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Paglinawan A.C.,Mapua Institute of Technology | Paglinawan C.C.,Mapua Institute of Technology | Avendano G.O.,Mapua Institute of Technology | Wang Y.-H.,CYCU | Chung W.-Y.,CYCU
2011 International Symposium on Integrated Circuits, ISIC 2011 | Year: 2011

A novel power management system with mode switching that widely applies to implantable biomedical devices is presented. Controlling the power transceiver output, monitor and simultaneously have special applications in the power path, are some of its major functions. Furthermore, a new temperature sensor and a temperature feedback regulated charger were designed for long term monitoring and small temperature variations. It also includes a system-on-enable (SOE) circuit and power feedback to increase system stability and accuracy. Moreover, constant power on the novel multi-level comparator was developed to reduce power and area consumption at the same time. The system also boasts a novel drug driver circuitry for implantable glucose biosensing applications. The whole system was fabricated in a TSMC 0.35μm 2P4M 3.3/5V CMOS technology it occupies a small area of 2.382 × 2.374 mm 2 (core size = 2.200 × 1.086 mm 2) and only dissipated 36.3mW of power. The transistors were designed in moderate inversion region to arrive at high performance and low power consumption. An in-depth analysis of the proposed system has been undertaken, and experimental results match the circuit simulations. © 2011 IEEE.

Chang R.-H.,Chung Yuan Christian University | Young M.N.,Mapua Institute of Technology | Hildawa M.I.,Massachusetts Institute of Technology | Santos I.J.R.,Massachusetts Institute of Technology | Pan C.-H.,CYCU
Lecture Notes in Engineering and Computer Science | Year: 2015

Modern portfolio theory pioneered by Markowitz assumed that the market is efficient and investors are rational and homogeneous, however investors may have different perception on the market. Behavioral portfolio optimization is seeking an optimal portfolio suitable for the investor's characteristic and perspective. On the other hand, irrationalities, such as over/under- reaction, representativeness and mental accounting, have been shown to exist among investors and that the potential collective influence of irrational behaviors may stimulate the stock prices and likely cause large price movement. This study considers the portfolio optimization problem taking the advantage of price movements of stocks caused by these irrational behaviors while still considering the prospect of the investor. We consider behavioral stock (called B-stock) that can be significantly impacted by over-reaction and under-reaction of the investors. Through statistical testing, we determine the behavioral stocks and when will the positive effect on return will more likely to take place when over-reaction and under-reaction occurs. In considering the prospect of the investor, we apply SP/A theory to assign the weights on the future returns and, based on the scenarios, we apply a sample mixed integer program to determine the portfolio that has the most likely chance to have the positive price effect from the B-stocks while the return is within a predetermined loss threshold. This model is a combination of the risk-seeking and safety-first criterions. From the back tests, the empirical results are consistent with the expectation and they are promising compared with the market and mean-variance model.

Chang K.-C.,Chung Yuan Christian University | Hsu M.-H.,Chung Yuan Christian University | Lu H.-I.,Center for Nanotechnology at | Lai M.-C.,Chung Yuan Christian University | And 7 more authors.
Carbon | Year: 2014

Nanocasting was used to develop epoxy/graphene composites (EGCs) as corrosion inhibitors with hydrophobic surfaces (HEGC). The contact angle of water droplets on a sample surface can be increased from ∼82 (epoxy surface) to ∼127 (hydrophobic epoxy and EGC). It should be noted that EGC coating was found to provide an excellent corrosion protection effect on cold-rolled steel (CRS) electrode. Enhancement of corrosion protection using EGC coatings could be attributed to the following three reasons: (1) epoxy could act as a physical barrier coating, (2) the hydrophobicity repelled the moisture and further reduced the water/corrosive media adsorption on the epoxy surface, preventing the underlying metals from corrosion attack, and (3) the well-dispersed graphene nanosheets (GNSs) embedded in HEGC matrix could prevent corrosion owing to a relatively higher aspect ratio than clay platelets, which enhances the oxygen barrier property of HEGC. © 2013 Elsevier Ltd. All rights reserved.

