Automatic Ventilation Research Articles

Clinical impact of Candida respiratory tract colonization and acute lung infections in critically ill patients with COVID-19 pneumonia

Coronavirus disease 2019 (COVID-19), which is attributable to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has been causing a worldwide health issue. Airways colonization by Candida spp. is prevalent among patients on automatic ventilation in intensive care units (ICUs). This research aimed to ascertain the risk factors and roles of Candida spp. respiratory tract colonization, and Candida lung infection during the progression of COVID-19 pneumonia in critically ill patients. In total, Candida spp. were recovered in 69 from 100 immunosuppressed patients with COVID-19. Bronchoscopy was used to collect the Bronchoalveolar lavage (BAL) specimens. For the identification of Candida spp. PCR sequencing was done using the ITS1 and ITS4 primers. The amplification of the HWP1 gene was conducted to identify the Candida albicans complex. The antifungal activities of fluconazole, itraconazole, voriconazole, amphotericin B and caspofungin against Candida spp. were evaluated using the Clinical and Laboratory Standards Institute M60. In 63.77% of the patients, Candida respiratory colonization at D0 and D14 had no impact on the severity of COVID-19. In comparison to C. albicans strains, Candida respiratory disorder with C. glabrata had influenced the severity of COVID-19 for critically ill patients following adjustment for the risk factors of COVID-19 (P < 0.05). Amphotericin B and caspofungin showed superior activity against all Candida spp. All antifungal agents showed 100% sensitivity against the two C. africana strains. Our observation on patients who used automatic ventilation, respiratory colonization by Candida spp. was not seen to influence the infection or death caused by COVID-19. Amphotericin B and caspofungin showed superior activity against all Candida spp. and were recommended for the treatment regime of pulmonary candidiasis associated with COVID-19 infection. Although “Candida pneumonia” is rarely being reported in critically ill patients, Candida airway colonization mainly by Candida albicans is common especially among patients with diabetes, malignancies, and kidney disorders.

Decreasing of the air humidity by the ventilation control in the St. Barbara mine

The St. Barbara mine is a visitor mine having a large amount of timbering support which is deteriorating fast due to the high humidity conditions. The air conditioning system of mining is not suitable and also expensive for implementation in a shallow non-productive mine. As there are no usual air contaminants in the visitor mines, ventilation could be powered only when a dew point of outside air is below the strata temperature. Applying this rule would certainly avoid condensation, but also raises a potential for partial dehumidification of mine walls as moisture can evaporate in these conditions. A microclimate analysis, based on one-year data, has showed that these favorable conditions of the outside air occur through the major part of the year. Their availability is mostly 100%, but during summertime there are periods when it drops down to 13%. A real time monitoring system with programable microcontroller allows the automatic ventilation control and adjustment to the psychrometric conditions.

Automatic Ventilation and Air Conditioning System for Educational Training

The air quality from closed spaces is very important for people or for technological processes. The heating, ventilation and air conditioning installations ensure the maintenance of the air parameters in the rooms served within pre-established limits, throughout the year, regardless of the variation of meteorological factors, the degree of occupancy of the rooms or the development of production processes. The paper presents an automatic ventilation, heating and air conditioning system made on a small scale. Climatic parameters can be monitored and controlled in two ways: in local mode and also in remote mode. In local mode, the control of the installation is done with a Mega 2560 development system made around the Atmega 2560 microcontroller, which processes the information received from the DHT22 temperature and humidity sensor. Information about parameters and system status is displayed on the local screen. The WeMos D1 R2 WiFi development system based on an ESP8266 wireless microcontroller with Wi-Fi 802.11 compatible with the IDE-Arduino development environment was used for the remote control. All information is transmitted wirelessly to an online platform, called Cayene that allows their storage and control. The platform referred to offers a number of graphical features that do not involve costs for users. The system can be used both for educational purposes for engineering students, but can be adapted for real practical applications.

