Taeyong Lee

Ewha Womans University · Department of Mechanical & Biomedical Engineering

When a force deforms an elastic object, practical experience suggests that the resulting displacement will be in the same direction as the force. This property is known as positive stiffness. Less familiar is the concept of negative stiffness, where the deforming force and the resulting displacement are in opposite directions. (Negative stiffness i...

Foot abnormality has become a public health concern. Early detection of pathological soft tissue is therefore an important preventive measure, especially in older people who generally have a higher risk of foot pathology. However, the interpretation of plantar tissue stiffness data – whether to normalize the data or to separate the data on the basi...

With increasing life expectancy and mortality rates, the burden of osteoporotic hip fractures is continually on an upward trend. In terms of prevention, there are several osteoporosis treatment strategies such as anti-resorptive drug treatments, which attempt to retard the rate of bone resorption, while promoting the rate of formation. With respect...

This study was conducted to determine whether prolonged and repetitive exercise stiffens the plantar soft tissue. Healthy female subjects in their early 20s with a similar body mass index but different majors (13 engineers (controls) and 13 ballet dancers) were recruited. Tissue thickness was measured using ultrasound, while peak stress, stress dis...

This study investigates the relationship between plantar tissue stiffness and selected parameters, including age, diabetes mellitus (DM) duration, body mass index (BMI), and HbA1c level. 70 diabetes patients with no foot problems were recruited. The plantar soft tissue at the 2nd sub-metatarsal head (MTH) pad was examined using the novel indentatio...

The interest in research and development for additive manufacturing (AM) processes has grown significantly over the last years and attracts both industry and academia alike. Among the available AM technologies, stereolithography (SLA) is one of the most discussed, researched, and employed. On the other hand, being based on thermoset resins, all the...

Background Foot deformities can cause abnormal biomechanics of the ankle joint and the development of osteoarthritis. It was hypothesized that foot deformities would be related to medial ankle osteoarthritis, and this study investigated this relationship using radiographic measurements. Methods Seventy-six ankles of 76 patients (32 men and 44 wome...

In this research, the improvement in sheet metal formability obtained through the utilization of a mineral grease in solid oil type (SMG) pressure medium in the hydrodynamic deep drawing process assisted by radial pressure (HDDRP) was investigated by experiments and finite element method (FEM) simulations on flat‐bottom cups realized with pure copp...

Fiber reinforcement orientation in thermoplastic injection-molded components is both a strength as well as a weak point of this largely employed manufacturing process. Optimizing the fiber orientation distribution (FOD) considering the shape of the part and the applied loading conditions allows for enhancing the mechanical performances of the produ...

This research presents an automatic algorithm, implemented in a Visual Basic Architecture (VBA), for the optimization of the gate location in thermoplastic injection molding of short fibers reinforced composite materials. The algorithm receives, as input, the geometry of the component and, according to the user’s choice, defines the injection point...

Design and process optimization are key aspects of manufacturing engineering. This contribution details a machine learning (ML) methodology capable of learning from simulation results, experimental data, or sensor signals, and able to predict and optimize specific user-defined process and design parameters. The prediction-optimization algorithm is...

The matter of stabilization has always attracted attention from both academia and industry. In the case of bikes, kickboards, and scooters, simple stabilizer designs have been explored but are rarely applied in commercial products. In this research, a small-scale, customizable, two-wheels design, is proposed and connected to a retroactive closed-lo...

Subject classification through CCTV footage is of key importance for suspect screening and identification in a police investigation. Recent literature showed that the walking posture evolves during the lifetime and acquires specific features characteristic to age range and gender. In this research, time-dependent spatial positions and rotations of...

Fracture risk prediction, especially for osteoporotic patients, has always been a matter of interest for academia and physicians alike. Prediction tools, such as FRAX®, are practical and useful but presents some biases, i.e. the clinical history, medical prescription, ethnicity, and is limited to a femoral neck BMD input. This contribution investi...

