Updating for Externalists

The externalist says that your evidence could fail to tell you what evidence you do or not do have. In that case, it could be rational for you to be uncertain about what your evidence is. This is a kind of uncertainty which orthodox Bayesian epistemology has difficulty modeling. For, if externalism is correct, then the orthodox Bayesian learning norms of conditionalization and reflection are inconsistent with each other. I recommend that an externalist Bayesian reject conditionalization. In its stead, I provide a new theory of rational learning for the externalist. I defend this theory by arguing that its advice will be followed by anyone whose learning dispositions maximize expected accuracy. I then explore some of this theory’s consequences for the rationality of epistemic akrasia, peer disagreement, undercutting defeat, and uncertain evidence

Indifference to Anti-Humean Chances

An indifference principle says that your credences should be distributed uniformly over each of the possibilities you recognise. A chance deference principle says that your credences should be aligned with the chances. My thesis is that, if we are anti-Humeans about chance, then these two principles are incompatible. Anti-Humeans think that it is possible for the actual frequencies to depart from the chances. So long as you recognise possibilities like this, you cannot both spread your credences evenly and defer to the chances. I discuss some weaker forms of indifference which will allow anti-Humeans to defer to the chances

A Model-Invariant Theory of Causation

I provide a theory of causation within the causal modeling framework. In contrast to most of its predecessors, this theory is model-invariant in the following sense: if the theory says that C caused (didn't cause) E in a causal model, M, then it will continue to say that C caused (didn't cause) E once we've removed an inessential variable from M. I suggest that, if this theory is true, then we should understand a cause as something which transmits deviant or non-inertial behavior to its effect

A subjectivist’s guide to deterministic chance

I present an account of deterministic chance which builds upon the physico-mathematical approach to theorizing about deterministic chance known as 'the method of arbitrary functions'. This approach promisingly yields deterministic probabilities which align with what we take the chances to be---it tells us that there is approximately a 1/2 probability of a spun roulette wheel stopping on black, and approximately a 1/2 probability of a flipped coin landing heads up---but it requires some probabilistic materials to work with. I contend that the right probabilistic materials are found in reasonable initial credence distributions. I note that, with some normative assumptions, the resulting account entails that deterministic chances obey a variant of Lewis's 'principal principle'. I additionally argue that deterministic chances, so understood, are capable of explaining long-run frequencies

The Causal Decision Theorist's Guide to Managing the News

According to orthodox causal decision theory, performing an action can give you information about factors outside of your control, but you should not take this information into account when deciding what to do. Causal decision theorists caution against an irrational policy of 'managing the news'. But, by providing information about factors outside of your control, performing an act can give you two, importantly different, kinds of good news. It can tell you that the world in which you find yourself is good in ways you can't control, and it can also tell you that the act itself is in a position to make the world better. While the first kind of news does not speak in favor of performing an act, I believe that the second kind of news does. I present a revision of causal decision theory which advises you to manage the news about the good you stand to promote, while ignoring news about the good the world has provided for you

Mitigating Fatigue of Cantilevered Overhead Sign Structures due to Natural and Truck-Induced Wind Gusts

Cantilevered overhead sign structures (COSS) are widely used across highways in the U.S. Several cases of failures have been reported for such structures due to fatigue wind loads. The structure’s dynamic characteristics such as natural frequency and critical damping are responsible for its behavior to these loads. When the frequency of wind gusts load matches the fundamental frequency of the OSS, resonance occurs, which causes excessive vibrations. Consequently, fatigue stresses increase and may exceed the fatigue critical limit, resulting in failure. Vibrations and fatigue stresses amplitudes are dependent on the structure’s natural frequency. The objective of this study is investigating natural frequencies of COSS in order to mitigate fatigue stresses due to natural and truck–induced wind gusts. Investigating damping and other fatigue wind loads are out of the scope in this study. Alterations in factors such as the members’ configuration, arrangement, sizes, and layout of the structure control its stiffness and mass distribution which controls its natural frequency and consequently, fatigue stresses. A parametric study was considered in order to investigate the effect of these factors and recommend the best layout between 4–chord, 2–chord, and monotube COSS in mitigating fatigue. Structures were designed according to the American Association of State Highway and Transportation Officials (AASHTO) 2013, Standard Specifications for Structural Supports for Highway Signs, Luminaires, and Traffic Signals (mentioned hereafter as the AASHTO Support Specifications (2013)) and modeled using commercial finite element analysis software. Wind pressure power spectral density and time history loading functions were applied on these structures to simulate natural and truck–induced wind gusts, respectively. Eventually, on the contrary of the 2–chord structure, slanted monotube COSS with curved end post was found to have least mass, highest frequency and nearly smallest fatigue stresses

