189 research outputs found

    A rolling horizon approach for the locomotive routing problem at the Canadian National Railway Company

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    Cette thèse étudie le problème du routage des locomotives qui se pose à la Compagnie des chemins de fer nationaux du Canada (CN) - le plus grand chemin de fer au Canada en termes de revenus et de taille physique de son réseau ferroviaire. Le problème vise à déterminer la séquence des activités de chaque locomotive sur un horizon de planification donné. Dans ce contexte, il faut prendre des décisions liées à l'affectation de locomotives aux trains planifiés en tenant compte des besoins d'entretien des locomotives. D’autres décisions traitant l'envoi de locomotives aux gares par mouvements à vide, les déplacements légers (sans tirer des wagons) et la location de locomotives tierces doivent également être prises en compte. Sur la base d'une formulation de programmation en nombres entiers et d'un réseau espace-temps présentés dans la littérature, nous introduisons une approche par horizon roulant pour trouver des solutions sous-optimales de ce problème dans un temps de calcul acceptable. Une formulation mathématique et un réseau espace-temps issus de la littérature sont adaptés à notre problème. Nous introduisons un nouveau type d'arcs pour le réseau et de nouvelles contraintes pour le modèle pour faire face aux problèmes qui se posent lors de la division de l'horizon de planification en plus petits morceaux. Les expériences numériques sur des instances réelles montrent les avantages et les inconvénients de notre algorithme par rapport à une approche exacte.This thesis addresses the locomotive routing problem arising at the Canadian National Railway Company (CN) - the largest railway in Canada in terms of both revenue and the physical size of its rail network. The problem aims to determine the sequence of activities for each locomotive over the planning horizon. Besides assigning locomotives to scheduled trains and considering scheduled locomotive maintenance requirements, the problem also includes other decisions, such as sending locomotives to stations by deadheading, light traveling, and leasing of third-party locomotives. Based on an Integer Programming formulation and a Time-Expanded Network presented in the literature, we introduce a Rolling Horizon Approach (RHA) as a method to find near-optimal solutions of this problem in acceptable computing time. We adapt a mathematical formulation and a space-time network from the literature. We introduce a new type of arcs for the network and new constraints for the model to cope with issues arising when dividing the planning horizon into smaller ones. Computational experiments on real-life instances show the pros and cons of our algorithm when compared to an exact solution approach

    Remote Working Burnout: Empirical Study from TOE and Technostress Model

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    Work stress and burnout negatively impact the individual and companies. Remote working exacerbates these issues due to the lack of company support and social interactions. Yet, research on identifying factors contributing to stress and burnout in remote workspaces and differentiating the components of stress and burnout in this context is limited. This work presents and empirically evaluates a conceptual framework, based on the Technology – Organization – Environment framework and the technostress theory, which aims to address these gaps. In particular, the model proposed here distinguishes between technostress, work stress, and burnout. Future work to examine the model will use a survey instrument for data gathering, as well as confirmatory factor analysis and partial least squares for analysis

    A Study of the Adsorption Characteristics of Cobalt and Caesium from a Solution by Using Vietnamese Bentonite

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    The radioactive waste produced from the construction of a nuclear power plant is a controversial topic. The resulting radioactive waste contains 60Co and 137Cs isotopes that are the most difficult to remove. Bentonite is widely used as an adsorbent for heavy metals. An important factor is the safe operation of waste management at a nuclear power plant to be built in Vietnam. Therefore, a method of degrading complexes of radionuclides and the adsorption of radionuclides onto Vietnamese Bentonite was implemented in this study. In current literature, UV radiation and heating with oxidising substances are used in general for degrading complexes of radionuclides. The experimental results for the adsorption of Co(II) and Cs+ onto VNB suggest that VNB can be used in the future for large-scale liquid waste treatment due to its low cost, high efficiency, and environmentally friendliness

