Frontiers in Additive Manufacturing

Ryan Wicker 한국정밀공학회 2011 한국정밀공학회 학술발표대회 논문집 Vol.2011 No.6월

Redundancy Minimizing Techniques for Robust Transmission in Wireless Networks

Kacewicz, Anna,Wicker, Stephen B. The Korea Institute of Information and Commucation 2009 Journal of communications and networks Vol.11 No.6

In this paper, we consider a wireless multiple path network in which a transmitting node would like to send a message to the receiving node with a certain probability of success. These two nodes are separated by N erasure paths, and we devise two algorithms to determine minimum redundancy and optimal symbol allocation for this setup. We discuss the case with N = 3 and then extend the case to an arbitrary number of paths. One of the algorithms minimum redundancy algorithm in exponential time is shown to be optimal in several cases, but has exponential running time. The other algorithm, minimum redundancy algorithm in polynomial time, is sub-optimal but has polynomial worstcase running time. These algorithms are based off the theory of maximum-distance separable codes. We apply the MRAET algorithm on maximum-distance separable, Luby transform, and Raptor codes and compare their performance.

Cure depth control for complex 3D microstructure fabrication in dynamic mask projection microstereolithography

Choi, Jae-Won,Wicker, Ryan B.,Cho, Seok-Hyun,Ha, Chang-Sik,Lee, Seok-Hee Emerald Group Publishing Limited 2009 RAPID PROTOTYPING JOURNAL Vol.15 No.1

<B>Purpose</B> - The paper's aim is to explore a method using light absorption for improving manufacturing of complex, three-dimensional (3D) micro-parts with a previously developed dynamic mask projection microstereolithography (MSL) system. A common issue with stereolithography systems and especially important in MSL is uncontrolled penetration of the ultraviolet light source into the photocrosslinkable resin when fabricating down-facing surfaces. To accurately fabricate complex 3D parts with down-facing surfaces, a chemical light absorber, Tinuvin 327™ was mixed in different concentrations into an acrylate-based photocurable resin, and the solutions were tested for cure depths and successful micro-part fabrication. <B>Design/methodology/approach</B> - Tinuvin 327 was selected as the light absorber based on its high absorption characteristics (~0.4) at 365?nm (the filtered light wavelength used in the MSL system). Four concentrations of Tinuvin 327 in resin were used (0.00, 0.05, 0.10, and 0.15 percent (w/w)), and cure depth experiments were performed. To investigate the effects of different concentrations of Tinuvin 327 on complex 3D microstructure fabrication, several microstructures with overhanging features such as a fan and spring were fabricated. <B>Findings</B> - Results showed that higher concentrations of Tinuvin 327 reduced penetration depths and thus cure depths. For the resin with 0.15 percent (w/w) of the Tinuvin 327, a cure depth of ~30?µm was achieved as compared to ~200?µm without the light absorber. The four resin solutions were used to fabricate complex 3D microstructures, and different concentrations of Tinuvin 327 at a given irradiance and exposure energy were required for successful fabrication depending on the geometry of the micro-part (concentrations of 0.05 and 0.1 percent (w/w) provided the most accurate builds for the fan and spring, respectively). <B>Research limitations/implications</B> - Although two different concentrations of light absorber in solution were required to demonstrate successful fabrication for two different micro-part geometries (a fan and spring), the experiments were performed using a single irradiance and exposure energy. A single solution with the light absorber could have possibly been used to fabricate these micro-parts by varying irradiance and/or exposure energy, although the effects of varying these parameters on geometric accuracy, mechanical strength, overall manufacturing time, and other variables were not explored. <B>Originality/value</B> - This work systematically investigated 3D microstructure fabrication using different concentrations of a light absorber in solution, and demonstrated that different light absorption characteristics were required for different down-facing micro-features.

Fabrication of 3D biocompatible/biodegradable micro-scaffolds using dynamic mask projection microstereolithography

Choi, J.W.,Wicker, R.,Lee, S.H.,Choi, K.H.,Ha, C.S.,Chung, I. Elsevier 2009 Journal of materials processing technology Vol. No.

