• Clean Technology
• /
• v.26 no.1
• /
• pp.22-29
• /
• 2020

Recently, as the fine dust is increased and the emission regulations of diesel engines have been tightened, interest in diesel soot filtration devices has rapidly increased. There is specifically a demand for the technological development of higher diesel exhaust gas after-treatment device efficiency. As part of this, many studies were conducted to increase exhaust gas treatment efficiency by improving the flow uniformity of the exhaust gas in the diesel particulate filter (DPF) and reducing the pressure drop between the inlet and the outlet of DPF. In this study, the effects of pressure drop by the flow rate and temperature of exhaust gas, DPF I/O ratio, Ash, and PM amount in diesel reduction device were simulated via a 12" diameter DPF and diesel oxidation catalyst (DOC) using ANSYS Fluent. As the flow rate and temperature decreased, the pressure drop decreased, whereas the PM amount affected the pressure drop more than the ash amount and the pressure drop was lower in anisotropic DPF than isotropic DPF. In the case of DPF flow uniformity, it was constant regardless of the various variables of DPF. In ESC and ETC conditions, the filtration efficiency for PM was similar regardless of anisotropic and isotropic DPF, but the filtration efficiency for PN (particle number) was higher in anisotropic DPF than isotropic DPF.

• Atmosphere
• /
• v.27 no.1
• /
• pp.29-40
• /
• 2017

The $PM_{10}$ and $PM_{2.5}$ particles over the Yellow Sea of Korea were collected by ship-borne observation during two cruises in spring, 2015. Their water-soluble ionic components such as $NH_4^+$, $Na^+$, $K^+$, $Mg^{2+}$, $Ca^{2+}$, $SO_4^{2-}$, $NO_3^-$, $Cl^-$, $F^-$, $CH_3COO^-$, $HCOO^-$, and $CH_3SO_3^-$ were analyzed, in order to examine the pollution characteristics of the secondary aerosol components. The comparative study of particle size distribution has resulted that $NH_4^+$, $nss-SO_4^{2-}$, $nss-Mg2+$, $nss-K^+$, $HCOO^-$, and $CH_3SO_3^-$ species mostly existed in fine particle mode. Meanwhile, nss-F-and sea-salt species were distributed in both fine and coarse particle mode, $NO_3^-$, $nss-Ca^{2+}$, $CH_3COO^-$ species were rich in coarse particle mode. The concentrations of secondary pollutants($nss-SO_4^{2-}$, $NO_3^-$, $NH_4^+$) increased in fine particles, and those of natural components ($nss-Ca^{2+}$, Sea-salt) increased in coarse particles. $NH_4^+$ exists as the form of $(NH_4)_2SO_4$ and $NH_4NO_3$, and mostly as $(NH_4)_2SO_4$ in fine particles. $NH_4NO_3$ has lower content compared to $(NH_4)_2SO_4$, and it mostly existed in fine particles at Yellow Sea I and in coarse particles at Yellow Sea II. The concentration ratios of $NO_3^-/nss-SO_4^{2-}$ for Yellow Sea I and Yellow Sea II were 0.52 and 0.16 in coarse particles, and they were 0.64 and 0.38 in fine particles, respectively, showing that the stationary source emissions were more important than mobile source emissions in Yellow Sea II (except Passage II-4).

• Proceedings of the Korea Water Resources Association Conference
• /
• 2015.05a
• /
• pp.610-610
• /
• 2015

