Transport Modal Selection and Inventory Levels in the Context of Global Supply Chains

In this dissertation, I study the transport modal selection in global supply chains and its effects on operational performance. First, I examine the factors that affect the transport modal selection and propose that revenue drivers and cost drivers of decision makers determine their transport modal selection in pursuit of profit maximization. Then, I study the effects of the use of air shipping in export on shippers' operational performance in terms of inventory levels. In the first essay, this study examines the macro and micro factors that affect the decision of transport modal choice in global supply chains. The factors affecting modal decision are classified as the characteristics of industry, mode, shipment, and region. This study proposes that the decision maker of the modal choice aims to maximize its own profit, taking the revenue drivers and cost drivers into account. The results show that both importers and exporters use more air shipping for high-value products and when there is a positive sales surprise. Large importers and exporters have a smaller proportion of air shipping compared with small ones. While an importer's modal decision is highly associated with demand dynamics, an exporter's decision is more determined by gross margin and cost of capital but less by demand variation. In the second essay, this study examines the effects of air share on manufacturing inventories. As globalization expands a firm's geographic coverage of business, the literature indicates that globalization has led to higher inventory levels due to longer supply chains. The experience in the U.S. domestic market showing that air transport plays a more important role in the practice of JIT after the deregulation in 1978 could be applicable to global markets. This study finds that the usage of air shipping in export can effectively reduce manufacturers' inventory levels at a diminishing rate. In addition, transportation modal selection is associated with profit maximization. It is found that the demand variation contributes to more use of air shipping. In addition, higher gross margins, cost of capital, and the relevance to timeliness facilitate firms to use air shipping to capture the demand and shorten the cash cycle. Furthermore, the industries with larger major players have higher shares of ocean shipping because of risk pooling advantage. For practioners, the results are used to develop guidelines for transport modal decision including the breakeven point of carrying costs based on total cost minimization and optimal air shares based on profit maximization. This study reiterates that a firm should pursue profit maximization rather than total cost minimization only

Achieving Excellence for California’s Freight System: Developing Competitiveness and Performance Metrics; Incorporating Sustainability, Resilience, and Workforce Development

This study explores the question of whether California\u27s freight system is staying competitive with other US regions. A novel analytical framework compares supply chain performance metrics across multiple US states and regions for seaports, airports, highways, freight rail service, and distribution centers by combining the Performance Evaluation Matrix (PEM), Competitive Position Matrix (CPM), and Business Process Management (BPM) approaches. Analysis of industry data and responses from structured interviews with 30 freight industry experts across 5 transportation sectors suggests that California\u27s freight system is competitive for seaports, airports, and freight rail; however, highways and distribution centers have room for improvement with respect to travel time reliability and operation costs, and California should prioritize infrastructure investments here. To stay competitive with the Texas and North East regions, state investments could also expand seaport container terminals and air cargo handling facilities, improve intermodal port connections and management of flows of chassis, container trucks, empty containers to ameliorate cargo backlogs and congestion on highways, at the ports, and at warehouses. The state could also invest in inland ports, transporting goods by rail directly from seaports to the Inland Empire or Central Valley

(meso-5,5,7,12,12,14-Hexamethyl-1,4,8,11-tetra­azacyclo­tetra­deca­ne)copper(II) bis­(O,S-dibenzyl dithio­phosphate)

In the crystal structure of the title compound, [Cu(C16H36N4)](C14H14O2PS2)2, the CuII atom is located on an inversion center and is chelated by four N atoms of the macrocyclic meso-5,5,7,12,12,14- hexa­methyl-1,4,8,11-tetra­azacyclo­tetra­decane ligand in a square-planar geometry, with Cu—N distances of 2.013 (3) and 2.014 (3) Å. In the crystal structure, one O,S-dibenzyl dithio­phosphate counter-anion links with the CuII complex cation through N—H⋯O and N—H⋯S hydrogen bonding. During the synthesis, the structure of the anion re-arranged from O,O′-dibenzyl dithio­phosphate in the starting material to O,S-dibenzyl dithio­phosphate in the title compound

“TELE-commuting” During the COVID-19 Pandemic and Beyond: Unveiling State-wide Patterns and Trends of Telecommuting in Relation to Transportation, Employment, Land Use, and Emissions in Calif

Telecommuting, the practice of working remotely at home, increased significantly (25% to 35%) early in the COVID-19 pandemic. This shift represented a major societal change that reshaped the family, work, and social lives of many Californians. These changes also raise important questions about what factors influenced telecommuting before, during, and after COVID-19, and to what extent changes in telecommuting have influenced transportation patterns across commute modes, employment, land use, and environment. The research team conducted state-level telecommuting surveys using a crowd-sourced platform (i.e., Amazon Mechanical Turk) to obtain valid samples across California (n=1,985) and conducted state-level interviews among stakeholders (n=28) across ten major industries in California. The study leveraged secondary datasets and developed regression and time-series models. Our surveys found that, compared to pre-pandemic levels, more people had a dedicated workspace at home and had received adequate training and support for telecommuting, became more flexible to choose their own schedules, and had improved their working performance—but felt isolated and found it difficult to separate home and work life. Our interviews suggested that telecommuting policies were not commonly designed and implemented until COVID-19. Additionally, regression analyses showed that telecommuting practices have been influenced by COVID-19 related policies, public risk perception, home prices, broadband rates, and government employment. This study reveals advantages and disadvantages of telecommuting and unveils the complex relationships among the COVID-19 outbreak, transportation systems, employment, land use, and emissions as well as public risk perception and economic factors. The study informs statewide and regional policies to adapt to the new patterns of telecommuting

