View full-text article in PMC Sensors (Basel). 2017 May 17;17(5):1144. doi: 10.3390/s17051144 Search in PMC Search in PubMed View in NLM Catalog Add to search Copyright and License information © 2017 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/). PMC Copyright notice Model 1. Integer Programming Minimize: ∑i∈V∑j∈V(yij×tij) (0) Subject to: ∑i∈{0}∪Vsxij=∑i∈{0}∪Vs xji≤1, ∀j∈{0}∪Vs, (1) ∑i∈Vsxi0=∑i∈Vsx0i=1, (2) ∑i∈S∑j∈Sxij<|S|, ∀S⊂{0}∪Vs (3) zijk≤xjk, ∀i∈Vt,∀j,k∈{0}∪Vs, (4) ∑j∈{0}∪Vs∑k∈{0}∪Vszijk=1, ∀i∈Vt, (5) ∑i∈Vyij=∑i∈Vyji=1, ∀j∈Vt, (6) ∑i∈Vyij=∑i∈Vyji≤1, ∀j∈{0}∪Vs, (7) ∑i∈{0}∪Vs∑j∈Vtyij=∑i∈{0}∪Vs∑j∈Vtyji=∑i∈{0}∪Vs∑j∈{0}∪Vsxij, (8) ∑j∈Vtyij=∑j∈{0}∪Vsxij, ∀i∈{0}∪Vs, (9) ∑k∈{0}∪Vszijk≥yji,∀i∈Vt, ∀j∈{0}∪Vs, (10) ∑j∈{0}∪Vszijk≥yik,∀i∈Vt, ∀k∈{0}∪Vs, (11) 2×yij≤max{ziab+zjab}, ∀i,j∈Vt, ∀a,b∈{0}∪Vs, (12) ∑j∈S1∑j∈S1yij<|S1|, ∀S1⊂V, (13) tab×xab≤∑i(ziab×si)+∑i∈R∪{a,b}∑j∈R∪{a,b}(yij×tij)≤θ, ∀a,b∈{0}∪Vs, R=f(a,b), (14) xii=0, ∀i∈{0}∪Vs, (15) yii=0, ∀i∈V, (16) yij=0, ∀i,j∈{0}∪Vs, (17) xij, yij, zijk∈{0,1}, ∀i ∈Vt, j,k∈{0}∪Vs.