21 results on '"Jungmin Lee"'
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2. Analysis of Rainwater Quality and Temperature Reduction Effects Using Rainwater Harvesting Facilities
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JongSoo Choi, JungMin Lee, MyeongIn Kim, JaeHyeon Lee, and YoungTae Cho
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rainwater harvesting facilities ,rainwater quality analysis ,temperature reduction ,water circulation facilities ,heatwaves ,Building construction ,TH1-9745 - Abstract
As eco-friendly complexes develop, interest in eco-friendly facilities is also growing. Particularly, rainwater harvesting facilities have demonstrated positive effects by reducing runoff to mitigate urban flooding and recycling water for landscaping and cleaning purposes. In this study, we analyzed the quality of stored rainwater, which has improved by excluding initial runoff, and examined the temperature reduction effects of road sprinkling and mist spraying. Road sprinkling decreased the temperature of asphalt and permeable pavements by approximately 15 °C, with permeable pavements maintaining the reduced temperature for a longer time. The indoor experiments with mist spraying showed a temperature reduction effect of 3.4 °C. The quality analysis of the rainwater harvesting facilities revealed that the water quality was suitable for irrigation and landscaping by excluding the initial runoff. This study confirms the effectiveness of rainwater utilization in mitigating urban heat islands and improving water circulation within cities.
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- 2024
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3. Validation of the Korean Version of the Health Care Climate Questionnaire among Cancer Survivors
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Hyun-E Yeom, Jungmin Lee, and Young-Joo Kim
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chronic illnesses ,health care climate questionnaire ,supportive environment ,Medicine - Abstract
Healthcare professionals should support autonomy in their patients in order for them to maintain the motivation to cope actively with their conditions. The Health Care Climate Questionnaire (HCCQ) is useful for assessing patients’ perceptions of the autonomy support provided to them. We aimed to validate the psychometric properties of the Korean version of the HCCQ (HCCQ-K) among Korean cancer survivors. This study evaluated the factor structure, concurrent validity, and internal consistency. Data from 367 cancer survivors were analyzed using confirmatory factor analysis (CFA), Pearson’s correlations, and Cronbach’s α values. The CFA validated that the single-factor structure of the HCCQ-K had an excellent fit that was consistent with that of the original English version. Concurrent validity was confirmed by moderate correlations between the HCCQ-K and both psychological well-being and self-management. Reliability was verified by satisfactory internal consistency, with a Cronbach’s α value of 0.91 and strong item-total and inter-item correlations. The HCCQ-K is therefore a valid and reliable tool for assessing autonomy support provided by healthcare professionals to Korean cancer survivors. The HCCQ-K may help healthcare professionals understand their patients’ needs for autonomy support and develop strategies to motivate active coping behaviors.
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- 2024
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4. Anti-Melanogenic Effects of Lilium lancifolium Root Extract via Downregulation of PKA/CREB and MAPK/CREB Signaling Pathways in B16F10 Cells
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Seokmuk Park, Nayeon Han, Jungmin Lee, Jae-Nam Lee, Sungkwan An, and Seunghee Bae
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melanogenesis ,anti-melanogenic effect ,melanin ,B16F10 ,α-melanocyte stimulating hormone (α-MSH) ,Lilium lancifolium ,Botany ,QK1-989 - Abstract
Hyperpigmentation disorders causing emotional distress require the topical use of depigmenting agents of natural origin. In this study, the anti-melanogenic effects of the Lilium lancifolium root extract (LRE) were investigated in B16F10 cells. Consequently, a non-cytotoxic concentration of the extract reduced intracellular melanin content and tyrosinase activity in a dose-dependent manner, correlating with the diminished expression of core melanogenic enzymes within cells. LRE treatment also inhibited cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB)/microphthalmia-associated transcription factor signaling, which regulates the expression of tyrosinase-related genes. Upon examining these findings from a molecular mechanism perspective, LRE treatment suppressed the phosphorylation of protein kinase A (PKA), p38, and extracellular signal-related kinase (ERK), which are upstream regulators of CREB. In addition, L-phenylalanine and regaloside A, specifically identified within the LRE using liquid chromatography-mass spectrometry, exhibited inhibitory effects on melanin production. Collectively, these results imply that LRE potentially suppresses cAMP-mediated melanogenesis by downregulating PKA/CREB and mitogen-activated protein kinase (MAPK)/CREB signaling pathways. Therefore, it can be employed as a novel therapeutic ingredient of natural origin to ameliorate hyperpigmentation disorders.
