bluuebunny/crossref_metadata_2025 huggingface dataset:
A fluid flow simulation in the cooling systems of the metal cutting process
Authors: Olaru I
Published: August 2019

During processing of cutting materials due to friction between tools and materials, a considerable amount of heat is released to the development of high cutting forces. Excess heat from the cutting area may aggravate the cutting process, the surfaces resulting from the cutting process may have a several defects. By simulating the flow phenomena on the computer, different forms of nozzles that send the liquid to the work area are studied to make the cutting process more efficient. This study attempts to simulate the flow of cooling fluid in an integrated system and also to quantify the amount of heat entering the workpiece during the machining processes. Simulation using the finite element method for the machining area was done for conventional cutting processes, taking into account the environment. The simulation also takes into account the convective cooling of the working fluid in the MQL system. By assessing the cooling efficiency of different lubrication conditions of the coolant, based on their convective heat transfer coefficient and the temperature in the cutting zone.
Analysis of the noise emissions of a common-rail pump before and after an endurance test
Authors: Petrea N D , Bujoreanu C , Alaci S
Published: August 2019

One of the problems of the modern era that we are facing nowadays, besides the pollution caused by fuel burning, is the level of noise pollution in constant growth in agglomerated cities. The main source of noise is the transport sector where the number of passenger cars had dramatically increased in recent years. Most of the vehicles around the world are powered by internal combustion engines equipped with a fuel injection system and a small percentage with an electric one. Researchers have shown that noise pollution affects human health from a psychological and physical point of view. Due to the manufacturing process of high-pressure pumps, some pumps mounted on the engine and running under certain conditions can produce a higher audible noise than the engine. The paper presents an experimental investigation on a high-pressure pump that provides a comparison between the noise level at the beginning of its lifetime and that resulting after an endurance test performed on a special test bench. It has been found that the greatest contributor to noise emissions is the high-pressure pump outlet valve when it opens. To improve the sound quality of the high-pressure pump, it is essential to further develop the outlet valve design and better control over the manufacturing process.
Simplified computer code for modelling fuel jet
Authors: Sabau A
Published: August 2019

That paper presents a simplified mathematical model used in computer code for modelling the fuel jets. The used equations describe a fuel jet with minimum physical phenomena (jet atomization, droplets vaporization, droplets interaction with gases, and droplets collisions). It was considered that the fuel jet does not react with the surrounding gases. The thick spray regime is analysed and a collision function is deduced. A multi-component non-reacting turbulent flow is taken into consideration. The method used for solving the equations of the model is a combination between Eulerian fluid and Lagrangian particle calculation. The calculated results (jet penetration and mixing-fractions) is compared with experimental data.
Viscous fluid dissipation system model acting on the active principle
Authors: Scheaua F
Published: August 2019

There are solutions in terms of seismic isolation and energy dissipation that are successfully applied all over the world to building structures but also to high-way and rail infrastructure elements represented by bridges and viaducts. These structures must remain functional even after they have been requested by a considerable magnitude earthquake. This is why research activities aiming the development and modernization of these mechanical systems, which play a decisive role in ensuring the optimal stability of these structures, are justified. Fluid dissipation systems were originally developed as passive protection systems but over time they have been constructively improved with intelligent control systems that have the potential to considerably increase the efficiency of these systems by making use direct control over the amount of energy which can be dissipated through these protection systems. Such a dissipative viscous fluid system is described in this paper as a more evolved constructive system than the passive principle model. Active control over the operation of this device is materialized by altering the working fluid flow rates through the constructional elements of the dissipation device assembly. This flow rate adjustment is made by means of a flow controller present within the control unit. The mathematical model characterizing the functioning of an active viscous fluid dissipation system is presented, as well as a numerical analysis describing the function of such a dissipative system depending on the additional mass of the isolated structure to which the protective device is attached. The numerical analysis is based on a set of specific values presented in the paper. These dissipation systems are primarily used in bridge or viaduct structures, being responsible for limiting the relative displacements between the structural elements where they are mounted. This method provides greater security through the rigid connection achieved between the structural frames acting as anchorages. Entry into action is made in the occurrence of a seismic event when the piston displacement is recorded and by changing the momentarily flow rate values of the circulating fluid the amount of energy dissipated is adjusted by means of the viscous fluid device. There are presented the advantages and disadvantages related to the use of such seismic energy dissipative systems attached to the construction structures.
The frictional contact of coated bodies. Part I – The sliding contact
Authors: Spinu S , Cerlinca D , Musca I
Published: August 2019

