Dual Barrier Research Articles

Improvement of Attention-Deficit/Hyperactivity Disorder Symptoms in School-Aged Children, Adolescents, and Young Adults With Autism via a Digital Smartglasses-Based Socioemotional Coaching Aid: Short-Term, Uncontrolled Pilot Study.

BackgroundPeople with autism spectrum disorder (ASD) commonly experience symptoms related to attention-deficit/hyperactivity disorder (ADHD), including hyperactivity, inattention, and impulsivity. One-third of ASD cases may be complicated by the presence of ADHD. Individuals with dual diagnoses face greater barriers to accessing treatment for ADHD and respond less positively to primary pharmacologic interventions. Nonpharmacologic technology-aided tools for hyperactivity and inattention in people with ASD are being developed, although research into their efficacy and safety remains limited.ObjectiveThe objective of this preliminary study was to describe the changes in ADHD-related symptoms in children, adolescents, and young adults with ASD immediately after use of the Empowered Brain system, a behavioral and social communication aid for ASD running on augmented reality smartglasses.MethodsWe recruited 8 children, adolescents, and young adults with ASD (male to female ratio of 7:1, mean age 15 years, range 11.7-20.5 years) through a Web-based research signup form. The baseline score on the hyperactivity subscale of the Aberrant Behavioral Checklist (ABC-H), a measure of hyperactivity, inattention, and impulsivity, determined their classification into a high ADHD-related symptom group (n=4, ABC-H≥13) and a low ADHD-related symptom group (n=4, ABC-H<13). All participants received an intervention with Empowered Brain, where they used smartglasses-based social communication and behavioral modules while interacting with their caregiver. We then calculated caregiver-reported ABC-H scores at 24 and 48 hours after the session.ResultsAll 8 participants were able to complete the intervention session. Postintervention ABC-H scores were lower for most participants at 24 hours (n=6, 75%) and for all participants at 48 hours (n=8, 100%). At 24 hours after the session, average participant ABC-H scores decreased by 54.9% in the high ADHD symptom group and by 20% in the low ADHD symptom group. At 48 hours after the session, ABC-H scores compared with baseline decreased by 56.4% in the high ADHD symptom group and by 66.3% in the low ADHD symptom group.ConclusionsThis study provides initial evidence for the possible potential of the Empowered Brain system to reduce ADHD-related symptoms, such as hyperactivity, inattention, and impulsivity, in school-aged children, adolescents, and young adults with ASD. This digital smartglasses intervention can potentially be targeted at a broader array of mental health conditions that exhibit transdiagnostic attentional and social communication deficits, including schizophrenia and bipolar disorder. Further research is required to understand the clinical importance of these observed changes and to conduct longitudinal studies on this intervention with control groups and larger sample sizes.

A physics‐based threshold voltage model for hetero‐dielectric dual material gate Schottky barrier MOSFET

AbstractThis paper presents the analytical model of threshold voltage for hetero‐dielectric dual material gate Schottky barrier (SB) metal oxide semiconductor field effect transistor (MOSFET). The threshold voltage model is derived on the basis of the surface potential model. The threshold voltage is extracted using transconductance change method. The two‐dimensional surface potential, electric field, and threshold voltage model for the hetero‐dielectric dual material gate SB‐MOSFET are developed using 2‐D Poisson's equation, which satisfies the boundary conditions. Moreover, the model precisely depict the impact of hetero‐gate dielectric and gate oxide thickness on the surface potential, and threshold voltage of the hetero‐dielectric dual material gate SB and compared with single material gate SB‐MOSFET. Finally, a good agreement between the model results and numerical simulated results is achieved.

Excellent dielectric performance and nonlinear electrical behaviors of Zr-doped CaCu3Ti4O12 thin films

The dielectric and nonlinear current–voltage properties of CaCu3Ti4−xZr x O12 (x = 0, 0.05, 0.1, 0.15 and 0.2) thin films prepared by the modified sol–gel method and annealed at 750 °C for 1 h were systematically studied. Zr doping resulted in a significant reduction in the mean grain size from 177.4 to 42.9 nm. The dielectric properties of the thin films increased significantly with the increase of Zr content from x = 0 to 0.2, indicating the importance of microstructure in controlling the dielectric properties of CaCu3Ti4−xZr x O12 thin films. A highly frequency-independent giant dielectric permittivity from 102 to 106 Hz was successfully achieved in CaCu3Ti3.8Zr0.2O12 thin film, which possessed a very high dielectric permittivity value of 7591 and a very low tanδ value of 0.023 at 1 kHz. The results indicated that reduction in the mean grain size affected the number of polarized ions per unit volume n0 (to improve e′) and the number of grain boundaries (to reduce tanδ). CaCu3Ti3.75Zr0.15O12 thin film showed the highest nonlinear coefficient (5.8) and lowest leakage current (131 μA). In addition, the relaxation mechanism based on the internal barrier layer capacitance model and the back-to-back dual Schottky barrier model were used to explain the dielectric properties and the nonlinear electrical behaviors of the samples.

