Effects of Neodymium and Calcium on the Thermal Stability of AZ71 Magnesium Alloys

Cheng‑Feng Yue,Shi‑Jei Huang,Jhewn‑Kuang Chen,Hsien‑Tsung Li,Kam‑Shau Chan 대한금속·재료학회 2018 METALS AND MATERIALS International Vol.24 No.2

The effects of an addition of 0–2 wt% Nd on thermal stability of 0–3 wt% Ca-containing modified AZ71 magnesium alloyswas investigated. The ignition temperature was found to increase from that of AZ71, 574, to 825 °C with the addition of0.5 wt% Ca and 1 wt% Nd. The ignition temperature was further increased to 1114 °C when 3 wt% Ca was added. The CaandNd-added AZ71 was isothermally maintained at a temperature of 500 °C in air for 12 h. The MgO–CaO–Nd2O3 formedon the surface to improve the thermal stability of the AZ71–xCa–yNd alloys. While both the tensile strength and ductilitydecreased with the Ca concentration in the alloy, an addition of 1 wt% Nd was found able to alleviate the degradation effectsof Ca on the tensile strength and ductility at 170 °C. Both solid solution formation and precipitation strengthening contributedto the increase in toughness. AZ71 containing 0.5–2 wt% Ca and 1 wt% Nd provides the optimum combination of ignitionresistance and mechanical properties.

The Use of a Multiple Risk Level Model to Tackle the Duration of Risk for Construction Activity

Hsien-Kuan Chang,Wen-der Yu,Shao-Tsai Cheng,Tao-Ming Cheng 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.6

The project evaluation and review technique (PERT) is the most well-known method to handle the risk due to uncertain activity durations, previous studies show that the β-distribution-based PERT estimation tends to be over-optimistic and it offers no control of the project in terms of risk duration. This study proposes a multiple risk-level (MRL) model that uses a site spatial constraint, environmental effects and the “5 Ms” of construction management to tackle the duration of risk during a construction project. A Risk-based Critical Path Scheduling Method (R-CPSM) that uses MRL is developed to calculate the duration of the project. A case study using a project selected from a previous study is used to compare the four estimation methods: two traditional PERT methods (3.2σs and 6σs), a Monte Carlo Simulation and the proposed MRL model. The results show that, compared with traditional approaches to estimate durations of uncertain activity, the proposed R-CPSM method is more systematic that can be combined with a cost estimation process and offers a rectification mechanism that dynamically monitors and adjusts the important factors that affect the risk duration. This method gives a more realistic estimate that is in agreement with the results of previous studies.

A Single-Stage LED Tube Lamp Driver with Input-Current Shaping for Energy-Efficient Indoor Lighting Applications

Cheng, Chun-An,Chang, Chien-Hsuan,Cheng, Hung-Liang,Chung, Tsung-Yuan,Tseng, Ching-Hsien,Tseng, Kuo-Ching The Korean Institute of Power Electronics 2016 JOURNAL OF POWER ELECTRONICS Vol.16 No.4

This study proposes a single-stage light-emitting diode (LED) tube lamp driver with input-current shaping for T8/T10-type fluorescent lamp replacements. The proposed AC-DC LED driver integrates a dual-boost converter with coupled inductors and a half-bridge series-resonant converter with a bridge rectifier into a single-stage power conversion topology. This paper presents the operational principles and design considerations for one T8-type 18 W-rated LED tube lamp with line input voltages ranging from 100 V rms to 120 V rms. Experimental results for the prototype driver show that the highest power factor (PF = 0.988), lowest input current total harmonic distortion (THD = 7.22%), and highest circuit efficiency (η = 92.42%) are obtained at an input voltage of 120 V. Hence, the proposed driver is feasible for use in energy-efficient indoor lighting applications.

Behavior-Based Manipulator Programming Based on Extensible Agent Behavior Specification Language

Hsien-I Lin,Chia-Hsien Cheng 제어로봇시스템학회 2014 제어로봇시스템학회 국제학술대회 논문집 Vol.2014 No.10

Endowing a robot with skills to perform manipulative tasks has an important role in developing an intelligent robot. To manipulate objects, a robot needs perception and action skills. However, designing the programming framework to integrate a variety of skills in a robot system is a challenging task and significantly influences the robot performance. In this paper, we present a behavior-based manipulator programming framework which is based on Extensible Agent Behavior Specification Language (XABSL) to manage behaviors in a robot system. To achieve the flexibility and reusability of robot behaviors required for practice applications, the proposed concept is to implement a programming framework for robot manipulation into two steps: first, perception and action behaviors are created to endow a robot with fundamental skills to perform manipulative tasks; second, using the XABSL framework, the created behaviors are simply planned by an option graph. Because behaviors are planned to be activated by certain stimuli and respond accordingly, programming robot manipulative tasks becomes simpler. Moreover, by the programming framework for robot manipulative tasks, the programming effort is reduced considerably. In our experiments, we provide an extensive validation of the proposed behavior-based programming framework on the manipulative tasks such as stacking cubes and solving rubik’s cube.

