• Journal of Applied and Pure Mathematics
• /
• 제6권3_4호
• /
• pp.105-117
• /
• 2024

In the classical sense, it is known that it is impossible to construct a vector space over the entire set of real numbers with the help of simple interval arithmetic. In this article, it has shown that a vector space can be constructed in the classical sense by helping Markov's extended interval arithmetic on the interval valued Cesaro sequence spaces of non-absolute type. As a result of the positive answers, this idea was extended by us with some theorems. Consequently, a new perspective was gained to the construction of new types of sequence spaces by using different algebraic operations on interval-valued sequence spaces.

• Wind and Structures
• /
• 제36권1호
• /
• pp.15-29
• /
• 2023

To better estimate the non-Gaussian extreme wind pressures for high-rise buildings, a data-driven revised Hermitetype peak factor estimation model is proposed in this papar. Subsequently, a comparative study on three types of methods, such as Hermite-type models, short-time estimate Gumbel method (STE), and new translated-peak-process method (TPP) is carried out. The investigations show that the proposed Hermite-type peak factor has better accuracy and applicability than the other Hermite-type models, and its absolute accuracy is slightly inferior to the STE and new TPP methods for non-Gaussian wind pressures by comparing with the observed values. Moreover, these methods generally overestimate the Gaussian wind pressures especially the STE.

• Journal of Mechanical Science and Technology
• /
• 제19권8호
• /
• pp.1632-1648
• /
• 2005

The effects of Reynolds number on the non-nulling calibration of a typical cone-type five-hole probe have been investigated for the representative Reynolds numbers in turbomachinery. The pitch and yaw angles are changed from - 35 degrees to 35 degrees with an angle interval of 5 degrees at six probe Reynolds numbers in range between $6.60{\times}10^3\;and\;3.17{\times}10^4$. The result shows that not only each calibration coefficient itself but also its Reynolds number dependency is affected significantly by the pitch and yaw angles. The Reynolds-number effects on the pitch- and yaw-angle coefficients are noticeable when the absolute values of the pitch and yaw angles are smaller than 20 degrees. The static-pressure coefficient is sensitive to the Reynolds number nearly all over the pitch- and yaw-angle range. The Reynolds-number effect on the total-pressure coefficient is found remarkable when the absolute values of the pitch and yaw angles are larger than 20 degrees. Through a typical non-nulling reduction procedure, actual reduced values of the pitch and yaw angles, static and total pressures, and velocity magnitude at each Reynolds number are obtained by employing the calibration coefficients at the highest Reynolds number ($Re=3.17{\times}10^4$) as input reference calibration data. As a result, it is found that each reduced value has its own unique trend depending on the pitch and yaw angles. Its general tendency is related closely to the variation of the corresponding calibration coefficient with the Reynolds number. Among the reduced values, the reduced total pressure suffers the most considerable deviation from the measured one and its dependency upon the pitch and yaw angles is most noticeable. In this study, the root-mean-square data as well as the upper and lower bounds of the reduced values are reported as a function of the Reynolds number. These data would be very useful in the estimation of the Reynolds-number effects on the non-nulling calibration.

• 산업경영시스템학회지
• /
• 제34권2호
• /
• pp.60-67
• /
• 2011

Since the non-metric Multidimensional scaling (nMDS), a data visualization technique, provides with insights about engineering, economic, and scientific applications, it is widely used for analyzing large non-metric multidimensional data sets. The nMDS requires a fitness function to measure fit of the proximity data by the distances among n objects. Most commonly used fitness functions are nonlinear and have a difficulty to find a good configuration. In this paper, we propose a new fitness function, an absolute value type, and show its advantages.

• 한국지진공학회논문집
• /
• 제21권5호
• /
• pp.215-226
• /
• 2017

In this paper, an experimental study was carried out for vibration control of cable bridges with structurally flexible characteristics. For the experiment on vibration control, a model bridge was constructed by reducing the Seohae Grand Bridge and the shear type MR damper was designed using the wind load response measured at Seohae Grand Bridge. The shear type MR damper was installed in the vertical direction at the middle span of the model bridge, and dynamic modeling was performed using the power model. The tests of the vibration control were carried out by non-control, passive on/off control and Lyapunov control method on model bridge with scaled wind load response. The performance of the vibration control was evaluated by calculating absolute maximum displacement, RMS displacement, absolute maximum acceleration, RMS acceleration, and size of applied power using the response (displacement, acceleration, etc.) from the model bridge. As a result, the power model was effective in simulating the nonlinear behavior of the MR damper, and the Lyapunov control method using the MR damper was able to control the vibration of the structure and reduce the size of the power supply.

