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We present an ultraviolet spectroscopic survey of strong H I absorbers in theintergalactic medium, probing their evolution over the last 6-7 Gyr atredshifts $0.24 \leq z \leq 0.84$. We measure column densities $N_{\rm HI} \,({\rm cm}^{-2})$ from the pattern of Lyman-series absorption lines and fluxdecrement at the Lyman limit (LL) when available. We analyzed 220 H I absorbersin ultraviolet spectra of 102 active galactic nuclei (AGN) taken by the CosmicOrigins Spectrograph aboard the Hubble Space Telescope with G130M/G160Mgratings (1134-1795 \AA). For 158 absorbers with $\log N_{\rm HI} \geq 15$, themean frequency is $d {\cal N}/dz = 4.95 \pm 0.39$ over pathlength $\Delta z =31.94$ ($0.24 \leq z \leq 0.84)$. We identify 8 Lyman Limit Systems (LLS, $\logN_{\rm HI} \geq 17.2$) and 54 partial systems (pLLS) with $16.0 \leq \logN_{\rm HI} < 17.2$. Toward 159 AGN between $0.01 < z_{\rm abs} < 0.84$ with$\Delta z \approx 48$, we find four damped Ly$\alpha$ absorbers (DLA) with $(d{\cal N}/dz)_{\rm DLA} = 0.083^{+0.066}_{-0.040}$ at $\langle z \rangle =0.18$. The mean LLS frequency between $z = 0.24-0.48$ is $(d {\cal N}/dz)_{\rmLLS} = 0.36^{+0.20}_{-0.13}$ fitted to $N(z) =(0.25^{+0.13}_{-0.09})(1+z)^{1.14}$. For 54 pLLS we find $(d {\cal N}/dz)_{\rmpLLS} = 1.69\pm0.23$ at $\langle z \rangle = 0.39$, a frequency consistent withgaseous halo sizes $R \approx 100 h^{-1}~{\rm kpc}$ for ($0.3-3L^*$) galaxies.A maximum-likelihood analysis yields a distribution $f(N,z) = C_0 N^{-\beta}(1+z)^{\gamma}$ with $\beta = 1.48 \pm 0.05$ and $\gamma =1.14^{+0.88}_{-0.89}$ for $15 \leq \log N_{\rm HI} \leq 17.5$. The far-UVopacity gradient is $d \tau_{\rm eff} / dz \approx (0.444)(1+z)^{1.14}$ overthe range $15 \leq \log N_{\rm HI} \leq 17$, implying mean LyC optical depth$\tau_{\rm eff} \approx 0.3-0.5$ toward sources at $z = 1-2$.

An Ultraviolet Survey of Low-Redshift Partial Lyman-Limit Systems with the HST Cosmic Origins Spectrograph