On priority queues with impatient customers

In this paper, we study three different problems where one class of customers is given priority over the other class. In the first problem, a single server receives two classes of customers with general service time requirements and follows a preemptive-resume policy between them. Both classes are impatient and abandon the system if their wait time is longer than their exponentially distributed patience limits. In the second model, the low-priority class is assumed to be patient and the single server chooses the next customer to serve according to a non-preemptive priority policy in favor of the impatient customers. The third problem involves a multi-server system that can be used to analyze a call center offering a call-back option to its impatient customers. Here, customers requesting to be called back are considered to be the low-priority class. We obtain the steady-state performance measures of each class in the first two problems and those of the high-priority class in the third problem by exploiting the level crossing method. We furthermore adapt an algorithm from the literature to obtain the factorial moments of the low-priority queue length of the multi-server system exactly.      

Isonitriles as efficient ligands in Suzuki-Miyaura reaction

Isonitrile palladium complexes [(RNC)₂PdCl₂] were prepared and tested in Suzuki reaction of 4-chloroanisol. (AdNC)₂PdCl₂ was found the most effective catalyst and was used in phenylation of several chloro and bromoaromatic substrates.     

Photodissociation of t-butyl nitrite by UV and blue photons

The photodissociation of t-butyl nitrite at 266, 355, 454, 474 and 494 nm has been studied by probing the NO(X²Π) fragment. Either two lasers at different wavelengths were used for dissociating and probing or a single laser was used for both. The results show strong dependence of the vibrational and rotational excitation of the NO on the photodissociation wavelength.     

A survey on multi-objective evolutionary algorithms for many-objective problems

Multi-objective evolutionary algorithms (MOEAs) are well-suited for solving several complex multi-objective problems with two or three objectives. However, as the number of conflicting objectives increases, the performance of most MOEAs is severely deteriorated. How to improve MOEAs’ performance when solving many-objective problems, i.e. problems with four or more conflicting objectives, is an important issue since a large number of this type of problems exists in science and engineering; thus, several researchers have proposed different alternatives. This paper presents a review of the use of MOEAs in many-objective problems describing the evolution of the field, the methods that were developed, as well as the main findings and open questions that need to be answered in order to continue shaping the field.