10,352 research outputs found
FINDING THE SHORTEST-PATH IN RAILROAD SYSTEMS USING THE SUPER-NETWORK
No full textThe shortest path problem is discussed to develop an automatic control system of the railroad in a factory. The super-network is proposed and an algorithm is given to find the shortest path on the super-network. The super-network is useful to model the railroad system because it can represent important factors in finding paths which cannot be represented by an ordinary network. An example is also given to show how a railroad system can be modelled using a super-network and how the shortest path can be found by the proposed algorithm
Ab initio study of superoxide anion-water clusters O-2(-) (H2O)(n=1-5)
No full textThe structures, energies, spectra, and charge transfer to solvent (CTTS) energies of the hydrated superoxide anion clusters have been investigated using both density functional calculations (DFT) with Becke-3-parameters employing Lee-Yang-Parr functionals (B3LYP) and second-order Moller-Plesset perturbation (MP2) calculations employing highly diffuse basis sets. Given the good agreement of our predicted results with the experimental spectra and enthalpy, it would be interesting if the CTTS energies could be experimentally determined.X1135sciescopu
Finite element simulation of three dimensional superplastic blow forming
No full textSuperplastic blow forming processes are simulated with a finite element method which adopts the convective coordinates system. The code developed is applied to cylindrical cup and the square cup blow forming processes to predict the optimum forming pressure cycle. The numerical result demonstrates the validity and accuracy by comparing with the experimental result and the numerical result by a continuum finite element method The numerical results also provide the pole height, the intermediate and final deformed shapes and the thickness distribution with respect to time
Simulation of superplastic forming diffusion bonding with finite-element analysis using the convective coordinate system
No full textSuperplastic-forming processes are simulated with finite-element analysis in the convective coordinate system. The finite-element code developed is applied to blow-forming processes for demonstration of its validity by predicting the optimum forming pressure cycle. The numerical results provide the pole height and intermediate deformed shapes with variation of the forming time, as well as thickness distribution. The results are compared with those from the experiment and finite-element analysis with a continuum element. The finite-element code is applied to the analysis of a superplastic-forming/diffusion-bonding (SPF/DB) process of four-sheet sandwich parts. The result shows that the deformed shape with the three-dimensional analysis is different from that with the two-dimensional plane strain because of the end effect, and so is the thickness distribution. The analysis enables accurate prediction of thickness distribution, which is necessary for the good design of multi-sheet sandwich parts such as an aircraft part. (C) 1999 Elsevier Science S.A. All rights reserved
Vibration characteristics of a 75 kW turbo machine with air foil bearings
No full textAir foil bearings are very attractive bearing systems,for turbomachinery because they have several advantages over conventional bearings in terms of oil-free environment, low power loss, long life, and no maintenance. However, most of the developed machines using air foil bearings are limited to small and high-speed rotors of 60,000-120, 000 rpm, since the increase in power of turbomachinery requires lower rotor speed and greater loading in bearings, which makes it difficult to use air foil bearings for large machines. In this paper a 75 kW turboblower using air foil bearings is introduced, and the vibration characteristics of the machine have been investigated experimentally under a wide range of operating conditions, including compressor surge in the performance test. The machine is designed to be fully air lubricated and air cooled, and its operating speed is 20,000-26,000 rpm with maximum pressure ratio of 1.8. The results show that the air foil bearings offer adequate damping to ensure dynamically stable operation in the whole range.The work reported herein was supported by Neuros Co., Ltd. The authors express their appreciation to the company for their
help in preparing the test rig
Low-power and area-efficient FIR filter implementation suitable for multiple taps
No full textThis paper describes a 32-tap finite impulse response (FIR) filter with two 16-tap macros suitable for multiple taps. The derived condition for a coded coefficient and data block shows 35% savings in power consumption and 44% improvement in occupied area compared to a typical radix-4 modified Booth algorithm. According to the condition and separated shifting-accessing clock scheme, we have implemented a 32-tap FIR filter in 0.6-mum CMOS technology with three levels of metal. The chip that occupies 2.3 X 2.5 mm(2) of silicon area has an operating frequency of 20 MHz and consumes 75 mW at V-dd = 3.3 V
Regulation of 6S RNA biogenesis by switching utilization of both sigma factors and endoribonucleases
No full textIn Escherichia coli, 6S RNA functions as a modulator of RNA polymerase sigma(70)-holoenzyme activity, but its biosynthetic pathway remains uncharacterized. In this study, to further understand the regulatory circuit of 6S RNA biosynthesis for the modulation of Esigma(70) activity, we have characterized the biogenesis of 6S RNA. We reveal that there are two different precursors, a long and a short molecule, which are transcribed from the distal P2 and proximal P1 promoter, respectively. Transcription from the P2 promoter is both sigma(70)- and sigma(S)-dependent, whereas, in contrast, P1 transcription is sigma(70)- but not sigma(S)-dependent. Both precursors are processed to generate the 5' end of 6S RNA, and while the long precursor is processed exclusively by RNase E, the short precursor is processed by both RNase G and RNase E. Our data indicate that the switching of the utilization of both sigma factors and endoribonucleases in the biogenesis of 6S RNA would play an essential role in modulating its levels in E.coli
Numerical simulation of the superplastic moving die forming process with a modified membrane finite element method
No full textIn superplastic forming, a number of processes have been developed and designed to reduce the thickness deviation that is inevitable in simple female-die forming. Some of the forming processes require tool movements for better thickness distribution than simple female forming. It is-common to use techniques based on male tool movement for relatively deep and complex shapes. The process has to deal with the optimum pressure cycle considering the moving die, the thickness distribution and the final shape. Calculation of the thickness distribution is a key for the optimum process design to produce good quality parts of uniform thickness distribution. In this paper, superplastic forming processes with a moving die are simulated with the finite element method (FEM) with modified membrane elements in the convective coordinate system. The numerical result provides the optimum pressure cycle and intermediate deformed shapes with the variation of the forming time as well as the thickness distribution. The result is compared with that obtained from simple female-die forming to demonstrate that the thickness distribution with a moving die is more uniform than that with a simple female die. The analysis enables accurate prediction of the thickness distribution in blow forming processes with a moving die. (C) 2001 Elsevier Science B.V. All rights reserved
New intergrid transfer operator in multigrid method for P-1-nonconforming finite element method
No full textFor a second-order elliptic boundary value problem, We develop an intergrid transfer operator in multigrid method for the P-1-nonconforming finite element method. This intergrid transfer operator needs smaller computation than previous intergrid transfer operators. Multigrid method with this operator converges well, (C) 1999 Elsevier Science Inc. All rights reserved
Surface tensions and differential enthalpies of dilution of the lithium bromide plus lithium iodide+1,3-propanediol plus water system
No full textThe lithium bromide + lithium iodide + 1,3-propanediol + water (LiBr/LiI mole ratio = 4 and (LiBr + LiI)/HO(CH2)(3)OH mass ratio = 4) solution was chosen as one of the potential candidates for an air-cooled absorption chiller. For this system, the surface tensions and differential enthalpies of dilution were measured at various temperatures and absorbent (LiBr + LiI + HO(CH2)(3)OH) concentration ranges by using the capillary rise method and an Isoperibol solution calorimeter, respectively. The measured data were well correlated with the simple polynomial equations. The deviations between the experimental and calculated values in the surface tension and differential enthalpy of dilution measurements were 0.10 and 2.8%.This
research was performed for Greenhouse Gas Research Center, one
of the critical Technology-21 programs, funded by the Ministry of
Science and Technology of Korea, and also was supported partially
by the Brain Korea 21 Project
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