• 대한기계학회:학술대회논문집
• /
• 대한기계학회 2001년도 춘계학술대회논문집E
• /
• pp.125-130
• /
• 2001

Experimental and analytical researches have been conducted on the twin-fluid atomizers for better droplet breakup during the past decades. But, the studies on the disintegration mechanism still present a great challenge to understand the drop behavior and breakup structure. In an effort to describe the aerodynamic behavior of the sprays issuing from the internal mixing counter-swirling nozzle, the spatial distribution of axial (U) radial (V) and tangential (W) components of droplet velocities are investigated across the radial distance at several axial locations of Z=30, 50, 80, 120 and 170mm, respectively. Experiments were conducted for the liquid flow rates which was kept constant at 7.95 g/s and the air injection pressures were varied from 20 kPa to 140 kPa. Counter-swirling internal mixing nozzles manufactured at angles of $15^{\circ},\;30^{\circ},\;45^{\circ}$ and $60^{\circ}$ the central axis with axi-symmetric tangential-drilled holes was considered. The distributions of velocities and turbulence intensities are comparatively analyzed. PDPA is installed to specify spray flows, which have been conducted along the axial downstream distance from the nozzle exit. Ten thousand of sampling data was collected at each point with time limits of 30 second. 3-D automatic traversing system is used to control the exact measurement. It is observed that the sprays with all swirl angle have the maximum SMD for on air injection pressure of 20 kPa and 140 kPa with centerline, respectively. The nozzle with swirl angle of $60^{\circ}$ has vest performance.

• 한국환경성돌연변이발암원학회지
• /
• 제23권3호
• /
• pp.99-102
• /
• 2003

IARC classified areca quid as a human carcinogen. Areca quid chewed in Taiwan includes Piper betle inflorescence, which contains high concentrations of safrole (15 mg/fresh weight). Safrole is a documented rodent hepatocarcinogen, and chewing areca quid may contribute to human exposure (420 $\mu$m in saliva). The carcinogenicity of safrole is mediated through 1'-hydroxysafrole formation, followed by sulfonation to an unstable sulfate that reacts to form DNA adducts. Using human liver microsomes and Escherichia coli membranes expressing bicistronic human P450s, CYP2E1 and CYP2C9 were identified as the main P450s involved in the activation of safrole. We have demonstrated the presence of stable safrole-dGMP adducts in human oral tissues following areca quid chewing using $^{32}$ P-postlabeling and HPLC mass spectrometry methods. By studying 88 subjects with a known AQ chewing history and 161 matched controls, we have demonstrated that the presence of safrole-DNA adducts in peripheral blood cells was correlated to AQ chewing, and CYP2E1 seemed to play an important role in the modulation of safrole-DNA adduct formation. We have also shown that safrole can form stable safrole-DNA adducts as well as oxidative damages in rodent liver. However, the stable safrole-DNA adducts may represent a more significant initial lesion as compared to the rapidly repaired safrole-induced 8-hydroxy-2'-deoxyguanosine. This oxidative DNA damage is mediated through the formation of hydoryxchavicol, the major safrole metabolite in human urine. Hydroxychavicol may have gone through two-electron oxidation to the o-quinone; then via one-electron reduction to semiquinone radicals to generate oxidative DNA damage. However, these reactive metabolites can be efficiently conjugated by GSH. These data suggest that safrole may contribute to the initiation of oral carcinogenesis through safrole-DNA adduct and not oxidative DNA damage. In addition, CYP2E1 may modulate this adduct formation.

• 소성∙가공
• /
• 제7권2호
• /
• pp.168-176
• /
• 1998

Hot workability of the AA5083 alloy ws investigated by torsion test at temperature ranges of $350{\sim}520^{\circ}C$ and strain rates of 0.5, 1.0, and 3.0/sec. The flow stress and hot ductility of the AA5083 alloy as a function of deformation variables such as temperature and train rate were studied. The microstructural evolution of the AA5083 alloy was studied in relation to Zener-Hollomon parameter (Z=exp( /RT) Also the hot restoration mechanism of the AA5083 alloy was small when Z val-ues were higher than $1.73{\times}1016/sec(370^{\circ}C,\;0.5/sec)$ In addition the difference microstructures during hot deformation. It was found that the increase of flow curves and deformed microstructures during hot deformation. It was found that the increase of flow stress of the AA5083 alloy was small when Z val-ues were higher than $1.73{\times}1016/sec(370^{\circ}C.\;0.5/sec)$. However under the low Z values less than $1.73{\times}1016/sec(370^{\circ}C,\;0.5/sec)$ the flow stress increase with increasing the Z values. The large dispersoid particles in the matrix grain decreased the flow strain of the AA5083 alloy because it caused the stress concentration during hot deformation.

