Facetting value of helical thread surface received by enveloping

В морской технике применяются различные резьбовые соединения. Детали судовых механизмов подвергаются в процессе работы вибрациям и переменным нагрузкам, которые приводят их к разрушениям, потере герметичности и к внеплановым остановкам судовых машин.. Для повышения эксплуатационных свойств и увеличения срока службы резьбовых соединений проводят анализ качества сопрягаемых поверхностей, в частности, параметров шероховатости. В предлагаемой статье исследуется величина огранки винтовой поверхности резьбы образующаяся при осуществлении нового метода изготовления резьбы огибанием. Процесс обработки металла, к которому относится новый метод нарезания, заключается в касании лезвия инструмента и обрабатываемого материала прерывистым касанием. Нарезание резьбы осуществляется, специальной червячной фрезой. При прерывистом резании обрабатываемая поверхность оказывается, как бы составленной из отдельных криволинейных площадок (граней), Линия стыка граней имеет определенную высоту по нормали к поверхности, при нарезании резьбы - к винтовой поверхности. Высота стыка граней определяет качественный показатель шероховатости поверхности, называемый волнистостью. При нарезании резьбы червячной фрезой высота стыка граней (волнистость винтовой поверхности) зависит от числа зубьев фрезы. Задача исследования состоит в том, чтобы выяснить, каким должно быть число зубьев фрезы для получение заданной шероховатости винтовой поверхности резьбы и как это влияет на качество поверхности резьбы. Так же в статье рассмотрено графическое описание процесса получения огранки резьбы и пример расчета числа гребенок фрезы. There are many different thread joints used on marine facilities. While in operation, components of the mechanisms undergo vibrations with repeated stresses that leads to their failures, loss of tightness, and unscheduled shutdowns of the equipment. The analyses of joint surfaces quality, e.g. roughness parameters, are conducted to enhance serviceability of the thread joints and to prolong their lifespan. The article studies facetting value of a helical thread surface while applying a new method of thread production – enveloping. The new method of cutting that is a process of metal treatment involves non-continuous contacting an instrument blade and the material being cut. The cutting of the thread is done with a special hob cutter. Due to the non-continuous cutting, a treated surface becomes as if consisting of curved pads or faces. The faces junction line has a specific normal line level towards the surface and towards the helical surface during the cutting. The height of the junction defines qualitative indicator of the surface roughness known as undulation. When cutting the thread with a hob cutter the height of the faces junction - undulation of a helical surface – depends on a cutter teeth number. The research objective is to specify the cutter teeth number needed to achieve the required roughness of a thread helical surface as well as to determine how it influences on the quality of the thread surface. The paper also provides several drawings illustrating the process of obtaining the thread facetting and the example of calculation of a cutter chaser number.

The Promotion of Festuca sinensis under Heavy Metal Treatment Mediated by Epichloë Endophyte

To more clearly clarify the relationship between the Epichloë endophyte and its host, F. sinensis, the effects of Epichloë endophyte on F. sinensis performance under heavy metal treatment was investigated. The growth performance and physiology variations of F. sinensis with (E+) and without the endophyte (E−) were evaluated after they were subjected to Zn2+ and Cd2+ treatments. The results showed that heavy metal treatments had significant effects on plants, as the performance of plants under Zn2+ and Cd2+ treatments was significantly different with plants under control treatment (p < 0.05). Cd2+ treatments showed a hormesis effect, whereas Zn2+ did not. The endophyte increased host heavy metal stress tolerance by promoting host growth as the E+ plants had significantly higher plant height, tiller number, root length (p < 0.05). The endophyte also promoted ion uptake by the host and induced endogenous hormone production (p < 0.05). These results suggested that the Epichloë endophyte regulated host growth and physiology to improve association tolerance to environmental conditions. This study provides another example that the Epichloë endophyte can increase plant tolerance to metal stress.

Photocatalysis for Heavy Metal Treatment: A Review

Environmental and human health are threatened by anthropogenic heavy metal discharge into watersheds. Traditional processes have many limitations, such as low efficiency, high cost, and by-products. Photocatalysis, an emerging advanced catalytic oxidation technology, uses light energy as the only source of energy. It is a clean new technology that can be widely used in the treatment of organic pollutants in water. Given the excellent adaptability of photocatalysis in environmental remediation, it can be used for the treatment of heavy metals. In this comprehensive review, the existing reported works in relevant areas are summarized and discussed. Moreover, recommendations for future work are provided.