In light of the progressive aging of the world population, skeletal fragility and osteoporosis are ever growing issues [1] and showed to be largely influenced by a low bone mineral density (BMD) [2]. Widespread risk assessment tools, such as FRAX®, are employed by physicians to evaluate the likelihood of developing major osteoporotic fracture (MOF)...

Increase of life expectancy and aging population increases the incidence of osteoporosis and hip fracture, making their prevention and treatment a major social challenge for public health. Dual-energy X-ray Absorptiometry (DXA) scan is the most widely used method for bone mineral density (BMD) measurement. However, the areal BMD does not reflect th...

Background Organogenesis from tonsil-derived mesenchymal cells (TMSCs) has been reported, wherein tenogenic markers are expressed depending on the chemical stimulation during tenogenesis. However, there are insufficient studies on the mechanical strain stimulation for tenogenic cell differentiation of TMSCs, although these cells possess advantages...

Many elderly people use hip protectors to prevent hip fractures from sideways falls. These hip protectors absorb or shunt away the energy applied to the greater trochanter. Herein, shear-thickening polymer (STP)-based hip protectors composed of STP and polyurethane foam are studied. The purpose of this study was to identify the main factor that red...

Background Stationary cycling is commonly used for postoperative rehabilitation of physical disabilities; however, few studies have focused on the three-dimensional (3D) kinematics of rehabilitation. This study aimed to elucidate the three-dimensional lower limb kinematics of people with healthy musculoskeletal function and the effect of sex and ag...

Background Kinetic data obtained during gait can be used to clarify the biomechanical pathogenesis of osteoarthritis of the lower extremity. This study aimed to investigate the difference in ankle varus moment between the varus angulation and medial translation types of medial ankle osteoarthritis, and to identify the radiographic measurements asso...

Background: Stationary cycling is commonly used for postoperative rehabilitation of physical disabilities, but few studies have focused on the three-dimensional (3D) kinematics of rehabilitation. This study aimed to elucidate the three-dimensional lower limb kinematics of musculoskeletally healthy people and the effect of sex and age on kinematics...

Shear-thickening polymer (STP) has a unique property of increasing its viscosity with an increase in shear strain to attenuate the application of force, implying that it can be used as a material for hip protectors. This study introduces a new hip protector composed of STP and compares its force attenuation capacity to that of other commercial hip...

The mechanical properties of the plantar soft tissue are known to vary in diabetic patients, indicating that parameter identification of the mechanical properties of the foot tissue using an indentation test is clinically important for possible early diagnosis and interventions of diabetic foot. However, accurate mechanical characterization of the...

The use of variable stiffness shoes (VSS) has been found to be conducive to reducing external knee adduction moment (EKAM). However, it is still unknown whether the claimed biomechanical effects of VSS remain after the subjects have adapted to the footwear. The objective of the study is to examine the effects of VSS immediately upon usage, as well...

Background: Osteolytic metastasis is a common destructive form of metastasis, in which there is an increased bone resorption but impaired bone formation. It is hypothesized that the changed mechanical properties of tumor affected bone cells could inhibit its mechanosensing, thus contributing to differences in bone remodeling. Methods: Here, atom...

Identifying the viscous properties of the plantar soft tissue is crucial not only for understanding the dynamic interaction of the foot with the ground during locomotion, but also for development of improved footwear products and therapeutic footwear interventions. In the present study, the viscous and hyperelastic material properties of the planta...

External hip protectors are used by the elderly in preventing hip fracture due to sideway falls. There are some commercial hip protectors which has both energy absorbing and energy shunting properties. In this study, a novel hip protector using shear thickening polymer (STP) is studied. The purpose of this work is to determine the optimal thickness...

Objectives: This study investigated the correlation between bone mineral density (BMD)/trabecular bone score (TBS) and body mass index (BMI), height and weight in Korean adults. Methods: We enrolled 2555 female participants in their 20s–80s and 1631 male participants in their 20s–70s. Participants with history of previous vertebral surgeries or cur...

To clarify the mechanism underlying the development of foot disorders such as diabetic ulcers and deformities, it is important to understand how the foot surface elongates and contracts during gait. Such information is also helpful for improving the prevention and treatment of foot disorders. We therefore measured temporal changes in the strain dis...

