• Geomechanics and Engineering
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• 제14권6호
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• pp.533-544
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• 2018

The importance of using materials cost effectively to enhance the strength and reduce the cost, and weight of earth fill materials in geotechnical engineering led researchers to seek for modifying the soil properties by adding proper additives. Lightweight fill materials made of soil, binder, water, and Expanded polystyrene (EPS) beads are increasingly being used in geotechnical practices. This paper primarily investigates the behavior of sandy soil, modified by EPS particles. Besides, the mechanical properties of blending sand, EPS and the binder material such as fly ash and cement were examined in different mixing ratios using a number of various laboratory studies including the Modified Standard Proctor (MSP) test, the Unconfined Compressive Strength (UCS) test, the California Bearing Ratio (CBR) test and the Direct Shear test (DST). According to the results, an increase of 0.1% of EPS results in a reduction of the density of the mixture for 10%, as well as making the mixture more ductile rather than brittle. Moreover, the compressive strength, CBR value and shear strength parameters of the mixture decreases by an increase of the EPS beads, a trend on the contrary to the increase of cement and fly ash content.

• 한국자동차공학회논문집
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• 제6권5호
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• pp.104-110
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• 1998

In automotive industries, various processes for the cost reduction have been investigated lively. As one of them, powder metallurgy becomes influential. Compared to other methods used for he manufacture of steel components the Powder metallurgy process is competitive primarily due to the small number of production steps to reach the final geometry and thereby also the energy-efficiency. In this paper, to alter present forging process into powder metallurgy process by which the automotive clutch disc spline hub is manufactured machining process, the mechanical properties of sintered materials is investigated by specimen test. Selecting the 3 kinds of materials-SMF 4040, SMF 9060 and DHP-1, their properties according to heat treatment such as carburizing -tempering and plasma-nitrodizing are compared. By result of specimen test - tensile test, compression ring test, Impacting test, measurment of hardness, and microstructure analysis - we concluded that SMF 9060 and carburizing-tempering heat treatment is an optimal material and heat treatment method for the spline hub. It will be able to reduce manufacturing cost and weight.

• 소성∙가공
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• 제26권1호
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• pp.55-62
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• 2017

This paper proposes the process to develop a light-weighting automotive door assembly using high strength steel with low cost penalty. In recent years, the automotive industry is making an effort to reduce the vehicle weight. In this study, inner panels for automotive front door using thinner sheets and quenchable boron steel were designed to reduce the weight of conventional one. In order to evaluate the stiffness properties for the proposed door design, the several static tests were conducted using the finite element method. Based on the simulation results, geometry modifications of the inner panels were taken into account in terms of thickness changes and cost saving. Furthermore, a prototype based on the proposed design has been made, and then static stiffness test carried out. From the results, the proposed door is proved compatible and weight reduction of 11.8% was achieved. It could be a reference process for automotive industry to develop the similar products.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 추계학술대회 논문집
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• pp.115-119
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• 2011

Instead of very expensive sound record and professional measurement microphones the low cost Surface Mounted Device (SMD) microphones are proposed for practical barrier ANC system. FRF of the microphones and theirs sensitivity to the wind interferences are evaluated in semi anechoic chamber. The improvement of feedforward algorithm noise reduction index was evaluated based on measured coherence function between tested SMD and reference microphone. Test was performed at various wind speed from 1 m/s to 5 m/s.

• Structural Engineering and Mechanics
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• 제64권4호
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• pp.427-436
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• 2017

Concrete technologists have used ultrasonic pulse velocity test for decades to evaluate the properties of concrete. However, the presented research work focuses on the use of ultrasonic pulse velocity test to study the degradation in steel-concrete bond subjected to increasing loading. A detailed experimental investigation was conducted by testing five identical beam specimens under increasing loading. The loading was increased from zero till failure in equal increments. From the experimentation, it was found that as the reinforced concrete beams were stressed from control unloaded condition till complete failure, the propagating ultrasonic wave velocity reduced. This reduction in wave velocity is attributed to the initiation, development, and propagation of internal cracking in the concrete surrounding the steel reinforcement. Using both direct and semidirect methods of testing, results of reduction in wave velocity with evidence of internal cracking at steel-concrete interface are presented. From the presented results and discussion, it can be concluded that the UPV test method can be successfully employed to identify zones of poor bonding along the length of reinforced concrete beam. The information gathered by such testing can be used by engineers for localizing repairs thereby leading to saving of time, labor and cost of repairs. Furthermore, the implementation strategy along with real-world challenges associated with the application of the proposed technique and area of future development have also been presented.

