Time filter

Source Type

Lexington, VA, United States

The Virginia Military Institute is a state-supported military college in Lexington, Virginia, the oldest such institution in the United States. Unlike any other senior military college in the United States, and in keeping with its founding principles, VMI enrolls only military cadets and awards baccalaureate degrees exclusively. VMI offers cadets strict military discipline combined with a spartan, physically and academically demanding environment. The Institute grants degrees in 14 disciplines in engineering, the science, and the liberal arts.While VMI has been called the "West Point of the South", it differs from the federal service academies in several respects. For example, the living conditions at VMI are far more austere than at the service academies. Also, while all cadets must participate in the Reserve Officers' Training Corps , they are afforded the flexibility of pursuing civilian endeavors or accepting a commission in any of the active or reserve components of any of the US military branches upon graduation. Wikipedia.

Smythe A.B.,Virginia Military Institute
Integrative and Comparative Biology | Year: 2015

Marine nematodes of the order Enoplida may represent the earliest lineage of nematodes and have a variety of fixed and movable feeding structures in their stomas. This study used an 18S ribosomal RNA phylogeny of the orders Enoplida and Triplonchida (subclass Enoplia) to explore the evolution of these feeding structures in light of previous hypotheses based solely on morphology. The Enoplida and Triplonchida were found to be paraphyletic, as several taxa currently classified as Triplonchida, such as Rhabdodemania, were found to be part of the Enoplida clade. The position of Rhabdodemania within Enoplida was unclear, but a close relation to Enoplidae and Thoracostomopsidae was not supported, making it unlikely that its movable odontia are homologous with the mandibles of these families. A member of Anticomidae was well-supported as the base of the clade containing Phanodermatidae, Enoplidae, and Thoracostomopsidae, suggesting that taxa with buccal rods and mandibles evolved from nematodes with unarmed stomas. The Phanodermatidae were shown to be more closely related to the Enoplidae and Thoracostomopsidae than were the Leptosomatidae, suggesting that the buccal rods of the phanoderms (rather than the mandibular ridge/odontia complex of the Leptosomatidae), may be the origin of the mandibles. © 2015 The Author 2015. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. Source

Swenty M.K.,Virginia Military Institute | Graybeal B.A.,U.S. Federal Highway Administration
Materials and Structures/Materiaux et Constructions | Year: 2015

Differential displacements are commonly induced between precast reinforced concrete members during construction such as in connections on staged bridge construction projects. The ultimate bond strength between reinforcing bars (rebar) and an embedment material used in the connections may be affected. A pullout test was devised to compare the early age ultimate bond strength developed in specimens with and without differential displacements. A range of different grout and concrete materials (embedment materials) used within typical connections were tested. Maximum relative displacements at right angles to #13M (13 mm diameter) rebar ranged from 2.5 to 0.13 mm (a bar diameter–displacement ratio ranging from 10 to 200). These displacements were imparted from casting until the embedment materials reached final set. Pullout testing on both static and displaced test specimens was subsequently performed at approximately 24 h after casting. When the rebar displaced 1.3 mm or more (a bar diameter–displacement ratio of 20 or less), reduced bond capacity was observed in all embedment materials tested. When the rebar displaced 0.25 mm or less (a bar diameter–displacement ratio of 100 or more), the results indicate insignificant variations in bond strength regardless of embedment material type. These results show that large displacements applied prior to final set of the embedment material can have a detrimental effect on the pure bond strength. © 2014, RILEM. Source

Yuan D.,Texas A&M University | Zhao D.,Texas A&M University | Timmons D.J.,Virginia Military Institute | Zhou H.-C.,Texas A&M University
Chemical Science | Year: 2011

A Cd MOF with twisted partially augmented the net was synthesized. Activation at increasing temperatures revealed an unprecedented stepwise transition from microporosity to mesoporosity. This thermal treatment may serve as an alternative approach for the preparation of mesoporous MOFs. © The Royal Society of Chemistry 2011. Source

Zhao D.,Texas A&M University | Timmons D.J.,Virginia Military Institute | Yuan D.,Texas A&M University | Zhou H.-C.,Texas A&M University
Accounts of Chemical Research | Year: 2011

Metal-organic frameworks (MOFs) - highly crystalline hybrid materials that combine metal ions with rigid organic ligands - have emerged as an important class of porous materials. The organic ligands add flexibility and diversity to the chemical structures and functions of these materials. In this Account, we summarize our laboratorys experience in tuning the topology and functionality of MOFs by ligand design.These investigations have led to new materials with interesting properties. By using a ligand that can adopt different symmetry conformations through free internal bond rotation, we have obtained two MOFs that are supramolecular stereoisomers of each other at different reaction temperatures. In another case, where the dimerized ligands function as a D 3-Piedfort unit spacer, we achieve chiral (10,3)-a networks.In the design of MOF-based materials for hydrogen and methane storage, we focused on increasing the gas affinity of frameworks by using ligands with different geometries to control the pore size and effectively introduce unsaturated metal centers (UMCs) into the framework. Framework interpenetration in PCN-6 (PCN stands for porous coordination network) can lead to higher hydrogen uptake. Because of the proper alignment of the UMCs, PCN-12 holds the record for uptake of hydrogen at 77 K/760 Torr. In the case of methane storage, PCN-14 with anthracene-derived ligand achieves breakthrough storage capacity, at a level 28% higher than the U.S. Department of Energy target.Selective gas adsorption requires a pore size comparable to that of the target gas molecules; therefore, we use bulky ligands and network interpenetration to reduce the pore size. In addition, with the help of an amphiphilic ligand, we were able to use temperature to continuously change pore size in a 2D layer MOF. Adding charge to an organic ligand can also stabilize frameworks. By ionizing the amine group within mesoMOF-1, the resulting electronic repulsion keeps the network from collapsing, giving rise to the first case of mesoporous MOF that demonstrates the type IV isotherm. We use dendritic hexacarboxylate ligands to synthesize an isoreticular series of MOFs with (3,24)-connected network topology. The cuboctahedral cages serve as building blocks that narrow the opening of the mesocavities into microwindows and stabilize these MOFs. The resulting materials have exceptionally high surface areas and hydrogen uptake capacities.Despite the many achievements in MOF development, there is still ample opportunity for further exploration. We will be continuing our efforts and look forward to contributing to this blossoming field in the next decade. © 2010 American Chemical Society. Source

Cobb B.R.,Virginia Military Institute | Rumi R.,University of Almeria | Salmeron A.,University of Almeria
Computers and Operations Research | Year: 2013

This paper examines optimal policies in a continuous review inventory management system when demand in each time period follows a log-normal distribution. In this scenario, the distribution for demand during the entire lead time period has no known form. The proposed procedure uses the Fenton-Wilkinson method to estimate the parameters for a single log-normal distribution that approximates the probability density function (PDF) for lead time demand, conditional on a specific lead time. Once these parameters are determined, a mixture of truncated exponentials (MTE) function that approximates the lead time demand distribution is constructed. The objective is to include the log-normal distribution in a robust decision support system where the PDF that best fits the historical period demand data is used to construct the lead time demand distribution. Experimental results indicate that when the log-normal distribution is the best fit, the model presented in this paper reduces expected inventory costs by improving optimal policies, as compared to other potential approximations. © 2013 Elsevier Ltd. Source

Discover hidden collaborations