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Development of Prototype Stylus Prototype for Large Optics Testing
Yang, Ho-Soon,Walker, David Optical Society of Korea 2001 Current Optics and Photonics Vol.5 No.2
The authors discuss a prototype stylus profilometer designed to measure large optics. It consists of a low contact force type probe system, laser reference system, interferometric distance measurement system, and horizontal driving system. The probe contacts the surface ; the height and the horizontal distances of the measurement points are measured by the interferometer. The freely propagated laser beam provides the reference line during the measurement. The developed stylus profilometry shows only $\pm$60 nm of P-V error for the 157 mm diameter spherical mirror.
Regulation of floral organ abscission of Arabidopsis thaliana
Sung Ki Cho,David Chevalier,Clayton Larue,Tsung-Luo Jinn,Shuqun Zhang,John C. Walker 한국작물학회 2007 한국작물학회 학술발표대회 논문집 Vol.2007 No.11
Organ abscission is a programmed cell separation process that results in the detachment of an entire organ from a plant. Our goal is to understand the signaling pathway that regulates this physiological process. The receptor-like protein kinase, HAESA (HAE), and its paralog, HAESA-like 2 (HSL2), are both expressed in the floral abscission zones in Arabidopsis thaliana. Loss-of-function analyses of either gene do not show any phenotypical change, but the hae hsl2 double mutant shows an abscission-defect phenotype. Examination of the abscission zone by light and scanning electron microscopy showed that the abscission zone in the hae hsl2 appears structurally normal. The force required to remove the petals in wild type and hae hsl2 flowers was measured using a petal breakstrength meter. The force required to remove petals from the hae hsl2flowers at all stages of development was similar to that of wild type flowers that have not yet begun to abscise their petals. Taken together, these data support the role of HAE and HSL2 in the activation of cell separation, rather than differentiation of the abscission zone. Ethylene is also known to promote abscission; therefore we tested the ethylene-induced triple response and the effect of exogenous treatment on floral organ in the hae hsl2, revealing that HAE and HSL2 act independently of ethylene. This implies that the HAE is critical for floral abscission in concert with the action of HSL2.
Synergistic photocurrent addition in hybrid quantum dot: Bulk heterojunction solar cells
Kim, Gi-Hwan,Walker, Bright,Zhitomirsky, David,Heo, Jungwoo,Ko, Seo-Jin,Park, Jongnam,Sargent, Edward H.,Young Kim, Jin Elsevier 2015 Nano energy Vol.13 No.-
<P><B>Abstract</B></P> <P>We investigate the effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs). The PbS QD layer is able to function as a photosensitizing layer to improve short circuit current density (<I>J</I> <SUB>SC</SUB>) and power conversion efficiency (PCE) by exploiting solar flux in the near infrared region up to 1100nm. The increase in <I>J</I> <SUB>SC</SUB> is well represented by changes observed in the external quantum efficiency of devices with and without the PbS QD layer, including the region of the first exciton transition where only the PbS QD layer absorbs. Remarkably, enhanced performance was observed in QD-OSCs consisting of just a 13nm thick PbS QD layer and 150nm PTB7:PC<SUB>71</SUB>BM layer, exhibiting a <I>J</I> <SUB>SC</SUB> of 17.0mAcm<SUP>−2</SUP>, and PCE of 8.30% (8.58% for champion device) compared to reference devices without PbS QD which produced a <I>J</I> <SUB>SC</SUB> of 15.4mAcm<SUP>−2</SUP> and PCE of 7.56%.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We have fabricated hybrid solar cells using a PbS QD layer and PTB7/PC<SUB>71</SUB>BM layer. </LI> <LI> The device is built on PTB7:PC<SUB>71</SUB>BM bulk heterojunction and a PbS QD layer. </LI> <LI> The PbS QD layer acts as a photosensitizing layer to improve the device performance. </LI> <LI> Additional photocurrent leads to enhancement in performance in hybrid solar cells. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>The effect of a thin PbS quantum dot (QD) layer on the performance of hybrid quantum-dot-organic solar cells (QD-OSCs) was investigated. The PbS QD layer is able to function as a photosensitizing layer with PTB7/PC<SUB>71</SUB>BM bulk heterojunction to improve short circuit current density from 15.4mAcm<SUP>−2</SUP> to 17.0mAcm<SUP>−2</SUP> and power conversion efficiency from 7.56% to 8.30%. </P> <P>[DISPLAY OMISSION]</P>
DESIGN CONCEPT FOR SINGLE CHIP MOSAIC CCD CONTROLLER
HAN WONYONG,JIN Ho,WALKER DAVID D.,CLAYTON MARTIN The Korean Astronomical Society 1996 Journal of The Korean Astronomical Society Vol.29 No.suppl1
The CCDs are widely used in astronomical observations either in direct imaging use or spectroscopic mode. However, the areas of available sensors are too small for large imaging format. One possibility to obtain large detection area is to assemble mosaics of CCD, and drive them simultaneously. Parallel driving of many CCDs together rules out the possibility of individual tuning; however, such optimisation is very important, when the ultimate low light level performance is required, particularly for new, or mixed devices. In this work, a new concept is explored for an entirely novel approach, where the drive waveforms are multiplexed and interleaved. This simultaneously reduces the number of leadout connections and permits individual optimisation efficiently. The digital controller can be designed within a single EPLD (Erasable Programmable Logic Device) chip produced by a CAD software package, where most of the digital controller circuits are integrated. This method can minimise the component. count., and improve the system efficiency greatly, based on earlier works by Han et a1. (1996, 1994). The system software has an open architecture to permit convenient modification by the user, to fit their specific purposes. Some variable system control parameters can be selected by a user with a wider range of choice. The digital controller design concept allows great flexibility of system parameters by the software, specifically for the compatibility to deal with any number of mixed CCDs, and in any format, within the practical limit.
Highly selective trace ammonium removal from dairy wastewater streams by aluminosilicate materials
Elaine O’Connor,Oisin N. Kavanagh,Drahomir Chovan,David G. Madden,Patrick Cronin,Ahmad B. Albadarin,Gavin M. Walker,Alan Ryan 한국공업화학회 2020 Journal of Industrial and Engineering Chemistry Vol.86 No.-
Water is a key solvent, fundamental to supporting life on earth. It is equally important in many industrialprocesses, particularly within agricultural and pharmaceutical industries, which are major drivers of theglobal economy. The results of water contamination by common activity in these industries is well knownand EU Water Quality Directives and Associated Regulations mandate that NH4+ concentrations ineffluent streams should not exceed 0.3 mg L 1, this has put immense pressure on organisations andindividuals operating in these industries. As the environmental andfinancial costs associated with waterpurification begin to mount, there is a great need for novel processes and materials (particularlyrenewable) to transform the industry. Current solutions have evolved from combating toxic sludge to theuse of membrane technology, but it is well known that the production of these membrane technologiescreates a large environmental footprint. Zeolites could provide an answer; their pore size and chemistryenable efficient removal of aqueous based cations via simple ion exchange processes. Herein, wedemonstrate efficient removal of NH4+ via both static and dynamic methodology for industrialapplication. Molecular modelling was used to determine the cation–framework interactions which willenable customisation and design of superior sorbents for NH4+ capture in wastewater.