Advanced Nondestructive Evaluation I

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Authors: Dae Gon Woo, Han Sung Kim, Chang Yong Ko, Beob Yi Lee, Gye Rae Tack, Young Ho Kim
Abstract: In the present study, changes of morphologies and mechanical characteristics in the lumbar vertebrae of the ovariectomised (OVX) rats were investigated and analyzed by Finite Element (FE) and Rapid-Prototyped (RP) models based on micro-computed tomography (micro-CT). In previous researches, there were many studies about morphology such as bone mineral density and trabecular microstructure. However, detecting and tracking local changes were few in the trabecular and cortical bone of the lumbar vertebrae for the OVX rats. Experimental and simulated studies were used to investigate mechanical characteristics of the lumbar vertebral bones for the OVX rats. Three dimensional (3D) geometries of the models (RP and FE models), generated from in-vivo micro-CT scan data, were obtained from the 4th lumbar of the OVX rats. Three specimens (whole vertebral, trabecular and cortical bone models) were generated and analyzed in the simulated compression tests. For further verification, the experimental compression test for RP models ‘instead of real bone specimens’ was performed to indirectly validate the results of the simulated compression test for the FE models. The results were similar to those of the compression test simulated by micro-FE analysis. The present study showed the efficiency of the combined method (FE and RP techniques based on in-vivo micro-CT) as a nondestructive evaluation.
Authors: Jung Hwa Hong, Young Hwan Park, Sang Ok Ko, Soon Hyuck Lee, Gon Khang
Abstract: In this study, a minimally invasive assessment using bone strain generated potential (SGP) was developed to examine the amount of osseointegration (OI) at bone-implant interface. SGP is generated by interstitial fluid flow in porous bone structure. Four experimental white New Zealand rabbits underwent pure titanium implant insertion surgery to tibia after amputation. After surgery, two animals were kept in small cages with minimal movement (Group 1). In contrast, the other rabbits were kept in a large cage that was large enough for jumping and walking (Group 2). At the end of the 5 weeks, all experimental animals were euthanized and the amputated tibia-implants were harvested. Then, a quasi-static force was applied to a bone site near the bone-implant interface for each tibia-implant specimen. Also, SGPs were measured near the interface using needle or probe electrodes. After the measurements, digital radiographs were taken to check the amount of OI for the interfaces. Full OI was observed for animals in Group 1. However, incomplete OI was found for animals in Group 2. Also, significant difference was found for mean SGP values between Group 1 and 2. The results could imply that SGP could be used as a minimally invasive assessment method to check the OI at the bone-implant interface.
Authors: Yong Hoon Rim, Young Jin Kim, Sang Sik Lee, Joung H. Mun
Abstract: Equinus gait, defined as walking on one forefoot or both forefeet, has long been considered an undesirable characteristic in patients with a variety of neuromuscular disorders. In the equinus gait, the heel contact pattern is changed according to the severity, because an excessive ankle plantar flexion instigates rearfoot lifting in patients. However, no biomechanical severity index exists to evaluate the rehabilitation procedure of equinus gait. Therefore, we developed an SIEG (Severity Index of Equinus Gait) for nondestructive evaluation of the equinus gait and to validate the index with regard to 11 kinematic and kinetic factors of gait analysis. In this study, the 3-D heel contact pattern was considered for the development of a severity index. In order to verify the result, we compared the developed severity index values with ankle joint kinematic and kinetic factors in 3 test groups. As a result, the average SIEG values ranged between 10.45 (Normal group) and 26.61 (Severe group) and the highest correlation with regard to the 3 groups was shown in the developed severity index. Additionally, we also presented a fuzzy model using Takagi-Sugeno-Kang(TSK) logic with regard to the 12 factors in order to more accurately classify equinus gait.
Authors: Yong Hoon Rim, Ahn Ryul Choi, Sang Sik Lee, Joung H. Mun
Abstract: The purpose of this study is to calculate the length and velocity change of gastrocnemius and soleus muscle-tendon complex (MTC) for diagnosis and estimation of the rehabilitation procedure of the patient from non-invasive 3D markers. The previous method measuring the length of MTC has been dependant on the regression equation based on the rotation angle in the sagittal plane. However, in view of the fact that movement analysis is based on the human body having a variety of structure, the measurement using merely rotation angle and regression equation which not based on each subject shank and foot length might not be accurate. In order to overcome these limitations, the length change of MTC is calculated, employing 3D MTC model accompanied with the trajectory data of markers attached anatomical landmarks, each subject measurements and femur condyle radius. Basically, more accurate length change could be acquired through the 3D trajectory data of markers in comparing with 2D data based on the rotation angle. As our study, the difference of the gastrocnemius length change between 3D marker trajectory based method and the method using a 2-D angle was approximately 4% (2cm) at maximum contraction and 1% (0.5cm) at maximum relaxation. Similarly, the difference in terms of the soleus was approximately 0.7% (0.3cm) at maximum contraction and 0.5% (0.2cm) at maximum relaxation.
