The Experts below are selected from a list of 8559 Experts worldwide ranked by ideXlab platform

Sung R. Choi - One of the best experts on this subject based on the ideXlab platform.

  • foreign object damage behavior in a silicon nitride ceramic by spherical projectiles of steels and brass
    Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2008
    Co-Authors: Sung R. Choi
    Abstract:

    Abstract Assessments of foreign object damage (FOD) of a commercial, gas-turbine grade, in situ toughened silicon nitride ceramic (AS800) were made using different projectile materials at ambient temperature. AS800 flexure Target Specimens rigidly supported were impacted at their centers in a velocity range from 100 to 450 m/s by spherical projectiles with a diameter of 1.59 mm. Three different projectile materials were used including hardened steel, annealed steel, and brass. Post-impact strength of each Target Specimen impacted was determined as a function of impact velocity to appraise the severity of local impact damage. For a given impact velocity, the extent of FOD was greatest for hardened steel projectiles, least for brass projectiles, and intermediate for annealed steel projectiles. The key material parameter affecting FOD the most was identified as the hardness (or yield stress) of projectile materials. Prediction of impact force as a function of impact velocity for each projectile material was made based on a quasi-static plastic model incorporated with the average ‘contact yield pressure’ determined from static indentation testing.

  • foreign object damage phenomenon by steel ball projectiles in a sic sic ceramic matrix composite at ambient and elevated temperatures
    Journal of the American Ceramic Society, 2008
    Co-Authors: Sung R. Choi
    Abstract:

    Foreign object damage (FOD) phenomenon of a gas-turbine grade SiC/SiC ceramic matrix composite (CMC) was determined at 25° and 1316°C using impact velocities ranging from 115 to 440 m/s by 1.59-mm diameter steel ball projectiles. Two types of Target-Specimen support were employed at each temperature: fully supported and partially supported. For a given temperature, the degree of impact damage increased with increasing impact velocity, and was greater in partial support than in full support. The elevated-temperature FOD resistance of the composite, particularly in partial support at higher impact velocities ≥350 m/s, was significantly less than the ambient-temperature counterpart, attributed to a weakening effect of the composite. In full support, frontal contact stresses played a major role in generating composite damage; whereas, in partial support both frontal contact and backside tensile stresses were combined sources of damage generation. Formation of cone cracks initiating from impact site was also one of the key damage features. The SiC/SiC composite was able to survive higher energy impacts without complete structural failure, as compared with gas-turbine grade AS800 and SN282 monolithic silicon nitrides.

  • effect of projectile materials on foreign object damage of a gas turbine grade silicon nitride
    ASME Turbo Expo 2005: Power for Land Sea and Air, 2005
    Co-Authors: Sung R. Choi, Ramakrishna T Bhatt, Zsolt Racz, David N Brewer, John P Gyekenyesi
    Abstract:

    Foreign object damage (FOD) behavior of AS800 silicon nitride was determined using four different projectile materials at ambient temperature. The Target test Specimens rigidly supported were impacted at their centers by spherical projectiles with a diameter of 1.59 mm. Four different types of projectiles were used including hardened steel balls, annealed steel balls, silicon nitride balls, and brass balls. Post-impact strength of each Target Specimen impacted was determined as a function of impact velocity to better understand the severity of local impact damage. The critical impact velocity where Target Specimens fail upon impact was highest with brass balls, lowest with ceramic ball, and intermediate with annealed and hardened steel balls. Degree of strength degradation upon impact followed the same order as in the critical impact velocity with respect to projectile materials. For steel balls, hardened projectiles yielded more significant impact damage than annealed counterparts. The most important material parameter affecting FOD was identified as hardness of projectiles and was correlated in terms of critical impact velocity, impact deformation, and impact load.Copyright © 2005 by ASME

Fumitaka Koga - One of the best experts on this subject based on the ideXlab platform.

