A distributed acoustic system may comprise an interrogator which includes a single photon detector, an umbilical line comprising a first fiber optic cable and a second fiber optic cable attached at one end to the interrogator, and a downhole fiber attached to the umbilical line at the end opposite the interrogator. A method for optimizing a sampling frequency may comprise identifying a length of a fiber optic cable connected to an interrogator, identifying one or more regions on the fiber optic cable in which a backscatter is received, and optimizing a sampling frequency of a distributed acoustic system by identifying a minimum time interval that is between an emission of a light pulse such that at no point in time the backscatter arrives back at the interrogator that corresponds to more than one spatial location along a sensing portion of the fiber optic cable.

Provided is a method for manufacturing a grain-oriented electrical steel sheet. The method comprises: hot rolling a slab to obtain a hot rolled sheet; subjecting the hot rolled sheet to hot band annealing as necessary; subjecting the hot rolled sheet to cold rolling; subjecting the cold rolled sheet to decarburization annealing; applying an annealing separator having MgO as a main component onto a surface of the decarburization annealed sheet and subjecting the decarburization annealed sheet to final annealing to form the forsterite film; and applying an insulating coating treatment liquid onto the final annealed sheet and subjecting the final annealed sheet to flattening annealing to form a tension-applying insulating coating. A difference in total tensions between one and opposite surfaces of the sheet is less than 0.5 MPa. A difference in tensions between the forsterite films in one and opposite surfaces of the sheet is 0.5 MPa or more.

Provided is a method for manufacturing a grain-oriented electrical steel sheet. The method comprises: hot rolling a slab to obtain a hot rolled sheet; subjecting the hot rolled sheet to hot band annealing as necessary; subjecting the hot rolled sheet to cold rolling; subjecting the cold rolled sheet to decarburization annealing; applying an annealing separator having MgO as a main component onto a surface of the decarburization annealed sheet and subjecting the decarburization annealed sheet to final annealing to form the forsterite film; and applying an insulating coating treatment liquid onto the final annealed sheet and subjecting the final annealed sheet to flattening annealing to form a tension-applying insulating coating. A difference in total tensions between one and opposite surfaces of the sheet is less than 0.5 MPa. A difference in tensions between the forsterite films in one and opposite surfaces of the sheet is 0.5 MPa or more.

A device for detecting motion of a surface includes a light source for emitting light, a focusing lens configured to focus the light, and a detector configured to receive the focused light reflected off the surface and to detect motion of a distribution pattern of the reflected light. The motion of the distribution pattern of the reflected light is indicative of the motion of the surface. A conic constant of the focusing lens is in the range from □1.5 to □0.5, and a diameter of the focusing lens is at least 60% of the distance from the focusing lens to a beam waist of the focused light. When the conic constant and the diameter are within the above-mentioned ranges, the device is suitable for handheld apparatuses for free-hand measurements of small motions of surfaces. A handheld apparatus can be for example an apparatus for detecting eye pressure.

A distributed acoustic sensing (DAS) system for determining an acoustic event may include an interferometer and an acoustic event detection processing device. The interferometer may measure DAS data from sensed signals from a sensing fiber deployed in a wellbore. The acoustic event detection processing device may determine an acoustic event in the wellbore from an out-of-band signal using the DAS data by performing operations. The operations can include determining a first acoustic event and a second acoustic event from the DAS data. The operations can include determining a first set of aliased frequencies from the first acoustic event and a second set of aliased frequencies form the second acoustic event. The operations can include determining, using an intersection of the first set of aliased frequencies and the second set of aliased frequencies, a frequency or amplitude of out-of-band signals that are usable to determine the at least one acoustic event.

A non-blind area real-time monitoring and alarming system for an accident on a freeway is provided, which belongs to the field of photoelectric technology and can solve the existing problems in whole journey information monitoring for freeways, such as failure to cover all freeway sections and lack of all-weather and prompt monitoring, and being subject to severe environments such as rain, fog and snow, or conditions such as poor visibility at night. The system includes a distributed sound wave detection fiber-optic cable, a sound wave signal demodulator, a network switch, a workstation, and a monitoring terminal. A fiber-optic sensing network composed of a series of reflection nodes distributed at equal distances is utilized to monitor sound wave signals from traffic accidents efficiently in real time without blind areas, accurately locate a traffic incident by analyzing frequency components, and transmit alarming information in time.

A thermo-fluorescent optical fiber including a core able to propagate light and a sheath, the fiber carrying at least at one of its ends or at one site along its length, devoid of sheath, the optical fiber being provided with a probe consisting of a matrix having thermo-fluorescent particles, the matrix being photo-polymerized. Also provided is a method that relates to manufacturing such an optical fiber as well as to its applications.

A measurement apparatus (100) includes a laser light source (11), a beep splitter (121), an optical path converter (122), and a light reception unit (111). The beep splitter (121) branches laser light emitted from the laser light source (11) into first branch light and second branch light and irradiates a target object (1) with the first branch light. The optical path converter (122) converts a direction of the second branch light to a direction in which a structure (2) is irradiated with the second branch light and irradiates the structure (2) with the second branch light. The light reception unit (111) receives first reflected light obtained in a manner that the first branch light is reflected by the target object (1) and second reflected light obtained in a manner that the second branch light is reflected by the structure (2).

A measurement apparatus (100) includes a laser light source (11), a beep splitter (121), an optical path converter (122), and a light reception unit (111). The beep splitter (121) branches laser light emitted from the laser light source (11) into first branch light and second branch light and irradiates a target object (1) with the first branch light. The optical path converter (122) converts a direction of the second branch light to a direction in which a structure (2) is irradiated with the second branch light and irradiates the structure (2) with the second branch light. The light reception unit (111) receives first reflected light obtained in a manner that the first branch light is reflected by the target object (1) and second reflected light obtained in a manner that the second branch light is reflected by the structure (2).

A voice activation system for a vehicle. The voice activation system for a vehicle which has at least one sound panel capable of providing vibrations of a user's voice from the outside of the vehicle into an inside area of the vehicle. A laser listening device is operably connected to the panel for receiving vibrations from a user's voice. A controller receives a pre-identified command of the user from the laser listener and operates an action in the vehicle in response thereto.