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Tytuł:
Tuning the Laser Ignition Properties of Nitrocellulose-Nitroglycerine-Hexogen Propellants via Incorporation of Carbon Nanotubes
Autorzy:
Shi, Xianrui
Jia, Yongjie
Chen, Linyu
Tian, Lu
Shen, Jinpeng
Pei, Chonghua
Powiązania:
https://bibliotekanauki.pl/articles/27787977.pdf
Data publikacji:
2021
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
nitrocellulose-nitroglycerine-hexogen propellants
NC-NG-RDX propellants
multi-walled carbon nanotubes
CNTs
light absorption
photothermal conversion
laser ignition
Opis:
Near infrared laser ignition is challenging owing to the poor near infrared laser absorption of nitrocellulose-nitroglycerine-hexogen (NC-NG-RDX) propellants. Less than 1 wt.% of carbon nanotubes (CNTs) were uniformly dispersed into the NC-NG-RDX propellants to tune its near infrared laser ignition property. The effects of CNTs on the thermal decomposition, near infrared light absorption and thermal conductivity of NC-NG-RDX propellants were studied. The near infrared laser ignition property of NC-NG-RDX propellants doped with CNTs were investigated compared with raw NC-NG-RDX propellant. The decomposition property and thermal conductivity of NC-NG-RDX propellants doped with CNTs were little changed due to the small quantity of CNTs. The laser reflectivity of the composite propellants decreased obviously as the content of CNTs was increased because of the high laser absorption property of CNTs. The laser ignition performance of the composites propellants is substantially improved by the incorporation of 0.5 wt.% or less CNTs and the successful ignition time decreases remarkably. Higher CNT content, such as 0.75 wt.% can lead to failure of laser ignition due to the excessive laser absorption efficiency and heating rate of the radiated region of the composite propellants together with inefficient deflagration. Our research reveals that the appropriate proportion of CNTs can potentially be used as a laser sensitizer for realizing effective infrared laser ignition of NC-NG-RDX propellants.
Źródło:
Central European Journal of Energetic Materials; 2021, 18, 3; 385--404
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Trace muscovite dissolution separation from vein quartz by elevated temperature and pressure acid leaching using sulphuric acid and ammonia chloride solutions
Autorzy:
Lin, M.
Pei, Z.-Y.
Lei, S.-M.
Liu, Y.-Y.
Xia, Z.-J.
Xie, F.-X.
Powiązania:
https://bibliotekanauki.pl/articles/110755.pdf
Data publikacji:
2018
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
vein quartz
muscovite
sulphuric acid
ammonium chloride
acid leaching
Opis:
Effects of sulphuric acid and ammonia chloride on muscovite dissolution were studied in acid leaching of vein quartz under elevated temperature and pressure. The leaching processes have been studied in detail by analyzing sources of impurity minerals, optimizing leaching process, analyzing leaching kinetics of Al in muscovite and charactering leaching mechanism of muscovite. The results showed that elements of Al and K mainly occurred in muscovite, and 98.10% or more of muscovite could be removed by acid leaching, while the process had limited influence on the particle size of quartz sand. Leaching of Al in the quartz ore was mainly controlled by chemical reaction. A calcination process and ammonia chloride were used for reducing chemical reaction resistance by damaging crystal structure of muscovite and providing stable acid leaching environment. Combined with the calcination process, muscovite, as a main gangue mineral, was effectively extracted during acid leaching of vein quartz at elevated temperature and pressure.
Źródło:
Physicochemical Problems of Mineral Processing; 2018, 54, 2; 448-458
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The impact of working capital management on manufacturing firms’ profitability – an emerging market perspective
Autorzy:
Arulanandam, Benedict Valentine
Glinkowska-Krauze, Beata
Tan, Pei Yu
Powiązania:
https://bibliotekanauki.pl/articles/27313256.pdf
Data publikacji:
2023
Wydawca:
Politechnika Śląska. Wydawnictwo Politechniki Śląskiej
Tematy:
working capital
profitability
manufacturing companies
kapitał obrotowy
rentowność
przedsiębiorstwa produkcyjne
Opis:
Purpose: This study aims to investigate the effects of working capital management on firm profitability of listed manufacturing companies in Malaysia. Design/methodology/approach: This study uses account payables, inventory turnover, account receivables, cash conversion cycle, firm size, growth, leverage and current ratio as accounting information variables. Secondary data was collected for all variables over a ten-year period, i.e. 2009 to 2018 and was obtained from the annual report published via Bursa Malaysia (Malaysian Stock Exchange) official website. Data was analyzed by using IBM SPSS Statistics Subscription software. Descriptive statistics, correlation analysis and multiple regression analysis were utilized in this study. Findings: The results revealed that inventory turnover in days, account receivables and firm size have a positive significant relationship with manufacturing firms’ profitability, while account payables and cash conversion cycle have a positive insignificant relationship. Research limitations/implications: The sample size is too small for any generalization. A mixed method approach in the future could contribute to a holistic finding. Practical implications: Since these variables contained significant influence on firm profitability, it is recommended that listed manufacturing companies should prepare a complete and timely manner of accounting information based on the regulation context in Malaysia. Social implications: It provides an empirical evidence on the importance of working capital management amongst the manufacturing concerns in Malaysia and its impact on its business sustainability. Originality/value: This study contributes to the limited research on working capital management involving manufacturing companies in Malaysia. Paper Type: Research Paper.
