Improved High-Pressure, High-Temperature (HPHT) Materials Qualification using Dissolved H₂S Concentration as the Sour Service Scalable Metric

Gas phase H<sub>2</sub>S partial pressure (P<sub>H2S</sub>) is associated with sulfide stress cracking (SSC) and is routinely used as the ‘scalable’ parameter to qualify materials for high-pressure, high-temperature (HPHT) wells. Candidate materials for HPHT wells routinely require ANSI/NACE MR0175/ISO 15156 compliance because a few mole ppm of H<sub>2</sub>S at high pressure may place the well beyond the 0.05 psia (0.3 kPa) sour service threshold. P<sub>H2S</sub> has been accepted historically as the scalable sour severity parameter. However, as the total pressure increases, the relationship between P<sub>H2S</sub> and the dissolved H<sub>2</sub>S concentration becomes non-linear. This limits the robustness of P<sub>H2S</sub> as the sour severity metric. Thus, ISO 15156-1:2020 now permits the use of H2S fugacity (f<sub>H2S</sub>), H<sub>2</sub>S activity (a<sub>H2S</sub>), and H<sub>2</sub>S aqueous concentration (C<sub>H2S</sub>) as alternatives for sour testing. This recent revision is based on evidence that f<sub>H2S</sub> and C<sub>H2S</sub> each provide better correlations to SSC at elevated total pressures than P<sub>H2S</sub>. This paper will address the merits and challenges of using f<sub>H2S</sub> or C<sub>H2S</sub> to define sour severity: We argue that C<sub>H2S</sub> is a practical, experimentally verifiable approach, which can be used to validate ionic-equation of state (EOS) frameworks used to characterize mildly sour HPHT environments.

New Results and Applications about the Level Crossing Rate of SC Receiver output Signal in the Presence of Gamma Shadowing and k-μ or Rician Multipath Fading

In this paper,the wireless communication system with dual SC receiver operating over shadowed multipath fading channel is considered. The multipath fadingis k-μor Rician.The received signal experiences the short term fading which is resulting in SC receiver envelope variation and Gamma long term fading resulting in SC receiver envelope power variation. The closed form expressions for joint probability density functions of SC receiver output signal envelope and their first derivative of SC receiver output signal envelope are calculated for both, k-μand Rician fading. These expressions are used for evaluation of average level crossing rate of SC receiver output signal envelopes. The numerical expressions are plotted to show the effect of Rician fading severity parameter and Gamma shadowing severity parameter on the average level crossing rate of SC receiver output signal envelope.

Creasing severity and reverse-side cracking

Crease cracking can be detrimental to the functionality and appearance of paperboard-based pack-aging. The effect of creasing severity on the degree of reverse-side crease cracking (bead-side of the crease) of paperboard was investigated. Samples were creased with a range of rule and channel geometries, and the cracking degree was quantified as the percent of cracked length relative to the total length of the crease. The cracking degree was typically below 5% at low crease penetration depths, but was exponentially higher beyond a critical penetration depth. A rule and channel combination with a wider clearance shifted the critical depth to larger values. The creasing severity parameter, termed the creasing draw, converged the cracking degree data from different rule and channel combinations to a single curve. The creasing draw was derived from the same analytical expres-sions as the transverse shear strain and quantifies the length of paper that is drawn into the channel during creasing. The critical draw is defined as the draw at which cracking becomes greater than 5%, which corresponds with the point at which cracking becomes exponential. The critical draw is a material/system parameter that defines the level below which cracking is minimal.

Steam Explosion Conditions Highly Influence the Biogas Yield of Rice Straw

Straws are agricultural residues that can be used to produce biomethane by anaerobic digestion. The methane yield of rice straw is lower than other straws. Steam explosion was investigated as a pretreatment to increase methane production. Pretreatment conditions with varying reaction times (12–30 min) and maximum temperatures (162–240 °C) were applied. The pretreated material was characterized for its composition and thermal and morphological properties. When the steam explosion was performed with a moderate severity parameter of S0 = 4.1 min, the methane yield was increased by 32% compared to untreated rice straw. This study shows that a harsher pretreatment at S0 > 4.3 min causes a drastic reduction of methane yield because inert condensation products are formed from hemicelluloses.

LEVEL CROSSING RATE OF MACRODIVERSITY OUTPUT PROCESS IN THE PRESENCE OF η-μ SHORT TERM FADING AND GAMMA LONG TERM FADING

In this paper macrodiversity reception with macrodiversity selection combining (SC) receiver and two microdiversity MRC receivers operating over shadowed multipath fading channel is studied. Received signal experiences short term fading and correlated Gamma long term fading resulting in system performance degradation. Level crossing rate (LCR) of η-μ random process and level crossing rate of signals at outputs of microdiversity MRC receivers are efficiently calculated. By using these derived formulas, level crossing rate of macrodiversity SC receiver output signal process is calculated. By using this result, average fade duration (AFD) of the proposed wireless communication system can be calculated. The influence of η-μ short term fading severity parameter, Gamma long term fading severity parameter and Gamma long term correlation coefficient on level crossing rate is analysed and studied.

Performance of macro diversity wireless communication system operating in Weibull multipath fading environment

In this paper, we consider wireless mobile radio communication system with macro diversity reception. Signal is subject to Weibull small scale fading and Gamma large scale fading resulting in system performance degradation. Receiver uses macro diversity selection combining (SC) technique in order to reduce the impact of long term fading effects, and two micro diversity SC branches are used to mitigate Weibull short term fading effects on system performance. Probability density function (PDF), and cumulative distribution function (CDF), as well as level crossing rate (LCR) and average fade duration (AFD) of the SC receiver output signal envelope are evaluated. The obtained expressions converge rapidly for all considered values of Weibull fading parameter and Gamma shadowing severity parameter. Mathematical results are studied in order to analyze the influence of Weibull fading parameter and Gamma shadowing severity parameter on statistical properties of the SC receiver output signal.