• International Journal of Highway Engineering
• /
• v.5 no.4 s.18
• /
• pp.23-35
• /
• 2003

In this study, compaction evaluating program based on ASTM critria is developed bu analyzing the results of laboratory tests. And the laboratory tests such as compaction test, triaxial test and resonance column test of subgrade soils are performed to develop compaction management methodology at seven test sites. Especially, to figure out chararteristic with changing compactive efforts, the test was carried out at five levels of compactive efforts at each soil sample. Database was set up from the test results. With the methodology using mechanical property - the elastic modulus, the gap between road design and management and road construction management is narrowed. The regression equation of G/$G_{max}$ is proposed at each strain level of subgrade soils according to AASHTO criteria, and the relationship between fundamental properties of soil mass and degree of compaction is derived as well. The development of compaction management and field compaction management method is proposed by the elastic modulus based on mechanical tests.

• Proceedings of the Korean Society of Applied Pharmacology
• /
• 1996.04a
• /
• pp.19-29
• /
• 1996

The neurological manifestations of AIDS include dementia, encountered even in the absence of opportunistic superinfection or malignancy. The AIDS Dementia Complex appears to be associated with several neuropathological abnormalities, including astrogliosis and neuronal injury or loss. How can HIV-1 result in neuronal damage if neurons themselves are only rarely, if ever, infected by the vitus\ulcorner In vitro experiments from several different laboratiories have lent support to the existence of HIV- and immune-related toxins. In one recently defined pathway to neuronal injury, HIV-infected macrophages/microglia as well as macrophages activated by HIV-1 envelope protein gp120 appear to secrete excitants/neurotoxins. These substances may include arachidonic acid, platelet-activating factor, free radicals (NO - and O$_2$), glutamate, quinolinate, cysteine, cytokines (TNF-${\alpha}$, IL1-B, IL-6), and as yet unidentified factors emanating from stimulated macrophages and possibly reactive astrocytes. A final common pathway for newonal suscepubility appears to be operative, similar to that observed in stroke, trauma, epilepsy, and several neurodegenerative diseases, including Huntington's disease, Parkinson's disease, and amyotrophic lateral sclerosis. This mechanism involves excessive activation of N-methyl-D-aspartate (NMDA) receptor-operated channels, with resultant excessive influx of Ca$\^$2+/ leading to neuronal damage, and thus offers hope for future pharmacological intervention. This chapter reviews two clinically-tolerated NMDA antagonists, memantine and nitroglycerin; (ⅰ) Memantine is an open-channel blocker of the NMDA-associated ion channel and a close congener of the anti-viral and anti-parkinsonian drug amantadine. Memantine blocks the effects of escalating levels of excitotoxins to a greater degree than lower (piysiological) levels of these excitatory amino acids, thus sparing to some extent normal neuronal function. (ⅱ) Niuoglycerin acts at a redox modulatory site of the NMDA receptor/complex to downregulate its activity. The neuroprotective action of nitroglycerin at this site is mediated by n chemical species related to nitric oxide, but in a higher oxidation state, resulting in transfer of an NO group to a critical cysteine on the NMDA receptor. Because of the clinical safety of these drugs, they have the potential for trials in humans. As the structural basis for redox modulation is further elucidated, it may become possible to design even better redox reactive reagents of chinical value. To this end, redox modulatory sites of NMDA receptors have begun to be characterized at a molecular level using site-directed mutagenesis of recombinant subunits (NMDAR1, NMDAR2A-D). Two types of redox modulation can be distinguished. The first type gives rise to a persistent change in the functional activity of the receptor, and we have identified two cysteine residues on the NMDARI subunit (#744 and #798) that are responsible for this action. A second site, presumably also a cysteine(s) because <1 mM N-ethylmaleimide can block its effect in native neurons, underlies the other, more transient redox action. It appears to be at this, as yet unidentified, site on the NMDA receptor that the NO group acts, at least in recombinant receptors.

• Journal of the Korea Concrete Institute
• /
• v.17 no.1 s.85
• /
• pp.77-84
• /
• 2005

The steel slag, a by-product which is produced by refining pig iron during the manufacture of steel, is mainly used as road materials after aging. It is necessary to age steel slag for long time in air because the reaction with water and free-CaO in steel slag could make the expansion of volume. This problem prevents steel slag from being used as aggregate for concrete. However, steel slag used in this study was controled by a air-jet method which rapidly cools substance melted at a high temperature. The rapidly-chilled method would prevent from generation of free-CaO in steel slag. This study dealt with the influence of the using rate of rapidly-chilled steel slag on flow, dosage of SP, W/C ratio, and strength of mortar by statistical experimental design. Also, the results of this experiment were approved by statistical analysis methods, such as analysis of variance and F-testing. As results of F-testing, this paper proved at $1\%$ level of significance that the more the using rate of rapidly-chilled steel slag increased, the more this affected the enhancement of flow, the decrease of dosage of SP and W/C ratio, and the development of compressive strength. Also, considering the fluidity and compressive strength of mortar, it is desirable to use $75\%$ of rapidly-chilled steel slag for river sand.

