Evacuation Simulation of Confined Spaces in Petrochemical Facilities

PresentationWith the development of petrochemical industry, confined space evacuation has been a major safety issue due to the potential fatalities and injuries caused by inadequate emergency responses. In this work, two existing software, BuildingEXODUS and FDS+Evac, were used to simulate the Required Safe Egress Time (REST) in different evacuation environments. Vertical and horizontal storage tanks were constructed by using these two simulation software. Then, different parameters such as occupant load, with and without internal obstruction, and exit size were studied in different simulation scenarios. The simulation results from the software have shown a good agreement with those from the field experiments. It is found that the REST of vertical storage tank is nearly half of that of horizontal storage tank. The work has demonstrated a concept that the fire safety software could be used to simulate evacuations from confined spaces in petrochemical facilities

A Deep Dive into Blockchain Selfish Mining

This paper studies a fundamental problem regarding the security of blockchain on how the existence of multiple misbehaving pools influences the profitability of selfish mining. Each selfish miner maintains a private chain and makes it public opportunistically for the purpose of acquiring more rewards incommensurate to his Hashrate. We establish a novel Markov chain model to characterize all the state transitions of public and private chains. The minimum requirement of Hashrate together with the minimum delay of being profitable is derived in close-form. The former reduces to 21.48% with the symmetric selfish miners, while their competition with asymmetric Hashrates puts forward a higher requirement of the profitable threshold. The profitable delay increases with the decrease of the Hashrate of selfish miners, making the mining pools more cautious on performing selfish mining.Comment: 6 pages, 13 figure

ODN: Opening the Deep Network for Open-set Action Recognition

In recent years, the performance of action recognition has been significantly improved with the help of deep neural networks. Most of the existing action recognition works hold the \textit{closed-set} assumption that all action categories are known beforehand while deep networks can be well trained for these categories. However, action recognition in the real world is essentially an \textit{open-set} problem, namely, it is impossible to know all action categories beforehand and consequently infeasible to prepare sufficient training samples for those emerging categories. In this case, applying closed-set recognition methods will definitely lead to unseen-category errors. To address this challenge, we propose the Open Deep Network (ODN) for the open-set action recognition task. Technologically, ODN detects new categories by applying a multi-class triplet thresholding method, and then dynamically reconstructs the classification layer and "opens" the deep network by adding predictors for new categories continually. In order to transfer the learned knowledge to the new category, two novel methods, Emphasis Initialization and Allometry Training, are adopted to initialize and incrementally train the new predictor so that only few samples are needed to fine-tune the model. Extensive experiments show that ODN can effectively detect and recognize new categories with little human intervention, thus applicable to the open-set action recognition tasks in the real world. Moreover, ODN can even achieve comparable performance to some closed-set methods.Comment: 6 pages, 3 figures, ICME 201

Analytical Solution for 2D and 3D Lamb Problem in Saturated Soil Incorporating Effects of Compressibility of Solid and Pore Fluid

In this paper, to avoid the complexity, a simple and efficient analytical solution is derived for both 2D and 3D Lamb problems, respectively, in saturated soil under harmonic excitations. Unlike the existing solutions, the proposed solutions for both 2D and 3D Lamb problems in saturated soil under harmonic excitation are capable of well revealing the effect of compressibility of both liquid phase and solid phase on the ground displacements. By applying Fourier transforms and Hankel transforms on the governing equations of wave propagation in saturated soil, wave equations are transformed to ordinary differential equations. Combining the boundary conditions and draining conditions on the ground surface, the displacement solutions on the surface of saturated porous soil due to line and point harmonic excitations are derived, respec-tively. Then, the solutions in frequency domain are obtained by inverse integral transforms. In the meanwhile, for the sake of discussion without losing its generality, the non-dimensional solutions for three-dimensional Lamb problem are derived. The effectiveness and accuracy of the proposed solutions are demonstrated by employing three different approaches. Finally, parametric studies are conducted to investigate the effects of the governing parameters (i.e., exciting frequency, bulk modulus of soil matrix, and bulk modulus of pore fluid) on variation of non-dimensional displacement with the increasing distance away from the excitation source. The results indicate that, in contrast to the effect of the compressibility of soil matrix, the exciting frequency as well as the compressibility of the pore fluid play significant role in affecting the variation of displacement on ground surface subjected to excitations, which particularly highlights that the compressibility of the pore fluid should be carefully considered for evaluating the ground movements

