• 대한화학회지
• /
• 제19권5호
• /
• pp.317-324
• /
• 1975

$Na^+,\;Ca^{2+},\;Ni^{2+},\;Al^{3+}$ 이온이 포화된 montmorillonite상에 여러 溫度에서 일어난 $H_2O와\;D_2O$의 氣相吸着에 관하여 연구하였다. 吸着으로 인하여 생긴 OH의 IR 신축진동 band를 computer에 의하지 않고 4개의 Gauss 成分으로 나누었다. 물과 silanol OH기와의 共鳴理論은 $3625cm^{-1}와\;2680cm^{-1}$로 증명되었다. $3400cm^{-1}$와 2475cm 에서의 broad한 吸收는 吸着된 물과 水素結合을 일으키고 있는 silanol OH의 신축진동에 의한 것이었고 $3650cm^{-1}와\;2345cm^{-1}$ band는 吸着된 $H_2O와\;D_2O$에 의한 것이었다. 吸着水와 表面 OH사이의 水素結合은 精電氣的 相互作用에 의한 것임이 밝혀졌다.

• Structural Engineering and Mechanics
• /
• 제74권3호
• /
• pp.365-380
• /
• 2020

The focus of this paper is to develop an analytical approach based on an efficient shear deformation theory with stretching effect for bending stress analysis of cross-ply laminated composite plates subjected to transverse parabolic load and line load by using a new kinematic model, in which the axial displacements involve an undetermined integral component in order to reduce the number of unknowns and a sinusoidal function in terms of the thickness coordinate to include the effect of transverse shear deformation. The present theory contains only five unknowns and satisfies the zero shear stress conditions on the top and bottom surfaces of the plate without using any shear correction factors. The governing differential equations and its boundary conditions are derived by employing the static version of principle of virtual work. Closed-form solutions for simply supported cross-ply laminated plates are obtained applying Navier's solution technique, and the numerical case studies are compared with the theoretical results to verify the utility of the proposed model. Lastly, it can be seen that the present outlined theory is more accurate and useful than some higher-order shear deformation theories developed previously to study the static flexure of laminated composite plates.

• PNF and Movement
• /
• 제13권3호
• /
• pp.135-143
• /
• 2015

Purpose: The purpose of this study was to assess the effect of the proprioceptive neuromuscular facilitation (PNF) relaxation technique (hold relax; HR, contract relax; CR) and static stretch (SS) on hamstring flexibility and vertical jump performance in healthy adults over a four-week period. Methods: Twenty-four healthy adults volunteered to participate in PNF and static stretch sessions. The subjects were divided into three groups as follows: 8 subjects in the SS group, 8 subjects in the HR group, and 8 subjects in the CR group. In the HR and CR groups, contractions lasted 15 seconds per trial and consisted of 5 sets of 15 seconds of hamstring contraction immediately followed by 15 seconds of passive static hamstring stretching. For the static group, the participants were asked to stretch by hanging a leg over a table for 30 seconds. Subjects in all groups performed the exercises three days per week for 4 weeks. The active straight leg raising (ASLR) test, active knee extension (AKE) test, and vertical jump test were performed before the intervention and after 1, 2, and 4 weeks. Results: The SS, HR, and CR techniques effected positive improvement in hamstring flexibility and vertical jump performances but neither of the stretching methods had any statistically significant different effects according to group, although there were interactions (between group and time) in the ALSR group from 1 week to 2 week and in the AKE test from pretest to 1 week. Conclusion: Based on the results of the current study, SS, HR, and CR were shown to affect hamstring flexibility and vertical jump performance in healthy adults. In particular, it was determined that within a short period, hamstring flexibility could be attributed more to CR than to SS.

• Steel and Composite Structures
• /
• 제47권5호
• /
• pp.551-568
• /
• 2023

In this research, a new two-dimensional (2D) and quasi three-dimensional (quasi-3D) higher order shear deformation theory is devised to address the bending problem of functionally graded plates resting on an elastic foundation. The displacement field of the suggested theories takes into account a parabolic transverse shear deformation shape function and satisfies shear stress free boundary conditions on the plate surfaces. It is expressed as a combination of trigonometric and exponential shear shape functions. The Pasternak mathematical model is considered for the elastic foundation. The material properties vary constantly across the FG plate thickness using different distributions as power-law, exponential and Mori-Tanaka model. By using the virtual works principle and Navier's technique, the governing equations of FG plates exposed to sinusoidal and evenly distributed loads are developed. The effects of material composition, geometrical parameters, stretching effect and foundation parameters on deflection, axial displacements and stresses are discussed in detail in this work. The obtained results are compared with those reported in earlier works to show the precision and simplicity of the current formulations. A very good agreement is found between the predicted results and the available solutions of other higher order theories. Future mechanical analyses of three-dimensionally FG plate structures can use the study's findings as benchmarks.

• 폴리머
• /
• 제39권3호
• /
• pp.441-452
• /
• 2015

Twin-screw kneader is an efficient polymer processing equipment. In this paper, the mixing performance of one novel intermeshing counter-rotating twin-screw kneader with different tip angles of the male rotor is simulated using the mesh superimposition technique (MST). Statistical analysis is carried out for the flow field using particle tracking technique, and distributive mixing performance is evaluated using the residence time distribution and segregation scale, while the dispersive mixing performance is estimated using the parameters such as shear rate, stretching rate and mixing index. The results show that the best distributive mixing performance is achieved when the tip angle is 0o, while the optimal dispersive mixing performance is obtained when the tip angle is 20o. The results in this paper provide a data basis for the selection of parameters and optimization of the performance for the screw rotors.

