• Geomechanics and Engineering
• /
• v.28 no.6
• /
• pp.613-624
• /
• 2022

A study of the evolution of overburden fractures under the solid-fluid coupling state was conducted based on the geological and mining characteristics of the coal seam depth, weak strata cementation, and high-intensity mining in the mining areas of West China. These mining characteristics are key to achieving water conservation during mining or establishing groundwater reservoirs in coal mines. Based on the engineering background of the Daliuta Coal Mine, a non-hydrophilic simulation material suitable for simulating the weakly cemented rock masses in this area was developed, and a physical simulation test was carried out using a water-sand gushing test system. The study explored the spatial distribution and dynamic evolution of the fractured zone in the mining overburden under the coupling of stress and seepage. The experimental results show that the mining overburden can be vertically divided into the overall migration zone, the fracture extension zone and the collapse zone; additionally, in the horizontal direction, the mining overburden can be divided into the primary fracture zone, periodic fracture zone, and stop-fracture zone. The scope of groundwater flow in the overburden gradually expands with the mining of coal seams. When a stable water inrush channel is formed, other areas no longer generate new channels, and the unstable water inrush channels gradually close. Finally, the primary fracture area becomes the main water inrush channel for coal mines. The numerical simulation results indicate that the overlying rock breaking above the middle of the mined-out area allows the formation of the water-conducting channel. The water body will flow into the fracture extension zone with the shortest path, resulting in the occurrence of water bursting accidents in the mining face. The experimental research results provide a theoretical basis for the implementation of water conservation mining or the establishment of groundwater reservoirs in western mining areas, and this theoretical basis has considerable application and promotion value.

• Journal of Korea Water Resources Association
• /
• v.41 no.8
• /
• pp.773-784
• /
• 2008

The present study was carried out to examine flow properties in linear drainage channels such as road surface drainage facilities. The finite difference formulation for the varied flow analysis was solved for flow profiles in the channels. Starting the first step at the control section, the Newton-Raphson method was applied for producing numerical solutions of the equation. We considered two types of linear drainage channels, a channel with one outlet at downstream end and a channel with two outlets at both ends. Moreover, the flow analysis for various channel slopes was performed. However, we considered channels with the two outlets of slopes satisfying the condition that the both ends are the control section. The maximum of those slopes was decided from the relation between the channel slope and the location of control section. The flow of a channel with one outlet was calculated upward and downward from the control section existing in channel or upward from the control section at downstream end. The flow of a channel with two outlets at both ends were calculated for upstream and downstream channel segments divided by the water dividend, respectively and the flow analysis was completed when the water depth at the water dividend calculated from upstream end was equal to that calculated from downstream end. If the slope was larger than the critical slope, the channel with two outlets was likely to behave like the channel with one outlet. The maximum water depth was investigated and compared with that calculated additionally from the uniform flow analysis. The uniform flow analysis was likely to lead a excessive design of a drainage channel with mild slope.

• Journal of Satellite, Information and Communications
• /
• v.2 no.2
• /
• pp.1-9
• /
• 2007

In this paper, we describe the performance degradation of satellite Wibro system and compensation method in the high-speed railroad channel environment. High-speed railroad channel environment is divided into LOS channel and tunnel. In the LOS channel, signal blocking caused by railroad power feeder structures can be a critical problem which is can be solved with antenna diversity. On the other hand, multi path interference phenomenon, representable by propagation model of Optic Fiber, occurred in the tunnel may be another obstacle. These satellite Wibro system performance degradations in railroad channel environment are addressed and adequate compensation methods are proposed and verified through computer simulation. In addition, the ICI caused by Doppler shift in OFDM system is analyzed with its compensation method.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
• /
• 2001.05a
• /
• pp.359-362
• /
• 2001

Analog communication systems using AM, FM modem have been developed. Digital communication systems using digital modems, which is by expansion of digital hardware skill have been recently developed. In order to accomplish a reliable communication it is important to overcome ocean environmental channel characteristics such as transmission loss, ambient noise and multipath effect etc. Specially, the effect of multipath is the most important element that determines the performance of underwater communication system in shallow water. Multipath channel can be divided a vertical and horizontal channel. the former is defined the channel to have large path-delay times between a direct wave and reflected waves. The latter shows relatively small path-delay times between a direct and reflected waves in compared with a vertical channel. In this paper, The performance of FSK, PSK and DPSK modem with respect to the vertical and horizontal multipath communication channels it described and compared.

• The Research Journal of the Costume Culture
• /
• v.27 no.5
• /
• pp.496-511
• /
• 2019

The purpose of this study was to create a theoretical structure for the concept of purchasing risks by identifying the structure of purchasing risks that lead to obstacles in the purchasing decisions of consumers in fashion consumption via online channels. This was a secondary research using books, articles, prior researches, and academic journals on the five topics of "characteristics of fashion consumption," "the concept of purchasing risks," "purchasing risks by product types," "purchasing risks by channel types," and "purchasing risks of fashion consumption on online shopping channels." According to the arguments of prior researches, the study divided the purchasing risks of fashion consumption through online shopping into four categories : (1) fundamental purchasing risks including financial risk and time loss risk pertaining to any product or channel, (2) online channel purchase risks, which include risks in payment, Information leaks, and delivery and return/exchange risk, (3) fashion product risk related to product quality or experience of other people, which includes social risks and risks associated with quality, and (4) the online channel${\times}$fashion product risks, which include the aesthetic and psychological hazards especially amplified in online channels. The four risk factors were then described with a concept map to systemize the multi-dimensional and stereoscopic psychological structure of purchasing risks. Of the four risk factors, consumers placed the most emphasis on the online channel${\times}$fashion product risks, hence, reducing this risk factor is of utmost priority for marketing of online shopping channels.

