Measurement of heat/mass transfer at second stage vane endwall according to step heights

Journal of Mechanical Science and Technology - Recently, domestic gas turbines are primarily operated under partial loads. Hence, thermal expansion of components decreases, leading to a...     

A study on squeal noise reduction considering the pad shape of the disc brake system for urban railway vehicles

Journal of Mechanical Science and Technology - In this paper, to help reduce the squeal noise produced during the braking of urban railway vehicles, the shape of the disc brake pad was investigated...     

Chute design of mackerel automatic grader using multibody dynamics

An automatic mackerel grader is a machine that automatically sorts mackerel according to size. The chute spreads the mackerel to allow the latter to enter each roller evenly. Sorting is simulated to confirm that the multibody dynamics model of the automatic grader correctly sorts the mackerel. This process is completed according to the shape of the chute to confirm the effect on performance. A new shape of the chute and the application are proposed and evaluated by a comparison with conventional chute shapes. RecurDyn, a multi-body dynamics program, is used for the sorting simulation. The contact parameters are defined by Hertzian contact theory using the material information of mackerel and C/S steel. A rigid-body mackerel model is used to express the behavior of mackerel. Sorting is simulated for each shape. The sorting accuracy and error of the new shape are compared with those of two existing shapes. The new shape shows a 0.29 mm sorting error and better sorting accuracy than the existing shapes.     

Aircore mechanism during draining based on influence of pressure difference and drain port diameter

An understanding of the mechanism of aircore phenomenon during draining is very important. In this study, numerical simulations were conducted for different pressurized and suction pressure water tanks, as well as for different drain port diameters, to explain and validate the proposed aircore mechanism. It was found that increasing the pressure at the top surface of the tank results in suppression of the aircore, whereas an increase in the suction pressure at the drain port outlet enhances the development of the aircore. For different drain port diameters, it was observed that the duration of the aircore during draining decreases with a decrease in the drain port diameter, and that the aircore is suppressed for a very small drain port diameter.     

Counter-current air-water flow in narrow rectangular channels with offset strip fins

Counter-current two-phase flows of air-water in narrow rectangular channels with offset-strip fins have been experimentally investigated in a 760 mm long and 100 mm wide test section with 3.0 and 5.0 mm gap widths. The two-phase flow regime, channel-average void fractions and two-phase pressure gradients were studied. Flow regime transition occurred at lower superficial velocities of air than in the channels without fins. In the bubbly and slug flow regimes, elongated bubbles rose along the subchannel formed by fins without lateral movement. The critical void fraction for the bubbly-to-slug transition was about 0.14 for the 3 mm gap channel and 0.2 for the 5 mm gap channel, respectively. Channel-average void fractions in the channels with fins were almost the same as those in the channels without fins. Void fractions increased as the gap width increased, especially at high superficial velocity of air. The presence of fins enhanced the two-phase distribution parameter significantly in the slug How, where the effect of gap width was almost negligible. Superficial velocity of air dominated the two-phase pressure gradients. Liquid superficial velocity and channel gap width has only a minor effect on the pressure gradients.     

The kinetics of carbochlorination of titania slag

The kinetics of the carbochlorination of titania slag with chlorine gas and petroleum coke were determined. The porosity created, when easily chlorinated components of the slag such as iron oxide are rapidly reacted, had a significant effect on the chlorination of the slag. The effects of temperature, chlorine partial pressure, and initial particle size were determined, and a rate equation that incorporates these effects in the ranges of experimental conditions used in this work was developed. The results of this work show that the chlorination kinetics of titania slag are quite different from those of rutile with which most previous studies were concerned.     

Experimental and Numerical Studies in a Vortex Tube

The present investigation deals with the study of the internal flow phenomena of the counter flow type vortex tube using experimental testing and numerical simulation. Visualization was carried out using the surface tracing method, injecting dye on the vortex tube wall using a needle. Vortex tube is made of acrylic to visualize the surface particle tracing and the input air pressure was varied from 0.1 MPa to 0.3 MPa. The experimentally visualized results on the tube show that there is an apparent sudden changing of the trajectory on the vortex tube wall which was observed in every experimental test case. This may indicate the stagnation position of the vortex flow. The visualized stagnation position moves towards the vortex generator with increase in cold flow ratio and input pressure. Three-dimensional computational study is also conducted to obtain more detailed flow information in the vortex tube. Calculated total pressure, static pressure and total temperature distributions in the vortex tube were in good agreement with the experimental data. The computational particle trace on the vortex tube wall is very similar to that observed in experiments.     

Meta analysis of classification algorithms for pattern recognition

Various classification algorithms became available due to a surge of interdisciplinary research interests in the areas of data mining and knowledge discovery. We develop a statistical meta-model which compares the classification performances of several algorithms in terms of data characteristics. This empirical model is expected to aid decision making processes of finding the best classification tool in the sense of providing the minimum classification error among alternatives     

A Structural Solution to Communication Dilemmas in a Virtual Community

In a many-to-many communication setting like a virtual community, individuals may be strongly tempted to free-ride on others' contributions, which would eventually lead to the collapse of the community. To find a structural solution to the "communication dilemma," this study compared the performances of 2 communication structures—one based on the interpersonal networks (network-generalized exchange: N_EX; e.g., blogs) and the other based on a public electronic bulletin board (group-generalized exchange: G_EX). In a 2 × 2 × 2 longitudinal between-subject experiment, it was found that changing G_EX to N_EX could increase the contributions made by individuals. Furthermore, N_EX was found to be an effective structure for N-person communication particularly when a large number of individuals were involved. The findings imply that an individual's cooperative motivation is a function of the incentive structure of a particular form of information exchange, which means that altering the exchange form may be a possible solution to the communication dilemmas in virtual communities.