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Flows over Concave Surfaces: Development of Pre-set Wavelength Görtler Vortices
Winoto, S.H.,Tandiono,Shah, D.A.,Mitsudharmadi, H. 한국유체기계학회 2008 International journal of fluid machinery and syste Vol.1 No.1
The development of pre-set wavelength Grtler vortices are studied in the boundary-layer flows on concave surfaces of 1.0 and 2.0 m radius of curvature. The wavelengths of the vortices were pre-set by thin wires of 0.2 mm diameter placed 10 mm upstream and perpendicular to the concave surface leading edge. Velocity contours were obtained from velocity measurements using a single hot-wire anemometer probe. The most amplified or dominant wavelength is found to be 15 mm for free-stream velocity of 2.1 m/s and 3.0 m/s on the concave surface of R = 1 m and 2 m, respectively. The velocity contours in the cross-sectional planes at several streamwise locations show the growth and breakdown of the vortices. Three different regions can be identified based on the growth rate of the vortices. The occurrence of a secondary instability mode is also shown in the form of mushroom-like structures as a consequence of the non-linear growth of the Grtler vortices. By pre-setting the vortex wavelength to be much larger and much smaller than the most amplified one, the splitting and merging of Grtler vortices can be respectively observed.
Ionic Liquids Containing 1,1-Dicyano-1-acetylmethanide Anion as Potential Electrolytes
Winoto, Haryo Pandu,Agarwal, Shalu,Im, Jin-Kyu,Cheong, Min-Serk,Lee, Je-Seung Korean Chemical Society 2012 Bulletin of the Korean Chemical Society Vol.33 No.9
Various types of room temperature ionic liquids (RTILs) containing 1,1-dicyano-1-acetylmethanide anion ($[C(CN)_2(COCH_3)]^-$, $[DCNAcC]^-$) were prepared and their physical and electrochemical properties were studied. All of these ILs exhibited high thermal stabilities over $200^{\circ}C$ and relatively high ionic conductivities up to 29.4 $mS\;cm^{-1}$ at $80^{\circ}C$. Although the ionic conductivity of IL containing bis(trifluoromethanesulfonyl)-imide ($[Tf_2N]^-$) anion is higher than that of ILs bearing $[DCNAcC]^-$ anion, the specific capacitance of ILs bearing $[DCNAcC]^-$ anion are higher than that of IL containing $[Tf_2N]^-$ anion and showed high temperature dependence. Such favorable electrochemical properties of these ILs are likely to be attributed to the efficient dissociation of cation and anion at higher temperature and enhanced electrosorption of $[DCNAcC]^-$ anion at the electrode.
Concave Surface Boundary Layer Flows in the Presence of Streamwise Vortices
Winoto, Sonny H.,Tandiono, Tandiono,Shah, Dilip A.,Mitsudharmadi, Hatsari Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1
Concave surface boundary-layer flows are subjected to centrifugal instability which results in the formation of streamwise counter-rotating vortices. Such boundary layer flows have been experimentally investigated on concave surfaces of 1 m and 2 m radius of curvature. In the experiments, to obtain uniform vortex wavelengths, thin perturbation wires placed upstream and perpendicular to the concave surface leading edge, were used to pre-set the wavelengths. Velocity contours were obtained from hot-wire anemometer velocity measurements. The most amplified vortex wavelengths can be pre-set by the spanwise spacing of the thin wires and the free-stream velocity. The velocity contours on the cross-sectional planes at several streamwise locations show the growth and breakdown of the vortices. Three different vortex growth regions can be identified. The occurrence of a secondary instability mode is also shown as mushroom-like structures as a consequence of the non-linear growth of the streamwise vortices. Wall shear stress measurements on concave surface of 1 m radius of curvature reveal that the spanwise-averaged wall shear stress increases well beyond the flat plate boundary layer values. By pre-setting much larger or much smaller vortex wavelength than the most amplified one, the splitting or merging of the streamwise vortices will respectively occur.
