Why the determinacy condition is a weak criterion in rational expectations models

This paper disputes what Blanchard and Kahn have reported as the solution of linear rational expectation(RE) systems many years ago. Their method leads to traditional determinacy condition which is used very much nowadays. In this paper we have a new look to the mathematical procedure of this solution method and the main problem in their solution will be shown. We introduce a new methodology for modeling the systems with expectation, while in future this way of modeling can be used to replace traditional RE models.Rational expectation; Determinacy condition; Stability; Uniqueness; Predictive control

Why the determinacy condition is a weak criterion in rational expectations models

This paper disputes what Blanchard and Kahn have reported as the solution of linear rational expectation(RE) systems many years ago. Their method leads to traditional determinacy condition which is used very much nowadays. In this paper we have a new look to the mathematical procedure of this solution method and the main problem in their solution will be shown. We introduce a new methodology for modeling the systems with expectation, while in future this way of modeling can be used to replace traditional RE models

Numerical modeling of the effect of Anderson's stress regimes on the volume of sand production in oil wellbores

Sand production is a complex mechanism that reduces oil and gas production and leads to wellbore instability, tubing erosion, and even erosion of surface installations. The hydrodynamic action of the flow on the surface leads to the breakup of solid particles from the surface. This is one of the main sources of sand production. The sand production may be affected by the combination of flow rate and the stress regime around the wellbore. In this paper, sand production in a vertical wellbore is numerically studied. A 3D finite element model in various stress regimes (i.e., normal, strike-slip, and reverse based on Anderson's classification) presenting various conditions of reservoirs was used. A typical drawdown pressure was chosen to simulate the production in the wellbore. The numerical model uses a sand production criterion based on the velocity of the fluid flow, the porosity of formation, transport concentration, and sand production coefficient to determine the initiation of sand production. The sand production volume was determined for a duration of a week in all cases. The most erosion of materials in all models occurred near the junction of the wellbore and perforation. This is an expected result since based on rock mechanics, the junction of the wellbore and perforation is also the location of the most stress concentration. It was concluded that the collaboration of high-stress concentration and high-pressure drawdown caused the excessive sanding problem. The results of the paper provide insight into the effect of stress regimes and orientation of perforation on the volume of sand production

A Scientometric Methodology Based on Co-Word Analysis in Gas Turbine Maintenance

Evaluation of scientific journals has a profound effect on the future of scientific research so that different institutes and countries can set appropriate goals and invest with less risk in various scientific fields. Accordingly, this article presents a new method based on a combination of co-word analysis and social network analysis to extract the hotspot topics. Using HistCite, NodeXL, and VOSviewer, then combining their results, the desired analysis is conducted for six time periods. Based on the bibliographic parameters in HistCite and by defining an index, the first five periods are selected such that both quantity and quality of articles in each period are maximum compared to other years, while the sixth time period contains the latest research. For each of the six periods, the co-word networks as created in VOSviewer are analyzed. Next, based on a combination of network centralities developed in NodeXL, the hotspot keywords are specified which are then validated and aggregated using the bibliographic parameters in HistCite. The results reveal five important time periods in gas turbine maintenance. The hotspot keywords obtained for the last period show that in recent years, some topics including gas turbine fault prognosis, neural network-based approaches, big data analysis, sensor fault diagnosis, blade availability, economic analysis and useful life estimation are prominent subjects in gas turbine maintenance

Raloxifene adjunctive therapy for postmenopausal women suffering from chronic schizophrenia: a randomized double-blind and placebo controlled trial

