• 한국구조물진단유지관리공학회 논문집
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• 제20권6호
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• pp.73-83
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• 2016

포스트텐션 공법을 적용한 콘크리트 부재의 정착구역에서 정착판 근처의 지압응력은 일반적으로 높은 프리스트레스 하중에 의해 발생한다. 따라서 단면의 효율적인 활용과 콘크리트 부재의 파괴로 이어질 수 있는 균열제어를 위해 적절한 정착판의 크기가 제시되어야 한다. 본 연구에서는 도로교설계기준 및 PTI 등에 의해 사각형 정착판과 원형 정착판의 유효면적에 대한 관계식을 제안하였다. 또한 정착판의 형상에 따라 형상계수를 제안하였으며, 유한요소해석을 통해 적절성을 분석하였다.

• Journal of Electrical Engineering and Technology
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• 제11권6호
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• pp.1645-1655
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• 2016

A Dynamic Voltage Restorer (DVR) model is proposed to eliminate the short-term voltage disturbances that occur in the grid-connected mode, the switching between grid-connected mode and the stand-alone mode of a Microgrid. The proposed DVR structure is based on a conventional cascaded H-bridge multilevel inverter (MLI) topology; a novel composite control strategy is presented, which could ensure the compensation ability of voltage sag by the DVR. Moreover, the compensation to specified order of harmonic is added to implement effects that zero-steady error compensation to harmonic voltage in specified order of the presented control strategy; utilizing wind turbines-batteries units as DC energy storage components in the Microgrid, the operation cost of the DVR is reduced. When the Microgrid operates under stand-alone mode, the DVR can operate on microsource mode, which could ease the power supply from the main grid (distribution network) and consequently be favorable for energy saving and emission reduction. Simulation results validate the robustness and effective of the proposed DVR system.

• 소성∙가공
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• 제26권2호
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• pp.115-120
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• 2017

Porthole extrusion process is a very effective metal forming process to produce aluminum profiles with hollow sections. The structure of porthole extrusion die is very complex. In this process, the billet is divided by porthole bridge, and then the divided billet is welded in the welding chamber. The welding pressure in the welding chamber is very important. The higher welding pressure improves the quality of the aluminum profiles. Therefore, the objective of this study is to develop a new porthole extrusion die for improving the welding pressure in the welding chamber by using numerical analysis. The effectiveness of the new porthole extrusion die was verified by using numerical analysis. Through numerical analysis, the welding pressures in the welding chamber between the new porthole die and the conventional porthole die were compared with each other.

• 한국안전학회지
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• 제30권1호
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• pp.52-59
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• 2015

The aim of the paper is to introduce the statistical definition of the specified compressive strength of the concrete to be used for safety evaluation of the existing structure in domestic practice and to present the practical method to obtain the specified strength by utilizing the non-destructive test data as well as the limited number of core test data. The statistical definition of the specified compressive strength of concrete in the design codes is reviewed and the consistent formulations to statistically estimate the specified strength for assessment are described. In order to prevent estimating an unrealistically small value of the specified strength due to limited number of data, it is proposed that the information from the non-destructive test data is combined to that of the minimum core test data. The the sample mean, standard deviation and total number of concrete test are obtained from combined test data. The proposed procedures are applied to an example test data composed of the artificial numerical values and the actual evaluation data collected from the bridge assessment reports. The calculation results show that the proposed statistical estimation procedures yield reasonable values of the specified strength for assessment by applying the non-destructive test data in addition to the limited number of core test data.

• 전력전자학회논문지
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• 제22권1호
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• pp.75-81
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• 2017

This paper presents a design and parallel control strategy of 1.8 kW low-voltage DC-DC converter (LDC) for mild hybrid electric vehicles to improve their power density, system efficiency, and operation stability. Topology and control scheme are important on the LDC for mild hybrid electric vehicles to achieve high system efficiency and power density because of their very low voltage and large current in input and output terminals. Therefore, the optimal topological structure and control algorithm are examined, and a detailed design methodology for the power and control stages is presented. A working sample of 1.8 kW LDC is designed and implemented by applying the adopted topology and control strategy. Experimental results indicate 92.45% of the maximum efficiency and 560 W/l of power density.

• Structural Monitoring and Maintenance
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• 제7권2호
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• pp.109-124
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• 2020

Benefiting from the massive monitoring data collected by the Structural health monitoring (SHM) system, scholars can grasp the complex environmental effects and structural state during structure operation. However, the monitoring data is often missing due to sensor faults and other reasons. It is necessary to study the recovery method of missing monitoring data. Taking the structural temperature monitoring data of Nanjing Dashengguan Yangtze River Bridge as an example, the long short-term memory (LSTM) network-based recovery method for missing structural temperature data is proposed in this paper. Firstly, the prediction results of temperature data using LSTM network, support vector machine (SVM), and wavelet neural network (WNN) are compared to verify the accuracy advantage of LSTM network in predicting time series data (such as structural temperature). Secondly, the application of LSTM network in the recovery of missing structural temperature data is discussed in detail. The results show that: the LSTM network can effectively recover the missing structural temperature data; incorporating more intact sensor data as input will further improve the recovery effect of missing data; selecting the sensor data which has a higher correlation coefficient with the data we want to recover as the input can achieve higher accuracy.

