Simultaneous Charging/Discharging of Phase Change Materials: Characterization of Natural Convection Process

In recent decades, latent heat storage in phase change materials (PCMs) received considerable attention. This is due to their high latent heat capacity, which is essentially required for managing and overcoming the temporal mismatch between energy supply and demand. Thus, at the time of energy availability at supply side, it is stored in PCMs so as to be extracted later on when it is needed. In order to provide continuous operation, there are some periods when a thermal storage has to be simultaneously charged and discharged. Most studies focused either on charging, discharging, or consecutive charging and discharging process, while limited work has been conducted for the case of simultaneous charging and discharging (SCD). The first objective of this dissertation is to develop a numerical model to analyze the heat transfer mechanism within a horizontal PCM storage under SCD. Since the possible heat transfer mechanisms within PCMs are conduction, convection or a combination of both, two models are used to identify the mechanism under SCD; i.e. the pure conduction (PC) model and combined conduction and natural convection (CCNC) model. The PC model is a hypothetical model, which neglects the natural convection during phase change process; however, the CCNC model is the real case one. Validation of the model results by comparison with experimental data shows an acceptable agreement both under melting and solidification. Therefore, the developed model can be used to numerically study the phase change process in PCMs. Natural convection is the result of density changes, which create buoyancy forces within melted PCM and plays a significant role during melting. Currently, the most widely used method to account for natural convection is the effective thermal conductivity method. The method considers an artificial increase in thermal conductivity values to take into consideration the effect of natural convection by comparing the results with experimental data. Two major shortcomings of this method are that first, it is tedious to obtain the proper value and second, the method does not provide information about the melting front location. In this dissertation, a novel simplified front tracking method is presented to replace the thermal conductivity method. The novel method is based on considering two separate melting fronts for the upper and lower halves of a horizontal thermal storage system. Therefore, two dimensionless correlations are developed to map the results of the simple PC model to that of the complicated CCNC model based on the presented logic. The method essentially creates a link between CCNC and PC models, which is also missing in the literature. Based on verification, the correlations can provide results within ±15% discrepancy

Cold thermal energy storage in solid-liquid transition of carbon dioxide: Investigating the possibility

Industrial freezing is an energy-intensive process which is growing due to the increasing demand. This is exerting stress on electrical grids, especially at peak hours. To tackle this issue, thermal energy storage has received attention; however, there is a gap in terms of suitable materials for thermal energy storage with temperatures below -40 °C commonly needed in these applications. In this paper, the solid-liquid phase change of carbon dioxide has been conceptually considered for thermal energy storage in a special type of heat exchangers known as pillow plate heat exchangers. Characteristically, these heat exchangers can withstand very high pressures which is a technical requirement for carbon dioxide thermal energy storage. This paper discusses the potential system layout and challenges ahead of this technology, along with the proposal for further investigation to verify the concept.Cold thermal energy storage in solid-liquid transition of carbon dioxide: Investigating the possibilityacceptedVersio

The Relationship between Organizational Culture and Customers' Satisfaction in Meli Bank Branches in Tehran

ABSTRACT The present study examined the relationship between organizational culture and customers' satisfaction in Iranian banking industry which is relatively a new topic of this kind. Another distinguishing aspect of this study is the employment of Dennison's Model to examine organizational culture and the use of Servqual's Model to explore customers' satisfaction; which are among the latest and most effective models for understanding organizational culture and customers' satisfaction. In addition, the structure of organizational culture model is capable of covering different aspects of organizational culture on one hand, and examining how culture is related to the organization's outputs, on the other. The present study examined the relationship between organizational culture and customers' satisfaction based on the four dimensions of organizational participation, adaptability, compatibility, and mission. The results of the Spearman Correlation Test indicated that there is a positive and significant relationship between organizational culture and customers' satisfaction

The effect of powder/liquid ratio on microleakage of resin-modified glass-ionomer

Introduction: Resin modified glass-ionomer cement (RMGI) is prepared by manual mixing of powder and liquid. Different mixing ratios influence on the RMGI properties. The aim was to compare the effect of different mixing ratios on the microleakage of RMGI. Materials &Methods: In this in vitro study, 60 Class V cavities (3×2×1.5 mm) with the gingival margin of 1 mm apical to the cement-enamel junction were prepared on the buccal and lingual surfaces of 30 sound premolars. The teeth were randomly divided into 6 groups. Group 1: The manufacturer’s recommended ratio, without conditioning; Group2: The manufacturer’s recommended ratio with conditioning; Group 3: 20% lower than the manufacturer’s ratio without conditioning; Group4: 20% lower than the manufacturer’s ratio with conditioning; Group 5: 20% higher than the manufacturer’s ratio without conditioning; Group6: 20% higher than the manufacturer’s ratio with conditioning. After thermocycling, the microleakage was evaluated using silver nitrate staining. The teeth were cut into two mesial and distal halves, and the microleakage at occlusal and gingival margins was recorded based on a 0‒3 scoring system under a stereomicroscope. Data were analyzed using Kruskal-Wallis and Mann-Whitney tests with significance level at P<0.05. Results: The maximum microleakage at gingival margins was recorded for group 4, which was significantly higher than that of group 2 and 6 (P=0.043 and P=0.043, respectively). No significant differences were observed in the microleakage between occlusal and gingival margins. Conclusion: A 20% reduction in P/L ratio of RMGI increases the gingival microleakage when surface conditioning was applied

