1,721,986 research outputs found
Do Han Jun
No full text학위논문(박사)아주대학교 일반대학원 :전자공학과,2012. 2This thesis presents a vlaveless thermopneumatic micropump using surface tension. This micropump uses the surface tension and capillary attraction to control the flow for simple structure without any moving part such as a membrane or valve. In this dissertation, the influences of geometries of the micro channel and micro pillar on the performance of the micropump are compared. Commercial finite volume method (FVM) simulation software is used to simulate micropump operations.
First, theories of microfluid mechanics are presented in chapter 2. And the valveless thermopneumatic micropump with simple structure is designed, fabricated, simulated and tested in this chapter. This micropump discharges the fluid using thermopneumatic pressure and fills the fluid using negative pressure and capillary attraction. And during the refill time the micro channel works like a valve using surface tension. Therefore the flow can be controlled without any additional components. This micropump operates at 3.5V for 4 seconds to discharge and its size is 11.7 x 8.8 x 0.7 cm3. And the height of micro structure is 80 ㎛.
Second, various micropump geometries are designed to improve the micropump performance especially to reduce the backward flow loss. In the chapter 3, the influences of the micropump geometries such as the channel direction angle and the expansion angle on the micropump performance are compared with experimental tests and FVM simulations. In this chapter, six different geometries of micropumps are designed with three different channel direction angles and two different expansion angles. For more accurate comparison, three geometries with the same effective pump chamber are additionally designed. In this chapter, micropump size is 11.7 x 8.8 x 1.7 cm3 and the height of the micro structure is 100 ㎛. And these pumps discharge 120 nL for 4 - 7seconds. The channel direction angle affects to the backward flow loss and the expansion angle affects to the refill time and backward flow loss.
Third, micro pillar structures are designed to improve the efficiency of the micropump operations especially to reduce the backward flow loss and discharge time. And the influences of geometries of the micro pillars on the micropump performance are compared with experimental tests and FVM simulations. Various micro pillar structures are designed with four different locations and five different sizes. Micro pillar structures increase the surface area and the surface tension. Therefore they reduce the backward flow loss. In this chapter, micropump size is 11.7 x 8.8 x 1.7 cm3 and the height of micro structure is 100 ㎛. And these pumps discharge 100 nL for 4 seconds. And locations and sizes of the micro pillar structures affect to the backward flow loss.ABSTRACT i
LIST OF FIGURES v
LIST OF TABLES xi
Chapter I. INTRODUCTION 1
1.1 Microfluidic devices 1
1.2 Review of micropumps 2
1.3 Research objectives 4
Chapter II. The VALVELESS THERMOPNEUMATIC MICROPUMP STRUCTURE 6
2.1 Characteristics of the microfluid 6
2.2 Theory to design the micro channel 7
2.1.1 Capillary force 8
2.1.2 Surface tension 9
2.1.3 Flow resistance 12
2.3 Valveless thermopneumatic micropump 13
2.3.1 Structure 13
2.3.2 Operation sequence 15
2.3.3 Simulation results 18
2.3.4 Fabrication process 20
2.3.5 Experimental results 24
2.4 Summary 28
Chapter III. THE INFLUENCE OF GEOMETRY ON THE MICROPUMP OPERATION 29
3.1 Design and operation 29
3.2 Structure 40
3.3 Simulation results 45
3.4 Fabrication 53
3.5 Experimental results 57
3.3 Summary 68
Chapter IV. THE INFLUENCE OF A MICROPILLAR ON THE MICROPUMP 69
4.1 Design 70
4.2.1 Design of principles 70
4.2.2 Design of micro pillar structure 74
4.2 Simulation results 78
4.3 Fabrication 86
4.4 Experimental results 89
4.5 Summary 101
Chapter V. Conclusions and Outlook 102
REFERENCES 104Maste
무증상성인에서 컴퓨터단층촬영을 이용한 고관절 cam변형의 빈도
No full textPURPOSE: Femoroacetabular impingement (FAI) which restricts range of hip motion is regarded as an important cause leading to early development of degenerative arthritis. Although three-dimensional imaging such as CT and MRI are regarded as precise imaging modalities for three dimensional morphology of FAI, the modalities have several limitations for screening tool in out-patient clinic. The paucity of morphologic data of FAI in Korean makes it difficult to choose which method of radiograph is the most useful to screen out general orthopedic problems. We postulated the distribution of cam deformity have individual variation in Korean population. Thus we investigated the distribution of cam deformity in asymptomatic Korean population.
