• Journal of the Korean Society of Propulsion Engineers
• /
• v.18 no.4
• /
• pp.9-17
• /
• 2014

In this study, in order to improve the ignitability of high energy aluminum powder, natural oxide films (alumina) were chemically removed, and instead nickel coat was applied. We used an electroless plating for nickel coating and confirmed quantitatively and qualitatively a time-dependent degree of nickel coating through analysis of surface by SEM/EDS. We also conducted element analysis by XRD and thermal properties by TGA/DSC in air oxidizer environment. There results explained the ignition enhancement mechanism of the nickel-coated aluminum powder in air. The difference between coated and un-coated aluminum powder, the effectiveness of coated powder has better ignitability.

• Environmental Engineering Research
• /
• v.25 no.3
• /
• pp.345-355
• /
• 2020

This study has been carried out to evaluate the leaching behavior of Tunisian phosphogypsum (PG) tailings in Skhira city (southern Tunisia). Two PG samples, including old and freshly deposited samples, were characterized in terms of physical, geotechnical, mechanical, chemical and mineralogical properties. Special attention was paid to their leaching behavior when subjected to standard leaching tests. Our results indicated that both samples are mainly composed of more than 31.85% CaO and 31.4% SO3, indicating the predominance of gypsum. This was further confirmed by XRD patterns that revealed the presence of characteristic reflections of gypsum, brushite, quartz and Maladrite. Compressive strength after 90 d exceeded 769 kPa, but still lower than that of natural sand (1,800 kPa). Leaching test was proposed as an appropriate method to determine the released contaminants from PG. The obtained results showed that Fluorine and Phosphorus are the most released elements from PG with 40 and 30%, respectively. The released Se, Cd, and Zn were the only trace elements that exceeded the threshold limits. It seemed that leached element concentrations were independent aging or particle size of the PG. Based on the assessment of leaching behavior, an integrated management approach of the PG deposits was proposed.

• Analytical Science and Technology
• /
• v.17 no.4
• /
• pp.302-307
• /
• 2004

Determination of actinides in the environmental sample requires separation of each element. This procedure is tedious and time consuming. And also, the detection limits of some nuclides using alpha spectrometry are rather higher. To overcome the lower detection limit and complicated separation procedure, a simple analytical technique for the determination of actinide isotopes in the environmental samples was developed and applied to IAEA and NIST reference sediment samples. For the separation of actinides from matrix, anion exchange resin and TRU-spec extraction chromatography resin were used and chemical yields were obtained using natural uranium, thorium, $^{242}Pu$ and $^{243}Am$ tracers. For overcoming the higher detection limits of U and Th in alpha spectrometry, neutron activation analysis was applied. Using combined method, the detection limit was increased about 10 times. The activity values of each isotope were consistent with the reference values reported by IAEA and NIST.

• Korean Institute of Interior Design Journal
• /
• v.21 no.5
• /
• pp.254-263
• /
• 2012

This study found out the change of spacial form of detached house in Korea on a 10-year basis from 1980s though analysis on the architecture of each period. For the subject houses of this study, the detached houses introduced repeatedly as excellent cases in technical journals for architecture were collected among those completed by architects who designed numerous houses and a survey was conducted on 18 detached houses of 18 architects among the in urban style houses in Seoul and suburban style houses in the suburbs of Seoul. Through this study, it could be found that, as the morphological application of traditional architecture was settled with spatial concept, the external spatial form of the detached houses in Korea after 1980s was changed to westernized form but the internal spacial form had been continuously changing suitable to our emotion by reflecting the living habit and taste with the traditional attitude to perceive and accept the nature. As for the change in the forms of interior space, vertical space with more than two floors became common. Front porch and stair hall, which were located at the center of a house and became an important spacial element that overlapped family's moving line, changed to open and bright space that used transparent glass and increased the space to contact the open air, reflecting our living habit and taste that preferred the feeling of internal openness. A Private space, main room, was more segmented and luxurious, and a public space, living room, secured the independency by getting close to symbolic yard. As for the change in the form of exterior space, the form of façade window has been changing in its location and size and brought free images due to the advancement of technology and material. The shape of roofs was borrowed from western style and a lot of geometrical forms that break away from the concept of angle rater and eaves are appearing.

