Slow Temperature Changes Research Articles

Instability Compensation of Recording Interferometer in Phase-Sensitive OTDR.

In the paper, a new method of phase measurement error suppression in a phase-sensitive optical time domain reflectometer is proposed and experimentally proved. The main causes of phase measurement errors are identified and considered, such as the influence of the recording interferometer instabilities and laser wavelength instability, which can cause inaccuracies in phase unwrapping. The use of a Mach-Zender interferometer made by 3 × 3 fiber couplers is proposed and tested to provide insensitivity to the recording interferometer and laser source instabilities. It is shown that using all three available photodetectors of the interferometer, instead of just one pair, achieves significantly better accuracy in the phase unwrapping. A novel compensation scheme for accurate phase measurements in a phase-sensitive optical time domain reflectometer is proposed, and a comparison of the measurement signals with or without such compensation is shown and discussed. The proposed method, using three photodetectors, allows for very good compensation of the phase measurement errors arising from common-mode noise from the interferometer and laser source, providing a significant improvement in signal detection. In addition, the method allows the tracking of slow temperature changes in the monitored fiber/object, which is not obtainable when using a simple low-pass filter for phase unwrapping error reduction, as is customary in several systems of this kind.

Novel Lyapunov-based rapid and ripple-free MPPT using a robust model reference adaptive controller for solar PV system

The technological, economic, and environmental benefits of photovoltaic (PV) systems have led to their widespread adoption in recent years as a source of electricity generation. However, precisely identifying a PV system's maximum power point (MPP) under normal and shaded weather conditions is crucial to conserving the maximum generated power. One of the biggest concerns with a PV system is the existence of partial shading, which produces multiple peaks in the P–V characteristic curve. In these circumstances, classical maximum power point tracking (MPPT) approaches are prone to getting stuck on local peaks and failing to follow the global maximum power point (GMPP). To overcome such obstacles, a new Lyapunov-based Robust Model Reference Adaptive Controller (LRMRAC) is designed and implemented to reach GMPP rapidly and ripple-free. The proposed controller also achieves MPP accurately under slow, abrupt and rapid changes in radiation, temperature and load profile. Simulation and OPAL-RT real-time simulators in various scenarios are performed to verify the superiority of the proposed approach over the other state-of-the-art methods, i.e., ANFIS, INC, VSPO, and P&O. MPP and GMPP are accomplished in less than 3.8 ms and 10 ms, respectively. Based on the results presented, the LRMRAC controller appears to be a promising technique for MPPT in a PV system.

ADAPTIVE PHYSIOLOGICAL ACTIVITY OF THE FISH DURING THERMAL-STRESS AND THERMAL ADAPTATION

The Indian major carp Catla catla subjected to slow temperature change from 22°C to 32°C (heat-adaptation) and 32°C to 22°C (cold-adaptation) at the rate of 1°C /60hrs showed a gradual elevation of Rate of heart beat in heat-adaptation and gradual decrease of rate of heart beat in the case of cold-adaptation and in both cases reached the control values within 35days. whereas Catla catla exposed abruptly to a temperature change from 22°C to 32°C and vice-versa at the rate of 1°C/hr. exhibited neither elevation nor decrease in the Rate of heart beat and they could not reach the control values within 35 days. Stress is a physiological load acting upon the fish, whereas adaptation is a slow process of compensation without physiological load.

Probabilistic assessment of induced seismicity at the Alberta No. 1 geothermal project site

Alberta No. 1 (ABNo1) is a geothermal project targeting deep carbonate, conglomerates, and sandstone formations in a potential production and injection zone for geothermal energy exploitation within the Municipal District of Greenview south of Grande Prairie, Alberta, Canada. In geothermal systems without a steam fraction (typically systems under 170 °C), rapid widespread pore pressure changes and slow temperature changes have led to increased deviatoric stresses, resulting in induced seismicity. A concern for the ABNo1 Geothermal Project is that anthropogenic seismicity from oil, gas, and well field fluid injection has created felt events in Alberta. Thus, at the beginning of this type of project, it is prudent to review the potential for induced seismicity. In this study, a geomechanical study of the Leduc and Granite Wash Formations, two potential geothermal fluid exploitation zones, has been undertaken based on borehole geophysics and regional injection-induced earthquake data. Determining subsurface properties such as state of stress, pore pressure, and fault properties, however, poses uncertainties in the absence of actual data from the target formations. Geomechanical analysis results (with associated uncertainties) are used to assess the potential for injection-induced earthquakes. A Monte Carlo probability analysis is employed to estimate the likelihood of slippage of the known faults close to the ABNo1 Geothermal Project. A cumulative distribution function of the critical pore pressure on each fault is derived from the local tectonic stress state and Mohr–Coulomb shear parameter analyses. The resultant probabilistic fault stability maps can serve as a baseline for future fluid injection projects in the region including wastewater disposal, hydraulic fracture stimulation, CO2 sequestration, as well as geothermal energy extraction.

