Vent Opening Research Articles

A Simulation of the Broiler Growth Rate Using Artificial Neural Networks

To simulate the broiler growth the input variables were: day of year, vents opening, wind velocity, external temperature and absolute humidity, the maximum, average and minimum of the internal temperature and absolute humidity. For that purpose, two techniques were applied, a multi-layer perceptron (MLP) static Neural Network (NN) and the Layered Digital Dynamic Network (LDDN) which were applied to a set of experimental data obtained from a broiler cycle of production. The performance for both techniques was compared using: mean squared error (MSE), mean absolute error (MAE) and model efficiency (EF). The model evaluation measurements showed the superiority of the LDDN compared with MLP. The results from the sensitivity analysis found that the variable day of year was the most important variable to predict the broiler growth rate, so using this variable as the only input variable in the model, efficiency of 0.995 was reached for simulation.

전산유체역학을 통한 간척지 내 벤로형 온실의 자연환기량 분석

Recently, the Korean government announced a new development plan for a large-scale greenhouse complex in reclaimed lands. Wind environments of reclaimed land are entirely different from those of inland. Many standard books for ventilation design didn't include qualitative standard for natural ventilation. In this study, natural ventilation rates were analyzed to suggest standard for ventilation design of venlo type greenhouse built on reclaimed land. CFD (Computational Fluid Dynamics) simulation models were designed according to the number of spans, wind conditions and vent openings. The wind profile at a reclaimed land was designed using ESDU (Engineering Sciences Data Unit) code. Using the designed CFD simulation model, ventilation rates were computed using mass flow rate and tracer gas decay method. Additionally computed natural ventilation rates were evaluated by comparing with ventilation requirements. As a result of this study, ventilation rates were decreased with increasing of the number of spans. Ventilation rates were linearly increased with increasing of wind speed. When the wind speed was , only side vent was open and wind direction was , homogeneity of ventilation rate at 0~1 m height is the worst. Finally, chart for computing natural ventilation rate was suggested. The chart was expected to be used for establishing standard of ventilation design.

Insight into Vent Opening Probability in Volcanic Calderas in the Light of a Sill Intrusion Model

The aim of this paper is to discuss a novel approach to provide insights on the probability of vent opening in calderas, using a dynamic model of sill intrusion. The evolution of the stress field is the main factor that controls the vent opening processes in volcanic calderas. On the basis of previous studies, we think that the intrusion of sills is one of the most common mechanism governing caldera unrest. Therefore, we have investigated the spatial and temporal evolution of the stress field due to the emplacement of a sill at shallow depth to provide insight on vent opening probability. We carried out several numerical experiments by using a physical model, to assess the role of the magma properties (viscosity), host rock characteristics (Young’s modulus and thickness), and dynamics of the intrusion process (mass flow rate) in controlling the stress field. Our experiments highlight that high magma viscosity produces larger stress values, while low magma viscosity leads to lower stresses and favors the radial spreading of the sill. Also high-rock Young’s modulus gives high stress intensity, whereas low values of Young’s modulus produce a dramatic reduction of the stress associated with the intrusive process. The maximum intensity of tensile stress is concentrated at the front of the sill and propagates radially with it, over time. In our simulations, we find that maximum values of tensile stress occur in ring-shaped areas with radius ranging between 350 m and 2500 m from the injection point, depending on the model parameters. The probability of vent opening is higher in these areas.

Lava flow hazards—An impending threat at Miyakejima volcano, Japan

Abstract The majority of the historic eruptions recorded at Miyakejima volcano were fissure eruptions that occurred on the flanks of the volcano. During the last 1100 years, 17 fissure eruptions have been reported with a mean interval of about 76–78 years. In the last century, the mean interval between fissure eruptions decreased to 21–22 years, increasing significantly the threat of lava flow inundations to people and property. Here we quantify the lava flow hazards posed by effusive eruptions in Miyakejima by combining field data, numerical simulations and probability analysis. Our analysis is the first to assess both the spatiotemporal probability of vent opening, which highlights the areas most likely to host a new eruption, and the lava flow hazard, which shows the probabilities of lava-flow inundation in the next 50 years. Future eruptive vents are expected in the vicinity of the Hatchodaira caldera, radiating from the summit of the volcano toward the costs. Areas more likely to be threatened by lava flows are Ako and Kamitsuki villages, as well as Miike port and Miyakejima airport. Thus, our results can be useful for risk evaluation, investment decisions, and emergency response preparation.