Molecular and Biochemical Insights Into Early Responses of Hemp to Cd and Zn Exposure and the Potential Effect of Si on Stress Response

With the intensification of human activities, plants are more frequently exposed to heavy metals (HM). Zinc (Zn) and cadmium (Cd) are frequently and simultaneously found in contaminated soils, including agronomic soils contaminated by the atmospheric fallout near smelters. The fiber crop Cannabis sativa L. is a suitable alternative to food crops for crop cultivation on these soils. In this study, Cd (20 μM) and Zn (100 μM) were shown to induce comparable growth inhibition in C. sativa. To devise agricultural strategies aimed at improving crop yield, the effect of silicon (Si; 2 mM) on the stress tolerance of plants was considered. Targeted gene expression and proteomic analysis were performed on leaves and roots after 1 week of treatment. Both Cd- and Zn-stimulated genes involved in proline biosynthesis [pyrroline-5-carboxylate reductase (P5CR)] and phenylpropanoid pathway [phenylalanine ammonia-lyase (PAL)] but Cd also specifically increased the expression of PCS1-1 involved in phytochelatin (PC) synthesis. Si exposure influences the expression of numerous genes in a contrasting way in Cd- and Zn-exposed plants. At the leaf level, the accumulation of 122 proteins was affected by Cd, whereas 47 proteins were affected by Zn: only 16 proteins were affected by both Cd and Zn. The number of proteins affected due to Si exposure (27) alone was by far lower, and 12 were not modified by heavy metal treatment while no common protein seemed to be modified by both CdSi and ZnSi treatment. It is concluded that Cd and Zn had a clear different impact on plant metabolism and that Si confers a specific physiological status to stressed plants, with quite distinct impacts on hemp proteome depending on the considered heavy metal.

Combined Exposure to Metals in Drinking Water Alters the Dopamine System in Mouse Striatum

Environmental exposure to arsenic (As), lead (Pb), and cadmium (Cd) frequently occurs; however, data on the specific effects of combined exposure on neurotransmission, specifically dopaminergic neurotransmission, are lacking. In this study, motor coordination and dopamine content, along with the expression of tyrosine hydroxylase (TH), dopamine transporter (DAT), vesicular monoamine transporter 2 (VMAT2), and dopamine receptors (DRs), were examined in the striatum of adult male mice following exposure to drinking water containing As, Pb, and/or Cd. We found that exposure to a metal mixture impaired motor coordination. After 4 weeks of treatment, a significant decrease in dopamine content and expression of TH, DAT, and VMAT2 was observed in the striatum of metal-mixture-treated mice, compared to the controls or single-metal-exposed groups. However, DRD1 and DRD2 expression did not significantly change with metal treatment. These results suggest that altered dopaminergic neurotransmission by the collective action of metals may contribute to metal-mixture-induced neurobehavioral disorders.

Simultaneous Removal of Heavy Metals And Bioelectricity Generation In Microbial Fuel Cell Coupled With Constructed Wetland: An Optimization Study On Substrate And Plant Types

A microbial fuel cell coupled with constructed wetland (CW-MFC) was built to remove heavy metals (Zn and Ni) from sludge. The performance for the effects of substrates (granular activated carbon (GAC), ceramsite) and plants (Iris pseudacorus, Water hyacinth) towards the heavy metal treatment as well as electricity generation were systematically investigated. The CW-MFC systems possessed higher Zn and Ni removal efficiencies as compared to CW. The maximal removal rates of Zn (76.88%) and Ni (66.02%) were obtained in system CW-MFC based on GAC and Water hyacinth (GAC- and WH-CW-MFC). Correspondingly, the system produced the maximum voltage of 534.30 mV and power density of 70.86 mW·m-3, respectively. Plant roots and electrodes contributed supremely to the removal of heavy metals, especially for GAC- and WH-CW-MFC systems. The coincident enrichment rates of Zn and Ni reached 21.10% and 26.04% for plant roots, 14.48% and 16.50% for electrodes, respectively. A majority of the heavy metals on the sludge surface were confirmed as Zn and Ni. Furthermore, the high-valence Zn and Ni were effectively reduced to low-valence or elemental metals. This study provides a theoretical guidance for the optimal construction of CW-MFC and the resource utilization of sludge containing heavy metals.