A checklist for integrating student empirical studies with research and teaching goals

The use of empirical studies with students in software engineering helps researchers gain insight into new or existing techniques and methods. However, due mainly to concerns of external validity, questions have been raised about the value of these types of studies. The authors of this paper draw on their experiences of conducting a large number of empirical studies in university courses in three countries (Italy, Norway, and the United States) to address this important issue. This paper first identifies the requirements that research and pedagogy place on a valid empirical study with students. This information is then used as the basis for a checklist that provides guidance for researchers and educators when planning and conducting studies in university courses. The goal of this checklist is to help ensure that these studies have as much research and pedagogical value as possible. Finally, an example application of the checklist is provided to illustrate its use.     

DC‐to‐AC power conversion on a ‘boost’ converter

In this article, we provide an approximate sliding mode control‐based solution to the DC–AC power conversion problem on a ‘boost’ converter. The approach uses the flatness property of the system as a pivot for generating a sequence of minimum phase output reference trajectory candidates. The generated candidates are obtained as differential parameterizations of the minimum phase inductor current variable in terms of the non‐minimum phase desired output capacitor voltage. The associated residual dynamics of the ideal sliding motions is shown to reasonably approximate the desired biased sinusoidal output capacitor voltage signal. Copyright © 2001 John Wiley & Sons, Ltd.     

The role of replications in Empirical Software Engineering

Replications play a key role in Empirical Software Engineering by allowing the community to build knowledge about which results or observations hold under which conditions. Therefore, not only can a replication that produces similar results as the original experiment be viewed as successful, but a replication that produce results different from those of the original experiment can also be viewed as successful. In this paper we identify two types of replications: exact replications, in which the procedures of an experiment are followed as closely as possible; and conceptual replications, in which the same research question is evaluated by using a different experimental procedure. The focus of this paper is on exact replications. We further explore them to identify two sub-categories: dependent replications, where researchers attempt to keep all the conditions of the experiment the same or very similar and independent replications, where researchers deliberately vary one or more major aspects of the conditions of the experiment. We then discuss the role played by each type of replication in terms of its goals, benefits, and limitations. Finally, we highlight the importance of producing adequate documentation for an experiment (original or replication) to allow for replication. A properly documented replication provides the details necessary to gain a sufficient understanding of the study being replicated without requiring the replicator to slavishly follow the given procedures.

How perspective-based reading can improve requirements inspections

Because defects constitute an unavoidable aspect of software development, discovering and removing them early is crucial. Overlooked defects (like faults in the software system requirements, design, or code) propagate to subsequent development phases where detecting and correcting them becomes more difficult. At best, developers will eventually catch the defects, but at the expense of schedule delays and additional product-development costs. At worst, the defects will remain, and customers will receive a faulty product. The authors explain their perspective based reading (PBR) technique that provides a set of procedures to help developers solve software requirements inspection problems. PBR reviewers stand in for specific stakeholders in the document to verify the quality of requirements specifications. The authors show how PBR leads to improved defect detection rates for both individual reviewers and review teams working with unfamiliar application domains     

Comparing four approaches for technical debt identification

Software systems accumulate technical debt (TD) when short-term goals in software development are traded for long-term goals (e.g., quick-and-dirty implementation to reach a release date versus a well-refactored implementation that supports the long-term health of the project). Some forms of TD accumulate over time in the form of source code that is difficult to work with and exhibits a variety of anomalies. A number of source code analysis techniques and tools have been proposed to potentially identify the code-level debt accumulated in a system. What has not yet been studied is if using multiple tools to detect TD can lead to benefits, that is, if different tools will flag the same or different source code components. Further, these techniques also lack investigation into the symptoms of TD “interest” that they lead to. To address this latter question, we also investigated whether TD, as identified by the source code analysis techniques, correlates with interest payments in the form of increased defect- and change-proneness. Comparing the results of different TD identification approaches to understand their commonalities and differences and to evaluate their relationship to indicators of future TD “interest.” We selected four different TD identification techniques (code smells, automatic static analysis issues, grime buildup, and Modularity violations) and applied them to 13 versions of the Apache Hadoop open source software project. We collected and aggregated statistical measures to investigate whether the different techniques identified TD indicators in the same or different classes and whether those classes in turn exhibited high interest (in the form of a large number of defects and higher change-proneness). The outputs of the four approaches have very little overlap and are therefore pointing to different problems in the source code. Dispersed Coupling and Modularity violations were co-located in classes with higher defect-proneness. We also observed a strong relationship between Modularity violations and change-proneness. Our main contribution is an initial overview of the TD landscape, showing that different TD techniques are loosely coupled and therefore indicate problems in different locations of the source code. Moreover, our proxy interest indicators (change- and defect-proneness) correlate with only a small subset of TD indicators.     