Comparative Study between Automatic Tube Compensation (ATC) and Pressure Support Ventilation (PSV) as a Mode of Weaning from Mechanical Ventilation in Patients with Respiratory Failure

Abstract Background Weaning covers the entire process of liberating the patient from mechanical support and from the endotracheal tube (ETT). Weaning from mechanical ventilation (MV) is a challenge. Its prolongation is related to increased mortality. Aim of the Work is to assess the value of ATC in predicting successful weaning and hastening the weaning process. This study will compare the benefits and effects of ATC versus PSV as weaning modes on spontaneous breathing trials and work of breathing. Patients and Mehtods This prospective non randomized was done on 50 adult patients admitted to the Critical Care Medicine Department in Ain shams University Hospital presenting with ARF and mechanically ventilated for at least 24 hours. They were divided into two groups: Group I “ATC group” Each underwent a 1-hour spontaneous breathing trial, using ATC mode and Group II “PSV group” PSV mode was used. Results In the present study we have found that the use of ATC during a spontaneous breathing trial was as effective as PSV in predicting the ability of patients to maintain spontaneous, unassisted breathing for more than 48 hours after removal of the endotracheal tube. In our study, there was no significant difference in the number of patients who tolerated the spontaneous breathing trial and then extubated between ATC and PSV groups (60 % vs. 56% respectively, p &amp;gt; 0.05). Both modes had comparable sensitivity, and +ve predictive value. Sensitivity was 80.0% versus 75.0% and the positive predictive value was 88.0%, versus 87.0% for ATC versus PSV respectively. The specificity was comparable (76.8% versus 80.0 % in ATC versus PSV respectively). ATC group had higher negative predictive than PSV group (82.0% versus 70.1%, respectively). In our study, criteria for successful extubation were met in 56.0%. In ATC group 60.0% met the criteria for successful extubation vs. 60% in PSV group. In the present study it was found that male patients were the most predominant in both groups (72.0% in ATC group and 68% in PSV group). This is expected as cigarette smoking is prevalent among males and is the single most important and most prevalent risk factor for the development of COPD. In our study, about one third of patients had COPD exacerbation as a cause for ARF. Conclusion In ICU population, ATC was safe, reliable, and can be reasonably used for weaning trials. ATC confers a potential benefit in weaning duration, weaning category, number of Ss, failure of first SBT extubation outcome, ICU length of stay, complication, and mortality rate. In addition, ATC improves the predictive value of RR/TV and IWI in predicting weaning success.

Analytical Study of the Automatic Ventilation System for the Intake of Polluted Air from the Pigsty

The microclimate of a pigsty is determined by the combination of temperature, relative humidity, chemical and mechanical composition of the air, which have a significant impact on animal productivity and must be maintained within strict limits due to the physiological needs and capabilities of animals. An appropriate ventilation system has been created to ensure the removal of air from the pigsty. The purpose of the study is to establish the dependence of the operating parameters of the automatic ventilation system on the air quality in the pigsty, taking into account the permissible concentrations of gases. The developed automatic ventilation system for polluted air intake is located in the middle of the livestock house under the ceiling and consists of a central air duct, to which air intake pipes are connected. Air intake pipes are placed in the middle above each pen where animals are kept. Intake dampers with servomechanisms, temperature, humidity, and air quality sensors are installed at the inlet of the air intake pipes. The outlet of the central air intake duct is connected to the exhaust fan. Intake dampers with servomechanisms and sensors of temperature, humidity, and air quality are connected to the control unit by electrical wires. As a result of analytical studies of the automatic ventilation system for polluted air intake from a pigsty, the conditions for its effective operation have been mathematically substantiated. The developed technique and the algorithm implemented based on the Mathematica software package allows calculating the area of holes that form intake dampers with servomechanisms in the air intake pipes. The distribution of velocities in the air intake pipes and the distribution diagram of the area of holes that form intake dampers with servomechanisms in the air intake pipes are determined taking into account the design and technological parameters of the ventilation system and the distribution of the gas concentration (carbon dioxide, ammonia, and hydrogen sulphide) over the pens

Evolution and Characteristics of Bag-Valve-Mask Ventilation During Pandemic: A Review of the Literature

