bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Combining Extended‐Release Carvedilol and Lisinopril in Hypertension: Results of the COSMOS Study
Authors: Bakris George L. , Iyengar Malini , Lukas Mary Ann , Ordronneau Paul , Weber Michael A.
Published: July 2010

J Clin Hypertens (Greenwich). 2010;12:678–686. ©2010 Wiley Periodicals, Inc.

Hypertension treatment commonly requires multiple agents to achieve target blood pressure (BP). β‐Blockers and angiotensin‐converting enzyme inhibitors (ACEIs) are commonly co‐prescribed in clinical practice although few data are available that test their additivity on BP lowering. The efficacy and safety of once‐daily extended‐release carvedilol (carvedilol CR) combined with the ACEI lisinopril in a double‐blind, randomized, factorial design study were studied. Patients (N=656) with stage 1 or 2 hypertension were randomized evenly to 1 of 15 groups for 6 weeks: carvedilol CR monotherapy 20 mg, 40 mg, or 80 mg/d; lisinopril monotherapy 10 mg, 20 mg, or 40 mg/d; or 1 of 9 combinations of carvedilol CR plus lisinopril initiated simultaneously. Primary efficacy measures (assessed by ambulatory BP monitoring [ABPM]) were change from baseline in 24‐hour mean diastolic BP (DBP) and in trough (20–24 hours) DBP. Continuous efficacy variables were assessed using analysis of covariance. Whether any combination dose was superior to its monotherapy components was assessed using the Hung AVE procedure. Despite the presence of additional BP lowering observed with most of the combinations compared with their monotherapy components, the Hung AVE test was not significant for either primary efficacy measures. Post hoc analyses of the high‐dose combination groups (carvedilol CR/lisinopril regimens of 80/10 mg, 80/20 mg, 80/40 mg, 20/40 mg, and 40/40 mg) showed a significant treatment difference compared with both carvedilol CR 80 mg and lisinopril 40 mg for 24‐hour mean DBP but not for trough DBP. With the exception of dizziness, individual adverse events did not increase with ascending doses or combinations. The superiority of initiating combination treatment with carvedilol CR and lisinopril compared with the monotherapy components was not demonstrated with the ABPM measurements. Nonetheless, the post hoc assessment combining all high‐dose groups did produce significant 24‐hour mean BP reduction when compared with the high‐dose monotherapy groups. The tolerability profile of initiating combination therapy was generally comparable to the initiation of treatment with monotherapy.
The oral health of homeless adolescents and young adults and determinants of oral health: preliminary findings
Authors: Chi Donald , Milgrom Peter
Published: July 2010

A survey was administered to 55 homeless adolescents and young adults aged 14 to 28 years who presented for care at a community health center in Seattle, Washington in 2005. Forty‐five valid surveys were analyzed. The aim of the study was to identify factors associated with self‐reported oral health. The most common self‐reported dental problem was sensitive teeth (52.6%), followed by discolored teeth (48.6%), toothache (38.5%), or a broken tooth (37.8%). Dental problems were associated with lower self‐reported oral health, while non‐high school graduates, mixed race youths, and methamphetamine users had significantly higher self‐reported oral health. Among homeless youths, addressing dental problems with direct dental care may improve self‐perceived oral health. The relationships between methamphetamine use and education level, on the one hand, and self‐reported oral health, on the other, are complex and may be modified by age.
Molecular identification of roots from a grassland community using size differences in fluorescently labelled PCR amplicons of three cpDNA regions
Authors: TAGGART JOHN M. , CAHILL JR JAMES F. , McNICKLE GORDON G. , HALL JOCELYN C.
Published: July 2010

Elucidating patterns of root growth is essential for a better understanding of the functioning of plant‐dominated ecosystems. To this end, reliable and inexpensive methods are required to determine species compositions of root samples containing multiple species. Previous studies use a range of PCR‐based approaches, but none have examined a species pool greater than 10 or 30 when evaluating mixed and single species samples, respectively. We present a method that evaluates size differences in fluorescently labelled PCR amplicons (fluorescent fragment length polymorphism) of the trnL intron and the trnT‐trnL and trnL‐trnF intergenic spacers. Amplification success of the trnT‐trnL spacer was limited, but variation in the trnL intron and the trnL‐trnF spacer was sufficient to distinguish over 80% of the 95 species (97% of the 77 genera) evaluated from a diverse fescue grassland community. Moreover, we identified species known to be present in mixed samples of 4, 8, 12, and 16 species on average 82% of the time. However, this approach is sensitive to detecting species known to be absent (false positives) when using our key of 95 species. Comparing unknowns to a limited species pool ameliorates this problem, comparable to a researcher using prior knowledge of what species could be found in a sample to constrain the identification of species. Comparisons to other methods and future improvements are discussed. This method is efficient, cost‐ effective and broadly applicable to many ecosystems.
Downregulation and Upregulation of Glial Connexins May Cause Synaptic Imbalances Responsible for the Pathophysiology of Bipolar Disorder
Authors: Mitterauer Bernhard J.
Published: July 2010

