• Korean Journal of Environmental Biology
• /
• v.33 no.1
• /
• pp.1-6
• /
• 2015

Increased harmful algal blooms by cyanobacteria are threatening public health and limiting human activities related with freshwater ecosystems. Phosphorus (P) has long been suggested as a critical nutrient for cyanobacterial bloom through field research in Canada during the 1970s, proposing a P-based freshwater management guideline. However, recently, nitrogen (N) has also been highlighted as an impacting nutrient on cyanobacterial harmful algal blooms (CyanoHABs). Due to the intensive and frequent observation of Microcystis, this kind of paradigm shift from P limitation to season-dependent N or P limitation has an important implication for a dual nutrient management strategy in eutrophic freshwaters. Through recent international researches, general strategies to control CyanoHABs in lakes and reservoirs are as follows: a dual nutrient (N & P) reduction, wastewater collection and treatment, pre-treatment of influent water in buffer zones, dredging of sediment, reduction of residence time, algal collection, and precipitation and flocculation of cyanobacteria. In addition, sustainable and integrative freshwater algae management should be carried out, based on the ecological aspect, because cyanobacteria are not the target organism to be eradicated, but an essential microbial member in the freshwater ecosystem.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.11 no.3
• /
• pp.22-26
• /
• 1974

The effects of anisotropic mechanical stress applied normal to the surface of p-n junctions have been investigated. As the stress increased, the breakdown voltage was decreased and the breakdown mode became softer. Within a certain limitation in the applied stress, the above phenomena werw reversibbe, though relaxation and hysteresis phenomena were observed. The time constant of relaxation depended upon the shape of the stressing tip, but for the given tip and device a unique time constant was obtained. The stress.dependence of breakdown voltage showed a good linearity up to about 3.0${\times}10^4$ kgw/$\textrm{cm}^2$, when the flat tip of radius 15$\mu$ was used, and the temperatere-dependence of breakdown voltage under the stress also showed a good linearity in the temperature range of 100 to $300^{\circ}K$.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.177-179
• /
• 1990

Recently, it is reported that the behaviour of PECVD under high electric field and current condition has a major effect on MNS device degradation. In this paper, we evaluated the breakdown and TDDB characteristics of Laser assisted PECVD SiN films which is introduced new deposited method. And also, long term insulator breakdown reliability is described by examing time dependent dielectric breakdown under positive voltage. Failure tines against electric field are examined and acceleration factors are obtained for each case. From these data, breakdown wearout limitation for Laser Assisted PECVD SiN film can be characterized.

• Journal of Korean Society on Water Environment
• /
• v.30 no.1
• /
• pp.1-7
• /
• 2014

The purpose of this study was to investigate the nitrification characteristics of biological aerated filter (BAF) packed with ceramic media, especially focusing on nitrite build-up during nitrification. When increasing the nitrogen load above $1.63kgNH_4{^+}-N/m^3{\cdot}d$, ammonium removal efficiency decreased to less than 60% and the nitrite ratio ($NO_2{^-}-N/NO_x-N$) of higher than 75% was achieved due to the inhibitory free ammonia (FA, $NH_3-N$) concentration and oxygen limitation. FA inhibition, however, is not recommended strategy to promote nitrite build-up since FA concentration in the reactor is coupled with decreased ammonium removal efficiency. Nitrite ratio in the effluent was also affected by aeration rate and influent ammonium concentration. Ammonium oxidation was enhanced at a higher aeration rate regardless of influent ammonium concentration but, the nitrite ratio was dependent on both aeration rate and influent ammonium concentration. While a higher nitrite ratio was obtained when BAFs were fed with $50mgNH_4{^+}-N/L$ of influent, the nitrite ratio significantly decreased for a greater influent concentration of $200-300mgNH_4{^+}-N/L$. Taken together, aeration rate, influent ammonium concentration and FA concentrations kept in the BAF were found to be critical variables for nitrite accumulation in the BAF system.

• Journal of Software Assessment and Valuation
• /
• v.16 no.1
• /
• pp.89-94
• /
• 2020

In this paper, we propose a software algorithm that can configure n-key roll-over that detects all keys without limitation on the number of pressed keys in the dynamic scanning detection of a keyboard composed of a matrix. The proposed algorithm uses the timer interrupt of the microcontroller for computer keyboard control, so that a constant and accurate detection interval can be obtained, and an accurate debounce time can be provided. In order to confirm the effectiveness of the proposed algorithm, a microcontroller was connected to a toy keyboard constructed in the form of a clavier and experiments were conducted. As a result of the experiment, it was confirmed that detection of all keys was performed accurately regardless of the number of keys pressed.