• 한국유체기계학회 논문집
• /
• 제11권3호
• /
• pp.22-29
• /
• 2008

Clean and renewable energy technologies using ocean energy give us non-polluting alternatives to fossil and nuclear-fueled power plants to meet establishment of countermeasures against the global warming and growing demand for electrical energy. Among the ocean energy resources, wave power takes a growing interest because of its enormous amount of potential energy in the world. Therefore, various types of wave power conversion system to capture the energy of ocean waves have been developed. However, suitable turbine type is not normalized yet because of relatively low efficiency of the turbine systems. The purpose of this study is to investigate the internal flow and performance characteristics of a cross-flow type hydro turbine, which will be built in a caisson for wave power generation. Numerical simulation using a commercial CFD code is conducted to clarify the effects of the turbine rotation speed and flow rate variation on the turbine characteristics. The results show that the output power of the cross-flow type hydro turbine with symmetric nozzle shape is obtained mainly from Stage 2. Turbine inlet configuration should be designed to obtain large amount of flow rate because the static pressure and absolute tangential velocity are influenced considerably by inlet flow rate.

• 한국과학교육학회지
• /
• 제42권1호
• /
• pp.33-49
• /
• 2022

본 연구는 창의 과정과 산물의 구조적 관계를 분석한 정량적 자료와 정성적 자료를 활용하여 초등학생의 과학 창의성 유형을 탐색하였다. 이를 위해 초등학교 5학년 105명의 학생이 창의 과정과 산물을 나타내는 과학 창의성 검사 도구에 응답한 내용과 그중 과학 창의성이 가장 높았던 4명을 대상으로 주로 어떤 과정으로 창의 산물을 냈는지 면담하여 자료를 수집하였다. 검사 결과에 대해 상관관계 및 구조방정식 분석을 하였고 면담 자료와 함께 유형화의 참고자료로 사용하였다. 연구 결과는 다음과 같다. 첫째, 창의 과정과 산물의 구조방정식 모형은 절대적합지수와 증분적합지수 측면에서 적합도가 검증되었다. 둘째, 지식, 탐구기능 중 관찰, 창의적 사고기능의 창의 과정 중 창의적 사고기능만이 창의 산물에 유의한 영향을 미쳤다. 셋째, 창의적 사고기능 중 과학 창의성 산물과의 연관성은 확산적 사고, 수렴적 사고, 연관적 사고 순으로 나타났다. 넷째, 초등학생의 과학 창의성은 산물에 따라 창의형, 유용형, 독창형, 비창의형으로 유형이 나뉜다. 그중 비창의형은 세부적으로 진부형, 반복형, 미응답형, 비타당형, 추상형으로 나뉜다. 다섯째, 초등학생은 창의 과정에서 지식 혹은 관찰 중 하나를 주로 사용하는 양상을 보였는데, 이에 따라 지식 지향형, 관찰 지향형으로 유형화할 수 있다. 또한, 창의적 사고기능을 얼마나 다양하게 사용했는지에 따라 DT형, DT-CT형, DT-CT-AT형 등으로 나눌 수 있다. 이 연구는 교육자와 연구자가 과학 창의성 교육에 실질적으로 고려해야 할 점을 시사하고 있다.

• 한국농공학회지
• /
• 제17권4호
• /
• pp.3962-3969
• /
• 1975

1. When the frame of the experimental apparatus was directly fixed on the platform, result from the spectrum density analysis showed that the generated vibration frequecy of the system was nearly-same as the system's own characteristic vibration frequency, 80Hz, in the case of the forcing vibration frequency was 7.5 to 22.5Hz. The reduction ratio of acceleration by balanced type model compare to non-balanced type one was 26.66 percent. 2. When the frame of experimental apparatus was fixed on the platform with putting a shock absorbing rubber between the frame and the platform, the generated vibration frequency of the system was same as forcing vibration frequency. When either frequency or the amplitude of the forcing vibration was increased, the acceleration ratio was increased too. The average reduction ratio was resulted 44.77 per cent. It was concluded that this method of acceleration measurement(the method using a shock absorbing rubber) was a reaonable method, because actual machine will work under such condition. As the vibration frequency and aptitude were increased, the absolute magnitude of acceleration was increased. 3. unbalanced rotating parts, and unbalanced moment of inertia of links were supposed to be causing factors of residual vibration in spite of using the balanced type oscillating mole drainer. This fact suggested that the attachment of the counter weight on the rotating parts which satisfy the condition mw$.$rw=m0e, was necessary. And also, it was expected that the shock absorbing effect could be improved by putting the shock absorbing materials between the moving parts and their supports.

