• Computers and Concrete
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• 제33권3호
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• pp.309-324
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• 2024

Internal curing, a widely used method for mitigating early-age shrinkage in concrete, also offers notable advantages for concrete durability. This paper explores the potential of internal curing by partial replacement of sand with fine lightweight aggregate for enhancing the behavior of high-performance concrete at elevated temperatures. Such a technique may prove economical and safe for the construction of skyscrapers, where explosive spalling of high-performance concrete in fire is a potential hazard. To reach this aim, the physico-mechanical features of internally cured high-strength concrete specimens, including mass loss, compressive strength, strain at peak stress, modulus of elasticity, stress-strain curve, toughness, and flexural strength, were investigated under different temperature exposures; and to predict some of these mechanical properties, a number of equations were proposed. Based on the experimental results, an advanced stress-strain model was proposed for internally cured high-performance concrete at different temperature levels, the results of which agreed well with the test data. It was observed that the replacement of 10% of sand with pre-wetted fine lightweight expanded clay aggregate (LECA) not only did not reduce the compressive strength at ambient temperature, but also prevented explosive spalling and could retain 20% of its ambient compressive strength after heating up to 800℃. It was then concluded that internal curing is an excellent method to enhance the performance of high-strength concrete at elevated temperatures.

• 대한안전경영과학회지
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• 제26권2호
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• pp.79-86
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• 2024

Scientific exploration of how occupational health risks relate with occupational illnesses are essential for mitigating health-related issues in industries. This study analyzed the risk scores obtained by occupational health risk assessments at 3,172 manufacturing companies and examined their effects on occupational illness. Statistical analyses revealed that companies with an occupational health manager (scored 89.1 out of 100) had significantly higher activity scores of health management compared to those without (78.2). However, companies with a history of occupational illness (79.1) or those classified as high-risk industries (85.2) had significantly lower activity scores than their counterparts (81.7, 87.3). In addition, regression analyses using factor analysis showed that latent risk factors such as cardiovascular disease/job stress, health management, and musculoskeletal problem significantly influenced the risk of occupational illness. The activity factors such as health management, work environment management, and regulatory complaisance significant impacted the reduction of occupational illness. The findings of this study can be used to improve the occupational health risk assessment method and utilized in effectively managing occupational risks in industries.

• Journal of Electrical Engineering and Technology
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• 제10권1호
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• pp.188-194
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• 2015

This paper proposes a generalized regression neural network (GRNN) based algorithm for data interpolation and design optimization of brushless dc (BLDC) motor. The procedure makes use of magnet length, stator slot opening and air gap length as design variables. Cogging torque and average torque are treated as performance indices. The optimal design necessitates mitigating the cogging torque and maximizing the average torque by varying design variables. The data set for interpolation and ensuing design optimisation using GRNN is obtained by modeling a standard BLDC motor using finite element analysis (FEA) tool MagNet 7.1.1. The performance indices of the standard motor obtained using FEA are validated with an experimental model and an analytical method. The optimal design is authenticated using particle swarm optimization (PSO) algorithm and the performance indices of the optimal design obtained using GRNN is validated using FEA. The results indicate the suitability of GRNN as an interpolation and design optimization tool for a BLDC motor.

• 제어로봇시스템학회논문지
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• 제19권1호
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• pp.34-39
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• 2013

This paper proposes the implementation of robust fuzzy controller for designing intelligent wind farm and mitiagating the fluctuation of wind power generator. The existing researches are limited to individual wind turbine with variable speed so that it is necessary to study the multi-agent wind turbine power system. The scopes of these studies include from the arrangements of each power turbine to the control algorithms for the wind farm. For solving these problems, we introduce the composition of intelligent wind farm and use the T-S (Takagi-Sugeno) fuzzy model which is suitable for designing fuzzy controller. The control object in wind farm enables the minimizing the fluctuation of wind power generator. Simulation results for wind fram which is modelled as mathematically are demonstrated to visualize the feasibility of the proposed method.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2000년도 하계종합학술대회 논문집(2)
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• pp.221-225
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• 2000

We designed asynchronous event logic library with 0.25$\mu\textrm{m}$ CMOS technology and interface chip for heterogeneous system with high-speed asynchronous FIFO operating at 1.6㎓. Optimized asynchronous standard cell layouts and Verilog models are designed for top-down design methodology. A method for mitigating a design bottleneck when it comes to tolerate clock skew is described. This communication scheme using clock control circuits, which is used for the free of synchronization failures, is analyzed and implemented. With clock control circuit and FIFO, high-speed communication between synchronous modules operating at different clock frequencies or with asynchronous modules is performed. The core size of implemented high-speed 32bit-interface chip for heterogeneous system is about 1.1mm ${\times}$ 1.1mm.

