• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.2
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• pp.391-398
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• 2009

In this study, we introduce the design methodology of an optimized fuzzy cascade controller with the aid of hierarchical fair competition-based genetic algorithm(HFCGA) for ball & beam system. The ball & beam system consists of servo motor, beam and ball, and remains mutually connected in line in itself. The ball & beam system determines the position of ball through the control of a servo motor. The displacement change the position of ball leads to the change of the angle of the beam which determines the position angle of a servo motor. Consequently the displacement change of the position of the moving ball and its ensuing change of the angle of the beam results in the change of the position angle of a servo motor. We introduce the fuzzy cascade controller scheme which consists of the outer(1st) controller and the inner(2nd) controller as two cascaded fuzzy controllers, and auto-tune the control parameters(scaling factors) of each fuzzy controller using HFCGA. The inner controller controls the position of lever arm which corresponds to the position angle of a servo motor and the outer controller decides the set-point value of the inner controller. HFCGA is a kind of parallel genetic algorithms(PGAs), and helps alleviate the premature convergence being generated in conventional genetic algorithms (GAs). For a detailed comparative analysis from the viewpoint of the performance results and the design methodology, the proposed method for the ball & beam system which is realized by the fuzzy cascade controller based on HFCGA, is presented in comparison with the conventional PD cascade controller based on serial genetic algorithms.

• Korean Journal of Applied Biomechanics
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• v.24 no.4
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• pp.329-338
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• 2014

The purpose of this study was to analyze of the rider postural alignments according to the fitting of stirrups lengths during walk of high level riders. Participants selected as subject were consisted of horse riders of high level (age: $47.66{\pm}3.51yrs$, height: $168.40{\pm}4.84cm$, body weight: $73.36{\pm}15.58kg$, low extremity length: $94.76{\pm}3.98cm$, career: $23.33{\pm}5.77yrs$) and walk with 3 types of stirrup lengths(ratio of low extremity 68.04%, 73.25%, 78.48%). The variables analyzed were consisted of the displacement of Y axis (center of mass, head, thigh, shank and foot), FR angle, LR angle, dynamic postural stability index (DPSI), coefficient of variation (CV%), and distance (X axis) of low extremity limb between right and left. The displacement of Y axis in COM, thigh, shank, foot limbs were not statistically significant, but movements of head showed greater distance of B type and C type than that of A type during 1 stride of walk. The FR and LR angle in trunk of horse rider, dynamic postural stability index and, coefficient of variation didn't show significant difference statistically according to the fitting of stirrup lengths. Also the distance (X axis) of low extremity in thigh and shank didn't show significant difference statistically in between right and left, but right and left foot showed greater distance in C type than that of B and A types during walk in horse back riding. The hip and ankle joint angle not statistically significant according to stirrups lengths, But knee joint angle showed more extended according to the increase of stirrups lengths during stance and swing phase in walk.

• Journal of Korean Tunnelling and Underground Space Association
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• v.10 no.3
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• pp.245-256
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• 2008

The steel rib, one of the main support of tunnel, plays a very important role to stabilize tunnel excavation surface until shotcrete or rockbolt starts to perform a supporting function. In general, a steel rib at the horizontal funnel is being installed in the direction of gravity which is known favorable in terms of constructability and stability. However, as the direction of principal stress at the inclined tunnel wall is different from that of gravity, the optimum direction of steel rib could be different from that at the horizontal tunnel. In this study, a numerical method was used to analyze the direction of force that would develope displacement at the inclined tunnel surface, and that direction could be the optimum direction of steel rib. The support efficiency of steel rib could be maximized when the steel rib was installed to resist the displacement of the tunnel. Three directions which were recommended for the inclined tunnels in the Korea Tunnel Design Standard were used for the numerical models of steel rib direction. In conclusion, the results show that all displacement angle of the models are almost perpendicular to the tunnel surface regardless of face angle. So if the steel rib would be installed perpendicular to the inclined tunnel surface, the support efficiency of steel rib could be maximized.

