• Journal of the Korean Society of Marine Environment & Safety
• /
• v.28 no.4
• /
• pp.459-468
• /
• 2022

Long-term data analyses and bioassay experiments were conducted to assess limiting nutrients in Cheonsu Bay and Taean sea. First, long-term nutrient data (2004-2016) provided by the National Water Quality Monitoring Network were used to assess potential limiting nutrients. Analysis of the long-term data showed that the dissolved inorganic nitrogen/dissolved inorganic phosphate (DIN/DIP) ratio was mostly below 16, with N limitation being dominant. A subsequent analysis using the concentration ratios of N, P, and Si showed that N limitation was dominant during summer and autumn but that Si limitation occasionally occurred during winter and spring in relatively limited areas. However, the dominant limiting nutrient was not determined. The nutrient analysis of the field water collected during the bioassay experiment showed that DIN/DIP revealed P limitation at all stations in March and May, whereas N limitation was dominant in July and October. In the analysis using the concentration ratios of N, P, and Si, P and Si limitation appeared in March and May, but there were points with no dominant limiting nutrient. However, N limitation was dominant in July and October. In the bioassay experiment for assessment of the actual limiting nutrient, the results showed no specific limiting nutrient in March, whereas NH₄⁺ and NO₃^- showed responses in May, July, and October, which confirmed that N was a substantial limiting nutrient directly involved in phytoplankton growth during this period.

• ALGAE
• /
• v.29 no.1
• /
• pp.27-34
• /
• 2014

Availability of nutrients is known to influence marine primary production; and it is of general interest to see how nutrient limitation mediates phytoplankton responses to solar ultraviolet radiation (UVR, 280-400 nm). The red tide diatom Skeletonema costatum was cultured under nitrate (N)-limited and N-replete conditions and exposed to different solar irradiation treatments with or without UV-A (315-400 nm) and UV-B (280-315 nm) radiation. Its photochemical quantum yield decreased by 13.6% in N-limited cells as compared to that in N-replete ones under photosynthetically active radiation (PAR)-alone treatment, and the presence of UV-A or UV-B decreased the yield further by 2.8 and 3.1%, respectively. The non-photochemical quenching (NPQ), when the cells were exposed to stressful light condition, was higher in N-limited than in N-replete grown cells by 180% under PAR alone, by 204% under PAR + UV-A and by 76% under PAR + UV-A + UV-B treatments. Our results indicate that the N limitation exacerbates the UVR effects on the S. costatum photosynthetic performance and stimulate its NPQ.

• Ocean Science Journal
• /
• v.40 no.3
• /
• pp.109-117
• /
• 2005

Daily changes in phytoplankton abundance and species composition were monitored from July to September 2003 (n=47) to understand which factors control the abundance at a station in Jangmok Bay. During the study, the phytoplankton community was mainly composed of small cell diatoms and dinoflagellates, and the dominant genera were Chaetoceros, Nitzschia, Skeletonema and Thalassionema. Phytoplankton abundance varied significantly from $6.40{\times}10^4$ to $1.22{\times}10^7$ cells/l. The initially high level of phytoplankton abundance was dominated by diatoms, but replacement by dinoflagellates started when the NIP ratio decreased to <5.0. On the basis of the N/P and Si/N ratios, the sampling periofd could be divided into two: an inorganic silicate limitation period (ISLP, $14^{th}$ $July-12^{th}$ of August) and an inorganic nitrogen limitation period (INLP, $13^{th}$ of August - the end of the study). Phosphate might not limit the growth of phytoplankton assemblages in the bay during the study period. This study suggests that phytoplankton abundance and species composition might be affected by the concentrations of inorganic nutrients (N and Si), and provides baseline information for further studies on plankton dynamics in Jangmok Bay.