    Active Voltage Control (AVC) for Reducing Three-phase Voltage Fluctuations

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    The paper presents an active voltage compensator (AVC) to prevent voltage fluctuations on the load in both voltage’s rise and fall directions. This AVC is designed based on modeling a three-phase four-branch inverter according to the large-signal average model and the small-signal model—calculation and design of d-q channel controller and 0 channel controller by the frequency-domain method. This AVC significantly reduces production interruptions while protecting equipment life reduction. The theory results are proven through MATLAB/Simulink simulation

    Morphological characteristics and genetic diversity of <em>Terapon jarbua</em> (Forrskäl, 1775) in Central, Vietnam

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    Many environmental factors affect the morphology of migratory fish species, such as salinity, water flow rate, and temperature. However, studies on changes in fish morphology under environmental variations from salt water to brackish water are still limited in many fish species, especially in *Terapon jarbua*. This study aims to investigate the differences in the morphological parameters of *T. jarbua* between the coastal sea (seawater) and lagoon (brackish water); and between male and female fish based on a landmark morphological approach. Additionally, the genetic diversity of *T. jarbua* populations in Central Vietnam was elucidated using the mitochondrial DNA cytochrome oxidase subunit I (mtDNA COI) sequence as a molecular marker. The analytical results indicated no sexual dimorphism in the *T. jarbua* population, yet conformational differences exist between the two studied aquatic species. The analysis of 42 mtDNA COI sequences collected from Central Vietnam identified 13 haplotypes with medium genetic diversity and low genetic differentiation between the Tam Giang lagoon and Thua Thien Hue coastal (Fst = 0.028) and not significant (p = 0.126). Most haplotypes obtained are present in reference populations, indicating a high genetic exchange between populations. We proposed that the *T. jarbua* population in Central Vietnam has a stable connection with neighboring populations (China, Taiwan, Philippines, Indonesia, Malaysia, Bangladesh, India, and Pakistan)

    Numerical modeling of thermal dust polarization from aligned grains in the envelope of evolved stars with updated POLARIS

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    Magnetic fields are thought to influence the formation and evolution of evolved star envelopes. Thermal dust polarization from magnetically aligned grains is potentially a powerful tool for probing magnetic fields and dust properties in these circumstellar environments. In this paper, we present numerical modeling of thermal dust polarization from the envelope of IK Tau using the magnetically enhanced radiative torque (MRAT) alignment theory implemented in our updated POLARIS code. Due to the strong stellar radiation field, the minimum size required for RAT alignment of silicate grains is ∼0.005−0.05 μm\sim 0.005 - 0.05\,\rm\mu m. Additionally, ordinary paramagnetic grains can achieve perfect alignment by MRAT in the inner regions of r<500 aur < 500\,\rm au due to stronger magnetic fields of B∼10B\sim 10 mG - 1G, producing thermal dust polarization degree of ∼10 %\sim 10\,\%. The polarization degree can be enhanced to ∼20−40%\sim 20-40\% for grains with embedded iron inclusions. We also find that the magnetic field geometry affects the alignment size and the resulting polarization degree due to the projection effect in the plane-of-sky. We also study the spectrum of polarized thermal dust emission and find the increased polarization degree toward λ>50 μm\lambda > 50\,\rm\mu m due to the alignment of small grains by MRAT. Furthermore, we investigate the impact of rotational disruption by RATs (RAT-D) and find the RAT-D effect cause a decrease in the dust polarization fraction. Finally, we compare our numerical results with available polarization data observed by SOFIA/HAWC+ for constraining dust properties, suggesting grains are unlikely to have embedded iron clusters and might have slightly elongated shapes. Our modeling results suggest further observational studies at far-infrared/sub-millimeter wavelengths to understand the properties of magnetic fields and dust in AGB envelopes.Comment: 27 pages, 23 figures, 1 table, to be submitte

    Overcoming Fear of Developing Country: A Case Report of Retroperitoneal Laparoscopic Partial Nephrectomy for T3a Renal Cell Carcinoma

