Searcharxiv⌕ Search

arXiv subjects

Jungsoo Kim

Publications and source records attributed to Jungsoo Kim.

At least 19 recordsLinked to original sources
arXiv2025

Noise disturbance and lack of privacy: Modeling acoustic dissatisfaction in open-plan offices

Open-plan offices are well-known to be adversely affected by acoustic issues. This study aims to model acoustic dissatisfaction using measurements of room acoustics, sound environment during occupancy, and occupant surveys (n = 349) in 28 offices representing a diverse range of workplace parameters. As latent factors, the contribution of $\textit{lack of privacy}$ (LackPriv) was 25% higher than $\textit{noise disturbance}$ (NseDstrb) in predicting $\textit{acoustic dissatisfaction}$ (AcDsat). Room acoustic metrics based on sound pressure level (SPL) decay of speech ($L_{\text{p,A,s,4m}}$ and $r_{\text{C}}$) were better in predicting these factors than distraction distance ($r_{\text{D}}$) based on speech transmission index. This contradicts previous findings, and the trends for SPL-based metrics in predicting AcDsat and LackPriv go against expectations based on ISO 3382-3. For sound during occupation, $L_{\text{A,90}}$ and psychoacoustic loudness ($N_{\text{90}}$) predicted AcDsat, and a SPL fluctuation metric ($M_{\text{A,eq}}$) predicted LackPriv. However, these metrics were weaker predictors than ISO 3382-3 metrics. Medium-sized offices exhibited higher dissatisfaction than larger ($\geq$50 occupants) offices. Dissatisfaction varied substantially across parameters including ceiling heights, number of workstations, and years of work, but not between offices with fixed seating compared to more flexible and activity-based working configurations. Overall, these findings highlight the complexities in characterizing occupants' perceptions using instrumental acoustic measurements.

eess.AS↗
arXiv2023

Reliability and repeatability of ISO 3382-3 metrics based on repeated acoustic measurements in open-plan offices

This paper investigates variability in the key ISO 3382-3:2012 metrics, based primarily on the repeatability and reliability of these metrics, using repeated measurements in open-plan offices. Two types of repeated measurements were performed in offices, Type1 (n=36), where the same path over workstations was measured from opposite ends, and Type2 (n=7), where two different measurement paths were measured. Overall, most of the Type1 results seem reasonable considering repeats were conducted in complicated room acoustic environments, while Type2 repeats would benefit from larger sample sizes in future studies. Some recommendations are outlined for the ISO 3382-3 methodology vis-a-vis Type1 and Type2 repeats, including future research directions that go beyond increased sample sizes. (This is an abridged version of the abstract. Please see the paper for the full abstract)

eess.AS↗
arXiv2023

Auditory distraction in open-plan office environments: The effect of multi-talker acoustics

Within the soundscapes of open-plan offices, irrelevant speech has consistently been reported as the most distracting, and causing performance decrements for workers. Notwithstanding this generalization, the 'babble' created by multiple simultaneously active talkers can sometimes provide beneficial sound masking, but due to spatial release from masking (SRM), speech may still be sufficiently intelligible up to a certain number of talkers (estimated to be about four). This was explored within a highly-realistic office simulation, where the cognitive performance, and subjective distraction of participants were tested. The experimental design was a 4x2 factorial (4 talker numbers, 2 levels of broadband sound masking, as the factors). The results indicated that within lower sound pressure level (SPL) of broadband sound masking, multi-talker sound environments degraded cognitive tasks performance more than those with a single talker, suggesting SRM effects. For higher SPL broadband sound masking, the cognitive test scores were similar within the different talker numbers. The subjective distraction increased monotonically with the number of talkers, with higher distraction within lower SPL broadband sound masking. Overall, the results call into question the single talker assumption (being the most distracting) within the international standard for measuring open-plan office acoustic environments (ISO 3382-3:2012). Soundscapes with 4 simultaneous talkers were still not adequately providing beneficial 'babble' masking, and were more distracting than 1 active talker. In conclusion, it is suggested that the acoustics environment of open-plan offices needs better characterization by incorporating some of the complexity and psychoacoustics of multi-talker scenarios.

q-bio.QM↗
arXiv2023

Sound in occupied open-plan offices: Objective metrics with a review of historical perspectives

