Physical Sciences and Mathematics Commons^™

Spatial And Orientational Control Of Liquid Crystal Alignment Using A Surface Localized Polymer Layer, Lu Lu, Tatiana Sergan, Vassili Sergan, Philip J. Bos

Philip J. Bos

We present an alignment method for the surface contacting liquid crystal (LC) director. This method allows complete control of the polar pretilt angle as a function of position in a liquid crystal device, and has the potential of controlling the azimuthal orientation of LC. Important considerations of this method are to form a thin layer of reactive monomers at the LC cell interior surface, and to control the deleterious effects of flow due to polymerization induced concentration gradients. To achieve these, the voltage and frequency of the applied electric field and the UV intensity during the polymerization process are significant.

Recurrent Geomagnetic Storms And Relativistic Electron Enhancements In The Outer Magnetosphere: Istp Coordinated Measurements, D N. Baker, X Li, Niescja E. Turner, J H. Allen, L F. Bargatze, J B. Blake, R B. Sheldon, H E. Spence, R D. Belian, G D. Reeves, S G. Kanekal, B Klecker, R P. Lepping, K Ogilvie, R A. Mewaldt, T Onsager, H J. Singer, G Rostoker

Niescja E. Turner

New, coordinated measurements from the International Solar-Terrestrial Physics (ISTP) constellation of spacecraft are presented to show the causes and effects of recurrent geomagnetic activity during recent solar minimum conditions. It is found using WIND and POLAR data that even for modest geomagnetic storms, relativistic electron fluxes are strongly and rapidly enhanced within the outer radiation zone of the Earth's magnetosphere. Solar wind data are utilized to identify the drivers of magnetospheric acceleration processes. Yohkoh solar soft X-ray data are also used to identify the solar coronal holes that produce the high-speed solar wind streams which, in turn, cause the recurrent …

A Multispacecraft Istp Study: Substorm Evolution From The Solar Wind To The Magnetosphere And Ionosphere, T Pulkkinen, D Baker, Niescja Turner, H Singer, J Blake, H Spence, L Frank, J Sigwarth, T Mukai, S Kokubun, R Nakamura, C Russell, H Kawano, F Mozer, J Slavin, R Lepping, R Anderson, G Reeves, L Zelenyi

Niescja E. Turner

An isolated substorm event on May 15, 1996, was recorded by an unprecedented suite of satellites both in the solar wind and in the magnetosphere. We show data from various instruments onboard several ISTP satellites to discuss both the prompt response of the dayside magnetosphere to the changes in the interplanetary magnetic field and the following substorm evolution in the nightside tail.

Solar Wind-Magnetosphere Coupling During An Isolated Substorm Event: A Multispacecraft Istp Study, T I. Pulkkinen, D N. Baker, Niescja E. Turner, H J. Singer, L A. Frank, J B. Sigwarth, J Scudder, R Anderson, S Kokubun, R Nakamura, T Mukai, J B. Blake, C T. Russell, H Kawano, F Mozer, J A. Slavin

Niescja E. Turner

Multispacecraft data from the upstream solar wind, polar cusp, and inner magnetotail are used to show that the polar ionosphere responds within a few minutes to a southward IMF turning, whereas the inner tail signatures are visible within ten min from the southward turning. Comparison of two subsequent substorm onsets, one during southward and the other during northward IMF, demonstrates the dependence of the expansion phase characteristics on the external driving conditions. Both onsets are shown to have initiated in the midtail, with signatures in the inner tail and auroral oval following a few minutes later.

A Substorm Onset Observed By The Polar Spacecraft In Conjunction With The Image Chain, P Toivanen, D Baker, W Peterson, A Viljanen, Niescja Turner, X Li, C Kletzing

Niescja E. Turner

No abstract provided.

Reply To Comment On "Evaluation Of The Tail Current Contribution To Dst", Niescja Turner, D Baker, T Pulkkinen, R Mcpherron

Niescja E. Turner

Turner et al. [2000] analyzed the contribution of cross-tail currents to the Dst index. In order to estimate this contribution we used modified versions of the Tsyganenko models which had been adjusted to match spacecraft data in the tail, and we isolated a tail region and calculated its influence. We concluded that the tail currents were responsible for around 25% of the Dst response during moderately disturbed times. Maltsev and Ostapenko [2002] conclude that our estimate was low by a factor of 2, owing to that fact that we neglected dayside currents and that the model we used systematically underestimates …

Magnetospheric Response Times Following Southward Imf Turnings, Niescja E. Turner, D N. Baker, T I. Pulkkinen, H J. Singer, F Mozer

Niescja E. Turner

No abstract provided.

