• Structural Engineering and Mechanics
• /
• 제86권1호
• /
• pp.1-16
• /
• 2023

The free vibration of temperature-dependent functionally graded plates (FGPs) resting on a viscoelastic foundation is investigated in this paper using a newly developed simple first-order shear deformation theory (FSDT). Unlike other first order shear deformation (FSDT) theories, the proposed model contains only four variables' unknowns in which the transverse shear stress and strain follow a parabolic distribution along the plates' thickness, and they vanish at the top and bottom surfaces of the plate by considering a new shape function. For this reason, the present theory requires no shear correction factor. Linear steady-state thermal loads and power-law material properties are supposed to be graded across the plate's thickness. Uniform, linear, non-linear, and sinusoidal thermal rises are applied at the two surfaces for simply supported FGP. Hamilton's principle and Navier's approach are utilized to develop motion equations and analytical solutions. The developed theory shows progress in predicting the frequencies of temperature-dependent FGP. Numerical research is conducted to explain the effect of the power law index, temperature fields, and damping coefficient on the dynamic behavior of temperature-dependent FGPs. It can be concluded that the equation and transformation of the proposed model are as simple as the FSDT.

• Journal of Acupuncture Research
• /
• 제23권1호
• /
• pp.15-23
• /
• 2006

목적 : 경사계와 각도기로 경추, 요추 및 견관절의 운동 범위를 반복 측정하여 두 도구의 측정자내 신뢰도 우위를 추정하여 보고자 하였다. 방법 : 각 관절에 별다른 증상이 없는 104명의 학생들을 대상으로 경추, 요추 및 견관절의 능동 운동 범위를 경사계와 각도기로 각 도구 당 2회씩 측정하였다. 측정하기 바로 전에, 한 명의 교육자가 경사계와 각도기를 이용한 경추, 요추 및 견관절의 운동 범위 측정 방법을 교육하였다. 104명은 두 명 씩 쌍을 이룬 후 각도기, 경사계, 각도기, 경사계를 이용하는 순서로 서로의 경추, 요추 및 견관절의 운동 범위를 측정하였다. 결과 : 견관절의 수평 외전과 외회전에서 경사계의 측정값이 각도기의 측정값보다 통계적으로 의미 있게 안정적으로 반복되었다(P<0.05, 독립 이 표본 t-검정). 결론 : 견관절의 운동 범위 측정에 있어서 경사계가 각도기보다 높은 측정자내 신뢰도를 가지는 것으로 추정되어, 경사계와 각도기의 신뢰도를 급간내 상관 계수(intraclass correlation coefficient)를 이용하여 비교해보는 연구의 예비 조사로서 실시된 이번 연구의 결과는 향후 시행될 연구에 있어서 견관절의 운동 범위 측정에 보다 집중적인 연구를 진행할 수 있는 근거를 마련하였다.

• 대한조선학회논문집
• /
• 제52권1호
• /
• pp.25-33
• /
• 2015

Following the previous works on the natural frequency of heaving circular cylinder, i.e. Lee and Lee (2013) and Kim and Lee (2013), an investigation of the same spirit on the 2-dimensional cylinder of Lewis form has been conducted. As before, the natural frequency is defined as that corresponding to the local maximum of the MCFR (Modulus of Complex Frequency Response), which is given by the equation of motion in the frequency domain analysis. Hydrodynamic coefficients were found by using the Ursell-Tasai method, and numerical results for them were obtained up to much higher frequencies than before, for which the method was known as numerically unstable in the past. For a wide range of H, the beam-draft ratio, and ${\sigma}$, the sectional area coefficient, including their practical ranges for a ship, results for the natural frequency were computed and presented in this work. Two approximate values for the natural frequency, one proposed by Lee (2008) and another one by the damped harmonic oscillator, were also compared with the current results, and for most cases it was observed that the current result is between the two values. Our numerical results showed that the values of the local maximum of MCFR as well as the natural frequencye increase as ${\sigma}$ increases while H decreases. At present, extension of the present finding to the 3-dimensional ship via the approximate theory like the strip method looks promising.

