• 한국농공학회:학술대회논문집
• /
• 한국농공학회 2001년도 학술발표회 발표논문집
• /
• pp.379-385
• /
• 2001

A series of standard consolidation tests and repeated loading consolidation tests were peformed with 2 kinds of peat sampled in Chonbuk area to study the consolidation characteristics of peat. The samples had following physical properties : 58% and 72% of organic content, 487% and 685% of natural moisture content and 7.02 and 9.72 of initial void ratio, respectively. And compression index $C_{c}$ and coefficient of secondary consolidation $C_{\alpha}$ were increased steeply when the consolidation load exceed about 2.5 and 3 times of each preload as like the characteristics of peat. The dependance on consolidation pressure of $C_{C}\;and\;C_{\alpha}$ in peatl and the maximum values, 2.9-3.8 and 0.3-0.4 were larger than that of normal clay, respectively.

• 한국농공학회지
• /
• 제24권3호
• /
• pp.84-91
• /
• 1982

This study was conducted to investigate the consolidation characteristics of repeated increasing and decreasing load m marine clay. Consolidation test was performed by the whole repetition of increasing and decreasing load and the partial repetition of increasing and decreasing load. The results obtained were as follows: 1. The void ratio e was decreased according to the increase of preloading and the repe- tition of increasing and decreasing load. 2. In case of the partial repetition of increasing and decreasing load the compression index Cc was decreased with the increase of preloading and the repetition of increa- sing and decreasing load 3. The expansion rate was greatly increased with the whole repetition of increasing and decreasing load and it was inclined to be increased with the increase of preloading in case of the partial repetition. 4. The coefficient of volume compressibility were decreased according to the repetition of increasing and decreasing load 5. The secondary consolidation coefficient was decreased with the repetition of increasing and decreasing load. Especially in case of the partial repetition, the peaks of secon- dary consolidation curves could be found to move toward the vicinity of preloading.

• 농업과학연구
• /
• 제10권1호
• /
• pp.110-117
• /
• 1983

본(本) 연구(硏究)는 쌍곡선법(雙曲線法)을 이용(利用)해서 하중(荷重) 증가율(增加率)이 이차압밀(二次壓密)에 마치는 영향(影響)을 구명(究明)하기 위하여, 아산만(牙山灣)의 해성점토(海成粘土)에 대(對)하여 시험(試驗)한 것으로 그의 결과(結果)를 요약(要略)하면 다음과 같다. 1. 쌍곡선법(雙曲線法)에 의(依)한 이차압밀량산정(二次壓密量算定) 값은 Casagrande의 log t 법(法)에 의(依)한 값보다 약간 작았으나, 그 차이(差異)는 미소(微小)하였고 쌍곡선법(雙曲線法)으로는 하중(荷重) 증가율(增加率)이 작을 때에도 쉽게 이차압밀량(二次壓密量)을 산정(算定)할 수 있었다. 2. 하중증가율(荷重增加率)이 작을수록 이차압밀비(二次壓密比)는 크게 나타났으며 하중증가율(荷重增加率)이 작을때 일어나는 심하곡선(沈下曲線)의 creep 현상(現象)은 이차압밀(二次壓密)에 기인(起因)한 것이라 생각된다. 3. 일차압밀중(一次壓密中)에 생기는 이차압밀(二次壓密)는 과압밀영역(過壓密領域)에서는 불규칙(不規則)했으나, 과압밀영역(過壓密領域)에서는 하중증가율(荷重增加率)이 작을수록 증가현상(增加現象)을 보였다. 4. 이차압밀계수(二次壓密係數)는 하중(荷重)의 증가(增加)에 따라 점차 증가(增加)하여 선행하중근처(先行荷重近處)에서 변곡점(變曲点)을 이루었고 하중(荷重)이 $2kg/cm^2$부터는 감소현상(減少現象)을 나타냈으며 이차압밀계수(二次壓密係數)는 하중증가율(荷重增加率)과 무관(無關)함을 보였다. 5. 이차압밀계수(二次壓密係數)와 압축지수(壓縮指數)는 비례관계(比例關係)를 나타냈다.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2008년도 추계 학술발표회
• /
• pp.1115-1123
• /
• 2008

