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Nation-wide systematic and comprehensive measurements of air quality criteria species have been made over 340 sites currently in Korea since 1990. Using these data, temporal and spatial trends of SO₂, PM10, NO₂, O3, CO and Ox(NO₂+O₃) were analyzed to characterize and evaluate implementing efficiency of air quality policy and regulations. Due to strict and effective policy to use cleaner fuels in late 1980s and 1990s, the primary pollutants, such as SO₂, CO, and PM10 decreased sharply by early 2000s in all parts of Korea. After this period, their concentrations declined with much lower rates in most parts of Korea. In addition, isolated but noticeable numbers of places, especially in major ports, newly developing towns and industrial parks, sustained high levels or even showed further degradation. Despite series of emission control strategies were enforced since early 1990s, NO₂ concentrations haven’t changed much till 2005, due to significant increase in number of automobiles. Nevertheless, we confirmed that the staggering levels of NO₂ and PM10 improved evidently after 2005, especially in Seoul Metropolitan Area (SMA), where enhanced regulations for NO₂ and PM10 emissions was imposed to automobiles and large emission sources. However, their decreasing trends were much lessened in recent years again as current air quality improvement strategies has been challenged to revise further. In contrast to these primary species, annual O₃, which is secondary product from NO₂ and volatile organic compounds (VOCs), has increased consistently with about 0.6 ppbv per year in every urban part of Korea, while yearly average of daily maximum 8-hour O₃ in summer season had a much higher rate of 1.2 ppbv per year. Increase of O₃ can be explained mainly by reductions of NO emission. Rising background O₃ in the Northeast Asia and increasing oxidizing capacity by changing photochemistry were likely causes of observed O₃ increase. The future air quality policy should consider more effective ways to lower alarming level of O₃ and PM10.

Association between short-term exposure to fine particulate matter (PM2.5) and mortality or morbidity varies geographically, and this variation could be due to different chemical composition affected by local sources. However, there have been only a few Asian studies possibly due to limited monitoring data. Using nationwide regulatory monitoring data of PM2.5 chemical components in South Korea, we aimed to compare the associations between daily exposure to PM2.5 components and mortality across six major cities. We obtained daily 24-h concentrations of PM2.5 and 11 PM2.5 components measured from 2013 to 2015 at single sites located in residential areas. We used death certificate data to compute the daily counts of nonaccidental, cardiovascular, and respiratory deaths. Using the generalized additive model, we estimated relative risks of daily mortality for an interquartile range increase in each pollutant concentration, while controlling for a longer-term time trend and meteorology. While elemental carbon was consistently associated with nonaccidental mortality across all cities, nickel and vanadium were strongly associated with respiratory or cardiovascular mortality in Busan and Ulsan, two large port cities. Our study shows that PM2.5 components responsible for PM2.5-associated mortality differed across cities depending on the dominant pollution sources, such as traffic and oil combustion.

Understanding the drivers of urban ozone (O3) formation is challenging and requires uncovering the non-linear relationship between O3 and its precursors. We used a novel method to differentiate between background O3 levels and local photochemical O3 generation using the observation-based O3 production efficiency (OPE) from decade-long observations including nitrogen dioxide (NO2), nitrogen monoxide (NO), reactive nitrogen compounds (NOy), O3, and 56 volatile organic compounds (VOCs) covering eight years (2009–2016). In this study, we employed Ox (=O3+NO2), and defined OPEx as the number of Ox molecules produced from the oxidation of a single NOx molecule, and estimates the local contribution (in %) to total O3 from the slope of the Ox−NOz(=NOy–NOx) linear regression. We thus identified the local urban O3 formation regime using the relationship of several factors, including nitrogen oxide (NOx), VOC/NOx, NO2, NOz, and long-range transported Ox, and suggested how O3 can be reduced in the Seoul Metropolitan Area (SMA). The results show that the regional background dominates the annual level of Ox with a contribution of about 66 ± 11%, while photochemical production acts as a stronger factor influencing the annual variability of Ox than regional background. Regional background varies by transport evidenced by its good correlation with the west wind fraction, whereas photochemical production depends on the VOC/NOx ratio, which is high in summer and low in winter. The relationship between photochemical production and VOC/NOx indicates that the transition of the Ox formation regime occurs at a VOC/NOx ratio of approximately 4 in the SMA. Urban environments with NOx > 20 ppb typically lie in low VOC/NOx zone, where reduced NO2 emissions lead to decreased NOz but increased OPEx, with no discernible change in photochemical Ox production. Thus, NOx emission reductions in urban environments would have a negligible effect on Ox reduction. In contrast, suburban environments such as usually NOx

Background/AimRecent epidemiological studies suggested that the association between short-term exposure to fine particle matter(PM2.5) and mortality was possibly due to the association with some ch...

