The mechanical properties of stone structures are generally characterized according to the strength of the stone used. An ultrasonic velocity method that does not damage cultural heritages is used to measure the strength of stone. However, there is no correction involved for surface roughness and thickness of the stone in the ultrasonic method currently used. In addition, a contact agent such as grease can cause contamination on the surface of a cultural heritage.

현재 건설현장에서는 부순모래 콘크리트의 비파괴 강도 추정을 일반적으로 슈미트 해머를 이용한 반발경도법이나 초음파를 이용한 초음파속도법, 이 둘을 조합한 복합법을 이용하고 있으며 기존의 천연골재를 사용한 콘크리트에 의해 얻어진 여러 가지 제안식들에 적용시켜 추정하고 있다. 따라서 본 연구의 목적은 전형적인 파괴시험과 코어채취 그리고 초음파속도법을 이용하여 부순모래 콘크리트의 강도 추정식을 제안하고자 하였다. 실험의 변수는 양생재령과 양생조건 그리고 콘크리트의 설계기준강도이다.

Echo sounder and Doppler sonar are to theultra-sonic transducers for measuring the depth and the ship's speed respectively. To measure the depth and speed with a single transducer, it is required to control the ultra-sonic beam to optional direction. In the past, the direction of the transducer itself is varied, but such a method provoked much problems in the mechanical design of the equipment. This paper deals with the method to control beam direciton by the phase control of the plural arrangement of transducers, and the results are studied by a computer simulation. The remarkable results of the study is condensed as follows; 1. The greater the interval of arrangement between transducers, the sharper the radiation pattern is, but in this case, the level of undesired sidelobe is also increased. 2. The control of radiation pattern up to 60 degree can be achieved by an adequate arrangement of more than 10 transducers. 3. It is shown that a simultaneous measurement of both depth and speed can be achieved by alternating directivity of the pulse by the method proposed in this paper.