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The production practices in Shendong mining area show that the CO concentration at the return air corner of shallow coal seams often exceeds the limit, but the temperature of the residual coal in the goaf has not significantly increased, and no other indicative gas of spontaneous combustion in coal seams has been detected. In order to provide scientific basis for CO management at the return air corner of the fully mechanized mining face in Shendong mining area and the prevention and control of coal seam spontaneous combustion fires, based on the "three zones" distribution parameters of spontaneous combustion of coal in goaf and the characteristic parameters of spontaneous combustion of coal, and based on the mechanism of CO production in shallow buried mining area, the source and influencing factors of CO in working face were analyzed, and the calculation model of CO concentration at the return air corner in working face was established. The concentrations of CO at the return air corner in different working faces in Shendong mining areas were calculated by using the model. The results showed that the relative error between the observed and measured values remained between 0.32% and 6.92%. The quantitative analysis of the proportion of CO production from each source to the total production of CO in the return air corner is of great significance to the effective control of CO concentration in the air return corner of the working face. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Once a fire breaks out in an electric bus, it can easily lead to mass casualties and severe injuries, resulting in significant property damage and social impact. The high-temperature smoke and toxic gases in an electric bus fire are key factors that cause a large number of casualties, both of which are closely related to ventilation conditions. In view of this, this study utilized the Fire Dynamics Simulator (FDS 6) software to establish a three-dimensional experimental model of an electric bus. Numerical simulations of the fire combustion process in the electric bus under different ventilation conditions were conducted. Multiple fire scenes were established based on varying ventilation areas, different wind speeds, and diverse window opening positions. This study specifically analyzed the temperature and CO concentration variations under different fire scenes. By comparing the simulation results under different ventilation conditions, it can be concluded that when an electric bus catches fire, opening 100% of the windows, the wind speed is 8 m/s, and opening the rear window of the electric bus first can minimize the fire risk. Through the numerical simulation of electric bus fires under various conditions, this study analyzed the impact of different ventilation conditions on electric bus fires, providing a theoretical basis for firefighting and rescue efforts as well as personnel evacuation in electric bus fire incidents, with the ultimate goal of maximizing public safety. [ABSTRACT FROM AUTHOR]

In the present study, premixed ammonia-methane combustion within a two-layer porous burner was investigated experimentally in order to evaluate the pollutant emissions. The effects of alumina spheres diameter, equivalence ratio and ammonia fraction on the flame stability limits, CO and NO pollutant emissions were considered. The tests were performed for equivalence ratios from 0.8 to 1, ammonia fraction from 20% to 80% and a range of alumina spheres diameters from 5 to 40 mm. Measurements illustrated that increasing the equivalence ratio improved the flame stability limits regardless of ammonia fraction while flame stability limits decreased with increasing the ammonia fraction. Results indicated that for the mixtures with ammonia content less than 50%, increasing ammonia fraction caused increase in NO emission regardless to the equivalence ratio, while for mixtures with ammonia fractions higher than 50%, the NO emission decreased slightly as ammonia content increased. Meanwhile, with increasing the ammonia fraction, CO concentration decreased at examined equivalence ratios. It was found that increasing equivalence ratio increased the NO emission, while CO concentration decreased as equivalence ratio increased. Measurements proved that decreasing the diameter of alumina spheres caused decrease of NO and CO quantities regardless to equivalence ratio. [ABSTRACT FROM AUTHOR]

This study estimates the steady-state performance of a proton exchange membrane fuel cell (PEMFC) under conditions of air depletion in the preferential oxidation reactor (PrOx) and fuel depletion at the anode, which has not been previously studied. Considering the detailed chemical reactions of the reforming process, the composition of the reformed gas at the anode inlet is determined using the temperature and pressure data measured at various state points in the PEMFC system. To calculate the voltage loss at the anode due to the air depletion in PrOx or reformate gas depletion before the anode, the electrochemical reaction of the reformed gas in the anode catalyst layer is studied. The calculations show that when the fuel entering the anode or air entering the PrOx decreases, the amount of CO at the anode increases depending on the reduction, resulting in activation loss at the anode, and thereby leading to power loss. This analysis of the power loss in a PEMFC due to a lack of air or fuel can serve as an auxiliary diagnostic tool to identify faulty parts in the Balance of Plant (BOP).

