피스톤 링 마찰력 측정시스템 개발

학위논문(박사) -- 서울대학교대학원 : 공과대학 기계항공공학부, 2022. 8. 민경덕.Due to the piston dynamics and its wide lubricating range, various factors can affect the friction change, including piston and ring designs, and environmental parameters such as engine oil temperature, engine speed, and in-cylinder pressure. It is important to separate the total piston friction into two major friction parts, piston skirt friction and ring friction to observe the effect of each factor on the piston friction. Though various measurement methods for the piston friction have been developed in the past, the piston ring friction has not been investigated separately from the entire piston friction considering both engine motoring and firing conditions. A new measurement system was developed to examine the piston ring friction in detail based on floating liner method. In comparison to conventional floating liner experiments, one another piston was adopted above the conventional crank-piston system to minimize friction from thrust force. The measuring piston is connected with the conventional piston by adding an extended connecting rod in between. The new system has double pistons. Therefore, with the new system, the measuring piston tends to move straight up and down in the liner. The piston secondary motion including the piston thrust and angular motion can be minimized nearly zero with the new system. Because of its structural characteristic, the piston skirt friction, from the interaction between the piston skirt and the liner, can be excluded with the new system. In addition, the irregular piston ring behavior such as piston ring twist and fluttering from the piston tilting motion can also be excepted. The friction changes from the interaction solely between the piston ring and the liner can be measured. This allows the parametric study of the friction force that occurs only in the piston ring. The new system has been built up as a reliable system through many updates. To implement the stable combustion with the floating liner, a gas seal has to be applied. However, it is difficult to maintain the liner in a floating state and seal the combustion gas at the same time. To compromise these two opposite aspects, several gas sealing methods were reviewed and tested. The gas seal showed the same sealing performance with the conventional fixed liner. Moreover, in order to minimize the disturbing extra force factors on floating liner and to measure only the friction force, the extra force factors are eliminated in two approaches. The system is modified to minimize these factors. On the other hand, the extra force factors are measured to exclude the effective amount from the measured friction data. Furthermore, the geometrical change of the entire system was made for more reliable friction measurement. With the modified system, only piston can be taken out from the engine, and the boundary conditions can be maintained throughout the several repetitive experiments. The data repeatability was confirmed with the experimental results. Various factors affecting lubrication conditions of piston rings were tested. The piston friction force is measured under the main engine operating conditions, which include engine oil temperature, engine speed, and in-cylinder pressure. Friction data shows a good agreement with the Stribeck curve as the engine operating parameter changes. Additionally, the tension effect of Oil Control Ring (OCR) was examined. The friction force change follows the amount of OCR tension changes. Through the experimental results drawn with the new system, it is possible to provide a quantitative analysis on friction. The newly developed device can highly contribute to fundamental piston ring researches.