• Proceedings of the Korean Operations and Management Science Society Conference
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• 2003.05a
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• pp.744-748
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• 2003

Developing an interactive satellite multi­media system, such as a digital video broadcasting (DVB) return channel via satellite (RCS) system, is gaining popularity over the world To accommodate the increasing traffic demand we are motivated to investigate an alternative for improving return channel utilization We develop an efficient method for optimal packet scheduling in an interactive satellite multimedia system using hybrid CDMA/TDMA channels. We formulate the timeslot-code assignment problem as a binary integer programming (BIP) problem, where the throughput maximization is the objective, and decompose this BIP problem into two sub-problems for the purpose of solution efficiency. With this decomposition, we promote the computational efficiency in finding the optimal solution of the original BIP problem Since 2001, ETRI has been involved in a development project where we have successfully completed an initial system integration test on broadband mobile Internet access via Ku-band channels using the proposed resource allocation algorithm.

• Proceedings of the Korea Society for Industrial Systems Conference
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• 1999.05a
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• pp.53-57
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• 1999

본 논문에서는 입출력간의 연관관계가 트리구조로 표현되는 DTG(Directed tree graph)에 의한 고속병렬다치논리회로를 설계하는 알고리즘과 DTG의 각 절점에 코드를 할당하는 알고리즘을 제안한다. 임의의 절점을 갖는 DTG에 대하여 본 논문에서는 절점들이 매개변수에 의하여 표현될 때 양의 정수로 표현되도록 논리레벨 P를 할당하고 각 레벨에 각기 다른 잉여절점을 추가하여 회로를 설계한다. 또한, 절점들의 입출력 관계를 단지 하나의 매개변수 m$_{i}$를 이용하여 전달행렬 A를 구하기 때문에 더 빠르고 간단하게 회로를 설계할 수 있다. 본 논문에서 제안한 알고리즘은 Nakajima 등에 의해 제안된 알고리즘으로는 설계가 가능하지 않았던 임의의 절점을 가지는 DTG에 대해서도 회로를 설계할 수 있는 장점이 있다. 또한, 자연수 내에서 선형성, 정규성, 및 가시적인 장점을 가지며 절점수의 감소를 통한 처리속도의 향상, 회로 구성의 간략화 및 비용절감등의 장점등이 있다.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.33 no.4
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• pp.134-139
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• 1984

This paper presents the computer program to design the synchronous sequential logic circuit. The computer program uses the MASK method to get the circuit of optimal cost. The computer program takes as an input, the minimal reduced state transition table where each state has its internal code. As an output,the optimal design of synchronous sequential logic circuit is generated for each flipflop type of JK,T,D, and RS respectively. And these circuits for 4 flipflop types are evaluated and sorted in ascending order of their costs, so that the user can select the proper flipflop type and its circuit. Furthermore,the proposed computer program may be applied to state assignment with its facility of cost evaluation.

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.45-58
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• 2017

Recent investigations have pointed out that current code provisions specifying that the stiffness of reinforced concrete elements is strength independent, and therefore can be estimated prior to any strength assignment, is incorrect. A strength allocation strategy, suitable for preliminary structural design of medium height wall-frame dual systems, is presented for allocating strength in such buildings and estimating the dependable rigidities. The design process may be implemented by either the approximate continuous approach or the stiffness matrix method. It is based on the concept of the inelastic equivalent single-degree-of-freedom system which, the last few years, has been used to implement the performance based seismic design. The aforesaid strategy may also be used to determine structural configurations of minimum rotation distortion. It is shown that when the location of the modal centre of rigidity, as described in author's recent papers, is within a close distance from the mass axis the torsional response is mitigated. The methodology is illustrated in ten story building configurations, whose torsional response is examined under the ground motion of Kobe 1995, component KJM000.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6A
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• pp.820-831
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• 1999

In this paper, we have compared the performance of a D-TDMA protocol with that of a CDMA protocol, in radio access system for integrated voice/data services.The D-TDMA protocol is based on a generic dynamic channel assignment approach to be followed a combination of “circuit mode” reservation for voice calls, along with dynamic first-come-first served assignment of remaining capacity for data messages. In the CDMA protocol, we have used the voice activity detection to reduce the interface power of other mobiles in internal and external cells, and analyzed the interference power ratio. Also we have computed BER(Bit Error Rate) by using this interference power ratio and evaluated voice blocking probability(voice packet loss probability) and data transmission delay, according to average data length and average data arrival rate.We have found the CDMA protocol achieves comparatively higher performance for short data length, regardless of data arrival rate. Otherwise, the data transmission delay of D-TDMA protocol is shorter than that of the CDMA protocol for long data message.