Cool and warm ionotropic receptors control multiple thermotaxes in Drosophila larvae.

Animals are continuously confronted with different rates of temperature variation. The mechanism underlying how temperature-sensing systems detect and respond to fast and slow temperature changes is not fully understood in fly larvae. Here, we applied two-choice behavioral assays to mimic fast temperature variations and a gradient assay to model slow temperature changes. Previous research indicates that Rhodopsin 1 (Rh1) and its phospholipase C (PLC) cascade regulate fast and slow temperature responses. We focused on the ionotropic receptors (IRs) expressed in dorsal organ ganglions (DOG), in which dorsal organ cool-activated cells (DOCCs) and warm-activated cells (DOWCs) rely on IR-formed cool and warm receptors to respond to temperature changes. In two-choice assays, both cool and warm IRs are sufficient for selecting 18°C between 18°C and 25°C but neither function in cool preferences between 25°C and 32°C. The Rh1 pathway, on the other hand, contributes to choosing preferred temperatures in both assays. In a gradient assay, cool and warm IR receptors exert opposite effects to guide animals to ∼25°C. Cool IRs drive animals to avoid cool temperatures, whereas warm IRs guide them to leave warm regions. The Rh1 cascade and warm IRs may function in the same pathway to drive warm avoidance in gradient assays. Moreover, IR92a is not expressed in temperature-responsive neurons but regulates the activation of DOWCs and the deactivation of DOCCs. Together with previous studies, we conclude that multiple thermosensory systems, in various collaborative ways, help larvae to make their optimal choices in response to different rates of temperature change.

Experimental study of temperature change effect on distributed acoustic sensing continuous measurements

Distributed fiber-optic sensing is useful in geophysical exploration and monitoring applications. Distributed temperature sensing (DTS) is used for measuring and monitoring temperature and distributed acoustic sensing (DAS) for recording the seismic wavefield. However, DAS measurements also are sensitive to temperature changes. To understand and quantify the DAS signature of temperature changes during water injections at CO2CRC Otway site, a series of experiments have been conducted at the Curtin University/National Geosequestration Laboratory (NGL) well research facility and Curtin rock-physics laboratory. Overall, three DAS cables are examined. Two fibers are tested in the laboratory and one cable, which is installed behind the casing in the Curtin/NGL well, is examined in the well. Laboratory measurements and observations made during analysis of passive DAS and DTS field data recorded in four Otway wells demonstrate that DAS is sensitive to long-period temperature changes, and its response is proportional to the time derivative of temperature. Induced fiber strain is linearly related to slow temperature change, and this dependency can be estimated for a particular cable. Obtained proportionality constants between strain and temperature change indicate some dependency on the cable type/design and acquisition setup, but they are all of the same order of magnitude. DAS measurements also can be affected by low-frequency noise possibly associated with the effect of temperature on the DAS acquisition unit itself. The results can help compensate for the effect of temperature on low-frequency DAS signals and show that DAS can be used as a distributed temperature sensor if direct temperature measurements are not available.

Gas-insulated transmission lines state classification and fault chamber location based on the divergence characteristics of temperature parameters

SuTong GIL (Gas-insulated transmission lines) is a critical connection for the UHV AC loop network in East China, therefore, its state classification and fault chamber location are extremely important for the operation and maintenance. Besides, because of the slow and flat temperature change of the GIL, it is difficult to realize state classification and fault chamber location from the perspective of temperature. Based on the temperature rise effect, this paper defines the ratio of heat-temperature (QT) and the change rate of the ratio of heat-temperature (θ) as the characteristic parameters. Based on the boundary equations, the state is divided into the normal, the critical and the abnormal state. More importantly, the fault chamber location can be achieved by studying the temperature transition characteristics. To verify the effectiveness of this method, the three-dimensional Multi-physics coupling model is established through COMSOL. Each state is simulated at different current changes. The trend and value range of the characteristic parameters in different states are obtained. The result shows that the value of QT and θ at the abnormal state are dozens of times higher than other two states. The fault location simulation shows that the QT on the left is 4 times higher than that on the right, and the θ on the left is 10 times higher than that on the right. This method can realize state classification and fault chamber location accurately.