Winoto, Haryo Pandu,Fikri, Zuhroni Ali,Ha, Jeong-Myeong,Park, Young-Kwon,Lee, Hyunjoo,Suh, Dong Jin,Jae, Jungho Elsevier 2019 Applied Catalysis B Vol.241 No.-
<P><B>Abstract</B></P> <P>A novel bifunctional catalyst that enables an efficient one-pot conversion of furfural into γ-valerolactone (GVL) has been developed by anchoring heteropolyacid (HPA) on Zr-Beta zeolite. The catalysts were prepared by a post-synthesis procedure, which consists of the dealumination of Al-Beta, incorporation of Zr into the beta framework through solid-state ion-exchange and impregnation of the HPA. Zr-Beta is used as a Lewis acid catalyst to catalyze the transfer hydrogenation of furfural and levulinic acid/ester using 2-propanol as a hydrogen donor. To deal with the inability of Zr-Beta to catalyze the hydrolytic ring-opening of furans toward GVL, phosphotungstic acid (HPW) and silicotungstic acid (HSiW) were introduced to the Zr-Beta as BrØnsted acid sites. The characterization of the catalysts using XRD, UV–vis and XPS as well as TPD of ammonia and FT-IR spectroscopy of the adsorbed pyridine revealed that the HPA/Zr-Beta possesses both isolated Lewis and BrØnsted acid sites. When they were applied to the one-pot cascade conversion of furfural, the initial activity of the HPA/Zr-Beta toward GVL production were 2–3 times greater than that for Zr-Beta due to the enhanced hydrolytic ring-opening of the furans promoted by the added BrØnsted acidity. Especially, HPW loaded Zr-Beta demonstrated a remarkable GVL yield of ∼70% at 433 K after 24 h due to its high thermal stability and stronger BrØnsted acidity, and its activity far surpasses that of the conventional Sn-Al-Beta zeolite (∼40%). Overall, this study demonstrates that an incorporation of HPA into Lewis acid Sn- or Zr-Beta zeolites is an effective strategy to create isolated Lewis and BrØnsted acid sites within a single catalyst, thereby allowing the selective cascade catalysis for the cost-effective production of high-value chemicals.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Heteropolytungstae (HPW)-loaded Zr-Beta is synthesized via a simple post-synthesis method. </LI> <LI> The method consists of dealumination of Al-Beta followed by sequential incorporation of Zr and HPW. </LI> <LI> HPW/Zr-Beta zeolite possesses both isolated Lewis and Brønsted acid sites. </LI> <LI> Transfer hydrogenation and ring-opening reactions is effectively combined using a single catalyst. </LI> <LI> One-pot cascade conversion of furfural to GVL with a high yield (∼70%) is achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Strategic Ignorance in Argumentation-Based Negotiation
Pinata Winoto 한국지능시스템학회 2008 한국지능시스템학회 학술발표 논문집 Vol.18 No.1
We argue that agents may benefit from strategic ignorance in argumentation-based negotiation (ABN). We assume our agents are selfish myopic, and residing in open systems. Some analytical results that can be used for designing agent reasoning on strategic ignorance are provided.
Haryo Pandu Winoto,안병성,재중호 한국공업화학회 2016 Journal of Industrial and Engineering Chemistry Vol.40 No.-
A bifunctional Sn-Al-Beta zeolite which possesses isolated Lewis and Brønsted acid sites was prepared bya post-synthesis procedure and applied to the one-pot conversion of furfural to g-valerolactone (GVL), avalue-added chemical. Sn-Al-Beta was capable of catalyzing a cascade of the transfer hydrogenation andhydrolysis of furfural to GVL by the interplay of Lewis and Brønsted acid sites. The degree ofdealumination and the tin-incorporation method largely influence the acid properties of the catalyst andthe catalyst selectivity. A high yield of GVL up to 60% was obtained with Sn-Al-Beta 7 (Si/Sn = 63 and Si/Al = 473) at 180 8C in 2-butanol.
Ionic Liquids Containing 1,1-Dicyano-1-acetylmethanide Anion as Potential Electrolytes
Haryo Pandu Winoto,Shalu Agarwal,임진규,정민석,이제승 대한화학회 2012 Bulletin of the Korean Chemical Society Vol.33 No.9
Various types of room temperature ionic liquids (RTILs) containing 1,1-dicyano-1-acetylmethanide anion ([C(CN)2(COCH3)]−, [DCNAcC]−) were prepared and their physical and electrochemical properties were studied. All of these ILs exhibited high thermal stabilities over 200 oC and relatively high ionic conductivities up to 29.4 mS cm−1 at 80 oC. Although the ionic conductivity of IL containing bis(trifluoromethanesulfonyl)- imide ([Tf2N]−) anion is higher than that of ILs bearing [DCNAcC]− anion, the specific capacitance of ILs bearing [DCNAcC]− anion are higher than that of IL containing [Tf2N]− anion and showed high temperature dependence. Such favorable electrochemical properties of these ILs are likely to be attributed to the efficient dissociation of cation and anion at higher temperature and enhanced electrosorption of [DCNAcC]− anion at the electrode.
Cheah, Kean Wee,Lee, Thong-See,Winoto, S.H. Korean Society for Fluid machinery 2011 International journal of fluid machinery and syste Vol.4 No.1
The objective of present work is to use numerical simulation to investigate the complex three-dimensional and secondary flow structures developed at the inlet and impeller in a centrifugal pump at design and off-design points. The pump impeller is shrouded with 6 backward swept blades and with a specific speed of 0.8574. The characteristic of the pump is measured experimentally with straight and curved intake sections. Numerical computation is carried out to investigate the pump inlet flow structures and subsequently the flow field within the centrifugal pump. The numerical results showed that strong interaction between the impeller eye and intake section. Secondary flow structure occurs upstream at the pump inlet has great influence on the pump performance and flow structure within the impeller.