• Information and Communications Magazine
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• v.13 no.4
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• pp.56-63
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• 1996

In this paper, the phisical layer of 4.3008 Mcps wideband CDMA which is proposed as the standard of personal communication service system is introduced. It is designed to fit 5 MHz bandwidth by using $28{\times}2^n$ Hadamard code. 13 kbps CELP vocoder is chosen as the main one and 32 kbps ADPCM can be applied. In the reverse link, the burst pilot scheme is proposed and produces the increase of capacity compared with the continuous pilot method. In order to maintain the service quality when the signaling data is increased, the information data and signaling data are time-multiplexed and making use of signaling activity brings the increase of capacity. QPSK data and QPSK spreading, variable frame size, and code pair assignment for high data rate are accomplished and then information data is transmited up to 64 kbps. It is expected that the proposed techiniques here are used in the FPLMTS.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.14 no.12
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• pp.2724-2729
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• 2010

This paper presents a method of constructing the sequential digital systems over finite fields. We assign all elements in finite fields to digit codes using mathematical properties of finite fields. Also, we discuss the operational characteristics and properties of the building block T-gate which is used to implement the sequential digital systems over finite fields. Then, we implemented sequential digital systems without feed-back. The sequential digital systems without feed-back is constructed as following steps. First, we assign the states in state-transition diagram to state digit codes, then obtain the state function and predecessor table which is explaining the relationship between present states and previous states. Next, we obtained the next-state function from state function and predecessor table. Finally we realize the circuit using T-gate and decoder. The proposed method is more efficiency and systematic than previous method.

• Journal of the Korean Institute of Intelligent Systems
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• v.12 no.2
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• pp.171-176
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• 2002

This paper describes a new automated analysis system for model plane engine. An automatic finite element (FE) mesh generation technique, which is based on the fuzzy knowledge processing and computational geometry technique, is incorporated into the system, together with one of commercial FE analysis codes, ANSYS, and one of commercial solid modelers, Designbase, The system allows a geometry model of concern to be automatically converted to different FE models, depending on physical phenomena of plane engine to be analyzed, i.e. deformation analysis, thermal analysis and so on. The FE models are then automatically analyzed by the FE analysis code. Among a whole process of analysis, the definition of a geometry model, the designation of local node patterns, the assignment of material properties and boundary conditions onto the geometry model are only the interactive processes to be done by a user. The interactive operations can be processed in a few minutes. The other processes which are time consuming and labour-intensive in conventional CAE systems are fully automatically performed in a personal computer environment. The proposed analysis system is successfully applied to evaluate a model plane entwine.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.15 no.9
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• pp.1965-1970
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• 2011

This paper proposes the method of switching function implementation using switching function extraction based on graph over finite fields. After we deduce the matrix equation from path number of directional graph, we propose the switching function circuit algorithm, also we propose the code assignment algorithm for nodes which is satisfied the directional graph characteristics with designed circuits. We can implement more optimal switching function compare with former algorithm, also we can design the switching function circuit which have any natural number path through the proposed switching function circuit implementation algorithms. Also the proposed switching function implementation using graph theory over finite fields have decrement number of input-output, circuit construction simplification, increment arithmetic speed and decrement cost etc.

• Communications for Statistical Applications and Methods
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• v.23 no.1
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• pp.1-20
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• 2016

Causal inference methodologies have been developed for the past decade to estimate the unconfounded effect of an exposure under several key assumptions. These assumptions include, but are not limited to, the stable unit treatment value assumption, the strong ignorability of treatment assignment assumption, and the assumption that propensity scores be bounded away from zero and one (the positivity assumption). Of these assumptions, the first two have received much attention in the literature. Yet the positivity assumption has been recently discussed in only a few papers. Propensity scores of zero or one are indicative of deterministic exposure so that causal effects cannot be defined for these subjects. Therefore, these subjects need to be removed because no comparable comparison groups can be found for such subjects. In this paper, using currently available causal inference methods, we evaluate the effect of arbitrary cutoffs in the distribution of propensity scores and the impact of those decisions on bias and efficiency. We propose a tree-based method that performs well in terms of bias reduction when the definition of positivity is based on a single confounder. This tree-based method can be easily implemented using the statistical software program, R. R code for the studies is available online.