Accepted and presented at The Design of Medical Devices Conference (DMD2016)

The ankle plays an important role in human walking. Biomechanical studies show that the ankle generates more power than hip and knee in walking Motivated by this reality, researchers have expended a significant amount of efforts in creating energetically active (i.e., powered) TT prostheses. Typical examples include the multiple prototypes developed by the MIT Biomechatronics Group (e.g., Ref. [2]), the SPARKy prosthesis, and the Vanderbilt transtibial prosthesis. These prostheses are all powered with electric motors, augmented with mechanical springs to simulate the elastic characteristics of the biological ankle. For example, the prosthesis design by Au et al. uses springs in series with the electric motor to form a series elastic actuator, and an additional spring is used to simulate the energy storage-and-return feature in the ankle loading and push-off Compared with the actuation approaches in the aforementioned works, pneumatic actuation is a strong competitor with its multiple advantages. Pneumatic actuators have higher power density than electric motors in general. More importantly, a pneumatic actuator features a physically existing elasticity that can be adjusted via pressure regulation. As such, a pneumatically actuated prosthesis has a potential of simulating the elasticity of the biological ankle without using mechanical springs, significantly simplifying the system design. However, such potential has not been utilized in existing pneumatic TT prostheses (e.g., Ref. [3]). In this paper, a new control approach, namely, variable series elasticity control (VSEC), is presented, which provides effective control of a pneumatically actuated TT prosthesis, leveraging the aforementioned elasticity in pneumatic actuators. Methods The powered TT prosthesis that serves as the basis of this work is the Alabama Powered Prosthetic Limb-Ankle (APPL-A) To model the joint elasticity, the linear stiffness of the pneumatic cylinder can be expressed as where K is the stiffness, R is the universal gas constant, T is the air temperature, L is the stroke, x is the displacement with respect to the middle point of the stroke, L da and L db are the dead lengths of chambers a (rodless chamber) and b (chamber with rod), respectively, and m a and m b are the air masses in chambers a and b, respectively. It can be clearly observed from this equation that the actuator stiffness is a function of chamber air masses m a and m b . Similar to the stiffness, the equilibrium point x e can also be expressed as a function of the chamber air masses where A r is the rod cross-sectional area. Combining Eqs. (1) and (2), the air masses can be calculated based on a set of desired stiffness-equilibrium point Subsequently, the desired pressure is compared with the measured chamber pressure to determine the initial valve commands: open the chamber to pneumatic supply if the measured pressure is lower than desired, otherwise open the chamber to exhaust. When the desired pressure is reached, close the chamber until the state machine transitions to the next phase. Note that the attainable chamber pressure is limited to the range as defined by the supply pressure (150 psi, or 1034 kPa, as dictated by the maximum pressure rating of the control valve, VQ1300K-5B1, SMC Corporation, Tokyo, Japan) and atmosphere pressure. As such, specia

Swing-phase detection of locomotive mode transitions for smooth multi-functional robotic lower-limb prosthesis control

Robotic lower-limb prostheses, with their actively powered joints, may significantly improve amputee users’ mobility and enable them to obtain healthy-like gait in various modes of locomotion in daily life. However, timely recognition of the amputee users’ locomotive mode and mode transition still remains a major challenge in robotic lower-limb prosthesis control. In the paper, the authors present a new multi-dimensional dynamic time warping (mDTW)-based intent recognizer to provide high-accuracy recognition of the locomotion mode/mode transition sufficiently early in the swing phase, such that the prosthesis’ joint-level motion controller can operate in the correct locomotive mode and assist the user to complete the desired (and often power-demanding) motion in the stance phase. To support the intent recognizer development, the authors conducted a multi-modal gait data collection study to obtain the related sensor signal data in various modes of locomotion. The collected data were then segmented into individual cycles, generating the templates used in the mDTW classifier. Considering the large number of sensor signals available, we conducted feature selection to identify the most useful sensor signals as the input to the mDTW classifier. We also augmented the standard mDTW algorithm with a voting mechanism to make full use of the data generated from the multiple subjects. To validate the proposed intent recognizer, we characterized its performance using the data cumulated at different percentages of progression into the gait cycle (starting from the beginning of the swing phase). It was shown that the mDTW classifier was able to recognize three locomotive mode/mode transitions (walking, walking to stair climbing, and walking to stair descending) with 99.08% accuracy at 30% progression into the gait cycle, well before the stance phase starts. With its high performance, low computational load, and easy personalization (through individual template generation), the proposed mDTW intent recognizer may become a highly useful building block of a prosthesis control system to facilitate the robotic prostheses’ real-world use among lower-limb amputees

AUTOMATED ADVERTISEMENT CREATION SYSTEM

An advertisement creation system generates sizeless creatives and renders the creatives as display advertisements of any arbitrary dimension. The system extracts text assets and image assets from creatives provided by an advertiser. In particular, the system selects assets to display based on scores for the respective text assets and image assets. The system then combines selected text assets and image assets to generate a final creative. Finally, the system optimizes the final creative and renders the final creative for display

