Inventory Management under Product Mis-identification/Shipment Errors

“Wrong-product” delivery - the delivery of a product different from that desired - is a significant, but as yet unexplored problem in supply-chain management research. There are basically two reasons for wrong-product delivery: either the wrong product is mistakenly ordered or the right product is ordered but the wrong product is picked/shipped. This paper defines and analyzes the “wrong-product delivery” problem using a 2-product newsvendor model. Two non-substitutable products may be ordered at the beginning of each time period. However, whenever product i is ordered, then with known probability i, product j is delivered; i, j = 1, 2(i 6= j). First, we analyze the “no-recourse scenario”, where management correctly stores whatever was received, but takes no other action. We establish the form of the optimal policy and conduct sensitivity analysis. Although our modeling framework is simple, our results are unexpected and non-intuitive. For example, it is well known that in the single-product newsvendor model, increasing the uncertainty of demand or supply will yield an increase in the corresponding target basestocks and safety stocks. However, increasing the risk of a wrong-product error yields a decrease in the corresponding basestocks and safety stocks. Further, although target basestocks in the single-product newsvendor model are invariant to increases in on-hand inventory, we show that the target basestock for either product is non-decreasing as its inventory increases. We also demonstrate that the cost impact of wrong-product uncertainty is comparable, if not larger than, the cost impact of demand uncertainty. Next, we analyze the “recourse scenario” where management is able to correct errors but only by incurring a fixed cost of $K. We show that it is optimal to take recourse when the wrong-product uncertainty is sufficiently small, but not take recourse when the wrong-product uncertainty is high. In strategic terms, our analysis provides insight into the cost impact of wrong-product errors, and, hence, the importance of reducing them.Supply chain management, Inventory management, Shipment errors, Ordering errors, Yield management, Unreliable supply

An Empirical Study of Service Differentiation for Weapon System Service Parts

The question of how to effectively manage items with heterogeneous attributes and differing service requirements has become increasingly important to supply chains that support the delivery of after-sales service. However, there has been little investigation to date on how organizations actually manage inventory levels under such circumstances. This study provides such an investigation, focusing on the logistic system used to manage consumable service parts for weapon systems in the U.S. military. Our findings, based on interviews and rigorous analysis of part attribute and performance data, suggest that in practice a part\u27s service level is negatively affected by an item\u27s cost and is less affected by attributes such as its priority code. We introduce a simple inventory model to explain our empirical findings and explore how variations in item attributes can interact with an inventory policy to affect system performance. Based on this model, we recommend using explicit service-level targets for priority categories to achieve performance consistent with part priority. We show, using military data, that a service differentiation strategy can be an effective way of allocating inventory investment by providing higher service for critical parts at the expense of accepting lower service levels for parts with less importance

Model Predictive Control with Fault Detection and Diagnosis for Multivariable Systems

The feedback control system design technique of Model Predictive Control (MPC) has been vastly used in the chemical and process engineering industry, due to its ability to handle dynamics with multiple inputs and multiple outputs, which are essentially the majority of today's engineering systems. In addition, the field of Fault Detection and Diagnosis (FDD) in control systems also has been extensively researched over the past decades as it is critical for the controller to realize when and if a fault has occurred within a system. However, due to the high computational requirements, it is often challenging to implement FDD based MPC algorithms in resource limited real world systems. This thesis addresses the development of MPC algorithms with combined state and fault estimation. Firstly, a novel Quadratic Programming (QP) formulation is developed for a recently proposed efficient MPC method along with simultaneous state and fault estimation. Another contribution is the enhancement of a standard integral action MPC algorithm (which has an implicit fault tolerance capability), to provide state and actuator fault estimation in real time. This work focuses on faults which are modeled as a Loss Of Effectiveness (LOE). The algorithm to estimate the system faults and states simultaneously is a simple observer based method which can be tuned beforehand, thus eliminating the need for on-line real time complex calculations. Lastly, a third contribution of this thesis is the application of the above methods to design MPC based flight control systems for fixed wing aircraft. Simulations are presented to demonstrate the effectiveness of the proposed methods

Building Reliable Air-Travel Infrastructure Using Empirical Data and Stochastic Models of Airline Networks

