Modelling performance of ocean-thermal energy conversion cycle according to different working fluids

Ocean Thermal Energy Conversion (OTEC) is a promising renewable energy technology with the concept to harness the energy stored at the surface seawater (SSW) and the cold deep seawater (DSW). The operation is based on the Rankine cycle, and involves at a minimum temperature difference of 20 K of the SSW and DSW to generate electricity. This research focuses on the economic efficiency of different working fluids used in the OTEC Rankine cycle. The various working fluids include ammonia, ammonia-water mixture (0.9), propane, R22, R32, R134a, R143a, and R410a. Most of the existing commercial OTEC systems use ammonia as the working medium despite its toxic nature. This study shows that the ammonia-water mixture still gives the best results in terms of heat transfer characteristics because of its greater transport properties and stability compared to other fluids. However, fluids such as propane and R32 can also be used as a substitute for ammonia-water mixture despite having slightly lower efficiency, because they are non-toxic and safer towards the environment. The same developmental model was used to present the proposed modified OTEC Rankine cycle, which shows a 4% increase in thermal cycle efficiency. This study reveals economically efficient and environmentally friendly working fluids

Thermal comfort survey in office buildings in Bandung, Indonesia

The comfort state of office building’s occupants is crucial since its related to the worker’s productivity. This comfort temperature of people from tropical climate might be different from temperate climate area. This study aimed to investigate thermal comfort and adaptive behaviour of occupants in office buildings with different ventilation modes: air-conditioned, mixed-mode, and free running. On February and March 2015, approximately 400 responses has been obtained through field surveys in three office buildings Bandung, Indonesia. The results has shown quite different comfort range between occupants in three ventilation modes: 24.7 oC, 26.3 oC, and 27.5 oC operative comfort temperature for FR, CL, and MM accordingly

Production of Gymnemic Acid Depends on Medium, Explants, PGRs, Color Lights, Temperature, Photoperiod, and Sucrose Sources in Batch Culture of Gymnema sylvestre

Gymnema sylvestre (R.Br.) is an important diabetic medicinal plant which yields pharmaceutically active compounds called gymnemic acid (GA). The present study describes callus induction and the subsequent batch culture optimization and GA quantification determined by linearity, precision, accuracy, and recovery. Best callus induction of GA was noticed in MS medium combined with 2,4-D (1.5 mg/L) and KN (0.5 mg/L). Evaluation and isolation of GA from the calluses derived from different plant parts, namely, leaf, stem and petioles have been done in the present case for the first time. Factors such as light, temperature, sucrose, and photoperiod were studied to observe their effect on GA production. Temperature conditions completely inhibited GA production. Out of the different sucrose concentrations tested, the highest yield (35.4 mg/g d.w) was found at 5% sucrose followed by 12 h photoperiod (26.86 mg/g d.w). Maximum GA production (58.28 mg/g d.w) was observed in blue light. The results showed that physical and chemical factors greatly influence the production of GA in callus cultures of G. sylvestre. The factors optimized for in vitro production of GA during the present study can successfully be employed for their large-scale production in bioreactors

Radiation pattern reconfigurable fm antenna

In this work, a radiation pattern reconfigurable antenna design using compact printed spiral monopoles that operates at 102 MHz is reported. The proposed antenna changes its radiation behaviour that responds towards a desired direction with the use of RF switches. The antenna is printed on a 76.6mm × 50mm PCB layer providing more than 20MHz bandwidth at -10 dB threshold and is easily fabricated with low manufacturing cost. The antenna was also simulated on 500mm × 500mm ground plane that represents the roof top of a vehicl

