• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.17 no.8
• /
• pp.2157-2169
• /
• 2023

In order to handle the problem that puncture patterns will change the position distribution of original information bits and frozen bits in polar codes, which affects performance of puncture polar codes further, a minimum row weight and polar spectrum based puncture polar codes construction algorithm (called PA-MRWP) is proposed in this paper. The algorithm calculates row weight of generator matrix and sorts the row weight in ascending order first. Next, the positions with the minimum row weight are selected as initial puncture positions. If the rows with the same row weight cannot all be punctured, polar spectrum based auxiliary puncture scheme is used. In sub-channels with the same row weight, rows corresponding to the polarized sub-channels with higher reliability are selected as puncture positions to construct puncture vector, and the reliability is calculated based on polar spectrum. It is actually a two-step selection strategy, the proposed minimum row weight puncture (MRWP) algorithm is used for primary selection and polar spectrum based auxiliary puncture is used for adjustment. Simulation results show that, compared with worst quality puncture (WQP) algorithm, the proposed PA-MRWP algorithm and Gaussian approximation-aided minimum row weight puncture (GA-MRWP) algorithm provide gains of about 0.46 dB and 0.29 dB at bit error rate (BER) of 10^-4, respectively when code length N=400, code rate R=1/2. In addition, the proposed puncture algorithms improve the BER performance significantly with respect to quasi-uniform puncture (QUP) algorithm.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.17 no.10
• /
• pp.2822-2843
• /
• 2023

All aspects of human life have become increasingly dependent on data in the last few decades. The development of several applications causes an enormous issue on data volume in current years. This information must be safeguarded and kept in safe locations. Massive volumes of data have been safely stored with cloud computing. This technology is developing rapidly because of its immense potentials. As a result, protecting data and the procedures to be handled from attackers has become a top priority in order to maintain its integrity, confidentiality, protection, and privacy. Therefore, it is important to implement the appropriate security measures in order to prevent security breaches and vulnerabilities. An improved version of Modular Encryption Standard (IMES) based on layered modelling of safety mechanisms is the major focus of this paper's research work. Key generation in IMES is done using a logistic map, which estimates the values of the input data. The performance analysis demonstrates that proposed work performs better than commonly used algorithms against cloud security in terms of higher performance and additional qualitative security features. The results prove that the proposed IMES has 0.015s of processing time, where existing models have 0.017s to 0.022s of processing time for a file size of 256KB.

• Journal of Hydrogen and New Energy
• /
• v.32 no.4
• /
• pp.245-255
• /
• 2021

Various studies about metallic bipolar plates have been conducted to improve fuel cell performance through flow field design optimization. These research works have been mainly focused on fuel cells for vehicle, but not fuel cells for building. In order to reduce the price and volume of fuel cell stacks for building, it is necessary to apply a metallic flow field, In this study, for a metallic flow field applied to a fuel cell for building, the effect of a change in the flow field shape on the performance of a polymer electrolyte membrane fuel cell was confirmed using a model and experiments with a down-sizing single cell. As a result, the flow field using a metal foam outperforms the channel type flow field because it has higher internal differential pressure and higher reactants velocity in gas diffusion layer, resulting in higher water removal and higher oxygen concentration in the catalyst layer than the channel type flow field. This study is expected to contribute to providing basic data for selecting the optimal flow field for the full stack of polymer electrolyte membrane fuel cells for buildings.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.29 no.8C
• /
• pp.1025-1033
• /
• 2004

This paper covers the detection of covert direct sequence spread spectrum signal without the PN(Pseudo Noise) code information. Due to its low probability of interception, the difficulty of spectrum surveillance increases. Detection parameters are the signal existence of given bandwidth, the length of spreading sequence used by transmitter, and the identification of spreading code for detected chip length. The triple correlation function(TCF) value which is one of the higher order statistical signal processing techniques can be used to detect spread spectrum signal without a prior knowledge, but, it has weakness that TCF results depend on the spread data sequence in actual application. This paper proposes the new scheme that not only overcomes the weakness but also presents better performance than the traditional TCF scheme. The performance comparison of conventional TCF with proposed technique shows that the triple correlation estimator(TCE) has better detection capability.

