• 제목/요약/키워드: Mathematical Models

검색결과 1,795건 처리시간 0.031초

Uniform Fractional Band CAC Scheme for QoS Provisioning in Wireless Networks

  • Rahman, Md. Asadur;Chowdhury, Mostafa Zaman;Jang, Yeong Min
    • Journal of Information Processing Systems
    • /
    • 제11권4호
    • /
    • pp.583-600
    • /
    • 2015
  • Generally, the wireless network provides priority to handover calls instead of new calls to maintain its quality of service (QoS). Because of this QoS provisioning, a call admission control (CAC) scheme is essential for the suitable management of limited radio resources of wireless networks to uphold different factors, such as new call blocking probability, handover call dropping probability, channel utilization, etc. Designing an optimal CAC scheme is still a challenging task due to having a number of considerable factors, such as new call blocking probability, handover call dropping probability, channel utilization, traffic rate, etc. Among existing CAC schemes such as, fixed guard band (FGB), fractional guard channel (FGC), limited fractional channel (LFC), and Uniform Fractional Channel (UFC), the LFC scheme is optimal considering the new call blocking and handover call dropping probability. However, this scheme does not consider channel utilization. In this paper, a CAC scheme, which is termed by a uniform fractional band (UFB) to overcome the limitations of existing schemes, is proposed. This scheme is oriented by priority and non-priority guard channels with a set of fractional channels instead of fractionizing the total channels like FGC and UFC schemes. These fractional channels in the UFB scheme accept new calls with a predefined uniform acceptance factor and assist the network in utilizing more channels. The mathematical models, operational benefits, and the limitations of existing CAC schemes are also discussed. Subsequently, we prepared a comparative study between the existing and proposed scheme in terms of the aforementioned QoS related factors. The numerical results we have obtained so far show that the proposed UFB scheme is an optimal CAC scheme in terms of QoS and resource utilization as compared to the existing schemes.

유도전동기 드라이브의 고성능 제어를 위한 PI, FNN 및 ALM-FNN 제어기의 비교연구 (Comparative Study of PI, FNN and ALM-FNN for High Control of Induction Motor Drive)

  • 강성준;고재섭;최정식;장미금;백정우;정동화
    • 한국조명전기설비학회:학술대회논문집
    • /
    • 한국조명전기설비학회 2009년도 춘계학술대회 논문집
    • /
    • pp.408-411
    • /
    • 2009
  • In this paper, conventional PI, fuzzy neural network(FNN) and adaptive teaming mechanism(ALM)-FNN for rotor field oriented controlled(RFOC) induction motor are studied comparatively. The widely used control theory based design of PI family controllers fails to perform satisfactorily under parameter variation nonlinear or load disturbance. In high performance applications, it is useful to automatically extract the complex relation that represent the drive behaviour. The use of learning through example algorithms can be a powerful tool for automatic modelling variable speed drives. They can automatically extract a functional relationship representative of the drive behavior. These methods present some advantages over the classical ones since they do not rely on the precise knowledge of mathematical models and parameters. Comparative study of PI, FNN and ALM-FNN are carried out from various aspects which is dynamic performance, steady-state accuracy, parameter robustness and complementation etc. To have a clear view of the three techniques, a RFOC system based on a three level neutral point clamped inverter-fed induction motor drive is established in this paper. Each of the three control technique: PI, FNN and ALM-FNN, are used in the outer loops for rotor speed. The merit and drawbacks of each method are summarized in the conclusion part, which may a guideline for industry application.

  • PDF

컴퓨터 시뮬레이션을 이용한 항만설계 및 부산항 3단계 개발 계획에 대한 응용에 관한 연구 (A Study on the Microcomputer Aided port Design Simulation and its Application to the Third Stage Busan Port Development Project.)

