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•Conductive media was synthesized by coating PANI on PET bead and PVDF pellet.•Surface polymerization and dipping method were compared by microscopic analysis.•Spectrum peaks ...confirmed successful PANI coating on PET bead and PVDF pellet.•PVDF pellet with higher surface area showed more deposit of PANI than PET bead.•PANI-PVDF pellet produced methane production rate at 22 % faster than uncoated one.
In this study, polyethylene terephthalate (PET) beads and polyvinylidene fluoride (PVDF) pellets were coated with polyaniline (PANI) via the dipping and surface polymerization methods. Both materials were evaluated to determine whether the conductive polymer could improve methane production rates under anaerobic conditions. With a higher surface area, PVDF pellets facilitated more PANI deposition than PET beads, and this was more pronounced using surface polymerization than with the dipping method. The Fourier transform infrared (FTIR) and X-ray photoelectron spectroscopy (XPS) peaks demonstrated the successful coating of both PET beads and PVDF pellets with PANI. However, at a PANI concentration of 1 M, there was no significant difference in the spectrum peak obtained from both surface polymerization and dipping. The surface impedances of PET beads and PVDF pellets decreased after being coated with PANI, confirming increased surface conductivity. The methane production rate of PET beads coated with PANI was 9% higher than that of uncoated beads. Similarly, the methane production rate of PANI-coated PVDF pellets was 25% higher than that without pellets in the presence of seed biomass only.
본 논문에서는 Tobit 모형과 Heckit 모형을 소개한다. 이러한 모형은 절단된 자료의 분석에 사용되는데, 이때 절단된 자료란 연속형 자료가 아닌 특정 지점에서 절단이 발생하게 되거나 일정한 지점에서 개체가 양의 확률로 개체의 다수가 분포, 다른 영역에서는 연속형의 형태로 분포하는 자료를 의미한다. 이때 절단된 형태의 자료라는 특성을 고려하여 일반적인 ...선형회귀모형을 적합하는 경우 발생하는 문제점을 교정하고자 Tobit 및 Heckit 모형을 사용하나, 두 모형의 차이점이 명확하게 고려되지 않고 종종 혼용된 채 사용되었다. 따라서 여기서는 절단된 자료의 형태를 가정별로 세분화하여 모의자료를 통해 먼저 모형의 적합성을 비교하였으며, 이후 실제 자료를 바탕으로 모형을 적합하였다. 그 결과 절단 여부에 영향을 주는 잠재변수가 없는 경우 Tobit 및 Heckit 모형 모두 잘 적합되나 Tobit 모형이 간소하면서도 참값에 더 근접하게 적합되는 것을 확인하였다. 하지만 절단 여부에 영향을 주는 잠재변수가 존재하는 경우에는 Heckit 모형만 적합이 잘 되는 것을 확인하였다.
In this paper, Tobit and Heckit models are introduced. These models have been used for analyzing censored data. Censoring occurs at a specific point and a large number of observations are distributed with a positive probability at a certain point. Censoring can occur due to observing limitation or exogenous variables. Tobit and Heckit models are used to correct sample selection bias, which can occur when an ordinary linear regression model is fitted to censored data. However, the difference between the two models is not clearly accounted for; hence, they have often been used interchangeably. Therefore, the suitability of the models was validated through simulated data, and demonstrated through real data. As the result, it was confirmed that both Tobit and Heckit models are well-fitted to the data censored due to observing limitation, although Tobit model was fitted parsimoniously. In contrast, only Heckit model is well-fitted to the data censored due to exogenous variables.
Prediction models of heavy rain damage using machine learning based on big data were developed for the Seoul Capital Area in the Republic of Korea. We used data on the occurrence of heavy rain damage ...from 1994 to 2015 as dependent variables and weather big data as explanatory variables. The model was developed by applying machine learning techniques such as decision trees, bagging, random forests, and boosting. As a result of evaluating the prediction performance of each model, the AUC value of the boosting model using meteorological data from the past 1 to 4 days was the highest at 95.87% and was selected as the final model. By using the prediction model developed in this study to predict the occurrence of heavy rain damage for each administrative region, we can greatly reduce the damage through proactive disaster management.
A high-performance photocatalytic ceramic membrane was developed by direct growth of a TiO2 structure on a macroporous alumina support using a hydrothermal method. The morphological nanostructure of ...TiO2 on the support was successfully controlled via the interaction between the TiO2 precursor and a capping agent, diethylene glycol (DEG). The growth of anatase TiO2 nanorods was observed both on the membrane surface and pore walls. The well-organized nanorods TiO2 reduced the perturbation of the alumina support, thus controlling the hydrolysis rate of the TiO2 precursor and reducing membrane fouling. However, a decrease in the amount of the DEG capping agent significantly reduced membrane permeability, owing to the formation of nonporous clusters of TiO2 on the support. Distribution of the organized TiO2 nanorods on the support was very effective for the improvement of the organic removal efficiency and antifouling under ultraviolet illumination. The TiO2 nanostructure associated with the reactive crystalline phase, rather than the amount of layered TiO2 formed on the support, which was found to be the key to controlling photocatalytic membrane reactivity. These experimental findings would provide a new approach for the development of efficacious photocatalytic membranes with improved performance for wastewater treatment.
