• Nuclear Engineering and Technology
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• v.51 no.8
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• pp.1964-1969
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• 2019

The safety and efficiency of nuclear reactors largely depend on the monitoring and control of nuclear radiation. Due to the unique nuclear-physical characteristics, Hf is one of the most promising materials for the manufacturing of the control rods and the emitters of neutron detectors. It is proposed to use the Compton neutron detector with the emitter made of Hf in the In-core Instrumentation System (ICIS) for monitoring the neutron field. The main advantages of such a detector in comparison the conventional β-emission sensors are the possibility of reaching of a higher cumulative radiation dose and the absence of signal delays. The response time of the detection is extremely important when a nuclear reactor is operating near its critical operational parameters. Taking Hf as an example, the general principles for calculating the chains of materials transformation under neutron irradiation are reported. The influence of ^179m1Hf on the Hf composition changing dynamics and the process of transmutants' (Ta, W) generation were determined. The effect of these processes on the absorbing properties of Hf, which inevitably predetermine the lifetime of the detector and its ability to generate a signal, is estimated.

• KOREAN JOURNAL OF PACKAGING SCIENCE & TECHNOLOGY
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• v.12 no.1
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• pp.35-40
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• 2006

Cushioning systems, which are cushion material and its designed configuration, are important to protect fragile items since they act as buffers between the impact force and the fragile product. As cushioning materials, several plastic foams are commonly used in industry. However, the utilization of the plastic material has been causing a solid waste problem and pollution. Thus, as an alternative cushion material to the plastic foams, a corrugated cushion, which is considered environmentally friendly and cheap material, was put into drop tests and its impact shock attenuation was investigated. Flat and free drop data were recorded and compared to the dynamic shock of EPS cushion. In addition, the mathematical model of the shock attenuation of the corrugated cushion was developed. The result showed that the corrugated cushion gave an excellent protection for items that were subjected to the limited number of drops. There was no significant difference of the shock absorbing ability between the EPS and corrugated cushions. Energy density model of cushioning material successfully explained the mechanical behavior and fatigue of the corrugated cushions.

• Korean Journal of Human Ecology
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• v.13 no.6
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• pp.985-995
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• 2004

The purpose of this study is to provide useful footwear information for manufacturers and teenagers so that they can produce or purchase proper footwear that would minimize discomfort. For this study, 486 junior high school students were surveyed with a questionnaire. SPSS WIN10 was used to process a statistical analysis such as ferq., factor analysis, t-test, ANOVA(LSD), crosstab, and coefficient correlation. The results are as follows: A significant difference existed between male and female students in purchasing footwear and using evaluation criteria. When they wear shoes for a long time, they usually experience numbness in toes, blisters, heel, bottom on the feet and peeled skin. Female students experienced more foot injuries than males. There were meaningful correlations among purchasing, evaluation criteria, and satisfaction of footwear. Providing proper information is believed very important for teenagers in choosing right footwear. Footwear manufacturers should help them produce suitable shoes, and further help them establish different marketing strategies. To ease the foot discomfort, shoes should be developed with various widths and sizes. Shock absorbing soles and more flexible materials are also necessary.

• KIEAE Journal
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• v.10 no.3
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• pp.51-56
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• 2010

The sound insulation performance is one of the important factor that determined the amenity of housing life in residential building. Especially, Apartment house represents a korea habitation. So the importance of privacy and noise problems between habitable rooms are emphasized in these habitation. This study investigates and find a problem of sound insulation performance of partition wall of the apartment house in current state. The measurements were carried out in apartment house with and without a stair hall. And the measurements also carried out in current state and installing a sound absorbing material in receiving room and changing a front door and installing a inner door. In spite of the same partition wall, difference results were showed according to the stair hall. It is appeared that sound insulation performance without stair hall is 6-7dB(Dw) higher than that with stair hall. In case of without stair hall, sound insulation performance is Dw 49 for single number quantity for airbone sound. And In case of changing a front door and installing a inner door sound insulation performance is Dw 57 for single number quantity for airbone sound. The Results of measuring on the changes a front door and installed a inner door indicated that the flanking sound through front door influenced the sound insulation performance.

• Journal of electromagnetic engineering and science
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• v.13 no.2
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• pp.73-85
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• 2013

In this paper we present an alternative approach to addressing the problem of designing cloaks for radar targets, which have been dealt with in the past by using the transformation optics (TO) algorithm. The present design utilizes realistic materials, which can be fabricated in the laboratory, and are wideband as well as relatively insensitive to polarization and incident angle of the incoming wave. The design strategy, presented herein, circumvents the need to use metamaterials for cloak designs that are inherently narrowband, dispersive and highly sensitive to polarization and incident angle. A new interpretation of the TO algorithm is presented and is employed for the design of radar cross section-reducing absorbers for arbitrary targets, and not just for canonical shapes, e.g., cylinders. The topic of performance enhancement of the absorbers by using graphene materials and embedded frequency structure surfaces is briefly mentioned. The design procedure for planar absorbing covers is presented and their performance as wrappers of general objects is discussed. A number of test cases are included as examples to illustrate the application of the proposed design methodology, which is a modification of the classical TO paradigm.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2013.10a
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• pp.338-345
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• 2013