  • 김환수
    • 한국항해항만학회:학술대회논문집
    • /
    • 한국항해항만학회 1991년도 하계학술발표회 한국항해학회
    • /
    • pp.45-48
    • /
    • 1991
  • This work aims to introduce the concept of microcomputer aided port design simulation methodology including the analysis of the mathematical models to be implemented and apply it to the Third Stage Busan Part Development Project. In the Busan case study the size of the proposed turning basin of the new terminal together with the operational stra-tegies of berthing and unberthing was examined In addition the safety of ships' entry and exit through the projection new breakwaters was as-certained. From the application of simulation to the Busan project it was found that the proposed dredging area was not sufficiently wide enough for a modelled container ship to perform A type unberthing (in which the ship turns to port as she monoeuvres away from No.1 berth with the ass-istance of tuges) especially in a strong easterly wind., It is therefore recommended that Busan pilots should be advised to use B type unberthing strategy in which the ship goes astern from No.1 berth to the turning area in front of No.2 berth(where the ship turns 180 degrees clockwise) especially when the wind is very strong. It is also recommended that a sea buoy be placed outside the new breakwaters as this was found to im-prove the safety of ship manoeuvres through the breakwaters significant-ly. Another recommendation is that the Korean Hydrodynamic Office carry out a detailed survey of the currents in the water area near the new breakwaters. once they have been constructed. In addition it is to be recommended that a current meter be placed at the recommended sea buoy pardised by erroneous current information

  • PDF

자전거용 크랭크 일체형 자동변속기에 대한 특성 해석 (Characteristics Analysis of CVT with Built-in Crank for Bicycle)

  • 백승엽
    • 한국산학기술학회논문지
    • /
    • 제16권2호
    • /
    • pp.963-969
    • /
    • 2015
  • 자전거는 환경공해 능력과 웰빙에 대한 관심증가 때문에 가장 유망한 미래 교통수단 중의 하나이다. 실제 자전거에 적용될 무단변속기를 제작하기 전에 신뢰성이 확보된 시뮬레이션 프로그램을 통하여 문제점을 초기에 확인하고, 각 링크의 소재 및 두께 등의 설계인자 최적화와 능력을 평가할 필요가 있다. 이 같은 과정을 통하여 무단 변속기 시스템 설계 과정에서의 소요비용을 줄일 수 있다. 본 논문에서는 설계인자를 확정하기 위해 응력해석을 수행되었으며. 전체 모델링 중에서 각 링크와 조인트 부분을 주요 설계인자로 가정하고 각각의 링크 및 조인트의 영향도 및 작동 시 받은 응력들을 CAE를 통해 확인하였다. 또한, 해석 영역에 대하여 적절한 수학적 모델링을 통해 맥동 현상을 계산할 수 있는 전용 code를 개발하였으며, 이를 Matlab에 적용하여 해석 결과를 graphic화하여 분석하였다.

적외선센서를 이용한 용접품질 제어에 관한 연구 (A Study on the Control of the Welding Quality Using a Infrared sensor)

  • 김일수;손준식;김학형;서주환;김인주
    • 한국정밀공학회:학술대회논문집
    • /
    • 한국정밀공학회 2005년도 추계학술대회 논문집
    • /
    • pp.754-758
    • /
    • 2005
  • Optimization of process variables such as arc current, welding voltage and welding speed in terms of the weld characteristics desired is the key step in achieving high quality and improving performance characteristics without increasing the cost. Consequently, incorrect settings of those process variables give rise to deviations in the welding characteristics from the desired bead geometry. Therefore, trainee welders are referred to the tabulated information relating different metal types and thickness as to recommend the desired values of process variables. Basically, the bead geometry plays an important role in determining the mechanical properties of the weld. So that it is very important to select the process variables for obtaining optimal bead geometry. However, it is difficult for the traditional identification methods to provide an accurate model because the optimized welding process is non-linear and time-dependent. In this paper, the possibilities of the Infra-red sensor in sensing and control of the bead geometry in the automated welding process are presented. Infra-red sensor is a well-known method to deal with the problems with a high degree of fuzziness so that the sensor is employed to build the relationship between process variables and the quality characteristic the proposed above respectively. Based on several neural networks, the mathematical models are derived from extensive experiments with different welding parameters and complex geometrical features. The developed system enables to select the optimal welding parameters and control the desired weld dimensions during arc welding process.

