Essays On Perioperative Services Problems In Healthcare

One of the critical challenges in healthcare operations management is to efficiently utilize the expensive resources needed while maintaining the quality of care provided. Simulation and optimization methods can be effectively used to provide better healthcare services. This can be achieved by developing models to minimize patient waiting times, minimize healthcare supply chain and logistics costs, and maximize access. In this proposal, we study some of the important problems in healthcare operations management. More specifically, we focus on perioperative services and study scheduling of operating rooms (ORs) and management of necessary resources such as staff, equipment, and surgical instruments. We develop optimization and simulation methods to coordinate material handling decisions, inventory management, and OR scheduling. In Chapter 1 of this dissertation, we investigate material handling services to improve the flow of surgical materials in hospitals. The ORs require timely supply of surgical materials such as surgical instruments, linen, and other additional equipment required to perform the surgeries. The availability of surgical instruments at the right location is crucial to both patient safety and cost reduction in hospitals. Similarly, soiled material must also be disposed of appropriately and quickly. Hospitals use automated material handling systems to perform these daily tasks, minimize workforce requirements, reduce risk of contamination, and reduce workplace injuries. Most of the literature related to AGV systems focuses on improving their performance in manufacturing settings. In the last 20 years, several articles have addressed issues relevant to healthcare systems. This literature mainly focuses on improving the design and management of AGV systems to handle the specific challenges faced in hospitals, such as interactions with patients, staff, and elevators; adhering to safety standards and hygiene, etc. In Chapter 1, we focus on optimizing the delivery of surgical instrument case carts from material departments to ORs through automated guided vehicles (AGV). We propose a framework that integrates data analysis with system simulation and optimization. We test the performance of the proposed framework through a case study developed using data from a partnering hospital, Greenville Memorial Hospital (GMH) in South Carolina. Through an extensive set of simulation experiments, we investigate whether performance measures, such as travel time and task completion time, improve after a redesign of AGV pathways. We also study the impact of fleet size on these performance measures and use simulation-optimization to evaluate the performance of the system for different fleet sizes. A pilot study was conducted at GMH to validate the results of our analysis. We further evaluated different policies for scheduling the material handling activities to assess their impact on delays and the level of inventory required. Reducing the inventory level of an instrument may negatively impact the flexibility in scheduling surgeries, cause delays, and therefore, reduce the service level provided. On the other hand, increasing inventory levels may not necessarily eliminate the delays since some delays occur because of inefficiencies in the material handling processes. Hospitals tend to maintain large inventories to ensure that the required instruments are available for scheduled surgery. Typically, the inventory level of surgical instruments is determined by the total number of surgeries scheduled in a day, the daily schedule of surgeries that use the same instrument, the processing capacity of the central sterile storage division (CSSD), and the schedule of material handling activities. Using simulation-optimization tools, we demonstrate that integrating decisions of material handling activities with inventory management has the potential to reduce the cost of the system. In Chapter 2 we focus on coordinating OR scheduling decisions with efficient management of surgical instruments. Hospitals pay more attention to OR scheduling. This is because a large portion of hospitals\u27 income is due to surgical procedures. Inventory management of decisions follows the OR schedules. Previous work points to the cost savings and benefits of optimizing the OR scheduling process. However, based on our review of the literature, only a few articles discuss the inclusion of instrument inventory-related decisions in OR schedules. Surgical instruments are classified as (1) owned by the hospital and (2) borrowed from other hospitals or vendors. Borrowed instruments incur rental costs that can be up to 12-25\% of the listed price of the surgical instrument. A daily schedule of ORs determines how many rental instruments would be required to perform all surgeries in a timely manner. A simple strategy used in most hospitals is to first schedule the ORs, followed by determining the instrument assignments. However, such a strategy may result in low utilization of surgical instruments owned by hospitals. Furthermore, creating an OR schedule that efficiently uses available surgical instruments is a challenging problem. The problem becomes even more challenging in the presence of material handling delays, stochastic demand, and uncertain surgery duration. In this study, we propose an alternative scheduling strategy in which the OR scheduling and inventory management decisions are coordinated. More specifically, we propose a mixed-integer programming model that integrates instrument assignment decisions with OR scheduling to minimize costs. This model determines how many ORs to open, determines the schedule of ORs, and also identifies the instrument assignments for each surgery. If the level of instrument inventory cannot meet the surgical requirements, our model allows instruments to be rented at a higher cost. We introduce and evaluate the solution methods for this problem. We propose a Lagrangean decomposition-based heuristic, which is an iterative procedure. This heuristic separates the scheduling problem from the inventory assignment problem. These subproblems are computationally easier to solve and provide a lower bound on the optimal cost of the integrated OR scheduling problem. The solution of the scheduling subproblem is used to generate feasible solutions in every iteration. We propose two alternatives to find feasible solutions to our problem. These alternatives provide an upper bound on the cost of the integrated scheduling problem. We conducted a thorough sensitivity analysis to evaluate the impact of different parameters, such as the length of the scheduling horizon, the number of ORs that can be used in parallel, the number of surgeries, and various cost parameters on the running time and quality of the solution. Using a case study developed at GMH, we demonstrate that integrating OR scheduling decisions with inventory management has the potential to reduce the cost of the system. The objective of Chapter 3 is to develop quick and efficient algorithms to solve the integrated OR scheduling and inventory management problem, and generate optimal/near-optimal solutions that increase the efficiency of GMH operations. In Chapter 2, we introduced the integrated OR scheduling problem which is a combinatorial optimization problem. As such, the problem is challenging to solve. We faced these challenges when trying to solve the problem directly using the Gurobi solver. The solutions obtained via construction heuristics were much farther from optimality while the Lagrangean decomposition-based heuristics take several hours to find good solutions for large-sized problems. In addition, those methods are iterative procedures and computationally expensive. These challenges have motivated the development of metaheuristics to solve OR scheduling problems, which have been shown to be very effective in solving other combinatorial problems in general and scheduling problems in particular. In Chapter 3, we adopt a metaheuristic, Tabu search, which is a versatile heuristic that is used to solve many different types of scheduling problems. We propose an improved construction heuristic to generate an initial solution. This heuristic identifies the number if ORs to be used and then the assignment of surgeries to ORs. In the second step, this heuristic identifies instrument-surgery assignments based on a first-come, first-serve basis. The proposed Tabu search method improves upon this initial solution. To explore different areas of the feasible region, we propose three neighborhoods that are searched one after the other. For each neighborhood, we create a preferred attribute candidate list which contains solutions that have attributes of good solutions. The solutions on this list are evaluated first before examining other solutions in the neighborhood. The solutions obtained with Tabu search are compared with the lower and upper bounds obtained in Chapter \ref{Ch2}. Using a case study developed at GMH, we demonstrate that high-quality solutions can be obtained by using very little computational time

