• 기술혁신연구
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• 제5권1호
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• pp.206-222
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• 1997

The conventional analysis with which justifies government intervention of the private sector's innovation activities is the market failure approach. According to such analysis, fund allocation through autonomous market mechanisms is not optimal in technology financing because of the disparity between the desirable level of investment for society as a whole and that for private firms. To optimize the fund allocation, public policies such as subsidy, preferencial loan and venture capital investment programs are designed for technology development projects performed by private firms. They, however, have not been effective in increasing private investment for such projects. In most cases, it was found that little considerations given to the relationship between uncertainty embodied in technology development projects and each types of financing. With respect to optimizing fund allocation, technology development projects should be financed by different means according to their probability of success and the expected value of technology. Employing various theoretical models on financing decision-making we verify here that technology development projects to be supported by commercial banks or venture capital institutions is limited contingent upon levels of uncertainty adn expected value. Under the assumption that financial institutions are risk averse, loan or investment can be available only if the probability of success of the project is higher than the probability premium and the current market rate of interest. Therefore, the projects that have lower probability of success and/or small expected return are excluded from commercial loan or investment programs. However, the remaining projects, whose probability of success is low but with high expected return, may be applied under government subsidy programs. To achieve optimality of fund allocation and to activate technology financing, we conclude that there should be a systematic division of role among financial institutions including government commercial banks, and venture capital institutions.

• 대한수의학회지
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• 제50권1호
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• pp.43-48
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• 2010

Animal disease surveillance system, defined as the continuous investigation of a given population to detect the occurrence of disease or infection for control purposes, has been key roles to assess the health status of an animal population and, more recently, in international trade of animal and animal products with regard to risk assessment. Especially, for a system aiming to determine whether or not a disease is present in a population sensitivity of the system should be maintained high enough not to miss an infected animal. Therefore, when planning the implementation of surveillance system a number of factors that affecting surveillance sensitivity should be taken into account. Of these parameters sample size is of important, and different approaches are used to calculate sample size, usually depending on the objective of surveillance systems. The purpose of this study was to evaluate the sensitivity of the current national serological surveillance programs for four selected bovine diseases assuming a specified sampling plan, to examine factors affecting the probability of detection, and to provide sample sizes required for achieving surveillance goal of detecting at least an infection in a given population. Our results showed that, for example, detecting low level of prevalence (0.2% for bovine tuberculosis) requires selection of all animals per typical Korean cattle farm (n = 17), and thus risk-based target surveillance for high risk groups can be an alternative strategy to increase sensitivity while not increasing overall sampling efforts. The minimum sample size required for detecting at least one positive animal was sharply increased as the disease prevalence is low. More importantly, high reliability of prevalence estimation was expected with increased sampling fraction even when zero-infected animal was identified. The effect of sample size is also discussed in terms of the maximum prevalence when zero-infected animals were identified and on the probability of failure to detect an infection. We suggest that for many serological surveillance systems, diagnostic performance of the testing method, sample size, prevalence, population size, and statistical confidence need to be considered to correctly interpret results of the system.

• 마케팅과학연구
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• 제18권1호
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• pp.33-58
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• 2008

본 연구는 서비스실패가 아니라 제품실패 이후, 회복노력의 효과를 실패심각성에 따라 확인하는 것이다. 회복노력은 보상노력, 장점노력 및 단점노력으로 구분되었다. 보상노력은 실패상황을 직접적으로 되돌리려는 의도로 구체적인 보상을 제공하는 방안으로, 장점노력은 제품실패를 초래하는 이유가 특정한 장점을 추구하는 과정에서 불가피하게 발생할 수 있는 문제임을 언급하는 것과 같이 추가적인 상대적 장점을 설명하는 방식으로, 그리고 단점노력은 자사제품이 서비스실패를 초래할 수 있는 문제점을 지니고 있는 반면에 경쟁제품은 또 다른 측면의 단점을 지니고 있다는 점을 부각시켜 소비자의 자사제품에 대한 부정적 태도를 회복시키려고 방안이라고 개념화되었다. 그러한 회복노력들이 실질적으로 효과가 있다고 결론을 내리기 위해서, 회복노력이 제공되지 않는 상황과 비교하여 소비자의 태도나 의향이 우호적인지 검토된다. 가설검증을 위해 화장품산업에서 소비자들을 대상으로 가상적인 시나리오를 이용한 실험을 실시하였다. 연구 결과, 전반적으로 회복노력들은 효과적인 전략임이 확인되었고, 보상노력은 장점노력이나 단점 노력보다 효과적이었다. 특히 심각성이 높은 실패조건에서 단점노력은 장점노력보다 긍정적인 제품태도를 유도하였다. 심각성이 낮은 실패조건에서 장점노력과 장점노력의 효과는 기대할 수 없었다.

