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Safe Operation (safe + operation)
Selected AbstractsSurgical treatment of liver metastases from pancreatic cancerHPB, Issue 2 2006Hidehisa Yamada PhD Abstract Pancreatic cancer is a disease with a poor prognosis. Most patients are diagnosed at an advanced and unresectable stage. Even if the primary cancer is radically removed, postoperative recurrence frequently occurs. Generally, metastatic liver tumors from pancreatic cancer are not indicated for surgical treatment. Here we evaluate the results of performing hepatectomy for liver metastases of pancreatic cancer. In our institute, six patients with liver metastases from pancreatic cancer were treated by partial hepatectomy. Overall 1-, 3- and 5-year survival rates of six patients after hepatectomy were 66.7%, 33.3% and 16.7%, respectively, and one patient was alive for 65.4 months. Performing a hepatectomy for liver metastases of pancreatic cancer, when combined with a pancreas resection, was recently considered to be a safe operation, and one that might offer prolonged survival for highly selected patients with curative resection of liver metastases. In the future, it will be necessary to develop new multi-modality therapies to improve the prognosis of pancreatic cancer. [source] D2 gastrectomy , a safe operation in experienced hands,INTERNATIONAL JOURNAL OF CLINICAL PRACTICE, Issue 6 2005R.S. Date Summary In the contemporary practice, surgery is the only potentially curative treatment available for gastric cancer. However, there is no consensus on the extent of surgical resection. Advantages of D2 gastrectomy in terms of morbidity, mortality, local recurrence and survival are confirmed in Japanese as well as some European trials. In our hospital, all patients with operable gastric cancer are treated with D2 gastrectomy along with splenectomy and distal pancreatectomy followed by jejunal pouch reconstruction. The study was undertaken to evaluate our practice in terms of postoperative morbidity and mortality. All the patients who had total gastrectomy for gastric carcinoma from January 1995 to December 2000 were included in the study. During this 6-year period, 33 patients underwent potentially curative D2 gastrectomy. Postoperative morbidity and mortality were 18 and 9%, respectively. There were no anastomotic leaks. Three (9%) patients developed dysphasia, of which two (6%) had anastomotic stricture requiring dilatation. We feel D2 gastrectomy with splenectomy and distal pancreatectomy when performed electively is a safe procedure in experienced hands. Oesophago-jejunal anastomosis can be safely performed using circular stapler. [source] Linear PI control of batch exothermic reactors with temperature measurementINTERNATIONAL JOURNAL OF ROBUST AND NONLINEAR CONTROL, Issue 3 2006Jose Alvarez-Ramirez Abstract A wide variety of speciality materials and fine chemicals such as plastics, pharmaceutical and microelectronics components are produced in batch reactors. The nonlinear, transient and finite-time features of the batch reactors give rise to complex process and control design problems. In particular, the safe operation of exothermic reactors depends on the adequate functioning of a temperature tracking controller, and to a good extent, the same is true for the attainment of a suitable compromise between productivity and product quality attributes. While the stabilization problem of continuous exothermic chemical reactors has been recently addressed with rigorous asymptotic-stability methods, the same kind of studies have not yet been performed for the finite-time batch reactor case. In this paper, the problem of designing a temperature tracking controller for an exothermic batch reactor, with n species and m reactions, is addressed under the following premises: (i) only the reactor temperature is measured, (ii) the (typically uncertain) reaction rate and heat exchange nonlinear functions are unknown, (iii) the controller must be linear and easy to tune, and (iv) the closed-loop reactor motion must be stable in a suitable sense. The combination of industrial-oriented inventory control concepts in conjunction with singular perturbation results yields a linear controller with a combined feedforward-PI feedback structure, antireset windup scheme, and conventional-like tuning rules. The controller: (i) tracks, arbitrarily fast and close, a prescribed temperature trajectory, with admissibly deviated concentration motions, and (ii) quickly recovers the behaviour of an exact model-based nonlinear I/O linearizing controller. The proposed design is put in perspective with the geometric and IMC nonlinear control approaches. Copyright © 2005 John Wiley & Sons, Ltd. [source] Game theoretic approach to multiobjective designs: Focus on inherent safetyAICHE JOURNAL, Issue 1 2006Anjana Meel Abstract A method for designing processes that are inherently safer,with the primary focus on disturbances having the potential for unbounded hazardous responses,is introduced. In cases where safety is not threatened (as in isothermal fermentation reactors), but product quality can rapidly degrade, this method provides designs that ensure high product quality (as in pharmaceutical processes). Using game theory, the method accounts for the trade-offs in profitability, controllability, safety and/or product quality, and flexibility. For nonlinear processes that are hard to control; that is, have an unstable and/or nonminimum-phase steady state, over a wide range of operating conditions, extended bifurcation diagrams are introduced. When a steady state is nonminimum phase, the process may exhibit inverse response. The steady states of processes are classified on the basis of instability and nonminimum-phase behavior to segregate the operating regimes into distinct zones. Locally optimal designs, one corresponding to each zone, are obtained first. These are compared with other locally optimal designs at alternate operating conditions, and/or process reconfigurations, to obtain the globally optimal design using game theory. Four indices,profitability, controllability, safety and/or product quality, and flexibility,characterize the optimality of a design. A novel index for safe operation and/or product quality at a steady state is formulated as a function of the eigenvalues of the Jacobian of the process model and the Jacobian of the process zero dynamics, providing a quantitative measure of instability and nonminimum-phase behavior. The application of the proposed method to an isothermal, continuous stirred-tank reactor (CSTR) with van der Vusse reactions, an exothermic CSTR, and an anaerobic fermentor with substrate and product inhibition is presented. © 2005 American Institute of Chemical Engineers AIChE J, 2006 [source] Steady-state multiplicity, flashback, and control issues in CH4 radiant burnersAICHE JOURNAL, Issue 9 2004M. Bizzi Abstract Methane is