최근 지구 온난화에서 기인하는 기후, 생태계 변화가 가속화되면서 본 위기를 극복하기 위한 다양한 노력이 범국가적 차원에서 논의되고 있다. 지구 온난화의 주범으로 꼽히는 자동차 내연기관에서의 이산화탄소 배출로 인해 내연기관 자동차의 생산을 중단하고 판매를 금지하는 법을 오는 2035년부터 독일을 제외한 유럽 국가에서 시행하게 된다. 그러나 여전히 실 도로의 많은 교통수단이 내연기관을 사용하고 있고, 하이브리드 및 전기차로의 인프라 변경 과정에서 내연기관의 활용은 필연적이다. 내연기관에서의 연비를 향상시키고 이산화탄소를 줄이는 방법에는 다양한 효율 저감 인자를 개선시키는 방법이 있는데, 본 연구에서는 내연기관 기계적 마찰 손실에 기여하는 바가 큰 피스톤 링 마찰력에 대한 실험적 연구를 수행하였다. 피스톤 링 마찰력을 줄이고 개선하기 위해서는 우선 실제 내연기관에서의 피스톤 링 마찰력을 정량적으로 측정하는 것이 중요하다. 피스톤 링 마찰력을 측정하기 위해 다양한 측정방법이 고안, 개발되었으나, 여전히 해당 장비의 신뢰성이 엔진 고온 고압의 연소상황에서 현저히 떨어지며, 피스톤 링에 집중된 기초적인 측정 장비가 엔진 전체 구동 상황을 반영하기 어려운 실정이다. 따라서 본 연구에서는 엔진 모터링, 연소 조건에서 모두 구동 가능한 피스톤 링 마찰력 측정 장치를 개발하고 그 성능을 다양한 조건에서의 실험 결과를 기반으로 마찰 기초 이론과 비교, 검증하였다. 본 연구에서 새로 연구 개발한 피스톤 링 마찰력 측정 시스템은 기존의 부동라이너 기법을 활용하고 있으며, 실험 조건을 연구의 목적에 따라 다양하게 변경할 수 있는 단기통 엔진으로 제작, 완성되었다. 선행연구에서의 부동 라이너 기법은 엔진 연소시에 오직 피스톤 및 링 팩의 마찰력을 측정할 수 있는 장점을 가지나, 기존 피스톤-크랭크 시스템을 사용하여 피스톤 이차 거동까지 반영되므로, 순수 피스톤 링에서 기인하는 마찰력을 측정하기 어렵고, 피스톤 이차 거동에 의한 큰 피스톤 측력의 작용으로 부동 라이너에 추가 진동이 작용하여 마찰력 측정에 어려움이 있다. 그러나 본 장치는 이중 피스톤 구조를 고안하여, 기존 피스톤-크랭크 장치에 연장 콘로드를 활용하여 하나의 피스톤을 더 얹는 방식으로, 피스톤 측력을 0에 가까운 수준으로 크게 줄였다. 따라서 새롭게 개발된 장치는 구조적 특징으로 피스톤 측력에 의한 부동라이너의 추가 진동을 줄여 마찰력 데이터의 신뢰성을 높일 수 있다. 또한 피스톤의 각운동, 즉 피스톤 경사각(Piston Tilting Angle)의 영향을 기존 피스톤-크랭크 시스템 대비 1/17 수준으로 줄일 수 있어, 피스톤 경사각으로 인해 발생하는 피스톤 링의 무작위적 각운동이 마찰력에 끼치는 영향을 배제할 수 있다. 따라서 본 장치로 피스톤 이차 거동에 의한 피스톤 스커트 마찰력 뿐만 아니라, 피스톤 경사각 발생에 의해 무분별하게 생성되는, 피스톤 링 Twist, Fluttering 현상에서 기인한 마찰력 변화 또한 배제한 순수 피스톤 링 제원에 따른 마찰력 측정을 가능케 하였다. 개발된 장비가 기존의 선행연구에서의 현상, 기초 마찰 이론에 근거한 마찰력 변화를 잘 따라가는지 확인하기 위해 다양한 엔진 구동 조건에서의 실험을 수행하였다. 피스톤 상면에 압력이 걸리지 않는 상황에서 엔진 속도, 오일 온도에 따른 피스톤 링 마찰력 변화를 확인하는 기초적인 실험을 수행하였고, 피스톤 상면에 압력이 걸리는 모터링, 연소 조건에서의 마찰력 또한 측정하였다. 측정된 마찰력 데이터는 마찰 기초 이론인 Stribeck curve를 잘 따라가며, 윤활 조건의 변화에 따라서 마찰력 값의 변화를 확인할 수 있었다. 또한 세가지 피스톤 링에서 오일 컨트롤 링(OCR)의 장력 변화에 따른 마찰력 변화를 오일 온도, 엔진 속도에 따라 관찰하여, 오일 컨트롤 링 장력의 변화량이 마찰력에 기인하는 정도를 본 개발된 장비를 통해 확인할 수 있음을 입증하였다. 따라서 새롭게 고안된 본 장비를 활용하여 피스톤 링 개발 단계에서, 개발 방향에 대한 마찰력 측면에서의 정량적인 지표를 높은 신뢰도로 제공할 수 있다. 더욱이 본 장비에서 측정된 데이터는 추후 보다 신뢰성 높은 피스톤 링 마찰 시뮬레이션 모델 구축에 중요한 검증 자료로 활용될 수 있을 것이다.Abstract i List of Figures vii List of Tables xiv Nomenclature xv Chapter 1. Introduction 1 1.1 Research background and motivations 1 1.2 Literature review 7 1.2.1 Piston rings 7 1.2.2 Piston ring dynamics 10 1.2.3 Calculation of piston ring friction 13 1.2.4 Piston friction measurement 25 1.3 Research objectives 29 1.4 Structure of the thesis 30 Chapter 2. Development Process of a New Piston Ring Friction Measurement System Engine V1 31 2.1 Design concept 31 2.2 Engine structure 43 2.3 In-cylinder gas sealing method 48 2.4 Experimental setup & conditions 59 2.5 Experimental results from Engine V1 68 2.6 Remaining issues from Engine V1 77 Chapter 3. Development Process of a New Piston Ring Friction Measurement System Engine V2 78 3.1 Design improvements from Engine V1 78 3.2 Extra force elimination 87 Chapter 4. System Verification 101 4.1 Base piston ring friction study 101 4.1.1 Oil temperature effect 106 4.1.2 Engine speed effect 112 4.1.3 Data repeatability 118 4.1.4 Each ring friction 120 4.1.5 Engine load effect 123 4.1.6 Piston thrust force effect 128 4.2 Piston ring design parameter study 133 4.2.1 Ring tension effect 133 Chapter 5. Conclusion and Future Works 138 5.1 Conclusion 138 5.2 Future works 141 References 146 국 문 초 록 153박