• Journal of the Korea Concrete Institute
• /
• v.17 no.5 s.89
• /
• pp.709-716
• /
• 2005

The objective of this study is to develop a high ductile fiber reinforced mortar, ECC(Engineered Cementitious Composite) with using raw material commercially available in Korea. A single fiber pullout test and a wedge splitting test were employed to measure the bond properties in a matrix and the fracture toughness of mortar matrix respectively, which are used for designing mix proportion suitable for achieving strain-hardening behavior at a composite level. Test results showed that the properties tended to increase with decreasing water-cement ratio. A high ductile fiber reinforced mortar has been developed by employing micromechanics-based design procedure. Micromechanical analysis was initially peformed to properly select water-cement ratio, and then basic mixture proportion range was determined based on workability considerations, including desirable fiber dispersion without segregation. Subsequent direct tensile tests were performed on the composites with W/C's of 47.5% and 60% at 28 days that the fiber reinforced mortar exhibited high ductile uniaxial tension property, represented by a maximum strain capacity of 2.2%, which is around 100 times the strain capacity of normal concrete. Also, compressive tests were performed to examine high ductile fiber reinforced mortar under the compression. The test results showed that the measured value of compressive strength was from 26MPa to 34 MPa which comes under the strength of normal concrete at 28 days.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
• /
• v.13 no.2
• /
• pp.138-144
• /
• 2020

Currently, an autonomous vehicle studies are working to develop a four-level autonomous vehicle that can cope with emergencies. In order to flexibly respond to an emergency, the autonomous vehicle must move in a direction to minimize the damage, which must be conducted by judging all the states of the road, such as the surrounding pedestrians, road conditions, and surrounding vehicle conditions. Therefore, in this paper, we suggest a passenger detection and sharing system to detect the passenger situation inside the autonomous vehicle and share it with V2V to the surrounding vehicles to assist in the operation of the autonomous vehicle. Passenger detection and sharing system improve the weighting method that recognizes passengers in the current vehicle to identify the passenger's position accurately inside the vehicle, and shares the passenger's position of each vehicle with other vehicles around it in case of emergency. So, it can help determine the driving of a vehicle. As a result of the experiment, the body pressure sensor applied to the passenger recognition sub-module showed about 8% higher accuracy than the conventional resonant sensor and about 17% higher than the piezoelectric sensor.

• 대한공업교육학회지
• /
• v.30 no.1
• /
• pp.106-119
• /
• 2005

Many problems with the offline class, which is the traditional education type in corporations or universities, were indicated and people hoped that e-learning, which is web-based instruction, would solve these problems. However, e-learning also has weak points in that it should be self-paced and media-based in many ways. Therefore, when considering the good and weak points of offline classes and e-learning, blended learning seems to be necessary. Until now, blended learning has usually been used in corporations, and there have been almost no studies on the effectiveness or management of blended learning in universities. Thus, in this study, I would like to design blended classes, manage them at the level of university classes, and verify the effectiveness of blended classes, by comparing academic achievement, student participation, and student satisfaction. The subject students who signed up for Computer & Technology at C University in 2005 were divided into three study groups: offline class, online class, and blended class. The offline class was taught using the traditional class teaching method. For the online class and the blended class, multimedia contents were developed and a different LMS was used. The results of 13 weeks of teaching are as follows. For the academic achievement in the offline, online and blended classes, there was no statistically significant difference (f=2.387, p=.096). But when comparing the average achievement, the average of the blended class was higher than that of the other classes, so that it can be said that the blended class has positive effects on academic achievement. Second, when comparing the learners' participation in the online class and the blended class, the total posts were 85 and 138 respectively, which shows a considerable difference. The hit counts for each post in the online class and the blended class are 10 and 20, respectively. Moreover, the login counts for subjects are 3 in the online class and 4 in the blended class. In the questionnaire for the students' academic satisfaction in the online class and the blended class, all of the 15 items showed higher satisfaction in the blended class. Considering all these results, if adequate media are properly combined, the blended class is better than either the pure online class or the pure offline class.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.11
• /
• pp.259-272
• /
• 2019

Steel-concrete single-leaf blast-resistant doors are protective structures consisting of a steel box and reinforced concrete slab. By the domestic blast-resistant doors, the structure is not designed efficiently because few studies have examined the effects of variables, such as the blast pressure, rebar ratio, and steel plate thickness on the structural behavior. In this study, the structural behavior of the doors was analyzed using the FE method, and the support rotation and ductility ratio used to classify the structural performance were reviewed. The results showed that the deflection changes more significantly when the plate thickness increases than when the rebar spacing is a variable. This is because the strain energy absorbed by the door is reduced considerably when the plate thickness increases, and as a result, the maximum deflection becomes smaller. According to a comparison of the calculated values of the support rotation and the ductility ratio, the structural performance of the doors could be classified based on the support rotation of one degree and ductility ratio of three. On the other hand, more explosion tests and analytical studies will be needed to classify the damage level.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.10 no.12
• /
• pp.3626-3631
• /
• 2009

