bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Etching Temperature on the Surface Texturing of Si{100} in an Extremely Low Concentration Tmah for Minimized Reflectivity
Authors: Gupta Arti , Pal Prem , Sharma Chandra Shekhar
Published: May 2020

Among various renewable energy resources, solar energy is one of the most abundant energy available in nature. The solar energy can be utilized by converting photon energy into electrical energy by using solar cells as energy harvesters. Silicon-based solar cells dominate the current photovoltaic market because of its higher efficiency, excellent stability, non-toxicity, lower processing cost and excellent reliability in the outdoor conditions.1 However, the silicon solar cell efficiency can be further increased by reducing the front surface reflection from silicon, which is greater than 35%. In order to reduce the reflection from silicon surface, surface texturing is done where silicon surface is intentionally made rough. Wet anisotropic etching is most widely used in surface texturing of silicon because of its high throughput and lower cost. Potassium hydroxide (KOH) and tetramethylammonium hydroxide (TMAH) are two most extensively used alkaline solution for surface texturing of silicon. 2-4 In these two etchants, TMAH is preferred because it is fully compatible with CMOS process and also provide high etch selectivity between silicon and silicon dioxide. Surface texturing using low concentration TMAH (<5%) results in high surface roughness. This is a remarkable observation that can be applied in solar cell industries to minimize the reflection from silicon front surface.

In this work, we have studied the effect of very low concentration TMAH (1.0-0.1 wt%) without adding any additive and agitation during etching for surface texturing of Si{100} surface. The main objective of this study is to achieve an optimized etched surface topography at lowest possible etching concentration and etching time to minimize the reflectance for application in solar cells. The average solar weighted reflectance (Rsw) of around 10% is obtained in a very mild etching conditions. Compared to the previous results reported in literatures and also the mild etching conditions, reflectance values obtained in this work are quite promising for large area surface texturing of silicon solar cell panels for enhancement in their efficiency. In addition, the use of very low concentration TMAH minimizes the chemical waste. This also helps in adopting the technique for fabricating anti-reflective silicon surfaces at large scale.

References:

1. C. S. Solanki, Solar photovoltaics: fundamentals, technologies and applications, p. 16, PHI Learning Pvt. Ltd., (2015).

2. P. Papet, O. Nichiporuk, A. Kaminski, Y. Rozier, J. Kraiem, J.F. Lelievre, A. Chaumartin, A. Fave, and M. Lemiti, Sol. Energy Mater. Sol. Cells, 90, 2319–2328 (2006).

3. P. Pal and K. Sato, Silicon Wet Bulk Micromachining for MEMS, p. 24, Jenny Standford Publishing, New York, (2017).

4. P. Pal, K. Sato, M. A. Gosalvez, and M. Shikida, J. Micromechanics Microengineering, 17, 2299–2307 (2007).
(Invited) A Brief Overview and Future Outlook on the Progress of III-Nitride Semiconductors Research
Authors: Freitas Jaime A.
Published: May 2020

The increasing need for devices capable of performing under extreme condition of power and temperature, and opto-electronic devices operating in the UV-Vis spectral range has been the principal driving force for research interest in III-Nitrides semiconductors over the last three decades. Progress in bulk growth and film deposition techniques for homo- and hetero-epitaxial growth of III-Nitride semiconductors has led to successful fabrication and commercialization of an increasing number of devices that are revolutionizing both the optoelectronic and electronic device industries.

Many relevant figures of merit related to electronic device performance scale superlinearly with the band gap; hence, ultra-wide band gap (UWBG) materials (Eg > 3.4 eV) have the potential for far superior performance than conventional WBG materials such as GaN and SiC. UWBG materials will be critical enablers of future electronic components and systems, and a fundamental understanding of their synthesis and properties is critical to exploiting their advantages. In particular, cubic boron nitride (c-BN), among the semiconductor materials in the UWBG group (c-BN, AlN, Ga2O3, and diamond), with a band gap of ~6 eV and thermal conductivity of 13 W/mK (second only to diamond, 20 W/mK) offers the best combination of breakdown voltage and specific on-resistance. Another advantage of c-BN over other UWBG semiconductors is that it can be doped with donors and acceptors, enabling the fabrication of bipolar devices.

The development of high quality GaN substrates and device grade films will be reviewed and a brief overview of the intrinsic properties of the WBG and UWBG semiconductors will be presented.
(Invited) Mottronics in Strongly Correlated Nickel Oxides
Authors: Shi Jian
Published: May 2020

The discovery of hydrogen-induced electron localization in d-band electron correlated perovskites has opened a new paradigm for exploring novel electronic phases of condensed matters and applications in emerging field-controlled electronic devices (e.g. Mottronics). We report the discovery of an unexpected high-concentration doping effect in defective regions for correlated oxides. It enables electronic conductance by tuning the Fermi-level in Mott-Hubbard band and shaping the lower Hubbard band state into a partially filled configuration. We perform interface engineering and grain boundary designs for correlated heterostructures, and achieve a Mottronic device that switches its band gap from above 3 eV to 0 eV. We control and quantify the interfacial aggregation of hydrogen to establish its correlation with the electrical transport properties. The present work unveils new materials physics in correlated materials and suggests novel doping strategies for developing Mottronic and iontronic devices.
Demonstration of EDL Modulated FET Biosensors with Impedance Analysis
Authors: Wu Chang-Run , Wang Shin-Li , Chen Po-Hsuan , Chen Jung-Chih , Wang Yu-Lin
Published: May 2020

The Electric double layer (EDL) gated FET biosensor has been applied to detecting the different biomarkers such as mi-RNA, protein, cell, and heavy metal ion and get successful results. In the past, we made efforts in research on how to develop portable FET biosensors. In this research, the mechanism of antibody-based FET biosensor is deeply investigated. The enhanced EDL is applied to improve the sensitivity of antibody-based FET biosensor and detect protein in high ionic concentration such as physiological salt concentration directly.

