Effect of oxidizing treatment on electrocatalytic activity of boron‑doped amorphous carbon thin films

Chen‑Song Wang,Ni Suo,Hao Huang,Ai‑min Wu,Guo‑Zhong Cao,Gui‑Feng Zhang 한국탄소학회 2019 Carbon Letters Vol.29 No.5

Boron-doped amorphous carbon (BDAC) thin films with a regular oxygen reduction reaction (ORR) catalytic activity were synthesized in a hot filament chemical vapor deposition device using a mixture of CH4 and H2 as a gas source and B2O3 as a boron source and then oxidized in air at 380–470 °C for 15–75 min. Scanning electron microscope, transmission electron microscope, Raman spectroscopy, X-ray photoelectron spectroscopy, and electrochemical tests were used to characterize the physical and electrochemical properties of the BDAC catalysts. It was concluded that the BDAC catalyst oxidized at 450 °C for 45 min showed the best ORR catalytic activity in alkaline medium. The oxygen reduction potential and the transfer electron number n, respectively, are − 0.286 V versus Ag/AgCl and 3.24 from the rotating disk electrode experiments. The treated carbon film has better methanol resistance and stability than the commercial Pt/C catalyst.

A large-area free-standing graphene oxide multilayer membrane with high stability for nanofiltration applications

Chen, Long,Li, Yanhui,Chen, Lina,Li, Na,Dong, Chenglong,Chen, Qiong,Liu, Beibei,Ai, Qing,Si, Pengchao,Feng, Jinkui,Zhang, Lin,Suhr, Jonghwan,Lou, Jun,Ci, Lijie Elsevier 2018 CHEMICAL ENGINEERING JOURNAL -LAUSANNE- Vol.345 No.-

<P><B>Abstract</B></P> <P>A flexible and free-standing graphene oxide and nylon 6 (GO@nylon 6) multilayer nanofiltration membrane was prepared by a layer-by-layer assembly process. The combination of electrospinning and electrospraying technique was employed, which can facilely prepare large-area membrane with size of 20 × 30 cm. The mechanical stability of multilayer membrane has enhanced significantly due to the tightly locked structure achieved by nylon 6 nanofibers network. The novel GO@nylon 6–13 multilayer nanofiltration membrane demonstrated a pure water flux up to 11.15 L m<SUP>−2</SUP> h<SUP>−1</SUP> bar<SUP>−1</SUP>, while keeping high organic dye rejection rate (>95% for methylene blue, and >99% for methyl orange). The rejections rate of the Na<SUB>2</SUB>SO<SUB>4</SUB>, NaCl, CuSO<SUB>4</SUB>, and Pb(NO<SUB>3</SUB>)<SUB>2</SUB> were 56.5%, 27.6%, 36.7%, and 18.9%, respectively. Furthermore, GO@nylon 6–13 multilayer nanofiltration membrane also demonstrated a high flux of some common organic solvents (8.4, 5.3, and 0.8 L m<SUP>−2</SUP> h<SUP>−1</SUP> bar<SUP>−1</SUP> for methanol, ethanol, and NMP, respectively), showing excellent chemical stability for separation process in those solvents.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Large-area GO@nylon 6 multilayer nanofiltration membrane was prepared. </LI> <LI> The multilayer structure enhances the mechanical stability. </LI> <LI> The multilayer membrane demonstrates a high water flux. </LI> <LI> The multilayer membrane shows high rejection rate for organic dyes. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>Photograph and cross-section SEM image of GO@nylon 6 multilayer nanofiltration membrane, the inset shows the water contact angle.</P> <P>[DISPLAY OMISSION]</P>

Identification of flutter derivatives of bridge decks using stochastic search technique

Ai-Rong Chen,Fu-You Xu,Ru-Jin Ma 한국풍공학회 2006 Wind and Structures, An International Journal (WAS Vol.9 No.6

A more applicable optimization model for extracting flutter derivatives of bridge decks is presented, which is suitable for time-varying weights for fitting errors and different lengths of vertical bending and torsional free vibration data. A stochastic search technique for searching the optimal solution of optimization problem is developed, which is more convenient in understanding and programming than the alternate iteration technique, and testified to be a valid and efficient method using two numerical examples. On the basis of the section model test of Sutong Bridge deck, the flutter derivatives are extracted by the stochastic search technique, and compared with the identification results using the modified least-square method. The Empirical Mode Decomposition method is employed to eliminate noise, trends and zero excursion of the collected free vibration data of vertical bending and torsional motion, by which the identification precision of flutter derivatives is improved.

Identification of flutter derivatives of bridge decks using stochastic search technique

Chen, Ai-Rong,Xu, Fu-You,Ma, Ru-Jin Techno-Press 2006 Wind and Structures, An International Journal (WAS Vol.9 No.6

A more applicable optimization model for extracting flutter derivatives of bridge decks is presented, which is suitable for time-varying weights for fitting errors and different lengths of vertical bending and torsional free vibration data. A stochastic search technique for searching the optimal solution of optimization problem is developed, which is more convenient in understanding and programming than the alternate iteration technique, and testified to be a valid and efficient method using two numerical examples. On the basis of the section model test of Sutong Bridge deck, the flutter derivatives are extracted by the stochastic search technique, and compared with the identification results using the modified least-square method. The Empirical Mode Decomposition method is employed to eliminate noise, trends and zero excursion of the collected free vibration data of vertical bending and torsional motion, by which the identification precision of flutter derivatives is improved.

