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Wyszukujesz frazę "Zheng, Wei" wg kryterium: Autor


Tytuł:
Toughness, Forbidden Subgraphs, and Hamilton-Connected Graphs
Autorzy:
Zheng, Wei
Broersma, Hajo
Wang, Ligong
Powiązania:
https://bibliotekanauki.pl/articles/32361744.pdf
Data publikacji:
2022-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
toughness
forbidden subgraph
Hamilton-connected graph
Hamiltonicity
Opis:
A graph G is called Hamilton-connected if for every pair of distinct vertices {u, v} of G there exists a Hamilton path in G that connects u and v. A graph G is said to be t-tough if t·ω(G − X) ≤ |X| for all X ⊆ V (G) with ω(G − X) > 1. The toughness of G, denoted τ (G), is the maximum value of t such that G is t-tough (taking τ (Kn) = ∞ for all n ≥ 1). It is known that a Hamilton-connected graph G has toughness τ (G) > 1, but that the reverse statement does not hold in general. In this paper, we investigate all possible forbidden subgraphs H such that every H-free graph G with τ (G) > 1 is Hamilton-connected. We find that the results are completely analogous to the Hamiltonian case: every graph H such that any 1-tough H-free graph is Hamiltonian also ensures that every H-free graph with toughness larger than one is Hamilton-connected. And similarly, there is no other forbidden subgraph having this property, except possibly for the graph K1 ∪ P4 itself. We leave this as an open case.
Źródło:
Discussiones Mathematicae Graph Theory; 2022, 42, 1; 187-196
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
On Implicit Heavy Subgraphs and Hamiltonicity of 2-Connected Graphs
Autorzy:
Zheng, Wei
Wideł, Wojciech
Wang, Ligong
Powiązania:
https://bibliotekanauki.pl/articles/32083821.pdf
Data publikacji:
2021-02-01
Wydawca:
Uniwersytet Zielonogórski. Wydział Matematyki, Informatyki i Ekonometrii
Tematy:
implicit degree
implicit o-heavy
implicit f-heavy
implicit c-heavy
Hamilton cycle
Opis:
A graph G of order n is implicit claw-heavy if in every induced copy of K1,3 in G there are two non-adjacent vertices with sum of their implicit degrees at least n. We study various implicit degree conditions (including, but not limiting to, Ore- and Fan-type conditions) imposing of which on specific induced subgraphs of a 2-connected implicit claw-heavy graph ensures its Hamiltonicity. In particular, we improve a recent result of [X. Huang, Implicit degree condition for Hamiltonicity of 2-heavy graphs, Discrete Appl. Math. 219 (2017) 126–131] and complete the characterizations of pairs of o-heavy and f-heavy subgraphs for Hamiltonicity of 2-connected graphs.
Źródło:
Discussiones Mathematicae Graph Theory; 2021, 41, 1; 167-181
2083-5892
Pojawia się w:
Discussiones Mathematicae Graph Theory
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:
Research on the Spin-Hamiltonian Parameters and Local Structure for the Tetragonal $Mo^{5+}$ Centers in $CaWO_{4}$ Crystal
Autorzy:
Mei, Y.
Zheng, W.
Wei, C.
Powiązania:
https://bibliotekanauki.pl/articles/1377649.pdf
Data publikacji:
2014-12
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
76.30.He
71.70.Ch
75.10.Dg
Opis:
The spin-Hamiltonian parameters (g factors $g_{∥}$, $g_{⊥}$ and hyperfine structure constants $A_{∥}(A)$, $A_{⊥}(A)$, $A_{∥}(B)$ and $A_{⊥}(B)$, A(A) and A(B) belonging to isotopes $\text{}^{95}Mo^{5+}$ and $\text{}^{97}Mo^{5+})$ of $Mo^{5+}$ ion at the tetragonally-compressed tetrahedral $W^{6+}$ site in $CaWO_4$ crystal are calculated from the high-order perturbation formulae based on the two-mechanism model, where besides the contributions to spin-Hamiltonian parameters due to the crystal-field mechanism concerning the crystal-field excited states in the extensively-applied crystal-field theory, those due to charge-transfer mechanism concerning charge-transfer excited states (which are omitted in crystal-field theory) are included. The calculated results are in reasonable agreement with the experimental values. The calculations show that for the high-valence state $d^{n}$ ions (e. g., $Mo^{5+}$ considered) in crystals, the contributions due to charge-transfer mechanism should be taken into account in the studies of spin-Hamiltonian parameters. The local structure of $Mo^{5+}$ center in $CaWO_4$ crystal due to the impurity-induced local lattice relaxation is estimated from the calculations. The results are discussed.