Chang K.-C.,Chung Yuan Christian University | Ji W.-F.,Chung Yuan Christian University | Lai M.-C.,Chung Yuan Christian University | Hsiao Y.-R.,Chung Yuan Christian University | And 5 more authors.
Polymer Chemistry | Year: 2014

In this paper, the surface of a PMMA/graphene nanocomposite (PGN) with biomimetic hydrophobic structures was first prepared by the nanocasting technique and applied in corrosion protection coatings. First of all, a transparent soft template with negative patterns of a Xanthosoma sagittifolium leaf can be fabricated by thermal curing of the polydimethylsiloxane (PDMS) pre-polymer in molds at 60°C for 4 h, followed by detaching the PDMS template from the surface of the natural leaf. Subsequently, PGN with a hydrophobic surface (HPGN) of the biomimetic natural leaf was fabricated, using PDMS as the negative template, through casting onto a cold rolled steel (CRS) electrode. The surface morphology of as-synthesized hydrophobic PMMA (HP) and PGN coatings was found to show lots of micro-scaled mastoids, each decorated with many nano-scaled wrinkles, which were investigated systematically by scanning electron microscopy (SEM). The contact angle (CA) of a water droplet on the sample surface can be increased from ∼80°for the PMMA surface to ∼150°for HP and HPGN and the sliding angle (SA) decreased from ∼60°to 5°. The morphological studies of the dispersion capability of graphene nanosheets (GNSs) in the polymer matrix can be carried out by observation under a transmission electron microscope (TEM). It should be noted that HPGN coating was found to reveal an advanced corrosion protection effect on the CRS electrode as compared to that of neat PMMA and HP coatings based on a series of electrochemical corrosion measurements in a 3.5 wt% NaCl electrolyte. The enhancement of corrosion protection of HPGN coatings on the CRS electrode could be interpreted by the following two possible reasons: (1) the hydrophobicity repelled the moisture and further reduced the water/corrosive media adsorption on the epoxy surface, preventing the underlying metals from corrosion attack, as evidenced by contact angle (wettability) measurements. (2) The well-dispersed GNSs embedded in the HPGN matrix could hinder corrosion due to their relatively higher aspect ratio than clay platelets, which further effectively enhance the oxygen barrier property of HPGN, as evidenced using a gas permeability analyzer (GPA). This journal is © 2014 The Royal Society of Chemistry.

Ji W.-F.,Chung Yuan Christian University | Chang K.-C.,Chung Yuan Christian University | Lai M.-C.,Chung Yuan Christian University | Li C.-W.,Chung Yuan Christian University | And 4 more authors.
Composites Part A: Applied Science and Manufacturing | Year: 2014

In this study, the effects of different carboxylic groups content for thermally reduced graphene oxides (TRGs) in improving physical properties of PMMA composites was reported. The PMMA/thermally reduce graphene oxides (TRGs) composites (PTC) were prepared by an easy and environmentally friendly UV-curing method in the presence of TRGs with different carboxylic groups content TRGs and then characterized by Fourier-Transformation infrared spectroscopy. The different levels of TRGs with higher carboxylic group contents were observed the better dispersion capability in PTC than TRGs with lower carboxylic groups content and non-functionalized TRGs based on the morphological observation of transmission electron microscopy (TEM). The better dispersion capability of the TRGs with higher carboxylic group contents in PTC membranes was found to lead significant enhanced thermal stability (TGA, DSC), mechanical strength (DMA), thermal conductivity (HD) and gas permeability (GPA). © 2014 Elsevier Ltd. All rights reserved.

