Effects of Additives of CaO and Rare-Earth Oxides on the Sintering Behavior of AlN Ceramics

Chih-Hung Chu,Yun-Hwei Shen,Chih-Peng Lin,Shaw-Bing Wen 한국물리학회 2008 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.52 No.5

The effect of additives of CaO plus three different rare-earth oxides (Y, Sm and Gd, separately) on the sintering behavior of AlN ceramics has been evaluated at 1700℃ by using a MoSi2 heater and ambient atmosphere. The results of density measurements show that the atomic weight of the rare-earth element may substantially affect the apparent density of the sintered AlN specimen due to the kinetics of atomic diffusion during sintering. The optimum results of this study show that these additives are effective in obtaining an apparent density of 3.26 g/cm3 (approaching a 100 % theoretical density of AlN). The Vicker's hardness of the sintered AlN can reach a high value of 1310 kg/mm2 and an apparent density of 3.34 g/cm3. A longer soaking time of between 3 and 5 h is necessary to practically eliminate the minor oxide phases. The effect of additives of CaO plus three different rare-earth oxides (Y, Sm and Gd, separately) on the sintering behavior of AlN ceramics has been evaluated at 1700℃ by using a MoSi2 heater and ambient atmosphere. The results of density measurements show that the atomic weight of the rare-earth element may substantially affect the apparent density of the sintered AlN specimen due to the kinetics of atomic diffusion during sintering. The optimum results of this study show that these additives are effective in obtaining an apparent density of 3.26 g/cm3 (approaching a 100 % theoretical density of AlN). The Vicker's hardness of the sintered AlN can reach a high value of 1310 kg/mm2 and an apparent density of 3.34 g/cm3. A longer soaking time of between 3 and 5 h is necessary to practically eliminate the minor oxide phases.

Thermal conductivity of micro hot-pressed AlN ceramics fabricated using a conventional MoSi2 heating element furnace

Chih-Peng Lin,Chih-Hung Chu,Shaw-Bing Wen,Yun-Hwei Shen 한양대학교 세라믹연구소 2011 Journal of Ceramic Processing Research Vol.12 No.5

AlN samples doped with sub-micron Y2O3 and CaO powders as sintering additives obtained using the micro hot-pressed (MHPed) sintering method in a MoSi2 heating element furnace were investigated. The minor amounts of secondary phases were identified as Al5Y3O12, CaYAl3O7, and CaAl4O7, which are related to the low sintering temperature as well as the removal of oxygen-related defects in the system. Relative densities of over 96% of the theoretical value were obtained after sintering at 1600 oC for 8 h, indicating that an adequate amount of additives and the use of the micro hot-pressed (MHPed) sintering process help improve the densification and thermal conductivity of AlN ceramics. The high thermal conductivity of 130Wm−1K−1was attributed to the purification of the AlN lattice, the elimination of some secondary phases, and the grain boundary phase distribution.

ANALYZING ISUAL SPECTROPHOTOMETER DATA USING A TWO-COLOR DIAGRAM METHOD

CHEN ALFRED BING-CHIH,CHIANG PO-SHIH,HUANG TIAN-HSIANG,KUO CHENG-LING,WANG SHI-CHUN,SU HAN-TZONG,HSU RUE-RoN,CHANG MING-HUI,CHANG YEOU-SHIN,LIU TIE-YUE,MENDE STEPHEN B.,FREY HARALD U.,FUKUNISHI HIROSH The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2

Transient luminous events (TLEs; sprites, elves, jets and etc.) are lightning-related optical flashes occurring above thunderstorms. Since the first discovery of sprites in 1989, scientists have learned a great deal about the morphological, spectroscopic and electromagnetic characteristics of TLEs through ground and spacecraft campaigns. However, most of the TLE studies were based on events recorded over US High Plains. To elucidate the possible biasing effects, space-borne observations are needed and have their merits. Imager of sprites and Upper Atmospheric Lightning (ISUAL) on the FORMOSAT-2 satellite is the first instrument to carry out a true global measurement of TLEs from a low- earth orbit. In this short paper, we apply a common astronomical data analysis technique, two-color diagram, on the ISUAL spectrophotometer (SP) data. By choosing appropriated bandpasses and converting the measured flux of TLEs into the unit of magnitude, two-color diagrams of TLEs can be constructed. We demonstrate that two-color diagrams, which were constructed from the narrow-band spectrophotometer data, can be used to classify different types of TLEs and trace their temporal evolution. The amount of reddening due to Earth's atmosphere can also be estimated from two-color diagrams assembled from the broad-band spectrophotometer data.

Optimization of extraction process for bioactive compounds from Litsea cubeba fruits

Chih-Lun Cheng,Gui-Bing Hong 한국화학공학회 2018 Korean Journal of Chemical Engineering Vol.35 No.1

Response surface methodology (RSM) was applied to evaluate the extraction of active compounds from Litsea cubeba fruits. A central composite design (CCD) with five levels and three process parameters (extraction temperature, extraction time and ethanol concentration) was used to investigate the influence of the extraction temperature, extraction time and ethanol concentration on the multiple response variables (TPC, DPPH and ABTS assays). The results of the ANOVA analysis show that the quadratic term of the ethanol concentration was significant for all the response variables. The quadratic model was highly significant (P<0.05) for all the response variables. After optimizing for multi-response, the optimal conditions were determined as an extraction temperature of 42.3 oC, extraction time of 126.4min and ethanol concentration of 51%. Moreover, the extract of Litsea cubeba fruit attested possessing tyrosinase inhibitory activity, with an IC50 value of 5,720 μg mL−1. The second-order kinetic model represented the kinetic data very well. In addition, the obtained values of the effective diffusivities were in the range of 2.28-5.83×10−11m2s−1.

