Synthesis of poly(ethylene glycol)‐based hydrogels and their swelling/shrinking response to molecular recognition

To synthesize the novel molecular‐ and pH‐stimulus‐responsive hydrogel, we prepared poly(ethylene glycol)‐based hydrogel containing ionic groups. We evaluated the fundamental swelling/shrinking properties of the hydrogels synthesized by various conditions. Decreasing the molecular weight of a crosslinker provided the increasing of the equilibrium swelling ratio. Also, the equilibrium swelling ratio was changed by the introduction of functional ionic monomers and its compositions. Furthermore, the swelling/shrinking behaviors of the hydrogels were affected by the environmental condition of aqueous solution, in fact the hydrogels were considerably shrunk (to one‐fifth volume) using a di‐ionic solute in the aqueous solution through the ionic interactions between the hydrogel and the solutes. Additionally, the specific shrinking to diamine compounds was also observed in response to pH change. These results clearly show the swelling/shrinking responsibility of the hydrogels toward the molecular recognitions and its pH conditions. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 3153–3158     

Catalytic activity of carbon-supported iridium oxide for oxygen reduction reaction as a Pt-free catalyst in polymer electrolyte fuel cell

Iridium oxide supported on Vulcan XC-72 carbon black (IrO₂/C) as a cathode catalyst for polymer electrolyte fuel cell (PEFC) has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD) measurement. The IrO₂ particles were 8-160 nm in diameter. The oxygen electroreduction activity was studied by cyclic voltammetry (CV). It was found that IrO₂/C had high oxygen reduction reaction (ORR) activity. The performance of the membrane electrode assemble (MEA) was also tested in a single PEFC and showed that IrO₂/C catalyst would be potential candidates for use as cathode catalyst in PEFC.     

Electronic coupling in covalently-linked MM quadruple bonds: M2δ to ligand π conjugation

Dimetal tetracarboxylates, M₂(O₂CR)₄, where R=alkyl and M=Mo or W, can be linked in a perpendicular or parallel manner through the agency of a variety of ligands to give ‘dimers of dimers’ [M₂(O₂CR)₃]₂(bridge), or extended chains. A ring of formula [M₂(O₂CR)₂(bridge)]₄ is an alternative to a chain [M₂(O₂CR)₃]₂(bridge)₂]_∞ and ‘molecular squares’ of formula [(RNCHNR)₂M₂(bridge)]₄ have recently been reported by Cotton and Murillo, where M=Mo and Rh and R=p-MeOC₆H₄. The electronic coupling between the M₂ units manifests itself in electrochemical data and in the electronic spectra of the compounds. The electronic coupling occurs by M₂δ to ligand π-conjugation and specific examples are illustrated for the bridging ligands oxalate, perfluoroteraphthalate, 1,8-anthracenedicarboxylate and 2,7-dioxynaphthyridine. Correlations of a variety of spectroscopic data and computations employing density functional theory are presented.     

Carbon nanohorns-coated microfibers for use as free-standing electrodes for electrochemical power sources

We report the first direct laser based synthesis of carbon nanohorns onto carbon microfibrous, for the straightforward fabrication, of free-standing (binderless) electrodes. These carbon nanohorns have diameters as small as 2–4 nm and were found to cover uniformly the microfibrous substrates. The carbon nanohorns-based electrodes developed here are shown to open new prospects for the development of advanced electrochemical power sources. In particular, their possible applications in either lithium-ion batteries or supercapacitors or fuel cell technologies are demonstrated.     

Traction performance evaluation of a 78-kW-class agricultural tractor using cone index map in a Korean paddy field

The cone index (CI), as an indicator of the soil strength, is closely related to the traction performance of tractors. This study evaluates the traction performance of a tractor in terms of the CI during tillage. To analyze the traction performance, a field site was selected and divided into grids, and the CI values at each grid were measured. The CI maps of the field sites were created using the measured CI. The traction performance was analyzed using the measured traction load. The traction performance was grouped at CI intervals of 400 kPa to classify it in terms of the CI. When the CI decreased, the engine speed and tractive efficiency (TE) decreased, while the engine torque, slip ratio, axle torque, traction force, and dynamic traction ratio (DTR) increased. Moreover, the DTR increased up to approximately 13%, and the TE decreased up to 9%. The maximum TE in the DTR range of 0.45–0.55 was higher than approximately 80% for CI values above 1500 kPa. The DTR and TE results obtained in terms of the CI can help efficiently design tractors considering the soil environmental conditions.     