BACKGROUND: Cumulative evidence from epidemiological, preclinical and clinical studies suggests estrogens may have psychoprotective effects in schizophrenic patients. Selective Estrogen Receptor Modulators could have therapeutic benefits in schizophrenia for both sexes without being hazardous to gynecological tissues or having feminizing effects. Few studies have been conducted regarding the effects of raloxifene on postmenopausal women suffering from schizophrenia. We conducted this placebo-controlled trial to compare the add-on effect of raloxifene to risperidone versus risperidone with placebo. METHODS: This was an 8-week, parallel-group, placebo-controlled trial undertaken at two universities affiliated psychiatric Hospitals in Iran. Forty-six postmenopausal women with the definite diagnosis of schizophrenia were enrolled in the study. Patients received risperidone (6 mg/day in 3 divided doses) combined with either placebo (N = 23) or 120 mg/day of raloxifene (N = 23) for 8 weeks. Patients were assessed by a psychiatrist at baseline and at 2 and 8 weeks after the start of medical therapy. Efficacy was defined as the change from baseline to endpoint in score on Positive and Negative Syndrome Scale (PANSS). RESULTS: For PANSS scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 1.77, p = 0.18]. For positive subscale scores, there was marginal significant interaction between intervention type and time [F (2, 47) = 2.93, p = 0.06] and there was substantial main effect for time [F (2, 47) = 24.39, p = 0.001] within both groups showing reduction in positive subscale scores across the three time periods. In addition, the main effect comparing two types of intervention was significant [F (1, 48) = 3.78, p = 0.02]. On the other hand, for negative subscale scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 1.43, p = 0.23]. For general subscale scores, the main effect comparing two types of intervention was not significant [F (1, 48) = 0.03, p = 0.86]. CONCLUSIONS: According to our findings, raloxifene as an adjunctive treatment to risperidone was only superior in improvement of positive symptoms and it was not effective in treating negative and general psychopathology symptoms. TRIAL REGISTRATION: The trial was registered at the Iranian registry of clinical trials: IRCT201205131556N4

A predictive multi-agent approach to model systems with linear rational expectations

Expectation formation plays a principal role in economic systems. We examine and revise the standard rational expectations (RE) model, generally taken as the best paradigm for expectations modelling, and suggest a new method to model rational expectations. Conventional conditions that assert the stability and uniqueness of popular solution methods are shown to be insufficient. The agent-based new modelling approach suggested in this paper will be shown to lead to uniquely stable solutions

A predictive multi-agent approach to model systems with linear rational expectations

Expectation formation plays a principal role in economic systems. We examine and revise the standard rational expectations (RE) model, generally taken as the best paradigm for expectations modelling, and suggest a new method to model rational expectations. Conventional conditions that assert the stability and uniqueness of popular solution methods are shown to be insufficient. The agent-based new modelling approach suggested in this paper will be shown to lead to uniquely stable solutions

Iranian clinical practice guideline for amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a rapidly progressive neurodegeneration involving motor neurons. The 3–5 years that patients have to live is marked by day-to-day loss of motor and sometimes cognitive abilities. Enormous amounts of healthcare services and resources are necessary to support patients and their caregivers during this relatively short but burdensome journey. Organization and management of these resources need to best meet patients' expectations and health system efficiency mandates. This can only occur in the setting of multidisciplinary ALS clinics which are known as the gold standard of ALS care worldwide. To introduce this standard to the care of Iranian ALS patients, which is an inevitable quality milestone, a national ALS clinical practice guideline is the necessary first step. The National ALS guideline will serve as the knowledge base for the development of local clinical pathways to guide patient journeys in multidisciplinary ALS clinics. To this end, we gathered a team of national neuromuscular experts as well as experts in related specialties necessary for delivering multidisciplinary care to ALS patients to develop the Iranian ALS clinical practice guideline. Clinical questions were prepared in the Patient, Intervention, Comparison, and Outcome (PICO) format to serve as a guide for the literature search. Considering the lack of adequate national/local studies at this time, a consensus-based approach was taken to evaluate the quality of the retrieved evidence and summarize recommendations

A Scientometric Methodology Based on Co-Word Analysis in Gas Turbine Maintenance

Evaluation of scientific journals has a profound effect on the future of scientific research so that different institutes and countries can set appropriate goals and invest with less risk in various scientific fields. Accordingly, this article presents a new method based on a combination of co-word analysis and social network analysis to extract the hotspot topics. Using HistCite, NodeXL, and VOSviewer, then combining their results, the desired analysis is conducted for six time periods. Based on the bibliographic parameters in HistCite and by defining an index, the first five periods are selected such that both quantity and quality of articles in each period are maximum compared to other years, while the sixth time period contains the latest research. For each of the six periods, the co-word networks as created in VOSviewer are analyzed. Next, based on a combination of network centralities developed in NodeXL, the hotspot keywords are specified which are then validated and aggregated using the bibliographic parameters in HistCite. The results reveal five important time periods in gas turbine maintenance. The hotspot keywords obtained for the last period show that in recent years, some topics including gas turbine fault prognosis, neural network-based approaches, big data analysis, sensor fault diagnosis, blade availability, economic analysis and useful life estimation are prominent subjects in gas turbine maintenance