Microstructure and Mechanical Properties of (TiZrHf)50(NiCoCu)50 High Entropy Alloys

Chih‑Hsuan Chen,Yue‑Jin Chen,Jia‑Jyun Shen 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.5

The microstructure and mechanical properties of pseudo-binary (TiZrHf)50(NiCoCu)50 high entropy alloys(HEAs) with B2 matrix were investigated in this study. The studied HEAs includes Ti40Zr10Ni40Co5Cu5,Ti30Zr20Ni30Co10Cu10,Ti25Zr25Ni16.67Co16.67Cu16.67,Ti30Zr10Hf10Ni30Co10Cu10,Ti20Zr15Hf15Ni20Co15Cu15,andTi16.67Zr16.67Hf16.67Ni16.67Co16.67Cu16.67. XRD and SEM analyses revealed that all studied HEAs were a mixture of B2 andC15 intermetallic phases, instead of a single solid solution, due to their highly negative enthalpy of mixing and the relativelylarge difference in atomic radii. The B2 matrix was found capable of forming a solid solution of all six elements in a widecomposition range. The lattice constants of B2 and C15 phases increase linearly with increasing the difference in atomicradii. Additionally, the microhardness of these HEAs increases from 409 to 595 HV with the increasing difference in atomicradii as well. Compression tests demonstrated substitution of Zr with Hf can improve the ductility. In all studied HEAs, theTi30Zr10Hf10Ni30Co10Cu10HEA achieves a great balance between yield strength, ultimate compressive strength, and fracturestrain of 1574 MPa, 1933 MPa, and 6.5%, respectively.

Turning Dynamics and Equilibrium of Two-Wheeled Vehicles

Chih-Keng Chen,Thanh-Son Dao,Chih-Kai Yang 대한기계학회 2005 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.19 No.1S

The equations of motion of two-wheeled vehicles, e g bicycles or motorcycles, are developed by using Lagrange's equations for quasi-coordinates The pure rolling constraints between the ground and the two wheels ale considered m the dynamical equations of the system For each wheel, two nonholonomic and two holonomic constraints are introduced in a set of differentials algebraic equations (DAE) The constraint Jacobian matrix is obtained by collecting all the constraint equations and converting them into the velocity form Equilibrium, an algorithm for searching for equilibrium points of two-wheeled vehicles and the associated problems are discussed Formulae for calculating the radii of curvatures of ground-wheel contact paths and the reference point are also given<br/>

Effects of aging on the phase transformation and sintering properties of coprecipitated Al₂O₃-ZrO₂ powders

Chih-Cheng Chen,Hsing-I Hsiang,Fu-Su Yen 한양대학교 세라믹연구소 2008 Journal of Ceramic Processing Research Vol.9 No.1

In this study, the effects of aging on the crystalline phases, crystallite sizes and sintering properties of coprecipitated Al₂O₃- ZrO₂ powders are investigated using thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffractometry (XRD), dilatometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coprecipitated Al₂O₃- ZrO₂ powder aging in the solution promoted the dissolution and reprecipitation process, which resulted in the boehmite structure subsequently transforming into bayerite. The densification and microstructural development of the coprecipitated Al₂O₃-ZrO₂ powders were dependent upon the aging time which shifted the θ→α-Al₂O₃ phase transformation to a higher temperature, lowered the crystallite growth rate, and prevented the occurrence of intragranular ZrO₂ particles during sintering. In this study, the effects of aging on the crystalline phases, crystallite sizes and sintering properties of coprecipitated Al₂O₃- ZrO₂ powders are investigated using thermogravimetry (TG), differential thermal analysis (DTA), X-ray diffractometry (XRD), dilatometry, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Coprecipitated Al₂O₃- ZrO₂ powder aging in the solution promoted the dissolution and reprecipitation process, which resulted in the boehmite structure subsequently transforming into bayerite. The densification and microstructural development of the coprecipitated Al₂O₃-ZrO₂ powders were dependent upon the aging time which shifted the θ→α-Al₂O₃ phase transformation to a higher temperature, lowered the crystallite growth rate, and prevented the occurrence of intragranular ZrO₂ particles during sintering.

