Background: Lumbar lordosis is a result of muscle shortening and may cause low back pain. Objective: To examine the effects of static and dynamic stretching on lumbar lordosis and low back pain in university students. Stretching is an intervention that can be applied to shortened muscles; however, very few studies have compared the effects of static and dynamic stretching on lumbar lordosis and low back pain. Design: Randomized controlled clinical trial (single-blind) Methods: The 12 selected subjects were randomly assigned static stretching and dynamic stretching groups each containing six students. The subjects in each group performed their respective stretching programs for 17 minutes, 3 times a week for 4 weeks. Lumbar lordotic angle, low back pain, and Oswestry Disability Index (ODI) were measured before and after the intervention. Results: Intragroup comparisons showed significant reductions in lumbar lordotic angle and low back pain in the static stretching group while the dynamic stretching group showed significant decreases in lumbar lordotic angle, low back pain, and ODI. The intergroup comparisons showed significantly greater differences between pre- and post-intervention in lumbar lordotic angle and low back pain in the dynamic stretching group compared to those in the static stretching group while ODI did not show any intergroup difference. Conclusions: The results of this study indicated that, while both static and dynamic stretching helped to reduce the lumbar lordotic angle and low back pain, dynamic stretching was more effective in alleviating lumbar lordotic angle and low back pain compared to static stretching.

Background: Limitations in hip flexion caused by tight hamstrings lead to excessive lumbar flexion and low back pain. Accordingly, many studies have examined how to stretch the hamstring muscle. However, no study has focused on the effect of hamstring eccentric exercise for tight hamstrings on trunk forward bending. Objects: We compared the short-term effect of hamstring eccentric exercise (HEE) and hamstring static stretching (HSS) on trunk forward bending in individuals with tight hamstrings. Methods: Thirty individuals with tight hamstrings participated in the study. The subjects were randomly allocated to either a HEE or HSS group. To determine whether the hamstrings were tight, the active knee extension (AKE) test was performed, and the degree of hip flexion was measured. To assess trunk forward bending, subjects performed the fingertip to floor (FTF) and modified modified Schober tests, and the degree of trunk forward bending was measured using an inclinometer. We used paired t-tests to compare the values before and after exercise in each group and independent t-tests to compare the two groups on various measures Results: The FTF test results were improved significantly after the exercise in both groups, and AKE for both legs increased significantly in both groups. There was no significant difference in the hip angles, mmS test results, or degree of trunk forward bending between groups after the exercise. No test results differed significantly between the two groups at baseline or after the exercise. Both groups increased hamstring flexibility and trunk forward bending. Conclusion: HSS and the HEE groups increased hamstring flexibility and trunk forward bending. However, HEE has additional benefits, such as injury prevention and muscle strengthening.

기존 내진보강시스템의 문제점을 개선하기 위한 듀얼프레임형 내진보강시스템은 기존구조체, 외부보강체, 댐퍼로 구성된다. 듀얼시스템은 지진발생시 주기차이로 인하여 기존구조체와 외부보강체 사이에서 상대변형이 발생되고 이를 댐퍼가 대응하여 안정적으로 지진에너지를 흡수하여 내진성능을 확보한다. 본 논문에서는 듀얼시스템의 구조성능을 분석하기 위하여 정적반복가력실험을 수행한다. 실험결과, 듀얼시스템 실험체는 비보강 실험체와 유사한 손상상태를 나타내었다. 이와 같이 나타난 이유는 정적실험 시 기존구조체를 강제 이력 시켰기 때문이다. 하지만 하중-변형관계곡선에서 핀칭현상이 완화되는 것으로 나타났고, 안정적인 이력거동을 통하여 비보강 실험체에 비해 5.3배 더 많은 에너지를 흡수하였다. 또한 동일한 층간변형각 및 누적 변형에 대해서도 더 많은 에너지를 흡수할 수 있음에 따라 듀얼시스템을 적용할 경우 내진성능을 향상시킬 것으로 판단된다. 또한 듀얼시스템을 실무에 적용하기 위해서는 설계프로세스 등에 대한 연구가 필요하며, 본 논문을 추후 연구의 기초자료로 제시하고자 한다.

