• The Journal of the Korea institute of electronic communication sciences
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• v.9 no.4
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• pp.417-424
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• 2014

In this paper, a dual-band circular ring monopole antenna with semi-circular strip for WLAN(Wireless Local Area Networks)/WiMAX(World interoperability for Microwave Access) applications. The proposed antenna is based on a planar monopole design, and composed of half circular strip for dual-band operation which cover WLAN and WiMAX frequency bands. To obtain the optimized parameters, we used the simulator, Ansoft's High Frequency Structure Simulator(HFSS) and found the parameters that greatly effect antenna characteristics. Using the obtained parameters, the antenna is fabricated. The numerical and experiment results demonstrated that the proposed antenna satisfied the -10 dB impedance bandwidth requirement while simultaneously covering the WLAN and WiMAX bands. And characteristics of gain and radiation patterns are obtained for WLAN/WiMAX frequency bands.

• Korean Journal of Heritage: History & Science
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• v.43 no.3
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• pp.208-241
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• 2010

This study was conducted to examine the chronology of Taesil Seokham(Taesil Stone Boxes) stored in Taesil of the Joseon Palace and classify the styles to discuss how these boxes have developed. By doing so, this study defined the archaeological styles of taesil seokhams in the chronological order. Although taesil seokhams are placed when taesil are first created, they do not have any texts engraved on them and it is difficult to gain information only from examining taesil seokham. However, Taejiseok(memorial stones buried in Taesil) and Agibi(gravestones buried in Taesil) were created along with taesil. These resources were examined and compared with literature records to find when each taesil seokhams was created. The critical elements to consider for the chronological arrangement were both the cover and container of the boxes and the transition of their style could be classified into four major stages. In detail, the Joseon Dynasty's taesil seokhams initially inherited the style of the Goryeo Dynasty to be formed into rectangular boxes. Through the transition of the mid and late 15th Century, the semi-circular cover with cylindrical container became the popular style in the late 15th Century. In the late 16th Century, the style of the previous period was further developed to add some decorative elements, such as projecting ornaments, but the ornaments were added for functional purposes rather than artistic purposes. However, the style went back to the semi-circular cover with cylindrical container in the early 17th Century. From the mid 17th Century, various styles appeared with ornaments only on the cover, cone-shaped cover with no ornament, or mortar-like container. However, a new style of cone-shaped cover with ornament emerged between the early and mid 18th Century and continued to stay until the mid 18th Century. In the mid 18th Century, the cover remained unchanged, but the container became a keyhole-shaped space with one side forming a "ㄷ" shape. However, in the late 18th Century, the most typical style of the semi-circular cover with cylindrical container reappeared to show that this is the most universal style. Last, in the mid 19th Century, the cover changed from semi-circular to rectangular with flat top. After this, the taesil seokhams began to disappear. In terms of style, it can be classified into four stages. In the early Joseon Dynasty, the taesil seokhams were underdeveloped and inherited the style of the Goryeo Dynasty (Stage I; 1401~mid-15C), but Joseon's unique style began to develop from the late 15th Century (Stage II; 1477~1641). After that, partial ornaments were added for adornment (Stage III; 1660~1754), but the typical style reappeared in the late 18th Century to finally degrade in the late Joseon Dynasty of the mid 19th Century (Stage IV; 1790~1874). This arrangement of style and chronology would greatly help archaeologists anticipate the time and owner of taesil seokhams even if only taesil seokhams are discovered without any records. * Tae(胎) : Placenta and umbilical cord * Taesil(胎室) : A facility(chamber) of burying Tae(胎) in rite when royal descendants are born.

