Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large v...Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9)with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9)is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.展开更多
We systematically investigate the planar transport properties of the two-dimensional layered compound GaGeTe. The results reveal distinct anisotropies in both the longitudinal and planar Hall resistances as the magnet...We systematically investigate the planar transport properties of the two-dimensional layered compound GaGeTe. The results reveal distinct anisotropies in both the longitudinal and planar Hall resistances as the magnetic field is rotated within the plane, which are well-captured by the planar Hall effect(PHE) model. Further analysis indicates that the primary contribution to the PHE in GaGeTe arises from its ferromagnetic component and anisotropic orbital resistance, rather than topologically nontrivial chiral anomaly. This work deepens our understanding of the PHE mechanism and offers valuable insights for the development of planar Hall sensors based on two-dimensional materials.展开更多
The antiferromagnetic(AFM)semimetal NdSb is well known for the interplay between its exotic magnetism and topological properties.However,its magnetism remains poorly understood.In this study,we thoroughly investigated...The antiferromagnetic(AFM)semimetal NdSb is well known for the interplay between its exotic magnetism and topological properties.However,its magnetism remains poorly understood.In this study,we thoroughly investigated the magnetization of NdSb single crystals with a high magnetic field(H)of up to 30T applied in various directions.We found that the AFM phase is suppressed by a magnetic field of 9.41T when H‖[100]and 11.25T when H‖[110],whereas the suppression field ranges from 9.41 to 10.67T with a hysteresis of 1.26T when H‖[111].The magnetization of H‖[100],which is an easy direction with a typical magnetic transition,was studied in detail.The AFM phase with H‖[100]was suppressed at lower temperatures,disappearing at approximately 6.25 K.The critical exponents β=0.234(3),γ=0.824(6),and δ=4.90(6)were obtained for H‖[100],and aligned with a tricritical mean-field model.Analysis of the critical behavior suggests a fieldinduced tricritical phenomenon for H‖[100].An H-T phase diagram for an NdSb single crystal was constructed for H‖[100],revealing a field-induced first-order transition and a tricritical point(TCP)at T_(tr)=6.25K and H_(tr)=9.41 T.The clarification of the multiple magnetic phases and transitions in NdSb provides crucial insights into the correlation between its magnetism and topology.展开更多
Ⅰ.SAMPLE SYNTHESIS.Single erystals of NdSb were synthesized by an In-fhux method.High purity chemical elements of Nd(99.9% purity,Alfa Aesar),8b(99.999%,Aladdin),and In beads(99.99%,Aladdin)were thoroughly mixed in a...Ⅰ.SAMPLE SYNTHESIS.Single erystals of NdSb were synthesized by an In-fhux method.High purity chemical elements of Nd(99.9% purity,Alfa Aesar),8b(99.999%,Aladdin),and In beads(99.99%,Aladdin)were thoroughly mixed in a glove-box filledwith argon atmosphere,maintaining an atomie ratio of Nd:Sb:in=1:1:20.展开更多
Flexible job shop scheduling problems(FJSP)have received much attention from academia and industry for many years.Due to their exponential complexity,swarm intelligence(SI)and evolutionary algorithms(EA)are developed,...Flexible job shop scheduling problems(FJSP)have received much attention from academia and industry for many years.Due to their exponential complexity,swarm intelligence(SI)and evolutionary algorithms(EA)are developed,employed and improved for solving them.More than 60%of the publications are related to SI and EA.This paper intents to give a comprehensive literature review of SI and EA for solving FJSP.First,the mathematical model of FJSP is presented and the constraints in applications are summarized.Then,the encoding and decoding strategies for connecting the problem and algorithms are reviewed.The strategies for initializing algorithms?population and local search operators for improving convergence performance are summarized.Next,one classical hybrid genetic algorithm(GA)and one newest imperialist competitive algorithm(ICA)with variables neighborhood search(VNS)for solving FJSP are presented.Finally,we summarize,discus and analyze the status of SI and EA for solving FJSP and give insight into future research directions.展开更多
Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liqui...Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liquid.In this work we report the synthesis and magnetism study of the monocrystalline Mn_(2)Ga_(2)S_(5),featuring both the van derWaals structure and a bilayered triangular Mn lattice.Magnetic susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature θ_(w)~-260 K and a high spin S=5/2 Mn^(2+) state.However,no long range magnetic order has been found down to 2 K,and a spin freezing transition is found to occur at around 12 K well below its θ_(w).This yields a frustration index of f=-θ_(w)/T_(f)≈22,an indication that the system is highly frustrated.The absence of a double-peak structure in magnetic specific heat compared with the TM_(2)S_(4) compounds implies that the spin freezing behavior in Mn_(2)Ga_(2)S_(5)is a result of the competition between exchange interactions and the 2D crystalline structure.Our results suggest that the layered Mn_(2)Ga_(2)S_(5)would be an excellent candidate for investigating the physics of 2D magnetism and spin disordered state.展开更多
We systematically investigate in-plane transport properties of ternary chalcogenideBi_(2)Rh_(3)Se_(2).Upon rotating the magnetic field within the plane of the sample, one can distinctly detect the presence of both pla...We systematically investigate in-plane transport properties of ternary chalcogenideBi_(2)Rh_(3)Se_(2).Upon rotating the magnetic field within the plane of the sample, one can distinctly detect the presence of both planar Hall resistance and anisotropic longitudinal resistance, and the phenomena appeared are precisely described by the theoretical formulation of the planar Hall effect (PHE). In addition, anisotropic orbital magnetoresistance rather than topologically nontrivial chiral anomalies dominates the PHE in Bi_(2)Rh_(3)Se_(2). The finding not only provides another platform for understanding the mechanism of PHE, but could also be beneficial for future planar Hall sensors based on two-dimensional materials.展开更多
We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitio...We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a 3 × 3 × 2 modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate Ⅰ phase, named as C-Ⅰ phase, to the low temperature commensurate Ⅱ(C-Ⅱ) phase. All the results can be understood in terms of charge density wave(CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.展开更多
Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals.We demonstrate that the carrier density,as well as the mobility,of Dirac semimeta...Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals.We demonstrate that the carrier density,as well as the mobility,of Dirac semimetal Cd_(3)As_(2) nanoplates can be effectively tuned via in situ thermal treatment at 350 K for one hour,resulting in non-monotonic evolution by virtue of the thermal cycling treatments.The upward shift of Fermi level relative to the Dirac nodes blurs the surface Fermi-arc states,accompanied by an anomalous phase shift in the oscillations of bulk states,due to a change in the topology of the electrons.Meanwhile,the oscillation peaks of bulk longitudinal magnetoresistivity shift at high fields,due to their coupling to the oscillations of the surface Fermi-arc states.Our work provides a thermal control mechanism for the manipulation of quantum states in Dirac semimetal Cd_(3)As_(2) at high temperatures,via their carrier density.展开更多
Given that group technology can reduce the changeover time of equipment,broaden the productivity,and enhance the flexibility of manufacturing,especially cellular manufacturing,group scheduling problems(GSPs)have elici...Given that group technology can reduce the changeover time of equipment,broaden the productivity,and enhance the flexibility of manufacturing,especially cellular manufacturing,group scheduling problems(GSPs)have elicited considerable attention in the academic and industry practical literature.There are two issues to be solved in GSPs:One is how to allocate groups into the production cells in view of major setup times between groups and the other is how to schedule jobs in each group.Although a number of studies on GSPs have been published,few integrated reviews have been conducted so far on considered problems with different constraints and their optimization methods.To this end,this study hopes to shorten the gap by reviewing the development of research and analyzing these problems.All literature is classified according to the number of objective functions,number of machines,and optimization algorithms.The classical mathematical models of single-machine,permutation,and distributed flowshop GSPs based on adjacent and position-based modeling methods,respectively,are also formulated.Last but not least,outlooks are given for outspread problems and problem algorithms for future research in the fields of group scheduling.展开更多
