A microfabricated microconcentrator for sensors and chromatography

The detection and quantitative measurement of trace components is a challenging task. The key component in such an instrument is the concentration step where the analytes are accumulated before the analysis. In this research, simple and inexpensive processes for the microfabrication of microconcentrator that can be used with sensors and as an injector in GC were developed. Analytes are selectively concentrated in the microconcentrator. Rapid electrical heating of the microconcentrator releases the adsorbed species as a 66 concentration pulse , which serves as an injection for the detection system. The relatively small size of the microconcentrator allows it to be heated and cooled rapidly. The microconcentrator serves the dual purposes of sample concentration and injection. The devices were fabricated on 6-inch silicon substrate using standard photolithographic processes. First, a microheater embedded in silicon wafer was fabricated. The channels were lined with a conductive layer by sputtering metal film through which an electric current could be passed causing Ohmic heating. The preconcentration was done on thin-film polymeric layer deposited in the channel. Rapid heating of the conductive layer caused the desorption pulse to be injected into the sensor/detector. Several channel configurations were fabricated with a width between 50 to 456 μ-m depth between 35 and 350 μ-m and length between 6 and 19 cm. The separation distance between the channels was varied such that the entire microheater fitted in a 1cm 2 area. Due to their small size, the microconcentrators could be fabricated more than 50 at a time on a 6-inch silicon wafer. In the first part of this research, the heating characteristics of the microheaters are studied. Deposition of metals to form a resistive heating element in microchannels was demonstrated. It was found that temperature as high as 360°C could be attained in a ten seconds. The microconcentrator was effective as a concentrator plus injector. It exhibited high signal enhancement and precision

Information Quality for Mobile Internet Services: A Theoretical Model with Empirical Validation

Providing customers with high quality of information is a key determinant for the success of the mobile Internet. This study aims at identifying the important dimensions of information quality in increasing user satisfaction and customer loyalty for mobile Internet services. In order to achieve this goal, we propose a general model of information quality with four dimensions. The dimensions were constructed by expanding prior research in information quality in order to reflect the characteristics of the mobile Internet. We hypothesize that the four dimensions are positively related to user satisfaction and customer loyalty, and that their relative importance varies according to user goals. To validate the hypothesized model, we conducted a large-scale Internet survey with mobile Internet users. The results indicate that some dimensions are more important than others in increasing user satisfaction and loyalty, and relative importance of the dimensions varies according to the intended goals of mobile Internet contents

The role of hindsight in transcriptional regulation during Drosophila melanogaster development

In Drosophila melanogaster, hindsight (hnt) encodes a putative Zinc-finger transcription factor that is expressed in a highly complex pattern during development. Despite an apparent wealth of information regarding the dynamic expression pattern of hnt, the cellular response and defined target genes of Hnt remain largely unknown. Hnt is important in various developmental processes, and recent work suggests that Hnt function is downstream of the Notch (N) signaling pathway. Interestingly, the mammalian homolog of hnt is RAS-Responsive Element Binding Protein 1 (RREB1), which functions by binding to the RAS-responsive elements of the target gene promoters. Ras is a key downstream effector of the highly conserved Epidermal Growth Factor Receptor (EGFR) signaling pathway, yet the relationship between Hnt and EGFR signaling has not been extensively studied using the powerful approach of Drosophila genetics. This study involved a detailed examination of hnt mutant phenotypes and phenotypes associated with Hnt overexpression. Overall, this work revealed striking similarities between egfr and hnt mutant embryos. In particular, hnt mutant embryos were found to resemble egfr mutant embryos in their failure to properly develop peripheral nervous system (PNS) structures known as chordotonal organs and in their inability to recruit neighbouring secretory oenocytes. In addition, Hnt overexpression was found to induce ectopic DPax2 expression in an EGFR-dependent manner within the embryo. This relationship was also examined in a second developmental context, the pupal retinal neuroepithelium. Overall, the data presented suggests that Hnt’s primary function in the development of the PNS is associated with potentiating EGFR signaling