수공구조물의 설계에서는 홍수빈도분석을 통해 산정된 특정 재현기간에서의 확률수문량이 설계기준으로 사용된다. 그러나 최근 기후변화로 인해 이상기후 현상이 심해짐에 따라 수문기상자료의 정상성을 가정하는 기존의 홍수빈도분석은 변화되는 수문현상을 적절히 표현하지 못하는 경우가 많다. 본 연구에서는 확률분포의 모수가 시간에 따라 변화하는 비정상성 빈도분석기법을 적용하였으며 확률분포의 모수들을 최우추정법으로 추정하였다. 또한, 분위수 추정과정에서도 비정상성을 고려하여 정상성 가정에서 산정된 재현기간 및 위험도와 비교분석하였다. 확률분포는 GEV 분포를 사용하여 정상성 및 비정상성 모형 4개를 구축하였다. 특히, 비정상성 모형은 위치모수만 선형 경향성을 가지는 경우, 규모모수만 선형경향성을 가지는 경우, 위치 및 규모모수가 선형경향성을 가지는 경우의 3가지로 구분하여 적용하였다. 구축된 4개의 모형 중 적합모형을 선정하기 위해 우도비 검정과 Akaike 정보기준을 사용하였으며 적합모형선정 절차를 체계적으로 구축하고 적용하여 적합모형을 선정하였다. 본 연구에서 구축된 비정상성 홍수빈도분석 기법은 우리나라의 8개 다목적댐 (충주댐, 소양강댐, 안동댐, 임하댐, 합천댐, 대청댐, 섬진강댐, 주암댐)으로부터 취득된 과거 관측 댐 유입량을 대상으로 하여 적용되었다. 우도비 검정과 Akaike 정보기준을 이용한 적합 모형 선정 결과 합천댐과 섬진강댐이 비정상성 GEV 모형에 적합한 것으로 분석되었고, 나머지 지점의 다목적댐들은 정상성 모형에 적합한 것으로 분석되었다. 합천댐과 섬진강댐의 경우 비정상성 가정에서 산정된 재현기간이 정상성 가정에서 산정된 재현기간보다 매우 작게 산정되었으며 확률수문량과 위험도는 크게 산정되었다. 적합모형으로 정상성 모형이 선정된 6개의 다목적댐 중 소양강댐은 Mann-Kendall 비모수 경향성 검정 결과 유의하지는 않지만 비교적 큰 선형경향성을 가지고 있었다. 비록 비정상성 모형이 적합모형으로 선정되지는 않았지만 소양강댐에 비정상성 모형을 가정하여 재현기간과 확률수문량, 위험도를 분석한 결과 정상성 모형 가정에서 산정한 결과와 상당한 차이가 있었다. 이와 같은 결과는 수문자료의 정상성과 비정상성을 고려한 홍수빈도분석이 향후 수공구조물의 설계에 있어서 신뢰성 있는 확률수문량을 결정하는데 도움이 될 것으로 판단된다.

• Tuberculosis and Respiratory Diseases
• /
• v.41 no.2
• /
• pp.144-151
• /
• 1994

Background: Miliary tuberculosis almost always results from the discharge of infected caseous material into the blood stream, usually from a well hidden lymph node in the presentation of this disease in the past four decades, and although it is seen less frequent1y today than previously, its presentation and manifestation may require greater suspicion and diligence by the physician. We investigated the clinical characteristics, predisposing factors and accompanying diseases of miliary tuberculosis and tried to acquire the early diagnosis and treatment of this disease. Methods: A retrospective clinical study was done on 40 cases of miliary tuberculosis admitted to Hanyang University Hospital from Mar. 1989 to Dec.1992. The study investigated age and sex distribution, seasonal distribution, duration of symptoms before admission, pre-disposing factors, clinical symptoms, biochemical findings, chest X-ray findings, extrapulmonary tuberculosis associated with miliary tuberculosis, prognosis and mortality rate. Results: 1) The patients were most common in the age group between 20 and 29(23%) and the ratio of male to female was 1.4:1(male 23 : female 17). 2) Sputum smears for tubercle bacilli were positive in 5 cases(13%). 3) The most common clinical symptoms were fever with chilling(47.5%), coughing(47.5%), second most common symptom was dyspnea(32.5%), and the physical findings on admission were tachycardia(30%), weight loss(27.5%), meningeal signs(17.5%) in order. 4) The predisposing factors were heavy alcohol drinking(6 cases), steroid use(3 cases), pregnancy(2 cases) etc. 5) The chest X-ray findings on admission were miliary shadow only(40%), in addition pneumonic infiltration, pleurisy, and calcification in order. 6) The extrapulmonary tuberculosis associated with miliary tuberculosis were tuberculous meningitis(30%), bone and joint tuberculosis(17.5%), intestinal tuberculosis(15%) in order. 7) Biochemical findings were increased SGOT/SGPT(32.5%), increased alkaline phosphatase(32.5%), hypoalbuminemia(15%), hyponatremia(15%) etc. 8) About 4-6 weeks later after treatment(INH, RFP, PZA, EMB), 26 cases(65%) were improved on clinical symptoms or chest X-ray, 12 cases(30%) were stationary or aggravated, and 2 cases(5%) were died. Conclusion: For the early diagnosis and treatment of miliary tuberculosis, we must see its presentation and manifestation with greater interest and suspicion and investigate its predisposing factors and accompanying diseases.

