Piecewise linearisation of the first order loss function for families of arbitrarily distributed random variables

We discuss the problem of computing optimal linearisation parameters for the first order loss function of a family of arbitrarily distributed random variable. We demonstrate that, in contrast to the problem in which parameters must be determined for the loss function of a single random variable, this problem is nonlinear and features several local optima and plateaus. We introduce a simple and yet effective heuristic for determining these parameters and we demonstrate its effectiveness via a numerical analysis carried out on a well known stochastic lot sizing problem

Tinjauan Kuat Tekan Dan Kuat Lentur Dinding Panel Beton Ringan Dengan Perkuatan Tulangan Wiremesh

The use of panel wall as an efficient and alternaltif technology innovation that initially using conventional brick wall that takes a many time in its application and has no reinforcement inside it. This study conducted a review of compressive strength and flexural strength of lightweight concrete panel wall with wiremesh strengthening reinforcement. Where coarse aggregate in the form of tile fragments with the average dimensions is 2 cm and the type of wiremesh reinforcement is M4, fabrication size diameter is 4 mm and circle is 15 cm x 15 cm. With the planned mix design using f.a.s 0.45 and the testing of panel wall is done when the age of a concrete wall panel is 28 days, because at the concrete age of 28 days, the concrete has reached optimum strength. The research using specimen such as concrete cylinders and panel wall in the form of concrete slab. Where the concrete cylinder with diameter dimensions of 15 cm and height of 30 cm amounted to 3 samples, obtained an average compressive strength of 14.504 MPa and an average concrete density of 2030 kg / m3 which are lighter than conventional concrete that average density is 2400 kg / m3, so that the coarse aggregate concrete in the form of tile fragments can be classified as lightweight concrete. And specimen panel wall with the dimensions of length is 100 cm, width is 50 cm, and thick is 7 cm, total is 15 samples with 5 samples without wiremesh strengthening reinforcement and 10 samples using wiremesh strengthening reinforcement. In the pressure test is gained an average compressive strength of 2,571 MPa (without reinforcement) and 2.897 MPa (with reinforcement), then it obtained an increase in the compressive strength of the panel wall of 12.68%. Then in the bending test is gained an average flexural strength of 1,728 MPa (without reinforcement) and 3.461 MPa (with reinforcement), then it obtained an increase in the flexural strength of the wall panel of 100.289%

Bi-criterion procedures to support logistics decision making: cost and uncertainty

In practical decision making, one often is interested in solutions that balance multiple objectives. In this study we focus on generating efficient solutions for optimization problems with two objectives and a large but finite number of feasible solutions. Two classical approaches exist, being the constraint method and the weighting method, for which a specific implementation is required for this problem class. This paper elaborates specific straightforward implementations and applies them to a practical allocation problem, in which transportation cost and risk of shortage in supplied livestock quality are balanced. The variability in delivered quality is modelled using a scenario-based model that exploits historical farmer quality delivery data. The behaviour of both implementations is illustrated on this specific case, providing insight in (i) the obtained solutions, (ii) their computational efficiency. Our results indicate how efficient trade-offs in bi-criterion problems can be found in practical problems

Influence of different methods of treating natural açai fibre for mortar in rural construction

Received: January 20th, 2021 ; Accepted: April 15th, 2021 ; Published: May 4th, 2021 ; Correspondence: [email protected]çai is a typical Amazonian fruit that has enormous potential for use in medicines and foods, whose consumption has been growing year after year. One of the major environmental impacts related to Açai is the generation of agro-industrial wastes, which are disposed of in landfills. One of the major problems related to the reuse of natural fibres in cementitious materials is related to their durability due to the alkalinity of the matrix. Thus, the objective of this work was to evaluate three different methodologies for surface treatment of Açai fibre, by immersion in NaOH, KOH and Ca(OH)2 solution to mortar application in rural construction. After the treatments, the fibres were added in a proportion of 2.5 and 5.0% in relation to the cement mass, in addition to the reference mortar (without fibre) in the making of the prismatic specimens (40×40×160 mm) and cured for 28 days in room temperature. Right after the curing period, the specimens were evaluated according to the mechanical strength of flexion and compression, workability, water absorption by capillarity and mass density in the hardened state of each methodology. The results showed that the best treatment methodology is with NaOH solution, with the addition of 5% Açai fibre in relation to the cement mass, producing a suitable mortar for use in rural buildings

