• Tunnel and Underground Space
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• v.33 no.5
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• pp.425-434
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• 2023

To measure the wear amount of the TBM disk cutter in real time, it is important not only to automate the measurement using sensors, but also to stably transmit the measured data to the information processing system. In this study, we investigated the viability of utilizing Bluetooth Low Energy (BLE) technology to wirelessly transmit sensor data from the TBM cutter head to a receiver located at the chamber's rear. Through laboratory experiments, we analyzed the Received Signal Strength Index (RSSI) of the receiver considering various signal strength of the transmitter, separation distances between the transmitter and receiver and chamber fill materials. Our results demonstrate that wireless data transmission is feasible across all tested conditions when the transmitter signal strength is 0 dBm or higher.

• Tunnel and Underground Space
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• v.34 no.1
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• pp.54-70
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• 2024

Utilization of completed open-pit for mining waste disposal is an alternative method of tailing storage facility (TSF), which can minimize the area and cost required for the installation of TSF. However, long-term tailing disposal into open-pit has a potential risk of reducing mechanical stability of surrounding rock mass by acting as an additional load. In this research, a realistic open-pit tailing disposal scenario of 60,400 hours was established based on the case of Marymia gold mine, Australia. Mechanical stability of surface pillar between open-pit and underground stope was analyzed numerically by using Sigma/W, under different stope geometry and rock mass conditions. Simulation results showed that long-term tailing disposal into open-pit can significantly increase the failure probability of surface piller. This result suggests that mechanical stability of mine geometry should be conducted beforehand of open-pit tailing disposal.

• Journal of Korean Tunnelling and Underground Space Association
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• v.26 no.5
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• pp.403-419
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• 2024

Advance rate significantly affects both the construction period and cost in tunnel blasting. As such, there has been persistent research dedicated to the development of innovative blasting technique aimed at enhancing the advance rate. This paper aims to provide fundamental insights into the differences in advance rate and the powder factor between two- and three-free-face blasting, laying the groundwork for the advancement of tunnel blasting techniques. Large-scale cement mortar specimens were fabricated, and blasting tests were conducted for both two- and three-free-face blasting. Experimental findings were then compared with those from numerical simulation. Notably, an increase in the number of free faces, under uniform conditions, significantly improved the advance rate while reducing the powder factor. The outcomes of this study serve as crucial groundwork for devising blasting patterns employing three-free-face blasting, characterized by improved advance rates and minimized powder factors. Consequently, the anticipated outcomes include an overall improvement in tunnel advance rates and a reduction in the number of drilling holes and the amounts of explosives.

• Tunnel and Underground Space
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• v.34 no.5
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• pp.449-460
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• 2024

The roughness of rock joint surfaces is considered a critical factor in determining the stability of underground spaces and tunnels, leading to attempts to measure it using various devices. This study explored the applicability of portable 3D scanner for measuring rock joint roughness in comparison to laser scanner. By constructing various one-dimensional roughness profiles using laser scanner and portable 3D scanner, and calculating the Z₂(statistical roughness parameter) for comparison, it was found that the portable 3D scanner tends to underestimate roughness compared to the laser scanner. The variations in roughness and Z₂ showed very similar patterns between the two devices. Through Direct shear tests that induced wear on the specimens, differences in roughness and Z₂ due to wear were compared using the portable 3D scanner, confirming variations in roughness height and Z₂ related to wear.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.149-153
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• 2006

Precipitation is the most important component and critical to the study of water and energy cycle. This study investigates the propagation of precipitation retrieval uncertainty in the simulation of hydrologic variables for varying spatial resolution on two different vegetation cover. We explore two remotely sensed rain retrievals (space-borne IR-only and radar rainfall) and three spatial grid resolutions. An offline Community Land Model (CLM) was forced with in situ meteorological data In turn, radar rainfall is replaced by the satellite rain estimates at coarser resolution $(0.25^{\circ},\;0.5^{\circ}\;and\;1^{\circ})$ to determine their probable impact on model predictions. Results show how uncertainty of precipitation measurement affects the spatial variability of model output in various modelling scales. The study provides some intuition on the uncertainty of hydrologic prediction via interaction between the land surface and near atmosphere fluxes in the modelling approach.