Robust performance of a membrane bioreactor for removing antibiotic resistance genes exposed to antibiotics: Role of membrane foulants

Antibiotic resistance genes (ARGs) are an emerging concern in wastewater treatment plants (WWTPs), as dissemination of ARGs can pose a serious risk to human health. Few studies, however, have quantified ARGs in membrane bioreactors (MBRs), although MBRs have been widely used for both municipal and industrial wastewater treatment. To reveal the capacity of MBRs for removal of ARGs and the response of membrane fouling after antibiotic exposure, five typical ARG subtypes (sulI, sulII, tetC, tetX and ereA) and int1 were quantified affiliated by systematic membrane foulants analysis in a laboratory-scale anoxic/aerobic membrane bioreactor (A/O-MBR). Sulfamethoxazole and tetracycline hydrochloride additions increased ARG abundances by 0.5–1.4 orders of magnitude in the activated sludge, while the ARG removal performance of the membrane module remained stable (or even increased with ARG absolute abundance in several cases), with the abundance of removed ARGs ranging from 0.6 to 5.6 orders of magnitude. Specifically, the distribution of ARGs in membrane foulants accounted for 13%–25% of the total absolute abundance of all tested MBR samples. Indeed, substantial fouling occurred after the antibiotic additions, with the mean concentrations of soluble microbial product (SMP) and extracellular polymeric substance (EPS) increasing by 340% and 220%, respectively, in a membrane fouling cycle; moreover, the contents of EPS and SMP in the membrane foulants were significantly correlated with the ARG absolute abundance of membrane foulants (p < 0.05), among which more significant correlations occurred between both the protein and polysaccharide of foulants than that with humic acid. The dense membrane fouling layer and the membrane itself constituted dual barriers that effectively avoided the leakage of ARGs from the membrane module. Our findings provide fundamental insights into the proliferation and removal of ARGs in MBR systems, and highlight the contribution of membrane fouling to ARG removals in terms of the potential of MBR as an effective strategy to reduce ARG levels in WWTP effluent.

Electron heating and mode transition in dual frequency atmospheric pressure argon dielectric barrier discharge

Plasma ionization, excitation, mode transitions and associated electron heating mechanisms in atmospheric pressure dielectric barrier discharges (DBD) driven by dual radio frequency sources are investigated in this paper. The electrons are found to be heated mainly by the high frequency component in the plasma bulk when discharged in α mode. On the contrary, the low frequency component is primarily responsible for heating in the sheath which is caused by intense motion in the sheath. It was also found that variation of the lower frequency component ratio could effectively modulate the electron energy distribution as determined from time averaged EEDF. The results above have demonstrated that the independent control of plasma parameters via non-linear synergistic effect between the dual frequency sources can be achieved through reasonable selection of processing parameters.

Perceptions of U.S. Veterans Affairs and community healthcare providers regarding cross-system care for heart failure.

This study explores perceptions of US Veterans Affairs (VA) and non-VA healthcare providers caring for Veterans with heart failure (HF) regarding Veteran knowledge and motivations for dual use, provider roles in recommending and coordinating dual use, systems barriers and facilitators, and suggestions for improving cross-system care. Twenty VA and 11 non-VA providers participated in semi-structured interviews, which were analyzed using parallel qualitative content and discourse analysis. VA and non-VA providers described variable HF knowledge and self-management among Veterans, and both groups described the need for improved education addressing medication adherence, self-care, and management of acute symptoms. Both groups described highly limited roles for providers in shaping choices surrounding dual use. VA and non-VA providers had significantly different perceptions regarding the availability, quality, and effectiveness of VA HF services. Multiple non-VA providers expressed frustration with and difficulty in contacting VA providers, accessing records, and making referrals into the VA system. Suggestions for improved care focused on patient education and care coordination. Dual healthcare system use for Veterans is increasingly common. Similarities and contrasts in perceptions of VA and non-VA providers are instructive and should be incorporated into future policy and program initiatives.

