Correction due to finite speed of light in absolute gravimeters

Correction due to finite speed of light is among the most inconsistent ones in absolute gravimetry. Formulas reported by different authors yield corrections scattered up to 8 $\mu$Gal with no obvious reasons. The problem, though noted before, has never been studied, and nowadays the correction is rather postulated than rigorously proven. In this paper we make an attempt to revise the subject. Like other authors, we use physical models based on signal delays and the Doppler effect, however, in implementing the models we additionally introduce two scales of time associated with moving and resting reflectors, derive a set of rules to switch between the scales, and establish the equivalence of trajectory distortions as obtained from either time delay or distance progression. The obtained results enabled us to produce accurate correction formulas for different types of instruments, and to explain the differences in the results obtained by other authors. We found that the correction derived from the Doppler effect is accountable only for $\frac23$ of the total correction due to finite speed of light, if no signal delays are considered. Another major source of inconsistency was found in the tacit use of simplified trajectory models

Partial Cholecystectomy Safe and Effective

Patients undergoing surgical treatment for calculous disease were considered to have had a partial cholecystectomy performed when a part of the gall bladder wall was retained for technical reasons. Forty patients underwent partial cholecystectomy: for chronic cholecystitis (20), acute cholecystitis (4), Mirizzi's syndrome (14), portal hypertension or partially accesible gall bladder (one patient each). Four patients (10%) developed infective complications and two patients had retained common bile duct stones. In a mean follow up period of 13 months (range 1–36 mths), only 3 patients have ongoing mild dyspeptic symptoms while the rest have remained asymptomatic. Partial cholecystectomy has been found to be a safe and effective procedure in difficult cholecystectomy situations, since it combines the merits of cholecystectomy and cholecystostomy

Folded Lightweight Actuator Positioning System (FLAPS)

Precision actuation of mechanical structures on small spacecraft is challenging. Current solutions include single-use actuators, which rely on pyrotechnics and springs, and multiple-use actuators, which typically consume more size, weight, and power than available on CubeSats. The Folded Lightweight Actuated Positioning System (FLAPS) demonstrates the use of a simple rotary shape memory alloy (SMA) actuator in a bending architecture, along with a feedback control loop for repeatable and precise deployment. The FLAPS mechanism consists of a pair of SMA strips mounted to a hinge assembly, with one side attached to the CubeSat bus and the other to the deployable element. A custom actuator shape was manufactured using oven annealing. SMA actuation is achieved using joule heating. Feedback control is provided by a closed-loop PID control scheme, feedback sensor, and controller board. The FLAPS actuator is currently being developed for CubeSat solar panel positioning and drag control. Other potential FLAPS applications include aperture repositioning, deployable radiators, and steerable antennas. The FLAPS team will validate the actuator system in a microgravity environment on a parabolic fight in late 2019

Finding Bugs in Cryptographic Hash Function Implementations

Cryptographic hash functions are security-critical algorithms with many practical applications, notably in digital signatures. Developing an approach to test them can be particularly difficult, and bugs can remain unnoticed for many years. We revisit the NIST hash function competition, which was used to develop the SHA-3 standard, and apply a new testing strategy to all available reference implementations. Motivated by the cryptographic properties that a hash function should satisfy, we develop four tests. The Bit-Contribution Test checks if changes in the message affect the hash value, and the Bit-Exclusion Test checks that changes beyond the last message bit leave the hash value unchanged. We develop the Update Test to verify that messages are processed correctly in chunks, and then use combinatorial testing methods to reduce the test set size by several orders of magnitude while retaining the same fault-detection capability. Our tests detect bugs in 41 of the 86 reference implementations submitted to the SHA-3 competition, including the rediscovery of a bug in all submitted implementations of the SHA-3 finalist BLAKE. This bug remained undiscovered for seven years, and is particularly serious because it provides a simple strategy to modify the message without changing the hash value returned by the implementation. We detect these bugs using a fully-automated testing approach

Modeling Distillers Dried Grains with Solubles (DDGS) Mass Flow Rate as Affected by Drying and Storage Conditions

Ethanol production in 2015 was over 15 million gallons in the United States, and it is projected to increase in the next few years to meet market demands. With the continued growth in the ethanol industry, there has been enormous expansion in distillers grains production. Because the local market for distillers dried grains with solubles (DDGS) is often saturated, it is essential to transport DDGS long distances, across the United States and to international markets. Caking and agglomeration of DDGS particles in hoppers and other storage structures are typical during transportation. The current study deals with DDGS prepared by combining condensed distillers solubles (CDS) with distillers wet grains and then drying at varying temperatures. DDGS was stored in conical hoppers under varying ambient temperature, consolidation pressure, and time conditions. We investigated the effects of CDS (10, 15, and 20% wb), drying temperature (100, 200, and 300°C), drying time (20, 40, and 60 min), cooling temperature (0, 25, and 50°C), consolidation pressure (0, 1.72, and 3.43 kPa), and consolidation time (0, 3, and 6 days) levels on various flow parameters. To examine these factors, Taguchi’s experimental design with an L18 orthogonal array was implemented. Response surface modeling yielded mass flow rate = f(Hausner ratio, angle of repose) with R2 = 0.99, and it predicted moisture content for good, fair, and poor flow. Results showed that drying temperature, drying time, and cooling type were the main factors in predicting mass flow rate. The Johansson model for predicted mass flow rate was calibrated with experimental data, and a new parameter, compressibility factor, with a value of 0.96 g2/(min cm3), was determined to quantify the divergence of compressible and cohesive materials (such as DDGS) for free-flowing bulk solids. Thus, the predicted models may be beneficial for quantitative understanding of DDGS flow

An Introduction to Statistical Issues and Methods in Metrology for Physical Science and Engineering

This article provides an overview of the interplay between statistics and measurement. Measurement quality affects inference from data collected and analyzed using statistical methods while appropriate data analysis quantifies the quality of measurements. This article brings material on statistics and measurement together in one place as a resource for practitioners. Both frequentist and Bayesian methods are discussed

How handwriting reduces negative online ratings

This research investigates whether handwriting during the tourism experience reduces subsequent negative and extreme online rating scores. We portray that handwriting, due to a more deeply rooted elaboration of information, activates emotional empathy. Study 1, a field experiment in the hospitality context, suggests that handwriting reduces the extremeness of subsequent online rating scores. Study 2 compares handwritten vs. typed comments and complements the initial findings by clarifying the mediating role of emotional empathy on this relationship. We discuss the boundary conditions for the effect and offer practical implications on how to nudge tourists to reduce negative online rating scores. Hotel operators should use their enhanced emotional bonding with tourists when competing with peer-to-peer operators