Modelling of hydrocarbon gas and liquid leaks from pressurized process systems

The hydrocarbon leaks from process systems potentially lead to hazardous consequences with regard to human safety, environmental pollution and valuable assets. The hydrocarbon leaks may be gas leaks, liquid leaks or multiphase leaks. The gas leaks have the highest potential of damage due to explosion accidents. both gas and oil leaks can create long-lasting fires threatening personnel safety and structural integrity of process plants and offshore platforms. One common method for limiting the consequences associated with a process emergency is the rapid depressurization or blowdown of pressurized process systems. There is experimental evidence that the assumption of thermodynamic equilibrium is not appropriate during rapid depressurization, since the two phases show an independent temperature evolution. The current work proposes a model for the simulation of the blowdown of vessels containing two-phase (gas–liquid) hydrocarbon fluids, considering partial phase equilibrium between phases. Two phases may be present either already at the beginning of the blowdown process (for instance in gas–liquid separators) or as the liquid is formed from flashing of the vapour due to the cooling induced by pressure decrease. In addition, the transient behaviour of hydrocarbon leaks from pressurized process systems during depressurization is also included in the model providing the inputs for risk assessments. The model is based on a compositional approach, and it takes into account coupled effects of internal heat and mass transfer processes, as well as heat transfer with the vessel wall and the external environment. The vapour liquid equilibria calculations are performed using dynamic link library provided by the comprehensive pressure volume temperature and physical properties package ‘Multiflash’. Numerical simulations show a generally good agreement with experimental measurements.publishedVersio

Adaptive Selection of the Optimal Strategy to Improve Precision and Power in Randomized Trials

Benkeser et al. demonstrate how adjustment for baseline covariates in randomized trials can meaningfully improve precision for a variety of outcome types. Their findings build on a long history, starting in 1932 with R.A. Fisher and including more recent endorsements by the U.S. Food and Drug Administration and the European Medicines Agency. Here, we address an important practical consideration: *how* to select the adjustment approach -- which variables and in which form -- to maximize precision, while maintaining Type-I error control. Balzer et al. previously proposed *Adaptive Prespecification* within TMLE to flexibly and automatically select, from a prespecified set, the approach that maximizes empirical efficiency in small trials (N$<$40). To avoid overfitting with few randomized units, selection was previously limited to working generalized linear models, adjusting for a single covariate. Now, we tailor Adaptive Prespecification to trials with many randomized units. Using $V$-fold cross-validation and the estimated influence curve-squared as the loss function, we select from an expanded set of candidates, including modern machine learning methods adjusting for multiple covariates. As assessed in simulations exploring a variety of data generating processes, our approach maintains Type-I error control (under the null) and offers substantial gains in precision -- equivalent to 20-43\% reductions in sample size for the same statistical power. When applied to real data from ACTG Study 175, we also see meaningful efficiency improvements overall and within subgroups.Comment: 10.5 pages of main text (including 2 tables, 2 figures) + 14.5 pages of Supporting Inf

Measuring Interventional Robustness in Reinforcement Learning

Recent work in reinforcement learning has focused on several characteristics of learned policies that go beyond maximizing reward. These properties include fairness, explainability, generalization, and robustness. In this paper, we define interventional robustness (IR), a measure of how much variability is introduced into learned policies by incidental aspects of the training procedure, such as the order of training data or the particular exploratory actions taken by agents. A training procedure has high IR when the agents it produces take very similar actions under intervention, despite variation in these incidental aspects of the training procedure. We develop an intuitive, quantitative measure of IR and calculate it for eight algorithms in three Atari environments across dozens of interventions and states. From these experiments, we find that IR varies with the amount of training and type of algorithm and that high performance does not imply high IR, as one might expect.Comment: 17 pages, 13 figure

A theorem for a fluid Stokes flow

A sphere theorem for non-axisymmetric Stokes flow of a viscous fluid of viscosity &#956;e past a fluid sphere of viscosity &#956;i is stated and proved. The existing sphere theorems in Stokes flow follow as special cases from the present theorem. It is observed that the expression for drag on the fluid sphere is a linear combination of rigid and shear-free drags

Completely given up sale of cigarette at a village in Sri Lanka

Background and challenges to implementation “Katthapahuwa” is a village with 1341 population locates in Kurunegala district. Among the social issues, cigarette consumption was high; at baseline server reveled that ¾ (341) of adult male consume cigarettes. There were 21 cigarette vendors scatted all over the village. Nearly 1550 cigarettes were sold per day its value was USD 504.16. Intervention or response Interventions started in late March 2016, with developing a youth club at the village in collaboration with Sanasa Rural Development Bank. ADIC had trained 16 village youth leaders to overcome cigarette issue and they had identified one of the strategy was to reduce the cigarette availability at the village. Firstly, youth leaders met the vendors' association (VA) and emphasized regarding how Tobacco Company cheated vendors for small profit and explained that how much money they have stolen from our village. Future educated VA on their children also will be trapped by the tobacco industry. The main argument was made by the VA that if vendors stop selling cigarette, selling of other goods may reduce because customers move to other shops. We explained them that majority of the customers come not for cigarette but Tobacco Company taught you that business runs lost if not sell cigarettes. Finally the VA decided to stop sell cigarettes. Vendors needed one month period because they already purchased cigarettes. Mid Jun of 2016, all vendors stopped cigarette selling totally. The youth team organized an event to appreciate service of vendors. Interactions continually maintain with vendors by the youth group today too. Results and lessons learnt 21 vendors totally stopped cigarette selling, nearly USD 15124.92 money served for month. End year server reveled that significantly decreasing of cigarette use by 43% (147) and 13 persons quitted use. Conclusions and key recommendations The decline of cigarette consumption in a village can have a big effect on the stop sale of cigarettes

Tobacco industry tactics to retail vendors in Sri Lanka

Background and challenges to implementation Mainly Tobacco industry depends on retail tobacco vendors. Community groups and heath people are empowered to minimize the availability of cigarettes in respective areas. Hence, Tobacco Company has started to lobby retail vendors for continuing selling cigarettes. Intervention or response A study was carried out by ADIC with cigarette retail vendors in Hambantota city. A structured questioner and observation were used as data collection methods. Trained field officers interviewed 31 retail tobacco vendors. Questions were related to knowledge of harm done by cigarette and attitude on Tobacco Company. Observation was used to identify cigarette promotions inside retail shops. Results and lessons learnt Result reveled that the main reason (25 out of 31 responds) for cigarette selling is as an essential item of a shop. Even cigarette profit is comparative to low it helps to sell other goods. 8 Vendors stated that they had participated conferences organized by Tobacco Company. Tobacco company educated vendors on what benefit the business could got by selling cigarettes. Another strategy has been identified during the study. Tobacco Company has been introduced award system for cigarette vendors. It is named as " Abisheka " (anointed vendors). Six cigarette vendors named as anointed vendors. Those vendors got certificates and privilege cards for business. Attitude regarding cigarette business examined at the study. 18 vendors of 31 did justification of harm done by cigarette because they made argument that other product may harm. They did not believe tobacco industry do marketing to children majority of responds (77%) said that smoking was adult choice. Cigarette promotions could be identified in different ways because tobacco promotion was prohibited. We found that promotional item such as board was displayed as a vendor's message. Awarded shops got colourfull cashier point and showcase for cigarettes. Conclusions and key recommendations Tobacco industry cheats vendors as Trojans to continuing cigarette selling