Wave trapping by dual porous barriers near a wall in the presence of bottom undulation

Trapping of oblique surface gravity waves by dual porous barriers near a wall is studied in the presence of step type varying bottom bed that is connected on both sides by water of uniform depths. The porous barriers are assumed to be fixed at a certain distance in front of a vertical rigid wall. Using linear water wave theory and Darcy's law for flow past porous structure, the physical problem is converted into a boundary value problem. Using eigenfunction expansion in the uniform bottom bed region and modified mild-slope equation in the varying bottom bed region, the mathematical problem is handled for solution. Moreover, certain jump conditions are used to account for mass conservation at slope discontinuities in the bottom bed profile. To understand the effect of dual porous barriers in creating tranquility zone and minimum load on the sea wall, reflection coefficient, wave forces acting on the barrier and the wall, and surface wave elevation are computed and analyzed for different values of depth ratio, porous-effect parameter, incident wave angle, gap between the barriers and wall and slope length of undulated bottom. The study reveals that with moderate porosity and suitable gap between barriers and sea wall, using dual barriers an effective wave trapping system can be developed which will exert less wave force on the barriers and the rigid wall. The proposed wave trapping system is likely to be of immense help for protecting various facilities/ infrastructures in coastal environment.

Electrical Characteristics of Dual Layered Tunnel Barrier with High Speed and Good Retention for Charge Trap Flash Memory

In this paper, we investigate the electrical characteristics of SiO2/ZrO2 hybrid tunnel oxide in MAONOS structure in an effort to improve program and erase speed as well as retention endurance. Inserting ZrO2 into the conventional MAONOS structure increased the programmed Vth variation to 5.8 V, and increased the erased Vth variation to -3.2 V at 15 MV/cm. The results can be understood in terms of reduced the F-N tunneling barrier due to high-k ZrO2 in the tunneling oxide. In addition, Zr diffusion in SiO2 caused the formation of ZrxSi1-XO2 at the interface region, which reduced the energy band gap of SiO2. The retention property of the hybrid tunnel oxide varied depending on the thickness of SiO2. For thin SiO2 less than 30 Å, the retention properties of the tunneling oxides were poor compared with those of the SiO2-only tunneling oxides. However, the hybrid tunneling oxides with SiO2 thickness thicker than 40 Å yielded improved retention behavior compared with those of the SiO2-only tunneling oxides. The detailed analysis in charge density of ZrO2 was carried out by ISPP test. The obtained charge density was quite small compared to that of the total charge density, which indicates that the inserted ZrO2 layer serves as a tunneling material rather than charge storage dielectric.

Dry granular flow interaction with dual-barrier systems

Multiple barriers are commonly installed along predicted geophysical flow paths to intercept large flow volumes. The main criterion for multiple-barrier design is volume retained. The velocity of the incoming (far-field) undisturbed flow is also sometimes used, although this neglects the influence of other obstacles on the flow characteristics. This study investigates the influence of upstream flow–barrier interaction on downstream runup and impact mechanisms of a dual rigid barrier system. Four physical flume tests were performed using dry sand to investigate flow interaction with dual barriers. Moreover, three-dimensional finite-element simulations were conducted to back-analyse the flume tests and to investigate the effects of upstream barrier height and barrier spacing on downstream impact characteristics. Two key interaction mechanisms that alter downstream flow are identified: (a) flow momentum redirection (i.e. runup) at the upstream barrier, reducing pre-impact momentum at the downstream; and (b) downstream flow-thinning. Runup mechanisms at the upstream barrier and flow-thinning between the two successive barriers have profound effects on dynamic impact pressures at the downstream barrier. When the upstream barrier height is taller than twice the maximum flow thickness, flow energy can be dissipated effectively by momentum redirection. The downstream barrier height and design impact pressure can be reduced up to 17% and 35% for dry sand flows, respectively.

Dual barrier InAlN/AlGaN/GaN-on-silicon high-electron-mobility transistors with Pt- and Ni-based gate stacks

In this work, we report the performance of 3 µm gate length “dual barrier” InAlN/AlGaN/GaN HEMTs on Si substrates with gate–drain contact separations in the range 4–26 µm. Devices with Pt- and Ni-based gates were studied and their leakage characteristics are compared. Maximum drain current IDS of ∼1 A mm−1, maximum extrinsic transconductance gm ∼203 mS mm−1 and on-resistance Ron ∼4.07 Ω mm for gate to drain distance LGD = 4 µm were achieved. Nearly ideal sub-threshold swing of ∼65.6 mV dec−1 was obtained for LGD = 14 µm. The use of Pt-based gate metal stacks led to a two to three orders of magnitude gate leakage current decrease compared to Ni-based gates. The influence of InAlN layer thickness on the transistor transfer characteristics is also discussed.

