• Journal of Dental Rehabilitation and Applied Science
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• v.18 no.3
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• pp.217-224
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• 2002

The purpose of this study was to evaluate the influence of saliva contamination on the resin bonding of the etched metal retainers. The test samples were made of Verabond, and divided into 3 groups. Retainers in group1 had normally etched metal surfaces. Retainers in group2 had normally etched metal surfaces which were saliva-contaminated for 30 seconds and cleaned with streaming, luke-warm for 1 minute and dried thoroughly. Retainers in group3 had normally etched metal surfaces which were saliva- contaminated for 30 seconds and dried thoroughly without water-cleansing. Each 3 group specimen was watched on SEM. A resin core, 5mm in diameter and 6mm in length, was made of Panavia using Teflon mold on the each specimen. These 3 groups were tested to evaluate shear bond strength, using universal testing machine. The results were as follows : 1. The shear bond strength showed no significant difference between group1 and group2. 2. The shear bond strength showed significant difference between group1 and group3. 3. The shear bond strength significant difference between group2 and group3. 4. Scanning electron microscope photographs of group1 and group2 showed no signs of contamination but of group3 showed somewhat contaminated.

• KSII Transactions on Internet and Information Systems (TIIS)
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• v.14 no.4
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• pp.1579-1602
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• 2020

In the design of production system, buffer capacity allocation is a major step. Through polymorphism analysis of production capacity and production capability, this paper investigates a buffer allocation optimization problem aiming at the multi-stage production line including unreliable machines, which is concerned with maximizing the system theoretical production rate and minimizing the system state entropy for a certain amount of buffers simultaneously. Stochastic process analysis is employed to establish Markov models for repairable modular machines. Considering the complex structure, an improved vector UGF (Universal Generating Function) technique and composition operators are introduced to construct the system model. Then the measures to assess the system's multi-state reliability and structural complexity are given. Based on system theoretical production rate and system state entropy, mathematical model for buffer capacity optimization is built and optimized by a specific genetic algorithm. The feasibility and effectiveness of the proposed method is verified by an application of an engine head production line.

• Korea-Australia Rheology Journal
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• v.18 no.2
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• pp.103-107
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• 2006

Organic-inorganic composite of polyaniline and barium titanate (PANI-$BaTiO_3$) was synthesized via an in-situ oxidation polymerization of aniline in the presence of barium titanate ($BaTiO_3$) nanoparticles dispersed in an acidic medium. Barium titanate has large electric resistance and relatively high dielectric constant which is one of the essential properties for its electrorheological (ER) applications. The microstructure and composition of the obtained PANI/$BaTiO_3$ composite were characterized by SEM, FT-IR and XRD. In addition, we also employed a rotational rheometer to investigate the rheological performance of the ER fluids based on both pure PANI particle and PANI/$BaTiO_3$ composite. It was found that the composite materials possess much higher yield stresses than the pristine PANI due to unique dielectric properties of the inorganic $BaTiO_3$ particles. Finally, we also examined dynamic yield stress by analyzing its extrapolated yield stress data as a function of electric field strengths. Using the critical electric field strengths deduced, we further found that the universal yield stress equation collapses their data onto a single curve.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1367-1372
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• 2007

Over the past decade, many computational researches have been performed to investigate quantitative relationships between load-displacement and material properties. But piling-up which causes errors to estimate mechanical material properties remains the most significant unresolved issue in nano-indentation test. This study has estimated quantitative aspects of the effects of material properties, especially work hardening exponent, on piling up/sinking in response of various materials. Using FE Analysis, piling up/sinking in response when material is indented by sharp indenter is investigated to evaluate the effects of material properties. From the FE analysis result, quantitative relationships between piling up/sinking in height and material properties is assessed using dimensional analysis which is used to define scaling variables and universal functions. And nano-indentaion test is performed to verify this relation on various materials. From the result of comparison with prediction from dimensional function and experiment, the work hardening exponent was found to have greater influence on the piling up/sinking in height during the nano-indentation than other material properties, such as elastic modulus and yield stress.

• The Journal of Korea Robotics Society
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• v.4 no.1
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• pp.1-9
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• 2009

Radio Frequency Identification (RFID) is an automatic identification method. Information such as identification, logistics history, and specification of products are written and stored into the memory of RFID tags (that is, transponders), and retrieved through RF communication between RFID reader device and RFID tags. RFID systems have been applied to many fields of transportation, industry, logistics, environment, etc in order to improve business efficiency and reduce maintenance cost as well. Recently, some research results are announced in which RFID devices are combined with other sensors for mobile robot localization. In this paper, design of multi-protocol baseband for RFID reader device is proposed, and the baseband modem is implemented into SoC (System On a Chip). The baseband modem SoC for multi-protocol RFID reader is composed of several IP (Intellectual Property) blocks such as multi-protocol blocks, CPU, UART(Universal Asynchronous Receiver and Transmitter), memory, etc. As a result, the SoC implemented with FPGA(Field Programmable Gate Array) is applied to real product. It is shown that the size of RFID Reader module designed with the FPGA becomes smaller, and the SoC chip price for the same function becomes cheap. In addition, operation performance could be the same or better than that of the product with no SoC applied.

