Using ground penetrating radar to understand the failure of the Koh Ker Reservoir, Northern Cambodia.

Ground penetrating radar, probing, and excavation were used to create a contour map of the topography of a buried laterite pavement forming the spillway of a large abandoned reservoir at the Angkorian‐period city of Koh Ker in Cambodia. Calculations of the flow velocity of water through the spillway, based on the topography of the laterite surface, demonstrate that this outlet was even less adequate for passing the flow of water from the Stung Rongea catchment than had been estimated previously by Lustig, Klassen, Evans, French, & Moffat (2018). We argue that this design flaw contributed substantially to the failure of the reservoir’s dike, possibly during the first rainy season after construction, which may have contributed to Koh Ker’s remarkably short‐lived tenure as the political center of the Khmer Empire.

Self-Reinforcing Electricity Price Dynamics under the Variable Market Premium Scheme

We report a potential self-reinforcing design flaw in the variable market premium scheme that occurs if variable renewable energy power plants receiving a premium become price-setting in the market. A high share of renewable energy is a goal of many countries on their transformation path to a sustainable future. Accordingly, policies like feed-in tariffs have been in place for many years in many countries to support investment. To foster market alignment, variable market premia have been introduced in at least 12 European countries and a further dozen additional countries world-wide. We demonstrate both with a mathematical model and different scenarios of an agent-based simulation that the combination of variable premia and a high share of hours in which renewables are price-setting may lead to a self-reinforcing downward spiral of prices if unchecked. This is caused by the market premium opening up the bidding space towards negative prices. We discuss possible objections and countermeasures and evaluate the severity of this market design flaw.

The Crisis of Representative Democracy

This chapter discusses the crisis of democracy. While this crisis can be attributed in part to specific empirical corruptions, which are themselves likely the result of contingent external shocks, the crisis of democracy can also be traced, more fundamentally, to an original design flaw: the restriction of democratic representation to “electoral” representation. The main problem is that representative democracy was designed on the basis of electoral premises that prevent even its best, most democratized contemporary versions from reaching the full potential of genuine “popular rule,” that is, a rule that empowers all equally. The chapter then looks at the internal problems to a core principle of representative government: the principle of elections. It also addresses the “realists'” objections that there is no crisis of democracy since representative democracy is working as intended.

To Err is Human, To Forget is Device-related: A Cautionary Note for Endoscopists

Background: In the United States, ∼5 million endoscopies are performed annually. Contaminated endoscopes account for more nosocomial infections than any other medical device, but the vast majority of such events go unreported. We found no reports in the literature or the FDA Manufacturer and User Facility Device Experience (MAUDE) database of the incident described below. Methods: During a colonoscopy, the operator noticed resistance while advancing a clipping wire through the channel. A balloon-tipped catheter sheath was then extruded into the colonic lumen. The sheath and endoscope were withdrawn without incident, and the procedure was completed with a different endoscope. According to equipment logs, the last time that type of balloon-tipped catheter was used occurred 20 days prior, resulting in 20 patients having potentially been exposed to an incompletely disinfected device. Interrogation of the endoscope with various inserts revealed that the presence of a retained sheath would allow passage of all types of guide wires, (snips, snares, etc), including the cleaning brush. The only device whose passage would have been prevented by a retained sheath was a vascular clipping device. A review of procedure notes and interviews of involved physicians revealed that such clippings were performed as recently as 2 days prior to the incident, thus reducing the number of potentially exposed to 2, plus the index. The county and state health departments were notified, a MAUDE report was filed, and patients were notified and offered free testing for bloodborne and enteric pathogens. Discussion: The root causes of the exposure included the absence of a closed-loop feedback for removable components (similar to an operating room sponge count), an inexperienced endoscopy technologist, and, in our opinion, a design flaw of the sheath that allows the sheath to enter the channel. Specifically, unlike other sheath brands, this brand lacks a large, irremovable warning flag that precludes channel entry (Fig. 1). Had we not been able to trace the use of each individual endoscope (n = 45) in the clinic and link each to specific patients, procedures, and reprocessing logs, we would have had no way to determine the extent of exposures. This incident, which we present as a cautionary tail to others, highlights (1) a possible equipment design flaw, (2) the importance of closed-loop feedbacks for removable components, (3) the criticality of detailed procedure notes along with granular cleaning and reprocessing logs traceable to every endoscope, and (4) the challenge of communicating risk of disease transmission to patients.Funding: NoneDisclosures: None

Factory-mounted and retrofit passive resistance sensors adapted to monitor moisture content in timber bridges

The biggest threats to the longevity of a timber bridge are rot and decay. Wood protection by design, inspections, and monitoring of the bridge for elevated moisture content will ensure that the full service life of the structure can be achieved. Today’s sensors for moisture content measurements are limited in their functionality and range. This paper presents a sensor that can be both factory installed and retrofitted, which can measure the moisture content through the cross-section of the member in a timber bridge. The sensor has been mounted on Sundbron bridge during manufacturing and retrofitted on Gislaved bridge. The ensuing measurements helped to adjust a design flaw on Gislaved bridge. Monitoring of Sundbron showed that the bridge deck dried up after the bridge had been exposed to sleet and snow during the on-site assembly of the stress laminated bridge deck.