• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2409-2413
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• 2007

Time resolved phosphorescence of Dibromobenzophenone (DBBP) choleic acid crystal was observed at 4.2 K as functions of excitation energy and delay time. The experimental results reveal that the energy transfer efficiency is dependent on the excitation energy, i.e. the density of acceptors sites. As the excitation energy or delay time increases, the resonance phosphorescence does not broaden and shift gradually, rather a broad luminescence band develops about 290 cm?1 to lower energy of the resonance phosphorescence. The observation implies that energy transfer from high to low energy sites in this system is controlled by emission of phonons or vibrons. The data of time resolved experiments were analyzed in terms of a mechanism involving direct donor-acceptor excitation transport by exchange coupling. It was concluded that an isotropic twodimensional exchange interaction topology is consistent with energy transfer in this system.

• Proceedings of the IEEK Conference
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• 1999.11a
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• pp.97-100
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• 1999

Mobile network applications are growing and this requires a fast and efficient transport method between the BS(Base Station) and the MSC(Mobile Switching Center). One possible solution is to use ATM and a voice CODEC standard which compresses 64kbps voice data to less than 8kbps. The low bit tate and small-sized packets made by the voice CODEC imply that significant amount of link bandwidth would be wasted, if this small-sized packet is carried by one ATM cell. The cell assembly delay increases if one ATM cell is fully filled with the small-sized packets. For the bandwidth-efficient transmission of low-rate, short, and variable length packets in delay sensitive applications, AAL-2 was standardized. This paper evaluates performance of AAL-2 by using voice CODEC standard.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2009.01a
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• pp.668-672
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• 2009

In wireless ad-hoc network, knowing the available bandwidth of the time varying channel is imperative for live video streaming applications. This is because the available bandwidth is varying all the time and strictly limited against the large data size of video streaming. Additionally, adapting the encoding rate to the suitable bit-rate for the network, where an overlarge encoding rate induces congestion loss and playback delay, decreases the loss and delay. While some effective rate controlling methods have been proposed and simulated well like VTP (Video Transport Protocol) [1], implementing to cooperate with the encoder and tuning the parameters are still challenging works. In this paper, we show our result of the implementation experiment of VTP based encoding rate controlling method and then introduce some techniques of our parameter tuning for a video streaming application over wireless environment.

• Journal of the Korean Society for Aviation and Aeronautics
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• v.27 no.1
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• pp.20-25
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• 2019

To prepare for the ever-increasing demand for air transport, airport operators should be well aware of the timing of the saturation of the facility and increase the capacity of the airport through extension or extension. The capacity of an airport is determined by the smallest value of the facilities that make up the airport, but it is generally customary to determine the capacity of the costly and time-consuming runway as a whole for the airport. For analyzing the capacity of the runway capacity, the study used the most accurate microscopic air traffic simulation, Simmod-PRO, to analyze the saturation time of three runways currently in Incheon International Airport's operation, and calculate the appropriate time for operation of the 4th runway. The study also calculate the relocation of Airport's high-speed exit taxiway for analyzing the increasing of capacity.

• Journal of Genetic Medicine
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• v.18 no.1
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• pp.44-47
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• 2021

Cerebral creatine deficiency syndrome (CCDS) is a disorder where a defect is present in transport of creatine in the brain. Creatine plays an essential role in the energy metabolism of the brain. This is a genetic disorder, autosomal recessive or X linked, characterized by intellectual disability, speech and language delay, epilepsy, hypotonia, etc. Until recently very few number of cases have been reported. Here we report a case of 1.5-year-old boy who had epilepsy (epileptic spasm and generalized tonic clonic seizure), intellectual disability, microcephaly, hypotonia and speech delay. His magnetic resonance imaging of brain showed cortical atrophy and electroencephalography showed burst suppression pattern. The diagnosis was confirmed by clinical exome sequencing which showed novel mutation of SLC6A8+ in exon 9, suggestive of X linked recessive CCDS. The patient was then treated with glycine, L-arginine and creatine monohydrate with multiple antiepileptic drugs.