It is very important to investigate air pollutants emissions emitted from open burning in order to control nonpoint sources effectively. In this study, we utilized incineration simulator proposed by U.S EPA and investigated emissions of CO, OC/EC, from household waste and biomass burning to estimate pollutant emissions by illegal incineration of biomass wastes. Emission factor of OC was estimated as 17.1 g/kg for rice strew, 23.5 g/kg for barley, 10.3 g/kg for corn stover, 4.3 g/kg for unseasoned wood, respectively. In case of EC, it was calculated as 1.6 g/kg for rice strew, 4.3 g/kg for barley, 1.4 g/kg for corn stover, 0.6 g/kg for unseasoned wood, respectively. Most of the pollutants emissions were emitted at the stage 1 and 2. In the stage 3, the pollutants concentration decreased gradually. To estimate emissions and build inventory for biomass burning, we need to know accurate activity data. We, therefore, used activity data of both survey results of previous study and statistical data of National Statistical Office. However, we need to perform additional experiments in the future to obtain more accurate activity data for various cases.

Korea has experienced dramatic development and has become highly industrialized and urbanized during the past 40 years, which has resulted in rapid economic growth. Due to the industrialization and urbanization, however, air pollutant emission sources have increased substantially. Rapid increases in emission sources have caused Korea to suffer from serious air pollution. An air pollutant emissions inventory is one set of essential data to help policymakers understand the current status of air pollution levels, to establish air pollution control policies and to analyze the impacts of implementation of policies, as well as for air quality studies. To accurately and realistically estimate administrative district level air pollutant emissions of Korea, we developed a Korean Emissions Inventory System named the Clean Air Policy Support System (CAPSS). In CAPSS, emissions sources are classified into four levels. Emission factors for each classification category are collected from various domestic and international research reports, and the CAPSS utilizes various national, regional and local level statistical data, compiled by approximately 150 Korean organizations. In this paper, we introduced for the first time, a Korean national emissions inventory system and release Korea’s official 2007 air pollutant emissions for five regulated air pollutants.

Stationary combustion sources such as coal-fired power plants, waste incinerators, industrial manufacturing, etc. are recognized as major sources of mercury emissions. Due to rapid economic growth, zinc production in Korea has increased significantly during the last 30 years. Total zinc production in Korea exceeded 739,000 tons in 2008, and Korea is currently the third largest zinc producing country in the world. Previous studies have revealed that zinc smelting has become one of the largest single sectors of total mercury emissions in the World. However, studies on this sector are very limited, and a large gap in the knowledge regarding emissions from this sector needs to be bridged. In this paper, Hg emission measurements were performed to develop emission factors from zinc smelting process. Stack sampling and analysis were carried out utilizing the Ontario Hydro method and US EPA method 101A. Preliminary data showed that concentrations in the flue gas ranged from 4.56 to with an average of , Hg(p) concentrations ranged from 0.03 to with an average of , and RGM concentrations ranged from 0.23 to with an average of . To date, emission factors of 7.5~8.0 g/ton for Europe, North America and Australia, and of 20 or 25 g/ton for Africa, Asia and South America are widely accepted by researchers. In this study, Hg emission factors were estimated using the data measured at the commercial facilities as emissions per ton of zinc product. Emission factors for mercury from zinc smelting pross ranged from 4.32 to 12.96 mg/ton with an average of 8.31 mg/ton. The emission factors that we obtained in this study are relatively low, considering Hg contents in the zinc ores and control technology in use. However, as these values are estimated by limited data of single measurement of each, the emission factor and total emission amount must be updated in future.

