Public History at the U.S. House of Representatives

Smock, Raymond W.

doi:10.2307/3378126

Cited by 3 publications

(1 citation statement)

References 2 publications

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“…A universal testing machine was used for compression tests to measure the elastic modulus of the seeds, as shown in Figure 2a. The static friction coefficient of seed-seed pairs was measured using the slope method [23], as shown in Figure 2b. The simple pendulum test was employed to determine the seed-seed and seed-wall restitution coefficients [24], as shown in Figure 2c,d.…”

Section: Physical and Mechanical Test Analysis Of Seedsmentioning

confidence: 99%

Determination of Ellipsoidal Seed–Soil Interaction Parameters for DEM Simulation

Xu,

Fu,

et al. 2024

Agriculture

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During precision sowing, the contact process between the soil and seeds cannot be ignored. The constitutive relationship of soil is relatively complex, with characteristics such as high nonlinearity, while the contact mechanism between the soil and seeds is unclear. To better understand the contact between seeds and soil, it is necessary to establish a reasonable contact model. Ellipsoidal seeds, such as soybean, red bean, and kidney bean seeds, were adopted as research objects. In this paper, we used the discrete element method to establish an ellipsoidal seed–soil contact model. The JKR + bonding model was adopted for describing the adhesion between soil particles, and the Hertz–Mindlin new restitution (HMNS) model was used for ellipsoidal seed particles to eliminate the multiple contact point issue when modeling with the multi-sphere filling method. Moreover, both simulations and experiments were conducted to calibrate the interaction parameters between soil and seeds. The path of steepest ascent test and Box‒Behnken design (BBD) tests were also used, as well as direct shear tests. Thus, certain soil parameter values were obtained, namely the JKR surface energy was 4.436 J/m2, the normal stiffness per unit area was 2.86 × 106 N/m3, the shear stiffness per unit area was 5.54 × 105 N/m3, the critical normal stress was 1833 Pa, and the critical shear stress was 3332 Pa. In addition, the simulation parameters for ellipsoidal seeds were obtained from previous works. Moreover, to obtain more accurate ellipsoidal seed–soil interaction parameters, collision tests, static friction tests, and rolling friction tests were adopted. A single-factor test was used to calibrate the ellipsoidal seed–soil interaction parameters. The calibration results were as follows: the collision restitution coefficients of ellipsoidal seeds with soil were all 0.25. The static friction coefficient of soybeans with soil was 0.6, that of red beans with soil was 0.65, and that of kidney beans with soil was 0.5. The rolling friction coefficient of soybeans with soil was 0.1, that of red beans with soil was 0.14, and that of kidney beans with soil was 0.14. Finally, the rationality of parameter selection was verified through piling tests between ellipsoidal seeds and soil. The relative error of the angle of repose of soybean/soil was 2.99%, that of red bean/soil was 0.60%, and that of kidney bean/soil was 0.55%. Thus, the feasibility and rationality of the contact models between the ellipsoidal seeds and soil established in this paper, as well as the parameter selection, were verified.

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Section: Physical and Mechanical Test Analysis Of Seedsmentioning

confidence: 99%

Determination of Ellipsoidal Seed–Soil Interaction Parameters for DEM Simulation

Xu,

Fu,

et al. 2024

Agriculture

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Prologue to a Farce or a Tragedy? Accessing Government Records in the Wake of 9/11/2001

Smock¹

2003

The Public Historian

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Access to some federal government records has become more difficult since the terrorist attacks of 9/11/2001. Some records previously opened have been reclassified. Records related to the infrastructure of cities, construction plans of government buildings, development of military weapons, biological warfare subjects, and biographical information on U. S. citizens were the first categories to be tightened. Historians should keep a watchful eye on these developments. Balancing issues of national security with the public's right to government information is a crucial debate in a democracy that depends on information to make proper judgments about the workings of government.

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Government and Professional Ethics: The Case of Federal Historians

Reuss¹

1999

The Public Historian

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Public History at the U.S. House of Representatives

Cited by 3 publications

References 2 publications

Determination of Ellipsoidal Seed–Soil Interaction Parameters for DEM Simulation

Determination of Ellipsoidal Seed–Soil Interaction Parameters for DEM Simulation

Prologue to a Farce or a Tragedy? Accessing Government Records in the Wake of 9/11/2001

Government and Professional Ethics: The Case of Federal Historians

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