Flight delays have been a growing issue and they have reached an all-time high in recent years, with the airlines’ on-time performance at its worst level in 2007 since 1995. The goal of this paper is to build stochastic models of airline networks and utilize publicly available data to answer the following policy questions: Which are the bottleneck airports in the US air-travel infrastructure? How would increasing airport capacity at these airports alleviate delay propagation? What are the appropriate metrics for measuring the robustness of airline schedules? How could these schedules be made more robust? Which flight in an aircraft rotation is a bottleneck flight? The contribution of this paper is two-fold. First, we develop stochastic models, using empirical data, to analyze the propagation of delays through air-transportation networks. Second, our analysis enables us to make policy recommendations regarding managing bottleneck resources in the air-travel infrastructure

CLINICAL STUDY TO EVALUATE THE EFFICACY OF YOGIC SHUDDHIKRIYA (CLEANSING PROCEDURE) AND MADHUDAK (HONEY AND WATER) IN THE MANAGEMENT OF STHAULYA (OBESITY)

Life in today’s materialistic era, has become miserable. As a matter of fact, human life is becoming luxury oriented day by day despite all the odds. According to ecological approach, disease is nothing but a mal-adjustment of human being to his environment. The disruption in environment brings about lifestyle disorders. The sedentary lifestyle of today’s era leads to the non-communicable epidemic of Obesity. Hence for the management of Obesity the therapy which offers modification in the lifestyle will be selected from Yogic Shat-shuddhikriyas i.e. Kapalbhati in comparison with dietary therapy of Madhudak (Honey and Water) as mentioned by Ayurvedic sages. In the present study, 60 patients with features of obesity as per Ayurvedic classics and body mass index more than 25 kg/m2 were selected. This patients will be randomly divided into experimental and control group, containing thirty subjects in each. In experimental group patients were made to perform Kapalbhati yogic shuddhikriya daily at morning whereas in comparison for control group dietary therapy of Madhudak. The study reveals that there was a remarkable decrease in subjective and objective parameters in both the groups, but Kapalbhati therapy is found more effective in every aspects of obesity. Average percentage of relief in experimental group is 27.85% and in control group is 9.93%. Hence to prevent this smoldering problem of present era the ‘Sciences of life’ i.e. Yoga offers the lifestyle modifying, time effective, free of cost, objective therapy (Adravyabhoot chikitsa) through its basic principles

Retrospective evaluation of whole exome and genome mutation calls in 746 cancer samples

Funder: NCI U24CA211006Abstract: The Cancer Genome Atlas (TCGA) and International Cancer Genome Consortium (ICGC) curated consensus somatic mutation calls using whole exome sequencing (WES) and whole genome sequencing (WGS), respectively. Here, as part of the ICGC/TCGA Pan-Cancer Analysis of Whole Genomes (PCAWG) Consortium, which aggregated whole genome sequencing data from 2,658 cancers across 38 tumour types, we compare WES and WGS side-by-side from 746 TCGA samples, finding that ~80% of mutations overlap in covered exonic regions. We estimate that low variant allele fraction (VAF < 15%) and clonal heterogeneity contribute up to 68% of private WGS mutations and 71% of private WES mutations. We observe that ~30% of private WGS mutations trace to mutations identified by a single variant caller in WES consensus efforts. WGS captures both ~50% more variation in exonic regions and un-observed mutations in loci with variable GC-content. Together, our analysis highlights technological divergences between two reproducible somatic variant detection efforts

Supply chain coordination with service -differentiated customer classes

Supply chains can often be characterized by multiple customer segments differentiated by their service requirement (in terms of product availability, response times or fillrates). This dissertation studies strategies and methodologies for managing service differentiated supply chains. Our approach is to combine an extensive field study with a rigorous analysis of inventory policies. This research was directly motivated by a supply chain research project with the US Navy and the Defense Logistics Agency. The first part of the dissertation reports on an extensive empirical and field study of the logistics system used to support service parts for weapon systems in the military. This study tests the relationships between the drivers of performance in the military logistics system. This study also provides important insights into how companies can effectively manage parts with heterogeneous attributes and service requirements. The second part analyzes a threshold inventory rationing policy as a strategy for providing service differentiation for customer classes. By using a cost framework, we develop a tractable and implementable solution to the threshold rationing problem which minimizes total inventory costs. Our numerical study shows that threshold rationing policies are most beneficial when there exists a significant difference in the service requirements for the two customer classes, and when the high priority customer demand is a small fraction of total demand. The cost savings in these cases by using threshold rationing policies could be as high as 30%. The final part of the dissertation uses a game-theory framework for analyzing decentralized supply chains. Our analysis confirms that a fixed pricing mechanism can lead to incentive problems for a service differentiated supply chain. An incentive compatible pricing mechanism can be constructed by charging a price differential for customers with high and low service requirements. Our analysis also shows that by using, delivery guarantees, the overall supply chain costs can be minimized. Thus, the last part of this dissertation provides a framework for pricing differentiated service requirements in a decentralized supply chain