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    INTRODUCTION: Renal cell carcinoma poses significant challenges in kidney diseases, particularly in the context of the T3 stage, where treatment strategies remain controversial. The utilization of laparoscopic partial nephrectomy, particularly in developing countries, has been restricted for such patients, primarily due to limited infrastructure and concerns about recurrence risk and long-term pathologic outcomes. PRESENTATION OF CASE: In this report, we present a case of a 64-year-old male diagnosed with T3aN0M0 renal cell carcinoma (RCC). Abdominal computed tomography revealed a 5.2 × 5.2 × 5.1 cm mass on the right upper part of the kidney with a possible thrombus in the superior renal polar vein. The patient underwent successful treatment with retroperitoneal laparoscopic partial nephrectomy (LPN), leading to the preservation of kidney function with/min/1.73 m2 GFR reduced after one year postoperative (estimated GFR from 85 mL/min/1.73 m2 to 81.79 mL/min/1.73 m2). The patient was discharged after three days; no recurrence was observed during the follow-up. DISCUSSION: For stage T3a RCC, studies show that LPN induces comparable long-term outcomes to radical nephrectomy, with advantages such as preserved kidney function, reduced operative time, blood loss, and shorter hospital stays. However, due to infrastructure constraints and limited access to robotic-assisted surgery in our country, coupled with concerns about tumor recurrence, laparoscopic radical nephrectomy is predominantly employed for similar patients. Our case represents one of the very first cases in which we successfully treated a patient diagnosed with T3a RCC using retroperitoneal laparoscopic partial nephrectomy. CONCLUSION: Laparoscopic partial nephrectomy is a reliable choice for T3aN0M0 RCC with good long-term outcomes and preserved renal function, especially by the hands of an experienced laparoscopic surgeon

    An in-situ thermoelectric measurement apparatus inside a thermal-evaporator

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    At the ultra-thin limit below 20 nm, a film's electrical conductivity, thermal conductivity, or thermoelectricity depends heavily on its thickness. In most studies, each sample is fabricated one at a time, potentially leading to considerable uncertainty in later characterizations. We design and build an in-situ apparatus to measure thermoelectricity during their deposition inside a thermal evaporator. A temperature difference of up to 2 K is generated by a current passing through an on-chip resistor patterned using photolithography. The Seebeck voltage is measured on a Hall bar structure of a film deposited through a shadow mask. The measurement system is calibrated carefully before loading into the thermal evaporator. This in-situ thermoelectricity measurement system has been thoroughly tested on various materials, including Bi, Te, and Bi2_2Te3_3, at high temperatures up to 500 K

    Extracting Conditions Optimization and Bioactivity of Polysaccharides from the Pods of Haricot Vert

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    Polysaccharides from the pods of haricot vert (Phaseolus vulgaris L.) were extracted using a simple heating method, by varying extracting temperature, heating time, solid-to-liquid ratio, and solvent compositions. The obtained results were processed using statistical analysis that helped to identify the optimal conditions for the polysaccharides’ extraction process. This study represents a promising production method of bioactive polysaccharides extract in the food and pharmaceutical industry

    Factors affecting the creativity of high school students

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    Creativity is a vital personality quality of each individual. Each person has their potential for creativity, and it can be nurtured and developed in an appropriate and safe environment. The purpose of the study was to find out which factors from schools and students themselves affect creativity as well as the association between creativity and age, gender and giftedness of students, which then a basis to adjust and establish appropriate methods from schools, families, and students themselves to develop elements and their creativity. The study was conducted on 108 high school students in three grades from giftedness and non-giftedness schools. The data was collected through a survey method using a self-constructed questionnaire and drawing creativity test TCT-DP to determine students' creativity levels and personal information. The study's finding, which uses mathematical methods and one-way analysis of variance, reveals that factors affecting elements and creativity level are objective factors including education environment from school; behavior of teachers, and subjective factors including interests, perspectives, and thoughts of students. It was also found that there were no significant differences in the components of creativity and creativity among students in different grades, gender, and groups of giftedness schools
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