The distributed hybrid flow shop scheduling problem(DHFSP),which integrates distributed manufacturing models with parallel machines,has gained significant attention.However,in actual scheduling,some adjacent machines ...The distributed hybrid flow shop scheduling problem(DHFSP),which integrates distributed manufacturing models with parallel machines,has gained significant attention.However,in actual scheduling,some adjacent machines do not have buffers between them,resulting in blocking.This paper focuses on addressing the DHFSP with blocking constraints(DBHFSP)based on the actual production conditions.To solve DBHFSP,we construct a mixed integer linear programming(MILP)model for DBHFSP and validate its correctness using the Gurobi solver.Then,an advanced iterated greedy(AIG)algorithm is designed to minimize the makespan,in which we modify the Nawaz,Enscore,and Ham(NEH)heuristic to solve blocking constraints.To balance the global and local search capabilities of AIG,two effective inter-factory neighborhood search strategies and a swap-based local search strategy are designed.Additionally,each factory is mutually independent,and the movement within one factory does not affect the others.In view of this,we specifically designed a memory-based decoding method for insertion operations to reduce the computation time of the objective.Finally,two shaking strategies are incorporated into the algorithm to mitigate premature convergence.Five advanced algorithms are used to conduct comparative experiments with AIG on 80 test instances,and experimental results illustrate that the makespan and the relative percentage increase(RPI)obtained by AIG are 1.0%and 86.1%,respectively,better than the comparative algorithms.展开更多
To meet the multi-cooperation production demand of enterprises,the distributed permutation flow shop scheduling problem(DPFSP)has become the frontier research in the field of manufacturing systems.In this paper,we inv...To meet the multi-cooperation production demand of enterprises,the distributed permutation flow shop scheduling problem(DPFSP)has become the frontier research in the field of manufacturing systems.In this paper,we investigate the DPFSP by minimizing a makespan criterion under the constraint of sequence-dependent setup times.To solve DPFSPs,significant developments of some metaheuristic algorithms are necessary.In this context,a simple and effective improved iterated greedy(NIG)algorithm is proposed to minimize makespan in DPFSPs.According to the features of DPFSPs,a two-stage local search based on single job swapping and job block swapping within the key factory is designed in the proposed algorithm.We compare the proposed algorithm with state-of-the-art algorithms,including the iterative greedy algorithm(2019),iterative greedy proposed by Ruiz and Pan(2019),discrete differential evolution algorithm(2018),discrete artificial bee colony(2018),and artificial chemical reaction optimization(2017).Simulation results show that NIG outperforms the compared algorithms.展开更多
The single crystalline nanostructure of organic semiconductors provides a very promising class of materials for applications in modern optoelectronic devices. However, morphology control and optoelectronic property mo...The single crystalline nanostructure of organic semiconductors provides a very promising class of materials for applications in modern optoelectronic devices. However, morphology control and optoelectronic property modulation of high quality single crystalline samples remain a challenge. Here, we report the morphology-controlled growth of single crystalline nanorod arrays of perylene- 3,4,9,10-tetracarboxylic dianhydride （IrFCDA）. We demonstrate that, unlike FTCDA film, PTCDA nanorods exhibits optical waveguide features, enhanced absorption, and Frenkel excitation emission in the visible region. Additionally, we measured the electrical properties of PTCDA nanorods, including the conductivity along the growth direction of the nanorod, which is roughly 0.61 S-m i （much higher than that of pure crystalline PTCDA films）.展开更多
The superconductivity and nontrivial topological electronic state are key hallmarks of topological superconductors.Here,we focus on the transport signals of possible topological surface state in the topological superc...The superconductivity and nontrivial topological electronic state are key hallmarks of topological superconductors.Here,we focus on the transport signals of possible topological surface state in the topological superconductor candidate β-PdBi_(2) nanoflake with a thickness of 21 nm.The resistance demonstrates a semiconductor-metal transition followed by an upturned behavior as the temperature decreases.A large and unsaturated longitudinal magnetoresistance(MR),accompanied by distinct Shubnikov-de Hass oscillation in Hall resistance,is observed.An analysis of Hall resistance reveals that the carriers present the characteristics of relativistic particles with small effective mass and extremely high mobility.The angle-dependent quantum oscillations demonstrate a two-dimensional Fermi surface topology.A giant anisotropic MR as large as 98%is detected when rotating the magnetic field.These results provide the possible transport signals of a nontrivial topological electronic state,establishing a further understanding of the topological properties of the low-dimensional topological superconductor candidate β-PdBi_(2).展开更多
