Behavior of biodegradable oil under impulse voltages

The properties of Palm Oil (PO) and Coconut Oil (CO) offer the potential for transformers with non-toxicity, high fire and flash points and better environmental compatibility while compared with those filled with Mineral Oil (MO). This potential has led to intensive studies of electrical performance of biodegradable oil especially in evaluating the electrical performance under lightning impulse voltage in recent years. This paper presents the investigation on the impulse breakdown voltage of PO and CO in such a uniform field. The PO used in this study is Refined, Bleached and Deodorized Palm Oil (RBDPO) Olein type. Two testing methods, rising-voltage and up-and-down are considered for both oils with different gap distances (2.0 mm and 3.8 mm). Testing methods including rising-voltage method and up-and-down method have no notable influence on the breakdown voltages of RBDPOs and CO compared to MO.IntroductionThe majority of transformers in the power system network are oil filled type. The main functions of the oil used in a transformer are to act as electrical insulation, cooling medium and information carrier. Up to now, the main oil insulation used in a transformer is Mineral Oil (MO) since it is proven to be successfully applied in practice for many years. Natural and synthetic esters are considered as the alternative for conventional MO due to the high fire safety and environmental friendliness. Extensive studies were conducted looking into the chemical, physical and electrical properties of natural and synthetic esters [1-3]. Another possible alternative for ester based oils are Palm Oil (PO) and Coconut Oil (CO). PO is derived from palm kernel which can be further separated to produce Crude Palm Oil (CPO) and Crude Palm Kernel Oil (CPKO) [4-5]. Further processing of CPO can produced Refined, Bleaching and Deodorized Palm Oil (RBDPO). The most common PO considered for transformers application is RBDPO. On the other hand, CO is extracted from kernel of matured coconut palm. The CO can be further processed to produce a neutralized, bleached and deodorized CO and is currently the type of oil investigated for the transformers’ application [6]. Transformer in service shall be exposed to voltages in excess of the normal operating voltage, such as transient overvoltage due to lightning impulse or switching impulse. Therefore the increasing interests among researchers press for comprehensive investigations on electrical performance of these liquids especially under impulse voltage [7]. This paper presents breakdown strengths of biodegradable oils (RBDPOs and CO) and MO in a uniform sphere-sphere electrode under impulse voltages. The influences of voltage polarities (positive and negative) and testing methods (rising-voltage and up-and-down) on the breakdown behavior are investigated

Lensing in an interior Kottler solution

We derive the interior Kottler solution of the incompressible fluid and show that the bending of light in this solution does depend on the cosmological constant.Comment: The inner Kottler solution derived and used in this paper is not new. Corresponding references to Stuchlik (2000) and Boehmer (2003) are added. Also added: a numerical example and a figure. This is the version accepted by Gen. Rel. Grav. However it includes a short passage that an anonymous referee had me suppress

Modeling and kinetic determination in affinity precipitation of trypsin

A mathematical model was proposed to allow the analysis of kinetic enzyme in experimental of affinity precipitation system. The methodology was tested using a system composed of enzyme, ethylene glycol and conjugated PABA-poly (NIPAM). N-isopropylacrylamide (NIPAM) is one of the monomers that have appealed to a great deal of investigation in the recent years. Its homopolymer NIPAM possesses temperature sensitivity and can act as a functional polymer with great potential. A water soluble ligand bound polymer has been synthesized by Electron Beam Irradiation for the purpose of affinity precipitation of trypsin. The affinity polymer was formed by ligand-PABA. The binding efficiency of trypsin to this polymer was dependent upon the ratio of (NIPAM), mercaptopropionic acid (MPA) as a chain transfer reagent and p-aminobenzamidine (PABA) as ligand that used in the polymer synthesis. The amount of precipitated of poly (NIPAM) present in the polymer solution also greatly affected the trypsin binding efficiency. The total binding capacity of trypsin molecules to ligand molecules approached the theoretical value which was considerably higher than that of insoluble gel matrices. Bound trypsin could be easily eluted by the ethylene glycol solution. At low molecular weight of poly (NIPAM), the conjugate polymer solution was very stable and retained its high capacity for trypsin recovery over a long period of time. The proposed analysis and simulation of kinetic parameters may be helpful in affinity precipitation technique for advanced application

Effect of laser surface modification (LSM) on laser energy absorption for laser brazing

