Thermodynamic Properties of the Polymer Solutions

Lee, Woong-Ki,Pak, Hyung- Suk Korean Chemical Society 1985 Bulletin of the Korean Chemical Society Vol.6 No.6

A statistical mechanical approach to elucidate the solvent effects on the high polymer solutions has been carried out on the basis of the simple model of liquids improved by Pak. In our works, the partition function of the polymer solutions is formulated by the lattice model and our simple treatment of liquid structures. For the ideal polymer solutions proposed by Flory, thermodynamic functions of the polymer solutions are obtained and equations of mixing properties and partial molar quantities are derived from the presented partition function of the polymer solutions. Partial molar quantities are calculated for the rubber solutions in carbon disulfide, benzene and carbon tetrachloride. Comparisons have been made between our equations and those of Flory's original paper for partial molar properties of the rubber-benzene system. Comparing the experimental data of the osmotic pressure of polystyrene-cyclohexane system with our calculated values and those of Flory's, our values fit to the agreeable degrees better than those of Flory's.

A Theory of Polymer Adsorption from Solution

Lee, Woong-Ki,Pak, Hyung-Suk Korean Chemical Society 1987 Bulletin of the Korean Chemical Society Vol.8 No.1

A statistical thermodynamical treatment for polymer adsorption from solution is presented. The canonical partition function for the polymer solution in the presence of a surface or an impermeable interface is formulated on the basis of usual quasi-crystalline lattice model, Bragg-Williams approximation of random mixing, and Pak's simple treatment of liquid. The present theory gives the surface excess ${\Gamma}_{exc}$ and the surface coverage ${\phi}^s_2$ of the polymer as a function of the chain length x, the Flory-Huggins parameter x, the adsorption energy parameter $x_s$, and polymer concentration $v_2$. Present theory is also applicable to the calculation of interfacial tension of polymer solution against water. For the idealized flexible polymer, interfacial tensions according to our theory fit good to the experimental data to the agreeable degrees.

Physical Adsorption of Gases on Heterogeneous Solid Surfaces

Pak, Hyung-Suk 서울대학교 교양과정부 1972 論文集 Vol.4 No.-

The absorption isotherms for argon and nitrogen gas adsorbed on heterogeneous graphite surface are calculated at 77.5˚K and 90.1˚K by developing theoretically the distribution function of the potential energy barrier for the adsorbed molecule in lateral direction of the surface. The calculated values of the isotherms are in good agreements with those of the observed.

Effects of Emergency Care-related Health Policies during the COVID-19 Pandemic in Korea: a Quasi-Experimental Study

Pak Yun-Suk,Ro Young Sun,Kim Se-Hyung,Han So-Hyun,Ko Sung-keun,Kim Taehui,Kwak Young Ho,Heo Tag,Moon Sungwoo 대한의학회 2021 Journal of Korean medical science Vol.36 No.16

Background: The purpose of this study was to review the nationwide emergency care-related health policies during the coronavirus disease 2019 (COVID-19) pandemic disaster in Korea and to analyze the effects of the policies on the safety of patients who visit emergency departments (EDs) during this period. Methods: This study is a quasi-experiment study. The study population was patients who visited all 402 EDs in Korea between December 31, 2019 and May 13, 2020, using the National Emergency Department Information System (NEDIS) database. The study period was classified into 5 phases according to the level of national crisis warning of infectious disease and the implementation of emergency care-related health policies, and all study phases were 27 days. The primary outcome was in-hospital mortality, and the secondary outcome was length of stay (LOS) in the ED during the COVID-19 outbreak. Results: The number of ED visits during the study period was 2,636,341, and the in-hospital mortality rate was 1.4%. The number of ED visits decreased from 803,160 in phase 1 to 496,619 in phase 5 during the study period. For in-hospital mortality, the adjusted odds ratio (OR) (95% confidence interval) was 0.77 (0.74–0.79) in phase 5 compared to phase 3. Additionally, by subgroup, the ORs were 0.69 (0.57–0.83) for the patients with acute myocardial infarction and 0.76 (0.67–0.87) for severe trauma in phase 5 compared to phase 3. The ED LOS increased while the number of ED visits decreased as the COVID-19 pandemic progressed, and the ED LOS declined after policy implementation (beta coefficient: −5.3 [−6.5 to −4.2] minutes in phase 5 compared to phase 3). Conclusion: Implementing appropriate emergency care policies in the COVID-19 pandemic would have contributed to improving the safety of all emergency patients and reducing in-hospital mortality by preventing excessive deaths.

