• The Journal of Korean Physical Therapy
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• 제23권1호
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• pp.29-35
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• 2011

Purpose: The purpose of this study was to identify the effect of neck exercises on neck-shoulder posture and pain of high school students with neck disorders. Methods: Twenty seven subjects were randomly assigned to one of 3 groups a craniocervical flexion training group (CCFT), a neck strengthening exercise group (ST), and a basic stretching exercise group (CG). CCFT and ST exercised five times a week for eight weeks under the researcher's guidance. The control group performed basic stretching exercises. Diagnostic radiologic equipment was used for the measurement of neck-shoulder posture. Neck disability index, and numeric rating scales were used. Results: The CCFT showed a significant pre-post treatment difference on measures of neck flexion angle and forward shoulder angle changes compared to the ST and CG groups (p<0.05). The CCFT group also showed a significantly greater improvement on the neck disability index and numeric rating scales changes than the ST and CG groups (p<0.01). Conclusion: Because CCFT decreases neck flexion angle, forward shoulder angle, neck disability index, and pain in the forward head posture, it is useful for treating patients with neck disorders.

• Steel and Composite Structures
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• 제38권2호
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• pp.165-176
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• 2021

Existing research on confined concrete filled steel tubular (CCFT) columns has been mainly focused on static or cyclic loading. In this paper, square section CCFT and CFT columns were tested under both static and impact loading, using a 10,000 kN capacity compression test machine and a drop weight testing equipment. Research parameters included bonded and unbonded fiber reinforced polymer (FRP) wraps, with carbon, basalt and glass FRPs (or CFRP, BFRP, and GFRP), respectively. Time history curves for impact force and steel strain observed are discussed in detail. Experimental results show that the failure modes of specimens under impact testing were characterized by local buckling of the steel tube and cracking at the corners, for both CCFT and CFT columns, similar to those under static loading. For both static and impact loading, the FRP wraps could improve the behavior and increase the loading capacity. To analyze the dynamic behavior of the composite columns, a finite element, FE, model was established in LS-DYNA. A simplified method that is compared favorably with test results is also proposed to predict the impact load capacity of square CCFT columns.

• Steel and Composite Structures
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• 제33권2호
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• pp.181-194
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• 2019

This paper presents an efficient approach to generate a new empirical formula to predict the axial compression capacity (ACC) of circular concrete-filled tube (CCFT) columns using the artificial neural network (ANN). A total of 258 test results extracted from the literature were used to develop the ANN models. The ANN model having the highest correlation coefficient (R) and the lowest mean square error (MSE) was determined as the best model. Stability analysis, sensitivity analysis, and a parametric study were carried out to estimate the stability of the ANN model and to investigate the main contributing factors on the ACC of CCFT columns. Stability analysis revealed that the ANN model was more stable than several existing formulae. Whereas, the sensitivity analysis and parametric study showed that the outer diameter of the steel tube was the most sensitive parameter. Additionally, using the validated ANN model, a new empirical formula was derived for predicting the ACC of CCFT columns. Obviously, a higher accuracy of the proposed empirical formula was achieved compared to the existing formulae.

• 한국전문물리치료학회지
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• 제29권3호
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• pp.180-186
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• 2022

Background: The craniocervical flexion test (CCFT) was developed for the activation and endurance of deep cervical flexors. However, the muscle thickness and muscle thickness changing ratio of the sternocleidomastoid (SCM) and deep cervical flexor (DCF) muscles in subjects with and without forward head posture (FHP) have not been reported. Objects: To determine the difference in thickness of the SCM and DCF muscles and the difference in the muscle thickness changing ratio between SCM, DCF, and DCF/SCM 20 mmHg and DCF/SCM 30 mmHg between subjects with and without FHP. Methods: Thirty subjects with and without FHP were enrolled. The muscle thickness of the SCM and DCF was measured when maintained at a baseline pressure of 20 mmHg and a maximum pressure of 30 mmHg using a pressure biofeedback unit during the CCFT. Ultrasonography was used to capture images of SCM and DCF muscle thickness during the CCFT, which was calculated using the picture archiving and communication system (PACS). Results: We observed a significant difference within the pressure main effect between SCM and DCF at a baseline pressure of 20 mmHg and a maximum pressure of 30 mmHg (p < 0.05). However, there was no significant difference in the muscle thickness and muscle thickness changing ratio for SCM and DCF during CCFT between subjects with and without FHP. Conclusion: There was no significant difference in the muscle thickness recruitment pattern during CCFT in posture changes between subjects with and without FHP.

• Steel and Composite Structures
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• 제17권5호
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• pp.735-751
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• 2014

Concrete-filled steel tube (CFT) composite columns, either circular (CCFT) or rectangular (RCFT), have many economical and aesthetic advantages but the behavior of their connections are complicated. This study aims to investigate, through an experimental program, the performance and behavior of different connections configurations between circular concrete filled steel tube columns (CCFT) and gusset plates subjected to shear and axial compression loadings. The study included seventeen connection subassemblies consisting of a fixed length steel tube and gusset plate connected to the tube end with different details tested under half cyclic loading. A notable effect was observed on the behavior of the connections due to its detailing changes with respect to capacity, failure mode, ductility, and stress distribution.

