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Li C.-H.,National Dong Hwa University | Hu S.-H.,Dahan Institute of Technology | Tay K.-W.,Wufeng University | Fu Y.-P.,National Dong Hwa University
Ceramics International | Year: 2012

This study investigates Sm 0.5Sr 0.5CoO 3-δ (SSC)-Ce 0.8Sm 0.2O 1.9 (SDC) composite cathodes with a gradual change in composition from electrolyte to the cathode in an attempt to discover a potential approach applicable to solid oxide fuel cells (SOFCs). The gradual change in composition from electrolyte to cathode shows the decline in charge transfer resistance (R 2) and gas phase diffusion resistance (R 3). Because the value of R 3 is always larger than R 2 and R 3 significantly dominates the total cathode polarization resistance (R P) at temperatures within the range of 750-850 °C, i.e., in this temperature range, the rate-determining step is dominated by the diffusion or dissociative adsorption of oxygen. The functionally gradient cathode with a graded interface between cathode and electrolyte reveals both a higher exchange current density (i 0) and a lower activation energy for oxygen reduction reaction (ORR), which suggests that the ORR kinetics can be improved by using the configuration of a functionally gradient cathode. © 2011 Elsevier Ltd and Techna Group S.r.l. All rights reserved.

Peng C.-C.,National Cheng Kung University | Hsue A.W.-J.,Dahan Institute of Technology | Chen C.-L.,National Cheng Kung University
Nonlinear Dynamics | Year: 2011

This study presents robust control architecture in the sense of variable structure control via a backstepping design. By using systematic backstepping design techniques, closed-loop behavior of an n-order nonlinear system can be transformed into a stability and convergence problem of a fast switched 2nd order system. There are two main parts contained within the proposed control algorithm; one is a nominal control effort generated according to the Lyapunov stability criterion during recursive backstepping processes, and the other belongs to a smooth robust control law designed to eliminate the effects of unknown lumped perturbations. Finally, a Genesio system is used as an illustrated example to demonstrate the robustness of the control algorithm. The feasibility and properties of the proposed method are given by numerical simulations. © 2010 Springer Science+Business Media B.V.

Huang C.-H.,Dahan Institute of Technology | Lin S.-K.,National Chung Hsing University | Chang C.-S.,Sudan University of Science and Technology | Chen H.-J.,National Chung Hsing University
Construction and Building Materials | Year: 2013

Two types of Class F fly ash with 4.6% and 7.8% loss on ignition were used for an experimental investigation dealing with concrete incorporating very high volumes of Class F fly ash (HVFA). A rational mix design method was developed for concrete with 20-80% fly ash replacement for cement. Tests were performed for fresh and hardened concrete properties. Test results indicated that the setting times and the air content of fly-ash concrete increased as the fly ash replacement level increased. The compressive and flexural strength of the HVFA concrete mixtures demonstrated continuous and significant improvement at late ages of 91 and 365 days. Relation was formulated for flexural and compressive strength for all grades of HVFA concrete. The concrete mixture containing low-LOI fly ash exhibited superior mechanical properties than those of the corresponding mixture containing high-LOI fly ash. These results confirm the feasibility that up to 80% of Class F fly ash can be suitably used as cement replacement in concrete by using a rational mixture proportions. © 2013 Elsevier B.V. All rights reserved.

Huang C.-H.,Dahan Institute of Technology | Wang S.-Y.,National Chung Hsing University
Construction and Building Materials | Year: 2013

This study assesses the possible use of water treatment sludge for the production of lightweight aggregate (LWA), and focuses on the engineering properties of concrete made from this LWA. The experiments in this study involve 10 sludges from ten water treatment plants in Taiwan. All sludges can be used to manufacture LWAs in the laboratory, and exhibit a particle density (ρa) of 0.65-2.05 g/cm3 and water absorption of 0.5-15%. Five sludges are suitable for manufacturing both structural LWA (ρa = 1.2-1.8 g/cm3) and non-structural LWA (ρa < 1.0 g/cm3), and the other five sludges are only suitable for manufacturing structural LWA. The sludge collected from the Hsing-Zu plant was successfully used to produce both structural and non-structural LWA on a large scale using a commercial rotary kiln. The resulting aggregates possessed a particle density of 1.35 g/cm3 or 0.98 g/cm3 and a bulk density of 726 kg/m3 or 518 kg/m3 for the structural LWA and non-structural LWA, respectively. The structural LWA meets the ASTM C330 requirements, with a bulk density less than 880 kg/m3 for light coarse aggregate, and is a suitable LWA for structural concrete. The engineering properties of the concrete made from the structural LWA comply with the requirements of structural lightweight concrete. © 2013 Elsevier Ltd. All rights reserved.