• Journal of the Korean Institute of Navigation
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• v.7 no.1
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• pp.1-32
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• 1983

The delay due to congestion has recently attracted widespread attention with the analysis of over-all operation at the port. But, the complexity of the situation is evident in view of the large number of factors which impinge on the considerable end. Queueing theory is applicable to a large scale transportation system which is associated with arrivals of vessels in a large port. The attempt of this paper is to make an extensive analysis of the port transport system and its economic implications from the viewpoint that port is one of the physical distribution facilities and a kind of queueing system which includes ships and cargoes as port customer. By analyzing the real data on the Port of Pusan, it is known that this port can be represented as a set of multi-channel with identical setof Poisson arrival and Erlang service time, and also it is confirmed that the following formula is suitable to calculate the mean delay in this port, namely, $W_4={\frac{\rho}{\lambda(1-\rho)} {\frac{e_N(\rho{\cdot}N)}{D_{N-1}(\rho{\cdot}N)}$ where, ${\lambda}$: mean arrival rate $\mu$: mean servicing rate; N: number of servicing channel; ${\rho}$: utillization rate (${\lambda}/N{\mu}$) $e_N$: the Poisson function Coming to grips with the essentials of the cost of delay due to congestion, a simple ship journey cost model is adopted and the operating profit sensitivity to variation in port time is examined, and for purpose of a future development for port princing service the marginal cost is approximately calculated on the basis of queueing theory.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.21 no.4
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• pp.911-925
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• 1996

Emerging service classes need an error model which efficiently satisfies the requirements for each media and application. However limited flexibility in the error control has been provided. Therefore we propose a new error control model which applies error control scheme per media flexibly with respect to ETL(Error Tolerance Leverl) and delay. In order to select the error control scheme in this model, the attributes of media(i.e., ETL, isochronism), the attributes of application(i.e., delay) and environment parameters(i.e., packet loss ration, network types, connection modes of the application) are considered as effect factors.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.13 no.1
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• pp.291-304
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• 2019

This paper proposes a dynamic-tiling-based bandwidth-efficient (DTBE) virtual reality (VR) streaming scheme. We consider 360-degree VR contents with multiple view points such as the front, back, upper, and bottom sides. At a given time, the focus of a client is always bound to a certain view among multiple view points. By utilizing this perspective, under our proposed scheme, tiles with high encoding rates are selectively assigned to the focused view where multiple view points consist of multiple tiles with different encoding rates. The other tiles with low encoding rates are assigned to the remaining view points. Furthermore, for reducing view adaptation delay, we design a novel rapid view adaptation mechanism that selectively delivers an I-frame during view point updates by using frame indexing. We implement the proposed scheme on a commercial VR test bed where we adopt the MPEG media transport (MMT) standard with high-efficiency video coding (HEVC) tile modes. The measurement-based experiments show that the proposed scheme achieves an average data usage reduction of almost 65.2% as well as average view adaptation delay reduction of almost 57.7%.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.229.1-229.1
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• 2016

본 연구에서는 Hole Transporting Layer(HTL)와 Electron Transporting Layer(ETL)의 두께에 의한 특성을 비교해보기 위해서 각각 0, 10, 20 nm로 HTL, ETL 두께를 달리한 형광 OLED소자를 제작하였다. ETL의 두께가 얇아질수록 $V_{TH}$ 값은 2.5V에서 0.9 V로 낮게 나타났고 소자의 전체 두께와 on voltage는 비례한다는 특성을 발견할 수 있었다. HTL과 ETL이 두꺼울수록 각 layer에서 carrier들의 이동에 delay가 생기고 emission layer에서 표면까지 거리가 생기기 때문이다. ETL의 두께가 두꺼울수록 높은 luminance 값을 나타내는 차이를 보여주고 있다. Hole에 비해 이동도가 작은 electron은 emission layer까지 늦게 전달되어, EML내에서 비교적 cathode쪽에 가까운 곳에서 exciton이 형성되기 때문이다. CE에도 더 두꺼운 ETL을 가진 소자가 더 높은 CE값 가짐을 확인할 수 있다. 모든 소자가 $200mA/cm^2$에서 가장 높은 CE값을 나타낸 이유는 $200mA/cm^2$에서 electron-hole 결합이 만들어내는 exciton형성이 가장 많기 때문이다. PE, QE도 ETL 두께가 두꺼울수록 특성을 향상이다. 결론적으로 ETL의 두꺼울수록 current density값이 감소함을 보이고 있는 반면 turn on voltage, luminance, efficiency 증가함을 볼 수 있다.

• Proceedings of the IEEK Conference
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• 2002.06c
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• pp.47-50
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• 2002

In this paper, the efficient transmission technique of real time video data over 3G wireless networks is presented. To understand the transmission characteristic of 3G networks on real time video data, we implemented the data transport structure of 3G wireless networks. Also this research is based on current 3G wireless network specification of 3GPP, 3GPP2 standard organization to evaluate the result over real 3G wireless network environment. The retransmission by radio link layer results in the delay factor. To implement video data transmission efficiently, we Propose to use both no-retransmission and forward error correction method.