Jonathan Stallrich

North Carolina State University | NCSU · Department of Statistics

The rise of internet-based services and products in the late 1990's brought about an unprecedented opportunity for online businesses to engage in large scale data-driven decision making. Over the past two decades, organizations such as Airbnb, Alibaba, Amazon, Baidu, Booking.com, Alphabet's Google, LinkedIn, Lyft, Meta's Facebook, Microsoft, Netfli...

Automatically personalizing complex control of robotic prostheses to improve gait performance, such as gait symmetry, is challenging. Recently, human-in-the-loop (HIL) optimization and reinforcement learning (RL) have shown promise in achieving optimized control for each individual user in the field of wearable robots. However, HIL optimization met...

In practice, optimal screening designs for arbitrary run sizes are traditionally generated using the D-criterion with factor settings fixed at +/- 1, even when considering continuous factors with levels in [-1, 1]. This paper identifies cases of undesirable estimation variance properties for such D-optimal designs and argues that generally A-optima...

Chemical agents released into the environment can induce oxidative stress in organisms, which is detrimental for health. Although environmental exposures typically include multiple chemicals, organismal studies on oxidative stress derived from chemical agents commonly study exposures to individual compounds. In this work, we explore how chemical mi...

Articular cartilage has unique load-bearing properties but has minimal capacity for intrinsic repair. Here, we used three-dimensional weaving, additive manufacturing, and autologous mesenchymal stem cells to create a tissue-engineered, bicomponent implant to restore hip function in a canine hip osteoarthritis model. This resorbable implant was spec...

Weighted optimality criteria allow an experimenter to express hierarchical interest across estimable functions through a concise weighting system. We show how such criteria can be implicitly influenced by the estimable functions’ minimum variances, leading to nonintuitive variance properties of the optimal designs. To address this, we propose a new...

Poly(lactic acid) (PLA) is an attractive biomaterial due to its biocompatibility, biodegradability, and fiber-forming ability. However, the polymer is highly susceptible to both hydrolytic and thermal degradation during processing. Melt processing conditions typically involve high temperature and shear, whereas to prevent premature degradation, PLA...

The invasive Halyomorpha halys invades crop fields from various bordering habitats, and its feeding on crops has caused significant economic losses. Thus, H. halys is considered a perimeter-driven threat, and research on alternative management tactics against it has focused on intervention at crop edges. Woodlands adjacent to crop fields contain ma...

Chemical agents released into the environment can induce oxidative stress in organisms, which is detrimental for health and has been linked to neurodegenerative diseases. C. elegans has been important as model organism to understand oxidative stress caused by chemical agents. In this work, we explore how chemical mixtures drive the oxidative stress...

Despite the vast amount of literature on supersaturated designs (SSDs), there is a scant record of their use in practice. We contend this imbalance is due to conflicting recommendations regarding SSD use in the literature as well as the designs’ inabilities to meet practitioners’ analysis expectations. To address these issues, we first summarize pr...

Optimizing an expensive, black-box function f(⋅) is challenging when its input space is high-dimensional. Sequential design frameworks first model f(⋅) with a surrogate function and then optimize an acquisition function to determine input settings to evaluate next. Optimization of both f(⋅) and the acquisition function benefit from effective dimens...

Objective: To evaluate accuracy of articular surfaces determined by use of 2 perpendicular CT orientations, micro-CT, and laser scanning. Sample: 23 cat cadavers. Procedures: Images of antebrachia were obtained by use of CT (voxel size, 0.6 mm) in longitudinal orientation (CTLO images) and transverse orientation (CTTO images) and by use of mic...

Background: Establishing gait symmetry is a major aim of amputee rehabilitation and may be more attainable with powered prostheses. Though, based on previous work, we postulate that users transfer a previously-learned motor pattern across devices, limiting the functionality of more advanced prostheses. The objective of this study was to preliminar...

In this paper, we propose a new method for constructing supersaturated designs that is based on the Kronecker product of two carefully-chosen matrices. The construction method leads to a partitioning of the columns of the design such that the columns within a group are correlated to the others within the same group, but are orthogonal to any factor...

The goal of this study was to implement powerful mixture design techniques, commonly used in process optimization, to investigate enhanced adverse effects upon co-exposure to environmental cyanotoxins. Exposure to cyanobacteria, which are found ubiquitously in environmental water reservoirs, have been linked to several neurodegenerative diseases. D...

Infrastructure as code (IaC) scripts are used to automate the maintenance and configuration of software development and deployment infrastructure. IaC scripts can be complex in nature, containing hundreds of lines of code, leading to defects that can be difficult to debug, and lead to wide-scale system discrepancies such as service outages at scale...

Simultaneous and proportional control (SPC) of neural-machine interfaces uses magnitudes of smoothed electromyograms (EMG) as control inputs. Though surface (sEMG) electrodes are common for clinical neural-machine interfaces, intramuscular (iEMG) electrodes may be indicated in some circumstances (e.g. for controlling many degrees of freedom). Howev...

Use of infrastructure as code (IaC) scripts helps software teams manage their configuration and infrastructure automatically. Information technology (IT) organizations use IaC scripts to create and manage automated deployment pipelines to deliver services rapidly. IaC scripts can be defective, resulting in dire consequences, such as creating wide-s...

State-of-the-art robotic hand prosthetics generate finger and wrist movement through pattern recognition (PR) algorithms using features of forearm electromyogram (EMG) signals, but re- quires extensive training and is prone to poor predictions for conditions outside the training data (Peerdeman et al., 2011; Scheme et al., 2010). We propose a novel...