Mass casualty incidents such as those that are being experienced during the novel coronavirus disease (COVID-19) pandemic can overwhelm local healthcare systems, where the number of casualties exceeds local resources and capabilities in a short period of time. The introduction of patients with worsening lung function as a result of COVID-19 has strained traditional ventilator supplies. To bridge the gap during ventilator shortages and to help clinicians triage patients, manual resuscitator devices can be used to deliver respirations to a patient requiring breathing support. For patients who require ventilatory support, manual ventilation is a vital procedure. It has to be performed by experienced healthcare providers that are regularly trained for the use of bag-valve-mask (BVM) in emergency situations. We will present, a historical view on manual ventilation’s evolution throughout the last decades. Artificial ventilation has developed progressively and research is still going on to improve the actual devices used. Throughout the past years, a brand-new generation of ventilators was developed, but little was done for manual ventilation. Manual ventilation through BVM can be replaced by automatic ventilation which illustrates that the Tidal Volume vs. Time graph of the automated system is similar to the graph produced by manual operation of the BVM and to the graph produced by a human subject. The use of an automatic manually operated device may improve ventilation efficiency and decrease the risk of pulmonary overdistention, while decreasing the ventilation rate.

Design of Low-cost Automated Ventilator Using AMBU-bag

본 연구는 COVID-19의 ëŒ€ìœ í–‰ìœ¼ë¡œ 인해 자동 인공 호흡기의 공급이 ì„¸ê³„ì ì¸ 긴급 수요에 비해 원활하지 않은 상황에 도움이 ë ìˆ˜ìžˆëŠ” ì €ê°€í˜• 응급 인공 호흡기의 설계 및 구현을 ì œì•ˆí•œë‹¤. AMBU-bagê³¼ 기성용 ìž„ë² ë””ë“œ 마이크로 컨트롤러 보드를 사용하여 구현이 ìš©ì´í•˜ê³ ë¹„ìš©ì„ 최소화했다. 또한, 3D í”„ë¦°íŒ ì€ ì „ 세계 ê¸°ì— ê³¼ ì „ë¬¸ê°€ë“¤ì´ í”„ë¡œí† íƒ€ìž í•˜ë“œì›¨ì–´ë¥¼ 구축하는 데 사용하는 반면, 주변 환경에서 쉽게 êµ¬í• ìˆ˜ 있는 재료는 많은 첨단 ê¸°ìˆ ì— ì ‘ê·¼í•˜ê¸° ì–´ë ¤ìš´ 국가의 사람들이 ì‹œìŠ¤í œì„ ì œì¡°í• ìˆ˜ 있도록 한다. 설계한 간이 인공호흡기 모형의 특징은 암부 백을 자동화 했다는 ì , 3d í”„ë¦°íŒ ì„ 사용하지 않는다는 ì , ì†ë„ì¡°ì ˆì´ 가능하다는 ì ì´ë‹¤. 속도 ì¡°ì ˆì´ 가능하게 함으로써 사용하는 환자의 상황에 맞게 환기가 가능하다. 연구 시 ë³´ì™„í• ì ìœ¼ë¡œëŠ” 첫 번째, 사용한 와이퍼 모터의 구동 ì‹œìž‘ì ì„ ê³ ì •í•˜ê¸° ì–´ë µë‹¤ëŠ” 것이다. 이를 보완하기 위한 방법으로 위치 피드백기능이 있는 브러시 DC모터로 교체하는 방법이 있다. 두 번째로 팔부분과 ê³ ì • 틀이 나무 재질이라 암부 백을 ìž¥ê¸°ì ìœ¼ë¡œ 압축하는 ê³¼ì •ì—ì„œ 암부백이 ë§ˆëª¨ë ê°€ëŠ¥ì„± 있다는 것이다. 이를 보완하기 위해 암부백이 닿는 틀과 팔 부분을 실리콘과 같은 재료로 감싸 마찰을 최소화해야 í• í•„ìš”ê°€ 있다. This study proposes the design and implementation of a low-cost emergency ventilator which can be helpful during the COVID-19 pandemic where the supply of automatic ventilators is not smooth compared with the urgent demand worldwide. Easy implementation and lower price were made possible by using AMBU-bag and off-the-shelf embedded microcontroller board. Moreover, while 3D printing is used by companies and experts around the world to build prototype hardware, materials which are readily available from surrounding environments so that people in countries where it is difficult to access many advanced technologies could manufacture the system. The design features AMBU-bag automation, not use 3D printing, and it can contrl speed. By allowing speed control, ventilation can be performed according to the conditions of the patient being used. A complementary point in the study is that it is difficult to fix the start point of the wiper motor used first. A method for complementing this is a method for replacing the brush DC motor with a position feedback function. Secondly, the AMBU-bag may wear out in the long-term process of compressing the AMBU-bag because the arm and the fixing frame are made of wood. To complement this, the part of fixing frame and arm parts that the AMBU-bag touches need to be wrapped in a material such as silicon to minimize friction. Keywords: BVM, COVID-19, Emergency, Respiration