Power and performance trade-off in DS-CDMA receivers based on adaptive LMS-MMSE multi-user detector.

Thesis (M.Sc.Eng.)-University of Natal, Durban, 2003.Third generation cellular communication systems based on CDMA techniques have shown great scope for improvement in system capacity. Over the last decade, there has been significant interest in DS-CDMA detectors. The conventional detector, the optimal detector and a number of sub-optimal multi-user detectors (MUD) have been extensively analyzed in the literature. Recently, the reduction of power consumption in DS-CDMA systems has also become another important consideration in both system design and in implementation. In order to support wireless multimedia services, all CDMA-based systems for third generation systems have a large bandwidth and a high data rate, therefore the power consumed by the digital signal processor (DSP) is high. This thesis focuses on power consumption in the adaptive Minimum Mean Square Error (MMSE) detector which is based on the Least Mean Square (LMS) algorithm. This thesis presents a literature survey on MUD and adaptive filter algorithms. A system model of the quantized LMS-MMSE MUD is proposed and its performance is analyzed. The quantization effects in the finite precision LMS-MMSE adaptive MUD including the steady-state weight covariance, mean square error (MSE) and bit error rate (BER) versus wordlength of data and coefficient are investigated when both the data and filter coefficients are quantized. The effects of wordlength size on power consumption are investigated and the tradeoff between the power consumption and performance degradation and the optimal allocation of bits to data and to LMS coefficients under power constraint is presented

Theoretical and Experimental Evaluation of Chemical Reactivity

Reactive chemicals are presented widely in the chemical and petrochemical process industry. Their chemical reactivity hazards have posed a significant challenge to the industries of manufacturing, storage and transportation. The accidents due to reactive chemicals have caused tremendous loss of properties and lives, and damages to the environment. In this research, three classes of reactive chemicals (unsaturated hydrocarbons, self-reacting chemicals, energetic materials) were evaluated through theoretical and experimental methods. Methylcyclopentadiene (MCP) and Hydroxylamine (HA) are selected as representatives of unsaturated hydrocarbons and self-reacting chemicals, respectively. Chemical reactivity of MCP, including isomerization, dimerization, and oxidation, is investigated by computational chemistry methods and empirical thermodynamic–energy correlation. Density functional and ab initio methods are used to search the initial thermal decomposition steps of HA, including unimolecular and bimolecular pathways. In addition, solvent effects are also examined using water cluster methods and Polarizable Continuum Models (PCM) for aqueous solution of HA. The thermal stability of a basic energetic material, Nitroethane, is investigated through both theoretical and experimental methods. Density functional methods are employed to explore the initial decomposition pathways, followed by developing detailed reaction networks. Experiments with a batch reactor and in situ GC are designed to analyze the distribution of reaction products and verify reaction mechanisms. Overall kinetic model is also built from calorimetric experiments using an Automated Pressure Tracking Adiabatic Calorimeter (APTAC). Finally, a general evaluation approach is developed for a wide range of reactive chemicals. An index of thermal risk is proposed as a preliminary risk assessment to screen reactive chemicals. Correlations are also developed between reactivity parameters, such as onset temperature, activation energy, and adiabatic time to maximum rate based on a limited number, 37 sets, of Differential Scanning Calorimeter (DSC) data. The research shows broad applications in developing reaction mechanisms at the molecular level. The methodology of reaction modeling in combination with molecular modeling can also be used to study other reactive chemical systems

