Design And Optimization Of Organic Rankine Cycle For Low Temperature Geothermal Power Plant

Rising oil prices and environmental concerns have increased attention to renewable energy. Geothermal energy is a very attractive source of renewable energy. Although low temperature resources (90C to 150C) are the most common and most abundant source of geothermal energy, they were not considered economical and technologically feasible for commercial power generation. Organic Rankine Cycle (ORC) technology makes it feasible to use low temperature resources to generate power by using low boiling temperature organic liquids. The first hypothesis for this research is that using ORC is technologically and economically feasible to generate electricity from low temperature geothermal resources. The second hypothesis for this research is redesigning the ORC system for the given resource condition will improve efficiency along with improving economics. ORC model was developed using process simulator and validated with the data obtained from Chena Hot Springs, Alaska. A correlation was observed between the critical temperature of the working fluid and the efficiency for the cycle. Exergy analysis of the cycle revealed that the highest exergy destruction occurs in evaporator followed by condenser, turbine and working fluid pump for the base case scenarios. Performance of ORC was studied using twelve working fluids in base, Internal Heat Exchanger and turbine bleeding constrained and non-constrained configurations. R601a, R245ca, R600 showed highest first and second law efficiency in the non-constrained IHX configuration. The highest net power was observed for R245ca, R601a and R601 working fluids in the non-constrained base configuration. Combined heat exchanger area and size parameter of the turbine showed an increasing trend as the critical temperature of the working fluid decreased. The lowest levelized cost of electricity was observed for R245ca followed by R601a, R236ea in non-constrained base configuration. The next best candidates in terms of LCOE were R601a, R245ca and R600 in non-constrained IHX configuration. LCOE is dependent on net power and higher net power favors to lower the cost of electricity. Overall R245ca, R601, R601a, R600 and R236ea show better performance among the fluids studied. Non constrained configurations display better performance compared to the constrained configurations. Base non-constrained offered the highest net power and lowest LCOE

Missing the point: re-evaluating the earliest lithic technology in the Middle Orinoco

The Culebra site, located in close proximity to the Atures Rapids, is one of the very few open-air occupations in the entire Orinoco valley that is thought to date to the early Holocene. Following renewed excavations in this location, we characterize the stone technology in unprecedented detail and perform both quantitative and qualitative analyses of the assemblage deposited in the first cultural layers. Additionally, we directly date the sediment forming the depositional context of the assemblage using stratigraphically stable components of soil organic matter. Coupled with our stratigraphic and paedological data, the deposit is, contrary to established estimates, shown to date to the late Holocene, well after the appearance of ceramics in the region. The toolkit identified through the lithic analysis, therefore, does not reflect an Archaic hunter–gatherer adaptation as previously assumed. Our findings are placed in the context of previous research in the Orinoco and lowland South America more broadly. More work is needed to understand the changing role of different stone tool reduction sequences with reference to adaptational strategies and bioclimatic variability

Approaches to terpenoid natural products using reactive intermediates

Two attempted syntheses of a functionalized ring system common to kaurenoid natural products is presented. One of the attempts employed a bridgehead enone as a dienophile in a Diels-Alder reaction. One example in this series resulted in the synthesis of the tetracyclic ring system, but the angular C-8 (kaurene numbering) methyl group could not be added. Another example in this series resulted in the synthesis of a tricyclic intermediate containing the carbons to form the fourth ring, but this could not be cyclized. The other approach employed a Michael addition followed by an oxy-ene reaction for the synthesis of the tetracyclic framework, but a suitable precursor for the oxy-ene reaction was not realized. Also described is an attempted cyclization of a bicyclic intermediate to a tricyclic intermediate that contained functionality to prepare the bicyclo (3.2.1) octene ring system using a variety of reagents, but with no success;A synthesis of an advanced intermediate toward the synthesis of trixikingolide is also described. This synthesis employed bridgehead carbocation chemistry in the construction of a key intermediate. A tricyclic intermediate is prepared by a regioselective intramolecular aldol condensation. This intermediate contains the necessary functionality to synthesize the pentacyclic ring system common to this class of natural products

Maximizing ORC performance with optimal match of working fluid with system design

This article compares constrained system design to non-constrained system design for the basic Organic Rankine Cycle (ORC). The 12 working fluids studied include eight dry-type, three isentropic, and one wet-type fluids. The ORC model was developed using Aspen HYSYS® and validated with data obtained from the literature. The constrained design compared the performance of working fluids for a fixed heat exchanger and turbine configuration. A non-constrained design was studied by altering the design specifications for the heat exchangers and turbine to match the working fluid. An energy and exergy analysis was performed using first and second law efficiency. The exergy analysis was also used to study exergy destruction across the ORC components. Cost analysis was performed by comparing the levelized cost of electricity (LCOE) for each working fluid in both designs. It was observed that non-constrained design favored working fluids with higher critical temperatures. Switching from constrained to non-constrained design lowered the LCOE for higher critical temperature working fluids such as R601, R601a, R123, R245ca, R245fa, R600, and R236ea. R245ca, R601, and R236ea show 11%, 10%, and 9% decrease in LCOE, respectively. No significant change in efficiency is observed for lower critical temperature working fluids such as R236fa and R134a. Also, no increase in net power was observed for lower critical temperature working fluids, suggesting that modifying design does not affect the performance of ORC. LCOE increased for R600a, R152a, and R227ea and remained unchanged for R236fa and R134a

