of temperature, strain rate and carbon in interstitial solid solution on the yield and flow stresses were studied in the tem-10-6 dynes and x*0 = 1.3b, which are in accord with the thermally activated overcoming of interstitial carbon atoms by dislocation as the rate controlling mechanism. (Received April 6, 1973) Carbon atoms as well as nitrogen and oxygen atoms, which are found in interstitial solid solution, strengthen titanium at low temperatures. Their relative effectiveness in raising the flow stress of titanium is reported to have the ratios of nitrogen, oxygen and carbon as, for example, 2.0:1.0:0.75 by Conrad(1). These interstitial solutes influence mainly the thermal component of the flow stress, the effect being larger as the temperature is decreased.To establish the separate effects of nitrogen and oxygen on the flow stress of titanium, the present authors have prepared Ti-N and Ti-O alloys by starting with high purity material and doping with various amounts of nitrogen and oxygen and have identified the mechanism of strengthening by deriving the thermal activation parameters (2)(3). As a followup, a series of Ti-C alloys were prepared by starting with the same high purity titanium and doping with various amounts of carbon and the effect of carbon on the mechanical behavior of titanium at low temperature was investigated.

Second-harmonic generation (SHG) and electro-optic (EO) modulation were studied on thermally poled twin-hole fiber. Metal electrode wires were inserted into the side holes. The typical poling condition was 2.5 kV, 300 ºC, and 40 min. SHG was measured using a Q-switched Nd:YAG laser. The SH power did not depend on the applied forward or reverse voltages. SHG without poling was also measured, then the maximum power was about 1/18 that of the poled SHG. EO modulation was performed using a twin-hole fiber inserted to a fiber-optic Mach-Zehnder interferometer. An AC modulation voltage was applied to the electrodes together with a DC bias voltage. Without poling, the modulation output was obtained only when a DC bias voltage was applied simultaneously. After poling, a modulation output was obtained without any bias voltage, and for the forward DC bias the modulation output increased with the bias voltage. For the reverse DC bias the modulation output showed the minimum for a bias voltage. The origin of the second-order nonlinearities and the other effects in the above SHG and EO modulation are discussed considering charge layers.