Causal counterfactuals without miracles or backtracking

If the laws are deterministic, then standard theories of counterfactuals are forced to reject at least one of the following conditionals: 1) had you chosen differently, there would not have been a violation of the laws of nature; and 2) had you chosen differently, the initial conditions of the universe would not have been different. On the relevant readings—where we hold fixed factors causally independent of your choice—both of these conditionals appear true. And rejecting either one leads to trouble for philosophical theories which rely upon counterfactual conditionals—like, for instance, causal decision theory. Here, I outline a semantics for counterfactual conditionals which allows us to accept both (1) and (2). And I discuss how this semantics deals with objections to causal decision theory from Arif Ahmed

Decision and foreknowledge

My topic is how to make decisions when you possess foreknowledge of the consequences of your choice. Many have thought that these kinds of decisions pose a distinctive and novel problem for causal decision theory (CDT). My thesis is that foreknowledge poses no new problems for CDT. Some of the purported problems are not problems. Others are problems, but they are not problems for CDT. Rather, they are problems for our theories of subjunctive supposition. Others are problems, but they are not new problems. They are old problems transposed into a new key. Nonetheless, decisions made with foreknowledge illustrate important lessons about the instrumental value of our choices. Once we've appreciated these lessons, we are left with a version of CDT which faces no novel threats from foreknowledge

Behavior Of Fillet Welds In Skewed Joints

Fillet weld connections are very common in steel structures because they are easier and cheaper than other types of welded connections, such as groove welds. Several studies were performed on fillet weld of right dihedral angle, such as T-joints weld, to specify its capacity and failure mechanisms under different load directions. Nevertheless, the fillet weld strength analysis is based solely on the shear strength of the weld. Additionally, many of the current details commonly used for T-Joints were based on the requirements for groove welds. Fillet weld design concepts for skewed T-joints in the AWS D1.1 and AISC specifications are the same as the fillet weld of right T-Joints. Except for the weld throat dimension. Incomplete fusion may occur in fillet weld in acute angles. Also, the root opening requirement of being less than or equal to 3/16 in. is based on the fabrication tolerances in AWS D1.1. The main objective of this research was determining the capacity of fillet weld in skewed joints and developing practical design methods. Secondary objectives were determining the impact of changing weld’s dihedral angle, size, and loading direction on skewed weld strength and determining the total weld strength of the skewed joint. The study includes theoretical (mathematical models), analytical (finite element analysis modeling) and experimental investigations. The analytical model was validated and calibrated by the testing results. Thirty five Specimens were prepared for the experimental study. Different mathematical models were proposed and compared with the results of finite element analysis and testing to determine an accurate mathematical representation of skewed welds. Flux-cored arc welding process was used for the tested specimens. The base metal was A572 Grade 50 steel and the weld metal was 70 ksi strength electrode. The tensile mechanical properties of the weld metal were determined from ancillary tests. The welded skewed joints were fabricated with different changing parameters: the dihedral angle, weld size, and loading direction. The load-deformation curve and strength of the welds in skewed joints were recorded from testing. The curves were used in strain compatibility application of fillet welds on both sides of skewed T-Joints to determine if the individual strength of each side can be added to obtain the total strength of the joint. Practical design procedures for skewed weld that are guided by the AISC Steel Construction Manual were proposed and compared with current procedures. Design examples are provided to show the effect of the skewed weld angle on the design of fillet welds. Prequalified status for skewed T-joints was established. Additionally, symbol for skewed T-joints fillet weld were proposed to avoid the confusion with PJP weld symbol