Scientific Units and Technology History

Shot peening is a cold working process that bombards a surface with small spherical media to induce compressive residual stresses. These compressive stresses counteract tensile stresses during service, significantly delaying fatigue crack initiation and propagation in welds and springs. The other options (normalizing, spheroidizing, martempering) are heat treatments that primarily alter microstructure, not surface stress state.

Ohm is the SI unit of electrical resistance, which opposes current flow in a circuit. Conductance is the reciprocal of resistance (measured in siemens), inductance opposes changes in current (measured in henry), and capacitance stores charge (measured in farad).

Siemens is the SI unit of electrical conductance, which is the measure of how easily electric current flows through a material. It is the reciprocal of resistance (ohm). Inductance is measured in henry, capacitance in farad, and resistance in ohm.

Lux is the SI unit of illuminance, which measures luminous flux (light power perceived by human eye) per unit area. It is distinct from luminous intensity (candela) or luminous flux (lumen). Illuminance describes how much light falls on a surface.

Curie is a unit of radioactivity (specifically, activity of radioactive sources), measuring the number of nuclear decays per second. It quantifies how radioactive a substance is, not bond strength, reaction rates, or isotope counting.

N95 masks are specifically designed to filter at least 95% of airborne particles and are recommended for preventing H1N1 influenza transmission. The other options (N007, W585i, SN59) are not standard respirator designations.

James Watt made crucial improvements to the steam engine design in the late 18th century, making it practical for industrial use. While Thomas Newcomen built an earlier steam engine, Watt's innovations (separate condenser, etc.) are historically credited as the breakthrough. Einstein and Marconi worked in other fields.

N95 masks are specifically designed to filter at least 95% of airborne particles and are recommended for preventing H1N1 influenza transmission. The other options (N007, W585i, SN59) are not standard respirator designations.

James Watt made crucial improvements to the steam engine design in the late 18th century, including the separate condenser, which made steam engines much more efficient and practical for industrial use.

James Watt's improvements to the steam engine, including the separate condenser design, made it efficient enough for widespread industrial use in the late 18th century.

N95 respirator masks are designed to filter at least 95% of airborne particles and are commonly used to prevent the spread of respiratory infections like H1N1 influenza.

The N95 respirator mask filters at least 95% of airborne particles and is recommended by health organizations during influenza outbreaks including H1N1. The number indicates filtration efficiency (95%). Options A, B, and C are fictitious codes designed to look similar to the correct answer.