• Bulletin of the Korean Chemical Society
• /
• v.28 no.2
• /
• pp.220-224
• /
• 2007

Second-order rate constants (kN) have been determined spectrophotometrically for reactions of 2,4-dintrophenyl 2-furoate (2) with a series of alicyclic secondary amines in 80 mol % H2O/20 mol % dimethyl sulfoxide (DMSO) at 25.0 oC. The furoate 2 is more reactive than 2,4-dintrophenyl benzoate (1) toward all the amines studied. The higher acidity of 2-furoic acid (pKa = 3.16) compared with benzoic acid (pKa = 4.20) has been suggested to be responsible for the reactivity order, at least in part. The Brønsted-type plots for the reactions of 1 and 2 are curved downwardly, indicating that the aminolyses of both 1 and 2 proceed through a zwitterionic tetrahedral intermediate (T±) with a change in the rate-determining step on changing the amine basicity. Dissection of the kN values into their microscopic rate constants has revealed that the pKao and k2/k-1 ratios for the reactions of 1 and 2 are identical, indicating that the nature of the nonleaving group (i.e., benzoyl and 2-furoyl) does not affect the reaction mechanism. The k1 values have been found to be larger for the reactions of 2 than for those of 1, which is fully responsible for the fact that the former is more reactive than the latter.

• International Journal of Naval Architecture and Ocean Engineering
• /
• v.13 no.1
• /
• pp.617-627
• /
• 2021

Underwater Acoustic Channels (UAC) have inherent sparse characteristics. The traditional adaptive equalization techniques do not utilize this feature to improve the performance. In this paper we consider the Variable Adaptive Subgradient Projection (V-ASPM) method to derive a new sparse equalization algorithm based on the Minimum Symbol Error Rate (MSER) criterion. Compared with the original MSER algorithm, our proposed scheme adds sparse matrix to the iterative formula, which can assign independent step-sizes to the equalizer taps. How to obtain such proper sparse matrix is also analyzed. On this basis, the selection scheme of the sparse matrix is obtained by combining the variable step-sizes and equalizer sparsity measure. We call the new algorithm Sparse-Control Proportional-MSER (SC-PMSER) equalizer. Finally, the proposed SC-PMSER equalizer is embedded into a turbo receiver, which perform turbo decoding, Digital Phase-Locked Loop (DPLL), time-reversal receiving and multi-reception diversity. Simulation and real-field experimental results show that the proposed algorithm has better performance in convergence speed and Bit Error Rate (BER).

• Korean Journal of Materials Research
• /
• v.28 no.4
• /
• pp.235-240
• /
• 2018

We propose a speedy two-step deposit process to form an Au electrode on hole transport layer(HTL) without any damage using a general thermal evaporator in a perovskite solar cell(PSC). An Au electrode with a thickness of 70 nm was prepared with one-step and two-step processes using a general thermal evaporator with a 30 cm source-substrate distance and $6.0{\times}10^{-6}$ torr vacuum. The one-step process deposits the Au film with the desirable thickness through a source power of 60 and 100 W at a time. The two-step process deposits a 7 nm-thick buffer layer with source power of 60, 70, and 80 W, and then deposits the remaining film thickness at higher source power of 80, 90, and 100 W. The photovoltaic properties and microstructure of these PSC devices with a glass/FTO/$TiO_2$/perovskite/HTL/Au electrode were measured by a solar simulator and field emission scanning electron microscope. The one-step process showed a low depo-temperature of $88.5^{\circ}C$ with a long deposition time of 90 minutes at 60 W. It showed a high depo-temperature of $135.4^{\circ}C$ with a short deposition time of 8 minutes at 100 W. All the samples showed an ECE lower than 2.8 % due to damage on the HTL. The two-step process offered an ECE higher than 6.25 % without HTL damage through a deposition temperature lower than $88^{\circ}C$ and a short deposition time within 20 minutes in general. Therefore, the proposed two-step process is favorable to produce an Au electrode layer for the PSC device with a general thermal evaporator.

• Journal of Microbiology and Biotechnology
• /
• v.6 no.3
• /
• pp.209-212
• /
• 1996

A two-step cooling technique has been developed for cryopreservation of suspension cultured Scutellaria baicalensis cells. Efficient regrowth of cryopreserved cells was obtained in cryoprotected cells with a mixture of 1.5 M glycerol and 0.4 M sucrose in Schenk and Hildebrandt medium without pretreatment in high osmotic medium. Optimum freezing conditions were found to be a cooling rate of $0.5^{\circ}C$ min from $4^{\circ}C$ to $-40^{\circ}C$, and then retaining samples at $-40^{\circ}C$ for 30 min prior to plunging into liquid nitrogen. A regrowth rate of approximately 95$%$ was obtained after three month storage in liquid nitrogen. Callus cultures established from the cryopreserved cells were found to produce the same patterns of flavonoid accumulation and retain their baicalin producing activity.