  • gasless single port access endoscopic surgery in urology minimum incision endoscopic surgery mies
    International Journal of Urology, 2009
    Co-Authors: Kazunori Kihara, Satoru Kawakami, Yasuhisa Fujii, Hitoshi Masuda, Fumitaka Koga
    Abstract:

    Minimum incision endoscopic surgery (MIES) is a gasless, single-port access, cost-effective, and minimally invasive surgery that has been in development since the late 1990s. Use of MIES has steadily increased in Japan and Asia and has been introduced into Europe and the USA. In 2006, MIES was certified by the Japanese government as an advanced surgery and since 2008 it has been covered by the Japanese universal health insurance system as a new surgical technique. Briefly, MIES involves an initial minimum incision (a single port) that permits extraction of the Target Specimen. A wide working space through the port is then made by separating the anatomical plane extraperitoneally. This is maintained with special retractors instead of gas insufflation. All instruments including an endoscope are inserted through the port and the operation is completed. The size of the port can be tailored to the situation if necessary, which contributes to preclusion of patient selection. The procedure uses only two disposable devices that are inexpensive, resulting in low equipment costs. Surgeons have the benefits of magnified vision through endoscopy as well as stereovision and panoramic vision of naked eyes through the port, which reduces the technical demands of the procedure. Techniques for two basic MIES procedures allow MIES to be performed for most urological organs and in extraordinary cases by their modifications. Thus, the MIES system permits minimally invasive surgery without use of CO2 gas, which is ideal from medical, environmental and economic perspectives, is cost-effective and minimizes patient selection.

Unal Coskun - One of the best experts on this subject based on the ideXlab platform.

  • Comprehensive and quantitative analysis of white and brown adipose tissue by shotgun lipidomics
    Elsevier, 2019
    Co-Authors: Michal Grzybek, Alessandra Palladini, Vasileia Ismini Alexaki, Michal A Surma, Kai Simons, Triantafyllos Chavakis, Christian Klose, Unal Coskun
    Abstract:

    Objective: Shotgun lipidomics enables an extensive analysis of lipids from tissues and fluids. Each Specimen requires appropriate extraction and processing procedures to ensure good coverage and reproducible quantification of the lipidome. Adipose tissue (AT) has become a research focus with regard to its involvement in obesity-related pathologies. However, the quantification of the AT lipidome is particularly challenging due to the predominance of triacylglycerides, which elicit high ion suppression of the remaining lipid classes. Methods: We present a new and validated method for shotgun lipidomics of AT, which tailors the lipid extraction procedure to the Target Specimen and features high reproducibility with a linear dynamic range of at least 4 orders of magnitude for all lipid classes. Results: Utilizing this method, we observed tissue-specific and diet-related differences in three AT types (brown, gonadal, inguinal subcutaneous) from lean and obese mice. Brown AT exhibited a distinct lipidomic profile with the greatest lipid class diversity and responded to high-fat diet by altering its lipid composition, which shifted towards that of white AT. Moreover, diet-induced obesity promoted an overall remodeling of the lipidome, where all three AT types featured a significant increase in longer and more unsaturated triacylglyceride and phospholipid species. Conclusions: The here presented method facilitates reproducible systematic lipidomic profiling of AT and could be integrated with further –omics approaches used in (pre-) clinical research, in order to advance the understanding of the molecular metabolic dynamics involved in the pathogenesis of obesity-associated disorders. Keywords: Shotgun mass spectrometry, Lipidomics, Adipose tissue, Method validation, Lipid extraction, Mouse, Chow and high-fat diet, Lipid remodelin

  • comprehensive and quantitative analysis of white and brown adipose tissue by shotgun lipidomics
    bioRxiv, 2018
    Co-Authors: Michal Grzybek, Alessandra Palladini, Vasileia Ismini Alexaki, Michal A Surma, Kai Simons, Triantafyllos Chavakis, Christian Klose, Unal Coskun
    Abstract:

    Shotgun lipidomics enables an extensive analysis of lipids from tissues and fluids. Each Specimen requires appropriate extraction and processing procedures to ensure good coverage and reproducible quantification of the lipidome. Adipose tissue (AT) has become a research focus with regard to its involvement in obesity-related pathologies. However, the quantification of the AT lipidome is particularly challenging due to the predominance of triacylglycerides, which elicit high ion suppression of the remaining lipid classes. We present a new and validated method for shotgun lipidomics of AT, which tailors the lipid extraction procedure to the Target Specimen and features high reproducibility with a linear dynamic range of at least 4 orders of magnitude for all lipid classes. Utilizing this method, we observed tissue-specific and diet-related differences in three AT types (brown, gonadal, inguinal subcutaneous) from lean and obese mice. Brown AT exhibited a distinct lipidomic profile with the greatest lipid class diversity and responded to high-fat diet by altering its lipid composition, which shifted towards that of white AT. Moreover, diet-induced obesity promoted an overall remodelling of the lipidome, where all three AT types featured a significant increase in longer and more unsaturated triacylglyceride and phospholipid species. The here presented method facilitates reproducible systematic lipidomic profiling of AT and could be integrated with further -omics approaches used in (pre-)clinical research, in order to advance the understanding of the molecular metabolic dynamics involved in the pathogenesis of obesity-associated disorders.

