44 results about "Coverage density" patented technology

The invention relates to a high-density rapid detection method based on z-component transmitting channel waves. The method is achieved by the following steps: (1) collecting data; (2) processing the data by firstly setting an observation system (that is, inputting shots and receiver points coordinates), collecting z-component channel waves by the observation system, and then performing channel wave data analysis, bandpass filtering and imaging in sequence; (3) interpreting the data by comprehensively judging chasms, falling columns and other geological abnormal developmental conditions in the working face based on the combination of the imaging result and the geological data disclosed by the working face laneway, and making an integrated interpretation map of the geological structure in the working face. The method greatly increases the work efficiency, allows the construction of the wide-span working face (more than 1000 m) to be completed within 8 hours, collects the Z-component channel wave signals at the same time by the measurement points which are arranged on the laneway lateral walls, increases the ray coverage density, collects the information as much as possible, and improves the detection precision.

The invention relates to a supporting membrane of a transmission electron microscope sample and a manufacturing method for the transmission electron microscope sample. The supporting membrane of the transmission electron microscope sample consists of a porous micro-gate supporting membrane substrate and a single-layer graphene oxide film which covers the substrate, wherein the coverage density ofthe single-layer graphene oxide film on porous micro-gate is 0.7*10<-6>-14*10<-6> mg / mm<2>, 0.7*10<-6>-3.5*10<-6> mg / mm<2> preferably. The single-layer graphene oxide film can serve as a carrying membrane of the transmission electron microscope sample to manufacture the transmission electron microscope sample. The invention has the advantages that: the novel supporting membrane of the transmission electron microscope sample is designed and prepared; compared with the conventional carbon supporting membrane, the supporting membrane is smaller in thickness, stronger in mechanism strength and better in material dispersion effect; and the supporting membrane is used for carrying a material which is observed by a transmission electron microscope, so that higher resolution and higher definitioncan be obtained.

The present invention discloses a composite generation method based on information system testing for coverage density, which adopts a framework (as shown) that: (1) input parameters and parameter values of information system to be tested are described through XML files according to the specification of the tested system; (2) the testing use cases needed to appear and the testing use cases which cannot appear through combination in pairs are assigned; (3) the values of all the input parameters are combined one by one on the basis of coverage density so as to generate a testing use case; (4) the testing use case finally generated is expressed and output in the format of the XML files. The composite generation method can be widely applied to embedded system testing, distributed system testing, web page testing, graphical interface testing, protocol testing, configuration and compatibility testing, etc., is easy to append constraints among the parameters and consider the parameter combinations needed to be covered, is easy to consider the priority among the parameters, is simple and effective in the calculation method of coverage density, and has good expansibility.

The invention provides a preparation method of a nano ferroferric oxide loaded graphene compound, and relates to a preparation method of a nano ferroferric oxide loaded graphene compound having high dispersity, large coverage density and controllable particle size. The preparation method comprises the following steps: preparing a 5-15 mg / mL mixed stock solution of sodium hydroxide and diethylene glycol; then preparing a 0.5-3.5 mg / mL mixed solution of graphene oxide and diethylene glycol; and taking the mixed stock solution of sodium hydroxide and diethylene glycol, and then quickly adding into the mixed solution to obtain the nano ferroferric oxide loaded graphene compound. The nano ferroferric oxide loaded graphene compound prepared by the method has the advantages of pure ferroferric oxide crystalline phase, small size, no aggregation and high coverage rate. Thus, the compound has wide application prospects in the aspects such as magnetic separation, biological medical treatment, electromagnetic materials and the like.

The invention discloses a fingerprint locating method and server. An establishing stage and an updating stage of a fingerprint database are carried out simultaneously, and the problem that a traditional fingerprint locating method firstly and manually establishes a fingerprint database to consume a lot of labor and materials and be small in coverage density and unchanged in fingerprint database is solved. In actual engineering application, the fingerprint database is automatically established and continuously updated automatically to keep pace with the environmental change, so that resources are saved, and the locating accuracy is improved. The fingerprint database is in a steady state finally and can further slowly adapt to the environmental change. In statistical time, the locating accuracy of the fingerprint locating method and server is stable, the fingerprint locating method and server is better than a traditional locating algorithm, and the divergence of the locating accuracy of the traditional locating algorithm on the same point in different moments is reduced.