Synthetic jet을 이용한 3차원 날개 능동 유동제어에 관한 수치적 연구

학위논문 (박사)-- 서울대학교 대학원 : 협동과정 계산과학전공, 2014. 8. 김종암.본 연구는 3차원 날개 형상의 공력 성능을 향상시키기 위하여 synthetic jet을 이용한 공력 특성 향상 메커니즘에 관하여 수치적 연구를 수행하였다. 본 연구를 통하여 synthetic jet의 출구 형상에 따른 유동 특성 파악을 통해 유동제어에 효과적인 출구 형상을 도출하고, 이로부터 얻은 synthetic jet의 형상을 3차원 날개에 적용하여 고 받음각에서의 박리유동 제어 특성을 분석하였다. Synthetic jet의 출구 형상은 jet vortex의 발달 과정 및 전체적인 jet momentum에 영향을 주기 때문에 유동제어 특성에 큰 영향을 미치는 요인 중 하나이다. 이에 유동제어에 효과적인 출구 형상을 도출하기 위해 평판에서 유입류가 존재할 경우 사각형과 원형 출구 형상에 대하여 jet vortex 유동 구조 및 유동제어 가능성을 분석하였다. 사각형 출구 형상의 경우, jet 출구 직후에서는 큰 와류를 발생시키지만 출구 끝에서 발생하는 회전 유동에 의해 jet에 의한 효과가 급격히 감소함을 확인하였다. 원형 출구 형상의 경우, 사각형 출구 형상보다 균일한 jet vortex를 생성하고 유입류 방향으로 보다 멀리까지 jet의 영향이 미치는 유동구조를 가지고 있어 사각형 출구 형상보다 유동제어에 효과적임을 확인하였다. 또한 원형 출구 형상의 hole gap과 hole diameter의 변화에 따른 유동 구조 및 유동 특성을 비교 분석함으로써 유동제어 효과를 극대화 할 수 있는 원형출구 형상을 도출하였다. 다양한 수치 해석 결과의 분석을 통해서 도출된 원형 출구 형상의 synthetic jet을 적용하여 동체-날개 혼합 형상의 유동제어를 수행하였다. 풍동 실험과 수치해석을 통해 받음각의 변화에 따른 3차원 날개의 유동 분석을 수행한 결과, 날개의 받음각 증가에 따라 앞전에서부터 발생한 와류유동은 붕괴하게 되며 날개 바깥쪽 부분에 서부터는 박리 유동이 발달함을 확인하였다. 이에 와류 붕괴 현상과 박리 유동을 제어하기 위하여 앞전 부근에 jet을 위치시켰다. 풍동 실험을 통하여 앞전에 위치한 jet을 모두 작동 시켜 유동제어 효과를 확인하였다. 또한 고성능, 저전력 구동을 위하여 jet의 개수에 따른 유동제어 성능을 평가하였다. 수치해석을 통하여 jet의 위치에 따른 유동제어 메커니즘을 확인하고 위치에 따라 유동제어를 수행할 경우 와류 붕괴 현상을 지연시키고 박리 유동을 제어할 수 있음을 확인하였다. 또한 고속에서의 유동제어 가능성을 확인하기 위하여 저속에서의 유동제어 전략을 고속에서 확장 적용하여 고속의 동체-날개 혼합형상에서도 효과적인 유동제어 방법을 통하여 고 받음각의 공력 성능을 향상 시킬 수 있음을 확인하였다. 본 연구에서 도출된 연구 결과는 유동제어에 효과적인 능동유동제어 시스템의 설계 및 무인 전투기 형상을 포함한 3차원 날개 형상의 공력 성능 향상 방안 수립에 활용될 수 있을 것이다.The present study deals with flow characteristics of synthetic jets for efficient flow control performance. It consists of two parts: flow characteristics of synthetic jets depending on exit configuration and flow control using synthetic jets over Blended Wing Body (BWB) configuration. In first part, flow characteristics of synthetic jets have been computationally investigated for different exit configurations under a cross flow condition. The exit configuration of a synthetic jet substantially affects the process of vortex generation and evolution, which eventually determines the mechanism of jet momentum transport. Two types of exit configurations were considered: one is a conventional rectangular exit, and the other is a series of circular holes. The interactions of synthetic jets with a freestream were performed by analyzing the vortical structure characteristics. The effectiveness of flow control was evaluated by examining the behavior of the wall shear stress. It was observed that the circular exit provides better performance than the rectangular exit in terms of sustainable vortical structure and flow control capability. According to a hole gap and a hole diameter of circular exit, comparative studies were then conducted with all the other parameters fixed. Detailed computations reveal that the hole gap yields a much more significant effect on flow characteristics than the hole diameter, which turned out to be relatively minor. Based on the strength and the persistency of jet vortices, the circular exit with a suitable hole gap formed critical jet vortices that beneficially affected separation control. This indicates that the flow control performance of circular exit array could be remarkably improved by applying a suitable dimensionless hole parameter. Based on the results of exit configuration, the second part deals with flow control strategy over BWB configuration. Flow structures were examined by analyzing the baseline characteristics of BWB configuration when synthetic jet was off. Based on the aerodynamic data and flow structure, a strategy for flow separation control on BWB configuration was established. Based on the aerodynamic data and flow structure, synthetic jet actuators were installed to prevent leading-edge stall at a relatively high angles of attack. All-actuators-on case and selective-actuators-on case were examined to find effective flow control method. Two types of exit locations are considered for analyzing flow mechanism: one is outboard array jets, and the other is inboard array jets. The interactions of synthetic jets with a free stream were performed by analyzing the vortical structure and the surface pressure characteristics. The effectiveness of flow control was evaluated by examining the aerodynamic coefficient and flow structures. As a result, the vortex breakdown point is moved toward the outboard section by synthetic jets, and the separation flow shows a stable structure. Based on the flow structure in overall speed rage, flow control strategy of low speed flight is applied to flow control of high speed flight. This shows effective flow control strategy applicable to all speed flight. Through numerical analyses on flow characteristics of synthetic jets, it is observed that the synthetic jets under suitable actuating conditions beneficially change the local flow feature and vortex structure to bring a significant improvement of the wing aerodynamics acting on the three-dimensional aircraft configuration in the stall angle.Chapter I Introduction 1 1.1 Literature Review 1 1.1.1 Synthetic Jet 1 1.1.2 Piezoelectirically-driven Synthetic Jet 3 1.1.3 Lambda Wing Aerodynamics 4 1.1.4 Flow Separation on Lambda Wing Flight Mechanics 5 1.1.5 1303 UCAV Configuration 7 1.2 Objectives and Contributions 10 1.3 Organization of Thesis 11 Chapter II Numerical Approaches 12 2.1 Governing Equations 12 2.2 Turbulence Models 14 2.2.1 The Standard Menters k-ω SST Model 14 2.2.2 The k-ω SST Model (Menter et al., 2003) 18 2.2.3 SST-DES Model (Strelets et al., 2001) 19 2.2.4 Zonal SST-DES Model (Menter et al., 2003) 21 2.3 Pseudo-Compressibility Method 22 2.4 Transformation of the Incompressible Navier-Stokes Equations with Turbulence Model 27 2.5 Space Discritizaion Method 31 2.5.1 Differencing of Inviscid Flux Terms 31 2.5.2 Upwind Differencing Method 33 2.5.3 Low Dissipative Upwind Differencing Method 38 2.5.4 Higher Order Spatial Accuracy 39 2.6 Time Integration Method 41 2.6.1 Dual Time Stepping 42 2.6.2 Pseudo-Time Discretization 44 2.6.3 LU-SGS Scheme 47 2.7 Synthetic Jet Boundary Condition 50 Chapter III Flow Characteristics of Synthetic Jets 51 3.1 Two Types of Synthetic Jet Exit 51 3.2 Code Validation 53 3.3 Characteristics of Rectangular and Circular Exits 55 3.3.1 Flow Structures 55 3.3.2 Flow Control Effectiveness 58 3.4 Characteristics of Circular Exits Depending on Hole Parameter 60 3.4.1 Variation of Hole Gap 60 3.4.2 Variation of Hole Diameter 62 Chapter IV Active Flow Control of Wing 63 4.1 Experimental Reference 63 4.1.1 BWB Configuration 63 4.1.2 Experimental Setup 64 4.2 Baseline Analysis 65 4.2.1 Code Validation 65 4.2.2 Flow Characteristics of BWB Configuration 67 4.3 Flow Control of BWB Configuration 69 4.3.1 Flow Control Depending on Jet Location 69 4.3.2 Application of Flow Control in High Speed Flight 72 Conclusion 75 References 77Docto