Accurate identification of the material properties of the plantar soft tissue is important for computer-aided analysis of foot pathologies and design of therapeutic footwear interventions based on subject-specific models of the foot. However, parameter identification of the hyperelastic material properties of plantar soft tissues usually requires a...

Engineering structures may be sensitive to vibrations such that their normal functioning is impaired due to the presence of vibrations. A material capable of dissipating energy of vibration by means of heat tends to have better mechanical damping properties. However, due to the demands on structural stability, the material needs to have sufficient...

The purpose of this study is to assess the correlation of trabecular bone score (TBS) to variable factors, i.e. sex, age, body size and BMD. Moreover, we want to find variables of correlation coefficient change with aging. We randomly selected 2,906 subjects (1726 female and 1180 male, age range 20’s to 70’s) from several hospitals in Korea. Partic...

The purpose of this study is to understand the changes of TBS scores in Asian females by comparing 1990’s and 2010’s DXA images. We have compared the DXA images of 3774 Korean females (age: 20–79) to Japanese (age: 20–79). While Korean DXA images were obtained in 2014 and 2015, Japanese data were obtained in 1996. Participants who have abnormal DXA...

Nowadays, low back pain becomes a common healthcare problem. Poor or unsuitable seat design is related to the discomfort and other healthcare problems of users. The aim of this study is to investigate the influence of seat design variables on the compressive loadings of lumbar joints. A basis that includes a musculoskeletal human body model and a c...

Purpose Bone metastasis invariably increases morbidity and mortality. This study compares the effects of ibandronate and paclitaxel on bone structure and its mechanical properties and biochemical turnover in resorption markers using an immunocompetent Walker 256-Sprague-Dawley model, which was subjected to tumor-induced osteolysis. Materials and M...

Background: There have been some disagreements on the comparison of disc pressures in the standing and sitting postures in literature. Most research on in vivo pressure needle measurement found higher disc pressure in sitting than in standing. The disc pressure data can help to advocate better postures for clinical advice. Objective: The aim of...

Human trabecular bone is known to be structurally very complex. The geometrical distribution of trabecular bone has major effects on its ability to perform its physiological function of load-bearing efficiently. Idealized unit cell models are very helpful in understanding the significance of micro-level properties on macro-level behavior. There is...

Most in-vivo indentation techniques are limited by the lack of adequate indentation into the plantar soft tissue. The purpose of this study is therefore to assess the effect of deformation depth on plantar soft tissue behavior and to establish a guideline for the minimum indentation depth that is sufficient to quantify critical plantar soft tissue...

Bone mineral density (BMD) is used as a sole parameter in the diagnosis of osteoporosis. Due to the ease of acquirement of BMD, clinical diagnosis still involves its usage although the limitations of BMD are quite well-established. Therefore, this preliminary study hoped to reduce the errors introduced by BMD alone by incorporating geometric and st...

Objectives Osteoporosis is a prevalent problem amongst the elderly. Bone mineral density (BMD) obtained from dual X-ray absorptiometry (DXA) is the gold standard in diagnosing osteopenia (-1.0 < t < -2.5) and osteoporosis (t > -2.5). However, following osteoporosis therapy, increases in BMD may be unreliable. Although hip fracture risk can be reduc...

The nonlinearity of plantar soft tissue is seldom examined because of the small extent of deformation induced during indentation for measurement purposes. Furthermore, in most indentation experiments, the metatarsophalangeal joint (MTPJ) angle is not well controlled, although it has been proven to have a significant stiffening effect on sub-metatar...

15% of Diabetes Mellitus (DM) patients suffer high risk of ulceration and 85% of the amputation involving DM population is caused by non-healing ulcers. These findings elucidate the fact that foot ulcer can result in major amputation especially to the DM and elderly population. Therefore, early diagnosis of abnormally stiffened plantar soft tissue...