• Journal of Korea Water Resources Association
• /
• v.35 no.6
• /
• pp.753-762
• /
• 2002

In-stream vegetation is an essential element of a stream channel. Vegetation plays an important role in flood control and the natural environment in stream channels. This research investigates the relationship between in-stream vegetation and stream changes. This study investigates the distribution characteristic of vegetation in some rivers of Korea. Although there are many physical factors that cause changes to streams, this research verified that in-stream vegetation caused sediment deposition. A hydraulic model experiment was conducted. Tests were conducted in a simulated gravel bed stream (bed slope 1/200) with Phragmites japonica. The average diameter of the bed load used was 0.3 mm and 27 kg were uniformly supplied for 1 hour under same hydraulic conditions. The deposition and scouring as well as the change of flow differed according to the density and arrangement of the Phragmites japonica. In-stream vegetation and stream channel change are closely related because deposition and scouring affects the distribution of vegetation.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.12 no.4
• /
• pp.434-439
• /
• 2019

This paper proposed a control algorithm to compensate the delay time to improve the signal to noise, and the proposed control algorithm estimate the target information to apply the continuous wave radar equation. The proposed control algorithm improves the output signal of each array element bv multiplying the weight of the receive signal to the signal to noise ratio. Radar radiate a signal in spatial and the target information is estimated by the echoed signal from the target. But the signal in the wireless communication environment occurs the delay time due to the multipath which appear human and natural structures. It is difficult to accurately estimate the desired information because of the degradation for the system performance due to the interference signal and the signal distortion. The target information can be improved by compensating the delay signal to apply the weight to the received signal by using the uniform linear array antenna. As a simulation result, we show that the performance of the proposed control algorithm and the non-compensated delay time are compared. The proposed control algorithm proved that the target distance estimation information is improved.

• Industry Promotion Research
• /
• v.6 no.1
• /
• pp.33-42
• /
• 2021

Human beings have to do economic activities according to their aptitude and innate ability for a living. Human beings invest a lot of effort and spend a lot of time to gain social status and honor via economic activities. In order to make their lives more valuable as members of society, first they should know their own nature. Because it is important for choosing a job. From a study on the use of personality psychology of classical astrology, it was found that the native shows disposition and personality psychology differently depending on the change of yin and yang. Since human behavior is determined by natural personality and the influence of the surrounding environment, knowing personality makes people expect job choices and changes. Therefore, it is expected that it will be helpful to classify native's occupational aptitude of personality type from research on the use of personality psychology of classical astrology.

• Design Convergence Study
• /
• v.17 no.3
• /
• pp.1-19
• /
• 2018

Hand rehabilitation training tools are used in hospitals and at home for patients and users who require recovery of disabled hands and improvement in overall hand function. However, existing training tools are not organized into a progressive system, and they lead to repeatability operations over a period of time. As a result, patients feel free and cannot be motivated by rehabilitation, and continuous rehabilitation training is difficult. Based on this argument, the study combines one of the elements of the game called the "Cat's cradle" to enable the user to feel achievement through play and to achieve natural rehabilitation through unconsciousness. After examining the characteristics of the tool, the user's environment, the relevance of the Cat's cradle game to the training tool and to the patient's continued rehabilitation was established. And design elements were derived through professional interviews. Later, design guidelines and prototypes have been created to complement the problems associated with guidelines and prototypes by conducting usability testing and design element assessment.