• Journal of the korean society of oceanography
• /
• v.34 no.2
• /
• pp.86-94
• /
• 1999

An investigation was conducted to determine limiting nutrients in the bay systems of the southern coastal area of Korea. The elemental composition of C, N, and P in suspended particulate matter was monitored nearly monthly in Chinhae and Koje Bays and seasonally in Deukryang Bay for 2 years. Atomic C:N ratio in particulate matter ranges from 4.3 to 9.6, typical of marine phytoplankton. C:P and N:P ratios vary from the Redfield ratio to 229 (C:P) and 37 (N:P). A constant C:N ratio of 6.87 from regression of particulate C and N concentrations demonstrates that the particulate matter in the systems originates from primary production. C:P and N:P ratios from regression of C on P and N on P are well associated with changes in salinity. The low N:P ratio of 13.1 implies N limitation in the environments of the systems. This seems to result from the low N:P ratio of nutrients released across sediment-water interface. Phytoplankton response, expressed here as the increase of chlorophyll a, to N addition also verifies N limitation for phytoplankton communities. In heavy rainfall season (from June to September), the addition of excessive N via streams into the stratified coastal water proliferates phytoplankton greatly. During the phytoplankton blooms, C:P and N:P ratios are much higher than the Redfield ratio, implying P limitation. This results from the high N:P ratio in nutrients supplied from stream waters. Strong stratification during the blooms also interrupts the supply of nutrients, particularly p, from bottom waters. Dependent upon precipitation, this tendency shows great inter-annual variation.

• Journal of Society of Occupational Therapy for the Aged and Dementia
• /
• v.12 no.2
• /
• pp.1-11
• /
• 2018

Objective : The aim of this study was to compare the sociodemographic characteristics, depression, quality of life, and unmet medical need in elders with and without limitation of activity by aging or dementia. Method : The data were used for raw data of seventh national health and nutrition examination survey (2016). We compared sociodemographic characteristics, depression, quality of life, and unmet medical needs between elders with limitation of activity by aging or dementia (n = 32) and elders without limitation of activity (n = 1201). Result : Elders with limitation of activity were significantly older than elders without limitation of activity (p<.001), income was lower (p<.05) and married status had more bereavement (p<.001). The elders with limitation of activity had higher depression (p<.001) and lower quality of life (p<.001) than elders without limitation of activity. Unmet medical need was greater than elders without limitation of activity (p<.001). Conclusion : Elders with limitation of activity showed that they did not receive enough medical services than elders without limitation of activity. These results suggest that the welfare system for the health care of population with aging or dementia needs to be improved.

• Korean Journal of Ecology and Environment
• /
• v.37 no.1 s.106
• /
• pp.36-46
• /
• 2004

We evaluated the effect of limiting nutrients and N/P ratio on the growth of phytoplankton in a small eutrophic reservoir from November 2002 to December 2003. Nutrient limitation was investigated seasonally using nutrient enrichment bioassay (NEB). DIN/DTP and TN/TP ratio (by weight) of the reservoir during the study period ranged 17${\sim}$187 and 13${\sim}$60, respectively. Most of nitrogen in the reservoir account for $NO_3$-N, but sharp increase of ammonia was evident during the spring season. Seasonal variation of dissolved inorganic phosphorus concentration was relatively small. DTP ranged 26.5${\sim}$10.1 ${\mu}g\;P\;L^{-1}$, and the highest and lowest concentration was observed in August and December, respectively. Chlorophyll a concentration ranged 28.8${\sim}$109.7 ${\mu}g\;L^{-1}$, and its temporal variation was similar to that of cell density of phytoplankton. Dominant phytoplankton species were Bacillariphyceae (Melosira varians) and Chlorophyceae (Dictyosphaerium puchellum) in Spring (March${\sim}$April). Cyanophyceae, such as Osillatoria spp., Microcystis spp., Aphanizomenon sp. dominated from May to the freezing time. TN/TP ratio ranged from 46 to 13 (Avg. 27${\pm}$6) from June to December when cyanobacteria (Microcystis spp.) dominated. p limitation for algal growth measured in all NEB experiments (17cases), while N limitation occurred in 8 out of 17 cases. The growth rates of phytoplankton slightly increased with decreasing of DIN/DTP ratio. Evident increase was observed in the N/P ratio of > 30, and it was sustained with DTP increase until 50 ${\mu}g\;P\;L^{-1}$. Under the same N/P mass ratio with the different N concentrations (0.07, 0.7and 3.5 mg N $L^{-1}$), Microcystis spp. showed the highest growth rate in the N/P ratio of< 1 with nitrogen concentration of 3.5 mg N $L^{-1}$). The responses of phytoplankton growth to phosphate addition were clearly greater with increase of N concentration. These results indicate that the higher nitrogen concentration in the water likely induce the stronger P-limitation on the phytoplankton growth, while nitrogen deficiency is not likely the case of nutrient limitation.

