Membrane evaluation for the treatment of acidic clear filtrate

The total effluent load of a paper mill can be significantly decreased by recycling of purified clear filtrate (CF) back to paper-making process. The CF treated with membranes can be reused, for instance, as wire section shower water and in the dilution of chemicals. The main requirements for a membrane in CF treatment are high filtration capacity, high retention of turbidity and low fouling tendency. Previous studies have shown that the regenerated cellulose (RC) ultrafiltration (UF) membrane C30F (current trade name UC030T) is especially suitable for the treatment of paper mill process waters. Every paper-making process is, however, different. Thus, filtration experiments are required in order to find the most optimal membrane for the treatment of a certain process water. In this study the best membrane for the treatment of acidic clear filtrate (ACF) was searched. The performance of the C30F membrane was compared with five UF and three microfiltration (MF) membranes. The results revealed that in addition to the C30F membrane, also some other membranes produced high filtration capacity with ACF (approximately 200 L/(m²h bar)). All the tested membranes also retained over 90% of turbidity. The extremely hydrophilic C30F membrane had, however, lower fouling tendency compared to the other tested membranes. Therefore, it was concluded that the C30F membranes were the best possible membrane for the ACF treatment.     

Laser-assisted friction stir processing of IN738LC nickel-based superalloy: stir zone characteristics

Friction stir processing (FSP) of high softening-temperature materials such as nickel-based superalloys is considered to be difficult. Laser heating of a localised area ahead of the FSP tool was used to provide sufficient plasticity during the FSP of IN738LC nickel-based superalloy. The stir zone (SZ) microstructure of the friction stir processed and laser-assisted friction stir processed were characterised. Laser-assisted friction stir processing (LAFSP) produced a defect-free pass, but FSP resulted in generation of a discontinuity in the SZ. Both lower volume fraction of partially dissolved γ′ precipitates and coarser grain structure of SZ in LAFSP led to more ductility of the SZ material and elimination of the defects.     

Laser pressure welding of aluminium and galvannealed steel

Dissimilar metal joints of galvannealed steel and commercially available pure aluminium (A1050) sheets were produced by changing the laser power and the roller pressure by the laser pressure welding method. In this method, the YAG laser beam was irradiated into a flare groove made by these dissimilar metal sheets. In addition, the laser beam was scanned at various frequencies and patterns through the fθ lens using two-dimensional scanning mirrors. Then the sheets were pressed by the pressure rolls to be joined. The compound layers in the weld interface were observed by optical microscope, and the layer thicknesses were measured. The thicknesses were in the range of 7–20 μm. The mechanical properties of welded joints were evaluated by the tensile shear test and the peel test. In the tensile shear test, the strengths of the joints produced under the most welding conditions were so high that the fracture occurred through the base aluminium sheet. In the peel test of the specimens subjected to the laser beam of 1200–1400 W power under the roller pressure of 2.94 kN, the specimen fracture took place in the base aluminium sheet. Even if the compound layer was thick, high joint strength was obtained. In order to know the reason for such high strength of joints with thick compound layers and the joining mechanism, the compound layer was observed by the HR-TEM. The TEM observation results revealed that the main phase in the compound layer was the solid solution of Al + Zn. Moreover, the intermetallic compound was identified as FeAl, Fe₂Al₅, Fe₄Al₁₃, and Fe₂Al₅Zn_0.4 phase by electron diffraction. The Fe₃Zn₁₀ (Γ phase) of Fe–Zn intermetallic compound was confirmed on a Fe base material. It is assumed that the joining areas were heated in a range of 782°C more than 665°C, a melting point of Al, by laser irradiation because the δ_lk phase aspect was not confirmed. Because the surfaces of A1050 and Zn plated layer were melted thinly, the layer was over 10 μm thicker. The reason for the production of high strength joints with the relatively thick intermetallic compound layer was attributed to the formation of (Al + Zn) phase with finely dispersed intermetallic compounds.     

HR-TEM observation of laser pressure weld of galvannealed steel and pure aluminium

Laser pressure welding was conducted by changing the laser power and the roller pressure in the previous experiment. It was revealed that dissimilar metal welding of galvannealed steel and pure aluminium was feasible in a wide range of welding conditions. When the roller pressure was more than 1.96 kN at the laser powers equal to or less than 1400 W, the joint strengths were so high that the specimens in the tensile shear and the peel tests fractured in the A1050 parent metal.

In order to know the reason for such high strengths of joints with thick compound layers and the joining mechanism, the compound layer was observed by HR-transmission electron microscopy (TEM). The TEM observation results revealed that the main phase in the compound layer was the solid solution of Al + Zn. Moreover, the intermetallic compound was identified as FeAl, Fe₂Al₅, Fe₄Al₁₃ and Fe₂Al₅Zn_0.4 phase by electron diffraction. The Fe₃Zn₁₀ (Γ phase) of Fe–Zn intermetallic compound was confirmed on a Fe base material. It is guessed that the joining areas were heated at a range of 782°C more than 665°C, a melting point of Al, by laser irradiation because the δ_lk phase aspect was not confirmed. Because the surfaces of A1050 and Zn plated layer were melted thinly, the layer was over 10 μm thicker. The reason for the production of high-strength joints with a relatively thick intermetallic compound layer was attributed to the formation of (Al + Zn) phase with finely dispersed intermetallic compounds.     