Induction motors play an increasing importance in industrial manufacturing. Therefore, the state monitoring systems also have been considering as the key in dealing with their negative effect by absorbing faulty symptoms in motors. There are numerous proposed systems in literature, in which, several kinds of signals are utilized as the input. To solve the multiple faults problem of induction motors, like the proposed system, the vibration signals is good candidate. In this study, a new signal processing scheme was utilized, which transforms the time domain vibration signal into the spatial domain as an image. Then the spatial features of converted image then have been extracted by applying the dominant neighbourhood structure (DNS) algorithm. In addition, these feature vectors were evaluated to obtain the fruitful dimensions, which support to discriminate between states of motors. Because of reliability, the conventional one-against-all (OAA) multi-class support vector machines (MCSVM) have been utilized in the proposed system as classifier module. Even though examined in severity levels of signal-to-noise ratio (SNR), up to 15dB, the proposed system still reliable in term of two criteria: true positive (TF) and false positive (FP). Furthermore, it also offers better performance than five state-of-the-art systems.

• Structural Engineering and Mechanics
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• v.51 no.4
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• pp.685-705
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• 2014

This paper presents a new formulation for forward scalar wave simulations in semi-infinite media. Perfectly-Matched-Layers (PMLs) are used as a wave absorbing boundary layer to surround a finite computational domain truncated from the semi-infinite domain. In this work, a hybrid formulation was developed for the simulation of scalar wave motion in two-dimensional PML-truncated domains. In this formulation, displacements and stresses are considered as unknowns in the PML domain, while only displacements are considered to be unknowns in the interior domain. This formulation reduces computational cost compared to fully-mixed formulations. To obtain governing wave equations in the PML region, complex coordinate stretching transformation was introduced to equilibrium, constitutive, and compatibility equations in the frequency domain. Then, equations were converted back to the time-domain using the inverse Fourier transform. The resulting equations are mixed (contain both displacements and stresses), and are coupled with the displacement-only equation in the regular domain. The Newmark method was used for the time integration of the semi-discrete equations.

• Proceedings of the Korean Society for Emotion and Sensibility Conference
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• 2001.05a
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• pp.147-155
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• 2001

Nasucon lamp and Russian ones, which are coated with some special materials on the glass bulb, gave good clinical results for a cancer therapy. They are experimentally studied with Automatic Bioelectric Response Recorder on the six placements of the electrodes (two feet, two hands and two foreheads). They reduced the current rather than the control (natural) state. However infrared lamp and Chinese God light did not reduced the value current. Hemoglobin in blood. Brown gas, Ti$_3$SiC$_2$ and Nasucon have planar crystallizing $\pi$-bonding bonding layer and covalent bonding one in sequence commonly and thus the alternating magnetic fields are protected. Nasucon lamp and Russian ones utilized electric bulbs in order to generate alternating magnetic fields and to produce absorbing force.

• 한국신재생에너지학회:학술대회논문집
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• 2011.05a
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• pp.119.2-119.2
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• 2011

Dye-sensitized solar cells (DSSC) are currently attracting wide spread academic and commercial interest for the conversion of sunlight into electricity because of their easy manufacturing process and high efficiency. The solar energy conversion efficiencies of DSSC are strongly dependent on dye molecules adsorbed on the TiO2 surface which used for photosensitization of sun light, since an excited state of dye could inject an electron into the conduction band of semiconductor. We have developed novel organic dyes which have phenothiazine moieties as an electron donor in their charge-transfer chromophore for application of DSSCs. We had synthesized a series of phenothiazine derivatives which have different wave length absorbing chromophore in the molecule with high molar extinction coefficient. The photovoltaic performance of DSSC composed of organic chromophores with broad wavelength absorption property were measured and evaluated by comparison with that of pristine ruthenium dye.

• Electrical & Electronic Materials
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• v.7 no.1
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• pp.15-24
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• 1994

For increasing the insulating proper-ties and the reliability of composite materials due to environmental aging, the electrical and mechanical characteristics of moisture absortion specimens and moisture desorption specimens were investigated. After moisture absorption wt% and moisture desorption wt% increased with time, a state of saturation arrived subsequent to a constant time. Moisture absorption constants with the layers of glass fiber showed 0.0117 in 1 layer, 0.0123 in 2 layers and 0.0152 in 3 layers. Electrical and mechanical characteristics dropped significantly with moisture absorbing in composite materials. Although moisture dried completly at 70.deg. C, it is impossible to obtain the electrical and mechanical characteristics before moisture absorption. Many defaults by moisture in composite materials exist at interface between epoxy matrix and filler.