S.N. Gupta developed the EOQ (Economic Order Quantity) model, which is a widely used inventory management technique.

The EOQ model aims to find the optimal order quantity that minimizes the total inventory costs, which include ordering costs, holding costs, and shortage costs.

The EOQ model assumes that demand is constant over time, which is a simplification of real-world conditions.

The formula for calculating the EOQ is EOQ = \sqrt{2DS/H}, where D is the annual demand, S is the ordering cost, and H is the holding cost per unit per year.

The EOQ model is significant because it provides a mathematical framework for determining the optimal order quantity that minimizes total inventory costs.

P.C. Mahalanobis developed the VED classification system, which is used to categorize inventory items based on their criticality.

The three categories of items in the VED classification system are Vital (items that are essential for production), Essential (items that are important but not critical), and Desirable (items that are not essential but are useful).

The VED classification system is used to prioritize items for inventory control, with Vital items receiving the highest priority, followed by Essential and Desirable items.

C.R. Rao developed the ABC classification system, which is another method for categorizing inventory items based on their value and usage.

The three categories of items in the ABC classification system are A (items with high value and usage), B (items with moderate value and usage), and C (items with low value and usage).

The ABC classification system is used to prioritize items for inventory control, with A items receiving the highest priority, followed by B and C items.

R.C. Bose developed the HML classification system, which is a simplified version of the ABC classification system.

The three categories of items in the HML classification system are High (items with high value and usage), Medium (items with moderate value and usage), and Low (items with low value and usage).

The HML classification system is used to prioritize items for inventory control, with High items receiving the highest priority, followed by Medium and Low items.

S.N. Gupta developed the SDE model, which is a more sophisticated inventory management model that takes into account service level, demand variability, and economic order quantity.

The SDE model considers three key factors: service level (the probability of meeting customer demand), demand variability (the uncertainty in demand), and economic order quantity (the optimal order quantity that minimizes total inventory costs).