Hard coatings provide low friction, high wear resistance and corrosion protection that improve the tribological performances of the machine elements undergoing contact load. In lack of analytical solutions, a numerical study is performed in this paper for a better understanding of the engineering applications of hard coatings with consideration of friction. A previous study on the frictionless contact of bi-layered materials is extended by considering the effect of friction on the contact stress state. The assumption of a sliding contact in which the shear tractions do not affect the pressure distribution is adopted. This simplification, often present in the literature, decouples the contact problems in the normal and in the tangential direction and allows for a pressure distribution solution that is independent of the frictional regime. The shear tractions are subsequently obtained from a kinetic Coulomb-type friction law, under the assumption that the normal load is kept constant. The stress state in the coated system results by superposition of stresses due to the normal and the shear tractions. The frequency response functions needed for the calculation of the six stress tensor components induced by the shear tractions are presented for clarity and completeness. The convolution between these functions and the contact stresses is performed in the frequency domain for improved algorithmic efficiency. The performed contact analysis proves the ability of the numerical method to provide insight on the critical contact condition for plasticity failure, and to assist the optimal design of hard coatings.
Acoustic pressure and flame generation determinations in case of mechanical and gas-dynamic processes for small caliber weapons
Authors: Zvincu N-D , Mandache-Dodoiu A-D , Nistoran G-D , Haller L O
Published: August 2019

This paper presents results on the subject of the noise and flame generated by firing different weapons systems as part of determining safety measures for the weapons operators and specific safety distances for the involved personnel. Firing involves a series of mechanical and gas-dynamic processes sustained in a very short amount of time, some perceptible, some partially perceptible by humans, others not, therefore the use of high-speed camera and specialized software for assessments is required. Evaluations of the acoustic pressure produced by different small caliber weapons were achived using Bruel & Kjaer microphone and sonometer placed at different distances of interest from the barrel. The A frequency curve, based on contour courves of constant strength, was used in order to display the results obtained as the standard values indicated by the sonometer would not be identical to the perception of sound by the human ear. Determinations to evaluate the flame at the muzzle were also conducted.
Structural and kinematic aspects of some bar mechanisms for deployable structures
Authors: Doroftei I A , Bujoreanu C , Doroftei I
Published: August 2019

Transformable structures in architecture can change their shape or function in response to varying climatic conditions, changing environment and needs for different functional requirements or to emergency situations. Depending on how the transformation is doing, transformable structures can be deployable or demountable, as a kit-parts system. Deployable structures can also be divided in four main groups: spatial bar structures; foldable plate structures; tensegrity structures; and membrane structures. In this paper, some planar bar mechanisms proposed by Ten Fold Engineering company, which can be integrated in deployable structures, will be discussed.
Analysing the influence of a radial compliant tool in robotic milling operations
Authors: Ivan A M , Parpala R C , Coman C G
Published: August 2019

This article presents the experimental research performed by the authors in the field of robotic low force milling operations using radial compliant end effectors in order to identify the general advantages and limitations offered by this approach when compared to conventional (non-compliant) tools. The experiments were conducted using a Kawasaki FS 10 E articulated arm robot with six axes. The experimental data was collected using a Kistler 9257B dynamometer for three different materials: aluminium, plastic and wood. For each material, several different milling operations were performed: chamfering, slotting and lateral milling. The evaluation for the two approaches was done by analysing the tool behaviour during machining operation, by measuring the machining forces generated by the milling process and by observing the surface quality resulted after machining. The experimental results led to the conclusion that the main limitation for radial compliant end effectors usage lies with slotting operations and with materials that have hard to remove chips. The results obtained in this work will be used, together with further experimental research, to identify the limitations and opportunities of available robotic equipment in milling applications with respect to machined materials, feeds and speeds, as well as trajectory planning.
Comparative analysis between using an articulated arm robot and a conventional machine in milling applications
Authors: Ivan A M , Parpala R C , Coman C G , Nicolescu A F
Published: August 2019

The scope of this article is to perform a comparative analysis between low force milling operations performed by an articulated arm industrial robot and a conventional milling machine on an aluminium workpiece. The research sought to compare the machining force levels, tool behaviour and surface aspect in order to identify the nature of stiffness limitations for industrial robots. The expected force levels under normal circumstance were up to 100 N. The experiments were conducted using a Kawasaki FS 10 E articulated arm robot with six degrees of freedom. The experimental data was collected using a Kistler 9257B dynamometer. The experimental procedures were first conducted using the industrial robot approach. Several milling passes were performed using both full radial tool engagement and a lateral depth of cut equal to 2/3 of the tool diameter. The machining force values were compared for each axis, with focus on both machining force levels, variations and resulted surface aspect. Regarding tool behaviour and machining results, these aspects were observed directly during and after each operation. The main conclusion of the experimental procedures was that the biggest stiffness issues appeared along Z axis and also appeared with greater chip thickness.
Research on the influence of straightness deviations on positioning precision of Cartesian industrial robots
Authors: Luncanu A , Stan G
Published: August 2019

