scholarly journals Testing the Impact of Braking Algorithm Parameters on Acceleration and Braking Distance for a Suspended Monorail with Regard to Acceptable Travel Speed in Hard Coal Mines

Energies ◽  
2021 ◽  
Vol 14 (21) ◽  
pp. 7275
Author(s):  
Jerzy Świder ◽  
Kamil Szewerda ◽  
Krzysztof Herbuś ◽  
Jerzy Jura
Keyword(s):  
Numerical Simulations ◽  
Coal Mines ◽  
Travel Speed ◽  
Hard Coal ◽  
Speed Limit ◽  
Emergency Braking ◽  
Increased Risk ◽  
Braking Distance ◽  
Braking Force ◽  
The Impact

Increasing the maximum speed limit of suspended monorails, which became a very popular means of auxiliary transport, is one of the aspects of improving the efficiency of work in underground coal mines. It is especially important to enable higher (than allowed by the law) travel speed, when moving the crew to and from the workplace, which is often very distant from the shaft, and can take more than one hour of travel. Increasing this speed will make it possible to extend the effective working time of miners, which should have a positive impact on the economics of the mine. However, driving at a higher speed is also associated with increased risk of a negative impact of dynamic overload to people, e.g., during emergency braking of the suspended monorail. The concept of sequential emergency braking was developed in order to avoid excessive deceleration affecting passengers and the operator of the monorail, as well as to minimize the dynamic loads acting on the rail suspensions and on the roadway support frames, which could cause serious accidents. The developed assumptions with regard to the new method of braking are innovative in the area related to hard coal mining, where there are currently no such solutions. According to the principles of the developed concept, the total braking force was divided into two stages. The activation of the second stage depends on the deceleration measured after the time delay from activation of the first stage of braking. We present the results of the numerical simulations, which aimed to analyze the impact of changing the parameters of the braking algorithm on the braking deceleration, the braking time, and the braking distance. The possibility of changing the braking force and downward emergency braking on a high inclination angle were also taken into account during the numerical simulations. Use of the developed emergency braking algorithm enables the optimization of this process at a higher speed than is currently used. This aspect is also very important in increasing the safety for people travelling at a higher speed limit. The numerical simulations provide knowledge for safety in terms of the dynamic overload during emergency braking, without injury risk to miners or damage to equipment.

Working conditions and occupational pathology of coal miners in the Arctic

2019 ◽  
pp. 452-457 ◽  
Author(s):  
S. A. Gorbanev ◽  
S. A. Syurin ◽  
N. M. Frolova
Keyword(s):  
Coal Mining ◽  
Working Conditions ◽  
Occupational Diseases ◽  
Climatic Factors ◽  
Coal Mines ◽  
The Arctic ◽  
Morbidity Rate ◽  
Coal Miners ◽  
Increased Risk ◽  
The Impact

Introduction. Due to the impact of adverse working conditions and climate, workers in coal-mining enterprises in the Arctic are at increased risk of occupational diseases (OD).The aim of the study was to study the working conditions, causes, structure and prevalence of occupational diseases in miners of coal mines in the Arctic.Materials and methods. Th e data of social and hygienic monitoring “Working conditions and occupational morbidity” of the population of Vorkuta and Chukotka Autonomous District in 2007–2017 are studied.Results. It was established that in 2007–2017 years, 2,296 ODs were diagnosed for the first time in 1851 coal mines, mainly in the drifters, clearing face miners, repairmen and machinists of mining excavating machines. Most often, the ODs occurred when exposed to the severity of labor, fibrogenic aerosols and hand-arm vibration. The development of professional pathology in 98% of cases was due to design flaws of machines and mechanisms, as well as imperfections of workplaces and technological processes. Diseases of the musculoskeletal system (36.2%), respiratory organs (28.9%) and nervous system (22.5%) prevailed in the structure of professional pathology of miners of coal mines. Among the three most common nosological forms of OD were radiculopathy (32.1%), chronic bronchitis (27.7%) and mono-polyneuropathy (15.4%). In 2017, coal miners in the Arctic had a professional morbidity rate of 2.82 times higher than the national rates for coal mining.Conclusions. To preserve the health of miners of coal mining enterprises, technical measures to improve working conditions and medical interventions aimed at increasing the body’s resistance to the effects of harmful production and climatic factors are necessary.

