• 한국콘텐츠학회논문지
• /
• 제15권4호
• /
• pp.530-544
• /
• 2015

우리는 지식정보화사회라고 일컬어지는 현대사회를 살아가고 있다. 급변하고 있는 미래사회를 준비하기위해 국가적 사회적으로 창의성이 높은 인재양성을 요구하고 있으며, 이에 따라 학교와 가정에서도 창의성과 문제해결력을 기르기 위한 노력과 관심을 기울이고 있다. 특히, 교육현장에서는 '글로벌 창의 인재'육성 및 국가경쟁력 강화를 위하여 STEAM교육과 소프트웨어 교육을 도입하여 추진하고 있다. 따라서 본 연구에서는 소프트웨어교육을 위한 프로그래밍 언어로 언급되고 있는 비주얼 프로그래밍 언어 중 MIT에서 개발한 앱인벤터(App Inventor)를 활용하여 STEAM 교육에 활용할 수 있는 방안을 제시하고 전문가집단 평가를 통해 검증 및 평가를 실시하였다. 평가결과는 수정 및 보완하여 앱인벤터를 활용한 STEAM 프로그램을 완성하였으며, 이를 토대로 실제적인 STEAM 교수학습 방법을 제시하였다. 본 연구의 목적은 앱인벤터를 활용한 STEAM 프로그램을 개발하는 것이며, 이를 위하여 기존의 STEAM 프로그램이 갖는 한계점을 분석하고, 앱인벤터를 활용한 STEAM 프로그램을 개발하고 제시함으로써 이를 극복하고자 하였다. 아울러, 앱인벤터가 갖는 교육용 프로그래밍 언어로써의 특징과 활용방안을 살펴봄으로써 향후 소프트웨어 교육의 방향과 교수학습방안도 함께 제시하였다.

• 대한조선학회논문집
• /
• 제51권3호
• /
• pp.259-264
• /
• 2014

Tip vortex cavitation (TVC) is important for naval ships and research vessels that require raising the cavitation inception speed to maximum possible values. The concepts for alleviating the tip vortex are summarized by Platzer and Souders (1979), who carried out a thorough literature survey. Active control of TVC involves the injection of a polymer or water from the blade tip. The main effect of such mass injection (both water and polymer solutions) into the vortex core is an increase in the core radius, consequently delaying TVC inception. However, the location of the injection port needs to be selected with great care in order to ensure that the mass injection is effective in delaying TVC inception. In the present study, we propose a semi-active control scheme that is achieved by attaching a thread at the propeller tip. The main idea of a semi-active control is that because of its flexibility, the attached thread can be sucked into the low-pressure region closer to the vortex core center. An experimental study using a scale model was carried out in the cavitation tunnel at the Seoul National University. It was found that a flexible thread can effectively suppress the occurrence of TVC under the design condition for a model propeller.

• 전기전자학회논문지
• /
• 제20권3호
• /
• pp.285-290
• /
• 2016

고속 인터페이스에서 채널 대역폭에 의해 생기는 ISI는 최대 데이터 전송속도를 제한한다. ISI를 제거하는 가장 보편적인 기술로 DFE가 있다. 빠른 데이터 송수신을 위해서는 DFE가 효과적으로 ISI를 제거하는 것도 중요하지만 피드백 지연 등을 완화시켜 회로 자체의 최대 동작 주파수도 증가시켜야 한다. 또한, 싱글 엔디드 시그널링에서는 DFE가 ISI뿐만이 아닌 고주파 잡음도 효과적으로 제거하여야 한다. 한편, 데이터 전송 속도가 올라감에 따라 늘어 나는 ISI 및 고주파 잡음을 제거하기위한 DFE 구성품의 수가 증가한다. 이는 곧 추가의 전력소모를 야기하므로 고속 동작뿐만 아니라 저전력 동작도 주목할 필요가 있다. 본 논문에서는 ISI와 고주파 잡음을 효과적으로 제거하는 고속 DFE 및 저전력으로 동작하는 DFE의 동작 방식과 이들이 갖고 있는 장단점을 소개한다.

