• Proceedings of the SAREK Conference
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• 2008.11a
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• pp.493-498
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• 2008

Particles or deposit formed by corrosion of the pipe material bring about bad influences on the heating systems with inconvenience, energy loss and so on. In order to obtain the non-corrosive environments, the circulation hot water should properly be treated in several ways to satisfy one or more conditions of the followings: suitable pH-level, low hardness, low oxygen content, low conductivity, low level of chlorides and sulphur compounds and low level of solid particles. This experimental study was carried out to develope the new guidelines on the optimal water quality and directions for water quality management in heating systems. As results, it was recommended that the heating water be maintained pH-level not less than 8, hardness contents as $CaCO_3$ no more than 50 mg/L, turbidity no more than 10 NTU and T-Fe contents 1 mg/L below.

• Biomedical Science Letters
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• v.21 no.1
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• pp.40-49
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• 2015

Mesenchymal stem cells (MSCs) have the ability to self-renew and differentiate into multi-lineage cells, thus highlighting the feasibility of using umbilical cord blood-derived MSCs (UCB-MSCs) for cell-therapy and tissueengineering. However, the low numbers of UCB-MSC derived from clinical samples requires that an ex vivo expansion step be implemented. As most stem cells reside in low oxygen tension environments (i.e., hypoxia), we cultured the UCBMSCs under 3% $O_2$ or 21% $O_2$ and the following parameters were examined: proliferation, senescence, differentiation and stem cell specific gene expression. UCB-MSCs cultured under hypoxic conditions expanded to significantly higher levels and showed less senescence compared to UCB-MSCs cultured under normoxic conditions. In regards to differentiation potential, UCB-MSCs cultured under hypoxic and normoxic conditions both underwent similar levels of osteogenesis as determined by ALP and von Kossa assay. Furthermore, UCB-MSCs cultured under hypoxic conditions exhibited higher expression of OCT4, NANOG and SOX2 genes. Moreover, cells expanded under hypoxia maintained a stem cell immnunophenotype as determined by flow cytometry. These results demonstrate that the expansion of human UCB-MSCs under a low oxygen tension microenvironment significantly improved cell proliferation and differentiation. These results demonstrate that hypoxic culture can be rapidly and easily implemented into the clinical-scale expansion process in order to maximize UCB-MSCs yield for application in clinical settings and at the same time reduce culture time while maintaining cell product quality.

• KSBB Journal
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• v.15 no.5
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• pp.514-520
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• 2000

Simultaneous nitrification and denitrification of ammonia and organic compounds-containing wastewater were performed in a fluidized bed biofilm reactor with polysulfone(PS) hollow fiber as a double layer biomass carrier. The PS hollow fiber fragment has both aerobic and anoxic environments for the nitrifiaction and denitrification at the shell and lumen-side respectively. The reactor system showed about 80% nitrification efficiency stably throughout the ammonia load conditions applied in the experiment. Denitrification efficiency depended on organic load and C/N ratio. High free ammonia concentration and low dissolved oxygen resulted in nitrite accumulation which leads to enhance organic carbon efficiency in denitrification when compared to nitrate denitrification. The simultaneous nitrification and denitrification reactor system has an economic advantages in reduced chemical cost of organic carbon for denitrification as well as compact reactor configuration.

• Nutrition Research and Practice
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• v.4 no.6
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• pp.455-461
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• 2010

The tumor microenvironment, particularly sufficient nutrition and oxygen supply, is important for tumor cell survival. Nutrition deprivation causes cancer cell death. Since apoptosis is a major mechanism of neuronal loss, we explored neuronal apoptosis in various microenvironment conditions employing neuroblastoma (NB) cells. To investigate the effects of tumor malignancy and differentiation on apoptosis, the cells were exposed to poor microenvironments characterized as serum-free, low-glucose, and hypoxia. Incubation of the cells in serum-free and low-glucose environments significantly increased apoptosis in less malignant and more differentiated N-type IMR32 cells, whereas more malignant and less differentiated I-type BE(2)C cells were not affected by those treatments. In contrast, hypoxia (1 % $O_2$) did not affect apoptosis despite cell malignancy. It is suggested that DLK1 constitutes an important stem cell pathway for regulating self-renewal, clonogenicity, and tumorigenicity. This raises questions about the role of DLK1 in the cellular resistance of cancer cells under poor microenvironments, which cancer cells normally encounter. In the present study, DLK1 overexpression resulted in marked protection from apoptosis induced by nutrient deprivation. This in vitro model demonstrated that increasing severity of nutrition deprivation and knock-down of DLK1 caused greater apoptotic death, which could be a useful strategy for targeted therapies in fighting NB as well as for evaluating how nutrient deprived cells respond to therapeutic manipulation.