In this study, an algorithm applying deep learning to the truss structures was proposed. Deep learning is a method of raising the accuracy of machine learning by creating a neural networks in a computer. Neural networks consist of input layers, hidden layers and output layers. Numerous studies have focused on the introduction of neural networks and performed under limited examples and conditions, but this study focused on two- and three-dimensional truss structures to prove the effectiveness of algorithms. and the training phase was divided into training model based on the dataset size and epochs. At these case, a specific data value was selected and the error rate was shown by comparing the actual data value with the predicted value, and the error rate decreases as the data set and the number of hidden layers increases. In consequence, it showed that it is possible to predict the result quickly and accurately without using a numerical analysis program when applying the deep learning technique to the field of structural analysis.

Optimization was performed on the static dynamic behavior of a simply supported laminated composite plate. Thickness optimization was performed with respect to Gr/E laminated composites with simultaneous mechanical load, thermal load and hygro-load. Displacement, fundamental frequency and composite damping were imposed as constraints for optimization. The results of the optimization were much better than those of the conventional methods.

Long-span marine bridges are generally designed as long-span bridges in order to secure the running route of the ship and reduce the cost and time of the bridge pier construction. In long-span bridges, the range of load resistance transmitted by the superstructure and cable is determined by the mast and foundation. In the other words, the range of designable span length would be determined by the mast and foundation condition. The floating bridge is a type in which the superstructure is supported by the force of buoyancy without the pier mounted on the seabed so that the buoyancy of the floating bridge is balanced by the dead load and buoyancy of the structure. As a technique to overcome the weakness of existing long span bridges, it is possible to consider the type of cable supported bridges with floating tower. In this study, according to the tendon arrangement and initial tension distribution, the static global performance of the long-span bridges with floating tower were evaluated.

The purpose of this study was to investigate the effect of heel off stairway walking exercise on the increase of muscle activity and balance activity of the ankle joint muscles in university students with functional ankle instability. The conservative treatment for the control group consisted of stairway walking (n=10) and the experimental group consisted of heel off stairway walking (n=11). The therapeutic intervention of the control and experimental groups was performed a total of 12 exercise sessions, 3 times per week for 4 weeks. To compare the two groups, the level of ankle disability was assessed by using the EMG, BT4 and Pedoscan in pre-treatment and post-treatment. Muscle activity increased in both the experimental groups and control groups in each group, however there was no significant difference between the groups. Balance ability did not show any significant difference. This study demonstrates that heel-off stairway walking is effective in significantly increasing muscle activity, however did not significantly improve balance ability.

목적: 동체시력의 특성을 파악하기 위해 동체시력과 정지시력, 순간시력 및 안구움직임의 관계를 분석하였다. 방법: 20-30대 일반인 40명을 대상으로 동체시력, 고대비 및 저대비 정지시력, 순간시력, 주시 및 홱보기 안구움직임을 측정하였다. 동체시력은 상하좌우 방향으로 반전된 Snellen E 시표를 임의로 투사하여 측정하였으며, 시표의 방향을 식별할 수 있는 최고 각속도를 동체시력으로 지정하였다. 정지시력은 4 m 거리 에서 logMAR 시표를 이용하여 측정하였고, 시표의 대비에 따라 고대비(100%) 및 저대비(10%) 시력으로 나 누었다. 순간시력은 다섯 자리 숫자 시표를 이용하여 평가하였고, 시표 노출 시간은 14 ms와 7 ms이었다. 안구움직임은 고정형 안구추적장치를 이용하여 측정하였다. NYSOA King-Devick 검사의 하위 세 가지 시표를 읽는 동안 주시 및 홱보기 안구움직임을 추적하였다. 결과: 동체시력은 고대비 정지시력(r=-0.43, p=0.01), 저대비 정지시력(r=-0.40, p=0.01)과 통계적으 로 유의한 상관관계를 보였다. 순간시력은 동체시력과 상관관계가 없었고(r=-0.29, p=0.07), 시표 식별 시 개입되는 시기억능력(visual memory)의 영향을 축소시켰을 때에도 상관성이 없었다(r=-0.10, p=0.57). 동 체시력과 주시 및 홱보기 안구움직임은 상관관계를 보이지 않았다(fixation counts: r=0.07, p=0.65, fixation duration: r=0.27, p=0.10, saccade counts: r=0.02, p=0.93, saccade duration: r=0.01, p= 0.98, saccade amplitude: r=0.22. p=0.18, saccadic velocity: r=0.23, p=0.15). 다중회귀분석 결과, 동체시력에 영향을 미치는 요인은 고대비 정지시력으로 나타났다(β=-0.43, p=0.01). 결론: 동체시력은 고대비 및 저대비 정지시력에 따른 시각 능력 및 시각의 질과 관련이 있었다. 정지시력, 순간시력 및 안구움직임 중 동체시력에 영향을 미치는 성분은 고대비 정지시력이었으며, 순간시력이나 안구움직임이 동체시력에 미치는 영향은 추가적인 분석이 필요하다고 사료된다.

