• Journal of the Korean Operations Research and Management Science Society
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• v.3 no.2
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• pp.75-90
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• 1978

The objective of this paper is to demonstrate how System Dynamics Approach may be used to develop new ways of analyzing and projecting manpower requirements and resources. For this purpose, a System Dynamics Model is presented as an example. An examination of the model will show that a System Dynamics modeling approach is an innovative and useful tool for manpower policy analysis and planning. Second, with minor modifications, the model may be used for manpower policy analysis and planning for any skilled personnel in Korea. For example, a similar model nay be built for engineers to analyze the effects of alternative policies about engineering education, sur as the number of available places in the various institutions of training, scholarships and loans, and the duration of training. An engineer's model may also be used to make the projections of the supply and requirements of engineers in the future according to various alternative assumptions where each assumption represents a policy option.

• Applied Science and Convergence Technology
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• v.24 no.3
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• pp.47-52
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• 2015

The correlation between admittance and dielectric spectroscopy of dielectric relaxation in lead scandium noibate, have been investigated. Lead scandium niobate, with composition $PbSc_{0.5}Nb_{0.5}O_3$, was prepared by conventional solid state synthesis. Conductance Y'(G), susceptance Y"(B) and capacitance C of lead scandium niobate as a function of frequency and temperature were measured. From the temperature-dependence of RLC circuit, insight into physical significance of the dielectric properties of lead scandium niobate is obtained. The relative strong frequency dependent of dielectric properties in lead scandium niobate is observed, and the phase transition occurred at a broad temperature region. Also, the value of critical exponent ${\gamma}$=1.6 showed on heating process. The long relaxation times part enlarged diffuse by conductivity effects with increasing temperature, and the ordering between $Sc^{3+}$ and $Nb^{5+}$ in PSN influences complex admittance and dielectric properties. Confirmed the typical characteristic of lead-type relaxor in the Raman spectra of lead scandium niobate and major ranges are between 400 and $900cm^{-1}$.

• Applied Science and Convergence Technology
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• v.25 no.4
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• pp.77-80
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• 2016

The $PbSc_{1/2}Nb_{1/2}O_3$ ceramics at a relatively low temperature of $1300^{\circ}C$ was successful synthesized. Solid state reaction of two-step process is not necessary. The dielectric constant, dielectric loss and admittance of ceramic samples were determined. The pyroelectric characteristics are in good agreement with the dielectric properties. Ferroelectric properties of well-formed the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics are in agreement with broad distribution of relaxation phenomenon. Relatively strong frequency dependent of dielectric constant is observed at about $110^{\circ}C$. The distinct thermal hysteresis was observed in the measurement of the dielectric constant and dielectric loss. The critical exponents of during cooling and heating measurements in the $PbSc_{1/2}Nb_{1/2}O_3$ ceramics were 1.14 and 1.59 at 1 kHz, respectively.

• Applied Science and Convergence Technology
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• v.24 no.6
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• pp.215-218
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• 2015

A pyroelctric properties of Ni(x)-doped PMNT systems were analyzed. Modified PMNT samples were prepared using the columbite structure method. Pyroelectric current, polarization, dielectric constant and dissipation factor of Ni-doped PMNT samples were measured as a function of temperature. By adding a small amount of NiO, pyroelectricity of PMNT is increased. Unlike the normal $ABO_3$ ferroelectric, Ni-doped PMNT showed properties for relaxor ferroelectric of causing the successive phase transition over a wide temperature. The optimum conditions for obtaining compositions with improvement ferroelectric properties are a nominal addition of 0.02 mole% Ni. Also, Ni-doped PMNT ferroelectric showed excellent pyroelectric figures of merit in the vicinity of room temperature. The pyroelectric coefficient ($0.00524C/m^2K$ at $25^{\circ}C$) and figures of merit ($F_v{\sim}0.039m^2/C$ and $F_d{\sim}0.664{\times}10^{-4}Pa^{-1/2}$) of composition PMNT with 0.02 mole% Ni are comparable to the earlier reports on lead-type pyroelectrics.

• Structural Engineering and Mechanics
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• v.85 no.4
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• pp.461-468
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• 2023

Edible coatings are one of the most innovative methods to preserve the quality and increase the shelf life of fresh fruits and vegetables. A successful edible coating should have a barrier against gases, especially oxygen and water vapor, and have good surface characteristics. Today, chitosan coating is widely used due to its properties, such as non-toxic, biodegradable, and biocompatibility. Is. Coating the surface of fruits and vegetables with chitosan increases shelf life due to reducing weight loss and reducing respiration rate and also reduces decay due to its antimicrobial and anti-fungal effect. This work discusses the effect of using chitosan coating containing chamomile extract to increase fresh vegetables'shelf life. In addition to increasing the shelf life of vegetables, this method can be used as a solution for the economic management of human resources. The results of this method confirm the successful synthesis of these nanoparticles, and the results of applying this food coating on vegetables have been successful. They have increased the shelf life of vegetables such as basil and spinach.