Robustness of mainstream anammox activity at bench and pilot scale

New technologies and processes, such as mainstream anammox, aim to reduce energy requirements of wastewater treatment and improve effluent quality. However, in municipal wastewater (MWW) anammox system are often unstable due to process control disturbance, influent variability, or unwanted nitrite oxidizing bacteria (NOB). This study examines the anammox system by focusing on anammox activity and its robustness in a mainstream environment. An 8 m3 pilot-scale sequencing batch reactor (SBR) receiving pretreated MWW (with external nitrite addition) was seeded with pre-colonized carriers. Within six months at 12–20 °C an anammox activity of 200 gN·m−3·d−1 was achieved. After the startup an anammox activity of 260 ± 83 gN·m−3·d−1 was maintained over 450 days. The robustness of the anammox activity was analyzed through three disturbance experiments. Anammox biofilm on carriers were exposed to dissolved oxygen (DO = 1.6 mg·L−1, intermittent aeration), organic loading rate (OLR, C/N increased from 2:1 to 5:1) and temperature disturbances (20 °C to 12 °C) in triplicate 12 L bench scale reactors. The anammox activity and microbial community was monitored during these disturbances. The DO and OLR disturbance experiments were replicated at pilot scale to investigate upscaling effects. Bench and pilot scale anammox activity were unaffected by the DO disturbance. Similarly, an increase in OLR did not deteriorate the bench and pilot scale anammox activity, if nitrate was available. When, at bench scale, the reactor temperature was reduced from 20 °C to 12 °C overnight, anammox activity decreased significantly, this was not the case for the slow seasonal temperature changes (12–25 °C) at pilot scale where no strong temperature dependency was detected in winter. Metagenomic analysis revealed a broad range of Brocadiaceae species with no single dominant anammox species. Anammox thrive under mainstream conditions and can withstand typical process disruptions.

When energy efficiency goes out the window: How highly insulated buildings contribute to energy-intensive ventilation practices in Germany

Many national and international climate goals focus on lowering resource consumption in the building sector. In Germany, this is attempted in large part through increasing the thermal insulation of buildings, in order to achieve average room temperatures of 19 °C with as little heating energy as possible. However, research on the Energy Performance Gap shows that predicted heating-energy savings are seldom reached. Based on a case study conducted in six energy-efficient multi-apartment buildings in Southern Germany, we offer an explanation rooted in practice theory: There appears to be a mismatch between households’ practices and the building’s properties. While households have diverse and changing temperature needs, and a desire for quick adaptation, the energy-efficient building provides homogenous temperatures and slow temperature change. This leads households to open windows often and for long periods of time in order to reach their thermal comfort needs – even in the height of winter. The direct and indirect losses of heating energy from the observed ventilation practices can contribute to the Energy Performance Gap of energy-efficient buildings. If energy-efficient building regulations incorporated more realistic assumptions about household practices, the building designs could become more adequate and the estimated energy savings more realistic, potentially reducing the magnitude of Energy Performance Gaps.

Post-glacial lake development and paleoclimate in the central Hudson Bay Lowlands inferred from sediment records

