High Pairs Research Articles

Type Synthesis of Variable Compression Ratio Engine Mechanisms

Type synthesis of two-degrees-of-freedom (DOF) planar mechanisms has been carried out using graph theory to determine the possible kinematic structures of variable compression ratio (VCR) engine mechanisms with two to three independent loops, and has resulted in the structures of 87 mechanisms satisfying search specification. By applying evaluation criteria to the enumerated mechanisms, the kinematic structures of three mechanisms are selected as suitable VCR engine mechanisms and verified by analysis results. In this research, VCR engine mechanisms with revolute joints and only one prismatic joint are enumerated, and the basic method to determine the VCR engine mechanisms with higher pairs is discussed. The procedure used in this research can be utilized to determine the kinematic structures of desired mechanisms and the results can be used as an atlas of two-DOF adjustable slider-crank mechanisms.

A Note on Equivalent Linkages of Direct-Contact Mechanisms

In this paper, the inequivalence of the direct-contact mechanisms and their equivalent four-bar linkages in jerk analysis is discussed. Kinematic analyses for three classical types of direct-contact mechanisms consisting of: (a) higher pairs with permanently invariant curvature centers, (b) higher pairs with suddenly changed curvature, and (c) higher pairs with continuously varying curvature are performed, respectively, through their representative case studies. The analyzed results show that the equivalent four-bar linkage cannot give a correct value of jerk for most situations in the three case studies. Subsequently, the concept of “equivalent six-bar linkage” for direct-contact mechanisms is proposed in order to discuss the infeasibility of the equivalent four-bar linkage for jerk analysis. It is found that the suddenly changed or continuously varying curvature of the higher pairs is not considered in sudden or continuous link-length variations of the equivalent four-bar linkage, which further leads to inconsistency between the angular accelerations of the coupler and the contact normal, and finally results in the infeasibility of the equivalent four-bar linkage for jerk analysis of most direct-contact mechanisms. It is also found that the concept of equivalent six-bar linkage could be applied to evaluate more higher-order time derivatives for most direct-contact mechanisms. The presented case studies and discussion can give demonstrations for understanding the inequivalence of the direct-contact mechanisms and their equivalent four-bar linkages in the aspect of jerk analysis.

Теоретические положения синтеза сопряженных зацеплений

The conditions for the synthesis of conjugate couplings are systematized on the basis of a single geometric-kinematic criterion, which consists in the equality of the velocity projections of the points of the active surfaces that make up the higher pair on the common contact-normal to these surfaces. The technology of formation of a family of conjugate couplings by a two — parameter envelope by an involute helicoid or its particular varieties-a circular cone or plane-is theoretically justified

Proposed parameter for the characterization of friction in cylindrical gears teeth contact

Gear mechanisms are widely used in technical applications, mainly for transmitting rotational motion between two axes with constant transmission ratio via a higher pair. Significant friction energy loss in the pair between teeth highlights the importance of estimating the mechanical work lost by friction within this contact. In a previous study, the coefficient of rolling friction between a cylindrical body and a flat face body was found based on the decrease of oscillations amplitude of a cycloidal pendulum. The basic idea of the present paper follows the observation that in the case of a gear mechanism, the relative motion between the wheels can be taken as relative motion of their axodes. In this regard, a pendulum obtained from a mobile cylindrical gear with attached rod and a fixed corresponding rack is considered. The law of motion of the cycloidal pendulum is applied for the proposed pendulum and an “equivalent rolling friction coefficient” which characterises the friction between the teeth of the pinion and the rack is found. The differential equation modelling the motion of the pinion-rack pendulum is difficult to obtain, which is explained by the analysis of the involute gear field of a general cylindrical gear mechanism.

OPTIMIZATION OF PARAMETERS OF CAM MECHANISMS

The problem of task setting for cam mechanisms parameters optimization is discussed in the light of a system approach. The modern state of cam gear optimization synthesis is analyzed. Various criteria such as cam profile wear, maximum pressure angle, mechanism dimensions, etc. are set as objective functions at gear parameters optimization. Constraints can be imposed on the maximum value of pressure angle, the minimum value of curvature radii of cam profile convex and concave sections, the maximum value of contact stresses etc. The presence of a large number of criteria makes it difficult to solve the problem within the framework of a system approach to design. It is proved that minimization of the objective function (the maximum contact stresses in the highest pair), which characterizes the cam profile wear, leads to a criterion decrease, which characterizes the maximum normal wear. It is also proved that with first or second mentioned criteria, it is not necessary to impose constraints on the values of the maximum pressure angle and the minimum curvature radius of the cam profile convex portion.

