Analysis of the static yield stress for giant electrorheological fluids

Youngwook P. Seo,최형진,서용석 한국유변학회 2017 Korea-Australia rheology journal Vol.29 No.3

Cheng et al. (2010)'s experimental results for the static yield stress of giant electrorheological (GER) fluids over the full range of electric field strengths were reanalyzed by applying Seo’s scaling function which could include both the polarization and the conductivity models. The Seo’s scaling function could correctly fit the yield stress behavior of GER suspensions behavior after if a proper normalization of the yield stress data was taken which collapse them onto a single curve. The model predictions were also contrasted with recently proposed Choi et al.’s scaling function to rouse the attention for a proper consideration of the GER fluid mechanisms.

Development the On-line Rice flour Discrimination Technology Using Hyperspectral Imaging System

( Youngwook Seo ),( Ahyeong Lee ),( Giyoung Kim ) 한국농업기계학회 2019 한국농업기계학회 학술발표논문집 Vol.24 No.2

Rice is the most important staple food across the world especially in Korean. Recently, rice gains popularity in US because it is one of the most healthy and gluten-free food material. In the view of rice processing, composition and characteristics of rice components such as carbohydrate, protein, and amylose are important. In order to produce commercial scale rice product s, automatic evaluation technology for the products in the processing is necessary. Hyperspectral imaging technology can acquire spectral and spatial information of the target materials at the same time so that it can provide an effective solution for the agro-food quality evaluation. Three kinds of flour samples, short white rice (Mimyeon, 75.6㎛, 14%), wheat (strong flour, 36.6 ㎛, 13.3%), and tapioca (tapioca starch, 27.5㎛, 14%) were prepared in a sample container of 5 × 5 × 2 cm. Samples were measured and classified in real time using on-line hyperspectral imaging system (wavelength : 930 ~ 1,700 nm, image : 320 pixels) with 60 Hz conveying speed. Colors in CIELAB color space of the each sample were measured using colorimeter. CIE L*a*b* values of wheat flour were 95.6±0.14, -1.00±0.04, 9.36±0.04, rice flour were 97.8±0.12, -1.02± 0.02, 3.48±0.04, and tapioca flour were 98.7±0.09, -0.27±0.04, 2.5±0.12, respectively. Based on these color informations, we developed an on-line model for the flour identification using hyperspectral imaging system. The model and the hyperspectral imaging system showed great potential for classifying three different types of flours.

A simplified model for analyzing the flow behavior of electrorheological fluids containing silica nanoparticle-decorated polyaniline nanofibers

Seo, Youngwook P.,Choi, Hyoung Jin,Seo, Yongsok The Royal Society of Chemistry 2012 SOFT MATTER Vol.8 No.17

<P>A new rheological model was applied to the analysis of the electrorheological behavior of a fluid containing silica nanoparticle-decorated polyaniline nanofibers. The model's predictions were compared with the experimental data, revealing that the proposed model correctly predicted the shear stress behavior both quantitatively and qualitatively. The shear stress data of the electrorheological fluid showing aligned fibers' structural reformation as a function of the shear rate agreed well with the new model which required fewer parameters than the CCJ (Cho–Choi–Jhon) model. The static yield stress was found to be quadratically dependent on the field strength, in agreement with the predictions of the polarization model. A scaling function was used to model the yield stress behavior of the electrorheological fluid over a range of electric fields, and it correctly predicted the static yield stress behavior both quantitatively and qualitatively.</P> <P>Graphic Abstract</P><P>A new rheological model was applied to the analysis of the electrorheological behavior of a fluid containing silica nanoparticle-decorated polyaniline nanofibers. The model's predictions were compared with the experimental data, revealing that the proposed model correctly predicted the shear stress behavior both quantitatively and qualitatively. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c2sm07275k'> </P>

A New Strategy of Fine Tuning of A Polymer Melt Rheology

Youngwook P. Seo,Yongsok Seo 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Development of Rice-paper Manufacturing Machine and Evaluation Rice-paper Physical Property

