Comparison of MINLP formulations for global superstructure optimization

Superstructure optimization is a powerful but computationally demanding task that can be used to select the optimal structure among many alternatives within a single optimization. In chemical engineering, such problems naturally arise in process design, where different process alternatives need to be considered simultaneously to minimize a specific objective function (e.g., production costs or global warming impact). Conventionally, superstructure optimization problems are either formulated with the Big-M or the Convex Hull reformulation approach. However, for problems containing nonconvex functions, it is not clear whether these yield the most computationally efficient formulations. We therefore compare the conventional problem formulations with less common ones (using equilibrium constraints, step functions, or multiplications of binary and continuous variables to model disjunctions) using three case studies. First, a minimalist superstructure optimization problem is used to derive conjectures about their computational performance. These conjectures are then further investigated by two more complex literature benchmarks. Our analysis shows that the less common approaches tend to result in a smaller problem size, while keeping relaxations comparably tight—despite the introduction of additional nonconvexities. For the considered case studies, we demonstrate that all reformulation approaches can further benefit from eliminating optimization variables by a reduced-space formulation. For superstructure optimization problems containing nonconvex functions, we therefore encourage to also consider problem formulations that introduce additional nonconvexities but reduce the number of optimization variables.

UNDERSTANDING CONFLICT MATERIALS AND CONFLICT RESOLUTION THROUGH PICTURED E-MODULES FOR SENIOR HIGH SCHOOL STUDENTS

There has been an increase in teacher creativity to develop various learning media during the pandemic. This paper has the aim of showing one form of developing high school Civics teaching materials, namely conflict and conflict resolution in the form of a Picture E-Module. There are two problem formulations, namely (1) what is the form of the illustrated E-Modul on Conflict and Conflict Resolution material for high school students? (2) how is the validity of the media and the validity of the illustrated E-Module material? Using the Research and Development (R&D) research method of the Bord and Gall model, the E-Modul trial was conducted on class XII students in four high schools in the city of Padang, with a total of 203 students as respondents. The feasibility of this E-Module in terms of media validity has been tested by two experts with a validity result of 79.1% (Valid). For the validity of the material has been tested by 203 students obtained a validity value of 73.8% (good). The results of the media test and validity test show that this E-Module is quite effective in being used as a learning medium to improve students' understanding of Pancasila and Citizenship Education subjects, especially Conflict and Conflict Resolution materials

Pro Bono Legal Aid by Advocates: Guarantee of Justice for the Poor

The implementation of legal aid is a manifestation of Indonesia as a legal state that guarantees the human rights of citizens to equality before the law which is guaranteed in the 1945 Constitution. Within the framework of implementing this citizen's human rights, the provision of free legal aid is, among other things, obligated to advocates based on Article 22 Law on advocates and their implementing regulations. From this, two problem formulations were made as follows: What is the juridical review of the provision of pro bono legal aid? And what is the role of advocates in providing pro bono legal aid? This research is based on normative legal research, which is a research conducted by reviewing and analyzing legal materials and legal issues related to the problems studied. The results of the author's discussion found that free legal aid is the right of the poor to obtain the same justice as other communities, so that the protection of their rights is well fulfilled and the principle of equality before the law. Advocates are obliged to provide free legal aid to justice seekers, and to obtain free legal assistance, justice seekers must submit a written application to an advocate organization or legal aid institution.

Specificity of early-career general practitioners’ problem formulations in patients presenting with dizziness: a cross-sectional analysis