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- 2023
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5. Hypoglycemic Effect of an Herbal Decoction (Modified Gangsimtang) in a Patient with Severe Type 2 Diabetes Mellitus Refusing Oral Anti-Diabetic Medication: A Case Report
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Sungjun Joo, Hyonjun Chun, Jisu Lee, Seungmin Seo, Jungmin Lee, and Jungtae Leem
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diabetes mellitus ,hyperglycemia ,east Asian traditional medicine ,integrative medicine ,herbal medicine ,case report ,Medicine (General) ,R5-920 - Abstract
There is growing interest in alternative therapies for type 2 diabetes mellitus (T2DM) because some patients refuse to receive conventional therapies. In East Asia, herbal medicines are often used to treat T2DM, and modified Gangsimtang (mGST) is prescribed to treat a condition called wasting thirst (消渴), which resembles T2DM. This study reported the treatment of hyperglycemia using herbal medicines without oral hypoglycemic agents or insulin therapy. Case presentation: A 36-year-old man with obesity was diagnosed with T2DM four years prior to hospitalization and experienced blood glucose level reduction from 22.2–27.8 mmol/L (400–500 mg/dL) to 5.6–11.1 mmol/L (100–200 mg/dL) by using herbal medicines. He visited D Korean Medicine Hospital with chronic polydipsia and general weakness as chief complaints. He was diagnosed with T2DM on the basis of a hemoglobin A1c level of 11.7% and 2 h postprandial blood glucose level of >25.0 mmol/L (450 mg/dL). Moreover, he was diagnosed with a “dual deficiency of qi and yin” (氣陰兩虛) because of ordinary symptoms (素證). During his 30-day inpatient treatment, the patient received mGST 120 mL thrice daily; as a result, his postprandial blood glucose level decreased from 25.3 mmol/L (455 mg/dL) to 8.6 mmol/L (154 mg/dL), polydipsia decreased (visual analog scale score decreased from six to one), and triglyceride levels decreased from 11.7 mmol/L (1031 mg/dL) to 2.0 mmol/L (174 mg/dL). Plasma glucose levels remained stable for 6 months after the treatment, and no adverse events were observed over 200 days. We administered an herbal decoction to decrease plasma glucose levels without using oral hypoglycemic agents or insulin. Conclusions: Herbal decoctions such as mGST can reduce hyperglycemia in patients with T2DM who refuse conventional therapy.
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- 2023
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6. Psychometric Evaluation of the Korean Version of the Perceived Costs and Benefits Scale for Sexual Intercourse
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Hee-Jung Jang, Jungmin Lee, and Soo-Hyun Nam
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condom use ,safe sex ,schools ,sexual behavior ,social norms ,Medicine - Abstract
This study aimed to evaluate the psychometric properties of the Korean version of the perceived costs and benefits scale (K-PCBS) for sexual intercourse to deepen our understanding of the complex psychosocial and interpersonal elements influencing young people’s sexual decision-making. The study participants were 227 college students in South Korea aged 18–25 years. Two factors were extracted through factor analysis, accounting for 61.05% and 58.18% of the variance for perceived costs and perceived benefits, respectively, and showed a good model fit in the K-PCBS. Reliability was high, as indicated by Cronbach’s alphas of 0.87 and 0.84 for the perceived costs and perceived benefits subscales, respectively. The results indicate that the K-PCBS may serve as an appropriate instrument for measuring South Korean youth’s cost and benefit analysis regarding their sexual decision-making. Our study makes a significant contribution to the literature and field because it identifies the underlying feelings and attitudes of young adults toward engaging in sexual activities using the K-PCBS for sexual intercourse, which has good reliability, validity, and internal consistency.
