Possibility of Inducing Compressive Residual Stresses in Welded Joints of SS400 Steels

Since the welded constructions produce easily stress corrosion cracking (SCC) or fatigue disruption in corrosive medium or under ripple load, two methods inducing compressive stress on structural surfaces by anti-welding-heating treatment (AWHT) and explosion treatment (ET) are presented. The results show that they are good ways to resisting SCC on the welded SS400 steel or other components.     

Broadband absorption spectroscopy in turbid media by combined frequency-domain and steady-state methods

A technique for measuring broadband near-infrared absorption spectra of turbid media that uses a combination of frequency-domain (FD) and steady-state (SS) reflectance methods is presented. Most of the wavelength coverage is provided by a white-light SS measurement, whereas the FD data are acquired at a few selected wavelengths. Coefficients of absorption (mu(a)) and reduced scattering (mu(s)') derived from the FD data are used to calibrate the intensity of the SS measurements and to estimate mu(s)' at all wavelengths in the spectral window of interest. After these steps are performed, one can determine mu(a) by comparing the SS reflectance values with the predictions of diffusion theory, wavelength by wavelength. Absorption spectra of a turbid phantom and of human breast tissue in vivo, derived with the combined SSFD technique, agree well with expected reference values. All measurements can be performed at a single source-detector separation distance, reducing the variations in sampling volume that exist in multidistance methods. The technique uses relatively inexpensive light sources and detectors and is easily implemented on an existing multiwavelength FD system.     

Cyclo(RGD)‐Decorated Reduction‐Responsive Nanogels Mediate Targeted Chemotherapy of Integrin Overexpressing Human Glioblastoma In Vivo

Cyclo(Arg‐Gly‐Asp) peptide (cRGD) decorated disulfide (SS) containing poly(vinyl alcohol) nanogels (cRGD‐SS‐NGs) with an average diameter of 142 nm prepared by inverse nanoprecipitation, “click” reaction, and cRGD conjugation are developed for targeted treatment of integrin overexpressing human glioblastoma in vivo. Doxorubicin (DOX) release from cRGD‐SS‐NGs is highly inhibited under physiological conditions, while accelerated at endosomal pH and in response to cytoplasmic concentration of glutathione. Confocal microscopy shows that cRGD‐SS‐NGs facilitate the cellular uptake and intracellular DOX release in α_vβ₃ integrin overexpressing human glioblastoma U87‐MG cells. DOX‐loaded cRGD‐SS‐NGs present much better killing activity toward U87‐MG cells than that for nontargeted nanogels determined by MTT assay. The in vivo imaging and biodistribution studies reveal that DOX‐loaded cRGD‐SS‐NGs have a much better tumor targetability toward human U87‐MG glioblastoma xenograft in nude mice. Also the tumor growth is effectively inhibited by treatment with DOX‐loaded cRGD‐SS‐NGs, while continuous tumor growth is observed for mice treated with nondecorated nanogels as well as free DOX. Furthermore, the treatment with DOX‐loaded cRGD‐SS‐NGs has much fewer side effects, rendering these nanogels as a new platform for cancer chemotherapy in vivo.     

Dual reciprocity boundary element analysis of nonlinear diffusion: temporal discretization

This article presents an application of higher order time integration schemes in the dual reciprocity boundary element analysis of nonlinear transient diffusion problems involving nonlinear boundary conditions as well as temperature-dependent material properties. Multistep θ-methods, cubic Hermitian schemes and one-step least squares method have been considered. An error estimate based on the conservation of thermal energy has been presented to assess the accuracy of the numerical solutions. Numerical results are presented for a set of representative test problems to demonstrate the usefulness of the presented time integration algorithms.     

