• Journal of Environmental Science International
• /
• v.14 no.9
• /
• pp.861-871
• /
• 2005

This study was carried out to get more operational characteristics of Anoxic(anaerobic)-Oxic-Anoxic-Oxic $(AO)_2$ sequencing batch biofilm reactors (SBBRs) at the low TOC concentration, The operating time in anoxic (anaerobic) time to oxic time was I : I. Experiments were conducted to find the effects of the aeration time distribution on the organic matters and nutrients removal. Three lab-scale reactors were fed with synthetic wastewater based on glucose as carbon source. During studies, the operation mode was fixed. The first aeration time to the second aeration time in SBBR-I was 2 : 3, and those in SBBR-2 and SBBR-3 were I : 4 and 3 : 2, respectively. The organic removal efficiency didn't show large difference among three reactors of different aeration time distribution. However, from these study results, the optimum aeration time distribution in the first and the second aeration time for biological nutrient removal was shown as 3 : 2. The release of phosphorus was inhibited at the second non-aeration period because of the low TOC concentration and the nitrate produced by the nitrification at the first aeration period.

• Journal of Distribution Science
• /
• v.10 no.8
• /
• pp.15-23
• /
• 2012

This study is an attempt to explore the nature and characteristics of strategic impact of green strategy by environmental capital, corporate reputation, and technology strengths on the firm's performance across countries. The main question addressed in this paper relates to how corporate sustainability, corporate reputation, technology strength, and capabilities influence the firm's economic performance with respect to diverse dimensions of performance measures including sustained growth through the leading firms across countries in the United States, Canada, Europe, and Asia-Pacific countries. Particularly, this study attempts to empirically explore the directions and magnitudes of the operational links between new emerging strategic core competencies (e.g., sustainability green strategy by environmental focus for more sustainable path, corporate reputation by corporate social responsibility and image enhancement, and technology strengths to develop a new product and market) and the firm's economic performance with respect to diverse dimensions of performance such as accounting (ROE and EOA) - and market-based performance (Market value and Tobin's q). Considering all possible limitations that might exist with regard to selected samples and methods, this study demonstrates that environmental sustainability, corporate reputation, technological capabilities and competencies through R&D intensity and patent are most likely to be significantly associated with most market-based performance measures, but the strategic significance of other variables such as capital intensity, leverage, and administrative cost efficiency on performance tends to be different depending on which performance measure is used across different countries with diverse economic and business contexts.

• Atmosphere
• /
• v.32 no.2
• /
• pp.135-148
• /
• 2022

This study investigates the influence of atmospheric river (AR) on precipitation over South Korea with a focus on regional characteristics. The 42-year-long catalog of ARs, which is obtained by applying the automatic AR detection algorithm to ERA5 reanalysis data and the insitu precipitation data recorded at 56 weather stations across the country are used to quantify their relationship. Approximately 51% of the climatological annual precipitation is associated with AR. The AR-related precipitation is most pronounced in summer by approximately 58%, while only limited fraction of precipitation (26%) is AR-related in winter. The heavy precipitation (> 30 mm day^-1) is more prone to AR activity (59%) than weak precipitation (5~30 mm day^-1; 33%) in all seasons. By grouping weather stations into the four sub-regions based on orography, it is found that the contribution of AR precipitation to the total is largest in the southern coast (57%) and smallest in the eastern coast (36%). Similar regional variations in AR precipitation fractions also occur in weak precipitation events. The regional contrast between the northern and southern stations is related to the seasonal variation of AR-frequency. In addition, the regional contrast between the western and eastern stations is partly modulated by the orographic forcing. The fractional contribution of AR to heavy precipitation exceeds 50% in all seasons, but this is true only in summer along the eastern coast. This result indicates that ARs play a critical role in heavy precipitation in South Korea, thus routine monitoring of ARs is needed for improving operational hydrometeorological forecasting.

