Bicriteria robotic operation allocation in a flexible manufacturing cell

Consider a manufacturing cell of two identical CNC machines and a material handling robot. Identical parts requesting the completion of a number of operations are to be produced in a cyclic scheduling environment through a flow shop type setting. The existing studies in the literature overlook the flexibility of the CNC machines by assuming that both the allocation of the operations to the machines as well as their respective processing times are fixed. Consequently, the provided results may be either suboptimal or valid under unnecessarily limiting assumptions for a flexible manufacturing cell. The allocations of the operations to the two machines and the processing time of an operation on a machine can be changed by altering the machining conditions of that machine such as the speed and the feed rate in a CNC turning machine. Such flexibilities constitute the point of origin of the current study. The allocation of the operations to the machines and the machining conditions of the machines affect the processing times which, in turn, affect the cycle time. On the other hand, the machining conditions also affect the manufacturing cost. This study is the first to consider a bicriteria model which determines the allocation of the operations to the machines, the processing times of the operations on the machines, and the robot move sequence that jointly minimize the cycle time and the total manufacturing cost. We provide algorithms for the two 1-unit cycles and test their efficiency in terms of the solution quality and the computation time by a wide range of experiments on varying design parameters.     

Authentication and authorization infrastructure for Grids—issues,technologies, trends and experiences

Authentication and authorization for Grids is a challenging security issue. In this paper, key issues for the establishment of Grid authentication and authorization infrastructures are discussed, and an overview of major Grid authentication and authorization technologies is presented. Related to this, recent developments in Grid authentication and authorization infrastructures suggest adoption of the Shibboleth technology which offers advantages in terms of usability, confidentiality, scalability and manageability. When combined with advanced authorization technologies, Shibboleth-based authentication and authorization infrastructures provide role-based, fine-grained authorization. We share our experience in constructing a Shibboleth-based authentication and authorization infrastructure and believe that such infrastructure provides a promising solution for the security of many application domains.     

Differentiation of Mechanically and Chemically Extracted Hazelnut Oils Based on their Sterol and Wax Profiles

The sterol and wax content of solvent extracted (SEHO) and cold pressed hazelnut oils (CPHO) were compared. A total of 48 samples from 19 hazelnut varieties were collected for two successive crop years from four different geographical districts in Turkey. Hazelnuts were processed to oil with a laboratory scale press, than the remaining oil in cake was extracted with n‐hexane. CPHO and SEHO were evaluated for their wax, sterol and squalene contents. Results showed that sterol, squalene and wax contents of all individual cultivars were higher in SEHO than those of CPHO, indicating the higher solubility of these compounds in solvent. Total sterol contents ranged between 1088.56 (Kargalak)—1609.39 mg/kg (Mincane) for CPHO and 1590.86 (Çak?ldak)—2897.26 mg/kg (Mincane) for SEHO. Hazelnut oils were found to be richer of C36‐38 esters than C40‐46 group. Total wax content was between 24.19 (Kargalak)—94.58 mg/kg (Ku?) for CPHO and 81.46 (Kargalak)—160.92 mg/kg (Akçakoca) for SEHO. The squalene amounts of the samples obtained by hexane extraction were between 499.75 (Allahverdi)—885.36 mg/kg (Cavcava), while it varied between 288.55 (Kargalak)—647.68 mg/kg (Mincane) in cold pressed oils. Significant and obvious variations between SEHO and CPHO were verified by principal component and hierarchical cluster analysis. Geographical discrimination was also achieved by discriminant analysis.     

