• The Journal of the Acoustical Society of Korea
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• v.20 no.1
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• pp.68-76
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• 2001

Sonar is the system that detects objects and finds their location in water by using the echo ranging technique. In order to have excellent performance in variable environment, acoustic characteristics of this system must be analyzed accurately. In this paper, based on the finite element analysis, modeling and analysis of acoustic characteristics of underwater acoustic sensors are preformed. Couplings between piezoelectric and elastic materials, and fluid and structure systems associated with the modeling of piezoelectric underwater acoustic sensors are formulated. In the finite element modeling of unbounded acoustic fluid, IWEE (Infinite Eave Envelop Element) is adopted to take into account the infinite domain. When an incidence wave excites the surface of Tonpilz underwater acoustic sensor, the scattered wave on the sensor is founded by satisfying the radiation condition at the artificial boundary approximately. Based on this scattering analysis, the electrical response of the underwater acoustic sensor under incidence, so called RVS (Receiving Voltage Signal) is founded accurately. This will devote to design Sonar systems accurately.

• Korean Institute of Interior Design Journal
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• v.19 no.1
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• pp.46-54
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• 2010

Since the accomplishment of industrialization and mechanization, human and the nature have gone farther their own way. Human depending on technology have been increasingly expanding and developing their artificial space and as times go by in such a way, estrangement between the human and nature has resulted in dissatisfaction of human's instinctual desire and devastation of human's living. People, to deal with such challenge, begins taking a look at the nature. In introducing the nature into the modern architecture, a physical natural element is often directly taken into or the shape that could be inferred from the nature is taken. The study was intended to identify the characteristics of the pattern introducing the nature into the modern architecture, as mentioned in the former case, which is summarized as follows, Introduction of the nature contains a variety of functions in the space and it creates the new space by integrating the internal and external space which becomes boundaryless integrated space. The boundary in the building tends to be getting more ambiguous, while the space accommodating the nature serves the interface, playing a role of intermediator for both the internal and external space. It functions the open public place that helps build the natural community among the users but taking the nature into the inner space, and it is used to attempt to change the interior of the building or for ventilation lighting or energy-saving purpose. The spatial meaning was found to have varied depending on pattern of the nature introduced. Such conclusions mentioned hereon is expected to help forecast and understand the forthcoming space accommodating the nature when reviewing the pattern of introducing the nature appeared In modern architecture.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.25 no.11
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• pp.1519-1524
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• 2021

In this paper, we propose a method that uses fuzzy decision tree based health pre-diagnosis system of oriental medicine. The proposed fuzzy decision tree based health pre-diagnosis system uses the data from the past which has been pre-trained to get the boundary values based on entropy then, when the user inputs the symptoms, the top 5 diseases that causes those symptoms are extracted. With the extracted top 5 diseases, the system provides information on those diseases with the cause and how to treat them with folk remedies. The database of the diseases and their symptoms is established with the information based on the various books that the oriental doctor recommended then reviewed by the oriental doctor for confirmation. By utilizing the data from the past to train the symptoms of the diseases, the proposed oriental medicine-based health pre-diagnosis system method could provide more accurate diagnosis results faster.

• Journal of the Korean Orthopaedic Association
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• v.53 no.6
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• pp.459-465
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• 2018

Of the many factors that affect the clinical outcomes of orthopedic surgery, the surgical procedure is the most important. Robotics have been developed to perform the surgical procedures more accurately and consistently. Robotic surgical procedures in the orthopedic field were developed 20 years ago. Some designs of surgical robots have disappeared due to practical problems and complications, and an another design of surgical robots is emerging. To date, the use of robot surgery in arthroplasty is still controversial in terms of the clinical outcomes, practicality, and cost-effectiveness, even though it has been reported to be effective in the alignment and positioning of components in the field of artificial joints. Early robotic surgery was based mainly on active robot surgery according to the scheduled operation without the intervention of the operator. Recently the semi-active system of robotic surgery has been introduced. In a semi-active system, the robot constrains the surgeon to a haptic boundary defined by the computer based on the 3-dimensional imaging preoperative plan, and the operator can change the preoperative plan through real-time feedback during operation.

• Geophysics and Geophysical Exploration
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• v.21 no.4
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• pp.231-243
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• 2018

Streaming potential (SP) arises from fluid flow through effectively connected pores. From this potential, formation water information as well as fluid flow properties can be estimated. As micro particles being located in boundary between subsurface porous media and fluid are charged to form electrical double layer, fluid flow caused by several reasons generates SP, one of electrokinetic phenomena. Occurrence mechanism of SP is complex and signal strength is relatively weak compared to noise. However, application of self potential survey using SP to monitoring of formation fluid is expanding because of its' convenience of exploration without artificial source and repetitiveness of signal. This paper accounts for the occurrence mechanism of SP studied before, including governing equations and analyzes previous various case studies of SP according to the change of physical properties of materials. It helps to increase understanding about SP and also lays the foundations of the application of SP to fields.

