• 제목/요약/키워드: Upper Bound

검색결과 967건 처리시간 0.026초

Pseudostatic analysis of bearing capacity of embedded strip footings in rock masses using the upper bound method

  • Saeed Shamloo;Meysam Imani
    • Geomechanics and Engineering
    • /
    • 제34권4호
    • /
    • pp.381-396
    • /
    • 2023
  • The present paper evaluates seismic bearing capacity of rock masses subjected to loads of strip footings using the upper bound method. A general formula was proposed to evaluate the seismic bearing capacity considering both the horizontal and vertical accelerations of the earthquake and the effects of footing embedment depth simultaneously. Modified Hoek-Brown failure criterion was employed for the rock mass. Some comparisons were made with the available solutions and the finite element numerical models to show the accuracy of the developed upper bound formulations. The obtained results show significant improvement compared to the other available solutions. By increasing the horizontal earthquake acceleration from 0.1 to 0.3, the bearing capacity was reduced by up to 39%, while the effect of the vertical earthquake acceleration depends on its direction. An upward acceleration in the range of zero to 0.2 results in an increase in the bearing capacity by up to 24%, while the downward earthquake acceleration has an adverse effect. Also, by increasing the embedment depth of the footing from zero to 5 times the footing width, the value of seismic bearing capacity was raised about 86%. The obtained results were presented as design tables for use in practical applications.

LDPC 코드와 터보 코드의 성능 상향 한계 분석 (Analysis of Bounding Performance for LDPC codes and Turbo-Like Codes)

  • 정규혁
    • 한국통신학회논문지
    • /
    • 제31권2A호
    • /
    • pp.138-143
    • /
    • 2006
  • 본 논문은 특정한 LDPC 코드와 특정한 인터리버를 가진 터보 코드의 맥시멈 라이클리후드(maximum-likelihood) 디코딩 성능의 상향 한계를 보인다. 현재까지의 연구는 균등 인터리버의 가정을 하거나 또는 앙상블 코드를 사용하여 LDPC 코드와 터보 코드의 성능 상향 한계를 계산하였다. 이러한 성능 상향 한계는 모든 코드 또는 모든 인터리버에 대한 평균 성능만을 표시하게 된다. 제안된 성능 상향 한계는 단순 한계(simple bound)와 정확한 짧은 거리의 항들을 포함하는 추정된 무게 분포를 기초하고 있다. 만약 둘 중에 하나만 사용하게 되면 정확한 성능 상향 한계를 얻을 수 가 없다.

Solving Linear Problems with Generalized Variable Upper Bounds

  • Yang, Kwang-Min
    • 한국경영과학회지
    • /
    • 제17권3호
    • /
    • pp.171-180
    • /
    • 1992
  • This paper proposes a solution approach to linear problems with many constraints of variable upper bound (VUB) type. This type of constraints are commonly found in various scheduling type problems for which tighter bounds are essential to achieve an efficiency in enumeration. An analytical framework based on factorization is adopted to devise a solution approach to the problem and extend it for more generalized VUB problem (GVUB). This research shows why the VUB type constraints are amenable to the factorization and gives a unified approach to generalized upper bound(GUB) problems, VUB problems and GVUB problems. Implementation issues are also included.

  • PDF

APPROXIMATION OF THE QUEUE LENGTH DISTRIBUTION OF GENERAL QUEUES

  • Lee, Kyu-Seok;Park, Hong-Shik
    • ETRI Journal
    • /
    • 제15권3_4호
    • /
    • pp.35-45
    • /
    • 1994
  • In this paper we develop an approximation formalism on the queue length distribution for general queueing models. Our formalism is based on two steps of approximation; the first step is to find a lower bound on the exact formula, and subsequently the Chernoff upper bound technique is applied to this lower bound. We demonstrate that for the M/M/1 model our formula is equivalent to the exact solution. For the D/M/1 queue, we find an extremely tight lower bound below the exact formula. On the other hand, our approach shows a tight upper bound on the exact distribution for both the ND/D/1 and M/D/1 queues. We also consider the $M+{\Sigma}N_jD/D/1$ queue and compare our formula with other formalisms for the $M+{\Sigma}N_jD/D/1$ and M+D/D/1 queues.

  • PDF

Branch and Bound Approach for Single-Machine Sequencing with Early/Tardy Penalties and Sequence-Dependent Setup Cost

  • Akjiratikarl, Chananes;Yenradee, Pisal
    • Industrial Engineering and Management Systems
    • /
    • 제3권2호
    • /
    • pp.100-115
    • /
    • 2004
  • The network representation and branch and bound algorithm with efficient lower and upper bounding procedures are developed to determine a global optimal production schedule on a machine that minimizes sequence-dependent setup cost and earliness/tardiness penalties. Lower bounds are obtained based on heuristic and Lagrangian relaxation. Priority dispatching rule with local improvement procedure is used to derive an initial upper bound. Two dominance criteria are incorporated in a branch and bound procedure to reduce the search space and enhance computational efficiency. The computational results indicate that the proposed procedure could optimally solve the problem with up to 40 jobs in a reasonable time using a personal computer.

