bluuebunny/crossref_metadata_2025 huggingface dataset:
The Use of Sealing Ball Staged Fracturing
Authors: Wang Xingzun , Liu Gangzhi , Wang Da , J. Michael
Published: January 2011

Technologies for horizontal well fracturing in China include multi-staged fracturing and hydraulic jetting. As in many other parts of the world, this type of well stimulation employs mechanical zonal isolation or sand and polymer plugs. All of these technologies are used by us in a number of reservoirs but they depend on the presence of newly targeted and intentionally perforated sections of horizontal wells that are not already perforated. However, because most horizontal wells in the mature Huabei oilfield have been producing for a very long time and the perforations are all along the horizontal sections, it is practically impossible to use the technologies mentioned above.

To prevent multiple fracture initiation in a given section, sealing-ball staged fracturing has been developed and has been used successfully in horizontal wells of the Huabei field. Three kinds of sealing balls, whose densities are <1, 1 and >1 g/cc, are pumped between stages of fracturing and they can seal perforations at 360° around the horizontal well section. Higher- permeability zones are sealed off preferentially. Because staged fracturing can be carried out effectively without stopping the pumps, while running ball sealers downhole, the process can be accomplished in a significantly shorter period of time than other techniques.

In this paper we present field case studies of staged hydraulic fracturing using ball sealers and we demonstrate the success of this form of zonal isolation in both execution and, especially, post-fracture well performance. We also provide guidelines for the effective length of horizontal well section where ball sealers can be used for zonal isolation.
Unconventional Shale Oil and Gas-Condensate Reservoir Production, Impact of Rock, Fluid, and Hydraulic Fractures
Authors: Orangi A. , Nagarajan N. R. , Honarpour M. M. , Rosenzweig J.
Published: January 2011

Development of unconventional oil and gas reservoirs, particularly the shale gas, gas-condensate, and shale oil, has gained tremendous momentum in recent years. Energy companies aggressively are adding unconventional hydrocarbon resources to their portfolios. The unconventional resources usually refer to ultra low permeability reservoirs that cannot be produced at economic rates or volumes without stimulation of near well-bore regions. New technologies of horizontal well coupled with staged hydraulic fracturing have made the development of these reservoirs an economic reality. But often, the initial attractive production rates decline fast and thus making them economically marginal and sometimesoperationally unattractive. In order to efficiently produce these reservoirs, it is important to understand the flow mechanism and the controlling rock and fluid parameters that significantly impact thelong term production performance of these resources.

We have conducted detailed reservoir simulation studies to investigate the impact of rock and fluid properties and the drainage area of hydraulically fractured wells in a standard development pattern. The simulation of horizontal wells with 14-stage hydraulic fractures was conducted in a shale reservoir containing a wide spectrum of rock and fluid types, dry gas to gas-condensate, and oil. An extensive compositional reservoir simulation was conducted using both radial grid and sector model. Short term production data from several horizontal wells and long term production data from one vertical well were used for history matching and model calibration. A number of cases have been run with a wide range of fracture, matrix and fluid properties considering condensate banking, fracture patterns, pore volume compressibility, and relative permeability. The results showed Cumulative oil production is sensitive to fluid properties, particularly to the GORSevere drop in productivity is observed due to matrix and fracture compaction and condensate bankingThe drainage area and the contact area of the fractures with the reservoir are often limited in spite of extensive hydraulic fracturesPerformance is also found to be sensitive to fracture permeability and matrix relative permeabilityFracture interference is limited and may occur in the late life of the reservoir
Channel Fracturing - A Paradigm Shift in Tight Gas Stimulation
Authors: Johnson J. , Turner M. , Weinstock C. , Peña A. , Laggan M. , Rondon J. , Lyapunov K.
Published: January 2011

The hydraulic Channel Fracturing technique relies on the engineered creation of a network of open channels within the proppant pack, which provides for highly conductive paths for the flow of fluids from the reservoir to the wellbore. This paper provides a comprehensive summary of the implementation of this technique in ultra-low permeability, gas-bearing formations.

The Lance formation in the Jonah field near Pinedale, Wyoming was selected for this study. This formation comprises fluvial sand bodies with 0.0005 to 0.05 mD permeability and 35 to 55% gas saturation. The formation requires hydraulic fracturing for economic production. Key historical issues for the stimulation of this formation using gelled fluids and sand as proppant are limited fluid recovery and consequential formation and fracture conductivity impairments. Slick-water treatments have rendered moderate gains in production mainly in low-prospect zones with some occurrence of near-wellbore screen-outs. Moderate increases in production from using ceramic proppants have been gained at the expense of significant increase in stimulation costs.

Hydrocarbon production, treating pressure and fracturing fluid recovery data from a thirteen-well campaign in the Jonah field are summarized in the manuscript. Results indicate that the implementation of the channel fracturing technique increased initial gas production and estimated recovery over conventional fracturing methodologies. Positive features that were also observed during this campaign such as reduced net pressure increase estimates from pre- and post-frac shut-in pressure measurements, reduced tendency for vertical fracture growth and elimination of near-wellbore screen-outs are also reported and discussed.