• Journal of the Microelectronics and Packaging Society
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• v.23 no.1
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• pp.11-15
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• 2016

The organic light emitting diodes (OLEDs) have been studied as large flexible displays, light source and hard wares of internet of things. However, OLEDs show some drawbacks in terms of external environments due to the low work function of the metals and the reactive organic materials. In particular, the operation functions of the OLEDs tend to deteriorate rapidly by exposing the oxygen and moisture. So as to prevent it, domestic and overseas studies underway in various method such as ALD, PVD, CVD. But it has complex process and high cost. Therefore In order to protect devices from the external environments, it is important to develop the passivation thin films of low-cost and simple process which can prevent the devices from the penetration of the oxygen and moistures. In this study, to improve the reliability, passivation thin films were coated onto the green OLEDs by spin coating method and investigated the changes of the optical properties of the prepared devices at various doping concentrations of sodium alginate (SA). The passivation solutions were synthesized by using polyvinyl alcohol (PVA) host material with a dopant of SA which were added with the amounts of 10, 20 and 40 wt% into the PVA. As a result, the best barrier properties of the OLEDs were obtained for the samples with 40 wt% SA. Finally, the passivation films can be optimized by using the mixture solution of PVA and SA materials.

• Journal of information and communication convergence engineering
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• v.9 no.4
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• pp.475-482
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• 2011

In this research, we have attempted to estimate the water quality of fish farms in terms of parameters such as water temperature, dissolved oxygen, pH, and salinity by employing observational data obtained from a coastal ocean observatory of a national institution located close to the fish farm. We requested and received marine data comprising nine factors including water temperature from Korea Hydrographic and Oceanographic Administration. For verifying our results, we also established an experimental fish farm in which we directly placed the sensor module of an optical mode, YSI-6920V2, used for self-cleaning inside fish tanks and used the data measured and recorded by a environment monitoring system that was communicating serially with the sensor module. We investigated the differences in water temperature and salinity among three areas - Goheung Balpo, Yeosu Odongdo, and the experimental fish farm, Keumho. Water temperature did not exhibit significant differences but there was a difference in salinity (significance <5%). Further, multiple regression analysis was performed to estimate the water quality of the fish farm at Keumho based on the data of Goheung Balpo. The water temperature and dissolved-oxygen estimations had multiple regression linear relationships with coefficients of determination of 98% and 89%, respectively. However, in the case of the pH and salinity estimated using the oceanic environment with nine factors, the adjusted coefficient of determination was very low at less than 10%, and it was therefore difficult to predict the values. We plotted the predicted and measured values by employing the estimated regression equation and found them to fit very well; the values were close to the regression line. We have demonstrated that if statistical model equations that fit well are used, the expense of fish-farm sensor and system installations, maintenances, and repairs, which is a major issue with existing environmental information monitoring systems of marine farming areas, can be reduced, thereby making it easier for fish farmers to monitor aquaculture and mariculture environments.

• 한국해양학회지
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• v.29 no.2
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• pp.183-187
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• 1994

The oxygen and carbon isotopic compositions of the foraminiferal species, Elphidirm dtigoense and Ammonia beccarii tepida, of the tidal flat in the Gomso Bay of the western coast of Korea have been measured. This work was intended to study the relationship between oxygen and carbon isotopic compositions of the foraminifera and present oceanographic environments, and also the difference between two foraminiferal species. The values of $\delta$/SUP 18/O and $\delta$/SUP 13/C of E. dtigoense varied from - 3.20% to + 0.58% and from - 5.26% to - 0.93%, respectively. The values of $\delta$/SUP 18/O and $\delta$/SUP 13/C of A. beccarii tepida varied from - 1.11% to + 0.61% and from - 2.04% to - 1.40%, respectively. Mo significant variations in these values occur from the samples among the upper, middle and lower tidal zones except for the one from the upper tidal zone that has extremely low value. The difference between the two foraminiferal species was 0.20% and 1.63% in the average values of $\delta$/SUP 18/O and $\delta$/SUP 13/C, respectively. The relationship between $\delta$/SUP 18/O and $\delta$/SUP 13/C values was positive in interspecies of two species.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.55-55
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• 2018