• Journal of Oral Medicine and Pain
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• v.38 no.2
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• pp.149-159
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• 2013

The purpose of this study was to investigate the relationship between horizontal morphology of lateral pterygoid muscle and onset of temporomandibular joint disorders. Randomly selected 150 subjects, assigned with equal number in terms of gender and age group, were included. The axial and sagittal images in their magnetic resonance images of the temporomandibular joints were used to measure the morphologic characteristics of lateral pterygoid muscles and temporomandibular joints. The measurement variables were maximal horizontal width and insertion angle to the condyle, position of the articular disc, condylar deformity, and joint effusion. In addition, presence or absence of the temporomandibular joint pain was examined through history and palpation of the joints. The relationships among measurement variables were analyzed and the results were as follow. The insertion angle of the lateral pterygoid muscle to the condyle was higher in the joint of anterior disc displacement without reduction than that in the joint of normal disc position. In addition, the maximal horizontal width of the lateral pterygoid muscle was significantly increased in joints with pain than those without pain. Also, the insertion angle was significantly higher in younger age group and the maximal width was significantly greater in male than in female. These results suggest that high insertion angle of lateral pterygoid muscle might be an important anatomic predisposing factor for anterior disc displacement in temporomandibular joint and muscular activity of lateral pterygoid muscle might be affected by preauricular pain. In conclusion, there might be a bi-directional interaction between lateral pterygoid muscle and joint in the progression of anterior disc displacement in temporomandibular joint.

• Restorative Dentistry and Endodontics
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• v.19 no.2
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• pp.345-371
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• 1994

Restorative procedures can lead to weakening tooth due to reduction and alteraton of tooth structure. It is essential to prevent fractures to conserve tooth. Among the several parameters in cavity designs, cavity isthmus and depth are very important. In this study, MO amalgam cavity was prepared on maxillary first premolar. Three dimensional. finite element models were made by serial photographic method and cavity depth(1.7mm, 2.4mm) and isthmus (11 4, 1/3, 1/2 of intercuspal distance) were varied. linear, eight and six-nodal, isoparametric brick elements were used for the three dimensional finite element model. The periodontal ligament and alveolar bone surrounding the tooth were excluded in these models. Three types model(B, G and R model) were developed. B model was assumed perfect bonding between the restoration and cavity wall. Both compressive and tensile forces were distributed directly to the adjacent regions. G model(Gap Distance: 0.000001mm) was assumed the possibility of play at the interface simulated the lack of real bonding between the amalgam and cavity wall (enamel and dentin). When compression occurred along the interface, the forces were transferred to the adjacent regions. However, tensile forces perpendicular to the interface were excluded. R model was assumed non-connection between the restoration and cavity wall. No force was transferred to the adjacent regions. A load of 500N was applied vertically at the first node from the lingual slope of the buccal cusp tip. This study analysed the displacement, von Mises stress, 1 and 2 direction normal stress and strain with FEM software ABAQUS Version 5.2 and hardware IRIS 4D/310 VGX Work-station. The results were as follows: 1. G model showed stress and strain patterns between Band R model. 2. B model and G model showed the bending phenomenon in the displacement. 3. R model showed the greatest amount of the displacement of the buccal cusp followed by G and B model in descending order. G model showed the greatest amount of the displacement of the lingual cusp followed by B and R model in descending order. 4. B model showed no change of the displacement as increasing depth and width of the cavity. G and R model showed greater displacement of the buccal cusp as increasing depth and width of the cavity, but no change in the displacement of the lingual cusp. 5. As increasing of the width of the cavity, stress and strain were not changed in B model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in G and R model. The possibility of the tooth fracture was increased. 6. As increasing of the depth of the cavity, stress and strain were not changed in B and G model. Stress and strain were increased on the distal marginal ridge and buccopulpal line angle in R model. The possibility of the tooth fracture was increased.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.27 no.3
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• pp.372-380
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• 2003