It is concluded that the Channel Fracturing technique is a viable alternative to conventional fracturing methods for more efficient and effective stimulation of complex tight gas formations.
Experimental Evaluation of Guar Fracture Fluid Filter Cake Behavior
Authors: Xu Ben , Hill A. D. , Zhu Ding , Wang Lei
Published: January 2011

Guar gum and its derivatives have been the most commonly used polymers to increase the viscosity of fracturing fluids. However, the conductivity of many fractures created with guar-based polymers is low because of residual unbroken polymer gel remaining in the fracture. This residue can cause permeability impairment in the proppant pack resulting in low fracture conductivity and decreased effective fracture length. In this study, we experimentally evaluated two important aspects of the gel damage process - the thickness of the polymer gel filter cake that is created as fracture fluid filtrate leaks off into the formation, and the yield stress of the concentrated polymer gel that accumulates in the fracture. The thickness of the filter cake created during the leakoff process was measured as a function of the polymer loading and the volume of leakoff. We created the filter cake following the procedure described by Ayoub et al. (2006), then measured the filter cake thickness with a precise laserprofilometer. We found that the filter cake thickness varied linearly with leakoff volume, meaning that the gel concentration factor is constant for this guar polymer fluid. The concentrated polymer filter cakes created by leakoff behave rheologically as Herschel-Bulkley fluids having a yield stress. The yield stress of this material is a critical parameter influencing whether or not the gel can be removed from the fracture. We measured the yield stress of borate-crosslinked guar polymer fracture fluids at concentrations up to 200 lb/mgals using a unique flat plate device. The yield stresses of th polymer filter cakes were found to depend strongly on the concentration of both polymer and breaker.
Morphology of Partial Globozoospermia
Authors: Dam Anika H. , Ramos Liliana , Dijkman Henry B. , Woestenenk Rob , Robben Hannie , van den Hoven Leonie , Kremer Jan A.
Published: January 2011

ABSTRACT: Total globozoospermia is a rare sperm morphology disorder that consists of 100% round‐headed, acrosomeless spermatozoa. There is also a larger group of patients whose sperm cells are partially acrosomeless. The aim of this investigation was to describe partial globozoospermia compared to total globozoospermia and normozoospermia. Ejaculates from 10 patients with more than 50% acrosomeless spermatozoa (partial globozoospermia), 3 patients with total globozoospermia, and 9 normozoospermic controls were analyzed with light microscopy, transmission electron microscopy, and flow cytometry. Qualitative and quantitative examination of spermatozoa from the 3 groups shows differences in the percentage of round‐headed sperm cells and acrosome malformation. Total globozoospermia presents as a homogenous kind of teratozoospermia. Partial globozoospermia is a distinctive sperm malformation with an increased proportion of round‐headed sperm cells and acrosome malformations compared to normozoospermia, which exists separately from total globozoospermia. It thereby contains oval sperm cells that may have distinctive malformations of the sperm head matrix, but also morphologically normal sperm cells that may be used in a clinical setting.
Association Between Serum Testosterone and Sex Hormone–Binding Globulin and Exercise Capacity in Men: Results of the Study of Health in Pomerania (SHIP)
Authors: Koch Beate , Glaser Sven , Schaper Christoph , Krebs Alexander , Nauck Matthias , Dorr Marcus , Haring Robin , Volzke Henry , Felix Stephan B. , Ewert Ralf , Wallaschofski Henri , Friedrich Nele
Published: January 2011

ABSTRACT:Testosterone exerts a widespread pattern of effects on metabolism and body composition, and interest is gaining in its correlation with physical fitness. The main focus of our study was to investigate the association of total serum testosterone and sex hormone–binding globulin (SHBG) levels on exercise capacity and maximal power output in men using a cross‐sectional, population‐based adult cohort. From the Study of Health in Pomerania (SHIP), 624 men age 25 to 85 years who underwent a standardized progressive incremental exercise protocol on a cycle ergometer were included in the analyses. Exercise capacity was characterized by oxygen uptake at anaerobic threshold (V′O2at θL) and peak exercise (V′O2peak) as well as maximal power output at peak exertion. Multivariable linear regression analyses adjusted for age, sex, body mass index, physical activity, and smoking were performed. Further, linear regression analyses with cubic splines and sensitivity analyses were undertaken. At peak exercise performance, testosterone and SHBG levels showed no associations withV′O2peak,V′O2at θL as well as maximal power output, even after controlling for confounding factors including age, body mass index, physical activity, and smoking. An adverse association between the free testosterone index andV′O2at θL was found. Linear regression analyses with cubic splines did not change the main results. In conclusion, this is the first study focusing on the association of total serum testosterone and SHBG on exercise capacity and physical performance in healthy volunteers based on a large‐scale population‐based study. After adjustment for relevant influencing factors, neither total serum testosterone nor SHBG levels had any interference with peak exercise capacity, aerobic exercise capacity, or maximal power output in men.
Long‐Term Effects of Dimethandrolone 17β‐Undecanoate and 11β‐Methyl‐19‐Nortestosterone 17β‐Dodecylcarbonate on Body Composition, Bone Mineral Density, Serum Gonadotropins, and Androgenic/Anabolic Activity in Castrated Male Rats
Authors: Attardi Barbara J. , Marck Brett T. , Matsumoto Alvin M. , Koduri Sailaja , Hild Sheri A.
Published: January 2011