In vivo bioluminescence reporter gene imaging for the activation of neuronal differentiation induced by neuronal activator neurogenin 1 (Ngn1) in neuronal precursor cells

학위논문 (석사)-- 서울대학교 대학원 : 의학과 핵의학 전공, 2013. 2. 정재민.Purpose: The facilitation capability of neuronal lineages derived from transplanted stem cells is essential to improve the low efficacy of neuronal differentiation in stem cell therapy in vivo. Neurogenin 1 (Ngn1), a basic helix-loop-helix factor, has been used as an activator of neuronal differentiation. In this study, we monitored the in vivo activation of neuronal differentiation by Ngn1 in neuronal precursor cells using neuron-specific promoter-based optical reporters. Methods: The NeuroD promoter coupled with the firefly luciferase reporter system (pNeuroD-Fluc) was used to monitor differentiation in F11 neuronal precursor cells. In vitro luciferase activity was measured and normalized by protein content. The in vivo-jetPEITM system was used for in vivo transgene delivery. The IVIS 100 imaging system was used to monitor in vivo luciferase activity. Results: The Ngn1-induced neuronal differentiation of F11 cells generated neurite outgrowth within 2 days of Ngn1 induction. Immunofluorescence staining demonstrated that early and late neuronal marker expression (βIII-tubulin, NeuroD, MAP2, NF-M, and NeuN) was significantly increased at 3 days after treatment with Ngn1. When Ngn1 and the pNeuroD-Fluc vector were co-transfected into F11 cells, we observed an approximately 11-fold increase in the luciferase signal. An in vivo study showed that bioluminescence signals were gradually increased in Ngn1-treated F11 cells until 3 days. Conclusions: In this study, we examined the in vivo tracking of neuronal differentiation induced by Ngn1 using an optical reporter system. This reporter system could be used effectively to monitor the activation efficiency of neuronal differentiation in grafted stem cells treated with Ngn1 for stem cell therapy.I. Introduction II. Materials and Methods III. Results IV. Discussion V. Reference VI. Korean AbstractMaste