Remote sensing and petrological observations on the 2012–2013 fissure eruption at Tolbachik volcano, Kamchatka: Implications for reconstruction of the eruption chronology

Abstract We present a reconstruction of the chronological sequence of events that took place during the first days of the 2012–2013 Tolbachik fissure eruption using petrological data and remote sensing methods. We were forced to use this approach because bad weather conditions did not allow direct observations during the first two days of the eruption. We interpreted infrared images from the scanning radiometer VIIRS Suomi NPP and correlated the output with the results of the geochemical study, including comparison of the ash, deposited at the period from 27 to 29 November, with the samples of lava and bombs erupted from the Menyailov and Naboko vents. We argue that the compositional change observed in the eruption products (the decrease of SiO 2 concentration and K 2 O/MgO ratio, increase of MgO concentration and Mg#) started approximately 24 h after the eruption began. At this time the center of activity moved to the southern part of the fissure, where the Naboko group of vents was formed; therefore, this timeframe also characterizes the timing of the Naboko vent opening. The Naboko group of vents remained active until the end of eruption in September 2013.

The tadpoles of the hylid frogs (Anura: Hylidae: Hypsiboas and Osteopilus) of Hispaniola

Hispaniolan hylid frogs are represented by four endemic species: Hypsiboas heilprini, Osteopilus dominicensis, O. pulchrilineatus and O. vastus. There are two tadpole ecomorphs represented in the hylid frogs of Hispaniola: lentic (O. dominicensis and O. pulchrilineatus) and lotic (H. heilprini and O. vastus). Tadpoles of the four species may be found sympatrically, but in different microhabitats. Hispaniolan hylid tadpoles reach a moderate size (up to 57 mm in total length is recorded in H. heilprini), and differ from those of Peltophryne, Rhinella, Leptodactylus and Lithobates (the other genera with free-living larvae present on the island), by having the oral discs not emarginated and, from the first three taxa, by a dextral vent opening. Oral deformities observed in most tadpoles of H. heilprini from Ébano Verde, Cordillera Central, were caused by the chytrid fungus Batrachochytrium dendrobatidis. An identification key is also provided.

Shifts in the eruptive styles at Stromboli in 2010-2014 revealed by ground-based InSAR data.

Ground-Based Interferometric Synthetic Aperture Radar (GBInSAR) is an efficient technique for capturing short, subtle episodes of conduit pressurization in open vent volcanoes like Stromboli (Italy), because it can detect very shallow magma storage, which is difficult to identify using other methods. This technique allows the user to choose the optimal radar location for measuring the most significant deformation signal, provides an exceptional geometrical resolution, and allows for continuous monitoring of the deformation. Here, we present and model ground displacements collected at Stromboli by GBInSAR from January 2010 to August 2014. During this period, the volcano experienced several episodes of intense volcanic activity, culminated in the effusive flank eruption of August 2014. Modelling of the deformation allowed us to estimate a source depth of 482 ± 46 m a.s.l. The cumulative volume change was 4.7 ± 2.6 × 105 m3. The strain energy of the source was evaluated 3–5 times higher than the surface energy needed to open the 6–7 August eruptive fissure. The analysis proposed here can help forecast shifts in the eruptive style and especially the onset of flank eruptions at Stromboli and at similar volcanic systems (e.g. Etna, Piton de La Fournaise, Kilauea).

The thermal behavior of Trombe wall system with venetian blind: An experimental and numerical study

The increasing interest in studying a Trombe wall with venetian blind (VBTW) has heightened the need for computational tools suitable to predict its thermal behavior. In this paper, a dynamic numerical model of a building with a VBTW was developed. Experiment has been conducted to study the temperature field of the whole building system in cold weather. It was found that the simulation results were in good agreement with the experimental data. The comparisons between the room with the classic Trombe wall and that with the VBTW were made based on the proposed model. The results demonstrated: the optimum time to open air vents of the VBTW was approximately 1.5h earlier than that of the classic Trombe wall after sunrise; the air average temperature for room with the VBTW was about 5.5°C higher compared to that with the classic Trombe wall in the daytime; the heat loss of the VBTW was smaller at night. The average predicted mean vote for the three rooms (room with the VBTW, room with the classic Trombe wall and room without Trombe wall) were −1.0, −1.5 and −2.2 in the daytime respectively. In conclusion, a building integrated with the VBTW can not only reduce heating energy needs but also achieve an acceptable condition of comfort in cold weather.