ABSTRACT: The potent androgens dimethandrolone 17β‐undecanoate (DMAU) and 11β‐methyl‐19‐nortestosterone 17β‐dodecylcarbonate (11β‐MNTDC) are in development for androgen replacement therapy and hormonal contraception in men. They can be delivered either orally or as long‐acting injectables. In the current study, their long‐term effects on body composition (percentage lean and fat mass); bone mineral density (BMD); serum gonadotropin levels; and weights of the prostate, seminal vesicles, and levator ani muscle were assessed. Four‐week‐old male rats were sham‐operated (intact) or castrated (Cx) and treated subcutaneously for 16 weeks postsurgery with vehicle (Cx, intact), DMAU, or 11β‐MNTDC every 4 weeks; testosterone enanthate (TE) every 2 weeks; or a testosterone (T) implant. There were significant differences in body weights over time with a general trend of intact = Cx + T = Cx + TE > Cx + 11β‐MNTDC > Cx > Cx + DMAU. At week 18, rats were evaluated by dual‐energy x‐ray absorptiometry using the whole‐body function of the Hologic software. The percentage lean body mass and BMD were lower (P < .05) in Cx rats than intact rats but equivalent in all groups of androgen‐treated Cx rats and intact rats (P > .05). The highest percentage body fat was observed in Cx rats. Only DMAU‐ and 11β‐MNTDC–treated rats had lower percentage body fat compared with Cx rats (P < .05). Prostate, seminal vesicles, and levator ani muscle weights, corrected for final body weight, were decreased (P < .05) in Cx compared with intact rats and increased to varying extents in androgen‐treated Cx rats compared with Cx rats (P < .05). The most marked increases were observed in the DMAU‐treated rats in which prostate and seminal vesicle weights/kg body weight were 2.4 to 2.7 times those of intact rats, and levator ani muscle weights were increased approximately 1.5‐fold. Blood was collected from the tail vein at weeks 4, 8, 12, and 16 for measurement of serum levels of androgens and at necropsy at week 18 for measurement of serum gonadotropins. Serum levels of luteinizing hormone and follicle‐stimulating hormone were greatly elevated in Cx rats at week 18 and suppressed to levels comparable to those in intact rats by DMAU, 11β‐MNTDC, and T implants (P > .05). Collectively, our data indicate that androgen replacement with DMAU or 11β‐MNTDC in Cx rats resulted in favorable changes in body composition and maintenance of BMD comparable to those of T.
G708E Mutation in the Androgen Receptor Results in Complete Loss of Androgen Function
Authors: Rajender Singh , Pooja Singh , Gupta Nalini J. , Chakrabarty Baidyanath , Singh Lalji , Thangaraj Kumarasamy
Published: January 2011

ABSTRACT: End‐organ resistance to androgens, called androgen insensitivity syndrome (AIS), is a rare disorder. The most common cause of AIS is mutations(s) in the androgen receptor (AR) gene; however, a significant number of these mutations have not been functionally analyzed. In the present study, we analyzed a case of complete AIS for mutations in the AR gene. Sequencing of the entire coding region of the AR gene revealed a 2650G>A mutation (mRNA sequence reference) in exon 4 of the gene, resulting in replacement of glycine with glutamate at codon 708 in the ligand‐binding domain of the AR protein. The mutation was absent in 200 normal male individuals analyzed to look at its occurrence in general population. In vitro androgen‐binding and transactivation assays showed that the mutation resulted in approximately 65% loss of ligand binding and almost complete loss of transactivation function. Complete AIS in this individual was due to a G708E substitution in the AR protein.
Sexual Dysfunction in Female Patients With Neurodermatitis
Authors: Ermertcan Aylin Türel , Gencoglan Gulsum , Temeltas Gokhan , Horasan Gonul Dinc , Deveci Artuner , Ozturk Ferdi
Published: January 2011

ABSTRACT: Neurodermatitis is a chronic disease affecting the patient's psychosocial status and quality of life. It is associated with a variety of psychologic problems, including demoralization, depression, anxiety, obsessive‐compulsive disorder, and sleep disturbances. Coexistence of sexual dysfunction, especially in women, with several systemic diseases has gained interest in recent years. In this study, we evaluated sexual function in female patients with neurodermatitis. We enrolled 89 women (43 patients, 46 controls) in the study. Quality of life was assessed with the Dermatology Life Quality Index (DLQI), and the Female Sexual Function Index (FSFI) was used to determine sexual function. Individuals with psychiatric disorders and/or those using antidepressants were excluded. The total DLQI score was 11.95 ± 5.65 in patients with neurodermatitis. The total FSFI score was significantly lower in patients compared with healthy controls (22.76 ± 5.31 and 28.83 ± 3.50, respectively; P = .001). Domain scores of FSFI (desire, arousal, lubrication, orgasm, and satisfaction) except pain were significantly lower in patients with neurodermatitis (P = .001). The pain score was also lower in patients than controls, but the difference was not statistically significant (P = .073). Neurodermatitis may be associated with sexual dysfunction, and patients with neurodermatitis should be evaluated with regard to sexual function to provide a better quality of life.
Castration‐ and Aging‐Induced Changes in the Expression of Zinc Transporter and Metallothionein in Rat Prostate
Authors: Iguchi Kazuhiro , Morihara Naoaki , Usui Shigeyuki , Hayama Minoru , Sugimura Yoshiki , Hirano Kazuyuki
Published: January 2011