• Journal of the Korean earth science society
• /
• v.41 no.5
• /
• pp.447-458
• /
• 2020

This study presents the K-means clustering analysis-based classification of the meteorological patterns affecting the occurrence of high PM₁₀ concentration in the southeastern region of the Korean peninsula for the last five years (2014-2018). Regional differences in Busan, Ulsan, and Gyeongnam related to high PM₁₀ episodes, were clarified through the statistical comparison study using synoptic scale meteorological elements using NCEP (National Centers for Environmental Prediction/FNL (Final Operational Global Analysis) re-analysis meteorological data. Meteorological patterns were classified into a total of five categories (C1-C5). The incidence of each cluster was 24.8% (C1), 21.3% (C2), 20.4% (C3), 17.3% (C4), and 16.2% (C5), respectively. The high PM₁₀ concentration in the southeastern region resulted from long and short range transports (C1, C3, C5) from outside of the region, and the emissions (C2, C4) inside the region. In the high PM₁₀ episodes in Busan, Ulsan, and Gyeongnam regions, meteorological characteristics such as different geopotential height and wind speed at 500 hPa in each cluster and the change in the location of high pressure over Korean Peninsula is strongly associated with the dispersion of PM₁₀ around inventories in the region and the tendency of long-range transportation of PM₁₀ emitted from outside of region.

• Journal of Korean Society of Water and Wastewater
• /
• v.37 no.6
• /
• pp.363-373
• /
• 2023

Numerous studies have established a correlation between sociodemographic characteristics and water usage, identifying population as a primary independent variable in mid- to long-term demand forecasting. Recent dramatic sociodemographic changes, including urban concentration-rural depopulation, low birth rates-aging population, and the rise in single-person households, are expected to impact water demand and supply patterns. This underscores the necessity for operational and managerial changes in existing water supply systems. While sociodemographic characteristics are regularly surveyed, the conducted surveys use aggregate units that do not align with the actual system. Consequently, many water demand forecasts have been conducted at the administrative district level without adequately considering the water supply system. This study presents an upward water demand forecasting model that accurately reflects real water facilities and consumers. The model comprises three key steps. Firstly, Statistics Korea's SGIS (Statistical Geological Information System) data was reorganized at the DMA level. Secondly, DMAs were classified using the SOM (Self-Organizing Map) algorithm to consider differences in water facilities and consumer characteristics. Lastly, water demand forecasting employed the PCR (Principal Component Regression) method to address multicollinearity and overfitting issues. The performance evaluation of this model was conducted for DMAs classified as rural areas due to the insufficient number of DMAs. The estimation results indicate that the correlation coefficients exceeded 0.9, and the MAPE remained within approximately 10% for the test dataset. This method is expected to be useful for reorganization plans, such as the expansion and contraction of existing facilities.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.1
• /
• pp.29-34
• /
• 2009

This study was performed under four operational conditions for nitrogen removal in metal finishing wastewater. The conditions include electrode gap, reducing agent, the recycling of treated wastewater in 1st step and the simultaneous treatment of nitrate and other materials. Result showed that the removal efficiency of $NO_3{^-}-N$ was highest at the electrode gap of 10 mm. As the electrode gap was shorter than 10 mm, the removal efficiency of $NO_3{^-}-N$ decreased due to increasing in concentration polarization on electrode. And, in case that the electrode gap was longer than 10 mm, the removal efficiency of $NO_3{^-}-N$ increased with an increase in energy consumption. Because hydrogen ions are consumed when nitrate is reduced, reducing reaction of nitrate was effected more in acid solution. As 1.2 excess amount of zinc was injected, the removal efficiency of $NO_3{^-}-N$ increased due to increasing in amount of reaction with nitrate. As the effluent from 1st step in the reactor was recycled into the 1st step, the removal efficiency of $NO_3{^-}-N$ increased. Because the zinc were detached from the cathode and concentration-polarization was decreased due to formation of turbulence in the reactor. The presence of $NH_4{^+}-N$ did not affect the removal efficiency of $NO_3{^-}-N$ but the addition of heavy metal decreased the removal efficiency of $NO_3{^-}-N$. As chlorine is enough in wastewater, the simultaneous treatment of nitrate and ammonia nitrogen may be possible. The problem that heavy metal decrease the removal efficiency of $NO_3{^-}-N$ may be solved by increasing current density or using front step of electrochemical process for heavy metal removal.