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- 2023
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7. Korean Version of the Nursing Student Attitudes and Knowledge toward Lesbian, Gay, Bisexual, and Transgender Patients Scale
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Hye-Young Min, Jungmin Lee, James Montegrico, and Hee-Jung Jang
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attitudes ,knowledge ,LGBT ,nursing students ,sexual orientation ,quality of care ,Medicine - Abstract
Aim: This study aimed to analyze the reliability and validity of a Korean version of the Nursing Student Attitudes and Knowledge Toward Lesbian, Gay, Bisexual, and Transgender Patients (K-NAKL) Scale, which measures health and heterosexual attitudes toward LGBT individuals. Background: Lesbian, gay, bisexual, and transgender (LGBT) individuals often face discrimination and a lack of care experience on the part of healthcare professionals. Introduction: In South Korea, the current knowledge and attitude measurement tools for medical staff regarding LGBT individuals are limited, as they only focus on homosexuality and do not account for different sexual orientations. Methods: The participants were 217 nursing college students aged 18–25. The item–total correlations method and Cronbach’s alpha coefficient were used to analyze internal consistency reliability. Face validity, content validity, construct validity, and criterion validity testing were conducted to establish scale validity. We made sure to follow STROBE guidelines when carrying out this research. Results: The K-NAKL is a culturally appropriate instrument used to measure the attitudes and knowledge of Korean nursing students when it comes to LGBT health. Discussion: As LGBT health is increasingly gaining social interest, the nursing education curriculum needs to produce culturally competent graduates to meet the health needs of this vulnerable and marginalized population. The current study contributes to that goal. Conclusion: The K-NAKL is a valid and reliable tool with which to measure attitudes and knowledge regarding LGBT health among Korean nursing students. Implications for nursing: The K-NAKL can enable Korean nursing students to increase their knowledge and improve their attitudes when caring for the LGBT population. Implications for nursing policy and health policy: The study highlights the importance of incorporating LGBT-related health education into nursing curricula and developing inclusive policies to improve the quality of care and health outcomes for LGBT individuals.
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- 2023
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8. Grapevine Endophyte Endornavirus and Two New Endornaviruses Found Associated with Grapevines (Vitis vinifera L.) in Idaho, USA
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Jennifer Dahan, Gardenia E. Orellana, Jungmin Lee, and Alexander V. Karasev
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grapevine endophyte endornavirus ,grapevine endornaviruses 1 and 2 ,Chardonnay ,Cabernet franc ,Microbiology ,QR1-502 - Abstract
Five virus genomes, ranging between 12.0 and 12.3 kb in length and identified as endornaviruses, were discovered through a high-throughput sequencing (HTS) analysis of the total RNA samples extracted from two wine grape cultivars collected in the State of Idaho. One was found in a declining Chardonnay vine and was determined to be a local isolate of grapevine endophyte endornavirus (GEEV), and four others represented two novel endornaviruses named grapevine endornavirus 1 (GEV1) and grapevine endornavirus 2 (GEV2). All three virus genomes span a large, single open reading frame encoding polyproteins with easily identifiable helicase (HEL) and RNA-dependent RNA polymerase (RdRP) domains, while the GEV2 polyprotein also contains a glycosyltransferase domain. The GEV1 genome found in an asymptomatic Cabernet franc vine was related to, but distinct from, GEEV: the 5′-proximal, 4.7 kb segment of the GEV1 genome had a 72% identical nucleotide sequence to that of GEEV, while the rest of the genome displayed no significant similarity to the GEEV nucleotide sequence. Nevertheless, the amino acid sequence of the RdRP domain of GEV1 exhibited the closest affinity to the RdRP of GEEV. GEV2 was found in declining Chardonnay and asymptomatic Cabernet franc vines as three genetic variants exhibiting a 91.9–99.8% nucleotide sequence identity among each other; its RdRP had the closest affinity to the Shahe endorna-like virus 1 found in termites. In phylogenetic analyses, the RdRP and HEL domains of the GEV1 and GEV2 polyproteins were placed in two separate clades inside the large lineage of alphaendornaviruses, showing an affinity to GEEV and Phaseolus vulgaris endornavirus 1, respectively.
