Here are the directions to
Yonsei University.

Class Code Class Title Class Description
MST2110 DIFFERENTIAL EQUATIONS FOR MATERIALS SCIENCE (1) The purpose is to understand various differential equations necessary for the study and research of materials science and to understand how to solve them. The theoretical foundations of ordinary differential equations, partial differential equations, series solutions, and various transformation methods will be covered in the lecture. In addition, by actively utilizing specific examples of various differential equations that are frequently encountered in the field of materials science, it helps to cultivate the basic mathematical abilities required as a material engineering degree and to improve the engineering application ability directly related to problem solving in material systems.
MST2120 NUMERICAL MATHEMATICS IN MATERIALS SCIENCE AND ENGINEERING (2) Basic numerical analysis methods (nonlinear equations, simultaneous linear equations, matrices, simultaneous ratio linear equations, health law, numerical integration, ordinary differential equations) for mathematical and physical model setting and analysis and various process design in each field of metal and materials engineering , partial differential equations).
MST2130 SOLID STATE CHEMISTRY Approach and understand materials from the perspective of atomic structure, molecular structure, chemical bonding, structure formation principle and coordination structure, and explain from the viewpoint of valence bond theory and molecular orbital theory. In order to understand the bonding structural characteristics of these materials, the physical properties of simple compounds are studied, and through this, the ability to understand the functional properties of materials is cultivated.
MST3310 SOLID STATE PHYSICS In order to understand the basic concepts and principles of solids, students learn about the theories of lattice vibrations, free electron models, and energy bands of solids.
Class Code Class Title Class Description
MST2210 INTRODUCTION TO MATERIALS SCIENCE (1) As an introductory course on new materials engineering, the bonds between atoms constituting inorganic materials such as metals, ceramics, and semiconductors, crystal structures, crystal defects and mechanical properties and strengthening mechanisms of materials, electrical/magneto-optical properties of materials, and microstructures of materials This course lectures on the fundamentals of materials engineering, such as the effects on mechanical properties, diffusion in solids, phase diagrams, and phase changes.
MST2220 INTRODUCTION TO MATERIALS SCIENCE (2) This course deals with the basic knowledge of materials mainly based on organic matter. In the first half of the lecture, basic organic chemistry, intermolecular forces, and chemical properties of organic materials such as polymer synthesis are lectured, and in the second half, physical properties of organic materials such as analysis and physical properties of organic materials are lectured. Finally, various applications and possibilities of organic materials are introduced.
MST2230 THERMODYNAMICS OF MATERIALS (1) The ability to analyze the thermodynamic properties of materials and reactions by introducing the basic laws of thermodynamics along with the introduction of the concepts of equilibrium states and equations of state of materials and applying the basic laws of thermodynamics to chemical reactions and phase changes related to materials processing based on this understanding taught to cultivate.
MST2240 THERMODYNAMICS OF MATERIALS (2) Based on thermodynamics I (basic concepts and laws), lectures are given on material reaction equilibrium, material phase transition, multi-component system phase diagram and interfacial thermodynamics, and thermodynamic applications.
MST2260 CRYSTALLOGRAPHY The properties of the material depend mainly on the type of element constituting the material and the arrangement by the bonding between the elements. This lecture uses lattice, unit cell, symmetric element, crystal system, point group, and space group to access functional properties through structural understanding when atoms or atoms form crystals by periodic and regular repetition of materials. Understand the crystal structure geometrically and cultivate the ability to use crystal compounds through the application.
MST3220 PHASE EQUILIBRIUM AND TRANSFORMATION The concept of equilibrium, phase diagram, diffusion of atoms, nucleation and growth theory, diffusion and non-diffusion transformation, phase transformation kinetics, microstructure formation, etc. are lectured.
Class Code Class Title Class Description
MST2100 GATEWAY TO MATERIALS WORLD Based on the principles of basic science and applied engineering, new material engineering develops innovative materials that can be used in various fields such as metal, ceramic, polymer, bio, and semiconductor. In this subject, we will look at the overall learning and research contents of new material engineering, and explore the basic principles and industrial application examples necessary to carry out deep learning of new material engineering in the future.
MST2310 MATERIALS ENGINEERING LABORATORY (1) Three themes are selected and tested from six themes: mechanical, electrical, electrochemical, optical, microstructure of materials, thermal and thin film materials.
