A class of generalized Birnbaum-Saunders distributions for reliability modeling

In this paper, we generalize the Birnbaum-Saunders (BS) distribution by two ways. One is based on the mixture representation of BS distribution, and a flexible weight is adopted to describe the kurtosis of the distribution. The other way is based on the transformation property of BS distribution, and we incorporate a power parameter in the transformation to describe the skewness of the distribution. Then a four-parameter BS distribution including skewness and kurtosis parameters is induced by combining the two ways. The properties of these generalized BS distributions are investigated. Then, the expectation maximization (EM) algorithm is proposed to estimate the parameters. Real data analysis is performed to illustrate the superiority of the generalized BS distributions. Finally, some potential generalizations are discussed.     

Solubility and stability of lorazepam in bile salt/soya phosphatidylcholine-mixed micelles

In the present study, the solubility and stability of the drug lorazepam, which was solubilized in bile salt/soya phosphatidylcholine-mixed micelles (BS/SPC-MMs), were investigated. The solubility of lorazepam could be enhanced substantially in different bile salts and also in sugar ether, whereas the solubility in Pluronic F68 (Pl.F68) was of lower order. Moreover, the addition of SPC to different BS solutions greatly enhanced their solubilizing capacities toward lorazepam; this could be correlated with the ability of the formed MM to reduce the surface tension. The stability study showed that lorazepam degradation followed apparent first-order degradation kinetics in phosphate buffer, as well as in the BS/SPC-MM, with highly enhanced stability in the latter system. The stabilizing effect of BS/SPC-MM was higher in the case of trihydroxy BS than for dihydroxy BS. From an Arrhenius plot with degradation constants in a temperature range from 30°C to 60°C, a shelf stability of about 10 months could be calculated for BS/SPC-MM at 5°C. The solubility studies in BS/SPC-MM showed a recrystallization and a polymorphic transition from modification II to I.     

Intermetallic Compounds in the Banded Structure and Their Effect on Mechanical Properties of Al/Mg Dissimilar Friction Stir Welding Joints

Dissimilar friction stir welding(FSW) between aluminum and magnesium alloy was performed, using various tool rotational speed(TRS) at a ?xed travel speed, with tool offset to aluminum to investigate the formation of intermetallic compounds(IMCs) in the banded structure(BS) zone and their effect on mechanical properties. Large quantities of IMCs, in the form of alternating bands of particles or lamellae, were found in the BS zone, where drastic material intermixing occurred during FSW. The BS microstructural characters in terms of the morphology of the bands and the quantity and distribution of IMC particles varied with TRS. All welds exhibited brittle fracture mode with their fracture paths propagating mainly in/along the IMCs in the BS. It is shown that these BS microstructural characters have signi?cant effect on the mechanical properties of the joints. Suggestions on tailoring the BS microstructure were proposed for improving the strength of the BS zone and the ?nal mechanical properties of the Al/Mg FSW joints.     

Effect of cathodic hydrogen-charging current density on the hydrogen diffusivity in nanostructured bainitic steels

ABSTRACT

The effect of cathodic hydrogen-charging current on the effective hydrogen diffusivity in nanostructured bainitic steels produced at transformation temperatures 200°C (BS200) and 350°C (BS350) was investigated and compared to that of mild steel. The effective hydrogen diffusivity at 10?mA?cm^?2 was the lowest for BS200, followed by BS350 and mild steel, due to the finer microstructure and higher dislocation density in the bainitic ferrite of BS200. Increase in the hydrogen-charging current density, i.e. 20 and 30?mA?cm^?2, increased the effective hydrogen diffusivity of mild steel by 37 and 135%, and BS350 by 49 and 150%, respectively. For BS200, the increase was not significant (2%) at 20?mA?cm^?2, but increased by 34% at 30?mA?cm^?2.

This paper is part of a thematic issue on Hydrogen in Metallic Alloys     

A study of BS.5750 aspirations in small companies

This paper outlines the main findings of a research study which examined the experiences of small companies in relation to approaching the BS.5750/ISO 9000 quality system series. In general, small companies are not aware of the fundamental concepts of a quality system, many of the activities outlined in BS.5750 are not practised and, even when they are, they are not documented. The main motivation for introducing a quality system which meets the requirements of BS.5750 is customer pressure. Difficulties encountered by small companies are selecting which part of the standard to apply, understanding and applying the appropriate clauses of BS.5750 to their own specific situations, and writing procedures.     