The model of the pathophysiology of bipolar disorder proposed is based on imbalances in tripartite synapses caused by dysregulations of connexin expression in the astrocytic syncytium. If the expression of connexins is downregulated, a compensatory upregulation of astrocytic receptors may occur and be responsible for the pathophysiology of depression. Conversely, if the expression of connexins is upregulated, the expression of the astrocytic receptors may be downregulated and be responsible for the pathophysiology of mania. In depression, a relative lack of neurotransmitters exerts a protracted synaptic information processing, whereas in mania a relative increase of neurotransmitters may accelerate synaptic information processing. In addition, the modulatory role of gliotransmitters may be affected in bipolar disorder. Since the dysregulations of connexins impair the astrocytic syncytium, these disorders could be explanatory for cognitive impairment both in depression and in mania. Finally, the testability of this model is discussed.
Development, implementation and benefits of a rheumatology‐specific electronic medical record application with automated display of outcome measures
Authors: MALAVIYA Anand N. , GOGIA Shashi B.
Published: July 2010

Objectives:  To make a rheumatology‐specific electronic medical record (EMR) application for easy clinical data entry, automated display of outcome measures in real‐time that generates well laid‐out print‐outs; and provides an easily retrievable database for clinical analysis and research.

Methods:  Highly labour‐intensive ‘MS‐WORD®’ template used earlier provided the basic framework for developing rheumatology‐EMR applications. The authors, a rheumatologist and a soft tissue surgeon with expertise in developing medical software, successfully created a rheumatology‐EMR application over a period of 2½ years using the same basic flow of work as used in the old ‘MS‐WORD®’ template.

Results:  The resulting EMR application form has a standard medical record documenting demographic data, complete diagnosis, appropriate dates, visit number, disease status, history, physical examination, investigations, follow‐up and prescription page (with automatic updates wherever applicable). Mathematical calculations required for outcome measures (DAS, DAS28, CDAI, SDAI, AS‐DAS, BASDAI, BASFI, BASMI, SLE‐DAI and others) are embedded in the software, with automated updating as the examination of the musculoskeletal system proceeds in real time. Following implementation of this EMR application, more patients are being seen, patient waiting lists have been reduced; more time is available for academic and teaching work, without compromising the quality of notes, and print‐outs for patients. Data retrieval has simplified clinical research with increased numbers of abstracts being presented and research papers being published.

Conclusion:  Healthcare workers with understanding of the basic principles of computers and softwares should interact with software engineers who are either themselves medical doctors or are familiar with the workflow and clinical evaluation processes to create an efficient speciality‐specific EMR application.
Blockage of Notch1 signaling modulates the T‐helper (Th)1/Th2 cell balance in chronic hepatitis B patients
Authors: Pei Jinxian , Tang Zhenghao , Zang Guoqing , Yu Yongsheng
Published: July 2010

Aim:  Chronic hepatitis B virus (HBV) infection is thought to involve the imbalance of T‐helper (Th)1/Th2 cells. Many procedures found Notch signaling involved the proliferation and differentiation of T lymphocytes during development and peripheral functions. The aim of this study was to discover the effect of blockage of Notch1 signaling to Th cells and the mechanisms involved in chronic hepatitis B patients.

Methods:  CD4+ T cells from hepatitis B patients and healthy volunteers were isolated, and Notch1 expression of CD4+ T cells was determined by reverse transcription polymerase chain reaction (RT–PCR). Blockage of Notch1 signaling of peripheral blood mononuclear cells (PBMC) from chronic hepatitis B patients, Th1‐ and Th2‐type cytokines were assayed by enzyme‐linked immunosorbent assay and levels of T‐bet, GATA‐3 mRNA were measured by RT–PCR.

Results:  Notch1 expression of CD4+ T cells from chronic hepatitis B patients was upregulated, on the contrary to that from acute hepatitis B patients and healthy volunteers. Blockage of Notch1 signaling can strongly inhibit the production of Th2‐type cytokines and the expression of GATA‐3; the production of Th1‐type cytokines and the expression of T‐bet, however, were enhanced.

Conclusion:  Blockage of Notch1 signaling could regulate the immune balance of Th1/Th2 in chronic hepatitis B patients, which may be mediated partly by regulating transcription factors T‐bet and GATA‐3.
Un modèle analytique d’évaluation de l’audit interne faisant appel aux fonctions de croyance, à l’usage de l’auditeur externe
Authors: DESAI VIKRAM , ROBERTS ROBIN W. , SRIVASTAVA RAJENDRA
Published: July 2010