Mine fire is a very dangerous underground disaster. In order to better study the situation and influence range of mine fire, this paper uses Ventsim to establish a three-dimensional visual ventilation model of Yushuling coal mine. The fire simulation of coal mining face and central substation is carried out by simulation method to study the change law of CO concentration, visibility and temperature in different places. The results show that the CO concentration and visibility change greatly in the downstream of the fire source point when a fire occurs in the coal face; As for the temperature, the temperature at the fire source varies greatly, and the temperature below the inclined air shaft hardly changes; All of them show a decreasing trend with the increase of the distance from the fire source; In case of fire in central substation, there are great changes in all substances in the roadway before and after the air door is opened and closed; After the air door is closed, the CO concentration drops sharply, the change rate at the end of the fire is reduced, the end time is advanced to half of the original, the temperature change is relatively small, and the visibility remains low for a long time after the damper is closed and the recovery time is late. The research results have important guiding significance for the escape of underground fire.

In order to explore the indoor air quality during different cooking procedures, a very common kitchen in China is selected for experimental research. An indoor air quality meter is used to measure the temperature, relative humidity, and CO and CO2 concentrations of the indoor air above the stove when people cook four different dishes under different ventilation patterns in the kitchen. The results indicate that the heat and gas consumed during cooking are closely related to the temperature and concentrations of CO and CO2. Some cooking procedures such as boiling water are related to the indoor air temperature and relative humidity in the kitchen. In addition, in kitchens without mechanical ventilation, natural ventilation shows a more significant positive effect on controlling temperature, relative humidity, and concentrations of CO and CO2 during cooking procedures. [ABSTRACT FROM AUTHOR]

The increasing quantity of air pollutants generated by automobiles can cause significant harm in relatively enclosed indoor environments. Studying the distribution of pollutants under different conditions in underground parking garages is of great significance for improving indoor air quality and reducing casualties in the event of a fire. This article presents a geometric model of an underground parking garage based on PHOENICS modeling. The related results of CO concentration distribution and fire temperature distribution under ventilation and fire conditions are obtained. Based on the CO concentration and velocity distribution as well as the temperature distribution during a fire, reasonable suggestions are proposed to improve indoor air quality and reduce casualty rates in fire incidents. The results show that under ventilation conditions, adjusting the position of the induced ventilation fan can maintain CO concentrations below 30 ppm in partitions one to three and below 37 ppm in partitions four to six. The temperature of smoke gases remained below 50 °C during the evacuation time, and only a small area exhibited CO levels exceeding 2000 ppm. The existing ventilation exhaust system provides effective fire protection, as it minimally affects personnel evacuation due to the relatively lower smoke temperature. [ABSTRACT FROM AUTHOR]

Copyright of Mining & Metallurgy (10057854) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Single-ended tunnels are a typical structure and an important part during tunnel construction. In the case of a fire in a single-ended tunnel, forced ventilation is commonly used to create a safe area near the excavation face. This work is aimed at examining the effects of fire location and air volume on fire development for single-ended tunnel fires with forced ventilation. A single-ended tunnel was built in Fire Dynamics Simulator (FDS), and twenty simulation tests were carried out. In the simulation, the distribution of flow field, temperature, and CO concentration in the tunnel were measured and analyzed. The results show that three regions can be identified based on airflow directions and velocity: (1) turbulent flow zone, (2) turbulent flow transition zone, and (3) steady flow zone. It was found that the maximum ceiling temperature rise decreases first with the distance between the fire source and the excavation face (XL), and then increases with a further increase in XL. The simulation results also showed that CO can easily accumulate on the ventilation duct side at the fire source position and the opposite side of the ventilation duct 5.0–15.0 m downstream of the fire source. Both the CO concentration and the maximum ceiling temperature rise decrease with increasing air volume, while the larger forced air volume will result in a higher risk for the downstream regions. The present results are of practical importance in firefighting and personnel evacuation in single-ended tunnels with a forced ventilation system. [ABSTRACT FROM AUTHOR]

