• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.620-627
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• 2019

In this study, ignition delay characteristics of various bio aviation fuels (Bio-ADD, Bio-6308, Bio-7720) produced by HEFA process using different raw materials were compared and analyzed. In order to confirm the feasibility of applying bio aviation fuel to actual system, ignition delay characteristics of petroleum-based aviation fuel (Jet A-1) and blended aviation fuel (50:50, v:v) also analyzed. Ignition delay time of each aviation fuel was measured by using CRU, surface tension measurement and GC/MS and GC/FID analysis were performed to interpret the results. As a result, ignition delay time of Jet A-1 was the longest at all temperature because it contains aromatic compounds about 22.8%. The aromatic compounds can produce benzyl radical which is thermally stable and has low reactivity with oxygen during decomposition process. In the case of bio aviation fuels, ignition delay times were measured similarly because the ratio of n-paraffin/iso-paraffin constituting each aviation fuel is similar (about 0.12) and the composition ratio of cycloparaffin also has no difference. In addition, ignition delay times of blended aviation fuels (50:50, v:v) were measured close to the mean value those of each fuel so it was confirmed that it can be applied without any changing or improving of existing system.

• Clean Technology
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• v.25 no.3
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• pp.238-244
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• 2019

In this study, the ignition characteristics of petroleum-based aviation fuel (Jet A-1), bio aviation fuel (Bio-6308), and blended aviation fuel (50:50, v:v) were analyzed in accordance with change of temperature and pressure. The ignition delay time of each aviation fuel was measured by combustion research unit (CRU) and the compositions of the fuels were analyzed by GC/MS and GC/FID for qualitative and quantitative results. From the results, it was confirmed that the ignition delay times of all aviation fuels were shortened with increasing temperature and pressure. In particular, the effect of temperature was larger than the effect of pressure. Also, the ignition delay time of Jet A-1 was the longest at all measurement conditions, and it was judged that this result is because of the structurally stable characteristics of the benzyl radical generated during the oxidation reaction of the aromatic compound (about 22.48%) in Jet A-1. Also, it was confirmed that Jet A-1 had no section where the degree of shortening of ignition delay time was decreased by increasing temperature, which was because the benzyl radical inhibits the response that can affect the negative temperature coefficient (NTC). The ignition characteristics of blended aviation fuel (50:50, v:v) showed a similar tendency to those of Jet A-1, rather than to those of Bio-6308, so that the blended aviation fuel (50:50, v:v) can be applied to the existing system without any change.

• Convergence Security Journal
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• v.18 no.3
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• pp.113-122
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• 2018

The issue of security on the Korean peninsula is facing the greatest upheaval in 2018 with the inter-Korean summit and the US-North Korea summit. North Korea has pursued the parallel policy developing military and economic at the same time. However, North Korea is changing its route to give up nuclear weapons and focus on the economy through summit talks. Since the change in North Korea is similar to that of Libya in the past, it is necessary to analyze why North Korea is trying to abandon its nuclear program and how the process is flowing compared to the case of Libya. The Libya model was constructed and analyzed in terms of international and domestic perpectives and recognition of the situation by leadership. North Korea's nuclear policy was evaluated based on the Libya model. The nuclear development of Libya and North Korea has caused diplomatic and economic pressures from the international community and ultimately led to instability of the regime. Two countries have tried to abandon nuclear program in order to solve the instability of the regime, also gain the economic reward insead. Libya took economic benefits and secured some of the stability of the regime, but the regime collapsed under the wave of democracy due to the influx of foreign capital and ideas. North Korea will seek diplomatic and economic gains with the example of Libya, but will try to limit as much as possible the culture of democracy and the full opening that can be incidental.

• The Journal of the Acoustical Society of Korea
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• v.38 no.1
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• pp.56-65
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• 2019

The Indo-Pacific bottlenose dolphins (Tursiops aduncus) are a toothed whale using echolocation clicks and have been studied continuously abroad. However, most studies on this whale's clicks were performed about captive animals and, in Korea, only the studies of the whistle sounds of this animal were done. In this paper, acoustic characteristics of clicks were analyzed about the free-ranging Indo-Pacific bottlenose dolphins living in the coast of the Jeju Island. Acoustic parameters such as signal duration, 1st and 2nd peak frequency, 3 dB and 10 dB bandwidth for acoustic characteristics were calculated and compared with those of Australian species. As a result, the signal durations had average of $38{\mu}s$ and most clicks were within range of $20{\mu}s-60{\mu}s$. The two types of bandwidths showed both narrowband and broadband characteristics, and bimodal signal characteristics were confirmed through the 1st peak frequencies(average of $96kHz{\pm}18kHz$) and the 2nd peak frequencies(average of $69kHz{\pm}19kHz$).

• Convergence Security Journal
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• v.21 no.1
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• pp.201-208
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• 2021

The purpose of this study is to investigate reunification perception among groups with different cognitive bias(anchoring bias) through empirical studies. This study assumes that cognitive bias occurs according to the content of N. Korea provided in school education, and that the cognitive bias formed in youth creates a difference in perception of N. Korea and reunification. For empirical study, a survey of reunification awareness conducted by the Institute for Peace an Unification Studies-Seoul National University was used, and the two groups are divided into A-group that chose "anti-communism or security" and B-group that did "reunification interests, multi-culturalism and understanding North Korea" according to N. Korea content which was encountered in school education during adolescence. A-group recognized N. Korea as a hostile target even after becoming an adult, while B-group regarded N. Korea as a one of dialogue and cooperation. This analysis illustrates the existence of cognitive bias between the two groups because of N. Korea content which was given in school education. A-group had a lower percentage than B-group in terms of the benefits of reunification to S. Korea and the need for more dialogue and compromise with N. Korea. However, there was no difference between two groups in terms of acceptance of N. Korean defectors. This research result could be a reference to the direction of school education policies relating to reunification in that early school education affects reunification awareness and perception related with N. Korea even in adulthood.