• 전기전자학회논문지
• /
• 제26권2호
• /
• pp.292-298
• /
• 2022

역광 조명에서 촬영된 영상은 한 장면에 지나치게 밝은 부분과 어두운 부분이 혼재되어 있어서 이를 전역적인 처리로 화질을 개선하는데는 한계가 있다. 본 논문은 역광 촬영된 사진을 각각 어두운 영역과 밝은 영역을 개선하는 두 장의 가상 영상으로 만들어 이를 원본 영상과 함께 라플라시안 피라미드로 융합하여 사진의 품질을 개선하는 방안에 대해 소개한다. 제안된 기법은 두 장의 가상 영상을 만들 때 LUT로 단순화할 수 있는 히스토그램 스트레칭과 감마변환을 활용하여 연산 부담을 저감하였다. 또한 색상 강화된 영상을 얻기 위해 HSV 좌표계를 사용하여 휘도에 대해서만 명암 변환을 실시하였다. 제안된 기법은 표준 영상 데이터 세트를 사용하여 몇 가지의 NIQA 지표를 산출하여 그 효용성을 보였다.

• Physical Therapy Rehabilitation Science
• /
• 제11권4호
• /
• pp.464-470
• /
• 2022

Objective: Axillary web syndrome (AWS) is a condition comprising fibrous band-like cords that appear in the axilla of patients after axillary lymph node dissection (ALND) during breast cancer surgery and result in pain and reduced mobility. The cords appearing with AWS are hardened veins or lymphatic vessels. Manual therapy and stretching are recommended for pain control and mobility improvement. Therefore, this study investigated the effect of cytoskeletal manual therapy (CMT), which is a new soft tissue mobilization technique. Design: A case report Methods: A 41-year-old woman with AWS after breast cancer surgery and ALND visited a physical therapy clinic because of shoulder pain, decreased function, and decreased mobility. The cords were palpable and pain occurred 2 weeks after surgery. CMT was performed three times per week for a total of 6 weeks. Her pain intensity, range of motion (ROM), and shoulder function were measured. Results: Measurements were performed after 2 weeks and 6 weeks of CMT and evaluated using the numeric pain rating scale (NPRS). Her pain intensity largely decreased after 2 weeks (4-point score reduction) and after 6 weeks (5-point score reduction) of CMT. After CMT, her full ROM was restored and her shoulder function was improved (7-point score reduction). Conclusions: CMT is effective for pain control, mobility improvement, and functional improvement of patients with AWS.

• 보존과학회지
• /
• 제38권2호
• /
• pp.117-123
• /
• 2022

본 연구는 한국의 고대 유리에서 납바륨유리 3점, 납유리 3점, 포타쉬유리 10점 그리고 소다유리 10점을 중심으로 라만분광분석법을 이용하여 고대 유리의 융제 분류와 납유리에서 납의 정량 분석에 대한 가능성을 분석하였다. 분석 결과, 신축 진동 영역에서 납바륨유리가 1040 cm^-1, 납유리가 1000 cm^-1으로 라만 피크 에너지의 차이를 보이며 포타쉬유리와 소다유리는 굽힘 진동 영역에서 Na과 K 양이온의 차이에 따라 포타쉬유리는 490 cm^-1에서, 소다유리는 560 cm^-1에서 라만 피크의 차이를 보인다. 이외에 납유리는 PbO 함량에 따라 라만 스펙트럼의 적색 편이가 비례하므로 이를 통하여 납유리의 주성분인 PbO의 함량을 정량적으로 분석할 수 있다. 즉, 라만분광분석법으로 납바륨, 납, 포타쉬 그리고 소다유리에 대한 분류와 납유리에서 PbO 함량을 측정할 수 있는 가능성이 확인된다.

• Coupled systems mechanics
• /
• 제2권2호
• /
• pp.159-174
• /
• 2013

The present work aims at investigating the nonlinear dynamics, bifurcations, and stability of an axially accelerating beam with an intermediate spring-support. The problem of a parametrically excited system is addressed for the gyroscopic system. A geometric nonlinearity due to mid-plane stretching is considered and Hamilton's principle is employed to derive the nonlinear equation of motion. The equation is then reduced into a set of nonlinear ordinary differential equations with coupled terms via Galerkin's method. For the system in the sub-critical speed regime, the pseudo-arclength continuation technique is employed to plot the frequency-response curves. The results are presented for the system with and without a three-to-one internal resonance between the first two transverse modes. Also, the global dynamics of the system is investigated using direct time integration of the discretized equations. The mean axial speed and the amplitude of speed variations are varied as the bifurcation parameters and the bifurcation diagrams of Poincare maps are constructed.

• 한국고분자학회:학술대회논문집
• /
• 한국고분자학회 2006년도 IUPAC International Symposium on Advanced Polymers for Emerging Technologies
• /
• pp.355-355
• /
• 2006

In this study, we have applied principal component analysis-based 2D (PCA2D) correlation spectroscopy to the temperature-dependent IR spectra of biodegradable poly(hydroxyalkanoate). PCA2D analysis reveals clearly that there are two components in crystalline band of C=O stretching mode without being hampered by noise. To better understand the thermal behavior of biodegradable poly(hydroxyalkanoate), eigenvalue manipulating transformation (EMT) technique was also employed. By uniformly lowering the power of a set of eigenvalues associated with the original data, the subtle contributions from minor eigenvectors are highlighted. Details of thermal behavior of biodegradable poly(hydroxyalkanoate) studied by PCA2D correlation spectroscopy with EMT will be discussed.