• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.03a
• /
• pp.221-228
• /
• 2002

Thickness of concrete lining, voids at the back of lining or shotcrete are very important elements for inspecting the safety of tunnels. Therefore, the inspection of tunnel lining structure means to investigate the inner layer boundaries of the structure. For this purpose, seismic reflection survey is the most desirable method if it works in good conditions. However, the conventional seismic reflection method can not be properly used for investigating thin layers in the lining structure. In other words, to detect the inner boundaries, it is desirable for the wavelength of source to be less than the thickness of each layer and for the receiver to be capable of detecting high frequency(ultrasonic) signals. To this end, new appropriate source and receiver devices should be developed above all for the ultrasonic reflection survey. This paper deals primarily with the development of source and receiver devices which are essential parts of field measuring system. Interests are above all centered in both the radiation pattern, energy, frequency content of the source and the directional sensitivity of the receiver. With these newly devised ones, ultrasonic physical modeling has been performed on 3-D physical model composed of bakelite, water-proof and concrete, The measured seismograms showed a clear separation of wave arrivals reflected from each layer boundary. Furthermore, it is noteworthy that reflection events from the bottom of concrete below water-proof could be also observed. This result demonstrates the usefulness of the both devices that can be applied to benefit the ultrasonic reflection survey. Future research is being focus on dealing with at first an optimal configuration of source and receiver devices well coupled to tunnel wall, and further an efficient data control system of practical use.

• The Korean Journal of Applied Statistics
• /
• v.35 no.4
• /
• pp.485-499
• /
• 2022

Controlling the total survey error including sampling error and non-sampling error is very important in sampling design. Non-sampling error caused by non-response accounts for a large proportion of the total survey error. Many studies have been conducted to handle non-response properly. Recently, a lot of non-response imputation methods using machine learning technique and traditional statistical methods have been studied and practically used. Most imputation methods assume MCAR(missing completely at random) or MAR(missing at random) and few studies have been conducted focusing on MNAR (missing not at random) or NN(non-ignorable non-response) which cause bias and reduce the accuracy of imputation. In this study, we propose a non-response imputation method that can be applied to non-ignorable non-response. That is, we propose an imputation method to improve the accuracy of estimation by removing the bias caused by NN. In addition, the superiority of the proposed method is confirmed through small simulation studies.

• Journal of the Korean Society of Fisheries and Ocean Technology
• /
• v.58 no.2
• /
• pp.141-152
• /
• 2022

As a method to understand the ecological habits around the artificial reef, various reports such as fishing gear survey, diving, sound survey, underwater CCTV and camera, etc. are reported. Among them, the sound survey method is carried out by installing an acoustic system on the ship and can be investigated regardless of the marine environment such as time constraints and turbidity. Such method, however, takes a lot of manpower and time as the ship travels at a constant speed. Investigations around artificial reefs are being conducted in an artificial way, and a lot of time and labor are consumed as such. Maritime buoys have been operated for various purposes such as route signs, weather observation, marine environment monitoring and defense monitoring for navigation safety in the past, but studies on monitoring systems for ecological habits and distribution of fish using marine buoys are remarkably insufficient. Therefore, this study aims to develop a system that allows users to directly monitor fish group detector data by estimating the distribution of fish groups around artificial reefs and using wireless communication at sea. In order to confirm the suitability of the maritime buoy used in this study, it was operated to compare data using LTE-equipped buoys capable of wireless communication and a data logger-type system buoy. Data transmission of buoys capable of LTE communication was carried out in a 10-minute ON, 10-minute OFF method due to the limitation of the power supply capacity, and data of the data logger-type buoy received full data. We compared and analyzed the data received from the two fish detectors. It is expected that real-time monitoring of the wireless buoy detection device using LTE will be possible through future research.

• Journal of the Korea Safety Management & Science
• /
• v.15 no.4
• /
• pp.145-152
• /
• 2013

The purpose of this study was to investigate the effect of risk awareness on injury experience in quick delivery service workers. Risk awareness has complicate characteristics such as its level of worker and worker's decision about the level of other's risk perception. Data were collected by interview survey with structured questionnaire about injury experience, risk perception, work characteristics, and socio-demographic characteristics of quick delivery service workers by cross sectional survey design in 2012. The sample size was 120 respondent of quick delivery service workers. Statistical method for this study was hierarchical logistic regression method with 3 different models using socio-demographic characteristics and work characteristics and risk perception, etc. The difference between the level of risk perception of quick delivery service and other's was statistically significant effect on the experience of injury. Especially the higher the level of risk perception of quick delivery service workers is than other's, the lower the injury experience of quick delivery service worker is. The limitation of this study can be found in survey design. The future study for investigation of mechanism of the combined effect of risk perception of quick delivery service workers and others on injury experience.