• Journal of The Korean Society of Grassland and Forage Science
• /
• v.8 no.1
• /
• pp.33-39
• /
• 1988

Insufficient herbage during the fall in the temperate areas of the world has been a serious limitation in animal production, but leafy brassicae are potentially very useful for extending the grazing season when the growth and quality of grass is poor. This study was conducted to determine the effects of cutting stage and N fertilization on dry matter (DM) yield, forage quality and chemical composition of forage rape (Brassica napus Subsp. oleifera). The experiment was conducted in the Experimental Livestock Farm of Seoul Nat'l Univ., at Suweon, during 1985- 1986. The results obtained are summarized as follows: 1. DM percentage and yield significantly increased as the growth period was prolonged and decreased as the N fertilization increased, but in-vitro dry matter digestibility (IVDMD) was unaffected by the treatments. 2. Plant height, DM yield and $NO_3$-N content significantly increased as the rate of N fertilization increased and DM percentage decreased, but the IVDMD was unaffected. 3. The forage rape had high percentage of crude protein and ash. Glutamic acid, pro!ine and aspartic acid were the major amino acids. Concentration of P, Ca and Mg were high.

• Proceedings of the Microbiological Society of Korea Conference
• /
• 2001.11a
• /
• pp.113-120
• /
• 2001

The production of microcystins from Microcystis aeruginosa was investigated in a P-limited continuous culture and a batch culture. The microcystin content of M aeruginosa was higher at a lower $\mu$, whereas the microcystin (MC)-producing rate was linearly proportional to $\mu$. The ratios of the MC-producing rate to the C-fixation rate were higher at a lower $\mu$. Consequently, increases in the microcystin content per dry weight along with the production of the more toxic form, MC-LR, were both observed under more P-limited conditions. The microcystin content of M. aeruginosa exhibited a high correlation with the total N content regardless of N-fixed or P-fixed culture. The microcystin concentration was investigated from spring to autumn in 1999 in the Daechung Reservoir, Korea. The dominant species in the algal blooming season was Microcystis. When the microcystin concentration exceeded about 100 ng $1^{-1}$ the ratio of particulate to dissolved total nitrogen (TN) or total phosphorus (TP) interestingly converged at a value of 0.6. The microcystin concentration was lower than 50 ng $1^{-1}$ at a particulate N:P ratio below 8, whereas the microcystin concentration varied quite substantially from 50 ng $1^{-1}$ to 250 ng $1^{-1}$ at a particulate N:P ratio> 8.

• Journal of Microbiology and Biotechnology
• /
• v.7 no.6
• /
• pp.391-396
• /
• 1997

Two series of carbon sources, linear primary $C_1$~$C_9$ alcohols and linear $C_2$~$C_{10}$ monocarboxylic acids were tested for PHA synthesis in Paracoccus denitrificans. The results showed that the growth-associated synthesis of PHA could be referred only to the carbon sources with odd number of carbon except methanol. For all carbon sources with even number of carbon, nitrogen limitation was required to induce PHA synthesis in P. denitrificans. Poly(3-hydroxyvalerate)[P(3HV)] homopolymer was synthesized from $C_5$, $C_7$, and $C_9$ while growing in the presence of nitrogen, but the nitrogen depletion in the later growth period incorporated 3-hydroxybutyrate(3HB) unit into the polymer chain. The optimum C/N ratio for P(3HV) homopolymer production was found to be 10 when the strain was grown on 10 ml/l of valeric acid for 96 h. P. denitrificans synthesized P(3HB-co-3HV) copolymers from n-hexanoic and n-octanoic acid. The microstructural characterics of the P(3HB-co-3HV) copolymer from n-propanol was investigated using $^13C$-nuclear magnetic resonance spectroscopy, showing a structural heterogeneity.

• Journal of Microbiology and Biotechnology
• /
• v.22 no.2
• /
• pp.234-238
• /
• 2012

Recombinant Escherichia coli displaying organophosphorus hydrolase (OPH) was used to overcome the diffusion barrier limitation of organophosphorus pesticides. A new anchor system derived from the N-terminal domain of ice-nucleation protein from Pseudomonas syringae InaV (InaV-N) was used to display OPH onto the surface. The designed sequence was cloned in the vector pET-28a(+) and then was expressed in E. coli. Tracing of the expression location of the recombinant protein using SDS-PAGE showed the presentation of OPH by InaV-N on the outer membrane, and the ability of recombinant E. coli to utilize diazinon as the sole source of energy, without growth inhibition, indicated its significant activity. The location of OPH was detected by comparing the activity of the outer membrane fraction with the inner membrane and cytoplasm fractions. Studies revealed that recombinant E. coli can degrade 50% of 2 mM chlorpyrifos in 2 min. It can be concluded that InaV-N can be used efficiently to display foreign functional protein, and these results highlight the high potential of an engineered bacterium to be used in bioremediation of pesticide-contaminated sources in the environment.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 2001.10a
• /
• pp.179-183
• /
• 2001

Vibration isolation of mechanical systems, in general is achieved through either passive or active vibration control system. Although passive vibration isolators offer simple and reliable means to protect mechanical system from vibration environment, passive vibration isolator has inherent performance limitation. Whereas, active vibration isolator provide significantly superior vibration-isolation performance. Recently, many studied and applications are carried out in this field. In this study, vibration-isolation characteristics of active vibration control system using electromagnetic force actuator are investigated. Some control algorithms. Optimal Feedforward are used for active vibration isolation. Form the experimental results of each control algorithms, active vibration isolation characteristics are investigated.