Abstract: A quartz glass provides an opaque quartz glass having high light-shielding property, excellent mechanical strength and excellent cleaning resistance against hydrofluoric acid. By setting the maximum width of the amorphous bubbles existing in the opaque quartz glass to an average of 3 to 15 ?m and the density to 2.15 g/cm3 or more, the mechanical strength after baking and the cleaning resistance by hydrofluoric acid are improved. The opaque quartz glass has a whiteness at a thickness of 10 mm of 75 to 90%, the reflectance of light with a wavelength of 0.24 to 2.6 ?m at a thickness of 4 mm is 60 to 85%, and the bending strength after baking is 95 MPa. In addition, a foaming agent may be mixed in the opaque quartz glass. An opaque quartz glass having cleaning resistance against acid can be obtained.

Abstract: A work estimation device (200) includes a watching region estimation unit (220), an object detection unit (210), a contact degree calculation unit (230), and a work estimation unit (250). The watching region estimation unit (220) estimates a watching region which is a region a user watches, with using information indicating a line of sight of the user. The object detection unit (210) detects, from a video that shows a work object the user is using and at least one target candidate object which is a candidate for a work target of the user, the work object and the at least one target candidate object. The contact degree calculation unit (230) calculates a contact degree indicating a degree of contact between the work object and each target candidate object which is included in the at least one target candidate object, on a basis of the watching region. The work estimation unit (250) estimates work of the user on a basis of the work object and the contact degree.

Abstract: There is provided an elevator rope tension measurement system that can reduce measurement error when the tension of the rope of an elevator is quantitatively measured. An elevator rope tension measurement system includes a vibration waveform collection unit configured to collect a vibration waveform of a rope of an elevator; and a frequency calculation unit configured to select, based on a measurement resolution calculated from a collection time period and a collection cycle for collecting the vibration waveform by the vibration waveform collection unit, a method for calculating a frequency of the vibration waveform collected by the vibration waveform collection unit.

Abstract: There is provided a building facility vibration measurement device that can easily ascertain whether specs are sufficient for measurement of vibration of a building facility. A building facility vibration measurement device includes: an acceleration detection unit configured to detect acceleration; an acceleration collection unit configured to collect the acceleration detected by the acceleration detection unit; an accuracy calculation unit configured to calculate detection accuracy of the acceleration from information on the acceleration collected by the acceleration collection unit; and a judgement unit configured to, based on the detection accuracy calculated by the accuracy calculation unit, judge whether vibration of a building facility can be measured.

Abstract: A voltage control apparatus includes a processor. The processor sets an intermediate voltage output from a first device in a first period to a first voltage, changes the intermediate voltage from the first voltage to a second voltage, returns the second voltage in a second period to the first voltage, detects a first and a second input power of the first device corresponding to the first and the second period, detects a third input power of the first device when the second voltage is output from the first device, when a difference between the first input power and the second input power is equal to or smaller than a threshold value, detects a minimum input power of the first input power and the third input power, and controls the intermediate voltage output by setting the intermediate voltage when the minimum input power is applied to the first device.