• 제목/요약/키워드: removing rate

검색결과 585건 처리시간 0.041초

실내용 공기청정기 유형별 실내환경개선 성능에 대한 비교평가 (Comparative Efficiency Evaluation of Air Cleaners for Improving Indoor Air Quality)

  • 나경호;손진석;성기준;장영기
    • 환경영향평가
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    • 제14권3호
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    • pp.109-115
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    • 2005
  • This study was conducted to evaluate the efficiency of indoor air cleaners and to inform how to select them correctly to the users. The efficiencies of removing suspended bacteria per hour were $64.3{\pm}13.1%$ for filter, wet, and complex type, respectively, which showed the complex type was the most efficient. The removal efficiencies of formaldehyde (HCHO) after two hours operation of air cleaners showed 88.3% and 81.1% for filter and wet type, respectively. The efficiency of complex type, with removal rate of 55.5~58.4%, was decreased after 30 minutes operation. Therefore, it is recommended to perform over 60 minutes when doing air cleaner certification test for HCHO removal efficiency. Generally, air cleaners having low wind volume showed higher efficiency. All tested air cleaners had no potential for removing of volatile organic compounds (VOCs), which is toxic substances, and it is desirable to develop a device which can control these substances. The results also confirmed that there was no ozone production from all tested air cleaners. And it is recommended to ventilate for 20 minutes every four hours to maintain 50% ventilation status.

소규모 오수처리 시스템에서의 제올라이트에 의한 질소 제거 (Nitrogen Removal using Zeolite at On-site Wastewater Treatment System)

  • 방천희;권순국
    • 한국농공학회지
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    • 제44권2호
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    • pp.161-173
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    • 2002
  • Recently, absorbent biofilters, which are inexpensive and easy to manacle, have been supplied to the rural areas, but have limitations in removing the nutrients effectively. Accordingly, as an alternative plan. natural zeolites were arranged in front or at the rear of the absorbent biofilters, and their removal efficiency for nitrogen and, ultimately, their applicability to the on-site wastewater treatment system were studied. Furthermore, the same experiments were carried out on artificial zeolites, made from coal ashes at National Honam Agricultural Experiment Station, to compare natural zeolites with artificial ones. Treated wastewater through the Absorbent Biofilter showed 22.6% nitrogen removal efficiency, while 64.6% was attained when natural Zeolites were placed in front of the absorbent biofilters (Zeolite-Aerobic process). As an addition, phosphorus was also efficiently removed. On the other hand, Aerobic-Zeolite process, which arranged natural zeolites at the rear of the biofilters, did not have significantly higher nitrogen removal as compared to the treatment using only the absorbent biofilters. Furthermore, upon regeneration of the natural zeolite, the ion exchange rate was fecund to increase over 10% as compared to before regeneration. Our results show that natural zeolites, applied to the on-site wastewater treatment system through the Zeolite-Aerobic process, not only increase the removal efficiency of nutrients, but, by choosing the appropriate regeneration time, can also be cast-effective. Artificial zeolites, on the other hand, though more efficient in removing nutrients, cannot be regenerated and, therefore, are not cost-effective.

고정화 질산균, 탈질균을 이용한 합성폐수의 처리 특성 (Treatment Characteristics of Synthetic Wastewater using Immobilized Nitrobacteria, Denitrobacteria)

  • 원찬희;허영덕;윤재성
    • 상하수도학회지
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    • 제11권4호
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    • pp.63-70
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    • 1997
  • The objectives of this study were to find out the optimum treatment conditions for removing nitrogen in a synthetic wastewater by using microorganisms immobilized with PVA-Freezing method. The samples used as influents to the laboratory scale treatment units were a synthetic wastewater. The experiments in this study were mainly directed to collect the data of nitrogen and organic matter removal efficiencies for the different hydraulic and internal recycle rates conditions, temperature and influent C/N ratios. The removal efficiencies of nitrogen and organic matters were investigated for the operating conditions of HRT 2~12hours, internal recycle rates 50~400%, temperatures $15{\sim}30^{\circ}C$ and C/N ratios 2.5~7.5. The adequate internal recycle rate for removing T-N and $BOD_5$ in the synthetic wastewater was found to be about 300% at the temperature of $30^{\circ}C$ when the ratio of carbon contents to the nitrogen (C/N) in the influent was around 5.5. Under these conditions, the final effluent concentrations of T-N and $BOD_5$ were 8.7 and 8.4 mg/l, respectively.