Exploring the roles of multidimensional versus unidimensional construct of destination social responsibility in explaining destination trust and relationship continuity

Funding: This study was supported by 2021 Research Grant from Kangwon National University.Peer reviewedPublisher PD

A case report of the use of rituximab and the Epidermolysis Bullosa Disease Activity Scoring Index (EBDASI) in a patient with epidermolysis bullosa acquisita with extensive esophageal involvement

A 49-year-old man with recalcitrant mechanobullous epidermolysis bullosa acquisita (EBA) with significant esophageal involvement was treated with rituximab. EBA is a chronic autoimmune subepidermal bullous disease. It is characterized by skin fragility and scarring caused by circulating and tissue bound antibodies to type VII collagen. EBA is often unresponsive or poorly responsive to conventional immunosuppressive therapies such as corticosteroids, methotrexate, and cyclosporine. The burden of long-term use of immunosuppressants also limits their use in the treatment of chronic autoimmune diseases such as EBA. Since a validated and objective way of measuring disease activity in patients with EBA has not been described, we used the Epidermolysis Bullosa Disease Activity Scoring Index (EBDASI), for hereditary EB, as a surrogate to measure disease severity and activity in our patient with EBA. After three courses of rituximab over three years, our patient has achieved near complete clinical remission from disease activity. The patient’s response suggests that treatment with rituximab may be a valuable treatment regimen for severe mechanobullous EBA, which is demonstrated by paralleled declines in objective disease activity scores, the EBDASI. This is in line with recently observed beneficial effects of rituximab in the management of EBA.</p