Evolutionary algorithms for multi-objective flexible job shop cell scheduling

The multi-objective flexible job shop scheduling in a cellular manufacturing environment is a challenging real-world problem. This recently introduced scheduling problem variant considers exceptional parts, intercellular moves, intercellular transportation times, sequence-dependent family setup times, and recirculation requiring minimization of makespan and total tardiness, simultaneously. A previous study shows that the exact solver based on mixed-integer nonlinear programming model fails to find an optimal solution to each of the ‘medium’ to ‘large’ size instances considering even the simplified version of the problem. In this study, we present evolutionary algorithms for solving that bi-objective problem and apply genetic and memetic algorithms that use three different scalarization methods, including weighted sum, conic, and tchebycheff. The performance of all evolutionary algorithms with various configurations is investigated across forty-three benchmark instances from ‘small’ to ‘large’ size including a large real-world problem instance. The experimental results show that the transgenerational memetic algorithm using weighted sum outperforms the rest producing the best-known results for almost all bi-objective flexible job shop cell scheduling instances, in overall

A benchmark dataset for multi-objective flexible job shop cell scheduling

This data article presents a description of a benchmark dataset for the multi-objective flexible job shop scheduling problem in a cellular manufacturing environment. This problem considers intercellular moves, exceptional parts, sequence-dependent family setup and intercellular transportation times, and recirculation requiring minimization of makespan and total tardiness simultaneously. It is called a flexible job shop cell scheduling problem with sequence-dependent family setup times and intercellular transportation times (FJCS-SDFSTs-ITTs) problem. The dataset has been developed to evaluate the multi-objective evolutionary algorithms of the FJCS-SDFSTs-ITTs problems that are presented in ‘Evolutionary algorithms for multi-objective flexible job shop cell scheduling’. The dataset contains forty- three benchmark instances from ‘small’ to ‘large’, including a large real-world problem instance. Researchers can use the dataset to evaluate the future algorithms for the FJCS-SDFSTs- ITTs problems and compare the performance with the existing algorithms

Laparoscopy-Assisted Percutaneous Cholangiography in Biliary Atresia Diagnosis: Comparison with Open Technique

Introduction. Biliary atresia is a surgical cause of prolonged jaundice, which needs to be diagnosed with cholangiography that has traditionally been performed via laparotomy. Laparoscopic assistance has lately been introduced to avoid unnecessary laparotomy. We aim to evaluate the benefits of the laparoscopy-assisted cholangiography and compare it to the traditional procedure via laparotomy. Patients and Method. The medical records of the cases who had undergone cholangiography for prolonged jaundice between 2007 and 2014 were analyzed. The patients were grouped according to cholangiography technique (laparotomy/laparoscopy). The laparoscopy and laparotomy groups with patent bile ducts were focused and compared in terms of operation duration, postoperative initiation time of enteral feeding, and full enteral feeding achievement time. Results. Sixty-one infants with prolonged jaundice were evaluated between 2007 and 2014. Among the patients with patent bile ducts, operation duration, postoperative enteral feeding initiation time, and the time to achieve full enteral feeding were shorter in laparoscopy group. Conclusion. Laparoscopic cholangiography is safe and less time-consuming compared to laparotomy, with less postoperative burden. As early age of operation is a very important prognostic factor, laparoscopic evaluation should be an early option in work-up of the infants with prolonged jaundice with direct hyperbilirubinemia, for diagnosis/exclusion of biliary atresia

Sprememba volumna sljudastih peščenih tal iz stare delte reke Gediz po likvifakciji

