1. Lesson 9 (Nov. 10) Technical Statements in The Passive Form (“By” and the agent)

2. “By” + Who-Agent Examples (from Workshop 3) – People usually find oil deep in the ground. Oil is usually found deep in the ground by people. – Workers use the derrick to lift sections of pipe. The derrick is used by workers to lift sections of pipe. In the above examples, we have added “ by + who- agents ”: – Who find oil?  People. – Who use the derrick?  Workers. In technical writing, most passive sentences have no who-agent. The who-agents are not always necessary unless precision is needed.

3. “By” + Who-Agent Examples where the who-agent is meaningful: – The laws of motion were discovered by Isaac Newton. – The inductor motor was first conceived by Nikola Tesla. – Newtonian mechanics were reformulated by Lagrange into what is known as Lagrangian mechanics.

4. On the other hand, what-agents are more frequently needed for complete information. The following sentences will not be complete without by + what-agents : – Many car engines are cooled by water. – Old trains are powered by steam. – The frequency content of a signal is obtained by Fourier Transform. – Fresh water can be obtained by distillation. … by what? “By” + What-Agent

5. “By” + Doing-What-Agent The what-agent gives a general idea of how something is done: Many car engines are cooled by water. Sometimes it is necessary to explain a process in more detail. The what-agent can be expanded into a doing-what-agent. – Many car engines are cooled by circulating water through the engine assembly. – The frequency content of a signal is obtained by performing Fourier Transform on the time series.

6. “By” + Doing-What-Agent The basic structure: What is done by doing what else. Example: The following two sentences have the same meaning, but the second is more precise. – Fresh water can be obtained by distillation. – Fresh water can be obtained by distilling salt water. subject passive form: The what-agent is replaced by the doing-what-agent be + past participle

7. Complete the sentences with “by” + doing-what-agents Engines are cooled by … (circulate, water, through assembly) Engines are cooled by circulating water through the assembly. A simplified model is obtained by … (linearize, equations of motion) … linearizing the equations of motion The signal can be amplified by … (increase, gain, amplifier) … increasing the gain of the amplifier. Before an analog-to-digital conversion, a signal must be pre- processed by … (filter, high-frequency content) … filtering the high-frequency content.

8. Complete the sentences with “by” + doing-what-agents The presence of oil cannot be determined by … (study, surface, rocks) … studying the surface of rocks. High bit rates need to be achieved by … (increase, transmission rate) … increasing the transmission rate. High-order functions can be approximated by … (add, hidden layers, artificial neural network) … adding hidden layers to the ANN. In OFDM communication systems, channel estimation is performed by …(transmit, pilot symbols, among data) … transmitting pilot symbols among the data.