X2 Tests For The Choice Of The Regularization Parameter In Nonlinear Inverse Problems, J. L. Mead, C. C. Hammerquist

Jodi Mead

We address discrete nonlinear inverse problems with weighted least squares and Tikhonov regularization. Regularization is a way to add more information to the problem when it is ill-posed or ill-conditioned. However, it is still an open question as to how to weight this information. The discrepancy principle considers the residual norm to determine the regularization weight or parameter, while the χ2 method [J. Mead, J. Inverse Ill-Posed Probl., 16 (2008), pp. 175–194; J. Mead and R. A. Renaut, Inverse Problems, 25 (2009), 025002; J. Mead, Appl. Math. Comput., 219 (2013), pp. 5210–5223; R. A. Renaut, I. Hnetynkova, and J. L. …

Corrosion Behavior Of A High Strength Low Alloy Steel Under Hydrostatic Pressure In Deep Ocean, Hai-Jing Sun, Li Liu, Ying Li

Journal of Electrochemistry

The corrosion behavior of a high strength low alloy steel (HSLA steel) in 3.5% NaCl solution under hydrostatic pressure (HP) in deep ocean has been investigated by performing weight loss measurement, obtaining potentiodynamic polarization curve and emplying electrochemical impedance spectroscopy (EIS) using the set up for simulation of deep sea environment in laboratory. The results were compared with that at atmospheric pressure and the influence of HP was emphatically discussed. The results revealed identical corrosion mechanism for HSLA steel at 3.5 × 106 Pa and 1 × 105 Pa. Howevere, the development of such a corrosion process was remarkably accelerated …

Corrosion Resistance Of Low Pressure Cold Sprayed Al Coating On Q235 Steel In Seawater, Xiang-Bo Li, Li-Kun Xu, Shan-Guang Qiu, Jia Wang, Guo-Sheng Huang, Cai-Chang Dong

Journal of Electrochemistry

Taking aluminium (Al) powder mixed with 10% (by volume) of Al2O3 powder as raw materials, the Al coating was prepared on the Q235 carbon steel substrate using a portable low pressure cold spraying equipment. Through the measurements of the corrosion potential and potentiodynamic polarization, the electrochemical corrosion behavior of the low pressure cold sprayed Al coating in seawater was studied in comparison with those of the Al coatings deposited with high pressure cold spray and thermal spray processes. At the same time, the surface and cross-section morphologies of these coatings were observed with scanning electron microscope. The results showed that …

Preparation Of Benzoquinone From Phenol By Electrooxidation, Dong-Fang Niu, Cheng-Kai Yu, Xin-Sheng Zhang

Journal of Electrochemistry

The benzoquinone was prepared from phenol by electrooxidation in an H-type cell with cation exchange membrane, in which lead plates were used both as an anode and a cathode, while H₂SO₄ was used as a supporting electrolyte. The effects of current density, concentration of sulphuric acid, concentrations of benzoquinone in electrolyte and extractant on the yields and efficiencies of electrolysis were investigated. Under the optimized conditions of current density being 4 A·dm^-2, concentration of sulphuric acid 1 mol·L^-1, passed charge 3.2 A·h, the yield and current efficiency of benzoquinone could reach 68% and …

Synthesis Of Pani/Nihcf Nanocomposite Particles And Eqcm Measurement Of Ion Exchange Properties In Solutions Containing Cd2+, Yu-Jiao Yang, Xiao-Gang Hao, Xu-Li Ma, Zhong-De Wang, Zhong-Lin Zhang, Nian-Chen Han

Journal of Electrochemistry

The PANI/NiHCF nanocomposite particles were synthesized on the CNTs-modified Pt substrate by one-step co-polymerization using cyclic voltammetry. Electrochemical quartz crystal microbalance (EQCM) technique was adopted to investigate the polymerization process of the nanocomposite particles and the mechanism of ion exchange in aqueous solution containing Cd²⁺． The morphology and structure of the as-prepared composite particles were characterized by scanning electron microscope (SEM), transmission electron microscope (TEM), and Fourier transform infrared spectroscopy (FT-IR). Combined with cyclic voltammetry (CV) and energy dispersive spectroscopy (EDS), the electrochemical behavior and the mechanism of ion exchange were also investigated in electrolytes of Cd^{2+ …}

Electrocatalytic Properties Of The Keggin-Type Co(Ii)-Substituted Heteropolyanion Pw11O39Co(Ii)(H2O)5-, Bin Wang, Chong-Tai Wang, Ying-Jie Hua, Jin-Yuan Liu, Liang-Fei Zheng

