Local-time Dependence of Chemical Species in the Venusian Mesosphere

Observed chemical species in the Venusian mesosphere show local-time variabilities. SO2 at the cloud top exhibits two local maxima over local time, H2O at the cloud top is uniformly distributed, and CO in the upper atmosphere shows a statistical difference between the two terminators. In this study, we investigated these local-time variabilities using a three-dimensional (3D) general circulation model (GCM) in combination with a two-dimensional (2D) chemical transport model (CTM). Our simulation results agree with the observed local-time patterns of SO2, H2O, and CO. The two-maximum pattern of SO2 at the cloud top is caused by the superposition of the semidiurnal thermal tide and the retrograde superrotating zonal (RSZ) flow. SO2 above 85 km shows a large day–night difference resulting from both photochemistry and the subsolar-to-antisolar (SS-AS) circulation. The transition from the RSZ flows to SS-AS circulation can explain the CO difference between two terminators and the displacement of the CO local-time maximum with respect to the antisolar point. H2O is long-lived and exhibits very uniform distribution over space. We also present the local-time variations of HCl, ClO, OCS, and SO simulated by our model and compare to the sparse observations of these species. This study highlights the importance of multidimensional CTMs for understanding the interaction between chemistry and dynamics in the Venusian mesosphere.

A close up of daily temperature and moisture in two Mexican high-elevation forests

The scarcity of meteorological stations and the strong need for climatic information in alpine forests require the use of large-scale climatic algorithms but the lack of in situ information produces high uncertainty on their suitability. In this study, we used linear mixed models to study the topographic effect (elevation and aspect) and time variations (from hourly to monthly) on temperature (T) and relative humidity (RH) with a 5-year instrumental database. Furthermore, we compared climatic information from a geographical algorithm and our in-situ data. Our data covered two mountains (Tláloc-TLA and Jocotitlán-JOC, State of México), four elevation belts (from 3500 m to 3900 m a.s.l.), and two aspects (Northwest and Southwest). We found differences for average temperature (TLA = 7.56 °C ± 0.03 °C and JOC = 6.98 °C ± 0.02 °C), and relative humidity between mountains (TLA = 69.3% ± 0.12% and JOC = 72.5% ± 0.13%,). The most significant variables explaining T were the elevation (Δ= -0.36 °C by 100 m) and aspect, while the aspect was relevant for RH. May was the warmest month (9.50 °C ± 0.10 °C for average temperature) while September the wettest for both mountains (85.1% ± 0.30% and 87.4% ± 0.25 % RH, respectively). Despite the higher correlations between climatic sources (up to r = 0.83), the geographical algorithm overestimates T and underestimates RH. We propose that when climatic information from geographical algorithms is used in alpine forests, calibrations are needed whenever possible with in situ information.

Adsorption of Iron (Fe) Heavy Metal in Acid Mine Drainage from Coal Mining

Adsorption is one of effective method to overcome acid mine drainage issue because of its economy and abundant availability of adsorbents. The research aimed to analyze the adsorption effectiveness and capacity of composite as the iron adsorbent in acid mine drainage. Composite consists of claystone from coal overburden, zeolite, and activated carbon from coconut shell. This study used experimental approaches in laboratory. Types of mineral contained in adsorbent materials (claystone, zeolite, and activated carbon) were: kaolinite, mordenite, and cristobalite. Composites were constructed with the following ratios: 50:25:25, 25:25:50, and 25:50:25 (Claystone[C] : Zeolite[Z] : Activated carbon[A]). The composite with a ratio of 25:25:50 had the greatest surface area of 62.44 m2/g, according to the results of the surface area analyzer test. Adsorption was performed in a batch system with a hot plate stirrer and composite mass of 2.5, 5, and 7.5 grams, for contact time variations of 30, 60, 90, 120, and 150 minutes. The adsorption test revealed that the composite was successful in increasing the pH of acid mine drainage to neutral (7.0) and lowering the Fe concentration to meet the quality standard. The best effectiveness of iron lowering was 99,35% with composite mass of 5 grams. However, the 2.5 grams composite mass is more efficient in terms of efficiency because it can lower the Fe concentration to 0.1484 mg/l with only 30 minutes contact time, ensuring that the Fe concentration fulfills the quality standard. The composite with a mass of 2.5 grams has the best adsorption capacity (1,286 mg/g).