• Smart Structures and Systems
• /
• v.32 no.5
• /
• pp.319-338
• /
• 2023

The study presents a new hybrid data-driven method by combining radial basis functions neural networks (RBF-NN) with the Jaya algorithm (JA) to provide effective structural health monitoring of arch dams. The novelty of this approach lies in that only one user-defined parameter is required and thus can increase its effectiveness and efficiency, as compared to other machine learning techniques that often require processing a large amount of training and testing model parameters and hyper-parameters, with high time-consuming. This approach seeks rapid damage detection in arch dams under dynamic conditions, to prevent potential disasters, by utilizing the RBF-NNN to seamlessly integrate the dynamic elastic modulus (DEM) and modal parameters (such as natural frequency and mode shape) as damage indicators. To determine the dynamic characteristics of the arch dam, the JA sequentially optimizes an objective function rooted in vibration-based data sets. Two case studies of hyperbolic concrete arch dams were carefully designed using finite element simulation to demonstrate the effectiveness of the RBF-NN model, in conjunction with the Jaya algorithm. The testing results demonstrated that the proposed methods could exhibit significant computational time-savings, while effectively detecting damage in arch dam structures with complex nonlinearities. Furthermore, despite training data contaminated with a high level of noise, the RBF-NN and JA fusion remained the robustness, with high accuracy.

• The Journal of the Petrological Society of Korea
• /
• v.17 no.1
• /
• pp.16-35
• /
• 2008

We study metamorphism of metasedimetary rocks and origin and evolution of leucogranite form Samcheok area, northeastern Yeongnam massif, South Korea. Metamorphic rocks in this area are composed of metasedimentary migmatite, biotite granitic gneiss and leucogranite. Metasedimentary rocks, which refer to major element feature of siliclastic sediment, are divided into two metamorphic zones based on mineral assemblages, garnet and sillimanite zones. According to petrogenetic grid of mineral assemblages, metamorhpic P-T conditions are $740{\sim}800^{\circ}C$ at $4.8{\sim}5.8\;kbar$ in the garnet zone and $640-760^{\circ}C$ at 2.5-4.5kbar in sillimanite zone. The leucogranite (Imwon leucogranite) is peraluminous granite which has high alumina index (A/CNK=1.31-1.93) and positive discriminant factor value (DF > 0). Thus, leucogranite is S-type granite generated from metasedimentary rocks. Major and trace element diagram ($R_1-R_2$ diagram and Rb vs. Y+Nb etc.) show collisional environment such as syn-collisional or volcanic arc granite. Because Rb/sr ratio (1.8-22.9) of leucogranites is higher than Sr/Ba ratio (0.21-0.79), leucogranite would be derived from muscovite dehydrate melting in metasedimentary rocks. Leucogranites have lower concentration of LREE and Eu and similar that of HREE relative to metasedimentary rocks. To examine difference of REEs between leucogranites and metasedimentary rocks, we perform modeling using volume percentage of a leucogranite and a metasedimenatry rock from study area and REE data of minerals from rhyolite (Nash and Crecraft, 1985) and melanosome of migmatite (Bea et al., 1994). Resultants of modeling indicate that LREE and HREE are controlled by monazites and garnet, respectively, although zircon is estimated HREE dominant in some leucogranite without garnet. Because there are many inclusions of accessary phases such as monazite and zircon in biotites from metasedimentary rocks. leucogranitic magma was mainly derived from muscovite-breakdown in metasedimenary rocks. Leucogranites can be subdivided into two types in compliance with Eu anomaly of chondrite nomalized REE pattern; the one of negative Eu anomaly is type I and the other is type II. Leucogranites have lower Eu concetnrations than that of metasedimenary rocks and similar that of both type. REE modeling suggest that this difference of Eu value is due to that of components of feldspars in both leucogranite and metasedimentary rock. The tendency of major ($K_2O$ and $Na_2O$) and face elements (Eu, Rb, Sr and Ba) of leucogranites also indicate that source magma of these two types was developed by anatexis experienced strong fractionation of alkali-feldspar. Conclusionally, leucogranites in this area are products of melts which was generated by muscovite-breakdown of metasedimenary rock in environment of continetal collision during high temperature/pressure metamorphism and then was fractionated and crystallized after extraction from source rock.