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Degradation of gas-phase toluene by $TiO_2$ loaded on carbon fibers using Atomic Layer Deposition (ALD) under UV irradiation

  • Luo, Yuan;Kim, Myoung-Joo;Seo, Hyun-Ook;Kim, Kwang-Dae;Tai, Wei Sheng;Kim, Young-Dok
    • 한국진공학회:학술대회논문집
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    • 한국진공학회 2009년도 제38회 동계학술대회 초록집
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    • pp.349-349
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    • 2010
  • $TiO_2$ thin films were prepared on C fibers, and photocatalytic activity of these films for removing gas-phase toluene was studied. $TiO_2$ films were deposited on C fiber with 0.5 A-per-cycle growth rate by Atomic Layer Deposition (ALD) using TTIP (titanium tetra-isopropoxide) and $H_2O$ as precursors. The catalysts were characterized by Brunauer-Emmett-Teller (BET) for surface area and Scanning Electron Microscope (SEM) for morphology, respectively. Moreover, the samples were further characterized by X-ray Photoelectron Spectroscopy (XPS). As a function of $TiO_2$ thickness, no significant change in the photocatalytic activity could be identified. Interestingly, the bare-carbon fiber showed an even higher photocatalytic activity than the $TiO_2$ thin films for removing toluene. Origin of the high photocatalytic activity of the bare C fiber is discussed.

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벨트식 유회수기의 접촉각이 회수율에 미치는 영향에 관한 실험적 연구 (An Experimental Study on the Effect of Contact Angle for Recovery Rate of a Belt Skimmer)

  • 송동업;윤경환
    • 대한기계학회논문집B
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    • 제22권12호
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    • pp.1702-1714
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    • 1998
  • Removal of spilled oil over the sea and the river has become one of the urgent problems in these days. Removing oil using mechanical devices was recommended because chemical dispersion could cause the secondary contamination in the environment. In the present study a series of experiments were carried out to study the effect of operating conditions, especially, the angle between the belt and the fluid surface on the rate of recovery for the spilled oil using a belt skimmer. Three different types of operation, namely, upward pickup, downward pickup and up-and-downward pickup situations have been investigated for various contact angles, belt speeds and oil thicknesses to find the effects on the recovery rate. The highest rate of oil recovery was found in the case of a contact angle of $45^{\circ}$ and downward pickup. Furthermore, an optimal belt speed was found to reach the saturated recovery rate for a given oil thickness.

싸이클론 전해환원방법을 이용한 LiBr 용액내의 Cu 불순물 제거에 관한 연구 (Removal of Cu impurities in LiBr solution using cyclone electrowinning method)

  • 박다정;이규환
    • 한국표면공학회지
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    • 제57권2호
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    • pp.92-97
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    • 2024
  • The LiBr aqueous solution, which is the absorption liquid of absorption refrigerator, must be replaced periodically because the concentration of impurities such as Cu2+, Fe2+, Ca2+, etc., increases due to corrosion of the tubes as the period of use increases, and the refrigeration efficiency decreases significantly. In order to reuse the waste absorption liquid, flocculation-precipitation method is mainly applied to precipitate the impurities, which requires hundreds of times the concentration of impurities and generates additional waste. In this study, a process for removing Cu ion impurities from cyclone electrolyzer by electrolytic reduction is presented in a small-scale facility without additional waste. It was confirmed that Cu ion impurities can be removed down to 1 ppm by electrolytic reduction process, and to further improve the removal rate, the mass transfer rate was increased by using a cyclone electrolyzer. The removal rate of Cu ions increased with the increase of flow rate and current density, and it was confirmed that Cu was removed at a rate of 1.48 ppm/h under the condition of 330 mL/sec and 2.5 mA/cm2.

대장암 검진-50세 이하부터 시작하는 것은 필요한 것인가? (Colon Cancer Screening-Is It Necessary to Start under the Age of 50?)

  • 신종범
    • Journal of Digestive Cancer Research
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    • 제11권3호
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    • pp.141-146
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    • 2023
  • Colorectal cancer is the third most common cancer worldwide. The occurrence of colon cancer can be prevented by removing precursor lesions. Several countries are making efforts to prevent the occurrence of colon cancer via screening programs. Korea is also following suite by screening individuals < 50 years of age. Currently, the incidence of colon cancer among the young is increasing globally, and Korea has a high colon cancer incidence rate among individuals in their 20s and 40s. Therefore, it may be necessary to start the screening individuals < 50 years of age to detect the cancer's manifestation early. Moreover, advanced adenomas associated with poor prognosis can be detected early, the overall screening rate can be increased, and death from colon cancer at a young age can be prevented. Although the period of colorectal cancer screening has been expanded, the overall colorectal cancer screening rate has not. Additionally, increasing the screening rate among individuals > 50 years could reduce the mortality rate at a lower cost. Although the incidence of colon cancer is increasing in younger individuals, the evidence to conclude that screening at the age of < 50 years has a meaningful impact on the incidence and survival rates of colon cancer remains insufficient. Therefore, rather than following the trend and performing screening early, an approach that actively selects cases where tests for colorectal cancer diagnosis are required is warranted.