Among the first generations of industrial robots used in various industries were the Cartesian industrial robots. The main advantages of these positioning systems are its flexibility and fast positioning capability. The reduced time of generating and programming of the industrial robots trajectory is a particular advantage of these systems. Over the years, a number of factors have been discovered that affect the positioning precision of Cartesian industrial robots. Presently among these factors that are affecting the positioning precision of a Cartesian industrial robot are the dimensional deviations and the geometrical deviations present in their structures. Among the geometric deviations, affecting the positioning accuracy of a Cartesian industrial robot there is the straightness deviation of the linear kinematic links. Due to the existence of straightness deviations in the linear kinematic links of the Cartesian industrial robot, it is necessary to use methods to minimize the positioning errors of industrial robots within the linear axes. In this article are presented methods of determining the values of rectilinear deviations and utilizing them in an optimized kinematic system. By choosing this method to minimize positioning error by designers in current generations of Cartesian industrial robots and systems using linear kinematic links, both positioning errors and trajectory generation times are diminished, resulting in the economic and technological efficiency of the products and services they offer.
On designing an automated tool for capacitors removal from waste printed circuits boards
Authors: Stamate C , Doroftei I , Chirita D , Burlacu A
Published: August 2019

The mass electronics sector is one of the most important sources of waste, both in terms of volume and materials content with dangerous effects on the environment. Printed Circuit Boards (PCBs) are the most valuable component embedded into Electrical and Electronic Equipment (EEEs). The current amount of electronic systems is impressive while manual dismantling is a very common and non-efficient solution. On average, waste PCB accounts almost from 3% to 5% of the overall weight of waste electrical and electronic equipment. At this time, in Romania, the implemented solutions for waste PCB reduction are in a research phase, with no existing technological procedures that can be replicated. In the context of the TRADE-IT project we aim to design replicable architectures for waste printed boards reduction. Starting from the largest base plate and continuing to the smallest size, Extended ATX, ATX, Micro ATX, Mini ITX are some of the most used boards in a computer. When choosing a base plate from the ATX and/or microATX range, the shape factor must fit on a universal support bracket. The shape factor identifies the size of the circuit board, the location of the slots, and the location of the display board that comes out on the back of the computer. The shape factor also identifies the location of the holes that are used to mount the base plate in the universal clamp holder. Taking into account that capacitors represent approximately 8.6% of the PCB mass, we aim at designing an automated driven tool for their removal. The design is based on a robotic arm for motion manoeuvring, a programmable screwdriver and a custom-made end tool. In the current phase the proposed design was evaluated on controlled individual tests. The initial results highlight the feasibility of the proposed design while uncovering potential challenges for real-time implementation.
Study on the aerodynamic force which acts in the case of a train type multiple unit electric
Authors: Arsene S , Sebesan I , Manea I
Published: August 2019

This paper seeks to analyse the values of the aerodynamic resistance forces occurring during the movement of a train type multiple unit electric whit are running in Romania. Taking into account what has been said so far in the literature, regarding the fact that the aerodynamic forces acting on the vehicles are directly proportional to the square of the traveling speed, it is intended to estimate the values of these forces in the case of the proposed train for analysis. An exact determination is difficult to achieve and requires very high costs in terms of both the measuring equipment and the actual realization of the experiment. To avoid this, we will opt for a numerical analysis of aerodynamic force measurements. In this regard, the geometric shape of the train will be first modelled and then inserted into an airflow simulation program.
Energy consumption and CO2 and NOx emissions minimised in an intermittent ceramic kiln – “ECONOMICK kiln”
Authors: Fortuna A , Fortuna D M , Martini E , Pozzovivo A
Published: August 2019

ECONOMICK LIFE project developed an innovative shuttle kiln for ceramic production, which consumes about 47% less energy than actually existing ones and, so, allows the industry to reduce costs, CO2, NOx, HF, SOx and dust emissions, and raw materials. A patented technology is used to recover heat from flue gases to pre-heat combustion air. Significantly, this technology does not use flues or other pipes and above all does not alter the fluid dynamics of the flue gases in any way, which therefore remain identical to those of a traditional shuttle kiln. This advantage, with the possibility of adjusting the flame speed, is important as it optimises the flue gas/piece thermal exchange and does not affect either uniformity of firing or energy savings at low temperatures. This patented technology allows to use preheated combustion air and to reduce max temperature in the burner body, adjusting flame speed. Further, a specific software allows to preserve a preselected air/gas ratio and to use different values in function of the firing cycle. A careful selection of the refractory materials, resulting in a lining that minimises thermal inertia and at the same time allow a cool wall temperature of below 50°C.
The trend of higher engineering education towards achieving technological development
Authors: Garbuz V , Topala P
Published: August 2019