The hybrid flow shop group scheduling problem(HFGSP)with the delivery time windows has been widely studied owing to its better flexibility and suitability for the current just-in-time production mode.However,there are...The hybrid flow shop group scheduling problem(HFGSP)with the delivery time windows has been widely studied owing to its better flexibility and suitability for the current just-in-time production mode.However,there are several unresolved challenges in problem modeling and algorithmic design tailored for HFGSP.In our study,we place emphasis on the constraint of timeliness.Therefore,this paper first constructs a mixed integer linear programming model of HFGSP with sequence-dependent setup time and delivery time windows to minimize the total weighted earliness and tardiness(TWET).Then a penalty groups-assisted iterated greedy integrating idle time insertion(PG IG ITI)is proposed to solve the above problem.In the PG IG ITI,a double decoding strategy is proposed based on the earliest available machine rule and the idle time insertion rule to calculate the TWET value.Subsequently,to reduce the amount of computation,a skip-based destruction and reconstruction strategy is designed,and a penalty groups-assisted local search is proposed to further improve the quality of the solution by disturbing the penalized groups,i.e.,early and tardy groups.Finally,through comprehensive statistical experiments on 270 test instances,the results prove that the proposed algorithm is effective compared to four state-of-the-art algorithms.展开更多
基金supported by the National Key Research and Development Program(Grant Nos.2024YFA1611200 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.12141002 and 52088101)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB1270000)。
文摘Rare-earth based frustrated magnets have attracted great attention as excellent candidates for magnetic refrigeration at sub-Kelvin temperatures,while the experimental identification of systems exhibiting both large volumetric cooling capacity and reduced working temperatures far below 1K remains a challenge.Here,through ultra-low temperature magnetism and thermodynamic characterizations,we unveil the large magnetocaloric effect(MCE)realized at sub-Kelvin temperatures in the frustrated Kagome antiferromagnet Gd_(3)BWO_(9)with T_(N)∼1.0 K.The isothermal magnetization curves indicate the existence of field(B)induced anisotropic magnetic phase diagrams,where four distinct magnetic phases for B‖c-axis and five magnetic phases for B‖ab-plane are identified at T<T_(N).The analysis of magnetic entropy S(B,T)data and direct adiabatic demagnetization tests reveal remarkable cooling performance at sub-Kelvin temperatures featured by a large volumetric entropy density of 502.2 mJ/K/cm^(3)and a low attainable minimal temperature T_(min)∼168mK from the initial cooling condition of 2K and 6 T,surpassing most Gd-based refrigerants previously documented in temperature ranges of 0.25–4 K.The realized T_(min)∼168mK far below T_(N)∼1.0K in Gd_(3)BWO_(9)is related to the combined effects of magnetic frustration and criticality-enhanced MCE,which together leave substantial magnetic entropy at reduced temperatures by enhancing spin fluctuations.
基金Project supported by the National Key Research and Development Program of China (Grant No. 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos. U19A2093 and 11904002)+1 种基金the Excellent Youth Project of the Natural Science Foundation of Anhui Province, China (Grant No. 2308085Y07)the Anhui Provincial Major Science and Technology Project (Grant No. s202305a12020005)。
文摘We systematically investigate the planar transport properties of the two-dimensional layered compound GaGeTe. The results reveal distinct anisotropies in both the longitudinal and planar Hall resistances as the magnetic field is rotated within the plane, which are well-captured by the planar Hall effect(PHE) model. Further analysis indicates that the primary contribution to the PHE in GaGeTe arises from its ferromagnetic component and anisotropic orbital resistance, rather than topologically nontrivial chiral anomaly. This work deepens our understanding of the PHE mechanism and offers valuable insights for the development of planar Hall sensors based on two-dimensional materials.
