• Bulletin of the Korean Chemical Society
• /
• v.30 no.11
• /
• pp.2577-2583
• /
• 2009

Presented are the formation of iron oxide layers on evaporator tubes in an actual fossil power plant operated under all volatile treatment (AVT) condition and an experimental simulation of iron oxide formation in the presence of ferrous and ferric ions. After actual operations for 12781 and 36326 hr in the power plant, two iron oxide layers of magnetite on the evaporator tubes were found: a continuous inner layer and a porous outer layer. The experimental simulation (i.e., artificial corrosion in the presence of ferrous and ferric ions at 100 ppm level for 100 hr) reveals that ferrous ions turn the continuous inner oxide layer on tube metal to cracks and pores, while ferric ions facilitate the production of porous outer oxide layer consisting of large crystallites. Based on a comparison of the oxide layers produced in the experimental simulation with those observed on the actually used tubes, we propose possible routes for oxid layer formation schematically. In addition, the limits of the proposed corrosion routes are discussed in detail.

• Current Photovoltaic Research
• /
• v.10 no.1
• /
• pp.28-32
• /
• 2022

We investigated the optical and electrical characteristics of ITO/Ag/ITO (IAI) 3-layer thin films prepared by using RF/DC sputtering. To measure the thickness of all thin film samples, we used scanning electron microscopy. As a function of Ag thickness we characterized the optical transmittance and sheet resistance of the IAI samples by using UV-Visible spectroscopy and Hall measurement system, respectively. While the thickness of both ITO thin films in the 3-layered IAI samples were fixed at 50 nm, we varied Ag layer thickness in the range of 0 nm to 11 nm. The optical transmittance and sheet resistance of the 3-layered IAI thin films were found to vary strongly with the thickness of Ag film in the ITO (50 nm)/Ag(t₀)/ITO (50 nm) thin film. For the best transparent conducting oxide (TCO) electrode, we obtained a 3-layered ITO (50 nm)/Ag (t₀ = 8.5 nm)/ITO (50 nm) that showed an avrage optical transmittance, AVT = 90.12% in the visible light region of 380 nm to 780 nm and the sheet resistance, R_□ = 7.24 Ω/□.

• Asian-Australasian Journal of Animal Sciences
• /
• v.12 no.5
• /
• pp.695-701
• /
• 1999

The hypothalamus is the classic site of synthesis of arginine vasotocin as neurohypophyseal hormone in the chicken. However, high concentrations of arginine vasotocin were also measured in ovarian tissues by radioimmunoassay. At first, we observed specific positive signal of mRNA encoding AVT in the hypothalamus by Northern hybridization. However, we could not find any specific bands in ovarian and uterine tissues. For evidence of transcription of the arginine vasotocin gene ingonadal tissues of the chicken, this study has applied the polymerase chain reaction as a highly sensitive assay. The hypothalamus, the four largest preovulatory ovarian follicles and the shell gland (uterus) were collected at 4 h and 20 h before oviposition. The ovarian follicular tissues were separated into granulose theca interns and theca externa layers. The uterine tissues were separated into myometrium and endometrium The extracted mRNA was converted to cDNA by reverse-transcriptase using oligo-$d(T)_{15}$ primer. Then, the cDNA was amplified by Vent polymerase and arginine vasotocin specific primers. The amplification reaction was incubated by 30 cycles successively, $95^{\circ}C$, $55^{\circ}C$ and $72^{\circ}C$ earth for 1 min. Te comparisons of the mRNA levels encoding arginine vasotocin between the tissues were determined by semi-quantification methods. After amplification of the cDNA, the PCR products were detected in hypothalamus, ovarian tissues and uterine tissues. The results of semi-quantification showed that the levels of arginine vasotocin mRNA in ovarian iud uterine tissues were about from 1/50 to 1/1000 when compared to that in the hypothalamus. The very low levels of mRNA encoding arginine vasotocin in ovarian and uterine tissues probably led us to conclude that arginine vasotocin may play a role of local mediate acting autocrine and/or paracrine.