• Journal of Radiation Protection and Research
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• v.47 no.3
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• pp.111-133
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• 2022

The exciting advancement related to the "modeling of digital human" in terms of a computational phantom for radiation dose calculations has to do with the latest hype related to deep learning. The advent of deep learning or artificial intelligence (AI) technology involving convolutional neural networks has brought an unprecedented level of innovation to the field of organ segmentation. In addition, graphics processing units (GPUs) are utilized as boosters for both real-time Monte Carlo simulations and AI-based image segmentation applications. These advancements provide the feasibility of creating three-dimensional (3D) geometric details of the human anatomy from tomographic imaging and performing Monte Carlo radiation transport simulations using increasingly fast and inexpensive computers. This review first introduces the history of three types of computational human phantoms: stylized medical internal radiation dosimetry (MIRD) phantoms, voxelized tomographic phantoms, and boundary representation (BREP) deformable phantoms. Then, the development of a person-specific phantom is demonstrated by introducing AI-based organ autosegmentation technology. Next, a new development in GPU-based Monte Carlo radiation dose calculations is introduced. Examples of applying computational phantoms and a new Monte Carlo code named ARCHER (Accelerated Radiation-transport Computations in Heterogeneous EnviRonments) to problems in radiation protection, imaging, and radiotherapy are presented from research projects performed by students at the Rensselaer Polytechnic Institute (RPI) and University of Science and Technology of China (USTC). Finally, this review discusses challenges and future research opportunities. We found that, owing to the latest computer hardware and AI technology, computational human body models are moving closer to real human anatomy structures for accurate radiation dose calculations.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2022.05a
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• pp.428-430
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• 2022

Image processing is playing an important part in automation and artificial intelligence systems, such as object tracking, object recognition and classification, and the importance of IoT technology and automation is emphasizing as interest in automation increases. However, in a system that requires detailed data such as an image boundary, a precise noise removal algorithm is required. Therefore, in this paper, we propose a filtering algorithm based on the pixel value distribution pattern to minimize the information loss in the filtering process. The proposed algorithm finds the distribution pattern of neighboring pixel values with respect to the pixel values of the input image. Then, a weight mask is calculated based on the distribution pattern, and the final output is calculated by applying it to the filtering mask. The proposed algorithm has superior noise removal characteristics compared to the existing method and restored the image while minimizing blurring.

• Earthquakes and Structures
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• v.26 no.2
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• pp.149-162
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• 2024

Aiming at the current research on the dynamic response analysis of the vehicle-bridge system under earthquake, which fails to comprehensively consider the impact of seismic wave incidence angles, terrain effects and soil-structure dynamic interaction on the bridge structure, this paper proposes a multi-point excitation input method that can consider the oblique incidence seismic P Waves based on the viscous-spring artificial boundary theory, and verifies the accuracy and feasibility of the input method. An overall numerical model of vehicle-bridge-soil foundation system in valley terrain during oblique incidence of seismic P-wave is established, and the effects of seismic wave incidence characteristics, terrain effects, soil-structure dynamic interactions, and vehicle speeds on the dynamic response of the bridge are analyzed. The research results indicate that with an increase in P wave incident angle, the vertical dynamic response of the bridge structure decreased while the horizontal dynamic response increased significantly. Traditional design methods which neglect multi-point excitation would lead to an unsafe structure. The dynamic response of the bridge structure significantly increases at the ridge while weakening at the valley. The dynamic response of bridge structures under earthquake action does not always increase with increasing train speed, but reaches a maximum value at a certain speed. Ignoring soil-structure dynamic interaction would reduce the vertical dynamic response of the bridge piers. The research results can provide a theoretical basis for the seismic design of vehicle-bridge systems in complex mountainous terrain under earthquake excitation.

• Economic and Environmental Geology
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• v.57 no.1
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• pp.17-23
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• 2024

Ground penetrating radar (GPR) survey is a geophysical method that utilizes electromagnetic waves reflecting from a boundary where the electromagnetic property changes. As the frequency of the antenna is about 25 MHz ~ 1 GHz, it is effective to acquire high resolution images of underground pipe, artificial structure, underground cavity, and underground structure. In this study, we analyzed the change of signals reflected from the same underground objects according to the arrangement of transceiver antennas used in ground penetrating radar survey. The antenna used in the experiment was 200 MHz, and the survey was performed in the vertical direction across the sewer and the parallel direction along the sewer to the sewer buried under the road, respectively. A total of five antenna array methods were applied to the survey. The most used arrangement is when the transmitting and receiving antennas are all perpendicular to the survey line (PR-BD). The PR-BD arrangement is effective when the object underground is a horizontal reflector with an angle of less than 30°, such as the sewer under investigation. In this case study, it was confirmed that the transmitter and receiver antennas perpendicular to the survey line (PR-BD) are the most effective way to show the underground structure. In addition, in the case where the transmitting and receiving antennas are orthogonal to each other (XPOL), no specific reflected wave was observed in both experiments measured across or parallel to the sewer. Therefore, in the case of detecting undiscovered objects in the underground, the PR-BD array method in which the transmitting and receiving antennas are aligned in the direction perpendicular to the survey line taken as a reference and the XPOL method in which the transmitting and receiving antennas are orthogonal to each other are all used, it can be effective to apply both of the above arrangements after setting the direction to 45° and 135°.

• Geomechanics and Engineering
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• v.36 no.2
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• pp.183-204
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• 2024

In current investigation, a novel beam finite element model is formulated to analyze the buckling and free vibration responses of functionally graded porous beams resting on Winkler-Pasternak elastic foundations. The novelty lies in the formulation of a simplified finite element model with only three degrees of freedom per node, integrating both C⁰ and C¹ continuity requirements according to Lagrange and Hermite interpolations, respectively, in isoparametric coordinate while emphasizing the impact of z-coordinate-dependent porosity on vibration and buckling responses. The proposed model has been validated and demonstrating high accuracy when compared to previously published solutions. A detailed parametric examination is performed, highlighting the influence of porosity distribution, foundation parameters, slenderness ratio, and boundary conditions. Unlike existing numerical techniques, the proposed element achieves a high rate of convergence with reduced computational complexity. Additionally, the model's adaptability to various mechanical problems and structural geometries is showcased through the numerical evaluation of elastic foundations, with results in strong agreement with the theoretical formulation. In light of the findings, porosity significantly affects the mechanical integrity of FGP beams on elastic foundations, with the advanced beam element offering a stable, efficient model for future research and this in-depth investigation enriches porous structure simulations in a field with limited current research, necessitating additional exploration and investigation.