Optimizing a black-box function is challenging when the underlying function is non-linear and dependent on a large number of input variables. Expected improvement ($EI$) algorithms balance exploration of the design space and identification of the global maximizer, but they struggle in high dimensions. Reducing the dimension of the design space to i...

Traditional surveys used to create species distribution maps and estimate ecological relationships are expensive and time consuming. Citizen science offers a way to collect a massive amount of data at negligible cost and has been shown to be a useful supplement to traditional analyses. However, there remains a need to conduct formal surveys to firm...

Machines and humans become mechanically coupled when lower limb amputees walk with powered prostheses, but these two control systems differ in adaptability. We know little about how they interact when faced with real-world physical demands (e.g. carrying loads). Here, we investigated how each system (i.e. amputee and powered prosthesis) responds to...

ContextUser activity logs should capture evidence to help answer who, what, when, where, why, and how a security or privacy breach occurred. However, software engineers often implement logging mechanisms that inadequately record mandatory log events (MLEs), user activities that must be logged to enable forensics. GoalThe objective of this study is...

Biases against women in the workplace have been documented in a variety of studies. This paper presents a large scale study on gender bias, where we compare acceptance rates of contributions from men versus women in an open source software community. Surprisingly, our results show that women’s contributions tend to be accepted more often than men’s...

Computer generation of experimental designs, for reasons including flexibility, speed, and ease of access, is the first line of approach for many experimentalists. The algorithms generating designs in many popular software packages employ optimality functions to measure design effectiveness. These optimality functions make implicit assumptions abou...

Using a multi-country data set of over 600 survey participants, we show that psychographics and various attributes of the mobile app context are predictive of user privacy preferences. In particular, we find that a user's decision-making style is predictive of their privacy preferences, with users who are more independent decision makers tending to...

Context: The security goals of a software system provide a foundation for security requirements engineering. Identifying security goals is a process of iteration and refinement, leveraging the knowledge and expertise of the analyst to secure not only the core functionality but the security mechanisms as well. Moreover, a comprehensive security plan...

Biases against women in the workplace have been documented in a variety of studies. This paper presents the largest study to date on gender bias, where we compare acceptance rates of contributions from men versus women in an open source software community. Surprisingly, our results show that women's contributions tend to be accepted more often than...

Biases against women in the workplace have been documented in a variety of studies. This paper presents the largest study to date on gender bias, where we compare acceptance rates of contributions from men versus women in an open source software community. Surprisingly, our results show that women's contributions tend to be accepted more often than...

We compared the effectiveness of an under-trellis cover crop treatment (CC, Festuca rubra) and an 85-cmwide herbicide-treated strip treatment (HTS) and rootstock (101-14, 420-A, or riparia) for regulating vegetative growth and improving fruit composition in Cabernet Sauvignon over a six- to seven-year period of data collection. The cover crop reduc...

The fertility of lactating Holstein cows is severely reduced during periods of heat stress. Despite this reduction in fertility, however, some inseminations conducted during heat stress result in successful pregnancies from which heifer calves are born. Many of these heifer calves are retained and raised to enter the milking herd as replacement ani...

Normal QQ-plots of studentized residuals for linear mixed models by state. (TIF)

Frequency histogram of mature-equivalent milk produced by Georgia cattle by season of calving and heat stress category. (TIF)

A series of experiments in Virginia, USA apple orchards evaluated the temporal effects of natural enemies on Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) colonies on potted and mature apple trees. Exclusion cage studies using potted trees resulted in increasing colony numbers on fully caged trees and declining colony numbers or colony extin...

Heat stress at the time of conception affects the subsequent milk production of primiparous Holstein cows; however, it is unknown whether these effects are maintained across multiple lactations. Therefore, the objective of the current study was to examine the relationship between periconceptional heat stress and measurements of milk production and...

The standard approach to finding optimal experimental designs employs conventional measures of design efficacy, such as the $A$, $E$, and $D$-criterion, that assume equal interest in all estimable functions of model parameters. This paper develops a general theory for weighted optimality, allowing precise design selection according to expressed rel...

Models based on simple air temperature–water temperature relationships have been useful in highlighting potential threats to coldwater-dependent species such as Brook Trout Salvelinus fontinalis by predicting major losses of habitat and substantial reductions in geographic distribution. However, spatial variability in the relationship between chang...

Brown marmorated stink bug, Halyomorpha halys (Stål), injury to late-season apple cultivars was measured at harvest in 2011 and 2012 in commercial orchards in four mid-Atlantic states. In each orchard block, a border zone (adjacent to woods), an interior zone (near orchard center), and an intermediate zone (between border and interior zones) compri...

Consider a linear model with targeted parameters [Inline formula]. We derive a necessary and sufficient condition on the matrix M for the average variance of functions [Inline formula] to be proportional to the A value for comparing designs. This establishes the full range of interpretations of the A criterion.

Researchers collaborate on scientific projects that are often measured by both the quantity and the quality of the resultant peer-reviewed publications. However, not all collaborators contribute to these publications equally, making metrics such as the total number of publications and the H-index insufficient measurements of individual scientific i...

Irreversible electroporation (IRE) is a non-thermal focal ablation technique that uses a series of brief but intense electric pulses delivered into a targeted region of tissue, killing the cells by irrecoverably disrupting cellular membrane integrity. This study investigates if there is an improved local anti-tumor response in immunocompetent (IC)...

Opportunistic pathogens represent a unique challenge because they establish and grow within drinking water systems, yet the factors stimulating their proliferation are largely unknown. The purpose of this study was to examine the influence of pipe materials, disinfectant type, and water age on occurrence and persistence of three opportunistic patho...