Microstereolithography (μSL) technology can fabricate three-dimensional (3D) tissue engineered scaffolds with controlled biochemical and mechanical micro-architectures. A μSL system for tissue engineering was developed using a Digital Micromirror Device (DMD(TM)) for dynamic pattern generation and an ultraviolet (UV) lamp filtered at 365nm for crosslinking the photoreactive polymer solution. The μSL system was designed with x-y resolution of ∼2μm and a vertical (z) resolution of ∼1μm. To demonstrate the use of μSL in tissue engineering, poly(propylene fumarate) (PPF) was synthesized with a molecular weight of ∼1200Da. The viscosity of the PPF was reduced to ∼150cP (at 50<SUP>o</SUP>C) by mixing with diethyl fumarate (DEF) in the ratio of 7:3 (w/w). Finally, ∼2% (w/w) of bis(2,4,6-trimethylbenzoyl) phenylphosphine oxide (BAPO) was added to the solution to serve as a photoinitiator. Cure depth experiments were performed to determine the curing characteristics of the synthesized PPF, and the resulting system and prepolymer were used to construct a 3D porous scaffold with interconnected pores of ∼100μm. Scanning electron microscopy (SEM), and micro-computed tomography (μCT) images of the micro-architecture illustrate that the developed μSL system is a promising technology for producing biodegradable and biocompatible 3D micro-scaffolds with fully interconnected pores.

Low-Level Polarimetric Radar Signatures in EnKF Analyses and Forecasts of the May 8, 2003 Oklahoma City Tornadic Supercell: Impact of Multimoment Microphysics and Comparisons with Observation

Dawson II, Daniel T.,Wicker, Louis J.,Mansell, Edward R.,Jung, Youngsun,Xue, Ming Hindawi Limited 2013 Advances in meteorology Vol.2013 No.-

<P>The impact of increasing the number of predicted moments in a multimoment bulk microphysics scheme is investigated using ensemble Kalman filter analyses and forecasts of the May 8, 2003 Oklahoma City tornadic supercell storm and the analyses are validated using dual-polarization radar observations. The triple-moment version of the microphysics scheme exhibits the best performance, relative to the single- and double-moment versions, in reproducing the low-<SUB>ZDR</SUB>hail core and high-<SUB>ZDR</SUB>arc, as well as an improved probabilistic track forecast of the mesocyclone. A comparison of the impact of the improved microphysical scheme on probabilistic forecasts of the mesocyclone track with the observed tornado track is also discussed.</P>

Redundancy Minimizing Techniques for Robust Transmission in Wireless Networks

Anna Kacewicz,Stephen B. Wicker 한국통신학회 2009 Journal of communications and networks Vol.11 No.6

In this paper, we consider a wireless multiple path network in which a transmitting node would like to send a message to the receiving node with a certain probability of success. These two nodes are separated by N erasure paths, and we devise two algorithms to determine minimum redundancy and optimal symbol allocation for this setup. We discuss the case with N = 3 and then extend the case to an arbitrary number of paths. One of the algorithms minimum redundancy algorithm in exponential time is shown to be optimal in several cases, but has exponential running time. The other algorithm, minimum redundancy algorithm in polynomial time, is sub-optimal but has polynomial worstcase running time. These algorithms are based off the theory of maximum-distance separable codes. We apply the MRAET algorithm on maximum-distance separable, Luby transform, and Raptor codes and compare their performance.

Dynamic Modeling of Coupled Tendon-Driven System for Surgical Robot Instrument

김지언,이민철,Ryan Blaine Wicker,윤성민 한국정밀공학회 2014 International Journal of Precision Engineering and Vol.15 No.10

This paper is the study of a surgical instrument which directly performs MIS(Minimally Invasive surgery) on a patient, instead of asurgeon. The instrument used in robot assisted laparoscopy adopts a tendon driven mechanism so that it generates hand-like surgicalmotion through aperture of trocar. To create a high DOF of motion in restricted spaces, cable systems for end-effector have beenorganized by serial kinematic chains which can cause interference among joints sharing same axis. Also, to prevent the elongationof any cable, composited and pre-extended cables, which show nonlinear characteristics, are used in surgical instrument tendonsystem. As aforementioned difficulty and complexity, there are not many studies about measuring or estimating the operating forceof instruments without sensors, which is needed for safety but still impossible in commercial systems. This paper derives governinga dynamic model of a coupled cable pulley structure while considering the material tensile characteristics of the cables. The derivedmodel can estimate the operating force on end-effector as well as states of all inner pulleys without encoders. This paper proves theavailability of proposed methodology with comparison of numerical analysis and the experimental test of 2 DOF serial kinematicchained cable pulley link apparatus.