Braking Distance of Hoist Conveyances Required for Safe Stopping Under the Conditions of Emergency Braking

2017 ◽  
Vol 62 (2) ◽  
pp. 279-288 ◽  
Author(s):  
Stanisław Wolny
Keyword(s):  
Equations Of Motion ◽  
Industrial Test ◽  
Operational Parameters ◽  
Constant Elasticity ◽  
Emergency Braking ◽  
Elastic Strings ◽  
Braking Distance ◽  
Analytical Formulas ◽  
Braking Force ◽  
Time Required

Abstract This study investigates selected aspects of the dynamic behaviour of mine hoists during the emergency braking in an event of overtravel. Characteristics of the braking force that needs to be applied in the headgear and in the pit bottom to arrest the conveyance in the event of an overtravel are derived from laboratory and industrial test data and recalling the results reported in literature. The real hoist installation is replaced by a model whereby the equations of motion of rope elements are written as for elastic strings, taking into account the variable length of the hoisting rope section between the Koepe pulley and the conveyance being arrested in the head tower. Analytical formulas are provided whereby the displacement of the top conveyance with the payload for the constant elasticity coefficient of the hoisting rope section between the conveyance being arrested in the head tower and the Koepe pulley is expressed as the function of the braking force and of the operational parameters of the hoist gear. The hoist operation is investigated in the event of emergency braking, taking into account the two aspects of the cycle: - the time required for the conveyance to be stopped, - the distance travelled by the conveyance until it is stopped. The results of the dynamic analysis of the hoist installation in the conditions of emergency braking may be utilised in selection of the effective and adequate braking system guaranteeing the safety of the system operation.

scholarly journals Assessment of the functional functionality of passenger car brake systems by changing the braking distance during operation

2021 ◽  
Vol 13 (1) ◽  
pp. 78-86
Author(s):  
Alexander Nazarov ◽  
◽  
Vitalii Kashkanov ◽  
Ivan Nazarov ◽  
Yevhen Ivanchenko ◽  
...  
Keyword(s):  
Operating Conditions ◽  
Passenger Cars ◽  
Passenger Car ◽  
Emergency Braking ◽  
Braking System ◽  
Braking Distance ◽  
Braking Force ◽  
Braking Process ◽  
Relative Change

The article discusses a methodology for assessing the functional suitability of brake systems to change the braking path of passenger cars, taking into account various operating conditions. The goal is achieved by using the method of mathematical modeling of the emergency braking process, taking into account the possible operating conditions of cars performing emergency braking at certain initial speeds, in particular, exceeding 100 km / h. Based on the analysis of scientific sources, it has been established that the determination of the braking efficiency of a vehicle classically occurs on the verge of blocking all wheels with known methods of distributing braking forces between the axles of the vehicle. In this case, the standards set the maximum value of the minimum deceleration and braking distance. In addition, the jump in the maximum possible value of the braking force between the wheels of each axle makes it possible to compare it with the requirements of DSTU 3649: 2010, and the assessment of the magnitude of this jump for each braking of the car is to establish its functional suitability. As a result, according to the magnitude of the jump in the maximum possible value of the braking distance, the change in the maximum allowable braking force of the car sets, and according to the magnitude of its jump, it is possible to assess the functional suitability of its braking system. As a result, the use of expert information on the value of jumps in the maximum possible value of the braking force of a car, affecting the braking torques and braking coefficient, can reduce the amount of experimental research and significantly reduce the time to reach an objective decision on the functional suitability of the brake systems of operated cars. The paper presents the results of theoretical studies of passenger cars Chevrolet Aveo, Lada Priora and Forza with different loads, performing emergency braking at an initial speed of 40-150 km / h on a road with dry asphalt concrete. The boundaries of the coefficient of the relative change in the braking distance of the tested passenger car, at which it is possible to make a conclusion about the functional suitability of its braking system, have been established.