Destructive analysis of the nuclide composition of spent fuel of WWER-440, WWER-1000, and RBMK-1000 reactors

The results of analysis of spent nuclear fuel (SNF) by destructive methods, carried out systematically at the Khlopin Radium Institute for over 20 years till the mid-1990s, are presented. These data constitute the experimental base for the development of nondestructive methods, correction of calculation programs, substantiation of correlation techniques of determination of individual components of SNF, and for some other purposes. The isotope compositions of U, Pu, Am, and Cm and the fuel burn-up values are presented for 81 SNF samples from WWER-440, WWER-1000, and RBMK-1000 reactors. The burn-up values are determined with ¹⁴⁸Nd, ^{145 + 146}Nd, and ¹³⁷Cs monitors. The utilized methods, including ion-exchange and distribution chromatography, electromigration, and coprecipitation, as well as α-ray spectrometry, luminescence analysis, and mass spectrometry, are briefly discussed. The principal method utilized is isotope dilution α-ray spectrometry or isotope dilution mass spectrometry. A number of isotopes certified as reference samples of different categories, prepared at the Radium Institute, served as spikes. A combination of these methods allows the isotope composition to be estimated accurately to within ≤0.15% for U, ≤0.5% for Pu, and 3–5% for Am and Cm. The accumulated data set for the SNF from WWER and RBMK reactors is presented.     

Carbon nanotubes grown on stainless steel to form plate and probe electrodes for chemical/biological sensing

This paper describes the fabrication and evaluation of carbon nanotube (CNT) electrodes grown on stainless steel (SS) plate and wire for electrochemical sensor applications. Multi-wall carbon nanotubes with different diameters were grown on the SS plate and wire by chemical vapor deposition from an ethylene precursor. The SS provides a good electrical and mechanical connection to the CNT, and the SS is a tough substrate. The SS part of the electrode was electrically insulated from the analyte so that only the CNT were active in sensing. Cyclic voltammetry for the reduction of 6 mM K3Fe(CN)6 in a 1.0 M KNO3 supporting electrolyte was performed to examine the redox behavior of the CNT-SS electrode. The cyclic voltammograms showed sigmoidal-like shapes, indicating that mass transport around the electrodes is dominated by radial diffusion. Based on the cyclic voltammograms, the effective area of the CNT-SS electrodes and the number of individual CNTs were estimated. These results indicate that the CNT-SS plate and wire electrodes are good candidates to develop practical in vivo biosensors.     

The microstructural observation and wettability study of brazing Ti-6Al-4V and 304 stainless steel using three braze alloys

Both Ti-6Al-4V and 304 stainless steels (304SS) are good engineering alloys and widely used in industry due to their excellent mechanical properties as well as corrosion resistance. Well-developed joining process can not only promote the application of these alloys, but also can provide designers versatile choices of alloys. Brazing is one of the most popular methods in joining dissimilar alloys. In this study, three-selected silver base filler alloys, including Braze 580, BAg-8 and Ticusil®, are used in vacuum brazing of 304SS and Ti-6Al-4V. Based upon dynamic sessile drop test, Braze 580 has the lowest brazing temperature of 840°C, in contrast to 870°C for BAg-8 and 900°C for Ticusil® braze alloy. No phase separation is observed for all brazes on 304SS substrate. However, phase separation is observed for all specimens brazed above 860°C on Ti-6Al-4V substrate. The continuous reaction layer between Braze 580 and 304SS is mainly comprised of Ti, Fe and Cu. The thickness of reaction layer at Braze 580/Ti-6Al-4V interface is much larger than that at Braze 580/304SS interface. Meanwhile, a continuous Cu-Sn-Ti ternary intermetallic compound is found at the Braze 580/Ti-6Al-4V interface. Both Ticusil® and BAg-8 brazed joint have similar interfacial microstructures. Different from the Braze 580 specimen, there is a thick Cu-Ti-Fe reaction layer in both BAg-8/304SS and Ticusil®/304SS interfaces. The formation of Cu-Ti-Fe interfacial layer can prohibit wetting of BAg-8 and Ticusil® molten brazes on 304SS substrate. Meanwhile, continuous Ti₂Cu and TiCu layers are observed in Ti-6Al-4V/BAg-8 and Ti-6Al-4V/Ticusil® interfaces.     