This study has provided some of the first experimental results of NMOSFET hot-carrier degradation for the analog circuit application. After hot-carrier stress under the whole range of gate voltage, the degradation of NMOSFET characteristics is measured in saturation region. In addition to interface states, the evidences of hole and electron traps are found near drain depending on the biased gate voltage, which is believed to the cause for the variation of the transconductance($g_m$) and the output conductance($g_{ds}$). And it is found that hole trap is a dominant mechanism of device degradation in a low-gate voltage saturation region, The parameter degradation is sensitive to the channel length of devices. As the channel length is shortened, the influence of hole trap on the channel conductance is increased. Because the magnitude of $g_m$ and $g_{ds}$ are increased or decreased depending on analog operation conditions and analog device structures, careful transistor design including the level of the biased gate voltage and the channel length is therefore required for optimal voltage gain ($A_V=g_m/g_{ds}$) in analog circuit.

• Korean Journal of Poultry Science
• /
• v.22 no.3
• /
• pp.179-188
• /
• 1995

In Experiment 1, microbial assays were conducted on 57 feed ingredient samples to determine the content of total folic acid using Lactobacillus casei(ATCC 7469). Folic acid contents of feed samples pretreated with conjugase, ${\alpha}$-amylase, and a mixture of protease(Pronase)were corn, 09${\pm}$1.18($\pi$g${\pm}$SD); fish meal, 23.05${\pm}$1.27; milo, 29.34${\pm}$0.55; bakery meal, 25.80${\pm}$6.93; meat and bone meal, 56.76${\pm}$4.97; wheat middlings, 85.14${\pm}$2.56; and soybean meal, 193.97${\pm}$3.98. Experiments 2 and 3 were conducted to determine the effects of dietary supplemental folic acid and methionine on the performance of starting broiler chicks for 18 days. Four levels of dietary folic acid(0.24. 0.54,1.14 and 2.34mg/kg) and four levels of dietary methionine(0.45, 0.53,0.61, and 0.69%) were fed in a factorial design. The basal diet was based on corn, isolated soybean protein, meat and bone meal, and fish meal. It contained adequate amounts of all nutrients except methionine and folic acid in both experiments. Increased growth rate was observed in chicks fed the basal diet supplemented with either folic acid or methionine. Total dietary folic acid and methionine plus cysteine requirements for optimum growth were estimated to be 1.80 mg/kg and 0.89% in Experiment 2, and 1.47 mg/kg and 0.91% in Experiment 3, respectively. There were interactions between dietary folic acid and methionine on weight gain in both experiments. Chicks fed diets containing 2.34 mg folic acid /kg tended to display slow growth rate in both experiments. There was a significant linear feed conversion response to folic acid in Experiment 2, and a significant quadratic feed conversion resuonse to methionine in Experiment 3. There were both linear and quadratic liver folic acid responses to dietary folic acid in both experiments. There was no indication that dietary methionine had any effect on liver folic acid content. The incidence of tibial dyschondroplasia increased with increasing supplemental methionine, but were no significant differences detected at 5% level.

• Progress in Superconductivity
• /
• v.5 no.1
• /
• pp.50-54
• /
• 2003

We have fabricated $∂^2$$B_{z}$ /$∂x^2$ type planar gradiometers and studied their properties in operation under various field conditions. $YBa_2$$Cu_3$$O_{7}$ film was deposited on $SrTiO_3$ (100) substrate by a pulsed laser deposition (PLD) system and patterned into a device by the photolithography with ion milling technique. The device consists of 3 pickup loops designed symmetrically Inner dimension and the width of the square side loops are 3.6 mm and 1.2 mm, respectively, and the corresponding dimensions of the center loop are 2.0 mm and 1.13 mm. The length of baseline gradiometer is 5.8 mm. Step-edge junction width is 3.0 $\mu\textrm{m}$ and the hole size of the SQUID loop is 3 $\mu\textrm{m}$ ${\times}$ 52 $\mu\textrm{m}$. The SQUID inductance is estimated to be 35 pH. The device was formed on a 20 mm ${\times}$ 10 mm substrate. We have tested the behavior of the device in various field conditions. The unshielded gradiometer was stable under extremely hostile conditions on a laboratory bench. Noise level 0.45 pT/$\textrm{cm}^2$/(equation omitted)Hz and 0.84 pT/$\textrm{cm}^2$/(equation omitted)Hz at 1 Hz for the shielded and the unshielded cases, which correspond to equivalent field noises of 150 fT/(equation omitted)Hz and 280 fT/(equation omitted)Hz, respectively. In spite of the short baseline of 5.8 mm, the high common-mode-rejection-ratio of the gradiometer, $10^3$, allowed us to successfully record magnetocardiogram of a human subject, which demonstrates the feasibility of the design in biomagnetic studies.