Research on the Performance of Protocols and the Evaluation Metric for VIDEO Transmissions in an Ad Hoc Network

Chen, Ruey-Shin,Chao, Louis R.,Chen, Ching-Piao,Tsai, Chih-Hung The Korean Society for Quality Management 2009 The Asian Journal on Quality Vol.10 No.1

Video transmission effectiveness in the Ad Hoc network is becoming important recently, if different routing protocols are applied. Some researchers conclude that the reactive protocols are better for file transfer protocol (FTP) and constant bit rate (CBR) or hypertext transfer protocol (HTTP) transmission in an Ad Hoc wireless network but the performance report of video transmission is not much. This study adopts Qualnet (Network Simulator) as a simulation tool for environmental designing and performance testing, and employs an experimental design with eight groups. Our experiment shows that: (1) The performance of AODV (reactive) protocol is better than DSDV, ZRP and DSR when the transmission load has only one video stream; (2) Proactive (DSDV) and Hybrid protocols (ZRP) are better for a smaller Ad Hoc network when it transmits a video stream with some applications (VoIP, FTP and CBR). We conclude that packet loss rate is sensitive to the quality of video transmission and it has negative relationship with Peak Signal-to-Noise Ratio (PSNR) value. In addition, our experiment also shows that PSNR is a simple Metric for the performance evaluation of video transmission.

Pricing and Hedging European Energy Derivatives: A Case Study of WTI Oil Options

Chih-Chen Hsu,Shih-Kuei Lin,Ting-Fu Chen 한국증권학회 2014 Asia-Pacific Journal of Financial Studies Vol.43 No.3

This study extends the mean-reversion dynamic framework of (Pilipovic, Energy risk: Valuingand managing energy derivatives, 1997) and (Schwartz, The stochastic behavior of commodityprices: Implications for pricing and hedging, Journal of Finance 52, 1997, 923) and focuses ondeveloping a variety of continuous-time commodity-pricing and hedging models by analyzingthe pricing and hedging errors found in an empirical investigation of options contracts onlight sweet crude oil traded on the New York Mercantile Exchange. Thus, this study contributesto furthering the applicability of the models developed. The inclusion of the benchmarkBlack-Scholes pricing model generates systematic biases that are consistent with (Bakshi, Caoand Chen, Handbook of Quantitative Finance and Risk Management, 2010). The mean-reversionjump-diffusion and seasonality option-pricing model best describes the extreme pricevolatility experienced during a financial collapse, but the mean-reversion and seasonalityoption-pricing model offers the best pricing and hedging capability for other periods. Theperformances of hedging models are generally consistent with pricing errors.

Studying confined polymers using single-molecule DNA experiments

Chih-Chen Hsieh,Patrick S. Doyle 한국유변학회 2008 Korea-Australia rheology journal Vol.20 No.3

The development of fluorescence microscopy of single-molecule DNA in the last decade has fostered a bold jump in the understanding of polymer physics. With the recent advance of nanotechnology, devices with well-defined dimensions that are smaller than typical DNA molecules can be readily manufactured. The combination of these techniques has provided an unprecedented opportunity for researchers to examine confined polymer behavior, a topic far less understood than its counterpart. Here, we review the progress reported in recent studies that investigate confined polymer dynamics by means of single-molecule DNA experiments.

Precipitation Behavior of σ Phase in Fusion Zone of Dissimilar Stainless Steel Welds during Multi-Pass GTAW Process

( Chih Chun Hsieh ),( Tao Chih Chang ),( Dong Yih Lin ),( Ming Che Chen ),( Wei Te Wu ) 대한금속재료학회 ( 구 대한금속학회 ) 2007 METALS AND MATERIALS International Vol.13 No.5

