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Inventory issues involving quality degradation are complex to resolve and harm company performance. This study proposes an integrated production-inventory model for multi-item raw materials with exponential quality degradation. The proposed model is based on a finished product that requires several materials that degrade quality in the food industry. The proposed model's objective function is to maximize profits using the decision variables and an optimal number of raw material shipments ( m j ), production time cycle (T ), and the number of finished product shipments (n ). The grey wolf optimizer (GWO) algorithm is proposed in this study to solve this problem. A case study was conducted on the Indonesian food industry, which produces a finished product from five raw materials. The results demonstrated that the proposed GWO algorithm could solve the production-inventory model problem. A sensitivity analysis of the research is also presented to investigate the impact of changes in the variable rate of quality degradation (k ), rate of production (P ), and demand (D ). [ABSTRACT FROM AUTHOR]

In this study, a combined policy is provided for production control and preventive maintenance for processes that are vulnerable to quality decline. To meet customers demand, production control tackles the issues of production rate regulation and the best size for finished product safety stock. To reduce the number of non-compliant items, plans for preventative maintenance are considered. When the production process begins to make non-compliant parts and is stopped to carry out restoration action, a safety stock is also designed to alleviate shortages. Based on the combined policy, analytical models are provided taking into account all conceivable scenarios and sub-policies that may arise, as well as all possible safety stock level value ranges and the point at which the production processes deviates from the in-control state. To determine the combined optimal policy, a numerical method has been built minimizing the total incurred cost. A simulation program is built, and a sensitivity study is conducted in order to verify and certify the analytical findings and prove the robustness of the proposed approach. The suggested integrated policy is shown to perform better than alternative ones taken into consideration in the literature and in practice by comparison research. [ABSTRACT FROM AUTHOR]

Evaporite bearing formations extending in large areas in Turkey affect quality of water resources. The Derincay basin is an example to the impacts of evaporites on the adjacent alluvial aquifers. Miocene-Pliocene aged evaporites cover nearly one-third of the basin and mostly surround the low elevated alluvial sand-gravel aquifer. The higher quality of the groundwater in the upstream regions, where the evaporites do not crop out or partially crop out, turns into low to very low quality in the downstream areas due to the large extents of the evaporites. Waters from the evaporites increase TDS, Ca, SO, Na, and Cl in the alluvium aquifer, particularly in the downstream region of the basin. EC values rise from 1000-1300 μS/cm to over 5000 μS/cm from upstream to downstream. 'High salinity but low sodium hazard' category for the upstream parts turns into 'very high salinity' and 'medium-high sodium hazard' for the downstream regions on the salinity diagram. Groundwater in the upstream parts falls in 'good to permissible' class; however, the class turns into 'permissible to doubtful' and 'doubtful to unusable' classes for the downstream on the Wilcox diagram. Ca-bicarbonate type in the upstream region turns into Ca-sulfate type in the downstream region due to the evaporite effect. This study indicates three main sources affecting the quality of groundwater of the alluvium aquifer in the Derincay basin: extent of the evaporite formations in the catchment area, recharge from the evaporite springs, and dilution with relatively high-quality stream waters. [ABSTRACT FROM AUTHOR]

The food quality has always played an important role in the retail process since it has been considered as a direct factor to influence a consumer's purchase decision. In this paper, we formulate an inventory model for perishable foods, in which the demand depends on the price and quality that decays continuously. The objective is to determine a joint dynamic pricing and preservation technology investment strategy while maximizing the total profit from selling a given initial inventory of foods. We first prove the existence of an optimal solution based on Filippov-Cesari theorem. Then, we obtain all the candidates and provide the conditions that make a certain candidate be an optimal solution according to Pontryagin's maximum principle. Next, we present an effective algorithm to search for the optimal strategy. Finally, two numerical examples are employed to illustrate the solution procedure and the results, followed by sensitivity analysis and managerial insights. [ABSTRACT FROM AUTHOR]

In this paper, we aim at improving the video quality degradation due to high motions or scene changes. An improved frame-layer bit allocation scheme for H.264/AVC rate control is proposed. First, current frame is pre-encoded in 16×16 modes with a fixed quantization parameter (QP). The frame coding complexity is then measured based on the resulting bits and peak signal-to-ratio (PSNR) in the pre-coding stage. Finally, a bit budget is calculated for current frame according to its coding complexity and inter-frame PSNR fluctuation, combined with the buffer status. Simulation results show that, in comparison with the H.264 adopted rate control scheme, our method is more efficient to suppress the sharp PSNR drops caused by high motions and scene changes. The visual quality variations in a sequence are also relieved. [ABSTRACT FROM AUTHOR]