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Unbalanced snow distribution, which leads to an excessive snow load in a local area, is one of the main reasons for building collapses. The formation of uneven snowdrifts is closely related to the shape of the building as it seriously affects the turbulent structure and drifting snow process. Unfortunately, the design codes of different countries for applying snow load on building structures cannot give a clear explanation because of the discrepancies between them. Therefore, a series of reduced scale field measurements of snowdrifts on roofs were conducted to clarify such discrepancies. Firstly, the size effect of model scaling was investigated by observing snowdrifts around two models with a scale ratio of 1/2. The results show that the size effect has little influence on the snowdrift pattern on the premise of satisfying the similarity criterion. Thereafter, the snowdrift characteristics of two-level roofed and gable roofed buildings were explored and analyzed through the comparison with different national load codes and collapsed building cases. Overall, the provisions of the Chinese load code differ from the measurement results, which leads to an underestimation of roof snow load. ISO 4355 and Canadian NBC codes could give a better prediction of the snow load by comparison.

A new method for selecting dimensionless relaxation time in the lattice Boltzmann model was proposed based on similarity criterion and gas true physical parameters. At the same time, the dimensionless relaxation time was modified by considering the influence of the boundary Knudsen layer. On this basis, the second-order slip boundary condition of the wall was considered, and the key parameters in the corresponding combined bounce-back/specular-reflection boundary condition were deduced to build a new model of unconventional gas microscale flow simulation based on the lattice Boltzmann method suitable for high temperatures and high pressures. The simulation results of methane gas flow driven by body force in infinite micro-channels and flow driven by inlet-outlet pressure differential in long straight channels were compared with the numerical and analytical solutions in the literature to verify the accuracy of the model, and the dimensionless relaxation time modification was formally optimized. The results show that the new model can effectively characterize the slippage effect, compression effect, gas density and the effect of boundary Knudsen layer in the micro-scale flow of unconventional natural gas. The new model can achieve a more comprehensive characterization of the real gas flow conditions and can be used as a basic model for the simulation of unconventional gas flow on the micro-nano scale.

Degradable fibers and particulates are the typical diverting agents which can temporarily plug the preexisting hydraulic fractures and redirect the treating fluid to the under-stimulated area. However, it is still unclear how the plugging is initiated and formed in the hydraulic fracture. In this paper, a large-scale visualized experimental system is built based on the similarity criterion to observe the dynamic plugging performance of fibers and particulates in a mimicked hydraulic fracture. Through a series of comparative experiments, it is found that the plugging process starts from the attachment of fibers on fracture bottoms, roofs and faces, then the attached fibers keep capturing the flowing particulates to form scattered plugged zones, finally one flow channel is formed and gradually narrowed until it is plugged completely. Results indicate that the fibers initiate the plugging process, while the particulates accelerate the following plugging process and withstand the pressure difference by acting as the skeleton of the plugged zone. It is suggested that particulates need to be injected into the hydraulic fracture with fibers at least 50 seconds after the injection of fibers, and the ratio between fibers and particulates is recommended to be 1:1. As the fracture width increases, the plugging rate is reduced accordingly. Adding big particulates whose diameters are 60%–80% of the fracture width can improve the plugging effect significantly.

In recent years, underground pipe gallery has become more and more important. Its Special working environment makes temperature monitoring and control increasingly important. paper applies heat-transfer differential equation to the cable to obtain the similarity criterion of cable temperature distribution. After calculating the electric cabin model with different fire separations, it is found that the temperature distribution of the same ampacity in different fire separations conforms to certain rules. The temperature distribution of different ampacity in the same fire separation is also regular: the ampacity rises. 5%, temperature rises by 7%. As a result, the fitting formulas of the current carrying capacity, the length of the fire separation and the location of the highest temperature were also proposed.