Kapasitas Daya Pembangkit Listrik Tenaga Mikrohidro di Alue Dua Aceh Utara

The utilization of micro hydropower plant is intended for providing electricity at Alue Dua village in North Aceh. A problem associated with the implementation of the micro-hydropower plant in the village is that the water flowrate of the run-of-river is varied at 117 litres per second during the wet season and at 36 litres per second during the dry season. This variation affects the speed of the water turbine and the capacity of power generated by its generator. Therefore to stabilize the output power and voltage of the generator during the course of the year, this paper aims to regulate the intake water flowing into the water turbine by controlling the opening vent valve from 0% up to 100% and controlling the electrical load connected to the generator. The speed of the water turbine was measured using the tachometer. It was found that the generator can produce electricity at its rated power 40 kVA during the wet season by opening the valve at 100% and at 12 kVA with the opening valve at 30% during the dry season. Opening the vent valve at 100% during the dry season can drain the water within 12 minutes

The effect of vent size and congestion in large-scale vented natural gas/air explosions

A typical building consists of a number of rooms; often with windows of different size and failure pressure and obstructions in the form of furniture and décor, separated by partition walls with interconnecting doorways. Consequently, the maximum pressure developed in a gas explosion would be dependent upon the individual characteristics of the building. In this research, a large-scale experimental programme has been undertaken at the DNV GL Spadeadam Test Site to determine the effects of vent size and congestion on vented gas explosions. Thirty-eight stoichiometric natural gas/air explosions were carried out in a 182 m3 explosion chamber of L/D = 2 and KA = 1, 2, 4 and 9. Congestion was varied by placing a number of 180 mm diameter polyethylene pipes within the explosion chamber, providing a volume congestion between 0 and 5% and cross-sectional area blockages ranging between 0 and 40%. The series of tests produced peak explosion overpressures of between 70 mbar and 3.7 bar with corresponding maximum flame speeds in the range 35–395 m/s at a distance of 7 m from the ignition point. The experiments demonstrated that it is possible to generate overpressures greater than 200 mbar with volume blockages of as little as 0.57%, if there is not sufficient outflow through the inadvertent venting process. The size and failure pressure of potential vent openings, and the degree of congestion within a building, are key factors in whether or not a building will sustain structural damage following a gas explosion. Given that the average volume blockage in a room in a UK inhabited building is in the order of 17%, it is clear that without the use of large windows of low failure pressure, buildings will continue to be susceptible to significant structural damage during an accidental gas explosion.

Exploring the influence of vent location and eruption style on tephra fall hazard from the Okataina Volcanic Centre, New Zealand

