Cold and wet: Diatoms dominate the phytoplankton community during a year of anomalous weather in a Great Lakes estuary

As sentinels of climate change and other anthropogenic forces, freshwater lakes are experiencing ecosystem disruptions at every level of the food web, beginning with the phytoplankton, a highly responsive group of organisms. Most studies regarding the effects of climate change on phytoplankton focus on a potential scenario in which temperatures continuously increase and droughts intersperse heavy precipitation events. Like much of the conterminous United States in 2019, the Muskegon River watershed (Michigan, USA) experienced record-breaking rainfall accompanied by unusually cool temperatures, affording an opportunity to explore how an alternate potential climate scenario may affect phytoplankton. We conducted biweekly sampling of environmental variables and phytoplankton in Muskegon Lake, a Great Lakes Area of Concern that connects to Lake Michigan. We compared environmental variables in 2019 to the previous eight years using long-term data from the Muskegon Lake Observatory buoy, and annual monitoring excursions provided historical phytoplankton data. Under cold and wet conditions, diatoms were the single dominant division throughout the entire growth season – an unprecedented scenario in Muskegon Lake. In 10 of the 13 biweekly sampling days in 2019, diatoms comprised over 75% of the phytoplankton community in the lake by count, indicating that the spring diatom bloom persisted through the fall. Additionally, phytoplankton seasonal succession and abundance patterns typically seen in this lake were absent. In a world experiencing reduced predictability, increased variability, and regional climate anomalies, studying periods of extreme weather events may offer insight into how natural systems will be affected and respond under future climate scenarios.     

Complex study of protective Cr3C2–NiAl coatings deposited by vacuum electro-spark alloying,pulsed cathodic arc evaporation,magnetron sputtering,and hybrid technology

Coatings were obtained by vacuum electro-spark alloying (VESA), pulsed cathodic arc evaporation (PCAE), magnetron sputtering (MS) techniques and VESA-PCAE-MS hybrid technology using Cr₃C₂–NiAl electrodes. The structure of the coatings was analyzed using scanning and transmission electron microscopy, X-ray diffraction and energy-dispersive spectroscopy. Mechanical properties were determined by nanoindentation, while tribological properties were assessed using pin-on-disk tribometer. Corrosion resistance was estimated by voltammetry in 1 N H₂SO₄ and 3.5%NaCl solutions. Oxidation resistance tests were performed at 800°С in air. The VESA coating had the highest thickness, low friction coefficient and high wear resistance. PCAE coating demonstrated the highest hardness (24 GPa) and elastic recovery (59%), oxidation resistance and superior corrosion resistance both in 1 N H₂SO₄ (i_corr = 70 μА/cm²) and 3.5%NaCl (i_corr = 0.74 μА/cm²) solutions. The MS coating had average mechanical properties and low corrosion current density (71 μА/cm²) in 1 N H₂SO₄. Deposition of coatings using VESA-PCAE-MS hybrid technology led to an increase in corrosion and oxidation resistance at least by 1.5 times in comparison with the VESA coating.     

An automated treatment planning strategy for highly noncoplanar radiotherapy arc trajectories

Radiation therapy is a technology-driven cancer treatment modality that has experienced significant advances over the last decades, due to multidisciplinary contributions that include engineering and computing. Recent technological developments allow the use of noncoplanar volumetric modulated arc therapy (VMAT), one of the most recent photon treatment techniques, in clinical practice. In this work, an automated noncoplanar arc trajectory optimization framework designed in two modular phases is presented. First, a noncoplanar beam angle optimization algorithm is used to obtain a set of noncoplanar irradiation directions. Then, anchored in these directions, an optimization strategy is proposed to compute an optimal arc trajectory. The computational experiments considered a pool of twelve difficult head-and-neck tumor cases. It was possible to observe that, for some of these cases, the optimized noncoplanar arc trajectories led to significant treatment planning quality improvements, when compared with coplanar VMAT treatment plans. Although these experiments were done in a research environment treatment planning software (matRad), the conclusions can be of interest for a clinical setting: automated procedures can simplify the current treatment workflow, produce high-quality treatment plans, making better use of human resources and allowing for unbiased comparisons between different treatment techniques.     