Les auteurs ont pour but de faire progresser la recherche dans le domaine de l’évaluation de l’audit interne en élaborant un modèle d’évaluation de la fonction d’audit interne qui tient compte des relations entre les facteurs précis qu’utilisent les auditeurs externes pour évaluer la solidité de cette fonction. Le modèle repose sur trois facteurs définis par les normes d’audit et par les travaux de recherche antérieurs : la compétence, la qualité du travail et l’objectivité. Les auteurs élaborent une expression analytique du modèle à l’aide du cadre de référence des fonctions de croyance afin de dépasser les limites des études antérieures. Leurs résultats révèlent que la modélisation de la relation « et » est essentielle à l’évaluation de la solidité de la fonction d’audit interne. Au chapitre des relations, l’analyse montre que, lorsque celle qui unit ces trois facteurs est solide ou parfaite, la fonction d’audit interne demeure d’une grande solidité, même en présence d’éléments probants positifs ou négatifs à l’égard de l’un des facteurs. Ce résultat persiste dans la mesure où les niveaux de croyance au sujet des deux autres facteurs sont élevés. Les auteurs démontrent en outre comment la qualité de la gouvernance d’entreprise influe sur l’évaluation de la fonction d’audit interne et comment il est possible de recourir à l’analyse coûts‐avantages dans ce contexte pour mieux déterminer la quantité de travail d’audit externe qu’exige le respect des normes. L’analyse des auteurs révèle que l’étendue du travail d’audit devant être réalisé par l’auditeur externe dépend de la solidité de la fonction d’audit interne et de l’importance des coûts associés aux litiges et au respect de la réglementation auxquels le vérificateur externe doit faire face.
L’incidence de la vente à découvert sur les réactions du marchéà la publication des résultats
Authors: LASSER DENNIS J. , WANG XUE , ZHANG YAN
Published: July 2010

Les auteurs examinent l’incidence de la demande inhérente que supposent les positions courtes en étudiant dans quelle mesure les réactions des cours boursiers à la publication des résultats dépendent du niveau des positions courtes. Selon leurs constatations, si les nouvelles publiées sont extrêmement positives ou extrêmement négatives, la demande inhérente entraîne à la hausse le cours des actions à proximité de la date de la publication des résultats, la hausse étant plus prononcée dans le cas des nouvelles positives que des nouvelles négatives. Plus précisément, la réaction initiale du marchéà des résultats imprévus extrêmement positifs est plus importante dans le cas d’entreprises ayant des niveaux élevés de positions à découvert. En revanche, lorsque les résultats imprévus sont extrêmement négatifs, la réaction initiale du marché est moins négative dans le cas d’entreprises dont le niveau des positions à découvert est élevé. Les auteurs constatent au surplus que l’ampleur du mouvement réactif suivant la publication des résultats est plus modeste (plus marquée) dans le cas de résultats imprévus extrêmement positifs (négatifs) pour les entreprises dont les positions à découvert sont importantes.
The Effect of Short Selling on Market Reactions to Earnings Announcements
Authors: LASSER DENNIS J. , WANG XUE , ZHANG YAN
Published: July 2010

This paper examines the effect of the inherent demand implied by short interest by studying how stock price reactions to earnings announcements depend on the level of short interest. We find that, for extreme good and bad news events, the inherent demand increases stock prices around the earnings announcement date, with the effect being stronger for good news relative to bad news. Specifically, the initial market reaction to an extreme positive earnings surprise is larger for firms with high levels of short interest. On the other hand, for an extreme negative earnings surprise event, the initial market reaction is less negative for heavily shorted firms. Furthermore, we find that the post‐earnings‐announcement drift is smaller (larger) in magnitude for extreme positive (negative) earnings surprises for the heavily shorted firms.
The Economic Value of Auditing and Its Effectiveness in Public School Operations
Authors: SAITO YOSHIE , MCINTOSH CHRISTOPHER S.
Published: July 2010

We examine the impact of auditing on public school operations with two objectives: to investigate whether audits provide economic benefits to stakeholders and how complex compliance rules impact auditing effectiveness. Utilizing auditing time data and a unique opportunity presented by the Quality Basic Education Act in Georgia, we estimate the relative performance of school district operations employing a stochastic frontier estimation technique. We find that auditing produces real economic benefits for stakeholders by mitigating inefficiency in the use of school resources. We also find that stringent compliance rules reduce an audit’s effectiveness but auditors’ experience can help to overcome the problems. The lack of disclosure of auditing costs hinders the ability to conduct a cost–benefit analysis of new requirements. Our analysis supports the notion that auditing is vital to establish governance mechanisms and disclosure of auditing costs is important to adequately evaluate a new policy. Data are available from the public sources identified in the text.
The World Has Changed—Have Analytical Procedure Practices?
Authors: TROMPETER GREG , WRIGHT ARNOLD
Published: July 2010

Analytical Procedures (APs) provide a means for auditors to evaluate the “reasonableness” of financial disclosures by comparing a client’s reported performance to expectations gained through knowledge of the client based on past experience and developments within the company and its industry. Thus, APs are fundamentally different than other audit tests in taking a broader perspective of an entity’s performance vis‐à‐vis its environment. As such, APs have been found to be a cost‐effective means to detect misstatements, and many have argued that a number of prior financial frauds would have been detected had auditors employed effective APs. With several dramatic and far‐reaching developments over the past decade, the current study examines whether and how APs have changed during this period. In particular, we focus on the impact of significant “enablers” and “drivers” of change such as technological advancements and the enactment of the Sarbanes‐Oxley Act. We also compare our findings to an influential study of the practices of APs by Hirst and Koonce (1996) that was conducted over 10 years ago. We interview 36 auditors (11 seniors, 13 managers, and 12 partners) from all of the Big 4 firms using a structured questionnaire. The data reveal some similarities in findings when compared to prior research (e.g., auditors continue to use fairly simple analytical procedures). However, there are a number of significant differences reflecting changes in AP practices. For instance, as a result of technology auditors now rely more extensively on industry and analyst data than previously. Further, auditors report that they develop more precise quantitative expectations and use more non‐financial information. They also appear to rely more on lower level audit staff to perform APs, conduct greater inquiry of non‐accounting personnel, and are willing to reduce substantive testing to a greater extent as a result of APs conducted in the planning phase. Finally, the Sarbanes‐Oxley Act has had an impact in greater consideration and knowledge of internal controls, which is seen as the most important factor driving the use and reliance on APs.
Uterine torsion diagnosed in a mare at 515 days' gestation
Authors: López C. , Carmona J. U.
Published: July 2010