A Vision-Based Collision Warning System by Surrounding Vehicles Detection

( Bing-fei Wu ),( Ying-han Chen ),( Chih-chun Kao ),( Yen-feng Li ),( Chao-jung Chen ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.4

To provide active notification and enhance drivers` awareness of their surroundings, a vision-based collision warning system that detects and monitors surrounding vehicles is proposed in this paper. The main objective is to prevent possible vehicle collisions by monitoring the status of surrounding vehicles, including the distance to the other vehicles in front, behind, to the left and to the right sides. In addition, the proposed system collects and integrates this information to provide advisory warnings to drivers. To offer the correct notification, an algorithm based on features of edge and morphology to detect vehicles is also presented. The proposed system has been implemented in embedded systems and evaluated on real roads in various lighting and weather conditions. The experimental results indicate that the vehicle detection ratios were higher than 97% in the daytime, and appropriate for real road applications.

A P2P-to-UPnP Proxy Gateway Architecture for Home Multimedia Content Distribution

( Chih-lin Hu ),( Hsin-cheng Lin ),( Yu-feng Hsu ),( Bing-jung Hsieh ) 한국인터넷정보학회 2012 KSII Transactions on Internet and Information Syst Vol.6 No.1

Deploying advanced home networking technologies and modern home-networked devices in residential environments provides a playground for new home applications and services. Because home multimedia entertainment is among the most essential home applications, this paper presents an appealing home media content sharing scenario: home-networked devices can discover neighboring devices and share local media content, as well as enormous amounts of Internet media content in a convenient and networked manner. This ideal scenario differs from traditional usages that merely offer local media content and require tedious manual operations of connection setup and file transfer among various devices. To achieve this goal, this study proposes a proxy gateway architecture for home multimedia content distribution. The proposed architecture integrates several functional mechanisms, including UPnP-based device discovery, home gateway, Internet media provision, and in-home media content delivery. This design addresses several inherent limitations of device heterogeneity and network interoperability on home and public networks, and allows diverse home-networked devices to play media content in an identical and networked manner. Prototypical implementation of the proposed proxy gateway architecture develops a proof-of-concept software, integrating a BitTorrent peer-to-peer client, a UPnP protocol stack, and a UPnP AV media server, as well as media distribution and management components on the OSGi home gateway platform. Practical demonstration shows the proposed design and scenario realization, offering users an unlimited volume of media content for home multimedia entertainment.

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>

Relationships between Antioxidants and Quality Characteristics from Velvet Antlers of Formosan Sambar Deer

Shih-Lin Cheng,You-Ling Jian,Chih-Ming Chen,Bing-Tsan Liu 한국축산식품학회 2017 한국축산식품학회지 Vol.37 No.4

The quality characteristics of velvet antlers obtained from Formosan sambar deer (Cervus unicolor Swinhoi) (SDVA), harvested from 63 to 81 d during the velvet antler growth period, were evaluated by investigating the relationships between antioxidant levels; including content, activity, and content/activity ratios, and physical properties; including shear force values, color, and Ca content. The hardness of samples from base velvet antler sections increased, and that the color of these samples tended to become reddish-yellow (redder and more yellow), suggesting that the Ca content in the base section of the sample was not ossified yet. Samples from the upper sections of velvet antler showed higher superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) content (3.91 to 1.50 mg/mL, 2.53 to 0.90 mg/mL, and 3.95 to 1.58 mg/mL, respectively) than did samples from the middle and base sections (p<0.05). The activity and content/activity ratios of GPX measured in the upper section were also found to be significantly greater than in the middle and base sections (p<0.05). We further observed that the content and activity of GPX was significantly and negatively correlated with Ca content, shear force values, and the content/activity ratio of this antioxidant (p<0.01). The study findings may serve as a reference index for quality evaluations of velvet antlers of Formosan sambar deer in future.

GROUND OBSERVATIONS OF SPRITES AND OTHER TLES IN TAIWAN

WANG YUN-CHING,HSU RUE-RON,SU HAN-TZONG,CHEN ALFRED BING-CHIH,LEE YI-JEN,KUO CHENG-LING,TSAY WEAN-SHUN,CHANG CHAN-KAO,WANG SHI-CHUN,LEE LOU-CHUANG,LIU TIE-YUE The Korean Astronomical Society 2005 Journal of The Korean Astronomical Society Vol.38 No.2

Sprites, elves and blue jets are collectively denominated as the upper atmospheric transient luminous events (TLEs). They are recently discovered optical flashes between active thunderstorms and the ionosphere. In this report, a brief introduction to the most important characteristics of TLEs is given. Since 2001, scientists from the National Cheng Kung University have been performing yearly summer campaigns from various locations in Taiwan. The main achievements of their yearly campaign are presented.