Chang K.C.,Chung Yuan Christian University | Hsu C.H.,Chung Yuan Christian University | Ji W.F.,Chung Yuan Christian University | Chang C.H.,Chung Yuan Christian University | And 4 more authors.
Express Polymer Letters | Year: 2014

In this study, electroactive polyimide (EPI)/graphene nanocomposite (EPGN) coatings were prepared by thermal imidization and then characterized by Fourier transformation infrared (FTIR) and transmission electron microscope (TEM). The redox behavior of the as-prepared EPGN materials was identified by in situ monitoring for cyclic voltammetry (CV) studies. Demonstrating that EPGN coatings provided advanced corrosion protection of cold-rolled steel (CRS) electrodes as compared to that of neat EPI coating. The superior corrosion protection of EPGN coatings over EPI coatings on CRS electrodes could be explained by the following two reasons. First, the redox catalytic capabilities of amino-capped aniline trimer (ACAT) units existing in the EPGN may induce the formation of passive metal oxide layers on the CRS electrode, as indicated by scanning electron microscope (SEM) and electron spectroscopy for chemical analysis (ESCA) studies. Moreover, the well-dispersed carboxyl-graphene nanosheets embedded in the EPGN matrix hinder gas migration exponentially. This would explain enhanced oxygen barrier properties of EPGN, as indicated by gas permeability analysis (GPA) studies. © BME-PT.

Chang K.C.,Chung Yuan Christian University | Ji W.F.,Chung Yuan Christian University | Li C.W.,Chung Yuan Christian University | Chang C.H.,Chung Yuan Christian University | And 3 more authors.
Express Polymer Letters | Year: 2014

We present comparative studies on the effect of varying the carboxylic-group content of thermally reduced graphene oxides (TRGs) on the anticorrosive properties of as-prepared poly(methyl methacrylate) (PMMA)/TRG composite (PTC) coatings. TRGs were formed from graphene oxide (GO) by thermal exfoliation. The as-prepared TRGs were then characterized using Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Subsequently, the PTC materials were prepared via a UV-curing process and then characterized using FTIR spectroscopy and transmission electron microscopy (TEM). PTC coatings containing TRGs with a higher carboxylic-group content exhibited better corrosion protection of a cold-rolled steel electrode that those with a lower carboxylic-group content. This is because the well-dispersed TRG with a higher carboxylic-group content embedded in the PMMA matrix effectively enhances the oxygen barrier properties of the PTC. This conclusion was supported by gas permeability analysis. © BME-PT.

Hong Y.-Y.,Chung Yuan Christian University | Lai Y.-Z.,CYCU | Hsiao M.-C.,CYCU | Chang Y.-R.,INER | And 2 more authors.
2012 IEEE International Conference on Power System Technology, POWERCON 2012 | Year: 2012

Development of microgrid is one of the solutions for keeping the power system intact to embed the distributed generations while considering renewable energies for substantial environment. This paper investigates the operation modes for the first outdoor microgrid test bed in Taiwan, whose generation capacity is 517.5-kW. The distributed generations in the microgrid system, which has 18 AC buses and 4 DC buses, include gas turbine, wind-turbine, PV and battery. The models of rectifier, booster and inverter are considered for both transient and dynamic simulations. The operation modes (power flow and voltage-frequency) are studied for both conditions of grid-tied and islanding operations. Preliminary simulation results reveal that proper operation modes for gas-turbine generations are crucial while other distributed generations are operated in the power mode. © 2012 IEEE.

Wellem T.,CYCU | La Y.-K.,CYCU
Electronics Letters | Year: 2016

A sketch-guided filtering scheme for assisting superspreader detection in the measurement of high-speed network traffic is proposed. The scheme comprises of an array of linear-counting sketches that rapidly eliminates flows with potentially low fan-out during a measurement interval. Based on the results of simulations obtained using realworld network traces, the filter can eliminate up to 90% of the flows of non-superspreader sources and improve the accuracy of superspreader identification. Furthermore, the proposed scheme has a smaller fan-out estimation error and consumes less memory than previously developed approaches. The hardware implementation can process network traffic at a throughput of 27 Gbit/s. © 2016 The Institution of Engineering and Technology.

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