Japan and Europe have adopted significantly different ventilation modes with regard to traffic conditions (with or without congestion). This study focuses on the smoke behavior of different ventilation modes by conducting a 3D CFD analysis of smoke distribution and CO concentration variation and then comparing these modes based on two groups (relatively low target velocity: 0 and 1 m/s; relatively high target velocity: 2 and 3 m/s). The considered fire size is 30 MW for four longitudinal gradients (0, 2, 4, and 6%). In the simulation results, velocities of both 0 and 1 m/s reveal good performance in maintaining the stratification of smoke and ensuring the safety of the environment in 10 min in the occurrence of traffic jams. However, in 15 min, the smoke conditions change. Thus, it is difficult to distinguish which ventilation mode (0 and 1 m/s) shows relatively better performance during traffic congestion. When traffic is uncongested, the comparison of Um = 2 and 3 m/s reveals that a target velocity of Um = 2 m/s (lower than critical velocity) can also prevent the risk of smoke on the upstream side because no descending phenomenon is observed. Moreover, Um = 2 m/s causes the relatively slow propagation of descending smoke, increasing the possibility of evacuation once a second traffic incident occurs on the downstream side of the fire source. [ABSTRACT FROM AUTHOR]

Efficient tunnel ventilation is essential for ensuring construction safety and protecting personnel health during tunnel construction. This study proposes a demand-controlled ventilation (DCV) method on the basis of deep learning algorithm to both improve pollutant removal efficiency and reduce energy consumption. The DCV method utilizes a two-layer bidirectional long short-term memory algorithm (BiLSTM) to predict pollutant concentrations. The air volume is dynamically adjusted based on the gaseous pollutant removal requirements. The coefficient of ventilation performance (COVP) is proposed to evaluate the performance of two ventilation methods (DCV and constant air-volume ventilation (CAV)) through computational fluid dynamics (CFD) simulations. The results show that the DCV results in a lower maximum average CO concentration and higher removal efficiency in the heading area (372.3 mg/m3) than the CAV does (404.1 mg/m3). The fan's energy consumption of DCV is 64.6% lower than that of CAV during a 1000 s ventilation period. The COVPs for both methods exhibit temporal variation and achieves their maximums (2.25 for DCV and 0.741 for CAV) after reaching the constraint conditions (air volume threshold). The DCV method expedites pollutant elimination, reduces construction waiting period, and minimizes energy consumption, providing a novel application of a deep learning algorithm in construction engineering. • Demand-controlled ventilation method (DCV) based on the BiLSTM algorithm. • The ventilation time of DCV is 62 s shorter than the current ventilation method. • The DCV method results in a 64.6% decrease in fan energy consumption at 1000 s. • The COVPs for both methods are 2.25 (DCV) and 0.741 (constant air-volume). • DCV offers a new decontaminating and energy-saving route for engineering practice. [ABSTRACT FROM AUTHOR]

Objectives: The SARS-CoV-2 pandemic has forced choirs to pause or at least to restrict rehearsals and concerts. Nevertheless, an uncertainty about the risks of infection while singing remains, especially with regard to distances, duration of singing, number of singers and their positions in the room, size of the room as well as ventilation strategies. Based on the assumption that CO 2 is a suitable indicator for the exhaled aerosols in a room, it is the aim of this study to deduce recommendations for a choir rehearsal with a minimum risk of infection., Methods: During two choir rehearsals in a typical, nonventilated classroom, we installed 30 CO 2 sensors, which allow spatial and temporal evaluation of the CO 2 dispersion during singing. Various singing and ventilation phases were applied and the rates of CO 2 increase during singing as well as its decrease during ventilation phases were evaluated and compared for different scenarios., Results: The measurements reveal a linear relation between the duration of singing, size of the room and number of persons. For our size of the room of 200 m 3 the average CO 2 increase is 1.83 ppm/min per person. Masks or pure breathing without singing do - in contrast to aerosol dispersion - not influence the rate of CO 2 increase. CO 2 disperses fast and homogeneously on horizontal planes. However, a vertical layering with a maximum CO 2 concentration is observed near the ceiling. Shock ventilation shows the largest CO 2 decrease within the first 5 min, after 10 min of ventilation the outside base concentration of 400 ppm is reached again., Conclusion: The evaluated relations allow to calculate safe singing times for a defined number of singers and size of the room until a critical threshold of 800 ppm is reached. Furthermore, in order to monitor the actual CO 2 concentration during choir rehearsal, just one CO 2 sensor is representative for the air quality and CO 2 concentration of the whole room and thus considered sufficient. For an early warning, it should be installed near the ceiling. Direct singing into a sensor should be avoided. A ventilation time of just 5 min is recommended which represents a compromise between strong CO 2 reduction and still sufficient room temperature during winter time., (Copyright © 2022 The Authors. Published by Elsevier Inc. All rights reserved.)

