• Asia-Pacific Journal of Atmospheric Sciences
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• v.54 no.4
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• pp.563-573
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• 2018

An Expert Seasonal Prediction System for operational Seasonal Outlook (ESPreSSO) is developed based on the APEC Climate Center (APCC) Multi-Model Ensemble (MME) dynamical prediction and expert-guided statistical downscaling techniques. Dynamical models have improved to provide meaningful seasonal prediction, and their prediction skills are further improved by various ensemble and downscaling techniques. However, experienced scientists and forecasters make subjective correction for the operational seasonal outlook due to limited prediction skills and biases of dynamical models. Here, a hybrid seasonal prediction system that grafts experts' knowledge and understanding onto dynamical MME prediction is developed to guide operational seasonal outlook in Korea. The basis dynamical prediction is based on the APCC MME, which are statistically mapped onto the station-based observations by experienced experts. Their subjective selection undergoes objective screening and quality control to generate final seasonal outlook products after physical ensemble averaging. The prediction system is constructed based on 23-year training period of 1983-2005, and its performance and stability are assessed for the independent 11-year prediction period of 2006-2016. The results show that the ESPreSSO has reliable and stable prediction skill suitable for operational use.

• International Journal of Computer Science & Network Security
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• v.21 no.1
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• pp.49-54
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• 2021

Relative to the outer surface of the mastic coating, the reliability of the available waterproofing resource is determined by the ability to stabilize the structural characteristics in difficult climatic conditions. Organic components of mastic as a result of solar radiation, elevated temperatures and their alternating change, atmospheric oxidants, especially in industrial areas, have a tendency to self-polymerization and loss of low molecular weight components. This is the gradual loss of deformability and the transition to brittleness with its tendency to crack as the reasons for the gradual transition from normal to emergency operating condition.The presented mechanism of functioning of the coating surface indicates the expediency of increasing its components, able to stabilize the structure and prevent changes in deformability.Durability, hydrophobicity, water displacement, water absorption are accepted as estimating indicators. The main dependences of the influence of the lost additional components of mastic on the operational properties of the formed coating characterize the ability to provide successful resistance to environmental influences and longer stability. As a result, mastic acquires additional service life.

• Journal of Positioning, Navigation, and Timing
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• v.10 no.4
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• pp.243-251
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• 2021

Real-Time Kinematic (RTK) is a phase-based differential GNSS technique and uses additional observations from permanent reference stations to mitigate or eliminate effects like atmospheric delays or satellite clocks and orbit errors. In particular, as the position accuracy required in the fields of autonomous vehicles and drones is gradually increasing, the demand for RTK-based precise navigation that can provide cm-level position is increasing. Recently, with the rapid growth of the open-source software market, the use of open-source software for building navigation system of unmanned vehicles, which is difficult to mount an expensive GNSS receivers, is gradually increasing. RTKLIB is an open-source software package that can perform RTK positioning and is widely used for research and education purposes. However, since the performance and stability of RTK algorithm of RTKLIB is inevitably inferior to that of commercial GNSS receivers, users need to verify whether RTKLIB can satisfy the navigation performance requirements of unmanned vehicles. Therefore, in this paper, the performance evaluation of the RTK positioning algorithm of RTKLIB was performed using GNSS observation data acquired in a dynamic environment. Therefore, in this paper, the RTK positioning performance of RTKLIB was evaluated using GNSS observation data acquired in a dynamic environment. Our results show that the current RTK algorithm of RTKLIB is not suitable for precise navigation of unmanned vehicles.

• Journal of Sensor Science and Technology
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• v.31 no.6
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• pp.361-365
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• 2022

Advanced packaging demands are driven by the need for dense integration systems. Consequently, stacked packaging technology has been proposed instead of reducing the ultra-fine patterns to secure economic feasibility. This study proposed an effective packaging process technology for semiconductor devices using a 9-inch dicing die attach film (DDAF), wherein the die attach and dicing films were combined. The process involved three steps: tape lamination, dicing, and bonding. Following the grinding of a silicon wafer, the tape lamination process was conducted, and the DDAF was arranged. Subsequently, a silicon wafer attached to the DDAF was separated into dies employing a blade dicing process with a two-step cut. Thereafter, one separated die was bonded with the other die as a substrate at 130 ℃ for 2 s under a pressure of 2 kgf and the chip was hardened at 120 ℃ for 30 min under a pressure of 10 kPa to remove air bubbles within the DAF. Finally, a curing process was conducted at 175 ℃ for 2 h at atmospheric pressure. Upon completing the manufacturing processes, external inspections, cross-sectional analyses, and thermal stability evaluations were conducted to confirm the optimality of the proposed technology for application of the DDAF. In particular, the shear strength test was evaluated to obtain an average of 9,905 Pa from 17 samples. Consequently, a 3D integration packaging process using DDAF is expected to be utilized as an advanced packaging technology with high reliability.