• 한국자동차공학회논문집
• /
• 제15권1호
• /
• pp.64-70
• /
• 2007

Raising exhaust gas temperature during cold-start period is very crucial to improve emission performance of SI engines because it enhances the performance of catalyst in the early stage of engine start. In this study, control variables such as ignition timing, idle speed actuator(ISA) opening and fuel injection duration were extensively investigated to analyze variations in exhaust gas temperature and engine stability during cranking period. Experimental results showed that spark timing affected engine stability and exhaust gas temperature but the effects were small. On the other hand, shortened injection duration and increased ISA opening led to a significant increase in exhaust gas temperature. Under such conditions, increase in cranking time was also observed, showing that it becomes harder to start the engine. Based on these observations, a pseudo fuel-air ratio, defined as a ratio of fuel injection time to degree of ISA opening, was introduced to analyze the experimental results. In general, decrease in pseudo fuel-air ratio raised exhaust gas temperature with the cost of stable and fast cranking. On the contrary, an optimal range of the pseudo fuel-air ratio was found to be between 0.3 to 0.5 where higher exhaust gas temperatures can be obtained without sacrificing the engine stability.

• 멤브레인
• /
• 제13권2호
• /
• pp.88-100
• /
• 2003

테일러 와류흐름 여과에서 평균기공 1.2 ${\mu}m$인 셀룰로우스 에스테르 정밀막으로 이루어진 내부원통의 회전속도와 슬러리의 농도, 입자의 크기에 따른 여과선속의 변화를 실험을 통하여 알아보았다. 여과선속은 압력차에 비례하고 저항에 반비례하였으며, 시간에 따른 케이크 층의 저항 변화를 회전속도, 슬러리의 농도, 입자의 크기에 따라 검토하였다. 회전속도가 증가할수록 케이크 저항이 감소하고 짧은 시간에 준정상 상태에 도달하였다 슬러리의 농도를 증가시킬수록 초기 저항이 급격히 증가하였고 높은 저항값에서 준정상 상태가 유지되었으나, 준정상 상태에 도달하는 시간은 농도에 무관하였다. 입자 크기가 작을 때 저항이 크게 나타남을 관찰하였는데, 입자 크기가 작을수록 막 기공을 막을 확률이 더 높고 전단력에 의해 영향을 덜 받기 때문이라 생각할 수 있다. 본 연구에서 제안한 모델식은 입자의 퇴적과 제거항으로 나누어져 있는데, 실험상수의 평균값을 사용하여 실험결과와 잘 일치하였다.

• Physical Therapy Rehabilitation Science
• /
• 제13권3호
• /
• pp.332-342
• /
• 2024

Objective: With the proportion of the elderly population in Korea reaching 17.5% in 2022 and projected to increase to 20.6% by 2025, 30.1% by 2035, and 43% by 2050, the accelerated aging of the population is raising societal concerns about elderly care. Maintaining mobility is crucial for a healthy and independent old age. Design: Cross-sectional study Methods: This study investigates the effects of dual-task performance on gait variables and cognitive function in older adults. This cross-sectional study involved 60 older adults aged 65 and above, categorized into a dementia group (Korean version of Montreal Cognitive Assessment (MoCA-K) score ≤ 22) and a control group (MoCA-K score ≥ 23). Cognitive and gait functions were assessed using the GAITRite system (GAITRite system, CIR Systems Inc., USA), measuring gait variables (speed, stride length, etc.) before and after dual-task performance. The assessments were conducted under a single-blind condition, and data were analyzed using SPSS (ver. 25.0, SPSS Inc., USA). Results: The dementia group scored lower on cognitive assessments compared to the control group (p<0.05). In dual-task performance evaluations, the dementia group exhibited longer total task times and lower accuracy than the control group (p<0.001), while reaction times were longer but not statistically significant. GAITRite system analysis revealed that the dementia group had reduced gait speed and stride length compared to the control group (p<0.05). However, the difference in gait time was not statistically significant. The study results indicate that older adults with dementia show significant differences in cognitive function and gait performance, with notable impacts under dual-task conditions. Conclusions: These findings underscore the effect of cognitive decline on gait and provide valuable insights for predicting gait and cognitive function deterioration in dementia, which can aid in developing fall prevention strategies.