• Steel and Composite Structures
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• v.45 no.1
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• pp.147-157
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• 2022

This study assessed the compressive and tensile strengths and modulus of elasticity of waste polyethylene terephthalate (PET) using the ASTM standard tests. In addition, short carbon and glass fibers were mixed with waste PET to examine the improvements in ductility and strength during compression. The bonding was examined via field-emission scanning electron microscopy. The strength degradation of the waste PET tested under UV was 40-50%. However, it had a compressive strength of 32.37 MPa (equivalent to that of concrete), tensile strength of 31.83 MPa (approximately ten times that of concrete), and a unit weight of 12-13 kN/m3 (approximately half that of concrete). A finite element analysis showed that, compared with concrete, a waste PET pile foundation can support approximately 1.3 times greater loads. Mixing reinforcing fibers with waste PET further mitigated this, thereby extending ductility. Waste PET holds excellent potential for use in foundation piles, especially while mitigating brittleness using short reinforcing fibers and avoiding UV degradation.

• Korean Journal of Applied Biomechanics
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• v.21 no.2
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• pp.153-159
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• 2011

The purpose of this study was to develop an innovative training model and method to improve the posture and motion, while pulling up during weight lifting by evaluating the problems of Korean weight lifters performing this motion. To investigate the effectiveness of the new training method substitute members of the Korean national weight lifting team performed both the original pull up technique and new pulling training technique while kinetics and kinematics were recorded. For this study, the first phase of the new training method is more appropriate than the original training with the pull up drop slow deadlift to the knee joint. For the second phase, the new training motion is deemed to be more effective than the current box deadlift motion. Also, this new motion corrects the posture as there is more anterior hip joint motion(about 10 cm) and the knee flexes to about 120 degrees. For the third phase, starting about 10cm above the knee the box snatch high pull up is identified as a more suitable training method. For the forth phase, the box top snatch method is judged to be a more effective training method than the original top snatch training method.

• Journal of The Korean Association For Science Education
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• v.24 no.1
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• pp.76-89
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• 2004

Recent studies of science and technology "in-the-making" revealed that the process of designing material artifacts is not a straightforward application of prior images or theories by one (or more) person(s) isolated from his or her (their) environment. Rather, designing is a process contingent on the social and material setting for both engineering designers and students. Over the past decade, designing technological artifacts has emerged as an important learning environment in science classrooms. Through the analyses of a large database concerning an innovative simple machines curriculum for sixth-and seventh-grade students, we accumulated valid evidence for the nature of the designing process and science learning through it. In this paper, we show that design actions intertwine with the transformation of the objectified raw materials and artifact, the designer collective, and the mediating tools enabling that transformation, which constitute the elements of an activity from the perspective of cultural-historical activity theory. We conceptualize the continuous change of relation between material artifacts, designers, and tools throughout the design activity as co-evolution. Two episodes were selected to exemplify synchronic and diachronic change of relations inherent in co-evolving activity system. Finally, we discuss the implications of co-evolution during design activity for science learning.

• Journal of Engineering Education Research
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• v.5 no.1
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• pp.19-26
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• 2002

This paper presents a virtual laboratory system which can be creating efficiencies in the learning process. The proposed virtual laboratory system for electrical circuits provides interactive learning environment under which the multimedia capabilities of world-wide web can be enhanced. The virtual laboratory system is implemented to describe the on-campus laboratory, the learners can obtain similar experimental data through it. In the proposed virtual laboratory system, every activity occurred in the virtual laboratory will be recorded on database and printed it out on the preliminary report form. The database connectivity is made by PHP and the virtual laboratory environment is set up slightly differently for each learner The virtual laboratory system is composed of four important components : Principle classroom, Simulation classroom, Virtual experiment classroom and Management system. Learning efficiencies as well as faculty productivity are increased in this innovative teaching and learning environment.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.14 no.5
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• pp.1-16
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• 2011

This study was intended to develop and suggest 'residents-driven and citizen-participatory restoration procedures' for degraded ecosystems in BaigDooDaeGahn. With some concerns of current engineering-focused restoration approach for damaged ecosystem, the proposed procedures were designed based on the analysis of several case studies on citizen participatory projects such as the Habitat Movement, the Taean tidal wetland restoration effort in Korea, and some historical and innovative cases in Japan and the United States. The suggested procedures were considered to be a dialectical spiral model which was consisted of two goal axis, six system elements, four developmental stages, and five restoration steps. The new system and procedures were applied to damaged farmland areas (about 0.3 ha) on the top of BaigDooDaeGahn, Kangneung city with participation of more than 100 local residents and a dozen of citizen from Seoul. Both high level of possibilities and some barriers for future extended application were identified and adopted for the final version of the proposed procedures for ecological restoration.