The technical-scientific progress, rapidly evolving technologies, developing of innovative processes in the sphere of production, the effect of the economy globalization, etc. require a rethinking and complete reformatting of the education system in general and particularly, of that one related to engineering. This paper analyses development trends of higher technical education in the world and particularly in the Republic of Moldova. It is analysed the dynamic evolution of the number of students and graduates ethnic domain specifically for Moldova in order to elucidate this issue. There were realised three studies attended by students from engineering specialties, young engineering specialists and their employers. Research results highlight the key role of knowledge and skills that young professionals must possess to achieve technical performance, scientific and economic information in accordance with international standards. With an accelerated technological progress, it is clear that we are on the top of a new era of machine learning, machine doing and finally, of a true artificial intelligence (AI). It is a central point in history that presents both opportunities and challenges. And undoubtedly, the most significant social and economic impact will be on the job - it is required to determine what work will be performed and by whom. In this aspect, application of exponential technologies is analysed in order to strengthen labor and accelerate business growth, as we enter the Fourth Industrial Revolution. In this new era, the transition to innovations based on combinations of technologies, force companies to reconsider how they do business, including requirements put forward in preparing new specialists in the labor market. Their actions should be oriented in training a generation of self-motivated and responsible engineers of the highest quality, able to participate in solving societal and engineering challenges of the XXI century through creative and viable solutions.
Management elements of conception and development of scientific research projects
Authors: Ioana A , Costoiu M , Tufeanu D , Semenescu A , Marcu D
Published: August 2019

The concept of a scientific research project offer must be based on the analysis of the four types of resources: the human resources, the financial resources, the material resources and the informational resources. We note the importance of the human resource quality. In the following figure we present the main elements of the design algorithm of a research project. The feasibility study (otherwise very complex) is of great importance for the success and viability of the project. We have developed the algorithm for designing a scientific research project. Thus, we have devised several items, in a non-fortuitous order: formulation of the theme, resources analysis, feasibility study, offer formulation, project drawing, project implementation, project evaluation, dissemination. We have critically analyzed several definitions of a scientific research project. For example, “a set of investments and other planned activities to achieve specific objectives within a predetermined time frame and budget”, or, “a planned action that is a set of interrelated and coordinated activities to achieve specific objectives within a given budget and a period of determined time”. We also analyze the key functions of a scientific research project: specifying the issue to be addressed, specifying the objectives to be achieved, specifying the activities to be undertaken to achieve the objectives, specifying the revenue (or resources) needed for the deployment activities, identifying and specifying the responsibilities of the different organizations involved in implementation of the project, allowing technical and administrative reviews of the project, the basis for monitoring and evaluating the project that can be done either during the project’s implementation, or after the project has been completed. We have formulated in the article specific concepts on: “a development program is sustainable when it is able to provide an appropriate level of benefits over a longer period of time after the financial, managerial and technical assistance from the external donor ended”, or, “for most projects sustainability is a default, and donors and recipients wait and take responsibility that certain aspects of the activity will continue. Failure to make explicit sustainability as part of the project’s training and implementation process may lead to lack of benefit”.
Friction phenomenon study for chain link – guide contact in translational oscillatory motions
Authors: Lates M T , CGavrila C
Published: August 2019

The fuel consumptions of the automobiles are hardly influenced by the friction between the components of their mechanical transmissions being in relative motion. One of the main parts of the automobiles mechanical transmissions is represented by the chain drive transmission. The frictions inside the chain drive transmissions could be split in: the friction inside the chain, between its components (links, bolts); the friction between the chain links and the sprockets; the friction between the chain links and the active part of the tensioning guide. The aim of the paper is to investigate the friction phenomenon in the chain link – guide contact for a set of normal forces, velocities and temperatures. The tests are achieved for sets of motions frequencies, normal loads and oil bath temperatures; according to these, there are determined the dynamic friction coefficients (during the motions) and the static friction coefficients (at the end parts of the strokes). The results show graphically the variations of the static and dynamic friction coefficients with the motions frequencies, the normal loading forces and the oil bath temperatures. The conclusions are useful in order to identify the functioning cases where the frictional loses are small.
A thermodynamic optimization of a gas turbine cycle with a supplementary regenerator
Authors: Memet F , Faitar C
Published: August 2019

