Design and Construction Challenges of a Federal Laboratory Building: A Case Study

This paper presents a case study regarding design and construction challenges of a federal laboratory building. The case study illustrates the successful collaboration of two federal agencies, General Services Administration (GSA) and Centers for Disease Control and Prevention (CDC). Creative methods were used to resolve complex design, construction, and budgetary issues. This paper describes lessons learned from a specific laboratory project on issues such as: A master plan and its role in locating secure laboratory buildings, site planning issues, contracting mechanisms, building security, energy, project development, design and construction excellence, and funding. Although CDC and GSA approved the release of this paper, the authors offer a disclaimer that the opinions and conclusions drawn in the papers are those of the authors, and are not necessarily shared by the CDC and GSA.     

Effects of ultrasonic waves on carbon dioxide solubility in brine at different pressures and temperatures

The adverse impacts of CO₂ emission on the global warming highlight the importance of carbon capture and storage technology and geological storage of CO₂ under solubility trapping mechanisms. Enhancing the solubility of CO₂ in formation water has always been the focus of research in the area of CO₂ sequestration. Ultrasound techniques are one of the environmentally friendly methods that use high-intensity acoustic waves to improve gas solubility in liquids. Ultrasonic waves can alter the properties of different phases that lead to chemical reactions and provide a means to increase the solubility of CO₂ in connate water. In this study, we investigated the effects of ultrasound on the solubility of CO₂ in connate water under different conditions of pressure, temperature, and salinity. The results showed that the solubility of CO₂ was improved with increasing pressure under ultrasonic effects. However, the solubility of CO₂ was inversely proportional to the increase in brine salinity and temperature. Therefore, it was concluded that the solubility of CO₂ might be enhanced in the presence of ultrasound.     

Strategic policy analysis for infrastructure rehabilitation using system dynamics

Recent requirements for sustainable development and increasing trend for public–private partnerships (PPPs) have added additional complexities to the policy-making process in the infrastructure management domain. To support policy analysis, this paper presents a system dynamics (SD) model to analyse the impact of different strategic policies (e.g. budgeting, PPP involvement) on infrastructure serviceability, backlog accumulation and sustainability. The proposed model has been implemented on a network of school buildings from the Toronto District School Board asset inventory. Four sets of experiments with different policy scenarios over a 50-year strategic planning horizon have been conducted to investigate policies related to rehabilitation, budget distribution, government investment and PPP involvement. The proposed model was implemented on a commercial SD software incorporating all the dynamic interactions among the strategic parameters. The experiment results show that the model works as a practical decision support tool that enables asset managers to test the effectiveness of various strategic policy scenarios on long-term infrastructure performance.     

Distribution and Sources of Polycyclic Aromatic Hydrocarbons (PAHs) in Surface Sediments from the Northern Part of the Persian Gulf (Hormuzgan Province)

Sediments from the intertidal areas of Hormuzgan province in northern part of Persian Gulf (Iran) were investigated for the levels and possible sources of 15 polycyclic aromatic hydrocarbons (PAHs). Samples of sediments were collected from twelve sampling sites and analyzed for PAHs by gas chromatography–mass spectrometry (GC-MS). The results showed that the total concentrations of PAHs ranged from 765 to 1898 ng/g dry weight. Composition pattern in the sediment samples from 12 sampling sites was dominated by 4-ring PAH compounds. Molecular indices based on ratios of PAH concentrations were used to differentiate PAHs from pyrolitic, petrogenic and mixed origins. The results of study suggested that the main sources of PAHs in the sediment were mixed with pyrolitic and petrogenic inputs. According to the US sediments quality guidelines (SQGs) (ERL/ERM) sediments of the mentioned region did not show any ecotoxicological risk for benthic organisms.     

Maximizing the returns of LIDAR systems in wind farms for yaw error correction applications

Wind energy is an important source of renewable energy with significant untapped potential around the world. However, the cost of wind energy production is high, and efforts to lower the cost of energy generation will help enable more widespread use of wind energy. Yaw error reduces the efficiency of turbines as well as lowers the reliability of key components in turbines. Light detection and ranging (LIDAR) devices can correct the yaw error; however, they are expensive, and there is a trade‐off between their costs and benefits. In this study, a stochastic discrete‐event simulation was developed that models the operation of a wind farm. We maximize the net present value (NPV) changes associated with using LIDAR devices in a wind farm and determine the optimum number of LIDAR devices and their associated turbine stay time as a function of number of turbines in the wind farm for specific turbine sizes. The outcome of this work will help wind farm owners and operators make informed decisions about purchasing LIDAR devices for their wind farms.     