액체 질소족수소화물의 구조와 성질

박형석,성용길,안운선 서울대학교 교양과정부 1969 論文集 Vol.1 No.-

The transient state theory of significant liquid structure has been applied to Ammonia, phosphine, arsine and stibine. The liquid partition functions are derived according to the transient state theory. The various thermodynamic properties such as molar volume, vapor pressure, entropy of vaporization and critical point properties are calculated. The results show better agreement with experimental observations than the results obtained from the original significant liquid strutcure theory.

A Lattice Statistical Thermodynamic Study of Bilayer Amphiphile Molecules

Pak, Young-Shang,Pak, Hyung-Suk Korean Chemical Society 1990 Bulletin of the Korean Chemical Society Vol.11 No.5

In order to elucidate conformational properties of bilayer semiflexible amphiphile molecules, we derive a expression of free energy separation with respect to bilayer width, and segment density profiles on the basis of cubic lattice model. Our result shows that at the moderate surface coverage region (i.e., ${\sigma}$ < 0.35), bilayer system tends to have thermodynamically favorable bilayer width corresponding to free energy minimum condition resulting from the major contribution of attractive interaction between chain segments. However such a favorable bilayer width do not occur in the region of high surface converage (i.e., ${\sigma}$> 0.4) where repulsive interaction between chain segments is considered to be dominant.

Theory of Surface Tension and Viscosity of Liquid

박형석,Pak, Hyung-suk Korean Chemical Society 1968 대한화학회지 Vol.12 No.1

액체 분자는 고체, 천이상태 및 기체와 같은 자유도를 갖는다는 액체구조에 관한 천이상태이론을 적용하여 액체의 표면장력과 점도를 계산하여 측정 치와 좋은 일치를 얻었다. 표면장력을 계산함에 있어서 표면 각층의 밀도는 이웃 층 사이의 밀도를 주는 관계식으로부터 쉽게 얻었다. 그리고 액체가 점성 흐름을 할때 활성화된 분자는 흐르는 방향으로는 기체와 같은 자유도를 가지나, 이에 직교한 평면상에서는 천이상태 및 기체와 같은 자유도를 갖는다고 가정하였다.

Theoretical Approach for physicochemical factors affecting human toxicity of dioxins

황인철,Hyung Suk Pak 환경독성보건학회 1999 한국독성학회 심포지움 및 학술발표회 Vol.- No.-

후방 염전 비구에 시행한 비구 주위 절골술 -증례 보고-

장재석 ( Jae Suk Chang ),손현철 ( Hyun Chul Son ),박재형 ( Jai Hyung Pak ),김기형 ( Ki Hyung Kim ) 대한고관절학회 2003 Hip and Pelvis Vol.15 No.2

액체구조에 관한 천이상태이론의 물에 대한 적용

박형석,장세현,Pak, Hyung-Suk,Chang, Sei-Hun 대한화학회 1966 대한화학회지 Vol.10 No.2

The partition function for liquid water is developed according to the transient state theory of significant liquid structure proposed by Pak, Ahn and Chang. This theory assumes that the molecules may possess solid-like, transient and gas-like degrees of freedom in liquid state. Although liquid water has several special properties, for example, minimum molar volume at 4^{\circ}C$, the general theory of liquid can be applied successfully. The theoretically calculated values for thermodynamic properties at the liquid temperature range and for the critical properties are in good agreement with the observed values. 박형석, 안운선과 장세헌이 제안한 액체구조에 관한 천이상태이론을 물에 적용시켜 액체상태에 있는 물의 상태합을 구했다. 이 이론은 액체의 분자가 고체와 같은 자유도, 천이상태의 자유도 및 기체와 같은 자유도를 갖는다는 것이다. 물은 4^{\circ}C$에서 그의 부피가 최소로 되는 등 특유한 성질들을 가졌지만 이 액체이론이 잘 적용된다. 이 이론을 써서 계산한 물의 몰부피, 증가압, 엔트로피, 증발열 및 일정한 압력에서의 비열 그리고 임계점에서의 성질 등은 실측치와의 좋은 일치를 보여준다.