Teaching Software Evolution in Open Source

Most software engineering courses require students to develop small programs from scratch, but professional engineers typically work on the evolution of large software systems. Using open source software and a software change process model can narrow this gap without imposing excessive demands on students or instructors.     

Model-based testing of software and systems: recent advances and challenges

Model-based testing is focused on testing techniques which rely on the use of models. The diversity of systems and software to be tested implies the need for research on a variety of models and methods for test automation. We briefly review this research area and introduce several papers selected from the 22nd International Conference on Testing Software and Systems (ICTSS).     

Generating asynchronous test cases from test purposes

Context

Input/output transition system (IOTS) models are commonly used when next input can arrive even before outputs are produced. The interaction between the tester and an implementation under test (IUT) is usually assumed to be synchronous. However, as the IUT can produce outputs at any moment, the tester should be prepared to accept all outputs from the IUT, or else be able to block (refuse) outputs of the implementation. Testing distributed, remote applications under the assumptions that communication is synchronous and actions can be blocked is unrealistic, since synchronous communication for such applications can only be achieved if special protocols are used. In this context, asynchronous tests can be more appropriate, reflecting the underlying test architecture which includes queues.

Objective

In this paper, we investigate the problem of constructing test cases for given test purposes and specification input/output transition systems, when the communication between the tester and the implementation under test is assumed to be asynchronous, performed via multiple queues.

Method

When issuing verdicts, asynchronous tests should take into account a distortion caused by the queues in the observed interactions. First, we investigate how the test purpose can be transformed to account for this distortion when there are a single input queue and a single output queue. Then, we consider a more general problem, when there may be multiple queues.

Results

We propose an algorithm which constructs a sound test case, by transforming the test purpose prior to composing it with the specification without queues.

Conclusion

The proposed algorithm mitigates the state explosion problem which usually occurs when queues are directly involved in the composition. Experimental results confirm the resulting state space reduction.     

Increase in the Charge State of the Uranium Ion Beam Generated by the MEVVA Ion Source

The Metal Vapor Vacuum Arc (MEVVA) ion source and its modifications are investigated at the Institute of Theoretical and Experimental Physics (ITEP). In a series of the experiments, the possibility of increasing the charge state of the generated uranium ion beam was revealed. The charge state increases as a result of developing a high-current vapor vacuum arc discharge from the source cathode to an auxiliary anode located in an increasing axial magnetic field. The uranium ion beam with a total current of 150 mA was obtained, U⁷⁺ uranium ions being 10% of the current.     

Test selection based on communicating nondeterministic finite-statemachines using a generalized Wp-method

Presents a method of generating test sequences for concurrent programs and communication protocols that are modeled as communicating nondeterministic finite-state machines (CNFSMs). A conformance relation, called trace-equivalence, is defined within this model, serving as a guide to test generation. A test generation method for a single nondeterministic finite-state machine (NFSM) is developed, which is an improved and generalized version of the Wp-method that generates test sequences only for deterministic finite-state machines. It is applicable to both nondeterministic and deterministic finite-state machines. When applied to deterministic finite-state machines, it yields usually smaller test suites with full fault coverage than the existing methods that also provide full fault coverage, provided that the number of states in implementation NFSMs are bounded by a known integer. For a system of CNFSMs, the test sequences are generated in the following manner: a system of CNFSMs is first reduced into a single NFSM by reachability analysis; then the test sequences are generated from the resulting NFSM using the generalized Wp-method     

Coaxial Alginate Hydrogels: From Self-Assembled 3D Cellular Constructs to Long-Term Storage

Alginate as a versatile naturally occurring biomaterial has found widespread use in the biomedical field due to its unique features such as biocompatibility and biodegradability. The ability of its semipermeable hydrogels to provide a favourable microenvironment for clinically relevant cells made alginate encapsulation a leading technology for immunoisolation, 3D culture, cryopreservation as well as cell and drug delivery. The aim of this work is the evaluation of structural properties and swelling behaviour of the core-shell capsules for the encapsulation of multipotent stromal cells (MSCs), their 3D culture and cryopreservation using slow freezing. The cells were encapsulated in core-shell capsules using coaxial electrospraying, cultured for 35 days and cryopreserved. Cell viability, metabolic activity and cell–cell interactions were analysed. Cryopreservation of MSCs-laden core-shell capsules was performed according to parameters pre-selected on cell-free capsules. The results suggest that core-shell capsules produced from the low viscosity high-G alginate are superior to high-M ones in terms of stability during in vitro culture, as well as to solid beads in terms of promoting formation of viable self-assembled cellular structures and maintenance of MSCs functionality on a long-term basis. The application of 0.3 M sucrose demonstrated a beneficial effect on the integrity of capsules and viability of formed 3D cell assemblies, as compared to 10% dimethyl sulfoxide (DMSO) alone. The proposed workflow from the preparation of core-shell capsules with self-assembled cellular structures to the cryopreservation appears to be a promising strategy for their off-the-shelf availability.     

Wear resistance of coatings manufactured by electric spark plating with Al-Sn electrodes

The effect of the anomalously high wear of the quenched steel counterbody was found during the testing of coatings manufactured by electric spark plating (ESP) with an AlSn alloy (20 wt % Sn). The presence of SnO₂ nanofibers in the coating composition, which are formed during the ESP with an electrode tool made of this alloy, is assumed to be the main reason for the above effect.     

Phenomena at three-phase electroslag remelting

The electroslag remelting (ESR) process is widely used to produce high-quality ingots and billets for high-alloyed steels and alloys.Both the single-phase and three-phase alternating current diagram with bifilar and monofilar connection are in use for heavy ingot manufacturing.The numerical simulation of the three-phase bifilar circuit for the 120 t three-phase bifilar six-electrode ESR furnace at different variants of electric connection was presented and discussed.At the bifilar diagram of power supply,the geometrical location of electrodes in a mould holds critical importance for performances:the close location of bifilar pair electrodes provides the highest heat productivity,but the equidistant location of electrodes gives a much more uniform heat distribution.The monofilar mulit-electrode diagram of three-phase connection without phase shift shows the most uniform distribution of potential and heat generation as well as a favorable magnetic field that makes this kind the most promising for providing a high quality of heavy ingots.