Post-liquefaction settlement characteristics of micaceous sands are not well investigated topic. Currently available charts relating post-liquefaction volumetric strain to relative density were developed for clean sand. Estimation of post-liquefaction settlement of micaceous sands, therefore, may stay on the unsafe side, since there is evidence indicating that mica grains could increase volume change tendency. Influence of mica content on post-liquefaction volumetric strain of sand-mica mixtures is studied in this article. Soil samples were prepared at various relative densities. Influence of fine content that could be present in the field was also investigated on tamped natural field samples recovered from boreholes drilled in a highly populated alluvial site known as the Old Gediz River Delta of Izmir. It was found that increasing mica content at a certain relative density resulted in higher volumetric strains as compared with the data on clean sands. It is deduced that influence of mica grains on sand behavior depends on initial void ratio of sand. Effects of mica grains decrease with increasing of relative density. Simple empirical relationships were derived relating mica content and relative density to volumetric strain. It was also noticed that fine content accelerated and increased post-liquefaction volumetric strains.Posedanje sljudastega peska po likvifakciji ni dovolj raziskano. Trenutno so na voljo preglednice o volumskem raztezku čistega peska po likvifakciji v odvisnosti od relativne gostote. Ocena posedanja sljudastih tal po likvifakciji je zato negotova, ker obstajajo dokazi, da lahko sljudasta zrna povečajo tendenco po spremembi volumna. Članek preučuje vpliv vsebnosti sljude na volumski raztezek zmesi peska in sljude. Pripravili smo vzorce zemljin različne relativne gostote. Preučili so tudi vpliv vsebnosti prahu, ki je lahko prisoten na terenu, v zbitih naravnih vzorcih, pridobljenih na terenu iz vrtin v gosto naseljenem področju stare delte reke Gediz v Izmirju. Ugotovili so, da ima povečanje vsebnosti sljude pri določeni relativni gostoti posledično višji volumski raztezek v primerjavi s čistim peskom. Zaključek je pokazal, da je vpliv sljudastih zrn na obnašanje peska odvisen od začetnega količnika por v pesku. Vpliv zrn sljude se zmanjšuje s povečanjem relativne gostote. Empirično so izpeljali enostavne odnose med vsebnostjo sljude in relativno gostoto ter volumskim raztezkom. Opazili so tudi, da je vsebnost prahu pospešila in povečala volumski raztezek po likvifakciji

Numerical investigation of a stand alone solar hydrogen energy system effects of PEFC degradation

An existing stand-alone solar energy system producing hydrogen for energy storage is numerically investigated focusing on the degradation of Polymer Electrolyte Fuel Cell (PEFC) and its effects on the overall performance of the system. The system consists of Photovoltaic (PV) panels, polymer electrolyte based electrolyzers, H2 and O2 storage tanks and a commercial PEFC stack. A PEFC is numerically investigated both as new and as degraded (for about two years). Using a variety of observed degradation patterns reported in the literature, the degraded PEFC is parametrically analyzed by using ANSYS Fluent. The investigated parameters are the membrane equivalent weight, the Catalyst Layer (CL) porosity and viscous resistance, the Diffusion Layer (GDL) porosity and viscous resistance, and the bipolar plate contact resistance. By comparing the simulation results for the new and the degraded fuel cells, it is concluded that the effects of overall degradation on cell potential is significant -- being about 20% around the operating point of the fuel cell. This degraded fuel cell is incorporated into the TRNSYS model of the energy system, and then the effects of the PEFC degradation on the performance of the energy system are estimated. It is observed that the degradation has substantial impact on the overall system performance. System down time of approximately one month is possible. Thus, the stand-alone system is not capable of operating continuously for a complete year when the polymer electrolyte based components are degraded

CFD Modeling and Analysis of a Shell-and-Tube Heat Exchanger

A shell-and-tube heat exchanger is modeled and numerically analyzed using a commercial finite volume CFD package. The heat exchanger is small, has a single shell and a single tube pass, and its shell side is baffled. The baffles are 25% or 36% cut single-segmental baffles. Tube layout is the staggered layout with a triangular pitch. There is no leakage from baffle orifices and no gap between the baffles and the shell. It is observed that the shell side flow and the temperature distributions are very sensitive to modeling choices such as mesh, order of discretization and turbulence modeling. Various turbulence models are tried for the first and second order discretizations using two different mesh densities. CFD predictions of shell side pressure drop and overall heat transfer coefficient are obtained and compared with Kern and Bell-Delaware method results. After selecting the best modeling approach, the sensitivity of the results to flow rates and the baffle spacing is investigated. It is observed that the flow and temperature fields obtained from CFD simulations can provide valuable information about the parts of the heat exchanger design that need improvement. Correlation based approaches may indicate the existence of the weakness but CFD simulations can also pin point the source and the location of it. Using CFD together with experiments may speed up the design process and may improve the final design