Dark fermentative hydrogen production from sucrose and molasses

There are many factors affecting the dark fermentative hydrogen production. The interaction of these factors, that is, their combined effects, should be investigated for better design of the systems with stable and higher hydrogen yields. This study aimed to investigate the combined effects of initial substrate, pH, and biomass (or initial substrate to biomass) values on hydrogen production from sucrose and sugar‐beet molasses. Therefore, optimum initial chemical oxygen demand (COD), pH, and volatile suspended solids (VSS) or initial substrate to biomass (VSS) ratio (S/X_o) values leading to the highest dark fermentative hydrogen production were investigated in batch reactors. An experimental design approach (response surface methodology) was used. Results revealed that when sucrose was the substrate, maximum hydrogen production yield (HY) of 2.3 mol H₂/mol sucrose_added was obtained at initial pH of 7 and COD of 10 g/L. Initial S/X_o values studied (4–20 g COD/g VSS) had no effect on HY, while the initial pH was found as the parameter mostly affecting both HY and hydrogen production rate (HPR). When substrate was molasses, initial COD concentration was the only variable affecting HY and HPR. Maximum of both was achieved at 10 g/L initial COD. Initial VSS values studied (2.5–7.5 g/L) had no effect on HPR and HY. This study also indicated that molasses leads to homoacetogenesis for potentially containing intrinsic microorganism and/or natural constituents; thus, sucrose is more advantageous for hydrogen production via fermentation. Homoacetogenesis should be prevented for effective optimization via response surface methodology, if substrate is a natural carbon source potential to have intrinsic microorganisms. Copyright © 2017 John Wiley & Sons, Ltd.     

Strain scaling law for flux pinning in practical superconductors. Part 1: Basic relationship and application to Nb3Sn conductors

Critical current and flux pinning densities have been determined for a series of Nb₃Sn, V₃Ga, Nb₃Ge, and NbTi conductors as a function of uniaxial tensile strain in magnetic fields ranging from 4 to 19 T. An empirical relationship has been found at 4.2 K that describes these data over the entire range of field under both compressive and tensile strain. The pinning force F has been found to obey a scaling law of the form $\text{F = [B}{}_{\mathrm{c2}}\text{1(?)]}{}^{\mathrm{n}}\text{f(b)}$, where B_c2¹ is the strain-dependent upper-critical field determined from high-field critical-current measurements and f(b) is a function only of the reduced magnetic field $\text{b  B/B}{}_{\mathrm{c2}}\text{1}$. The detailed shape of f(b) depends on the super-conducting material and reaction conditions, but n was found to be nearly constant for a given type of superconductor. For Nb₃Sn conductors n = 1 ± 0.3, for multifilamentary V₃Gan?1.3, for CVD-Nb₃Ge tape n?1.6, and for multifilamentary NbTi n?3.3. The importance of this relationship is that, for these conductors at least, it is possible to measure F at one strain and then immediately be able to predict F (and thus the critical current) at other strain levels simply by scaling the results by [B_c21(?)]ⁿ. Part I of this paper presents the basic uniaxial-strain scaling relationship and focuses on its application to Nb₃Sn conductors. The strain scaling law with n = 1 ± 0.3 was found to hold for all Nb-Sn based conductors examined thus far, including commercial-multifilamentary conductors, extremely fine-filament composites, partially-reacted specimens, ‘insitu’ conductors, and Nb-Hf/Cu-Sn-Ga conductors. The detailed dependence of B_c21 on strain was-found to be nearly universal for highly-reacted commercial Nb₃Sn specimens, greatly simplifying the application of the scaling law to this group of practical superconductors. These results are discussed within the context of flux pinning models and a general scaling relation is proposed which unifies the usual temperature-scaling relation with this strain-scaling relation.     

Rapid Light‐Triggered Drug Release in Liposomes Containing Small Amounts of Unsaturated and Porphyrin–Phospholipids

Prompt membrane permeabilization is a requisite for liposomes designed for local stimuli‐induced intravascular release of therapeutic payloads. Incorporation of a small amount (i.e., 5 molar percent) of an unsaturated phospholipid, such as dioleoylphosphatidylcholine (DOPC), accelerates near infrared (NIR) light‐triggered doxorubicin release in porphyrin–phospholipid (PoP) liposomes by an order of magnitude. In physiological conditions in vitro, the loaded drug can be released in a minute under NIR irradiation, while liposomes maintain serum stability otherwise. This enables rapid laser‐induced drug release using remarkably low amounts of PoP (i.e., 0.3 molar percent). Light‐triggered drug release occurs concomitantly with DOPC and cholesterol oxidation, as detected by mass spectrometry. In the presence of an oxygen scavenger or an antioxidant, light‐triggered drug release is inhibited, suggesting that the mechanism is related to singlet oxygen mediated oxidization of unsaturated lipids. Despite the irreversible modification of lipid composition, DOPC‐containing PoP liposome permeabilization is transient. Human pancreatic xenograft growth in mice is significantly delayed with a single chemophototherapy treatment following intravenous administration of 6 mg kg^?1 doxorubicin, loaded in liposomes containing small amounts of DOPC and PoP.     