• Archives of design research
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• v.16 no.2
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• pp.233-242
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• 2003

Whit trade increasingly taking place on the global stale, packaging becomes even more important However, there is only a fine line between the balance of waste created by damaged goods and waste created by over-packaging. A vast quantity of material is used by the packaging industry for the reason of bringing products safely to the customers. In this research I gathered 87 samples of various kinds of confectionery to analyse the actual conditions of the appropriate packaging. As a result, the rate of the needless space excluding actual contents comes to over 60% which clearly says that the most products are over-packaged. Despite assertions from the packaging industry that all packaging is necessary in reducing product waste, the research shows us the fact that it's over-packaged. What needs to be questioned, here, is the level of materials we use in packaging our products, and how we can continue to decrease that amount and recycle what we do use. In the future where materials and resources become more scarce, and therefore more expensive, and the methods of disposal become more costly and accountable, designers and manufacturers constantly need rethink and improve methods of packaging.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.17 no.4
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• pp.323-335
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• 1992

In this paper, an adaptive cosine transform coding scheme which incorporate human visual properties into the coding scheme is investigated. Human vision is relatively sensitive to mid-frequency band, and insensitive to very low and very high frequency band. These property was mathematically modelled with MTF(Modulation Transfer Function) through many psychovisual experiment. DCT transforms energy in spatial domain into frequency domain, so can exploit the MTF very efficiently. Another well-known visual characteristics is spatial masking effect that visibility of noise is less in regions of high activity than in regions of low activity. Proposed coding scheme imploys quantization matrix which represent the properties of these spatial frequency response of human vision, and adaptively quality of an image. To compute the activity index of an image block, simple operation is performed in spatial domain, and according to activity index. block of low activity region is more exactly quantized relatively than that of high activity region. Results showed that, at low bit rate, the subjective quality of the reconstructed images by proposed coding scheme is acceptible than that of coding scheme without HVS properties.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.258-265
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• 2011

A zero-dimensional global model simulator for atmospheric pressure oxygen plasmas has been developed. The simulation model considers the configurations similar to that of plasma needle device. The simulation results show that those species of O, $O_3$, $O_2*$ and ${O_2}^+$ have the highest density in sequence. Electrons dissipate most of their energy through the collisions with oxygen molecules. If the input power increases, the density of most species also increases as much as three-boy collision for the creation of ozone is weakened and hence the density of ozone decreases. The body to volume ratio also affects the plasma density.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2008.04a
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• pp.909-915
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• 2008

Researches for time delay estimation had been studied broadly. However studies about factors for time delay estimation are insufficient, especially in case of real environment application. In 1997, Brandstein and Siverman announced that performance of time delay estimation deteriorates as reverberant time of room increases. Even though reverberant time of room is same, performance of estimation is different as the specific part of signals. In order to know that reason, we studied and analyzed the factors for time delay estimation using speech signal and room impulse response. In result, we can know that performance of time delay estimation is changed by different R/D ratio and signal characteristics in spite of same reverberant time.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.1
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• pp.119-124
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• 2010

The MAC layer in ad-hoc network which makes network of nodes without infrastructure for a time has became an issue to reduce delay, allocate fairly bandwidth, control TX/RX power and improve throughput. Specially, the problem to reduce power consumption in ad-hoc network is very important part as ad-hoc devices use the limited battery. For solution of the problem, many power control algorithms, such as distribute power control, PCM (Power Control MAC) and F-PCF (Fragmentation based PCM), are proposed to limit power consumption until now. Although the algorithms are designed to minimize power consumption, the latency communication zone is generated by power control of RX/TX nodes. However the algorithms don't suitably reuse the space. In this paper proposes the algorithm to improve data throughput through Spatial Reuse based on a power control method.