• Journal of the Korean Institute of Telematics and Electronics
• /
• v.9 no.5
• /
• pp.19-26
• /
• 1972

A newly developed quartz frequency modulator utili3ing a V. V. C. diode is briefly described. Its electrical characteristics-including modulation linearity, modulation distortion, and carrier frequency stability depending upon the variation of the environmental temperature and the applied power voltage, etc.-are suitable for the modulator of a mobile or a portable F.M. transmitter according to the experimental results. The excellent over-all electrical characteristics were proved from the experimental development of the two kinds of transceivers. One is the single channal transceiver which contains a direct frequency modulator at the carrier frequency of 52.750 MHg. The other is the dual channel transceiver (the frequencies are selected from about 40 channels without tuning adjustment) whose operational frequency is composed of a modulated frequency of 10.7 MHz and the frequency generated at a channel control oscillator, As mentioned above, it is realized that the electrical characteristics of this modulation method are suitable for portable F. M. transceivers.

• Korean Journal of Materials Research
• /
• v.17 no.5
• /
• pp.289-292
• /
• 2007

Although piezoelectric bimorph that is using as the sensor in medical and industrial measurement has large displacement, it has problems including efficiency in generating force, energy convergence, and response. Its application is being limited based on the change in resonance frequency with temperature. In this study, to overcome the disadvantages, PZT piezoelectric ceramics was prepared and produced a parallel type piezoelectric bimorphs. In addition, by using the finite element method. the configuration of piezoelectric bimorph was designed and the displacement of the bimorph based on applied electric pressure and the wave pattern were measured. By analyzing the resonance characteristics of the bimorph in the temperature range of $-60{\sim}80^{\circ}C$, an attempt was made to study the operational characteristics and temperature reliability of vortex flowmeter sensor. As a result, the resonance frequency of the bimorph was gradually increased with the temperature from $-60{\sim}80^{\circ}C$. The deflection of the bimorph was found to strongly depend on both the applied electric field waveform and the environmental temperature.

• Journal of Environmental Impact Assessment
• /
• v.21 no.1
• /
• pp.15-24
• /
• 2012

The purpose of this study is to understand the process and characteristics of social impact caused by development projects through research and analysis on issues presented during development projects carried out in Korea. Furthermore, on the basis this analysis, this study proposes possible improvement measure environmental impact assessment for minimizing social impact of development projects in the future. Issues related to development projects are generated mainly by the following three causes. Initial social impact can occur when a development project directly causes certain changes in natural, living and social environment. Operational problems related to assessment are another cause of social impact, and it can also occur when changes in natural and living environment work in tandem with social environment sphere. Social impact of development projects is not brought about solely by changes in social environment, but is the result of interaction of factors such as changes in social, natural, living environment and problems related to assessment or operation/management. As to why the current environmental impact assessment could not provide satisfactory solution to the issues mentioned above, this study suggests the following reasons: limitations of assessment method used in social environment category, difficulties in defining assessment criteria, limitations inherent in criterion referenced assessment method, insufficient issue-making in local community, and lack of participation on the part of local residents. Possible solutions for these limitations are as follows: 1) To identify local issues in social environment category through participation of local experts in scoping stage, 2) To adopt deliberative method for local participation, 3) To utilize social survey technique.

• Journal of Korean Society for Quality Management
• /
• v.29 no.3
• /
• pp.18-38
• /
• 2001

This paper attempts to identify variables which affect Korean electronic commerce(EC) venture's strategies for the international market entry decision making. Especially in the perspective of quality management perspective, it is highly relevant question which factors are critical when the industry has high technology driven characteristics such as EC, product quality related factors or environmental factors. Technology competence, operational competence, local marketing competence, psychological barriers, domestic competition level, and local infrastructure level are included to generate the explaining model for international market entry decision. The result is that the higher technology competence and local marketing competence are the significant factors. The higher the perception in these factors, the higher the intention to enter the international market in EC industry. These factors play a pivotal role in determining to go abroad the foreign EC market. Our finding implies that the subjective confidence on quality of EC solution(technology competence) and venture's capability of maintaining it(local marketing competence) are the important factors, when EC ventures make the decisions to enter the foreign markets.