Advances in mechanical weed control technologies

Mechanical weed control can be grouped into three categories: full-width cultivators, inter-row cultivators and intra-row cultivators. This chapter will highlight the most recent and relevant advances within each category. The focus will be on novel inventions and developments of mechanical devices, designs, and the weed problems they are meant to solve. Moreover, automation technologies that assist weeding operations are becoming increasingly important and will be given special attention.

Tuning of frictional properties in torsional contact by means of disk grading

The contact of two surfaces in relative rotating motion occurs in many practical applications, from mechanical devices to human joints, displaying an intriguing interplay of effects at the onset of sliding due to the axisymmetric stress distribution. Theoretical and numerical models have been developed for some typical configurations, but work remains to be done to understand how to modify the emergent friction properties in this configuration. In this paper, we extend the two-dimensional (2D) spring-block model to investigate friction between surfaces in torsional contact. We investigate how the model describes the behavior of an elastic surface slowly rotating over a rigid substrate, comparing results with analytical calculations based on energy conservation. We show that an appropriate grading of the tribological properties of the surface can be used to avoid a non-uniform transition to sliding due to the axisymmetric configuration.

Economic method of oil production based on electrophoresis

Electrophoresis can be considered as a fundamentally new method of lifting oil without the use of producing wells and mechanical devices, with the help of which it is supposed to organize oil extraction from explored fields with a reduction in its cost by 70-80%. The source of electricity for the implementation of the proposed method of oil recovery based on electrophoresis can be a method of autonomous generation of electricity based on atmospheric electricity. This method is based on the operation of a natural generator consisting of the Earth, the atmosphere, the ionosphere and the Earth›s magnetic field.The proposed energy source is simple in design, convenient to use. As a result, the resulting energy is very cheap and environmentally friendly. The use of such an installation can be carried out in any area of the Earth. Keywords: oil production; electrophoresis; electric field; atmospheric electricity; carbon; the cost of lifting oil.

Prognostic factors of cerebral revascularisation in acute ischemic stroke at Hanoi Heart Hospital

Background: Considering the effectiveness of treatment for acute ischemic stroke (AIS)patients, the most expected method is immediate revascularization using intravenous thrombolysis or mechanical thrombectomy, or both methods. Objective: “Find factors related to post-treatment outcomes of acute ischemic stroke patients undergoing cerebral revascularization”. Method: Cross-sectional, prospective, descriptive analysis with convenient sample size. Results: From February 2018 to August 2021, 83 patients were hospitalized with a diagnosis of acute ischemic stroke or acute ischemic stroke and had cerebral revascularision either by thrombolysis or mechanical devices or both. 6.02% of them had cerebral thrombosis with mechanical devices and stenting of cerebral/carotid arteries. Mean age was 66.37±11.82 (range 31to 91 years). Mean NIHSS score was 12.57±6.70. The rate of complete recanalization was 91.56%. The mRS score of 0-2 points accounted for 48.19% at the time of discharge and 54.21% at 30 days after discharge. The rate of death or severe illness at discharge accounted for 14.45%. 30 days all-cause mortality after discharge accounted for 25.3%. Conclusion: The rate of complete reperfusion in patients with acute cerebral infarction at Hanoi Heart Hospital and good recovery rate is quite high. Factors that related to the treatment efficacy of patients with acute ischemic stroke were NIHSS score, ASPECT score, occlusion site, pre-reperfusion parenchymal damage and the selection of appropriate reperfusion measures.

DETERMINATION OF THE ACOUSTO-OPTICAL DEFLECTOR PARAMETERS FOR A LASER-RADIATION ROCKET GUIDANCE SYSTEM

The work is devoted to the development of an acousto-optic deflector for a laser-beam guidance system (LLSN) of missiles. LLSN is used in semiautomatic portable missile systems to destroy hostile targets of various types. An analysis of the methods for constructing such systems has shown that the most promising devices with pulse-code modulation using semiconductor pulsed lasers. The article provides a diagram and describes the principle of operation of the LLSN with pulse-code modulation. A problematic issue in the implementation of such a system is the development of a device for deflecting a laser beam, through which the missile is guided to a target. Scanning mechanical devices that are currently in use have a complex design, significant dimensions and weight, and limited performance. The article proposes to use an acousto-optic deflector to deflect the laser beam within the information field of the guidance system, which is devoid of these disadvantages, since it replaces the mechanical scanning device with an electronic one. The purpose of the article is to determine the main parameters of the acousto-optical deflector. The article discusses the principle of operation of an acousto-optic deflector. It is noted that glasses based on germanium chalcogenides, in particular, glass with the composition Ge2.17As39.13S58.70, have especially low values of acoustic losses (α <1 dB / cm). The largest deflection angle of the laser beam will be observed with Bragg diffraction. Relationships are given that can be used to determine the main characteristics of the deflector: the angle of deflection of the laser beam, the modulation frequency of the acoustic wave, resolution, speed, and others. When using the above ratios for the typical parameters of the existing guidance system, the values of the indicated characteristics are calculated.