• Journal of Powder Materials
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• v.29 no.1
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• pp.41-46
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• 2022

In this study, we report the microstructure and characteristics of Ag-SnO₂-Bi₂O₃ contact materials using a controlled milling process with a subsequent compaction process. Using magnetic pulsed compaction (MPC), the milled Ag-SnO₂-Bi₂O₃ powders have been consolidated into bulk samples. The effects of the compaction conditions on the microstructure and characteristics have been investigated in detail. The nanoscale SnO₂ phase and microscale Bi2O3 phase are well-distributed homogeneously in the Ag matrix after the consolidation process. The successful consolidation of Ag-SnO₂-Bi₂O₃ contact materials was achieved by an MPC process with subsequent atmospheric sintering, after which the hardness and electrical conductivity of the Ag-SnO₂-Bi₂O₃ contact materials were found to be 62-75 HV and 52-63% IACS, respectively, which is related to the interfacial stability between the Ag matrix, the SnO₂ phase, and the Bi₂O₃ phase.

• Journal of the Korean Society of Radiology
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• v.12 no.6
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• pp.719-725
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• 2018

After 9/11 attacks in the U.S, Terrorism has increased the number of unspecified casualties through multi-use facility terror attacks compared to the past. The subsequent London bombings and the self-destruction of Pakistan increased people's fear and social anxiety. As international events have been held in Korea recently, awareness and concern over radioactive terrorism and security management of radioactive materials are increasing. In this paper, we compared the results of different meteorological conditions using HotSpot Code. After creating a possible terror scenario in Korea, sources likely to be use in RDD and Dirty bomb were investigated. The meteorological condition was selected by comparing the Pasquill-Gifford stability class with the most stable condition F and the most unstable condition A. The result value of the A and F condition through simulation were shown not to cause citizens to die from acute effects due to radiological effects. The range of radioactivity is different according to the wind speed and the meteorological stability, and the degree of radioactivity dilution is different according to meteorological conditions. Analysis results are expected to be used for initial response in the event of a radioactive terrorist attack.

• Journal of Korean Society for Atmospheric Environment
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• v.30 no.6
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• pp.586-599
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• 2014

During the last two decades, indoor air quality and volatile organic compounds (VOCs) have been of concern in Korean society due to their nature of potential health impacts. In order to investigate the pollution levels of VOCss in indoor environments, establishment of a solid test method for monitoring the airborne VOCss is essential. In Korea, a method based on adsorbent sampling and GC analysis coupled with thermal desorption was proclaimed as the Korea Standard Method for Indoor Air Quality Test. This study was carried out to examine some inherent problems of the VOCs measurement method. The VOCs method does not describe in detail preparing the standard samples. The standard samples may be prepared by impregnation of either liquid standard solutions or a mixture of standard gases. In this study, we investigated the optimal temperature condition for transferring the liquid standards onto a standard adsorbent tube. As a result, keeping the impregnation temperature at $250^{\circ}C$ will be recommended in regard of the boiling points of multiple target analytes and the thermal stability of the adsorbent. We also demonstrated some problems associated with handling of a syringe used for transferring the standard solutions onto the adsorbent tubes, and a best way to get rid of the syringe problems was suggested. Finally, a number of field works were conducted to evaluate the performance of adsorbent sampling methods. Comparison of different adsorbent tubes, i.e. tube packed with single sorbent (Tenax) and double sorbents (Tenax with Carbotrap), revealed that 30 to 40% differences between the two groups, implying that sampling efficiency is depending on the volatility and the strength of adsorbents. However, duplicate precisions for VOCs sampling with a same type of adsorbent and at same flow rates appeared to be satisfactory to be all within 20%, which is a quality control guideline. Distributed volume precisions were also found to be within a guideline value, 25%, although the precision was in general inferior to the duplicate precision. The Korea indoor VOCs test method should be more refined and improved in many aspects, particularly procedure and instrumentation for preparing the standard samples and specification of quality control assessment.