Peng J.-L.,National Yunlin University of Science and Technology | Wu C.-W.,National Yunlin University of Science and Technology | Chan S.-L.,Hong Kong Polytechnic University | Huang C.-H.,Dahan Institute of Technology
Journal of Constructional Steel Research | Year: 2013

Scaffold design has become a popular research topic in recent years, likely because of the high rate of collapse for this structural form and its nature of under estimated loads close to the design loads, as opposed to permanent structures under remote statistical live and wind loads. This paper investigates the load capacities and failure modes of the system scaffold structure in various setups in construction and it is based on experimental tests supplemented by analyses. The parameters for system scaffolds studied in this paper include number of stories, ground heights, boundary conditions, presence of diagonal bracings and joint positions. The numerical studies quantify the load capacity of a system scaffold against addition of diagonal bracings. However, the load capacities of a system scaffold structure with varied spigot-joint positions on vertical props and with varied ground heights do not affect much the load capacity. Since the axial force of diagonal bracings on a system scaffold structure does not significantly increase with the vertical load, the diagonal bracings of the structure can be reduced in size for cost saving. A comparison between analyses and experimental tests conducted in this study confirmed the joint stiffness of different members used in the system scaffolds. Using the joint stiffness, the ultimate design loads of the system scaffolds with different number of stories were computed and quantified. The findings will be useful for accurate determination of the ultimate load capacity of complex system scaffolds used in construction sites. © 2013 Elsevier Ltd. All rights reserved.

Fu Y.-P.,National Dong Hwa University | Li C.-H.,National Dong Hwa University | Hu S.-H.,Dahan Institute of Technology
Journal of the Electrochemical Society | Year: 2012

This study investigates the electrochemical properties of three different configurations of Sm 0.5Sr 0.5CoO 3-δ (SSC)-based cathodes and attempts to discover a potential approach applicable to solid oxide fuel cells (SOFCs). The functionally gradient SSC cathode and Ce 0.8Sm 0.2O 1.9 (SDC)-infiltrated SSC cathode both reveal the better electrochemical properties compared to that of the 70 SSC- 30 SDC composite cathode. The functionally gradient Sm 0.5Sr 0.5CoO 3-δ cathode with better interface of SSCSDC may be achieved by the gradual change in composition from electrolyte to cathode, resulting in the decline in charge transfer resistance and gas phase diffusion resistance. Whereas, the dramatic decrease in cathode polarization resistance for SDC-infiltrated SSC cathode is mainly attributed to the creation of SDCSSC phase boundaries. The newly formed SDC on the SSC surface with highly porous would allow gas-phase molecules to easily diffuse to the SDCSSC boundaries, which considerably increase the electrochemical sites for oxygen reduction reaction (ORR). The SDC-infiltrated SSC cathode reveals the lowest cathode polarization resistance (R P), the lowest activation energies of cathode polarization resistance and the lowest over activation energy for the ORR among all cathode configurations. Noticeably, the cathode performance in SOFCs can be significantly improved by infiltrating nanoparticles of SDC into an SSC porous backbone. © 2012 The Electrochemical Society.

Liu H.-Y.,Dahan Institute of Technology | Yen R.Y.,Tamkang University
IEEE Transactions on Vehicular Technology | Year: 2010

For joint maximum-likelihood (ML) frequency tracking and channel estimation using orthogonal frequency-division multiplexing (OFDM) training blocks in OFDM communications over mobile wireless channels, a major difficulty is the local extrema or multiple-solution complication arising from the multidimensional log-likelihood function. To overcome this, we first obtain crude ML frequency-offset estimators using single-time-slot samples from the received time-domain OFDM block. These crude frequency estimators are shown to have unique closed-form solutions. We then optimally combine these crude frequency estimators in the linear-minimum-mean-square-error (LMMSE) sense for a more accurate solution. Finally, by alternatively updating the LMMSE frequency estimator and the ML channel estimator through adaptive iterations, we successfully avoid the use of a multidimensional log-likelihood function, hence obviating the complex task of global solution search and, meanwhile, achieve good estimation performance. Our estimators have mean square errors (MSEs) tightly close to Cramer-Rao bounds (CRBs) with a wide tracking range. © 2006 IEEE.