• Journal of Environmental Science International
• /
• v.15 no.6
• /
• pp.513-525
• /
• 2006

In recent decades, biofiltration has been widely accepted for the treatment of contaminated air stream containing low concentration of odorous compounds or volatile organic compounds (VOCs). In this study, conventional biofilters packed with flexible synthetic polyurethane (PU) foam carriers were operated to remove toluene from a contaminated air stream. PU foams containing various amounts of pulverized activated carbon (PAC) were synthesized for the biofilter media and tested for toluene removal. Four biofilter columns were operated for 60 days to remove gaseous toluene from a contaminated air stream. During the biofiltration experiment, inlet toluene concentration was in the range of 0-150 ppm and EBRT (i.e., empty bed residence time) was kept at 26-42 seconds. Pressure drop of the biofilter bed was less than 3 mm $H_2O/m$ filter bed. The maximum removal capacity of toluene in the biofilters packed with PU-PAC foam was in the order of column II (PAC=7.08%) > column III (PAC=8.97%) > column I (PAC=4.95%) > column IV (PAC=13.52%), while the complete removal capacity was in the order of column II > column I > column III > column IV. The better biofiltration performance in column II was attributed to higher porosity providing favorable conditions for microbial growth. The results of biodegradation kinetic analysis showed that PU-PAC foam with 7.08% of PAC content had higher maximum removal rate ($V_m$=14.99 g toluene/kg dry material/day) than the other PU-PAC foams. In overall, the performance of biofiltration might be affected by the structure and physicochemical properties of PU foam induced by PAC content.

• Journal of the Korean Institute of Gas
• /
• v.22 no.6
• /
• pp.16-27
• /
• 2018

Since 2014, the Korean government has begun distributing LPG pipelines and LPG tankers to mountainous or island areas where it is difficult to open urban gas supply chains. When installing LPG supply facilities at village level and county level, it supplied consumers with 10 times higher quasi-low pressure (25 kPa to 100 kPa) than conventional gas supply pressure, increasing the risk of gas accident. Due to the pressure that is 10 times higher than the conventional gas supply pressure, large amounts of gas are released at a faster rate when leaked. In order to secure safety of quasi-low-pressure gas pipes, excess flow valves for quasi-low-pressure gas pipes are not developed and are not supplied in Korea. Therefore, Korea Gas Safety Corporation is investigating the performance standards and products of the excess flow valves in order to localize the excess flow valves.

• Structural Engineering and Mechanics
• /
• v.90 no.3
• /
• pp.253-261
• /
• 2024

This research explores a new finite element model for the free vibration analysis of bi-directional functionally graded (BDFG) beams. The model is based on an efficient higher-order shear deformation beam theory that incorporates a trigonometric warping function for both transverse shear deformation and stress to guarantee traction-free boundary conditions without the necessity of shear correction factors. The proposed two-node beam element has three degrees of freedom per node, and the inter-element continuity is retained using both C1 and C0 continuities for kinematics variables. In addition, the mechanical properties of the (BDFG) beam vary gradually and smoothly in both the in-plane and out-of-plane beam's directions according to an exponential power-law distribution. The highly elevated performance of the developed model is shown by comparing it to conceptual frameworks and solution procedures. Detailed numerical investigations are also conducted to examine the impact of boundary conditions, the bi-directional gradient indices, and the slenderness ratio on the free vibration response of BDFG beams. The suggested finite element beam model is an excellent potential tool for the design and the mechanical behavior estimation of BDFG structures.