Best Effort Minimal Routing for Fly-Over: A Light Weight Distributed Mechanism for Energy Efficient Network-On-Chip

Scalable Networks-on-Chip (NoCs) have become the de facto interconnection mechanism in large scale Chip Multiprocessors. NoCs devour a large fraction of the on-chip power budget of which static NoC power consumption is becoming the dominant component as technology scales down. Hence, reducing static NoC power consumption is critical for energy-efficient computing. Previous research suggests power-gating routers attached to inactive cores so as to save static power, but requires centralized control and global network knowledge. Moreover, packet deliveries in irregular power-gated network suffer from detour or waiting time overhead to either route around or wake up off routers. Fly-Over (FLOV) is a distributed power-gating mechanism to minimize static power consumption in NoCs without the need for global network information. However, the existing FLOV routing algorithm introduces unnecessary detours and pressurizes the routers in AON column resulting in high packet latencies and network congestion. This work proposes FLOV+, Best-Effort Minimal Routing Algorithm for Fly-Over (FLOV) to route the packets using the shortest path in an irregular power-gated network and also relieve the stress on the AON column. This routing algorithm aims to minimize the average packet latency and to sustain throughput in network with power-gated routers. Synthetic workload evaluations show that the proposed algorithm reduces average packet latency upto 9.84% in an 8-dimensional mesh network. Simulation results also show 50% and 40% improvement in the network throughput for restricted FLOV and generalized FLOV power gating mechanisms respectively

Anorganische Festkörper-Aspekte von Koordinationspolymeren: Synthese, Struktur und Eigenschaften neuer Übergangsmetall-Komplexe.

In this work investigations on the synthesis, structures and properties of new coordination polymers based on zinc(II) halides and N-donor ligands are reported. The major goal of this work focus on the preparation of new coordination compounds via thermal decomposition reactions of suitable ligand rich precursor compounds, which includes investigation of such reactions concerning structure property relationships, mechanistic aspects and the parameters which will influence the product formation. In contrast to the preparation of such compounds in solution, thermal decomposition reactions have several advantegous. The results of this work clearly proves that the compounds prepared by thermal decomposition reaction are obtained very pure and in almost quantitative yield. By this method also thermodynamic metastable compounds and polymorphic modifications can be prepared, which in part, cannot be isolated in solution. If such reactions are investigated in detail, a large number of different species can be identified even for very simple systems. Based on previous investigations on copper(I)halide coordination polymers, this work clearly shows, that thermal decomposition reactions can be used also for the discovery and preparation of a wide range of new compounds.In dieser Arbeit wird über die Darstellung, die Strukturen und die Eigenschaften von neuen Koordinationspolymeren auf der Basis von Zink(II)halogeniden und N-Donorliganden berichtet. Das wesentliche Ziel dieser Untersuchungen besteht darin, Koordinationsverbindungen über thermische Abbaureaktionen geeigneter ligandenreicher Vorläuferverbindungen darzustellen. Dies beinhaltet Untersuchungen derartiger Reaktionen hinsichtlich von Struktur-Eigenschafts-Beziehungen, mechanistischen Aspekten und der Parameter, welche die Produktbildung beeinflussen. Im Gegensatz zur Synthese in Lösung, bieten thermische Abbaureaktionen eine Reihe von Vorteilen. Die Ergebnisse dieser Arbeit zeigen eindeutig, dass die Verbindungen, die über thermische Abbaureaktionen dargestellt wurden, in hoher Reinheit und quantitativer Ausbeute isoliert werden können. Dabei können auch thermodynamisch metastabile Verbindungen und polymorphe Modifikationen erhalten werden, welche in Lösung zum Teil nicht isoliert werden können. Werden derartige Reaktionen im Detail untersucht, können auch für sehr einfache Verbindungsklassen eine Vielzahl neuer Verbindungen identifiziert werden. Aufbauend auf früheren Ergebnissen über Kupfer(I)halogenid-Koordinationspolymere wurde daher bewiesen, dass sich thermische Abbaureaktionen für die Entdeckung und Darstellung eine ganzen Reihe von Verbindungen eignen