Recently, amorphous oxides such as InGaZnO (IGZO) and InZnO (IZO) as a channel layer of an oxide TFT have been attracted by advantages such as high mobility, good uniformity, and high transparency. In order to apply such an amorphous oxide TFTs to a display, the stability in various environments must be ensured. In the InGaZnO which has been studied in the past, Ga elements act as a suppressor of oxygen vacancy and result in a decreased mobility at the same time. Previous studies have been showed that the InZnO, which does not contain Ga, can achieve high mobility, but has relatively poor stability under various instability environments. In this study, the TFTs using $IZO/Al_2O_3$ double layer structure were studied. The introduction of an $Al_2O_3$ interlayer between source/drain and channel causes superior electrical characteristics and electrical stability as well as reduced contact resistance with optimally perfect ohmic contact. For the IZO and $Al_2O_3$ bilayer structures, the IZO 30nm IZO channels were prepared at $Ar:O_2=30:1$ by sputtering and the $Al_2O_3$ interlayer were depostied with various thickness by ALD at $150^{\circ}C$. The optimal sample exhibits considerably good TFT performance with $V_{th}$ of -3.3V and field effect mobility of $19.25cm^2/Vs$, and reduced $V_{th}$ shift under positive bias stress stability, compared to conventional IZO TFT. The enhanced TFT performances are closely related to the nice ohmic contact properties coming from the defect passivation of the IZO surface inducing charge traps, and we will provide the detail mechanism and model via electrical analysis and transmission line method.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.5
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• pp.77-88
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• 2022

This study aims to understand the relationship between the distribution of fish species in the two water ecosystems and the habitat factors according to the survey period targeting Gwanggyo Lake Park in the city. There are studies on the appearance and distribution of species by applying eDNA to freshwater ecosystems. However, in the domestic, streams are the target, and studies on the relationship between species distribution and habitat environment in two water environments are lacking. We conducted to analyze the species list and relationship with habitat factors using eDNA research in May and October at 21 points in Gwanggyo Lake Park, Suwon City, which were connected to lakes and streams. As a result, there was no species difference in the water environment according to the survey period. However, the total number of reads during the spawning season(May) was 3,126,482, which was more than double that after the spawning season(October). Tolerant species appeared in Woncheon Lake with a slow or stagnant flow, but there was no significant correlation between species and habitat factors depending on the survey period. On the other hand, intermediate and sensitive species appeared in the Woncheon stream with high flow. There was a significant correlation between the low temperature during the spawning season and the high dissolved oxygen content after the spawning season(P<0.001, Tem.: 20.7±2.6℃, DO: 8.6±1.7). It is expected that environmental DNA will be used to survey species and suggest monitoring methods according to the survey period.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.5
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• pp.704-723
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• 2000

This study was undertaken to evaluate the tensile bond strength of In-Ceram alumina core treat-ed by ion assisted reaction(IAR). Ion assisted reaction is a prospective surface modification technique without damage by a keV low energy ion beam irradiation in reactive gas environments or reactive ion itself. 120 In-Ceram specimens were fabricated according to manufacturer's directions and divided into six groups by surface treatment methods of In-Ceram alumina core. SD group(control group): sandblasting SL group: sandblasting + silane treatment SC group: sandblasting + Siloc treatment IAR I group: sandblasting + Ion assisted reaction with argon ion and oxygen gas IAR II group: sandblasting + Ion assisted reaction with oxygen ion and oxygen gas IAR III group: sandblasting + Ion assisted reaction with oxygen ion only For measuring of tensile bond strength, pairs of specimens within a group were bonded with Panavia 21 resin cement using special device secured that the film thickness was $80{\mu}m$. The results of tensile strength were statistically analyzed with the SPSS release version 8.0 programs. Physical change like surface roughness of In-Ceram alumina core treated by ion assistad reaction was evaluated by Contact Angle Measurement, Scanning Electron Microscopy, Atomic Force Microscopy; chemical surface change was evaluated by X-ray Photoelectron Spectroscopy. The results as follows: 1. In tensile bond strength, there were no statistically significant differences with SC group, IAR groups and SL group except control group(P<0.05). 2. Contact angle measurement showed that wettability of In-Ceram alumina core was enhanced after IAR treatment. 3. SEM and AFM showed that surface roughness of In-Ceram alumina core was not changed after IAR treatment. 4. XPS showed that IAR treatment of In-Ceram alumina core was enabled to create a new functional layer. A keV IAR treatment of In-Ceram alumina core could enhanced tensile bond strength with resin cement. In the future, this ion assisted reaction may be used effectively in various dental materials as well as in In-Ceram to promote the bond strength to natural tooth structure.