Źródło:
Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska; 2023, 169; 9--32
1641-3466
Pojawia się w:
Zeszyty Naukowe. Organizacja i Zarządzanie / Politechnika Śląska
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
The effect of the ionizing radiation on the tribological properties of thermoplastic polymers rubbing against steel
Wpływ dawki promieniowania gamma na właściwości tribologiczne wybranych polimerów termoplastycznych współpracujących ze stalą
Autorzy:
Niemiec, A.
Kujawa, M.
Wieleba, W.
Powiązania:
https://bibliotekanauki.pl/articles/188965.pdf
Data publikacji:
2016
Wydawca:
Stowarzyszenie Inżynierów i Techników Mechaników Polskich
Tematy:
gamma irradiation
PEEK
PEI
PET
PA6
microhardness
friction coefficient
promieniowanie gamma
mikrotwardość
współczynnik tarcia
Opis:
The paper describes the effects of gamma radiation doses on the tribological and mechanical properties of selected thermoplastic polymers: PEEK, PEI, PET, and PA6. Samples of those polymers were irradiated with gamma rays of energy 1, 1.2, 3, 4, 5 MeV and with the intensity of the radiation beam 4, 7, 10, 30, 40 μA. With an increasing dose of radiation, properties such as microhardness, the friction coefficient of polymers, and the wear rate are changed. The chemical structure of the irradiated polymer may be changed by crosslinking but also by chain scission. The modified polymers may be used in medical science, electronics, and space technology. In this article, we report the results of steel C45 – thermoplastics (PEEK, PEI, PET, and PA6) friction couple during the slip motion. The analysis is focused on the friction coefficient, wear rate, and microhardness. Kinematic parameters of the experiment in slide movement were constant and defined by the following values: contact pressure p = 1MPa and sliding velocity v = 1m/s. The authors observed that, as gamma radiation dose increased, the microhardness and friction coefficient increased and their wear intensity decreased. Polymers change their microstructure and molecular structure when they are subjected to gamma ray irradiation, which results in modification on many important physical and chemical properties.
Celem niniejszej pracy było określenie wpływu dawki promieniowania gamma na właściwości tribologiczne i mechaniczne wybranych polimerów termoplastycznych: PEEK, PEI, PET, PA6. Wraz ze wzrostem dawki tego promieniowania właściwości takie jak microhardness, współczynnik tarcia statycznego oraz intensywność zużycia ulegają zmianie. Wymienione właściwości mogą być modyfikowane na skutek zachodzących zmian w strukturze chemicznej naświetlonych polimerów poprzez sieciowanie łańcuchów polimerowych, ale także ich rozerwanie. Zmodyfikowane polimery mogą być wykorzystane m.in. w medycynie, elektronice i technologii kosmicznej. W pracy opisano badania par ślizgowych stal C45 – wybrany polimer. Analizie poddano wartości współczynnika tarcia statycznego oraz intensywności zużycia materiału. Dla wszystkich analizowanych przypadków wartości parametrów ruchowych były stałe: siła nacisku wynosiła 1 MPa, a prędkość ślizgowa 1 m/s. Eksperyment wykazał zwiększenie wartości mikrotwardości i współczynnika tarcia oraz zmniejszenie intensywności zużycia.