• Architectural research
• /
• v.12 no.2
• /
• pp.53-62
• /
• 2010

The purpose of this study is to examine design preferences for the sales spaces of duty-free shops (DFSs) by conducting image evaluations. The results will help improve quality by influencing designs for the construction, extension or remodeling of these shops. An image measurement method, the semantic differential method, was used to measure cognitive structure using photos of shops. Photos were collected of the DFS at Jeju Island, as well as photos of brand stores designed by architects. Two sets of 16 photos (32 different photos in all) were selected according to photo classification standards and design concepts, both decided by reviewing previous studies and related materials. The evaluation and survey were done by two sets of subjects: sales employees, who have experience and special knowledge of the evaluation of sales space; and students majoring in architecture. To strengthen the evaluation results, I conducted a preliminary survey and a main survey, verifying and complementing findings. 116 surveys were conducted, of which 14 were of poor quality and rejected, leaving and 102 to be analyzed. The collected surveys were statistically analyzed, using SPSS 12.0 for Windows. Reliability, image profile, factor and multi-dimensional scaling analyses were conducted. As a result, image evaluation structure and characteristics were obtained for sales spaces of DFSs, confirming the difference between them and other spaces.

• Journal of the Korean School Mathematics Society
• /
• v.6 no.1
• /
• pp.101-113
• /
• 2003

The purpose of this study is to analyze students misunderstood types relate to trigonometric function and to devise its teaching method using GSP. To do this, we performed several steps as followings: First, we performed questionnaire survey to 70 students belong to second year at high school to find students comprehension degree about radian angle representation and trigonometric function graph. Second, we devised the teaching-learning materials relate to trigonometric function graph using GSP. And then, we used them in the class of 35 students who are at the time to learn trigonometric function in the first year at high school. Third, we conducted Questionnaire survey to students studied through teaching and learning materials using GSP. As a result of doing the survey, we found that general students were interested in the class using GSP and they could also operate computer without difficulty.

• The Journal of the Society of Korean Medicine Diagnostics
• /
• v.18 no.3
• /
• pp.137-148
• /
• 2014

Objectives This study was conducted to derive consensus about physical attributes in pressure pulse waveform and pulse conditions by Delphi study. Methods Delphi research was conducted for 2 rounds via e-mail. 8 Professors who lecture on a diagnostics of K. M. from the society of Korean medicine diagnostics were participated in this survey. They were asked for answering about series of definition for a physical attribute in pressure pulse waveform and combination for physical attributes of pulse conditions. Results 4 survey items were decided to have high validity and 9 survey items were decided to come to consensus about a physical attribute in pressure pulse waveform. 6 pulse condition were decided to come to consensus. Conclusion Using Delphi method, physical attributes in pressure pulse waveform and combinations of physical attribute in pulse condition come to consensus.

• IE interfaces
• /
• v.17 no.4
• /
• pp.482-489
• /
• 2004

As the functional characteristics of passenger cars have reached to a satisfactory level, customers place more concerns with the aesthetic aspects of interior designs. The present study developed satisfaction models of passenger car interior materials for six parts including crash pad, steering wheel, transmission gearshift knob, audio panel, metal grain, and wooden grain. Eight to fifteen material design variables such as color, embossing, and smoothness were defined for the six interior parts based on literature survey, customer reviews, and expert opinions. A satisfaction survey was conducted for 30 vehicles with 30 participants ($mean{\pm}SD$ of age = $28.7{\pm}6.6$) by using a modified magnitude estimation scale. Based on the survey results, the material design variables were screened from statistical, technical, and practical aspects. With the screened variables, satisfaction models were developed by using the quantification I method for the six interior parts, indicating the importance of material design variables and preferred material properties.

• Environmental Analysis Health and Toxicology
• /
• v.30 no.sup
• /
• pp.5.1-5.5
• /
• 2015

Objectives To protect public health from risk, the Minister of Environment in Korea legislated an act concerning the registration and evaluation of chemical substances. In this study, we estimated the value of a statistical life (VSL) of carcinogenic chemicals to evaluate the socioeconomic analysis in Korea. Methods The estimation of the health benefit can be calculated through an individual's VSL and willingness to pay (WTP). To estimate the VSL and WTP, we used a contingent valuation method through a web-based survey. Results The survey is conducted with 1434 people living in Seoul and six large cities. An analysis of the survey is essential to review the distribution of the characteristics of the target population. The statistically significant variables affecting the WTP are location, age, household income, quality of life. Through the review of data, we secured statistical validity. The WTP was estimated as 41205 Korean won (KRW)/person, and the estimated VSL appeared as 796 million KRW/person. Conclusions There is a case in which the amount of statistical life value is estimated in connection with domestic environmental policy, fine dust, etc. However, there are no cases of evaluation for chemical. The utilization of this result is possible for conducting other study with chemicals.

• Bulletin of the Korean Mathematical Society
• /
• v.48 no.4
• /
• pp.791-812
• /
• 2011

This is a survey on American options. An American option allows its owner the privilege of early exercise, whereas a European option can be exercised only at expiration. Because of this early exercise privilege American option pricing involves an optimal stopping problem; the price of an American option is given as a free boundary value problem associated with a Black-Scholes type partial differential equation. Up until now there is no simple closed-form solution to the problem, but there have been a variety of approaches which contribute to the understanding of the properties of the price and the early exercise boundary. These approaches typically provide numerical or approximate analytic methods to find the price and the boundary. Topics included in this survey are early approaches(trees, finite difference schemes, and quasi-analytic methods), an analytic method of lines and randomization, a homotopy method, analytic approximation of early exercise boundaries, Monte Carlo methods, and relatively recent topics such as model uncertainty, backward stochastic differential equations, and real options. We also provide open problems whose answers are expected to contribute to American option pricing.