Considerations regarding Ex d IIB + H2 method of protection for flameproof electrical equipment

The flameproof enclosure type of protection is still one of the safest because it is based on a very simple and, therefore, unlikely fallible technology. If an explosive atmosphere penetrates an enclosure producing a trigger, the explosion occurs, but it remains confined within the enclosure. Engineers settled the concept that, for IIC areas, have to be necessarily used equipment with cylindrical flame paths, which usually feature a round-shape body that make more complicated the construction of panel boards. EN 60079-1 standard, states that flanged flame paths are allowed in the presence of hydrogen, therefore, in recent years, started the production of “Ex d” explosion-proof enclosures which are usable, as well as with gases of Group IIB, even in the presence of hydrogen. This means that the equipment can be used in an environment containing explosive atmosphere with hydrogen. Acetylene is, therefore excluded, but it has to be considered that the environments with the presence of hydrogen are much more frequent than those with acetylene. The purpose of this paper is to assist manufacturers design flameproof equipment that satisfies the requirements of the standard for group IIB and hydrogen applications in order to smooth the path for certification.

Indoor air quality evaluation in naturally cross-ventilated buildings for education using age of air

Natural ventilation (NV) is a strategy of bioclimatic design to promote hygrothermal comfort and indoor air quality (IAQ). Nowadays, COVID-19 pandemic highlights the review of ventilation standards. In Mexico, the IAQ standard states a minimum of 6 ACH for educational buildings. ACH considers NV as an ideal piston flow and does not provide information of indoor airflow distribution. In this work, new age of air associated parameters are proposed, considering the indoor airflow distribution: the air renovation per hour (ARH) and the renovation parameter R. An isolated educational building located in a rural region is studied. Four window configurations of cross-ventilation are considered. All configurations have one windward window located at bottom. The configurations axial and upward have one leeward window at bottom and top, respectively. While, configurations corner and upward corner have one lateral side window at bottom and top, respectively. A CFD model of the educational building is validated with experiments. The axial configuration has the best performance according to ACH, nevertheless has the worst performance according to ARH and R. The results show that NV evaluation using ACH can lead to wrong decisions. An improvement of NV standard with the age of air associated parameters is recommended.

Technical Note: Classical and statistical thermodynamic treatment of adsorption and desorption kinetics and rates

Adsorption and desorption represent the initial processes of the interaction of gas species with the condensed phase. It has important implications for evaluating heterogeneous (gas-to-solid) and multiphase chemical kinetics involved in catalysis, environmental interfaces, and, in particular, aerosol particles. When describing gas uptake, gas-to-particle partitioning, and the chemical transformation of aerosol particles the desorption lifetime is a crucial parameter to assess the underlying chemical kinetics such as surface reaction and surface-to-bulk transfer. The desorption lifetime, in turn, depends on the desorption free energy which is affected by the chosen adsorbate model and standard states. To assess the impact of those conditions on desorption energy and, thus, desorption lifetime, we provide a complete classical and statistical thermodynamic treatment of the adsorption and desorption process considering transition state theory for two typically applied adsorbate models, the 2D ideal gas and the 2D ideal lattice gas, the latter being equivalent to Langmuir adsorption. Both models apply to solid and liquid substrate surfaces. We derive the thermodynamic and microscopic relationships for adsorption and desorption equilibrium constants, adsorption and desorption rates, first-order adsorption and desorption rate coefficients, and the corresponding pre-exponential factors. Although, some of these derivations can be found in the literature, this study aims to bring all derivations into one place to facilitate the interpretation and analysis of desorption energies for their application in multiphase chemical kinetics. This exercise allows for a microscopic interpretation of the underlying processes including the surface accommodation coefficient and highlights the importance of the choice of adsorbate model and standard states when analyzing and interpreting adsorption and desorption processes. We demonstrate how the choice of adsorbate model choice affects equilibrium surface concentrations and coverages, desorption rates, and decay of the adsorbate species with time. In addition, we show how those results differ when applying a concentration- or activity-based description. Our treatment demonstrates that the pre-exponential factor can differ by orders of magnitude depending on the choice of adsorbate model with similar effects on the desorption lifetime, yielding significant uncertainties in the desorption energy. Furthermore, uncertainties in surface coverage and assumptions in standard surface coverage can lead to significant changes in desorption energies derived from measured desorption rates. Providing a comprehensive thermodynamic and microscopic representation aims to guide theoretical and experimental assessments of desorption energies and estimate potential uncertainties in applied desorption energies and corresponding desorption lifetimes important for improving our understanding of multiphase chemical kinetics.