When constructing projects such as road embankments, bridge approaches, dikes or buildings on soft, compressible soils, significant settlements may occur due to the consolidation of these soils under the superimposed loads. The compressibility of the soil skeleton of a soft clay is influenced by such factors as structure and fabric, stress path, temperature and loading rate. Although it is possible to determine appropriate relations and the corresponding material parameters in the laboratory, it is well known that sample disturbance due to stress release, temperature change and moisture content change can have a profound effect on the compressibility of a clay. The early research of Tezaghi and Casagrande has had a lasting influence on our interpretation of consolidation data. The 24 hour, incremental load, oedometer test has become, more or less, the standard procedure for determining the one-dimensional, stress-strain behavior of clays. An important notion relates to the interpretation of the data is the ore-consolidation pressure ${\sigma}_p$, which is located approximately at the break in the slope on the curve. From a practical point of view, this pressure is usually viewed as corresponding to the maximum past effective stress supported by the soil. Researchers have shown, however, that the value of ${\sigma}_p$ depends on the test procedure. furthermore, owing to sampling disturbance, the results of the laboratory consolidation test must be corrected to better capture the in-situ compressibility characteristics. The corrections apply, strictly speaking, to soils where the relation between strain and effective stress is time independent. An important assumption in Terzaghi's one-dimensional theory of consolidation is that the soil skeleton behaves elastically. On the other hand, Buisman recognized that creep deformations in settlement analysis can be important. this has led to extensions to Terzaghi's theory by various investigators, including the applicant and coworkers. The main object of this study is to suggestion the modified compression index value to predict settlements by back calculating the $C_c$ from different numerical models, which are giving best prediction settlements for multi layers including very thick soft clay.

• Journal of Acupuncture Research
• /
• 제35권2호
• /
• pp.75-80
• /
• 2018

Background: The aim of this study was to assess the feasibility of conducting a clinical study of using acupuncture for chronic pain in patients with osteoporotic thoracolumbar vertebral compression fractures (VCFs) in the outpatient setting. Methods: A prospective case-series attempting to recruit 20 participants was performed from February 11, 2016, to December 31, 2016. We provided Manual and electrical acupuncture was provided one 1 to three 3 times a week, for 6 weeks, up to 18 sessions. The primary clinical outcome was the average pain intensity as measured by the visual analog scale (VAS) at 6 weeks. Secondary outcomes included back-specific dysfunction (Oswestry disability index), quality of life (quality of life questionnaire-26), patient-reported improvement, use of other healthcare resources, and adverse events at 6 weeks. Use of healthcare resources and adverse events were additionally followed-up at 12 weeks by telephone. Results: Of 33 patients screened, a total of 7 were enrolled in the study. Manual and electrical acupuncture was provided 1 to 3 times a week, for 6 weeks, up to 18 sessions. We observed reduced pain intensity at 6 weeks in all participants. The change in the quality of life and back-specific dysfunction was inconsistent among participants. Mild, temporary adverse events were observed in three patients. Conclusion: In our clinical setting, it was not feasible to recruit sufficient participants and to assess the efficacy of acupuncture for chronic pain after osteoporotic thoracolumbar VCFs under a year. Strategies to improve recruitment and to identify barriers to participation are required for future clinical trials.

• 천문학회지
• /
• 제34권4호
• /
• pp.313-315
• /
• 2001

Some authors have concluded that spiral structures and shocks do not develop if an adiabatic index $\gamma$ > 1.16 is adopted in accretion disc modelling, whilst others have claimed that they obtained well defined spirals and shocks adopting a $\gamma$ = 1.2 and a $M_2/ M_1$ = 1 stellar mass ratio. In our opinion, it should be possible to develop spiral structures for low compressibility gas accretion discs if the primary component is a black hole. We considered a primary black hole of 8M0 and a small secondary component of 0.5M$\bigodot$ to favour spiral structures formations and possible spiral shocks via gas compression due to a strong gravitational attraction. We performed two 3D SPH simulations and two 2D SPH simulations and characterized a low compressibility model and a high compressibility model for each couple of simulations. 2D models reveal spiral structures existence. Moreover, spiral shocks are also evident in high compressibility 2D model at the outer disc edge. We believe that we could develop even well defined spiral shocks considering a more massive primary component.