Challenges in Developing a Bessel-Beam Based Ultrafast Ablation Probe

Instruments and Experimental Techniques - With its elongated depth of focus, Bessel beams offer rapid and high aspect ratio ablation capability, in contrast to Gaussian beam counterparts. In this...     

Retraining local and global buckling behavior of steel plastic hinges using CFRP

Carbon fiber-reinforced polymer (CFRP) composites have been shown to be particularly well suited for external strengthening of reinforced concrete members. However, there is limited information about how they can be used to strengthen steel structures that are susceptible to local and global instabilities. This paper discusses test results of full-scale steel flexural specimens subjected to reversed cyclic loading, some of which are wrapped with CFRP in the plastic hinge region. The main variables investigated are lateral bracing, to study the effect of CFRP wrapping on local buckling and lateral torsional buckling, wrapping scheme, and number of layers of fibers. The test results show that application of CFRP in the plastic hinge region of flexural members has substantial benefits. In particular, the CFRP wraps can increase the size of the yielded plastic hinge region, slow down the occurrence of local buckling, and delay lateral torsional buckling. These benefits reduce strain demands in the critical plastic hinge region and substantially improve energy dissipation capacity within the plastic hinge region.     

The effect of liposome on dyeing mohair/wool blends

The aim of this study was to examine the use of liposome in the dyeing of wool and mohair fibres with acid dyestuffs. Soybean lecithin and cholesterol were used to form the liposome membrane utilised in the dyebath. Liposome production was performed according to the thin lipid layer method (Bangham Method) using a rotary evaporator. Two different forms of liposome were used for dyeing wool and mohair fibres. In its first form, liposome was utilised as an auxiliary agent, where it was added to a conventional dyebath at the beginning of the process. In its second form, dyes were encapsulated with liposome and then used in dyeing. The effects of these two different forms of liposome were compared with conventional dyeing. Dyeing was carried out at depths of shade of 0.5%, 1.0% and 2.0% using three different concentrations of liposome (0.33%, 0.66% and 1.33%). An analysis of K/S values, fastness to washing, and the alkali solubility of fibres was conducted. The fibre samples dyed in the presence of liposome exhibited very good fastness to light (grade 8). The wash fastness test results of the liposomal‐dyed samples were significantly better (grade 4‐5) than for those samples which were conventionally dyed. In the presence of liposome, the tensile strength of fibres was 20 gf, whereas it was 11 gf without liposomes.     

An experimental investigation on the durability of railway ballast material by magnesium sulfate soundness

In this study, the durability of railway ballast material is investigated by magnesium sulfate soundness tests. Two types of ballast aggregates, which are produced from basaltic rocks and currently used as railway ballast in such high speed railway routes in Turkey, are investigated regarding their resistance against freezing–thawing (FT) and traffic loads. Firstly, the mineralogical and physico-mechanical properties of rocks are determined. Then the degradation of investigated ballast aggregates is determined by magnesium sulfate soundness and Los Angeles abrasion (LAA) tests. The natural FT effects are simulated by magnesium sulfate soundness tests up to 40 cycles, whereas the traffic loads are represented by LAA tests up to 3000 revolutions. The ballast fouling that leads to such problems are also investigated within the scope in the present study. The degree of ballast fouling is quantified as fouling index (FI) which is determined using the crushed particles generated after LAA tests. It is concluded from laboratory studies that rock properties considered are considerably influenced by simulated FT cycles. It is also achieved from the laboratory studies that magnesium sulfate soundness and Los Angeles abrasion tests are good indicators to clarify the fragmentation mechanism of the ballast aggregate in laboratory scale. In conclusion several empirical formulas are developed to predict LAA and FI for each rock type. The proposed empirical formulas could be utilized as a pre-design tool for new railway routes in design stage provided that the investigated ballast aggregates are considered.