MST2320 MATERIALS ENGINEERING LABORATORY (2) Three themes are selected and tested from six themes: mechanical, electrical, electrochemical, optical, microstructure of materials, thermal and thin film materials.
MST3310 MATERIALS DESIGN & CHARACTERIZATION It is intended to acquire relevant knowledge and improve problem-solving and creative thinking by applying Problem-based learning to topics related to six small fields of material engineering (material mechanical properties, material electrical, material electrochemical, material, material optical, microstructure and thermal properties).
MST3320 DESIGN FOR RESEARCH Creative thinking and cooperation are cultivated through acquisition of basic and applied knowledge necessary for industrial sites based on experimental practice and comprehensive experimental design methods.
MST3410 ELECTRONIC PROPERTIES OF ENGINEERING Through lectures on electrical/magnetic properties such as conductive materials, semiconductors, magnetic materials, and dielectrics, the relationship between basic theories and properties is understood, and further, the application of each material is taught.
MST3420 MECHANICAL PROPERTIES OF MATERIALS It teaches the basic principles of the relationship and interpretation of stress and strain on materials, the properties of plan diagrams, the stress of beams, and the deflection of beams. In addition, the strength of the material, crack growth mechanism, and fracture behavior are taught, and the reliability and life of the ceramic material are predicted based on the crack growth mechanism by comparing ceramics and metals. In addition, by teaching the thermal properties of materials, students can understand the mechanical and thermal properties of materials to contribute to the application of materials and the development of new materials and physical properties.
MST3430 OPTICAL PROPERTIES OF MATERIALS Based on the basic theory of optics and lectures on the interaction of light and materials, the understanding of optical materials is broadened and the applications of various optical materials are taught.
MST3440 MATERIALS CHEMISTRY For the essential understanding of material properties, basic knowledge of the relationship between chemical bonding of solid matter and material properties is taught. It also provides examples of representative materials that are most commonly used in the field of practical materials and teaches how the micro/nano-level chemical properties of these materials relate to material behavior.
MST3450 TRANSPORT PHENOMENA IN MATERIALS SCIENCE AND ENGINEERING To help students in material engineering and new material engineering understand the principles of material engineering, application, and material property development, and develop the creative ability to design equipment and research and develop new materials, they study related physical and chemical basic theories, laws and hydrodynamics.
MST3460 FUNDAMENTALS OF SURFACES AND INTERFACES Interfaces recognized as defects inside materials have recently been developed and studied as new mechanisms capable of controlling the physical properties of materials. In this subject, we study the properties, structures, analysis methods, and control mechanisms of interfaces made up of different materials.
MST3470 MECHANICS OF SOLID MATERIALS Lectures on stress/strain rate relationships, coordinate transformation, and breakdown based on elastic dynamics, material structure and defects, and mechanical behavior on the force applied to the material, moment-induced displacement and stress.
MST3480 THE STRUCTURE OF MATERIALS Based on the classification of crystalline, amorphous, and liquid crystal structural materials, the relationship between the bonds/structures and properties and the relationship between defects contained in the material properties are studied in relation to the microstructure.
MST3490 MATERIAL REACTION KINETICS Lectures on the theory of interfacial chemical reaction rate at the gas phase/liquid phase, liquid phase, and gas phase/solid phase interface applied in the field of material engineering, factors on the chemical reaction rate, and their effects.
MST3500 DESIGN OF POLYMER MATERIALS Analyzes the mechanical, chemical, electrical, and optical properties of materials and microstructures that control the formation of polymers from molecular structures to engineering materials, and lectures on their applications.
MST3510 COMPUTER MODELLING IN MATERIALS SCIENCE AND ENGINEERING Computerized lectures on calculating the equilibrium state of materials, analyzing solidification and heat treatment processes, designing alloys and materials, analyzing metal oxidation reactions, calculating material performance, and analyzing welding.
MST3520 INTRODUCTION TO SEMICONDICTOR ENGINEERING It helps to understand energy bands and doping through lectures on basic physical properties of semiconductor materials, and based on this, silicon processes such as oxidation, diffusion, implantation, e-beam, sputtering, CVD, etc., device operation theory such as p-n diode, MOSFET transistor, silicon, and compound semiconductor.