Mapping Nanomechanical Properties of Basal Surfaces in Metastatic Intestinal 3D Living Organoids with High-Speed Scanning Ion Conductance Microscopy

Studying mechanobiology is increasing of scientific interests in life science and nanotechnology since its impact on cell activities (e.g., adhesion, migration), physiology, and pathology. The role of apical surface (AS) and basal surface (BS) of cells played in mechanobiology is significant. The mechanical mapping and analysis of cells mainly focus on AS while little is known about BS. Here, high-speed scanning ion conductance microscope as a powerful tool is utilized to simultaneously reveal morphologies and local elastic modulus (E) of BS of genotype-defined metastatic intestinal organoids. A simple method is developed to prepare organoid samples allowing for long-term BS imaging. The multiple nano/microstructures, i.e., ridge-like, stress-fiber, and E distributions on BS are dynamically revealed. The statistic E analysis shows softness of BS derived from eight types of organoids following a ranking: malignant tumor cells > benign tumor cells > normal cells. Moreover, the correlation factor between morphology and E is demonstrated depending on cell types. This work as first example reveals the subcellular morphologies and E distributions of BS of cells. The results would provide a clue for correlating genotype of 3D cells to malignant phenotype reflected by E and offering a promising strategy for early-stage diagnosis of cancer.     

Contribution of Ti addition to characteristics of extruded Cu40Zn brass alloy prepared by powder metallurgy

The aim of this paper was to investigate the properties of Cu40ZnTi for the purpose of developing a new high-strength, lead-free brass by powder metallurgy. The effect of Ti addition on precipitation hardening behavior of Cu40Zn (denoted as BS40) brass was studied with respect to mechanical properties and microstructures. BS40 and Cu40Zn − 1.0 wt.%Ti (denoted as BS40-A) brass powders were prepared by water atomization process, and β phase was retained in the raw powders predominately. The BS40 powder and Ti powder were elementally mixed to prepare Cu40Zn + 0.5 wt.%Ti (denoted as BS40-B) and Cu40Zn + 1.0 wt.%Ti (denoted as BS40-C) premixed powders. The alloy powders and premixed powders were solidified at 1053 K for 600 s by spark plasma sintering (SPS) and extruded subsequently. It was observed that Cu₂ZnTi intermetallic compound (IMC) and CuZnTi metastable phase resulted from the reaction between Ti and CuZn showed distinct grain refinement effect on extruded Cu40Zn brass. Thus, the excellent strengthening effect processes by precipitation hardening and deform working was obtained, which responding to an yield strength of 345 MPa, and a ultimate tensile strength of 597 MPa, showed 65.9% and 30.4% higher than that of extruded Cu40Zn brass, respectively.     

Characterization and utilization of a Bonner sphere set based on gold activation foils

Bonner sphere (BS) sets which use activation foils as the central thermal neutron sensor have advantages over active BS systems in certain environments, for example, pulsed fields, or fields with high photon components. In such environments, they may be the only type of neutron spectrometer which can be used. This paper describes work, using both measurements and calculations, to validate the response functions for a BS set based on gold activation foils. As an illustration of the use of such a system, a measurement is described of the contaminant neutron spectrum in the treatment room of a 21 MV hospital linear accelerator providing photon beams for radiotherapy.     

Influence of two-tier structuring on the performance of black silicon-based MSM photodetectors

Black silicon, fabricated by alkaline anisotropic etching along with metal-assisted etching, consists of regular distributed micro-scale pyramids and irregular distributed nano-scale pores, in which the pore size plays an important role in the performance of the black silicon-based metal–semiconductor–metal photodetectors (BS MSM PDs). It is found that the dark current characteristic of BS MSM PD is different from that of traditional silicon MSM PD, and the former has negative differential resistance in part of its operating range because of the quantum tunneling effect exists in black silicon. Moreover, it is interesting to note that BS MSM PD with longer metal-assisted etching time (larger nanopore size) has higher responsivity at high bias voltage but lower responsivity at low bias voltage.     

Mixed-model assembly line sequencing using beam search

In today's manufacturing environments, companies have to produce a large variety of products in small quantities on a single assembly line. In this paper, we use a beam search (BS) approach to solve the model-sequencing problem of mixed-model assembly lines (MMALs). Specifically, we develop six BS algorithms for part-usage variation and load-leveling performance measures. The results of computational experiments indicate that the proposed BS methods are competitive with the well-known heuristics in the literature. A comprehensive bibliography is also provided.     

