Chemical Oxidation of Thiocyanate Ion by Ozone

Thiocyanate ion and weak ammonia liquor from a coking operation were ozonated in a semi-batch reactor. In a typical case, 500 mg/L thiocyanate ion disappeared in 8 minutes using an ozone dose of 82 mg/min at pH 7. The cyanide ion concentration was maximized immediately after the thiocyanate ion disappeared. The ozone-to-thiocyanate ion stoichiometric molar ratio was found to be 2.0 ± 0.2. The rate constants for the reaction of thiocyanate ion and cyanide ion with ozone under the typical conditions listed above were 5.4 × 10⁴ L²/(mmole²-min) and 1.5 L/(mmole-min), respectively.     

Wideband direction-of-arrival estimation using frequency-domain frequency-invariant beamformers: an analysis of performance

This paper presents an extension of the wideband direction-of-arrival estimation method using frequency-domain frequency-invariant beamformers (Do-Hong et al., 2003) with an analysis of performance. An asymptotic expression for the root-mean-square error and a resolution threshold of signal-to-noise-ratio for resolving directions of sources are shown. A comparison of analysis and simulation as well as numerical results are also presented.     

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川东北部宣汉—开江地区目前为川东地区天然气勘探的主要区块，钻井中井漏普遍，给钻井生产带来重大损失，严重影响井下施工安全。因此，正确认识漏失的性质、原因以预防和采取有效措施治理井漏是宣汉—开江地区钻井中迫切需要解决的问题。文章对宣汉—开江地区恶性井漏的特点及地质因素进行了分析，该区恶性井漏的特点是漏失井段长，漏失层段多，漏速大，漏失量大；沙溪庙组—自流井组、嘉五1亚段及飞仙关组地层恶性井漏特征明显，发生的频率高。资料表明，发生恶性井漏的漏层的漏失通道及储液空间主要为大型溶洞或大型裂缝系统；纵向压力剖面上，近地表正常静水柱压力带常发生恶性井漏，压力过渡带恶性井漏发生的频率相对较高，异常高压带较少发生恶性井漏；不同的压力带及复杂压力系统共存条件下，容易产生新的漏失通道或储液空间，诱发恶性漏失。     

Parametric optimization of multichannel rejection filters

The number of channels of a multichannel rejection filter (MRF) has been optimized by the energy and probabilistic criteria. The matrix of MRF coefficients is defined. The paper includes analysis of the gain in signal detection effectiveness, in the presence of interference, as compared to the single-channel rejection filter.     

Current status of existing railway bridges in Vietnam: An overview of steel deficiencies

Currently, the deterioration of bridge conditions is causing many problems. Therefore, the work reported in this paper was carried out to survey the present condition of railway bridges in Vietnam, concentrating on steel deficiencies. Literature reviews were initiated to identify common defects with site inspections and personal interviews to ascertain their validity. Finding the defects draws an overall picture of Vietnamese railway bridges that are in poor physical condition, thus providing poor serviceability. Besides structural failure, local defects were already identified, consisting of corrosion, fatigue, functional obsolescence and aging. New problems that have been identified are human invasions and missing elements. It is widely considered that overload, collision impacts, adverse climate conditions and poor maintenance are the main causes. Additionally, this paper includes previous wars, improper data keeping, and elemental burglary as country-specific causes. It suggests that maintenance efforts should be prioritized to eliminate these deficiencies. Trained maintenance crews need to be established and further research should be carried out to create an adequate maintenance management system in Vietnam.     

Structural evolution of alumina supported Mo-W carbide nanoparticles synthesized by precipitation from homogeneous solution

The synthesis of alumina-supported Mo-W carbide nanoparticles from the propane carburization of precursor metal sulphide, itself, obtained via precipitation from homogeneous solution (PFHS) has been investigated. Carburization temperature and time as well as the temperature-composition and time-temperature interaction effects were also found to be important determinants of the BET surface area, pore volume, surface chemical nature and extent of carburization. Thermogravimetry revealed that the metal sulphide conversion proceeds via a two-stage process involving substitutionary reaction in which S atom is replaced with carbon atom in the metal lattice. SEM images also confirmed that although temperature is detrimental to high surface area, the presence of spherical nanoagglomerates (25-35 nm) is indicative of the high dispersion offered by precipitation from homogeneous solution.     

An analysis of wideband direction-of-arrival estimation for closely-spaced sources in the presence of array model errors

This letter presents an analysis of wideband direction-of-arrival (DOA) estimation for closely-spaced sources using arbitrary antenna array taking into account the effect of array model error, which is important issue in practical implementation. Based on this analysis, a new wideband DOA estimation method without array calibration is then developed to deal with the effects of array errors. The performance improvement of the proposed method in the presence of array errors is shown in simulation results.