基金supported by the National Key R&D Program of China(Grant No.2024YFA1611103)the National Natural Science Foundation of China(Grant Nos.12374128,12374129,12074386,11974181,12204006,and 12250410238)+6 种基金the Fujian Natural Science Foundation Project(Grant No.2024J08082)the Foundation for the Introduction of High-Level Talents and the Scientific Research Launch Project of Sanming University(Grant No.113/KD23016P)Fujian Key Technology Innovation Projects(University Category)(Grant No.2022G02010)the Anhui Provincial Major S&T Project(Grant No.202305a12020005)the Alliance of International Science Organizations(Grant Nos.ANSO-VF-2022-03 and ANSO-VF-2023-03)supported by the Basic Research Program of the Chinese Academy of Sciences Based on Major Scientific Infrastructures(Grant No.JZHKYPT-2021-08)the High Magnetic Field Laboratory of Anhui Province under Contract No.AHHMFX-2020-02。
文摘The antiferromagnetic(AFM)semimetal NdSb is well known for the interplay between its exotic magnetism and topological properties.However,its magnetism remains poorly understood.In this study,we thoroughly investigated the magnetization of NdSb single crystals with a high magnetic field(H)of up to 30T applied in various directions.We found that the AFM phase is suppressed by a magnetic field of 9.41T when H‖[100]and 11.25T when H‖[110],whereas the suppression field ranges from 9.41 to 10.67T with a hysteresis of 1.26T when H‖[111].The magnetization of H‖[100],which is an easy direction with a typical magnetic transition,was studied in detail.The AFM phase with H‖[100]was suppressed at lower temperatures,disappearing at approximately 6.25 K.The critical exponents β=0.234(3),γ=0.824(6),and δ=4.90(6)were obtained for H‖[100],and aligned with a tricritical mean-field model.Analysis of the critical behavior suggests a fieldinduced tricritical phenomenon for H‖[100].An H-T phase diagram for an NdSb single crystal was constructed for H‖[100],revealing a field-induced first-order transition and a tricritical point(TCP)at T_(tr)=6.25K and H_(tr)=9.41 T.The clarification of the multiple magnetic phases and transitions in NdSb provides crucial insights into the correlation between its magnetism and topology.
文摘Ⅰ.SAMPLE SYNTHESIS.Single erystals of NdSb were synthesized by an In-fhux method.High purity chemical elements of Nd(99.9% purity,Alfa Aesar),8b(99.999%,Aladdin),and In beads(99.99%,Aladdin)were thoroughly mixed in a glove-box filledwith argon atmosphere,maintaining an atomie ratio of Nd:Sb:in=1:1:20.
基金supported in part by the National Natural Science Foundation of China(61603169,61773192,61803192)in part by the funding from Shandong Provincial Key Laboratory for Novel Distributed Computer Software Technologyin part by Singapore National Research Foundation(NRF-RSS2016-004)
文摘Flexible job shop scheduling problems(FJSP)have received much attention from academia and industry for many years.Due to their exponential complexity,swarm intelligence(SI)and evolutionary algorithms(EA)are developed,employed and improved for solving them.More than 60%of the publications are related to SI and EA.This paper intents to give a comprehensive literature review of SI and EA for solving FJSP.First,the mathematical model of FJSP is presented and the constraints in applications are summarized.Then,the encoding and decoding strategies for connecting the problem and algorithms are reviewed.The strategies for initializing algorithms?population and local search operators for improving convergence performance are summarized.Next,one classical hybrid genetic algorithm(GA)and one newest imperialist competitive algorithm(ICA)with variables neighborhood search(VNS)for solving FJSP are presented.Finally,we summarize,discus and analyze the status of SI and EA for solving FJSP and give insight into future research directions.
基金supported by the National Natural Science Foundation of China(Grant Nos.U1832214,11774007,U2032213,and 12104461).