• Korean Chemical Engineering Research
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• v.59 no.2
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• pp.296-303
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• 2021

The objective of this study is to investigate the applicability of a Cu-supported honeycomb catalyst as a catalyst for decomposition of a low toxic liquid propellant based on ammonium dinitramide (ADN). A mixture of copper, lanthanum, and alumina was supported on the honeycomb support by wash coating to prepare a Cu-La-Al/honeycomb catalyst. We elucidated that the effect of metal loading on the physicochemical properties of Cu-La-Al/honeycomb catalyst and catalytic performance in decomposition of the ADN-based liquid propellant. As the number of wash coatings increased, the amount of active metal Cu was increased to 4.1 wt%. The BET surface area of the Cu-La-Al/honeycomb catalyst was in the range of 3.1~4.1 ㎡/g. The micropores were hardly present in Cu-La-Al/honeycomb catalysts, however, the mesopores and macropores were well developed. The Cu (2.7 wt%)-La-Al/honeycomb catalyst exhibited the highest activity in the decomposition of the ADN-based liquid propellant, which is attributed to the largest surface area, the largest pore volume, and the well-developed mesopores and macropores.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.6
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• pp.251-257
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• 2021

An underwater platform operating a passive sonar needs to acquire the target position to perform its mission. In an environment where sea-floor reflections exist, the position of a target can be estimated using the difference in the arrival time between the signals received through multipaths. In this paper, a method of localization for passive sonar is introduced, based on the EKF (Extended Kalman Filter) using the multipath time difference of arrival in underwater environments. TMA (Target Motion Analysis) requires accumulated measurements for long periods and has limitations on own-ship movement, allowing it to be used only in certain situations. The proposed method uses an EKF, which takes measurements of the time differences of the signal arrival in multipath environments. The method allows for target localization without restrictions on own-ship movement or the need for an observation time. To analyze the performance of the proposed method, simulation according to the distance and depth of the target was performed repeatedly, and the localization error according to the distance and water depth were analyzed. In addition, the correlation with the estimated position error was assessed by analyzing the arrival time difference according to the water depth.

• Journal of Convergence for Information Technology
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• v.11 no.6
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• pp.262-269
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• 2021

The Ministry of National Defense is re-establishing the role of the Army in accordance with the defense reform and is promoting the Warrior Platform, a next-generation individual combat system. The Warrior Platform project is divided into three stages and is being promoted. In the first stage, the quality and performance of individual items are improved, in the second stage, items between system development are integrated, and in the third stage, the combat capability is maximized by developing an integrated unit weapon system. In this paper, detailed sub-items for the five essential required competencies (survival, lethality, mobility, sustainability, Communication) that are considered for building an effective warrior platform are presented. We also present a plan that can be used to prepare a specific master plan for the Army's Warrior Platform project by using Analytic Hierarchy Process(AHP) and selecting the priority of the five required capabilities and detailed sub-items for different unit types. As a result of analyzing the priorities of the four types of units with different mission types, we find that there are differences for each unit. These results are expected to be used as useful reference materials for setting the future direction for the development of warrior platform.

• Journal of Digital Convergence
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• v.19 no.7
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• pp.155-162
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• 2021

The purpose of this study is to investigate effects of management support for health and safety on workers' safety perception. Since the 1990s, Korea's national competitiveness has been rising rapidly, but efforts to prevent and cope with industrial accidents are still insufficient. Particularly there is a big movement to strengthen corporate responsibility for serious accidents in the 2020s. In this study structural equation model(SEM) was constructed and quantitatively analyzed in order to know how management's support affects the organization, system, and communication related to safety and health in the company, and ultimately how it has an effect on workers' safety perception. 4,169 questionnaires conducted by the Institute for Occupational Safety and Health were used as observation variables, and 5 hypotheses were established and were verified in SEM. As management support increases, organization & institution for a safe workplace, communication related with safety and health within the company become more active. Finally management support has a positive effect on workers' safety perception. The results of this study imply that management needs to increase awareness of the importance of safety and health before all measures such as organizations, institutions, and communication related to safety and health.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.2
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• pp.67-75
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• 2021

The structure of universities needs to be adjusted and reformed to cope with the decrease in admission resources and the quality of education due to the low birth rate and aging population. Such a policy is receiving much attention. To analyze the relative efficiency of private universities in Korea from the perspective of resource and performance, this study evaluated the efficiency of private university operation by applying a DEA(Data Envelopment Analysis) technique. The DEA measurements were compared with the diagnosis results of the department of education (Government) in 2018. The input and output variables used in the research analysis were utilized by the university's notification materials (public disclosure information). An analysis of the operational efficiency showed that 48% (12 universities) of the 25 DMUs (Decision Making Unit) were efficient for DEA-BCC models and that some of the capacity-building universities were operating efficiently. In addition, the DEA analysis found ways to improve inefficient groups through DEA-Additive results. This paper can be meaningful because it confirmed the relative efficiency of private universities and suggested improvement directions through the DEA method, which is characterized by the simultaneous consideration of various input and output factors. This will help apply the limited resources related to the input and output elements of each university.