ЭКСПЕРИМЕНТАЛЬНОЕ ИЗУЧЕНИЕ ТЕПЛОВЫХ И ДЕФОРМАЦИОННЫХ ПОЛЕЙ В ПРОЦЕССЕ РАЗРУШЕНИЯ ЭШЕЛОНИРОВАННЫХ РАЗЛОМОВ И ИЗМЕНЕНИЯ ГЕОЛОГИЧЕСКИХ УСЛОВИЙ

The article presents results of experimental studies using a bi-axial servo-control system to apply load on samples with extensional and compressional en echelon faults. During the experiments, variations of temperature and thermal images were recorded synchronously by a multi-path contact-type thermometric apparatus and a thermal image system, respectively. A digital CCD camera was employed to synchronously collect images of specimens’ surfaces. The digital speckle correlation method (DSCM) was utilized to analyze the images and to define displacements and strain fields. Our experimental results show that temperature fields have clear responses to opposite stress states in the jog areas of both types of the en echelon faults. Prior to failure of the jog area, its temperature is the highest at the compressional en echelon faults and the lowest at the extensional en echelon faults. Records by DSCM give evidence that mean strain of the jog area is the highest at compressional en echelon faults and the lowest at the extensional en echelon faults. It is revealed that deformation of the en echelon faults occurs in two stages, developing from stress build-up and fault propagation in the jog area to unstable sliding along the fault. Correspondingly, the mechanism of heating-up converts from strain heating into friction heating. During the period of transformation of the temperature rising mechanism, three events are observed in the jog area and its vicinity. Analyses of our experimental results demonstrate that variations of temperatures in the jog area can be indicative of fault sliding and suggest sliding directions. Observations and studies of temperature changes during transformation of the temperature rising mechanism at sensitive portions of faults are of great importance for early detection of precursors of unstable slip on active faults.В статье представлены результаты экспериментального изучения эшелонированных разломов растяжения и сжатия с приложением нагрузки к двуосной автоматически регулируемой модели. В ходе эксперимента производились синхронные замеры температур и тепловых сигналов. Для этого были использованы, соответственно, многоканальный термометрический прибор контактного типа и система регистрации тепловых сигналов. Синхронные снимки поверхностей экспериментальных образцов были получены при помощи цифровой видеокамеры на основе устройства с зарядовой связью. Был применен цифровой метод спекл-корреляции (DSCM) для анализа снимков и определения смещений и деформационных полей. Была установлена очевидная реакция тепловых полей на состояния напряжения противоположных типов в зонах сочленения эшелонированных разломов обоих типов. Перед полным разрушением зоны сочленения самые высокие значения температуры зарегистрированы на эшелонированных разломах сжатия, самые низкие – на эшелонированных разломах растяжения. С помощью метода DSCM самые высокие значения среднего напряжения в зоне сочленения дислокаций зарегистрированы на эшелонированных разломах сжатия, самые низкие – на эшелонированных разломах растяжения. В процессе деформирования эшелонированных разломов выявлены две стадии, развивающиеся от накопления напряжений и прорастания разлома в зону сочленения дислокаций до неустойчивого скольжения по разлому. Соответственно трансформируется механизм нагревания – с нагревания напряжением до нагревания трением. В самой зоне сочленения дислокаций и поблизости от неё в процессе трансформирования механизма повышения температуры наблюдались три фазы. Анализ полученных нами экспериментальных данных показал, что вариации температуры в зоне сочленения дислокации могут указывать на смещения по разлому и позволяют предположить направление смещения. Наблюдение за изменениями температуры и их изучение в процессе трансформирования механизма повышения температуры на чувствительных отрезках разломов имеют большое значение в плане раннего выявления предвестников неустойчивого смещения по активным разломам