scholarly journals Determining the Impact of Different Factors on the Occurrence of Road Transportation Incidents

2021 ◽  
pp. 115-122
Author(s):  
Allahverdi Jamal oglu Sharifov ◽  
Keyword(s):  
Influencing Factor ◽  
Travel Speed ◽  
Road Accidents ◽  
Road Transportation ◽  
Braking Distance ◽  
The Impact

It is important to be aware of the influence of various factors on the occurrence of road accidents. The most influencing factor on the braking distance of a car is its speed. The travel speed is quadratically proportional to the braking distance. In this regard, when analyzing the values of other indicators, we keep them constant, and the degree of influence of changes in the speed value in different intervals is set in percent.

Numerical Study on the Influence of Blockage Ratio on Hydrogen Turbulent Premixed Flames in a Small Scale Obstructed Chamber

2020 ◽  
Author(s):  
M. Elshimy ◽  
S. Ibrahim ◽  
W. Malalasekera
Keyword(s):  
Experimental Data ◽  
Numerical Simulations ◽  
Flame Structure ◽  
Premixed Flames ◽  
Numerical Results ◽  
Small Scale ◽  
Blockage Ratio ◽  
Increased Risk ◽  
The Impact ◽  
Flame Position

Abstract Although hydrogen is a clean and renewable fuel, there is still a need to understand and evaluate the potential risks posed in the event of an accidental explosion. This paper presents large eddy simulation (LES) numerical analysis for lean hydrogen premixed flames propagating inside a small laboratory combustion chamber with built in solid obstructions. The small-scale chamber is 0.625 litres in volume with three removable turbulence generating baffles and a square solid obstacle. A lean equivalence ratio of 0.7 is selected in this study. The LES model is utilised to investigate the influence of obstruction configuration and area blockage ratio on the flame characteristics and the generated combustion over-pressure. The LES turbulence technique is used with an in-house computational fluid dynamics (CFD) model for compressible flows. The numerical simulations are carried out with various arrangements of the baffle plates and a solid obstacle to examine the effects of the area blockage ratio and generated turbulence on the flame structure and generated over-pressure. Two different area blockage ratios of 0.24 and 0.5 are studied. Four configurations with different baffle arrangements are studied to examine the resulting turbulence effects on the generated over-pressure, flame position-time traces and flame transient speed following ignition. Direct comparisons are made between the different baffle/flow configurations to identify the various effects of an increased area blockage ratio. Numerical results showing the flame structure at various time windows after ignition are presented and compared with published experimental images. High speed laser induced fluorescence (LIF-OH) images of the reaction zones obtained from the experiments at a rate of 5 kHz provide the flame position data and convey the impact of the turbulence generated by the baffles and solid obstacle on the propagating flame structure [1]. The pressure is recorded at a rate of 25 kHz using a piezo-electric pressure transducer in the base plate of the chamber [2]. The rise in over-pressure as a result of increased turbulence due to additional baffles and an increased area blockage ratio is found to be consistent with experimental data. This is also found to be consistent for the flame position-time and speed-time traces across all configurations. Main points of interest such as the peak over-pressure, maximum rate of pressure rise and the flame propagation trends are also observed along with variations in flame speed as the flame interacts with the baffles and obstacles. Validation of the numerical results against available published experimental data conveys good agreement confirming the ability of the numerical model to predict numerical results for an increased area blockage ratio. Further numerical simulations are also carried out for flame/flow parameters where experimental data is unavailable due to physical limitations. Satisfactory agreement between numerical results and experimental data endorses further predictions for computational models in studying vented hydrogen explosions where there is an increased risk or limited experimental data.

