• Journal of Korean Society of Environmental Engineers
• /
• v.27 no.3
• /
• pp.316-322
• /
• 2005

In this study, the concentration of 17 dioxin congeners in the soil samples near a waste incinerator with respect to distance from incinerator and wind directions were investigated. The effect of PCB source was investigated using the cluster analysis method. The total concentration and I-TEQ concentration of dioxin ranged from 31.065 to 7,257.499 pg/g(dry weight) and from 0.099 to 35.191 pg I-TEQ/g(dry weight.), respectively. There was a weak correlation(not statistically significant) observed between soil concentration and wind direction, and the distance from the incinerator. The reason may be due to the presence of the local combustion sources other than the target incinerator. The fraction of PCDFs and PCDDs was also examined to study the effect of incinerator. The fraction of PCDFs was decreased with the distance from the incinerator. The influence of target incinerator was found within a 500-meter radius. The high concentration in the for site was due to small incinerators and the use of agricultural chemicals such as PCP. To investigate the relationship between soil near the incinerator and the sources, the cluster analysis was conducted using the congener pattern. As a result soil samples were divided into four groups and were qualitatively estimated the influence of sources such as incinerator and PCP by comparing the congener pattern of each roups. It was thought that a cluster analysis was a useful statistical method for the source estimation of dioxin.

• The Journal of Engineering Geology
• /
• v.27 no.2
• /
• pp.153-164
• /
• 2017

The geological factors for causing ground subsidence are very diverse. It can be affected by any geological or extrinsic influences, and even within the same geological factor, the soil depression impact factor can be determined by different physical properties. As a result of reviewing a large number of papers and case histories, it can be seen that there are seven categories of ground subsidence factors. The depth and thickness of the overburden can affect the subsidence depending on the existence of the cavity, whereas the depth and orientation of the boundary between soil and rock are dominant factors in the ground composed of soil and rock. In case of soil layers, more various influencing factors exist such as type of soil, shear strength, relative density and degree of compaction, dry unit weight, water content, and liquid limit. The type of rock, distance from the main fracture and RQD can be influential factors in the bedrock. When approaching from the hydrogeological point of view, the rainfall intensity, the distance and the depth from the main channel, the coefficient of permeability and fluctuation of ground water level can influence to ground subsidence. It is also possible that the ground subsidence can be affected by external factors such as the depth of excavation and distance from the earth retaining wall, groundwater treatment methods at excavation work, and existence of artificial facilities such as sewer pipes. It is estimated that to evaluate the ground subsidence factor during the construction of underground structures in urban areas will be essential. It is expected that ground subsidence factors examined in this study will contribute for the reliable evaluation of the ground subsidence risk.

• Journal of Navigation and Port Research
• /
• v.47 no.4
• /
• pp.191-201
• /
• 2023

The provision of onboard Internet services is recognized as one of the measures to enhance the appeal of seafarers and improve seafarer welfare. This study aims to investigate the influence of seafarers' leisure activities using the Internet on shipboard culture. Shipboard culture was examined using Hofstede's cultural dimensions theory. An empirical analysis was conducted on crewmembers regarding their Internet-based leisure activities and the shipboard culture. As a result, it was observed that sociability activities through the Internet while onboard significantly influenced power distance, uncertainty avoidance, and long-term orientation. The investigation of shipboard culture revealed uncertainty avoidance, masculinity, and long-term orientation, along with low power distance and individualism cultures. In addition, an analysis of shipboard culture according to seafarers' characteristics showed significant differences in certain shipboard cultures based on seafarers' attributes.

• Journal of the Korean Society of Manufacturing Technology Engineers
• /
• v.22 no.1
• /
• pp.85-91
• /
• 2013

The machinability of wear-resistible tungsten carbides and the tool wear behavior in machining of V30 and V50 tungsten carbides using PCD (Poly Crystalline Diamond) cutting tool was investigated to understand machining characteristics. This material is one of the difficult-to-cut materials in present, but their usage has been already broadened to every commercial applications such as mining tools, and impact resistant tools etc. Summary of the results are as follows. (1) Tool wear progression of PCD tools in turning of wear-resistible tungsten carbides were observed specially fast in primary cutting distance within 10m. (2) Three components of cutting resistance in this research were different in balance from the ordinary cutting such as that cutting of steel or cast iron. Those were expressed large value by order of thrust force, principal force, feed force. (3) If presume from viewpoint of high efficient cutting within this research, a proper cutting speed was 15m/min and a proper feed rate was 0.1mm/rev. In this case, it was found that the tool life of PCD tool was cutting distance until 230m approximately. (4) In cutting of wear-resistible tungsten carbides such as V30 and V50, it was recognized that the tool wear rate of V30 was very fast as compared with V50. (5) When the depth of cut was 0.1mm, there was no influence of the feed rate on the feed force. And the feed force tended to decrease as the cutting distance was long, because the tool was worn and the tool edge retreated. (6) It was observed that the tungsten carbides were adhered to the flank.

• Journal of the Korea Institute of Information and Communication Engineering
• /
• v.19 no.6
• /
• pp.1368-1373
• /
• 2015

Recently, There is increasing interest in the IoT(Internet of Thing) as intelligent information service that enables communication between people and things based on internet. In particular the demand for indoor location-based services with the development of smart devices is rapidly increasing. Using the RSSI signal that is provide to the BLE(Bluetooth Low Energy) for Indoor location information measurement calculates distance information between beacon and mobile terminal. However, simply using the RSSI signal to the distance measurement has a difficult to get the indoor location information due to the influence of the signal interference and the weather. In this paper, by performing an operation for obtaining a reliable distance information from the signal information of iBeacon we propose a system for providing reliable indoor location.