• 한국기계가공학회지
• /
• 제19권12호
• /
• pp.62-69
• /
• 2020

The demand for industrial robots is proliferating with production automation. Industrial robots are used in various fields, such as logistics, welding, and assembly. Generally, six degrees of freedom are required to move freely in space. However, the palletizing robot used for material management and logistics systems typically has four degrees of freedom. In designing such robots, their main parts, such as motors and reducers, need to be adequately selected while satisfying payload requirements and speed. Hence, this study proposes a practical method for selecting the major parts based on dynamic analysis using ADAMS. First, the acceleration torques for the robot motion were found from the analysis, and then the friction torques were evaluated. This study introduces a constant-speed torque constant instead of friction coefficient. The RMS torque and maximum power of each motor were found considering the above torques. After that, this study recommends the major specifications of all motors and reducers. The proposed method was applied to a palletizing robot to verify the suitability of the pre-selected main parts. The verification result shows that the proposed method can be successfully applied to the early design stage of industrial robots.

• 대한전자공학회논문지SP
• /
• 제44권3호
• /
• pp.8-15
• /
• 2007

최근 멀티미디어 데이터를 효율적으로 전송, 저장 관리 및 검색하는 기술이 중요한 핵심 기술로 대두되고 있다. 그 중에서 멀티미디어 정보 검색의 경우 사용자가 원하는 정보를 표현할 수 있는 사용자 인터페이스 기술과 원하는 정보를 사용자에게 신속하고 정확하게 보여주는 기술의 필요성이 증대하고 있다. 본 논문에서는 MPEG으로 압축된 영상 정보에서 장면의 전환점인 컷을 효과적으로 검출하여 동영상을 분할하는 기법을 제안한다. 컷 검출(Cut detection)은 MPEG 비디오 시퀀스에서 동영상을 분할하는 가장 기본적이면서 중요한 기초 작업이며, 비디오 색인 및 검색을 위한 첫 번째 단계이다. 기존의 방법들은 프레임간을 비교하기 때문에 물체의 빠른 움직임이나 카메라의 움직임, 후레쉬의 섬광 등 화면 변화에 따라 오검출이 생기는 단점이 있다. 제안하는 컷 검출 기법은 먼저 입력영상을 DCT의 DC를 이용하여 샷을 검출한다. 이렇게 검출된 샷으로 데이터베이스를 구성하고, MPEG-7의 시각 기술자 중 HMMD 컬러 모델과 에지 히스토그램을 사용하여 영상에서 특징을 추출하였다. 그리고 제안하는 매칭 기법에 따라 단계별 검색을 수행하였다. 이 실험을 통해서 기존 방법들보다 높은 검색률을 보이는 개선된 동영상 분할 시스템을 설계하였다.

• 한국운동역학회지
• /
• 제27권4호
• /
• pp.269-278
• /
• 2017

Objective: The purpose of this study was to develop a goal setting method for increasing the probability of a holed in a side inclined putting stroke. Method: Three-dimensional video data was recorded at a frequency of 120 hz per second after synchronizing 19 infrared motion capture systems (Qualisys, Gothenburg, Sweden). Putting green used a polycarbonate plate ($1.2{\times}2.4{\times}0.01meter$) with coefficient of friction (${\mu}=0.062$) and a real curve of the actual hole. Results: The velocity ratio between the club and the ball was 1:1.6 under various ball speed conditions in this study. The overall position of the break is 1 m to 1.4 m from the point where the ball leaves. If there is a slope, the ball follows the target line by the straightening force, and when it reaches 1 m position, the straightening force decreases by 30~50% and reaches to the deviation (break) point which is severely influenced by the slope. From here, the ball is aimed in a direction other than the target, and the size is affected by the slope. Conclusion: If there is a side slope, the ball moves away from the straight line, and the larger the slope, the closer the break point is to the starting point of the ball. Therefore, it is necessary to calculate the degree of departure according to the slope carefully, and it is preferable that the slower the speed is, the more the influence of the slope becomes. It is preferable to use the center of the hole as a reference when calculating the departure.

• 한국실내디자인학회논문집
• /
• 제19권6호
• /
• pp.83-90
• /
• 2010

Emotional interest in the 1970s, Japan started from the technical and engineering beyond the scope, period late structuralist entering the world has been the subject of interest, as well as in academic research is becoming the main theory. In addition, communication between various disciplines such as humanities through the study of consilience and fusion, the human life to continue as a subject, its importance has risen. So this study are to design for the study of emotion through the human heart in space and how the expression of emotions and can be validated in a study. GSD to evaluate the action (verb) and emotional words (adjective) related to two variables to measure the degree of correlation coefficient was an experiment to find out. Picasso painting, it is 'difficult to understand', 'special', 'interesting', 'not interested', 'confused', 'fun', 'anxious', 'dark', 'cool', 'hard' to have relevance, such as the distribution of emotional words, and as a result of the move was a lot of work. This result can be obtained through the arcane resistance of the cubist paintings that make a lot of body movements. In Renoir painting 'stable', 'warm', 'soft', 'easy to understand', 'bright', 'boring', 'curious', such as emotional words ranged to have a relationship with this behavior is less motion in space. This result can be obtained through the understanding of the Impressionist paintings that are less body movements. As a result, space design, emotional design in the evaluation (GSD) for the empirical analysis that evaluated the feasibility and future of the emotional space of the design could be based in the area is considered.