On-demand Antimicrobial Treatment with Antibiotic-Loaded Porous Silicon Capped with a pH-Responsive Dual Plasma Polymer Barrier.

Chronic wounds are a major socio-economic problem. Bacterial infections in such wounds are a major contributor to lack of wound healing. An early indicator of wound infection is an increase in pH of the wound fluid. Herein, we describe the development of a pH-responsive drug delivery device that can potentially be used for wound decontamination in situ and on-demand in response to an increase in the pH of the wound environment. The device is based on a porous silicon film that provides a reservoir for encapsulation of an antibiotic within the pores. Loaded porous silicon is capped with dual plasma polymer layers of poly(1,7-octadiene) and poly(acrylic acid), which provide a pH-responsive barrier for on-demand release of the antibiotic. We demonstrate that release of the antibiotic is inhibited in aqueous buffer at pH 5, whereas the drug is released in a sustainable manner at pH 8. Importantly, the released drug was bacteriostatic against the Pseudomonas aeruginosa wound pathogen. In the future, incorporation of the delivery device into wound dressings could potentially be utilized for non-invasive decontamination of wounds.

2-D analytical modeling for electrostatic potential and threshold voltage of a dual work function gate Schottky barrier MOSFET

A two-dimensional analytical model for the surface potential and threshold voltage of a dual work function Schottky barrier (SB) MOSFET is presented. The developed model considers the effects of the varying gate metal work function, gate and drain voltages, and different doping concentrations, gate dielectric permittivity, and silicon thickness. For solving the electrostatic potential of the SB-MOSFET by using Poisson’s equation with appropriate boundary conditions, parabolic approximation has been considered. The proposed device has also incorporated the effect of barrier height lowering at the metal/semiconductor contacts. The results of our modeled surface potential and the threshold voltage, match with technology computer aided design simulations.

Dual problem of sorptive barrier design with a multiobjective approach

Sorptive barrier technology is a recently developed tool to separate hazardous contaminants from friendly environment. The design of sorptive barrier refers to configuring different amendments with sorptive ability of organic pollutant, which is an integer programming problem and a relatively time consuming problem as well. In this paper, sorptive barrier design is newly modeled in a biobjective optimization approach, in which the dual problem of sorptive barrier design is deduced. The objectives are to minimize the financial cost and the amount of pollutant leaking through barriers. Then an opposition-based adaptive multiobjective differential evolution algorithm (MODEA-OA) is applied to handle the proposed model. The Pareto optimal front obtained by MODEA-OA spreads accurately and evenly in all three instances tested. To select extreme optimal solutions, the original and dual sorptive barrier design problems can be solved simultaneously. This study suggests that modeling barrier design as a multiobjective optimization problem is an effective approach.

Associations Between Sex Education and Contraceptive Use Among Heterosexually Active, Adolescent Males in the United States

PurposeThis study examined associations between reports of receiving education on topics commonly included in sex education (e.g., abstinence only, comprehensive) prior to age 18 years and contraceptive use at the last sex among heterosexually active, 15- to 20-year-old males in the United States. MethodsCross-sectional data from 539 males participating in the 2011–2013 National Survey of Family Growth were analyzed. Bivariate and multinomial logistic regression analyses adjusting for confounding estimated associations between receipt of seven sex education topics (e.g., information on HIV/AIDS, how to say no to sex) and contraceptive use at the last sex (i.e., dual barrier and female-controlled effective methods, female-controlled effective method only, barrier method only, and no method). ResultsNearly, all participants (99%) reported receiving sex education on at least one topic. Education on sexually transmitted diseases (94.7%) and HIV/AIDS (92.0%) were the most commonly reported topics received; education on where to get birth control was the least common (41.6%). Instruction about birth control methods (adjusted odds ratio [AOR] = 3.01; 95% confidence interval [CI] = 1.32–6.87) and how to say no to sex (AOR = 3.39; CI = 1.33–8.64) were positively associated with dual contraception compared to no use. For each additional sex education topic respondents were exposed to, their odds of using dual methods compared to no method was 47% greater (AOR = 1.47; CI = 1.16–1.86). ConclusionsExposure to a larger number of sex education topics is associated with young men's report of dual contraception use at the last sex. Comprehensive sex education, focusing on a range of topics, may be most effective at promoting safer sex among adolescent males.