• 조명전기설비학회논문지
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• 제13권1호
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• pp.94-101
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• 1999

본 논문은 PWM인버터 장치의 스위칭 서지에 관한 문제를 분석한 것이다. 교류 전동기의 효율적인 속도제어를 위한 가변속 구동 장치의 적용이 증가함에 따라 전동기와 가변속 구동장치에 관련된 고장이 발생한다. 산업용 전동기 설비에 PWM 드라이브의 도입은 때때로 높은 과도전압 피크에 의한 상권선 사이 절연파괴를 낳을 수 있다. 높은 스위칭 주파수와 결합한 전동기 케이블 길이는 적?한 드라이브 동작을 위한 매우 민감한 문제가 된다. 케이블 길이와 높은 스위칭주파수의 결과는 전동기와 인버터에 영향을 미칠 수 있다. 전동기 권선 절연레벨이 낮을 때, 높은 피크전압과 빠른 전압상승시간에 의해 생겨난 고장 확률은 높다. 전압반사는 전동기 용량, 여러 가변속 구동장치와 상승시간에 대해 계산하였으며 이를 도식적으로 나타내었다. 인버터 구동 교류 전동기 시스템에서 전동기 단자 과전압과 전압상승률을 줄이기 위한 필터효과도 언급하였다. 연구결과 전동기 용량과 전동기 절연정격 레벨이 낮을수록 그리고 스위칭 시간과 케이블 길이가 짧을수록 절연파괴의 가능성이 높아짐을 알 수 있었다.

• Computers and Concrete
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• 제29권4호
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• pp.263-278
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• 2022

Limestone calcined clay cement (LC³) is a low carbon alternative to conventional cement. Literature shows that using limestone and calcined clay in LC³ increases the thermal degradation of LC³ pastes and can increase the magnitude of fire risk in LC³ concrete structures. Higher thermal degradation of LC³ paste prompts this study toward understanding the fire performance of LC³ concrete and the associated magnitude of fire risk. For fire performance, concrete prepared using ordinary Portland cement (OPC), pozzolanic Portland cement (PPC) and LC³ were exposed to 16 scenarios of different elevated temperatures (400℃, 600℃, 800℃, and 1000℃) for different durations (0.5 h, 1 h, 2 h, and 4 h). After exposure to elevated temperatures, mass loss, residual ultrasonic pulse velocity (rUPV) and residual compressive strength (rCS) were measured as the residual properties of concrete. XRD (X-ray diffraction), TGA (thermogravimetric analysis) and three-factor ANOVA (analysis of variance) are also used to compare the fire performance of LC³ with OPC and PPC. Monte Carlo simulation has been used to assess the magnitude of fire risk in LC³ structures and devise recommendations for the robust application of LC³. Results show that LC³ concrete has weaker fire performance, with average rCS being 11.06% and 1.73% lower than OPC and PPC concrete. Analysis of 106 fire scenarios, in Indian context, shows lower rCS and higher failure probability for LC³ (95.05%, 2.22%) than OPC (98.16%, 0.22%) and PPC (96.48%, 1.14%). For robust application, either LC³ can be restricted to residential and educational structures (failure probability <0.5%), or LC³ can have reserve strength (factor of safety >1.08).

• 한국지반공학회논문집
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• 제39권10호
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• pp.27-39
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• 2023

극한홍수에 대응하기 위한 홍수 위험도 관리의 필수 요소인 홍수 위험도 평가를 위해서는 댐 및 하천제방과 같은 홍수방어시설에 대하여 여러 파괴 메커니즘을 고려한 신뢰도 해석을 수행해야 한다. 본 연구에서는 수위급강하에 의한 제체 사면의 시간에 따른 확률론적 안정성 평가에 대하여 연구하였다. 유한요소 해석에 의한 침투해석 결과를 사면안정 해석에 연동하여 Monte Carlo Simulation을 수행함으로써 수위급강하에 따른 제체의 시간의존적 거동을 연구하고 파괴확률을 계산하여 제방의 취약도 곡선을 작성하였다. 수위급강하에 의한 사면의 파괴확률은 특정 수위까지는 매우 작은 값을 유지하지만, 그 이상에서는 수위가 증가함에 따라 급격하게 증가하는 현상을 보였다. 또한 취약도 곡선은 수위 하강 속도에 크게 영향을 받았다. 수위 저하 속도는 수문 시나리오에 의한 수위의 변동해석을 통하여 결정되므로 수위급강하에 따른 제방 제외지 사면의 안정성은 기후변화에 따라 크게 영향을 받을 것으로 판단된다.

