• 한국정밀공학회지
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• 제33권5호
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• pp.385-392
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• 2016

Recently in the display industry, demands for high-luminance and resolution of display devices have been steadily increasing. Generally, micro linear patterns are applied to an optical film in order to improve its properties of light. However, these patterns are easily viewed to eyes and moire phenomenon can be occurred. Micro random patterns are proposed as a method to solve these problems, increasing light-luminance and light-diffusion. However, conventional pattern manufacturing technologies have long processing times and high costs making it difficult to apply to large area molds. In order to combat this issue, micro-random patterns are formed by using a roll to plate indentation method along with abrasive paper tools composed of AlSiO2, SiC, and diamond grains. Also, forming properties, such as size and fill-factor of random patterns, are analyzed depending on type, mesh of abrasive paper tools, and indentation forces.

• 미술이론과 현장
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• 제5호
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• pp.25-41
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• 2007

Despite continuous efforts to redraw the boundaries between art and culture, the conventional concept of originality has persisted in approaches to the practice of contemporary art. In the discourse of originality, various forms of lesser arts that employ the method of replication have been referred to as kitsch, or "rear-guard," the opposite of avant-garde. This categorization points to the contested issue regarding the oppositional relation between modernism and mass culture. With its easily accessible content and financial affordability, mass culture has become both an irresistible attraction and a most powerful threat to modernism. This threat has instigated a discursive system that has situated mass culture as a cultural other of modernism. Taking the marginalized category of kitsch as the area of contention, this paper examines a discursive repression of kitsch. It analyzes the conceptual framework that defends originality and autonomy in art and, conversely, degrades kitsch as an inferior and dangerous cultural category. Greenberg'S concept of kitsch as a by-product of industrialization evolved into the criticism that advocates the autonomy of art. The Frankfurt School scholars, particularly Theodor Adorno and Max Horkheimer, practiced comparable cultural critiques. Focusing on mass culture such as film, radio, and television, instead of art works, they critically analyzed the system of mass culture and theorized the negative implications of the ubiquitous presence of kitsch. Some critics, on the other hand, perceived the growth of mass culture as opening possibilities in cultural development. Walter Benjamin and Harold Rosenberg asserted the socio-cultural dynamics of mass culture underlining the potential for continual transformation in reality and in the subject. They acknowledged that technological advances changed the condition of creation and enabled unmediated interactions between media. By scrutinizing conflicting views on kitsch, this paper intends to reassess arts that draw "the forces of the outside."

• 생체재료학회지
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• 제22권4호
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• pp.235-248
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• 2018

Background: Injectable hydrogels have been extensively researched for the use as scaffolds or as carriers of therapeutic agents such as drugs, cells, proteins, and bioactive molecules in the treatment of diseases and cancers and the repair and regeneration of tissues. It is because they have the injectability with minimal invasiveness and usability for irregularly shaped sites, in addition to typical advantages of conventional hydrogels such as biocompatibility, permeability to oxygen and nutrient, properties similar to the characteristics of the native extracellular matrix, and porous structure allowing therapeutic agents to be loaded. Main body: In this article, recent studies of injectable hydrogel systems applicable for therapeutic agent delivery, disease/cancer therapy, and tissue engineering have reviewed in terms of the various factors physically and chemically contributing to sol-gel transition via which gels have been formed. The various factors are as follows: several different non-covalent interactions resulting in physical crosslinking (the electrostatic interactions (e.g., the ionic and hydrogen bonds), hydrophobic interactions, ${\pi}$-interactions, and van der Waals forces), in-situ chemical reactions inducing chemical crosslinking (the Diels Alder click reactions, Michael reactions, Schiff base reactions, or enzyme-or photo-mediated reactions), and external stimuli (temperatures, pHs, lights, electric/magnetic fields, ultrasounds, or biomolecular species (e.g., enzyme)). Finally, their applications with accompanying therapeutic agents and notable properties used were reviewed as well. Conclusion: Injectable hydrogels, of which network morphology and properties could be tuned, have shown to control the load and release of therapeutic agents, consequently producing significant therapeutic efficacy. Accordingly, they are believed to be successful and promising biomaterials as scaffolds and carriers of therapeutic agents for disease and cancer therapy and tissue engineering.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2008년 영문 학술대회
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• pp.690-699
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• 2008