Molecular characterization of Chickpea chlorotic dwarf virus strain D in Chickpea (Cicer arietinum) from District Dera Ismail Khan Khyber Pakhtunkhwa, Pakistan

Chickpea chlorotic dwarf virus (CpCDV), a member of genus Mastrevirus (family Geminiviridae) is an important viral pathogen of chickpea and other legume crops in Middle East, North Africa, India and Pakistan. Among sixteen known strains of CpCDV three are known to infect legume crops in Punjab province of Pakistan. In this study diversity of CpCDV was explored in Khyber Pakhtunkhwa (KP) province of Pakistan. In year 2016, during a survey in the chickpea growing areas of district Dera Ismail Khan, CpCDV infected plants were identified. Leaf samples were collected, and a diagnostic PCR confirmed mastreivrus infection in 4 out of 100 samples. From these samples full-length genome of CpCDV was amplified using specific back-to-back primers. Virus molecules were sequenced to their entirety and sequence analysis of a molecule KRF4 (GenBank accession # KY952837) showed the highest pair wise sequence identity of 97% with a CpCDV molecule (KM229787) isolated from chickpea plant. An SDT analysis revealed it to be the D strain of CpCDV and a recombination detection program (RDP) showed it to be a recombinant between C (KM229780) and L (KT634301) strains of CpCDV. Thus, further supporting the intra-species recombination for CpCDV and presence of the same strain in chickpea growing areas of Pakistan other than Punjab province. This is the first identification of CpCDV (genus Mastrevirus family Geminiviridae) from chickpea (Cicer arietinum) plants in District Dera Ismail Khan, KP province, Pakistan.

English

A study on the importance of Newcastle disease (ND) in village chickens was conducted among farmers, poultry traders and community leaders using a focus group discussion (FGD) on village chicken production in eight communities of Bauchi State, Nigeria. Participatory epidemiologic tools of proportional piling and pair wise ranking were used by all the participants of FGD to rank by importance common diseases of village chickens in their communities. Disease and predation were identified by all the participants in each community as major constraints affecting village chicken production. Among the common diseases listed in each community, ND received the highest proportional piling scores of 146/249 (69.9%) in Chinade, 35/105 (32.4%) in Jalam, 183/261(70.1%) in Udubo, 149/244 (61.1%) in Kafin Madaki, 80/183 (43.7%) in Gongoro, 175/270 (64.8%) in Dass, 126/243 (50.8%) in Kutaru and 173/288 (60.1%) in Toro. ND also received the highest pair wise ranking scores of all the listed diseases of 3/4 in Dass, 4/5 in Chinade, Gongoro and Toro respectively; 5/6 in Jalam and Udubo and 6/7 in Kafin Madaki. ND which locally was known as Farin Kashi or Mai kere occurs between November and February with symptoms of snick/rales, greenish/ whitish diarrhoea and mortality in the neighbourhood. The results identified ND and predation as the major constraints to village chickens production with ND being ranked as the most important disease affecting village chickens in Bauchi State. The study recommends the prioritization of ND by Bauchi State Government and other Non-Governmental Organization for the purpose of disease control. Key words: Newcastle disease, Nigeria, village chickens, focus group discussion, proportional piling exercise, pair wise ranking.