The purpose of this study was to investigate the effects of lumbar stabilization and sling exercise on visual analogue scale (VAS), Korean Oswestry Disability Index (KODI), and stability index (ST) in patients with chronic lower back pain (CLBP). This study included participants with a VAS scale of 6 or higher and a KOD of 20-40%. They were randomly divided into a mat group (n=15) to perform lumbar stabilization exercises and a sling group (n=15) to perform sling exercises, and then they underwent a four-week experiment. The experimental results of this study were as follows: the VAS and KODI showed a statistically significant difference (P<.05) and a larger effect size within each group after the intervention, it exhibited no statistically significant difference between the two groups (P>.05). There were significant differences in ST before and after intervention in each group (P<.05), however there was no significant difference between the groups. The present study suggest that the effects of lumbar stabilization exercise and sling exercise are similar.

Recently, a new long span composite rahmen bridge has been developed to complement the short span concrete rahmen bridges. In this study, a static bending test was carried out for steel composite rahmen bridges developed for the purpose of decreasing negative moment at the end of steel girder and positive moment at the center of steel girder by introducing a horizontal prestress to the upper flange of the steel girder end. From this, the reinforcement effect of the introduction to the horizontal prestress was verified and the structural safety for the steel composite rahmen bridges was evaluated. As a result, the maximum tensile strain and the maximum compressive strain of the DL specimen at 800 kN were 16% and 12% smaller than those of the CR specimen, respectively. From this, the DL specimen decreased compressive strain due to the tensile strain of the upper flange caused by introducing the horizontal prestress at the end of the steel girder, and the tensile strain of the lower flange also decreased.

Background:Limitation of hamstring extensibility is often associated with various musculoskeletal problems such as alterations in posture and walking patterns. Thus, certain appropriate strategies need to be established for its management.Objects:The aim of this study was to compare the effects of the neural mobilization technique and static stretching exercises on popliteal angle and hamstring compliance in young women with short hamstring syndrome (SHS).Methods:Thirty-three women with SHS were randomly assigned to either group-1 (n1=17) that underwent the neural mobilization technique or group-2 (n2=16) that underwent the static stretching exercises. Outcome measures included the active popliteal angle (APA) and a hamstring’s electromyographic (EMG) activity at a maximum popliteal angle of the baseline. Intervention for each group was performed for a total time of 3-min (6 sets of a 30-sec application).Results:There were significant interactions between time and group in the APA [group-1 (pre-test to post-test): 69.70±8.14° to 74.14±8.07° and group-2: 68.66±7.42° to 70.52±7.92°] (F1,31=6.678, p=.015) and the EMG activity of the hamstring (group-1: 1.12±.30μV to .69±.31μV and group-2: 1.19±.49μV to 1.13±.47 μV)(F1,31=6.678, p=.015). Between-group comparison revealed that the EMG activity of the hamstring was significantly different at post-test between the groups (p<.05). Furthermore, in within-group comparison, group-1 appeared to be significantly different for both variables between pre- and post-test (p<.05); however, group-2 showed significant difference in only the APA between pre- and post-test (p<.05).Conclusion:These findings suggest that the neural mobilization technique and static stretching exercises may be advantageous to improve hamstring compliance in young women with SHS, resulting in a more favorable outcome in the neural mobilization technique.

