Effect of Flow Induced Parameters on the Output of A High Repetition Rate Dye Laser

The factors influencing the optical path stability in a dye laser flow cell are studied numerically and experimentally. A specially designed curved metallic dye flow cell providing a gain medium of 25 mm x 0.5 mm x 0.2 mm along with a compact resonator mechanical assembly is used in the study. The same configuration with gain medium of 15 mm x 0.5 mm x 0.2 mm is successfully used for single mode dye laser. The effects of flow induced vibrations on dye flow cell are studied with and without mechanically coupling it with the resonator structure for flow speeds varying from 1.33 m/s to 6.67 m/s at laser pump position. The effect of the mechanical instability, velocity fluctuation and temperature fluctuations in flowing dye solution on dye laser performance are studied at different flow speeds. These results are compared with the dye laser output parameters and found to be in good agreement. This study is useful in designing a high stability narrowband dye laser.

Methods of evaluation of production and technological work with shipbuilding

Оценка и анализ производственно-технологических работ судостроительных предприятий обусловлен необходимостью обеспечения конкурентоспособности вновь создаваемых объектов морской техники с показателями качества на уровне лучших мировых образцов с одновременным повышением темпов технико-экономического развития их производства. Названная проблема диктует необходимость адекватной оценки состояния технического оснащения производства, а также наиболее эффективных направлений вложения средств на техническое перевооружение. Техническое оснащение производства во многом зависит от уровня автоматизации, механизации технологических процессов, объёмов ручных работ, конструктивно-технологических особенностей создаваемых объектов морской техники, серийности производства и т.д. Для судостроения, судового машиностроения с учётом единичного и мелкосерийного производства характерна высокая доля ручного труда, особенно при выполнении механомонтажных работ. В статье предложен принципиально новый подход к оценке производственно-технологических работ (уровней технического оснащения производства) судостроительных предприятий. Приведены результаты расчётов и оценки на примере переделов (видов работ) механомонтажного производства для группы отечественных судостроительных предприятий. Предложенный метод оценки производственно-технологических работ (потенциалов) универсален для любых видов судостроительных и машиностроительных работ. Evaluation and analysis of production and technological works of shipbuilding enterprises is conditioned by the need to ensure the competitiveness of newly created marine equipment facilities with quality indicators at the level of the world's best samples, while increasing the pace of technical and economic development of their production. This problem dictates the need for an adequate assessment of the state of technical equipment of production, as well as the most effective ways of investing funds for technical re-equipment. The technical equipment of production largely depends on the level of automation, mechanization of technological processes, the volume of manual work, the design and technological features of the created objects of marine equipment, serial production, etc. For shipbuilding, marine engineering, taking into account single and small-scale production, a high proportion of manual labor is characteristic, especially when performing mechanical installation work. The article proposes a fundamentally new approach to the assessment of production and technological works (levels of technical equipment of production) of shipbuilding enterprises. The results of calculations and estimates on the example of repartitions (types of work) are given mechanical assembly production for a group of domestic shipbuilding enterprises. The proposed method of evaluation of production and technological works (potentials) is universal for all types of shipbuilding and machine-building works.

Case Study of Strength Calculation and the Possible Repair Options for Screw Thread Damages

Thread Strength and repair capability are critical to successful screw joints for any mechanical assembly. This paper explores the effect of the thread damage utilizing hand calculations, the margin of safety (MOS) for internal & external threads and compares with the required design criteria limit. Hence, the reduction in thread capability is analyzed in terms of shear and bearing strength of threads. This paper also emphasizes the Industry-standard repair techniques such as Helical inserts, Oversize inserts, and Twinserts with limitations and expected process/techniques. Advanced thread repairs in the market such as solid-body thread inserts (key-style, Time-sert, Big-sert) are also discussed Keywords: Thread damages, Shear strength, bearing strength. STI (Screw thread insert)

Analysis and Evaluation of Piecewise Linear Systems With Coulomb Friction Using a Hybrid Symbolic-Numeric Computational Method

A general formulation of piecewise linear systems with discontinuous force elements is provided in this paper. It has been demonstrated that this class of nonlinear systems is of great importance due to their ability to accurately model numerous scientific and engineering phenomena. Additionally, it is shown that this class of nonlinear systems can demonstrate a wide spectrum of nonlinear motions and in fact, the phenomenon of weak chaos is observed in a mechanical assembly for the first time. Despite such importance, efficient methods for fast and accurate evaluation of piecewise linear systems’ responses are lacking and the methods of the literature are either incompatible, very slow, very inaccurate, or bear a combination of the aforementioned deficiencies. To overcome this shortcoming, a novel symbolic-numeric method is presented in this paper that is able to obtain the analytical response of piecewise linear systems with discontinuous elements in an efficient manner. Contrary to other efficient methods that are based on stationary steady state dynamics, this method will not experience failure upon the occurrence of complex motion and is able to capture the entirety of the dynamics.