Kazunori Kihara - One of the best experts on this subject based on the ideXlab platform.

  • gasless single port access endoscopic surgery in urology minimum incision endoscopic surgery mies
    International Journal of Urology, 2009
    Co-Authors: Kazunori Kihara, Satoru Kawakami, Yasuhisa Fujii, Hitoshi Masuda, Fumitaka Koga
    Abstract:

    Minimum incision endoscopic surgery (MIES) is a gasless, single-port access, cost-effective, and minimally invasive surgery that has been in development since the late 1990s. Use of MIES has steadily increased in Japan and Asia and has been introduced into Europe and the USA. In 2006, MIES was certified by the Japanese government as an advanced surgery and since 2008 it has been covered by the Japanese universal health insurance system as a new surgical technique. Briefly, MIES involves an initial minimum incision (a single port) that permits extraction of the Target Specimen. A wide working space through the port is then made by separating the anatomical plane extraperitoneally. This is maintained with special retractors instead of gas insufflation. All instruments including an endoscope are inserted through the port and the operation is completed. The size of the port can be tailored to the situation if necessary, which contributes to preclusion of patient selection. The procedure uses only two disposable devices that are inexpensive, resulting in low equipment costs. Surgeons have the benefits of magnified vision through endoscopy as well as stereovision and panoramic vision of naked eyes through the port, which reduces the technical demands of the procedure. Techniques for two basic MIES procedures allow MIES to be performed for most urological organs and in extraordinary cases by their modifications. Thus, the MIES system permits minimally invasive surgery without use of CO2 gas, which is ideal from medical, environmental and economic perspectives, is cost-effective and minimizes patient selection.

Trejo Adrian - One of the best experts on this subject based on the ideXlab platform.

  • Impacting Testing Of High Temperature Ceramics Through The Use Of A Vitiated Heater For Hot And Cold Fire Collisions
    ScholarWorks@UTEP, 2009
    Co-Authors: Trejo Adrian
    Abstract:

    Material testing is a crucial step during the design process as particular materials serve as safety and life saving conditions. In this study, a MoSi2 is chosen as the Target Specimen to undergo impact under high temperatures. An impact apparatus is designed and constructed for the purpose of propelling alumina particles at high velocities. A nozzle using compressed nitrogen gas is used to fire the particle at the desired velocities. Due to the possibility of thermal shock occurring at higher temperatures, a separate nozzle utilizing vitiation heating is designed to fire the particle at equally higher temperatures to prove the lack of thermal shock. Throughout the experiment, measurements including particle velocity, exit temperature, Specimen temperature, and damage of the Specimen are documented in both the cold test nozzle and vitiated heating test nozzle to propose a reliable method in the impact testing of materials

  • Impacting testing of high temperature ceramics through the use of a vitiated heater for hot and cold fire collisions
    ScholarWorks@UTEP, 2009
    Co-Authors: Trejo Adrian
    Abstract:

    Material testing is a crucial step during the design process as particular materials serve as safety and life saving conditions. In this study, a MoSi 2 is chosen as the Target Specimen to undergo impact under high temperatures. An impact apparatus is designed and constructed for the purpose of propelling alumina particles at high velocities. A nozzle using compressed nitrogen gas is used to fire the particle at the desired velocities. Due to the possibility of thermal shock occurring at higher temperatures, a separate nozzle utilizing vitiation heating is designed to fire the particle at equally higher temperatures to prove the lack of thermal shock. Throughout the experiment, measurements including particle velocity, exit temperature, Specimen temperature, and damage of the Specimen are documented in both the cold test nozzle and vitiated heating test nozzle. Ultimately, the design of the impact apparatus is such that it may used as a characterization tool. Although the final results focus on the characterization of the MoSi 2 Specimen and the damage associated, the impact apparatus may be used to characterize materials at any temperature application and is not limited to characterizing ceramics