Doctor of Philosophy (PhD), Ohio University, 2021, Industrial and Systems Engineering (Engineering and Technology)

Many Grocery stores have begun offering a service called “Click and Collect” (C&C). Customers using this service can order their groceries online and collect them at the store or have them delivered to their desired location. The way customer orders are fulfilled in grocery stores is similar to some warehouse order fulfillment. Therefore, warehouse order picking methods can be used in grocery stores to create an efficient C&C service. Currently, workers in the stores typically travel with a cart to storage shelves to retrieve products to fulfill C&C customer orders, which is similar to the warehouse order picking process. To reduce/eliminate worker travel, automated storage/retrieval equipment can be installed in the store. One type of equipment for storing items is the vertical lift module (VLM). Worker travel in the grocery stores can be reduced by using VLMs to store fast-moving SKUs. In this research, different order picking methods are developed to improve the efficiency of C The first part of the research is to determine the best batching method to achieve a better service rate. The batching heuristics studied in this dissertation are order-based batching (OBB), time-based batching (TBB), and hybrid batching (HB). The results show that in traditional order picking, HB offers faster order ready times than both OBB and TBB. The improvements in ready time with HB are small compared with OBB. TBB offers faster pick times compared with the other two batching heuristics. 4 The second part of the research is to develop a mathematical model for VLM throughput. Fast-moving SKUs are stored in the VLM so that high demand products can be picked at a faster pace. The mathematical model developed in this research can determine the expected pick time for a given batch of orders. The results show that the VLM order picking offers faster pick times and ready times compared with traditional picking. The third part of the dissertation is to develop an optimization model that (open full item for complete abstract)

Committee: Masel Dale (Advisor) Subjects: Industrial Engineering

Doctor of Philosophy, The Ohio State University, 2019, Earth Sciences

Tide gauges record relative sea level (RSL), i.e. the vertical position of the sea surface relative to the adjacent land mass or relative to the seafloor under the gauge. A tide gauge cannot distinguish between a rise in sea level or subsidence of the land or seawall or pier that supports the gauge. Absolute sea level (ASL) refers to the level or height of the sea surface stated in some standard geodetic reference frame, e.g. ITRF2008. Since satellite altimeters make a geometrical measurement of sea level, this constitutes a determination of ASL. Satellite altimeters suffer from instrumental drift and thus need to be calibrated using tide gauges. This requires us to estimate the rate of RSL change at each tide gauge and convert this into an estimate of the rate of ASL change. This is done using a GPS station located at or near the tide gauge, since it can measure the vertical velocity of the lithosphere – often referred to as vertical land motion, VLM – which allows us to exploit the relationship ASL = RSL + VLM. This goal has motivated geodesists to build dozens of continuous GPS (or CGPS) stations near tide gauges – an agenda sometimes referred to as the CGPS@TG agenda. Unfortunately, a significant fraction of all long-lived tide gauges – especially those in the Pacific - have also recorded non-steady land motion caused by earthquakes. Rather than simply delete such datasets from the agenda, this thesis explores a new analytical method, based on the concept of a geodetic station trajectory model, that allows us to compute RSL and ASL rates even at tide gauges affected by regional earthquakes. We illustrate this method using two tide gauges (PAGO and UPOL) and three GPS stations (ASPA, SAMO and FALE) located in the Samoan islands of the Southwest Pacific. In addition to managing the impact of large regional earthquakes, we also seek new approaches to reducing noise in RSL rate estimates by suppressing the higher frequency sea level changes associated with ocean (open full item for complete abstract)

Committee: Michael Bevis (Committee Chair); C.K. Shum (Committee Member); Loren Babcock (Committee Member); Michael Barton (Committee Member) Subjects: Earth; Geological; Geophysical; Geophysics; Geotechnology; Ocean Engineering; Oceanography