• 대한기계학회논문집B
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• 제27권9호
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• pp.1299-1308
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• 2003

This paper is studied to investigate the effect of slits and swirl vanes on the development of turbulent flow fields in gun-type gas burner with a cone type baffle plate because this gas burner is generally composed of eight slits and swirl vanes. All of turbulent characteristics including mean velocities were measured in the horizontal plane and cross section by using X-type hot-wire probe from hot-wire anemometer system. This experiment is carried out at flow rate 450 l/min in the test section of subsonic wind tunnel. Slits cause the fast jets, and then they have the characteristic that the flow is not adequately spread to radial direction and has long flow length and very small flow velocity distribution in the central part. On the contrary, swirl vanes does not have long enough for adequate flow length to downstream because the rotational flow diffuses remarkably to radial direction. However, the suitable arrangement between slits and swirl vanes causes effective flow width and flow length, and then it promotes fast flow mixing over the entire region including central part to increase turbulence more largely and effectively. Therefore, it is thought as a very desirable design method in gun-type gas burner to locate slits on the outside of swirl vanes.

• 한국위성정보통신학회논문지
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• 제12권1호
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• pp.72-75
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• 2017

본 논문은 소형화와 고이득을 위하여 패치 안테나에 원형 슬릿을 구현하였으며 900 MHz 대역에서 동작이 되도록 설계하였다. 사각형 모양의 패치형태를 변형하여 안테나 크기를 일차적으로 줄였으며 나아가 패치 안에 원형 슬릿을 추가하여 추가적으로 안테나의 크기를 감소시켰다. 원형슬릿의 개수와 반지름을 설계 변수로 설정하여 원하는 대역에서 반사손실을 약 -30 dB까지 되도록 Tuning 하였으며 방사패턴의 최대 이득도 약 4 dBi에 이르도록 안테나의 설계를 수행하였다. 원형슬릿이 존재하지 않는 경우 대비 약 20 MHz 정도의 공진 주파수 하향천이를 구현하여 본 논문에서 설계한 안테나의 소형화가 달성되었음을 증명하였다.

• 대한전자공학회논문지TC
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• 제41권10호
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• pp.103-108
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• 2004

본 논문에서는 크로스 개구결합 급전 구조의 소형 GPS 단말기용 안테나를 소형화하기 위해 대칭적인 4개의 T-슬릿이 방사 패치에 부설되었다. 부설된 슬릿 주위에 표면 전류 경로의 증가는 등가적인 인덕턴스 성분을 유기하고 공진형 안테나의 저차 모드의 공진 주파수를 낮추어 안테나의 소형화 특성을 개선함을 확인하였다 슬릿 부설에 따른 공진 주파수는 2.545GHz에서 1.575GHz로 약 44.65%까지 감소시킬 수 있었으며, 안테나 소형화를 위해 부설된 슬릿이 원편파 기본 동작 모드에 미치는 영향을 법선 전기장 성분을 통해 확인하였다. 측정된 안테나의 임피던스 대역폭(VSWR≤2)과 3dB 축비 대역폭은 21MHz와 19MHz로 양호한 특성을 나타내었다.

• Journal of Mechanical Science and Technology
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• 제15권7호
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• pp.906-920
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• 2001

This paper presents three-dimensional mean velocities, turbulent intensities and Reynolds shear stresses measured in the Y-Z plane of the gas swirl burner with a cone type baffle plate by using an X-type hot-wire probe. This experiments is carried out at the flow rate of 450ℓ/min which is equivalent to the combustion air flow rate necessary to heat release 15,000 kcal/hr in a gas furnace. Mean velocities and turbulent intensities etc. show that their maximum values exist around the narrow slits situated radially on the edge of and in front of a burner. According to downstream regions, they have a peculiar shape like a starfish because the flows going out of the narrow slits and the swirl vanes of an inclined baffle plate diffuse and develop into inward and outward of a burner. The rotational flow due to the inclined flow velocity going out of swirl vanes of a cone type baffle plate seems to decrease the magnitudes of mean velocities V and W respectively by about 30% smaller than those of mean velocity U. The turbulent intensities have large values of 50%∼210% within the range of 0.5

• 한국가시화정보학회지
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• 제6권2호
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• pp.33-38
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• 2008

The effect of the radial temperature gradient and the presence of slits in the wall of outer of two cylinders involved in creating a Taylor-Couette flow was investigated by measuring the velocity field inside the gap. The slits were azimuthally located along the inner wall of the outer cylinder and the number of slits used in this study was 18. The radius ratio and aspect ratio of the models were 0.825 and 48, respectively. The heating film wrapped around the inner cylinder was used for generating the constant heat flux and we ensured the constant temperature condition at the outer space of the outer cylinder. The velocity fields were measured by using the PIV(particle image velocimetry) method. The refractive index matching method was applied to remove image distortion. The results were compared with plain wall configuration of Taylor-Couette flow. From the results, the presence of slits in the wall of outer cylinder and temperature gradient increased the flow instability.

