One of the tasks of an oil company is to fulfil site demands. Since not all sites have production, it is essential to transport products between sites. The order of pumping operations is determined by the scheduling plan. The scheduling plan includes the type and quantity of products to be delivered, the start of deliveries, and routes. The type and quantity of products to be delivered, the start of deliveries and routes are included in the scheduling plan. A scheduling plan is feasible if it does not contain inconsistencies. Checking a one-month schedule is a complex task in real multi-source mesh-like pipeline networks, thus it is advisable to use a discrete event simulation system. This work presents improvements on our previous simulation model. In the improved simulation model, it is possible to reroute, split, and reverse the flow direction of the products in the pipe, amongst other things.

Industrial applications nowadays are facing the complexity of the problem of finding an optimal energy supply composition. Heating and electricity needs vary throughout a year and need to be addressed. There is usually power available from the market, but a company has other investment options to consider, such as solar power, or utilization of local biomass. Fixed and proportional investment and operational costs must be compared to long-term cost-efficiency. The P-Graph framework is an effective tool in the design and synthesis of process networks, and is capable of showing optimal decisions. In the present work, a new P-Graph model was implemented to address the synthesis of the energy supply options of a manufacturing plant in Hungary. Compared to the original approach, a multi-periodic scheme was applied for heating and electricity demands. Also, the pelletizer and biogas plant investments are modeled in the P-Graph with a new technique that better reflects equipment capacities and flexible input ratios. The best solutions in this case study in terms of total costs are listed. It can be concluded that a long-term investment horizon is needed for the incorporation of sustainable energy sources into the system to be cost-efficient.

A P-Graph model is developed to address energy supply options of a manufacturing plant. Today’s industrial facilities usually have a wide range of options to supply its needs in terms of heat, electricity or water. It is difficult to find the most suitable solution, as several factors must be taken into consideration, including fixed and proportional investment and operational costs, sustainability requirements and variable availability of resources. The P-Graph framework is an effective tool in the synthesis of process networks, which involves the P-Graph modeling tool, rigorous mathematical formulation and algorithms, as well as the utilization of Mixed-Integer Linear Programming models. In this work, the energy supply options of an electronic device manufacturing plant are examined. Decisions can be made about the sources of heat and electricity, including buying energy directly from the market or possibly investing into more economic biogas furnaces, a pelletizer, solar cells, with utilization of several different raw materials as energy sources.

An event-driven simulation system is presented here for the transportation of liquid through pipeline network. An oil company produces various products in refineries and transport them mainly through pipelines to depots where the products are sold. A schedule is required for the transportation. The schedule defines the type of product to be transported, its amount, the start and end time of the transport, and the path. A schedule is called feasible if it takes into consideration tank capacity, product availability, deadlines, etc. Naturally, it is essential to check the feasibility of a schedule. Manual feasibility checking can be carried out only for a short time period, 3-4 days, and only if the complexity of pipeline network is modest. If schedules are needed for longer time periods, as long as 30 days, then a simulation model for the movements in the pipelines is needed. The implemented simulation system is applied by an Eastern-European oil company. The reduced stock levels and the better schedule means more efficient operation, less energy consumption, and less impact on the environment.

The P-graph (process graph) framework is an effective tool for process-network synthesis (PNS). Here we extended it to multi-period operations. The efficacy of the P-graph methodology has been demonstrated by numerous applications. The unambiguous representation of processes and the availability of the axioms defining combinatorially feasible structures facilitates the development of efficient algorithms to determine maximal structures, solution structures, and optimal structure for processes. However, it is presumed that single-period operation prevails. It implies that the operating conditions and the load of each operating unit remain unchanged, i.e., steady-state operation. This is usually true for the chemical industry but often not in agriculture or where seasonal effects are important. The current work proposes a multi-period operation wherein the load of operating units varies from period to period to accommodate demand, assuming operating conditions remain steady in each period. A modeling technique is proposed to represent operating units in the multi-period operation. The different periods are connected by "fictitious" streams, which ensures, that the unit is sized properly. (C) 2015 Elsevier Ltd. All rights reserved.

A new modeling technique is presented here for handling multi-period operations in process-network synthesis (PNS) problems by the P-graph (process graph) framework. Until now, the P-graph framework could only handle single-period operating units. It means that the operating conditions and the load of each unit remain unchanged throughout its operation. This assumption is usually true for the chemical industry but may be false in agriculture or in other areas where seasonal effects are important. Hence, the current work proposes the notion of multi-period operation wherein the load of an operating unit may vary from period to period. Subsequently, a modeling technique is proposed to represent operating units in the multi-period operation. The idea is to represent separately the physical body of an operating unit and the operations in each period. Surprisingly, to achieve these tasks, there is no need to dramatically change or augment the basic structure of the P-graph methodology, e. g. with a new type of multi-period unit, but the already available constituents are adequate.