Impact tests were conducted to study the effect of angle ply and metal laminate on impact damage characteristics of Fiber Metal laminates (FML). Impact tests were conducted using drop weight impact machine and damage behavior were analyzed by comparing with load-displacement curve and surface observation and microscopic observation of cross sections. The effect of angle ply on impact characteristics of FML are influenced by property of metal laminate. i.e., when the metal laminate is not enough to strong to prevent fiber debonding, Angle ply FML is superior to singly oriented ply (SOP) FML because angle ply enhance the stiffness by fiber supports and prevent (rack propagation. However, when the metal laminate is enough to strong to prevent fiber debonding, SOP FML is superior to Angle ply FML because the fiber of lower ply in Angle ply FML are more stressed than that of SOP FML.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.11a
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• pp.417-418
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• 2007

• Proceedings of the Korean Geotechical Society Conference
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• 2003.03a
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• pp.463-468
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• 2003

This paper studied the effects of inclination of piles on pile behaviors. The following are the conclusions of this study. (1) When all the piles are inclined to a same direction, the piles reaction, maximum moment and horizontal displacement of footing increase as the angle of inclination increases. (2) When the piles of each opposite side are inclined symmetrically, the vertical reaction either increases or decreases in proportion to the angle of inclination. In this case, the vertical reaction of inclined piles decreases but the vertical reaction of non-Inclined piles increases.

• The korean journal of orthodontics
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• v.36 no.2 s.115
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• pp.136-144
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• 2006

The purpose of this study was to determine whether association exists between temporomandibular joint (TMJ) characteristics in transcranial radiographs and TMJ internal derangement and to evaluate the validity of transcranial radiographs in diagnosis of internal derangement. Transcranial radiographs and magnetic resonance imaging (MRI) of 113 TMJs from 76 subjects were used for this study and all TMJs were classified into 3 groups according to the results of MRI: normal disk position, disk displacement with reduction, and disk displacement without reduction. Transcranial analysis included linear measurement of joint spaces and condylar head angle measurement. To determine any relationship between transcranial measurements according to disk displacement, one-way ANOVA was used. The results showed that condyle-fossa relationship in standard transcranial radiographs had no relationships with disk displacement. And, as disk displacement progressed, condylar angle between head and neck increased significantly. This result can be interpreted that condylar head angle reflects structural hard tissue change according to internal derangement progress. But this is insufficient in the determination of internal derangement. Therefore, although still clinically helpful, the validity of standard transcranial radiographs to diagnose TMJ internal derangement was questioned.

• Journal of Korean Foot and Ankle Society
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• v.13 no.2
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• pp.113-117
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• 2009

Purpose: To evaluate the short-term results of medial displacement calcaneal osteotomy without flexor digitorum longus transfer for flexible flatfoot deformity. Materials and Methods: Twenty four patients (25 feet) who had undergone medial displacement calcaneal osteotomy without flexor digitorum longus transfer for flexible flatfoot between July 2004 and May 2007 were included. The mean age was 43.6 years (16~78 years). The mean follow-up was 26 months (14~50 months). Clinical outcomes were assessed using American Orthopaedic Foot and Ankle Society (AOFAS) score and visual analogue scale (VAS). Six radiographic parameters were measured from weightbearing radiographs to assess the difference between preoperative and postoperative radiographs. Results: The mean AOFAS score improved from 57.9 points preoperatively to 89.2 points at latest follow-up (p=0.000). The mean VAS improved from 62 points preoperatively to 23 points at latest follow-up (p=0.000). The mean talonavicular coverage angle on anteroposterior (AP) view changed from 20.2 degrees to 16.0 degrees (p=0.002). The mean calcaneal pitch angle on lateral view changed from 12.6 degrees preoperatively to 14.5 degrees at latest follow-up (p=0.001). Regarding these radiographic parameters, the difference between interobserver measurements was larger than that between pre- and post-operative measurements. The calcaneus was transferred medially by average 11.8 mm (p=0.003), which was 27.9% of the width of calcaneal tuberosity (p=0.000). The mean talo-first metatarsal angle on AP and lateral views, and navicular height on lateral view were not significantly changed. Conclusion: Medial displacement calcaneal osteotomy without flexor digitorum longus transfer for flexible flatfoot could lead to improve the clinical outcomes, although the restoration of medial longitudinal arch was not clinically significant.