• Title/Summary/Keyword: Overflow

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Characteristics of Reservoir Behavior According to Establishment Range of Waterproof Mat During Overflow (차수매트 포설 범위에 따른 저수지 월류시 거동 특성)

  • Kim, Young-Ik;Lee, Ik-Sang;Choi, Don-Hwan;Im, Eun-Sang;Kim, Yong-Seong
    • Journal of The Korean Society of Agricultural Engineers
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    • v.52 no.2
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    • pp.59-66
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    • 2010
  • This study was performed to develop the embankment protection method that can reduce demage by prevention of embankment loss and collapse from overflow due to heavy rain and flood. For overflow test, model dam was prepared and embankment behaviors were monitored with the established piezometer and strain meter during overflow. As a result of overflow test for model dam, in case of embankment without waterproof mat, the lower end of embankment was collapsed within 40 seconds after beginning of overflow. On the other hand, in case of embankment with waterproof mat, embankment collapse didn't occurred during overflow. Accordingly, establishment of waterproof mat for embankment showed that be absolutely effective for the embankment protection during overflow in reservoir. Also, it showed that the minimum establishment range of waterproof mat to prevent embankment collapse in reservoir is from maximum storage level to the lower end of embankment.

Development of Wave Overtopping-Overflow Transition Model Based on Full-scale Experiments

  • Mase, Hajime;Kim, Sooyoul;Hasegawa, Makoto;Jeong, Jae-Hoon;Yoon, Jong-Sung
    • Journal of Ocean Engineering and Technology
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    • v.34 no.2
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    • pp.128-135
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    • 2020
  • When high waves and storm surge strike simultaneously, the characteristics of the fluid field change drastically from overtopping according to the wave runup height to overflow through a transition state that combines overtopping and overflows. However, an estimation model or evaluation method has not yet been established because there is not enough engineering data. This study developed a wave overtopping-overflow transition model based on a full-scale experiment involving wave overtopping and overflow transition, which appropriately reproduced the effect of waves or the temporal change in inundation flow. Using this model to perform a calculation for the wave overtopping and overflow transition process under typical circumstances, this study determined the wave runup height and features of the inundation flow under time series changes as an example.

A Study of Buffer Overflow Prevention Technique for Secure System (안전한 시스템을 위한 Buffer Overflow 대응기법분석에 관한 연구)

  • 조진호;황현욱;박종백
    • Proceedings of the Korean Information Science Society Conference
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    • pp.608-610
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    • 2000
  • Buffer Overflow는 가장 핵심적인 해킹기법중의 하나이다. 현재 해킹피해의 대부분을 차지하며 local attack뿐 아니라 remote attack까지 가능하므로 이를 이해함은 보안을 이해하는 차원에서 매우 중요하다. 본 논문에서는 Buffer Overflow의 원리와 최근 발생한 시스템의 해킹 형태를 살펴보고, 이를 방지할 수 있는 기법들을 분석하여 Buffer Overflow에 대응할 수 있는 모습을 그려보고자 한다.

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Implementation of a function translator converting vulnerable functions for preventing buffer overflow attacks (버퍼 오버플로우 공격 방지를 위한 취약 함수 변환기 구현)

  • Kim, Ik Su;Cho, Yong Yun
    • Journal of Korea Society of Digital Industry and Information Management
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    • v.6 no.1
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    • pp.105-114
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    • 2010
  • C language is frequently used to develop application and system programs. However, programs using C language are vulnerable to buffer overflow attacks. To prevent buffer overflow, programmers have to check boundaries of buffer areas when they develop programs. But vulnerable programs frequently result from improper programming habits and mistakes of programmers. Existing researches for preventing buffer overflow attacks only inform programmers of warnings about vulnerabilities and not remove vulnerabilities in advance so that the programs still include vulnerabilities. In this paper, we propose a function translator which prevents creating programs including buffer overflow vulnerabilities. To prevent creating binary from source including vulnerabilities, the proposed translator searches vulnerable functions which cause buffer overflows, and converts them into secure functions. Accordingly, developing vulnerable programs by programmers which lack in knowledge on security can be prevented.

A Study on Accalerated Vocous Condition in Siphon Spillway (싸이폰식 여수토의 진공촉진에 대한 연구)