International concern regarding pollution related to maritime transport sector and energy efficiency desiderate have determined specialists to search for more suitable alternatives to internal combustion engines. Due to their advantages, gas turbine systems are met in different marine propulsion applications, such as passenger ships or military vessels. Gas turbines will be even more intensively used in the future, an outcome of this reality being the need of their performance increment. A direction to be followed, considered in this study, is the combination between the improvement of the gas turbine efficiency by including a regenerator in the layout of the plant and, also, the rise of the temperature at the inlet of the turbine (TIT). Will be considered an open cycle gas turbine. The thermodynamic analysis is about the assessment of different influences such as: regenerative effectiveness versus the heat added in the combustor, regenerative effectiveness versus the work consumed by the compressor, regenerative effectiveness versus the thermal efficiency, regenerative effectiveness versus the specific fuel consumption, temperature at inlet of the turbine (TIT) versus the thermal efficiency. The results obtained will indicate the fact that both actions will lead to a gain in the performance of this technology.
Automation of the lamination process for automotive applications
Authors: Popa L , Popa V
Published: August 2019

The article addresses the design of an automation system for the lamination process of the cars, which has as inputs different types of transducers, and as outputs the command of a linear pneumatic motor. The layered and self-supporting laminated structures of motor vehicles are manufactured from a thermoplastic substrate and a flexible sheet material in one direction rolling and cutting operation. The installation for producing these laminates is a casting press having two casting plates, each of which comprises a component of a pair of cutting means. It is used a CPU 315-2 PN / DP, which is a medium-sized program memory processor and it is often used in automation structures. This processor can also be used as distributed intelligence (master or slave). The implementation of the code sequence to work on this processor is done in one of the specific languages to the programmable machines. The software used in programming is STEP 7. The stored information is not erased when the processor is disconnected. The usefulness of programmable machines has simplified the approach of an automated system.
Study of dimensional changes during washing process for 1:1 interlock cotton yarns
Authors: Szabo M , Babanatis-Merce R M , Barbu I , Babanatsas T , Jitaru L
Published: August 2019

The paper proposes a study regarding the dimensional changes during washing process for the 1:1 interlock structures made of 100% cotton yarn with Nm 58/1. The interlock 1:1 structures which are studied are made of 100% cotton yarns, with Z torsion, on Monarch circular knitting machines, with diameter of 30 inch, fineness 20E and 72 knitting systems. Tubular meterage knitwear resulted from this process. After the knitting, the structures were laid for relaxation, and then they were subjected to the washing, drying and relaxation operation. The loosening of the knits for 72 hours was done in air-conditioned areas respecting the parameters of the standard atmosphere to balance the internal tensions introduced into the structures during the knitting and washing operations. The structure parameters of the knitwear modify after the relaxation before finishing process, after finishing and after washing process. The machines where the structures were produced are new generation knitting machines and finishing. After knitting and relaxation of the fabrics, the finishing and washing processes were applied with a minimum tension of the structures, de-watering was made with uniform pressure air-blowing installations on entire length and surface of the tubular knitting, in this way replacing the classical centrifugation machines, which had a dynamic action on knitwear and increased the wrinkling.
The universities’ contribution to economic prosperity through technology transfer
Authors: Taousanidis N , Taousanidis A
Published: August 2019

Our economy is a knowledge-based economy an economy founded on the production, distribution and use of knowledge. Thus a connection of main economic actors (firms) to main knowledge producers (universities) is necessary. The process of technology transfer from universities to market is however not simple and consumes resources and infrastructure. European universities face this challenge in a way not similar to the American ones, looking for great revenues, strengthening of basic research and local growth. The latter is analysed in this work and proposals are made to universities, to match society’s expectations without jeopardizing their core mission, education and research.
Method for avoiding cracks during drying of masonry units made of illite raw material
Authors: Vasic M , Radojevic Z
Published: August 2019

Drying is one of the most important steps in the production process of masonry units. In order to prevent the formation of cracks during drying information’s about the moisture migration rate variability as well as the material strength variability through drying are necessary. The main goal of this paper was to find a solution how to prevent the crack formation at the beginning (during the first hour) of the drying for the drying sensitive illite raw material. The first step was to record a series of isothermal Deff – MR curves at different drying air temperatures and constant drying air velocity and humidity. As it was already reported all moisture transport mechanisms during isothermal drying are visible on those curves. Characteristic spots registered on these curves were then transposed on the experimentally registered figure material strength us moisture content. It was found that the material strength for the cracked masonry units at the beginning of drying was around 0.09 MPa and that the time of cracking was near the characteristic spot B. Registered material strength and the crack time position (spot B) has additionally confirmed that the drying sensitivity of the raw material are obviously related with the present clay mineral constituents structure and the initial moisture content of the green heavy clay units. Using the Deff values registered for each experiment in the spot B we were able to calculate the maximal moisture transport rate and consequently the proper drying air parameters which are safe and which will not initialize the formation of the cracks at the beginning of the drying.
On a small size floating dock structural analysis in oblique design waves by 3D-FEM approach
Authors: Burlacu E , Domnisoru L
Published: August 2019