French Fries-Like Bismuth Oxide: Physicochemical Properties, Electrical Conductivity and Photocatalytic Activity

Bismuth oxide synthesis using hydrothermal method has been conducted. This study aims to examine the effect of the hydrothermal reaction time on product characteristics and photocatalytic activity in degrading methyl orange dye. Bismuth oxide synthesis was initiated by dissolving bismuth nitrate pentahydrate (Bi(NO3)3.5H2O) and Na2SO4 in a distilled water and added NaOH gradually. The solution formed was transferred into a Teflon-lined autoclave and heated at 120 °C with time variations of 8–16 h. The formation of bismuth oxide was indicated by the vibrations of the Bi−O−Bi and Bi−O groups and the crystal structure consisting of a-Bi2O3, β-Bi2O3, and g-Bi2O3. In addition, the highest photocatalytic activity can be examined through several factors, such as: content of Bi−O−Bi and Bi−OH groups, crystal structure, band gap values, morphology, and surface area, acquired as a result of the effect of hydrothermal reaction time. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Pilot-Assisted OFDM for Underwater Acoustic Communication

Multicarrier techniques have made it possible to wirelessly transmit data at higher rates for underwater acoustic (UWA) communication. Several multicarrier techniques have been explored in the past for wireless data transmission. OFDM is known to fight off inter-symbol interference due to the orthogonality of its subcarriers. However, due to time variations, OFDM suffers from intercarrier interference. As the UWA channel is both a time and frequency variant, channel estimation becomes complex. We propose a pilot-based channel estimation technique and explore two equalizers for improving the error performance of an OFDM-based UWA system. Both the equalizers employ pilot subcarriers to estimate the UWA channel. One equalizer is a least squares (LS) equalizer and the other is a zero forcing (ZF) equalizer. Using computer simulations, it is observed that, for an acceptable error performance, the number of pilots should be one-fourth the number of subcarriers. Moreover, if the energy of the pilots is increased without changing the overall symbol energy, the error performance degrades. It is also noted that both the LS and ZF equalizers give an acceptable error performance with the ZF performing marginally better than the LS. Furthermore, the error performance of the proposed system is evaluated as a function of the transmitter-receiver distance and an acceptable error performance is observed even at 1250 m.

In-depth temperature and smoke production of charring wood under a constant external heat flux

The combustion characteristics of charring wood have been studied experimentally in a well-ventilated environment of a smoke chamber. A numerical simulation has also been performed for a limited case, with the Fire Dynamics Simulator, to estimate the burning environment. A horizontally placed specimen (ponderosa pine) with a moisture content of 0% or 20% is exposed to a radiant flux (25 kW/m2), with or without flaming ignition. Simultaneous measurements of the specimen’s in-depth temperature and the mass loss determine the charring front (rate) at 300 °C and the gasification rate, respectively. These condensed-phase conditions relate directly to real-time variations of gas-phase quantities: the specific optical density of smoke and the concentrations of toxic gases measured by a Fourier transform infrared gas analyzer. In-depth temperature trends are similar whether the flame exists, whereas the smoke and toxicants’ concentrations are substantially different. After the charring front moves through the specimen, the oxidative pyrolysis continues under the irradiation at high temperatures (up to ∼550 °C). Carbon monoxide and acrolein are produced continuously throughout the test, and the results indicate strong correlations. Although char formation of wood is favorable for fire safety, consequent incomplete combustion produces smoke and toxicants.

