• Explosives and Blasting
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• v.33 no.2
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• pp.25-39
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• 2015

The common underwater rock removal methods involve underwater blasting and crane's chisel dropping impact method. From an environmental point of view, these methods cause ground vibrations and underwater noise. At the site for this study, a method of dropping heavyweight chisel is selected to remove the underwater bedrock near the ferry rack in the course of improving the cargo handling ability of the loading dock. A prediction formula for the vibration was obtained based on the measurement and evaluation of the vibrations caused by the chisel dropping impacts during the test droppings. The prediction formula was successfully applied to the main construction for securing the stability of the structure.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.194-203
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• 2021

With the recent increase in maintenance works on water and sewer pipes as well as district heating supply pipes, pavement cutting work using pavement cutter is on the rise. The pavement cutting operation generates considerable dust (cutting sludge) as well as noise; therefore, it is necessary to apply eco-friendly technologies that have low noise and dust recovery capability. Thus far, various equipment for recovering dust have been developed; however, there is a limitation in that the environmental friendliness is not quantified. Therefore, in this study, we developed a low-noise, dust-recovery type pavement cutter that can fundamentally remove the causes of environmental hazards such as noise and dust and evaluated the eco-friendliness of the pavement cutting process performed by this cutter. To this end, an integrated water cooling-sludge recovery system composed of a vacuum device and a sludge suction unit was developed, and the developed system was applied to a pavement cutter. Subsequently, the developed equipment was applied to the test bed, and data related to its eco-friendliness were collected and evaluated. The results showed that the cutting sludge recovery rate of the developed equipment was greater than 83%, the noise level was approximately 82 - 83 dB, and the sound power level was 115 dB. The results of this study will be used as basic data to develop improved pavement cutters in the future with improved cutting sludge recovery performance and lower noise.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.10
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• pp.2596-2601
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• 2009

Gouging is defined as the removal of weld metal and base metal from the opposite of a partially welded joint to facilitate complete joint penetration. Since the work by current method needs skillful welding and grinding, there is a limit on the increase of operation efficiency. Noise and dust from the weld gouging also deteriorate the work place and cause environmental problems. In this study, the gouging work by cutting method is proposed to overcome the defects from weld gouging such as low productivity, severe noise, dense dust, and so on. The developed cutting gouging system removes material as much as $13,565mm^3/min$, and enlarge the labor productivity as three times compared to that by weld gouging method.

• Journal of the Korean GEO-environmental Society
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• v.1 no.1
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• pp.71-78
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• 2000

In this study, the evaluation for effective utilization of waste landfill was performed by field test to use waste landfill as construction site(Nangido in Seoul). This site had been formed by dredging the household waste, building debris and industrial waste for fifteen years(78'3~93'3). The site where dynamic compaction test was divided by 4 yards. Yard-1, 2 were not eliminated widening of cover soil and Yard-3, 4 were eliminated it. Dynamic Compaction Pilot Test was carried out by the 15ton heavy tamper with drop height of 20m in Yard-1, 3 and with drop height of 15m in Yard-2, 4. We evaluated the compaction efficiency, optimum compaction number and noise vibration through field test, monitoring. As a result, if the countermeasures against vibration and noise by the method utilize, the dynamic compaction method is suitable for using in waste landfill as a construction site among the ground improvement method.

• Journal of the Korea Society of Computer and Information
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• v.24 no.11
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• pp.153-161
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• 2019

In this paper, we proposed a method to measure the feed intake of cattle using the cattle's gulp downing sounds. To measure the sound of cattle's gulp downing, the recording is performed through a wearable device attached to the cattle's neck. A lot of noises are recorded according to the ranching environment. This paper proposed a method for spectralizing raw gulping sound data containing white noise and removing white noise through the signal transformation using a filter. This allows the feed intake to be measured. Through the proposed white noise reduction method, it was possible to extract only the cattle's gulp downing sound, and through this, the number of cattle's gulp downing could be measured. The proposed method in this paper makes it possible to measure cattle's feed intake easily, so that estrus prediction, health care for cattle, and feed management can be done efficiently.