  • PDF

멀티로터 무인비행로봇 동역학적 모델링 및 제어기법 연구 (Dynamic Modeling and Control Techniques for Multi-Rotor Flying Robots)

  • 김현;정헌술;정길도;이덕진
    • 대한기계학회논문집A
    • /
    • 제38권2호
    • /
    • pp.137-148
    • /
    • 2014
  • 멀티로터는 여러 개의 로터로 이루어진 무인 비행로봇으로써, 로터의 개수에 따라서 트라이로터, 쿼드로터, 헥사로터, 옥토로터 등으로 나누어 진다. 멀티로터는 수직이착륙(VTOL) 및 높은 기동성으로 인하여 다른 무인 비행로봇에 비하여 건물이 밀집되어 있는 도심과 같은 지역의 정찰 및 감시 등 여러 응용분야에 적합하게 활용될 수 있다. 본 논문에서는 멀티로터란 이름으로 연구되고 있는 트라이로터, 쿼드로터, 헥사로터 및 옥토로터 비행로봇에 대한 통합된 동역학적 모델링에 관한 수식을 도출 및 비교 분석을 수행하고, 획득된 수식을 이용하여 각각의 멀티로터 동작원리 및 제어기법에 대한 연구를 수행하였다. 유도된 멀티로터의 동역학 모델링을 이용하여 각각의 멀티로터 형태에 따른 구동원리와 그에 따라 작용하는 힘과 모멘트에 대한 관계식을 유도하였으며, 연속루프닫음기법 기반자세 및 고도제어기를 적용하여 각각의 멀티로터 비행로봇의 구동 및 제어 성능을 시뮬레이션을 통해 검증하였다.

사행수로에서의 유속 및 분산특성에 관한 실험적 연구 (An Experimental Study of Flow and Dispersion Characteristics in Meandering Channel)

  • 박성원;서일원
    • 한국방재학회:학술대회논문집
    • /
    • 한국방재학회 2008년도 정기총회 및 학술발표대회
    • /
    • pp.799-802
    • /
    • 2008
  • General behaviors based on hydraulic characteristics of natural streams and channels have been recently analyzed and developed via various numerical models. However in the states of natural hydraulics, an experimental research must be performed simultaneously with the mathematical analysis due to effects of hydraulic properties such as meander, sediment, and so on. In this study based on 2-D advection-dispersion equation, flow and tracer experiments were performed in the S-curved meandering laboratory channel with a rectangular cross-section. The channel was equipped with instrument carriages which was equipped with an auto-traversing system to be used with velocity measuring sensors throughout the depth and breadth of the flow field. To measure concentration distribution of the salt solution was adjusted to that of the flume water by adding methanol and a red dye (KMnO4) was added to aid the visualization of the tracer cloud, the tracer was instantaneously injected into the flow as a full-depth vertical line source by the instantaneous injector and the initial concentration of the tracer was 100,000 mg/l. The secondary current as well as the primary flow pattern was analyzed to investigate the flow distribution in the meandering channels. The velocity distribution of the primary flow for all cases skewed toward the inner bank at the first bend, and was almost symmetric at the crossovers, and then shifted toward the inner bank again at the next alternating bend. Thus, one can clearly notice that the maximum velocity occurs taking the shortest course along the channel, irrespective of the flow conditions. The result of the tracer tests shows that pollutant clouds are spreading following the maximum velocity lines in each cases with various mixing patterns like superposition, separation, and stagnation of pollutant clouds. Flow characteristics in each cases performed in this study can be compared with tracer dispersion characteristics with using evaluation of longitudinal and transverse dispersion coefficients(LDC, TDC). As expected, LDC and TDC in meandering parts have been evaluated with increasing distribution and straight parts have effected to evaluate minimum of LDC and TDC due to symmetric flow patterns and attenuations of secondary flow.