We compile a multi-proxy Holocene record from North Raft Lake located in the sub-Arctic Hudson Bay Lowlands, Canada. Specifically, we use subfossil chironomid, diatom, and pollen assemblages, non-pollen palynomorphs, sedimentary chlorophyll a, magnetic susceptibility, and organic matter content to characterize terrestrial and lake processes and to track paleoclimate following land emergence from the postglacial Tyrrell Sea. Following recession of the Tyrrell Sea (~ 6600 cal yr BP), pollen assemblages are indicative of a salt marsh environment with the establishment of an opportunistic chironomid assemblage. By ~ 6200 cal yr BP, isostatic uplift reduced the marine influence and pollen and palynomorph assemblage changes indicate that North Raft Lake became a closed-basin freshwater system. At this time, pollen assemblages signify the establishment of a forested peatland dominated by Picea, and chironomid taxa indicate warming water temperatures. The North Raft Lake pollen/palynomorph record captures a warm and moist mid-Holocene (Holocene Thermal Maximum) period starting ~ 6200 cal yr BP. During this period, an increase in pollen concentration and a shift to higher abundances of Larix indicate watershed-scale succession and enhanced local ecosystem productivity. Shifts in chironomid taxa at ~ 5000 cal yr BP are indicative of abrupt limnological changes suggesting wet conditions that caused an expansion of littoral habitat. The gradual transition into Neoglacial cooling is signaled by an increase in the abundances of cold-stenothermal chironomid taxa and a small decline in pollen-reconstructed temperatures. Marked changes occur in the mid-twentieth century with the appearance of diatoms in notable abundances for the first time in the lake’s sedimentary record, the arrival of new chironomid littoral taxa, and unprecedented increases in sedimentary chlorophyll a and organic matter content. Throughout the North Raft Lake Holocene sediment record, the pollen trends suggest slow centennial-scale changes in temperature and precipitation, whereas chironomid assemblages indicate abrupt mid-Holocene and twentieth century limnological changes, stressing that biota in lakes of the Hudson Bay Lowlands may change substantially under future scenarios of global climate warming.

Thermal acclimation of flies from three populations of Drosophila melanogaster fails to support the seasonality hypothesis

In seasonal environments, natural selection should favor genotypes that acclimate to slow and predictable changes in temperature. Selective pressure for acclimation should be especially strong for animals that complete many generations per year, because seasonal warming or cooling causes offspring to experience different temperatures than their parents did. Here, we studied variation in acclimation capacity among three populations of Drosophila melanogaster. We used a reverse acclimation design to see whether developmental acclimation persisted throughout adulthood. Flies developed from fertilization to adulthood at either 16° or 26 °C. Then, flies either remained at the same temperature or moved to the other temperature for 7 days. We measured fecundity at seven temperatures ranging from 14° to 36°C. Genotypes from North Carolina and Vermont laid more eggs at 16 °C after spending the larval and adult stages at 16 °C, instead of 26 °C. In both populations, the benefit of acclimation to 16 °C during development was erased by acclimation to 26 °C during adulthood. In contrast to our prediction, genotypes from Indiana laid fewer eggs at 16 °C or 26 °C after developing at this temperature. Overall, these data provide only weak support for the models of optimal acclimation in seasonal environments.

Abomasal nematode species differ in their in vitro response to exsheathment triggers.

A crucial step in the infection process of grazing ruminants by gastro-intestinal nematodes is the exsheathment of the infective third-stage larva following ingestion. Recently, heat shock was shown to play an important role in the carbon dioxide (CO2)-dependent exsheathment response in Haemonchus contortus. The current in vitro study set out to evaluate the role of heat shock in other abomasal species. In rumen fluid, all species tested exsheathed rapidly and efficiently in response to heat shock and CO2. This response was significantly higher compared to slow temperature changes, supporting the hypothesis that heat shock plays an important role in vivo. However, in artificial buffer, the effect of heat shock was species-dependent. For H. contortus and Ostertagia leptospicularis, the response in artificial buffer was similar to rumen fluid. In contrast, Ostertagia ostertagi and Teladorsagia circumcincta exsheathment was significantly lower and/or slower in artificial buffer, and there was no benefit of heat shock. For these two species, it appears that there are co-factors in the rumen fluid, in addition to heat shock and CO2, contributing to exsheathment. Overall, the data indicate that there are significant differences between abomasal species in their response to exsheathment triggers.

