Zhi Zhang

Dr. Zhi Zhang


Research Focus & Metrics

Academic Career Length

5Years (2022-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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9 February 2023 in Entropy
Verified
Journal Article
Open access
PDF file
SGShi-Jie Gao
Shi-Jie Gao
CMChang-Lin Mei
Chang-Lin Mei
QXQiu-Xia Xu
Qiu-Xia Xu
ZZZhi Zhang
Zhi Zhang
Multiscale estimation for geographically weighted regression (GWR) and the related models has attracted much attention due to their superiority. This kind of estimation method will not only improve the accuracy of the coefficient estimators but also reveal the underlying spatial scale of each explanatory variable. However, most of the existing multiscale estimation approaches are backfitting-based iterative procedures that are very time-consuming. To alleviate the computation complexity, we propose in this paper a non-iterative multiscale estimation method and its simplified scenario for spatial autoregressive geographically weighted regression (SARGWR) models, a kind of important GWR-related model that simultaneously takes into account spatial autocorrelation in the response variable and spatial heterogeneity in the regression relationship. In the proposed multiscale estimation methods, the two-stage least-squares (2SLS) based GWR and the local-linear GWR estimators of the regression coefficients with a shrunk bandwidth size are respectively taken to be the initial estimators to obtain the final multiscale estimators of the coefficients without iteration. A simulation study is conducted to assess the performance of the proposed multiscale estimation methods, and the results show that the proposed methods are much more efficient than the backfitting-based estimation procedure. In addition, the proposed methods can also yield accurate coefficient estimators and such variable-specific optimal bandwidth sizes that correctly reflect the underlying spatial scales of the explanatory variables. A real-life example is further provided to demonstrate the applicability of the proposed multiscale estimation methods.

7 November 2022 in Sustainability
Verified
Journal Article
Open access
PDF file
FWFen-Jiao Wang
Fen-Jiao Wang
CMChang-Lin Mei
Chang-Lin Mei
ZZZhi Zhang
Zhi Zhang
QXQiu-Xia Xu
Qiu-Xia Xu
Using local spatial statistics to explore local spatial association of geo-referenced data has attracted much attention. As is known, a local statistic is formulated at a particular sampling unit based on a prespecific proximity relationship and the observations in the neighborhood of this sampling unit. However, geostatistical data such as meteorological data and air pollution data are generally collected from meteorological or monitoring stations which are usually sparsely located or highly clustered over space. For such data, a local spatial statistic formulated at an isolate sampling point may be ineffective because of its distant neighbors, or the statistic is undefinable in the sub-regions where no observations are available, which limits the comprehensive exploration of local spatial association over the whole studied region. In order to overcome the predicament, a local-linear geographically weighted interpolation method is proposed in this paper to obtain the predictors of the underlying spatial process on a lattice spatial tessellation, on which a local spatial statistic can be well formulated at each interpolation point. Furthermore, the bootstrap test is suggested to identify the locations where local spatial association is significant using the interpolated-value-based local spatial statistics. Simulation with comparison to some existing interpolation and test methods is conducted to assess the performance of the proposed interpolation and the suggested test methods and a case study based on PM2.5 concentration data in Guangdong province, China, is used to demonstrate their applicability. The results show that the proposed interpolation method performs accurately in retrieving an underlying spatial process and the bootstrap test with the interpolated-value-based local statistics is powerful in identifying local patterns of spatial association.

10 August 2022 in Annals of the American Association of Geographers
Verified
Journal Article
Closed access
ZZZhi Zhang
Zhi Zhang
CMChang-Lin Mei
Chang-Lin Mei
HYHua-Yi Yu
Hua-Yi Yu
Geographically and temporally weighted regression (GTWR) models have been widely used to explore spatiotemporal nonstationarity where all the regression coefficients are assumed to be varying over both space and time. In reality, however, constant, only temporally varying, and only spatially varying coefficients might also be possible depending on the underlying effects of the explanatory variables on the response variable. Therefore, the development of inference and estimation methods for such special types of the coefficients is essential to the deep understanding of spatiotemporal characteristics of the regression relationship. In this article, an average-based approach, relying on a modified estimation of the conventional GTWR models, is proposed to calibrate the GTWR models with the special types of the coefficients, on which a statistical test is formulated to simultaneously infer constant, temporally varying, and spatially varying coefficients. The simulation study shows that the test method is of valid Type I error and satisfactory power and the average-based estimation method yields more accurate estimators for the special types of the coefficients. A real-life example based on Beijing house prices is given to demonstrate the applicability of the test and estimation methods as well as the extensibility of the test in model selection.

24 August 2026 in Mathematics
Verified
Journal Article
Open access
PDF file
AZAoyu Zheng
Aoyu Zheng
XLXiaolong Liang
Xiaolong Liang
HZHaitao Zhong
Haitao Zhong
ZZZhi Zhang
Zhi Zhang
ZLZuolin Lyu
Zuolin Lyu
MZMingfa Zheng
Mingfa Zheng
Emergency response missions employing heterogeneous multi-UAVs are challenged by both the tight coupling between task assignment and motion control and the inherent difficulty in obtaining full probability distributions of stochastic disturbances. In practice, only partial moment information—typically the mean, covariance, and support set—can be estimated. To address this, the paper proposes a distributionally robust integrated “decision–control” framework. A bi-level optimization model is established: the upper level minimizes the maximum mission completion time across all platforms, while the lower level solves minimum-time optimal control problems under kinematic constraints, with the two levels coupled through task execution times. Given only the mean, covariance, and support set of disturbances, an ambiguity set is constructed, and by leveraging duality theory and semidefinite programming, the distributionally robust chance constraints on site reachability are equivalently transformed into deterministic safety margins. A two-stage trajectory planning method is further designed to decouple accumulated time estimation from robust constraint enforcement, ensuring computational tractability. Simulation results across multiple disturbance configurations show that, whereas deterministic planning yields an overall mission success rate of only about 0.7%, the proposed framework consistently achieves success rates above 99.9% and effectively balances workload among multiple UAVs. These results validate the practical benefit of the framework in providing reliable emergency response plans under limited distributional information.


13 August 2026 in Mathematics
Verified
Journal Article
Open access
PDF file
ZLZuolin Lyu
Zuolin Lyu
MZMingfa Zheng
Mingfa Zheng
XSXiuchao Song
Xiuchao Song
ZLZongpu Li
Zongpu Li
ZZZhi Zhang
Zhi Zhang
AZAoyu Zheng
Aoyu Zheng
This paper presents a method for determining weight coefficients in multi-objective UAV task assignment under a competitive data-collection setting, where two UAV companies independently visit each other’s sensor nodes. In this setting, each company expresses operational intent through weights for data value, distance utility, and flight safety. Our own weights are prescribed by higher-level planning, whereas the competitor’s latent weights must be estimated from observed visit assignments. To estimate these weights, we apply Approximate Bayesian-Inspired Inference, which also provides a measure of the associated inference uncertainty. Subsequently, a purpose-built fuzzy rule base translates the inferred weights into response weights, while the fuzziness of this mapping is quantified as a second source of uncertainty. From these two uncertainty measures, an adaptive coefficient is derived that blends the planning and response weights into the final task assignment. Under controlled synthetic settings, numerical experiments demonstrate that the inference procedure outperforms direct loss-minimization baselines in both accuracy and speed, and that the adaptive fusion effectively balances planning adherence with responsiveness to competitor behavior.