Continuous hydrothermal synthesis of HT-LiCoO2 in supercritical water

A detailed investigation was made into the production of high temperature lithium cobalt oxide (HT-LiCoO₂) particles by continuous hydrothermal synthesis via the reaction of cobalt nitrate, lithium hydroxide, and hydrogen peroxide. The experiments were carried out in both subcritical and supercritical water, at temperatures ranging from 300 to 411 °C, with residence times less than 1 min in all instances. Although Co₃O₄ particles were synthesized in subcritical water at similar reaction conditions designed for comparison, well-ordered particles of HT-LiCoO₂ were obtained in supercritical water. In supercritical conditions, the variations in temperature and residence time did not have significant impacts on the average particle size, particle size distribution, or morphology of obtained HT-LiCoO₂. However, it was important to supply excessive lithium hydroxide and hydrogen peroxide in order to synthesize single-phased HT-LiCoO₂ particles without undesired by-products. The hydrothermal synthetic route for LiCoO₂, CoO, and Co₃O₄ in both subcritical and supercritical conditions was postulated.     

Extraction of mangiferin from Mahkota Dewa (Phaleria macrocarpa) using subcritical water

A pharmacological active component, mangiferin, was extracted from Mahkota Dewa using subcritical water extraction. The subcritical water extractions were carried out at temperatures ranging 323–423 K, pressures ranging 0.7–4.0 MPa, and extraction times ranging 1–7 h. Extraction yield of mangiferin was measured using high-performance liquid chromatography (HPLC). The extraction yield was strongly dependent on the temperature while weakly dependent on the extraction pressure. As the extraction temperature increased, the extraction mangiferin yield increased, possibly resulting from the decrease in polarity of subcritical water at higher temperature. At an optimal extraction condition of 373 K, 4.0 MPa and extraction time of 5 h, the extraction yield of mangiferin was 21.7 mg/g. This value was close to the extraction yield with methanol (25.0 mg/g) and higher than those with water (18.6 mg/g) or ethanol (13.2 mg/g) at their boiling points.     

Effects of Silicon on Growth,Yield and Fruit Quality of Cantaloupe under Drought Stress

Silicon - Silicon (Si) plays an important role in mitigating adverse effects of various biotic and abiotic stresses including drought. Polyhouse experiment was conducted to evaluate the effects of...     

Smart packaging: sensors for monitoring of food quality and safety

The development of chemical sensors and biosensors over several decades has been investigated resulting in novel and very interesting sensor devices with great promise for many areas of applications including food technology. The incorporation of such sensors into the food packaging technology has resulted what we call smart or intelligent packaging. These are truly integrated and interdisciplinary systems that invoke expertise from the fields of chemistry, biochemistry, physics and electronics as well as food science and technology. Smart packaging utilises chemical sensor or biosensor to monitor the quality & safety of food from the producers to the costumers. This technology can result in a variety of sensor designs that are suitable for monitoring of food quality and safety, such as freshness, pathogens, leakage, carbon dioxide, oxygen, pH, time or temperature. Thus, this technology is needed as on-line quality control and safety in term of consumers, authorities and food producers, and has great potential in the development of new sensing systems integrated in the food packaging, which are beyond the existing conventional technologies, like control of weight, volume, colour and appearance.     

A review of current practice in constructability improvement: case studies on construction projects in Indonesia

The concept of constructability emerged in the late 1970s, evolved from studies into how improvement can be achieved to increase cost efficiency and quality in the construction industry. It is an approach that links the design and construction processes. The studies in the USA, UK and, later, in Australia have demonstrated that improved constructability has lead to significant savings in both cost and time required for completing construction projects. However, in implementing constructability improvement, it is important to consider the uniqueness of the construction industry in a specific country. To improve constructability in Indonesian construction projects, two main questions need to be answered: how is construction integrated into planning and design in existing practice and how can constructability be improved. Case studies indicate that the contractual relationships between the project team members determine the options for early involvement of construction personnel, and that the current constructability practices have had some positive impacts on project performance. In addition to a reduction in constructability problems, current constructability practices have enabled significant economic savings.     

Total organic carbon disappearance kinetics for supercritical water oxidation of dimethyl methylphospate used as a chemical agent simulant

Supercritical Water Oxidation (SCWO) has been proven to be a powerful technology to treat a wide range of wastes, but there are few references in the literature about the application of SCWO to chemical weapon agents. In this work, SCWO has been tested to treat a chemical agent stimulant, dimethyl methylphosphonate (DMMP), which is similar to the nerve agent VX and GB (Sarin) in its structure. The experiments were performed in an isothermal tubular reactor with H₂O₂ as an oxidant. The reaction temperatures ranged from 398 to 633 ‡C at a fixed pressure of 24 MPa. The conversion of DMMP was monitored by analyzing total organic carbon (TOC) on the liquid effluent samples. It was found that the oxidative decomposition of DMMP proceeded rapidly and a high TOC decomposition up to 99.99% was obtained within 11 seconds at 555 ‡C. An assumed first-order global power-law rate expression was determined with activation energy of 32.35±2.21 kJ/mol and a pre-exponential factor of 54.63±1.45 s ’ to a 95% confidence level. By taking into account the dependence of the reaction rate on oxidant concentration, a global power-law rate expression was regressed from the complete set of data. The resulting activation energy was 42.00±0.41 kJ/ mol; the pre-exponential factor was 66.56±0.48l ^1.31 mmol^-0.31 s^-1; and the reaction orders for DMMP (based on TOC) and oxidant were 0.96±0.02 and 0.35±0.04, respectively.     