ЭКСПЕРИМЕНТАЛЬНОЕ ИССЛЕДОВАНИЕ ДЕФОРМАЦИОННОГО ПРОЦЕССА НА РАЗЛОМЕ В МЕТАСТАБИЛЬНОМ СОСТОЯНИИ ПЕРЕД ЗЕМЛЕТРЯСЕНИЕМ

According to the steady state of fault and energy balance, we provided a new idea to observe the precursors for a stressed fault. The meta-instability (or sub-instability) state of a fault is defined as the transition phase from peak stress to critical stress of fast instability (earthquake generation) during a full period of slow loading and fast unloading. The accumulative deformation energy begins to release in this stage. Identifying its deformation before fast instability would be beneficial to obtain premonitory information, and to evaluate the seismic risks of tectonic regions. In this study, we emphasized to analyze deformation process of the meta-instable stage with stain tensor data from a straight precut fault in granite at a slow loading rate, and observed the tempo-spatial features during the full deformation process of the fault. Two types of tectonic zones and instabilities occur on the stick-slip fault. The low- and high-value segments in the volume strain component appear along the fault strike with a load increment. The former first weakens and then becomes initial energy release segments; the latter forms strong stress-interlocking areas and finally turns into the initial region of fast instability. And there are two stages in the entire instable process of the fault: the initial stage is associated with the release of the low volume strain segments, which means fault pre-slips, slow earthquakes or weak earthquakes. The second one characterizes a strong earthquake through the release of high volume strain parts. The rupture acceleration in the first stage promotes the generation of the second. Moreover, fault instability contains two types of strain adjustments along the fault: the front-like strain change along the transition segments from low- to high- strain portions with volume strain release, and the compressive strain pulse of fault instability after the volume strain release extends to a certain range with loading increment. In laboratory experiments, the front-type strain occurs about 12 seconds before fast fault instability; the compressive pulse initiates within less than 0.1 second, and then the fault turns quickly into a dynamic strain adjustment, which appears quasi-synchronously between different measurement points, and, finally, an earthquake is generated.Предлагается новый подход к выделению предвестников землетрясения в зоне разлома с высоким уровнем напряжений, опирающийся на понятия его устойчивого состояния и энергетического баланса. В условиях экспериментального воспроизведения модели прерывистого «stick-slip» в пределах полного цикла медленной нагрузки и быстрой разгрузки деформируемого образца с разрезом, имитирующим разлом, предельные состояния его метастабильности и метанестабильности при пиковом критическом напряжении определяются как переходная фаза от устойчивости к неустойчивости со спонтанной генерацией импульсной подвижки (т.е. генерации землетрясения). С переходом модельного разлома в состояние метанестабильности стартует процесс медленного, пространственно-дискретного, избирательного высвобождения накопленных на нем напряжений. Выявление этого процесса до его перехода в стадию быстрой нестабильности имеет важное прогнозное значение для превентивной оценки риска в тектонически активных регионах. В выполненном авторами экспериментальном исследовании проанализированы вариации тензора напряжений в нагруженном гранитном образце с прямолинейным разрезом в течение метанестабильной стадии, а также проведено наблюдение пространственно-временных особенностей этого параметра в течение всего процесса деформации модельного разлома.Установлено, что по простиранию разлома имеют место сегменты с низкими и высокими значениями объемной деформации, которым соответствуют два типа нестабильности. Первые закладываются на участках с пониженной прочностью и становятся сегментами начального высвобождения энергии в начальную стадию нестабильности. Вторые, наоборот, характерны для участков упрочнения разлома, где происходит блокировка напряжений, и впоследствии превращаются в начальные области быстрой нестабильности.В рамках процесса нестабильности разлома выделены две стадии. В первую стадию происходит реализация небольших медленных сдвиговых смещений на разломе в пределах сегментов первого типа, именуемых в литературе предсмещениями, низкочастотными, медленными или тихими землетрясениями и т.д. Сегментация развивается с ускорением, что способствует переходу деформационного процесса во вторую стадию, когда происходит быстрое динамической объединение сегментов обоих типов с реализацией большого смещения по разлому, что соответствует сильному землетрясению в природе.В условиях нестабильности разлома зафиксированы два типа деформации вдоль его простирания: фронтальная миграция деформации вдоль сегментов первого типа при смещениях по ним к сегментам второго и импульс деформации сжатия после реализации объемной деформации после смещения, распространяющийся на определенное расстояние в условиях роста приложенной к образцу нагрузки. В выполненных экспериментах фронтальная деформация возникала примерно за 12 с до быстрой нестабильности разлома, а импульс сжатия начинается менее чем за 0,1 с до неё. Динамическая деформация на разломе проявляется квазисинхронно по простиранию разлома во всех точках измерения

