Hygrothermal durability of bond in FRP-strengthened masonry

Fiber reinforced polymers (FRPs) are accepted as an efficient material for external strengthening of masonry structures. Previous researches have shown that the bond between FRP and the substrate plays an important role in the effectiveness of this strengthening technique. Extensive investigations have been devoted to the characterization of the short-term bond behavior, while its durability and long-term performance requires further studies. In this regard, a full experimental program for investigating the environmental durability of bond in FRP-strengthened masonry is crucial for understanding the degrading mechanisms. This paper presents the results of an experimental program aimed at investigating the hygrothermal durability of bond in FRP-strengthened bricks. Accelerated ageing tests were performed on the FRP-strengthened brick elements and the bond degradation was periodically investigated by visual inspection and by conventional single-lap shear bond tests. The changes in the properties of material constituents have also been monitored. The obtained results are presented and critically discussed.This work was developed within the framework of the RILEM Technical Committee "223-MSC: Masonry Strengthening with Composite Materials". The financial support from the project FP7-ENV-2009-1-244123-NIKER of the 7th Framework Program of the European Commission is gratefully acknowledged. The first author also acknowledges the financial support of the Portuguese Science Foundation (Fundacao de Ciencia e Tecnologia, FCT), through grant SFRH/BD/80697/2011

Effects of Salinity Stress on Gas Exchange, Growth, and Nutrient Concentrations of Two Citrus Rootstocks

A greenhouse study was undertaken to assess the salt tolerance of two citrus rootstocks, namely, Bakraii (Citrus sp.) and Trifoliate orange (Poncirus trifoliata). A factorial experiment through a completely randomized design (CRD) with three replications and four levels of salt including 0, 20, 40 and 60 mM NaCl was conducted. After eight weeks of treatment, number of leaves, plant height, leaf area, wet and dry weight of leaf, stem and root, length of root, chlorophyll content, net CO2 assimilation rate (ACO2), stomatal conductance (gs), transpiration (E) and water use efficiency (WUE) and ion concentrations were measured. Salinity decreased growth and net gas exchange. Trifoliate orange showed the most decrease in growth indices and net gas exchange compared with Bakraii. The ability to limit the transfer of sodium to leaves in low levels of salt was observed in Trifoliate orange, but this ability was not observed in high levels of salt. Results showed that accumulation of chloride in leaves and roots were less in Bakraii compared to the Trifoliate orange. The lower Cl- concentration in leaves of Bakraii than trifoliate orange suggests that the salinity tolerance of Bakraii is associated with less transport of Cl- to the leaves. Salinity increased K+ and decreased Mg2+ and Ca2+ concentrations in leaves of both rootstocks. It is proposed that salt stress effect on plant physiological processes such as changes in plant growth, Cl- and Na+ toxicity, and mineral distribution, decreases chlorophyll content and reduces the photosynthetic efficiency of these citrus species

Effects of Salinity on Growth and Physiological Characteristics of Two Tomato Cultivars (Super Strain–B and Red Clud) in Hydroponic Conditions

Salinity is one of the greatest factors that limit the producion of horticultural crops in many parts of the world, especially in arid and semi-arid areas. Tomato (Lycopersicon esculentum L.) is an annual herbacious plant whose annual global production is over 80 million tons. In areas with warm and dry climate which are suitable for the production of tomatoes, salt is considered a major problem. This research was done in order to study the salinity effects on growth and physiological characteristics of tomato plant cultivars Super strain–B and Red clud. Firstly, seeds were planted in metal trays filled with sand in the greenhouse environment with sufficient moisture, and then seedlings in two leaf stages were transplanted to hydroponics’ medium with a Johnson nutritional solution. After establishment, the five levels of salinity treatments including, zero (control), 40, 80, 120 and 160 mM of Nacl were applied in three replications. The results showed that salt stress significantly reduces shoot and root dry weight, number of leaves, leaf area, leaf chlorophyll content, and stress index (Fv/Fm) of both cultivars. Specific leaf area (SLA) in both cultivars decreased due to salinity treatment however, this reduction was not significant in Red clud cultivar. Salinity also significantly increased the amount of proline in shoots in both cultivars. The results were suggestive of the relative resistance of tomato plant cultivar Red clud in comparison with Super strain-B to salinity conditions