文摘Geometrical frustration in low-dimensional magnetic systems has been an intriguing research aspect,where the suppression of conventional magnetic order may lead to exotic ground states such as spin glass or spin liquid.In this work we report the synthesis and magnetism study of the monocrystalline Mn_(2)Ga_(2)S_(5),featuring both the van derWaals structure and a bilayered triangular Mn lattice.Magnetic susceptibility reveals a significant antiferromagnetic interaction with a Curie-Weiss temperature θ_(w)~-260 K and a high spin S=5/2 Mn^(2+) state.However,no long range magnetic order has been found down to 2 K,and a spin freezing transition is found to occur at around 12 K well below its θ_(w).This yields a frustration index of f=-θ_(w)/T_(f)≈22,an indication that the system is highly frustrated.The absence of a double-peak structure in magnetic specific heat compared with the TM_(2)S_(4) compounds implies that the spin freezing behavior in Mn_(2)Ga_(2)S_(5)is a result of the competition between exchange interactions and the 2D crystalline structure.Our results suggest that the layered Mn_(2)Ga_(2)S_(5)would be an excellent candidate for investigating the physics of 2D magnetism and spin disordered state.
基金supported by the National Natural Science Foundation of China (Grant Nos.U19A2093,11904002,and 12074372)the Excellent Youth Project of Natural Science Foundation of Anhui Province (Grant No.2308085Y07)。
文摘We systematically investigate in-plane transport properties of ternary chalcogenideBi_(2)Rh_(3)Se_(2).Upon rotating the magnetic field within the plane of the sample, one can distinctly detect the presence of both planar Hall resistance and anisotropic longitudinal resistance, and the phenomena appeared are precisely described by the theoretical formulation of the planar Hall effect (PHE). In addition, anisotropic orbital magnetoresistance rather than topologically nontrivial chiral anomalies dominates the PHE in Bi_(2)Rh_(3)Se_(2). The finding not only provides another platform for understanding the mechanism of PHE, but could also be beneficial for future planar Hall sensors based on two-dimensional materials.
基金supported by the National Natural Science Foundation of China(Grant Nos.U19A2093,11904002,U2032214,U2032163,and 11774353)the National Key Research and Development Program of China(Grant No.2017YFA0403502)+1 种基金the Natural Science Foundation of Anhui Province(Grant No.1908085QA15)the Youth Innovation Promotion Association CAS(Grant No.2017483)。
文摘We report comprehensive transport, electron microscopy and Raman spectroscopy studies on transition-metal chalcogenides Cu1.89Te single crystals. The metallic Cu1.89Te displays successive metal-semiconductor transitions at low temperatures and almost ideal linear MR when magnetic field up to 33 T. Through the electron diffraction patterns, the stable room-temperature phase is identified as a 3 × 3 × 2 modulated superstructure based on the Nowotny hexagonal structure. The superlattice spots of transmission electron microscopy and scanning tunneling microscopy clearly show the structural transitions from the room-temperature commensurate Ⅰ phase, named as C-Ⅰ phase, to the low temperature commensurate Ⅱ(C-Ⅱ) phase. All the results can be understood in terms of charge density wave(CDW) instability, yielding intuitive evidences for the CDW formations in Cu1.89Te. The additional Raman modes below room temperature further reveal that the zone-folded phonon modes may play an important role on the CDW transitions. Our research sheds light on the novel electron features of Cu1.89Te at low temperature, and may provide potential applications for future nano-devices.
基金the National Key Research and Development Program of China(Grant No.2016YFA0401003)the National Natural Science Foundation of China(Grant Nos.11804340,11774353,U19A2093,and U1732274)the CAS/SAFEA International Partnership Program for Creative Research Teams of China。
文摘Tunable carrier density plays a key role in the investigation of novel transport properties in three-dimensional topological semimetals.We demonstrate that the carrier density,as well as the mobility,of Dirac semimetal Cd_(3)As_(2) nanoplates can be effectively tuned via in situ thermal treatment at 350 K for one hour,resulting in non-monotonic evolution by virtue of the thermal cycling treatments.The upward shift of Fermi level relative to the Dirac nodes blurs the surface Fermi-arc states,accompanied by an anomalous phase shift in the oscillations of bulk states,due to a change in the topology of the electrons.Meanwhile,the oscillation peaks of bulk longitudinal magnetoresistivity shift at high fields,due to their coupling to the oscillations of the surface Fermi-arc states.Our work provides a thermal control mechanism for the manipulation of quantum states in Dirac semimetal Cd_(3)As_(2) at high temperatures,via their carrier density.
