PREFORM OPTIMIZATION OF FUNCTIONAL BEVEL GEAR FOR WARM FORGING PROCESSES

Risky Ayu Febriani,박홍석,Saurabh Kumar,이창명 한국자동차공학회 2020 International journal of automotive technology Vol.21 No.5

Optimizing the design of the preform shapes used in warm forging processes is important for improving quality and reducing cost. The main objective of this study was to optimize the design of a preform shape for a bevel gear to obtain a good product and to improve the efficiency of the warm forging process. Quality parameters included in the fitness function were form-filling, preform volume, and complexity. First, basic principles pertaining to the cross sections, thickness, and concave radius of a bevel gear preform were applied in conjunction with certain theoretical expressions and empirical methods to produce an initial preform shape and initial geometry. Subsequently, mathematical evaluation models of the fitness function were generated to optimize the preform shape. Finally, a genetic algorithm was applied to solve the multi-objective optimization problem, and the best solution was determined considering the accuracy of the results, within the close proximity set generated by the multi-objective genetic algorithm optimization. The optimal preform shape was decreased in weight by approximately 8 % and its flash dimensions were decreased by about 5 % compared to the initial preform shape. This research is expected to improve the efficiency of fabricating bevel gears by means of warm forging processes.

From Reading Nonsensical Jabberwocky to Proposing Topics for English Pedagogy

Riski Lestiono 한국영어어문교육학회 2023 영어어문교육 Vol.29 No.3

Portrayed as a monster and villain, narrated in seven stanzas in an iambic tetrameter metrics, Jabberwocky is a phenomenal poem. This poem, loaded with “esoteric” and nonce words, was mostly researched in the realms of translation and psycholinguistics, leading to a dearth of studies in L2 pedagogy. The posed question was “What are some latent themes or topics for ELT material development that can be revealed from the discernibly nonsensical language of Lewis Carroll’s Jabberwocky poem?” Descriptive phenomenological design suited this study’s purpose to delineate emic language pedagogical aspects of this poem. Thematic analysis was employed by performing a 6-step framework. This current study has yielded three main themes that propose Jabberwocky poem as an alternative source of English material development. The latent themes circumnavigate around morphology, syntax, and phonology. Morphologically, L2 learners could delve further to the two-word-formation processes, namely: portmanteau and coinage. Syntactically, Jabberwocky poem can hone the skill in detecting parts of speech. Phonologically, the concept of phonaesthesia fosters sound interpretation. This study rounds off by thanking Lewis Carroll for sharp-wittedly writing Jabberwocky poem and proposing an alternative to material developers as well as English teachers and practitioners to incorporate this work of art into their instructions.

Shelf-Lifetime Stability of Planar ZnO/MAPbI₃-Based Perovskite Solar Cells

Riski Titian Ginting,Mi-Kyung Jeon,Neetesh Kumar,Jae-Wook Kang 한국고분자학회 2016 한국고분자학회 학술대회 연구논문 초록집 Vol.41 No.2

Low-temperature operation of perovskite solar cells: With efficiency improvement and hysteresis-less

Ginting, Riski Titian,Jung, Eun-Seon,Jeon, Mi-Kyoung,Jin, Won-Yong,Song, Myungkwan,Kang, Jae-Wook unknown 2016 Nano energy Vol.27 No.-

<P><B>Abstract</B></P> <P>Methylammonium lead iodide perovskite solar cells (PSCs) based on a solution-processed ZnO electron transporting layer were systematically investigated at low-temperature operating conditions. The power conversion efficiency gradually improved from 14.2% to 15.5% as the temperature decreased from 298 to 253K, mainly owing to increments of short circuit current density and open circuit voltage. In addition, the improvements in photocurrent related to the high charge carrier mobility, owing to the ideal nondispersive charge transport and fast electron transport lifetime at low temperature. Strikingly, hysteresis was suppressed with decreasing temperature related to the inhibition or relatively slow of ionic migration at reversed poling direction. This finding shows promising result of PSCs working efficiently under low temperature condition.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Under low-temperature operation, the efficiency of perovskite solar cell improved from 14.2% to 15.5%. </LI> <LI> Hysteresis was suppressed with decreasing temperature. </LI> <LI> To reveal the mechanisms underlying the observed improvements, the structural, optical, and electrical properties of the solar cells was characterized. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Plasmonic Effect of Gold Nanostars in Highly Efficient Organic and Perovskite Solar Cells