The sensor response is obtained by directly detecting the different concentrations of C-reactive protein (CRP) in physiological salt concentration. The absolute drain current from our device is analyzed and converted to potential drop in solution by giving different gate voltages during measurement. Furthermore, the total impedance on our sensor chip is also obtained by Agilent B1530/B1500A. Combining with FET sensor electrical signals and total impedance analysis, the sensor performance at different gate bias can be characterized.

The result shows sensor response is higher when the higher gate bias is applied to our device. This implies that the high charge density enhances the EDL, causing the higher signal. Furthermore, according to impedance analysis, the total impedance change causing by antibody-antigen interaction is dominated by the imaginary part which proves that our sensor sensing mechanism comes from the capacitive effect. The sensor performance is also analyzed by detecting protein in different salt concentrations. With increasing salt concentration, the total change of potential drop increases. Again, the higher salt concentration enhances the EDL.

In conclusion, the mechanism of EDL-modulated FET biosensor is investigated in this study. The unique EDL-modulated FET biosensor not only overcome the charge screening effects in high ionic concentration but also improve the sensitivity by increasing salt concentration. And we can also operate at different gate bias to optimize the drain current signal. Moreover, the impedance analysis shows the dominance of the imaginary part which can prove the sensor response is from the capacitance effect.

Figure 1
Pore-Scale Performance Analysis of Ordered Microstructures As Gas Diffusion Layers in Fuel Cells
Authors: Niblett Daniel , J. Niasar Vahid , Mularczyk Adrian , Eller Jens , Holmes Stuart
Published: May 2020

Emerging from the advances in both manufacturing and computational modelling techniques, it is possible to investigate the performance of an ordered microstructure manufactured by high resolution additive manufacturing processes. In a previous study, we have investigated the direct simulation of effective transport properties [1] and within this work, two-phase flow dynamics coupled with the appropriate boundary conditions present in an operating fuel cell (microporous layer defects and gas channel coupling) on an idealised carbon paper and ordered lattice microstructures.

OpenFOAM was used to simulate two-phase flow in the void space of both the porous structures and gas channels coupled with the Volume of Fluid (VoF) method in 2D and 3D simulations. The effective electrical conductivity and permeability was determined for each structure for comparison. To more accurately envisage the replacement of traditional materials with the new conceptual material, more accurate boundary conditions were investigated, including injection from an imposed micro-porous layer defect which was extracted from an SEM image shown in Figure 1. Additionally, coupling the dynamic effects of the gas channel on the fluids within the porous domains allowed for additional insight to the stability of the two-phase flow.

Pore-scale simulations illustrate that only certain ordered structures will promote beneficial two-phase flow in fuel cells in terms of reducing the amount of flooding and oxygen diffusional resistance. Alternatively, it has been shown that the ordered microstructures improve both electrical conductivity and permeability if they can be made from the same carbon material. The ordering of structures to be used as new micro and nano materials is a new area of investigation, which would provide further evidence of performance improvements due to structures.

Furthermore, the dynamic two-phase flow effects on local clusters of water have been investigated and analyses to show how both the gas channels supplying oxygen and microporous layer defects can significantly affect the fluid dynamics including; droplet growth, detachment and transport within the gas channels. This work and its findings was validated by the comparison of the VoF method to mCT data for water injection through a standard GDL and with growth and detachment in the channel. The results showed good agreement between the interface dynamics, location and shape.

[1] D. Niblett, V. Joekar-Niasar, and S. Holmes, “Optimisation of Fuel Cell Gas Diffusion Layers using Ordered Microstructural Design,” Journal of The Electrochemical Society, vol. 167, no. 7, p. 013520, 2018.

Figure 1 - Simulation of water injection into reconstructed ordered and carbon paper microstructures to evaluate the performance of the materials in management of water.

Figure 1
Segmenting Water Observed with X-Ray Computed Tomography in Gas Diffusion Layers of Polymer Electrolyte Fuel Cells Using Convolutional Neural Networks
Authors: Shum Andrew , Parkinson Dilworth Y. , Zenyuk Iryna V.
Published: May 2020

Gas diffusion layers (GDLs) are responsible for oxygen delivery to the catalyst layer and water management in polymer electrolyte fuel cells (PEFCs). With x-ray computed tomography (CT) – a non-destructive technique, one can observe water transport through the GDL, and also assess local wettability. With ability of X-ray CT to capture dynamics of water transport the quantity of data and the time required to process the data increases. There is a need to further automate data processing and analysis through machine learning; in particular, convolutional neural networks (CNNs). CNNs can be applied to a multitude of image processing tasks such as finding centers of rotation for CT data [1], removal of reconstruction artifacts [1], and denoising of data sets [2]. However, CNNs are probably most known for their ability to perform segmentation/labeling.