A pregnant mare with a history of prolonged gestation (∼515 days) and suspected diagnosis of fetal mummification was examined. Rectal palpation revealed that the left broad ligament of the uterus was dorsal and medial to the right uterine ligament and it was not possible to observe the cervix during vaginal examination. Transabdominal ultrasound revealed fluid in the uterus, fetal membranes and the uterine walls defined and thickened. Free fluid was not seen in the peritoneal cavity. Laboratory tests (blood cell count and clinical chemistry) were normal. Based on clinical history, physical examination and ultrasound findings, a chronic uterine torsion with fetal death was diagnosed and the mare was subjected to exploratory celiotomy. The uterus was strongly adhered to the peritoneum of the ventral abdominal wall and there were multiple adhesions to the colon. Hysterotomy was performed to remove the fetus and to permit repositioning of the uterus. When the fetus was removed, a large devitalised grey tissue area of the right ventral uterine horn was observed. Multiple adhesions prevented a rescue hysterectomy and euthanasia of the patient was performed. During the necropsy, a 180° cranial cervix clockwise uterine torsion was observed. This rare case of uterine torsion appears to be the most chronic case reported in the equine literature.
Treatment of appendicular osteosarcoma in a horse
Authors: Gutierrez‐Nibeyro S. D. , Sullins K. E. , Powers B. E.
Published: July 2010

A 14‐year‐old Arabian gelding was examined for a mass on the lateral aspect of the left tarsus and proximal lateral metatarsus. Radiography revealed a predominately osteolytic lesion involving the fourth tarsal bone and the proximal third and fourth metatarsal bone. Results of histopathological examination of the mass prior to surgery were consistent with an undifferentiated sarcoma. The mass was surgically excised and the remaining bone defect treated with absorbable beads containing cisplatin. Histology and immunohistochemistry of the mass removed at surgery revealed a telangiectatic osteosarcoma. The surgical site healed uneventfully and the horse was performing as a low level jumper 8.5 years after surgery.
Hydrocarbon Impacts on Diesel HCCI Engine Cycles
Authors: Zheng Ming , Asad Usman , Han Xiaoye , Wang Meiping , Reader Graham T.
Published: July 2010

Thermal efficiency and NOx emission comparisons are made between the homogeneous charge compression ignition (HCCI) and the conventional diesel cycles on a number of common-rail diesel engine platforms of high compression ratios with conventional diesel fuel and dimethyl ether as a surrogate fuel. The empirical studies have been conducted under independently controlled exhaust gas recirculation (EGR), intake boost, and exhaust backpressure. The energy relevance of the combustible substances such as carbon monoxide and hydrocarbon species in the engine exhaust has been evaluated quantitatively. However, the impact of the hydrocarbons produced during the HCCI cycles on the attainment of ultra low levels of NOx is less understood and it is unclear if the hydrocarbon species are a precursor to the ultra low NOx and also contribute in part to the NOx reduction. Therefore, the chemical impact of the hydrocarbon species on the NOx emission under low temperature combustion cycles has been examined with crank-angle resolved in-cylinder sampling techniques and fast-response emission analyzers. This paper intends to identify the major impacts of the hydrocarbons on the fuel efficiency and emissions of diesel HCCI cycles.
Investigation and Modification of KIA Pride Engine Intake Valve Timing
Authors: Sadeghkazemi Mehdi , Torabi Amir , Neyestani Javad
Published: July 2010

In this paper, the situation of KIA pride engine intake valve timing has been investigated. To achieve this goal, the geometry of combustion chamber with intake and exhaust valves and runners has been modeled in CATIA. The developed geometry has been transferred to ICEM_CFD package for mesh generation process. In this package, the appropriate grid has been generated for KIVA-3V code, considering all the limitation (1, 2). The simulation process has been accomplished for different engine speeds and validated using available experimental data. Considering the amount of air in combustion chamber right after inlet valve closes, the best valve timing to have maximum volumetric efficiency has been determined. By applying this modification to intake valve timing, the volumetric efficiency increased about 15 percent at low engine speeds. The results of this research can be used for VVT design for the engine.
Intake-Air Oxygen-Enrichment of Diesel Engines as a Power Enhancement Method and Implications on Pollutant Emissions
Authors: Zannis Theodoros C. , Hountalas Dimitrios T. , Yfantis Elias A. , Papagiannakis Roussos G. , Levendis Yiannis A.
Published: July 2010