• The Journal of Asian Finance, Economics and Business
• /
• 제7권12호
• /
• pp.1167-1174
• /
• 2020

This study aims to evaluate the effect of computerized tax services in improving tax performance by moderating governance principles in Jordanian tax income departments. The study is based on a questionnaire distributed to income tax auditors, who were chosen by the simple random sampling method, so that 170 questionnaires were subjected to statistical analysis. The study models were formulated in the form of simple and multiple regression equations to test the hypotheses of the study, in addition to relying on One Sample T-test to calculate the mean of questionnaire answers. The most prominent research results is that the application of tax governance principles through the provision of computerized tax services is reflected in the increase in confidence between taxpayers and income tax departments, the efficiency of tax performance, and tax proceeds. Also, the study pointed out the importance of the income tax departments to prepare strategic plans regarding the development and the follow-up of modern technologies related to computerized tax services. It especially regards linking and collecting tax from taxpayers such as via electronic tax payment and collection system, in order to ensure the speed of completion, accuracy of calculation, and raising the efficiency of tax performance.

• Journal of information and communication convergence engineering
• /
• 제8권1호
• /
• pp.89-94
• /
• 2010

The most important of rule-base system is the knowledge base that determines the power of rule-base system. The important form of this knowledge is how to descript kinds of rules. The Rule-Base System (RBS) has been using in many field that need reflect quickly change of business rules in management system. As far, when develop the Rule-Based System, we must make a rule engine with a general language. There are three disadvantage of in this developed method. First, while there are many data that must be processed in the system, the speed of processing data will become very slow so that we cannot accept it. Second, we cannot change the current system to make it adaptive to changes of business rules as quickly as possible. Third, large data make the rule engine become very complex. Therefore, in this paper, we propose the two important methods of raising efficiency of Rule-Base System. The first method refers to using the Relational database technology to process the rules of the Rule-Base System, the second method refers to a algorithm of according to Quine McCluskey formula compress the rows of rule table. Because the expressive languages of rule are still remaining many problems, we will introduce a new expressive language, which is Rule-Base Data Model short as RBDM in this paper.

• Advances in environmental research
• /
• 제4권4호
• /
• pp.219-231
• /
• 2015

In recent years, raising air pollutants has become as a big concern, especially in metropolitan cities such as Tehran. Therefore, forecasting the level of pollutants plays a significant role in air quality management. One of the forecasting tools that can be used is an artificial neural network which is able to model the complicated process of air pollution. In this study, we applied two different methods of artificial neural networks, the Multilayer Perceptron (MLP) and Radial Basis Function (RBF), to predict the hourly air concentrations of toluene in Tehran. Hourly temperature, wind speed, humidity and $NO_x$ were selected as inputs. Both methods had acceptable results; however, the RBF neural network produced better results. The coefficient of determination ($R^2$) between the observed and predicted data was 0.9642 and 0.99 for MLP and RBF neural networks, respectively. The results of the mean bias errors (MBE) were 0.00 and -0.014 for RBF and MLP, respectively which indicate the adequacy of the models. The index of agreement (IA) between the observed and predicted data was 0.999 and 0.994 in the RBF and the MLP, respectively which indicates the efficiency of the models. Finally, sensitivity analysis related to the MLP neural network determined that temperature was the most significant factor in air concentration of toluene in Tehran which may be due to the volatile nature of toluene.

• KSTLE International Journal
• /
• 제1권2호
• /
• pp.101-106
• /
• 2000

Variable displacement axial piston pumps are widely used for raising the energy level of the fluid in hydraulic systems. And the regulator is the device which regulates the discharge flow of the piston pump by controlling the swivel angle. The regulator receives the hydraulic pilot pressure and controls the pump output flow depending on the machine load and engine speed. This work deals with constant power control (horsepower control) in the design of a regulator by using a bent-axis type piston pump. In order to effectively use engine power, we must keep the horsepower from the engine to the pump constant. Therefore the regulator operates the constant power control. As a result, optimum power usage is obtained by accurately following the power hyperbola. This study focused on developing a simulation model of a regulator. First, the governing equations of the regulator are derived, and analysis is performed by computer simulation, which can identify significant parameters of regulator. As a result, the variation of the swivel angle, flow rate, hyperbolic curve, inner leakage and responsibility are simulated, and significant parameters of a regulator are identified.