Although CNNs have proven to be widely applicable to image processing and analysis, it has also become apparent that individual pairings of architecture and application must be validated [1]. As such, we focus on the use of CNNs to segment synchrotron X-ray CT data sets for water within various GDLs. The water is tracked for an in-situ evaporation/condensation experiment. Knowledge of the water's location and shape as a function of time is necessary to understand local GDL’s wettability and its effect on PEFC performance. The challenge these samples present to more traditional segmentation methods is the low contrast between water and carbon fibers. Depending on the composition of a GDL, binder, polytetrafluoroethylene (PTFE), and the microporous layer (MPL) may also be present in the same narrow window of gray-scale values. Separating these phases is essential in evaluating the material's water transport properties. We will present results from both our efforts with CNNs and the specific PEFC experiment that produced the data sets.

References:

1. Yang, X.; DeCarlo, F.; Phatak, C.; Gursoy, D. A Convolutional Neural Network Approach to Calibrating the Rotation Axis for X-ray Computed Tomography. J. Synchrotron Radiat. 2017, 24, 469-475, DOI: 10.1107/s1600577516020117.

2. Pelt, D.M.; Sethian, J.A. A Mixed-Scale Dense Convolutional Neural Network for Image Analysis. Proc. Natl. Acad. Sci. U. S. A., Early Ed. 2018, 115 (2), 254-259, DOI: 10.1073/pnas.1715832114.
Preparation of Unique Flower-like Pt-Ni Alloy Catalysts As the Cathode of a PEMFC By Electrodeposition Technique
Authors: Huang Jen-Hui , Yeh Tsung-Kuang , Wang Mei-Ya
Published: May 2020

The hydrogen economy can play an important role in the low-carbon economy, and fuel cells technology is an essential part of the hydrogen economy. The proton exchange membrane fuel cell (PEMFC) is one kind of electrochemical reaction device with the advantages of low temperature operation, high conversion efficiency and noiseless, which is expected to widely utilizes in public transportations.

The oxygen reduction reaction (ORR) at the cathode is the rate-determining step in a PEMFC. To enhance the ORR efficiency at the cathode, the unique flower-like platinum-nickel binary alloy catalysts were deposited on the carbon cloth by potentiostatic electrodeposition, effectively improve the oxygen absorption and desorption paths on the surface. The Pt-Ni binary alloy catalysts with the shorter lattice spacings and the effect of high-index facets would increase the electrochemical surface areas (ECSAs) of the catalyst and power density. The samples with the pure platinum and commercial Pt catalyst were also prepared as comparison.

Morphology, particle size, chemical bonding, and elemental composition were characterized by SEM, TEM, XRD, XPS and ICP-MS. In addition, the electrochemical characteristics of the Pt-Ni catalysts were investigated via cyclic voltammetry (CV) and linear sweep voltammetry (LSV) analysis in 0.1 M perchloric acid solution. In single cell test, the peak power density of PEMFC with Pt-Ni cathode was 700 mW/cm2
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Sulfonated and Partially Fluorinated Poly(aryl) Multiblock-Co-Ionomer- and Blend Membranes As Proton Conductors for PEM Electrolysis
Authors: Kerres Jochen A. , Bender Johannes , Mayerhöfer Britta , Trinke Patrick , Bensmann Boris , Hanke-Rauschenbach Richard , Thiele Simon
Published: May 2020

The core of a PEM water electrolyzer is represented by the proton conductive membrane. While nowadays PFSA-based materials such as Nafion are state of the art in large scale energy applications, there is a strong need for development of cost efficient alternatives, which exhibit reduced gas crossover, high ionic conductivity and durability.

Here, we present proton exchange membranes based on two different concepts: Blends of partially fluorinated polybenzimidazole and pyridine side-chain-modified polysulfones (3K-BM) as well as arylene main-chain multiblock co-ionomers (MB-O).

The 3K-BM ionomer membranes represent a blend of hydrophilic partially fluorinated and sulfonated aromatic polyethers with two hydrophobic components: F6-PBI and pyridine-modified PSU [1]. Proton conductivity is achieved by the hydrophilic parts of the material whereas the hydrophobic components ensure stability and enable adjustment of mechanical properties.

MB-O consists of hydrophobic and hydrophilic building blocks, which are synthesized via step-growth polycondensation. The former blocks are partially fluorinated aromatics, whereas the latter ones are based on sulfonated nonfluorinated aromatics [2].

Multiblock-co-ionomers are capable of forming nanophase-separated structures [2,3], which are tunable by varying the ratio of hydrophilic and hydrophobic proportions.

In addition to the polymer synthesis and membrane preparation, ex-situ characterization including NMR spectroscopy, gel permeation chromatography, thermogravimetric analysis, H2-crossover analysis via linear-sweep-voltammetry and AC impedance spectroscopy have been performed with our novel materials. First preliminary in-situ tests in a PEM electrolysis cell have already yielded high performances, which can potentially be increased further by optimization of electrodes with respect to binders for the respective membrane material.

Acknowledgements

This work has been funded by the German Federal Ministry of Education and Research (BMBF) as part of the project: “Increasing Lifespan and Power of Polymer Electrolyte Membrane Electrolysers through High Power Membrane Electrode Assemblies (POWER-MEE)“

References

[1] J. Kerres, A. Ullrich, M. Hein, J. Polym. Sci.: Part A: Polym. Chem. 39 (2001) 2874–2888

[2] F. Schönberger, J. Kerres, J.Polym. Sci. Part A: Polym. Chem. 45 (2007) 5237–5255.