• Journal of Korean Society on Water Environment
• /
• v.28 no.6
• /
• pp.804-812
• /
• 2012

This study contemplated domestic and other country's effluent limitation standards and suggested a methodology to establish technology-base limitation value. Current effluent limitation regulates industrial point sources discriminated by discharge flow rate and by regional distinction in Korea. Discharged $BOD_5$ load from large-scale plants(flow rate above $2,000\;m^3/day)$ exceeds 50% of overall industrial wastewater, which present rationale for discrimination based on plant size. However, regional distinction and pollutant- specific regulation might be insufficient to meet practical effectiveness of wastewater management policy, due to the nearly same limitation. Water quality data and treatment methods were investigated in hospital industry. And their distribution of effluent $BOD_5$ concentrations was statistically analyzed to suggest limitation value. Effluent $BOD_5$ concentrations showed lognormal distribution and $95^{th}$ percentile was corresponded to 87.9 mg/L, which could be suggested as tentative effluent limitation in hospital industry. The $95^{th}$ percentile of log-transformed distribution showed similar value of 86.5 mg/L. This study demonstrated reasonable methodology for establishing effluent limitation reflecting wastewater characteristic and treatment technology in separately categorized industry.

• Journal of the Korean Society of Physical Medicine
• /
• v.4 no.4
• /
• pp.257-267
• /
• 2009

Purpose：The purpose of this study is to examine the effectiveness of ultrasound and myofascial release in patients who have opening mouth limitation and temporomandibular disorder. Methods：Twenty students were randomly assigned to a myofascial release group(n=10) or an ultrasound group(n=7). Each group was treated for 15 minutes per a every treatment session for four weeks. Cervial range of motion(CROM) was used to measure cervical R.O.M., and a mm(millimeter) graduated ruler was used to measure opening mouth limitation. Results：Results of the follows : 1. The neck extension of range of motion of both groups was significantly increased in length of time (p<.05). 2. The neck flexion of range of motion of both groups was significantly increased (p<.05). 3. The quantity of opening mouth of temporomandibular joint of both groups was significantly increased (p<.05). Conclusion：These data suggest that myofascial release and ultrasound are beneficial to increasing a functional recovery of neck(flexion and extension) and opening mouth.

• Journal of applied mathematics & informatics
• /
• v.19 no.1_2
• /
• pp.311-326
• /
• 2005

The paper deals with the problem of selective harvesting in a prey-predator model with predator self limitation. Criteria for local stability and global stability for both the exploited and unexploited system are derived. The effort has been considered as a dynamic variable and taxation as a control instrument to protect the fish populations from over exploitation. Finally, the optimal taxation policy is discussed with the help of control theory.

• The Transactions of the Korean Institute of Electrical Engineers
• /
• v.43 no.2
• /
• pp.318-329
• /
• 1994

This paper deals with the finite wordlength effect on the performance of digital PID controllers. The finite wordlength, one of the major limitation factors in digital controllers, results on two kinds of quantization error : the signal quantization error and the coefficient quantization error. This paper derives the variance of the plant output due to the signal quantization error. Using stability margins as performance criterion, the statistical wordlength concept is adopted for coefficient wordlength selection. Finally, the experimental results exhibit satisfactory performance of the digital PID controller with statistical coefficient wordlength.