Melatonin inhibits endothelin-1 and induces endothelial nitric oxide synthase genes expression throughout hepatic ischemia/reperfusion in rats

The production of reactive oxygen species (ROS) and dysfunction of vasculature play a central role in the pathophysiology of hepatic ischemia/reperfusion (I/R) injury. The aim of this study was to evaluate the beneficial effects of melatonin on reducing liver I/R injury in rats. Four study groups were formed: (1) saline - administered, control group (Control), (2) melatonin-administered group (MEL), (3) saline -administered I/R group (I/R) and (4) melatonin-administered I/R group (MEL+ I/R). Melatonin was injected intraperitoneally (15 mg/kg) 20 min before ischemia and immediately after reperfusion. After reperfusion, blood and ischemic liver tissues were collected. The group subjected to ischemia showed a significant increase in the serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels, as well as an increase in hepatic malondialdehyde (MDA) concentration. These increases were significantly inhibited by melatonin. Although, I/R augmented the endothelin-1 (ET-1) gene expression and the level of big endothelin-1 (big ET-1) in liver tissue, melatonin attenuated these increases. Conversely, non-significant decrease in endothelial nitric oxide synthase (eNOS) mRNA expression in I/R group was significantly elevated by melatonin in MEL+ I/R group. Melatonin exerts beneficial effects on ischemia/reperfusion liver injury through its anti-oxidative function as well as regulation of hepatic microcirculation.Key words: Melatonin, oxidative stress, ischemia/reperfusion injury, endothelin and nitric oxide synthase

Investigation of the effect of geometric and operating parameters on thermal behavior of vertical shell-and-tube latent heat energy storage systems

In this study, the effect of the geometrical and operational parameters on vertical cylindrical shell-and-tube LHTES systems is investigated. Four different ratios of the shell-to-tube radius are considered with the phase change material (PCM) on the shell side and the heat transfer fluid (HTF) flowing through the tube. The PCM temperature distributions are measured and compared experimentally among the studied storage units. A weighting method is utilized to calculate the average PCM temperature, liquid fraction, and stored energy fraction to evaluate the performance of the storage units. The results show that a shell to tube radius ratio of 5.4 offers better system performance in terms of the charging time and stored energy in the studied LHTES systems. Furthermore, the effects of HTF flow rate and temperature on the storage performance are studied. The HTF flow rate does not show a significant effect on the storage performance; however, the HTF temperature shows large impacts on the charging time. As the HTF temperature increases from 70 to 80 °C, the charging time reduces by up to 68% depending on the radius ratio

An In vitro Evaluation of Antimicrobial Efficacy of new Nano-zinc Oxide Eugenol (NZOE)

Introduction: This interventional in-vitro study aimed to evaluate the antimicrobial activity of a new Nano Zinc OxideEugenol (NZOE) sealer in comparison with AH26 and Pulpdent common root canal sealers against endodontic pathogens. Methods: The antimicrobial efficacy of three sealers(NZOE, AH26 and Pulpdent)  against Enterococcus faecalis (ATCC 29212), Escherichia coli (ATCC 25922), Streptococcus mutans (ATCC700610), Candida albicans (ATCC 90028), and Staphylococcus aureus (ATCC 25923)  were evaluated by Direct Contact Test (DCT) at five  different time intervals 0, 2, 14, 48 hours and 7 days. The results were statistically analyzed using SPSS software and Kruskal–Wallis at 5% significance level. Results: All three tested sealers had antimicrobial activity against microorganisms involved in this study. Fresh NZOE sealer eliminated all microorganisms tested, except the strain of E. faecalis colony which was reached to zero after 2 hours. However, AH26 and Pulpdent failed to completely kill all of the E. faecalis colony during the entire observation period. Also, NZOE showed a significant antimicrobial action (

A survey of feeding habits of economic benthic feeder fishes in the southern of Caspian Sea (Rutilus frissi kutum, Rutilus rutilus caspicus, Cyprinus carpio, Liza auratus and Liza saliens)