• Journal of Korean Society of Steel Construction
• /
• v.18 no.6
• /
• pp.769-782
• /
• 2006

As the ambient vibration test (AVT) of railway bridges has a limited range of speed, it has a limitation in examining the dynamic behavior of bridges accordingto speed. Thus, in order to analyze the correlation between the speed of a train passing over a bridge and the bridge's dynamic response, we conducted a speed-increasing experiment using a real diesel locomotive. To analyze the acceleration response characteristics, we attached seven vertical accelerometers at equal intervals throughout the entire section of the bridge except the supports, and one horizontal accelerometer to the middle span. Linear variable differential transformers (LVDT) were installed at the bridge's center in both vertical and horizontal directions to investigate the vertical and horizontal behaviors. The test train was statically loaded at the center and at the end of the bridge. And its speed was increased from 5 km/h to 90 km/h. With data obtained from the experiment, the vibration level was evaluated in each direction by the filtering frequency, and the level of horizontal vibration was examined in comparison with vertical vibration. The displacement and wheel load variation was analyzed by speed.

• The Journal of The Korea Institute of Intelligent Transport Systems
• /
• v.3 no.2 s.5
• /
• pp.129-140
• /
• 2004

In this paper, we conduct the research about optimal aggregation interval of travel time data on interrupted traffic flow and verify the reliability of AVI collected data by using car plate matching method in RTMS for systematic collection and analysis of link travel time data on interrupted traffic flow rural arterial. We perform Kolmosorov-Smirnov test on AVT collected sample data and on entire population data, and conclude that the sample data does not represent pure random sampling and hence includes sample collection error. We suggest that additional review is necessary to investigate the effectiveness of AVI collected sample data as link representative data. We also develop statistical model by applying two estimation techniques namely point estimation and interval estimation for calculating optimal aggregation interval. We have implemented our model and determine that point estimate is preferable over interval estimate for exactly selecting and deciding optimal aggregation interval. Our final conclusion is that 5-minute aggregation interval is optimal to estimate travel time in RTMS, as is currently being used our investigation is based on AVI data collected from Yang-ji to Yong-in $42^{nd}$ National road.

• Smart Structures and Systems
• /
• v.25 no.4
• /
• pp.487-499
• /
• 2020

This paper proposes a novel approach to model updating for a large-scale cable-stayed bridge based on ambient vibration tests coupled with a hybrid metaheuristic search algorithm. Vibration measurements are carried out under excitation sources of passing vehicles and wind. Based on the measured structural dynamic characteristics, a finite element (FE) model is updated. For long-span bridges, ambient vibration test (AVT) is the most effective vibration testing technique because ambient excitation is freely available, whereas a forced vibration test (FVT) requires considerable efforts to install actuators such as shakers to produce measurable responses. Particle swarm optimization (PSO) is a famous metaheuristic algorithm applied successfully in numerous fields over the last decades. However, PSO has big drawbacks that may decrease its efficiency in tackling the optimization problems. A possible drawback of PSO is premature convergence leading to low convergence level, particularly in complicated multi-peak search issues. On the other hand, PSO not only depends crucially on the quality of initial populations, but also it is impossible to improve the quality of new generations. If the positions of initial particles are far from the global best, it may be difficult to seek the best solution. To overcome the drawbacks of PSO, we propose a hybrid algorithm combining GA with an improved PSO (HGAIPSO). Two striking characteristics of HGAIPSO are briefly described as follows: (1) because of possessing crossover and mutation operators, GA is applied to generate the initial elite populations and (2) those populations are then employed to seek the best solution based on the global search capacity of IPSO that can tackle the problem of premature convergence of PSO. The results show that HGAIPSO not only identifies uncertain parameters of the considered bridge accurately, but also outperforms than PSO, improved PSO (IPSO), and a combination of GA and PSO (HGAPSO) in terms of convergence level and accuracy.