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- 2023
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9. Microbubble Delivery Platform for Ultrasound-Mediated Therapy in Brain Cancers
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Kibeom Kim, Jungmin Lee, and Myoung-Hwan Park
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microbubble ,ultrasound ,brain cancer ,blood-brain barrier ,drug delivery ,Pharmacy and materia medica ,RS1-441 - Abstract
The blood-brain barrier (BBB) is one of the most selective endothelial barriers that protect the brain and maintains homeostasis in neural microenvironments. This barrier restricts the passage of molecules into the brain, except for gaseous or extremely small hydrophobic molecules. Thus, the BBB hinders the delivery of drugs with large molecular weights for the treatment of brain cancers. Various methods have been used to deliver drugs to the brain by circumventing the BBB; however, they have limitations such as drug diversity and low delivery efficiency. To overcome this challenge, microbubbles (MBs)-based drug delivery systems have garnered a lot of interest in recent years. MBs are widely used as contrast agents and are recently being researched as a vehicle for delivering drugs, proteins, and gene complexes. The MBs are 1–10 μm in size and consist of a gas core and an organic shell, which cause physical changes, such as bubble expansion, contraction, vibration, and collapse, in response to ultrasound. The physical changes in the MBs and the resulting energy lead to biological changes in the BBB and cause the drug to penetrate it, thus enhancing the therapeutic effect. Particularly, this review describes a state-of-the-art strategy for fabricating MB-based delivery platforms and their use with ultrasound in brain cancer therapy.
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- 2023
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10. A Size-Cuttable, Skin-Interactive Wearable Sensor for Digital Deciphering of Epidermis Wavy Deformation
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Wonki Hong, Jungmin Lee, and Won Gu Lee
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electronic sticker ,wrist bandage ,epidermis deformation and fluctuation ,body curvature ,digital medicine ,Biotechnology ,TP248.13-248.65 - Abstract
Body shape and curvature are vital criteria for judging health. However, few studies exist on the curvature of the body. We present a skin-interactive electronic sticker that digitally decodes the epidermis deformation in a hybrid cartridge format (disposable bandages and non-disposable kits). The device consists of two functional modes: (1) as a thin electronic sticker of 76 μm thickness and a node pitch of 7.45 mm for the measurement of body curvature in static mode, and (2) as a wrist bandage for the deciphering of skin wave fluctuations into a colored core-line map in dynamic mode. This method has high detection sensitivity in the static mode and high accuracy of 0.986 in the dynamic mode, resulting in an F1 score of 0.966 in testing by feedforward deep learning. The results show that the device can decipher 32 delicate finger folding gestures by measuring skin depths and positions via image segmentation, leading to an optimal core line in a color map. This approach can help provide a better understanding of skin wave deflection and fluctuations for potential wearable applications, such as in delicate skin-related gesture control in the metaverse, rehabilitation programs for the brain-degenerate, and as a detector of biophysical state relating to body shape and curvature in the field of digital medicine.
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- 2022
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11. Rupture Risk of Intracranial Aneurysm and Prediction of Hemorrhagic Stroke after Liver Transplant
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Hye-Mee Kwon, In-Gu Jun, Kyoung-Sun Kim, Young-Jin Moon, In Young Huh, Jungmin Lee, Jun-Gol Song, and Gyu-Sam Hwang
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end-stage liver disease ,intracranial aneurysm ,mortality ,prediction ,intracranial hemorrhage ,Neurosciences. Biological psychiatry. Neuropsychiatry ,RC321-571 - Abstract
Postoperative hemorrhagic stroke (HS) is a rare yet devastating complication after liver transplantation (LT). Unruptured intracranial aneurysm (UIA) may contribute to HS; however, related data are limited. We investigated UIA prevalence and aneurysmal subarachnoid hemorrhage (SAH) and HS incidence post-LT. We identified risk factors for 1-year HS and constructed a prediction model. This study included 3544 patients who underwent LT from January 2008 to February 2019. Primary outcomes were incidence of SAH, HS, and mortality within 1-year post-LT. Propensity score matching (PSM) analysis and Cox proportional hazard analysis were performed. The prevalence of UIAs was 4.63% (n = 164; 95% confidence interval (CI), 3.95–5.39%). The 1-year SAH incidence was 0.68% (95% CI, 0.02–3.79%) in patients with UIA. SAH and HS incidence and mortality were not different between those with and without UIA before and after PSM. Cirrhosis severity, thrombocytopenia, inflammation, and history of SAH were identified as risk factors for 1-year HS. UIA presence was not a risk factor for SAH, HS, or mortality in cirrhotic patients post-LT. Given the fatal impact of HS, a simple scoring system was constructed to predict 1-year HS risk. These results enable clinical risk stratification of LT recipients with UIA and help assess perioperative HS risk before LT.
