Seasonal inventory

Seasonal inventory measures the amount by which the inflow of product exceeds its sales (beyond cycle and safety inventory). Seasonal inventory is built up solely to deal with anticipated spikes in demand. 

In a petroleum refinery a large number of different products are produced, and the demand for some of these products is seasonal. For instance, there is not much need for residential fuel oil in the summer. The price of products also varies from day to day. To optimize the company s profit, it is therefore necessary periodically to vary the amount of each product produced. This can be done by changing the amounts of material sent to cracking units and reformers and by changing the conditions in these and other process steps. Some petroleum companies provide a computer with the data on market prices, current inventories, and crude oil compositions. The computer output then specifies the operating conditions that will yield the greatest profit for the company. The computer could then make the changes in these conditions directly, or this could be done manually. 

The amount of product sold may vary seasonally or randomly. The usual way to adjust for this is to increase or decrease the feed rate to the system, according to expected demand for the product or the size of the product inventory. The altering of the feed rate, in turn, increases or decreases the feed to each of the succeeding units, and eventually the output is changed. This is diagrammed in Figure 7-3 and is called mass balance control in the feed direction. 

The model was forced with agricultural application data of the insecticide DDT compiled by Semeena and Lammel (2003). Statistical data of DDT consumption reported by member of the UN states to Food and Agriculture Organisation (FAO) were combined with other published data (details in Semeena and Lammel (2003)). The emission inventory assumed 100 % of p,p -DDT. After scaling the DDT consumption with crop land distribution, the data were extrapolated to the model grid. The result was a data set with spatially and temporally varying applications (accumulated application and temporal evolution shown in Figure 3.1). No seasonal or diurnal variation of the applications is considered. 

Another important feature of the case study scenario and the resulting cost model is inventory control. High seasonality effects and long campaign durations necessitate considerable build-up of stocks. To avoid an unbalanced build-up of stock, soft constraints for safety stock and maximum stock levels are used. To achieve an even better inventory leveling across products and locations, piece-wise linear cost functions for falling below safety stock as well as for exceeding maximum stock levels are employed. 

Seasonal inventories of sedimentary chloropigments indicated that there are differences in timing between the maximum chlorophyll and pheopigment inventories in Long Island Sound estuary (Sun et al., 1994). These differences in inventories likely reflect... 

The ratio of working capital to total capital investment varies with different companies, but most chemical plants use an initial working capital amounting to 10 to 20 percent of the total capital investment. This percentage may increase to as much as 50 percent or more for companies producing products of seasonal demand because of the large inventories which must be maintained for appreciable periods of time. 

Cosmic radiation and H2-H2O exchange reactions in the upper atmosphere produce and maintain a small atmospheric HT inventory. However, at the present time the man-made one appears to be by far the largest part of the atmospheric HT. Since 1949, the tritium content of ahnospheric hydrogen molecules has been measured after being extracted from the so-called neon fraction obtained at liquid air plants. The values have increased from 10 TU in 1954 to 10 TU in the 1960s, in comparison with 10 TU in 1949. Monitoring of HT in 1971 and 1972 showed that HT did not undergo seasonal fluctuations, observed in HTO, and variations were small around a mean of approximately 46 HT molecules per mg of air. ... 

Figure 17. 2 Schematic representation of the seasonal variations in physical forces, discharges, and suspended sediment inventory on the Amazon shelf (from Nittrouer and DeMaster 1996, and Kineke et. al. 1996). The suspended sediment inventories include the fluid mud layers, which can comprise more the 90% of the suspended material on the shelf. The timing of the 4 AmasSeds cruises are shown at the bottom of the figure. In the upper figure NBC refers to the North Brazilian Coastal Current,...

Figure 16.7 Seasonal and interannual variations in NOs concentrations at Station ALOHA. Shown are (A) the 16-year data set on NOs (nM) in the upper 200 m as well as the summer vs. winter climatologies. Note the log scale in both graphs. (B) integrated (0-100 m) inventories of NO3 showing aperiodic irgections of NO3 into the upper euphotic zone. Note the lower graph presents the data on a log scale to emphasize the extreme temporal variability in N03 inventory which exceeds a factor of300 over the 16-year observation period,...

Water balances on river basins for a season or for a year can be used to check predicted groundwater infiltration, evaporation, or precipitation in the basin. Prepare a water balance, in symbols, for a large river basin and its reservoir, including the physical processes indicated in Fig. P2.4 (all symbols are for 1 year and S = storage or inventory). 

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