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Dynamic Characteristics for Fuel Shutoff Valve of a Gas Generator (가스발생기 연료개폐밸브의 동적 거동)

  • Lee, Joong-Youp;Huh, Hwan-Il
    • Journal of the Korean Society of Propulsion Engineers
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    • v.14 no.4
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    • pp.1-9
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    • 2010
  • Fuel shutoff valve of a gas generator controls propellant mass flowrate of a rocket engine, by using pilot pressure and spring force. The developing fuel shutoff valve can be self sustained even though pilot pressure is removed in an actuator. Therefore, it is necessary to analyze the characteristics of the forces with respect to the opening and closing of the valve in order to evaluate its performance. In light of this, the valve has been designed to adjust the control pressure for the opening of the poppet and to determine the working fluid pressure at which the valve starts to close. This paper also has been designed dynamic model using the AMESim and predicted flow coefficient of the valve by Fluent CFD analysis. Various results from the prediction and the analysis have been compared with experiments. Finally, dynamic characteristics of the valve have been verified with experimental results.

Konjac Glucomannan Derived Carbon Aerogels for Multifunctional Applications

  • Lian, Jie;Li, Jiwei;Wang, Liang;Cheng, Ru;Tian, Xiuquan;Li, Xue;Zhou, Jian;Duan, Tao;Zhu, Wenkun
    • Nano
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    • v.13 no.10
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    • pp.1850113.1-1850113.11
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    • 2018
  • Environmental and energy issues have always been a hot topic of global research. Oil leakage has caused great damage to the environment, affecting a wide area and it is difficult to clean up. In most cases, carbon-based adsorbents are typically utilized to remove oil spills because of their economic benefits and high adsorbent efficiency. At the same time, its excellent material properties can also be used for the preparation of supercapacitors. In this paper, the carbon aerogels were prepared by the one-step method. The prepared materials endowed a 3D network structure with a huge number of micropores and mesoporous, and the material is light-weight, stable, hydrophobic and has affinity for oil (17.02 g/g) to the KGM carbon aerogel. Through the physicchemical characterization, the KGM carbon aerogel shows specific surface area is 689m2/g, high water contact angle (136.64) and excellent reusability (more than 15 cycle times). In addition, we also discussed the electrochemical properties of the material and obtained the specific electrical capacity of 139 F/g under the condition of 1 A/g.

Assessment and Understanding of Chronotype (일주기 유형의 평가와 이해)

  • Kim, Somin;Kim, Seog Ju
    • Sleep Medicine and Psychophysiology
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    • v.26 no.1
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    • pp.5-15
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    • 2019
  • Chronotype (CT) is defined as an inter-individual difference in sleep-wake cycles and daily activities. Previous studies have suggested that this individual difference can influence our biological and psychological functioning. Literature regarding the psychometric properties and validity of CT measures are reviewed. We provide an overview of biological indicators (sleep-wake cycle, body temperature, cortisol, and melatonin) that are used for distinguishing two chronotypes: morningness (MT) and eveningness (ET). We also review the differences between CT in relation to personality traits and the occurrence of psychopathology. In addition, the methodological limitations of studies on CT are discussed. Finally, future research directions in terms of CT are proposed.

Evaluation of the Potential of Commercial Vitamin Drinks to Induce Tooth Erosion

  • Kim, Han-Na;Yoon, Tae-Lim;Min, Ji-Hyun
    • Journal of dental hygiene science
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    • v.19 no.3
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    • pp.154-161
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    • 2019
  • Background: The market for vitamin drinks is expanding both in Korea and worldwide. However, it was difficult to find studies regarding the possibility of tooth erosion induction due to vitamin drinks. The purpose of the present in vitro study was to evaluate the effect of tooth erosion caused by a few commercial vitamin beverages on bovine teeth enamel in terms of erosion depth and fluorescence loss. Methods: Three experimental groups (vitamin drinks), a positive control group (Coca-Cola), and a negative control group (mineral water) were established. Each group consisted of 5 specimens obtained from sound bovine teeth. The pH and titratable acidity of beverages were measured. Specimens were immersed in the beverages and artificial saliva for 6 and 18 hours, respectively. This cycle was repeated for 5 days. The depth of the tooth loss caused by tooth erosion (erosion depth) and maximum loss of fluorescence (Max ΔF) were measured using the microscope and quantified light-induced fluorescence-digital, respectively. For the statistical analysis, the Kruskal-Wallis test and ANOVA were used to compare the erosion depth and Max ΔF of the enamel surfaces. In addition, Spearman correlations were estimated. Results: The pH of the three vitamin beverages ranged from 2.65 to 3.01, which is similar to that of the positive control group. All beverages, except mineral water, had sugar and acidic ingredients. Vitamin drinks and the positive control, Coca-Cola, caused tooth erosion lesions, and showed significant differences in erosion depth compared to mineral water (p<0.05). The vitamin beverages with low pH were associated with high erosion depth and Max ΔF. Conclusion: Vitamin drinks have the potential to cause tooth erosion.