An electrochemical immunoassay protocol for the simultaneous measurements of proteins, based on the use of different inorganic nanocrystal tracers is described. The multiprotein electrical detection ...capability is coupled to the amplification feature of electrochemical stripping transduction (to yield fmol detection limits) and with an efficient magnetic separation (to minimize nonspecific adsorption effects). The multianalyte electrical sandwich immunoassay involves a dual binding event, based on antibodies linked to the nanocrystal tags and magnetic beads. Carbamate linkage is used for conjugating the hydroxyl-terminated nanocrystals with the secondary antibodies. Each biorecognition event yields a distinct voltammetric peak, whose position and size reflects the identity and level, respectively, of the corresponding antigen. The concept is demonstrated for a simultaneous immunoassay of β2-microglobulin, IgG, bovine serum albumin, and C-reactive protein in connection with ZnS, CdS, PbS, and CuS colloidal crystals, respectively. These nanocrystal labels exhibit similar sensitivity. Such electrochemical coding could be readily multiplexed and scaled up in multiwell microtiter plates to allow simultaneous parallel detection of numerous proteins or samples and is expected to open new opportunities for protein diagnostics and biosecurity.
Earthwork is seemingly guesswork, but it requires a high level of accuracy and precise planning. Differences between earthwork design and finishing levels cause project delays and cost overrun due to ...the time-consuming nature of earthwork re-work. Therefore, error-free earthwork planning and design review is a key to the success of earthwork projects. This study utilized an integrated approach of an unmanned aerial vehicle (UAV)-based point cloud and BIM (Building Information Modeling) to verify the design and to operate the earthwork planning. The integrated approach was proposed and applied to a 420 square meters housing construction project to review an original earthwork design and create an earthwork plan for excavator work. As a result, errors in earthwork design that caused by inaccurate initial DEM was revealed, thus the earthwork design was revised with a UAV-based point cloud map. Additionally, the integrated approach was able to generate an explicit task sequence for an excavator.
Effect of mechanical scouring driven by granular activated carbon (GAC) fluidization on membrane fouling was investigated using a laboratory-scaled, fluidized membrane reactor filtering the effluent ...from anaerobic fluidized bed bioreactor (AFBR) in domestic wastewater treatment. The GAC particles were fluidized by recirculating a bulk solution only through the membrane reactor to control membrane fouling. The membrane fouling was compared with two different feed solutions, effluent taken from a pilot-scaled, AFBR treating domestic wastewater and its filtrate through 0.1-μm membrane pore size. The GAC fluidization driven by bulk recirculation through the membrane reactor was very effective to reduce membrane fouling. Membrane scouring under GAC fluidization decreased reversible fouling resistance effectively. Fouling mitigation was more pronounced with bigger GAC particles than smaller ones as fluidized media. Regardless of the fluidized GAC sizes, however, there was limited effect on controlling irreversible fouling caused by colloidal materials which is smaller than 0.1 μm. In addition, the deposit of GAC particles that ranged from 180 to 500 μm in size on membrane surface was very significant and accelerated fouling rate. Biopolymers rejected by the membranes were thought to play a role as binding these small GAC particles on membrane surface strongly.
Excavators are typical machinery in the construction industry, and have advantages when applied in various tasks. Among various tasks of excavators, loading a dump truck is a very important task that ...could be automated. However, most of the previous studies are focused on the excavation/digging operation, and the studies on the loading efficiency are limited. Therefore, the spatial factors affecting loading operation were identified and investigated with regard to the different types of the movements of the machine in this study. To observe changes in the loading time according to the affecting factors, two main hypotheses were examined as follows: 1) loading time changes according to the height difference and distance between the excavator and dump truck; and 2) loading time changes by the rotation angle. In order to verify the hypotheses, the movements of three excavators were studied under the different conditions of the spatial factors. We believe that the automation of loading operation for excavators can benefit from the results of hypothesis validation, and from the analysis of the detailed loading operation in relation to the categorized movement and the patterns of loading operation.
•The spatial factors affecting the loading operation of excavation work were identified.•The loading operation was broken down into several movements to collect data.•The relationship between loading efficiency and spatial factors of excavators was analyzed.•Two hypotheses on the loading efficiency were examined based on the truck loading cycle time.
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