In this paper a conventional approach for design and analysis of subsonic air vehicle is used. First of all subsonic aerodynamic coefficients are calculated using Computational Fluid Dynamics(CFD) tools and then wind-tunnel model was developed that integrates vehicle components including control surfaces and initial data is validated as well as refined to enhance aerodynamic efficiency of control surfaces. Experimental data and limited computational fluid dynamics solutions were obtained over a Mach number range of 0.5 to 0.8. The experimental data show the component build-up effects and the aerodynamic characteristics of the fully integrated configurations, including control surface effectiveness. The aerodynamic performance of the fully integrated configurations is comparable to previously tested subsonic vehicle models. Mathematical model of the dynamic equations in 6-Degree of Freedom(DOF) is then simulated using MATLAB/SIMULINK to simulate trajectory of vehicle. Effect of altitude on range, Mach no and stability is also shown. The approach presented here is suitable enough for preliminary conceptual design. The trajectory evaluation method devised accurately predicted the performance for the air vehicle studied. Formulas for the aerodynamic coefficients for this model are constructed to include the effects of several different aspects contributing to the aerodynamic performance of the vehicle. Characteristic parameter values of the model are compared with those found in a different set of similar air vehicle simulations. We execute a set of example problems which solve the dynamic equations to find the aircraft trajectory given specified control inputs.

• Coupled systems mechanics
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• 제4권4호
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• pp.279-295
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• 2015

The article presents a theoretical-experimental approach developed for modeling the coefficient of sliding friction in the dynamic system tool-workpiece in slide diamond burnishing of low-alloy unhardened steels. The experimental setup, implemented on conventional lathe, includes a specially designed device, with a straight cantilever beam as body. The beam is simultaneously loaded by bending (from transverse slide friction force) and compression (from longitudinal burnishing force), which is a reason for geometrical nonlinearity. A method, based on the idea of separation of the variables (time and metric) before establishing the differential equation of motion, has been applied for dynamic modeling of the beam elastic curve. Between the longitudinal (burnishing force) and transverse (slide friction force) forces exists a correlation defined by Coulomb's law of sliding friction. On this basis, an analytical relationship between the beam deflection and the sought friction coefficient has been obtained. In order to measure the deflection of the beam, strain gauges connected in a "full bridge" type of circuit are used. A flexible adhesive is selected, which provides an opportunity for dynamic measurements through the constructed measuring system. The signal is proportional to the beam deflection and is fed to the analog input of USB DAQ board, from where the signal enters in a purposely created virtual instrument which is developed by means of Labview. The basic characteristic of the virtual instrument is the ability to record and visualize in a real time the measured deflection. The signal sampling frequency is chosen in accordance with Nyquist-Shannon sampling theorem. In order to obtain a regression model of the friction coefficient with the participation of the diamond burnishing process parameters, an experimental design with 55 experimental points is synthesized. A regression analysis and analysis of variance have been carried out. The influence of the factors on the friction coefficient is established using sections of the hyper-surface of the friction coefficient model with the hyper-planes.

