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Shijie Sun,Maolin Tian,Hongtian Xiao,Ying Wang 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7
The mechanical characteristics of materials are the key to numerical calculation, thedetermination of material parameters of jointed rock mass is conundrum in academia. For thepurpose of more efficiently and accurately select the mechanical parameters of the jointedrock masses, in this paper, a new method is proposed which for constructing a numericalmodel of jointed rock masses, which based on the Geological Strength Index (GSI) and theprinciples of damage mechanics. With the help of basic concepts of damage mechanics, thejoint equivalent coefficient is proposed, establishing the relationship between GSI and jointspacing. The selection way for the mechanical parameters of a jointed rock masses is given incombination with the Hoek-Brown strength criterion. Then, a numerical calculation model isconstructed by utilizing 3DEC numerical simulation software to discuss the stability of theadjoining rock under the condition of different GSIs, which is successfully applied to theWangjialing coal mine project. The numerical results match quite closely with the fieldconditions, the maximum error is 18%, the minimum error is 5.6%, verifying the rationalityand accuracy of this way and providing a new way for the accurate numerical simulation ofjointed rock masses.
Evaluating the Environmental Benefits of Personalized Travel Incentives in Dynamic Carpooling
Yanshuo Sun,Shijie Chen,Qianwen Guo 대한토목학회 2022 KSCE Journal of Civil Engineering Vol.26 No.7
In a dynamic carpooling system, drivers and riders with their own intended travel plans are matched on short notice. The performance of such a system largely depends on the carpool participants’ travel flexibility (the extent to which a detour is tolerated or the willingness to accept a slightly different drop-off location). To increase travel flexibility, an incentive scheme can be introduced for carpool participants to opt for. For instance, a driver specifies how much she/he expects to be compensated (e.g., $5) if the earliest departure time is shifted to be earlier than the originally scheduled time by a certain amount (e.g., 10 minutes). Similarly, an interested passenger reports the expected incentive to willingly accept a different destination (such as a nearby transit stop or coffee shop) deviating from the request. In this dynamic carpool matching problem with incentives, the following decisions are jointly optimized from the perspective of a carpool matching coordinator: 1) incentive allocations to drivers and riders, 2) assignments of riders to drivers, and 3) vehicle routes of drivers. A case study based on data from Washington, D.C. is conducted to evaluate the potential of the personalized incentives offered to carpool participants in mitigating the environmental impact of transportation (quantified by the reduction of vehicle miles traveled). Two notable findings are reported. First, one dollar of incentive could reduce vehicle miles travelled by 2.88 in one benchmark case. Second, driver incentives are shown to be much more effective than rider incentives under reasonable cost assumptions.
A Novel Energy Storage System based on Flywheel for Improving Power System Stability
Wu, Jinbo,Wen, Jinyu,Sun, Haishun,Cheng, Shijie The Korean Institute of Electrical Engineers 2011 Journal of Electrical Engineering & Technology Vol.6 No.4
In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.
Microstructural Evolution of a High W Content Ni-Based Superalloy at γ′ Sub-Solvus Temperatures
Sigeng Zhou,Naicheng Sheng,Shijie Sun,Shigang Fan,Jinjiang Yu,Guichen Hou,Jinguo Li,Yizhou Zhou,Xiaofeng Sun 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.1
The evolution of γ′ phase and γ/γ′ eutectic during short-time heat treatment of the Ni-based superalloy with high W content,K416B are investigated. In this study, high temperature Differential Scanning Calorimetry (DSC) is employed to designthe heat treatment experiments and the precipitate temperature of secondary γ′ is found in the cooling curve. The standardcoarsening model is applied to figure out the coarsening rate constant of γ′ precipitate. On this basis, a novel method isproposed to predict the globularization time of γ phase in γ/γ′ eutectic during the heat treatment process. As holding temperatureincreases, more γ lamellae convert to platelets before reaching thermodynamic equilibrium. Electron microscopyobservations exhibit the boundary splitting and necking formation on the γ plate surface. Moreover, the dissolution kineticsof γ phase is quantitatively assessed by JMAK model. The volume fraction descends rapidly in the initial stage, and thenreach to a threshold. Above proposed approaches are validated via various heat treatment experiments.
Effect of Mg12Nd and Mg3Nd On the Corrosion Behavior of Mg‒3 wt%Nd Alloy in Saline Solution
Kaihua Yuan,Jianfeng Wang,Yufeng Sun,Shijie Zhu,Hairong Liu,Shaokang Guan 대한금속·재료학회 2023 METALS AND MATERIALS International Vol.29 No.5
In this paper, the precipitates of the Mg‒3 wt%Nd alloy in the as-cast state and after heat treatment at 540 ℃ for 12 h wereinvestigated and related to the corrosion behavior in saline solution. For the as-cast specimen, the network and sphericalβ-phases (Mg12Nd) act as the anodes relative to Mg matrix at the initial stage of immersion in saline solution. Withincreasing the immersion time, the intergranular corrosion caused by the preferential dissolution of the reticular β-phaseleads to the detachment of Mg fragments. For the heat-treated specimen, the plate-shaped β1-phases (Mg3Nd) distributedevenly in the grain interior act as the micro-cathodes. The corrosion pits are prone to extend horizontally and connectedeach other, resulting in an uniform corrosion status and a relatively lower corrosion rate. This result is helpful for developingthe biomedical Mg‒Nd base alloys with a good degradation property by adjusting the precipitation of intermetallics.
A Novel Energy Storage System based on Flywheel for Improving Power System Stability
Jinbo Wu,Jinyu Wen,Haishun Sun,Shijie Cheng 대한전기학회 2011 Journal of Electrical Engineering & Technology Vol.6 No.4
In this paper, a novel flywheel energy storage device, called the flexible power conditioner, which integrates both the characteristics of the flywheel energy storage and the doubly-fed induction machine, is proposed to improve power system stability. A prototype is developed and its principle, composition, and design are described in detail. The control system is investigated and the operating characteristics are analyzed. The test results based on the prototype are presented and evaluated. The test results illustrate that the prototype meets the design requirement on power regulation and starting, and provides a cost-effective and effective means to improve power system stability.