Since the development of the laser in the 1960s a rapid development of research interests in science and technology took place. Since then, the need of laser application in industrials such as automotive, aerospace and electronics is increasing because of several advantages like automation worthiness, noncontact processing and product quality improvement. In this present study, the effect of Laser Surface Modification (LSM) on pure copper plate towards the laser energy absorption during indirect laser brazing process was studied. The laser brazing experiment was conducted inside a chamber under controlled vacuum pressure with 400Pa and irradiated with constant 140 Watt laser power. The defocusing features for laser brazing was used in order to find better focal position. Accordingly, the focal length for this laser brazing experiment was set to the focus point at 124 mm from the focal plane. Meanwhile, during LSM process, laser parameters such as laser scanning speed and focus length have been kept constant throughout the surface modification process. Yet, the laser power and laser frequency have been varied from 9 Watt to 27 Watt and 10 kHz to 80 kHz respectively. Apparently, surface roughness due to surface removal and oxide layer formation were presented during LSM process. These two surface integrities were found to be the factors of increasing laser energy absorption. It was discovered that an increase in surface roughness and oxide layer formation can absorb more laser energy which then results an increase in brazing temperature during laser brazing. This is because, increasing surface roughness will scatter the laser energy over a larger surface area, multiply the reflections in the surface irregularities while the oxide layer will enhance the interference phenomena of laser energy occurring inside the oxide layer. Both mechanisms increase laser energy absorptivity during laser brazing which results a high brazing temperature

Keterlibatan Suami dalam Menjaga Kehamilan Istri di Puskesmas Kecamatan Kuta Alam Banda Aceh, Provinsi Nangroe Aceh Darussalam

Husbands involved in reproductive health is known to give positive impacts especially for mother health services. Husbands may take major roles in supporting during pregnancy. It has not been known how the husbands take parts in supporting and careing their wives' pregnanies. The objectives of this study were to find out husbands' involvement in taking care their wives' pregnacies (cheking their nutrition/food, cheking their pregnancies from the early stage, and making sure that giving births are assissted by health workers) based on age, education, and occupation of the husbands. This study was a cross sectional study located at Kuta Alam sub district (Banda district). The respondents were 96 husbands of pregnant mothers who lived at the Kuta Alam community Health Center's areas, Banda Aceh. Data collection used structural interview to responsdents and analysed by Chi-square test. Result of the study showed: 1) More than 75% husbands were commonly involved in care of safe guarding the pregnancy of their wives. In the process of healthy reproduction, especially on the stage of pregnancy, the involvement and care of husbands are expected to grow; 2) The husbands' education level, age and the occupational were significant (p < 0,05) to influence of providmg cares on nutrition/food to the pregnant wives, on early-stage pregnancy chek-up and in making sure that giving birth was taken care by paramedics. The continuing of the study is needed to implement in remote areas to cover the problems of gender's roles, especially husbands who linked with reproductive health

Thermal Performance of Naturally Ventilated Classroom in the Faculty of Engineering Hasanuddin University, Gowa Campus

This study aims to identify the thermal performance of naturally ventilated classrooms of the new campus of Faculty of Engineering, Hasanuddin University in Gowa. The natural ventilation system has three main functions that are to provide healthy air for occupants, to provide thermal comfort to the occupants, and to cool the fabrics in the building interior. Thermal comfort perceived by the user is determined by many factors, including physical, psychological, etc. This research was conducted by using the experimental method with research analysis using CFD (Computational Fluid Dynamics) simulation method. The input parameters in the simulation were obtained through field measurement in the form of room dimension, ventilation open area, and microclimate parameter. The simulation is carried out at maximum open conditions in existing ventilation system with open and closed class door treatment. The simulation treatment of airflow input speeds were 0.25, 0.5, 0.75, and 1 m/s. The results showed that the existing ventilation system of Classroom at Faculty of Engineering (FoE) Hasanuddin University (Unhas) with an opening ratio of 16.59 to 22.76% of the floor area is good enough to flow and distribute comfortable air movement inside the classroom, especially at airflow speeds above 0.5 m/s

Mechanical properties of kenaf fibre thermoplastic polyurethane-natural rubber composites