Background: Several researchers have searched for subgroups in the heterogeneous population of patients with non-specific low back pain (LBP). To date, subgroups have been identified based on psychological profiles and the variation of pain.Methods: This multicentre prospective observational study explored the 6- month clinical course with measurements of bothersomeness that were collected from weekly text messages that were sent by 176 patients with LBP. A hierarchical cluster analysis, Ward's method, was used to cluster patients according to the development of their pain.Results: Four clusters with distinctly different clinical courses were described and further validated against clinical baseline variables and outcomes. Cluster 1, a "stable" cluster, where the course was relatively unchanged over time, contained young patients with good self-rated health. Cluster 2, a group of "fast improvers" who were very bothered initially but rapidly improved, consisted of patients who rated their health as relatively poor but experienced the fewest number of days with bothersome pain of all the clusters. Cluster 3 was the "typical patient" group, with medium bothersomeness at baseline and an average improvement over the first 4-5 weeks. Finally, cluster 4 contained the "slow improvers", a group of patients who improved over 12 weeks. This group contained older individuals who had more LBP the previous year and who also experienced most days with bothersome pain of all the clusters.Conclusions: It is possible to define clinically meaningful clusters of patients based on their individual course of LBP over time. Future research should aim to reproduce these clusters in different populations, add further clinical variables to distinguish the clusters and test different treatment strategies for them.

OBJECTIVE:This study critically evaluates a new method of collecting frequent data using mobile phones and text messages. Fluctuating conditions such as low back pain (LBP) need frequent monitoring to describe the clinical course in detail and to account for individual and subgroup variations.STUDY DESIGN AND SETTING:In this multicentre prospective observational study, 262 subjects with nonspecific LBP were followed with weekly text messages for 6 months, with the question "How many days this previous week has your low back pain been bothersome?" The text replies were instantly recorded in a data file to be merged with baseline and follow up data (age, gender, pain intensity, duration, and self- rated health) collected through ordinary questionnaires. The response rate, user-friendliness, and compliance of this method were evaluated.RESULTS:The mean response rate for the text messages throughout the study was 82.5% and was unaffected by season. The method was found to be user friendly. Dropout was not affected by age and gender, but compliance was possibly somewhat affected by outcome.CONCLUSION:Weekly text messages are a useful method of data collection to examine the clinical course of LBP in the primary care sector.

Aim The aim of this study was to describe, by means of weekly measures, the course of low back pain (LBP) in chiropractic patients. The primary outcome was number of days with bothersome pain, which was analyzed for association with known predictor variables (gender, leg pain, occupation and self rated health). Patients were followed for six months. Method A novel approach is used: short message services, SMS, sent to the respondents9 mobile phones. Using specifically designed software, respondents received an SMS every week, which they responded to also using SMS. The question was: “How many days this previous week has your low back pain been bothersome (i.e. affected your daily activities or routines)? Please answer by a number from 0 to 7.” Baseline variables were collected during the chiropractic consultation. Patients were further assessed at the 4 th visit. A follow-up questionnaire was sent to the respondents at the end of the six months. The associations of the primary outcome with baseline variables were investigated using mixed linear models. Preliminary results Compliance among 244 patients was high; 82.5 %. In the final model, duration (more or less than 30 days the previous year), EQ5D start score (self rated health) and self-rated improvement at the 4 th visit were significantly associated with the number of days with bothersome pain during the following 26 weeks. Conclusion Using this method of data collection, we have evaluated the course of the LBP condition in detail. The method seems promising because of good compliance and minimal recall bias.

Industries and cities have different functionalities for society but they share several energy aspects. Industries often produce excess energy (low temperature heat in particular) and cities have a considerable heat demand. Linking cities and industries therefore can be advantageous for both sides. Industries can increase their revenue by selling excess heat and cities can integrate this energy in district heating. In terms of emissions there are several advantages: a central emission source for heat production which can be handled much easier compared to several small heating units, as well as the overall improvement in energy efficiency of the city-industry complex.Important factors for analyzing and optimizing such energy links are the resources for the energy production, district heating costs and time related load profiles. In a first step process synthesis using the P-graph method (Friedler et al., 1995; Halasz et al., 2005, Friedler 2009) is employed to find a stable economical technology network, integrating existing facilities and new technologies (such as CHP and direct solar energy utilization) that use available resources. In a second step this network is evaluated with the help of the Sustainable Process Index (SPI) to indicate ecological hot spots (Narodoslawsky et. al., 1995).A case study in Austria analyses the feasible energy link between a brewery and the neighboured city including possible energy resources and district heating.