Based on the similarity criterion, volcanic rock samples were taken from outcrops to make experimental models. Water flooding experiments of five-spot well pattern, nine-spot well pattern, five-spot to nine-spot well pattern, the relationship between relative well and fracture positions, and injection rate in dissolution vug-cave reservoirs with/without fractures were carried out to analyze variation regularities of development indexes, find out development characteristics of water flooding with different well patterns and sort out the optimal water flooding development mode. For dissolution vug-cave reservoirs without fractures, five-spot well pattern waterflooding has very small sweeping area, serious water channeling and low oil recovery. When the well pattern was adjusted from five-spot to nine-spot well pattern, oil recovery could be largely improved, but the corner well far from the injector is little affected. In dissolution vug-cave reservoirs with fractures, when the injector and producer are not connected by fractures, the fractures could effectively connect the poorly linked vugs to improve the development effect of water flooding. Whether there are fractures or not in dissolution vug-cave reservoirs, the development effect of nine-spot well-pattern is much better than that of five-spot well pattern and five-spot to nine-spot well pattern, this is more evident when there are fractures, and the edge well has better development indexes than corner well. At the high-water cut stage of water flooding with nine-spot well pattern, the oil recovery can be further improved with staggered line-drive pattern by converting the corner well into injection well. It is helpful to increase the oil production of corner well of nine-spot well pattern by increasing the injection rate, and improve ultimate oil recovery, but the water-free production period would be greatly shortened and water-free recovery would decrease. Key words: similarity criterion, dissolution vug-cave reservoir, water flooding, injection-production well pattern, well placement, injection rate, development index, oil recovery

Fractured reservoirs are complicated due to the coexistence of matrix and fracture systems. In particular, the matrix of buried-hill metamorphic fractured reservoirs (BHMFRs) has plenty of micro-fractures and a few dissolution pores rather than common pores in sandstone. The storage and heterogeneity features, such as the storage ratio between matrix and fractures, and the distribution of fractures, significantly affect the performances of waterflooding and EOR techniques. With the objective of finding effective waterflooding mode and EOR techniques in such reservoirs, the BHMFR of JZ25-1S in Bohai Bay in China was taken as an example. First, static imbibition experiments using a novel imbibition cell were conducted. Then, 3D large-scale models of BHMFRs using outcrops were designed based on the similarity criterion and employed to conduct the experiments of waterflooding and followed EOR techniques. The results show that co-current imbibition is principal and gravity is the dominant force of imbibition for BHMFRs. Because imbibition is slow, most of the yield comes from the macro-fractures. Both water-free recovery and waterflooding recovery increase as the decrease of the storage ratio of matrix to fractures. Pulsing cyclic water-injection is better than intermittently cyclic water-injection. In BHMFRs with heterogeneity of fracture density, injection in the area with low fracture density and production in the area with high fracture density can achieve better effects than the reverse scenario for both waterflooding and followed EOR techniques. If gas flooding is selected as the EOR technique, producer should be perforated at the lower layers of the reservoir. Suitable gel particles not only get a good EOR effect by effective plugging, but also can create a more favorable condition for surfactant flooding. In our experiments, another 2–4% of OOIP was produced by PPG flooding. Surfactant can enhance the oil recovery by both removing the adsorbed oil on the fracture surface and promoting imbibition in matrix. 3–5% of OOIP was recovered by surfactant flooding and soaking in our experiments.

In order to provide efficient and reliable method for structural design and optimization of upper assembly and lower assembly of a free standing hybrid riser, a numerical calculation model and model test device for the upper assembly and lower assembly of a free-standing hybrid riser were established independently based on similarity criterion and correlative elastic-plastic mechanics theories and methods. The static and dynamic numerical calculations and corresponding tests for the upper assembly and lower assembly of a free-standing hybrid riser were carried out. The results show that the deviation between numerical simulation results and experimental results is less than 6.83%, and the dynamic test results coincide with the dynamic results of numerical simulation. The results of the above study demonstrate that the accuracy and reliability of numerical results for static and dynamic responses of the upper assembly and lower assembly and suggestions on further optimization for upper assembly and lower assembly of a free standing hybrid riser are given based on numerical simulation and test results. These results provide guidance for structural optimization of the upper assembly and lower assembly of a free-standing hybrid riser.

In order to obtain performance characteristics of special media turbomachinery conveniently and accurately, it is essential to study the similarity method for turbomachinery with different working media. Based on kinematic similarity, a new similarity method, consisting of a new similarity criterion and performance transfer methods, is presented in this paper. In order to validate the method, helium turbomachinery are investigated and air is used as the substitute working medium to simulate the helium turbomachinery. Both the velocity triangle and flow field are contrasted between helium and air turbomachinery when they achieve the similarity criterion derived. Performance map of helium turbomachinery obtained by the performance transfer methods is also compared with that obtained by numerical simulation. Results show that, the new similarity method proposed can be applied to obtaining performance characteristics of special media turbomachinery accurately.