Intra-operative cutaneous temperature monitoring with zero-heat-flux technique (3M SpotOn) in comparison with oesophageal and arterial temperature

Continuous monitoring of core temperature is essential during major surgery as a way of improving patient safety. Oesophageal probes or specific arterial catheters are invasive methods used in this setting. A new noninvasive device based on zero-heat-flux (ZHF) technique (SpotOn) seems promising but has been poorly investigated during rapid core temperature changes (RCTC). To assess the accuracy of a SpotOn sensor vs. an oesophageal probe or specific arterial catheter during a slow change in core temperature of less than 1 °C within 30 min and RCTC ≥ 1 °C within 30 min. Prospective observational study. Operating rooms at the University Hospital of Poitiers, France. Fifty patients scheduled for major abdominal surgery under general anaesthesia were enrolled from June 2015 to March 2016. Data from 49 patients were finally analysed. Among these, 15 patients were treated with hyperthermic intraperitoneal chemotherapy. Each patient had a ZHF sensor placed on the skin surface of the forehead (TempZHF) and an oesophageal probe (TempEso) used as a reference method. Twenty-two patients also had a thermodilution arterial catheter (TempArt) placed in the axillary artery. Core temperature was continuously recorded from the three devices after induction of anaesthesia. Comparison of temperature measurements between methods was made using the Bland and Altman method during two separate periods according to the speed of core temperature changes. Compared with TempEso, bias and limits of agreement for TempZHF were 0.1 ± 0.5 °C during slow core temperature changes periods and 0.6 ± 1.8 °C during RCTC periods (P = 0.0002). Compared with TempArt, these values were -0.1 ± 0.4 and 0.5 ± 1.7 °C, respectively (P = 0.0039). The ZHF sensor was well tolerated. A SpotOn sensor using the ZHF method seems reliable for core temperature monitoring during abdominal surgery when variations in core temperature are slow rather than rapid. ClinicalTrials.gov identifier: NCT02869828.

Математическое моделирование влияния релаксационных процессов на температурные поля в упругом полупространстве

The article examines the relaxation processes that occur in an elastic solid medium when it is heated and cooled, especially their influence on the temperature field. Besides, we considered in this paper the heat equation of parabolic type arising in the theory of thermal conductivity for different modes of heating the border. We present a solution of the boundary value problem of nonstationary heat conduction for an infinite plate with the following regimes of loading the boundaries: a single slow temperature change at the border, a single instantaneous temperature variation at the border, and, finally, multiple instantaneous changes of temperature at the border. In order to solve these three heat problems, they were brought to a dimensionless form. Then the operational calculus method was applied. The essence of the method consists in the following. According to the obtained analytical solutions three-dimensional graphics characterizing the relaxations processes were built in the computer algebra system Wolfram Mathematica for different ranges of the Fourier criterion.

Badania doświadczalne wybranych źródeł błędów w profilowych pomiarach nierówności powierzchni

In the paper experimental results of research regarding selected errors in profile measurements of surface asperities were presented. Influence of synchronization of measurement tracks, errors coming from rotation and possibilities of measurement devices as well as interference from conditions in both: high and low frequencies were discussed. It was shown that repeatability of the first point and even slow temperature changes around a measurement device have a great influence on fidelity of results.

Reversibility of Asphaltene Precipitation Using Temperature-Induced Aggregation

In this work, kinetic asphaltene precipitation was investigated using temperature fluctuations. Asphaltene precipitation was previously identified as a fully reversible process by altering the solution pressure or composition but only partially reversible using temperature changes. Slow kinetic asphaltene precipitation plays a critical role in the accurate monitoring of asphaltene precipitation, and previous reversibility studies need to be revisited in light of this phenomenon. Previous studies used a combination of precipitant addition and temperature changes to conclude that precipitated asphaltenes do not fully redissolve when the mixture temperature is changed. Modeling results reveal that precipitated asphaltenes should not be expected to redissolve, regardless of the magnitude of temperature changes, after a precipitant (e.g., dodecane) is added to the mixture. Consequently, this study was designed to isolate the influence of slow kinetics, precipitant addition, and temperature changes on the solubility and reversibility of asphaltene precipitation. Temperature cycling experiments were performed to investigate the reversibility of asphaltene precipitation and revealed that the process is fully reversible with temperature changes. This finding reinforces that, for the system in this study, asphaltene phase behavior is controlled by equilibrium thermodynamics and not a colloid stabilization model.

A Study of Temperature and Aging Effects on Eigenfrequencies of Concrete Bridges for Health Monitoring

This paper discusses the influence of environmental factors and of normal material aging on the eigenfrequencies of concrete bridges based on monitoring data registered during 4 years of a specific bridge. It is a new composite steel-concrete bridge built in 2006 in Luxembourg. The measurements are analyzed and compared to literature data. The final objective is the use of real monitored eigenfrequencies for structural health monitoring and damage detection based on identification of stiffness losses in practical applications. Therefore, it is very important to identify and compensate for outdoor influences namely temperature, excitation force level and normal aging effects, like creep and shrinkage of concrete and their impact on material properties. The present paper aims at describing these effects in order to separate them from damage effects. It is shown that temperature change rates and temperature gradients within the bridge have an influence on the eigenfrequencies. Hence the key idea for assessment from the full database is to select only measurements with small temperature differences and slow temperature change rates.