Background: Short foot exercise (SFex) is often prescribed and performed in the sport and rehabilitation fields to strengthen intrinsic foot muscles. However, SFex is difficult to perform because of lack of feedback methods. Objects: The aim of this study was to compare the effects of SFex with and without electromyography (EMG) biofeedback on the medial longitudinal arch (MLA) of healthy individuals who maintained a static standing position. Methods: All participants (14 males and 12 females) were randomly divided into two groups (biofeedback and non-biofeedback groups). The EMG activity of the abductor hallucis (AbdH) and tibialis anterior (TA) and the MLA angle on the dominant leg side were measured with the participant in the standing position in the pre- and post-intervention conditions. The intervention session consisted of 15 minutes of SFex with (biofeedback group) or without (non-biofeedback group) EMG biofeedback. The groups were compared using two-way repeated measures analysis of variance. Results: The post-intervention activities of the AbdH muscle (p<.05) and the AbdH/TA ratio (p<.05) were significantly greater in the biofeedback group than in the non-biofeedback group. The activity of the TA (p<.05) and the MLA angle (p<.05) in the biofeedback group were significantly lower in the post-intervention condition than in the pre-intervention condition. Conclusion: The present findings demonstrate that the combination of SFex and EMG biofeedback can effectively facilitate the muscle activity of the AbdH and strengthen the medial longitudinal arch.

PURPOSES : This paper presents a comparison study between dynamic and static analyses of falling weight deflectometer (FWD) testing, which is a test used for evaluating layered material stiffness. METHODS: In this study, a forward model, based on nonlinear subgrade models, was developed via finite element analysis using ABAQUS. The subgrade material coefficients from granular and fine-grained soils were used to represent strong and weak subgrade stiffnesses, respectively. Furthermore, the nonlinearity in the analysis of multi-load FWD deflection measured from intact PCC slab was investigated using the deflection data obtained in this study. This pavement has a 14-inch-thick PCC slab over finegrained soil. RESULTS: From case studies related to the nonlinearity of FWD analysis measured from intact PCC slab, a nonlinear subgrade modelbased comparison study between the static and dynamic analyses of nondestructive FWD tests was shown to be effectively performed; this was achieved by investigating the primary difference in pavement responses between the static and dynamic analyses as based on the nonlinearity of soil model as well as the multi-load FWD deflection. CONCLUSIONS : In conclusion, a comparison between dynamic and static FEM analyses was conducted, as based on the FEM analysis performed on various pavement structures, in order to investigate the significance of the differences in pavement responses between the static and dynamic analyses.

The simplified plate theory is presented for static and free vibration analysis of power-law(P) and sigmoid(S) Functionally Graded Materials(FGM) plates. This theory considers the parabolic distribution of the transverse shear stress, and satisfies the condition that requires the transverse shear stress to be zero on the upper and lower surfaces of the plate, without the shear correction factor. The simplified plate theory uses only four unknown variables and shares strong similarities with classical plate theory(CPT) in many aspects such as stress-resultant expressions, equation of motion and boundary conditions. The material properties of the plate are assumed to vary according to the power-law and sigmoid distributions of the volume fractions of the constituents. The Hamilton’s principle is used to derive the equations of motion and Winkler-Pasternak elastic foundation model is employed. The results of static and dynamic responses for a simply supported FGM plate are calculated and a comparative analysis is carried out. The results of the comparative analysis with the solutions of references show relevant and accurate results for static and free vibration problems of FGM plates. Analytical solutions for the static and free vibration problems are presented so as to reveal the effects of the power law index, elastic foundation parameter, and side-to-thickness ratio.