Application of pineapple fiber in the development of sustainable mortars

Received: January 27th, 2021 ; Accepted: May 12th, 2021 ; Published: October 5th, 2021 ; Correspondence: [email protected] to the great worldwide increase in pineapple production, countries like Brazil and India have problems regarding the correct disposal of residues from the production of this fruit. One of the possibilities is the reuse of these residues in the form of fibers in cementitious materials, as is the case with mortars. As a result, the objective of this work is to evaluate the application of pineapple fibers in mortars in the proportion of 1: 4 (cement: sand) with addition of fiber treated in NaOH in the proportion of 3 and 6%. The properties of mechanical resistance, water absorption, mass density and adhesion were evaluated, aiming to apply the mortar in coatings of rural environments. The results indicate that the fibers reduced the mortar density and increased the mechanical strength. However, there was a reduction in adherence, especially with the use of 6% fiber, in addition to an increase in water absorption. Based on the results, it is concluded that it is feasible to use 3% of pineapple fiber for the production of coating mortars in rural environments because the results obtained in the investigation are compatible with this application and with the established normative limits

A simple heuristic for perishable inventory control under nonstationary stochastic demand

In this paper, we study the single-item single-stocking location non-stationary stochastic lot sizing problem for a perishable product. We consider fixed and proportional ordering cost, holding cost and penalty cost. The item features a limited shelf life, therefore we also take into account a variable cost of disposal. We derive exact analytical expressions to determine the expected value of the inventory of different ages. We also discuss a good approximation for the case in which the shelf-life is limited. To tackle this problem, we introduce two new heuristics that extend Silver’s heuristic and compare them to an optimal Stochastic Dynamic Programming policy in the context of a numerical study. Our results demonstrate the effectiveness of our approach

Neuromuscular excitability changes produced by sustained voluntary contraction and response to mexiletine in myotonia congenita

Objective: To investigate the cause of transient weakness in myotonia congenita (MC) and the mechanism of action of mexiletine in reducing weakness. Methods: The changes in neuromuscular excitability produced by 1. min of maximal voluntary contractions (MVC) were measured on the amplitude of compound muscle action potentials (CMAP) in two patients with either recessive or dominant MC, compared to control values obtained in 20 healthy subjects. Measurements were performed again in MC patients after mexiletine therapy. Results: Transient reduction in maximal CMAP amplitude lasting several minutes after MVC was evident in MC patients, whereas no change was observed in controls. Mexiletine efficiently reduced this transient CMAP depression in both patients. Discussion: Transient CMAP depression following sustained MVC may represent the electrophysiological correlate of the weakness clinically experienced by the patients. In MC, the low chloride conductance could induce self-sustaining action potentials after MVC, determining progressive membrane depolarization and a loss of excitability of muscle fibers, thus resulting in transient paresis. Mexiletine may prevent conduction block due to excessive membrane depolarization, thus reducing the transient CMAP depression following sustained MVC

Hepatic hemangioma in celiac patients : data from a large consecutive series

Background and Aims. Hepatic hemangioma (HH) has a widely ranging prevalence. The etiology is unclear; however, associations with autoimmune disorders have been described. We aimed at evaluating the prevalence of HH in celiac disease. Methods. Ninety-seven consecutive patients with celiac disease (18 M, 79 F, median age 41, and range 17-84 years) underwent liver ultrasound between January 2011 and 2012. The findings were compared with those of 1352 nonceliac patients (581 M, 771 F, median age 50, and range 16-94 years), without liver disease or previously detected HH, who underwent US in the same period. Results. Ultrasonographic findings consistent with HH were observed in 14 celiac patients (14.4%), a prevalence significantly higher than in controls (69 cases, 5.1%) (P=0.0006). Subgroup analysis showed that, among women, the prevalence of HH was 16.4% in the celiac disease group (13/79) compared with 5.9% in controls (46/771) (P=0.002). In celiac setting, HH had a median diameter of 1.3 cm and presented as a single lesion in 12 cases (86%). Conclusions. Our findings are consistent with a significantly higher prevalence of HH in celiac patients. Although mechanisms underlying this association remain unclear, autoimmune and metabolic processes, as well as alterations of gut-liver axis equilibrium, could play a role