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- 2021
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12. Uncertainty of Rate of Change in Korean Future Rainfall Extremes Using Non-Stationary GEV Model
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Jiyu Seo, Jeongeun Won, Jeonghyeon Choi, Jungmin Lee, Suhyung Jang, Okjeong Lee, and Sangdan Kim
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Bayesian inference ,climate change ,GEV distribution ,non-stationarity ,rainfall extremes ,rate of change ,Meteorology. Climatology ,QC851-999 - Abstract
Interest in future rainfall extremes is increasing, but the lack of consistency in the future rainfall extremes outputs simulated in climate models increases the difficulty of establishing climate change adaptation measures for floods. In this study, a methodology is proposed to investigate future rainfall extremes using future surface air temperature (SAT) or dew point temperature (DPT). The non-stationarity of rainfall extremes is reflected through non-stationary frequency analysis using SAT or DPT as a co-variate. Among the parameters of generalized extreme value (GEV) distribution, the scale parameter is applied as a function of co-variate. Future daily rainfall extremes are projected from 16 future SAT and DPT ensembles obtained from two global climate models, four regional climate models, and two representative concentration pathway climate change scenarios. Compared with using only future rainfall data, it turns out that the proposed method using future temperature data can reduce the uncertainty of future rainfall extremes outputs if the value of the reference co-variate is properly set. In addition, the confidence interval of the rate of change of future rainfall extremes is quantified using the posterior distribution of the parameters of the GEV distribution sampled using Bayesian inference.
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- 2021
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13. Sex Differences in the Influence of Sleep on Body Mass Index and Risk of Metabolic Syndrome in Middle-Aged Adults
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Hyun-E Yeom and Jungmin Lee
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body mass index ,metabolic syndrome ,sex characteristics ,sleep disorders ,Medicine - Abstract
Poor sleep and obesity are intimately related to cardiovascular diseases. We aimed to examine whether the influence of sleep and body mass index (BMI) on the risk of metabolic syndrome (MetS) differed by sex in middle-aged people. It is a cross-sectional study of 458 Korean participants who completed self-administered surveys; the data were analyzed using the PROCESS macro for SPSS. We found that both sleep and BMI were significant predictors of MetS risk in women, particularly by the role of BMI connecting the impact of sleep to MetS risk. However, the association was not found in men, showing that BMI, but not sleep, was a significant predictor of MetS. This sex-related difference was due to different relationships between sleep and BMI, indicating that BMI was more dependent on sleep quality for women than for men. Therefore, a sex-specific approach to decrease the risk of MetS is warranted.
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- 2020
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14. A Dual-Padded, Protrusion-Incorporated, Ring-Type Sensor for the Measurement of Food Mass and Intake
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Wonki Hong, Jungmin Lee, and Won Gu Lee
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dietary monitoring ,healthcare ,ring-type biosensor ,personalized digital medicine ,Chemical technology ,TP1-1185 - Abstract
Dietary monitoring is vital in healthcare because knowing food mass and intake (FMI) plays an essential role in revitalizing a person’s health and physical condition. In this study, we report the development of a highly sensitive ring-type biosensor for the detection of FMI for dietary monitoring. To identify lightweight food on a spoon, we enhance the sensing system’s sensitivity with three components: (1) a first-class lever mechanism, (2) a dual pad sensor, and (3) a force focusing structure using a ring surface having protrusions. As a result, we confirmed that, as the food arm’s length increases, the force detected at the sensor is amplified by the first-class lever mechanism. Moreover, we obtained 1.88 and 1.71 times amplification using the dual pad sensor and the force focusing structure, respectively. Furthermore, the ring-type biosensor showed significant potential as a diagnostic indicator because the ring sensor signal was linearly proportional to the food mass delivered in a spoon, with R2 = 0.988, and an average F1 score of 0.973. Therefore, we believe that this approach is potentially beneficial for developing a dietary monitoring platform to support the prevention of obesity, which causes several adult diseases, and to keep the FMI data collection process automated in a quantitative, network-controlled manner.