A study on in-cylinder flow field of a 125cc motorcycle engine at low engine speeds

The in-cylinder flow characteristics of a four-stroke, four-valve, pent-roof small engine of motorcycle at engine speeds from 2000 rpm to 4000 rpm were studied using computational fluid dynamics (CFD). The aim of this study was to investigate the in-cylinder flow characteristics of small engines, including tumble, swirl, turbulent kinetic energy (TKE), angular momentum, in-cylinder air mass, turbulent velocity, turbulent length scale, and air flow pattern (in both intake and compression strokes) under motoring conditions. The engine geometry was created using SolidWorks, then was exported and analyzed using CONVERGE, a commercial CFD method. Grid independence analysis was carried out for this small engine and the turbulence model was observed using the renormalized group (RNG) k-ɛ model. The pressure boundary conditions were used to define the fluid pressure at the intake and exhaust of the port. The results showed that the increase in the engine speed caused the swirl flow in the small engine to be irregularly shaped. The swirl flow had a tendency to be stable and almost constant in the beginning of the compression stroke and increased at the end of compression stroke. However, the increase of in engine speed had no significant effect on the increase in tumble ratio, especially during the intake stroke. There was an increase in tumble ratio due to the increase in engine speed at the end of compression stroke, but only a marginal increase. The increase in engine speed had no significant effect on the increase in angular momentum, TKE, or turbulent velocity from the early intake stroke until the middle of the intake stroke. However, the angular momentum increased due to the increase in engine speed from the middle of the intake stroke to the end of compression stroke, and the angular momentum achieved the biggest increase when the engine speed rose from 3000 to 4000 rpm by 10 % at the end of the intake stroke. The increase in engine speed caused an increase of TKE and turbulent velocity from the middle of intake stroke until the end of compression stroke. Moreover, the biggest increase of TKE and turbulent velocity occurred when the engine speed rose from 3000 to 4000 rpm at the middle of intake stroke around 50 % and 25 %, respectively. Turbulent length scales appeared to be insensitive to increasing engine speed, especially in the intake stroke until 490 °CA. From that point, the value of the turbulent length scale increased as engine speed increased. The biggest increase in the turbulent length scales occurred when the intake valve was almost closed (around 20 %) and the engine speed was within two specific ranges (2000 to 3000 rpm and 3000 to 4000 rpm). Regarding the effect of engine speed, there were no significant effects upon the accumulated air mass in the small engine. The increase in engine speed caused an increase of turbulence in the combustion chamber during the late stages of the compression stroke. The increase in turbulence enhanced the mixing of air and fuel and made the mixture more homogeneous. Moreover, the increase in turbulence directly increased the flame propagation speed. Further research is recommended using a new design with several types of intake ports as well as combinations of different intake ports and some type of piston face, so that changes in air flow characteristics in small engines can be analyzed. Finally, this study is expected to help decrease the number of experiments necessary to obtain optimized systems in small engines.

     

Polarimetric Classification in a Tailings Deposition Area at the Timika Mine Site, Indonesia

Abstract.  Preliminary results indicate that polarimetric synthetic aperture radar (SAR) data can be useful in characterizing remote tailings sites in Indonesia. Recent launches of polarimetric radar satellites offer new opportunities to use such data. Wishart polarimetric radar classification was used to map tailings conditions and vegetative stress. We assessed the accuracy of our analysis and found that almost all scatterers could be discriminated properly, and that the technique was particularly useful in distinguishing saturated versus relatively dry tailings. Since tropical regions are subject to severe atmospheric disturbances, tailings stability is a major issue; there is thus high potential value in using radar remote sensing to aid revegetation and tailings stabilization.     

Lipid production by Lipomyces starkeyi using sap squeezed from felled old oil palm trunks

1. Download : Download high-res image (272KB)
2. Download : Download full-size image

     

Real time on-package freshness indicator for guavas packaging

A novel on-package color indicator has been fabricated based on bromophenol blue, and tests have been conducted to assess the freshness of guava (Psidium guajava L.). Bromophenol blue (BPB) was immobilized onto bacterial cellulose membrane via absorption method. The BPB/cellulose membrane as color indicator works based on pH decrease as the volatile organic compounds (e.g. acetic acid), produced gradually in the package headspace during developing of guava. Subsequently the color of the indicator will change from blue to green for over-ripe indication, which can be visible to the naked eye. The results showed that the color indicator could be used to determine the state of freshness of the guava at ambient condition (28–30 °C). The color change of the indicators reflects the pH of headspace of the guava packaging. Furthermore, it also in similar trends to the change of several parameters (soluble solids content, texture and sensory evaluation) that normally used to characterize the freshness of guava. Therefore, the indicator can be used for real time visual monitoring of freshness state of packaged guavas.