Open-plan offices (OPOs) have been around for more than half a century now, chronicling the vicissitudes of workplace topography amongst other factors. This paper addresses one such factor - the sound environment in occupied OPOs in relation to several objective workplace parameters, using measurements in contemporary OPOs and comparisons with studies over the last 50 years. Omnidirectional and binaural sound measurements were conducted in 43 offices during typical working hours. The results describe variation in several acoustic and psychoacoustic metrics, and present statistical models that predict these metrics as a function of the number of workstations in offices. LA,eq of 53.6 dB is typical for occupied OPOs, with spectral slope of approximately -4 dB/octave. LA,eq values do not vary much over the workplace parameters studied (e.g., floor plate area, work activity, etc), except for -2.7 dB and -4.1 dB differences between offices with/without carpeting, and offices with ceiling absorption but with/without carpeting, respectively; most likely from reduced floor impact noise leading to speech level reduction. Sound fluctuation, as characterised by the metric Noise Climate (NCl: LA10 - LA90) and the psychoacoustic Fluctuation Strength (FS), decreases significantly with increasing number of workstations in OPOs. This suggests lesser auditory distraction in larger offices, which needs further investigation. In terms of historical trends, OPOs have become quieter over the years, especially background noise quantified as LA90, although there are several subtleties. Overall, current findings can inform several OPO design perspectives including policy documents, provide values for laboratory simulations of OPO acoustic environments, help interpret subjective impressions of OPO occupants, etc.

eess.AS↗
arXiv2020

Remarkable low-energy properties of the pseudogapped semimetal Be$_5$Pt

We report measurements and calculations on the properties of the intermetallic compound Be$_5$Pt. High-quality polycrystalline samples show a nearly constant temperature dependence of the electrical resistivity over a wide temperature range. On the other hand, relativistic electronic structure calculations indicate the existence of a narrow pseudogap in the density of states arising from accidental approximate Dirac cones extremely close to the Fermi level. A small true gap of order 3 meV is present at the Fermi level, yet the measured resistivity is nearly constant from low to room temperature. We argue that this unexpected behavior can be understood by a cancellation of the energy dependence of density of states and relaxation time due to disorder, and discuss a model for electronic transport. With applied pressure, the resistivity becomes semiconducting, consistent with theoretical calculations that show that the band gap increases with applied pressure. We further discuss the role of Be inclusions in the samples.

cond-mat.mtrl-sci↗
arXiv2020

A New Update Rule of RLSEKF-based Joint-estimation Filters for Real-time SOH SOC Identification

In order to accurately estimate the SOC and SOH of a lithium-ion battery used in an electric vehicle (EV), we propose an Adaptive Diagonal Forgetting Factor Recursive Least Square (ADFF-RLS) for accurate battery parameter estimation. ADFFRLS includes two new proposals in the existing DFF-RLS; The first is an excitation tag that changes the behavior of the DFFRLS and the EKF according to the dynamics of the input data. The second is auto-tuning that automatically finds the optimal value of RLS forgetting factor based on condition number (CN). Based on this, we proposed a joint estimation algorithm of ADFF-RLS and Extended Kalman Filter (EKF). To verify the accuracy of the proposed algorithm, we used experimental data of hybrid pattern battery cells mixed with dynamic and static patterns. In addition, we added a current measurement error that occurs when measuring at EV, and realized data that is closer to actual environment. This data was applied to two conventional estimation algorithms (Coulomb counting, Single EKF), two joint estimation algorithms (RLS & EKF, DFF-RLS & EKF) and ADFF-RLS & EKF. As a result, the proposed algorithm showed higher SOC and SOH estimation accuracy in various driving patterns and actual EV driving environment than previous studies.

eess.SY↗
arXiv2019

A Class of Compounds Featuring Frustrated Triangular Magnetic Lattice CsRESe$_2$ (RE=La-Lu): Quantum Spin-Liquid Candidates

A triangular lattice selenide series of rare earth (RE), CsRESe2, were synthesized as large single crystals using a flux growth method. This series stabilized in either trigonal (R-3m) or hexagonal (P63/mmc) crystal systems. Physical properties of CsRESe2 were explored by magnetic susceptibility and heat capacity measurements down to 0.4 K. Antiferromagnetic interaction was observed in all magnetic compounds, while no long-range magnetic order was found, indicating the frustrated magnetism. CsDySe2 presents spin freezing at 0.7 K, revealing a spin-glass state. CsCeSe2 and CsYbSe2 present broad peaks at 0.7 K and 1.5 K in the magnetization, respectively, suggesting the short-range interactions between magnetic rare earth ions. The lack of signature for long-range magnetic order and spin freezing down to 0.4 K in these compounds (RE = Ce, Yb) implies their candidacy for quantum spin liquid state.

cond-mat.mtrl-sci↗
arXiv2019

Field-induced magnetic transition and spin fluctuation in quantum spin liquid candidate CsYbSe$_2$