In this study we have enhanced the structural assessment analysis of a river-shipyard small size floating dock, with length overall of 60 m, for equivalent quasi-static oblique design wave conditions. The small size floating dock hull has two constructive layouts for the water ballast side tanks. The oblique design wave heading angle is in the range of 0 to 360 deg. The floating dock equilibrium in oblique equivalent design waves is achieved by own non-linear three parameters iterative program. The numerical analyses are done on full extended 3D-FEM structural models, from side to side and from stern to bow, of the small size floating dock, with specific boundary conditions for global and local strength computations. The modelling of the external oblique equivalent design wave pressure has requested to develop specialized user functions into FEM code. There are considered several loading scenarios of the small size floating dock, according to the shipbuilding classification societies. The structural assessment is based on three criteria: yielding stress, buckling and freeboard limit values. The numerical results of the structural assessment for the small size floating dock in oblique equivalent design waves made possible to establish the wave design height limits, according to the safety criteria restrictions.
The structural evaluation of a large floating dock in head design waves by strength criteria
Authors: Burlacu E , Domnisoru L
Published: August 2019

This study is developed for the strength analysis of a large floating dock, with length over all of 209.2 m, obtained from a conversion of an off-shore barge. The docking operations are evaluated by global and local strength criteria. The first operation scenario includes an entire translation process of a ship from the quay to the floating dock railway system, in a river shipyard location, including the main intermediate steps. A second set of operation scenarios include several trial docking cases, at full capacity, considering also the initial state without docking ship that is specific for transit condition between ports. The structural numerical analysis is developed on a very large 3D-FEM model, one sided, full extended over the length, involving an own iterative algorithm for the dock and head design wave equilibrium parameters computation and user functions for the quasi-static head wave pressure application on the external dock shell. The large floating dock has operations in sheltered and unsheltered environments and can be relocated on river and costal waterways, under specific wave’s conditions, according to the shipbuilding classification societies design rules. The numerical results are making possible to evaluate the several operations of the large floating dock by strength criteria.
Numerical study of a container ship model for the uncoupled parametric rolling
Authors: Deleanu D , Dumitrache C L
Published: August 2019

Parametric roll on ships is a resonance phenomenon whose onset causes heavy roll oscillations leading to dangerous situations for the ship, the cargo and the crew. It affects both small vessels with marginal stability and large container ships if four conditions are met simultaneously: the wave length and ship length are approximately equal, the frequency of encounter wave is twice the roll natural frequency, the ship’s roll damping is low enough and the wave height exceeds a limit value characteristic to each vessel. For a container ship, the first two conditions result in a time-varying geometry of the submerged hull and thus to a periodic variation of the transverse stability. In the last two decades, several mathematical models for parametric rolling have been proposed by scientists. In the paper, we cancelled the couplings terms between heave, pitch and roll in a 3 DOF model proposed by Neves and Rodriguez to obtain an uncoupled 1 DOF model for the parametric roll. Even if it seems too simplistic, such a model based on Mathieu type equation is a good start to capture the basic features of the analysed phenomenon. There are no less than seven parameters that can influence the ship stability and the appearance of large roll amplitudes. By modifying two of these parameters one by one and keeping the others constant, a series of colour plots have been drown that capture the role played by the ship’s parameters in obtaining dangerous roll amplitudes or too short times to take countermeasures. Analysing the instability regions suggested by these colour plots, one can imagine control measures to reduce the roll amplitudes, such as changing the forward velocity or the heading angle. The data used in the paper have been obtained from experiments with a container ship model in a towing tank followed by expansion to a full scale ship.
Fluid Structure Interaction (FSI) analysis on ballast tank in-line ejector
Authors: Dumitrache C L , Deleanu D
Published: August 2019