• Journal of Advanced Navigation Technology
• /
• v.26 no.5
• /
• pp.261-271
• /
• 2022

This paper is the study in Korea to secure new frequency resources available at sea among terrestrial DTV (Digital TV) broadcasting bands. Focusing on Incheon and Jejudo in the west Sea of Korea, the possibility of using TVWS frequencies of DTV broadcast signals (channels 14-51, 470~698 MHz) was studied. According to the analysis, three channels, channel 19 (503 MHz), channel 37 (611 MHz) and channel 39 (623 MHz) can be used as TVWS available channels without interference with DTV in all nearby seas such as Incheon Port and Jeju Port. On the other hand, two channels, Channel 23 (527 MHz) and Channel 33 (587 MHz), were divided into strong DTV signals in the section between Incheon Port and Jeju Port, making it difficult to use them as available frequencies for TVWS on the west coast.

• The Journal of Korean Institute of Communications and Information Sciences
• /
• v.25 no.5B
• /
• pp.871-878
• /
• 2000

A divided matched filter-reference filter(MF-RF) technique for LEO satellite packet transmission is proposed to increase the packet throughput in the presence of severe Doppler shift and fading. To overcome the severe Doppler shift, the divided matched filter is adopted where the integration region of matched filter is divided and ouputs of divided matched filer are added to decide the correct pseudo-noise (PN) phase. To maintain the constant false alarm rate in time varying interference and fading channel, the adaptive threshold for acquisition is obtained from the reference filter. As a performance measure, average acquisition time and packet throughput are used, and the effets of the parameters, i.e., Doppler shift, chip energy to noise ratio, user velocity, standard deviation of shadowing, and preamble length are shown.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.14 no.5
• /
• pp.1177-1189
• /
• 1994

This paper aims to develop the numerical model for prediction of the channel migration by analyzing of sediment and flow characteristics with patterns of channel in alluvial rivers. Flow in rivers constitutes to be the meandering or the braided form and rarely straight channel through morphologically stable patterns with mutual actions between the flowing water and bed materials. In order to develop the model for simulation of the channel migration, the channels are divided into two types with positive or negative sign by the direction of curvature radius of the centerline channel ($r_c$). That is, the single bend-channel consists of only one curvature of positive or negative sign and the multi-bend channel consists of two more curvatures of positive or negative sign, respectively. The model analyzes the sediment and flow characteristics under the influence of superelevation, spiral motion, irregularity in bed topography and depth-averaged velocity of channels. For reliability of this model, the single bend-channel and the multi bend channel are compared with experiment data in other models and the measured field data in the Keum-River, respectively. As a result, the both com parisians turn out to be excellent.

• Journal of IKEEE
• /
• v.15 no.2
• /
• pp.179-189
• /
• 2011

This paper presents an SVC based multi-channel transmission technique. Transmission of high definition multimedia and its service efficiency can be significantly improved by the proposed method. In this method, the HD stream is divided into the two layer streams, i.e., a base layer stream and an enhancement layer stream. The divided streams are transmitted through a primary channel and an auxiliary channel, respectively. The proposed technique provides a noble mode switching technique which enables a seamless service of HD multimedia even under the conditions of abrupt and intermittent deterioration of the auxiliary channel. When the enhancement layer stream is disrupted by the channel monitoring in the mode switching algorithm, the algorithm works further to maintain the spatial and time resolution of the HD multimedia by upsampling and interpolating the base layer stream, consequently serving for the non disrupted play of the media. Moreover, the adoption of an adaptive switching algorithm significantly reduces the frequency of channel disruption avoiding the unnecessary switching for the short period variations of the channel. The feasibility of the proposed technique is verified through the simulation study with an example application to the simultaneous utilization of both Ku and Ka bands for HD multimedia broadcasting service. The rainfall modeling and the analysis of the satellite channel attenuation characteristics are performed to simulate the quality of service performance of the proposed HD broadcasting method. The simulation results obtained under a relatively poor channel (weather) situations show that the average lasting period of enhancement layer service is extended from 9.48[min] to 23.12[min] and the average switching frequency is reduced from 3.84[times/hour] to 1.68[times/hour]. It is verified in the satellite example that the proposed SVC based transmission technique best utilizes the Ka band channel for the service of HD broadcasting, although it is characterized by its inherent weather related poor reliability causing severe limitations in its independent application.

• Journal of Global Scholars of Marketing Science
• /
• v.13
• /
• pp.159-181
• /
• 2004

The purposes of this study are following. First, we want to review the relationship between trust and precedent variables including shared value, communication and opportunistic behavior in the on-line and off-line channel. Second, building the relationship among variables from previous research, we develop the research model. Third, based on the empirical analysis, we want to build the relationship among variables. Fourth, based on results of analysis, we want to elicit implications for marketing management from the trust in on-line channel in order to enhance the relationship commitment and customer loyalty. Theoretical implications of this study are following. First, under the multiple channel retailing environment, trust in on-line channel is influenced by the trust in off-line channel that the company is operating. Previous researches couldn't found this result because these researches divided on-line and off-line channel separatedly, Second, under the multiple channel retailing environment, on-line or off-line relational attributes including shared value, opportunistic behavior and communication have a effect on trust or relationship commitment So, shared value, opportunistic behavior and communication are very important variables having a effect on trust and relationship commitment in not only off-line channel but also on-line channel. Third, trust and relationship commitment were important mediate variables in multiple channel environment. This result goes with previous researches in single channel.