ABSTRACT: Prostate tissue contains high concentrations of zinc. Zinc content in the prostate gland changes in prostatic disease, such as benign prostate hyperplasia and prostate cancer, which occur more frequently with increasing age. Prostate zinc content is also known to decrease after castration in animal models. It is not clear how prostate zinc content is regulated; therefore, to clarify the mechanisms underlying zinc homeostasis, we examined zinc content and the expression of zinc transporters and metallothioneins in the prostates of aged or castrated rats. Zinc concentration was measured by flame atomic absorption spectrometry. The mRNA expression of zinc transporters and metallothioneins was determined by real‐time reverse transcriptase polymerase chain reaction analysis. The expression of the zinc transporter Slc30a2 (Znt2) in ventral prostate (VP) of aged rats (21 months) was approximately 21‐fold higher than that in VP of young rats (4 months), and zinc levels in VP of young rats increased significantly compared with that in aged rats. Zinc content in lateral prostate (LP) and dorsal prostate did not differ between young and aged rats. Decreased metallothionein‐3 (Mt3) expression was observed in LP of castrated rats, and this reduction was prevented by testosterone replacement. Zinc content and Mt3 expression levels correlated significantly in rat LP. Our findings suggest that Mt3 could play a critical role in zinc homeostasis in rat LP.
Erectile Dysfunction: A Harbinger or Consequence: Does Its Detection Lead to a Window of Curability?
Authors: Miner Martin M.
Published: January 2011

ABSTRACT: Erectile dysfunction (ED) is a marker of increased cardiovascular (CVS) risk and may indicate the need for aggressive evaluation for cardiovascular disease (CVD). In younger men with ED, the Framingham risk assessment has inadequate sensitivity. There is a need to develop a more sensitive risk‐stratification protocol for this population. We sought to develop an algorithm for the evaluation and management of the ED patient. A search of literature published from 1998 to 2009 was performed. Search terms included the following: endothelial dysfunction; and erectile dysfunction combined with coronary artery disease (CAD), metabolic syndrome, or cardiac biomarkers. Searches revealed 107 references. These studies were evaluated with use of levels of evidence for the Centers of Evidence‐Based Medicine. On the basis of these studies, recommendations for the evaluation and management of the patient with ED were developed. Newer, nontraditional markers and procedures may identify ED patients at risk for subsequent CVS events earlier or more easily than traditional risk assessments. Clear practice guidelines for risk stratification are being developed, and data are sufficient to propose an algorithm for these patients. The presence of ED should prompt assessment of cardiac risk and aggressive risk factor treatment. Available risk assessment factors should initially be used to stratify each patient. ED patients younger than 60 years of age and with no clinical CVD are at risk of CAD events (>10%) and should undergo further risk assessment. Additional tests of arterial damage and biomarkers may aid in refinement of risk for future cardiac events. Patients with ED can be classified into low‐, intermediate‐, and high‐risk categories. A proposed algorithm can be used to direct the assessment of cardiometabolic risk in patients with ED.
Investigation of the underwater noise produced by ships by means of intensity method
Authors: Kozaczka Eugeniusz , Domagalski Jacek , Gloza Ignacy
Published: January 2011

Investigation of the underwater noise produced by ships by means of intensity method

This paper presents results of research on spectral structure of underwater noise acoustic field radiated into water by selected ships moving in shallow waters. Underwater acoustic field of ships in motion is associated with acoustic activity of ship mechanisms and equipment under work. Vibration energy radiated by the mechanisms and devices is transmitted by ship structural elements to surrounding water where it is propagated in the form of acoustic waves of a wide frequency band. In this paper are presented results of the research on propagation of energy of acoustic waves in the near fiel, obtained from acoustic pressure measurements by means of two sensors located close to each other.
Problems of welding in shipbuilding - an analytic-numerical assessment of the thermal cycle in HAZ with three dimensional heat source models in agreement with modelling rules
Authors: Ranatowski Eugeniusz
Published: January 2011

Problems of welding in shipbuilding - an analytic-numerical assessment of the thermal cycle in HAZ with three dimensional heat source models in agreement with modelling rules

This part is continuation of PART II. Analytic solutions for the temperature distribution in HAZ - presented in the previous part of this article are transformed for computer calculation with used Mathcad programme. There are established algorithms in moving and stationary systems for thermal cycle calculating. Finally, a few analytical examples with use of C-I-N and D-E models are demonstrated.
Rhetorical Evaluation of Seventeenth Century Prefaces to English Treatises on Midwifery
Authors: Sánchez-Cuervo Margarita
Published: January 2011

Rhetorical Evaluation of Seventeenth Century Prefaces to English Treatises on Midwifery

This study tries to offer a rhetorical account of the main arguments and figures encountered in 17th c. English prefaces, dealing with the art of midwifery and the delivery of children. I foreground a main causal argument wherein the author states the necessity for a treatise of this delicate nature and proposes the motives for its requirement. In doing so, some other reasonings support the causation and provide the reader with more evidence for a good performance at childbirth. In addition, the arguments are enhanced by the presence of some figures of communion that contribute to the rhetorical organisation, and help to portray the prologue as an expository discourse. The insistence on complying with the author's directions, and the urge not to follow some predecessors' work also suggests the new authority that the early modern English preface writer is acquiring.
On the Relationship Between Grammaticalization and Reanalysis
Authors: Jarad Najib
Published: January 2011