widely employed as a source of energy in combustion systems. Among the currently available technologies, radiant heaters offer high thermal efficiency and low environmental impact in comparison with atmospheric burners. The present work deals with the modeling of methane combustion in a noncatalytic metal fiber burner, represented by means of one-dimensional transient equations. The model accounts for a detailed reaction mechanism, radiation within the porous medium, longitudinal heat and mass transfer. After its validation, the model was employed to analyze a typical stability problem that affects these systems: under given operating conditions (low specific power inputs and excess of air) the occurrence of flashback may in fact preclude the safe operation of the system. As a consequence of energy radiation in the upstream direction, the burner upstream surface and the plenum chamber might become hot enough to heat in turn the gas feedstock, thus eventually determining flashback. In this paper, the mechanism of flashback is numerically investigated as a function of the burner structure and operating conditions by means of a model analysis so as to single out regions of flashback occurrence and a criterion for safe operation. Finally, some guidelines are outlined for a cheap and effective control of the system, paving the way for possible improvement of currently adopted control systems. © 2004 American Institute of Chemical Engineers AIChE J, 50: 2276,2286, 2004 [source] Quantitative framework for reliable safety analysisAICHE JOURNAL, Issue 1 2002Haitao Huang The effectiveness of any methodology used to identify hazards in chemical processes affects both safety and economics. To achieve maximum safety at minimum cost, a conservative, but realistic, analysis must be carried out. An approach to hazard identification is proposed based on a detailed process model which includes nonlinear dynamics and uncertainty. A new modeling framework, the region-transition model (RTM), is developed, which enables the simulation of regions of the operating space through an extension of the hybrid state transition system formalism. The RTM is illustrated on a nonlinear batch reactor with parameter uncertainty. A safety-verification algorithm identifies regions of the input space (initial conditions and external inputs) which guarantee safe operation. The algorithm is successfully applied to three examples: a tank with overflow and underflow, a batch reactor with an exothermic reaction, and a CSTR with feed preheating. [source] Conduct of operations: A control system for your most important safety componentPROCESS SAFETY PROGRESS, Issue 1 2000Paul Haas Instrumentation and control engineers go to great lengths to ensure availability and operability of control and information display systems for process system operation, especially for safety systems. It is critically important to maintain equipment performance within the bounds of safe operation. The most crucial safety components in your facility are the human beings controlling, maintaining, monitoring, and managing the process and equipment. Have you ever given much thought to the control systems operated by humans in your facility? [source] Equipment Dealers'Perceptions of a Community-based Rollover Protective Structures Promotion CampaignTHE JOURNAL OF RURAL HEALTH, Issue 2 2001Timothy W. Struttmann M.S.P.H ABSTRACT Farming is one of the most hazardous occupations, and tractor overturns are the leading cause of agricultural fatalities. This article examines a community-based injury intervention designed to increase the number of rollover protective structures (ROPS) and seat belts on tractors and to promote safe operation of farm tractors in two counties. Equipment dealers who sell retrofit ROPS kits to farmers were a critical component of the intervention. Interviews were conducted with dealers after the 31-month intervention period to understand their perceptions, any difficulties they experienced as a result of the project and how a similar project could be improved. Comments were analyzed in relation to theories of persuasion. Results indicated that dealers believed the intervention was successful in producing behavior change among some farmers. Dealers also provided important insights into why some farmers continued to resist retrofitting tractors with ROPS. Recommendations are offered for designers of community-based interventions beyond the ROPS project described here. [source] P/Pd Types Of Override Control SystemsASIAN JOURNAL OF CONTROL, Issue 4 2002Yaw-Ying Tsai ABSTRACT The override control provides protective action against abnormal operation and/or incipient process failure. In terms of control theory, it is a logic-based switching system and, in terms of operation, it is usually activated between the soft constraint and the hard constraint. It is used in all process industries, and most PID control loops are patched with some type of override system. Despite widespread application, little research has been done to analyze override control systems. In this work, the properties of the override control are explored. The stability of the override control is also studied. Counter to intuition, many well-known override systems may exhibit instability and lead to oscillatory responses as the process approaches constraints. Approaches are proposed for the design of override control systems to ensure inherent safe operation. [source] Outcome of pylorus-preserving gastrectomy for early gastric cancerBRITISH JOURNAL OF SURGERY (NOW INCLUDES EUROPEAN JOURNAL OF SURGERY), Issue 9 2008S. Morita Background: Pylorus-preserving gastrectomy has been introduced as a function-preserving operation for early gastric cancer in Japan. The aim of this study was to investigate the safety and radicality of the procedure. Methods: Between 1995 and 2004, 611 patients with apparent early gastric cancer in the middle third of the stomach had pylorus-preserving gastrectomy. The short-term surgical and long-term oncological outcomes of these operations were assessed. Results: The accuracy of preoperative diagnosis of early gastric cancer was 94·3 per cent. Nodal involvement was seen in 62 patients (10·1 per cent). There were no postoperative deaths. Complications developed in 102 patients (16·7 per cent). Major complications, such as leakage and abscess, were observed in 19 (3·1 per cent). The most common complication was gastric stasis, occurring in 49 (8·0 per cent). The overall 5-year survival rate in patients with early gastric cancer was 96·3 per cent. Conclusion: Pylorus-preserving gastrectomy is a safe operation with an excellent prognosis in patients with early gastric cancer. It is recommended as the standard procedure for early gastric cancer in the middle third of the stomach. Copyright © 2008 British Journal of Surgery Society Ltd. Published by John Wiley & Sons, Ltd. [source] | ||||||||||||||||