• Asian Spine Journal
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• 제12권6호
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• pp.967-972
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• 2018

Study Design: Biomechanical study. Purpose: To investigate the relative stiffness of a new posterior pelvic fixation for unstable vertical fractures of the sacrum. Overview of Literature: The reported operative fixation techniques for vertical sacral fractures include iliosacral screw, sacral bar fixations, transiliac plating, and local plate osteosynthesis. Clinical as well as biomechanical studies have demonstrated that these conventional techniques are insufficient to stabilize the vertically unstable sacral fractures. Methods: To simulate a vertically unstable fractured sacrum, 12 synthetic pelvic models were prepared. In each model, a 5-mm gap was created through the left transforaminal zone (Denis zone II). The pubic symphysis was completely separated and then stabilized using a 3.5-mm reconstruction plate. Four each of the unstable pelvic models were then fixed with two iliosacral screws, a tension band plate, or a transiliac fixation plus one iliosacral screw. The left hemipelvis of these specimens was docked to a rigid base plate and loaded on an S1 endplate by using the Zwick Roell z010 material testing machine. Then, the vertical displacement and coronal tilt of the right hemipelves and the applied force were measured. Results: The transiliac fixation plus one iliosacral screw constructions could withstand a force at 5 mm of vertical displacement greater than the two iliosacral screw constructions (p=0.012) and the tension band plate constructions (p=0.003). The tension band plate constructions could withstand a force at $5^{\circ}$ of coronal tilt less than the two iliosacral screw constructions (p=0.027) and the transiliac fixation plus one iliosacral screw constructions (p=0.049). Conclusions: This study proposes the use of transiliac fixation in addition to an iliosacral screw to stabilize vertically unstable sacral fractures. Our biomechanical data demonstrated the superiority of adding transiliac fixation to withstand vertical displacement forces.

• 한국산학기술학회논문지
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• 제20권1호
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• pp.470-476
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• 2019

일반적으로 열차 제동을 위한 제동력은 압축공기를 활용하여 제공된다. 열차에 상황별로 적절 제동력을 가하기 위해 사용하는 압력밸브 시스템은 복잡한 유동 회로를 가진다. 이를 일반적인 기계가공으로 제작 시, 유로형상 설계에 제약이 있는 반면, 3D 프린팅 기법으로 제작시 유동 효율을 증대할 수 있는 유로형상 제작이 가능하다. 따라서 이번 연구에서는 기존의 제작 방식으로 유로를 제작하는 경우와, 3D프린팅의 장점을 살려, 자유로운 형상의 유로를 제작하는 경우를 비교하여, 압력 밸브 시스템 내의 압축공기 유동의 현상을 해석적으로 분석하였다. 해석을 위한 조건으로는, 유로 방향이 바뀔 때 유로의 곡률 크기, 유로의 직경, 입구 및 저장소 압력의 크기, 그리고 압축공기의 초기 온도로 구분하였다. 압력손실의 최소화 및 유동 특성의 균일성이 제동 효율 개선에 영향을 주는 요인이므로, 수치해석을 통한 연구를 통해 일반적인 기계가공을 통한 직각 유로 형상보다는 3D 프린팅을 통한 곡률 유로의 경우가 제동효율 개선에 유리함을 확인하였다.

• Advances in aircraft and spacecraft science
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• 제6권2호
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• pp.117-144
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• 2019

High Altitude and Long Endurance (HALE) aircraft are capable of providing intelligence, surveillance and reconnaissance (ISR) capabilities over vast geographic areas when equipped with advanced sensor packages. As their use becomes more widespread, the demand for additional range, endurance and payload capability will increase and designers are exploring non-conventional configurations to meet the increasing demands. One such configuration is the joined-wing concept. A joined-wing aircraft is one that typically connects a front and aft wings in a diamond shaped planform. One such example is the Boeing SensorCraft configuration. While the joined-wing configuration offers potential benefits regarding aerodynamic efficiency, structural weight, and sensing capabilities, structural design requires careful consideration of elastic buckling resulting from the aft wing supporting, in compression, part of the forward wing structural loading. It has been shown already that this is a nonlinear phenomenon, involving geometric nonlinearities and follower forces that tend to flatten the entire configuration, leading to structural overload due to the loss of the aft wing's ability to support the forward wing load. Severe gusts are likely to be the critical design condition, with flight control system interaction in the form of Gust Load Alleviation (GLA) playing a key role in minimizing the structural loads. The University of Victoria Center for Aerospace Research (UVic-CfAR) has built a 3-meter span scaled and flexible wing UAV based on the Boeing SensorCraft design. The goal is to validate the nonlinear structural behavior in flight. The main objective of this research work is to perform Ground Vibration Tests (GVT) to characterize the dynamic properties of the scaled flight vehicle. Results from the experimental tests are used to characterize the modal dynamics of the aircraft, and to validate the numerical models. The GVT results are an important step towards a safe flight test program.