ObjectivesDizziness is a common and challenging clinical presentation in general practice. Failure to determine specific aetiologies can lead to significant morbidity and mortality. We aimed to establish frequency and associations of general practitioner (GP) trainees’ (registrars’) specific vertigo provisional diagnoses and their non-specific symptomatic problem formulations.DesignA cross-sectional analysis of Registrar Clinical Encounters in Training (ReCEnT) cohort study data between 2010 and 2018. ReCEnT is an ongoing, prospective cohort study of registrars in general practice training in Australia. Data collection occurs once every 6 months midtraining term (for three terms) and entails recording details of 60 consecutive clinical consultations on hardcopy case report forms. The outcome factor was whether dizziness-related or vertigo-related presentations resulted in a specific vertigo provisional diagnosis versus a non-specific symptomatic problem formulation. Associations with patient, practice, registrar and consultation independent variables were assessed by univariate and multivariable logistic regression.SettingAustralian general practice training programme. The training is regionalised and delivered by regional training providers (RTPs) (2010–2015) and regional training organisations (RTOs) (2016–2018) across Australia (from five states and one territory).ParticipantsAll general practice registrars enrolled with participating RTPs or RTOs undertaking GP training terms.Results2333 registrars (96% response rate) recorded 1734 new problems related to dizziness or vertigo. Of these, 546 (31.5%) involved a specific vertigo diagnosis and 1188 (68.5%) a non-specific symptom diagnosis. Variables associated with a non-specific symptom diagnosis on multivariable analysis were lower socioeconomic status of the practice location (OR 0.94 for each decile of disadvantage, 95% CIs 0.90 to 0.98) and longer consultation duration (OR 1.02, 95% CIs 1.00 to 1.04). A specific vertigo diagnosis was associated with performing a procedure (OR 0.52, 95% CIs 0.27 to 1.00), with some evidence for seeking information from a supervisor being associated with a non-specific symptom diagnosis (OR 1.39, 95% CIs 0.92 to 2.09; p=0.12).ConclusionsAustralian GP registrars see dizzy patients as frequently as established GPs. The frequency and associations of a non-specific diagnosis are consistent with the acknowledged difficulty of making diagnoses in vertigo/dizziness presentations. Continuing emphasis on this area in GP training and encouragement of supervisor involvement in registrars’ diagnostic processes is indicated.

Implementation of Legal Aid by the Local Government (Case Study of the Local Government of Jember Regency)

Basically, the right to obtain defense from an advocate or public defender (access to legal counsel) is a human right of all people and is one of the elements to obtain justice for everyone. However, in reality, local governments generally only provide legal assistance on a non-litigation basis where its implementation does not burden the regional budget at all. Based on this, the researchers made two problem formulations, namely 1). How to protect the community through the provision of legal aid and 2). How is the implementation of the provision of legal aid by the local government? The author uses a normative juridical research approach. From the results of the study, it was found that the provision of legal aid is not only regulated in the Constitution but is also regulated in the regulations below it up to the Regional Regulation level. Local governments can allocate funds for the implementation of legal aid in the APBD.

IMPLEMENTATION OF THE GOVERNMENT'S DISCRETION IN INDONESIA, AUTHORITY, AND RESPONSIBILITY IN THE MANAGEMENT OF GOVERNMENT

The research entitled "Implementation of the Government's Discretionary Authority and Accountability in the Administration of Government" has five problem formulations. First, how is the implementation of discretionary authority in the administration of Government? Second, there are obstacles in the exercise of discretionary authority. The third is how to overcome obstacles. Fourth, the limits of discretion in decision making. Fifth, Government Instruments. The purpose of this study was to identify and analyze the five problem formulations above. This research is qualitative descriptive The results of this study indicate that the exercise of discretionary authority in the administration of Government is a logical consequence of the welfare state where the welfare state government is a state power that is given the task and responsibility for the welfare of its citizens. In contrast, discretionary authority does not mean that it can be used freely. However, it must follow the rules written in Law Number 30 of 2004 concerning Good Governance and Principles of Good Governance (AAUPB). The implementation of discretionary authority in the administration of Government also has several obstacles that cause the Government to be less efficient and less effective. Efforts to overcome these obstacles are not easy because they must involve all parties, namely legislative power, executive power, and judicial power. This is also, of course, requires the role of citizens. These things are to ensure the implementation of discretionary authority in the administration of Government so that it is efficient and effective in realizing people's welfare.