Źródło:
Acta Physica Polonica A; 2014, 126, 6; 1275-1279
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A source discrimination method of mine water-inrush based on 3D spatial interpolation of rare classes
Analiza dyskryminacyjna źródeł wycieków wody do kopalni na podstawie trójwymiarowej interpolacji danych o zdarzeniach rzadkich
Autorzy:
Jiang, Qiong
Zhao, Weidong
Zheng, Yong
Wei, Jiajia
Wei, Chao
Powiązania:
https://bibliotekanauki.pl/articles/219790.pdf
Data publikacji:
2019
Wydawca:
Polska Akademia Nauk. Czytelnia Czasopism PAN
Tematy:
analiza dyskryminacyjna źródeł wycieków
wyciek wód
jakość wód
kryterium Bayesowskie
kategoria zdarzeń rzadkich
source discrimination
water inrush
water quality
Bayesian classifier
rare class
Opis:
When the distribution of water quality samples is roughly balanced, the Bayesian criterion model of water-inrush source generally can obtain relatively accurate results of water-inrush source identification. However, it is often difficult to achieve desired classification results when training samples are imbalanced. Sample imbalance is common in the source identification of mine water-inrush. Therefore, we propose a three-dimensional (3D) spatial resampling method based on rare water quality samples, which achieves the balance of water quality samples. Based on the virtual water sample points distributed by the 3D grid, the method uses the 3D Inverse Distance Weighting (IDW) method to interpolate the groundwater ion concentration of the virtual water samples to achieve oversampling of rare water samples. Case study in Gubei Coal Mine shows that the method improves overall discriminant accuracy of the Bayesian criterion model by 5.26%, from 85.26% to 90.69%. In particular, the discriminative precision of the rare class is improved from 0% to 83.33%, which indicates that the method can improve the discriminant accuracy of the rare class to large extent. In addition, this method increases the Kappa coefficient of the model by 19.92%, from 52.26% to 72.19%, increasing the degree of consistency from “general” to “significant”. Our research is of significance to enriching and improving the theory of prevention and treatment of mine water damage.
W przypadku zrównoważonych danych o jakościowym rozkładzie próbek, zastosowanie kryterium Bayesowskiego do modelowania źródeł wycieków daje stosunkowo dokładne wyniki w analizie dyskryminacyjnej źródeł wycieków wody kopalnianej. Jednakże w przypadku niezrównoważonych danych, pożądane efekty kategoryzacji są niezmiernie trudne do uzyskania. Dane o składzie próbek są w znacznej mierze niezrównoważone, i jest to powszechny problem napotykany przy identyfikacji źródeł wycieków. W obecnej pracy zaproponowano więc trójwymiarową (3D) metodę powtórnego próbkowania z wykorzy-staniem próbek wód z kategorii zdarzeń rzadkich, tak by uzyskać zrównoważony zbiór danych. W oparciu o wirtualne punkty na trójwymiarowej siatce, wykorzystano trójwymiarową metodęśredniej ważonej odległością (Inverse Distance Weighing – IDW) do interpolacji stężenia jonów w wodach gruntowych w wirtualnych próbkach wody, w celu nadpróbkowania dla kategorii zdarzeń rzadkich. Studium przypadku kopalni węgla Gubei pokazuje, że metoda poprawia dokładność dopasowania modelu w oparciu o kryterium Bayesowskie o 5.25% (z 85.26% na 90.96 %). W szczególności, dokładność rozróżniania i dyskryminacji próbek należących do kategorii zdarzeń rzadkich wzrasta od 0% do 83.33%, co oznacza bardzo znaczna poprawę. Ponadto, wartość współczynnika Kappa wzrasta o 19.92%, od 52.26 % do 72.19%, tym samym podnosząc poziom zgodności metody z poziomu ogólnego na „znaczący”. Prowadzone przez nas badania mają poważne znaczenie z punktu widzenia udoskonalenia teorii leżących u podstaw metod i technik zapobiegania i kontroli wycieków wód kopalnianych.