Increasing the in-cylinder oxygen availability of diesel engines is an effective method to improve combustion efficiency and to reduce particulate emissions. Past work on oxygen-enrichment of the intake air, revealed a large decrease of ignition delay, a remarkable decrease of soot emissions as well as reduction of CO and unburned hydrocarbon (HC) emissions while, brake specific fuel consumption (bsfc) remained unaffected or even improved. Moreover, experiments conducted in the past by authors revealed that oxygen-enrichment of the intake air (from 21% to 25% oxygen mole fraction) under high fuelling rates resulted to an increase of brake power output by 10%. However, a considerable increase of NOx emissions was recorded. This manuscript, presents the results of a theoretical investigation that examines the effect of oxygen enrichment of intake air, up to 30%v/v, on the local combustion characteristics, soot and NO concentrations under the following two in-cylinder mixing conditions: (1) lean in-cylinder average fuel/oxygen equivalence ratio (constant fuelling rate) and (2) constant in-cylinder average fuel/oxygen equivalence ratio (increased fuelling rate). A phenomenological engine simulation model is used to shed light into the influence of the oxygen content of combustion air on the distribution of combustion parameters, soot and nitric oxide inside the fuel jet, in all cases considered. Simulations were made for a naturally aspirated single-cylinder DI diesel engine “Lister LV1” at 2500 rpm and at various engine loads. The outcome of this theoretical investigation was contrasted with published experimental findings.
Application of an Experimental EGR System to a Medium Speed EMD Marine Engine
Authors: Hedrick John , Fritz Steven G. , Stewart Ted
Published: July 2010

This paper focuses on quantifying emission reductions associated with various on-engine technologies applied to Electro-Motive Diesel two-cycle diesel engines, which are very popular in marine and locomotive applications in North America. This paper investigates the benefits of using exhaust gas recirculation (EGR), separate circuit aftercooler, and retarded injection timing on a EMD 12-645E7 marine engine. The EGR system alone provided up to a 32.9% reduction in brake specific Nitrogen Oxides (NOx) emissions while demonstrating less than one percent increase in cycle brake specific fuel consumption (BSFC). The brake specific particulate matter emissions increased somewhat, but at a modest rate based on the amount of NOx emission reduction. When the enhanced aftercooler system was combined with the addition of EGR, there was a 31.9% reduction in NOx and essentially no change to the BSFC when compared to the baseline test. The minimum manifold air temperature (MAT) was limited due to the size of the standard EMD aftercooler heat exchanger that is fitted on the engine. No efforts to modify the turbocharger to improve the turbo match to take advantage of the lower manifold air temperatures and the corresponding lower exhaust energy. Once 4° static injection timing retard was introduced, along with the EGR and the minimum MAT, a maximum NOx reduction of 49% was realized with only a 1.1% increase over the baseline BSFC.
UHC and CO Emissions Sources From a Light-Duty Diesel Engine Undergoing Late-Injection Low-Temperature Combustion
Authors: Ekoto Isaac W. , Colban William F. , Miles Paul C. , Aronsson Ulf , Andersson O¨ivind , Park Sung Wook , Foster David E. , Reitz Rolf D.
Published: July 2010

Low load carbon monoxide (CO) and unburned hydrocarbon (UHC) emissions sources are examined in an optically accessible, light-duty diesel engine employing a late-injection, low-temperature combustion strategy. The study focus is to identify the cause of the rapid degradation in emissions and efficiency as injection timing is retarded. The in-cylinder progression of mixing and combustion processes is examined through ultraviolet planar laser-induced fluorescence (UV PLIF) imaging of hydrocarbon spatial distributions. Spectrally-resolved, deep-UV LIF measurements are also used to construct late-cycle spatial distributions of CO, C2, and polycyclic aromatic hydrocarbons within the clearance volume. Engine-out emissions measurements and numerical results from both detailed chemistry homogeneous reactor and multidimensional simulations complement the measurements. The measured spatial distributions show that while most fuel accumulates on the bowl-pip during high-temperature heat-release, much of it is transported into the squish-volume by the reverse squish flow. Homogeneous reactor simulations further show that expansion cooling quenches reactions, preventing the transition to high-temperature heat-release for mixtures with an equivalence ratio below 0.6. Lean squish-volume mixtures, coupled with wall heat losses, severely inhibit squish volume fuel oxidation. Further retarding injection timing exacerbates quenching, resulting in a two-fold increase in UHC emissions and a 33% increase in CO, primarily from the squish-volume.
Modeling the Performance of an IDI Diesel Engine With Intake Admission of Hydrogen in Low Concentrations
Authors: Xiao F. , Karim G. A.
Published: July 2010

A 3D-CFD model based on KIVA 3 is described. It is developed with a “reduced” detailed chemical kinetics of 294 elementary reaction steps with 79 chemical species for diesel fuel combustion which includes 20 steps for the oxidation of hydrogen. The model was employed to examine the combustion characteristics of diesel/dual fuel operation in an IDI diesel engine with a swirl chamber while injecting relatively large diesel fuel quantities with low concentrations of hydrogen intake admission. The predicted results of such an operation are compared with those of the corresponding diesel engine operation with air over a wide range of diesel and hydrogen operating equivalence ratios. Relatively good agreement was demonstrated between predicted values and corresponding experimental results. Some apparent limitations of the model were identified and potential remedial measures were outlined.
A Comparison Between Two-Position Variable Compression Ratio and Continuously Variable Compression Ratio Engines Using Numerical Simulation
Authors: Malpress Ray , Buttsworth David R.
Published: July 2010