Implementation of a three-qubit Toffoli gate in a single step

Chen, Ai Min,Cho, Sam Young,Kim, Mun Dae American Physical Society 2012 Physical review. A. Atomic, molecular, and optical Vol.85 No.3

THE CONTACT LENS RELATED CASE REPORTS IN PEDIATRIC POPULATION II

Chen, Ai-Hong,Kim, Douk-Hoon,Sung, A-Young The Korean Ophthalmic Optics Society 2005 한국안광학회지 Vol.10 No.3

The cause of poor visual acuity was connected to the damage by the ocular trauma related. Especially the most cause of visual disorder was identified as irregular pupil by ocular damage. Therefore most patients stopped the wearing of the contact lens immediately by the visual decrease effects from irregular pupil disorder. But we had suggested that the contact lens wear was a very intensive visual therapy. We had identified the visual recover from several tests using the contact lens treatment.

Effect of Under and Over Refractive Correction on Visual Acuity Performance using Two Different Charts

Chen, Ai-Hong,Shah, Siti Salwa Mohamad,Rosli, Saiful Azlan The Korean Ophthalmic Optics Society 2013 한국안광학회지 Vol.18 No.3

Purpose: The purpose of this study was to investigate the effect of under and over refractive correction on visual acuity performance and the variation of the visual performance measurement using two different visual acuity charts. Methods: Ten young adults, aged between 19 and 25 years old, were recruited. Inclusion criteria: no history of ocular injury or pathology with a best-corrected visual acuity of 6/6 on dominant eye. The over and under refractive corrections were induced using minus and plus spherical ophthalmic lenses in 0.50 D steps up to 3.00 D; as well as using three axis orientations of cylindrical ophthalmic lenses ($45^{\circ}$, $90^{\circ}$ and $180^{\circ}$) in 0.50 D steps. The variation of visual acuity performance measurements was investigated using Bailey-Lovie LogMAR chart and Landolt C chart. Results: The visual acuity changes with lenses were significantly different between two charts [F = 49.15, p < 0.05 with plus spherical ophthalmic lenses and F = 174.38, p < 0.05 with minus spherical ophthalmic lenses]. The visual acuity changes with three different cylindrical axis showed no significant difference between Bailey-Lovie LogMAR chart [F = 2.35, p > 0.05] and Landolt C chart [F = 3.12, p = 0.05]. Conclusions: The over and under refractive correction affected the visual acuity performance differently. The Landolt C chart and Bailey-Lovie LogMAR chart demonstrated variation in measurements.

Eye Dominance and Reading Speed

Chen, Ai-Hong,Mustapha, Nurfazliha,Rahman, Muhamad Irwan The Korean Ophthalmic Optics Society 2011 한국안광학회지 Vol.16 No.3

Purpose: The aim of this study was to investigate eye dominance and reading performance based on eye movements and reading speed. Methods: The eye dominance of 30 subjects was determined using the sighting test (hole formed by hands). The subjects were asked to read the numerical reading material aloud in English from left to right and from right to left at random. The number of saccades, regressions, and inter-fixations per minute was calculated using Visual-Oculography (VOG) and the reading speed was recorded as number of characters per minute using stopwatch. Results: No significant differences in reading speed among right and left eye dominant subjects as they read from left to right and right to left directions (p>0.05). However, left eye dominant subjects were found to read significantly faster compared to right eye dominant subjects in both directions of reading (p<0.05). In term of eye movement patterns, no significant differences in saccades, regressions, and inter-fixations per minute were found between subjects with right eye dominance and left eye dominance for both reading directions (p>0.05). Conclusions: Reading performance in term of eye movement and speed was not affected by eye dominance, but subjects with left eye dominance read faster than subjects with right eye dominance.

Relation between Quantum Entanglement and the Berry Phase in Systems of Two Interacting Qubits

Ai Min Chen,Yao Heng Su,Sam Young Cho 한국물리학회 2010 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.57 No.4

Quantum entanglement and the Berry phase are investigated in systems of two interacting qubits. The interaction between the qubits is considered as an XXZ-type exchange interaction, which can make the qubits entangled. A slowly rotating external field is also applied for the Berry phases of the system within the adiabatic theorem. Analytic expressions for the eigenvalues and eigen-wavefunctions of the system are obtained in terms of the interaction parameters and external fields. The competition between the interaction and the external field is shown to be determine a characteristic behavior of the Berry phases and concurrences. The relation between the Berry phase and entanglement for the eigenstates of the system is found to be unique as the interaction strengths vary. The way in which anisotropy of the interaction reveals the unique relations between the Berry phases and the entanglements is discussed.

Strength and Deformation Characteristics of Silty Sand Improved by Gravel

Ai-jun Chen,Jia-sheng Zhang 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.2

Silty sand is a poor filler of highway and railway subgrade, and various physical and chemical improving methods have been applied to increase the strength and stability of silty sand. Adding gravel to silty sand is a routine physical improving method. In this paper, large-scale triaxial tests were carried out on silty sand and improved soil which is obtained by adding 4 different proportions of gravel into the silty sand in order to analyze the strength and deformation characteristics of the improved soil. The stress-strain relations obtained from tiaxial tests were analyzed and the effect of coarse particles and fine particles on the strength and deformation of the specimen were also analyzed. The test results show that with more coarse particles and under a higher confining pressure, a greater deviator stress is required to produce the same axial strain. The increase of coarse particles helps to enlarge the angle of internal friction and cohesion, while the increase of fine particles decreases the angle of internal friction and cohesion. Under low confining pressure, the soil specimens with more coarse particles exhibit evident shear dilation. Under high confining pressure, the soil specimens produce a greater volume strain. Adding appropriate amount of gravel into the silt soil can increase its strength and restrain its deformation, but excessive amount of gravel may produce too much volume deformation.