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Papers by Christian Davis

Journal of transportation engineering, Nov 1, 1989

Résumé/Abstract The proposed model includes the following objectives:(1) Minimization of risk;(2)... more Résumé/Abstract The proposed model includes the following objectives:(1) Minimization of risk;(2) minimization of risk of special population categories;(3) minimization of travel time; and (4) minimization of property damages. A capacitated and a noncapacitated version of ...

La pandemia de la COVID-19 ha evidenciado algunos retos para la integridad y eficiencia en la con... more La pandemia de la COVID-19 ha evidenciado algunos retos para la integridad y eficiencia en la contratación pública peruana. Este artículo analiza los procedimientos que las entidades públicas han usado para contratar los bienes y servicios necesarios para atender la emergencia sanitaria: la contratación directa por situación de emergencia, las contrataciones menores o iguales a ocho unidades impositivas tributarias, la comparación de precios, los catálogos electrónicos de acuerdos marco, el contrato por encargo y la contratación internacional. Este análisis incluye oportunidades de mejora para un mejor uso de la contratación pública.

La problemática radica en que el abogado puede abusar de su posición e inclinar en su propio bene... more La problemática radica en que el abogado puede abusar de su posición e inclinar en su propio beneficio los intereses de su patrocinado. E incluso si opta por privilegiar el interés de su cliente, su actuación puede generar en los terceros, una apariencia indebida. Sumario: 1.1ntroducción 2.Definición y problemática de la situación 3.Valores en juego 3.1.EI abogado y su cliente 3.1.1.Deber de diligencia en el patrocinio 3.1.2.Deber de confianza 3.1.3.Deber de lealtad 3.2.EI abogado y sus deberes con la profesión 3.2.1.Deber de independencia 3.2.2.Dignidad y decoro profesional 3.2.3.Deber de apariencia ética 3.3.EI abogado y la entidad sujeto de su interés 3.3.1.0bligaciones con el interés propio 4.Análisis crítico de la solución planteada por el Código 4.1.Comunicar al cliente 4.2.Abstenerse de realizar el encargo 4.3.Consentimiento del cliente 4.4.EI abogado no acepta o renuncia el encargo ya iniciado 4.5.EI abogado continúa con el encargo 5.Sanciones ante el incumplimiento del artículo 29° del Código de Ética 5.1.Medidas judiciales 5.2.Medidas colegiales 6.1deas principales.

Transportation Research Record, 1994

1.1 Background In March I995, the Principal Investigators met with Ms. Susan Maloney, Highway Saf... more 1.1 Background In March I995, the Principal Investigators met with Ms. Susan Maloney, Highway Safety Program Manager. She described the HSP in general and the need for assistance in designing and conducting surveys and analyzing the results for the two ...

We investigate our novel and new technique for analysing Intelligence, Surveillance and Reconnais... more We investigate our novel and new technique for analysing Intelligence, Surveillance and Reconnaissance (ISR) in military engagements. This is a small part of the work that has been carried out at the Defence Science and Technology Organisation (DSTO) and the Western Australian Centre of Excellence in Industrial Optimisation (WACEIO) to assess the value of ISR systems when the friendly operational commander is conducting Manoeuvre Warfare, which requires the friendly force that is relatively small and mobile be advantageously positioned in space and time to disrupt the strength and will to fight of the enemy force [2, 3]. Mathematical models of the ISR operations are developed for a generic engagement between the friendly and enemy forces, and then demonstrated using a maritime battle that necessitates the collection of information on the dispositions of the enemy scouts and their threats by a satellite (Option 1), an Unmanned Aerial Vehicle (UAV) (Option 2) or both of these ISR systems (Option 3) prior to commencing hostilities. For the parametric choices that define these options, the results show that Option 3 is the best, Option 1 is the second best and Option 2 is the third best. Furthermore, the results show that our technique will assist with gaining a deeper understanding of how the ISR operations impact on the operational commander's objective.

Bone porosity is important for several reasons. The use of mercury intrusion porosimetry is shown... more Bone porosity is important for several reasons. The use of mercury intrusion porosimetry is shown to be a promising technique for establishing pore size distribution and pore connectivity.

Transportation Research Board Special Report, 1981

The theory of poroelasticity deals with the mechanics of a fluid-saturated porous medium. A simpl... more The theory of poroelasticity deals with the mechanics of a fluid-saturated porous medium. A simplified description of the theory and its significance in relation to the growth and resorption of bone is presented.

Transportation Research Record, 1995

Matthew holds a BS, MEng, and PhD in Mechanical Engineering from Lehigh University. He is current... more Matthew holds a BS, MEng, and PhD in Mechanical Engineering from Lehigh University. He is currently a Post-Doc Research Associate working on a novel snake-like robot with construction, aerospace, and rescue capabilities through his company Impossible Incorporated LLC. The project tied for second place in the 2016 Lemelson-MIT invention competition. As part of his duties he is the professor for the Technical Entrepreneurship Capstone and the senior mechanical engineering lab course at Lehigh. Most recently he was the recipient of the 2017 John B. Ochs award for Faculty Achievement in Entrepreneurship Education.