Corrosion Nature in [CoN/AlN]n Multilayers Obtained from Laser Ablation

The aim of this work is the improvement of the electrochemical behavior of industrial steel using [CoN/AlN]n multilayered system via reactive Pulsed Laser Deposition (PLD) technique with a Nd: YAG laser (λ = 1064 nm) on Silicon (100) and AISI 302 steel substrates. In this work was varied systematically the bilayer period (Λ) and the coatings were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and the chemical composition was determined by means of X-ray photoelectron spectroscopy (XPS). The maximum corrosion resistance for the coating with (Λ) equal to 34.7 nm, corresponding to n = 30 bilayered. The polarization resistance and corrosion rate were around 7.62 × 105 kOhm × cm2 and 7.25 × 10−5 mm/year, these values were 6.3 × 105 and 78.6 times better than those showed by the uncoated 302 stainless steel substrate (1.2 kOhm × cm2 and 0.0057 mm/year), respectively. The improvement of the electrochemical behavior of the steel 302 coated with this [CoN/AlN]n can be attributed to the presence of several interfaces that act as obstacles for the inward and outward diffusions of Cl− ions, generating an increment in the corrosion resistance. The electrochemical results found in the [CoN/AlN]n open a possibility of future applications in mechanical devices that require high demands in service conditions.

Design of mechanical devices for the elderly to move and live alone

With the increasing aging of the population, the demand for elderly assistance machinery is increasing. By comparing the advantages and disadvantages of the existing elderly assistance devices and analyzing the daily activities and care needs of the elderly, this paper determines the main functions of the mechanical devices for the elderly to move around alone and proposes a general design scheme. Based on the overall design plan, the main mechanisms such as axillary support mechanism, sitting mechanism, posture adjustment mechanism and wheel mechanism were designed, and the operability and stability of the device were improved through the linkage of the variable cell mechanism. Virtual prototype modeling was carried out by solidworks to verify the rationality of the structure. The device not only has better function, but also has simpler structure and lower maintenance cost, which is more suitable for market demand.

Electrostatic Zipping Actuators—Analysis of the Pull-In Effect Depending on the Geometry Parameters

Continuous work on a new generation of actuators, referred to as artificial muscles, resulted in the initiation of work on electrostatic zipping actuators, the concept of which is derived from micro electro-mechanical devices. Despite partial knowledge of their basic operating parameters, a question remains whether electrostatic zipping actuators are able to meet the expectations in the context of generated forces and control possibilities. In order to get closer to the answer to this question, the authors of this work created a solution method using FEM, which allowed them to conduct a series of concentric contraction tests of the desired solution. In addition to the basic features of the actuators tested, such as their length, thickness and width, for the first time the size of the weld surface, to which the loading force was applied, was taken into account. The results of the investigations show the possibility of adjusting the supply voltage range to the application requirements, but most importantly, they present the variability of the pull-in strain parameter. In extreme configurations, its value increases from ~10% to ~26%. The results obtained emphasize the need for further analysis of electrostatic zipping actuators using FEM. It will make it possible to precisely define the characteristics of this technology as well as its limits. These activities will provide the ultimate answer to the potential of electrostatic zipping actuators as artificial muscles.

Frailty and Different Exercise Interventions to Improve Gait Speed in Older Adults after Acute Coronary Syndrome

Background and Objectives: The world’s population is rapidly aging, and it is estimated that, by 2050, every sixth person on earth will be older than 65 years. Around 30% of older adults entering cardiac rehabilitation (CR) meet the criteria of frailty. Frailty identification has not been included in the routine evaluation of CR patients yet, and there is a lack of evidence on what training regimen for improving physical performance in frail people is optimal. Therefore, the aim of our study was to determine the prevalence of frailty and to evaluate the effect of two different complementary training programs on the gait speed of older vulnerable and frail patients with acute coronary syndrome and mid-range-to-preserved left ventricular ejection fraction (≥40%) during short-term CR. Materials and Methods: This randomized controlled trial was conducted from January 2020 to September 2021. CR participants (n = 97) with a mean age of 73.1 ± 5.3 years were randomly allocated into three groups: control (CG, n = 32), intervention-1 (IG-1, n = 32) and intervention-2 (IG-2, n = 33). The patients of all three groups attended a usual inpatient CR program, and two intervention groups additionally received different resistance and balance training programs 3 days a week: the IG-1 underwent complementary training with traditional means of physical therapy, while the IG-2 underwent complementary training with mechanical devices. The mean CR duration was 18.9 ± 1.7 days. Frailty was assessed with the Edmonton Frail Scale, and the 5 m walk test was used to evaluate gait speed. Results: Frailty was determined in 37.1% of participants, and 42.3% met the criteria of being vulnerable. After CR, the gait speed of frail and vulnerable patients significantly improved in all three groups (p < 0.05). In the IG-2, slow gait speed was reversed to normal in the overwhelming majority of patients (p < 0.05), while the CG had the greatest proportion of patients who remained to be slow after CR (p < 0.05). Conclusions: A considerable part of patients entering CR are frail or vulnerable; therefore, it is of crucial importance to assess frailty status in all older people. All three CR programs improved gait speed in frail and vulnerable older patients with ischemic heart disease. Complementary resistance and balance training with mechanical devices more effectively reversed slow gait speed to normal during short-term CR.