Necessary and Sufficient Conditions on Partial Orders for Modeling Concurrent Computations

Partial orders are used extensively for modeling and analyzing concurrent computations. In this paper, we define two properties of partially ordered sets: width-extensibility and interleaving-consistency, and show that a partial order can be a valid state based model: (1) of some synchronous concurrent computation iff it is width-extensible, and (2) of some asynchronous concurrent computation iff it is width-extensible and interleaving-consistent. We also show a duality between the event based and state based models of concurrent computations, and give algorithms to convert models between the two domains. When applied to the problem of checkpointing, our theory leads to a better understanding of some existing results and algorithms in the field. It also leads to efficient detection algorithms for predicates whose evaluation requires knowledge of states from all the processes in the system

A review of Amlapitta

Over the last several decades our diet has become unhealthy and our lifestyle sedentary. These factors have resulted in an ever-increasing prevalence of the lifestyle disease. Among the environmental factors, lifestyle factors in particular being overweight, incorrect dietary habits, lack of regular physical activity and smoking have frequently been resulted in various gastrointestinal diseases. Lifestyle is an essential factor in heath. Unhealthy behavior can lead to illness, disability and even death. Earlier the diet used to include a lot of vegetables and fruits which gave nutritional value. With the fast-paced modern lifestyle the diet has also become fast. In a competitive world people have no time to cook meal or sit and eat slowly. People resort to fast foods frozen foods loaded with preservatives and skip on healthy nutritional food. Along with poor eating habits lack of physical fitness is a significant problem in modern lifestyle. Use of mobile phones, television, computers longer commutes have contributed to sleep deprivation. Lifestyle modifications are currently used as first line of treatment for subjects with gastrointestinal diseases