scholarly journals Analysis of the Impact of Unscheduled Downtimes on their Availability in Machine Operations

2018 ◽  
Vol 1 (1) ◽  
pp. 145-151
Author(s):  
Jarosław Brodny
Keyword(s):  
High Reliability ◽  
Coal Mines ◽  
Working Environment ◽  
Hard Coal ◽  
Fundamental Parameters ◽  
Automation Systems ◽  
External Conditions ◽  
The Cost ◽  
The Impact ◽  
Very High

Abstract Unscheduled downtimes in machine operation are one of the main reasons behind their low availability. Such downtimes are caused by miscellaneous factors and remain difficult to identify in a number of cases. This particularly refers to enterprises that conduct their activities in changing external conditions, such as hard coal mines, where exploitation is carried out in extremely complicated, changeable and dangerous conditions. The process of coal production makes use of various machines that must be adapted to these conditions. The specificity of the working environment makes it necessary for these machines to exhibit high reliability, readiness and efficiency. These features, in turn, make the cost of the machines very high. It is therefore reasonable to make the best use of their capabilities, which translates into the effectiveness of the entire production process. The article concentrates on determining the availability of these machines. It has been assumed that availability is one of the fundamental parameters that define the effective utilisation of machines. The tests were conducted for a longwall shearer as well as an armoured face conveyor and a main haulage conveyor in one of the hard coal mines in Poland. Industrial automation systems were used to determine unscheduled downtimes in the operation of these machines, as well as their time structure and causes. The results obtained indicate that the number of unscheduled downtimes represents a serious problem in mining exploitation.

Zinc Depletion Increases Readmission in Older Patients: An Example of Interactions Between Nutrition and Disease

2017 ◽  
Vol 87 (1-2) ◽  
pp. 10-16 ◽  
Author(s):  
Salah Gariballa ◽  
Awad Alessa
Keyword(s):  
Nutritional Status ◽  
Inductively Coupled Plasma ◽  
Older Patients ◽  
Controlled Trial ◽  
Prognostic Indicators ◽  
Hospitalised Patients ◽  
Increased Risk ◽  
Co Morbidity ◽  
The Impact ◽  
Poor Nutrition

Abstract. Background: ill health may lead to poor nutrition and poor nutrition to ill health, so identifying priorities for management still remains a challenge. The aim of this report is to present data on the impact of plasma zinc (Zn) depletion on important health outcomes after adjusting for other poor prognostic indicators in hospitalised patients. Methods: Hospitalised acutely ill older patients who were part of a large randomised controlled trial had their nutritional status assessed using anthropometric, hematological and biochemical data. Plasma Zn concentrations were measured at baseline, 6 weeks and at 6 months using inductively- coupled plasma spectroscopy method. Other clinical outcome measures of health were also measured. Results: A total of 345 patients assessed at baseline, 133 at 6 weeks and 163 at 6 months. At baseline 254 (74%) patients had a plasma Zn concentration below 10.71 μmol/L indicating biochemical depletion. The figures at 6 weeks and 6 months were 86 (65%) and 114 (70%) patients respectively. After adjusting for age, co-morbidity, nutritional status and tissue inflammation measured using CRP, only muscle mass and serum albumin showed significant and independent effects on plasma Zn concentrations. The risk of non-elective readmission in the 6-months follow up period was significantly lower in patients with normal Zn concentrations compared with those diagnosed with Zn depletion (adjusted hazard ratio 0.62 (95% CI: 0.38 to 0.99), p = 0.047. Conclusions: Zn depletion is common and associated with increased risk of readmission in acutely-ill older patients, however, the influence of underlying comorbidity on these results can not excluded.