Current Mathematical Methods Used in QSAR/QSPR Studies

This paper gives an overview of the mathematical methods currently used in quantitative structure-activity/property relationship (QASR/QSPR) studies. Recently, the mathematical methods applied to the regression of QASR/QSPR models are developing very fast, and new methods, such as Gene Expression Programming (GEP), Project Pursuit Regression (PPR) and Local Lazy Regression (LLR) have appeared on the QASR/QSPR stage. At the same time, the earlier methods, including Multiple Linear Regression (MLR), Partial Least Squares (PLS), Neural Networks (NN), Support Vector Machine (SVM) and so on, are being upgraded to improve their performance in QASR/QSPR studies. These new and upgraded methods and algorithms are described in detail, and their advantages and disadvantages are evaluated and discussed, to show their application potential in QASR/QSPR studies in the future

Experimental verification and improvement of heat transfer tube local wall temperature measurement method

To ensure the measuring accuracy of the wall temperature, the outer wall temperature measurement values by using three kinds of thermocouple welding methods were analyzed and evaluated in the paper, including single-point flush-mounted in the wall groove method, single-point insert-mounted in the wall groove, and outer surface direct welding method, based on the application of a tube-in-tube condensing heat exchanger. And the impacts of silver, tin, and thermal resistance adhesive as filling materials on wall temperature measurement were also investigated, and the results were compared to that obtained without filling materials. The results showed that the wall temperatures measured by the three welding methods were lower than the theoretically calculated value. And the wall temperature measured by the outer surface direct welding method was lowest under the same experimental conditions. The wall temperatures measured by single-point flush-mounted and insert-mounted in the wall groove methods were also affected by different welding filling materials. It was found that the greater the thermal resistance of filling materials, the smaller the heat loss. By analyzing the reasons for the low measured value of wall temperature, a new wall temperature measurement method was developed to improve the accuracy of the current measurement method. Meanwhile, the outer wall temperature measurement experiments of vertical and horizontal heat transfer tubes were carried out to validate and calibrate the improved outer wall temperature measurement method. The results showed that the average outer wall temperature deviation measured by the improved wall temperature measurement method ranged from −0.82% to +2.29% for vertical tubes and −4.75% to −1.44% for horizontal tubes, and the improved measurement method had good measurement accuracy

EXPERIMENTAL STUDY OF THERMAL AND STRAIN FIELDS DURING DEFORMATION OF EN ENCHELON FAULTS AND ITS GEOLOGICAL IMPLICATIONS

The article presents results of experimental studies using a bi-axial servo-control system to apply load on samples with extensional and compressional en echelon faults. During the experiments, variations of temperature and thermal images were recorded synchronously by a multi-path contact-type thermometric apparatus and a thermal image system, respectively. A digital CCD camera was employed to synchronously collect images of specimens’ surfaces. The digital speckle correlation method (DSCM) was utilized to analyze the images and to define displacements and strain fields. Our experimental results show that temperature fields have clear responses to opposite stress states in the jog areas of both types of the en echelon faults. Prior to failure of the jog area, its temperature is the highest at the compressional en echelon faults and the lowest at the extensional en echelon faults. Records by DSCM give evidence that mean strain of the jog area is the highest at compressional en echelon faults and the lowest at the extensional en echelon faults. It is revealed that deformation of the en echelon faults occurs in two stages, developing from stress build-up and fault propagation in the jog area to unstable sliding along the fault. Correspondingly, the mechanism of heating-up converts from strain heating into friction heating. During the period of transformation of the temperature rising mechanism, three events are observed in the jog area and its vicinity. Analyses of our experimental results demonstrate that variations of temperatures in the jog area can be indicative of fault sliding and suggest sliding directions. Observations and studies of temperature changes during transformation of the temperature rising mechanism at sensitive portions of faults are of great importance for early detection of precursors of unstable slip on active faults