상아모세포 분화와 상아질 형성 과정에서 CPNE7과 NFI-C의 역할

학위논문 (박사)-- 서울대학교 대학원 : 치의과학과, 2017. 2. 박주철.During the process of tooth morphogenesis, numerous signaling molecules and transcription factors mediate odontoblast differentiation and dentin formation through sequential epithelial-mesenchymal interactions. Dentin is formed by odontoblasts which secrete extracellular matrix (ECM) proteins. Among ECM proteins, dentin sialophosphoprotein (DSPP) is the most abundant ECM in dentin. However, the precise function and molecular mechanisms of odontoblast differentiation are still under investigation. In the present study, we investigated biological function and mechanisms of Cpne7 and NFI-C in regulation of odontoblast differentiation. Cpne7 was expressed in preameloblasts and inner enamel epithelium.The secreted Cpne7 was translocated to differentiating odontoblasts. In odontoblasts, Cpne7 promoted odontoblastic markers and mineralized nodule formationin vitro. Moreover, Cpne7 induces the differentiation of dental pulp cells into odontoblasts and dentin formation in vivo. Mechanistically, Cpne7interacted with Nucleolin and Cpne7-Nucleoin complex promoted the expression of Dspp. Zinc deficiency is involved in bone malformations and oral disease. Mice deficient in zinc transporter Zip13 show connective tissue and skeletaldisorders, abnormal incisor teeth, and reduced root dentin formation in the molar teeth and share a morphologically similar phenotype tonuclear factor I-C (NFI-C)-deficient mice. In the present study, we determined the NFI-C signaling on odontoblastdifferentiation and dentin formation with altered zinc concentration. Zinc enhanced the binding efficiency of NFI-C and phosphorylation of Smad2/3(p-Smad2/3) in the cytoplasm. In zinc deficiency, NFI-C accumulated into nucleus, and NFI-C bound to the Dspp promoter and regulated Dspp gene transcription. Furthermore, zinc deficiency condition promotedDSPP expression in odontoblasts and dentin mineralization, while zinc sufficiency condition decreased DSPP expression and slightly delayeddentin mineralization. Taken together, Cpne7 and NFI-C signaling regulate odontoblast differentiation and dentin formation through modulation of Dspp gene transcription.CHAPTER I. GENERAL INTRODUCTION 1 CHAPTER II. CPNE7, a preameloblast-derived factor, regulates odontoblastic differentiation of mesenchymal stem cells 6 1. ABSTRACT 7 2. INTRODUCTION 8 3. MATERIALS AND METHODS 10 4. RESULTS 19 5. DISCUSSION 45 CHAPTER III. Zinc Balance is Critical for NFI-C Mediated Regulation of Odontoblast Differentiation 49 1. ABSTRACT 50 2. INTRODUCTION 51 3. MATERIALS AND METHODS 54 4. RESULTS 62 5. DISCUSSION 81 CHAPTER IV. CONCLUDING REMARKS 87 REFERENCES 89 ABSTRACT IN KOREAN 96Docto

Conceptual framework and evaluation process of apparel quality

학위논문(박사)--서울대학교 대학원 :의류학과,1997.Docto

(The)Effect of TPO (thyroid peroxidase) gene transfection on radioiodide kinetics in ARO-NIS cells

Thesis(master`s)--서울대학교 대학원 :협동과정 종양생물학전공,2004.Thesis(master`s)-

개에서 Doppler 초음파를 이용한 Ureteral jet 현상의 평가

학위논문 (석사)-- 서울대학교 대학원 : 수의학과, 2015. 2. 최민철.The ureteral jet is the phenomenon caused by forceful ejection of urine from the vesicoureteral junction (VUJ) into the urinary bladder. This study was performed to identify distinct ureteral jets using color Doppler ultrasonography (US), to provide insight into ureteral obstruction and to contribute to the study of the urodynamics and function of the ureter in dogs. Color Doppler US was applied to detect urinary flow from the right ureteral orifice in eight healthy beagle dogs. Under anesthesia, 0.9% saline (2.5 ml/kg/h) and diuretic (furosemide, 0.5 mg/kg) were administered intravenously in order to detect a distinct ureteral jet. In addition, the frequency, velocity, duration and waveform of the ureteral jets were recorded. In eight of the eight dogs (100%), the ureteral jet was clearly visualized from 2 min to 5 min (mean, 3.57 minSD, ±0.90 min) under diuresis and anesthesia. The measured frequency, mean peak velocity and mean duration of the right ureteral jet in seven dogs were 9.86±3.09 jets/min, 34.07±10.02 cm/s and 2.82±1.08 s, respectively. One dog was excluded from the examination because of the different direction of the right ureteral jet. Six patterns of ureteral jet waveform were identified in seven dogs. Moreover, during the period measured at 10 min from the point to 10 min after the initial jet, only three waveforms were identified. The results showed that Doppler US for ureteral jet could be potentially useful in assessing ureteral abnormalities, such as obstruction, ectopic ureter and function of the ureter in dogs.Introduction Materials and Methods Results 1. Detection of the ureteral jet 2. Direction of the ureteral jet 3. Initial time of the ureteral jet 4. Doppler waveforms of the ureteral jet 5. Duration of the ureteral jet 6. Peak velocity of the ureteral jet 7. Frequency of the ureteral jet Discussion References 국문 초록Maste

