Z. Zhang

IROS Conference 2025 Conference Paper

Compact Modular Surgical System with a Novel RCM Mechanism for Laparo-Endoscopic Single-Site Surgery

• Z. Zhang
• Chin-Boon Chng
• Chee-Kong Chui

This paper presents a novel robotic system designed to address the challenges of a robotic-assisted Laparo-Endoscopic single-site (LESS) surgery. While numerous studies have explored mechanisms enabling Remote Center of Motion (RCM) for minimally invasive procedures, few have investigated the interactions of multiple (≥2) manipulators within an integrated system. The proposed robotic system features an arc-shaped mainframe for positioning and mounting of five-bar Spherical Parallel Mechanism (SPM). A conventional straight-shaft surgical tool is inserted through a linear guide rail aligned with the pointing axis leading into the RCM. To account for the physical dimensions of the closed-chain linkages, a modified Denavit-Hartenberg parameterization is adopted to assign spherical linkage frames. This design approach ensures self-collision avoidance within the parallel mechanism and enables systematic evaluation of the distal end-effector’s linear motion characteristics. Furthermore, we investigate the basic functions of SPM manipulators through a prototype experiment, providing preliminary insights that could inform future enhancement of surgical techniques for robotic-assisted LESS procedures.

YNICL Journal 2019 Journal Article

Validations of apomorphine-induced BOLD activation correlations in hemiparkinsonian rhesus macaques

• J.E. Quintero
• Yi Ai
• A.H. Andersen
• P. Hardy
• R. Grondin
• Z. Guduru
• D.M. Gash
• G.A. Gerhardt

Identification of Parkinson's disease at the earliest possible stage of the disease may provide the best opportunity for the use of disease modifying treatments. However, diagnosing the disease during the pre-symptomatic period remains an unmet goal. To that end, we used pharmacological MRI (phMRI) to assess the function of the cortico-basal ganglia circuit in a non-human primate model of dopamine deficiency to determine the possible relationships between phMRI signals with behavioral, neurochemical, and histological measurements. Animals with unilateral treatments with the neurotoxin, 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP), that expressed stable, long-term hemiparkinsonism were challenged with the dopaminergic receptor agonist, apomorphine, and structure-specific phMRI blood oxygen level-dependent (BOLD) activation responses were measured. Behavioral, histopathological, and neurochemical measurements were obtained and correlated with phMRI activation of structures of the cortico-basal ganglia system. Greater phMRI activations in the basal ganglia and cortex were associated with slower movement speed, decreased daytime activity, or more pronounced parkinsonian features. Animals showed decreased stimulus-evoked dopamine release in the putamen and substantia nigra pars compacta and lower basal glutamate levels in the motor cortex on the MPTP-lesioned hemisphere compared to the contralateral hemisphere. The altered neurochemistry was significantly correlated with phMRI signals in the motor cortex and putamen. Finally, greater phMRI activations in the caudate nucleus correlated with fewer tyrosine hydroxylase-positive (TH+) nigral cells and decreased TH+ fiber density in the putamen. These results reveal the correlation of phMRI signals with the severity of the motor deficits and pathophysiological changes in the cortico-basal ganglia circuit.

EAAI Journal 2009 Journal Article

An iterative agent bidding mechanism for responsive manufacturing

• M.K. Lim
• Z. Zhang
• W.T. Goh

In today's market, the global competition has put manufacturing businesses in great pressures to respond rapidly to dynamic variations in demand patterns across products and changing product mixes. To achieve substantial responsiveness, the manufacturing activities associated with production planning and control must be integrated dynamically, efficiently and cost-effectively. This paper presents an iterative agent bidding mechanism, which performs dynamic integration of process planning and production scheduling to generate optimised process plans and schedules in response to dynamic changes in the market and production environment. The iterative bidding procedure is carried out based on currency-like metrics in which all operations (e. g. machining processes) to be performed are assigned with virtual currency values, and resource agents bid for the operations if the costs incurred for performing them are lower than the currency values. The currency values are adjusted iteratively and resource agents re-bid for the operations based on the new set of currency values until the total production cost is minimised. A simulated annealing optimisation technique is employed to optimise the currency values iteratively. The feasibility of the proposed methodology has been validated using a test case and results obtained have proven the method outperforming non-agent-based methods.

YNIMG Journal 2008 Journal Article

Impact of exercise on caudate and putamen in a non-human primate model of Parkinson's disease

• Rehana K. Leak
• Z. Zhang
• S.L. Castro
• B.J. Lopresti
• C.A. Mathis
• M.J. Zigmond
• J.L. Cameron

YNIMG Journal 2008 Journal Article

Increased survival of nigrostriatal dopaminergic neurons following a toxic MPTP insult in the exercising primate: A [11C]DTBZ PET study

• Brian J. Lopresti
• Z. Zhang
• M.J. Zigmond
• R.K. Leak
• C.A. Mathis
• J.L. Cameron

ECAI Conference 1992 Conference Paper

From Multiple Objects Motion Analysis To Behavior-Based Object Recognition

• Nassir Navab
• Z. Zhang

I&C Journal 1989 Journal Article

Coding for write-efficient memory

• R. Ahlswede
• Z. Zhang

We introduce write-efficient memories (WEM) as a new model for storing and updating information on a rewritable medium. There is a cost ϕ: X × X → R ∞ assigned to changes of letters. A collection of subsets C = {Ci: 1 ≤ i ≤ M} of X n is an (n, M, D) WEM code, if Ci ∩ Cj = ⊘ for all i ≠ j and if D max = max l⩽i, j⩽MxnϵCjYnϵC1 max min ∑ j=1 n ϕ(xt, yt)⩽D. D max is called the maximal correction cost with respect to the given cost function. The performance of a code C can also be measured by two parameters, namely, the maximal cost per letter d C = n −1 D max and the rate of the size r C = n −1 log M. The rate achievable with a maximal per letter cost d is thus R(d)= sup c: dc⩽d rc. This is the most basic quantity (the storage capacity) of a WEM ( X n, ϕ n ) n = 1 ∞. We give a characterization of this and related quantities.