• Journal of Power Electronics
• /
• v.12 no.1
• /
• pp.104-112
• /
• 2012

In this paper a new method for the design of a simple PI controller is presented and it has been applied in the control of a Boost based PFC rectifier. The Strength Pareto evolutionary algorithm, which is based on the Pareto Optimality concept, used in Game theory literature is implemented as a multi-objective optimization approach to gain a good transient response and a high quality input current. In the proposed method, the input current harmonics and the dynamic response have been assumed as objective functions, while the PI controller's gains of the PFC rectifier (Kpi, Tpi) are design variables. The proposed algorithm generates a set of optimal gains called a Pareto Set corresponding to a Pareto Front, which is a set of optimal results for the objective functions. All of the Pareto Front points are optimum, but according to the design priority objective function, each one can be selected. Simulation and experimental results are presented to prove the superiority of the proposed design methodology over other methods.

• Journal of Nutrition and Health
• /
• v.36 no.7
• /
• pp.684-690
• /
• 2003

This study has investigated the bioavailability of calcium in eggshell powder (ESP) for the purpose of reutilizing eggshells as the calcium source. The experiment was designed 2 ${\times}$ 2 factorial method with two sources, CaCO$_3$ and ESP, and two levels, 0.2% and 0.4% calcium. Weanling SD rats were assigned randomly to one of 4 groups and provided by one of the isocaloric, 20% casein based 4 different experimental diets for 4weeks. Deionized water was given and environment was kept from any contamination of minerals. The body weight, diet intake, feed efficiency ratio (FER), bone growth, Ca contents of bones, and apparent absorption were measured. FER (0.38 - 0.40) and kidney weight were not different among groups and the weight and length, Ca content, strength of two bones Tibia and Femur were not affected by Ca sources except Femur Ca content. Ca content of Femur was greater in ESP groups than that of CaCO$_3$ groups. The body weight gain, bone growth, the Ca contents and strength of bones were significantly greater in 0.4% calcium groups suggesting 0.2% calcium is not sufficient for the optimum growth in the growing rats. These results indicate that ESP be a proper Ca source comparable or superior to CaCO$_3$. However the apparent absorption rate of final 3 days of feeding did not support the observed results showing lower rate in ESP than CaCO$_3$ groups. Further study be needed in the absorption aspect.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 1995.11a
• /
• pp.217-220
• /
• 1995

By substituting Cd$\^$2+/ into both A-site and B-site in PNN-PZ-PT ternary perovskite material, it is possible to determine the effects of the substitution site of Cd$\^$2+/ on sintering behavior. Sintering was performed in the temperature range from 1000$^{\circ}C$ to 1300$^{\circ}C$. The substitution site of Cd$\^$2+/ is identified by XPS spectra. Although Cd$\^$2+/ is substituted into both A-site and B-site in PNN-PZ-PT, Cd$\^$2+/ prefers A-site to B-site. The density is influenced by substitution site of Cd$\^$2+/. If Cd$\^$2+/ replaces Pv$\^$2+/, weight gain is observed during sinterig process. On the contrary, if Cd$\^$2+/ replaces Ni$\^$2+/, weight loss is promoted during sintering. From these weight changes, it is believed that Cd$\^$2+/ changes the bonding strength between B-site cation and oxygen of octahedron in perovskite structure. The changes of lattice parameters as a function of Cd$\^$2+/ content were consistent with those of the bonding strength. The densities of A-site-doped compositions were higher than those of B-site-doped composition.

• Composites Research
• /
• v.12 no.6
• /
• pp.83-89
• /
• 1999

The impact strength and fracture behavior of rubber/polymer composites were investigated with respect to two factors: (i) characteristic ratio, $C_{\infty}$ as a measure of chain flexibility of the polymer matrix and (ii) the rubber particle size in polymer blend system. In this study C was controlled by the composition ratio of polyphenylene oxide (PPO) and polystyene (PS). Izod impact test and fractographic observation of the fracture surface using scanning electron microscope were conducted. Finite element analysis were carried out to gain understanding of plastic deformation mechanism (shear yielding and crazing) of these materials. Shear yielding was found to be enhanced when the flexibility of matrix polymer was relatively low and the rubber particles were small.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2008.04a
• /
• pp.785-788
• /
• 2008

Ceramics manufactures in the nation produced more than 5,000 tons of waste pottery a year increasing industrial waste quantity. However, Almost researches were made to reduce environmental pollution and recycle waste ware. It is needed that they are used as recycled materials in order to prevent environmental pollution and gain economic profits. Therefore, the purpose of this study is to present the method of utilizing the recycled cements that are obtained from waste pottery. The test results that replacement of waste pottery powder by cement admixture at the level 10% had effect on the stripping strength(compressive strength). Also, When GBFS and WP used by cement admixture, WP is better than GBFS.

