The 3C Alternative

The method is an alternative to what the creators of 3C view as flawed MRP approaches. In particular, they object to the reliance on forecasts inherent in the MRP methodology. In their view, two conditions favor the 3C method  

Product requirements that are difficult to forecast accurately 

Better for close operations with minimal transportation requirements 

Can take advantage of EOQ economies for operations involving high setup costs Fast, does not require counting or tracking of inventory Simplicity compatible with visible signaling (e.g., the two-bin system and kanban approaches) Easier to predict time requirements once orders are placed 

Some companies expense items in this category 

In the 3C method, supply chain capacity, the first C, is the governing parameter over the amount of inventory in the system. Under 3C control, the chain should have a sufficient number of any one part on hand to produce to the capacity of the chain for usage of that part. To the extent parts are common, then the overall inventory is less, since a single part will support several products. 

Changes in the targets occur only at times when product or market changes make it necessary. 

The authors have performed simulations demonstrating that 3C bests the MRP method in many cases. We believe 3C is a valuable addition to thinking about both supply chain systems and rules of the road among partners. In our discussion of system needs in Chapter 28, we stated we believe that supply chain management will call for simpler rule making with respect to inventory maintenance and restocking rules. 3C fulfills the criterion for simpler methods. 

Throughout this book, we have described the barriers to more effective supply chains. We have also described many of the tools and techniques that address this barrier. One initiative addresses both the cultural and technical barriers to collaboration among supply chain partners. The initiative is collaborative planning, forecasting, and replenishment (CPFR). CPFR requires a business relationship between partners and has taken root in the retail industry. Collaboration strives to better match demand and supply, improve inventory management practices, and capitalize on new systems through sharing. CPFR is primarily a link between retailers and their manufacturer suppliers. It is expected that the concepts will expand to other industries. 

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Using the 3C alternative to MRP addresses a number of issues raised in this book, as indicated in Table 31.2. 3C is demand driven. Therefore, for the maker of innovative products trying to reduce market mediation costs, the method will save money through its linking mles. For functional products with high commonality, such as generic drugs and food products, the method provides a viable postponement procedure. 

MRP schedules have two logical flaws that, according to critics, limit their effectiveness. The first is that MRP requirements are based on forecasts. With cloudy crystal balls, MRP causes overstocking of items that don t sell and xmderstocking of those that do. The second flaw is the assumption of infinite capacity. Associated with this is the use of fixed lead times. As a result, forecasts may make impossible demands on the production process. Actual lead times vary with the workload. When backlogs go up, lead times are likely to go up as well. (Refer to the "3C" alternative to MRP in Chapter 29 for an approach that addresses tirese two shortcomings.)... 

In any supply chain effort, the "best" systems solution may not require a computer at all. Going into an effort with a preconceived idea that the solution requires a computer application is a mistake. This is particularly true in the case of many SCM applications. There are alternatives to consider either as a final or interim solution on the way to new systems. One such method, called the 3C alternative to MRP, is described in Qiapter 29. 

Our studies have shown that covalent and recoupled pair bonding are competitive alternatives. The results for SF2 show that it is possible to find states of the same compound that involve pure covalent bonding, a recoupled pair bond dyad, or a mixture of covalent and recoupled pair bonding. There is no suggestion in the 3c-4e model that such variety is possible. The 3c-4e model offers only limited insight into the excited states of a compound where the bonding may be very different from that in the ground state. 

C Alternative to ERP Provides added details on the working of the 3C methodology for those interested in implementing the approach... 

C alternative A method that uses capacity, ccmmonality, and consumption to MRP as a basis for control of material in the supply chain. The... 

Applying the third alternative, it was established that this structure is, in fact, an example of a network from a weU-known type structure that many chemists are familiar with from general chemistry courses, namely the rutile (the most common form of Ti02) structure. From a topology point of view, this is one of the most symmetric, and also most abundant, of the six- and three-connected nets (6c,3c nets) and it has the symbol rtl. ... 

The more common biosynthetic route to unsaturated acids is aerobic desaturation, an oxygen-dependent process. However microorganisms in an anaerobic environment produce unsaturated acids by an alternative non-oxygen-dependent pathway which is a modification of the de novo pathway. For example, 9c-l6 l(palmitoleic acid) and llc-18 l (vaccenic acid) are produced as shown below. 2-Hydroxydecanoate is dehydrated to the 3c isomer (rather than the more usual 2t acid) and then chain-extended to 16 1 and 18 1 acids. 

Two important articles published in 1990 appeared to settle the discussion about the two alternative bonding models in favor of the 3c-4e model [84,85]. Magnusson published the results of HF calculation on about 50 hypervalent or closely related Lewis-valent molecules using a double-z quality basis set including polarization... 

The donor-acceptor formation can be considered by transfer of electrons from the donor to the acceptor. In principle one can assume donor-acceptor interaction from A (donor) to B (acceptor) or alternatively, since B (A) has also occupied (unoccupied) orbitals, the opposite charge transfer, from B to A. Such a view refers to mutual electron transfer and has been commonly estabUshed for the analysis of charge transfer spectra of n-complexes [12]. A classical example for a donor-acceptor complex, 2, involving a cationic phosphorus species has been reported by Parry et al. [13]. It is considered that the triaminophosphines act as donor as well as an acceptor towards the phosphenium cation. While 2 refers to a P-donor, M-donors are in general more common, as for example amines, 3a, pyridines, 3b, or the very nucleophilic dimethylaminopyridine (DMAP) [ 14], 3c. It is even a strong donor towards phosphorus trichloride [15]. 

The range of structural alternatives explored by valency-deficient carbon species and the subtle interplay of substituents is remarkable. Scheme 7.6 (ORTEP adapted from reference 31) illustrates an example of an X-ray structure clearly describing a localized [C-H C+] carbenium ion (A) where a symmetric bridging structure [C-H-C] + (B) could have been assumed. In this case it is proposed that a charge-transfer interaction between the resonance delocalized cation and the adjacent electron-rich carbazol moiety may be responsible for the stabilization of the localized form over the three-center, two-electron (3c-2e) bridging structure. 

Although the generalization to localized three-center bonds inevitably involves certain complications, important simplifications of the localized Lewis-structure picture remain. In the case of 3c/4e co-bonding, the corrections can often be adequately described in terms of two-term resonance between alternative two-center bonding patterns. In the case of 3c/2e T-bonding, the resonance-theoretic description (although possible in principle) becomes unwieldy. However, in terms of the single best three-center localized Lewis-structure description (or the resonance mixture of symmetry-equivalent structures), one can still identify specific localized donor-acceptor interactions (e.g., of type) that dominate the delocaliza-... 

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