Mercury emissions concentrations, emission factors, and the total national emission from major anthropogenic sources in Korea for the year 2007 were estimated. Uncontrolled and controlled mercury emission factors and the total emission from each source types are presented. The annual national mercury emission from major anthropogenic sources for the year 2007, on average was 12.8 ton which ranged from 6.5 to 20.2 ton. Averaged emissions of elemental, oxidized, and particulate mercury were estimated at 8.25 ton, 3.69 ton, and 0.87 ton, respectively. Due to the removal of a major portion of particulate and oxidized mercury species, elemental mercury was dominant in stack emission. About 54.8% of mercury emission was contributed by industrial sources, 45.0% by stationary combustion sources and 0.02% by mobile sources. Thermal power plants, oil refineries, cement kilns and incinerators (municipal, industrial, medical, sewage sludge) were the major mercury emitters, contributing about 26%, 25%, 21% and 20%, respectively to the total mercury emission. Other sources (crematory, pulp and paper manufacturing, nonferrous metals manufacturing, glass manufacturing) contributed about 8% of the total emission. Priority should be given in controlling mercury emissions from coal-fired power plants, oil refineries, cement kilns and waste incinerators. More measurements including natural and re-emission sources are to be carried out in the future in order to have a clear scenario of mercury emission from the country and to apply effective control measures.

Although production of sewage sludge increases every year, its proper treatment has only been recently raised as a new issue, as current landfill and ocean dumping arrangements are expected to become increasingly difficult to manage in the future. The Korean Ministry of Environment plans to diversify its processing facilities and expand its processing systems by 2011, with the purpose of processing all sludge produced in Korea. According to this plan, incineration (including incineration of municipal wastes) will process 30% of the entire sewage sludge throughout the country in 2011. This study reviews the characteristics of PAH, which is one of the organic substances found in sewage sludge during the incinerating process. The total amount of PAH produced from sewage sludge incineration was found to be 6.103 mg/kg on average, and investigation performed on 16 PAHs of inlets and outlets of the air control devices at five full-scale incineration facilities showed that concentrations of the PAHs on the inlet and on the outlet ranged from 3.926 to 925.748 μg/m 3 and from 1.153 to 189.449 μg/m 3 , respectively. In the case of the incineration facility fed with municipal waste (95%) and sewage sludge (5%), the total of the PAH emissions concentration was higher than that found at the incineration facilities used exclusively to treat sewage. The combustion of waste vinyl and plastics contained in municipal waste fed into the facility might contribute to the high levels of PAHs in the stack gas. However more investigation is needed on the production mechanism of PAHs at different operating conditions of the incineration facilities, such as the types of waste, and other relevant factors.

The results of HAPs emission data using TRI (Toxic Release Inventory), SODAM (Source Data Management system) were investigated and the emissions of 7 heavy metals from their sources and emission processes were also analyzed. Questionnaire for source data analysis as well as the stack sampling were carried out for 17 factories among 6 selected industrial types. The annual amount of emissions was estimated based on the measured concentration and flow rates. All sources were operated with high efficiency control devices and the concentration levels of all heavy metals were shown to be below 0.1 to of regulation standard. The highest emission source of heavy metals was steel manufacturing industry with the annual emission of 342.9 kg/yr and followed by hazardous waste incinerator, paint manufacturing, nonferrous metal manufacturing, rolling & press goods manufacturing and storage battery manufacturing. In the case of Hg, the emissions were quite significant from electric acros of steel manufacturing industry, although the concentration level was below the emission standard, showing the necessity of specific care for its management.

In this study, we have investigated waste incinerators which are one of the major HAPs emission sources. In order to obtain more reliable HAPs emission data from waste incinerators, direct sampling for the possible pollutants from the stack was carried out and the analysis was performed. The purpose of study was to understand the emission status from waste incinerators and recognize the problems and finally to set up a strategy to reduce the HAPs emissions from waste incinerators. The emission concentrations of 8 species of heavy metals and 16 species of PAHs have been analyzed for the first time in Korea. Not only the emission characteristics of HAPs from waste incinerators were identified, but also the analysis of reduction efficiencies for control devices such as BF and wet scrubbing systems was carried out.

The development of domestic plant specific emission factors is very important to estimate reliable national emissions management. This study, for the reason, was carried out to obtain advances emission factor for Carbon Dioxide () by source-specific emission tests from the iron and steel industry sector which is well known as one of the major sources of greenhouse gases (). Emission factors estimated in this study were compared with those of IPCC for evaluation and they were found to be of similar level in the case of . There was no good information available on plant specific emission factors from the iron and steel industry in Korea so far. The major emission sources of examined from the iron and steel manufacturing precesses were a hot blast stove, coke oven, sintering furnace, electric arc furnace, heating furnace, and so on. In this study, the concentration of from the hot blast stove process was the highest among all processes. The emission factors for a ton of Steel and Iron products (using B-C oil) were estimated to be 0.315 tonne (by Tier 3 method) and 4.89 tonne. In addition, emission factor of for heating furnace process was the highest among all process. Emission factors estimated in this study were compared with those of IPCC for evaluation and they were found to be of similar level in the case of .