Designing heat exchanger with spatially variable surface area for passive cooling of PEM fuel cell

The purpose of this work was to design a heat exchanger for a Polymer Electrolyte Membrane (PEM) fuel cell, which would ensure such a temperature profile along the fuel cell cathode channel resulting in close to 100% relative humidity along the channel without external humidification. To achieve this, 3D numerical simulations of a single PEM fuel cell were performed using commercial Computational Fluid Dynamics (CFD) software (ANSYS Fluent). Based on the simulation results a variable surface area finned heat exchanger was designed which allows for passive fuel cell cooling. The results indicate that it is possible to obtain such temperature and relative humidity conditions inside the fuel cell cathode channel, using a passive heat exchanger with variable surface area

Designing heat exchanger with spatially variable surface area for passive cooling of PEM fuel cell

The purpose of this work was to design a heat exchanger for a Polymer Electrolyte Membrane (PEM) fuel cell, which would ensure such a temperature profile along the fuel cell cathode channel resulting in close to 100% relative humidity along the channel without external humidification. To achieve this, 3D numerical simulations of a single PEM fuel cell were performed using commercial Computational Fluid Dynamics (CFD) software (ANSYS Fluent). Based on the simulation results a variable surface area finned heat exchanger was designed which allows for passive fuel cell cooling. The results indicate that it is possible to obtain such temperature and relative humidity conditions inside the fuel cell cathode channel, using a passive heat exchanger with variable surface area

Intraabdominal Hemorrhage Due to Spontaneous Rupture of Superior Mesenteric Artery

Spontaneous rupture of mesenteric vessel is an extremely rare entity in children. We describe a 14-year-old boy who was presented with an acute abdomen and hemorrhagic shock without any history of trauma. Rupture of superior mesenteric artery was found at laparotomy. An attempt of vascular repair was failed due to vascular fragility. As whole midgut necrosis was developed, extended intestinal resection from 3th duodenal segment to descending colon and closure of duodenal and colonic ends were performed. Abdominal compartment syndrome, duodenal fistula and sepsis were encountered as major postoperative complications during his early postoperative period. Both abdominal compartment syndrome and duodenal fistula ceased after three weeks. Diagnosis of Ehlers Danlos Syndrome Type IV could be established according to his specific facial features, thin translucent skin, propensity to bleeding, rupture of mesenteric vessel and histopathological findings. Total parenteral nutrition was applied for energy requirement . A spontaneous femoral arteriovenous fistula was developed at the third month which was managed conservatively. He died 5 months later, while waiting for intestinal transplant. Ehlers Danlos Type IV diagnosis without any identical vascular lesion was also verified in his twin brother. Ehlers Danlos Syndrome Type IV should be kept in mind in cases of abdominal apoplexy. Repair of vascular complications could be impossible due to abnormal type III collagen leaded vascular fragility. [Cukurova Med J 2014; 39(2.000): 408-411

Jejunal Replacement of Stomach in Two Children with Total Gastric Necrosis

Total gastrectomy is an extremely rare procedure in children and experience with its replacement is very limited. We present two patients who had jejunal replacement due to total gastric necrosis. The first patient was a- 2-year-old boy who admitted with a history of caustic ingestion. He was taken operation because of gastric perforation and necrosis. Anastomosis was applied by using jejunal segments. The second patient was an 11-years-old girl who left diaphragmatic hernia and acute gastric volvulus. At laparotomy, Total gastrectomy and Hunt-Lawrence type gastroesophostomy were made. Reconstruction with jejunum is thought as a good option in total gastric necrosis according to our 2 patient experiences. [Cukurova Med J 2014; 39(2.000): 403-407