Relation Between Gravitational Mass and Baryonic Mass for Non-Rotating and Rapidly Rotating Neutron Stars

With a selected sample of neutron star (NS) equations of state (EOSs) that are consistent with the current observations and have a range of maximum masses, we investigate the relations between NS gravitational mass Mg and baryonic mass Mb, and the relations between the maximum NS mass supported through uniform rotation (Mmax) and that of nonrotating NSs (MTOV). We find that for an EOS-independent quadratic, universal transformation formula (Mb=Mg+A×M2g)(Mb=Mg+A×Mg2), the best-fit A value is 0.080 for non-rotating NSs, 0.064 for maximally rotating NSs, and 0.073 when NSs with arbitrary rotation are considered. The residual error of the transformation is ∼ 0.1M⊙ for non-spin or maximum-spin, but is as large as ∼ 0.2M⊙ for all spins. For different EOSs, we find that the parameter A for non-rotating NSs is proportional to R−11.4R1.4−1 (where R1.4 is NS radius for 1.4M⊙ in units of km). For a particular EOS, if one adopts the best-fit parameters for different spin periods, the residual error of the transformation is smaller, which is of the order of 0.01M⊙ for the quadratic form and less than 0.01M⊙ for the cubic form ((Mb=Mg+A1×M2g+A2×M3g)(Mb=Mg+A1×Mg2+A2×Mg3)). We also find a very tight and general correlation between the normalized mass gain due to spin Δm = (Mmax − MTOV)/MTOV and the spin period normalized to the Keplerian period PP, i.e., log10Δm=(−2.74±0.05)log10P+log10(0.20±0.01)log10Δm=(−2.74±0.05)log10P+log10(0.20±0.01), which is independent of EOS models. These empirical relations are helpful to study NS-NS mergers with a long-lived NS merger product using multi-messenger data. The application of our results to GW170817 is discussed

Numerical simulation of the blasting vibration response of shallow buried tunnel in complex urban environment

Base on the phase I project of Nanjing metro line IV, the blasting vibration response of shallow buried tunnel in complex urban environment was studied with ANSYS/LS-DYNA, the real load change was simulated with the loading way of measured stress curve, and there was a consistent between numerical simulation results and the measured data. The numerical results indicated that the velocity distribution in different directions were close in the close area (0-2 m); the vertical seismic wave attenuated at the fastest speed in the transferring process, and the radial seismic wave attenuated the fastest in the excavation direction ; in the distance from 2 m to 5 m, the tangential and radial vibration of the initiating side were both obviously larger than the other side of the core tube, which was still more violent than the vertical vibration, and the difference decreases with the distance increases. In the surrounding rocks , the radial vibration velocity was the biggest and attenuated at the fastest speed, which was close to linear attenuation ;the tangential vibration velocity is the smallest with the a relatively gentler damping, the vertical vibration attenuated until 8 m and then increased gradually and the resultant velocity obeyed the exponential damping law

Prevention of in-stent restenosis with endothelial progenitor cell (EPC) capture stent placement combined with regional EPC transplantation: An atherosclerotic rabbit model

Background: Even with drug-eluting stents, the risk of in-stent restenosis (ISR) remains high. The goal of this study was to investigate the use of an endothelial progenitor cell (EPC) capture stent plus regional EPC transplantation to reduce the ISR rate. Methods: Endothelial progenitor cell capture stents were fabricated using fibrin gel and anti-CD34 plus anti-VEGFR-2 dual antibodies. Twenty male New Zealand white rabbits established as an atherosclerotic model were randomly divided into two groups: group 1 (n = 10), in which EPC capture stents were deployed into the right iliac artery; and group 2 (n = 10), in which sirolimus-eluting stents were placed. In both groups, EPCs were transplanted into target vessels beyond the stents, with outflow blocked. Radiologic-pathologic correlation outcomes were reviewed after 2 months.  Results: The technical success rate of EPC capture stent placement plus EPC transplantation was 100%. The ISR rate in group 1 was lower than in group 2 (1/10 vs. 4/10; p > 0.05). Minimal luminal diameters were larger in group 1 than in group 2 (computed tomographic angiography, 1.85 ± 0.15 mm vs. 1.50 ± 0.20 mm; duplex ultrasound, 1.90 ± 0.10 mm vs. 1.70 ± 0.30 mm; p > 0.05). Transplanted EPCs were tracked positively only in group 1. Pathologic analysis demonstrated neointimal hyperplasia thickness of 0.21 ± 0.09 mm in group 1 vs. 0.11 ± 0.07 mm in group 2 (p < 0.05).  Conclusion: Endothelial progenitor cell capture stent placement plus local EPC transplant decreases the ISR rate through thrombosis reduction rather than through neointimal hyperplasia inhibition