Separation of methane from different gas mixtures using modified silicon carbide nanosheet: Micro and macro scale numerical studies

This research discusses the separation of methane gas from three different gas mixtures, CH₄/H₂S, CH₄/N₂ and CH₄/CO₂, using a modified silicon carbide nanosheet (SiCNS) membrane using both molecular dynamics (MD) and computational fluid dynamics (CFD) methods. The research examines the effects of different structures of the SiCNSs on the separation of these gas mixtures. Various parameters including the potential of the mean force, separation factor, permeation rate, selectivity and diffusivity are discussed in detail. Our MD simulations showed that the separation of CH₄/H₂S, and CH₄/CO₂ mixtures was successful, while simulation demonstrated a poor result for the CH₄/N₂ mixture. The effect of temperature on the diffusivity of gas is also discussed, and a correlation is introduced for diffusivity as a function of temperature. The evaluated value for diffusivity is then used in the CFD method to investigate the permeation rate of gas mixtures.     

Automated Dataset Generation for Training Peer-to-Peer Machine Learning Classifiers

Peer-to-peer (P2P) classifications based on flow statistics have been proven accurate in detecting P2P traffic. A machine learning classification is affected by the quality and recency of the training dataset used. Hence, to classify P2P traffic on-line requires the removal of these limitations. In this paper, an automated training dataset generation for an on-line P2P traffic classification is proposed to allow frequent classifier retraining. A two-stage training dataset generator (TSTDG) is proposed by combining a 3-class heuristic and a 3-class statistical classification to automatically generate a training dataset. In the heuristic stage, traffic is classified as P2P, non-P2P, or unknown. In the statistical stage, a dual Decision Tree is built based on a dataset generated in the heuristic stage to reduce the amount of classified unknown traffic. The final training dataset is generated based on all flows that are classified in these two stages. The proposed system has been evaluated on traces captured from a campus network. The overall results show that the TSTDG can generate an accurate training dataset by classifying around 94 % of total flows with high accuracy (98.59 %) and a low false positive rate (1.27 %).     

CRN synthesis of β-SiAlON from a nanocomposite precursor of mesoporous silica–alumina (Al-SBA-15) with poly 4-vinyl pyridine

This paper reports the use of a nanocomposite precursor of mesoporous silica?Calumina (Al-SBA-15) with poly 4-vinyl pyridine (P4VP) to synthesise ??-SiAlON by carbothermal reduction and nitridation under N₂ at 1,450?°C. Small-angle XRD, SEM/TEM, ²⁹Si and ²⁷Al MAS-NMR and BET specific surface area measurements of the Al-SBA-15 and P4VP/Al-SBA-15 composite confirmed the mesoporous structure and the presence of Al in the precursors, while surface polymerization of the Al-SBA-15 was indicated by ²⁹Si-NMR. Firing the nanocomposite in a N₂ atmosphere forms the nitride phase, depending on the amount and type of carbon present, on the surface area of the precursor. Even with these precursors of high surface area, the present result was obtained using approximately twice the stochiometric amount of carbon.     

Lipid Flip‐Flop and Pore Nucleation on Zwitterionic Bilayers are Asymmetric under Ionic Imbalance

Lipid flip‐flop and its associated transient pore formation are key thermodynamic properties of living cell membranes. However, there is a lack of understanding of whether ionic imbalance that exists ubiquitously across cell membranes affects lipid flip‐flop and its associated functions. Potential of mean force calculations show that the free‐energy barrier of lipid flip‐flop on the extracellular leaflet reduces with the presence of ionic imbalance, whereas the barrier on the intracellular leaflet is generally not affected. The linear decrease of the activation energy of lipid flip‐flop on the extracellular leaflet is consistent with the experimentally measured conductance–voltage relationship of zwitterionic lipid bilayers. This suggests: 1) lipid flip‐flop has a directionality under physiological conditions and phospholipids accumulate at a rate on the order of 105 µm^?2 h^?1 on the cytoplasmic side of cell membranes; 2) ion permeation across a lipid membrane is moderated by lipid flip‐flop; 3) the energy barrier of pore formation is aligned with the weaker leaflet that has a lower energy of lipid flip‐flop. The asymmetry of lipid flip‐flop and pore nucleation may have substantial implications for protein translocation, signaling, enzymatic activities, vesicle fusion, and transportation of biomolecules on cell membranes.