• Advances in Computational Design
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• 제1권4호
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• pp.297-313
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• 2016

The flexural strength of circular concrete-filled tubes (CCFT) can be estimated by several codes such as ACI, AISC, and Eurocode 4. In AISC and Eurocode, two methods are recommended, which are the strain compatibility method (SCM) and the plastic stress distribution method (PSDM). The SCM of AISC is almost the same as the SCM of the ACI method, while the SCM of Eurocode is similar to the ACI method. Only the assumption of the compressive stress of concrete is different. The PSDM of Eurocode approach is also similar to the PSDM of AISC, but they have different definitions of material strength. The PSDM of AISC is relatively easier to use, because AISC provides closed-form equations for calculating the flexural strength. However, due to the complexity of calculation of circular shapes, it is quite difficult to determine the flexural strength of CCFT following other methods. Furthermore, all these methods give different estimations. In this study, an effort is made to review and compare the codes to identify their differences. The study also develops a computing program for the flexural strength of circular concrete filled tubes under pure bending that is in accordance with the codes. Finally, the developed computing algorithm, which is programmed in MATLAB, is used to generate design aid graphs for various steel grades and a variety of strengths of steel and concrete. These design aid graphs for CCFT beams can be used as a preliminary design tool.

• 한국전문물리치료학회지
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• 제23권3호
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• pp.11-20
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• 2016

Background: A forward head posture (FHP) is one of the most common types of poor head posture in patients with neck disorder. A prolonged FHP might increase pressure on the posterior cranio-cervical structure and exhibit reduced performance on a cranio-cervical flexion test (CCFT). CCFT is included to activate deep cervical flexor muscles and inhibit excessive activation of superficial cervical flexor muscles. Therefore, the selective activation of deep cervical flexors is needed for effective exercise for FHP. Objects: The purpose of this study was to compare muscle thickness between longus colli (Lco) and sternocleidomastoid (SCM) using ultrasonography in subjects with FHP depending on head support. Methods: This was a cross-sectional, case-control research design study. The ultrasonographic images of Lco and SCM were taken in 17 subjects with FHP during the 5 phases of the CCFT with and without a head support. Towel was used for supporting head to make the neutral head position in supine. Changes in muscle thickness during the test were calculated to infer muscle activation. Data were analyzed using repeated measures of two-way analysis of variance with the significance level of .05. Results: When subjects performed the CCFT with head support, there was a significant difference in muscle thickness of Lco and SCM (p<.05). According to a post hoc paired t-test, change of thickness of Lco was greater at all phases, and change of thickness of SCM muscle was less at phase 4 and 5 in condition with head support (p<.01) compared to condition without head support (p<.01). Conclusion: The result of this study suggest that applying head support for neutral head position during CCFT could be a useful method for activating Lco muscle without excessive activation of SCM muscle.

• Steel and Composite Structures
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• 제13권5호
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• pp.437-449
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• 2012

Concrete filled steel tube (CFST) structures have recently seen wide use in China, but studies of the shear problem of CFST are inadequate. This paper presents an experimental study on the shear capacity of circular concrete filled steel tube (CCFT) specimens with and without axial compression force. Shear capacity, ductility, and damage modes of CCFTs were investigated and compared. Test results revealed the following: 1) CCFTs with a small shear span ratio may fail in shear in a ductile manner; 2) Several factors including section size, material properties, shear span ratio, axial compression ratio, and confinement index affect the shear capacity of CCFTs. Based on test results and analysis, this paper proposes a design formula for the shear capacity of CCFTs.

• 대한물리의학회지
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• 제8권2호
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• pp.253-261
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• 2013

PURPOSE: The Purpose of this study was to investigate the changes in the thickness of Sternocleidomastoid muscle(SCM) and deep cervical flexor muscle(DCF) through CranioCervical Flexion Exercise(CCFEx) Using Sling. METHODS: Subjects were randomly allocated two group: control group (n=21) without neck pain, experimental group (n=17) with pain. Muscle thickness was measured using CranioCervical Flexion Test(CCFT) and ultrasonography before or after intervention. RESULTS: In experimental group, compared with muscle thickness of exercise before, SCM thickness rate of change was slightly decreased according to pressure increased after exercise(p<.05). CONCLUSION: The results of this study showed that CCFEx using sling is effective for SCM and DCF of choric neck pain patients.

• 한국산업정보학회:학술대회논문집
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• 한국산업정보학회 2000년도 추계공동학술대회논문집
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• pp.703-710
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• 2000

기존의 비상구 표시등은 20-30(W) 정도의 많은 전력 소모와 2천시간 정도의 짧은 램프 수명 등으로 인해 전기에너지의 소모가 많으며, 부피가 커 시공 및 설치가 어렵다. 따라서, 본 논문에서는 도광판을 사용한 비상등의 개발에 관하여 연구하기 위하여 가시광선 투과율이 94%이상으로 높고 가공이 용이한 투명 PMMA(Poly Methyl Meth Acrylate)판에 광반사면을 광학적 시뮬레이션에 의해 설계된 V자형 홈선을 가공하여 비상등의 도광판으로 사용한다. 이 구조는 기존의 비상등에 비해 광이용 효율이 높고, 설계의 자유도가 높아질 것으로 기대된다. 또한, CCFT(Cold Cathode Fluorecent Tube) 램프, 광확산필름, 프리즘필름, 몰드프레임 등을 이용하여 광이용 효율을 극대화하는 구조를 고안하고, 인버터 구동을 위한 주변회로 시스템을 개발하여 초절전형 평판 비상등 시스템의 양산 기술을 확보함을 목적으로 한다. 이로부터 휘도 2000cd/$m^2$, 휘도균일도 90%이상의 특성과 기존의 비상등 대비 전기 에너지 50%이상이 절감 가능한 비상등이 개발될 수 있다.