Pre-ozonation for high recovery of nanofiltration (NF) membrane system: Membrane fouling reduction and trace organic compound attenuation

This study demonstrated the use of nanofiltration (NF) membrane with pre-ozonation for surface water brine treatment. Pre-ozonation, used for fouling control, with relatively low ozone doses (0.1−0.4mgO3/mg DOC ratios) significantly reduced organic fouling potential. A classical pore blocking model revealed that the dominant fouling mechanism was cake filtration. Based on a statistical correlation test, macromolecules (apparent molecular weight >10kDa) of typtophan-like aromatic protein and soluble microbial-like matter exhibited strong correlation to fouling potential. Small molecules (<1600Da) of UV-absorbing matter were also correlated with fouling potential whereas bulk parameters such as SUVA displayed relatively lower correlation with fouling potential. Trace organic compound (TOrC) attenuation by ozone, membranes, and combination of ozone and membranes were also examined. Greater than 70% removal of the 17 TOrCs was achieved at 0.4mgO3/mg DOC ratio. The NF membrane (NF90) alone also could remove more than 90% of TOrCs. When pre-ozonation was performed with the NF membrane, all TOrCs tested were removed to less than the limits of detection. In conclusion, the application of pre-ozonation to NF membrane not only can alleviate organic fouling potential, but also can function as a dual barrier for ensuring removal of TOrCs for water treatment.

Evaluation of chitosan hydrochloride-alginate as enteric micro-probiotic-carrier with dual protective barriers

In this study, the cells-free and cells-loaded chitosan hydrochloride-alginate (CHC-Alg) microcapsules were firstly fabricated with polyelectrolyte complexes via an orifice-polymerization method. Scanning electron microscope images showed that the CHC-Alg microcapsules had a typical shell-core structure and the model probiotic cells (Bacillus licheniformis) were embedded in the core in cells-loaded microcapsules. The microcapsules prepared had good thermal stability and moisture property (3.89%). Cells survival and release studies showed that the number of probiotic cells released from the cells-loaded microcapsules (approx. 6.36logCFUml−1) was 6.19logCFUml−1 when they were performed in the simulated gastric fluid (SGF, pH 2.0) for 1h and subsequently in the simulated intestinal fluid (SIF, 0.3%) for 4h. The CHC-Alg microcapsules with favorable swelling performances were helpful to permeate the harsh acid to protect the cells in the SGF (pH 2.0). The CHC-Alg microcapsules effectively protected the model probiotic cells, which was attributed to the “dual protective barriers” of the shell-core structure, that is, the primary barrier of the Alg hydrogel layer formed with a compact polymer matrix and the secondary barrier of the PEC film formed on the surface. The microcapsules prepared could be used as an enteric micro-probiotic-carrier for designing potential probiotic delivery systems.

Protein adsorption capability on polyurethane and modified-polyurethane membrane for periodontal guided tissue regeneration applications

Periodontal disease if left untreated can result in creation of defects within the alveolar ridge. Barrier membranes are frequently used with or without bone replacement graft materials for achieving periodontal guided tissue regeneration (GTR). Surface properties of barrier membranes play a vital role in their functionality and clinical success. In this study polyetherurethane (PEU) membranes were synthesized by using 4,4′-methylene-diphenyl diisocyanate (MDI), polytetramethylene oxide (PTMO) and 1,4-butane diol (BDO) as a chain extender via solution polymerization. Hydroxyl terminated polydimethylsiloxane (PDMS) due to having inherent surface orientation towards air was used for surface modification of PEU on one side of the membranes. This resulting membranes had one surface being PEU and the other being PDMS coated PEU. The prepared membranes were treated with solutions of bovine serum albumin (BSA) in de-ionized water at 37°C at a pH of 7.2. The surface protein adsorptive potential of PEU membranes was observed using Attenuated Total Reflectance Fourier Transform Infrared Spectroscopy (ATR-FTIR), Raman spectroscopy and Confocal Raman spectroscopy. The contact angle measurement, tensile strength and modulus of prepared membranes were also evaluated. PEU membrane (89.86±1.62°) exhibited less hydrophobic behavior than PEU-PDMS (105.87±3.16°). The ultimate tensile strength and elastic modulus of PEU (27±1MPa and 14±2MPa) and PEU-PDMS (8±1MPa and 26±1MPa) membranes was in required range. The spectral analysis revealed adsorption of BSA proteins on the surface of non PDMS coated PEU surface. The PDMS modified PEU membranes demonstrated a lack of BSA adsorption. The non PDMS coated side of the membrane which adsorbs proteins could potentially be used facing towards the defect attracting growth factors for periodontal tissue regeneration. Whereas, the PDMS coated side could serve as an occlusive barrier for preventing gingival epithelial cells from proliferating and migrating into the defect space by facing the soft tissue flaps. This study demonstrates the potential of a dual natured PEU barrier membrane for use in periodontal tissue engineering applications and further investigations are required.