Uncertainties in modelling volcanic hazards are often amplified in geographically large systems which have a diverse eruption history that comprises variable eruption styles from many different vent locations. The ~700 km2 Okataina Volcanic Centre (OVC) is a caldera complex in New Zealand which has displayed a range of eruption styles and compositions over its current phase of activity (26 ka–present), including one basaltic maar-forming eruption, one basaltic Plinian eruption and nine rhyolitic Plinian eruptions. All three of these eruption styles occurred within the past 3.5 ky, and any of these styles could occur in the event of a future eruption. The location of a future eruption is also unknown. Future vents could potentially open in one of three different areas which have been activated in the past 26 ky at the OVC: the Tarawera linear vent zone (LVZ) (five eruptions), the Haroharo LVZ (five eruptions) or outside of these LVZs (one eruption). A future rhyolitic or basaltic Plinian eruption from the OVC is likely to generate widespread tephra fall in loads that will cause significant disruption and have severe socio-economic impacts. Past OVC tephra hazard studies have focused on evaluating hazard from a rhyolitic Plinian eruption at select vent locations in the OVC’s Tarawera LVZ. Here, we expand upon past studies by evaluating tephra hazard for all possible OVC eruption vent areas and for both rhyolitic and basaltic Plinian eruption styles, and explore how these parameters influence tephra hazard forecasts. Probabilistic volcanic hazard model BET_VH and advection–diffusion model TEPHRA2 were used to assess the hazard of accumulating ≥10 kg m−2 of tephra from both basaltic Plinian and rhyolitic Plinian eruption styles, occurring from within the Tarawera LVZ, the Haroharo LVZ or other potential vent areas within the caldera. Our results highlight the importance of considering all the potential vent locations of a volcanic system, in order to capture the full eruption catalogue in analyses (e.g. 11 eruptions over 26 ky for the OVC versus only five eruptions over 26 ky for the Tarawera LVZ), as well as the full spatial distribution of tephra hazard. Although the Tarawera LVZ has been prominently discussed in studies of OVC hazard because of its recent activity (1886 and ~1315 ad), we find that in the event of a future eruption, the estimated likelihood of a vent opening within the Haroharo LVZ (last eruption 5.6 ka) is equivalent (<1 % difference) to that for the Tarawera LVZ (31.8 compared to 32.5 %). Including both the Haroharo LVZ and the Tarawera LVZ as possible source areas in the hazard analysis allows us to assess the full spatial extent of OVC tephra fall hazard. By considering both basaltic Plinian and rhyolitic Plinian eruption styles, as well as multiple vent location areas, we present a hazard assessment which aims to reduce bias through incorporating a greater range of eruption variables.

Quantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 1. Vent opening maps

AbstractCampi Flegrei is an active volcanic area situated in the Campanian Plain (Italy) and dominated by a resurgent caldera. The great majority of past eruptions have been explosive, variable in magnitude, intensity, and in their vent locations. In this hazard assessment study we present a probabilistic analysis using a variety of volcanological data sets to map the background spatial probability of vent opening conditional on the occurrence of an event in the foreseeable future. The analysis focuses on the reconstruction of the location of past eruptive vents in the last 15 ka, including the distribution of faults and surface fractures as being representative of areas of crustal weakness. One of our key objectives was to incorporate some of the main sources of epistemic uncertainty about the volcanic system through a structured expert elicitation, thereby quantifying uncertainties for certain important model parameters and allowing outcomes from different expert weighting models to be evaluated. Results indicate that past vent locations are the most informative factors governing the probabilities of vent opening, followed by the locations of faults and then fractures. Our vent opening probability maps highlight the presence of a sizeable region in the central eastern part of the caldera where the likelihood of new vent opening per kilometer squared is about 6 times higher than the baseline value for the whole caldera. While these probability values have substantial uncertainties associated with them, our findings provide a rational basis for hazard mapping of the next eruption at Campi Flegrei caldera.

Quantifying volcanic hazard at Campi Flegrei caldera (Italy) with uncertainty assessment: 2. Pyroclastic density current invasion maps

AbstractCampi Flegrei (CF) is an example of an active caldera containing densely populated settlements at very high risk of pyroclastic density currents (PDCs). We present here an innovative method for assessing background spatial PDC hazard in a caldera setting with probabilistic invasion maps conditional on the occurrence of an explosive event. The method encompasses the probabilistic assessment of potential vent opening positions, derived in the companion paper, combined with inferences about the spatial density distribution of PDC invasion areas from a simplified flow model, informed by reconstruction of deposits from eruptions in the last 15 ka. The flow model describes the PDC kinematics and accounts for main effects of topography on flow propagation. Structured expert elicitation is used to incorporate certain sources of epistemic uncertainty, and a Monte Carlo approach is adopted to produce a set of probabilistic hazard maps for the whole CF area. Our findings show that, in case of eruption, almost the entire caldera is exposed to invasion with a mean probability of at least 5%, with peaks greater than 50% in some central areas. Some areas outside the caldera are also exposed to this danger, with mean probabilities of invasion of the order of 5–10%. Our analysis suggests that these probability estimates have location‐specific uncertainties which can be substantial. The results prove to be robust with respect to alternative elicitation models and allow the influence on hazard mapping of different sources of uncertainty, and of theoretical and numerical assumptions, to be quantified.