• Journal of Conservation Science
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• v.7 no.1
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• pp.1-8
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• 1998

The production techniques of a gilt-bronze buckle which was presumably a product of the Koryo dynasty were investigated. The X-ray area map indicates that the gilt layer was made by gilt-bronze method. EDS analysis shows that the gilt layer contains copper as well as gold. The microstructure of a textile adhered to the back of the buckle reveals that the material is woven hemp. Triangular and semicircular chisels were used to engrave patterns. After the boundaries of the patterns were engraved with triangular chisels the internal regions were carved with semicircular patterns. The procedure and the shape of the chisels were also investigated.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2003.05a
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• pp.677-682
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• 2003

The non-linear dynamic characteristics of a semi-circular pipe conveying fluid are investigated when the pipe is clamped at both ends. To consider the geometric non-linearity for the radial and circumferential displacements, this study adopts the Lagrange strain theory for large deformation and the extensible dynamics based on the Euler-Bernoulli beam theory for slenderness assumption. By using the Hamilton principle, the non-linear partial differential equations are derived for the in-plane motions of the pipe, considering the fluid inertia forces as a kind of non-conservative forces. The linear and non-linear terms in the governing equations are compared with those in the previous study, and some significant differences are discussed. To investigate the dynamic characteristics of the system, the discretized equations of motion are derived form the Galerkin method. The natural frequencies varying with the flow velocity are computed fen the two cases, which one is the linear problem and the other is the linearized problem in the neighborhood of the equilibrium position. Finally, the time responses at various flow velocities are directly computed by using the generalized- method. From these results, we should to describe the non-linear behavior to analyze dynamics of a semi-circular pipe conveying fluid more precisely.

• Korean Journal of Optics and Photonics
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• v.4 no.3
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• pp.309-316
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• 1993

We find the vectorial solution of the optical waveguide with semicircular cross-section by expanding the electromagnetic fields of the waveguide into the series of trigonometric and Bessel funtions and by applying the boundary conditions at the finitely selected points on the interface of the core and the cladding. We find also the propagation constants and the energy distributions of the eigenmodes and discuss its properties. As a result of computation, we find that the electromagnetic fields of the even modes about the symmetric axis of the semircular shape are nearly the same as those of the odd modes except that E and H of the odd modes are replaced by -H and E and that the even and odd modes are degenerated as the ratio of refractive index of the core and cladding approaches to 1.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.220-220
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• 2017

일반적으로 XP-SWMM 모형을 이용한 침수모의를 실시할 경우 과부하 맨홀에 손실계수의 적용 시와 미적용 시에 침수 범위의 차이가 상이함에도 불구하고 보다 실제적인 침수면적의 모의를 위하여 에너지 손실 적용에 대한 도시침수해석의 구체적인 연구가 미흡한 실정이다. 또한 과부하관거에서의 배수능력을 증대하기 위하여 설치되는 맨홀 내 인버트의 침수저감 효과에 대한 분석이 필요한 실정이다. 이원 등(2015)은 군자배수구역을 대상으로 손실계수의 적용 방안 및 손실계수 적용에 따른 침수면적의 변화를 분석하였으나, 맨홀의 형상 및 인버트의 설치유무에 대한 사항을 고려하지 않았다. 그러므로 기 산정된 과부하 맨홀에서의 손실계수를 적용 및 인버트 설치에 따른 침수범위 변화의 분석이 필요할 것으로 판단된다. 본 연구에서는 손실계수 및 인버트 설치 여부에 따른 침수범위의 변화를 분석하기 위하여 도림천의 도림1배수분구를 대상으로 XP-SWMM을 활용하여 침수해석을 실시하였다. 김정수(2010)가 수리모형실험을 통하여 인버트를 설치하지 않은 기본형 맨홀에서 산정된 손실계수 0.61과 반원형, U자형 인버트를 각각 설치했을 시에 0.37, 0.30으로 산정된 손실계수를 XP-SWMM모형의 각 과부하 맨홀에 적용하였다. 침수모의 결과 과부하 맨홀에 손실계수를 적용하지 않은 경우의 침수면적은 21.14 ha로 모의되어 실제 침수면적과 약 60 % 정도의 일치율을 보였으나, 인버트를 설치하지 않은 기본형 맨홀의 손실계수를 적용한 경우의 침수면적은 37.12 ha로 모의되어 실제 침수면적인 35.65 ha와 거의 유사하게 나타났다. 또한 반원형 인버트를 고려한 경우의 침수면적은 28.04 ha, U자형 인버트 설치를 고려한 경우의 침수면적은 25.90 ha로 모의되었다. 인버트를 미적용한 경우의 침수면적과 비교하면 침수면적이 각각 24 %, 30 % 감소하였다. 따라서 도시 침수피해를 저감하기 위해 과부하 맨홀에 인버트를 설치한다면 맨홀내의 에너지 손실이 저감되고 배수능력이 향상되어 침수피해 면적과 침수심을 감소시킬 수 있을 것으로 판단된다.

