In situ estimation of equivalent porosity and strength of aluminum die-casting floor panel by simple loading test and finite element method

Journal of Mechanical Science and Technology - A simple estimation method of equivalent porosity and strength of scrapped aluminum die-casting floor panel is suggested in which various defects like...     

A study on 65 % potential efficiency of the gas turbine combined cycle

Journal of Mechanical Science and Technology - This study investigates the possibility of achieving 65 % efficiency in a gas turbine combined cycle. Several options to realize it were compared. A...     

Pulsed current activated combustion synthesis and consolidation of ultrafine NbSi2 from mechanically activated powders

Dense ultrafine NbSi₂ was synthesized using the pulsed current activated combustion synthesis (PCACS) method within 2 min and in one step from mechanically activated powders of Nb and 2Si. Simultaneous combustion synthesis and densification were accomplished under the combined effects of a pulsed current and mechanical pressure. Highly dense NbSi₂ with a relative density of up to 98 % was produced under simultaneous application of a 60 MPa pressure and a pulsed current. The average grain size and mechanical properties (hardness and fracture toughness) of the compound were investigated.     

Optical design of a static solar concentrator using Fresnel lenses

We present an optical design for a static solar concentrator for a photovoltaic cell (SCPV). The concentrator consists of two Fresnel lenses, one concave and one convex. The SCPV was designed and optimized using ray-tracing computer simulations. The performance of the SCPV was demonstrated using two settings: static mode and periodic mode with passive bi-yearly angle adjustments. Even without an active tracking system, the SCPV achieved an average Concentration ratio (CR) in the range of 1.94-2.86. The CR was distributed non-uniformly throughout the year, and the value and season of the highest CR were different for the two settings. The optimal mode for SCPV use can be chosen by balancing specific preferences regarding the target season for peak performance, maximum average CR, and maintenance frequency.

     

Multibody dynamic analysis of a duplicate bimodal tram

This study aimed to dynamically analyze a simulated bimodal tram by determining the motion equations for computer-aided analysis with Newton-Euler equations of motion, which algebraically represent motion. We utilized the multi-body dynamics analysis program, MSC.Adams, to evaluate the equations of motion, running stability, curving performance, and ride comfort of the simulated bimodal tram in comparison with single fleet and double fleet trams. For the double fleet tram, the characteristic equation was deduced to control the all-wheel steering mechanism by independently moving all the wheels characterizing an articulated vehicle. Our study aimed to design a double fleet bimodal tram. We confirmed that domestic and international standards were satisfied via the design and analysis of the simulation. Steering control equations are the significant preliminary data for coupling device research and development for double fleet bimodal trams.     

A multi-fluid nonrandom lattice fluid model: General derivation and application to pure fluids

A multi-fluid nonrandom lattice fluid model with no temperature dependence of close packed volumes of a mer, segment numbers and energy parameters of pure systems is presented. The multi-fluid nonrandom lattice fluid (MF-NLF) model with the local composition concept was capable of describing properties for complex systems. However, the MF-NLF model has strong temperature dependence of energy parameters and segment numbers of pure systems; thus empirical correlations as functions of temperature were represented for reliable and convenient use in engineering practices. The MF-NLF model without temperature dependence of pure parameters could not predict thermodynamic properties accurately. It was found that the present model with three parameters describes quantitatively the vapor pressure and the saturated density for the pure fluid.     

A study on carbon coating to silicon and electrochemical characteristics of Si-C/Li cells

The aim of this paper is to study the electrochemical behavior of Si-C material synthesized by heating a mixture of silicon and polyvinylidene fluoride (PVDF) in the ratios of 5, 20, and 50 wt%. The particle size of the synthesized material was found to be increased with increase in the PVDF ratio. The coexistence of silicon with carbon was confirmed from the XRD analysis. A field emission scanning electron microscope (FESEM) study performed with the material proved the improvement in coating efficiency with increase in the PVDF ratio. Coin cells of the type 2025 were made by using the synthesized material, and the electrochemical properties were studied. An electrode was prepared by using the developed Si-C material. Si-C|Li cells were made with this electrode. A charge|discharge test was performed for 20 cycles at 0.1 C hour rate. Initial charge and discharge capacities of Si-C material derived from 20 wt% of PVDF was found to be 1,830 and 526 mAh|g, respectively. Initial charge/discharge characteristics of the electrode were analyzed. The level of reversible specific capacity was about 216mAh/g at Si-C material derived from 20 wt% of PVDF, initial intercalation efficiency (IIE), intercalation efficiency at initial charge/discharge, was 68%. Surface irreversible specific capacity was 31 mAh/g, and average specific resistance was 2.6 ohm * g.     

Controlled release of bovine serum albumin using MPEG–PCL diblock copolymers as implantable protein carriers

MPEG–PCL diblock copolymers consisting of methoxy polyethylene glycol (MPEG) and poly(?‐caprolactone) (PCL) as drug carriers were synthesized by ring‐opening polymerization. It is possible to control the balance between hydrophilic and hydrophobic by changing the MPEG and the ratio of ?‐CL to MPEG. Implantable wafers were easily fabricated by the direct compression method after physical mixing of diblock copolymers and bovine serum albumin–fluorescein isothiocyanate (BSA‐FITC) as a model protein drug. The BSA release from wafers prepared by MPEG–PCL diblock copolymers were higher than that from PCL with the physical blending of MPEG. The wafers prepared by a variety of MPEG–PCL diblock copolymers exhibited the controlled BSA release profiles with a dependence on MPEG–PCL diblock copolymer compositions. In addition, the changing of MPEG and PCL molecular weights within MPEG–PCL diblock copolymer controlled the initial burst of BSA. We confirmed that the diblock copolymers could be served as protein delivery carrier in implantable wafer form. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102:1561–1567, 2006     

Preparation of porous thin films of a partially aliphatic polyimide

A thermally labile polymer, poly(propylene glycol), was modified to obtain PPG having an amino end group. PPG was incorporated into a partially aliphatic polyimide based on an alicyclic dianhydride, and this afforded triblock copolymers containing various amounts of PPG blocks. The thermal properties of the copolymers were investigated by thermogravimetric analysis and differential scanning calorimetry. The thermal decomposition of the PPG block in the copolymers was carried out at 240°C under various pressures to obtain porous polyimide films. The pores remained during the thermolysis under a reduced pressure of 710 mmHg, whereas they collapsed under (near) atmospheric pressure. The pore size increased as the amount of the PPG block in the copolymers increased. The dielectric constants of the porous polyimides varied from 2.60 to 2.42 with the original copolymer composition. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 532–538, 2006     

The process design and simulation for the methanol production on the FPSO (floating production,storage and off-loading) system

A process for methanol production from 100 MM scfd of stranded gas and CO₂ is proposed and simulated using a commercial process simulator, PRO/II v.9.1, for a FPSO (floating production, storage, off-loading) system. The process consists of Steam-CO₂ Reforming (SCR), methanol synthesis, a Reverse Water-Gas Shift (RWGS) reaction and ancillaries with recycle streams to SCR and RWGS. All reactors were simulated using the Gibbs reactor model. Also, the Plug Flow Reactor (PFR) model with reaction rate equations was used for the methanol reactor and the result was compared to the Gibbs reactor model. To maximize the use of the carbon source in stranded gas and CO₂ while avoiding an undesirable increase in process size, the optimum recycle ratios were calculated with a satisfying constraint, a steam-to-carbon ratio ≥ 1 in the SCR. In the proposed Methanol-FPSO process the RWGS reactor can maximize CO₂ utilization and case studies were performed to analyze the influence of RWGS.