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In situ reduction of gold nanoparticles in PDMS matrices and applications for large strain sensing
Donghyeon Ryu,Kenneth J. Loh,Robert Ireland,Mohammad Karimzada,Frank Yaghmaie,Andrea M. Gusman 국제구조공학회 2011 Smart Structures and Systems, An International Jou Vol.8 No.5
Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite’s strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.
In situ reduction of gold nanoparticles in PDMS matrices and applications for large strain sensing
Ryu, Donghyeon,Loh, Kenneth J.,Ireland, Robert,Karimzada, Mohammad,Yaghmaie, Frank,Gusman, Andrea M. Techno-Press 2011 Smart Structures and Systems, An International Jou Vol.8 No.5
Various types of strain sensors have been developed and widely used in the field for monitoring the mechanical deformation of structures. However, conventional strain sensors are not suited for measuring large strains associated with impact damage and local crack propagation. In addition, strain sensors are resistive-type transducers, which mean that the sensors require an external electrical or power source. In this study, a gold nanoparticle (GNP)-based polymer composite is proposed for large strain sensing. Fabrication of the composites relies on a novel and simple in situ GNP reduction technique that is performed directly within the elastomeric poly(dimethyl siloxane) (PDMS) matrix. First, the reducing and stabilizing capacities of PDMS constituents and mixtures are evaluated via visual observation, ultraviolet-visible (UV-Vis) spectroscopy, and transmission electron microscopy. The large strain sensing capacity of the GNP-PDMS thin film is then validated by correlating changes in thin film optical properties (e.g., maximum UV-Vis light absorption) with applied tensile strains. Also, the composite's strain sensing performance (e.g., sensitivity and sensing range) is also characterized with respect to gold chloride concentrations within the PDMS mixture.
Unsupervised Spoken Language Understanding for a Multi-Domain Dialog System
Donghyeon Lee,Minwoo Jeong,Kyungduk Kim,Seonghan Ryu,Lee, Gary Geunbae IEEE 2013 IEEE - ACM Transactions on Audio, Speech, and Lang Vol.21 No.11
<P>This paper proposes an unsupervised spoken language understanding (SLU) framework for a multi-domain dialog system. Our unsupervised SLU framework applies a non-parametric Bayesian approach to dialog acts, intents and slot entities, which are the components of a semantic frame. The proposed approach reduces the human effort necessary to obtain a semantically annotated corpus for dialog system development. In this study, we analyze clustering results using various evaluation metrics for four dialog corpora. We also introduce a multi-domain dialog system that uses the unsupervised SLU framework. We argue that our unsupervised approach can help overcome the annotation acquisition bottleneck in developing dialog systems. To verify this claim, we report a dialog system evaluation, in which our method achieves competitive results in comparison with a system that uses a manually annotated corpus. In addition, we conducted several experiments to explore the effect of our approach on reducing development costs. The results show that our approach be helpful for the rapid development of a prototype system and reducing the overall development costs.</P>
An MCFC operation optimization strategy based on PID auto-tuning control
Lee, Donghyeon,Cheon, Yujin,Ryu, Jun-Hyung,Lee, In-Beum Pergamon Press 2017 International journal of hydrogen energy Vol.42 No.40
<P><B>Abstract</B></P> <P>Molten Carbonate Fuel Cell (MCFC) has been emerging as a promising renewable power system. It is still challenging to operate the MCFC to meet its varying demands because of its nonlinearity and complex dynamics. This paper proposes a novel MCFC operation framework based on PID auto-tuning control. A case study is presented to illustrate the applicability of the strategy with some comments.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The operation of molten carbonate fuel cells is challenging because of nonlinearity and complex dynamics. </LI> <LI> The power output of MCFCs should be adjusted to meet the varying demand. </LI> <LI> A PID auto-tuning controller design is proposed to optimize the operation of MCFC systems. </LI> <LI> A mathematical model of the MCFC is developed and validated with commercial data. </LI> </UL> </P>
Kim, Donghyeon,Lim, Daeseong,Ryu, Hyeonjeong,Lee, Jungjun,Ahn, Sung Il,Son, Bong Soo,Kim, Seung-Joo,Kim, Chang Hae,Park, Jung-Chul ACS AMERICAN CHEMICAL SOCIETY 2017 Inorganic Chemistry Vol.56 No.20
<P>Blue-emitting Ca2-xMgxSiO4:Ce (0.0 <= x <= 1.0) phosphors were successfully synthesized and characterized. Rietveld refinement revealed that four main phases exist within the solid-solution range of CaO-MgO-SiO2, namely, beta-Ca2SiO4 (Mg (x) = 0.0), Ca14Mg2(SiO4)(8) (Mg (x) = 0.25), Ca3Mg(SiO4)(2) (Mg (x) = 0.5), and CaMgSiO4 (Mg (x) = 1.0). The variation of the IR modes was more prominent with increasing Mg2+ content in the Ca2-xMgxSiO4 materials. The sharing of O atoms of the SiO4- tetrahedra by the MgO6-octahedra induced weakening of the Si O bonds, which resulted in the red shift of the [SiO4] internal modes and appearance of a Mg-O stretching vibration at similar to 418 cm(-1). Raman measurement revealed that the change of the Ca-O bond lengths because of the Mg2+-substitution directly reflected the frequency shift of the Si-O stretching-Raman modes. Notably, the thermal stability of Ca2-xMgxSiO4:Ce (Mg (x) > 0.0) phosphors was superior to that of beta-Ca2SiO4:Ce (Mg (x) = 0.0) as confirmed by temperature-dependent photoluminescence (PL) measurements. This indicated that Mg2+ ions play an important role in enhancement of the thermal stability. In combination with the results from PL and electroluminescence (EL), it was elucidated that the luminous efficiency of Ca2-xMgxSiO4:Ce (Mg (x) = 0.1) was approximately twice as much as beta-Ca2SiO4:Ce (Mg (x) = 0.00), directly indicating a 'Mg2+-substitution effect'. The large enhancements of PL, EL, and thermal stability because of Mg2+-substitution may provide a platform in the discovery of more efficient phosphors for NUV-LEDs.</P>
Pancreatic Pseudocyst after Endoscopic Ultrasound-Guided Fine Needle Aspiration of Pancreatic Mass
Kwanghyun Chung,Ji-Kon Ryu,Hong Sang Oh,Ji Yeon Seo,Eunhyo Jin,Donghyeon Lee,Yong-Tae Kim,Yong Bum Yoon 대한소화기내시경학회 2012 Clinical Endoscopy Vol.45 No.4
Endoscopic ultrasound-guided fine needle aspiration (EUS-FNA) is well known as a safe diagnostic procedure. We report the first case of pancreatic pseudocyst after EUS-FNA of the pancreatic body mass. A 60-year-old male underwent EUS-FNA for incidentally detected pancreatic solid mass which was suspected as neuroendocrine tumor. Two weeks later, the patient visited emergency room with acute abdominal pain and right upper quadrant tenderness; leukocytosis and elevated C-reactive protein, amylase, and lipase levels were noted. Computed tomography discovered newly developed 11.5×9.5 cm sized cystic mass communicating with the main pancreatic duct. Cyst fluid analysis revealed amylase level of 3,423 U/L and fluid culture isolated Streptococcus parasanguinis. The cystic mass corresponds with pancreatic pseudocyst. FNA induced main pancreatic duct injury and fluid leakage may cause it. Endoscopists who perform EUS-FNA must remember that pancreatic main duct injury can occur as one of severe complications and that it could be treated successfully with endoscopic internal drainage.