• 대한치과교정학회지
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• 제49권2호
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• pp.73-80
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• 2019

Objective: The purpose of this study was to compare the static (SFF) and kinetic frictional forces (KFF) of a computer-aided design and computer-aided manufacturing lingual bracket (CAD/CAM-LB) with those of conventional LB (Con-LB) and Con-LB with narrow bracket width (Con-LB-NBW) under 3 tooth displacement conditions. Methods: The samples were divided into 9 groups according to combinations of 3 LB types (CAD/CAM-LB [Incognito], Con-LB [7th Generation, 7G], and Con-LB-NBW [STb]) with 3 displacement conditions (no displacement [control], maxillary right lateral incisor with 1-mm palatal displacement [MXLI-PD], and maxillary right canine with 1-mm gingival displacement [MXC-GD]; n = 6/group). While drawing a 0.016-inch copper or super-elastic nickel-titanium archwire with 0.5 mm/min for 5 minutes in a chamber maintained at $36.5^{\circ}C$, SFF and KFF were measured. The Kruskal-Wallis method with Bonferroni correction was performed. Results: The Incognito group demonstrated the highest SFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD, Stb-MXC-GD] < [7G-MXC-GD, 7G-MXLI-PD, 7G-control] < [Incognito-MXLI-PD, Incognito-control, Incognito-MXC-GD]; p < 0.001). However, there were no significant differences in SFF among the 3 displacement conditions within each bracket group. Within each displacement condition, the Incognito group demonstrated the highest KFF, followed by the 7G and STb groups ([STb-control, STb-MXLI-PD] < Stb-MXC-GD < 7G-MXLI-PD < [7G-control, 7G-MXC-GD] < [7G-MXC-GD, Incognito-MXLI-PD, Incognito-control] < [Incognito-control, Incognito-MXC-GD]; p < 0.001). MXC-GD exhibited higher KFFs than MXLI-PD in the same bracket group. Conclusions: The slot design and ligation method of the CAD/CAM-LB system should be modified to reduce SFF and KFF during the leveling/alignment stage.

• 한국산학기술학회논문지
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• 제20권7호
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• pp.166-172
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• 2019

금속 일체형 판재 도어 임팩트 빔 개발을 위해 단면 형상의 최적설계를 진행하였다. 기존의 도어 임팩트는 충격을 흡수하는 강관과 양쪽에 브라켓을 용접하여 자동차에 설치하는 구조로 이루어졌다. 하지만, 브라켓을 설치하기 위한 용접작업은 생산성을 떨어뜨리고 생산단가를 증가시키는 과정이다. 이러한 단점을 극복하기 위해 일체형 판재 도어 임팩트 빔의 개발은 반드시 필요한 공정이다. 본 논문에서는 일체형 판재 도어 임팩트의 단면 형상을 수치해석의 방법으로 제안하는 연구를 진행하였다. 외부 충격에 대한 반력 하중 및 생산성을 고려하여 엔지니어의 직관적인 설계 형상 6가지에 대하여 수치해석을 진행하였다. 객관적인 비교를 위해 3점 굽힘 하중 실험을 모사하는 유한요소해석을 진행하였다. 형상과 치수가 상이한 6가지의 단면 형상 중 최적의 형상을 선정하고, 상세 설계를 위해 단면형상의 높이와 폭의 치수를 변화시키며 해석을 진행하였다. 이를 통해, 일체형 판재 도어 임팩트의 최적의 단면 형상을 제안하였다.