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- 2020
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15. Numerical Characterization for Electrical Conductivity of Two-Dimensional Nanocomposite Systems with Conducting Fiber Fillers
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Jungmin Lee, Yesol Yun, Sang Hyun Lee, and Jinyoung Hwang
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nano-composites ,Monte Carlo simulation ,percolation networks ,electrical conductivity ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
Hybrid nanotube composite systems with two different types of fillers attract considerable attention in several applications. The incorporation of secondary fillers exhibits conflicting behaviors of the electrical conductivity, which either increases or decreases according to the dimension of secondary fillers. This paper addresses quantitative models to predict the electrical performance in the configuration of two dimensional systems with one-dimensional secondary fillers. To characterize these properties, Monte Carlo simulations are conducted for percolating networks with a realistic model with the consideration of the resistance of conducting NWs, which conventional computational approaches mostly lack from the common assumption of zero-resistance or perfect conducting NWs. The simulation results with nonperfect conductor NWs are compared with the previous results of perfect conductors. The variation of the electrical conductivity reduces with the consideration of the resistance as compared to the cases with perfect conducting fillers, where the overall electrical conductivity solely originates from the contact resistance caused by tunneling effects between NWs. In addition, it is observed that the resistance associated with the case of invariant conductivity with respect to the dimension of the secondary fillers increases, resulting in the need for secondary fillers with the increased scale to achieve the same electrical performance. The results offer useful design guidelines for the use of a two-dimensional percolation network for flexible conducting electrodes.
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- 2020
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16. Mistaken Identity: Clarification of Rubus coreanus Miquel (Bokbunja)
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Jungmin Lee, Michael Dossett, and Chad E. Finn
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species adulteration ,cha tian pao ,bramble ,caneberry ,blackcap ,Organic chemistry ,QD241-441 - Abstract
In the U.S., there has been a recent surge in Korean black raspberry products available and in the number of reports about this species appearing in the scientific literature. Despite this, the majority of products sold and the work carried out has been on Rubus occidentalis L., not R. coreanus Miquel. The importance of accurate recognition of all starting material is multiplied for research downstream, including genetics/genomics, plant breeding, phenolic identification, food processing improvements and pharmacokinetic investigations. An overview of distinguishing characteristics separating R. coreanus from R. occidentalis will be presented. Research conducted on correctly identified fruit will also be summarized to aid future studies that might showcase the unique qualities that bokbunja can offer.
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- 2014
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17. Effect of Low-Temperature Pyrolysis on the Properties of Jute Fiber-Reinforced Acetylated Softwood Kraft Lignin-Based Thermoplastic Polyurethane
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Hyun-gyoo Roh, Sunghoon Kim, Jungmin Lee, and Jongshin Park
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lignin ,acetylated lignin ,thermoplastic polyurethane ,jute fiber ,low-temperature pyrolysis ,short-fiber-reinforced elastomers ,Organic chemistry ,QD241-441 - Abstract
Short jute fiber-reinforced acetylated lignin-based thermoplastic polyurethane (JF reinforced ASKLTPU) was prepared and characterized as a short-fiber-reinforced elastomer with carbon-neutrality and biodegradability. The acetylated softwood kraft lignin-based thermoplastic polyurethane (ASKLTPU) was prepared with polyethylene glycol (PEG) as a soft segment. Short jute fiber was modified using low-temperature pyrolysis up to the temperatures of 200, 250, and 300 °C in order to remove non-cellulosic compounds of jute fibers for enhancing interfacial bonding and reducing hydrophilicity with the ASKLTPU matrix. JF-reinforced ASKLTPUs with fiber content from 5 to 30 wt % were prepared using a melt mixing method followed by hot-press molding at 160 °C. The JF-reinforced ASKLTPUs were characterized for their mechanical properties, dynamic mechanical properties, thermal transition behavior, thermal stability, water absorption, and fungal degradability. The increased interfacial bonding between JF and ASKLTPU using low-temperature pyrolysis was observed using scanning electron microscopy (SEM) and also proved via interfacial shear strength measured using a single-fiber pull-out test. The mechanical properties, thermal properties, and water absorption aspects of JF-reinforced ASKLTPU were affected by increased interfacial bonding and reduced hydrophilicity from low-temperature pyrolysis. In the case of the degradation test, the PEG component of ASKLPTU matrix highly affects degradation and deterioration.