The rapid development of AmboVent: a simple yet sustainable ventilation solution for use in a pandemic

Introduction COVID-19 (SARS-CoV-2) emerged at the end of 2019, generating a rapidly evolving pandemic, raising serious global health implications. Among them was the fear of a mechanical ventilator shortage due to COVID-19’s high contagion rate and pathophysiology. Fears of a ventilator shortage unleashed a wave of innovations. Material and method This manuscript describes the AmboVent, a ventilator, rapidly developed with a sense of urgency, by a group of Israeli volunteers. Results Using a decentralized approach, we worked extensively and managed within ten days to create a working ventilator. It utilizes a 64-year-old technological concept, the bag valve mask (BVM), sometimes known by the proprietary name Ambu bag, which we transformed into an automatic, controlled, and feature-rich ventilator by endowing it with contemporary computing technology. Conclusions Applying a functional rather than a commercial-oriented approach can result in the ad hoc development of lifesaving solutions during a rapidly spreading pandemic.

Real-time infrared image processing for control and monitoring of greenhouse system

Providing microclimate conditions in greenhouse systems is very important in terms of growing desired products. In addition, remote sensing and data analysis processes need to be developed and expanded to perform fast and perfect monitoring and control in these systems. An application of remote sensing with infrared imaging in greenhouse systems has been developed. It is proposed to obtain the mean temperature inside the greenhouse via infrared images, the air relative humidity with psychrometric chart application, and the soil moisture values with the multiple regression analysis method. The control and monitoring of automatic irrigation, heating, humectation, ventilation, and lighting systems were carried out via the MATLAB–GUI interface. The desired conditions for the carnation plant were ensured in the greenhouse, and 24-h data were obtained. The digital and visual application findings showed that the designed system is more advantageous in terms of ease of use, monitoring, and simultaneous recording compared with the traditional sensor control systems.

Application of automatic control furnace for combustion of biomass briquette fuel for tobacco curing

Applying biomass energy for curing flue-cured/Virginia tobacco heating is the best way to realize green tobacco production. Aiming to satisfy the heating demand for flue-cured tobacco curing, a new heating device that uses biomass briquettes as fuel for curing tobacco is adopted the first time, which was developed using modern mature electromechanical and computer technology. The new device consists of automatic feeding, ash cleaning, ventilation, and ignition systems governed by an intelligent tobacco-curing controller designed for specific curing characteristics. The results of experiments conducted with an original direct combustion coal furnace, bulk curing barn, and controlled coal-fired heating indicated that the heat supply of the new device could satisfy the heat demand during the tobacco curing process, with a good performance-controlling difference of ?0.5?C between the actual and target dry-bulb temperature in the barn. With its unattended heating management and use of fully burning fuel, the new device sharply decreased the cost of manual operation and tobacco leaves required per kilogram compared to a coal furnace. Considering the shape of its structure, the new device could be used to heat homes or small-scale boilers if the chip procedure of the controller is altered.