Administrative mass data linking minimal/zero false positives

ABSTRACT
 ObjectivesPart of eHealth project in Scotland to assign a health index to all electronic patient records. One off extracts from live and historical records were posted to a record linkage department where deterministic and Newcombe probability mass matching was performed to assign the Scottish GP registration (CHI) number. These were real world administrative matches with emphasis on minimal false positives rather than maximum acceptable match rates.
 ApproachEarly investigations examined the causes of false positive matching. A running window of incomer match scores, instead of only the highest pair score indicated that highest pair Binit scores, even well above acceptance threshold yielded spurious matches and that lower scoring pair matches for the same incomer were more acceptable. A single threshold would not work. The customers were invited to clerically check the matches; their heuristic strategies were observed and incorporated into an automated partitioning exercise.
 ResultsDeterministic match rates below 70% were considered very poor. 70-80% poor, 80-85% average, 85-90% good, >90% excellent. The residual unmatched incomers were processed using Newcombe methods, then through the partitioning exercise. 90-95% (deterministic+residual) match rates were viewed as average, 95-98 % as good, 98-100% as excellent. Several deterministic match runs were passed through the residue process early in the exercise, any false positive thrown up by this caused a change in the deterministic process to eradicate errors. Roughly 1000 linkage exercises were done for the eHealth project.
 ConclusionsThis was a joint exercise where the linkage department delivered potential match pairs to the customer. The customer then decided on the partitions they were willing to accept. All the potential pairs were sent with a checking engine to view the outcome. Most elected to accept only deterministic matches. Some accepted linkage department advice; often the linkers would clerically flag accepted and rejected pair matches for the customers to review. There was a pilot administrative matching project to assign the health index to social service data in Scotland called eCare which started after the eHealth exercise; in both, the customers were requested to alert us with any false positives - no alerts were received. The same methods were used in the recent exercise to de-duplicate and merge all Glasgow's hospital records; the customer was very used to the methodology, so more checking work by the linker was accepted to achieve higher match rates. A method to estimate false positive rates is proposed.

A New Resolution about Calculating Degree of Freedom Planar Mechanism with Higher Pairs

A detailed study on the calculating of planar mechanism degree of freedom-including gear pair was carried out in detail. By the analysis of the basis concept of constraint, the constraint type of bogus higher pair was introduced. Based on the constraint type, the classical Grübler-Kutzbach formula of planar mechanism degree of freedom is beyond doubt. In addition, the correct-ness and practicality the method for the calculation of the freedom of planer mechanism was proved. It is believed that the work will provided instructive guidance for the calculating of planar mecha-nism degree of freedom and design of planar gear-link mechanism.

The Research on Variety of Instantaneous Transmission-Ratio of Gear Pump with Circular-Arc Tooth Profile

According to basic law of tooth profile meshing and principle of higher pair to be replaced with lower pair of planar mechanism, the calculating formula which is used for calculation of transmission ratio of gear pump with circular-arc tooth profile is obtained. The calculating results indicate that stability of transmission ratio of gear pump are very effected by the difference between concave arc radius of tooth profile of pinion and convex arc radius of tooth profile of wheel gear. The smaller the difference of radiuses, the more severe the wave of velocity while meshing.

Analysis of the Bennett linkage in the geometry of tori

Spatial link mechanisms with revolute pairs (7R) can be analyzed only on the basis of a three-bar mechanism with a higher pair in the form of two general tori. These mechanisms have special positions, where mobility is changeable. These special positions include bifurcation points, dead points or extreme positions. A situation when two tori overlap distinguishes one type of these positions. A kinematic system with a higher pair becomes an invariable immobile system. In an equivalent structure of a 7R mechanism, three links form an invariable immobile system, and the remaining four may have one or two degrees of additional freedom. Two spatial dyads of the 7R mechanism may form (e.g. in a synthesis process) a 4R system of the Bennett linkage, which is equivalent to two identical and overlapping tori. This paper focuses on presenting such a special case.

Kinematic analysis of a universal spatial mechanism containing a higher pair based on tori

An analysis of a mechanism that involves a higher pair in the form of two tori contacting each other superficially at one point is described in this paper. The analysis is conducted using the matrix method. Depending on the dimensions and relative positions of tori, this mechanism has many special cases from the analytical point of view. The presented model may also serve to describe link mechanisms which are kinematically equivalent to a mechanism with a higher pair.

Antifriction Effect of Micro-Deep Holes for Higher Pair Components

Higher pair contacting components is worn more severely than lower pair contacting components due to the larger contact stress on the contact line. To improve antifriction of higher pair contacting components, the paper proposes a new method by which a large number of micro-deep holes are fabricated on the surface of the contacting component. When higher pair operates, contact stress near the contact line will cause obvious elastic deformation and the volume of the micro-deep holes near the contact line will change, resulting in absorbing oil and squeezing oil. Then an oil film with certain pressure is generated around the micro-deep holes, which will improve the lubrication of components greatly. In addition, a test is carried out and its result shows that the cylindrical roller with micro-deep holes performed better in terms of antifriction than the smooth cylindrical roller.

