Zhichao Zheng

• PhD in Management, Department of Decision Sciences, NUS Business School
• Professor (Associate) at Singapore Management University

In this paper, we analyze mixed 0-1 linear programs under objective uncertainty. The mean vector and the second-moment matrix of the nonnegative objective coefficients are assumed to be known, but the exact form of the distribution is unknown. Our main result shows that computing a tight upper bound on the expected value of a mixed 0-1 linear progr...

In this paper we investigate a stochastic appointment-scheduling problem in an outpatient clinic with a single doctor. The number of patients and their sequence of arrivals are fixed, and the scheduling problem is to determine an appointment time for each patient. The service durations of the patients are stochastic, and only the mean and covarianc...

This paper is motivated by the following question: How to construct good approximation for the distribution of the solution value to linear optimization problem, when the random objective coefficients follow a multivariate normal distribution? Using Stein's Identity, we show that the least squares normal approximation of the random optimal value ca...

In this paper, we review recent advances in the distributional analysis of mixed integer linear programs with random objective coefficients. Suppose that the probability distribution of the objective coefficients is incompletely specified and characterized through partial moment information. Conic programming methods have been recently used to find...

Purpose Real-time risk monitoring is critical but challenging in intensive care units (ICUs) due to the lack of real-time updates for most clinical variables. Although real-time predictions have been integrated into various risk monitoring systems, existing systems do not address uncertainties in risk assessments. We developed a novel framework bas...

Two-stage screening programs for colorectal cancer (CRC) detection typically involve a first-stage test that evaluates fecal-hemoglobin (f-Hb) concentration in stool samples, with positive results leading to a recommended second-stage diagnostic test (colonoscopy). We explore the design of the first-stage test—specifically the selection of f-Hb cut...

Weaning patients from mechanical ventilators is a crucial decision in intensive care units (ICUs), significantly affecting patient outcomes and the throughput of ICUs. This study aims to improve the current extubation protocols by incorporating predictive information on patient health conditions. We develop a discrete-time, finite-horizon Markov de...

Background Deep sternal wound infection (DSWI) constitutes a serious complication after coronary artery bypass grafting (CABG) surgery. The aim of this study is to evaluate the dose-response relationship between glycated hemoglobin (HbA1c) level and the risk of DSWI after CABG. Methods PubMed, Scopus, and Cochrane Library databases were searched t...

Problem definition: With the rapid growth of the gig economy, on-demand staffing platforms have emerged to help companies manage their temporary workforce. This emerging business-to-business context motivates us to study a new form of supply chain coordination problem. We consider a staffing platform managing an on-demand workforce to serve multipl...

Objectives Telemedicine enables patients to communicate with physicians effectively, especially during the COVID-19 pandemic. However, few studies have explored the use of online healthcare platforms for a comprehensive range of specialties during the COVID-19 pandemic. This study aimed to investigate how telemedicine services were affected by the...

This study examines the impact of coronavirus disease 2019 (COVID-19) test accuracy (i.e., sensitivity and specificity) on the progression of the pandemic under two scenarios of limited and unlimited test capacity. We extend the classic susceptible– exposed–infectious–recovered model to incorporate test accuracy and compare the progression of the p...

Background and objectives: There is an ongoing controversy regarding the risks of restrictive and liberal red blood cell (RBC) transfusion strategies. This meta-analysis assessed whether transfusion at a lower threshold was superior to transfusion at a higher threshold, with regard to thrombosis-related events, that is, whether these outcomes can...

Container liner shipping is the primary mode of moving manufactured products across continents. Partly due to inherent uncertainties at sea and ports, the liner shipping industry has long had a notorious reputation of schedule delays and unreliable on-time performance. This paper formulates a new approach to incorporate schedule reliability targets...

The novel coronavirus disease 2019 (COVID-19) has caused a global pandemic. Some studies have suggested a negative association between sunlight intensity and COVID-19 infection, alluding to the belief that it might be safe to go out on sunny days. This paper examined whether solar radiation mitigated the association between human mobility and COVID...

A key challenge in the resource allocation problem is to find near-optimal policies to serve different customers with random demands/revenues, using a fixed pool of capacity (properly configured). Three classes of allocation policies, responsive (with perfect hindsight), adaptive (with information updates), and anticipative (with forecast informati...

Two-stage screening programs are widely adopted for early colorectal cancer (CRC) detection. Individuals receiving positive outcomes in the first-stage (initial) test are recommended to undergo a second-stage test (colonoscopy) for further diagnosis. We study the initial test design—i.e., selecting cutoffs to report test outcomes—to balance the tra...

We study an M/M/1/K queue where customers can reschedule their appointments. Rescheduled customers show up with higher probabilities, incurring lower no-show costs, but rescheduling also frees up slots that may not be filled later, leading to wasted service capacity and lower throughput. The system manager aims to minimize the long-run average cost...

Problem definition: With the rapid growth of the sharing economy, on-demand staffing platforms have emerged to help companies manage their temporary workforce. This emerging business-to-business context motivates us to study a new form of supply chain coordination problem. We consider a staffing platform managing on-demand workforce to serve multip...

