Large neighborhood search for the bike request scheduling problem

This paper introduces an efficient algorithm for the bike request scheduling problem (BRSP). The BRSP is built around the concept of request, defined as the pickup or dropoff of a number of identical items (bikes) at a specific station, within a certain time window, and with a certain priority. The aim of the BRSP is to sequence requests on (and hence determine the routes of) a set of vehicles, in such a way that the sum of the priorities of the executed requests is maximized, all time windows are respected, and the capacity of the vehicles is not exceeded. The generation of the set of requests is explicitly not a part of the problem definition of the BRSP. The primary application of the BRSP, from which it derives its name, is to determine the routes of a set of repositioning vehicles in a bike sharing system, although other applications exist. The algorithm introduced in this paper is based on a set of related greedy randomized adaptive search procedure followed by variable neighborhood descent (GRASP + VND) operators embedded in a large neighborhood search (LNS) framework. Since this paper presents the first heuristic for the BRSP, a computational comparison to existing approaches is not possible. We therefore compare the solutions found by our LNS heuristic to those found by an exact solver (Gurobi). These experiments confirm that the proposed algorithm scales to realistic dimensions and is able to find near‐optimal solutions in seconds.     

Effects of air purification of indoor PM2.5 on the cardiorespiratory biomarkers in young healthy adults

Ambient fine particulate matter (PM_2.5), as one of the predominant air pollutants, has achieved effective control in recent years in China. Whether the use of indoor air purifiers is still necessary needs further exploration. A randomized crossover trial was conducted in 54 healthy students in Beijing, China. Participants were randomized assigned to the use of real or sham high-efficiency particulate air filter (HEPA) for a week and changed the status after a washout period. Health measurements of cardiorespiratory biomarkers were performed at the end of each period. Linear mixed-effects models were used to evaluate the association between PM_2.5 exposure and cardiorespiratory biomarkers. Compared with sham air purification, average diastolic blood pressure (DBP), fractional exhaled nitric oxide (FeNO), and 8-isoprostane (8-isoPGF2α) levels decreased significantly in the real purification. The effects of indoor air purification on lung function indicators including forced expiratory volume in one second (FEV₁), peak expiratory flow (PEF), and forced expiratory flow between the 25th and 75th percentile of forced vital capacity (FEF_25%–75%) were also significant. Our findings showed a protective effect of indoor HEPA air purifiers on cardiorespiratory health of young healthy adults reflected by the decreased blood pressure, respiratory inflammation, and systematic oxidative stress and improved lung function.     

A supplemental computer-assisted intervention programme to prevent early reading difficulties in Spanish learners: A stratified random control trial

Difficulties in implementing effective instruction for at-risk students arise from two challenges: the transfer of evidence-based knowledge and the lack of economic resources. Computer-assisted programmes offer a suitable solution, providing quality instruction using low-cost resources. Thirty-two first-grade students with early learning difficulties were identified and paired based on at least three of the pre-intervention reading measures (reading efficiency of monosyllabic and disyllabic items, words, pseudowords and text reading speed). Each pair was assigned to one of two different intervention programmes: a computer-assisted intervention programme (CAIP) focused on syllables or the programme provided by the Spanish State School Assistance Services (SSAS). Every week, the CAIP participants received in pairs four 15-min training sessions on syllable decoding plus one 30-min group comprehension session. The CAIP was delivered by trainee students. The SSAS programme typically consisted of a 1-hr individual or in small groups sessions per week delivered by trained practitioners. Both programmes were administered for 11 weeks. The CAIP intervention showed better results than the SSAS intervention for both decoding and comprehension, with moderate to large effect sizes.     

Effectiveness of portable HEPA air cleaners on reducing indoor PM2.5 and NH3 in an agricultural cohort of children with asthma: A randomized intervention trial

We conducted a randomized trial of portable HEPA air cleaners with pre-filters designed to also reduce NH₃ in non-smoking homes of children age 6-12 with asthma in Yakima Valley (Washington, USA). Participants were recruited through the Yakima Valley Farm Workers Clinic asthma education program. All participants received education on home triggers while intervention families additionally received two HEPA cleaners (child's sleeping area, main living area). Fourteen-day integrated samples of PM_2.5 and NH₃ were measured at baseline and one-year follow-up. We fit ANCOVA models to compare follow-up concentrations in HEPA vs control homes, adjusting for baseline concentrations. Seventy-one households (36 HEPA, 35 control) completed the study. Most were single-family homes, with electric heat and stove, A/C, dogs/cats, and mean (SD) 5.3 (1.8) occupants. In the sleeping area, baseline geometric mean (GSD) PM_2.5 was 10.7 (2.3) μg/m³ (HEPA) vs 11.2 (1.9) μg/m³ (control); in the living area, it was 12.5 (2.3) μg/m³ (HEPA) vs 13.6 (1.9) μg/m³ (control). Baseline sleeping area NH₃ was 62.4 (1.6) μg/m³ (HEPA) vs 65.2 (1.8) μg/m³ (control). At follow-up, HEPA families had 60% (95% CI, 41%-72%; p < .0001) and 42% (19%-58%; p = .002) lower sleeping and living area PM_2.5, respectively, consistent with prior studies. NH₃ reductions were not observed.     