MST3530 PHYSICAL CERAMICS Chemical bonding and structure of ceramic materials, defect structure and defect reaction equilibrium, diffusion theory and defect diffusion in ceramic solids, diffusion and ion conductivity, and application principles of ion conductivity materials.
MST3540 SINTERING : THEORY AND PROCESS Understanding material migration based on thermodynamics and diffusion theory and its engineering applications. Understanding the principles of sintering process such as densification and particle growth. Theory and practice related to interfacial thermodynamics, solid phase sintering, liquid phase sintering, pressurized sintering, etc. Understand sintering-related material processes.
MST3550 X-RAY DIFFRACTION Based on the generation and properties of X-rays, crystal geometry, diffraction theory, structural factors, real space, and diffraction conditions in the counter-lattice space, crystal structure, azimuth relations, residual stress, and co-composition analysis methods in bulk and thin film materials are taught.
MST3560 BIO & ORGANIC MATERIAL ENGINEERING Completion of the basic courses in organic chemistry and biochemistry required to understand the properties and reactions of biological and organic materials and to apply them.
MST3570 JOINING OF MATERIALS This paper discusses the bonding methods of various materials such as metal, ceramic, etc. (Brazing, soldering, adhesive bonding, and ceramic and plastic bonding), and changes in microstructure and physical properties according to bonding.
MST3580 MATERIALS CHARACTERIZATION Understanding material properties using Diffractometer, Spectroscopy, Microscopy, etc.: All functional properties of a material, such as electrical, optical, magnetic, thermal, mechanical, etc., can be understood by composition including structure and chemical bonding of the material. In other words, through the study of the structure and composition of the material, it is possible to control and improve the various functional characteristics of the material, and through this, the ability to utilize the material can be cultivated. This lecture doubles the ability to understand materials by learning principles such as X-ray Diffractometer (XRD), Fourier Transformed Infra-red (FT-IR), and Scanning Electron Microscopy (SEM), which are essential for material engineers to understand these materials.
MST3590 PHYSICAL CHEMISTRY FOR MATERIALS SCIENCE The concept of Equilibrium, Structure, and Change aims to understand and mathematically describe the various properties of matter. We will give lectures on thermodynamics and thermochemistry that discuss the basic properties of Matter and the correlation of Matter-System-Energy, such as Enthalpy, Entropy, and Free energy.
MST3600 SOLIDIFICATION OF METALS AND ALLOYS Basic theories on crystal growth and solidification of pure metals, alloys, ceramics and various new materials, atomic migration and interfacial formation at high-liquid solidification interface, heat transfer during solidification, redistribution of solute atoms, solidification of single and multi-phase alloys, coagulation thermodynamics, and single crystal growth.
MST3620 SEMICONDUCTOR PROCESSING Unit processes (photographic etching, oxidation, diffusion, ion implantation, thin film deposition, wiring and contact, packaging) of semiconductor processes are mainly taught, and a comprehensive approach is also introduced at the same time. In order to improve the understanding of the course, practice, practice, and presentation of silk are also conducted at the same time.
MST3640 ELECTROCHEMISTRY IN MATERIALS PROCESSING The thermodynamic and speedological theories of ionics and electronics and their applications are taught for electrochemical systems consisting of electrodes/electrolytes.
MST4310 CREATIVE MATERIAL DESIGN It is a design project subject that encourages students to create creative ideas and conduct research on new technologies and product development in order to promote the understanding of theories and principles of new material engineering majors and to enhance the practical application of acquired knowledge.
MST4320 GRADUATE THESIS Based on research results conducted in connection with material system design, research results are analyzed, supplementary experiments are conducted, reports are prepared, and research results are presented. Through this, lectures and practical education on report preparation and presentation are conducted.
MST4410 THIN FILM MATERIALS This article discusses the basic principles of thin film formation applied to next-generation semiconductors, nano-bio devices, nano-flexible batteries, and display devices, phase transformation of thin film materials, diffusion and electrical conductivity in transparent oxides, and defects and stress.
MST4420 ENVIRONMENTAL DEGRADATION OF MATERIALS AND ITS PREVENTION The principle of corrosion, electrochemical, corrosion, metal degradation at high temperature, high temperature material, material selection, method and method, electrochemical of plating, electroplating, chemical plating, PVD and CVD, metal coloring, anodization, application plating, phosphoric acid heat treatment, etc.