What Types of Defects Are Really Discovered in Code Reviews?

Research on code reviews has often focused on defect counts instead of defect types, which offers an imperfect view of code review benefits. In this paper, we classified the defects of nine industrial (C/C++) and 23 student (Java) code reviews, detecting 388 and 371 defects, respectively. First, we discovered that 75 percent of defects found during the review do not affect the visible functionality of the software. Instead, these defects improved software evolvability by making it easier to understand and modify. Second, we created a defect classification consisting of functional and evolvability defects. The evolvability defect classification is based on the defect types found in this study, but, for the functional defects, we studied and compared existing functional defect classifications. The classification can be useful for assigning code review roles, creating checklists, assessing software evolvability, and building software engineering tools. We conclude that, in addition to functional defects, code reviews find many evolvability defects and, thus, offer additional benefits over execution-based quality assurance methods that cannot detect evolvability defects. We suggest that code reviews may be most valuable for software products with long life cycles as the value of discovering evolvability defects in them is greater than for short life cycle systems.     

Effect of ultrasound on removal of persistent organic pollutants (POPs) from different types of soils

A new and promising technology is utilization of sonochemistry on decontamination of polluted soil. The feasibility of this technology on treatment of contaminated soils (synthetic clay, natural farm clay, and kaolin) was studied by using two target persistent organic pollutants (POPs): hexachlorobenzene (HCB) and phenanthrene (PHE). The soils were highly contaminated in 500 mg/kg. The laboratory experiments were conducted with various conditions (moisture, power, and time duration). The effects of these parameters on ultrasonication (as well as the removal of contaminants) were examined. The reasonable moisture ratio of the slurry could be in range of 2:1–3:1. The process did not change pH values of soils. Experimental results showed that ultrasonication has a potential to reduce the high concentrations of these POPs.     

Core business concentration vs. corporate diversification in the US electric utility industry: Synergy and deregulation effects

Many economists such as Wilson (2002) [Wilson, R., 2002. Architecture of power market, Econometrica, 70, 1299–1340] have considered that there are similarities between electricity and gas services in the US electric utility industry. Hence, they expect a synergy effect between them. However, the two businesses do not have technology similarities at the level that the gas service produces a synergy effect with electricity. To examine whether there is a synergy effect of corporate diversification in the industry, we compare electricity-specialized firms with diversified utility firms in terms of their financial performance and corporate value. The comparison indicates that core business concentration is more effective for electric utility firms than corporate diversification under the current US deregulation policy.     

Precise Measurements of the Vapor-Liquid Equilibria (VLE) of HFC-32/134a Mixtures Using a New Apparatus

A new apparatus for precise measurements of the vapor-liquid equilibria of mixtures by the circulation method has been developed. This apparatus has two special components: a high-stability temperature control system and a helium pressurization system. The temperature in the liquid bath surrounding the sample cell is kept constant within ±0.5mK. The helium pressurization system increases the pressure of the sampled mixture when measuring the compositions at low temperatures by gas chromatography. With these components, the uncertainty in measuring the vapor-liquid equilibria has been reduced. Using this apparatus, the vapor-liquid equilibria of HFC-32/134a mixtures were measured in a temperature range of 263.15 to 293.15K. These results are in good agreement with the calculated results from REFPROP (Ver. 6.01) with a relative pressure difference of about 2%.     

Characterization of the microbial community in an anaerobic ammonium-oxidizing biofilm cultured on a nonwoven biomass carrier

The enrichment and characterization of anaerobic ammonium-oxidizing biofilm cultures are ongoing in our laboratories. Biomass, with a predominately red color, demonstrating simultaneous removal of ammonium and nitrite under autotrophic and anoxic conditions, which is characteristic of anaerobic ammonium-oxidizing planctomycetes, was enriched and maintained for an extended period on a polyester nonwoven carrier. To investigate the bacterial composition of the mature biofilm community, 16S rDNA sequences were amplified by PCR and comparative analyses using DNA databases were conducted. Only one sequence had a notable similarity (92.2%) to that of the first discovered anaerobic ammonium-oxidizing planctomycete and lesser, yet significant, similarities to the 16S rDNA sequences of other recently reported anaerobic ammonium-oxidizing strains. The newly discovered strain (designated KSU-1) reported here was dominant among detectable members of the biofilm community. By fluorescence imaging, KSU-1 was shown to form spherical clusters wrapped in a thin layer of Zoogloea sp. Possible interactions and interdependencies of these two species are discussed with regard to the putative unculturability of the anaerobic ammonium-oxidizing planctomycetes.