• Journal of Biomedical Engineering Research
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• v.30 no.1
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• pp.94-102
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• 2009

In this paper, we propose a hearing impairment simulator considering reduced frequency selectivity of the hearing impaired, and verify it's performance through experiments. The reduced frequency selectivity was embodied by spectral smearing using linear prediction coding(LPC). The experiments are composed of 4 kinds of tests; pure tone test, speech reception threshold(SRT) test, and word recognition score(WRS) test without spectral smearing and with spectral smearing. The experiments of the hearing impairment simulator were performed with 9 subjects who have normal hearing. The amount of spectral smearing was controlled by LPC order. The percentile score of WRS test without smearing is $89.78{\pm}2.420%$. The scores of WRS with 24th LPC order and with 8th LPC order are $88.00{\pm}3.556%$ and $83.78{\pm}2.123%$ respectively. It is verified that WRS score is lowered by decreasing LPC order. This is a reasonable result considering that spectral smearing is getting heavier according to decreasing LPC order. It is confirmed that spectral smearing using LPC simulates the reduced frequency selectivity of the hearing impaired and affects the clearness of speech reception.

• Journal of Welding and Joining
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• v.33 no.3
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• pp.40-46
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• 2015

Welding is one of the most fundamental and necessary work in the industry that demand sophistication of skilled workers. This study is to introduce welding simulator as a training tool, to verify its effectiveness and to measure satisfaction of the trainees. A group of freshman students at a Korea Polytechnics College in their twenties with less experience of welding participated in the study. They were divided into two groups and took a traditional training course (comparison group) and a training course with welding simulator applied reality/haptic technology (experimental group) for same hours respectively. To evaluate training effect, a national certificate test and a survey based on Phillips' ROI (Return on Investment) methodology were conducted by the students and the college respectively. And satisfaction survey among the students based on Kirkpatrick's Four-Level Evaluation Model was also carried out. The results showed that all students in the experimental group passed the national certificate test and the ROI of the experimental group for five years were 110% higher than the comparison group. Furthermore, 25% more students in the experimental group replied "very satisfied" about the overall training course and 75% more students in the same group found that the simulation was very similar to the real welding.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.06a
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• pp.896-902
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• 2005

An orthopedic surgeon normally gets the operational parameters of total knee arthroplasty from medical images(CT, MRI). Anatomical axis, mechanical axis, the width and height of femur, or tibia are the most important parameters related with accomplishment of TKA. This paper presents a methodology of simulation that virtually operates TKA according to 2D medical images. Using this simulator, some important parameters for operation can be achieved before hand. The simulator provides the 3D computational model of a knee joint and then derives the proper size of implant corresponding to the joint. The whole process of TKA can be simulated such as clipping a knee joint, assembling the joint and its implants, visualizing all the operation steps, deriving some crucial parameters such as anatomical axis and cutting thickness, and predicting the result of TKA. Some examples are given and discussed to validate the methodology.

• International Journal of Control, Automation, and Systems
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• v.5 no.6
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• pp.643-651
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• 2007

The various blood pressure simulators have been proposed to evaluate and improve the performance of the automatic sphygmomanometer. These have some problems such as the deviation of the actual blood pressure waveform, limitation in the blood pressure condition of the simulator, or difficulty in displaying the blood flow. An improved simulator using disturbance observer is proposed to supplement the current problems of the blood pressure simulator. The proposed simulator has an artificial arm model capable of feeding appropriate fluids that can generate the blood pressure waveform to evaluate the automatic sphygmomanometer. A controller was designed and thereafter, simulation was performed to control the output signal with respect to the reference input in the fluid dynamic model using the proposed proportional control valve. To minimize the external fluctuation of pressure applied to the artificial arm, a disturbance observer was designed on the plant. A hybrid controller combined with a proportional controller and feed-forward controller was fabricated after applying a disturbance observer to the control plant. Comparison of the simulations between the conventional proportional controller and the proposed hybrid controller indicated that even though the former showed good control performance without disturbance, it was affected by the disturbance signal induced by the cuff. The latter exhibited an excellent performance under both situations.

• Journal of Biomedical Engineering Research
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• v.28 no.6
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• pp.768-776
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• 2007

A new type of the fluid circulation blood pressure simulator was proposed to enhance the blood pressure simulator used for the development and evaluation of automatic sphygmomanometers. Various pressure waveform of fluid flowing in the pipe was reproduced by operating the proportional control valve after applying a pressure on the fluid in pressurized oil tank. After that, appropriate fluid was supplied by operating the proportional control valve, which enabled to reproduce various pressure wave of the fluid flowing in the tube. To accomplish this work, the mathematical model was carefully reviewed in cooperating with the proposed simulator. After modeling the driving signal as input signal and the pressure in internal tube as output signal, the simulation on system parameters such as internal volume, cross-section of orifice and supply pressure, which are sensitive to dynamic characteristic of system, was accomplished. System parameters affecting the dynamic characteristic were analyzed in the frequency bandwidth and also reflected to the design of the plant. The performance evaluator of fluid dynamic characteristic using proportional control signal was fabricated on the basis of obtained simulation result. An experimental apparatus was set-up and measurements on the dynamic characteristic, nonlinearity, and rising and falling response was carried out to verify the characteristic of the fluid dynamic model. Controller was designed and thereafter, simulation was performed to control the output signal with respect to the reference input in the fluid dynamic model using the proposed proportional control valve. Hybrid controller combined with an proportional controller and feed-forward controller was fabricated after applying a disturbance observer to the control plant. Comparison of the simulations between the conventional proportional controller and the proposed hybrid simulator indicated that even though the former showed good control performance.

