• Computers and Concrete
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• v.17 no.5
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• pp.613-628
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• 2016

In this study, the influence of coarse aggregate size and type on chloride penetration of concrete was investigated, and the grey correlation analysis was applied to find the key influencing factor. Furthermore, the proposed 6-10-1 artificial neural network (ANN) model was constructed, and performed under the MATLAB program. Training, testing and validation of the model stages were performed using 81 experiment data sets. The results show that the aggregate type has less effect on the concrete permeability, compared with the size effect. For concrete with a lower w/b, the coarse aggregate with a larger particle size should be chose, however, for concrete with a higher w/c, the aggregate with a grading of 5-20 mm is preferred, too large or too small aggregates are adverse to concrete chloride diffusivity. A new idea for the optimum selection of aggregate to prepare concrete with a low penetration is provided. Moreover, the ANN model predicted values are compared with actual test results, and the average relative error of prediction is found to be 5.62%. ANN procedure provides guidelines to select appropriate coarse aggregate for required chloride penetration of concrete and will reduce number of trial and error, save cost and time.

• Journal of the Korean Society of Systems Engineering
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• v.10 no.1
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• pp.33-41
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• 2014

New design concept of Reactor Coolant System (RCS) including a reactor assembly for the SMR is introduced in this work. An exploration of new type of reactor that is advanced from proposed SMRs is performed by using systems engineering approach. In this point of view project structured on three main phases; needs analysis (NA), concept exploration (CE), and concept definition (CD). Main objectives as an output of the CE stage are a small size, low cost, shortening the schedule, and enhancing safety. The SMRs usually have a small size requirement. In order to meet the size requirement and to achieve a productivity, in other words, easiness to manufacture, this paper suggests an integrated PWR design concept through researching predecessors. Although the integrated PWR concept provides many advantages, it has disadvantages that composite of maintenance and a low availability problem. Therefore, this paper comes up with a run-to-fail design concept based on modular design to address the maintenance problem and to maximize the availability of SMRs as well as to be compatible with the overall-SMRs including Barge Mounted(BM)type.

• Journal of Korea Foundry Society
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• v.18 no.6
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• pp.541-549
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• 1998

Microstructural characteristics of hypereutectic Al-Si alloys during reheating at semi-solid temperature have been investigated. The size and morphology of primary Si particles in wedge-type mold-cast ingot has been compared with hot-rolled sheet and Si particulate reinforced Al composite. Effects of P and Sr addition on the morphological changes of primary Si particles have been also investigated. Observation of the solidification microstructures of the wedge-type mold-cast ingot at different cooling rates showed that alloying elements such as P and Sr affect the morphology of Si particles, especially in the area solidified at a slow cooling rate. Negligible change in the size of primary crystals was observed after reheating experiment, but ${\alpha}-halo$ formed around the Si particles and fine particles of Si precipitated in the surrounding area of the Si particles. In addition, there seemed to be no coarsening with increasing of holding time and the region of ${\alpha}-halo$ being decreased. Nucleation and recrystallization was accelerated with addition of alloying elements during hot rolling resulting in a decrease of primary Si particle size. In the case of extruded specimens, morphological change of primary Si particles was not observed after reheating. No ${\alpha}-halo$ formation was observed in Si reinforced Al composite because of the oxide film formed on the Si particles which acted as a diffusion barrier between substrate and the primary Si particles.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.3
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• pp.340-347
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• 2004

Ultra-small size, high-performance, solenoid-type RF chip inductors utilizing low-loss A1$_2$O$_3$ core materials were investigated. The dimensions of the RF chip inductors fabricated were 1.0mm${\times}$0.5mm${\times}$0.5mm and copper coils were used. The materials (96％ A1$_2$O$_3$) and shape (I-type) of the core, the diameters (40${\mu}{\textrm}{m}$) and position (middle) of the coil, and the lengths (0.35mm) of solenoid were determined by a high-frequency structure simulator (HFSS) to maximize the performance of the inductors. The high-frequency characteristics of the inductance (L) and quality-factor (Q) of the developed inductors were measured using a RF impedance/material analyzer (E4991A with E16197A test fixture). The developed inductors exhibit an inductance of 11 to 11.3nH and a qualify factor of 22.3 to 65.7 over the frequency ranges of 250 MHz to 1.7 GHz, and show results comparable to those measured for the inductors prepared by Coilcraft$^{TM}$. The simulated data described the high-frequency data of the L and Q of the fabricated inductors well.

• Journal of Korean Academy of Nursing
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• v.44 no.2
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• pp.170-178
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• 2014

Purpose: This study was to develop a breastfeeding promotion program and to test effects of the program on levels of breast discomfort, breast size, sodium in breast milk, and type of feeding in mothers with breast engorgement following cesarean birth. Methods: A non-synchronized non-equivalent control group pretest-posttest design was used in this study. The participants were 70 postpartum mothers who were admitted to a postpartum care center and experienced breast engorgement following cesarean birth. The planned nursing intervention was the breastfeeding promotion program consisting of breast massage and 1:1 breastfeeding education, counseling, and support focusing on individualized problem solving provided for 10 days. Fifty-three women completed the program (experimental group 26, control group, 27). Measurements were level of breast discomfort, breast size, sodium in breast milk and type of feeding at pre and posttest. Results: Women who participated in the program experienced lower scores for breast discomfort, greater decrease in breast size, lower levels of sodium in breast milk, and practiced breastfeeding more than those in the control group. Conclusion: Results indicate that this breastfeeding promotion program is effective in reducing breast engorgement and improving breastfeeding practices, and is therefore recommended to enhance breastfeeding promotion practice in postpartum care centers.