• 전기학회논문지P
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• 제58권4호
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• pp.404-409
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• 2009

A DC power system has many loads with various functions. In particular, these sizable loads take the form of power electronic converters. When they are tightly regulated, the loads appear as constant power loads and result in negative incremental input impedance. Under certain conditions the effect of such loads on the power system is causes instability. In this paper, converter with a large storage capacitor and a lag compensator is proposed as a DC bus conditioner to mitigate the voltage transients on the bus. In addition, the proposed control approach has the advantage of performing both the functions of mitigating the voltage bus transients and maintaining the level of energy stored. Simulation and experimental results showed that the proposed control method was operated well in a small-scale DC power system that contained subsystems with constant power characteristics, such as DC/DC converters and electrical drives.

• Earthquakes and Structures
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• 제18권3호
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• pp.313-320
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• 2020

The usage of conventional tuned mass damper (TMD) was proved as an effective method for passive mitigating vortex-induced vibration (VIV) of a bridge deck. Although a variety of linear TMD systems have been so far utilized for vibration control of suspension bridges, a sensitive TMD mechanism to wind spectrum frequency is lacking. Here, we introduce a bistable tuned mass damper (BTMD) mechanism which has an exceptional sensitivity to a broadband input of vortex shedding velocity for suppressing VIV in suspension bridge deck. By use of the Monte Carlo simulation, performance of the nonlinear BTMD is shown to be more efficient than the conventional linear TMD under two different wind load excitations of harmonic (sinusoidal) and broadband input of vortex shedding. Consequently, an appropriate algorithm is proposed to optimize the design parameters of the nonlinear BTMD for Kap Shui Mun Bridge, and then the BTMD system is localized for the interior deck of the suspension bridge.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2008년도 제39회 하계학술대회
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• pp.265-266
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• 2008

The interest on harmonics which is one of the matters related with power quality problem is not limited in only the system where the large scale industrial load is connected. The harmonics phenomenon not only causes the malfunction of devices, but also lowers the energy efficiency of power system. This paper focuses on the harmonic analysis process to establish the harmonic mitigation method, considering the harmonics distortion as a major cause to reduce the energy efficiency of a skyscraper. A system diagram of building is modelled with PSCAD simulator. Based on the harmonic analysis results of it, the electrical locations with the high priority to install the mitigating devices are selected. Finally, the result of PSCAD simulations and the site-measured data are compared, verifying that they reach a common conclusion.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2002년도 ITC-CSCC -3
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• pp.1610-1613
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• 2002

This paper analyses the performance of PE-IPDL technique fer the wireless mobile position location, which have been considered as a major candidate for 3GPP position location due to its capability in mitigating the hearability problem and DOP problem. To improve the location performance of PE-IPDL, this paper introduces the high-resolution estimation technique for the first arrival multipath delay, and simulation results verify its superiority. For a systematic analysis of above location method, its performances are exploited by obeying the CODIT channel model specially bad urban channel environment. Simulation results verify its efficiency of enhancing the degree of accuracy in positioning.

• International Journal of Fluid Machinery and Systems
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• 제4권1호
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• pp.47-56
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• 2011

Our previous experimental and numerical investigations of decelerated swirling flows in conical diffusers have demonstrated that water jet injection along the symmetry axis mitigates the pressure fluctuations associated with the precessing vortex rope. However, for swirling flows similar to Francis turbines operated at partial discharge, the jet becomes effective when the jet discharge is larger than 10% from the turbine discharge, leading to large volumetric losses when the jet is supplied from upstream the runner. As a result, we introduce the flow-feedback approach for supplying the jet by using a fraction of the discharge collected downstream the conical diffuser. Experimental investigations on mitigating the pressure fluctuations generated by the precessing vortex rope and investigations of pressure recovery coefficient on the cone wall with and without flow-feedback method are presented.