Possible Reduction of the ٍٍEffect of Salinity on Bean (Phaseolus vulgaris) with Application of Salicylic Acid

Salinity is the most important environmental stress that reduces plants growth and yield. It has been shown that salicylic acid, as an endogenous signal, is responsible for inducing stress tolerance in plants. In this experiment, the effect of salicylic acid and sodium chloride on growth of bean (Phaseolus vulgaris) was studied. When bean plants were at two-leaf stage, they were sprayed by three concentrations of salicylic acid (0, 0.5 and 1 mM). Then, plants were treated with two concentrations of sodium chloride (zero and 100 mM) for 14 days. The results showed that salinity caused a significant reduction in fresh and dry weight of root and shoot, relative chlorophyll content, percentage of relative water content (RWC) of leaf, stress index and significant increase in proline and soluble sugars as compared to the control treatment. Plants that were treated with both concentrations of salicylic acid showed higher fresh and dry weights. Also, application of salicylic acid in both concentrations, in saline conditions, improved the percentage of leaf RWC, amount of relative chlorophyll and chlorophyll fluorescence (Fv/Fm) of leaves as compared to control plants. In summary, it was concluded that spraying of salicylic acid on bean plants could improve growth and thus resistance to salinity under saline conditions

Comparison of the Effect of 1-MCP and Low-Pressure Air on Shelflife of Strawberry Fruit (Fragaria ananassa cv. Camarossa)

Strawberry (Fragaria×ananassa) has tasteful, fragrant and nutritious fruits. But, because of delicate texture and high metabolic activities of the fruits at maturity, are very sensitive and easily decayed, and thus have short shelflife. Ethylene is one of the main causes of postharvest fruit losses, which could reduce the shelflife of strawberry. Therefore, an experiment was carried out to examine the effect of 1 µL/L 1-MCP treatment and low-pressure air pretreatment at 0.2 atm in 2 hours on apparent and physicochemical characteristics of strawberry fruit, cultivar Camarossa, during storage in cold store. The study was performed as split plots in time, based on complete randomized design with 3 replications. The results showed that the highest marketability (90%), fruit firmness (7.95 N), titrable organic acids (1.15 g/100 cc), vitamin C (78.13 mg/100 cc) and total soluble solids (10.48 %) and the lowest amount of apparent decay (13.3 %), acidity (3.63) and taste index (9.04) were obtained in 1-MCP and low-pressure air treatments, which shows the effect of treatments on reducing the rate of biochemical variations in fruit texture. Correlation coefficients between all treatments were significant (P≤0.01). Meanwhile, the positive effect of 1-MCP on appearance and studied physicochemical characteristics was more than low-pressure air pretreatment. Even, the combination of these two treatments had no significant difference with 1-MCp treatment alone. In general, this observation depicts the more positive and significant effect of 1-MCP treatment in delaying the maturity and improving the qualitative traits of strawberry fruits after being stored in cold storage

Effect of Putrescine and 1-MCP on Quality Attributes and Storage Life of Strawberry Fruits (Fragaria ananassa Cv. Selva)

Ethylene is an important contributor to the acceleration of fruit ripening and postharvest losses of fruit. Thus, anti ethylene substances could increase storage life of fruits. Thus the effects of 0 (control), 0.5, 0.75 and 1 µL L-1 of 1-MCP and putrescine with 0 (control), 0.5, 1 and 1.5 mM on the storage life (1°C) during 21 day in strawberry fruit Cv. Selva were studied and appearance and the physicochemical characteristics of fruits were measured. A factorial experiment through complete randomized design (CRD) was used. The highest marketability, firmness, citric acid (TA), total soluble solids (TSS), vitamin C and the lowest amount of appearance decay, pH and the ratio of TSS/TA were observed in the treatment of 0.75 and 1 µL L-1 of 1-MCP and 1 and 1.5 mM of putrescine. The results obtained from the experiment showed a positive effect of 1-MCP and putrescine on the storage life of strawberry. The results further showed that the use of 1-MCP and putrescine can act as an effective strategy in postharvest technology of strawberry fruit