Deposition of nanoparticles onto carbon surfaces is described. Metal and / or metal oxide ions are deposited on a carbon surface by electrodeposition, such as by immersing a carbon and an anode in a salt bath, and applying a number of electrical pulses having a defined pulse width. The size, coverage density, and metallic composition of the nanoparticles may be affected by the pulse width of the electrical pulses, the number of electrical pulses, and the chemical composition of the salt bath, respectively. The carbon may be anodized before electrodeposition. If the carbon is a carbon precursor, after electrodeposition, the carbon precursor is carbonized to form a carbon. After electrodeposition, the carbon may be activated to form an activated carbon. The nanoparticles may serve as catalysts for activation rugosity of mesoporous carbons. The catalytically activated carbon materials may be used in all manner of devices that contain carbon materials.

The invention discloses a steel shell of an alkaline zinc-manganese dioxide cell. The steel shell of the alkaline zinc-manganese dioxide cell comprises a current collector steel shell, wherein the inner wall of the current collector steel shell is coated with a graphene-modified conductive coating, and the thickness of the conductive coating is 0.01 microns to 20 microns. The coverage density and the adhesive property between the conductive coating and the inner surface of the steel shell are improved; the radial resistance of a cell and the interface resistance between an anodal ring and the steel shell are reduced; by using the steel shell of the alkaline zinc-manganese dioxide cell, the high-current discharge performance of the alkaline zinc-manganese dioxide cell is further improved.

The invention relates to positioning data based mobile police service management, and particularly relates to a positioning data based service line patrol assessment method. The positioning data based service line patrol assessment method comprises buffer area establishment and segmentation of a line patrol path, mapping of positioning data, interpolation compensation of the positioning data and restoration compensation of the line patrol path; the line patrol path forms a grid through establishing and segmenting a buffer area, the positioning data is mapped to the grid according to the spatial position and distance, labeling is performed on the grid, data coverage of the grid is compensated in an interpolation manner so as to form relatively complete grid data mapping, and finally a line patrol path is fitted through the grid. The method provided by the invention emphatically solves a problem of positioning data based multi-vehicle line patrol attendance matching in service management, problems of positioning data line matching of multiple vehicles on multiple lines, insufficient positioning data coverage density, loss of positioning data and the like exist when attendance checking is performed on service patrolling through the positioning data, and the problems are solved through data buffering for the line patrol path and compensation for positioning data coverage.

The invention discloses a dynamic brain functional magnetic resonance imaging method and system. The method includes the steps that high-time low-space-resolution navigation data S<NAV> and high-space low-time-resolution dynamic image data S are collected in (k,t) space; the navigation data S<NAV> are decomposed through singular values to obtain a model order L and a time primary function phi[l](t), and Tikhonov regularization constraint is conducted by combining with the image data S to solve a space primary function cl(k); interpolation recovery with the high-time high-space coverage density is conducted on the (k,t) space through the model order L, the time primary function phi[l](t) and the space primary function cl(k), Fourier inversion is then conducted, and therefore a high-time-resolution and high-space-resolution dynamic brain function magnetic resonance image is obtained. By means of the method and the system, quality of the reconstructed image is improved, and meanwhile the high-time-resolution and high-space-resolution dynamic brain function magnetic resonance image is obtained.

The invention relates to an ultra-sensitive SERS substrate and a preparation method thereof. A superstrong plasma coupling effect is produced while the Cu nanometer particles are separated from a Cu film by use of graphene, so that the sensitivity of the SERS based on copper can be obviously promoted. By use of full copper material, the cost of the structure is greatly lowered. The Cu nanometer particles are directly paved on the Cu film growth with graphene on the surface by virtue of a chemical vapor deposition (CVD) method in the preparation process, and the complex graphene transferring process is omitted. Furthermore, the coverage density of the Cu nanometer particles of the structure is adjustable, and sandwich structure substrates with different Cu nanometer particles coverage densities can be obtained after the Cu film is soaked in the acetone for a certain time. The preparation method is convenient and fast.