Ginting, Riski Titian,Kaur, Sandeep,Lim, Dong-Kwon,Kim, Jung-Mu,Lee, Joong Hee,Lee, Seung Hee,Kang, Jae-Wook American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.41

<P>Herein, a novel strategy is presented for enhancing light absorption by incorporating gold nanostars (Au NSs) into. both the active layer of organic solar cells (OSCs) and the rear-contact hole transport layer of perovskite solar cells (PSCs). We demonstrate that the power conversion efficiencies of OSCs and PSCs with embedded, Au NSs are improved by 6 and 14%, respectively. We find that pegylated Au NSs are greatly dispersable in a chlorobenzene solvent, which enabled complete blending of Au NSs with the active layer. The plasmonic contributions and accelerated charge transfer are believed to improve the short-circuit current density and the fill factor. This study demonstrates the roles of plasmonic nanoparticles in the improved optical absorption, where the improvement in OSCs was attributed to surface plasmon resonance (SPR) and in PSCs was attributed to-both SPR and the backscattering effect. Additionally, devices including Au NSs exhibited a better charge separation/transfer, reduced charge recombination rate, and: efficient charge transport. This work provides a comprehensive understanding of the roles of plasmonic Au NS particles in OSCs and PSCs, including an insightful approach for the further development of high-performance optoelectronic devices.</P>

Bioremediation of Crude Oil by White Rot Fungi Polyporus sp. S133

( Kristanti Risky Ayu ),( Tony Hadibarata ),( Tadashi Toyama ),( Yasuhiro Tanaka ),( Kazuhiro Mori ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.9

The bioremediation potential of crude oil by Polyporus sp. S133 pre-grown in wood meal was investigated in two separate experiment trials; liquid medium and soil. The effect of three nutrients (glucose, polypeptone, and wood meal), oxygen flow, and some absorbent on the efficiency of the process was also evaluated. Degradation of crude oil in soil was significantly increased with an addition of oxygen flow and some absorbent (kapok and pulp). The highest degradation rate of crude oil was 93% in the soil with an addition of 10% kapok. The present study clearly demonstrates that, if suitably developed, Polyporus sp. S133 could be used to remediate soil contaminated with crude oil.

Dual Light Trapping and Water-Repellent Effects of a Flexible-Based Inverse Micro-Cone Array for Organic and Perovskite Solar Cells

Ginting, Riski Titian,Jeon, Eun-Bi,Kim, Jung-Mu,Jin, Won-Yong,Kang, Jae-Wook American Chemical Society 2018 ACS APPLIED MATERIALS & INTERFACES Vol.10 No.37

<P>A simple and cost-effective fabrication process of a flexible-based inverse micro-cone array (i-MCA) structure textured on flexible transparent conductive electrodes (TCEs) was successfully demonstrated via a micro-imprinting process. The flexible i-MCA films exhibited an extremely high total transmittance of ∼93% and a haze of ∼95% with reduced reflectance while simultaneously demonstrating water-repellent properties. Introducing i-MCA on the illuminating side of organic solar cells (OSCs)- and perovskite solar cells-rigid glass substrate showed improved power conversion efficiencies (PCEs) due to the light trapping effect by multiple light bounces between cone array structures (forward scattering). This results in an increase of the optical path length in the photoactive layer. Similarly, flexible TCEs embedded with textured i-MCA increased the PCE by 14% for flexible OSCs. More importantly, i-MCA-TCE-based OSCs were highly flexible with 98% retention from the initial PCE at both 0° and at 60° even after 2000 bending cycles at a radius of 2 mm. This finding demonstrates that textured i-MCA is promising for improving: (a) the light harvesting efficiency of solar cells when installed in low-/high-latitude locations and (b) the wearable technology where a flexible device attached on curved objects could retain the PCE, even at an oblique angle, with respect to the normal incidence angle.</P> [FIG OMISSION]</BR>

