• 산업경영시스템학회지
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• 제36권1호
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• pp.36-43
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• 2013

Many retailer store managers are experiencing the situation where some customers balk at purchasing products if the stock is low. In this paper, we extend the single period newsvendor model in an environment of customer balking behavior occurring at double threshold inventory levels assuming the chance of sales during balking is a discrete function of inventory level. Our analysis is based on the assumption that only the mean and the variance of demand are known, without assuming any specific distributional form. We derive the explicit general expression of optimal order quantity with unknown distribution of demand with double threshold inventory levels of customer balking. Then, we illustrate the concepts developed here through simple numerical examples and conclude the future research topics under balking situation.

• 대한인간공학회지
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• 제24권1호
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• pp.9-17
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• 2005

81.1% of traffic accidents is attributed to the drivers. In this regard, D/E model is a practical and effective method in terms of the cost and time in evaluating the road hazardousness. To examine the validity of the threshold values by the levels of demand We selected 10 subjects and collected their physiological signals while they were driving on Honam Highway (Jeonju ${\leftrighttarro}$ Hoideog section). Based on the collected data, the hazardous road condition was evaluated using the new threshold values of the effort level determined by cluster analysis. In applying the D/E model, a decision method based on the demand level was suggested, using a traffic accident prediction model. Additionally, the limit value of the effort level was determined using the drivers' physiological signal data collected at the highway. A comparison analysis of the two D/E models revealed no significant difference: The existing method and the clustering method determined 9 and 7 hazardous road zones, respectively, while actual traffic accidents were reported in 6 and 4 zones, respectively among the predicted road hazardous zones. However, the latter method suggested a more scientific and rational basis in determining the limit value of the Effort level. In conclusion, although D/E model has a great merit as a pioneering method to reflect human factors in evaluating the road hazardousness, it is believed that this method could be improved by a more dynamic method that considers the traffic conditions and the individual physiological signal of the drivers simultaneously in determining a better limit.

• 대한산업공학회지
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• 제33권3호
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• pp.312-321
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• 2007

We address a disposal issue of returned products in a product recovery system where a single product is stocked in order to meet a demand from customers who may return products after usage. Product returns occur randomly and can be accepted for remanufacturing or disposed of depending on the state of the system. We examine the structure of the optimal disposal policy for returned product that utilizes the information of the inventory of both serviceable and remanufacturable products. Numerical study indicates that it can be characterized by a monotonic threshold type of the curve. A disposal is allowed only when the remanufacturable inventory level exceeds a threshold which is the function of the inventory level of serviceable product and it is decreasing as the serviceable inventory level increases. Sensitivity analysis also indicates that the optimal disposal policy and the optimal profit have monotonic properties with respect to system parameters.

• International journal of advanced smart convergence
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• 제8권4호
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• pp.169-178
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• 2019

Due to the characteristics of an ad hoc network without a control center, self-organization, and flexible topology, the trust evaluation of the nodes in the network is extremely difficult. Based on the analysis of ad hoc networks and the blockchain technology, a blockchain-based node-level trust evaluation model is proposed. The concepts of the node trust degree of the HASH list on the blockchain and the perfect reward and punishment mechanism are adopted to construct the node trust evaluation model of the ad hoc network. According to the needs of different applications the network security level can be dynamically adjusted through changes in the trust threshold. The simulation experiments demonstrate that ad-hoc on-demand distance vector(AODV) Routing protocol based on this model of multicast-AODV(MAODV) routing protocol shows a significant improvement in security compared with the traditional AODV and on-demand multipath distance vector(AOMDV) routing protocols.

• 품질경영학회지
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• 제40권4호
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• pp.441-452
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• 2012

Purpose: In this paper, we have considered a problem of newsvendor model in an environment of random yields in quality and customer balking behavior, in which only the mean and the variance of the demand are known. In practice, the distributional information of the demand is very limited and only the mean and variance are guessed by experience. In addition, due to the customers balking behavior occurring when the available inventory level decreases, the product's demand becomes a function of inventory level so that the classical newsvendor's optimal order quantity is no longer optimal. Methods: We have developed an optimal order quantity model that enables us to incorporate the random yield of a product and the customer balking information such as a threshold inventory level of balking and the corresponding probability of a sale during the balking. Results: We illustrated the concepts developed here through simple numerical examples and showed the robustness of our model in a various setting of parameters. Conclusion: This paper provides a useful analysis showing that our distribution-specific and distribution-free approach to the optimal order quantity in the newsboy model can act as an effective tools to match supply with demand for these product lines.