Multifeature Fusion Vehicle Detection Algorithm Based on Choquet Integral

Vision-based multivehicle detection plays an important role in Forward Collision Warning Systems (FCWS) and Blind Spot Detection Systems (BSDS). The performance of these systems depends on the real-time capability, accuracy, and robustness of vehicle detection methods. To improve the accuracy of vehicle detection algorithm, we propose a multifeature fusion vehicle detection algorithm based on Choquet integral. This algorithm divides the vehicle detection problem into two phases: feature similarity measure and multifeature fusion. In the feature similarity measure phase, we first propose a taillight-based vehicle detection method, and then vehicle taillight feature similarity measure is defined. Second, combining with the definition of Choquet integral, the vehicle symmetry similarity measure and the HOG + AdaBoost feature similarity measure are defined. Finally, these three features are fused together by Choquet integral. Being evaluated on public test collections and our own test images, the experimental results show that our method has achieved effective and robust multivehicle detection in complicated environments. Our method can not only improve the detection rate but also reduce the false alarm rate, which meets the engineering requirements of Advanced Driving Assistance Systems (ADAS)

Spatial-temporal variation of the land surface temperature field and present-day tectonic activity

This study attempts to acquire information on tectonic activity in western China from land surface temperature (LST) field data. On the basis of the established relationship between heat and strain, we analyzed the LST distribution in western China using the satellite data product MODIS/Terra. Our results show that: 1. There are departures from annual changes of LST in some areas, and that these changes are associated with the activity of some active tectonic zones. 2. When annual-change background values caused by climate factors are removed, the long-period component (LSTLOW) of temperature residual (ΔT) of the LST is able to serve as an indicator for tectonic activity. We have found that a major earthquake can produce different effects on the LST fields of surrounding areas. These effects are characterized by both rises and drops in temperature. For example, there was a noteworthy temperature decline associated with the Sumatran M9 earthquake of 2004 in the Bayan Har-Songpan block of central Tibetan Plateau. 3. On the other hand, the LST field of a single area may respond differently to major shocks occurring in different areas in the regions surrounding China. For instance, the Kunlun M 8.1 event made the LST on the Longmen Mountains fault zone increase, whereas the Zaisan Lake M 7.9 quake of 2003, and the Sumatran M 9 event of 2004, caused decreases in the same area’s LST. 4. The variations of land surface temperature (LST) over time are different in different tectonic areas. These phenomena may provide clues for the study of tectonic deformation processes. On the basis of these phenomena, we use a combination of temperature data obtained at varied depths, regional seismicity and strain results obtained with GPS measurements, to test the information related to tectonic activity derived from variations of the LST field, and discuss its implications to the creation of models of regional tectonic deformation

Salient Region Detection Using Diffusion Process with Nonlocal Connections

Diffusion-based salient region detection methods have gained great popularity. In most diffusion-based methods, the saliency values are ranked on 2-layer neighborhood graph by connecting each node to its neighboring nodes and the nodes sharing common boundaries with its neighboring nodes. However, only considering the local relevance between neighbors, the salient region may be heterogeneous and even wrongly suppressed, especially when the features of salient object are diverse. In order to address the issue, we present an effective saliency detection method using diffusing process on the graph with nonlocal connections. First, a saliency-biased Gaussian model is used to refine the saliency map based on the compactness cue, and then, the saliency information of compactness is diffused on 2-layer sparse graph with nonlocal connections. Second, we obtain the contrast of each superpixel by restricting the reference region to the background. Similarly, a saliency-biased Gaussian refinement model is generated and the saliency information based on the uniqueness cue is propagated on the 2-layer sparse graph. We linearly integrate the initial saliency maps based on the compactness and uniqueness cues due to the complementarity to each other. Finally, to obtain a highlighted and homogeneous saliency map, a single-layer updating and multi-layer integrating scheme is presented. Comprehensive experiments on four benchmark datasets demonstrate that the proposed method performs better in terms of various evaluation metrics