Disclosed are an apparatus and a method for non-contact sample analysis using terahertz waves. The apparatus includes an emission unit radiating terahertz waves onto a sample provided with a conductive material layer, and a receiving unit receiving terahertz waves reflected from the sample or terahertz waves passing through the sample. The apparatus further includes a characteristic analysis unit including at least one selected from a group consisting of a sheet resistance analysis unit analyzing a sheet resistance of the conductive material layer, a coverage density analysis unit analyzing a coverage density of the conductive material layer, a component analysis unit analyzing a component of the conductive material layer, and a thickness analysis unit analyzing a thickness of the conductive material layer by using the received terahertz waves, a display unit displaying a result derived from the characteristic analysis unit as an image, and an input unit configured to input information to the characteristic analysis unit.

The invention relates to a user perception based wireless network optimization method and a user perception based wireless network optimization system. The user perception based wireless network optimization method includes that user terminal devices acquire signals in the locations of user terminals, perform quality analysis on the signals and send request messages to satellite equipment when signal quality is lower than a set threshold value; the satellite equipment locates the user terminals and sends location information of the user terminals to the corresponding user terminal devices; the user terminal devices send the location information and signal quality parameters of the user terminals to wireless access points; the wireless access points forward the information sent by the user terminal devices to a data analysis platform; the data analysis platform performs storage analysis on the information sent by the wireless access points, analyzes the stored information statistically, judges that one specific wireless access point with problems or access point coverage density in a region is insufficient if the wireless access point is poor in signal quality within a coverage range, and informs network optimization personnel of further troubleshooting the device and the region with problems.

The invention provides a method and apparatus for acquiring a multi-mode positioning fingerprint database. The method includes the steps of S1, dividing a positioning area by using a first granularity to acquire initial grids; and S2, performing, according to a determination result of whether non-cellular access points exist in the initial grids, corresponding processing on the initial grids to obtain second-level grids. The corresponding operation is performed by determining whether the non-cellular access points exist in the grids, the grid division granularity can be dynamically adjusted according to the signal density in an area to be positioned so that the quantization noise of the positioning grids is in proportion to the signal coverage density of the grids, and the multi-mode positioning fingerprint database is high in accuracy and low in cost of operation and maintenance at the same time.

The present invention relates to a metallic cable, which comprises a cable core and a metal cladding around the cable core, wherein, the metal cladding is in an arc interlock buckled armor structure. Metallic cables in such a structure have greatly improved flexural property and can be laid smoothly; in addition, one or more cable cores can be combined into a cable as required for power transmission, control system, signal transmission, or illumination circuit, etc., and metal cladding can be added around the cable in an arc interlock buckled form to serve as a protective sheath and an earthing system for the cable to increase safety margin and protect the cable cores well; in addition, the coverage density of the metal cladding can be up to 100 percent, and therefore the shielding effect is more outstanding. The metal cable in the present invention is simple and practical in structure, and can be widely used especially in the building industry.

The invention relates to a catalyst element for a recombinator for eliminating hydrogen from accident atmospheres, in which the technical problem of continuously efficiently converting both small and large amounts of hydrogen with the atmospheric air-oxygen present in the safety containers within a broad concentration range, and routing away the reaction heat arising in the process to such an extent that the respective ignition temperature is not reached in the present mixture is resolved by having the catalyst element exhibit a flat basic body (2), which is arranged within the area of flow through the recombinator, wherein the surface of the basic body (2) over which the accident atmosphere flows has a varying coverage density with catalyst material (3).

The invention discloses an electroencephalogram relaxing degree identifying method and an electroencephalogram relaxing degree identifying device based on frequency domain and phase space. The electroencephalogram relaxing degree identifying method comprises the following steps: acquiring electroencephalogram sequence signals to be processed, and carrying out extracting to obtain signal waves; calculating the energy of the signal waves, calculating the frequency mean square root of the signal waves according to the energy of the signal waves and brain waves, thus obtaining the characteristic quantity in the frequency domain space; according to the signal waves and the electroencephalogram sequence signals to be processed, forming a two-dimensional chart containing the signals, and counting the signal coverage density on each two-dimensional chart, thus obtaining the characteristic quantity in the phase space; and classifying the characteristic quantity in the phase space and the characteristic quantity in the frequency domain space of the electroencephalogram sequence signals to be processed by adopting a pre-trained classifier, and carrying out identification according to the classifying result, thus obtaining the electroencephalogram relaxing degree. With the method and the device, the characteristics in different angles of each brain wave can be comprehensively extracted, and thus the accurate identification for the electroencephalogram relaxing degree is realized.