[3] H. Ghassemi, J. E. McGrath, T. A. Zawodzinski, Polymer 47 (2006) 4132-4139
Understanding of Fouling of Ion Exchange Membranes in Reverse Electrodialysis
Authors: Lim Seohee , Park Jin-Soo
Published: May 2020

Reverse electrodialysis(RED) is an energy conversion technology to convert chemical energy generated by concentration gradient into electrochemical energy. Mixing of two bodies with different concentration is common phenomena observed at places where river water meets sea water. When two bodies are mixed, energy of high concentration body suddenly transport to that of low concentration body. It is too short to extract the energy from the process. Thus, controlled concentration gradient could be formed in RED stacks which are alternately arranged by a cation- and an anion-exchange membrane between two electrodes. For the application of RED in several field sites, most of the technology using membranes needs fouling control to minimize a decrease in performance. In this study, the fouling phenomena of ion exchange membranes for various foulants possibly found in seawater and river water were investigated. Electrical resistance is used as indicator to evalue the degree of contamination by positively, negatively and non-charged foulants. The fouled membranes were regenerated, and the electric resistance and the degree of contamination with regeneration time were measured.

Acknolwedgment

This work was conducted under the framework of the Research and Development Program of the Korea Institute of Energy Research (KIER) (Project Number: B9-2441).
Combustion Synthesis and Electrochemical Characterization of Pd-Based Nanostructures for PEMFCs
Authors: Medina Rojano Victor Alberto , Montes de Oca Yemha María Guadalupe , Estrada-Arce Elsa Miriam , Chinarro Eva , del Rio Carmen , Romero-Romo Mario Alberto , Palomar-Pardavé Manuel
Published: May 2020

The use of proton exchange membrane fuel cells as viable energy conversion alternatives, coupled with the apparent diminution of internal combustion engines in transport means, brings in the opportunity to evaluate novel materials, while decreasing the use of noble expensive metals in the electrodes; overall the fuel cell efficiency is improved. This work deals with the synthesis of Pd-based electrocatalysts through a combustion method. Electrocatalysts were characterization by XRD and SEM (as shown in Figure 1). The electrochemical evaluation was carried out with a Fuel Cell Test System, see Figure 2.

Figure 1
Depleted Fullerene Soot As Support Materials of Pt-Base Catalysts for Oxygen Reduction Reaction
Authors: Li Hengyi
Published: May 2020

The carbon materials containing metal nanoparticles were filtrated from two kinds of depleted fullerene soot including C60 (denoted as DFS) and GdC82(GDFS), respectively. The structure of depleted carbon materials was investigated by XRD, Raman, SEM and TEM. The DFS and GDFS show onion like morphology with Fe and Fe, Gd nanoparticles, respectively. The obtained carbon materials were used as support materials of Pt-based alloy catalysts (Pt-DFS and Pt-GDFS) synthesized from H2 heat treatment for oxygen reduction reaction. The half-wave and onset potentials of Pt-DFS and Pt-GDFS were 1.1, 0.89 V and 1.1 V, 0.93 V (vs. RHE), respectively, in 0.5 mol L-1 H2SO4solutions. The ECSA of Pt-GDFS has no obvious decrease during 8000 CV cycles in acid solutions indicating good stability on oxygen reduction reaction.
Silicon Doping Titanium Dioxide to Produce Highly Conductive and Durable Catalyst Supports for Fuel Cells
Authors: Sullivan Mason Thomas , Alipour Moghadam Esfahani Reza , Easton E. Bradley
Published: May 2020

The demand for clean energy has increased significantly over the last few decades with technological advancements. Proton exchange membrane fuel cells (PEMFCs) are one such advancement with reportedly high efficiencies. Indeed, extensive research and development on all aspects regarding this technology has been done over the past two decades. However, this technology still requires more advanced electrode materials. Platinum (Pt), which exhibits high activity in the oxygen reduction reaction (ORR), is the most common and efficient electrocatalyst used in anode and cathode materials in PEMFCs. Pt is a noble metal, expensive and limited in supply. In order to maximize the efficiency of the Pt catalyst, supporting materials onto which the Pt catalyst is dispersed can play a crucial role. Traditionally, Pt nanoparticles (NPs) are dispersed onto high surface area carbonaceous materials (Pt/C) to maximize the efficiency of Pt catalyst. However, carbon is known to suffer from electrochemical degradation (ie. carbon corrosion) under harsh conditions of PEMFC, resulting in either/or Pt agglomeration and dissolution, decreasing the electroactivity of Pt catalyst.