• Journal of Biosystems Engineering
• /
• 제31권6호
• /
• pp.514-523
• /
• 2006

Production of green pepper has been increased due to customer's preference and a projected ten-year boom in the industry in Korea. This study was carried out to develop an automatic grading and sorting system for green pepper using machine vision. The system consisted of a feeding mechanism, segregation section, an image inspection chamber, image processing section, system control section, grading section, and discharging section. Green peppers were separated and transported using a bowl feeder with a vibrator and a belt conveyor, respectively. Images were taken using color CCD cameras and a color frame grabber. An on-line grading algorithm was developed using Visual C/C++. The green peppers could be graded into four classes by activating air nozzles located at the discharging section. Length and curvature of each green pepper were measured while removing a stem of it. The first derivative of thickness profile was used to remove a stem area of segmented image of the pepper. While pepper is moving at 0.45 m/s, the accuracy of grading sorting for large, medium and small pepper are 86.0%, 81.3% and 90.6% respectively. Sorting performance was 121 kg/hour, and about five times better than manual sorting. The developed system was also economically feasible to grade and sort green peppers showing the cost about 40% lower than that of manual operations.

• 대한한의학회지
• /
• 제30권3호
• /
• pp.98-105
• /
• 2009

Objective: Increased aortic and carotid arterial augmentation index (AI) is associated with the risk of cardiovascular disease. The most widely used approach for determining central arterial AI is by calculating the aortic pressure waveform from radial arterial waveforms using a transfer function. But how the change of waveform by applied pressure and the pattern of the change rely on subject's characteristics has not been recognized. In this study, we use a new method for measuring radial waveform and observe the change of waveform and the deviation of radial AI in the same position by applied pressure. Method: Forty-six non-patient volunteers (31 men and 15 women, age range 21-58 years) were enrolled for this study. Informed consent in a form approved by the institutional review board was obtained in all subjects. Blood pressure was measured on the left upper arm using an oscillometric method, radial pressure waves were recorded with the use of an improved automated tonometry device. DMP-3000(DAEYOMEDI Co., Ltd. Ansan, Korea) has robotics mechanism to scan and trace automatically. For each subject, we performed the procedure 5 times for each applied pressure level. We could thus obtain 5 different radial pulse waveforms for the same person's same position at different applied pressures. All these processes were repeated twice for test reproducibility. Result: Aortic AI, peripheral AI and radial AI were higher in women than in men (P<0.01), radial AI strongly correlated with aortic AI, and radial AI was consistently approximately 39% higher than aortic AI. Relationship between representative radial AI of DMP-3000 and peripheral AI of SphygmoCor had strongly correlation. And there were three patterns in change of pulse waveform. Conclusion: In this study, it is revealed the new device was sufficient to measure how radial AI and radial waveform from the same person at the same time change under applied pressure and it had inverse-proportion to applied pressure.

• 터널과지하공간
• /
• 제26권4호
• /
• pp.316-326
• /
• 2016

본 연구는 화강암에 존재하는 결 이방성이 간접인장강도에 미치는 영향을 평가하였다. 표준 간접인장시험 및 3개의 서로다른 중공 크기에 대한 중공 간접인장시험을 수행하였다. 2차원 개별요소 수치해석을 통해 간접인장시험에서의 파괴 과정 및 메커니즘을 고찰하였다. 간접인장강도는 화강암의 결에 따라 하드웨이, 그레인, 리프트 면의 순으로 감소하였다. 중공 간접인장강도는 일반 간접인장강도에 비해 2.5~6.4배 정도 크게 나타났으며, 중공 크기가 클수록 크게 나타났다. 중공 시편에 대한 간접인장 파괴 유형은 중공 크기 및 결과 하중방향 각도에 영향을 받는 것으로 나타났다.

• Journal of Microbiology and Biotechnology
• /
• 제17권1호
• /
• pp.37-43
• /
• 2007

A gene encoding inulin fructotransferase (di-D-fructofuranose 1,2': 2,3' dianhydride [DFA III]-producing IFTase, EC 4.2.2.18) from Bacillus sp. snu-7 was cloned. This gene was composed of a single, 1,353-bp open reading frame encoding a protein composed of a 40-amino acid signal peptide and a 410-amino acid mature protein. The deduced amino acid sequence was 98% identical to Arthrobacter globiformis C11-1 IFTase (DFA III-producing). The enzyme was successfully expressed in E. coli as a functionally active, His-tagged protein, and it was purified in a single step using immobilized metal affinity chromatography. The purified enzyme showed much higher specific activity (1,276 units/mg protein) than other DFA III-producing IFTases. The recombinant and native enzymes were optimally active in very similar pH and temperature conditions. With a 103-min half-life at $60^{\circ}C$, the recombinant enzyme was as stable as the native enzyme. Acidic residues and cysteines potentially involved in the catalytic mechanism are proposed based on an alignment with other IFTases and a DFA IIIase.