中小型逆变器的电磁兼容设计

通过分析中小型逆变器电磁干扰形成的主要原因,从控制电路设计、主电路设计、软件设计三方面介绍提高逆变器电磁兼容能力的措施,重点对软开关技术,随机调制技术进行了分析.     

Monte Carlo criticality analysis under material distribution uncertainty

Analysis framework under material distribution uncertainty is not yet established for the Monte Carlo (MC) criticality calculation of continuously mixed media formed via molten core concrete interaction. To approach this issue, one group cross-sections have specifically been prepared for burned fuel, stainless steel and concrete, and the effect of spatially continuous variation of volume fractions is inspected. Trigonometric functions and randomized Weierstrass functions (RWFs) are utilized to represent the spatially continuous variation. Here, trigonometric functions enable the amount of each material to be exactly preserved, and RWF is a randomized trigonometric series that can be generated within specified upper and lower bounds. With these functions, one can assess the influence of indeterminate material distribution. MC particle transport is conducted using the delta-tracking. Numerical results indicate that the effective multiplication factor (k_eff) under RWF variation can depart significantly from the k_eff of a reference uniform medium. These numerical results also show that the deterministic modeling of spatial variation provides a bound measure for extreme results from random realizations.     

Influence of inhomogeneous static magnetic field-exposure on patients with erosive gastritis: a randomized,self- and placebo-controlled,double-blind,single centre,pilot study

This pilot study was devoted to the effect of static magnetic field (SMF)-exposure on erosive gastritis. The randomized, self- and placebo-controlled, double-blind, pilot study included 16 patients of the 2nd Department of Internal Medicine, Semmelweis University diagnosed with erosive gastritis. The instrumental analysis followed a qualitative (pre-intervention) assessment of the symptoms by the patient: lower heartburn (in the ventricle), upper heartburn (in the oesophagus), epigastric pain, regurgitation, bloating and dry cough. Medical diagnosis included a double-line upper panendoscopy followed by 30 min local inhomogeneous SMF-exposure intervention at the lower sternal region over the stomach with peak-to-peak magnetic induction of 3 mT and 30 mT m⁻¹ gradient at the target site. A qualitative (post-intervention) assessment of the same symptoms closed the examination. Sham- or SMF-exposure was used in a double-blind manner. The authors succeeded in justifying the clinically and statistically significant beneficial effect of the SMF- over sham-exposure on the symptoms of erosive gastritis, the average effect of inhibition was 56% by p = 0.001, n = 42 + 96. This pilot study was aimed to encourage gastroenterologists to test local, inhomogeneous SMF-exposure on erosive gastritis patients, so this intervention may become an evidence-based alternative or complementary method in the clinical use especially in cases when conventional therapy options are contraindicated.     

A multiobjective GRASP–VND algorithm to solve the waste collection problem

In this paper, the waste collection problem (WCP) of a city in the south of Spain is addressed as a multiobjective routing problem that considers three objectives. From the company's perspective, the minimization of the travel cost is desired as well as that of the total number of vehicles. Additionally, from the employee's point of view, a set of balanced routes is also sought. Four variants of a multiobjective hybrid algorithm are proposed. Specifically, a GRASP (greedy randomized adaptive search procedure) with a VND (variable neighborhood descent) is combined. The best GRASP–VND algorithm found is applied in order to solve the real‐world WCP of a city in the south of Spain.     

Scheduling jobs with ready times and precedence constraints on parallel batch machines using metaheuristics

In this paper, we discuss a scheduling problem for parallel batch machines where the jobs have ready times. Problems of this type can be found in semiconductor wafer fabrication facilities (wafer fabs). In addition, we consider precedence constraints among the jobs. Such constraints arise, for example, in scheduling subproblems of the shifting bottleneck heuristic when complex job shop scheduling problems are tackled. We use the total weighted tardiness as the performance measure to be optimized. Hence, the problem is NP-hard and we have to rely on heuristic solution approaches. We consider a variable neighborhood search (VNS) scheme and a greedy randomized adaptive search procedure (GRASP) to compute efficient solutions. We assess the performance of the two metaheuristics based on a large set of randomly generated problem instances and based on instances from the literature. The obtained computational results demonstrate that VNS is a very fast heuristic that quickly leads to high-quality solutions, whereas the GRASP is slightly outperformed by the VNS approach. However, the GRASP approach has the advantage that it can be parallelized in a more natural manner compared to VNS.