Two-dimensional triangular-lattice materials with spin-1/2 are perfect platforms for investigating quantum frustrated physics with spin fluctuations. Here we report the structure, magnetization, heat capacity and inelastic neutron scattering (INS) results on cesium ytterbium diselenide, CsYbSe$_2$. There is no long-range magnetic order down to 0.4 K at zero field. The temperature dependent magnetization, $M(T)$, reveals an easy-plane magnetic anisotropy. A maximum is found in $M(T)$ around \emph{T}$\sim$1.5 K when magnetic field $H$ is applied in the $ab$ plane, indicating the short-range interaction. The low-temperature isothermal magnetization $M(H)$ shows a one-third plateau of the estimated saturation moment, that is characteristic of a two-dimensional frustrated triangular lattice. Heat capacity shows field-induced long-range magnetic order for both $H||c$ and $H||ab$ directions. The broad peak in heat capacity and highly damped INS magnetic excitation at $T$=2 K suggests strong spin fluctuations. The dispersive in-plane INS, centered at the (1/3 1/3 0) point, and the absence of dispersion along $c$ direction suggests 120$^{\circ}$ non-collinear 2D-like spin correlations. All these results indicate that the two-dimensional frustrated material CsYbSe$_2$ can be in proximity to the triangular-lattice quantum spin liquid. We propose an experimental low-temperature $H$-$T$ phase diagram for CsYbSe$_2$.

cond-mat.str-el↗
arXiv2019

Synthesis, magnetization and heat capacity of triangular lattice materials NaErSe$_2$ and KErSe$_2$

In this paper we report the synthesis, magnetization and heat capacity of the frustrated magnets \emph{A}ErSe$_2$(\emph{A}=Na,K) which contain perfect triangular lattices of Er$^{3+}$. The magnetization data suggests no long-range magnetic order exists in \emph{A}ErSe$_2$(\emph{A}=Na,K), which is consistent with the heat capacity measurements. Large anisotropy is observed between the magnetization within the \emph{ab} plane and along the \emph{c} axis of both compounds. When the magnetic field is applied along \emph{ab} plane, anomalies are observed at 1.8 $μ_B$ in NaErSe$_2$ at 0.2 T and 2.1 $μ_B$ in KErSe$_2$ at 0.18 T. Unlike NaErSe$_2$, a plateau-like field-induced metamagnetic transition is observed for H$\|$\emph{c} below 1 K in KErSe$_2$. Two broad peaks are observed in the heat capacity below 10 K indicating possible crystal electric field(CEF) effects and magnetic entropy released under different magnetic fields. All results indicate that \emph{A}ErSe$_2$ are strongly anisotropic, frustrated magnets with field-induced transition at low temperature. The lack of signatures for long-range magnetic order implies that these materials are candidates for hosting a quantum spin liquid ground state.

cond-mat.mtrl-sci↗
arXiv2016

Generalized Heegaard splittings and the disk complex

Let $M$ be an orientable, irreducible $3$-manifold and $(\mathcal{V},\mathcal{W};F)$ a weakly reducible, unstabilized Heegaard splitting of $M$ of genus at least three. In this article, we define an equivalent relation $\sim$ on the set of the generalized Heegaard splittings obtained by weak reductions and find special subsets of the disk complex $\mathcal{D}(F)$ named by the "equivalent clusters", where we can find a canonical function $Φ$ from the set of equivalent clusters to the set of the equivalent classes for the relation $\sim$. As an application, we prove that if $F$ is topologically minimal and the topological index of $F$ is at least three, then there is a $2$-simplex in $\mathcal{D}(F)$ formed by two weak reducing pairs such that the equivalent classes of the generalized Heegaard splittings obtained by weak reductions along the weak reducing pairs for the relation $\sim$ are different. In the last section, we prove $Φ$ is a bijection if the genus of $F$ is three. Using it, we prove there is a canonical function $Ω$ from the set of components of $\mathcal{D}_{\mathcal{VW}}(F)$ to the set of the isotopy classes of the generalized Heegaard splittings obtained by weak reductions and describe what $Ω$ is.

math.GT↗
arXiv2016

On the group action of $Mod(M,F)$ on the disk complex

Let $(\mathcal{V},\mathcal{W};F)$ be a weakly reducible, unstabilized, Heegaard splitting of genus at least three in an orientable, irreducible $3$-manifold $M$. Then $Mod(M,F)$ naturally acts on the disk complex $\mathcal{D}(F)$ as a group action. In this article, we prove if $F$ is topologically minimal and its topological index is two, then the orbit of any element of $\mathcal{D}(F)$ for this group action consists of infinitely many elements. Moreover, we prove there are at most two elements of $\mathcal{D}(F)$ whose orbits are finite if the genus of $F$ is three.