Efficiency and emissions mapping of a light duty diesel - natural gas engine operating in conventional diesel and RCCI modes

Reactivity Controlled Compression Ignition (RCCI) is a promising dual-fuel Low Temperature Combustion (LTC) mode with significant potential for reducing NOx and particulate emissions while improving or maintaining thermal efficiency compared to Conventional Diesel Combustion (CDC) engines. The large reactivity difference between diesel and Natural Gas (NG) fuels provides a strong control variable for phasing and shaping combustion heat release. In this work, the Brake Thermal Efficiencies (BTE), emissions and combustion characteristics of a light duty 1.9L, four-cylinder diesel engine operating in single fuel diesel mode and in Diesel-NG RCCI mode are investigated and compared. The engine was operated at speeds of 1300 to 2500 RPM and loads of 1 to 7 bar BMEP. Operation was limited to 10 bar/deg Maximum Pressure Rise Rate (MPRR) and 6% Coefficient of Variation (COV) of IMEP. The engine performance was investigated using a combination of RCCI control variables including NG/diesel Blend Ratio (BR), diesel injection fuel split, and Start of Injection (SOI) timing for diesel injections. The RCCI map was generated using different injection strategies (single and double injections) and up to 20% EGR Exhaust Gas Recirculation (EGR) at higher loads to obtain the best brake thermal efficiency. In addition, the majority of the required energy (more than 80%) in RCCI operating points was provided from NG. The results showed a maximum of 5% increase in brake thermal efficiency and 92% reduction in NOx in RCCI combustion mode compared to the CDC mode

Data-driven modeling and predictive control of combustion phasing for RCCI engines

Reactivity controlled compression ignition (RCCI) engines center on a combustion strategy with higher thermal efficiency, lower particulate matter (PM), and lower oxides of nitrogen (NOx) emissions compared to conventional diesel combustion (CDC) engines. However, real time optimal control of RCCI engines is challenging during transient operation due to the need for high fidelity combustion models. Development of a simple, yet accurate control-oriented RCCI model from physical laws is time consuming and often requires substantial calibrations. To overcome these challenges, data-driven models can be developed. In this paper, a data-driven linear parameter-varying (LPV) model for an RCCI engine is developed. An LPV state space model is identified to predict RCCI combustion phasing as a function of multiple RCCI control variables. The results show that the proposed method provides a fast and reliable route to identify an RCCI engine model. The developed model is then used for the design of a model predictive controller (MPC) to control crank angle for 50% fuel burnt (CA50) for varying engine conditions. The experimental results show that the designed MPC with the data-driven LPV model can track desired CA50 with less than 1 crank angle degree (CAD) error against changes in engine load

Effect of diesel injection strategies on natural gas/diesel RCCI combustion characteristics in a light duty diesel engine

Reactivity controlled compression ignition (RCCI) combustion mode is an attractive combustion strategy due to its potential in satisfying the strict emission standards. In this study, the effects of direct injection (DI) strategies on the combustion and emission characteristics of a modified light duty RCCI engine, fueled with natural gas (NG) and diesel were numerically investigated. In this way, Converge CFD code employing a detail chemical kinetics mechanism was used for 3D simulation of combustion process and emissions prediction. NG with higher octane number (ON) is mixed with air through intake port, while diesel fuel with lower ON is directly injected into the combustion chamber during compression stroke by means of split injection strategy. The effects of several parameters, including the premixed ratio (PR) of NG, diesel fuel fraction in first and second injection pulses, first and second start of injection timing (SOI1 and 2), injection pressure and the spray angle on the engine performance and emission characteristics are investigated. The results indicate that these parameters have significant effects on the light duty RCCI engine performance and engine out emissions. Also, it was demonstrated that by decreasing the first injection pressure from 450 to 300 bar, the gross indicated efficiency increases by 5% and CA50 is retarded by 4 CAD. Moreover, by reducing the spray angle from 144° to 100°, the gross indicated efficiency decreases by 4% and CA50 is advanced by 6 CAD. The results showed that reduction in NOx emission is achievable, while controlling HC and CO emissions, by means of increasing the NG fraction, advancing the SOI1, increasing the fuel fraction in first DI injection with lower injection pressure and employing a wider injector spray angle