A surrogate-based multiobjective metaheuristic and network degradation simulation model for robust toll pricing

Robust transportation network design problems generally rely on systems engineering methods that share common research gaps. First, problem sizes are constrained due to the use of multi-objective solution algorithms that are notoriously inefficient due to computationally expensive function evaluations. Second, link disruptions at a network level are difficult to model realistically. In this paper, a stochastic search metaheuristic based on radial basis functions is proposed for constrained multiobjective problems. It is proven to converge, and compared with conventional metaheuristics for four representative test problems. A scenario simulation method based on multivariate Bernoulli random variables that accounts for correlations between link failures is proposed to sample scenarios for a mean-variance toll pricing problem. Four tests are conducted on the classical Sioux Falls network to gain some insights into the algorithm, the simulation model, and to the robust toll pricing problem. The first test empirically measures the efficiency of the simulation algorithm and approximate Pareto set by obtaining a standard error in the ε-indicator measure for a given number of scenarios and iterations. The second test compares the dominance of the proposed heuristic’s solutions with a conventional multiobjective genetic algorithm by comparing the average ε-indicator. The third test quantifies the gap due to falsely assuming that link failures are independent of each other when they are not. The last test quantifies the value of having the flexibility to adapt a Pareto set of toll pricing solutions to changing probability regimes such as peak and off-peak hurricane or snow seasons.     

遇上天堂鸟

<正>百达翡丽应用"掐丝珐琅"——这种极为珍罕的艺术形式,不仅缔造了手工制作手表的传奇,还表明了保护这门传统工艺的决心。手腕上惊艳见到百达翡丽,就见到那美得让人永不能忘却的天堂鸟——拍打着五彩斑斓的羽毛,摇摆着硕大艳丽的尾翼,腾空飞起,有如满天彩     

Lattice expansion in seamless bilayer graphene constrictions at high bias

Our understanding of sp(2) carbon nanostructures is still emerging and is important for the development of high performance all carbon devices. For example, in terms of the structural behavior of graphene or bilayer graphene at high bias, little to nothing is known. To this end, we investigated bilayer graphene constrictions with closed edges (seamless) at high bias using in situ atomic resolution transmission electron microscopy. We directly observe a highly localized anomalously large lattice expansion inside the constriction. Both the current density and lattice expansion increase as the bilayer graphene constriction narrows. As the constriction width decreases below 10 nm, shortly before failure, the current density rises to 4 × 10(9) A cm(-2) and the constriction exhibits a lattice expansion with a uniaxial component showing an expansion approaching 5% and an isotropic component showing an expansion exceeding 1%. The origin of the lattice expansion is hard to fully ascribe to thermal expansion. Impact ionization is a process in which charge carriers transfer from bonding states to antibonding states, thus weakening bonds. The altered character of C-C bonds by impact ionization could explain the anomalously large lattice expansion we observe in seamless bilayer graphene constrictions. Moreover, impact ionization might also contribute to the observed anisotropy in the lattice expansion, although strain is probably the predominant factor.     

Freezing of strawberries by immersion in CaCl2 solutions

The present investigation studied the freezing of strawberries by immersion in CaCl₂ solutions, analysing drip loss, pectin content and the degree of esterification of the pectins, total and cell-wall bonded calcium contents, the ratio bonded calcium/total calcium, and textural parameters. In addition, the effect of immersion in pectin methylesterase (PME) solutions prior to immersion freezing (IF) was analysed. The firmness of thawed fruit decreased by approximately 74% with respect to fresh strawberries, and neither IF-CA (freezing by immersion in CaCl₂ solution) nor PME–IF-CA (immersion in PME solution + freezing by immersion in CaCl₂ solution) provided significant benefit in maintaining firmness when compared to slow freezing (SF). However, IF provided a significant benefit in reducing drip loss of thawed strawberries when compared to SF, but pre-treatment with PME did not provide any additional benefit.     

