• Elastomers and Composites
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• v.41 no.1
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• pp.27-39
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• 2006

In this study, modified DA-MMT filled NR/DA-MMT nanocomposites were manufactured by a latex method and a compounding method. Cure characteristics and mechanical properties of the Cloisite 15A, carbon black, Na-MMT filled NR compounds and the DA-MMT filled NR compound by a latex method were also evaluated. The filler content of all compounds was 10phr except the carbon black filled compound. Degree of intercalation and dispersion was characterized by X-ray diffraction (XRD) and transmission electron microscope (TEM). According to the XRD diffraction pattern and TEM analysis, extensive intercalation and homogeneous dispersion of the clay were obtained after the two-roll milling. Although the layer distance was increased, some parts of DA-MMT showed the layer distance of Na-MMT after vulcanization. DA-MMT filled NR compounds showed the highest ODR torques, tensile strength, modulus, and tear energy. The NR/DA-MMT nanocomposite (by a latex method) compared with a NR/DA-MMT nanocomposite (by a compounding method) was found that the improvement of the mechanical properties was mainly due to the degree of dispersion of the clay.

• Geophysics and Geophysical Exploration
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• v.25 no.1
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• pp.14-25
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• 2022

The passive surface wave method measures seismic signals from ambient noises or vibrations of natural phenomena without using an artificial source. Since passive sources are usually in lower frequencies than artificial ones being able to ensure the information on deeper geological structures, the passive surface wave method can investigate deeper geological structures. In the passive method, frequency dispersion curves are obtained after data acquisition, and the dispersion curves are analyzed by assuming 1D-layered earth, which is like the method of active surface wave survey. However, when computing dispersion curves, the passive method first obtains and analyzes coherence curves of received signals from a set of receivers based on spatial autocorrelation. In this review, we explain how passive surface wave methods measure signals, and make data processing and interpretation, before analyzing field application cases.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.32 no.7A
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• pp.657-665
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• 2007

In this paper, it is investigated that the limitation due to the asymmetry of optical power and chromatic dispersion with respect to optical phase conjugator (OPC) for compensating optical signal distortion of WDM channels in mid-span spectral inversion (MSSI) technique is overcame by using OPC position offset and optimal dispersion coefficients of fiber sections, which depend on OPC position offset. It is confirmed that overall WDM channels are efficiently compensated by applying the optimal parameter values obtained from the proposed method into 24 channels ${\times}\;40\;Gbps$ WDM system with non zero - dispersion shifted fiber (NZ-DSF) of 1,000 km, such as power penalties of inter-channel are reduce to almost 3.5 dB from the infinite value. It is also confirmed that the flexible design of WDM system with OPC is possible by using the optimal parameters, in which OPC is placed at ${\pm}15\;km$ from 500 km for efficiently compensating overall channels.

• Journal of Advanced Navigation Technology
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• v.10 no.2
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• pp.103-113
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• 2006

The numerical methods of finding the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are proposed, which are able to effectively compensate overall channels in $8{\times}40$ Gbps WDM system with non zero-dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem but the condition in the case of applying the OPC into multi-channels WDM system.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.12 no.5
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• pp.59-76
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• 2009

This study was conducted to supply basic data for restoration and management of forests in Civilian Control Zone, with surveying naturalized plants around abandoned military camps. The total study sites are 72 abandoned military camps, from Gosung in east region to Paju in west region of Civilian Control Zone. The naturalized index of total area is 12.6%, and naturalized index of east and middle regions are 12.1% and 8.4%. But its index of west region is 15.9%. These results are due to geographical characteristics. The east and middle regions are in steep mountainous districts, and so but west region is flat district, and so naturalized plants was imported by only army. But west region is in flat districts, and so imported method of naturalized plants is very various. The main naturalized plants are Ambrosia trifida and Ambrosia artemisiifolia var. elatior in Civilian Control Zone. The main dispersion pattern of naturalized plants are gravity dispersion pattern ($D_4$) and wind and water dispersion pattern ($D_1$). The all naturalized plants are photophilic plants in survey sites. And so, if abandoned military camps are recovered to forests, the naturalized plants are disappeared because of the change of sunlight condition. So it is necessary to manage and recover forests, even if that area is Civilian Control Zone.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.37 no.2
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• pp.227-232
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• 2013