The purpose of this study is to investigate the precipitation characteristics of σ phase in the fusion zone of stainless steel welds at various welding passes during a tungsten arc welding (GTAW) process. The morphology, quantity, and chemical composition of the δ-ferrite and σ phase were analyzed using optical microscopy (OM), a ferritscope (FS), a X-ray diffractometer (XRD), scanning electron microscopy (SEM), an electron probe micro-analyzer (EPMA), and a wavelength dispersive spectrometer (WDS), respectively. Massive δ-ferrite was observed in the fusion zone of the first pass welds during welding of dissimilar stainless steels. The σ phase precipitated at the inner δ-ferrite particles and decreased δ-ferrite content during the third pass welding. The σ and δ phases can be stabilized by Si element, which promoted the phase transformation of δ→σ + γ2 in the fusion zone of the third pass welds. It was found that the σ phase was a Fe-Cr-Si intermetallic compound found in the fusion zone of the third pass welds during multi-pass welding.

Graphite-based selectorless RRAM: improvable intrinsic nonlinearity for array applications

Chen, Ying-Chen,Hu, Szu-Tung,Lin, Chih-Yang,Fowler, Burt,Huang, Hui-Chun,Lin, Chao-Cheng,Kim, Sungjun,Chang, Yao-Feng,Lee, Jack C. The Royal Society of Chemistry 2018 Nanoscale Vol.10 No.33

<P>Selectorless graphite-based resistive random-access memory (RRAM) has been demonstrated by utilizing the intrinsic nonlinear resistive switching (RS) characteristics, without an additional selector or transistor for low-power RRAM array application. The low effective dielectric constant value (<I>k</I>) layer of graphite or graphite oxide is utilized, which is beneficial in suppressing sneak-path currents in the crossbar RRAM array. The tail-bits with low nonlinearity can be manipulated by the positive voltage pulse, which in turn can alleviate variability and reliability issues. Our results provide additional insights for built-in nonlinearity in 1<I>R</I>-only selectorless RRAMs, which are applicable to the low-power memory array, ultrahigh density storage, and in-memory neuromorphic computational configurations.</P>

The association of ambient air pollution with airway inflammation in schoolchildren.

Chen, Bing-Yu,Chan, Chang-Chuan,Lee, Chung-Te,Cheng, Tsun-Jen,Huang, Wen-Chuan,Jhou, Ji-Ci,Han, Yueh-Ying,Chen, Chu-Chih,Guo, Yue Leon School of Hygiene and Public Health of the Johns H 2012 American Journal of Epidemiology Vol.175 No.8

<P>The biologic mechanisms involved in airway inflammatory response to air pollution are not clearly understood. The authors conducted a longitudinal study to investigate whether exposure to ambient air pollutants affected inflammatory cells and mediators from nasal lavage in schoolchildren. Study participants were 100 elementary and middle-school students in New Taipei City, Taiwan. A structured respiratory health questionnaire was administered in September 2007, followed by monthly measurement of nasal inflammation from October 2007 to November 2009. During the study period, daily concentrations of air pollutants were obtained from the Environmental Protection Administration monitoring station and the Aerosol Supersite. Mixed-effects models were applied to examine the association between air pollution and nasal inflammatory cells and mediators, including percentages of neutrophils, eosinophils, and monocytes in lavaged cells and interleukin-8. A total of 824 measurements were obtained from 100 participants over a period of 10 months. The level of particulate matter with an aerodynamic diameter of 2.5 μm or less (PM(2.5)) was found to be associated with percentage of neutrophils (β = 3.45%, 95% confidence interval: 0.89, 6.01) and interleukin-8 level (β = 29.98 pg/mL, 95% confidence interval: 3.26, 56.69) in the nasal lavage on the day of exposure. In this longitudinal cohort study of schoolchildren, results indicated that exposure to PM(2.5) might induce nasal inflammation.</P>

An advanced glycation end product (AGE)-receptor for AGEs (RAGE) axis restores adipogenic potential of senescent preadipocytes through modulation of p53 protein function.

Chen, Chih-Yu,Abell, Allison Martorano,Moon, Yang Soo,Kim, Kee-Hong American Society for Biochemistry and Molecular Bi 2013 The Journal of biological chemistry Vol.288 No.15