Journal of Electrochemistry

The electrochemical properties of the Keggin-type Co(II)-substituted heteropolyanion PW₁₁O₃₉Co(II)(H₂O)^5- (PW₁₁Co), as well as the electrocatalytic properties of PW₁₁Co towards the anodic oxidations of H₂O₂ and CH₃OH were studied using the electrochemical methods such as cyclic voltammetry and AC impedance spectroscopy in this paper. An electrocatalytic mechanism of PW₁₁Co as an anodic medium was also proposed. It was found that PW₁₁Co showed a pair of pseudo-reversible redox peaks at the potentials of 1.367 V/1.266 V, corresponding to the redox responses of …

A Comparative Study In Pretreatments Of Acid Chemical Wastewater By Electrochemical Oxidation And Ozonation, Han-Shui Liu, Su Yu, Shao-Ping Tong, Chun-An Ma

Journal of Electrochemistry

Under the condition of keeping certain acidity, the pretreatment efficiency of an acid chemical wastewater (pH 0.85) by electrochemical oxidation was compared with that by ozonation. The results showed that the electrochemical oxidation pretreatment could obtain a better result than the ozonation at pH 0.85. After the addition of 2 g·L^-1 NaCl and with the electrochemical oxidation pretreatment at 30 mA·cm^-2, the removal rate of chemical oxygen demand (CODCr) reached 43.4%, and the value of biochemical oxygen demand/chemical oxygen demand (BOD₅/COD_Cr) also increased from 0.034 to 0.14 in 20 minutes, indicating significantly improvement …

Corrosion Behavior Of Zinc Covered With Thin Electrolyte Layers Under External Electric Field, Xu-Jie Yuan, Jun-Xi Zhang, Shi-Ming Zhang, Tian Tan, Qi-Meng Chen

Journal of Electrochemistry

The corrosion behavior of zinc covered with thin electrolyte layers (TELs) under an application of external electric field was investigated by performing corrosion potential and cathodic polarization current measurements. The results showed that the Ecorr and ic values first increased and then decreased with the increase of electrolyte layer thickness. Pure zinc exhibited the maximum corrosion potential as the TELs increased to 400 μm under the controls of cathodic process and corrosion products. The application of external electric field resulted in either a negative shift in corrosion potential of zinc or an increase of cathodic current. The effect of external …

Experimental Design Methodology Applied To The Oxidation Of Quinolines In Aqueous Medium By Electro-Fenton Process, Souissi Souhaila Trabelsi, Nihal Oturan, Nizar Bellakhal, Mehmet A. Oturan

Journal of Electrochemistry

The degradation behavior of 8-hydroxyquinoleine sulfate (8-HQS), a model molecule of quinolines, was studied in an aqueous medium by electro-Fenton process using a carbon felt cathode and a platinum anode. The great oxidation ability of this process is due to a large production of hydroxyl radical (OH) by electrochemically induced Fenton’s reagent (H2O2, Fe2+). Hydroxyl radicals are very powerful oxidizing agents which react on organics up to complete mineralization. A factorial experimental design was used for determining the operating parameters on the degradation of 8-HQS in an aqueous medium. The results showed that the current intensity and the initial concentration …

Electrochemically Switched Separation Of Yttrium Ion Using Electroactive Nickel Hexacyanoferrate Thin Films In Rare Earth Metal Solution, Hao Zhang, Xiao-Gang Hao, Zhong-De Wang, Zhong-Lin Zhang, Xu-Li Ma, Yi-Bing Li, Shi-Bin Liu

Journal of Electrochemistry

Electroactive nickel hexacyanoferrate (NiHCF) thin films were synthesized by cathodic deposition and investigated as electrochemically switched ion exchange (ESIX) materials for the separation of Y³⁺ from aqueous solutions. In 0.1 mol·L^-1 Y(NO₃)₃ solution, cyclic voltammetry (CV) combined with electrochemical quartz crystal microbalance (EQCM) technique was used to investigate the electroactivity, reversibility of the film electrodes and the mechanism of ion exchange. The electrochemical behavior of NiHCF film electrodes was also compared with that in Sr(NO₃)₂ solutions. The ion selectivity of the film was investigated in 0.1 mol·L^-1 solutions containing [Y(NO_{3 …}

Thoughts On The Complex Relation Between Linked Data, Semantic Annotations, And Ontologies, Krzysztof Janowicz, Pascal Hitzler

Computer Science and Engineering Faculty Publications

The relation between data, annotations, and schemata seems straightforward at first: Data are annotated with additional meta information according to some schemata in order to expose additional non-intrinsic characteristics relevant to the meaningful interpretation of said data. However, on closer examination, things are not as simple. Focusing on geo-information retrieval, we will try to disentangle the aforementioned relations. We will report from our own experience and from observations gathered by editing papers about ontologies and Linked Data for the Semantic Web journal.