Ejectors are common devices on board liquid carrier vessels and meet on both cargo and ballast tanks. The “in-line” ejector presented in this paper is an original model that was designed with NX Siemens, using information and technical data from a worldwide supplier of high quality marine products. This paper presents a static analysis of fluid’ influence which passing through an ejector on its metal structure using Ansys. From a previous work we took into account the data obtained with CFD (computer fluid dynamic) analysis. The pressure and fluid temperature fields were imported and applied to the meshed ejector model with finite elements, obtaining data on deformations and equivalent stresses and elastic strain.
The vehicle movement using computational fluid dynamics method
Authors: Nedelcu A-T , Faitar C , Stan L , Buzbuchi N , Dumitrache L M
Published: August 2019

Underwater vehicles represent underwater robots able to perform tasks without or with a minimum human intervention. Research and development of this vehicles have growing as a result of excellent characteristics operated in different situation. Before discussing the steady motion of underwater vehicle, it is necessary to examine the hydrometeorological condition founded in respectively area. Interaction between the water surface and the atmosphere determine the development and appearance of hydrodynamic processes. The main current encountered in Black Sea Basin moves in a cyclonic direction to the edge of the continental platform and surrounds the entire basin. Using the data in-situ regarding the influence of marine current for different steps of depths, the underwater vehicle reacts different and have to change his input data to follow the right course. This paper provides an intuitive modeling and simulation approach to obtain a distribution of current influence along the underwater vehicle body. The software SolidWorks and Ansys Fluent are used to realize the vehicle design and the simulation. The Ansys software is a powerful tool used for solving problems involving fluid mechanis. The condition imposed for simulation, was generated and determinate in-situ by Current Meter Model 106.
Numerical investigation on fast displacement ship hydrodynamics
Authors: Pacuraru S , Pacuraru F , Presura A
Published: August 2019

In last decade, sustained efforts have been made to improve ship energy efficiency, to reduce fuel consumption and carbon dioxide emissions by means of optimizing the hull forms and propulsion system. The aim of the present paper is to search for solutions to improve the fast-displacement hull forms of passenger ships that navigate on the Danube river and the Black Sea coast, leading to high energy efficiency, reduced emissions and minimised shore-side effects. To investigate the flow around a 31 m fast-displacement monohull passenger ship, a series of 5 numerical simulations for a range of speeds between 4.5 and 12.5 m/s were performed in order to estimate the forces acting on the ship, but also to analyse the hydrodynamic parameters of the flow. Based on the first series of calculation, several solutions to improve the hydrodynamic performance of the hull are considered. The two most effective solutions found have been the trim edge and the interceptor. Different configurations and angles have been systematically investigated in order to find the most efficient geometrical parameters. Finally, the hull with trim wedge leads to a reduction of the power consumption by 2.4 to 5.5% and the interceptor by 2.8 to 8.8%, for speeds higher than 8.4 m/s. For speeds lower than 8.4 m/s the power consumption is higher than bare hull. Moreover, the solutions proposed are easy to implement for new built ships, but also for ships in operation.
Application of coagulant obtained through charge reversal of sawdust-derived cellulose nanocrystals in the enhancement of water turbidity removal
Authors: Nkalane Aphiwe , Oyewo Opeyemi A , Leswifi Taile , Onyango Maurice S
Published: August 2019

Sawdust-derived cellulose nanocrystals (CNC) were functionalized using hexadecyltrimethylammonium bromide (HDTMA-Br) as a cationic surfactant to produce novel coagulant for application in reducing water turbidity. The modified CNC was characterized using Fourier transform infra-red spectroscopy, x-ray diffraction, scanning electron microscopy, transmission electron microscopy and zetametry. Upon functionalization, the surface charge was reversed from −39 mV to +22 mV by introducing amine group to the CNC matrix. The microscopic analyses revealed that CNC has a narrow particle size range and rod-like morphology. The XRD analysis showed increased peak intensity upon modification, indicating enhanced crystallinity of the CNC; and an additional peak around 30.1° appeared, which was attributed to the presence of HDTMA on the surface of CNC. Turbidity tests was conducted using both simulated and environmental water samples, and the effects of CNC modification reaction time, solution pH, coagulant dosage and initial turbidity levels were evaluated. Results reveal that turbidity reduction increased with an increase in reaction time and coagulant dosage, and decreases in initial turbidity level and solution pH. The performance of the modified CNC coagulant in turbidity reduction complied with the South African national standard (SANS 241:2015) for drinking water quality.
Vezatin is required for the maturation of the neuromuscular synapse
Authors: Koppel Natasha , Friese Matthew B. , Cardasis Helene L. , Neubert Thomas A. , Burden Steven J.
Published: August 2019