Sustainable Urban Regeneration in Taiwanese Old Urban Districts: From a User's Perspective

Cheng, Hsien-Hsin,Lin, Chao-Chih Sustainable Building Research Center 2010 International journal of sustainable building tech Vol.1 No.1

The researchers intend to approach urban regeneration issues in old urban districts from a user's perspective. Instead of experts' evaluation and professional disciplines, this research relies on the users' perceptions about the factors of the built environment on a liveable urban district. The case study areas are two historic districts in Tainan city - Chihkan district and Minsheng greenpark district. In order to measure the users' attitudes about regeneration issues, the researchers use Likert scale in questionnaire for users to fill in the right scale of their perception. The users to be surveyed can classify into two groups: 1) inhabitants in a district, 2) tourists in a district. As for inhabitants, questionnaire mainly concerns the liveability issues of an old district, for instance, the impact of high density on life quality, or satisfaction about local traffic; whilst for tourists, questionnaire concentrates on cultural tourism issues, for instance, the attractiveness of gourmet, cultural heritage or the degree of importance they feel about the retailing stores, and department stores in old districts etc. After collecting the questionnaires from both two groups, multivariate analysis is used in coding. By factor analysis, the key constructs concerning a liveable district can be concluded with priority order, for instance, cultural heritage as the most important construct, a neighbourhood for all social hierarchy as the second important construct, and a convenient neighbourhood as the third important construct and others. By descriptive statistics, the tourists' attitudes about historic districts can also be summarized, for instance, which element is more appealing to most tourists, or how important do most tourists feel about reused old buildings etc. Research results can be used to build regeneration strategies fit to the need of districts.

Microstructure and Texture Evolution of AA 6063 During an Ex-ECAE Process

Cheng-Hsien Liu,Hsin-Chih Lin,Yu-Tung Hsu 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.3

Equal channel angular extrusion (ECAE) has been studied at the lab scale for many years. However, few successful industrial applications of the ECAE process have been reported. In the present work, a process referred to as Ex-ECAE that was composed of two processes of the direct extrusion and the ECAE via route C, was developed. The Ex-ECAE process was developed to refine the microstructure of the extrudate, particular the coarse grain layer (CGL) on the surface of the extrudate. The Ex-ECAE die with a die angle of 120° contained three segments and was used in the conventional direct extrusion press. The high friction and the continuous routes of the ECAE resulted in asymmetric dead metal zones (DMZs) to be formed at the corners of the die channel. It revealed that the visible grains in the CGL were refined and became invisible due to the intense shear deformation as the CGL flowed along the boundaries of the asymmetric DMZs. The textures of the Ex-ECAE at the various segments were studied by EBSD. This study demonstrated that the ECAE process could be scaled up using the extrusion press. Success or lack of success depended on the capacity of the extrusion press and the die design.

The feasibility of detecting endometrial and ovarian cancer using DNA methylation biomarkers in cervical scrapings

Cheng-Chang Chang,Hui-Chen Wang,Yu-Ping Liao,Yu-Chih Chen,Yu-Chun Weng,Mu-Hsien Yu,Hung-Cheng Lai 대한부인종양학회 2018 Journal of Gynecologic Oncology Vol.29 No.1

Objective: We hypothesized that DNA methylation of development-related genes may occur in endometrial cancer (EC)/ovarian cancer (OC) and may be detected in cervical scrapings. Methods: We tested methylation status by quantitative methylation-specific polymerase chain reaction for 14 genes in DNA pools of endometrial and OC tissues. Tissues of EC/normal endometrium, OC/normal ovary, were verified in training set using cervical scrapings of 10 EC/10 OC patients and 10 controls, and further validated in the testing set using independent cervical scrapings in 30 EC/30 OC patients and 30 controls. We generated cutoff values of methylation index (M-index) from cervical scrapings to distinguish between cancer patients and control. Sensitivity/specificity of DNA methylation biomarkers in detecting EC and OC was calculated. Results: Of 14 genes, 4 (PTGDR, HS3ST2, POU4F3, MAGI2) showed hypermethylation in EC and OC tissues, and were verified in training set. POU4F3 and MAGI2 exhibited hypermethylation in training set were validated in independent cases. The mean M-index of POU4F3 is 78.28 in EC and 20.36 in OC, which are higher than that in controls (6.59; p<0.001 and p=0.100, respectively), and that of MAGI2 is 246.0 in EC and 12.2 in OC, which is significantly higher that than in controls (2.85; p<0.001 and p=0.480, respectively). Sensitivity and specificity of POU4F3/MAGI2 were 83%–90% and 69%–75% for detection of EC, and 61% and 62%–69% for the detection of OC. Conclusion: The findings demonstrate the potential of EC/OC detection through testing for DNA methylation in cervical scrapings.