• Korean Journal of Human Ecology
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• v.15 no.4
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• pp.563-572
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• 2006

The purpose of this study was to analyze on child counseling service of child welfare policy in Korea. Child counseling services are the most primary services in child welfare. The services have a function of supporting and reinforcing children, so they can grow positively through a desirable relationship with their parents in their family. As child welfare facilities operated politically in Korea, we discussed in this study about the current status of public/private child counseling centers. Through such discussion, we analyzed the current child counseling works in Korea and suggested a future direction of such works. The main results obtained were as follows. First, There were 41 guidance centers for children in Korea, and public guidance centers were 6, and private 35. Second, There were much more guidance centers in Holt Children's Services than in any other centers. Third, In terms of the occurrence of the cases, common children were about 56%, and nonintervention of abuse children were about 13.7% of the total cases. In conclusion, political and systematic support on the establishment of professional public child counseling centers with specialized experts and facilities must be provided in order to activate universal child counseling services for both protection-needed and ordinary children. Furthermore, such political and systematic support must be provided to the establishment and fluent operation of private child counseling centers.

• The Journal of the Acoustical Society of Korea
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• v.10 no.3
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• pp.13-18
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• 1991

In this study, the analysis technique of fracture stress using the reflection coefficient of SAW reflected from a brittle solid with surface crack has been studied. Fracture stress of brittle solid with surface crack has been obtained by the function of the critical stress intensity factor and the maximum normalized stress intensity factor of the crack in the body. And the maximum normalized stress intensity factor of a surface crack can be inferred from a measurement of reflection coefficient of SAW. In experiment, the surface cracks ranging from 0.5mm to 0.9mm in crack depth has been made at the center of each Pyrex disc, and the SAW wedge transducer has been set up for the pitch-catch mode. It has been compared the theoretical values of the fracture stress calculated from the reflection coefficient of SAW with the values of the fracture stress measured from UTM.

• Journal of the Korean housing association
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• v.13 no.4
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• pp.19-26
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• 2002

Despite its relatively small size, at least compared to other architectural programs, the house figures large in the cultural imagination. Closely identified with the individual and nuclear family, it has been frequently considered as an expression of widely held, even universal, values. Conversely, the private house has also been emblematic of more subjective desires, that change not only from person to person but from generation to generation. Certain conclusions can be drawn about the status of the private house at the end of the century, both as cultural invention and as a product of the autonomous discipline of architecture. The contemporary loftlike living space is similarly associated with work, given its emergence as an alternative home for individuals wanting space in which to live and work. In the case of what might be called the "un-private house", it is ofen a digital presence and the change of family system. This study was conducted to define the un-private house through public/private. The architectural characteristics of un-private house are as follows; 1) Alternatives- large open space with multiple function and collective free plan 2) Dematerialization- steel and glass with visual openness and ambiguity 3) Digital & Interfaces- fold and screen using technology and program. Especially, the un-private house is designed to provide individuals with emotional, superficial, and synergistic space, focusing on the personal life-style.

• Fibers and Polymers
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• v.5 no.2
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• pp.122-127
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• 2004

In this study, we evaluated the effect of the molecular weight of the polymer on electrospun poly(ethylene terephthalate) (PET) nonwovens, and their mechanical properties as a function of the linear velocity of drum surface. Polymer solutions and electrospun PET nonwovens were characterized by means of viscometer, tensiometer, scanning electron microscope(SEM), wide angle X-ray diffraction measurement (WAXD) and universal testing machine (UTM). By keeping the uniform solution viscosity, regardless of molecular weight differences, electrospun PET nonwovens with similar average diameter could be obtained. In addition, the mechanical properties of the electrospun PET nonwovens were strongly dependent on the linear velocity of drum surface. From the results of the WAXD scan, it was found that the polymer took on a particular molecular orientation when the linear velocity of drum surface was increased. The peaks became more definite and apparent, evolving from an amorphous pattern at 0 m/min to peaks and signifying the presence of crystallinity at 45 m/min.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.10 no.5
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• pp.223-227
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• 2010

Since the most of existing virtual model house used non-immersive type virtual reality technology, it was made to control using direct input type device such as keyboard and mouse. But in this paper realized not only direct data entry method but also indirect data entry method using eyetracking technology through universal webcam for virtual model house based upon modeling. In this paper showed the position of pointer controlled according to the relative movement of pupils or the part of function related to the equipment entry called by comparing the value of gray after extracting the area of pupil in the user' video data received from webcam. Such a method provided the convenience of navigation and interface to the user.