This paper intends to review possible application in the high strength area through compressive strength estimation of the simulated high strength concrete member using Rock Test Hammer and suggest it as a reference data for the strength estimation technique of the ultra high strength concrete in the future. From the results of test, in the low strength area less than 15MPa and normal strength area in 15∼60MPa, as shown on the existing studies, it is indicated that P Type Schmidt Hammer in the low strength area and N Type Schmidt Hammer in the normal strength area have high correlation of rebound-compressive strength. As the Rock Test Hammer indicated more or less reduced accuracy in the low strength area and the normal strength area but high correlation on the high strength area (50∼100MPa) defined on this test, it is determined that it would be possible to make the fastest and simplest compressive strength estimation on the site where the high strength concrete is applied. As was resulted above the experiments, on the basis of the result of Rebound Hardness Method and Compressive Strength on the high strength area which is over 50MPa, the conclusion is drawn which is Fc=4.409e0.059R through regression analizing the relations of Compressive Strength which is based on Rebound Hardness Method.

One of the main problems concerning the shallow seismic survey is how to generate high frequency signals with large amplitudes using small seismic sources. If one could focus the seismic energy in the direction of the survey line, it will be much helpful in identifying the first break. In this research, we have used hammer as an impulsive source and compared the signal powers generated by different shapes of the hammer plates: circular, square, and rectangular. The experiment was conducted by calculating the power spectral density function to compare the frequency spectrum and signal power. In the direction perpendicular to the long side of the rectangular plate, the largest seismic energy with the highest frequency was achieved even with the same weights of hammer plates. Our conclusion is that it is more efficient to use a rectangular plate than a circular (or square) one when conducting a 2-D shallow seismic survey.

This paper presents an investigation on dynamic characteristics of Heunginjimun through both ambient vibration and impact hammer tests. Heunginjimun, treasure No. 1 in Seoul, Korea, is a traditional wooden structure. Ambient vibration test is performed and spectrum analysis of time history is carried out to identify dominant frequency contents of Heunginjimun. Impact hammer test is undertaken to find the natural frequency of Heunginjimun with frequency response functions and phase information. Test results show that natural frequencies are 1.lHz, l.5Hz, 3.2Hz and 4.2Hz in two principal axes. Natural frequencies obtained by the tests are used to find the lateral stiffness of Heunginjimun. Simple dynamic models for Heunginjimun are suggested based on the moment resistance from joint beams and the restoring force due to column rocking. Lateral stiffness is found with identified natural frequencies and simple dynamic models.

이 논문은 날개응에의 소매응애과(Haplozetidae)에 속하는 신종 제주소매응애(신칭: Incabates barbatus sp.nov.)를 기재한 것이다. 이 신종은 일본에서 기록된 1. major와 매우 닳았으나, 1. major는 가슴등판센털(머리끝털, ro, 지게털, la)과 감각털의 머리가 매끈한 반면 신종은 머리끝털(ro)과 지게털(la)의 중간부분 바깥쪽에 거치들이 나 있고, 감각기 머리 표면에 작은 돌기가 나 있어 거칠다. Incabates속에는 현재까지 신종을 포함하여 모두 9종이 기록되었는데, 이들에 대한 검색표를 작성하였다.

The numerical model was developed to estimate the transient behavior of pressure waves in pipe systems. The computational algorithm was proposed to model the water hammer phenomenon in a pipe system with pump shutdown at midstream and sudden valve closure at downstream. To predict the pressure head and the flow velocity as a function of time as a result of rapidly closing a valve and pump shutdown, two boundary conditions at the ends considering pump operation and valve control can be implemented as specified equations of the pressure head and flow velocity based on the characteristics method. It was shown that the effects of transient flow make it determine the needs for protection devices, such as surge tanks, surge relief valves, or air valves, at various points in the system against overpressure and low pressure. It produced reasonably good performance with the results of the proposed transient model for pipeline systems. The proposed numerical model can be used as an efficient tool for the safety assessment of hydropower plants due to water hammer.

Recently, because pepople are taking a great interest in the water supply system and the related facilities are getting larger, the surge suppression is very important problem. Accordingly, We carried out both numerical simulation and field tests to confirm the safety of intake pumping station.

본 연구에서는 피로 손상된 용접이음의 피로수명 향상을 위한 방법으로 햄머피닝 처리법의 적용성을 검토하기 위하여 면외거셋 필렛 용접이음과 하중비전달형 리브 필렛 용접이음의 피로실험을 실시하였다. 본 실험에서는 면외거셋과 리브를 필렛 용접한 후 햄머피닝 처리를 하지 않은 용접그대로의 시험편, 용접후 햄머피닝 처리한 시험편, 그리고 용접그대로 시험편의 피로수명의 50% 시점에 햄머피닝 처리를 한 시험편의 피로실험을 실시하였다. 그리고 햄머피닝 처리에 의한 면외거셋과 리브 용접토우부의 형상 및 표면응력의 변화를 측정하였다. 그 결과, 햄머피닝처리에 의해 30~83MPa의 압축잔류응력이 도입 되었으며, 이로 인하여 강구조물의 제작시 용접후에 햄머피닝 처리를 실시하면 피로수명을 크게 향상 시킬 수 있을 뿐만 아니라, 이를 공용기간이 예상 피로수명의 50% 이하인 강구조물의 용접이음에 적용하여도 최소 1.3배 이상의 피로수명과 피로한계 향상효과를 기대할 수 있음을 제시하였다.

To improve fatigue strength of fillet-welded joints by hammer-peening treatment, fatigue tests were carried out on three types of longitudinal out-of-plane gusset fillet-welded joints and transverse non-load carrying cruciform rib fillet-welded joints: as-welded joints, post-weld hammer peened joints and hammer peened joints at 50% of as-welded joint’s fatigue life. From the test results, the effect of hammer-peening treatment on fatigue behavior of the fillet-welded joints were presented

저등급 석탄인 갈탄(lignite)을 순환 유동층 가스화기(circulating fluidized bed gasifier)의 효과적인 가스화를 위한 공급탄으로 제조하기 위하여 모든 조건들은 동일하고 스크린의 크기만을 변경하여 목적하는 입도분포 특성을 달성하는 최적조건을 찾기 위한 실험을 수행하였다. 가스화기 공급탄은 0.045~1 mm 크기로 85 wt% 이상이 요구되며 이러한 입도분포를 갖는 공급탄을 제조하기 위해서는 경제적이면서도 효과적인 공정 설계가 반드시 필요하다. 따라서 본 연구는 중국산 갈탄을 해머밀로 효과적으로 분쇄하기 위하여 다구치 설계를 사용하였으며, 설계조건에 따른 실험결과 및 통계분석 결과 95% 유의수준에서 1차 스크린의 크기는 3 mm, 2차 스크린의 크기는 1.3 mm인 경우가 최적화된 조건인 것으로 나타났다.