• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.3
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• pp.229-235
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• 2010

Optimum values of fin performance and dimensions for an annular fin with a rectangular profile and a pipe with variable inner radius are determined by using a variable separation method. The range of ambient convection characteristic number that results in optimum heat loss is listed. The optimum heat loss, corresponding optimum fin effectiveness, fin length, and fin height are presented as a function of the inner radius of the pipe, inner fluid convection characteristic number, fin volume, and ambient convection characteristic number. One of the results shows that the optimum heat loss, fin effectiveness and fin length increase linearly with the inner radius of the pipe when both the fin volume and fin-base radius are fixed.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.19 no.1
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• pp.111-119
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• 1994

In this paper we propose a reversible image coding methods with progressive build-up function by bit-plane of multi-lavel image. Firstly, the differencial conversion is applied to reduce the entropy of source images. Then the bit-plane sequences of converted images are coded by means of the newly designed VFRL(Variable to Fixed Run-Llength) code and the RDHC(Run-length Dynamic Huffman Coding). We aim to the simple construction to reduce the complexity. The computer simulated results show that the proposed methods are very effective to the multi-level digital images. For "GIRL" and "COUPLE" of 1EEE monochromatic standard images, the compressibility are superior to the results obtained by the well-known universal codes.own universal codes.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.2
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• pp.676-682
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• 2018

As the IoT world including WSNs develops, the number of sensor systems that sense information according to the environment based on the principle of IoT is increasing. In order to perform security for each sensor system in such a complicated environment, the security modules must be varied. These problems make hardware/software implementation difficult when considering the system efficiency and hacking/cracking. Therefore, to solve this problem, this paper proposes a pseudorandom number generator (FLT: Pseudo-random Number Generator with Fixed Length Tap unrelated to the variable sensing nodes) with a fixed-length tap that generates a pseudorandom number with a constant period, irrespective of the number of sensing nodes, and has the purpose of detecting anomalies. The proposed FLT-LFSR architecture allows the security level and overall data formatting to be kept constant for hardware/software implementations in an IoT environment. Therefore, the proposed FLT-LFSR architecture emphasizes the scalability of the network, regardless of the ease of implementation of the sensor system and the number of sensing nodes.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.16 no.2
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• pp.41-47
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• 2016

The times of multiplication for encryption and decryption of cryptosystem is primarily determined by implementation efficiency of the modular exponentiation of $a^b$(mod m). The most frequently used among standard modular exponentiation methods is a standard binary method, of which n-ary($2{\leq}n{\leq}6$) is most popular. The n-ary($1{\leq}n{\leq}6$) is a square-and-multiply method which partitions $b=b_kb_{k-1}{\cdots}b_1b_{0(2)}$ into n fixed bits from right to left and squares n times and multiplies bit values. This paper proposes a variable-length partition algorithm that partitions $b_{k-1}{\cdots}b_1b_{0(2)}$ from left to right. The proposed algorithm has proved to reduce the multiplication frequency of the fixed-length partition n-ary method.

• Structural Engineering and Mechanics
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• v.84 no.3
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• pp.295-310
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• 2022

This paper proposes a modified bar simulation method for analyzing the shear lag effect of variable sectional box girder with multiple cells. This theoretical method formulates the equivalent area of stiffening bars and the allocation proportion of shear flows in webs, and re-derives the governing differential equations of bar simulation method. The feasibility of the proposed method is verified by the model test and finite element (FE) analysis of a simply supported multi-cell box girder with constant depth. Subsequently, parametric analysis is conducted to explore the mechanism of shear lag effect of varied sectional cantilever box girder with multiple cells. Results show that the shear lag behavior of variable box-section cantilever box girder is weaker than that of box girder with constant section. It is recommended to make the gradient of shear flow in the web with respect to span length vary as smoothly as possible for eliminating the shear lag effect of box girder. An effective countermeasure for diminishing shear lag effect is to increase the number of box chambers or change the variation manner of bridge depth. The shear lag effect of varied sectional cantilever box girder will get more server when the length of central flanges is shorter than 0.26 or longer than 0.36 times of total width of top flange, as well as the cantilever length exceeds 0.29 times of total length of box's flange. Therefore, the distance between central webs can adjust the shear lag effect of box girder. Especially, the width ratio of cantilever plate with respect to total length of top flange is proposed to be no more 1/3.