Fabrication of TiO2 Coated Si Nano Particle using Silicon Sawing Sludge (실리콘 절삭 슬러지를 이용한 TiO2 코팅 나노 실리콘 입자의 제조)

  • Seo, Dong Hyeok;Yim, Hyeon Min;Na, Ho Yoon;Kim, Won Jin;Kim, Ryun Na;Kim, Woo-Byoung
    • Journal of Powder Materials
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    • v.28 no.5
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    • pp.423-428
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    • 2021
  • Here, we report the development of a new and low-cost core-shell structure for lithium-ion battery anodes using silicon waste sludge and the Ti-ion complex. X-ray diffraction (XRD) confirmed the raw waste silicon sludge powder to be pure silicon without other metal impurities and the particle size distribution is measured to be from 200 nm to 3 ㎛ by dynamic light scattering (DLS). As a result of pulverization by a planetary mill, the size of the single crystal according to the Scherrer formula is calculated to be 12.1 nm, but the average particle size of the agglomerate is measured to be 123.6 nm. A Si/TiO2 core-shell structure is formed using simple Ti complex ions, and the ratio of TiO2 peaks increased with an increase in the amount of Ti ions. Transmission electron microscopy (TEM) observations revealed that TiO2 coating on Si nanoparticles results in a Si-TiO2 core-shell structure. This result is expected to improve the stability and cycle of lithium-ion batteries as anodes.

Study of the Progressive Party Case Records through the Lens of Archival Science (진보당 형사사건기록에 대한 기록학적 고찰)

  • Lee, JuYoung;Jeon, HyunSoo
    • The Korean Journal of Archival Studies
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    • no.77
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    • pp.109-150
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    • 2023
  • Prior researchers interpreted the records of criminal cases involving the Progressive Party from a historical perspective. In marked contrast to existing trends, this study examines the Progressive Party case records through the lens of archival science. This study dissects the Progressive Party case records as a single and complete record group and at each stage of their life cycle from police investigation through criminal prosecution to trial. This approach enables a holistic analysis of archival characteristics of the records. This study begins with an appraisal of the nature and types of case records generated and maintained by the various agencies in light of the investigatory authorities delegated to each institution. This study then dissects the police, prosecution, and Counter Intelligence Corps records leading up to the indictment of Progressive Party members as well as the court records of the trial that followed. In particular, this study reveals the insufficiency and illegality of the evidence against the defendants in the Progressive Party case from an archival standpoint. Setting aside the admissibility or strength of the evidence under criminal law, the present study demonstrates that the records lack reliability, authenticity, and integrity-the fundamental attributes required for evidentiary efficacy of records from an archival standpoint.

Chlorophyll contents and expression profiles of photosynthesis-related genes in water-stressed banana plantlets

  • Sri Nanan Widiyanto;Syahril Sulaiman;Simon Duve;Erly Marwani;Husna Nugrahapraja;Diky Setya Diningrat
    • Journal of Plant Biotechnology
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    • v.50
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    • pp.127-136
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    • 2023
  • Water scarcity decreases the rate of photosynthesis and, consequently, the yield of banana plants (Musa spp). In this study, transcriptome analysis was performed to identify photosynthesis-related genes in banana plants and determine their expression profiles under water stress conditions. Banana plantlets were in vitro cultured on Murashige and Skoog agar medium with and without 10% polyethylene glycol and marked as BP10 and BK. Chlorophyll contents in the plant shoots were determined spectrophotometrically. Two cDNA libraries generated from BK and BP10 plantlets, respectively, were used as the reference for transcriptome data. Gene ontology (GO) enrichment analysis was performed using the Database for Annotation, Visualization, and Integrated Discovery (DAVID) and visualized using the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway prediction. Morphological observations indicated that water deficiency caused chlorosis and reduced the shoot chlorophyll content of banana plantlets. GO enrichment identified 52 photosynthesis-related genes that were affected by water stress. KEGG visualization revealed the pathways related to the 52 photosynthesisr-elated genes and their allocations in four GO terms. Four, 12, 15, and 21 genes were related to chlorophyll biosynthesis, the Calvin cycle, the photosynthetic electron transfer chain, and the light-harvesting complex, respectively. Differentially expressed gene (DEG) analysis using DESeq revealed that 45 genes were down-regulated, whereas seven genes were up-regulated. Four of the down-regulated genes were responsible for chlorophyll biosynthesis and appeared to cause the decrease in the banana leaf chlorophyll content. Among the annotated DEGs, MaPNDO, MaPSAL, and MaFEDA were selected and validated using quantitative real-time PCR.

