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Background Managing unilateral vertically displaced sacral fractures remains a challenge. A triangular osteosynthesis (TOS), which involves fixing the fractured sacrum using unilateral spinopelvic fixation and a supplemental ilio-sacral screw, continues to gain popularity as it facilitates early mobilization and improves the long-term outcome. However, it has limitations, such as destruction of the L5-S1 joint, the need for additional removal surgery, and an increased risk of infection due to the large incision. An S1 pediculoiliac construct was proposed to overcome this limitations. Its use also has complications, however, including a painful hardware prominence due to the traditional iliac screw, excessive soft tissue retraction, and limited reduction capability. Case Description A 20-year-old woman fell from a height of 6 meters and sustained a vertical shear type sacral fracture on the left side with substantial vertical displacement. We reduced and fixed the fracture using a TOS using an S1 pedicle screw and an S2 alar iliac screw (S2AIS). The patient was allowed immediate weight-bearing as tolerated. We achieved good reduction and union with a small vertical incision, without the destruction of L5-S1 joints, a symptomatic implant prominence, or wound complications. Conclusions For unilateral vertically unstable sacral fractures, TOS using S1 pedicle screws and S2AIS is safe and has the advantage such as maintaining mobility in the lumbar pelvic region, small size wounds, and reduced soft tissue damage, and it may have a potentially low infection rate. Further studies are needed to determine the specific indications and validate the effectiveness of this procedure.

This study investigated the characteristics of transmission routes of COVID-19 cluster infections (⩾10 linked cases within a short period) in Gangwon Province between 22 February 2020 and 31 May 2021. Transmission routes were divided into five major categories and 35 sub-categories according to the relationship between the infector and the infectee and the location of transmission. A total of 61 clusters occurred during the study period, including 1741 confirmed cases (55.7% of all confirmed cases (n = 3125)). The the five major routes of transmission were as follows: ‘using (staying in) the same facility (50.7%), ‘cohabiting family members’ (23.3%), ‘social gatherings with acquaintances’ (10.8%), ‘other transmission routes’ (7.0%), and ‘social gatherings with non-cohabiting family members/relatives’ (5.5%). For transmission caused by using (staying in) the same facility, the highest number of confirmed cases was associated with churches, followed by medical institutions (inpatient), sports facilities, military bases, offices, nightlife businesses, schools, restaurants, day-care centres and kindergarten, and service businesses. Our analysis highlights specific locations with frequent transmission of infections, and transmission routes that should be targeted in situations where adherence to disease control rules is difficult.

Dynamic wireless charging (DWC) is an emerging technology that enables the batteries of electric vehicles (EVs) to charge automatically while the vehicles are in motion. The DWC-EV system addresses the challenges inherent in battery technology, such as the short driving range, long recharging time, and high price. Compared with conventional plug-in EVs, the DWC-EV can charge a battery more frequently because it can be done while the EV is in motion from the charging infrastructure installed on the road. In this paper, we analyze how this frequent-charging characteristic of DWC-EV can affect the battery lifetime in the DWC-EV. We first introduce a mathematical model to evaluate the economic cost of the DWC-EV for a given battery size. A battery degradation model is incorporated to account for the quantitative relationship between the installation of the charging infrastructure and battery life extension. We then use the model to analyze how the economic cost varies with the size of the battery. Our preliminary findings provide insight into the relationship between DWC from the charging infrastructure and the battery’s lifetime. Note to Practitioners —There is a tradeoff between power track allocation and battery size in DWC buses. It has been known that DWC buses need not equip a large battery because the battery can be charged frequently from the power track along the route. Also, it has been agreed that frequent shallow charging with DWC can improve the battery’s lifetime compared to infrequent deep charging. We verify these common beliefs and agreement with a mathematical approach with a widely used battery lifetime estimation model. Our quantitative model indicates that the DWC can positively improve battery lifetime, but this positive effect is always true only when the battery is large enough, even if the battery is charged frequently with DWC. The presented optimization model suggests that the lifelong economic benefit of DWC-based bus transit can be realized with optimal allocation of the power track with a sufficiently large battery.

We present a new algorithm for application to path synthesis of a four-bar linkage with continuous variables called the Hybrid Taguchi random coordinate search algorithm (HTRCA). The HTRCA combines two algorithms of the Taguchi method (TM) and the random coordinate search algorithm (RCA). The RCA adjusts one variable simultaneously with two directions and various step sizes in random order to escape a local minimum. Since the RCA modifies one variable at a time according to the random order, the result of the RCA is sensitive to an initial condition of variables. The TM was adopted to generate nearly optimal initial conditions. Using the TM, the approximate optimal value can be found in even multi-modal functions. Also, the TM is used with different setting values to escape a local minimum point by changing two or more variables in one step. By combining the two methods, a global optimal value can be found efficiently. Seven test functions were optimized and the robust and efficient performance was verified by comparison with other hybrid optimization algorithms. Finally, path synthesis of four-bar linkage is done by the developed optimization algorithm, and the result is compared to previous works on the same problem with evolutionary algorithm.

Recently, high-strength strands with greater yield and tensile strength than ordinary strands have been developed in several countries. However, the influences of the high-strength strands on flexural members and code provisions have not been fully identified to date. In this study, five large post-tensioned girders were tested to investigate the effect of high-strength strands on the flexural behavior based on the concrete compressive strength and the tensile strength of the strands. The test results indicated that the actual flexural behaviors showed good agreement with the predictions of the current code, regardless of the tensile strength of the strands. The specimens exhibited ductile behavior, and the crack patterns were similar in all the specimens. Certain specimens under service load exhibited crack widths and stress in the tensile reinforcements that slightly exceeded the limit in the current codes. Because the excess was not considerable, reasonable crack control can be achieved by the proper arrangement of deformed rebars. However, further study is required to create clear guidelines.

