• Smart Structures and Systems
• /
• 제13권3호
• /
• pp.453-471
• /
• 2014

The fault diagnosis of rolling element bearings has drawn considerable research attention in recent years because these fundamental elements frequently suffer failures that could result in unexpected machine breakdowns. Artificial intelligence algorithms such as artificial neural networks (ANNs) and support vector machines (SVMs) have been widely investigated to identify various faults. However, as the useful life of a bearing deteriorates, identifying early bearing faults and evaluating their sizes of development are necessary for timely maintenance actions to prevent accidents. This study proposes a new two-layer structure consisting of support vector regression machines (SVRMs) to recognize bearing fault patterns and track the fault sizes. The statistical parameters used to track the fault evolutions are first extracted to condense original vibration signals into a few compact features. The extracted features are then used to train the proposed two-layer SVRMs structure. Once these parameters of the proposed two-layer SVRMs structure are determined, the features extracted from other vibration signals can be used to predict the unknown bearing health conditions. The effectiveness of the proposed method is validated by experimental datasets collected from a test rig. The results demonstrate that the proposed method is highly accurate in differentiating between fault patterns and determining their fault severities. Further, comparisons are performed to show that the proposed method is better than some existing methods.

• 생물환경조절학회지
• /
• 제23권2호
• /
• pp.109-115
• /
• 2014

본 연구에서는 모형실험을 통하여 다짐도 및 매입깊이에 따른 나선철항의 인발저항력을 검토하였다. 그 결과 다짐도 및 매입깊이가 증가할수록 인발저항력은 증가하는 것으로 나타났으며, 특히 다짐률 85%의 지반조건에서 인발저항력은 매입깊이 25cm, 30cm, 35cm 및 40cm별로 각각 48.9kgf, 57.9kgf, 86.2kgf 및 116.6kgf로 다른 지반조건일 때 보다 현저하게 높은 인발저항력이 나타났다. 그리고 다짐률에 따른 인발저항력은 각 매입깊이 조건별(30cm, 35cm 및 40cm)로 다짐률 75% 및 85%에서 급격하게 증가하는 유사한 경향이 나타났다. 나선철항의 인발저항력은 지반의 다짐률에 따라 상당한 차이를 보였으며 극한인발저항력의 최대값은 다짐률 85%의 지반조건 및 매입깊이 40cm에서 116.6kgf로 나타났다. 이는 나선철항의 제원을 고려해 볼 때 매우 높은 것으로 판단된다. 따라서 평소 나선철항 주변 지반의 유지관리를 철저히 한다면 바람에 대한 피해를 효과적으로 경감시켜 줄 수 있을 것으로 판단된다. 그리고 나선철항은 플라스틱 필름을 고정하는 용도뿐만 아니라 온실 형태별로 개수 및 간격 등 적절한 설치방법이 제시된다면 온실의 구조적 안정성에도 기여를 할 수 있을 것으로 예상된다. 또한 본 연구의 결과를 검토해 볼 때 온실에 나선설항의 설치시 유용한 효과를 기대하기 위해서는 매입깊이 35cm 이상 그리고 다짐률은 85%이상을 적용해야 할 것으로 판단되며, 본 실험에서 다짐률 85%에 해당하는 모형지반의 상대밀도는 67%정도 였다.