Effects of singular administration of six different probiotics on growth performance, feed utilization, whole body composition and hematological parameters of juvenile olive flounder (Paralichthys olivaceus)

Intan Riski Mauliasari,Kye-Yoon Yoon,Sanaz Khosravi,Seong-Mok Jeong,Sang-Min Lee 한국수산해양기술학회(구 한국어업기술학회) 2018 한국수산해양기술학회 학술발표대회 Vol.2018 No.11

A Simple Approach Low-Temperature Solution Process for Preparation of Bismuth-Doped ZnO Nanorods and Its Application in Hybrid Solar Cells

Ginting, Riski Titian,Lee, Hock Beng,Tan, Sin Tee,Tan, Chun Hui,Jumali, Mohd. Hafizuddin Hj.,Yap, Chi Chin,Kang, Jae-Wook,Yahaya, Muhammad American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.1

<P>A simple low-temperature solution processed bismuth-doped ZnO nanorods (NRs) and poly(3-hexylthiophene) (P3HT) were used as electron acceptor and donor, respectively, in a hybrid inorganic-organic photovoltaic system. Controlling Bi precursor concentration via solution processing (hydrothermal method) plays an important role in altering the morphology, structure, and intrinsic defects of ZnO NRs. Interstitial doping of BiBi2O3 into ZnO (BiZO) NRs results in simultaneous improvement of the open circuit voltage and short circuit current density primarily due to prolonged charge carrier recombination lifetime, increased donor-acceptor interfacial areas with efficient exciton dissociation, and charge carrier mobility. As a result, the power conversion efficiency of the 2 wt % BiZO NRs-P3HT device was significantly enhanced by 55% compared with that of the pristine device. Overall, our study highlighted the immense potential of BiZO NRs as an excellent electron acceptor for fabrication of hybrid optoelectronic devices.</P>

A novel design of hybrid transparent electrodes for high performance and ultra-flexible bifunctional electrochromic-supercapacitors

Ginting, Riski Titian,Ovhal, Manoj Mayaji,Kang, Jae-Wook Elsevier 2018 Nano energy Vol.53 No.-

<P><B>Abstract</B></P> <P>In this study, a simple and cost-effective method of fabricating hybrid transparent conductive electrodes (TCEs) based on embedded silver nanowires (Ag NWs)/PEDOT: PSS was developed with the addition of low-temperature synthesis of Ni(OH)<SUB>2</SUB> and polyethylenimine ethoxylated (PEIE) composites as a novel interlayer. The hybrid TCEs with a Ni(OH)<SUB>2</SUB>-PEIE interlayer exhibit remarkable volumetric capacitance of 443 F cm<SUP>−3</SUP> with transparency of 86%, which is one of the highest values reported to date in the transparent supercapacitor. The fabricated bifunctional solid-state electrochromic-supercapacitor device with a transparency of 80% shows stable cyclic stability up to 10,000 charge/discharge cycles, extremely high coloration efficiency of 517 cm<SUP>2</SUP> C<SUP>−1</SUP> at 633 nm, and a fast switching speed (<0.6 s). The noted improvement is mainly caused by the Ni(OH)<SUB>2</SUB>-PEIE interlayer influence the pore density of PEDOT: PSS which provides high surface area, thus resulting in efficient charge transfer pathways and fast ion diffusion. Moreover, a capacitance retention of 90% is achieved even after 8000 bending cycles at a bending radius of 1 mm and 15 times of crumpling is tolerated without noticeable degradation, implying excellent mechanical robustness and flexibility. The results present the significant potential of transparent hybrid electrodes for efficient energy storage and electrochromicity with stable transmittance changes, even during fast charge/discharge processes, demonstrating their potential as smart wearable energy storage devices.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The bifunctional solid-state electromic-supercapacitor device showed a reversible electrochromic effect during charge/discharge cycles. </LI> <LI> High coloration efficiency of 517 cm<SUP>2</SUP> C<SUP>−1</SUP> at 633 nm, and fast switching speed (<0.6 s). </LI> <LI> High areal capacitance of 3.3 mF cm<SUP>−2</SUP> and excellent cyclic stability with a device transparency of 80%. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>