Mathematical modeling of the heat transfer and flow field of liquid refrigerants in a hydrofluidization system with a stationary sphere

Hydrofluidization is a method of chilling and freezing of foods that uses a circulating system that pumps the refrigerating liquid upwards through orifices and/or nozzles into a refrigerating vessel, thereby creating submerged agitating jets and increasing heat transfer to foods during freezing. The objective of this work was to develop a model to estimate the fluid flow and heat and mass transfer in a hydrofluidization system. A study case of modeling and validating the heat transfer to a single stationary copper sphere of 20-mm diameter impinged by a single round jet of liquid was carried out using computational fluid dynamics. The simulations were performed using parameters such as: velocity of the liquid at the orifice exit (2.36–7.07 m s⁻¹), temperature of the liquid refrigerant (−5 to −15 °C) and distance between the orifice and the stagnation point of the sphere (1 and 5 cm). In general, the errors of the model were in the order of magnitude of the uncertainty of the experimental data of Nusselt number averaged over the sphere surface. Also, the simulated heat transfer and flow field parameters were comparable with those obtained in literature for similar systems.     

Homelessness and smoking cessation: insights from focus groups.

Smoking prevalence among homeless persons is approximately 70%, yet little is known about tobacco use patterns or smoking cessation practices in this population. We assessed smoking attitudes and behaviors, psychosocial and environmental influences on smoking, barriers to and interest in quitting, and preferred methods for cessation among some homeless smokers. Six 90-min focus groups of current smokers (N = 62) were conducted at homeless service facilities. Participants had a mean age of 41.5 years (SD = 9.3), were predominantly male (69.4%) and African American (59%), and smoked an average of 18.3 cigarettes/day. Although most reported that they were motivated to quit, a number of barriers to quitting were identified. Participants reported that the pervasiveness and social acceptance of tobacco use in homeless settings contributed to smoking more cigarettes per day, adopting alternative smoking behaviors such as smoking cigarette butts and making their own cigarettes, and experiencing difficulty in quitting. High levels of boredom and stress also were cited as reasons for continued smoking. Smoking frequently occurred in combination with alcohol or illicit drug use or to achieve a substitute "high." Most participants (76%) reported that they planned to quit smoking in the next 6 months. Many were interested in using pharmacotherapy in combination with behavioral treatments. Results suggest that, although motivated to quit smoking, homeless smokers are faced with unique social and environmental barriers that make quitting more difficult. Interventions must be flexible and innovative to address the unique needs of homeless smokers. Smoking restrictions at homeless service facilities and funding for smoking cessation assistance in this underserved population may help to reduce prevalence.     

NaCl Nanoparticles as a Cancer Therapeutic

Many inorganic nanoparticles are prepared and their behaviors in living systems are investigated. Yet, common electrolytes such as NaCl are left out of this campaign. The underlying assumption is that electrolyte nanoparticles will quickly dissolve in water and behave similarly as their constituent salts. Herein, this preconception is challenged. The study shows that NaCl nanoparticles (SCNPs) but not salts are highly toxic to cancer cells. This is because SCNPs enter cells through endocytosis, bypassing cell regulations on ion transport. When dissolved inside cancer cells, SCNPs cause a surge of osmolarity and rapid cell lysis. Interestingly, normal cells are much more resistant to the treatment due to their relatively low sodium levels. Unlike conventional chemotherapeutics, SCNPs cause immunogenic cell death or ICD. In vivo studies show that SCNPs not only kill cancer cells, but also boost an anticancer immunity. The discovery opens up a new perspective on nanoparticle‐based therapeutics.     

Brewster's angle attenuator for terahertz pulses

A variable attenuator for terahertz (THz) pulses is developed on the basis of the change in reflectivity of lithium niobate wafers with incident angle in a Brewster configuration. We can vary the THz field transmission from 22% to 54%, a change of a factor of 2.5, while preserving the shape of the THz pulse spectrum. Changes in the THz spectrum are shown to be much smaller when the Brewster attenuator is used than when either the near-infrared pump power or the bias voltage on a THz photoconductive antenna is varied. The Brewster attenuator should prove especially useful for varying THz field strength in nonlinear optical studies that use broadband THz pulses.