Energy-Efficient Resource Optimization for Massive MIMO Networks Considering Network Load

This paper investigates the resource optimization problem for a multi-cell massive multiple-input multiple-output (MIMO) network in which each base station (BS) is equipped with a large number of antennas and each base station (BS) adapts the number of antennas to the daily load profile (DLP). This paper takes into consideration user location distribution (ULD) variation and evaluates its impact on the energy efficiency of load adaptive massive MIMO system. ULD variation is modeled by dividing the cell into two coverage areas with different user densities: boundary focused (BF) and center focused (CF) ULD. All cells are assumed identical in terms of BS configurations, cell loading, and ULD variation and each BS is modeled as an M/G/m/m state dependent queue that can serve a maximum number of users at the peak load. Together with energy efficiency (EE) we analyzed deployment and spectrum efficiency in our adaptive massive MIMO system by evaluating the impact of cell size, available bandwidth, output power level of the BS, and maximum output power of the power amplifier (PA) at different cell loading. We also analyzed average energy consumption on an hourly basis per BS for the model proposed for data traffic in Europe and also the model proposed for business, residential, street, and highway areas.     

New UK guidance on the use of concrete in aggressive ground

The UK guidance for specification of concrete in aggressive ground has been revised following the discovery of the thaumasite form of sulfate attack in the foundations to highway bridges in England in 1998. Interim advice was issued in the Report of the Thaumasite Expert Group in January 1999. Following consultation with industry, a new BRE Special Digest 1 was published in September 2001 (to replace Digest 363) and parallel amendments to the current BS 5328 were drafted. New concepts are introduced for ground assessment and concrete specification. Allowance is now made for the oxidation of sulfides in the ground and there is a new classification for the aggressive chemical environment. Concrete specification additionally takes into account the required structural performance level, the carbonate content of aggregates, and the need for additional protective measures. Compatible guidance is being put in place for the UK Highways Agency and for BS 8500, the UK complementary standard to the European Standard BS EN 206-1, which will replace BS 5328 in December 2003.     

Lessons from the Sampoong department store collapse

This paper summarises the report of the committee of inquiry into the collapse, by punching shear, of the Sampoong department store in Seoul, Korea in 1995. It examines the adequacy of the design and calculates, using ACI 318-89, BS 8110-85 and Gardner 96, the contribution of the various deficiencies to the probability of failure. ACI 318 does not predict the collapse but BS 8110 and Gardner 96 predict a large probability of collapse. Both BS 8110 and Gardner 96 include size effect and reinforcement ratio.     

Evaluation of mechanical properties of banana and sisal fiber reinforced epoxy composites: Influence of glass fiber hybridization

In this work, the effect of glass fiber hybridization with the randomly oriented natural fibers has been analyzed. The banana (B), sisal (S) fibers were chopped and woven E-glass (G) synthetic fibers were reinforced with epoxy matrix. Nine different kinds of laminates were prepared in the following stacking sequence of B, S, BS, G/B/G, G/S/G, G/BS/G, G/B/G/B/G, G/S/G/S/G and G/BS/G/BS/G. Mechanical properties like tensile strength, flexural strength and impact strength were evaluated and compared. Interfacial analysis was also carried out with the help of Scanning Electron Microscope (SEM) to study the micro structural behavior of the tested specimen. It was observed that the addition of two and three layer of glass fiber can improve the tensile strength by a factor of 2.34 and 4.13 respectively. The flexural properties were enhanced on banana–sisal fiber with two layers of glass fibers rather than three layers and the laminate with sisal and three glass ply offers better impact strength.     

Measurement of the neutron fluence and dose spectra using an extended bonner sphere and a tissue-equivalent proportional counter

A conventional Bonner Sphere (BS) set consisting of six polyethylene spheres was modified to enhance its response to a high-energy neutron by putting a lead shell inside a polyethylene moderator. The response matrix of an extended BS was calculated using the MCNPX code and calibrated using a 252Cf neutron source. In order to survey the unknown photon and neutron mixed field, a spherical tissue equivalent proportional counter (TEPC) was constructed and assembled as a portable measurement system. The extended BS and the self-constructed TEPC were employed to determine the dosimetric quantities of the neutron field produced from the thick lead target bombarded by the 2.5 GeV electron beam of Pohang Accelerator Laboratory (PAL) and the neutron calibration field of Korea Atomic Energy Research Institute (KAERI).     

The biological seal of the implant–soft tissue interface evaluated in a tissue-engineered oral mucosal model

For dental implants, it is vital that an initial soft tissue seal is achieved as this helps to stabilize and preserve the peri-implant tissues during the restorative stages following placement. The study of the implant–soft tissue interface is usually undertaken in animal models. We have developed an in vitro three-dimensional tissue-engineered oral mucosal model (3D OMM), which lends itself to the study of the implant–soft tissue interface as it has been shown that cells from the three-dimensional OMM attach onto titanium (Ti) surfaces forming a biological seal (BS). This study compares the quality of the BS achieved using the three-dimensional OMM for four types of Ti surfaces: polished, machined, sandblasted and anodized (TiUnite). The BS was evaluated quantitatively by permeability and cell attachment tests. Tritiated water (HTO) was used as the tracing agent for the permeability test. At the end of the permeability test, the Ti discs were removed from the three-dimensional OMM and an Alamar Blue assay was used for the measurement of residual cells attached to the Ti discs. The penetration of the HTO through the BS for the four types of Ti surfaces was not significantly different, and there was no significant difference in the viability of residual cells that attached to the Ti surfaces. The BS of the tissue-engineered oral mucosa around the four types of Ti surface topographies was not significantly different.     