The increasing quantity of air pollutants generated by automobiles can cause significant harm in relatively enclosed indoor environments. Studying the distribution of pollutants under different conditions in underground parking garages is of great significance for improving indoor air quality and reducing casualties in the event of a fire. This article presents a geometric model of an underground parking garage based on PHOENICS modeling. The related results of CO concentration distribution and fire temperature distribution under ventilation and fire conditions are obtained. Based on the CO concentration and velocity distribution as well as the temperature distribution during a fire, reasonable suggestions are proposed to improve indoor air quality and reduce casualty rates in fire incidents. The results show that under ventilation conditions, adjusting the position of the induced ventilation fan can maintain CO concentrations below 30 ppm in partitions one to three and below 37 ppm in partitions four to six. The temperature of smoke gases remained below 50 °C during the evacuation time, and only a small area exhibited CO levels exceeding 2000 ppm. The existing ventilation exhaust system provides effective fire protection, as it minimally affects personnel evacuation due to the relatively lower smoke temperature.

Carbon monoxide (CO) is the main component of vehicle exhaust in highway tunnels, which is one of the important parameters for the design of ventilation in road tunnels. It is very necessary to predict the CO concentration accurately and quickly to provide a reference for tunnel ventilation system control and mitigating the concentration of CO timely and to ensure the health and safety of the people in the tunnel. At the same time, it is beneficial to the green and energy-saving operation of the tunnel. Based on the field monitoring data of the road tunnel, random forest (RF) model of CO concentration prediction was established with the four influencing factors, i. e., monitor position, traffic, vehicle speed, wind speed. The model was employed to predict the concentration of CO in a 3 300-long road tunnel and the predictive values were compared with the real values. The results show that the CO concentration prediction model based on Random Forest has good prediction accuracy, which can predict the concentration of CO accurately. The RMSE and R 2 of the testing dataset is 0. 497 4 and 0. 943 7, respectively, which is significantly better than those of the linear regression model and support vector machine (SVM) model. The prediction model can be extended to predict the CO concentration of another tunnel. The RMSE and R 2 of the validation dataset is 0. 909 5 and 0. 729 5, respectively. That is, the CO concentration in the tunnel can be predicted under the condition of known monitor position, traffic, vehicle speed, wind speed. The model provides a reference for tunnel ventilation system control or safety warning. The position of monitor point has the greatest influence on the CO concentration in the tunnel, and the CO gas concentration is the highest at the exit of the tunnel. With the increase of wind speed, the concentration of CO gas in the tunnel gradually decreases. [ABSTRACT FROM AUTHOR]

The shallow thick coal seam in the western mine area in China usually adopts the extraction ventilation method. The surface air leakage makes the wind flow disorderly, and the oxygen of the air penetrates the goaf and interacts with the residual coal in goaf to oxidize the coal. Therefore, the coal spontaneous combustion is likely to occur, and the harmful gas such as carbon monoxide exceeds the standard, causing seriously effects on the normal mining of the mine. At present, field measurements, theoretical analysis and experimental research methods are generally used to analyze the gas concentration field and temperature field of coal spontaneous combustion in goaf caused by surface air leakage. However, the spontaneous combustion experiment of surface air leakage is relatively complex. It is difficult to use theoretical analysis and experimental research methods to obtain the influence law of surface air leakage on coal spontaneous combustion in goaf from a three-dimensional perspective.In order to solve the above problems, according to the characteristics of shallow thick coal seam in northwest China, a three-dimensional numerical calculation model is established. Combined numerical simulation and field measurement methods are used to analyze the distribution of 'three zones' in the surface air leakage goaf area of shallow thick coal seam. The methods also analyze the distribution law of O2 concentration field, CO concentration field, temperature field and pressure field in goaf under different working conditions. Moreover, the field validation is carried out by the ZD5 coal mine fire multi-parameter monitoring device. The results show that the distribution of the 'three zones' and the O2 concentration field in goaf are greatly affected by the surface air leakage. It is found that O2 is easily accumulated at the top of the goaf, which changes the gas flow field distribution in goaf. The concentration range of high volume fraction O2 (volume fraction 18%-23%) in goaf is 0-270 m along the strike direction of the goaf and 3-20 m along the vertical direction of the goaf. In particular, O2 is sufficient in the range of 0-80 m along the strike direction of the goaf and 3-8 m along the vertical direction of the goaf. In this area, there is a certain amount of residual coal and heat is not easily dissipated, raising the risk of coal spontaneous combustion. The pressure at the corner of return air roadway in goaf is the smallest, -10 Pa, the pressure at the return air roadway outlet is the lowest, and the pressure at the air inlet is the highest. The pressure gradually increases along the inclined direction, the vertical direction and the strike direction. The temperature distribution is similar to the CO distribution in goaf. The goaf floor is little affected by the air leakage from the surface, but largely affected by the corner of the intake air roadway of the working face. The heat accumulation and CO accumulation are basically the same as the situation of no air leakage. From the middle of the goaf, the temperature and CO are mainly affected by the surface air leakage, presenting an 'O' ring distribution. At the top of the goaf,the temperature and CO reach maximum values at the junction of each fracture zone and the goaf, then decrease along both sides. The maximum value appears at the junction of the deepest fracture zone and the goaf.