• Geomechanics and Engineering
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• 제5권5호
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• pp.485-497
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• 2013

The factor of safety is the most common measure of the safety margin for slopes. When the traditionally defined factor is used in kinematic approach of limit analysis, calculations can become elaborate, and iterative methods have to be used. To avoid this inconvenience, the safety factor was defined in terms of the work rates that are part of the work balance equation used in limit analysis. It was demonstrated for two simple slopes that the safety factors calculated according to the new definition fall close to those calculated using the traditional definition. Statistical analysis was carried out to find out whether, given normal distribution of the strength parameters, the distribution of the safety factor can be approximated with a well-defined probability density function. Knowing this function would make it convenient to calculate the probability of failure. The results indicated that the normal distribution could be used for low internal friction angle (up to about $16^{\circ}$) and the Johnson distribution could be used for larger angles ${\phi}$. The data limited to two simple slopes, however, does not allow assuming these distributions a priori for other slopes.

• Journal of Communications and Networks
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• 제16권5호
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• pp.568-577
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• 2014

We consider a mobile content delivery network (mCDN) in which special mobile devices designated as caching servers (caching-server device: CSD) can provide mobile stations with popular contents on demand via device-to-device (D2D) communication links. On the assumption that mobile CSD's are randomly distributed by a Poisson point process (PPP), an optimization problem is formulated to determine the probability of storing the individual content in each server in a manner that minimizes the average caching failure rate. Further, we present a low-complexity search algorithm, optimum dual-solution searching algorithm (ODSA), for solving this optimization problem. We demonstrate that the proposed ODSA takes fewer iterations, on the order of O(log N) searches, for caching N contents in the system to find the optimal solution, as compared to the number of iterations in the conventional subgradient method, with an acceptable accuracy in practice. Furthermore, we identify the important characteristics of the optimal caching policies in the mobile environment that would serve as a useful aid in designing the mCDN.

• 대한임베디드공학회논문지
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• 제12권1호
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• pp.43-62
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• 2017

Mobile pulse scanning Light Detection And Ranging (LIDAR) are essential components of intelligent vehicles capable of autonomous travel. Obstacle detection functions of autonomous vehicles require very low failure rates. With the increasing number of autonomous vehicles equipped with scanning LIDARs to detect and avoid obstacles and navigate safely through the environment, the probability of mutual interference becomes an important issue. The reception of foreign laser pulses can lead to problems such as ghost targets or a reduced signal-to-noise ratio. This paper will show the probability that any two scanning LIDARs will interfere mutually by considering spatial and temporal overlaps. We have conducted four experiments to investigate the occurrence of the mutual interference between scanning LIDARs. These four experimental results introduced the effects of mutual interference and indicated that the interference has spatial and temporal locality. It is hard to ignore consecutive mutual interference on the same line or the same angle because it is possible the real object not noise or error. It may make serious faults because the obstacle detection functions of autonomous vehicle rely on heavily the scanning LIDAR.

• 방사성폐기물학회지
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• 제19권3호
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• pp.307-322
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• 2021

This study developed an analytical methodology for the mechanical integrity of spent nuclear fuel (SNF) cladding tubes under external pinch loads during transportation, with reference to the failure mode specified in the relevant guidelines. Special consideration was given to the degraded characteristics of SNF during dry storage, including oxide and hydride contents and orientations. The developed framework reflected a composite cladding model of elastic and plastic analysis approaches and correlation equations related to the mechanical parameters. The established models were employed for modeling the finite elements by coding their physical behaviors. A mechanical integrity evaluation of 14 × 14 PWR SNF was performed using this system. To ensure that the damage criteria met the applicable legal requirements, stress-strain analysis results were separated into elastic and plastic regions with the concept of strain energy, considering both normal and hypothetical accident conditions. Probabilistic procedures using Monte Carlo simulations and reliability evaluations were included. The evaluation results showed no probability of damage under the normal conditions, whereas there were small but considerably low probabilities under accident conditions. These results indicate that the proposed approach is a reliable predictor of SNF mechanical integrity.