Auctions - Donation based culinary subscription platform

  • Dong-Yeon Lee;Gi-Hwan Ryu
    • International Journal of Internet, Broadcasting and Communication
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    • v.16 no.4
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    • pp.16-20
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    • 2024
  • This platform is a platform that broadcasts the chef's cooking scenes live and teaches individual subscribers personalized cooking through auctions.The platform delivers the chef's hands-on cooking demonstration to customers in real time, and the auction-winning customers get the opportunity to participate in exclusive live broadcasts with the chef.This provides customers with an immersive learning experience, providing them with an opportunity to enhance not only culinary knowledge but also in-depth understanding and practical cooking skills.This platform places a lot of weight on social contributions beyond just commercial purposes The dishes created by the chef through live broadcasts are delivered directly to the socially underprivileged, especially the vulnerable in need of help, in collaboration with donor organizations. This demonstrates that cooking can be a means of embodying social values, not just commercial activities. In this way of operation, we want to realize a culture of sharing through cooking and combine the platform's existence value with social responsibility. Additionally, the platform provides customers with a variety of sales methods, with some popular content produced as meal kits based on clicks, subscriber reactions, and evaluation by restaurant experts. These meal kits are provided on a regular basis through the subscription system or sold in a way that the general consumer can also purchase individually. Some of the profits from meal kit sales lead to donations again, allowing the platform to have a virtuous cycle structure that continues to create social value. In conclusion, the platform redefines the modern culinary experience through a model that combines advanced culinary education with social sharing. It is creating a sustainable ecosystem that provides subscribers with special cooking experiences and in-depth academic opportunities, and at the same time provides practical help to the socially underprivileged through donations and sharing. Closely combined with culinary education, interaction, and social responsibility, the platform contains innovative attempts to incorporate the educational and social values of cooking to shed light on its new meaning and value.

Screening Method to Identify Watermelon Cultivars Resistant to Acidovorax citrulli, the Cause of Bacterial Fruit Blotch

  • Soo Min Lee;Gahyeon Kim;Hun Kim;Gyung Ja Choi
    • The Plant Pathology Journal
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    • v.40 no.6
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    • pp.593-602
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    • 2024
  • Acidovorax citrulli is a causative pathogen for bacterial fruit blotch (BFB) in Cucurbitaceae, including watermelon. The most effective method to control this plant disease is to cultivate resistant cultivars. Herein, this study aimed to establish an efficient screening method to determine the resistance of watermelon cultivars against A. citrulli. To this end, we explored the virulence of seven A. citrulli isolates belonging to clonal complex group I or II based on gltA gene analysis. Furthermore, we evaluated the BFB occurrence in the seedlings of two arbitrarily selected watermelon cultivars according to the growth stage of the watermelon seedlings, inoculum concentration, and incubation temperature after inoculation in a humidity chamber. Taken together, we established the following method to determine the resistance of watermelon cultivars against A. citrulli: watermelon seedlings at the fully expanded two-leaf stage can be spray-inoculated with an A. citrulli bacterial suspension at a concentration of 1.0 × 106 cfu/ml; after incubation for 48 h at 28℃ in a humidity chamber, the plants were cultivated in a growth chamber at 25℃ with 80% relative humidity under a 12-h light/dark cycle; and BFB occurrence on the plants can be investigated at 7 dpi by visual estimation of the diseased leaf area (%). Based on these experimental methods, we investigated the resistance degree of 43 commercial watermelon cultivars against A. citrulli KACC 17005. Therefore, our results can provide important information for the development of resistant cultivars against A. citrulli.