基金This work is partially supported by the National Natural Science Foundation of China(Grant Nos.61803192,61966012,61973203,and 62106073)Guangyue Young Scholar Innovation Team of Liaocheng University(Grant No.LCUGYTD2022-03)+1 种基金the Youth Innovation Talent Introduction and Education Program support from Shandong Province Colleges and Universities,the Natural Science Foundation of Hunan Province(Grant No.2021JJ40116)the Natural Science Foundation of Shandong Province(Grant Nos.ZR2021QE195 and ZR2021QF036).
文摘Given that group technology can reduce the changeover time of equipment,broaden the productivity,and enhance the flexibility of manufacturing,especially cellular manufacturing,group scheduling problems(GSPs)have elicited considerable attention in the academic and industry practical literature.There are two issues to be solved in GSPs:One is how to allocate groups into the production cells in view of major setup times between groups and the other is how to schedule jobs in each group.Although a number of studies on GSPs have been published,few integrated reviews have been conducted so far on considered problems with different constraints and their optimization methods.To this end,this study hopes to shorten the gap by reviewing the development of research and analyzing these problems.All literature is classified according to the number of objective functions,number of machines,and optimization algorithms.The classical mathematical models of single-machine,permutation,and distributed flowshop GSPs based on adjacent and position-based modeling methods,respectively,are also formulated.Last but not least,outlooks are given for outspread problems and problem algorithms for future research in the fields of group scheduling.
基金This work was jointly supported by the National Natural Science Foundation of Shandong Province(No.ZR2023MF022)National Natural Science Foundation of China(Nos.61973203,62173216,and 62173356)Guangyue Youth Scholar Innovation Talent Program Support from Liaocheng University(No.LCUGYTD2022-03).
文摘The distributed hybrid flow shop scheduling problem(DHFSP),which integrates distributed manufacturing models with parallel machines,has gained significant attention.However,in actual scheduling,some adjacent machines do not have buffers between them,resulting in blocking.This paper focuses on addressing the DHFSP with blocking constraints(DBHFSP)based on the actual production conditions.To solve DBHFSP,we construct a mixed integer linear programming(MILP)model for DBHFSP and validate its correctness using the Gurobi solver.Then,an advanced iterated greedy(AIG)algorithm is designed to minimize the makespan,in which we modify the Nawaz,Enscore,and Ham(NEH)heuristic to solve blocking constraints.To balance the global and local search capabilities of AIG,two effective inter-factory neighborhood search strategies and a swap-based local search strategy are designed.Additionally,each factory is mutually independent,and the movement within one factory does not affect the others.In view of this,we specifically designed a memory-based decoding method for insertion operations to reduce the computation time of the objective.Finally,two shaking strategies are incorporated into the algorithm to mitigate premature convergence.Five advanced algorithms are used to conduct comparative experiments with AIG on 80 test instances,and experimental results illustrate that the makespan and the relative percentage increase(RPI)obtained by AIG are 1.0%and 86.1%,respectively,better than the comparative algorithms.
基金This work was jointly supported by the National Natural Science Foundation of China(Nos.61803192,61973203,61966012,61773192,61603169,61773246,and 71533001)Thanks for the support of Shandong province colleges and universities youth innovation talent introduction and education program.