Geometry of a mechanism with a higher pair in the form of two elliptical tori

This paper presents one of the problems of kinematic analysis of one degree of freedom single-loop spatial mechanism. The problem lies in geometric modeling of mechanisms in such a manner that a model may cover as many structures which include the most common kinematic connection of links as possible. As a result of this approach, a model of a three-link mechanism with a higher kinematic pair consisting of two elliptical tori was obtained. Particular cases of this model are kinematic structures which, after meeting some conditions, become models of mechanisms with revolute, prismatic, cylindrical, spherical pairs or universal joint. In this way, a model of such a mechanism was created where detailed mechanisms are obtained through a change of parameter values.

Chromosome pairing in hybrids between hexaploid bread wheat and tetraploid crested wheatgrass (Agropyron cristatum)

To transfer drought and cold tolerance from crested wheatgrass, Agropyron cristatum (2n = 4x = 28; PPPP genomes) to bread wheat, Triticum aestivum (2n = 6x = 42; AABBDD), intergeneric hybrids (2n = 5x = 35; ABDPP) were synthesized. The F, hybrids were perennial like the male wheatgrass parent. Their morphology was almost intermediate between the two parents. A low-pairing (LP) hybrid and a high-pairing (HP) hybrid were studied. The LP hybrid, with apparently functional Phi (the pairing regulator that suppresses homoeologous pairing), had a mean of 0.14 III + 1.16 ring II + 3.17 rod II + 25.91 I, with a c (the mean arm-pairing frequency) of 0.206. If A, cristatum were an autotetraploid, its haploid complement (PP) in the hybrid should form approximately 7 II. The mean of only 4.33 II (of which about 1.0 bivalent probably involved the A, B and D genomes of wheat) would suggest a certain degree of divergence between the two P genomes. The HP hybrid had 0.03 chain IV + 0.47 III + 2.98 ring II + 5.89 rod II + 15.73 I, with c= 0.460. Such a high pairing probably involved both autosyndesis (pairing within the ABD component and within the PP component of the ABDPP hybrid) and allosyndesis (pairing between the parental complements), and could have occurred only if Phl was partially inactivated. Homoeologous pairing of chromosomes of P with wheat chromosomes seems sufficient to facilitate the transfer of desirable traits of A. cristatum into wheat.

Abundance and Distribution of Harlequin Ducks in the Hudson and James Bay Area, Québec

Abstract As part of the Hydro-Quebec Grande-Baleine (Great Whale) hydroelectric project feasibility studies, Harlequin Duck (Histrionicus histrionicus) surveys were conducted in 1990 and 1991 in the eastern Hudson Bay and James Bay drainage basins. A total of 142 and 420 Harlequin Ducks were counted in 1991 and 1992, respectively, of which 142 (1991) and 356 (1992) were found in the area surveyed both years. Most individuals were in pairs and the overall sex-ratio did not deviate significantly from 1:1. The highest numbers of Harlequin Ducks counted over the two years were found on the Little Whale River, Des Loups-Marins Lake, and Nastapoka, A l'Eau Claire and Boutin Rivers. Highest pair densities were observed in June 1992 on rivers located in tundra and forest tundra i.e., the lower Little Whale, A l'Eau Claire and Nastapoka Rivers, and near D'Iberville Lake. In 1992, pair densities varied between 0.003 and 0.093 pair/km, depending on the watershed, and followed a latitudinal gradient. Two broods were ...