Superheated Steam Scrubbing and Utilization for Power Generation

Superheated steam from high enthalpy vapor dominated geothermal fields offers an opportunity to extract greater exergy per unit flow with higher thermodynamic output efficiency compared to conventional geothermal wells. The first full scale well drilled with the objective to deliver superheated steam, IDDP-1, produced steam with an enthalpy of > 3070 kJ/kg and pressure up to 15 MPa. Flow rate up to 48 kg s-1 of steam was achieved which might result in power output up to 48 MW. Utilizing the superheated steam, however, faces challenges because of dissolved silica and chloride carried with the superheated steam. The silica that is present in the superheated steam precipitates when lowering down the pressure which can cause scaling. Presence of chloride in steam causes problem related to corrosion if the steam temperature drops below the acid dew point temperature. In order to avoid the corrosion due to the temperature drop, it is, therefore, necessary to do mitigate the impurities before utilization. However, applying traditional methods for mitigation, like wet scrubbing, causes loss in the steam superheat and hence output exergy. This work aims to develop a method to utilize the superheated steam consisting of high chloride and silica content as experienced in high enthalpy vapor dominated geothermal fields in a more efficient way than is currently available. To achieve this, a step by step approach is followed in this work. The first step aims to study silica particle transport and deposition in superheated steam flow using Computational Fluid Dynamic (CFD). For this, advection-diffusion model based on Euler-Euler approach is implemented using OpenFOAM. The implemented model was validated by experimental measurements for silica particle deposition in superheated steam flow. Experiments were performed to understand the effect of different parameters on particle deposition velocity. The results from the measurements show agreement with the simulated results. An increase in deposition velocity in the diffusion-impaction regime is observed, signifying silica particle agglomeration as an important factor controlling deposition. The second step aims to propose a method for scrubbing acid gas and silica impurities from the steam without loss in its superheat. To achieve scrubbing without loss in superheat, boiling point elevation property of aqueous potassium carbonate solution is exploited. A power cycle utilizing the scrubbing method is proposed while considering the parameters affecting deposition as concluded from the computational study. A comparison study of the thermodynamic performance of the proposed cycle for the case of IDDP-1 well is done where it is compared to that of the cycle utilizing traditional wet scrubbing. Simulation results for the production curve of IDDP-1 well show an increase in utilization efficiency up to 7% and an increase in net work output up to 12% using aqueous potassium carbonate for scrubbing compared to basic wet scrubbing. The third step aims at computational modeling and experimental study on aqueous potassium carbonate droplets in superheated steam to obtain a better understanding of the proposed scrubbing method. For this, a computational model using the Eulerian-Lagrangian approach is developed in OpenFOAM. Effect of injected solution salt concentration on droplet temperature and concentration were studied using model simulation and experiments. Results from the simulations were in accordance with experimental results, where an increase in boiling point elevation with the increase in injected salt solution concentration was observed. The final step aims at performance analysis of the proposed method using experiments for silica scrubbing from superheated steam using aqueous potassium carbonate solution. Measurements for the effect of injected salt solution concentration on scrubbing efficiency and degree of superheat retained while scrubbing are done. Results from the experiments show an increase in the degree of superheat retained and an increase in scrubbing efficiency with increased aqueous salt concentration. The overall study demonstrates a technique for scrubbing superheated steam using aqueous potassium carbonate. The proposed technique helps in retaining the steam superheat while scrubbing. To study the behavior of the scrubbing medium in the superheated steam, a computational model for simulating salt solution droplets in superheated steam is developed and validated experimentally. In addition, advection-diffusion model is implemented for simulating silica particle deposition in superheated steam flow. The results from the model simulation were validated experimentally.Með því að nýta yfirhitaða gufu úr þurrgufusvæðum með háu vermisinnihaldi fæst vökvi með hærra orkuinnihald á massaeiningu sem gefur kost á hærri varmafræðilegri nýtni samanborið við nýtingu á hefðbundnum jarðhitaholum. Fyrsta framleiðsluholan sem boruð var með það að markmiði að flytja yfirhitaða gufu, IDDP-1, skilaði gufu með vermi > 3070 kJ/kg og þrýsting að 15 MPa. Massaflæði úr borholunni var allt að 48 kg s-1 sem gæti skilað orkuframleiðslu upp á 48 MW. Nýting yfirhitaðrar gufu felur í sér áskoranir vegan uppleysts kísíls og klórs sem gufan ber með sér. Kísillinn getur fallið út þegar þrýstingur gufunnar er lækkaður og valdið skeljun. Klóríð í gufunni getur valdið tæringarvandamálum þegar hitastig gufunnar fellur niður fyrir sýrudaggarmark. Til að koma í veg fyrir tæringu vegna hitastigslækkunar er nauðsynlegt að hreinsa óhreinindin úr áður en til nýtingar kemur. Hefðbundnar aðferðir eins og vothreinsun valda tapi á yfirhitun og þar með orkutapi. Markmiðið með þessu verkefni var að þróa nýja og skilvirkari aðferð til að nýta yfirhitaða gufu með háu klór- og kísilinnihaldi líkt og finna má í þurrgufusvæðum. Verkefninu var skift í þrjá fasa. Fyrsti fasinn var að rannsaka flutning og áfellingu kísils í yfirhitaðri gufu með því að nota aðferðir úr tölulegri straumfræði (CFD). Massaburðar-sveimis líkan (Advection-diffusion) byggt á Euler-Euler aðferð var notað í OpenFoam. Líkanið var sannreynt með mælingum fyrir áfellingu kísilagna úr yfirhitaðri gufu. Með tilraunum voru rannsökuð áhrif ýmissa stærða á áfellingarhraða agnanna. Niðurstöður úr mælingunum eru í samræmi við niðurstöður úr líkanagerðinni. Aukning varð á áfellingarhraða á sveimistregðufærslu (diffusion-impaction) svæðinu sem sýnir að kekkjun kísilagnanna er mikilvægur þáttur þegar kemur að áfellingu. Annar fasinn fólst í að þróa aðferð við að hreinsa sýru á gasformi og kísilagnir úr gufunni án þess að tapa yfirhitun hennar. Til að hreinsa gufunnar án þess að tapa yfirhitai, var nýttur sá eiginleiki kalíum karbónat lausnar að hafa hærra suðumark en hreint vatn. Orkuferli sem nýtir þessa hreinsunaraðferð var lagt til þar sem tekið var tillit til þátta sem stjórna áfellingarhraðanum skv. niðurstöðum úr fyrsta fasanum. Varmafræðileg greining var gerð á því orkuferli og sem og orkuferli sem nýtir hefðbundna vothreinsun. Niðurstöður útreikninga þar sem kennilína IDDP-1 holunnar var notuð, sýna aukningu í nýtni upp á 7% og aukningu á heildarvinnu um 12% með því að nýta kalíum karbónat lausnina í stað hefðbundinnar vothreinsunar. Þriðji fasi verkefnisins fjallaði um hegðun dropa úr kalíum karbónat saltlausn í yfihitaðri gufu, og fólst bæði í tilraunum og tölvulíkanagerð. Tölvulíkan byggt á Eulerian-Lagrangian aðferð var þróað í OpenFOAM. Áhrif styrks lausnarinnar á dropahitastig og styrk karbonat lausnarinnar voru rannsökuð með líkanagerð og tilraunum. Niðurstöður úr líkönum voru í samræmi við niðustöður tilraunanna þar sem aukning á suðumarkshækkun með hækkun á saltstyrk var staðfest. Lokafasinn var að framkvæma afkastagreiningu á þessari aðferð með því að gera tilraunir á afköstum þess að hreinsa kísil úr yfirhitaðri gufu með kalíum karbónat lausn. Mælingar voru gerðar á áhrifum styrks saltlausnarinnar á hreinsunarnýtni og hversu vel yfirhitun var við haldið. Niðurstöðurnar sýna að meiri yfirhitun er viðhaldið og aukning verður í hreinsunarnýtni með auknum styrk á saltlausninni. Þessi rannsókn kynnir og greinir aðferð við að hreinsa yfirhitaða gufu með því að nota kalíumkarbónatlausn. Með þessari aðferð má viðhalda yfirhitun gufunnar á sama tíma og hún er hreinsuð. Til að rannsaka hegðun hreinsimiðilsins í yfirhituðu gufunni var tölvulíkan búið til til að herma eftir hegðum dropum saltlausnarinnar í yfirhitaðri gufu og voru þessar niðurstöður sannreyndar með tilraunum. Að auki var massaburðar-sveimis líkan þróað til að herma áfellingu kísilagna í yfirhitaðri gufu. Það líkan var jafnframt sannreynt með tilraunum