Źródło:
Archives of Mining Sciences; 2019, 64, 2; 321-333
0860-7001
Pojawia się w:
Archives of Mining Sciences
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Application of a biconical dense medium cyclone to pre-treat a low-grade Pb-Zn sulfide ore
Autorzy:
Jian, Sheng
Sun, Wei
Zheng, Yong-xing
Powiązania:
https://bibliotekanauki.pl/articles/110536.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
Pb-Zn sulfide ore
Low-grade ore
Pretreatment
Biconical dense medium cyclone
Opis:
A biconical dense medium cyclone (BDMC) was applied to reject the gangue from a low-grade Pb-Zn sulfide ore for the first time. Based on mineralogy and heavy liquid separation tests, it was found that the rejection of gangue by the BDMC prior to grinding and flotation was promising. The results revealed that the particle size clearly affected the heavy liquid separation process. The effects of several parameters, such as medium specific gravity (SG), spigot diameter, tilt angle, cone angle and medium/ore mass ratio, on the yield of floats and on the metal recoveries in the floats were examined and the optimal parameters were determined. The results showed that 51.22% of floats were obtained with a lead recovery of 7.92% and a zinc recovery of 12.50%. The extended tests were further carried out with the BDMC being capable of throughputs about 3 t/h, which verified the results obtained in the laboratory experiments. The use of this equipment to pre-treat the refractory ore is promising.
Źródło:
Physicochemical Problems of Mineral Processing; 2019, 55, 4; 981-990
1643-1049
2084-4735
Pojawia się w:
Physicochemical Problems of Mineral Processing
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Fault Diagnosis of Sensors for T-type Three-Level Inverter-fed Dual Three-Phase Permanent Magnet Synchronous Motor Drives
Autorzy:
Wang, Xueqing
Wang, Zheng
Wang, Wei
Cheng, Ming
Powiązania:
https://bibliotekanauki.pl/articles/1193713.pdf
Data publikacji:
2019
Wydawca:
Politechnika Wrocławska. Oficyna Wydawnicza Politechniki Wrocławskiej
Tematy:
fault diagnosis
sensor fault
T-type inverter
three-level inverter
dual
three-phase
PMSM
Opis:
To improve the reliability of motor system, this paper investigates the sensor fault diagnosis methods for T-type inverter-fed dual three-phase permanent magnet synchronous motor (PMSM) drives. Generally, a T-type three-level inverter-fed dual three-phase motor drive utilizes four phase-current sensors, two direct current (DC)-link voltage sensors and one speed sensor. A series of diagnostic methods have been comprehensively proposed for the three types of sensor faults. Both the sudden error change and gradual error change of sensor faults are considered. Firstly, the diagnosis of speed sensor fault was achieved by monitoring the error between the rotating speed of stator flux and the value from speed sensor. Secondly, the large high-frequency voltage ripple of voltage difference between the estimated voltage and the reference voltage was used to identify the voltage sensor faults, and the faulty voltage sensor was determined according to the deviation of voltage difference. Thirdly, the abnormal current amplitude on harmonic subspace was adopted to identify the current sensor faults, and the faulty current sensor was located by distinguishing the current trajectory on harmonic subspace. The experiments have been taken on a laboratory prototype to verify the effectiveness of the proposed fault diagnosis schemes.
Źródło:
Power Electronics and Drives; 2019, 4, 39; 165-176
2451-0262
2543-4292
Pojawia się w:
Power Electronics and Drives
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Simplified Model for Predicting Fabric Thermal Resistance According to its Microstructural Parameters
Uproszczony model dla przewidywania oporu termicznego tkanin w zależności od ich parametrów mikrostruktury
Autorzy:
Wei, J.
Xu, S.
Liu, H.
Zheng, L.
Qian, Y.
Powiązania:
https://bibliotekanauki.pl/articles/233513.pdf
Data publikacji:
2015
Wydawca:
Sieć Badawcza Łukasiewicz - Instytut Biopolimerów i Włókien Chemicznych
Tematy:
fabric model
thermal resistance
microstructure
correlation coefficient
model tkaniny
opór termiczny tkanin
mikrostruktura
współczynnik korelacji
Opis:
This paper presents a modified model to calculate the thermal resistance of woven and knitted fabrics according to the microstructural parameters. The model was established by analysing the heat transfer process in the simplified basic unit of the fabrics. The model was modified and checked by experimental values of various fabric samples. Pearson correlation coefficients between the thermal resistance and fabric structural parameters were calculated. Results indicate that fabric thermal resistance can be predicted by the modified equation satisfactorily. The Pearson correlation coefficient from high to low follows such a sequence: fabric thickness, fabric volume density, fabric structural parameter a, fibre volume density, and fibre thermal conductivity.