Smad3 와 NFI-C 시그널 조절 아연의 역할

학위논문 (석사)-- 서울대학교 대학원 : 협동과정뇌과학전공, 2011.2. 이승복.Maste

Cell-non-autonomous neurogenesis by exosome-mediated transfer of neurogenic miRNA in microfluidic system

학위논문 (박사)-- 서울대학교 융합과학기술대학원 : 융합과학기술대학원 분자의학및바이오제약학과, 2016. 2. 이동수.Neuronal cells release small vesicles known as secretory exosomes containing mRNAs, miRNAs and proteins to exchange signals as a form of intercommunication between cells. MicroRNAs (miRNAs) such as miR-124 or miR-9 play an important role in regulation of neuronal differentiation. Intercellular transfer of neurogenic microRNA (miRNA) induces neurogenesis and exosomes can mediate miRNA delivery from the leading differentiated cells to neighboring undifferentiated cells. The aim of this study is to confirm cell-non-autonomous miRNA/exosome-mediated differentiation of neural progenitor cells and to visualize exosomes carrying this neurogenic miRNA from leading to neighboring cells. F11 cells, neural progenitor cells, were stably transfected with reporter vector of pRV-effLuc/3xPT_miR-193a which luciferase signal could be turned off by binding of the identified miRNA to the triplicates of miRNA binding site in the 3' UTR of effLuc. Exosomes were isolated from the conditioned media and characterized by western blot. Transwell chambers system and microfluidic device were used to examine exosome-mediated miRNA transfer. The CMV-driven GFP-tagged CD63 vector was used to visualize endogenous exosomes. Target genes of MiR-193a considered as neurogenic miRNAs were related to cell proliferation, differentiation and axon guidance. Neurite outgrowth and neuronal marker expression such as βIII-tubulin, NeuroD and MAP2 were observed 3 days after identified MiR-193a treatment. Isolated exosomes were characterized for protein markers such as CD63, TSG101. qRT-PCR results showed that exosomes isolated from conditioned media in differentiated F11 cells highly increased miR-193a level. In addition to 2D co-culture and transwell culture setting, fluorescence signals of incorporated GFP-exosomes were detected within 2 days after co-culture with GFP-exosomes producing cells. Time-lapse live-cell confocal imaging using microfluidic device visualized the transport of single exosomes from differentiated to undifferentiated F11 cells. MiR-193a within the exosomes from differentiated donor F11 cells reached the recipient cells and was taken up to lead them to neuronal differentiation, showing increased neuronal marker expression. And these phenomenon were also reproduced in NE-4C, neural stem cells. Inhibition of the exosomal production by manumycin-A and treatment of anti-miR-193a in the differentiated donor cells failed to induce neurogenesis in undifferentiated recipient cells. These findings indicate that exosomes of neural progenitors and neurogenic miRNA within these exosomes propagate cell-non-autonomous differentiation to neighboring progenitors, which was captured visually on microfluidic device to delineate the roles of extracellular vesicles mediating neurogenesis of population of homologous progenitor cells.INTRODUCTION 12 1) Extracellular vesicles (EVs) 13 2) MicroRNA (miRNA) 15 3) Neurogenesis 18 4) MiRNA microarray 19 5) Co-culture system 19 6) MiRNA optical reporter gene 21 MATERIALS AND METHODS 23 Microarray Analysis 23 Gene Annotation Analysis 24 Cell culture and transfection 24 Quantitative reverse transcription-PCR 26 Immunofluorescence staining 26 In vitro luciferase assay 28 Preparation and characterization of exosomes 28 Fluorescent labeling of exosomes and cells 28 Transwell assay 29 Western blotting 30 Microfluidic cell culture device 31 Time-lapse imaging of exosomes 32 Bioluminescence imaging 33 Statistical analysis 33 Results 34 Identification of miR-193a newly associated with neurogenesis in Ngn1-overexpressing F11 cells 34 Enhanced neuronal differentiation in neural progenitor cells by overproduction of miR-193a 35 Elevated levels of miR-193a in differentiated F11 cell-derived exosomes 37 Exosomes-mediated transfer of miR-193a from differentiated cells to undifferentiated cells 38 Visualization of transport of individual exosomes using a microfluidic device 41 Reporting the action of exosomally delivered miR-193a in recipient F11-UD cells on microfluidic chamber 42 Discussion 84 Reference 92 Abstract in Korean 104Docto

