Abstract: Proposed is a method in which a server presents content through a chat room. The method may include acquiring information about a keyword or theme of the content, information about a condition for presenting the content, and information about the chat room, wherein the chat room is related to the keyword or theme and a plurality of users are able to participate in the chat room. The method may also include providing the chat room to a user terminal in association with the information about the keyword or theme of the content. The method may further include searching for the content in a content pool based on the keyword or theme, and when the condition for presenting the content is satisfied, presenting at least some items of the searched content to the user terminal through the chat room.

Abstract: An organic light emitting device including: a substrate defining a first pixel region and a second pixel region; and an organic light emitting diode over the substrate. The organic light emitting diode includes a transmissive electrode, a reflective electrode facing the transmissive electrode and an emissive layer disposed between the transmissive electrode and the reflective electrode. The emissive layer includes a first emissive layer and a second emissive layer. The first emissive layer is in the first pixel region and includes: a first blue emitting material layer including a first blue fluorescent compound, and a second blue emitting material layer including a second blue fluorescent compound and a blue phosphorescent compound. The second emissive layer is in the second pixel region and includes: a first green emitting material layer including a first green delayed fluorescent compound, and a second green emitting material layer including a second green delayed fluorescent compound.

Abstract: An organic compound having the following structure of Chemical Formula, and an organic light emitting diode and an organic light emitting display device including the organic compound are disclosed. The organic light emitting diode and the organic light emitting display device can improve its luminous efficiency and color purity, reduce its driving voltage and enhance its luminous efficiency and luminous lifetime by applying the organic compound.

Abstract: Proposed is a method of manufacturing a carbon precursor fiber for a gas diffusion layer having excellent tensile properties (e.g., strength and modulus) by controlling the cross-sectional shape of carbon fiber. The method includes preparing a polyacrylonitrile-based copolymer, preparing spinning products by spinning a spinning solution containing the polyacrylonitrile-based copolymer in a coagulation bath, and obtaining a carbon precursor fiber by drawing the spinning products through heat treatment. The coagulation bath includes an amount of about 60% to 90% by volume of methanol and an amount of about 10% to 40% by volume of dimethylformamide based on the total volume of the coagulation bath.

Abstract: An apparatus for measuring the strength of concrete using a surface wave velocity including an ultrasonic transmission and reception probe is provided. The apparatus is configured to include a surface wave velocity measurement device including an ultrasonic transmission probe and an ultrasonic reception probe. Further, a method of constructing the slip form of a concrete column member is provided. The method is capable of reducing the construction period by raising a concrete form rapidly and safely using a method of determining the slip-up time of the slip form based on the strength of concrete measured by the apparatus.

Abstract: An apparatus for measuring the strength of concrete using a surface wave velocity including an ultrasonic transmission and reception probe is provided. The apparatus is configured to include a surface wave velocity measurement device including an ultrasonic transmission probe and an ultrasonic reception probe. Further, a method of constructing the slip form of a concrete column member is provided. The method is capable of reducing the construction period by raising a concrete form rapidly and safely using a method of determining the slip-up time of the slip form based on the strength of concrete measured by the apparatus.