Multimedia Data Fusion, Shangbo Zhou, Henry Leung, Fenghui Yao

Computer Science Faculty Research

Multimedia data is widely used in the world such as image, video, text, and audio. For obtaining better sensing performance, research on multimedia data fusion (MDF) is active and extensive around the world. In medical systems, a body part could be imaged with different sensors such as computed tomography and magnetic resonance imaging. In video surveillance, the interest is in the identification, recognition, and tracking of people by numerous cameras. All of these cases illustrate the importance of MDF in real-life applications. A number of mathematical methods have been researched in MDF such as statistics, fuzzy mathematical, stochastic differential theory, …

Anaerobic Biotransformation Of Environmental Pollutants Stimulated By Electric Field: Electron-Transfer Mechanisms And Application Examples, Chun-Hua Feng, Dao-Hai Xie, Yun-Meng Pang, Tao Han, Chao-Hai Wei

Journal of Electrochemistry

The ability of some microorganisms to accept electrons from an electrode for the reduction of terminal electron acceptors in anaerobic environments has attracted growing interest on the electric field-stimulated biological reduction technology, which may open new possibility for the sustainable wastewater treatment and bioremediation in the field of environmental engineering. Here, we reviewed the extracellular electron transfer mechanism which is thought to play a key role in determining the feasibility and efficiency for the anaerobic biotransformation of environmental pollutants. Possible mechanisms that may be involved in bioelectrochemical reactors (BERs) with biocathodes include indirect electron transfer via hydrogen generated from water …

Continuous Electroextraction And Concentration Technology, Qiong Ren, Wen Liao, Zu-Cheng Wu

Journal of Electrochemistry

Electrodeionization process combined electrodialysis with ion exchange provides a method to produce pure water and ultrapure water due to the ions accumulated in the resin instantaneously to reduce the system resistance. Meanwhile, large numbers of hydrogen ions and hydroxyl ions are dissociated by water hydrolysis, thus, the ion exchange resins are in-situ regenerated electrochemically. This technology has been utilized to retrieve useful ions which are enriched in the concentrated compartment from a dilute solution. This hybrid process is consequently developed as a new type of extraction and concentration technology and has been gradually employed in the recoveries of heavy metals, …

An Investigation Of Photocatalytic Degradation Reactions Of Pollutants By Combination Of (Photo)Electrochemical Measurements, Wen-Hua Leng, Hong-Qiao Zhu

Journal of Electrochemistry

Semiconductor photocatalysis plays a critical role in the environment protection and future energy development. (Photo)electrochemical measurements are powerful tools for studying the kinetics and mechanism of photocatalytic reactions, since photo-carriers, as reactants of photocatalytic reactions, are involved in the interfacial transfer and recombination of semiconductor/electrolyte interface. This review describes the part of our recent results regarding aqueous photocatalytic decontamination obtained by these methods, and the focus of future work in this field is suggested.

Basic Principles And Applications Of Secm In Metal Corrosion, Fa-He Cao, Yan Xia, Wen-Juan Liu, Lin-Rong Chang, Jian-Qing Zhang

Journal of Electrochemistry

Scanning electrochemical microscopy (SECM) is chemical microscopy with higher spatial resolution. After 24 years of development, SECM has been widely applied in mapping and kinetics study of heterogeneous electron transfer in localized processes at solid-liquid or liquid-liquid interfaces. The fundamentals and recent advances of SECM in corrosion applications are described, including SECM mapping and kinetics on localized corrosion of metal or coating. Research work of SECM in corrosion by our group is also introduced. Future applications of SECM in corrosion are highlighted.

An Investigation Of Thin Films Formed On Zinc By Spectroscopic Ellipsometry, Juan Zuo, Ying Chen, Chang-Jian Lin, Andreas Erbe

Journal of Electrochemistry

The formation of natural oxide films on polycrystalline zinc surface, the growth of natural oxide films in different atmospheres, as well as the electrochemical process of metal zinc in alkaline carbonate solution, studied recently by using spectroscopic ellipsometry in our group, are introduced. The objective of this paper is to outline that the optical, electrical properties, the change and growth kinetics of zinc metal oxide film on the surface can be investigated by in-situ and ex-situ ellipsometry, which makes significant sense to evaluate the overall performance of zinc oxide layer.