Synthesis, Crystal Structure and Thermal Reactivity of [ZnX 2 (2-chloropyrazine)] (X = Cl, Br, I) Coordination Compounds

Reaction of zinc(II) halides with 2-chloropyrazine in different solvents leads to the formation of five new coordination compounds that contain either only 2-chloropyrazine or additional water molecules as donor ligands. In the ligand-rich 1:2 compound catena[bis(2-chloropyrazine-N)]di-Μ-chlorozinc(II) ( 1 ) the zinc atom is coordinated by two 2-chloropyrazine ligands and four chlorine atoms in an octahedral fashion. The zinc atoms are connected by the chloride atoms forming linear chains. In the isotypic ligand-rich 1:2 compounds bis(2-chloropyrazine-N)dibromozinc(II) ( 2 ) and bis(2-chloropyrazine-N)diiodozinc(II) ( 3 ) discrete complexes are found in which each zinc atom is coordinated by two 2-chloropyrazine ligands and two halide atoms within distorted tetrahedra. The 1:1 compounds aqua-(2-chloropyrazine-N)dibromozinc(II) ( 4 ) and aqua-(2-chloropyrazine-N)diiodozinc(II) ( 5 ) are also isotypic and form discrete complexes in which the zinc atoms are surrounded by two halide atoms, one 2-chloropyrazine ligand and one water molecule. Upon heating, compounds 1 – 5 form ligand-deficient 1:1 and 2:1 compounds of composition [ZnX 2 (2-chloropyrazine)] (X = halide) and [(ZnX 2 ) 2 (2-chloropyrazine)]. X-ray powder diffraction shows that identical ligand-deficient intermediates are obtained on decomposition of either [ZnX 2 L 2 ] (L = 2-chloropyrazine) or the [ZnX 2 L(H 2 O)] complexes. DFT calculations suggest that the formation of the [ZnX 2 L(H 2 O)] complex is energetically favoured for the heavier halide anions. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008)Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/57924/1/605_ftp.pd

Bis(pyridazine-κN)bis­(seleno­cyanato-κN)zinc

The asymmetric unit of the title compound, [Zn(NCSe)2(C4H4N2)2], consists of one ZnII cation, located on a twofold rotation axis, one seleno­cyanate anion and one pyridazine ligand in general positions. The ZnII atom is coordinated by two N-atoms of two pyridazine ligands and two terminal N-bonded seleno­cyanate anions within a slightly distorted tetra­hedral coordination environment. In the crystal, discrete complex mol­ecules are arranged in layers parallel to the ac plane, with ZnII⋯ZnII distances of 8.0906 (6) Å along the a axis and of 9.0490 (7) or 9.3604 (7) Å along the c axis. The complex mol­ecules are further linked via weak Se⋯Se inter­actions, with Se⋯Se distances of 3.8235 (9) Å

Numerical Modelling of Flow Over Aerator of Orifice Spillway

Source: ICHE Conference Archive - https://mdi-de.baw.de/icheArchiv

Bis(3-methyl­pyridine-κN)bis­(thio­cyanato-κN)zinc

The asymmetric unit of the title compound, [Zn(NCS)2(C6H7N)2], consists of one Zn2+ cation and two thio­cyanate anions, all situated on special positions with site symmetry .m., and one 3-methyl­pyridine ligand. The zinc cation is coordinated by four N atoms of two terminal N-bonded thio­cyanate anions and of two symmetry-related 3-methyl­pyridine co-ligands, defining a slightly distorted tetra­hedral coordination polyhedron

(Di-2-pyridyl sulfide-κ2 N,N′)diiodidozinc(II)

The title compound, [ZnI2(C10H8N2S)], contains a six-membered chelate ring adopting a boat conformation in which the Zn atom is coordinated by two iodide ions and by the two pyridyl N atoms of a single di-2-pyridyl sulfide ligand within a slightly distorted tetra­hedron. The Zn, S and I atoms are located on a crystallographic mirror plane. As usual for this type of complex, the sulfide group does not participate in zinc coordination. The dihedral angle between the two pyridine rings is 60.1 (1)°