• Journal of Public Diplomacy
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• v.2 no.1
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• pp.97-115
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• 2022

What is the relationship between city diplomacy and public diplomacy in the United States? Whilst this question is often raised among scholars and practitioners of public diplomacy, a concrete and systematic response to it seems difficult to locate. This paper addresses the question by relying on earlier research based on empirical analysis of data from semi-structured interviews with city officials with international purview in the United States as well as with current and former officials at the U.S. Department of State who have worked on topics related to city diplomacy. The research and analysis that informs this paper and the diagrams it offers are hinged on design principles and adopt an architecture studio style approach to data analysis. Further, multidimensional scaling and correspondence analysis are used to visualize the convergence and divergence between the functions of public diplomacy, as introduced by Nicholas Cull, and the functions of city diplomacy that this paper introduces. This is done to first, provide a framework for understanding the dynamics between city diplomacy and public diplomacy; and second, uncover the policy intervention space that could guide policies for making U.S. city diplomacy and public diplomacy more strategically aligned.

• Journal of Practical Engineering Education
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• v.16 no.3_spc
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• pp.267-274
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• 2024

One challenge with teaching practical programming classes is the standardization of development tools on student computers. This is particularly true when a complicated setup process is required before beginning to code, or in remote classes, such as those necessitated by the COVID-19 pandemic, where the instructor cannot provide individual troubleshooting assistance. In such cases, students who encounter problems during the setup process may give up on the class altogether before even beginning to code. Therefore, this paper recommends using GitHub Codespaces as a tool for implementing standardized student development environments from day one. Codespaces provides Docker containers that an instructor can configure in such a way as to enable students to practice installing various coding tools within a controlled space, while also providing a language-specific, fully optimized development environment. In addition, Codespaces may be used more effectively in collaboration with GitHub Classroom, which helps instructors manage both the starter code and coding environment in which students work. In this paper, we compare two semesters of university Node.JS programming classes that utilized different development environments: one localized on student computers, the other containerized in Codespaces online. Then, we discuss how GitHub Codespaces and GitHub Classroom can be used to increase the effectiveness of practical programming classes while also increasing student engagement and programming confidence in class.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.38 no.3
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• pp.221-227
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• 2010

Recent development in seeker technology explores a new seeker design in which, with larger field-of-view (FOV), optical parts are strapped down to a body (hence, called as a body-fixed seeker or a strapdown seeker). This design has several advantages such as comparatively easier maintenance and calibration by removing complex mechanical moving parts, increasing reliability, and cost savings. On the other hand, the strapdown seeker involves difficulties in implementing guidance laws since it does not directly provide inertial LOS rates. Instead, information for generating guidance commands should be extracted by estimating missile/target relative motion utilizing target images on the image plane of a strapdown seeker. In this research, a new framework based on an unscented Kalman filter is developed for estimating missile/target relative motion on the simplified assumption of a point source target. Performance of a terminal guidance algorithm, in which guidance command is generated based on the estimated relative motion, is demonstrated by a missile/target engagement simulation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.1
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• pp.20-28
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• 2014

In this paper, based on the characteristics of proportional navigation, a composite guidance law is proposed for impact angle control of passive homing missiles maintaining the lock-on condition of the seeker. The proposed law is composed of two guidance commands: the first command is to keep the look angle constant after converging to the specific look angle of the seeker, and the second is to impact the target with terminal angle constraint and is implemented after satisfying the specific line of sight(LOS) angle. Because the proposed law considers the seeker's filed-of-view(FOV) and acceleration limits simultaneously and requires neither time-to-go estimation nor relative range information, it can be easily applied to passive homing missiles. The performance and characteristics of the proposed law are investigated through nonlinear simulations with various engagement conditions.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.3
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• pp.199-212
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• 2014

This paper describes an autonomous air combat guidance law using a Virtual Pursuit Point (VPP) in one-on-one close engagement for Unmanned Combat Aerial Vehicle (UCAV). The VPPs that consist of virtual lag and lead points are introduced to carry out tactical combat maneuvers. The VPPs are generated based on fighter's aerodynamic performance and Basic Fighter Maneuver (BFM)'s turn circle, total energy and weapon characteristics. The UCAV determines a single VPP and executes pursuit maneuvers based on a smoothing function which evaluates probabilities of the pursuit types for switching maneuvers with given combat states. The proposed law is demonstrated by high-fidelity real-time combat simulation using commercial fighter model and X-Plane simulator.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.43 no.6
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• pp.497-506
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• 2015

A composite guidance law for impact angle control against nonstationary nonmaneuvering targets is proposed. The proposed law is based on the characteristics of proportional navigation and generates two kinds of guidance commands during the homing phase. The first command is to keep the desired look angle, and the second is to attack the target with impact angle constraint. The switch of guidance phases occurs when the specific light-of-sight(LOS) angle determined from the engagement information is satisfied. The calculation method of the maximum achievable impact angle is also proposed to design easily the desired impact angle within the missile capability. Numerical simulations are performed to investigate the performance and characteristics of the proposed law.