W artykule przedstawiono zmodyfikowany model pozwalający obliczyć opór termiczny tkanin i dzianin w zależności od parametrów ich mikrostruktury. Model został skonstruowany poprzez analizę procesu przepływu ciepła przez uproszczoną jednostkę płaskiego materiału włókienniczego. Model został sprawdzony w praktyce przez badanie różnych próbek tkanin i dzianin. Przy ocenie zastosowano porównanie współczynników korelacji Pearsona między oporem termicznym i parametrami strukturalnymi. Wyniki wskazują, że termiczną izolację płaskich materiałów włókienniczych można przewidzieć w zadowalającym stopniu przez zaproponowane zmodyfikowane równania. Współczynniki korelacji Pearsona począwszy od dużych do małych można uszeregować dla następujących parametrów: grubość tkaniny, gęstość właściwa tkaniny, parametry strukturalne, gęstość właściwa włókien i przewodność cieplna włókien.
Źródło:
Fibres & Textiles in Eastern Europe; 2015, 4 (112); 57-60
1230-3666
2300-7354
Pojawia się w:
Fibres & Textiles in Eastern Europe
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
A unified calculation of the optical and EPR spectral data for the trigonal Cr³⁺ center in Cr³⁺-doped α-RbAl(SO₄)₂·12H₂O alum crystal
Autorzy:
Li, Xiao-Wu
Mei, Yang
Wei, Cheng-Fu
Zheng, Wen-Chen
Powiązania:
https://bibliotekanauki.pl/articles/1070555.pdf
Data publikacji:
2016-03
Wydawca:
Polska Akademia Nauk. Instytut Fizyki PAN
Tematy:
71.70.Ch
76.30.Fc
78.40.Ha
78.55.Hx
Opis:
The optical band positions and the spin-Hamiltonian parameters (g factors g_{∥}, g_{⊥}, and zero-field splitting parameter D) of alum α-RbAl(SO₄)₂·12H₂O:Cr³⁺ are calculated by diagonalizing the 120× 120 complete energy matrix based on the two-spin-orbit-coupling-parameter model. The model takes into account not only the contributions due to the spin-orbit-coupling parameter of central d^{n} ion in the conventional crystal field theory, but also those due to ligands via covalence effect. The calculation indicates that the fourteen observed spectral data (eleven optical band positions and three spin-Hamiltonian parameters) can be reasonably and uniformly explained with four adjustable parameters (the Racah parameters B, C, intrinsic parameter A̅₄(R) in the superposition model, and the trigonal distortion angle β). The calculations also suggest that contrary to the previous findings, the trigonal distortion of Cr³⁺ (entering the Al³⁺ site in the host crystal) center in α-RbAl(SO₄)₂·12H₂O is induced mainly by the oxygen (or water) octahedron around the Cr³⁺ ion rather than the more distant neighbors.
Źródło:
Acta Physica Polonica A; 2016, 129, 3; 340-343
0587-4246
1898-794X
Pojawia się w:
Acta Physica Polonica A
Dostawca treści:
Biblioteka Nauki
Artykuł
Tytuł:
Acoustic emission characteristics of deep granite under triaxial cylic loading and unloading
Autorzy:
Pei, Feng
Zhang, Yue-Zheng
Zhao, Ji-Wei
Geng, Jing-Ming
Powiązania:
https://bibliotekanauki.pl/articles/1402362.pdf
Data publikacji:
2020
Wydawca:
Politechnika Wrocławska. Wydział Geoinżynierii, Górnictwa i Geologii. Instytut Górnictwa
Tematy:
deep granite
acoustic emission
frequency spectrum
precursory feature recognition
Opis:
In order to obtain the damage and AE characteristics of deep granite, TAW-2000 electrohydraulic servo rigid testing equipment and PCI-2 acoustic emission acquisition system were used to clarify the relationship between AE characteristics and stress level under conventional triaxial and cyclic loading and unloading. The results show that: AE characteristic parameters such as counts and energy under different confining pressures have good consistency in reflecting cracks growth process, which correspond to the stress level of rock sample; Before the critical failure, the AE amplitude increases significantly and extremely high peak frequency and extremely low peak frequency began to appear; The phenomenon that peak frequency band number increases significantly can be used as the precursor of rock failure; The change trend of characteristic parameters, amplitude and peak frequency band were related to the stress level of rock, and the loading path has little influence on it, which verified the effectiveness of AE precursory feature recognition; FR value decreases continuously with the increase of cyclic stress level and overall trend is downward, which indicated that AE memory gradually decreases as the stress level increases; From the perspective of damage mechanics, the AE characteristics of rock before failure are explained reasonably by the development of damage rate.
Źródło:
Mining Science; 2020, 27; 209-225
2300-9586
2353-5423
Pojawia się w:
Mining Science
Dostawca treści:
Biblioteka Nauki
Artykuł

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