Key genes, such as Agrin, Lrp4, and MuSK, are required for the initial formation, subsequent maturation, and long-term stabilization of mammalian neuromuscular synapses. Additional molecules are thought to function selectively during the evolution and stabilization of these synapses, but these molecular players are largely unknown. Here, we used mass spectrometry to identify vezatin, a two-pass transmembrane protein, as an acetylcholine receptor (AChR)–associated protein, and we provide evidence that vezatin binds directly to AChRs. We show that vezatin is dispensable for the formation of synapses but plays a later role in the emergence of a topologically complex and branched shape of the synapse, as well as the stabilization of AChRs. In addition, neuromuscular synapses in vezatin mutant mice display premature signs of deterioration, normally found only during aging. Thus, vezatin has a selective role in the structural elaboration and postnatal maturation of murine neuromuscular synapses.
CasPDB: an integrated and annotated database for Cas proteins from bacteria and archaea
Authors: Tang Zhongjie , Chen ShaoQi , Chen Ang , He Bifang , Zhou Yuwei , Chai Guoshi , Guo FengBiao , Huang Jian
Published: August 2019

Clustered regularly interspaced short palindromic repeats (CRISPR) and associated proteins (Cas) constitute CRISPR–Cas systems, which are antiphage immune systems present in numerous bacterial and most archaeal species. In recent years, CRISPR–Cas systems have been developed into reliable and powerful genome editing tools. Nevertheless, finding similar or better tools from bacteria or archaea remains crucial. This requires the exploration of different CRISPR systems, identification and characterization new Cas proteins. Archives tailored for Cas proteins are urgently needed and necessitate the prediction and grouping of Cas proteins into an information center with all available experimental evidence. Here, we constructed Cas Protein Data Bank (CasPDB), an integrated and annotated online database for Cas proteins from bacteria and archaea. The CasPDB database contains 287 reviewed Cas proteins, 257 745 putative Cas proteins and 3593 Cas operons from 32 023 bacteria species and 1802 archaea species. The database can be freely browsed and searched. The CasPDB web interface also represents all the 3593 putative Cas operons and its components. Among these operons, 328 are members of the type II CRISPR–Cas system.
Effects of oligosaccharides on the growth and stress tolerance of Lactobacillus plantarum ZLP001 in vitro, and the potential synbiotic effects of L. plantarum ZLP001 and fructo-oligosaccharide in post-weaning piglets1
Authors: Wang Jing , Wang Sixin , Liu Hui , Zhang Dongyan , Wang Yamin , Ji Haifeng
Published: August 2019

In this study, we evaluated the effects of seven oligosaccharides on the growth rate and stress tolerance of Lactobacillus plantarum ZLP001 in vitro, and the potential synbiotic effects of the most effective oligosaccharide [fructo-oligosaccharide (FOS)] and L. plantarum ZLP001 on the growth performance, apparent nutrient digestibility, fecal microbiota, and serum immune index in weaning piglets. Most oligosaccharides were utilized as carbohydrate sources by L. plantarum ZLP001, but we observed obvious differences in the bacterial growth depending on oligosaccharide type and concentration. Oligosaccharides and glucose significantly alleviated the decrease in L. plantarum ZLP001 viability in artificial gastric fluid, whereas none of the sugars affected viability in artificial intestinal fluid. FOS and galacto-oligosaccharide significantly improved the viability of L. plantarum ZLP001 under heat stress (65 °C for 15 and 30 min). FOS and soybean oligosaccharide significantly increased the viability of L. plantarum ZLP001 in response to cold stress (4 °C for 30 and 60 days). On the basis of the findings of in vitro experiments, we selected FOS for in vivo studies. Eighty-four weaned piglets were randomly assigned to one of the following groups: control (basal diet, no additives), freeze-dried L. plantarum ZLP001 (4.2 × 109 CFU/g, 2 g/kg diet), FOS (5 g/kg diet), and combination (0.2% L. plantarum ZLP001 + 0.5% FOS). Body weight and feed consumption were recorded for determinations of the average daily gain (ADG), average daily feed intake (ADFI), and feed-to-gain ratio (F/G). On day 28, fresh fecal samples were collected to evaluate the apparent digestibility of nutrients and microbiota, and serum samples were collected to determine the immune status. L. plantarum ZLP001 plus FOS significantly increased ADG and decreased the F/G ratio compared with the no-additive control. The combination treatment also increased the apparent nutrient digestibility of dry matter and crude protein. Compared with the control and single supplementation, the combination treatment had a significant regulatory effect on the intestinal microbiota, as evidenced by increases in Lactobacillus spp. and a decrease in Enterobacteriaceae. In addition, the combination treatment increased the concentrations of serum IFN-γ and immunoglobulin G. In conclusion, FOS can be utilized well by L. plantarum ZLP001 and can be combined with it as a potential synbiotic that shows synergistic effects in weaning piglets.