Fracture toughness of high strength seamless pipe steel from SE(T) and SE(B) specimens evaluated by different standards

Recently released, BS 8571:2014 standard offers an alternative for the experimental determination of fracture toughness and resistance curves of metallic materials from SE(T) specimens. Similar in stress conditions and constraint to cracked tubes, specimens in SE(T) geometry should yield less conservative toughness values than conventional high‐constraint specimens, such as SE(B) geometry. However, the convention to determine the J‐integral fracture toughness proposed in the new BS standard is different from ASTM standards. In this work, SE(T) and SE(B) specimens of similar dimensions of a tough high‐strength seamless pipe steel were tested following the BS 8571:2014 and ASTM E1820‐16 standards, respectively. Because of the different standardized definitions, SE(T) specimens yield lower fracture toughness than SE(B) specimens, which could lead to more conservative results in structural integrity analysis. This investigation also suggests the introduction of the blunting line concept in the BS 8571:2014 standard in order to minimize this problem.     

Utilization of barley straws as biosorbents for Cu2+ and Pb2+ ions

The potential to remove Cu(2+) and Pb(2+) ion from aqueous solutions through biosorption using barley straw (BS) was investigated in batch experiments. The main parameters influencing Cu(2+) and Pb(2+) ion sorption on BS were: initial metal ion concentration, amount of adsorbent, contact time and pH value of solution. The influences of initial Cu(2+) and Pb(2+) ion concentration (0.1-1mM), pH (2-9), contact time (10-240 min) and adsorbent amount (0.1-1.0 g) have been reported. Equilibrium isotherms have been measured and modelled. The percent adsorption of Cu(2+) and Pb(2+) ions increased with an increase in pH and dosage of treated BS. The biosorptive capacity of the BS was dependent on the pH of Cu(2+) and Pb(2+) ion solution. Adsorption of Cu(2+) and Pb(2+) ion was in all cases pH dependent showing a maximum at equilibrium pH value at 6.0. The equilibrium sorption capacities of Cu(2+) and Pb(2+) after 2h were 4.64 mg/g and 23.20mg/g for BS, respectively. The adsorption data fit well with the Langmuir isotherm model and the experimental result inferred that complexation on surface, adsorption (chemisorption) and ion exchange is one of the major adsorption mechanisms for binding Cu(2+) and Pb(2+) ion to the sorbents.     

BS600高强钢油罐车罐体轻量化研究

目的 为了有效降低油罐车的能源消耗和污染物排放,完成油罐车罐体减重30%的轻量化目标。基于有限元仿真与试验,验证使用高强钢替代罐体原材料实现油罐车轻量化方案的可行性。方法 利用ANSYS有限元软件,在3种不同工况下,对使用新材料的罐体进行强度、刚度分析;基于仿真结果,对3.5 mm厚的BS600高强钢板材进行焊接试验、金相组织观察以及拉伸试验,以评估BS600钢的焊接性能;对焊接后的BS600钢材进行小件和大件的弯曲试验,以验证BS600钢的弯曲性能。结果 在3种工况下,罐体的最大应力为288 MPa,小于材料的许用应力,罐体强度满足要求;罐体的最大变形量为5.92 mm,刚度满足要求;焊接后拉伸试样的抗拉强度为720～730 MPa,高于母材强度;焊接接头断口的断裂特性为韧性断裂与脆性断裂的混合断裂;弯曲后的小件BS600板材未出现裂纹,弯曲后的大件罐体焊缝缺陷数量较少,焊缝质量良好。结论 所设计的高强钢材料的厚度符合罐体各工况要求,高强钢的成形工艺可行性良好。罐体减重能达到30%,具有良好的工程应用价值。     

Strain gauge proof hydraulic testing of commercial pressure vessels

Some aspects of the philosophy of shakedown are presented relevant to the requirement of the British pressure vessel code British Standard BS 55(X): 1994 for proof hydraulic pressure tests on vessels containing features not covered in the design rules within BS 55(X). The difficulties in achieving the objective of the test are discussed. Examples are provided from the experiences gathered from such proof hydraulic tests on over 50 commercial pressure vessels.