Time-dependent crashworthiness of polyurethane foam

Mechanics of Time-Dependent Materials - Time-dependent stress–strain relationship as well as crashworthiness of polyurethane foam was investigated under constant impact energy with different...     

Dansameum regulates hepatic lipogenesis and inflammation in vitro and in vivo

Food Science and Biotechnology - Although the clinical guidelines for nonalcoholic fatty liver disease (NAFLD) therapy recommended hepato-protection and exercise to reduce body weight, no...     

Influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors

Hybrid finite element analysis was used to analyze the influence of bearing stiffness on the static properties of a planetary gear system with manufacturing errors. The effects of changes in stiffness were similar for most of the manufacturing errors. State variables were most affected by the stiffness of the planet bearings. Floating either the sun or carrier helps to equal load sharing and minimizes the critical tooth stress. The effects of a floating sun and carrier are similar, but it is not recommended that both float, because this can induce greater critical tooth stress. Planet bearing stiffness should be optimized. Both load sharing and critical tooth stress should be considered to determine optimal bearing stiffness.     

Precision measurements of reaction wheel disturbances with frequency compensation process

The reaction wheel, an actuator for satellite attitude control, produces disturbance torque and force as well as axial control torque. The disturbances are so crucial to the pointing stability of this high precision satellite that a measurement of disturbances is necessary for such a satellite. The measurement table that is equipped with several load cells is one of the favorite types of measurement devices. The disturbance force and torque caused by the wheel's rotation, however, stimulate the elasticity of the loadcells from the measurement table and induce the vibration of the table. This then causes the measurement error, which is especially large near the resonance frequencies of the table. In order to reduce this type of error, a calibration process with frequency compensation is suggested in this paper. The “filtered” disturbance spectrum is obtained from the raw data and the degradation of data accuracy caused by the table vibration is alleviated. Since the exact measurement is made possible by this compensation process even in the resonance area, the measurement range can be expanded up to the frequency area including the resonance frequencies. The compensation method has been adopted for the HAU measurement table where three uni-directional loadcells are used. The validity of the use of uni-directional loadcells is also tested theoretically.     

Pressure drop in motionless mixers

A motionless mixer consists of a straight pipe or transfer tube containing the mixing elements that are used to cut, fold, twist, and re-combine the mixing fluid. The number of elements and their shape required in any application depend on the complexity of the mixing process. The objectives of this study are to develop new motionless mixers and to perform the experimental investigation of pressure drop in order to evaluate the performance of the new ones. Glycerin is used as a mixing fluid. Pressure drop is measured using a hydraulic manometer and correlations of friction factor are proposed as a function of Re. The friction factors of Sulzer SMX mixer are in qualitative good agreement with the published data. On the average, the friction factors of SSC and YNU mixers are about 36% lower than and 6% higher than that of the Sulzer one.     

Parametric study for conductor design of KSTAR PF coils

Large superconducting magnets such as ITER (International Thermonuclear Experimental Research) or KSTAR (Korean Superconducting Tokamak Advanced Research) magnet system adopted a cable-in-conduit conductor (CICC) using a forced-flow cooling system. Main optimization criteria for the conductor design of superconducting magnet system are stability margin and CICC cooling requirements. A zero-dimensional method is applied for the calculation of stability and the conductor optimization. In order to increase conductor performance, three different strands, ITER HP-I and HP-TI, and KSTAR HP-III, are tested. The strand characteristics of KSTAR HP-III are measured in the Samsung’s PPMS and Jc measurement system, and applied for this study. Also, the strand diameters, 0.81 mm and 0.78 mm are considered for this study, due to design change. Based on this result, the proposed configuration of CICC has been fabricated.     

Multifunctional Smart Textronics with Blow‐Spun Nonwoven Fabrics

Here, the fabrication of nonwoven fabric by blow spinning and its application to smart textronics are demonstrated. The blow‐spinning system is composed of two parallel concentric fluid streams: i) a polymer dissolved in a volatile solvent and ii) compressed air flowing around the polymer solution. During the jetting process with pressurized air, the solvent evaporates, which results in the deposition of nanofibers in the direction of gas flow. Poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVdF‐HFP) dissolved in acetone is blow‐spun onto target substrate. Conductive nonwoven fabric is also fabricated from a blend of single‐walled carbon nanotubes (SWCNTs) and PVdF‐HFP. An all‐fabric capacitive strain sensor is fabricated by vertically stacking the PVdF‐HFP dielectric fabric and the SWCNT/PVdF‐HFP conductive fabric. The resulting sensor shows a high gauge factor of over 130 and excellent mechanical durability. The hierarchical morphology of nanofibers enables the development of superhydrophobic fabric and their electrical and thermal conductivities facilitate the application to a wearable heater and a flexible heat‐dissipation sheet, respectively. Finally, the conductive nonwoven fabric is successfully applied to the detection of various biosignals. The demonstrated facile and cost‐effective fabrication of nonwoven fabric by the blow‐spinning technique provides numerous possibilities for further development of technologies ranging from wearable electronics to textronics.     

Separation of hydroxybenzoic acid isomers using the molecular imprinting technique

Molecular imprinting polymers (MIPs) for salicylic acid (SA), 3‐hydroxybenzoic acid (3HBA), and 4‐hydroxybenzoic acid (4HBA) were synthesized using styrene and 4‐vinylpyridine (4‐VPy) as functional monomer and divinylbenzene (DVB) as crosslinker. The adsorption characteristics of hydroxybenzoic acid (HBA) isomers on each MIP were investigated. The materials used for the polymerization of each 3HBA and 4HBA‐MIPs were adsorbed relatively well. This verifies that the MIPs that can adsorb template selectively were synthesized. However, SA‐MIP had no molecular imprinting effect. SA has intramolecular hydrogen bond and it is difficult to adsorb on recognition site of SA‐MIP, because its structure differs from that of recognition site of SA‐MIP. It indicates that SA‐MIP had no recognition effect. 1,2,3,4‐Tetrahydro‐1‐naphthol (THN)‐MIP was synthesized, which is similar to SA with intramolecular hydrogen bond. SA was separated selectively using THN‐MIP. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007     

Development of small robot using piezoelectric benders

Abstract

In this paper, a piezoelectric small robot was proposed and experimented. The piezoelectric bender of the actuator was composed of trapezoid ceramics which were attached on both surfaces of the elastic body. And an X-shaped structure was composed of four piezoelectric ceramic benders. When AC voltages which have different duty ratio were applied to the four benders, the motion of straight line according to a stick slip of the bender tips was obtained. A FEA simulation was used to analyze the motion of straight line. The output characteristics of the prototype actuator which was fabricated based on the analysis data were measured.     

Design of an ambulatory piezoelectric actuator which has T-shape stator

Abstract

T-shaped ambulatory piezoelectric actuator which can be used for various purposes such as lifesaving and environmental monitoring was proposed. The actuator consists of eight piezoelectric benders, t-shaped stator, and four legs, and it is very simple in structure and has the advantages of being easily manufactured and downsizing. It is also driven by four legs and can be moved forward and backward. The piezoelectric bender was composed of a carbon body and a ceramic plate. Vibration motions of the piezoelectric benders in x and z axes were transfer to the legs and the elliptical displacements at the ends of the legs were obtained by combination of the phase difference of 90 degrees. Characteristics of the actuators were simulated by finite element analysis, and the optimized prototype actuator was fabricated and experimented.