• 대한한방종양학회지
• /
• 제4권1호
• /
• pp.211-232
• /
• 1998

Because there were lots of side effects and tolerances to the existing anticancer therapeutics, the experiment extracting the anticancer effect from medicinal herbs is in progress liviely. Therefore the purpose of this study were to research the tendency and the course of anticancer studies. To research the tendency of anticancer studies, medicinal herbs of fifty three experimental papers were analyzed and to examine the course of studies, anticancer papers in the medical world were used. The obtained results were as follows: Methods of herbal medicinal treatments were elimination the pathogenic factor(祛邪) and supporting healthy energy(扶正) method used. In this study, immediately tumor bearing and immune response were the most important point. The subject of immediately tumor bearing was not in the specific cancer but in the influence on the life span of general cencerous cells. In the experimental study of immune response, the effect on NK cell activity of medicinal herbs most studied. The combined usage of medicinal herbs and anticancer agent mostly intended to know whether it inhibits the tumor cell growth. The serum test and blood cell number test show if medicinal herbs inhibit side effect of anticancer agent. More than 80 percents of used medicinal herbs, there were anticancer activities. However anticancer experimental studies using medicinal herbs two weak points. The one, it was difficult to choose a prescription according to differentiation of symptoms and signs(辨證論) of the Oriental Medicine, because we put to the test not a man but a mouse. The other, as we observed the indirect effect of the whole physiological regulation caused by synergic effects of the complex prescription, we don't understand the detailed mechanism of the herb. Therefore, if the anticancer effect of the herb is proved the experiment, we should research the concrete medical action of medicinal herbs and immunological analysis of herbal medicines to the body.

• 한국정밀공학회지
• /
• 제22권1호
• /
• pp.47-52
• /
• 2005

In this paper, the effect of TiN-coating on product quality such as dimensional accuracy and surface roughness is experimentally investigated. A punch of SKD11 material in cold forging an automotive bearing shaft and its related process found in a cold forging company are selected as the test example. The effect of TiN-coating is revealed in a quantitative manner. It is to be noted that TiN-coating is effective in controlling the dimensional accuracy and surface roughness as well as in increasing tool lift.

• Biomolecules & Therapeutics
• /
• 제8권2호
• /
• pp.199-205
• /
• 2000

On the inter-order protoplast fusants of Lentinus edodes and Ganoderma lucidum was the antitumor activity test performed and the fusant P22 was selected. The hot water extract of the cultured mycelia of P22 were purified by DEAE-cellulose chromatographya and the resulting purified fraction was designated as P22A. It was found to be a proteoglycan whose molecular weight was 47 kDa. When examined for immunopotentiation activity, P22A increased the number of colony forming unit in the bone marrow stem cells to 3-folds. It also potentiated the secretion of nitric oxide in activated macrophages to 2-folds. In humoral immune response, it increased the activities of the alkaline phosphatase in differentiated B cells to 1.6-folds and the number of plaque forming cells to 1.8-folds. In cellular immune response, it restored the depressed response of delayed type hypersensitivity in tumor bearing mice to normal level. These results suggest that P22A have potential to restore the decreased immune activity of the tumor bearing mice to normal level.

• 항공우주시스템공학회지
• /
• 제1권4호
• /
• pp.37-41
• /
• 2007

Labyrinth seal is most common way to protect the bearings installed in Reaction wheel. In spite of wide applications, no such research was found about the sealing utility of the Labyrinth seal in the condition of vacuum and high temperature. In this research, we tried to verify the utility of Labyrinth seal. Numerical analysis had been executed to predict the benefit of the Labyrinth seal and also experiments were performed to verify the utilization. Two Bearings were installed at the vacuum chamber, one was assembled with Labyrinth seal and the other was stand alone. After executing the vacuum test, it was found to be the stand alone bearing had lost more weight than the one that was assembled with the labyrinth seal. In this result, it is verified that the Labyrinth seal has useful function to preserve the lubricant that affects to the life-cycle of the Bearing.

• Computers and Concrete
• /
• 제29권1호
• /
• pp.47-57
• /
• 2022

The increase in waste tires has brought serious environmental problems. Using waste tires rubber particles as aggregate in concrete can reduce pollution and decrease the usage of natural aggregate. The paper describes an investigation on flexural bearing capacity of self-compacting concrete (SCC) pavement slabs containing crumb rubber. Cyclic loading tests with different stress ratios and loading frequencies are carried out on SCC pavement slabs containing crumb rubber. Based on Paris Law and test data, the fatigue life of SCC pavement slab containing crumb rubber is discussed, and a revised mathematical model is established to predict the fatigue life of SCC pavement slab containing crumb rubber. The model applies to different stress ratios and loading frequencies. The fatigue life of SCC pavement slab containing crumb rubber is affected by the stress ratio and loading frequency. The fatigue life increases with the increase of stress ratio and loading frequency. Real-time acoustic emission (AE) signals in the SCC pavement slab containing crumb rubber under cyclic loading are measured, and the characteristics of crack propagation in the SCC pavement slab containing crumb rubber under different stress ratios and loading frequencies are compared. The AE signals provide abundant information of fracture process zone and crack propagation. The variation of AE ringing count, energy and b-value show that the fracture process of SCC pavement slab containing crumb rubber is divided into three stages.