A family of methods with three-term recursion formulae

A state-of-the-art survey of a family of vector iterative methods with three-term recursion formulae is presented. The methods can be classified under two broad categories. The Chebyshev semi-iterative type of methods and the conjugate gradient type of methods. Relationships between the iteration parameters of the methods are established and computational techniques for estimating these parameters are presented. Numerical tests confirm the superiority of the conjugate gradient method for linear problems and the Chebyshev semi-iterative methods for nonlinear problems.     

Characterization of aluminium-matrix composites made by compocasting and its variations

Compocasting (semisolid-semisolid, SS) and its two variations: SL (semisolid-liquid) and LL (liquid-liquid) process routes are used to make 2024Al reinforced with 3 mm and 12 mm long FP-alumina fibres. Squeeze-casting is used as a complementary casting technique. The effect of processing route on microstructure and the mechanical properties of these composites is studied. The SS route produces composites with uniform fibre distribution, but casting is difficult due to the high viscosity of the slurry. The SL route gives good fibre distribution and the casting is easy. The LL route allows addition of a large amount of fibres but gives castings with a non-uniform fibre distribution, which lowers the failure strains and reduces the strength of the composites drastically. The addition of alumina fibres to 2024Al increases its modulus of elasticity considerably. The observed modulus values show good agreement with the theoretical predictions. The strength values are somewhat lower than the theoretical predictions. This is because the composites failed at strains slightly lower than the fibre failure strain. Absence of fibre pull-out indicates that a good fibre matrix bond has been produced in each case.     

Berechnungs- und experimentelle Verfahren zur Charakterisierung thermischer Mikroeigenspannungen in Stückverbunden

Theoretical and Experimental Methods for the Determination of Thermal Residual Microstresses in Particle Reinforced Metal Matrix Composites Particle reinforced metal matrix composites (PMMCs) comprising quasi ceramic hard phases in a metal matrix are used for wear protection in industry. During cooling residual microstresses emerge due to differences in the physical and mechanical properties of the metal matrix and the hard phases. Furtheron, the amount and distribution of the residual microstresses are influenced by the hard phase size, shape and distribution. For characterizing the residual microstress state theoretical methods (analytical and FEM calculations) as well as experimental methods (dilatometry, Micro-Moiré-methods, X-ray diffraction, angle dispersive neutron diffraction, neutron time-of-flight spectroscopy, torsion pendulum tests, differential calorimetry and ultra sonic absorption test) are used and assessed.     

Development of Deformation-Semisolid-Casting （D-SSC） Process and Applications to Some Aluminum Alloys

Recent advances in the semisolid casting technologies are introduced for aluminum alloys.The advantages of the rheocast and thixocast methods to fabricate alloys with refined spheroidizedα-Al particles are described. The deformation-semisolid-casting （D-SSC） process developed by the author＇s group is presented.The D-SSC process is extremely effective to produce microstructures of refined intermetallic compound particles as well as the spheroidizedα-Al particles in the Al-Si based alloys containing highly concentrated Fe.In the D-SSC processed Al-Si-Cu alloy high elongation of about 20% was achieved even contained concentrated impurity of Fe.The D-SSC process is also useful to produce wrought aluminum alloys with microstructures of refinedα-Al particles.     

Detection of trace impurities by time-of-flight mass spectrometry with laser-induced evaporation

A method for the determination of trace impurities of tens of ppm in solid materials is proposed, based on laser-induced evaporation of the substance in a vacuum in the forced congruence mode with simultaneous analysis of the evaporation products using a time-of-flight mass spectrometer. The results of measurements of the relative composition of impurities in α-corundum obtained from aluminum hydroxide (AlOOH) powder by high-temperature annealing (1500 and 1800°C) are presented. The necessity of comparative analysis is caused by a substantial difference in the measurement results for impurities in the initial material obtained by conventional methods. The reported values of the relative composition of impurities are in a good agreement with the results of inductively coupled plasma mass spectrometry.     