Contribution of metal vapor mass at periphery part of pulsed arc to electromagnetic force in weld pool

The arc welding has been used in various welding methods because it is inexpensive and high in strength after welding. However, it is a problem that accidents such as collapse of the bridge occur because of the welding defects. The welding of low cost and high productivity is required without the welding defects. The pulsed TIG welding is inexpensive and capable of high‐quality welding. The electromagnetic force contributing to penetration changes because the transient response of arc temperature and iron vapor generated from anode occurs. However, the analysis of pulsed TIG welding with metal vapor has been elucidated only metal vapor concentration near anode with transient phenomenon and heat flux. Thus, the theoretical elucidation of penetration depth with control factor has not been researched. In this paper, the contribution of metal vapor mass at the periphery part of pulsed arc to the electromagnetic force in the weld pool is elucidated. As a result, the iron vapor mass at periphery part decreased with increasing the frequency. The iron vapor was stagnated at axial center within one cycle. The electromagnetic force to the penetration depth direction in weld pool increased at axial center. Therefore, the metal vapor mass at periphery part plays an important role for the electromagnetic force increment at axial center.     

Q690钢焊接接头微观组织对冷裂纹的影响研究

分析了Q690钢手工电弧焊与气体保护焊焊接冷裂纹产生与微观组织的联系。结果表明: 焊接冷裂纹起源于斜Y坡口根部, 沿熔合区、焊缝扩展至焊缝表面;2种工艺焊接的接头组织硬度均较母材高, 而塑性较差。热影响区为马氏体、贝氏体与铁素体混合组织, 焊缝组织由先共析铁素体、侧板条铁素体、贝氏体和针状铁素体等组成, 针状铁素体抗裂纹扩展能力较其他组织强。在2种焊接方法对应断口中观察到了冷裂纹起裂、扩展与断裂区的不同形貌, 起裂与扩展区存在塑性变形, 而断裂区为解理断裂。     

二氧化碳气体保护焊在厚板上的应用

板厚为 5 5mm的 16Mn钢采用CO2 半自动气保焊建造大型转炉炉体的可能性和可靠性如何 ?目前尚缺少足够的试验数据。为了给转炉工程的施工焊接提供可靠数据 ,确保焊接质量 ,对板厚 5 5mm16Mn钢CO2 半自动的焊接性能进行了一系列的试验研究     

Simplification of the Plasma Load of Negative-Pulse-Bias Source Used in Arc Ion Plating

Based on the voltage and current fluctuating phenomenon in the arc plasma load under the negative-pulse-bias, usingthe plasma physics theory and analysis of computer simulation expatiates that the nature of plasma load in vacuumarc plasma is a capacitance     

新型AXQ1-200A直流内燃弧焊机

针对目前国内内燃弧焊机结构复杂、控制损耗大、效率低等状况,研发了一种新型AXQ1-200 A直流内燃弧焊机.详细介绍了新型AXQ1-200 A直流内燃弧焊机的原理、结构特点及技术参数.该设备整机轻巧,移动方便,操作维护简便,既可提供用于野外手工电弧焊接的直流焊接电源,又可提供DC 220 V/3 000 W的辅助电源.     

OPGW雷击断股的机理及对策

针对OPGW雷击断股问题,指出了雷电形成电弧时产生的高温是OPGW雷击断股的主要原因,对不同状况下OPGW雷击断股的主要因素进行了剖析,同时制定出相应的预防措施.对广东省500 kV江茂乙线OPGW雷击情况进行具体分析,认为原材料缺陷、加工工艺缺陷、接地方式、雷击形成的电弧损害和光缆抗雷击能力不足等都能引起OPGW断股,指出了提高OPGW抗雷击能力需解决的关键问题.     

NSA-500-1型氩弧焊机VD9不同接法对引弧和稳弧的影响

从一起NSA－500－1型氩弧焊机故障，分析其高压脉冲旁路二极管VD9不同接法对引弧、稳弧及设备安全的影响。