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Jung, Hoimin,Jung, Kijung,Hong, Mannkyu,Kwon, Seongyeon,Kim, Kunsoon,Hong, Soon Hyeok,Choi, Tae-Lim,Baik, Mu-Hyun American Chemical Society 2018 JOURNAL OF THE AMERICAN CHEMICAL SOCIETY - Vol.140 No.2
<P>Grubbs-type olefin metathesis catalysts are known to cyclopolymerize 1,6-heptadiynes to afford conjugated polyenes containing five- or six-membered carbocycles. Although high levels of regioselectivity up to >99:1 were observed previously for the formation of five-membered rings, it was neither possible to deliberately obtain six-membered rings at similar levels of selectivity nor understood why certain catalysts showed this selectively. Combining experimental and computational methods, a novel and general theory for what controls the regiochemistry of these cyclopolymerizations is presented. The electronic demands of the ruthenium-based Fischer carbenes are found to innately prefer to form five-membered rings. Reducing the electrophilicity of the carbene by enforcing a trigonal-bipyramidal structure for the ruthenium, where stronger π-backdonation increases the electron density on the carbene, is predicted to invert the regioselectivity. Subsequent experiments provide strong support for the new concept, and it is possible to completely switch the regioselectivity to a ratio of <1:99.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jacsat/2018/jacsat.2018.140.issue-2/jacs.7b11968/production/images/medium/ja-2017-119686_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ja7b11968'>ACS Electronic Supporting Info</A></P>
Ergonomic Evaluation and Improvement of Bus Seat Armrest Design
Hayoung Jung,Seunghoon Lee,Moonjin Kim,Hoimin Choi,Heecheon You 대한인간공학회 2017 大韓人間工學會誌 Vol.36 No.2
Objective:The present study is intended to develop an improved bus seat armrest design by evaluating various bus armrest designs from ergonomic aspects. Background: An ergonomic armrest design which considers the sitting postures and body shapes of passengers can improve the convenience and comfort of a bus seat. Method: Subjective satisfaction of each of five design dimensions (length, width, height from seatpan, shape, and angle) was evaluated for seven bus seat armrest designs in various sizes and shapes by 58 participants (28 males and 33 females) using a 7-point scale (1: very dissatisfied, 4: neutral, and 7: very satisfied). Improved bus seat armrest designs adjustable in length and rotatable to the left or right (sliding and rotating armrest, SRA) with a concave, flat, or convex shape of the upper part were developed by considering the preferred design features and the body size and shape in sitting posture and needs of passengers and then compared with a conventional armrest. Results: A bus seat armrest with a wide width (40~50mm), a long length (360mm), a lower height (213mm), and a curved shape was found significantly preferred in terms of comfort. The proposed armrest designs (SRA-convex, SRA-flat, and SRAconcave) improved satisfaction by 46~62% for length suitability, 184~216% for width suitability, 205~214% for angle suitability, 138~181% for contact area suitability, and 49~64% for height suitability, 138~174% for comfort, and 93~111% for overall satisfaction. Conclusion: The preferred design features and passengers" needs of bus seat armrest were identified and the SRA designs were recommended for better usability. Application: The ergonomic design process of bus seat armrest employed in the present study can be applied to designing armrests in various vehicles for better convenience and comfort.