• International Journal of Highway Engineering
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• v.11 no.2
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• pp.1-15
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• 2009

Surface of exposed aggregate concrete pavements is consists of exposed coarse aggregate by removing upper 2$\sim$3mm mortar of concrete slab. Exposed aggregate concrete pavements have advantages of maintaining low-noise and adequate skid-resistance level during the performance period. In order to provide the successful exposed concrete aggregate pavement, uniform distribution of the coarse aggregate on pavement surface through adequate the mix design and exposing method. The mix design in concrete pavement is generally designed on the basis of strength, but mix design of exposed aggregate pavement employed in this study includes the consideration of noise and skid resistance, as well as strength. Smaller of maximum coarse aggregate is known to be effective for reduce noise level. Optimum mix design and exposing method of fine-size exposed aggregate portland cement concrete pavement that can reducing the noise and maintain the adequate level of skid resistance are proposed in this study. To consider the variation of optimum exposing time due to the hardening speed of mortar by climatic condition, quantitative is also suggested measurement of hardening state.

• Proceedings of the Acoustical Society of Korea Conference
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• autumn
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• pp.189-192
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• 1999

수중소음체의 음원 특징을 해석하기 위해서는 배경잡음과 해면$\cdot$해저반사파의 영향이 적은 심해에서 측정하여 분석하여야 한다. 그러나 측정의 어려움으로 인공 수조에서 측정하여 수면과 수조벽에 의해 발생되는 반사파들을 제거하여 신호 고유의 특징을 해석한다 이러한 반사파들의 부가효과를 보상하여 수중소음체의 신호특징을 해석하기 위하여 정합필터배열처리(Matched Filter Array Process : MFAP)기법을 적용하고자 할 때 각 센서에 적용되는 정합필터는 처리시간의 문제로 인해 필터길이를 제한하여 구성되게 된다 정합필터는 수조의 임펄스응답함수의 시역전함수로 정의되는데 필터길이에 따라 수신신호 특징 개선 정도가 좌우된다 본 연구에서는 인공수조에서 부가되는 반사파들의 효과를 보상하여 수신신호 특징 개선을 위해 정합필터배열처리기법을 적용할 때 각 센서의 정합필터의 시간길이가 특징 개선에 미치는 영향을 신호대잡음비(SNR)로 정의하여 분석하였고 수조의 특성에 따른 최적의 정합필터 시간길이를 제안하고자 한다.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.05a
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• pp.409-412
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• 2005

Just as the vibration modes of a beam are dependent on its end constraints or boundary conditions. Vibration modes of a tire are dependent on its patch and spindle constraints. This dependence is key to understanding the dynamic properties of a tire and is apparent in various analytical and experimental investigations in the literature. One of the main task in a modal analysis is the measurement of the Frequency Response Function (FRFs). Because all the subsequent analysis is based on these FRFs, their quality is critically important in obtaining accurate modal parameter estimates. In rotating systems, FRFs are frequently contaminated by harmonic peaks related to such factors as imbalance, misalignment. This harmonic peaks appear in the FRFs as sharp spikes, which can be erroneously treated in modal curve-fitting procedures as structural modes. The harmonic peaks removal method is demonstrated by application to modal analysis on rotating tires. The results show substantial improvement in FRF quality.

• Journal of KSNVE
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• v.8 no.1
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• pp.157-170
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• 1998

This paper proposes a new technique to formulate the finite element model of a sandwich beam by using GHM (Golla-Hughes-McTavish) internal auxiliary coordinates to account for frequency dependence. Through the use of auxiliary coordinates, the equation of motion of undamped mass and stiffness matrix form is extended to encompass viscoelastic damping matrix. However, this methods all suffer from an increase in order of the final finite element model which is undesirable in many applications. Here we propose to combine the GHM method with model reduction techniques to remove the objection of increased model order.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1596-1600
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• 2000

We propose a novel adaptive feed forward controller (AFC) design method for rejecting the effect of micro actuator resonance in the design of dual-stage actuator servo systems for disk drives. Microactuator's resonance is one of important issues in dual-stage actuator servo, which varies up to ${\pm}10%$ per product and even during operation. We derive an adaptive algorithm for the proposed AFC design, which turns out to be identical to the delayed-x LMS algorithm which is a special form of the filtered-x LMS algorithm. In the algorithm, coefficients of the AFC are adapted by the residuals of constrained structure defined in such a way that the coefficients become time invariant. Contrary to the conventional AFC, it considers the phase delay of closed-loop transfer function at resonance frequency for system stability. We also apply an adaptive algorithm with frequency tracking capability. The frequency tracking algorithm is induced by the orthogonality of AFC coefficients. Computer simulations are carried out to demonstrate effect of the proposed AFCs.