• Wind and Structures
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• v.10 no.5
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• pp.421-435
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• 2007

A two-dimensional flutter analysis method (2d-3DOF method) was developed to simultaneously investigate the relationship between oscillation parameters and aerodynamic derivatives of three degrees of freedom, and to clarify the coupling effects of different degrees of freedom in flutter instability. With this method, the flutter mechanism of two typical bridge deck sections, box girder section and two-isolated-girder section, were numerically investigated, and both differences and common ground in these two typical flutter phenomena are summarized. Then the flutter stabilization effect and its mechanism for long-span bridges with box girders by using central-slotting were studied by experimental investigation of aerodynamic stability and theoretical analysis of stabilizing mechanism. Possible explanation of new findings in the evaluation trend of critical wind speed through central vent width is finally presented.

• Journal of Korean Foot and Ankle Society
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• v.11 no.2
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• pp.226-231
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• 2007

Purpose: To evaluate the clinical outcomes and radiographic results of open reduction and internal fixation for intraarticular calcaneal fractures. Materials and Methods: We reviewed 20 cases of calcaneal fractures managed with open reduction and internal fixation from March 2003 to January 2005. We used the computed tomographic classification system proposed by Sanders et al to classify these fractures. Preoperative and postoperative Bohler's angle, heel height (calcaneal facet height) and calcaneal length, calcaneal width were measured. The Creighton-Nebraska Health Foundation Assessment score was used for clinical evaluation. Results: There were 12 cases of type II fractures, 5 of type III fractures and 3 of type IV fractures. The mean clinical score was 84.3 for type II, 82.6 for type III and 56.1 for type IV. The mean preoperative $B{\ddot{o}}hler$ angle was $6.1^{\circ}$ and final was $22.8^{\circ}$. The mean preoperative calcaneal facet height was 76.6 mm and final was 80.3 mm (The mean calcaneal facet height was changed from preop 76.6 mm to postop 80.3 mm). The mean preoperative calcaneal length was 88.2 mm and final was 92.6 mm. The mean preoperative width was 38.1 mm and final was 35.6 mm. Conclusion: Open reduction and internal fixation showed good results for type II and III fractures, but for type IV fractures the clinical result was significantly worse than the other types. However, type IV fractures still had restoration of (should be restored in) $B{\ddot{o}}hler's$ angle, calcaneal facet height, calcaneal length and width which may be helpful in later subtalar fusion.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.3
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• pp.97-103
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• 1999

This paper investigates reduction of acoustic noise and cogging torque in a BLDC motor with larger stator slot open width. Using energy method, cogging torque is analytically determined with airgap MMF function and airgap permeance function and confirmed by FEM analysis. It shows that the cogging torque is firstly governed by NL GNL BNL with the fundamental period of NL, where NL is the least common multiple of the number of slots and the number of poles, GNL, airgap permeance function and BNL, airgap MMF function. It also shows that there exist several tooth width which minimizes the cogging torque, for the motors that smaller slot open width or stator teeth notching is not available. And it proposes a teeth pairing with two different tooth width which can effectively eliminate the cogging torque and thus the acoustic noise. Experimental results show that the proposed teeth pairing reduces the cogging torque by 85% and the acoustic noise by 3.1dB.

• Proceedings of the Korean Society of Marine Engineers Conference
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• 2012.06a
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• pp.157-157
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• 2012

The Characteristics of the drag reduction of a square prism having a detached splitter plate at the wake side was investigated by measuring of fluid force on the square prism and by visualization of the field using PIV. The experimental parameters were the width ratios(H/B=0.5~1.5) of splitters to the prism width and the gap ratios (G/B=0~2) between the prism and the splitter plate. The drag reduction rate was increased with H/B, and was increased and decreased with G/B. The maximum drag reduction rate was represented by 24.2% at H/B=1.5 and G/B=0.5. The two vortices were generated by the splitter plate at the wake region of the prism. The direction of the vortex was clockwise at the upside of the splitter plate and counterclockwise at the downside.