MST4430 INTRODUCTION TO SOFT MATERIALS Its purpose is to understand physicochemically the polymers, colloids, amphoteric materials, liquid crystals, and biological magnetic assembly materials. Rather than complex mathematical/physical theories, the emphasis is on qualitatively understanding the synthesis and properties of these soft materials. It also introduces a wide range of real-world examples of them in our daily lives and in nature.
MST4440 COMPOSITE MATEIRLAS : DESING,PROCESS AND PROPERTIES Theoretical/engineering understanding and application of composite material, material compounding principle, reinforcement and base material, composite material manufacturing process, composite material properties. New technology-based next generation composite material.
MST4450 MANUFACTURING PROCESSES OF MATERIALS Lectures on basic theory of material processing/molding, hot and cold processes, friction and lubrication, metal forging and rolling, extrusion, wire drawing, plate processing, and material special molding/processing processes.
MST4460 METALLIC ALLOY DESIGN To establish thermodynamic and kinetics concepts for new alloy design, multi-component state diagram, diffusion and solid-phase transition are taught, and the actual alloy state diagram is designed using thermodynamic calculations, and alloy design process is performed to manufacture and evaluate properties.
MST4470 COLLOID SCEINCE AND ENGINEERING It relates to the physical/chemical properties and processes of a liquid or solid dispersion system present in a liquid phase. In the first half of this lecture, interfacial energy between materials, stability of dispersion systems, and synthesis of colloidal materials will be discussed, and in the second half, processes and applications using colloidal materials will be introduced. This lecture generally deals with colloids in the form of metal, ceramic, polymer, organic, or hybrid between materials.
MST4480 INFORMATION STORAGE MATERIALS It studies existing magnetic recording materials and various materials that store spin information through hard disk drive (HDD), and learns the principle and application of spintronics for storing the latest information.
MST4490 MICROSYSTEM ENGINEERING Lectures on materials and micro-processes for the fabrication of micro-mechanical or electronic devices at a three-dimensional level. In particular, an example of a representative microsystem element having a functional material is introduced.
MST4500 MATERIALS ENGINEERING MANAGEMENT & LEADERSHIP Understanding and considering basic management terms such as financial statements, cash flows, profits, depreciation, and cost inference required as an introduction to the material industry and material engineering guidance.
MST4510 NANOSTRUCTRUED MATERILAS : SCIENCE AND TECHNOLOGY Scientific understanding of the physical, mechanical, and chemical behavior of materials in nano-scale and their engineering applications. Theory and technology of the synthesis/analysis/characteristics/application of nanomaterials and the principles of nanomaterials.
MST4520 CERAMIC PARTS AND MATERIALS FOR DISPLAY & ENERGY DEVICE With the depletion of fossil fuels, the need for alternative energy is emerging. As a solution to this problem, an energy conversion device that can efficiently use infinite solar energy, i.e., a solar cell, is studied theoretically from material to device. In addition, the types and manufacturing processes of solar cells are classified, and the design and structure improvement of materials to improve energy conversion efficiency are learned.
MST4530 DEVICE MATERIALS Basic theory of CMOS, elemental design, CV-analysis and theory, transistor theory, silicon substrate engineering, sensor..the application of equipotential materials
MST4540 MAGNETIC MATERIALS AND DEVICES Magnetism theory, magnetization process, magnetic domain, magnetic anisotropy, magnetostriction, magnetism, magnetism, magnetostriction, magnetism, and spin application elements such as ferromagnetic, paramagnetic, ferromagnetic, and antimagnetic.
MST4550 ELECTRONIC CERAMICS Basic theories and applications of advanced electronic ceramics such as dielectric, ferroelectric, piezoelectric, and various radio communications and packaging materials.
MST4570 BIO MATERIALS Understand the structure and properties of representative biomaterials such as enzymes, nucleic acids, and antibodies, and introduce applications such as considering biological systems that combine modern chemical analysts with biomaterials, medical diagnosis, and environmental monitoring.
MST4580 NANO ELECTRONIC DEVICES Through understanding the operating principle of MOSFET devices and the ultra-fine manufacturing process, the limitations of ultra-fine device manufacturing through the existing top-down method and the bottom-up nanostructure manufacturing method including nano-imprint are taught. In addition, the principle of operation and design manufacturing method of sensor devices using nanostructures will be taught.
