Explain how hydrogen is used in shielding gases, and why it is restricted to stainless steels.
What will be an ideal response?
Hydrogen is not an inert gas and is not used as a primary shielding gas. However, it can be added to argon when deep penetration and high welding speeds are needed. It also improves the weld surface cleanliness and bead profile on some grades of stainless steel that are very sensitive to oxygen. Hydrogen additions are restricted to stainless steels because hydrogen is the primary cause of porosity in aluminum welds. It can cause porosity in carbon steels and, in highly restrained welds, underbead cracking in carbon and low alloy steels.
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Indicate whether the statement is true or false.
In a typical mineral soil in optimal condition for plant growth, approximately what percentage of the pore space would be filled with water and what percentage filled with air?
A) 50% water and 50% air B) 25% water and 75% air C) 10% water and 90% air D) 25% water and 25% air E) 90% water and 10% air
Some open-loop automatic control systems are self-regulating.
Answer the following statement true (T) or false (F)
Which of the following is true about clients associating with an AP?
A. an AP can reject the request based on the client MAC address B. a client can be associated to multiple APs simultaneously for fault tolerance C. a client can reassociate with another AP in a BSS D. if a client is not preconfigured for a specific AP, it will not attempt to associate at all