Physics perspectives of heavy-ion collisions at very high energy

Heavy-ion collisions at very high colliding energies are expected to produce a quark-gluon plasma (QGP) at the highest temperature obtainable in a laboratory setting. Experimental studies of these reactions can provide an unprecedented range of information on properties of the QGP at high temperatures. We report theoretical investigations of the physics perspectives of heavy-ion collisions at a future high-energy collider. These include initial parton production, collective expansion of the dense medium, jet quenching, heavy-quark transport, dissociation and regeneration of quarkonia, photon and dilepton production. We illustrate the potential of future experimental studies of the initial particle production and formation of QGP at the highest temperature to provide constraints on properties of strongly interaction matter.Comment: 35 pages in Latex, 29 figure

Is world view neutral education possible and desirable? : A Christian response to liberal arguments.

The main object of this thesis is to find out why it so often is assumed that education can and should be neutral between world views, and to argue against this. It is also discussed what the world view basis of the common school should be when neutrality is impossible. The idea of a common school that inculcates common values without taking a stand between different religions and secular world views, is central in today's idea of liberal education. It is argued here that however thin the common basis for the school is, certain world view presuppositions will always be conveyed, at least implicitly. It is easier to see the world view presuppositions in one account of education if it is contrasted with another. An account is given of Christian education, emphasizing its view of reality and human nature, the meaning of life and the corresponding purpose of education. Contrasted with this, an analysis of J. White's and K. Strike's accounts of education based on common values only, shows that they both convey world view presuppositions that are incompatible with a Christian view and therefore not neutral. The argument of incompatibility is strengthened by a discussion of T. H. McLaughlin's three different accounts of common, world view neutral education, Catholic education, and liberal religious education. Several kinds of argument for the possibility and desirability of world view neutral education are analysed, and it is claimed that none of them is valid. Some imply a shallow understanding of religion, others a biased view of education. It is argued that liberal education in many ways is more likely to indoctrinate than Christian education IS. Finally, it is argued that it is desirable to have Christian education in state schools, and the degree to which this is possible is discussed

Baichuan 2: Open Large-scale Language Models

Large language models (LLMs) have demonstrated remarkable performance on a variety of natural language tasks based on just a few examples of natural language instructions, reducing the need for extensive feature engineering. However, most powerful LLMs are closed-source or limited in their capability for languages other than English. In this technical report, we present Baichuan 2, a series of large-scale multilingual language models containing 7 billion and 13 billion parameters, trained from scratch, on 2.6 trillion tokens. Baichuan 2 matches or outperforms other open-source models of similar size on public benchmarks like MMLU, CMMLU, GSM8K, and HumanEval. Furthermore, Baichuan 2 excels in vertical domains such as medicine and law. We will release all pre-training model checkpoints to benefit the research community in better understanding the training dynamics of Baichuan 2.Comment: Baichuan 2 technical report. Github: https://github.com/baichuan-inc/Baichuan

A Novel Self-Actuated Linear Drive for Long-Range-of-Motion Electromechanical Systems

Obtaining powered linear movement over a long range of motion is a common yet challenging task, as the majority of linear actuators have limited ranges of motion as determined by their functioning mechanisms. In this paper, the authors present a novel belt-based self-actuated linear drive (B-SALD), in which a self-powered moving platform slides on a slotted track with essentially unlimited range of motion (only limited by the length of the track). Unlike the traditional rack-and-pinion mechanism, the B-SALD system uses a double-sided timing belt as the power-transmitting element. With the teeth on its inner surface, the belt interacts with a timing pulley for its own circulation; with the teeth on its outer surface, the belt interacts with a linear rail with parallel slots and drives the translation of the moving platform. The unique functioning mechanism generates multiple distinct advantages: no lubrication is required; the slotted track is simple and inexpensive to manufacture; and it provides an inherent compliance to buffer shock loading. With the experiments conducted on a preliminary prototype, it has been demonstrated that the B-SALD is able to provide accurate positioning and continuous motion control, an overall mechanical efficiency of 70% over the majority of the load range, and the capability of generating large force output in the desired manner

Double-Acting Sleeve Muscle Actuator for Bio-Robotic Systems

This paper presents a new type of muscle-like actuator, namely double-acting (DA) sleeve muscle actuator, which is suitable for the actuation of biologically-inspired and biomedical robotic systems, especially those serving human-assistance purposes (prostheses, orthoses, etc.). Developed based on the traditional pneumatic muscle actuator, the new DA sleeve muscle incorporates a unique insert at the center. With the insert occupying the central portion of the internal volume, this new actuator enjoys multiple advantages relative to the traditional pneumatic muscle, including a consistent increase of force capacity over the entire range of motion, and a significant decrease of energy consumption in operation. Furthermore, the insert encompasses an additional chamber, which generates an extension force when pressurized. As such, this new actuator provides a unique bi-directional actuation capability, and, thus, has a potential to significantly simplify the design of a muscle actuator-powered robotic system. To demonstrate this new actuator concept, a prototype has been designed and fabricated, and experiments conducted on this prototype demonstrated the enhanced force capacity and the unique bi-directional actuation capability