Applications Of Spectroscopic Ellipsometry In Corrosion Investigation, Ling-Jie Li, Yu-Ling He, Jing-Lei Lei, Sheng Tao Zhang

Journal of Electrochemistry

As a highly-sensitive and non-destructive in situ technique, spectroscopic ellipsometry has been widely applied in corrosion investigation to acquire the dynamic information of the “electrode-medium” interface during corrosion. This paper lays out some representative demonstrations in several established optical models used to interpret data obtained with spectroscopic ellipsometry in corrosion investigation. In addition, the latest trends in development of this technique are analyzed.

Finding Rare Agn: Xmm-Newton And Chandra Observations Of Sdss Stripe 82, Stephanie M. Lamassa, C. Megan Urry, Nico Cappelluti, Francesca Civano

Dartmouth Scholarship

We have analysed the XMM–Newton and Chandra data overlapping ∼16.5 deg² of Sloan Digital Sky Survey Stripe 82, including ∼4.6 deg² of proprietary XMM–Newton data that we present here. In total, 3362 unique X-ray sources are detected at high significance. We derive the XMM–Newton number counts and compare them with our previously reported Chandra logN–logS relations and other X-ray surveys. The Stripe 82 X-ray source lists have been matched to multiwavelength catalogues using a maximum likelihood estimator algorithm. We discovered the highest redshift (z = 5.86) quasar yet identified in an X-ray survey. We …

Methyl Halide Production By Calcareous Periphyton Mats From The Florida Everglades, Ann Eileen Raffel

Dissertations and Theses

Methyl halides are trace gases with both natural and anthropogenic origins. Once generated, these gases transport chlorine and bromine into the stratosphere, where they play an important role in ozone depleting catalytic cycles. The Florida Everglades is one location where methyl halide emissions have been proposed to be elevated due to high primary production and ionic halogens. This region also provides a unique study environment due to salt water intrusions, which occur during storm or low marsh water level-high tide events. The purpose of this research was twofold. First, quantification of methyl chloride (CH₃Cl) and methyl bromide (CH …

Reflectance Anisotropy Of Gd5si2ge2 And Tb5si2.2ge1.8, S. J. Lee, Joong Mok Park, J. E. Snyder, David C. Jiles, Deborah L. Schlagel, Thomas A. Lograsso, A. O. Pecharsky, David W. Lynch

Professor David Lynch

Reflectance difference (RD) spectra for the a–b plane of the single crystals of Gd5Si2Ge2and b–c planes of Gd5Si2Ge2 and Tb5Si2.2Ge1.8 were obtained in the photon energy range of 1.5–5.5 eV. Several peaks were observed for these crystals in the measured spectrum range. Similar features were observed in the RD spectra for the b–c planes ofGd5Si2Ge2 and Tb5Si2.2Ge1.8, while different features were observed for the a–b plane and b–c plane of Gd5Si2Ge2. The RD spectra for the crystals arise not only from the surface anisotropy but also from the bulk anisotropy due to the monoclinic structure of the bulk crystal.

Counting The Impossible: Sampling And Modeling To Achieve A Large State Homeless Count, Jennifer L. Priestley, Jane Massey

Jennifer L. Priestley

Objective: Using inferential statistics, we develop estimates of the homeless population of a geographically large and economically diverse state -- Georgia.

Methods: Multiple independent data sources (2000 U.S. Census, the 2006 Georgia County Guide, Georgia Chamber of Commerce) were used to develop Clusters of the 150 Georgia Counties. These clusters were used as "strata" to then execute traified sampling. Homeless counts were conducted within the sample counties, allowing for multiple regression models to be developed to generate predictions of homeless persons by county.

Results: In response to a mandate from the US Department of Housing and Urban Development, the State …

Multi-Organizational Networks: Three Antecedents Of Knowledge Transfer, Jennifer L. Priestley, Subhashish Samaddar

Jennifer L. Priestley

Researchers have demonstrated that organizations operating within formal networks are more likely to experience knowledge transfer, and the associated benefits of knowledge transfer, than would organizations operating outside of a network. However, limited research attention has been given to how the established antecedents of knowledge transfer are affected by the different forms that multi-organizational networks can assume. Using two case studies, we develop six testable propositions regarding how three of the established antecedents of knowledge transfer —absorptive capacity, shared identity and causal ambiguity—would be affected by the different characteristics, which define multi-organizational network form. We discuss these propositions and raise …