The study investigates the effect of different types of visual images, i.e., static images versus dynamic images, on English vocabulary learning. Eighty-four students in the fourth grade of an elementary school participated in this study, and they were divided into two experimental groups and a control group. One of the experimental groups utilized static images, and the other group, videos as dynamic images in vocabulary learning. The control group was provided with the definition or the explanation of each target word in L1. The results of the study manifested that the static image group showed higher scores for the post test than the dynamic image group. The comparison of the pre and post affective tests demonstrated that the static image group showed an improvement in confidence in language learning and the dynamic image group showed positive change in the attitude of all three areas: interest, confidence, and aroused motivation. The analysis of the open-ended questionnaires showed that many participants in the static image group tended to use pictures as retrieval cues to remember vocabulary.

The vehicle weight and alternative light materials development like aluminum alloys are hot issues around the world. In order to obtain the goal of the weight reduction of automobiles, the researches about lighter and stronger suspension links have been studies without sacrificing the safety of automotive components. Therefore, in present study, the structure analysis of the torque strut links made by aluminum alloys (A356) was performed by using CAE (computer aided engineering) to investigate the light weight design process from the reference of the rear suspension torque strut link which was made by STKM11A steel and was already proven in the commercial market. Especially, the simulated maximum von Mises stresses after strength analysis were normalized as fatigue limit and these were converted to the WF (weight factor) of the same type as the fatigue safety factor suggested and named like that in present study. From these, it was suggested that the fatigue properties of the torque strut could be simply predicted only from this static CAE simulation.

In this study, the fracture property of the bonded structure with aluminum foam is analyzed by using the closed aluminium foam for impact absorber. DCB and TDCB specimens manufactured with the single lap joint method of mode 3 are designed by varying the thickness. The static analysis through ANSYS finite element program is carried out on the specimen model due to each thickness. Also, the static experiment is performed in order to verify the analysis result. This study aims at comparing the shear strengths of the bonded structures of DCB and TDCB made with aluminum foam and investigating the mechanical properties.

Separately from a single body, crash box is maufactured into the two alumnae by bonding adhesive. Crashbox has the property to absorb the shock by impact transferred to the car body at the collision between cars. In this study, the structural effect and performance are investigated according to the positions of holes punched at this crash box. The optimal structure is investigated for optimal design data of aluminum crash box. The equivalent stresses of study models distributed by compressive loads are compared with each other by using the analysis program of ANSYS. Total energies and mechanical strengths of study models at the real situation are also analyzed. As analysis results, the maximum equivalent stresses of 40880MPa, 42368MPa, 43176MPa, 44960MPa and 43476MPa are shown at study models due to the hole positions of 10mm, 15mm, 20mm, 25mm and 30mm from the upper plane of crash box respectively. Also, the total energy on analysis are verified within the error range of 10 % by comparing that on experiment at the hole position of 10mm. It is thought that the crash box due to the hole position from the upper plane of crash box can be effectively designed through this study result.

As a part of light weight, the adhesive has been applied to joint the mechanical structure. The porous material is used with aluminum foam in case of the structure bonded with only adhesive. In order to confirm the durability, it is necessary to investigate the fracture toughness at the bonded joint. So, the fracture property at joint interface of aluminum foam different from the non-porous material becomes especially important. In this study, the tapered double cantilever beams(TDCB) with the type of mode Ⅲ are manufactured with aluminum foam. The fracture toughness at the joint of the structure bonded with only a adhesive can be obtained. The static analyses are carried out and verified the results by the experiment. As the results of static analyses, the reaction forces ranged from 0.30 to 0.41 kN at all specimens are shown when the forced displacements are proceeded as much as 7 to 9 mm. As the results of analyses and experiments are compared with each other, there is a little bit of difference between these results. Through the result of this study, the mechanical properties at TDCB specimens with the type of mode Ⅲ can be understood.