• 조명전기설비학회논문지
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• 제16권4호
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• pp.101-107
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• 2002

본 논문은 종래형 전해수 발생장치의 평판전극을 슬릿형 평행평판전극 구조로 함으로써 고효율의 강전해수 발생장치를 제안하였다. 염화나트륨이 용해된 수도수와 일반 수도수를 본 강전해수 발생장치에 인입하였을 때 전해수 생성공간내의 공간전하제한작용을 크게 감소시키면서 또한 이 전해수 생성공간내의 전계분포를 집중시킬 수 있는 슬릿형 평행평판전극을 설정하고, 이러한 슬릿의 형태와 개수증가가 수중 이온분리집속성능에 미치는 영향과 산화성물질 생성에 미치는 영향을 연구 검토하였다. 실험결과 수중 강전해수 발생장치내에 슬릿을 형성함으로써 전해수 발생공간내의 전계를 집중시키고 분리집속된 고농도의 이온들에 의한 공간전하 제한작용을 크게 감소시켜 저전력에서 기존의 전해수 발생장치보다 훨씬 고농도의 강전해수와 산화성물질 용존수를 얻을 수 있었다.

• Steel and Composite Structures
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• 제16권6호
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• pp.657-679
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• 2014

This paper describes a series of compression tests performed on cold-formed steel channel sections with perforations in the web (thermal studs) fabricated from a galvanized steel plate whose thickness ranged from 1.0 mm to 1.6 mm and nominal yield stress was 295 MPa. The structural behavior and performance of thermal studs undergoing local, distortional, or flexural-torsional buckling were investigated experimentally and analytically. The compression tests indicate that the slits in the web had significant negative effects on the buckling and ultimate strength of thin-walled channel section columns. The compressive strength of perforated thermal studs was estimated using equivalent solid channel sections of reduced thickness instead of the studs. The direct strength method, a newly developed and adopted alternative to the effective width method for designing cold-formed steel sections in the AISI Standard S100 (2004) and AS/NZS 4600 (Standard Australia 2005), was calibrated to the test results for its application to cold-formed channel sections with slits in the web. The results verify that the DSM can predict the ultimate strength of channel section columns with slits in the web by substituting equivalent solid sections of reduced thickness for them.

• 한국전기전자재료학회논문지
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• 제15권9호
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• pp.822-829
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• 2002

This paper deals with the distribution characteristics of the current density and axial magnetic flux density for each slits made on the contact electrode in the vacuum interrupter with axial magnetic field type using 3-dimension finite element analysis. It has been known that the presence of an axial magnetic field parallel to the current flow in the arc plasma can increase the high current breaking capacity of vacuum interrupter by carrying out the arc plasma from constricted mode to diffusion mode. The axial magnetic field is created of itself by current flow in the segments of coil electrode behind the contact electrode. The analyzed results show that if the slits are made in the contact electrode, they can increase the current density and axial magnetic flux density in the contact electrode surface and at the gap distance, which is due to decrease the effect of eddy currents flowing in the contact electrode. The phase shift due to eddy currents, defined 3s time difference between the maximum value of current and axial magnetic field, is decreased still more by increasing the number of slits made in the contact electrode at the center point of gap distance. These results demonstrate that 3-dimension finite element analysis has a great deal of merits in the development and evaluation of new electrode at the design of vacuum interrupter.

• Earthquakes and Structures
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• 제23권1호
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• pp.59-73
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• 2022

In this study, the seismic behavior of an all-steel buckling-restrained (AB) steel plate shear wall (SPSW) with incline slits under fire and cyclic loading was investigated. ABSPSW was composed of two thin steel infill plates with a narrow distance from each other, which were embedded with incline slits on each plate. These slits were in opposite directions to each other. The finite element (FE) numerical model was validated with three test specimens and after ensuring the modeling strategy, the parametric study was performed by considering variables such as wall plate thickness, slit width, strip width between two slits, and degree of temperature. A total of 256 FE numerical models were subjected to coupled temperature-displacement analysis. The results of the analysis showed that the high temperature reduced the seismic performance of the ABSPSW so that at 917℃, the load-bearing capacity was reduced by 92%. In addition, with the increase in the temperature, the yield point of the infill plate and frame occurred in a small displacement. The average decrease in shear strength at 458℃, 642℃, and 917℃ was 18%, 46%, and 92%, respectively, compared to the shear strength at 20℃. Also, with increasing the temperature to 917℃, ductility increased by an average of 75%

• International Journal of Fluid Machinery and Systems
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• 제5권2호
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• pp.60-64
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• 2012

The helical flow regime was investigated by using DPIV when the rotating Reynolds number is small. The wall slits were azimuthally located along the inner wall of outer cylinder and the slits number of each model was 9 and 18, another plain wall model was also studied for comparison purpose. The helical vortex flow regime can be observed in all the three models. The negative temperature gradients determine the direction of the rotation and movement of the helical vortex. But the helical wavy vortex flow can only be found in the plane and 9-slit models. And the result showed that the existence of slit wall accelerated the transition process.