Fu Y.-P.,National Dong Hwa University | Hu S.-H.,Dahan Institute of Technology
Ceramics International | Year: 2010

Magnesium-substituted lithium ferrite of different composition (Li 0.5Fe 2.5-xMg xO 4-δ) were prepared for x = 0.0-1.0 by conventional ceramic technique. The crystal structure characterization and morphology were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM). Initial permeability and quality factor were measured in the frequency range of 1 kHz to 100 MHz. The permeability decreased gradually from μ (f = 10 MHz) = 34.0 for Li 0.5Fe 2.5O 4 to μ (f = 10 MHz) = 11.5 for Li 0.5Fe 1.5Mg 1.0O 4. Electrical conductivity measurements were carried in the range of 250-700 °C in air. The maximum electrical conductivity, σ 700 °C = 0.1274 S/cm has been found to be for Li 0.5Fe 2.5O 4 specimen. With increasing Mg-substituted content, the decreased in the electrical conductivity. © 2010 Elsevier Ltd and Techna Group S.r.l.

Huang C.-H.,Dahan Institute of Technology
Journal of Materials in Civil Engineering | Year: 2014

To investigate the effect of reinforcement corrosion on the bond properties between concrete and reinforcing steel bar, pullout tests were conducted on a total of 20 specimens using corroded reinforcement bars embedded in concrete specimens. No. 3 (9.5-mm diameter) and No. 6 (19-mm diameter) bars corroded by an accelerated corrosion method were selected for testing. Two groups of corrosion specimens were prepared: one was whole-surface corroded (100%), and the other was partial-surface corroded with 40, 60, and 100% corrosion. Each group of specimens included four levels of corrosion: 3, 5, 10, and 15%. Results indicate that the tensile strength of steel bar decreases with the increase of corrosion level. Corrosion levels less than 3% present a minor tensile-strength reduction of approximately 3%, whereas the tensile strength may decrease to 75-90% when the corrosion level increases more than 10%. The critical bond strength and ultimate bond strength of corroded bars may increase slightly with corrosion level less than 3%, but tend to decrease as the corrosion level exceeds 3% and, likewise, to decrease with increasing corroded-surface percentage of steel bar. The range of partial-surface corrosion shows no significant effect on yield strength and ultimate strength of the steel bar. However, the critical bond strength and ultimate bond strength in a reinforcing steel bar decrease with the percentage of corroded surface for various corrosion levels when the corroded area increases from 40-100%. © 2014 American Society of Civil Engineers.

Hu S.-H.,Dahan Institute of Technology | Hu S.-C.,National Dong Hwa University
Journal of the Air and Waste Management Association | Year: 2014

Incineration is a traditional method of treating sewage sludge and the disposal of derived ash is a problem of secondary waste treatment. In this study, sewage sludge ash (SSA) was coated with ferrite through a ferrite process and then used as an adsorbent for ionic dyes (methylene blue [MB] and Procion Red MX-5B [PR]). The modified SSA possessed surface potential that provided electrostatic attraction toward MB and PR. Adsorbent FA10 (named on the basis of being produced from 10 g of SSA in the ferrite process) was used for the adsorption of MB. Ideal pH for adsorption was 9.0 and maximum adsorption capacity based on Langmuir isotherm equation was 22.03 mg/g. Adsorbent FA2.5 (named on the basis of being produced from 2.5 g of SSA in the ferrite process) was used for PR adsorption. Ideal pH for adsorption was 3.0 and the maximum adsorption capacity (calculated as above) was 28.82 mg/g. Kinetic results reveal that both MB and PR adsorption fit the pseudo-second-order kinetic model better than the pseudo-first-order model. The values of activation energy calculated from rate constants were 61.71 and 9.07 kJ/mol for MB and PR, respectively. Magnetic modified adsorbent could be synthesized from sewage sludge ash (SSA). In this study, the adsorption ability of SSA toward ionic dye (methylene blue [MB] and Procion Red MX-5B [PR]) was enhanced by ferrite process. The synthesized Fe3O4 can act as an active site and provide electrostatic attraction toward cationic dye and anionic dye at different pH. The application of magnetic modified adsorbent in wastewater treatment can not only recycle the SSA, but also make SSA become an environmentally friendly material. © 2014 Copyright 2013 A&WMA.

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