• KIEAE Journal
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• v.14 no.1
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• pp.83-89
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• 2014

The residents' demand for the comfortable life is promoting development of wall and window which has high sound insulation performance. To develop wall system, various aspects should be considered on the environment, material, construction and structure. Especially focusing on the acoustical view, the economical solution is one of the most critical point. Recently the interest on the partition wall is being increased, because it is useful for the Rahmen type apartment which is considered as an alternative to reduce floor impact sound. This study examines simplified measurement method of airborne sound insulation applied small size specimen, in order to save money to be used for the standard specimen then to promote the development process. The results showed that the simplified method could be effective for the wall system the sound insulation performance upto Rw 50 dB, and for the judgement of rank order of sound insulation performance of the similar wall type while developing.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07a
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• pp.135-138
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• 2002

VCO(Voltage Controlled Oscillator) is one of the main components governing the size, performance and power consumption of telecommunication devices. As the devices become much smaller, VCO need to have much smaller size with better characteristics. Buried type passive components of L,C,R were developed previously and the structure of these components are good for minimizing the size of VCO. Our own library of passive components is used in simulation and fabrication of VCO circuit, and surface mounted components like varactor diode are analysed using the measurement circuit designed by ourselves. Two-Dimensional simulation of VCO circuit and local three-Dimensional structure simulation are performed and their relation is obtained. In structure of multi-layered VCO, some components governing the characteristics of VCO are selected and placed on the top of oscillator for the good tuning process. In resonator part, the stripline structure and low loss glass/ceramic material are used to get higher Q value. In our research, a VCO oscillates in the 2.3∼2.36 GHz band is developed.

• Proceedings of the KSME Conference
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• 2001.11b
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• pp.758-763
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• 2001

This paper presents twin spray characteristics of two impinging F-O-O-F type injectors in which fuel and oxidizer impinge on each other to atomize under the various conditions. The droplet size and velocity in the impinging spray flow field were measured using a PDPA. The droplet size and velocity were investigated at mixture ratios of 1.5, 2.0, 2.47 and 3.0 for four injectors in which two single F-O-O-F injectors were arranged at intervals of 20.8, 31.2, 41.6 and 62.4mm respectively. In general, the arithmetic mean diameter, SMD and standard deviation of droplet size in the interaction area (X=0 and Y=0mm) were smaller. The axial velocity in the interaction area was slightly higher. Considering the behavior of impinged droplets using the We number calculated by using the axial velocity instead of the relative velocity in line C in Fig. 1(b) for four injectors, it is consumed that the We number over 500 had the possibility to disintegrate, and the We number below 500 had it to cohere after impingement of twin spray. The results of this study can be used for the design of a nozzle for liquid propellant rockets.

• Tribology and Lubricants
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• v.24 no.2
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• pp.96-103
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• 2008

PTFE is generally utilized as the form of composites with adding various fillers. The purpose of this paper lies on clarifying the friction and wear properties of the PTFE coating layer on steel. Especially, the effects of PTFE powder size for coating and surface roughness of the counter material on the properties are investigated. Sliding friction and wear tests are conducted at several sliding speeds by employing two types of PTFE coating layer using different powder sizes. One type of coating layer is composed of uniform fine powder, whereas the other type is made up of mixture powder of different sizes. As results, it is found that PTFE coating layer are effective to improve the wear resistance and to reduce the friction coefficient. It is clear that PTFE coating layers are abrasively removed by asperities of the counter material during sliding contact. However, PTFE coating layer with uniform fine powder shows somewhat better wear resistance than that with mixture powder of different sizes in low sliding speed region. It can be seen that the wear of the coating layer are drastically reduced because wear fragment from counter material are transferred to the coating layer. On the other hand, friction coefficient is shown not to be directly related with PTFE powder size in coating layer.

• Journal of Korean Neurosurgical Society
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• v.60 no.3
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• pp.327-334
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• 2017

To review recent advances in endoscopic techniques for treating intraventricular lesions via transcortical passage. Articles in PubMed published since 2000 were searched using the keywords 'endoscopy,' 'endoscopic,' and 'neuroendoscopic.' Of these articles, those describing intraventricular lesions were reviewed. Suprasellar arachnoid cysts (SACs) can be treated with ventriculo-cystostomy (VC) or ventriculo-cysto-cisternostomy (VCC). VCC showed better results compared to VC. Procedure type, fenestration size, stent placement, and aqueductal patency may affect SAC prognosis. Colloid cysts can be managed using a transforaminal approach (TA) or a transforaminal-transchoroidal approach (TTA). However, TTA may result in better exposure compared to TA. Intraventricular cysticercosis can be cured with an endoscopic procedure alone, but if pericystic inflammation and/or ependymal reaction are seen, third ventriculostomy may be recommended. Tumor biopsies have yielded successful diagnosis rates of up to 100%, but tumor location, total specimen size, endoscope type, and vigorous coagulation on the tumor surface may affect diagnostic accuracy. An ideal indication for tumor excision is a small tumor with friable consistency and little vascularity. Tumor size, composition, and vascularity may influence a complete resection. SACs and intraventricular cysticercosis can be treated successfully using endoscopic procedures. Endoscopic procedures may represent an alternative to surgical options for colloid cyst removal. Solid tumors can be safely biopsied using endoscopic techniques, but endoscopy for tumor resection still results in considerable challenges.