MST4590 NON-CRYSTALLINE MATERIALS Define/classify amorphous materials, compare/evaluate their manufacturing methods and physical properties. Glass, which is a representative amorphous material, is classified by function, and systematic knowledge of the processes from manufacturing glass applied to each function to characteristic evaluation is acquired. In addition, we learn about the design and development of amorphous materials applicable to display and solar cells.
MST4600 INFORMATION & DISPLAY MATERIALS Lectures on the theory of thin film deposition of displays, semiconductors, and information materials, processes (Evaporation, Sputtering, CVD, Solution Process), and basic display theory (LCD, OLED).
MST4610 SEMICONDUCTOR DEVICES Semiconductor material characteristics, theory and application of semiconductor devices such as P-N junction diode, MOSFET, MESFET, BJT, etc.
MST4620 INTRODUCTION TO FUEL CELL FUNDAMENTALS It understands the composition and driving principle of fuel cell, which is the core of the energy environment field, and teaches basic theoretical education such as basic electrochemical, gas/ion/electron transfer, inhomogeneous catalyst reaction, catalytic reaction theory, etc.
MST4630 FERROUS MATERIALS The classification and classification of steel materials, state diagram, phase transition and microstructure control, mechanical properties of steel, stainless steel, welding structure, alloying element effects, and the manufacturing process of steel materials are taught.
MST4640 OPTICAL MATERIALS Among the representative industries using light, we learn about the field of information transmission and storage. The reason for using light will be considered, and the structure, operating principle, and required characteristics of parts/materials used in each field will be lectured from the perspective of materials. They also raise their own problems and discuss extensively the solutions to improve them.
MST4650 FRACTURE MECHANICS Destruction of materials is the first consideration in the use of materials and system design. As new material development becomes active, a destruction mechanism that cannot be explained by the existing material destruction dynamics is observed, and thus, research on a new theory based on an understanding of the existing theory is needed. In this subject, the development process and application of fracture mechanics are introduced first, and the application and development are studied in depth.
MST4660 MATERIALS IN ENERGY STORAGE DEVICES Based on material electrochemical, the theory of electrochemical energy storage and conversion materials, primary/secondary batteries, fuel cells, electrochemical capacitors, and electrochemical sensors to which the theory is applied are taught.
MST4670 FUNCTIONAL BIOMATERIALS AND DEVICES Introduction and application studies of bio-functional devices that combine biomaterials such as enzymes, DNA, RNA, antibodies, and neurotransmitters with sensors and actuator elements manufactured through semiconductor processes.
MST4690 PYROMETALLURGICAL PROCESSING Physical theory, thermodynamic theory, and kinetics theory related to the high-temperature process of materials are taught, and based on this, high-temperature reactions of steel and non-ferrous materials and high-temperature manufacturing processes are taught.
MST4700 SPECIAL TOPICS IN BIOMATERIALS Introduction to the manufacturing methods and applications of medical biomaterials including implants.
MST4710 CERAMICS PROCESSING Overall understanding of ceramic processes, such as synthesis and evaluation of ceramic powder for fine ceramic manufacturing, colloidal interfacial chemistry, dispersion, molding process, and drying theory.
MST4720 MICRO AND NANO FABRICATION After a brief overview of semiconductor/electronic device manufacturing processes, lectures are given on each of the processes, such as nanoimprinting, soft lithography, self-assessment, and variable printing-based processes. Simultaneously learning about the various physical, chemical, and material engineering phenomena and principles inherent in each process method. In addition, the above-described non-traditional pattern forming methods are also taught about examples applied/applied to actual electronic device manufacturing.
MST4730 HYBRID MATERIALS This study seeks to introduce the synthesis and application of hybrid materials between metal, ceramic, polymer, and organic materials in the nano unit. I would like to first deal with the basic characteristics of various types of materials and lecture on the various characteristics obtained by combining each material.
MST4740 ORGANIC MATERIALS PROCESSING It deals with process-related organic material characteristics through understanding basic hydrodynamics and viscoelasticity, and lectures on the principles and applications of many applicable organic material processes such as polymer processing, coating, film, emulsion process, thin film process, surface modification process, and self-assembly process.
MST4750 HEAT AND SURFACE TREATMENT Lectures on steel condition diagram, constant temperature metamorphosis, continuous cooling metamorphosis, smallness and hardening ability of steel, surface hardening treatment through carburization and immersion, residual stress during heat treatment, and cause and prevention of specimen deformation and cracks.
