Effect of root pass filler metal on microstructure and mechanical properties in the multi-pass welding of duplex stainless steels

This paper is focused on the estimation of the effect of root pass chemical composition, in multi-pass GTA Weldments, on microstructure and mechanical properties of duplex stainless steel welds. We used two different filler metals, the super duplex ER 2594 and duplex ER 2209. Microstructures of different passes of welded joints are investigated using optical microscope and scanning electron microscope. The relationship between mechanical properties, corrosion resistance, and microstructure of welded joints is evaluated. It is found that the tensile and toughness properties of the first weldment, employing the combination of ER 2594 in the root pass and ER 2209 in the remaining, are better than that of the second weldment employing ER 2209 all passes, due to the root pass grains refinement and its alloy elements content as chromium Cr and nitrogen N. The microstructure indicates the presence of austenite in different forms on the weld zone of ER 2209, same in the case of ER 2594, but with higher content and finer grains size, in particular Widmanstätten austenite WA. Potentiodynamic polarization tests of the first weld metal evaluated in 3.5% NaCl solution at room temperature have been demonstrated a corrosion resistance higher than that of the second weld metal. This work addressed the improvement of the corrosion resistance using appropriate filler metal without getting any structural heterogeneity and detrimental changes in the mechanical properties.     

An Approach to Preliminary Design of Precast Pretensioned Concrete Bridge Girders

Abstract: This paper presents an approach to the preliminary design of simple span precast pretensioned highway bridge girders using mathematical optimization methods. This type of bridge system is competitive for short and medium spans but also can accommodate long-span bridges if girder splicing and continuity are introduced. The bridge design problem is formulated as a nonlinear programming problem and is solved by the projected lagrangian algorithm. Several design objectives are investigated either separately or simultaneously with the aim of achieving cost-efficient bridge designs. The approach is used to generate a new set of five optimal girder sections and then to determine the girder spacing and span length capability of each precast girder. The five sections types (A, B, C, D, and E) proposed herein are more cost-effective than the corresponding Canadian standard sections because for similar depths they achieve greater span length and girder spacing while requiring less concrete and prestressing steel. This study also enables identification of the governing design requirements (serviceability and/or ultimate limit states active constraints) that may be adopted as optimality criteria when simplified preliminary designs of this bridge type for different design codes and girder sections are required.     

The optimal class size for object-oriented software

A growing body of literature suggests that there is an optimal size for software components. This means that components that are too small or too big will have a higher defect content (i.e., there is a U-shaped curve relating defect content to size). The U-shaped curve has become known as the "Goldilocks Conjecture." Recently, a cognitive theory has been proposed to explain this phenomenon and it has been expanded to characterize object-oriented software. This conjecture has wide implications for software engineering practice. It suggests 1) that designers should deliberately strive to design classes that are of the optimal size, 2) that program decomposition is harmful, and 3) that there exists a maximum (threshold) class size that should not be exceeded to ensure fewer faults in the software. The purpose of the current paper is to evaluate this conjecture for object-oriented systems. We first demonstrate that the claims of an optimal component/class size (1) above) and of smaller components/classes having a greater defect content (2) above) are due to a mathematical artifact in the analyses performed previously. We then empirically test the threshold effect claims of this conjecture (3) above). To our knowledge, the empirical test of size threshold effects for object-oriented systems has not been performed thus far. We performed an initial study with an industrial C++ system and repeated it twice on another C++ system and on a commercial Java application. Our results provide unambiguous evidence that there is no threshold effect of class size. We obtained the same result for three systems using four different size measures. These findings suggest that there is a simple continuous relationship between class size and faults, and that, optimal class size, smaller classes are better and threshold effects conjectures have no sound theoretical nor empirical basis     

Nd recovery from magnetic waste and its preliminary analysis by neutron activation analysis

The products of the new information and communication technologies (NTIC), whose life often not exceed three years, became consumables to the computer image and other waste that contains neodymium and praseodymium (rare earths); in this field of management, treatment, and recycling of waste, we propose the recovery of elements such as neodymium and praseodymium, from the super-magnet Nd–Fe–B. Our study provides a simple and inexpensive process. The implementation scheme of our project consists of a first step in developing a plan of experience that has been made specifically to perform the optimization of operating conditions of the precipitation process. This experimental design was inspired by a statistical technique advanced design of experiments known factorial design. The method begins by embrittlement in liquid nitrogen (?196°C), dissolution in an acidic solution and recovered by a unit operation of chemical engineering, we add an oxalic acid solution to precipitate Nd as neodymium oxalate, followed by purification of neodymium and praseodymium. For characterization we used the following techniques. The neutron radiography, the neutron activation analysis (NAA) and the scanning electron microscope coupled with EDX. The identification of the most intense peaks in the XRD spectrum shows the presence of a single compound which hydrated neodymium oxalate chemical formula Nd₂(C₂O₄)₃10H₂O. The counting of γ spectrum shows that the purity of the precipitate is higher than 99%. Then, the thermal decomposition transforms this powder to neodymium oxide. After the reduction we obtain pure neodymium, the analytical balance shows that this magnet contains 26% of neodymium.     

In-vehicle WLAN radio-frequency communication characterization

Recently, new standards have emerged in the telecommunication industry, which provide an open global specification that enables mobile devices to access and interact with information and services instantly. These mobile devices are, for example, laptops and personal digital assistants. These emerging standards, generically called wireless "x" area networks (WxAN), will in the future be frequently operated from inside vehicles as part of the deployment of mobile offices and to support advanced intelligent transportation system services. These wireless networks currently operate between 1-6 GHz, although 60 GHz could be used when the technology will be economically viable. These mobile devices are frequently put to use in vehicles. To be ensure that portable equipment left in a jacket pocket somewhere in the trunk can interact with other car equipment or portable objects elsewhere in the car needs some investigation. Thus, this paper characterizes radio-frequency propagation inside vehicle bodies, with passengers, in order to evaluate the effectiveness of such a WxAN in vehicle environments.     