Metal oxides, such as TiO2, Nb2O5, and SiO2, have been extensively studied as alternative fuel cell catalyst supports to carbon-based materials for the ORR. Metal oxides are cheap, corrosion-resistant, and possess a large surface area. Unfortunately, these metal oxides are semi-conductive, making them impractical for fuel cell materials. Recently, there has been great interest to develop metal oxides with high electrical conductivity for fuel cell application. Among all conductive metal oxides, titanium suboxides (TixO2x-1) have shown great promise as replacements for carbon-supporting material in fuel cells. Herein, we are reporting an advanced, highly conductive metal oxide through Si-doping TiO2, yielding Ti3O5-Si (hereinafter referred to as TOS). The resulting Pt/TOS catalyst support exhibits remarkable electroactivity and durability toward the oxygen reduction reaction (ORR). Also, under advanced stability protocols including startup-shutdown and load-cycling, Pt/TOS demonstrates high stability and durability compared to commercial Pt/C (see Figure 1). This enhanced electroactivity and stability of Pt/TOS is attributed to the strong metal-support interaction (SMSI) occurring through electron donation from TOS support to the Pt nanoparticles.

Figure 1
Flexible Anode Catalysts for Direct Hydrazine Fuel Cells
Authors: Zabielaitė Aušrinė , Balčiūnaitė Aldona , Šimkūnaitė-Stanynienė Birutė , Naruskevicius Leonas , Tamašauskaitė-Tamašiūnaitė Loreta , Norkus Eugenijus
Published: May 2020

In this study we report a facile approach for fabrication of flexible anode catalysts consisting of a fiber-shaped cobalt deposited on the polyimide (PI) surface for direct hydrazine fuel cells (DHFCs). At first, a thin copper layer has been deposited on the PI surface using electroless metal plating method. Then, the fiber-shaped cobalt coating has been plated by the electrochemical deposition method from the electrolyte containing CoSO4, NaOH and N-(2-Hydroxyethyl) ethylenediamine. For comparison, the cobalt layer that has the smooth structure has been deposited on the flexible PI surface via electroless deposition using morpholine borane as a reducing agent.

The morphology and composition of the prepared flexible catalysts have been characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The activity of catalysts has been investigated with respect to the oxidation of hydrazine in an alkaline medium.

The results of electrochemical measurements showed that the deposited cobalt layer that has a fiber-shaped structure on the flexible PI surface exhibits an enhanced electrocatalytic activity towards the oxidation of hydrazine as compared with that for cobalt catalyst that has a smooth structure. Moreover, the prepared flexible catalysts seem to be a promising anode material for DHFCs.
Characterisation of Tantalum Carbide As a Support for Iridium Based Oxygen Evolution Reaction Catalyst for Polymer Electrolyte Membrane Water Electrolysis
Authors: Rezaei Nafiseh , Peppley Brant A
Published: May 2020

Due to the high price and limited production of iridium metal, reducing the iridium loading is a matter of great concern. One approach to lower the iridium loading is the deposition of Ir-based electrocatalysts on a low cost support, which not only enhances the dispersion of electrocatalysts but also improves the electrochemical stability. Another approach is increasing the surface area of the support. The larger the surface area of a support, the better the dispersion of the catalyst on the support. This implies a larger number of available active sites. Ball milling is a simple and environmentally friendly method to reduce the support particle size and increase the surface area of the support. The effect of TaC support surface area on the performance of the supported Ir-based catalyst was studied by Karimi et al. [1]. They found that a 7-fold increase in the TaC support surface area (from 0.9 m2/g to 6.2 m2/g) improves the performance of the supported catalyst by around 50%.

In this work, TaC was selected as a support and ball milled with mono-sized (3 mm in diameter) spherical zirconia balls for 7 and 14 days. The particle size and surface area of ball milled TaC were analyzed using Scanning Electron Microscopy (SEM)/ImageJ and nitrogen physisorption methods, respectively. It was observed that ball milling decreases the particle size and increases the surface area of support. After 14 days of ball milling, the TaC showed smaller particle size and larger surface area compared to after 7 days of ball milling. Evaluating the support stability prior to catalyst stability is a crucial process to eliminate unsuitable supports. The electrochemical stability of TaC as a support was evaluated in a strong acidic environment (0.5M H2SO4) and at an oxidizing voltage using cyclic voltammetry (CV) and (EIS).

[1] F. Karimi and B. A. Peppley, “Metal Carbide and Oxide Supports for Iridium-Based Oxygen Evolution Reaction Electrocatalysts for Polymer-Electrolyte-Membrane Water Electrolysis,” Electrochim. Acta, vol. 246, pp. 654–670, 2017.
Acid-Doped Hydrogels for Robust Ion Transport in Electrochemical Catalyst Layers
Authors: Katzenberg Adlai , Munoz Cesar , Chen Brian , Siboonruang Tana , Modestino Miguel Antonio
Published: May 2020

Polymer-electrolyte membranes (PEMs) are ubiquitous to state-of-the-art electrochemical devices. Polymer electrolyte materials have been historically limited to a small class of perfluorinated sulfonic-acid ionomers (PFSAs). Structural changes in PFSA ionomers observed under low humidity and confined length scales (<100’s of nanometers) limit proton conduction and mass transport in the catalyst layer, restricting current density in state-of-the-art devices. Heterogeneous catalyst layer morphology and complex formulation-performance relationships make these limitations difficult to assess. We propose an alternative class of polymer electrolyte based on a thermally crosslinked poly(acrylic acid)-poly(vinyl alcohol) scaffold doped with sulfuric acid, with ion-exchange capacity (IEC) tuned via the dopant concentration. We achieved IEC over 10 meq g-1, well above the upper-limit for PFSAs, and proton conductivity as high as 350 mS cm-1. Notably, proton conductivity was robust across the length (<100 nm film thickness) and humidity scales relevant to electrochemical device operation. The doped-hydrogel electrolyte was employed in a microelectrode vapor-fed water electrolyzer and achieved current densities up to 8 orders of magnitude higher than Nafion under low humidity operation. In this poster, I will present a facile method for fabricating electrolyte-doped hydrogel thin-films with tunable IEC. Furthermore, I will discuss transport properties of these materials across the range of humidity and thicknesses relevant for electrochemical catalyst layers. Finally, I will discuss the use of an electrochemical model system to isolate and systematically study ionomer performance under relevant operating conditions, providing a crucial link between material properties and performance in-operando. The results presented here underscore the potential value of tailoring materials chemistry to specific requirements of individual device components in membrane-electrode assemblies.
High‐Performance Direct Methanol Fuel Cells with PGM‐Free Cathode
Authors: Shi Qiurong , He Yanghua , Wu Gang
Published: May 2020