Pembuatan Karbon Aktif dari Limbah Plastik PET (Polyethylene terephthalate) Menggunakan Aktivator KOH

Pengunaan plastik setiap hari mengakibatkan terjadinya penumpukan sampah plastik yang dapat mencemari lingkungan dan menjadi salah satu masalah serius yang harus ditangani karena plastik tidak dapat terdegradasi. Plastik merupakan senyawa yang unsur penyusun utamanya adalah karbon dan hidrogen. Sehingga limbah plastik berpotensi sebagai pembuatan karbon aktif dan akan membuat limbah plastik menjadi lebih bermanfaat. Penelitian ini bertujuan untuk mengetahui pengaruh konsentrasi aktivator dan waktu aktivasi terhadap proses aktivasi fisika kimia sehingga menghasilkan produk karbon aktif yang sesuai dengan SNI 06-3730-1995. Plastik PET terlebih dahulu dikarbonasi pada temperatur 480oC selama 2 jam menggunakan furnace hingga membentuk arang. Lalu, direndam dalam aseton selama 24 jam. Setelah itu disaring dan dikeringkan menggunakan oven pada temperatur 110oC selama 3 jam dan dilanjutkan dengan proses aktivasi fisika pada temperatur 750oC selama 2 jam. Karbon yang telah teraktivasi fisika selanjutnya diaktivasi secara kimia dengan menggunakan KOH konsentrasi 1 M, 2 M, 3 M, dan 4M dengan variasi waktu 2 jam dan 4 jam. Diperoleh hasil terbaik yaitu pada karbon aktif dengan konsentrasi KOH 4 M dan waktu aktivasi 2 jam dengan nilai daya serap iod sebesar 980,17 mg/g, kadar abu 0,28%, kadar air 7,55%, dan kadar volatile matter 3,47%. Karbon aktif yang diperoleh telah memenuhi SNI 06-3730-1995.The use of plastic every day results in the accumulation of plastic waste that can pollute the environment and was a serious problem that must be addressed because plastic cannot be degraded. Plastic was a compound whose main constituent elements were carbon and hydrogen. So that plastic waste has the potential to produce activated carbon and will make plastic waste more useful. This study aims to determine the effect of activator concentration and activation time on the physical-chemical activation process so as to produce activated carbon products in accordance with SNI 06-3730-1995. PET plastik was first carbonated at a temperature of 480oC for 2 hours using a furnace to form charcoal. Then, soaked in acetone for 24 hours. After that it was filtered and dried using an oven at a temperature of 110oC for 3 hours and continued with the physical activation process at a temperature of 750oC for 2 hours. The physically activated carbon was then chemically activated using KOH concentrations of 1 M, 2 M, 3 M, and 4 M with time variations of 2 hours and 4 hours. The best results were obtained on activated carbon with a concentration of KOH 4 M and an activation time of 2 hours with an iodine absorption value of 980.17 mg/g, 0.28% ash content, 7.55% water content, and volatile matter levels 3,47%. Activated carbon obtained has complied with SNI 06-3730-1995.

Analisis Struktur Mikro dan Kekerasan Paduan Aluminium ADC 12 Hasil Proses Pengecoran Semi Solid dengan Proses Perlakuan Panas

This research aims to analyze the effect of providing additional heat treatment and artificial aging with variations in temperature of quenching and variations in aging time of ADC12 semi-solid casting result which include hardness and microstructure values. The Selected quenching temperature variations are 10°C, 30°C and 50°C. While the aging time variations are 0 h, 1 h, 3 h, 5 h, 7 h, 9 h, 11 h and 13 h. The tests carried out are hardness testing as well as microstructure that will be used to calculate the grain size values and structural density. The highest hardness value was at 180°C, 10°C cooling media variation with 5 h aging time is 83.10 HB. While the smallest grain size value was at the temperature of 10°C cooling media with an aging time of 5 h is 42.797 µm. The optimal value lies at a temperature of 10°C with an aging time of 5 h resulting hardness 83.7911 HB, the average of grain size is 13.5995 µm and the grain density value is 0.8892 with desirability reaching 0.920.