A recovery and replacement-based coverage hole elimination method comprises the following steps of (1) calculating the coverage degree, energy coverage density, hole number, and redundant node number by using a grid method after the random deployment of N nodes; (2) calculating the number of nodes carried by a mobile robot; (3) calculating recovery and replacement paths for the mobile robot according to the principle that the redundant node closest to the certain hole is used to patch the hole; (4) enabling the robot to conduct the recovering and replacing of the nodes; (5) charging the recovered nodes immediately after the moved nodes come back to an energy station and charging the moved nodes; and (6) getting back to the step (2) and retriggering the recovering and replacing of the nodes.

The invention discloses an electroencephalogram relaxation degree identification method based on the time domain and the phase space. The method comprises the steps that an original electroencephalogram signal is cut into slices, the to-be-processed sequence signals of electroencephalogram are generated; signal waves are extracted from the to-be-processed sequence signals of the electroencephalogram; energy parameters of the signal wave are calculated, based on the maximum value of the energy parameters and the rate of change ratios of the equipotential energy parameters of the brainwave, the characteristic quantity in the time domain space for the to-be-processed sequence signals of the electroencephalogram is obtained; according to the signal wave and the to-be-processed sequence signals of the electroencephalogram, a two-dimensional chart containing signals is formed, and the signal coverage density on the two-dimensional chart is statistically measured, the phase-space characteristic quantity of the sequence signals of the electroencephalogram is obtained; classifications and identifications are carried out according to the characteristic quantity in the time domain and the characteristic quantity in the phase space, and the relaxation degree of the electroencephalogram is obtained. The invention also provides an electroencephalogram relaxation identification device based on the time domain and the phase space, the characteristics at different angles of each brain wave can be fully extracted, so that the accurate identification of the relaxation degree of the electroencephalogram is achieved.

A method for producing a sinter layer connection between a substrate and a chip resulting in an electric and thermal connection therebetween and in reduced mechanical tensions within the chip. The method produces a sinter layer by applying a multitude of sinter elements of a base material forming the sinter layer in structured manner on a contact area of a main surface of a substrate; placing a chip to be joined to the substrate on the sinter elements; and heating and compressing the sinter elements to produce a structured sinter layer connecting the substrate and chip and extending within the contact area, the surface coverage density of the sinter elements on the substrate in a center region of the contact area being greater than the surface coverage density of the sinter elements in an edge region of the contact area, and at least one through channel, extending laterally as to the substrate's main surface being provided towards the contact area's edge. A large-area sinter element is situated in the contact area's center region, and circular sinter elements is situated in a contact area edge region. The sinter elements may also have notches. Also described is a related device.

The invention discloses a big data method and device for intelligent prediction of criminal events. The method comprises steps: according to historical criminal events in a preset historical time period of a preset area, a deep learning algorithm is used to predict source criminal events and the number; the position parameters of a first subarea and the number of source criminal events are substituted into a pre-established normal distribution function, and the density contribution of the source criminal events in the first subarea is acquired; the total number of historical criminal events issubstituted into the pre-established normal distribution function, the density contribution of aftershock criminal events in the first subarea is acquired; and according to the density contribution of the source criminal events in the first subarea and the density contribution of aftershock criminal events in the first subarea, the criminal event coverage density of the first subarea is determined. Through the above mode, the method and the device can be applied to conditions of multiple centers and complex social community layout in domestic cities and can predict the criminal events in different domestic areas more accurately.

The invention provides an InSAR time sequence surface deformation monitoring method based on a surface stress-strain model, and the method comprises the steps: 1, collecting a time sequence SAR imagecovering a to-be-monitored region, achieving the registration and differential interference of the time sequence SAR image based on existing software, and generating an interferogram meeting a presettime-space baseline threshold value; and 2, constructing a local Delaunay triangulation network based on all pixel points in the interferogram. According to the invention, the surface stress-strain model is used to describe a physical and mechanical relationship between surface adjacent point deformations; the precision of InSAR time sequence earth surface deformation monitoring can be obviously improved; modeling and parameter solving are carried out on the basis of an arc section formed by adjacent points, an interference pattern does not need to be unwound, the InSAR data processing efficiency can be effectively improved, and the physical and mechanical relationship of the observation data in space is considered, so that a high-precision InSAR deformation monitoring result with large space coverage density can be obtained without masking a low-coherence region in the interference pattern.