Step and Step-Nc as a Tool for Big Data in Cloud Manufacturing

The terms big data, cloud manufacturing, predictive and additive manufacturing, and Internet of Things (IoT) are being most commonly used in the manufacturing industry nowadays. These terms are related to the fourth industrial revolution that emphasizes automation and data exchange between manufacturing tools/elements. Communication occurs between machines, products and even technicians or operators through various technologies while creating records of each interaction resulting in rapid growth of amount of data to be stored. Data acquisition is not a major issue since a structure or framework can properly connect these data in improving manufacturing efficiency. However, lack of effort in collecting and storing manufacturing data in the whole product life cycle process has made integration to be almost difficult to achieve. In this study, the adoption of STEP-NC method/technique was demonstrated in suiting the current explosion of big data in the industrial and manufacturing sector. The proposed methodology was developed through a study of an entity file structure and hierarchical concept in STEP and STEP-NC in gathering manufacturing data in a unified database. The challenge would be in making sense of the data, revealing the patterns in it and using them for operational improvements. The outcome of this study will be useful to support strategic decision making in product manufacturing

Social network sites (SNS) utilization in learning landscape - systematic literature review

Social network sites (SNS) have been widely used around the world to facilitate communication and engagement in the education landscape. The availability of various SNS types and their different functions have provided instructors and students with options in adding value to their learning process. However, there still lack of guidance on how to choose and strategize SNS utilization in learning. This paper explores SNS utilization by instructors and students in supporting the learning environment. The resources of the data are taken from four digital databases and analyzed using thematic analysis. The findings show the current types of SNS most used for learning purposes are Facebook, Twitter, YouTube and WhatsApp. The main uses of these SNS are identified as being for communication, collaboration, sharing information, enhancing learning and social connection

FPGA technology in process tomography

The aims of this paper are to provide a review of the process tomography applications employing field programmable gate arrays (FPGA) and to understand current FPGA related researches, in order to seek for the possibility to applied FPGA technology in an ultrasonic process tomography system. FPGA allows users to implement complete systems on a programmable chip, meanwhile, five main benefits of applying the FPGA technology are performance, time to market, cost, reliability, and long-term maintenance. These advantages definitely could help in the revolution of process tomography, especially for ultrasonic process tomography and electrical process tomography. Future work is focused on the ultrasonic process tomography for chemical process column investigation using FPGA for the aspects of low cost, high speed and reconstructed image quality

Electrical and magnetic properties of Ga substituted La2/3 Ca 1/3 MnO3 perovskite

Electrical and magnetic properties of gallium substitution for calcium in ABO3 typed colossal magnetoresistance (CMR) La2/3Ca1/3MnO3 (LCMO) perovskite were studied using DC four point probe and AC susceptometer. La2/3 (Ca1-xGax)1/3MnO3 (LCGMO) samples of concentration of x = 0.6, 0.7 and 0.8 were prepared using the solid state reaction method. Gallium substituted samples show the effect of decreasing Mn4+ concentration and of lattice distortion by incorporation of smaller gallium ionic radius. Electrical transport studies indicate samples with Ga concentration x=0.6 and 0.7 exhibit metal to insulator transition (MIT) at low temperature (50K) and sample x=0.8 only shows insulating behavior with increasing Ga concentration. AC susceptibility studies indicate all samples exhibit ferromagnetic to paramagnetic transition with an antiferromagneric ordering at low temperature showing the effect of decreasing Mn4+ concentration affecting double exchange mechanism and thus magnetic ordering of the samples

Potential of oil palm trunk starch as flocculant for contaminant of emerging compound removal

In this preliminary study, a natural flocculant is developed from an oil palm trunk. The flocculant further tested for its ability in turbidity and COD removal with additional of atrazine in wastewater and demineralised water matrix. At the optimum dosage of 20mg/L, the developed cationic OPT starch able to remove around 95% turbidity and 85% COD. In addition, the cationic OPT starch also show the ability to remove spiked atrazine from both water matrixes to the maximum range of 55-85%. In conclusion, the developed oil-palm based flocculant show great potential for real-world application with added cost-effective benefits

Study on the superconducting properties of Mn substituted YBCO

We have performed a study on the superconducting properties of Y1-xMnxBa2Cu3O7-δ with various Mn doping (x = 0.00, 0.25, 0.30, 0.35, 0.40 and 0.45). All of the samples displayed significant Meissner effect. XRD patterns indicate the existence of unknown peaks belonging to the impurities. A decrease in grain size as the concentration of Mn increases was observed from the SEM micrographs. The resistivity results showed the shifting in TC(R=0) towards low temperature as the Mn concentration increases