In order to analyze the influence of opening area ratio on natural ventilation in city tunnel under block transportation, dimensionless analysis, model experiment and CFD (computational fluid dynamics) simulation are used to evaluate the velocity distribution, temperature distribution and the pollutants concentration. The similarity criterion of thermal-pressure ventilation and proportional constant of the heat with the same temperature distribution are obtained by the dimensionless analysis about the thermal buoyancy and gravity of the most adverse section at block transportation. According to the similarity conditions, several groups of model experiments and computer models are built. Results of the model experiments and CFD simulations show that with the increase of opening area ratio, the effect of the natural ventilation improves at the beginning, but as opening area ratio continues to increase, the role of natural wind pressure outside tunnel is strengthened. There are some uncertainties of the natural wind pressure which might lead to the ventilation effect decline. With the increase of opening area ratio, the construction cost of vent shaft increases observably at the same time. So it is of great significance for city tunnel to choose an appropriate opening area ratio which can meet the requirements of ventilation under the block transportation without superfluous cost of blindly increasing opening area ratio investment.

Tahe Oilfield, located in Tarim Basin, Northwest China, is a typical carbonate fracture-vuggy reservoir. Nitrogen gas flooding is a vital technology for improving oil recovery by enlarging sweep volume in fracture-vuggy reservoirs. However, gas channeling restricts further application of nitrogen gas flooding. This paper studied the characteristics of gas channeling in fracture-vuggy carbonate reservoirs using physical simulation. Visual physical models and macroscopic physical models were designed and fabricated based on similarity criterion. Nitrogen gas flooding experiments were conducted in both types of models. Experimental results demonstrated that once the dominant channel of gas is formed, the remaining oil cannot be effectively swept. The greater the areal heterogeneity of fracture-vuggy carbonate reservoir is, the easier the formation of gas channeling is. Gas channeling was accompanied by a large amount of oil and water production. The initial gas channeling was followed by several additional occurrences of gas channeling. In addition, PIR risk assessment method was proposed to predict gas channeling by assigning values to each coefficient of P, I and R. This method verified by oilfield data can be used to prevent and evaluate the risk of gas channeling in fracture-vuggy carbonate reservoirs.

Formal assessment of structural similarity is − next to protein structure prediction − arguably the most important unsolved problem in proteomics. In this paper we propose a similarity criterion based on commonalities between the proteins’ hydrophobic cores. The hydrophobic core emerges as a result of conformational changes through which each residue reaches its intended position in the protein body. A quantitative criterion based on this phenomenon has been proposed in the framework of the CASP challenge. The structure of the hydrophobic core − including the placement and scope of any deviations from the idealized model − may indirectly point to areas of importance from the point of view of the protein’s biological function. Our analysis focuses on an arbitrarily selected target from the CASP11 challenge. The proposed measure, while compliant with CASP criteria (70–80% correlation), involves certain adjustments which acknowledge the presence of factors other than simple spatial arrangement of solids.

It is well known that the flowing of oil and gas in fracture and cave does not obey Darcy law, which makes it unable to interpret parameters correctly when doing well testing for those kinds of formation for having no flowing test used to correct corresponding flowing equations. Based on similarity criterion, a physical experimental method for gas flowing from cave to wellbore through fracture has been built up. The characteristics of fluid flowing in fracture and cave can be seen clearly according to log–log curves with the measured data, which was obtained from the experimental model test and dealt with Savitzky-Golay filtering method. In addition, a new mathematical model reflecting those transient-flow behaviors as well as its solution has been presented in this paper. Log–log curves obtained from our new model could reflect the characteristics of flowing in fracture and cave. The results showed that test experiments can reflect the influence of large-scaled cave and fracture on the flowing characteristics and the new model can be applied to explain parameters of fracture and cave for similar cases.

A classification method is suggested and applied to distinguish the variants of synoptic-scale patterns inducing heavy, widespread, and steady rains in the Czech Republic. The method is based on divisive hierarchical clustering of the 78 heaviest rainfall events that affected various parts of the Czech territory in the warmer half-years from 1958 to 2002. The degree of moisture flux close to the rainfall area is selected as a similarity criterion for clustering. Subsequently, a fuzzy approach is employed to assess the membership degree of the individual events to four clusters obtained by the second level of divisive clustering. Weighted averaging of synoptic-scale thermodynamic patterns is used to determine four main variants of causal synoptic-scale conditions typical of these fuzzy clusters. Two frontal and two cyclonic variants are distinguished. The frontal variants are characterized by the recurring passage of cold frontal waves, possibly followed by the rapid passage of a frontal wave cyclone. Heavy rains occur mostly on the warm side of the quasi-stationary frontal boundary, where the intense southern component of moisture flux occurs. In the case of the passage of the frontal wave cyclone, heavy rains appear in the cold rearward sector of the cyclone, where the intense northern component of moisture flux develops. The cyclonic variants are characterized by the slow passage of a cyclone across Central Europe along various trajectories. Heavy rains are always located in the cold sector of the cyclone, which is surrounded by anomalous moisture flux that is continuously supplying the rainfall area with a large amount of moisture. The results of the present study open the door to a quantitative evaluation of thermodynamic conditions typical of heavy, widespread, and steady rains in the Czech Republic.

