Question

Difficulty: MediumTransportation Modes and Network Connectivity

A regional transport network connects 55 agricultural collection hubs (v=5v = 5) using 77 primary road segments (e=7e = 7) in a single connected network (p=1p = 1). What is the Alpha index (α\alpha) of this network graph?

  1. 0.600.60Answer
  2. B
    1.401.40
  3. C
    0.400.40
  4. D
    0.710.71

Answer

The Alpha index of the transport network is 0.600.60.
The correct answer is 0.600.60. The Alpha index evaluates circuit redundancy in a network graph using the formula α=ev+p2v5\alpha = \frac{e - v + p}{2v - 5}. Substituting e=7e = 7, v=5v = 5, and p=1p = 1 yields 75+12(5)5=35=0.60\frac{7 - 5 + 1}{2(5) - 5} = \frac{3}{5} = 0.60.

Step-by-Step Solution

1
Calculate the actual number of fundamental circuits (uu) present in the network using u=ev+pu = e - v + p.
u=75+1=3u = 7 - 5 + 1 = 3 circuits.
The cyclomatic number uu measures the actual redundancy (number of closed loops) in a network graph.
2
Calculate the maximum possible number of circuits in a planar graph with v=5v = 5 using 2v52v - 5.
Maximum circuits =2(5)5=5= 2(5) - 5 = 5.
In planar network topology, the maximum theoretical number of circuits for vv vertices is 2v52v - 5.
3
Calculate the Alpha index (α\alpha) by dividing the actual circuits by the maximum possible circuits.
α=u2v5=35=0.60\alpha = \frac{u}{2v - 5} = \frac{3}{5} = 0.60.
The Alpha index measures network connectivity as a ratio between 00 (tree network with no circuits) and 11 (fully connected planar network).

Key Concept

Alpha Index of Network Connectivity

Alternative Method

Calculate the cyclomatic number u=75+1=3u = 7 - 5 + 1 = 3. Then express uu as a percentage of the maximum possible planar circuits 2(5)5=52(5) - 5 = 5, giving 3/5=60%=0.603/5 = 60\% = 0.60.
Estimated Time:1m 15s
Rate this question