HPMC (hydroxypropyl methylcellulose) as a fat replacer improves the physical properties of low‐fat tofu

Shin, Woo‐,Kyoung,Wicker, Louise,Kim, Yookyung John Wiley Sons, Ltd 2017 Journal of the science of food and agriculture Vol.97 No.11

<P>CONCLUSION: HPMC improved the texture of the low-fat tofu by creating a harder texture and reducing syneresis. HPMC is an effective fat replacer for lower fat soymilk. (C) 2017 Society of Chemical Industry</P>

Intermittent Embedding of Wire into 3D Prints for Wireless Power Transfer

김지언,Charlie Sullivan,Alexander Hillstrom,Ryan Wicker 한국정밀공학회 2021 International Journal of Precision Engineering and Vol.22 No.5

3D printing is rapidly moving into the realm of electronics and fully functioning devices. These devices include 3D printed plastic parts with conductive materials embedded in the plastic using additive manufacturing techniques to produce functioning circuits. However, current materials and techniques limit the amount of power that can be supplied to embedded circuits. The state of the art for embedding traditional conductive materials, such as solid metal wire, uses the continuous application of heat. Continuous heat often overheats and damages the previously printed layer of plastic material potentially ruining the part and device. Additionally, current devices with embedded electronics require either external power or embedded energy storage such as a battery. Both the continuous application of heat and the need for power affect design choices and can severely limit potential use cases of the device. This research presents analysis and demonstration of embedding traditional copper wires onto a plastic substrate using intermittent application of heat and pressure using a traditional Fused Filament Fabrication plastic print nozzle at specific points, herein referred to as embedding instances. Detailed analysis of the interaction of a heating element (print nozzle), metal wire, and plastic substrate are provided to give context for the new technology presented. High thermal conductivity in the wire conducts heat away from the heating element quickly, and continuous application of heat to the wire can melt the plastic substrate along the wire, damaging previously embedded sections of wire, especially at the start of the embedding process and after turning sharp corners while embedding the wire. Applying heat for short periods at intermittent locations is presented as a solution to this problem while still melting the plastic enough to produce the bonding necessary for the wire to be embedded into the previous printed layer of plastic substrate. This technique is then used to manufacture a pair of identical parts, each with an embedded antenna intended for wireless power transfer. Once the first layer of wire antenna is embedded, additional layers of plastic are deposited to embed the copper wire completely within the part. Four separate embedded antenna layers of embedded wire are connected to create a multi layered, multi coil antenna in two identical parts. Experiments were then run to prove the viability of wireless power transfer from one part to the other.

클라우드 기반 3D 프린팅 활용 생산 시스템 통합 연구

김지언,David Espaline,Eric MacDonald,Ryan B. Wicker,김다혜,성지현,이재욱 한국기계가공학회 2015 한국기계가공학회지 Vol.14 No.3

After the US government declared 3D printing technology a next-generation manufacturing technology, there have been many practical studies conducted to expand 3D printing technology to manufacturing technologies, called AMERICA MAKES. In particular, the Keck Center, located at the University of Texas at El Paso, has studied techniques for easily combing the 3D stacking process with space mobility and expanded these techniques to simultaneous staking techniques for multiple materials. Additionally, it developed convergence manufacturing techniques, such as direct inking techniques, in order to produce a module structure that combines electronic circuits and components, such as CUBESET. However, in these studies, it is impossible to develop a unified system using traditional independent through simple sequencing connections. This is because there are many problems in the integration between the stacking modeling of 3D printers and post-machining, such as thermal deformations, the precision accuracy of 3D printers, and independently driven coordinate problems among process systems. Therefore, in this paper, the integration method is suggested, which combines these 3D printers and subsequent machining process systems through an Internet-based cloud. Additionally, the sequential integrated system of a 3D printer, an NC milling machine, machine vision, and direct inking are realized.