Weaning patients from mechanical ventilators is a crucial decision in intensive care units (ICUs), significantly affecting patient outcomes and the throughput of ICUs. This study aims to improve the current extubation protocols by incorporating predictive information on patient health conditions. We develop a discrete-time, finite-horizon Markov de...

When it comes to the impacts of air pollution on the healthcare system, previous studies mostly focus on the increased patient demand due to air pollution-related health deterioration, taking a demand-side perspective. We extend this stream of literature from a provider-side perspective by studying how air pollution can affect doctors’ work perform...

When it comes to the impacts of air pollution on the healthcare system, previous studies mostly focus on the increased patient demand due to air pollution-related health deterioration, taking a demand-side perspective. We extend this stream of literature from a provider-side perspective by studying how air pollution can affect doctors’ work perform...

This study examines the impact of coronavirus disease 2019 (COVID-19) test accuracy (i.e., sensitivity and specificity) on the progression of the pandemic under two scenarios of limited and unlimited test capacity. We extend the classic susceptible– exposed–infectious–recovered model to incorporate test accuracy and compare the progression of the p...

Acute kidney injury (AKI) is a frequent complication of cardiac surgery, which can lead to higher mortality and long-term renal function impairment. The effect of perioperative renin-angiotensin system inhibitors (RASi) therapy on AKI incidence in patients undergoing cardiac surgery remains controversial. We reviewed related studies in PubMed, Scop...

A key challenge in the resource allocation problem is to find near-optimal policies to serve different customers with random demands/revenues, using a fixed pool of capacity (properly configured). In this paper, we study the properties of three classes of allocation policies—responsive (with perfect hindsight), adaptive (with information updates),...

Container liner shipping is the primary mode of moving manufactured products across continents. Partly due to inherent uncertainties at sea and ports, the liner shipping industry has long had a notorious reputation of schedule delays and unreliable on-time performance. This paper formulates a new approach to incorporate schedule reliability targets...

Container liner shipping is the primary mode of moving manufactured products across continents. Partly due to inherent uncertainties at sea and ports, the liner shipping industry has long had a notorious reputation of schedule delays and unreliable on-time performance. This paper formulates a new approach to incorporate schedule reliability targets...

SEPSIS-3 DEFINITION: Sepsis is defined as life-threatening organ dysfunction due to a dysregulated host response to infection. The clinical criteria of sepsis include organ dysfunction, which is defined as an increase of two points or more on the sequential organ failure assessment (SOFA). For patients with infection, an increase of 2 SOFA points y...

In many production environments, a fixed network of capacity is shared flexibly between multiple products with random demands. What is the best way to configure the capacity of the production network and to allocate the available capacity, to meet pre-determined fill rate requirements? We develop a new approach for network capacity configuration an...

Background: Extubation is a critical step in the intensive care unit (ICU). In this study, we aim to investigate the risk factors for both extubation failure and deterioration with further mechanical ventilation (MV). Methods: Data were collected from a cardiothoracic ICU in a tertiary hospital. The risk factors for extubation failure and deteri...

Weaning patients from mechanical ventilators is a critical decision in intensive care units (ICUs), especially during the COVID-19 pandemic. In this study, we aim to improve the extubation decision for ventilated patients by exploiting data analytics and predictive information. We develop a discrete-time, finite-horizon Markov decision process (MDP...

We study the effects of rescheduling on no-show behavior in an outpatient appointment system for both new and follow-up patients. Previous literature has primarily focused on new patients and investigated the role of waiting time on no-show probability. We offer a more nuanced understanding of this costly phenomenon. Using comprehensive clinical da...

In many production environments, a fixed network of capacity is shared flexibly between multiple products with random demands. What is the best way to configure the capacity of the production network and to allocate the available capacity, to meet pre-determined fill rate requirements? We develop a new approach for network capacity configuration an...

A key challenge in the resource allocation problem is to find near-optimal policies to serve different customers with random demands/revenues, using a fixed pool of capacity (properly configured). In this paper, we study the properties of three classes of allocation policies—responsive (with perfect hindsight), adaptive (with information updates),...

Resource pooling strategies have been widely used in industry to match supply with demand. However, effective implementation of these strategies can be challenging. Firms need to integrate the heterogeneous service level requirements of different customers into the pooling model and allocate the resources (inventory or capacity) appropriately in th...

We study the design of a healthcare appointment system with a single physician and a group of patients whose service durations are stochastic. The challenge is to find the optimal arrival sequence for a group of mixed patients such that the total expected cost of patient waiting time and physician overtime is minimized. While numerous simulation st...

We study the effects of rescheduling on no-show behavior in an outpatient appointment system for both new and follow-up patients. Previous literature has primarily focused on new patients and investigated the role of waiting time on no-show probability. We offer a more nuanced understanding of this costly phenomenon. Using comprehensive clinical da...

We propose a new multiple-benchmark tracking-error model for the portfolio selection problem. We construct a strategy to track the performance of the highest return from a set of benchmarks, by minimizing a quadratic loss function. The portfolio rule constructed this way retains features of the linear combination rule, with weights mainly determine...

An inherent challenge of using Performance-Based Logistics (PBL) contracts for aircraft maintenance, repair and overhaul (MRO) services is pricing. As with traditional bricks and mortar services, underpriced contracts cannot cover costs, while overpriced contracts lose out to competition. Furthermore MRO services have an additional element of uncer...