계사 내 이산화탄소 기반의 자동 환기 시스템에 관한 설계

계사 내 이산화탄소 기반의 자동 환기 시스템에 관한 설계

Low-pressure support vs automatic tube compensation during spontaneous breathing trial for weaning

BackgroundDuring spontaneous breathing trial, low-pressure support is thought to compensate for endotracheal tube resistance, but it actually should provide overassistance. Automatic tube compensation is an option available in the ventilator to compensate for flow-resistance of endotracheal tube. Its effects on patient effort have been poorly investigated. We aimed to compare the effects of low-pressure support and automatic tube compensation during spontaneous breathing trial on breathing power and lung ventilation distribution.ResultsWe performed a randomized crossover study in 20 patients ready to wean. Each patient received both methods for 30 min separated by baseline ventilation: pressure support 0 cmH2O and automatic tube compensation 100% in one period and pressure support 7 cmH2O without automatic tube compensation in the other period, a 4 cmH2O positive end-expiratory pressure being applied in each. Same ventilator brand (Evita XL, Draeger, Germany) was used. Breathing power was assessed from Campbell diagram with esophageal pressure, airway pressure, flow and volume recorded by a data logger. Lung ventilation distribution was assessed by using electrical impedance tomography (Pulmovista, Draeger, Germany). During the last 2 min of low-pressure support and automatic compensation period breathing power and lung ventilation distribution were measured on each breath. Breathing power generated by the patient’s respiratory muscles was 7.2 (4.4–9.6) and 9.7 (5.7–21.9) J/min in low-pressure support and automatic tube compensation periods, respectively (P = 0.011). Lung ventilation distribution was not different between the two methods.ConclusionsWe found that ATC was associated with higher breathing power than low PS during SBT without altering the distribution of lung ventilation.

Automatic tailoring of the lowest PEEP to abolish tidal expiratory flow limitation in seated and supine COPD patients

In COPD patients, the development of tidal expiratory flow limitation (EFLT) results in intrinsic positive end-expiratory pressure (PEEPi), leading to increased work of breathing and worsening patient-ventilator interaction. An external PEEP can mitigate these consequences, but how to optimize its value it is still unknown. To measure the minimum PEEP able to abolish EFLT by a new automatic non-invasive ventilation (NIV) mode in stable hypercapnic COPD patients in the seated and supine positions. Twenty-six hypercapnic COPD patients (mean±SD: FEV1%pred = 39.2 ± 16.1, FEV1/FVC%pred = 46.3 ± 16.3%) were studied while receiving NIV during two consecutive 15-min periods, with patients studied seated in the first and supine in the second. A ventilator able to identify EFLT breath-by-breath by using the forced oscillation technique optimized in real-time PEEP to the lowest pressure able to abolish EFLT (PEEPO). The ventilator was always able to identify a PEEPO. Its values were highly variable among patients and increased from median(iqr) 4.0 (0.03) (range: 4.0-8.3cmH2O) to 6 (6.1) cmH2O (range: 4.0-15.7 cmH2O) when patients moved from the seated to the supine position, respectively. PEEPO in supine position did not correlate to any spirometric or anthropometric variable. PEEPO in COPD patients is highly variable and increases in supine position. It is not predicted by spirometric nor anthropometric variables, but had a considerable variability among the patients. We suggest that PEEPo may be used as a phenotyping variable in COPD patients.

Automatic ventilation control algorithm considering the indoor environmental quality factors and occupant ventilation behavior using a logistic regression model

Building occupants find it difficult to achieve the optimal indoor environment quality (IEQ) through natural ventilation. To solve this problem, this study aimed to develop an automatic ventilation control algorithm considering the IEQ factors and occupant ventilation behavior. The algorithm was developed in four steps: (i) real-time collection of data on the IEQ factors and occupant ventilation behavior; (ii) development of the automatic ventilation control algorithm using logistic regression; (iii) determination of the automatic ventilation control algorithm using receiver operating characteristic curve analysis; and (iv) evaluation of the automatic ventilation control algorithm's performance according to the indoor environmental standards. Through this process, the logistic regression model with ridge regression (area under curve: 0.865), with the highest classification accuracy, was selected. Then Youden's index was used to define the decision criterion (i.e., optimal cutoff value) for the logistic regression model. As a result, the decision criterion for opening and closing the windows or doors was 0.533. When the developed algorithm was compared with the indoor environmental standards to analyze its performance, the compliance rate of the opening of the windows or doors based on the monitored data was 77.6%, but it increased to 99% based on the data classified by the developed algorithm. It is expected that if the automatic ventilation control algorithm is embedded in a building ventilation system, which is connected to various IEQ measurement sensors, it will offer a customized building ventilation system to the building occupants.

