Numerade

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Questions 1. Define hardness. What is Mohs scale of hardness? 2. Why it is necessary to specify load-indenter combination in Rockwell hardness test? 3. How is Brinell hardness measured. Show that BHN varies as P/D2 where P is the load and D is the indenter diameter. 4. Why is the included angle between opposite faces of the Vickers indenter 136°? 5. What is microhardness? Why sometime it is necessary? 6. What is engineering stress and strain? 7. What is Hook's law? 8. What is elastic and proportional limit? 9. How is the elastic modulus measured from the stress-strain curve? 10. What is yield stress?

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Choose the most convenient method between elimination and substitution to solve the below system of linear equations.\\ $\begin{cases} 10x - \frac{5}{2}y = -5\\ 9x + 9y = -12 \end{cases}$

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Question 39 Sleep disorder characterized by temporary breathing cessations and continuous awakenings A) Sleep apnea B) Sleep walking C) Narcolepsy D) Insomnia 2 Points

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The mass of 56Fe is 55.9349 u and the mass of 56Co is 55.9399 u. Which isotope decays into the other and by what process? [--Decay order---]by [-Process--- In a piece of rock from the Moon, the 87Rb content is assayed to be 1.8910^10 atoms per gram of material and the 7r content is found to be 1.06^10 atoms per gram. The relevant decay s (a) Determine the age of the rock.

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3. a) You have a friend who is terrified of microbes. Convince them that not all microbes are harmful. Cite at least two specific reasons with examples. b) Why is it often recommended to eat yogurt after finishing an antibiotic treatment? c) Both Lactobacilli spp. and Candida spp. bacteria are resident flora of the vaginal microbiome. Explain what it means for both Lactobacilli spp. and Candida spp. to be resident flora. d) Lactobacilli spp. maintain an acidic vaginal environment by producing lac.c acid. Identify and define the catabolic process via which Lactobacilli spp. most likely produce lactic acid. What does it tell you about the oxygen levels in the vagina? e) Explain how excessive cleaning of the vaginal environment could lead to a yeast infection by resident Candida spp. In your response, reference and define the terms competitive exclusion and dysbiosis. f) The bacteria involved in the production of kimchi and cheese also produce lactic acid to maintain acidic environments. This acidic environment inhibits the growth of spoilage bacteria like Pseudomonas spp. Explain how and why the acidic environment would interfere with at least one specific process in Pseudomonas spp., preventing growth and thus spoilage.

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A 50-year project has a cost of $500,000 and has annual cash flows of $100,000 in years 1-25, and $200,000 in years 26-50. The company's required rate is 8%. Given this information, calculate the IRR of the project. Solve without Excel (can use financial calculator).

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a concave mirror has a focal length of 50 cm. calculate the object distance if a virtual image is formed from the mirror

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7. Evaluate \iint_S y \,dS, where S is the part of the surface z = 1 - 2x - 2y in the first octant.

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b. OH OH OH H OH OH 1) NH$_2$OH, pH 4-5, HCl 2) Ac$_2$O, pyr 3) NaOCH$_3$, CH$_3$OH Fischer projection

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Question 2 (20 marks) a) Briefly explain the meaning of the term spinning reserve. (2 marks) b) State the constraints needed to maintain a flat bus voltage profile as well to limit overloading. (2 marks) c) Three plants of total capacity 500 MW are scheduled for operation to supply a total load of 310 MW. Determine the optimal load schedule if the IC curves and limitations are: $\qquad = 30 + 0.12P_1$ $\qquad = 40 + 0.20P_2$ $\qquad = 10 + 0.16P_3$ $30 \le P_1 \le 150$ MW $20 \le P_2 \le 100$ MW $50 \le P_3 \le 250$ MW

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gabriel m.