( Youngwook Seo ),( Jong-ryul Park ),( Hoeman Park ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.2

In order to resolve the redundant rice issue, development of rice processing machinery is an alternative solution. We developed the rice-paper manufacturing machine for performance test and finding optimal recipe rice-paper producing. Capacity of a machine is 30kg/h, input power is 220V, and consuming electric power is 3kW. The size of machine is 2774(L) × 500(W) × 1675(H) mm, and which consists of three parts as input, steam, delivery. Input part looks after half of cylinder which can manage of dropping quantity of mixed materials using a tap and knob. Mixed materials can be steamed moving through conveyer belt over steaming bin. Steaming bin can contain water of 10 liter, and water level sensor detects the water quantity so that the level of water is below than 3 liter, alarm rings then fill up the water to 10 liter. Steam bin has electric heating elements and its target temperature is 110°C. Conveying belt over the steam bin moves 1.5 rotates per second which is changeable speed depends on the condition of mixed materials. Thin and long rice paper moves on conveying belt then had cut using a plastic cutter. Processed rice paper moves to output part. Mixed materials with rice powder, starch powder and water has different physical properties. Rice powder 1,000g, tapioca starch 200g, and 60°C water 1,800 ㎖ can be produced rice paper quality. However, further study is necessary to find an optimal recipe using a few rice varieties and starches.

Effect of cold plasma on inactivation of pathogens on citrus

Youngwook Seo,Hoeman Park,Jong Ryul Park 한국산업식품공학회 2018 학술대회 및 심포지엄 Vol.2018 No.04

This study is done to evaluate a dry sterilization method of plant pathogens on the citrus during storage. Cold plasma technique based on dielectric barrier discharge (DBD) technology was used for plasma actuating. Citrus was stored both cold (5℃, 90%RH) and ambient (18℃, 50%RH) store and analyzed for 3 weeks. Treatment (N=24) and control samples (N=48) were randomly divided for each group. The specification of the DBD plasma actuator is as follows: input voltage is 130 V, current is 0.3 A, flow rate is 15L/min, actuator operation time is 5 seconds (ON), and break time is 30 minutes (OFF). Concentration of ozone was 1.0~3.7 ppm and nitrogen dioxide was 0.5~2.5 ppm. Sterilized air was circularized by a diaphragm pump through a transparent Teflon pipe connected to the chamber and the actuator. Every 3~4 days, the selected samples were rinsed and then inoculated with potato dextrose agar (PDA) for 5 days. Cell number was counted by hemocytometer. Physical properties such as weight, color, soluble solid contents (SSC) and rigidity of peel were measured and compared during storage. Color and rigidity was measured four spots through equator of fruits.

Physical properties of several instant Tteokbokki

Youngwook Seo,Jongryul Park,Giyoung Kim 한국산업식품공학회 2021 학술대회 및 심포지엄 Vol.2021 No.10

Cold Plasma Technique for Mandarin Storage at Room Temperature

( Youngwook Seo ),( Hoeman Park ),( Jong Ryul Park ) 한국농업기계학회 2018 한국농업기계학회 학술발표논문집 Vol.23 No.1

This study is done to evaluate a dry sterilization method of microorganisms during storage of mandarin at room temperature. Dielectric barrier discharge (DBD) technology was used for plasma actuator. Mandarin (N=480) was divided by 2 groups for treatment (N=240) and control (N=240) group and stored for 5 weeks. Ten samples from each group were selected for each test such as physical changes (weight, color, hardness, and soluble solids content (SSC)) were observed. In addition, 30 samples in each group observed non-destructive properties as well as weight, color for 5 weeks. The specification of the DBD plasma actuator is as follows. The voltage is 150V, flow rate is 15L/min, actuator operation time is 15 seconds (ON), and break time is 15 minutes (OFF). Sterilized air was circularized by a diaphragm pump through a transparent Teflon pipe connected to the chamber and the actuator. Every 5 days, 1g of skin of the selected 10 samples was rinsed and then inoculated with potato dextrose agar (PDA) for 7 days in 25℃. Cell number was counted by applying image processing method (OpenCFU).