On the Relationship Between Grammaticalization and Reanalysis

This paper seeks to explain and exemplify the relationship between grammaticalization and reanalysis, two important processes of grammatical change which occur in language. The ultimate goal of this paper is to prove that whilst the two are crucially related, they are not mutually dependent and can extensively occur alone. The paper focuses on the shift of for from the thematic function and/or case realizer to the modern pure complementizer status.
Telling it Straight: A Comparison of Selected English and Polish Idioms From the Semantic Field of Speaking
Authors: Szczepaniak Renata , Adamska-Sałaciak Arleta
Published: January 2011

Telling it Straight: A Comparison of Selected English and Polish Idioms From the Semantic Field of Speaking

This paper attempts to illustrate one way of achieving greater precision in presenting idiomatic equivalents by implementing the functionally-oriented methodological instrument devised by Dobrovol'skij and Piirainen (2005). A small-scale analysis along the three parameters of semantics, syntax and pragmatics is carried out with a view to identifying and explaining all cross-linguistic contrasts and similarities between selected English and Polish near-equivalent idioms from the semantic field of speaking. The empirical data of this study includes corpus evidence, apart from the available monolingual, bilingual and phraseological dictionaries. The resultant descriptions of the idiomatic expressions attest the validity of a functional approach to contrastive idiom analysis, which, unlike judgments based on the superficial properties of idioms (i.e. their lexical components, structure), reveals that differences in images will not always prevent idioms with similar actual meaning from being regarded as equivalents. On the other hand, closeness of underlying imagery does not guarantee identity with respect to all parameters of comparison (especially pragmatics).
Spontaneous Use of Vocabulary Learning Strategies
Authors: Zybert Jerzy
Published: January 2011

Spontaneous Use of Vocabulary Learning Strategies

The paper argues that language learners employ learning strategies naturally. To corroborate the claim it presents a research on vocabulary learning strategies and provides a quantitative and qualitative analysis of the findings and concludes with some pedagogical suggestions.
Intertextual transactions in American and Irish fictions By Andrzej Kopcewicz
Authors: Ambroży-Lis Paulina
Published: January 2011

Intertextual transactions in American and Irish fictions By Andrzej Kopcewicz
Scribal Intrusion in the Texts of Gamelyn
Authors: VáZquez Nila
Published: January 2011

Scribal Intrusion in the Texts of Gamelyn

One of most important steps in the process of editing a manuscript is the identification and correction of the mistakes made by the scribe or scribes involved in its copying process in order to obtain the best text. In some cases, the changes introduced by the scribe, or by the editor who was supervising his work, can easily be noticed because we find out "physical" elements throughout the folio, such as dots under a word as a sign of expunction or carets indicating that a missing word is being added. However, there are many instances of scribal intrusion where only a detailed analysis of the text itself, or even the comparison of different manuscripts, can lead us to the identification of a modified reading. For instance, orthographical changes due to the dialectal provenance of the copyist, or altered lines with a regular aspect. The purpose of this article is to analyse the scribal amendments that appear in some of the earliest copies of The tale of Gamelyn: Corpus Christi College Oxford MS 198 (Cp), Christ Church Oxford MS 152 (Ch), Fitzwilliam Museum McClean 181 (Fi), British Library MS Harley 7334 (Ha4), Bodleian Library MS Hatton Donat. 1 (Ht), British Library MS Lansdowne 851 (La), Lichfield Cathedral MS 29 (Lc), Cambridge University Library Mm. 2.5 (Mm), Petworth House MS 7 (Pw) and British Library MS Royal 18 C.II (Ry2).
Focus on Focus A Review Article of Aspects of the Grammar of Focus: A Minimalist View by Przemysław Tajsner
Authors: Szwedek Aleksander
Published: January 2011

Focus on Focus A Review Article of Aspects of the Grammar of Focus: A Minimalist View by Przemysław Tajsner
Focus in Focus. Replying Professor Szwedek
Authors: Tajsner Przemysław
Published: January 2011

Focus in Focus. Replying Professor Szwedek
The Language that is Not. A Reply to Professor Tajsner
Authors: Szwedek Aleksander
Published: January 2011

The Language that is Not. A Reply to Professor Tajsner
Synchronous Study of Ferroresonance and Inrush Current Phenomena and their Related Reasons in Ground Power Networks
Authors: Akrami Amin , Ghaderi Mohammad , Ghadi Saeed
Published: January 2011

Synchronous Study of Ferroresonance and Inrush Current Phenomena and their Related Reasons in Ground Power Networks

Energizing the power transformers usually results in flowing very high inrush currents. This harmful current can be minimized using controlled switching and considering the value of residual flux. But nowadays, developing the ground power networks results in high increment of ferroresonance phenomenon occurrence due to the line' capacitance reactance and nonlinear inductive reactance of power transformer's core. In this study, these transient phenomena and their cause have studied synchronously.
Correlation Analysis between Grounding Resistance and Diurnal Variations of Upper Soil Resistivity during March 2010 in Balozhi, Latvia
Authors: Kizhlo Marina , Kanbergs Arvids , Kizhlo Mihails
Published: January 2011

Correlation Analysis between Grounding Resistance and Diurnal Variations of Upper Soil Resistivity during March 2010 in Balozhi, Latvia

The accurate measurement of soil resistivity and grounding system resistance is fundamental to electrical safety. However, geological and meteorological factors can have a considerable effect on the accuracy of conventional measurements and the validity of the measurement methods. This paper examines some aspects of grounding measurements and grounding system performance in the context of both geological and meteorological effects.