math.GT↗
arXiv2015

On the disk complexes of weakly reducible, unstabilized Heegaard splittings of genus three III - Generalized Heegaard splittings and mapping classes

Let $M$ be an orientable, irreducible $3$-manifold admitting a weakly reducible genus three Heegaard splitting as a minimal genus Heegaard splitting. In this article, we prove that if $[f]$, $[g]\in Mod(M)$ give the same correspondence between two isotopy classes of generalized Heegaard splittings consisting of two Heegaard splittings of genus two, say $[\mathbf{H}]\to[\mathbf{H}']$, then there exists a representative $h$ of the difference $[h]=[g]\cdot[f]^{-1}$ such that (i) $h$ preserves a suitably chosen embedding of the Heegaard surface $F'$ obtained by amalgamation from $\mathbf{H}'$ which is a representative of $[\mathbf{H}']$ and (ii) $h$ sends a uniquely determined weak reducing pair $(V',W')$ of $F'$ into itself up to isotopy. Moreover, for every orientation-preserving automorphism $\tilde{h}$ satisfying the previous conditions (i) and (ii), there exist two elements of $Mod(M)$ giving correspondence $[\mathbf{H}]\to[\mathbf{H}']$ such that $\tilde{h}$ belongs to the isotopy class of the difference between them.

math.GT↗
arXiv2015

On the disk complexes of weakly reducible, unstabilized Heegaard splittings of genus three I - the Structure Theorem

Let (V,W;F) be a weakly reducible, unstabilized, genus three Heegaard splitting in an orientable, irreducible 3-manifold M and DVW(F) the subset of the disk complex D(F) consisting of simplices having at least one vertex from V and at least one vertex from W. In this article, we describe the shape of DVW(F) and prove that there is a function from the components of DVW(F) to the isotopy classes of the generalized Heegaard splittings obtained by weak reductions from (V,W;F), where this function describes how the thick levels are embedded in the relevant compression bodies.

math.GT↗
arXiv2012

On critical Heegaard splittings of tunnel number two composite knot exteriors

In this article, we prove that a tunnel number two knot induces a critical Heegaard splitting in its exterior if there are two weak reducing pairs such that each weak reducing pair contains the cocore disk of each tunnel. Moreover, we prove that a connected sum of two 2-bridge knots or more generally that of two $(1,1)$-knots can induce a critical Heegaard splitting in its exterior as the examples of the main theorem. Finally, we give an equivalent condition for a weak reducing pair to be determined by a compressing disk uniquely when the manifold is closed, irreducible and the Heegaard splitting is of genus three and unstabilized.

math.GT↗
arXiv2012

On unstabilzed genus three critical Heegaard surfaces

Let $M$ be a compact orientable irreducible 3-manifold and $H$ be an unstabilized genus three Heegaard splitting of $M$. In this article, we will define a simplicial complex of weak reducing pairs for $H$ and find several properties of this complex. Using this method, we will prove that an unstabilized Heegaard splitting of genus three is critical in a certain condition. In addition, we will show that the standard genus three Heegaard splitting for $T^3$ and the induced Heegaard splitting of the three component chain exterior by a certain tunnel system are critical as examples of the main theorem.

math.GT↗
arXiv2010

Rectangle condition for compression body and 2-fold branched covering

We give the rectangle condition for strong irreducibility of Heegaard splittings of $3$-manifolds with non-empty boundary. We apply this to a generalized Heegaard splitting of a $2$-fold covering of $S^3$ branched along a link. The condition implies that any thin meridional level surface in the link complement is incompressible. We also show that the additivity of knot width holds for a composite knot satisfying the condition.

math.GT↗
arXiv2010

A note on the nearly additivity of knot width

Let k be a knot in S3. In [8], H.N. Howards and J. Schultens introduced a method to construct a manifold decomposition of double branched cover of (S3, k) from a thin position of k. In this article, we will prove that if a thin position of k induces a thin decomposition of double branched cover of (S3,k) by Howards and Schultens' method, then the thin position is the sum of prime summands by stacking a thin position of one of prime summands of k on top of a thin position of another prime summand, and so on. Therefore, k holds the nearly additivity of knot width (i.e. for k = k1#k2, w(k) = w(k1)#w(k2) - 2) in this case. Moreover, we will generalize the hypothesis to the property a thin position induces a manifold decomposition whose thick surfaces consists of strongly irreducible or critical surfaces (so topologically minimal.)

math.GT↗