  • 김시원
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.6 no.2
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    • pp.816-825
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    • 1964
  • 1. Outline: The flow of the siphon spillway is very intricate and affected by vacuous condition. It is an intresting problem to make vacuum rapidly in_siphon, i.e, to provoke the perfect siphonaoge with the lowest water-level of overflow. The hydraulic experiments of siphon spillway have practiced at the Masan Lake, Haenam, the province of Junnam and gained rational and economical results which cannot be odtained by calculation. 2. Experiment: The model scale was a half of that of the prototype. 3. Results and discussion: In the experiments of 14 runs, washing, overflow water level, outlet, water level of cushion, phenomenon of water flying and water pressure of every part, etc. were studied. a) The relation of overflow water-level at siphon inlet and deflector When the elevation of the deflector is 10. 65m and the form of deflector O.4m long is the hypotenuse of an $45^{\circ}$ isosceles triangle, the over flow water-level is the minimum, i. e. the siphonage was excellent. There is no effect by the rising of overflow water-Ievel between 11.95m to 1O.65m of deflector elevation (in the first plan, it is 11.05m). But the overflow water-level rises remarkably in the outside region of the above limits. b) The relation of overflow water-level, the length of cushion and standard height of the base. The reduction of the length of cushion brings the rising of overflow waterlevel, and the rising of the standard height of the base brings the rising of overflow water level. For the long cushion length and low standard height of the base, it cannot be expeted to have the falling of overflow water-level. The most satisfactory data were obtained at 5.20m of the base standard height and 6.1m of the length of cushion. The first vah,le planned was 5.70 m and 4.30m.

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Estimation of Overflow Probabilities in Parallel Networks with Coupled Inputs

  • Lee, Jiyeon;Kweon, Min Hee
    • Communications for Statistical Applications and Methods
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    • v.8 no.1
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    • pp.257-269
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    • 2001
  • The simulation is used to estimate an overflow probability in a stable parallel network with coupled inputs. Since the general simulation needs extremely many trials to obtain such a small probability, the fast simulation is proposed to reduce trials instead. By using the Cramer’s theorem, we first obtain an optimally changed measure under which the variance of the estimator is minimized. Then, we use it to derive an importance sampling estimator of the overflow probability which enables us to perform the fast simulation.

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NEW BOUNDS ON THE OVERFLOW PROBABILITY IN JACKSON NETWORKS

  • Lee, Ji-Yeon
    • Journal of the Korean Statistical Society
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    • v.32 no.4
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    • pp.359-371
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    • 2003
  • We consider the probability that the total population of a stable Jackson network reaches a given large value. By using the fluid limit of the reversed network, we derive new upper and lower bounds on this probability, which are sharper than those in Glasserman and Kou (1995). In particular, the improved lower bound is useful for analyzing the performance of an importance sampling estimator for the overflow probability in Jackson tandem networks. Bounds on the expected time to overflow are also obtained.

Studies on the flow stabilization around the turbine suction with utilizing the surface water overflow at small-hydraulic power plant (표층수의 월류를 통한 소수력빌전소 수차터빈측의 유동안정화 연구)

  • Lee, Sungmyung;Kim, Cheolhan;Yoo, Gunjong;Kim, Wonseok
    • 한국신재생에너지학회:학술대회논문집
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    • pp.165.2-165.2
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    • 2011
  • Flow with suction to water turbine must be in stable state at small hydraulic power plant. But because of water level fluctuation and water gate effect according to irregular supply of cooling water, it would happen to produce bubble and vortex and finally lead to problems in power-plant system. With utilizing the concept design of double size gate, surface water overflowed the overhead of gate for stable flow at suction. We developed the overflow condition and analyzed the design factor with existed one such as water level(overflow amount) and overhead of water gate(overflow figure). Flow test and CFD simulation say that flow have stable state around suction and 20% of wave reduction effect at surface layer after surface water overflow.

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COMPARISONS OF LOSS FORMULAS FOR A CIRCUIT GROUP WITH OVERFLOW TRAFFIC

  • Park, Chul-Geun;Han, Dong-Hwan
    • Journal of applied mathematics & informatics
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    • v.30 no.1_2
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    • pp.135-145
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    • 2012
  • Traditionally, ERM (Equivalent Random Method) is used to determine number of circuits in an overflow circuit group with rough traffic which has vmr(variance to mean ratio) greater than one. Recently, IPP(Interrupted Poisson Process) approximate method which represents the collective feature of the overflow has been introduced. The negative binomial loss formula can be applied to determine the required number of circuits in the overflow circuit group. In this paper, we deal with the negative binomial loss formula and determination method of number of circuits. We also analyze and compare these three loss formulas.

SPH Modeling of Surge Overflow over RCC Strengthened Levee

  • Li, Lin;Amini, Farshad;Rao, Xin;Tang, Hongwu
    • International Journal of Ocean System Engineering
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    • v.2 no.4
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    • pp.200-208
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    • 2012
  • Surge overflow may cause damage on earthen levees. Levee strengthened on the levee crest and landward-side slope can provide protection against the erosion damage induced by surge overflow. In this paper, surge overflow of a roller compacted concrete RCC strengthened levee was studied in a purely Lagrangian and meshless approach, the smoothed particle hydrodynamics (SPH) method. After verifying the developed model with analytical solution and comparing the results with full-scale experimental data, the roughness and erosion parameters were calibrated. The water thickness, flow velocity, and erosion depth at crest, landward-side slope and toe were calculated. The characteristics of flow hydraulics and erosion on the RCC strengthened levee are given. The results indicate that the RCC strengthened levee can resist erosion damage for a long period.