The invention discloses an image capture-based image capture push system for door curtains. The image capture push system comprises at least one hanging mechanism, a sliding rail, sliding blocks, an image capture unit, an image analysis unit, a control unit and linear motors, wherein the image capture unit is arranged on a door frame, and is used for capturing a human body entering the induction area of the door frame and generating an image signal; the image analysis unit is used for analyzing to obtain the coverage density of the human body in an image; the control unit is used for calculating the coverage density of the human body in the image to obtain the width value of the human body in the image, working out a width value to which door curtain bodies on the door frame need to be pushed, and converting the width value into a drive signal for controlling the motion of each motor and outputting the drive signal; the linear motors are respectively and fixedly arranged on the sliding blocks; each linear motor is used for driving the corresponding the sliding block according to the drive signal to do linear motion in the sliding rail so as to push the door curtain bodies on the hanging mechanism, and the stagger width between the door curtain bodies is driven to reach the width value to which the door curtain bodies need to be pushed. The image capture-based image capture push system disclosed by the invention automatically detects and calculates the width value to which the door curtains need to be pushed, and is more automatic and intelligent, and is capable of conveniently providing a pedestrian path.

The present invention discloses a method and a device dedicated for removing the SO2 pollutant in the flue gas. The method makes the limestone slurry drop into fine mist and electrifies the mist by electrostatic spraying mode, mixes the mist with the flue gas containing SO2 in opposite flow direction for reaction, absorbs the SO2 of the flue gas into liquid phase, and oxidizes the liquid phase desulfurization product to gypsum by blowing air. The device is provided with two parts, wherein the upper part is a slurry washing and absorbing region and the lower part is an air agitating and oxidizing region. The method adopts electrostatic spraying mode, is good in mist droplet dispersibility and high in coverage density, thereby strengthening the gas-liquid mass transfer of the desulfurization and improving the desulfurization efficiency. The invention realizes the electrostatic spraying, SO2 absorption and product oxidization in one reactor, not only realizes high efficiency for removing SO2 pollutant, but also effectively prevents secondary pollution.

The invention discloses a door curtain automatic control pushing device based on image collection. The door curtain automatic control pushing device comprises a plurality of hanging mechanisms, and further comprises a sliding rail, sliding blocks and a pushing mechanism; the pushing mechanism comprises an image sensor, an image analyzer, a controller and linear motors corresponding to the sliding blocks in number; the image sensor conducts collection on the human body entering a door frame sensing area and generates image signals; the image signals are analyzed through the image analyzer to obtain the coverage density of the human body in an image; the controller conducts calculation on the coverage density of the human body in the image to obtain a width value of the human body in the image; a needed push-open width value of door curtain bodies on a door frame is calculated to be converted into driving signals for outputting; and the linear motors push the sliding blocks to perform linear motion in the sliding rail according to the driving signals so that the staggered width between door curtain bodies can achieve the needed push-open width value. By means of the door curtain automatic control pushing device, the needed push-open width value of the door curtain is automatically detected and calculated; automation and intelligence are achieved; and pedestrian paths can be conveniently achieved.

The invention discloses a self-adaptive setting method and a self-adaptive setting device of a network-access searching time interval of a multi-mode multi-standby handheld mobile terminal device, which aims at solving the problems of the prior art that shortage of self-adaptive setting time of the network searching waiting time interval for different types of wireless access technologies leads to the bad user experience. The self-adaptive setting device of the network-access searching time interval of the multi-mode multi-standby handheld mobile terminal device comprises a searching waiting time calculator, a speed measuring module, a coverage density parameter calculator which is provided with a service parameter database, an access remote access Trojan (RAT) searching execution module and an RAT analysis module, wherein the output end of the speed measuring module and the output end of the coverage density parameter calculator are connected with the searching waiting time calculator, the input end of the access RAT searching execution module is connected with the searching waiting time calculator, and the output end of the RAT analysis module is connected with the coverage density parameter calculator. The self-adaptive setting device is simple in structure, complete in functions and high in practical value and popularization value.