Thermal durability and fracture behavior of layered Yb-Gd-Y-based thermal barrier coatings in thermal cyclic exposure

The effects of structural design on the thermal durability and fracture behavior of Yb-Gd-Y-based thermal barrier coatings (TBCs) were investigated through thermal cyclic exposure tests, such as furnace cyclic thermal fatigue (FCTF) and jet engine thermal shock (JETS) tests. The effects of composition in the bond coat and feedstock purity for the buffer layer on its lifetime performance were also examined. To overcome the drawbacks of Yb-Gd-Y-based material with inferior thermal durability due to poor mechanical properties and low coefficient of thermal expansion, a buffer layer was introduced in the Yb-Gd-Y-based TBC systems. In FCTF tests, the TBCs with the buffer layer showed a longer lifetime performance than those without the buffer layer, showing the longest thermal durability in the TBC with the Co-Ni-based bond coat and the buffer layer of regular purity. In JETS tests, the TBC with the Ni-based bond coat and the buffer layer of high purity showed a sound condition after 2000cycles, showing better thermal durability for TBC with the Co-Ni-based bond coat rather than that with the Ni-based bond coat in the single layer coating without the buffer layer. The buffer layer effectively enhanced the thermal durability in slow temperature change (in the FCTF test), while the bond-coat composition and the feedstock purity for the buffer layer were found to be important factor to improve the thermal durability of the TBC in fast temperature change (in the JEET test). Finally, these research findings allow us to control the structure, composition, and feedstock purity in TBC system for improving the thermal durability in cyclic thermal environments.

An approach to consider lateral heat conduction effects in the evaluation process of transient heat transfer measurements using TLC

The standard transient evaluation technique for the experimental determination of heat transfer coefficients with Thermochromic Liquid Crystals is based on a one-dimensional heat conduction model inside a semi-infinite wall. However, complex flow situations induced by obstacles like cylinders, skewed ribs or vortex generators lead to spatially varying heat transfer coefficients and therefore to lateral conduction effects. Kingsley-Rowe et al. [1] developed an analytical empirical correction method considering these effects for flat two-dimensional heat conduction problems and an ideal step change of the fluid reference temperature. This method is expanded to capture three-dimensional heat conduction situations and slow transient fluid reference temperature changes. Transient simulations for twelve different heat transfer coefficient distributions and three different reference temperature histories constitute the pool of data for the determination of the empirical constants and the validation of the method. The results showed an appropriate correction of the heat transfer coefficients received by the standard evaluation method. Therefore the presented method offers the opportunity to consider three-dimensional heat conduction effects in a fast and efficient way in combination with the standard evaluation process.

Study of structural break points in global and hemispheric temperature series by piecewise regression

The study of climate trends taking into consideration possible structural changes is important for understanding climate development characterized by a stochastic trend or by a determined one.In the paper global and hemisphere temperature anomalies are modeled by piecewise linear regression and break points in the temperature evolution are found. It was demonstrated that the used method allowed finding of breaks characterized by long time trends (low frequency processes) as well as abrupt changes (fast frequency processes). The obtained break points for slow temperature change are close to the ones found by other authors however additional conditions (as segment length, gradient and others) are not used here. The results for higher break point numbers are like the ones of step slope models. It was demonstrated that the successive phases of warming and cooling and most of the break points subdividing these periods in the Northern Hemisphere are introduced by the Atlantic multidecadal oscillation. Because the strong quasi periodicity of the Atlantic multidecadal oscillation the authors recommend the removal of its influence on the temperature from the temperature series before studies of trends or structural changes. The Northern Hemisphere temperature data after the removal of the Atlantic multidecadal oscillation influence show structures like the Southern Hemisphere temperatures. Model selection by the Schwarz–Bayesian Information Criterion developed by Liu, Wu and Zidek (LWZ criterion) shows that models with only one break point are to be preferred.