Two types of variable compression ratio engine are considered: i) a continuously variable compression ratio (VCR) device that optimises engine efficiency at all loads, and ii) a VCR device that allows the engine to operate at one of two discrete compression ratios. The simulated engine configuration uses late intake valve closing (LIVC). A maximum geometric compression ratio (GCR) of 17:1 is adopted in the simulations resulting in a constant effective compression ratio of 10.2:1 in all configurations. Reduction from full load is achieved in the simulation with LIVC until the maximum GCR is reached after which lower loads are achieved through throttling. In the two-position VCR engine simulation, the full load range is achieved through throttling in combination with LIVC. At part load, in combination with LIVC, the VCR devices increase the geometric compression ratio to return the effective compression ratio to that for full load in each case. Fuel consumption for the New European Driving Cycle (NEDC) is assessed via numerical simulation for a representative vehicle. The simulations indicate that the increase in net fuel consumption over a driving cycle is effectively no different for the two-position VCR engine relative to a continuously variable CR and this justifies further research into two-position VCR technology. Net fuel consumption can also be improved by the use of a limited acceleration that maintains the engine in the reduced compression stroke configuration. An acceleration rate with a driver feedback mechanism is proposed which, in combination with a two-position VCR engine, shows potential for significant reduction in fuel consumption of greater than 15% relative to the full compression, fixed CR configuration for the NEDC.
Experimental Investigations on the Effect of Long Term Biodiesel Usage on Thermal Decomposition of CI Engine Crankcase Oil
Authors: Bhale Purnanand V. , Deshpande Nishikant V. , Deshpande Piyush N.
Published: July 2010

The gradual depletion of world petroleum reserves, increases in prices of petroleum based fuels and environmental pollution due to exhaust emissions have encouraged studies to search for alternative fuels. Biodiesel is an alternative diesel fuel consisting of alkyl monoesters of fatty acids derived from vegetable oils. It has been the focus of considerable amount of recent research because it is renewable and reduces the emission of some pollutants. The desirability of developing biodiesel from different tree borne oil seeds and decreasing the dependency on petroleum based fuels has been discussed by many over the last few decades. However some of the important issues like compatibility of biodiesel with the crankcase lubricating oil, thermal stability of lubricating oil with biodiesel usage, changes in physical and chemical properties of lubricating oil with biodiesel etc. have not been sufficiently investigated. This needs to be addressed in order to ensure the long term acceptability of biodiesel in an existing family of diesel engines. In the present work these issues have been addressed. For this purpose engine endurance tests were conducted on CI engines. Two new single cylinder four stroke CI engines were operated for 512 hours each for diesel and 100% biodiesel fuel. The endurance tests were conducted as per BIS 10000 part IX norms. Biodiesel from Jatropha oil was prepared in-house using transesterification process. The sample of lubricating oil was collected through a one way valve connected to the crankcase sump after every 128 hours intervals. Thermograviometric analysis (TGA) was used to evaluate the thermal stability of lubricating oil samples obtained from both the engines. The thermal decomposition of lubricating oil samples were measured as a function of various reaction parameters such as temperature, time and heating rates. This TGA test involves a weight change as the oil was heated. The weight loss data of the sample was logged using the in situ computer. Early decomposition of biodiesel fueled engine lubricating oil was observed as compared to diesel fueled engine lubricating oil. The changes in viscosity of lubricating oil were also monitored during the endurance test and discussed in detail. A higher level of crank case dilution was observed in case of biodiesel as compared to diesel.
Experimental Investigations of Porosity, Diameter and Length of Ceramic Diesel Particulate Filter (DPF)
Authors: Deshpande Nishikant V. , Kongre Suhas C. , Deshpande Piyush N. , Singh Rajan
Published: July 2010

Diesel engine is the most efficient power plant among all known types of internal combustion engines. The Diesel engine is a major candidate to become the power plant of the future. Environmental benefits of Diesel such as low green house gas emissions are balanced by growing concern with emission of Nitrogen oxide (NOx) and Diesel Particulates (PM). The concern over Diesel particulate has increased in recent year because of health concerns. The objective of this research work is to identify the possibility of development of foam type diesel particulate filters (DPF) with indigenous ceramic materials which are easily available and cheaper. While developing the foam type diesel particulate filters, the main aim is to develop required porous structure for DPF with substantial strength, with low back pressure to minimize loss of engine performance, and with high trapping efficiency to reduce the particulate matter. The objective of this research work is also to investigate the effect of new developed filters without any regeneration arrangement and without any control or monitoring system, on the reduction of dry particulate matter and on the performance of diesel engine in terms of parameters like smoke density, back pressure, brake thermal efficiency and brake power. Use of DPF reduces smoke density with back pressure in acceptable limit. Parameters like brake power loss, increase in brake specific fuel consumption and decrease in brake thermal efficiency are caused by increased engine back pressure created by installation of the DPF system. This power penalty is within permissible limits, but can be further reduced by incorporating a regeneration system.
Combustion Development and Exhaust Emissions of a Dual-Fuel DI Diesel Engine With Variable In-Cylinder Bulk Flow and Methane Supply Strategies
Authors: Carlucci Antonio P. , Laforgia Domenico , Saracino Roberto
Published: July 2010