Secret Key Generation from Common Randomness over Ultra-wideband Wireless Channels

  • Huang, Jing Jing;Jiang, Ting
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • 제8권10호
    • /
    • pp.3557-3571
    • /
    • 2014
  • We develop a secret key generation scheme using phase estimation in ultra-wideband (UWB) wireless fading channels. Based on the reciprocity theorem, two terminals extract the phase of the channel as a common random source to generate secret bits. Moreover, we study the secret key rate by a pair of nodes observing correlated sources and communicating to achieve secret key agreement over public communication channels. As our main results, we establish a more practical upper bound from Cramer-Rao bound (CRB) and compare it with a universally theoretical upper bound on the shared maximum key rate from mutual information of correlated random sources. Derivation and numerical examples are presented to demonstrate the bound. Simulation studies are also provided to validate feasibility and efficiency of the proposed scheme.

제어이득의 하한을 이용한 새로운 슬라이딩 모드제어 (Sliding Mode Control Using the Lower Bound of Control Gain)

  • 유병국
    • 제어로봇시스템학회논문지
    • /
    • 제9권9호
    • /
    • pp.664-668
    • /
    • 2003
  • A new sliding mode control method based on the lower bound of control gain is presented. Although the magnitube of the proposed control input is larger than that of the conventional control input using both lower and upper bounds, the positive-negative exchanging chattering is reduced and reaching mode is shorter. Because the proposed scheme needs only the lower bound of control gain, it is applicable to the system whose upper bound of control gain is doubtful to determine such as the control gain depends on the system states. It is proved that the proposed control method guarantees the sliding condition. The analysis of differences between the conventional method and the proposed method is given. The validity of the proposed control strategy is shown through a 2nd-order nonlinear system example.

Degrees of Freedom of Y Channel with Single-Antenna Users: Transmission Scheme and Beamforming Optimization

  • Long, Wei;Gao, Hui;Lv, Tiejun;Yuen, Chau
    • KSII Transactions on Internet and Information Systems (TIIS)
    • /
    • 제8권12호
    • /
    • pp.4305-4323
    • /
    • 2014
  • In this paper, we investigate the degrees of freedom (DOF) of the Y channel consisting of three single-antenna users and a two-antenna common access relay, where each user intends to exchange independent messages with the other two users with the assistance of the relay. We show that the DOF of this particular scenario is 1.5. In order to prove this result, we firstly derive a DOF upper bound based on cut-set bound by allowing cooperation among users, which shows that the total DOF is upper bounded by 1.5. Then we propose a novel transmission scheme based on asymmetric signal space alignment (ASSA) to demonstrate the achievability of the upper bound. Theoretical evaluation and numerical results confirm that the upper bound can be achieved by utilizing ASSA, which also proves the optimality of the ASSA-based scheme in terms of DOF. Combining the upper bound and achievability, we conclude that the exact DOF is 1.5. Moreover, we present a novel iterative joint beamforming optimization (I-JBO) algorithm to further improve the sum rate. Numerical simulations have been provided to demonstrate the convergence speed and performance advantage of the I-JBO algorithm.

Robust Stability Condition and Analysis on Steady-State Tracking Errors of Repetitive Control Systems

  • Doh, Tae-Yong;Ryoo, Jung-Rae
    • International Journal of Control, Automation, and Systems
    • /
    • 제6권6호
    • /
    • pp.960-967
    • /
    • 2008
  • This paper shows that design of a robustly stable repetitive control system is equivalent to that of a feedback control system for an uncertain linear time-invariant system satisfying the well-known robust performance condition. Once a feedback controller is designed to satisfy the robust performance condition, the feedback controller and the repetitive controller using the performance weighting function robustly stabilizes the repetitive control system. It is also shown that we can obtain a steady-state tracking error described in a simple form without time-delay element if the robust stability condition is satisfied for the repetitive control system. Moreover, using this result, a sufficient condition is provided, which ensures that the least upper bound of the steady-state tracking error generated by the repetitive control system is less than or equal to the least upper bound of the steady-state tracking error only by the feedback system.

상계해법에 의한 원형빌렛으로부터 인볼루트 헬리컬핀을 가진 제품의 비틀림 압출가공법에 관한 연구 (A Study of the Twisting and Extrusion Process of the Product with Involute Helical Fin from the Round Billet by the Upper Bound Analysis)

  • 박대윤;진인태
    • 소성∙가공
    • /
    • 제10권4호
    • /
    • pp.302-310
    • /
    • 2001
  • The twisting and extrusion process of the product with involute helical fin from the round billet is developed by the upper bound analysis. The twisting of extruded product is caused by the twisted inclined die surface connecting the die enterance section and the die exit section linearly. In the analysis, the internal shear surface is defined as the curved twisted plane from the twisting of die surface and the shear work is calculated by the consumption of shear energy. The increase rate of angular velocity is determined by the minimization of plastic work. The angular velocity of die exit can be controlled by the land length and the length of inclined die. The alular velocity assums to be increased linearly by the axial distance from the die enterance to the die exit. The results of the analysis show that the angular velocity of the extruded product increases with the die twisting angle, the reduction of area, and decreases with the die length, the friction constant.

  • PDF