• Title/Summary/Keyword: Reduction Rate Test

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A study for High Efficiency Dewatering of Sludge Contained Fine Particles (미세입자(微細粒子)를 함유(含有)한 슬러지의 고효율(高效率) 탈수(脫水) 연구)

  • Lee, Jung-Eun;Lee, Jae-Keun
    • Resources Recycling
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    • v.15 no.4 s.72
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    • pp.36-43
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    • 2006
  • There was some difficulty dewatering properties due to small porosity diameter of cake, when pigment sludge contained fine particle was formed by cake under the dewatering. It was difficult to dewater the sludge with fine particles with the conventional mechanical dewatering method. This study was to improve the dewatering rate as discharging the water from porosity of cake easily, supplying the low heat to the cake layer. Thermal dewatering equipment of piston type to keep up constant temperature on the cake was set up and relative experiment was conducted for sludge of 200 g with fine pigment particle. As test results. filtration of 176.8 g, cake weight of 19.4 g, cake thickness of 4.2 mm was measured, and it was analyzed that the water content of cake was 47 wt% and dewatering velocity, which moaned the residual d교 sloid amount per dewatering area, was $2.1DS\;m^{2}{\cdot}cycle$. This results showed that filtration increased, cake weight and thickness decreased and dewatering velocity increased against mechanical dewatering method. And water content of cake decreased about 30%, so the result which dewatering rate improved was drew generally. The reason is that the inner vapor pressure working at the cake porosity increased as applying the low heat to the cake layer, which lead to discharge the water from porosity easily. Therefore, this study was estimated by the useful technology for sludge reduction.

Field Application and Maintenance of sidewalk concrete block for PV Power Generation (태양광 발전을 위한 보도형 콘크리트 블록의 현장 적용과 유지관리)

  • Kim, Bong-Kyun;Kim, Yun-Yong
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.5
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    • pp.75-83
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    • 2019
  • In order to fulfill the obligation to voluntarily reduce greenhouse gas emissions under the Paris Climate Agreement, the proportion of coal and nuclear power generation is reduced worldwide and national efforts are being made to spread renewable energy including solar power generation. Korea also intends to increase the proportion of renewable energy generation to 30~35% by 2040 by introducing laws and regulations. In addition, while the country is trying to apply solar power generation to sidewalks and roads, there is no research related to it in Korea. Therefore, as a precedent study to develop solar power generation roads, solar power generation concrete blocks applicable to sidewalks and plazas were developed and the applicability was evaluated by constructing them on the site. As a result of indoor experiment, compressive strength was measured by 25.5~35.7MPa and flexural strength was measured by 5.1~10.5MPa, which showed that all domestic standards were satisfied. However, the higher the unit cement amount, the lower the strength was measured according to the mixing of the broken fine aggregate. The absorption rate was 5.7%, which satisfied the domestic standard of 7% or less. As a result of the freeze-thawing test, the reduction rate of the compressive strength after 100 cycles was up to 6.3%. As a result of measuring the settlement amount after construction, the maximum of 2.498mm was measured and irregular settlement occurred in the overall area, which is because the resolution of the sand layer was poor during construction. Maintenance techniques of sidewalk concrete block and solar panel need to be established more efficiently through long-term operation in the further.

Ecotoxicity Evaluation of PFCs using Marine Invertebrate, Sea Urchin (Mesocentrotus nudus) (둥근성게(Mesocentrotus nudus)를 이용한 과불화화합물의 생태독성평가)