• Journal of the Korea Concrete Institute
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• v.21 no.5
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• pp.661-668
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• 2009

Effective beam width model(EBWM) has been used for analysis of post-tensioned(PT) flat plate slab frames under lateral loads. The accuracy of this model in predicting lateral drifts and unbalanced moments strongly depends on the estimated effective stiffness of PT flat plate slabs. As moments on the slab due to lateral loads increases, cracks occur which leads to stiffness reduction in slabs. For analyzing PT flat plate slab structure under lateral loads with good precision, reduction in slab stiffness has to be accurately estimated for EBWM. For this purpose, this study collected test results of PT flat plate system conducted by former researches. And this study reduced the width of slab so that the stiffness of the EBWM converged into the lateral stiffness of each test specimens by trial and error. By conducting nonlinear regression analysis using the stiffness ratio of the reduced width of slab to the effective width of EBWM with respect to the level of slab moments, an equation for calculating stiffness reduction factor for slab is proposed. For verifying the accuracy of the proposed equation, this study compared with the test result of the PT flat plate frame. It is shown that the EBWM with the proposed equation predicts the actual stiffness of the PT specimen which varied according to the level of applied moment.

• Journal of Environmental Impact Assessment
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• v.17 no.1
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• pp.1-9
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• 2008

Non-point pollution is caused by many diffusive sources, unlike a point pollution derived from industrial wastewater treatment plants or sewage treatment plants. Runoff of non-point pollutants is originated from rainfall or thawing in short period of time moving over and through the a ground surface. They cause ill effect on the quality of neighboring aquatic environment. To prevent effectively the wash off from non-point pollutant, it should be immediately reduced at the source or be treated after gathering of runoff water. This study has been carried out for the best width of riparian buffer zone. So we implemented the experiment in terms of its depth, width and kind of vegetations and calculated the reduction of pollutants loading. The experimental zone encompasses the watershed of Namhan River (Kyunggido Yangpyunggun Byungsanri). The region was divided into 5 land cover sectors : grass, reed, pussy willow, mixed(grass+pussy willow) and natural zone to compare effectiveness of vegetation. Water samples from four points have been collected in different depths. And the pollutant removal efficiency by sectors with different plant species was yielded through influent with one of each sample. And we obtained the correlation between the width of riparian buffer zone and the removal efficiency of pollutants. Using correlation result, the width of riparian buffer zones which needs to improve the water quality of river could be derived.

• Structural Engineering and Mechanics
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• v.21 no.4
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• pp.451-468
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• 2005

Effective beam width models are commonly used to obtain the lateral stiffness of flat plate structures. In these models, an effective beam width is defined as the width when the flexural stiffness of the beam element equals the slab stiffness. In this present study, a method to obtain effective beam widths that considers the effects of connection geometry and slab cracking is analytically proposed. The rectangularity of the vertical member for the connection geometry and the combined effects of creep and shrinkage for the slab cracking are considered. The results from the proposed method are compared with experimental results from a test structure having nine slab-column connections.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1997.03a
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• pp.249-252
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• 1997

Mini-mill process which is one of the new steel making process to be able to produce the hot rolled strip by thin slab caster, was completed in the kwangyang steel work. The new process was constructed liquid core deduction, tandem reduction unit, induction heater, coil box and finishing mill to be varied width. Therefore, in oder to make sure of target strip width, analysis of actual plant data was done to fine out amount of width deviation. Finally, the predication system of width in the mini-mill process was developed to included temperature caculation model.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.10 s.340
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• pp.29-34
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• 2005

The maximum quantization error has serious effect on the performance of fixed-width multipliers that receive W-bit inputs and produce W-bit products. In this paper, we analyze the error bound of fixed-width modified Booth multipliers. Then, the estimation method for the number of additional columns for fixed-width multipliers is proposed to limit the maximum quantization error within a desired bound. In addition, it is shown that our methodology can be extended to reduced-width multipliers. By simulations, it is shown that the proposed error analysis method is useful to the practical design of fixed-width modified Booth multipliers.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.5
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• pp.831-836
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• 1989

It was found that the effect of the friction between the roll and the workpiece on the spread ratio in flat rolling processes varies with the width-to-height ratio and the reduction in height by Tozawa, Oh and kobayashi numerically. In the present study, the barrelling profile accompanying the width spread was predicted by using the energy method proposed by Kato, which is known to be one of the most advanced method for the three dimensional analysis of the rolling process. The modified velocity field was applied to compute the width spread and the result was verified by experiments. the analysis by the energy method gave the result that the spread ratio increases with the friction factor when the width-to-height ratio is 1 and decreases when the ratio is larger then 2, being consistent with the results of Tozawa and Oh. Nevertheless the cold rolling experiment for pure aluminium showed that the spread ratio decreases with the increasing friction factor irrespective of the width-to-hight ratio.