• The Journal of Korean Academy of Prosthodontics
• /
• v.30 no.1
• /
• pp.1-14
• /
• 1992

The purpose of this study was to evaluate the accuracy of reproduction of stone casts made from complete-arch impressions using different trays. The trays used were : 1) nonperforated custom tray, 2) perforated custom tray, 3) nonperforated Rim-Lock tray, 4) perforated stock tray. Impressions were made from an dentulous acrylic resin model with metal inserts in first premolars and second molars. Transverse distance, sagittal distance and diagonal distance were measured using 4 landmarks. Measurements were made by using 3 dimensional measuring machine. The impression material used was an addition silicone. Impressions were poured at once with a Type IV dental stone. Data were analyzed using ANOVA and student t-test with a sample size of five. The results were as follows : 1. There were statistical differences in amount of dimensional change in according to the tray types. In amount of mean dimensional change, perforated custom tray was the first smallest, nonperforated custom tray was the second, nonperforated Rim-Lock tray and perforated stock tray were the largest. 2. There were statistical differences in amount of dimensional change between nonperforated custom tray and nonperforated Rim-Lock tray, and between perforated custom tray perforated stock tray. 3. There were satistical differences in amount of dimensional change between nonperforated custom tray and perforated custom tray, but there was not a statistical difference between nonperforated Rim-Lock tray and perforated stock tray. 4. There was not a statistical difference in amount of dimensional change between upper and lower arch in all tray types.

• Fire Science and Engineering
• /
• v.22 no.2
• /
• pp.30-37
• /
• 2008

We have performed the inflammability test for various flooring materials through a radiant heat panel tester by using the specification KSISO 9239-1 (an examination method of flooring materials) that has been set as an international standard for the fire prevention means of interior flooring materials. We have measured the flame spread distance, critical heat flux and smoke density generated by the fire of various flooring materials while using the radiant heat panel tester. The measurement result has shown the burning characteristics different from each other by the respective flooring materials and we could see that the surface materials and construction elements influence greatly on the heat release and smoke generation. We could see that the evaluation method above is an important test method in evaluating the critical heat flux, smoke generation and flame spread distance that are Important factors in studying for fire risks and it is judged that setting and applying a fire evaluation method of flooring materials suitable for the domestic construction use would be relevant.

• Journal of Korean Society of Transportation
• /
• v.28 no.4
• /
• pp.157-166
• /
• 2010

The aim of this paper was to estimate efficiency using a directional distance function to compare performances of bus agencies to determine if they have made efforts to operate efficiently and reduce emissions and accidents since public transportation reforms 2004. Drivers, mechanics, staff, buses, and fuel were used as input data and vehicle-kilometers (a desirable output), accident costs, and emission costs (undesirable outputs) as output data during June 2005. As a result, the efficiency with undesirable outputs was lower than the efficiency without undesirable outputs. However, the number of efficient agencies was more in case of the consideration of undesirable outputs. The reason is that the number of agencies whose possibility to reduce undesirable outputs are less than the possibility to reduce inputs was increasing, while the efficiency deviation among agencies was larger in case of the consideration of undesirable outputs. Meanwhile, the increase of CNG buses and operating speed and the improvement of mechanical efficiency had positive influence on the efficiency.

• Structural Engineering and Mechanics
• /
• v.61 no.4
• /
• pp.527-538
• /
• 2017

The evaluation of the loss-of-support conditions of frictional beam-to-column connections using simplified numerical models describing the transverse response of a portal-like structure is presented in this paper considering the effects of the seismic-hazard disaggregation. Real earthquake time histories selected from European Strong-motion Database (ESD) are used to show the effects of the seismic-hazard disaggregation on the beam loss-of-support conditions. Seismic events are classified according to different values of magnitudes, epicentral distances and soil conditions (stiff or soft soil) highlighting the importance of considering the characteristics of the seismic input in the assessment of the loss-of-support conditions of frictional beam-to-column connections. A rigid and an elastic model of a frame of a precast industrial building (2-DoF portal-like model) are presented and adopted to find the minimum required friction coefficient to avoid sliding. Then, the mean value of the minimum required friction coefficient with an epicentral distance bin of 10 km is calculated and fitted with a linear function depending on the logarithm of the epicentral distance. A complete parametric analysis varying the horizontal and vertical period of vibration of the structure is performed. Results show that the loss-of-support condition is strongly influenced by magnitude, epicentral distance and soil conditions determining the frequency content of the earthquake time histories and the correlation between the maxima of the horizontal and vertical components. Moreover, as expected, dynamic characteristics of the structure have also a strong influence. Finally, the effect of the column nonlinear behavior (i.e. formation of plastic hinges at the base) is analyzed showing that the connection and the column are a series system where the maximum force is limited by the element having the minimum strength. Two different longitudinal reinforcement ratios are analyzed demonstrating that the column strength variation changes the system response.

• Journal of The Korean Association of Information Education
• /
• v.8 no.1
• /
• pp.15-23
• /
• 2004

In this study, we analyzed the login frequencies and the learner's results of an examination related in the teacher's information distance learning. The results of analysis are as follows. First, most of learners connected to the learning system in school at office hours. And the login frequencies on Sunday are high remarkably in test pole. Seconds, the on-line assessment and the ratio of completion is high the learner who participation with a fellow worker than the learner who not so. But because of the low allotment of marks about on-line estimation, it hardly influence in the last results. Third, the ratio allotment of marks about on-line estimation is suitable $20{\sim}30%$. Forth, learners of low grade are higher the login frequencies, the last results is high. Therefore the operator of the learning system estimates ability of learners by pre-test and must have continues and encouragement about leaners of law grade.