• 한국조경학회지
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• 제21권3호
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• pp.51-64
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• 1993

Meeting the rapidly increasing demand for natural outdoor recreation, Korea Forestry Administration established 26 places of $\ulcorner$Natural Recreation Forest$\lrcorner$ zones. By 2000 year, 100 zones were planned to cover the entire country. But there was no accurate information about demand of $\ulcorner$Natural Recreation Forest$\lrcorner$. Therefore, this study was carried out to forecast the quantitive demand of $\ulcorner$Natural Recreation Forest$\lrcorner$. To forecast the 'demand of 2001 year, forecasting unit was determined to $\ulcorner$Visitor. Day$\lrcorner$, and three quantifing methods were applied. The results of demand by each forecating method were as follows: 1) Questionnaire survey method for willingness to participate was 16,651,000(visitor. day). 2) application of similiar situation threshold method was 14,540,000(visitor. day). 3) Demand partition method by secondary data was 10,775,000(visitor, day). Comprised of these results. The scope estimate of $\ulcorner$Natural Recreation Forest$\lrcorner$ demand was proposed as 8,110,000(Minimum) - 27,088,000(Miximum). The point estimate of demand which were proposed as strategic guidelines was 16,651,000(visitor. day). These results implied that recently announced 111 predetermined $\ulcorner$Natural Recreation Forest$\lrcorner$ zones supposed to be overcrowded meeting the forcasted demand level of 2001 year.

• 산업융합연구
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• 제19권6호
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• pp.21-35
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• 2021

본 연구의 목적은 노동에 대한 수요가 구직자의 교육에 대한 결정에 어떤 영향을 미치는가를 분석함에 있다. 혁신과 기술진보가 노동에 대한 수요를 줄이고 노동시장의 불확실성을 증대시키는 상황에서 본 연구는 노동자의 교육에 대한 투자가 노동에 대한 수요에 어떻게 의존하는가를 판단하는데 도움이 되는 이론적 구조를 제공하고자 한다. 본 연구의 결과는 다음과 같다. 첫째, 노동에 대한 수요가 감소할수록 교육에 대한 수요는 일반적으로 증가한다. 하지만 이런 결과는 반드시 성립하는 것은 아니다. 둘째, 감소하는 노동에 대한 수요에 대하여 노동자가 교육에 대한 수요를 증가시키는 것은 노동자의 (애로우-프랏 절대위험기피계수로 측정한) 위험기피도가 어떤 수준을 상회하는 경우에만 성립한다. 셋째, 노동에 대한 수요가 감소하더라도 노동자에 대한 보수가 그의 교육에 대한 투자를 반영하지 않는 경우, 노동자는 오히려 교육에 대한 투자를 줄인다.

• 대한산업공학회지
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• 제30권1호
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• pp.58-64
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• 2004

In order to determine the level of safety on highway driving, the relationship between the psychophysiological signal and driving condition was investigated. In particular, a Demand-Effort model was conceptualized and used in this study to diagnose the suitability of driving by reading the patterns of psychophysiological signals. To run the model, threshold values were determined to categorize the high, moderate and low level of effort. To examine the sensitivity of the model, a cross-validation process was performed by collecting additional data. Further investigation need to be conducted to improve the sensitivity of the model for practical application.

• Communications for Statistical Applications and Methods
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• 제11권3호
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• pp.631-641
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• 2004

In this paper, a model for an inventory whose stock decreases with time is considered. When a deliveryman arrives, if the level of the inventory exceeds a threshold $\alpha$, no stock is delivered, otherwise a delivery is made. It is assumed that the size of a delivery is a random variable Y which is exponentially distributed. After assigning various costs to the model, we calculate the long-run average cost and show that there exist unique value of arrival rate of deliveryman $\alpha$, unique value of threshold $\alpha$ and unique value of average delivery m which minimize the long-run average cost.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.213-220
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• 2018

본 논문은 동종업계의 경쟁업체가 시장을 독점하고 있는 상황에서, 신규로 점포를 개설하여 경쟁업체 고객을 빼앗아 경쟁업체 점포를 문을 닫게 하여 생존할 수 있는 점포위치를 결정하는 생존 점포 개설 위치 선정 문제(SFLP)를 다룬다. 이 문제는 포화된 시장에서 문을 여는 점포보다 문을 닫는 점포가 훨씬 많아지고 있는 현실에서 점포를 신규로 개설하고자 할 때 부닥치는 난제이다. 이 문제에 대해 Serra et al.는 반복적 휴리스틱 집중 알고리즘을, Han et al.은 반복적인으로 최대 고객 확보 위치를 찾는 알고리즘을 제안하였다. 그러나 이들 방법은 다수의 위치들에 대해 반복적으로 계산하는 어려움이 있다. 본 논문에서는 경쟁업체 인접 지점들만을 대상으로 경쟁업체 점포를 폐쇄시키면서 최대 고객을 확보할 수 있는 지점으로 해를 구하고, 최소 고객 확보 지점을 최대 고객을 확보한 다른 경쟁업체 점포를 폐쇄시킬 수 있는 지점으로 변경하는 과정을 수행하였다. 제안된 알고리즘은 단순하면서도 MS-Excel을 활용하여 해를 구할 수 있는 장점을 갖고 있다.