Thermodynamic aspects of Cr2O3 reduction by carbon

In order to save resources of chromium, technology of flux-cored wire surfacing is of great practical interest. In this case Cr2O3 chromium oxide and carbon as a reducing agent are used as fillers. Thermodynamic assessment of probability of 16 reactions between them under standard conditions and for certain reactions under conditions different from standard was carried out using tabulated thermodynamic data of reactants in temperature range of 1500 – 3500 K. The following states were considered as standard states for reactants: Cr(ref) (reference state, melting point 2130 K, boiling point 2952 K), Cr(liq), Cr(gas), Cr2O3 (cr, liq), Cr2O3 (gas), C(ref), and as possible reaction products and standard states for them CO(gas), CO2 (gas), Cr23C6 (сr), Cr7C3 (cr), Cr3C2 (cr). Probability of reactions was estimated using standard Gibbs energy and the Gibbs energy calculated using the Van Goff isotherm equation. Dissolution of chromium in metal of surfacing bath or probable partial pressures of CO and CO2 in gas phase was taken into account and was calculated from equilibrium of carbon gasification reaction. Presence of carbon in flux-cored wire with chromium oxide Cr2O3 as a reducing agent will necessarily lead to occurrence of reduction reactions with generation of chromium carbides, and possibly chromium itself. Generation of Cr7C3 (сr) carbide is likely. With longer life time of chromium oxide and carbon at a temperature above 2500 K, generation of chromium as a component of the surfacing bath is more thermodynamically probable than generation of its carbides. Chromium oxide has the highest reactivity in Cr2O3 (liq) state. Direct reduction is preferential. Generation of CO(gas) as a product of carbon oxidation is more probable. Dissolution of chromium in metal increases thermodynamic probability of reactions with its generation and further reduces probability of reactions in which chromium is the starting material.

Health Education of Mother and Child to Reduce Prevalence of Stunting in Medokan Semampir Surabaya

Background: Stunting is a chronic nutritional problem in infants characterized by a length or height that is lacking compared to age. The prevalence of stunting in Medokan Semampir Village was 30.48% while the WHO standard states that free stunting if it is less than 20%. Purpose: This activity aims to provide knowledge and skills to mothers who will and already have a toddler to prevent stunting in RW 02 Medokan Semampir. Methods: This program was implemented in 4 steps those are planning, acting, observing, and evaluating. Results: The results of the health examination for toddlers who participated in the activity showed that there were no cases of stunting, but there were 3 toddlers who were underweight, so it needed to be increasingly inadequate nutrition. Whereas the mother’s examination showed 6 people who had low Hb levels and 2 people had high blood sugar levels. Toddler massage training provides the skills of mothers who had toddlers and toddler cadres in RW 02 to take independent action on their babies. Balanced nutrition counseling, exclusive breastfeeding, and mandatory immunization rose participant awareness in efforts to prevent stunting. Whereas the socialization of dental and oral health provided knowledge on how to clean the teeth of mothers and toddlers correctly and safely to avoid dental caries which can cause stunting in toddlers. Conclusion: This program was very useful for mothers and toddlers because it provides knowledge and skills in efforts to prevent the incidence of stunting toddlers.