An extensive experimental campaign was performed on a diesel common rail research engine, converted to operate in dual-fuel mode, in order to investigate the effects of in-cylinder bulk flow and methane supply strategies on combustion and emissions. Three different bulk flow structures of the charge were induced inside the cylinder by activating/deactivating the two different inlet valves of the engine (i.e. swirl and tumble). Methane was injected into the inlet manifold at different pressure levels, varying the injector position. In order to obtain a stratified-like air-methane mixture, the injector was mounted very close to the inlet valve, while, to obtain a homogeneous-like one, methane was injected more upstream. By combining the two different positions of the injector and the three bulk flow structures, seven different engine inlet setups were tested, at different values of engine speed and load. Moreover, the effects of various pilot injection parameters, such as injection advance, diesel fuel quantity and rail pressure, were investigated. From in-cylinder pressure and heat release curves some output parameters, representative for combustion development, were calculated while emissions concentrations in the exhaust gases were measured. Main and interaction effects on dual-fuel combustion and exhaust emissions of all the operating parameters described above were studied by means of DOE technique, in order to perform a synthetic and complete analysis of the combustion behavior. The obtained results showed that the charge bulk motion produced by the swirl inlet valve is able to induce a more rapid and complete combustion of the air-methane mixture inside the cylinder. At low engine loads, this results in a contemporary reduction of unburned hydrocarbons and nitrogen oxides content at the exhaust, especially injecting the methane at high pressure and in stratified-like configuration. Furthermore, the analysis of the exhaust pollutant concentrations revealed that complex interactions effects between some unexpected operating parameters exist, such as between pilot injection pressure and engine inlet configuration. Generally, it was demonstrated that the stratified-like configuration of methane injection is an effective method to reduce unburned hydrocarbon emissions at the engine exhaust.
The Effect of Oil Evaporation From the Cylinder Wall on Oil Consumption of a Gasoline Engine
Authors: Harigaya Yasuo , Yamasuga Kazuyoshi , Suzuki Michiyoshi , Iijima Naoki , Takiguchi Masaaki , Shimada Akiko
Published: July 2010

A new oil evaporation model was developed, combining a thermo-hydrodynamic lubrication model with a conventional oil evaporation model considering the energy balance on the oil film surface. This model assumed that there was evaporation loss of the oil film on the cylinder wall. In addition, the effects of the oil film thickness and types of lubricant in the evaporated oil from the liner were examined. Moreover, the calculated evaporative oil was compared with the measured oil consumption of a gasoline engine. The relationship between the evaporated oil, the lubricant viscosity, and the oil film thickness were clarified using this model. The results showed that the calculated oil evaporation from the cylinder wall closely corresponded to the measured oil consumption under low load conditions.
Control Development for Smoke Reduction Through Inlet Manifold Air Injection During Transient Loading of Marine Diesel Engines
Authors: Papalambrou G. , Kyrtatos N. P.
Published: July 2010

This paper addresses the reduction of smoke emissions and improvement of load acceptance in a turbocharged marine diesel engine, during transient operation involving rapid load increases. Model Predictive Control (MPC) provided the optimal quantity of injected air in the engine while minimizing smoke density (opacity), with constraint not to exceed a limit in intake manifold pressure, in order to avoid surge in the compressor. System identification methods were used to determine control models at various operating points of the engine. Transient response experiments were performed on a full-scale marine diesel test engine on a transient test bed, using real-time MPC configuration. Results comparing the opacity under air injection model predictive control with the standard engine operation without air injection, during the same transient, show reduction in opacity level while avoiding surge.
Calibration of a Knock Prediction Model for the Combustion of Gasoline-Natural Gas Mixtures
Authors: Pipitone Emiliano , Beccari Stefano
Published: July 2010

Gaseous fuels, such as Liquefied Petroleum Gas (LPG) and Natural Gas (NG), thank to their good mixing capabilities, allow complete and cleaner combustion than normal gasoline, resulting in lower pollutant emissions and particulate matter. Moreover natural gas, which is mainly constituted by methane, whose molecule has the highest hydrogen/carbon ratio, leads also to lower ozone depleting emissions. The authors in a previous work (1) experienced the simultaneous combustion of gasoline and natural gas in a bi-fuel S.I. engine, exploiting so the high knock resistance of methane to run the engine with an ‘overall stoichiometric’ mixture (thus lowering fuel consumption and emissions) and better spark advance (which increases engine efficiency) even at full load: the results showed high improvements in engine efficiency without noticeable power losses with respect to the pure gasoline operation. With the aim to provide a knock prevision submodel to be used in engine thermodynamic simulations for a knock-safe performance optimization of engines fuelled by NG/gasoline mixtures, the authors recorded the in-cylinder pressure cycles under light knocking condition for different engine speed, loads and natural gas fraction (i.e. the ratio between the injected natural gas mass and the total fuel mass), and used the gas pressure data to calibrate a classical knock-prediction model: as shown, the results obtained allow to predict the onset of knocking in a S.I. engine fuelled with a gasoline-natural gas mixture with any proportion between the two fuels, with a maximum error of 5 CAD.
Investigation of Hydrogen Emissions in Partially Premixed Diesel Combustion
Authors: Northrop William F. , Vanderpool Lucas M. , Madathil Praveen V. , Assanis Dennis N. , Bohac Stanislav V.
Published: July 2010