Spatial Perception Enhancement in Assembly Training Using Augmented Volumetric Playback

Conventional training and remote collaboration systems allow users to see each other’s faces, heightening the sense of presence while sharing content like videos or slideshows. However, these methods lack depth information and a free 3D perspective of the training content. This paper investigates the impact of volumetric playback in a Mixed Reality (MR) spatial training system. We describe the MR system in a mechanical assembly scenario that incorporates various instruction delivery cues. Building upon previous research, four spatial instruction cues were explored; “Annotation”, “Hand gestures”, “Avatar”, and “Volumetric playback”. Through two user studies that simulated a real-world mechanical assembly task, we found that the volumetric visual cue enhanced spatial perception in the tested MR training tasks, exhibiting increased co-presence and system usability while reducing mental workload and frustration. We also found that the given tasks required less effort and mental load when eye gaze was incorporated. Eye gaze on its own was not perceived to be very useful, but it helped to compliment the hand gesture cues. Finally, we discuss limitations, future work and potential applications of our system.

Fake News Detection Using ML

Fake news is depicted as a story that is made up with an aim to mislead or to swindle the peruser. We have introduced a reaction for the undertaking of phony news disclosure by utilizing Deep Learning structures. Because of various number of instances of phony news the outcome has been an augmentation in the in the spread of phony news. Due to the wide impacts of the immense onsets of phony news, people are conflicting if not by huge helpless finders of phony news. The most liked of such exercises consolidate "boycotts" of sources and producers that are not trustworthy. While these instruments are used to make an inexorably unique complete beginning to end plan, we need to address continuously inconvenient situations where logically strong sources and makers discharge fake news. As, the objective of this endeavor was to make a mechanical assembly for perceiving the language designs that portray phony and confirmed news using AI, AI and customary language getting ready techniques. The consequences of this undertaking exhibit the breaking point with respect to AI and AI to be huge. We have developed a model that gets numerous no of normal indications of veritable and phony news and additionally an application that aides in the portrayal of the order decision.

Development of a sensor and measurement platform for water quality observations: design, sensor integration, 3D printing, and open-source hardware

A measurement and development platform for collecting water quality data (the WaterWatcher) was developed. The platform includes sensors to measure turbidity, total dissolved solids (TDS), and water temperature as variables that are often collected to assess water quality. The design is extensible for research and monitoring purposes, and all design files are provided under open-source permissive licenses for further development. System design and operation are discussed for illustrative purposes. A block diagram indicates elements of mechanical, electrical, and software design for this system. The mechanical assembly used to house circuit boards and sensors is designed using 3D printing for rapid prototyping. The electronic circuit board acts as a carrier for an Arduino 32-bit microcontroller board and an associated cellular module along with a GPS for geolocation of water quality measurements. The cellular module permits data transfer for Internet of Things (IoT) functionality. System operation is set up using a command line interface (CLI) and C++ code that allows for calibration coefficients and human readable transfer functions to be defined so that sensor voltages are related to physical quantities. Data are cached on a secure digital (SD) card for backup. The circuit was calibrated, and system operation assessed by deployment on an urban reservoir. Biogeochemical cycles were identified in the collected data using spectrogram and semivariogram analyses to validate system operation. As a system with hardware and software released under an open source license, the WaterWatcher platform reduces the time and effort required to build and deploy low-cost water quality measurement sensors and provides an example of the basic hardware design that can be used for measurements of water quality.

Large fluctuations of the fusion intermediate help SARS-CoV-2 capture host cell membranes

Cell entry of SARS-CoV-2 is accomplished by the S2 subunit of the spike S protein on the virion surface by fusion of viral and host cell membranes. Fusion requires the prefusion S2 to transit to its potent, fusogenic form, the fusion intermediate (FI). However, the FI structure is unknown, detailed computational models of the FI are not available, and the mechanisms of fusion and entry remain unclear. Here, we constructed a full-length model of the CoV-2 FI by extrapolating from known CoV-2 pre- and postfusion structures. Atomistic and coarse-grained simulations showed the FI is a remarkably flexible mechanical assembly executing large orientational and extensional fluctuations due to three hinges in the C-terminal base. Fluctuations lead to a large fusion peptide exploration volume and may aid capture of the host cell target membrane and define the clock for fluctuation-triggered refolding and membrane fusion. This work suggests several novel potential drug targets.

An on-line path planning of assembly robots based on FOVS

To improve the accuracy and efficiency of path planning for the mechanical assembly process of products, an on-line path planning method for mechanical assembly process robots based on visual field space is proposed in this paper. Firstly, to predict and describe the assembly process, the concept of field-of-view space (FOVS) is proposed. Secondly, image processing is carried out by knowledge base to judge the assembly type and current assembly state, and the initial assembly path is given. Then, the assembly process is integrated and solved, and the location estimation of obstacles are given according to the FOVS. Finally, the ant colony algorithm is improved to get the final assembly optimization path. Comparing the algorithm with the ACS algorithm in the aspect of path planning. The length of path planning is reduced by 2%, and the algorithm time is reduced by 0.5s, the accuracy and efficiency have been effectively improved. the result shows that the algorithm is effective.