ABSTRAK Terminal Arjosari merupakan terminal terpadu di Kota Malang. Aktivitas kendaraan bermotor seperti bus dan motor, menghasilkan emisi gas buang kendaraan berupa karbon monoksida (CO) yang berpotensi meningkatkan pencemaran udara di terminal tersebut. Penelitian kualitas udara di Terminal Arjosari dilakukan untuk mengetahui kadar konsentrasi CO di terminal tersebut dan pengaruh jumlah kendaraan serta kecepatan angin terhadap konsentrasi CO. Pengambilan sampel dilakukan dengan menggunakan metode purposive sampling dengan titik samplingyang berlokasi di pintu masuk bus (PMB) dan pintu masuk mobil pribadi (PMM). Pengambilan sampel dilakukan pada pagi, siang, dan sore hari di 3 hari yang berbeda. Hasil pengukuran menunjukkan bahwa konsentrasi CO cenderung lebih tinggi pada pagi hari di PMB dan PMM. Konsentrasi CO berdasarkan titik pengambilan sampel memiliki perbedaan yang signifikan. Berdasarkan Peraturan Pemerintah Nomor 41 Tahun 1999 dan Peraturan Gubernur Jawa Timur Nomor 10 Tahun 2009, konsentrasi CO yang didapatkan berada di bawah baku mutu. Jumlah kendaraan memiliki pengaruh sebesar 71.35% terhadap konsentrasi CO pada PMB dengan hubungan yang berbanding lurus sedangkan pada PMM sebesar 59.63%. Kecepatan angin mempengaruhi konsentrasi CO sebesar 61.68% diPMB dan sebesar 42.28% di PMM dengan hubungan yang berbanding terbalik. Kata kunci: konsentrasi CO, pintu masuk bus, pintu masuk mobil pribadi ABSTRACT Arjosari Terminal is an integrated terminal in Malang City. Motorized vehicle activities, such as bus and motorcycles, produce vehicle exhaust emissions in a form of carbon monoxide (CO) which has the potential to increase air pollution. Air quality research needs to be carried out to determine the level of CO concentration in the terminal and the effects of wind speed and number of vehicles to CO concentration. Sampling was carried out using the purposive sampling method with sampling point is the entrance of the bus (PMB) and the entrance of private cars (PMM). Sampling was carried out in the morning, afternoon, and evening on 3 different days. The results show that CO concentrations tend to be higher in the morning at PMB and PMM. The CO concentration based on the sampling point has a significant difference. Based on Government Regulation No. 41/1999 and East Java Governor Regulation No 10/2009, CO concentrations obtained are below the quality standard. The number of vehicles has an influence of 71.35% on CO concentrations at PMB and 59.63% at PMM with a directly proportional relationship. Wind speed affects the concentration of CO by 61.68% at PMB and 42.28% at PMM with an inverse relationship. Keywords : CO concentration, bus entrance, private cars entrance

Single-ended tunnels are a typical structure and an important part during tunnel construction. In the case of a fire in a single-ended tunnel, forced ventilation is commonly used to create a safe area near the excavation face. This work is aimed at examining the effects of fire location and air volume on fire development for single-ended tunnel fires with forced ventilation. A single-ended tunnel was built in Fire Dynamics Simulator (FDS), and twenty simulation tests were carried out. In the simulation, the distribution of flow field, temperature, and CO concentration in the tunnel were measured and analyzed. The results show that three regions can be identified based on airflow directions and velocity: (1) turbulent flow zone, (2) turbulent flow transition zone, and (3) steady flow zone. It was found that the maximum ceiling temperature rise decreases first with the distance between the fire source and the excavation face (XL), and then increases with a further increase in XL. The simulation results also showed that CO can easily accumulate on the ventilation duct side at the fire source position and the opposite side of the ventilation duct 5.0–15.0 m downstream of the fire source. Both the CO concentration and the maximum ceiling temperature rise decrease with increasing air volume, while the larger forced air volume will result in a higher risk for the downstream regions. The present results are of practical importance in firefighting and personnel evacuation in single-ended tunnels with a forced ventilation system.