An 8 M /spl times/ 32 GDDR (graphic DDR) SDRAM operating up to 800-MHz clock (CLK) frequency is described. The GDDR SDRAM demands an effective control of CAS latency due to the large and wide number of CAS latencies at the CLK frequency. A wave-pipelined CAS latency control circuit is proposed to provide stable operation for the large and wide number of CAS latencies. The increase of CAS latency also causes a degradation of data bus efficiency at high-speed operation due to the large gap between input data (DINs) and output data (DOUTs) at the operation of write followed by read. A gapless write to read scheme improves the data bus efficiency by separating write data-path from read data-path for different banks accesses. Partial array activation commands can reduce the peak current, preventing the reduction of the data retention time of DRAM cells at high-speed operation. The GDDR SDRAM operates successfully at the CLK frequency of 800 MHz at 2.1 V and 700 MHz at 1.8 V, respectively. The power consumption is measured to be /spl sim/2 W at 1.9 V.

This paper presents a salient clock deskewing method with a mixed-mode delay-locked loop (MDLL) for high-speed synchronous DRAM applications. The presented method not only solves the resolution problem of conventional digital deskewing circuits, but also improves the jitter performance to the level of well-designed analog deskewing circuits, while keeping the power consumption and locking speed of digital deskewing circuits. The whole deskewing circuit is fabricated in a 3.3-V 0.6-/spl mu/m triple-metal CMOS process and occupies a die area of 0.45 mm/sup 2/. Measured rms jitter is 6.38 ps. The power consumption of the entire chip, including I/O peripherals, is 33 mW at 200 MHz with a 3.3-V supply.

A prototype 1 Gbit synchronous DRAM with independent subarray-controlled isolation and hierarchical decoding schemes is demonstrated to alleviate the difficulties encountered in high-density devices with regard to failure analysis and performance optimization. The scheme to isolate memory arrays from "hard" defects and to overcome the dc leakages of "soft" defects with external sources allows monitoring of the leakage current for the defect analysis and testing of the device without being limited by the capabilities of on-chip voltage sources. A hierarchical decoding scheme with a dynamic CMOS series logic predecoder achieves improvements in circuit speed, power, and complexity. As a result, evaluation of the prototype devices can be facilitated, and the optimized circuit schemes achieve enhanced circuit performance. A fully working 1 Gbit synchronous DRAM with a chip size of 570 mm/sup 2/ was fabricated using a 0.16 /spl mu/m CMOS process and tested for excellent functionality up to 143 MHz.

This paper describes several new circuit design techniques for low V/sub CC/ regions: 1) a charge-amplifying boosted sensing (CABS) scheme which amplifies the sensing voltage difference (/spl Delta/V/sub BL/) as well as the V/sub GS/ margin by boosting the sensing node voltage with a voltage dependent boosting capacitor and 2) an I/O current sense amplifier with a high gain using a cross-coupled current mirror control scheme and reduced temperature sensitivity using a simple temperature-compensation scheme. An experimental 16 Mb DRAM chip with the 0.18-/spl mu/m twin-well, triple-metal CMOS process has been fabricated, and an access time from the row address strobe (t/sub RAC/) of 28 ns at V/sub cc/=1.5 V and T=25/spl deg/C has been obtained.

This paper describes a 32-bank 1 Gb DRAM achieving 1 Gbyte/s (500 Mb/s/DQ pin) data bandwidth and the access time from RAS of 31 ns at V/sub cc/=2.0 V and 25/spl deg/C. The chip employs (1) a merged multibank architecture to minimize die area; (2) an extended small swing read operation and a single I/O line driving write scheme to reduce power consumption; (3) a self-strobing I/O schemes to achieve high bandwidth with low power dissipation; and (4) a block redundancy scheme with increased flexibility. The nonstitched chip with an area of 652 mm/sup 2/ has been fabricated using 0.16 /spl mu/m four-poly, four-metal CMOS process technology.