Authors: Tae Yong Sim, Seung Eel Oh, Sang Sik Lee, Joung H. Mun
Abstract: In golf, it is crucial that unintended shots, such as slices, be minimized. However, it has proven rather difficult to improve golf performance via investigations of the causes of slicing, as this particular phenomenon is induced by a cooperative effect by each segment of the body, rather than by a single postural anomaly. Thus, the objective of this study was to isolate and characterize the factors causing slicing, and to present possibilities for the improvement of golf performance via the minimization of the number of slices executed, using a three dimensional motion capture system, combined with multiple regression analysis, artificial neural network, and fuzzy logic techniques. This study obtained some interesting results, such as the following: (1) We isolated 9 slice-inducing factors, using a stepwise method. (2) Our artificial neural network (ANN) accurately separated 'slice' from 'normal' shots (classification rate: 100%). (3)We could present the possibility of reducing the number of slice using the fuzzy logic. We expect that our data might be eventually used to improve golf performance.
Authors: Hyo Shin Kim, Youn Soo Kim, Joung H. Mun
Abstract: This study was aimed at predicting moments with respect to diameters of wires for evaluating stability of the upper cervical spine fixed with wires based on the finite element analysis. In case of the severe atlanto-axial instability, several surgical methods have been tried and the posterior fixation using wires has been widely used because of the sufficient stability and high rate of bony adhesion. The diameters of wires applied in this study were 0.7 mm, 0.9 mm and 1.25 mm. 1.5 Nm is the moment for the normal physiological range of motion of the upper cervical spine in cadaver models. However, if this moment is applied to the occiput, an excessive load occurs at the occipito-atlantal joint and clinical problems can break out realistically. Thus, it is necessary to predict moments for evaluating stability with respect to diameters of wires. The results showed that 0.7 mm wire allowed the biggest moment while 1.25 mm wire allowed the smallest moment. In addition, the upper cervical spine fused with wires was stabilized effectively as the load increased.
Authors: Yong K. Moon, Yu H. Song, Jae H. Kim, Sang Sik Lee, Joung H. Mun
Abstract: The objective of this study was to develop an Ethernet-based telemedical blood pressure monitor. Although telemedical applications utilizing a variety of media are currently available, present systems do not provide remote signals with regard to integrated vital information, including blood pressure and pulse rate. In addition, the existing systems are largely embedded-structure, single-access, single-process models. Thus, we developed an Ethernet-based blood pressure monitor which includes a client/server structure, and is a real-time multi-access and multi-process system. The client for the developed system uses the Microsoft Comm Control in Microsoft Visual Basic and ODBC to connect Microsoft Chart Control with DB for a user interface. The server is programmed with the J2SE development platform, in a multi-thread structure. The system is capable of receiving data simultaneously. A TCP/IP socket was used for the Ethernet connection. The JDBC was applied to connect with the database for the saving, searching, and sampling of the data. The data transfer failure rate of the developed system was determined to be less than 0.05%.
Authors: Sang Sik Lee, Ki Young Shin, Joung H. Mun
Abstract: The objective of this study was to develop a portable, wireless surface EMG of a noninvasive type. The limitations of the existing system include its large size and the necessity of a wire. Therefore, this study focused on the development of a portable and wireless type of EMG. The developed EMG, which has 10 channels, is composed of an electrode for the measurement of the EMG signal, a preamplifier for initial processing, a second amplifier, an A/D converter, and a Bluetooth module for wireless communication. The communication of the developed EMG used a UART (Universal Asynchronous serial Receiver and Transmitter) and Bluetooth protocols. The rate of serial communication was set to 723kbps. This system is able to obtain 2,000 Hz in each channel. The data transfer success rate of the developed EMG is 100%.
Authors: Sang Sik Lee, Ki Young Shin, Joung H. Mun
Abstract: Currently available foot pressure sensors (FPS), which usually include a capacitive sensor and a piezoresistive sensor, tend to exhibit characteristically slow response times. Therefore, we used PZT (lead zirconate-titanate) ceramic in this study, as it responds more quickly than the currently-used materials. We have developed an algorithm which can be applied to the PZT ceramic-based measurement of foot pressure. This algorithm was also verified in experiments. In this study, we fabricated the electronic circuits and a sensor on the basis of the newly-developed algorithm, and then verified the algorithm experimentally.
Authors: Hyeon Ki Choi, Si Yeol Kim
Abstract: A computer-graphics based biomechanical model was constructed to investigate the kinematics of foot joints during the stance-phase of walking. In the model, all joints were assumed to act as monocentric, single degree of freedom hinge joints. To obtain the inputs to the model, the motion of foot segments was captured during the gait by a four-camera video system. The model fitted in an individual subject was simulated with these motion data. The ranges of motion of the first tarsometatarsal joint and the first metatarsophanlangeal joint were 8  ∼13  and -13  ∼ 48  respectively. The kinematic data of joints were similar to those of the previous studies. Our method based on the graphical computer model is considered useful for kinematic analysis of small joints including foot joints. Also, the results of this study will provide important information to the biomechanical studies which deal with human gait.

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