Realizing natural ventilation potential through window control: The impact of occupant behavior

As an increasingly popular green building technology, natural ventilation (NV) is an effective solution for better thermal comfort and lower HVAC system energy consumption. However, to achieve NV’s full potential in practice, it is critical to control windows and HVAC systems. Three main types of control schemes are examined in this study: spontaneous occupant control, informed occupant control, and fully automatic control. Five representative climates, ranging from hot, temperate, to severely cold, are tested for the effectiveness of each control scheme. The results confirmed the superior performance of the fully automatic system, especially with the model predictive control algorithm, which demonstrates a cooling energy saving of 17%–80%, with zero discomfort degree hours. Neither the informed or spontaneous occupant controls are able to maintain the indoor temperature within the comfort range at all times. In particular, the informed occupant operation following the fixed-schedule four-times-daily signals shows the worst thermal control capacity and leads to 1500–4000 discomfort degree hours. In terms of energy performance, the informed occupant control, by following the heuristic control signals, shows the least energy savings and even indicates energy waste in some scenarios. Based on the study’s results, it is recommended to either adopt the fully automatic natural ventilation control system to achieve maximum energy-saving potential or allow occupant autonomy for natural ventilation controls to achieve a lower budget for initial installation and maintenance cost.

APPLICATION OF PHYTOMONITORING FOR ESTIMATING THE WATER STRESS INDEX

Cultivation of thermophilic vegetable crops in Siberian conditions is possible only if the limiting environmental factors of their habitat (heat and moisture availability) are brought to the optimum zone. This requires continuous phytomonitoring of habitat characteristics and plant status indicators performed by a phytomonitor with a set of sensors. Based on the results of phytomonitoring, the production process of the crops to be grown is managed in the real-time mode by conducting technological operations aimed at changing the limiting factor. A scheme has been developed for managing the production process of vegetable crops in canopies. To improve the heat supply, it is proposed to use protective screens with automatic control of inflow-and-exhaust ventilation. The basis is the automatic control scheme with feedbacks. Automatic ventilation control is carried out by measuring the air temperature inside the canopy and forming a signal to activate the mechanism drive. The water availability of plants is estimated by the value of the water stress index, calculated on the basis of measurements of air temperature and humidity and leaf temperature. An algorithm for calculating the water stress index has been developed and experiments have been conducted to measure the characteristics of the habitat and indicators of the state of plants in laboratory and field conditions. The characteristic of changes in the water stress index of plants inside and outside the canopy was obtained. Based on the value of the water stress index, it was concluded that the plants are adequately supplied with water. The results of the experiments showed high reliability of the phytomonitor and a set of sensors. Further studies will focus on improving the production process management system using phytomonitoring in real time based on the methodology of evapotranspiration calculation.

On the controlling of temperature: A proposal for a real-time controller in broiler houses

ABSTRACT: Environmental conditions in broiler houses, specifically temperature, are key factors that should be controlled to ensure appropriate environment for broiler rearing. In countries with tropical/subtropical climate, like Brazil, high temperatures produce heat stress to animals, affecting the production process. This research proposes a real-time model to control temperature inside broiler houses. The controller is a self-correcting model that makes real-time decisions on the ventilation system operation (exhaust fans) together with temperature prediction at the facility. The model involves partial differential equations (PDE) whose parameters are updated according to data registered in real-time. Some experiments were carried out at a pilot farm in the municipality of Jundiai, Sao Paulo State, Brazil, for different periods during winter and summer. The results based on simulations in comparison with the current automatic ventilation system show that the model is consistent to keep temperature under control for an efficient production. The model achieved a bias of 0.6 °C on average in comparison with the ideal temperature, whereas the automatic controller measured a bias of 3.3 °C, respectively. Future lines suggest that this approach could be useful in many other situations that involve environmental control for livestock production.