Modeling and analysis of spherical micromanipulator dynamics based on the stick-slip effect

A spherical micromanipulator is a micro robotic system largely applied to the micro/nano precision positioning, which is composed of a seat, a micro-ball and 3 piezoelectric tubes with ruby balls on the top. Rotations with 3-DOFs of the micro-ball are achieved with the relative displacements brought by the frictions between the ruby balls and the micro-ball. The stick-slip effect exists in this friction movement, whose nonlin- ear characteristic leads to the serious complication of the sys- tem dynamics. A dynamic model of the micromanipulator with stick-slip characteristic is established under the condition of simplifying spherical higher pair joints. Based on the dynamic friction model, a method of numerical analysis is used to value the effects played by several parameters. The dynamic model is demonstrated by simulations. The rotation experiment is also done, and the validity of the micromanipulator dynamic model is further proved by the results.

Adjacent martix method of identifying isomorphism to planar kinematic chain with multiple joints and higher pairs

Adjacent martix method of identifying isomorphism to planar kinematic chain with multiple joints and higher pairs

Elevated spring testosterone increases parasite intensity in male red grouse

The expression of testosterone-dependent sexual traits might signal the ability of their bearers to cope with parasite infections. According to the immunocompetence handicap hypothesis (IHH), such signals would be honest because physiological costs of testosterone, such as a reduced ability to control parasite infections, would prevent cheating. We tested whether testosterone would affect the outcome of a standardized parasite challenge in red grouse, using a main parasite of the species, the nematode Trichostrongylus tenuis. We caught males in spring, removed their nematode parasites, and implanted them with testosterone or empty implants, as controls. After 1 month, they were reinfected with a standard dose of infective T. tenuis parasites. When challenged, testosterone males had relatively less globulin relative to albumin plasma proteins than control males, an indication that they had experienced increased physiological stress. Testosterone-treated males had significantly more T. tenuis parasites than controls in the next autumn and also had more coccidia and lost more weight than controls. Testosterone-treated males nevertheless benefited from their elevated spring testosterone: they had bigger sexual ornaments than controls both in spring and autumn, and they tended to have a higher pairing and breeding success than controls. Our results supported the IHH in showing that elevated testosterone impaired the ability of males to cope with a standardized challenge by a dominant parasite. Testosterone thus plays a key role in mediating trade-offs between reproductive activities and parasite defense, and testosterone-dependent comb size might honestly signal the ability of red grouse to control T. tenuis infection.

Synthesis and cytological characterization of trigeneric hybrids of durum wheat with and withoutPh1

Wild grasses in the tribe Triticeae, some in the primary or secondary gene pool of wheat, are excellent reservoirs of genes for superior agronomic traits, including resistance to various diseases. Thus, the diploid wheatgrasses Thinopyrum bessarabicum (Savul. and Rayss) A. Love (2n = 2x = 14; JJ genome) and Lophopyrum elongatum (Host) A. Love (2n = 2x = 14; EE genome) are important sources of genes for disease resistance, e.g., Fusarium head blight resistance that may be transferred to wheat. By crossing fertile amphidiploids (2n = 4x = 28; JJEE) developed from F1 hybrids of the 2 diploid species with appropriate genetic stocks of durum wheat, we synthesized trigeneric hybrids (2n = 4x = 28; ABJE) incorporating both the J and E genomes of the grass species with the durum genomes A and B. Trigeneric hybrids with and without the homoeologous-pairing suppressor gene, Ph1, were produced. In the absence of Ph1, the chances of genetic recombination between chromosomes of the 2 useful grass genomes (JE) and those of the durum genomes (AB) would be enhanced. Meiotic chromosome pairing was studied using both conventional staining and fluorescent genomic in situ hybridization (fl-GISH). As expected, the Ph1-intergeneric hybrids showed low chromosome pairing (23.86% of the complement), whereas the trigenerics with ph1b (49.49%) and those with their chromosome 5B replaced by 5D (49.09%) showed much higher pairing. The absence of Ph1 allowed pairing and, hence, genetic recombination between homoeologous chromosomes. Fl-GISH analysis afforded an excellent tool for studying the specificity of chromosome pairing: wheat with grass, wheat with wheat, or grass with grass. In the trigeneric hybrids that lacked chromosome 5B, and hence lacked the Ph1 gene, the wheat-grass pairing was elevated, i.e., 2.6 chiasmata per cell, a welcome feature from the breeding standpoint. Using Langdon 5D(5B) disomic substitution for making trigeneric hybrids should promote homoeologous pairing between durum and grass chromosomes and hence accelerate alien gene transfer into the durum genomes.