MST4760 HIGH TEMPERATURE MATERIALS The most basic theories and principles, and application technologies of the manufacturing process of materials used at high temperatures, room temperature and high temperature physical properties, and thermodynamic behavior at high temperatures will be given. In addition, the high temperature generation theory and combustion process necessary to obtain the high temperature required for drying, firing, heat treatment, etc. related to the manufacturing process and use of the material are mainly taught based on thermodynamic perspective.
MST4770 SELECTED TOPICS IN MATERIALS SCIENCE (1) It is a course to introduce and discuss the latest research fields and technologies that are of special interest in material engineering.
MST4780 LIGHT METALLIC ALLOYS Lectures are given on the types of lightweight alloys such as aluminum, magnesium, and titanium groups, phase transformation characteristics, mechanical characteristics, new alloy design and development trends, and industrial application.
MST4790 MATERIALS RECRYCLING Lectures on reprocessing and recycling techniques of materials using chemical reactions and physical treatments.
MST4800 SELECTED TOPICS IN MATERIALS SCIENCE (2) It is a course to introduce and discuss the latest research fields and technologies that are of special interest in material engineering.
MST4810 MECHANICS AND MATERIALS PLASTICITY Based on material dynamics, stress and strain during elastic and plastic deformation, properties of anisotropic materials, high-temperature deformation behavior of materials, basic dynamics for destruction and fatigue, and deformation properties related to microstructure are taught.
MST4820 BIOMATERIALS ENGINEERING Understanding the self-assembly phenomenon, introducing the synthesis and design method of self-assembled molecules, and introducing the biotechnology application method using self-assembled nanomaterials.
MST4830 ORGANIC MOLECULAR MATERIALS Lectures on the characteristics, design, synthesis, and device analysis of organic and bio-materials.
MST4840 HIGH TEMPERATURE PHYSICAL CHEMISTRY OF MATEIRLALS PROCESSING AND THE ENVIRONMENT Specific thermodynamic reactions and material transfer phenomena included in the high-temperature material production process are examined. In particular, lectures will be focused on high-temperature reduction and refining reactions and coagulation based on the production of steel, aluminum, and copper, which are essential for state-based projects. In addition, we will look at the environmental impact of process waste generated by these high-temperature material processes and the technologies for recycling them.
MST4850 ELECTRONIC STRUCTURE THEORY FOR MATERIALS:BACK TO THE BASICS This lecture was opened to understand the basic concepts of electronic structure and agglomerated material system theory based on the first principle. It will help understand the concepts learned at import time by covering a range of examples, from relevant academic research and industrial applications of high-performance materials to nanotechnology. The final goal of this lecture is to utilize modern density functional theory and advanced atomic modeling to understand and interpret the properties of real-world materials (electronic/magnetic/optical devices, sensors, hardcoating, etc.). Lecture materials will be provided for a wide range of students to take by excluding difficult mathematical expressions as much as possible and focusing on chemical and physical concepts first.
MST4860 SYSTEMATIC CHEMISTRY OF THE ELEMENTS In this lecture, we will systematically understand the elements in the periodic table. The class will focus on the periodic properties of all elements including metal and non-metal elements, and you will learn the basic properties of compounds composed of each element and its elements. In the first year of undergraduate school, it was learned that physicochemical characteristics tended to show a tendency according to the period and family of the periodic table, but this is not so simple. In other words, it is necessary to understand the element 'comprehensively' based on the concept of the bonding model, structure, and reactivity of the compound (complex composed of elements). In fact, given that modern technological societies have developed using known elements and compounds of those elements, such knowledge will be very useful in all fields of science and technology.
MST4880 PROCESS DESIGN FOR THIN FILM MATERIALS This lecture discusses the process principles and design of thin film materials for future displays, energy harvesting, bio, flexible using catalyst materials, and self-healing related device materials.
Warning: include(m31_1_4.php): failed to open stream: No such file or directory in /yonsei0206/www/m31_1.php on line 39 Warning: include(m31_1_4.php): failed to open stream: No such file or directory in /yonsei0206/www/m31_1.php on line 39 Warning: include(): Failed opening 'm31_1_4.php' for inclusion (include_path='.:/usr/local/php74/lib/php') in /yonsei0206/www/m31_1.php on line 39