Development of a test system to analyze different hip fracture osteosyntheses under simulated walking

The mechanical complications of osteosyntheses after hip fractures are previously investigated by mostly static or dynamic uniaxial loading test systems. However, the physiologic loading of the hip joint during a normal gait is a multiplanar, dynamic movement. Therefore, we constructed a system to test osteosyntheses for hip fractures under physiologic multiplanar loading representative of normal gait. To evaluate the testing system, 12 femora pairs were tested under 25,000 cycles with two standard osteosyntheses (Proximal Femoral Nail Antirotation/Gamma3 Nail). For angular movement, the varus collapse to cut out (proportional to(CO)) (proportional to(CO) = 4.8 degrees +/- 2.1 degrees for blade and proportional to(CO) = 7.8 degrees +/- 3.8 degrees for screw) was the dominant failure mode, and only slight rotational angle shifts (proportional to(Rot)) (proportional to(Rot) = 1.7 degrees +/- 0.4 degrees for blade and proportional to(Rot) = 2.4 degrees +/- 0.3 degrees for screw) of the femoral head around the implant axis were observed. Angular displacements in varus direction and rotation were higher in specimens reinforced with screws. Hence, the cut out model and the migration directions showed a distinction between helical blade and hip screw. However, there were no significant differences between the different implants. The new setup is able to create clinical failures and allows to give evidence about the anchorage stability of different implant types under dynamic gait motion pattern

Extensible synthetic file servers? or: Structuring the glue between tester and system under test

We discuss a few simple scenarios of how we can design and develop a compositional synthetic file server that gives access to external processes – in particular, in the context of testing, gives access to the system under test – such that certain parts of said synthethic file server can be prepared as off-the-shelf components to which other specifically written parts can be added in a kind of plug-and-play fashion.\ud \ud The approaches only deal with the problem of accessing the system under test from the point of view of offered functionality, and compositionality, but do not consider efficiency or performance. \ud \ud The study is rather preliminary, and only very limited practical experiments have been performed

Pseudo-noise test set for communication system evaluation

A test set for communications systems is described which includes a pseudo noise sequence generator providing a test signal that is fed to a pair of signal channels. The first channel includes a spectrum shaping filter and a conditioning amplifier. The second channel includes a variable delay circuit, a spectrum shaping filter matched to the first filter, and an amplifier. The output of the first channel was applied to the system under test. The output of the system and the output of the second channel are compared to determine the degree of distortion suffered by the test signal due to the communications system

Using status messages in the distributed test architecture

If the system under test has multiple interfaces/ports and these are physically distributed then in testing we place a tester at each port. If these testers cannot directly communicate with one another and there is no global clock then we are testing in the distributed test architecture. If the distributed test architecture is used then there may be input sequences that cannot be applied in testing without introducing controllability problems. Additionally, observability problems can allow fault masking. In this paper we consider the situation in which the testers can apply a status message: an input that causes the system under test to identify its current state. We show how such a status message can be used in order to overcome controllability and observability problems

Simple system for locating ground loops

A simple low-cost system for rapid identification of the cables causing ground loops in complex instrumentation configurations is described. The system consists of an exciter module that generates a 100 kHz ground loop current and a detector module that determines which cable conducts this test current. Both the exciter and detector are magnetically coupled to the ground circuit so there is no physical contact to the instrumentation system under test

Extending stream X-machines to specify and test systems with timeouts

Stream X-machines are a kind of extended finite state machine used to specify real systems where communication between the components is modeled by using a shared memory.In this paper we introduce an extension of the Stream X-machines formalism in order to specify delays/timeouts.The time spent by a system waiting for the environment to react has the capability of affecting the set of available outputs of the system. So, a relation focusing on functional aspects must explicitly take into account the possible timeouts.We also propose a formal testing methodology allowing to systematically test a system with respect to a specification. Finally, we introduce a test derivation algorithm. Given a specification, the derived test suite is sound and complete, that is, a system under test successfully passes the test suite if and only if this system conforms to the specification

Short-run learning dynamics under a test-based accountability system : evidence from Pakistan

Low student learning is a common finding in much of the developing world. This paper uses a relatively unique dataset of five semiannual rounds of standardized test data to characterize and explain the short-term changes in student learning. The data are collected as part of the quality assurance system for a public-private partnership program that offers public subsidies conditional on minimum learning levels to low-cost private schools in Pakistan. Apart from a large positive distributional shift in learning between the first two test rounds, the learning distributions over test rounds show little progress. Schools are ejected from the program if they fail to achieve a minimum pass rate in the test in two consecutive attempts, making the test high stakes. Sharp regression discontinuity estimates show that the threat of program exit on schools that barely failed the test for the first time induces large learning gains. The large change in learning between the first two test rounds is likely attributable to this accountability pressure given that a large share of new program entrants failed in the first test round. Schools also qualify for substantial annual teacher bonuses if they achieve a minimum score in a composite measure of student test participation and mean test score. Sharp regression discontinuity estimates do not show that the prospect of future teacher bonus rewards induces learning gains for schools that barely did not qualify for the bonus.Tertiary Education,Education For All,Secondary Education,Teaching and Learning,Primary Education

Putting formal specifications under the magnifying glass: Model-based testing for validation

A software development process is effectively an abstract form of model transformation, starting from an end-user model of requirements, through to a system model for which code can be automatically generated. The success (or failure) of such a transformation depends substantially on obtaining a correct, well-formed initial model that captures user concerns. Model-based testing automates black box testing based on the model of the system under analysis. This paper proposes and evaluates a novel model-based testing technique that aims to reveal specification/requirement-related errors by generating test cases from a test model and exercising them on the design model. The case study outlined in the paper shows that a separate test model not only increases the level of objectivity of the requirements, but also supports the validation of the system under test through test case generation. The results obtained from the case study support the hypothesis that there may be discrepancies between the formal specification of the system modeled at developer end and the problem to be solved, and using solely formal verification methods may not be sufficient to reveal these. The approach presented in this paper aims at providing means to obtain greater confidence in the design model that is used as the basis for code generation

A new test methodology based on structural resonance for mode I fatigue delamination growth in an unidirectional composite

A specific device has been set up to test by vibration resonance the mode I fatigue delamination growth onset of composite laminates. This test system, based on the DCB test specimen, is a mass-spring-specimen dynamic system designed to resonate. The defined operating conditions allow performing delamination propagation tests under imposed load and stopping the test under reproducible conditions, identical to the ones recommended in the ASTM-D6115 standard. This system allows fatigue tests to be driven up to 100Hz, reducing the time taken by a factor of ten without detrimental heat being generated in the material. The effect of frequency on the fatigue delamination growth on mode I has been investigated through a comparison with standard tests performed at 10Hz. A decrease in resistance to the propagation of delamination is observed with the increase in frequency for the composite studied. This frequency effect seems to be a strain rate effect and was taken in consideration by using dynamical critical energy restitution rate for the G-N curve plotting