SOME THERMODYNAMIC ASPECTS OF WO3 REDUCTION BY ALUMINUM

Technology of arc surfacing using flux cored wire, in which tungsten oxide (WO3) and aluminum are used as fillers, is of interest for practical application in order to save tungsten. Thermodynamic estimation of probability of 14 reactions between them under standard conditions was carried out using tabular thermodynamic data of reagents in temperature range 1500 – 3500 K. This interval includes temperature at the drop surface on the electrode at time of separation, so are temperatures at the arc periphery and in the upper layers of surfacing bath. The following states were considered as standard states for reagents: WO3(solid), WO3(liquid), WO3(gas); Al(ref), Al(liquid), Al(gas), Al2(gas), and as possible reaction products and standard states for them: W(ref), W(liquid), W(gas), Al2O3(solid), W; Al2O3(liquid), AlO(gas), AlO2(gas), Al2O(gas), Al2O2(gas). Reduction reactions of the oxide were recorded at 1 mole O2 . Probability of reactions was evaluated using standard Gibbs energy of reactions. Calculations were carried out in four stages. Aggregate states of oxide, metal and structure of aluminum vapor, in which oxide and metal have the greatest chemical affinity for each other were established on the first and second stages. At the third and fourth stages, the most probable state was determined for metallic tungsten and the most probable composition, and aggregate state of aluminum oxide formed as a result of alumothermy of Al2O3(solid, liquid); Al2O3(liquid); AlO(gas); AlO2(gas); Al2O(gas); Al2O2(gas). According to Al – W system state diagram, there are a number of intermediates between tungsten and aluminum: W2Al, WAl3 , WAl4 , WAl5 , WAl7 , WAl12 ; however, a search for thermodynamic properties for them shows that data are available only on melting pattern (congruent or in-congruent) and temperature of transformation. No other thermodynamic data. At the same time, based on results of our previous work on restoration of tungsten oxide by carbon and silicon, it can be predicted that aluminides of a free-frame will necessarily be formed. Performed thermodynamic analysis shows that presence in flux-cored wire used for surfacing, along with tungsten oxide WO3as an aluminum reducing agent, will necessarily lead to occurrence of reduction reactions with formation of tungsten aluminides, and possibly tungsten itself. Tungsten oxide has the highest reactivity, being in state of WO3(gas). Aluminum itself has the highest chemical affinity for WO3(gas) in form of Al2(gas) and Al(gas). Al2O(gas) appears most likely as an oxidation product of aluminum.

Introductory Note

In 2016, the jurisprudence of ICSID tribunals and ad hoc committees largely followed established lines. However, two jurisdictional decisions evidenced that the Salini test seems to have been almost eviscerated. The use of the GATS MFN clause to access investment arbitration was rejected in Menzies and forged documents led to the inadmissibility of investment claims in Churchill Mining. The Philip Morris case addressed core issues of host state regulatory measures and investment protection standards. Several cases clarified the role of compensation as a legality requirement for expropriation, while others made the due diligence standard states owe under full protection and security more precise and one tribunal held that an investor could not even import more favourable substantive standards under the applicable MFN clause. Two annulment committees ruled on the impartiality and independence of arbitrators and the issue of “surprise arguments.”

A High Gain Microstrip Patch Array for 5 GHz WLAN Applications

This paper presents the design, fabrication and measurement of a high gain 4-elements linear patch array, which uses the corporate feed technique with inset for excitation resonating at 5.216 𝐺𝐻z. is used as a dielectric substrate for the proposed array structure. The designed array is simulated and optimized by using CST microwave studio software. The element of the array is designed using the transmission-line model equations. The ground plane is made defective by incorporating slots and the reflective ground is utilized to enhance the gain of the array. The simulated and measured results for various parameters of the array are presented. The comparison between simulated and measured results show good agreement with little deviation. The optimized dimensions of the proposed design provides a maximum gain of 9.019 dB and a maximum directivity of 12.81 dBi. The antenna has been designed for the range which is one of the ranges for band for wireless local area networks (WLAN) applications as the standard states.