We are reporting the results of grounding measurements using the 3-point method with ground resistivity tester type M416. The measurements were conducted during selected period from 2010 March 1 to March 31 in Balozhi, Latvia. We also noted that the resistivity of the upper layer significantly varied from a point to another, reflecting difference in water content in the upper soil layer due to local topography and other parameters.
Electrical Measuring Techniques — Expectations for Increasing Accuracy
Authors: Matiss Imants , Purvinsh Andris
Published: January 2011

Electrical Measuring Techniques — Expectations for Increasing Accuracy

Multi parameter testing by Calibrated Disturbing Factors (CDF) methodology may present interest as more sophisticated mean for increasing metrological qualities of electrical testing techniques. Detailed analysis of a set of validation parameters, such as thickness and dielectric permeability of plates, demonstrates advantage of this approach in comparison with single parameter tests.
A PLL Scheme for Synchronization with Grid Voltage Phasor in Active Power Filter Systems
Authors: Krievs Oskars , Steiks Ingars , Ribickis Leonids
Published: January 2011

A PLL Scheme for Synchronization with Grid Voltage Phasor in Active Power Filter Systems

Voltage source inverters connected to the grid in applications such as active power filters require synchronization with the grid voltage. Since in practice the grid voltage can be unbalanced and distorted, but the operation of the whole active filter control system is strongly dependant on precise estimation of grid voltage phase, the fundamental positive sequence phasor of the grid voltage has to be extracted. In this paper a system for smooth estimation of the position of the voltage phasor at the point of common coupling of a parallel active filter system is presented using a sinusoidal signal integrator and a simple software PLL. The performance of the proposed system is verified by simulation and experimental results. The proposed PLL scheme can also be used in other vector oriented control systems.
Matrix Converter Bi-directional Switch Power Loss and Cooling Condition Estimation for Integrated Drives
Authors: Sokolovs Alvis , Galkin Ilya
Published: January 2011

Matrix Converter Bi-directional Switch Power Loss and Cooling Condition Estimation for Integrated Drives

In this paper power loss estimation of bi-directional switch of matrix converter is done by means of calculation and experiments. For safe operation of power devices an efficient cooling system of specific device must be designed. This work is part of a greater project of integrated matrix converter AC drives and the cooling problem here is viewed in context of this task. It is necessary to develop a compact power board and cooling system to extract excessive heat from power devices.
Troubleshooting of Matrix Frequency Converter Conducted and Radiated Emissions
Authors: Asmanis Gundars , Ribickis Leonids , Novikovs Vladimirs
Published: January 2011

Troubleshooting of Matrix Frequency Converter Conducted and Radiated Emissions

Matrix converter inherently exhibits sinusoidal input current waveforms and has less stressful output voltage waveforms, but it is causing problems with conducted and radiated emissions. This paper deals with matrix converter emitted disturbances from point of view of electromagnetic compatibility (EMC) standard EN61800-3 and allocates the sources of undesirable emissions using standard equipment used for EMC assessment according to variety international EMC standards and discusses methodology of troubleshooting flow, using low cost equipment available in almost every laboratory of Industrial Electronics and Electrical Engineering.
Application of Astatic State Observers in Electromechanotronic Modules
Authors: Gnezdov Nikolay , Kolganov Aleksey , Lebedev Sergey
Published: January 2011

Application of Astatic State Observers in Electromechanotronic Modules

The authors offer a synthesis method of state observers with high-order astatism. There are no errors caused by the action of arbitrary external disturbances in reduced variables of such observers. The observers also restore the instantaneous values of disturbances. The authors present a calculation method of ultimate realizable dynamics of observers during their realization in microprocessor control system which calculates in numbers with fixed point without overflowing of variables. The description of experimental installation and software is given.
Algorithm for Public Electric Transport Schedule Control for Intelligent Embedded Devices
Authors: Alps Ivars , Potapov Andrey , Gorobetz Mikhail , Levchenkov Anatoly
Published: January 2011

Algorithm for Public Electric Transport Schedule Control for Intelligent Embedded Devices

In this paper authors present heuristics algorithm for precise schedule fulfilment in city traffic conditions taking in account traffic lights. The algorithm is proposed for programmable controller. PLC is proposed to be installed in electric vehicle to control its motion speed and signals of traffic lights. Algorithm is tested using real controller connected to virtual devices and real functional models of real tram devices. Results of experiments show high precision of public transport schedule fulfilment using proposed algorithm.
Pancheshwar Multipurpose Project: Nepal's Portion of Power
Authors: Pun Sant Bahadur
Published: January 2011