Content Authentication and Forge Detection using Perceptual Hash for Image Database

Popularity of digital technology is very high. Number of digital images are being created and stored every day. This introduces a problem for managing image databases and security of images. One cannot determine if an image already exists in a database without exhaustively searching through all the entries. Further complication arises from the fact that two images appearing identical to the human eye may have distinct digital representations, making it difficult to compare a pair of images. Also the security of database server is questionable. The proposed framework provides the content authentication and forges detection of image. This can be done by generating perceptual image hash using SIFT algorithm, Perceptual image hash also known as perceptual image signature. It has been proposed as a primitive method to solve problems of image content authentication. The perceptual image hash is generated by using the perceptual features that are in accordance with human’s visual characteristics. It allows tampering of images to permissible extent e.g. improving slight brightness or contrast in image. A perceptual image hash is expected to be able to survive unintentional distortion and reject malicious tampering within an acceptable extend .Therefore it provides a more efficient approach to analyzing changes of image perceptual content and make sure database server is authenticated or not

TLM : a friend in learning and understanding maths

‘Raju hurry up, Rupa is throwing the ball,’ Payal called out to Raju loudly and ran away from the Pittul. Raju, Payal, Rupa and some of their friends are playing the game of Pittul. They are not able to arrange the Pittul. Rupa is repeatedly advising that the heavier stones should be placed at the bottom and the lighter ones on top, but Raju could not do it and got out. At that moment, Payal’s mother called Payal, ‘Come on, it is very late, you have been playing for a long time, come home and study now.’ ‘Ma, it is Sunday today, please let me play,’ Payal pleaded, but her mother did not listen to her and asked all the other children too to go home. Payal went home reluctantly

Longitudinal association between preschool fussy eating and body composition at 6 years of age: The Generation R Study

Background: Children's fussy eating behavior has been related to both underweight and overweight in cross-sectional studies, but the direction of these associations and the relation with more detailed measures of body composition remains unclear. We aimed to examine whether fussy eating at age 4 years is longitudinally related to body mass index (BMI), fat mass index (FMI) and fat-free mass index (FFMI) at 6 years of age. Methods: This study was embedded in Generation R, a population-based, prospective cohort. Data were available for 4191 children. The Children's Eating Behaviour Questionnaire (CEBQ), administered at age 4 years, was used to derive a fussy eating profile. This profile is characterized by high scores on food avoidant scales and low scores on food approach scales. At age 6 years, height and weight were measured at our research center. Body fat and fat-free mass were measured using Dual-energy-X-ray absorptiometry. We used age- and sex-specific standard deviation scores (SDS) for all outcomes. Results: After adjustment for confounders, the fussy eating profile was related to lower BMI-SDS (B=-0.37, 95 % CI: -0.47;-0.26), lower FMI-SDS (B=-0.22, 95 % CI: -0.33;-0.12) and lower FFMI-SDS (B=-0.41, 95 % CI: -0.54;-0.29). When adjusting for baseline BMI at 4 years, the fussy eating profile predicted a 0.11 lower BMI-SDS at age 6 (95 % CI: -0.19;-0.04). This change in BMI was mainly due to a decrease in FFMI (B=-0.19, 95 % CI: -0.29;-0.09). Fussy eaters also had a higher risk of becoming underweight than non-fussy eaters (OR=2.28, 95 % CI: 1.34;3.87). Conclusions: Our findings suggest that young fussy eaters are at risk of having a lower fat free mass and of becoming underweight over a 2-year period. This implies that fussy eaters may benefit from careful monitoring to prevent an adverse growth development

Biology and ecology of the invasive lionfishes, Pterois miles and Pterois volitans

The Indo-Pacific lionfishes, Pterois miles and P. volitans, are now established along the U.S. southeast coast, Bermuda, Bahamas, and are becoming established in the Caribbean. While these lionfish are popular in the aquarium trade, their biology and ecology are poorly understood in their native range. Given the rapid establishment and potential adverse impacts of these invaders, comprehensive studies of their biology and ecology are warranted. Here we provide a synopsis of lionfish biology and ecology including invasion chronology, taxonomy, local abundance, reproduction, early life history and dispersal, venomology, feeding ecology, parasitology, potential impacts, and control and management. This information was collected through review of the primary literature and published reports and by summarizing current observations. Suggestions for future research on invasive lionfish in their invaded regions are provided