文摘To meet the multi-cooperation production demand of enterprises,the distributed permutation flow shop scheduling problem(DPFSP)has become the frontier research in the field of manufacturing systems.In this paper,we investigate the DPFSP by minimizing a makespan criterion under the constraint of sequence-dependent setup times.To solve DPFSPs,significant developments of some metaheuristic algorithms are necessary.In this context,a simple and effective improved iterated greedy(NIG)algorithm is proposed to minimize makespan in DPFSPs.According to the features of DPFSPs,a two-stage local search based on single job swapping and job block swapping within the key factory is designed in the proposed algorithm.We compare the proposed algorithm with state-of-the-art algorithms,including the iterative greedy algorithm(2019),iterative greedy proposed by Ruiz and Pan(2019),discrete differential evolution algorithm(2018),discrete artificial bee colony(2018),and artificial chemical reaction optimization(2017).Simulation results show that NIG outperforms the compared algorithms.
文摘The single crystalline nanostructure of organic semiconductors provides a very promising class of materials for applications in modern optoelectronic devices. However, morphology control and optoelectronic property modulation of high quality single crystalline samples remain a challenge. Here, we report the morphology-controlled growth of single crystalline nanorod arrays of perylene- 3,4,9,10-tetracarboxylic dianhydride （IrFCDA）. We demonstrate that, unlike FTCDA film, PTCDA nanorods exhibits optical waveguide features, enhanced absorption, and Frenkel excitation emission in the visible region. Additionally, we measured the electrical properties of PTCDA nanorods, including the conductivity along the growth direction of the nanorod, which is roughly 0.61 S-m i （much higher than that of pure crystalline PTCDA films）.
基金supported by the National Natural Science Foundation of China(Grant Nos.U19A2093,11904002,and U2032163)the National Key Research and Development Program of China(Grant No.2021YFA1600201)the Youth Innovation Promotion Association of Chinese Academy of Sciences(Grant No.2021117)。
文摘The superconductivity and nontrivial topological electronic state are key hallmarks of topological superconductors.Here,we focus on the transport signals of possible topological surface state in the topological superconductor candidate β-PdBi_(2) nanoflake with a thickness of 21 nm.The resistance demonstrates a semiconductor-metal transition followed by an upturned behavior as the temperature decreases.A large and unsaturated longitudinal magnetoresistance(MR),accompanied by distinct Shubnikov-de Hass oscillation in Hall resistance,is observed.An analysis of Hall resistance reveals that the carriers present the characteristics of relativistic particles with small effective mass and extremely high mobility.The angle-dependent quantum oscillations demonstrate a two-dimensional Fermi surface topology.A giant anisotropic MR as large as 98%is detected when rotating the magnetic field.These results provide the possible transport signals of a nontrivial topological electronic state,establishing a further understanding of the topological properties of the low-dimensional topological superconductor candidate β-PdBi_(2).
基金This work was supported by the Natural Science Foundation of Shandong province(No.ZR2023MF022)National Natural Science Foundation of China(Nos.61973203,61803192,62106073,and 61966012)Guangyue Young Scholar Innovation Team of Liaocheng University(No.LCUGYTD2022-03).
文摘The hybrid flow shop group scheduling problem(HFGSP)with the delivery time windows has been widely studied owing to its better flexibility and suitability for the current just-in-time production mode.However,there are several unresolved challenges in problem modeling and algorithmic design tailored for HFGSP.In our study,we place emphasis on the constraint of timeliness.Therefore,this paper first constructs a mixed integer linear programming model of HFGSP with sequence-dependent setup time and delivery time windows to minimize the total weighted earliness and tardiness(TWET).Then a penalty groups-assisted iterated greedy integrating idle time insertion(PG IG ITI)is proposed to solve the above problem.In the PG IG ITI,a double decoding strategy is proposed based on the earliest available machine rule and the idle time insertion rule to calculate the TWET value.Subsequently,to reduce the amount of computation,a skip-based destruction and reconstruction strategy is designed,and a penalty groups-assisted local search is proposed to further improve the quality of the solution by disturbing the penalized groups,i.e.,early and tardy groups.Finally,through comprehensive statistical experiments on 270 test instances,the results prove that the proposed algorithm is effective compared to four state-of-the-art algorithms.