The method discloses a method for extracting an elevation of a height measuring foot point through CryoSat-2 SARIn mode L1b level waveform data. The method comprises the following steps of 1) extracting echo coherence and differential phase information from the CryoSat-2 SARIn mode L1b level data; 2) carrying out smoothing processing on echo coherence and differential phase data; 3) carrying out threshold segmentation according to echo coherence, and taking an area where the coherence is greater than a threshold as an alternative area; 4) merging the alternative areas to obtain an effective differential phase to be unwrapped; 5) carrying out relative phase unwrapping in a time delay direction; 6) calculating an three-dimensional coordinate of an elevation point through a differential phase;7) converting a reference coordinate system; and 8) carrying out absolute phase unwrapping based on an external DEM. In the invention, a high-precision height measuring foot point elevation can be obtained from L1b level data; compared with L2 level data released by ESA, there is a larger foot point coverage density, and the digital elevation model with a higher resolution can be acquired to obtain a finer terrain.

The present invention discloses a multi-stage grid line solar cell, which comprises a solar cell. The front surface of the solar cell is provided with a first-level electrode and a second-level electrode, wherein the first-level electrode and the second-level electrode are vertically arranged in the staggered manner. The first-level electrode or the second-level electrode is provided with a vertical third-level electrode. The width of the third-level electrode is smaller than the width of the first-level electrode and the width of the second-level electrode. The density of the third-level electrode is larger than the density of the first-level electrode and the density of the second-level electrode. According to the multi-stage grid line solar cell, on the basis of two-level electrodes, a thinner third-level electrode is additionally arranged, so that the electrode coverage density is improved. The collection of a fine current is improved and the fine current is finally converged to figure and busbar electrodes. Therefore, on the condition that the current electrode total area remains substantially constant, the line width, the number of the electrode wire coverage density for each electrode at each of different levels are optimized. The current collection capability is improved.

The invention discloses an intelligent bus station based on pressure detection. The intelligent bus station includes a station body, and also includes a detection mechanism that includes a power supply, N pressure sensors, a signal collector, a controller and a wireless transmitter, wherein N is a natural number more than 1; the base plate of the station body is divided into N areas, and one pressure sensor is arranged in each area; the N pressure sensor constitutes a pressure sensing array and is connected to the signal collector; the signal collector is sequentially connected to the controller and the wireless transmitter; the stress of each area is sensed by the pressure sensor, and signals are input into the controller after being collected by the signal collector; the controller generates an image about stress distribution situation of the pressure sensing array and obtains the coverage density value of the image; the wireless transmitter sends the obtained coverage density value of the image to an external server. The intelligent bus station based on pressure detection can detect accurately and sensitively, has the functions of automatic detecting and transmitting, and is intelligent.

The invention discloses a bus stop monitoring system based on pressure detection. The bus stop monitoring system comprises a pressure sensing array, a signal collection unit, a control unit, a data transmitting unit and a server. The signal collection unit is used for controlling the pressure sensing array to collect signals and transmitting the collected signals. The control unit comprises an image generation module, an image analysis module and an execution module. The image generation module is used for receiving the collected signals and generating images of the stress distribution condition of the pressure sensing array. The image analysis module is used for analyzing the images and obtaining the coverage density value of the images. The execution module is used for outputting the coverage density value of the images to the data transmission unit. The data transmission unit is used for sending the coverage density value of the received images to the server. The server is used for receiving the coverage density value of the images and obtaining the distribution condition of waiting passengers of a bus stop. The bus stop monitoring system can conduct detection sensitively, has automatic detection and transmission functions and brings convenience to management of a whole bus system.

The invention discloses a geological disaster automatic monitoring device and method of a surface stay cable force measurement type, and relates to the field of geological disaster monitoring. The device comprises a remote monitoring end and at least one tension testing units. Each tension testing unit comprises one fixed pile and at least one tension net, wherein each tension net comprises a main force-bearing stay cable, n branch stay cables and n preset monitoring point anchor piles. The method comprises the steps: setting the device on a to-be-monitored slope A, obtaining and recording the basic monitoring value of each force measurement sensor on any one tension net A on the to-be-monitored slope A, and judging whether landslide happens to the to-be-monitored slope A or not through the changes of all force measurement sensors on the device. According to the invention, the device can achieve the direct monitoring of the tendency of the potential energy of a landslide mass through the stay cable force measurement type, is simple and convenient in implementation, is low in cost, is high in coverage density of regional monitoring points, and can find the symptom of landslide early.