• Journal of the Korean Ceramic Society
• /
• v.51 no.2
• /
• pp.57-63
• /
• 2014

Bottom ash can be used as pelletizing seeds in unsintered artificial lightweight aggregates, so it can be called as 'cold-bonded aggregates'. In the present study, the mechanical and chemical characteristics of bottom ash aggregates cold-bonded with fly ash were investigated. The crushing strength and the water transfer characteristic of the aggregates, which may affect the strength gain of the concrete, were evaluated. Moreover, the degree of hydration and the hydration products of the aggregates were analyzed to verify the chemical stability of the aggregates. Compared to commercialized artificial lightweight aggregates manufactured by sintering process, cold-bonded fly/bottom ash aggregates had similar levels of water transfer characteristics, while having lower strengths. The calcium hydroxide in the aggregates was almost completely consumed after 28 days moist curing.

• The Transactions of The Korean Institute of Electrical Engineers
• /
• v.62 no.2
• /
• pp.232-238
• /
• 2013

In this paper we describe the maximum energy transfer of CSA(Capacitive Switching Antenna). CSA which is radiated antenna system contain energy storage and switch, antenna needs to high voltage source for electrical field radiation experiment. In this experiment we employed Marx generator as a charging source. CSA can radiate electrical field more efficiently by varying antenna capacitance. The electromagnetic generation system which was using CSA has some advantages which are more simple and more effective compared to exist system. We evaluated the performance of electromagnetic wave generating system using CSA. As a result UWB gain of system is 0.47, It is higher level than exist system is 0.3. Radiated electrical field strength at 1m is 70kV/m. It is measured by D-dot sensor and gap distance is 20mm. Center frequency of CSA is approximately 25MHz. When vary the antenna gap distance from 50mm to 20mm, we can find the radiation field strength is decrease and antenna center frequency is increased. We also simulated the energy transfer efficiency to compare with experiment result. Consequentially, CSA needs to appropriate capacitance which is similar value from marx generator for maximum energy transfer, and gap is less than 1mm to increase the CSA capacitance.

• Geomechanics and Engineering
• /
• v.18 no.3
• /
• pp.277-289
• /
• 2019

In this study, an innovative anchoring approach has been developed dealing with all relevant aspects in consideration of previous works. An ultimate pulling force calculation of anchor is presented from a geotechnical point of view. The proposed umbrella anchor focuses not only on the friction resistance capacity, but also on the axial capacity of the composite end structure and the friction capacity occurring around the wedge. Even though the theoretical background is proposed, in-situ application requires high-level mechanical design. Hence, the required parts have been carefully improved and are composed of anchor body, anchor cap, connection brackets, cutter vanes, open-close ring, support elements and grouting system. Besides, stretcher element made of aramid fabric, interior grouting system, guide tube and cable-locking apparatus are the unique parts of this design. The production and placement steps of real sized anchors are explained in detail. Experimental results of 52 pullout tests on the weak dry soils and 12 in-situ tests inside natural soil indicate that the proposed approach is conservative and its peak pullout value is directly limited by a maximum strength of anchored soil layer if other failure possibilities are eliminated. Umbrella anchor is an alternative to conventional anchor applications used in all types of soils. It not only provides time and workmanship benefits, but also a high level of economic gain and safe design.

• Advances in concrete construction
• /
• v.11 no.3
• /
• pp.183-192
• /
• 2021

Due to economic and environmental benefits, increasing the substitution ratio of ordinary cement by industry by-products like fly ash (FA) is one of the best approaches to reduce the impact of the concrete industry on the environment. However, as the substitution rate of FA increases, it will have an adverse impact on the performance of cement-based materials, so the actual substitution rate of FA is limited to around 10-30%. Therefore, in order to increase the early-age strength of high replacement (30-70%) low-calcium ultrafine FA blended cement paste, sodium sulfate and calcium sulfate dihydrate were used to improve the reactivity of FA. The results show that sodium sulfate has a significant enhancement effect on the strength of the composite pastes in the early and late ages, while calcium sulfate dihydrate has only a slight effect in the late ages. The addition of sodium sulfate in the cement-FA blended system can enhance the gain rate of non-evaporation water, and can decrease the Ca(OH)2 content. In addition, when the sulfate chemical activators are added, the ettringite content increases, and the surface of the FA is dissolved and hydrated.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.5 no.2
• /
• pp.97-104
• /
• 2010

In this study, the effect of blast furnace slag and gypsum addition on strength development of fly ash substituted concrete is investigated experimentally. As a result, the fluidity represented a similar or larger level than that of OPC but showed a tendency to decrease the fluidity according to the increase in the replacement level of BS and GS for the FA replacement concrete. In the case of the air content, although it showed a larger decrease compared to that of OPC, it also represented that BS and GS did not affect the air content significantly. Regarding the compressive strength in the case of the replacement of BS and GS for the FA 10% replacement concrete, it showed a higher early strength than OPC. Whereas, in the case of the BS 5% replacement and GS 1% incorporation for the FA 10% replacement concrete showed the most excellent performance due to its high strength. In the correlation of the compressive strength according to the kinds of admixtures, it was evident that the GS incorporation played an important role in high strength gain.