An adaptive fuzzy k-nearest neighbour classifier (AFNNC) for EMG signal decomposition is presented and evaluated. The developed classifier uses an adaptive assertion-based classification approach for setting a minimum classification threshold. The similarity criterion used for grouping motor unit potentials (MUPs) is based on a combination of MUP shapes and two modes of use of motor unit firing pattern information: passive and active. The performance of the developed classifier was evaluated using synthetic signals with specific properties and experimental signals and compared with the performance of an adaptive template matching classifier, the adaptive certainty classifier (ACC). Across the sets of simulated and experimental EMG signals used for comparison, the AFNNC had better average classification performance overall, but due to the assignment of higher numbers of MUPs it made relatively more errors. Nonetheless, these increased error rates would still be acceptable for most clinical uses of decomposed EMG data. An independent and a related set of simulated signals were used for testing. For the independent simulated signals of varying intensity, the AFNNC had on average an improved correct classification rate (CCr) (8.1%) but an increased error rate (Er) (1.5%) compared to ACC. For the related simulated signals with varying amounts of shape and/or firing pattern variability, the AFNNC on average had an improved CCr (5%) but a slightly increased Er (0.3%) compared to ACC. For experimental signals, the AFNNC on average had improved CCr (6%) but an increased Er (2.1%) compared to ACC. The greatest gains in AFNNC performance relative to that of the ACC occurred when the variability of MUP shapes within motor unit potential trains was high suggesting that compared to a template matching assignment strategy the NN assignment paradigm is better able to ameliorate the classification problems caused by MUP instability.

In the analysis of recurrent time series the estimation of repetitive transient signals in currently achieved by the well known averaging technique. The efficiency of this technique depends on the accuracy of the alignement process and on the constancy in shape and width of the averaged signals. A typical example is the Highly Amplified ECG signal. In previous works we showed the advantage of selective averaging based on shape classification. The similarity criterion used in such a classification was derived from the Distribution Function Method. In this paper we compare this criterion to an other one using correlation, first by simulation and secondly on real ECG signals. The ability for the two approaches to give significantly different classes is studied.

The paper reports an investigation of the application of the similarity theory, strain energy density concept and fracture mechanics to the fracture toughness ( K IC ) determination. The method K IC determination is described using R -similarity criterion of plastic deformation instability. It allows to determine the true K IC value for ductile steels using specimens not satisfying linear fracture mechanics requirements.

A similarity criterion is proposed for a confined, isothermal, axisymmetric swirling jet system. This criterion has been derived in essentially two different manners, firstly by integrating the differential equations of motion under certain assumptions and secondly by considering the overall changes in the system. The criterion indicates that two dimensionless parameters, a Swirl Number and the Craya-Curtet number for confined swirling jets, characterize the system completely. Experimental investigations on such a confined, swirling jet system are also presented. The data indicate that essential features of the jet such as entrainment, radial profiles of axial velocity and decay of centre-line velocity exhibit uniform behaviour with variations in the value of the two parameters. Also, the static pressure variation along the wall of the confining duct is in qualitative agreement with the criterion. The experimental data are consistent with the theoretically derived similarity criterion for confined swirling turbulent jets.

Fillmore (1969) has offered a semantic “role” analysis for some verbs of judging. In the present case study, we subject Fillmore's own similarity judgments for a set of verbs of judging to structural analysis, employing nonmetric multidimensional scaling and hierarchical clustering techniques. We compare the results with those yielded by more ordinary subjects and seek to assess the revealingness of the hierarchical solution relative to the distinctions made by Fillmore in his theoretical analysis. A number of methodological issues are discussed, perhaps most important whether subjects can consistently employ the same similarity criterion throughout their judgments, or whether, at least for some semantic domains, they may rather use a series of different criteria, with particular pairs or subsets of terms selecting now one criterion, now another. The latter procedure, which was employed here by Fillmore, raises some serious problems with regard to the interpretation of the results of structural analyses of similarity data.