  • Choi, Hoon;Lee, Ju-Wook;Lee, Seung-Min;Jeon, Hyung-Ju;Heo, Seung;Hwang, Un-Ki
    • Journal of Marine Life Science
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    • v.6 no.2
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    • pp.80-87
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    • 2021
  • In this study, the toxic effects of PFOA and PFOS potassium salt on Mesocentrotus nudus using 10 min-fertilization rate and 48 h-normal embryogenesis were confirmed through the calculation of toxicity values such as Non-observed effective concentration, Low-observed effective concentration, and 50% of effective concentration. The case of 10 min-fertilization rate and 48 h-normal embryogenesis showed the concentration-dependent reduction pattern when exposed to PFOA and PFOS potassium salt, in tested concentration, respectively. The EC50 values of 10 min-fertilization rates for PFOA and PFOS potassium salt were 1346.43 mg/l and 536.18 mg/l, respectively, and the EC50 values of 48 h-normal embryogenesis were 42.67 mg/l and 17.81 mg/l, respectively. Both toxicity test methods showed high toxicity sensitivity to PFOS potassium salt. Recent studies have shown that the concentration of PFOA and PFOS in the marine environment has continuously decreased, and it is not enough to show acute toxicity to sea urchin. However, PFOA and PFOS have a very long half-life and can accumulate throughout the life of marine life, so it is still observed at a high concentration in shellfish. Therefore, a study on chronic toxicity through the whole-life cycle of marine organisms in coastal environments should be needed.

Electrochemical Characteristics of Dopamine coated Silicon/Silicon Carbide Anode Composite for Li-Ion Battery (리튬이온배터리용 도파민이 코팅된 실리콘/실리콘 카바이드 음극복합소재의 전기화학적 특성)

  • Eun Bi Kim;Jong Dae Lee
    • Korean Chemical Engineering Research
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    • v.61 no.1
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    • pp.32-38
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    • 2023
  • In this study, the electrochemical properties of dopamine coated silicon/silicon carbide/carbon(Si/SiC/C) composite materials were investigated to improve cycle stability and rate performance of silicon-based anode active material for lithium-ion batteries. After synthesizing CTAB/SiO2 using the Stöber method, the Si/SiC composites were prepared through the magnesium thermal reduction method with NaCl as heat absorbent. Then, carbon coated Si/SiC anode materials were synthesized through polymerization of dopamine. The physical properties of the prepared Si/SiC/C anode materials were analyzed by SEM, TEM, XRD and BET. Also the electrochemical performance were investigated by cycle stability, rate performance, cyclic voltammetry and EIS test of lithium-ion batteries in 1 M LiPF6 (EC: DEC = 1:1 vol%) electrolyte. The prepared 1-Si/SiC showed a discharge capacity of 633 mAh/g and 1-Si/SiC/C had a discharge capacity of 877 mAh/g at 0.1 C after 100 cycles. Therefore, it was confirmed that cycle stability was improved through dopamine coating. In addition, the anode materials were obtain a high capacity of 576 mAh/g at 5 C and a capacity recovery of 99.9% at 0.1 C/0.1 C.

Quality Reporting of Radiomics Analysis in Mild Cognitive Impairment and Alzheimer's Disease: A Roadmap for Moving Forward

  • So Yeon Won;Yae Won Park;Mina Park;Sung Soo Ahn;Jinna Kim;Seung-Koo Lee
    • Korean Journal of Radiology
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    • v.21 no.12
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    • pp.1345-1354
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    • 2020
  • Objective: To evaluate radiomics analysis in studies on mild cognitive impairment (MCI) and Alzheimer's disease (AD) using a radiomics quality score (RQS) system to establish a roadmap for further improvement in clinical use. Materials and Methods: PubMed MEDLINE and EMBASE were searched using the terms 'cognitive impairment' or 'Alzheimer' or 'dementia' and 'radiomic' or 'texture' or 'radiogenomic' for articles published until March 2020. From 258 articles, 26 relevant original research articles were selected. Two neuroradiologists assessed the quality of the methodology according to the RQS. Adherence rates for the following six key domains were evaluated: image protocol and reproducibility, feature reduction and validation, biologic/clinical utility, performance index, high level of evidence, and open science. Results: The hippocampus was the most frequently analyzed (46.2%) anatomical structure. Of the 26 studies, 16 (61.5%) used an open source database (14 from Alzheimer's Disease Neuroimaging Initiative and 2 from Open Access Series of Imaging Studies). The mean RQS was 3.6 out of 36 (9.9%), and the basic adherence rate was 27.6%. Only one study (3.8%) performed external validation. The adherence rate was relatively high for reporting the imaging protocol (96.2%), multiple segmentation (76.9%), discrimination statistics (69.2%), and open science and data (65.4%) but low for conducting test-retest analysis (7.7%) and biologic correlation (3.8%). None of the studies stated potential clinical utility, conducted a phantom study, performed cut-off analysis or calibration statistics, was a prospective study, or conducted cost-effectiveness analysis, resulting in a low level of evidence. Conclusion: The quality of radiomics reporting in MCI and AD studies is suboptimal. Validation is necessary using external dataset, and improvements need to be made to feature reproducibility, feature selection, clinical utility, model performance index, and pursuits of a higher level of evidence.