Performing process simulations is extremely important for the oil industry. One of the fields of application is to schedule and coordinate the supply, distribution, and storage of raw materials, semi-finished, and finished bulk products in a logistics system. A novel simulation method has been introduced here for scheduling the transport of liquids through a pipeline network to ensure the balance among product availability, sales, and transport in each production and distribution point, to display the actual timetable and its effects, and to identify supply–demand imbalances in a model.

A novel simulation method is introduced here for transporting liquids through a pipe network in the oil industry. The aim is to ensure the balance among product availability, sales, and transport in each production and distribution point, to display the actual schedule and its effects, and to identify inconsistencies. The product pipelines connect sites where tanks are available to store liquids temporarily. The tanks are uploaded and downloaded continuously according to a schedule. This schedule is to be validated, i.e., it must be ensured if a planned operation can be performed, e.g., at download there are enough liquid in the source tank and at upload there is enough free capacity in the target tank.

Among chiropractors the use of long-term treatment is common, often referred to as "maintenance care". Although no generally accepted definition exists, the term has a self-explanatory meaning to chiropractic clinicians. In public health terms, maintenance care can be considered as both secondary and tertiary preventive care. The objective of this study was to explore what factors chiropractors consider before recommending maintenance care to patients with low back pain (LBP).

BACKGROUND:It is clinically important to be able to select patients suitable for treatment and to be able to predict with some certainty the outcome for patients treated for low back pain (LBP). It is not known to what degree outcome among chiropractic patients is affected by psychological factors.OBJECTIVES:To investigate if some demographic, psychological, and clinical variables can predict outcome with chiropractic care in patients with LBP.METHODS:A prospective multi-center practice-based study was carried out, in which demographic, clinical and psychological information was collected at base-line. Outcome was established at the 4(th )visit and after three months. The predictive value was studied for all base-line variables, individually and in a multivariable analysis.RESULTS:In all, 55 of 99 invited chiropractors collected information on 731 patients. At the 4(th )visit data were available on 626 patients and on 464 patients after 3 months. Fee subsidization (OR 3.2; 95% CI 1.9-5.5), total duration of pain in the past year (OR 1.5; 95% CI 1.0-2.2), and general health (OR 1.2; 95% CI 1.1-1.4) remained in the final model as predictors of treatment outcome at the 4(th )visit. The sensitivity was low (12%), whereas the specificity was high (97%). At the three months follow-up, duration of pain in the past year (OR 2.1; 95% CI 1.4-3.1), and pain in other parts of the spine in the past year (OR1.6; 1.1-2.5) were independently associated with outcome. However, both the sensitivity and specificity were relatively low (60% and 50%). The addition of the psychological variables did not improve the models and none of the psychological variables remained significant in the final analyses. There was a positive gradient in relation to the number of positive predictor variables and outcome, both at the 4(th )visit and after 3 months.CONCLUSION:Psychological factors were not found to be relevant in the prediction of treatment outcome in Swedish chiropractic patients with LBP.

BACKGROUND:Chiropractic treatment for low back pain (LBP) can often be divided into two phases: Initial treatment of the problem to attempt to remove pain and bring it back into its pre-clinical or maximum improvement status, and "maintenance care", during which it is attempted to maintain this status. Although the use of chiropractic maintenance care has been described and discussed in the literature, there is no information as to its precise indications. The objective of this study is to investigate if there is agreement among Swedish chiropractors on the overall patient management for various types of LBP-scenarios, with a special emphasis on maintenance care.METHOD:The design was a mailed questionnaire survey. Members of the Swedish Chiropractors' Association, who were participants in previous practice-based research, were sent a closed-end questionnaire consisting of nine case scenarios and six clinical management alternatives and the possibility to create one's own alternative, resulting in a "nine-by-seven" table. The research team defined its own pre hoc choice of "clinically logical" answers based on the team's clinical experience. The frequency of findings was compared to the suggestions of the research team.RESULTS:Replies were received from 59 (60%) of the 99 persons who were invited to take part in the study. A pattern of self-reported clinical management strategies emerged, largely corresponding to the "clinically logical" answers suggested by the research team. In general, patients of concern would be referred out for a second opinion, cases with early recovery and without a history of previous low back pain would be quickly closed, and cases with quick recovery and a history of recurring events would be considered for maintenance care. However, also other management patterns were noted, in particular in the direction of maintenance care.CONCLUSION:To a reasonable extent, Swedish chiropractors participating in this survey appear to agree on the clinical management for different cases of LBP.