Źródło:
Tribologia; 2016, 269, 5; 133-145
0208-7774
Pojawia się w:
Tribologia
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on the purification capacity of rain garden paving structures for rainfall runoff pollutants
Autorzy:
Liu, Weijia
Pei, Qingbao
Dong, Wenbiao
Chen, Pengfan
Powiązania:
https://bibliotekanauki.pl/articles/22673516.pdf
Data publikacji:
2022
Wydawca:
Polska Akademia Nauk. Czasopisma i Monografie PAN
Tematy:
rain garden
rainfall runoff
abatement rate
pollutants removal rate
ogród deszczowy
odpływ opadów
stopa redukcji
wskaźnik usuwania zanieczyszczeń
Opis:
Rain gardens are one of the best measures for rainfall runoff and pollutant abatement in sponge city construction. The rain garden system was designed and developed for the problem of severely impeded urban water circulation. The rain gardens monitored the rainfall runoff abatement and pollutant removal capacity for 46 sessions from January 2018 to December 2019. Based on these data, the impact of rain gardens on runoff abatement rate and pollutant removal rate was studied. The results obtained indicated that the rain garden on the runoff abatement rate reached 82.5%, except with extreme rainfall, all fields of rainfall can be effectively abated. The removal rate of suspended solid particles was the highest, followed by total nitrogen and total phosphorus, the total removal rate in 66.35% above. The rain garden is still in the “youth stage”, and all aspects of the operation effect are good.
Źródło:
Archives of Environmental Protection; 2022, 48, 3; 28--36
2083-4772
2083-4810
Pojawia się w:
Archives of Environmental Protection
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study on the Detonation Parameters of Aluminized Explosives Based on a Disequilibrium Multiphase Model
Autorzy:
Pei, H.
Nie, J.
Jiao, Q.
Powiązania:
https://bibliotekanauki.pl/articles/358535.pdf
Data publikacji:
2014
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
nonideal explosives
velocity of detonation
detonation pressure
relaxation timescale
Opis:
Detonation models are usually based on the classical Euler equations of gas dynamics under the assumption of thermodynamic equilibrium. However reported data show the Chapman-Jouguet (CJ) detonation parameters of nonideal explosives based on thermodynamic equilibrium codes are significantly different from experimental results. Based on the conventional CJ model, a new multiphase flow model, not in thermal equilibrium, was considered in this study. This approach was applied to compute the velocity of detonation for several aluminized explosives. The predictions are better than the CJ equilibrium model and are in excellent agreement with experimental data. All of the deviations for the velocity of detonation (VOD) are less than 4%.
Źródło:
Central European Journal of Energetic Materials; 2014, 11, 4; 491-500
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Study of the Effect of DINA on the Polymorphic Transition of ε-CL-20 in Composite Modified Double Base Propellants
Autorzy:
Wu, Zongkai
Zheng, Wei
Pei, Jiangfeng
Chen, Zhiqun
Zhang, Jun
Song, Xiuduo
Wang, Jiangning
Zhang, Dongxiang
Zhao, Fengqi
Powiązania:
https://bibliotekanauki.pl/articles/27788019.pdf
Data publikacji:
2021
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Przemysłu Organicznego
Tematy:
CMDB propellant
CL-20
DINA
polymorphic transition
Opis:
Abstract: The polymorphic transition of 2,4,6,8,10,12-hexanitro-2,4,6,8,10,12-hexaazatetracyclo[5.5.0.05,9.03,11]dodecane (CL-20) is influenced by the materials and conditions used in the preparation of propellants, and limits the application of ε-CL-20 in solid propellants. In the present work, the effect of dinitroxydiethylnitramine (DINA) on the polymorphic transition of ε-CL-20 in CMDB propellants was investigated by Raman spectroscopy and the Calvet microcalorimeter method. The performance of propellants with CL-20 as affected by DINA was studied by the theoretical prediction of their energetic parameters, stability, combustion, and mechanical tests, respectively. The results showed that the polymorphic transition temperature of ε-CL-20 to α-CL-20 can be reduced to 75 °C by DINA. Expansion of the crystal volume during the process of the ε-CL-20 to α-CL-20 transition will produce obvious cracks in the surface of the crystals. NC/NG can inhibit the effect of DINA on the polymorphic transition of ε-CL-20. The theoretically predicted results indicated that adding DINA will not lower the energy level of CMDB propellants containing CL-20. The DSC and VST results showed that CL-20 has good compatibility and thermal stability with DINA. The burning rate tests revealed that adding DINA decreases the burning rates of CMDB propellants containing CL-20. Mechanical property testing showed that adding DINA can clearly improve the mechanical properties of CMDB propellants containing CL-20. The results of these investigations suggested that DINA has no effect on the crystalline stability of ε-CL-20 in the solventless extrusion process, which contributes to a significant understanding of practical applications and provides guidance for applied research on the use of CL-20 in propellants.