Gray Wolf optimization method for automatic ventilation systems of clean accessories

The manufacturing processes complication leads to cost increasing of equipment service and maintenance costs. An important role in overcoming these factors is played by modern automatic control systems, regulators optimization and adaptation of control systems to changing conditions. Today, the actual problem remains the adjustment and optimization of automatic control systems, especially complex structures.The article researches the population optimization algorithm "Gray wolf" as applied to the search for optimal PID-controller settings. A cascade automatic control system with two PID regulators optimized for a minimum of integral IAE, ISE quality criteria, as well as control time is considered. The advantage of the method under investigation is shown in a comparing with the Hook-Jeeves zero-order optimization method. The mathematical modeling of the automatic control system of air temperature in a clean room with the “Grey wolf” optimization method is performed. Attention is focused on the convenience of using the method, since it does not require an accurate setting of the initial parameters of the regulators. This eliminates the need for an a priori knowledge of the customizable system dynamics by the user. The commissioning of control parameters optimizing systems will help to increase the efficiency of the equipment in conditions of variable operating modes. The recommended area of the method used is the complex structures of automatic control systems, where the search for optimal settings by classical methods is difficult or does not exist.

Rolled plastic film damage simulation considering surface roughness useful for greenhouse roof automatic ventilation

Greenhouses are capable of producing a variety of high-value crops year-round. A novel Japanese greenhouse design is gaining popularity because of its automated rolled-up ventilation system that is integrated into the roof. However, due to the frequent movement of the roll-up system, the plastic film deteriorates rapidly and typically lasts for only three or four months. In order to better understand the film deterioration, we studied the mechanics involved at the point of contact between the film and the metal greenhouse frame. We found that film deformation and failure were closely related to stretching and creasing, and these processes were observed at the microscope level. In this paper, the plastic film damage was investigated through the rolling contact analysis focusing on the pipe surface roughness. We found that at the inside film surface the larger strain is caused by the pipe surface roughness. This larger strain generates the wave deformation of the film, crease and line scar whose number increases with increasing the roughness of the arch pipe. The effects of pipe coating and perforated film are discussed to prevent the film damage.

Feasibility of automatic ventilation technology for sea freight ofProteacut flower products

Advances in cold storage and transport technologies have seen the development of automatic ventilation technology and dynamic controlled atmosphere (DCA). Instead of using the commonly used fixed, open air exchange ventilation (AirEx) at 15,000 L fresh air h(-1) during shipping of Proteaceae stems, the new technologies restrict ventilation to gas concentrations that are near the set limits. Ventilation only occurs at O-2 levels near the lower O-2 limit (LOL) and at levels below the CO2 toxicity limit of the products. The gas exchange dynamics and ventilation requirements of sea freighted Protea cut flowers from South Africa (SA) are largely unknown, which has been a limiting factor to the introduction of automatic ventilation as an alternative within sea freight shipping. Furthermore, the suitability of current sea freight technology for Proteaceae cut flowers that are shipped from SA to Europe is under question due to inconsistencies in product quality upon arrival at their markets. The low storage temperature, AirEx ventilation and lengthy cold storage period have been identified as possible causes of quality loss during sea freight. The feasibility of the use of automatic ventilation technology during exports to distant markets was evaluated by determining the LOL values of the Protea cut flower products when stored at low O-2 concentration and assessing the toxicity tolerance in high CO2 atmosphere. Determination of the LOL was done using a fluorescence interactive response monitor (FIRM) sensor attached to a DCA system. High CO2 tolerance was tested by increasing the CO2 concentration stepwise from 5 to 15% CO2 atmospheric concentration (5-10-15% CO2). The LOL values of the products ranged from 0.08-0.25% O-2. AirEx atmosphere led to higher moisture loss than high CO2 atmosphere, with insignificant differences between AirEx and low O-2 atmosphere. The products stored in AirEx and high CO2 atmospheres had comparable flower head and leaf quality. The flower head and leaf quality of products stored in low O-2 was better than that of products stored in AirEx atmosphere.