  • PDF

Mathematical model for reactive transport of heavy metals in soil column: Based on PHREEQC and HP1 simulators

  • Tameh, Fatemeh Izadi;Asadollahfardi, Gholamreza;Darban, Ahmad Khodadadi
    • Advances in environmental research
    • /
    • 제6권1호
    • /
    • pp.67-81
    • /
    • 2017
  • Mining activities play a significant role in environmental pollution by producing large amounts of tailings which comprise heavy metals. The impressive increase in mining activities in recent decades, due to their high influence on the industry of developing countries, duplicates the need for a substantial effort to develop and apply efficient measures of pollution control, mitigation, and abatement. In this study, our objective was to investigate the effect of simulation of the leachate, pH and inflow intensity of transport of $Pb^{2+}$, $Zn^{2+}$, and $Cd^{2+}$ through Lakan lead and zinc plant tailings, in Iran, and to evaluate the modeling efficiency by comparing the modeling results and the results obtained from previous column studies. We used the HP1 model and the PHREEQC database to simulate metals transport through a saturated soil column during a 15 day time period. The simulations assumed local equilibrium. As expected, a lower pH and inflow intensity increased metal transport. The retardation of heavy metals followed the order $Zn^{2+}$ > $Pb^{2+}$ > $Cd^{2+}$ and the removal concentrations of Cd, Pb, and Zn at the inflow intensity critical scenario, and Cd and Pb at inflow acidity critical scenario exceeded the allowable EPA and Iranian's 1053 standard thresholds. However, although the simulation results generally agreed well with the results of the column study, improvements are expected by using multi-dimensional models and a kinetic modeling approach for the reactions involved. The results of such investigations will be highly useful for designing preventative strategies to control reactive transport of hazardous metals and minimize their environmental effects.

퍼지집합과 베이지안 확률 기법을 이용한 암설사면지형 분포지역 추출에 관한 연구 (The Study on the Extraction of the Distribution Potential Area of Debris Landform Using Fuzzy Set and Bayesian Predictive Discriminate Model)

  • 위눈솔;장동호
    • 한국지형학회지
    • /
    • 제24권3호
    • /
    • pp.105-118
    • /
    • 2017
  • The debris slope landforms which are existent in Korean mountains is generally on the steep slopes and mostly covered by vegetation, it is difficult to investigate the landform. Therefore a scientific method is required to come up with an effective field investigation plan. For this purpose, the use of Remote Sensing and GIS technologies for a spatial analysis is essential. This study has extracted the potential area of debrisslope landform formation using Fuzzy set and Bayesian Predictive Discriminate Model as mathematical data integration methods. The first step was to obtain information about debris locations and their related factors. This information was verified through field investigation and then used to build a database. In the second step, the map that zoning the study area based on the degree of debris formation possibility was generated using two modeling methods, and then cross validation technique was applied. In order to quantitatively analyze the accuracy of two modeling methods, the calculated potential rate of debrisformation within the study area was evaluated by plotting SRC(Success Rate Curve) and calculating AUC(Area Under the Curve). As a result, the prediction accuracy of Fuzzy set model wes 83.1% and Bayesian Predictive Discriminate Model wes 84.9%. It showed that two models are accurate and reliable and can contribute to efficient field investigation and debris landform management.

난류 유동을 갖는 가스 포일 스러스트 베어링의 성능 예측 (Performance Predictions of Gas Foil Thrust Bearings with Turbulent Flow)

  • 문진혁;김태호
    • Tribology and Lubricants
    • /
    • 제35권5호
    • /
    • pp.300-309
    • /
    • 2019
  • Gas foil thrust bearings (GFTBs) support axial loads in oil-free, high speed rotating machinery using air or gas as a lubricant. Due to the inherent low viscosity of the lubricant, GFTBs often have super-laminar flows in the film region at operating conditions with high Reynolds numbers. This paper develops a mathematical model of a GFTB with turbulent flows and validates the model predictions against those from the literature. The pressure distribution, film thickness distribution, load carrying capacity, and power loss are predicted for both laminar and turbulent flow models and compared with each other. Predictions for an air lubricant show that the GFTB has high Reynolds numbers at the leading edge where the film thickness is large and relatively low Reynolds numbers at the trailing edge. The predicted load capacity and power loss for the turbulent flow model show little difference from those for the laminar flow model even at the highest speed of 100 krpm, because the Reynolds numbers are smaller than the critical Reynolds number. On the other hand, refrigerant (R-134a) lubricant, which has a higher density than air, had significant differences due to high Reynolds numbers in the film region, in particular, near the leading and outer edges. The predicted load capacity and power loss for the turbulent flow model are 2.1 and 2.3 times larger, respectively, than those for the laminar flow model, thus implying that the turbulent flow greatly affects the performance of the GFTB.