Experimental Study of an Iron-Based Metal-Organic Framework as Flame Retardant for Poly (methyl methacrylate) (PMMA)

PresentationPoly (methyl methacrylate) (PMMA) is a kind of widely used thermoplastic in the family of poly (acrylic ester)s due to its good mechanical properties, like good moldability, high resistance to UV light and weathering, high strength, and excellent dimensional stability. However, PMMA is also characterized by limited heat resistance, poor thermal stability, and high flammability. Metal-organic frameworks (MOFs) are a new class of porous materials, which possess unique physicochemical properties and have attracted considerable interests from different fields, such as energy, gas storage and separation, and catalysis. Additionally, because of their inorganic−organic hybrid nature, MOFs are usually compatible with polymers to form composites. PCN-250 is an iron-based MOF with nitrogen-containing structure and it is chemically stable and physically robust. So far, it can be economically synthesized in large scale. In this study, PCN-250 is used as a potential flame retardant for PMMA. To evaluate the performance of PCN-250 with different concentrations, the thermostability and flame retardancy of the PMMA composites are systematically investigated using thermal gravimetric analysis (TGA) and cone calorimetry. This study will give us some insight about the application of MOFs as a new kind of flame retardant to enhance and improve the fire safety of polymer materials

An extracellular protein expression system in Escherichia coli implies potential application

Escherichia coli is commonly used as a host for the extracellular production of proteins. However, its secretion capacity is often limited to a frustratingly low level compared with other expression hosts, because E. coli has a complex cell envelope with two layers. We recently identified the catalytic domain of a cellulase (Cel-CD) from Bacillus sp. that can be secreted into the medium from recombinant E. coli in large quantities without its native signal peptide. By subcellular location analysis, we verified that the secretion was a two-step process via the SecB-dependent pathway through the inner membrane and an unknown pathway through the outer membrane. However, the N-terminal region of Cel-CD is polar and hydrophilic, which showed no similarities to other typical signal sequences. Random mutagenesis experiment suggested that the N-terminal sequence is a compromising result of transportation through inner and outer membranes. This is the first report that a non-classical signal peptide can guide recombinant proteins out of the cells from cytoplasm. Both the Cel-CD and its N-terminal sequence can serve as carriers for efficient extracellular production of select target proteins with a concentration from 101 to 691 mg/L in flask cultivation. This protein can degrading cellulose efficiently in the culture medium indicating a great potential. Therefore, a recombinant E.coli that can directly utilize cellulose as sole carbon source by fusion Cel-CD with a b-glucosidase was constructed. Recombinant strains were confirmed to use the amorphous cellulose as well as cellobiose as the sole carbon source for growth. Furthermore, both strains were engineered with poly (3-hydroxybutyrate) (PHB) synthesis pathway to demonstrate the production of biodegradable polyesters directly from cellulose materials without exogenously added cellulases. The results suggested that this system has a potential application in lignocellulosic biomass degradation and biochemical biofuel production. These guidelines have been prepared in the format that should be used for the abstract submission. Authors should replace the text of this template in order to prepare their abstracts. Fonts, sizes and spacing should be used as they are used in this document. Page size is US 8.5 inch x 11 inch, top and bottom margin 0.8 inches, left and right margin 0.8 inches. Body text should be written in Arial, 10 pt, single spacing. The Abstract, in English, should introduce the proposed paper’s subject, summarize its contents, explain any unique aspects, and clearly indicate the specific relevance to the themes of the Conference. Do not sub-divide the text into separate sections. References may be included at the bottom. Reference Exploring the N-terminal role of a heterologous protein in secreting out of Escherichia coli, Biotechnol Bioeng. 2016 Dec;113(12):2561-2567. doi: 10.1002/bit.26028. Epub 2016 Jun 14. Construction of cellulose-utilizing Escherichia coli based on a secretable cellulose, Microb Cell Fact. 2015 Oct 9;14:159. doi: 10.1186/s12934-015-0349-7