MATERIALS AND METHODS: From Jan 2011 to Dec 2015, hip CT images of 120 subjects without any history around hip joint were evaluated. A computer program which reconstructs three dimensional model from CT scan was used to provide sectional images which cross the central axis of femoral head and neck. Alpha angle was measured in each sectional images. Alpha angle above 55 degrees were regarded as cam deformity.
RESULTS: Mean alpha angle was 43.5°(34.7-56.1°) in 3 o’clock, 51.24°(39.5-58.8°) in 2 o’clock, 52.45° (43.3-65.5°) in 1 o’clock, 44.09°(36.8-49.8°) in 12 o’clock, 40.71°(33.5-45.8°) in 11 o’clock, 39.21°(34.1-44.6°) in 10 o’clock. Alpha angle in 1 and 2 o’clock was significantly larger than any locations (P<0.01). The prevalence of cam deformity was 15% and 15.8% in 1 and 2 o’clock, respectively.
CONCLUSION: Cam deformity of FAI was observed on 25.8% of asymptomatic hip. The most common region of cam deformity was antero-superior area of femoral head-neck junction (1 and 2 o’clock). The present study first reported the prevalence and the distribution of cam deformity in asymptomatic Korean population. The results would provide anatomical comprehension of cam deformity for diagnosis and surgical treatments.목적: 대퇴비구 충돌(Femoroacetabular impingement: FAI)은 고관절의 운동 범위를 감소시키는 것은 물론 초기 관절염의 초래하는 중요한 원인으로 추정되고 있다. 단순 방사선 촬영 단독보다 CT 나 MRI 와 같은 단층 촬영이 더욱 정확한 진단적 방법으로 간주되지만 외래에서 매번 적용하기에는 제한이 따른다. 우리나라 성인의 FAI에 대한 단층 촬영의 데이터가 부족하여 저자들은 한국인에서 cam 형 충돌의 위치가 개인마다 다를 것으로 가설을 수립하였다. 이에 컴퓨터 단층촬영을 이용하여 무증상성인의 cam 형 변형의 빈도를 측정하고자 한다.
대상 및 방법: 2011년 1월부터 2015년 12월까지 본원에서 120개 고관절에 특이병력 없는 무증상 성인 120명의 고관절 CT영상을 이용하였다. CT영상을 INFINITT Xelis 프로그램을 이용하여 골 두-경부 중심점을 잇는 선을 중심으로 근위 대퇴부를 시계 시스템을 이용하여 3차원적으로 분할하여 각 구간에서 알파각도를 측정하였다. 알파각도는 55도 보다 큰 값이면 고관절 Cam형 충돌로 판정하였다.
결과: 3시부터 10시(대퇴골 전방에서 후방)방향으로의 평균 알파각은 3시에서 43.5°(34.7-56.1°), 2시에서 51.24°(39.5-58.8°), 1시에서 52.45° (43.3-65.5°), 12시에서 44.09°(36.8-49.8°), 11시에서 40.71°(33.5-45.8°)였고 10시에서는 39.21°(34.1-44.6°)이었다. 전상방부(1시 및 2시)의 평균 알파각이 제일 컸고(P<0.01) 고관절Cam형 충돌과 관련된 영상의학적 소견의 빈도는 1시 및 2시에서 각각 15% 및 15.8%였다.
결론: 무증상 성인에서 cam형 충돌은 25.8%에서 발견 되었고 가장 호발하는 위치는 전상방부(1시 및 2시)였다. 한국에서 처음 시계 시스템으로 알파값을 측정한 결과를 보여주어 FAI에대한 관절경적 치료나 돌출부 제거술(bumpectomy)을 하는 수술의사들에게 도움이 될 것으로 생각된다.Ⅰ. INTRODUCTION 1
Ⅱ. MATERIALS AND METHODS 3
A. MATERIALS 3
B. METHODS 3
C. STATISTICAL ANALYSIS 4
Ⅲ. RESULTS 8
Ⅳ. DISCUSSION 11
Ⅴ. CONCLUSION 16
REFERENCES 17
국문요약 21Docto
Comparison of bonded/unbonded stem-cement interface in toal hip replacement
No full text학위논문(석사) - 한국과학기술원 : 기계공학전공, 2002.2, [ iv, 40 p. ]한국과학기술원 : 기계공학전공
CAMPrints: Leveraging the "Fingerprints" of Digital Cameras to Combat Image Theft
No full textGoing Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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