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- 2018
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18. Preparation and Characterization of Superabsorbent Polymers Based on Starch Aldehydes and Carboxymethyl Cellulose
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Jungmin Lee, Soohee Park, Hyun-gyoo Roh, Seungtaek Oh, Sunghoon Kim, Myounguk Kim, Donghyun Kim, and Jongshin Park
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superabsorbent polymers ,polysaccharides ,carboxymethyl cellulose ,starch aldehydes ,citric acid ,Organic chemistry ,QD241-441 - Abstract
Superabsorbent polymers (SAPs) are crosslinked hydrophilic polymers that are capable of absorbing large amounts of water. Commercial SAPs are mostly produced with acrylic acid that cannot be easily biodegraded. Therefore, in this study, polysaccharide-based SAPs using carboxymethyl cellulose as a major component were prepared. Starch aldehydes and citric acid were selected due to their environment-friendly, non-toxic, and biodegradable properties compared to conventional crosslinking agents. Starch aldehydes were prepared by periodate oxidation, which forms aldehyde groups by taking the places of C–OH groups at C-2 and C-3. Furthermore, starch aldehydes were analyzed through the change in FT-IR spectra, the aldehyde quantitation, and the morphology in FE-SEM images. In the crosslinking of polysaccharide-based SAPs, the acetal bridges from starch aldehydes led to a large amount of water entering the network structure of the SAPs. However, the ester bridges from citric acid interfered with the water penetration. In addition, the swelling behavior of the SAPs was analyzed by the Fickian diffusion model and the Schott’s pseudo second order kinetics model. The relationship between swelling behavior and morphology of the SAPs was analyzed by FE-SEM images. In conclusion, polysaccharide-based SAPs were well prepared and the highest equilibrium swelling ratio was 87.0 g/g.
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- 2018
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19. Effects of Covalent Functionalization of MWCNTs on the Thermal Properties and Non-Isothermal Crystallization Behaviors of PPS Composites
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Myounguk Kim, Jungmin Lee, Hyun-gyoo Roh, Dahyun Kim, Juhee Byeon, and Jongshin Park
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poly(phenylene sulfide) ,multi-walled carbon nanotubes ,covalent functionalization ,thermal property ,non-isothermal crystallization behavior ,Organic chemistry ,QD241-441 - Abstract
In this study, a PPS/MWCNTs composite was prepared with poly(phenylene sulfide) (PPS), as well as pristine and covalent functionalized multi-walled carbon nanotubes (MWCNTs) via melt-blending techniques. Moreover, the dispersion of the MWCNTs on the PPS matrix was improved by covalent functionalization as can be seen from a Field-Emission Scanning Electron Microscope (FE-SEM) images. The thermal properties of the PPS/MWCNTs composites were characterized using a thermal conductivity analyzer, and a differential scanning calorimeter (DSC). To analyze the crystallization behavior of polymers under conditions similar with those in industry, the non-isothermal crystallization behaviors of the PPS/MWCNTs composites were confirmed using various kinetic equations, such as the modified Avrami equation and Avrami-Ozawa combined equation. The crystallization rate of PPS/1 wt % pristine MWCNTs composite (PPSP1) was faster because of the intrinsic nucleation effect of the MWCNTs. However, the crystallization rates of the composites containing covalently-functionalized MWCNTs were slower than PPSP1 because of the destruction of the MWCNTs graphitic structure via covalent functionalization. Furthermore, the activation energies calculated by Kissinger’s method were consistently decreased by covalent functionalization.