• The Journal of the Acoustical Society of Korea
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• v.40 no.4
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• pp.270-277
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• 2021

In the power ultrasound fields, the flange position for fixing the transducer is an important factor influencing on electro-mechanical efficiency of the transducer. We suggested a practical method that can determine the installation position of the flange for different resonance modes of the bolt-clamped type Langevin ultrasonic transducer. A semicircular wedge-shaped jig was manufactured and moved along the lateral surface of the transducer. The vibration characteristics were examined after a constant pressure was applied to the semicircular wedge-shaped jig. By observing the change of the input admittance of the transducer depending on the position of the pressure application, the optimum position for the flange installation could be determined. The resonant modes of the transducer were calculated by a Mason's equivalent circuit, and the particle velocity distribution for each resonance mode was calculated by a transmission line model. Since the optimum positions determined from an experimental result show a good correspondence with the node positions of the vibration modes calculated by the transmission line model, the validity of the suggested method was verified.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.15 no.11
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• pp.1051-1061
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• 2004

In this Paper, a new antenna(VHMDA) characteristics of half-circular/elliptical disc-loaded planar antennas with horizontally top-loaded small disc is studied by simulation and measurements with additional resonant structure. The transfer function characteristics of Gaussian pulse from the designed UWB transmitter antenna has been investigated. The radiation pattern of the proposed antenna in azimuth is nearly omni-directional response, which is usulally required in conventional monopole antenna. In addition to that, the simulation and measured results show that the return loss characteristics of VHDMA covers considerably large bandwidth with small area. From the measured results of the circular and half-circular disc-loaded monopole antennas with small disc mounted on the top, it is found that the half disc-loaded monopole antenna with additional structure can be comparable to the circular disc-loaded monopole antenna in respect o( size and electrical performances. Surface wave and dielectric losses often caused by the printed antenna using high dielectric constant does not occur in metallic planar antenna with good impedance matching and without lossy matching unit. This structure implies that the performance of return loss is directly related with the radiation efficiency.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.19 no.3
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• pp.329-335
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• 2008

This paper proposes a miniaturized half-circular-slot UWB antenna. Using an analysis of the neld patterns, we show that the original circular-slot UWB antenna operates on a series of multi-pole radiation based on $TE_n$ modes, and a perfect magnetic wall exists along an axis of symmetry on the antenna. Using the perfect magnetic wall we designed and fabricated the miniaturized UWB antenna on RF-60A substrate with t=0.64mm, ${\varepsilon}_r=6.15\;and\;tan\;{\delta}=0.0025$, which not only has the half size of the original but also maintains UWB characteristics. The measured gain of the miniaturized antenna is $-2.1{\sim}4.3dBi$, which is comparable with the gain, $-2.7{\sim}3.1dBi$, of the original circular-slot UWB antenna. The radiation pattern is also similar to that of the original antenna.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.23 no.10
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• pp.1269-1274
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• 2019

The paper presents a design of simple four-element microstrip-patch array antenna that is suitable for 5G applications. The proposed array consists of four rectangular microstrip patch elements with semicircular etches made on both sides of each elements. The antenna is fed using the combination of series and corporate feeding networks. The size of the ground is also changed to improve the antenna frequency. Finally, yagi elements are also added to improve the directive gain of the antenna. The presented microstrip patch array is able to achieve wide frequency bandwidth of 21.95-31.86 GHz. The antenna has also attained gain of 9.7 dB at 28 GHz and has maintained high gain and high directivity throughout the frequency band. The proposed array antenna fed by series-corporate feeding network, with low profile and simple structure is a good candidate for 5G applications.