Evaluation of Nonthermal Plasma Treatment by Measurement of Stored Citrus Properties

( Youngwook Seo ),( Jong-ryul Park ),( Hoe Man Park ) 한국농업기계학회 2018 바이오시스템공학 Vol.43 No.4

Decay of fruit is one of the greatest issues in fruit storage. Purpose: In this study, citrus sterilization was performed to evaluate a dry sterilization method using an atmospheric-pressure nonthermal plasma treatment based on a dielectric-barrier discharge technique. Methods: Citrus samples were stored under four different environmental conditions as follows: group A had cold storage with plasma treatment with a temperature of 6.2 ± 1.0℃ and relative humidity (RH) of 93.4 ± 8.2%, group B had ambient-temperature storage with 22.9 ± 2.3℃ and 82.1 ± 4.5% RH, group C ambient-temperature storage with plasma treatment with 25.3 ± 2.2℃ and 90.0 ± 2.8% RH, and group D had cold storage with 5.7 ± 1.0℃ and 93.4 ± 6.5% RH. Results: As a result of citrus surface sterilization by plasma treatment, treatment groups A and C together showed an average of 16.1 CFU/mL of mold colonies, while control groups B and D showed an average of 2.2ⅹ10² CFU/mL or approximately 13 times greater than the treatment groups. Regarding the mean concentration of aerobic bacteria colonies, the treatment groups (A and C) and control groups (B and D) showed an average of 7.1 CFU/mL and 1.9ⅹ10³ CFU/mL, respectively. This is approximately a 270-fold difference in the concentration of pathogen colonies between treatment and control groups. Conclusions: The results showed the potential of nonthermal plasma treatment for citrus storage in enhancing storage duration and quality preservation.

Classification model using subset feature based on a genetic algorithm of VNIR hyperspectral imaging data for organic residuals

( Youngwook Seo ),( Chansong Hwang ),( Moon S. Kim ),( Ahyeong Lee ),( Bal-geum Kim ),( Jongguk Lim ),( Giyoung Kim ),( Jaekyung Jang ) 한국농업기계학회 2020 한국농업기계학회 학술발표논문집 Vol.25 No.1

Hyperspectral imaging technology has emerged as an non-destructive and reliable analysis and discriminant technology for agri-food safety assessment. The technology provides the 3D cub e data with spatial and spectral data. The size of the 3D cube data set is larger than hundreds MB (in the case of 1000 pixels × 1004 pixels × 128 bands). The real-time detection and classification technology is essential for food safety assessment. To reduce the size of data is finding the optimal bands from the whole spectral data. In this study, a genetic algorithm (GA) is implemented to find subset features from 128 wavelengths and applied to develop a classification model. On the stainless steel plate, six spinach droplets were placed on each well according to the concentrations. Original juice of spinach is 100%, and additional five levels were diluted with distilled water as follows: 1:5 (20%), 1:10 (10%), 1:20 (5%), 1:50 (2%), and 1:100 (1%), respectively. VNIR hyperspectral images were obtained using a line-scan hyperspectral imaging system and concentration prediction models were developed with multivariate analysis methods. Support vector machine with 39 selected bands using the genetic algorithm showed accuracy a s 90.65% and the kappa coefficient was 0.88. The overall accuracy of PLS-DA and LDA showed reasonable accuracy as 72.13% and 85.06%, respectively. Using feature selection such as gen etic algorithm, we can reduce the dimensionality of the 3D cube data so that it is helpful to develop a rapid and real-time classifier for food safety. VNIR (400-1000 nm) hyperspectral imaging system and chemometric classification models with sub-set data based on genetic algorithm showed a potential for developing an safety assessment technology for agro-food processing machines or facilities.