• Journal of the Korean Society of Radiology
• /
• v.12 no.7
• /
• pp.895-908
• /
• 2018

As modern science is developed and advanced, examination and number of times using radiation are increasing daily. General diagnostic X-ray generator is installed on stationary form, But X-ray generator was developed because patient who is in the intensive care unit, operation room, emergency room can not move to general x-ray room. What we examine patient by x-ray generator is certainly necessary, So patient exposure is inevitable. but reducing radiation exposure is highly important matter about radiation technology, guardian, patient in the same hospital room, nurse etc. For this reason, rule regarding safety control of diagnostic x-ray generator revised for radiation worker, patient and protector proclaim that mobile diagnostic x-ray shield must placed in case of examine different location excluding operation room, emergency room, intensive care unit. But, radiogical technologist is having a lot of difficulties to examine with mobile x-ray generator, diagnostic x-ray shield partition, image plate and lead apron. So, when we use x-ray generator, we manufacture shield tools can be attached to the mobile x-ray generator On behalf of x-ray shield partition and conduct analysis and in comparison to part of body and distribution of dose rate and find way to reduce radiation exposure through distribution of dose rate of patient within the radiogical technologist, medical team. Mobile x-ray generator aimed at SHIMADZU inc. R-20, We manufactured equipment for shielding x-ray scattered x-ray by installing shielding wall from side to side based on support beam on the mobile x-ray generator. Shielding wall when moving can be folded and designed to expand when examine. Experiment measured five times in each by an angle for dose rate of eyes, thyroid, breast, abdomen and gonad on exposure condition of upper and lower extremity, chest, abdomen which is examined many times by mobile x-ray generator. We used dosimeter RSM-100 made by IJRAD and measured a horizontal dose rate by body part. The result of an experiment, shielding decreasing rate of the front and the rear showed 77 ~ 98.7%. Therefore using self-production shielding wall reduce scattered x-ray occurrence rate and confirm can decrease exposure dose consequently. Therefore, through this study, reduction result which is used shielding wall of self-production will be a role of shielding optimization and it could be answer about reduction of medical exposure recommended by ICRP 103.

• Journal of the Korean earth science society
• /
• v.42 no.3
• /
• pp.278-295
• /
• 2021