Exploring lava‐flow hazards at Pico Island, Azores Archipelago (Portugal)

AbstractPico, the youngest island of the Azores Archipelago (Portugal), is characterized by a central volcano and a 30‐km‐long fissure zone. Its eruption rate is the highest of the Azores islands, with more than 35 eruptions in the last 2000 years. Here, we estimate the lava‐flow hazard for Pico Island by combining the vent opening probability derived from the spatial distribution of eruptive fissures, the classes of expected eruptions inferred from the physical and chemical characteristics of historical eruptions, and the lava‐flow paths simulated by the MAGFLOW model. The most likely area to host new eruptions is along a WNW–ESE trend centred on the central volcano, with the highest hazard affecting the two main residential zones of Lajes do Pico and Madalena. Our analysis is the first attempt to assess the lava‐flow hazard for Pico Island, and may have important implications for decision‐making in territorial management and future land‐use planning.

Effects of Configuration and Headspace Mixing on the Accuracy of Closed Chambers for DairyFarm Gas Emission Measurement

<abstract><title><italic>Abstract. </italic></title> This study was aimed at evaluating the influence of chamber configuration (enclosure area and height), the use of a mixing fan and the wind speed induced by the fan at the emitting surface (head space mixing) on the accuracy for the closed chamber in gas emission measurement at low emission rates (≤3000 g SF₆ m^-2 h^-1). A calibration system was designed to generate a reference flux, and SF₆ was used as the target gas. Accuracy or chamber performance was defined based on the agreement between the calculated reference and chamber fluxes, which were not affected by chamber configuration. Four unvented closed chambers with two floor diameters (300 and 400 mm) and three different heights (200, 300, and 400 mm) were tested at seven different emission rates (from 684 ±72 to 2958 ±144 g m^-2 h^-1). Chamber configuration was correlated with the reference flux of sulfur hexafluoride (SF₆), and the tested chambers underestimated the reference fluxes by 21.5% ±13.6% (average ±SD). Chamber enclosure area did not affect the chamber performance while the height significantly impacted measurement accuracy. A chamber height of 300 mm was recommended to measure low gas emission rates. The positive air pressure induced by the mixing fan in the headspace increased with the fan speed, but the chamber performance was not affected by the mixing fan at lower emission rates. For our tested conditions, a mixing fan was not necessary and a vent opening balancing the air pressure inside and outside a chamber was not recommended.

The effect of vent openings on the microclimate inside multi-span greenhouses during summer and winter seasons

In research literature, little attention has been applied to the effect of vent openings on greenhouse climates during cooling and dehumidification processes with natural ventilation, which would provide guidelines for greenhouse management. To address this problem, a 3D CFD model was successfully designed based on 11-span plastic greenhouses. The model was validated with the measured air temperature and relative humidity, and then used to investigate the effects of vent configuration and opening size on the greenhouse climate. The simulations show that the vent configuration affects greenhouse microclimate patterns and the spatial and temporal variations of the internal climate. Meanwhile, the vent opening size affects greenhouse dehumidification time, air temperature and relative humidity during the dehumidification process. Finally, the assessments of ventilation performance highlight that the roof plus side opening is most suitable for summer cooling, while the roof opening is most suitable for winter dehumidification.

Influence on Vertical Shading Device Orientation and Thickness on the Natural Ventilation and Acoustical Performance of a Double Skin Facade

A research showed that shading devices integrated within double skin facades (DSFs) could not only decrease direct solar heat gain but also screen unwanted sound transmission. Many researches also indicated that shading device configuration affected airflow patterns, the air velocity, and the air temperature in a DSF air cavity. At acoustical standpoints, other researches described that shading devices acted as sound barriers, however, the area of a DSF's vent opening could led to an increase in noise transmission. Therefore, the proper controls of shading devices inside a DSF air cavity can contribute to thermal and acoustical comfort with avoiding overheating and noise transmission. This study aimed at evaluating the correlation between natural ventilation potential and noise transmission loss based on the degree of orientation and thickness of vertical shading devices inside a DSF air cavity. The initial findings indicated that vertical shading devices should be controlled appropriately for balancing the requirements of thermal performance, natural ventilation efficiency and noise transmission loss.