Partially premixed combustion strategies offer many advantages for compression ignition engines. One such advantage for engines operating on diesel fuels is the simultaneous reduction of soot and NOX achievable over a wide range of equivalence ratios. Though often not measured in engine experiments, gaseous H2 is a byproduct of incomplete combustion and can be useful for the regeneration of aftertreatment devices. Correlations for the exhaust concentration of H2, mostly derived from experiments with homogeneous spark ignition engines, indicate that it is emitted either in proportion to CO directly or as a function of a pseudo-water gas shift equilibrium constant. In this work, H2 is measured over a range of equivalence ratios in a multi-cylinder diesel engine operating in a partially premixed low temperature combustion (LTC) mode using both low sulfur diesel fuel and soy-based biodiesel. Biodiesel was found to have the same bulk gas emissions of major species including H2 over the range of equivalence ratio in LTC for a constant load and combustion phasing. It also was found that the experimental H2 concentration was near the value predicted by the equilibrium constant for equivalence ratios greater that 0.9 but was increasingly lower for leaner points.
Predicted Qualitative Effects of Alternate Liquid Fuels on Heavy-Duty Compression-Ignition Engines
Authors: Chen Gong
Published: July 2010

It is always desirable for a heavy-duty compression-ignition engine, such as a diesel engine, to possess a capability of using alternate liquid fuels without significant hardware modification to the engine baseline. Because fuel properties vary between various types of liquid fuels, it is important to understand the impact and effects of the fuel properties on engine operating and output parameters. This paper intends and attempts to achieve that understanding and to predict the qualitative effects by studying analytically and qualitatively how a heavy-duty compression-ignition engine would respond to the variation of fuel properties. The fuel properties considered in this paper mainly include the fuel density, compressibility, heating value, viscosity, cetane number, and distillation temperature range. The qualitative direct and end effects of the fuel properties on engine bulk fuel injection, in-cylinder combustion, and outputs are analyzed and predicted. Understanding these effects can be useful in analyzing and designing a compression-ignition engine for using alternate liquid fuels.
Two-Step Concept for Low-Pressure Direct Hydrogen Injection
Authors: Zanforlin S. , Poerio T. , Frigo S. , Gentili R.
Published: July 2010

In this paper, a low-pressure hydrogen direct-injection solution is presented that entails low storage residual pressure (∼12 bar). The injection is realised in two steps. First, hydrogen is simply metered by an electro-injector (a conventional one for Compressed Natural Gas - CNG application) that feeds a small intermediate chamber. Next, hydrogen enters the cylinder by means of a mechanically-actuated valve which allows higher flow than any electro-injector. Injection must end early enough to allow good charge homogeneity and, in any case, before in-cylinder pressure rise constraints hydrogen admission. Backfire is avoided by starting injection at intake valve closing. A prototype has been realised modifying a single-cylinder 650 cc production engine with three intake valves. The central one has been modified and properly timed to in-cylinder inject hydrogen from the intermediate chamber. Hydrogen injection through different-shape poppet valves in a quiescent, constant volume has been simulated in order to investigate the effects of valve and seat-valve geometries in controlling fuel-air mixing in the cylinder. Additional predictions for the actual engine configuration indicate that an acceptable fuel distribution can be obtained in the combustion chamber at the spark timing, with equivalence ratios in the ignition region that are inside the flammability range of the mixture for all the operating conditions (loads and speeds) that have been considered.
Numerical and Experimental Investigation on Combustion and Emission Characteristics of DME Fuel in a Compression Ignition Engine
Authors: Ryu Bong Woo , Youn In Mo , Roh Hyun Gu , Park Sung Wook , Lee Chang Sik
Published: July 2010

The characteristics of spray behavior and combustion of DME (dimethyl ether) were investigated using experimental and numerical approaches. For experiments, injection rates and macroscopic spray characteristics were investigated at various injection parameters by using an injection rate system and a spray visualization system. The combustion and emission characteristics were also obtained from the modified engine for DME fuel and emission measurement equipment. For numerical approaches, the combustion characteristics of DME fueled engine were predicted by a 3D-CFD code, the KIVA code coupled with the CHEMKIN (KIVA-CHEMKN) and spray behavior and evaporation were calculated by considering the thermo-chemical properties of DME. In order to calculate the fuel oxidation and emission formation such as NOx, a detailed chemical kinetic mechanism which was composed of 83 species and 360 reaction paths was considered. To simulate soot emission, two-step phenomenological model was applied. Both experimental and numerical results indicate that injection delay, ignition delay, and combustion duration of DME are shorter than that of diesel because of good evaporation and mixing characteristics. The pressure history predicted by the KIVA code agrees well with the measurements from the test engine. The amount of NOx emission was predicted by the reduced NOx mechanism shows good agreements to the experiments.