• Proceedings of the Korean Geotechical Society Conference
• /
• 1999.03a
• /
• pp.3-46
• /
• 1999

A new method called SRICOS is proposed to predict the scour depth z versus time t around a cylindrical bridge pier of diameter D founded in clay. The steps involved are ; 1. taking samples at the bridge pier site, 2. testing them in an Erosion Function Apparatus called the EFA to obtain the scour rate z versus the hydraulic shear stress applied $\tau$, 3. predicting the maximum shear stress r max which will be induced around the pier by the water flowing at ν Ο before the scour hole starts to develop, 4. using the measured z versus r curve to obtain the initial scour rate zi corresponding to r max , 5. predicting the maximum depth of scour zmax for the pier, 6. using zi and zmarx to develop the hyperbolic function describing the scour depth z versus time t curve, and 7. reading the z vs. t curve at a time corresponding to the duration of the flood to find the scour depth which will develop around the pier. A new apparatus is developed to measure the z vs t curve of step 2, a series of advanced numerical simulations are performed to develop an equation for the $\tau$ max value of step 3, and a series of flume tests are performed to develop an equation for the zmax value of step 5. The method is evaluated by comparing predictions and measurements in 42 flume experiments.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.7 no.9
• /
• pp.2312-2325
• /
• 2013

In this paper, we propose a preprocessing method that it is to correct the distortion of text area in Korean signboard images as a preprocessing step to improve character recognition. Distorted perspective in recognizing of Korean signboard text may cause of the low recognition rate. The proposed method consists of four main steps and eight sub-steps: main step consists of potential vertical components detection, vertical components detection, text-boundary estimation and distortion correction. First, potential vertical line components detection consists of four steps, including edge detection for each connected component, pixel distance normalization in the edge, dominant-point detection in the edge and removal of horizontal components. Second, vertical line components detection is composed of removal of diagonal components and extraction of vertical line components. Third, the outline estimation step is composed of the left and right boundary line detection. Finally, distortion of the text image is corrected by bilinear transformation based on the estimated outline. We compared the changes in recognition rates of OCR before and after applying the proposed algorithm. The recognition rate of the distortion corrected signboard images is 29.63% and 21.9% higher at the character and the text unit than those of the original images.

• Korean Journal of Food Science and Technology
• /
• v.33 no.6
• /
• pp.706-713
• /
• 2001

The influencing factor in drying characteristics of fluidized bed drying with different drying conditions for husked barley were carried out. This fluidized drying mechanism of husked barley was consisted of consecutive two falling rate parts, first falling rate period and second falling rate period without showing constant rate period. The drying rate constant was increased with decreasing charged amount and relative humidity and increasing air temperature and air velocity. Since the drying rate constant expressed by Arrhenius type equation in the falling rate period showed good linearity, the falling rate period was condsidered as the controlling step. The activation energy of first falling step was 1,100 cal/gmol, while for second falling step the values showed 1,600 cal/gmol.

• Clinical and Experimental Reproductive Medicine
• /
• v.19 no.2
• /
• pp.163-168
• /
• 1992

This study was carried out to set up the ovum bank for ovum donation and to determine the best freezing method for human immature oocytes. Human immature follicular oocytes were cryopreserved by slow freezing and rapid thawing method. Immature follicular oocytes were treated by propanediol(PROH) solution by 2 and 4 step method in protocols A & B, respectively. In protocol C, immature oocytes were exposed to sucrose prior to treatment of PROH by 4 step method. We compared survival rate, maturation rate, and fertilization rate of immature oocytes among three protocols. Results were as follows. 1. Oocytes treated by the protocol C showed the highest survival rate( 70.3 %) and maturation rate(34.6%) after thawing. 2. Survival rate of oocytes treated by the protocol C was significantly higher than that of the protocol B after thawing(p<0.05). In conclusion, treatment of oocytes with sucrose prior to expose PROH was the best freezing method. Sucrose may have reduced the toxic effect of cryoprotectant to oocytes. We failed to induce fertilization of oocytes, which were treated by any protocols, by conventional insemination method, but obtained 28.8% fertilization rate by using partial zona dissection(PZD) method. This result suggests that micromanipulation(PZD) of the thawed oocytes before insemination will improve the fertilization rate.

• YAKHAK HOEJI
• /
• v.44 no.6
• /
• pp.578-587
• /
• 2000

The purpose of the present study was to design and prepare the optimum formulation for the oral administration of titrated extract of the unsaponifiable fraction of Zea mays L. (ETIZM). For this purpose, we simulated the blood concentration of ETIZM after its oral administration, changing the dissolution rate constants $(0.05{\sim}20\;hr^{-1})$. In vivo parameters, such as absorption rate constant $(k_a)$, elimination rate constant (k) and volume of distribution (Vd), were incorporated in the simulation on the basis of the experiments and literatures. When the dissolution rate constant $(k_r)$ is over $5\;hr^{-1}$, the absorption process appears to be the rate limiting step for the transport of ETIZM from the G.I. ract to the blood circulation. While less than $5\;hr^{-1}$, the dissolution rate considered to be the rate limiting step. Moreover, the optimum blood concentration was shown in the range from 1 to $5\;hr^{-1}$ of $k_r$ in the simulation. To design and prepare the tablets on the basis of the above results, 7 formula containing HPMC, PEG 4000 and PEG 6000 (1-5%, respectively) were prepared and evaluated. The tablets containing PEG 4000 (1%), PEG 6000 (1%) or PEG 4000 (5%) satisfy the optimum $k_r$ range ($1-5\;hr^{-1}$). These formulations, therefore, will be able to show the more effective blood concentration, compared with the commercial products after the oral administration.

• Journal of Advanced Marine Engineering and Technology
• /
• v.29 no.7
• /
• pp.736-743
• /
• 2005

In this study, three different types of mechanical ventilation systems are compared based on their ventilation characteristics: tracer gas concentration decay characteristics, and ventilation effectiveness by calculating actual ventilation air flow rate. The experiments are performed by using a step-down method for measuring tracer gas. $CO_{2}$ gas, concentration in the model chamber. Application of a mixing factor, k, was used and measured values ranged from 0.68 to 0.77. The Type 2 ventilation system was found to have the highest ventilation effectiveness rather than the Types 1 and 3.