Characterisation of the magmatic signature in gas emissions from Turrialba Volcano, Costa Rica

Abstract. The equilibrium composition of volcanic gases with their magma is often overprinted by interaction with a shallow hydrothermal system. Identifying the magmatic signature of volcanic gases is critical to relate their composition to properties of the magma (temperature, fO2, gas-melt segregation depth). We report measurements of the chemical composition and flux of the major gas species emitted from Turrialba Volcano during March 2013. Measurements were made of two vents in the summit region, one of which opened in 2010 and the other in 2012. We determined an average SO2 flux of 5.2 ± 1.9 kg s-1 using scanning ultraviolet spectroscopy, and molar proportions of H2O, CO2, SO2, HCl, CO and H2 gases of 94.16, 4.03, 1.56, 0.23, 0.003 and 0.009% respectively by open-path Fourier transform infrared (FTIR) spectrometry and a multi-species gas-sensing system. Together, these data imply fluxes of 88, 8, 0.44, 5 × 10-3 and 1 × 10-3 kg s-1 for H2O, CO2, HCl, CO and H2 respectively. Although H2S was detected, its concentration could not be resolved. HF was not detected. The chemical signature of the gas from both vents was found to be broadly similar. Following the opening of the 2010 and 2012 vents we found limited to negligible interaction of the magmatic gas with the hydrothermal system has occurred and the gas composition of the volcanic plume is broadly representative of equilibrium with the magma. The time evolution of the gas composition, the continuous emission of large quantities of SO2, and the physical evolution of the summit area with new vent openings and more frequent eruptions all point towards a continuous drying of the hydrothermal system at Turrialba's summit at an apparently increasing rate.

A new Volcanic managEment Risk Database desIgn (VERDI): Application to El Hierro Island (Canary Islands)

One of the most important issues in modern volcanology is the assessment of volcanic risk, which will depend – among other factors – on both the quantity and quality of the available data and an optimum storage mechanism. This will require the design of purpose-built databases that take into account data format and availability and afford easy data storage and sharing, and will provide for a more complete risk assessment that combines different analyses but avoids any duplication of information. Data contained in any such database should facilitate spatial and temporal analysis that will (1) produce probabilistic hazard models for future vent opening, (2) simulate volcanic hazards and (3) assess their socio-economic impact. We describe the design of a new spatial database structure, VERDI (Volcanic managEment Risk Database desIgn), which allows different types of data, including geological, volcanological, meteorological, monitoring and socio-economic information, to be manipulated, organized and managed. The root of the question is to ensure that VERDI will serve as a tool for connecting different kinds of data sources, GIS platforms and modeling applications. We present an overview of the database design, its components and the attributes that play an important role in the database model. The potential of the VERDI structure and the possibilities it offers in regard to data organization are here shown through its application on El Hierro (Canary Islands). The VERDI database will provide scientists and decision makers with a useful tool that will assist to conduct volcanic risk assessment and management.

Determinants of ventilation behavior in naturally ventilated dwellings: Identification and quantification of relationships

BackgroundVentilation in dwellings is essential for well-being and health. However, insight in determinants of ventilation behavior is still limited. AimIdentifying determinants of ventilation behavior and quantifying relationships. Secondly, identifying households characteristics associated with low ventilation activity. MethodsIn a cross sectional study, ordinal and binary logistic regression analyses were performed, in a large population based survey, to identify determinants of window and vent opening behavior in the main living areas during the heating season in naturally ventilated dwellings. Relationships were quantified. ResultsWindow opening behavior was associated (although not always consistently between models) positively with household size, negatively with disposable income (living- and bedroom), and with ethnicity (association different in direction between room types). Furthermore, window opening behavior was positively associated with ‘respondent or partner does not have a paid income’ (living room only), presence of females and age of the oldest occupant (bedroom only). In addition, significant associations were found between dwelling characteristics and window opening behavior, including the presence of vents (strong negative association, both room types), type of dwelling (association different in direction between room types), and the overall heat transfer coefficient by transmission. A smaller number of household and dwelling characteristics was found associated with vent opening behavior. ConclusionWindow and vent opening behavior was associated with a range of both household and dwelling characteristics. More research is needed to confirm associations.