Japan and Europe have adopted significantly different ventilation modes with regard to traffic conditions (with or without congestion). This study focuses on the smoke behavior of different ventilation modes by conducting a 3D CFD analysis of smoke distribution and CO concentration variation and then comparing these modes based on two groups (relatively low target velocity: 0 and 1 m/s; relatively high target velocity: 2 and 3 m/s). The considered fire size is 30 MW for four longitudinal gradients (0, 2, 4, and 6%). In the simulation results, velocities of both 0 and 1 m/s reveal good performance in maintaining the stratification of smoke and ensuring the safety of the environment in 10 min in the occurrence of traffic jams. However, in 15 min, the smoke conditions change. Thus, it is difficult to distinguish which ventilation mode (0 and 1 m/s) shows relatively better performance during traffic congestion. When traffic is uncongested, the comparison of Um = 2 and 3 m/s reveals that a target velocity of Um = 2 m/s (lower than critical velocity) can also prevent the risk of smoke on the upstream side because no descending phenomenon is observed. Moreover, Um = 2 m/s causes the relatively slow propagation of descending smoke, increasing the possibility of evacuation once a second traffic incident occurs on the downstream side of the fire source.

Background: The mental and physical comfort of students in the classroom is very important because it affects students’ learning. The structure of negative emotional states, including stress, anxiety, and depression is influenced by the building environment and its physical features. Objectives: The present study aimed to survey the relationship between ventilation by window opening and female student’s stress, anxiety, and depression in high school classrooms. Methods: The current study was conducted as a quasi-experimental method, using pre-test and post-test with the control group. Statistical population of this study was female students studying at Shiraz high schools during 2016 - 2017. A total of 384 students were selected randomly using Cochran’s formula for participation in the study. The students in 14 classrooms were divided into two groups of intervention and control. The pre-test was used for assessing stress, anxiety, and depression in DASS-21 questionnaires. The intervention group was then allowed to improve the air quality for 6 weeks by opening the window in the classroom. However, this discretion was not given to students in the control group. After 6 weeks of post-test, DASS 21 questionnaire was used. Results: The mean stress score in the intervention group was 20.36 ± 4.326 at pre-test and 19.91 ± 5.162 at post-test and in the control group was 20.28 ± 5.348 at pre-test and 19.91 ± 5.162 at post-test. The mean anxiety score in the intervention group was 20.15 ± 4.705 at pre-test and 18.55 ± 4.673 at post-test and in the control group was 19.12 ± 5.272 at pre-test and 18.92 ± 5.0 at post-test. Also, the mean depression score in the intervention group was 18.29 ± 4.878 at pre-test and 18.53 ± 4.750 at post-test and in the control group was 17.83 ± 5.501 at pre-test and 17.28 ± 5.375 at post-test. Ventilation by window opening could significantly decrease the level of stress (P < 0.001) and anxiety (P < 0.001) but no significant difference was observed in depression (P = 0.067). Conclusions: Ventilation by window opening in the classroom could reduce the stress and anxiety of female high school students in eight weeks, but did not affect the level of depression.

The toxicity of CO threatens the life of people in the fire site. In this study, flame retardants of nano magnesium hydroxide particles and water-soluble flame retardant 8124 are used to be mixed into the aqueous film forming fire extinguishing agent (AFFF). Smoke-suppressed fire extinguishing agent was prepared in Waring-Blender mixing cup and then stirred at 3,000 r/min for 5 min. The new extinguishing agent shows a good performance of absorption of CO and reducing the flue gas temperature. The concentration of CO was decreased below 131 ppm and flue gas temperature was basically kept below 40°C, which was 367 ppm and 83.1°C less than that in free-fire. Using new extinguishing agent can effectively reduce the harm to the trapped personnel and firemen in the fire site. It was of great significance. The harm of CO concentration below 131 ppm and flue gas temperature below 40°C was low. The time to reach the maximum CO concentration and the maximum flue gas temperature was delayed, which ensures that people have more time to escape. Even if there was not enough time to escape, people will not be seriously threatened.