Thermoplastic polyurethane-natural rubber TPUR-NR composites filled with treated and untreated kenaf fiber as filler were prepared at different TPUR and NR contents. The content of kenaf fiber was maintained at 12.5 wt % and the fiber was treated with 6 % solution of sodium hydroxide (NaOH), then dried for 24 hours in 100 °C, hot blended with polymer components, pulverized and pressed. The mechanical properties of the composites such as tensile, flexural and impact strength were determined, and their dependence on NaOH treatment of kenaf fibers was investigated. The analysis using scanning electron microscope (SEM) was implemented to identify the effect of alkali treatment on the microstructure of kenaf fiber and TPUR-NR composites. An improvement of fiber surface roughness and bonding between the fiber and polymer as well as an increase in impact energy and elongation at break of the composites was observed

All static spherically symmetric perfect fluid solutions of Einstein's Equations

An algorithm based on the choice of a single monotone function (subject to boundary conditions) is presented which generates all regular static spherically symmetric perfect fluid solutions of Einstein's equations. For physically relevant solutions the generating functions must be restricted by non-trivial integral-differential inequalities. Nonetheless, the algorithm is demonstrated here by the construction of an infinite number of previously unknown physically interesting exact solutions.Comment: Final form to appear in Phys Rev D. Includes a number of clarification

Assessment-schedule matching in unanchored indirect treatment comparisons of progression-free survival in cancer studies

Background The timing of efficacy-related clinical events recorded at scheduled study visits in clinical trials are interval censored, with the interval duration pre-determined by the study protocol. Events may happen any time during that interval but can only be detected during a planned or unplanned visit. Disease progression in oncology is a notable example where the time to an event is affected by the schedule of visits within a study. This can become a source of bias when studies with varying assessment schedules are used in unanchored comparisons using methods such as matching-adjusted indirect comparisons. Objective We illustrate assessment-time bias (ATB) in a simulation study based on data from a recent study in second-line treatment for locally advanced or metastatic urothelial carcinoma, and present a method to adjust for differences in assessment schedule when comparing progression-free survival (PFS) against a competing treatment. Methods A multi-state model for death and progression was used to generate simulated death and progression times, from which PFS times were derived. PFS data were also generated for a hypothetical comparator treatment by applying a constant hazard ratio (HR) to the baseline treatment. Simulated PFS times for the two treatments were then aligned to different assessment schedules so that progression events were only observed at set visit times, and the data were analysed to assess the bias and standard error of estimates of HRs between two treatments with and without assessment-schedule matching (ASM). Results ATB is highly affected by the rate of the event at the first assessment time; in our examples, the bias ranged from 3 to 11% as the event rate increased. The proposed method relies on individual-level data from a study and attempts to adjust the timing of progression events to the comparator’s schedule by shifting them forward or backward without altering the patients’ actual follow-up time. The method removed the bias almost completely in all scenarios without affecting the precision of estimates of comparative effectiveness. Conclusions Considering the increasing use of unanchored comparative analyses for novel cancer treatments based on single-arm studies, the proposed method offers a relatively simple means of improving the accuracy of relative benefits of treatments on progression times

Estimasi Karbon Tersimpan pada Tegakan Pohon di Hutan Pantai Pulau Kotok Besar, Bagian Barat, Kepulauan Seribu

The high activity of urban communities anthropogenic especially in Jakarta City cause high rates of carbon emissions. This problem is increased with the high rate of deforestation which is high enough in urban areas. One of ecosystem that can reduce carbon emissions is coastal forest ecosystem. Forests can reduce carbon emissions in the atmosphere and storing it in various compartments such as vegetation, litter and soil organic matter. One of the islands which have a coastal forest with good enough condition is Kotok Besar Island, the cluster of Seribu Islands. This study aims to estimate the carbon stored in tree stands at coastal forest region of west side of Kotok Besar Island, Seribu Islands. Methods of calculating carbon stock was done by making the observation plots and distributed by random sampling method to calculate diameter at breast height (dbh) and identify the type of tree stands were found in the observation plots. dbh data was inserted into allometric equation to obtain the potential of stored carbon estimates. The results showed that the coastal forest of west side of the Kotok Besar Island have the number of plant species that dominate as many as four species, which consists of Thespesia populnea, Casuarina sp., Calophyllum sp., and Cocos nucifera. Biomass value is 853.94 tons / ha and potential of carbon stored is 426.97 tons/ha