Microfluidic room temperature ionic liquid droplet generation depending on the hydrophobicity and interfacial tension

We have characterized micro-droplet generation using water immiscible hexafluorophosphate ([PF₆])- and bis(trifluoromethylsulfonyl)imide ([Tf₂N])-based room temperature ionic liquids (RTILs). The interfacial tension between total 7 RTILs and phosphate buffered saline (PBS) was measured using a tensiometer for the first time. PBS is one of the most commonly used buffer solutions in cell-related researches. The measured interfacial tension ranges from 8.51 to 11.62 and from 9.56 to 13.19 for [Tf₂N]- and [PF₆]-based RTILs, respectively. The RTILs micro-droplets were generated in a microfluidic device. The micro-droplet size and generation frequency were determined based on continuous monitoring of light transmittance at the interface in microchannel. The size of RTIL micro-droplets was inversely proportional to the increase of PBS solution flow rate and RTILs hydrophobicity, while droplet generation frequency was proportional to those changes. The measured size of RTILs droplets ranged from 0.6 to 10.5 nl, and from 1.0 to 17.1 nl for [Tf₂N]- and [PF₆]-based RTILs, respectively. The measured frequency of generated RTILs droplets ranged from 2.3 to 37.2 droplet/min, and from 2.7 to 17.1 droplet/min for [Tf₂N]- and [PF₆]-based RTILs, respectively. The capillary numbers were calculated depending on the RTILs, and ranged from 0.51×10^-3 to 1.06×10^-3 and from 5.00×10^-3 to 8.65×10^-3, for [Tf₂N]- and [PF₆]-based RTILs, respectively. The interfacial tension between RTILs and PBS will contribute to developing bioprocesses using immiscible RTILs. Also, the RTILs micro-droplets will enable the high-throughput monitoring of various biological and chemical reactions using RTILs as new reaction media.     

In situ neutron diffraction study of the microstructure and tensile deformation behavior in Al-added high manganese austenitic steels

In situ neutron diffraction experiments were performed to measure the tensile deformation behavior of high manganese austenitic steels with different Al contents (0, 1.5, 2.0, 3.0 wt.%). Significant variations of peak shift, broadening and asymmetry of the diffraction peaks were observed in the plastic region with the measurement. Diffraction peak profile analysis was applied to determine microstructural parameters such as stacking/twinning fault probabilities, dislocation density and stacking fault energy (SFE). These parameters are quantitatively correlated to the yield strength, serrated flow and strain hardening rate during tensile deformation. The main results showed that the twin/stacking fault probability considerably decreases from 0.05 to 0.01 and dislocation density from 10¹⁶ to 4 × 10¹⁵ m⁻² as a function of Al addition, while SFE (γ) increases from 20 to 45 mJ m⁻² with the relationship of γ = 8.84 wt.% Al + 19.0 mJ m⁻². Such microstructural parameters are also in good agreement with the results of the misorientation and pattern quality map obtained by the electron backscatter method.     

Simulation and Fabrication Studies of Semi‐superjunction Trench Power MOSFETs by RSO Process with Silicon Nitride Layer

In this letter, we propose a new RESURF stepped oxide (RSO) process to make a semi‐superjunction (semi‐SJ) trench double‐diffused MOSFET (TDMOS). In this new process, the thick single insulation layer (SiO₂) of a conventional device is replaced by a multilayered insulator (SiO₂/SiN_x/TEOS) to improve the process and electrical properties. To compare the electrical properties of the conventional RSO TDMOS to those of the proposed TDMOS, that is, the nitride_RSO TDMOS, simulation studies are performed using a TCAD simulator. The nitride_RSO TDMOS has superior properties compared to those of the RSO TDMOS, in terms of drain current and on‐resistance, owing to a high nitride permittivity. Moreover, variations in the electrical properties of the nitride_RSO TDMOS are investigated using various devices, pitch sizes, and thicknesses of the insulator. Along with an increase of the device pitch size and the thickness of the insulator, the breakdown voltage slowly improves due to a vertical field plate effect; however, the drain current and on‐resistance degenerate, owing to a shrinking of the drift width. The nitride_RSO TDMOS is successfully fabricated, and the blocking voltage and specific on‐resistance are 108 V and 1.1 mΩcm², respectively.     

Theoretical cross-wind speed against rail vehicle derailment considering the cross-running wind of trains and the dynamic wheel-rail effects

In this paper, a theoretical formula was proposed that predicts the derailment index due to a cross wind applied to a rail vehicle considering the cross running wind condition of two running trains as well as the dynamic wheel-rail effects. The recently developed derailment theory on a wheelset was applied to this new cross wind derailment formula. Contrary to the conventional formulas, this new derailment formula was derived considering a dynamic derailment coefficient (Q/P) under normal running, the friction coefficient between the wheel and the rail, the wheel load variation, the cross running wind effects, and the cross wind. Using this proposed formula, the derailment pattern and the critical cross wind speed of derailment could be predicted for various cross running wind conditions of two running trains. Finally, for some typical examples, the results of this proposed formula were compared and verified with those of the conventional formulas and the numerical simulation of multi-body dynamics software, Recurdyn.     

A suggested color scheme for reducing perception-related accidents on construction work sites

Changes in workforce demographics have led to the need for more sophisticated approaches to addressing the safety requirements of the construction industry. Despite extensive research in other industry domains, the construction industry has been passive in exploring the impact of a color scheme; perception-related accidents have been effectively diminished by its implementation. The research demonstrated that the use of appropriate color schemes could improve the actions and psychology of workers on site, thereby increasing their perceptions of potentially dangerous situations. As a preliminary study, the objects selected by rigorous analysis on accident reports were workwear, safety net, gondola, scaffolding, and safety passage. The colors modified on site for temporary facilities were adopted from existing theoretical and empirical research that suggests the use of certain colors and their combinations to improve visibility and conspicuity while minimizing work fatigue. The color schemes were also tested and confirmed through two workshops with workers and managers currently involved in actual projects. The impacts of color schemes suggested in this paper are summarized as follows. First, the color schemes improve the conspicuity of facilities with other on site components, enabling workers to quickly discern and orient themselves in their work environment. Secondly, the color schemes have been selected to minimize the visual work fatigue and monotony that can potentially increase accidents.     

Optimal Reference Vector Selection Algorithm in Subspace Interference Alignment to Maximize System Throughput

Arbitrary reference vectors have been adopted in conventional subspace alignment as transmitting vectors at the transmitter side. Inter-cell interference among users can be eliminated using orthogonal vectors to the chosen reference vectors at the receiver side. However, in this case, the sum-rate varies using different reference vectors, even though the channel values remain constant, and vice versa. In this paper, we analyzed the variation of sum-rate corresponding to reference vectors. An optimal reference vector selection algorithm based on subspace interference alignment is proposed to increase multi-cell capacity. The proposed algorithm adopts reference vectors with small variance. Simulation results show that the proposed algorithms provide about 50 % higher sum-rate than does the conventional subspace interference alignment algorithm.     

Development of Predictive Model based Control Scheme for a Molten Carbonate Fuel Cell (MCFC) Process

International Journal of Control, Automation and Systems - To improve availability and performance of fuel cells, the operating temperature of a molten carbonate fuel cells (MCFC) stack should be...