Spalling Prevention of High Strength concrete Corresponding to the Various Heating Curves (가열온도곡선 변화에 따른 고강도 콘크리트의 폭렬방지특성)

  • Han, Cheon-Goo;Pei, Chang-Chun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.13 no.3 s.55
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    • pp.127-134
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    • 2009
  • This study investigated their properties of spalling resistance and residual compressive strength after fire test corresponding to various ISO, RABT heating curves, and contents of hybrid organic fiber of high strength concrete. The results were summarized as following. As fundamental characters of concrete with hybrid organic fiber, the flowability was directly declined as the increase of fiber contents, and air contents were decreased or increased a little bit, but there was not big difference. The compressive strength was gradually declined sluggishly at 28 days. As properties of fire resistance, in case of RABT heating curves, compare with ISO heating curves a spalling aspect showed till range that has much contents of hybrid organic fiber, but they are mostly peeling spalling, which means spalling aspect didn't happen to inside. In conclusion, in case of W/B 25% high strength concrete, the spalling was prevented over 0.04% of contents of fiber at ISO heating curve and over 0.10% of contents of fiber at the RABT heating curve. In case of spalling was prevented, mass reduction rate according to the change of heating temperature curves showed around 7% at ISO heating curves and around 9% at RABT heating curves. The residual compressive strength rate corresponding to the change of heating temperature curves showed 50%~60% at ISO heating temperature curves and 30%~35% at RABT heating temperature curves in case of spalling was prevented.

Effect of Cathode Porosity on the Cathodic Polarization Behavior of Mixed Conducting LSCF(La0.6Sr0.4Co0.2Fe0.8O3) (혼합전도체 LSCF(La0.6Sr0.4Co0.2Fe0.8O3) 양극의 기공률에 따른 양극분극 특성)

  • Yun, Joong-Cheul;Lee, Jong-Ho;Kim, Joosun;Lee, Hae-Weon;Kim, Byong-Ho
    • Journal of the Korean Ceramic Society
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    • v.42 no.4
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    • pp.251-259
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    • 2005
  • In order to characterize the influence of the reaction-site density on the cathodic polarization property of LSCF, we chose the porosity of LSCF as a main controlling variable, which is supposed to be closely related with active sites for the cathode reaction. To control the porosity of cathodes, we changed the mixing ratio of fine and coarse LSCF powders. The porosity and pore perimeter of cathodes were quantitatively analyzed by image analysis. The electrochemical half cell test for the cathodic polarization was performed via 3-probe AC-impedance spectroscopy. According to the investigation, the reduction of oxygen at LSCF cathode was mainly controlled by following two rate determining steps; i) surface diffusion and/or ionic conduction of ionized oxygen through bulk LSCF phase, ii) charge transfer of oxygen ion at cathode/electrolyte interface. Moreover, the overall cathode polarization was diminished as the cathode porosity increased due to the increase of the active reaction sites in cathode layer.

