Retailer’s optimal ordering policy for deteriorating items with maximum lifetime under supplier’s trade credit financing

Many products such as fruits, vegetables, pharmaceuticals, volatile liquids, and others not only deteriorate continuously due to evaporation, obsolescence, spoilage, etc. but also have their expiration dates (i.e., a deteriorating item has its maximum lifetime). Although numerous researchers have studied economic order quantity (EOQ) models for deteriorating items, few of them have taken the maximum lifetime of a deteriorating item into consideration. In addition, a supplier frequently offers her/his retailers a permissible delay in payments in order to stimulate sales and reduce inventory. There is no interest charge to a retailer if the purchasing amount is paid to a supplier within the credit period, and vice versa. In this paper, we propose an EOQ model for a retailer when: (1) her/his product deteriorates continuously, and has a maximum lifetime, and (2) her/his supplier offers a permissible delay in payments. We then characterize the retailer’s optimal replenishment cycle time. Furthermore, we discuss a special case for non-deteriorating items. Finally, we run several numerical examples to illustrate the problem and provide some managerial insights.     

Improving the visual quality of size invariant visual cryptography scheme

In order to reduce the pixel expansion of visual cryptography scheme (VCS), many size invariant visual cryptography schemes (SIVCS’s) were proposed. However, most of the known SIVCS’s have bad visual quality and thin line problems, hence the known SIVCS’s are only suitable to encrypt coarse secret images. In this paper, we notice that the variance of the darkness levels of the pixels also reflects the visual quality of the recovered secret image, as well as the average contrast. We verify, analytically and experimentally, the effectiveness of the variance to be a criterion for evaluating the visual quality of the recovered secret image. Furthermore, we propose two multi-pixel encryption size invariant visual cryptography schemes (ME-SIVCS’s) which improve the visual quality of the recovered secret image by reducing the variance of the darkness levels. In addition, the proposed ME-SIVCS’s can be used to encrypt fine secret images since they avoid some known thin line problems. Experimental results and comparisons are also given to show the effectiveness of the proposed ME-SIVCS’s. Finally, we give suggestions on obtaining good visual quality for the recovered secret image.     

A Novel （n, n） Secret Image Sharing Scheme Based on Sudoku

Recently, Chang et al. proposed a Sudoku-based secret image sharing scheme. They utilized the Sudoku grid to generate meaningful shadow images, and their scheme satisfied all essential requirements. Based on Chang et al.'s scheme, we propose a novel (n, n) secret image sharing scheme based on Sudoku. In the proposed scheme, a secret image can be shared among n different cover images by generating n shadow images, and the secret image can be reconstructed without distortion using only these n shadow images. Also, the proposed scheme can solve the overflow and underflow problems. The experimental results show that the visual quality of the shadow images is satisfactory. Furthermore, the proposed scheme allows for a large embedding capacity.     

Sharing more information in gray visual cryptography scheme

Visual cryptography scheme (VCS) shares a binary secret image into several binary shadows, and the secret image can be visually revealed by stacking qualified shadows without computation. From the point of view of sharing secret information, VCS is not efficiency because of the large size expansion and low visual quality. In this paper, we introduce a general gray visual cryptography scheme, which can share more information, called Sharing More Information Gray Visual Cryptography Scheme (SMIGVCS). All the shadow pixels of VCS embed additional information to generate gray shadows of SMIGVCS, and the embedded information comes from the shadows of a polynomial-based secret sharing scheme (PSSS). In the revealing process, a vague secret image is visually decoded by stacking qualified shadows, and more information is revealed by computation. Compared with the two-in-one image secret sharing scheme (TiOISSS), our SMIGVCS can achieve smaller shadow size with acceptable visual quality.     

基于像素置乱技术的多重双随机相位加密法

提出一种基于像素置乱技术的多重双随机相位加密法,对该加密法中像素置乱操作的原理进行了阐述,并且提出在光学上实现像素置乱操作和解置乱操作的途径.在计算机上模拟实现了该加密法,并且得到很好的加密解密结果.仿真结果证实仅用部分加密图像来解密也能够得到原图像,并且得到随着待解密的加密图像像素的增加,解密图像的信号能量、噪声以及信噪比的变化曲线.最后分析比较了该加密法与双随机相位加密法,得到该加密法与双随机相位加密法相比具有更高的保密性,而且解密图像的信噪比也不会因为引入像素置乱操作而降低.     

Optimal manufacturer’s replenishment policies in the EPQ model under two levels of trade credit policy

In 2007, Huang proposed the optimal retailer’s replenishment decisions in the EPQ model under two levels of trade credit policy, in which the supplier offers the retailer a permissible delay period M, and the retailer in turn provides its customer a permissible delay period N (with N < M). In this paper, we extend his EPQ model to complement the shortcoming of his model. In addition, we relax the dispensable assumptions of N < M and others. We then establish an appropriate EPQ model to the problem, and develop the proper theoretical results to obtain the optimal solution. Finally, a numerical example is used to illustrate the proposed model and its optimal solution.     

一种基于DAA的强匿名性门限签名方案

针对目前大多数门限签名方案不能实现签名成员匿名或匿名效果比弱的问题,该文提出了一种带有子密钥分发中心的强匿名性(n, t)门限签名方案。方案主要基于可信计算组织在其v1.2标准中采用的直接匿名认证(Direct Anonymous Attestation, DAA)方案,以及零知识证明和Feldman门限秘密共享等技术实现。相较已有方案,该方案即使在签名验证者和子密钥分发中心串通的情况下,也能够实现子签名的不可追踪性,也即可确保子签名成员的强匿名性。分析显示,方案除具有强匿名性外还具备签名子密钥不可伪造、子签名可验证以及一定的鲁棒性等特征。该方案在匿名表决等一些对匿名性要求较高的场合中有着重大的应用价值。     

Nested Visual Cryptography Scheme

A new nested visual cryptography scheme is proposed for n cooperated user groups. It can encode the secret image consists of black and white pixels into share images which should be distributed to each user in each group. To decode the secret, users in at least k out of n groups should be present, and at least p out of q users should provide their shares for each attendant group （where p and q can be distinct for each group）. For the proposed scheme, the known scheme can be regarded as a simple instance which has only one user in each group. Compared to S-extended visual cryptography scheme, there is no need to enumerate all the user sets which can decode the secret.     

基于椭圆曲线密码体制的动态秘密共享方案

文章给出了一个基于椭圆曲线公钥密码体制的动态秘密共享方案，有效地解决了共享秘密的动态更新，子密钥动态分配和欺诈问题，且易于实现，效率高。方案的安全性基于求解有限域上椭圆曲线离散对数的困难性。