Quasi-Schreier Domains II

We study a class of integral domains characterized by the property that every nonzero finite intersection of principal ideals is a directed union of invertible ideals.     

Experimental investigation on the sound pressure level for a high thermal capacity burner during a running cycle

In many research or technical expertise studies the maximum noise level of a boiler is associated with the maximum thermal load of the burner. However, this type of air injected burners presents a complex running cycle with different functioning periods, where different parts (engine, fan, flame) of the burner are running separately or in the same time. In this study we are focused on the analysis, by experimental measurements, of the entire functioning cycle of a boiler by pointing out the noise differences and their importance when doing an experimental acoustical investigation. The entire 1/3 octave spectrum of the sound pressure level (SPL) was recorded during a complete running cycle by means of logging software associated to the sound meter. The sound equivalent level was calculated for each period of the running cycle and compared to the norms and with two theoretical prediction models that take into account the heating power and the boiler room volume. It was found that the most accurate data are obtained when the measurements are done in one-third octave. The maximum noise level was established to be not for the maximum thermal load period, but for the ventilation period of the boiler (before gas injection) with 82.1 dB at 125 Hz. A shut down delay was detected at the end of the cycle with 13 s for higher frequencies, due to the vibration of the boiler parts. Two 3D graphical representations point out the most important frequencies characterizing each running state of the burner. Compared to the noise curve (NC85) the minimum differences between the admissible values and the ones produced by the burner were found to be around 5.5 dB and therefore no acoustical treatment was needed. The results of the SPL prediction models matched the experimental data only for some of the boiler cycle periods and for only some of the frequencies. This type of detailed experiment investigation of the burner noise highlights the periods of the running cycle and the frequencies where the noise level requires acoustical treatment.     

Almost Schreier monoids

In an earlier paper, we introduced and studied the class of commutative integral domains D having the following property: if a, b₁, b₂ ? D{a, b_1, b_2 \in D} and a|b ₁ b ₂, there exist an integer k ≥ 1 and a₁, a₂ ? D{a_1, a_2 \in D} such that a ^k = a ₁ a ₂ and a_i|b_i^k , i = 1, 2{a_i|b{_i}^k , i = 1, 2} . In this paper, we show that many of our earlier results are purely multiplicative in the sense they can be extended to the setting of commutative cancellative monoids.     

LCM-splitting sets in some ring extensions

Let be a saturated multiplicative set of an integral domain . Call an lcm splitting set if and are principal ideals for every and . We show that if is an -stable overring of (that is, if whenever and is principal, it follows that and if is an lcm splitting set of , then the saturation of in is an lcm splitting set in . Consequently, if is Noetherian and is a (nonzero) prime element, then is also a prime element of the integral closure of . Also, if is Noetherian, is generated by prime elements of and if the integral closure of is a UFD, then so is the integral closure of .

     

A Facile Route to Cyclic and Acyclic Alkyl-Arginines

Treatment of commercially available alkyl and cycloalkyl thioureas with methyl iodide provides the corresponding S-alkylisothiouronium iodide which reacts directly with ornithine to yield the title compounds.     

Activation energy for the ignition of the catalytic oxidation of methanol in oscillatory regime

The overall activation energy for the ignition of thermokinetic oscillations observed (in a dynamic calorimeter) during the heterogeneous catalytic oxidation of methanol on Pd/LiAl₅O₈ were obtained and discussed by a PdO_x redox cycle.     

Disorientated optical polarization devices

By using a pure operatorial (nonmatrix) approach to some of the variable composite polarization devices, we show that for some values of the variable internal parameters, these devices lose their anisotropy. Their principal axes, or more generally their eigenvectors, become undetermined, i.e., in this sense, the anisotropic devices get "disorientated."     

Determination,speciation and distribution of mercury in soil in the surroundings of a former chlor-alkali plant: assessment of sequential extraction procedure and analytical technique

Background

The paper presents the evaluation of soil contamination with total, water-available, mobile, semi-mobile and non-mobile Hg fractions in the surroundings of a former chlor-alkali plant in connection with several chemical soil characteristics. Principal Component Analysis and Cluster Analysis were used to evaluate the chemical composition variability of soil and factors influencing the fate of Hg in such areas. The sequential extraction EPA 3200-Method and the determination technique based on capacitively coupled microplasma optical emission spectrometry were checked.

Results

A case study was conducted in the Turda town, Romania. The results revealed a high contamination with Hg in the area of the former chlor-alkali plant and waste landfills, where soils were categorized as hazardous waste. The weight of the Hg fractions decreased in the order semi-mobile?>?non-mobile?>?mobile?>?water leachable. Principal Component Analysis revealed 7 factors describing chemical composition variability of soil, of which 3 attributed to Hg species. Total Hg, semi-mobile, non-mobile and mobile fractions were observed to have a strong influence, while the water leachable fraction a weak influence. The two-dimensional plot of PCs highlighted 3 groups of sites according to the Hg contamination factor. The statistical approach has shown that the Hg fate in soil is dependent on pH, content of organic matter, Ca, Fe, Mn, Cu and SO₄^2- rather than natural components, such as aluminosilicates. Cluster analysis of soil characteristics revealed 3 clusters, one of which including Hg species. Soil contamination with Cu as sulfate and Zn as nitrate was also observed.

Conclusions

The approach based on speciation and statistical interpretation of data developed in this study could be useful in the investigation of other chlor-alkali contaminated areas. According to the Bland and Altman test the 3-step sequential extraction scheme is suitable for Hg speciation in soil, while the used determination method of Hg is appropriate.

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