• 드라이브 ㆍ 컨트롤
• /
• 제15권4호
• /
• pp.48-54
• /
• 2018

The hydraulic servo actuator has always operated very precisely with high frequency and small displacement, and is used continuously for a long time. The hydraulic servo actuator of the test equipment used in the accelerated life test in order to guarantee the service life of the automotive parts failed earlier than the products before finishing the test. This study performed an analysis on the cause of the failure of the hydraulic servo actuator used in the test equipment, changed the design of the actuator to solve the root cause of the main failure mode, and developed the improved servo actuator. Based on above process, this study established a better performances and longer lifetime of the servo actuator after testing.

• 한국신뢰성학회지:신뢰성응용연구
• /
• 제15권4호
• /
• pp.241-247
• /
• 2015

Purpose : The demand for higher fuel economy vehicles has helped develop fuel-efficient vehicles such as a CVVL called continuous variable valve lift. Existing CVVL has been applying DC type motor to control intake valve, but recently some car parts manufacturers have been developing a BLDC type CVVL motor for improvements of endurance performance. The purpose of this study is to find the potential failure mechanism of the CVVL BLDC moto in early stage of development based on the design properties and design the accelerated life test model. Methods : CVVL BLDC is consist of brushs, coil, magnetic, PCB, bearing and so on. Each component has a latent failure mechanism caused by temperature, humidity, vibration. By analysis result of the failure mechanism, thermal fatigue is the most important factor of a durability of CVVL BLDC motor. So, we designed a new accelerated life test model for guarantee of the CVVL BLDC motor. Results : A crack occurred on via hole in test using the conditions we designed, so we did change the design to avoid this failure. The via hole dimension is changed a little larger, as a result we achieve improvements in reliability of the CVVL BLDC motor. By applying various kinds and extreme level of stresses, we can find the operating limits of products. Conclusion : In thesis, We analyzed the failure mechanism of CVVL BLDC and designed an accelerated life test method to give a guarantee for reliability. Based on the test results, we could improve the reliability of developments by change of design.

• Physical Therapy Rehabilitation Science
• /
• 제6권4호
• /
• pp.159-163
• /
• 2017

Objective: Persons with stroke have a tendency to exhibit asymmetric weight-bearing during sit-to-stand because due to the attempt to support themselves with the non-paretic foot. However, there are few devices that can assist with sit-to-stand (STS) performance. This study was designed to investigate the use of the elastic band with rings (EBR) in improving weight-bearing effectively in persons with stroke during STS training. Design: Cross-sectional study. Methods: Thirteen stroke survivors participated in the study. An EBR was applied onto the patient during STS activity. The foot pressure was measured before and after wearing the EBR, with a 5-minute rest period between measurements. Subjects were asked to perform each test twice with and without the EBR. Bilateral feet pressures were measured with standing posture being divided into the forward and backward aspects. The foot contact pressure during STS activity was measured with the CONFORMat System. Results: With EBR, the forward pressure of the affected foot significantly increased while the less-affected forward foot pressure significantly decreased (p=0.015 and p=0.023, respectively). The backward foot pressure did not differ significantly in the two limbs, and there was no difference with and without the EBR in terms of the total pressure of the affected foot. There was a significant difference with and without the EBR in the total pressure of the less-affected foot (p<0.05). Conclusions: STS training with the EBR has been shown to improve weight-bearing of both feet while decreasing the total pressure of the less-affected foot in stroke survivors. Therefore, we suggest that the EBR is a useful tool for STS training for persons with stroke in the clinic.