Supply chain coordination with service -differentiated customer classes

Supply chains can often be characterized by multiple customer segments differentiated by their service requirement (in terms of product availability, response times or fillrates). This dissertation studies strategies and methodologies for managing service differentiated supply chains. Our approach is to combine an extensive field study with a rigorous analysis of inventory policies. This research was directly motivated by a supply chain research project with the US Navy and the Defense Logistics Agency. The first part of the dissertation reports on an extensive empirical and field study of the logistics system used to support service parts for weapon systems in the military. This study tests the relationships between the drivers of performance in the military logistics system. This study also provides important insights into how companies can effectively manage parts with heterogeneous attributes and service requirements. The second part analyzes a threshold inventory rationing policy as a strategy for providing service differentiation for customer classes. By using a cost framework, we develop a tractable and implementable solution to the threshold rationing problem which minimizes total inventory costs. Our numerical study shows that threshold rationing policies are most beneficial when there exists a significant difference in the service requirements for the two customer classes, and when the high priority customer demand is a small fraction of total demand. The cost savings in these cases by using threshold rationing policies could be as high as 30%. The final part of the dissertation uses a game-theory framework for analyzing decentralized supply chains. Our analysis confirms that a fixed pricing mechanism can lead to incentive problems for a service differentiated supply chain. An incentive compatible pricing mechanism can be constructed by charging a price differential for customers with high and low service requirements. Our analysis also shows that by using, delivery guarantees, the overall supply chain costs can be minimized. Thus, the last part of this dissertation provides a framework for pricing differentiated service requirements in a decentralized supply chain

Hot filament activated chemical vapor deposition of nitride and carbide thin films.

A novel method of Hot Filament activated Chemical Vapor Deposition (HFCVD) has been explored for the deposition of nitride and carbide thin films. This method was employed to obtain silicon nitride, titanium nitride and boron carbide thin films. This hot filament assisted activation of stable molecules helps in reducing the deposition temperatures and in obtaining thin films at high rates. In this method, the stable precursor gases, such as ammonia, methane and hydrogen, are decomposed at the surface of a resistively heated tungsten filament (1500\sp\circC to 1850\sp\circC). These activated precursors further downstream react with the source gases to form the desired film on a temperature controlled substrate. Various thin film characterization techniques were used to evaluate the properties of these films. Elemental composition of the films was determined by X-ray photoelectron spectroscopy (XPS) and Rutherford backscattering spectroscopy (RBS). The film thicknesses were measured by single-wavelength ellipsometry, RBS and cross sectional scanning electron microscopy. The microstructure was studied with X-ray diffraction and electron microscopy. The bonding configuration in the films was analyzed with Fourier transformed infrared and Raman spectroscopies. Very high deposition rates (up to 2000 A/min) were obtained for silicon nitride at low substrate temperatures (245-370\sp\circC). The silicon nitride films were amorphous and had low hydrogen content. They also showed very low etch rates in buffered hydrofluoric acid solution. These silicon nitride films also showed strong visible photoluminescence (PL). The PL in these films has been characterized in detail and a qualitative model is proposed for the origin of PL. The titanium nitride films were polycrystalline with grain sizes between 300 and 1000 A. The substrate temperature had a strong influence on the grain orientation. These films showed low resistivity, good conformality and diffusion barrier properties. The diffusion barrier performance was tested for both aluminum and copper films. We also performed preliminary studies on low temperature (450\sp\circC) deposition of boron carbide films for hard protective coating applications. The films were amorphous as determined by transmission electron microscopy. Preliminary wear testing showed that these films adhere well and have high hardness.Ph.D.Chemical EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104286/1/9513336.pdfDescription of 9513336.pdf : Restricted to UM users only