China's shutdown due to COVID-19 in 2020 reduced air pollutant emissions, which is located on the windward side of South Korea. The positive temperature anomaly and negative zonal wind anomaly from northern Mongolia to South Korea through eastern China presented warm and stationary air masses during January and February 2020. Decreased concentrations of PM10, NO₂, and O₃ were measured at Seokmo-ri and Pado-ri, located in the central-western region of South Korea, due to decreased emissions in China from January to March 2020. After China's shutdown from January to March 2020, in Pado-ri, the ratio of monthly average concentrations in that period with those of PM10 and O₃ in the last four years decreased by approximately 0.7-4.7% and 9.2-22.8%, respectively. In January 2020, during the Lunar New Year holidays in China, concentrations of PM10, NO₂, and O₃ at Seokmo-ri and Pado-ri decreased just as much as it did during the same period in the last four years. However, average concentrations in January 2020 decreased before and after the Lunar New Year holidays in China when compared with those in January of the last four years. In Seokmori, ratios of actual and predicted values (${\bar{O}_s$/M) for PM10, NO₂, and O₃ concentrations were calculated as 70.8 to 89.7%, 70.5 to 87.1%, and 72.5 to 97.1%, respectively, during January and March 2020. Moreover, those of Pado-ri were 79.6 to 93.5%, 67.7 to 84.9%, and 83.7 to 94.6%, respectively. In January 2020, the aerosol optical depth (AOD) data showed a higher distribution than that of the last four years due to photochemical reactions in regions from northern Mongolia to eastern China and the Korean Peninsula. However, the decrease in AOD values compared with those of the last four years was attributed to the decrease in emissions of precursors that generate secondary aerosols in China during March 2020.

• Journal of the Korean Society of Marine Environment & Safety
• /
• v.27 no.7
• /
• pp.924-942
• /
• 2021

The expansion of the Changjiang Diluted Water (CDW) plume during summer is known to be a major factor influencing phytoplankton diversity, community structure, and the regional marine environment of the northern East China Sea (ECS). The discharge of the CDW plume was very high in the summer of 2020, and cruise surveys and stationary monitoring were conducted to understand the dynamics of changes in environmental characteristics and the impact on phytoplankton diversity and community structure. A cruise survey was conducted from August 16 to 17, 2020, using R/V Eardo, and a stay survey at the Ieodo Ocean Research Station (IORS) from August 15 to 21, 2020, to analyze phytoplankton diversity and community structure. The southwestern part of the survey area exhibited low salinity and high chlorophyll a fluorescence under the influence of the CDW plume, whereas the southeastern part of the survey area presented high salinity and low chlorophyll a fluorescence under the influence of the Tsushima Warm Current (TWC). The total chlorophyll a concentrations of surface water samples from 12 sampling stations indicated that nano-phytoplankton (20-3 ㎛) and micro-phytoplankton (> 20 ㎛) were the dominant groups during the survey period. Only stations strongly influenced by the TWC presented approximately 50% of the biomass contributed by pico-phytoplankton (< 3 ㎛). The size distribution of phytoplankton in the surface water samples is related to nutrient supplies, and areas where high nutrient (nitrate) supplies were provided by the CDW plume displayed higher biomass contribution by micro-phytoplankton groups. A total of 45 genera of nano- and micro-phytoplankton groups were classified using morphological analysis. Among them, the dominant taxa were the diatoms Guinardia flaccida and Nitzschia spp. and the dinoflagellates Gonyaulax monacantha, Noctiluca scintillans, Gymnodinium spirale, Heterocapsa spp., Prorocentrum micans, and Tripos furca. The sampling stations affected by the TWC and low in nitrate concentrations presented high concentrations of photosynthetic pico-eukaryotes (PPE) and photosynthetic pico-prokaryotes (PPP). Most sampling stations had phosphate-limited conditions. Higher Synechococcus concentrations were enumerated for the sampling stations influenced by low-nutrient water of the TWC using flow cytometry. The NGS analysis revealed 29 clades of Synechococcus among PPP, and 11 clades displayed a dominance rate of 1% or more at least once in one sample. Clade II was the dominant group in the surface water, whereas various clades (Clades I, IV, etc.) were found to be the next dominant groups in the SCM layers. The Prochlorococcus group, belonging to the PPP, observed in the warm water region, presented a high-light-adapted ecotype and did not appear in the northern part of the survey region. PPE analysis resulted in 163 operational taxonomic units (OTUs), indicating very high diversity. Among them, 11 major taxa showed dominant OTUs with more than 5% in at least one sample, while Amphidinium testudo was the dominant taxon in the surface water in the low-salinity region affected by the CDW plume, and the chlorophyta was dominant in the SCM layer. In the warm water region affected by the TWC, various groups of haptophytes were dominant. Observations from the IORS also presented similar results to the cruise survey results for biomass, size distribution, and diversity of phytoplankton. The results revealed the various dynamic responses of phytoplankton influenced by the CDW plume. By comparing the results from the IORS and research cruise studies, the study confirmed that the IORS is an important observational station to monitor the dynamic impact of the CDW plume. In future research, it is necessary to establish an effective use of IORS in preparation for changes in the ECS summer environment and ecosystem due to climate change.