Źródło:
Central European Journal of Energetic Materials; 2021, 18, 2; 165--182
1733-7178
Pojawia się w:
Central European Journal of Energetic Materials
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Sliding mode tracking control for unmanned helicopter using extended disturbance observer
Autorzy:
Ullah, Ihsan
Pei, Hai-Long
Powiązania:
https://bibliotekanauki.pl/articles/229728.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
unmanned helicopter
external disturbances
sliding mode control
extended disturbance observer
mismatched uncertainty
Opis:
This paper presents a robust control technique for small-scale unmanned helicopters to track predefined trajectories (velocities and heading) in the presence of bounded external disturbances. The controller design is based on the linearized state-space model of the helicopter. The multivariable dynamics of the helicopter is divided into two subsystems, longitudinallateral and heading-heave dynamics respectively. There is no strong coupling between these two subsystems and independent controllers are designed for each subsystem. The external disturbances and model mismatch in the longitudinal-lateral subsystem are present in all (matched and mismatched) channels. This model mismatch and external disturbances are estimated as lumped disturbances using extended disturbance observer and an extended disturbance observer based sliding mode controller is designed for it to counter the effect of these disturbances. In the case of heading-heave subsystem, external disturbances and model mismatch only occur in matched channels so a second order sliding mode controller is designed for it as it is insensitive to matched uncertainties. The control performance is successfully tested in Simulink.
Źródło:
Archives of Control Sciences; 2019, 29, 1; 169-199
1230-2384
Pojawia się w:
Archives of Control Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on visible light indoor positioning algorithm based on fire safety
Autorzy:
Li, Mao
Jiang, Feng
Pei, Cong
Powiązania:
https://bibliotekanauki.pl/articles/174338.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
indoor positioning algorithm
camera
indoor positioning system
Opis:
From the perspective of ensuring life safety, combined with the advantages of high-speed time response and energy conservation of white light emitting diodes (LEDs), the visible light indoor positioning algorithm based on fire safety is proposed in the paper. First, the model is designed which needs three LED lights arranged in a straight line and positioned in the geographically north direction on the top of the model. Then, the proposed algorithm is discussed and analyzed when the camera is located at the center of the model and facing north, when the camera is located at the center of the model and the angle is rotated, and when the camera is located at any position of the model, respectively. It can accurately calculate the current position of the camera, its response speed is fast and the positioning accuracy is high. Furthermore, this paper also verifies the practicability and reliability of the algorithm by designing the visible light indoor positioning system based on fire safety rescue in natural environment and smoke environment. The experimental results show that the positioning error does not exceed 0.70 cm in smoke environment.
Źródło:
Optica Applicata; 2020, 50, 2; 209-222
0078-5466
1899-7015
Pojawia się w:
Optica Applicata
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Research on vertical change trend of environmental indicators of mining face and its assessment in gold mine
Autorzy:
Cao, Y.
Ji, H.
Pei, F.
Powiązania:
https://bibliotekanauki.pl/articles/89116.pdf
Data publikacji:
2017
Wydawca:
Politechnika Wrocławska. Wydział Geoinżynierii, Górnictwa i Geologii. Instytut Górnictwa
Tematy:
mining face
environmental indicators
change trend
gray cluster analysis
environmental quality grade
Opis:
This paper presents interpretation of results of a series of monitoring tests on O2, CO2, dust, noxious gases, microclimate, noise and illumination, conducted in seven mining faces of a metal mine, with vertical depths of -30 m, -70 m, -110 m, -150 m, -190 m, -230 m and -300 m. Through research on a vertical trend of a particular factor, several findings can be concluded as follows: concentration of CO2 rises up, while O2 decreases with deeper mining depth; concentrations of noxious gases increase with the deeper mining depth; dust amount exceeds seriously the limit, and grows linearly with the mining depth; dry-bulb temperature, effective temperature and relative humidity demonstrate a linear increase with the mining depth; sound pressure level in mining faces seriously exceed the limit value, and may cause a great harm to miners; illumination values in most mining faces are lower, comparing to the standard. Comprehensive evaluation of environmental quality of faces is carried out by introducing a model of grey clustering combined with G1-method, to determine the weight values and classify quality of the working environment. Results reveal that the environmental quality grade (EQG) of mining faces decrease with the increasing depth. In particular, EQG is excellent when above -150 m exploitation level, at which it becomes mediocre, and changes to bad when below -150 m.