• 대한치과기공학회지
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• 제9권1호
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• pp.5-19
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• 1987

The factors which impact on the productivity of medical organization are technique, manager, raw materials, management style, manpower structure, job construction, and so on. Human resources is the most important factor among them, but the productivity of serice organization can not be measured easily. The purpose of this study was to verify the effect of laboratory status, the degree of job cognition, and stress on the productivity of dantal prosthetic products, and to fine out the factors which impact on the productivity. The results were as follows: 1. The job characteristice of crown bridge laboratory part and porcelain laboratory part similar to each other. Also partial denture laboratory part and complete denture laboratory part were similar to each other. But that of orthodontic laboratory part was different from other. 2. the degree of job cognition made significant difference statisfically according to job characteristics of each dental laboratorise. 3. The correlation coefficient between job cognition of dental laboratory technician and workshop environment was.23, but the correlation between job cognition job stress appeared reversely, its coefficient was-.17. 4. The productivity of technician engaged in dental laboratory was much heigher than that of technician engaged in dental clinical laboratory room, and each were different in the degree of job cognition. 5. the most important factors which impact one the performance productivity of dental laboratory technician were the fact whether he married or not and his status.

• 한국생산제조학회지
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• 제22권1호
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• pp.92-99
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• 2013

The ratio of mobility handicapped was 12,110,000 in late 2009 about 24.4% of total population. The number of handicapped population is increasing continuously due to traffic accidents and industrial disasters. Therefore, the purpose of this research is to suggest a design for passengers on wheelchairs to get into and off to raise handicapped or elderly people's right of mobility. The scope of this research is mobility handicapped especially wheelchair passengers who use vans, small buses, and trains. The ramp design of vans is module form. The ramp is moved with screw jack and guides are installed on each side to increase stability. Moreover, a bridge was installed for smooth getting in and off of the van. The ramp design for small bus is lowed by 200m in order not to have obstacle such as speed bump when getting in or off. In order to reduce vulnerable environment and administration, air slide cylinder was chosen. Lastly, for the ramp design of train, the principle of link was used that the simpler structure made the weight lighter and installation in the train became easier. If we look at the conjugation condition of heterogeneous materials to produce a ramp, proper welding condition for cold steel plate and stainless plate is 3kW output and 3-5m/min of welding speed using laser beam seems proper.

• Macromolecular Research
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• 제15권1호
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• pp.59-64
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• 2007

Star-shaped, nonlinear optical (NLO) material was synthesized and its optical, thermal, and electro-optic properties were investigated. Three NLO-active dipolar chromophores containing a phenylene ring substituted with a bulky alkyl chain as a conjugation bridge were chemically bonded to the core of 1,1,1-tris(4-hydroxyphenyl)ethane to form a dendritic architecture. The chemical structure and purity of the chromophore were verified by NMR spectroscopy. The chromophore exhibited a broad absorption band centered at around 608 nm tailing up to 760 nm in toluene solution and also showed a discernible solvatochromic shift in more polar solvent. The chloroform solution of the dendrimer produced an absorption band with a red-shifted maximum as large as 28 nm when compared to that of the toluene solution. It was thermally stable up to $275^{\circ}C$ in a nitrogen atmosphere and had a glass transition temperature of $76^{\circ}C$. In a preliminary result, the polymer film containing the dendritic compound exhibited a shift of 19 pm/V taken at $1.55{\mu}$.

• 한국안전학회지
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• 제29권6호
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• pp.87-93
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• 2014

In this study, the reinforced concrete rahmen bridge damaged by the chloride attack was investigated. According to the investigation, the degraded concretes on cantilever kerb and end part were intensively observed. Thus, the chloride content test and half-cell method were performed to evaluate the degraded parts. As a result, the contents of chloride on degraded parts were C and D grade. On the other hand, the half-cell potential values of rebar in degraded concrete were measured with the minor corrosion. This rebar corrosion is expected to progressing. Chloride content D grade is due to expansion pressure by corrosion of rebar and freeze-thaw by permeate water, could see progresses rapidly degradation. In order to prevent chloride attack to concrete deck caused by deicing salts, corresponding to the chloride critical concentration must maintain grade b or at least grade c. Chloride condition evaluation standard apply to evaluation of marine structure chloride attack with chloride attack by deicing salts.