Photothermal absorption spectroscopy of individual semiconductor nanocrystals

Photothermal heterodyne detection is used to record the first room-temperature absorption spectra of single CdSe/ZnS semiconductor nanocrystals. These spectra are recorded in the high cw excitation regime, and the observed bands are assigned to transitions involving biexciton and trion states. Comparison with the single nanocrystals photoluminescence spectra leads to the measurement of spectral Stokes shifts free from ensemble averaging.     

Efficient biexciton emission in elongated CdSe/ZnS nanocrystals

We use a combination of low-temperature magneto-optical and lifetime spectroscopies to study the band-edge exciton fine structure of highly photostable single CdSe/ZnS nanocrystals (NCs). Neutral NCs displaying multiline emission spectra and multiexponential photoluminescence (PL) decays are studied as a function of temperature and external magnetic fields. Three different fine structure regimes are identified as a function of the NC aspect ratio. In particular, we identify an optically inactive ground exciton state, whose oscillator strength is tuned up under magnetic field coupling to bright exciton states, and attribute it to the zero angular momentum ground exciton state of elongated NCs. We also show evidence for highly efficient biexciton emission in these NCs, with radiative yields approaching unity in some cases.     

Durability Monitoring for Improved Service Life Predictions of Concrete Bridge Decks in Corrosive Environments

Abstract: The development of an effective strategy for the inspection and monitoring of the nation's critical bridges has become necessary due to aging, increased traffic loads, changing environmental conditions, and advanced deterioration. This article presents the development of a probabilistic mechanistic modeling approach supported by durability monitoring to obtain improved predictions of service life of concrete bridge decks exposed to chlorides. The application and benefits of this approach are illustrated on a case study of a reinforced concrete barrier wall of a highway bridge monitored over 10 years. It is demonstrated that service life predictions using probabilistic models calibrated with selected monitored field data can provide more reliable assessments of the probabilities of reinforcement corrosion and corrosion‐induced damage compared to using deterministic models based on standard data from the literature. Such calibrated probabilistic models can help decision makers optimize intervention strategies as to how and when to repair or rehabilitate a given structure, thus improving its life cycle performance, extending its service life and reducing its life cycle cost.     

Mapping of chromosome 3p deletions in human epithelial ovarian tumors

Epithelial ovarian tumors frequently display deletions on the short arm of chromosome 3 suggesting the existence of tumor suppressor genes within the deleted regions. We have recently established a primary tissue culture system as a model to investigate the genetic events associated with ovarian cancer. The frequencies of loss of heterozygosity (LOH) at 16 loci representative of chromosome 3p in 33 tumor biopsies and 47 ovarian primary cultures derived from unselected ovarian cancers were examined. This repertoire also included benign and borderline tumors as well as malignant ovarian ascites. LOH was observed in 25 (31%) samples for at least one marker: 21 of 58 malignant, two of 12 borderline and two of 10 benign specimens. Chromosome 3p loss was not restricted to ovarian tumors of high grade and stage. LOH was observed in both cultured and non cultured tumors and ascites. A spontaneously immortalized cell line derived from a malignant ovarian ascites, OV-90, displayed LOH of the majority of markers suggesting loss of one homolog of chromosome 3p. The pattern of deletion displayed by these 25 samples enabled the determination of at least two distinct regions of overlapping deletions on chromosome 3p extending from D3S1270 to D3S1597 and from D3S1293 to D3S1283. In addition, a region proximal to D3S1300 was deleted in a subset of samples. Although loss of loci overlapping these three regions (Regions I, II and III) were observed in malignant and benign tumors, in borderline tumors loss was observed of markers representative of Region III only. While RARbeta is presently included in Region II, the minimal regions of deletion exclude VHL, TGFBR2, PTPase(gamma) and FHIT as candidate tumor suppressors in ovarian tumorigenesis.     

Study by AES and EELS spectroscopies of antimony and phosphorus evaporated on massive indium and on cleaned InP

In this paper, we give some results related to interaction mechanism between the elements V such as antimony or phosphorus with the metal indium. We used both powerful spectroscopy methods the Auger electron spectroscopy (AES) and the electron energy loss spectroscopy (EELS) for which the spectra were recorded in direct mode N(E). The antimony was evaporated on pure In metal or on cleaned InP surface involving the In metal because of its cleaning by the argon ion bombardment at low energy 300 eV. The antimony flow composed of Sb₄ species arrived with a thermal energy on the In metal surface. Such an energy was sufficient to their diffusion into the In matrix because of the low melting point of In metal (123 °C). A nucleation phenomenon occurred between Sb₄ and the In metal to form small islands of antimony metal in bulk. Further antimony evaporation enabled to increase the size of these islands towards the surface. However, the antimony evaporated on cleaned InP reacted chemically with the In metal distributed on the InP surface to form a thin layer of InSb. The inner stoichiometric layers of InP and the size of Sb₄ species and also the stability of InP versus the temperature impeded the interdiffusion phenomenon of antimony to occur deeply into the InP matrix. The InSb layer played the role to stabilise the surface of the InP compound versus the heating at 450 °C and the electron irradiation of 4 KeV energy. But, the phosphorus evaporation on In metal or on cleaned InP led to form chemical bonds InP. The phosphorus flow included chemical species P and P₂ with a thermal energy able to stimulate the chemical reactivity process between indium and phosphorus to form the InP compound.