 포함하는 레시틴 오가노겔을 개발하였다. 이 시스템은 안정할 뿐만 아니라 경피 흡수 실험에서도 높은 흡수율을 보였다. 본 오가노겔 제형에 적합한 원료들을 선별한 결과, 수화된 레시틴, 해바라기유, dipropylene glycol (DPG), polyethylene glycol (PEG)이 이 시스템에서 주로 사용되었다. 레시틴 오가노겔의 제조에 적합한 원료의 함량은 phase ternary diagram 작성을 통하여 결정하였다. 제조된 레시틴 오가노겔을 organoleptic characteristics, stability, pH, rheology, phase transition temperatures, microscopic analysis, skin penetration 실험을 통해 평가하였다. 본 연구 결과를 통해 본 논문에서 제시하는 레시틴 오가노겔 제형은 안정한 상태에서 난용성 물질을 높은 농도로 피부에 효과적으로 전달할 수 있는 제형으로 활용될 수 있을 것이라 생각된다.