Effect of tin on melting temperature and microstructure of Ag–Cu–Zn–Sn filler metals

Abstract

To develop low melting point filler metals for brazing TiNi shape memory alloy (SMA) and stainless steel (SS), a series of Ag–22Cu–Zn–Sn (wt-%) filler metals have been studied. Using differential thermal analysis (DTA) analysis, the melting temperatures of Ag–22Cu–Zn–Sn filler metals were determined. The results show that the increase of zinc and tin contents drastically decreases the solidus and liquidus temperatures of the Ag–22Cu–Zn–Sn filler metals and the melting temperatures of the Ag–22Cu–18Zn–Sn filler metals with 5–8 wt-%tin are < 650°C. Metallographic observations indicate that the increase of zinc and tin in the Ag–22Cu–Zn–Sn filler metals helps the formation of eutectic structure and inhibits the formation of α-Ag and α-Cu solid solutions, but the increase of tin also causes the formation of Ag₃Sn and Cu₄₁Sn₁₁ brittle compounds. The results of mechanical property tests of the laser brazed joints of TiNi SMA and SS show that the proper increase of zinc and tin in Ag–22Cu–Zn–Sn filler metals is favourable for improving the strength of the laser brazed joints of TiNi SMA and SS.     

A review of soft errors and the low α-solder bumping process in 3-D packaging technology

This study reviews soft errors in modern electronic assemblies, through silicon via (TSV), and low α-solder bumping techniques for 3-D microelectronic packaging. The TSV fabrication involves deep reactive ion-etching process of Si wafers to form vertical holes, which are further filled with copper and joined to solder bumps. The solder bumps in close proximity to Si die thus impose a serious threat of soft errors. These soft errors responsible for the malfunction of electronic systems have become a critical issue in miniaturized and high-density packaging, like 3-D packaging. Various low α-solder bumping techniques have been reported to minimize these errors in modern microelectronic devices. A low α-solder is one that has low levels of α-particle emission, as compared to the conventional solder. In addition, it improves the performance and reliability of the solder joints, prompting the need to adopt low α-solder for bumping in TSV packaging. Thus, this paper discusses the various aspects of TSV fabrication, functional layer deposition, Cu filling into TSV, and low α-solder bumping on TSV by solder ball reflow methods.     

扩频信号的声光谱相关检测

传统检测扩频信号的声光技术,是将扩频信号建模为随机平稳过程,而扩频信号是被伪随机码调制的周期信号,应建模为循环平稳随机过程。基于声光技术与循环谱相关技术,提出了扩频信号的声光谱相关检测方法。建立了基于声光时间积分的声光谱相关检测模型,分析了当干扰瞄准扩频接收机时,扩频信号在循环频率α=1/Tc的循环谱,给出了循环谱峰的检测公式TcRs1/。仿真实验结果表明,与传统的声光技术检测扩频信号的功率谱相比,在光电检测阵列上检测的循环谱峰,谱峰旁瓣几乎为零,并可多获得约3dB的增益,表明声光谱相关检测方法具有更优异的检测和抗干扰性能。     

An Overview of the Shainin System™ for Quality Improvement

The Shainin System™ (SS) is the name given to a problem solving system, with its associated strategies and tools, developed by Dorian Shainin, and widely used and promoted in the manufacturing sector. Dorian Shainin also called this system Statistical Engineering, reflecting his engineering education and background. The consulting firm, Shainin LLC, offers the system under the trademarked name Red X® Strategy. Much of SS is neither well documented, nor adequately discussed in peer-reviewed journals. The goal of this article is to provide an overview of SS, a critical assessment, and a brief comparison with other industrial problem solving systems. The emphasis is on a discussion of the guiding philosophy and principles. Some specific SS tools are examined and compared with alternative methods. In our assessment, the Shainin System is valuable for many types of problems and many of its elements have been, or should be, incorporated into other process improvement methodologies. However, many of the statistical tools and methods promoted in conjunction with SS are neither novel nor necessarily the best.     