After the proverbial 13 year 'ban bas', the 1996 Mahakali treaty was "re-activated" in 2009 when Nepal and India constituted the Pancheshwar Development Authority to fnalize the Detailed Project Report of Pancheshwar Multipurpose Proj-ect and thereafter undertake the execution, operation and maintenance of the project. In this context, the article reverts back to the ratifcation time of the Mahakali treaty in 1996 and dwells exclusively on the issues then raised pertaining to Nepal’s portion of power from Pancheshwar project. The then prime minister and water resources minister gave CPN-UML party gen-eral secretary and the CPN-UML Mahakali study team coordinator written replies (a) on India being "forced to buy" Nepal's portion of power, (b) that "relevant alternatives" meant "thermal and gas plants and excludes hydropower plants", and iii) that "savings in cost to the benefciaries as compared with the relevant alternatives" meant the same as "avoided cost of alterna-tive principle." No attempts were made to elicit the Government of India's interpretations on these vital issues. Instead, while the water resources minister claimed Rs 21 billion annually from the sale of Nepal's portion of Pancheshwar power to India, the not-to-be outwitted party secretary claimed an astronomical annual revenue of Rs 120 billion. The now incumbent prime minister has come up with another attractive fgure of Rs 45.88 billion annually. The article attempts to point out that if due diligence is not undertaken immediately on the ambiguities prevailing in the Mahakali treaty and the letters of exchange, then Nepal may well end up as like Paraguay vis-a-vis Brazil on the 14,000 MW Itaipu hydropower project.Key words: Pancheshwar Multipurpose Project; Mahakali treaty; Avoided cost; Power revenues; NepalDOI: 10.3126/hn.v6i0.4186Hydro NepalVol 6, January 2010Page :1-6Uploaded Date: 23 January, 2011
The Use of Self Supporting Capacity of Rock Mass for Sustainable Hydropower: An Analysis of the Middle Marsyangdi Headrace Tunnel, Nepal
Authors: Shrestha Kiran K. , Panthi Krishna K
Published: January 2011

The history of hydropower development in the Himalaya indicates that many tunnels have suffered from cost over- runs and delays. These issues are directly dependent on the quality of rock mass and the permanent rock support applied in underground excavation. Right judgment and proper evaluation of the self supporting capability of the rock mass and the use of optimum rock support systems help considerably in reducing construction cost and delays. This paper examines such issues as geological conditions in the Himalayas and varying approaches and costs in tunnel construction. An assessment is made regarding the exclusion of permanent concrete lining in the headrace tunnel of the 72MW Middle Marsyangdi Hydroelectric Project in Nepal. The project has 5.2 km fully concrete lined headrace tunnel that passes through fair to poor rock mass. The evaluation is based on the use of actually recorded rock mass quality of the headrace tunnel during construction and rock support principle used at the comparable Khimti Hydro Project headrace tunnel. The evaluation includes calculation of equivalent tunnel section for similar headloss, stability analysis, assessment of possible water leakage, and required injection grouting measures. We conclude that the headrace tunnel without permanent concrete lining was possible and would have been equally stable, at considerable fnancial savings.Key words: Equivalent tunnel section; Squeezing; Tunnel lining; Stability analysis; Leakage control; Hydropower; NepalDOI: 10.3126/hn.v6i0.4188Hydro Nepal Vol 6, January 2010Page : 18-26Uploaded Date: 23 January, 2011
Climate Change: Uncertainty for Hydropower Development in Nepal
Authors: Pathak Mahesh
Published: January 2011

There is a worldwide consensus that climate change is a real, rapidly advancing and widespread threat facing this century. This is a crucial issue in Himalayan and special in Nepal because of its possible impact on water resource, biodiversity, and consequence on economic growth of the region. The increase trend of glacial retreat and variability on temperature and participation has the direct impact on the water resource and hydropower development. Mountain regions are particularly vulnerable, both because warming trends are higher and the impacts are magnifed by the extreme changes in altitude over small distances. It indicates the great variability of hydro-climatic variability in major rivers and their tributaries. Decrease runoff will have direct impact on the hydropower development, but there is uncertainty about the role of spatial variability of changing climatic scenarios and their possible impact for hydropower development in large and middle rivers. This paper presents the scenarios of climate change in Nepal in terms of hydro-climatic variability. The frst part describes hydro-climatic variability and its uncertainty for hydropower development, and the second part deals with the mitigation of uncertainties. Key words: Climate change; Deglaciation; GLOF; Water resource; Hydrological cycle; Hydropower; Himalayas; NepalDOI: 10.3126/hn.v6i0.4190  Hydro Nepal Vol 6, January 2010 Page : 31-34 Uploaded Date:  24 January, 2011
Control Global Warming by Reducing Atmospheric CO2 to Carbon and Producing Energy
Authors: Vineel R. , Dixit Savita
Published: January 2011

A multipurpose plant setup is discussed using the concept of House Process and various other techniques to achieve objectives like reducing atmospheric CO2 to carbon and thus reduce global warming, production of hydrogen gas, to produce electricity, to provide energy feedback for improved effciency. These objectives are obtained by a six stage process. In the 1st stage atmospheric CO2 is absorbed using an improvised version of House Process. In the 2nd stage, CO2 is pro-duced by heating NaHCO3, a by-product of House Process. In the 3rd stage, reaction of the produced CO2 with Mg occurs, to get Magnesium Oxide and Carbon. The 4th stage consists of recovery of Mg from its oxide by using a modifed House Process and consequent electrolysis of MgCl2.The 5th stage, energy produced by the exothermic reactions is used to produce steam and produce electrical energy by rotating a turbine. Finally, hydrogen gas is produced by the reaction of steam and magnesium. Thus the various objectives are achieved.Key words: House Process; Modifed house process; Fuel cell; Multipurpose plant; Electric energy production; Hydrogen production; Capturing atmospheric CO2DOI: 10.3126/hn.v6i0.4192Hydro Nepal Vol 6, January 2010Page : 38-41Uploaded Date: 24 January, 2011
Effects of Methanol on the Treatability of Black Liquor using UASB Reactor
Authors: Ali Arshad , Hashmi Hasim Nisar , Q. Intikhab A.
Published: January 2011