The M-regression estimator has recently been widely used to build spectral estimators in time series models. In this paper, we extend this approach when the data follow a periodic autoregressive moving average process. We introduce an estimator of the parameters based on the classical Whittle estimator. The finite sample size performances of the proposed estimator are analyzed under the scenarios of PARMA processes with and without additive outliers. Under the non-contaminated scenario, our estimator and the maximum Gaussian and Whittle likelihood estimators have similar behaviors. However, in the contaminated case, the two last estimators are severely biased, while the proposed estimator is robust. As a real data application, carbon monoxide concentrations are analyzed. A PARMA model is fitted and the data are forecasted with the model. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fire smoke is one of the most important factors causing casualties, but also has the potential to bring some harm to the surrounding environment. In this work, the longitudinal temperature profile and the pollutant toxicity of a ceiling jet induced by a wall-attached fire with different tunnel slopes, were numerically and experimentally investigated by using a 1:8 reduced-scale inclined tunnel. The results show that for a given heat release rate (HRR), the flame extension is longer and the temperature decay is slower in ceiling jets induced by a wall-attached fire than for similar free-burning fires, because the air entrainment is restricted by the tunnel side walls. Further, the uphill pollutant toxicity was found to be higher with greater HRR and lower tunnel slope. Finally, a correlation between the non-dimensional longitudinal smoke temperature and CO concentration could be established for the inclined tunnel fire. • Longer flames and higher temperatures are induced by a wall-attached fire compared to a free-burning fire. • The pollutant toxicity is analyzed and discussed as a function of the tunnel slope. • A correlation between temperature and CO concentration in an inclined tunnel is proposed. [ABSTRACT FROM AUTHOR]

• The interface reaction on the Sn-0.7Cu-10Bi-0.15Co/Co couple was studied. • The Co diffusion was inhibited and Co concentration reduced on the interface. • The dynamic equilibrium of IMCs growth and dissolution is broken. • Driven by adsorption force, the IMCs particles reassemble and grow. The interface reaction between the Sn-0.7Cu-10Bi-0.15Co and Co substrate during multiple reflow cycles and the growth and evolution rhythm of intermetallic compounds (IMCs) were investigated. The results showed that as the reflow cycles increased in number, different growth morphologies and evolution rules of the IMCs layer including its primary growth, dissolution and secondary growth appeared. In the primary stage of multiple reflows, Co could be continuously diffused from the Co substrate to the IMCs/solder interface to provide enough Co for the growth of IMCs layer. As the IMCs layer became thick, the diffusion of Co to the interface was inhibited, and the dynamic equilibrium of IMCs growth was broken. When the growth rate was higher than the dissolution rate, the IMCs layer grew as a whole and whereas the IMCs were dissolved. And under the action of adsorption force, the dissolved IMCs particles re-aggregated and grew. [ABSTRACT FROM AUTHOR]

In a tunnel fire, the production of smoke and toxic gases remains the principal prejudicial factors to users. The heat is not considered as a major direct danger to users since temperatures up to man level do not reach tenable situations that after a relatively long time except near the fire source. However, the temperatures under ceiling can exceed the thresholds conditions and can thus cause structural collapse of infrastructure. This paper presents a numerical analysis of smoke hazard in tunnel fires with different aspect ratio by large eddy simulation. Results show that the CO concentration increases as the aspect ratio decreases and decreases with the longitudinal ventilation velocity. CFD predicted maximum smoke temperatures are compared to the calculated values using the model of Li et al. and then compared with those given by the empirical equation proposed by kurioka et al. A reasonable good agreement has been obtained. The backlayering length decreases as the ventilation velocity increases and this decrease fell into good exponential decay. The dimensionless interface height and the region of bad visibility increases with the aspect ratio of the tunnel cross-sectional geometry.