Activation of retinoic acid receptors by soy isoflavone daidzein

학위논문 (석사)-- 서울대학교 대학원 : 약학과, 2013. 2. 이미옥.Retinoids modulate keratinocyte proliferation, differentiation, collagen synthesis and degradation, inflammatory response, and reduce sebum production in the skin. They have been used as therapeutic agents for diverse skin diseases such as aged skin, acne and skin cancer. Retinoids actions are mediated by retinoic acid receptors (RARs). Among the three isotypes, RARα,β and γ, RARα and RARγ are expressed and regulate retinoid target genes in the skin. Here, we found that extracts of two different soy beans, Glycine max and Rhynchosia Nulubilis increased transcriptional activity of RARα and RARγ. Further fractionation revealed that among the fractions, ethyl acetate fractions up-regulated transcriptional activity of RARs. HPLC analysis of the extracts and ethyl acetate fractions showed that daidzin and genistin are the major constituents of the fractions. Daidzin and its aglycone form, daidzein induce RAR transcriptional activity in dose-dependent manner. Genistin and genistein also up-regulated RAR transcriptional activity but their effects were weaker than that of daidzin and daidzein. Time resolved-fluorescence resonance energy transfer (TR-FRET) analysis demonstrated that daidzein bound both RARα and RARγ ligand binding domains and recruited co-activators. Daidzein increased RAR target genes, RARα and RARγ mRNA in time dependent manner in the keratinocyte, HaCaT. ChIP analysis showed that daidein treatment enhanced recruitment of RARα, RARγ, and p300 on functional RARE in the RARγ2 promoter. Protein levels of RARα and RARγ were reduced by daidzein, similar to the reduction by all-trans retinoic acid. Matrix metallopeptidase-9, which degrades collagen and enhances skin aging, was up-regulated by TNFα treatment, and its mRNA level and gelatinolytic activity were reduced by daidzein. Together, these results suggest that daidzein may be a functional ligand of retinoic acid receptors and it could be a therapeutic candidate for skin diseases as an alternative of retinoid. Also, these findings could explain a new mechanism of anti-skin aging effects of daidzeinABSTRACT ................................................................................................. i CONTENTS ................................................................................................. iii LIST OF FIGURES .................................................................................. ⅴ Ⅰ. INTRODUCTION ............................................................................. 1 Ⅱ. PURPOSE OF THE STUDY ...................................................... 6 Ⅲ. MATERIALS AND METHODS ............................................... 7 Ⅳ. RESULTS ............................................................................................ 13 1. Soybean extracts and EA fractions of extracts increase RAR transcriptional activity....................................................... 13 2. Soy isoflavones induce transcriptional activity of RARα and RARγ......................................................................................... 14 3. Daidzein is an agonistic ligand of RARα and RARγ......... 14 4. Daidzein enhances mRNA level of RARα and RARγ in HaCaT cells............................................................. 15 5. Daidzein suppresses the expression and enzymatic activities of MMP-9.................................................................... 16 Ⅴ. DISCUSSION ................................................................................... 27 REFERENCES ........................................................................................... 32 국문초록 ........................................................................................................ 40Maste