• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2004.05a
• /
• pp.71-74
• /
• 2004

Recently, with the wide shortage of natural sand resources, it has been increasingly used the crushed sand. rushed sand is made by the process of crushing the rocks artificially, which has different particle properties compared with that of natural sand. Because such different panicle properties of crushed sand results in an undesirable effects of concrete. improvement technology for crushed sand particle properties like grain shape and fine particle needed during the manufacturing process. In this paper, improvement technology of grain shape and fine particle is reported. According to test results, adequate investment for manufacturing facilities like impact crusher and abrasion test machine is required to meet the advanced grain shape and grading of crushed sand. Based on the investigation of test result, mixing of natural land and crushed sand with given proportion can achieve the improvement of grain shape. For improving excessive fine panicle contents. current manufacturing system also can enhance the existing technology for fine particle without additional investment. It can be concluded that adequate investment and research can improve the quality of crushed sand.

• Journal of the Korea Concrete Institute
• /
• v.12 no.4
• /
• pp.103-111
• /
• 2000

The influence of the improvement of grain shape of the coarse aggregate to the unit powder content of concrete and the fine aggregate ratio for the increase of the flowability and segregation resistance of high performance concrete was examined. According to the experimental results, flowability and compacting of concrete presents best states in the S/a which has the smallest 패야 ratio. The coarse aggregate after improvement of grain shape, that has changed from the 0.68 of spherical rate of disk shape to 0.73, led fine aggregate ratio to be down 6% (i.e from 47% to 41%). The improvement of grain shape of the coarse aggregate also led the lowest unit powder content to be down 60kg/㎥ (ie from 530kg/㎥ to 470kg/㎥). And approximate 10% of unit water content has been reduced as unit powder content was down. However, the compressive strength after the improvement of grain shape of the coarse aggregate decreased to 5% due to decrease of adhesiveness of the aggregate and cement paste.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.10a
• /
• pp.21.2-274
• /
• 1999

This study aims to examine the influence of the unit powder content of concrete and the fine aggregate ration of high flowing concrete after the improvement of grain shape of the coarse aggregate. According to the experimental results, flowbility and compating of concrete presents the best states in the S/a which has the smallest void ratio. The coarse aggregate after improvement of grain shape has been changed from 0.68 circular ratio of disc shape to 0.73 circular shape. It lead to be down 6% of fine aggregate ratio (from 47% to 41%), which is satisfactory to compacting. Also, the improvement of grain shape of the coarse aggregate lead the lowest unit powder content to be down 60kg/㎥ from (530kg/㎥ to 470kg/㎥). And about 11% unit water content can be reduced as unit powder conent is down.

• Transactions of Materials Processing
• /
• v.9 no.2
• /
• pp.120-127
• /
• 2000

Recently, most of researches for sheet metal deep drawing process have been performed on the formability of axisymmetric shape, but there are not any concrete reports on the formability of non-axisymmetric shape. In addition, the conventional shape radius of the punch and die has been determined by trial-and-error using industrial experience and post processing test, and only approximate shape radius of the punch and die has been presented. In this study, the optimal shape radius of the punch and die in deep drawing process with biaxisymmetric blank shape is proposed. Through the deep drawing experiment, especially it is found that in order to obtain the optimal products, and improvement of formability can be researched by selection of such punch and die shape radius that gives an adequate thickness distribution in all processes.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 1999.08a
• /
• pp.452-456
• /
• 1999

Newly constructed plate shape control system, using attached shape measuring instruments and work roll bender, was put in service in No. 2 Plate Mill, POSCO. Recently, customers demand the improvement of flatness and plate crown accuracy. Many competition Plate Mill introducted shape control system, for example, pair cross mill, work roll bender which includes shape measuring instrument and shape control mathematical models, and No. 2 Plate Mill, POSCO introducted work roll bender and shape measuring instruments. This report describes the properties of No. 2 Plate Mill shape control system and work roll bender.

• Korean Journal of Computational Design and Engineering
• /
• v.8 no.4
• /
• pp.212-221
• /
• 2003

In order to reduce the lead-time and cost, the technology of rapid prototyping (RP) has been widely used. A new rapid prototyping process, transfer-type variable lamination manufacturing process by using expandable polystyrene foam (VLM-ST), has been developed to reduce building time, apparatus cost and additional post-processing. At the same time, VLM Slicer, the CAD/CAM software for VLM-ST has been developed. In this study, algorithms for accuracy improvement of VLM-ST, which include offset and overrun of a cutting path and generation of a reference shape are developed. Offset algorithm improves cutting accuracy, overrun algorithm enables the VLM-ST process to make a shape of sharp edge and reference shape generation algorithm adds additional shape which makes off-line lamination easier. In addition, proposed algorithms are applied to practical CAD models for verification.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.65 no.1
• /
• pp.58-64
• /
• 2016

In this paper, the design of rotor shape was performed for improvement of start-up characteristics and efficiency in single-phase LSPM. In order to improve the start-up characteristics, shape of rotor aluminium cage bar was changed. Through arrangement of permanent magnets and installation of flux barriers, it was performed torque ripple reduction and efficiency improvement. Cogging torque and back-EMF is calculated by the no-load analysis, start-up time is calculated by the start-up state analysis, efficiency and torque ripple is calculated by steady state analysis. The characteristics of the motor were calculated through FEM.

• Journal of the Korea Society of Computer and Information
• /
• v.6 no.4
• /
• pp.104-109
• /
• 2001

In this paper, we designed a 3D shape measuring system with high speed and high measurement resolution using line-shaped sine stripes of a LCD projector We proposed an effective method to improve measurement efficiency for a 3D shape measuring system by finding the deficient shape information areas and recovering the shape information efficiently. We experimentally confirmed the improvement of measurement efficiency. Deficient shape information areas can be inevitably existed in a acquired image caused by the camera view angle and surface shapes of an object. The measurement efficiency is turned out to be improved by extracting these shadow areas and recovering the shape information efficiently using both a variable rated normalization and a variable sized phase recovering windows.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.1
• /
• pp.68-74
• /
• 2015

This paper describes about the efficiency improvement of switched reluctance generator (SRG) over the rated speed region. Since the current shape has a great influence on the loss of the machine, so the system efficiency can be improved by optimizing the current shape. In case the wide speed range application such as wind power and medium size hydraulic power generation, a method of switching angle control is suggested to obtain the wanted current shapes. In order to verify the method, the experimental platform is set up. The feasibility of the theory is verified by simulation and experimental results.

• Journal of computational fluids engineering
• /
• v.17 no.4
• /
• pp.56-68
• /
• 2012

Nowadays, Unmanned Combat Air Vehicle(UCAV) has become an important aircraft system for the national defense. For its efficiency and survivability, shape optimization of UCAV is an essential part of its design process. In this paper, shape optimization of UCAV was processed for aerodynamic performance improvement and Radar Cross Section(RCS) reduction using Multi Objective Genetic Algorithm(MOGA). Lift and induced drag, friction drag, RCS were calculated using panel method, boundary layer theory, Physical Optics(PO) approximation respectively. In particular, calculation applied Radar Absorbing Material(RAM) was performed for the additional RCS reduction. Results are indicated that shape optimization is performed well for improving aerodynamic performance, reducing RCS. Further study will be performed with higher fidelity tools and consider other design segments including structure.