International Journal of Engineering Science, Dec 1, 1972

Two-phase poroelastic material is taken as a model of the bone, in the sense that the osseous tis... more Two-phase poroelastic material is taken as a model of the bone, in the sense that the osseous tissue is considered as a perfectly elastic solid and the fluid substances filling the cavities as a viscous compressible fluid. Biot's theory of consolidation is adopted, assuming interconnections between the cavities. For a transversely isotropic body the theory leads to seven linear constitutive equations, connecting seven stress components with seven defo~ation components, by means of eight material eoeficients. The theory is applied to beam-like structural elements by using the procedure of Michell, consisting of representation of stress and deformation components as rational integral functions of the axial coordinate z. General equations are derived for two particular cases; (a) when the stress and strain components do not depend on z, (b) when the latter are linear functions of 2. The first case corresponds to the action of terminal couples (both flexural and torsional); the second case is associated with the action of terminal forces. Illustrative examples are solved, involving (a) cyIindrical bending of poroelastic plates by terminal couples, (b) pure bending of poroelastic beams of arbitrary cross section having one axis of symmetry, (c) pure torsion of poroelastic beams of arbitrary cross section. The explicit solution of the case (b) shows that the behavior of the poroelastic material is analogous to that of a three-element visco-elastic model. This agrees qualitatively with the experimental findings of Sedlin for bones. 1. INT~ODUCTlO~

Journal of Applied Mechanics, Sep 1, 1971

Two-phase poroelastic material is taken as a model of the living bone in the sense that the osseo... more Two-phase poroelastic material is taken as a model of the living bone in the sense that the osseous tissue is treated as a linear isotropic perfectly elastic solid, and the fluid substances filling the pores as a perfect fluid. Using Biot’s equations, derived in his consolidation theory, four coupled governing differential equations for the propagation of harmonic longitudinal waves in circularly cylindrical bars of poroelastic material are derived. A longer manipulation reduces the task of solution to a single ordinary differential equation with variable coefficients and a regular singular point. The equation is solved by Frobenius’ method. Three boundary conditions on the curved surface of the bar, expressing the absence of external loading and the permeability of the surface, supply a system of three linear equations in three unknown coefficients. A nontrivial solution of the system gives two phase velocities of propagation of longitudinal waves in agreement with the finding of Biot for an infinite medium. A simplification to the purely elastic case yields the elementary classical result for the longitudinal waves.

Mathematical biosciences, Aug 1, 1970

Abstract Two-phase isotropic homogeneous poroelastic material is taken as a model of the living b... more Abstract Two-phase isotropic homogeneous poroelastic material is taken as a model of the living bone in the sense that the osseous tissue is considered as a linear perfectly elastic solid and the fluid substances filling the cavities as a Newtonian viscous fluid. Using the Heinrich-Desoyer formulation of the consolidation theory of Terzaghi-Biot adapted to the spherical bodies and the Laplace transformation, the pressure head function is determined first. The complimentary solution of the equation for the displacement of the solid phase is then adapted from the classical elastic solution in terms of the Legendre polynomials. For simplicity, only the axisymmetric case is considered. The integration constants are determined from the third governing equation as well as from the boundary and initial conditions. Three illustrative examples are investigated in detail, assuming hydrostatic load: (1) a thick-walled shell if the fluid pressure may be disregarded, (2) a solid poroelastic sphere, (3) a thin-walled poroelastic shell. In case 2, the rheological model describing the behavior of the body seems to correspond to the Kelvin-Voigt model proposed for osseous tissues by Zarek and Edwards.

Journal of the Operational Research Society, Apr 1, 1994

(ConnDOT) was charged with investigating the possibility of reducing costs by operating with fewe... more (ConnDOT) was charged with investigating the possibility of reducing costs by operating with fewer than 13 equipment repair facilities. Using a mixed-integer programming model, we helped ConnDOT identify options for achieving savings without sacrificing quality of service. A key feature of the model is that it establishes repair capacities based on the past performance of benchmark facilities within the system. As we developed recommendations, we gave serious consideration to factors outside the context of the model and to feedback received from ConnDOT personnel. Ultimately, we proposed two options-one containing ten facilities and the other 11. The net present values of savings offered by these options are estimated at over 5.0millionand5.0 million and 5.0millionand3.1 million, respectively. While the 11-facility option is lower in savings, it has advantages in that it: (1) satisfies concerns highlighted by ConnDOT Maintenance; (2) is easier to implement than the ten-facility option; and (3) represents less of a current commitment, which is beneficial if future consideration of additional changes is likely. These advantages contributed to the 11-facility option being the one most widely preferred within ConnDOT.