Thrombophilia and risk of VTE recurrence according to the age at the time of first VTE manifestation

VASA ◽  
2015 ◽  
Vol 44 (4) ◽  
pp. 313-323 ◽  
Author(s):  
Lea Weingarz ◽  
Marc Schindewolf ◽  
Jan Schwonberg ◽  
Carola Hecking ◽  
Zsuzsanna Wolf ◽  
...  
Keyword(s):  
Factor V Leiden ◽  
Cox Proportional Hazards ◽  
First Episode ◽  
Factor V ◽  
Factor V Leiden Mutation ◽  
Younger Patients ◽  
Risk Of Recurrence ◽  
G20210a Mutation ◽  
Increased Risk ◽  
The Impact

Abstract. Background: Whether screening for thrombophilia is useful for patients after a first episode of venous thromboembolism (VTE) is a controversial issue. However, the impact of thrombophilia on the risk of recurrence may vary depending on the patient’s age at the time of the first VTE. Patients and methods: Of 1221 VTE patients (42 % males) registered in the MAISTHRO (MAin-ISar-THROmbosis) registry, 261 experienced VTE recurrence during a 5-year follow-up after the discontinuation of anticoagulant therapy. Results: Thrombophilia was more common among patients with VTE recurrence than those without (58.6 % vs. 50.3 %; p = 0.017). Stratifying patients by the age at the time of their initial VTE, Cox proportional hazards analyses adjusted for age, sex and the presence or absence of established risk factors revealed a heterozygous prothrombin (PT) G20210A mutation (hazard ratio (HR) 2.65; 95 %-confidence interval (CI) 1.71 - 4.12; p < 0.001), homozygosity/double heterozygosity for the factor V Leiden and/or PT mutation (HR 2.35; 95 %-CI 1.09 - 5.07, p = 0.030), and an antithrombin deficiency (HR 2.12; 95 %-CI 1.12 - 4.10; p = 0.021) to predict recurrent VTE in patients aged 40 years or older, whereas lupus anticoagulants (HR 3.05; 95%-CI 1.40 - 6.66; p = 0.005) increased the risk of recurrence in younger patients. Subgroup analyses revealed an increased risk of recurrence for a heterozygous factor V Leiden mutation only in young females without hormonal treatment whereas the predictive value of a heterozygous PT mutation was restricted to males over the age of 40 years. Conclusions: Our data do not support a preference of younger patients for thrombophilia testing after a first venous thromboembolic event.

Percutaneous Coronary Intervention in Patients with Diabetes and Multivessel or Left Main Disease – a Review

2012 ◽  
Vol 7 (1) ◽  
pp. 37
Author(s):  
Donald E Cutlip ◽  
Keyword(s):  
Percutaneous Coronary Intervention ◽  
Coronary Artery ◽  
Statistical Significance ◽  
Bare Metal Stents ◽  
Coronary Intervention ◽  
Metal Stents ◽  
Increased Risk ◽  
Percutaneous Coronary ◽  
Patients With Diabetes ◽  
The Impact

Coronary artery disease in patients with diabetes is frequently a diffuse process with multivessel involvement and is associated with increased risk for myocardial infarction and death. The role of percutaneous coronary intervention (PCI) versus coronary artery bypass grafting (CABG) in patients with diabetes and multivessel disease who require revascularisation has been debated and remains uncertain. The debate has been continued mainly because of the question to what degree an increased risk for in-stent restenosis among patients with diabetes contributes to other late adverse outcomes. This article reviews outcomes from early trials of balloon angioplasty versus CABG through later trials of bare-metal stents versus CABG and more recent data with drug-eluting stents as the comparator. Although not all studies have been powered to show statistical significance, the results have been generally consistent with a mortality benefit for CABG versus PCI, despite differential risks for restenosis with the various PCI approaches. The review also considers the impact of mammary artery grafting of the left anterior descending artery and individual case selection on these results, and proposes an algorithm for selection of patients in whom PCI remains a reasonable strategy.

Sign in / Sign up

Export Citation Format

Share Document