Value of CT in the Discrimination of Fatal from Non-Fatal Stercoral Colitis

Cheng-Hsien Wu,Chen-Chih Huang,Li-Jen Wang,Yon-Cheong Wong,Chao-Jan Wang,Wan-Chak Lo,Being-Chuan Lin,Yung-Liang Wan,Chuen Hsueh 대한영상의학회 2012 Korean Journal of Radiology Vol.13 No.3

Objective: Clinical presentation and physical signs may be unreliable in the diagnosis of stercoral colitis (SC). This study evaluates the value of computed tomography (CT) in distinguishing fatal from non-fatal SC. Materials and Methods: Ten patients diagnosed as SC were obtained from inter-specialist conferences. Additional 13 patients with suspected SC were identified via the Radiology Information System (RIS). These patients were divided into two groups; fatal and non-fatal SCs. Their CT images are reviewed by two board-certified radiologists blinded to the clinical data and radiographic reports. Results: SC occurred in older patients and displayed no gender predisposition. There was significant correlation between fatal SC and CT findings of dense mucosa (p = 0.017), perfusion defects (p = 0.026), ascites (p = 0.023), or abnormal gas (p = 0.033). The sensitivity, specificity, and accuracy of dense mucosa were 71%, 86%, and 81%, respectively. These figures were 75%, 79%, and 77% for perfusion defects; 75%, 80%, and 78% for ascites; and 50%, 93%, and 78% for abnormal gas, respectively. Each CT sign of mucosal sloughing and pericolonic abscess displayed high specificity of 100% and 93% for diagnosing fatal SC, respectively. However, this did not reach statistical significance in diagnosing fatal SC. Conclusion: CT appears to be valuable in discriminating fatal from non-fatal SC. Objective: Clinical presentation and physical signs may be unreliable in the diagnosis of stercoral colitis (SC). This study evaluates the value of computed tomography (CT) in distinguishing fatal from non-fatal SC. Materials and Methods: Ten patients diagnosed as SC were obtained from inter-specialist conferences. Additional 13 patients with suspected SC were identified via the Radiology Information System (RIS). These patients were divided into two groups; fatal and non-fatal SCs. Their CT images are reviewed by two board-certified radiologists blinded to the clinical data and radiographic reports. Results: SC occurred in older patients and displayed no gender predisposition. There was significant correlation between fatal SC and CT findings of dense mucosa (p = 0.017), perfusion defects (p = 0.026), ascites (p = 0.023), or abnormal gas (p = 0.033). The sensitivity, specificity, and accuracy of dense mucosa were 71%, 86%, and 81%, respectively. These figures were 75%, 79%, and 77% for perfusion defects; 75%, 80%, and 78% for ascites; and 50%, 93%, and 78% for abnormal gas, respectively. Each CT sign of mucosal sloughing and pericolonic abscess displayed high specificity of 100% and 93% for diagnosing fatal SC, respectively. However, this did not reach statistical significance in diagnosing fatal SC. Conclusion: CT appears to be valuable in discriminating fatal from non-fatal SC.

Investigation of Visual Perception Under Zen-Meditation Based On Alpha-Dependent F-VEPs

Liao, Hsien-Cheng,Liu, Chuan-Yi,Lo, Pei-Chen The Korean Society of Medical and Biological Engin 2006 의공학회지 Vol.27 No.6

Variation of brain dynamics under Zen meditation has been one of our major research interests for years. One issue encountered is the inaccessibility to the actual meditation level or stage as a reference. In this paper, we propose an alternative strategy for investigating the human brain in response to external flash stimuli during Zen meditation course. To secure a consistent condition of the brain dynamics when applying stimulation, we designed a recording of flash visual evoked potentials (F-VEPs) based on a constant background EEG (electroencephalograph) frontal $\alpha-rhythm$ dominating activities that increase significantly during Zen meditation. Thus the flash-light stimulus was to be applied upon emergence of the frontal $\alpha-rhythm$. The alpha-dependent F-VEPs were then employed to inspect the effect of Zen meditation on brain dynamics. Based on the experimental protocol proposed, considerable differences between experimental and control groups were obtained. Our results showed that amplitudes of P1-N2 and N2-P2 on Cz and Fz increased significantly during meditation, contrary to the F-VEPs of control group at rest. We thus suggest that Zen meditation results in acute response on primary visual cortex and the associated parts.

Tight-Binding Theory for Coupling Asymmetric Photonic Crystal Waveguides

Szu-Cheng Cheng,Chih-Hsien Huang,Wen-Feng Hsieh 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.53 No.2

The physical properties of asymmetric photonic-crystal directional couplers are studied under the tight-binding model, which asumes that the field distribution of photonic-crystal waveguides is localized around periodic defects. The couplings of nearby defects betwen two asymmetric waveguides cause two dispersion relations to split further whereas the couplings of nearby defects within an individual waveguide cause the sinusoidal modulations of the dispersion curves. The field-envelope distributions of the coupler are expresed by using the eigenmodes of the tight- binding equations and are consistent with the comparing results from nite-dierence time-domain simulations.