• Journal of the Korean earth science society
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• v.28 no.7
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• pp.936-946
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• 2007

Analytical geopotential field in balance with the sectoral mode (the first symmetric mode with respect to the equator) of the Rossby-Haurwitz wave on the inclined rotation axis was derived in presence of superrotation background flow. The balanced field was obtained by inverting the divergence equation with the time derivative being zero. The inversion consists of two steps, i.e., the evaluation of nonlinear forcing terms and the finding of analytical solutions based on the Poisson's equation. In the second step, the forcing terms in the from of Legendre function were readily inverted due to the fact that Legendre function is the eigenfunction of the spherical Laplacian operator, while other terms were solved either by introducing a trial function or by integrating the Legendre equation. The balanced field was found to be expressed with six zonal wavenumber components, and shown to be of asymmetric structure about the equator. In association with asymmetricity, the advantageous point of the balanced field as a validation method for the numerical model was addressed. In special cases where the strength of the background flow is a half of or exactly the same as the rotation rate of the Earth it was revealed that one of the zonal wavenumber components vanishes. The analytical balanced field was compared with the geopotential field which was obtained using a spherical harmonics spectral model. It was found that the normalized difference lied in the order of machine rounding, indicating the reliability of the analytical results. The stability of the sectoral mode of Rossby-Haurwitz wave and the associated balanced field was discussed, comparing with the flrst antisymmetric mode.

• Journal of Korean Society for Atmospheric Environment
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• v.21 no.2
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• pp.191-204
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• 2005

Building and furnishing materials and consumer product are important sources of volatile organic compounds(VOCs) and other aldehydes in the indoor environment. Some available evidence indicates that VOCs can cause adverse health effects to the building occupants and contribute to some of the symptoms of what we call, 'Sick House Syndrome' in Korea. The aims of this study were to evaluate the efficiency of emission system and to investigate comparison of the emission characteristics of different building materials such as wall-papers, paints, and adhesives. The emission of VOCs from building materials were determined in the small chambers defining the temperature, relative humidity, and ventilation rate in this study. VOCs were sampled for 20 minutes using Tenax-TA tubes and analysed by GC-MS with thermal desorption. The stability of conditions for temperature and relative humidity in this small chamber system showed that the fluctuation of temperature was between 25.4$\pm$0.3$^{\circ}C$ and that of relative humidity was 50.2$\pm$0.6$\%$ under the airflow rate of 167 mL/min. The emission tests from building materials resulted in TVOC emission rates of 0.011 $\~$ 3.108 mg/m$^{2}$h after 7 days. The general wall-papers emitted toluene abundantly and the natural wall-papers mainly emitted n-butanol and a minor amount of alkanes compound such as n -tetradecane. The remainder consisted of toluene, m,p -xylene, and styrene. The paints mainly emitted toluene and the adhesives mainly emitted chloroform as well as toluene. As a result, this study is expected to suggest meaningful data for future studies in exposure control through selecting healthy building materials and for the establishment of guidelines for various building materials in Korea.

• Atmosphere
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• v.26 no.2
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• pp.227-241
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• 2016

This study investigated the cause of the heavy snowfall that occurred in the East Coast of Korea from 6 February to 14 February 2014. The synoptic conditions were analyzed using blocking index, equivalent potential temperature, potential vorticity, maritime temperature difference, temperature advection, and ground convergence. During the case period, a large blocking pattern developed over the Western Pacific causing the flow to be stagnant, and there was a North-South oriented High-to-Low pressure system over the Korean Peninsula because of this arrangement. The case period was divided into three parts based on the synoptic forcing that was responsible for the heavy snowfall; detailed analyses were conducted for the first and last period. In the first period, a heavy snowfall occurred over the entire Korean Peninsula due to strong updrafts from baroclinic instability and a low pressure caused by potential vorticity located at the mid-troposphere. In the lower atmosphere, a North-South oriented High-to-Low pressure system over the Eastern Korea intensified the easterly airflow and created a convergence zone near the ground which strengthened the upslope effect of the Taebaek Mountain range with a cumulative fresh snowfall amount of 41 cm in the East Coast region. In the last period, the cold air nestled in the Maritime Province of Siberia and Manchuria strengthened much more than that in the first half and extended to the East Sea. The temperature difference between the 850 hPa air and the SST was large and convective clouds developed over the sea. The highest cumulative fresh snow amount of 39.7 cm was recorded in the coastal area during this period. During the entire period, vertically oriented equivalent potential temperature showed neutral stability layer that helped the cloud formation and development in the East Coast. The 2014 heavy snowfall case over the East Coast provinces of Korea were due to: 1) stagnation of the system by blocking pattern, 2) the dynamic effect of mid-level potential vorticity of 1.6 PVU, 3) the easterly air flow from North-South oriented High-to-Low pressure system, 4) the existence of vertically oriented neutral stable layer, and 5) the expansion of strong cold air into the East Sea which created a large temperature difference between the air and the ocean.