Chapter 10.9, Problem 2P

Consider the cones K = = {(x1, x2, x3) | € R³ : X3 ≥√√√2x² + 3x² M = = {(21,22,23) (x1, x2, x3) Є R³: x3 > + 2 3 Prove that M = K*. Hint: Adapt the proof from the lecture notes for finding the dual of the Lorentz cone. Alternatively, prove the formula (AL)* = (AT)-¹L*, for any cone LC R³ and any 3 × 3 nonsingular matrix A with real entries, where AL = {Ax = R³ : x € L}, and apply it to the 3-dimensional Lorentz cone with an appropriately chosen matrix A.

I am unable to solve part b.

Let M = M₁U M₂ UM3 and K M₁ = {(x1, x2) ER²: 2 ≤ x ≤ 8, 2≤ x ≤8}, M₂ = {(x1, x2)™ € R² : 4 ≤ x₁ ≤ 6, 0 ≤ x2 ≤ 10}, M3 = {(x1, x2) Є R²: 0 ≤ x₁ ≤ 10, 4≤ x ≤ 6}, ¯ = cone {(1, 2), (1,3)†} ≤ R². (a) Determine the set E(M,K) of efficient points of M with respect to K. (b) Determine the set P(M, K) of properly efficient points of M with respect to K.

5.17 An aluminum curtain wall panel 12 feet high is attached to large concrete columns (top and bottom) when the temperature is 65°F. No provision is made for differen- tial thermal movement vertically. Because of insulation between them, the sun heats up the wall panel to 120°F but the column to only 80°F. Determine the consequent compressive stress in the curtain wall. CONCRETE COLUMNS CONNECTIONS Stress= ALUMINUM WALL PANEL 12'-0"

6.2 יך 4" 2" 2" Find the centroid of the following cross-sections and planes. X= Y=

Find the directional derivative of the function at P in direction V

6.4 49 Find the centroid of the following cross-sections and planes. X=_ Y= C15 XAO (CENTERED) KW14x90

5.18 The steel rails of a continuous, straight railroad track are each 60 feet long and are laid with spaces be- tween their ends of 0.25 inch at 70°F. a. At what temperature will the rails touch end to end? b. What compressive stress will be produced in the rails if the temperature rises to 150°F? T= Stress= L= 60' 25 @T=70°F

Strength of Materials Problems 5.16 A long concrete bearing wall has vertical expansion joints placed every 40 feet. Determine the required width of the gap in a joint if it is wide open at 20°F and just barely closed at 80°F. Assume α = 6 × 10-6/°F. Width= CONCRETE BEARING WALL EXPANSION JOINT 40' 40' 40' 293