• The korean journal of orthodontics
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• v.25 no.3 s.50
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• pp.263-271
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• 1995

The purpose of this study nab to evlauate and compare the effect of the variable factors of wire on the elastic properties of looped rectangular wire. Five variable factors were presented-material(Hi-T, blue Elgiloy), wire size(.016'$\;\times\;$.022', .018'$\;\times\;$.025'), loop length(15mm, 20mm), loop configuration(open loop, closed loop), gabling (non-gable, gable). So, the total 256 specimens were divided into 32 groups, and each of those nab pulled on Instron testing machine. The load-deflection curve of each wire obtained, from which force, range in elastic limit, and stiffness were computed and analyzed statistically. The results were obtained as follows : 1. All of the variable factors - wire material, size, loop length loop configuration, and gabling - took a significant effect on load-deflection rate of looped wire. 2. The force at elastic limit was the smallest in the group of Hi-T, .016'$\;\times\;$.022', 20mm loop length, open loop, non-gable, and the largest in the group of blue Elgiloy, .018'$\;\times\;$.025', 15mm loop length, closed loop, non-gable. 3. The range at elastic limit was the smallest in the group of Hi-T, .018'$\;\times\;$.025', 15mm loop length, open loop, non-gable, and the largest in the group of HI-T, .016'$\;\times\;$.022', 20mm loop length, closed loop, gable. 4. Loop configuration and loop length were the most effective factors on the elastic properties of looped wires, and gabling was the least effective.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.29A no.10
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• pp.1-7
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• 1992

This paper proposes reservation-based multiple access with variable frame length (RMAV) which is a new multiple access scheme for indoor and outdoor wireless data communications. RMAV is based on the slot reservation scheme and adopts a frame structure with variable frame length. The frame length increases as the number of active terminals and/or the system load increases. As a result, RMAV is adapted to the changes in the traffic pattern, and it offers short delay in light load conditions and high throughput in heavy load conditions. The performance of RMAV is evaluated by simulations. In addition, it is compared with the performance of PRMA(packet reservation multiple access).

• New & Renewable Energy
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• v.5 no.1
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• pp.40-46
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• 2009

Optimization of a rectangular profile annular fin with variable pipe inside radius is presented. This optimum procedure is based on fixed fin height and is made by using variables separation method. The optimum heat loss, corresponding optimum fin length and optimum fin efficiency are presented as a function of pipe inside radius, fin half height, inside fluid convection characteristic number and ambient convection characteristic number. One of results shows that the optimum fin length increases linearly with increase of pipe inside radius for fixed fin height and fin base radius.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.8 no.12
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• pp.4324-4342
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• 2014

Previous papers analyzed the throughput performance of the CDMA ALOHA system in Rayleigh fading channel, but they assume that the channel coefficient of Rayleigh fading was the same in the whole packet, which is not realistic. We recently proposed the finite-state Markov channel (FSMC) model to the throughput analysis of DS uncoded CDMA/unslotted ALOHA networks for fixed length data traffic in the mobile environment. We now propose the FSMC model to the throughput analysis of coded DS CDMA/unslotted ALOHA networks with variable length data traffic and one or two user classes in the mobile environment. The proposed DS CDMA/unslotted ALOHA wireless networks for two user classes with access control can maintain maximum throughput for the high priority user class under high message arrival per packet duration.

• Proceedings of the KIEE Conference
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• 2001.07a
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• pp.226-228
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• 2001

this paper presents the distance relay using wavelet transform and least square error method. Wavelet transform detect the faults in the high frequency region and remove the noises in the low frequency region. The variable window length LSE determine optimal window length to each fault case and estimate fault impedance very quickly.