• 한국기계가공학회지
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• 제19권9호
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• pp.71-77
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• 2020

In recent years, as a consequence of the technological advancements in the automobile industry and changes in consumer demands, the reduction of noise inside vehicles rather than vehicle performance has increasingly become an important factor of interest. To date, most studies have focused on noise and vibration reduction techniques for the engine and drive system of vehicles. In this research, a comparative analysis for reducing the effect of vehicle seatbelts on the transient response is performed using the test of vehicle conditions and transient response analysis in accordance with seatbelt conditions. After the sensitivity analysis, the specifications for improvement were designed based on the transient response analysis. It was confirmed that the transient response characteristics were improved by the transient response analysis and vehicle conditions test. Through computer-aided engineering, the transient response characteristics of seatbelts were checked with less cost and time.

• 소음진동
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• 제6권6호
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• pp.709-715
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• 1996

In recent years, the piping vibration in many Power Plants is being increased by the aged generating facilities due to a long time use. Generally, the pressure fluctuations associated with the flow-induced excitations in this case are broadband in nature. Mainly, the dominant sources of vibration are a vortex-shedding, plane waves and boundary layer turbulence. The peak level of the spectrum is proportional to the dynamic head. A severe disturbance in pipeline results in the generation of intense broadband internal sound waves which can propagate through the piping system. The characteristic frequencies of operating loads of 20%, 57%, 70%, 100% are 4 - 6 Hz and coincide with the results from impact hammering test and FEM analysis. We chose the wire energy absorbing rope restraint as a vibration reduction method after reviewing the various conditions such as site, installing space and economic cost etc. After installation, the vibration level was reduced about 54% in velocity.

• 한국환경과학회지
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• 제26권3호
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• pp.269-280
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• 2017

To lower the operational cost of microbubble generation by electrolysis, optimization of parameters limiting the process must be carried out for the process to be fully adopted in environmental and industrial settings. In this study, four test electrodes were used namely aluminum, iron, stainless steel, and Dimensionally Sable Anode (DSA). We identified the effects and optimized each operational parameter including NaCl concentration, current density, pH, and electrode distance to reduce the operational cost of microbubble generation. The experimental results showed that was directly related to the rate and cost of microbubble generation. Adding NaCl and narrowing the distance between electrodes caused no substantial changes to the generation rate but greatly decreased the power requirement of the process, thus reducing operational cost. Moreover, comparison among the four electrodes operating under optimum conditions revealed that aluminum was the most efficient electrode in terms of generation rate and operational cost. This study therefore presents significant data on performing costefficient microbubble generation, which can be used in various environmental and industrial applications.

• 반도체디스플레이기술학회지
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• 제22권1호
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• pp.49-53
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• 2023

In this paper, we propose an antirandom pattern-based test method considering power consumption to compensate for the problem that the fault coverage through random test decreases or the test time increases significantly when the DUT circuit structure is complex or large. In the proposed method, a group unit test pattern generation process and rearrangement process are added to improve the problems of long calculation time and high-power consumption, which are disadvantages of the previous antirandom test.

• 산업공학
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• 제20권1호
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• pp.41-48
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• 2007

The main purpose of this paper is cost reduction in absurd pilot positive expense and human accident prevention which is caused by in the pilot selection process. We use classification models such as logistic regression, decision tree, and neural network based on aptitude test results of 505 ROK Air Force applicants in 2001~2004. First, we determine the reliability and propriety against the aptitude test system which has been improved. Based on this conference flight simulator test item was compared to the new aptitude test item in order to make additional yes or no decision from different models in terms of classification accuracy, ROC and Response Threshold side. Decision tree was selected as the most efficient for each sequential flight training result and the last flight training results predict excellent. Therefore, we propose that the standard of pilot selection be adopted by the decision tree and it presents in the aptitude test item which is new a conference flight simulator test.