냉각공기에 의한 환경 친화적 절삭가공기술 (Environment-Friendly Metal Cutting Technology using Cooled Air)

  • 이종항;조웅식;정준기;박철우;김영중
    • 한국정밀공학회지
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    • 제18권6호
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    • pp.114-120
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    • 2001
  • It is necessary to develop a new metal cutting technology which does not use cutting fluid, since cutting fluid can have undesirable effect on workers's health and working environment. For this to be possible, it is necessary to replace the conventional method of using cutting fluid, whose basic functions are removing chip and heat, and providing lubrication between tool and chip. In this work, cooled air is utilized in order to replace cutting fluid. Experiments were carried out while cutting workpiece with HSS flat endmill under a variety of supply conditions for cooled air. Also the performance characteristics of the air cooling system. which was built for the experiments, were carefully analyzed. For the reliable operation of air cooling system. moisture contained in the cooled air had to be removed before being supplied to the workpiece and tools. It was found that depending on the amount of its flow rate the temperature of cooled air changes at the time of injection from the nozzle. The flow rate of cooled air also plays an important role in removing the accumulated chip on the workpiece. After comparing the flank wear for the three cases of using cooled air, cutting fluid, and pure dry technique, it was demonstrated that the level of flank wear was similar for the cases of cooled air and cutting fluid. The pure dry technique, however, showed higher level of flank wear than cooled air.

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예초관리에 따른 Kentucky bluegrass의 품종간의 생육과 Thatch 축적 I. 예초잔여물의 제거 하에서의 품종간의 차이 (The Growth and Thatch Accumulation of Kentucky Bluegrasses as Affected by Cutting Management. Varietal Differences under Removing Clipping Residues)

  • 윤용범;이주삼
    • 아시안잔디학회지
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    • 제6권1호
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    • pp.29-37
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    • 1992
  • This experiment was carried out in order to study the changes of morphological characters of the growth and thatch accumulation in :3 varieties of Kentucky bluegrass under removing clipping residues as affected by cutting management. The varieties used were Park, Kenhiuc and Newport.The results obtained are as follows; 1. The dry weight of leaf. stem and number of tiller was highest at 22. June and lowest at 21. Aug in alt varieties. And then the dry weight of rhizome, root and thatch increased with growth progressed) Tabte 3). 2. The relationship of the dry weight of biological yield and number of tillers was quadratic ally increased in the growth stage of spring($R^2$= 0.982**), and linearlly increased in the growth stage of autumn(r 0.944*)(Fig. 1). :3. The dry weight of thatch increased as an exponentially equation in alt :3 varieties of Kentucky blue-grass(Fig. 2). Thatch increased rate(TIR) can used to estimate the specifying a quantity of thatch accumulation from the turf. Thatch increase rate equation as follows. where TH$_2$ is the dry weightof thatch at T$_2$ survey time and TH$_1$ is the dry weight of thatch at $TH_1$ is the dry weight of thatch at $T_1$ survey time. $TIR(mg/cm^2/day)=\frac{Ln\;TH_2 - Ln\; TH_1}{T_2 - T_1}$ 4. Correlation coefficients between the dry weight of thatch and leaf weight was -0.633(P>0.05), and number of tiller of tillers was -0.666(P>0.5), respectively. It means that thatch accumu-lation increased with growth depression of leaf and stem.

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공동주택 전열교환기 필터종류 및 두께에 따른 미세먼지 제거율 평가 (Evaluation of Particulate Matter Removal Rate according to Filter Type and Thickness of Total Heat Exchanger in Apartment Houses)

  • 송용우
    • 토지주택연구
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    • 제11권4호
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    • pp.93-98
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    • 2020
  • This study examined the particulate removal performance of three different types of air filters inside a heat exchanger. Of interest was the ability of each filter type in reducing the transmission of outdoor particulate matter of PM10 from entering an apartment while the heat exchanger was in operation. The study tested one commonly used medium filter (E11 grade) and two HEPA filters (H13 grade) of different thicknesses. Two different concentrations of particulate matter were used in the experiment to address different ambient air quality conditions in Korea, 32.75 ㎍/㎥ and 67.26 ㎍/㎥. Study results indicated that under the particulate matter concentration of 32.75 ㎍/㎥, all three filters were capable of removing more than 95% of the fine dust. However at a particulate matter concentration of 67.26 ㎍/㎥, the medium E11 grade filter was only able to remove about 90% of the particulates whereas the HEPA H13 grade filters were able to remove 95% or more of the particulates. The thicker HEPA filter (40T) was also more effective in removing particulates than the thinner HEPA filter (20T) by about 1.6 to 3 percentage points. Based on the findings of this study, it is recommended that HEPA filters of 20T thickness or greater be used during the high air pollution seasons of winter and spring in Korea while medium filters can be used during the other seasons to reduce outdoor air pollution transmission indoors.