Physical Properties of Recycled Sidewalk Pavement Using Wood Chip (Wood Chip을 사용한 자원순환형 보도 포장체의 물성에 관한 연구)

  • Yu, Hyeok-Jin;Choi, Jae-Jin
    • Journal of the Korean Recycled Construction Resources Institute
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    • v.5 no.2
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    • pp.91-96
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    • 2010
  • The purpose of this study is to find problems about pedestrian road of tourist resort and to make new type of sidewalk pavement with wood chip and binder using urethane resin on the parks and tourist resort. The wood chip pavement has new economics and durability with comfortable texture. Samples of these pavement materials were tested for tensile strength, permeability and ball rebound value. Also, after immersion for 24 hours, tensile strength, samples' thickness and weight were measured and discussed the strength reduction according to the water immersion. Tensile strength experimentation was examined on dry condition and water immersion. The result of examination on dry condition was 1.06MPa and on water immersion was 0.67MPa. The results showed 36.8% decreasing rate of tensile strength. Permeability experiment test based on field permeability method of pavement were conducted as a result, permeability coefficients were in the range of 0.67~0.78mm/s that all exceeds object permeability coefficient. Elasticity experiment was based on elasticity test method of Japan road association. GB coefficient was 21% and SB coefficient was 10%. GB coefficient and SB coefficient increased if fine aggregate were increased.

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A Text Mining-based Intrusion Log Recommendation in Digital Forensics (디지털 포렌식에서 텍스트 마이닝 기반 침입 흔적 로그 추천)

  • Ko, Sujeong
    • KIPS Transactions on Computer and Communication Systems
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    • v.2 no.6
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    • pp.279-290
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    • 2013
  • In digital forensics log files have been stored as a form of large data for the purpose of tracing users' past behaviors. It is difficult for investigators to manually analysis the large log data without clues. In this paper, we propose a text mining technique for extracting intrusion logs from a large log set to recommend reliable evidences to investigators. In the training stage, the proposed method extracts intrusion association words from a training log set by using Apriori algorithm after preprocessing and the probability of intrusion for association words are computed by combining support and confidence. Robinson's method of computing confidences for filtering spam mails is applied to extracting intrusion logs in the proposed method. As the results, the association word knowledge base is constructed by including the weights of the probability of intrusion for association words to improve the accuracy. In the test stage, the probability of intrusion logs and the probability of normal logs in a test log set are computed by Fisher's inverse chi-square classification algorithm based on the association word knowledge base respectively and intrusion logs are extracted from combining the results. Then, the intrusion logs are recommended to investigators. The proposed method uses a training method of clearly analyzing the meaning of data from an unstructured large log data. As the results, it complements the problem of reduction in accuracy caused by data ambiguity. In addition, the proposed method recommends intrusion logs by using Fisher's inverse chi-square classification algorithm. So, it reduces the rate of false positive(FP) and decreases in laborious effort to extract evidences manually.

A Study on the Removal Efficiency of Harmful Pollutants in the Cooking Chamber (조리실내의 유해오염물질 제거율에 관한 연구)

  • Kwon, Woo-Taeg;Lee, Woo-Sik
    • Culinary science and hospitality research
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    • v.22 no.8
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    • pp.149-156
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    • 2016
  • The purpose of this study is to reduce the contaminants (total volatile organic compounds (TVOCs), fine particle, odor and total airborne bacteria) during cooking process in cooking chamber, and to decrease the health damage in indoor space that has bad work environment. In order to solve the shortcomings of existing air purifiers and remove all kinds of pollutants effectively, this study focused on the development of indoor air purifiers which are made of bar type. Bio-ceramics filter which combines activated carbon and loess. The air cleaners developed with 4 measuring items including TVOCs, particulate matter, complex odor and total airborne bacteria were measured comparing their pre-service test to their post-service test after a period of time. The measured results showed higher removal efficiency of 91.02% as the concentration of TVOCs was reduced from $2,500{\mu}g/m^3$ to $223{\mu}g/m^3$. Second, the particulate matter removal ratio was 97.51% efficient with average concentration of $26.68{\mu}g/m^3$. Third, the odor showed 95.20% reduction as air dilution ratio averaged out at 144. Last, total airborne bacteria was eliminated by over 94% showing the changeable concentration from $787{\sim}814CFU/m^3$ to $47{\sim}40CFU/m^3$. In addition, the removal rate of harmful pollutants is excellent, and it is expected that the environment of the existing poor cooking room will be greatly improved by using the developed air purifier in combination with the ventilation device and the stove hood.