• Tribology and Lubricants
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• v.33 no.1
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• pp.1-8
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• 2017

Drag torque reduction in a wet clutch pack is a key aspect of the design process of the dual clutch transmission (DCT) system. In order to reduce the drag torque caused by lubricant shear resistance, recently developed wet clutch pack systems of DCT, as well as automatic transmission and other four-wheel drive (4WD) couplings, frequently utilize wavy wet clutch pads. Therefore, wavy shape of friction pad are made on the groove patterns like waffle pattern for the reduction of drag torque. Additionally, the groove patterns are designed with larger channels at several locations on the friction pad to facilitate faster outflow of lubricant. However, channel performance is a function of the waviness of the friction pad at the location of the particular channel. This is because the discharge sectional area varies according to the waviness amplitude at the location of the particular channel. The higher location of the additional channel on the friction pad results in a larger cross-sectional area, which allows for a larger flow discharge rate. This results in reduction of the drag torque caused by the shear resistance of DCTF, because of marginal volume fraction of fluid (VOF) in the space between the friction pad and separator. This study computes the VOF in the space between the friction pad and separator, the hydrodynamic pressure developed, and the shear resistance of friction torque, by using CFD software (FLUENT). In addition, the study investigates the dependence of these parameters on the location and waviness amplitude of the channel pattern on the friction pad. The paper presents design guidelines on the proper location of high waviness amplitude on wavy friction pads.

• Tuberculosis and Respiratory Diseases
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• v.45 no.2
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• pp.437-443
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• 1998

Pulmonary alveolar proteinosis is characterized by the accumulation of PAS positive lipoproteinaceous or amorphous proteinaceous material in the alveolar space with spared delicate septal architecture of the lung interstitium and impaired gas exchange of alveoli. We experienced a case of secondary pulmonary alveolar proteinosis in a 41 year old male patient who have occupational history of engagement as a mason over 4year. He compalined exertional dyspnea and chest discomfort, and presented fine inspiratory crackle at both lower lung field, numerous fine nodular denisties in both lung field with peripheral sparing. Light microscopic finding of lung tissue obtained by transbronchiallung biopsy revealed homogenous eosinophilic colloid-like luminal content in the alveolar space, and electron microscopy of bronchoalveolar lavage fluid concentrate showed electron-dense multilamellated structures. To treat the disease, we tried whole lung lavage of right lung with isotonic saline under general anesthesia. After whole lung lavage of right lung, he showed markid improvement of symptom and partial improvement of chest X-ray findings. The patient has been followed for 12 month until now, with no evidence of aggravation.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.37 no.10
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• pp.1002-1009
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• 2009

Precision guidance filter design for a tactical missile with a strapdown seeker aided by low-cost strapdown sensors has been addressed in this paper. The low-cost strapdown sensors consist of an IMU with 3-axis accelerometers and gyroscopes, 3-axis magnetometers, and a barometer. Missile's position, velocity, attitude, and bias error of the barometer are considered as state variables. Since the state and measurement equations are highly nonlinear, we adopt UKF(Unscented Kalman Filter). The proposed guidance filter has a function of a navigation filter if target position error is not considered. In the case that the target position error is introduced, the proposed filter can effectively estimate the relative states of the missile to the true target. For specific engagement scenarios, we can observe that observability problems occur.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.46 no.9
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• pp.742-751
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• 2018

In this paper, we propose a time varying biased proportional navigation guidance law that controls the impact angle under Field-of-View(FOV) and the acceleration limit of the missile. The proposed law is composed of three stages in consideration of the FOV limitation. Since the bias directly affects the acceleration at each stage, the final bias value of the previous stage becomes the initial bias value of the next stage when the stage is switched. In addition, the impact angles were controlled by judging whether impact angles were reached in consideration of engagement conditions and physical constraints.