In this study, mercury (Hg) leaching characteristics of the waste treatment residues (fly ash, bottom ash, sludge, and phosphor powder) generated from various sources (municipal, industrial, medical waste incinerators, sewage sludge incinerator, oil refinery, coal-fired power plant, steel manufacturing plant, fluorescent lamp recycler, and cement kiln) in Korea were investigated. First, both Hg content analysis and toxicity characteristic leaching procedure (TCLP) testing was conducted for 31 collected residue samples. The Hg content analysis showed that fly ash from waste incinerators contained more Hg than the other residue samples. However, the TCLP values of fly ash samples with similar Hg content varied widely based on the residue type. Fly ash samples with low and high Hg leaching ratios (RL) were further analyzed to identify the major factors that influence the Hg leaching potential. Buffering capacity of the low-RL fly ash was higher than that of the high-RL fly ash. The Hg speciation results suggest that the low-RL fly ashes consisted primarily of low-solubility Hg compounds (Hg2Cl2, Hg(0) or HgS), whereas the high-RL fly ashes contain more than 20% high-solubility Hg compounds (HgCl2 or HgSO4).

These days, personal information privacy and security is getting an important issue. In various commercial and other application cases, because of convenience and efficiency, personal information is always stored and used by organizations and companies systems. These information have different sensitivity level of privacy among each subject. Usually, the organizations and companies protect the information in a simply way, regarding all the information as the same level. For seeking a more reasonable and flexible resolvable way, in this paper, we propose a policy-based access control mechanism which strictly verifies accessing users so that to ensure the privacy and security of personal information. In our proposed mechanism, information subjects establish their own access control policy for the sensitive personal information, and the individuals' personal information stored in the database of organizations and companies is encrypted with different keys. By this way, we can easily control the access of information users according to personal and organizational privacy policy.

with wide operating voltage range of 1.8~ to 3.6~ for battery based portable applications. Low power during data retention is obtained with Vcc and temperature variable self refresh which is programmable after packaging using electrical fuses. High performance is achieved at low voltage with dual VPPs for well bias and on-chip high voltage power supply, dual threshold voltages for NMOS and voltage variable sensing control. The 16M has a measured RAS access time of 58ns at 1.8~ and 83°C. This paper describes a I6M DRAM

Integrating FSG dual damascene interconnects using MSQ-based sacrificial via filler has been previously shown. When applying such via filler to a Cu/low-k OSG integration, however, the requisite O/sub 2/-ashing induces an inevitable damage to the low-k OSG due to the challenge in selectively eliminating such filler using conventional wet chemistry. By employing an inorganic HSQ that can readily be removed per dilute fluoric acid cleaning in low-k OSG structure, we demonstrated not only a more viable technology with lower defect density at each process step, e.g., photolithography and etching, but also a simpler process that selectively removes the filler material relative to the existing technology based on MSQ and/or organic fillers.

This 32-bank 1 Gb DRAM features: (1) a merged bank architecture (MBA) that results in only 3% die area penalty for 32-bank operation; (2) a source-synchronous I/O interface (SSI) that achieves 1 GB/s bandwidth with low power consumption; (3) flexible block redundancy that allows freedom of repair to anywhere within each half-Gb array; and (4) extended small swing read and single-I/O line driving write which result in 30% power reduction. The DRAM chip is implemented in a 0.16 /spl mu/m twin-well CMOS process.

A fully working 16M DRAM on a Thin Film Silicon On Insulator (TFSOI) is made with 0.5 /spl mu/m CMOS technology. This is, to the best of our knowledge, the highest density SOI DRAM ever achieved. LOCOS isolation and Local Implantation post Field oxidation (LIF) are introduced to suppress the edge transistor effect in NMOS. A reduced n/sup +//p/sup +/ dose in S/D implantation is the key process for a high density TFSOI-DRAM to suppress the defect generation during process while drain-source breakdown voltage (BVds) being increased. The shmoo plot of supply voltage vs. TRAC at 25/spl deg/C for a TFSOI-DRAM is demonstrated. RAS access time, TRAC, is 50 ns at 3.0 V Vcc which is faster by 20% than that of the equivalent bulk-Si device.

DLL and improved I/O circuits are for 500 Mb/s/pin DDR SDRAM. This digitally-controlled DLL has inherent duty cycle correction capability, enabling fast re-locking upon standby-mode exit. Data input circuits, such as internal delay control and digital sense amplifier, reduce setup/hold window to 0.3 ns. The output data driver has 62% decreased pattern-dependent skew.