This study proposes a method for predicting the reliability of the barrel in small arms by analyzing the dispersion. The periodicity with which the barrel needs to be changed can be determined by detecting the inner surface directly or by inspecting scratches inside the barrel using an optical sensor. However, soldiers and directors in the logistics command need a more easy way to check the periodicity of barrel. Therefore, this study focuses on the relation between the firing round and the dispersion. A simple equation can be experimentally derived from pre-tests and analyses. This equation is confirmed through firing tests. In this sense, it can be easily applied to determine the periodicity with which the barrel of small arms needs to be changed in the field army.

• Korean Journal of Agricultural Science
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• v.41 no.4
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• pp.315-319
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• 2014

Mean densities of two-spotted spider mite (TSM), Tetranichus urticae Koch adults from January to April in 2014 to investigate the occurrence and dispersion pattern of T. urticae on purpose of developing a monitoring method in the strawberry PVC house. Difference of density of T. urticae adult on middle and both side of leaf wasn't significantly. Density of T. urticae in investigation at different furrows and investigating points was the highest at the right and left sides of a furrow in strawberry PVC house. In results of comparing the dispersion incides of Taylor's power law (TPL) with Iwao's patchiness regression (IPR), TPL described better mean-relationship for the dispersion indieces compared to IPR. Slopes and intercepts of TPL from leaf samples did not differ among surveyed regions. Also, Distribution of T. urticae in a strawberry PVC house was the gravitation of the distribution because b and ${\beta}$ values of TPL and IPR was bigger than 1.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.17 no.6 s.109
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• pp.546-555
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• 2006

In this paper, the numerical methods of finding the optimal position of optical phase conjugator(OPC) and the optimal fiber dispersions are proposed, which are able to effectively compensate overall channels in $8{\times}40$ Gbps WDM system with non zero-dispersion shifted fiber(NZ-DSF) as an optical fiber. And the compensation characteristics in the system with two induced optimal parameters are compared with those in the system with mid-span spectral inversion (MSSI) technique in order to confirm the availability of the proposed methods. It is confirmed that the optimal parameter values induced in this approach are very useful to effectively compensate overall channels in WDM system with OPC. And, it is confirmed that two optimal parameters depend on each other, but less related with the searching procedure. The methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which is a serious problem of applying the OPC into multi-channels WDM system.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.10 no.10
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• pp.1854-1862
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• 2006

The numerical methods of finding out the optimal position of optical phase conjugator (OPC) and the optimal fiber dispersions are prosed, which are able to effectively compensate overall channels in $8{\times}40Gbps$Gbps WDM system with non zero - dispersion shifted fiber (NZ-DSF) as an optical fiber. And BER characteristics in the system with two induced optimal parameters are compared with those in the system with the currently used mid-span spectral inversion (MSSI) in order to confirm the availability of the proposed methods. It is confirmed that the applying two induced optimal parameters into WDM system contribute to reduce power penalty to 4 times than that of WDM system with the conventional MSSI. Thus, the methods proposed in this research will be expected to alternate with the method of making a symmetrical distribution of power and local dispersion in real optical link which generates a serious problem if it was not made but it is the condition in the case of applying the OPC into multi-channels WDM system.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.30 no.3A
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• pp.168-177
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• 2005

In this paper, we numerically investigated the optimum pump light power resulting best compensation of pulse distortion due to both chromatic dispersion and self phase modulation (SPM) in long-haul 3×40 Gbps wavelength division multiplexing (WDM) systems. We used mid-span spectral inversion (MSSI) method with path-averaged intensity approximation (PAIA) as compensation approach, which have highly nonlinear dispersion shifted fiber (HNL-DSF) as nonlinear medium of optical phase conjugator (OPC) in the mid-way of total transmission line. We confirmed that HNL-DSF is an useful nonlinear medium in OPC for wideband WDM transmission, and in order to achieve the excellent compensation the pump light power is selected to equal the conjugated light power into the latter half fiber section with the input light power of WDM channel depending on total transmission length. Also we confirmed that compensation degree of WDM channel with small conversion efficiency is improved by using pump light power increasing power conversion ratio upper than 1.