• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.9
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• pp.2261-2270
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• 1995

Flow patterns were measured in an unshrouded centrifugal impeller. The flow rate in measurements was fixed at the value corresponding to a nearly zero incidence at the blade inlet. By using a single slanted hot-wire probe and a Kiel probe mounted on the impeller hub disk, the 3-D relative velocities and the rotary stagnation pressures were measured in seven circumferential planes from the inlet to the outlet of the impeller rotating at 700rpm, which diameter is 0.39 meter, and the static pressures and the slip factor at the impeller outlet were calculated from the measured values. From the measured data, the primary/secondary flows, the leakage flows, the wake-jet flows, static pressure distribution on blade surfaces and the wake production mechanism in the impeller passage were investigated.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2995-3000
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• 2008

Understanding of the impinging behavior of an electrically charged spray is essential in determining appropriate operating conditions for electro-spraying of paints, surface coating materials and insecticides. In the present work, the wall impact behavior of an electrically charged drop has been investigated and compared with that of a neutral drop experimentally. The critical Sommerfeld number representing the spread-splash boundary for the charged drop impacting on the dielectric substrate turned out to be larger compared to that for the neutral drop with the same surface condition. The change of the transition boundary is due to the increase in the surface wettability of the drop on the substrate. However, with the electrically conducting substrates, the charging effect on the transition boundary appeared negligible. This is because the electric discharging time is much shorter than the time required for the flattened drop to reach its maximum extent.

• Proceedings of the Korea Information Processing Society Conference
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• 2019.05a
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• pp.109-110
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• 2019

사물인터넷(IoT: Internet of Things)과 스마트 홈은 사용자의 명령 없이 사물에 다양한 센서를 부착해 실시간으로 네트워크상에서 데이터를 상호교환하는 기술로 발전하고 있다. 특히 각종 기기들이 개발됨에 따라 데이터 공유와 강화된 서비스 기술이 요구되고, 기기들을 연결하기 위한 간단한 무선통신 기술이 중요하다. 본 논문에서는 스피커와 마이크를 이용하여 기기 간 비가청 음파통신방법을 제안한다. 사용자의 귀에는 잘 들리지 않으며, 통신이 자유롭게 이루어지기 위해 16kHz~21kHz 주파수대역의 비가청 음파를 사용하여 송·수신한다. 또한, 다른 신호들의 충돌과 잡음, 간섭을 대비하기 위해 이중주파수를 사용한다. 본 시스템은 단일주파수와 비교하여 더 많은 기기 간 통신이 가능하게 해주며, 3m 안에서 높은 통신 속도와 정확도를 제공한다.

• TTA Journal
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• s.131
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• pp.30-39
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• 2010

급격한 기후변화에 의한 집중호우 및 소리 없이 쌓이는 폭설과 잦은 매머드급 태풍 그리고 지진과 해일, 화산활동 등의 자연재해가 언제 어떻게 일어날지 모르는 상황에서 국가는 국민의 생명과 재산을 보호해야 할 막중한 과제를 안고 있습니다. 또한 자연재해뿐 아니라 공공기관에 대한 테러와 자원쟁탈을 위한 국지적인 전쟁과 같은 참사가 지구상에서 수시로 발생하고 있으며, 원자로의 방사능 누출과 지하철이나 철도의 충돌사고 및 가스폭발사고와 초고층 대형 빌딩이나 지하터널, 해저터널 같은 대형구조물의 붕괴 등 인공재난이 수시로 발생하고 있습니다. 이와 같이 재난발생은 대형화 및 다양화되고 있으며, 복합화된 형태로 발생하여 단일 기관으로는 대응하는 데 어려움이 있어서 범 국가적인 통합지휘체계에 의한 재난 관리 및 재난 대응이 필요합니다. 이러한 대형 참사를 사전에 예방하고, 재난 발생시 신속히 대응하여 인명과 재산피해를 최소화하는 방안으로 어떠한 재난 통신 방안이 있으며, 관련 기술 표준과 선진국 등의 구축사례를 통하여 우리나라는 제대로 재난 통신 및 방송이 구축되어 있는 지 살펴보고 이를 통하여 유비무환(有備無患) 및 거안사위(居安思危)의 정신으로 언제 닥칠지 모르는 국가재난에 미리미리 대비하는 계기가 되었으면 합니다.

• Cross-Cultural Studies
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• v.46
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• pp.85-112
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• 2017

Donald Trump, the $45^{th}$ president of the United States, has revived the 'English Only' policy since the beginning of his presidential campaign. The monolingualism not only underscores his extremely conservative ideas, but it also reflects the nativist tendency that prevents the demographic and cultural transformation of the US, which is accelerated by globalization and transnational migration. In particular, Donald Trump tries to reconfirm the mainstream American culture that is now thought to have been threatened by Hispanization and the growing number of Spanish speakers. This paper examines the effects of "code-switching" and the possibility of a bilingual community by contrasting Donald Trump with Gloria $Anzald{\acute{u}}a$, one of the representative Latina writers who created a "border language." Borderlands/La Frontera (1987) includes Spanish glossaries and expressions to represent her bilingual realities, while attempting to translate from English to Spanish, and vice versa. However, the text occasionally demonstrates the impossibility of translation. In doing so, $Anzald{\acute{u}}a$ indirectly states that it is indispensable to present both languages at the stage; she also invites monolingual readers to make more efforts to learn and better understand the Other's language. A "border language" she attempts to embody throughout the text is created in the process of encounters, conflicts, and negotiations among languages of different ethnicities, classes and generations. It does not signify an established form: rather it appears as a constantly transforming language, which can provide us with new perspectives and an alternative way of communication beyond monolingualism.