Reviewing 25 Years of Testing Technique Experiments

Mature knowledge allows engineering disciplines the achievement of predictable results. Unfortunately, the type of knowledge used in software engineering can be considered to be of a relatively low maturity, and developers are guided by intuition, fashion or market-speak rather than by facts or undisputed statements proper to an engineering discipline. Testing techniques determine different criteria for selecting the test cases that will be used as input to the system under examination, which means that an effective and efficient selection of test cases conditions the success of the tests. The knowledge for selecting testing techniques should come from studies that empirically justify the benefits and application conditions of the different techniques. This paper analyzes the maturity level of the knowledge about testing techniques by examining existing empirical studies about these techniques. We have analyzed their results, and obtained a testing technique knowledge classification based on their factuality and objectivity, according to four parameters.     

Sliding Mode ∑‐Δ Modulation Control of the Boost Converter

A switched implementation of average dynamic output feedback laws trough a ∑‐Δ‐modulator, widely known in the classic communications and analog signal encoding literature, not only frees the sliding mode control approach from state measurements and the corresponding synthesis of sliding surfaces in the plant's state space, but it also allows to effectively transfer all desired closed loop features of an uniformly bounded, continuous, average output feedback controller design into the more restrictive discrete‐valued (ON‐OFF) control framework of a switched system. The proposed approach is here used for the input‐output sliding mode stabilization of the “boost” DC‐to‐DC converter. This is achieved by means of a well known passivity based controller but any other output feedback design would have served our purposes. This emphasizes the flexibility of the proposed sliding mode control design implementation through ∑‐Δ‐modulators.     

Physical characterization methods for iron oxide contrast agents encapsulated within a targeted liposome-based delivery system

Intact liposome-based targeted nanoparticle delivery systems (NDS) are immobilized by non-selective binding and characterized by scanning probe microscopy (SPM) in a fluid imaging environment. The size, size distribution, functionality, and stability of an NDS with a payload consisting of a super-paramagnetic iron oxide contrast agent for magnetic resonance imaging are determined. SPM results are combined with information obtained by more familiar techniques such as superconducting quantum interference device (SQUID) magnetometry, dynamic light scattering, and electron microscopy. By integrating the methods presented in this work into the NDS formulation and manufacturing process, size-dependent statistical properties of the complex can be obtained and the structure-function relationship of individual, multi-component nanoscale entities can be assessed in a reliable and reproducible manner.     

Enhanced liquid biofuel production from crude palm oil over synthesized NiMoW-ZSM-5/MCM-41 catalyst

Micro-mesoporous ZSM-5/MCM-41 composites were prepared and then loaded with varied contents of NiMoW by the wet impregnation method. The hydrocracking conversion of crude palm oil to liquid biofuels with the prepared catalysts was carried out in a batch reactor at 400°C for 2 h. ZSM-5/MCM-41 composite exhibited 51.00% conversion with a yield of 9.23% gasoline, 20.60% kerosene, and 21.17% diesel. Upon loading of NiMoW, the catalysts exhibited an improved conversion (≥ 62.60%) and a reduced formation of coke, which resulted from combined properties of ZSM-5 with MCM-41 and the presence of dispersed NiMoW. The contents of impregnated metals also affected the performance of catalysts. Using ANOVA analysis (p < 0.05), we found that 8:8:8 wt.% NiMoW-ZSM-5/MCM-41 catalyst was suitable for the production of biofuels, when considering the efficiency and cost-effectiveness.     

Spatial and temporal control of the degree of cure in polymer composite structures

This paper describes current efforts to apply spatially and temporally localized microwave processing techniques to ensure uniformity of material properties in polymer composite materials. In large polymer composite structures, high temperatures caused by exothermic resin cure can degrade the mechanical properties of the composite. In this work, resin cure temperature data was obtained during microwave processing from a series of thermocouples embedded at various lateral locations relative to the microwave source and uniformly through the thickness of the composite structure. Using this temperature information, the potential for localized microwave‐accelerated cure to reduce the occurrence of material degradation from resin over‐temperature was evaluated. In addition, a theoretical model is presented that helps elucidate the influence of the microwave parameters on the temperature profile.