Direct methanol fuel cells (DMFCs) hold great promise for applications ranging from portable power for electronics to transportation. However, apart from the high costs, current Pt‐based cathodes in DMFCs suffer significantly from performance loss due to severe methanol crossover from anode to cathode. The migrated methanol in cathodes tends to contaminate Pt active sites through yielding a mixed potential region resulting from oxygen reduction reaction and methanol oxidation reaction. Therefore, highly methanol‐tolerant cathodes must be developed before DMFC technologies become viable. The newly developed MOF‐based Fe‐N‐C cathode exhibits high methanol tolerance and exceeds the performance of current Pt cathodes, as evidenced by both rotating disk electrode and DMFC tests. In addition to the highly oxygen-reduction active atomically dispersed FeN4 sites, the unique morphology of MOF-derived carbon in Fe‐N‐C cathodes provides a more unique porous structure. DMFC tests with various methanol concentrations are systematically studied using the best performing Fe‐N‐C catalyst. At feed concentrations greater than 2.0 M, the obtained DMFC performance from the Fe‐N‐C cathode is found to start exceeding that of a Pt/C cathode. This work will open a new avenue to use PGM-free cathode for advanced DMFC technologies with increased performance and at significantly reduced cost.
Combined CO2-Electroreduction Towards Formate Production and HMF Oxidation
Authors: Lin Roger , Guo Jiaxun , Seifitokaldani Ali
Published: May 2020

Recent advancement on carbon dioxide reduction reaction (CO2RR) has shown promising results on CO2 conversion to value-added carbon products as renewable fuels or valuable chemical feedstocks. Formic acid is one of the products that requires low applied voltage in CO2RR. However, it remains with a low full cell energy efficiency, mainly due to the large full cell applied potential. Traditionally, the anodic reaction is carried out with oxygen evolution reaction (OER), which requires a higher applied potential on the counter electrode. This work reports a viable alternative anodic reaction on electro-oxidative upgrading of biomass-derived 5-hydroxymethylfurfural (HMF) into valorized chemicals such as furandicarboxylic acid (FDCA) using Ni-based catalyst. Experimental results have demonstrated that in the combined electrolyzer, the Faradaic efficiency of formate can increase from 41% to 76%, while keeping the applied potential as low as 2 V for achieving a current density of 10 mA/cm2. In addition, at the anode, the Faradaic efficiency reached 60% towards FDCA using the same combined setup. It is postulated that due to the lower overpotential at anode, the cathodic potential becomes more negative for the same current density, and hence a higher Faradaic efficiency towards formate can be attained. Moreover, compared to conventional systems with OER, the combined system is able to produce a value-added product such as FDCA with a considerable FE, approaching a more economic application.
Preferred Service Investment in the Dual-Channel Supply Chain: Leader-Follower Relationships and Product Characteristics
Authors: Zhao Wanmei , Ye Chunming , Ding Xiaodong
Published: May 2020

This paper examines the influence that members’ preferred service investments have on their decision-making and profits in a dual-channel supply chain. We discuss changes in the supplier’s and retailer’s decision-making and optimal profits with reference to their different preferred service investment combination modes and their different leader-follower relationships. We also provide classified comparisons of the supplier’s and retailer’s optimal profits by referring to four types of product characteristics combination modes that are assessed across two channels. By providing classifications and comparisons, we put forward operational insights for the supplier and retailer who have direct implications for their optimal decisions and profits, including selling products with higher homogeneity between two channels, choosing the retailer as the leader of the supply chain, and confirming appropriate preference combination mode under a certain product characteristics. We analyze the influences of the preferred service investment levels as well as preference intensities of the supplier and retailer on their strategies and profits in their respective advantaged states and obtain some enlightenment about the cooperation strategies and relationship-building methods of the supplier and retailer in the actual process of their participation in the dual-channel supply chain operation.
Prevalence and Risk Factors of Childhood Hypertension in Urban-Rural Areas of China: A Cross-Sectional Study
Authors: Liang Xiaohua , Xiao Lun , Luo Yetao , Xu Jiapei
Published: May 2020