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- 2017
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20. Changes of Lignin Molecular Structures in a Modification of Kraft Lignin Using Acid Catalyst
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Sunghoon Kim, Seungtaek Oh, Jungmin Lee, Hyun-gyoo Roh, and Jongshin Park
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soft wood kraft lignin ,lignin-carbohydrate-complex (LCC) ,aliphatic chain modification ,polymer blend ,biodegradability ,compatibility ,Technology ,Electrical engineering. Electronics. Nuclear engineering ,TK1-9971 ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Microscopy ,QH201-278.5 ,Descriptive and experimental mechanics ,QC120-168.85 - Abstract
The purpose of this study is to modify lignin for better blending with general purpose synthetic polymers. The possible advantages by using this modification would be cost reduction, better physical properties, and biodegradability. In this study, butyrolactone-modified lignin (BLL) and tetrahydrofuran-modified lignin (THFL) were used for aliphatic chain modification of lignin using an acid-catalyzed esterification method in order to mimic the relation of lignin-carbohydrate-complex (LCC) and cellulose. The results of several analyses indicated that lignin was well modified. It was confirmed that the lignin was modified as expected and the reaction sites of the modification, as well as the reaction behaviors, were varied by the reagent types. The result of X-ray diffraction analysis (XRD) analysis indicated that modified lignin/polymer blends increased the crystallinity due to their good compatibility. It can be confirmed that the type of alkyl chain and the miscibility gap between the alkyl chain-matrix affected the mechanical properties enormously in the fungi-degradable environment. From this study, a new method of lignin modification is proposed, and it is found that modified lignin retains the property of the substituted aliphatic chain well. This method could be a proper lignin modification method.
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- 2016
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21. Numerical Characterization for Electrical Conductivity of Two-Dimensional Nanocomposite Systems with Conducting Fiber Fillers
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Jinyoung Hwang, Yesol Yun, Sanghyun Lee, and Jungmin Lee
- Subjects
Materials science ,02 engineering and technology ,Conductivity ,010402 general chemistry ,01 natural sciences ,lcsh:Technology ,Article ,Electrical resistivity and conductivity ,General Materials Science ,Composite material ,lcsh:Microscopy ,Electrical conductor ,Monte Carlo simulation ,lcsh:QC120-168.85 ,Nanocomposite ,electrical conductivity ,lcsh:QH201-278.5 ,lcsh:T ,Contact resistance ,021001 nanoscience & nanotechnology ,0104 chemical sciences ,Conductor ,percolation networks ,lcsh:TA1-2040 ,Percolation ,Electrode ,nano-composites ,lcsh:Descriptive and experimental mechanics ,lcsh:Electrical engineering. Electronics. Nuclear engineering ,0210 nano-technology ,lcsh:Engineering (General). Civil engineering (General) ,lcsh:TK1-9971 - Abstract
Hybrid nanotube composite systems with two different types of fillers attract considerable attention in several applications. The incorporation of secondary fillers exhibits conflicting behaviors of the electrical conductivity, which either increases or decreases according to the dimension of secondary fillers. This paper addresses quantitative models to predict the electrical performance in the configuration of two dimensional systems with one-dimensional secondary fillers. To characterize these properties, Monte Carlo simulations are conducted for percolating networks with a realistic model with the consideration of the resistance of conducting NWs, which conventional computational approaches mostly lack from the common assumption of zero-resistance or perfect conducting NWs. The simulation results with nonperfect conductor NWs are compared with the previous results of perfect conductors. The variation of the electrical conductivity reduces with the consideration of the resistance as compared to the cases with perfect conducting fillers, where the overall electrical conductivity solely originates from the contact resistance caused by tunneling effects between NWs. In addition, it is observed that the resistance associated with the case of invariant conductivity with respect to the dimension of the secondary fillers increases, resulting in the need for secondary fillers with the increased scale to achieve the same electrical performance. The results offer useful design guidelines for the use of a two-dimensional percolation network for flexible conducting electrodes.
- Published
- 2020
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