• 한국산학기술학회논문지
• /
• 제16권6호
• /
• pp.4291-4297
• /
• 2015

실내공간에서 인간의 쾌적감 및 불쾌적감 등의 감성을 측정하기 위하여 뇌파(EEG)측정을 많이 사용하고 있으나, 뇌파(EEG)측정은 접촉식으로써 실험에 제한적이다. 그러나 진동이미지기술은 웹캠 카메라를 이용하여 인간의 감성을 측정할 수 있는 비접촉식 방법으로써 실내공간에 적용하기에 적합하다고 판단된다. 따라서 인간의 감성을 측정할 수 있는 접촉식인 뇌파(EEG)와 비접촉식인 진동이미지기술의 상관변수를 도출하고자 한다. 본 연구에서는 소리크기 60[dB] 및 90[dB]과 로즈마리 및 쟈스민 향기에 대한 피험자의 뇌파(EEG)와 진동이미지기술의 상관분석을 하였다. 피험자는 건강상태를 점검하여 대학생 남자 3명으로 선별하여 10회 반복 실험하였고, 실험기간은 약 한 달간 진행되었으며, 측정실의 조건은 온도 25[$^{\circ}C$], 상대습도 50[%], 조도 1.000[lux] 및 기류속도 0.02[m/sec]로 하였다. 뇌파(EEG) 23가지 지표(절대${\theta}$, 상대${\theta}$, 절대$S{\alpha}$, 상대$S{\alpha}$, 절대${\alpha}$, 상대${\alpha}$, 절대${\beta}$, 상대${\beta}$, 절대$\gamma$, 상대$\gamma$, 절대$F{\alpha}$, 상대$F{\alpha}$, 절대SMR, 상대SMR, $SMR/{\theta}$, $SMR+M{\beta}/{\theta}$, 절대$H{\beta}$, 상대$H{\beta}$, $H{\beta}/{\alpha}$, 절대$M{\beta}$, 상대$M{\beta}$, SEF50, ASEF50)와 진동이미지기술 10가지 지표(긴장/불안, 억제, 신경과민증, 밸런스, 매력, 자신감, 의심, 스트레스, 공격성, 에너지)를 상관 분석한 결과 뇌파(EEG)의 상대${\gamma}$파와 진동이미지기술의 신경과민증 지표가 (${\pm}$).414와 (${\pm}$).424로 높은 정적상관관계로 분석되었다.

• Journal of Gastric Cancer
• /
• 제16권1호
• /
• pp.34-42
• /
• 2016

Purpose: Early gastric cancer cases that are estimated to meet indications for treatment before endoscopic submucosal resection are often revealed to be out-of-indication after the treatment. We investigated the short-term treatment outcomes in patients with early gastric cancer according to the pretreatment clinical endoscopic submucosal resection indications. Materials and Methods: We retrospectively reviewed the medical records of patients with early gastric cancer that met the pretreatment endoscopic submucosal resection indications, from 2004 to 2011. Curative resection rate and proportion of out-of-indication cases were compared according to the pre-endoscopic submucosal resection indications. Pre-endoscopic submucosal resection factors associated with out-of-indication in the final pathological examination were analyzed. Results: Of 756 cases, 660 had absolute and 96 had expanded pre-endoscopic submucosal resection indications. The curative resection rate was significantly lower in the patients with expanded indications (64.6%) than in those with absolute indications (81.7%; P<0.001). The cases with expanded indications (30.2%) were revealed to be out-of-indication more frequently than the cases with absolute indications (13.8%; P<0.001). Age of >65 years, tumor size of >2 cm, tumor location in the upper-third segment of the stomach, and undifferentiated histological type in pre-endoscopic submucosal resection evaluations were significant risk factors for out-of-indication after endoscopic submucosal resection. Conclusions: Non-curative resection due to out-of-indication occurred in approximately one-third of the early gastric cancer cases that clinically met the expanded indications before endoscopic submucosal resection. The possibility of additional surgery should be empha-sized for patients with early gastric cancers that clinically meet the expanded indications.