Barrel‐Shaped Oil Skimmer Designed for Collection of Oil from Spills

Superhydrophobic–superoleophilic (SS) materials have the prospect to be used in oil‐spill cleanup as treated felts because of their complete oil‐absorbing and water‐repelling properties. The main issues affecting the practical application of the SS materials are the low volume‐based absorption capacity (resulting in a high cost), the requirement for mechanical handling (squeeze out the oil) for recycling, and low storage stability of the collected oil. In this study, a barrel‐shaped oil skimmer mainly composed of an SS Cu foam and a glass barrel is developed as a potential step‐change device to enable separation of oil and water. The SS Cu active component is fabricated by chemical etching and stearic acid modification. The demonstrator oil skimmer quickly and selectively absorbs and collects a variety of oils from a polluted water surface, showing a high separation efficiency and volume‐based absorption capacity. The device can be easily scaled up. In addition to the high absorption capacity, the as‐prepared oil skimmer filters and collects the floating oil into the barrel, removing the traditional mechanical handling. Moreover, the as‐prepared oil skimmer also shows good storage stability; no oil escapes from the skimmer under harsh conditions. The findings presented in this study facilitate a novel, simple, and low‐cost approach for oil‐spill cleanup.     

Biocompatible carbohydrate-functionalized stainless steel surfaces: a new method for passivating biomedical implants

A convenient method for passivating and functionalizing stainless steel is described. Several methods of coating stainless steel (SS) samples with silica were investigated and of these methods, a thin (less than 15 nm thick) layer of silica created by atomic layer deposition (ALD) was found to give superior performance in electrochemical testing. These interfaces were then used as a platform for further functionalization with molecules of biological interest. Specifically, the SS samples were functionalized with biologically significant carbohydrates [N-acetyl-D-glucosamine (GlcNAc) and D-galactose (Gal)] that contain trialkoxysilane derivatives as chemical handles for linking to the surface. The presence and biological availability of these moieties on the silica coated SS were confirmed by XPS analysis and an enzyme-linked lectin assay (ELLA) using complementary lectins that specifically recognize the surface-bound carbohydrate. This method has the potential of being adapted to the functionalization of stainless steel biomedical implants with other biologically relevant carbohydrates.     

Influence of colloidal silica sol on fresh properties of cement paste as compared to nano-silica powder with agglomerates in micron-scale

Influence of colloidal silica sol (SS) with mono-dispersed nano-particles on fresh properties of cement paste was investigated as compared to nano-silica powder (NS) with agglomerates in micron-scale. The SS addition showed a much greater influence on sedimentation and rheological behavior of the paste than the NS incorporation, because the nano-particles in SS coagulate immediately once cement is mixed into water containing SS, forming loose floc and coating layer around cement particles. The loose floc cannot function as fillers to release free water, but possesses a more open microstructure, leading to a higher free water retention capacity than the agglomerates in NS. However, addition of SS presented an obviously better accelerating effect on cement hydration than that of NS, though the nano-particles in SS are nearly the same as those in NS in primary particle size and the flocs in the paste with SS addition are typically larger than the agglomerates in NS, implying that the acceleration may have nothing to do with the seeding effect. Through detecting calcium-absorbing properties of NS and SS, it is found that the accelerating effect is highly dependent on the rapid depletion of calcium ions in the paste. Finally, it was interestingly found that the CH crystals are even more prone to grow along (0001) plane with larger size in the paste with SS addition, because the coagulated gel network in the paste slows down the diffusion rate of the released ions and eliminate the convection in the system, thus the 3D nucleation and growth of the CH crystals were suppressed.