Objective. The increased blood pressure level in children and adolescents is recognized as an essential predictor of adulthood cardiovascular disease. This study aimed to ascertain the prevalence and the urban-rural disparity of childhood hypertension in the southwest of China. Methods. Using stratified cluster sampling in urban and rural areas, a total of 13597 primary school children aged 6∼12 years living in the Southwest of China were included. The prevalence of hypertension was analyzed. The risk factors were collected by questionnaires, and the risk factors of childhood hypertension were analyzed by the logistic regression model. Results. The prevalence of hypertension was 13.75%, 9.02%, and 17.47% in total, urban, and rural children, respectively, and the urban-rural difference was 8.44% (95%CI: 7.32%, 9.56%). Children with obesity, maternal gestational hypertension, >10 months of breastfeeding, or low family income had a significantly increased prevalence of hypertension (29.4%, 20.00%, 16.31%, and 16.25%, respectively). Rural residence, intake of more pickle (in rural), maternal gestational hypertension (in urban), low birth weight (in rural), obesity, increased heart rate, and red blood cell counts were the risk factors of childhood hypertension. The adjusted R2 values were 13.61%, 23.25%, 10.88%, 11.12%, 12.23%, and 25.04% in the full models excluding and including serum indexes for total, urban, and rural children, respectively. Conclusions. The prevalence of childhood hypertension is significant in the Southwest of China and alarming in rural areas, which requires community intervention. Children living in rural areas combined with obesity, low social economic status, dietary imbalance, and abnormal lipid metabolism were associated with an increased risk of hypertension, and routine care programs should be conducted to prevent childhood hypertension.
Reliability Modeling for Multistate System with Preventive Maintenance under Customer Demand
Authors: Qin Jinlei , Li Zheng
Published: May 2020

The performance level of a multistate system (MSS) can vary among different values rather than only two states (perfect functioning and complete failure). To improve the reliability of MSSs, a maintenance strategy has been adopted to satisfy customer demand, and reliability modeling of MSS with preventive maintenance and customer demand is proposed. According to the regular degradation and random failure at each state, based on the Markov random process, the proposed MSS with preventive maintenance can be modeled to satisfy the customer demand in a specific state. This model can also be adapted to compute other reliability indices. Based on this model, the effect of different preventive maintenance actions on the reliability indices can be analyzed and further compared. Two numerical examples have been illustrated to show the validity of the proposed model. The reliability model presented in this study can be used to assess the type of MSS and help reliability engineers to compare different maintenance actions quantitatively and make optimal decisions.
Effectiveness and Safety of Acupuncture Moxibustion Therapy Used in Breast Cancer‐Related Lymphedema: A Systematic Review and Meta‐Analysis
Authors: Jin Huimin , Xiang Yuying , Feng Yuqian , Zhang Yiting , Liu Shan , Ruan Shanming , Zhou Huamiao
Published: May 2020

Objective. To evaluate the effectiveness and safety of acupuncture moxibustion therapy (AMT) for the breast cancer‐related lymphedema (BCRL). Methods. Four English databases (MEDLINE, PubMed, Embase, and Cochrane CENTRAL) and four Chinese databases were searched from their inception to Feb 1, 2020. Eligible randomized controlled trials (RCTs) investigating AMT against any type of controlled intervention in patients for BCRL and assessing clinically relevant outcomes (total effective rate, circumference difference, and Karnofsky performance score) were included. The methodological quality of all selected trials was estimated in accordance with the guidelines published by the Cochrane Collaboration. Review Manager 5.3 was used to conduct analyses. Results. Twelve eligible RCTs are confirmed. Most of the trials selected are regarded as low methodological quality. Compared with Western medicine, physiotherapy, and functional training, traditional AMT has significantly higher treatment effect (RR 1.03 (95% CI: 1.22, 1.45); p < 0.00001). In comparison with physiotherapy, AMT is better in reducing edema symptoms (MD = −0.77; 95% CI (−1.13–0.41); p < 0.00001). Moreover, pooled results demonstrate that AMT results in better outcomes than functional training and Western medicine in improving Karnofsky performance score of BCRL patients (SMD = 0.69; 95% CI (0.38–1.00); p < 0.00001). Conclusion. This systematic review and meta‐analysis provides evidence that AMT is serviceable and safe in treating BCRL. With the limited number of available studies and methodology drawbacks, further high‐quality RCTs with reasonable designs are still warranted.
Multilevel Security Network Communication Model Based on Multidimensional Control
Authors: Cao Lifeng , Lu Xin , Gao Zhensheng , Han Mengda , Du Xuehui
Published: May 2020

To solve the problems associated with the application of multilevel security to actual networks, such as flexibility, availability, security, and secure communication, this study proposes a multilevel security network communication model based on multidimensional control. In the model, access control is retained on the basis of security labels. In addition, relational restraints among protection domains, credibility degree restraints of subjects on security attributes, aggregation inference control restraints, and secure tunnel control restraints are introduced and applied. Thus, secure information exchange within a multilevel security network information system is ensured. Moreover, using this model, multilevel security virtual networks with logical and independent characteristics can be built to accomplish secure interconnection and communication between nonequivalent members, thereby reducing the probability of information leakage. Finally, the security of the model is confirmed by applying the nontransitive, noninterference theory, and the typical application of the model in actual networks is described.
Evaluation of Zhenwu Decoction Effects on CYP450 Enzymes in Rats Using a Cocktail Method by UPLC‐MS/MS
Authors: Hong Li-li , Wang Qian , Zhao Ya-ting , Zhang Sheng , Zhang Kai-qi , Chen Wei-dong , Peng Can , Liu Li , Wang Hong-song
Published: May 2020