• The Journal of the Korea institute of electronic communication sciences
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• v.18 no.6
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• pp.1321-1330
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• 2023

This study attempts to address the problem of 3D pose estimation for multiple human objects through a single image generated during the character development process that can be used in augmented reality. In the existing top-down method, all objects in the image are first detected, and then each is reconstructed independently. The problem is that inconsistent results may occur due to overlap or depth order mismatch between the reconstructed objects. The goal of this study is to solve these problems and develop a single network that provides consistent 3D reconstruction of all humans in a scene. Integrating a human body model based on the SMPL parametric system into a top-down framework became an important choice. Through this, two types of collision loss based on distance field and loss that considers depth order were introduced. The first loss prevents overlap between reconstructed people, and the second loss adjusts the depth ordering of people to render occlusion inference and annotated instance segmentation consistently. This method allows depth information to be provided to the network without explicit 3D annotation of the image. Experimental results show that this study's methodology performs better than existing methods on standard 3D pose benchmarks, and the proposed losses enable more consistent reconstruction from natural images.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.2
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• pp.139-146
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• 2011

The breaking wave pressure occurs when a plunging breaker instantaneously impinges on structural surface, and appears differently depending on whether or not to form air pockets at the instant of contact. The Wagner type normally forms a single pressure peak at the contact spot due to the direct collision of water volume to the structure whereas in the Bagnold type the time lagged oscillation of the air pocket causes pressure peaks even at areas away from the spot. In the present study, the Bagnold's impact pressure is numerically and experimentally investigated for the bulkhead of an underwater tunnel under construction which is subjected to nearby breaking waves. A numerical solver of Navier-Stokes equations was applied to reproduce the breaking waves near a bulkhead, and the results showed the Bagnold's impact pressure occurring on the back (land side) face of the bulkhead. The existence of the impact pressure was also verified by a hydraulic model testing, and it was found that the experimental results well conformed to their numerical counterparts.

• Journal of Advanced Navigation Technology
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• v.13 no.4
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• pp.551-558
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• 2009

Most of clustering schemes focusing on the energy efficiency have only a cluster head in each cluster, thus the energy consumption of cluster head in a cluster can rapidly increase. To reduce the energy consumption, recently, the dual-layered clustering which is separated a cluster ranges into two parts, i.e., data aggregation layer and data transmission layer, based on a sensor equipped with geographical positioning system (GPS), was proposed. However, the logical regions existing within the dual-layered clustering range can not distinguish efficiently. This scheme leads to many messages collision and transmission delay among member nodes. In this paper, to solve these problems, we propose a separated dual-layered routing scheme using the position information and the cluster radius. Proposed scheme clearly distinguish the dual-layered clustering range and gets the balanced number of member nodes in each cluster. Therefore, the proposed routing scheme could prolong the overall network life time about 10% compared to the previous two layered clustering scheme and LEACH.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.12A
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• pp.1852-1861
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• 1999

In this paper, CDMA Reservation ALOHA scheme which can reduce multiple access interference and packet collision is proposed to support multi-traffic such as voice and random data with and without priority. In this scheme, the time slot is divided into two stage, access and transmission stage. Only packets with spreading codes assigned from base station in access stage can transmit their packets in transmission stage, so MAI can be reduced. To reduce packer collision in access stage, the code reservation and access permission probability are used. Code reservation is allowed for voice traffic and continuous traffic with priority using piggyback and access permission probability based on the estimation of the number of contending users in the steady-state is adaptively applied to each traffic terminal. Also, we analyzed and simulated the numerical performances required for each traffic using Markov chain modeling in a single cell environment.

• Journal of the Institute of Electronics Engineers of Korea TC
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• v.44 no.5
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• pp.7-15
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• 2007

In wireless communication networks, single-radio single-channel architecture degrades throughput and end-to-end delay due to half-duplex transmission of wireless node and route intra interference. Also, In contention-based MAC (Medium Access Control) architecture, channel contention reduces throughput and packet collision enlarges end-to-end delay. In this paper, we use multi-radio multi-channel architecture which will make wireless node to operate in full duplex mode, and exclude route intra interference. Based on this architecture, we propose a new link metric, ccf which reflects the characteristics of a contention-based wireless link, and propose a routing path metric MCCR considering channel switching delay and route intra interference. MCCR is compared with MCR by simulation, the performance of a route established by MCCR outperforms the performance of a route by MCR in terms of throughput and end-to-end delay.