• Journal of Korean Academy of Nursing
• /
• v.30 no.5
• /
• pp.1170-1180
• /
• 2000

This study was a quasi-experimental study to confirm the effects of a memory training program using efficacy sources. The purpose was to develop an effective memory training program for elderly people and to identify the effects of the memory training program. This study was carried out between February 24 and July 18, 1999 and the subjects of the study were 102 elderly people who were participants at a welfare institute in Seoul. The experimental group (51) and the control group (51) were assigned by means of participation order. The control group was matched to the experimental group and was selected considering age, sex, and religion. The experimental group participated in the memory training program. The memory training program was based on the literature of Fogler & Stern (1994), Wang & Lee (1990), Lee (1991) and Lee (1993). The memory training program was given twice a week for two weeks with each program lasting two hours. Task centered memory self-efficacy was measured using the Memory Self-Efficacy Scale developed by Berry & Dennehey (1989) and Meta Memory was measured by the MIA developed by Dixon et al. (1988) Memory performance was measured by the word list developed by Cho Sung Won (1995) and the face recognition task (Face Recognition Task developed for this study). Data were analyzed by SPSS PC and the results are described below. 1. The experimental group which participated in the Memory Training Program showed higher task centered memory self-efficacy scores as compared to the control group (t=4.354, P=.0001). 2. The experimental group which participated in the Memory Training Program showed higher metamemory scores as compared to the control group (t=4.733, P=.0001). 3. The experimental group which participated in the Memory Training Program showed higher memory performance scores as compared to the control group (t=7.500, P=.0001). The memory performance involved an immediate word recall task, a delayed word recall task, a word recognition task, and the face recognition task. 4. In the experimental group, there was significant correlation between the task centered memory self-efficacy scores and the metamemory scores (r=.382, P=.006), but the correlation between the task centered memory self-efficacy scores and the memory performance scores and between the metamemory scores and the memory performance scores were not significant. The results showed that task centered memory self-efficacy, meta memory and memory performance improved following the Memory Training Program including the memory process, changes in memory with aging, and appropriate use of memory strategies. Memory Training Program is an effective nursing intervention for improving memory in elderly people and, also, in people with complaints of memory loss.

• Journal of Ginseng Research
• /
• v.4 no.1
• /
• pp.16-30
• /
• 1980

In order to increase the production of ginseng, a cultural experiment was carried out under different types of natural forest condition. Seedlings were transplanted with three spacing (70,90 and plants per 1.62m2) under the broad leaved, needle and mixed forest. The obtained results are as follows. 1 Growth of aerial part of ginseng plant. 1) Vegetative growth under forest condition of very poor as compared with ordinary cultivation, but there was no significant in number of leaf and teasel. 2) Stem diameter and stem length under the different forest types were a little difference. However petiole length and number of leafet showed an increasing trend in broad leaved forest as compared with other forest types. 3) The withering date of aerial part of ginseng plant in the needle forest was later than of others. 2. Fresh weight of ginseng root per plant was decreasing in the order of broad leaved forest, needle and mixed forest, needle and sized forest respectively. However the root weight was much smaller than that of ordinary cultivated one. 3. No big difference was observed in the growth of both aerial and root among the planting density 4. Nitrogen content in ginseng root under forest was lower, but calcium content In root was higher than that of ordinary one. 5. Fat and fiber content of ginseng root under forest showed higher than that of ordinary one. 6. The saponin content of ginseng root grown under forest condition was higher than that of ordinary ginseng root. According to high performance liquid chromatogram of saponin, only difference from ordinary cultivated ginseng root was that ginsenoside Re showed higher peak than ginsenoside Rg1.

• The Journal of the Korea Contents Association
• /
• v.9 no.9
• /
• pp.218-225
• /
• 2009

The present research aims to analyze empirically the effect of group cohesiveness and supervisor trust which tax investigators recognize while performing tax administrative duties on the team commitment and in-role behavior. The result of the analysis showed that tax investigators' higher group cohesiveness and supervisor trust resulted in higher team commitment, and that higher team commitment in turn resulted in higher in-role behavior, thereby raising the efficiency of tax investigators' activities as well as tax payers' satisfaction with tax services. Therefore in order to improve the efficiency of tax organizations and team performance, the managers of the organizations must set solid goals, develop solid strategies appropriate for situation, and make proper compensations for investigators' achievements. In addition, there would have to be an organic improvement In all the relevant areas, including organization, personnel management, work style, compensation and welfare, in order to raise tax investigators' work desire.