This thesis is aimed at shedding light on the effects of the Zhenwu decoction (ZWD) on the activities and mRNA expressions of seven CYP450 isoenzymes. In the first step, we determined the main chemical compounds of ZWD by high‐performance liquid chromatography (HPLC). Next, 48 male (SD) rats were randomly divided into the normal saline (NS) group and the ZWD low‐ (2.1875 g/kg), medium‐ (4.375 g/kg), and high‐ (8.75 g/kg) dose groups (12 per group). All rats were gavaged once daily for 28 consecutive days. A mixed solution of seven probe drugs was injected into 24 rats through the caudal vein after the last intragastric administration. Lastly, a validated cocktail method and real‐time quantitative reverse‐transcription polymerase chain reaction (RT‐qPCR) were used to detect pharmacokinetic parameters and mRNA expressions, respectively. Compared with the NS group, ZWD at medium‐ and high‐dose groups could significantly induce CYP2C6 (P < 0.05) activity, while the mRNA expression (P < 0.05) increased only in the high‐dose group. Additionally, CYP2C11 activity was induced and consistent with mRNA expression (P < 0.05). Moreover, ZWD could induce the activity of CYP3A1 (P < 0.05), but the mRNA expression showed no significant differences except in high‐dose groups. Additionally, ZWD has no effects on CYP1A2, CYP2B1, CYP2C7, and CYP2D2. In conclusion, the significant inductive effects of ZWD on three CYP450 isoenzymes indicated that when ZWD was coadministrated with drugs mediated by these enzymes, not only should the potential herb‐drug interactions (HDIs) be observed, but the dosage adjustment and tissue drug concentration should also be considered. Furthermore, the approach described in this article can be applied to study the importance of gender, age, and disease factors to HDI prediction.
Peripheral Refraction in Myopic Children with and without Atropine Usage
Authors: Sun Han-Yin , Lu Wei-Yang , You Jhen-Yu , Kuo Hui-Ying
Published: May 2020

Purpose. To compare the patterns of relative peripheral refractions of myopic children who were currently on atropine treatment for myopia control and myopic children who did not use atropine.Methods. Chinese children (n = 209) aged 7 to 12 years participated in the study, 106 used atropine and 103 did not. Participants were also classified into three groups: emmetropes (SE: +0.50 to −0.50 D), low myopes (SE: −0.50 to −3.00 D), and moderate myopes (SE: −3.00 to −6.00 D). The central and peripheral refractions along the horizontal meridians (for both nasal and temporal fields) were measured in 10-degree steps to 30 degrees.Results. There were no statistically significant differences in spherical equivalent and astigmatism of the three refractive groups in either the nasal or temporal retina. The atropine group showed a significant relative myopia in the temporal 30° field in spherical equivalent compared to the emmetropic group (t49 = 3.36,P=0.02). In eyes with low myopia, the atropine group had significant relative myopia in the nasal 30° and temporal 30° fields (t118 = 2.59,P=0.01;t118 = 2.06,P=0.04), and it is also observed at 20° and 30° of the nasal field for the moderate myopic group (t36 = 2.37,P=0.02;t2.84 = 2.84,P=0.01).Conclusion. Significant differences in relative peripheral refraction were found between the atropine group and its controls. The findings suggested that the eyes that received atropine may have a less prolate shape and thus explain why using atropine is effective in controlling myopia progression.
Sex Differences in the Outcomes of Elderly Patients with Acute Coronary Syndrome
Authors: Tai Shi , Li Xuping , Yang Hui , Zhu Zhaowei , Tang Liang , Fu Liyao , Hu Xinqun , Fang Zhenfei , Guo Yonghong , Zhou Shenghua
Published: May 2020

Background. The impact of sex on the outcome of patients with acute coronary syndrome (ACS) has been suggested, but little is known about its impact on elderly patients with ACS. Methods. This study analyzed the impact of sex on in-hospital and 1-year outcomes of elderly (≥75 years of age) patients with ACS hospitalized in our department between January 2013 and December 2017. Results. A total of 711 patients were included: 273 (38.4%) women and 438 (61.6%) men. Their age ranged from 75 to 94 years, similar between women and men. Women had more comorbidities (hypertension (79.5% vs. 72.8%, p=0.050), diabetes mellitus (35.2% vs. 26.5%, p=0.014), and hyperuricemia (39.9% vs. 32.4%, p=0.042)) and had a higher prevalence of non-ST-segment elevation ACS (NSTE-ACS) (79.5% vs. 71.2%, p=0.014) than men. The prevalence of current smoking (56.5% vs. 5.4%, p<0.001), creatinine levels (124.4 ± 98.6 vs. 89.9 ± 54.1, p<0.001), and revascularization rate (39.7% vs. 30.0%, p=0.022) were higher, and troponin TnT and NT-proBNP tended to be higher in men than in women. The in-hospital mortality rate was similar (3.5% vs. 4.4%, p=0.693), but the 1-year mortality rate was lower in women than in men (14.7% vs. 21.7%, p=0.020). The multivariable analysis showed that female sex was a protective factor for 1-year mortality in all patients (OR = 0.565, 95% CI 0.351–0.908, p=0.018) and in patients with STEMI (OR = 0.416, 95% CI 0.184–0.940, p=0.035) after adjustment. Conclusions. Among the elderly patients with ACS, the 1-year mortality rate was lower in women than in men, which could be associated with comorbidities and ACS type.