Highlights • Vehicle fire experiments carried out in a full-scale model tunnel. • The distribution of the smoke layer height obeyed a quartic polynomial trend. • The dominant factor driving smoke flow was the buoyancy or ventilation state. • At 60 m from the fire source, the CO concentration had decayed by 50%. Abstract To research the smoke flow patterns and their effects on personnel evacuation during a tunnel fire, a full-scale model of an immersed 150 m tunnel was constructed, taking the Hong Kong–Zhuhai–Macao Bridge immersed tunnel in China as the prototype. A series of fire tests, including pool fires and vehicle fires, were developed to simulate a real fire scenario. The characteristic parameters describing the smoke flow were measured, including smoke layer height, smoke spread velocity, and CO concentration. Their development behaviors and main influence factors were explored, and finally smoke flow patterns were examined. The results showed that smoke stratification appeared, which was measured by smoke layer height. The smoke layer height distribution along the tunnel was found to obey a quartic polynomial trend (goodness of fit > 95%). From this, the safety distances were predicted to be 20 m in windy conditions and 80–90 m in still (no wind) conditions. Thus, the longitudinal velocity plays a leading role. Around the fire source or in still conditions, the buoyancy of the smoke is the critical factor driving smoke flow; the influence of other factors is no more than ±20%. However, other conditions depended on the ventilation state. CO concentration decreased sharply with increasing distance from the fire source. At a distance of 60 m, CO concentration decayed by 50%. [ABSTRACT FROM AUTHOR]

Copyright of Renewable Energy / Vidnovluvana Energetyka is the property of Institute of Renewable Energy of NAS of Ukraine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Copyright of Journal of Engineering for Thermal Energy & Power / Reneng Dongli Gongcheng is the property of Journal of Engineering for Thermal Energy & Power and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper presents a study on rapid hardening behaviors of β-CS by accelerated carbonation curing. β-CS cubes compacted at various molding pressures were subjected to different CO concentration for accelerated carbonation curing. The CO uptake and microstructure changes were analyzed by thermogravimetric analysis (TG), QXRD, FT-IR and MAS-NMR. The results indicated that CO uptake was affected by molding pressure and CO concentration seriously. TG analysis indicated that the carbonation reaction was rapid in the first hour. The carbonation degree reached 21.6% and giving a compressive strength of 85.7 MPa after 6 h carbonation in 99.9% CO concentration. And it showed a much less carbonation degree in 20.0% CO. Calcite, vaterite and amorphous silica-rich phase formed in the carbonation progress. The FT-IR and NMR analysis indicated β-CS was decalcified to C-S-H gel and further decalcified to formation of an amorphous silica gel composed of Q and Q silicate tetrahedral. The chain length of C-S-H gel increased from to 2.67 to 6.36 with prolonged carbonation time, showing a lower C/S ratio and higher polymerization and also resulting in a lower C-S-H content. [ABSTRACT FROM AUTHOR]

In this study, the effect of CO concentration and ambient relative humidity (RH) on accelerated and natural carbonation of 18 concrete mixtures produced with nine different cement types is investigated. Increasing the CO concentration from 0.045 to 1 and 4 % at 57 % RH does not alter the relative carbonation resistance between the concrete mixtures. The increase of RH from 57 to 70 and 80 % RH at 4 % CO shows a water-to-cement ratio and cement-specific effect that affects the relative carbonation resistance between the concrete mixtures. The carbonation resistance at 4 % CO and 57 % RH allows assessing the carbonation resistance of concrete in sheltered and with restrictions in unsheltered outdoor exposure. The carbonation resistance below 70 % RH is mainly governed by the CO buffer capacity. However, in the accelerated tests at 80 % RH and in the unsheltered outdoor exposure capillary condensation is of increased importance. [ABSTRACT FROM AUTHOR]

CO concentrations in different plant communities (larch, birch, lilac, and grassland) were measured during the growing season in the Heilongjiang Forest Botanical Garden to study diurnal variation, seasonal and annual dynamics and factors that impact CO concentration in different spaces. CO concentration in different communities in green lands had an obvious diurnal variation, chronically decreasing, and temperature influenced the lilac area and the grassland. Seasonally, CO was lowest in the larch green land (344.03 ± 23.03 μmol/mol) and highest in the grassland (360.13 ± 22.43 μmol/mol). The overall trend in CO concentration was autumn > spring > summer; temperature is the main factor controlling variation in CO concentrations during the growing season; the CO concentration at the larch, birch, lilac, and grassland types of sites was negatively correlated with land surface temperature and air temperature, and the CO concentration at the larch and birch sites was positively correlated with atmospheric pressure. Without any obvious annual change law, further study and observation are needed. [ABSTRACT FROM AUTHOR]