Present study analyzed the stomach contents of individuals belonging to five fish’s species in order toInvestigate seasonal changes in feeding strategy and diet composition in the South coast of the Caspian Sea (Gilan and Mazandaran provinces) from late March until late May 2010 using the research ship Gillan and fishing with batoom trawl nets and fishing blades insoles bony fishes in the depths of less than 60 meters. The average length and the total weight of Rutilus frisii kutum, Rutilus rutilus caspicus, Cyprinus carpio, Liza auratus and Liza saliens respectively were 36/9 ± 8/5 cm , 562/9 ± 353/2 g, 23/2 ± 3/2 cm , 202 ± 101/6 g, 24/6 ± 8/1 cm , 249/8 ± 242 g, 32/2 ± 8/9 cm , 320/9 ± 242/8 g, 22/7 ± 2/6 cm and 82/9 ± 52/2 g repectively. Using the method of Shorygin and Costello highly nourishing food strategy and different species of fishes were studied. The results of this study showed that Rutilus frisii kutum fed generally of Balanus and Cerastorderma In order of importance after Bivalvia, Gastropoda, Crabs, Fish eggs, Filamentous alge in GI Rutilus frisii kutum presence, but feeding it of Bivalvia (in particular Cerastorderma) was much more than the other food. The results of present study showed that under the influence of compatibility and behavioral mechanisms, ecological, physiological and nutritional importance of Rutilus frisii kutum Bivalvia. The results of studies were showed that Bivalvia was feeding the dominant Rutilus frisii kutum , while the results of this study showed that despite Bivalvia present importance in feeding the of this species, it seems that its presence in such digestion decreased. As well as the dominant food of Rutilus rutilus caspicus was fish, but generally from Detrite fed. This study showed that feeding the dominant species of Cyprinus carpio, Liza auratus and Liza saliens of Detrite was. The most important food items after ditrit for the Cyprinus carpio in order of importance include the Bivalvia, Gastropoda, Oligochaeta, Abra ovata, Nereis, Fish eggs, Filamentous alge, was. The Liza auratus dietary habits also showed that after ditrit the most importance in nutrition related to Foraminifera, Porifera and Balanus, and for Liza saliens to Gastropoda, Bivalvia and Porifera. The results showed that the mullet the greater the intensity of feeding fishes than other species were, Rutilus frisii kutum in between of Cyprinidae the greater the intensity of feeding fishes than other species were (0/05 > P). The values of this indicator in the lower longitudinal in all fish species investigated were more than high longitudinal groups. The feeding intensity at different times of sampling for all species investigated showed that in all species at times extremely reduced the reproductive index (0/05 > P). As well as the diversity foods in the lower longitudinal in all fish species investigated were more than high longitudinal groups. In conclusion, our results demonstrated Food strategy have changed based on physiological changes, metabolism activity, behaviour, and the amount of food available

Analysis of the present condition of the transfer of ownership sales and its impacts on Iran's Law

In Iranian law, the sale contract consists of two mutual acquisitions formed together. These acquisitions are in the same level regarding their positions (Article 338 of Iranian Civil Code). However, in spite of being in the same level, transposition of two acquisitions are possible, since dichotomy in time of credit affairs allows us to maintain causing correlation of commitments and to separate them from each other at the same time. Therefore, although traditional view of legal and jurisprudential issues does not accept such a condition, following a new approach and focusing on credit reasons, it is possible to accept transposition in the effect of contracts. The issue examined in this research is that the parties may agree to "temporally" submit the transfer of ownership based on their ‘will’, since the field of credit affairs follows sides` determination aside from developmental affairs. Based on the principle of determination prominence and article 10 of the Civil Code, such agreements should be corrected based on sentences, and hence we should not deal with law issues by ignoring ‘will’ of parties as a result of inappropriate and philosophical interpretations

Psychosocial, social and financial problems with coping strategies among families with thalassemic patients

Background&Objective: Thalassemia is an inherited and chronic hemolytic disorder. Like other diseases it can make psychological, social and financial problems for both patients and families. The necessity of this research is to teach the way of treating the psychosocial problems of this illness and to increase the quality of patients and families life. It is also a descriptive study to examine psychosocial and financial disorders and coping strategies among families with patients suffering major beta thalassemia Materials&Methods: 320 parents (229 of mothers and 91 of fathers) were included in this study. These families were those who were visited clinics associated with Gorgan's University. Data collection was done using a self structured questionnaire as well as Mc Cubin and Thompson scale for identifying coping strategies. Results: Findings revealed many problems, such as: stress for disease (82.8%) and the patients' vague future (81.8%). The mentioned problems were of psychological disorders. And about social problems: 33.8% of patients families were deprived of having picnics in their free times and helping the patient meddles the routine work of homes in 30.1% of families. The financial problems: the cost of traveling and providing the medicine (63.8%). In addition 97.5% of families had faith and reliance in God in order to help them and to believe their child's illness as a reality. It is apparent that families use different kinds of method in order to cope with psychological, social and financial problems and to face the disease. Conclusion: Most of families have a strong belief in religion and as a result they believe that any kind of problems and especially disease is one of ways to reach God. This is the idea which helps them to face this disease stoutly