Źródło:
Mining Science; 2017, 24; 99-115
2300-9586
2353-5423
Pojawia się w:
Mining Science
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Reliability study on non-contact traction power supplysystem based on fuzzy grey relational FTA
Autorzy:
Pei, Yanxia
Li, Xin
Powiązania:
https://bibliotekanauki.pl/articles/1841276.pdf
Data publikacji:
2021
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
FTA
grey relational degree
ICPT technology
reliability research
trapezoidal fuzzy number
triangular fuzzy number
szary stopień relacyjny
technologia ICPT
badania wiarygodności
trapezoidalna liczba rozmyta
trójkątna liczba rozmyta
Opis:
The traction power supply system based on Inductively Coupled Power Transfer (ICPT) technology is one of the new traction power supply technologies that will bedeveloped in the future. As the core part of rail transit energy transfer and conversion, thetraction power supply system is not only the critical system for the safe operation of railtransit, but also the main source of its failures, so it is of great significance to study itsreliability. In this paper, the reliability analysis of the non-contact traction power supplysystem based on mobile ICPT technology is carried out using the method of (Fault Tree Analysis) FTA combined with triangular fuzzy theory and grey relational theory. Firstly,the fault tree of the system is established, and the minimum cut sets and structure functionof the fault tree are obtained. Then the triangular fuzzy numbers are introduced to representthe probability of the bottom events, and the fuzzy probability of the top event and the fuzzyimportance of the bottom events are determined, after that, the maximum probability offailure of the top event is obtained. Finally, the grey relational degrees of each minimum cutset are obtained and ranked. Furthermore, in order to prove the correctness of this method,the trapezoidal fuzzy FTA is introduced and compared with it. Both research results showthat the loosely coupled transformer and Insulated Gate Bipolar Transistor (IGBT) moduleare the weak links of the system. The results obtained are consistent and realistic, whichproves the correctness of the method selected in this article.
Źródło:
Archives of Electrical Engineering; 2021, 70, 2; 253-270
1427-4221
2300-2506
Pojawia się w:
Archives of Electrical Engineering
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Quantification of lower extremity physical exposures in various combinations of sit/stand time duration associated with sit-stand workstation
Autorzy:
Pei, Huining
Yu, Suihuai
Babski-Reeves, Kari
Chu, Jianjie
Qu, Min
Tian, Baozhen
Li, Wenhua
Powiązania:
https://bibliotekanauki.pl/articles/2164098.pdf
Data publikacji:
2017-05-16
Wydawca:
Instytut Medycyny Pracy im. prof. dra Jerzego Nofera w Łodzi
Tematy:
electromyography
ergonomic intervention
perceived level of discomfort
root mean square
body mass index
gender differences
Opis:
Background Sit-stand workstations are available for office work purposes but there is a dearth of quantitative evidence to state benefits for lower limb outcomes while using them. And there are no guidelines on what constitutes appropriate sit/stand time duration. The primary aim of this study has been to compare muscle activity and perceived discomfort in the lower extremity during various combinations of sit/stand time duration associated with a sit-stand workstation separately and to evaluate the effects of the sit-stand workstation on the lower extremity during the text entry task. Material and Methods During the 5 days, all participants completed a 2-h text entry task each day for various sit/stand time duration combinations as follows: 5/25 min, 10/20 min, 15/15 min, 20/10 min, 25/5 min. Lower extremity muscular exposure of 12 male and 13 female participants was collected at 8 sites by surface electromyography and body discomfort was calculated by a questionnaire under those 5 conditions. Results Results have demonstrated that lower extremity muscle activity has been significantly varied among the 5 sit/stand time duration groups. Perceived level of discomfort (PLD) has not differed significantly for 9 out of 10 body parts. Conclusions The muscle activity of the thigh region was influenced by sit/stand time duration significantly. Ergonomic exposures of lower extremity when using a sit-stand workstation were increased, particularly during the long time standing posture. Results indicate that body mass index (BMI) and gender were not significant factors in this study. Combination of sit/stand time duration 25/5 min appears to show positive effects on relief of muscle exposure of back of thigh in the shifts of sitting and standing work position. Med Pr 2017;68(3):315–327
Źródło:
Medycyna Pracy; 2017, 68, 3; 315-327
0465-5893
2353-1339
Pojawia się w:
Medycyna Pracy
Dostawca treści:
Biblioteka Nauki
Artykuł
Wyświetlanie 1-15 z 54

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