In recent years a considerable increase in interest in the development of processes based upon renewable resources has occurred. One reason for this development is the call for more sustainable and environmentally benign production processes and products.Increased utilisation of renewable resources, however, poses new challenges to chemical and process industries. These challenges arise from increased competition for renewable but still finite resources, the de-centralised production of the renewable resources and the complexity of the raw materials. These new challenges require new approaches to process development, as production systems become more complex and interlinked, logistical considerations become increasingly important and new technological solutions must be adapted to local and regional settings. As the structure of complex production systems must be newly developed and optimised, process synthesis will play an increasingly important role in process development. (C) 2006 Elsevier Ltd. All rights reserved.

The application of process synthesis to the European sugar industry is a valuable support for decision-making in an industry severely hit by deregulation of agrarian markets. The paper offers a broader view on possible pathways for utilizing sugar beet. Results of sensitivity analysis using the P-graph approach and a branched and bound MINLP optimization method reveal the impact of price variations for ethanol and sugar on the core structure of sugar plants. This information may help to set the strategy for the sugar sector in Europe in the years following deregulation of the market.

OBJECTIVES:(1) To describe the low back pain (LBP) pattern at baseline; (2) to describe the long-term outcome pattern; (3) to investigate the presence of distinct subgroups in relation to outcome; (4) to establish whether short-term outcome is a predictor of long-term outcome.METHODS:A 3- to 6- and 12- to 18-month, multicenter practice-based, prospective descriptive study was performed in private chiropractic practices in Sweden. Fifty-eight of 64 previously compliant chiropractors each recruited a maximum of 30 consecutive patients with LBP. Complete baseline clinical information was provided on 1054 patients, of which 93% were interviewed approximately 3 months later, and 57% responded to a questionnaire at approximately 12 months. Chiropractic treatment was decided by the treating chiropractor. Twelve descriptive subgroups were created based on (1) duration of LBP at baseline, (2) duration of LBP in the past year, and (3) LBP pattern in the past year. The predictive value was tested for outcome status at the fourth visit. Information on self-reported LBP status and improvement over the past months were collected.RESULTS:Patients were spread in a U-shaped fashion from benign to severe with the 2 extreme groups being most prevalent. About half the participants reported "no LBP in the past week" at 3 months and somewhat fewer at 12 months. Almost 75% claimed to be definitely better at 3 months, and approximately 50% at 12 months. Specific predictive subgroups can be identified, mainly in relation to the past-year history of LBP. Improvement at the fourth visit is a predictor of long-term outcome.CONCLUSION:Knowledge of specific subgroups may improve the quality of care and the selection of homogeneous study populations in clinical trials.

Objective The aim of this study was to develop a predictive model for treatment outcome in patients with low back pain (LBP) receiving chiropractic treatment. Methods This multicenter practice-based predictive validity study was conducted in private chiropractic practices in Sweden. Of 64 previously compliant chiropractors, 58 recruited a maximum of 30 consecutive patients with LBP each. Information was provided on 1061 patients, of which 1057 questionnaires were valid. Chiropractic treatment was decided by the treating chiropractor. The outcome variable was the self-reported “definite improvement” at the fourth visit. The predictor variables included model 1, 3 hypothesized prognostic groups (best, intermediate, and least favorable) based on clinical information collected at baseline and at the second visit; and 4 additional models based on the following variables: age, sex, pain intensity during past 24 hours, description of disability, duration and pattern of pain during present attack, total duration of pain, and pain pattern during the past 12 months. Results Three of our factors were best at predicting the absence of improvement by the fourth visit and were able to correctly classify 79% of patients and to cover 74% of the receiver operated characteristics curve. These were (1) no definite overall improvement by the second treatment, (2) presence of leg pain, and (3) the minimum total duration of pain over the last 12 months being 30 days. Conclusion In this study, patients with LBP who also had leg pain and LBP occurring sufficiently frequently or having lasted sufficiently long to add up to at least 30 days in the past year, and who did not report definite general improvement by the second treatment were not good candidates for short-term recovery. It is suggested that patients who fit the criteria of potential nonresponders should be carefully monitored to allow a selective approach of care.