A flow of 2.0 m3 /s is carried in a rectangular channel of 1.8 m width at a depth of 1.0 m (section 1). There is an upward step of 0.18 m together with a contraction where b reduces to 1.4 m (section 2).

a) Draw the side view and top view of the channel described above.

b) Calculate the specific energy at section 1 and plot the specific energy curve. Show y1, E1, V1 2 /2g on the curve.

c) Find the water depth on the step (i.e. y2) and check the choking condition (i.e. state if choking occurs).

d) If choking occurs what is the necessary change in specific energy and depth at section 1 to overcome choking?

Prob. 4-68 A piston–cylinder device contains 2.2 kg of nitrogen initially at 100 kPa and 25C. The nitrogen is now compressed slowly in a polytropic process during which PV^1.3 = constant until the volume is reduced by one-half. Determine the work done and the heat transfer for this process.

4–69    Reconsider Prob. 4–68. Using EES (or other) software,plot the process described in the problem on a P-V diagram, and investigate the effect of the poly- tropic exponent n on the boundary work and heat transfer. Let the polytropic exponent vary from 1.0 to 1.4. Plot the boundary work and the heat transfer versus the polytropic exponent, and discuss the results.

You purchase an expensive O2 microelectrode and use it to measure the dissolved O2 profile in a sediment core that you obtained from Long Island Sound. You find that the O2 concentration on the water-sediment interface is 240 mol/L, and it sharply drops to 40 mol/L at 0.2 cm deep in the sediment. If the corresponding dissolved O2 diffusion coefficient (Ds) in porewater seawater is 1.0 × 10-5 cm2 /s. The porosity () of sediment is approximately constant over the sampled interval with  = 0.9. Calculate the diffusive flux of O2 across the sediment – water interface assuming Fick’s First Law of diffusion for porous media in 1-dimension. Make sure that you indicate the sign of the flux (into or out of the sediment).

You have 520 g of aluminum at an initial temperature of 350 °C. (Aluminum has a specific heat capacity c = 0.214 cal/(g°C).) You place it into a beaker filled with 860 g of water at an initial temperature of 18 °C. (Water has a specific heat capacity c = 1.0 cal/(g°C).) Assume that no phase changes or chemical reactions occur during this time.

Calculate the final temperature of the aluminum~and water.​

Calculate the amount of heat that enters the water.

Calculate the amount of heat that enters the aluminum

Calculate the amount of additional heat required to take the water you have, that was heated to the final temperature that you calculated in question 10, and convert it to steam at 100 °C.

The extinction coefficients of the four natural nucleoside-5’monophosphates pdA, pdG, pdC and pdT at 260 nm are 1.506*10⁴ , 1.218*10⁴ , 7.10*10³ , and 8.56*10³ L/mol/cm, respectively (Cavaluzzi, M.J., Nucleic Acids Res., 2004, 32, e13). Please determine:

a) The extinction coefficient of a single-stranded, 5’-phosphorylated Dickerson Dodecamer sequence d(pCGCGAATTCGCG).

Answer: ε260 = 1.244*10^5. HOw they got that?

b) Please calculate absorbance and percent transmittance of a 10 micromolar (μM) solution of the single-stranded Dickerson Dodecamer, as described in (a), at 260 nm when a cell with the path length of 1.0 cm was used.

What is A? %T?

I don't know the answer for that.

Cd2+ and Pb2+ ions in a polluted water sample are measured by complexation. In a first titration, 50.00 mL of water at pH 10 is titrated by 40.09 mL of 0.004870 M EDTA. In a second titration, a 75.00 mL aliquot of water is first treated with an excess of KCN to mask the cadmium in Cd(CN)4 2- before being titrated by 31.44 mL of the same EDTA solution. Calculate the concentrations of Cd2+ and Pb2+ in the polluted water sample. Cd2+ + 4 CN- <===> Cd(CN)4 Kf = 1.0 x 10^19 Cd2+ + Y4- <===> CdY2- Kf = 2.9 x 10^16 Pb2+ + Y4- <===> PbY2- Kf = 1.1 x 10^18 aY4- = 0.36

Gallery Corporation makes two products, footballs and baseballs. Additional information follows:

                                                                                             Footballs            Baseballs

Demand (Units)                                                                        2,000                3,000

Selling price per unit $30 $8

Total variable costs per unit $ 12 $ 4

Fixed costs 10,000              5,250

Yards of leather per unit 1.25            0.25

Direct labor hours required per unit 0.75                   1.0

Assume that Gallery is able to purchase only 2,500 yards of leather and wishes to maximize its income. Total labor hours available for production is 4,600 hours.

Required:

1. Identify the limiting factor.     
2. What will be the sales at which Gallery Corp will be at maximum profit by considering limiting factor.    

The magnetic flux through a 10.0-cm2cm2 loop is 8.0 T⋅cm2T⋅cm2, and the magnetic field at the location of the loop is uniform. Choose all correct answers.

Check all that apply.

I thought it was just B and D but apparently I'm wrong, can someone explain?

The constant-speed magnetization curve for a 25-kW, 250-V dc machine at a speed of 1200 r/min is shown in figure below. This machine is separately excited and has an armature resistance of 0.14 Ω. This machine is to be operated as a dc generator while driven from a synchronous motor at constant speed. a. What is the rated armature current of this machine? b. With the generator speed held at 1200 r/min and if the armature current is limited to its rated value, calculate the maximum power output of the generator and the corresponding armature voltage for constant field currents of (i) 1.0 A, (ii) 2.0 A and (iii) 2.5 A. c. Repeat part (b) if the speed of the synchronous generator is reduced to 900 r/min.