Tissue glycation, that occurs naturally through ageing and can be sometimes accelerated by disease such as diabetes mellitus, is clinically claimed to have induced irregular collagen alignment and increased collagen fibril density in patients [1]. This hence increases tissue stiffness and leads to plantar injury, i.e. ulcer. In the USA, 85% of all...

Many engineering structures are required to minimize vibrations. Vibrations in a system can be reduced by changing the design of the structure or by using a new material which has better mechanical damping. Damping materials are desirable as they convert mechanical energy to heat. As most engineering structures are load bearing, the material used n...

Millet Trail Running Shoe Development using Biomechanical research - Design concept

The growing ageing population and high prevalence of knee osteoarthritis (OA) in athletes across nations have created a strong demand for improved non-invasive therapeutic alternatives for knee OA. The aim of this study is to investigate the effect of the variable stiffness shoe (VSS), a new non-invasive therapeutic approach, on external knee adduc...

The bone mineral density (BMD) is a measure of the quantity of mineral present in the bone. The BMD provides an approximate indication of the bone quality, and is usually employed for fracture prediction in a clinical scenario. The buckling ratio (BR) is a measure of the geometry of the bone. It quantifies the distribution of the bone material, and...

INTRODUCTION Hip fracture often results in injury and loss in mobility in the elderly and is a growing concern especially with increasing life expectancy and heavy socio-economic costs. Although hip fracture risk can be reduced with the aid of drugs, treated patients still face considerable risk as most people who sustain hip fracture do not have g...

The existence of local osteoporosis necessitates patient-specific analysis. Lower and higher ranges of local buckling ratio were found at femoral necks for adequate and inadequate drug response groups, respectively (grouped based on fracture loads). Management of hip fracture risk should be targeted at local geometric abnormalities causing instabil...

A study on outsole and insole effect by evaluatiing the kinetics and kinematics

Femoral shaft fractures are common in both the young and elderly due to high-impact trauma and low-impact trauma, respectively. Its treatment by indirect reduction through use of locking compression plates (LCPs) has been on the rise. The LCP possess several advantages in fracture fixation, combining angular stability through use of locking screws...

In this study, the bone mineral density (BMD), geometry, macroscopic viscoelastic properties and mechanical strength in five different groups of Sprague-Dawley rats (sham operated, ovariectomized with vehicle, parathyroid hormone and/or ibandronate administration) were examined by peripheral quantitative computed tomography (pQCT), dynamic mechanic...

Besides bone mineral density (BMD), structural and nano-level viscoelastic properties of bone are also crucial determinants of bone strength. However, treatment induced viscosity changes in osteoporotic bone have seldom been characterized. In this study, the effects of anabolic, antiresorptive and concurrent treatments on ovariectomized rat bones w...

Sclerosis (tissue hardening) development is a common occurrence in slow growing or benign osteolytic lesions. However, there is lack of knowledge on the mechanical and material property changes associated with sclerotic bone response. The immune system is postulated to play a relevant role in evoking sclerotic bone responses. In this study, localiz...

The investigation of the biomechanics of human spine in different sitting postures becomes more important as humans spend an increasing amount of time in sitting postures in daily life. The purpose of this research is to investigate the effect of different sitting postures on spinal angles and joint forces in the pain-free human body by the applica...

The functions of the gastrocnemius-soleus (G-S) complex and other plantar flexor muscles are to stabilize and control major bony joints, as well as to provide primary coordination of the foot during the stance phase of gait. Geometric positioning of the foot and transferring of plantar loads can be adversely affected when muscular control is abnorm...

This study investigates the altered thoracohumeral kinematics when forearm rotation is restricted while performing five activities requiring pronation and supination. Two splints simulated both a fixed-supinated or fixed-neutral forearm in six healthy subjects; the three-dimensional coupled relationship among motion about the forearm, elbow, and sh...

Reduction of the vibration noise from submarine propellers is of interest in naval operations. Such an objective can be achieved via the use of materials with the ability to dissipate energy of vibration by means of heat, i.e. high damping materials. An additional problem is that the extreme hydrostatic pressure environment of a submarine requires...