• The korean journal of orthodontics
• /
• v.29 no.4 s.75
• /
• pp.467-481
• /
• 1999

Cleft lip and/or palate is one of the most common congenital craniofacial anomalies. According to previous epidemiologic studies, incidence of cleft lip and/or palate has been increasing nowadays. However, there is no report about epidemiologic study of cleft lip and/or palate patients who visited dept. of orthodontics in Korea. So the purpose of this study was to provide the epidemiological characteristics and important basic clinical data for the diagnosis and the treatment of the cleft lip and/or palate patients. With the orthodontic and cleft charts, diagnostic models and X-ray films from 250 patients with cleft lip and/or palate who visited Dept. of Orthodontics, Seoul National University Dental Hospital during the last 11 years, the authors investigated patient's visiting yew, types of cleft, patient's gender, and Angle's classification of malocclusion, and surgery timing. The results were as follows ; 1. The number of cleft patients who visited Dept. of Orthodontics, SNUDH increased during 1988-1990 and then it declined until 1992. From 1993 to 1996, it showed a stationary trend. After 1997 it showed an overwhelmingly increasing trend. 2. In the cleft type, the ratio of cleft lip cleft lip and alveolus cleft palate : cleft lip and palate was 7.6:19.2:9.6:63.6. In cleft position, unilateral clefts were more than bilateral ones (cleft lip 79:21, cleft lip and alveolus 77:23, cleft lip and palate 75.5:24.5). In cleft side, left clefts were mote than right clefts (cleft lip 53.3:46.7 cleft lip and alveolus 59.5:40.5, cleft lip and palate 59.2:40.8). 3. In gender ratio, males were more than females in cleft lip (57.9:42.1), cleft lip and alveolus (68.8:31.2) and cleft lip and palate (76.1:23.9). But in cleft Palate females were more than males as 41.7: 58.3. 4. In the age groups, 7-12 year group was the most abundant as $52\%$, and then 0-6 year group ($20.4\%$), 13-18 year group ($17.2\%$), more than 18 yew group ($10.4\%$) were followed as descending order. 5. Most of the cleft lip repair surgeries were operated in 0-3 month ($60.3\%$) and 4-6 month ($17.9\%$). 6. The cleft palate repair surgeries were done in 1-2 year ($31.7\%$), 0-1 year ($25.6\%$), 2-3 year ($12.1\%$), more than 5 year ($11.6\%$) as descending order. 7. The lip scar revision surgeries were done before admission at elementary school in $60\%$. (4-6 you ($27.5\%$), 6-8 year ($19.6\%$), more than 10 year ($19.6\%$), 2-4 year ($13.7\%$) as descending order) 8. The rhinoplasties were done before admission at elementary school in $51.7\%$. (0-2 year ($7.1\%$), 2-4 year ($14.3\%$), 4-6 year ($21.4\%$), 6-8 year ($14.3\%$)). 9. The pharyngeal flap were done at 6 Y (72.5 months) after birth on average and there was even distribution of surgery timing. 10. In relationship between Angle's classification of malocclusion and cleft types, Class I was most abundant and Class III, Class II were followed as descending order in cleft lip group. But Class III was most abundant and Class I, Class II were followed as descending order in cleft lip and alveolus group, cleft palate group, and cleft lip and Palate group. The percentage of frequency in Class III malocclusion was overwhelmingly higher in cleft lip and palate group than any other groups. 11. Because the frequency of class III malocclusion was most prevalent in all age groups, anterior crossbite was the most common chief complaint of cleft patients.