Measurement of Electron Density and Ion Collision Frequency with Dual Assisted Grounded Electrode DBD in Atmospheric Pressure Helium Plasma Jet**supported by National Natural Science Foundation of China (No. 11105093), the Technological Project of Shenzhen, China (No. JC201005280485A), and the Planned S&T Program of Shenzhen, China (No. JC201105170703A)

The properties of a helium atmospheric-pressure plasma jet (APPJ) are diagnosed with a dual assisted grounded electrode dielectric barrier discharge device. In the glow discharge, we captured the current waveforms at the positions of the three grounded rings. From the current waveforms, the time delay between the adjacent positions of the rings is employed to calculate the plasma bullet velocity of the helium APPJ. Moreover, the electron density is deduced from a model combining with the time delay and current intensity, which is about 1011 cm−3. In addition, The ion-neutral particles collision frequency in the radial direction is calculated from the current phase difference between two rings, which is on the order of 107 Hz. The results are helpful for understanding the basic properties of APPJs.

Chitosan Coagulation to Improve Microbial and Turbidity Removal by Ceramic Water Filtration for Household Drinking Water Treatment.

The use of porous ceramic filters is promoted globally for household water treatment, but these filters are ineffective in removing viruses from water. In order to increase virus removal, we combine a promising natural coagulant, chitosan, as a pretreatment for ceramic water filters (CWFs) and evaluate the performance of this dual barrier water treatment system. Chitosan is a non-toxic and biodegradable organic polymer derived by simple chemical treatments from chitin, a major source of which is the leftover shells of crustacean seafoods, such as shrimp, prawns, crabs, and lobsters. To determine the effectiveness of chitosan, model test water was contaminated with Escherichia coli K011 and coliphage MS2 as a model enteric bacterium and virus, respectively. Kaolinite clay was used to model turbidity. Coagulation effectiveness of three types of modified chitosans was determine at various doses ranging from 5 to 30 mg/L, followed by flocculation and sedimentation. The pre-treated supernatant water was then decanted into the CWF for further treatment by filtration. There were appreciable microbial removals by chitosan HCl, acetate, and lactate pretreatment followed by CWF treatment, with mean reductions (95% CI) between 4.7 (±1.56) and 7.5 (±0.02) log10 for Escherichia coli, and between 2.8 (±0.10) and 4.5 (±1.04) log10 for MS2. Turbidity reduction with chitosan treatment and filtration consistently resulted in turbidities < 1 NTU, which meet turbidity standards of the US EPA and guidance by the World Health Organization (WHO). According to WHO health-based microbial removal targets for household water treatment technology, chitosan coagulation achieved health protective targets for both viruses and bacteria. Therefore, the results of this study support the use of chitosan to improve household drinking water filtration processes by increasing virus and bacteria reductions.

Effects of wind barrier design and closed coal storage on spontaneous ignition of coal stockpiles

Effects of wind barrier design on spontaneous ignition of coal stockpiles are investigated numerically. A wind barrier changes air flow pattern around a stockpile and spontaneous heating is affected by design factors of a wind barrier. The distance between a wind barrier and a stockpile is selected as a design factor in the stockpile with both a single and a dual barriers and air blowing from the bottom of the stockpile is applied aerodynamically by installation of a wind barrier. As the distance increases, spontaneous ignition is accelerated slightly with a single barrier and significantly with a dual barrier. A dual barrier with longer distance than a critical one doesn't have retard effect any more compared with the stockpile without any barriers. Air blowing induced by a barrier installation is effective when wind speed is higher than a critical one, but partial air blowing is not. Air blowing should be made from the entire domain of the bottom. As a method to root out spontaneous ignition, i.e., free of self-ignition, a closed stockpile is proposed here. Spontaneous heating depends strongly on the size of the silo covering the pile and it is verified that a compact one with a small volume can suppress ignition completely, where maximum temperature in the pile increases initially and finally, falls down below a critical value for self-ignition.