This paper presents a multi-component layout optimization method that incorporates a parametric and topology optimization method to determine the optimal configuration of a permanent magnet actuator (PMA). The optimal position and size of the rectangular-type PM are obtained by the design sensitivities of size parameters. The level set-based topology optimization method, which can guarantee a high degree of freedom in geometrical change, is employed to obtain the optimal distribution of the ferromagnetic material (FM) that can affect the path of the magnetic flux. The optimization problem is formulated to maximize the magnetic force of the PMA under the fixed volume fraction constraint of each material. The magnetic properties of the PM and FM, such as the magnetic relative reluctivity and the direction of the remanent magnetic flux, are calculated by the geometric parameters and the sign of the level set function. To confirm the effectiveness of the proposed method, a design example of a simple C-core actuator is provided.

This paper proposes a new level-set-based topology optimization method for magnetic actuator design using remeshing techniques that can generate meshes on the exact structural boundaries to improve the accuracy of finite-element analysis. Two remeshing techniques, such as the modified adaptive mesh method and the extended finite-element method (XFEM), are introduced for the optimization process. To control the computational time with meshing that is economical and analysis that is accurate, a new resolution parameter that can manage the level of mesh density around the level-set boundaries is employed in the modified adaptive mesh method. In the XFEM, the enrichment term in the element shape function is employed to track the exact outer boundary of the actuator. The optimization problem is formulated to maximize the magnetic force between the core and an armature under the volume constraint of the ferromagnetic material. To verify the effectiveness of the proposed method, it is applied to an electromagnetic problem for an optimal C-core actuator design that is very sensitive to structural boundaries.

We investigated whether income level has long-term effects on mortality rate in stroke patients and whether this varies with time after the first stroke event, using the National Health Insurance Service National Sample Cohort data from 2002 to 2015 in South Korea. The study population was new-onset stroke patients &ge, 18 years of age. Patients were categorized into Category (1) insured employees and Category (2) insured self-employed/Medical Aid beneficiaries. Each category was divided into three and four income level groups, retrospectively. The study population comprised of 11,668 patients. Among the Category 1 patients (n = 7720), the low-income group&rsquo, s post-stroke mortality was 1.15-fold higher than the high-income group. Among the Category 2 patients (n = 3948), the lower income groups had higher post-stroke mortality than the high-income group (middle-income, aOR (adjusted odds ratio) 1.29, low-income, aOR 1.70, Medical Aid beneficiaries, aOR 2.19). In this category, the lower income groups&rsquo, post-stroke mortality risks compared to the high-income group were highest at 13&ndash, 36 months after the first stroke event(middle-income, aOR 1.52, low-income, aOR 2.31, Medical Aid beneficiaries, aOR 2.53). Medical Aid beneficiaries had a significantly higher post-stroke mortality risk than the high-income group at all time points.

A wireless charging or inductive charging electric vehicle (EV) is a type of EVs with a battery that is charged from a charging infrastructure, using a wireless power transfer technology. Wireless charging EVs are classified as stationary or dynamic charging EVs. Stationary charging EVs charge wirelessly when they are parked, and dynamic charging EVs can charge while they are in motion. The online electric vehicle developed at the Korea Advanced Institute of Science and Technology is an example of a commercially available dynamic charging transportation system. Numerous studies have reported that one of the benefits of dynamic charging is that it allows smaller and lighter batteries to be used, due to frequent charging using the charging infrastructure embedded under roads. In this paper, we quantitatively analyze the benefits of dynamic charging with an economic model of battery size and charging infrastructure allocation, using a mathematical optimization model. Particularly, we analyze by how much battery size can be reduced and what the cost saving of reducing the battery size is with the model. We also show that the dynamic charging can be beneficial to battery life.

Introduce a new type of electric vehicle called On-line Electric Vehicle (OLEV).The battery in the OLEV is charged wirelessly while the vehicle is in motion.The charge is done from the power transmitter installed under the road.Optimal allocation of the power transmitters is presented.The MIP model is solved using CPLEX and provides insights into system design. We introduce a new type of electric-powered transportation system called the On-Line Electric Vehicle ( OLEV TM ) developed by Korea Advanced Institute of Science and Technology (KAIST). The battery in the OLEV is charged remotely from power transmitters installed under the road using the innovative wireless charging technology. One of the successful commercial applications of the OLEV is the KAIST shuttle bus system operating on the KAIST campus. In this paper, we address the OLEV's system design issues. The key design and economic parameters of the OLEV are the battery size and the allocation of the power transmitters that wirelessly supply the electric energy to the vehicle. We first construct a general mathematical model for optimally allocating the power transmitters and determining the size of the battery for a transportation system with wireless charging electric vehicles. Then we apply the model to a specific model that is currently operating. We are particularly interested in the OLEV system operating in a closed environment in which vehicles operate under regulated velocity and less traffic. The OLEV shuttle bus currently operating at KAIST is a good example of the system under a closed environment. We are particularly concerned about the closed environment system since it is the potential application area where the OLEV-based transportation is effectively commercialized. The optimization problem is constructed in the form of a Mixed Integer Programming (MIP) model. The sensitivity analysis is presented using the vehicle operational data collected from the OLEV shuttle buses. The sensitivity analysis provides meaningful insight into the OLEV-based transportation system design. We also explain how the general model can be extended to different transportation systems other than the closed environment.