Strategies for Increasing the Competitiveness of Krakatau Steel Company in The Free Trade Area of Batam to Support the Defense Equipment

The steel plate market in the Batam Free Trade Zone is very large, namely 75% of the Indonesian market share. PT Krakatau Steel's steel plate products are not competitive in the Batam Free Trade Area, especially in terms of price and long delivery times. So, a strategy is needed to increase competitiveness. This type of research is a quasi-qualitative research method with interviews, questionnaires, observation, and literature study. In this study, there are two problem formulations, namely how to determine the criteria for competitiveness and how to improve the strategy for increasing the competitiveness of PT Krakatau Steel's steel plate in the Batam Free Trade Area. In determining the criteria for competitiveness, AHP analysis is used. For strategies to increase competitiveness using the SWOT-AHP analysis. The results showed that the criteria affecting the competitiveness of steel were Manufacture Strategy with a weighting value of 0.526 with sub-criteria for cost, quality, delivery, and flexibility. The SWOT analysis shows that the strategy currently used by PT Krakatau Steel is SO. Based on the results of the SWOT-AHP analysis research, it was found that the competitiveness of PT Krakatau Steel could still be improved with the ST strategy which was more relevant to the situation in the Batam Free Trade Area.

Exploiting Potentialities of Dynamic Satellites for Future Space-based Quantum Network: Downlink Scheduling and Orbital Deployment

With the goal of a space-based quantum network is to have satellites distribute keys between any nodes on the ground, we consider an evolved quantum network from a near-term form, in which a space-based relay, Micius, executes a sequence of Satellite QKD (SatQKD) missions, allowing any two cities to have a shared key. Accordingly, we develop a comprehensive framework integrated with precise orbital modelling and a cloud statistics model to enable a preassessment of SatQKD. Using this framework, we consider three different scheduling strategies and estimate the keys that can be delivered to cities. By the assistance of using different optimizations on scheduling problem formulations, it is possible to allows for the possibility to consider strategies for different missions such as extending connection for distant nodes, prioritized delivery to nodes with higher privileges, and promoting keys utilization. We also provide a comparison of the total number of keys delivered using different-altitude satellites. It is demonstrated that the plan for constructing a low-Earth orbit (LEO) satellite constellation is more efficient than that for employing an expensive high-orbit satellite to an execution of scheduling SatQKD.

Solutions to Plastic Pollution: A Conceptual Framework to Tackle a Wicked Problem

There is a broad willingness to act on global plastic pollution as well as a plethora of available technological, governance, and societal solutions. However, this solution space has not been organized in a larger conceptual framework yet. In this essay, I propose such a framework, place the available solutions in it, and use it to explore the value-laden issues that motivate the diverse problem formulations and the preferences for certain solutions by certain actors. To set the scene, I argue that plastic pollution shares the key features of wicked problems, namely, scientific, political, and societal complexity and uncertainty as well as a diversity in the views of actors. To explore the latter, plastic pollution can be framed as a waste, resource, economic, societal, or systemic problem. Doing so results in different and sometimes conflicting sets of preferred solutions, including improving waste management; recycling and reuse; implementing levies, taxes, and bans as well as ethical consumerism; raising awareness; and a transition to a circular economy. Deciding which of these solutions is desirable is, again, not a purely rational choice. Accordingly, the social deliberations on these solution sets can be organized across four scales of change. At the geographic and time scales, we need to clarify where and when we want to solve the plastic problem. On the scale of responsibility, we need to clarify who is accountable, has the means to make change, and carries the costs. At the magnitude scale, we need to discuss which level of change we desire on a spectrum of status quo to revolution. All these issues are inherently linked to value judgments and worldviews that must, therefore, be part of an open and inclusive debate to facilitate solving the wicked problem of plastic pollution.

A Survey on Problem Formulations and (Meta)Heuristic-Based Solutions in Automated Assembly of Parallel Test Forms

Parallel test forms are ubiquitous in the educational, aptitude, achievement, and licensure testing. The problem of automated assembling of parallel test forms has been extensively explored for almost 40 years. Many different mathematical models of the problem formulations and a plenty of different solutions have emerged over the last two decades, indicating that the problem has matured. However, its investigation is still challenging, especially today, when the importance of distance learning and remote knowledge testing is rapidly growing. The diversity of proposed approaches originated notably from the variety of scientific fields involved such as psychometrics, applied mathematics, operations research, and artificial intelligence. Majority of solutions of the problem are (meta)heuristics-based, since they consider the problem as a combinatorial optimization problem which is NP-hard. In this paper, a comprehensive review of this research field, referring to related works since 1985, is conducted. Problem formulations and solutions of the problem are separately classified. Possible avenues of future research are pointed out.