Investigation of the soil thrust interference effect for tracked unmanned ground vehicles (UGVs) using model track tests

The traction force of a tracked unmanned ground vehicle (UGV) depends on the soil thrust generated by the shearing action on the soil-track interface. In the development of soil thrust, because the continuous-track system consists of a number of single-track systems connected to each other, interference occurs between the adjacent single-track systems through the surrounding soil. Thus, the total soil thrust of the continuous-track system is not equal to the sum of the soil thrust of each single-track system, and the interference effect needs to be carefully considered. In this study, model track tests were conducted on model single-, double-, and triple-track systems according to relative density of soil and shape ratio (i.e., the length of the track plate to grouser depth). The test results indicated that the interference effect reduced soil thrust due to the overlapping shear zones between adjoining single-track systems. The loss of soil thrust increased as the relative density of the soil increased and the shape ratio decreased. Based on these findings, a soil thrust multiplier that can be utilized to assess the soil thrust of a continuous-track system was developed.     

Dynamics of ball-like flames in extremely low-speed counterflow field in near-lean limit low-Lewis number mixture

For the understanding of ball-like flame behavior in counterflow field, transient three-dimensional computations with thermal-diffusion model were conducted for a low-Lewis number mixture near lean limit. Three types of flame behaviors were confirmed: stable spherical ball-like flame (spherical BLF) in A ≤ 0.010, stable non-spherical ball-like flame (non-spherical BLF) in 0.01 < A < 0.089 and splitting ball-like flame (splitting BLF) in A ≥ 0.089, where A is ordinary stretch rate normalized with laminar burning velocity S_L and thermal diffusivity α. Analysis of flame structure for non-spherical BLF located its center at the stagnation point showed that the maximum temperature on the stagnation plane was higher than that on the counterflow axis because of the small difference between the flame curvatures on the stagnation plane and that on the counterflow axis. With the increase of stretch rate, the maximum temperature of the non-spherical BLF on the stagnation plane increased and the position of maximum temperature got away from the stagnation point. The maximum temperature on the counterflow axis decreased and the position of maximum temperature got closer to the stagnation point. Existence of unburned fuel was also confirmed near the stagnation point at A = 0.085. Thus, net fuel velocity was newly introduced to evaluate the effect of the unburned fuel diffusion. The profile of the net fuel velocity revealed two peaks in the case of A < 0.050 and four peaks in the case of A > 0.050. In the case A > 0.050, the inner two peaks were found to be due to the diffusion of unburned fuel to the outward direction. The analyses on the peak positions showed that the flame splitting occurs when the positions of the inner two peaks of the net fuel velocity are located outside of the reference flame ball radius.     

Novel separation medium spongy monolith for high throughput analyses

Sponge-like material was utilized as novel chromatographic media for high throughput analyses. The pore size of the sponge-like material was several dozen micrometer, and was named spongy monolith because it consists of continuous structured copolymers, which was made of poly(ethylene-co-vinyl acetate), such as monolithic materials including silica monoliths and organic polymer monoliths. The spongy monolith was packed into a stainless steel column (100 mm × 4.6 mm I.D.) and evaluated in liquid chromatography (LC) with an on-line column-switching LC concentration system. The results indicate that the packed column could be used with high flow rates and low back pressure (9.0 mL/min at 0.5 MPa). Furthermore, bisphenol A was quantitatively recovered by on-line column-switching LC concentration with the spongy monolithic column. Additionally, the adsorption capacity and physical strength of the media was enhanced via chemical modification of spongy monoliths using glycerol dimethacrylate. The results compared with original spongy monolith demonstrated that a higher adsorption capacity was achieved on a shorter column, and a stable low back pressure was obtained at high throughput elution even with a longer column.     

Tire-ice model development for the simulation of rubber compounds effect on tire performance

The material properties of the rubber compounds, which are highly dependent on temperature, have a vital role in the tire behavior. A comprehensive study on the effect of the rubber properties on tire performance, for different temperatures, as well as different road conditions is required to adequately predict the performance of tires on ice.In this study, a theoretical model has been developed for the tire-ice interaction. The temperature changes obtained from the model are used to calculate the height of the water film created by the heat generated due to the friction force. Next, the viscous friction coefficient at the contact patch is obtained. By using the thermal balance equation at the contact patch, the dry friction is obtained. Knowing the friction coefficients for the dry and wet regions, the equivalent friction coefficient is calculated. The model has been validated using experimental results for three similar tires with different rubber compounds properties. The model developed can be used to predict the temperature changes at the contact patch, the tire friction force, the areas of wet and dry regions, the height of the water film for different ice temperatures, different normal load, etc.