• The Korean Journal of Physiology and Pharmacology
• /
• 제1권1호
• /
• pp.35-43
• /
• 1997

Cis-dichlorodiammine platin${\mu}M$II (Cisplatin), an effective chemotherapeutic agent, induces acute renal failure by unknown mechanisms. To investigate direct toxic effects of cisplatin on the renal proximal tubular transport system, LLC-$PK_1$ cell line was selected as a cell model and the sugar transport activity was evaluated during a course of cisplatin treatment. Cells grown to confluence were treated with cisplatin for 60 min, washed, and then incubated for up to 5 days. At appropriate intervals, cells were tested for sugar transport activity using ${\alpha}-methyl-D-[^{14}C]glucopyranoside$ (AMG) as a model substrate. In cells treated with 100 ${\mu}M$ cisplatin, the AMG uptake was progressively impaired after 3 days. The viability of cells was not substantially changed with cisplatin of less than 100 ${\mu}M$, but it decreased markedly with 150 and 200 ${\mu}M$. In cisplatin-treated cells, the $Na^+$ -dependent AMG uptake was drastically inhibited with no change in the $Na^+$ -independent uptake. Kinetic analysis indicated that Vmax was suppressed, but Km was not altered. The $Na^+$ -dependent phlorizin binding was also decreased in cisplatin-treated cells. However, the AMG efflux from preloaded cells was not apparently retarded by cisplatin treatment. These data indicate that the cisplatin treatment impairs $Na^+$ -hexose cotransporters in LLC-$PK_1$ cells and suggest strongly that defects in transporter function at the luminal plasma membrane of the proximal tubular cells constitute an important pathogenic mechanism of cisplatin nephrotoxicity.

• Wind and Structures
• /
• 제30권6호
• /
• pp.663-678
• /
• 2020

Robust semi-active vibration control of wind turbines using tuned mass dampers (TMDs) is a promising technique. This study investigates a 1.5 megawatt wind turbine controlled by eight different types of tuned mass damper systems of equal mass: a passive TMD, a semi-active varying-spring TMD, a semi-active varying-damper TMD, a semi-active varying-damper-and-spring TMD, as well as these four damper systems paired with an additional smaller passive TMD near the mid-point of the tower. The mechanism and controllers for each of these TMD systems are explained, such as employing magnetorheological dampers for the varying-damper TMD cases. The turbine is modelled as a lumped-mass 3D finite element model. The uncontrolled and controlled turbines are subjected to loading and operational cases including service wind loads on operational turbines, seismic loading with service wind on operational turbines, and high-intensity storm wind loads on parked turbines. The displacement and acceleration responses of the tower at the first and second mode shape maxima were used as the performance indicators. Ultimately, it was found that while all the semi-active TMD systems outperformed the passive systems, it was the semi-active varying-damper-and-spring system that was found to be the most effective overall - capable of controlling vibrations about as effectively with only half the mass as a passive TMD. It was also shown that by reducing the mass of the TMD and adding a second smaller TMD below, the vibrations near the mid-point could be greatly reduced at the cost of slightly increased vibrations at the tower top.

• Journal of Microbiology and Biotechnology
• /
• 제19권12호
• /
• pp.1557-1564
• /
• 2009

Human CDX2 is known as a caudal-related homeodomain transcription factor that is expressed in the intestinal epithelium and is important in differentiation and maintenance of the intestinal epithelial cells. The caudal-related homeobox proteins bind DNA according to a helix-turn-helix structure, thereby increasing the structural stability of DNA. A cancer-tumor suppressor role for Cdx2 has been shown by a decrease in the level of the expression of Cdx2 in colorectal cancer, but the mechanism of transcriptional regulation has not been examined at the molecular level. We developed a large-scale system for expression of the recombinant, novel CDX2, in Escherichia coli. A highly purified and soluble CDX2 protein was obtained in E. coli strain BL21(DE3)RIL and a hexahistidine fusion system using Ni-NTA affinity column, anion exchange, and gel filtration chromatographies. The identity and secondary structure of the purified CDX2 protein were confirmed by MALDI-TOF MS, Western blot, and a circular dichroism analyses. In addition, we studied the DNA-binding activity of recombinant CDX2 by ELISA experiment and isolated human CDX2-binding proteins derived from rat cells by an immobilized GST-fusion method. Three CDX2-binding proteins were found in the gastric tissue, and those proteins were identified to the homeobox protein Hox-D8, LIM homeobox protein 6, and SMC1L1 protein.