• 한국농공학회지
• /
• 제18권4호
• /
• pp.4242-4250
• /
• 1976

The determination of the pre-consolidation load known to have a great effect on the consolidation characteristics of the soil have been researched and discussed in detail by many other researchers. A study was undertaken to investigate and compare the effect of pre-consolidation loads on the coefficient of permeability and the consolidation characterisics of soil through the consolidation test on the three types of soil samples. The results of this study are follows; 1. Large compression index is dependent on initial void ratio of the sample being used and the pressure-void ratio curve shows a curved linear relationship in over-consolidated area but a linear relationship in normally consolidated area.2. Settlement-time curve is S-shaped where the pressure is larger than pre-consolidation load and regardless of over-burden pressure, it is a similar straight line respectively in the secondary consolidation area. 3. Primary consolidation ratio of the sample increases almost linearly with the increase of over-burden pressure but the coefficient of volume compressibility decreases linearly with the increase of it. 4. Time factor of a certain degree of consolidation increases with over-burden pressure but the coefficient of consolidation decreases with it in over-consolidated area. There is a linear relationship between them in normally consolidated area. 5. The void ratio of completion point of primary consolidation decreases linearly with over-burden pressure. 6. The coefficient of permeability of sample decreases linearly with over-burden pressure in normally consolidated area, also it increases linearly with increment of the void ratio of the sample.

• 대한약침학회지
• /
• 제18권1호
• /
• pp.79-85
• /
• 2015

Objectives: A vertebral compression fracture (VCF) is characterized by back pain and fracture of a vertebral body on spinal radiography. VCFs of the thoraco lumbar spine are common in the elderly. In general, appropriate analgesics should be prescribed to reduce pain and, thus, promote early mobilization. The ideal treatment approach for VCFs has not been determined. In Korea, acupuncture and herbal medication have been used to treat VCFs for many years. There is empirical evidence that acupuncture might benefit patients with a VCF. However, no randomized, controlled, clinical trials evaluating the efficacy and the safety of acupuncture for treating a VCF have been published. Therefore, we designed a randomized, controlled, pilot, clinical trial to obtain information for the design of a further full scale trial. Methods: A five week protocol for a randomized, controlled, pilot, clinical trial is presented. Fourteen patients will be recruited and randomly allocated to two groups: a control group receiving interlaminar epidural steroid injections once a week for three weeks, and an experimental group receiving interlaminar epidural steroid injections plus acupuncture treatment (three acupuncture sessions per week for three weeks, nine sessions in total). The primary outcomes will be the pain intensity (visual analogue scale and PainVision$^{TM}$ system). The secondary outcome measurements will be the answers on the short form McGill pain questionnaire and the oswestry disability index. Assessments will be made at baseline and at one, three, and five weeks. The last assessment (week five) will take place two weeks after treatment cessation. This study will provide both an indication of feasibility and a clinical foundation for a future large scale trial. The outcomes will provide additional resources for incorporating acupuncture into existing treatments, such as nonsteroidal anti-inflammatory medications, narcotics and vertebral augmentation. This article describes the protocol.

• 대한기계학회논문집B
• /
• 제22권9호
• /
• pp.1317-1324
• /
• 1998

In general, DI gasoline engine has the advantages of higher power output, higher thermal efficiency, higher EGR tolerance and lower emissions due to the operation characteristics of increased volumetric efficiency, compression ratio and ultra-lean combustion scheme. In order to apply the concept of stratified charge into direct injection gasoline engine, some kinds of methodologies have been adapted in various papers. In this study, a reflector was adapted around the injector nozzle to apply the concept of stratified charge combustion which leads the air-fuel mixture to be rich near spark plug. Therefore, the mixture near the spark plug is locally rich to ignite while the lean mixture is wholly introduced into the combustion chamber. The characteristics of combustion is analyzed with the variations of fuel injection pressure and load in a stratified -charge direct injection single cylinder gasoline engine. The obtained results are summarized as follows ; 1. The MBT spark timing approached to TDC with the increase of load on account of the increase of evaporation energy, but has little relation with fuel injection pressure. 2. The stratification effects are apparent with the increase of injection pressure. It is considered by the development of secondary diffusive combustion and the increase of heat release of same region, but proceed rapidly than diesel engine. Especially, in the case of high pressure injection (l70bar) and high load (3.0kgf m), the diffusive combustion parts are developed excessively and results in the decrease of peak pressure than in the case of middle load. 3. The index of engine stability, COVimep value, is drastically decreased with the increase of load. 4. To get better performance of DI gasoline engine development, staged optimizaion must be needed such as injection pressure, reflector, intake swirl, injection timing, chamber shape, ignition system and so on. In this study, the I50bar injection pressure is appeared as the optimum.