This study was conducted on a laboratory scale UASB (upfow anaerobic sludge blanket) reactor, treating an actual pulping effluent at an organic loading rate and hydraulic retention time of 2.1 kg-COD/m3d and 44 hours, respectively. To investigate the impacts of methanol, it was subjected to the reactor with the feeding solution (substrate) in concentration ranging from 100 mgTOC/l to 700mgTOC/l. It was observed that the overall TOC and COD removal efficiency of the reactor was improved gradually from 36% and 34% to 57% and 55%, respectively, by increasing the concentration of methanol up to 600 mgTOC/l, but very little effects of methanol on the removal efficiency of lignin were observed. The lignin removal efficiency of the reactor slightly changed from 25% to 31%. The gas conversion rate was found to be improved slightly from 0.31[L-CH4/g-CODrem.day] to 0.34 [L-CH4/g-CODrem.day], with an average methane composition of 61%. Hence, addition of methanol to the reactor can improve the black liquor degradation up to certain extent.Key words: Black liquor; Methanol; UASB; Lignin; TOCDOI: 10.3126/hn.v6i0.4193Hydro Nepal Vol. 6, January 2010Page: 42-46Uploaded Date: 24 January, 2011
Calibration and Validation of SWAT Model for Low Lying Watersheds: A Case Study on the Kliene Nete Watershed, Belgium
Authors: Shrestha Narayan K. , Shakti P C , Gurung Pabitra
Published: January 2011

Use of easily accessible; public domain modeling software called Soil and Water Assessment Tool (SWAT) and its testing in watersheds has become essential to check developers' claims of its applicability. The SWAT model performance on Kliene Nete Watershed (Belgium) is examined. Given the watershed’s characteristic of a low lying; shallow ground water table, the test becomes an interesting task to perform. This paper presents calibration and validation of the watershed covering area of 581km2 . Flow separation is carried on using Water Engineering Time Series Processing tool (WETSPRO) and shows that around 60% of the total fow is contributed by base fow. Altogether seven SWAT model parameters have been calibrated with heuristic approach for the time frame of 1994-1998. Validation of these calibrated parameters in another independent time frame (1999-2002) is carried out. The parameter CH_k2 (Channel Effective Hydraulic Conductivity) is found to be the most sensitive. Nash Sutcliff Efficiency (NSE) values for the calibration and validation periods are found to be 74 and 67 percent-age, respectively. These ‘goodness-of-ft’ statistics, supported by graphical representations, show that the SWAT model can simulate such watershed with reasonable accuracy.Key words: SWAT; WETSPRO; Kliene Nete Watershed (Belgium); NSEDOI: 10.3126/hn.v6i0.4194Hydro Nepal Journal of Water, Energy and EnvironmentVol. 6, January 2010Page: 47-51Uploaded Date: 24 January, 2011
Revision of the West Seti Dam Design in Nepal
Authors: Thapa Anand B.
Published: January 2011

Recent research on the effects of seismic activity on concrete faced rock-filled dams (CFRD) is examined in light of the potential CFRD-type West Seti Dam under consideration in Nepal. Revision of Nepal’s West Seti Dam design is recom-mended.Key words: Concrete faced rock-filled dams (CFRD); Seismic activity; West Seti Dam; NepalDOI: 10.3126/hn.v6i0.4195Hydro Nepal Journal of Water, Energy and Environment Vol. 6, January 2010Page: 52-54Uploaded Date: 24 January, 2011
Modernization of Farmer's Managed Irrigation Systems in Nepal
Authors: Singh Achyut Man
Published: January 2011

The irrigation infrastructures in Farmer’s Managed Irrigation Systems (FMIS) of Nepal were mostly built from the local materials of mud, stone, and forest products with rudimentary traditional methods, practiced over many centuries. These systems are operated and maintained solely by the community farmers or an individual family. The Nepal Irrigation Sector Project (NISP), funded under the credit assistances of the World Bank, sponsored the modernization of these FMIS in the three western regions of Nepal from 1998 to 2004. The paper gives an account of the infrastructures built under the project to modernize the FMIS, and presents some facts about the impacts of the assistances to FMIS in relieving problems faced by farmers. The structures in the FMIS differ nominally according to the ecological region, due to the terrain and characteristics of the conveyance systems. In the hills, generally, lining and cross drainage structures are common; whereas, in the Terai, it is mostly the headworks structure due to lack of traditional materials as shrubs and forest products. The NISP assisted these FMIS with the participation of the users and their contribution in the civil works from seven to 15 percent. The users were involved in the design and construction of the infrastructures from the very initiation of the schemes. The project had good impacts on system performance and, thus, in agriculture production.Key words: FMIS; Irrigation; Participatory development; Water distribution; Modernization; NepalDOI: 10.3126/hn.v6i0.4196Hydro Nepal Journal of Water, Energy and EnvironmentVol. 6, January 2010Page: 55-60Uploaded Date: 24 January, 2011