• The Journal of Korean Physical Therapy
• /
• 제22권3호
• /
• pp.17-21
• /
• 2010

Purpose: This study was designed to investigate possibilities for quantitative analysis using the electromyography and sonography. For better understanding, we evaluated the correlation between the pressure pain threshold and sonography, spontaneous electrical activity in trigger points located in the upper trapezius muscle. Methods: Thirty three active subjects volunteered to participate in this study (n=33). They had a palpable taut band, exquisite spot tenderness of a nodule in a taut band, spontaneous pain, referred pain, jump sign, local twitch response, and a painful limit to full stretch range of motion. We measured Pressure pain threshold, density, white area index, root mean square, and reaction. Pearson’s correlation coefficient was calculated to estimate the relationship between the pressure pain threshold and other variables including density, white area index, root mean square, and reaction time. Results: There were significant correlations between pressure pain threshold and density (r=-0.75, p<0.01), and between pressure pain threshold and white area index (r=-0.74, p<0.01). A significant correlations between pressure pain threshold and root mean square (r=-0.59, p<0.01). The significant correlation was found between pressure pain threshold and reaction time (r=-0.64, p<0.01). Conclusion: These should indicate whether quantitative analysis can be done using the characteristics of electromyography and sonography.

• Bulletin of the Korean Chemical Society
• /
• 제23권11호
• /
• pp.1595-1603
• /
• 2002

In this paper we have presented the results of diffusion behavior of model systems for eight liquid n-alkanes ($C_{12}$-$C_{44}$) in a canonical (NVT) ensemble at several temperatures using molecular dynamics simulations. For these n-alkanes of small chain length n, the chains are clearly <$R_{ee}^2$>/6<$R_g^2$>>1 and non-Gaussian. This result implies that the liquid n-alkanes over the whole temperatures considered are far away from the Rouse regime, though the ratio becomes close to the unity as n increases. Calculated self-diffusion constants $D_{self}$ are comparable with experimental results and the Arrhenius plot of self-diffusion constants versus inverse temperature shows a different temperature dependence of diffusion on the chain length. The global rotational motion of n-alkanes is examined by characterizing the orientation relaxation of the end-to-end vector and it is found that the ratio ${\tau}1/{\tau}2$ is less than 3, the value expected for a isotropically diffusive rotational process. The friction constants ${\xi}$of the whole molecules of n-alkanes are calculated directly from the force auto-correlation (FAC) functions and compared with the monomeric friction constants ${\xi}_D$ extracted from $D_{self}$. Both the friction constants give a correct qualitative trends: decrease with increasing temperature and increase with increasing chain length. The friction constant calculated from the FAC's decreases very slowly with increasing temperature, while the monomeric friction constant varies rapidly with temperature. By considering the orientation relaxation of local vectors and diffusion of each site, it is found that rotational and translational diffusions of the ends are faster than those of the center.

• 한국분무공학회지
• /
• 제25권1호
• /
• pp.8-14
• /
• 2020

Recently, 1-D model-based engine development using virtual engine system is getting more attention than experimental-based engine development due to the advantages in time and cost. Injection rate profile is the one of the main parameters that determine the start and end of combustion. Therefore, it is essential to set up a sophisticated model to accurately predict the injection rate as starting point of virtual engine system. In this research, procedure of 1-D model setup based on AMESim is introduced to predict the dynamic behavior and injection rate of diesel injector. As a first step, detailed 3D cross-sectional drawing of the injector was achieved, which can be done with help of precision measurement system. Then an approximate AMESim model was provided based on the 3D drawing, which is composed of three part such as solenoid part, control chamber part and needle and nozzle orifice part. However, validation results in terms of total injection quantity showed some errors over the acceptable level. Therefore, experimental work including needle movement visualization, solenoid part analysis and flow characteristics of injector part was performed together to provide more accuracy of 1-D model. Finally, 1-D model with the accuracy of less than 10% of error compared with experimental result in terms of injection quantity and injection rate shape under normal temperature and single injection condition was established. Further work considering fuel temperature and multiple injection will be performed.