Clinical Correlation between Maxillary and Mandibular Midline to Facial and Dental Midline in Dentulous Individuals: A Hospital based study

BACKGROUND: One of the primary reasons for patient’s to seek prosthodontic treatment is esthetic or cosmetic reasons. The coincidence of dental midline between the maxillary and the mandibular teeth, and the coincidence of dental midline with the facial midline is an important factor governing esthetics. Keeping the above fact in mind the present study was planned to evaluate the relation between facial midline and dental midline and the relation between maxillary and mandibular midline in subjects. AIM OF STUDY: to evaluate the relationship between facial midline to dental midline and also relationship between maxillary to mandibular midline. METHODS: The present study was conducted on 100 Indian male and female individuals of 18 years of age group which included students, staff and patients of Tamil Nadu Government Dental College and Hospital, Chennai. Subjects included in the study were facially symmetrical, had full complement of teeth, healthy periodontium, Angle Class I occlusion, no history of orthodontic treatment and no individual teeth malpositioning. Subjects having any congenital or other facial deformities, badly decayed teeth and restored with crown and bridges were not considered with customised tru byte tooth indicator. RESULTS: Out of 100 subjects in 77, the maxillary midline was coinciding with facial midline, whereas in 23 subjects the maxillary midline was not coinciding with the facial midline. 23 does not coincide with 10 samples of RS (33.5%) and 13 samples of LS (56.5%). CONCLUSION: From the present study and various literature available it is assumed that there is not much difference in population in relation to facial midline and dental midline coincidence and in relation to sex. It can be suggested that when doing arrangement of teeth maxillary dental midline should be co-related to facial midline whereas mandibular midline shift either to right or left to an extent of 1-2.5mm is acceptable