• Journal of Biomedical Engineering Research
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• v.35 no.3
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• pp.35-41
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• 2014

In this study, joint angles of the lower extremity and inertial sensor data such as accelerations and angular velocities were measured during a ski simulator exercise in order to evaluate the skill of skiers. Twenty experts and twenty unskilled skiers were recruited for the study. All expert skiers held the certificates issued by the Korea Ski Instructors Association. A three-dimensional motion capture system and two inertial sensors were used to acquire joint movements, heel acceleration and heel angular velocity during ski simulator exercises. Pattern variation values were calculated to assess the variations in ski simulator motion of expert and unskilled skiers. Integral ratio of roll angular velocity was calculated to determine the parallel alignment of the two feet. Results showed that ski experts showed greater range of motion of joint angle, peak-to-peak amplitude(PPA) of heel acceleration and PPA of heel angular velocity than unskilled skiers. Ski experts showed smaller pattern variations than unskilled skiers. In addition, the integral ratio of roll angular velocity in ski experts was closer to 1. Inertial sensor data measurements during the ski simulator exercises could be useful to evaluate the skill of the skier.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.945-946
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• 2011

• The Journal of Korean Society for Radiation Therapy
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• v.17 no.2
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• pp.147-153
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• 2005

Purpose : We should use a computed tomography-simulator for the body measure and compensator manufacture process was practiced with TBI's positioning in process and to estimate the availability.,Materials and Methods : Patient took position that lied down. and got picture through computed tomography-simulator. This picture transmitted to Somavision and measured about body measure point on the picture. Measurement was done with skin, and used the image to use measure the image about lungs. We decided thickness of compensator through value that was measured by the image. Also, We decided and confirmed position of compensator through image. Finally, We measured dosage with TLD in the treatment department.,Results : About thickness at body measure point. we could find difference of $1{\sim}2$ cm relationship general measure and image measure. General measure and image measure of body length was seen difference of $3{\sim}4$ cm. Also, we could paint first drawing of compensator through the image. The value of dose measurement used TLD on head, neck, axilla, chest(lungs inclusion), knee region were measured by $92{\sim}98%$ and abdomen, pelvis, inquinal region, feet region were measured by $102{\sim}109%$.,Conclusion : It was useful for TBI's positioning to use an image of computed tomography-simulator in the process. There was not that is difference of body thickness measure point, but measure about length was achieved definitely. Like this, manufacture of various compensator that consider body density if use image is available. Positioning of compensator could be done exactly. and produce easily without shape of compensator is courted Positioning in the treatment department could shortened overall $15\{sim}20$ minute time. and reduce compensator manufacture time about 15 minutes.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2005.10a
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• pp.135-138
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• 2005

Robotic devices have been widely used in many medical applications due to their accuracy and programming ability. One of the applications is a virtual reality medical simulator, which trains medical personnel in a computer generated environment. In this paper, we are going to present an application, an epidural anesthesia trainer. Because performing epidural injections is a delicate task, it demands a high level of skill and precision from the physician. This trainer uses a robotic device and computer controlled solenoid valve to recreate interaction forces between the needle and the various layers of tissues around the spinal cord. The robotic device is responsible for generation of interaction forces in real time and can be used to be haptic guidance that allows the user to follow a previous recorded expert procedure and feel the encountered forces.

• Journal of Biomedical Engineering Research
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• v.41 no.1
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• pp.8-13
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• 2020

To develop cardiovascular simulator capable of implementing pulse waves similar to the human body, accurate information about reflection wave is required. However, the conclusion is still not clear and various discussions are underway. In this study, the pulse wave velocity of the tube used in the experiment was first determined by measuring the pressure waves at two points in a single tube system with the experimental device to implement the pulse wave transmission of blood vessels, and the superposition time and characteristics of the reflection wave were confirmed. After that, an air chamber was set at the reflection site, and the effect of the change of air volume on the reflection wave was investigated. Finally, the effect of the number of branches connected to a single tube on the reflection wave was investigated. The superposition time of the reflection wave can be controlled by the air volume of the air chamber, and the magnitude of the reflection wave is influenced by the number of reflection sites that generate the reflection wave. The results of this study may be of practical assistance to simulator researchers who want to implement pulse wave similar to clinical data. It is expected that the more results similar to clinical are provided, the greater the scope of the simulator's contribution to clinical cardiovascular research.